Lithium-ion battery

Abstract

In order to overcome the problems of insufficient high-temperature cycle performance and high-temperature storage performance of existing silicon-containing negative electrodes, provided is a lithium-ion battery, comprising a positive electrode, a negative electrode and a non-aqueous electrolyte. The positive electrode comprises a positive electrode material layer which comprises a positive electrode active material. The negative electrode comprises a negative electrode material layer which comprises a negative electrode active material, the negative electrode active material comprising a silicon-carbon composite material formed by compositing a silicon-based material and a graphite material. The non-aqueous electrolyte comprises a non-aqueous organic solvent, an electrolyte salt and an additive, the non-aqueous organic solvent comprising fluoroethylene carbonate, and the additive comprising lithium difluorophosphate and ethylene sulfate. The lithium-ion battery satisfies the following conditions: 0.6≤100*(D / F+10*L) / C≤2.5, 5≤D≤16, 400≤C≤700, 3≤F≤20 and 0.2≤L≤1. The lithium-ion battery can maintain good high-temperature cycle performance and high-temperature storage performance while having an increased energy density.

Description

A lithium ion battery TECHNICAL FIELD

[0001] The application belongs to the technical field of energy storage components and specifically relates to a lithium ion battery. BACKGROUND

[0002] Lithium ion batteries have the advantages of high working voltage, wide working temperature range, high energy density, large output power, no memory effect and long cycle life, and are not only widely used in 3C digital product fields such as mobile phones and notebook computers, but also have a broad application market in new energy vehicles and large-scale energy storage fields. With the rapid development of new energy, the application of non-aqueous electrolyte lithium ion batteries has also increased by leaps and bounds. However, with the urgent demand of terminal users for improving the endurance mileage of new energy vehicles, it is necessary to further improve the energy density of power batteries.

[0003] The higher the specific capacity of the negative electrode material is, the lower the overall mass of the battery is, and the higher the corresponding mass energy density is. Developing higher specific capacity positive and negative electrode materials, such as high-nickel ternary positive electrode materials with a nickel content of greater than or equal to 80% and silicon-based negative electrode materials, is one of the effective ways to improve the energy density of batteries. When the mass energy density requirement reaches 300 Wh / kg, silicon-based materials must be used as the negative electrode. Silicon-based negative electrode materials (4200 mAh / g) have a theoretical specific capacity much higher than that of graphite negative electrode materials (372 mAh / g), making them an important development direction for improving the energy density of lithium ion batteries. However, compared with graphite negative electrodes, silicon-based negative electrodes have a large volume effect (>300%) during the cycle process. After alloying with lithium, the volume of the silicon-based negative electrode changes significantly, causing the solid electrolyte interface film (SEI film) on the surface of the silicon-based negative electrode to continuously break and regenerate during the battery cycle process, leading to consumption of electrolyte and loss of active lithium, increase of interface impedance, and particularly in a high-temperature environment, the cycle performance and storage performance will be greatly deteriorated. The chemical vapor deposition technology (CVD method) stores silicon through a porous carbon skeleton. First, a high-molecular material is used to manufacture carbon particles with a porous structure similar to a sponge. Then, silane gas is introduced into the pores of the porous carbon particles, and the gas is deposited into silicon nanoparticles dispersed in the pores of the porous carbon through high-temperature pyrolysis. This method can control the prepared nanomaterials at a molecular scale, and the product morphology is good. At the same time, the silicon-carbon material produced by deposition has uniform composition and dense structure, and the volume expansion is buffered through the gaps in the porous carbon. However, this structure cannot completely overcome the problem of SEI film breaking during the cycle process, and the rate and high-temperature storage performance of the gas-phase silicon-carbon are poorer than those of the pre-lithium silicon-oxygen, and there is no obvious advantage in cycle performance at a low addition amount. SUMMARY

[0004] The lithium ion battery provided by the application can solve the problems of the existing silicon-containing negative electrode, such as insufficient high-temperature cycle performance and insufficient high-temperature storage performance.

[0005] The technical scheme adopted by the application to solve the above technical problems is as follows:

[0006] The application provides a lithium ion battery, which comprises a positive electrode, a negative electrode and a non-aqueous electrolyte, the positive electrode comprises a positive electrode material layer comprising a positive electrode active material, the negative electrode comprises a negative electrode material layer comprising a negative electrode active material, the negative electrode active material comprises a silicon-carbon composite material composed of a silicon-based material and a graphite material, wherein the silicon-based material comprises a porous carbon matrix and silicon-based particles, the silicon-based particles are distributed in the pores of the porous carbon matrix, the non-aqueous electrolyte comprises a non-aqueous organic solvent, an electrolyte salt and an additive, the non-aqueous organic solvent comprises fluoroethylene carbonate, and the additive comprises lithium difluorophosphate and vinyl sulfate.

[0007] The lithium ion battery satisfies the following conditions:

[0008] 0.6 <= 100 * (D / F+10*L) / C <= 2.5, and 5 <= D <= 16, 400 <= C <= 700, 3 <= F <= 20, 0.2 <= L <= 1.

[0009] Wherein, D is the median particle size D50 of the silicon-carbon composite material, and the unit is mu m.

[0010] C is the gram capacity of the negative electrode material layer, and the unit is mAh / g.

[0011] F is the mass percentage content of fluoroethylene carbonate in the non-aqueous electrolyte, and the unit is %.

[0012] L is the mass percentage content of lithium difluorophosphate in the non-aqueous electrolyte, and the unit is %.

[0013] Optionally, the lithium ion battery satisfies the following conditions:

[0014] 0.9 <= 100 * (D / F+10*L) / C <= 1.85.

[0015] Optionally, the median particle size D50 of the silicon-carbon composite material is 7-14 mu m.

[0016] Optionally, the gram capacity C of the negative electrode material layer is 450-600 mAh / g.

[0017] Optionally, the mass percentage content F of fluoroethylene carbonate in the non-aqueous electrolyte is 5%-15%.

[0018] Optionally, the mass percentage content L of lithium difluorophosphate in the non-aqueous electrolyte is 0.3%-0.8%.

[0019] Optionally, in the negative active material, the mass ratio of the silicon-based material and the graphite material is (0.03-0.45):1, and / or

[0020] The mass percentage of the silicon element is 2%-12% based on the total mass of the negative material layer.

[0021] Optionally, the mass percentage of the vinyl sulfonate is 0.05%-1% based on the total mass of the non-aqueous electrolyte;

[0022] Preferably, the mass percentage of the vinyl sulfonate is 0.1%-0.5%.

[0023] Optionally, the additive further comprises at least one of a sulfonic acid lactone compound, a cyclic carbonate compound, a phosphate compound, a borate compound, and a nitrile compound.

[0024] Optionally, the sulfonic acid lactone compound comprises at least one of 1,3-propane sulfonic acid lactone, 1,4-butane sulfonic acid lactone, and 1,3-propylene sulfonic acid lactone; and / or

[0025] The cyclic carbonate compound comprises at least one of vinylene carbonate, vinyl ethylene carbonate, methylene vinylene carbonate, or a compound shown in structural formula 1:

[0026] In the structural formula 1, R 21 , R 22 , R 23 , R 24 , R 25 , and R 26 are each independently selected from one of a hydrogen atom, a halogen atom, and a C1-C5 group; and / or

[0027] The phosphate compound comprises at least one of tris(trimethylsilyl) phosphate, tris(triethylsilyl) phosphate, or a compound shown in structural formula 2:

[0028] In the structural formula 2, R 31 , R 32 , and R 33 are each independently selected from a C1-C5 saturated hydrocarbon group, a C1-C5 unsaturated hydrocarbon group, a C1-C5 halogenated hydrocarbon group, -Si(C m H 2m+1 )3, m is a natural number of 1-3, and at least one of R 31 , R 32 , and R 33 is an unsaturated hydrocarbon group; and / or

[0029] The borate compound includes at least one of tris(trimethylsilyl) borate and tris(triethylsilyl) borate; and / or

[0030] The nitrile compound includes at least one of butanedinitrile, pentanedinitrile, hexanetristitnitrile, hexanedinitrile, heptanedinitrile, octanedinitrile, nonanedinitrile, decanedinitrile.

[0031] According to the lithium ion battery provided by the application, the silicon-based material is added in the graphite material, the porous carbon matrix is selected to load the silicon-based particles, the porous carbon matrix has a plurality of long and narrow pores, the porous carbon matrix forms a cross-linked three-dimensional network structure, the silicon-based particles are distributed in the cross-linked pores, the expansion of the silicon-based particles can be effectively limited, and the conductivity of the silicon-based particles is improved; meanwhile, the fluoroethylene carbonate is used as the non-aqueous organic solvent, and the lithium difluorophosphate and the ethylene sulfate are used as the additives, the inventors find through a large number of studies that when the median particle size D of the silicon-carbon composite material, the gram capacity C of the negative electrode material layer, the mass percentage F of the fluoroethylene carbonate and the mass percentage L of the lithium difluorophosphate satisfy the condition 0.6≤100*(D / F+10*L) / C≤2.5, and 5≤D≤16, 400≤C≤700, 3≤F≤20, 0.2≤L≤1, the lithium ion battery obtained can maintain relatively optimal high-temperature cycle performance and high-temperature storage performance while improving the energy density, it is speculated that the fluoroethylene carbonate and the lithium difluorophosphate both provide support in the process of constructing the positive and negative electrode interface film, especially when they are adapted to the silicon-carbon composite material, in order to form a dense and high-thermal-stability interface film on the surface of the silicon-carbon composite material, the contents of the two are related to the characteristics of the negative electrode material, specifically, the median particle size of the silicon-carbon composite material affects its specific surface area, and then affects the amount of fluoroethylene carbonate and lithium difluorophosphate required to form the interface film, and the gram capacity of the negative electrode material layer is related to the silicon content thereof, and determines the expansion rate of the negative electrode active material, and then affects the requirement for the anti-expansion strength of the interface film, when the median particle size D of the silicon-carbon composite material, the gram capacity C of the negative electrode material layer, the mass percentage F of the fluoroethylene carbonate and the mass percentage L of the lithium difluorophosphate are in a synergistic state, a stable and dense interface film can be formed on the surface of the silicon-carbon composite material, the negative electrode is well protected, the interface film is prevented from being broken in the high-temperature charge-discharge cycle, and then the high-temperature performance of the silicon-containing lithium ion battery is improved, and the service life is prolonged. DETAILED DESCRIPTION

[0032] In order to make the technical problems, technical solutions and beneficial effects of the present application clearer, the present application will be further described in detail below with examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the present application.

[0033] The embodiment of the present application provides a lithium ion battery, which comprises a positive electrode, a negative electrode and a non-aqueous electrolyte, the positive electrode comprises a positive electrode material layer comprising a positive electrode active material, the negative electrode comprises a negative electrode material layer comprising a negative electrode active material, the negative electrode active material comprises a silicon-carbon composite material composed of a silicon-based material and a graphite material, wherein the silicon-based material comprises a porous carbon matrix and silicon-based particles, the silicon-based particles are distributed in the pores of the porous carbon matrix, the non-aqueous electrolyte comprises a non-aqueous organic solvent, an electrolyte salt and an additive, the non-aqueous organic solvent comprises fluoroethylene carbonate, and the additive comprises lithium difluorophosphate and vinyl sulfate.

[0034] The lithium ion battery satisfies the following conditions:

[0035] 0.6 <= 100 * (D / F+10*L) / C <= 2.5, and 5 <= D <= 16, 400 <= C <= 700, 3 <= F <= 20, 0.2 <= L <= 1.

[0036] Wherein, D is the median particle size D50 of the silicon-carbon composite material, and the unit is mu m.

[0037] C is the gram capacity of the negative electrode material layer, and the unit is mAh / g.

[0038] F is the mass percentage content of fluoroethylene carbonate in the non-aqueous electrolyte, and the unit is %.

[0039] L is the mass percentage content of lithium difluorophosphate in the non-aqueous electrolyte, and the unit is %.

[0040] The silicon-based material has a porous carbon matrix, and the porous carbon matrix has a plurality of long and narrow pores, so that the porous carbon matrix forms a cross-linked three-dimensional network structure, and the silicon-based particles are distributed in the cross-linked pores. On the one hand, the three-dimensional network structure of the porous carbon matrix can accommodate and limit the expansion of the silicon-based particles, improve the damage of the expansion of the silicon-based particles to the structure of the composite material in the battery cycle process, thereby helping to improve the cycle stability of the composite material in the battery; on the other hand, the specific pore distribution and structure of the porous carbon matrix help the silicon to occupy the pores in the carbon skeleton and disperse in the carbon material, and the cross-linked carbon skeleton with high conductivity can realize efficient electron transmission, so that the silicon-carbon composite material has high specific capacity and good conductivity, and helps to reduce the polarization of the battery when applied to the battery.

[0041] In order to form a stable interface film on the surface of the above-mentioned silicon-based material, the inventors have found through a large number of studies that when the median particle size D of the silicon-carbon composite material, the gram capacity C of the negative electrode material layer, the mass percentage content F of fluoroethylene carbonate, and the mass percentage content L of lithium difluorophosphate satisfy the condition 0.6≤100*(D / F+10*L) / C≤2.5, and 5≤D≤16, 400≤C≤700, 3≤F≤20, 0.2≤L≤1, the obtained lithium ion battery can maintain relatively optimal high-temperature cycle performance and high-temperature storage performance while improving the energy density. It is speculated that both fluoroethylene carbonate and lithium difluorophosphate provide support during the construction of the positive-negative electrode interface film, especially when they are adapted to the silicon-carbon composite material, the contents of the two are related to the characteristics of the negative electrode material. Specifically, the median particle size of the silicon-carbon composite material affects its specific surface area, and in turn affects the amount of fluoroethylene carbonate and lithium difluorophosphate required to form the interface film. The gram capacity of the negative electrode material layer is related to the silicon content, which determines the expansion rate of the negative electrode active material, and in turn affects the requirement for the anti-expansion strength of the interface film. When the median particle size D of the silicon-carbon composite material, the gram capacity C of the negative electrode material layer, the mass percentage content F of fluoroethylene carbonate, and the mass percentage content L of lithium difluorophosphate are in a synergistic state, a stable and dense interface film can be formed on the surface of the silicon-carbon composite material, which provides good protection for the negative electrode, avoids the rupture of the interface film during high-temperature charge-discharge cycling, and in turn improves the high-temperature performance of the silicon-containing lithium ion battery and prolongs the service life.

[0042] In preferred embodiments, the lithium ion battery satisfies the following condition:

[0043] 0.9≤100*(D / F+10*L) / C≤1.85.

[0044] When the median particle size D of the silicon-carbon composite material, the gram capacity C of the negative electrode material layer, the mass percentage content F of fluoroethylene carbonate, and the mass percentage content L of lithium difluorophosphate further satisfy the above condition, the ion conductivity of the negative electrode interface film can be further improved, and the battery impedance can be reduced.

[0045] In specific embodiments, the median particle size D50 of the silicon-carbon composite material can be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or 16 μm.

[0046] In preferred embodiments, the median particle size D50 of the silicon-carbon composite material is 7-14 μm.

[0047] The median particle size D50 of the silicon-carbon composite material is related to the specific surface area of the silicon-carbon composite material. The smaller the median particle size D50 of the silicon-carbon composite material, the larger the specific surface area of the silicon-carbon composite material, the more sites for lithium ion exchange with the non-aqueous electrolyte, which is beneficial to reducing the lithium ion deintercalation and intercalation resistance, but the surface of the silicon-based particles exposed to the electrolyte increases, which requires more consumption of fluoroethylene carbonate and lithium difluorophosphate in the process of battery formation. When the median particle size D50 of the silicon-carbon composite material is in the above range, it is beneficial to adapt to the added fluoroethylene carbonate and lithium difluorophosphate to form a complete interface film.

[0048] In specific embodiments, the gram capacity C of the negative electrode material layer can be 400 mAh / g, 410 mAh / g, 440 mAh / g, 460 mAh / g, 480 mAh / g, 490 mAh / g, 500 mAh / g, 510 mAh / g, 540 mAh / g, 560 mAh / g, 580 mAh / g, 590 mAh / g, 610 mAh / g, 640 mAh / g, 660 mAh / g, 680 mAh / g or 700 mAh / g.

[0049] In preferred embodiments, the gram capacity C of the negative electrode material layer is 450-600 mAh / g.

[0050] The gram capacity of the negative electrode material layer is related to the amount of silicon contained therein. The higher the gram capacity of the negative electrode material layer, the higher the energy density of the battery, and at the same time, the volume expansion phenomenon caused by silicon is more obvious, and the cycle performance and high-temperature performance of the battery decrease. When the gram capacity C of the negative electrode material layer is too low, the energy density of the lithium ion battery is insufficient; when the gram capacity C of the negative electrode material layer is too high, the interface film formed by fluoroethylene carbonate and lithium difluorophosphate cannot well adapt to the volume change in the charging and discharging process, leading to the rupture of the interface film, and then continuously consuming the electrolyte in the cycle process, especially under high temperature conditions, thereby affecting the service life of the battery.

[0051] In specific embodiments, the mass percentage content F of fluoroethylene carbonate in the non-aqueous electrolyte can be 3%, 4%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%.

[0052] In preferred embodiments, the mass percentage content F of fluoroethylene carbonate in the non-aqueous electrolyte is 5%-15%.

[0053] After the high-energy-density cathode is compounded with the silicon-carbon composite material, the system stability is further destroyed due to the positive-negative electrode cross-interference: the side reaction between the silicon-based material expansion and the oxygen release of the cathode is accelerated, and the gas production is aggravated due to the self-decomposition and electrochemical decomposition of the fluoroethylene carbonate at high temperature, the positive-negative electrode balance is broken, and the performance is rapidly attenuated. By adding the fluoroethylene carbonate in the non-aqueous electrolyte, not only can the interface film be formed on the positive-negative electrode, but also the lithium consumption can be inhibited, and the material body can be protected. If the mass percentage content F of the fluoroethylene carbonate in the non-aqueous electrolyte is too low, it is difficult to form a complete interface film on the positive-negative electrode surface, and the protection effect on the positive-negative electrode is limited; if the mass percentage content F of the fluoroethylene carbonate in the non-aqueous electrolyte is too high, the lithium consumption is increased, and the performance of the battery is deteriorated.

[0054] In specific embodiments, the mass percentage content L of lithium difluorophosphate in the non-aqueous electrolyte can be 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1%.

[0055] In preferred embodiments, the mass percentage content L of lithium difluorophosphate in the non-aqueous electrolyte is 0.3% to 0.8%.

[0056] By the combined use of the fluoroethylene carbonate and lithium difluorophosphate, the content relationship between the two can be adjusted to optimize the control of the interface film components, the fluoroethylene carbonate forms organic matter, and the lithium difluorophosphate forms inorganic matter, which can not only ensure the stability of the silicon-carbon composite material, but also optimize the lithium ion transmission channel and effectively inhibit the impedance growth.

[0057] In some embodiments, in the negative electrode active material, the mass ratio of the silicon-based material to the graphite material is (0.03-0.45):1.

[0058] In some embodiments, the mass percentage content of the silicon element is 2% to 12% based on the total mass of the negative electrode material layer being 100%.

[0059] In preferred embodiments, the mass percentage content of the silicon element is 3% to 10% based on the total mass of the negative electrode material layer being 100%.

[0060] In some embodiments, the mass percentage content of the vinyl sulfate is 0.05% to 1% based on the total mass of the non-aqueous electrolyte being 100%.

[0061] In preferred embodiments, the mass percentage content of the vinyl sulfate is 0.1% to 0.5%.

[0062] High specific energy systems require higher silicon content, and the corresponding amount of fluoroethylene carbonate will be more. The protection of fluoroethylene carbonate to the negative electrode will be enhanced, but its intrinsic decomposition gas and electrochemical decomposition gas will induce positive electrode crosstalk, causing the positive electrode structure to be damaged. Therefore, introducing a small amount of vinyl sulfate as a sacrificial additive is beneficial to optimize the interface film structure. Unlike the large amount of additive used as a film-forming agent, in the present application, it is used as a trace sacrificial agent to construct a layer of interface film base dominated by sulfur elements on the surface of the positive and negative electrode materials, and further modify and construct a high-elasticity and high-strength interface film rich in LiF and organic matter, to ensure that the interface film is not easily broken and detached due to expansion and side reactions, and to control its optimal content of ≤0.5% to avoid the impedance increase caused by its introduction.

[0063] In some embodiments, the additive further comprises at least one of a sulfolactone compound, a cyclic carbonate compound, a phosphate compound, a borate compound, and a nitrile compound.

[0064] In some embodiments, the content of the additive is 0.01%-10% based on 100% of the total mass of the non-aqueous electrolyte.

[0065] In some embodiments, the sulfolactone compound comprises at least one of 1,3-propane sulfolactone, 1,4-butane sulfolactone, and 1,3-propylene sulfolactone.

[0066] In some embodiments, the cyclic carbonate compound comprises at least one of vinylene carbonate, vinyl ethylene carbonate, methylene vinylene carbonate, or a compound represented by structural formula 1:

[0067] In the structural formula 1, R 21 , R 22 , R 23 , R 24 , R 25 , R 26 are each independently selected from one of a hydrogen atom, a halogen atom, and a C1-C5 group.

[0068] In some embodiments, the phosphate compound comprises at least one of tris(trimethylsilyl) phosphate, tris(triethylsilyl) phosphate, or a compound represented by structural formula 2:

[0069] In the structural formula 2, R 31 , R 32 , R 33 are each independently selected from a C1-C5 saturated hydrocarbon group, a C1-C5 unsaturated hydrocarbon group, a C1-C5 halogenated hydrocarbon group, -Si(C m H 2m+1)3, m is a natural number of 1-3, and R 31 , R 32 , R 33 at least one of which is an unsaturated hydrocarbon group.

[0070] In preferred embodiments, the phosphate compound of structural formula 2 can 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.

[0071] In some embodiments, the borate compound includes at least one of tris(trimethylsilyl) borate and tris(triethylsilyl) borate.

[0072] In some embodiments, the nitrile compound includes at least one of butanedinitrile, pentanedinitrile, hexanetristitnitrile, hexanedinitrile, heptanedinitrile, octanedinitrile, nonanedinitrile, and decanedinitrile.

[0073] In other embodiments, the additive can further include other additives that improve battery performance, such as additives that improve battery safety performance, such as flame retardant additives, such as fluorinated phosphate esters, and phosphazenes, or additives that prevent overcharging, such as t-amylbenzene and t-butylbenzene.

[0074] It should be noted that, unless otherwise specified, the content of any optional substance in the additive is less than 10%, preferably, the content is 0.01-5%, more preferably, the content is 0.1%-2%. Specifically, the content of any optional substance in the additive can be 0.01%, 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%, or 10%.

[0075] In some embodiments, the non-aqueous organic solvent further includes at least one of an ether solvent, a nitrile solvent, a carbonate solvent, a carboxylate solvent, and a sulfone solvent.

[0076] In some embodiments, the ether-based solvent includes a cyclic ether or a chain ether, preferably a chain ether having 3 to 10 carbon atoms and a cyclic ether having 3 to 6 carbon atoms, and the cyclic ether can specifically but not exclusively be at least one of 1,3-dioxolane (DOL), 1,4-dioxane (DX), a crown ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH3-THF), 2-trifluoromethyltetrahydrofuran (2-CF3-THF); and the chain ether can specifically but not exclusively be dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethyleneglycol di-n-propyl ether, ethyleneglycol di-n-butyl ether, diethyleneglycol dimethyl ether. Since the chain ether has high solvating ability for 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-based compound can be used alone or in combination of two or more in any combination and ratio. The amount of the ether-based compound to be added is not particularly limited and is arbitrary within a range that does not significantly impair the effects of the high-density lithium ion battery according to the present application, and is usually 1% or more by volume, preferably 2% or more by volume, and more preferably 3% or more by volume, in a non-aqueous solvent volume ratio of 100%, and is usually 30% or less by volume, preferably 25% or less by volume, and more preferably 20% or less by volume.

[0077] In some embodiments, the nitrile-based solvent can specifically but not exclusively be at least one of acetonitrile, glutaronitrile, and malononitrile.

[0078] In some embodiments, the carbonate-based solvent includes a cyclic carbonate or a chain carbonate, and the cyclic carbonate can specifically be, but is not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (GBL), and butylene carbonate (BC); and the chain carbonate can specifically be, but is 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 is not particularly limited and is arbitrary within a range that does not significantly impair the effects of the lithium ion battery of the present application, but in the case of using one alone, the lower limit of the content is generally 3% by volume, preferably 5% by volume, relative to the total amount of the solvent of the nonaqueous electrolyte. By setting this range, it is possible to avoid a decrease in the electric conductivity due to a decrease in the dielectric constant of the nonaqueous electrolyte, and to easily bring the large-current discharge characteristics, the stability with respect to the negative electrode, and the cycle characteristics of the nonaqueous electrolyte battery to a good range. In addition, the upper limit is generally 90% by volume, preferably 85% by volume, more preferably 80% by volume. By setting this range, it is possible to improve the oxidation / reduction resistance of the nonaqueous electrolyte, thereby contributing to an improvement in the stability at the time of high-temperature storage. The content of the chain carbonate is not particularly limited and is generally 15% by volume, preferably 20% by volume, more preferably 25% by volume, relative to the total amount of the solvent of the nonaqueous electrolyte. In addition, it is generally 90% by volume, preferably 85% by volume, more preferably 80% by volume. By bringing the content of the chain carbonate within the above range, it is possible to easily bring the viscosity of the nonaqueous electrolyte to an appropriate range, to suppress a decrease in the ionic conductivity, and to further contribute to bringing the output characteristics of the nonaqueous electrolyte battery to a good range. In the case of using two or more kinds of chain carbonates in combination, it is sufficient to bring the total amount of the chain carbonates to the above range.

[0079] In some embodiments, it can also be preferable to use a chain carbonate having a fluorine atom (hereinafter referred to simply as "fluorinated chain carbonate"). The number of fluorine atoms possessed by the fluorinated chain carbonate is not particularly limited as long as it is 1 or more, but is generally 6 or less, preferably 4 or less. In the case where the fluorinated chain carbonate has a plurality of fluorine atoms, these fluorine atoms can be bonded to the same carbon or to different carbons. As the fluorinated chain carbonate, there can be mentioned, for example, fluorinated dimethyl carbonate derivatives, fluorinated ethyl methyl carbonate derivatives, fluorinated diethyl carbonate derivatives, and the like.

[0080] The carboxylic acid ester-based solvent includes a cyclic carboxylic acid ester and / or a chain carbonate. As examples of the cyclic carboxylic acid ester, there can be mentioned, for example, at least one of γ-butyrolactone, γ-valerolactone, and δ-valerolactone. As examples of the chain carbonate, there can be mentioned, for example, at least one of methyl acetate (MA), ethyl acetate (EA), propyl acetate (EP), butyl acetate, propyl propionate (PP), and butyl propionate.

[0081] In some embodiments, the sulfone-based solvent includes a cyclic sulfone and a chain sulfone, preferably, in the case of a cyclic sulfone, a compound having generally 3 to 6 carbon atoms, preferably 3 to 5 carbon atoms, and in the case of a chain sulfone, a compound having generally 2 to 6 carbon atoms, preferably 2 to 5 carbon atoms. The amount of the sulfone-based solvent added is not particularly limited and is arbitrary within a range that does not significantly impair the effects of the lithium ion battery of the present application, and is generally 0.3% by volume or more, preferably 0.5% by volume or more, more preferably 1% by volume or more, and, in addition, is generally 40% by volume or less, preferably 35% by volume or less, more preferably 30% by volume or less, with respect to the total amount of the solvent of the nonaqueous electrolyte. In the case where two or more kinds of sulfone-based solvents are used in combination, the total amount of the sulfone-based solvents may be within the above range. When the amount of the sulfone-based solvent added is within the above range, a nonaqueous electrolyte excellent in high-temperature storage stability tends to be obtained.

[0082] In some embodiments, the positive electrode active material is selected from at least one of LiFe 1-x’ M’ x’ PO4, LiMn 2-y’ M y’ O4, and LiNi x Co y Mn z M 1-x-y-z O2, wherein M’ is selected from at least one of Mn, Mg, Co, Ni, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, Zr, W, V, or Ti, M is selected from at least one of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, Zr, W, V, or Ti, and 0≤x’<1, 0≤y’≤1, 0≤y≤1, 0≤x≤1, 0≤z≤1, x+y+z≤1.

[0083] In some embodiments, the positive electrode material layer further includes a positive electrode binder and a positive electrode conductive agent, and the positive electrode active material, the positive electrode binder, and the positive electrode conductive agent are blended to obtain the positive electrode material layer.

[0084] The positive electrode binder includes at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride, polytetrafluoroethylene, a copolymer of vinylidene fluoride-hexafluoropropylene, a copolymer of tetrafluoroethylene-hexafluoropropylene, a copolymer of tetrafluoroethylene-perfluoroalkyl vinyl ether, a copolymer of ethylene-tetrafluoroethylene, a copolymer of vinylidene fluoride-tetrafluoroethylene, a copolymer of vinylidene fluoride-trifluoroethylene, a copolymer of vinylidene fluoride-trichloroethylene, a copolymer of vinylidene fluoride-vinylidene fluoride, a copolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, a thermoplastic polyimide, a thermoplastic resin such as polyethylene and polypropylene, an acrylic resin, and a styrene butadiene rubber.

[0085] The positive electrode conductive agent includes at least one of conductive carbon black, conductive carbon sphere, conductive graphite, conductive carbon fiber, carbon nanotube, graphene or reduced graphene oxide.

[0086] In some embodiments, the positive electrode current collector includes an electron-conducting metal material, preferably, the positive electrode current collector includes at least one of Al, Ni, tin, copper, stainless steel, and in more preferred embodiments, the positive electrode current collector is selected from aluminum foil.

[0087] In some embodiments, the negative electrode further includes a negative electrode current collector, and the negative electrode active material layer covers the surface of the negative electrode current collector. The negative electrode current collector includes an electron-conducting metal material, preferably, the negative electrode current collector includes at least one of Al, Ni, tin, copper, stainless steel, and in more preferred embodiments, the negative electrode current collector is selected from copper foil.

[0088] In some embodiments, the negative electrode active 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 active material layer.

[0089] The negative electrode binder includes at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride, polytetrafluoroethylene, a copolymer of vinylidene fluoride-hexafluoropropylene, a copolymer of tetrafluoroethylene-hexafluoropropylene, a copolymer of tetrafluoroethylene-perfluoroalkyl vinyl ether, a copolymer of ethylene-tetrafluoroethylene, a copolymer of vinylidene fluoride-tetrafluoroethylene, a copolymer of vinylidene fluoride-trifluoroethylene, a copolymer of vinylidene fluoride-trichloroethylene, a copolymer of vinylidene fluoride-vinylidene fluoride, a copolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, thermoplastic polyimide, thermoplastic resin such as polyethylene and polypropylene, acrylic resin, and styrene butadiene rubber.

[0090] The negative electrode conductive agent includes at least one of conductive carbon black, conductive carbon sphere, conductive graphite, conductive carbon fiber, carbon nanotube, graphene or reduced graphene oxide.

[0091] In some embodiments, the lithium ion battery further includes a separator between the positive electrode and the negative electrode.

[0092] The separator can be a conventional separator, and can be a ceramic separator, a polymer separator, a non-woven fabric, an inorganic-organic composite separator, etc., including but not limited to single-layer PP (polypropylene), single-layer PE (polyethylene), double-layer PP / PE, double-layer PP / PP and triple-layer PP / PE / PP, etc.

[0093] The application is further described below by way of examples.

[0094] Table 1

[0095] Example 1

[0096] The present embodiment is used to illustrate the lithium ion battery and the preparation method thereof disclosed by the present application, which comprises the following operation steps:

[0097] The positive electrode preparation step is: mixing high-nickel ternary positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), conductive carbon black and binder polyvinylidene fluoride in N-methylpyrrolidone to obtain a positive electrode slurry, uniformly coating the positive electrode slurry on both sides of an aluminum foil, drying, calendering and vacuum drying, and welding an aluminum lead wire by using an ultrasonic welding machine to obtain a positive electrode plate, the thickness of the electrode plate is between 120-150 μm, and the compaction density of the positive electrode material is controlled to be 3.45 g / cm 3

[0098] The negative electrode preparation step is: mixing silicon-carbon composite material (silicon-based material + graphite mixture, wherein the silicon-based material comprises a porous carbon matrix and silicon-based particles distributed in the porous carbon matrix, which is obtained by chemical vapor deposition (CVD method), and the mass content of silicon in the silicon-based material is 50%, hereinafter referred to as gas-phase silicon), conductive carbon black, binder polyacrylic acid and carboxymethyl cellulose in deionized water in a mass ratio of 94.2:1.2:3.0:1.5 to obtain a negative electrode slurry, coating the negative electrode slurry on both sides of a copper foil, drying, calendering and vacuum drying, and welding a nickel lead wire by using an ultrasonic welding machine to obtain a negative electrode plate, the thickness of the electrode plate is between 120-150 μm, and the compaction density of the negative electrode material is controlled to be 1.65 g / cm 3 , the median particle size of the silicon-carbon composite material, the content of Si element in the silicon-carbon composite material and the gram capacity of the negative electrode material layer are shown in Table 1;

[0099] The non-aqueous electrolyte preparation step is: mixing fluoroethylene carbonate, ethylene carbonate and methyl ethyl carbonate, adding LiPF6 with a concentration of 1 mol / L after mixing, and adding an additive, the mass percentage content of fluoroethylene carbonate and the additive in the non-aqueous electrolyte is shown in Table 1.

[0100] The separator preparation step is: using a three-layer isolation film of polypropylene, polyethylene and polypropylene, and the thickness is 20 μm;

[0101] ​The battery assembly step is as follows: placing a three-layer separator with a thickness of 20 μm between the positive plate and the negative plate, then winding the sandwich structure of the positive plate, the negative plate and the separator, then flattening the winding body and placing it into an aluminum plastic shell, welding the tab, and then sealing the aluminum plastic shell to obtain the battery core to be injected with electrolyte; cutting the prepared electrolyte and injecting it into the battery core, and then sealing after 1 h of static state, and then measuring the retention capacity of the battery after storage at 45 °C for 48 h.

[0102] Then, the first charge of the conventional formation is carried out according to the following steps: 0.05C constant current charging for 3 h, 0.1C constant current charging for 2 h, 0.2C constant current charging for 2 h, standing for 1 h, aging at 45 °C for 48 h, and then further constant current charging at 0.2C to 4.2V, and constant current discharging at 0.2C to 2.75V.

[0103] Examples 2-18

[0104] Examples 2-18 are used to illustrate the preparation method of the lithium ion battery disclosed in the present application, including most of the operation steps in Example 1, and the difference is that:

[0105] The silicon-carbon composite material, the median particle size, the content of silicon element, the gram capacity of the negative electrode material layer (by adjusting the content of the silicon-based material in the silicon-carbon composite material), and the selection and content of the fluoroethylene carbonate and the additive in the non-aqueous electrolyte are shown in Table 1.

[0106] Comparative Examples 1-16

[0107] Comparative Examples 1-16 are used to compare the preparation method of the lithium ion battery disclosed in the present application, including most of the operation steps in Example 1, and the difference is that:

[0108] The silicon-carbon composite material, the median particle size, the content of silicon element, the gram capacity of the negative electrode material layer (by adjusting the content of the silicon-based material in the silicon-carbon composite material), and the selection and content of the fluoroethylene carbonate and the additive in the non-aqueous electrolyte are shown in Table 1.

[0109] Performance test

[0110] The lithium ion battery prepared above is subjected to the following performance test:

[0111] 1) High-temperature storage performance: the battery after formation is charged to 4.2V at 1C constant current and constant voltage, and then discharged to 2.75V at 1C constant current, and the initial discharge capacity is recorded, and then the battery is charged to 4.2V at 1C constant current and constant voltage, and the initial volume of the battery is tested using the drainage method, and then the battery is stored at 60 °C for 30 d, and then the retention capacity of the battery is measured after the battery is cooled to room temperature and discharged to 2.75V at 1C, and the volume of the battery after storage is tested. The calculation formula is as follows:

[0112] Battery capacity retention rate (%) = retained capacity / initial capacity x 100%;

[0113] Battery storage volume expansion (%) = (volume after storage - initial volume) / initial volume x 100%;

[0114] 2) High temperature cycle performance test: After formation, the battery was charged to 4.2V at 1C constant current and constant voltage, and then discharged to 2.75V at 1C constant current at 45°C. The retention rate of the 1000th cycle capacity was calculated after 1000 cycles of charge / discharge. The calculation formula is as follows:

[0115] 1000th cycle capacity retention rate (%) = (1000th cycle discharge capacity / first cycle discharge capacity) x 100%;

[0116] 1000th cycle impedance growth rate (%) = [(1000th cycle impedance - first cycle discharge capacity) / first cycle discharge capacity] x 100%;

[0117] (1) The test results obtained from Examples 1 to 13 and Comparative Examples 1 to 16 are filled in Table 2.

[0118] Table 2

[0119] From the test results of Examples 1-13 and Comparative Examples 1-16, in the battery system using a porous carbon-supported gas-phase silicon negative electrode, the addition of fluoroethylene carbonate as a non-aqueous organic solvent in a non-aqueous electrolyte, the use of lithium difluorophosphate and ethylene sulfate as additives, and the control of the median particle size D of the silicon-carbon composite material, the gram capacity C of the negative electrode material layer, the mass percentage content F of fluoroethylene carbonate, and the mass percentage content L of lithium difluorophosphate to satisfy the condition 0.6≤100*(D / F+10*L) / C≤2.5, and 5≤D≤16, 400≤C≤700, 3≤F≤20, and 0.2≤L≤1, the resulting lithium ion battery has a relatively high high-temperature storage capacity retention rate, a relatively low volume expansion rate, a relatively high high-temperature cycle capacity retention rate, and a relatively low impedance growth rate. It is speculated that this is because fluoroethylene carbonate and lithium difluorophosphate jointly promote the construction of the negative electrode interface film (SEI film), especially when matched with the silicon-carbon composite material. In order to generate a negative electrode interface film on the surface of the silicon-carbon composite material that is both dense and has high thermal stability, the concentrations of fluoroethylene carbonate and lithium difluorophosphate must be coordinated with the characteristics of the negative electrode material. Specifically, the median particle size (D) of the silicon-carbon composite material determines its specific surface area, which directly affects the amount of fluoroethylene carbonate and lithium difluorophosphate required to form the negative electrode interface film. At the same time, the gram capacity (C) of the negative electrode material layer is related to the amount of silicon, which controls the volume change, i.e. the expansion rate, of the negative electrode active material, thereby defining the anti-expansion strength required for the negative electrode interface film. When the median particle size D of the silicon-carbon composite material, the gram capacity C of the negative electrode material layer, the mass percentage content F of fluoroethylene carbonate, and the mass percentage content L of lithium difluorophosphate reach a state of balance, a stable and dense negative electrode interface film can be constructed on the surface of the silicon-carbon composite material. This film can effectively protect the negative electrode from damage and prevent the SEI film from breaking down during high-temperature charging and discharging, thereby significantly improving the performance of the silicon-containing lithium ion battery under high-temperature conditions and extending the overall life of the battery. This synergistic optimization not only ensures the integrity and stability of the negative electrode interface film, but also improves the reliability and safety of the battery under extreme conditions, ultimately achieving a comprehensive improvement in battery performance.

[0120] From the test results of Examples 1-13, when the median particle size D of the silicon-carbon composite material, the gram capacity C of the negative electrode material layer, the mass percentage content F of fluoroethylene carbonate, and the mass percentage content L of lithium difluorophosphate further satisfy the condition 0.9≤100*(D / F+10*L) / C≤1.85, and 7≤D≤14, 450≤C≤600, 5≤F≤15, and 0.3≤L≤0.8, the resulting lithium ion battery has higher high-temperature storage performance and high-temperature cycle performance.

[0121] From the test results of Comparative Examples 1 and 2, it can be seen that when the porous carbon loaded gas-phase silicon in the negative electrode active material is replaced by a silicon-carbon material or silicon monoxide, the volume expansion rate of the lithium ion battery at 60°C is significantly increased, indicating that the battery system provided by the present application is more suitable for the negative electrode active material of porous carbon loaded gas-phase silicon compared to other silicon-containing materials.

[0122] From the test results of Comparative Examples 3-16, it can be seen that when the values of D, C, F and L do not satisfy the limitation of 0.6≤100*(D / F+10*L) / C≤2.5, or the values of D, C, F and L are too high or too low, the high-temperature performance of the lithium ion battery is deteriorated, indicating that there is a mutual influence between the median particle size D, the gram capacity C of the negative electrode material layer, the mass percentage content F of fluoroethylene carbonate and the mass percentage content L of lithium difluorophosphate. Only when the four reach a better balance, can they significantly improve the high-temperature stability of the negative electrode interface film.

[0123] (2) The test results of Examples 1, 14-15 are filled in Table 3.

[0124] Table 3

[0125] From the test results of Examples 1, 14-15, it can be seen that in the battery system provided by the present application, vinyl sulfate is added as a trace amount of sacrificial agent to construct a layer of interface film substrate dominated by sulfur element on the surface of the positive and negative electrode materials, and then a high-elasticity and high-strength interface film rich in LiF and organic matter is further constructed to ensure that the interface film is not easily broken and detached due to expansion and side reactions. The improvement of the high-temperature stability of the negative electrode interface film is beneficial, but excessive addition of vinyl sulfate will affect the content of components derived from fluoroethylene carbonate and lithium difluorophosphate in the negative electrode interface film. Therefore, excessive addition of vinyl sulfate will actually lead to deterioration of the high-temperature stability of the negative electrode interface film.

[0126] (3) The test results of Examples 1, 16-18 are filled in Table 4.

[0127] Table 4

[0128] From the test results of Examples 1, 16-18, it can be seen that in the battery system provided by the present application, the addition of other film-forming additives such as lithium difluoro(oxalato)borate (LiODFB), 1,3-propane sultone (PS) and vinylene carbonate (VC) has a certain improvement on the high-temperature performance of the lithium ion battery, indicating that the addition of other film-forming additives will participate in film formation together with the fluoroethylene carbonate and lithium difluorophosphate in the present application, thereby improving the stability of the interface film on the surface of the positive and negative electrode material layers and further improving the cycle stability and high-temperature performance of the battery.

[0129] The above descriptions are only the preferred embodiment of the application, not intended to limit the application and any modification, equivalent replacement and improvement made within the spirit and principle of the application shall be included in the protection scope of the application.

Claims

1. A lithium-ion battery, characterized by, The lithium ion battery comprises a positive electrode, a negative electrode and a non-aqueous electrolyte, the positive electrode comprises a positive electrode material layer comprising a positive electrode active material, the negative electrode comprises a negative electrode material layer comprising a negative electrode active material, the negative electrode active material comprises a silicon-carbon composite material in which a silicon-based material is compounded with a graphite material, wherein the silicon-based material comprises a porous carbon matrix and silicon-based particles, the silicon-based particles are distributed in the pores of the porous carbon matrix, the non-aqueous electrolyte comprises a non-aqueous organic solvent, an electrolyte salt and an additive, the non-aqueous organic solvent comprises fluoroethylene carbonate, and the additive comprises lithium difluorophosphate and vinyl sulfate. The lithium ion battery satisfies the following condition: 0.6≤100*(D / F+10*L) / C≤2.5, and 5≤D≤16, 400≤C≤700, 3≤F≤20, 0.2≤L≤1. Wherein, D is the median particle size D50 of the silicon-carbon composite material, in units of μm; C is the gram capacity of the negative electrode material layer, in units of mAh / g; F is the mass percentage content of fluoroethylene carbonate in the non-aqueous electrolyte, in units of %; L is the mass percentage content of lithium difluorophosphate in the non-aqueous electrolyte, in units of %.

2. The lithium-ion battery of claim 1, wherein, The lithium ion battery satisfies the following condition: 0.9≤100*(D / F+10*L) / C≤1.

85.

3. The lithium-ion battery of claim 1, wherein, The median particle size D50 of the silicon-carbon composite material is 7-14 μm.

4. The lithium-ion battery of claim 1, wherein, The gram capacity C of the negative electrode material layer is 450-600 mAh / g.

5. The lithium-ion battery of claim 1, wherein, The mass percentage content F of fluoroethylene carbonate in the non-aqueous electrolyte is 5%-15%.

6. The lithium-ion battery of claim 1, wherein, The mass percentage content L of lithium difluorophosphate in the non-aqueous electrolyte is 0.3%-0.8%.

7. The lithium-ion battery of claim 1, wherein, In the negative electrode active material, the mass ratio of the silicon-based material to the graphite material is (0.03-0.45):

1.

8. The lithium-ion battery of claim 1, wherein, The mass percentage content of silicon element is 2%-12% based on the total mass of the negative electrode material layer.

9. The lithium-ion battery of claim 1, wherein, The mass percentage content of vinyl sulfate is 0.05%-1% based on the total mass of the non-aqueous electrolyte.

10. The lithium-ion battery of claim 9, wherein, The mass percentage content of vinyl sulfate is 0.1%-0.5%.

11. The lithium-ion battery of claim 1, wherein, The additive further comprises at least one of a sulfonic acid lactone compound, a cyclic carbonate compound, a phosphate compound, a borate compound and a nitrile compound.

12. The lithium-ion battery of claim 11, wherein, The sulfonic acid lactone compound comprises at least one of 1,3-propane sulfonic acid lactone, 1,4-butane sulfonic acid lactone and 1,3-propylene sulfonic acid lactone.

13. The lithium-ion battery of claim 11, wherein, The cyclic carbonate compound includes at least one of vinylene carbonate, vinyl ethylene carbonate, methylene vinyl carbonate, or a compound represented by Structural Formula 1: In the structural formula 1, R 21 , R 22 , R 23 , R 24 , R 25 , R 26 are each independently selected from one of a hydrogen atom, a halogen atom, a C1-C5 group.

14. The lithium-ion battery of claim 11, wherein, The phosphate compound includes at least one of tris(trimethylsilyl)phosphate, tris(triethylsilyl)phosphate, or a compound of structural formula 2: In the structural formula 2, R 31 , R 32 , R 33 are each independently selected from a C1-C5 saturated hydrocarbon group, a C1-C5 unsaturated hydrocarbon group, a C1-C5 halogenated hydrocarbon group, -Si(C m H 2m+1 )3, m is a natural number of 1 to 3, and R 31 , R 32 , R 33 at least one of which is an unsaturated hydrocarbon group.

15. The lithium-ion battery of claim 11, wherein, The borate compound comprises at least one of tris(trimethylsilyl) borate and tris(triethylsilyl) borate.

16. The lithium-ion battery of claim 11, wherein, The nitrile compound comprises at least one of butanedinitrile, pentanedinitrile, hexanetritrile, hexanedinitrile, heptanedinitrile, octanedinitrile, nonanedinitrile and decanedinitrile.

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