WO2024032171A1 - 一种锂离子电池 - Google Patents

一种锂离子电池 Download PDF

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Publication number
WO2024032171A1
WO2024032171A1 PCT/CN2023/102471 CN2023102471W WO2024032171A1 WO 2024032171 A1 WO2024032171 A1 WO 2024032171A1 CN 2023102471 W CN2023102471 W CN 2023102471W WO 2024032171 A1 WO2024032171 A1 WO 2024032171A1
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Prior art keywords
lithium
ion battery
carbonate
battery according
positive electrode
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PCT/CN2023/102471
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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 WO2024032171A1 publication Critical patent/WO2024032171A1/zh

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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00Secondary cells; Manufacture thereof
    • H01M10/05Accumulators with non-aqueous electrolyte
    • H01M10/056Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564Accumulators 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
    • H01M10/0566Liquid materials
    • H01M10/0567Liquid materials characterised by the additives
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00Secondary cells; Manufacture thereof
    • H01M10/05Accumulators with non-aqueous electrolyte
    • H01M10/052Li-accumulators
    • H01M10/0525Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00Electrolytes
    • H01M2300/0017Non-aqueous electrolytes
    • H01M2300/0025Organic electrolyte
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10Energy storage using batteries

Definitions

  • the invention belongs to the technical field of energy storage devices, and specifically relates to a lithium-ion battery.
  • Lithium-ion batteries are widely used in 3C digital, power tools, aerospace, energy storage, power vehicles and other fields due to their high specific energy, no memory effect, long cycle life and other advantages.
  • the rapid development of electronic information technology and consumer products has great impact on lithium-ion batteries.
  • the high voltage and high energy density of batteries put forward higher requirements.
  • Lithium cobalt oxide (LCO) is currently the mainstream cathode material for 3C lithium batteries.
  • the market demand is rising steadily, so the production of LCO is steadily increasing year by year.
  • With the industrialization of fast charging ( ⁇ 2C) and high-voltage ( ⁇ 4.45V) LCO it has elevated LCO to a new development platform.
  • the uneven temperature distribution inside the battery is related to the uneven current distribution inside the battery.
  • Uneven current distribution can easily cause the battery to fail during charging.
  • During the discharge process local overcharge or over-discharge occurs, as well as inconsistencies in side reaction speeds, which in turn lead to inconsistencies in the battery's internal decay rate.
  • reducing the temperature rise of the battery during high-rate charge and discharge is also important for improving the service life of the battery.
  • Crucial. How to solve the problem of excessive battery temperature is an urgent problem that needs to be solved to improve the performance of lithium-ion batteries.
  • the present invention provides a lithium-ion battery.
  • the invention provides a lithium ion battery, including a positive electrode, a negative electrode, a non-aqueous electrolyte and a separator.
  • the separator is located between the positive electrode and the negative electrode.
  • the positive electrode includes a positive electrode material layer including a positive electrode active material, so The positive active material includes lithium cobalt oxide, the non-aqueous electrolyte includes a non-aqueous organic solvent, a lithium salt and additives, and the additives include a compound represented by Structural Formula 1:
  • n 0 or 1
  • A is selected from C or O
  • X is selected from R 1 and R 2 are each independently selected from H, R 1 and R 2 is not selected from H at the same time, and X, R 1 and R 2 contain at least one sulfur atom;
  • the lithium-ion battery meets the following conditions:
  • q is the porosity of the separator, in %
  • h is the thickness of the positive electrode material layer, in ⁇ m
  • m is the mass percentage content of the compound represented by Structural Formula 1 in the non-aqueous electrolyte, in %;
  • the maximum surface temperature T max and the minimum surface temperature T min of the lithium-ion battery during discharge to 100% DOD at 25°C at 2C meet the following conditions:
  • the lithium-ion battery meets the following conditions:
  • the porosity q of the separator is 15% to 30%.
  • the thickness h of the cathode material layer is 60 ⁇ m to 110 ⁇ m.
  • the mass percentage content m of the compound represented by Structural Formula 1 in the non-aqueous electrolyte is 0.1% to 1.0%.
  • the compound represented by the structural formula 1 is selected from at least one of the following compounds:
  • the charging cut-off voltage of the lithium-ion battery is 4.4V ⁇ 4.7V.
  • the non-aqueous organic solvent includes ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propylene carbonate, butyl acetate, ⁇ -butyrolactone, propyl propionate, propylene carbonate, etc.
  • ethylene carbonate dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propylene carbonate, butyl acetate, ⁇ -butyrolactone, propyl propionate, propylene carbonate, etc.
  • the additive also includes at least one of cyclic sulfate ester compounds, sultone compounds, cyclic carbonate compounds, phosphate ester compounds, borate ester compounds and nitrile compounds;
  • the additive amount is 0.01% to 30%.
  • the cyclic sulfate compound is selected from vinyl sulfate, propylene sulfate, vinyl methyl sulfate, at least one of;
  • the sultone compound is selected from at least one of 1,3-propane sultone, 1,4-butane sultone, and 1,3-propene sultone;
  • the cyclic carbonate compound is selected from vinylene carbonate, ethylene ethylene carbonate, methylene vinyl carbonate, fluoroethylene carbonate, trifluoromethylethylene carbonate, bisfluoroethylene carbonate or structural formula At least one of the compounds shown in 2,
  • R 21 , R 22 , R 23 , R 24 , R 25 , and R 26 are each independently selected from one of hydrogen atoms, halogen atoms, and C1-C5 groups;
  • the phosphate compound is selected from at least one of tris(trimethylsilane)phosphate, tris(trimethylsilane)phosphite or the compound represented by structural formula 3:
  • R 31 , R 32 , and R 33 are each independently selected from C1-C5 saturated hydrocarbon groups, unsaturated hydrocarbon groups, halogenated hydrocarbon groups, -Si(C m H 2m+1 ) 3 , and m is 1 to is a natural number of 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(trimethylsilane)borate and tris(triethylsilane)borate;
  • the nitrile compound is selected from succinonitrile, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrinitrile, adiponitrile, pimelonitrile, suberonitrile, azelonitrile, and sebaconitrile. of at least one.
  • the compound represented by Structural Formula 1 is added as an additive to the non-aqueous electrolyte.
  • the compound represented by Structural Formula 1 decomposes under electrochemical conditions during the first formation process of the battery to form in the positive and negative electrodes.
  • An interface film is formed on the surface.
  • the synergistic effect between the separator, the cathode material layer and the compound represented by structural formula 1 can be fully exerted , forming a stable interface film with high ionic conductivity on the surface of the positive and negative electrodes, improving the diffusion efficiency of lithium salt, significantly reducing the heat generation during the high-current discharge process of the lithium-ion battery, and improving the consistency of the temperature rise at various locations in the lithium-ion battery, thereby While ensuring the high cycle life and performance consistency of lithium-ion batteries, it also improves the safety performance of lithium-ion batteries.
  • Embodiments of the present invention provide a lithium ion battery, including a positive electrode, a negative electrode, a non-aqueous electrolyte and a separator.
  • the separator is located between the positive electrode and the negative electrode.
  • the positive electrode includes a positive electrode material layer including a positive electrode active material.
  • the positive active material includes lithium cobalt oxide
  • the non-aqueous electrolyte includes a non-aqueous organic solvent
  • a lithium salt and an additive the additive includes a compound represented by Structural Formula 1;
  • n 0 or 1
  • A is selected from C or O
  • X is selected from R 1 and R 2 are each independently selected from H, R 1 and R 2 are not selected from H at the same time, and X, R 1 and R 2 contain at least one sulfur atom;
  • the lithium-ion battery meets the following conditions:
  • q is the porosity of the separator, in %
  • h is the thickness of the positive electrode material layer, in ⁇ m
  • m is the mass percentage content of the compound represented by Structural Formula 1 in the non-aqueous electrolyte, in %;
  • the compound represented by Structural Formula 1 is added as an additive to the non-aqueous electrolyte.
  • the compound represented by Structural Formula 1 decomposes under electrochemical conditions during the first formation of the battery to form an interface film on the surface of the positive and negative electrodes.
  • the inventor passed a large amount of The study found that during the film formation process of the compound represented by structural formula 1, the content of the compound represented by structural formula 1, the porosity of the separator and the thickness of the cathode material layer will affect the film-forming quality of the interface film, as well as the lithium salt
  • the diffusion efficiency of ions between the positive and negative electrodes leads to the temperature change of the lithium-ion battery during charge and discharge.
  • the porosity q of the separator, the thickness h of the positive electrode material layer and the structural formula 1 in the non-aqueous electrolyte When the mass percentage content m of the compound satisfies the condition 0.1 ⁇ h/q*m ⁇ 15, the synergistic effect between the separator, the cathode material layer and the compound represented by structural formula 1 can be fully exerted, and high ion conductivity can be formed on the surface of the cathode and cathode.
  • Stable interface film with high efficiency improves the diffusion efficiency of lithium salt, significantly reduces the heat generation during high-current discharge of lithium-ion batteries and improves the consistency of temperature rise at various locations of the lithium-ion battery, thereby ensuring a high cycle life of the lithium-ion battery and performance consistency while improving the safety performance of lithium-ion batteries.
  • the compound represented by the structural formula 1 is:
  • A is selected from C or O
  • X is selected from R 1 and R 2 are each independently selected from H, R 1 and R 2 are not simultaneously selected from H, and X, R 1 and R 2 contain at least one sulfur atom.
  • the compound represented by the structural formula 1 is:
  • A is selected from C or O
  • X is selected from R 1 and R 2 are each independently selected from H, R 1 and R 2 are not simultaneously selected from H, and X, R 1 and R 2 contain at least one sulfur atom.
  • the lithium-ion battery meets the following conditions:
  • the porosity q of the separator can be 10%, 13%, 15%, 16%, 18%, 21%, 23%, 24%, 26%, 27%, 29%, 30 %, 32%, 33%, 35%, 39%, 41%, 43%, 46%, 49% or 50%.
  • the porosity q of the separator is 15% to 30%.
  • the porosity of the separator is too small, lithium ions cannot shuttle smoothly between the separators, which will reduce the dynamic performance of the lithium-ion battery and increase the battery impedance. This not only results in accelerated heat generation and increased temperature rise when the battery is discharged with high current, And it will lead to worse thermal stability and consistency of the overall battery; if the porosity of the separator is too large, the separator cannot effectively block the shuttle process of harmful impurities between the positive and negative electrodes, deteriorating the electrochemical performance of the battery, and in severe cases
  • the positive and negative electrodes may be in direct contact or easily penetrated by lithium dendrites, causing a short circuit.
  • the thickness h of the positive electrode material layer can be 50 ⁇ m, 51 ⁇ m, 55 ⁇ m, 58 ⁇ m, 60 ⁇ m, 61 ⁇ m, 65 ⁇ m, 68 ⁇ m, 70 ⁇ m, 71 ⁇ m, 75 ⁇ m, 78 ⁇ m, 80 ⁇ m, 81 ⁇ m, 85 ⁇ m, 88 ⁇ m, 90 ⁇ m , 91 ⁇ m, 95 ⁇ m, 98 ⁇ m, 100 ⁇ m, 101 ⁇ m, 105 ⁇ m, 108 ⁇ m, 110 ⁇ m, 111 ⁇ m, 115 ⁇ m, 118 ⁇ m, 120 ⁇ m, 121 ⁇ m, 125 ⁇ m, 128 ⁇ m or 130 ⁇ m.
  • the thickness h of the cathode material layer is 60 ⁇ m to 110 ⁇ m.
  • the mass percentage content m of the compound represented by Structural Formula 1 in the non-aqueous electrolyte solution can 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%, 2.0%, 2.3%, 2.7% or 3.0%.
  • the mass percentage content m of the compound represented by Structural Formula 1 in the non-aqueous electrolyte is 0.1% to 1.0%.
  • the content of the compound represented by Structural Formula 1 in the non-aqueous electrolyte is within the above range, it is beneficial to form a high ionic conductivity and stable interface film on the surface of the positive and negative active materials, thereby forming a solid-liquid interface
  • the fast ion channel promotes the diffusion of lithium ions, significantly reduces the heat generation during high-current discharge of lithium cobalt oxide batteries and improves the consistency of temperature distribution, reducing the risk of thermal runaway of the battery.
  • the compound represented by Structural Formula 1 is selected from at least one of the following compounds:
  • the lithium-ion battery is a pouch battery or a hard-shell battery.
  • the lithium salt is selected from LiPF 6 , LiBOB, LiDFOB, LiPO 2 F 2 , LiBF 4 , LiSbF 6 , LiAsF 6 , LiN(SO 2 CF 3 ) 2 , LiN(SO 2 C 2 F 5 ) 2 , LiC(SO 2 CF 3 ) 3 , LiN(SO 2 F) 2 , LiClO 4 , LiAlCl 4 , LiCF 3 SO 3 , Li 2 B 10 Cl 10 , LiSO 2 F, LiTOP (lithium trioxalate phosphate), At least one of LiDODFP (lithium difluorodioxalate phosphate), LiOTFP (lithium tetrafluorooxalate phosphate) and lower aliphatic carboxylic acid lithium salt.
  • LiPF 6 LiBOB, LiDFOB, LiPO 2 F 2 , LiBF 4 , LiSbF 6 , LiAsF 6 , LiN(SO 2 CF 3 ) 2 ,
  • 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, in the non-aqueous electrolyte solution, the concentration of the lithium salt can be 0.5 mol/L, 1 mol/L, 1.5 mol/L, 2 mol/L, or 2.5 mol/L.
  • the cathode active material may further include LiFe 1-x' M' x' PO 4 , LiMn 2-y' M y' O 4 and LiN x Co y Mn z M 1-xyz O 2 At least one of them, wherein M' is selected from at least one of Mn, Mg, Co, Ni, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V or Ti, and M is selected from Fe, Co , at least one of 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 active material can also be selected from one or more of sulfide, selenide and halide.
  • the positive active material also includes LiFePO 4 , LiFe 0.6 Mn 0.4 PO 4 , LiNi 0.5 Co 0.2 Mn 0.3 O 2 , LiNi 0.6 Co 0.2 Mn 0.2 O 2 , LiNi 0.8 Co 0.1 Mn 0.1 O 2 , LiNi At least one of 0.5 Co 0.2 Mn 0.2 Al 0.1 O 2 , LiMn 2 O 4 , and LiNi 0.8 Co 0.1 Al 0.1 O 2 .
  • the charging cut-off voltage of the lithium-ion battery is 4.4V-4.7V.
  • the cathode further includes a cathode current collector, and the cathode material layer is formed on the surface of the cathode current collector.
  • the positive electrode current collector is selected from metal materials that can conduct electrons.
  • the positive electrode current collector includes Al, Ni, tin, At least one of copper and stainless steel.
  • the positive electrode current collector is selected from aluminum foil.
  • the cathode material layer further includes a cathode binder and a cathode conductive agent.
  • the positive electrode binder includes polyvinylidene fluoride, a copolymer of vinylidene fluoride, polytetrafluoroethylene, a copolymer of vinylidene fluoride-hexafluoropropylene, a copolymer of tetrafluoroethylene-hexafluoropropylene, tetrafluoroethylene- Copolymer of perfluoroalkyl vinyl ether, copolymer of ethylene-tetrafluoroethylene, copolymer of vinylidene fluoride-tetrafluoroethylene, copolymer of vinylidene fluoride-trifluoroethylene, copolymer of vinylidene fluoride-trichloroethylene Copolymers, vinylidene fluoride-fluorovinyl copolymers, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymers, thermoplastic polyimides, polyethylene and poly
  • the positive conductive agent includes at least one of conductive carbon black, conductive carbon balls, conductive graphite, conductive carbon fiber, carbon nanotubes, graphene or reduced graphene oxide.
  • the negative electrode includes a negative electrode material layer including a negative electrode active material.
  • the negative 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 can include graphite, hard carbon, soft carbon, graphene, mesophase carbon microspheres, etc.
  • the silicon-based negative electrode can include silicon materials, silicon oxides, silicon-carbon composite materials, silicon alloy materials, etc.
  • the tin-based negative electrode can It can include tin, tin carbon, tin oxide, and tin metal compounds
  • the lithium negative electrode can include metallic lithium or lithium alloy.
  • the lithium alloy may specifically be at least one of lithium silicon alloy, lithium sodium alloy, lithium potassium alloy, lithium aluminum alloy, lithium tin alloy and 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 conductive agent are the same as those of the positive electrode binder and the positive electrode conductive agent respectively, and will not be described again here.
  • the negative electrode further includes a negative electrode current collector, and the negative electrode material layer is formed on a surface of the negative electrode current collector.
  • the negative electrode current collector is selected from metal materials that can conduct electrons.
  • the negative electrode current collector includes at least one of Al, Ni, tin, copper, and stainless steel.
  • the negative electrode current collector Selected from copper foil.
  • the non-aqueous organic solvent includes at least one of ether solvents, nitrile solvents, carbonate solvents and carboxylate solvents.
  • ether solvents include cyclic ethers or chain ethers and their fluorinated products, preferably chain ethers with 3 to 10 carbon atoms and cyclic ethers with 3 to 6 carbon atoms.
  • Cyclic ethers are specifically It can be but is not limited to 1,3-dioxopentane (DOL), 1,4-dioxane (DX), crown ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH 3 -THF) , at least one of 2-trifluoromethyltetrahydrofuran (2-CF 3 -THF);
  • the chain ether can be, but is not limited to, dimethoxymethane, diethoxymethane, ethoxymethoxy Methane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether.
  • chain ethers have high solvating power with lithium ions and can improve ion dissociation
  • dimethoxymethane, diethoxymethane, and ethoxymethoxy are particularly preferred because they have low viscosity and can impart high ionic conductivity.
  • Methane One type of ether compound may be used alone, or two or more types of ether compounds may be used in any combination and ratio.
  • the amount of the ether compound added is not particularly limited and is arbitrary within the range that does not significantly destroy the effect of the high-pressure lithium ion battery of the present invention. When the non-aqueous solvent volume ratio is 100%, the volume ratio is usually 1% or more, and the preferred volume is 100%.
  • the volume ratio is 2% or more, and more preferably, the volume ratio is 3% or more.
  • 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 may satisfy the above range.
  • the amount of the ether compound added is within the above-mentioned preferred range, it is easy to ensure the improvement effect of the ion conductivity by increasing the degree of lithium ion dissociation and reducing the viscosity of the chain ether.
  • the negative electrode active material is a carbon-based material, the phenomenon of co-intercalation of chain ether and lithium ions can be suppressed, so the input-output characteristics and charge-discharge rate characteristics can be achieved within an appropriate range.
  • the nitrile solvent may be, but is not limited to, at least one of acetonitrile, glutaronitrile, and malononitrile.
  • the carbonate solvent includes cyclic carbonate or chain carbonate.
  • the cyclic carbonate can be, but is not limited to, ethylene carbonate (EC), propylene carbonate (PC), and ⁇ -butyrolactone. At least one of (GBL) and butylene carbonate (BC); the chain carbonate can be, but is not limited to, dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), At least one of dipropyl carbonate (DPC).
  • DMC dimethyl carbonate
  • EMC ethyl methyl carbonate
  • DEC diethyl carbonate
  • DPC dipropyl carbonate
  • the content of the cyclic carbonate 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 lower limit of the content is relative to the total amount of solvent in the non-aqueous electrolyte.
  • the volume ratio is 3% or more, and preferably the volume ratio is 5% or more.
  • the upper limit of the volume ratio is usually 90% or less, preferably 85% or less, and more preferably 80% or less.
  • the content of the chain carbonate is not particularly limited, but is usually 15% or more by volume, preferably 20% or more, and more preferably 25% or more by volume relative to the total amount of solvent in the non-aqueous electrolyte solution.
  • the volume ratio is usually 90% or less, preferably 85% or less, and more preferably 80% or less.
  • the viscosity of the non-aqueous electrolyte solution can be easily brought into an appropriate range, thereby suppressing a decrease in ion conductivity, thereby contributing to bringing the output characteristics of the non-aqueous electrolyte battery into a favorable range.
  • the total amount of the linear carbonates may satisfy the above range.
  • chain carbonates having fluorine atoms may also be preferably used.
  • the number of fluorine atoms contained in the fluorinated linear carbonate is not particularly limited as long as it is 1 or more, but it is usually 6 or less, preferably 4 or less.
  • these fluorine atoms may be bonded to the same carbon or to different carbons.
  • the fluorinated chain carbonate include fluorinated dimethyl carbonate derivatives, fluorinated ethyl methyl carbonate derivatives, and fluorinated diethyl carbonate derivatives.
  • Carboxylic acid ester solvents include cyclic carboxylic acid esters and/or chain carbonic acid esters.
  • the cyclic carboxylic acid ester include at least one kind selected from ⁇ -butyrolactone, ⁇ -valerolactone, and ⁇ -valerolactone.
  • chain carbonates include: methyl acetate (MA), ethyl acetate (EA), propyl acetate (EP), butyl acetate, propyl propionate (PP), butyl propionate, At least one of ethyl fluoroacetate.
  • the sulfone solvent includes cyclic sulfone and chain sulfone.
  • cyclic sulfone it usually has 3 to 6 carbon atoms, preferably 3 to 5 carbon atoms.
  • chain sulfone In the case of sulfone, it is usually a compound having 2 to 6 carbon atoms, preferably 2 to 5 carbon atoms.
  • the amount of sulfone solvent added 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 relative to the total amount of solvent in the non-aqueous electrolyte is usually 0.3% or more, and the preferred volume ratio is 0.5% or more, more preferably 1% or more by volume, and usually the volume ratio is 40% or less, preferably 35% or less, more preferably 30% or less.
  • the total amount of the sulfone solvents may satisfy the above range.
  • the added amount of the sulfone solvent is within the above range, a non-aqueous electrolyte solution that is excellent in high-temperature storage stability tends to be obtained.
  • the non-aqueous organic solvent is a mixture of cyclic carbonate and chain carbonate.
  • the additive further includes at least one of cyclic sulfate ester compounds, sultone compounds, cyclic carbonate compounds, phosphate ester compounds, borate ester compounds and nitrile compounds. ;
  • the additive amount is 0.01% to 30%.
  • the cyclic sulfate compound is selected from vinyl sulfate, propylene sulfate, vinyl methyl sulfate, at least one of;
  • the sultone compound is selected from at least one of 1,3-propane sultone, 1,4-butane sultone, and 1,3-propene sultone;
  • the cyclic carbonate compound is selected from vinylene carbonate, ethylene ethylene carbonate, methylene vinyl carbonate, fluorine At least one of ethylene carbonate, trifluoromethyl ethylene carbonate, bisfluoroethylene carbonate or the compound represented by structural formula 2,
  • R 21 , R 22 , R 23 , R 24 , R 25 , and R 26 are each independently selected from one of hydrogen atoms, halogen atoms, and C1-C5 groups;
  • the phosphate compound is selected from at least one of tris(trimethylsilane)phosphate, tris(trimethylsilane)phosphite or the compound represented by structural formula 3:
  • R 31 , R 32 , and R 33 are each independently selected from C1-C5 saturated hydrocarbon groups, unsaturated hydrocarbon groups, halogenated hydrocarbon groups, -Si(C m H 2m+1 ) 3 , and m is 1 to is a natural number of 3, and at least one of R 31 , R 32 , and R 33 is an unsaturated hydrocarbon group;
  • the phosphate compound represented by the structural formula 3 may be tripropargyl phosphate, dipropargyl methyl phosphate, dipropargyl ethyl phosphate, or dipropargyl propyl phosphate.
  • Phosphate ester dipropargyl trifluoromethyl phosphate, dipropargyl-2,2,2-trifluoroethyl phosphate, dipropargyl-3,3,3-trifluoropropyl phosphate, Dipropargyl hexafluoroisopropyl phosphate, triallyl phosphate, diallyl methyl phosphate, diallylethyl phosphate, diallyl propyl phosphate, diallyl triphosphate Fluoromethylphosphate, diallyl-2,2,2-trifluoroethylphosphate, diallyl-3,3,3-trifluoropropylphosphate, diallylhexafluoroisopropyl At least one of the base phosphates;
  • the borate compound is selected from at least one of tris(trimethylsilane)borate and tris(triethylsilane)borate;
  • the nitrile compound is selected from succinonitrile, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrinitrile, adiponitrile, pimelonitrile, suberonitrile, azelonitrile, and sebaconitrile. of at least one.
  • the additives may also include other additives that can improve battery performance: for example, additives that improve battery safety performance, specifically flame retardant additives such as fluorinated phosphates, cyclophosphazene, or tert-amylbenzene. , tert-butylbenzene and other anti-overcharge additives.
  • the amount of any optional substance in the additives added to the non-aqueous electrolyte is less than 10%, preferably, the amount added is 0.1-5%, more preferably , the addition amount is 0.1% to 2%.
  • the amount of any optional substance 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 additive when the additive is selected from fluoroethylene carbonate, the total mass of the non-aqueous electrolyte is 100% Calculated, the added amount of the fluoroethylene carbonate is 0.05% to 30%.
  • This embodiment takes the preparation of lithium-ion batteries as an example to illustrate the present invention, including the following steps:
  • EC ethylene carbonate
  • DEC diethyl carbonate
  • EMC ethyl methyl carbonate
  • LiPF 6 lithium hexafluorophosphate
  • the slurry is evenly coated on both sides of the aluminum foil, dried, rolled and vacuum dried, and the aluminum lead wire is welded with an ultrasonic welder to obtain a positive electrode plate.
  • the thickness of the positive electrode material layer after vacuum drying is shown in Table 2.
  • a negative electrode slurry is obtained.
  • the slurry is coated on both sides of the copper foil, dried, rolled and vacuum dried, and a nickel lead wire is welded with an ultrasonic welder to obtain a negative plate.
  • the thickness of the plate is between 120-150 ⁇ m.
  • a three-layer separator with a thickness of 20 ⁇ m is placed between the positive plate and the negative plate.
  • the porosity of the separator is shown in Table 2. Then the sandwich structure composed of the positive plate, the negative plate and the separator is rolled, and then the rolled body is pressed After flattening, put it into an aluminum foil packaging bag and vacuum bake it at 85°C for 48 hours to obtain the battery core to be injected.
  • the nonaqueous electrolyte prepared above was injected into the battery core, sealed in a vacuum, and left to rest for 24 hours.
  • Examples 2 to 25 are used to illustrate the lithium-ion battery and its preparation method disclosed in the present invention, including most of the operating steps in Example 1, and the differences are:
  • the negative electrode active materials used in Examples 2 to 25 are as shown in Table 2.
  • Comparative Examples 1 to 18 are used to comparatively illustrate the lithium-ion battery disclosed in the present invention and its preparation method, including most of the operating steps in Example 1, and the differences are:
  • the negative electrode active materials used in Comparative Examples 1 to 18 the thickness of the positive electrode material layer, the porosity of the separator, and the types and mass percentages of additives in the non-aqueous electrolyte are shown in Table 2.
  • the lithium-ion battery is placed in a constant temperature environment of 25°C and discharged to 100% DOD at a current of 2C.
  • Battery capacity retention rate (%) last discharge capacity/first discharge capacity ⁇ 100%.
  • lithium cobalt oxide is used as the positive electrode active material, and the compound represented by structural formula 1 is added to the non-aqueous electrolyte.
  • the porosity q of the separator and the positive electrode When the thickness h of the material layer and the mass percentage content m of the compound shown in Structural Formula 1 in the non-aqueous electrolyte meet the preset condition 0.1 ⁇ h/q*m ⁇ 15, the obtained lithium-ion battery has a lower battery surface temperature.
  • the difference and higher cycle capacity retention rate indicate that the porosity q of the separator, the thickness h of the cathode material layer and the mass percentage content m of the compound represented by structural formula 1 in the non-aqueous electrolyte are for the compound represented by structural formula 1 in the cathode material.
  • the quality of the interface film formed on the surface of the layer has a great influence.
  • the interface film obtained under the conditions defined by the above relationship has high stability and good lithium ion diffusion performance. It cooperates with the porosity adjustment of the separator and the cathode material. Adjusting the thickness of the layer can significantly reduce the heat generated by the lithium-ion battery during high-current discharge, improve the consistency of the temperature rise of the lithium-ion battery at various locations, and effectively improve the cycle life and safety of the lithium-ion battery.
  • Example 1 (3) The test results obtained in Example 1 and Examples 18 to 22 are filled in Table 5.
  • Example 1 It can be seen from the test results of Example 1 and Examples 18 to 22 that for different compounds represented by Structural Formula 1, the porosity q of the separator, the thickness h of the cathode material layer and the thickness of the compound represented by Structural Formula 1 in the non-aqueous electrolyte are When the mass percentage content m meets the preset condition 0.1 ⁇ h/q*m ⁇ 15, it plays a similar role, and both have a better effect on improving the temperature rise problem of lithium-ion batteries, thereby effectively improving the performance of lithium-ion batteries.
  • the cycle life shows that the relational formula provided by the present invention is applicable to different compounds represented by structural formula 1.
  • Example 1 (4) The test results obtained in Example 1 and Examples 23 to 25 are filled in Table 6.
  • Example 1 From the test results of Example 1 and Examples 23 to 25, it can be seen that when the negative active material is graphite and silicon oxide mixed in different mass ratios, and satisfies the restriction of the relational expression of the present invention 0.1 ⁇ h/q*m ⁇ 15 When , it can also effectively reduce the discharge temperature range of the battery and improve the cycle capacity retention rate, indicating that under the system defined by the present invention, it mainly improves the positive electrode part of lithium ions. Therefore, this relationship limit is also applicable to Different anode materials and their combinations.

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Abstract

一种锂离子电池,包括正极、负极、非水电解液和隔膜,所述隔膜位于所述正极和所述负极之间,所述正极包括包含正极活性材料的正极材料层,所述正极活性材料包括钴酸锂,所述非水电解液包括有非水有机溶剂、锂盐和添加剂,所述添加剂包括结构式1所示的化合物:结构式1;所述锂离子电池满足以下条件:0.1≤h/q*m≤15;且10≤q≤50,50≤h≤130,0.01≤m≤3;所述锂离子电池在25℃下2C放电到100%DOD过程中的最高表面温度T max和最低表面温度T min满足以下条件:(T max-T min)/T min*100%≤30%。该锂离子电池在保证较高的循环寿命和性能一致性的同时,提高了安全性能。

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
锂离子电池由于具有高比能量、无记忆效应、循环寿命长等优点被广泛应用于3C数码、电动工具、航天、储能、动力汽车等领域,电子信息技术及消费产品的快速发展对锂离子电池高电压以及高能量密度提出了更高的要求。钴酸锂(LCO)是目前3C锂电池正极材料的主流,市场需求稳步上升,故LCO的产量逐年稳步增加。随着快充(≥2C)和高电压(≥4.45V)LCO的产业化,更是将LCO的提升到一个全新的发展平台。但是随着5G时代的到来,智能手机数据传输速度和处理能力相比2G、3G时代有显著提升,AR、高清视频、直播等应用场景加速落地,人们对手机性能的要求越来越高,推动手机硬件配置快速迭代,尤其是对3C数码电池的充放电速率和容量有了更高的要求。但与此同时,智能手机发热的问题也越来越严重,手机发烫、卡顿和死机时有发生,严重时甚至会导致主板烧坏乃至爆炸。然而,降低锂离子电池在放电过程中的温升以及温度分布的均匀性研究极少,通常电池内部的温度分布不均与电池内部电流分布的不均相关,电流分布不均容易导致电池在充放电的过程中发生局部的过充或过放,以及副反应速度的不一致,进而导致电池内部衰降速度的不一致;同时降低电池在大倍率充放电过程中的温升对于提升电池的使用寿命也至关重要。如何解决电池温度过高的问题是提高锂离子电池性能亟需解决的问题。
发明内容
针对现有锂离子电池在充放电过程中存在温升过高的问题,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、非水电解液和隔膜,所述隔膜位于所述正极和所述负极之间,所述正极包括包含正极活性材料的正极材料层,所述正极活性材料包括钴酸锂,所述非水电解液包括有非水有机溶剂、锂盐和添加剂,所述添加剂包括结构式1所示的化合物:
其中,n为0或1,A选自C或O,X选自R1、R2各自独立选自H、R1和 R2不同时选自H,且X、R1和R2中至少含有一个硫原子;
所述锂离子电池满足以下条件:
0.1≤h/q*m≤15;
且10≤q≤50,50≤h≤130,0.01≤m≤3;
其中,q为隔膜的孔隙率,单位为%;
h为正极材料层的厚度,单位为μm;
m为非水电解液中结构式1所示的化合物的质量百分比含量,单位为%;
所述锂离子电池在25℃下2C放电到100%DOD过程中的最高表面温度Tmax和最低表面温度Tmin满足以下条件:
(Tmax-Tmin)/Tmin*100%≤30%。
可选的,所述锂离子电池满足以下条件:
0.2≤h/q*m≤6。
可选的,所述隔膜的孔隙率q为15%~30%。
可选的,所述正极材料层的厚度h为60μm~110μm。
可选的,所述非水电解液中结构式1所示的化合物的质量百分比含量m为0.1%~1.0%。
可选的,所述结构式1所示的化合物选自以下化合物中的至少一种:


可选的,所述锂离子电池的充电截止电压为4.4V~4.7V。
可选的,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。
可选的,所述添加剂还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,所述添加剂的添加量为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2所示化合物中的至少一种,
所述结构式2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3所示化合物中的至少一种:
所述结构式3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,在非水电解液中加入有结构式1所示的化合物作为添加剂,结构式1所示的化合物在电池首次化成的过程中在电化学条件下分解以在正负极表面形成有界面膜,发明人通过大量研究发现,在结构式1所示的化合物成膜的过程中,结构式1所示的化合物的含量、隔膜的孔隙率和正极材料层的厚度会影响到该界面膜的成膜质量,以及影响锂盐离子在正负极之间的扩散效率,进而导致锂离子电池在充放电下的温度变化,具体的,当隔膜的孔隙率q、正极材料层的厚度h和非水电解液中结构式1所示的化合物的质量百分比含量m满足条件0.1≤h/q*m≤15时,能够充分发挥隔膜、正极材料层和结构式1所示的化合物之间的协同效应,在正负极表面形成高离子导电率的稳定界面膜,提高锂盐的扩散效率,明显减少锂离子电池大电流放电过程中的产热并改善锂离子电池各位置温升的一致性,从而在保证锂离子电池较高的循环寿命和性能一致性的同时,提高锂离子电池的安全性能。
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、非水电解液和隔膜,所述隔膜位于所述正极和所述负极之间,所述正极包括包含正极活性材料的正极材料层,所述正极活性材料包括钴酸锂,所述非水电解液包括有非水有机溶剂、锂盐和添加剂,所述添加剂包括结构式1所示的化合物;
其中,n为0或1,A选自C或O,X选自R1、R2各自独立选自H、R1和R2不同时选自H,且X、R1和R2中至少含有一个硫原子;
所述锂离子电池满足以下条件:
0.1≤h/q*m≤15;
且10≤q≤50,50≤h≤130,0.01≤m≤3;
其中,q为隔膜的孔隙率,单位为%;
h为正极材料层的厚度,单位为μm;
m为非水电解液中结构式1所示的化合物的质量百分比含量,单位为%;
所述锂离子电池在25℃下2C放电到100%DOD(放电深度)过程中的最高表面温度Tmax和最低表面温度Tmin满足以下条件:
(Tmax-Tmin)/Tmin*100%≤30%。
非水电解液中加入有结构式1所示的化合物作为添加剂,结构式1所示的化合物在电池首次化成的过程中在电化学条件下分解以在正负极表面形成有界面膜,发明人通过大量研究发现,在结构式1所示的化合物成膜的过程中,结构式1所示的化合物的含量、隔膜的孔隙率和正极材料层的厚度会影响到该界面膜的成膜质量,以及影响锂盐离子在正负极之间的扩散效率,进而导致锂离子电池在充放电下的温度变化,具体的,当隔膜的孔隙率q、正极材料层的厚度h和非水电解液中结构式1所示的化合物的质量百分比含量m满足条件0.1≤h/q*m≤15时,能够充分发挥隔膜、正极材料层和结构式1所示的化合物之间的协同效应,在正负极表面形成高离子导电率的稳定界面膜,提高锂盐的扩散效率,明显减少锂离子电池大电流放电过程中的产热并改善锂离子电池各位置温升的一致性,从而在保证锂离子电池较高的循环寿命和性能一致性的同时,提高锂离子电池的安全性能。
在一些实施例中,当n为0时,所述结构式1所示的化合物为:
其中,A选自C或O,X选自R1、R2各自独立选自H、R1和R2不同时选自H,且X、R1和R2中至少含有一个硫原子。
在一些实施例中,当n为1时,所述结构式1所示的化合物为:
其中,A选自C或O,X选自R1、R2各自独立选自H、R1和R2不同时选自H,且X、R1和R2中至少含有一个硫原子。
在优选的实施例中,所述锂离子电池满足以下条件:
0.2≤h/q*m≤6。
在具体的实施例中,所述隔膜的孔隙率q可以为10%、13%、15%、16%、18%、21%、23%、24%、26%、27%、29%、30%、32%、33%、35%、39%、41%、43%、46%、49%或50%。
在优选的实施例中,所述隔膜的孔隙率q为15%~30%。
若隔膜的孔隙率过小,则锂离子在隔膜间不能顺利穿梭,会降低锂离子电池的动力学性能并增大电池阻抗,不仅导致电池大电流放电时产热速率加快,温升增大,而且会导致整体电池的热稳定性和一致性更差;若隔膜的孔隙率过大,则隔膜不能够有效阻挡有害的杂质物质在正负极间的穿梭过程,劣化电池电化学性能,严重时会使正负极直接接触或易被锂枝晶刺穿而造成短路。
在具体的实施例中,所述正极材料层的厚度h可以为50μm、51μm、55μm、58μm、60μm、61μm、65μm、68μm、70μm、71μm、75μm、78μm、80μm、81μm、85μm、88μm、90μm、91μm、95μm、98μm、100μm、101μm、105μm、108μm、110μm、111μm、115μm、118μm、120μm、121μm、125μm、128μm或130μm。
在优选的实施例中,所述正极材料层的厚度h为60μm~110μm。
正极材料层厚度越厚,虽然有利于提升电池能量密度,但也极大的影响了锂离子在固相中的扩散,因此会在正极和负极内部都会产生较为显著的锂离子浓度梯度差,增加电池大电流放电过程中的极化现象,造成电池内部温度分布不均匀,导致副反应速度的不一致,进而导致电池内部衰降速度的不一致,严重影响电池的一致性;若正极材料层过低,则锂离子电池的能量密度降低,不利于商用化应用。
在具体的实施例中,所述非水电解液中结构式1所示的化合物的质量百分比含量m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%、2.0%、2.3%、2.7%或3.0%。
在优选的实施例中,所述非水电解液中结构式1所示的化合物的质量百分比含量m为0.1%~1.0%。
当非水电解液中结构式1所示的化合物的含量处于上述范围内时,有利于在正负极活性材料表面形成一种高离子电导率且稳定的界面膜,从而在固-液界面处形成快离子通道,促进锂离子的扩散,显著降低了钴酸锂电池大电流放电过程中的产热并改善温度分布的一致性,降低了电池的热失控风险。
在一些实施例中,所述结构式1所示的化合物选自以下化合物中的至少一种:


需要说明的是,以上仅是本发明优选的化合物,并不代表对于本发明的限制。
本领域技术人员在知晓结构式1所示的化合物的结构式的情况下,根据化学合成领域的公知常识可以知晓上述化合物的制备方法。例如:化合物7可通过以下方法制成:
将山梨醇、碳酸二甲酯、甲醇碱性物质催化剂氢氧化钾以及DMF等有机溶剂置于反应容器中,在加热条件下进行反应数小时后,加入一定量的草酸调节pH至中性,过滤、重结晶后即可得到中间产物1,接着将中间产物1、碳酸酯、二氯亚砜等在高温条件下发生酯化反应得到中间产物2,再使用高碘酸钠等氧化剂将中间产物2氧化即可得到化合物7。
在一些实施例中,所述锂离子电池为软包电池或硬壳电池。
在优选实施例中,所述锂盐选自LiPF6、LiBOB、LiDFOB、LiPO2F2、LiBF4、LiSbF6、LiAsF6、LiN(SO2CF3)2、LiN(SO2C2F5)2、LiC(SO2CF3)3、LiN(SO2F)2、LiClO4、LiAlCl4、LiCF3SO3、Li2B10Cl10、LiSO2F、LiTOP(三草酸磷酸锂)、LiDODFP(二氟二草酸磷酸锂)、LiOTFP(四氟草酸磷酸锂)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,所述正极活性材料还可包括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、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,所述正极活性材料还可以选自硫化物、硒化物、卤化物中的一种或几种。更为优选的,所述正极活性材料还包括LiFePO4、LiFe0.6Mn0.4PO4、LiNi0.5Co0.2Mn0.3O2、LiNi0.6Co0.2Mn0.2O2、LiNi0.8Co0.1Mn0.1O2、LiNi0.5Co0.2Mn0.2Al0.1O2、LiMn2O4、LiNi0.8Co0.1Al0.1O2中的至少一种。
在优选的实施例中,所述锂离子电池的充电截止电压为4.4V~4.7V。
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,所述正极材料层还包括正极粘结剂和正极导电剂。
所述正极粘结剂包括聚偏氟乙烯、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、聚乙烯及聚丙烯等热塑性树脂;丙烯酸类树脂;羟甲基纤维素钠;以及苯乙烯丁二烯橡胶中的至少一种。
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Al、Ni、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,所述非水有机溶剂包括醚类溶剂、腈类溶剂、碳酸酯类溶剂和羧酸酯类溶剂中的至少一种。
在一些实施例中,醚类溶剂包括环状醚或链状醚及其氟代物,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。醚类化合物的添加量没有特殊限制,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。醚类化合物的添加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、氟代乙酸乙酯中的至少一种。
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。砜类溶剂的添加量没有特殊限制,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。砜类溶剂的添加量在上述范围内时,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,所述添加剂还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;
优选的,以所述非水电解液的总质量为100%计,所述添加剂的添加量为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2所示化合物中的至少一种,
所述结构式2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3所示化合物中的至少一种:
所述结构式3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3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添加量为10%以下,优选的,添加量为0.1-5%,更优选的,添加量为0.1%~2%。具体的,所述添加剂中任意一种可选物质的添加量可以为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添加量为0.05%~30%。
以下通过实施例对本发明进行进一步的说明。
以下实施例和对比例涉及的化合物如下表所示:
表1
表2实施例和对比例各参数设计


实施例1
本实施例以制备锂离子电池为例对本发明进行说明,包括以下操作步骤:
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(LiPF6)至摩尔浓度为1mol/L,再加入化合物7,以非水电解液的总重量为100%计,化合物7在非水电解液中的质量百分含量如表2所示。
2)正极板的制备:
按94:3:3的质量比混合正极活性材料LiCoO2,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,真空干燥后的正极材料层厚度如表2所示。
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,隔膜的孔隙率如表2所示,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85℃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,将上述制备的非水电解液注入电芯中,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:0.1C恒流充电45min,0.2C恒流充电30min,0.5C恒流充电75min,二次真空封口,然后进一步以0.5C的电流恒流充电至4.45V,再恒压充电至电流下降至0.02C,搁置5min后,以0.5C的电流恒流放电至3.0V,得到一种LiCoO2/人造石墨锂离子电池。
实施例2~25
实施例2~25用于说明本发明公开的锂离子电池及其制备方法,包括实施例1中大部分操作步骤,其不同之处在于:
实施例2~25所采用的负极活性材料、正极材料层的厚度、隔膜孔隙率以及非水电解液中添加剂的种类及其质量百分含量如表2所示。
对比例1~18
对比例1~18用于对比说明本发明公开的锂离子电池及其制备方法,包括实施例1中大部分操作步骤,其不同之处在于:
对比例1~18所采用的负极活性材料、正极材料层的厚度、隔膜孔隙率以及非水电解液中添加剂的种类及其质量百分含量如表2所示。
性能测试
对上述制备得到的锂离子电池进行如下性能测试:
1、电池大电流放电表面温度极差测试
将锂离子电池置于25℃的恒温环境下,以2C的电流放电至100%DOD,采用红外摄像仪(型号:FLIR-SC325,帧率30fps)在放电的过程中监测锂离子电池的表面的温度,记录锂离子电池表面的最大温度值为Tmax,记录锂离子电池表面的最小温度值为Tmin,并通过Tmax和Tmin计算温度极差百分比:温度极差百分比=(Tmax-Tmin)/Tmin*100%。
2、循环性能测试
将锂离子电池置于25℃的恒温环境下,以1C的电流恒流充电至4.45V,再恒压充电至电流下降至0.02C,然后以2C的电流恒流放电至3.0V,如此循环800次,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%。
(1)实施例1~14和对比例1、5~18得到的测试结果填入表3。
表3

由实施例1~14和对比例1、5~18的测试结果可知,采用钴酸锂作为正极活性材料,在非水电解液中加入结构式1所示的化合物,同时隔膜的孔隙率q、正极材料层的厚度h和非水电解液中结构式1所示的化合物的质量百分比含量m满足预设条件0.1≤h/q*m≤15时,得到的锂离子电池具有较低的电池表面温度极差以及较高的循环容量保持率,说明隔膜的孔隙率q、正极材料层的厚度h和非水电解液中结构式1所示的化合物的质量百分比含量m对于结构式1所示的化合物在正极材料层表面形成的界面膜质量具有较大的影响,通过上述关系式限定条件下得到的界面膜具有较高的稳定性,同时具有较好的锂离子扩散性能,配合隔膜的孔隙率调节和正极材料层的厚度调节,能够明显减少锂离子电池在大电流放电过程中的产热,并改善锂离子电池在各位置温升的一致性,有效提高锂离子电池的循环寿命和安全性。
由实施例1~14的测试结果可知,当进一步满足优选条件0.2≤h/q*m≤6时,有利于进一步降低锂离子电池的电池表面温度极差以及提高锂离子电池的循环容量保持率,推测此时结构式1所示的化合物所形成的界面膜具有更好的离子电导率,从而有效降低所述正极材料层表面的界面阻抗,保证离子扩散速度,避免局部过热的问题。
由对比例5~10的测试结果可知,即使隔膜的孔隙率q、正极材料层的厚度h和非水电解液中结构式1所示的化合物的质量百分比含量m满足预设条件0.1≤h/q*m≤15的限定,但q值、h值或m值不满足其范围限定时,锂离子电池仍然不具有较好的避免过热和容量保持率的性能,说明q值、h值或m值在提高锂离子电池安全性能和循环性能方面具有较强的关联性。同样的,当q值、h值或m值满足其范围限定,但h/q*m值不满足上述预设条件时,也无法有效解决锂离子电池温升过高和循环性能下降的问题。
(2)实施例1、实施例15~17和对比例2~4得到的测试结果填入表4。
表4
由实施例1、实施例15~17和对比例2~4的测试结果可知,采用其它成膜添加剂替换本申请的结构式1所示的化合物,如氟代碳酸乙烯酯(FEC)、1,3,6-己烷三腈(HTCN)或二氟草酸硼酸锂(LiODFB),在满足类似条件的情况下,对于锂离子电池的性能提升并不如本发明提供的结构式1所示的化合物,说明,本发明提供的0.1≤h/q*m≤15仅针对结构式1所示的化合物该种特定的添加剂;同时,在本发明提供的电池体系中,额外加入氟代碳酸乙烯酯(FEC)、1,3,6-己烷三腈(HTCN)或二氟草酸硼酸锂(LiODFB),能够进一步降低电池 表面温度极差和提高循环容量保持率,说明其它添加剂对电池性能的提升机理与结构式1所示的化合物存在一定的差异,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。
(3)实施例1、实施例18~22得到的测试结果填入表5。
表5
由实施例1、实施例18~22的测试结果可知,对于不同的结构式1所示的化合物,隔膜的孔隙率q、正极材料层的厚度h和非水电解液中结构式1所示的化合物的质量百分比含量m满足预设条件0.1≤h/q*m≤15时,其起到的作用相似,均对于锂离子电池的温升问题具有较好的改善作用,进而有效提高了锂离子电池的循环寿命,说明本发明提供的关系式适用于不同的结构式1所示的化合物。
(4)实施例1、实施例23~25得到的测试结果填入表6。
表6
由实施例1、实施例23~25的测试结果可知,当负极活性材料采用石墨与氧化亚硅以不同的质量比混合时,且满足本发明的关系式0.1≤h/q*m≤15限定时,同样能够有效降低电池的放电温度极差和提高循环容量保持率,说明在本发明限定的体系下,主要是对于锂离子的正极部分起到了改进效果,因此,该关系式限定也适用于不同的负极材料及其组合。
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、非水电解液和隔膜,所述隔膜位于所述正极和所述负极之间,所述正极包括包含正极活性材料的正极材料层,所述正极活性材料包括钴酸锂,所述非水电解液包括有非水有机溶剂、锂盐和添加剂,所述添加剂包括结构式1所示的化合物:
    其中,n为0或1,A选自C或O,X选自R1、R2各自独立选自H、R1和R2不同时选自H,且X、R1和R2中至少含有一个硫原子;
    所述锂离子电池满足以下条件:
    0.1≤h/q*m≤15;
    且10≤q≤50,50≤h≤130,0.01≤m≤3;
    其中,q为隔膜的孔隙率,单位为%;
    h为正极材料层的厚度,单位为μm;
    m为非水电解液中结构式1所示的化合物的质量百分比含量,单位为%;
    所述锂离子电池在25℃下2C放电到100%DOD过程中的最高表面温度Tmax和最低表面温度Tmin满足以下条件:
    (Tmax-Tmin)/Tmin*100%≤30%。
  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:
    0.2≤h/q*m≤6。
  3. 根据权利要求1所述的锂离子电池,其特征在于,所述隔膜的孔隙率q为15%~30%。
  4. 根据权利要求1所述的锂离子电池,其特征在于,所述正极材料层的厚度h为60μm~110μm。
  5. 根据权利要求1所述的锂离子电池,其特征在于,所述非水电解液中结构式1所示的化合物的质量百分比含量m为0.1%~1.0%。
  6. 根据权利要求1所述的锂离子电池,其特征在于,所述结构式1所示的化合物选自以下化合物中的至少一种:


  7. 根据权利要求1所述的锂离子电池,其特征在于,所述锂离子电池的充电截止电压为4.4V~4.7V。
  8. 根据权利要求1所述的锂离子电池,其特征在于,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。
  9. 根据权利要求1所述的锂离子电池,其特征在于,所述添加剂还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,所述添加剂的添加量为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2所示化合物中的至少一种,
    所述结构式2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3所示化合物中的至少一种:
    所述结构式3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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