Electrolyte, lithium ion battery and electric device

Abstract

The application provides an electrolyte, a lithium ion battery and a power utilization device, and relates to the field of lithium ion batteries. The electrolyte comprises an oxazinone additive, and a general structure of the oxazinone additive is wherein R1 and R2 are independently selected from hydrogen, C1-C4 linear or branched alkyl, cycloalkyl and alkyl substituted by at least one halogen. The electrolyte additive of the application can optimize the negative electrode SEI and stabilize the positive electrode CEI, and can simultaneously realize the effects of improving high-temperature stability, improving high-voltage compatibility, inhibiting lithium dendrites and improving the rate, and overcomes the defect that the traditional electrolyte additive has single function. Compared with the conventional electrolyte, the electrolyte of the application is improved in the aspects of normal-temperature cycle performance, high-temperature cycle performance, rate performance, lithium dendrite inhibition effect and high-voltage cycle performance.

Description

Technical Field

[0001] This application relates to the field of lithium-ion batteries, and more particularly to an electrolyte, a lithium-ion battery, and an electrical device. Background Technology

[0002] Lithium-ion batteries, as the core power source for new energy vehicles, energy storage systems, and consumer electronics, have performance bottlenecks that are highly dependent on the interfacial stability of the electrolyte. Currently, commercially available carbonate-based electrolytes (EC / EMC / DMC+LiPF6) suffer from three major pain points: Poor stability of the anode SEI film: Carbonate solvent is prone to continuous reduction and decomposition on the surface of graphite / silicon-carbon anode, resulting in thickening of the SEI film, increased impedance, capacity decay, and shortened cycle life; High-voltage cathode interface failure: High-nickel ternary and lithium-rich manganese-based high-voltage cathodes accelerate solvent oxidation, damage the CEI film, and lead to transition metal dissolution and battery swelling. Performance degradation under extreme conditions: Under high temperature (≥60℃) storage / cycle, fast charging, and low temperature conditions, the electrolyte is prone to side reactions, which exacerbates the risk of lithium dendrite growth and seriously threatens battery safety.

[0003] To address the above issues, the industry typically adds electrolyte additives to the electrolyte. However, existing electrolyte additives have the following problems: Poor high-temperature stability: Existing electrolyte additives are prone to ring-opening and polymerization side reactions at high temperatures, which leads to an increase in electrolyte viscosity and gas production, causing battery swelling; Insufficient high voltage compatibility: Existing additives are prone to oxidation and decomposition under ≥4.5V high voltage, and cannot be adapted to next-generation high voltage cathode systems such as high-nickel ternary cathodes. Summary of the Invention

[0004] The purpose of this application is to provide an electrolyte, a lithium-ion battery, and an electrical device to solve the above-mentioned problems.

[0005] To achieve the above objectives, this application adopts the following technical solution: An electrolyte comprising an oxazinone additive, the general structural formula of which is: R1 and R2 are independently selected from hydrogen, C1-C4 straight-chain or branched alkyl, cycloalkyl, and alkyl substituted with at least one halogen.

[0006] In some embodiments, the structural formula of the oxazinone additive is as follows: .

[0007] In some embodiments, the mass fraction of oxazinone additives in the electrolyte is 0.05% to 3.0%.

[0008] In some embodiments, the electrolyte further includes a lithium salt; The lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide.

[0009] In some embodiments, the concentration of lithium salt in the electrolyte is 0.8~1.5 mol / L.

[0010] In some embodiments, the electrolyte further includes an organic solvent; The organic solvent includes at least one of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl propionate, and propyl propionate.

[0011] In some embodiments, the electrolyte further includes auxiliary additives, which include at least one of fluoroethylene carbonate, vinylene carbonate, 1,3-propanesulfonate lactone, and vinyl sulfate.

[0012] In some embodiments, the mass fraction of the auxiliary additives in the electrolyte is 0.5% to 3.0%.

[0013] This application also provides a lithium-ion battery, which includes the electrolyte described above.

[0014] This application also provides an electrical device, which includes the lithium-ion battery described above.

[0015] Compared with the prior art, the beneficial effects of this application include: The electrolyte additive of this application can optimize the negative electrode SEI and stabilize the positive electrode CEI. It can simultaneously achieve the effects of improving high temperature stability, improving high voltage compatibility, suppressing lithium dendrites, and improving rate performance, overcoming the shortcomings of traditional electrolyte additives with single functions. Compared with conventional electrolytes, the electrolyte of this application has improved in terms of room temperature cycling performance, high temperature cycling performance, rate performance, lithium dendrite suppression effect, and high voltage cycling performance.

[0016] Achieving synergistic protection of the positive and negative electrode interfaces: Through the synergistic effect of unsaturated double bonds (C=C), imine bonds (C=N), lactone rings (-O-CO-), and geminal dialkyl groups (-CR1R2) in oxazinone additive molecules, both the negative electrode SEI film and the positive electrode CEI film are optimized, solving the problem of the single function of existing electrolyte additives. Specifically, the additives of this application preferentially reduce and form a stable nitrogen- and oxygen-containing SEI film on the negative electrode surface, inhibiting solvent reduction and decomposition; and adsorb and form a dense CEI film on the positive electrode surface, inhibiting solvent oxidation and transition metal dissolution, thus solving the industry pain point that existing additives cannot simultaneously protect the positive and negative electrodes. Balancing interfacial film stability and rate performance: The steric hindrance effect of the geminal dialkyl groups in oxazinone additives precisely regulates the microstructure of the interfacial film, forming a "dense-loose" gradient porous structure, which ensures interfacial stability and reduces lithium-ion transport impedance, solving the problem of traditional additives that are difficult to balance good film-forming properties and low impedance. Significantly improves high-temperature storage and cycling performance: The thermal stability of the six-membered oxazinone ring in oxazinone additives is much higher than that of traditional electrolyte additives, which can avoid ring opening, gas generation and side reactions at high temperatures, and solve the problem of high-temperature failure of existing electrolyte additives. Adapted to high-voltage, high-energy-density battery systems: The electronic effect of unsaturated double bonds in oxazinone additives can enhance the molecular oxidation potential. The oxidation potential of the additives is >4.6V, which can stably form films in high-nickel ternary systems above 4.5V, solving the problem of incompatibility between existing additives and high-voltage systems; Highly effective suppression of lithium dendrite growth: The polar effect of imine bonds in oxazinone additives can uniformly distribute lithium ion flux, and the SEI film formed by double bond reduction can suppress lithium dendrite deposition. The dual effect improves the safety of fast charging and solves the safety hazards of lithium dendrites under fast charging conditions. Excellent electrolyte compatibility: The structure of the oxazinone additives in this application is highly compatible with conventional lithium salts, solvents, and auxiliary additives, with no side reactions, and can be directly applied to existing production lines without process modification.

[0017] The lithium-ion battery of this application uses an electrolyte containing oxazinone additives. Compared with traditional lithium-ion batteries, the lithium-ion battery of this application improves room temperature cycle performance, high temperature cycle performance, rate performance, high voltage cycle performance and safety.

[0018] The electrical equipment in this application includes the aforementioned lithium-ion battery. The electrical equipment in this application can be used stably in complex environments such as high temperature and high pressure, and has a long service life and good safety. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0020] Figure 1 The 6,6-dimethyl-2-vinyl-4H-1,3-oxazin-4-one used in Examples 1-5 1 H NMR spectrum; Figure 2 The 6,6-dimethyl-2-vinyl-4H-1,3-oxazin-4-one used in Examples 1-5 13 C NMR spectrum; Figure 3 The graphs show the 1C first charge-discharge curves of Example 1 and Comparative Example 1 at 25°C. Figure 4 The graphs show the rate performance of Examples 1, 2, and Comparative Example 1 at 25°C. Figure 5 The graph shows the capacity retention rate of Example 1 and Comparative Example 1 after 100 cycles at 4.5V using 1C. Detailed Implementation

[0021] As used in this article: "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0022] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0023] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0024] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0025] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (where K is any number representing a multiplier). It is important to understand that, unlike parts by mass, the sum of the mass parts of all components is not limited to 100 parts.

[0026] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0027] This application provides an electrolyte comprising an oxazinone additive, the general structural formula of which is: R1 and R2 are independently selected from hydrogen, C1-C4 straight-chain or branched alkyl, cycloalkyl, and alkyl substituted with at least one halogen.

[0028] The six-membered ring oxazinone structure in the additive of this application has a much higher thermal stability than the five-membered ring lactone (such as VC). The electronic effect of the unsaturated double bond can increase the molecular oxidation potential, making it suitable for high-voltage systems above 4.5V and high-temperature conditions above 60℃, thereby improving high-temperature stability and high-pressure stability.

[0029] In some embodiments, the structural formula of the oxazinone additive is as follows: .

[0030] In some embodiments, The preparation method includes: dissolving tert-butyl 3-methyl-2-oxobutyrate and DMAP in a solvent, and adding acryloyl isocyanate dropwise under nitrogen protection and at 0~5℃ (e.g., 0℃, 1℃, 2℃, 3℃, 4℃, 5℃ or any value between 0~5℃); after the addition is complete, the temperature is raised to 100~120℃ (e.g., 100℃, 110℃, 120℃ or any value between 100~120℃) and reacted for 5~10 hours (e.g., 5 hours, 7 hours, 10 hours or any value between 5~10 hours), concentrated under reduced pressure, and then recrystallized and purified to obtain the target product.

[0031] In some embodiments, the solvent includes toluene.

[0032] In some embodiments, the molar ratio of tert-butyl 3-methyl-2-oxobutyrate to acryloyl isocyanate is 1:(1.03-1.07), for example, any value between 1:1.03, 1:1.05, 1:1.07 or 1:(1.03-1.07).

[0033] In some embodiments, the molar ratio of tert-butyl 3-methyl-2-oxobutyrate to DMAP is 1:(0.003-0.007), for example, any value between 1:0.003, 1:0.005, 1:0.007 or 1:(0.003-0.007).

[0034] In some embodiments, the mass fraction of oxazinone additives in the electrolyte is 0.05% to 3.0%.

[0035] When the mass fraction of oxazinone additives in the electrolyte is 0.05%~3.0%, the oxazinone additive molecules can be fully adsorbed onto the surfaces of the positive and negative electrodes and undergo stepwise electrochemical reactions to form a uniform and continuous SEI / CEI dual-interface protective film. This film can effectively chelate transition metal ions dissolved from the positive electrode through intramolecular N and O coordination sites, suppressing metal shuttle side reactions. It also achieves a wide temperature range adaptability, including high-temperature swelling resistance and low-temperature brittleness resistance, thanks to the flexible six-membered heterocyclic framework. Simultaneously, the nitrogen-containing free radicals generated by the thermal decomposition of the heterocycle can impart basic flame retardant properties to the electrolyte. Furthermore, within this addition range, the additives are completely soluble in the carbonate system, resulting in a small increase in electrolyte viscosity, stable ionic conductivity, and optimal balance in the cell's first-cycle coulombic efficiency, long-cycle capacity retention, low gas expansion during high-voltage storage, and low-temperature discharge performance. However, if the mass fraction of oxazinone additives in the electrolyte is too low, or the amount added is insufficient, it cannot completely coat the electrode active sites, leading to interfacial film defects. Numerous pores and defects cause continuous side reactions between the solvent and the electrodes, rendering the transition metal chelation and flame retardant improvements largely ineffective. This results in a significant decline in the high-temperature and high-pressure cycling performance of the battery cell, increased self-discharge, and poor low-temperature discharge performance. If the mass fraction of oxazinone additives in the electrolyte is too high or the amount of oxazinone additives added is excessive, the excess additives that do not participate in film formation will significantly increase the overall viscosity of the electrolyte, reduce the lithium salt dissociation efficiency and ion conduction rate, causing a significant increase in the internal resistance of the battery cell and increased fast-charging polarization. Excess additives continue to undergo irreversible side reactions during long-term cycling, resulting in a large amount of gas production and severe gas expansion in the battery cell. At the same time, it consumes a large amount of active lithium, and the coulombic efficiency and usable capacity of the battery cell in the first cycle are significantly reduced.

[0036] The addition amount of oxazinone additives in electrolytes is low and the cost is controllable, which will not significantly increase the cost of electrolytes and has the prospect of large-scale industrial application.

[0037] For example, the mass fraction of oxazinone additives in the electrolyte is 0.05%, 0.1%, 0.2%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, or any value between 0.05% and 3.0%.

[0038] In some embodiments, the electrolyte further includes a lithium salt; The lithium salt includes at least one of lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0039] In some embodiments, the concentration of lithium salt in the electrolyte is 0.8~1.5 mol / L.

[0040] For example, the concentration of lithium salt in the electrolyte can be 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, or any value between 0.8 and 1.5 mol / L.

[0041] In some embodiments, the electrolyte further includes an organic solvent; The organic solvent includes at least one of ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), ethyl propionate (EP), and propyl propionate (PP).

[0042] In some embodiments, the organic solvent includes ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC), wherein the volume ratio of ethylene carbonate (EC) to ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) is 1:1:1.

[0043] In some embodiments, the electrolyte further includes auxiliary additives, which include at least one of fluoroethylene carbonate (FEC), vinylene carbonate (VC), 1,3-propanesulfonate lactone (PS), and ethylene sulfate (DTD).

[0044] Compared to electrolyte solutions that only add oxazinone additives without any auxiliary additives, introducing auxiliary additives such as VC and FEC can bring multiple performance gains: auxiliary additives can preferentially pre-deposit a thin organic SEI substrate on the negative electrode surface, further reducing the irreversible lithium consumption of oxazinone additives, slightly improving the cell's first-cycle coulombic efficiency, and simultaneously supplementing trace amounts of LiF. Inorganic components slightly enhance the rigidity of the interfacial film and slightly improve the stability of high-rate cycling. There is a positive synergistic interaction between the two. Specifically, the reduction potential of auxiliary additives (such as VC, FEC, etc.) is slightly higher than that of oxazinone additives. In the early stage of charging, auxiliary additives are reduced before oxazinone additives, forming a thin and uniform primary SEI substrate on the graphite negative electrode surface. This substrate is rich in oxygen-containing polar groups, which can adsorb more oxazinone additive molecules through hydrogen bonding and dipole interaction, enriching them at the electrode interface, increasing the local concentration of oxazinone additives, promoting the full electrochemical reaction of their vinyl and C=N groups, and rapidly constructing a composite SEI film with both a flexible heterocyclic framework and an inorganic LiF reinforcing phase. At the same time, the N and O coordination sites in the oxazinone additive molecules can capture trace amounts of HF generated by the decomposition of auxiliary additives, inhibiting the continuous corrosion of the positive electrode active material and aluminum foil current collector by HF, and alleviating the defects of hydrolysis and gas generation of auxiliary additives (such as FEC, etc.). The LiF generated by the decomposition of auxiliary additives can fill the tiny pores of the oxazinone organic interfacial film, making up for the lack of inorganic components in the pure oxazinone interfacial film.

[0045] In some embodiments, the mass fraction of the auxiliary additive in the electrolyte is 0.5% to 3.0%. If too much auxiliary additive is added, it will decompose preferentially in large quantities, occupying the active sites of the electrode, hindering the formation of the CEI protective film of oxazinone at the high potential of the positive electrode, destroying the synergistic regulation effect of the dual interface, and at the same time, the excessive auxiliary additive decomposes to generate a large amount of HF and gas, offsetting the core advantages of oxazinone in inhibiting dissolution and low gas expansion.

[0046] For example, the mass fraction of auxiliary additives in the electrolyte is 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, or any value between 0.5% and 3.0%.

[0047] This application also provides a lithium-ion battery, which includes the electrolyte described above.

[0048] This application also provides an electrical device, which includes the lithium-ion battery described above.

[0049] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0050] The raw material information used in the examples and comparative examples is as follows: The structural formula of 6,6-dimethyl-2-vinyl-4H-1,3-oxazin-4-one (VDMO) used in Examples 1-5 is as follows: .

[0051] The preparation method of 6,6-dimethyl-2-vinyl-4H-1,3-oxazin-4-one (VDMO) used in Examples 1-5 includes: adding 172.2 g (1 mol) of tert-butyl 3-methyl-2-oxobutyrate (CAS No.: 87670-16-4) and 0.61 g (0.005 mol, 0.005 eq) DMAP to anhydrous toluene, and adding 103.0 g (1.05 mol) of acryloyl isocyanate (CAS No.: 13641-97-9) dropwise under nitrogen protection at 0°C. After the addition is complete, the temperature is raised to 110°C and refluxed for 7 h to remove isobutylene. The product is then purified by recrystallization after concentration under reduced pressure to obtain the target product.

[0052] 6,6-Dimethyl-2-vinyl-4H-1,3-oxazin-4-one 1 H NMR spectrum as shown Figure 1 As shown, 6,6-dimethyl-2-vinyl-4H-1,3-oxazin-4-one 13 The C NMR spectrum is as follows Figure 2 As shown.

[0053] Structural characterization of 6,6-dimethyl-2-vinyl-4H-1,3-oxazin-4-one: 1 H NMR (600 MHz, CDCl3)δ (ppm): 5.00-5.55 (m, 3H), 2.10 (s, 3H), 1.05 (s, 9H); 13 C NMR (150 MHz, CDCl3) δ (ppm): 177.9 (C=O), 161.8 (Cq), 130.9 (CH), 123.6 (CH2), 52.4 (Cq), 51.5 (Cq), 28.1 (CH3, 3C, t-Bu).

[0054] The structural formula of 6-acetyl-2H-1,4-benzoxazine-3(4H)-one used in Comparative Example 3 is as follows: The CAS number is 26518-71-8.

[0055] The structural formula of 4,4-dimethyl-1,3-oxazin-6-one used in Comparative Example 4 is as follows: Purchased from Jiangsu Huasheng Lithium Battery Materials Co., Ltd.

[0056] I. Preparation of Electrolyte Example 1 Example 1: The electrolyte comprises a lithium salt, an organic solvent, an oxazinone additive, and auxiliary additives. The lithium salt is LiPF6, and the concentration of LiPF6 in the electrolyte is 1.0 mol / L. The organic solvent is a mixture of EC, EMC, and DMC in a 1:1:1 volume ratio. The oxazinone additive is VDMO, whose structural formula is [insert structural formula here]. The electrolyte contains 0.2% VDMO by mass and 1.0% FEC by mass as an auxiliary additive.

[0057] Example 1: The preparation method of the electrolyte includes: Solvent pretreatment: The organic solvent (water content <0.1ppm) was dried with 4Å molecular sieve for 72h in an argon atmosphere glove box, and the water content of the solvent was controlled to be ≤20ppm. Lithium salt dissolution: LiPF6 is slowly added to the dried mixed solvent and stirred until completely dissolved to obtain the basic electrolyte; Add oxazinone additives: Add VDMO to the basic electrolyte and stir until completely dissolved; Add auxiliary additive: Add auxiliary additive FEC and stir well; Filtration and impurity removal: The electrolyte is filtered through a 0.22μm organic filter membrane to remove impurities, and the final electrolyte is obtained and sealed and stored in a glove box.

[0058] Examples 2-5 The electrolyte was prepared according to the method of Example 1. The only difference between Examples 2-5 and Example 1 is that the electrolyte formulation is different from that of Example 1. The formulations of Examples 2-5 are shown in Table 1.

[0059] Table 1 Electrolyte Formulation Table for Examples 1-5

[0060] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that the electrolyte does not contain VDMO.

[0061] Comparative Example 2 The only difference between Comparative Example 2 and Example 3 is that the additives in the electrolyte are different, and the same mass fraction of VC (ethylene carbonate) is used to replace VDMO in the electrolyte.

[0062] Comparative Example 3 The only difference between Comparative Example 3 and Example 2 is that the additives in the electrolyte are different, and 6-acetyl-2H-1,4-benzoxazine-3(4H)-one of the same mass fraction is used to replace VDMO in the electrolyte.

[0063] Comparative Example 4 The only difference between Comparative Example 4 and Example 2 is that the additives in the electrolyte are different, and 4,4-dimethyl-1,3-oxazin-6-one of the same mass fraction is used to replace VDMO in the electrolyte.

[0064] Comparative Example 5 The only difference between Comparative Example 5 and Example 2 is that the additives in the electrolyte are different, and maleimide of the same mass fraction is used instead of VDMO in the electrolyte.

[0065] Comparative Example 6 The only difference between Comparative Example 6 and Example 1 is that the mass fraction of VDMO additive in the electrolyte is 4%.

[0066] The specific formulations of the electrolytes for Comparative Examples 1-6 are shown in Table 2.

[0067] Table 2 Electrolyte Formulation Table for Comparative Examples 1-6

[0068] II. Performance Testing The electrolytes of the examples and comparative examples were used to assemble batteries under the same conditions, and their electrochemical performance was tested under the same conditions, specifically including: Positive electrode preparation: NCM811 positive electrode active material, conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 90:5:5. N-methylpyrrolidone (NMP) was added and stirred into a uniform slurry. The slurry was coated onto an aluminum foil current collector, vacuum dried at 80℃ for 12 hours, and then rolled to a compaction density of 3.2 g / cm³. 3 Thus, a positive electrode sheet is obtained; Negative electrode preparation: Artificial graphite negative electrode active material, conductive carbon black, sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) were mixed in a mass ratio of 95:2:1.5:1.5. Deionized water was added and stirred to form a uniform slurry. This slurry was then coated onto a copper foil current collector, vacuum dried at 80℃ for 12 hours, and rolled to a compaction density of 1.6 g / cm³. 3 This yields the negative electrode sheet; Battery assembly: Using a positive electrode as the cathode, a negative electrode as the anode, and a polypropylene (PP) microporous membrane as the separator, a 2032 coin cell was assembled in a glove box under an argon atmosphere. The electrolyte prepared in the examples or comparative examples was injected, and electrochemical tests were performed after standing for 12 hours.

[0069] Room temperature cycling performance (capacity retention rate after 100 cycles at 25℃ and 1C): After the battery is left to stand at an ambient temperature of 25℃ until the temperature stabilizes, it is charged at 1C constant current and constant voltage to 4.3V, with a cutoff current of 0.05C, and left to stand for 10 min; then it is discharged at 1C constant current to 3.0V, and left to stand for 10 min to complete one charge-discharge cycle; 100 cycles are performed continuously, and the discharge capacity of the first cycle is recorded as the initial capacity. The capacity retention rate of the 100th cycle relative to the initial capacity is calculated.

[0070] High-temperature cycling performance (capacity retention rate after 100 cycles at 45℃): The battery was placed in a 45℃ constant temperature chamber for 2 hours to ensure that the overall battery temperature reached 45℃; it was charged to 4.3V using 1C constant current and constant voltage (cutoff current 0.05C), and then left to stand for 10 minutes; it was discharged to 3.0V using 1C constant current, and left to stand for 10 minutes, thus ending one cycle; it was continuously cycled for 100 cycles, and the discharge capacity of the first cycle was recorded as the initial capacity. The capacity retention rate of the battery after 100 cycles relative to the initial capacity was calculated.

[0071] High-temperature storage performance (capacity retention rate after 14 days of full charge storage at 60℃): The battery was charged to 4.3V at 25℃ using 1C, and the full charge capacity was recorded; then it was placed in a 60℃ constant temperature oven and sealed for 14 days; after being removed and cooled to room temperature, it was discharged at 1C to 3.0V, and the remaining capacity after high-temperature storage was measured. The capacity retention rate was calculated as: (remaining capacity after high-temperature storage / full charge capacity before high-temperature storage) × 100%. Rate performance (3C rate capacity retention): First, complete the charge and discharge at 0.2C, and use the 0.2C discharge capacity as the baseline capacity; then, use constant current discharge at 0.5C, 1C, 2C, and 3C in sequence (use a small current of 0.2C for charging to eliminate interference from charging differences), and record the discharge capacity at each rate; the capacity retention rate at each rate = corresponding rate discharge capacity / 0.2C baseline capacity × 100%, and the 3C rate capacity retention rate is used as the comparison index in Table 3; High-voltage cycle performance (capacity retention rate after 100 cycles at 4.5V high voltage 1C): The battery was stabilized at a constant temperature of 25℃, charged to 4.5V at 1C constant current and constant voltage, cut-off current 0.05C, and left to stand for 10 min; discharged to 3.0V at 1C constant current, and left to stand for 10 min constituted one cycle; after 100 consecutive cycles, the capacity retention rate after 100 high-voltage cycles was calculated based on the discharge capacity of the first cycle. The test results are shown in Table 3 and Figure 3 , Figure 4 , Figure 5 As shown.

[0072] Table 3 Performance Comparison of Examples and Comparative Examples

[0073] Lithium dendrite suppression: The performance of lithium dendrite suppression was tested using a Li / Li symmetric cell. A 2032 coin cell was assembled in an argon glove box, with lithium foil as the electrodes on both sides, a PP separator in the middle, and the electrolyte to be tested injected. After encapsulation, the cells were allowed to stand at 25°C for 12 hours for full impregnation, and then subjected to a test at 1 mA / cm² under constant temperature at 25°C. 2 A constant current deposition and stripping cycle was performed for 100 hours, with voltage data recorded every 10 seconds. The steady-state polarization voltage at the end of the 100-hour cycle was taken as the evaluation index. The test results are shown in Table 4.

[0074] Table 4 Comparison of Examples and Comparative Examples

[0075] As can be seen from Table 4, the polarization voltage of Examples 1-5 is lower than that of Comparative Examples 1-6. The lower the polarization, the more uniform the lithium ion deposition and the better the electrolyte suppresses lithium dendrites. This indicates that the electrolyte of Examples 1-5 is better at suppressing lithium dendrites than that of Comparative Examples 1-6.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0077] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the foregoing claims, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. An electrolyte, characterized in that, The electrolyte includes oxazinone additives, and the general structural formula of the oxazinone additives is as follows: R1 and R2 are independently selected from hydrogen, C1-C4 straight-chain or branched alkyl, cycloalkyl, and alkyl substituted with at least one halogen.

2. The electrolyte according to claim 1, characterized in that, The structural formula of the oxazinone additive is as follows: .

3. The electrolyte according to claim 1, characterized in that, The mass fraction of oxazinone additives in the electrolyte is 0.05% to 3.0%.

4. The electrolyte according to claim 1, characterized in that, The electrolyte also includes lithium salt; The lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide.

5. The electrolyte according to claim 4, characterized in that, The concentration of lithium salt in the electrolyte is 0.8~1.5 mol / L.

6. The electrolyte according to claim 1, characterized in that, The electrolyte also includes an organic solvent; The organic solvent includes at least one of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl propionate, and propyl propionate.

7. The electrolyte according to any one of claims 1-6, characterized in that, The electrolyte also includes auxiliary additives, which include at least one of fluoroethylene carbonate, vinylene carbonate, 1,3-propanesulfonate lactone, and vinyl sulfate.

8. The electrolyte according to claim 7, characterized in that, The mass fraction of the auxiliary additive in the electrolyte is 0.5% to 3.0%.

9. A lithium-ion battery, characterized in that, The lithium-ion battery includes the electrolyte according to any one of claims 1-8.

10. An electrical appliance, characterized in that, The electrical equipment includes the lithium-ion battery as described in claim 9.

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