A lithium-ion battery

Abstract

To overcome the technical problem of reduced battery safety and high / low temperature performance due to the poor thermal stability of lithium hexafluorophosphate (LiPF6) in existing lithium-ion batteries using non-aqueous electrolytes, this application provides a lithium-ion battery comprising a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte. The negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector. The negative electrode current collector includes a polymer material substrate layer and a metal layer formed on at least one surface of the polymer material substrate layer. The non-aqueous electrolyte includes a lithium salt, specifically lithium hexafluorophosphate and lithium difluorosulfonylimide. The lithium-ion battery satisfies the following conditions: 0.3≤S≤0.7, 0.3≤F≤0.7, 1.3≤C≤1.7, and 0.2≤d≤10. The lithium-ion battery provided by this application can form a uniform and complete electrolyte interface film at the negative electrode interface, buffering and mitigating the negative electrode expansion problem under high current, reducing lithium plating, and improving battery safety and high / low temperature performance.

Description

Technical Field

[0001] This invention belongs to the field of energy storage technology, and specifically relates to a lithium-ion battery. Background Technology

[0002] Lithium-ion batteries are currently the most popular and widely used rechargeable batteries due to their long lifespan and high energy density. With the further promotion of new energy vehicles, their driving range basically meets daily travel needs, but charging stations are not yet fully widespread. This has, to some extent, fueled strong consumer demand for fast charging of new energy vehicles. Under this market trend, lithium-ion batteries face the challenge of balancing safety and fast charging performance, prompting researchers to develop new approaches to reduce the risk of spontaneous combustion in new energy vehicles during fast charging. Currently, lithium hexafluorophosphate (LiPF6) is commonly used as the main lithium salt in lithium-ion batteries. However, during battery charging and discharging, LiPF6 has poor thermal stability and is prone to autocatalytic decomposition to form lithium fluoride (LiF) and phosphorus pentafluoride (PF5). LiF and PF5 further react with small amounts of water in the battery to form substances such as POF3, HF, and various acids, which further corrode the solid electrolyte film formed at the negative electrode interface, inducing electrode interface instability and reducing the battery's high and low temperature performance. Under harsh conditions, this can even lead to safety issues such as thermal runaway. Furthermore, given the demand for fast charging, although LiPF6 has high conductivity in electrolytes, Li... + Solvation, limiting Li + The movement speed, while the anion PF6 - Almost no solvation occurs, and most of the conductivity is due to PF6. - Contribution. Therefore, Li + The migration number is of great significance for improving the fast charging capability of lithium-ion batteries. Summary of the Invention

[0003] In view of the technical problem that lithium hexafluorophosphate, which is the main lithium salt in the electrolyte of existing lithium-ion batteries, has poor thermal stability, which reduces battery safety and high and low temperature performance, this application provides a lithium-ion battery.

[0004] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0005] This invention provides a lithium-ion battery, comprising a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte. The negative electrode comprises a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector. The negative electrode current collector comprises a polymer material substrate layer and a metal layer formed on at least one surface of the polymer material substrate layer. The non-aqueous electrolyte comprises a lithium salt, wherein the lithium salt comprises lithium hexafluorophosphate and lithium difluorosulfonylimide.

[0006] The lithium-ion battery meets the following conditions:

[0007] And 0.3≤S≤0.7, 0.3≤F≤0.7, 1.3≤C≤1.7, 0.2≤d≤10;

[0008] Where S is the molar concentration of lithium difluorosulfonylimide in the non-aqueous electrolyte, in mol / L;

[0009] F represents the molar concentration of lithium hexafluorophosphate in the non-aqueous electrolyte, in mol / L.

[0010] C is the compaction density of the negative electrode active material layer, in g / cm³. 3 ;

[0011] d represents the thickness of the polymer material substrate layer, in μm.

[0012] Preferably, the lithium-ion battery meets the following conditions:

[0013]

[0014] Preferably, the molar concentration S of lithium difluorosulfonyl imide in the non-aqueous electrolyte is 0.4 mol / L to 0.6 mol / L;

[0015] The molar concentration F of lithium hexafluorophosphate in the non-aqueous electrolyte is 0.5 mol / L to 0.7 mol / L.

[0016] Preferably, the negative electrode active material layer includes a negative electrode active material, which includes at least one of natural graphite, artificial graphite, graphene, mesophase micro carbon spheres, hard carbon, soft carbon, silicon, silicon-carbon composite or silicon oxide.

[0017] The compaction density C of the negative electrode active material layer is 1.4 g / cm³. 3 ~1.65g / cm 3 .

[0018] Preferably, the thickness d of the polymer material substrate layer is 2μm to 5μm;

[0019] Preferably, the polymer material substrate layer is selected from at least one of polycaprolactam, polyhexamethylene adipamide, poly(p-phenylene terephthalamide), poly(m-phenylene isophthalamide), polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, sodium polystyrene sulfonate, polyimide, polystyrene, polyethylene, polypropylene, polypropylene, polyvinyl alcohol, polyvinyl chloride, and polyvinylidene fluoride.

[0020] Preferably, the positive electrode includes a positive electrode active material layer, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes LiNi. x Coy Mn z L (1-x-y-z) At least one of O2, wherein L is selected from at least one of Al, Sr, Mg, Ti, Ca, Zr, Zn, Si, Cu, V, and Fe, 0≤x≤1, 0≤y≤1, 0≤z≤1, and 0≤x+y+z≤1; the compaction density of the positive electrode active material layer is 3.0 g / cm³. 3 -4.25g / cm 3 .

[0021] Preferably, the lithium salt further includes LiPO2F2, LiSbF6, LiAsF6, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiN(SO2C2F5)2, LiCl, LiBr, LiI, LiClO4, and LiB. 10 Cl 10 At least one of the following: LiAlCl4, lithium chloroborane, lithium difluorodioxane phosphate, lithium lower aliphatic carboxylic acids having four or fewer carbon atoms, lithium tetraphenylborate, and lithium imino.

[0022] The molar concentration of the lithium salt is 0.8 mol / L to 1.4 mol / L.

[0023] Preferably, the non-aqueous electrolyte further includes a non-aqueous organic solvent, which includes at least one of cyclic carbonates, linear carbonates, carboxylic acid esters, sulfones, ethers, and nitriles.

[0024] Preferably, the non-aqueous electrolyte further includes additives, which include at least one of cyclic sulfate compounds, sulfonyl lactone compounds, cyclic carbonate compounds, phosphate compounds, borate compounds, and nitrile compounds;

[0025] Based on the total mass of the non-aqueous electrolyte as 100%, the mass content of the additive is 0.01% to 30%.

[0026] Preferably, the cyclic sulfate compound is selected from at least one of vinyl sulfate, propylene sulfate, and methyl vinyl sulfate;

[0027] The sulfonyl lactone compound is selected from at least one of 1,3-propanesulfonyl lactone, 1,4-butanesulfonyl lactone, 1,3-propenesulfonyl lactone, and methylene disulfonate.

[0028] The cyclic carbonate compounds are selected from vinylene carbonate, ethylene ethylene carbonate, methylene carbonate, fluoroethylene carbonate, trifluoromethyl ethylene carbonate, difluoroethylene carbonate, or other compounds with the following structure.

[0029] At least one of the compounds shown in Formula 2:

[0030]

[0031] In structural formula 2, R 21 R 22 R 23 R 24 R 25 R 26 Each is independently selected from one of the following: hydrogen atom, halogen atom, or C1-C5 group;

[0032] The phosphate ester compound is selected from at least one of tris(trimethylsilane) phosphate, tris(trimethylsilane) phosphite, or the compound shown in structural formula 3:

[0033]

[0034] In structural formula 3, R 31 R 32 R 33 Each is independently selected from C1-C5 saturated hydrocarbon groups, unsaturated hydrocarbon groups, halohydrocarbon groups, and -Si(C m H 2m+1 )3, m is a natural number from 1 to 3, and R 31 R 32 R 33 At least one of them is an unsaturated hydrocarbon group;

[0035] The borate ester compound is selected from at least one of tri(triethylsilane)borate ester and tri(trimethylsilane)borate ester;

[0036] The nitrile compound is selected from at least one of butadionitrile, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrionitrile, adiponitrile, heptanonitrile, octadionitrile, nonadionitrile, and sebaconitrile.

[0037] Beneficial effects:

[0038] The lithium-ion battery provided in this application adds lithium hexafluorophosphate with a molar concentration of F mol / L and lithium bisfluorosulfonylimide with a molar concentration of S mol / L to the electrolyte, and the compaction density of the negative electrode active material layer is C g / cm³. 3 The thickness of the polymer substrate layer in the negative electrode current collector is d μm, and F, S, C, and d meet the preset conditions. By utilizing the higher conductivity and lithium-ion transference number of lithium bis(fluorosulfonyl)imide to reduce the battery's low-temperature impedance, and in conjunction with a high-tensile-strength negative electrode current collector, the high expansion caused by the negative electrode is well buffered on the negative electrode current collector containing a polymer material substrate layer, ensuring the adhesion between the negative electrode current collector and the active material. This enables high-flux Li-ion transfer under fast-charging conditions.+ The absence of lithium plating during negative electrode insertion helps improve battery cycle stability. Furthermore, the inherent high thermal stability of lithium bisfluorosulfonylimide, combined with a polymer substrate layer possessing good thermal insulation properties, ensures low thermal runaway performance in the battery system, thus enhancing battery safety. Detailed Implementation

[0039] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0040] This invention provides a lithium-ion battery, comprising a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte. The negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector. The negative electrode current collector includes a polymer material substrate layer and a metal layer formed on at least one surface of the polymer material substrate layer. The non-aqueous electrolyte includes a lithium salt, which includes lithium hexafluorophosphate and lithium difluorosulfonylimide.

[0041] The lithium-ion battery meets the following conditions:

[0042] And 0.3≤S≤0.7, 0.3≤F≤0.7, 1.3≤C≤1.7, 0.2≤d≤10;

[0043] Where S is the molar concentration of lithium difluorosulfonylimide in the non-aqueous electrolyte, in mol / L;

[0044] F represents the molar concentration of lithium hexafluorophosphate in the non-aqueous electrolyte, in mol / L.

[0045] C is the compaction density of the negative electrode active material layer, in g / cm³. 3 ;

[0046] d represents the thickness of the polymer material substrate layer, in μm.

[0047] In existing lithium-ion batteries, electrolytes primarily use lithium hexafluorophosphate (LiPF6) as the main lithium salt. LiPF6 suffers from poor thermal stability and readily decomposes during charging and discharging, producing acid that corrodes the negative electrode interface film, inducing interfacial instability and reducing battery safety and high / low temperature performance. Through extensive research, the inventors discovered that adding a lithium salt containing both lithium hexafluorophosphate and lithium difluorosulfonylimide to the electrolyte, along with a negative electrode comprising an active material layer and a current collector (formed as a composite of a metal layer and a polymer substrate layer), provides high tensile strength. This effectively buffers the high expansion of the negative electrode on the current collector, ensuring adhesion between the current collector and the active material. Consequently, under fast-charging conditions, the high flux of Li in the LiFSI electrolyte is significantly improved. + The absence of lithium plating during anode insertion helps improve battery cycle stability. Furthermore, the high thermal stability of lithium bisfluorosulfonylimide (LiFSI) combined with the thermal insulation effect of the anode current collector containing a polymer substrate layer in interrupting local current during thermal runaway ensures low thermal runaway performance of the battery system. Additionally, LiFSI itself further participates in the anode interfacial film formation process, forming a highly ionic and more stable interfacial film.

[0048] Specifically, lithium hexafluorophosphate with a molar concentration of F and lithium bisfluorosulfonyl imide with a molar concentration of S are added to the non-aqueous electrolyte of the lithium-ion battery. The compaction density of the negative electrode active material layer is C, and the thickness of the polymer material substrate layer in the negative electrode current collector is d. F, S, C, and d meet the preset conditions. By utilizing the higher conductivity and lithium-ion transference number of lithium bis(fluorosulfonyl)imide to reduce the battery's low-temperature impedance, and in conjunction with a high-tensile-strength negative electrode current collector, the high expansion caused by the negative electrode is well buffered on the negative electrode current collector containing a polymer material substrate layer, ensuring the adhesion between the negative electrode current collector and the active material. This enables high-flux Li-ion transfer under fast-charging conditions. + The absence of lithium plating during anode insertion contributes to improved battery cycle stability. Furthermore, the inherent high thermal stability of lithium bisfluorosulfonylimide, combined with a polymer substrate layer exhibiting good thermal insulation, ensures low thermal runaway performance and enhances battery safety. LiFSI also further participates in the anode interfacial film formation process, resulting in a highly ionic and more stable interfacial film.

[0049] like If the molar concentration ratio of lithium bis(fluorosulfonyl)imide to lithium hexafluorophosphate is less than 0.3, the polymer substrate layer in the negative electrode current collector is too thin, or the compaction density of the negative electrode is too high, the negative electrode will face high flux of Li. + Embedding causes significant volume expansion, and the polymer substrate layer in the negative electrode current collector cannot provide sufficient buffering. This reduces the adhesion between the negative electrode current collector and the negative electrode active material layer, leading to poor battery cycle performance, lithium plating, and the risk of thermal runaway. If the molar ratio of lithium difluorosulfonylimide to lithium hexafluorophosphate is greater than 6, the thickness of the polymer material substrate layer in the negative electrode current collector is too thick, or the compaction density of the negative electrode is too low, it will cause lithium difluorosulfonylimide to corrode the positive electrode current collector. On the other hand, the excessive thickness of the polymer material substrate layer will cause excessive contact resistance, increase the battery resistance, and reduce the low-temperature performance of the battery.

[0050] In some preferred embodiments, the lithium-ion battery satisfies the following conditions: Within this preferred range, it is more conducive for lithium-ion batteries to form an electrolyte interface film with better toughness, lower impedance, and more uniform and completeness at the negative electrode interface, and to buffer and mitigate the problem of negative electrode expansion under high current, reduce lithium plating, and improve battery safety and high and low temperature performance.

[0051] The molar concentration S of lithium bis(fluorosulfonyl)imide in the non-aqueous electrolyte is 0.3 mol / L to 0.7 mol / L. Lithium bis(fluorosulfonyl)imide possesses high ionic conductivity, lithium-ion transference number, and thermal stability, enabling the formation of a more resilient, uniform, and complete solid electrolyte interphase (SEI) film with lower impedance at the negative electrode interface. If the molar concentration of lithium bis(fluorosulfonyl)imide in the electrolyte is higher than 0.7 mol / L, the high content of lithium bis(fluorosulfonyl)imide can easily corrode the positive electrode current collector, degrading battery performance; if the molar concentration of lithium bis(fluorosulfonyl)imide is lower than 0.3 mol / L, it affects the formation of the solid electrolyte interphase film at the negative electrode interface, reducing battery safety and high / low temperature performance. Specifically, the molar concentration of lithium bis(fluorosulfonyl)imide in the electrolyte can be 0.3 mol / L, 0.35 mol / L, 0.4 mol / L, 0.5 mol / L, 0.55 mol / L, 0.6 mol / L, 0.65 mol / L, or 0.7 mol / L, etc.

[0052] In some preferred embodiments, the molar concentration S of lithium bisfluorosulfonylimide in the non-aqueous electrolyte is 0.4 mol / L to 0.6 mol / L. Within this preferred range, lithium bisfluorosulfonylimide can form a solid electrolyte film with better toughness, more uniformity and integrity, and lower impedance at the negative electrode interface, which is more conducive to improving battery safety and high and low temperature performance.

[0053] The molar concentration F of lithium hexafluorophosphate in the non-aqueous electrolyte is 0.5 mol / L to 0.7 mol / L. The addition of lithium hexafluorophosphate to the electrolyte helps form an SEI film at the negative electrode interface, improving the electrolyte's conductivity. If the molar concentration of lithium hexafluorophosphate in the electrolyte is higher than 0.7 mol / L, the high lithium hexafluorophosphate content increases side reactions, reduces the stability of the solid electrolyte film at the negative electrode interface, and affects battery safety and high / low temperature performance. If the molar concentration of lithium hexafluorophosphate in the electrolyte is lower than 0.3 mol / L, the electrolyte's conductivity decreases, affecting the formation of the solid electrolyte film at the negative electrode interface and reducing battery performance. Specifically, the molar concentration of lithium hexafluorophosphate can be 0.3 mol / L, 0.35 mol / L, 0.4 mol / L, 0.5 mol / L, 0.55 mol / L, 0.6 mol / L, 0.65 mol / L, or 0.7 mol / L, etc.

[0054] In some preferred embodiments, the molar concentration F of lithium hexafluorophosphate in the non-aqueous electrolyte is 0.3 mol / L to 0.7 mol / L.

[0055] In some preferred embodiments, the negative electrode active material layer includes a negative electrode active material, which includes at least one of natural graphite, artificial graphite, graphene, mesophase microcarbon spheres, hard carbon, soft carbon, silicon, silicon-carbon composites, or silicon oxide.

[0056] In some embodiments, the compaction density C of the negative electrode active material layer is 1.3 g / cm³. 3 ~1.7g / cm 3 If the compaction density of the negative electrode active material layer is higher than 1.7 g / cm³ 3 This affects electrolyte wetting and reduces battery performance; if the compaction density of the negative electrode active material layer is less than 1.3 g / cm³, it will negatively impact the battery's performance. 3 The bonding strength between the negative electrode active material layer and the negative electrode current collector is reduced. During the battery charge-discharge cycle, the negative electrode active material layer is easily peeled off from the negative electrode current collector, affecting the battery cycle performance. In addition, the compaction density is low, and the battery energy density is also low, which cannot meet the requirements for high energy density lithium-ion batteries.

[0057] In some preferred embodiments, the compaction density C of the negative electrode active material layer is 1.4 g / cm³. 3 ~1.65g / cm 3 .

[0058] In some embodiments, the thickness d of the polymer substrate layer in the negative electrode current collector is 0.2 μm to 10 μm. The polymer substrate layer in the negative electrode current collector has high tensile strength, providing sufficient buffering to offset the high flux of Li. +To address the issue of volume expansion caused by the negative electrode in a short period, it is crucial to ensure the adhesion between the negative electrode current collector and the negative electrode active material, improve battery cycle performance, and mitigate the risk of lithium plating and thermal runaway. A polymer substrate layer, synergistically formed with lithium bis(fluorosulfonyl)imide at the negative electrode interface, creates a more resilient, complete, and lower impedance solid electrolyte film, contributing to improved battery safety and high / low temperature performance. If the thickness of the polymer substrate layer in the negative electrode current collector exceeds 10 μm, the overall thickness of the current collector increases, which is detrimental to improving battery energy density. If the thickness of the polymer substrate layer is less than 0.2 μm, it cannot effectively buffer the volume expansion of the negative electrode, reducing the adhesion between the current collector and the negative electrode active material. This affects the stability of the negative electrode interface film during long-term cycling, and a thin polymer substrate layer cannot fully utilize its heat-insulating effect of interrupting local current during thermal runaway, thus reducing battery safety. The specific thickness d of the polymer material substrate layer in the negative electrode current collector can be 0.2μm, 1.0μm, 2.0μm, 3.0μm, 4.0μm, 5.0μm, 6.0μm, 7.0μm, 8.0μm, 9.0μm or 10μm, etc.

[0059] In some preferred embodiments, the thickness d of the polymer material substrate layer in the negative electrode current collector is 2μm to 5μm.

[0060] In some preferred embodiments, the polymer material substrate layer is selected from at least one of polycaprolactam (commonly known as nylon 6), polyhexamethylene adipamide (commonly known as nylon 66), poly(p-phenylene terephthalamide) (PPTA), poly(m-phenylene isophthalamide) (PMIA), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), sodium polystyrene sulfonate (PSS), polyimide (PI), polystyrene (PS), polyethylene (PE), polypropylene (PP), polypropylene (PPE), polyvinyl alcohol (PVA), polyvinyl chloride (PVC), and polyvinylidene fluoride (PVDF).

[0061] In some preferred embodiments, the negative electrode current collector comprises a first metal layer, a polymer substrate layer, and a second metal layer sequentially stacked. The first metal layer and the second metal layer may be selected from at least one of Ni, tin, copper, and stainless steel; in a more preferred embodiment, the first metal layer and the second metal layer are selected from copper foil. When both the first metal layer and the second metal layer are copper foil, the negative electrode current collector is prepared by preparing a substrate layer from a polymer material, and then depositing copper layers onto both sides of the polymer substrate layer using an advanced process, forming a copper-polymer substrate-copper composite material.

[0062] In some embodiments, the positive electrode includes a positive electrode active material layer, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes LiNi. x Co y Mn z L (1-x-y-z) At least one of O2, wherein L is selected from at least one of Al, Sr, Mg, Ti, Ca, Zr, Zn, Si, Cu, V, and Fe, 0≤x≤1, 0≤y≤1, 0≤z≤1, and 0≤x+y+z≤1; the compaction density of the positive electrode active material layer is 3.0 g / cm³. 3 -4.25g / cm 3 .

[0063] Within the aforementioned compaction density range, non-aqueous electrolytes can effectively wet the positive and negative electrodes, reducing battery impedance and polarization resistance, resulting in better performance for lithium-ion batteries. If the electrode compaction density is too high, the non-aqueous electrolyte will have difficulty wetting, increasing ion transport impedance and polarization, thus reducing the battery's initial capacity, energy density, and cycle performance. Conversely, if the electrode compaction density is too low, the adhesion between the active material layer and the substrate will be reduced, making it easier for the coating to detach from the substrate surface during battery cycling, affecting cycle performance, reducing battery life, and also decreasing the battery's energy density.

[0064] In some embodiments, the non-aqueous electrolyte comprises a non-aqueous organic solvent, which includes at least one of cyclic carbonates, linear carbonates, carboxylic acid esters, sulfones, ethers, and nitriles.

[0065] In some embodiments, the ether solvent includes cyclic ethers or chain ethers, preferably chain ethers with 3 to 10 carbon atoms and cyclic ethers with 3 to 6 carbon atoms. The cyclic ether may be, but is not limited to, at least one of 1,3-dioxolane (DOL), 1,4-dioxolane (DX), crown ethers, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH3-THF), and 2-trifluoromethyltetrahydrofuran (2-CF3-THF). The chain ether may be, but is not limited to, at least one of dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether, 1,3-dioxolane, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether. Because chain ethers have high solvation ability with lithium ions and can improve ion dissociation, dimethoxymethane, diethoxymethane, and ethoxymethoxymethane, which have low viscosity and can impart high ionic conductivity, are particularly preferred. One ether compound can be used alone, or two or more can be used in any combination and ratio. There are no particular limitations on the amount of ether compound added; it is arbitrary as long as it does not significantly impair the lithium-ion battery effect of the present invention. Typically, the volume ratio is 1% or more, preferably 2% or more, and more preferably 3% or more, when the non-aqueous solvent volume ratio is 100%. Furthermore, the volume ratio is typically 30% or less, preferably 25% or less, and more preferably 20% or less. When two or more ether compounds are used in combination, the total amount of ether compounds should meet the above-mentioned range. When the amount of ether compound added is within the above-mentioned preferred range, it is easy to ensure the improved ionic conductivity effect resulting from the increased lithium-ion dissociation degree and reduced viscosity of the chain ether. In addition, when the negative electrode active material is a carbon material, the phenomenon of co-intercalation between chain ethers and lithium ions can be suppressed, thus enabling the input-output characteristics and charge-discharge rate characteristics to reach an appropriate range.

[0066] In some embodiments, the nitrile solvent may be, but is not limited to, at least one of acetonitrile, glutaronitrile, and malononitrile.

[0067] In some embodiments, the carbonate solvent includes cyclic carbonates or chain carbonates. Cyclic carbonates may specifically include, but are not limited to, at least one of vinylene carbonate, ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (GBL), butylene carbonate (BC), and butenyl carbonate. Chain carbonates may specifically include, but are not limited to, at least one of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and dipropyl carbonate (DPC). The content of cyclic carbonates is not particularly limited and is arbitrary within a range that does not significantly impair the performance of the lithium-ion battery of this invention. However, when using a single cyclic carbonate, its lower limit relative to the total volume of the non-aqueous electrolyte solvent is typically 3% or more by volume, preferably 5% or more. By setting this range, a decrease in conductivity due to a decrease in the dielectric constant of the non-aqueous electrolyte can be avoided, making it easier to achieve good high-current discharge characteristics, stability relative to the negative electrode, and cycle characteristics of the non-aqueous electrolyte battery. Furthermore, the upper limit is typically 90% or less by volume, preferably 85% or less, and more preferably 80% or less. Setting this range improves the oxidation / reduction resistance of the non-aqueous electrolyte, thereby contributing to improved stability during high-temperature storage. The content of the chain carbonate is not particularly limited, but relative to the total amount of solvent in the non-aqueous electrolyte, it is typically 15% or more by volume, preferably 20% or more, and more preferably 25% or more. Additionally, it is typically 90% or less by volume, preferably 85% or less, and more preferably 80% or less. By keeping the chain carbonate content within the above range, it is easier to achieve an appropriate viscosity for the non-aqueous electrolyte, suppressing the decrease in ionic conductivity, and thus contributing to achieving a good range of output characteristics for the non-aqueous electrolyte battery. When using two or more chain carbonates in combination, the total amount of chain carbonate should satisfy the above range.

[0068] In some embodiments, fluorine-containing chain carbonates (hereinafter referred to as "fluorinated chain carbonates") are also preferably used. There is no particular limitation on the number of fluorine atoms in a fluorinated chain carbonate as long as it is 1 or more, but it is generally 6 or less, preferably 4 or less. When a fluorinated chain carbonate has multiple fluorine atoms, these fluorine atoms can be bonded to the same carbon atom or to different carbon atoms. Examples of fluorinated chain carbonates include dimethyl fluorinated carbonate derivatives, methyl ethyl fluorinated carbonate derivatives, and diethyl fluorinated carbonate derivatives.

[0069] Carboxylic acid ester solvents include cyclic carboxylic acid esters and / or chain carbonates. Examples of cyclic carboxylic acid esters include at least one of γ-butyrolactone, γ-valerolactone, and δ-valerolactone. Examples of chain carbonates include at least one of methyl acetate (MA), ethyl acetate (EA), propyl acetate (EP), butyl acetate, propyl propionate (PP), butyl propionate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, methyl trimethylacetate, and ethyl trimethylacetate.

[0070] In some embodiments, the sulfone solvent includes cyclic sulfones and chain sulfones. Preferably, in the case of cyclic sulfones, it is typically a compound with 3 to 6 carbon atoms, more preferably 3 to 5 carbon atoms; in the case of chain sulfones, it is typically a compound with 2 to 6 carbon atoms, more preferably 2 to 5 carbon atoms. There are no particular limitations on the amount of sulfone solvent added, and it is arbitrary within a range that does not significantly impair the performance of the lithium-ion battery of the present invention. Relative to the total amount of solvent in the non-aqueous electrolyte, it is typically 0.3% or more by volume, preferably 0.5% or more by volume, more preferably 1% or more by volume. Furthermore, it is typically 40% or less by volume, preferably 35% or less by volume, more preferably 30% or less by volume. When using two or more sulfone solvents in combination, the total amount of sulfone solvent should satisfy the above range. When the amount of sulfone solvent added is within the above range, a non-aqueous electrolyte with excellent high-temperature storage stability is tended to be obtained.

[0071] In a preferred embodiment, the solvent is a mixture of cyclic carbonates and chain carbonates.

[0072] In some embodiments, the non-aqueous electrolyte further includes additives, which include at least one of cyclic sulfate compounds, sulfonyl lactone compounds, cyclic carbonate compounds, phosphate compounds, borate compounds, and nitrile compounds;

[0073] Based on the total mass of the non-aqueous electrolyte as 100%, the amount of the auxiliary additive is 0.01% to 30%.

[0074] In some embodiments, the cyclic sulfate compounds include at least one of vinyl sulfate, propylene sulfate, and methyl vinyl sulfate;

[0075] The sulfonyl lactone compound is selected from at least one of 1,3-propanesulfonyl lactone, 1,4-butanesulfonyl lactone, 1,3-propenesulfonyl lactone, and methylene disulfonate.

[0076] The cyclic carbonate compound is selected from at least one of vinylene carbonate, ethylene ethylene carbonate, fluoroethylene carbonate, or the compound shown in structural formula 2:

[0077]

[0078] In structural formula 2, R 21 R 22 R 23 R 24 R 25 R 26 Each is independently selected from one of the following: hydrogen atom, halogen atom, or C1-C5 group;

[0079] The phosphate ester compound is selected from at least one of tris(trimethylsilane) phosphate, tris(trimethylsilane) phosphite, or the compound shown in structural formula 3:

[0080]

[0081] In structural formula 3, R 31 R 32 R 33 Each is independently selected from C1-C5 saturated hydrocarbon groups, unsaturated hydrocarbon groups, halohydrocarbon groups, and -Si(C m H 2m+1 )3, m is a natural number from 1 to 3, and R 31 R 32 R 33 At least one of them is an unsaturated hydrocarbon group;

[0082] The borate ester compound is selected from at least one of tri(triethylsilane)borate ester and tri(trimethylsilane)borate ester;

[0083] In a preferred embodiment, the unsaturated phosphate compound is selected from at least one of the following: triargyl phosphate, diallyl methyl phosphate, diallyl ethyl phosphate, diallyl propyl phosphate, diallyl trifluoromethyl phosphate, diallyl-2,2,2-trifluoroethyl phosphate, diallyl-3,3,3-trifluoropropyl phosphate, diallyl 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.

[0084] The nitrile compound is selected from at least one of butadionitrile, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrionitrile, adiponitrile, heptanonitrile, octadionitrile, nonadionitrile, and sebaconitrile.

[0085] In other embodiments, the additive may also include other additives that can improve battery performance: for example, additives that improve battery safety performance, such as flame retardant additives like fluorophosphates and cyclophosphonitriles, or overcharge prevention additives like tert-amylbenzene and tert-butylbenzene.

[0086] It should be noted that, unless otherwise specified, the amount of any one of the optional substances in the additives added to the non-aqueous electrolyte is generally less than 10%, preferably 0.05-5%.

[0087] In some embodiments, when the additive is selected from fluoroethylene carbonate, the amount of fluoroethylene carbonate added is 0.05% to 30% based on 100% of the total mass of the non-aqueous electrolyte.

[0088] In some embodiments, the lithium salt further includes LiPO2F2, LiSbF6, LiAsF6, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiN(SO2C2F5)2, LiCl, LiBr, LiI, LiClO4, and LiB. 10 Cl 10 At least one of the following: LiAlCl4, lithium chloroborane, lithium difluorodioxane phosphate, lithium lower aliphatic carboxylic acids having four or fewer carbon atoms, lithium tetraphenylborate, and lithium imino.

[0089] In the non-aqueous electrolyte, the concentration of the lithium salt is 0.8–1.4 mol / L.

[0090] In some embodiments, the positive electrode material layer further includes a positive electrode conductive agent and a positive electrode binder. The positive electrode conductive agent includes at least one of conductive carbon black, conductive carbon spheres, conductive graphite, SP, conductive carbon fiber, carbon nanotubes, graphene, or reduced graphene oxide; preferably carbon nanotubes, SP, or conductive graphite.

[0091] The positive electrode binder includes at least one of the following: polyvinylidene fluoride (PVDF), copolymers of PVDF, polytetrafluoroethylene (PTFE), copolymers of PVDF-hexafluoropropylene, copolymers of tetrafluoroethylene-hexafluoropropylene, copolymers of tetrafluoroethylene-perfluoroalkyl vinyl ethers, copolymers of ethylene-tetrafluoroethylene, copolymers of PVDF-tetrafluoroethylene, copolymers of PVDF-trifluoroethylene, copolymers of PVDF-trichloroethylene, copolymers of PVDF-fluorinated vinylides, copolymers of PVDF-hexafluoropropylene-tetrafluoroethylene, thermoplastic polyimide, polyethylene, and polypropylene; acrylic resins; sodium carboxymethyl cellulose; polyvinyl butyral; ethylene-vinyl acetate copolymer; polyvinyl alcohol; and styrene-butadiene rubber.

[0092] In some embodiments, the positive electrode material layer is obtained by blending a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder.

[0093] In some embodiments, the positive electrode further includes a positive electrode current collector, and the positive electrode material layer is formed on the surface of the positive electrode current collector.

[0094] The positive electrode current collector is selected from a metallic material that can conduct electrons. Preferably, the positive electrode current collector includes at least one of Al, Ni, tin, and stainless steel. In a more preferred embodiment, the positive electrode current collector is selected from aluminum foil.

[0095] 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.

[0096] The selectable ranges of the negative electrode adhesive and negative electrode conductive agent are the same as those of the positive electrode adhesive and positive electrode conductive agent, and will not be repeated here.

[0097] In some embodiments, the diaphragm includes a substrate layer and a surface coating disposed on at least one side of the substrate layer. The substrate layer includes, but is 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.

[0098] The present invention will be further illustrated by the following examples.

[0099] Example 1

[0100] This embodiment is used to illustrate a lithium-ion battery disclosed in this invention.

[0101] 1) Preparation of the negative electrode:

[0102] Using a PET (polyethylene terephthalate) polymer film as the substrate layer, a 20–80 nm thick copper layer was fabricated on both sides using magnetron sputtering and vacuum evaporation. Then, an electroplating process was used to thicken the copper layer to 1 μm, creating a sandwich-type negative electrode current collector consisting of a copper-polymer substrate layer and a copper core. The thickness d of the polymer substrate layer in the negative electrode current collector is shown in Table 1. The method for measuring the thickness d of the polymer substrate layer was as follows: after cutting the negative electrode sheet from its central region, a 0.5 cm wide cross-section was prepared on the SEM cross-sectional sample stage. The thickness d of the polymer substrate layer in the negative electrode current collector was measured and calculated at least three times, and then the average value was calculated.

[0103] Artificial graphite, conductive carbon black, styrene-butadiene rubber (SBR) binder, and carboxymethyl cellulose (CMC) are mixed in a mass ratio of 94:1:2.5:2.5 and dispersed in deionized water to obtain a negative electrode slurry. The negative electrode slurry is coated on the surface of the negative electrode current collector, and after drying, calendering, and vacuum drying, nickel leads are welded on using an ultrasonic welding machine to obtain a negative electrode sheet. The compaction density of the negative electrode material is controlled by the areal density and rolling thickness of the negative electrode material. The compaction density C of the negative electrode is shown in Table 1.

[0104] 2) Preparation of positive electrode sheet

[0105] The ternary cathode active material LiNi was mixed at a mass ratio of 93:4:3. 0.8 Co 0.1 Mn 0.1 O2, conductive carbon black (Super-P), and the binder polyvinylidene fluoride (PVDF) are dispersed in N-methyl-2-pyrrolidone (NMP) to obtain a positive electrode slurry. This slurry is then uniformly coated onto both sides of an aluminum foil. After drying, rolling, and vacuum drying, aluminum leads are welded on using an ultrasonic welder to obtain the positive electrode sheet. The thickness of the electrode sheet is between 120-150 μm. The compaction density of the positive electrode material is controlled by its areal density and rolling thickness, with the compaction density being approximately 3.0 g / cm³. 3 -4.25g / cm 3 between.

[0106] 3) Preparation of non-aqueous electrolyte

[0107] Ethylene carbonate (EC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC) are mixed in a mass ratio of EC:DEC:EMC = 1:1:1. After mixing, lithium hexafluorophosphate (LiPF6) with a molar concentration of F and lithium bisfluorosulfonylimide (LiFSI) with a molar concentration of S are added, along with additives. These additives may be at least one of cyclic sulfate compounds, sulfonyl lactone compounds, cyclic carbonate compounds, phosphate compounds, borate ester compounds, and nitrile compounds. The amount of additive used, as a percentage of the total mass of the non-aqueous electrolyte, ranges from 0.01% to 30%. Specific values ​​for F and S are shown in Table 1.

[0108] 4) Preparation of lithium-ion battery cells

[0109] A thick separator is placed between the positive and negative electrode plates. Then, the sandwich structure consisting of the positive electrode plate, negative electrode plate, and separator is wound up. The wound body is flattened and placed into a square aluminum metal shell. The leads of the positive and negative electrodes are welded to the corresponding positions on the cover plate. The cover plate and the metal shell are welded together using a laser welding machine. The cells are then vacuum baked at 75°C for more than 48 hours to obtain the cells to be injected with electrolyte.

[0110] 5) Electrolyte injection and formation of battery cells

[0111] In a glove box with the dew point controlled below -40°C, the non-aqueous electrolyte prepared above is injected into the battery cell, ensuring that the electrolyte fills all the gaps in the cell. After vacuum sealing, the cell is left to stand for 72 hours. Then, the first charge is performed according to the following steps: constant current charging at 0.05C for 180 minutes, constant current charging at 0.2C to 3.95V, secondary vacuum sealing, and then further constant current charging at 0.2C to the cutoff voltage of 4.25V. After resting at room temperature for 24 hours, the cell is discharged at a constant current of 0.2C to 3.0V.

[0112] Examples 2-21 and Comparative Examples 1-12

[0113] Examples 2-21 and Comparative Examples 1-12 are used to illustrate the lithium-ion battery disclosed in this invention, including most of the operating steps in Example 1. The differences are: the thickness d of the polymer material substrate layer in the negative electrode current collector, the compaction density C of the negative electrode active material layer, the molar concentration F of lithium hexafluorophosphate, and the molar concentration S of lithium difluorosulfonylimide are different; and the types and mass percentages of additives added to the electrolyte are different. The specific values ​​are shown in Table 1.

[0114] Table 1. Battery parameter design for Examples 1-21 and Comparative Examples 1-12

[0115]

[0116]

[0117] Performance testing

[0118] The lithium-ion batteries prepared in Examples 1-21 and Comparative Examples 1-12 were subjected to the following performance tests:

[0119] 1) Low-temperature DCIR performance: At 25℃, the conventionally formed battery was charged to 4.25V using a 0.5C constant current and constant voltage method, and then discharged to 3.0V using a 0.5C constant current method, undergoing two pre-cycles. Then, it was charged to 50% of its capacity using a 0.5C constant current and constant voltage method, and then left to rest at 0℃ for 3 hours. The battery was then charged and discharged at 0.1C, 0.2C, and 0.5C for 10 seconds each, with a 40-second rest period between each charge. The DCIR performance at 0℃ was calculated.

[0120] 2) High-temperature cycling performance: At 25℃, the conventionally formed battery was charged to 4.25V using a 0.5C constant current and constant voltage method, and then discharged to 3.0V using a 0.5C constant current method, undergoing two pre-cycles. Then, it was placed at 45℃ for 3 hours, charged to 4.25V using a 1C constant current and constant voltage method, and then discharged using a 1C constant current method. The first discharge capacity C0 was recorded. Subsequently, the battery was cycled at 1C / 1C within the 3V-4.25V voltage range. The discharge capacity after 400 cycles was recorded as C1. The calculation formula is as follows: Cycle capacity retention R = C1 / C0 × 100%;

[0121] 3) Lithium plating test:

[0122] At -10℃, the lithium-ion battery was charged and discharged three times at 0.2C, then fully charged to 4.25V at 0.2C with a cutoff current of 0.05C. The battery was then disassembled in a glove box to observe the lithium plating on the negative electrode.

[0123] 4) Needle prick test:

[0124] At 25℃, the capacity-balanced batteries were charged to 4.25V using a 1C constant current and constant voltage method, with a cutoff current of 0.05C. The lithium-ion batteries were then placed in an explosion-proof box, and steel needles with a diameter of 3mm were used for piercing at a speed of 25mm / s for 1 hour.

[0125] The results obtained from tests of Examples 1-18 and Comparative Examples 1-12 are entered into Table 2. The results obtained from tests of Examples 19-21 are entered into Table 3.

[0126] Table 2. Electrical performance test results of Examples 1-18 and Comparative Examples 1-12

[0127]

[0128] As shown in Tables 1 and 2, a comparison between Examples 1-18 and Comparative Examples 1-12 reveals that the molar concentration S of lithium bis(fluorosulfonyl)imide in the electrolyte, the molar concentration F of lithium hexafluorophosphate, the compaction density C of the negative electrode active material layer, and the thickness d of the polymer material substrate layer in the negative electrode current collector meet the preset conditions. The resulting battery exhibited high high-temperature cycle capacity retention, low low-temperature impedance, no lithium plating on the negative electrode, and high safety during nail penetration testing. This indicates that the negative electrode current collector, containing a high-tensile-strength polymer substrate layer and a conductive layer, effectively buffers high-flux Li-245. +The high expansion resulting from embedding the negative electrode ensures the adhesion between the negative electrode current collector and the active material. This, combined with the higher conductivity and lithium-ion transference number of lithium bis(fluorosulfonyl)imide, reduces the battery's low-temperature impedance, preventing lithium deposition at the negative electrode and improving the battery's cycle stability. The high thermal stability of lithium bis(fluorosulfonyl)imide, combined with the negative electrode current collector of the polymer substrate layer with good thermal insulation, ensures low thermal runaway performance of the battery system and improves the battery's needle penetration pass rate and safety performance. LiFSI itself further participates in the interface film formation process of the negative electrode, forming an interface film with high ionic conductivity and more stable toughness.

[0129] Comparing the test results of Examples 1-18, it can be seen that the molar concentration S of lithium bis(fluorosulfonyl)imide in the electrolyte, the molar concentration F of lithium hexafluorophosphate, the compaction density C of the negative electrode active material layer, and the thickness d of the polymer material substrate layer in the negative electrode current collector further meet the requirements. When 0.5≤F≤0.7, 0.4≤S≤0.6, 2≤d≤5, and 1.4≤c≤1.65, the lithium-ion battery exhibits low low-temperature impedance, high cycle capacity retention, and no lithium deposition. This indicates that the values ​​of S, F, d, and c in the electrolyte are within the preferred range of this application and satisfy the following relationship: The synergistic effect is better, and the battery has better high and low temperature performance and safety performance.

[0130] The test results of Comparative Examples 6-12 show that even if the molar concentrations S of lithium bis(fluorosulfonyl)imide in the electrolyte, F of lithium hexafluorophosphate, C of the compaction density of the negative electrode active material layer, and d of the polymer substrate layer in the negative electrode current collector meet the following conditions... While the F, S, d, or C values ​​are within their specified ranges, lithium-ion batteries still do not exhibit good high-temperature cycling and 0°C DCIR performance. Furthermore, lithium plating occurs at the negative electrode, and the battery's safety during the needle penetration process is insufficient. This indicates a strong correlation between the F, S, d, and C values ​​and their impact on improving the high and low temperature performance and safety of lithium-ion batteries. Although the batteries obtained in Comparative Examples 5 and 9 exhibit good low-temperature performance and safety, slight lithium plating occurs at the positive electrode, and the battery's cycle stability decreases. Similarly, as shown in Comparative Examples 1-5, when the F, S, d, or C values ​​meet their specified ranges, but... Failure to meet the above preset conditions will lead to deterioration of the battery's high and low temperature performance, especially a high proportion of smoke and fire during the battery nail penetration test, indicating poor battery safety performance. It can correlate various influencing factors and comprehensively analyze their impact on lithium-ion battery performance to achieve a better synergistic effect.

[0131] Table 3 Battery performance data for Examples 16 and 19-21

[0132]

[0133]

[0134] The test results from Examples 16 and 19-21 show that adding additives VC (ethylene carbonate), FEC (fluoroethylene carbonate), or PS (1-3-propanesulfonate lactone) to the non-aqueous electrolyte can further improve the high-temperature cycle capacity retention rate of the battery. This is presumably because lithium difluorosulfonylimide and the aforementioned additives jointly participate in the formation of the interface film on the electrode surface, resulting in an interface film with excellent thermal stability. This effectively reduces the reaction of the electrolyte on the electrode surface under high-temperature conditions, thereby improving the electrochemical performance of the battery. This indicates that adding additives to the electrolyte, synergistically with lithium difluorosulfonylimide, forms a stable interface film at the electrode interface, improving the high-temperature performance of the battery.

[0135] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A lithium-ion battery, characterized in that, The device includes a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte. The negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector. The negative electrode current collector includes a polymer material substrate layer and a metal layer formed on at least one surface of the polymer material substrate layer. The non-aqueous electrolyte includes a lithium salt, and the lithium salt includes lithium hexafluorophosphate and lithium difluorosulfonylimide. The lithium-ion battery meets the following conditions: 0.3 6, and 0.3≤S≤0.7, 0.3≤F≤0.7, 1.3≤C≤1.7, 0.2≤d≤10; Where S is the molar concentration of lithium difluorosulfonylimide in the non-aqueous electrolyte, in mol / L; F represents the molar concentration of lithium hexafluorophosphate in the non-aqueous electrolyte, in mol / L. C is the compaction density of the negative electrode active material layer, in g / cm³. 3 ; d represents the thickness of the polymer material substrate layer, in μm.

2. The lithium-ion battery according to claim 1, characterized in that, The lithium-ion battery meets the following conditions: 0.8 4.5。 3. The lithium-ion battery according to claim 1, characterized in that, The molar concentration S of lithium difluorosulfonylimide in the non-aqueous electrolyte is 0.4 mol / L to 0.6 mol / L; The molar concentration F of lithium hexafluorophosphate in the non-aqueous electrolyte is 0.5 mol / L to 0.7 mol / L.

4. The lithium-ion battery according to claim 1, characterized in that, The negative electrode active material layer includes a negative electrode active material, which includes at least one of natural graphite, artificial graphite, graphene, mesophase micro carbon spheres, hard carbon, soft carbon, silicon, silicon-carbon composite or silicon oxide. The compaction density C of the negative electrode active material layer is 1.4 g / cm³. 3 ~1.65g / cm 3 .

5. The lithium-ion battery according to claim 1, characterized in that, The thickness d of the polymer material substrate layer is 2μm~5μm.

6. The lithium-ion battery according to claim 5, characterized in that, The polymer material substrate layer is selected from at least one of polycaprolactam, polyhexamethylene adipamide, poly(p-phenylene terephthalamide), poly(m-phenylene isophthalamide), polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, sodium polystyrene sulfonate, polyimide, polystyrene, polyethylene, polypropylene, polypropylene, polyvinyl alcohol, polyvinyl chloride, and polyvinylidene fluoride.

7. The lithium-ion battery according to claim 1, characterized in that, The positive electrode includes a positive electrode active material layer, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes LiNi. x Co y Mn z L (1-x-y-z) At least one of O2, wherein L is selected from at least one of Al, Sr, Mg, Ti, Ca, Zr, Zn, Si, Cu, V, Fe, 0≤x≤1, 0≤y≤1, 0≤z≤1, 0≤x+y+z≤1; The compaction density of the positive electrode active material layer is 3.0 g / cm³. 3 -4.25g / cm 3 .

8. The lithium-ion battery according to claim 1, characterized in that, The lithium salts also include LiPO2F2, LiSbF6, LiAsF6, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiN(SO2C2F5)2, LiCl, LiBr, LiI, LiClO4, and LiB. 10 Cl 10 At least one of the following: LiAlCl4, lithium chloroborane, lithium difluorodioxane phosphate, lithium lower aliphatic carboxylic acids having four or fewer carbon atoms, lithium tetraphenylborate, and lithium imino. The molar concentration of the lithium salt is 0.8 mol / L to 1.4 mol / L.

9. The lithium-ion battery according to claim 1, characterized in that, The non-aqueous electrolyte also includes a non-aqueous organic solvent, which includes at least one of cyclic carbonates, linear carbonates, carboxylic acid esters, sulfones, ethers, and nitriles.

10. The lithium-ion battery according to claim 1, characterized in that, The non-aqueous electrolyte also includes additives, which include at least one of cyclic sulfate compounds, sulfonyl lactone compounds, cyclic carbonate compounds, phosphate compounds, borate compounds, and nitrile compounds. Based on the total mass of the non-aqueous electrolyte as 100%, the mass content of the additive is 0.01% to 30%.

11. The lithium-ion battery according to claim 10, characterized in that, The cyclic sulfate compound is selected from at least one of vinyl sulfate, propylene sulfate, and methyl vinyl sulfate; The sulfonyl lactone compound is selected from at least one of 1,3-propanesulfonyl lactone, 1,4-butanesulfonyl lactone, 1,3-propenesulfonyl lactone, and methylene disulfonate. The cyclic carbonate compound is selected from at least one of vinylene carbonate, ethylene ethylene carbonate, methylene carbonate, fluoroethylene carbonate, trifluoromethyl ethylene carbonate, difluoroethylene carbonate, or the compound shown in structural formula 2. Structural Formula 2 In structural formula 2, R 21 R 22 R 23 R 24 R 25 R 26 Each is independently selected from one of the following: hydrogen atom, halogen atom, or C1-C5 group; The phosphate ester compound is selected from at least one of tris(trimethylsilane) phosphate, tris(trimethylsilane) phosphite, or the compound shown in structural formula 3: Structural Formula 3 In structural formula 3, R 31 R 32 R 33 Each is independently selected from C1-C5 saturated hydrocarbon groups, unsaturated hydrocarbon groups, halohydrocarbon groups, and -Si(C m H 2m+1 )3, m is a natural number from 1 to 3, and R 31 R 32 R 33 At least one of them is an unsaturated hydrocarbon group; The borate ester compound is selected from at least one of tris(triethylsilane)borate ester and tris(trimethylsilane)borate ester; The nitrile compound is selected from at least one of butadionitrile, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrionitrile, adiponitrile, heptanonitrile, octadionitrile, nonadionitrile, and sebaconitrile.

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