WO2023000889A1 - 一种非水电解液及锂离子电池 - Google Patents

一种非水电解液及锂离子电池 Download PDF

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WO2023000889A1
WO2023000889A1 PCT/CN2022/099750 CN2022099750W WO2023000889A1 WO 2023000889 A1 WO2023000889 A1 WO 2023000889A1 CN 2022099750 W CN2022099750 W CN 2022099750W WO 2023000889 A1 WO2023000889 A1 WO 2023000889A1
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hydrocarbon group
compound
carbonate
structural formula
lithium
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French (fr)
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向书槐
周忠仓
易洋
胡时光
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Shenzhen Capchem Technology Co Ltd
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Shenzhen Capchem Technology Co Ltd
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Priority to US18/580,635 priority Critical patent/US20250087749A1/en
Priority to EP22845054.0A priority patent/EP4376150A4/en
Publication of WO2023000889A1 publication Critical patent/WO2023000889A1/zh
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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
    • 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
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • 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
    • 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
    • H01M10/0566—Liquid materials
    • H01M10/0568—Liquid materials characterised by the solutes
    • 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
    • H01M10/0566—Liquid materials
    • H01M10/0569—Liquid materials characterised by the solvents
    • 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
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • 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
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • 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
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic 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 lithium-ion batteries, in particular to a non-aqueous electrolyte and a lithium-ion battery.
  • power batteries are mainly lithium-ion batteries, and lithium-ion battery cells are mainly composed of positive electrodes, negative electrodes, diaphragms, and electrolytes.
  • the lithium ions in the positive electrode material of the battery are deintercalated and intercalated into the carbon negative electrode through the electrolyte.
  • the electrolyte components will preferentially obtain electrons, and react on the surface of the carbon negative electrode to produce Li 2 CO 3 , Li 2 O, LiOH and other compounds, thereby forming a passivation film on the surface of the negative electrode, which is called the solid electrolyte interface. film (SEI).
  • SEI solid electrolyte interface. film
  • the SEI film formed during the initial charging process can prevent the electrolyte from further decomposing on the surface of the carbon negative electrode, and also acts as a lithium ion conductor, allowing only lithium ions to pass through.
  • the electrode may change and cause the SEI film to rupture, which may cause the negative electrode to be exposed to the electrolyte again and continue to react with the electrolyte.
  • gas is generated, which increases the internal pressure of the lithium-ion battery and reduces the cycle life of the battery.
  • the volume change of the electrode is more obvious, and the SEI film is more likely to rupture, which leads to a more obvious decline in the electrochemical performance of the lithium-ion battery at high temperature. Therefore, the quality of the SEI film seriously affects the high-temperature performance of Li-ion batteries.
  • the present application provides a non-aqueous electrolyte and a battery.
  • the application provides a non-aqueous electrolytic solution, including solvent, lithium salt and at least one bicyclic compound shown in structural formula 1-1 to structural formula 1-3:
  • A is selected from carbonyl, C1-C10 hydrocarbon group, C1-C10 halogenated hydrocarbon group or C2-C10 carbonyl-containing hydrocarbon group
  • R 1 , R 2 , R 3 , R 4 are each independently selected from single bond, C1-C5 A hydrocarbon group or a C1-C5 halogenated hydrocarbon group; preferably, A is selected from carbonyl, a C1-C6 hydrocarbon group, a C1-C6 halogenated hydrocarbon group or a C2-C6 carbonyl-containing hydrocarbon group
  • R 1 , R 2 , R 3 , R 4 are each independently selected from a single bond, a C1-C3 hydrocarbon group or a C1-C3 halogenated hydrocarbon group.
  • X is selected from a single bond, a carbonyl group, a C1-C10 hydrocarbon group, a C1-C10 halogenated hydrocarbon group or a C2-C10 carbonyl-containing hydrocarbon group
  • R 1 ′, R 2 ′, R 3 ′, and R 4 ′ are independently is selected from single bond, C1-C5 hydrocarbon group or C1-C5 halogenated hydrocarbon group
  • X is selected from single bond, carbonyl, C1-C6 hydrocarbon group, C1-C6 halogenated hydrocarbon group or C2-C6 containing Carbonyl hydrocarbon group
  • R 1 ', R 2 ', R 3 ', R 4 ' are each independently selected from a single bond, a C1-C3 hydrocarbon group or a C1-C3 halogenated hydrocarbon group;
  • Y is selected from a single bond, a carbonyl group, a C1-C10 hydrocarbon group, a C1-C10 halogenated hydrocarbon group or a C2-C10 carbonyl-containing hydrocarbon group
  • R 1 ′′, R 2 ′′, R 3 ′′, and R 4 ′′ are each independently Y is selected from single bond, C1-C5 hydrocarbon group or C1-C5 halogenated hydrocarbon group; preferably, Y is selected from single bond, carbonyl, C1-C6 hydrocarbon group, C1-C6 halogenated hydrocarbon group or C2-C6 containing
  • R 1 ′′, R 2 ′′, R 3 ′′, and R 4 ′′ are each independently selected from a single bond, a C1-C3 hydrocarbon group, or a C1-C3 halogenated hydrocarbon group.
  • Structural Formula 1-1 Using the bicyclic compound shown in Structural Formula 1-1, Structural Formula 1-2 or Structural Formula 1-3 as an additive can greatly improve the film formation of the non-aqueous electrolyte on the positive and negative electrodes with a small amount of addition
  • the formed passivation film has greater flexibility, high stability, and relatively slow impedance growth, which improves the performance stability of the positive and negative electrode materials in the long-term cycle and prolongs the cycle life of the battery.
  • the stability of the passivation film at high temperatures is particularly excellent. Therefore, the battery obtained by using the non-aqueous electrolyte provided by the application is particularly suitable for working under high temperature conditions. , improving the environmental adaptability of the battery.
  • the mechanism for improving the performance of the passivation film for the bicyclic compounds shown in structural formula 1-1 to structural formula 1-3 is not very clear, but its mechanism of action is speculated to be: 1.
  • the bicyclic compounds shown in the above structural formulas 1-1 to 1-3 can undergo a reduction reaction on the negative electrode to open the ring to generate multivalent anion radicals, and the multivalent anion radicals further react to form larger molecular weight multivalent salts, multivalent salts
  • a regular network SEI film will be formed on the surface of the negative electrode. The surface of the SEI film has greater flexibility.
  • the bicyclic compounds shown in the structural formulas 1-1 to 1-3 because the two ring structures do not share Carbon atoms, thereby reducing the symmetrical distribution of polar groups, reducing the possibility of symmetrical distribution of charges in the molecule, making it easier to coordinate with lithium ions relative to molecules with higher symmetry, and with it in the electric field
  • the lower priority reaches the negative electrode for reduction, which helps to form a more stable SEI film on the surface of the electrode and improves the high-temperature performance of the lithium-ion battery.
  • the hydrocarbon groups can be linear hydrocarbon groups, branched chain hydrocarbon groups or cyclic hydrocarbon groups.
  • R 1 , R 2 , R 3 , R 4 , R 1 ′, R 2 ′, R 3 ′, R 4 ′ and R 1 ′′, R 2 ′′, R 3 ′′, R 4 ′′ are each independently selected from hydrocarbon groups
  • the hydrocarbon group can also be a linear hydrocarbon group, a branched chain hydrocarbon group or a cyclic hydrocarbon group.
  • X, Y or R 1 , R 2 , R 3 , R 4 , R 1 ′, R 2 ′, R 3 ′, R 4 ′, R 1 ′′, R 2 ′′, R 3 ′′, R 4 ′′ When selected from halogenated hydrocarbon groups, fluorinated hydrocarbon groups are preferred.
  • the bicyclic compound represented by the structural formula 1-1 is selected from one or more of the following compounds:
  • the bicyclic compound represented by the structural formula 1-2 is selected from one or more of the following compounds:
  • the bicyclic compound represented by the structural formula 1-3 is selected from one or more of the following compounds:
  • the mass percentage of the bicyclic compound is 0.01%-5.0%.
  • the mass percentage of the bicyclic compound is less than 0.01%, a complete passivation film cannot be formed on the surface of the negative electrode, so it is difficult to obviously improve the high temperature performance of the nonaqueous electrolyte battery.
  • the mass percentage of the bicyclic compound is higher than 5.0%, an excessively thick SEI passivation film is easily formed on the surface of the negative electrode, which instead increases the interface impedance and deteriorates the high-temperature performance of the battery.
  • the mass percentage of the bicyclic compound is 0.1%-3.0%.
  • the electrochemical performance of the prepared lithium ion battery is more excellent.
  • the non-aqueous electrolytic solution further includes at least one of cyclic sulfate ester compounds, cyclic sulfonate ester compounds, cyclic carbonate compounds, unsaturated phosphate ester compounds and nitrile compounds.
  • These substances are additives to the electrolyte, which can form a more stable SEI film on the surface of the graphite negative electrode, thereby significantly improving the cycle performance of the lithium-ion battery.
  • the cyclic sulfate ester compound includes at least one of vinyl sulfate, propylene sulfate or vinyl methyl sulfate. Based on the total mass of the non-aqueous electrolyte as 100%, the mass percentage of the cyclic sulfate ester compound is 0.01%-10%, preferably 0.1%-5%, more preferably 0.5%-3%.
  • the cyclic carbonate compound includes at least one of vinylene carbonate (VC), ethylene carbonate (VEC), fluoroethylene carbonate (FEC) or compounds shown in structural formula 2,
  • R 21 , R 22 , R 23 , R 24 , R 25 , and R 26 are each independently selected from a hydrogen atom, a halogen atom, and a C1-C5 group.
  • the compound represented by the structural formula 2 includes at least one of the compounds represented by the following compounds 2-1 to 2-6:
  • the cyclic carbonate compound can form a film together with the bicyclic compound shown in the structural formulas 1-1 to 1-3, and have a synergistic effect, thereby forming a passivation film with lower impedance, and further improving the high temperature of the lithium-ion battery. performance.
  • the specific type of the cyclic carbonate compound is not limited thereto.
  • the mass percentage of the cyclic carbonate compound is usually 0.01%-10%, preferably 0.1%-5%, more preferably 0.5%- 3%.
  • the mass percentage of the fluoroethylene carbonate (FEC) is usually 0.01-30%, preferably 0.1-10%, more preferably 0.5-5%.
  • the unsaturated phosphate compound is selected from at least one of the compounds shown in structural formula 3:
  • R 31 , R 32 , and R 33 are independently selected from C1-C5 saturated hydrocarbon groups, unsaturated hydrocarbon groups, halogenated hydrocarbon groups, -Si(C m H 2m+1 ) 3 , m is a natural number of 1 to 3, and R At least one of 31 , R 32 , and R 33 is an unsaturated hydrocarbon group.
  • the unsaturated phosphoric acid ester compound can be tripropargyl phosphate, dipropargyl methyl phosphate, dipropargyl ethyl phosphate, dipropargyl propyl phosphate, diacetylenic Propyl trifluoromethyl phosphate, Dipropargyl-2,2,2-trifluoroethyl phosphate, Dipropargyl-3,3,3-trifluoropropyl phosphate, Dipropargyl hexa Fluoroisopropyl Phosphate, Triallyl Phosphate, Diallyl Methyl Phosphate, Diallyl Ethyl Phosphate, Diallyl Propyl Phosphate, Diallyl Trifluoromethyl Phosphate , diallyl-2,2,2-trifluoroethyl phosphate, diallyl-3,3,3-trifluoropropyl phosphate, diallyl hexafluorois
  • the unsaturated phosphate ester compound shown in the structural formula 3 is used as a positive electrode film-forming additive to participate in the formation of a passivation film on the surface of the positive electrode material. reaction, protect the positive electrode, inhibit the dissolution of transition metals in the positive electrode material, and improve the impedance growth and capacity loss of the battery.
  • the unsaturated phosphate ester represented by structural formula 3 and the compounds represented by structural formulas 1-1 to 1-3 have a synergistic effect to form a dense and stable SEI film on the surface of the negative electrode, effectively preventing the reduction reaction of the electrolyte on the surface of the negative electrode and
  • the deposition of transition metals improves the interface between the negative electrode and the electrolyte, and slows down the side reactions at the electrode interface during storage or cycling, thereby improving the high-temperature storage and high-temperature cycle performance of the battery.
  • the weight percentage of the unsaturated phosphoric acid ester compound is 0.1%-2.0%.
  • the weight percentage of the unsaturated phosphate compound in the non-aqueous electrolyte is between 0.1% and 2.0%, it has a better effect of promoting the formation of the SEI film.
  • the phosphate compound is in the non-aqueous electrolyte
  • the percentage by weight in is less than 0.1% or greater than 2.0%, its lifting effect on the SEI film on the electrode will decrease.
  • nitrile compound comprises succinonitrile, glutaronitrile, ethylene glycol two (propionitrile) ether, hexanetrinitrile, adiponitrile, pimelonitrile, suberonitrile, azelanitrile, sebaconitrile one or more.
  • the inventors have found through a large number of experiments that the combined use of the bicyclic compounds represented by the structural formulas 1-1 to 1-3 provided by the present invention and the above-mentioned additives shows an obvious synergistic effect in improving the high-temperature cycle performance of the battery, indicating that the structural formula 1
  • the bicyclic compounds shown in -1 to 1-3 and the above-mentioned additives can form a film together on the surface of the electrode to make up for the film-forming defects of a single addition, obtain a more stable passivation film, and jointly improve battery cycle performance and high-temperature storage performance through synergistic effects.
  • the lithium salt is selected from LiPF 6 , LiBOB, LiDFOB, LiPO 2 F 2 , LiBF 4 , LiSbF 6 , LiAs F 6 , LiN(SO 2 CF 3 ) 2 , LiN(SO 2 C 2 F 5 ) 2. At least one of LiC(SO 2 CF 3 ) 3 , LiN(SO 2 F) 2 , and LiBETI.
  • the content of the lithium salt can vary within a wide range.
  • the content of the lithium salt is 0.1% to 15%, preferably 1% to 13%, more preferably 2 % ⁇ 10%.
  • the solvent includes one or more of ether solvents, nitrile solvents, carbonate solvents and carboxylate solvents.
  • ether solvents include cyclic ethers or chain ethers
  • cyclic ethers may be, but not limited to, 1,3-dioxolane (DOL), 1,4-dioxane (DX) , crown ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH3-THF), one or more of 2-trifluoromethyltetrahydrofuran (2-CF3-THF);
  • the chain ether is specifically It can be but not limited to one or more of dimethoxymethane (DMM), 1,2-dimethoxyethane (DME), diglyme (TEGDME).
  • the nitrile solvent may be, but not limited to, one or more of glutaronitrile and malononitrile.
  • Carbonate solvents include cyclic carbonates or chain carbonates. Cyclic carbonates can be, but not limited to, ethylene carbonate (EC), propylene carbonate (PC), ⁇ -butyrolactone (GBL), butylene carbonate One or more in ester (BC); Chain carbonate specifically can be but not limited to dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dipropyl carbonate One or more of (DPC).
  • DMC dimethyl carbonate
  • EMC ethyl methyl carbonate
  • DEC diethyl carbonate
  • DPC dipropyl carbonate One or more of (DPC).
  • Carboxylate solvents can be, but not limited to, methyl acetate (MA), ethyl acetate (EA), propyl acetate (EP), butyl acetate, propyl propionate (PP), butyl propionate one or more.
  • MA methyl acetate
  • EA ethyl acetate
  • EP propyl acetate
  • PP propyl propionate
  • the solvent includes at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate and propyl methyl carbonate.
  • the present application also provides a lithium-ion battery, including a positive electrode, a negative electrode, a separator, and the above-mentioned non-aqueous electrolyte.
  • the positive electrode includes a positive electrode active material selected from the group consisting of LiNix Co y Mnz M 1-xyz O 2 , LiCo 1-y My O 2 , LiNi 1-y My O 2 , LiMn At least one of 2-y My O 4 , LiFe 1-x' N x' PO 4 , wherein M is selected from Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga , at least one of Cr, Sr, V or Ti, and 0 ⁇ y ⁇ 1, 0 ⁇ x ⁇ 1, 0 ⁇ z ⁇ 1, x+y+z ⁇ 1; N is selected from Mn, Mg, Co, At least one of Ni, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V or Ti, and 0 ⁇ x' ⁇ 1.
  • M is selected from Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V or Ti, and 0 ⁇ x' ⁇ 1.
  • the positive electrode active material is selected from LiCoO 2 , LiNiO 2 , LiMn 2 O 4 , LiFePO 4 , LiFe 0.2 Mg 0.8 PO 4 , LiFe 0.4 Co 0.6 PO 4 , LiFe 0.6 Ni 0.4 PO 4 , LiFe 0.8 Cu 0.2 PO 4 4. At least one of LiFe 0.7 Zn 0.3 PO 4 .
  • the positive electrode further includes a positive electrode current collector for drawing current, and the positive electrode active material is covered on the positive electrode current collector.
  • the negative electrode includes a negative electrode active material
  • the negative electrode active material can be made of carbon materials, metal alloys, lithium-containing oxides, and silicon-containing materials.
  • the negative electrode further includes a negative electrode current collector for drawing current, and the negative electrode active material is covered on the negative electrode current collector.
  • the separator is arranged between the positive electrode and the negative electrode, and the separator is a conventional separator in the lithium ion battery field, which can be a polymer separator, a non-woven fabric, etc., including but not limited to single-layer PP (polypropylene), single-layer One-layer PE (polyethylene), double-layer PP/PE, double-layer PP/PP and three-layer PP/PE/PP separators.
  • a polymer separator including but not limited to single-layer PP (polypropylene), single-layer One-layer PE (polyethylene), double-layer PP/PE, double-layer PP/PP and three-layer PP/PE/PP separators.
  • the non-aqueous electrolytic solution provided by the application and the lithium-ion battery contain the bicyclic compound shown in structural formula 1-1, structural formula 1-2 or structural formula 1-3, which can be positive and negative for the non-aqueous electrolytic solution in a small amount of addition.
  • the film formation on the electrode has a great improvement effect.
  • the formed passivation film has greater flexibility, high stability, and relatively slow impedance growth, which improves the performance stability of the positive and negative electrode materials in long-term cycles.
  • the stability of the passivation film at high temperatures is particularly excellent, therefore, using the non-aqueous electrolyte provided by the application,
  • the obtained battery is especially suitable for working under high temperature conditions, and the environmental adaptability of the battery is improved.
  • EC ethylene carbonate
  • DEC diethyl carbonate
  • EMC ethyl methyl carbonate
  • LiPF 6 lithium hexafluorophosphate
  • positive electrode active material lithium nickel cobalt manganese oxide LiNi 0.5 Co 0.2 Mn 0.3 O 2 at a mass ratio of 93:4:3, conductive carbon black Super-P and binder polyvinylidene fluoride (PVDF), and then combine them Disperse in N-methyl-2-pyrrolidone (NMP) to obtain positive electrode slurry.
  • NMP N-methyl-2-pyrrolidone
  • the slurry is uniformly coated on both sides of the aluminum foil, dried, calendered and vacuum-dried, and an aluminum lead-out wire is welded with an ultrasonic welder to obtain a positive plate, the thickness of which is between 120-150 ⁇ m.
  • a three-layer separator with a thickness of 20 ⁇ m was placed between the positive plate and the negative plate, and then the sandwich structure composed of the positive plate, the negative plate and the separator was wound, and then the wound body was flattened and put into an aluminum foil packaging bag. °C for 48 hours under vacuum to obtain the cell to be filled.
  • Example 1 Place the lithium-ion battery made in Example 1 in an oven with a constant temperature of 45°C, charge it to 4.2V (LiNi 0.5 Co 0.2 Mn 0.3 O 2 /artificial graphite lithium-ion battery) at a constant current of 1C, and then charge it at a constant voltage to The current drops to 0.02C, and then discharges to 3.0V at a constant current of 1C, and this cycle is repeated, and the first discharge capacity and the last discharge capacity are recorded.
  • 4.2V LiNi 0.5 Co 0.2 Mn 0.3 O 2 /artificial graphite lithium-ion battery
  • Battery capacity retention rate (%) last discharge capacity/first discharge capacity ⁇ 100%.
  • Battery capacity retention rate (%) retention capacity/initial capacity ⁇ 100%;
  • Battery capacity recovery rate (%) recovery capacity / initial capacity ⁇ 100%;
  • Volume expansion rate (%) (battery thickness after storage-initial battery thickness)/initial battery thickness ⁇ 100%. The test results are shown in Table 2.
  • Embodiment 2-19 is used to illustrate the non-aqueous electrolyte of the present application, lithium ion battery and preparation method thereof, comprises most of the operation steps in embodiment 1, and its difference is:
  • Comparative example 1-9 is used for comparative illustration non-aqueous electrolytic solution of the present application, lithium ion battery and preparation method thereof, comprises most of the operating steps in embodiment 1, and its difference is:
  • Comparative example 4 the test result of embodiment 8-15 and comparative example 2-5 can know, compare traditional vinylene carbonate (VC), fluoroethylene carbonate (FEC), ethylene sulfate (DTD) and Tripropargyl phosphate, using the bicyclic compounds shown in the structural formula 1-1 to structural formula 1-3 provided by the application as an additive, can more significantly improve the storage performance and cycle performance of lithium-ion batteries at high temperatures, and produce less gas. It shows that the passivation film formed by the compounds represented by structural formula 1-1 to structural formula 1-3 has more excellent high temperature stability.
  • VC vinylene carbonate
  • FEC fluoroethylene carbonate
  • DTD ethylene sulfate
  • Tripropargyl phosphate Tripropargyl phosphate
  • Example 4 Comparing the test results of Example 4 and Examples 16-19, it can be seen that compared to the separate addition of the bicyclic compounds shown in Structural Formula 1-1 to Structural Formula 1-3, the bicyclic compounds shown in Structural Formula 1-1 to Structural Formula 1-3
  • the combination with vinylene carbonate (VC) improves the high-temperature cycle performance of the battery more significantly, indicating that the passivation film formed by the compound represented by structural formula 1 and vinylene carbonate (VC) has better high-temperature stability.
  • Comparative Example 18 and Comparative Example 6 show that, compared to the traditional combination additive of vinylene carbonate (VC) and ethylene sulfate (DTD), using the structural formula 1-1 to structural formula 1-3 provided by the application Combining the bicyclic compound shown with vinyl sulfate (DTD) further improves the passivation film formed by the compound shown in structural formula 1-1 to structural formula 1-3 has more excellent high temperature stability.
  • VC vinylene carbonate
  • DTD ethylene sulfate
  • Example 4 Comparing the test results of Example 4 and Comparative Example 7, it can be seen that the overall improvement of the high-temperature performance of Example 4 is more obvious, which may be attributed to the presence of hydrocarbon groups between the bicyclic rings of the compound shown in the structural formula 1-1 provided by the application.
  • hydrocarbon groups between the bicyclic rings of the compound shown in the structural formula 1-1 provided by the application On the one hand , which can reduce the symmetrical distribution of the polar groups of the molecule, and reduce the possibility of its net charge being evenly distributed in the molecule, so that it is easier to coordinate with lithium ions and preferentially reach the negative electrode for reduction; on the other hand, two rings can be added
  • the degree of freedom of movement enables the film-forming product to be closely combined with the negative electrode, and has higher flexibility, so that the overall performance of the lithium-ion battery is improved more significantly.
  • Example 8 Comparing the test results of Example 8 and Comparative Examples 7-8, it can be seen that the overall improvement of the high temperature performance of Example 8 is more obvious, which may be attributed to the SEI film formed by the bicyclic compound shown in the structural formula 1-2 provided by the application. Containing inorganic components and organic components, the SEI film is a more uniform organic-inorganic composite film on the atomic scale, which can not only improve the lithium ion conductivity, but also protect the structure of the positive and negative electrodes, improve the stability of the battery material, and better Insulate the contact between the positive and negative electrode materials and the electrolyte, thereby reducing the polarization of the battery, inhibiting the growth of impedance, and improving the high temperature performance of the battery.
  • Example 12 Comparing the test results of Example 12 and Comparative Example 9, it can be seen that the high temperature performance of Example 12 is more excellent, which may be attributed to the fact that the SEI film formed by the bicyclic compound shown in the structural formula 1-2 provided by the application contains both inorganic components and Organic components, the SEI film is a more uniform organic-inorganic composite film on the atomic scale, which can not only improve the lithium ion conductivity, but also protect the structure of the positive and negative electrodes, improve the stability of battery materials, and better isolate the positive and negative electrode materials Contact with the electrolyte, thereby reducing the polarization of the battery, inhibiting the growth of impedance, and improving the high temperature performance of the battery.
  • the non-aqueous electrolyte and the lithium-ion battery provided by the present application contain bicyclic compounds shown in structural formulas 1-1 to 1-3, which can enable the lithium-ion battery to form a stable SEI film during charging and discharging, and improve the lithium ion battery. Electrochemical performance of ion batteries at elevated temperatures.

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Abstract

本申请涉及锂离子电池技术领域，具体涉及一种非水电解液及锂离子电池。为克服现有锂离子电池高温性能不佳的技术问题，本申请提供了一种非水电解液，包括溶剂、锂盐以及结构式1-1至结构式1-3所示的双环化合物中的至少一种：同时，本申请还公开了包括上述非水电解液的锂离子电池。本申请提供的非水电解液及锂离子电池能够有效改善电池的高温循环性能和高温存储性能。

Description

一种非水电解液及锂离子电池 技术领域
本申请涉及锂离子电池技术领域，具体涉及一种非水电解液及锂离子电池。
背景技术
随着人们对电动汽车和混合电动汽车的性能要求越来越高，动力电池性能尤其是高温性能面临更多的挑战。目前动力电池主要以锂离子电池为主，锂离子电池电芯主要由正极、负极、隔膜以及电解液组成。在锂离子电池充电过程中，电池正极材料中的锂离子脱嵌出来，通过电解液嵌入碳负极中。在初始阶段，电解液成分会优先得电子，在碳负极表面反应产生Li 2CO 3、Li 2O、LiOH等化合物，从而在负极表面形成钝化膜，该钝化膜称为固体电解液界面膜(SEI)。在初始充电过程中形成的SEI膜能够阻止电解液进一步在碳负极表面分解，而且起到锂离子导体作用，只允许锂离子通过。但是，在后续的锂离子电池的充放电循环过程中，电极可能会发生变化导致SEI膜发生破裂，这可能会致使负极再次暴露在电解液中并持续与电解液发生反应，在消耗电解液的同时产生气体，从而导致锂离子电池的内压增加，降低电池的循环寿命。电池在高温条件下储存或充电循环使用时，电极体积变化更为明显，SEI膜更容易发生破裂，从而导致锂离子电池在高温条件下的电化学性能下降更为明显。因此，SEI膜的质量严重影响锂离子电池的高温性能。
为了提高锂离子电池的各项性能，许多科研者通过往电解液中添加不同的负极成膜剂，例如氟代碳酸乙烯酯、碳酸乙烯亚乙酯、1，3-丙烷磺酸内酯等添加剂来改善SEI膜的质量，从而改善电池的各项性能。虽然现有的成膜添加剂能够改善电池的某一性能，但改善的程度有限，特别是高温循环性能和存储性能，仍然不能满足市场的需要，如何开发一种能够进一步提高高温循环性能和存储性能的添加剂是亟需解决的问题。
发明内容
针对现有锂离子电池的高温循环和高温存储稳定性差的问题，本申请提供了一种非水电解液及电池。
本申请所采用的技术方案如下：
一方面，本申请提供了一种非水电解液，包括溶剂、锂盐以及结构式1-1至结构式1-3所示的至少一种双环化合物：
Figure PCTCN2022099750-appb-000001
其中，A选自羰基、C1-C10的烃基、C1-C10卤代烃基或C2-C10含羰基的烃基，R 1、R 2、R 3、R 4各自独立地选自单键、C1-C5的烃基或C1-C5的卤代烃基；优选的，A选自羰基、C1-C6的烃基、C1-C6的卤代烃基或C2-C6的含羰基的烃基，R 1、R 2、R 3、R 4各自独立地选自单键、C1-C3的烃基或C1-C3的卤代烃基。
Figure PCTCN2022099750-appb-000002
其中，X选自单键、羰基、C1-C10的烃基、C1-C10的卤代烃基或C2-C10的含羰基的烃 基，R 1′、R 2′、R 3′、R 4′各自独立地选自单键、C1-C5的烃基或C1-C5的卤代烃基；优选的，X选自单键、羰基、C1-C6的烃基、C1-C6的卤代烃基或C2-C6的含羰基的烃基，R 1′、R 2′、R 3′、R 4′各自独立地选自单键、C1-C3的烃基或C1-C3的卤代烃基；
Figure PCTCN2022099750-appb-000003
其中，Y选自单键、羰基、C1-C10的烃基、C1-C10的卤代烃基或C2-C10的含羰基的烃基，R 1″、R 2″、R 3″、R 4″各自独立地选自单键、C1-C5的烃基或C1-C5的卤代烃基；优选的，Y选自单键、羰基、C1-C6的烃基、C1-C6的卤代烃基或C2-C6的含羰基的烃基，R 1″、R 2″、R 3″、R 4″各自独立地选自单键、C1-C3的烃基或C1-C3的卤代烃基。
采用结构式1-1、结构式1-2或结构式1-3所示的双环化合物作为添加剂，能够在较小的添加量下对非水电解液在正负极上的成膜起到较大的改善作用，所成型的钝化膜具有较大的柔韧性，稳定性高，阻抗增长相对比较缓慢，提升了正负极材料在长期循环中的性能稳定性，延长了电池的循环寿命，同时，值得注意的是，相比于现有的一些常规添加剂，该钝化膜在高温下的稳定性尤其优异，因此，采用本申请提供的非水电解液，得到的电池特别适用于高温条件下的工作，提高了电池的环境适应性。
由于正负极上成膜机制较为复杂，对于结构式1-1至结构式1-3所示的双环化合物对于钝化膜的性能提升的机理并不十分明确，但其作用机理推测认为：1、所述结构式1-1至1-3所示的双环化合物能够在负极上发生还原反应开环生成多价阴离子自由基，多价阴离子自由基进一步发生反应形成较大分子量的多价盐，多价盐会在负极表面形成规整的网状结构SEI膜，该SEI膜表面具有较大的柔韧性，即使高温下SEI膜也不容易破裂，阻抗增加也相对比较缓慢，能有效减少电解液溶剂在负极上发生分解，减少气体的产生，从而提高锂离子电池在高温条件下的电化学性能；2、多价阴离子自由基进一步发生反应形成较大分子量的多价盐，多价盐具有更好的耐氧化特性，减缓电解液的氧化进程，能够显著提升锂离子电池的高温循环性能以及高温储存性能；3、所述结构式1-1至1-3所示的双环化合物，由于两个环状结构没有共享碳原子，从而减少极性基团对称分布的方式，减少电荷在分子中对称分布的可能性，从而使其相对于拥有更高对称性的分子更易与锂离子配位，并伴随其在电场作用下优先到达负极还原，有助于电极表面能够形成更稳固的SEI膜，改善锂离子电池的高温性能。
需要说明的是，在A、X、Y选自烃基或卤代烃基的情况下，烃基可以是直链烃基、支链烃基或环状烃基。在R 1、R 2、R 3、R 4、R 1′、R 2′、R 3′、R 4′及R 1″、R 2″、R 3″、R 4″各自独立地选自烃基或卤代烃基的情况下，烃基同样可以是直链烃基、支链烃基或环状烃基。在A、X、Y或R 1、R 2、R 3、R 4、R 1′、R 2′、R 3′、R 4′、R 1″、R 2″、R 3″、R 4″选自卤代烃基时，优选氟代烃基。
优选的，所述结构式1-1所示的双环化合物选自以下化合物中的一种或多种：
Figure PCTCN2022099750-appb-000004
Figure PCTCN2022099750-appb-000005
Figure PCTCN2022099750-appb-000006
所述结构式1-2所示的双环化合物选自以下化合物中的一种或多种：
Figure PCTCN2022099750-appb-000007
Figure PCTCN2022099750-appb-000008
所述结构式1-3所示的双环化合物选自以下化合物中的一种或多种：
Figure PCTCN2022099750-appb-000009
Figure PCTCN2022099750-appb-000010
优选的，以所述非水电解液的总质量为100％计，所述双环化合物的质量百分比为0.01％-5.0％。当双环化合物的质量百分比低于0.01％时，负极表面无法形成完整的钝化膜，从而难以明显改善非水电解液电池的高温性能。而当所述双环化合物的质量百分比高于5.0％时，负极表面容易形成过厚的SEI钝化膜，反而增加界面阻抗，劣化电池的高温性能。
更为优选的，以所述非水电解液的总质量为100％计，所述双环化合物的质量百分比为0.1％-3.0％。当所述双环化合物的质量百分比为0.5％-3.0％时，所制备的锂离子电池的电化学性能更为优异。
优选的，所述非水电解液还包括环状硫酸酯类化合物、环状磺酸酯类化合物、环状碳酸酯类化合物、不饱和磷酸酯类化合物和腈类化合物中的至少一种。这些物质为电解液的添加剂，能够在石墨负极表面形成更稳定的SEI膜，从而显著提高了锂离子电池的循环性能。
优选的，所述环状硫酸酯类化合物包括硫酸乙烯酯、硫酸丙烯酯或甲基硫酸乙烯酯中的至少一种。以所述非水电解液的总质量为100％计，所述环状硫酸酯类化合物的质量百分比为0.01％-10％，优选0.1％-5％，更优选0.5％-3％。
优选的，所述环状碳酸酯类化合物包括碳酸亚乙烯酯(VC)、碳酸乙烯亚乙酯(VEC)、氟代碳酸乙烯酯(FEC)或结构式2所示的化合物中的至少一种，
Figure PCTCN2022099750-appb-000011
所述结构式2中，R 21、R 22、R 23、R 24、R 25、R 26各自独立地选自氢原子、卤素原子、C1-C5基团中的一种。
更为优选的，所述结构式2所示化合物包括下述化合物2-1至2-6所示化合物中的至少一种：
Figure PCTCN2022099750-appb-000012
所述环状碳酸酯类化合物能与所述结构式1-1至1-3所示的双环化合物共同成膜，发生协同作用，从而形成阻抗更低的钝化膜，进一步提高锂离子电池的高温性能。当然，应当理解，所述环状碳酸酯类化合物的具体类型不限于此。
进一步优选的，以所述非水电解液的总质量为100％计，所述环状碳酸酯类化合物的质量百分比通常为0.01％-10％，优选0.1％-5％，更优选0.5％-3％。特别的，所述氟代碳酸乙烯酯(FEC)的质量百分比通常为0.01-30％，优选0.1-10％，更为优选0.5-5％。
优选的，所述不饱和磷酸酯类化合物选自结构式3所示化合物中的至少一种：
Figure PCTCN2022099750-appb-000013
R 31、R 32、R 33各自独立的选自C1-C5的饱和烃基、不饱和烃基、卤代烃基、-Si(C mH 2m+1) 3，m为1～3的自然数，且R 31、R 32、R 33中至少有一个为不饱和烃基。
更为优选的，所述不饱和磷酸酯类化合物可为磷酸三炔丙酯、二炔丙基甲基磷酸酯、二炔丙基乙基磷酸酯、二炔丙基丙基磷酸酯、二炔丙基三氟甲基磷酸酯、二炔丙基-2，2，2-三氟乙基磷酸酯、二炔丙基-3，3，3-三氟丙基磷酸酯、二炔丙基六氟异丙基磷酸酯、磷酸三烯丙酯、二烯丙基甲基磷酸酯、二烯丙基乙基磷酸酯、二烯丙基丙基磷酸酯、二烯丙基三氟甲基磷酸酯、二烯丙基-2，2，2-三氟乙基磷酸酯、二烯丙基-3，3，3-三氟丙基磷酸酯、二烯丙基六氟异丙基磷酸酯中的至少一种。
所述结构式3所示的不饱和磷酸酯类化合物作为正极成膜添加剂，参与正极材料表面钝化膜的生成，该钝化膜隔绝了电解液与正极界面，可以抑制电解液与正极界面的副反应，起到正极保护作用，同时抑制正极材料中过渡金属的溶出，改善电池的阻抗增长与容量损失。此外，所述结构式3所示的不饱和磷酸酯与结构式1-1至1-3所示化合物发生协同作用，在负极表面形成致密稳定的SEI膜，有效阻止电解液在负极表面的还原反应与过渡金属的沉积，改善负极与电解液的界面，减缓存储或循环过程中电极界面的副反应，从而改善电池高温存储和高温循环性能。优选地，以所述非水电解液的总质量为100％计，所述不饱和磷酸酯类化合物的重量百分含量为0.1％～2.0％。当所述不饱和磷酸酯类化合物在非水电解液中的重量百分比处于0.1％～2.0％之间时具有较好的促进SEI膜形成的作用，当所述磷酸酯类化合物在非水电解液中的重量百分比小于0.1％或大于2.0％时，其对电极上SEI膜的提升作用均会有所下降。
所述腈类化合物包括丁二腈、戊二腈、乙二醇双(丙腈)醚、己烷三腈、己二腈、庚二腈、辛二腈、壬二腈、癸二腈中的一种或多种。
发明人通过大量实验发现：本发明提供的结构式1-1至1-3所示的双环化合物与上述添加剂联合使用，在提升电池的高温循环性能方面体现出明显的协同提升的作用，说明结构式1-1至1-3所示的双环化合物与上述添加剂在电极表面共同成膜能够弥补单一添加的成膜缺陷，得到更加稳定的钝化膜，通过协同作用共同改善电池循环性能和高温储存性能。
优选的，所述锂盐选自LiPF 6、LiBOB、LiDFOB、LiPO 2F 2、LiBF 4、LiSbF 6、LiA sF 6、LiN(SO 2CF 3) 2、LiN(SO 2C 2F 5) 2、LiC(SO 2CF 3) 3、LiN(SO 2F) 2、LiBETI中的至少一种。
锂盐的含量可在较大范围内变动，优选情况下，所述锂离子电池非水电解液中，锂盐的含量为0.1％～15％，优选为1％～13％，更为优选2％～10％。
优选的，所述溶剂包括醚类溶剂、腈类溶剂、碳酸酯类溶剂和羧酸酯类溶剂中的一种或多种。
在一些实施例中，醚类溶剂包括环状醚或链状醚，环状醚具体可以但不限于是1，3-二氧戊烷(DOL)、1，4-二氧六烷(DX)、冠醚、四氢呋喃(THF)、2-甲基四氢呋喃(2-CH3-THF)，2-三氟甲基四氢呋喃(2-CF3-THF)中的一种或多种；所述链状醚具体可以但不限于是二甲氧基甲烷(DMM)、1，2-二甲氧基乙烷(DME)、二甘醇二甲醚(TEGDME)中的一种或多种。腈类溶剂具体可以但不限于是戊二腈、丙二腈中的一种或多种。碳酸酯类溶剂包括环状碳酸 酯或链状碳酸酯，环状碳酸酯具体可以但不限于是碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、γ-丁内酯(GBL)、碳酸亚丁酯(BC)中的一种或多种；链状碳酸酯具体可以但不限于是碳酸二甲酯(DMC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二丙酯(DPC)中的一种或多种。羧酸酯类溶剂具体可以但不限于是乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(EP)、乙酸丁酯、丙酸丙酯(PP)、丙酸丁酯中的一种或多种。
更为优选的，所述溶剂包括碳酸乙烯酯、碳酸丙烯酯、碳酸丁烯酯、碳酸二甲酯、碳酸二乙酯、碳酸甲乙酯和碳酸甲丙酯中的至少一种。
另一方面，本申请还提供一种锂离子电池，包括正极、负极、隔膜以及如上所述的非水电解液。
优选的，所述正极包括正极活性材料，所述正极活性材料选自LiNi xCo yMn zM 1-x-y-zO 2、LiCo 1-yM yO 2、LiNi 1-yM yO 2、LiMn 2-yM yO 4、LiFe 1-x′N x′PO 4中的至少一种，其中，M选自Fe、Co、Ni、Mn、Mg、Cu、Zn、Al、Sn、B、Ga、Cr、Sr、V或Ti中的至少一种，且0≤y≤1，0≤x≤1，0≤z≤1，x+y+z≤1；N选自Mn、Mg、Co、Ni、Cu、Zn、Al、Sn、B、Ga、Cr、Sr、V或Ti中的至少一种，且0≤x’＜1。
优选的，所述正极活性材料选自LiCoO 2、LiNiO 2、LiMn 2O 4、LiFePO 4、LiFe 0.2Mg 0.8PO 4、LiFe 0.4Co 0.6PO 4、LiFe 0.6Ni 0.4PO 4、LiFe 0.8Cu 0.2PO 4、LiFe 0.7Zn 0.3PO 4中的至少一种。
优选的，所述正极还包括用于引出电流的正极集流体，所述正极活性材料覆盖于正极集流体上。
优选的，所述负极包括负极活性材料，所述负极活性材料可由碳材料、金属合金、含锂氧化物及含硅材料制得。
优选的，所述负极还包括有用于引出电流的负极集流体，所述负极活性材料覆盖于所述负极集流体上。
优选的，所述隔膜设置在正极和负极之间，所述隔膜为锂离子电池领域的常规隔膜，可以是聚合物隔膜、无纺布等，包括但不限于单层PP(聚丙烯)、单层PE(聚乙烯)、双层PP/PE、双层PP/PP和三层PP/PE/PP等隔膜。
本申请提供的非水电解液及锂离子电池中含有结构式1-1、结构式1-2或结构式1-3所示的双环化合物，能够在较小的添加量下对非水电解液在正负极上的成膜起到较大的改善作用，所成型的钝化膜具有较大的柔韧性，稳定性高，阻抗增长相对比较缓慢，提升了正负极材料在长期循环中的性能稳定性，延长了电池的循环寿命，同时，值得注意的是，相比于现有的一些常规添加剂，该钝化膜在高温下的稳定性尤其优异，因此，采用本申请提供的非水电解液，得到的电池特别适用于高温条件下的工作，提高了电池的环境适应性。
具体实施方式
下面将结合本申请中的实施例，对本申请实施例中的技术方案进行清楚、完整的描述，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，本领域普通的技术人员在没有做出创造性劳动的前提下所获得的所有其它实施例，都属于本申请的保护范围。
以下通过实施例对本申请进行进一步的说明。
表1
Figure PCTCN2022099750-appb-000014
Figure PCTCN2022099750-appb-000015
注：以下实施例和对比例中采用的化合物1～12选自于表1。
实施例1
1)非水电解液的制备：
将碳酸乙烯酯(EC)、碳酸二乙酯(DEC)和碳酸甲乙酯(EMC)按质量比为EC∶DEC∶EMC＝1∶1∶1进行混合，然后加入六氟磷酸锂(LiPF 6)至摩尔浓度为1mol/L，以非水电解液的总重量为100％计，加入按表2中实施例1所示质量百分比的化合物1。
2)正极板的制备：
按93∶4∶3的质量比混合正极活性材料锂镍钴锰氧化物LiNi 0.5Co 0.2Mn 0.3O 2，导电碳黑Super-P和粘结剂聚偏二氟乙烯(PVDF)，然后将它们分散在N-甲基-2-吡咯烷酮(NMP)中，得到正极浆料。将浆料均匀涂布在铝箔的两面上，经过烘干、压延和真空干燥，并用超声波焊机焊上铝制引出线后得到正极板，极板的厚度在120-150μm之间。
3)负极板的制备：
按94∶1∶2.5∶2.5的质量比混合负极活性材料人造石墨，导电碳黑Super-P，粘结剂丁苯橡胶(SBR)和羧甲基纤维素(CMC)，然后将它们分散在去离子水中，得到负极浆料。将浆料涂布在铜箔的两面上，经过烘干、压延和真空干燥，并用超声波焊机焊上镍制引出线后得到负极板，极板的厚度在120-150μm之间。
4)电芯的制备：
在正极板和负极板之间放置厚度为20μm的三层隔膜，然后将正极板、负极板和隔膜组成的三明治结构进行卷绕，再将卷绕体压扁后放入铝箔包装袋，在75℃下真空烘烤48h，得到待注液的电芯。
5)电芯的注液和化成：
在露点控制在-40℃以下的手套箱中，将上述制备的电解液注入电芯中，经真空封装，静 止24h。
然后按以下步骤进行首次充电的常规化成：0.05C恒流充电180min，0.2C恒流充电至3.95V，二次真空封口，然后进一步以0.2C的电流恒流充电至4.2V，常温搁置24h后，以0.2C的电流恒流放电至3.0V，得到一种LiNi 0.5Co 0.2Mn 0.3O 2/人造石墨锂离子电池。
二、电池性能测试
(1)高温循环性能测试
将实施例1制作的锂离子电池置于恒温45℃的烘箱中，以1C的电流恒流充电至4.2V(LiNi 0.5Co 0.2Mn 0.3O 2/人造石墨锂离子电池)，再恒压充电至电流下降至0.02C，然后以1C的电流恒流放电至3.0V，如此循环，记录第1次的放电容量和最后一次的放电容量。
按下式计算循环的容量保持率：
电池容量保持率(％)＝最后一次的放电容量/第1次的放电容量×100％。
(2)高温储存性能测试
将实施例1制作的锂离子电池化成后在常温下用1C恒流恒压充至4.2V(LiNi 0.5Co 0.2Mn 0.3O 2/人造石墨锂离子电池)，测量电池初始放电容量及初始电池厚度，然后在60℃环境中储存30天后，以1C放电至3.0V，测量电池的保持容量和恢复容量及储存后电池厚度。计算公式如下：
电池容量保持率(％)＝保持容量/初始容量×100％；
电池容量恢复率(％)＝恢复容量/初始容量×100％；
体积膨胀率(％)＝(储存后电池厚度-初始电池厚度)/初始电池厚度×100％，测试结果如表2所示。
实施例2-19
实施例2-19用于说明本申请非水电解液、锂离子电池及其制备方法，包括实施例1中大部分的操作步骤，其不同之处在于：
所述非水电解液的制备步骤中：
以所述非水电解液的总重量为100％计，加入表2中实施例2-19所示质量百分比的组分。得到测试结果填入表2。
对比例1-9
对比例1-9用于对比说明本申请非水电解液、锂离子电池及其制备方法，包括实施例1中大部分的操作步骤，其不同之处在于：
以所述非水电解液的总重量为100％计，加入表2中对比例1-9所示质量百分比的组分。得到测试结果填入表2。
表2
Figure PCTCN2022099750-appb-000016
Figure PCTCN2022099750-appb-000017
对比实施例1-7与对比例1的测试结果可知，在电解液中添加结构式1-1至结构式1-3所示的双环化合物，能够在较大的添加范围内对电池的高温性能起到较好的提升作用，且随着结构式1-1至结构式1-3所示双环化合物的含量提升，电池的高温存储性能先提升后降低，尤其是，当化合物的含量为1％时，电池具有最佳的综合性能，这可能归因于，在锂离子电池充放电循环的过程中，电解液中双环化合物的含量为0.5-3.0％能够保证所形成的SEI膜薄厚适中，稳定性更好。
对比实施例4、实施例8-15与对比例2-5的测试结果可知，相比于传统的碳酸亚乙烯酯(VC)、氟代碳酸乙烯酯(FEC)、硫酸乙烯酯(DTD)和磷酸三炔丙酯，采用本申请提供的结构式1-1至结构式1-3所示的双环化合物作为添加剂，能够更加显著地改善锂离子电池在高温下的存储性能和循环性能，产气少，说明由结构式1-1至结构式1-3所示化合物形成的钝化膜具有更加优异的高温稳定性。
对比实施例4和实施例16-19的测试结果可知，相比于结构式1-1至结构式1-3所示的双环化合物的单独添加，结构式1-1至结构式1-3所示的双环化合物与碳酸亚乙烯酯(VC)的组合对于电池高温循环性能的提升更为明显，说明结构式1所示的化合物与碳酸亚乙烯酯(VC) 共同参与形成的钝化膜的高温稳定性较好。
对比实施例18和对比例6的测试结果可知，相比于传统的碳酸亚乙烯酯(VC)、硫酸乙烯酯(DTD)组合添加剂，采用本申请提供的结构式1-1至结构式1-3所示的双环化合物与硫酸乙烯酯(DTD)进行组合，进一步提升说明由结构式1-1至结构式1-3所示化合物形成的钝化膜具有更加优异的高温稳定性。
对比实施例4与对比例7的测试结果可知，实施例4的高温性能整体提升更为明显，这可能归因于本申请提供的结构式1-1所示化合物的双环之间含有烃基，一方面，可减少分子极性基团对称分布的方式，减少其净电荷在分子中平均分布的可能性，从而使其更易与锂离子配位并优先到达负极还原；另一方面，可增加两个环移动的自由度，使其成膜后的产物可与负极紧密结合，并具有更高的柔韧性，从而使锂离子电池的性能整体提升更为明显。
对比实施例8与对比例7-8的测试结果可知，实施例8的高温性能整体提升更为明显，这可能归因于本申请提供的结构式1-2所示的双环化合物形成的SEI膜同时含有无机组分和有机组分，该SEI膜为原子尺度上更为均匀的有机无机复合膜，既能够提高锂离子传导速率，又能够保护正负极结构，提高电池材料稳定性，更好的隔绝正负极材料与电解液之间的接触，从而降低电池极化，抑制阻抗增长，提高电池的高温性能。
对比实施例12与对比例9的测试结果可知，实施例12的高温性能更优异，这可能归因于本申请提供的结构式1-2所示的双环化合物形成的SEI膜同时含有无机组分和有机组分，该SEI膜为原子尺度上更为均匀的有机无机复合膜，既能够提高锂离子传导速率，又能够保护正负极结构，提高电池材料稳定性，更好的隔绝正负极材料与电解液之间的接触，从而降低电池极化，抑制阻抗增长，提高电池的高温性能。
综上，本申请提供的非水电解液及锂离子电池中含有结构式1-1至1-3所示的双环化合物，能够使锂离子电池在充放电过程中能够形成稳定的SEI膜，提高锂离子电池在高温条件下的电化学性能。
以上借助具体实施例对本申请做了进一步描述，但是应该理解的是，这里具体的描述，不应理解为对本申请的实质和范围的限定，本领域内的普通技术人员在阅读本说明书后对上述实施例做出的各种修改，都属于本申请所保护的范围。

Claims (10)

  1. 一种非水电解液，其特征在于，包括溶剂、锂盐以及结构式1-1至结构式1-3所示的双环化合物中的至少一种：
    Figure PCTCN2022099750-appb-100001
    其中，A选自羰基、C1-C10的烃基、C1-C10的卤代烃基或C2-C10的含羰基的烃基，R 1、R 2、R 3、R 4各自独立地选自单键、C1-C5的烃基或C1-C5的卤代烃基；
    Figure PCTCN2022099750-appb-100002
    其中，X选自单键、羰基、C1-C10的烃基、C1-C10的卤代烃基或C2-C10的含羰基的烃基，R 1′、R 2′、R 3′、R 4′各自独立地选自单键、C1-C5的烃基或C1-C5的卤代烃基；
    Figure PCTCN2022099750-appb-100003
    其中，Y选自单键、羰基、C1-C10的烃基、C1-C10的卤代烃基或C2-C10的含羰基的烃基，R 1″、R 2″、R 3″、R 4″各自独立地选自单键、C1-C5的烃基或C1-C5的卤代烃基。
  2. 根据权利要求1所述的非水电解液，其特征在于，所述结构式1-1所示的双环化合物选自以下化合物中的一种或多种：
    Figure PCTCN2022099750-appb-100004
    Figure PCTCN2022099750-appb-100005
    Figure PCTCN2022099750-appb-100006
    所述结构式1-2所示的双环化合物选自以下化合物中的一种或多种：
    Figure PCTCN2022099750-appb-100007
    Figure PCTCN2022099750-appb-100008
    所述结构式1-3所示的双环化合物选自以下化合物中的一种或多种：
    Figure PCTCN2022099750-appb-100009
    Figure PCTCN2022099750-appb-100010
  3. 根据权利要求1所述的非水电解液，其特征在于，以所述非水电解液的总质量为100％计，所述双环化合物的质量百分比为0.01％-5.0％。
  4. 根据权利要求1所述的非水电解液，其特征在于，所述非水电解液还包括环状硫酸酯类化合物、环状磺酸酯类化合物、环状碳酸酯类化合物、不饱和磷酸酯类化合物和腈类化合物中的至少一种。
  5. 根据权利要求4所述的非水电解液，其特征在于，所述环状硫酸酯类化合物选自硫酸乙烯酯、硫酸丙烯酯或甲基硫酸乙烯酯中的至少一种；
    所述环状磺酸酯类化合物选自1，3-丙烷磺内酯、1，4-丁烷磺内酯或1，3-丙烯磺内酯中的至少一种；
    所述环状碳酸酯类化合物选自碳酸亚乙烯酯、碳酸乙烯亚乙酯、氟代碳酸乙烯酯或结构式2所示化合物中的至少一种，
    Figure PCTCN2022099750-appb-100011
    所述结构式2中，R 21、R 22、R 23、R 24、R 25、R 26各自独立地选自氢原子、卤素原子、C1-C5基团中的一种；
    所述不饱和磷酸酯类化合物选自结构式3所示化合物中的至少一种：
    Figure PCTCN2022099750-appb-100012
    R 31、R 32、R 33各自独立的选自C1-C5的饱和烃基、不饱和烃基、卤代烃基、-Si(C mH 2m+1) 3，m为1～3的自然数，且R 31、R 32、R 33中至少有一个为不饱和烃基；
    所述腈类化合物包括丁二腈、戊二腈、乙二醇双(丙腈)醚、己烷三腈、己二腈、庚二腈、辛二腈、壬二腈、癸二腈中的一种或多种。
  6. 根据权利要求4所述的非水电解液，其特征在于，以所述非水电解液的总质量为100％计，所述环状硫酸酯类化合物的质量百分比为0.1-5.0％，所述环状磺酸酯类化合物的质量百分比为0.1％-5.0％，所述环状碳酸酯类化合物的质量百分比为0.1％-5.0％，所述不饱和磷酸酯类化合物的质量百分比为0.1％-2.0％，所述腈类化合物的质量百分比含量为0.1-5.0％。
  7. 根据权利要求1所述的非水电解液，其特征在于，所述锂盐选自LiPF 6、LiBOB、LiDFOB、LiPO 2F 2、LiBF 4、LiSbF 6、LiAsF 6、LiN(SO 2CF 3) 2、LiN(SO 2C 2F 5) 2、LiC(SO 2CF 3) 3、LiN(SO 2F) 2、LiBETI中的至少一种。
  8. 根据权利要求1所述的非水电解液，其特征在于，所述溶剂包括碳酸乙烯酯、碳酸丙烯酯、碳酸丁烯酯、碳酸二甲酯、碳酸二乙酯、碳酸甲乙酯和碳酸甲丙酯中的至少一种。
  9. 一种锂离子电池，其特征在于，包括正极、负极、隔膜以及权利要求1-8任一项所述的非水电解液。
  10. 根据权利要求9所述的锂离子电池，其特征在于，所述正极包括正极活性材料，所述正极活性材料选自LiNi xCo yMn zM 1-x-y-zO 2、LiCo 1-yM yO 2、LiNi 1-yM yO 2、LiMn 2-yM yO 4、LiFe 1- x′N x′PO 4中的至少一种，其中，M选自Fe、Co、Ni、Mn、Mg、Cu、Zn、Al、Sn、B、Ga、Cr、Sr、V或Ti中的至少一种，且0≤y≤1，0≤x≤1，0≤z≤1，x+y+z≤1；N选自Mn、Mg、Co、Ni、Cu、Zn、Al、Sn、B、Ga、Cr、Sr、V或Ti中的至少一种，且0≤x′＜1。
PCT/CN2022/099750 2021-07-22 2022-06-20 一种非水电解液及锂离子电池 Ceased WO2023000889A1 (zh)

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