WO2024229731A1 - 二次电池和用电装置 - Google Patents

二次电池和用电装置 Download PDF

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Publication number
WO2024229731A1
WO2024229731A1 PCT/CN2023/093164 CN2023093164W WO2024229731A1 WO 2024229731 A1 WO2024229731 A1 WO 2024229731A1 CN 2023093164 W CN2023093164 W CN 2023093164W WO 2024229731 A1 WO2024229731 A1 WO 2024229731A1
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WIPO (PCT)
Prior art keywords
electrolyte
secondary battery
negative electrode
positive electrode
active material
Prior art date
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PCT/CN2023/093164
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English (en)
French (fr)
Inventor
陈兴布
尹子伊
董苗苗
凌洋芳
吴李力
宋佩东
孙信
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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Priority to PCT/CN2023/093164 priority Critical patent/WO2024229731A1/zh
Priority to CN202380061820.9A priority patent/CN119731833A/zh
Priority to EP23936055.5A priority patent/EP4648168A4/en
Publication of WO2024229731A1 publication Critical patent/WO2024229731A1/zh
Priority to US19/273,230 priority patent/US20250349970A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • 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
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • 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
    • H01—ELECTRIC ELEMENTS
    • 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
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0565—Polymeric materials, e.g. gel-type or solid-type
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • 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
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • 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
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • 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
    • H01M4/52—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
    • H01—ELECTRIC ELEMENTS
    • 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
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0085—Immobilising or gelification of electrolyte
    • 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 technical field of secondary batteries, and in particular to a secondary battery and a preparation method thereof, and an electrical device.
  • secondary batteries are widely used in energy storage power supply systems such as hydropower, thermal power, wind power and solar power stations, as well as in many fields such as electric tools, electric bicycles, electric motorcycles and electric vehicles.
  • the present application has been made in view of the above-mentioned problems, and one of its objects is to provide a secondary battery having a high energy density.
  • the first aspect of the present application provides a secondary battery, comprising:
  • Electrolyte the amount of electrolyte in the secondary battery is 0.8g/Ah to 1.5g/Ah.
  • the electrolyte includes electrolyte solution.
  • the amount of electrolyte solution outside the bare cell of the secondary battery is ⁇ 0.1g/Ah.
  • the positive electrode and negative electrode of the secondary battery of the present application adopt a high compaction density; adopt an extremely low total amount of electrolyte, and minimize the bare cell external battery in the electrolyte that does not contribute to the capacity.
  • a separator is provided between the positive electrode sheet and the negative electrode sheet, a first highly liquid-absorbent polymer layer is provided on the surface of the separator, and the equilibrium swelling rate of the highly liquid-absorbent polymer in the first highly liquid-absorbent polymer layer is 150% to 300%.
  • the liquid retention capacity between the separator and the electrode sheet can be further improved, the electrolyte can be further concentrated inside the bare battery cell, and the energy density of the secondary battery can be improved.
  • a second highly liquid-absorbent polymer layer is provided on the surface of the positive electrode sheet and/or the negative electrode sheet, and the equilibrium swelling rate of the highly liquid-absorbent polymer in the second highly liquid-absorbent polymer layer is 150% to 300%. In this way, the energy density of the secondary battery can be further improved.
  • the coating weight of the highly liquid-absorbing polymer is 0.1 mg/cm 2 to 1.4 mg/cm 2 . In this way, the liquid retention requirements of the positive electrode sheet and the negative electrode sheet can be well met.
  • the coating weight of the highly liquid-absorbent polymer is 0.1 mg/cm 2 to 1.0 mg/cm 2 .
  • the superabsorbent polymer includes one or more of polyacrylate electrolytes, polyether electrolytes, polycarbonate electrolytes, polycarboxylate electrolytes, silicon-based electrolytes, polythiol electrolytes, maleic anhydride electrolytes, and polysulfate electrolytes.
  • the electrolyte further comprises a gel electrolyte, and the mass ratio of the gel electrolyte to the electrolyte is 1:(0.05-0.4). In this way, the electrolyte can be better locked in the bare cell, reducing the extrusion of the electrolyte due to the charging expansion of the high silicon pole piece.
  • the mass ratio of the gel electrolyte to the electrolyte solution is 1:(0.05 to 0.25).
  • the monomers forming the gel electrolyte include one or more of methyl methacrylate, methyl acrylate, ethyl methacrylate, ethyl acrylate, n-butyl methacrylate, butyl acrylate, n-octyl methacrylate, n-octyl acrylate, vinyl acetate, vinylene carbonate, vinylethylene carbonate, triethylene glycol dimethacrylate, diethylene glycol dimethacrylate, ethylene glycol dimethacrylate, allyl methacrylate, divinylbenzene, polyvinyl alcohol and styrene.
  • the initiator for forming the gel electrolyte includes one or more of a persulfate, an azo initiator, and an organic peroxide initiator.
  • the coating weight of the positive electrode active material is 25 mg/cm 2 to 35 mg/cm 2 . In this way, the energy density of the secondary battery can be further improved.
  • the compaction density of the positive electrode sheet is 3.5 g/cm 3 to 3.7 g/cm 3 . In this way, the total amount of electrolyte required in the positive electrode film layer can be further reduced, and the energy density of the secondary battery can be further improved.
  • the coating weight of the negative electrode active material is 7 mg/cm 2 to 10.5 mg/cm 2 . In this way, the energy density of the secondary battery can be further improved.
  • the compaction density of the negative electrode sheet is 1.6 g/cm 3 to 1.8 g/cm 3 . In this way, the total amount of electrolyte required in the negative electrode film layer can be further reduced, and the energy density of the secondary battery can be further improved.
  • the amount of electrolyte in the secondary battery is 0.9 g/Ah to 1.4 g/Ah. In this way, while meeting the required amount of electrolyte in the pores of the positive electrode sheet and the negative electrode sheet during charging and discharging, the energy density of the secondary battery is further improved.
  • the mass fraction of the silicon-based material in the negative electrode active material is 40% to 100%. In this way, the energy density of the secondary battery can be further improved.
  • a second aspect of the present application provides an electrical device, comprising the secondary battery of the first aspect of the present application.
  • the positive electrode plate and the negative electrode plate adopt a higher compaction density; an extremely low amount of electrolyte is used, and the amount of electrolyte outside the bare cell that does not contribute to the capacity is minimized; combined with a high-nickel ternary positive electrode material, a high-silicon negative electrode active material and a larger active material coating weight; the secondary battery can have a higher energy density.
  • FIG1 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG2 is an exploded view of the secondary battery of one embodiment of the present application shown in FIG1 ;
  • FIG. 3 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.
  • Secondary battery 51. Casing; 52. Electrode assembly; 53. Cover plate; 6. Electrical device.
  • range disclosed in the present application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range.
  • the range defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that a range of 60 to 110 and 80 to 120 is also expected.
  • the numerical range "a to b" represents an abbreviation of any real number combination between a and b, where a and b are both real numbers.
  • the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations.
  • a parameter is expressed as an integer ⁇ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.
  • the method includes steps (a) and (b), which means that the method The method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • the reference that the method may also include step (c) indicates that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.
  • the “include” and “comprising” mentioned in this application are open-ended or closed-ended.
  • the “include” and “comprising” may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.
  • the term "or” is inclusive.
  • the phrase “A or B” means “A, B, or both A and B”. More specifically, any of the following conditions satisfies the condition "A or B”: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).
  • the weight described in this application specification may be ⁇ g, mg, g, kg or other weight units known in the chemical industry.
  • the first aspect of the present application provides a secondary battery, comprising:
  • Electrolyte the amount of electrolyte in the secondary battery is 0.8g/Ah to 1.5g/Ah.
  • the electrolyte includes electrolyte solution.
  • the amount of electrolyte solution outside the bare cell of the secondary battery is ⁇ 0.1g/Ah.
  • the positive electrode and the negative electrode adopt a higher compaction density, which can reduce the electrolyte filling demand in the pores of the electrode film layer, and at the same time can reduce the interface contact between the active material and the electrolyte, reduce the side reaction between the active material and the electrolyte, and reduce the total electrolyte demand; adopt an extremely low total amount of electrolyte, and try to reduce the amount of electrolyte outside the bare battery cell that does not contribute to the capacity; adopt high-nickel ternary positive electrode materials, high-silicon negative electrode active materials and a large coating weight; through the combination of the above technical means, the secondary battery can have a higher energy density, and its energy density can reach more than 400Wh/kg.
  • the secondary battery does not need to use a lithium metal negative electrode with high activity and poor stability to increase the battery energy density, which can make the secondary battery have better stability.
  • the amount of electrolyte in a secondary battery includes the amount of electrolyte and the amount of gel electrolyte; wherein the electrolyte includes the electrolyte inside the bare cell and the electrolyte outside the bare cell.
  • Disassemble the secondary battery take out the bare cell, and weigh the remaining electrolyte in the battery casing to obtain the amount of electrolyte outside the bare cell; disassemble the bare cell, take out the gel electrolyte and electrolyte inside and weigh them; add the amount of gel electrolyte, the amount of electrolyte inside the bare cell, and the amount of electrolyte outside the bare cell to get the amount of electrolyte in the secondary battery.
  • the electrolyte outside the bare cell refers to the electrolyte that is free outside the bare cell, and this part of the electrolyte has no effect on the capacity of the secondary battery; therefore, in order to increase the energy density of the secondary battery, the proportion of the electrolyte outside the bare cell in the electrolyte should be reduced as much as possible.
  • the charging and discharging process of the secondary battery is accompanied by the deintercalation and consumption of Li, and the molar content of Li in the secondary battery will change when it is discharged to different states; in this application, the value range of a in the positive electrode active material LiaNixCoyMzO2 is limited to include the molar content of Li in different charging and discharging states of the secondary battery (usually the battery voltage is between 2V and 5V).
  • the coating weight of the positive electrode active material in the positive electrode sheet can be, but is not limited to , 19 mg/cm 2 , 20 mg/cm 2 , 22 mg/cm 2 , 24 mg/cm 2 , 26 mg/cm 2 , 28 mg/cm 2 , 30 mg/cm 2 , 32 mg/cm 2 , 34 mg/cm 2 , 36 mg/cm 2 , 38 mg/cm 2 , 40 mg/cm 2 , 42 mg/cm 2 , 44 mg/cm 2 , 45 mg/cm 2 ;
  • the compaction density of the positive electrode sheet can be, but is not limited to, 3.2 g/cm 3 , 3.3 g/cm 3 , 3.4 g/cm 3 , 3.5 g/cm 3 , 3.6 g/cm 3 , 3.7 g/cm 3 , 3.8 g/cm 3 ;
  • the mass fraction of the silicon-based material in the negative electrode active material can be,
  • the coating weight of the positive electrode active material is 25mg/ cm2 to 35mg/ cm2 . If the coating weight of the positive electrode active material in the positive electrode sheet is too low, the proportion of the active material will be reduced, and the weight proportion of the substrate, shell, auxiliary materials, etc. in the battery will be relatively increased, which will reduce the weight energy density of the battery; if the coating weight is too large, the positive electrode film layer will be too thick, and it will be difficult to achieve the set compaction density. Controlling the coating weight of the positive electrode active material within the range of 25mg/ cm2 to 35mg/ cm2 can further improve the energy density of the secondary battery.
  • the compaction density of the positive electrode sheet is 3.5 g/cm 3 to 3.7 g/cm 3 . In this way, the total amount of electrolyte required in the positive electrode film layer can be further reduced, and the energy density of the secondary battery can be further improved.
  • the coating weight of the negative electrode active material in the negative electrode sheet is 7 mg/cm 2 to 10.5 mg/cm 2 , which can further improve the energy density of the secondary battery.
  • the compaction density of the negative electrode sheet is 1.6 g/cm 3 to 1.8 g/cm 3 . In this way, the total amount of electrolyte required in the negative electrode film layer can be further reduced, and the energy density of the secondary battery can be further improved.
  • the amount of electrolyte in the secondary battery is 0.9 g/Ah to 1.4 g/Ah. In this way, while meeting the required amount of electrolyte in the pores of the positive electrode sheet and the negative electrode sheet during the charge and discharge process, the total amount of electrolyte is further reduced, thereby further improving the energy density of the secondary battery.
  • the mass fraction of the silicon-based material in the negative electrode active material is 40% to 100%.
  • a higher proportion of silicon-based material in the negative electrode active material can further improve the energy density of the secondary battery.
  • the secondary battery further includes a separator, which is disposed between the positive electrode sheet and the negative electrode sheet, and a distance between the separator and the positive electrode sheet is 0 ⁇ m to 20 ⁇ m.
  • a separator which is disposed between the positive electrode sheet and the negative electrode sheet, and a distance between the separator and the positive electrode sheet is 0 ⁇ m to 20 ⁇ m.
  • the spacing between the separator and the negative electrode plate is 0 ⁇ m to 20 ⁇ m. In this way, enough electrolyte can be filled between the negative electrode plate and the separator to better meet the liquid retention filling requirements of the negative electrode film layer, and the electrolyte can be further concentrated inside the bare cell, further reducing the amount of electrolyte outside the bare cell, thereby further improving the energy density of the secondary battery.
  • the spacing between the separator and the positive electrode sheet, and the spacing between the separator and the negative electrode sheet can be controlled by adjusting the winding tension when the positive electrode sheet, the separator and the negative electrode sheet are stacked and wound to form an electrode assembly.
  • the tension during winding of the pole piece can be appropriately increased; when it is necessary to increase the distance between the pole piece and the separator, the tension during winding of the pole piece can be appropriately reduced.
  • the winding tension is small, the distance between the pole piece and the separator after winding will be relatively large, which can accommodate more electrolyte; but if the winding tension is too small, the distance between the pole piece and the separator will be too large, affecting the dynamics of the battery and increasing the risk of lithium deposition. Therefore, it is necessary to control the size of the winding tension within an appropriate range so that the distance between the pole piece and the separator is within the set range.
  • a first highly liquid-absorbent polymer layer is further provided on the surface of the separator, and the equilibrium swelling rate of the highly liquid-absorbent polymer in the first highly liquid-absorbent polymer layer is 150% to 300%.
  • a second highly liquid-absorbent polymer layer is disposed on the surface of the positive electrode sheet and/or the negative electrode sheet, and the equilibrium swelling rate of the highly liquid-absorbent polymer in the second highly liquid-absorbent polymer layer is 150% to 300%.
  • the highly liquid-absorbent polymer on the surface of the positive electrode sheet and/or the negative electrode sheet, the liquid-retaining capacity between the separator and the electrode sheet in the bare cell can also be further improved, so that the electrolyte is further concentrated inside the bare cell, and the amount of electrolyte outside the bare cell is further reduced, thereby further improving the energy density of the secondary battery.
  • the above-mentioned highly liquid-absorbent polymer can be arranged only on one side surface of the isolation membrane, can be arranged on both opposite sides of the isolation membrane, can be arranged only on the surface of the positive electrode plate or the negative electrode plate, can be arranged on the surfaces of both the positive electrode plate and the negative electrode plate, and can also be arranged on the surface of both the isolation membrane and the surface of the electrode plate.
  • the equilibrium swelling rate of the super absorbent polymer can reflect the liquid retention capacity of the super absorbent polymer.
  • the coating weight of the highly liquid-absorbent polymer is 0.1 mg/cm 2 to 1.4 mg/cm 2. Controlling the coating weight of the highly liquid-absorbent polymer between 0.1 mg/cm 2 and 1.4 mg/cm 2 can well meet the liquid retention requirements of the positive electrode sheet and the negative electrode sheet.
  • the coating weight of the highly liquid-absorbent polymer can be, but is not limited to, 0.1 mg/cm 2 , 0.2 mg/cm 2 , 0.3 mg/cm 2 , 0.4 mg/cm 2 , 0.5 mg/cm 2 , 0.6 mg/cm 2 , 0.7 mg/cm 2 , 0.8 mg/cm 2 , 0.9 mg/cm 2 , 1.0 mg/cm 2 , 1.1 mg/cm 2 , 1.2 mg/cm 2 , 1.3 mg/cm 2 , and 1.4 mg/cm 2 .
  • the coating weight of the highly liquid-absorbent polymer is 0.1 mg/cm 2 to 1.0 mg/cm 2 . In this way, the amount of highly liquid-absorbent polymer can be further reduced while meeting the liquid retention requirements of the positive electrode sheet and the negative electrode sheet.
  • the highly liquid-absorbent polymer can be dissolved in an organic solvent such as acetone, and then the polymer can be coated on the surface of the isolation membrane or the electrode by spraying, dipping, roller coating, etc., thereby forming a coating of the highly liquid-absorbent polymer on the isolation membrane or the electrode.
  • an organic solvent such as acetone
  • the superabsorbent polymer includes one or more of polyacrylate electrolytes, polyether electrolytes, polycarbonate electrolytes, polycarboxylate electrolytes, silicon-based electrolytes, polythiol electrolytes, maleic anhydride electrolytes, and polysulfate electrolytes.
  • the electrolyte also includes a gel electrolyte, and the mass ratio of the gel electrolyte to the electrolyte is 1: (0.05-0.4).
  • the electrolyte's ability to retain liquid inside the bare cell and in the pores of the electrode film layer can be further enhanced, the electrolyte can be better locked in the bare cell, and the electrolyte can be squeezed out due to the charging and expansion of the high-silicon electrode.
  • the electrode interface wetting can be improved, and the capacity and other electrical properties of the gel electrolyte can be improved.
  • the mass ratio of gel electrolyte to electrolyte in the electrolyte can be but is not limited to 1:0.05, 1:0.08, 1:0.10, 1:0.12, 1:0.14, 1:0.16, 1:0.18, 1:0.20, 1:0.22, 1:0.24, 1:0.26, 1:0.28, 1:0.30, 1:0.32, 1:0.34, 1:0.36, 1:0.38, 1:0.40.
  • the mass ratio of the gel electrolyte to the electrolyte is 1:(0.05-0.25). In this way, the electrolyte's ability to retain liquid inside the bare cell and in the pores of the electrode film layer can be further enhanced, and the electrolyte can be better locked in the bare cell.
  • a certain amount of polymer monomers and initiators can be added to the electrolyte when the secondary battery is injected, and the polymer monomers are initiated to polymerize in situ under heating conditions to form a gel electrolyte. It is understood that the content of the gel electrolyte in the electrolyte can be adjusted and controlled by the amount of polymer monomers and initiators added to the electrolyte during injection.
  • the monomers forming the gel electrolyte include one or more of methyl methacrylate, methyl acrylate, ethyl methacrylate, ethyl acrylate, n-butyl methacrylate, butyl acrylate, n-octyl methacrylate, n-octyl acrylate, vinyl acetate, vinylene carbonate, vinylethylene carbonate, triethylene glycol dimethacrylate, diethylene glycol dimethacrylate, ethylene glycol dimethacrylate, allyl methacrylate, divinylbenzene, polyvinyl alcohol and styrene.
  • the initiator for forming the gel electrolyte includes one or more of a persulfate, an azo initiator, and an organic peroxide initiator.
  • a second aspect of the present application provides an electrical device, which includes the secondary battery of the first aspect of the present application.
  • the components, material types or contents of the batteries mentioned are applicable to both lithium-ion secondary batteries and sodium-ion secondary batteries.
  • a secondary battery is provided.
  • a secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator.
  • active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet.
  • the electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet.
  • the separator is set between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.
  • the positive electrode plate includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector.
  • the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • aluminum foil may be used as the metal foil.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector may be formed by forming a metal material on a polymer material substrate.
  • the metal material includes but is not limited to aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.
  • Polymer material substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • the positive electrode active material includes a high-nickel ternary positive electrode material; the coating weight of the positive electrode active material is 19 mg/cm 2 to 45 mg/cm 2 , and the compaction density of the positive electrode sheet is 3.2 g/cm 3 to 3.8 g/cm 3 ;
  • the weight ratio of the positive electrode active material in the positive electrode film layer is 80 to 100 weight %, based on the total weight of the positive electrode film layer.
  • the positive electrode film layer may also optionally include a binder.
  • the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE polytetrafluoroethylene
  • the weight ratio of the binder in the positive electrode film layer is 0 to 20 weight%, based on the total weight of the positive electrode film layer.
  • the positive electrode film layer may also optionally include a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the weight ratio of the conductive agent in the positive electrode film layer is 0-20 weight %, based on the total weight of the positive electrode film layer.
  • the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry, wherein the positive electrode slurry has a solid content of 40 mass percent (wt%) to 80wt%, and the viscosity at room temperature is adjusted to 5000 millipascals ⁇ seconds (mPa ⁇ s) to 25000 mPa ⁇ s, the positive electrode slurry is coated on the surface of the positive electrode collector, and after drying, the positive electrode sheet is formed by cold rolling; the compacted density of the positive electrode sheet is 3.2 grams/cubic centimeter (g/cm 3 ) to 3.8g/cm 3 , and can be optionally 3.5g/cm 3 to 3.7g/cm 3 .
  • a solvent such as N-methylpyrrolidone
  • Compacted density coating surface density/(thickness of the electrode after extrusion - thickness of the current collector).
  • the mass M of the positive electrode active material per unit area of the positive electrode film can be obtained by weighing using a standard balance.
  • the thickness T of the positive electrode film can be measured by using a micrometer, for example, a Mitutoyo 293-100 micrometer with an accuracy of 0.1 ⁇ m. It should be noted that the thickness of the positive electrode film described in this application refers to the thickness of the positive electrode film in the positive electrode sheet used for assembling the battery after cold pressing.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • copper foil may be used as the metal foil.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate.
  • the composite current collector may be formed by forming a metal material on a polymer material substrate.
  • the metal material includes but is not limited to copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.
  • the polymer material substrate includes but is not limited to polypropylene (PP), polyethylene terephthalate (PET ...PP), polyethylene terephthalate (PET), polyethylene terephthalate (PET), polyethylene terephthalate (PP), polyethylene terephthalate (PET), polyethylene terephthalate (PET), polyethylene terephthalate (PET), polyethylene terephthalate (PP), polyethylene terephthalate (PET), polyethylene terephthalate (PET), polyethylene terephthalate (PET), polyethylene terephthalate (PET), polyethylene terephthalate (PET), polyethylene terephthalate (PP), polyethylene terephthalate (PET), polyethylene terephthalate (PET), polyethylene terephthalate (PET), polyethylene terephthalate (PP), polyethylene terephthalate (PET), Polyethylene terephthalate (PET), Polyethylene terephthalate (PET), Polyethylene terephthal
  • the negative electrode active material may be a negative electrode active material for a battery known in the art.
  • the negative electrode active material of the lithium ion secondary battery includes a silicon-based material, and may also include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, tin-based materials, lithium titanate, etc.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys.
  • the tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used.
  • the negative electrode film layer may further include a binder.
  • the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • SBR styrene-butadiene rubber
  • PAA polyacrylic acid
  • PAAS sodium polyacrylate
  • PAM polyacrylamide
  • PVA polyvinyl alcohol
  • SA sodium alginate
  • PMAA polymethacrylic acid
  • CMCS carboxymethyl chitosan
  • the negative electrode film layer may further include a conductive agent.
  • the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the weight ratio of the conductive agent in the negative electrode film layer is 0 to 20 weight %, based on the total weight of the negative electrode film layer.
  • the negative electrode film layer may further include other additives, such as a thickener (such as sodium carboxymethyl cellulose (CMC-Na)), etc.
  • a thickener such as sodium carboxymethyl cellulose (CMC-Na)
  • the weight ratio of the other additives in the negative electrode film layer is 0 to 15 weight %, based on the total weight of the negative electrode film layer.
  • the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry, wherein the solid content of the negative electrode slurry is 30wt% to 70wt%, and the viscosity at room temperature is adjusted to 2000mPa ⁇ s to 10000mPa ⁇ s; the obtained negative electrode slurry is coated on the negative electrode current collector, and after a drying process, cold pressing such as rolling, a negative electrode sheet is obtained.
  • the compacted density of the negative electrode sheet is 1.1 grams per cubic meter (g/m 3 ) to 1.9g/m 3 .
  • the mass M of the negative electrode active material per unit area of the negative electrode membrane can be obtained by weighing using a standard balance.
  • the thickness T of the negative electrode film can be measured by using a micrometer, for example, a Mitutoyo 293-100 micrometer with an accuracy of 0.1 ⁇ m. It should be noted that the thickness of the negative electrode film described in this application refers to the thickness of the negative electrode film in the negative electrode sheet used for assembling the battery after cold pressing.
  • the electrolyte plays the role of conducting ions between the positive electrode and the negative electrode.
  • the present application has no specific restrictions on the type of electrolyte, which can be selected according to needs.
  • the electrolyte can be liquid, gel or all-solid.
  • the electrolyte includes an electrolyte solution.
  • the electrolyte solution includes an electrolyte salt and a solvent.
  • the electrolyte salt of the lithium ion secondary battery can be selected from one or more of lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium bisoxalatoborate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), lithium difluorobisoxalatophosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).
  • LiPF 6 lithium hexafluorophosphate
  • the electrolyte salt of the sodium ion secondary battery can be selected from one or more of sodium hexafluorophosphate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, sodium trifluoromethanesulfonate, sodium tetrafluoroborate, sodium difluorophosphate, sodium perchlorate, and sodium chloride.
  • the concentration of the electrolyte salt is generally 0.5 mol/L to 5 mol/L.
  • the solvent can be selected from one or more of fluoroethylene carbonate (FEC), ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS) and diethyl sulfone (FEC),
  • the electrolyte may also optionally include an additive.
  • the additive may It may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.
  • the electrolyte further comprises a gel electrolyte.
  • the secondary battery further includes a separator.
  • the present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation.
  • the materials of each layer can be the same or different, without particular limitation.
  • the isolation film has a thickness of 6 ⁇ m to 40 ⁇ m, and may be 12 ⁇ m to 20 ⁇ m.
  • the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.
  • the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery may also be a soft package, such as a bag-type soft package.
  • the material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.
  • FIG1 is a secondary battery 5 of a square structure as an example.
  • the outer package may include a shell 51 and a cover plate 53.
  • the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate are enclosed to form a receiving cavity.
  • the shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity.
  • the positive electrode sheet, the negative electrode sheet and the isolation film can be formed into an electrode assembly 52 by a winding process or a lamination process.
  • the electrode assembly 52 is encapsulated in the receiving cavity.
  • the electrolyte is infiltrated into the electrode assembly. 52.
  • the number of the electrode assembly 52 included in the secondary battery 5 can be one or more, and those skilled in the art can select one according to specific practical needs.
  • the secondary batteries 5 can be assembled into a battery module.
  • the number of secondary batteries 5 contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.
  • the plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module. Of course, they may also be arranged in any other manner. Further, the plurality of secondary batteries 5 may be fixed by fasteners.
  • the battery module may further include a housing having a housing space, and the plurality of secondary batteries 5 are housed in the housing space.
  • the battery modules described above may also be assembled into a battery pack.
  • the battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.
  • the battery pack may include a battery box and a plurality of battery modules disposed in the battery box.
  • the battery box includes an upper box body and a lower box body, and the upper box body can be covered on the lower box body to form a closed space for accommodating the battery modules.
  • the plurality of battery modules can be arranged in the battery box in any manner.
  • the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application.
  • the secondary battery, battery module, or battery pack can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device.
  • the electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.
  • a secondary battery, a battery module or a battery pack may be selected according to its usage requirements.
  • FIG3 is an example of an electric device.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • a battery pack or a battery module may be used.
  • the device may be a mobile phone, a tablet computer, a laptop computer, etc.
  • the device is usually required to be thin and light, and a secondary battery can be used as a power source.
  • the positive electrode active material LiaNixCoyMzO2 , the conductive agent superconducting carbon SP, and the binder PVDF are fully stirred and mixed in N- methylpyrrolidone solvent at a weight ratio of 98:1:1 to obtain a positive electrode slurry, and the positive electrode slurry is coated on the positive electrode current collector aluminum foil, dried, and cold pressed to obtain a positive electrode sheet.
  • the coating weight of the positive electrode active material is 30mg/ cm2
  • the compaction density of the positive electrode sheet is 3.5g/ cm3 .
  • the negative electrode active material graphite + silicon oxide, the conductive agent carbon nanotube + superconducting carbon, the binder styrene butadiene rubber SBR, and the thickener sodium carboxymethyl cellulose CMC are fully stirred and mixed in deionized water at a mass ratio of 94:2:3:1 to obtain a negative electrode slurry, and the negative electrode slurry is coated on the negative electrode current collector copper foil, dried, and cold pressed to obtain a negative electrode sheet.
  • the mass fraction of silicon-based material in the negative electrode active material is 40%, the coating weight of the negative electrode active material is 9mg/ cm2 , and the compaction density of the negative electrode sheet is 1.7g/ cm3 .
  • PE Polyethylene
  • the positive electrode sheet, the separator and the negative electrode sheet are stacked and wound to form a bare cell, and the bare cell is placed in an outer package to obtain a dry cell.
  • the spacing between the positive electrode sheet and the separator is adjusted to 20 ⁇ m, and the spacing between the negative electrode sheet and the separator is adjusted to 20 ⁇ m by controlling the tension during the winding of the electrode sheet.
  • the dry battery cell is injected with liquid in two times, and the mass ratio of the first injection to the second injection is 9:1.
  • the electrolyte raw material components of the first injection are: electrolyte mother liquor, monomer, initiator, with a mass ratio of 94.5:5:0.5; the organic solvent of the electrolyte mother liquor is a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC); the volume ratio of EC, EMC and DEC is 20:20:60; the lithium salt of the electrolyte mother liquor is LiPF 6 , with a concentration of 1 mol/L; the monomer is ethylene glycol dimethacrylate, and the initiator is azobis(ethylbutylnitrile) (AIBN).
  • AIBN azobis(ethylbutylnitrile)
  • the electrolyte for the secondary injection is only the mother electrolyte. After the primary injection, it is vacuum packaged, left to soak, and heated to polymerize the polymer monomers in the electrolyte raw materials to form a gel electrolyte, and then the mother electrolyte for the secondary injection is injected.
  • the total electrolyte amount of the battery cell is 1.3g/Ah
  • the mass ratio of the gel electrolyte to the liquid electrolyte in the electrolyte after heating and polymerization is 1:0.11
  • the amount of electrolyte outside the bare battery cell in the electrolyte is 0.05g/Ah.
  • This embodiment is basically the same as the embodiment 1, except that the high nickel ternary positive electrode material is different and the coating weight of the positive electrode active material is different.
  • This embodiment is basically the same as embodiment 1, except that the coating weight of the positive active material in the positive electrode sheet is different, and the coating weight of the negative active material in the negative electrode sheet is different.
  • the coating weight of the positive active material is 25 mg/cm 2
  • the coating weight of the negative active material is 7.5 mg/cm 2 .
  • This embodiment is basically the same as embodiment 1, except that the coating weight of the positive electrode active material in the positive electrode sheet is different, and the coating weight of the negative electrode active material in the negative electrode sheet is different.
  • the coating weight of the positive electrode active material was 35 mg/cm 2
  • the coating weight of the negative electrode active material was 10.5 mg/cm 2 .
  • This embodiment is basically the same as embodiment 1, except that the coating weight of the positive active material in the positive electrode sheet is different, and the coating weight of the negative active material in the negative electrode sheet is different.
  • the coating weight of the positive active material is 40 mg/cm 2
  • the coating weight of the negative active material is 12 mg/cm 2 .
  • This embodiment is basically the same as the embodiment 1, and the only difference is that the compaction density of the positive electrode sheet is different.
  • the compaction density of the positive electrode sheet in this embodiment is 3.7 g/cm 3 .
  • This embodiment is basically the same as the embodiment 1, and the only difference is that the compaction density of the positive electrode sheet is different.
  • the compaction density of the positive electrode sheet in this embodiment is 3.8 g/cm 3 .
  • This embodiment is basically the same as the embodiment 1, except that the coating weight of the negative electrode active material in the negative electrode sheet is different.
  • the coating weight of the negative electrode active material in this embodiment is 13 mg/cm 2 .
  • This embodiment is basically the same as the embodiment 1, and the only difference is that the compaction density of the negative electrode sheet is different.
  • the compaction density of the negative electrode sheet in this embodiment is 1.6 g/cm 3 .
  • This embodiment is basically the same as the embodiment 1, and the only difference is that the compaction density of the negative electrode sheet is different.
  • the compaction density of the negative electrode sheet in this embodiment is 1.8 g/cm 3 .
  • This embodiment is basically the same as the embodiment 1, except that the amount of electrolyte in the secondary battery is different.
  • the amount of electrolyte in this embodiment is 0.9 g/Ah.
  • This embodiment is basically the same as the embodiment 1, except that the amount of electrolyte in the secondary battery is different.
  • the amount of electrolyte in this embodiment is 1.4 g/Ah.
  • This embodiment is basically the same as embodiment 1, except that the amount of electrolyte in the secondary battery is different and the amount of electrolyte outside the bare cell is different.
  • the amount of electrolyte is 1.35 g/Ah, and the amount of electrolyte outside the bare cell is 0.1 g/Ah.
  • This embodiment is basically the same as the embodiment 1, except that: in this embodiment, polycarbonate diol super absorbent polymer is coated on both the positive electrode plate and the negative electrode plate, the coating weight of the super absorbent polymer on the positive electrode plate is 0.5 mg/cm 2 , and the coating weight of the super absorbent polymer on the negative electrode plate is 0.5 mg/cm 2 .
  • the equilibrium liquid absorption rate of the super absorbent polymer is 200%.
  • This embodiment is basically the same as the embodiment 1, and the only difference is that the distance between the separator and the positive electrode plate is different. In this embodiment, the distance between the separator and the positive electrode plate is 20 ⁇ m.
  • This embodiment is basically the same as the embodiment 1, and the only difference is that the distance between the separator and the negative electrode plate is different. In this embodiment, the distance between the separator and the negative electrode plate is 20 ⁇ m.
  • This embodiment is substantially the same as the embodiment 1, except that in this embodiment, a highly liquid-absorbent polymer is coated on the surface of the isolation film, the equilibrium swelling rate of the highly liquid-absorbent polymer is 200%, and the coating weight of the highly liquid-absorbent polymer is 0.5 mg/cm 2 .
  • This embodiment is basically the same as embodiment 17, except that the coating weight of the highly liquid-absorbent polymer on the surface of the isolation membrane is different.
  • the coating weight of the highly liquid-absorbent polymer on the surface of the isolation membrane is 1 mg/cm 2 .
  • This embodiment is basically the same as embodiment 17, except that the coating weight of the highly liquid-absorbent polymer on the surface of the isolation membrane is different.
  • the coating weight of the highly liquid-absorbent polymer on the surface of the isolation membrane is 1.4 mg/cm 2 .
  • This embodiment is basically the same as embodiment 1, except that the mass ratio of the gel electrolyte to the free liquid electrolyte in the electrolyte after heating and polymerization is different.
  • the mass ratio of the gel electrolyte to the free liquid electrolyte is 1:0.25.
  • This comparative example is basically the same as Example 1, except that the positive electrode active material used in Comparative Example 1 is different.
  • This comparative example is basically the same as Example 1, except that the coating weight of the positive electrode active material in the positive electrode sheet is different.
  • the coating weight of the positive electrode active material in the positive electrode sheet in Comparative Example 2 is 15 mg/cm 2 .
  • This comparative example is basically the same as Example 1, except that the compaction density of the positive electrode sheet is different.
  • the compaction density of the positive electrode sheet in Comparative Example 3 is 3.1 g/cm 3 .
  • This comparative example is basically the same as Example 1, except that the negative electrode active material in the negative electrode sheet is different.
  • This comparative example is basically the same as Example 1, except that the coating weight of the negative electrode active material in the negative electrode sheet is different.
  • the coating weight of the negative electrode active material in the negative electrode sheet is 15 mg/cm 2 .
  • This comparative example is basically the same as Example 1, except that the compaction density of the negative electrode sheet is different.
  • the compaction density of the negative electrode sheet in Comparative Example 6 is 1.0 g/cm 3 .
  • This comparative example is basically the same as Example 1, except that the amount of electrolyte in the battery cell is different.
  • the amount of electrolyte in the battery cell of Comparative Example 7 is 1.6 g/Ah.
  • This comparative example is basically the same as Example 1, except that the amount of electrolyte outside the bare cell is different.
  • the amount of electrolyte outside the bare cell is 0.2 g/Ah.
  • This comparative example is basically the same as Example 1, except that the mass ratio of the gel electrolyte to the liquid electrolyte in the electrolyte after heating and polymerization is different.
  • the mass ratio of the gel electrolyte to the liquid electrolyte in the electrolyte after heating and polymerization is 1:0, that is, no liquid electrolyte is contained.
  • the bare battery cell is taken out and the remaining electrolyte in the shell is weighed.
  • X-Ray CT is used to photograph and measure the distance between the isolation membrane and the pole piece.
  • the bare cell is retrieved and centrifuged to obtain the free liquid electrolyte in the bare cell, which is then combined with the remaining electrolyte in the shell and weighed to obtain the weight of the liquid electrolyte; the gel electrolyte on the bare cell is scraped off and weighed, and the part that cannot be scraped off is subjected to auxiliary calibration test of the mass of the gel electrolyte using a TG-MS thermogravimetric analyzer.
  • the dried polymer sample is weighed to obtain the dry weight Wd of the polymer
  • the electrolyte includes a solvent and a lithium salt
  • the solvent is a mixed solvent formed by EC, EMC and DEC in a volume ratio of 20:20:60
  • the lithium salt is LiPF 6 with a concentration of 1 mol/L
  • GED ED/M, unit is Wh/kg.
  • Comparative Example 3 and Examples 6 and 7 It can be seen from Comparative Example 3 and Examples 6 and 7 that the greater the positive electrode density, the more layers of active material can be filled in the same shell, and the weight energy density of the battery cell can be improved. However, too much density will destroy the active material particle structure and cause capacity loss, so the density cannot be too large.
  • Comparative Example 4 It can be seen from Comparative Example 4 that the mass proportion of silicon-based materials in the negative electrode is reduced, and the weight energy density is reduced. It can be seen from Comparative Example 5 and Example 8 that under the same positive electrode coating weight, if the coating weight of the negative electrode is too small, the problem of negative electrode lithium precipitation will occur, resulting in capacity loss; when the coating weight of the negative electrode is too large, there will be more ineffective negative electrode active materials, which will reduce the weight energy density, so the negative electrode coating weight needs to be within an appropriate range.

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Abstract

提供一种二次电池，包括：正极极片，其具有正极活性材料，正极活性材料包括Li aNi xCo yM zO 2，0.2≤a≤1.2，0.85≤x≤1，0≤y＜0.15，x+y+z＝1，M包括Mn和Al中的一种或多种；正极活性材料涂布重量为19～45mg/cm 2，压实密度为3.2～3.8g/cm 3；负极极片，其具有负极活性材料，其中硅基材料的质量分数为20％～100％，负极活性材料涂布重量为5～13mg/cm 2，压实密度为1.1～1.9g/cm 3；电解质，电解质的量为0.8～1.5g/Ah，电解质包括电解液，二次电池中裸电芯外电解液的量≤0.1g/Ah；并涉及相应的用电装置。

Description

二次电池和用电装置 技术领域
本申请涉及二次电池技术领域，特别是涉及一种二次电池及其制备方法、用电装置。
背景技术
近年来，随着二次电池的应用范围越来越广泛，二次电池广泛应用于水力、火力、风力和太阳能电站等储能电源系统，以及电动工具、电动自行车、电动摩托车和电动汽车等多个领域。
由于二次电池取得了极大的发展，对其能量密度也提出了更高的要求。因此，寻求一种具有高能量密度的二次电池，是本领域技术人员重点关注的方向之一。
发明内容
本申请是鉴于上述课题而进行的，其目的之一在于，提供一种二次电池，其具有较高的能量密度。
为了达到上述目的，本申请的第一方面提供了一种二次电池，包括：
正极极片，正极极片具有正极活性材料，正极活性材料包括LiaNixCoyMzO2，其中0.2≤a≤1.2，0.85≤x≤1，0≤y＜0.15，x+y+z＝1，M包括Mn和Al中的一种或多种；正极活性材料的涂布重量为19mg/cm2～45mg/cm2，正极极片的压实密度为3.2g/cm3～3.8g/cm3；
负极极片，负极极片具有负极活性材料，负极活性材料中硅基材料的质量分数为20％～100％，负极活性材料的涂布重量为5mg/cm2～13mg/cm2，负极极片的压实密度为1.1g/cm3～1.9g/cm3；及
电解质，二次电池中电解质的量为0.8g/Ah～1.5g/Ah，电解质包括电解液，二次电池中裸电芯外电解液的量≤0.1g/Ah。
本申请的二次电池中正极极片和负极极片采用较高的压实密度；采用极低的电解质总量，并尽量减少电解质中对容量发挥无贡献的裸电芯外电 解液的量；采用高镍三元正极材料、高硅负极活性材料和较大的涂布重量；通过上述技术手段相结合，可使二次电池具有较高的能量密度。
在任意的实施方式中，正极极片和负极极片之间设有隔离膜，隔离膜的表面设有第一高吸液聚合物层，第一高吸液聚合物层中的高吸液聚合物的平衡溶胀率为150％～300％。如此，可以进一步提高隔离膜与极片之间的保液能力，使电解质进一步集中在裸电芯的内部，提高二次电池的能量密度。
在任意的实施方式中，正极极片和/或负极极片表面设有第二高吸液聚合物层，第二高吸液聚合物层中的高吸液聚合物的平衡溶胀率为150％～300％。如此，可以进一步提高二次电池的能量密度。
在任意的实施方式中，高吸液聚合物的涂布重量为0.1mg/cm2～1.4mg/cm2。如此，可以很好地满足正极极片、负极极片的保液量需求。
在任意的实施方式中，高吸液聚合物的涂布重量为0.1mg/cm2～1.0mg/cm2。
在任意的实施方式中，高吸液聚合物包括聚丙烯酸酯类电解质、聚醚类电解质、聚碳酸酯类电解质、聚羧酸酯类电解质、硅基类电解质、聚硫醇类电解质、马来酸酐类电解质和聚硫酸酯类电解质中的一种或多种。
在任意的实施方式中，电解质还包括凝胶电解质，凝胶电解质和电解液的质量比为1：(0.05～0.4)。如此，可以将电解液更好地锁在裸电芯内，减少电解液因高硅极片充电膨胀作用而被挤出。
在任意的实施方式中，凝胶电解质和电解液的质量比为1：(0.05～0.25)。
在任意的实施方式中，形成凝胶电解质的单体包括甲基丙烯酸甲酯、丙烯酸甲酯、甲基丙烯酸乙酯、丙烯酸乙酯、甲基丙烯酸正丁酯、丙烯酸丁酯、甲基丙烯酸正辛酯、丙烯酸正辛酯、醋酸乙烯酯、碳酸亚乙烯酯、碳酸乙烯亚乙酯、三乙二醇二甲基丙烯酸酯、二乙二醇二甲基丙烯酸酯、乙二醇二甲基丙烯酸酯、甲基丙烯酸烯丙酯、二乙烯苯、聚乙烯醇和苯乙烯中的一种或多种。
在任意的实施方式中，形成凝胶电解质的引发剂包括过硫酸盐、偶氮类引发剂和有机过氧类引发剂中的一种或多种。
在任意的实施方式中，正极活性材料的涂布重量为25mg/cm2～35mg/cm2。如此，可以进一步提高二次电池的能量密度。
在任意的实施方式中，正极极片的压实密度为3.5g/cm3～3.7g/cm3。如此，可以进一步降低正极膜层中电解液的需求总量，进一步提高二次电池的能量密度。
在任意的实施方式中，负极活性材料的涂布重量为7mg/cm2～10.5mg/cm2。如此，可以进一步提高二次电池的能量密度。
在任意的实施方式中，负极极片的压实密度为1.6g/cm3～1.8g/cm3。如此，可以进一步降低负极膜层中电解液的需求总量，进一步提高二次电池的能量密度。
在任意的实施方式中，二次电池中电解质的量为0.9g/Ah～1.4g/Ah。如此，在满足充放电过程中正极极片和负极极片膜层孔隙中所需的电解质的需求量的同时，进一步提高二次电池的能量密度。
在任意的实施方式中，负极活性材料中硅基材料的质量分数为40％～100％。如此，可以进一步提高二次电池的能量密度。
本申请的第二方面提供一种用电装置，包括本申请第一方面的二次电池。
本申请的二次电池中，正极极片和负极极片采用较高的压实密度；采用极低的电解质量，并尽量减少电解质中对容量发挥无贡献的裸电芯外电解液的量；结合高镍三元正极材料、高硅负极活性材料和较大的活性材料涂布重量；可使二次电池具有较高的能量密度。
附图说明
为了更好地描述和说明本申请的实施例和/或示例，可以参考一幅或多幅附图。用于描述附图的附加细节或示例不应当被认为是对所公开的申请、目前描述的实施例和/或示例以及目前理解的这些申请的最佳模式中的任何一者的范围的限制。
图1是本申请一实施方式的二次电池的示意图；
图2是图1所示的本申请一实施方式的二次电池的分解图；
图3是本申请一实施方式的二次电池用作电源的用电装置的示意图。
附图标记说明：
5、二次电池；51、壳体；52、电极组件；53、盖板；6、用电装置。
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的二次电池和用电装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60～120和80～110的范围，理解为60～110和80～120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1～3、1～4、1～5、2～3、2～4和2～5。在本申请中，除非有其他说明，数值范围“a～b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0～5”表示本文中已经全部列出了“0～5”之间的全部实数，“0～5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方 法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
本申请说明书中所述的重量可以是μg、mg、g、kg等化工领域公知的重量单位。
目前，随着二次电池的应用范围越来越广泛，对二次电池的能量密度也提出了更高的要求。现有的高比能二次电池通常采用锂金属负极，由于锂金属负极的活性太强，稳定性极差，限制了锂金属负极高比能二次电池的实际应用。因此，寻求一种采用非锂金属负极，且具有较高能量密度的二次电池，已经成为本领域技术人员重点关注的方向之一。对此，本申请提供了一种二次电池，其无需采用锂金属负极，且具有较高的能量密度。
在一些实施方式中，本申请的第一方面提供了一种二次电池，包括：
正极极片，该正极极片具有正极活性材料，正极活性材料包括LiaNixCoyMzO2，其中0.2≤a≤1.2，0.85≤x≤1，0≤y＜0.15，x+y+z＝1，M包括Mn和Al中的一种或多种；正极活性材料的涂布重量为19mg/cm2～45mg/cm2，正极极片的压实密度为3.2g/cm3～3.8g/cm3；
负极极片，该负极极片具有负极活性材料，负极活性材料中硅基材料的质量分数为20％～100％，负极活性材料的涂布重量为5mg/cm2～13mg/cm2，负极极片的压实密度为1.1g/cm3～1.9g/cm3；
电解质，二次电池中电解质的量为0.8g/Ah～1.5g/Ah，电解质包括电解液，二次电池中裸电芯外电解液的量≤0.1g/Ah。
本申请的二次电池中，正极极片和负极极片采用较高的压实密度，可以降低极片膜层孔隙中的电解液填充需求量，同时可以减少活性物质与电解液的界面接触，减少活性物质与电解液之间的副反应，降低电解液的需求总量；采用极低的电解质总量，并尽量减少电解质中对容量发挥无贡献的裸电芯外电解液的量；采用高镍三元正极材料、高硅负极活性材料和较大的涂布重量；通过上述技术手段相结合，可使二次电池具有较高的能量密度，其能量密度可以达到400Wh/kg以上。并且，该二次电池无需采用活性很高、稳定性很差的锂金属负极来提高电池能量密度，可以使二次电池具有较好的稳定性。
可以理解，二次电池中电解质的量包括电解液的量和凝胶电解质的量；其中，电解液包括裸电芯内电解液和裸电芯外电解液。将二次电池拆开，取出裸电芯，将电池壳体内剩余的电解液进行称重，即得裸电芯外电解液的量；将裸电芯拆开，取出其内的凝胶电解质和电解液进行称重；将凝胶电解质的量、裸电芯内电解液的量和裸电芯外电解液的量相加，即为二次电池中电解质的量。裸电芯外电解液是指游离在裸电芯外部的电解液，该部分电解液对于二次电池的容量发挥不起作用；因此，为了提高二次电池的能量密度，应尽量降低电解质中裸电芯外电解液所占比例。
需要说明的是，二次电池在充放电过程中会伴随Li的脱嵌及消耗，二次电池在放电到不同状态时Li的摩尔含量会发生变化；本申请中对正极活性材料LiaNixCoyMzO2中a的取值范围限定包括了二次电池不同充放电状态下Li的摩尔含量(通常电池电压在2V～5V之间)。
可以理解，正极极片中正极活性材料的涂布重量可以为但不限于19mg/cm2、20mg/cm2、22mg/cm2、24mg/cm2、26mg/cm2、28mg/cm2、30mg/cm2、32mg/cm2、34mg/cm2、36mg/cm2、38mg/cm2、40mg/cm2、42mg/cm2、44mg/cm2、45mg/cm2；正极极片的压实密度可以为但不限于3.2g/cm3、3.3g/cm3、3.4g/cm3、3.5g/cm3、3.6g/cm3、3.7g/cm3、3.8g/cm3；负极活性材料中硅基材料的质量分数可以为但不限于20％、30％、40％、50％、60％、70％、80％、90％、100％；负极活性材料的涂布重量可以为但不限于5mg/cm2、6mg/cm2、7mg/cm2、8mg/cm2、9mg/cm2、10mg/cm2、11mg/cm2、12mg/cm2、 13mg/cm2；负极极片的压实密度可以为但不限于1.1g/cm3、1.2g/cm3、1.3g/cm3、1.4g/cm3、1.5g/cm3、1.6g/cm3、1.7g/cm3、1.8g/cm3、1.9g/cm3；二次电池中电解质的量可以为但不限于0.8g/Ah、0.9g/Ah、1.0g/Ah、1.1g/Ah、1.2g/Ah、1.3g/Ah、1.4g/Ah、1.5g/Ah；电解质中裸电芯外电解液的量可以为但不限于0g/Ah、0.01g/Ah、0.02g/Ah、0.03g/Ah、0.04g/Ah、0.05g/Ah、0.06g/Ah、0.07g/Ah、0.08g/Ah、0.09g/Ah、0.1g/Ah。
在其中一些实施方式中，正极活性材料的涂布重量为25mg/cm2～35mg/cm2。正极极片中正极活性材料的涂布重量过低，会使活性物质的占比减少，电池中基材、壳体、辅料等重量占比相对增大，使电池的重量能量密度降低；涂布重量过大又会使正极膜层过厚，难以达到设定的压实密度。将正极活性材料的涂布重量控制在25mg/cm2～35mg/cm2范围之内，可以进一步提高二次电池的能量密度。
在其中一些实施方式中，正极极片的压实密度为3.5g/cm3～3.7g/cm3。如此，可以进一步降低正极膜层中电解液的需求总量，进一步提高二次电池的能量密度。
在其中一些实施方式中，负极极片中负极活性材料的涂布重量为7mg/cm2～10.5mg/cm2。可以进一步提高二次电池的能量密度。
在其中一些实施方式中，负极极片的压实密度为1.6g/cm3～1.8g/cm3。如此，可以进一步降低负极膜层中电解液的需求总量，进一步提高二次电池的能量密度。
在其中一些实施方式中，二次电池中电解质的量为0.9g/Ah～1.4g/Ah。如此，在满足充放电过程中正极极片和负极极片膜层孔隙中所需的电解质的需求量的同时，进一步减少电解质的总用量，从而进一步提高二次电池的能量密度。
在其中一些实施方式中，负极活性材料中硅基材料的质量分数为40％～100％。如此，负极活性材料中采用更高比例的硅基材料，可以进一步提高二次电池的能量密度。
在其中一些实施方式中，二次电池还包括隔离膜，该隔离膜设置在正极极片和负极极片之间，且隔离膜与正极极片之间的间距为0μm～20μm。 通过将隔离膜与正极极片之间的间距控制在20μm以内，可以使正极极片与隔离膜之间填充足够多的电解质，更好地满足正极膜层的保液填充需求，并可使电解液主要集中在裸电芯的内部，减少裸电芯外电解液的量，从而有利于提高二次电池的能量密度。
在其中一些实施方式中，隔离膜与负极极片之间的间距为0μm～20μm。如此，可使负极极片与隔离膜之间填充足够多的电解质，更好地满足负极膜层的保液填充需求，并可使电解液进一步集中在裸电芯的内部，进一步减少裸电芯外电解液的量，从而进一步提高二次电池的能量密度。
在其中一些实施方式中，可以通过调节正极极片、隔离膜和负极极片层叠卷绕形成电极组件时的卷绕张力的大小，来控制隔离膜与正极极片之间的间距，以及隔离膜与负极极片之间的间距。
具体来说，当需要减小极片与隔离膜之间的间距时，可以适当地增大极片卷绕时的张力；当需要增大极片与隔离膜之间的间距时，可以适当地减小极片卷绕时的张力。当卷绕张力较小时，卷绕后极片与隔离膜之间的间距会相对较大，可以容纳较多的电解质；但若卷绕张力过小，极片与隔离膜之间的间距会过大，影响电池的动力学并增加析锂的风险。因此，需要控制卷绕张力的大小在合适范围内，以使极片与隔离膜之间的间距在设定范围之内。
在其中一些实施方式中，在隔离膜的表面还设置有第一高吸液聚合物层，该第一高吸液聚合物层中的高吸液聚合物的平衡溶胀率为150％～300％。通过在隔离膜的表面设置上述的高吸液聚合物，可以进一步提高裸电芯内隔离膜与极片之间的保液能力，使电解质进一步集中在裸电芯的内部，进一步减少裸电芯外电解液的量，从而进一步提高二次电池的能量密度。
在其中一些实施方式中，在正极极片和/或负极极片的表面设置有第二高吸液聚合物层，该第二高吸液聚合物层中的高吸液聚合物的平衡溶胀率为150％～300％。同样地，通过在正极极片和/或负极极片的表面设置上述的高吸液聚合物，同样可以进一步提高裸电芯内隔离膜与极片之间的保液能力，使电解质进一步集中在裸电芯的内部，进一步减少裸电芯外电解液的量，从而进一步提高二次电池的能量密度。
可以理解，可以只在隔离膜的一侧表面上设置上述的高吸液聚合物，可以在隔离膜相对的两侧表面上均设置上述的高吸液聚合物，可以只在正极极片或负极极片的表面上设置上述的高吸液聚合物，也可以在正极极片和负极极片的表面上均设置上述的高吸液聚合物，还可以在隔离膜的表面以及极片的表面均设置上述的高吸液聚合物。
需要说明的是，高吸液聚合物的平衡溶胀率大小可以反映高吸液聚合物的保液能力高低。高吸液聚合物的平衡溶胀率可以通过如下公式计算得到：Q＝Ws/Wd，其中Q为高吸液聚合物的平衡溶胀率，Ws为高吸液聚合物溶胀平衡后的聚合物重量，Wd为高吸液聚合物的干重。
可以理解，高吸液聚合物在与电解液溶剂接触时，由于聚合物交联点之间的分子链段仍然较长，具有相当的柔性，溶剂分子容易渗入聚合物内，引起聚合物体积膨胀；但交联点之间分子链的伸展会使其构象熵降低，使分子网产生弹性收缩力，阻止溶剂分子进入分子网；当这两种相反的作用相互抵消时，体系就达到了溶胀平衡状态，聚合物的体积不再变化。
在其中一些实施方式中，高吸液聚合物的涂布重量为0.1mg/cm2～1.4mg/cm2。将高吸液聚合物的涂布重量控制在0.1mg/cm2～1.4mg/cm2之间，可以很好地满足正极极片和负极极片的保液量需求。可以理解，高吸液聚合物的涂布重量可以为但不限于0.1mg/cm2、0.2mg/cm2、0.3mg/cm2、0.4mg/cm2、0.5mg/cm2、0.6mg/cm2、0.7mg/cm2、0.8mg/cm2、0.9mg/cm2、1.0mg/cm2、1.1mg/cm2、1.2mg/cm2、1.3mg/cm2、1.4mg/cm2。
在其中一些实施方式中，高吸液聚合物的涂布重量为0.1mg/cm2～1.0mg/cm2。如此，可以在满足正极极片和负极极片的保液量需求的同时，进一步减少高吸液聚合物的用量。
在其中一些实施方式中，可以将高吸液的聚合物溶解于有机溶剂如丙酮中，然后采用喷涂、浸涂、辊涂等方式将聚合物涂覆在隔离膜或极片的表面上，从而在隔离膜或极片上形成高吸液聚合物的涂层。
在其中一些实施方式中，高吸液聚合物包括聚丙烯酸酯类电解质、聚醚类电解质、聚碳酸酯类电解质、聚羧酸酯类电解质、硅基类电解质、聚硫醇类电解质、马来酸酐类电解质和聚硫酸酯类电解质中的一种或多种。
在其中一些实施方式中，电解质还包括凝胶电解质，凝胶电解质和电解液的质量比为1：(0.05～0.4)。通过采用特定含量的凝胶电解质，可以进一步增强电解液在裸电芯内部和极片膜层孔隙中的保液能力，将电解液更好地锁在裸电芯内，减少电解液因高硅极片充电膨胀作用而被挤出。同时，结合一定量的液态电解液，可以改善电极界面浸润，改善凝胶电解质的容量等电性能发挥。
可以理解，电解质中凝胶电解质和电解液的质量比可以为但不限于1：0.05、1:0.08、1:0.10、1:0.12、1:0.14、1:0.16、1:0.18、1:0.20、1:0.22、1:0.24、1：0.26、1:0.28、1:0.30、1:0.32、1:0.34、1:0.36、1:0.38、1:0.40。
在其中一些实施方式中，凝胶电解质和电解液的质量比为1：(0.05～0.25)。如此，可以进一步增强电解液在裸电芯内部和极片膜层孔隙中的保液能力，更好地将电解液锁在裸电芯内。
在其中一些实施方式中，可以在二次电池注液时在电解液中添加一定量的聚合物单体和引发剂，在加热条件下引发聚合物单体进行原位聚合，从而形成凝胶电解质。可理解，电解质中凝胶电解质的含量可以通过注液时电解液中聚合物单体和引发剂的添加量来进行调节和控制。
在其中一些实施方式中，形成凝胶电解质的单体包括甲基丙烯酸甲酯、丙烯酸甲酯、甲基丙烯酸乙酯、丙烯酸乙酯、甲基丙烯酸正丁酯、丙烯酸丁酯、甲基丙烯酸正辛酯、丙烯酸正辛酯、醋酸乙烯酯、碳酸亚乙烯酯、碳酸乙烯亚乙酯、三乙二醇二甲基丙烯酸酯、二乙二醇二甲基丙烯酸酯、乙二醇二甲基丙烯酸酯、甲基丙烯酸烯丙酯、二乙烯苯、聚乙烯醇和苯乙烯中的一种或多种。
在其中一些实施方式中，形成凝胶电解质的引发剂包括过硫酸盐、偶氮类引发剂和有机过氧类引发剂中的一种或多种。
本申请的第二方面提供了一种用电装置，该用电装置包括本申请第一方面的二次电池。
以下适当参照附图对本申请的二次电池和用电装置进行说明。
除非特别说明，否则提及的电池的组件、材料种类或含量同时适用于锂离子二次电池和钠离子二次电池。
本申请的一个实施方式中，提供一种二次电池。
通常情况下，二次电池包括正极极片、负极极片、电解质和隔离膜。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使离子通过。
【正极极片】
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极膜层。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，所述正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料形成在高分子材料基材上而形成。其中，金属材料包括但不限于铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等。高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)。
本申请的一些实施方式中，正极活性材料包括高镍三元正极材料；正极活性材料的涂布重量为19mg/cm2～45mg/cm2，正极极片的压实密度为3.2g/cm3～3.8g/cm3；
在一些实施方式中，正极活性材料在正极膜层中的重量比为80～100重量％，基于正极膜层的总重量计。
在一些实施方式中，正极膜层还可选地包括粘结剂。作为示例，所述粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。所述粘结剂在正极膜层中的重量比为0～20重量％，基于正极膜层的总重量计。
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，所述 导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。所述导电剂在正极膜层中的重量比为0-20重量％，基于正极膜层的总重量计。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料，其中所述正极浆料固含量为40质量百分比(wt％)～80wt％，室温下的粘度调整到5000毫帕·秒(mPa·s)～25000mPa·s，将正极浆料涂覆在正极集流体的表面，烘干后经过冷轧机冷压后形成正极极片；正极极片压实密度为3.2克/立方厘米(g/cm3)～3.8g/cm3，可选为3.5g/cm3～3.7g/cm3。
所述压实密度的计算公式为：
压实密度＝涂布面密度/(挤压后极片厚度-集流体厚度)。
单位面积正极膜片中正极活性物质的质量M的可使用标准天平称量得到。
所述正极膜片的厚度T可采用万分尺测量得到，例如可使用型号为Mitutoyo293-100、精度为0.1μm的万分尺测量得到。需要说明的是，本申请所述的正极膜片厚度是指经冷压压实后并用于组装电池的正极极片中的正极膜片的厚度。
【负极极片】
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极活性材料。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施方式中，所述负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料形成在高分子材料基材上而形成。其中，金属材料包括但不限于铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等，高分子材料基材包括但不限于聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲 酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等基材。
在一些实施方式中，负极活性材料可采用本领域公知的用于电池的负极活性材料。
作为示例，锂离子二次电池的负极活性材料包括硅基材料，还可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、锡基材料和钛酸锂等。所述硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至少一种。所述锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。
在一些实施方式中，负极膜层还可选地包括粘结剂。所述粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。所述粘结剂在负极膜层中的重量比为0～30重量％，基于负极膜层的总重量计。
在一些实施方式中，负极膜层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。所述导电剂在负极膜层中的重量比为0～20重量％，基于负极膜层的总重量计。
在一些实施方式中，负极膜层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。所述其他助剂在负极膜层中的重量比为0～15重量％，基于负极膜层的总重量计。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料，其中所述负极浆料固含量为30wt％～70wt％，室温下的粘度调整到2000mPa·s～10000mPa·s；将所得到的负极浆料涂覆在负极集流体上，经过干燥工序，冷压例如对辊，得到负极极片。负极极片压实密度1.1克/立方米(g/m3)～1.9g/m3。
单位面积负极膜片中负极活性物质的质量M的可使用标准天平称量得到。
所述负极膜片的厚度T可采用万分尺测量得到，例如可使用型号为Mitutoyo293-100、精度为0.1μm的万分尺测量得到。需要说明的是，本申请所述的负极膜片厚度是指经冷压压实后并用于组装电池的负极极片中的负极膜片的厚度。
【电解质】
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
在一些实施方式中，所述电解质包括电解液。所述电解液包括电解质盐和溶剂。
在一些实施方式中，锂离子二次电池的电解质盐可选自六氟磷酸锂(LiPF6)、四氟硼酸锂(LiBF4)、高氯酸锂(LiClO4)、六氟砷酸锂(LiAsF6)、双氟磺酰亚胺锂(LiFSI)、双三氟甲磺酰亚胺锂(LiTFSI)、三氟甲磺酸锂(LiTFS)、二氟草酸硼酸锂(LiDFOB)、二草酸硼酸锂(LiBOB)、二氟磷酸锂(LiPO2F2)、二氟二草酸磷酸锂(LiDFOP)及四氟草酸磷酸锂(LiTFOP)中的一种或几种。
钠离子二次电池的电解质盐可选自六氟磷酸钠、双氟磺酰亚胺钠、双三氟甲烷磺酰亚胺钠、三氟甲磺酸钠、四氟硼酸钠、二氟磷酸钠、高氯酸钠、氯化钠中的一种或几种。
所述电解质盐的浓度通常为0.5摩尔/升(mol/L)～5mol/L。
在一些实施方式中，溶剂可选自氟代碳酸乙烯酯(FEC)、碳酸亚乙酯(EC)、碳酸亚丙基酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸亚丁酯(BC)、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)、1,4-丁内酯(GBL)、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)及二乙砜(ESE)中的一种或几种。
在一些实施方式中，所述电解液还可选地包括添加剂。例如添加剂可 以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
在一些实施方式中，所述电解质还包括凝胶电解质。
【隔离膜】
在一些实施方式中，二次电池中还包括隔离膜。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，所述隔离膜的厚度为6μm～40μm，可选为12μm～20μm。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图1是作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图2，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔内。电解液浸润于电极组件 52中。二次电池5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。
在一些实施方式中，二次电池5可以组装成电池模块，电池模块所含二次电池5的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
在电池模块中，多个二次电池5可以是沿电池模块的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。
可选地，电池模块还可以包括具有容纳空间的外壳，多个二次电池5容纳于该容纳空间。
在一些实施方式中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。
在电池包中可以包括电池箱和设置于电池箱中的多个电池模块。电池箱包括上箱体和下箱体，上箱体能够盖设于下箱体，并形成用于容纳电池模块的封闭空间。多个电池模块可以按照任意的方式排布于电池箱中。
另外，本申请还提供一种用电装置，所述用电装置包括本申请提供的二次电池、电池模块、或电池包中的至少一种。所述二次电池、电池模块、或电池包可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以包括移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等，但不限于此。
作为所述用电装置，可以根据其使用需求来选择二次电池、电池模块或电池包。
图3是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装 置通常要求轻薄化，可以采用二次电池作为电源。
以下为一些实施例。
为了使本申请所解决的技术问题、技术方案及有益效果更加清楚，以下将结合实施例和附图对本申请进行进一步详细说明。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。以下对至少一个示例性实施例的描述实际上仅仅是说明性的，决不作为对本申请及其应用的任何限制。基于本申请中的实施例，本领域普通技术人员在没有付出创造性劳动前提下所获得的所有其他实施例都属于本申请保护的范围。
实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
一、实施例
实施例1
1)正极极片的制备
将正极活性材料LiaNixCoyMzO2与导电剂超导碳SP、粘结剂PVDF按重量比98：1：1在N-甲基吡咯烷酮溶剂中充分搅拌混合均匀得到正极浆料，将正极浆料涂覆于正极集流体铝箔上，烘干、冷压，得到正极极片。正极活性材料的涂布重量为30mg/cm2，正极极片的压实密度为3.5g/cm3。其中，正极活性材料化学式中a为1，x为0.92，y为0.05，x+y+z＝1，M为Mn。
2)负极极片的制备
将负极活性材料石墨+硅氧与导电剂碳纳米管+超导碳、粘结剂丁苯橡胶SBR、增稠剂羧甲基纤维素钠CMC按照质量比94：2：3：1在去离子水中充分搅拌混合均匀得到负极浆料，将负极浆料涂覆于负极集流体铜箔上，烘干、冷压，得到负极极片。负极活性材料中硅基材料的质量分数为40％，负极活性材料的涂布重量为9mg/cm2，负极极片的压实密度为1.7g/cm3。
3)隔离膜
采用聚乙烯(PE)隔离膜。
4)电芯组装
将正极极片、隔离膜和负极极片层叠卷绕组装形成裸电芯，将裸电芯置于外包装中，得到干电芯。在裸电芯的制备过程中，通过控制极片卷绕过程中的张力大小，调节正极极片与隔离膜之间的间距为20μm，负极极片与隔离膜之间的间距为20μm。
5)注液
对干电芯进行注液，注液时分两次注液，一次注液：二次注液的质量比为9：1。一次注液的电解质原料组分为：电解液母液、单体、引发剂，质量比为94.5：5：0.5；其中，电解液母液的有机溶剂为碳酸亚乙酯(EC)、碳酸甲乙酯(EMC)和碳酸二乙酯(DEC)的混合液；EC、EMC和DEC的体积比为20:20:60；电解液母液的锂盐为LiPF6，浓度为1mol/L；单体采用乙二醇二甲基丙烯酸酯，引发剂采用的是偶氮二乙丁晴(AIBN)。
二次注液的电解质仅为电解液母液。一次注液完毕后真空封装，静置浸渍，并加热使电解质原料中的聚合物单体发生聚合形成凝胶电解质，再注入二次注液电解液母液。其中，电芯的总电解质量为1.3g/Ah，加热聚合后电解质中凝胶电解质与液态电解液的质量比为1：0.11，电解液中裸电芯外电解液的量为0.05g/Ah。
实施例2
该实施例与实施例1基本相同，区别仅在于：高镍三元正极材料不同，正极活性材料的涂布重量。本实施例中高镍三元正极材料的化学式为LiaNixCoyMzO2，其中a为1，x为0.9，y为0.05，x+y+z＝1，M为Mn；正极活性材料的涂布重量为30.5mg/cm2。
实施例3
该实施例与实施例1基本相同，区别仅在于：正极极片中正极活性材料的涂布重量不同，负极极片中负极活性材料的涂布重量不同。本实施例中正极活性材料的涂布重量为25mg/cm2，负极活性材料的涂布重量为7.5mg/cm2。
实施例4
该实施例与实施例1基本相同，区别仅在于：正极极片中正极活性材料的涂布重量不同，负极极片中负极活性材料的涂布重量不同。本实施例 中正极活性材料的涂布重量为35mg/cm2，负极活性材料的涂布重量为10.5mg/cm2。
实施例5
该实施例与实施例1基本相同，区别仅在于：正极极片中正极活性材料的涂布重量不同，负极极片中负极活性材料的涂布重量不同。本实施例中正极活性材料的涂布重量为40mg/cm2，负极活性材料的涂布重量为12mg/cm2。
实施例6
该实施例与实施例1基本相同，区别仅在于：正极极片的压实密度不同。本实施例中正极极片的压实密度为3.7g/cm3。
实施例7
该实施例与实施例1基本相同，区别仅在于：正极极片的压实密度不同。本实施例中正极极片的压实密度为3.8g/cm3。
实施例8
该实施例与实施例1基本相同，区别仅在于：负极极片中负极活性材料的涂布重量不同。本实施例中负极活性材料的涂布重量为13mg/cm2。
实施例9
该实施例与实施例1基本相同，区别仅在于：负极极片的压实密度不同。本实施例中负极极片的压实密度为1.6g/cm3。
实施例10
该实施例与实施例1基本相同，区别仅在于：负极极片的压实密度不同。本实施例中负极极片的压实密度为1.8g/cm3。
实施例11
该实施例与实施例1基本相同，区别仅在于：二次电池中电解质的量不同。本实施例中电解质的量为0.9g/Ah。
实施例12
该实施例与实施例1基本相同，区别仅在于：二次电池中电解质的量不同。本实施例中电解质的量为1.4g/Ah。
实施例13
该实施例与实施例1基本相同，区别仅在于：二次电池中电解质的量不同，裸电芯外电解液的量不同。本实施例中电解质的量为1.35g/Ah，裸电芯外电解液的量为0.1g/Ah。
实施例14
该实施例与实施例1基本相同，区别仅在于：本实施例中在正极极片和负极极片上均涂覆聚碳酸脂二醇高吸液聚合物，正极极片上高吸液聚合物的涂布重量为0.5mg/cm2，负极极片上高吸液聚合物的涂布重量为0.5mg/cm2。高吸液聚合物的平衡吸液率为200％。
实施例15
该实施例与实施例1基本相同，区别仅在于：隔离膜与正极极片之间的间距不同。本实施例中隔离膜与正极极片之间的间距为20μm。
实施例16
该实施例与实施例1基本相同，区别仅在于：隔离膜与负极极片之间的间距不同。本实施例中隔离膜与负极极片之间的间距为20μm。
实施例17
该实施例与实施例1基本相同，区别仅在于：本实施例中在隔离膜的表面上涂覆高吸液聚合物，高吸液聚合物的平衡溶胀率为200％，高吸液聚合物的涂布重量为0.5mg/cm2。
实施例18
该实施例与实施例17基本相同，区别仅在于：隔离膜表面高吸液聚合物的涂布重量不同。本实施例中隔离膜表面的高吸液聚合物的涂布重量为1mg/cm2。
实施例19
该实施例与实施例17基本相同，区别仅在于：隔离膜表面高吸液聚合物的涂布重量不同。本实施例中隔离膜表面的高吸液聚合物的涂布重量为1.4mg/cm2。
实施例20
该实施例与实施例1基本相同，区别仅在于：加热聚合后电解质中凝胶电解质与游离液态电解液的质量比不同。本实施例中加热聚合后电解质 中凝胶电解质与游离液态电解液的质量比为1：0.25。
二、对比例
对比例1
该对比例与实施例1基本相同，区别仅在于：对比例1中所用的正极活性材料不同。对比例1中正极极片中所用的正极活性材料为高镍三元正极材料的化学式为LiaNixCoyMzO2，其中a为1，x为0.8，y为0.1，x+y+z＝1，M为Mn。
对比例2
该对比例与实施例1基本相同，区别仅在于：正极极片中正极活性材料的涂布重量不同。对比例2中正极极片中正极活性材料的涂布重量为15mg/cm2。
对比例3
该对比例与实施例1基本相同，区别仅在于：正极极片的压实密度不同。对比例3中正极极片的压实密度为3.1g/cm3。
对比例4
该对比例与实施例1基本相同，区别仅在于：负极极片中负极活性材料不同。对比例4中负极活性材料为石墨：硅氧＝95：5。
对比例5
该对比例与实施例1基本相同，区别仅在于：负极极片中负极活性材料的涂布重量不同。对比例5中负极极片中负极活性材料的涂布重量为15mg/cm2。
对比例6
该对比例与实施例1基本相同，区别仅在于：负极极片的压实密度不同。对比例6中负极极片的压实密度为1.0g/cm3。
对比例7
该对比例与实施例1基本相同，区别仅在于：电芯中电解质的量不同。对比例7的电芯中电解质的量为1.6g/Ah。
对比例8
该对比例与实施例1基本相同，区别仅在于：裸电芯外电解液的量不同。该对比例8中裸电芯外电解液的量为0.2g/Ah。
对比例9
该对比例与实施例1基本相同，区别仅在于：加热聚合后电解质中凝胶电解质与液态电解液的质量比不同。本实施例中加热聚合后电解质中凝胶电解质与液态电解液的质量比为1：0，即不含有液态电解液。
三、测试方法
1)裸电芯外电解液量测试
将裸电芯取出，壳体内剩余的电解液称重。
2)隔离膜与极片间间距测试
采用X-Ray CT对隔离膜与极片间间距拍摄测量。
3)凝胶电解质和电解液质量比测试
将裸电芯取回进行离心，得到裸电芯内的游离液态电解液，与壳体内剩余的电解液进行合并称重，得到液态电解液的重量；将裸电芯上的凝胶电解质刮下进行称重，无法刮取的部分采用TG-MS热重分析仪对凝胶电解质的质量进行辅助校准测试。
4)高吸液聚合物平衡溶胀率测试
将经干燥的聚合物样品称重，得到聚合物的干重Wd；
将其在常温下于电解液中浸泡24h，然后从电解液中取出，用滤纸除去表面的电解液后进行称重，得到溶胀平衡后的聚合物的重量Ws；其中，电解液包括溶剂和锂盐；溶剂为EC、EMC和DEC按体积比20:20:60形成的混合溶剂；锂盐为LiPF6，浓度为1mol/L；
聚合物的平衡溶胀率通过下式计算得到：Q＝Ws/Wd。
5)质量能量密度(GED)测试
对电芯进行测重，记为M；
在25℃下，以1/3C倍率电流恒流充电至4.25V，转为恒压充电，至电流降至0.05C倍率电流时停止充电，然后以1/3C倍率电流恒流放电至2.5V时停止放电，记录放电能量值ED；
GED＝ED/M，单位为Wh/kg。
以上各实施例和对比例的二次电池的参数和性能测试数据如表1、表2和表3所示。
表1


表2


表3


由表中数据可知：
从对比例1和实施例1、2可以看出，正极材料中Ni含量较高时，有利于获得更高的能量密度。
从对比例2和实施例1、3至5可以看出，涂布重量在35mg/cm2以下时，涂布重量越大，活性物质占电芯总重的比重越大，可以获得越高的重量能量密度，但涂布重量进一步增大时，厚电极的扩散阻抗恶化严重，电芯的容量发挥损失，使得重量能量密度不增反减。
从对比例3和实施例6、7可以看出，正极压密越大时，可以使相同壳体内填充更多层的活性物质，电芯的重量能量密度得以提升。但压密过大会使活性材料颗粒结构破坏，容量损失，故压密也不能过大。
从对比例4可以看出，负极中硅基材料的质量占比降低，重量能量密度下降。从对比例5和实施例8可以看出，相同的正极涂布重量下，若负极的涂布重量偏小，会出现负极析锂的问题，导致容量损失；当负极的涂布重量过大时，会有较多无效的负极活性材料，使重量能量密度降低，故负极涂布重量需在合适的范围内。
从对比例6和实施例9、10可以看出，负极压密越大时电芯的重量能量密度得以提升；但压密过大会使活性材料颗粒结构破坏，容量损失，故负极压密也不能过大，需要在合适的范围内。
从对比例7和实施例11、12可以看出，电芯的总电解质量越高，很多电解液会游离在裸电芯外部，对容量发挥没有帮助，降低重量能量密度。 总电解质量越低，重量能量密度越高，但电解质量过低会导致容量发挥损失。因此，电解质量也需控制在权要限定的范围。
从对比例8和实施例1、13可以看出，相同总电解质量下，裸电芯外游离的电解液越高，越不利于电芯容量的正常发挥，使得电芯的重量能量密度有所损失。
从实施例1、14、17至19中可以看出，在正负极表面或隔膜表面涂覆高吸液聚合物后，可以降低相同电解质量下裸电芯外部游离的电解液，从而降低容量损失，更有利于获得更高的重量能量密度。
从实施例1、15、16可以看出，适当调整正负极片和隔膜之间的间隙，也可以降低外部游离的电解液，获得更高的重量能量密度。
从对比例9和实施例1、20中可以看出，凝胶电解质结合适量的液态电解液可以改善电极浸润和容量发挥，获得更高的重量能量密度；但相同电解质总量下，液态电解液的比重越高，游离到裸电芯外无效的电解液会越多，从而不利于容量发挥。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (15)

  1. 一种二次电池，包括：
    正极极片，所述正极极片具有正极活性材料，所述正极活性材料包括LiaNixCoyMzO2，其中0.2≤a≤1.2，0.85≤x≤1，0≤y＜0.15，x+y+z＝1，M包括Mn和Al中的一种或多种；所述正极活性材料的涂布重量为19mg/cm2～45mg/cm2，所述正极极片的压实密度为3.2g/cm3～3.8g/cm3；
    负极极片，所述负极极片具有负极活性材料，所述负极活性材料中硅基材料的质量分数为20％～100％，所述负极活性材料的涂布重量为5mg/cm2～13mg/cm2，所述负极极片的压实密度为1.1g/cm3～1.9g/cm3；及
    电解质，所述二次电池中所述电解质的量为0.8g/Ah～1.5g/Ah，所述电解质包括电解液，所述二次电池中裸电芯外电解液的量≤0.1g/Ah。
  2. 根据权利要求1所述的二次电池，其特征在于，所述正极极片和所述负极极片之间设有隔离膜，所述隔离膜的表面设有第一高吸液聚合物层，所述第一高吸液聚合物层中的高吸液聚合物的平衡溶胀率为150％～300％。
  3. 根据权利要求1或2所述的二次电池，其特征在于，所述正极极片和/或所述负极极片表面设有第二高吸液聚合物层，所述第二高吸液聚合物层中的高吸液聚合物的平衡溶胀率为150％～300％。
  4. 根据权利要求2或3所述的二次电池，其特征在于，所述高吸液聚合物的涂布重量为0.1mg/cm2～1.4mg/cm2；
    可选地，所述高吸液聚合物的涂布重量为0.1mg/cm2～1.0mg/cm2。
  5. 根据权利要求2至4中任一项所述的二次电池，其特征在于，所述高吸液聚合物包括聚丙烯酸酯类电解质、聚醚类电解质、聚碳酸酯类电解质、聚羧酸酯类电解质、硅基类电解质、聚硫醇类电解质、马来酸酐类电解质和聚硫酸酯类电解质中的一种或多种。
  6. 根据权利要求1至5中任一项所述的二次电池，其特征在于，所述电解质还包括凝胶电解质，所述凝胶电解质和所述电解液的质量比为1：(0.05～0.4)；
    可选地，所述凝胶电解质和所述电解液的质量比为1：(0.05～0.25)。
  7. 根据权利要求6所述的二次电池，其特征在于，形成所述凝胶电解质的单体包括甲基丙烯酸甲酯、丙烯酸甲酯、甲基丙烯酸乙酯、丙烯酸乙酯、甲基丙烯酸正丁酯、丙烯酸丁酯、甲基丙烯酸正辛酯、丙烯酸正辛酯、醋酸乙 烯酯、碳酸亚乙烯酯、碳酸乙烯亚乙酯、三乙二醇二甲基丙烯酸酯、二乙二醇二甲基丙烯酸酯、乙二醇二甲基丙烯酸酯、甲基丙烯酸烯丙酯、二乙烯苯、聚乙烯醇和苯乙烯中的一种或多种。
  8. 根据权利要求6或7所述的二次电池，其特征在于，形成所述凝胶电解质的引发剂包括过硫酸盐、偶氮类引发剂和有机过氧类引发剂中的一种或多种。
  9. 根据权利要求1至8中任一项所述的二次电池，其特征在于，所述正极活性材料的涂布重量为25mg/cm2～35mg/cm2。
  10. 根据权利要求1至9中任一项所述的二次电池，其特征在于，所述正极极片的压实密度为3.5g/cm3～3.7g/cm3。
  11. 根据权利要求1至10中任一项所述的二次电池，其特征在于，所述负极活性材料的涂布重量为7mg/cm2～10.5mg/cm2。
  12. 根据权利要求1至11中任一项所述的二次电池，其特征在于，所述负极极片的压实密度为1.6g/cm3～1.8g/cm3。
  13. 根据权利要求1至12中任一项所述的二次电池，其特征在于，所述二次电池中所述电解质的量为0.9g/Ah～1.4g/Ah。
  14. 根据权利要求1至13中任一项所述的二次电池，其特征在于，所述负极活性材料中硅基材料的质量分数为40％～100％。
  15. 一种用电装置，包括权利要求1至14中任一项所述的二次电池。
PCT/CN2023/093164 2023-05-10 2023-05-10 二次电池和用电装置 Ceased WO2024229731A1 (zh)

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