Lithium ion battery

Abstract

In order to solve the problem that the high-temperature electrochemical performance of the lithium ion battery is affected due to high-voltage instability of the existing electrolyte, the invention provides a lithium ion battery which comprises a positive electrode, a negative electrode and a non-aqueous electrolyte, the positive electrode comprises a positive electrode material layer containing a positive electrode material, and the non-aqueous electrolyte comprises a non-aqueous organic solvent, electrolyte salt and an additive, the additive comprises fluoroethylene carbonate and a first additive, the first additive comprises a compound shown as a structural formula 1: # imgabs0 #, X is selected from # imgabs1 # or # imgabs2 #, R1 and R2 are respectively and independently selected from H, # imgabs3 # or # imgabs4 #, R1 and R2 are not simultaneously selected from H, and X, R1 and R2 at least contain one sulfur atom; the lithium ion battery satisfies the following conditions: 0.5 < = (a + 10c) / b-K90 < = 150, 0.5 < = a < = 9, 0.1 < = b < = 3, 0.01 < = c < = 1.1, and 0.1 < = K90 < = 25.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy storage electronic components, and particularly relates to a lithium-ion battery. Background Art

[0002] Lithium-ion batteries are widely used in various aspects of human society such as clothing, food, housing, and transportation due to their advantages of high specific energy, long cycle life, no memory effect, and low self-discharge rate. With the increasing requirements of the application market for the endurance time of lithium-ion batteries, it is urgent to further improve the volumetric energy density of the batteries. Limited by the properties of the raw materials used, increasing the charging voltage of the battery is the most common way to improve the volumetric energy density of the battery.

[0003] Increasing the battery voltage can effectively improve the battery capacity. However, the electrolyte is unstable under high voltage and is prone to decomposition. The by-products generated by the decomposition will damage the structures of the positive and negative electrodes of the battery, resulting in a rapid decline in the battery performance. At the same time, as the temperature increases, the stability of the non-aqueous electrolyte decreases, and this problem is particularly obvious at high temperatures. Therefore, improving the oxidation stability of the electrolyte and broadening the electrochemical window of the electrolyte are the only ways to develop high-voltage electrolytes. At present, the problem of the instability of traditional electrolytes under high voltage has not been solved, the battery capacity decays during cycling, and gas generation is serious, which is prone to safety hazards. Therefore, developing high-voltage electrolytes is still an important direction for the current electrolyte development. Summary of the Invention

[0004] Aiming at the problem that the existing electrolyte is unstable under high voltage and affects the high-temperature electrochemical performance of lithium-ion batteries, a lithium-ion battery is provided.

[0005] The technical solutions adopted by the present invention to solve the above technical problems are as follows: The present invention provides a lithium-ion battery, including a positive electrode, a negative electrode, and a non-aqueous electrolyte. The positive electrode includes a positive electrode material layer containing a positive electrode material. The non-aqueous electrolyte includes a non-aqueous organic solvent, an electrolyte salt, and an additive. The additive includes fluorinated ethylene carbonate and a first additive. The first additive includes a compound represented by Structural Formula 1: Structural Formula 1 Wherein, X is selected from or , R1 and R2 are each independently selected from H, , or , R1 and R2 are not simultaneously selected from H, and at least one of X, R1, and R2 contains a sulfur atom; the lithium-ion battery satisfies the following conditions: 0.5 ≤ (a + 10c) / b - K90 ≤ 150, and 0.5 ≤ a ≤ 9, 0.1 ≤ b ≤ 3, 0.01 ≤ c ≤ 1.1, 0.1 ≤ K90 ≤ 25; Among them, a is the mass percentage content of vinylene carbonate fluoride in the non-aqueous electrolyte, and the unit is %; b is the mass percentage content of the first additive in the non-aqueous electrolyte, and the unit is %; c is the evaporation rate of the non-aqueous electrolyte at 80 °C, and the unit is mg / min; K90 is the particle size distribution of the positive electrode material, and K90 = (D90 - D10) / D50.

[0006] Optionally, the lithium-ion battery satisfies the following conditions: 0.5 ≤ (a + 10c) / b - K90 ≤ 50.

[0007] Optionally, the mass percentage content a% of vinylene carbonate fluoride in the non-aqueous electrolyte is 1% to 8%.

[0008] Optionally, the mass percentage content b% of the first additive in the non-aqueous electrolyte is 0.2% to 2%.

[0009] Optionally, the evaporation rate c of the non-aqueous electrolyte at 80 °C is 0.01 to 1 mg / min.

[0010] Optionally, the particle size distribution K90 of the positive electrode material is 0.2 to 15.

[0011] Optionally, the positive electrode material includes a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder. Among them, the positive electrode active material includes: A nickel-containing material, and the nickel-containing material includes a material with the molecular formula Li q Ni x Co y M 1-x-y O 2-g R g or a Li q Ni x Co y M 1-x-y O 2-g R g material with a coating layer on its surface, where 0.9 ≤ q ≤ 1.2, 0.5 ≤ x ≤ 0.96, y > 0, 1 - x - y > 0, 0 ≤ g ≤ 1, M includes one or both of Mn and Al, and includes zero, one, or more of Sr, Mg, Ti, Ca, Zr, Zn, Si, Fe, B, Ga, Cr, W, V, Nb, Ce; and / or, A phosphate material, and the phosphate material includes a material with the molecular formula Li r Mn α Fe β A 1-α-β PO4-n G n The material or surface of n is provided with a coating layer of Li r Mn α Fe β A 1-α-β PO 4-n G n At least one of the materials, where 0.9 ≤ r ≤ 1.1, 0 ≤ α ≤ 0.8, 0.2 ≤ β ≤ 1, 0 ≤ n ≤ 0.1, A is selected from one or more of Ti, Mg, V, Cr, Zr, Nb, Zn, Al, Na, K, Mo, W, Ni, Co, Ga, Sn, Sb, Ge, and W; and / or, Lithium cobaltate material, the lithium cobaltate material includes lithium cobaltate or lithium cobaltate doped and / or coated and modified by any one or several elements of Ni, Mn, Mg, Al, Zr, W, F, B, Cr, Mo, and rare earth elements.

[0012] Optionally, the compound shown in Structural Formula 1 includes at least one of the following compounds: .

[0013] Optionally, the electrolyte salt includes at least one of LiPF6, LiBOB, LiPO2F2, LiBF4, LiSbF6, LiAsF6, LiN(SO2F)2, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiC(SO2CF3)3, LiClO4, LiAlCl4, LiCF3SO3, LiSO3F, Li2B 10 Cl 10 , lithium chloroborane, lithium trioxalate phosphate, lithium lower aliphatic carboxylate with less than 4 carbon atoms, or lithium tetraphenylborate.

[0014] Optionally, the additive further includes a second additive, and the second additive includes at least one of cyclic sulfate compounds, sultone compounds, cyclic carbonate compounds, phosphate compounds, borate compounds, and nitrile compounds.

[0015] Optionally, the cyclic sulfate compounds are selected from at least one of ethylene sulfate, propylene sulfate, vinyl methyl sulfate, , ; and / or The sultone compounds include at least one of 1,3-propane sultone, 1,4-butane sultone, and 1,3-propene sultone; and / or The cyclic carbonate compounds include at least one of vinylene carbonate, ethylene ethylene carbonate, ethylene methylene carbonate, or the compound shown in Structural Formula 2: Structural Formula 2 In the Structural Formula 2, R 21 , R 22 , R 23 , R 24 , R 25 , R 26 are each independently selected from a hydrogen atom, a halogen atom, or a C1-C5 group; and / or The phosphate compounds include the compound shown in Structural Formula 3: Structural Formula 3 In the Structural Formula 3, R 31 , R 32 , R 33 are each independently selected from a C1-C5 saturated hydrocarbon group, a C1-C5 unsaturated hydrocarbon group, a C1-C5 halogenated hydrocarbon group, -Si(C m H 2m+1 )3, and m is a natural number from 1 to 3; and / or The borate compounds include at least one of tris(trimethylsilyl) borate and tris(triethylsilyl) borate; and / or The nitrile compounds include at least one of butanedinitrile, pentanedinitrile, hexanetricarbonitrile, adiponitrile, pimelonitrile, suberonitrile, azelaonitrile, and sebaconitrile.

[0016] According to the lithium-ion battery provided by the present invention, in a non-aqueous electrolyte, a sulfuric acid ester compound having a polycyclic structure is used as a first additive, and fluoroethylene carbonate is added at the same time. The inventors have found through a large amount of research that when the mass percentage content a of fluoroethylene carbonate in the non-aqueous electrolyte, the mass percentage content b of the first additive in the non-aqueous electrolyte, the evaporation rate c of the non-aqueous electrolyte at 80 °C, and the particle size distribution K90 of the positive electrode material satisfy the conditions 0.5 ≤ (a + 10c) / b - K90 ≤ 150, and 0.5 ≤ a ≤ 9, 0.1 ≤ b ≤ 3, 0.01 ≤ c ≤ 1.1, 0.1 ≤ K90 ≤ 25, the non-aqueous electrolyte in the obtained lithium-ion battery has high high-voltage stability and high-temperature stability, and can effectively improve the high-temperature cycle performance and high-temperature storage performance of the lithium-ion battery. Specifically, the first additive and the fluoroethylene carbonate can participate in the formation of the solid electrolyte interface film on the surfaces of the positive and negative electrodes during the battery formation stage. At high voltages, this solid electrolyte interface film is beneficial to suppressing the continuous decomposition and side reactions of the non-aqueous electrolyte at the positive and negative electrode interfaces, and improving the high-temperature stability of the non-aqueous electrolyte. At the same time, the volatile components of the non-aqueous electrolyte and the particle size distribution of the positive electrode material play a regulating role in the high-temperature stability and uniformity of the solid electrolyte interface film formed by the first additive and the fluoroethylene carbonate. By regulating the evaporation rate of the non-aqueous electrolyte at 80 °C and the particle size distribution K90 of the positive electrode material, it is beneficial to improve the binding stability of the decomposition products of the first additive and the fluorinated cyclic carbonate on the surfaces of the positive and negative electrodes and the uniformity of film formation at each position of the electrolytic interface, making the solid electrolyte interface film more stable at high temperatures and having a high ion conduction efficiency, and improving the high-temperature performance of the lithium-ion battery. Detailed implementation mode

[0017] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention clearer, the present invention will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0018] An embodiment of the present invention provides a lithium-ion battery, including a positive electrode, a negative electrode and a non-aqueous electrolyte. The positive electrode includes a positive electrode material layer containing a positive electrode material. The non-aqueous electrolyte includes a non-aqueous organic solvent, an electrolyte salt and an additive. The non-aqueous organic solvent includes fluoroethylene carbonate. The additive includes fluoroethylene carbonate and a first additive. The first additive includes a compound represented by Structural Formula 1: Structural Formula 1 Wherein, X is selected from or , and R1 and R2 are each independently selected from H, , or , R1 and R2 are not simultaneously selected from H, and at least one of X, R1, and R2 contains a sulfur atom; the lithium-ion battery satisfies the following conditions: 0.5 ≤ (a + 10c) / b - K90 ≤ 150, and 0.5 ≤ a ≤ 9, 0.1 ≤ b ≤ 3, 0.01 ≤ c ≤ 1.1, 0.1 ≤ K90 ≤ 25; wherein, a is the mass percentage content of vinylene carbonate fluoride in the non-aqueous electrolyte, in %; b is the mass percentage content of the first additive in the non-aqueous electrolyte, in %; c is the evaporation rate of the non-aqueous electrolyte at 80 °C, in mg / min; K90 is the particle size distribution of the positive electrode material, K90 = (D90 - D10) / D50.

[0019] The inventors found through a large number of studies that when the mass percentage content a of vinylene carbonate fluoride in the non-aqueous electrolyte, the mass percentage content b of the first additive in the non-aqueous electrolyte, the evaporation rate c of the non-aqueous electrolyte at 80 °C, and the particle size distribution K90 of the positive electrode material satisfy the conditions 0.5 ≤ (a + 10c) / b - K90 ≤ 150, and 0.5 ≤ a ≤ 9, 0.1 ≤ b ≤ 3, 0.01 ≤ c ≤ 1.1, 0.1 ≤ K90 ≤ 25, the non-aqueous electrolyte in the obtained lithium-ion battery has high high-voltage stability and high-temperature stability, and can effectively improve the high-temperature cycling performance and high-temperature storage performance of the lithium-ion battery. Specifically, the first additive and the vinylene carbonate fluoride can participate in the formation of the solid electrolyte interface film on the surfaces of the positive and negative electrodes during the battery formation stage. At high voltages, this solid electrolyte interface film is beneficial to inhibiting the continuous decomposition and side reactions of the non-aqueous electrolyte at the positive and negative electrode interfaces, and improving the high-temperature stability of the non-aqueous electrolyte. At the same time, the volatile components of the non-aqueous electrolyte and the particle size distribution of the positive electrode material play a role in regulating the high-temperature stability and uniformity of the solid electrolyte interface film formed by the first additive and the vinylene carbonate fluoride. By controlling the evaporation rate of the non-aqueous electrolyte at 80 °C and the particle size distribution K90 of the positive electrode material, it is beneficial to improve the binding stability of the decomposition products of the first additive and the fluorinated cyclic carbonate on the surfaces of the positive and negative electrodes and the uniformity of film formation at each position of the electrolytic interface, making the solid electrolyte interface film more stable at high temperatures and having a high ion conduction efficiency, and improving the high-temperature performance of the lithium-ion battery.

[0020] In a preferred embodiment, the lithium-ion battery satisfies the following conditions: 0.5 ≤ (a + 10c) / b - K90 ≤ 50.

[0021] When the mass percentage content a of vinylene fluorophosphate in the non-aqueous electrolyte, the mass percentage content b of the first additive in the non-aqueous electrolyte, the evaporation rate c of the non-aqueous electrolyte at 80 °C, and the particle size distribution K90 of the positive electrode material further satisfy the above conditions, it is beneficial to further improve the stability of the non-aqueous electrolyte at high temperatures, and is conducive to improving the capacity performance and service life of the lithium-ion battery at high temperatures.

[0022] In a specific embodiment, the mass percentage content a of vinylene fluorophosphate in the non-aqueous electrolyte can be 0.5%, 1%, 1.5%, 2%, 2.6%, 3%, 3.6%, 4%, 4.6%, 5%, 5.6%, 6%, 6.7%, 7%, 7.7%, 8%, 8.7%, 9% or a range between any two of them.

[0023] In a preferred embodiment, the mass percentage content a% of vinylene fluorophosphate in the non-aqueous electrolyte is 1% - 8%.

[0024] Vinylene fluorophosphate can participate in the formation of the solid electrolyte interface film on the surfaces of the positive and negative electrodes, providing the LiF component in the solid electrolyte interface film, which is beneficial to improving the cycle stability of the lithium-ion battery. Moreover, vinylene fluorophosphate itself can improve the high-voltage resistance performance of the non-aqueous electrolyte. However, vinylene fluorophosphate is unstable at high temperatures. If the content of vinylene fluorophosphate is too low, it is difficult to form a relatively stable solid electrolyte interface film; if the content of vinylene fluorophosphate is too high, since the electrolyte containing vinylene fluorophosphate will become unstable at high temperatures, more HF will be generated at high temperatures, which will cause the dissolution of the positive electrode transition metal elements and deposition on the negative electrode, resulting in electron leakage at the negative electrode, causing the electrolyte to continuously decompose on the surface of the negative electrode, and then consuming the active Li at the negative electrode, leading to the attenuation of the battery capacity.

[0025] In a specific embodiment, the mass percentage content b of the first additive in the non-aqueous electrolyte can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.5%, 3% or a range between any two of them.

[0026] In a preferred embodiment, the mass percentage content b% of the first additive in the non-aqueous electrolyte is 0.2% - 2%.

[0027] The first additive is used to cooperate with fluoroethylene carbonate to jointly form a solid electrolyte interface film and provide a sulfur-containing component part, which is beneficial to inhibiting the deposition of metal ions, inhibiting side reactions between the non-aqueous electrolyte and the positive and negative electrodes, and improving the high-temperature performance of the lithium-ion battery. If the mass percentage content b of the first additive is too low, it is difficult to significantly improve the high-temperature performance of the lithium-ion battery. If the mass percentage content b of the first additive is too high, the thickness of the solid electrolyte interface film will be too large, resulting in a large impedance of the lithium-ion battery.

[0028] In a specific embodiment, the evaporation rate c of the non-aqueous electrolyte at 80 °C can be 0.01 mg / min, 0.05 mg / min, 0.1 mg / min, 0.15 mg / min, 0.2 mg / min, 0.25 mg / min, 0.3 mg / min, 0.35 mg / min, 0.4 mg / min, 0.45 mg / min, 0.5 mg / min, 0.6 mg / min, 0.7 mg / min, 0.8 mg / min, 0.9 mg / min, 1 mg / min, 1.05 mg / min, 1.1 mg / min or the range between any two of them.

[0029] In a preferred embodiment, the evaporation rate c of the non-aqueous electrolyte at 80 °C is 0.01 - 1 mg / min.

[0030] By regulating the evaporation rate c of the non-aqueous electrolyte at 80 °C, the content of volatile components in the non-aqueous electrolyte can be regulated, and then the composition of the solid electrolyte interface film can be regulated to improve its stability at high temperature and high voltage. At the same time, the change of the composition of the electrolyte under high-temperature conditions can be inhibited, so as to ensure the stability of the electrolyte and improve the high-temperature performance of the battery. If the evaporation rate c of the non-aqueous electrolyte at 80 °C is too low, it means that the fluidity of the non-aqueous electrolyte is poor, which will inhibit ion migration, resulting in a decline in kinetic performance and a suppression of the battery discharge capacity, and the rate performance is poor. If the evaporation rate c of the non-aqueous electrolyte at 80 °C is too high, it will affect the high-temperature stability of the solid electrolyte interface film, and the components volatilized at high temperature are likely to have an adverse effect on the function of the lithium-ion battery.

[0031] The evaporation rate c of the non-aqueous electrolyte at 80 °C is mainly affected by the solvent composition, the selection and content of lithium salt, and the selection and content of additives.

[0032] Specifically, the evaporation rate of the non-aqueous electrolyte is related to the composition of the lithium salt, solvent, and additive in the non-aqueous electrolyte, and can be regulated by adjusting the types and contents of the lithium salt, solvent, and additive in the electrolyte. In terms of the type of lithium salt, highly dissociating lithium salts such as LiFSI have a poorer ability to bind with solvent molecules, the solvent is more likely to dissociate, and the evaporation rate of the electrolyte increases. In terms of the lithium salt concentration, the higher the lithium salt content, the greater the electrolyte concentration, and the lower the evaporation rate of the electrolyte. In terms of the type of solvent, low-boiling solvents are more likely to evaporate, and the higher the content of low-boiling solvents, the greater the evaporation rate of the electrolyte. Therefore, it is necessary to strictly control the ratio of high-boiling solvents and low-boiling solvents in the electrolyte. In terms of the type of additive, the addition of additives with stronger polarity such as FEC, VC, and nitriles will preferentially combine with lithium ions and anions, displacing solvent molecules, resulting in an increase in the number of free solvent molecules and an increase in the evaporation rate of the electrolyte. However, due to the high-boiling characteristics of the additive molecules themselves and the increase in electrolyte concentration when additives are added, the evaporation rate of the electrolyte will be reduced to a certain extent. Generally speaking, the evaporation rate of the electrolyte can be regulated by adjusting the types and contents of the lithium salt, solvent, and additive in the electrolyte.

[0033] In some embodiments, the test method for the evaporation rate c of the non-aqueous electrolyte at 80 °C is as follows: S1. In a thermogravimetric analyzer, pass the purge gas through the thermobalance at a rate of 20 mL / min with a deviation of ±5%; S2. At room temperature, bring the heating furnace and gas path to equilibrium and measure the tare weight of the balance; S3. Enclose the test sample in a crucible with a crucible lid having a small hole with a pore diameter of 0.2 mm, and the sample amount is 10 mg with a deviation of ±2 mg; S4. Place the crucible containing the test sample into the thermogravimetric analyzer and stabilize parameters such as temperature and gas flow within ±1% of the set value; S5. Heat the instrument to the set temperature of 80 °C and perform the test at a constant temperature at this temperature. The temperature fluctuation range is ±1 °C. During the constant temperature process, continuously record the change in the mass of the test sample over time. The time is set to 30 min. If the test sample evaporates too quickly, use the actual time as the standard, and at the same time record the change in the temperature (°C) of the test sample; S6. Calculate the evaporation rate according to the formula. The calculation formula is: c=(m i -m f ) / 30 c is the evaporation rate of the non-aqueous electrolyte at 80 °C, and the unit is mg / min; m i is the initial mass of the test sample, and the unit is mg; m f is the final mass of the test sample, and the unit is mg.

[0034] In a specific embodiment, the particle size distribution K90 of the positive electrode material may be 0.1, 1.3, 2.5, 3.7, 4.9, 6.1, 7.3, 8.5, 9.7, 10.9, 12.1, 13.3, 14.5, 15.7, 16.9, 18.1, 19.3, 20.5, 21.7, 22.9, 24.1, 25 or a range between any two of them.

[0035] In a preferred embodiment, the particle size distribution K90 of the positive electrode material is 0.2 to 15.

[0036] The particle size distribution K90 of the positive electrode material = (D90 - D10) / D50; where D90: the particle size corresponding to when the cumulative particle size distribution percentage of the positive electrode material reaches 90%, D50: the particle size corresponding to when the cumulative particle size distribution percentage of the positive electrode material reaches 50%, D10: the particle size corresponding to when the cumulative particle size distribution percentage of the positive electrode material reaches 10%.

[0037] In the present invention, the positive electrode material refers to all the materials contained in the positive electrode material layer, including the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder. Since the content of the positive electrode active material in the positive electrode material layer accounts for the majority, the D90, D5o, and D10 of the positive electrode material actually mainly reflect the D90, D50, and D10 of the positive electrode active material.

[0038] In some embodiments, the particle sizes D90, D50, and D10 of the positive electrode material can be obtained by testing with a laser particle size analyzer. The testing method is as follows: disassemble the battery, soak and clean the positive electrode sheet with dimethyl carbonate, place it in a glove box and dry it in vacuum for 24 h. Use a small spatula to scrape about 2 - 3 g of the powder of the material layer (excluding the current collector). After pretreatment, place the sample in the sample injection chamber of the laser particle size analyzer, ultrasonically disperse it sufficiently (≥20 min, with no significant sedimentation), and perform the test after the light shielding rate is stable.

[0039] The particle size distribution K90 of the positive electrode material is related to the particle distribution and the voids between particles in the positive electrode material layer. During the battery formation process, it affects the contact surface area between the non-aqueous electrolyte and the positive electrode material, as well as the penetration efficiency and mass exchange efficiency of the non-aqueous electrolyte in the positive electrode material layer. Furthermore, it has an impact on the replenishment of the first additive, fluoroethylene carbonate, consumed at the positive electrode interface during the formation process. When the particle size distribution K90 of the positive electrode material is within the above range, it is beneficial to improve the uniformity and denseness of the solid electrolyte interface film on the positive electrode surface, thereby enhancing its ion conduction efficiency and high-temperature stability.

[0040] In some embodiments, the positive electrode material includes a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder. Among them, the positive electrode active material includes at least one of the following materials: A nickel-containing material, wherein the nickel-containing material comprises a material with a molecular formula of Li q Ni x Co y M 1-x-y O 2-g R g or a Li q Ni x Co y M 1-x-y O 2-g R g material with a coating layer on its surface, wherein 0.9 ≤ q ≤ 1.2, 0.5 ≤ x ≤ 0.96, y > 0, 1 - x - y > 0, 0 ≤ g ≤ 1, M comprises one or both of Mn and Al, and zero, one or more of Sr, Mg, Ti, Ca, Zr, Zn, Si, Fe, B, Ga, Cr, W, V, Nb, Ce; and R comprises one or more of N, F, S and Cl; and / or, A phosphate material, wherein the phosphate material comprises a material with a molecular formula of Li r Mn α Fe β A 1-α-β PO 4-n G n or a Li r Mn α Fe β A 1-α-β PO 4-n G n material with a coating layer on its surface, wherein 0.9 ≤ r ≤ 1.1, 0 ≤ α ≤ 0.8, 0.2 ≤ β ≤ 1, 0 ≤ n ≤ 0.1, A is selected from one or more of Ti, Mg, V, Cr, Zr, Nb, Zn, Al, Na, K, Mo, W, Ni, Co, Ga, Sn, Sb, Ge and W; and G comprises one or more of N, F, S and Cl; and / or, A lithium cobaltate material, wherein the lithium cobaltate material comprises lithium cobaltate or lithium cobaltate doped and / or coated and modified with any one or several elements of Ni, Mn, Mg, Al, Zr, W, F, B, Cr, Mo and rare earth elements.

[0041] In some embodiments, the compound shown in Structural Formula 1 comprises at least one of the following compounds: 。

[0042] The compound represented by Structural Formula 1 has a polycyclic structure. Compared with the monocyclic structure, the polycyclic structures each open their rings to participate in the formation of the interfacial film on the electrode surface, and the formed interfacial film components are more stable and dense, which has the effect of improving the structural strength of the interfacial film, and thus is beneficial to enhancing its high-temperature stability.

[0043] In some embodiments, the electrolyte salt includes at least one of LiPF6, LiBOB, LiPO2F2, LiBF4, LiSbF6, LiAsF6, LiN(SO2F)2, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiC(SO2CF3)3, LiClO4, LiAlCl4, LiCF3SO3, LiSO3F, Li2B 10 Cl 10 , lithium chloroborane, lithium trioxalate phosphate, lithium lower aliphatic carboxylate having 4 or less carbon atoms, or lithium tetraphenylborate.

[0044] Based on the mass of the non-aqueous electrolyte being 100%, the mass content of the electrolyte salt is 12 wt% - 15 wt%.

[0045] In some embodiments, the additive further includes a second additive, and the second additive includes at least one of cyclic sulfate compounds, sultone compounds, cyclic carbonate compounds, phosphate compounds, borate compounds, and nitrile compounds.

[0046] Preferably, based on the total mass of the non-aqueous electrolyte being 100%, the content of the additive is 0.01% - 30%.

[0047] In some embodiments, the cyclic sulfate compounds are selected from at least one of ethylene sulfate, propylene sulfate, vinyl methyl sulfate, , .

[0048] In some embodiments, the sultone compounds include at least one of 1,3-propane sultone, 1,4-butane sultone, and 1,3-propene sultone.

[0049] In some embodiments, the cyclic carbonate compounds include at least one of vinylene carbonate, ethylene vinylene carbonate, methylene vinylene carbonate, or the compound represented by Structural Formula 2: Structural Formula 2 In Structural Formula 2, R 21 , R 22 , R 23 , R 24 , R 25 , R26 Each independently selected from a hydrogen atom, a halogen atom, and a C1-C5 group.

[0050] In some embodiments, the phosphate compound includes the compound shown in Structural Formula 3: Structural Formula 3 In the Structural Formula 3, 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, and m is a natural number from 1 to 3.

[0051] In a preferred embodiment, the phosphate compound shown in Structural Formula 3 may be at least one of tris(trimethylsilyl) phosphate, tris(triethylsilyl) phosphate, tripropargyl 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, diallyl hexafluoroisopropyl phosphate.

[0052] In some embodiments, the borate compound includes at least one of tris(trimethylsilyl) borate and tris(triethylsilyl) borate.

[0053] In some embodiments, the nitrile compound includes at least one of succinonitrile, glutaronitrile, hexane trinitrile, adiponitrile, pimelonitrile, suberonitrile, azelaonitrile, sebaconitrile.

[0054] In other embodiments, the additive may further include other additives that can improve battery performance: for example, additives that enhance battery safety performance, specifically flame retardant additives such as fluorophosphate and cyclophosphazene, or overcharge prevention additives such as tert-amylbenzene and tert-butylbenzene.

[0055] It should be noted that, unless otherwise specified, generally, the content of any optional substance in the additive in the non-aqueous electrolyte is below 10%, preferably, the content is 0.1% - 5%, and more preferably, the content is 0.1% - 2%. Specifically, the content of any optional substance in the additive can be 0.05%, 0.08%, 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 7.8%, 8%, 8.5%, 9%, 9.5%, 10%.

[0056] In some embodiments, the positive electrode binder includes at least one of polyvinylidene fluoride, copolymers of vinylidene fluoride, polytetrafluoroethylene, copolymers of vinylidene fluoride - hexafluoropropylene, copolymers of tetrafluoroethylene - hexafluoropropylene, copolymers of tetrafluoroethylene - perfluoroalkyl vinyl ether, copolymers of ethylene - tetrafluoroethylene, copolymers of vinylidene fluoride - tetrafluoroethylene, copolymers of vinylidene fluoride - trifluoroethylene, copolymers of vinylidene fluoride - trichloroethylene, copolymers of vinylidene fluoride - fluoroethylene, copolymers of vinylidene fluoride - hexafluoropropylene - tetrafluoroethylene, thermoplastic polyimides, thermoplastic resins such as polyethylene and polypropylene; acrylic resins; and styrene - butadiene rubber.

[0057] The positive electrode conductive agent includes at least one of conductive carbon black, conductive carbon spheres, conductive graphite, conductive carbon fibers, carbon nanotubes, graphene, or reduced graphene oxide.

[0058] In some embodiments, the positive electrode further includes a positive electrode current collector, the positive electrode material layer is located on the surface of the positive electrode current collector, the positive electrode current collector includes 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, and in a more preferred embodiment, the positive electrode current collector is selected from aluminum foil.

[0059] In some embodiments, the negative electrode includes a negative electrode material layer, the negative electrode material layer includes a negative electrode active material, and the negative electrode active material includes at least one of carbon - based negative electrodes, silicon - based negative electrodes, tin - based negative electrodes, and lithium negative electrodes. Among them, the carbon - based negative electrode can include graphite, hard carbon, soft carbon, graphene, mesophase carbon microspheres, etc.; the silicon - based negative electrode can include silicon materials, silicon oxides, silicon - carbon composite materials, and silicon alloy materials, etc.; the tin - based negative electrode can include tin, tin - carbon, tin - oxygen, tin metal compounds; the lithium negative electrode can include metallic lithium or lithium alloys. The lithium alloy can specifically be at least one of lithium - silicon alloy, lithium - sodium alloy, lithium - potassium alloy, lithium - aluminum alloy, lithium - tin alloy, and lithium - indium alloy.

[0060] In some embodiments, the negative electrode active material includes at least one of graphite, hard carbon, soft carbon, graphene, and silicon-carbon composite materials.

[0061] 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.

[0062] In some embodiments, the negative electrode further includes a negative electrode current collector, and the negative electrode material layer covers the surface of the negative electrode current collector. The negative electrode current collector includes a metal material capable of conducting 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 foils.

[0063] In some embodiments, the negative electrode material layer further includes a negative electrode binder and a negative electrode conductive agent, and the negative electrode active material, the negative electrode binder, and the negative electrode conductive agent are blended to obtain the negative electrode material layer.

[0064] The negative electrode binder includes at least one of thermoplastic resins such as polyvinylidene fluoride, copolymers of vinylidene fluoride, polytetrafluoroethylene, copolymers of vinylidene fluoride - hexafluoropropylene, copolymers of tetrafluoroethylene - hexafluoropropylene, copolymers of tetrafluoroethylene - perfluoroalkyl vinyl ether, copolymers of ethylene - tetrafluoroethylene, copolymers of vinylidene fluoride - tetrafluoroethylene, copolymers of vinylidene fluoride - trifluoroethylene, copolymers of vinylidene fluoride - trichloroethylene, copolymers of vinylidene fluoride - fluoroethylene, copolymers of vinylidene fluoride - hexafluoropropylene - tetrafluoroethylene, thermoplastic polyimide, polyethylene, and polypropylene; acrylic resins; and styrene butadiene rubber.

[0065] The negative electrode conductive agent includes at least one of conductive carbon black, conductive carbon spheres, conductive graphite, conductive carbon fibers, carbon nanotubes, graphene, or reduced graphene oxide.

[0066] In some embodiments, the secondary battery further includes a separator, and the separator is located between the positive electrode and the negative electrode.

[0067] The separator can be an existing conventional separator, which can be a ceramic separator, a polymer separator, a non-woven fabric, an inorganic-organic composite separator, etc., including but not limited to single-layer PP (polypropylene), single-layer PE (polyethylene), double-layer PP / PE, double-layer PP / PP, and triple-layer PP / PE / PP separators.

[0068] The present invention will be further described below through examples.

[0069] Table 1 In Table 1, PC is propylene carbonate, EP is ethyl propionate, DFEA is ethyl 2,2-difluoroacetate, PP is propyl propionate, DEC is diethyl carbonate, EMC is ethyl methyl carbonate, EC is ethylene carbonate, LiPO2F2 is lithium difluorophosphate, LiFSI is lithium bis(fluorosulfonyl)imide, and PS is 1,3-propane sultone.

[0070] Example 1 This example is used to illustrate the lithium-ion battery and its preparation method disclosed in the present invention, and includes the following operating steps: 1) Preparation of non-aqueous electrolyte: Lithium hexafluorophosphate (LiPF6) is added to a non-aqueous organic solvent until the molar concentration reaches 1.05 mol / L, and then additives with the mass percentage content shown in Table 1 are added. Among them, the solvent composition in the non-aqueous organic solvent is shown in Table 1.

[0071] The evaporation rate of the non-aqueous electrolyte at 80 °C is detected and recorded in Table 1. The test method is as follows: 1. The purge gas passes through the thermogravimetric balance at a rate of 20 mL / min with a deviation of ±5%.

[0072] 2. The heating furnace and the gas path are brought to equilibrium at room temperature, and the tare weight of the balance is measured.

[0073] 3. 10 mg of the sample is encapsulated in a crucible with a crucible lid having specific small holes (hole diameter 0.2 mm).

[0074] 4. The crucible containing the sample is placed in a thermogravimetric analyzer, and parameters such as temperature and gas flow are stabilized within ±1% of the set value.

[0075] 5. The heating instrument is heated to the set temperature of 80 °C, and the test is carried out at a constant temperature at this temperature. The temperature fluctuation range is ±1 °C. During the constant temperature process, the change in the mass (mg) of the sample with time is continuously recorded. The time is set to 30 min. If the sample evaporates too fast, the actual time shall prevail. At the same time, the change in the sample temperature (°C) is recorded.

[0076] 6. The heating furnace is cooled down, and the crucible containing the sample is taken out.

[0077] 7. Calculate the evaporation rate according to the formula. The calculation formula is: c=(m i -m f ) / 30 c is the evaporation rate of the non-aqueous electrolyte at 80 °C, and the unit is mg / min; m iis the initial mass of the sample, in mg; m f is the final mass of the sample, in mg.

[0078] 2) Preparation of the positive electrode: Mix the positive electrode active material lithium cobalt oxide LiCoO2, conductive carbon black Super-P, and binder polyvinylidene fluoride (PVDF) in a mass ratio of 93:4:3, and then disperse them in N-methyl-2-pyrrolidone (NMP) to obtain a positive electrode slurry. The particle size distribution of the positive electrode material is shown in Table 1. Coat the slurry evenly on both sides of the aluminum foil, dry, calender, and vacuum dry it, and then weld an aluminum lead wire with an ultrasonic welder to obtain a positive electrode plate. The thickness of the electrode plate is between 120-150 μm.

[0079] 3) Preparation of the negative electrode: Mix the negative electrode active material artificial graphite, conductive carbon black Super-P, binder styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) in a mass ratio of 94:1:2.5:2.5, and then disperse them in deionized water to obtain a negative electrode slurry. Coat the slurry on both sides of the copper foil, dry, calender, and vacuum dry it, and then weld a nickel lead wire with an ultrasonic welder to obtain a negative electrode plate. The thickness of the electrode plate is between 120-150 μm.

[0080] 4) Preparation of the battery cell: Place a three-layer separator with a thickness of 20 μm between the positive electrode plate and the negative electrode plate, then stack the sandwich structure composed of the positive electrode plate, negative electrode plate, and separator, and then put it into an aluminum foil packaging bag and vacuum bake it at 75 °C for 48 h to obtain a battery cell to be filled with electrolyte.

[0081] 5) Filling and formation of the battery cell: In a glove box with the dew point controlled below -40 °C, inject the electrolyte prepared above into the battery cell, vacuum package it, and let it stand for 24 h.

[0082] Then carry out the conventional formation of the first charge according to the following steps: constant current charge at 0.05C for 180 min, constant current charge at 0.2C until 3.95V, secondary vacuum sealing, and then further constant current charge at 0.2C until 4.5V. After standing at room temperature for 24 hr, discharge at a constant current of 0.2C until 3.0 V.

[0083] Examples 2 to 31 Examples 2 to 31 are used to illustrate the lithium-ion battery and its preparation method disclosed in the present invention, including most of the operation steps in Example 1. The differences are as follows: Using the solvent and additive composition shown in Table 1, the evaporation rate of the non-aqueous electrolyte at 80 °C is recorded in Table 1; The particle size distribution of the positive electrode material is as shown in Table 1.

[0084] Comparative Examples 1-22 Comparative Examples 1-22 are used to illustrate the lithium-ion battery and its preparation method disclosed in the present invention, including most of the operating steps in Example 1, and the differences are as follows: Using the solvent and additive composition shown in Table 1, the evaporation rate of the non-aqueous electrolyte at 80 °C is recorded in Table 1; The particle size distribution of the positive electrode material is as shown in Table 1.

[0085] Performance Test 1. 60 °C Storage Test The lithium-ion battery after formation is charged at a constant current of 1C to 4.5V at room temperature, and then charged at a constant voltage until the current drops to 0.02C. Measure the initial discharge capacity of the battery, and then store it in an environment of 60 °C for 30 days, and discharge it to 3V at 1C. Calculate the swelling rate after 30 days of storage at 60 °C and the impedance growth rate after 30 days of storage at 60 °C through the following formula: Swelling rate after 30 days of storage at 60 °C (%) = (battery volume after storage - battery volume before storage) / battery volume before storage × 100%; Impedance growth rate after 30 days of storage at 60 °C (%) = (internal resistance of the battery after storage - internal resistance of the battery before storage) / internal resistance of the battery before storage × 100%.

[0086] 2. 45 °C Cycle Performance Test The lithium-ion battery is placed in a constant temperature environment of 45 °C, charged at a constant current of 1C to 4.5V, then charged at a constant voltage until the current drops to 0.02C, and then discharged at a constant current of 1C to 3.0V. Repeat this cycle 500 times. Calculate the swelling rate during the 45 °C cycle, the capacity retention rate during the 45 °C cycle, and the impedance growth rate during the 45 °C cycle according to the following formula: Swelling rate during the 45 °C cycle (%) = (battery volume after cycling - battery volume before cycling) / battery volume before cycling × 100%; Capacity retention rate of the battery during the 45 °C cycle (%) = discharge capacity of the last time / discharge capacity of the first time × 100%; Impedance growth rate during the 45 °C cycle (%) = (internal resistance of the battery after cycling - internal resistance of the battery before cycling) / internal resistance of the battery before cycling × 100%.

[0087] (1) The test results obtained from Examples 1-28 and Comparative Examples 1, 5-22 are filled in Table 2.

[0088] Table 2 From the test results of Examples 1 to 28 and Comparative Examples 1, 5 to 22, it can be seen that by adding a first additive and vinylene carbonate fluoride to the non-aqueous electrolyte simultaneously, and controlling the mass percentage content a of vinylene carbonate fluoride in the non-aqueous electrolyte, the mass percentage content b of the first additive in the non-aqueous electrolyte, the evaporation rate c of the non-aqueous electrolyte at 80 °C, and the particle size distribution K90 of the positive electrode material, so that the conditions 0.5 ≤ (a + 10c) / b - K90 ≤ 150, and 0.5 ≤ a ≤ 9, 0.1 ≤ b ≤ 3, 0.01 ≤ c ≤ 1.1, 0.1 ≤ K90 ≤ 25 are satisfied, the lithium-ion battery prepared shows a high capacity retention rate, a low impedance growth rate, and a low swelling rate during high-temperature storage and high-temperature charge-discharge cycling. It is speculated that this is because during the battery formation stage, the first additive and vinylene carbonate fluoride participate in the construction process of the solid electrolyte interface film on the surfaces of the positive and negative electrodes. Under high-voltage conditions, the formed solid electrolyte interface film can effectively inhibit the continuous decomposition of the non-aqueous electrolyte at the positive and negative electrode interfaces, reduce the occurrence of side reactions, and significantly enhance the high-temperature stability of the non-aqueous electrolyte. At the same time, the content of volatile components in the non-aqueous electrolyte and the particle size distribution of the positive electrode material play an important role in regulating the high-temperature stability and uniformity of the solid electrolyte interface film formed by the first additive and vinylene carbonate fluoride. By precisely controlling the evaporation rate of the non-aqueous electrolyte at 80 °C and reasonably controlling the particle size distribution parameter K90 of the positive electrode material, the binding strength of the decomposition products of the first additive and the fluorinated cyclic carbonate on the surfaces of the positive and negative electrodes can be improved, promoting more uniform film formation at each position of the electrolytic interface, and further enabling the solid electrolyte interface film to maintain higher stability and better ion conduction efficiency at high temperatures, ultimately achieving an overall improvement in the high-temperature performance of the lithium-ion battery.

[0089] From the comparison of the test results of Examples 1 to 28, it can be seen that when the mass percentage content a of vinylene carbonate fluoride in the non-aqueous electrolyte, the mass percentage content b of the first additive in the non-aqueous electrolyte, the evaporation rate c of the non-aqueous electrolyte at 80 °C, and the particle size distribution K90 of the positive electrode material further satisfy the conditions 0.5 ≤ (a + 10c) / b - K90 ≤ 50, and 1 ≤ a ≤ 8, 0.2 ≤ b ≤ 2, 0.01 ≤ c ≤ 1, 0.2 ≤ K90 ≤ 15, the high-temperature storage performance and high-temperature cycling performance of the lithium-ion battery can be further improved.

[0090] From the test results of Comparative Examples 3-12, if the mass percentage content a of vinylene carbonate fluoride in the non-aqueous electrolyte, the mass percentage content b of the first additive in the non-aqueous electrolyte, the evaporation rate c of the non-aqueous electrolyte at 80 °C, and the particle size distribution K90 of the positive electrode material are not within their respective specified ranges (0.5 ≤ a ≤ 9, 0.1 ≤ b ≤ 3, 0.01 ≤ c ≤ 1.1, 0.1 ≤ K90 ≤ 25), even if the condition 0.5 ≤ (a + 10c) / b - K90 ≤ 150 is satisfied, the prepared lithium-ion battery performs poorly in terms of high-temperature storage performance and high-temperature cycling performance. This indicates that whether it is the value of a, b, c, or K90, being too high or too low is not conducive to improving the high-temperature electrochemical performance of the lithium-ion battery. From the test results of Comparative Examples 13-22, it can be found that when the values of a, b, c, and K90 do not satisfy the limit of 0.5 ≤ (a + 10c) / b - K90 ≤ 150, even if they each satisfy the corresponding content range, the high-temperature storage capacity retention rate and high-temperature cycling capacity retention rate of the lithium-ion battery will still decrease, and the impedance will also increase, indicating that there is an interaction between the mass percentage content a of vinylene carbonate fluoride in the non-aqueous electrolyte, the mass percentage content b of the first additive in the non-aqueous electrolyte, the evaporation rate c of the non-aqueous electrolyte at 80 °C, and the particle size distribution K90 of the positive electrode material. Only when these four reach a good balance state can the performance of the lithium-ion battery be significantly improved.

[0091] (2) The test results obtained from Examples 1, 29-31 and Comparative Examples 2-4 are filled in Table 3.

[0092] Table 3 From the test results of Example 1 and Comparative Examples 1-4, it can be seen that replacing the first additive with other additives (lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, or 1,3-propane sultone) cannot play a role similar to that of the first additive, indicating that the role of the limiting relationship 0.5 ≤ (a + 10c) / b - K90 ≤ 150 in improving the performance of the lithium-ion battery is highly correlated with the structure of the first additive.

[0093] From the test results of Example 1 and Examples 29-31, it can be seen that in the battery system provided by the present invention, further adding lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, or 1,3-propane sultone can further reduce the impedance growth rate and gas expansion rate of the lithium-ion battery, indicating that lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, or 1,3-propane sultone can play a further enhancing role in the battery system provided by the present invention.

[0094] Examples 32-37 Examples 32 to 37 are used to illustrate the lithium-ion battery and its preparation method disclosed in the present invention, including most of the operation steps in Example 1, and the differences are as follows: The types of positive electrode active materials shown in Table 4 are adopted.

[0095] Fill the test results obtained in Example 1 and Examples 32 to 37 into Table 4.

[0096] Table 4 It can be seen from the test results of Example 1 and Examples 32 to 37 that in the battery system provided by the present invention, when the conditions 0.5 ≤ (a + 10c) / b - K90 ≤ 150, 0.5 ≤ a ≤ 9, 0.1 ≤ b ≤ 3, 0.01 ≤ c ≤ 1.1, and 0.1 ≤ K90 ≤ 25 are satisfied, using different positive electrode active materials has a certain improvement effect on the high-temperature storage performance and high-temperature cycling performance of the lithium-ion battery, indicating that the battery system of the present invention has universality for different positive electrode active materials.

[0097] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A lithium-ion battery, characterized in that, It includes a positive electrode, a negative electrode and a non-aqueous electrolyte. The positive electrode includes a positive electrode material layer containing a positive electrode material. The non-aqueous electrolyte includes a non-aqueous organic solvent, an electrolyte salt and an additive. The additive includes fluoroethylene carbonate and a first additive. The first additive includes a compound represented by Structural Formula 1: Structural Formula 1 wherein, X is selected from or , R1 and R2 are each independently selected from H, , or , R1 and R2 are not simultaneously selected from H, and at least one of X, R1, and R2 contains a sulfur atom; The lithium-ion battery satisfies the following conditions: 0.5 ≤ (a + 10c) / b - K90 ≤ 150, and 0.5 ≤ a ≤ 9, 0.1 ≤ b ≤ 3, 0.01 ≤ c ≤ 1.1, 0.1 ≤ K90 ≤ 25; Wherein, a is the mass percentage content of fluoroethylene carbonate in the non-aqueous electrolyte, with the unit of %; b is the mass percentage content of the first additive in the non-aqueous electrolyte, with the unit of %; c is the evaporation rate of the non-aqueous electrolyte at 80 °C, with the unit of mg / min; K90 is the particle size distribution of the positive electrode material, K90 = (D90 - D10) / D50.

2. The lithium-ion battery according to claim 1, characterized in that, The lithium-ion battery satisfies the following conditions: 0.5 ≤ (a + 10c) / b - K90 ≤ 50.

3. The lithium ion battery according to claim 1, wherein, The mass percentage content a% of fluoroethylene carbonate in the non-aqueous electrolyte is 1% - 8%.

4. The lithium-ion battery according to claim 1, characterized in that, The mass percentage content b% of the first additive in the non-aqueous electrolyte is 0.2% - 2%.

5. The lithium-ion battery according to claim 1, characterized in that, The evaporation rate c of the non-aqueous electrolyte at 80 °C is 0.01 - 1 mg / min.

6. The lithium-ion battery according to claim 1, characterized in that, The particle size distribution K90 of the positive electrode material is 0.2 - 15.

7. The lithium ion battery according to claim 1, characterized in that, The positive electrode material includes a positive electrode active material, a positive electrode conductive agent and a positive electrode binder. Among them, the positive electrode active material includes at least one of the following materials: A nickel-containing material, the nickel-containing material comprising a material having the formula Li q Ni x Co y M 1-x-y O 2-g R g or a Li q Ni x Co y M 1-x-y O 2-g R g material with a coating layer provided on its surface, wherein 0.9 ≤ q ≤ 1.2, 0.5 ≤ x ≤ 0.96, y > 0, 1 - x - y > 0, 0 ≤ g ≤ 1, M includes one or both of Mn and Al, and includes zero, one or more of Sr, Mg, Ti, Ca, Zr, Zn, Si, Fe, B, Ga, Cr, W, V, Nb, Ce; and / or, A phosphate material, the phosphate material comprising a material having the formula Li r Mn α Fe β A 1-α-β PO 4-n G n or a Li r Mn α Fe β A 1-α-β PO 4-n G n material having a coating layer provided on a surface thereof, wherein 0.9 ≤ r ≤ 1.1, 0 ≤ α ≤ 0.8, 0.2 ≤ β ≤ 1, 0 ≤ n ≤ 0.1, A is selected from one or more of Ti, Mg, V, Cr, Zr, Nb, Zn, Al, Na, K, Mo, W, Ni, Co, Ga, Sn, Sb, Ge, and W; and / or, Lithium cobaltate material, the lithium cobaltate material includes lithium cobaltate or lithium cobaltate doped and / or coated and modified by any one or several elements of Ni, Mn, Mg, Al, Zr, W, F, B, Cr, Mo and rare earth elements.

8. The lithium-ion battery according to claim 1, wherein, The compound represented by Structural Formula 1 includes at least one of the following compounds:

9. The lithium ion battery according to claim 1, characterized in that, The electrolyte salts include at least one of LiPF6, LiBOB, LiPO2F2, LiBF4, LiSbF6, LiAsF6, LiN(SO2F)2, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiC(SO2CF3)3, LiClO4, LiAlCl4, LiCF3SO3, LiSO3F, Li2B 10 Cl 10 , lithium chloroborate, lithium trioxalate phosphate, lithium lower aliphatic carboxylate having 4 or less carbon atoms, or lithium tetraphenylborate.

10. The lithium ion battery according to claim 1, characterized in that, The additive further includes a second additive. The second additive includes at least one of cyclic sulfate compounds, sultone compounds, cyclic carbonate compounds, phosphate compounds, borate compounds and nitrile compounds; The cyclic sulfate compound is selected from at least one of ethylene sulfate, propylene sulfate, vinyl methyl sulfate, , ; and / or, The sultone compounds include at least one of 1,3-propane sultone, 1,4-butane sultone, 1,3-propene sultone; and / or, The cyclic carbonate compounds include at least one of vinylene carbonate, ethylene vinylene carbonate, methylene vinylene carbonate or the compound represented by Structural Formula 2: Structural Formula 2 In the said structural formula 2, R 21 , R 22 , R 23 , R 24 , R 25 , R 26 are each independently selected from a hydrogen atom, a halogen atom, and a C1-C5 group; and / or, The phosphate compounds include the compound represented by Structural Formula 3: Structural Formula 3 In the said structural formula 3, R 31 , R 32 , R 33 are each independently selected from a saturated hydrocarbon group having 1 to 5 carbon atoms, an unsaturated hydrocarbon group having 1 to 5 carbon atoms, a halogenated hydrocarbon group having 1 to 5 carbon atoms, -Si(C m H 2m+1 )3, m is a natural number from 1 to 3; and / or, The borate compounds include at least one of tris(trimethylsilyl) borate and tris(triethylsilyl) borate; and / or, The nitrile compounds include at least one of succinonitrile, glutarodinitrile, hexanetricarbonitrile, adiponitrile, pimelonitrile, suberonitrile, azelaonitrile, sebaconitrile.

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