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EP-4468440-B1 - NON-AQUEOUS ELECTROLYTE SOLUTION AND SECONDARY BATTERY

EP4468440B1EP 4468440 B1EP4468440 B1EP 4468440B1EP-4468440-B1

Inventors

  • QIAN, Yunxian
  • LIU, Zhongbo
  • HU, Shiguang
  • DENG, YONGHONG
  • WANG, YONG
  • HUANG, Xiong

Dates

Publication Date
20260506
Application Date
20221207

Claims (15)

  1. A non-aqueous electrolyte, comprising an electrolyte salt, a non-aqueous organic solvent, and an additive, wherein the non-aqueous organic solvent comprises a carboxylate, and the additive comprises a compound represented by formula 1: where n is 0 or 1, A is selected from C or O, X is selected from or R 1 and R 2 are each independently selected from H, R 1 and R 2 are not selected from H simultaneously, and X, R 1 and R 2 at least contain one sulfur atom; wherein the non-aqueous electrolyte satisfies following conditions: 0.02 ≤ an/m ≤ 9, 0.01% ≤ a ≤ 5%, 5% ≤ m ≤ 70%, and 8% ≤ n ≤ 25%; where a is a mass percentage content of the compound represented by the formula 1 in the non-aqueous electrolyte, in %; m is a mass percentage content of the carboxylate in the non-aqueous electrolyte, in %; and n is a mass percentage content of the electrolyte salt in the non-aqueous electrolyte, in %; wherein a conductivity of the non-aqueous electrolyte at 25°C is greater than or equal to 5mS/cm.
  2. The non-aqueous electrolyte of claim 1, wherein the non-aqueous electrolyte satisfies a following condition: 0.2 ≤ an / m ≤ 4 .
  3. The non-aqueous electrolyte of claim 1, wherein the mass percentage content a of the compound represented by the formula 1 in the non-aqueous electrolyte is 0.05% to 3%.
  4. The non-aqueous electrolyte of claim 1, wherein the mass percentage content m of the carboxylate in the non-aqueous electrolyte is 10% to 60%.
  5. The non-aqueous electrolyte of claim 1, wherein the mass percentage content n of the electrolyte salt in the non-aqueous electrolyte is 10% to 20%.
  6. The non-aqueous electrolyte of claim 5, wherein the electrolyte salt is selected from one or more of: LiPF 6 , LiPO 2 F 2 , LiBF 4 , LiClO 4 , LiCF 3 SO 3 , LiN(SO 2 CF 3 ) 2 and LiN(SO 2 F) 2 .
  7. The non-aqueous electrolyte of claim 1, wherein the compound represented by the formula 1 is selected from one or more of following compounds 1-22:
  8. The non-aqueous electrolyte of claim 1, wherein the carboxylate comprises one or more of: methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, 2,2-difluoroethyl acetate, methyl butyrate, methyl isobutyrate, methyl trimethylacetate and ethyl trimethylacetate.
  9. The non-aqueous electrolyte of claim 1, further comprising an auxiliary additive, wherein the auxiliary additive comprises at least one of: a cyclic sulfate compound, a sultone compound, a cyclic carbonate compound, an unsaturated phosphate compound, a nitrile compound and a lithium oxalate borate.
  10. The non-aqueous electrolyte of claim 9, wherein the auxiliary additive is added in an amount of 0.01% to 30% based on a total mass of the non-aqueous electrolyte as 100%.
  11. The non-aqueous electrolyte of claim 9, wherein the cyclic sulfate compound is selected from at least one of: ethylene sulfate, propene sulfate or methyl ethylene sulfate; wherein the sultone compound is selected from at least one of: 1,3-propane sultone, 1,4-butane sultone or 1,3-propene sultone; or wherein the cyclic carbonate compound is selected from at least one of: vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate or a compound represented by formula 2, in the formula 2, R 21 , R 22 , R 23 , R 24 , R 25 and R 26 are each independently selected from one of: a hydrogen atom, a halogen atom or a C1-C5 group.
  12. The non-aqueous electrolyte of claim 9, wherein the unsaturated phosphate compound is selected from at least one of compounds represented by formula 3: in the formula 3, R 31 , R 32 and R 33 are each independently selected from a C1-C5 saturated hydrocarbon group, an unsaturated hydrocarbon group, a halogenated hydrocarbon group and -Si(C m H 2m+1 ) 3 , where m is a natural number of 1 to 3, and at least one of R 31 , R 32 and R 33 is an unsaturated hydrocarbon group; wherein the nitrile compound is selected from one or more of: succinonitrile, glutaronitrile, ethylene glycol bis(propionitrile)ether, hexane trinitrile, adiponitrile, pimelonitrile, suberonitrile, azelanitrile and sebaconitrile; or wherein the lithium oxalate borate is selected from one or more of: Li[B(C 2 O 4 ) 2 ] and Li[B(C 2 O 4 )F 2 ].
  13. The non-aqueous electrolyte of claim 1, wherein the non-aqueous organic solvent further comprises one or more of: cyclic carbonates, linear carbonates and ethers.
  14. The non-aqueous electrolyte of claim 13, wherein the cyclic carbonates comprise one or more of: vinylene carbonate, propene carbonate and ethylene carbonate; the linear carbonates comprise one or more of: dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate; or the ethers comprise one or more of: glycol dimethyl ether, 1,3-dioxolane and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropylether.
  15. A secondary battery, comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte according to any one of claims 1 to 14, wherein the positive electrode comprises a positive electrode material layer, and a compaction density of the positive electrode material layer is 3.5g/cm 3 or more, and the negative electrode comprises a negative electrode material layer, and a compaction density of the negative electrode material layer is 1.5g/cm 3 or more.

Description

FIELD The present invention relates to the technical field of energy storage battery devices, and more particularly to a non-aqueous electrolyte and a secondary battery. BACKGROUND A lithium-ion battery has been widely used in the field of 3C digital products such as mobile phones and notebook computers, as well as in the field of new energy vehicles due to its advantages of high operating voltage, wide operating temperature range, high energy density and power density, no memory effect and long cycle life. In recent years, with a continuous development of light and thin 3C digital products, a demand for a high energy density of the lithium-ion battery in a battery industry is higher and higher. At the same time, for a user side, fast charging has become a basic requirement of a battery. Therefore, there is an urgent need to increase an energy density of lithium-ion battery and improve a fast charging performance. CN112349961A discloses a non-aqueous electrolyte, comprising LiPF6, a mixture of ethylene carbonate (EC), propylene carbonate (PC) diethyl carbonate (DEC) and an additive. At present, there are mainly two ways to increase an energy density of a battery. One way is to increase a cutoff charge voltage of a positive electrode, and the other way is to pressurize an electrode active material layer to achieve a high density. However, after the cutoff charge voltage of the positive electrode is increased, the activity of the positive electrode is further improved. A side reaction between the positive electrode and an electrolyte is also exacerbated, resulting in the dissolution of transition metal ions at the positive electrode, thus resulting in the deterioration of a cycle performance of the battery. In addition, by using a high compaction electrode, a load of an electrode sheet may be improved, thus improving an overall energy density of the battery. However, due to a low porosity of the high compaction electrode, a liquid retention capacity of the battery is also reduced, so that the electrolyte is difficult to penetrate at an interface of the electrode sheet with a low porosity, thus increasing a contact internal resistance between the electrolyte and the electrode. The polarization of charge and discharge becomes larger during long term cycling, resulting in a sudden dive due to lithium precipitation. A lithium ion conduction channel of a high compaction electrode sheet is tortuous, resulting in difficulty in lithium ion transmission, so that a fast charging performance of the battery is very poor. To sum up, the way of increasing the energy density in the existing technology leads to the deterioration of the cycle performance and fast charging performance of the battery. Therefore, how to enable a high-voltage and high compaction lithium-ion battery to have good fast charging performance is an industry problem, which needs to be improved from various aspects such as an electrode material and an electrolyte. From the perspective of electrolyte, in the prior art, a carboxylate system with a high dielectric constant and a small viscosity is often selected as a solvent to improve the fast charging performance of the battery. However, the carboxylate is unstable under a high voltage and tends to generate decomposition products at a positive electrode side. The decomposition products migrate to a negative electrode to be reduced, and accumulate on a surface of the negative electrode, resulting in the increase of an impedance of the battery and rapid deterioration in later stages of the cycle. Therefore, it is urgent to improve the fast charging performance of the battery from the perspective of electrolyte. SUMMARY In view of a problem that it is difficult to combine an energy density, a cycle performance and a fast charging performance of an existing secondary battery, the present invention provides a non-aqueous electrolyte and a secondary battery. The technical solution used in the present invention to solve the above-mentioned technical problem is as follows. On the one hand, the present invention provides a non-aqueous electrolyte. The non-aqueous electrolyte includes an electrolyte salt, a non-aqueous organic solvent, and an additive. The non-aqueous organic solvent includes a carboxylate, and the additive includes a compound represented by formula 1: where n is 0 or 1, A is selected from C or O, X is selected from or R1 and R2 are each independently selected from H, R1 and R2 are not selected from H simultaneously, and X, R1 and R2 at least contain one sulfur atom. The non-aqueous electrolyte satisfies following conditions: 0.02 ≤ an/m ≤ 9, 0.01% ≤ a ≤ 5%, 5% ≤ m ≤ 70%, and 8% ≤ n ≤ 25%; where a is a mass percentage content of the compound represented by the formula 1 in the non-aqueous electrolyte, in %;m is a mass percentage content of the carboxylate in the non-aqueous electrolyte, in %; andn is a mass percentage content of the electrolyte salt in the non-aqueous electrolyte, in %. A cond