WO2024060131A1 - 电化学装置及其制备方法和电子装置 - Google Patents

电化学装置及其制备方法和电子装置 Download PDF

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WO2024060131A1
WO2024060131A1 PCT/CN2022/120528 CN2022120528W WO2024060131A1 WO 2024060131 A1 WO2024060131 A1 WO 2024060131A1 CN 2022120528 W CN2022120528 W CN 2022120528W WO 2024060131 A1 WO2024060131 A1 WO 2024060131A1
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positive electrode
active material
current collector
material layer
electrochemical device
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English (en)
French (fr)
Inventor
闫东阳
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Ningde Amperex Technology Ltd
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Ningde Amperex Technology Ltd
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Priority to PCT/CN2022/120528 priority Critical patent/WO2024060131A1/zh
Priority to CN202280007728.XA priority patent/CN116848686A/zh
Priority to EP22959141.7A priority patent/EP4576240A4/en
Publication of WO2024060131A1 publication Critical patent/WO2024060131A1/zh
Priority to US19/086,714 priority patent/US20250219049A1/en
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    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H01M10/0587—Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
    • H—ELECTRICITY
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
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    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
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    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/50—Current conducting connections for cells or batteries
    • H01M50/528—Fixed electrical connections, i.e. not intended for disconnection
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    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/50—Current conducting connections for cells or batteries
    • H01M50/531—Electrode connections inside a battery casing
    • H01M50/533—Electrode connections inside a battery casing characterised by the shape of the leads or tabs
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/50—Current conducting connections for cells or batteries
    • H01M50/531—Electrode connections inside a battery casing
    • H01M50/536—Electrode connections inside a battery casing characterised by the method of fixing the leads to the electrodes, e.g. by welding
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • H01M4/623—Binders being polymers fluorinated polymers
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of electrochemistry technology, and specifically to an electrochemical device, a preparation method thereof, and an electronic device.
  • Lithium-ion batteries electrochemical devices
  • electrochemical devices have the characteristics of high operating voltage, high energy density, long cycle life, and wide operating temperature range. These excellent characteristics enable lithium-ion batteries to be used in the three major fields of consumer electronics, power batteries, and energy storage. widely used.
  • the purpose of this application is to provide an electrochemical device, a preparation method thereof, and an electronic device to improve the energy density and safety performance of the electrochemical device.
  • the specific technical solutions are as follows:
  • a first aspect of the present application provides an electrochemical device, which includes an electrode assembly including a positive electrode piece.
  • the positive electrode sheet includes a positive electrode current collector, a first positive electrode active material layer provided on the first surface of the positive electrode current collector, and a second positive electrode active material layer provided on the second surface of the positive electrode current collector.
  • the first surface and the second surface are On the two opposite surfaces of the positive electrode current collector, the first positive electrode active material layer is provided with a first groove exposing the first surface.
  • the positive electrode tab also includes a positive electrode tab, the positive electrode tab includes a positive electrode connection part, the positive electrode connection part is at least partially located in the first groove and welded to the first surface, and the second surface corresponding to the first groove is activated by the second positive electrode Material layer covering.
  • the second cathode active material layer includes a second cathode active material, and the second cathode active material includes element M, and the element M includes at least one of manganese, iron, lanthanum, zirconium, or yttrium. Based on the total mass of the second positive active material, the mass percentage of manganese or iron is D%, 0.02 ⁇ D ⁇ 35.00, and the mass percentage of lanthanum, zirconium or yttrium is E%, 0.02 ⁇ E ⁇ 0.20.
  • the electrochemical device of the present application is provided with a first groove exposing the first surface in the first positive electrode active material layer, and the positive electrode connecting portion is at least partially located in the first groove and connected with the first
  • the surface is welded to form a single-sided slot embedded tab structure, and the second surface is provided with a second positive active material layer, which only requires an empty foil area to be retained on one side of the positive electrode piece, instead of the existing embedded tab structure.
  • the positive electrode tab structure requires empty foil areas on both sides, which can increase the energy density of the electrochemical device; it can also improve the problem of poor positive and negative electrode interfaces where the tabs are set, and reduce the risk of lithium precipitation.
  • the second cathode active material of the present application includes element M.
  • element M By selecting element M within the above range and regulating its content within the above range, it is beneficial to improve the thermal stability of the second cathode active material, thereby improving the aging of the cathode plate. problems, thereby improving the safety performance of electrochemical devices.
  • the energy density and safety performance of the electrochemical device can be improved.
  • the positive electrode connection portion and the first surface are laser welded.
  • Laser welding only requires energy to be provided on one side of the positive electrode current collector to melt the weld, which is more suitable for the electrode sheet structure of the present application.
  • Laser welding can improve the aging problem of the existing embedded tab structure positive electrode sheet, thereby improving the safety of the electrochemical device.
  • the positive electrode connection part is welded to the first surface to form a welding part, and the welding part penetrates the positive electrode tab and at least partially penetrates the positive electrode current collector.
  • the Dv50 of the second positive electrode active material is B ⁇ m
  • the welding strength between the positive electrode connection part and the positive electrode current collector is AN/m
  • the thickness of the positive electrode current collector is T ⁇ m
  • the thickness of the positive electrode current collector is T ⁇ m.
  • the tensile strength is S MPa, B/T ⁇ A ⁇ S.
  • 0.5 ⁇ B ⁇ 18 By regulating B within the above range, it is beneficial to reduce the deformation of the positive electrode sheet after cold pressing. 5 ⁇ A ⁇ 50. By regulating A within the above range, the risk of damage to the positive electrode current collector or loss of surface active substances caused by excessive welding energy can be reduced, and the risk of damage to the positive electrode current collector and positive electrode tabs caused by too low welding energy can be reduced. Risk of connection strength being too low. 4 ⁇ T ⁇ 14, 50 ⁇ S ⁇ 500. By adjusting T and S within the above range, it is beneficial to improve the endurance of the positive current collector, thereby improving the resistance of the positive electrode tab to falling off and improving the safety performance of the electrochemical device. .
  • the thermal conductivity of the cathode current collector is 30W ⁇ m -1 ⁇ K -1 to 400W ⁇ m -1 ⁇ K -1 , preferably 200W ⁇ m -1 ⁇ K -1 to 250W ⁇ m -1 ⁇ K -1 ;
  • the thermal conductivity of the positive tab is 30W ⁇ m -1 ⁇ K -1 to 400W ⁇ m -1 ⁇ K -1 , preferably 200W ⁇ m -1 ⁇ K -1 to 250W ⁇ m -1 ⁇ K -1 .
  • the electrochemical device includes a packaging bag, the electrode assembly is contained in the packaging bag, and the first surface faces the packaging bag, thereby improving the interface between the positive electrode piece-separator-negative electrode piece.
  • the electrode assembly further includes a negative electrode piece and a separator disposed between the positive electrode piece and the negative electrode piece.
  • the positive electrode piece, the separator and the negative electrode piece are stacked and arranged corresponding to the first groove.
  • the second positive active material layer on the second surface is in contact with the separator.
  • the negative electrode sheet includes a negative electrode current collector and negative electrode active material layers disposed on both surfaces of the negative electrode current collector, and the negative electrode active material layers on both surfaces of the negative electrode current collector are provided with exposed
  • a second groove is formed on the surface of the negative electrode current collector, and the second groove on one side of the negative electrode current collector is opposite to the second groove on the other side of the negative electrode current collector.
  • the negative electrode piece also includes a negative electrode tab, and the negative electrode tab includes a negative electrode connection part.
  • the negative electrode connection part is at least partially located in the second groove and is welded to the negative electrode current collector.
  • the welding includes ultrasonic welding or resistance welding.
  • ultrasonic welding or resistance welding can protect the negative electrode current collector and the negative electrode active material layer from being damaged.
  • the negative active material layer in this application includes graphite, which is beneficial to improving the material structure changes caused by laser welding heat on the negative active material layer, thereby reducing the risk of lithium precipitation.
  • the first cathode active material layer includes a first cathode active material, a first binder and a first conductive agent
  • the second cathode active material layer further includes a second binder and a second conductive agent.
  • Conductive agent; the first positive electrode active material or the second positive electrode active material includes lithium cobalt oxide, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium manganate, lithium iron phosphate, lithium iron manganese phosphate or lithium-rich manganese-based oxide
  • At least one of the above-mentioned ceramic materials can improve the heat resistance of the first positive electrode active material or the second positive electrode active material, reduce the impact of welding, and help improve the safety performance of the electrochemical device.
  • the first binder or the second binder includes polyvinylidene fluoride, vinylidene fluoride-fluorinated olefin copolymer, polyvinylpyrrolidone, polyacrylonitrile, polymethyl acrylate, polytetrafluoroethylene, carboxymethyl At least one of sodium cellulose, styrene-butadiene rubber, polyurethane, fluorinated rubber or polyvinyl alcohol; applying a binder within the above range to the positive electrode piece, the positive electrode piece has good structural stability and is conducive to improving Cycling and Swelling Performance of Electrochemical Devices.
  • the first conductive agent or the second conductive agent includes at least one of conductive carbon black, carbon nanotubes, conductive graphite, graphene or nanocarbon fibers. Selecting the above conductive agent will help improve the conductivity of the positive electrode piece.
  • the second cathode active material layer includes a first layer and a second layer arranged in a stack, the first layer is located between the cathode current collector and the second layer, and the second layer includes a second cathode active material layer.
  • the first layer includes ceramic materials, a third binder and a third conductive agent;
  • the ceramic materials include hafnium dioxide, strontium titanate, tin dioxide, cesium oxide, magnesium oxide, nickel oxide, calcium oxide, barium oxide, At least one of zinc oxide, zirconium oxide, yttrium oxide, aluminum oxide, titanium oxide, silicon dioxide, boehmite, magnesium hydroxide or aluminum hydroxide; selecting the above ceramic materials can improve the first positive electrode active material or the heat resistance of the second positive electrode active material to reduce the impact of welding; in addition, by selecting the above-mentioned ceramic materials and adhering a resistive layer with a large resistance on the surface of the positive electrode current collector, the positive electrode current collector and the negative electrode active material layer can be reduced Direct contact leads to internal shortage, which leads to the risk of combustion and explosion, thus improving the safety performance of electrochemical devices.
  • the third binder includes polyvinylidene fluoride, vinylidene fluoride-fluorinated olefin copolymer, polyvinylpyrrolidone, polyacrylonitrile, polymethyl acrylate, polytetrafluoroethylene, sodium carboxymethylcellulose, butyl styrene At least one of rubber, polyurethane, fluorinated rubber or polyvinyl alcohol; applying a binder within the above range to the positive electrode piece, the positive electrode piece has good structural stability and is conducive to improving the cycle performance of the electrochemical device and expansion properties.
  • the third conductive agent includes at least one of conductive carbon black, carbon nanotubes, conductive graphite, graphene or nanocarbon fibers. Selecting the above conductive agent will help improve the conductivity of the positive electrode piece.
  • the first layer further includes lithium iron phosphate.
  • Lithium iron phosphate has good heat resistance, which is conducive to improving the heat resistance of the first layer; in addition, the resistance of the lithium iron phosphate material in the first layer is relatively large, which can increase the short circuit when the positive and negative electrodes contact short circuit due to mechanical abuse. resistance, reducing short-circuit current; moreover, lithium iron phosphate can also deintercalate lithium, which is beneficial to increasing the capacity of electrochemical devices.
  • the particle size of lithium iron phosphate is small and has a nanometer-level particle size, which is beneficial to reducing the deformation of the positive electrode piece after rolling. It can reduce the risk of poor welding or even welding through the positive electrode current collector during welding, thus improving the electrochemical device. safety performance.
  • a second aspect of the application provides a method for preparing an electrochemical device, including:
  • a positive electrode current collector is provided, a first positive electrode active material layer is provided on the first surface of the positive electrode current collector, and a second positive electrode active material layer is provided on the second surface of the positive electrode current collector.
  • the first surface and the second surface are opposite to the positive electrode current collector.
  • the first positive active material layer is provided with a first groove exposing the first surface;
  • the second cathode active material layer includes a second cathode active material
  • the second cathode active material includes element M
  • the element M includes at least one of manganese, iron, lanthanum, zirconium or yttrium, based on the second cathode active material
  • the mass percentage of manganese or iron is D%, 0.02 ⁇ D ⁇ 35.00
  • the mass percentage of lanthanum, zirconium or yttrium is E%, 0.02 ⁇ E ⁇ 0.20.
  • the electrochemical device obtained by using the preparation method of the electrochemical device provided in the second aspect of the present application can improve the energy density and safety performance of the electrochemical device.
  • irradiating the positive electrode connection part with a laser causes the positive electrode connection part to be welded to the first surface, so that the connection strength between the positive electrode connection part and the positive electrode current collector can meet the requirements, thereby improving the resistance of the positive electrode tab. Shedding ability, thereby improving the safety performance of electrochemical devices.
  • a third aspect of the present application provides an electronic device, which includes the electrochemical device provided by the first aspect of the present application.
  • the electrochemical device provided by this application has high energy density and good safety performance, so that the electronic device of this application has a long endurance time and service life.
  • the present application provides an electrochemical device, a preparation method thereof, and an electronic device, wherein the electrochemical device is provided with a first groove exposing a first surface in a first positive electrode active material layer, and the positive electrode connecting portion is at least partially located on the first surface.
  • the electrochemical device is provided with a first groove exposing a first surface in a first positive electrode active material layer, and the positive electrode connecting portion is at least partially located on the first surface.
  • a single-sided slot-embedded tab structure is formed, and the second surface is provided with a second positive active material layer, so that only one side of the positive electrode plate needs to remain empty foil area , instead of requiring empty foil areas on both sides of the cathode tab of the existing embedded tab structure, it can increase the energy density of the electrochemical device; it can also improve the problem of poor positive and negative electrode interfaces where the tabs are set, and reduce lithium deposition risk.
  • the second cathode active material of the present application includes element M.
  • element M By selecting element M and regulating its content within the scope of the present application, it is beneficial to improve the thermal stability of the cathode active material, thereby improving the existing embedded
  • the aging problem of the positive electrode piece of the tab structure is improved, thereby improving the safety performance of the electrochemical device.
  • the energy density and safety performance of the electrochemical device can be improved.
  • Figure 1 is a schematic structural diagram of an electrode assembly with an embedded tab structure in the prior art
  • Figure 2 is a schematic structural diagram of an electrochemical device in an embodiment of the present application.
  • Figure 3 is a schematic structural diagram of a positive electrode plate in an embodiment of the present application.
  • Figure 4 is a cross-sectional view along the thickness direction of the positive electrode plate A-A in one embodiment of the present application
  • Figure 5 is a cross-sectional view along the thickness direction of the positive electrode plate A-A in another embodiment of the present application.
  • Figure 6 is a partial enlarged view of the welding portion formed by welding the positive electrode connection portion and the first surface in one embodiment of the present application;
  • Figure 7 is a cross-sectional view along the thickness direction of the positive electrode plate A-A in another embodiment of the present application.
  • Electrode assembly-1 positive electrode piece-10, positive electrode current collector-11, first positive electrode active material layer-12, second positive electrode active material layer-13, first groove-14, positive electrode tab-15, welding part -16, negative electrode piece-20, negative electrode current collector-21, negative active material layer-22, second groove-23, negative electrode tab-24, separator-30, packaging bag-40, first surface-111, Second surface-112, third layer-121, fourth layer-122, first layer-131, second layer 132, positive connection part-151, negative connection part-241.
  • the present application is explained by taking a lithium ion battery as an example of an electrochemical device.
  • the electrochemical device of the present application is not limited to lithium ion batteries, and may also be sodium ion batteries, etc.
  • the thickness direction of the electrode sheet in the unfolded state is defined as the z direction
  • the two directions perpendicular to the z direction are defined as the x direction and the y direction
  • the x direction and the y direction are perpendicular to each other
  • the x direction is the extension direction of the long side of the electrode sheet after unfolding
  • the y direction is the extension direction of the short side of the electrode sheet after unfolding.
  • the thickness direction of the electrode sheet in the wound state is defined as the z' direction
  • the two directions perpendicular to the z' direction are defined as the x' direction and the y' direction
  • the x' direction and the y' direction are perpendicular to each other
  • the y' direction is the extension direction of the winding center axis of the electrode sheet
  • the x' direction is the direction perpendicular to the y' direction in the plane of the electrode sheet.
  • the electrode sheet includes a positive electrode sheet and a negative electrode sheet.
  • the first aspect of the present application provides an electrochemical device.
  • the electrochemical device includes an electrode assembly 1 .
  • the electrode assembly 1 includes a positive electrode piece 10 , a negative electrode piece 20 , and a separator 30 .
  • Figure 3 is a schematic structural diagram of the positive electrode piece in one embodiment of the present application;
  • Figure 4 is a cross-sectional view of the positive electrode piece A-A along its thickness direction in one embodiment of the present application.
  • the positive electrode sheet 10 includes a positive current collector 11 .
  • the positive current collector 11 includes a first surface 111 and a second surface 112 .
  • the first surface 111 and the second surface 112 are two opposite sides of the positive current collector 11 . a surface.
  • the cathode plate 10 further includes a first cathode active material layer 12 disposed on the first surface 111 of the cathode current collector 11 and a second cathode active material layer 13 disposed on the second surface 112 of the cathode current collector 11 .
  • the first positive active material layer 12 is provided with a first groove 14 exposing a first surface 111
  • the positive electrode piece 10 further includes a positive tab 15 .
  • the positive electrode tab 15 includes a positive electrode connecting portion 151 , which is at least partially located in the first groove 14 and welded to the first surface 111 .
  • the second surface 112 corresponding to the first groove 14 is covered by the second cathode active material layer 13.
  • the second cathode active material layer 13 includes a second cathode active material.
  • the second cathode active material includes element M, and the element M includes manganese ( At least one of Mn), iron (Fe), lanthanum (La), zirconium (Zr) or yttrium (Y), based on the total mass of the second positive electrode active material, the mass percentage of manganese or iron is D%, 0.02 ⁇ D ⁇ 35.00, the mass percentage of lanthanum, zirconium or yttrium is E%, 0.02 ⁇ E ⁇ 0.20.
  • the above-mentioned second surface 112 corresponding to the first groove 14 is the area of the orthogonal projection of the sidewall of the first groove 14 on the second surface 112 of the positive electrode current collector 11 along the z direction.
  • the second surface 112 corresponding to the first groove 14 is covered by the second cathode active material layer 13 means that the side wall of the first groove 14 is on the second surface 112 of the cathode current collector 11 along the z direction.
  • the entire orthographic projection area is provided with the second positive electrode active material layer 13 .
  • the positive electrode connection portion 151 is a portion where the positive electrode tab 15 and the positive electrode current collector 11 overlap.
  • the above-mentioned positive electrode connecting portion 151 is at least partially located in the first groove 14, including all of the positive electrode connecting portion 151 located in the first groove 14 (as shown in FIG. 4) and part of the positive electrode connecting portion 151 located in the first groove 14 (as shown in FIG. 4). 5) two situations.
  • the inventor's research found that for an electrochemical device with an embedded tab structure, at the connection between the tab and the current collector, although the positive active material layer can be coated on the side of the current collector without the tab being welded to increase the energy density, the During the welding process of the tab, since the welding position will generate a lot of heat, the heat will be quickly conducted from one side of the current collector to the other side, causing the stability of the positive active material layer on the side of the unwelded tab to be affected, thus affecting the positive electrode. Therefore, the positive electrode sheet is more likely to age during use, and the active material layer may even fall off.
  • the active material layer on the side of the unwelded tab is more likely to have reduced adhesion and powder loss, resulting in a thicker thickness in the welding area. increases, resulting in a thickness difference from the non-welded area. Near the position where the thickness difference occurs, a large gap is formed between the positive electrode piece, the separator, and the negative electrode piece.
  • the side reactions in the gap increase and the impedance increases, resulting in the breakdown of the electrochemical device. Increased risk with lithium.
  • the area where both sides of the current collector are not coated with active materials i.e., the empty foil area
  • the empty foil area is an area where a large number of electrons flow, and its current density is the largest in the entire positive electrode sheet, which is easy to There is an overheating problem.
  • the electrochemical device of the present application is provided with a first groove exposing the first surface in the first positive active material layer, and the positive electrode connecting portion is at least partially located in the first groove and welded to the first surface, A single-sided slot embedded tab structure is formed, and a second cathode active material layer is provided on the second surface.
  • This allows only an empty foil area to be retained on one side of the cathode plate, instead of the existing embedded tab structure cathode.
  • the pole piece needs to retain empty foil areas on both sides, which can increase the energy density of the electrochemical device; it can also improve the problem of poor positive and negative electrode interfaces at the pole tabs, reducing the risk of lithium precipitation.
  • the second cathode active material of the present application includes element M.
  • element M By selecting element M within the above range and regulating its content within the above range, it is beneficial to improve the thermal stability of the second cathode active material, thereby improving the performance of the cathode plate. Stability can not only improve the aging and powder loss of the positive electrode during use due to overheating, but also improve the adhesion decrease and powder loss caused by the positive electrode being soaked in electrolyte or circulated for a long time during use, reducing powder loss. This may lead to the possibility of gaps between the positive electrode piece-separator-negative electrode piece, thereby reducing the risk of lithium precipitation in the negative electrode piece and thereby improving the safety performance of the electrochemical device.
  • the first cathode active material layer 12 and the second cathode active material layer 13 of the present application are respectively disposed on the first surface 111 and the second surface 112 of the cathode current collector 11 .
  • 112 denotes two opposite surfaces of the positive electrode current collector 11 in the thickness direction.
  • the “surface” here may be the entire area of the positive electrode current collector 11 , or may be a partial area of the positive electrode current collector 11 . There is no particular limitation in this application, as long as the purpose of the invention of this application can be achieved.
  • the positive electrode connecting part 151 and the first surface 111 are welded by laser.
  • the laser welding only needs to provide energy on one side of the positive electrode current collector 11 to melt the welding joint, which is more suitable for the present application. Pole piece structure.
  • the positive electrode connection part 151 is welded to the first surface 111 to form a welding part 16 , and the welding part 16 penetrates the positive electrode tab 15 and at least partially penetrates the positive electrode current collector 11 .
  • the connection strength between the positive electrode connecting portion 151 and the positive electrode current collector 11 is further improved, thereby further improving the resistance of the positive electrode tab to falling off and improving the safety performance of the electrochemical device.
  • the Dv50 of the second positive electrode active material is B ⁇ m
  • the welding strength between the positive electrode connection part 151 and the positive electrode current collector 11 is A N/m
  • the thickness of the positive electrode current collector 11 is T ⁇ m
  • the positive electrode The tensile strength of the current collector 11 is S MPa, B/T ⁇ A ⁇ S.
  • 0.5 ⁇ B ⁇ 18 By regulating B within the above range, it is beneficial to reduce the deformation of the positive electrode sheet after cold pressing. 5 ⁇ A ⁇ 50. By regulating A within the above range, the risk of damage to the positive electrode current collector 11 or the loss of surface active substances caused by excessive welding energy can be reduced, and the risk of damage to the positive electrode current collector 11 and the positive electrode caused by too low welding energy can be reduced. There is a risk that the connection strength of pole lug 15 is too low. 4 ⁇ T ⁇ 14, 50 ⁇ S ⁇ 500. By adjusting T and S within the above range, it is beneficial to improve the endurance of the positive electrode current collector 11, thereby improving the resistance of the positive electrode tab to falling off and improving the safety of the electrochemical device. performance.
  • the thermal conductivity of the positive electrode current collector 11 is 30W ⁇ m -1 ⁇ K -1 to 400W ⁇ m -1 ⁇ K -1
  • the thermal conductivity of the positive electrode tab 15 is 30W ⁇ m - 1 ⁇ K -1 to 400W ⁇ m -1 ⁇ K -1
  • the thermal conductivity of the positive electrode current collector 11 is 200W ⁇ m -1 ⁇ K -1 to 250W ⁇ m -1 ⁇ K -1
  • the thermal conductivity of the positive electrode tab 15 is 200W ⁇ m -1 ⁇ K -1 to 250W ⁇ m -1 ⁇ K -1 .
  • the positive electrode current collector 11 and the positive electrode tab 15 whose thermal conductivity is within the above range, it is beneficial to improve the heat dissipation performance of the positive electrode piece, thereby improving the aging problem of the positive electrode piece due to heat accumulation during the use of the electrochemical device, and thereby improving the performance of the positive electrode piece. Improve the safety performance of electrochemical devices.
  • the material of the positive electrode collector 11 of the present application may include aluminum, aluminum alloy, stainless steel, titanium and titanium alloy, nickel and nickel alloy, etc.
  • the material of the positive electrode tab 15 of the present application may include aluminum, aluminum alloy, stainless steel, titanium and titanium alloy, nickel and nickel alloy, etc.
  • the electrochemical device includes a packaging bag 40 , the electrode assembly 1 is contained in the packaging bag 40 , and the first surface 111 faces the packaging bag 40 .
  • the electrode assembly 1 is shaped after manufacturing, pressure will be applied; after the electrode assembly 1 is put into the packaging bag 40 , pressure is applied during the formation to make the positive electrode piece 10 and the negative electrode piece 20 come into close contact.
  • the first surface 111 faces the packaging bag 40, and when pressure is applied, the positive electrode tab 15 faces the pressure clamp.
  • the other side of the positive electrode tab 15 is contacted by the second positive electrode active material layer 13, which can better bear the force, thereby improving the positive electrode.
  • This application has no special restrictions on the packaging bag 40 and can be selected according to actual needs, as long as the purpose of the invention of this application can be achieved. For example, aluminum-plastic film packaging bags or steel-plastic film packaging bags can be used.
  • the separator 30 is disposed between the positive electrode piece 10 and the negative electrode piece 20.
  • the positive electrode piece 10, the separator 30 and the negative electrode piece 20 are stacked and arranged with the first
  • the second cathode active material layer 13 on the second surface 112 corresponding to the groove 14 is in contact with the separator 30 .
  • grooves also need to be provided on the second surface corresponding to the first groove.
  • a tape needs to be placed on this additional groove. The tape is in contact with the separator. The presence of the tape increases the thickness and causes the contact interface to be uneven, increasing the risk of lithium precipitation in the electrochemical device. Since there is no additional groove, there is no need to install adhesive paper, the thickness is reduced, and the smoothness of the interface is improved, which is beneficial to increasing the energy density of the electrochemical device.
  • the negative electrode sheet 20 includes a negative electrode current collector 21 and negative electrode active material layers 22 disposed on both surfaces of the negative electrode current collector 21 .
  • the negative electrode active material layer 22 on the surface is provided with second grooves 23 exposing the surface of the negative electrode current collector 21.
  • the second grooves 23 on one side of the negative electrode current collector 21 and the second grooves on the other side of the negative electrode current collector 21.
  • the grooves 23 are arranged oppositely; the negative electrode piece 20 also includes a negative electrode tab 24.
  • the negative electrode tab 24 includes a negative electrode connecting portion 241.
  • the negative electrode connecting portion 241 is at least partially located in the second groove 23 and is welded to the negative electrode current collector 21. The welding includes ultrasonic.
  • the negative active material layer 22 of the present application includes graphite, which is beneficial to improving the material structure changes caused by laser welding heat on the negative active material layer, thereby reducing the risk of lithium precipitation.
  • the first cathode active material layer 12 includes a first cathode active material, a first binder and a first conductive agent
  • the second cathode active material layer 13 further includes a second binder and a first conductive agent.
  • the second conductive agent; the first positive electrode active material or the second positive electrode active material includes lithium cobalt oxide, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium manganate, lithium iron phosphate, lithium iron manganese phosphate or lithium-rich manganese base At least one of the oxides; selecting the above ceramic material can improve the heat resistance of the first positive active material or the second positive active material, reduce the impact of welding, and help improve the safety performance of the electrochemical device.
  • the first binder or the second binder includes polyvinylidene fluoride, vinylidene fluoride-fluorinated olefin copolymer, polyvinylpyrrolidone, polyacrylonitrile, polymethyl acrylate, polytetrafluoroethylene, carboxymethyl At least one of sodium cellulose, styrene-butadiene rubber, polyurethane, fluorinated rubber or polyvinyl alcohol; applying a binder within the above range to the positive electrode piece, the positive electrode piece has good structural stability and is conducive to improving Cycling and Swelling Performance of Electrochemical Devices.
  • the first conductive agent or the second conductive agent includes at least one of conductive carbon black (Super P, Ketjen black, acetylene black), carbon nanotubes (CNTs), conductive graphite, graphene or nanocarbon fibers.
  • the above-mentioned carbon nanotubes may include, but are not limited to, single-walled carbon nanotubes and/or multi-walled carbon nanotubes. Selecting the above conductive agent will help improve the conductivity of the positive electrode piece.
  • the mass percentage of the first conductive agent is 0.5% to 5% based on the mass of the first cathode active material layer 12 . Based on the mass of the second positive active material layer 13, the mass percentage of the first conductive agent is 0.5% to 5%.
  • the first cathode active material or the second cathode active material may also include non-metal elements.
  • the non-metal elements include at least one of fluorine, phosphorus, boron or chlorine. These elements can further improve the performance of the cathode active material. stability.
  • This application has no particular limitation on the thickness of the first cathode active material layer 12 or the second cathode active material layer 13 , as long as the purpose of the invention of this application can be achieved.
  • the thickness of the first cathode active material layer 12 or the second cathode active material layer 13 is 30 ⁇ m to 120 ⁇ m.
  • the second cathode active material layer 13 includes a first layer 131 and a second layer 132 arranged in a stack.
  • the first layer 131 is located at the cathode current collector 11 and the second layer.
  • the second layer 132 includes a second cathode active material
  • the first layer 131 includes a ceramic material, a third binder and a third conductive agent
  • the ceramic material includes hafnium dioxide, strontium titanate, tin dioxide, oxide At least one of cesium, magnesium oxide, nickel oxide, calcium oxide, barium oxide, zinc oxide, zirconium oxide, yttria, aluminum oxide, titanium oxide, silicon dioxide, boehmite, magnesium hydroxide or aluminum hydroxide kind; selecting the above-mentioned ceramic material can improve the heat resistance of the first positive electrode active material or the second positive electrode active material and reduce the influence of welding; in addition, by selecting the above-mentioned ceramic material, a layer of large resistance is provided on the surface of the positive electrode current collector The resistance layer can reduce the risk of combustion and explosion caused by internal shortness, thereby improving the safety performance of the electrochemical device.
  • the third binder includes polyvinylidene fluoride, vinylidene fluoride-fluorinated olefin copolymer, polyvinylpyrrolidone, polyacrylonitrile, polymethylacrylate, polytetrafluoroethylene, sodium carboxymethylcellulose, and styrene-butadiene At least one of rubber, polyurethane, fluorinated rubber or polyvinyl alcohol; applying a binder within the above range to the positive electrode piece, the positive electrode piece has good structural stability and is conducive to improving the cycle performance of the electrochemical device and expansion properties.
  • the third conductive agent includes at least one of conductive carbon black (Super P, Ketjen black, acetylene black), carbon nanotubes, conductive graphite, graphene or nanocarbon fibers. Selecting the above conductive agent will help improve the conductivity of the positive electrode piece.
  • the first cathode active material layer 12 may include a stacked third layer 121 and a fourth layer 122 , with the third layer 121 located between the cathode current collector 11 and the fourth layer 122 .
  • the composition of the third layer 121 may be the same as the first layer 131
  • the composition of the fourth layer 122 may be the same as the composition of the second layer 132 , which will not be described again in this application.
  • the first layer 131 further includes lithium iron phosphate.
  • Lithium iron phosphate has good heat resistance, which is beneficial to improving the heat resistance of the first layer; moreover, the resistance of lithium iron phosphate material in the first layer is relatively large, which can reduce short-circuit resistance; moreover, lithium iron phosphate can also play a certain role capacity, which is beneficial to improving the capacity of electrochemical devices.
  • the particle size of lithium iron phosphate is small and has a nanometer-level particle size, which is beneficial to reducing the deformation of the positive electrode piece after cold pressing. It can reduce the risk of poor welding or even welding through the positive electrode current collector during welding, thereby improving the electrochemical device. safety performance.
  • This application has no special restrictions on the preparation method of lithium iron phosphate, as long as the purpose of the invention of this application can be achieved.
  • it can be prepared by the following method: using FeC 2 O 4 ⁇ 8H 2 O, MnCO 3 , NH 4 H 2 PO 4 , Li 2 CO 3 , and ZrO 2 as raw materials, mixing by ball milling, spray granulation, and adding H 2 Sintering and crushing in a reducing atmosphere to prepare nanoscale lithium iron phosphate powder doped with manganese and zirconium. Using nitrogen as the protective gas, the prepared powder is vacuum fed and placed in a rotary furnace.
  • the sucrose solution is continuously sprayed into the furnace, and the carbon layer coating is formed by rotating, stirring and sintering at 600°C to 800°C for 2 to 4 hours. , take samples after cooling, and obtain modified lithium iron phosphate powder, that is, the above-mentioned lithium iron phosphate material.
  • the average thickness of the carbon layer coating layer is 1 ⁇ m.
  • the molar ratio of raw materials can be changed to control the mass percentage of Fe, Mn and Zr in the lithium iron phosphate material.
  • the mass percentage of Fe in the lithium iron phosphate material will increase; if the proportion of FeC 2 O 4 ⁇ 8H 2 O is reduced, the mass percentage of Fe in the lithium iron phosphate material will be increased. reduce.
  • the negative active material layer 22 is disposed on two opposite surfaces of the negative current collector 21 in the thickness direction.
  • the “surface” here may be the entire area of the negative electrode current collector 21 or a part of the area of the negative electrode current collector 21. There is no particular limitation in this application, as long as the purpose of the invention of this application can be achieved.
  • the negative electrode current collector 21 may include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam or composite current collector.
  • This application has no particular limitation on the thickness of the negative electrode current collector 21 , as long as the thickness of the negative electrode current collector 21 can be achieved.
  • the thickness of the negative electrode current collector 21 is 4 ⁇ m to 10 ⁇ m.
  • the negative electrode active material layer 22 also includes a negative electrode active material.
  • the present application has no particular restrictions on the type of negative electrode active material, as long as the purpose of the present invention can be achieved.
  • the negative electrode active material may include at least one of mesophase microcarbon beads, hard carbon, soft carbon, silicon, silicon-carbon composite, SiO x (0 ⁇ x ⁇ 2), Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO 2 , spinel structure lithium titanate Li 4 Ti 5 O 12 , Li-Al alloy or metallic lithium.
  • the negative electrode active material layer 22 may also include a negative electrode conductive agent, and the present application has no particular restrictions on the negative electrode conductive agent, as long as the purpose of the present invention can be achieved, for example, it may include but is not limited to at least one of conductive carbon black (Super P, Ketjen black, acetylene black), carbon nanotubes (CNTs), carbon fibers, graphene, metal materials or conductive polymers, and the above-mentioned carbon nanotubes may include but are not limited to single-walled carbon nanotubes and/or multi-walled carbon nanotubes.
  • the above-mentioned carbon fibers may include but are not limited to vapor-grown carbon fibers and/or nanocarbon fibers.
  • the metal material may include but is not limited to metal powder and/or metal fiber. Specifically, the metal may include but is not limited to at least one of copper, nickel, aluminum or silver.
  • the conductive polymer may include but is not limited to at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene or polypyrrole. Based on the mass of the negative electrode active material layer 22, the mass percentage of the negative electrode conductive agent is 0.5% to 5%.
  • the thickness of the negative active material layer 22 is not particularly limited in this application, as long as the purpose of the invention of this application can be achieved.
  • the thickness of the single-sided negative active material layer may be 30 ⁇ m to 160 ⁇ m.
  • the materials of the negative electrode tabs include copper, copper alloy, nickel, stainless steel, titanium or nickel.
  • the electrolyte also includes non-aqueous solvents.
  • non-aqueous solvents can include but are not limited to carboxylic acid ester compounds, ether compounds or other organic solvents. at least one of the solvents.
  • the above carboxylate compounds may include, but are not limited to, methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, methyl propionate, propyl propionate, butyl propionate, methyl butyrate, butyric acid Ethyl ester, propyl butyrate, butyl butyrate, ⁇ -butyrolactone, 2,2-difluoroethyl acetate, valerolactone, butyrolactone, ethyl 2-fluoroacetate, 2,2-difluoroacetate Ethyl acetate, ethyl trifluoroacetate, ethyl 2,2,3,3,3-pentafluoropropionate, methyl 2,2,3,3,4,4,4,4-heptafluorobutyrate, 4,4,4-Trifluoro-3-(trifluoromethyl)butyric acid methyl ester, 2,2,3,3,4,4,5,5,
  • ether compounds may include, but are not limited to, glycol dimethyl ether, diglyme, tetraglyme, dibutyl ether, tetrahydrofuran, 2-methyltetrahydrofuran or bis(2,2,2 -At least one of trifluoroethyl) ethers.
  • the above-mentioned other organic solvents may include, but are not limited to, ethyl vinyl sulfone, methyl isopropyl sulfone, isopropyl sec-butyl sulfone, dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-Dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate or phosphoric acid at least one of the esters.
  • the electrochemical device of the present application also includes a separator 30.
  • the present application has no special limitation on the separator 30, as long as it can achieve the purpose of the invention of the present application.
  • the material of the separator can include but is not limited to polyethylene (PE), polypropylene (PP) , Polytetrafluoroethylene-based polyolefin (PO) separators, polyester films (such as polyethylene terephthalate (PET) films), cellulose films, polyimide films (PI), polyamide At least one of film (PA), spandex or aramid film, etc.
  • the type of separator may include, but is not limited to, at least one of woven membrane, non-woven membrane (non-woven fabric), microporous membrane, composite membrane, rolled membrane or spun membrane, etc.
  • the separator 30 of the present application may have a porous structure, and the size of the pore diameter is not particularly limited as long as the purpose of the invention of the present application can be achieved.
  • the size of the pore diameter may be 0.01 ⁇ m to 1 ⁇ m.
  • the thickness of the separator 30 is not particularly limited as long as the purpose of the invention of this application can be achieved.
  • the thickness may be 5 ⁇ m to 500 ⁇ m.
  • the electrochemical device of the present application is not particularly limited and may include any device that undergoes electrochemical reactions.
  • the electrochemical device may include, but is not limited to: a lithium ion secondary battery (lithium ion battery), a lithium polymer secondary battery, a lithium ion polymer secondary battery, and the like.
  • the lithium ion battery structure of the present application includes a wound structure or a laminated structure, etc.
  • the lithium-ion battery structure of this application includes but is not limited to soft-pack lithium-ion batteries, square hard-shell batteries, or cylindrical hard-shell batteries.
  • a second aspect of the application provides a method for preparing an electrochemical device, including:
  • a positive electrode current collector 11 is provided, a first positive electrode active material layer 12 is provided on the first surface 111 of the positive electrode current collector 11, and a second positive electrode active material layer 13 is provided on the second surface 112 of the positive electrode current collector 11.
  • the first surface 111 and the The two surfaces 112 are two opposite surfaces of the cathode current collector 11, and the first cathode active material layer 12 is provided with a first groove 14 exposing the first surface 111;
  • the positive electrode tab 15 is provided, and the positive electrode tab 15 is welded to the exposed first surface 111 of the first groove 14 so that the positive electrode connecting portion 151 of the positive electrode tab 15 is connected to the first surface 111 , and the first groove 14 corresponds to the first surface 111 of the positive electrode tab 15 .
  • the two surfaces 112 are covered by a second cathode active material layer 13.
  • the second cathode active material layer 13 includes a second cathode active material.
  • the second cathode active material includes element M.
  • the element M includes manganese, iron, lanthanum, zirconium or yttrium.
  • an insulating layer can be attached to the negative electrode active material layer facing the first groove to provide insulation.
  • an insulating layer can be attached to the first positive electrode active material layer and the second positive electrode active material layer facing the second groove to provide insulation.
  • the insulating layer may include at least one of single-sided tape or double-sided tape.
  • single-sided adhesive tape includes a base material layer and an adhesive layer.
  • the materials of the base material layer include but are not limited to polyfluoroolefin, polyethylene terephthalate, polyimide, polyamide-imide, polychloride At least one of ethylene or polyolefin (such as biaxially oriented polyolefin heat shrinkable film), and the polyfluoroolefin includes but is not limited to polytetrafluoroethylene or polyvinylidene fluoride.
  • the bonding layer includes bonding materials, which include but are not limited to carboxymethylcellulose, styrene-butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene, fluorinated rubber, polyurethane, polypropylene alcohol, sodium polyacrylate, At least one of polyetherimide or acrylate.
  • the electrochemical device obtained by using the preparation method provided in the second aspect of the present application can improve the energy density and safety performance of the electrochemical device.
  • the positive electrode connection part 151 is irradiated with laser so that the positive electrode connection part 151 and the first surface 111 are welded, so that the connection strength between the positive electrode connection part 151 and the positive electrode current collector 11 can meet the requirements, thereby improving The anti-falling ability of the positive electrode tab improves the safety performance of the electrochemical device.
  • This application has no special restrictions on laser welding equipment, as long as it can achieve the purpose of the invention.
  • it can be a commercially available laser welding machine.
  • This application can improve the welding strength between the positive electrode connection part and the positive electrode current collector by increasing the spot diameter and/or time of laser irradiation.
  • This application has no special restrictions on the spot diameter and time of laser irradiation, and can be adjusted according to actual welding requirements, as long as the purpose of the invention of this application can be achieved.
  • the preparation process of the electrochemical device of the present application may also include but is not limited to the following steps: stack the positive electrode sheet 10, the separator 30 and the negative electrode sheet 20 in order, and wind and fold them as needed to obtain a rolled structure.
  • the electrode assembly 1 is put into the packaging bag 40, the electrolyte is injected into the packaging bag 40 and sealed to obtain an electrochemical device; or, the positive electrode piece 10, the separator 30 and the negative electrode piece 20 are stacked in order, Then, the four corners of the entire laminated structure are fixed with tape to obtain the electrode assembly 1 of the laminated structure.
  • the electrode assembly 1 is placed in the packaging bag 40, and the electrolyte is injected into the packaging bag 40 and sealed to obtain an electrochemical device.
  • overcurrent prevention components, guide plates, etc. can also be placed in the packaging bag 40 as needed to prevent pressure rise inside the electrochemical device and overcharge and discharge.
  • the negative electrode current collector and the negative electrode tab in this application are welded by ultrasonic welding or resistance welding.
  • This application has no special restrictions on the welding process and can be selected according to actual welding requirements, as long as the purpose of the invention of this application can be achieved.
  • a third aspect of the present application provides an electronic device, which includes the electrochemical device provided by the first aspect of the present application.
  • the electrochemical device provided by the present application has high energy density and good safety performance, so that the electronic device of the present application has a long endurance time and service life.
  • electronic devices may include, but are not limited to, laptop computers, pen computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headsets, video recorders, LCD TV, portable cleaner, portable CD player, mini CD, transceiver, electronic notepad, calculator, memory card, portable recorder, radio, backup power supply, motor, automobile, motorcycle, power-assisted bicycle, bicycle, lighting equipment , toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries or lithium-ion capacitors, etc.
  • Disassemble the lithium-ion battery after discharging it to 0% SOC take out the positive electrode piece, soak it in dimethyl carbonate (DMC) for 30 minutes, clean the residual impurities on the surface of the positive electrode piece, and then dry it. Put the positive electrode piece into the muffle furnace and calcine it at 600°C for 4 hours in an air atmosphere. After taking it out, scrape the positive active material on the surface of the positive electrode current collector to obtain a powder sample.
  • Use aqua regia the volume ratio of concentrated nitric acid to concentrated hydrochloric acid is 1 ⁇ 3 Preparation
  • a metal ion solution was obtained, which was passed into an inductively coupled plasma emission spectrometer for testing to obtain the mass percentage of each metal element.
  • the high-speed rail tensile testing machine (model 3367) clamps both ends of the connection between the positive electrode tab and the positive electrode current collector (respectively, the positive electrode tab and the positive electrode current collector).
  • a universal thermal conductivity meter (model TC3200) using the hot-wire method was used to test the 5cm ⁇ 5cm sheet sample.
  • a high-speed rail tensile testing machine (model 3367) clamped the positive electrode current collector sample for a tensile test.
  • the sample width was 15 mm
  • the tensile speed was 50 mm/min
  • the obtained tensile strength S was recorded in MPa.
  • Disassemble the lithium-ion battery after it is fully charged take out the positive electrode piece, soak it in DMC for 30 minutes, clean the residual impurities on the surface of the positive electrode piece, and then dry it. Put the positive electrode piece into the muffle furnace and calcine it at 600°C for 4 hours in an air atmosphere. After taking it out, scrape the positive active material on the surface of the current collector and test it with a laser particle size analyzer to obtain the particles corresponding to 50% of the volume in the system distribution.
  • the diameter value is Dv50, and the unit is ⁇ m.
  • the lithium ion batteries obtained in the Examples or Comparative Examples were divided into two groups and cycled 500 times and 1000 times according to the above charging/discharging steps respectively.
  • Li(Ni 0.5 Co 0.2 Mn 0.3 )O 2 and lithium manganate (LMO) are mixed according to the mass ratio of 6:4 as the positive electrode active material (Dv50 is 15.1 ⁇ m).
  • the first positive electrode active material layer and the second positive electrode active material layer are both made from the above-mentioned positive electrode slurry.
  • the positive electrode slurry is evenly coated on the first surface of the positive electrode current collector aluminum foil with a thickness of 8 ⁇ m, and baked at 110°C. After drying, a positive electrode sheet coated with the positive electrode active material on one side was obtained with a thickness of the first positive electrode active material layer of 110 ⁇ m. Thereafter, the above steps were repeated on the second surface of the positive electrode current collector to obtain a positive electrode sheet coated with the positive electrode active material on both sides with a thickness of the second positive electrode active material layer of 110 ⁇ m. After the coating is completed, the positive electrode piece is cold-pressed, and then undergoes processes such as tab molding, striping, and laser cleaning to obtain a positive electrode piece with a first groove in the middle of the first positive active material layer.
  • the aluminum positive electrode tab is welded on the first groove by laser irradiation.
  • the specification of the positive electrode piece is 81.9mm ⁇ 1490mm, and the specification of the first groove is 20mm ⁇ 9mm.
  • the thermal conductivity of the positive electrode current collector (denoted as L) is 217.7W ⁇ m -1 ⁇ K -1
  • the thermal conductivity of the positive electrode tab (denoted as R) is 217.7W ⁇ m -1 ⁇ K -1
  • the positive electrode connection part is
  • the welding strength between the positive electrode current collectors is 28N/m
  • the tensile strength of the positive electrode current collectors is 156MPa.
  • Negative electrode slurry with a content of 60wt% and stir evenly.
  • the negative electrode slurry is evenly coated on one surface of the negative electrode current collector copper foil with a thickness of 8 ⁇ m, and dried at 110°C to obtain a negative electrode sheet with a coating thickness of 130 ⁇ m and a negative electrode active material layer coated on one side, and then Repeat the above steps on the other surface of the negative electrode piece to obtain a negative electrode piece coated with a negative electrode active material layer on both sides.
  • the negative electrode piece After the coating is completed, the negative electrode piece is cold-pressed, and then undergoes tab forming, striping, laser cleaning and other processes to obtain a negative electrode piece with a second groove in the middle of the negative active material layer on both sides. Weld the copper negative tab on one of the second grooves by ultrasonic treatment.
  • the specification of the negative electrode piece is 83.3mm ⁇ 1494mm, and the specification of the second groove is 20mm ⁇ 9mm.
  • LiPF 6 lithium salt lithium hexafluorophosphate
  • the electrode assembly into an aluminum plastic film packaging shell, place it in a vacuum oven at 85°C to dry for 12 hours to remove moisture, inject the electrolyte prepared above, vacuum seal, let it stand, and form (0.02C constant current charge to 3.5 V, and then charged to 3.9V with a constant current of 0.1C), shaped and capacity processed to obtain a lithium-ion battery.
  • Li(Ni 0.5 Co 0.2 Mn 0.3 )O 2 is used as the positive electrode active material (Dv50 is shown in Table 1), the rest is the same as in Example 1-1.
  • Mn-doped cobalt acid obtained by mixing lithium cobalt oxide (LiCoO 2 ) and manganese oxide (MnO 2 ) at a mass ratio of 25:1 and co-sintering at 850°C for 12 hours Except for using lithium as the positive electrode active material (Dv50 is shown in Table 1), the rest were the same as in Example 1-1.
  • Example 1-1 Except for ⁇ preparation of positive electrode sheet>, which is different from Example 1-1, the rest is the same as Example 1-1.
  • the positive electrode active material LiCoO 2 , conductive carbon black (Super P) and PVDF are mixed in a mass ratio of 98:1:1, and N-methylpyrrolidone (NMP) is added as a solvent to prepare a positive electrode slurry with a solid content of 75wt%, and stirred evenly.
  • the first positive electrode active material layer and the second positive electrode active material layer are both prepared using the positive electrode slurry, and the positive electrode slurry is evenly coated on the first layer on the first surface, and dried at 110°C to obtain a positive electrode sheet with a single-side coating of positive electrode active material and a thickness of 110 ⁇ m for the first positive electrode active material layer.
  • the above steps are repeated on the second surface of the positive electrode current collector to obtain a positive electrode sheet with a double-side coating of positive electrode active material and a thickness of 110 ⁇ m for the second positive electrode active material layer.
  • the positive electrode sheet is cold pressed, and then the first positive electrode active material layer is provided with a first groove in the middle through the tab forming, striping, laser cleaning, etc.
  • the first groove is used for welding the positive electrode tab.
  • the specifications of the positive electrode sheet are 81.9 mm ⁇ 1490 mm, and the specifications of the first groove are 20 mm ⁇ 9 mm.
  • the thermal conductivity of the positive current collector (denoted as L) is 217.7 W ⁇ m -1 ⁇ K -1
  • the thermal conductivity of the positive tab (denoted as R) is 217.7 W ⁇ m -1 ⁇ K -1 .
  • FeC 2 O 4 ⁇ 8H 2 O, MnCO 3 , NH 4 H 2 PO 4 , Li 2 CO 3 , and ZrO 2 are used as raw materials, and the molar ratio of the above raw materials is adjusted, and then ball milling Mix, spray granulate, sinter and crush in a reducing atmosphere containing H2 to prepare manganese- and zirconium-doped nanoscale lithium iron phosphate powder.
  • the prepared powder was vacuum fed and placed in a rotary furnace, continuously sprayed with sucrose solution, and rotated, stirred and sintered at 700°C for 3 hours to form a carbon layer coating.
  • Modified lithium iron phosphate powder namely lithium iron phosphate (LFP-1), in which the average thickness of the carbon layer coating layer is 1 ⁇ m.
  • the results were the same as in Example 1-1 except that the obtained LFP-1 was used as a positive electrode active material (Dv50 is shown in Table 1).
  • Zr-doped lithium cobalt oxide obtained by mixing LiCoO 2 and zirconium oxide (ZrO 2 ) at a mass ratio of 25:1 and sintering at 850°C for 12 hours was used as the positive electrode active material Except for (Dv50 is shown in Table 1), the rest was the same as in Example 1-1.
  • Example 1-1 The method is the same as Example 1-1 except that in ⁇ Preparation of Positive Electrode Sheet>, LiCoO 2 and yttrium fluoride (YF 3 ) are mixed in a mass ratio of 25:1 and co-sintered at 850°C for 10 hours to obtain Y-doped lithium cobalt oxide as the positive electrode active material (Dv50 is shown in Table 1).
  • LiCoO 2 and yttrium fluoride (YF 3 ) are mixed in a mass ratio of 25:1 and co-sintered at 850°C for 10 hours to obtain Y-doped lithium cobalt oxide as the positive electrode active material (Dv50 is shown in Table 1).
  • the La-doped lithium cobalt oxide obtained by mixing LiCoO 2 and lanthanum oxide (La 2 O 3 ) at a mass ratio of 25:1 and sintering at 950°C for 12 hours was used as the positive electrode. Except for the active material (Dv50 is shown in Table 1), the rest was the same as in Example 1-1.
  • LiCoO 2 is mixed with MnO 2 , ZrO 2 , YF 3 , and La 2 O 3 according to the mass ratio of 20:1:1:1:1, and is co-sintered at 950°C for 16 hours.
  • the results were the same as in Example 1-1 except that the obtained Mn+Zr+Y+La co-doped lithium cobalt oxide was used as the positive electrode active material (Dv50 is shown in Table 1).
  • LiCoO 2 and Li(Ni 0.5 Co 0.2 Mn 0.3 )O 2 are mixed according to the mass ratio of 8:2 as the positive electrode active material (Dv50 is shown in Table 1), the rest are as follows: Same as Example 1-1.
  • LiCoO 2 and Li(Ni 0.5 Co 0.2 Mn 0.3 )O 2 are mixed according to the mass ratio of 6:4 as the positive electrode active material (Dv50 is shown in Table 1), the rest are as follows: Same as Example 1-1.
  • Example 1-1 The process was the same as in Example 1-1 except that the Dv50 of the positive electrode active material was adjusted as shown in Table 2 in ⁇ Preparation of Positive Electrode Sheet>.
  • Example 1-9 Except that the laser spot diameter and the laser irradiation time are adjusted so that the welding strength between the positive electrode connecting portion and the positive electrode current collector is 5 N/m, the rest is the same as Example 1-9.
  • the thickness of the positive electrode current collector is 6 ⁇ m
  • the welding strength between the positive electrode connection part and the positive electrode current collector is 35N/m by adjusting the laser spot diameter and laser irradiation time
  • the tensile strength of the positive electrode current collector is 100MPa using aluminum foil. Same as Examples 1-9.
  • the welding strength between the positive electrode connection part and the positive electrode current collector is 35N/m by adjusting the laser spot diameter and laser irradiation time, and the tensile strength of the positive electrode current collector is 50MPa, which is made of aluminum alloy. The rest is the same as Example 1-9.
  • the positive electrode current collector is made of stainless steel with a thermal conductivity of 30 W ⁇ m -1 ⁇ K -1 and the positive electrode tab is made of stainless steel with a thermal conductivity of 30 W ⁇ m -1 ⁇ K -1 , the rest is the same as Example 1-9.
  • the material of the cathode current collector is an aluminum alloy with a thermal conductivity of 400W ⁇ m -1 ⁇ K -1
  • the material of the cathode tab is an aluminum alloy with a thermal conductivity of 400W ⁇ m -1 ⁇ K -1
  • the rest are the same as those in the examples. 1-9 are the same.
  • Example 1-1 Except that Li(Ni 0.5 Co 0.2 Mn 0.3 )O 2 and lithium manganate (LMO) are used as the cathode active material in a mass ratio of 5:5, the rest is the same as in Example 1-1:
  • Mn-doped lithium cobalt oxide obtained by mixing LiCoO 2 and MnO 2 at a mass ratio of 50:1 and co-sintering at 850°C for 4 hours was used as the positive electrode active material. Same as Example 1-1.
  • FeC 2 O 4 ⁇ 8H 2 O, MnCO 3 , NH 4 H 2 PO 4 , Li 2 CO 3 , and ZrO 2 are used as raw materials.
  • the molar ratio of the above raw materials is adjusted, and the molar ratio of the above raw materials is adjusted by ball milling.
  • nitrogen as the protective gas the prepared powder was vacuum fed and placed in a rotary furnace, continuously sprayed with sucrose solution, and rotated, stirred and sintered at 700°C for 3 hours to form a carbon layer coating.
  • Modified lithium iron phosphate powder namely lithium iron phosphate (LFP-2), in which the average thickness of the carbon layer coating layer is 1 ⁇ .
  • LFP-2 lithium iron phosphate
  • Dv50 positive electrode active material
  • the thickness of the first layer was 2 ⁇ m, the rest was the same as in Examples 1-4.
  • the method is the same as Example 1-1 except that in ⁇ Preparation of Positive Electrode Sheet>, Zr-doped lithium cobalt oxide obtained by mixing LiCoO2 and ZrO2 in a mass ratio of 18:1 and sintering them together at 850°C for 5 hours is used as the positive electrode active material.
  • Zr-doped lithium cobalt oxide obtained by mixing LiCoO 2 and ZrO 2 at a mass ratio of 50:1 and co-sintering at 850°C for 24 hours was used as the positive electrode active material. Same as Example 1-1.
  • Example 1-1 The rest is the same as in Example 1-1 except that in ⁇ Preparation of the positive electrode sheet>, a positive electrode sheet with a groove in the middle of both the first positive electrode active material layer and the second positive electrode active material layer is used.
  • Example 1-1 to Example 1-12 and Comparative Example 1 to Comparative Example 7 that a lithium-ion battery with the single-sided slot embedded tab structure and the type and content of element M of the present application, The problems of powder dropping and lithium precipitation are improved, and the energy density is improved, indicating that the lithium-ion battery of the present application has excellent safety performance and high energy density.
  • Example 1-1, Comparative Example 1 and Comparative Example 2 that when the content of Mn in the second positive electrode active material is too high (for example, Comparative Example 1), the cycle performance of the lithium ion battery is poor and the energy density is low. ; When the Mn content in the second positive electrode active material is too low (such as Comparative Example 2), it is not enough to maintain the stability of the pole piece near the welding area during the life cycle of the lithium-ion battery, which increases the risk of lithium precipitation after the lithium-ion battery is cycled. , there is powder falling phenomenon; by regulating the Mn content in the second positive electrode active material within the scope of this application, the safety performance and energy density of the lithium-ion battery are improved.
  • Examples 1-5 and Comparative Example 3 when the second positive electrode active material includes multiple elements such as Mn, Fe, and Zr, by regulating the content of the M element within the scope of the present application, the safety performance and performance of the lithium-ion battery can be improved. Energy density is improved. It can be seen from Examples 1-4 and Comparative Example 4 that by regulating the Fe content in the second positive electrode active material within the scope of the present application, the safety performance and energy density of the lithium-ion battery are improved. It can be seen from Examples 1-6, Comparative Examples 5 and 6 that when the content of Zr in the second positive electrode active material is too high (for example, Comparative Example 5), the lithium-ion battery produced has poor cycle performance and energy density.
  • the Dv50 of the second cathode active material, the thickness of the cathode current collector, and the welding strength between the cathode connection part and the cathode current collector usually affect the safety performance of the lithium-ion battery. From Examples 1-5, Examples 1-9 and Implementation It can be seen from Examples 2-1 to 2-7 that by adjusting the above parameters within the scope of the present application, a lithium-ion battery with good safety performance can be obtained.
  • the thermal conductivity of the cathode tab and cathode current collector usually affects the heat dissipation performance of the cathode tab. It can be seen from Examples 1-9, 2-8 and 2-9 that by regulating the thermal conductivity of the positive electrode tab and the positive electrode current collector within the scope of the present application, timely heat dissipation can be ensured and a large amount of heat accumulation can be avoided.
  • the binder in the second cathode active material layer corresponding to the cathode connection part is reduced to lose its adhesiveness after carbonization, thereby improving the lithium deposition problem of the negative electrode sheet corresponding to the welding area attachment, and can obtain a product with good safety performance of lithium-ion batteries.

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Abstract

本申请提供了一种电化学装置及其制备方法和电子装置。电化学装置包括电极组件，电极组件包括正极极片，正极极片为单面槽位嵌入式极耳结构，正极极片包括正极集流体和设置在正极集流体的第二表面的第二正极活性材料层，第二正极活性材料层包括第二正极活性材料，第二正极活性材料包括元素M，元素M包括锰、铁、镧、锆或钇中的至少一种。本申请的正极极片，可在现有的嵌入式极耳结构的基础上提升电化学装置的能量密度。同时，通过元素M可以改善第二正极活性材料的热稳定性，从而改善设置单面槽位嵌入式极耳结构时造成的正极极片老化问题，进而提高电化学装置的安全性能。

Description

电化学装置及其制备方法和电子装置 技术领域
本申请涉及电化学技术领域，具体涉及一种电化学装置及其制备方法和电子装置。
背景技术
锂离子电池(电化学装置)具有工作电压高，能量密度高、循环寿命长、工作温度范围宽等特性，这些优异的特性使锂离子电池在消费电子、动力电池和储能三大领域都实现了广泛应用。
常见的卷绕结构锂离子电池中，为了降低锂离子电池的阻抗，相对于将极耳设置与电极极片端部的方案，在更加靠近电极极片中心的位置的两面设置未涂覆区域，将极耳置于其中，这样的结构称为嵌入式极耳结构。
发明内容
本申请的目的在于提供一种电化学装置及其制备方法和电子装置，以提高电化学装置的能量密度和安全性能。具体技术方案如下：
本申请的第一方面提供了一种电化学装置，其包括电极组件，电极组件包括正极极片。正极极片包括正极集流体和设置在正极集流体的第一表面的第一正极活性材料层及设置在正极集流体的第二表面的第二正极活性材料层，第一表面和第二表面为正极集流体的相对的两个表面，第一正极活性材料层设有显露出第一表面的第一凹槽。正极极片还包括正极极耳，正极极耳包括正极连接部，正极连接部至少部分位于第一凹槽内并与第一表面焊接，与第一凹槽对应的第二表面被第二正极活性材料层覆盖。第二正极活性材料层包括第二正极活性材料，第二正极活性材料包括元素M，元素M包括锰、铁、镧、锆或钇中的至少一种。基于第二正极活性材料的总质量，锰或铁的质量百分含量为D％，0.02≤D≤35.00，镧、锆或钇的质量百分含量为E％，0.02≤E≤0.20。
本申请实施例的有益效果：本申请的电化学装置通过在第一正极活性材料层设置显露出第一表面的第一凹槽，正极连接部至少部分位于该第一凹槽内并与第一表面焊接，形成单面槽位嵌入式极耳结构，并使第二表面设置有第二正极活性材料层，实现了仅需在正极极片的一面保留空箔区，而不是如现有嵌入式极耳结构正极极片需两面均保留空箔区，能够提升电化学装置的能量密度；并且可以改善极耳设置处的正负极界面不良的问题，降低了析锂风险。同时，本申请的第二正极活性材料包括元素M，通过在上述范围内选择元素M并调控其含量在上述范围内，有利于改善第二正极活性材料的热稳定性，从而改善正极极片老化问题，进而提高电化学装置的安全性能。采用本申请的技术方案，可以实现提高电化学装置的能量密度和安全性能。
在本申请的一种实施方案中，正极连接部与第一表面通过激光焊接，激光焊接仅需要在正极集流体的单面提供能量就能使焊接处熔融，更适用于本申请的极片结构。通过激光焊接，能够改善现有嵌入式极耳结构正极极片的老化问题，进而提高电化学装置的安全性。
在本申请的一种实施方案中，正极连接部与第一表面焊接形成焊接部，焊接部贯穿正极极耳且至少部分穿透正极集流体。通过设置这样的结构，正极连接部与正极集流体之间 的连接强度得到进一步提高，从而进一步改善正极极耳的抗脱落能力，提高电化学装置的安全性能。
在本申请的一种实施方案中，第二正极活性材料的Dv50为Bμm，正极连接部与正极集流体之间的焊接强度为A N/m，正极集流体的厚度为Tμm，正极集流体的拉伸强度为S MPa，B/T×A＜S。通过调控B、A、T、S之间满足上述关系式，有利于正极连接部与正极集流体之间连接强度的提高，从而改善正极极耳的抗脱落能力，提高电化学装置的安全性能。
在本申请的一种实施方案中，0.5≤B≤18，通过调控B在上述范围内，有利于减少正极极片冷压后变形。5≤A≤50，通过调控A在上述范围内，能够降低因焊接能量过高导致的正极集流体破损或表面活性物质脱落风险，以及降低因焊接能量过低导致的正极集流体与正极极耳连接强度过低的风险。4≤T≤14，50≤S≤500，通过调控T和S在上述范围内，有利于正极集流体可承受能力的提高，从而改善正极极耳的抗脱落能力，提高电化学装置的安全性能。
在本申请的一种实施方案中，正极集流体的导热系数为30W·m -1·K -1至400W·m -1·K -1，优选为200W·m -1·K -1至250W·m -1·K -1；正极极耳的导热系数为30W·m -1·K -1至400W·m -1·K -1，优选为200W·m -1·K -1至250W·m -1·K -1。通过选择导热系数在上述范围内的正极集流体和正极极耳，有利于正极极片的散热性能的提高，从而改善电化学装置使用过程中因热量积聚导致的正极极片老化问题，进而改善电化学装置的安全性能。
在本申请的一种实施方案中，电化学装置包括包装袋，电极组件容纳在包装袋中，第一表面朝向包装袋，从而改善正极极片-隔膜-负极极片之间的界面。
在本申请的一种实施方案中，电极组件还包括负极极片和设置于正极极片和负极极片之间的隔膜，正极极片、隔膜和负极极片层叠设置，与第一凹槽对应的第二表面上的第二正极活性材料层与隔膜相接触。通过设置这样的结构，由于没有该额外设置的凹槽，因此无需设置胶纸，还降低了厚度，提高界面平整性，从而有利于提高电化学装置的能量密度。
在本申请的一种实施方案中，负极极片包括负极集流体和设置在负极集流体的两个表面的负极活性材料层，负极集流体的两个表面上的负极活性材料层均设有显露出负极集流体的表面的第二凹槽，负极集流体一侧的第二凹槽与负极集流体另一侧的第二凹槽相对设置。负极极片还包括负极极耳，负极极耳包括负极连接部，负极连接部至少部分位于第二凹槽内并与负极集流体焊接，焊接包括超声焊接或者电阻焊接。通过设置这样的结构，能够提高负极极耳的焊接强度，降低跌落失效风险。并且，采用超声焊接或者电阻焊接可以保护负极集流体以及负极活性材料层不被破坏。本申请的负极活性材料层包括石墨，有利于改善负极活性材料层受激光焊接热影响，导致材料结构变化，从而降低析锂风险。
在本申请的一种实施方案中，第一正极活性材料层包括第一正极活性材料、第一粘结剂和第一导电剂，第二正极活性材料层还包括第二粘结剂和第二导电剂；第一正极活性材料或第二正极活性材料包括钴酸锂、镍钴锰酸锂、镍钴铝酸锂、锰酸锂、磷酸铁锂、磷酸锰铁锂或富锂锰基氧化物中的至少一种；选择上述陶瓷材料，能够提高第一正极活性材料或第二正极活性材料的耐热性能，降低焊接的影响，有利于提高电化学装置的安全性能。 第一粘结剂或第二粘结剂包括聚偏二氟乙烯、偏氟乙烯-氟化烯烃的共聚物、聚乙烯吡咯烷酮、聚丙烯腈、聚丙烯酸甲酯、聚四氟乙烯、羧甲基纤维素钠、丁苯橡胶、聚氨酯、氟化橡胶或聚乙烯醇中的至少一种；将上述范围内的粘结剂应用于正极极片，正极极片具有良好的结构稳定性，有利于改善电化学装置的循环性能和膨胀性能。第一导电剂或第二导电剂包括导电炭黑、碳纳米管、导电石墨、石墨烯或纳米碳纤维中的至少一种。选择上述导电剂，有利于提高正极极片的导电性。
在本申请的一种实施方案中，第二正极活性材料层包括层叠设置的第一层和第二层，第一层位于正极集流体和第二层之间，第二层包括第二正极活性材料，第一层包括陶瓷材料、第三粘结剂和第三导电剂；陶瓷材料包括二氧化铪、钛酸锶、二氧化锡、氧化铯、氧化镁、氧化镍、氧化钙、氧化钡、氧化锌、氧化锆、氧化钇、三氧化二铝、氧化钛、二氧化硅、勃姆石、氢氧化镁或氢氧化铝中的至少一种；选择上述陶瓷材料，能够提高第一正极活性材料或第二正极活性材料的耐热性能，降低焊接的影响；另外，通过选择上述陶瓷材料，在正极集流体表面粘附一层阻值大的电阻层，能够降低正极集流体与负极活性材料层直接接触导致内短从而导致燃烧爆炸的风险，从而提高电化学装置的安全性能。第三粘结剂包括聚偏二氟乙烯、偏氟乙烯-氟化烯烃的共聚物、聚乙烯吡咯烷酮、聚丙烯腈、聚丙烯酸甲酯、聚四氟乙烯、羧甲基纤维素钠、丁苯橡胶、聚氨酯、氟化橡胶或聚乙烯醇中的至少一种；将上述范围内的粘结剂应用于正极极片，正极极片具有良好的结构稳定性，有利于改善电化学装置的循环性能和膨胀性能。第三导电剂包括导电炭黑、碳纳米管、导电石墨、石墨烯或纳米碳纤维中的至少一种。选择上述导电剂，有利于改善正极极片的导电性。
在本申请的一种实施方案中，第一层还包括磷酸铁锂。磷酸铁锂耐热性好，有利于提高第一层的耐热性能；并且，磷酸铁锂材料在第一层中的电阻较大，在机械乱用情况下导致正负极接触短路时可以提高短路电阻，降低短路电流；而且，磷酸铁锂还能进行脱嵌锂，有利于提高电化学装置的容量。另外，磷酸铁锂的粒径较小，具有纳米级别的粒径，有利于减少正极极片辊压后变形，在焊接时可以降低焊接不良甚至焊穿正极集流体的风险，从而提高电化学装置的安全性能。
本申请的第二方面提供了一种电化学装置的制备方法，包括：
提供正极集流体，在正极集流体的第一表面设置第一正极活性材料层，在正极集流体的第二表面设置第二正极活性材料层，第一表面和第二表面为正极集流体的相对的两个表面，第一正极活性材料层设置有显露第一表面的第一凹槽；
提供正极极耳，将正极极耳焊接于第一凹槽显露的第一表面，使得正极极耳的正极连接部与第一表面连接，第一凹槽对应的第二表面被第二正极活性材料层覆盖，第二正极活性材料层包括第二正极活性材料，第二正极活性材料包括元素M，元素M包括锰、铁、镧、锆或钇中的至少一种，基于第二正极活性材料的总质量，锰或铁的质量百分含量为D％，0.02≤D≤35.00，镧、锆或钇的质量百分含量为E％，0.02≤E≤0.20。
采用本申请第二方面提供的电化学装置的制备方法得到的电化学装置，可以提高电化学装置的能量密度和安全性能。
在本申请的一种实施方案中，用激光照射正极连接部使得正极连接部与第一表面焊接，能够使正极连接部与正极集流体之间的连接强度满足需求，从而改善正极极耳的抗脱落能力，从而提高电化学装置的安全性能。
本申请的第三方面提供了一种电子装置，其包括本申请第一方面提供的电化学装置。本申请提供的电化学装置具有高能量密度和良好的安全性能，从而本申请的电子装置具有较长的续航时间和使用寿命。
本申请提供了一种电化学装置及其制备方法和电子装置，其中，电化学装置通过在第一正极活性材料层设置显露出第一表面的第一凹槽，正极连接部至少部分位于该第一凹槽内并与第一表面焊接，形成单面槽位嵌入式极耳结构，并使第二表面设置有第二正极活性材料层，实现了仅需在正极极片的一面保留空箔区，而不是如现有嵌入式极耳结构正极极片需两面均保留空箔区，能够提升电化学装置的能量密度；并且可以改善极耳设置处的正负极界面不良的问题，降低析锂风险。同时，本申请的第二正极活性材料包括元素M，通过在本申请范围内选择元素M并调控其含量在本申请范围内，有利于改善正极活性材料的热稳定性，从而改善现有嵌入式极耳结构正极极片的老化问题，进而提高电化学装置的安全性能。采用本申请的技术方案，可以实现提高电化学装置的能量密度和安全性能。
附图说明
为了更清楚地说明本申请实施例和现有技术的技术方案，下面对实施例和现有技术中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，还可以根据这些附图获得其他的附图。
图1为现有技术中的嵌入式极耳结构的电极组件的结构示意图；
图2为本申请的一种实施方案中的电化学装置的结构示意图；
图3为本申请的一种实施方案中的正极极片的结构示意图；
图4为本申请的一种实施方案中的正极极片A-A截面沿其厚度方向的剖面图；
图5为本申请的另一种实施方案中的正极极片A-A截面沿其厚度方向的剖面图；
图6为本申请的一种实施方案中的正极连接部与第一表面焊接形成的焊接部的局部放大图；
图7为本申请的另一种实施方案中的正极极片A-A截面沿其厚度方向的剖面图。
附图说明：
电极组件-1，正极极片-10，正极集流体-11，第一正极活性材料层-12，第二正极活性材料层-13，第一凹槽-14，正极极耳-15，焊接部-16，负极极片-20，负极集流体-21，负极活性材料层-22，第二凹槽-23，负极极耳-24，隔膜-30，包装袋-40，第一表面-111，第二表面-112，第三层-121，第四层-122，第一层-131，第二层132，正极连接部-151，负极连接部-241。
具体实施方式
为使本申请的目的、技术方案、及优点更加清楚明白，以下参照附图并举实施例，对本申请进一步详细说明。显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员所获得的所有其他实施例，都属 于本申请保护的范围。
本申请的具体实施方式中，以锂离子电池作为电化学装置的例子来解释本申请，但是本申请的电化学装置并不仅限于锂离子电池，还可以是钠离子电池等。
本申请中，定义展开状态下电极极片的厚度方向为z方向，且将垂直于z方向的两个方向定义为x方向和y方向，x方向和y方向相互垂直，x方向为电极极片展开后长边的延伸方向，y方向为电极极片展开后短边的延伸方向。本申请中，定义卷绕状态下电极极片的厚度方向为z’方向，且将垂直于z’方向的两个方向定义为x’方向和y’方向，x’方向和y’方向相互垂直，y’方向为电极极片的卷绕中轴线的延伸方向，x’方向为电极极片平面内与y’方向垂直的方向。电极极片包括正极极片和负极极片。
现有的嵌入式极耳结构锂离子电池，在正极极片10中心附近的两面均具有未涂覆活性材料层的区域。具体参见图1，一方面，在正极集流体11与正极极耳15连接的位置，正极集流体11的两面均未设置正极活性材料层，由于该部分正极活性材料层的缺失，这种嵌入式极耳结构锂离子电池的能量密度有待提高；另一方面，设置正极极耳15需要两面设置凹槽并在凹槽上贴胶纸，且与凹槽面对的负极活性材料层22上也需要贴胶纸，导致贴有胶纸的区域厚度较厚，从而导致与凹槽对应区域的正负极界面较差，析锂风险较高。
有鉴于此，本申请的第一方面提供了一种电化学装置，如图2所示，电化学装置包括电极组件1，电极组件1包括正极极片10、负极极片20、隔膜30。图3为本申请的一种实施方案中的正极极片的结构示意图；图4为本申请的一种实施方案中的正极极片A-A截面沿其厚度方向的剖面图。参考图3和图4，正极极片10包括正极集流体11，正极集流体11包括第一表面111和第二表面112，第一表面111和第二表面112为正极集流体11的相对的两个表面。正极极片10还包括设置在正极集流体11的第一表面111的第一正极活性材料层12和设置在正极集流体11的第二表面112的第二正极活性材料层13。第一正极活性材料层12设有显露出第一表面111的第一凹槽14，正极极片10还包括正极极耳15。正极极耳15包括正极连接部151，正极连接部151至少部分位于第一凹槽14内并与第一表面111焊接。与第一凹槽14对应的第二表面112被第二正极活性材料层13覆盖，第二正极活性材料层13包括第二正极活性材料，第二正极活性材料包括元素M，元素M包括锰(Mn)、铁(Fe)、镧(La)、锆(Zr)或钇(Y)中的至少一种，基于第二正极活性材料的总质量，锰或铁的质量百分含量为D％，0.02≤D≤35.00，镧、锆或钇的质量百分含量为E％，0.02≤E≤0.20。
本申请中，上述与第一凹槽14对应的第二表面112，即第一凹槽14的侧壁沿z方向在正极集流体11的第二表面112上的正投影的区域。本申请中，与第一凹槽14对应的第二表面112被第二正极活性材料层13覆盖是指：第一凹槽14的侧壁沿z方向在正极集流体11的第二表面112上的正投影的区域全部设有第二正极活性材料层13。
本申请中，正极连接部151是正极极耳15与正极集流体11重合的部分。上述正极连接部151至少部分位于第一凹槽14内，包含全部正极连接部151位于第一凹槽14(如图4所示)和部分正极连接部151位于第一凹槽14内(如图5所示)两种情况。
发明人研究发现，对于嵌入式极耳结构电化学装置，在极耳与集流体的连接处，虽然 可以通过在集流体未焊接极耳的一面涂覆正极活性材料层以提高能量密度，但是在焊接极耳过程中，由于焊接位置会产生较多热量，热量会从集流体的一面快速传导到其另一面，导致未焊接极耳一面的正极活性材料层的稳定性受到影响，从而影响正极极片的稳定性，进而导致使用过程中正极极片更容易出现老化，甚至出现活性材料层脱落问题。由这种正极极片制成的电化学装置在多次充放电循环后，在焊接区域，未焊接极耳一面的活性材料层更容易出现粘接性下降和掉粉问题，导致焊接区域的厚度增加，从而与非焊接区域产生厚度差。在产生厚度差的位置附近，正极极片-隔膜-负极极片间产生较大空隙，电化学装置在充放电循环过程中，空隙处的副反应增加、阻抗增大，导致电化学装置的析锂风险增加。另外，电化学装置在充放电循环过程中，集流体两面均未涂覆活性材料的区域(即空箔区)是大量电子流过的区域，其电流密度是整个正极极片中最大的，容易出现过热问题。
基于上述研究发现，本申请的电化学装置通过在第一正极活性材料层设置显露出第一表面的第一凹槽，正极连接部至少部分位于该第一凹槽内并与第一表面焊接，形成单面槽位嵌入式极耳结构，并在第二表面设置第二正极活性材料层，实现了仅需在正极极片的一面保留空箔区，而不是如现有嵌入式极耳结构正极极片需两面均保留空箔区，能够提升电化学装置的能量密度；并且可以改善极耳设置处的正负极界面不良的问题，降低了析锂风险。同时，本申请的第二正极活性材料包括元素M，通过在上述范围内选择元素M并调控其含量在上述范围内，有利于改善第二正极活性材料的热稳定性，从而改善正极极片的稳定性，不仅可以改善由于过热造成使用过程中正极极片老化掉粉问题，还可以改善正极极片在使用中浸泡电解液或长期循环后加剧的粘接性下降和掉粉问题，降低掉粉导致的正极极片-隔膜-负极极片间产生空隙的可能性，从而降低负极极片的析锂风险，进而提高电化学装置的安全性能。
如图4所示，本申请的第一正极活性材料层12和第二正极活性材料层13分别设置在正极集流体11的第一表面111和第二表面112，第一表面111和第二表面112为正极集流体11的厚度方向上相对的两个表面。这里的“表面”可以是正极集流体11的全部区域，也可以是正极集流体11的部分区域，本申请没有特别限制，只要能实现本申请发明目的即可。
在本申请的一种实施方案中，正极连接部151与第一表面111通过激光焊接，激光焊接仅需要在正极集流体11的单面提供能量就能使焊接处熔融，更适用于本申请的极片结构。通过激光照射焊接处，不会对焊接处施加力的作用，能够减小对焊接处周围的第一正极活性材料层的影响，降低焊接振动导致的第一正极活性材料层粘结力减小、掉粉的风险；并且，激光焊接能量集中，也可以减小焊接热对周围的第一正极活性材料层的影响；从而通过激光焊接能够改善现有嵌入式极耳结构正极极片的老化问题，进而提高电化学装置的安全性。
在本申请的一种实施方案中，如图6所示，正极连接部151与第一表面111焊接形成焊接部16，焊接部16贯穿正极极耳15且至少部分穿透正极集流体11。通过设置这样的结构，正极连接部151与正极集流体11之间的连接强度得到进一步提高，从而进一步改善正极极耳的抗脱落能力，提高电化学装置的安全性能。
在本申请的一种实施方案中，第二正极活性材料的Dv50为Bμm，正极连接部151与正极集流体11之间的焊接强度为A N/m，正极集流体11的厚度为Tμm，正极集流体11的拉伸强度为S MPa，B/T×A＜S。通过调控B、A、T、S之间满足上述关系式，有利于正极连接部151与正极集流体11之间连接强度的提高，从而改善正极极耳的抗脱落能力，提高电化学装置的安全性能。本申请中，Dv50是指在体积基准的粒度分布中，从小粒径侧起、达到体积累积50％的粒径。本申请中，可以使用筛分工具筛选出符合不同Dv50要求的正极活性材料。
在本申请的一种实施方案中，0.5≤B≤18，通过调控B在上述范围内，有利于减少正极极片冷压后变形。5≤A≤50，通过调控A在上述范围内，能够降低因焊接能量过高导致的正极集流体11破损或表面活性物质脱落风险，以及降低因焊接能量过低导致的正极集流体11与正极极耳15连接强度过低的风险。4≤T≤14，50≤S≤500，通过调控T和S在上述范围内，有利于正极集流体11可承受能力的提高，从而改善正极极耳的抗脱落能力，提高电化学装置的安全性能。
在本申请的一种实施方案中，正极集流体11的导热系数为30W·m -1·K -1至400W·m -1·K -1，正极极耳15的导热系数为30W·m -1·K -1至400W·m -1·K -1。优选地，正极集流体11的导热系数为200W·m -1·K -1至250W·m -1·K -1，正极极耳15的导热系数为200W·m -1·K -1至250W·m -1·K -1。通过选择导热系数在上述范围内的正极集流体11和正极极耳15，有利于正极极片的散热性能的提高，从而改善电化学装置使用过程中因热量积聚导致的正极极片老化问题，进而改善电化学装置的安全性能。
从提高正极极片10散热性能的角度出发，本申请的正极集流体11的材料可以包含铝、铝合金、不锈钢、钛及钛合金、镍及镍合金等，本申请的正极极耳15的材料可以包含铝、铝合金、不锈钢、钛及钛合金、镍及镍合金等。
在本申请的一种实施方案中，如图2所示，电化学装置包括包装袋40，电极组件1容纳在包装袋40中，第一表面111朝向包装袋40。电极组件1在制造后进行整形，会施加压力；电极组件1装入包装袋40后，在化成时施加压力，使正极极片10和负极极片20紧密接触。第一表面111朝向包装袋40，则在施加压力时，正极极耳15朝向压力夹具，正极极耳15另外一面有第二正极活性材料层13抵接，能够更好的受力，从而改善正极极片10-隔膜30-负极极片20之间的界面。本申请对包装袋40没有特别限制，可以根据实际需要进行选择，只要能实现本申请发明目的即可。例如，可采用铝塑膜包装袋或钢塑膜包装袋。
在本申请的一种实施方案中，如图2所示，隔膜30设置于正极极片10和负极极片20之间，正极极片10、隔膜30和负极极片20层叠设置，与第一凹槽14对应的第二表面112上的第二正极活性材料层13与隔膜30相接触。现有的嵌入式极耳结构的电化学装置中，与第一凹槽对应的第二表面上也需要设置凹槽。此外，此额外设置的凹槽上还需要设置胶纸，胶纸与隔膜接触，胶纸的存在增加了厚度，且会导致接触界面不平整，增加电化学装置析锂风险。由于没有该额外设置的凹槽，因此无需设置胶纸，还降低了厚度，提高界面平整性，从而有利于提高电化学装置的能量密度。
在本申请的一种实施方案中，如图2所示，负极极片20包括负极集流体21和设置在负极集流体21的两个表面的负极活性材料层22，负极集流体21的两个表面上的负极活性材料层22均设有显露出负极集流体21的表面的第二凹槽23，负极集流体21一侧的第二凹槽23与负极集流体21另一侧的第二凹槽23相对设置；负极极片20还包括负极极耳24，负极极耳24包括负极连接部241，负极连接部241至少部分位于第二凹槽23内并与负极集流体21焊接，焊接包括超声焊接或者电阻焊接。通过设置这样的设置，能够提高负极极耳24的焊接强度，降低跌落失效风险。并且，采用超声焊接或者电阻焊接可以保护负极集流体21以及负极活性材料层22不被破坏。本申请的负极活性材料层22包括石墨，有利于改善负极活性材料层受激光焊接热影响，导致材料结构变化，从而降低析锂风险。
在本申请的一种实施方案中，第一正极活性材料层12包括第一正极活性材料、第一粘结剂和第一导电剂，第二正极活性材料层13还包括第二粘结剂和第二导电剂；第一正极活性材料或第二正极活性材料包括钴酸锂、镍钴锰酸锂、镍钴铝酸锂、锰酸锂、磷酸铁锂、磷酸锰铁锂或富锂锰基氧化物中的至少一种；选择上述陶瓷材料，能够提高第一正极活性材料或第二正极活性材料的耐热性能，降低焊接的影响，有利于提高电化学装置的安全性能。第一粘结剂或第二粘结剂包括聚偏二氟乙烯、偏氟乙烯-氟化烯烃的共聚物、聚乙烯吡咯烷酮、聚丙烯腈、聚丙烯酸甲酯、聚四氟乙烯、羧甲基纤维素钠、丁苯橡胶、聚氨酯、氟化橡胶或聚乙烯醇中的至少一种；将上述范围内的粘结剂应用于正极极片，正极极片具有良好的结构稳定性，有利于改善电化学装置的循环性能和膨胀性能。第一导电剂或第二导电剂包括导电炭黑(Super P、科琴黑、乙炔黑)、碳纳米管(CNTs)、导电石墨、石墨烯或纳米碳纤维中的至少一种。上述碳纳米管可以包括但不限于单壁碳纳米管和/或多壁碳纳米管。选择上述导电剂，有利于提高正极极片的导电性。在本申请中，基于第一正极活性材料层12的质量，第一导电剂的质量百分含量为0.5％至5％。基于第二正极活性材料层13的质量，第一导电剂的质量百分含量为0.5％至5％。
在本申请中，第一正极活性材料或第二正极活性材料还可以包含非金属元素，例如非金属元素包括氟、磷、硼或氯等中的至少一种，这些元素能进一步提高正极活性材料的稳定性。本申请对第一正极活性材料层12或第二正极活性材料层13的厚度没有特别限制，只要能够实现本申请发明目的即可。例如，第一正极活性材料层12或第二正极活性材料层13的厚度为30μm至120μm。
在本申请的一种实施方案中，如图7所示，第二正极活性材料层13包括层叠设置的第一层131和第二层132，第一层131位于正极集流体11和第二层132之间，第二层132包括第二正极活性材料，第一层131包括陶瓷材料、第三粘结剂和第三导电剂；陶瓷材料包括二氧化铪、钛酸锶、二氧化锡、氧化铯、氧化镁、氧化镍、氧化钙、氧化钡、氧化锌、氧化锆、氧化钇、三氧化二铝、氧化钛、二氧化硅、勃姆石、氢氧化镁或氢氧化铝中的至少一种；选择上述陶瓷材料，能够提高第一正极活性材料或第二正极活性材料的耐热性能，降低焊接的影响；另外，通过选择上述陶瓷材料，在正极集流体表面设置一层阻值大的电阻层，能够降低内短导致燃烧爆炸的风险，从而提高电化学装置的安全性能。第三粘结剂包括聚偏二氟乙烯、偏氟乙烯-氟化烯烃的共聚物、聚乙烯吡咯烷酮、聚丙烯腈、聚丙烯酸 甲酯、聚四氟乙烯、羧甲基纤维素钠、丁苯橡胶、聚氨酯、氟化橡胶或聚乙烯醇中的至少一种；将上述范围内的粘结剂应用于正极极片，正极极片具有良好的结构稳定性，有利于改善电化学装置的循环性能和膨胀性能。第三导电剂包括导电炭黑(Super P、科琴黑、乙炔黑)、碳纳米管、导电石墨、石墨烯或纳米碳纤维中的至少一种。选择上述导电剂，有利于改善正极极片的导电性。
本申请中，如图7所示，第一正极活性材料层12可以包括层叠设置的第三层121和第四层122，第三层121位于正极集流体11和第四层122之间。第三层121的组成可以与第一层131相同，第四层122的组成可以与第二层132的组成相同，本申请不再赘述。
在本申请的一种实施方案中，第一层131还包括磷酸铁锂。磷酸铁锂耐热性好，有利于提高第一层的耐热性能；并且，磷酸铁锂材料在第一层中的电阻较大，可降低短路电阻；而且，磷酸铁锂还能发挥出一定的容量，有利于提高电化学装置的容量。另外，磷酸铁锂的粒径较小，具有纳米级别的粒径，有利于减少正极极片冷压后变形，在焊接时可以降低焊接不良甚至焊穿正极集流体的风险，从而提高电化学装置的安全性能。
本申请对磷酸铁锂的制备方法没有特别限制，只要能实现本申请发明目的即可。例如，可以通过如下方法制备：以FeC 2O 4·8H 2O、MnCO 3、NH 4H 2PO 4、Li 2CO 3、ZrO 2为原料，通过球磨混合、喷雾造粒、在含有H 2的还原气氛中烧结、破碎，制备得到锰、锆掺杂处理的纳米级磷酸铁锂粉体。以氮气为保护气体，将制备得到的粉体真空进料后置于回转炉内，持续喷入蔗糖溶液，并在600℃至800℃下回转搅拌烧结2小时至4小时形成碳层包覆层，冷却后取样，得到改性的磷酸铁锂粉体，即上述磷酸铁锂材料。其中，碳层包覆层的平均厚度为1μm。通常情况下，可以改变原料的摩尔比来调控磷酸铁锂材料中Fe、Mn和Zr的质量百分含量。例如，提高FeC 2O 4·8H 2O的比例，磷酸铁锂材料中Fe的质量百分含量增加；降低FeC 2O 4·8H 2O的比例，磷酸铁锂材料中Fe的质量百分含量减少。
本申请中，负极活性材料层22设置于负极集流体21厚度方向上相对的两个表面上。这里的“表面”可以是负极集流体21的全部区域，也可以是负极集流体21的部分区域，本申请没有特别限制，只要能实现本申请发明目的即可。
本申请对负极集流体21没有特别限制，只要能够实现本申请发明目的即可。例如，负极集流体21可以包含铜箔、铜合金箔、镍箔、不锈钢箔、钛箔、泡沫镍、泡沫铜或复合集流体等。本申请对负极集流体21的厚度没有特别限制，只要能够实现本申请发明目的即可。例如，负极集流体21的厚度为4μm至10μm。
在本申请中，负极活性材料层22还包括负极活性材料。本申请对负极活性材料的种类没有特别限制，只要能够实现本申请发明目的即可。例如，负极活性材料可以包含中间相微碳球、硬碳、软碳、硅、硅-碳复合物、SiO x(0＜x≤2)、Li-Sn合金、Li-Sn-O合金、Sn、SnO、SnO 2、尖晶石结构的钛酸锂Li 4Ti 5O 12、Li-Al合金或金属锂等中的至少一种。在本申请中，负极活性材料层22还可以包括负极导电剂，本申请对负极导电剂没有特别限制，只要能够实现本申请发明目的即可，例如可以包括但不限于导电炭黑(Super P、科琴黑、乙炔黑)、碳纳米管(CNTs)、碳纤维、石墨烯、金属材料或导电聚合物中的至少一种，上述碳纳米管可以包括但不限于单壁碳纳米管和/或多壁碳纳米管。上述碳纤维可以包括但 不限于气相生长碳纤维和/或纳米碳纤维。上述金属材料可以包括但不限于金属粉和/或金属纤维，具体地，金属可以包括但不限于铜、镍、铝或银中的至少一种。上述导电聚合物可以包括但不限于聚亚苯基衍生物、聚苯胺、聚噻吩、聚乙炔或聚吡咯中的至少一种。基于负极活性材料层22的质量，负极导电剂的质量百分含量为0.5％至5％。
本申请对负极活性材料层22的厚度没有特别限制，只要能够实现本申请发明目的即可。例如，单面负极活性材料层的厚度可以为30μm至160μm。
本申请对负极极耳24的材料没有特别限制，只要能够实现本申请发明目的即可。例如负极极耳的材料包括铜、铜合金、镍、不锈钢、钛或镍等。
在本申请中，电解液中还包括非水溶剂，本申请对非水溶剂没有特别限制，只要能实现本申请发明目的即可，例如可以包括但不限于羧酸酯化合物、醚化合物或其它有机溶剂中的至少一种。上述羧酸酯化合物可以包括但不限于乙酸甲酯、乙酸乙酯、乙酸正丙酯、乙酸正丁酯、丙酸甲酯、丙酸丙酯、丙酸丁酯、丁酸甲酯、丁酸乙酯、丁酸丙酯、丁酸丁酯、γ-丁内酯、乙酸2,2-二氟乙酯、戊内酯、丁内酯、2-氟乙酸乙酯、2,2-二氟乙酸乙酯、三氟乙酸乙酯、2,2,3,3,3-五氟丙酸乙酯、2,2,3,3,4,4,4,4-七氟丁酸甲酯、4,4,4-三氟-3-(三氟甲基)丁酸甲酯、2,2,3,3,4,4,5,5,5,5-九氟戊酸乙酯、2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-十七氟壬酸甲酯或2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,9-十七氟壬酸乙酯中的至少一种。上述醚化合物可以包括但不限于乙二醇二甲醚、二乙二醇二甲醚、四乙二醇二甲醚、二丁醚、四氢呋喃、2-甲基四氢呋喃或双(2,2,2-三氟乙基)醚中的至少一种。上述其它有机溶剂可以包括但不限于乙基乙烯基砜、甲基异丙基砜、异丙基仲丁基砜、二甲亚砜、1,2-二氧戊环、环丁砜、甲基环丁砜、1,3-二甲基-2-咪唑烷酮、N-甲基-2-吡咯烷酮、甲酰胺、二甲基甲酰胺、乙腈、磷酸三甲酯、磷酸三乙酯、磷酸三辛酯或磷酸酯中的至少一种。
本申请的电化学装置还包括隔膜30，本申请对隔膜30没有特别限制，只要能够实现本申请发明目的即可，例如隔膜的材料可以包括但不限于聚乙烯(PE)、聚丙烯(PP)、聚四氟乙烯为主的聚烯烃(PO)类隔膜、聚酯膜(例如聚对苯二甲酸二乙酯(PET)膜)、纤维素膜、聚酰亚胺膜(PI)、聚酰胺膜(PA)、氨纶或芳纶膜等中的至少一种。隔膜的类型可以包括但不限于织造膜、非织造膜(无纺布)、微孔膜、复合膜、碾压膜或纺丝膜等中的至少一种。本申请的隔膜30可以具有多孔结构，孔径的尺寸没有特别限制，只要能实现本申请发明目的即可，例如，孔径的尺寸可以为0.01μm至1μm。在本申请中，隔膜30的厚度没有特别限制，只要能实现本申请发明目的即可，例如厚度可以为5μm至500μm。
本申请的电化学装置没有特别限制，其可以包括发生电化学反应的任何装置。在本申请的一种实施方案中，电化学装置可以包括但不限于：锂离子二次电池(锂离子电池)、锂聚合物二次电池或锂离子聚合物二次电池等。在本申请的一种实施方案中，本申请的锂离子电池结构包括卷绕型结构或叠片型结构等。本申请的锂离子电池结构包括但不限于软包型锂离子电池、方形硬壳电池或圆柱形硬壳电池等。
本申请的第二方面提供了一种电化学装置的制备方法，包括：
提供正极集流体11，在正极集流体11的第一表面111设置第一正极活性材料层12，在正极集流体11的第二表面112设置第二正极活性材料层13，第一表面111和第二表面 112为正极集流体11的相对的两个表面，第一正极活性材料层12设置有显露第一表面111的第一凹槽14；
提供正极极耳15，将正极极耳15焊接于第一凹槽14显露的第一表面111，使得正极极耳15的正极连接部151与第一表面111连接，第一凹槽14对应的第二表面112被第二正极活性材料层13覆盖，第二正极活性材料层13包括第二正极活性材料，第二正极活性材料包括元素M，元素M包括锰、铁、镧、锆或钇中的至少一种，基于第二正极活性材料的总质量，锰或铁的质量百分含量为D％，0.02≤D≤35.00，镧、锆或钇的质量百分含量为E％，0.02≤E≤0.20。
在本申请中，焊接正极极耳后，可以在第一凹槽面对的负极活性材料层上贴附绝缘层，以起到绝缘作用。同理，焊接负极极耳后，可以在第二凹槽面对的第一正极活性材料层和第二正极活性材料层上，分别贴附绝缘层，以起到绝缘作用。绝缘层可以包括单面胶或双面胶中的至少一种。本申请对绝缘层的材料没有特别限制，只要能实现本申请发明目的即可。例如，单面胶包括基材层和粘接层，基材层的材料包括但不限于聚氟烯烃、聚对苯二甲酸乙二醇酯、聚酰亚胺、聚酰胺酰亚胺、聚氯乙烯或聚烯烃(例如双向拉伸聚烯烃热缩膜)中的至少一种，聚氟烯烃包括但不限于聚四氟乙烯或聚偏二氟乙烯。粘接层包括粘结材料，粘结材料包括但不限于羧甲基纤维素、丁苯橡胶、聚偏二氟乙烯、聚四氟乙烯、氟化橡胶、聚氨酯、聚丙烯醇、聚丙烯酸钠、聚醚酰亚胺或丙烯酸酯中的至少一种。
采用本申请第二方面提供的制备方法得到的电化学装置，能够提高电化学装置的能量密度和安全性能。
在本申请的一种实施方案中，用激光照射正极连接部151使得正极连接部151与第一表面111焊接，可以使正极连接部151与正极集流体11之间的连接强度满足需求，从而改善正极极耳的抗脱落能力，从而提高电化学装置的安全性能。
本申请对激光焊接设备没有特别限制，只要能实现本申请发明目的即可，例如可以是市售的激光焊接机。本申请可以通过增加激光照射的光斑直径大小和/或时间来提高正极连接部和正极集流体之间的焊接强度。本申请对激光照射的光斑直径和时间没有特别限制，可以根据实际焊接需求进行调整，只要能实现本申请发明目的即可。
本申请的电化学装置的制备过程还可以包括但不限于以下步骤：将正极极片10、隔膜30和负极极片20按顺序堆叠，并根据需要将其卷绕、折叠等操作得到卷绕结构的电极组件1，将电极组件1放入包装袋40内，将电解液注入包装袋40并封口，得到电化学装置；或者，将正极极片10、隔膜30和负极极片20按顺序堆叠，然后用胶带将整个叠片结构的四个角固定好得到叠片结构的电极组件1，将电极组件1置入包装袋40内，将电解液注入包装袋40并封口，得到电化学装置。此外，也可以根据需要将防过电流元件、导板等置于包装袋40中，从而防止电化学装置内部的压力上升、过充放电。
本申请的负极集流体与负极极耳通过超声焊接或者电阻焊接进行焊接，本申请对焊接过程没有特别限制，可以根据实际焊接需求进行选择，只要能实现本申请发明目的即可。
本申请的第三方面提供了一种电子装置，其包括本申请第一方面提供的电化学装置。本申请提供的电化学装置具有高能量密度和良好的安全性能，从而本申请的电子装置具有 较长的续航时间和使用寿命。
本申请的电子装置没有特别限定，其可以是用于现有技术中已知的任何电子装置。在一些实施例中，电子装置可以包括但不限于笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池或锂离子电容器等。
实施例
以下，举出实施例及对比例来对本申请的实施方式进行更具体地说明。各种的试验及评价按照下述的方法进行。另外，只要无特别说明，“份”、“％”为质量基准。
测试方法与设备：
金属元素含量测试
将锂离子电池放电到0％SOC后拆解，取出正极极片，采用碳酸二甲酯(DMC)浸泡30分钟后，清洗掉正极极片表面的残余杂质后晾干。将正极极片放入马弗炉中，空气气氛下600℃煅烧4小时，取出后刮取正极集流体表面的正极活性材料，得到粉末样品，用王水(浓硝酸与浓盐酸体积比为1∶3配制)消解1小时后得到金属离子溶液，通入电感耦合等离子体发射光谱仪中进行测试，得到各金属元素的质量百分含量。
正极极耳与正极集流体之间的焊接强度测试
高铁拉力试验机(型号3367)夹住正极极耳与正极集流体的连接部位的两头(分别是正极极耳和正极集流体)，试样宽度k(mm)等于正极极耳宽度，拉伸速度50mm/min，记录拉伸过程中的最大力数值F 1(N)，则正极极耳与正极集流体之间的焊接强度A＝F 1/(k×100)，单位为N/m。
正极极耳与正极集流体导热系数测试
采用热线法通用型导热系数仪(型号TC3200)对片状试样5cm×5cm进行测试。
正极集流体的拉伸强度测试
高铁拉力试验机(型号3367)夹住正极集流体试样进行拉伸试验，试样宽度15mm，拉伸速度50mm/min，记录得到的拉伸强度S，单位为MPa。
活性材料的Dv50
将锂离子电池满放后拆解，取出正极极片，采用DMC浸泡30分钟后，清洗掉正极极片表面的残余杂质后晾干。将正极极片放入马弗炉中，空气气氛下600℃煅烧4小时，取出后刮取集流体表面的正极活性材料，通过激光粒度仪进行测试，得到体系分布中占50％体积对应的粒径数值为Dv50，单位为μm。
跌落测试
先将锂离子电池置于夹具中，测试锂离子电池的初始电压U 0。将易拉胶和锂离子电池贴好后，1分钟内使用5Kgf配重压紧，并静置12小时以上。然后使用自动跌落设备，将夹具从高度为1.8米的位置自由跌落到花岗岩表面。然后按照以下跌落顺序测试：上-下- 右上-右下-左上-左下，即完成一轮测试，共进行3轮即为18次(角度45度±15度)。然后，测试锂离子电池跌落测试后的电压U 1，若U 1为0则表示极耳从集流体表面脱落。最后，拆解锂离子电池观察正极极片的单面槽位焊接区域周围是否有掉粉。
循环测试
测试环境温度：25℃
每一圈的操作流程：将锂离子电池以2.6倍率(C)恒定电流充电到4.2V，再恒定电压充电到2.35C；2.35C恒定电流充电到4.25V，再恒定电压充电到2C，2C恒定电流充电到4.3V，再恒定电压充电到1.5C；1.5C恒定电流充电到4.38V，再恒定电压充电到1.2C；1.2C恒定电流充电到4.45V，再恒定电压充电到1C；1C恒定电流充电到4.48V，再恒定电压充电到0.1C。静置10分钟后，再给锂离子电池放电：以1.5C恒定电流放电到3.5V，再0.7C恒定电流放电到3V，最后再静置10分钟，结束一圈循环。将实施例或对比例得到的锂离子电池分为两组，分别按照上述充电/放电步骤循环500圈和1000圈。
析锂程度判断
在干燥房(湿度＜1.7％)拆解上述循环500圈、1000圈后的锂离子电池，拍照记录负极极片的析锂情况。以析锂面积的百分数来判断析锂程度，未发现析锂为无析锂；轻度析锂：0＜析锂面积的百分数≤5％；中度析锂：5＜析锂面积的百分数≤15％；重度析锂：析锂面积的百分数＞15％，其中析锂面积的百分数基于负极极片厚度方向的两个表面的负极活性材料层的面积总和来计算。
初始能量密度测试
在25℃的环境中，将锂离子电池按照下述操作流程充电，再进行放电，得出锂离子电池放电容量：锂离子电池以0.5C恒流充电至4.45V，再以4.45V恒压充电至0.025C，静置5分钟，以0.5C恒流放电至3.0V，静置5分钟，得出放电容量C。上述锂离子电池充电步骤完成后，用激光测厚仪测试锂离子电池的长L、宽W、高H，得到锂离子电池的体积V＝L×W×H。其初始能量密度(ED)＝C/V，单位为Wh/L。
实施例1-1
<正极极片的制备>
将Li(Ni 0.5Co 0.2Mn 0.3)O 2和锰酸锂(LMO)按照质量比6∶4混合作为正极活性材料(Dv50为15.1μm)，将上述正极活性材料、导电剂导电炭黑(Super P)、聚偏二氟乙烯(PVDF)按照质量比98∶1∶1混合，加入N-甲基吡咯烷酮(NMP)作为溶剂，调配成固含量为75wt％的正极浆料，并搅拌均匀。第一正极活性材料层和第二正极活性材料层均采用上述正极浆料制得，将正极浆料均匀涂覆在厚度为8μm的正极集流体铝箔的第一表面上，在110℃条件下烘干，得到第一正极活性材料层的厚度为110μm的单面涂布正极活性材料的正极极片。之后，在正极集流体的第二表面上重复以上步骤，得到第二正极活性材料层的厚度为110μm的双面涂布正极活性材料的正极极片。涂布完成后，将正极极片冷压，然后经过极耳成型、分条处理、激光清洗等工序后，得到第一正极活性材料层中间带有第一凹槽的正极极片。在第一凹槽上通过激光照射焊接铝正极极耳。正极极片的规格为81.9mm×1490mm，第一凹槽的规格为20mm×9mm。正极集流体的导热系数(记为L)为217.7W·m -1·K -1， 正极极耳的导热系数(记为R)为217.7W·m -1·K -1，正极连接部与正极集流体之间的焊接强度为28N/m，正极集流体的拉伸强度为156MPa。
<负极极片的制备>
将负极活性材料导电石墨、导电炭黑(Super P)、羧甲基纤维素钠和丁苯橡胶按照质量比为96.4∶1.5∶0.5∶1.6进行混合，然后加入去离子水作为溶剂，调配成固含量为60wt％的负极浆料，并搅拌均匀。将负极浆料均匀涂布在厚度为8μm的负极集流体铜箔的一个表面上，110℃条件下烘干，得到涂层厚度为130μm的单面涂布负极活性材料层的负极极片，然后在该负极极片的另一个表面上重复以上步骤，得到双面涂布有负极活性材料层的负极极片。涂布完成后，将负极极片冷压，然后经过极耳成型、分条处理、激光清洗等工序后，得到双面负极活性材料层中间均带有第二凹槽的负极极片。在其中一个第二凹槽上通过超声波处理焊接铜负极极耳。负极极片的规格为83.3mm×1494mm，第二凹槽的规格为20mm×9mm。
<电解液的制备>
在干燥氩气气氛手套箱中，将有机溶剂碳酸乙烯酯(EC)、碳酸亚丙酯(PC)、碳酸二乙酯(DEC)和丙酸乙酯(EP)以质量比EC∶PC∶DEC∶EP＝3∶1∶3∶3混合，然后向有机溶剂中加入锂盐六氟磷酸锂(LiPF 6)溶解并混合均匀，得到锂盐的浓度为1mol/L的电解液。
<隔膜的制备>
将PVDF和三氧化二铝陶瓷按照质量比9∶1进行混合，加入去离子水作为溶剂，调配成固含量12wt％的浆料，并搅拌均匀，将浆料均匀的涂覆在厚度为5μm的聚乙烯薄膜基材的一个表面，烘干后得到隔膜。
<锂离子电池的制备>
将正极极片、隔膜和负极极片按顺序叠好，使隔膜处于正极极片和负极极片中间起到隔离的作用，然后在第一凹槽面对的负极活性材料层上、以及第二凹槽面对的第一正极活性材料层和第二正极活性材料层上，分别贴附单面胶作为绝缘层，然后从一端卷绕得到电极组件。将电极组件装入铝塑膜包装壳中，放置在85℃真空烘箱中干燥12小时脱去水分，注入上述配好的电解液，经过真空封装、静置、化成(0.02C恒流充电至3.5V，再以0.1C恒流充电至3.9V)、整形、容量处理后得到锂离子电池。
实施例1-2
除了在<正极极片的制备>中，采用Li(Ni 0.5Co 0.2Mn 0.3)O 2作为正极活性材料(Dv50如表1所示)以外，其余与实施例1-1相同。
实施例1-3
除了在<正极极片的制备>中，采用钴酸锂(LiCoO 2)与氧化锰(MnO 2)按照质量比25∶1混合、在850℃下共同烧结12小时得到的Mn掺杂的钴酸锂作为正极活性材料(Dv50如表1所示)以外，其余与实施例1-1相同。
实施例1-4
除了<正极极片的制备>与实施例1-1不同以外，其余与实施例1-1相同。
<正极极片的制备>
将磷酸铁锂(LFP，Dv50如表1所示)、导电剂导电炭黑(Super P)、PVDF按照质量比98∶1∶1混合，加入N-甲基吡咯烷酮(NMP)作为溶剂，调配成固含量为75wt％的第一层浆料，并搅拌均匀。将第一层浆料均匀涂覆在厚度为8μm的正极集流体铝箔的第一表面上，在110℃条件下烘干，得到第一层的厚度为7μm的单面涂布正极活性材料的正极极片。之后，在正极集流体的第二表面上重复以上步骤，使得正极集流体表面双面涂布第一层。
将上述正极活性材料LiCoO 2、导电剂导电炭黑(Super P)、PVDF按照质量比98∶1∶1混合，加入N-甲基吡咯烷酮(NMP)作为溶剂，调配成固含量为75wt％的正极浆料，并搅拌均匀。第一正极活性材料层和第二正极活性材料层均采用上述正极浆料制得，将正极浆料均匀涂覆在第一表面上的第一层上，在110℃条件下烘干，得到第一正极活性材料层的厚度为110μm的单面涂布正极活性材料的正极极片。之后，在正极集流体的第二表面上重复以上步骤，得到第二正极活性材料层的厚度为110μm的双面涂布正极活性材料的正极极片。涂布完成后，将正极极片冷压，然后经过极耳成型、分条处理、激光清洗等得到第一正极活性材料层中间设有第一凹槽的正极极片，上述第一凹槽用于焊接正极极耳，正极极片的规格为81.9mm×1490mm，第一凹槽的规格为20mm×9mm。正极集流体的导热系数(记为L)为217.7W·m -1·K -1，正极极耳的导热系数(记为R)为217.7W·m -1·K -1。
实施例1-5
除了在<正极极片的制备>中，以FeC 2O 4·8H 2O、MnCO 3、NH 4H 2PO 4、Li 2CO 3、ZrO 2为原料，调整上述原料的摩尔比，通过球磨混合、喷雾造粒、在含有H 2的还原气氛中烧结、破碎，制备得到锰、锆掺杂处理的纳米级磷酸铁锂粉体。以氮气为保护气体，将制备得到的粉体真空进料后置于回转炉内，持续喷入蔗糖溶液，并在700℃下回转搅拌烧结3小时形成碳层包覆层，冷却后取样，得到改性磷酸铁锂粉体，即磷酸铁锂(LFP-1)，其中，碳层包覆层的平均厚度为1μm。将得到的LFP-1作为正极活性材料(Dv50如表1所示)以外，其余与实施例1-1相同。
实施例1-6
除了在<正极极片的制备>中，将LiCoO 2与氧化锆(ZrO 2)按照质量比25∶1混合、在850℃下共烧结12小时得到的Zr掺杂的钴酸锂作为正极活性材料(Dv50如表1所示)以外，其余与实施例1-1相同。
实施例1-7
除了在<正极极片的制备>中，将LiCoO 2与氟化钇(YF 3)按照质量比25∶1混合、在850℃下共烧结10小时得到的Y掺杂的钴酸锂作为正极活性材料(Dv50如表1所示)以外，其余与实施例1-1相同。
实施例1-8
除了在<正极极片的制备>中，将LiCoO 2与氧化镧(La 2O 3)按照质量比25∶1混合、在950℃下共烧结12小时得到的La掺杂的钴酸锂作为正极活性材料(Dv50如表1所示)以外，其余与实施例1-1相同。
实施例1-9
除了在<正极极片的制备>中，将LiCoO 2与MnO 2、ZrO 2、YF 3、La 2O 3按照质量比20∶1∶1∶1∶1混合、在950℃下共同烧结16小时得到的Mn+Zr+Y+La共掺杂的钴酸锂作为正极活性材料(Dv50如表1所示)以外，其余与实施例1-1相同。
实施例1-10
除了在<正极极片的制备>中，将LiCoO 2和Li(Ni 0.5Co 0.2Mn 0.3)O 2按照质量比8∶2混合作为正极活性材料(Dv50如表1所示)以外，其余与实施例1-1相同。
实施例1-11
除了在<正极极片的制备>中，将LiCoO 2和Li(Ni 0.5Co 0.2Mn 0.3)O 2按照质量比6∶4混合作为正极活性材料(Dv50如表1所示)以外，其余与实施例1-1相同。
实施例1-12
除了在<正极极片的制备>中，在制备第一层浆料时将LFP、三氧化二铝、导电炭黑(Super P)、PVDF按照质量比96∶1∶1∶2混合以外，其余与实施例1-4相同。
实施例2-1
除了在<正极极片的制备>中，除了如表2所示调整正极活性材料的Dv50以外，其余与实施例1-1相同。
实施例2-2至实施例2-3
除了按照表2调整正极集流体的厚度以外，其余与实施例1-9相同。
实施例2-4
除了通过调整激光光斑直径大小和激光照射时间使得正极连接部和正极集流体之间的焊接强度为5N/m以外，其余与实施例1-9相同。
实施例2-5
除了通过调整激光光斑直径大小和激光照射时间使得正极连接部和正极集流体之间的焊接强度为50N/m以外，其余与实施例1-9相同。
实施例2-6
除了正极集流体的厚度为6μm、通过调整激光光斑直径大小和激光照射时间使得正极连接部和正极集流体之间的焊接强度为35N/m、正极集流体拉伸强度为100MPa采用铝箔以外，其余与实施例1-9相同。
实施例2-7
除了正极集流体的厚度为14μm、通过调整激光光斑直径大小和激光照射时间使得正极连接部和正极集流体之间的焊接强度为35N/m、正极集流体拉伸强度为50MPa采用铝合金以外，其余与实施例1-9相同。
实施例2-8
除了正极集流体的材料采用导热系数为30W·m -1·K -1的不锈钢、正极极耳的材料采用导热系数为30W·m -1·K -1的不锈钢以外，其余与实施例1-9相同。
实施例2-9
除了正极集流体的材料采用导热系数为400W·m -1·K -1的铝合金、正极极耳的材料采用 导热系数为400W·m -1·K -1的铝合金以外，其余与实施例1-9相同。
对比例1
除了采用Li(Ni 0.5Co 0.2Mn 0.3)O 2和锰酸锂(LMO)按照质量比5∶5混合作为正极活性材料以外，其余与实施例1-1相同：
对比例2
除了在<正极极片的制备>中，采用LiCoO 2与MnO 2按照质量比50∶1混合、在850℃下共同烧结4小时得到的Mn掺杂的钴酸锂作为正极活性材料以外，其余与实施例1-1相同。
对比例3
除了在<正极极片的制备>中，以FeC 2O 4·8H 2O、MnCO 3、NH 4H 2PO 4、Li 2CO 3、ZrO 2为原料，调整上述原料的摩尔比，通过球磨混合、喷雾造粒、在含有H 2的还原气氛中烧结、破碎，制备得到锰、锆掺杂处理的纳米级磷酸铁锂粉体。以氮气为保护气体，将制备得到的粉体真空进料后置于回转炉内，持续喷入蔗糖溶液，并在700℃下回转搅拌烧结3小时形成碳层包覆层，冷却后取样，得到改性磷酸铁锂粉体，即磷酸铁锂(LFP-2)，其中，碳层包覆层的平均厚度为1μ覆。将得到的LFP-2作为正极活性材料(Dv50如表1所示)以外，其余与实施例1-1相同。
对比例4
除了在<正极极片的制备>中，第一层的厚度为2μm以外，其余与实施例1-4相同。
对比例5
除了在<正极极片的制备>中，采用LiCoO 2与ZrO 2按照质量比18∶1混合、在850℃下共同烧结5小时得到的Zr掺杂的钴酸锂作为正极活性材料以外，其余与实施例1-1相同。
对比例6
除了在<正极极片的制备>中，采用LiCoO 2与ZrO 2按照质量比50∶1混合、在850℃下共同烧结24小时得到的Zr掺杂的钴酸锂作为正极活性材料以外，其余与实施例1-1相同。
对比例7
除了在<正极极片的制备>中，采用第一正极活性材料层和第二正极活性材料层中间均带有凹槽的正极极片以外，其余与实施例1-1相同。
各实施例和各对比例的相关参数及性能测试如表1和表2所示。
表1
Figure PCTCN2022120528-appb-000001
Figure PCTCN2022120528-appb-000002
“/”表示该锂离子电池只能循环至200圈、无法循环至500/1000圈导致无该项测试结果；“-”表示锂离子电池只能循环至400圈、无法循环至500/1000圈导致无该项测试结果。
整体上，从实施例1-1至实施例1-12、对比例1至对比例7可以看出，具有本申请单面槽位嵌入式极耳结构和元素M种类及含量的锂离子电池，掉粉及析锂问题得到改善，能量密度得到提高，表明本申请的锂离子电池具有优异的安全性能和高的能量密度。
从实施例1-1、对比例1和对比例2可以看出，当第二正极活性材料中Mn的含量过高时(例如对比例1)，锂离子电池的循环性能差、能量密度较低；当第二正极活性材料中Mn的含量过低时(例如对比例2)，不足以维持锂离子电池生命周期内的焊接区域附近的极片稳定性，使得锂离子电池循环后析锂风险增加，有掉粉现象出现；通过调控第二正极活性材料中Mn含量在本申请范围内，锂离子电池的安全性能和能量密度得到提高。
从实施例1-5和对比例3可以看出，当第二正极活性材料中包括Mn、Fe、Zr多种元素时，通过调控M元素含量在本申请范围内，锂离子电池的安全性能和能量密度得到提高。从实施例1-4和对比例4可以看出，通过调控第二正极活性材料中Fe含量在本申请范围内，锂离子电池的安全性能和能量密度得到提高。从实施例1-6、对比例5和对比例6可以看出，当第二正极活性材料中Zr的含量过高时(例如对比例5)，制得的锂离子电池循环性能差、能量密度较低；当第二正极活性材料中Zr的含量过低时，不足以维持锂离子电池生命周期内的焊接区域附近的极片稳定性，使得锂离子电池循环后析锂风险增加，有掉粉现象出现；通过调控第二正极活性材料中Zr含量在本申请范围内，锂离子电池的安全性能和 能量密度得到提高。
表2
Figure PCTCN2022120528-appb-000003
从实施例1-5、实施例1-9、实施例2-1至实施例2-7可以看出，通过调控B、A、T、S之间满足关系式B/T×A＜S，有利于改善锂离子电池正极极耳的抗脱落能力，降低了负极极片的析锂风险，从而提高锂离子电池的安全性能。
第二正极活性材料的Dv50、正极集流体的厚度、正极连接部与正极集流体之间的焊接强度通常会影响锂离子电池的安全性能，从实施例1-5、实施例1-9以及实施例2-1至实施例2-7可以看出，通过调控上述参数在本申请范围内，能够得到具有良好安全性能的锂离子电池。
正极极耳和正极集流体的导热系数通常会影响正极极片的散热性能。从实施例1-9、实施例2-8和实施例2-9可以看出，通过调控正极极耳和正极集流体的导热系数在本申请范围内，可以保证及时散热，避免了大量热量累积在焊接区域附近，降低了正极连接部对应的第二正极活性材料层中的粘结剂碳化后失去粘接性，从而改善焊接区域附件对应的负极极片的析锂问题，能够得到具有良好安全性能的锂离子电池。
以上所述仅为本申请的较佳实施例，并不用以限制本申请，凡在本申请的精神和原则之内，所做的任何修改、等同替换、改进等，均应包含在本申请保护的范围之内。

Claims (16)

  1. 一种电化学装置，其包括电极组件，所述电极组件包括正极极片，所述正极极片包括正极集流体和设置在所述正极集流体的第一表面的第一正极活性材料层及设置在所述正极集流体的第二表面的第二正极活性材料层，所述第一表面和所述第二表面为所述正极集流体的相对的两个表面，所述第一正极活性材料层设有显露出所述第一表面的第一凹槽；
    所述正极极片还包括正极极耳，所述正极极耳包括正极连接部，所述正极连接部至少部分位于所述第一凹槽内并与所述第一表面焊接，与所述第一凹槽对应的第二表面被所述第二正极活性材料层覆盖；
    所述第二正极活性材料层包括第二正极活性材料，所述第二正极活性材料包括元素M，所述元素M包括锰、铁、镧、锆或钇中的至少一种；
    基于所述第二正极活性材料的总质量，锰或铁的质量百分含量为D％，0.02≤D≤35.00，镧、锆或钇的质量百分含量为E％，0.02≤E≤0.20。
  2. 根据权利要求1所述的电化学装置，其中，所述正极连接部与所述第一表面通过激光焊接。
  3. 根据权利要求1所述的电化学装置，其中，所述正极连接部与所述第一表面焊接形成焊接部，所述焊接部贯穿所述正极极耳且至少部分穿透所述正极集流体。
  4. 根据权利要求1所述的电化学装置，其中，所述第二正极活性材料的Dv50为Bμm，所述正极连接部与所述正极集流体之间的焊接强度为A N/m，所述正极集流体的厚度为T μm，所述正极集流体的拉伸强度为S MPa，B/T×A＜S。
  5. 根据权利要求4所述的电化学装置，其中，0.5≤B≤18，5≤A≤50，4≤T≤14，50≤S≤500。
  6. 根据权利要求1所述的电化学装置，其中，所述正极集流体的导热系数为30W·m -1·K -1至400W·m -1·K -1，所述正极极耳的导热系数为30W·m -1·K -1至400W·m -1·K -1。
  7. 根据权利要求1所述的电化学装置，其中，所述正极集流体的导热系数为200W·m -1·K -1至250W·m -1·K -1，所述正极极耳的导热系数范围为200W·m -1·K -1至250W·m -1·K -1。
  8. 根据权利要求1所述的电化学装置，其中，所述电化学装置包括包装袋，所述电极组件容纳在所述包装袋中，所述第一表面朝向所述包装袋。
  9. 根据权利要求1所述的电化学装置，其中，所述电极组件还包括负极极片和设置于所述正极极片和所述负极极片之间的隔膜，所述正极极片、所述隔膜和所述负极极片层叠设置，与所述第一凹槽对应的第二表面上的第二正极活性材料层与所述隔膜相接触。
  10. 根据权利要求9所述的电化学装置，其中，所述负极极片包括负极集流体和设置在所述负极集流体的两个表面的负极活性材料层，所述负极集流体的两个表面上的所述负极活性材料层均设有显露出所述负极集流体的表面的第二凹槽，所述负极集流体一侧的第二凹槽与所述负极集流体另一侧的第二凹槽相对设置；
    所述负极极片还包括负极极耳，所述负极极耳包括负极连接部，所述负极连接部至少部分位于所述第二凹槽内并与所述负极集流体焊接，所述焊接包括超声焊接或者电阻焊接；所述负极活性材料层包括石墨。
  11. 根据权利要求1所述的电化学装置，其中，第一正极活性材料层包括第一正极活性材料、第一粘结剂和第一导电剂，所述第二正极活性材料层还包括第二粘结剂和第二导电剂；
    所述第一正极活性材料或所述第二正极活性材料包括钴酸锂、镍钴锰酸锂、镍钴铝酸锂、锰酸锂、磷酸铁锂、磷酸锰铁锂或富锂锰基氧化物中的至少一种；
    所述第一粘结剂或所述第二粘结剂包括聚偏二氟乙烯、偏氟乙烯-氟化烯烃的共聚物、聚乙烯吡咯烷酮、聚丙烯腈、聚丙烯酸甲酯、聚四氟乙烯、羧甲基纤维素钠、丁苯橡胶、聚氨酯、氟化橡胶或聚乙烯醇中的至少一种；
    所述第一导电剂或所述第二导电剂包括导电炭黑、碳纳米管、导电石墨、石墨烯或纳米碳纤维中的至少一种。
  12. 根据权利要求1所述的电化学装置，其中，所述第二正极活性材料层包括层叠设置的第一层和第二层，所述第一层位于所述正极集流体和所述第二层之间，所述第二层包括所述第二正极活性材料，所述第一层包括陶瓷材料、第三粘结剂和第三导电剂；
    所述陶瓷材料包括二氧化铪、钛酸锶、二氧化锡、氧化铯、氧化镁、氧化镍、氧化钙、氧化钡、氧化锌、氧化锆、氧化钇、三氧化二铝、氧化钛、二氧化硅、勃姆石、氢氧化镁或氢氧化铝中的至少一种；
    所述第三粘结剂包括聚偏二氟乙烯、偏氟乙烯-氟化烯烃的共聚物、聚乙烯吡咯烷酮、聚丙烯腈、聚丙烯酸甲酯、聚四氟乙烯、羧甲基纤维素钠、丁苯橡胶、聚氨酯、氟化橡胶或聚乙烯醇中的至少一种；
    所述第三导电剂包括导电炭黑、碳纳米管、导电石墨、石墨烯或纳米碳纤维中的至少一种。
  13. 根据权利要求12所述的电化学装置，其中，所述第一层还包括磷酸铁锂。
  14. 一种电化学装置的制备方法，包括：
    提供正极集流体，在所述正极集流体的第一表面设置第一正极活性材料层，在所述正极集流体的第二表面设置第二正极活性材料层，所述第一表面和所述第二表面为所述正极集流体的相对的两个表面，所述第一正极活性材料层设置有显露所述第一表面的第一凹槽；
    提供正极极耳，将所述正极极耳焊接于所述第一凹槽显露的第一表面，使得所述正极极耳的正极连接部与所述第一表面连接，所述第一凹槽对应的第二表面被所述第二正极活性材料层覆盖，所述第二正极活性材料层包括第二正极活性材料，所述第二正极活性材料包括元素M，所述元素M包括锰、铁、镧、锆或钇中的至少一种，基于所述第二正极活性材料的总质量，锰或铁的质量百分含量为D％，0.02≤D≤35.00，镧、锆或钇的质量百分含量为E％，0.02≤E≤0.20。
  15. 根据权利要求14所述的制备方法，其中，用激光照射所述正极连接部使得所述正极连接部与所述第一表面焊接。
  16. 一种电子装置，其包括权利要求1至13任一项所述的电化学装置。
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