A lithium-ion battery

Abstract

To overcome the problem that LiFSI in existing lithium-ion batteries corrodes aluminum foil, affecting the cycle life of the lithium-ion battery, this invention provides a lithium-ion battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte. The positive electrode includes a positive current collector and a positive active material layer disposed on the positive current collector. The positive current collector is aluminum or an aluminum alloy. The non-aqueous electrolyte includes a non-aqueous organic solvent, a lithium salt, and additives. The lithium salt includes LiPF6 and LiFSI, and the additives include boron-containing oxides. The lithium-ion battery satisfies the following conditions: 0.1≤b / a≤5 and 0.05≤c / (b*d)≤10, 0.1≤a≤1.5, 0.1≤b≤1, 0.015≤c≤3, 0.4≤d≤1.8. The lithium-ion battery provided by this invention achieves both low impedance and excellent high-temperature cycle performance.

Description

Technical Field

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

[0002] Lithium-ion batteries have long been widely used in portable electronic devices due to their advantages such as high energy density, high operating voltage, no memory effect, and long lifespan. In recent years, with the rapid development of their application fields, people have put forward higher requirements for the energy density, rate performance, operating temperature, cycle life, and safety of lithium-ion batteries.

[0003] Metallic aluminum, with its low density, high conductivity, low cost, and ease of processing, is often used as the positive electrode current collector in lithium-ion batteries. Although its oxidation potential is only 1.39V (vs. Li / Li+), it can be used in batteries with operating voltages above 4V (vs. Li / Li+). This is mainly due to the naturally occurring dense oxide film on the surface of the aluminum foil. This film provides electronic conductivity without affecting the aluminum foil's use as a current collector in batteries, and provides ionic insulation, preventing contact between anions and solvents and the aluminum substrate, protecting the aluminum foil from corrosion and making it kinetically stable. This oxide film not only protects the aluminum current collector from electrolyte corrosion but also facilitates the adhesion and full contact of electrode composite materials (active materials, conductive agents, and binders) on its surface.

[0004] Electrolytes are a crucial component of lithium-ion batteries, and lithium salts, as the providers of lithium ions in the electrolyte, are a key factor determining its performance. Currently, the main lithium salt used in commercial electrolytes is LiPF6 (lithium hexafluorophosphate). However, LiPF6 has poor thermal and chemical stability and is highly sensitive to water, readily decomposing to produce acidic substances such as HF. This leads to the dissolution of transition metals on the surface of the positive electrode material, which then migrate to the surface of the negative electrode, damaging the solid-state interphase (SEI) film and reducing the capacity and lifespan of the lithium-ion battery. Therefore, there is a need for superior lithium salts with electrochemical performance comparable to LiPF6 while avoiding its drawbacks, such as sulfonylimide lithium salts (LiFSI, LiTFSI, etc.). In these lithium salts, the nitrogen atom is bonded to two electron-withdrawing sulfonyl groups, allowing for sufficient delocalization of the charge on the nitrogen atom. Consequently, their electrolytes exhibit ionic conductivity comparable to LiPF6-based electrolytes. Furthermore, these salts have thermal decomposition temperatures above 200°C and are less sensitive to water than LiPF6, making them promising new lithium salts to replace LiPF6. However, these lithium salts have a certain corrosive effect on aluminum foil and its surface oxide film at about 3.7V vs Li / Li+. Once the aluminum foil of the positive electrode current collector is corroded, it will cause the aluminum foil to lose electrons before the positive electrode active material during the charging stage, which will hinder the normal insertion and extraction of Li+. Al+ dissolved in the electrolyte will also catalyze the decomposition of the electrolyte. The corrosion products and electrolyte decomposition products will also increase the internal resistance of the battery, which will ultimately significantly affect the cycle life of the battery, limiting its application and greatly limiting the service life of lithium-ion batteries. Summary of the Invention

[0005] To address the problem that LiFSI in existing lithium-ion batteries corrodes aluminum foil and affects the cycle life of lithium-ion batteries, this invention provides a lithium-ion battery.

[0006] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0007] This invention provides a lithium-ion battery, comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte. The positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector. The positive electrode current collector is aluminum or an aluminum alloy. The non-aqueous electrolyte includes a non-aqueous organic solvent, a lithium salt, and an additive. The lithium salt includes LiPF6 and LiFSI, and the additive includes a boron-containing oxide compound.

[0008] The lithium-ion battery meets the following conditions:

[0009] 0.1≤b / a≤5 and 0.05≤c / (b*d)≤10, 0.1≤a≤1.5, 0.1≤b≤1, 0.015≤c≤3, 0.4≤d≤1.8;

[0010] Where a is the molar content of LiPF6 in the non-aqueous electrolyte, in mol / L;

[0011] b represents the molar content of LiFSI in the non-aqueous electrolyte, in mol / L;

[0012] c represents the mass of boron oxide compound per unit area on one side of the positive electrode current collector, in mg / cm². 2 .

[0013] d represents the surface roughness of the positive electrode current collector, in μm.

[0014] Optionally, the lithium-ion battery satisfies the following conditions:

[0015] 0.16≤b / a≤4, and 0.2≤c / (b*d)≤3.

[0016] Optionally, the molar content a of LiPF6 in the non-aqueous electrolyte is 0.2 to 1.2 mol / L.

[0017] Optionally, the molar content b of LiFSI in the non-aqueous electrolyte is 0.2–0.8 mol / L.

[0018] Optionally, the boron-containing oxide includes at least one of lithium difluorooxalate borate, lithium bis(oxalate borate), and tris(trimethylsilane)borate.

[0019] Optionally, the mass c of the boron oxide compound per unit area on one side of the positive electrode current collector is 0.5–1.8 mg / cm². 2 .

[0020] Optionally, the surface roughness d of the positive electrode current collector is 0.6-1.0 μm.

[0021] Optionally, the lithium salt may also include LiPO2F2, LiBF4, LiSbF6, LiAsF6, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiC(SO2CF3)3, LiClO4, LiAlCl4, LiCF3SO3, and Li2B. 10 Cl 10 At least one of LiSO3F, LiTOP, LiDODFP, LiOTF and lower aliphatic carboxylic acid lithium salts.

[0022] Optionally, the additive may further include at least one of cyclic sulfate compounds, sulfonyl lactone compounds, cyclic carbonate compounds, and phosphate compounds.

[0023] Optionally, the cyclic sulfate compound is selected from vinyl sulfate, propylene sulfate, methyl vinyl sulfate, etc. At least one of them;

[0024] The sulfonyl lactone compound is selected from at least one of 1,3-propanesulfonyl lactone, 1,4-butanesulfonyl lactone, and 1,3-propenesulfonyl lactone.

[0025] 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.

[0026] At least one of the compounds shown in Formula 1:

[0027]

[0028] In structural formula 1, 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;

[0029] The phosphate ester compound is selected from at least one of tris(trimethylsilane) phosphate, tris(trimethylsilane) phosphite, or the compound shown in structural formula 2:

[0030]

[0031] In structural formula 2, R 31 R 32 R 33 Each is independently selected from C1-C5 saturated hydrocarbon groups, C1-C5 unsaturated hydrocarbon groups, C1-C5 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.

[0032] The lithium-ion battery provided by this invention uses aluminum or its alloy as the positive electrode current collector, and adds LiPF6 and LiFSI as lithium salts and boron-containing oxides as additives in the non-aqueous electrolyte. Through extensive research, the inventors discovered that replacing part of the LiPF6 with LiFSI improves the thermal stability and ionic conductivity of the non-aqueous electrolyte. However, excessively high LiFSI levels increase the corrosiveness of the positive electrode current collector. Therefore, by controlling the addition of boron-containing oxides and the surface roughness of the positive electrode current collector, the low BO bond film-forming potential of the boron-containing oxides allows them to decompose into a protective film on the aluminum foil at these high potentials before LiFSI or impurities. Furthermore, the surface roughness of the positive electrode current collector affects the formation of this passivation film. Ultimately, when… When the molar content of LiPF6 (a) in the non-aqueous electrolyte, the molar content of LiFSI (b) in the non-aqueous electrolyte, the mass of boron oxide compound per unit area on one side of the positive electrode current collector (c), and the surface roughness (d) of the positive electrode current collector satisfy the conditions 0.1≤b / a≤5 and 0.05≤c / (b*d)≤10, 0.1≤a≤1.5, 0.1≤b≤1, 0.015≤c≤3, and 0.4≤d≤1.8, they exhibit good synergy. This ensures that the lithium-ion battery has low impedance and significantly inhibits the corrosion of the positive electrode current collector by LiFSI. After high-temperature cycling, the ratio of pitting corrosion marks on the positive electrode current collector to the total area of ​​the positive electrode current collector is less than 3%, enabling the battery to achieve both low impedance and excellent high-temperature cycling performance. Detailed Implementation

[0033] 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.

[0034] This invention discloses a lithium-ion battery, comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte. The positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector. The positive electrode current collector is aluminum or an aluminum alloy. The non-aqueous electrolyte includes a non-aqueous organic solvent, a lithium salt, and additives. The lithium salt includes LiPF6 (lithium hexafluorophosphate) and LiFSI (lithium bisfluorosulfonylimide). The additives include boron-containing oxide compounds.

[0035] The lithium-ion battery meets the following conditions:

[0036] 0.1≤b / a≤5 and 0.05≤c / (b*d)≤10, 0.1≤a≤1.5, 0.1≤b≤1, 0.015≤c≤3, 0.4≤d≤1.8;

[0037] Where a is the molar content of LiPF6 in the non-aqueous electrolyte, in mol / L;

[0038] b represents the molar content of LiFSI in the non-aqueous electrolyte, in mol / L;

[0039] c represents the mass of boron oxide compound per unit area on one side of the positive electrode current collector, in mg / cm². 2 .

[0040] d represents the surface roughness of the positive electrode current collector, in μm.

[0041] In the aforementioned battery system, when LiFSI replaces LiPF6 in a non-aqueous electrolyte, it corrodes the positive electrode current collector of the lithium-ion battery. Especially after high-temperature cycling, visible pitting corrosion can be observed on the surface of the aluminum foil of the positive electrode current collector. This is due to the unavoidable LiSO3F impurity in the LiFSI salt. The presence of LiSO3F causes the aluminum current collector to produce corrosion products Al(SO3F)3 during polarization. LiSO3F tends to accumulate in the depressions on the Al surface. The difference between the impurities and the aluminum foil material, as well as the unevenness of the aluminum foil surface, leads to uneven potential distribution on the aluminum foil surface. Corrosion is more likely and preferentially occurs in areas with higher potential. Consequently, the passivation film on the aluminum foil surface is corroded first in the depressions, and the corrosion products dissolve in the electrolyte, further exposing the aluminum foil body and intensifying corrosion, ultimately forming pitting corrosion marks. The rougher the aluminum foil surface, the more reactive sites there are, and the easier it is for the Al foil to corrode. However, an overly smooth Al foil is not conducive to the adhesion of active materials to its surface, significantly increasing the battery's internal resistance. While higher LiFSI content improves battery thermal stability and ionic conductivity, it also exacerbates corrosion. To mitigate this corrosion of the aluminum foil, this application incorporates boron-containing oxides into the non-aqueous electrolyte to form a more stable passivation film on the current collector surface. The BO bonds in the boron-containing oxides have low film-forming potentials, allowing them to decompose before LiFSI or impurities at these high potentials to form a protective film on the aluminum foil. Furthermore, because BF bonds are stronger than HF bonds, they reduce HF acid production caused by LiPF6 decomposition, thus minimizing the damage to the passivation film on the positive electrode current collector surface. However, the boron-containing oxide additive significantly increases battery impedance. Excessive impedance not only exacerbates internal side reactions during charging and discharging but also increases battery polarization, ultimately significantly degrading the battery's high-temperature cycle performance.

[0042] Through extensive research, the inventors discovered that when the molar content of LiPF6 (a) in the non-aqueous electrolyte, the molar content of LiFSI (b) in the non-aqueous electrolyte, the mass of boron oxide compounds per unit area on one side of the positive electrode current collector (c), and the surface roughness (d) of the positive electrode current collector satisfy the conditions 0.1≤b / a≤5 and 0.05≤c / (b*d)≤10, 0.1≤a≤1.5, 0.1≤b≤1, 0.015≤c≤3, and 0.4≤d≤1.8, they exhibit a good synergistic effect. This ensures that the lithium-ion battery has low impedance and significantly inhibits the corrosion of the positive electrode current collector by LiFSI. After high-temperature cycling, the ratio of pitting corrosion marks on the positive electrode current collector to the total area of ​​the positive electrode current collector is less than 3%, enabling the battery to achieve both low impedance and excellent high-temperature cycling performance.

[0043] In a preferred embodiment, the lithium-ion battery satisfies the following conditions:

[0044] 0.16≤b / a≤4, and 0.2≤c / (b*d)≤3.

[0045] When the molar content of LiPF6 (a) in the non-aqueous electrolyte, the molar content of LiFSI in the non-aqueous electrolyte (b), the mass of boron oxide compounds per unit area on one side of the positive electrode current collector (c), and the surface roughness (d) of the positive electrode current collector further meet the above conditions, the advantages of LiFSI can be fully utilized while its disadvantage of corroding aluminum foil can be suppressed. At the same time, the battery has low impedance and excellent high-temperature cycle performance. Ultimately, the battery achieves both low impedance and excellent high-temperature cycle performance, improving the battery's lifespan, practicality, and safety.

[0046] In some embodiments, the molar content 'a' of LiPF6 in the non-aqueous electrolyte can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.55 mol / L, 0.6 mol / L, 0.65 mol / L, 0.7 mol / L, 0.75 mol / L, 0.8 mol / L, 0.85 mol / L, 0.9 mol / L, 0.95 mol / L, 1 mol / L, 1.1 mol / L, 1.15 mol / L, 1.2 mol / L, 1.25 mol / L, 1.3 mol / L, 1.35 mol / L, 1.4 mol / L, 1.45 mol / L, or 1.5 mol / L.

[0047] In a preferred embodiment, the molar content a of LiPF6 in the non-aqueous electrolyte is 0.2 to 1.2 mol / L.

[0048] In some embodiments, the molar content b of LiFSI in the non-aqueous electrolyte can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.55 mol / L, 0.6 mol / L, 0.65 mol / L, 0.7 mol / L, 0.75 mol / L, 0.8 mol / L, 0.85 mol / L, 0.9 mol / L, 0.95 mol / L, or 1 mol / L.

[0049] In a preferred embodiment, the molar content b of LiFSI in the non-aqueous electrolyte is 0.2 to 0.8 mol / L.

[0050] LiPF6 and LiFSI together serve as electrolyte salts in the non-aqueous electrolyte. When the content of LiPF6 is too low and the content of LiFSI is insufficient, the overall electrolyte salt content in the non-aqueous electrolyte will be low, affecting the ionic conductivity of the non-aqueous electrolyte. When the content of LiPF6 is too high and the content of LiFSI is too low, the high-temperature stability of the non-aqueous electrolyte is insufficient and it is sensitive to moisture, easily decomposing to produce acidic substances such as HF. This leads to the dissolution of transition metals on the surface of the positive electrode active material and the current collector, catalyzing the decomposition of the electrolyte and aggravating the occurrence of side reactions, thus consuming active lithium and damaging SE on the surface of the negative electrode. The I film reduces the capacity and lifespan of lithium-ion batteries, affecting their high-temperature cycle performance and storage performance. When the content of LiFSI is too high and the content of LiPF6 is too low, it will corrode the positive electrode current collector. The dissolved Al ions will lose electrons before the positive electrode active material, resulting in the passivation of the positive electrode active material. The corrosion products will also adhere to the positive electrode interface, increasing the battery's internal resistance, and ultimately significantly deteriorating the battery's cycle performance. When the contents of both LiPF6 and LiFSI are too high, it will lead to an excessively high overall electrolyte salt content in the non-aqueous electrolyte, increasing the viscosity of the non-aqueous electrolyte, which is also detrimental to improving the ionic conductivity of the non-aqueous electrolyte.

[0051] In some embodiments, the boron-containing oxide includes at least one of lithium difluorooxalate borate (LiDFOB), lithium bis(oxalate borate) (LiBOB), and tris(trimethylsilane)borate (TMSB).

[0052] The boron ions produced by the decomposition of boron-containing oxides not only readily combine with F ions to form BF bonds, thereby removing HF acid and reducing the damage of HF acid to the passivation layer on the aluminum foil surface, but also the BO bonds can be oxidized and decomposed at the active sites on the aluminum foil surface before LiFSI, complexing with Al ions to form a network passivation film. This passivation film is more stable under high voltage and high temperature than the Al2O3 passivation film naturally formed on the aluminum foil surface, ultimately improving the high-temperature cycle performance of the battery and the aluminum foil corrosion problem.

[0053] In some embodiments, the mass c of the boron oxide compound per unit area on one side of the positive electrode current collector can be 0.015 mg / cm². 2 0.05 mg / cm 2 0.1 mg / cm 2 0.2 mg / cm 2 0.3 mg / cm 2 0.4 mg / cm 2 0.5 mg / cm 2 0.55 mg / cm 2 0.6 mg / cm 2 0.65 mg / cm 2 0.7 mg / cm 2 0.75 mg / cm 2 0.8 mg / cm 2 0.85 mg / cm 2 0.9 mg / cm 2 0.95 mg / cm 2 1mg / cm 2 1.1 mg / cm 2 1.15 mg / cm 2 1.2 mg / cm 2 1.25 mg / cm 2 1.3 mg / cm 2 1.35 mg / cm 2 1.4 mg / cm 2 1.45 mg / cm 2 1.5 mg / cm 2 1.55 mg / cm 2 1.6 mg / cm 2 1.65 mg / cm 2 1.7 mg / cm 2 1.75 mg / cm 2 1.8 mg / cm 2 1.9 mg / cm 2 2.1 mg / cm 2 2.2 mg / cm 2 2.4 mg / cm 2 2.7 mg / cm 2 2.9 mg / cm 2 Or 3mg / cm 2 .

[0054] In a preferred embodiment, the mass c of the boron oxide compound per unit area on one side of the positive electrode current collector is 0.5–1.8 mg / cm². 2 .

[0055] Specifically, the term "mass of boron oxides per unit area of ​​the positive electrode current collector (c)" refers to the value obtained by using the total mass of boron oxides in the non-aqueous electrolyte as the numerator and the total single-sided area of ​​the positive electrode current collector as the denominator.

[0056] If the non-aqueous electrolyte contains too much boron oxide, it will increase the electrolyte viscosity and form an excessively thick interfacial film at the positive and negative electrodes, affecting the conduction rate of lithium ions in the liquid phase and interfacial film, increasing battery impedance and polarization. Excessive polarization will lead to incomplete charging and discharging of the battery, thus reducing the initial capacity of the battery. If the non-aqueous electrolyte contains too little boron oxide, it will be difficult to provide good protection for the positive electrode current collector, affecting the passivation effect on the positive electrode current collector and having limited effect on improving the battery's cycle life.

[0057] In some embodiments, the surface roughness d of the positive electrode current collector can be 0.4 μm, 0.5 μm, 0.55 μm, 0.6 μm, 0.65 μm, 0.7 μm, 0.75 μm, 0.8 μm, 0.85 μm, 0.9 μm, 0.95 μm, 1 μm, 1.1 μm, 1.15 μm, 1.2 μm, 1.25 μm, 1.3 μm, 1.35 μm, 1.4 μm, 1.45 μm, 1.5 μm, 1.55 μm, 1.6 μm, 1.65 μm, 1.7 μm, 1.75 μm, or 1.8 μm.

[0058] In a preferred embodiment, the surface roughness d of the positive current collector is 0.6-1.0 μm.

[0059] The greater the surface roughness of the positive electrode current collector, the more reactive sites there are (active sites refer to lattice defect sites in metal crystals; for example, metal atoms located at edges are most likely to detach from the lattice because their lattice binding energy is weaker, and they have a larger contact area with the solvent, making them more easily adsorbed by the solvent), and the more easily the Al foil is corroded. Furthermore, under high temperature and high voltage conditions, the chemical reactivity of the electrolyte and the electrochemical reactivity at the electrode interface both increase, further exacerbating the corrosion of the Al foil. Conversely, if the surface roughness of the positive electrode current collector is too low, the current collector and the positive electrode active material layer cannot adhere tightly together. This not only affects the battery manufacturing process but also leads to delamination of the positive electrode current collector and positive electrode active material layer, increasing battery impedance and thus affecting the battery's electrochemical performance.

[0060] In some embodiments, the lithium salt further includes LiPO2F2, LiBF4, LiSbF6, LiAsF6, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiC(SO2CF3)3, LiClO4, LiAlCl4, LiCF3SO3, and Li2B. 10 Cl10 At least one of LiSO3F, LiTOP, LiDODFP, LiOTF and lower aliphatic carboxylic acid lithium salts.

[0061] In some embodiments, the concentration of the lithium salt in the non-aqueous electrolyte is 0.1 mol / L to 8 mol / L. In a preferred embodiment, the concentration of the lithium salt in the non-aqueous electrolyte is 0.5 mol / L to 2.5 mol / L. Specifically, the concentration of the lithium salt in the non-aqueous electrolyte can be 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, or 2.5 mol / L.

[0062] In some embodiments, the non-aqueous organic solvent has a mass content of 65% to 90% based on the total mass of the non-aqueous electrolyte being 100%.

[0063] Specifically, based on the total mass of the non-aqueous electrolyte as 100%, the mass content of the non-aqueous organic solvent can be 65%, 68%, 71%, 74%, 76%, 78%, 79%, 80%, 81.5%, 82%, 84%, 85%, 86%, 87%, 89%, or 90%.

[0064] In some embodiments, the non-aqueous organic solvent includes at least one of ether solvents, nitrile solvents, carbonate solvents, and carboxylic acid ester solvents.

[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 ethers may specifically include, but are not limited to, at least one of 1,3-dioxolane (DOL), 1,4-dioxane (DX), crown ethers, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH3-THF), and 2-trifluoromethyltetrahydrofuran (2-CF3-THF). The chain ethers may specifically include, but are not limited to, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl 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. Ether compounds can be used alone or in any combination and ratio of two or more. There are no particular restrictions on the amount of ether compounds added; it is arbitrary as long as it does not significantly impair the performance of the high-pressure lithium-ion battery of this 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 using two or more ether compounds in combination, the total amount of ether compounds should meet the above-mentioned range. When the amount of ether compounds added is within the above-mentioned preferred range, it is easy to ensure the improved ionic conductivity resulting from the increased lithium-ion dissociation degree and reduced viscosity of the chain ethers. Additionally, when the negative electrode active material is a carbon-based material, the phenomenon of co-intercalation between the 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 ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (GBL), and butylene carbonate (BC); 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 the present invention. However, when using only one type, its lower limit relative to the total volume of the non-aqueous electrolyte solvent is typically 3% or more, 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, preferably 85% or less, and more preferably 80% or less. By setting this range, the oxidation / reduction resistance of the non-aqueous electrolyte can be improved, thereby contributing to enhanced 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. Furthermore, 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 favorable range of output characteristics for the non-aqueous electrolyte battery. When using two or more chain carbonates in combination, it is sufficient to ensure that the total amount of chain carbonate meets 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), and butyl propionate.

[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 non-aqueous organic solvent is a mixture of cyclic carbonates and chain carbonates.

[0072] In some embodiments, the additive further includes at least one selected from cyclic sulfate compounds, sulfonyl lactone compounds, cyclic carbonate compounds, phosphate compounds, and nitrile compounds;

[0073] Preferably, the content of the additive is 0.01% to 30% based on the total mass of the non-aqueous electrolyte (100%).

[0074] In some embodiments, the cyclic sulfate compound is selected from vinyl sulfate, propylene sulfate, methyl vinyl sulfate, etc. At least one of them;

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

[0076] 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.

[0077] At least one of the compounds shown in Formula 1:

[0078]

[0079] In structural formula 1, R 21 R 22 R 23 R 24 R 25 R 26Each is independently selected from one of the following: hydrogen atom, halogen atom, or C1-C5 group;

[0080] The phosphate ester compound is selected from at least one of tris(trimethylsilane) phosphate, tris(trimethylsilane) phosphite, or the compound shown in structural formula 2:

[0081]

[0082] In structural formula 2, R 31 R 32 R 33 Each is independently selected from C1-C5 saturated hydrocarbon groups, C1-C5 unsaturated hydrocarbon groups, C1-C5 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;

[0083] In a preferred embodiment, the phosphate ester compound represented by structural formula 2 may be 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 content of any optional substance in the additive in the non-aqueous electrolyte is generally less than 10%, preferably 0.01-5%, and more preferably 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%.

[0087] In some embodiments, the additive includes fluoroethylene carbonate, and the amount of fluoroethylene carbonate added is 0.01% to 30% based on 100% of the total mass of the non-aqueous electrolyte.

[0088] In some embodiments, the positive electrode active material layer includes a positive electrode active material. The type and content of the positive electrode active material are not particularly limited and can be selected according to actual needs, as long as it is a positive electrode active material that can reversibly insert / extract lithium ions.

[0089] In a preferred embodiment, the positive electrode active material may be selected from LiFe. 1-x’ M' x’ PO4, LiMn 2-y’ M y’ O4 and LiNi x Co y Mn z M 1-x-y-z At least one of O2, wherein M' is selected from at least one of Mn, Mg, Co, Ni, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, or Ti, and M is selected from at least one of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, or Ti, and 0≤x'<1, 0≤y'≤1, 0≤y≤1, 0≤x≤1, 0≤z≤1, x+y+z≤1. The positive electrode active material may also be selected from one or more of sulfides, selenides, and halides. More preferably, the positive electrode active material may be selected from LiCoO2, LiFePO4, or LiFe... 0.8 Mn 0.2 PO4, LiMn2O4, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi0.8 Co 0.1 Mn 0.1 O2, LiNi 0.5 Co 0.2 Mn 0.2 Al 0.1 O2, LiNi 0.5 Co 0.2 Al 0.3 At least one of O2.

[0090] In some embodiments, the positive electrode active 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 active material layer.

[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 vinylidene, copolymers of PVDF-hexafluoropropylene-tetrafluoroethylene, thermoplastic polyimide, polyethylene, and polypropylene; acrylic resins; and styrene-butadiene rubber.

[0092] The positive electrode conductive agent includes at least one of conductive carbon black, conductive carbon spheres, conductive graphite, conductive carbon fiber, carbon nanotubes, graphene, or reduced graphene oxide.

[0093] In some embodiments, the negative electrode includes a negative electrode active material layer, which includes a negative electrode active material, and the negative electrode active material includes at least one of carbon-based negative electrode, silicon-based negative electrode, tin-based negative electrode, and lithium negative electrode. The carbon-based negative electrode may include graphite, hard carbon, soft carbon, graphene, mesophase carbon microspheres, etc.; the silicon-based negative electrode may include silicon materials, silicon oxides, silicon-carbon composite materials, and silicon alloy materials, etc.; the tin-based negative electrode may include tin, tin-carbon, tin oxide, and tin metal compounds; the lithium negative electrode may include metallic lithium or lithium alloys. Specifically, the lithium alloy may be at least one of lithium-silicon alloy, lithium-sodium alloy, lithium-potassium alloy, lithium-aluminum alloy, lithium-tin alloy, and lithium-indium alloy.

[0094] In a more preferred embodiment, the negative electrode active material is selected from at least one of graphite, hard carbon, soft carbon, graphene, and silicon-carbon composite materials.

[0095] In some embodiments, the silicon material is one or more of silicon nanoparticles, silicon nanowires, silicon nanotubes, silicon thin films, 3D porous silicon, and hollow porous silicon.

[0096] 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 is selected from a metallic material that can conduct electrons. Preferably, the negative electrode current collector includes at least one of Al, Ni, tin, copper, and stainless steel. In a more preferred embodiment, the negative electrode current collector is selected from copper foil.

[0097] 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. The negative electrode binder and the negative electrode conductive agent can be the same as the positive electrode binder and the positive electrode conductive agent, respectively, and will not be described in detail here.

[0098] In some embodiments, the battery further includes a separator located between the positive electrode and the negative electrode.

[0099] The diaphragm can be a conventional diaphragm, such as a ceramic diaphragm, a polymer diaphragm, a non-woven fabric, or an inorganic-organic composite diaphragm, 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 diaphragms.

[0100] Table 1

[0101]

[0102]

[0103]

[0104] The present invention will be further illustrated by the following examples.

[0105] Example 1

[0106] This embodiment illustrates the lithium-ion battery and its preparation method disclosed in this invention, and includes the following steps:

[0107] 1) Preparation of positive electrode sheet

[0108] Step 1: Add PVDF as a binder to NMP solvent and stir thoroughly to obtain PVDF adhesive.

[0109] Step 2: Add super P+CNT as a conductive agent to the PVDF adhesive and stir thoroughly.

[0110] Step 3: Continue to add the positive electrode active material shown in Table 1. The mass ratio of positive electrode active material, binder and conductive agent is 94:3:3 to obtain positive electrode slurry.

[0111] Step 4: The prepared positive electrode slurry is evenly coated on aluminum foil, and then dried, rolled, die-cut or slit to obtain the positive electrode sheet.

[0112] 2) Preparation of negative electrode sheet

[0113] Step 1: Weigh out each material according to the negative electrode sheet ratio of graphite (Shanghai Shanshan, FSN-1): conductive carbon (super P): sodium carboxymethyl cellulose (CMC): styrene-butadiene rubber (SBR) = 96.3:1.0:1.2:1.5 (mass ratio).

[0114] Step 2: First, add CMC to pure water at a solid content of 1.5% and stir thoroughly (e.g., stirring time 120 minutes) to prepare a transparent CMC solution.

[0115] Step 3: Add conductive carbon (super P) to the CMC adhesive solution and stir thoroughly (e.g., stirring time 90 min) to prepare the conductive adhesive.

[0116] Step 4: Continue adding graphite and stir thoroughly to obtain the desired negative electrode slurry.

[0117] Step 5: The prepared negative electrode slurry is evenly coated on copper foil, and then dried, rolled, die-cut or slit to obtain the negative electrode sheet.

[0118] 3) Preparation of non-aqueous electrolyte

[0119] Ethylene carbonate (EC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC) were mixed in a mass ratio of EC:DEC:EMC = 1:1:1. Lithium salts and boron-containing oxides LiBOB (lithium bis(oxalato)borate) were added in the molar proportions shown in Table 1. The mass of boron-containing oxides per unit area of ​​the positive electrode current collector was calculated based on the total mass of the boron-containing oxides LiBOB added to the non-aqueous electrolyte and the total single-sided area of ​​the positive electrode current collector, and the result was recorded in Table 1.

[0120] 4) Lithium-ion cell manufacturing

[0121] The prepared positive electrode sheet and the prepared negative electrode sheet are assembled into a stacked soft-pack battery cell.

[0122] 5) Electrolyte injection and formation of battery cells

[0123] In a glove box with the dew point controlled below -40°C, the non-aqueous electrolyte prepared above was injected into the cell, vacuum sealed, and left to stand for 72 hours. Then, the first charge was performed according to the following steps: 0.05C constant current charging for 180 min, 0.1C constant current charging for 120 min, 0.2C constant current charging for 120 min, followed by a second vacuum sealing, and then a full charge at 0.2C (100% SOC). After resting at room temperature for 72 hours, a full discharge at 0.2C (0% SOC) was performed.

[0124] Examples 2-26

[0125] Examples 2-26 illustrate the lithium-ion battery and its preparation method disclosed in this invention, including most of the operational steps in Example 1, with the following differences:

[0126] The mass of lithium salt, boron oxide additive, other additives, positive electrode active material, and boron oxide per unit area on one side of the positive electrode current collector, as shown in Examples 2-26 of Table 1, was used.

[0127] Comparative Examples 1-11

[0128] Comparative Examples 1-11 are used to compare and illustrate the lithium-ion battery and its preparation method disclosed in this invention, including most of the operation steps in Example 1, the difference being:

[0129] The mass of lithium salt, boron oxide additive, other additives, positive electrode active material, and boron oxide per unit area on one side of the positive electrode current collector, as shown in Comparative Examples 1 to 11 in Table 1, was used.

[0130] In Examples 1-26 and Comparative Examples 1-11, except for Example 23 where the boron-containing oxide compound was LiODFB (lithium difluorooxalate borate), the other boron-containing oxide compounds were all LiBOB.

[0131] Performance testing

[0132] The lithium-ion batteries prepared above were subjected to the following performance tests:

[0133] 1. DCIR test at 25℃

[0134] At room temperature (25°C), the lithium-ion battery is charged at a constant current to 50% of its capacity.

[0135] Charge at 0.1C constant current for 10 seconds and then let stand for 40 seconds; discharge at 0.1C constant current for 10 seconds and then let stand for 40 seconds, and record the termination voltage V1.

[0136] Charge at 0.2C constant current for 10s and then let stand for 40s; discharge at 0.2C constant current for 10s and then let stand for 40s, and record the termination voltage V2.

[0137] Charge at 0.5C constant current for 10 seconds and then let stand for 40 seconds; discharge at 0.5C constant current for 10 seconds and then let stand for 40 seconds, and record the termination voltage V3.

[0138] Plot a straight line with current on the x-axis and voltage on the y-axis. The slope of the line represents the impedance at 25℃. 2. High-temperature cycling performance test:

[0139] At 45℃, the lithium-ion battery is charged and discharged at a 1C rate within the charge / discharge cutoff voltage range until the capacity of the lithium-ion battery decays to 80% of its initial capacity, and the number of cycles is recorded. 3. Method for testing the pitting area of ​​the positive electrode current collector after high-temperature cycling test:

[0140] At 45°C, the lithium-ion battery was charged and discharged at a 1C rate within the charge / discharge cutoff voltage range until the capacity of the lithium-ion battery decreased to 80% of the initial capacity. After the high-temperature cycle was completed, the battery was disassembled in a nitrogen atmosphere in a glove box to obtain the positive electrode sheet. The positive electrode sheet was wiped with a cotton swab soaked in NMP to remove the positive electrode active material layer, exposing the positive electrode current collector. After taking pictures with a high-magnification (20x or more) microscope, different areas were analyzed, and the pitted areas of corrosion on the surface of the current collector were counted to obtain the area of ​​pitting corrosion.

[0141] (1) The test results obtained from Examples 1-14 and Comparative Examples 5-13 and 17-24 are filled in Table 2.

[0142] Table 2

[0143]

[0144]

[0145] The test results from Examples 1-14 and Comparative Examples 5-13 and 17-24 show that when LiMn2O4 is used as the positive electrode active material, and LiPF6 and LiFSI are added as lithium salts in the non-aqueous electrolyte, and boron-containing oxides are added as additives, and the molar content a of LiPF6 in the non-aqueous electrolyte, the molar content b of LiFSI in the non-aqueous electrolyte, the mass c of boron-containing oxides per unit area on one side of the positive electrode current collector, and the surface roughness d of the positive electrode current collector satisfy the following conditions: 0.1≤b / a≤5 and 0.05≤c / (b*d)≤10, 0.1≤a≤1.5, 0.1≤b≤1, 0.015≤c≤3, 0.4≤d≤1.8, the obtained lithium-ion battery exhibits lower impedance and higher high-temperature cycle life. Meanwhile, the pitting corrosion problem of the positive electrode current collector was significantly alleviated. This is presumably because LiFSI was used to replace part of LiPF6 as the lithium salt, which improved the stability and ionic conductivity of the non-aqueous electrolyte and effectively suppressed the decomposition of the non-aqueous electrolyte under high temperature conditions. The added boron-containing oxide has a low BO bond film-forming potential and preferentially forms a film on the exposed parts of the positive electrode current collector surface, rather than LiFSI or impurities. This suppresses the corrosion of the positive electrode current collector caused by the addition of LiFSI. At the same time, by controlling the surface roughness of the positive electrode current collector, the film quality and thickness of the boron-containing oxide are controlled. Ultimately, while ensuring the high-temperature stability of the battery electrolyte, corrosion of the positive electrode current collector is suppressed, enabling the battery to achieve both low impedance and excellent high-temperature performance.

[0146] The test results from Examples 1 to 14 show that when the molar content of LiPF6 (a) in the non-aqueous electrolyte, the molar content of LiFSI (b) in the non-aqueous electrolyte, the mass of boron oxide compound per unit area on one side of the positive electrode current collector (c), and the surface roughness (d) of the positive electrode current collector further satisfy the conditions 0.16 ≤ b / a ≤ 4 and 0.2 ≤ c / (b*d) ≤ 3, it is beneficial to further reduce battery impedance and extend high-temperature cycle life. It is speculated that at this time, the interface film formed by the boron oxide compound can more uniformly cover the surface of the positive electrode current collector. At the same time, the positive electrode active material layer and the positive electrode current collector have a lower contact resistance, thereby ensuring ion conduction performance and electronic conduction performance, and improving the cycle performance of lithium-ion batteries.

[0147] The test results of Comparative Examples 5–13 and 17–24 show that even if the molar content of LiPF6 (a) in the non-aqueous electrolyte, the molar content of LiFSI (b) in the non-aqueous electrolyte, the mass of boron oxide compound per unit area on one side of the positive electrode current collector (c), and the surface roughness (d) of the positive electrode current collector meet the conditions 0.1 ≤ b / a ≤ 5 and 0.05 ≤ c / (b*d) ≤ 10, the lithium-ion battery still does not exhibit low impedance and good high-temperature cycle performance if the values ​​of a, b, c, or d do not meet their respective range limits. This indicates that the values ​​of a, b, c, or d have a strong correlation in improving the performance of lithium-ion batteries. Similarly, when the values ​​of a, b, c, or d meet their respective range limits, the improvement in battery performance is not significant if the values ​​of b / a and c / (b*d) do not meet the aforementioned preset conditions.

[0148] (2) The test results obtained from Examples 15-22 and Comparative Examples 14-16 are filled in Table 3.

[0149] Table 3

[0150]

[0151] The test results of Examples 15-22 and Comparative Examples 14-16 show that using different types of positive electrode active materials will have a certain impact on the high-temperature cycle life of lithium-ion batteries. However, when other variables are adjusted, such as the molar content of LiPF6 in the non-aqueous electrolyte (a), the molar content of LiFSI in the non-aqueous electrolyte (b), the mass of boron oxide compound per unit area on one side of the positive electrode current collector (c), and the surface roughness of the positive electrode current collector (d), so that the b / a value and the c / (b*d) value meet the setting conditions of the present invention, the high-temperature cycle performance of lithium-ion batteries can also be positively improved. This shows that the limiting conditions provided by the present invention are applicable to different positive electrode active material battery systems.

[0152] (3) The test results obtained from Examples 1, 23-26 and Comparative Examples 1-4 are filled in Table 4.

[0153] Table 4

[0154]

[0155]

[0156] The test results of Examples 1, 23 and Comparative Examples 1 to 4 show that when different types of boron-containing oxides are used, they can also play a positive role in improving the high-temperature cycle performance of lithium-ion batteries and reduce battery impedance, indicating that the limiting conditions provided by the present invention are applicable to different boron-containing oxides.

[0157] The test results of Examples 1, 24-26 and Comparative Examples 1-4 show that the addition of vinylene carbonate (VC), fluoroethylene carbonate (FEC), or vinyl sulfate (DTD) to the battery system provided by the present invention can further improve the cycle life of the battery. This indicates that the performance enhancement mechanism of other additives differs from that of LiFSI and boron-containing oxides. Vinylene carbonate (VC), fluoroethylene carbonate (FEC), or vinyl sulfate (DTD) are mainly used for surface film formation of the active material layer of the positive and negative electrodes, while LiFSI is used to improve the stability and conductivity of the electrolyte, and boron-containing oxides are used to form a film on the surface of the positive electrode current collector, thereby improving the performance of lithium-ion batteries from different dimensions.

[0158] 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, and a non-aqueous electrolyte. The positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector. The positive electrode current collector is aluminum or an aluminum alloy. The non-aqueous electrolyte includes a non-aqueous organic solvent, a lithium salt, and additives. The lithium salt includes LiPF6 and LiFSI, and the additives include boron-containing oxides. The lithium-ion battery meets the following conditions: 0.16≤b / a≤4, and 0.2≤c / (b*d)≤3, 0.1≤a≤1.5, 0.1≤b≤1, 0.015≤c≤1.8, 0.4≤d≤1.8; Where a is the molar content of LiPF6 in the non-aqueous electrolyte, in mol / L; b represents the molar content of LiFSI in the non-aqueous electrolyte, in mol / L; c represents the mass of boron oxide compound per unit area on one side of the positive electrode current collector, in mg / cm². 2 ; d represents the surface roughness of the positive electrode current collector, in μm.

2. The lithium-ion battery according to claim 1, characterized in that, The molar content (a) of LiPF6 in the non-aqueous electrolyte is 0.2–1.2 mol / L.

3. The lithium-ion battery according to claim 1, characterized in that, The molar content b of LiFSI in the non-aqueous electrolyte is 0.2–0.8 mol / L.

4. The lithium-ion battery according to claim 1, characterized in that, The boron-containing oxide includes at least one of lithium difluorooxalate borate, lithium bis(oxalate borate), and tris(trimethylsilane)borate.

5. The lithium-ion battery according to claim 1 or 4, characterized in that, The mass c of boron oxide compound per unit area on one side of the positive electrode current collector is 0.5~1.8 mg / cm². 2 .

6. The lithium-ion battery according to claim 1, characterized in that, The surface roughness d of the positive electrode current collector is 0.6-1.0 μm.

7. The lithium-ion battery according to claim 1, characterized in that, The lithium salts also include LiPO2F2, LiBF4, LiSbF6, LiAsF6, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiC(SO2CF3)3, LiClO4, LiAlCl4, LiCF3SO3, and Li2B. 10 Cl 10 At least one of LiSO3F, LiTOP, LiDODFP, LiOTF and lower aliphatic carboxylic acid lithium salts.

8. The lithium-ion battery according to claim 1, characterized in that, The additives also include at least one of cyclic sulfate compounds, sulfonyl lactone compounds, cyclic carbonate compounds, and phosphate compounds.

9. The lithium-ion battery according to claim 8, characterized in that, The cyclic sulfate compounds are selected from vinyl sulfate, propylene sulfate, methyl vinyl sulfate, etc. , At least one of them; The sulfonyl lactone compound is selected from at least one of 1,3-propanesulfonyl lactone, 1,4-butanesulfonyl lactone, and 1,3-propenesulfonyl lactone. 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 1: Structural Formula 1 In structural formula 1, 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 2: Structural Formula 2 In structural formula 2, R 31 R 32 R 33 Each is independently selected from C1-C5 saturated hydrocarbon groups, C1-C5 unsaturated hydrocarbon groups, C1-C5 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.

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