Phosphorus-containing compound for lithium ion battery, nonaqueous electrolyte, and lithium ion battery

Abstract

Disclosed are a phosphorus-containing compound, a nonaqueous electrolyte, and a lithium ion battery. In the present application, an additive for a lithium ion battery is provided, the phosphorus-containing compound has a structure shown in formula (I), wherein the R1 and R2 groups are as described in the context of the present application, the phosphorus-containing compound is added in a nonaqueous electrolyte, and the internal resistance of the battery can be significantly reduced, particularly the internal resistance when the battery is fast-charged.

Description

Technical Field

[0001] This invention relates to the field of secondary batteries, and particularly to a phosphorus-containing compound, a non-aqueous electrolyte, and a lithium-ion battery for use in lithium-ion batteries. Background Technology

[0002] Lithium-ion batteries, as rechargeable batteries, possess advantages such as high energy density, low self-discharge, and long cycle life, and are widely used in electric vehicles, smart grids, and miniaturized electronic devices. In recent years, to improve the energy density of lithium-ion batteries, ternary cathode materials with high specific capacity and high reaction potential have been widely used in the market. While ternary cathode materials significantly improve energy density compared to lithium iron phosphate, their significant volume changes during charge-discharge cycles and rapid phase transitions in the cathode active material lead to a rapid increase in surface reactivity when exposed to air or high humidity. During storage or cycling, this can cause excessive gas production by reacting with flammable non-aqueous solvents in the non-aqueous electrolyte. Under fast charging conditions with high current, the battery system temperature rises rapidly, posing a very high risk of explosion.

[0003] To alleviate this phenomenon, existing technologies attempt to add electrolyte additives such as ethylene carbonate to non-aqueous electrolytes to form an SEI film on the electrode to improve battery life and stability. However, when these materials are used in batteries containing high-capacity ternary cathode materials, the internal resistance of the cell is significantly increased, which seriously affects the lithium-ion conduction performance.

[0004] In addition, the rapid charging process of ternary lithium-ion batteries is often accompanied by a sharp increase in the internal resistance of the battery, which destroys the internal dynamic performance of the battery, causes lithium plating, and increases the risk of battery rupture and explosion, thus limiting the further commercialization of ternary cathode materials with high specific capacity and high reaction potential.

[0005] Therefore, there is an urgent need in this field to study methods that can solve the above problems at low cost. Summary of the Invention

[0006] The purpose of this invention is to provide a phosphorus-containing compound for lithium-ion batteries, which, when added to the electrolyte of lithium-ion batteries, can resist the increase of internal resistance and effectively reduce the internal resistance during fast charging of the battery.

[0007] Another object of the present invention is to provide a non-aqueous electrolyte.

[0008] Another object of the present invention is to provide a lithium-ion battery.

[0009] Another object of the present invention is to provide a method for reducing the internal resistance of lithium-ion batteries during fast charging.

[0010] To address the aforementioned technical problems, the first aspect of this invention provides a phosphorus-containing compound for lithium-ion batteries, the phosphorus-containing compound having the structure shown in formula (I).

[0011]

[0012] Among them, R 1 Selected from C 1-6 Alkyl group, at least one hydrogen atom is R 1-1 Replacement C 1-6 Alkyl, C 2-6 Alkenyl group, at least one hydrogen atom is R 1-1 Replacement C 2-6 alkenyl, C 3-6 Cycloalkyl groups, at least one hydrogen atom is R 1-1 Replacement C 3-6 cycloalkyl,

[0013] R 1-1 Selected from halogens, nitro groups, and -N(R) a R b ), phenyl, R a and R b Independently hydrogen or C 1-4 alkyl;

[0014] R 2 Selected from C 1-6 Alkyl group, at least one hydrogen atom is R 2-1 Replacement C 1-6 Alkyl, C 2-12 Alkenyl group, at least one hydrogen atom is R 2-1 Replacement C 2-12 alkenyl, phenyl, at least one hydrogen atom is R 2-1 Substituted phenyl,

[0015] R 2-1 Selected from halogens, phenyl, C 1-4 Alkyl, hydroxyl, or C whose at least one hydrogen atom is substituted with a halogen 1-4 Alkyl group, at least one hydrogen atom is R 2-11 Substituted phenyl C 1-4 alkyl,

[0016] R 2-11 Hydroxyl or C 1-4 Alkyl group.

[0017] In some preferred embodiments, the C 1-6 Alkyl group is C 1-4 Alkyl, the C 1-4 The alkyl group is methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, or tert-butyl.

[0018] In some preferred embodiments, the C2-6 The alkenyl group is C 2-4 alkenyl, the C 2-4 The alkenyl group is vinyl, 1-propenyl, 2-propenyl, 1-n-butenyl, 2-n-butenyl, 3-n-butenyl, 1-isobutenyl, 2-isobutenyl or 1,3-butadienyl.

[0019] In some preferred embodiments, the C 3-6 The cycloalkyl group is cyclopropane, cyclobutane, cyclopentane, or cyclohexane.

[0020] In some preferred embodiments, the C 1-4 The alkoxy group can be methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, isobutoxy, or tert-butoxy.

[0021] In some preferred embodiments, the halogen is fluorine, chlorine, bromine, or iodine.

[0022] In some preferred solutions, R 1 Methyl, ethyl, n-propyl, isopropyl, R 1-1 Substituted methyl, R 1-1 Substituted ethyl, R 1-1 Substituted n-propyl, R 1-1 Substituted isopropyl, cyclohexyl or R 1-1 Substituted cyclohexyl groups,

[0023] R 1-1 For bromine, nitro, -NH2,

[0024] In some preferred solutions, R 1 Methyl, ethyl, isopropyl, cyclohexyl,

[0025] In some preferred solutions, R 2 Methyl, ethyl, n-propyl, n-butyl, phenyl, vinyl, 1-propenyl, 2-propenyl, or at least one hydrogen atom is present. 2-1 The substituted methyl group, at least one hydrogen atom is R 2-1 The substituted n-propyl group, with at least one hydrogen atom replaced by R 2 -1 Substituted vinyl, at least one hydrogen is R 2-1 Substituted phenyl,

[0026] R 2-1 It is trifluoromethyl, fluorine, phenyl or at least one hydrogen atom R 2-11 Substituted phenyl, R 2-11 It can be hydroxyl, methoxy, ethoxy, n-propoxy, or isopropoxy.

[0027] In some preferred solutions, R 2 The following are examples of vinyl groups: methyl, ethyl, n-propyl, n-butyl, 2-propenyl, phenyl, n-propyl with at least one hydrogen substituted by a phenyl group, ethyl with at least one hydrogen substituted by a phenyl group, vinyl with at least one hydrogen substituted by a trifluoromethyl group, vinyl with at least one hydrogen substituted by a fluorine group, vinyl with at least one hydrogen substituted by a trifluoromethyl group and / or a fluorine group, vinyl with at least one hydrogen substituted by a phenyl group, and vinyl with at least one hydrogen substituted by an R group. 2-11 Substituted phenyl, R 2-11 It is either hydroxyl or methoxy.

[0028] In some preferred solutions, R 2 Methyl, ethyl, n-propyl, n-butyl, 2-propenyl, phenyl

[0029] In some preferred embodiments, the phosphorus-containing compound is selected from any one or a combination of the following structures:

[0030]

[0031]

[0032] In some preferred embodiments, the phosphorus-containing compound is selected from... At least one of them.

[0033] A second aspect of the present invention provides a non-aqueous electrolyte comprising a non-aqueous solvent, an electrolyte, and the phosphorus-containing compound described in the first aspect of the present invention.

[0034] In some preferred embodiments, the electrolyte further includes additives, which include at least one of the following: cyclic carbonates, cyclic sulfonyl lactones, and cyclic sulfate lactones having carbon-carbon double or triple unsaturated bonds and / or fluorine atoms, preferably at least two: for example, cyclic carbonates and cyclic sulfonyl lactones having carbon-carbon double or triple unsaturated bonds and / or fluorine atoms.

[0035] In some preferred embodiments, the additives include: cyclic carbonates, cyclic sulfonates, and cyclic sulfates having carbon-carbon double or triple bonds, unsaturated bonds, and / or fluorine atoms.

[0036] In some preferred embodiments, the cyclic carbonate having carbon-carbon double or triple bonds, unsaturated bonds, and / or fluorine atoms is selected from vinylene carbonate (VC), ethylene ethylene carbonate (VEC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), or combinations thereof; more preferably, it is vinylene carbonate (VC).

[0037] In some preferred embodiments, the cyclic sulfonyl lactone includes 1,3-propanesulfonyl lactone (PS), 1,4-butanesulfonyl lactone, propenyl-1,3-sulfonyl lactone, or combinations thereof; more preferably, 1,3-propanesulfonyl lactone (PS).

[0038] In some preferred embodiments, the cyclic sulfate lactone is selected from vinyl sulfate (DTD), propylene sulfate, or a combination thereof; more preferably, it is vinyl sulfate (DTD).

[0039] In some preferred embodiments, the phosphorus-containing compound in the non-aqueous electrolyte comprises 0.01% to 20% by mass; more preferably 0.02% to 10%; even more preferably 0.02% to 5%; for example: 0.02%, 0.05%, 0.1%, 0.15%, 0.5%, 1%, 1.5%, 2%, 3% or 5%.

[0040] In some preferred embodiments, the non-aqueous electrolyte contains 0.01% to 10% by mass of the cyclic carbonate having carbon-carbon double or triple bonds and / or fluorine atoms.

[0041] In some preferred embodiments, the cyclic sulfonyl lactone is present in the non-aqueous electrolyte at a mass percentage of 0.01% to 10%.

[0042] In some preferred embodiments, the cyclic sulfate lactone content in the non-aqueous electrolyte is from 0.01% to 10% by mass.

[0043] In some preferred embodiments, the additives include vinylene carbonate (VC), 1,3-propanesulfonate lactone (PS), and vinyl sulfate (DTD).

[0044] In some preferred embodiments, the mass percentage ratio of the phosphorus-containing compound, the vinylene carbonate (VC), the 1,3-propanesulfonate lactone (PS), and the vinyl sulfate (DTD) in the electrolyte is (0.01-3):(0.5-3):(1-6):(0.5-6). For example: 5:5:10:5 (1:1:2:1), 1:2.5:2.5:5, 0.05:2.5:2.5:5 (1:50:50:100).

[0045] In some more preferred embodiments, the mass percentage ratio of the phosphorus-containing compound, the vinylene carbonate (VC), the 1,3-propanesulfonate lactone (PS), and the vinyl sulfate (DTD) in the electrolyte is (0.5-1.5):(2-3):(2-3):(4-6), more preferably (0.8-1.2):(2.2-2.8):(2.2-2.8):(4.5-5.5).

[0046] In some preferred embodiments, the electrolyte is selected from at least one of LiPF6, LiBF4, LiFSI, LiTFSI, LiBOB, LiODFP, LiODFB, LiPO2F2 and CF3SO3Li, preferably LiPF6.

[0047] In some preferred embodiments, the molar concentration of the electrolyte in the non-aqueous electrolyte is from 0.5 mol / L to 2 mol / L.

[0048] In some preferred embodiments, the non-aqueous solvent includes cyclic carbonates and chain carbonates;

[0049] The cyclic carbonate is selected from at least one of ethylene carbonate (EC) and propylene carbonate (PC);

[0050] The chain carbonate is selected from at least one of ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and dimethyl carbonate (DMC).

[0051] In some preferred embodiments, the non-aqueous solvent in the non-aqueous electrolyte has a mass percentage content of 60% to 85%.

[0052] A third aspect of the present invention provides a lithium-ion battery comprising a positive electrode, a negative electrode, a separator, and the non-aqueous electrolyte described in the second aspect of the present invention.

[0053] In some preferred embodiments, the positive electrode includes a current collector and a positive electrode active material layer coated on the current collector. The positive electrode active material layer includes a positive electrode active material, which includes any one or a combination of at least two of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, or lithium nickel cobalt aluminum oxide; for example, LiNi. 0.6 Co 0.3 Mn 0.1 O2.

[0054] In some preferred embodiments, the negative electrode includes a current collector and a layer of negative electrode active material coated on the current collector, wherein the negative electrode active material includes any one or a combination of at least two of soft carbon, hard carbon, artificial graphite, natural graphite, silicon, silicon oxide, silicon carbide, or lithium titanate; for example, artificial graphite or silicon.

[0055] In some preferred embodiments, the positive electrode active material layer further includes a binder and a conductive agent.

[0056] In some preferred embodiments, the negative electrode active material layer further includes a binder and a conductive agent.

[0057] A fourth aspect of the present invention provides a method for reducing the internal resistance of a lithium-ion battery during fast charging, the method comprising the step of using a non-aqueous electrolyte containing a phosphorus-containing compound as described in the first aspect of the present invention.

[0058] In some preferred embodiments, the method includes the step of using a non-aqueous electrolyte comprising the phosphorus-containing compound described in the first aspect of the invention, vinylene carbonate (VC), 1,3-propanesulfonate lactone (PS), and the vinyl sulfate (DTD).

[0059] Compared with the prior art, the present invention has at least the following advantages:

[0060] (1) This invention creatively develops a phosphorus-containing compound for lithium-ion batteries, which can be added as a functional additive to non-aqueous electrolytes to significantly reduce the internal resistance of the battery, especially the internal resistance during fast charging.

[0061] (2) The phosphorus-containing compound for lithium-ion batteries provided by the present invention helps to form a more stable and dense SEI film, inhibits the contact between the electrolyte and the positive and negative electrode active materials, thereby inhibiting the generation of gas at high temperature and reducing the volume expansion of the battery at high temperature.

[0062] (3) The phosphorus-containing compound for lithium-ion batteries provided by the present invention can significantly improve the cycle life and stability of lithium-ion batteries.

[0063] It should be understood that, within the scope of this invention, the above-described technical features of this invention and the technical features specifically described below (such as in the embodiments) can be combined with each other to form new or preferred technical solutions. Due to space limitations, they will not be described in detail here. Attached Figure Description

[0064] One or more embodiments are illustrated by way of example with reference to the accompanying drawings, and these illustrative descriptions do not constitute a limitation on the embodiments.

[0065] Figure 1 This is a graph showing the change in the DC internal resistance of the battery with the amount of compound 1 added according to an embodiment of the present invention;

[0066] Figure 2 This is a graph showing the change in the battery's fast-charging cycle capacity retention rate at high temperature as a function of the amount of compound 1 added, according to an embodiment of the present invention.

[0067] Figure 3 This is a graph showing the change in the volume expansion rate of the battery during high-temperature storage as a function of the amount of compound 1 added, according to an embodiment of the present invention. Detailed Implementation

[0068] Through extensive and in-depth research, the inventors have developed a new phosphorus-containing compound for lithium-ion batteries. When added to the electrolyte, the phosphorus-containing compound can decompose on the surface of the positive electrode to form a more robust SEI film, thereby improving the high-temperature cycle performance and stability of the battery. On the other hand, it can also improve the lithium-ion conductivity and reduce the internal resistance of the battery, especially during fast charging.

[0069] Phosphorus-containing compounds

[0070] In this invention, the phosphorus-containing compound has the structure shown in general formula (I).

[0071]

[0072] Among them, R 1 Selected from C 1-6 Alkyl group, at least one hydrogen atom is R 1-1 Replacement C 1-6 Alkyl, C 2-6 Alkenyl group, at least one hydrogen atom is R 1-1 Replacement C 2-6 alkenyl, C 3-6 Cycloalkyl groups, at least one hydrogen atom is R 1-1 Replacement C 3-6 cycloalkyl,

[0073] R 1-1 Selected from halogens, nitro groups, and -N(R) a R b ), phenyl, R a and R b Independently hydrogen or C 1-4 alkyl;

[0074] R 2 Selected from C 1-6 Alkyl group, at least one hydrogen atom is R 2-1 Replacement C 1-6 Alkyl, C 2-12 Alkenyl group, at least one hydrogen atom is R 2-1 Replacement C 2-12 alkenyl, phenyl, at least one hydrogen atom is R 2-1 Substituted phenyl,

[0075] R 2-1 Selected from halogens, phenyl, C 1-4 Alkyl, hydroxyl, or C whose at least one hydrogen atom is substituted with a halogen 1-4 Alkyl group, at least one hydrogen atom is R 2-11 Substituted phenyl C 1-4 alkyl,

[0076] R 2-11 Hydroxyl or C 1-4Alkyl group.

[0077] The following two methods are preferred as the phosphorus-containing compounds of the present invention.

[0078] Method 1

[0079]

[0080] R 1 and R 2 All are group A, and the carbon atom in group A bonded to the central atom P has an unsaturation degree of 0. For example, R 1 and R 2 All are alkyl groups, or optionally substituted alkyl groups. The substituents here can be various substituents, such as those replaced by halogens (fluorine, chlorine, bromine, or iodine), amino groups, or amine groups (-N(R)). a R b ), R a and R b Independently for C 1-4 In a preferred embodiment, R is substituted with at least one substituent such as alkyl, nitro, or aryl. 1 and R 2 All are unsubstituted alkyl groups, more preferably unsubstituted straight-chain alkyl groups.

[0081] Method 2

[0082]

[0083] R 1 and R 2 At least one group A' exists in the atom, and the carbon atom in group A' bonded to the central atom P has an unsaturation degree greater than 0. For example, R 1 and R 2 At least one group is selected from alkenyl, phenyl, and cycloalkyl, or optionally substituted alkenyl, phenyl, and cycloalkyl. The substituents here can be various substituents, such as halogens (fluorine, chlorine, bromine, or iodine), halogen-substituted alkyl groups (trifluoromethyl), hydroxyl, alkoxy, phenyl, substituted phenyl, etc.

[0084] [Non-aqueous electrolyte]

[0085] The non-aqueous electrolyte in this invention includes a non-aqueous solvent, an electrolyte, and a phosphorus-containing compound.

[0086] There are no particular limitations on the non-aqueous solvent used; it can be any formulation used in the art for non-aqueous solvents in lithium-ion batteries. Commonly used non-aqueous solvents in the art for lithium-ion batteries include cyclic carbonates and chain carbonates, more preferably a combination of both. As a cyclic carbonate, it is preferably selected from at least one of ethylene carbonate (EC) and propylene carbonate (PC); as a chain carbonate, it is preferably selected from at least one of ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and dimethyl carbonate (DMC). For example, in one embodiment of the present invention, the formulation of the non-aqueous solvent is: ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a mass ratio of 3:5:2.

[0087] The content of the non-aqueous solvent is not particularly limited and can be determined with reference to conventional non-aqueous solvent addition amounts in the art. In a preferred embodiment of the present invention, the mass percentage of the non-aqueous solvent in the non-aqueous electrolyte is 60% to 85%.

[0088] Preferably, the non-aqueous electrolyte in this invention further includes additives. Specific examples of additives include: (A) one or more nitriles selected from acetonitrile, propionitrile, butadiene nitrile, glutaronitrile nitrile, adiponitrile nitrile, heptacyanide nitrile, octanoic acid nitrile, and sebacate nitrile; (B) aromatic compounds with branched alkyl groups such as cyclohexylbenzene, fluorocyclohexylbenzene compounds (1-fluoro-2-cyclohexylbenzene, 1-fluoro-3-cyclohexylbenzene, 1-fluoro-4-cyclohexylbenzene), tert-butylbenzene, tert-pentylbenzene, and 1-fluoro-4-tert-butylbenzene, biphenyl, terphenyl (ortho, meta, para), diphenyl ether, fluorobenzene, difluorobenzene (ortho, meta, para), anisole, 2,4-difluoroanisole, and partially hydrogenated terphenyl compounds (1,2-dicyclohexylbenzene, 2-phenyldicyclohexyl, 1,2-diphenylcyclohexane, ortho-cyclohexylbiphenyl), etc. (C) is selected from one or more isocyanate compounds selected from methyl isocyanate, ethyl isocyanate, butyl isocyanate, phenyl isocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, octamethylene diisocyanate, 1,4-phenylene diisocyanate, ethyl 2-isocyanate acrylate and ethyl 2-isocyanate methacrylate. (D) is selected from one or more compounds containing triple bonds selected from 2-propynyl methyl carbonate, 2-propynyl acetate, 2-propynyl formate, 2-propynyl methacrylate, 2-propynyl methanesulfonate, 2-propynyl vinyl sulfonate, 2-propynyl 2-(methanesulfonyloxy)propionate, di(2-propynyl) oxalate, methyl 2-propynyl oxalate, ethyl 2-propynyl oxalate, di(2-propynyl) glutarate, 2-butyn-1,4-dimethyldimethanesulfonate, 2-butyn-1,4-dimethyldicarboxylate, and 2,4-hexadiyne-1,6-dimethyldimethanesulfonate. (E) Selected from 1,3-propanesulfonyl lactone, 1,3-butanesulfonyl lactone, 2,4-butanesulfonyl lactone, 1,4-butanesulfonyl lactone, 1,3-propenesulfonyl lactone, 2,2-dioxide-1,2-oxothiacyclopentane-4-ylacetate, 5,5-dimethyl-1,2-oxothiacyclopentane-4-one 2,2-dioxide, etc.; ethylene sulfite, hexahydrobenzo[1,3,2]dioxacyclopentane-2-oxide (also known as 1,2-cyclohexanediol cyclic sulfite), 5-vinyl-hexahydro-1,3,2-benzo[1,3,2]dioxacyclopentane-2-oxide (also known as 1,2-cyclohexanediol cyclic sulfite), 5-vinyl-hexahydro-1,3,2-benzo[1,3,2]dioxacyclopentane-2-oxide, etc. Cyclic sulfites such as dioxetyl-2-oxide and 4-(methylsulfonylmethyl)-1,3,2-dioxetane-2-oxide; sulfonates such as butane-2,3-dimethyldimethanesulfonate, butane-1,4-dimethyldimethanesulfonate, methylenemethane disulfonate, dimethylmethane disulfonate, and pentafluorophenylmethane sulfonate; and one or more cyclic or chain-like compounds containing S=O groups, such as divinyl sulfone, 1,2-bis(vinylsulfonyl)ethane, and bis(2-vinylsulfonylethyl) ether.(F) Cyclic acetals such as 1,3-dioxane, 1,3-dioxane, and 1,3,5-trioxane. (G) is selected from trimethyl phosphate, tributyl phosphate and trioctyl phosphate, tris(2,2,2-trifluoroethyl) phosphate, bis(2,2,2-trifluoroethyl) phosphate, bis(2,2,2-trifluoroethyl) phosphate, bis(2,2,2-trifluoroethyl) phosphate, bis(2,2,2-trifluoroethyl) 2,2-difluoroethyl phosphate, bis(2,2,2-trifluoroethyl) 2,2,3,3-tetrafluoropropyl phosphate, bis(2,2-difluoroethyl) 2,2,2-trifluoroethyl phosphate, bis(2,2,3,3-tetrafluoropropyl) 2,2,2-trifluoroethyl phosphate and (2,2,2-trifluoroethyl)(2,2,3,3-tetrafluoropropyl) phosphate, tris(1,1,1,3,3,3-hexafluoropropane-2-yl) phosphate, methyl methylene bisphosphonate, ethyl methylene bisphosphonate, and ethyl methylene bisphosphonate. The following are one or more phosphorus-containing compounds selected from methyl bisphosphonate, ethyl ethylene bisphosphonate, methyl butyl bisphosphonate, ethyl butyl bisphosphonate, methyl 2-(dimethylphosphoryl)acetate, ethyl 2-(dimethylphosphoryl)acetate, methyl 2-(diethylphosphoryl)acetate, ethyl 2-(diethylphosphoryl)acetate, 2-(diethylphosphoryl)acetate, methyl 2-(dimethoxyphosphoryl)acetate, ethyl 2-(dimethoxyphosphoryl)acetate, methyl 2-(diethoxyphosphoryl)acetate, ethyl 2-(diethoxyphosphoryl)acetate, 2-(diethoxyphosphoryl)acetate, 2-(diethoxyphosphoryl)acetate, methyl 2-(diethoxyphosphoryl)acetate, methyl 2-(diethoxyphosphoryl)acetate, methyl 2-(diethoxyphosphoryl)acetate, methyl 2-(diethoxyphosphoryl)acetate, methyl 2-(diethoxyphosphoryl)acetate, and methyl pyrophosphate and ethyl pyrophosphate. (H) Chain-like carboxylic anhydrides such as acetic anhydride and propionic anhydride, succinic anhydride, maleic anhydride, 3-allyl succinic anhydride, glutaric anhydride, itaconic anhydride, 3-sulfonyl-propionic anhydride, and other cyclic anhydrides. (I) Cyclic phosphazene compounds such as methoxypentafluorocyclotriphosphazene, ethoxypentafluorocyclotriphosphazene, phenoxypentafluorocyclotriphosphazene, and ethoxyheptafluorocyclotetraphosphazene.

[0089] The mass percentage of the "phosphorus-containing compound" in the electrolyte of the present invention can be from 0.01% to 20%; more preferably from 0.02% to 10%; even more preferably from 0.02% to 5%; for example: 0.02%, 0.05%, 0.1%, 0.15%, 0.5%, 1%, 1.5%, 2%, 3% or 5%.

[0090] The mass percentage of the other additives used in lithium-ion batteries in the electrolyte is not limited, but is preferably 0.1 to 10%, for example 1%.

[0091] In exploring the optimal use of the "phosphorus-containing compound" of this invention, the inventors unexpectedly discovered that the "phosphorus-containing compound" of this invention, together with at least one (preferably two) of cyclic carbonates or cyclic sulfonyl lactones having carbon-carbon double or triple bonds and / or fluorine atoms, can achieve a significant synergistic effect when added to a non-aqueous electrolyte. This increases the stability of the film-forming process and contributes to improving battery cycle performance. In a preferred embodiment of this invention, the electrolyte includes the "additive" of this invention, vinylene carbonate (VC), and 1,3-propanesulfonyl lactone (PS), with a mass percentage ratio of (0.01-3):(0.5-3):(1-6):(0.5-6). For example: 5:5:10:5 (1:1:2:1), 1:2.5:2.5:5, 0.05:2.5:2.5:5 (1:50:50:100).

[0092] Furthermore, the inventors have discovered that when the non-aqueous electrolyte includes the "phosphorus-containing compound" of this invention, and cyclic carbonates, cyclic sulfonates, and cyclic sulfates having carbon-carbon double or triple bonds and / or fluorine atoms, the synergistic effect of the four additives is more significant, further improving battery cycle performance. In a preferred embodiment of this invention, the electrolyte contains the phosphorus-containing compound, vinylene carbonate (VC), 1,3-propanesulfonate lactone (PS), and vinyl sulfate (DTD) in a mass percentage ratio of (0.01-3):(0.5-3):(1-6):(0.5-6), for example: 5:5:10:5 (1:1:2:1), 1:2.5:2.5:5, 0.05:2.5:2.5:5 (1:50:50:100).

[0093] As an electrolyte, it can be selected from at least one of LiPF6, LiBF4, LiFSI, LiTFSI, LiBOB, LiODFP, LiODFB, LiPO2F2 and CF3SO3Li, such as LiPF6.

[0094] There is no particular limitation on the content of the electrolyte; reference can be made to the range of electrolyte addition amounts commonly used in the art. In a preferred embodiment of the present invention, the molar concentration of the electrolyte in the non-aqueous electrolyte is from 0.5 mol / L to 2 mol / L.

[0095] Lithium-ion batteries

[0096] In this invention, the lithium-ion battery includes a positive electrode, a negative electrode, a separator, and the aforementioned non-aqueous electrolyte.

[0097] Components such as positive and negative electrodes other than those made of aqueous electrolyte can be used without special restrictions.

[0098] As a positive electrode, it includes a positive electrode current collector and a positive electrode active material layer coated on the current collector. The positive electrode active material layer includes a positive electrode active material, which can be a lithium-containing composite oxide. Specific examples of lithium-containing composite oxides include LiMnO2, LiFeO2, LiMn2O4, Li2FeSiO4, and LiNi. 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi5CO2Mn3O2, LizNi (1-x-y) Co x M y O2 (x, y, and z are values ​​satisfying 0.01≤x≤0.20, 0≤y≤0.20, and 0.97≤z≤1.20, and M represents at least one element selected from Mn, V, Mg, Mo, Nb, and Al), LiFePO4, and Li z CO (1-x) M x O2 (x and z are values ​​that satisfy 0≤x≤0.1 and 0.97≤z≤1.20, and M represents at least one element selected from the group consisting of Mn, Ni, V, Mg, Mo, Nb and Al).

[0099] Positive electrode active materials can also be Li z Ni (1-x-y) Co x M y O2 (x, y, and z are values ​​satisfying 0.01≤x≤0.15, 0≤y≤0.15, and 0.97≤z≤1.20, and M represents at least one element selected from Mn, Ni, V, Mg, Mo, Nb, and Al) or Li z CO (1-x) M x O2 (x and z are values ​​satisfying 0 ≤ x ≤ 0.1 and 0.97 ≤ z ≤ 1.20, and M represents at least one element selected from Mn, V, Mg, Mo, Nb, and Al). In a preferred embodiment of the present invention, the positive electrode active material is: LiNi 0.6 Co 0.3 Mn 0.1 O2.

[0100] In addition to the positive electrode active material, the positive electrode active material layer usually includes a conductive agent and a binder. The types and amounts of conductive agents and binders are not particularly limited and can be referred to the conventional practices in the field.

[0101] As a negative electrode, it includes a negative electrode current collector and a negative electrode active material layer coated on the current collector. The negative electrode active material layer includes a negative electrode active material, which is a material capable of inserting and deintercalating lithium. This includes, but is not limited to, carbon materials such as crystalline carbon (natural graphite and artificial graphite), amorphous carbon, carbon-coated graphite and resin-coated graphite, and oxide materials such as indium oxide, silicon oxide, tin oxide, lithium titanate, zinc oxide and lithium oxide. The negative electrode active material can also be lithium metal or a metal material that can form an alloy with lithium. Specific examples of metals that can form an alloy with lithium include Cu, Sn, Si, Co, Mn, Fe, Sb and Ag. Binary or ternary alloys containing these metals and lithium can also be used as negative electrode active materials. These negative electrode active materials can be used alone or in combination of two or more. From the perspective of high energy density, carbon materials such as graphite can be combined with Si-based active materials such as Si, Si alloys, and Si oxides as the negative electrode active material. From the perspective of balancing cycle performance and high energy density, graphite and Si-based active materials can be combined as the negative electrode active material. Regarding this combination, the mass ratio of the Si-based active material to the total mass of the carbon material and the Si-based active material can be 0.5% to 95%, 1% to 50%, or 2% to 40%. In a preferred embodiment of the present invention, the negative electrode active material is artificial graphite or silicon.

[0102] In addition to the negative electrode active material, the negative electrode active material layer usually includes a conductive agent and a binder. The types and amounts of conductive agents and binders are not particularly limited and can be referred to the conventional practices in the field.

[0103] There are no particular restrictions on the type of membrane used, but single-layer or multi-layered microporous films, woven fabrics, or non-woven fabrics of polyolefins such as polypropylene and polyethylene can be used.

[0104] [Lithium-ion Battery Manufacturing Methods]

[0105] This invention provides a process for preparing a lithium-ion battery, but it should be understood that the preparation method is not limited to this.

[0106] Step 1: Ingredient preparation. The battery ingredients containing the non-aqueous electrolyte described in this invention are mixed in a certain proportion, and the materials are stirred under high vacuum in a fully automatic system for 10 hours.

[0107] Step 2: Coating. An automatic feeding system is used to coat the positive and negative electrode sheets evenly.

[0108] Step 3: Roller compaction. Apply pressure to compact the positive and negative electrode materials.

[0109] Part Four: Slicing. Depending on the battery model, the positive and negative electrode plates need to be sliced ​​into the required widths.

[0110] Step 5: Sheet making and winding. A fully automatic sheet making machine is used to weld the positive and negative tabs onto the positive and negative electrode sheets. A fully automatic winding machine is then used to wind the positive and negative electrode sheets and the separator together into a cylindrical shape.

[0111] Step 6: Bottom grooving and vacuum drying. The core is placed inside the steel shell, the negative electrode tab is automatically welded, and the core is automatically grooved. Additionally, it undergoes high-vacuum, high-temperature baking to remove a small amount of moisture.

[0112] Step 7: Formation and capacity testing. Perform a charge-discharge test on it.

[0113] Step 8: Assemble the lithium battery.

[0114] The following lists the experimental groups and their effects, and details the general experimental procedures.

[0115] the term

[0116] Unless otherwise specified, the term "alkyl" as used herein refers to a linear or branched saturated monovalent hydrocarbon group, wherein the alkyl group may optionally be substituted with one or more substituents. In certain embodiments, the alkyl group is having a carbon number of 1 to 20 (C0). 1-20 ), 1 to 15 (C 1-15 ), 1 to 12 (C 1-12 ), 1 to 10 (C 1-10 ) or 1 to 6 (C 1-6 A linear saturated monovalent hydrocarbon group with 3 to 20 carbon atoms, or a hydrocarbon group with 3 to 20 carbon atoms. 3-20 ), 3 to 15 (C 3-15 ), 3 to 12 (C 3-12 ), 3 to 10 (C 3-10 ) or 3 to 6 (C 3-6 A branched, saturated monovalent hydrocarbon group with 1 carbon atom. The linear C used here... 1-6 and C with branches 3-6 Alkyl groups are also called "lower alkyl groups". Examples of alkyl groups include, but are not limited to, methyl, ethyl, propyl (including all isomers), n-propyl, isopropyl, butyl (including all isomers), n-butyl, isobutyl, tert-butyl, pentyl (including all isomers), and hexyl (including all isomers). For example, C 1-6 Alkyl refers to a linear saturated monovalent hydrocarbon group having 1 to 6 carbon atoms or a branched saturated monovalent hydrocarbon group having 3 to 6 carbon atoms. In one embodiment, the alkyl group is an optionally substituted alkyl group as described elsewhere herein.

[0117] Unless otherwise specified, the term "alkenyl" as used herein refers to a linear or branched monovalent hydrocarbon group having one or more (one to five in one embodiment) carbon-carbon double bonds. The alkenyl group may optionally be substituted with one or more substituents. Those skilled in the art will understand that the term "alkenyl" may also include groups having "cis" and "trans" configurations, or alternatively, "E" and "Z" configurations. Unless otherwise specified, the term "alkenyl" as used herein includes both linear and branched alkenyl groups. For example, C 2-6 Alkyl refers to a linear unsaturated monovalent hydrocarbon group having 2 to 6 carbon atoms or a branched unsaturated monovalent hydrocarbon group having 3 to 6 carbon atoms. In a particular embodiment, the alkenyl group is a linear unsaturated monovalent hydrocarbon group having 2 to 20 carbon atoms. 2-20 ), 2 to 15 (C 2-15 ), 2 to 12 (C 2-12 ), 2 to 10 (C 2-10 ) or 2 to 6 (C 1-6 A linear monovalent hydrocarbon group with 3 to 20 carbon atoms, or a hydrocarbon group with 3 to 20 carbon atoms. 3-20 ), 3 to 15 (C 3-15 ), 3 to 12 (C 3-12 ), 3 to 10 (C 3-10 ) or 3 to 6 (C 3-6 A branched monovalent hydrocarbon group containing 1 carbon atom. Examples of alkenyl groups include, but are not limited to, vinyl, propenyl-1-yl, propenyl-2-yl, allyl, butenyl, and 4-methylbutenyl. In certain embodiments, the alkenyl group is an optionally substituted alkenyl group as described elsewhere herein.

[0118] Unless otherwise specified, the term "cycloalkyl" as used herein refers to a fully or partially saturated cyclic bridged and / or unbridged hydrocarbon group or cyclic system, which may optionally be substituted with one or more substituents. In certain embodiments, the cycloalkyl group has a carbon density of 3 to 20 (C). 3-20 ), 3 to 15 (C 3-15 ), 3 to 12 (C 3-12 ), 3 to 10 (C 3-10 ) or 3 to 7 (C 3-7 ( ) carbon atoms. Examples of cycloalkyl groups include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, decahydronaphthyl, and adamantyl. In one embodiment, the cycloalkyl group is an optionally substituted cycloalkyl group as described elsewhere herein.

[0119] Unless otherwise specified, the term "alkoxy group" as used herein refers to a stable straight-chain or branched, or cyclic, hydrocarbon group, or a combination thereof, consisting of the indicated number of carbon atoms and one or more (one to three in one embodiment) O atoms. Examples of alkoxy groups include, but are not limited to, -O-CH3, -O-CF3, -O-CH2-CH3, -O-CH2-CH2-CH3, -O-CH-(CH3)2, and -O-CH2-CH2-O-CH3. In one embodiment, the alkoxy group is an optionally substituted alkoxy group as described elsewhere herein.

[0120] Unless otherwise specified, the term "aryl" as used herein refers to an optionally substituted monocyclic and / or polycyclic group or ring system comprising at least one aromatic hydrocarbon ring. In certain embodiments, the aryl group has 6 to 20, 6 to 15, or 6 to 10 ring atoms. Aryl groups include, but are not limited to, phenyl, naphthyl, fluorenyl, chamomileyl, anthraceneyl, phenanthryl, pyrene, biphenyl, and terphenyl. In certain embodiments, aryl also refers to a bicyclic, tricyclic, or tetracyclic carbocyclic ring, wherein one ring is an aromatic ring, and the other rings may be saturated, partially unsaturated, or aromatic, such as dihydronaphthyl, indenyl, indanyl, or tetrahydronaphthyl (naphthyl). In certain embodiments, aryl refers to a bicyclic, tricyclic, or tetracyclic ring system wherein at least one ring is an aromatic ring, and one or more rings are saturated or partially unsaturated, comprising one or more independent heteroatoms selected from O, S, and N. In certain embodiments, the aryl group may optionally be substituted by one or more substituents as described elsewhere herein.

[0121] Unless otherwise specified, the term "hydrogen" as used herein includes protons ( 1 H), deuterium ( 2 H), tritium ( 3 H) and / or mixtures thereof. In the compounds described herein, one or more hydrogen-occupied sites may be enriched with deuterium and / or tritium. Such isotopically enriched analogs may be prepared from suitable isotopically labeled starting materials available from commercial sources or by known literature procedures.

[0122] Unless otherwise specified, the term "hydroxyl" as used herein refers to -OH.

[0123] Unless otherwise specified, the term "amino" as used herein refers to -NH2.

[0124] Unless otherwise specified, the term "nitro" as used herein refers to -NO2.

[0125] Unless otherwise specified, the term "halogen" as used herein refers to fluorine, chlorine, bromine and / or iodine.

[0126] Unless otherwise specified, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should be noted that the terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the exemplary embodiments of this application.

[0127] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the present invention is further described below in conjunction with specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the manufacturer. Unless otherwise stated, percentages and parts are weight percentages and parts by weight. Unless otherwise specified, the experimental materials and reagents used in the following embodiments are commercially available.

[0128] Example 1: Preparation of non-aqueous electrolyte and lithium-ion battery

[0129] The non-aqueous electrolyte is prepared in a glove box with a nitrogen content of 99.999%, an actual oxygen content of 0.1 ppm, and a moisture content of 0.1 ppm.

[0130] Based on the total mass of the non-aqueous electrolyte being 100%, ethylene carbonate, methyl ethyl carbonate, and diethyl carbonate (in a mass ratio of 3:5:2) were mixed evenly. Then, fully dried lithium hexafluorophosphate was added to the aforementioned non-aqueous solvent, along with 1% (by mass) of Compound 1, 2.5% of vinylene carbonate, 2.5% of 1,3-propanesulfonate lactone, and 5% of vinyl sulfate, respectively, to achieve a lithium hexafluorophosphate concentration of 1 mol / L. This prepared a non-aqueous electrolyte for lithium-ion batteries. In the prepared non-aqueous electrolyte, the mass ratio of Compound 1, vinylene carbonate, 1,3-propanesulfonate lactone, and vinyl sulfate was 1:2.5:2.5:5.

[0131] The structure of compound 1 is as follows:

[0132] The non-aqueous electrolyte prepared in this embodiment can be injected into a pouch cell to prepare a lithium-ion battery according to conventional methods in the art. For specific preparation methods, please refer to: [The text then abruptly shifts to a seemingly unrelated topic about a positive electrode active material, LiNi...] 0.6 Co 0.3 Mn 0.1 O2, conductive agent acetylene black, and binder polyvinylidene fluoride are mixed thoroughly in an N-methylpyrrolidone solvent system at a mass ratio of 95:3:2. The mixture is then coated onto aluminum foil, dried, and cold-pressed to obtain a positive electrode sheet with a compacted density of 3.5 g / cm³. 3 .

[0133] The negative electrode active material graphite, conductive agent acetylene black, binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose were thoroughly mixed in a deionized water solvent system at a mass ratio of 96:2:1:1. The mixture was then coated onto copper foil, dried, and cold-pressed to obtain the negative electrode sheet with a compacted density of 1.65 g / cm³. 3 .

[0134] A diaphragm was obtained by using 9 μm thick polyethylene as the base membrane and coating the base membrane with a 3 μm thick nano-alumina coating.

[0135] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide insulation. This stacking process yields a bare battery cell. The bare cell is then placed in an aluminum-plastic film, baked at 80°C to remove moisture, injected with the appropriate electrolyte, and sealed. Following these processes, it undergoes settling, hot and cold pressing, formation, clamping, and capacity testing to obtain the finished soft-pack lithium-ion secondary battery.

[0136] Example 2: Preparation of non-aqueous electrolyte and preparation of lithium-ion battery

[0137] The non-aqueous electrolyte is prepared in a glove box with a nitrogen content of 99.999%, an actual oxygen content of 0.1 ppm, and a moisture content of 0.1 ppm.

[0138] Based on the total mass of the non-aqueous electrolyte as 100%, ethylene carbonate, methyl ethyl carbonate, and diethyl carbonate battery-grade organic solvents in a mass ratio of 3:5:2 were mixed evenly. Fully dried lithium hexafluorophosphate was then added to the above non-aqueous solvent, along with 0.02% of compound 4, 0.025% of vinylene carbonate, and 0.025% of 1,3-propanesulfonate lactone by mass, respectively, to achieve a lithium hexafluorophosphate concentration of 0.5 mol / L. This prepared a non-aqueous electrolyte for lithium-ion batteries. In the prepared non-aqueous electrolyte, the mass ratio of compound 4, vinylene carbonate, and 1,3-propanesulfonate lactone was 2:2.5:2.5.

[0139] The structure of compound 4 is as follows:

[0140] The non-aqueous electrolyte prepared above was injected into a pouch cell using the same method as in Example 1 to prepare a lithium-ion battery.

[0141] Example 3: Preparation of non-aqueous electrolyte and preparation of lithium-ion battery

[0142] The non-aqueous electrolyte is prepared in a glove box with a nitrogen content of 99.999%, an actual oxygen content of 0.1 ppm, and a moisture content of 0.1 ppm.

[0143] Based on the total mass of the non-aqueous electrolyte as 100%, ethylene carbonate, methyl ethyl carbonate, and diethyl carbonate battery-grade organic solvents in a mass ratio of 3:5:2 were mixed evenly. Then, fully dried lithium hexafluorophosphate was added to the above non-aqueous solvent, along with 5% (by mass) of compound 11, 5% of vinylene carbonate, 10% of 1,3-propanesulfonate lactone, and 5% of vinyl sulfate, respectively, to achieve a lithium hexafluorophosphate concentration of 2 mol / L. This prepared a non-aqueous electrolyte for lithium-ion batteries. In the prepared non-aqueous electrolyte, the mass ratio of compound 11, vinylene carbonate, 1,3-propanesulfonate lactone, and vinyl sulfate was 1:1:2:1.

[0144] The structure of compound 11 is as follows:

[0145] The non-aqueous electrolyte prepared above was injected into a pouch cell using the same method as in Example 1 to prepare a lithium-ion battery.

[0146] Example 4: Preparation of non-aqueous electrolyte and preparation of lithium-ion battery

[0147] The method for preparing the non-aqueous electrolyte in this embodiment is largely the same as in Example 1, except that only Compound 1 is used as an additive in the non-aqueous electrolyte, and vinylene carbonate, 1,3-propanesulfonate lactone, and vinyl sulfate are not used. The specific preparation method is as follows: Based on 100% of the total mass of the non-aqueous electrolyte, ethylene carbonate, methyl ethyl carbonate, and diethyl carbonate (in a mass ratio of 3:5:2) are mixed evenly with a battery-grade organic solvent. Sufficiently dried lithium hexafluorophosphate is then added to the above non-aqueous solvent, along with 1% by mass of Compound 1, to achieve a lithium hexafluorophosphate concentration of 1 mol / L. This prepares a lithium-ion battery non-aqueous electrolyte.

[0148] The non-aqueous electrolyte prepared above was injected into a pouch cell using the same method as in Example 1 to prepare a lithium-ion battery.

[0149] Comparative Example 1: Preparation of Non-Aqueous Electrolyte and Preparation of Lithium-ion Battery

[0150] The method for preparing the non-aqueous electrolyte in this embodiment is roughly the same as that in Example 1, except that compound 1 is not added to the non-aqueous electrolyte.

[0151] The non-aqueous electrolyte prepared above was injected into a pouch cell using the same method as in Example 1 to prepare a lithium-ion battery.

[0152] Test Example 1: Discharge DC Internal Resistance Test (DCIR) after 30 days of high-temperature storage at 60℃

[0153] The lithium-ion battery was placed at 60°C for 30 days, and then the SOC of the battery was set to 50%. The charge-discharge rate (C-rate) was increased sequentially to 0.2C, 0.5C, 1.0C, 1.5C, 2.0C, 2.5C and 3.0C. A linear equation was constructed from the cutoff point of the voltage when charging and discharging for 10 seconds at the corresponding charge-discharge rate (C-rate), and its slope was defined as DCIR.

[0154] Test Example 2: Capacity retention during high-temperature cycling at 45°C

[0155] At 45℃, the lithium-ion battery was charged at a constant current of 1C to 4.2V, then charged at a constant voltage of 4.2V until the current was less than 0.05C. After resting for 10 minutes, it was discharged at a constant current of 1C to 2.8V. The discharge capacity of the lithium-ion battery at this point was measured, which is the discharge capacity of the first cycle. The battery was cycled multiple times under the above conditions, and the capacity retention rate after 400 cycles was calculated. The capacity retention rate after cycling was calculated using the following formula:

[0156] Capacity retention rate (%) = (Discharge capacity after 400 cycles / Discharge capacity after the first cycle) × 100%.

[0157] Test Example 3: Volume expansion rate after 30 days of storage at 60℃

[0158] At 25°C, the lithium-ion battery was charged at a constant current of 1C to 4.2V, and then charged at a constant voltage to a current of 0.05C. The volume of the lithium-ion battery was measured and recorded as V0. The fully charged battery was then stored in a 60°C oven for 30 days, and the volume after storage was measured and recorded as V1. The volume expansion rate of the lithium-ion battery relative to its initial volume before storage was calculated using the following formula:

[0159] Volume expansion rate (%) = (V1-V0) / V0×100%.

[0160] The batteries prepared in Examples 1 to 4 and Comparative Example 1 were tested for their performance according to the above method, and the results are summarized in Table 1.

[0161] Table 1

[0162]

[0163]

[0164] The battery test results in Examples 1 and 4 and Comparative Example 1 show that adding the compound of the present invention can significantly reduce the DC internal resistance of the battery, improve the capacity retention rate during fast charging at high temperature, and reduce battery gas production and volume expansion.

[0165] The battery test results in Examples 1 and 4 show that the compound of the present invention can work synergistically with VC, PS, and DTD to further reduce the internal resistance of lithium-ion batteries and improve the fast charging cycle performance and storage performance of the cells at high temperatures.

[0166] The battery test results from Examples 1, 2, and 3 show that adding compounds 1, 4, and 11 to the non-aqueous electrolyte can reduce battery internal resistance to varying degrees, improve the high-temperature fast-charging cycle capability of the cell, and reduce high-temperature gas generation. The structure shown by compound 1 is significantly better than that of compounds 4 and 11. It should be noted that the formulations in Examples 2 and 3 are the results of the inventors' optimized experiments after controlling the compound structure and conducting content screening experiments. Although the mass percentage of other additives in their formulations is not exactly the same as in Example 1, they represent the optimal battery performance under the stated composition.

[0167] To further investigate the synergistic effect of compound 1 with other additives such as VC, PS, and DTD, and to identify the optimal non-aqueous electrolyte formulation, the inventors conducted a large number of formulation screening experiments. The following examples and test cases illustrate some of the experimental steps and results.

[0168] Example 5: Preparation of non-aqueous electrolyte and preparation of lithium-ion battery

[0169] In this embodiment, the contents of vinylene carbonate, 1,3-propanesulfonate lactone, and vinyl sulfate are kept constant, while the amount of compound 1 added to the electrolyte is changed.

[0170] In this embodiment, three different formulations of non-aqueous electrolytes were prepared. The method for preparing each non-aqueous electrolyte was roughly the same as in Example 1, except that the amount of compound 1 added varied. Compound 1 was added to the non-aqueous electrolyte at mass percentages of 0.05%, 0.5%, and 3%, respectively, while the concentrations of the non-aqueous solvent and lithium hexafluorophosphate remained unchanged, thus preparing non-aqueous electrolytes for lithium-ion batteries.

[0171] The non-aqueous electrolyte prepared above was injected into a pouch cell to prepare a lithium-ion battery using the same method as in Example 1. Battery performance was then tested according to the methods described in Test Examples 1-3. The structure was recorded in Table 2 below, and a curve showing the change in battery performance with the content of compound 1 was plotted. Figure 1-3 .

[0172] Table 2

[0173]

[0174] analyze Figure 1-3As the mass percentage of compound 1 in the non-aqueous electrolyte increases, the DC internal resistance and high-temperature storage gas expansion rate of the lithium-ion battery at high temperature both show a trend of first decreasing and then increasing, while the high-temperature fast-charging cycle capability shows a trend of first increasing and then decreasing. When the composition and content of other additives in the electrolyte remain unchanged, and the mass percentage of compound 1 is close to 1%, the high-temperature DC internal resistance is the lowest, the high-temperature storage gas expansion rate is the smallest, and the high-temperature fast-charging cycle capability is the best, achieving the optimal effect.

[0175] Those skilled in the art will understand that the above embodiments are specific examples of implementing the present invention, and in practical applications, various changes in form and detail may be made without departing from the spirit and scope of the present invention.

Claims

1. A phosphorus-containing compound for use in lithium-ion battery electrolytes, characterized in that, The phosphorus-containing compound has the structure shown in formula (I). (I)， Among them, R 1 Selected from C 1-6 Alkyl group, at least one hydrogen atom is R 1-1 Replacement C 1-6 Alkyl, C 2-6 Alkenyl group, at least one hydrogen atom is R 1-1 Replacement C 2-6 alkenyl, C 3-6 Cycloalkyl groups, at least one hydrogen atom is R 1-1 Replacement C 3-6 cycloalkyl, R 1-1 Selected from nitro, -N(R) a R b ), phenyl, R a and R b Each is independently hydrogen or C 1-4 alkyl; R 2 Selected from C 1-6 Alkyl group, at least one hydrogen atom is R 2-1 Replacement C 1-6 Alkyl, C 2-12 Alkenyl group, at least one hydrogen atom is R 2 -1 Replacement C 2-12 alkenyl, phenyl, at least one hydrogen atom is R 2-1 Substituted phenyl, R 2-1 Selected from phenyl, C 1-4 Alkyl, hydroxyl, or at least one hydrogen atom is R 2-11 Substituted phenyl, R 2-11 Hydroxyl or C 1-4 Alkyl group.

2. The phosphorus-containing compound according to claim 1, characterized in that, The C 1-6 Alkyl group is C 1-4 Alkyl, the C 1-4 The alkyl group is methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, or tert-butyl; And / or, the C 2-6 The alkenyl group is C 2-4 alkenyl, the C 2-4 The alkenyl group is vinyl, 1-propenyl, 2-propenyl, 1-n-butenyl, 2-n-butenyl, 3-n-butenyl, 1-isobutenyl, 2-isobutenyl or 1,3-butadienyl; And / or, the C 3-6 The cycloalkyl group is cyclopropane, cyclobutane, cyclopentane, or cyclohexane; And / or, the C 1-4 The alkoxy group can be methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, isobutoxy, or tert-butoxy.

3. The phosphorus-containing compound according to claim 1, characterized in that, R 1 Methyl, ethyl, n-propyl, isopropyl, R 1-1 Substituted methyl, R 1-1 Substituted ethyl, R 1-1 Substituted n-propyl, R 1-1 Substituted isopropyl, cyclohexyl or R 1-1 Substituted cyclohexyl groups, R 1-1 For nitro, -NH2, , , or ; And / or, R 2 Methyl, ethyl, n-propyl, n-butyl, phenyl, vinyl, 1-propenyl, 2-propenyl, or at least one hydrogen atom is present. 2-1 The substituted methyl group, at least one hydrogen atom is R 2-1 The substituted n-propyl group, with at least one hydrogen atom replaced by R 2-1 Substituted vinyl, at least one hydrogen is R 2-1 Substituted phenyl, R 2-1 For phenyl or at least one hydrogen atom is R 2-11 Substituted phenyl, R 2-11 It can be hydroxyl, methoxy, ethoxy, n-propoxy, or isopropoxy.

4. The phosphorus-containing compound according to claim 1, characterized in that, R 1 Methyl, ethyl, isopropyl, cyclohexyl, or ; And / or, R 2 The following are examples of compounds: methyl, ethyl, n-propyl, n-butyl, 2-propenyl, phenyl, n-propyl with at least one hydrogen substituted by a phenyl group, ethyl with at least one hydrogen substituted by a phenyl group, vinyl with at least one hydrogen substituted by a trifluoromethyl group and / or fluorine group, vinyl with at least one hydrogen substituted by a phenyl group, and vinyl with at least one hydrogen substituted by an R group. 2-11 Substituted phenyl, R 2-11 It is either hydroxyl or methoxy.

5. The phosphorus-containing compound according to claim 1, characterized in that, R 2 Methyl, ethyl, n-propyl, n-butyl, 2-propenyl, phenyl , , or .

6. The phosphorus-containing compound according to claim 1, characterized in that, The phosphorus-containing compound is selected from any one or a combination of the following structures: 、 、 、 、 、 、 、 、 、 。 7. A non-aqueous electrolyte, characterized in that, The non-aqueous electrolyte comprises a non-aqueous solvent, an electrolyte, and a phosphorus-containing compound as described in any one of claims 1 to 6.

8. The non-aqueous electrolyte according to claim 7, characterized in that, The non-aqueous electrolyte also includes additives, which include at least one of cyclic carbonates, cyclic sulfonates, and cyclic sulfates having carbon-carbon double or triple bonds, unsaturated bonds, and / or fluorine atoms.

9. The non-aqueous electrolyte according to claim 8, characterized in that, The cyclic carbonate having carbon-carbon double or triple bonds, unsaturated bonds and / or fluorine atoms is selected from vinylene carbonate, ethylene ethylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, or combinations thereof. And / or, the cyclic sulfonyl lactone is selected from 1,3-propanesulfonyl lactone, 1,4-butanesulfonyl lactone, propenyl-1,3-sulfonyl lactone, or combinations thereof; And / or, the cyclic sulfate lactone is selected from vinyl sulfate, propenol sulfate, or a combination thereof.

10. The non-aqueous electrolyte according to claim 7, characterized in that, The non-aqueous electrolyte also includes additives, including vinylene carbonate, 1,3-propanesulfonate lactone, and vinyl sulfate.

11. The non-aqueous electrolyte according to claim 10, characterized in that, The mass percentage ratio of the phosphorus-containing compound, the vinylene carbonate, the 1,3-propanesulfonate lactone, and the vinyl sulfate is (0.01-3):(0.5-3):(1-6):(0.5-6).

12. A lithium-ion battery, characterized in that, The lithium-ion battery includes a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte as described in any one of claims 7 to 11.

13. The lithium-ion battery according to claim 12, characterized in that, The positive electrode includes a current collector and a positive electrode active material layer coated on the current collector. The positive electrode active material layer includes a positive electrode active material, which includes any one or a combination of at least two of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, or lithium nickel cobalt aluminum oxide.

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