WO2024120053A1 - 一种锂离子电池 - Google Patents

一种锂离子电池 Download PDF

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WO2024120053A1
WO2024120053A1 PCT/CN2023/127475 CN2023127475W WO2024120053A1 WO 2024120053 A1 WO2024120053 A1 WO 2024120053A1 CN 2023127475 W CN2023127475 W CN 2023127475W WO 2024120053 A1 WO2024120053 A1 WO 2024120053A1
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lithium
positive electrode
ion battery
aqueous electrolyte
battery according
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PCT/CN2023/127475
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English (en)
French (fr)
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钱韫娴
胡时光
李红梅
向晓霞
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深圳新宙邦科技股份有限公司
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Publication of WO2024120053A1 publication Critical patent/WO2024120053A1/zh

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    • 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 invention belongs to the technical field of energy storage devices, and in particular relates to a lithium ion battery.
  • Lithium-ion batteries are widely used in electric vehicles and consumer products due to their advantages such as high voltage platform, low self-discharge, high output power, no memory effect, long cycle life and low environmental pollution. With the expansion of the application scope, especially with the popularization of smart phones and electric vehicles, the demand for the cycle life of lithium-ion batteries is increasing.
  • the positive electrode active material with strong oxidation activity can easily oxidize the electrolyte, causing the electrolyte to decompose and produce gas.
  • the prior art usually adds lithium difluorophosphate to the electrolyte, which can form a passivation film on the positive electrode surface, reduce the oxidation activity of the positive electrode active material, and thus improve the battery cycle life.
  • Additives usually have a higher occupied molecular orbital (HOMO) level than electrolyte solvents and lithium salts. Therefore, it will be oxidized before the main electrolyte components during the charging process, and then form a decomposition layer on the positive electrode surface to prevent further decomposition of the electrolyte.
  • HOMO occupied molecular orbital
  • This passivation film formed on the positive electrode surface is not stable enough, resulting in continuous oxidation and decomposition during the circulation and storage of lithium-ion batteries (especially at the end of circulation and storage).
  • the DC internal resistance of lithium-ion batteries during circulation and storage continues to increase, which seriously affects the use of lithium-ion batteries.
  • the introduction of traditional additives into the electrolyte will lead to an additional risk of increased moisture in the electrolyte.
  • the reaction of water and LiPF 6 will produce HF, which is harmful to the layered positive electrode active material, especially the cycle stability at high voltage.
  • the present invention provides a lithium ion battery.
  • the present invention provides a lithium ion battery, comprising a positive electrode, a negative electrode, a non-aqueous electrolyte and a separator disposed between the positive electrode and the negative electrode, wherein the positive electrode comprises a positive electrode material layer containing a positive electrode active material, the surface of the positive electrode material layer comprises a first amphoteric oxide, the surface of the separator comprises a second amphoteric oxide, the non-aqueous electrolyte comprises a non-aqueous organic solvent, PO 2 F 2 - and a lithium salt, and the lithium salt comprises lithium hexafluorophosphate;
  • the lithium-ion battery meets the following conditions:
  • a is the molar concentration of lithium hexafluorophosphate in the non-aqueous electrolyte, in mol/L;
  • m is the mass percentage of PO 2 F 2 - in the non-aqueous electrolyte, in %;
  • b is the percentage content of the first amphoteric oxide in the mass of the positive electrode material layer, in %;
  • c is the percentage of the second amphoteric oxide in the mass of the diaphragm, in %.
  • the lithium-ion battery meets the following conditions:
  • the molar concentration a of lithium hexafluorophosphate in the non-aqueous electrolyte is 0.7 to 1.2 mol/L.
  • the mass percentage content m of PO 2 F 2 - in the non-aqueous electrolyte is 0.05% to 0.5%.
  • the percentage content b of the first amphoteric oxide in the positive electrode material layer is 0.03% to 1%.
  • the percentage content c of the second amphoteric oxide in the mass of the diaphragm is 3% to 20%.
  • the first amphoteric oxide and the second amphoteric oxide are each independently selected from at least one of aluminum oxide, zirconium oxide, tungsten oxide and titanium oxide.
  • the positive electrode active material includes at least one of LiFe1 -x'M'x'PO4 , LiMn2 -y'M y'O4 and LiNixCoyMnzM1 - xyzO2 , sulfide, selenide, and halide, wherein M' is selected from at least one of Mn, Mg , Co , Ni, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V or Ti, M is selected from at least one of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V or Ti, and 0 ⁇ x' ⁇ 1, 0 ⁇ y' ⁇ 1, 0 ⁇ y ⁇ 1, 0 ⁇ x ⁇ 1, 0 ⁇ z ⁇ 1, x+y+z ⁇ 1.
  • the non-aqueous electrolyte further comprises an additive, wherein the additive comprises at least one of a cyclic sulfate compound, a sultone compound, a cyclic carbonate compound, a phosphate compound, a borate compound and a nitrile compound;
  • the content of the additive is 0.01% to 30%.
  • the cyclic sulfate ester compound is selected from vinyl sulfate, propylene sulfate, methyl vinyl sulfate, At least one of;
  • the sultone compound is selected from 1,3-propane sultone, 1,4-butane sultone, 1,3-propylene sultone, At least one of;
  • the cyclic carbonate compound is selected from at least one of vinylene carbonate, ethylene carbonate, methylene carbonate, fluoroethylene carbonate, trifluoromethylethylene carbonate, bisfluoroethylene carbonate or the compound shown in structural formula 1:
  • 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 phosphate compound is selected from at least one of tris(trimethylsilyl)phosphate, tris(trimethylsilyl)phosphite or the compound shown in structural formula 2:
  • R 31 , R 32 , and R 33 are each independently selected from a C1-C5 saturated hydrocarbon group, an unsaturated hydrocarbon group, a halogenated hydrocarbon group, and -Si(C m H 2m+1 ) 3 , m is a natural number of 1 to 3, and at least one of R 31 , R 32 , and R 33 is an unsaturated hydrocarbon group;
  • the borate compound is selected from at least one of tris(trimethylsilyl)borate and tris(triethylsilyl)borate;
  • the nitrile compound is selected from at least one of succinonitrile, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrinitrile, adiponitrile, pimelonitrile, suberonitrile, azelaic acid dinitrile and sebacononitrile.
  • the surface of the positive electrode material layer contains a first amphoteric oxide
  • the surface of the separator contains a second amphoteric oxide, which can react with lithium hexafluorophosphate added in the electrolyte to generate a large amount of beneficial PO 2 F 2 - .
  • PO 2 F 2 - can decompose on the positive electrode surface and cooperate with the first amphoteric oxide to form a passivation film, thereby reducing the oxidation activity of the positive electrode active material to the non-aqueous electrolyte.
  • the inventors have found through a large number of studies that when the molar concentration of lithium hexafluorophosphate in the non-aqueous electrolyte is a, the molar concentration of PO 2 F 2 in the non-aqueous electrolyte is -When the mass percentage content m, the mass percentage content b of the first amphoteric oxide in the positive electrode material layer and the mass percentage content c of the second amphoteric oxide in the separator satisfy the conditions 0.1 ⁇ m*(10*b+c)/a ⁇ 30, and 0.5 ⁇ a ⁇ 1.5, 0.01 ⁇ m ⁇ 0.8, 0.01 ⁇ b ⁇ 2, 0.5 ⁇ c ⁇ 30, the density of the passivation film generated on the surface of the positive electrode material layer can be effectively controlled to make it present a more stable state, thereby avoiding the rupture of the passivation film during the charge and discharge cycle of the battery, ensuring the cycle stability of the non-aqueous electrolyte and the positive electrode active material, and effectively improving the battery cycle performance.
  • An embodiment of the present invention provides a lithium ion battery, comprising a positive electrode, a negative electrode, a non-aqueous electrolyte and a separator disposed between the positive electrode and the negative electrode, wherein the positive electrode comprises a positive electrode material layer comprising a positive electrode active material, the surface of the positive electrode material layer comprises a first amphoteric oxide, the surface of the separator comprises a second amphoteric oxide, the non-aqueous electrolyte comprises a non-aqueous organic solvent, PO 2 F 2 - and a lithium salt, and the lithium salt comprises lithium hexafluorophosphate;
  • the lithium-ion battery meets the following conditions:
  • a is the molar concentration of lithium hexafluorophosphate in the non-aqueous electrolyte, in mol/L;
  • m is the mass percentage of PO 2 F 2 - in the non-aqueous electrolyte, in %;
  • b is the percentage content of the first amphoteric oxide in the mass of the positive electrode material layer, in %;
  • c is the percentage of the second amphoteric oxide in the mass of the diaphragm, in %.
  • the term “the percentage content of the first amphoteric oxide in the mass of the positive electrode material layer” refers to the relative mass content of the first amphoteric oxide based on the mass of the positive electrode active layer being 100%.
  • the term “the percentage content of the second amphoteric oxide in the mass of the separator” refers to the relative mass content of the second amphoteric oxide based on the mass of the separator being 100%.
  • the first amphoteric oxide on the surface of the positive electrode material layer and the second amphoteric oxide on the surface of the separator can react with lithium hexafluorophosphate added to the electrolyte to generate a large amount of beneficial PO 2 F 2 - .
  • reaction equation is: 2Al 2 O 3 +3PF 6 - ⁇ AlF 3 +3PO 2 F 2 - .
  • the material of the positive electrode material layer and the surface of the separator is a non-amphoteric oxide, such as magnesium oxide, boron oxide, silicon oxide, etc., it will show little or no reactivity to the decomposition of LiPF 6 , so no or very small amount of PO 2 F 2 - will be generated, which does not meet the conditional restrictions of this application and is not conducive to improving the battery cycle performance.
  • a non-amphoteric oxide such as magnesium oxide, boron oxide, silicon oxide, etc.
  • PO 2 F 2 - can decompose on the surface of the positive electrode and cooperate with the first amphoteric oxide to form a passivation film, thereby reducing the oxidation activity of the positive electrode active material to the non-aqueous electrolyte.
  • the inventors have found through a large number of studies that when the molar concentration a of lithium hexafluorophosphate in the non-aqueous electrolyte, the mass percentage content m of PO 2 F 2 - in the non-aqueous electrolyte, the percentage content b of the first amphoteric oxide in the mass of the positive electrode material layer, and the percentage content c of the second amphoteric oxide in the mass of the separator meet the conditions 0.1 ⁇ m*(10*b+c)/a ⁇ 30, and 0.5 ⁇ a ⁇ 1.5, 0.01 ⁇ m ⁇ 0.8, 0.01 ⁇ b ⁇ 2, 0.5 ⁇ c ⁇ 30, the density of the passivation film generated on the surface of the positive electrode material layer can be effectively controlled to make it present a more stable state, thereby avoiding the rupture of the passivation film during the charge and discharge cycle of the battery, ensuring the cycle stability of the non-aqueous electrolyte and the positive electrode active material, and effectively improving the battery cycle performance.
  • both the surface of the positive electrode material layer and the surface of the separator contain amphoteric oxides, which can give full play to the synergistic effect of the two, thereby being more conducive to improving the battery cycle life.
  • the surface of the positive electrode material layer or the separator contains amphoteric oxides, although PO 2 F 2 - can be generated, the amount of PO 2 F 2 - generated is small, and the battery performance cannot be significantly improved.
  • the lithium-ion battery meets the following conditions:
  • the mass percentage content m of PO 2 F 2 - in the non-aqueous electrolyte, the percentage content b of the first amphoteric oxide in the mass of the positive electrode material layer, and the percentage content c of the second amphoteric oxide in the mass of the separator further meet the above conditions, the kinetic performance and cycle performance of the battery can be better improved while ensuring the battery energy density.
  • the molar concentration a of lithium hexafluorophosphate in the non-aqueous electrolyte can be 0.5 mol/L, 0.6 mol/L, 0.7 mol/L, 0.8 mol/L, 0.9 mol/L, 1.0 mol/L, 1.1 mol/L, 1.2 mol/L, 1.3 mol/L, 1.4 mol/L or 1.5 mol/L.
  • the molar concentration a of lithium hexafluorophosphate in the non-aqueous electrolyte is 0.7-1.2 mol/L.
  • the overall electrolyte salt content in the non-aqueous electrolyte will be less, affecting the ionic conductivity of the non-aqueous electrolyte.
  • the mass percentage content m of PO 2 F 2 - in the non-aqueous electrolyte may be 0.01%, 0.02%, 0.03%, 0.05%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.6%, 0.7% or 0.8%.
  • the mass percentage content m of PO 2 F 2 - in the non-aqueous electrolyte is 0.05% to 0.5%.
  • PO 2 F 2 - in the non-aqueous electrolyte can be generated by the reaction of amphoteric oxides and PF 6 - anions, or can be added to the non-aqueous electrolyte by additional addition; when PO 2 F 2 - is generated by the reaction of amphoteric oxides and PF 6 - anions, the amount of PO 2 F 2 - generated in the non-aqueous electrolyte is affected by many factors.
  • the control voltage of the first formation of the battery and other conditions will lead to differences in the amount of PO 2 F 2 - generated in the non-aqueous electrolyte. Too little PO 2 F 2 - generation does not significantly improve the performance of the lithium ion battery, while too much PO 2 F 2 - generation will lead to a decrease in the main lithium salt lithium hexafluorophosphate, which is not conducive to the improvement of the ion conduction rate of the lithium ion battery.
  • the percentage content b of the first amphoteric oxide in the positive electrode material layer may be 0.01%, 0.02%, 0.05%, 0.08%, 0.1%, 0.2%, 0.4%, 0.5%, 0.7%, 0.9%, 1.0%, 1.1%, 1.3%, 1.5%, 1.8% or 2.0%.
  • the percentage content b of the first amphoteric oxide in the positive electrode material layer is 0.03% to 1%.
  • the first amphoteric oxide is arranged on the surface of the positive electrode material layer, which can isolate the direct contact between the strong oxidizing positive electrode active material and the non-aqueous electrolyte, inhibit the side reaction of the non-aqueous electrolyte on the surface of the strong oxidizing positive electrode material layer, reduce the amount of gas generated by the decomposition of the non-aqueous electrolyte, and thus well extend the service life of the battery.
  • the amphoteric oxide can not only neutralize the residual alkali on the surface of the positive electrode material layer, but also consume the HF generated in the electrolyte or during the use of the battery, inhibit the dissolution of transition metals in the positive electrode active material, improve the stability of the interface between the positive electrode active material and the electrolyte, ensure the acid-base balance of the battery system, and ultimately improve the electrochemical performance of the battery. If the percentage content b of the first amphoteric oxide in the mass of the positive electrode material layer is too low, it is not conducive to improving the structural stability of the positive electrode active material and the generation of PO2F2- , and if it is too high , it is not conducive to improving the energy density of the battery and reducing the internal resistance.
  • the percentage content c of the second amphoteric oxide in the mass of the diaphragm can be 0.5%, 0.7%, 0.9%, 1.0%, 1.1%, 1.3%, 1.5%, 1.8%, 2.0%, 2.3%, 2.7%, 3.0%, 3.3%, 3.7%, 4.0%, 4.3%, 4.7%, 5%, 8%, 10%, 13%, 15%, 16%, 18%, 21%, 23%, 24%, 26%, 27%, 29% or 30%.
  • the percentage content c of the second amphoteric oxide in the mass of the diaphragm is 3% to 20%.
  • the second amphoteric oxide on the surface of the diaphragm plays a key role in inhibiting or reducing the harmful crosstalk phenomenon produced by the positive electrode. It can effectively reduce the side reaction products produced by the positive electrode from entering the negative electrode through the diaphragm. At the same time, the second amphoteric oxide can further improve the electronic insulation, temperature resistance and mechanical strength of the diaphragm, which is crucial for realizing lithium-ion batteries with long cycle life and high safety characteristics.
  • the percentage content c of the second amphoteric oxide in the mass of the separator is within the above range, the generation of PO 2 F 2 ⁇ can be effectively promoted, while improving the safety performance of the battery.
  • the first amphoteric oxide and the second amphoteric oxide are each independently selected from at least one of aluminum oxide, zirconium oxide, tungsten oxide, and titanium oxide.
  • the first amphoteric oxide and the second amphoteric oxide are each independently selected from at least one of aluminum oxide, zirconium oxide and titanium oxide.
  • the diaphragm is a polyolefin or non-woven porous composite membrane, and the second amphoteric oxide is coated on at least one side of the diaphragm.
  • the diaphragm includes but is not limited to one or more composites of polypropylene, polyethylene, polyimide, and polyvinylidene fluoride.
  • the positive electrode active material includes at least one of LiFe1 -x'M'x'PO4 , LiMn2 -y'M y'O4 and LiNixCoyMnzM1 - xyzO2 , sulfide, selenide, and halide, wherein M' is selected from at least one of Mn, Mg , Co , Ni, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V or Ti, M is selected from at least one of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V or Ti, and 0 ⁇ x' ⁇ 1, 0 ⁇ y' ⁇ 1, 0 ⁇ y ⁇ 1, 0 ⁇ x ⁇ 1, 0 ⁇ z ⁇ 1, x+y+z ⁇ 1.
  • the positive electrode material layer further includes a positive electrode binder, and the positive electrode binder is selected from organic polymers.
  • the molecular weight of the organic polymer is 600,000 to 1.3 million.
  • the positive electrode material layer and the positive electrode current collector can have good bonding force and dynamic performance, and the battery can be guaranteed to have excellent capacity and cycle life.
  • the organic polymer includes polyvinylidene fluoride, copolymers of vinylidene fluoride, polytetrafluoroethylene, copolymers of vinylidene fluoride-hexafluoropropylene, copolymers of tetrafluoroethylene-hexafluoropropylene, copolymers of tetrafluoroethylene-perfluoroalkyl vinyl ether, copolymers of ethylene-tetrafluoroethylene, copolymers of vinylidene fluoride-tetrafluoroethylene, copolymers of vinylidene fluoride-trifluoroethylene, copolymers of vinylidene fluoride-trichloroethylene, copolymers of vinylidene fluoride-fluoroethylene, copolymers of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, thermoplastic polyimide, polyethylene, polypropylene, polyethylene
  • the positive electrode material layer further includes a positive electrode conductive agent
  • the positive electrode conductive agent includes at least one of conductive carbon black, conductive carbon balls, conductive graphite, conductive carbon fibers, carbon nanotubes, graphene, or reduced graphene oxide.
  • the positive electrode active material is selected from at least one of LiFe1 -x'M'x'PO4 , LiMn2 -y'M y'O4 and LiNixCoyMnzM1 -xyzO2 , wherein M' is selected from at least one of Mn, Mg , Co, Ni, Cu , Zn, Al, Sn, B, Ga, Cr, Sr, V or Ti, M is selected from at least one of Fe, Co, Ni, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V or Ti, and 0 ⁇ x' ⁇ 1, 0 ⁇ y' ⁇ 1, 0 ⁇ y ⁇ 1, 0 ⁇ x ⁇ 1, 0 ⁇ z ⁇ 1, x+y+z ⁇ 1.
  • the positive electrode active material may be selected from at least one of LiCoO2 , LiFePO4 , LiFe0.8Mn0.2PO4 , LiMn2O4 , LiNi0.5Co0.2Mn0.3O2 , LiNi0.6Co0.2Mn0.2O2 , LiNi0.8Co0.1Mn0.1O2 , LiNi0.5Co0.2Mn0.2Al0.1O2 and LiNi0.5Co0.2Al0.3O2 .
  • the positive electrode further includes a positive electrode current collector, and the positive electrode material layer is formed on a surface of the positive electrode current collector.
  • the positive electrode current collector is selected from a metal material that can conduct electrons.
  • the positive electrode current collector includes at least one of Al, Ni, tin, copper, and stainless steel.
  • the positive electrode current collector is selected from aluminum foil.
  • the negative electrode includes a negative electrode material layer, and the negative electrode material layer includes a negative electrode active material.
  • the negative electrode active material includes at least one of a carbon-based negative electrode, a silicon-based negative electrode, a tin-based negative electrode, and a lithium negative electrode.
  • the carbon-based negative electrode may include graphite, hard carbon, soft carbon, graphene, mesophase carbon microspheres, etc.
  • the silicon-based negative electrode may include silicon materials, silicon oxides, silicon-carbon composite materials, and silicon alloy materials, etc.
  • the tin-based negative electrode may include tin, tin carbon, tin oxygen, and tin metal compounds
  • the lithium negative electrode may include metallic lithium or a lithium alloy.
  • the lithium alloy may specifically be at least one of a lithium silicon alloy, a lithium sodium alloy, a lithium potassium alloy, a lithium aluminum alloy, a lithium tin alloy, and a lithium indium alloy.
  • the negative electrode material layer further includes a negative electrode binder and a negative electrode conductive agent, and the negative electrode active material, the negative electrode binder and the negative electrode conductive agent are blended to obtain the negative electrode material layer.
  • the selectable ranges of the negative electrode binder and the negative electrode conductor are the same as those of the positive electrode binder and the positive electrode conductor, respectively, and will not be described in detail here.
  • the negative electrode further includes a negative electrode current collector, and the negative electrode material layer is formed on the negative electrode current collector. s surface.
  • the negative electrode current collector is selected from a metal material that can conduct electrons.
  • the negative electrode current collector includes at least one of aluminum, nickel, tin, copper, and stainless steel.
  • the negative electrode current collector is selected from copper foil.
  • the lithium salt further includes at least one of LiBOB, LiDFOB, LiBF4 , LiSbF6 , LiAsF6 , LiN(SO2CF3) 2, LiN(SO2C2F5)2 , LiC ( SO2CF3 ) 3 , LiN( SO2F ) 2 , LiClO4 , LiAlCl4 , LiCF3SO3 , Li2B10Cl10 , LiSO2F , LiTOP, LiDODFP and lower aliphatic carboxylate lithium salts.
  • the concentration of the lithium salt in the non-aqueous electrolyte is 0.1 mol/L to 8 mol/L. In a preferred embodiment, the concentration of the lithium salt in the non-aqueous electrolyte is 0.5 mol/L to 2.5 mol/L. Specifically, the concentration of the lithium salt in the non-aqueous electrolyte may be 0.5 mol/L, 1 mol/L, 1.5 mol/L, 2 mol/L, or 2.5 mol/L.
  • the non-aqueous organic solvent includes at least one of an ether solvent, a nitrile solvent, a carbonate solvent, a carboxylate solvent, and a sulfone solvent.
  • the ether solvent includes a cyclic ether or a chain ether, preferably a chain ether with 3 to 10 carbon atoms and a cyclic ether with 3 to 6 carbon atoms.
  • the cyclic ether may be, but is not limited to, at least one of 1,3-dioxolane (DOL), 1,4-dioxolane (DX), crown ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH 3 -THF), and 2-trifluoromethyltetrahydrofuran (2-CF 3 -THF);
  • the chain ether may be, but is not limited to, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether.
  • the chain ether has a high solvation ability with lithium ions and can improve ion dissociation, dimethoxymethane, diethoxymethane, and ethoxymethoxymethane, which have low viscosity and can impart high ionic conductivity, are particularly preferred.
  • the ether compound may be used alone or in any combination and ratio.
  • the content of the ether compound is not particularly limited and is arbitrary within the range that does not significantly damage the effect of the high-density lithium-ion battery of the present invention.
  • the volume ratio is usually 1% or more, preferably 2% or more, and more preferably 3% or more in the non-aqueous solvent volume ratio of 100%.
  • the volume ratio is usually 30% or less, preferably 25% or less, and more preferably 20% or less.
  • the total amount of the ether compounds can be made to meet the above range.
  • the content of the ether compound is within the above preferred range, it is easy to ensure the improvement effect of ion conductivity brought about by the increase in lithium ion dissociation degree and the decrease in viscosity of the chain ether.
  • the negative electrode active material is a carbon-based material, the phenomenon of co-embedding of chain ethers and lithium ions can be suppressed, so that the input-output characteristics and charge-discharge rate characteristics can reach an appropriate range.
  • the nitrile solvent may specifically be but is not limited to at least one of acetonitrile, glutaronitrile, and malononitrile.
  • the carbonate solvent includes a cyclic carbonate or a chain carbonate
  • the cyclic carbonate can be specifically but not limited to at least one of ethylene carbonate (EC), propylene carbonate (PC), ⁇ -butyrolactone (GBL), and butylene carbonate (BC)
  • the chain carbonate can be specifically but not limited to at least one of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and dipropyl carbonate (DPC).
  • the content of the cyclic carbonate there is no special restriction on the content of the cyclic carbonate, and it is arbitrary within the range that does not significantly damage the effect of the lithium ion battery of the present invention, but when one is used alone, the lower limit of its content is usually 3% or more by volume, preferably 5% or more by volume, relative to the total amount of solvent in the non-aqueous electrolyte.
  • the lower limit of its content is usually 3% or more by volume, preferably 5% or more by volume, relative to the total amount of solvent in the non-aqueous electrolyte.
  • the upper limit is usually less than 90% by volume, preferably less than 85% by volume, and more preferably less than 80% by volume.
  • the content of is not particularly limited, and relative to the total amount of solvent in the nonaqueous electrolyte, is usually 15% or more by volume, preferably 20% or more by volume, and more preferably 25% or more by volume.
  • the volume ratio is 90% or less, preferably 85% or less by volume, and more preferably 80% or less by volume.
  • the content of the linear carbonate in the above range it is easy to make the viscosity of the nonaqueous electrolyte reach an appropriate range, suppress the reduction of ionic conductivity, and then contribute to making the output characteristics of the nonaqueous electrolyte battery reach a good range.
  • the total amount of the linear carbonate is made to meet the above range.
  • fluorinated chain carbonates chain carbonates with fluorine atoms
  • the number of fluorine atoms possessed by the fluorinated chain carbonate is not particularly limited as long as it is more than 1, but is generally less than 6, preferably less than 4.
  • these fluorine atoms can be bonded to the same carbon or to different carbons.
  • fluorinated chain carbonate fluorinated dimethyl carbonate derivatives, fluorinated ethyl methyl carbonate derivatives, fluorinated diethyl carbonate derivatives, etc. can be listed.
  • the carboxylate solvent includes cyclic carboxylate and/or chain carbonate.
  • cyclic carboxylate include at least one of ⁇ -butyrolactone, ⁇ -valerolactone, and ⁇ -valerolactone.
  • chain carbonate include at least one of methyl acetate (MA), ethyl acetate (EA), propyl acetate (EP), butyl acetate, propyl propionate (PP), and butyl propionate.
  • the sulfone solvent includes a cyclic sulfone and a chain sulfone.
  • a cyclic sulfone it is usually a compound with 3 to 6 carbon atoms, preferably 3 to 5 carbon atoms
  • a chain sulfone it is usually a compound with 2 to 6 carbon atoms, preferably 2 to 5 carbon atoms.
  • the content of the sulfone solvent is not particularly limited and is arbitrary within the range that does not significantly damage the effect of the lithium ion battery of the present invention.
  • the volume ratio is usually 0.3% or more, preferably 0.5% or more, and more preferably 1% or more. In addition, the volume ratio is usually 40% or less, preferably 35% or less, and more preferably 30% or less. In the case of using two or more sulfone solvents in combination, the total amount of the sulfone solvents can meet the above range. When the content of the sulfone solvent is within the above range, a non-aqueous electrolyte with excellent high temperature storage stability tends to be obtained.
  • the non-aqueous organic solvent includes at least one of ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propylene carbonate, butyl acetate, ⁇ -butyrolactone, propyl propionate, ethyl propionate, ethyl butyrate, methyl acetate, ethyl acetate, ethyl fluoroacetate and fluoroether.
  • the non-aqueous organic solvent is a mixture of cyclic carbonate and chain carbonate.
  • the additive includes at least one of a cyclic sulfate compound, a sultone compound, a cyclic carbonate compound, a phosphate compound, a borate compound, and a nitrile compound;
  • the content of the additive is 0.01% to 30%.
  • the cyclic sulfate ester compound is selected from vinyl sulfate, propylene sulfate, methyl vinyl sulfate, At least one of;
  • the sultone compound is selected from 1,3-propane sultone, 1,4-butane sultone, 1,3-propylene sultone, At least one of;
  • the cyclic carbonate compound is selected from at least one of vinylene carbonate, ethylene carbonate, methylene carbonate, fluoroethylene carbonate, trifluoromethylethylene carbonate, bisfluoroethylene carbonate or the compound shown in structural formula 1:
  • 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 phosphate compound is selected from at least one of tris(trimethylsilyl)phosphate, tris(trimethylsilyl)phosphite or the compound shown in structural formula 2:
  • R 31 , R 32 , and R 33 are each independently selected from a C1-C5 saturated hydrocarbon group, an unsaturated hydrocarbon group, a halogenated hydrocarbon group, and -Si(C m H 2m+1 ) 3 , m is a natural number of 1 to 3, and at least one of R 31 , R 32 , and R 33 is an unsaturated hydrocarbon group;
  • the phosphate compound shown in the structural formula 2 may be at least one of tripropargyl phosphate, dipropargyl methyl phosphate, dipropargyl ethyl phosphate, dipropargyl propyl phosphate, dipropargyl trifluoromethyl phosphate, dipropargyl-2,2,2-trifluoroethyl phosphate, dipropargyl-3,3,3-trifluoropropyl phosphate, dipropargyl hexafluoroisopropyl 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, and diallyl hexafluoroisopropyl phosphate;
  • the borate compound is selected from at least one of tris(trimethylsilyl)borate and tris(triethylsilyl)borate;
  • the nitrile compound is selected from succinonitrile, glutaronitrile, ethylene glycol bis (propionitrile) ether, hexane trinitrile, adiponitrile, pimelonitrile, At least one of suberonitrile, azelaic acid dicarbonitrile and sebaconitrile.
  • the additives may also include other additives that can improve battery performance: for example, additives that enhance battery safety performance, such as flame retardant additives such as fluorophosphates and cyclophosphazenes, or overcharge prevention additives such as tert-amylbenzene and tert-butylbenzene.
  • additives that enhance battery safety performance such as flame retardant additives such as fluorophosphates and cyclophosphazenes, or overcharge prevention additives such as tert-amylbenzene and tert-butylbenzene.
  • the content of any one of the optional substances in the additives in the non-aqueous electrolyte is less than 10%, preferably, the content is 0.1-5%, and more preferably, the content is 0.1% to 2%.
  • the content of any one of the optional substances in the additives can be 0.05%, 0.08%, 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 7.8%, 8%, 8.5%, 9%, 9.5%, 10%.
  • the content of the fluoroethylene carbonate is 0.05% to 30% based on the total mass of the non-aqueous electrolyte as 100%.
  • This embodiment is used to illustrate the lithium-ion battery disclosed in the present invention, comprising a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator disposed between the positive electrode and the negative electrode, wherein:
  • the positive electrode comprises a positive electrode material layer formed by mixing positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O 2 , conductive carbon black Super-P and a positive electrode binder, and the surface of the positive electrode material layer contains a first amphoteric oxide of a mass shown in Table 1;
  • the negative electrode comprises a negative electrode material layer prepared by mixing negative electrode active material artificial graphite, conductive carbon black Super-P, binder styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) in a mass ratio of 94:1:2.5:2.5;
  • the non-aqueous electrolyte includes a non-aqueous organic solvent, PO 2 F 2 - and a lithium salt
  • the lithium salt includes lithium hexafluorophosphate
  • the lithium hexafluorophosphate (LiPF 6 ) concentration and PO 2 F 2 - content in the non-aqueous electrolyte are shown in Table 1.
  • the diaphragm is a PE diaphragm, and the surface of the diaphragm contains a second amphoteric oxide of a mass as shown in the example of Table 1.
  • Examples 2 to 31 are used to illustrate the lithium ion battery disclosed in the present invention, and are mostly the same as Example 1, except that:
  • the positive electrode active material LiPF 6 concentration, mass content of PO 2 F 2 ⁇ , other additives and their content, the first amphoteric oxide and its mass content, and the second amphoteric oxide and its mass content shown in Examples 2 to 31 in Table 1 were used.
  • Comparative Examples 1 to 27 are used to compare and illustrate the lithium ion batteries disclosed in the present invention, and most of them are the same as Example 1, except that:
  • the positive electrode active materials, LiPF6 concentration, mass content of PO2F2- , other additives and their contents, first amphoteric oxides/other oxides and their mass contents, and second amphoteric oxides/other oxides and their mass contents shown in Examples 1 to 27 in Table 1 were used.
  • the preparation of the lithium ion batteries of the above-mentioned examples and comparative examples can be carried out by a known method without particular limitation. Examples thereof include: adding LiPO 2 F 2 synthesized by a known method to an electrolyte; allowing the active material, electrode plate, separator and other battery components to coexist in advance, and generating PO 2 F 2 - in the system when assembling the battery using an electrolyte containing LiPF 6 ; In this embodiment, any method can be used.
  • the method for measuring the PO 2 F 2 - content in the lithium ion battery is not particularly limited, and any known method may be used, including ion chromatography, 19 F NMR, and the like.
  • the lithium ion batteries of the embodiments and comparative examples were charged at a 1C rate and discharged at a 1C rate, and the battery capacity of the first charge and discharge was recorded.
  • a full charge and discharge cycle test was performed within a charge and discharge cut-off voltage (such as 3V to 4.2V) until the capacity of the lithium ion battery decayed to 80% of the initial capacity, and the initial capacity of the battery and the number of cycles were recorded.
  • lithium hexafluorophosphate can react to generate PO 2 F 2 - during the battery formation process, and PO 2 F 2 - further decomposes on the surface of the positive electrode active material and cooperates with the first amphoteric oxide to form a passivation film.
  • the first amphoteric oxide in the positive electrode material layer and the second amphoteric oxide on the separator can be regulated, and at the same time, the content of lithium hexafluorophosphate and PO 2 F 2 - can be controlled.
  • Example 1 and Comparative Examples 5 to 6 It can be seen from the test results of Example 1 and Comparative Examples 5 to 6 that the lack of either the first amphoteric oxide or the second amphoteric oxide will result in a significant decrease in the amount of PO 2 F 2 - , and at the same time, an increase in battery impedance and a decrease in the number of cycles. It can be seen from the test results of Example 1 and Comparative Examples 7 to 13 that when other oxides are used to replace the first amphoteric oxide and/or the second amphoteric oxide, they exhibit less reactivity or no reactivity to the decomposition of LiPF 6 , thereby generating no or very little PO 2 F 2 - , which does not meet the conditional restrictions of the present application and is not conducive to improving the battery cycle performance.

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Abstract

为克服现有锂离子电池存在钝化膜不稳定导致的循环性能不足的问题，本发明提供了一种锂离子电池，包括正极、负极、非水电解液和设置于所述正极与所述负极之间的隔膜，所述正极包括含有正极活性材料的正极材料层，所述正极材料层表面含有第一两性氧化物，所述隔膜表面含有第二两性氧化物，所述非水电解液包括非水有机溶剂、PO2F2 -和锂盐，所述锂盐包括六氟磷酸锂；所述锂离子电池满足以下条件：0.1≤m*(10*b+c)/a≤30，且0.5≤a≤1.5，0.01≤m≤0.8，0.01≤b≤2，0.5≤c≤30。本发明提供的锂离子电池具有较好的循环稳定性，有效提高电池循环寿命。

Description

一种锂离子电池 技术领域
本发明属于储能装置技术领域，具体涉及一种锂离子电池。
背景技术
锂离子电池由于具备高电压平台、自放电少、输出功率高、无记忆效应、循环寿命和环境污染小等优点而被广泛应用于电动汽车以及消费类产品中。随着应用范围的扩大，尤其是随着智能手机和电动车的普及，对锂离子电池的循环寿命的需求日益增加。
在锂离子电池使用过程中，具有强氧化活性的正极活性材料很容易氧化电解液，使电解液分解产气。现有技术通常在电解液中加入二氟磷酸锂，其可以在正极表面形成的钝化膜，降低正极活性材料的氧化活性，从而改善电池循环寿命。添加剂通常具有比电解质溶剂和锂盐更高的占据分子轨道(HOMO)水平。因此，它会在充电过程中在主要电解质成分之前被氧化，然后在正极表面形成分解层，以防止电解质进一步分解，这种在正极表面形成的钝化膜不够稳定，导致其在锂离子电池循环和存储使用过程中(尤其在循环和存储末期)发生持续氧化分解，锂离子电池循环和存储过程中的直流内阻不断增加，严重影响了锂离子电池的使用。更重要的是，将传统添加剂引入电解质会导致电解质中水分增加的额外风险，水和LiPF6的反应会产生HF，这对层状正极活性材料，尤其是在高电压下的循环稳定性有害。
发明内容
针对现有锂离子电池存在钝化膜不稳定导致的循环性能不足的问题，本发明提供了一种锂离子电池。
本发明解决上述技术问题所采用的技术方案如下：
本发明提供了一种锂离子电池，包括正极、负极、非水电解液和设置于所述正极与所述负极之间的隔膜，所述正极包括含有正极活性材料的正极材料层，所述正极材料层表面含有第一两性氧化物，所述隔膜表面含有第二两性氧化物，所述非水电解液包括非水有机溶剂、PO2F2 -和锂盐，所述锂盐包括六氟磷酸锂；
所述锂离子电池满足以下条件：
0.1≤m*(10*b+c)/a≤30，且0.5≤a≤1.5，0.01≤m≤0.8，0.01≤b≤2，0.5≤c≤30；
其中，a为非水电解液中六氟磷酸锂的摩尔浓度，单位为mol/L；
m为非水电解液中PO2F2 -的质量百分含量，单位为％；
b为第一两性氧化物占正极材料层质量的百分比含量，单位为％；
c为第二两性氧化物占隔膜质量的百分比含量，单位为％。
可选的，所述锂离子电池满足以下条件：
0.5≤m*(10*b+c)/a≤10。
可选的，所述非水电解液中六氟磷酸锂的摩尔浓度a为0.7～1.2mol/L。
可选的，所述非水电解液中PO2F2 -的质量百分含量m为0.05％～0.5％。
可选的，所述第一两性氧化物占正极材料层质量的百分比含量b为0.03％～1％。
可选的，所述第二两性氧化物占隔膜质量的百分比含量c为3％～20％。
可选的，所述第一两性氧化物和所述第二两性氧化物各自独立地选自氧化铝、氧化锆、氧化钨和氧化钛中的至少一种。
可选的，所述正极活性材料包括LiFe1-x’M’x’PO4、LiMn2-y’My’O4和LiNixCoyMnzM1-x-y-zO2、硫化物、硒化物、卤化物中的至少一种，其中，M’选自Mn、Mg、Co、Ni、Cu、Zn、Al、Sn、B、Ga、Cr、Sr、V或Ti中的至少一种，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≤x’＜1，0≤y’≤1，0≤y≤1，0≤x≤1，0≤z≤1，x+y+z≤1。
可选的，所述非水电解液还包括添加剂，所述添加剂包括环状硫酸酯类化合物、磺酸内酯类化合物、环状碳酸酯类化合物、磷酸酯类化合物、硼酸酯类化合物和腈类化合物中的至少一种；
以所述非水电解液的总质量为100％计，所述添加剂的含量为0.01％～30％。
可选的，所述环状硫酸酯类化合物选自硫酸乙烯酯、硫酸丙烯酯、甲基硫酸乙烯酯、中的至少一种；
所述磺酸内酯类化合物选自1,3-丙烷磺酸内酯、1,4-丁烷磺酸内酯、1,3-丙烯磺酸内酯、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、亚甲基碳酸乙烯酯、氟代碳酸乙烯酯、三氟甲基碳酸乙烯酯、双氟代碳酸乙烯酯或结构式1所示化合物中的至少一种：
所述结构式1中，R21、R22、R23、R24、R25、R26各自独立地选自氢原子、卤素原子、C1-C5基团中的一种；
所述磷酸酯类化合物选自三(三甲基硅烷)磷酸酯、三(三甲基硅烷)亚磷酸酯或结构式2所示化合物中的至少一种：
所述结构式2中，R31、R32、R33各自独立的选自C1-C5的饱和烃基、不饱和烃基、卤代烃基、-Si(CmH2m+1)3，m为1～3的自然数，且R31、R32、R33中至少有一个为不饱和烃基；
所述硼酸酯类化合物选自三(三甲基硅烷)硼酸酯和三(三乙基硅烷)硼酸酯中的至少一种；
所述腈类化合物选自丁二腈、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、癸二腈中的至少一种。
根据本发明提供的锂离子电池，正极材料层表面含有第一两性氧化物、隔膜表面含有第二两性氧化物，能够与电解液中添加的六氟磷酸锂反应，生成大量有益的PO2F2 -，在电池化成的过程中，PO2F2 -可以在正极表面分解并与第一两性氧化物配合形成钝化膜，降低正极活性材料对于非水电解液的氧化活性，更重要的是，发明人通过大量研究发现，当所述非水电解液中六氟磷酸锂的摩尔浓度a、所述非水电解液中PO2F2 -的质量百分含量m、所述第一两性氧化物占正极材料层质量的百分比含量b和所述第二两性氧化物占隔膜质量的百分比含量c满足条件0.1≤m*(10*b+c)/a≤30，且0.5≤a≤1.5，0.01≤m≤0.8，0.01≤b≤2，0.5≤c≤30时，能够有效控制在正极材料层表面生成的钝化膜的致密程度，使其呈现出更加稳定的状态，从而在电池的充放电循环中避免钝化膜的破裂，保证非水电解液和正极活性材料的循环稳定性，有效提高电池循环性能。
具体实施方式
为了使本发明所解决的技术问题、技术方案及有益效果更加清楚明白，以下结合实施例，对本发明进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。
本发明实施例提供了一种锂离子电池，包括正极、负极、非水电解液和设置于所述正极与所述负极之间的隔膜，所述正极包括含有正极活性材料的正极材料层，所述正极材料层表面含有第一两性氧化物，所述隔膜表面含有第二两性氧化物，所述非水电解液包括非水有机溶剂、PO2F2 -和锂盐，所述锂盐包括六氟磷酸锂；
所述锂离子电池满足以下条件：
0.1≤m*(10*b+c)/a≤30，且0.5≤a≤1.5，0.01≤m≤0.8，0.01≤b≤2，0.5≤c≤30；
其中，a为非水电解液中六氟磷酸锂的摩尔浓度，单位为mol/L；
m为非水电解液中PO2F2 -的质量百分含量，单位为％；
b为第一两性氧化物占正极材料层质量的百分比含量，单位为％；
c为第二两性氧化物占隔膜质量的百分比含量，单位为％。
在本发明的描述中，术语“第一两性氧化物占正极材料层质量的百分比含量”指的是以正极活性层的质量为100％计，所述第一两性氧化物的相对质量含量。术语“第二两性氧化物占隔膜质量的百分比含量”指的是，以所述隔膜的质量为100％计，所述第二两性氧化物的相对质量含量。
正极材料层表面的第一两性氧化物和隔膜表面的第二两性氧化物，能够与电解液中添加的六氟磷酸锂反应，生成大量有益的PO2F2 -。
反应方程式为：2Al2O3+3PF6 -→AlF3+3PO2F2 -。
以上以两性氧化物中Al2O3为例解释本发明的发明构思，由上述机理，本领域技术人员可以理解，正极材料层或隔膜表面的材料为其它两性氧化物时，同样可以实现本发明的发明目的。
若正极材料层和隔膜表面的材料为非两性氧化物时，例如氧化镁、氧化硼、氧化硅等，则对LiPF6的分解表现出较小的反应性或无反应性，从而不生成或生成极少量的PO2F2 -，不满足本申请的条件限制，也不利于电池循环性能的提升。
在电池化成的过程中，PO2F2 -可以在正极表面分解并与第一两性氧化物配合形成钝化膜，降低正极活性材料对于非水电解液的氧化活性，更重要的是，发明人通过大量研究发现，当所述非水电解液中六氟磷酸锂的摩尔浓度a、所述非水电解液中PO2F2 -的质量百分含量m、所述第一两性氧化物占正极材料层质量的百分比含量b和所述第二两性氧化物占隔膜质量的百分比含量c满足条件0.1≤m*(10*b+c)/a≤30，且0.5≤a≤1.5，0.01≤m≤0.8，0.01≤b≤2，0.5≤c≤30时，能够有效控制在正极材料层表面生成的钝化膜的致密程度，使其呈现出更加稳定的状态，从而在电池的充放电循环中避免钝化膜的破裂，保证非水电解液和正极活性材料的循环稳定性，有效提高电池循环性能。
同时，正极材料层表面和隔膜表面均含有两性氧化物，能够更加充分发挥二者的协同作用，从而更有利于电池循环寿命的提升，而当正极材料层或隔膜的表面只有一者含有两性氧化物，虽然也能够生成PO2F2 -，但是其生成的PO2F2 -量较少，同样无法使电池性能产生较大的提升。
在优选的实施例中，所述锂离子电池满足以下条件：
0.5≤m*(10*b+c)/a≤10。
当所述非水电解液中六氟磷酸锂的摩尔浓度a、所述非水电解液中PO2F2 -的质量百分含量m、所述第一两性氧化物占正极材料层质量的百分比含量b和所述第二两性氧化物占隔膜质量的百分比含量c满足进一步满足上述条件时，能够在保证电池能量密度的前提下，更好的提高电池的动力学性能和循环性能。
当m*(10*b+c)/a值过低时，不能有效抑制非水电解液在强氧化性正极材料层表面的副反应，并大大降低PO2F2 -的生成，电池的内阻增大，引起电解液的高温稳定性不足，影响电池的高温循环和存储等性能，劣化电池的循环寿命。
当m*(10*b+c)/a值过高时，会导致电池的能量密度和动力学性能的降低，电解液的电导率过低，增大电池极化，从而影响电池的正常使用，同时也会影响PO2F2 -的生成，不利于电池循环寿命的提升。
在一些实施例中，所述非水电解液中六氟磷酸锂的摩尔浓度a可以为0.5mol/L、0.6mol/L、0.7mol/L、0.8mol/L、0.9mol/L、1.0mol/L、1.1mol/L、1.2mol/L、1.3mol/L、1.4mol/L或1.5mol/L。
在优选的实施例中，所述非水电解液中六氟磷酸锂的摩尔浓度a为0.7～1.2mol/L。
当非水电解液中六氟磷酸锂的含量过低时，一方面会导致非水电解液中总体的电解质盐含量较少，影响非水电解液的离子导电能力，此外也会影响与正极材料层或隔膜表面两性氧化物的反应活性，从而降低两性氧化物与PF6 -阴离子反应生成PO2F2 -的量；当非水电解液中六氟磷酸锂的含量偏高时，会导致非水电解液的粘度增大，电导率降低，同样不利于非水电解液离子导电能力的提升。
在一些实施例中，所述非水电解液中PO2F2 -的质量百分含量m可以为0.01％、0.02％、0.03％、0.05％、0.07％、0.08％、0.09％、0.1％、0.15％、0.2％、0.25％、0.3％、0.35％、0.4％、0.45％、0.5％、0.6％、0.7％或0.8％。
在优选的实施例中，所述非水电解液中PO2F2 -的质量百分含量m为0.05％～0.5％。
在本发明中，所述非水电解液中的PO2F2 -可以通过两性氧化物与PF6 -阴离子反应生成，也可以通过额外添加的方式加入非水电解液中；当PO2F2 -由两性氧化物与PF6 -阴离子反应生成时，其中非水电解液中PO2F2 -的生成量的影响因素较多，除了两性氧化物的含量、六氟磷酸锂的浓度之外，两性氧化物的设置位置以及与非水电解液的接触面积，电池首次化成的控制电压等条件均会导致非水电解液中PO2F2 -的生成量的差异，过少的PO2F2 -生成对于锂离子电池的性能提升不明显，而过多的PO2F2 -生成会导致主锂盐六氟磷酸锂的下降，从而不利于锂离子电池的离子传导速率的提升。
在一些实施例中，所述第一两性氧化物占正极材料层质量的百分比含量b可以为0.01％、 0.02％、0.05％、0.08％、0.1％、0.2％、0.4％、0.5％、0.7％、0.9％、1.0％、1.1％、1.3％、1.5％、1.8％或2.0％。
在优选的实施例中，所述第一两性氧化物占正极材料层质量的百分比含量b为0.03％～1％。
第一两性氧化物设置在正极材料层表面，可以隔绝强氧化性的正极活性材料与非水电解液的直接接触，抑制非水电解液在强氧化性正极材料层表面的副反应，降低因非水电解液分解而产生的气体量，进而很好地延长电池的使用寿命。同时，两性氧化物既可以中和正极材料层表面残碱，又可以消耗电解液中或电池使用过程所产生的HF、抑制正极活性材料中过渡金属的溶出、改善正极活性材料和电解液界面的稳定性，保证电池体系的酸碱平衡，进而最终提高电池的电化学性能。所述第一两性氧化物占正极材料层质量的百分比含量b过低不利于正极活性材料的结构稳定性的提高和PO2F2 -的生成，过高则不利于电池的能量密度的提高和内阻的降低。
在一些实施例中，所述第二两性氧化物占隔膜质量的百分比含量c可以为0.5％、0.7％、0.9％、1.0％、1.1％、1.3％、1.5％、1.8％、2.0％、2.3％、2.7％、3.0％、3.3％、3.7％、4.0％、4.3％、4.7％、5％、8％、10％、13％、15％、16％、18％、21％、23％、24％、26％、27％、29％或30％。
在优选的实施例中，所述第二两性氧化物占隔膜质量的百分比含量c为3％～20％。
隔膜表面的第二两性氧化物在抑制或减少正极产生有害的串扰现象方面发挥关键作用，能够有效降低正极产生的副反应产物通过隔膜进入负极，同时第二两性氧化物可以进一步提升隔膜的电子绝缘性、耐温性能和机械强度，对于实现具有长循环寿命和高安全特性的锂离子电池来说至关重要。
当第二两性氧化物占隔膜质量的百分比含量c处于上述范围中时，能够有效促进PO2F2 -的生成，同时提高电池的安全性能。
在一些实施例中，所述第一两性氧化物和所述第二两性氧化物各自独立地选自氧化铝、氧化锆、氧化钨和氧化钛中的至少一种。
在优选的实施例中，所述第一两性氧化物和所述第二两性氧化物各自独立地选自氧化铝、氧化锆和氧化钛中的至少一种。
在一些实施例中，所述隔膜为聚烯烃或无纺布多孔复合膜，所述第二两性氧化物涂覆在隔膜至少一侧表面，所述隔膜包括但不限于聚丙烯、聚乙烯、聚酰亚胺、聚偏氟乙烯中的一种或几种复合体。
在一些实施例中，所述正极活性材料包括LiFe1-x’M’x’PO4、LiMn2-y’My’O4和LiNixCoyMnzM1-x-y-zO2、硫化物、硒化物、卤化物中的至少一种，其中，M’选自Mn、Mg、Co、Ni、Cu、Zn、Al、Sn、B、Ga、Cr、Sr、V或Ti中的至少一种，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≤x’＜1，0≤y’≤1，0≤y≤1，0≤x≤1，0≤z≤1，x+y+z≤1。
在一些实施例中，所述正极材料层还包括正极粘结剂，所述正极粘结剂选自有机聚合物， 所述有机聚合物的分子量为60～130万。
当所述正极粘结剂满足以上条件时，可使正极材料层与正极集流体具有良好的粘结力和动力学性能，并保证电池具有优异的容量和循环寿命。
在一些实施例中，所述有机聚合物包括聚偏氟乙烯、偏氟乙烯的共聚物、聚四氟乙烯、偏氟乙烯-六氟丙烯的共聚物、四氟乙烯-六氟丙烯的共聚物、四氟乙烯-全氟烷基乙烯基醚的共聚物、乙烯-四氟乙烯的共聚物、偏氟乙烯-四氟乙烯的共聚物、偏氟乙烯-三氟乙烯的共聚物、偏氟乙烯-三氯乙烯的共聚物、偏氟乙烯-氟代乙烯的共聚物、偏氟乙烯-六氟丙烯-四氟乙烯的共聚物、热塑性聚酰亚胺、聚乙烯、聚丙烯、聚对苯二甲酸乙二醇酯、聚甲基丙烯酸甲酯等热塑性树脂；丙烯酸类树脂；羟甲基纤维素钠；丁腈橡胶、聚丁橡胶、乙烯-丙烯橡胶、苯乙烯-丁二烯-苯乙烯嵌段共聚物或其氢化物、乙烯-丙烯-二烯三元共聚物、聚乙酸乙烯酯、间规-1,2-聚丁二烯、乙烯-乙烯乙酸酯中的至少一种。
在一些实施例中，所述正极材料层还包括正极导电剂，所述正极导电剂包括导电炭黑、导电碳球、导电石墨、导电碳纤维、碳纳米管、石墨烯或还原氧化石墨烯中的至少一种。
在一些实施例中，所述正极活性材料选自LiFe1-x’M’x’PO4、LiMn2-y’My’O4和LiNixCoyMnzM1-x-y-zO2中的至少一种，其中，M’选自Mn、Mg、Co、Ni、Cu、Zn、Al、Sn、B、Ga、Cr、Sr、V或Ti中的至少一种，M选自Fe、Co、Ni、Mg、Cu、Zn、Al、Sn、B、Ga、Cr、Sr、V或Ti中的至少一种，且0≤x’＜1，0≤y’≤1，0≤y≤1，0≤x≤1，0≤z≤1，x+y+z≤1。
在优选的实施例中，所述正极活性材料可选自LiCoO2、LiFePO4、LiFe0.8Mn0.2PO4、LiMn2O4、LiNi0.5Co0.2Mn0.3O2、LiNi0.6Co0.2Mn0.2O2、LiNi0.8Co0.1Mn0.1O2、LiNi0.5Co0.2Mn0.2Al0.1O2、LiNi0.5Co0.2Al0.3O2中的至少一种。
在一些实施例中，所述正极还包括正极集流体，所述正极材料层形成于所述正极集流体的表面。
所述正极集流体选自可传导电子的金属材料，优选的，所述正极集流体包括Al、Ni、锡、铜、不锈钢的至少一种，在更优选的实施例中，所述正极集流体选自铝箔。
在一些实施例中，所述负极包括负极材料层，所述负极材料层包括负极活性材料。
在优选实施例中，所述负极活性材料包括碳基负极、硅基负极、锡基负极、锂负极中的至少一种。其中碳基负极可包括石墨、硬碳、软碳、石墨烯、中间相碳微球等；硅基负极可包括硅材料、硅的氧化物、硅碳复合材料以及硅合金材料等；锡基负极可包括锡、锡碳、锡氧、锡金属化合物；锂负极可包括金属锂或锂合金。锂合金具体可以是锂硅合金、锂钠合金、锂钾合金、锂铝合金、锂锡合金和锂铟合金中的至少一种。
在一些实施例中，所述负极材料层还包括有负极粘结剂和负极导电剂，所述负极活性材料、所述负极粘结剂和所述负极导电剂共混得到所述负极材料层。
所述负极粘接剂和负极导电剂的可选择范围分别与所述正极粘结剂和正极导电剂相同，在此不再赘述。
在一些实施例中，所述负极还包括负极集流体，所述负极材料层形成于所述负极集流体 的表面。
所述负极集流体选自可传导电子的金属材料，优选的，所述负极集流体包括铝、镍、锡、铜、不锈钢的至少一种，在更优选的实施例中，所述负极集流体选自铜箔。
在一些实施例中，所述锂盐还包括LiBOB、LiDFOB、LiBF4、LiSbF6、LiAsF6、LiN(SO2CF3)2、LiN(SO2C2F5)2、LiC(SO2CF3)3、LiN(SO2F)2、LiClO4、LiAlCl4、LiCF3SO3、Li2B10Cl10、LiSO2F、LiTOP、LiDODFP和低级脂肪族羧酸锂盐中的至少一种。
在一些实施例中，所述非水电解液中，所述锂盐的浓度为0.1mol/L～8mol/L。在优选实施例中，所述非水电解液中，所述锂盐的浓度为0.5mol/L～2.5mol/L。具体的，所述非水电解液中，所述锂盐的浓度可以为0.5mol/L、1mol/L、1.5mol/L、2mol/L、2.5mol/L。
在一些实施例中，所述非水有机溶剂包括醚类溶剂、腈类溶剂、碳酸酯类溶剂、羧酸酯类溶剂和砜类溶剂中的至少一种。
在一些实施例中，醚类溶剂包括环状醚或链状醚，优选为碳原子数3～10的链状醚及碳原子数3～6的环状醚，环状醚具体可以但不限于是1,3-二氧戊烷(DOL)、1,4-二氧惡烷(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)中的至少一种；所述链状醚具体可以但不限于是二甲氧基甲烷、二乙氧基甲烷、乙氧基甲氧基甲烷、乙二醇二正丙基醚、乙二醇二正丁基醚、二乙二醇二甲基醚。由于链状醚与锂离子的溶剂化能力高、可提高离子解离性，因此特别优选粘性低、可赋予高离子电导率的二甲氧基甲烷、二乙氧基甲烷、乙氧基甲氧基甲烷。醚类化合物可以单独使用一种，也可以以任意的组合及比率组合使用两种以上。醚类化合物的含量没有特殊限制，在不显著破坏本发明高压实锂离子电池效果的范围内是任意的，在非水溶剂体积比为100％中通常体积比为1％以上、优选体积比为2％以上、更优选体积比为3％以上，另外，通常体积比为30％以下、优选体积比为25％以下、更优选体积比为20％以下。在将两种以上醚类化合物组合使用的情况下，使醚类化合物的总量满足上述范围即可。醚类化合物的含量在上述的优选范围内时，易于确保由链状醚的锂离子离解度的提高和粘度降低所带来的离子电导率的改善效果。另外，负极活性材料为碳基材料的情况下，可抑制因链状醚与锂离子共同发生共嵌入的现象，因此能够使输入输出特性、充放电速率特性达到适当的范围。
在一些实施例中，腈类溶剂具体可以但不限于是乙腈、戊二腈、丙二腈中的至少一种。
在一些实施例中，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)中的至少一种；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)中的至少一种。环状碳酸酯的含量没有特殊限制，在不显著破坏本发明锂离子电池效果的范围内是任意的，但在单独使用一种的情况下其含量的下限相对于非水电解液的溶剂总量来说，通常体积比为3％以上、优选体积比为5％以上。通过设定该范围，可避免由于非水电解液的介电常数降低而导致电导率降低，易于使非水电解质电池的大电流放电特性、相对于负极的稳定性、循环特性达到良好的范围。另外，上限通常体积比为90％以下、优选体积比为85％以下、更优选体积比为80％以下。通过设定该范围，可提高非水电解液的氧化/还原耐性，从而有助于提高高温保存时的稳定性。链状碳酸酯 的含量没有特殊限定，相对于非水电解液的溶剂总量，通常为体积比为15％以上、优选体积比为20％以上、更优选体积比为25％以上。另外，通常体积比为90％以下、优选体积比为85％以下、更优选体积比为80％以下。通过使链状碳酸酯的含量在上述范围，容易使非水电解液的粘度达到适当范围，抑制离子电导率的降低，进而有助于使非水电解质电池的输出特性达到良好的范围。在组合使用两种以上链状碳酸酯的情况下，使链状碳酸酯的总量满足上述范围即可。
在一些实施例中，还可优选使用具有氟原子的链状碳酸酯类(以下简称为“氟化链状碳酸酯”)。氟化链状碳酸酯所具有的氟原子的个数只要为1以上则没有特殊限制，但通常为6以下、优选4以下。氟化链状碳酸酯具有多个氟原子的情况下，这些氟原子相互可以键合于同一个碳上，也可以键合于不同的碳上。作为氟化链状碳酸酯，可列举，氟化碳酸二甲酯衍生物、氟化碳酸甲乙酯衍生物、氟化碳酸二乙酯衍生物等。
羧酸酯类溶剂包括环状羧酸酯和/或链状碳酸酯。作为环状羧酸酯的例子，可以列举如：γ-丁内酯、γ-戊内酯、δ-戊内酯中的至少一种。作为链状碳酸酯的例子，可以列举如：乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(EP)、乙酸丁酯、丙酸丙酯(PP)、丙酸丁酯中的至少一种。
在一些实施例中，砜类溶剂包括环状砜和链状砜，优选地，在为环状砜的情况下，通常为碳原子数3～6、优选碳原子数3～5，在为链状砜的情况下，通常为碳原子数2～6、优选碳原子数2～5的化合物。砜类溶剂的含量没有特殊限制，在不显著破坏本发明锂离子电池效果的范围内是任意的，相对于非水电解液的溶剂总量，通常体积比为0.3％以上、优选体积比为0.5％以上、更优选体积比为1％以上，另外，通常体积比为40％以下、优选体积比为35％以下、更优选体积比为30％以下。在组合使用两种以上砜类溶剂的情况下，使砜类溶剂的总量满足上述范围即可。砜类溶剂的含量在上述范围内时，倾向于获得高温保存稳定性优异的非水电解液。
在优选的实施例中，所述非水有机溶剂包括碳酸乙烯酯、碳酸二甲酯、碳酸二乙酯、碳酸甲乙酯、碳酸丙烯酯、乙酸丁酯、γ-丁内酯、丙酸丙酯、丙酸乙酯、丁酸乙酯、乙酸甲酯、乙酸乙酯、氟代乙酸乙酯和氟醚中的至少一种。
在优选的实施例中，所述非水有机溶剂为环状碳酸酯和链状碳酸酯的混合物。
在一些实施例中，所述添加剂包括环状硫酸酯类化合物、磺酸内酯类化合物、环状碳酸酯类化合物、磷酸酯类化合物、硼酸酯类化合物和腈类化合物中的至少一种；
以所述非水电解液的总质量为100％计，所述添加剂的含量为0.01％～30％。
在一些实施例中，所述环状硫酸酯类化合物选自硫酸乙烯酯、硫酸丙烯酯、甲基硫酸乙烯酯、中的至少一种；
所述磺酸内酯类化合物选自1,3-丙烷磺酸内酯、1,4-丁烷磺酸内酯、1,3-丙烯磺酸内酯、 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、亚甲基碳酸乙烯酯、氟代碳酸乙烯酯、三氟甲基碳酸乙烯酯、双氟代碳酸乙烯酯或结构式1所示化合物中的至少一种：
所述结构式1中，R21、R22、R23、R24、R25、R26各自独立地选自氢原子、卤素原子、C1-C5基团中的一种；
所述磷酸酯类化合物选自三(三甲基硅烷)磷酸酯、三(三甲基硅烷)亚磷酸酯或结构式2所示化合物中的至少一种：
所述结构式2中，R31、R32、R33各自独立的选自C1-C5的饱和烃基、不饱和烃基、卤代烃基、-Si(CmH2m+1)3，m为1～3的自然数，且R31、R32、R33中至少有一个为不饱和烃基；
在优选的实施例中，所述结构式2所示的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；
所述硼酸酯类化合物选自三(三甲基硅烷)硼酸酯和三(三乙基硅烷)硼酸酯中的至少一种；
所述腈类化合物选自丁二腈、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、癸二腈中的至少一种。
在另一些实施例中，所述添加剂还可包括其它能改善电池性能的添加剂：例如，提升电池安全性能的添加剂，具体如氟代磷酸酯、环磷腈等阻燃添加剂，或叔戊基苯、叔丁基苯等防过充添加剂。
需要说明的是，除非特殊说明，一般情况下，所述添加剂中任意一种可选物质在非水电解液中的含量为10％以下，优选的，含量为0.1-5％，更优选的，含量为0.1％～2％。具体的，所述添加剂中任意一种可选物质的含量可以为0.05％、0.08％、0.1％、0.5％、0.8％、1％、1.2％、1.5％、1.8％、2％、2.2％、2.5％、2.8％、3％、3.2％、3.5％、3.8％、4％、4.5％、5％、5.5％、6％、6.5％、7％、7.5％、7.8％、8％、8.5％、9％、9.5％、10％。
在一些实施例中，当添加剂选自氟代碳酸乙烯酯时，以所述非水电解液的总质量为100％计，所述氟代碳酸乙烯酯的含量为0.05％～30％。
以下通过实施例对本发明进行进一步的说明。
表1实施例和对比例各参数设计



实施例1
本实施例用于说明本发明公开的锂离子电池，包括正极、负极、非水电解液和设置于所述正极与所述负极之间的隔膜，其中：
所述正极包括由正极活性材料LiNi0.8Co0.1Mn0.1O2、导电碳黑Super-P和正极粘结剂混合而成的正极材料层，且所述正极材料层表面含有表1所示质量的第一两性氧化物；
所述负极包括以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)制备而成的负极材料层；
所述非水电解液包括非水有机溶剂、PO2F2 -和锂盐，锂盐包括六氟磷酸锂，有机溶剂包括质量比为EC:DEC:EMC＝1:1:1的碳酸乙烯酯(EC)、碳酸二乙酯(DEC)和碳酸甲乙酯(EMC)，所述非水电解液中六氟磷酸锂(LiPF6)浓度和PO2F2 -含量如表1所示。
所述隔膜为PE隔膜，其表面含有如表1实施例所示质量的第二两性氧化物。
实施例2～31
实施例2～31用于说明本发明公开的锂离子电池，大部分与实施例1相同，其不同之处在于：
采用表1中实施例2～31所示的正极活性材料、LiPF6浓度、PO2F2 -的质量含量、其它添加剂及含量、第一两性氧化物及其质量含量、第二两性氧化物及其质量含量。
对比例1～27
对比例1～27用于对比说明本发明公开的锂离子电池，大部分与实施例1相同，其不同之处在于：
采用表1中实施例1～27所示的正极活性材料、LiPF6浓度、PO2F2 -的质量含量、其它添加剂及含量、第一两性氧化物/其它氧化物及其质量含量、第二两性氧化物/其它氧化物及其质量含量。
上述实施例和对比例的锂离子电池的制备通过公知的方法进行即可，没有特别限定。可以举出例如：将通过公知的方法合成的LiPO2F2添加于电解液的方法；预先使活性物质、极板、隔膜等电池构成要素中共存，在使用包含LiPF6的电解液组装电池时使体系中产生PO2F2 - 的方法。在本实施方式中，可以使用任意方法。
作为测定上述的锂离子电池中的PO2F2 -的含量的方法，没有特别限制，只要是公知的方法就可以任意使用。具体可以列举：离子色谱法、19F NMR等。
性能测试
对上述锂离子电池进行如下性能测试：
1.循环性能测试：
在25℃下，将实施例和对比例的锂离子电池以1C倍率充电、以1C倍率放电，记录首次充放电的电池容量，在充放电截止电压(如3V～4.2V)内进行满充满放循环测试，直至锂离子电池的容量衰减至初始容量的80％，记录电池初始容量和循环圈数。
2.电池DCIR测试：
电池DCIR测试过程为：在25℃下，将锂离子二次电池搁置5分钟，以1C倍率恒流充电至上限截至电压(如4.2V)，再恒压充电至电流小于等于0.05C，此时电池的荷电状态(SOC)为100％，之后搁置5分钟，再以1C倍率恒流放电，将锂离子二次电池的荷电状态(SOC)调整至50％。搁置30min后，以1C的倍率放电10s，放电前的电压记为U1，放电后的电压记为U2。则电池的DCIR＝(U1-U2)/1C。
(1)实施例1～12和对比例1、14～27得到的测试结果填入表2。
表2

由实施例1～12和对比例1、14～27得到的测试结果可知，当所述非水电解液中六氟磷酸锂的摩尔浓度a、所述非水电解液中PO2F2 -的质量百分含量m、所述第一两性氧化物占正极材料层质量的百分比含量b和所述第二两性氧化物占隔膜质量的百分比含量c满足条件0.1≤m*(10*b+c)/a≤30，且0.5≤a≤1.5，0.01≤m≤0.8，0.01≤b≤2，0.5≤c≤30时，得到的锂离子电池具有较高的电池初始容量、较低的阻抗和较长的循环寿命，推测是因为六氟磷酸锂在电池化成过程中可反应生成PO2F2 -，PO2F2 -进一步在正极活性材料表面分解并与第一两性氧化物配合形成钝化膜，可通过对于正极材料层中第一两性氧化物和隔膜上第二两性氧化物的调控，同时通过控制六氟磷酸锂的含量以及PO2F2 -的质量，从而调节正极材料层表面钝化膜的致密程度，使其具有更加稳定的性质，进而在电池的充放电循环中避免钝化膜的破裂，保证非水电解液和正极活性材料的循环稳定性，有效提高电池循环性能。
由实施例1～12的测试结果可知，当所述非水电解液中六氟磷酸锂的摩尔浓度a、所述非水电解液中PO2F2 -的质量百分含量m、所述第一两性氧化物占正极材料层质量的百分比含量b和所述第二两性氧化物占隔膜质量的百分比含量c进一步满足条件0.5≤m*(10*b+c)/a≤10，且0.7≤a≤1.2，0.05≤m≤0.5，0.03≤b≤1，3≤c≤20时，有利于进一步提高电池的初始容量，降低电池阻抗并延长锂离子电池的循环寿命，推测此时得到的正极材料层表面的钝化膜具有更好的致密度和更低的厚度，降低锂离子电池的容量损耗，提高锂离子电池的循环性能。
由对比例14～27的测试结果可知，即使所述非水电解液中六氟磷酸锂的摩尔浓度a、所述非水电解液中PO2F2 -的质量百分含量m、所述第一两性氧化物占正极材料层质量的百分比含量b和所述第二两性氧化物占隔膜质量的百分比含量c满足条件0.1≤m*(10*b+c)/a≤30的限定，但a值、m值、b值或c值不满足其范围限定时，锂离子电池仍然不具有较高的初始容量和较好的循环性能，说明a值、m值、b值或c值在提升锂离子电池性能方面具有较强的关联性。同样的，当a值、m值、b值或c值满足其范围限定时，但m*(10*b+c)/a值不满足上述预设条件时，对于电池性能的提升也并不明显。
(2)实施例1和对比例5～13得到的测试结果填入表3。
表3

由实施例1和对比例5～6的测试结果可知，无论是缺少第一两性氧化物还是缺少第二两性氧化物，均会导致PO2F2 -量的较大程度的下降，同时，导致了电池阻抗的上升和循环圈数的减少。由实施例1和对比例7～13的测试结果可知，当采用其它氧化物替代所述第一两性氧化物和/或所述第二两性氧化物时，则对LiPF6的分解表现出较小的反应性或无反应性，从而不生成或生成极少量的PO2F2 -，不满足本申请的条件限制，也不利于电池循环性能的提升。
(3)实施例1、13～21得到的测试结果填入表4。
表4
由实施例1、13～21的测试结果可知，当采用不同的两性氧化物或其组合作为第一两性氧化物和第二两性氧化物时，只要a值、m值、b值或c值满足条件0.1≤m*(10*b+c)/a≤30，且0.5≤a≤1.5，0.01≤m≤0.8，0.01≤b≤2，0.5≤c≤30时，得到的锂离子电池均具有较高的初始容量和较好的循环性能，说明本发明提供的锂离子电池系统对于不同的两性氧化物具有通用性，同时也说明了两性氧化物的采用对本申请锂离子电池体系的必要性。
(4)实施例1、20～22和对比例2～4得到的测试结果填入表5。
表5
由实施例1、对比例2～4的测试结果可知，在锂离子的电解液中加入碳酸亚乙烯酯(VC)、硫酸乙烯酯(DTD)或氟代碳酸乙烯酯(FEC)作为成膜添加剂对于电池的提升作用明显不如本申请提供的电池体系对于锂离子电池的性能提升。
由实施例1、20～22的测试结果可知，在本发明提供的电池体系中，额外加入碳酸亚乙烯酯(VC)、硫酸乙烯酯(DTD)或氟代碳酸乙烯酯(FEC)，能够进一步降低电池阻抗和提高电池的循环寿命，说明其它添加剂对电池性能的提升机理与PO2F2 -存在一定的差异，两者在成膜上存在互补作用，进而提高了正极材料层表面的界面膜的质量。
(5)实施例1、23～31得到的测试结果填入表6。
表6
由实施例1、23～31的测试结果可知，当电池选用不同的正极活性材料时，且a值、m值、b值或c值满足条件0.1≤m*(10*b+c)/a≤30，且0.5≤a≤1.5，0.01≤m≤0.8，0.01≤b≤2，0.5≤c≤30时，同样具有高初始容量、较低的电池阻抗和优异的循环性能，电池可兼具高能量密度以及长循环寿命，说明本发明提供的电池体系适用于不同的正极活性材料。
以上所述仅为本发明的较佳实施例而已，并不用以限制本发明，凡在本发明的精神和原则之内所作的任何修改、等同替换和改进等，均应包含在本发明的保护范围之内。

Claims (16)

  1. 一种锂离子电池，其特征在于，包括正极、负极、非水电解液和设置于所述正极与所述负极之间的隔膜，所述正极包括含有正极活性材料的正极材料层，所述正极材料层表面含有第一两性氧化物，所述隔膜表面含有第二两性氧化物，所述非水电解液包括非水有机溶剂、PO2F2 -和锂盐，所述锂盐包括六氟磷酸锂；
    所述锂离子电池满足以下条件：
    0.1≤m*(10*b+c)/a≤30，且0.5≤a≤1.5，0.01≤m≤0.8，0.01≤b≤2，0.5≤c≤30；
    其中，a为非水电解液中六氟磷酸锂的摩尔浓度，单位为mol/L；
    m为非水电解液中PO2F2 -的质量百分含量，单位为％；
    b为第一两性氧化物占正极材料层质量的百分比含量，单位为％；
    c为第二两性氧化物占隔膜质量的百分比含量，单位为％。
  2. 根据权利要求1所述的锂离子电池，其特征在于，所述锂离子电池满足以下条件：
    0.5≤m*(10*b+c)/a≤10。
  3. 根据权利要求1所述的锂离子电池，其特征在于，所述非水电解液中六氟磷酸锂的摩尔浓度a为0.7～1.2mol/L。
  4. 根据权利要求1所述的锂离子电池，其特征在于，所述非水电解液中PO2F2 -的质量百分含量m为0.05％～0.5％。
  5. 根据权利要求1所述的锂离子电池，其特征在于，所述第一两性氧化物占正极材料层质量的百分比含量b为0.03％～1％。
  6. 根据权利要求1所述的锂离子电池，其特征在于，所述第二两性氧化物占隔膜质量的百分比含量c为3％～20％。
  7. 根据权利要求1所述的锂离子电池，其特征在于，所述第一两性氧化物和所述第二两性氧化物各自独立地选自氧化铝、氧化锆、氧化钨和氧化钛中的至少一种。
  8. 根据权利要求1所述的锂离子电池，其特征在于，所述正极活性材料包括LiFe1-x’M’x’PO4、LiMn2-y’My’O4和LiNixCoyMnzM1-x-y-zO2、硫化物、硒化物、卤化物中的至少一种，其中，M’选自Mn、Mg、Co、Ni、Cu、Zn、Al、Sn、B、Ga、Cr、Sr、V或Ti中的至少一种，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≤x’＜1，0≤y’≤1，0≤y≤1，0≤x≤1，0≤z≤1，x+y+z≤1。
  9. 根据权利要求1所述的锂离子电池，其特征在于，所述非水电解液还包括添加剂，所述添加剂包括环状硫酸酯类化合物、磺酸内酯类化合物、环状碳酸酯类化合物、磷酸酯类化合物、硼酸酯类化合物和腈类化合物中的至少一种。
  10. 根据权利要求9所述的锂离子电池，其特征在于，以所述非水电解液的总质量为100％计，所述添加剂的含量为0.01％～30％。
  11. 根据权利要求9所述的锂离子电池，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、甲基硫酸乙烯酯、 中的至少一种。
  12. 根据权利要求9所述的锂离子电池，其特征在于，所述磺酸内酯类化合物选自1,3-丙烷磺酸内酯、1,4-丁烷磺酸内酯、1,3-丙烯磺酸内酯、中的至少一种。
  13. 根据权利要求9所述的锂离子电池，其特征在于，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、亚甲基碳酸乙烯酯、氟代碳酸乙烯酯、三氟甲基碳酸乙烯酯、双氟代碳酸乙烯酯或结构式1所示化合物中的至少一种：
    所述结构式1中，R21、R22、R23、R24、R25、R26各自独立地选自氢原子、卤素原子、C1-C5基团中的一种。
  14. 根据权利要求9所述的锂离子电池，其特征在于，所述磷酸酯类化合物选自三(三甲基硅烷)磷酸酯、三(三甲基硅烷)亚磷酸酯或结构式2所示化合物中的至少一种：
    所述结构式2中，R31、R32、R33各自独立的选自C1-C5的饱和烃基、不饱和烃基、卤代烃基、-Si(CmH2m+1)3，m为1～3的自然数，且R31、R32、R33中至少有一个为不饱和烃基。
  15. 根据权利要求9所述的锂离子电池，其特征在于，所述硼酸酯类化合物选自三(三甲基硅烷)硼酸酯和三(三乙基硅烷)硼酸酯中的至少一种。
  16. 根据权利要求9所述的锂离子电池，其特征在于，所述腈类化合物选自丁二腈、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、癸二腈中的至少一种。
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