Lithium-ion battery electrolyte and lithium-ion battery

Abstract

This application relates to a lithium-ion battery electrolyte and a lithium-ion battery. The lithium-ion battery electrolyte of this application includes an organic solvent, a lithium salt, and a first additive; the first additive includes at least one material having the following structural formulas: [list of materials]. Wherein, R1 to R30 are each independently selected from one or more combinations of halogens, cyano groups, isocyanates, amino groups, alkyl groups with 1 to 4 carbon atoms, ester groups with 1 to 4 carbon atoms, and fluoroalkyl groups with 1 to 4 carbon atoms. The lithium-ion battery electrolyte of this application can improve the interfacial film structure between the electrode plates and the electrolyte in a lithium-ion battery, thereby enabling the lithium-ion battery to have higher charge-discharge efficiency and cycle capacity retention.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, and in particular to a lithium-ion battery electrolyte and a lithium-ion battery. Background Technology

[0002] With the continuous development of the new energy industry, higher demands are being placed on the performance of lithium-ion batteries. Lithium-ion batteries are prone to gas generation, severe capacity decay, and low charge / discharge efficiency during cycling, which in turn affects battery performance. In traditional lithium-ion batteries, the unstable film structure formed at the interface between the electrode plates and the electrolyte leads to increased impedance during cycling, resulting in low charge / discharge efficiency and severe capacity decay. Summary of the Invention

[0003] Therefore, it is necessary to provide a lithium-ion battery electrolyte and a lithium-ion battery. The lithium-ion battery electrolyte of this application can improve the interfacial film structure between the electrode plates and the electrolyte in a lithium-ion battery, thereby enabling the lithium-ion battery to have higher charge-discharge efficiency and cycle capacity retention.

[0004] In a first aspect, this application provides a lithium-ion battery electrolyte, comprising an organic solvent, a lithium salt, and a first additive;

[0005] The first additive includes at least one of the following materials having the following structural formula:

[0006] , , ,

[0007] , , ;

[0008] R1 to R30 are each independently selected from one or more combinations of hydrogen atoms, halogens, cyano groups, isocyano groups, amino groups, alkyl groups with 1 to 4 carbon atoms, ester groups with 1 to 4 carbon atoms, and fluoroalkyl groups with 1 to 4 carbon atoms.

[0009] In some embodiments, the first additive comprises at least one of the following materials having the following structural formula:

[0010] , , ,

[0011] , .

[0012] In some embodiments, the first additive accounts for 0.01% to 2% of the mass percentage of the lithium-ion battery electrolyte.

[0013] In some embodiments, a second additive is further included, the second additive comprising at least one of succinic anhydride, adiponitrile, hexanetrionitrile, ethylene glycol bis(propionitrile), phthalonitrile, isopropylmalonide, tris(trimethylsilane) phosphate, tris(trimethylsilyl)borate, tripropynyl phosphate, tripropylene phosphate, vinylene carbonate, ethylene ethylene carbonate, 1,3-propanesulfonate lactone, 1,4-butanesulfonate lactone, vinyl sulfite, methanedisulfonate, and vinyl sulfate.

[0014] In some embodiments, the second additive accounts for 0.1% to 10% of the mass percentage of the lithium-ion battery electrolyte.

[0015] In some embodiments, the organic solvent includes at least one of cyclic or chain carbonate solvents, carboxylic acid ester solvents, and fluorocarbonate solvents.

[0016] In some embodiments, the cyclic or chain carbonate organic solvent includes at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl propyl carbonate.

[0017] In some embodiments, the carboxylic acid ester solvent includes at least one of methyl formate, methyl acetate, methyl butyrate, ethyl acetate, ethyl propionate, propyl propionate, and γ-butyrolactone.

[0018] In some embodiments, the fluorocarbonate solvent includes at least one of fluoroethylene carbonate, fluoropropylene carbonate, and fluoroethylene carbonate.

[0019] In some embodiments, the lithium salt includes at least one of lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluorophosphate, lithium difluorophosphate, lithium difluoroborate, lithium tetrafluorooxalate phosphate, lithium trioxalate phosphate, lithium bis(oxalate borate), lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(perfluoro-1-butyryl)imide, lithium bis(pentafluoroethylsulfonyl)imide, and lithium bis(nonafluorobutylsulfonyl)imide.

[0020] Secondly, this application provides a lithium-ion battery, including a positive electrode, a negative electrode, and the lithium-ion battery electrolyte described in any one of the above.

[0021] In some embodiments, the positive electrode includes a positive electrode active material, which includes at least one of doped or undoped lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide.

[0022] In some embodiments, the negative electrode material includes at least one of graphite, silicon-carbon composite material, silicon-oxygen composite material, and lithium titanate.

[0023] The aforementioned lithium-ion battery electrolyte includes a first additive, which forms a stable interfacial protective film on the electrode surface, inhibiting the dissolution of transition metals in the electrode material and hindering the oxidative decomposition of the electrolyte, thereby alleviating battery gas generation. The organic flexible film polymerized by the first additive has oxidation resistance, and the abundant unsaturated structures in the first additive have high conductivity, which can enhance the charge transfer capability at the interface between the electrolyte and the electrode, thereby improving the charge and discharge efficiency of the lithium-ion battery and increasing the battery's cycle capacity retention rate. Attached Figure Description

[0024] Figure 1 Impedance diagrams of the electrolytes in Examples 4, 7 and Comparative Example 2 of this application;

[0025] Figure 2 The LSV curves are for the electrolytes in Example 1 and Comparative Example 1 of this application. Detailed Implementation

[0026] 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.

[0027] Unless otherwise defined, all 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 belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0028] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0029] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0030] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0031] One embodiment of this application provides a lithium-ion battery electrolyte, comprising an organic solvent, a lithium salt, and a first additive;

[0032] The first additive includes at least one of the following materials having the following structural formula:

[0033] , , ,

[0034] , , ;

[0035] R1 to R30 are each independently selected from one or more combinations of halogen, cyano, isocyano, amino, alkyl with 1 to 4 carbon atoms, ester with 1 to 4 carbon atoms, and fluoroalkyl with 1 to 4 carbon atoms.

[0036] The aforementioned lithium-ion battery electrolyte includes a first additive, which forms a stable interfacial protective film on the electrode surface, inhibiting the dissolution of transition metals in the electrode material and hindering the oxidative decomposition of the electrolyte, thereby alleviating battery gas generation. The organic flexible film polymerized by the first additive has oxidation resistance, and the abundant unsaturated structures in the first additive have high conductivity, which can enhance the charge transfer capability at the interface between the electrolyte and the electrode, thereby improving the charge and discharge efficiency of the lithium-ion battery and increasing the battery's cycle capacity retention rate.

[0037] In some embodiments, the first additive comprises at least one of materials having the following structural formula:

[0038] (A) (B) (C)

[0039] (D) (E).

[0040] The aforementioned first additive undergoes ring-opening polymerization on the electrode surface and deposits into the interfacial film during the lithium-ion battery formation stage, preventing the active materials in the electrode from further reacting with the electrolyte. Its specific unsaturated bonds form a molecular structure that creates a network or stereocrosslinking network, resulting in a denser and more stable film on the electrode surface with stronger protective properties. This effectively hinders the oxidative decomposition of the electrolyte, alleviates battery gas generation, and extends battery life. Simultaneously, the organic flexible film formed by the polymerization of the first additive exhibits oxidation resistance, and its abundant unsaturated structures provide high conductivity, enhancing the charge transfer capacity at the electrolyte-electrode interface, improving battery charge-discharge efficiency, and increasing cycle capacity retention.

[0041] In some embodiments, the first additive accounts for 0.01% to 2% of the mass percentage of the lithium-ion battery electrolyte. Within this range, the first additive has a good effect on improving the interfacial film structure between the electrode plates and the electrolyte in the lithium-ion battery. When the mass percentage of the first additive in the lithium-ion battery electrolyte is too high or too low, the first additive has a poor effect on improving the interfacial film structure between the electrode plates and the electrolyte in the lithium-ion battery. Optionally, the mass percentage of the first additive in the lithium-ion battery electrolyte is 0.01%, 0.02%, 0.03%, 0.05%, 0.08%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.85%, 1.9%, 1.95%, or 2%. Alternatively, the mass percentage of the first additive in the lithium-ion battery electrolyte can also be within the range of any two of the above percentages.

[0042] In some embodiments, a second additive is also included, comprising at least one of succinic anhydride, adiponitrile, hexanetrionitrile, ethylene glycol bis(propionitrile), phthalonitrile, isopropylmalonide, tris(trimethylsilane) phosphate, tris(trimethylsilyl)borate, tripropynyl phosphate, tripropylene phosphate, vinylene carbonate, ethylene ethylene carbonate, 1,3-propanesulfonate lactone, 1,4-butanesulfonate lactone, vinyl sulfite, methanedisulfonate, and vinyl sulfate.

[0043] In some embodiments, the lithium-ion battery electrolyte includes a variety of second additives. Exemplarily, the number of second additives in the lithium-ion battery electrolyte can be two, three, four, five, or six.

[0044] In some embodiments, the second additive accounts for 0.1% to 10% of the mass percentage of the lithium-ion battery electrolyte. Optionally, the second additive accounts for 0.1%, 0.2%, 0.3%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, or 10% of the mass percentage of the lithium-ion battery electrolyte. Alternatively, the second additive may also be within the range of any two of the above percentages.

[0045] In some embodiments, the organic solvent includes at least one of cyclic or chain carbonate solvents, carboxylic acid ester solvents, and fluorocarbonate solvents.

[0046] In some embodiments, the cyclic or chain carbonate organic solvent includes at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl propyl carbonate.

[0047] In some embodiments, the carboxylic acid ester solvent includes at least one of methyl formate, methyl acetate, methyl butyrate, ethyl acetate, ethyl propionate, propyl propionate, and γ-butyrolactone.

[0048] In some embodiments, the fluorocarbonate solvent includes at least one of fluoroethylene carbonate, fluoropropylene carbonate, and fluoroethylene carbonate.

[0049] In some embodiments, the lithium-ion battery electrolyte includes a variety of organic solvents. Exemplarily, the number of organic solvents in the lithium-ion battery electrolyte can be two, three, four, five, or six.

[0050] In some embodiments, the lithium salt includes at least one of lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluorophosphate, lithium difluorophosphate, lithium difluoroborate, lithium tetrafluorooxalate phosphate, lithium trioxalate phosphate, lithium bis(oxalate borate), lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(perfluoro-1-butyryl)imide, lithium bis(pentafluoroethylsulfonyl)imide, and lithium bis(nonafluorobutylsulfonyl)imide.

[0051] Another embodiment of this application provides a lithium-ion battery, including a positive electrode, a negative electrode, and a lithium-ion battery electrolyte as described above.

[0052] In some embodiments, the positive electrode includes a positive electrode active material, which includes at least one of lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide.

[0053] It is understood that lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide can be doped or undoped lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide.

[0054] In some embodiments, the negative electrode material includes at least one of graphite, silicon-carbon composite material, silicon-oxygen composite material, and lithium titanate.

[0055] The following are specific embodiments.

[0056] Example 1

[0057] Preparation of lithium-ion battery electrolyte:

[0058] The lithium-ion battery electrolyte was prepared in a glove box filled with 99.99% pure argon gas. The moisture content and oxygen content in the glove box were controlled to be ≤5ppm and the temperature was room temperature.

[0059] Ethylene carbonate, diethyl carbonate, and propyl propionate were uniformly mixed in a mass ratio of 3:2:5. Lithium hexafluorophosphate was then added and fully dissolved. Additive A was then added, followed by 1,3,6-hexanetrionitrile, lithium bis(oxalato)borate, 1,3-propanesulfonate lactone, and vinyl sulfate to obtain the lithium-ion battery electrolyte. The mass percentages of lithium hexafluorophosphate, additive A, 1,3,6-hexanetrionitrile, lithium bis(oxalato)borate, 1,3-propanesulfonate lactone, and 1% vinyl sulfate were respectively used in the lithium-ion battery electrolyte.

[0060] Battery fabrication: The prepared lithium-ion battery electrolyte is injected into the fully dried battery cell. The positive electrode active material is lithium cobalt oxide, the negative electrode material is graphite, and the separator is polyethylene (7μm). The battery is tested after being placed, formed, sealed, and tested.

[0061] Example 2

[0062] Preparation of lithium-ion battery electrolyte:

[0063] The lithium-ion battery electrolyte in Example 2 is basically the same as that in Example 1. The difference is that the first additive in Example 2 is additive B, which has a mass percentage of 0.8%.

[0064] Example 3

[0065] Preparation of lithium-ion battery electrolyte:

[0066] The lithium-ion battery electrolyte in Example 3 is basically the same as that in Example 1. The difference is that the first additive in Example 3 is additive C, which has a mass percentage of 0.2%.

[0067] Example 4

[0068] Preparation of lithium-ion battery electrolyte:

[0069] The lithium-ion battery electrolyte was prepared in a glove box filled with 99.99% pure argon gas. The moisture content and oxygen content in the glove box were controlled to be ≤5ppm and the temperature was room temperature.

[0070] Ethylene carbonate, propylene carbonate, diethyl carbonate, and propyl propionate were uniformly mixed in a mass ratio of 2:1:2:5. Then, lithium hexafluorophosphate was added and fully dissolved. Additive D was then added, followed by adiponitrile, vinylene carbonate, 1,3-propanesulfonate lactone, and lithium difluorophosphate to obtain the lithium-ion battery electrolyte. The mass percentages of the lithium-ion battery electrolyte are as follows: lithium hexafluorophosphate 12.5%, additive D 0.6%, adiponitrile 1%, vinylene carbonate 2%, 1,3-propanesulfonate lactone 1.5%, and lithium difluorophosphate 1%.

[0071] Battery fabrication: The prepared lithium-ion battery electrolyte is injected into the fully dried battery cell. The positive electrode active material is lithium cobalt oxide, the negative electrode material is graphite, and the separator is polyethylene (7μm). The battery is tested after being placed, formed, sealed, and tested.

[0072] Example 5

[0073] Preparation of lithium-ion battery electrolyte:

[0074] The lithium-ion battery electrolyte in Example 5 is basically the same as that in Example 4, except that the first additive in Example 5 is additive E, which has a mass percentage of 0.05%.

[0075] Example 6

[0076] The lithium-ion battery electrolyte in Example 6 is basically the same as that in Example 4, except that the first additive in Example 6 is additive A, which has a mass percentage of 0.3%.

[0077] Example 7

[0078] The lithium-ion battery electrolyte in Example 7 is basically the same as that in Example 4, except that the first additive in Example 7 is additive B, which has a mass percentage of 0.15%.

[0079] Example 8

[0080] Preparation of lithium-ion battery electrolyte:

[0081] The lithium-ion battery electrolyte was prepared in a glove box filled with 99.99% pure argon gas. The moisture content and oxygen content in the glove box were controlled to be ≤5ppm and the temperature was room temperature.

[0082] Ethylene carbonate, propylene carbonate, diethyl carbonate, and propyl propionate were uniformly mixed in a mass ratio of 1:1:4:4. Then, lithium hexafluorophosphate was added and fully dissolved. Additive E was then added, followed by succinate, vinylene carbonate, 1,3-propanesulfonate lactone, and lithium difluorophosphate to obtain the lithium-ion battery electrolyte. The mass percentages of lithium hexafluorophosphate in the lithium-ion battery electrolyte are as follows: lithium hexafluorophosphate 12.5%, additive E 0.2%, succinate 1%, vinylene carbonate 2%, 1,3-propanesulfonate lactone 1%, and lithium difluorophosphate 1%.

[0083] Battery fabrication: The prepared lithium-ion battery electrolyte is injected into the fully dried battery cell. The positive electrode active material is lithium cobalt oxide, the negative electrode material is graphite, and the separator is polyethylene (7μm). The battery is tested after being placed, formed, sealed, and tested.

[0084] Example 9

[0085] The lithium-ion battery electrolyte in Example 9 is basically the same as that in Example 8, except that the first additive in Example 8 is additive C, which has a mass percentage of 0.15%.

[0086] Example 10

[0087] The lithium-ion battery electrolyte in Example 10 is basically the same as that in Example 8. The difference is that the first additive in Example 10 is additive A and additive B, with a mass percentage of 0.2% and 0.1%, respectively.

[0088] Example 11

[0089] Preparation of lithium-ion battery electrolyte:

[0090] The lithium-ion battery electrolyte was prepared in a glove box filled with 99.99% pure argon gas. The moisture content and oxygen content in the glove box were controlled to be ≤5ppm and the temperature was room temperature.

[0091] Ethylene carbonate, methyl ethyl carbonate, and diethyl carbonate were uniformly mixed in a mass ratio of 3:5:2. Then, lithium hexafluorophosphate was added and fully dissolved. Additive A was then added, followed by tris(trimethylsilyl)borate, vinylene carbonate, ethylene carbonate, and difluorooxalate borate to obtain the lithium-ion battery electrolyte. The mass percentages of lithium hexafluorophosphate, additive A, tris(trimethylsilyl)borate, vinylene carbonate, ethylene carbonate, and difluorooxalate borate were 1% and 1% respectively, representing the total mass percentage of the lithium-ion battery electrolyte.

[0092] Battery fabrication: The prepared lithium-ion battery electrolyte is injected into the fully dried battery cell. The positive electrode active material is lithium nickel cobalt manganese oxide, the negative electrode material is graphite, and the separator is polyethylene (7μm). The battery is tested after being placed, formed, sealed, and tested.

[0093] Example 12

[0094] The lithium-ion battery electrolyte in Example 12 is basically the same as that in Example 11, except that the first additive in Example 12 is additive D, which has a mass percentage of 0.3%.

[0095] Example 13

[0096] The lithium-ion battery electrolyte in Example 13 is basically the same as that in Example 11, except that the first additive in Example 13 is additive E, which has a mass percentage of 0.8%.

[0097] Example 14

[0098] Preparation of lithium-ion battery electrolyte:

[0099] The lithium-ion battery electrolyte was prepared in a glove box filled with 99.99% pure argon gas. The moisture content and oxygen content in the glove box were controlled to be ≤5ppm and the temperature was room temperature.

[0100] Ethylene carbonate, propylene carbonate, methyl ethyl carbonate, and diethyl carbonate were uniformly mixed in a mass ratio of 2:1:5:2. Lithium hexafluorophosphate was then added and fully dissolved. Additive B was then added, followed by 1,3-propanesulfonate lactone, vinylene carbonate, vinyl sulfate, and difluorooxaloborate to obtain the lithium-ion battery electrolyte. The electrolyte composition by mass percentage is as follows: lithium hexafluorophosphate 12.5%, additive B 0.2%, 1,3-propanesulfonate lactone 1%, vinylene carbonate 1.5%, vinyl sulfate 0.5%, and difluorooxaloborate 1%.

[0101] Battery fabrication: The prepared lithium-ion battery electrolyte is injected into the fully dried battery cell. The positive electrode active material is lithium nickel cobalt manganese oxide, the negative electrode material is graphite, and the separator is polyethylene (7μm). The battery is tested after being placed, formed, sealed, and tested.

[0102] Example 15

[0103] The lithium-ion battery electrolyte in Example 15 is basically the same as that in Example 14, except that the first additive in Example 15 is additive A and additive B, with a mass percentage of 0.25% and 0.05%, respectively.

[0104] Example 16

[0105] The lithium-ion battery electrolyte in Example 16 is basically the same as that in Example 14, except that the first additive in Example 16 is additive A, which has a mass percentage of 0.5%.

[0106] Example 17

[0107] Preparation of lithium-ion battery electrolyte:

[0108] The lithium-ion battery electrolyte was prepared in a glove box filled with 99.99% pure argon gas. The moisture content and oxygen content in the glove box were controlled to be ≤5ppm and the temperature was room temperature.

[0109] Ethylene carbonate, methyl ethyl carbonate, and diethyl carbonate were uniformly mixed in a mass ratio of 3:4:3. Then, lithium hexafluorophosphate was added and fully dissolved. Additive B was then added, followed by fluoroethylene carbonate, vinylene carbonate, 1,3-propanesulfonate lactone, and lithium difluorosulfonamide to obtain the lithium-ion battery electrolyte. The mass percentages of lithium hexafluorophosphate, additive B, fluoroethylene carbonate, vinylene carbonate, 1,3-propanesulfonate lactone, and lithium difluorosulfonamide are as follows: lithium hexafluorophosphate 12.5%, additive B 0.3%, fluoroethylene carbonate 1%, vinylene carbonate 1.5%, 1,3-propanesulfonate lactone 1.5%, and lithium difluorosulfonamide 1%.

[0110] Battery fabrication: The prepared lithium-ion battery electrolyte is injected into the fully dried battery cell. The positive electrode active material is lithium nickel cobalt manganese oxide, the negative electrode material is graphite, and the separator is polyethylene (7μm). The battery is tested after being placed, formed, sealed, and tested.

[0111] Example 18

[0112] The lithium-ion battery electrolyte in Example 18 is basically the same as that in Example 17, except that the first additive in Example 18 is additive C, which has a mass percentage of 0.2%.

[0113] Example 19

[0114] The lithium-ion battery electrolyte in Example 19 is basically the same as that in Example 17, except that the first additive in Example 19 is additive D, which has a mass percentage of 0.35%.

[0115] Example 20

[0116] The lithium-ion battery electrolyte in Example 20 is basically the same as that in Example 17, except that the first additive in Example 20 is additive B, which has a mass percentage of 0.9%.

[0117] Comparative Example 1

[0118] The lithium-ion battery electrolyte in Comparative Example 1 is basically the same as that in Example 1, except that no first additive was added in Comparative Example 1.

[0119] Comparative Example 2

[0120] The lithium-ion battery electrolyte in Comparative Example 2 is basically the same as that in Example 4, except that no first additive was added in Comparative Example 2.

[0121] Comparative Example 3

[0122] The lithium-ion battery electrolyte in Comparative Example 3 is basically the same as that in Example 8, except that no first additive was added in Comparative Example 3.

[0123] Comparative Example 4

[0124] The lithium-ion battery electrolyte in Comparative Example 4 is basically the same as that in Example 11, except that no first additive was added in Comparative Example 4.

[0125] Comparative Example 5

[0126] The lithium-ion battery electrolyte in Comparative Example 5 is basically the same as that in Example 14, except that no first additive was added in Comparative Example 5.

[0127] Comparative Example 6

[0128] The lithium-ion battery electrolyte in Comparative Example 6 is basically the same as that in Example 17, except that no first additive was added in Comparative Example 6.

[0129] Lithium-ion battery performance testing:

[0130] 25℃ 0.7C / 0.7C room temperature cycle test: At 25℃, charge at a constant current of 0.7C to the upper limit voltage, then charge at a constant voltage until the current cutoff is 0.05C, and then discharge the battery at a constant current of 0.7C. The discharge capacity is recorded as C0. Repeat the charge and discharge cycle 100 times to obtain the discharge capacity C100 on the 100th cycle. The capacity retention rate is C100 / C0×100%. The upper limit voltage for charging lithium cobalt oxide batteries is 4.5V, and the upper limit voltage for nickel cobalt manganese oxide batteries is 4.2V.

[0131] 55℃ 0.7C / 0.7C High Temperature Cycling Test: The battery is charged at 55℃ with a constant current of 0.7C to the upper limit voltage, then charged with a constant voltage until the current cutoff is 0.05C, and then discharged with a constant current of 0.7C. The discharge capacity is recorded as C0. The charge and discharge cycle is repeated 100 times to obtain the discharge capacity C100 in the 100th cycle. The capacity retention rate is C100 / C0×100%. The upper limit voltage for charging lithium cobalt oxide batteries is 4.5V, and the upper limit voltage for nickel cobalt manganese oxide batteries is 4.2V.

[0132] The performance test results of the lithium-ion batteries prepared in Examples 1-20 and Comparative Examples 1-6 are shown in Table 1 below:

[0133] Table 1

[0134]

[0135] As shown in Table 1, compared to Examples 1-3, Comparative Example 2 to Examples 4-7, Comparative Example 3 to Examples 8-10, Comparative Example 4 to Examples 11-13, Comparative Example 5 to Examples 14-16, and Comparative Example 6 to Examples 17-20, the lithium-ion performance test results show that adding the first additive of this application to the lithium-ion battery electrolyte can improve the room temperature and high temperature cycle performance of the lithium-ion battery. Simultaneously, it can also improve the rate performance of the lithium-ion battery, indicating that at higher rates, the charge transfer capability at the interface between the electrolyte and the electrode plates is improved, enabling rapid lithium-ion transport and thus improving the cycle stability of the lithium-ion battery.

[0136] Reference Figure 1 As shown, from Figure 1 It can be seen that the lithium-ion batteries in Examples 4 and 7 have significantly lower impedance than the lithium-ion battery in Comparative Example 2, indicating that the interfacial protective film formed on the surface of the electrode sheet has high conductivity, which can improve the charge transfer capability at the interface between the electrolyte and the electrode sheet, and improve the rate performance of the lithium-ion battery.

[0137] Reference Figure 2 As shown, to study the stability of the electrolyte, this application performed LSV (Last Silicate Volume) tests on the electrolyte. A three-electrode electrolytic cell was used for the tests, with an inert platinum electrode as the working electrode and lithium metal as both the counter and reference electrodes. Figure 2 It can be seen that the oxidation current of the lithium-ion battery electrolyte in Comparative Example 1 increases slowly from 4.5V, indicating that the electrolyte has already begun to decompose. When the potential rises to 4.9V, the current increases significantly and sharply, indicating that the oxidation and decomposition of the electrolyte accelerates. In contrast, the lithium-ion battery electrolyte in Example 1, with the addition of additive A, only begins to decompose when the voltage rises to approximately 5.6V, demonstrating better electrolyte stability. This indicates that the electrolyte in Example 1 has better stability, which is beneficial for improving battery cycle capacity.

[0138] 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.

[0139] 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, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. A lithium-ion battery electrolyte, characterized in that, Including organic solvents, lithium salts, and a first additive; The first additive includes at least one of the following materials having the following structural formula: 、 、 、 、 、 ； R1 to R30 are each independently selected from one or more combinations of hydrogen atoms, halogens, cyano groups, isocyano groups, amino groups, alkyl groups with 1 to 4 carbon atoms, ester groups with 1 to 4 carbon atoms, and fluoroalkyl groups with 1 to 4 carbon atoms.

2. The lithium-ion battery electrolyte according to claim 1, characterized in that, The first additive includes at least one of the following materials having the following structural formula: 、 、 、 、 。 3. The lithium-ion battery electrolyte according to claim 1, characterized in that, The first additive accounts for 0.01% to 2% of the mass percentage of the lithium-ion battery electrolyte.

4. The lithium-ion battery electrolyte according to any one of claims 1 to 3, characterized in that, It also includes a second additive, which comprises at least one of succinic anhydride, adiponitrile, hexanetrionitrile, ethylene glycol bis(propionitrile), phthalonitrile, isopropylmalonide, tris(trimethylsilane) phosphate, tris(trimethylsilyl)borate, tripropynyl phosphate, tripropylene phosphate, vinylene carbonate, ethylene ethylene carbonate, 1,3-propanesulfonate lactone, 1,4-butanesulfonate lactone, vinyl sulfite, methanedisulfonate, and vinyl sulfate.

5. The lithium-ion battery electrolyte according to claim 4, characterized in that, The second additive accounts for 0.1% to 10% of the mass percentage of the lithium-ion battery electrolyte.

6. The lithium-ion battery electrolyte according to any one of claims 1 to 3, characterized in that, The organic solvent includes at least one of cyclic or chain carbonate solvents, carboxylic acid ester solvents, and fluorocarbonate solvents.

7. The lithium-ion battery electrolyte according to claim 6, characterized in that, The cyclic or chain-like carbonate organic solvents include at least one selected from ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl propyl carbonate; and / or, The carboxylic acid ester solvent includes at least one of methyl formate, methyl acetate, methyl butyrate, ethyl acetate, ethyl propionate, propyl propionate, and γ-butyrolactone; and / or, The fluorocarbonate solvents include at least one of fluoroethylene carbonate, fluoropropylene carbonate, and fluoroethylene carbonate.

8. The lithium-ion battery electrolyte according to any one of claims 1 to 3, characterized in that, The lithium salt includes at least one of lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluorophosphate, lithium difluorophosphate, lithium difluoroborate, lithium tetrafluorooxalate phosphate, lithium trioxalate phosphate, lithium bis(oxalate borate), lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(perfluoro-1-butyryl)imide, lithium bis(pentafluoroethylsulfonyl)imide, and lithium bis(nonafluorobutylsulfonyl)imide.

9. A lithium-ion battery, characterized in that, It includes a positive electrode, a negative electrode, and the lithium-ion battery electrolyte as described in any one of claims 1 to 8.

10. The lithium-ion battery according to claim 9, characterized in that, The positive electrode includes a positive electrode active material, which includes at least one of lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide; and / or, The negative electrode material includes at least one of graphite, silicon-carbon composite material, silicon-oxygen composite material, and lithium titanate.

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