Non-aqueous electrolyte and lithium-ion battery

Abstract

In order to solve the problem of insufficient high-temperature and low-temperature performance in existing lithium-ion batteries, provided is a non-aqueous electrolyte, comprising a non-aqueous organic solvent, a lithium salt and an additive, wherein the additive comprises a compound of structural formula 1, the non-aqueous organic solvent comprises a compound of structural formula 2, and the lithium salt comprises lithium bis(fluorosulfonyl)imide; structural formulas (1), (2); and the non-aqueous electrolyte satisfies the following conditions: (3), 4.5≤A≤13, 0.5≤B≤4, 5≤C≤30, and 1.120≤P≤1.240. Moreover, further disclosed is a battery comprising the non-aqueous electrolyte. The non-aqueous electrolyte can effectively improve the low-temperature performance of the battery on the premise of ensuring the high-temperature cycling performance and high-temperature storage performance of the battery.

Description

Non-aqueous electrolyte and lithium-ion battery Technical Field

[0001] The present invention belongs to the technical field of battery materials, and in particular relates to a non-aqueous electrolyte and a lithium-ion battery. Background Art

[0002] In recent years, lithium-ion batteries have been widely used in energy storage and power applications due to their high energy density and long cycle life. As lithium-ion battery applications become increasingly popular, consumer requirements for energy storage and new energy vehicles, as well as their application scenarios, continue to rise. Lithium-ion secondary batteries, represented by phosphates as active materials, offer significant advantages, including longer calendar life, low cost, and high safety. With recent improvements in materials and battery structure design to address energy density shortcomings, phosphate systems have gained a significant market share. However, a major drawback of phosphate systems is their poor intrinsic ion conductivity and insufficient low-temperature performance, which limits their application in passenger vehicles. In particular, as the electrode compaction and areal density of cylindrical battery cells continue to increase, the cell's electrolyte absorption rate slows during filling, leading to uneven electrolyte distribution. This not only affects production efficiency but also leads to high impedance, low capacity, and poor battery life. Black spots and lithium deposition are more likely to form in the center of the cell casing, and long-term cycling can lead to electrolyte drop, resulting in insufficient electrochemical performance at both high and low temperatures.

[0003] Based on the above technical problems, it is urgent to develop a lithium-ion battery electrolyte that takes into account both high and low temperature performance.

[0004] Summary of the Invention

[0005] In view of the problem that existing lithium-ion batteries have insufficient high and low temperature performance, the present invention provides a non-aqueous electrolyte and a lithium-ion battery.

[0006] The technical solutions adopted by the present invention to solve the above technical problems are as follows:

[0007] In one aspect, the present invention provides a non-aqueous electrolyte comprising a non-aqueous organic solvent, a lithium salt, and an additive, wherein the additive comprises a compound represented by Structural Formula 1, the non-aqueous organic solvent comprises a compound represented by Structural Formula 2, and the lithium salt comprises lithium bis(fluorosulfonyl)imide.

[0008] wherein n is an integer selected from 1 to 5, R1 and R2 are each independently selected from hydrogen, halogen, C1-C5 alkyl or C1-C5 haloalkyl, and R1 and R2 are not simultaneously selected from hydrogen;

[0009] wherein R3 is selected from a C1-C3 alkyl group or a halogenated alkyl group, and R4 is selected from a C1-C4 alkyl group or a halogenated alkyl group;

[0010] The non-aqueous electrolyte satisfies the following conditions:

[0011] And 4.5≤A≤13, 0.5≤B≤4, 5≤C≤30, 1.120≤P≤1.240;

[0012] Wherein, A is the mass percentage of lithium bis(fluorosulfonyl)imide in the non-aqueous electrolyte, in %.

[0013] B is the mass percentage of the compound represented by structural formula 1 in the non-aqueous electrolyte, in %;

[0014] C is the mass percentage of the compound represented by structural formula 2 in the non-aqueous electrolyte, in %;

[0015] P is the density of the non-aqueous electrolyte, in g / cm 3 .

[0016] Optionally, the non-aqueous electrolyte meets the following conditions:

[0017] Optionally, the mass percentage A of lithium bis(fluorosulfonyl)imide in the non-aqueous electrolyte is 6.5% to 12.7%.

[0018] Optionally, the mass percentage B of the compound represented by structural formula 1 in the non-aqueous electrolyte is 1% to 2.5%.

[0019] Optionally, the mass percentage C of the compound represented by structural formula 2 in the non-aqueous electrolyte is 15% to 25%.

[0020] Optionally, the density P of the non-aqueous electrolyte is 1.140-1.195 g / cm 3 .

[0021] Optionally, the compound represented by structural formula 1 includes one or more of the following compounds:

[0022] Optionally, the compound represented by structural formula 2 includes one or more of propyl propionate, ethyl propionate, ethyl acetate, difluoroethyl acetate, methyl acetate, methyl propionate, ethyl butyrate, propyl acetate, butyl acetate, and propyl butyrate.

[0023] Optionally, the lithium salt further includes lithium hexafluorophosphate, and the content ratio of the lithium hexafluorophosphate to the lithium bis(fluorosulfonyl)imide is (1% to 13%): (4.5% to 13%).

[0024] Optionally, the additive further comprises at least one of a cyclic sulfate compound, a sultone compound, a cyclic carbonate compound, a phosphate compound, a borate compound and a nitrile compound;

[0025] Preferably, the cyclic sulfate compound is at least one selected from vinyl sulfate, propylene sulfate, and methyl vinyl sulfate;

[0026] The sultone compound is selected from at least one of 1,3-propane sultone, 1,4-butane sultone, and 1,3-propene sultone;

[0027] The cyclic carbonate compound is selected from at least one of vinylene carbonate, vinyl ethylene carbonate, methylene carbonate, fluoroethylene carbonate, trifluoromethylethylene carbonate, bisfluoroethylene carbonate or the compound shown in Structural Formula 3:

[0028] In the structural formula 3, R 21 、R 22 、R 23 、R 24 、R 25 、R 26 Each is independently selected from a hydrogen atom, a halogen atom, and a C1-C5 group;

[0029] The phosphate compound is selected from at least one of tris(trimethylsilyl)phosphate, tris(triethylsilyl)phosphate, or the compound shown in structural formula 4:

[0030] In the structural formula 4, R 31 、R 32 、R 33 Each independently selected from a C1-C5 saturated hydrocarbon group, a C1-C5 unsaturated hydrocarbon group, a C1-C5 halogenated hydrocarbon group, -Si(C m H 2m+1 )3, m is a natural number from 1 to 3, and R 31 、R 32 、R 33 At least one of them is an unsaturated hydrocarbon group;

[0031] The borate compound is selected from at least one of tris(trimethylsilyl)borate and tris(triethylsilyl)borate;

[0032] The nitrile compound is selected from at least one of succinonitrile, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrionitrile, adiponitrile, pimelonitrile, suberonitrile, azelaic acid dinitrile and sebacononitrile.

[0033] In another aspect, the present invention provides a battery comprising a positive electrode, a negative electrode, and the non-aqueous electrolyte as described above.

[0034] The non-aqueous electrolyte provided by the present invention is suitable for a high-density battery system. In the non-aqueous electrolyte, lithium bis(fluorosulfonyl)imide is used as a lithium salt, a compound represented by structural formula 1 is added as an additive, and a compound represented by structural formula 2 is used as a non-aqueous organic solvent. The inventors have found through extensive research that when the mass percentage A of lithium bis(fluorosulfonyl)imide, the mass percentage B of the compound represented by structural formula 1, the mass percentage C of the compound represented by structural formula 2, and the density P of the non-aqueous electrolyte meet the conditions When 4.5≤A≤13, 0.5≤B≤4, 5≤C≤30, and 1.120≤P≤1.240, the obtained non-aqueous electrolyte can effectively improve the low-temperature performance of the battery while ensuring the high-temperature cycle performance and high-temperature storage performance of the battery. It is speculated that this is because the compound shown in structural formula 1 has good high-temperature stability, is not easily oxidized and reduced to open the ring during the battery charge and discharge process, and has a weak polarity, which easily promotes the dissociation of lithium bis(fluorosulfonyl)imide in the electrolyte, making FSI - Anions gradually become the dominant force in interfacial chemical reactions, affecting the film formation of lithium bis(fluorosulfonyl)imide on the negative electrode surface. The compound represented by structural formula 2 has a relatively low viscosity as a non-aqueous organic solvent. On the one hand, it offsets the viscosity increase caused by the compound represented by structural formula 1. On the other hand, by adjusting the density of the non-aqueous electrolyte, it also improves the permeability of the non-aqueous electrolyte, improves the ionic conductivity, affects the contact between the non-aqueous electrolyte and the negative electrode interface during the formation process, and adjusts the film density and stability of lithium bis(fluorosulfonyl)imide. Ultimately, a non-aqueous electrolyte that can take into account both high and low temperature performance is obtained. In particular, the non-aqueous electrolyte has a significant electrochemical performance improvement effect on high-density battery systems. DETAILED DESCRIPTION

[0035] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0036] In the description of the present invention, "density of the non-aqueous electrolyte" refers to the density of the non-aqueous electrolyte tested at a temperature of 25±0.1°C.

[0037] One embodiment of the present invention provides a non-aqueous electrolyte, comprising a non-aqueous organic solvent, a lithium salt, and an additive, wherein the additive comprises a compound represented by Structural Formula 1, the non-aqueous organic solvent comprises a compound represented by Structural Formula 2, and the lithium salt comprises lithium bis(fluorosulfonyl)imide;

[0038] wherein n is an integer selected from 1 to 5, R1 and R2 are each independently selected from hydrogen, halogen, C1-C5 alkyl or C1-C5 haloalkyl, and R1 and R2 are not both selected from hydrogen;

[0039] wherein R3 is selected from a C1-C3 alkyl group or a halogenated alkyl group, and R4 is selected from a C1-C4 alkyl group or a halogenated alkyl group;

[0040] The non-aqueous electrolyte satisfies the following conditions:

[0041] And 4.5≤A≤13, 0.5≤B≤4, 5≤C≤30, 1.120≤P≤1.240;

[0042] Wherein, A is the mass percentage of lithium bis(fluorosulfonyl)imide in the non-aqueous electrolyte, in %.

[0043] B is the mass percentage of the compound represented by structural formula 1 in the non-aqueous electrolyte, in %;

[0044] C is the mass percentage of the compound represented by structural formula 2 in the non-aqueous electrolyte, in %;

[0045] P is the density of the non-aqueous electrolyte, in g / cm 3 .

[0046] In the non-aqueous electrolyte, lithium bis(fluorosulfonyl)imide is used as a lithium salt, a compound shown in structural formula 1 is added as an additive, and a compound shown in structural formula 2 is used as a non-aqueous organic solvent. The inventors have found through extensive research that when the mass percentage A of lithium bis(fluorosulfonyl)imide, the mass percentage B of the compound shown in structural formula 1, the mass percentage C of the compound shown in structural formula 2 and the density P of the non-aqueous electrolyte meet the conditions When 4.5≤A≤13, 0.5≤B≤4, 5≤C≤30, and 1.120≤P≤1.240, the obtained non-aqueous electrolyte can effectively improve the low-temperature performance of the battery while ensuring the high-temperature cycle performance and high-temperature storage performance of the battery. It is speculated that this is because the compound shown in structural formula 1 has good high-temperature stability, is not easily oxidized and reduced to open the ring during the battery charge and discharge process, and has a weak polarity, which easily promotes the dissociation of lithium bis(fluorosulfonyl)imide in the electrolyte, making FSI -Anions gradually become the dominant force in interfacial chemical reactions, affecting the film formation of lithium bis(fluorosulfonyl)imide on the negative electrode surface. The compound represented by structural formula 2 has a relatively low viscosity as a non-aqueous organic solvent. On the one hand, it offsets the viscosity increase caused by the compound represented by structural formula 1. On the other hand, by adjusting the density of the non-aqueous electrolyte, it also improves the permeability of the non-aqueous electrolyte, improves the ionic conductivity, affects the contact between the non-aqueous electrolyte and the negative electrode interface during the formation process, and adjusts the film density and stability of lithium bis(fluorosulfonyl)imide. Ultimately, a non-aqueous electrolyte that can take into account both high and low temperature performance is obtained. In particular, the non-aqueous electrolyte has a significant electrochemical performance improvement effect on high-density battery systems.

[0047] In a preferred embodiment, the non-aqueous electrolyte satisfies the following conditions:

[0048] When the mass percentage A of lithium bis(fluorosulfonyl)imide, the mass percentage B of the compound shown in Structural Formula 1, the mass percentage C of the compound shown in Structural Formula 2 and the density P of the non-aqueous electrolyte further meet the above conditions, the film-forming quality of lithium bis(fluorosulfonyl)imide and the permeability of the electrolyte can be further improved, thereby improving the high-temperature cycle stability and low-temperature capacity retention rate of the battery.

[0049] In a specific embodiment, the mass percentage A of lithium bis(fluorosulfonyl)imide in the non-aqueous electrolyte can be 4.5%, 4.8%, 5.0%, 5.4%, 5.8%, 6.0%, 6.9%, 7.2%, 8.0%, 8.5%, 9.3%, 9.6%, 10.2%, 11.4%, 12.3%, 12.8%, 13%, or any range consisting of the above values.

[0050] In a preferred embodiment, the mass percentage A of lithium bis(fluorosulfonyl)imide in the non-aqueous electrolyte is 6.5% to 12.7%.

[0051] In the non-aqueous electrolyte, the lithium bis(fluorosulfonyl)imide is the main component involved in the formation of the passivation film on the surface of the negative electrode, and the film formation quality of the lithium bis(fluorosulfonyl)imide is affected by various factors. Specifically, when the mass percentage of the lithium bis(fluorosulfonyl)imide in the non-aqueous electrolyte is too low, a complete passivation film cannot be formed on the surface of the negative electrode during formation, and the battery will further consume other lithium salts or solvent components in the non-aqueous electrolyte during the cycle, thereby causing the battery capacity to decrease; when the mass percentage of the lithium bis(fluorosulfonyl)imide in the non-aqueous electrolyte is too high, it is easy to cause the film thickness on the surface of the negative electrode to be too large, thereby causing the battery impedance to increase, and affecting the low-temperature performance of the battery.

[0052] In a specific embodiment, the mass percentage B of the compound represented by structural formula 1 in the non-aqueous electrolyte can be 0.5%, 1%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4% or any range consisting of the above values.

[0053] In a preferred embodiment, the mass percentage B of the compound represented by structural formula 1 in the non-aqueous electrolyte is 1% to 2.5%.

[0054] The compound shown in the structural formula 1 is a cyclic structure with high stability. It is not easily oxidized and reduced to open the ring during the charge and discharge process of the battery. Its weak polarity makes the FSI- anion of lithium bis(fluorosulfonyl)imide more abundant in the solvent sheath. - Anions gradually become the dominant force in interfacial chemical reactions, and the desolvation kinetics are high, promoting the formation of a more complete SEI film at the negative electrode and reducing the electroreactive area of ​​the interfacial film. When the mass percentage of the compound represented by Structural Formula 1 in the non-aqueous electrolyte is too low, it is difficult to promote the film formation of lithium bis(fluorosulfonyl)imide. When the mass percentage of the compound represented by Structural Formula 1 in the non-aqueous electrolyte is too high, the high viscosity of the compound represented by Structural Formula 1 itself will affect the electrolyte's penetration efficiency in the positive and negative electrode material layers, reducing ionic conductivity and hindering the improvement of low-temperature performance.

[0055] In a specific embodiment, the mass percentage C of the compound represented by structural formula 2 in the non-aqueous electrolyte can be 5%, 8%, 9%, 10%, 12%, 14%, 17%, 19%, 21%, 22%, 24%, 27%, 29%, 30% or any range consisting of the above values.

[0056] In a preferred embodiment, the mass percentage C of the compound represented by structural formula 2 in the non-aqueous electrolyte is 15% to 25%.

[0057] The viscosity of the compound represented by Structural Formula 2 offsets the increased viscosity of the compound represented by Structural Formula 1. At the same time, the compound represented by Structural Formula 2 has a lower boiling point as a non-aqueous organic solvent. By adding the compound represented by Structural Formula 1, the boiling point of the non-aqueous electrolyte can be increased, so that the infiltration rate and high-temperature performance of the battery are balanced. On the other hand, the compound represented by Structural Formula 1 and the compound represented by Structural Formula 2 can make the dissociation efficiency of lithium bis(fluorosulfonyl)imide higher, the electrolyte fluidity is good, and the lithium ion penetration effect in the gap between the electrode and the diaphragm is better, avoiding the failure of electrical performance caused by local electrolyte consumption being too fast and unable to be filled evenly in time. When the mass percentage of the compound represented by Structural Formula 2 in the non-aqueous electrolyte is too low, the viscosity of the non-aqueous electrolyte is high, affecting the conduction and penetration efficiency of lithium ions on the electrode and the dissociation of lithium bis(fluorosulfonyl)imide. When the mass percentage of the compound represented by Structural Formula 2 in the non-aqueous electrolyte is too high, the boiling point of the non-aqueous electrolyte is low, affecting the high-temperature performance of the battery.

[0058] In a specific embodiment, the density P of the non-aqueous electrolyte is 1.120 g / cm 3 , 1.130g / cm 3 、1.145g / cm 3 、1.160g / cm 3 , 1.175g / cm 3 , 1.180g / cm 3 , 1.195g / cm 3 , 1.200g / cm 3 、1.210g / cm 3 , 1.220g / cm 3 , 1.225g / cm 3 、1.230g / cm 3 , 1.240g / cm 3 or any range consisting of the above values.

[0059] In a preferred embodiment, the density P of the non-aqueous electrolyte is 1.140-1.195 g / cm 3 .

[0060] The density of the non-aqueous electrolyte is affected by the type and content of each component therein. The density P of the non-aqueous electrolyte can to some extent reflect the overall filling capacity of the non-aqueous electrolyte in the electrode and the gap. When the density of the non-aqueous electrolyte is too low, the molar number of lithium salt per unit gap is low, and it is impossible to ensure that there are sufficient lithium ions to effectively and quickly repair the SEI film during the charge and discharge process, resulting in a decrease in film quality; when the density of the non-aqueous electrolyte is too high, the density of the non-aqueous organic solvent is relatively large. Although the molar number of lithium salt per unit gap is high, the slow migration rate will also cause the SEI film to repair at an insufficient speed.

[0061] In some embodiments, the compound represented by Structural Formula 1 includes one or more of the following compounds:

[0062] In some embodiments, the compound represented by structural formula 2 includes one or more of propyl propionate, ethyl propionate, ethyl acetate, difluoroethyl acetate, methyl acetate, methyl propionate, ethyl butyrate, propyl acetate, butyl acetate, and propyl butyrate.

[0063] In some preferred embodiments, R3 in Structural Formula 2 is selected from a C1-C3 alkyl group or a halogenated alkyl group, and R4 is selected from a C2-C3 alkyl group or a halogenated alkyl group. More preferably, the compound represented by Structural Formula 2 comprises one or more of propyl propionate, ethyl propionate, ethyl acetate, and difluoroethyl acetate.

[0064] In some embodiments, the lithium salt further comprises lithium hexafluorophosphate, and the content ratio of the lithium hexafluorophosphate to the lithium bis(fluorosulfonyl)imide is (1% to 13%): (4.5% to 13%).

[0065] The non-aqueous electrolyte further comprises a liquid selected from the group consisting of LiTFSI, LiBOB, LiDFOB, LiDFOP, LiPO2F2, LiBF4, LiSbF6, LiAsF6, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiC(SO2CF3)3, LiClO4, LiAlCl4, LiCF3SO3, LiSO3F, Li2B 10 Cl 10 , lithium chloroborane, lithium tetrafluorooxalophosphate, lithium trioxalophosphate, a lower aliphatic carboxylic acid lithium having 4 or less carbon atoms, or at least one lithium salt of lithium tetraphenylborate.

[0066] In some embodiments, the total weight percentage of the lithium salt in the non-aqueous electrolyte is 13% to 18%. Specifically, the total weight percentage of the lithium salt in the non-aqueous electrolyte can be 13%, 14%, 15%, 16%, 17%, or 18%.

[0067] In some preferred embodiments, the lithium salt includes at least LiPF6 and LiFSI.

[0068] In some embodiments, based on the total mass of the non-aqueous electrolyte being 100%, the mass content of the non-aqueous organic solvent is 65% to 90%.

[0069] 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%.

[0070] In some embodiments, the non-aqueous organic solvent further comprises at least one of an ether solvent, a nitrile solvent, a carbonate solvent, and a sulfone solvent.

[0071] In some embodiments, the ether solvent includes a cyclic ether or a chain ether, preferably a chain ether with 3 to 10 carbon atoms and a cyclic ether with 3 to 6 carbon atoms. The cyclic ether may be, but is not limited to, at least one of 1,3-dioxolane (DOL), 1,4-dioxolane (DX), a crown ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH3-THF), and 2-trifluoromethyltetrahydrofuran (2-CF3-THF). The chain ether may be, but is not limited to, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, and diethylene glycol dimethyl ether. Because chain ethers have high solvation ability with lithium ions and can improve ion dissociation, dimethoxymethane, diethoxymethane, and ethoxymethoxymethane are particularly preferred because they have low viscosity and can impart high ionic conductivity. The ether compound may be used alone or in any combination and ratio. The content of the ether compound is not particularly limited and is any amount that does not significantly impair the effect of the high-density lithium-ion battery of the present invention. The ether compound is generally present in an amount of 1% by volume or greater, preferably 2% by volume or greater, and more preferably 3% by volume or greater, based on 100% by volume of the non-aqueous solvent. Furthermore, the ether compound is generally present in an amount of 30% by volume or less, preferably 25% by volume or less, and more preferably 20% by volume or less.

[0072] In some embodiments, the nitrile solvent may be, but is not limited to, at least one of acetonitrile, glutaronitrile, and malononitrile.

[0073] In some embodiments, the carbonate solvent includes a cyclic carbonate or a chain carbonate. The cyclic carbonate can be, but is not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (GBL), and butylene carbonate (BC); the chain carbonate can be, but is not limited to, at least one of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and dipropyl carbonate (DPC). The content of the cyclic carbonate is not particularly limited and is arbitrary within the range that does not significantly damage the effect of the lithium-ion battery of the present invention. However, when using one alone, the lower limit of its content is generally 3% or more by volume, preferably 5% or more by volume, relative to the total amount of solvent in the non-aqueous electrolyte. By setting this range, the decrease in conductivity due to the decrease in the dielectric constant of the non-aqueous electrolyte can be avoided, and it is easy to achieve a good range of high current discharge characteristics, stability relative to the negative electrode, and cycle characteristics of the non-aqueous electrolyte battery. In addition, the upper limit is generally 90% or less by volume, preferably 85% or less by volume, and more preferably 80% or less by volume. By setting this scope, the oxidation / reduction tolerance of nonaqueous electrolyte can be improved, thereby contributing to the stability during high temperature storage. The content of linear carbonate is not particularly limited, and relative to the total amount of solvent of nonaqueous electrolyte, is usually more than 15% by volume, preferably more than 20% by volume, and more preferably more than 25% by volume. In addition, usually the volume ratio is less than 90%, preferably less than 85% by volume, and more preferably less than 80% by volume. By making the content of linear carbonate in the above-mentioned scope, it is easy to make the viscosity of nonaqueous electrolyte reach appropriate range, suppress the reduction of ionic conductivity, and then contribute to the output characteristics of nonaqueous electrolyte battery reach good scope. When using two or more linear carbonates in combination, make the total amount of linear carbonate meet the above-mentioned scope.

[0074] In certain embodiments, also can preferably use the linear carbonates with fluorine atoms (hereinafter referred to as " fluorinated linear carbonate ").The number of the fluorine atoms possessed by fluorinated linear carbonate is as long as being more than 1 then has no particular restrictions, but is generally below 6, preferably below 4.When fluorinated linear carbonate has a plurality of fluorine atoms, these fluorine atoms can be bonded on the same carbon, also can be bonded on different carbons.As fluorinated linear carbonate, can enumerate, fluorinated dimethyl carbonate derivatives, fluorinated ethyl methyl carbonate derivatives, fluorinated diethyl carbonate derivatives etc.

[0075] In some embodiments, the sulfone solvent includes a cyclic sulfone and a chain sulfone. Preferably, in the case of a cyclic sulfone, the compound generally has 3 to 6 carbon atoms, preferably 3 to 5 carbon atoms; in the case of a chain sulfone, the compound generally has 2 to 6 carbon atoms, preferably 2 to 5 carbon atoms. The content of the sulfone solvent is not particularly limited and is arbitrary within a range that does not significantly impair the effect of the lithium-ion battery of the present invention. The volume ratio is generally 0.3% or more, preferably 0.5% or more, and more preferably 1% or more relative to the total volume of the solvent in the non-aqueous electrolyte. In addition, the volume ratio is generally 40% or less, preferably 35% or less, and more preferably 30% or less. When two or more sulfone solvents are used in combination, the total amount of the sulfone solvents can be adjusted to meet the above range. When the sulfone solvent content is within the above range, a non-aqueous electrolyte with excellent high-temperature storage stability tends to be obtained.

[0076] In some embodiments, the additive further comprises at least one of a cyclic sulfate compound, a sultone compound, a cyclic carbonate compound, a phosphate compound, a borate compound, and a nitrile compound;

[0077] Preferably, based on the total mass of the non-aqueous electrolyte being 100%, the content of the additive is 0.01% to 10%.

[0078] In some embodiments, the cyclic sulfate compound is selected from at least one of vinyl sulfate, propylene sulfate, and methyl vinyl sulfate;

[0079] The sultone compound is selected from at least one of 1,3-propane sultone, 1,4-butane sultone, and 1,3-propene sultone;

[0080] The cyclic carbonate compound is selected from at least one of vinylene carbonate, vinyl ethylene carbonate, methylene carbonate, fluoroethylene carbonate, trifluoromethylethylene carbonate, bisfluoroethylene carbonate or the compound shown in Structural Formula 3:

[0081] In the structural formula 3, R 21 、R 22 、R 23 、R 24 、R 25 、R 26 Each is independently selected from a hydrogen atom, a halogen atom, and a C1-C5 group;

[0082] The phosphate compound is selected from at least one of tris(trimethylsilyl)phosphate, tris(triethylsilyl)phosphate, or the compound shown in structural formula 4:

[0083] In the structural formula 4, R 31 、R 32 、R 33 Each independently selected from a C1-C5 saturated hydrocarbon group, a C1-C5 unsaturated hydrocarbon group, a C1-C5 halogenated hydrocarbon group, -Si(C m H 2m+1 )3, m is a natural number from 1 to 3, and R 31 、R 32 、R 33 At least one of them is an unsaturated hydrocarbon group;

[0084] In a preferred embodiment, the phosphate compound shown in the structural formula 4 may be at least one of tripropargyl phosphate, dipropargyl methyl phosphate, dipropargyl ethyl phosphate, dipropargyl propyl phosphate, dipropargyl trifluoromethyl phosphate, dipropargyl-2,2,2-trifluoroethyl phosphate, dipropargyl-3,3,3-trifluoropropyl phosphate, dipropargyl hexafluoroisopropyl phosphate, triallyl phosphate, diallyl methyl phosphate, diallyl ethyl phosphate, diallyl propyl phosphate, diallyl trifluoromethyl phosphate, diallyl-2,2,2-trifluoroethyl phosphate, diallyl-3,3,3-trifluoropropyl phosphate, and diallyl hexafluoroisopropyl phosphate;

[0085] The borate compound is selected from at least one of tris(trimethylsilyl)borate and tris(triethylsilyl)borate;

[0086] The nitrile compound is selected from at least one of succinonitrile, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrionitrile, adiponitrile, pimelonitrile, suberonitrile, azelaic acid dinitrile and sebacononitrile.

[0087] In other embodiments, the additives may also include other additives that can improve battery performance: for example, additives that enhance battery safety, such as flame retardant additives such as fluorophosphates and cyclophosphazenes, or overcharge prevention additives such as tert-amylbenzene and tert-butylbenzene.

[0088] It should be noted that, unless otherwise specified, under normal circumstances, the content of any one of the optional substances in the additives in the non-aqueous electrolyte is less than 10%, preferably, the content is 0.01-5%, and more preferably, the content is 0.1% to 2%. Specifically, the content of any one of the optional substances in the additives 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%.

[0089] In some embodiments, the additive includes fluoroethylene carbonate, and based on the total mass of the non-aqueous electrolyte being 100%, the content of the fluoroethylene carbonate is 0.01% to 30%.

[0090] Another embodiment of the present invention provides a battery including a positive electrode, a negative electrode, and the non-aqueous electrolyte as described above.

[0091] In some embodiments, the positive electrode includes a positive electrode material layer, the positive electrode material layer includes a positive electrode active material, and the positive electrode active material includes LiFe 1-x’ M' x’ PO4、LiMn 2-y’ M y’ O4 and LiNi x Co y Mn z M 1-x-y-z One or more of O2, wherein M' is selected from one or more of Mn, Mg, Co, Ni, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, Nb, Ce, Zr, W or Ti, M is selected from one or more of Fe, Co, Ni, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, Nb, Ce, Zr, W or Ti, and 0≤x'<1, 0≤y'≤1, 0≤y≤1, 0≤x≤1, 0≤z≤1, x+y+z≤1.

[0092] In some preferred embodiments, the positive electrode active material may be selected from LiCoO2, LiFePO4, LiFe 0.4 Mn 0.6 PO4, LiMn2O4, LiNi 0.5 Co 0.2 Mn 0.3 O2、LiNi 0.6 Co 0.2 Mn 0.2 O2、LiNi0.6 Co 0.1 Mn 0.3 O2、LiNi 0.7 Co 0.1 Mn 0.2 O2、LiNi 0.8 Co 0.1 Mn 0.1 O2、LiNi 0.8 Co 0.15 Al 0.05 O2、LiNi 0.9 Co 0.05 Mn 0.05 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.

[0093] In some embodiments, the positive electrode material layer further includes a positive electrode binder and a positive electrode conductor, and the positive electrode active material, the positive electrode binder, and the positive electrode conductor are blended to obtain the positive electrode material layer.

[0094] The positive electrode binder includes polyvinylidene fluoride, a copolymer of vinylidene fluoride, polytetrafluoroethylene, a copolymer of vinylidene fluoride-hexafluoropropylene, a copolymer of tetrafluoroethylene-hexafluoropropylene, a copolymer of tetrafluoroethylene-perfluoroalkyl vinyl ether, a copolymer of ethylene-tetrafluoroethylene, a copolymer of vinylidene fluoride-tetrafluoroethylene, a copolymer of vinylidene fluoride-trifluoroethylene, a copolymer of vinylidene fluoride-trichloroethylene, a copolymer of vinylidene fluoride-fluoroethylene, a copolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, thermoplastic polyimide, a thermoplastic resin such as polyethylene and polypropylene; an acrylic resin; and at least one of styrene butadiene rubber.

[0095] The positive electrode conductive agent includes at least one of conductive carbon black, conductive carbon balls, conductive graphite, conductive carbon fibers, carbon nanotubes, graphene, or reduced graphene oxide.

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

[0097] In some embodiments, the negative electrode includes a negative electrode active material layer, wherein the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes at least one of a carbon-based negative electrode, a silicon-based negative electrode, a tin-based negative electrode, and a lithium negative electrode. Carbon-based negative electrodes may include graphite, hard carbon, soft carbon, graphene, mesocarbon microbeads, etc.; silicon-based negative electrodes may include silicon materials, silicon oxides, silicon-carbon composites, and silicon alloys; tin-based negative electrodes may include tin, tin-carbon, tin oxide, or tin metal compounds; and lithium negative electrodes may include metallic lithium or a lithium alloy. Specifically, the lithium alloy may be at least one of a lithium-silicon alloy, a lithium-sodium alloy, a lithium-potassium alloy, a lithium-aluminum alloy, a lithium-tin alloy, and a lithium-indium alloy.

[0098] 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.

[0099] 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.

[0100] In some embodiments, the negative electrode further comprises 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 an electron-conducting metal material. Preferably, the negative electrode current collector comprises 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.

[0101] In some embodiments, the negative electrode active material layer further includes a negative electrode binder and a negative electrode conductive agent. The negative electrode active material, the negative electrode binder, and the negative electrode conductive agent are blended together to form the negative electrode active material layer. The negative electrode binder and the negative electrode conductive agent may be the same as the positive electrode binder and the positive electrode conductive agent, respectively, and are not further described here.

[0102] In some embodiments, the battery further includes a separator, which is located between the positive electrode and the negative electrode.

[0103] The diaphragm can be an existing conventional diaphragm, which can be a ceramic diaphragm, a polymer diaphragm, a non-woven fabric, an inorganic-organic composite diaphragm, etc., including but not limited to single-layer PP (polypropylene), single-layer PE (polyethylene), double-layer PP / PE, double-layer PP / PP and three-layer PP / PE / PP diaphragms.

[0104] The present invention is further described below with reference to the following examples.

[0105] Table 1

[0106] Example 1

[0107] This embodiment is used to illustrate the lithium ion battery and its preparation method disclosed in the present invention, including the following steps:

[0108] The positive electrode preparation steps are as follows: positive electrode active material (LiFePO4, LFP), conductive carbon black (Super-P) and binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 96:2:2, dispersed in N-methyl-2-pyrrolidone (NMP) to obtain a positive electrode slurry, the positive electrode slurry is evenly coated on both sides of aluminum foil, and after drying, rolling and vacuum drying, aluminum lead wires are welded using an ultrasonic welder to obtain the positive electrode.

[0109] The negative electrode preparation steps are as follows: artificial graphite, conductive carbon black, binder styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) are mixed in a mass ratio of 94:1:2.5:2.5, dispersed in deionized water to obtain a negative electrode slurry, the negative electrode slurry is coated on both sides of aluminum foil, and the negative electrode is obtained after drying, rolling and vacuum drying, and nickel lead wires are welded with an ultrasonic welder.

[0110] The electrolyte preparation step is as follows: in a glove box with a water and oxygen content of less than 10 ppm, propyl propionate, ethylene carbonate and ethyl methyl carbonate are mixed according to the proportion relationship in Table 1, wherein the mass ratio of ethylene carbonate: (propyl propionate + ethyl methyl carbonate) is 30:70, and then lithium hexafluorophosphate, LiFSI, vinylene carbonate (VC) and the compound shown in Structural Formula 1 are added, wherein the mass percentage of VC in the non-aqueous electrolyte is 2%, and the contents of lithium hexafluorophosphate, LiFSI and the compound shown in Structural Formula 1 are as shown in Table 1.

[0111] Electrolyte density test: First, clean the density bottle, dry it, and cool it down, and weigh it with a thermometer and side hole cover; fill the density bottle with deionized water that has been freshly boiled and cooled to 20°±0.1℃, and then place the density bottle in a constant temperature water bath at 25±0.1℃ for half an hour, and align the liquid level in the side tube with the tube mouth, immediately cover the side hole cover, take out the density bottle, wipe the water on the outer wall with filter paper, and weigh it. Pour out the water sample in the density bottle, dry it, replace the deionized water with the electrolyte to be tested, repeat the above operation, and test the mass of the electrolyte to be tested at 25±0.1℃. Each sample is tested twice, and the difference between the two should not exceed 0.003g / cm 2 , and then calculate the average value and record it in Table 1.

[0112] The battery assembly steps are as follows: a three-layer separator with a thickness of 20μm is placed between the positive plate and the negative plate, and then the sandwich structure consisting of the positive plate, separator and negative plate is wound to form a columnar electrode group, which is placed in a nickel-plated cylindrical steel shell. The prepared electrolyte is injected into the steel shell battery cell, and then it is aged, hot-pressed, aged, and vacuum-sealed twice. The formation conditions are: 0.5C constant current charging for 180 minutes, and 0.1C constant current charging for 180 minutes. After 24 hours of storage, the battery is shaped and sealed, and then further charged at a constant current of 0.2C to 3.65V. After 24 hours of storage at room temperature, it is discharged at a constant current of 0.2C to 2.0V to obtain a lithium-ion secondary battery.

[0113] Examples 2 to 33

[0114] Examples 2 to 33 are used to illustrate the lithium-ion batteries and preparation methods disclosed in the present invention, and include most of the steps in Example 1, except that:

[0115] The positive electrode active materials shown in Examples 2 to 33, the content of lithium hexafluorophosphate, the content of LiFSI, the selection and content of the compound shown in Structural Formula 1, the selection and content of the compound shown in Structural Formula 2, other additives and their contents, and the density of the non-aqueous electrolyte are shown in Table 1.

[0116] When the positive electrode active material is selected from LiNi 0.8 Co 0.1 Mn 0.1 When O2 (NCM811), the mass ratio of the positive electrode active material (NCM811), conductive carbon black (Super-P) and binder polyvinylidene fluoride (PVDF) is 93:4:3, the charge and discharge voltage range is 3.0~4.25V, and the mass percentage of VC in the electrolyte is 0.5%.

[0117] Comparative Examples 1 to 27

[0118] Comparative Examples 1 to 27 are used to compare and illustrate the lithium ion batteries and preparation methods disclosed in the present invention, and include most of the operating steps in Example 1, except that:

[0119] The positive electrode active materials shown in Comparative Examples 1 to 27, the content of lithium hexafluorophosphate, the content of LiFSI, the selection and content of the compound shown in Structural Formula 1, the selection and content of the compound shown in Structural Formula 2, other additives and their contents, and the density of the non-aqueous electrolyte are shown in Table 1;

[0120] When the positive electrode active material is selected from LiNi 0.8 Co 0.1 Mn 0.1When O2 (NCM811), the mass ratio of the positive electrode active material (NCM811), conductive carbon black (Super-P) and binder polyvinylidene fluoride (PVDF) is 93:4:3, and the charge and discharge voltage range is 3.0~4.25V.

[0121] Performance Testing

[0122] The lithium-ion batteries prepared in the above examples and comparative examples were subjected to the following performance tests:

[0123] 1) Lithium deposition analysis: The battery with 50% SOC after formation was placed at -20°C for 10 hours, then cycled 20 times at 0.5C and fully charged. The battery was disassembled to observe the lithium deposition at the negative electrode interface.

[0124] 2) 25°C DCIR: Place the formed 50% SOC battery at 0°C for 10 hours. Charge and discharge the battery at 0.1C, 0.2C, and 0.5C for 10 seconds, with a 40-second rest period in between. Calculate the DCIR.

[0125] 3) -20℃ low-temperature discharge: At room temperature, charge the formed battery at 1C constant current and constant voltage to 3.65V (LFP) or 4.25V (NCM811) with a cut-off current of 0.02C. After standing for 5 minutes, discharge the battery at 0.5C constant current and constant voltage to 2.0V (LFP) or 3.0V (NCM811), and record the initial discharge capacity of the battery; then charge the battery at 1C constant current and constant voltage to 3.65V (LFP) or 4.25V (NCM811) with a cut-off current of 0.02C. After standing at -20℃ for 10 hours, discharge the battery at 1C constant current to 2.0V (LFP) or 3.0V (NCM811), and record the discharge capacity of the battery.

[0126] Capacity retention (%) = -20°C low-temperature discharge capacity / room-temperature initial discharge capacity × 100%.

[0127] 4) High temperature storage performance: At room temperature, the formed battery was charged to 3.65V (LFP) or 4.25V (NCM811) at 1C constant current and constant voltage, with a cut-off current of 0.02C. After standing for 5 minutes, it was discharged to 2.0V (LFP) or 3.0V (NCM811) at 0.5C constant current and constant voltage, and the initial discharge capacity of the battery was recorded; then it was charged to 3.65V (LFP) or 4.25V (NCM811) at 1C constant current and constant voltage, with a cut-off current of 0.02C; after the fully charged battery was stored in a 60°C constant temperature box for 30 days, it was discharged to 2.0V (LFP) or 3.0V (NCM811) at 1C constant current, and the battery retention capacity was recorded.

[0128] Capacity retention (%) = retained capacity after 30-day storage / initial discharge capacity × 100%.

[0129] (1) The test results obtained in Examples 1 to 21 and Comparative Examples 1 to 15 and 21 to 27 are shown in Table 2.

[0130] Table 2

[0131] From the test results of Examples 1 to 21 and Comparative Examples 1 to 15 and 21 to 27, it can be seen that in an electrolyte system using lithium bisfluorosulfonyl imide as the main lithium salt, the compound represented by Structural Formula 1 is added as an additive, and the compound represented by Structural Formula 2 is used as a non-aqueous organic solvent, the mass percentage A of lithium bisfluorosulfonyl imide, the mass percentage B of the compound represented by Structural Formula 1, the mass percentage C of the compound represented by Structural Formula 2, and the density P of the non-aqueous electrolyte have a significant correlation in improving the high and low temperature performance of the battery. When the mass percentage A of lithium bisfluorosulfonyl imide, the mass percentage B of the compound represented by Structural Formula 1, the mass percentage C of the compound represented by Structural Formula 2, and the density P of the non-aqueous electrolyte satisfy the relationship: When 4.5≤A≤13, 0.5≤B≤4, 5≤C≤30, and 1.120≤P≤1.240, the obtained lithium-ion battery has a low impedance, can have a high capacity retention rate under low temperature discharge conditions, and has a high capacity retention rate after high temperature storage, and does not have the problem of lithium precipitation. It is speculated that this is because lithium bis(fluorosulfonyl)imide forms a film on the surface of the negative electrode, and the compound shown in structural formula 1 has good high temperature stability. It is not easy to be oxidized and reduced and open the ring during the battery charge and discharge process, and its polarity is weak, which easily promotes the dissociation of lithium bis(fluorosulfonyl)imide in the electrolyte, making FSI - Anions gradually become the dominant force in interfacial chemical reactions, affecting the film formation of lithium bis(fluorosulfonyl)imide on the negative electrode surface. The compound represented by structural formula 2 has a relatively low viscosity as a non-aqueous organic solvent. On the one hand, it offsets the viscosity increase caused by the compound represented by structural formula 1. On the other hand, by adjusting the density of the non-aqueous electrolyte, it also improves the permeability of the non-aqueous electrolyte, improves the ionic conductivity, affects the contact between the non-aqueous electrolyte and the negative electrode interface during the formation process, and adjusts the film density and stability of lithium bis(fluorosulfonyl)imide, ultimately obtaining a non-aqueous electrolyte that can take into account both high and low temperature performance.

[0132] From the test results of Examples 1-21, it can be seen that when the mass percentage A of lithium bis(fluorosulfonyl)imide, the mass percentage B of the compound shown in Structural Formula 1, the mass percentage C of the compound shown in Structural Formula 2 and the density P of the non-aqueous electrolyte further meet the conditions When 6.5≤A≤12.7, 1≤B≤2.5, 15≤C≤25, and 1.140≤P≤1.195, the obtained lithium ion battery has the best comprehensive performance.

[0133] From the test results of Comparative Examples 1 to 15, it can be seen that when one or more of the A value, B value, C value and P value exceeds the limit range, even if the relationship formula is satisfied: The capacity retention rate of the lithium-ion battery obtained at low temperature or high temperature storage is also low, indicating that when the mass percentage A of lithium bis(fluorosulfonyl)imide, the mass percentage B of the compound shown in structural formula 1, the mass percentage C of the compound shown in structural formula 2 and the density P of the non-aqueous electrolyte are too high or too low, the film density and stability of lithium bis(fluorosulfonyl)imide on the surface of the negative electrode material layer will be affected, resulting in an increase in film resistance and the occurrence of lithium precipitation. From the test results of comparative examples 21 to 27, it can be seen that even if the A value, B value, C value and P value all meet the parameter range limits, If the value is too large or too small, it will lead to the deterioration of the low-temperature performance and high-temperature performance of the battery, indicating that the mass percentage A of lithium bis(fluorosulfonyl)imide, the mass percentage B of the compound shown in structural formula 1, the mass percentage C of the compound shown in structural formula 2 and the density P of the non-aqueous electrolyte have an impact on each other. When and only when the four reach a good balance, can the low-temperature performance and high-temperature performance of the lithium-ion battery be significantly improved.

[0134] (2) The test results obtained in Examples 22 to 26 and Comparative Examples 16 to 20 are entered in Table 3.

[0135] Table 3

[0136] From the test results of Examples 22 to 26 and Comparative Examples 16 to 20, it can be seen that when LiNi 0.8 Co 0.1 Mn 0.1 When O2 (NCM811) is used as the positive electrode active material system, the mass percentage A of lithium bis(fluorosulfonyl)imide, the mass percentage B of the compound represented by structural formula 1, the mass percentage C of the compound represented by structural formula 2, and the density P of the non-aqueous electrolyte satisfy the relationship: When 4.5≤A≤13, 0.5≤B≤4, 5≤C≤30, and 1.120≤P≤1.240, the effect played is similar to that of using LiFePO4 as the positive electrode active material, and both have a good improvement effect on the high and low temperature performance of the lithium-ion battery, effectively improving and reducing the impedance of the lithium-ion battery and reducing the occurrence of lithium dendrites, indicating that the relationship provided by the present invention is applicable to different positive electrode material systems.

[0137] (2) The test results obtained in Examples 18, 27 to 33 are entered in Table 4.

[0138] Table 4

[0139] From the test results of Examples 18 and 27 to 33, it can be seen that in the battery system provided by the present invention, when different compounds represented by Structural Formula 1 or different compounds represented by Structural Formula 2 are used, the high-temperature and low-temperature capacity retention rates of the lithium-ion battery can be improved, and the lithium plating at the negative electrode of the battery can be reduced. This illustrates the types of roles played by different compounds represented by Structural Formula 1 and different compounds represented by Structural Formula 2 in the battery system of the present invention, and the relationship provided by the present invention is applicable to different compounds represented by Structural Formula 1 and different compounds represented by Structural Formula 2.

[0140] 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 in the scope of protection of the present invention.

Claims

1. A non-aqueous electrolyte, characterized in that: It includes a non-aqueous organic solvent, a lithium salt and an additive, wherein the additive includes a compound shown in structural formula 1, the non-aqueous organic solvent includes a compound shown in structural formula 2, and the lithium salt includes lithium bis(fluorosulfonyl)imide; wherein n is selected from an integer of 1 to 5, R1 and R2 are each independently selected from hydrogen, halogen, C1 to C5 alkyl or C1 to C5 halogenated alkyl, and R1 and R2 are not simultaneously selected from hydrogen; Wherein, R3 is selected from C1-C3 alkyl or halogenated alkyl, and R4 is selected from C1-C4 alkyl or halogenated alkyl; The non-aqueous electrolyte meets the following conditions: And 4.5≤A≤13, 0.5≤B≤4, 5≤C≤30, 1.120≤P≤1.240; Wherein, A is the mass percentage of lithium bis(fluorosulfonyl)imide in the non-aqueous electrolyte, in %; B is the mass percentage of the compound represented by structural formula 1 in the non-aqueous electrolyte, in %; C is the mass percentage of the compound represented by structural formula 2 in the non-aqueous electrolyte, in %; P is the density of the non-aqueous electrolyte, in g / cm 3 .

2. The non-aqueous electrolyte according to claim 1, characterized in that The non-aqueous electrolyte meets the following conditions:

3. The non-aqueous electrolyte according to claim 1, characterized in that The mass percentage A of lithium bis(fluorosulfonyl)imide in the non-aqueous electrolyte is 6.5% to 12.7%.

4. The non-aqueous electrolyte according to claim 1, characterized in that The mass percentage B of the compound represented by structural formula 1 in the non-aqueous electrolyte is 1% to 2.5%.

5. The non-aqueous electrolyte according to claim 1, characterized in that The mass percentage C of the compound represented by structural formula 2 in the non-aqueous electrolyte is 15% to 25%.

6. The non-aqueous electrolyte according to claim 1, characterized in that The density P of the non-aqueous electrolyte is 1.140-1.195 g / cm 3 .

7. The non-aqueous electrolyte according to claim 1, characterized in that The compound represented by the structural formula 1 includes one or more of the following compounds:

8. The non-aqueous electrolyte according to claim 1, characterized in that The compound represented by the structural formula 2 includes one or more of propyl propionate, ethyl propionate, ethyl acetate, difluoroethyl acetate, methyl acetate, methyl propionate, ethyl butyrate, propyl acetate, butyl acetate, and propyl butyrate.

9. The non-aqueous electrolyte according to claim 1, characterized in that The lithium salt further comprises lithium hexafluorophosphate, and the content ratio of the lithium hexafluorophosphate to the lithium bis(fluorosulfonyl)imide is (1% to 13%): (4.5% to 13%).

10. The non-aqueous electrolyte according to claim 1, characterized in that The additive further includes at least one of cyclic sulfate compounds, sultone compounds, cyclic carbonate compounds, phosphate compounds, borate compounds and nitrile compounds.

11. The non-aqueous electrolyte according to claim 10, characterized in that The cyclic sulfate ester compound is selected from at least one of vinyl sulfate, propylene sulfate and methyl vinyl sulfate.

12. The non-aqueous electrolyte according to claim 10, characterized in that The sultone compound is selected from at least one of 1,3-propane sultone, 1,4-butane sultone and 1,3-propene sultone.

13. The non-aqueous electrolyte according to claim 10, characterized in that The cyclic carbonate compound is selected from at least one of vinylene carbonate, ethylene carbonate, methylene carbonate, fluoroethylene carbonate, trifluoromethylethylene carbonate, bisfluoroethylene carbonate or the compound shown in Structural Formula 3: In the structural formula 3, R 21 , R 22 , R 23 , R 24 , R 25 , R 26 Each is independently selected from a hydrogen atom, a halogen atom, and a C1-C5 group.

14. The non-aqueous electrolyte according to claim 10, characterized in that The phosphate compound is selected from at least one of tris(trimethylsilyl)phosphate, tris(triethylsilyl)phosphate or the compound shown in structural formula 4: In the structural formula 4, R 31 , R 32 , R 33 Each independently selected from a C1-C5 saturated hydrocarbon group, a C1-C5 unsaturated hydrocarbon group, a C1-C5 halogenated hydrocarbon group, -Si(C m H 2m+1 )3, m is a natural number from 1 to 3, and R 31 , R 32 , R 33 At least one of them is an unsaturated hydrocarbon group.

15. The non-aqueous electrolyte according to claim 10, characterized in that The borate compound is selected from at least one of tris(trimethylsilyl)borate and tris(triethylsilyl)borate.

16. The non-aqueous electrolyte according to claim 10, characterized in that The nitrile compound is selected from at least one of succinonitrile, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrinitrile, adiponitrile, pimelonitrile, suberonitrile, azelaic acid dinitrile and sebacononitrile.

17. A lithium ion battery, characterized in that: The invention comprises a positive electrode, a negative electrode and the non-aqueous electrolyte according to any one of claims 1 to 16.

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