Non-aqueous electrolyte and lithium ion battery

Abstract

The invention relates to a non-aqueous electrolyte and a lithium ion battery, the non-aqueous electrolyte comprises an electrolyte salt, an organic solvent, a first additive and a second additive, the chemical structure of the first additive is as shown in formula I; the chemical structure of the second additive is shown as a formula II. According to the non-aqueous electrolyte disclosed by the invention, two additives with specific structures are creatively added into a system, and the two additives cooperate with each other, so that the side reaction of lithium battery positive electrode transition metal dissolution and a negative electrode interface is reduced, the cycle stability is improved, and the application requirements of batteries at high temperature and high pressure are met.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and more particularly to a non-aqueous electrolyte and a lithium-ion battery. Background Technology

[0002] Lithium-ion batteries (LIBs) currently dominate the portable electronic device and electric vehicle markets and are evolving towards higher energy densities to meet the demands for longer driving range. Given that the energy density of LIBs largely depends on the product of the cathode material's specific capacity and its operating voltage, academia has invested significant effort in developing high-voltage cathode materials, including high-nickel (Ni) ternary materials, high-voltage LiCoO2, and spinel-type lithium nickel manganese oxide (LiNi0.5Mn1.5O4) cathodes. Among these, LNMO cathodes offer several advantages: they avoid the expensive and toxic element cobalt (Co), thus reducing costs, and they achieve higher operating voltages while maintaining cycle safety.

[0003] Despite this, the practical application of LNMO-based battery systems still faces numerous obstacles. Their performance degrades significantly under high voltage conditions. Traditional carbonate electrolytes suffer from severe oxidative decomposition under high voltage, and the resulting byproducts further affect the formation of an effective solid-state electrolyte interphase (SEI) film. The dissolution of Mn / Ni ions damages the LNMO crystal structure, generating interfacial side reactions and increasing the battery's internal impedance. Trace amounts of water in the battery react with LiPF6 to produce HF, which then attacks LNMO particles, exacerbating the dissolution of transition metal ions. Therefore, in-depth research into LNMO batteries, addressing the structural instability of the LNMO cathode under high voltage from the electrolyte perspective, is of great significance for improving the high-temperature, high-pressure performance and reliability of lithium-ion batteries. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a non-aqueous electrolyte and a lithium-ion battery. The electrolyte of the present invention can form stable CEI / SEI films at both the positive and negative electrodes of a nickel-manganese lithium-ion battery, reducing the dissolution of transition metal ions. This effectively reduces interfacial side reactions in lithium-ion batteries operating at high temperatures, thereby improving the performance of lithium-ion batteries at high temperatures.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a non-aqueous electrolyte for lithium nickel manganese oxide batteries, the non-aqueous electrolyte comprising an electrolyte, a non-aqueous organic solvent, and additives, the additives comprising a first additive and a second additive, the chemical structure of the first additive being shown in Formula I; the chemical structure of the second additive being shown in Formula II.

[0007] ;

[0008] Wherein, R1, R2, R3, and R4 are each independently selected from substituted or unsubstituted C1-C5 alkyl groups (e.g., C1 alkyl, C2 alkyl, C3 alkyl, C4 alkyl, C5 alkyl), substituted or unsubstituted C2-C5 alkenyl groups (e.g., C2 alkenyl, C3 alkenyl, C4 alkenyl, C5 alkenyl), substituted or unsubstituted C2-C5 ynynyl groups (e.g., C2 alkenyl, C3 alkenyl, C4 alkenyl, C5 alkenyl), and substituted or unsubstituted phenyl groups; wherein the substituents are selected from any one or at least a combination of two of C1-C3 alkyl groups (e.g., C1 alkyl, C2 alkyl, C3 alkyl), hydroxyl, halogen, cyano, and nitro groups.

[0009] In this invention, two additives as shown in the above general formula are added to a non-aqueous electrolyte system. The two additives work synergistically to form a dense and multi-atom-structured composite CEI protective layer at the interface between the lithium nickel manganese oxide cathode material and the electrolyte, effectively improving the high-temperature and high-pressure capability and cycle performance of the lithium nickel manganese oxide battery system, and achieving the goal of high energy density of the cell.

[0010] The chemical structure of the first additive contains a cyano group (-CN), which has antioxidant capabilities and can inhibit the oxidative decomposition of the electrolyte to a certain extent. The oxygen atom in the P=O group has high electronegativity, which complexes the transition metal ions in the positive electrode material, inhibits the dissolution of the positive electrode transition metal, and improves the stability of the positive electrode material. It can also form a stable solid electrolyte interface (CEI) film on the surface of the battery positive electrode by working together with the bifunctional groups. This can prevent solvent molecules from co-intercalating into the electrode material, reduce the structural damage of the electrode material during the charge and discharge process, and thus improve the cycle life of the battery.

[0011] The second additive helps improve the stability of the battery in high-temperature environments. During the charging and discharging process of the battery, especially under high-temperature conditions, the electrolyte is prone to decomposition and other reactions, which affect the battery performance and safety. The second additive can reduce the decomposition reaction activity of the electrolyte, thereby enhancing the thermal stability of the battery, improving the high-temperature cycle performance and storage performance of the battery. The second additive can also improve the compatibility between the electrode and the electrolyte, reduce adverse reactions on the electrode surface, and improve the coulombic efficiency and charge and discharge efficiency of the battery.

[0012] Preferably, the mass of the electrolyte salt is 2-22% based on 100% of the mass of the non-aqueous electrolyte, such as 2%, 4%, 6%, 8%, 10%, 13%, 15%, 18%, 20%, or 22%.

[0013] Preferably, the electrolyte comprises a lithium salt.

[0014] Preferably, the electrolyte salt comprises one or a combination of at least two of lithium difluorosulfonate, lithium difluorooxalate borate, lithium tetrafluoroborate, bis(oxalate) borate, lithium difluorobis(oxalate) phosphate, or lithium hexafluorophosphate, preferably lithium hexafluorophosphate.

[0015] Preferably, the mass of the non-aqueous electrolyte is 75-94%, such as 75%, 78%, 80%, 82%, 85%, 88%, 90%, 92%, or 94%, etc., based on 100% of the mass of the non-aqueous electrolyte.

[0016] Preferably, the non-aqueous organic solvent includes carbonate organic solvents and / or carboxylic acid ester organic solvents.

[0017] Preferably, the carbonate organic solvent includes cyclic carbonates and / or chain carbonates.

[0018] Preferably, the volume ratio of the cyclic carbonate to the chain carbonate is 2:8-4:6, such as 2.5:7.5, 3:7, 3.5:6.5 or 4:6.

[0019] In this invention, cyclic carbonates and chain carbonates are compounded in a certain proportion as a non-aqueous organic solvent, which not only helps to improve the overall dielectric constant of the electrolyte, but also ensures that the resulting non-aqueous electrolyte has low viscosity and good wettability on the surface of the lithium-ion battery electrode, thus ensuring the good operation of the lithium-ion battery.

[0020] Preferably, the cyclic carbonate includes any one or a combination of at least two of ethylene carbonate, propylene carbonate, or butene carbonate.

[0021] Preferably, the chain carbonate includes any one or a combination of at least two of diethyl carbonate, methyl ethyl carbonate, dimethyl carbonate, or methyl propyl carbonate.

[0022] Preferably, the carboxylic acid ester organic solvent includes any one or a combination of at least two of ethyl propionate, propyl propionate, ethyl acetate, ethyl butyrate, methyl acetate, propyl acetate, methyl propionate, or γ-butyrolactone.

[0023] Preferably, based on the mass of the non-aqueous electrolyte as 100%, the mass of the first additive is 0.2-4%, for example 0.2%, 0.5%, 1%, 1.3%, 1.8%, 2.2%, 2.5%, 2.7%, 3%, 3.2%, 3.5% or 4%, preferably 0.2-2%, and more preferably 0.4-1.5%.

[0024] Preferably, based on the mass of the non-aqueous electrolyte as 100%, the mass of the second additive is 0.2-2%, such as 0.2%, 0.3%, 0.4%, 0.5%, 0.7%, 0.9%, 1.3%, 1.5%, 1.8% or 2%, preferably 0.2-1%, and more preferably 0.4-1%.

[0025] In this invention, the combination of a first additive and a second additive at specific concentrations can more significantly reduce the cycle impedance and improve the cycle stability of lithium nickel manganese oxide batteries. When the concentration of the second additive is too low, the resulting interfacial film is not stable enough; when its concentration is too high, the battery impedance is large, affecting battery performance. When the concentration of the second additive is 0.4-1% and the concentration of the first additive is 0.4-1.5%, the prepared lithium nickel manganese oxide battery exhibits the best overall performance, resulting in a battery with good room temperature capacity retention and high high temperature capacity retention, thereby reducing the battery's cycle impedance and enhancing its cycle performance. Furthermore, it improves the cycle stability during battery cycling and suppresses the volume expansion of the pouch cell during high-temperature storage.

[0026] Preferably, the mass ratio of the first additive to the second additive is (0.5:1), for example, 0.5:1, 0.8:1, 1:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1, 2:1, etc.

[0027] Preferably, the first additive is a compound of the following composition:

[0028] ;

[0029] Preferably, the second additive is selected from any one or a combination of at least two of the following:

[0030] .

[0031] Preferably, the additive also includes lithium salt additives.

[0032] Preferably, the lithium salt additive is 0.2-3.0% by mass, based on 100% of the non-aqueous electrolyte, for example, 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5%, 2.7% or 3.0%.

[0033] Preferably, the lithium salt additive includes any one or a combination of at least two of lithium difluorosulfonylimide, lithium difluorooxalate borate, lithium tetrafluoroborate, lithium bis(oxalate borate), lithium difluorophosphate, lithium difluorobis(oxalate phosphate), or lithium tetraphenylborate.

[0034] In this invention, the use of lithium salt additives can further and effectively improve the battery's capacity retention rate and cycle life, and can effectively broaden the operating temperature range of lithium-ion batteries.

[0035] Preferably, the non-aqueous electrolyte also includes other additives;

[0036] Preferably, based on the mass of the non-aqueous electrolyte as 100%, the mass percentage of the other additives is 0.5-11.6%, such as 0.5%, 1%, 2%, 3%, 5%, 9%, 11%, or 11.6%.

[0037] Preferably, the other additives include any one or a combination of at least two of the following: vinylene carbonate, 1,3-propanesulfonate lactone, fluoroethylene carbonate, vinyl sulfite, vinyl sulfate, methanedisulfonate, ethylene ethylene carbonate, tris(trimethylsilane) phosphate, and tris(trimethylsilane) borate.

[0038] In a second aspect, the present invention provides a lithium-ion battery, the lithium-ion battery comprising a cell and an electrolyte, wherein the electrolyte is the non-aqueous electrolyte described in the first aspect.

[0039] Preferably, the battery cell includes a positive electrode, a negative electrode, and a separator, wherein the separator is disposed between the positive electrode and the negative electrode;

[0040] Preferably, the active material of the positive electrode is lithium nickel manganese oxide, or a combination of lithium nickel manganese oxide with any one or at least two of transition metal oxides, polyanionic compounds or Prussian blue analogues.

[0041] Preferably, the active material of the negative electrode includes one or a combination of at least two of the following: natural graphite, artificial graphite, soft carbon, hard carbon, mesophase carbon microspheres, graphene, graphynylene, lithium metal, nano-carbon, carbon nanotubes, elemental silicon, silicon oxide, silicon / copper oxide composite, AG composite, silicon alloy, elemental tin, tin oxide, tin-carbon composite, tin alloy, or lithium titanate.

[0042] Preferably, the active material of the negative electrode comprises a combination of graphite and silicon-based materials;

[0043] Preferably, the silicon-based material includes any one or a combination of at least two of elemental silicon, silicon oxide compounds, silicon / copper oxide composites, and silicon alloys;

[0044] Preferably, the silicon-based material in the active material of the negative electrode has a mass percentage of 10%-20%, such as 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%.

[0045] Preferably, the membrane material includes one of polyethylene, polypropylene, or composite ceramic membrane.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] The non-aqueous electrolyte provided by this invention comprises a first additive and a second additive with the aforementioned structure. These two additives work synergistically to form a dense, multi-atom-structured composite CEI protective layer at the interface between the lithium nickel manganese oxide cathode material and the electrolyte. This effectively stabilizes the electrode / electrolyte interface, inhibits oxidative decomposition of the electrolyte during cycling and damage to the cathode material structure, reduces the dissolution of transition metal ions, and improves the high-voltage cycle stability and thermal stability of the battery. The capacity retention rate is 69-92.1% under test conditions of 25℃ and 1C, and 60.6-83.2% under test conditions of 45℃ and 1C. Detailed Implementation

[0048] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0049] Some of the raw materials used in the following examples:

[0050] The CAS number of compound A in the following examples is 875826-91-8, purchased from Shandong Binruit New Material Co., Ltd.; the CAS number of compound B is 33027-66-6, purchased from Suzhou Yake Technology Co., Ltd.; the preparation method of compound C is described in Example 2 of CN115873039A; the preparation method of compound D is described in Example 1 of CN116285003A; and the preparation method of compound E is described in Example 3 of CN116285003A.

[0051] Example 1

[0052] This embodiment provides a non-aqueous electrolyte, the composition of which is (total amount 100%):

[0053] Electrolyte (lithium hexafluorophosphate) 12.5%, first additive (as shown in formula A below) 1%, second additive (as shown in formula B below) 0.5%, third additive (ethylene carbonate 2% + fluoroethylene carbonate 2% + tris(trimethylsilane)borate 0.5%) 4.5%, organic solvent (a mixture of methyl ethyl carbonate, dimethyl carbonate and fluoroethylene carbonate in a volume ratio of 6:2:1) balance.

[0054] Formula A Formula B

[0055] Example 2

[0056] This embodiment provides a non-aqueous electrolyte, the composition of which is (total amount 100%):

[0057] Electrolyte (lithium hexafluorophosphate) 12.5%, first additive (as shown in formula A below) 1%, second additive (as shown in formula C below) 0.5%, third additive (ethylene carbonate 2% + fluoroethylene carbonate 2% + ethylene sulfate 1%) 5%, organic solvent (a mixture of methyl ethyl carbonate, dimethyl carbonate and fluoroethylene carbonate in a volume ratio of 6:2:1) balance.

[0058] Formula A Formula C

[0059] Example 3

[0060] This embodiment provides a non-aqueous electrolyte, the composition of which is (total amount 100%):

[0061] Electrolyte (lithium hexafluorophosphate) 12.5%, first additive (as shown in formula A below) 1%, second additive (as shown in formula D below) 0.5%, third additive (ethylene carbonate 2% + fluoroethylene carbonate 2% + tris(trimethylsilane)borate 1%) 5%, organic solvent (a mixture of methyl ethyl carbonate, dimethyl carbonate and fluoroethylene carbonate in a volume ratio of 6:2:1) balance.

[0062] Formula A Formula D

[0063] Example 4

[0064] This embodiment provides a non-aqueous electrolyte, the composition of which is (total amount 100%):

[0065] Electrolyte (lithium hexafluorophosphate) 12.5%, first additive (as shown in formula A below) 1%, second additive (as shown in formula E below) 0.5%, third additive (ethylene carbonate 2% + fluoroethylene carbonate 2% + tris(trimethylsilane)borate 0.5%) 4.5%, organic solvent (a mixture of methyl ethyl carbonate, dimethyl carbonate and fluoroethylene carbonate in a volume ratio of 6:2:1) balance.

[0066] Formula A Formula E.

[0067] Example 5

[0068] This embodiment provides a non-aqueous electrolyte whose composition (total amount 100%) differs from that of Example 1 only in the mass ratio of the first additive to the second additive, specifically: the first additive is 0.3% and the second additive is 1.2%. Except for the solvent, all other components and their contents remain unchanged.

[0069] Example 6

[0070] This embodiment provides a non-aqueous electrolyte whose composition (total amount 100%) differs from that of Example 1 only in the mass ratio of the first additive to the second additive, specifically: the first additive is 1.2% and the second additive is 0.3%. Except for the solvent, all other components and their contents remain unchanged.

[0071] Example 7

[0072] This embodiment provides a non-aqueous electrolyte whose composition (total amount 100%) differs from that of Example 1 only in the content of the second additive. Specifically, the first additive is 1%, and the second additive is 0.2%, with the reduction made up by the organic solvent. All other components and their contents remain unchanged.

[0073] Example 8

[0074] This embodiment provides a non-aqueous electrolyte whose composition (total amount 100%) differs from that of Example 1 only in the content of the second additive. Specifically, the first additive is 1%, and the second additive is 0.3%, with the reduction made up by the organic solvent. All other components and their contents remain unchanged.

[0075] Example 9

[0076] This embodiment provides a non-aqueous electrolyte whose composition (total amount 100%) differs from that of Example 1 only in the content of the second additive. Specifically, the first additive is 1%, the second additive is 0.8%, and the content of the organic solvent is reduced accordingly. All other components and their contents remain unchanged.

[0077] Example 10

[0078] This embodiment provides a non-aqueous electrolyte whose composition (total amount 100%) differs from that of Example 1 only in the content of the second additive. Specifically, the first additive is 1%, the second additive is 2%, and the content of the organic solvent is reduced accordingly. All other components and their contents remain unchanged.

[0079] Example 11

[0080] This embodiment provides a non-aqueous electrolyte whose composition (total amount 100%) differs from that of Example 1 only in the content of the first additive, specifically: 0.2% first additive and 0.5% second additive, with the reduced amount made up by the organic solvent. All other components and their contents remain unchanged.

[0081] Example 12

[0082] This embodiment provides a non-aqueous electrolyte whose composition (total amount 100%) differs from that of Example 1 only in the content of the first additive, specifically: 2% first additive and 0.5% second additive, with the reduced amount made up by the organic solvent. All other components and their contents remain unchanged.

[0083] Example 13

[0084] This embodiment provides a non-aqueous electrolyte whose composition (total amount 100%) differs from that of Example 1 only in the formulation of the organic solvent, specifically a mixture of ethyl methyl carbonate, ethyl difluorocarbonate, and fluoroethylene carbonate in a volume ratio of 1:2:6. All other components and their contents remain unchanged.

[0085] Example 14

[0086] This embodiment provides a non-aqueous electrolyte whose composition (total amount 100%) differs from that of Example 1 only in the formulation of the organic solvent, specifically a mixture of methyl ethyl carbonate, trifluoroethyl methyl carbonate, and fluoroethylene carbonate in a volume ratio of 3:3:4. All other components and their contents remain unchanged.

[0087] Example 15

[0088] This embodiment provides a non-aqueous electrolyte whose composition (total amount 100%) differs from that of Example 1 only in that 0.2% lithium difluorophosphate is further added, and the content of organic solvent is correspondingly reduced. All other components and their contents remain unchanged.

[0089] Example 16

[0090] This embodiment provides a non-aqueous electrolyte whose composition (total amount 100%) differs from that of Example 2 only in that 2.5% lithium difluorosulfonylimide is further added, and the content of organic solvent is correspondingly reduced. All other components and their contents remain unchanged.

[0091] Comparative Example 1

[0092] This comparative example provides a non-aqueous electrolyte whose composition (total amount 100%) differs from that of Example 1 only in that it lacks the second additive, and the content of the first additive is 1.5%. All other components and their contents remain unchanged.

[0093] Comparative Example 2

[0094] This comparative example provides a non-aqueous electrolyte whose composition (total amount 100%) differs from that of Example 1 only in that it lacks the first additive and the content of the second additive is 1.5%. All other components and their contents remain unchanged.

[0095] Comparative Example 3

[0096] This comparative example provides a non-aqueous electrolyte whose composition (total amount 100%) differs from that of Example 1 only in that it lacks the first and second additives, the corresponding amounts of which are made up by organic solvents. All other components and their contents remain unchanged.

[0097] Comparative Example 4

[0098] This comparative example provides a non-aqueous electrolyte whose composition (total amount 100%) differs from that of Example 2 only in that it lacks the first and second additives, with the corresponding amounts made up by organic solvents. All other components and their contents remain unchanged.

[0099] The component formulations of the non-aqueous electrolytes in Examples 1-16 and Comparative Examples 1-4 are summarized in Table 1 below:

[0100] Table 1

[0101]

[0102]

[0103] Application Example 1-16 and Comparative Application Example 1-4

[0104] This application example provides a lithium-ion battery, the preparation method of which includes the following steps:

[0105] (1) Preparation of positive electrode

[0106] 1.5 wt% conductive carbon, 0.7 wt% KS-6, 1.5 wt% polyvinylidene fluoride, and the balance LiNi 0.5 Mn 1.5 O4 (the sum of the mass percentages of the four components is 100%) is stirred and dispersed in N-methylpyrrolidone to prepare a positive electrode slurry (solid content 68%), which is then coated onto a 15μm aluminum foil current collector. After cold pressing, slitting, and cutting, the positive electrode sheet is obtained.

[0107] (2) Preparation of negative electrode

[0108] A negative electrode slurry (60% solid content) is prepared by mixing 1.5 wt% conductive carbon black, 1.0 wt% carboxymethyl cellulose, 1.5 wt% styrene-butadiene rubber and the balance graphite (the sum of the mass percentages of the four components is 100%) with deionized water. The slurry is coated onto an 8 μm copper foil current collector and then cold-pressed, slit, and cut to obtain the negative electrode sheet.

[0109] Coating density: 15 g / cm³ on one side of the positive electrode 2 ; Negative electrode 7g / cm 2 .

[0110] (3) Preparation of non-aqueous electrolyte: Prepare electrolyte in a Mikelona glove box (filled with argon gas, with less than 10 ppm of gaseous water). First, mix organic solvents evenly according to the ratio. Add various additives to the evenly mixed solvent package. Finally, add electrolyte and mix until there is no residue at the bottom and the electrolyte is clear and turbid. Then, an electrolyte with normal color is obtained. Store it in a refrigerator at 10°C. The proportions of each group are shown in Table 1.

[0111] (4) Separator: A 9μm thick polyethylene is used as the base membrane, and a 3μm thick nano-alumina coating is coated on the base membrane to obtain the separator.

[0112] (5) Cell fabrication: The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrode to provide isolation, and the cells are stacked to obtain a bare cell.

[0113] (6) Cyclic Testing: Performance testing is a standard technique, briefly described below:

[0114] Performance test at room temperature (25℃): In a constant temperature test chamber, the test temperature is 25℃. Charge to 4.85V with 1C constant current and constant voltage, and the current is less than 0.03A. After resting for 5 minutes, discharge to 3.4V with 1C constant current. Cycle 400 times. Record the discharge capacity C1 of the first cycle and the discharge capacity C2 of the 100th cycle in steps. Calculate the capacity retention rate at room temperature cycle = C2 / C1×100%.

[0115] High temperature (45℃) performance test: In a constant temperature test chamber, the test temperature is 45℃. Charge to 4.85V with 1C constant current and constant voltage, and the current is less than 0.03A. After resting for 5 minutes, discharge to 3.4V with 1C constant current. Cycle 100 times. Record the discharge capacity C3 of the first cycle and the discharge capacity C4 of the 100th cycle in steps. The capacity retention rate at 45℃ cycle = C4 / C3×100%.

[0116] The test results of Examples 1-16 and Comparative Examples 1-4 are shown in Table 2.

[0117] Table 2

[0118]

[0119] The test results show that:

[0120] (1) The electrolyte of the present invention, by adding two specific additives, enables the nickel-manganese lithium oxide battery to have good capacity retention at room temperature and high capacity retention at high temperature, and can greatly suppress the volume expansion of the soft-pack battery during battery cycling. As shown in Examples 1-16, the capacity retention rate of the nickel-manganese lithium oxide battery assembled with the non-aqueous electrolyte is 69-92.1% under the test conditions of 25℃ and 1C, and the capacity retention rate is 83.2-60.6% under the test conditions of 45℃ and 1C.

[0121] (2) By comparing the data results of Application Example 1 and Application Example 5.12, it can be seen that the addition ratio of the two additives and their respective addition content affect the cycle performance and storage performance of lithium nickel manganese oxide batteries to a certain extent.

[0122] (3) By comparing the data results of Application Example 1 and Application Examples 13 and 14, it can be seen that the composition of the organic solvent in the system also affects the cycle performance and storage performance of the nickel manganese lithium battery to a certain extent.

[0123] (4) By comparing the data results of Application Example 1 and Application Examples 15 and 16, it can be seen that adding lithium salt additives to the system can further improve the cycle performance and storage performance of lithium nickel manganese oxide batteries.

[0124] (5) By comparing Example 1 with Comparative Examples 1-4, it can be seen that by adding two specific additives to the non-aqueous electrolyte, the present invention can reduce the cycle impedance of the lithium nickel manganese oxide battery and improve its cycle life, and reduce the storage gas production of the lithium nickel manganese oxide battery and improve its cycle performance. That is, the synergistic effect of the two additives can greatly improve the overall performance of the obtained lithium nickel manganese oxide. However, adding only the first additive or the second additive can improve the high-temperature cycle performance of the battery and reduce its storage gas production to a certain extent, but the single additive cannot exert the synergistic effect of the two additives, and therefore cannot significantly reduce the cycle impedance of lithium nickel manganese oxide and improve its cycle performance.

[0125] The applicant declares that the present invention is illustrated by the above embodiments to demonstrate the non-aqueous electrolyte and lithium-ion battery of the present invention, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A non-aqueous electrolyte, characterized in that, The non-aqueous electrolyte comprises an electrolyte, a non-aqueous organic solvent, and additives. The additives include a first additive and a second additive. The chemical structure of the first additive is shown in Formula I; the chemical structure of the second additive is shown in Formula II. ； R1, R2, R3, and R4 are each independently selected from substituted or unsubstituted C1-C5 alkyl, substituted or unsubstituted C2-C5 alkenyl, substituted or unsubstituted C2-C5 alkynyl, and substituted or unsubstituted phenyl groups; the substituents are selected from any one or a combination of at least two of C1-C3 alkyl, hydroxyl, halogen, cyano, and nitro groups.

2. The non-aqueous electrolyte according to claim 1, characterized in that, Based on the mass of the non-aqueous electrolyte being 100%, the mass percentage of the electrolyte is 2-22%. Preferably, the electrolyte comprises a lithium salt; Preferably, the electrolyte salt comprises one or a combination of at least two of lithium difluorosulfonate, lithium difluorooxalate borate, lithium tetrafluoroborate, bis(oxalate) borate, lithium difluorobis(oxalate) phosphate, or lithium hexafluorophosphate.

3. The non-aqueous electrolyte according to claim 1 or 2, characterized in that, Based on the mass of the non-aqueous electrolyte being 100%, the mass percentage of the non-aqueous organic solvent is 75-94%. Preferably, the non-aqueous organic solvent includes carbonate organic solvents and / or carboxylic acid ester organic solvents; Preferably, the carbonate organic solvent includes cyclic carbonates and / or chain carbonates; Preferably, the cyclic carbonate includes any one or a combination of at least two of ethylene carbonate, propylene carbonate, or butene carbonate; Preferably, the chain carbonate includes any one or a combination of at least two of diethyl carbonate, methyl ethyl carbonate, dimethyl carbonate, or methyl propyl carbonate. Preferably, the carboxylic acid ester organic solvent includes any one or a combination of at least two of ethyl propionate, propyl propionate, ethyl acetate, ethyl butyrate, methyl acetate, propyl acetate, methyl propionate, or γ-butyrolactone.

4. The non-aqueous electrolyte according to any one of claims 1-3, characterized in that, Based on the mass of the non-aqueous electrolyte as 100%, the mass percentage of the first additive is 0.2-4%, preferably 0.2-2%, and more preferably 0.4-1.5%.

5. The non-aqueous electrolyte according to any one of claims 1-4, characterized in that, Based on the mass of the non-aqueous electrolyte as 100%, the mass percentage of the second additive is 0.2-2%, preferably 0.2-1%, and more preferably 0.4-1%. Preferably, the mass ratio of the first additive to the second additive is (0.5-2):

1.

6. The non-aqueous electrolyte according to any one of claims 1-5, characterized in that, The first additive is the following compound: ； Preferably, the second additive is selected from any one or a combination of at least two of the following: 。 7. The non-aqueous electrolyte for lithium-ion batteries according to any one of claims 1-6, characterized in that, The additives also include lithium salt additives; Preferably, based on the mass of the non-aqueous electrolyte (100%), the mass percentage of the lithium salt additive is 0.2-3.0%. Preferably, the lithium salt additive includes any one or a combination of at least two of lithium difluorosulfonylimide, lithium difluorooxalate borate, lithium tetrafluoroborate, lithium bis(oxalate borate), lithium difluorophosphate, lithium difluorobis(oxalate phosphate), or lithium tetraphenylborate.

8. The non-aqueous electrolyte for lithium-ion batteries according to any one of claims 1-7, characterized in that, The non-aqueous electrolyte also includes other additives; Preferably, based on the mass of the non-aqueous electrolyte as 100%, the mass percentage of the other additives is 0.5-11.6%. Preferably, the other additives include any one or a combination of at least two of the following: vinylene carbonate, 1,3-propanesulfonate lactone, fluoroethylene carbonate, vinyl sulfite, vinyl sulfate, methanedisulfonate, ethylene ethylene carbonate, tris(trimethylsilane) phosphate, and tris(trimethylsilane) borate.

9. A lithium-ion battery, characterized in that, The lithium-ion battery includes a cell and an electrolyte, wherein the electrolyte is a non-aqueous electrolyte as described in any one of claims 1-8.

10. The lithium-ion battery according to claim 9, characterized in that, The battery cell includes a positive electrode, a negative electrode, and a separator, with the separator disposed between the positive electrode and the negative electrode; Preferably, the active material of the positive electrode is lithium nickel manganese oxide, or a combination of lithium nickel manganese oxide with any one or at least two of transition metal oxides, polyanionic compounds or Prussian blue analogues. Preferably, the active material of the negative electrode includes one or a combination of at least two of the following: natural graphite, artificial graphite, soft carbon, hard carbon, mesophase carbon microspheres, graphene, graphynylene, lithium metal, nano-carbon, carbon nanotubes, elemental silicon, silicon oxide, silicon / copper oxide composite, AG composite, silicon alloy, elemental tin, tin oxide, tin-carbon composite, tin alloy, or lithium titanate. Preferably, the active material of the negative electrode comprises a combination of graphite and silicon-based materials; Preferably, the silicon-based material includes any one or a combination of at least two of elemental silicon, silicon oxide compounds, silicon / copper oxide composites, and silicon alloys; Preferably, the silicon-based material in the active material of the negative electrode has a mass percentage content of 10%-20%. Preferably, the membrane material includes one of polyethylene, polypropylene, or composite ceramic membrane.

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