Electrolyte additive, electrolyte, lithium ion battery and electric device

Abstract

The invention relates to an electrolyte additive, an electrolyte, a lithium ion battery and an electric device. Wherein the electrolyte additive comprises a compound with a structural general formula as shown in a formula (I): # imgabs0 #, and m, n and p are independently selected from integers from 1 to 5. According to the electrolyte additive provided by the invention, a fluorocarbon side chain and a tertiary amine group in the compound with the structural general formula as shown in the formula (I) have a synergistic effect. On one hand, a fluorocarbon side chain has strong hydrophobicity, and a tertiary amine group has hydrophilicity, so that in a non-water environment, trace water is easily captured by the tertiary amine group, the contact between the trace water and an electrolyte salt is reduced, the electrolyte salt is prevented from being further decomposed to damage an interface and a positive electrode active material, and the cycle and storage performance of the battery under high voltage is improved; and on the other hand, H atoms on alkyl in a fluorocarbon side chain are all substituted by F atoms, so that the oxidation resistance of the electrolyte additive can be improved, and the electrolyte additive is prevented from being decomposed under high voltage.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to an electrolyte additive, an electrolyte, a lithium-ion battery, and an electrical device. Background Art

[0002] As lithium-ion batteries are widely used in electric vehicles, electronic products and other fields, users have put forward higher and higher requirements for their performance, especially higher energy density. Among them, increasing the charging voltage is one of the main methods to improve the energy density of batteries.

[0003] However, increasing the charging voltage will lead to instability of the positive electrode active material and the electrolyte, causing the electrolyte to decompose and produce gas, thereby affecting the life and safety of the battery. Summary of the invention

[0004] Based on this, it is necessary to provide an electrolyte additive, an electrolyte, a lithium-ion battery, and an electrical device to improve the cycle and storage performance of the battery under high voltage.

[0005] The first aspect of the present application provides an electrolyte additive, which includes a compound having a structural formula shown in formula (I):

[0006]

[0007] Here, m, n, and p are each independently selected from integers of 1 to 5.

[0008] In some embodiments, m, n, and p are the same.

[0009] In some embodiments, the compound having the general structural formula shown in formula (I) is selected from at least one of the following compounds:

[0010]

[0011] The second aspect of the present application provides an electrolyte, which includes a solvent, an electrolyte salt and the electrolyte additive provided by the first aspect.

[0012] In some embodiments, the mass percentage of the electrolyte additive in the electrolyte is 0.01% to 5%.

[0013] In some embodiments, the electrolyte salt includes one or more of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium perchlorate, lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, and lithium bis(trifluoromethanesulfonyl)imide.

[0014] In some embodiments, the electrolyte further includes other additives, and the other additives include one or more of sultone compounds, cyclic sulfate compounds, phosphate compounds, and borate compounds.

[0015] A third aspect of the present application provides a lithium-ion battery, which includes a positive electrode, a negative electrode, a separator, and the electrolyte provided in the second aspect.

[0016] In some embodiments, the charging cut-off voltage of the lithium-ion battery is ≥4.5V.

[0017] A fourth aspect of the present application provides an electrical device, which includes the lithium-ion battery provided in the third aspect.

[0018] Compared with the traditional technology, this application has at least the following beneficial effects:

[0019] The electrolyte additive provided in the present application, the carbon fluoride side chain and the tertiary amine group in the compound of the general structural formula shown in formula (I) have a synergistic effect. On the one hand, the carbon fluoride side chain has strong hydrophobicity and the tertiary amine group has hydrophilicity, so in a non-aqueous environment, trace water tends to gather around the tertiary amine group and form a tiny phase separation structure in the electrolyte, thereby being captured by the tertiary amine group, reducing the contact between trace water and the electrolyte salt, avoiding further decomposition of the electrolyte salt to destroy the interface and the positive electrode active material, and improving the cycle and storage performance of the battery at high voltage; on the other hand, the H atoms on the alkyl group in the carbon fluoride side chain are all replaced by F atoms, which can improve the oxidation resistance of the electrolyte additive, avoid the decomposition of the electrolyte additive under high pressure, and at the same time can form an interface film rich in LiF on the positive electrode surface, improve the interface chemistry, and thus show excellent high voltage resistance and thermal stability.

[0020] The above is only a possible speculation on the mechanism of the present application and does not constitute a limitation on the scope of protection of the present application. DETAILED DESCRIPTION

[0021] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0022] In the description of this application, unless otherwise defined, unspecified professional terms and professional words have the same meaning as those commonly understood by those skilled in the art and are common knowledge of those skilled in the art, and unspecified methods are conventional methods known to those skilled in the art. The term "multiple" in this application means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0023] In the present application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0024] In this application, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are deemed to be continuous and include the minimum and maximum values ​​of the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0025] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0026] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0027] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0028] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0029] The first aspect of the present application provides an electrolyte additive, which includes a compound having a structural formula shown in formula (I):

[0030]

[0031] Here, m, n, and p are each independently selected from integers of 1 to 5.

[0032] The electrolyte additive provided in the present application, the carbon fluoride side chain and the tertiary amine group in the compound of the general structural formula shown in formula (I) have a synergistic effect. On the one hand, the carbon fluoride side chain has strong hydrophobicity and the tertiary amine group has hydrophilicity, so in a non-aqueous environment, trace water tends to gather around the tertiary amine group and form a tiny phase separation structure in the electrolyte, thereby being captured by the tertiary amine group, reducing the contact between trace water and the electrolyte salt, avoiding further decomposition of the electrolyte salt to destroy the interface and the positive electrode active material, and improving the cycle and storage performance of the battery at high voltage; on the other hand, the H atoms on the alkyl group in the carbon fluoride side chain are all replaced by F atoms, which can improve the oxidation resistance of the electrolyte additive, avoid the decomposition of the electrolyte additive under high pressure, and at the same time can form an interface film rich in LiF on the positive electrode surface, improve the interface chemistry, and thus show excellent high voltage resistance and thermal stability.

[0033] The above is only a possible speculation on the mechanism of the present application and does not constitute a limitation on the scope of protection of the present application.

[0034] In the present application, m, n, and p may be the same or different.

[0035] In some embodiments, the compound having the general structural formula shown in formula (I) is selected from at least one of the following compounds:

[0036]

[0037] The second aspect of the present application provides an electrolyte, which includes a solvent, an electrolyte salt and the electrolyte additive provided by the first aspect.

[0038] In some embodiments, the mass percentage of the electrolyte additive in the electrolyte is 0.01% to 5%, including but not limited to 0.01%, 0.5%, 0.8%, 1%, 2%, 3%, 4%, 5%. Further, the mass percentage of the electrolyte additive in the electrolyte is 0.1% to 1%.

[0039] In some embodiments, the mass percentage of electrolyte salt in the electrolyte is 0.5% to 20%, including but not limited to 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, and 20%.

[0040] In some embodiments, the electrolyte salt includes one or more of lithium hexafluorophosphate (LiPF6), lithium hexafluoroarsenate (LiAsF6), lithium perchlorate (LiClO4), lithium bis(trifluorosulfonyl)imide (LiFSI), lithium tetrafluoroborate (LiBF4), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0041] Furthermore, the electrolyte salt includes one or more of lithium hexafluorophosphate (LiPF6), lithium hexafluoroarsenate (LiAsF6) and lithium tetrafluoroborate (LiBF4). The above electrolyte salts are sensitive to trace water in the electrolyte and easily react with water, thereby generating gas or destroying the electrode. The compound having the general structural formula shown in formula (I) as an electrolyte additive can effectively capture moisture and improve the stability of the electrolyte and the interface stability of the electrode.

[0042] In some embodiments, the solvent includes a non-aqueous organic solvent.

[0043] In some embodiments, the solvent includes one or more of a carbonate solvent, a carboxylate solvent, and an aromatic hydrocarbon solvent.

[0044] In some embodiments, the carbonate solvent includes halogenated carbonate and / or non-halogenated carbonate.

[0045] In some embodiments, the halogenated carbonate includes one or more of fluoroethylene carbonate, bisfluoropropylene carbonate, trifluoroethyl methyl carbonate, trifluoromethylethylene carbonate, 4-trifluoromethylethylene carbonate, chloroethylene carbonate, di(2,2,2-trifluoroethyl) carbonate, or 1,1,1,3,3,3-hexafluoroisopropyl acrylate.

[0046] In some embodiments, the non-halogenated carbonate includes one or more of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, or ethyl methyl carbonate.

[0047] In some embodiments, the carboxylate solvent includes halogenated carboxylate and / or non-halogenated carboxylate.

[0048] In some embodiments, the halogenated carboxylic acid ester includes one or more of propyl fluorobutyrate, propyl fluoroacetate, ethyl fluoroacetate, isopropyl fluoroacetate, butyl fluoropropionate, isopropyl fluoropropionate, ethyl fluorobutyrate, methyl fluoropropionate, ethyl fluoropropionate, or propyl fluoropropionate.

[0049] In some embodiments, the non-halogenated carboxylic acid ester includes one or more of ethyl acetate, methyl acetate, propyl butyrate, propyl acetate, isopropyl acetate, butyl propionate, isopropyl propionate, ethyl butyrate, methyl propionate, ethyl propionate or propyl propionate.

[0050] In some embodiments, the aromatic hydrocarbon solvent includes halogenated aromatic hydrocarbons and / or non-halogenated aromatic hydrocarbons.

[0051] In some embodiments, the halogenated aromatic hydrocarbon includes one or more of monofluorobenzene, difluorobenzene, 1,3,5-trifluorobenzene, trifluorotoluene, 2-fluorotoluene, or 2,4-dichlorotrifluorotoluene.

[0052] In some embodiments, the electrolyte further includes other additives, and the other additives include one or more of sultone compounds, cyclic sulfate compounds, phosphate compounds and borate compounds.

[0053] In some embodiments, the mass percentage of other additives in the electrolyte is 0.1% to 5%, including but not limited to 0.1%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, and 5.0%.

[0054] In some embodiments, the sultone compound is selected from one or more of 1,3-propane sultone, 1,4-butane sultone, and propenyl-1,3-sultone.

[0055] In some embodiments, the cyclic sulfate ester compound is selected from one or more of vinyl sulfate, 4-methylvinyl sulfate, and propylene sulfate.

[0056] In some embodiments, the cyclic sulfate ester compound is selected from one or more compounds having the following structural formula:

[0057]

[0058] In some embodiments, the phosphate compound is selected from at least one of a saturated phosphate compound and an unsaturated phosphate compound. The saturated phosphate compound includes tris(trimethylsilyl)phosphate; the unsaturated phosphate compound includes at least one of the compounds shown in formula (II):

[0059]

[0060] Among them, R 21 , R 22 , R 23 are independently selected from C1-C5 saturated hydrocarbon groups, unsaturated hydrocarbon groups, halogenated hydrocarbon groups, -Si(C m H 2m+1 )3, m is a natural number from 1 to 3, and R 21 , R 22 , R 23 At least one of them is an unsaturated hydrocarbon group.

[0061] In some embodiments, the borate ester compound is selected from one or more of tris(trimethylsilyl)borate and tris(triethylsilyl)borate.

[0062] A third aspect of the present application provides a lithium-ion battery, which includes a positive electrode, a negative electrode, a separator, and the electrolyte provided in the second aspect.

[0063] In some embodiments, the positive electrode includes a positive electrode active material layer and a positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode active material.

[0064] In some embodiments, the positive electrode active material includes one or more of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium iron manganese phosphate, lithium nickel manganese oxide, lithium-rich manganese-based materials, lithium vanadium phosphate and ternary materials. Among them, the ternary material includes one or more of lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide.

[0065] In some embodiments, the negative electrode includes a negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes but is not limited to one or more of graphite, soft carbon, hard carbon, a composite material of single crystal silicon and graphite, a composite material of silicon oxide and graphite, lithium titanate, and niobium pentoxide.

[0066] In some of the embodiments, a diaphragm commonly used in lithium-ion batteries is selected, for example, a porous polymer membrane prepared from polyolefin polymers such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer and ethylene / methacrylate copolymer, which can be used alone as a diaphragm or laminated together as a diaphragm included in the lithium-ion battery of the present application. Non-woven fabrics formed of polyester fibers, aramid fibers, glass fibers, etc. can also be used; as well as base membranes formed by ceramic particles such as silica, alumina, and titanium dioxide attached to their surfaces, etc.

[0067] In some embodiments, the charging cut-off voltage of the lithium-ion battery is ≥4.5V; preferably, the charging cut-off voltage of the lithium-ion battery is ≥4.9V.

[0068] In some embodiments, the positive electrode includes at least one positive electrode active material having a charge cut-off voltage higher than 4.5V; further preferably, the positive electrode includes at least one positive electrode active material having a charge cut-off voltage higher than 4.7V; particularly preferably, the positive electrode includes at least one positive electrode active material having a charge cut-off voltage higher than 4.9V.

[0069] It is understood that the positive electrode active material of the present application can be a mixture or a pure substance. When it is a pure substance, it can be a positive electrode active material with a charge cut-off voltage greater than 4.5 V. When it is a mixture, it can be a mixture of multiple positive electrode active materials with a charge cut-off voltage greater than 4.5 V, or it can be a mixture of one or more positive electrode active materials with a charge cut-off voltage greater than 4.5 V and one or more positive electrode materials with a charge cut-off voltage lower than 4.5 V.

[0070] In some embodiments, the positive electrode active material is a mixture, and a voltage platform of at least one positive electrode active material is higher than 4.5V.

[0071] In some embodiments, the positive electrode active material is a mixture, and a charge cut-off voltage of at least one positive electrode active material is ≥4.7V.

[0072] In some embodiments, the positive electrode active material is a mixture of a plurality of positive electrode active materials with a charge cut-off voltage ≥ 4.7V.

[0073] In some embodiments, the positive electrode active material is a pure substance.

[0074] It is understandable that a pure substance refers to a substance containing only one positive electrode active material, and the presence of impurities and non-positive electrode active material additives in a single positive electrode active material system should not be interpreted as the positive electrode active material system being a mixture.

[0075] In some embodiments, the positive electrode active material has a charge cut-off voltage greater than 4.9V.

[0076] In some embodiments, the positive electrode active material with a charge cut-off voltage greater than 4.5V accounts for more than 50wt% of all positive electrode active materials in the positive electrode active material layer; preferably, the positive electrode active material with a charge cut-off voltage greater than 4.5V accounts for more than 70wt% of all positive electrode active materials in the positive electrode active material layer; further preferably, the positive electrode active material with a charge cut-off voltage greater than 4.5V accounts for more than 90wt% of all positive electrode active materials in the positive electrode active material layer.

[0077] It is understandable that when a multilayer electrode is used, as long as one layer of the entire positive electrode active material layer meets the above-mentioned proportion requirements, it should be considered to be within the scope of protection of this application. The above-mentioned positive electrode active material layer should be understood as the active material layer containing the positive electrode active material with a charge cut-off voltage greater than 4.5V, rather than the entire positive electrode active material layer.

[0078] It is understood that lithium-ion batteries can be prepared and used according to conventional methods known in the art.

[0079] A fourth aspect of the present application provides an electrical device, which includes the lithium-ion battery provided in the third aspect.

[0080] The electrical device of the present application is not particularly limited, and it can be any electrical device known in the prior art. For example, the electrical device can include, but is not limited to, a laptop computer, a pen-input computer, a mobile computer, an electronic book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, an LCD television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, a car, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, an electric tool, a flashlight, a camera, a large household battery, and a lithium-ion capacitor.

[0081] The present application will be further described below with reference to specific embodiments and comparative examples.

[0082] In the following embodiments, comparative examples and test examples, the reagents, materials and instruments used are all commercially available unless otherwise specified.

[0083] The present application will be further described below with reference to specific embodiments and comparative examples.

[0084] Example 1

[0085] Electrolyte additives:

[0086] The electrolyte additive includes a compound having a structure represented by the following formula (I-1).

[0087]

[0088] Electrolyte:

[0089] The electrolyte includes electrolyte salt, solvent, the above electrolyte additives and other additives. The electrolyte salt is LiPF6; the solvent is a combination of FEC, EC and DEC in the ratio of FEC:EC:DEC=2:1:7; other additives include 1,3-propane sultone (PS) and tris(trimethylsilyl) phosphate (TMSP);

[0090] Among them, the mass proportion of electrolyte salt in the electrolyte is 13%; the mass proportion of electrolyte additive in the electrolyte is 1%; the mass proportions of PS and TMSP in the electrolyte are 3% and 2% respectively; the remainder is solvent.

[0091] Lithium-ion battery:

[0092] The lithium-ion battery comprises a positive electrode, a negative electrode and the above electrolyte. The positive electrode comprises a positive electrode active material, which is lithium nickel manganese oxide; the negative electrode comprises a negative electrode active material, which is graphite.

[0093] Example 2

[0094] Electrolyte additives:

[0095] The electrolyte additive includes a compound having a structure represented by the following formula (I-1).

[0096]

[0097] Electrolyte:

[0098] The electrolyte includes electrolyte salt, solvent, the above electrolyte additives and other additives. The electrolyte salt is LiPF6; the solvent is a combination of FEC, EC and DEC in the ratio of FEC:EC:DEC=2:1:7; other additives include 1,3-propane sultone (PS) and tris(trimethylsilyl) phosphate (TMSP);

[0099] Among them, the mass proportion of electrolyte salt in the electrolyte is 13%; the mass proportion of electrolyte additive in the electrolyte is 0.01%; the mass proportions of PS and TMSP in the electrolyte are 3% and 2% respectively; the remainder is solvent.

[0100] Lithium-ion battery:

[0101] The lithium-ion battery comprises a positive electrode, a negative electrode and the above electrolyte. The positive electrode comprises a positive electrode active material, which is lithium nickel manganese oxide; the negative electrode comprises a negative electrode active material, which is graphite.

[0102] Example 3

[0103] Electrolyte additives:

[0104] The electrolyte additive includes a compound having a structure represented by the following formula (I-1).

[0105]

[0106] Electrolyte:

[0107] The electrolyte includes electrolyte salt, solvent, the above electrolyte additives and other additives. The electrolyte salt is LiPF6; the solvent is a combination of FEC, EC and DEC in the ratio of FEC:EC:DEC=2:1:7; other additives include 1,3-propane sultone (PS) and tris(trimethylsilyl) phosphate (TMSP);

[0108] Among them, the mass proportion of electrolyte salt in the electrolyte is 13%; the mass proportion of electrolyte additive in the electrolyte is 5%; the mass proportions of PS and TMSP in the electrolyte are 3% and 2% respectively; the remainder is solvent.

[0109] Lithium-ion battery:

[0110] The lithium-ion battery comprises a positive electrode, a negative electrode and the above electrolyte. The positive electrode comprises a positive electrode active material, which is lithium nickel manganese oxide; the negative electrode comprises a negative electrode active material, which is graphite.

[0111] Example 4

[0112] Electrolyte additives:

[0113] The electrolyte additive includes a compound having a structure represented by the following formula (I-2).

[0114]

[0115] Electrolyte:

[0116] The electrolyte includes electrolyte salt, solvent, the above electrolyte additives and other additives. The electrolyte salt is LiPF6; the solvent is a combination of FEC, EC and DEC in the ratio of FEC:EC:DEC=2:1:7; other additives include 1,3-propane sultone (PS) and tris(trimethylsilyl) phosphate (TMSP);

[0117] Among them, the mass proportion of electrolyte salt in the electrolyte is 13%; the mass proportion of electrolyte additive in the electrolyte is 1%; the mass proportions of PS and TMSP in the electrolyte are 3% and 2% respectively; the remainder is solvent.

[0118] Lithium-ion battery:

[0119] The lithium-ion battery comprises a positive electrode, a negative electrode and the above electrolyte. The positive electrode comprises a positive electrode active material, which is lithium nickel manganese oxide; the negative electrode comprises a negative electrode active material, which is graphite.

[0120] Example 5

[0121] Electrolyte additives:

[0122] The electrolyte additive includes a compound having a structure represented by the following formula (I-3).

[0123]

[0124] Electrolyte:

[0125] The electrolyte includes electrolyte salt, solvent, the above electrolyte additives and other additives. The electrolyte salt is LiPF6; the solvent is a combination of FEC, EC and DEC in the ratio of FEC:EC:DEC=2:1:7; other additives include 1,3-propane sultone (PS) and tris(trimethylsilyl) phosphate (TMSP);

[0126] Among them, the mass proportion of electrolyte salt in the electrolyte is 13%; the mass proportion of electrolyte additive in the electrolyte is 1%; the mass proportions of PS and TMSP in the electrolyte are 3% and 2% respectively; the remainder is solvent.

[0127] Lithium-ion battery:

[0128] The lithium-ion battery comprises a positive electrode, a negative electrode and the above electrolyte. The positive electrode comprises a positive electrode active material, which is lithium nickel manganese oxide; the negative electrode comprises a negative electrode active material, which is graphite.

[0129] Example 6

[0130] Electrolyte additives:

[0131] The electrolyte additive includes a compound having a structure represented by the following formula (I-4).

[0132]

[0133] Electrolyte:

[0134] The electrolyte includes electrolyte salt, solvent, the above electrolyte additives and other additives. The electrolyte salt is LiPF6; the solvent is a combination of FEC, EC and DEC in the ratio of FEC:EC:DEC=2:1:7; other additives include 1,3-propane sultone (PS) and tris(trimethylsilyl) phosphate (TMSP);

[0135] Among them, the mass proportion of electrolyte salt in the electrolyte is 13%; the mass proportion of electrolyte additive in the electrolyte is 1%; the mass proportions of PS and TMSP in the electrolyte are 3% and 2% respectively; the remainder is solvent.

[0136] Lithium-ion battery:

[0137] The lithium-ion battery comprises a positive electrode, a negative electrode and the above electrolyte. The positive electrode comprises a positive electrode active material, which is lithium nickel manganese oxide; the negative electrode comprises a negative electrode active material, which is graphite.

[0138] Example 7

[0139] Electrolyte additives:

[0140] The electrolyte additive includes a compound having a structure represented by the following formula (I-5).

[0141]

[0142] Electrolyte:

[0143] The electrolyte includes electrolyte salt, solvent, the above electrolyte additives and other additives. The electrolyte salt is LiPF6; the solvent is a combination of FEC, EC and DEC in the ratio of FEC:EC:DEC=2:1:7; other additives include 1,3-propane sultone (PS) and tris(trimethylsilyl) phosphate (TMSP);

[0144] Among them, the mass proportion of electrolyte salt in the electrolyte is 13%; the mass proportion of electrolyte additive in the electrolyte is 1%; the mass proportions of PS and TMSP in the electrolyte are 3% and 2% respectively; the remainder is solvent.

[0145] Lithium-ion battery:

[0146] The lithium-ion battery comprises a positive electrode, a negative electrode and the above electrolyte. The positive electrode comprises a positive electrode active material, which is lithium nickel manganese oxide; the negative electrode comprises a negative electrode active material, which is graphite.

[0147] Example 8

[0148] Electrolyte additives:

[0149] The electrolyte additive includes a compound having a structure represented by the following formula (I-6).

[0150]

[0151] Electrolyte:

[0152] The electrolyte includes electrolyte salt, solvent, the above electrolyte additives and other additives. The electrolyte salt is LiPF6; the solvent is a combination of FEC, EC and DEC in the ratio of FEC:EC:DEC=2:1:7; other additives include 1,3-propane sultone (PS) and tris(trimethylsilyl) phosphate (TMSP);

[0153] Among them, the mass proportion of electrolyte salt in the electrolyte is 13%; the mass proportion of electrolyte additive in the electrolyte is 1%; the mass proportions of PS and TMSP in the electrolyte are 3% and 2% respectively; the remainder is solvent.

[0154] Lithium-ion battery:

[0155] The lithium-ion battery comprises a positive electrode, a negative electrode and the above electrolyte. The positive electrode comprises a positive electrode active material, which is lithium nickel manganese oxide; the negative electrode comprises a negative electrode active material, which is graphite.

[0156] Comparative Example 1

[0157] Electrolyte:

[0158] The electrolyte includes electrolyte salt, solvent and other additives. The electrolyte salt is LiPF6; the solvent is a combination of FEC, EC and DEC in the ratio of FEC:EC:DEC=2:1:7; other additives include 1,3-propane sultone (PS) and tris(trimethylsilyl) phosphate (TMSP);

[0159] Among them, the mass proportion of electrolyte salt in the electrolyte is 13%; the mass proportions of PS and TMSP in the electrolyte are 3% and 2% respectively; the remainder is solvent.

[0160] Lithium-ion battery:

[0161] The lithium-ion battery comprises a positive electrode, a negative electrode and the above electrolyte. The positive electrode comprises a positive electrode active material, which is lithium nickel manganese oxide; the negative electrode comprises a negative electrode active material, which is graphite.

[0162] Comparative Example 2

[0163] The electrolyte additive includes a compound having a structure represented by the following formula (I-1).

[0164]

[0165] Electrolyte:

[0166] The electrolyte includes electrolyte salt, solvent, the above electrolyte additives and other additives. The electrolyte salt is LiPF6; the solvent is a combination of FEC, EC and DEC in the ratio of FEC:EC:DEC=2:1:7; other additives include 1,3-propane sultone (PS) and tris(trimethylsilyl) phosphate (TMSP);

[0167] Among them, the mass proportion of electrolyte salt in the electrolyte is 13%; the mass proportion of electrolyte additive in the electrolyte is 20%; the mass proportions of PS and TMSP in the electrolyte are 3% and 2% respectively; the remainder is solvent.

[0168] Lithium-ion battery:

[0169] The lithium-ion battery comprises a positive electrode, a negative electrode and the above electrolyte. The positive electrode comprises a positive electrode active material, which is lithium nickel manganese oxide; the negative electrode comprises a negative electrode active material, which is graphite.

[0170] Comparative Example 3

[0171] Electrolyte additives:

[0172] The electrolyte additive includes a compound having a structure represented by the following formula (III).

[0173]

[0174] Electrolyte:

[0175] The electrolyte includes electrolyte salt, solvent, the above electrolyte additives and other additives. The electrolyte salt is LiPF6; the solvent is a combination of FEC, EC and DEC in the ratio of FEC:EC:DEC=2:1:7; other additives include 1,3-propane sultone (PS) and tris(trimethylsilyl) phosphate (TMSP);

[0176] Among them, the mass proportion of electrolyte salt in the electrolyte is 13%; the mass proportion of electrolyte additive in the electrolyte is 1%; the mass proportions of PS and TMSP in the electrolyte are 3% and 2% respectively; the remainder is solvent.

[0177] Lithium-ion battery:

[0178] The lithium-ion battery comprises a positive electrode, a negative electrode and the above electrolyte. The positive electrode comprises a positive electrode active material, which is lithium nickel manganese oxide; the negative electrode comprises a negative electrode active material, which is graphite.

[0179] Comparative Example 4

[0180] Electrolyte additives:

[0181] The electrolyte additive includes a compound having a structure represented by the following formula (IV).

[0182]

[0183] Electrolyte:

[0184] The electrolyte includes electrolyte salt, solvent, the above electrolyte additives and other additives. The electrolyte salt is LiPF6; the solvent is a combination of FEC, EC and DEC in the ratio of FEC:EC:DEC=2:1:7; other additives include 1,3-propane sultone (PS) and tris(trimethylsilyl) phosphate (TMSP);

[0185] Among them, the mass proportion of electrolyte salt in the electrolyte is 13%; the mass proportion of electrolyte additive in the electrolyte is 1%; the mass proportions of PS and TMSP in the electrolyte are 3% and 2% respectively; the remainder is solvent.

[0186] Lithium-ion battery:

[0187] The lithium-ion battery comprises a positive electrode, a negative electrode and the above electrolyte. The positive electrode comprises a positive electrode active material, which is lithium nickel manganese oxide; the negative electrode comprises a negative electrode active material, which is graphite.

[0188] Performance Testing

[0189] The lithium ion batteries of the above embodiments and comparative examples were subjected to high voltage cycle performance tests:

[0190] The test conditions are: at 25°C, the charge and discharge potential range is 3.5V to 4.9V, and the charging current is 1C to 4.5V. The specific test process is as follows:

[0191] The lithium-ion battery was charged at 4.5V constant voltage to a cut-off current ≤0.05C, left to stand for 5 minutes, and then discharged at 1C to 3V and left to stand for 5 minutes. This is a charge and discharge cycle process. The discharge capacity of the first cycle was recorded. The test results are shown in Table 1.

[0192] The lithium-ion battery was charged and discharged for 100 cycles according to the above method, and the discharge capacity of the 100th cycle was detected.

[0193] The capacity retention rate (%) of the lithium-ion battery after 100 cycles is calculated as follows: (discharge capacity of the lithium-ion battery after 100 cycles / discharge capacity of the lithium-ion battery after the first cycle)×100%. The calculation results are shown in Table 1.

[0194] Table 1

[0195]

[0196] By comparing Examples 1 to 8 with Comparative Examples 1 to 4, it can be seen that the use of the electrolyte additive of the present application improves the capacity performance and cycle performance of the lithium-ion battery under high voltage.

[0197] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0198] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. An electrolyte additive, It is characterized in that Including compounds having the general structural formula shown in formula (I): Here, m, n, and p are each independently selected from integers of 1 to 5.

2. The electrolyte additive according to claim 1, It is characterized in that m, n, and p are the same.

3. The electrolyte additive according to claim 1, It is characterized in that The compound having the general structural formula shown in formula (I) is selected from at least one of the following compounds:

4. an electrolyte, It is characterized in that The invention comprises a solvent, an electrolyte salt and the electrolyte additive according to any one of claims 1 to 3.

5. The electrolyte according to claim 4, It is characterized in that The mass percentage of the electrolyte additive in the electrolyte is 0.01% to 5%.

6. The electrolyte according to claim 4, It is characterized in that The electrolyte salt includes one or more of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium perchlorate, lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, and lithium bis(trifluoromethanesulfonyl)imide.

7. The electrolyte according to any one of claims 4 to 6, It is characterized in that The electrolyte further includes other additives, and the other additives include one or more of sultone compounds, cyclic sulfate compounds, phosphate compounds and borate compounds.

8. A lithium ion battery, It is characterized in that The lithium-ion battery comprises a positive electrode, a negative electrode, a separator and the electrolyte according to any one of claims 4 to 7.

9. The lithium ion battery according to claim 8, It is characterized in that The charging cut-off voltage of the lithium-ion battery is ≥4.5V.

10. An electrical device, It is characterized in that The electrical device comprises the lithium-ion battery according to claim 8 or 9.

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