Electrolyte additive, electrolyte, lithium ion battery, electric device

Abstract

This application relates to an electrolyte additive, an electrolyte, a lithium-ion battery, and an electrical device. The electrolyte additive comprises a compound having the general structural formula shown in formula (I), where m, n, and p are each independently selected from integers from 1 to 5. In the electrolyte additive provided in this application, the fluorocarbon side chain and the tertiary amine group in the compound with the general structural formula shown in formula (I) have a synergistic effect. On the one hand, the fluorocarbon side chain is strongly hydrophobic, and the tertiary amine group is hydrophilic. Therefore, in a non-aqueous environment, trace amounts of water are easily captured by the tertiary amine group, reducing the contact between trace amounts of water and the electrolyte salt, preventing further decomposition of the electrolyte salt and damage to the interface and positive electrode active material, and improving the battery's cycle and storage performance under high voltage. On the other hand, all H atoms on the alkyl groups in the fluorocarbon side chain are replaced by F atoms, which can improve the oxidation resistance of the electrolyte additive and prevent the electrolyte additive from decomposing under high voltage.

Description

Technical Field

[0001] This 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 Technology

[0002] With the widespread application of lithium-ion batteries in electric vehicles, electronic products, and other fields, users are placing increasingly higher demands on their performance, especially on higher energy density. Increasing the charging voltage is one of the main methods to improve battery energy density.

[0003] However, increasing the charging voltage can lead to instability in the positive electrode active material and electrolyte, causing electrolyte decomposition and gas production, which in turn affects the battery's lifespan and safety. Summary of the Invention

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

[0005] A first aspect of this application provides an electrolyte additive comprising compounds having the general structural formula shown in formula (I):

[0006]

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

[0008] In some implementations, 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] A second aspect of this application provides an electrolyte comprising a solvent, an electrolyte salt, and the electrolyte additives provided in the first aspect.

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

[0013] In some embodiments, the electrolyte salt includes one or more of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium perchlorate, lithium bisfluorosulfonylimide, lithium tetrafluoroborate, and lithium bistrifluoromethanesulfonylimide.

[0014] In some embodiments, the electrolyte also includes other additives, including one or more of sulfonyl lactones, cyclic sulfates, phosphates, and borates.

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

[0016] In some implementations, the charging cutoff voltage of the lithium-ion battery is ≥4.5V.

[0017] The fourth aspect of this application provides an electrical device that includes the lithium-ion battery provided in the third aspect above.

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

[0019] The electrolyte additive provided in this application exhibits a synergistic effect between the fluorocarbon side chain and the tertiary amine group in the compound of the general formula (I). On the one hand, the fluorocarbon side chain is strongly hydrophobic, while the tertiary amine group is hydrophilic. Therefore, in a non-aqueous environment, trace water tends to aggregate around the tertiary amine group and form a small phase-separated structure in the electrolyte, which is then captured by the tertiary amine group. This reduces the contact between trace water and electrolyte salt, preventing further decomposition of the electrolyte salt and damage to the interface and positive electrode active material, thus improving the battery's cycle and storage performance under high voltage. On the other hand, all H atoms on the alkyl groups in the fluorocarbon side chain are replaced by F atoms, which can improve the oxidation resistance of the electrolyte additive, prevent the electrolyte additive from decomposing under high voltage, and simultaneously form a LiF-rich interfacial film on the positive electrode surface, improving interfacial chemistry and thus exhibiting excellent high-voltage resistance and thermal stability.

[0020] The above is merely a possible speculation on the mechanism of this application and does not constitute a limitation on the scope of protection of this application. Detailed Implementation

[0021] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, a detailed description of specific embodiments of this application is provided below. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0022] In this application, unless otherwise defined, all technical terms and jargon not explicitly stated have the same meaning as commonly understood by those skilled in the art and are common knowledge to those skilled in the art. Methods not explicitly stated are all 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 explicitly specified.

[0023] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0024] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0025] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0026] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0027] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0028] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: 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] A first aspect of this application provides an electrolyte additive comprising compounds having the general structural formula shown in formula (I):

[0030]

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

[0032] The electrolyte additive provided in this application exhibits a synergistic effect between the fluorocarbon side chain and the tertiary amine group in the compound of the general formula (I). On the one hand, the fluorocarbon side chain is strongly hydrophobic, while the tertiary amine group is hydrophilic. Therefore, in a non-aqueous environment, trace water tends to aggregate around the tertiary amine group and form a small phase-separated structure in the electrolyte, which is then captured by the tertiary amine group. This reduces the contact between trace water and electrolyte salt, preventing further decomposition of the electrolyte salt and damage to the interface and positive electrode active material, thus improving the battery's cycle and storage performance under high voltage. On the other hand, all H atoms on the alkyl groups in the fluorocarbon side chain are replaced by F atoms, which can improve the oxidation resistance of the electrolyte additive, prevent the electrolyte additive from decomposing under high voltage, and simultaneously form a LiF-rich interfacial film on the positive electrode surface, improving interfacial chemistry and thus exhibiting excellent high-voltage resistance and thermal stability.

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

[0034] In this application, m, n, and p can 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] A second aspect of this application provides an electrolyte comprising a solvent, an electrolyte salt, and the electrolyte additives provided in the first aspect.

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

[0039] In some embodiments, the electrolyte salt is present in the electrolyte at a mass percentage of 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 bisfluorosulfonylimide (LiFSI), lithium tetrafluoroborate (LiBF4), and lithium bistrifluoromethanesulfonylimide (LiTFSI).

[0041] Furthermore, the electrolyte salt includes one or more of lithium hexafluorophosphate (LiPF6), lithium hexafluoroarsenate (LiAsF6), and lithium tetrafluoroborate (LiBF4). These electrolyte salts are sensitive to trace amounts of water in the electrolyte and readily react with water, thereby generating gas or damaging the electrode. Compounds with the general structure shown in formula (I) can effectively capture moisture as electrolyte additives, improving the stability of the electrolyte and the interfacial 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 carbonate solvents, carboxylic acid ester solvents, and aromatic hydrocarbon solvents.

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

[0045] In some embodiments, the halogenated carbonate includes one or more of fluoroethylene carbonate, difluoropropylene carbonate, trifluoroethyl methyl carbonate, trifluoromethyl ethylene carbonate, 4-trifluoromethyl ethylene 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 carboxylic acid ester solvent includes halocarboxylic acid esters and / or non-halocarboxylic acid esters.

[0048] In some embodiments, the halocarboxylic 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 esters include 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 also includes other additives, including one or more of sulfonyl lactones, cyclic sulfates, phosphates, and borates.

[0053] In some embodiments, other additives are present in the electrolyte at a mass percentage of 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 sulfonyl lactone compound is selected from one or more of 1,3-propanesulfonyl lactone, 1,4-butanesulfonyl lactone, and propenyl-1,3-sulfonyl lactone.

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

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

[0057]

[0058] In some embodiments, the phosphate ester compound is selected from at least one of saturated phosphate ester compounds and unsaturated phosphate ester compounds. The saturated phosphate ester compounds include tris(trimethylsilane) phosphate; the unsaturated phosphate ester compounds include at least one of the compounds shown in formula (II).

[0059]

[0060] Among them, R 21 R 22 R 23 Individually selected from C1-C5 saturated hydrocarbon groups, unsaturated hydrocarbon groups, haloalkyl groups, and -Si(C m H 2m+1 Any of the following 3, where 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(trimethylsilane)borate and tris(triethylsilane)borate.

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

[0063] In some embodiments, the positive electrode includes a positive electrode active material layer and a positive electrode current collector. 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. The ternary materials include 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, which includes, but is not limited to, one or more of graphite, soft carbon, hard carbon, composite materials of monocrystalline silicon and graphite, composite materials of silicon suboxide and graphite, lithium titanate, and niobium pentoxide.

[0066] In some embodiments, a porous polymer membrane prepared from polyolefin polymers such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer is selected as the separator commonly used in lithium-ion batteries. It can be used alone as a separator or laminated together as a separator included in the lithium-ion battery of this application. Nonwoven fabrics formed from polyester fibers, aramid fibers, glass fibers, etc. can also be used; as well as a base film formed by attaching ceramic particles such as silica, alumina, and titanium dioxide to their surface.

[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 with a charging cut-off voltage higher than 4.5V; more preferably, the positive electrode includes at least one positive electrode active material with a charging cut-off voltage higher than 4.7V; particularly preferably, the positive electrode includes at least one positive electrode active material with a charging cut-off voltage higher than 4.9V.

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

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

[0071] In some embodiments, the positive electrode active material is a mixture, and at least one of the positive electrode active materials has a charging cutoff voltage ≥ 4.7V.

[0072] In some embodiments, the positive electrode active material is a mixture of various positive electrode active materials with a charging cutoff 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. The presence of impurities or 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 charging cutoff voltage of the positive electrode active material is >4.9V.

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

[0077] It is understood that when using multilayer electrodes, as long as one layer of the entire positive electrode active material layer meets the above-mentioned proportion requirements, it should be considered to fall 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 positive electrode active material with a charging cutoff 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 this application provides an electrical device comprising the lithium-ion battery provided in the third aspect above.

[0080] The electrical device used in this application is not particularly limited and can be any electrical device known in the prior art. For example, the electrical device may include, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, household large-capacity batteries, and lithium-ion capacitors.

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

[0082] Unless otherwise specified, all reagents, materials and instruments used in the following examples, comparative examples and test cases are commercially available.

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

[0084] Example 1

[0085] Electrolyte additives:

[0086] Electrolyte additives include compounds having the structure shown in formula (I-1).

[0087]

[0088] Electrolyte:

[0089] The electrolyte comprises an electrolyte salt, a solvent, the aforementioned electrolyte additives, and other additives. The electrolyte salt is LiPF6; the solvent is a combination of FEC, EC, and DEC in a ratio of FEC:EC:DEC = 2:1:7; other additives include 1,3-propanesulfonyl lactone (PS) and tris(trimethylsilane) phosphate (TMSP);

[0090] The electrolyte salt accounts for 13% of the total mass of the electrolyte; the electrolyte additive accounts for 1% of the total mass of the electrolyte; PS and TMSP account for 3% and 2% of the total mass of the electrolyte, respectively; and the remainder is solvent.

[0091] Lithium-ion batteries:

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

[0093] Example 2

[0094] Electrolyte additives:

[0095] Electrolyte additives include compounds having the structure shown in formula (I-1).

[0096]

[0097] Electrolyte:

[0098] The electrolyte comprises an electrolyte salt, a solvent, the aforementioned electrolyte additives, and other additives. The electrolyte salt is LiPF6; the solvent is a combination of FEC, EC, and DEC in a ratio of FEC:EC:DEC = 2:1:7; other additives include 1,3-propanesulfonyl lactone (PS) and tris(trimethylsilane) phosphate (TMSP);

[0099] The electrolyte salt accounts for 13% of the total mass of the electrolyte; the electrolyte additive accounts for 0.01% of the total mass of the electrolyte; PS and TMSP account for 3% and 2% of the total mass of the electrolyte, respectively; and the remainder is solvent.

[0100] Lithium-ion batteries:

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

[0102] Example 3

[0103] Electrolyte additives:

[0104] Electrolyte additives include compounds having the structure shown in formula (I-1).

[0105]

[0106] Electrolyte:

[0107] The electrolyte comprises an electrolyte salt, a solvent, the aforementioned electrolyte additives, and other additives. The electrolyte salt is LiPF6; the solvent is a combination of FEC, EC, and DEC in a ratio of FEC:EC:DEC = 2:1:7; other additives include 1,3-propanesulfonyl lactone (PS) and tris(trimethylsilane) phosphate (TMSP);

[0108] The electrolyte salt accounts for 13% of the total mass of the electrolyte; the electrolyte additive accounts for 5% of the total mass of the electrolyte; PS and TMSP account for 3% and 2% of the total mass of the electrolyte, respectively; and the remainder is solvent.

[0109] Lithium-ion batteries:

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

[0111] Example 4

[0112] Electrolyte additives:

[0113] Electrolyte additives include compounds having the structure shown in formula (I-2).

[0114]

[0115] Electrolyte:

[0116] The electrolyte comprises an electrolyte salt, a solvent, the aforementioned electrolyte additives, and other additives. The electrolyte salt is LiPF6; the solvent is a combination of FEC, EC, and DEC in a ratio of FEC:EC:DEC = 2:1:7; other additives include 1,3-propanesulfonyl lactone (PS) and tris(trimethylsilane) phosphate (TMSP);

[0117] The electrolyte salt accounts for 13% of the total mass of the electrolyte; the electrolyte additive accounts for 1% of the total mass of the electrolyte; PS and TMSP account for 3% and 2% of the total mass of the electrolyte, respectively; and the remainder is solvent.

[0118] Lithium-ion batteries:

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

[0120] Example 5

[0121] Electrolyte additives:

[0122] Electrolyte additives include compounds having the structure shown in formula (I-3).

[0123]

[0124] Electrolyte:

[0125] The electrolyte comprises an electrolyte salt, a solvent, the aforementioned electrolyte additives, and other additives. The electrolyte salt is LiPF6; the solvent is a combination of FEC, EC, and DEC in a ratio of FEC:EC:DEC = 2:1:7; other additives include 1,3-propanesulfonyl lactone (PS) and tris(trimethylsilane) phosphate (TMSP);

[0126] The electrolyte salt accounts for 13% of the total mass of the electrolyte; the electrolyte additive accounts for 1% of the total mass of the electrolyte; PS and TMSP account for 3% and 2% of the total mass of the electrolyte, respectively; and the remainder is solvent.

[0127] Lithium-ion batteries:

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

[0129] Example 6

[0130] Electrolyte additives:

[0131] Electrolyte additives include compounds having the structure shown in formula (I-4).

[0132]

[0133] Electrolyte:

[0134] The electrolyte comprises an electrolyte salt, a solvent, the aforementioned electrolyte additives, and other additives. The electrolyte salt is LiPF6; the solvent is a combination of FEC, EC, and DEC in a ratio of FEC:EC:DEC = 2:1:7; other additives include 1,3-propanesulfonyl lactone (PS) and tris(trimethylsilane) phosphate (TMSP);

[0135] The electrolyte salt accounts for 13% of the total mass of the electrolyte; the electrolyte additive accounts for 1% of the total mass of the electrolyte; PS and TMSP account for 3% and 2% of the total mass of the electrolyte, respectively; and the remainder is solvent.

[0136] Lithium-ion batteries:

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

[0138] Example 7

[0139] Electrolyte additives:

[0140] Electrolyte additives include compounds having the structure shown in formula (I-5).

[0141]

[0142] Electrolyte:

[0143] The electrolyte comprises an electrolyte salt, a solvent, the aforementioned electrolyte additives, and other additives. The electrolyte salt is LiPF6; the solvent is a combination of FEC, EC, and DEC in a ratio of FEC:EC:DEC = 2:1:7; other additives include 1,3-propanesulfonyl lactone (PS) and tris(trimethylsilane) phosphate (TMSP);

[0144] The electrolyte salt accounts for 13% of the total mass of the electrolyte; the electrolyte additive accounts for 1% of the total mass of the electrolyte; PS and TMSP account for 3% and 2% of the total mass of the electrolyte, respectively; and the remainder is solvent.

[0145] Lithium-ion batteries:

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

[0147] Example 8

[0148] Electrolyte additives:

[0149] Electrolyte additives include compounds having the structure shown in formula (I-6).

[0150]

[0151] Electrolyte:

[0152] The electrolyte comprises an electrolyte salt, a solvent, the aforementioned electrolyte additives, and other additives. The electrolyte salt is LiPF6; the solvent is a combination of FEC, EC, and DEC in a ratio of FEC:EC:DEC = 2:1:7; other additives include 1,3-propanesulfonyl lactone (PS) and tris(trimethylsilane) phosphate (TMSP);

[0153] The electrolyte salt accounts for 13% of the total mass of the electrolyte; the electrolyte additive accounts for 1% of the total mass of the electrolyte; PS and TMSP account for 3% and 2% of the total mass of the electrolyte, respectively; and the remainder is solvent.

[0154] Lithium-ion batteries:

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

[0156] Comparative Example 1

[0157] Electrolyte:

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

[0159] The electrolyte salt accounts for 13% of the total mass of the electrolyte; PS and TMSP account for 3% and 2% of the total mass of the electrolyte, respectively; the remainder is solvent.

[0160] Lithium-ion batteries:

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

[0162] Comparative Example 2

[0163] Electrolyte additives include compounds having the structure shown in formula (I-1).

[0164]

[0165] Electrolyte:

[0166] The electrolyte comprises an electrolyte salt, a solvent, the aforementioned electrolyte additives, and other additives. The electrolyte salt is LiPF6; the solvent is a combination of FEC, EC, and DEC in a ratio of FEC:EC:DEC = 2:1:7; other additives include 1,3-propanesulfonyl lactone (PS) and tris(trimethylsilane) phosphate (TMSP);

[0167] The electrolyte salt accounts for 13% of the total mass of the electrolyte; the electrolyte additive accounts for 20% of the total mass of the electrolyte; PS and TMSP account for 3% and 2% of the total mass of the electrolyte, respectively; and the remainder is solvent.

[0168] Lithium-ion batteries:

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

[0170] Comparative Example 3

[0171] Electrolyte additives:

[0172] Electrolyte additives include compounds having the structure shown in formula (Ⅲ).

[0173]

[0174] Electrolyte:

[0175] The electrolyte comprises an electrolyte salt, a solvent, the aforementioned electrolyte additives, and other additives. The electrolyte salt is LiPF6; the solvent is a combination of FEC, EC, and DEC in a ratio of FEC:EC:DEC = 2:1:7; other additives include 1,3-propanesulfonyl lactone (PS) and tris(trimethylsilane) phosphate (TMSP);

[0176] The electrolyte salt accounts for 13% of the total mass of the electrolyte; the electrolyte additive accounts for 1% of the total mass of the electrolyte; PS and TMSP account for 3% and 2% of the total mass of the electrolyte, respectively; and the remainder is solvent.

[0177] Lithium-ion batteries:

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

[0179] Comparative Example 4

[0180] Electrolyte additives:

[0181] Electrolyte additives include compounds having the structure shown in formula (Ⅳ).

[0182]

[0183] Electrolyte:

[0184] The electrolyte comprises an electrolyte salt, a solvent, the aforementioned electrolyte additives, and other additives. The electrolyte salt is LiPF6; the solvent is a combination of FEC, EC, and DEC in a ratio of FEC:EC:DEC = 2:1:7; other additives include 1,3-propanesulfonyl lactone (PS) and tris(trimethylsilane) phosphate (TMSP);

[0185] The electrolyte salt accounts for 13% of the total mass of the electrolyte; the electrolyte additive accounts for 1% of the total mass of the electrolyte; PS and TMSP account for 3% and 2% of the total mass of the electrolyte, respectively; and the remainder is solvent.

[0186] Lithium-ion batteries:

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

[0188] Performance testing

[0189] High-voltage cycle performance tests were conducted on the lithium-ion batteries of the above embodiments and comparative examples:

[0190] The test conditions were: 25℃, charging / discharging potential range of 3.5V to 4.9V, and charging current of 1C to 4.5V. The specific test procedure is as follows:

[0191] The lithium-ion battery was charged at a constant voltage of 4.5V until the cutoff current was ≤0.05C. After resting for 5 minutes, it was discharged at 1C to 3V and then rested for 5 minutes. This is one charge-discharge cycle. 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 100 times according to the above method, and the discharge capacity of the 100th cycle was measured.

[0193] The capacity retention rate (%) of a 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 in the first cycle) × 100%. The calculation results are shown in Table 1.

[0194] Table 1

[0195]

[0196] Comparing Examples 1-8 with Comparative Examples 1-4, it can be seen that the electrolyte additive of this application improves the capacity performance and cycle performance of lithium-ion batteries under high voltage.

[0197] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above 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 embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

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

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

3. The electrolyte additive according to claim 1, 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, characterized in that, It includes solvents, electrolyte salts, and electrolyte additives as described in any one of claims 1 to 3.

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

6. The electrolyte according to claim 4, characterized in that, The electrolyte salt includes one or more of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium perchlorate, lithium bisfluorosulfonylimide, lithium tetrafluoroborate, and lithium bistrifluoromethanesulfonylimide.

7. The electrolyte according to any one of claims 4 to 6, characterized in that, The electrolyte also includes other additives, which include one or more of sulfonyl lactones, cyclic sulfates, phosphates, and borates.

8. A lithium-ion battery, characterized in that, The lithium-ion battery includes a positive electrode, a negative electrode, a separator, and the electrolyte as described in any one of claims 4 to 7.

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

10. An electrical device, characterized in that, The electrical device includes the lithium-ion battery as described in claim 8 or 9.

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