An electrolyte additive, an electrolyte comprising the same, and a lithium-ion secondary battery and use thereof

Abstract

The present invention provides an electrolyte additive, an electrolyte comprising the same, a lithium ion secondary battery and use thereof. The electrolyte additive comprises a substance represented by the following formula (1), wherein R1 is a substituted or unsubstituted C 1‑6 alkyl group, and R2 is selected from the group consisting of a substituted or unsubstituted C 1‑6 aliphatic hydrocarbon group, a 6-10 membered substituted or unsubstituted carbocyclic or heterocyclic aromatic group, wherein the heterocyclic aromatic group comprises 1 to 3 heteroatoms selected from N, S, O or any combination thereof.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion secondary batteries, and more specifically, to an electrolyte additive, an electrolyte containing the additive, a lithium-ion secondary battery, and their uses. Background Technology

[0002] With the rapid development of the economy and society, there is an increasingly urgent demand for lithium-ion batteries with high energy density and long cycle life. High-nickel / silicon-carbon lithium-ion batteries are considered a feasible solution to the current problems. However, the structural stability of high-nickel cathodes and silicon-carbon anodes is insufficient during electrical cycling, which may lead to a severe performance degradation of the battery under high temperature and high rate conditions.

[0003] During the charging and discharging process of lithium-ion batteries, the solvent may decompose, and the resulting substances form a positive electrolyte interphase (CEI) film on the positive electrode surface and a solid electrolyte interphase (SEI) film on the negative electrode surface. The CEI and SEI films effectively inhibit further reactions between the solvent and the electrodes. However, during battery cycling, the high-nickel positive electrode structure is unstable, and the CEI film is easily damaged, leading to the dissolution of transition metal ions. Furthermore, silicon negative electrode materials are prone to volume expansion during charging and discharging, causing the SEI film to rupture, resulting in electrode structural collapse and a significant decrease in battery performance.

[0004] Currently, a common method to improve battery performance is to add various film-forming additives to the electrolyte to form stable protective interfaces (CEI film and SEI film) on the surfaces of the positive and negative electrodes, respectively. In existing technologies, these film-forming additives include phosphate esters, nitriles, and sulfonates. During the first charge-discharge cycle, the film-forming additives preferentially decompose over the solvent, and their decomposition products form a stable and dense CEI film on the positive electrode surface. Furthermore, to protect the negative electrode, film-forming additives such as borates, nitrogen-containing lithium salts, and carbonates are added to form a stable negative electrode SEI film on the negative electrode surface during the first charge-discharge cycle. However, to simultaneously protect both the positive and negative electrodes, multiple additives need to be used in combination, which introduces more impurities, triggers side reactions, and increases the uncontrollability of the reaction process. Minimizing the types of additives and controlling their dosage are key to improving battery performance. Therefore, to address the problems mentioned above, it is still necessary to develop electrolyte additives that can effectively form SEI and CEI films while ensuring the electrical performance of lithium-ion secondary batteries. Summary of the Invention

[0005] The main objective of this invention is to provide an electrolyte additive, an electrolyte containing the same, a lithium-ion secondary battery, and its uses, in order to solve the problems in the prior art where the combined use of multiple electrolyte additives introduces more impurities, triggers side reactions, and increases the uncontrollability of the reaction process.

[0006] To achieve the above objectives, according to one aspect of the present invention, an electrolyte additive is provided, comprising a substance represented by the following formula (1):

[0007]

[0008] Where R1 is C, whether substituted or unsubstituted. 1-6 Alkyl group, and R2 is selected from substituted or unsubstituted C. 1-6 The group consisting of aliphatic hydrocarbon groups, 6-10 substituted or unsubstituted carbocyclic or heterocyclic aromatic groups, wherein the heterocyclic aromatic group comprises 1 to 3 heteroatoms selected from N, S, O or any combination thereof.

[0009] Furthermore, in the above-mentioned electrolyte additives, R1 is a halogen-substituted C 1-3 Alkyl or C 1-3 alkyl.

[0010] Furthermore, in the above-mentioned electrolyte additives, R2 is selected from C. 1-6 Alkylene, halogen or C 1-3 Alkyl-substituted C 1-6 Alkylene, phenylene, halogen or C 1-3 Alkyl-substituted phenylene, benzothiazolyl, and halogen or C 1-3 The group consisting of alkyl-substituted benzothiazolyl groups.

[0011] Furthermore, in the above-mentioned electrolyte additives, the substance represented by formula (1) is any one of the following:

[0012]

[0013] According to another aspect of the invention, an electrolyte is provided comprising an organic solvent, a lithium salt, and the electrolyte additives described above.

[0014] Furthermore, in the above electrolyte, based on the total weight of 100 parts by weight of organic solvent and lithium salt, the amount of electrolyte additive is in the range of 0.1 parts by weight to 1 part by weight.

[0015] Furthermore, in the above electrolyte, based on the total weight of 100 parts by weight of organic solvent and lithium salt, the amount of electrolyte additive is in the range of 0.1 parts by weight to 0.5 parts by weight.

[0016] Furthermore, in the above electrolyte, the lithium salt is selected from LiPF6, LiBF4, LiAsF6, LiCF3SO3, LiN(SO2F)2, LiN(SO2CF3)2, LiC(SO2CF3)3, Li2SiF6, or any combination thereof.

[0017] Furthermore, in the above electrolyte, the organic solvent is selected from the group consisting of propylene carbonate, butyl carbonate, fluoroethylene carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, ethylene carbonate, dimethyl carbonate, or any combination thereof.

[0018] According to another aspect of the present invention, a lithium-ion secondary battery is provided, comprising: a positive electrode, a negative electrode, a separator, and an electrolyte as described above.

[0019] According to another aspect of the invention, the use of the electrolyte additive described above in the preparation of electrolytes for lithium-ion secondary batteries and / or lithium-ion secondary batteries is provided.

[0020] The electrolyte additive of the present invention, the electrolyte containing the additive, the lithium-ion secondary battery, and the application thereof achieve the technical effects of improving electrode stability, reducing battery impedance, and improving battery high-temperature cycle performance and rate performance. Attached Figure Description

[0021] Figure 1 The results of rate discharge tests for Examples 2, 5, and Comparative Example 1 are shown; and

[0022] Figure 2 The float charge test results of Examples 2, 5 and Comparative Example 1 are shown. Detailed Implementation

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will be described in detail below with reference to the embodiments. The following embodiments are merely exemplary and do not constitute a limitation on the scope of protection of the present invention.

[0024] As explained in the background section, existing lithium-ion secondary batteries typically use a combination of multiple electrolyte additives to form CEI and SEI films at the positive and negative electrodes, respectively. However, this method introduces more impurities, triggers side reactions, and increases the uncontrollability of the reaction process. To address the problems in the prior art, a typical embodiment of the present invention provides an electrolyte additive comprising a substance represented by the following formula (1):

[0025]

[0026] Where R1 is C, whether substituted or unsubstituted.1-6 Alkyl group, and R2 is selected from substituted or unsubstituted C. 1-6 The group consisting of aliphatic hydrocarbon groups, 6-10 substituted or unsubstituted carbocyclic or heterocyclic aromatic groups, wherein the heterocyclic aromatic group comprises 1 to 3 heteroatoms selected from N, S, O or any combination thereof.

[0027] After conducting numerous experiments, the inventors of this invention were surprised to discover that when the compound of formula (1) is used as an electrolyte additive, it can be decomposed preferentially before the electrolyte during the first cycle of the lithium-ion secondary battery, and a solid electrolyte film is formed at both the positive and negative electrodes, that is, a CEI film is effectively formed at the positive electrode and an SEI film is formed at the negative electrode.

[0028] The compound selected in this invention is an internal salt series compound, in which different groups within the molecule carry positive and negative charges, but are electrically neutral overall. The positively charged morpholino group exhibits a strong electron-withdrawing effect, and can form a stable SEI film on the negative electrode surface when it decomposes into morpholino radical ions. At the same time, the negatively charged sulfonic acid group exhibits a strong electron-donating effect, and can be oxidized on the positive electrode surface when it decomposes into sulfonic acid group ions, thereby forming a stable CEI film. Since the internal salt compound of formula (1) of this application can simultaneously form an interfacial protective film on the positive and negative electrode surfaces, it effectively avoids the reaction between the solvent and the electrode, inhibits the dissolution of metal ions, and effectively improves electrode stability, reduces battery impedance, and improves battery cycle retention and rate performance. Furthermore, since only one electrolyte needs to be added when using the compound of formula (1) of this application, multiple additives do not need to be added at the same time to form a solid electrolyte film on both the positive and negative electrodes, the possibility of side reactions between electrolyte additives is eliminated, thereby effectively controlling the formation of impurities in the electrolyte and on the electrode surface, and thus reducing battery impedance.

[0029] Specifically, during the first cycle of the battery, the generation of hydrolysis product HF causes the compound of formula (1) to decompose into positively charged morpholine radical ions and negatively charged sulfate ions under the action of HF. The positively charged morpholine radicals combine with transition metal ions M on the positive electrode surface of the battery. n+ After cycling, a stable CEI film forms on the positive electrode surface to suppress transition metal dissolution. Because morpholine radicals have a cyclic structure, they can more effectively cover the positive electrode, thus protecting the positive electrode material from reaction with the electrolyte, preventing solvent-electrode reaction, and inhibiting metal ion dissolution. Negatively charged sulfate ions continuously react after gaining electrons at the negative electrode to form a network-like SEI film, thereby improving battery cycle performance and rate performance.

[0030] In some embodiments, R1 in formula (1) may be selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, neobutyl, n-pentyl, isopentyl, neopentyl, n-hexyl, isohexyl, or neohexyl. In other embodiments, R2 in formula (1) may be selected from C 1-6 The group consisting of sub-straight-chain aliphatic hydrocarbon groups, mono- or bicyclic subaromatic groups, and heterocyclic aromatic groups containing bicyclic rings. In a preferred embodiment, R2 may be selected from C. 1-6 Alkylene, C 1-6 imidene group, C 1-6 The group consisting of ynylene, phenylene, naphthylene, benzothiazolyl, benzofuranyl, benzothiophene, and benzopyrazolyl. In other embodiments, R2 may also be selected from C. 3-6 Alicyclic hydrocarbon group.

[0031] In some embodiments of the present invention, the electrolyte additive of formula (1) may comprise one or any combination of the following substituted or unsubstituted substances: N-methyl-N-(3-methanesulfonyl)morpholine, N-ethyl-N-(3-methanesulfonyl)morpholine, N-n-propyl-N-(3-methanesulfonyl)morpholine, N-isopropyl-N-(3-methanesulfonyl)morpholine, N-n-butyl-N-(3-methanesulfonyl)morpholine, N-isobutyl-N-(3-methanesulfonyl)morpholine, N-tert-butyl-N-(3-methanesulfonyl)morpholine, N-n-pentyl-N-(3-methanesulfonyl)morpholine, N-isopentyl-N-(3-methanesulfonyl)morpholine, N-neopentyl-N-(3-methanesulfonyl)morpholine, N-hexyl-N -(3-Methanesulfonyl)morpholine, N-isohexyl-N-(3-Methanesulfonyl)morpholine, N-neohexyl-N-(3-Methanesulfonyl)morpholine, N-methyl-N-(3-ethanesulfonyl)morpholine, N-ethyl-N-(3-ethanesulfonyl)morpholine, N-n-propyl-N-(3-ethanesulfonyl)morpholine, N-isopropyl-N-(3-ethanesulfonyl)morpholine N-n-Butyl-N-(3-ethanesulfonyl)morpholine, N-Isobutyl-N-(3-ethanesulfonyl)morpholine, N-tert-Butyl-N-(3-ethanesulfonyl)morpholine, N-n-Pentyl-N-(3-ethanesulfonyl)morpholine, N-Isopentyl-N-(3-ethanesulfonyl)morpholine, N-Neopentyl-N-(3-ethanesulfonyl)morpholine, N-n-Hexyl-N-(3- N-Isohexyl-N-(3-ethanesulfonyl)morpholine, N-neohexyl-N-(3-ethanesulfonyl)morpholine, N-methyl-N-(3-propanesulfonyl)morpholine, N-ethyl-N-(3-propanesulfonyl)morpholine, N-n-propyl-N-(3-propanesulfonyl)morpholine, N-isopropyl-N-(3-propanesulfonyl)morpholine, N-n-butyl N-N-(3-propanesulfonic acid)morpholine, N-isobutyl-N-(3-propanesulfonic acid)morpholine, N-tert-butyl-N-(3-propanesulfonic acid)morpholine, N-n-pentyl-N-(3-propanesulfonic acid)morpholine, N-isopentyl-N-(3-propanesulfonic acid)morpholine, N-neopentyl-N-(3-propanesulfonic acid)morpholine, N-hexyl-N-(3-propanesulfonic acid)morpholine Morpholine, N-isohexyl-N-(3-propanesulfonic acid)morpholine, N-neohexyl-N-(3-propanesulfonic acid)morpholine, N-methyl-N-(3-butanesulfonic acid)morpholine, N-ethyl-N-(3-butanesulfonic acid)morpholine, N-n-propyl-N-(3-butanesulfonic acid)morpholine, N-isopropyl-N-(3-butanesulfonic acid)morpholine, N-n-butyl-N- (3-Butyryl)morpholine, N-isobutyl-N-(3-Butyryl)morpholine, N-tert-butyl-N-(3-Butyryl)morpholine, N-n-pentyl-N-(3-Butyryl)morpholine, N-isopentyl-N-(3-Butyryl)morpholine, N-neopentyl-N-(3-Butyryl)morpholine, N-hexyl-N-(3-Butyryl)morpholineN-Isohexyl-N-(3-butyryl)morpholine, N-neohexyl-N-(3-butyryl)morpholine, N-methyl-N-(3-pentanesulfonic)morpholine, N-methyl-N-(3-hexanesulfonic)morpholine, N-ethyl-N-(3-pentanesulfonic)morpholine, or N-ethyl-N-(3-hexanesulfonic)morpholine.

[0032] In other embodiments, the electrolyte additive of formula (1) may comprise one or any combination of the following substituted or unsubstituted substances: N-methyl-N-p-sulfonylphenylmorpholine, N-ethyl-N-p-sulfonylphenylmorpholine, N-n-propyl-N-p-sulfonylphenylmorpholine, N-isopropyl-N-p-sulfonylphenylmorpholine, N-n-butyl-N-p-sulfonylphenylmorpholine, N-isobutyl-N-p-sulfonylphenylmorpholine, N-tert-butyl-N-p-sulfonylphenylmorpholine, N-n-pentyl-N-p-sulfonylphenylmorpholine, N-isopentyl-N-p-sulfonylphenylmorpholine, N-neopentyl-N-p-sulfonylphenylmorpholine, N-n-hexyl-N-p-sulfonylphenylmorpholine, N-isohexyl-N-p-sulfonylphenylmorpholine, N-isohexyl-N- -Phenylomorpholine sulfonate, N-neohexyl-N-p-phenylmorpholine sulfonate, N-methyl-N-(2'-methyl-4'-sulfonyl-phenyl-1')-morpholine, N-methyl-N-(2'-ethyl-4'-sulfonyl-phenyl-1')-morpholine, N-methyl-N-(3'-methyl-4'-sulfonyl-phenyl-1')-morpholine, N-methyl-N-(3'-ethyl-4'-sulfonyl-phenyl-1')-morpholine, N-methyl-N-(2',3'-dimethyl-4'-sulfonyl-phenyl-1')-morpholine, N-methyl-N-(2',5'-dimethyl-4'-sulfonyl-phenyl-1')-morpholine, N-methyl-N-(2',6'-(2',6'-)-morpholine '-Dimethyl-4'-sulfonic-phenyl-1')-morpholine, N-methyl-N-(2',3',5'-trimethyl-4'-sulfonic-phenyl-1')-morpholine, N-methyl-N-(2',3',6'-trimethyl-4'-sulfonic-phenyl-1')-morpholine, N-methyl-N-(2',3',5',6'-tetramethyl-4'-sulfonic-phenyl-1')-morpholine, N-ethyl-N-(2'-methyl-4'-sulfonic-phenyl-1')-morpholine, N-ethyl-N-(2'-ethyl-4'-sulfonic-phenyl-1')-morpholine, N-ethyl-N-(3'-methyl-4'-sulfonic-phenyl-1')-morpholine Phosphorus, N-ethyl-N-(3'-ethyl-4'-sulfonic-phenyl-1')-morpholine, N-ethyl-N-(2',3'-dimethyl-4'-sulfonic-phenyl-1')-morpholine, N-ethyl-N-(2',5'-dimethyl-4'-sulfonic-phenyl-1')-morpholine, N-ethyl-N-(2',6'-dimethyl-4'-sulfonic-phenyl-1')-morpholine, N-ethyl-N-(2',3',5'-trimethyl-4'-sulfonic-phenyl-1')-morpholine, N-ethyl-N-(2',3',6'-trimethyl-4'-sulfonic-phenyl-1')-morpholine, N-ethyl-N-(2',3',5',6'-Tetramethyl-4'-sulfonyl-phenyl-1')-morpholine, N-propyl-N-(2'-methyl-4'-sulfonyl-phenyl-1')-morpholine, N-propyl-N-(2'-ethyl-4'-sulfonyl-phenyl-1')-morpholine, N-propyl-N-(3'-methyl-4'-sulfonyl-phenyl-1')-morpholine, N-propyl-N-(3'-ethyl-4'-sulfonyl-phenyl-1')-morpholine, N-propyl-N-(2',3'-dimethyl-4'-sulfonyl-phenyl-1')-morpholine, N- N-propyl-N-(2',5'-dimethyl-4'-sulfonyl-phenyl-1')-morpholine, N-propyl-N-(2',6'-dimethyl-4'-sulfonyl-phenyl-1')-morpholine, N-propyl-N-(2',3',5'-trimethyl-4'-sulfonyl-phenyl-1')-morpholine, N-propyl-N-(2',3',6'-trimethyl-4'-sulfonyl-phenyl-1')-morpholine, or N-propyl-N-(2',3',5',6'-tetramethyl-4'-sulfonyl-phenyl-1')-morpholine.

[0033] In other embodiments, the electrolyte additive of formula (1) may comprise one or any combination of the following substituted or unsubstituted substances: N-methyl-N-p-sulfonated benzothiazomorpholine, N-ethyl-N-p-sulfonated benzothiazomorpholine, N-n-propyl-N-p-sulfonated benzothiazomorpholine, N-isopropyl-N-p-sulfonated benzothiazomorpholine, N-n-butyl-N-p-sulfonated benzothiazomorpholine, N-isobutyl-N-p-sulfonated benzothiazomorpholine, N-tert-butyl-N-p-sulfonated benzothiazomorpholine, N-n-pentyl-N-p-sulfonated benzothiazomorpholine, N-isopentyl-N-p-sulfonated benzothiazomorpholine, N-neopentyl-N-p-sulfonated benzothiazomorpholine, N-n-hexyl -N-p-Synosulfonated benzothiazomorpholine, N-isohexyl-N-p-Synosulfonated benzothiazomorpholine, N-neohexyl-N-p-Synosulfonated benzothiazomorpholine, N-methyl-N-(2'-methyl-5'-sulfonyl-benzothiazo-1')morpholine, N-methyl-N-(8'-methyl-5'-sulfonyl-benzothiazo-1')morpholine, N-methyl-N-(9'-methyl-5'-sulfonyl-benzothiazo-1')morpholine, N-methyl-N-(2'-ethyl-5'-sulfonyl-benzothiazo-1')morpholine, N-methyl-N-(8'-ethyl-5'-sulfonyl-benzothiazo-1')morpholine, N-methyl-N-(9'-ethyl-5'-sulfonyl-benzothiazo-1')morpholine, N-methyl-N-(2'-ethyl-5'-sulfonyl-benzothiazo-1')morpholine, N-methyl-N-(8'-ethyl-5'-sulfonyl-benzothiazo-1')morpholine, N-methyl-N-(9'-ethyl-5'-sulfonyl-benzothiazo-1')morpholine -1')morpholine, N-methyl-N-(2',8'-dimethyl-5'-sulfonic-benzothiazole-1')morpholine, N-methyl-N-(8',9'-dimethyl-5'-sulfonic-benzothiazole-1')morpholine, N-methyl-N-(2',9'-dimethyl-5'-sulfonic-benzothiazole-1')morpholine, N-methyl-N-(2',8',9'-trimethyl-5'-sulfonic-benzothiazole-1')morpholine, N-ethyl-N-(2'-methyl-5'-sulfonic-benzothiazole-1')morpholine, N-ethyl-N-(8'-methyl-5'-sulfonic-benzothiazole-1')morpholine, N-ethyl-N-(9'-methyl-5' ... -sulfonyl-benzothiazole-1')morpholine, N-ethyl-N-(2'-ethyl-5'-sulfonyl-benzothiazole-1')morpholine, N-ethyl-N-(8'-ethyl-5'-sulfonyl-benzothiazole-1')morpholine, N-ethyl-N-(9'-ethyl-5'-sulfonyl-benzothiazole-1')morpholine, N-ethyl-N-(2',8'-dimethyl-5'-sulfonyl-benzothiazole-1')morpholine, N-ethyl-N-(8',9'-dimethyl-5'-sulfonyl-benzothiazole-1')morpholine, N-ethyl-N-(2',9'-dimethyl-5'-sulfonyl-benzothiazole-1')morpholine, N-ethyl-N-(2',8'-dimethyl-5'-sulfonyl-benzothiazole-1')morpholine, N-ethyl-N-(2',8',9'-Trimethyl-5'-Sulfo-benzothiazole-1')morpholine, N-n-propyl-N-(2'-methyl-5'-sulfo-benzothiazole-1')morpholine, N-n-propyl-N-(8'-methyl-5'-sulfo-benzothiazole-1')morpholine, N-n-propyl-N-(9'-methyl-5'-sulfo-benzothiazole-1')morpholine, N-n-propyl-N-(2'-ethyl-5'-sulfo-benzothiazole-1')morpholine, N-n-propyl-N-(8'-ethyl-5'-sulfo-benzothiazole-1') Morpholine, N-n-propyl-N-(9'-ethyl-5'-sulfonyl-benzothiazole-1')morpholine, N-n-propyl-N-(2',8'-dimethyl-5'-sulfonyl-benzothiazole-1')morpholine, N-n-propyl-N-(8',9'-dimethyl-5'-sulfonyl-benzothiazole-1')morpholine, N-n-propyl-N-(2',9'-dimethyl-5'-sulfonyl-benzothiazole-1')morpholine, or N-n-propyl-N-(2',8',9'-trimethyl-5'-sulfonyl-benzothiazole-1')morpholine.

[0034] In a further embodiment of the present invention, the electrolyte additive may be a compound of the following formula (1):

[0035]

[0036] Wherein, R1 is a halogen-substituted C 1-3 Alkyl or C 1-3 alkyl.

[0037] In some embodiments of this application, the electrolyte additive of the present invention may comprise one or any combination of the following substituted or unsubstituted substances: N-chloromethyl-N-(3-methanesulfonyl)morpholine, N-dichloromethyl-N-(3-methanesulfonyl)morpholine, N-trichloromethyl-N-(3-methanesulfonyl)morpholine, N-fluoromethyl-N-(3-methanesulfonyl)morpholine, N-difluoromethyl-N-(3-methanesulfonyl)morpholine, N-trifluoromethyl-N-(3-methanesulfonyl)morpholine, etc. Phospholine, N-fluoroethyl-N-(3-methanesulfonate)morpholine, N-fluoropropyl-N-(3-methanesulfonate)morpholine, N-fluoroisopropyl-N-(3-methanesulfonate)morpholine, N-fluoromethyl-N-p-sulfonate phenylmorpholine, N-fluoroethyl-N-p-sulfonate phenylmorpholine, N-fluoropropyl-N-p-sulfonate phenylmorpholine, N-fluoromethyl-N-p-sulfonate benzothiazomorpholine, N-fluoroethyl-N-p-sulfonate benzothiazomorpholine or N-fluoropropyl-N-p-sulfonate benzothiazomorpholine.

[0038] In a further embodiment of the present invention, the electrolyte additive may be a compound of the following formula (1):

[0039]

[0040] Among them, R2 is chosen freely from C. 1-6 Alkylene, halogen or C 1-3 Alkyl-substituted C 1-6 Alkylene, phenylene, halogen or C 1-3 Alkyl-substituted phenylene, benzothiazolyl, and halogen or C 1-3 The group consisting of alkyl-substituted benzothiazolyl groups.

[0041] In some specific embodiments of the present invention, the electrolyte additive of the present invention may contain one or any combination of the following substances: N-methyl-N-(3-chloromethanesulfonate)morpholine, N-methyl-N-(3-fluoromethanesulfonate)morpholine, N-methyl-N-(3-fluoroethanesulfonate)morpholine, N-methyl-N-(3-fluoropropanesulfonate)morpholine, N-methyl-N-(2'-chloro-4'-sulfonate-phenyl-1')-morpholine, N-methyl-N-(2'-fluoro ... '-Methyl-3-fluoro-4'-sulfonic-phenyl-1')-morpholine, N-methyl-N-(2'-fluoro-3-fluoro-4'-sulfonic-phenyl-1')-morpholine, N-methyl-N-(2'-methyl-5'-sulfonic-benzothiazole-1')morpholine, N-methyl-N-(2'-fluoro-5'-sulfonic-benzothiazole-1')morpholine, N-methyl-N-(2',8'-difluoro-5'-sulfonic-benzothiazole-1')morpholine or N-methyl-N-(2'-fluoro-8'-methyl-5'-sulfonic-benzothiazole-1')morpholine.

[0042] In a preferred embodiment of the present invention, the electrolyte additive of the present invention may contain one or any combination of the following substances:

[0043]

[0044]

[0045] In one embodiment of this application, the electrolyte additive is N-methyl-N-(3-propanesulfonic acid)morpholine. During the first cycle of a lithium-ion secondary battery containing N-methyl-N-(3-propanesulfonic acid)morpholine, the electrolyte additive undergoes the following reaction: N-methyl-N-(3-propanesulfonic acid)morpholine decomposes into a positively charged N-methyl-N-propane moiety and a negatively charged sulfonic acid moiety under the catalysis of hydrogen fluoride. The positively charged N-methyl-N-propane moiety accumulates at the positive electrode of the lithium-ion secondary battery under the action of current and deposits on the surface of the positive electrode to form a CEI film. The negatively charged sulfonic acid moiety accumulates at the negative electrode of the lithium-ion secondary battery under the action of current and reacts under the action of lithium ions to form a network-structured SEI film. After the formation of the CEI film and the SEI film, both the positive and negative electrodes of the lithium-ion secondary battery are protected, thereby suppressing the dissolution of transition metal ions.

[0046] In another embodiment of this application, the electrolyte additive is N-methyl-N-p-sulfonate phenylmorpholine. During the first cycle of the lithium-ion secondary battery containing N-methyl-N-p-sulfonate phenylmorpholine, the electrolyte additive undergoes the following reaction: N-methyl-N-p-sulfonate phenylmorpholine decomposes into a positively charged N-methyl-N-benzene moiety and a negatively charged sulfonic acid moiety under the catalysis of hydrogen fluoride. The positively charged N-methyl-N-benzene moiety accumulates at the positive electrode of the lithium-ion secondary battery under the action of current and deposits on the surface of the positive electrode to form a CEI film. The negatively charged sulfonic acid moiety accumulates at the negative electrode of the lithium-ion secondary battery under the action of current and reacts under the action of lithium ions to form a network structure SEI film. After the formation of the CEI film and the SEI film, both the positive and negative electrodes of the lithium-ion secondary battery are protected, thereby suppressing the dissolution of transition metal ions.

[0047] In one embodiment of this application, the electrolyte additive is N-methyl-N-p-sulfonate benzothiazomorpholine. During the first cycle of a lithium-ion secondary battery containing N-methyl-N-p-sulfonate benzothiazomorpholine, the electrolyte additive undergoes the following reaction: N-methyl-N-p-sulfonate benzothiazomorpholine decomposes into a positively charged N-methyl-N-benzothiazolium moiety and a negatively charged sulfonic acid moiety under the catalysis of hydrogen fluoride. The positively charged N-methyl-N-benzothiazolium moiety accumulates at the positive electrode of the lithium-ion secondary battery under the action of current and deposits on the surface of the positive electrode to form a CEI film. The negatively charged sulfonic acid moiety accumulates at the negative electrode of the lithium-ion secondary battery under the action of current and reacts under the action of lithium ions to form a network-structured SEI film. After the formation of the CEI film and the SEI film, both the positive and negative electrodes of the lithium-ion secondary battery are protected, thereby suppressing the dissolution of transition metal ions.

[0048] In another typical embodiment of the present invention, an electrolyte is provided, comprising an organic solvent, a lithium salt, and the electrolyte additives described above. Because it contains the electrolyte additives of the present invention, the electrolyte of the present invention can effectively form a CEI film on the positive electrode surface and an SEI film on the negative electrode surface during the first cycle of the battery, thereby avoiding the reaction between the solvent and the electrode, inhibiting the dissolution of metal ions, improving electrode stability, reducing battery impedance, and improving battery cycle retention and rate performance. Furthermore, because the electrolyte of this application uses the electrolyte additives described above, only one electrolyte additive is needed instead of adding multiple additives simultaneously to form solid electrolyte films on both the positive and negative electrodes. This eliminates the possibility of side reactions between electrolyte additives, thereby effectively controlling the formation of impurities on the electrolyte and electrode surfaces, and thus reducing battery impedance.

[0049] In some embodiments of the present invention, the amount of electrolyte additive in the electrolyte is in the range of 0.1 parts by weight to 1 part by weight, based on the total weight of 100 parts by weight of organic solvent and lithium salt. Since the electrolyte additive of this application can simultaneously form both CEI and SEI films during the first cycle, no other film-forming additives are needed. Furthermore, adding the electrolyte additive of the present invention within the above range can effectively form an electrolyte film. When the amount of electrolyte additive is less than 0.1 parts by weight, a good and dense electrolyte film cannot be formed at both the positive and negative electrodes; while when the amount of electrolyte additive is greater than 1 part by weight, the formed electrolyte film is too thick, which will adversely affect the cycle efficiency of the lithium-ion secondary battery and adversely increase the battery impedance.

[0050] In different embodiments of the present invention, depending on the different combinations of lithium salt and organic solvent, the minimum amount of electrolyte additive, based on the total weight of 100 parts by weight of organic solvent and lithium salt, should be greater than 0.1 parts by weight, 0.11 parts by weight, 0.12 parts by weight, 0.13 parts by weight, 0.15 parts by weight, 0.16 parts by weight, 0.17 parts by weight, 0.18 parts by weight, or 0.19 parts by weight. Furthermore, depending on the different combinations of organic solvent and lithium salt, the maximum amount of electrolyte additive in the electrolyte, based on the total weight of 100 parts by weight of organic solvent and lithium salt, should be less than 1 part by weight, 0.9 parts by weight, 0.8 parts by weight, 0.7 parts by weight, 0.6 parts by weight, 0.5 parts by weight, 0.49 parts by weight, 0.48 parts by weight, 0.47 parts by weight, 0.46 parts by weight, 0.45 parts by weight, 0.44 parts by weight, 0.43 parts by weight, 0.42 parts by weight, 0.41 parts by weight, 0.4 parts by weight, 0.35 parts by weight, 0.3 parts by weight, 0.25 parts by weight, or 0.2 parts by weight.

[0051] Specifically, based on the total weight of 100 parts by weight of organic solvent and lithium salt, the amount of electrolyte additive in the electrolyte can be within the following ranges: 0.1 parts by weight to 1 part by weight, 0.2 parts by weight to 0.9 parts by weight, 0.3 parts by weight to 0.8 parts by weight, 0.4 parts by weight to 0.7 parts by weight, 0.5 parts by weight to 0.6 parts by weight, 0.1 parts by weight to 0.5 parts by weight, 0.1 parts by weight to 0.4 parts by weight, 0.1 parts by weight to 0.3 parts by weight. Parts, 0.1 to 0.2 parts by weight, 0.1 to 0.41 parts by weight, 0.11 to 0.4 parts by weight, 0.12 to 0.35 parts by weight, 0.13 to 0.3 parts by weight, 0.14 to 0.25 parts by weight, 0.15 to 0.2 parts by weight, 0.15 to 0.5 parts by weight, 0.13 to 0.5 parts by weight, or 0.12 to 0.25 parts by weight.

[0052] This invention does not impose any particular limitation on the lithium salt composition contained in the electrolyte; any lithium salt known in the prior art for use in lithium battery electrolytes can be employed. Examples of lithium salts include, but are not limited to: LiPF6, LiBF4, LiAsF6, LiCF3SO3, LiN(SO2F)2, LiN(SO2CF3)2, LiC(SO2CF3)3, Li2SiF6, or any combination thereof.

[0053] In this invention, the organic solvent for the non-aqueous electrolyte can be any non-aqueous solvent used to date for non-aqueous electrolyte solutions. Examples include, but are not limited to: linear or cyclic carbonates, such as ethylene carbonate, propylene carbonate, butyl carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, dipropyl carbonate, and fluoroethylene carbonate; ethers, such as 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, and diethyl ether; sulfones, such as sulfolane and methylsulfolane; nitriles, such as acetonitrile, propionitrile, and acrylonitrile; and esters, such as acetates, propionates, and butyrates. These non-aqueous solvents can be used alone or in combination. In some embodiments of the present invention, preferred electrolytes include ethylene carbonate, propylene carbonate, butyl carbonate, fluoroethylene carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, ethylene carbonate and / or dimethyl carbonate, and any combination thereof. In one preferred embodiment, at least one carbonate is used as the organic solvent of the electrolyte of the present invention. In other preferred embodiments, the above-mentioned non-aqueous solvents can be used in any combination to form an electrolyte solution that meets specific requirements.

[0054] In yet another exemplary embodiment of the present invention, a lithium-ion secondary battery is provided, which includes: a positive electrode sheet, a negative electrode sheet, a separator, and the electrolyte described above. Since the lithium-ion secondary battery of the present invention uses the electrolyte described above, it has excellent electrode stability, cycle retention rate, and rate performance.

[0055] The positive electrode sheet of the present invention includes a positive electrode current collector and a positive electrode active material layer containing a positive electrode active material. The positive electrode active material layer is formed on both surfaces of the positive electrode current collector. Metal foils such as aluminum foil, nickel foil, and stainless steel foil can be used as the positive electrode current collector.

[0056] The positive electrode active material layer contains one or two or more kinds of positive electrode materials that can absorb and release lithium ions as the positive electrode active material, and may contain additional materials such as a positive electrode binder and / or a positive electrode conductive agent when necessary.

[0057] Preferably, the positive electrode material is a lithium-containing compound. Examples of such lithium-containing compounds include lithium-transition metal composite oxides, lithium-transition metal phosphate compounds, and the like. Lithium-transition metal composite oxides are oxides containing Li and one or two or more transition metal elements as constituent elements, and lithium-transition metal phosphate compounds are phosphate compounds containing Li and one or two or more transition metal elements as constituent elements. Among them, the transition metal element is advantageously any one or two or more of Co, Ni, Mn, Fe, etc.

[0058] Examples of lithium-transition metal composite oxides include, for example, LiCoO2, LiNiO2, etc. Examples of lithium-transition metal phosphate compounds include, for example, LiFePO4, LiFe 1-u Mn u PO4(0 < u < 1), etc.

[0059] In some embodiments of the present application, the positive electrode material may be a ternary positive electrode material, such as lithium nickel cobalt aluminate (NCA) or lithium nickel cobalt manganate (NCM). Specific examples may be NCA, LixNiyCozAl1-y-zO2 (1 ≤ x ≤ 1.2, 0.5 ≤ y ≤ 1, and 0 ≤ z ≤ 0.5). NCM, LiNixCoyMnzO2 (x + y + z = 1, 0 < x < 1, 0 < y < 1, 0 < z < 1). Specific examples of the positive electrode material may include, but are not limited to, the following materials: LiNiO2, LiCoO2, LiCo 0.98 Al 0.01 Mg 0.01 O2, LiNi 0.5 Co 0.2 Mn 0.3 ]>O2, LiNi 0.8 Co 0.15 Al0.05 O2, LiNi 0.33 Co 0.33 Mn 0.33 O2, Li 1.2 Mn 0.52 Co 0.175 Ni 0.1 O2 and Li 1.15 (Mn 0.65 Ni 0.22 Co 0.13 )O2, LiFePO4, LiMnPO4, LiFe 0.5 Mn 0.5 PO4 and LiFe 0.3 Mn 0.7 PO4.

[0060] Furthermore, the cathode material can be any one or more of the following: oxides, disulfides, chalcogenides, conductive polymers, lithium cobalt oxide, lithium manganese oxide, nickel-cobalt-manganese ternary materials, etc. Examples of oxides include, for example, titanium oxide, vanadium oxide, manganese dioxide, etc. Examples of disulfides include, for example, titanium disulfide, molybdenum sulfide, etc. Examples of chalcogenides include, for example, niobium selenide, etc. Examples of conductive polymers include, for example, sulfur, polyaniline, polythiophene, etc. However, the cathode material can be a material different from those mentioned above.

[0061] Examples of positive electrode conductive agents include carbon materials such as graphite, carbon black, acetylene black, and Ketjenblack. These can be used alone or in combination of two or more. It is important to note that the positive electrode conductive agent can be a metallic material, a conductive polymer, or the like, as long as it is conductive.

[0062] Examples of positive electrode binders include, for example, synthetic rubbers and polymeric materials. Synthetic rubbers can be, for example, styrene-butadiene rubber, fluororubber, and ethylene propylene diene. Polymeric materials can be, for example, polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, lithium polyacrylate, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, and polyimide. These can be used alone or in combination of two or more of them.

[0063] The negative electrode sheet of the present invention includes a negative current collector and a negative active material layer containing a negative active material. The negative active material layer is formed on both surfaces of the negative current collector. Metal foils such as copper (Cu) foil, nickel foil, and stainless steel foil can be used as the negative current collector.

[0064] The negative electrode active material layer contains a material capable of absorbing and releasing lithium ions, and may contain additional materials, such as a negative electrode binder and / or a negative electrode conductive agent, if necessary. The details of the negative electrode binder and negative electrode conductive agent are, for example, the same as those of the positive electrode binder and positive electrode conductive agent.

[0065] The active material of the negative electrode is selected from any one or a combination of lithium metal, lithium alloy, carbon material, silicon or tin and their oxides.

[0066] Because carbon materials have a low potential when absorbing lithium ions, they can achieve high energy density and increase battery capacity. Additionally, carbon materials also function as conductive agents. Such carbon materials include, for example, natural graphite, artificial graphite, materials obtained by coating them with amorphous carbon, or similar materials. It should be noted that the shape of the carbon material can be fibrous, spherical, granular, flake-like, or similar. Silicon-based materials include nano-silicon, silicon alloys, silicon-carbon composites made of SiO₂ and graphite, preferably, SiO₂... w It is silicon suboxide, silicon oxide, or other silicon-based materials.

[0067] In addition, the anode material can be one or more of the following: readily graphitizable carbon, difficult-to-graphitizable carbon, metal oxides, and polymer compounds. Examples of metal oxides include, for example, iron oxide, ruthenium oxide, and molybdenum oxide. Examples of polymer compounds include, for example, polyacetylene, polyaniline, and polypyrrole. However, the anode material can be other materials different from those described above.

[0068] The separator of the present invention is used to separate the positive and negative electrodes in a battery, allowing ions to pass through while preventing short circuits due to contact between the two electrodes. The separator is, for example, a porous membrane formed of synthetic resin, ceramic, or similar material, and may be a laminated membrane in which two or more porous membranes are laminated. Examples of synthetic resins include, for example, polytetrafluoroethylene, polypropylene, polyethylene, cellulose, etc.

[0069] In embodiments of the invention, during charging, for example, lithium ions are released from the positive electrode and absorbed into the cathode by a non-aqueous electrolyte impregnated in a separator. During discharging, for example, lithium ions are released from the negative electrode and absorbed into the positive electrode by a non-aqueous electrolyte impregnated in a separator.

[0070] In another typical embodiment of the present invention, there is provided the use of the electrolyte additive described above in the present invention for preparing an electrolyte for a lithium-ion secondary battery and / or a lithium-ion secondary battery. After adding the electrolyte additive of the present application to the lithium-ion secondary battery, during the first charging cycle, the electrolyte additive of the present application will decompose preferentially to the electrolyte to generate morpholine radical ions and sulfonic acid group ions, thereby forming a CEI film and a SEI film on the surfaces of the positive and negative electrodes of the lithium-ion secondary battery respectively, effectively avoiding the reaction between the solvent and the electrode, inhibiting the dissolution of metal ions, and effectively improving the electrode stability, reducing the battery impedance, and improving the battery cycle retention rate and rate performance.

[0071] The following further describes the present application in detail with reference to specific embodiments, and these embodiments should not be construed as limiting the scope claimed in the present application.

[0072] Example 1

[0073] Preparation of negative electrode

[0074] Under vacuum and completely dry conditions, at a temperature of 20 °C, 94.0 g of silicon suboxide (SiO x , 1 < x < 2) and graphite powder mixture (where the amount of silicon suboxide is 9.4 g), 1.9 g of Super-P conductive agent, 3.15 g of CMC binder (sodium carboxymethyl cellulose) and styrene-butadiene rubber SBR (where the weight ratio of CMC to SBR is 1:1) are added to water and stirred evenly to obtain a negative electrode active material slurry. The negative electrode active material slurry is coated on a copper foil to obtain a negative electrode current collector, the negative electrode current collector is dried, and a negative electrode plate is formed by a stamping process.

[0075] Preparation of positive electrode

[0076] Under vacuum and completely dry conditions, at a temperature of 20 °C, 93.0 g of the positive electrode active material lithium nickel cobalt aluminate, 4.0 g of conductive carbon black and 3.0 g of polyvinylidene fluoride are mixed to obtain a positive electrode mixture, and the obtained positive electrode mixture is dispersed in N-methylpyrrolidone to obtain a positive electrode mixture slurry. Subsequently, the positive electrode mixture slurry is coated on an aluminum foil to obtain a positive electrode current collector, the positive electrode current collector is dried, and a positive electrode plate is formed by a stamping process.

[0077] Preparation of electrolyte

[0078] 20.0 g of ethylene carbonate, 62.0 g of dimethyl carbonate and 18.0 g of lithium hexafluorophosphate are mixed to prepare a basic electrolyte. 0.1 g of N-methyl-N-(3-propylsulfonic acid group) morpholine (MSPM) is added to the basic electrolyte to obtain the electrolyte of the battery, where MSPM is shown in the following chemical formula:

[0079]

[0080] Battery assembly

[0081] CR2016 coin cells were assembled in a dry laboratory. The positive electrode sheet prepared in the above steps was used as the positive electrode, and the negative electrode sheet as the negative electrode. The positive electrode, negative electrode, separator, and coin cell casing were assembled, and electrolyte was injected. The positive electrode, negative electrode, separator, and coin cell casing were then assembled again. After assembly, the cells were left to age for approximately 24 hours to obtain a lithium nickel cobalt manganese oxide coin cell.

[0082] Example 2

[0083] A lithium nickel cobalt manganese oxide button cell was prepared using the same method as in Example 1, except that 0.5 g of MSPM was added to the base electrolyte to obtain the electrolyte for the cell.

[0084] Example 3

[0085] A lithium nickel cobalt manganese oxide button cell was prepared using the same method as in Example 1, except that 1.0 g of MSPM was added to the base electrolyte to obtain the electrolyte for the cell.

[0086] Example 4

[0087] Lithium nickel cobalt manganese oxide button batteries were prepared using the same method as in Example 1, except that 0.1 g of MSIM was added to the base electrolyte to obtain the battery electrolyte, wherein MSIM has the following chemical formula:

[0088]

[0089] Example 5

[0090] A lithium nickel cobalt manganese oxide button battery was prepared using the same method as in Example 1, except that 0.5 g of MSIM was added to the base electrolyte to obtain the battery's electrolyte.

[0091] Example 6

[0092] A lithium nickel cobalt manganese oxide button battery was prepared using the same method as in Example 1, except that 1.0 g of MSIM was added to the base electrolyte to obtain the battery's electrolyte.

[0093] Comparative Example 1

[0094] Lithium nickel cobalt manganese oxide button batteries were prepared using the same method as in Example 1, except that no electrolyte additives were added.

[0095] Comparative Example 2

[0096] A lithium nickel cobalt manganese oxide button cell was prepared using the same method as in Example 1, except that 0.05 g of MSPM was added to the base electrolyte to obtain the electrolyte for the cell.

[0097] Comparative Example 3

[0098] A lithium nickel cobalt manganese oxide button cell was prepared using the same method as in Example 1, except that 3.0 g of MSPM was added to the base electrolyte to obtain the electrolyte for the cell.

[0099] Comparative Example 4

[0100] A lithium nickel cobalt manganese oxide button battery was prepared using the same method as in Example 1, except that 0.05 g of MSIM was added to the base electrolyte to obtain the battery's electrolyte.

[0101] Comparative Example 5

[0102] A lithium nickel cobalt manganese oxide button battery was prepared using the same method as in Example 1, except that 3.0 g of MSIM was added to the base electrolyte to obtain the battery's electrolyte.

[0103] Battery performance testing

[0104] Cycle retention rate and post-cycle impedance

[0105] At room temperature, charge-discharge and impedance tests were performed on the nickel-cobalt-manganese lithium coin cells of Examples 1-6 and Comparative Examples 1-5 at voltages between 3.0V and 4.2V. The cells from the examples and comparative examples were first subjected to one 0.1C cycle test at 25°C, followed by 100 cycles of 1C charge and discharge at 60°C to determine the cycle retention rate and impedance. The experimental results are shown in Table 1 below.

[0106] Example additive Cycle retention rate Impedance after cycling (Ω) Example 1 0.1% MSPM 68.71％ 31.28 Example 2 0.5% MSPM 75.71％ 28.26 Example 3 1% MSPM 65.69％ 35.09 Example 4 0.1% MSIM 60.84％ 31.73 Example 5 0.5% MSIM 74.27％ 33.29 Example 6 1% MSIM 68.32％ 40.23 Comparative Example 1 No additions 58.70％ 46.18 Comparative Example 2 0.05% MSPM 57.59％ 49.09 Comparative Example 3 3% MSPM 54.83％ 89.22 Comparative Example 4 0.05% MSIM 57.13％ 51.75 Comparative Example 5 3% MSIM 51.26％ 97.03

[0107] As can be seen from the comparative examples 1-6 and Comparative Example 1, the lithium-ion secondary battery using the electrolyte additive of the present invention exhibits a significantly increased cycle retention rate and a significantly reduced post-cycle impedance. A comparison of Example 3 and Comparative Example 2, and Example 5 and Comparative Example 4, shows that when the amount of electrolyte additive added is less than the range defined in this application, although the decrease in cycle retention rate is not significant, the post-cycle impedance increases significantly. This is because the amount of electrolyte additive is insufficient to form a complete and dense solid electrolyte film on the surfaces of the positive and negative electrodes, leading to the dissolution of transition elements in the electrodes. A comparison of Example 3 and Comparative Example 3, and Example 6 and Comparative Example 5, shows that when the amount of electrolyte additive added is greater than the range defined in this application, the cycle retention rate of the secondary battery decreases significantly and the post-cycle impedance increases significantly. This is because an excessively thick solid electrolyte film is formed on the surfaces of the positive and negative electrodes, thereby reducing the efficiency of lithium insertion and extraction.

[0108] Rate Discharge Test

[0109] The lithium nickel cobalt manganese oxide button batteries prepared according to Examples 2, 5, and Comparative Example 1 were subjected to rate discharge tests from 0.5C to 10C at 25°C. The test results are as follows: Figure 1 As shown.

[0110] pass Figure 1 It can be seen that Examples 2 and 5, which used the electrolyte additive of this application, both exhibited excellent rate discharge performance. In particular, Example 2 was able to maintain 90% of its discharge capacity even when subjected to a 5C rate discharge test.

[0111] Float charging test

[0112] The lithium nickel cobalt manganese oxide button batteries prepared according to Examples 2, 5, and Comparative Example 1 were subjected to float charge tests at 25°C. The test results are as follows: Figure 2 As shown.

[0113] pass Figure 2 It can be seen that, since no electrolyte additives were added in Comparative Example 1, its positive and negative electrodes were not protected by a solid electrolyte membrane. During the float charge test, because the electrodes were in direct contact with the electrolyte, the transition metals in the electrodes reacted with the electrolyte and dissolved into it, resulting in an increase in the float charge current. Examples 2 and 5 both showed float charge currents much lower than Comparative Example 1 (almost zero), indicating that batteries containing 0.5% MSPM or 0.5% MSIM form more stable CEI and SEI films.

[0114] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An electrolyte additive for lithium-ion secondary batteries, characterized in that, Includes substances represented by the following formula (1): Equation (1) in R1 is C with or without substitution. 1-6 Alkyl, and R2 selects C with free substitution or no substitution. 1-6 The group consisting of aliphatic hydrocarbon groups, 6-10 substituted or unsubstituted carbocyclic or heterocyclic aromatic groups, wherein the heterocyclic aromatic group comprises 1 to 3 heteroatoms selected from N, S, O or any combination thereof.

2. The electrolyte additive according to claim 1, characterized in that, R1 is a halogen-substituted C 1-3 Alkyl or C 1-3 alkyl.

3. The electrolyte additive according to claim 1, characterized in that, R2 selects C freely. 1-6 Alkylene, halogen or C 1-3 Alkyl-substituted C 1-6 Alkylene, phenylene, halogen or C 1-3 Alkyl-substituted phenylene, benzothiazolyl, and halogen or C 1-3 The group consisting of alkyl-substituted benzothiazolyl groups.

4. The electrolyte additive according to claim 1, characterized in that, The substance represented by formula (1) is any one of the following: , and .

5. An electrolyte comprising an organic solvent, a lithium salt, and an electrolyte additive according to any one of claims 1 to 4.

6. The electrolyte according to claim 5, characterized in that, The amount of electrolyte additive is in the range of 0.1 parts by weight to 1 part by weight, based on the total weight of 100 parts by weight of the organic solvent and the lithium salt.

7. The electrolyte according to claim 6, characterized in that, Based on the total weight of 100 parts by weight of the organic solvent and the lithium salt, the amount of the electrolyte additive is in the range of 0.1 parts by weight to 0.5 parts by weight.

8. The electrolyte according to claim 5, characterized in that, The lithium salt is selected from LiPF6, LiBF4, LiAsF6, LiCF3SO3, LiN(SO2F)2, LiN(SO2CF3)2, LiC(SO2CF3)3, Li2SiF6, or any combination thereof.

9. The electrolyte according to claim 5, characterized in that, The organic solvent is selected from the group consisting of propylene carbonate, butyl carbonate, fluoroethylene carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, ethylene carbonate, dimethyl carbonate, or any combination thereof.

10. A lithium-ion secondary battery, characterized in that, include: Positive electrode plate, Negative electrode plate, Diaphragm, and The electrolyte according to any one of claims 5 to 9.

11. The use of the electrolyte additive according to any one of claims 1 to 4 in the preparation of an electrolyte for a lithium-ion secondary battery or a lithium-ion secondary battery.

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