Non-aqueous electrolyte, lithium battery and electric equipment

Abstract

The invention relates to the field of lithium ion batteries, and discloses a non-aqueous electrolyte, a lithium battery and electric equipment. Three additives including the N-sulfonyl substituted 2-imidazolidinone derivative, the sulfur-containing compound and the trimethyl phosphite are added into the non-aqueous electrolyte, the three additives generate a synergistic effect, volume expansion of a silicon-based negative electrode is inhibited, excessive decomposition of the electrolyte is avoided, consumption of active lithium and excessive generation of an SEI film are slowed down, and the service life of the non-aqueous electrolyte is prolonged. Therefore, the comprehensive performance of the silicon-based negative electrode lithium ion battery is improved. From the non-aqueous electrolyte formula optimization direction, a series of problems of interface damage and the like caused by volume expansion of the silicon-based negative electrode are improved by a simple, economical and effective method, and the application range of the silicon-based negative electrode lithium battery is widened.

Description

Technical Field

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

[0002] The working principle of a lithium-ion battery is essentially an electrochemical intercalation and deintercalation reaction. Accompanied by redox reactions, lithium ions shuttle back and forth between the positive and negative electrodes, completing the intercalation / deintercalation process; hence, it is also called a rocking chair battery. Lithium-ion batteries are widely used in electronic devices, aerospace, new energy vehicles, and energy storage devices due to their advantages such as high energy density, good cycle performance, and long service life.

[0003] Currently, with the increasing maturity of new energy sources, lithium-ion batteries are playing an increasingly important role, especially high-energy-density batteries, which have become a research hotspot. Silicon, with its ultra-high theoretical energy density, is used in power batteries to improve vehicle range. Silicon is abundant and widely distributed in the Earth's crust, with a maximum theoretical specific capacity of 42000 mAh / g, a potential plateau 0.4V higher than graphite, and no lithium plating, making it one of the most promising anode materials. However, during battery charging and discharging, the silicon electrode material repeatedly contracts and expands during the extraction and insertion of lithium ions, with a volume change rate as high as 300%~400%, leading to particle crushing and shedding, causing anode deactivation. Simultaneously, the repeated volume changes of the silicon electrode during cycling continuously damage its surface solid electrolyte interphase (SEI) film. When the electrolyte comes into contact with the bare electrode, an SEI film is continuously generated, leading to electrolyte consumption, increased interfacial impedance, battery thickness expansion, and ultimately capacity decay. These problems are particularly severe under high-temperature conditions. To overcome a series of problems, such as interface damage caused by the volume expansion of silicon-based anodes, current research focuses primarily on two areas: silicon-based material structure design and electrolytes. Among these, optimizing electrolyte formulations and using additives to regulate the electrode-electrolyte interface is considered a simple and cost-effective method. Therefore, it is essential to develop a non-aqueous electrolyte for silicon-based anodes to address the shortcomings of existing technologies. Summary of the Invention

[0004] In view of this, the purpose of this application is to provide a non-aqueous electrolyte, which can be used in silicon-based anode lithium-ion batteries to effectively alleviate the instability of the SEI film and electrolyte side reactions caused by the volume expansion of the silicon-based anode during cycling, thereby improving the high-temperature cycling performance and storage performance of the battery. Another objective of this application is to provide silicon-based negative electrode lithium-ion batteries and electrical devices based on the aforementioned non-aqueous electrolyte.

[0005] In order to solve the above-mentioned technical problems / achieve the above-mentioned objectives, or at least partially solve the above-mentioned technical problems / achieve the above-mentioned objectives, as a first aspect of this application, a non-aqueous electrolyte is provided, comprising compound A, compound B, trimethyl phosphite, a non-aqueous organic solvent, and an electrolyte lithium salt; The compound A has the structure shown in Formula 1: Formula 1 R1 is selected from hydrogen and C1-C4 alkyl groups; R2 is selected from hydrogen, chloryl group, and C1-C3 alkyl group; R3, R4, R5, and R6 are each independently selected from hydrogen, C1-C4 alkyl groups, C2-C4 alkenyl groups, or halogens. Compound B includes sulfur-containing compounds.

[0006] Optionally, the mass percentage of compound A is 0.1-5%, the mass percentage of compound B is 0.1-4%, and the mass percentage of trimethyl phosphite is 0.05-2%.

[0007] Further optionally, the mass ratio of compound A to compound B is (1~5):(1~3).

[0008] Further, optionally, compound A comprises any one or two of the following compounds: Equation 1-1 Formula 1-2 Further optionally, the sulfur-containing compound includes vinyl sulfate, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, vinyl sulfite, methylene disulfonate, 1,3-propanediol cyclosulfonate, 1,4-propanediol cyclosulfonate, etc. One or more of butyryl lactones.

[0009] Optionally, the non-aqueous organic solvent includes ethylene carbonate, propylene carbonate, diethyl carbonate, methyl ethyl carbonate, dimethyl carbonate, butylene carbonate, methyl acetate, ethyl acetate, propyl acetate, propyl propionate, and γ-ethyl acetate. Butyrolactone, 1,3 Dioxolane, crown ether, 1,1,2,2 Tetrafluoroethyl 2,2,3,3 One or more of tetrafluoropropyl ether, ethylene glycol dimethyl ether, and ethylene glycol diethyl ether.

[0010] Optionally, the electrolyte lithium salt includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium difluorophosphate, lithium methanesulfonate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(oxalate-borate), lithium difluorooxalate-borate, lithium difluorobis(oxalate-borate), lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide.

[0011] As a second aspect of this application, a silicon-based negative electrode lithium battery is provided, comprising a silicon-based negative electrode and the non-aqueous electrolyte described in this application.

[0012] Optionally, the silicon-based anode includes one or more of the following: pure silicon anode, silicon-carbon anode, and silicon-oxygen anode.

[0013] As a third aspect of this application, an electrical device is provided, including the lithium battery described in this application, wherein the lithium battery provides electrical energy to the electrical device or serves as an energy storage unit for the electrical device.

[0014] This application incorporates three additives into a non-aqueous electrolyte: an N-sulfonyl-substituted 2-imidazolium ketone derivative, a sulfur-containing compound, and trimethyl phosphite. These three additives exhibit a synergistic effect, suppressing the volume expansion of the silicon-based anode, preventing excessive electrolyte decomposition, slowing the consumption of active lithium, and reducing the excessive formation of the SEI film, thereby improving the overall performance of the silicon-based anode lithium-ion battery. This application, through optimization of the non-aqueous electrolyte formulation, provides a simple and cost-effective solution to a series of problems, such as interface damage caused by the volume expansion of the silicon-based anode, thus expanding the application scope of silicon-based anode lithium batteries. Detailed Implementation

[0015] This application discloses a non-aqueous electrolyte, a lithium battery, and an electrical device. Those skilled in the art can refer to the content of this document and appropriately modify the process parameters to achieve the desired result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this application. The products, processes, and applications described in this application have been described through preferred embodiments. Those skilled in the art can obviously modify or appropriately change and combine the preparation methods described herein without departing from the content, spirit, and scope of this application to realize and apply the technology of this application. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0016] It should be noted that, in this document, relational terms such as "first" and "second," "step 1" and "step 2," and "(1)" and "(2)" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. Moreover, the embodiments and features described in this application can be combined with each other without conflict.

[0017] Based on the shortcomings of silicon-based negative electrode lithium batteries, the first aspect of this application provides a non-aqueous electrolyte comprising compound A, compound B, trimethyl phosphite, a non-aqueous organic solvent, and an electrolyte lithium salt. Compound A is a type of N-sulfonyl-substituted 2-imidazolium ketone derivative. Compound A is preferentially reduced at the negative electrode to form a Li-rich compound. x In nitrogen-containing SEI films, the high ionic conductivity of nitrogen compounds facilitates rapid diffusion of lithium ions within the SEI film, effectively reducing interfacial polarization resistance. Simultaneously, the highly electronegative nitrogen atoms can combine with HF and trace amounts of water in the system, reducing SEI film corrosion and electrolyte decomposition, alleviating battery gas generation, and improving battery cycle performance.

[0018] The compound A has the general formula shown in Formula 1: Formula 1 R1 is selected from hydrogen and C1-C4 alkyl groups; R2 is selected from hydrogen, chloryl group, and C1-C3 alkyl group; R3, R4, R5, and R6 are each independently selected from hydrogen, C1-C4 alkyl groups, C2-C4 alkenyl groups, or halogens. In some embodiments of this application, the chloroacyl group may be chloroformyl, chloroacetyl, or chloropropionyl; the alkyl group may be a straight-chain alkyl group, such as methyl, ethyl, n-propyl, or n-butyl; or it may be a branched alkyl group with a side chain, such as isopropyl or isobutyl. The alkenyl group may be a straight-chain alkenyl group, such as vinyl, 1-propenyl, 1-butenyl, 2-butenyl, or 3-butenyl; or it may be a branched alkenyl group with a side chain, such as 2-propenyl (allyl), isopropenyl, 1-methyl-2-propenyl, 1-methyl-1-propenyl, 2-methyl-2-propenyl, or 3-methyl-2-propenyl. In other embodiments of this application, R3, R4, R5, and R6 are all selected from hydrogen.

[0019] In other embodiments of this application, compound A comprises any one or two of the following compounds: Equation 1-1 Formula 1-2 Formula 1-1 has the Chinese name 1-methanesulfonyl-2-imidazolidineone and the CAS number 41762-76-9; Formula 1-2 has the Chinese name 1-chloroformyl-3-methanesulfonyl-2-imidazolidineone and the CAS number 41762-76-9.

[0020] In some embodiments of this application, compound B includes sulfur-containing compounds. Since a single additive often cannot simultaneously achieve multiple functions, this application simultaneously adds compounds A and B, both of which have sulfur-containing functional groups. These compounds synergistically form an interwoven network structure on the negative electrode surface, giving the SEI film excellent elasticity and toughness, enabling it to adapt to the expansion and contraction of the negative electrode during cycling, reducing the fragmentation of silicon-based materials, and thus contributing to improved cycle stability of silicon-based lithium-ion batteries. In other embodiments of this application, the sulfur-containing compounds include vinyl sulfate (DTD), 1,3-propanesulfonate lactone (PS), 1,3-propenesulfonate lactone (PES), vinyl sulfite (ES), methylene disulfonate (MMDS), 1,3-propanediol cyclosulfonate (PCS), and 1,4-propanediol cyclosulfonate (PCS). Butyryl lactone (1,4) This application introduces one or more of the following additives (BS): Trimethyl phosphite (TMP), which can undergo an oxidation reaction on the positive electrode surface to form a stable CEI film, inhibiting electrolyte decomposition and reducing the dissolution of transition metals in the positive electrode material. Therefore, the combined additives and multifunctional additives provided in this application produce a synergistic effect, inhibiting the volume expansion of the silicon-based negative electrode, preventing excessive electrolyte decomposition, slowing down the consumption of active lithium and the excessive formation of the SEI film, thereby improving the overall performance of the silicon-based negative electrode lithium-ion battery.

[0021] In some embodiments of this application, the combination of compound A and compound B includes, but is not limited to, any of the following: (1) 1-Methanesulfonyl-2-imidazolidineone (Formula 1-1) and 1,3-propanesulfonate lactone (PS); (2) 1-chloroformyl-3-methanesulfonyl-2-imidazolidineone (Formula 1-2) and 1,3-propanesulfonyl lactone (PS); (3) 1-Methanesulfonyl-2-imidazolidineone (Formula 1-1) and 1,3-propenesulfonyl lactone (PES). (4) 1-chloroformyl-3-methanesulfonyl-2-imidazolidineone (Formula 1-2) and 1,3-propenesulfonyl lactone (PES).

[0022] Controlling the ratio of compound A to compound B can comprehensively improve battery performance and maintain stability. For example, it can optimize interfacial membrane impedance, maintain the elasticity and toughness of the interfacial membrane, and control harmful components such as HF in the electrolyte. Compound A provides high ionic conductivity, which helps lithium ions diffuse rapidly in the SEI film. However, if there is too much compound A, the resulting interfacial film will be too rigid and unable to adapt to the repeated contraction and expansion of silicon particles, leading to cracking and silicon particle pulverization failure. On the other hand, if there is too much compound B, the SEI film will be too thick, resulting in increased lithium ion transport impedance, increased battery internal resistance, and the excessively thick interfacial film will be more prone to cracking and reconstruction during charging and discharging. Based on this, in order to further achieve better overall performance, in some embodiments of this application, the mass ratio of compound A to compound B is preferably (1~5):(1~3), such as 1:3, 1:1, 1:1.5, 5:3, 2:1, 5:1, or any value between the two.

[0023] Furthermore, based on concentration gradient experiments of compounds A, B, and trimethyl phosphite in the electrolyte, feedback from battery performance indicates that these additives provide a more comprehensive improvement in battery performance within a suitable concentration range. Too low a concentration has little effect on performance improvement, while too high a concentration has certain negative impacts on battery performance, such as a decrease in cycle performance and rate performance, and gas expansion at high temperatures. Excessive additive concentration can affect the film-forming components and increase film thickness, leading to increased impedance and gas generation. Therefore, in some embodiments of this application, the mass percentage of compound A is preferably 0.1-5%, for example 0.1%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, or any value between any two; the mass percentage of compound B is preferably 0.1-4%, for example 0.1%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, or any value between any two; the mass percentage of trimethyl phosphite is preferably 0.05-2%, for example 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, or any value between any two.

[0024] In some embodiments of this application, the non-aqueous organic solvent includes ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), butylene carbonate (BC), methyl acetate (MA), ethyl acetate (EA), propyl acetate (EP), propyl propionate (PP), and γ-ray diethyl acetate (GLA). Butyrolactone (GBL), 1,3 Dioxapentane (DOL), crown ether (CE), 1,1,2,2 Tetrafluoroethyl 2,2,3,3 One or more of tetrafluoropropyl ether (D2), ethylene glycol dimethyl ether (DME), and ethylene glycol diethyl ether (ECS). More preferably, one or more of ethylene carbonate (EC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), and ethyl acetate (EA), such as a mixed non-aqueous solvent of EC / DEC / EMC / EA. In other embodiments of this application, the non-aqueous solvent is 60-90% by mass, for example, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or any value between any two.

[0025] In some embodiments of the present application, the electrolyte lithium salt includes at least one or more than two of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO), lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), lithium methyl sulfonate (LiCH3SO3), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium difluoro bis(oxalato)phosphate (LiDFOP), lithium bis(trifluoromethylsulfonyl)imide (LiN(SO2CF3)2), and lithium bis(fluorosulfonyl)imide (LiFSI).

[0026] In some embodiments of the present application, the non-aqueous electrolyte may optionally further include other functional additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performances, such as additives for improving the overcharge performance of the battery, additives for improving the high-temperature or low-temperature performance of the battery, and the like.

[0027] In the second aspect of the present application, a lithium battery with a silicon-based negative electrode is provided, including a silicon-based negative electrode and the non-aqueous electrolyte described in the present application. More specifically, it includes a silicon-based negative electrode, a positive electrode, the non-aqueous electrolyte described in the present application, and a separator.

[0028] In some embodiments of the present application, the active material of the positive electrode is selected from one or more than two of lithium cobalt oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide; the molecular formula of the lithium nickel cobalt manganese oxide is LiNi x Co y Mn z M (1-x- y-z) O2 (0.4 < x < 0.9, x + y + z ≤ 1), and the molecular formula of the lithium nickel cobalt aluminum oxide is LiNi x Co y Al z N (1-x-y-z) O2 (0.4 < x < 0.9, x + y + z ≤ 1), where M is any one of Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, and Ti, and N is any one of Mg, Cu, Zn, Sn, B, Ga, Cr, Sr, V, and Ti. In some other embodiments of the present application, the active material of the positive electrode is LiNi 0.8 Co 0.1 Mn 0.1 O2.

[0029] In some embodiments of the present application, the silicon-based negative electrode includes one or more than two of a pure silicon negative electrode, a silicon-carbon negative electrode, and a silicon-oxygen negative electrode.

[0030] In some embodiments of this application, both the positive electrode and the silicon-based negative electrode are prepared by coating an electrode slurry formed from active material, conductive agent, binder, and solvent onto a current collector, followed by drying, rolling, and die-cutting. The mass ratio of the active material, conductive agent, and binder is 95~99%:0.5~2.5%:0.5~2.5%.

[0031] The conductive agent can be selected from some conventional conductive agents in the art, including but not limited to superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers. The binder can be selected from some conventional binders in the art, including but not limited to polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), and polyvinyl alcohol (PVA). The solvent can be selected from N-methylpyrrolidone (NMP) and water, depending on the material chosen. The current collector can be a metal foil or a composite current collector. For example, copper foil or aluminum foil can be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. Composite current collectors can be formed by forming metallic materials (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer substrates (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0032] In some embodiments of this application, the positive electrode, silicon-based negative electrode, and separator can be fabricated into an electrode assembly by a winding process or a stacking process.

[0033] In some embodiments of this application, the lithium-ion battery may include an outer packaging. This outer packaging can be used to encapsulate the aforementioned electrode components and the non-aqueous electrolyte. In other embodiments of this application, the outer packaging of the lithium-ion battery may be a hard shell, such as a hard plastic shell, aluminum shell, or steel shell. The outer packaging of the lithium-ion battery may also be a soft pack, such as a pouch.

[0034] In a third aspect of this application, an electrical device is provided, including the lithium-ion battery described in this application. The lithium-ion battery provides electrical energy to the electrical device and can also be used as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0035] In the comparative experiments provided in this application, unless otherwise specified, all experimental conditions and materials are kept consistent to ensure comparability. Unless otherwise specified, all experimental materials and reagents used in the examples are commercially available.

[0036] The following provides a further description of a non-aqueous electrolyte, lithium battery, and electrical device provided in this application.

[0037] Example 1: (1) Preparation of non-aqueous electrolyte In an argon-filled glove box (O2 < 1 ppm, H2O < 1 ppm), ethylene carbonate (EC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), and ethyl acetate (EA) were mixed uniformly in a mass ratio of 2:1:6:3. This mixed solvent served as a non-aqueous organic solvent. Additive compounds A and B, and trimethyl phosphite (TMP) were then added. After thorough mixing, lithium hexafluorophosphate was added and mixed uniformly to obtain a silicon-based non-aqueous electrolyte for the negative electrode.

[0038] (2) Preparation of positive electrode LiNi 0.8 Co 0.1 Mn 0.1 O2, binder PVDF and conductive agent SuperP are mixed in a mass ratio of 96%:2.0%:2.0%, with NMP as solvent, to form a lithium-ion battery positive electrode slurry of a certain viscosity. The mixed slurry is then evenly coated on both sides of aluminum foil, and after drying, rolling and die-cutting, a positive electrode sheet is obtained.

[0039] (3) Preparation of negative electrode A lithium-ion battery negative electrode slurry of a certain viscosity is prepared by uniformly dispersing and mixing silicon / carbon composite material, conductive agent SuperP, thickener CMC, and binder SBR in a mass ratio of 95.5%:1.5%:1.4%:1.6% with deionized water as solvent. The slurry is then uniformly coated on both sides of copper foil, and the negative electrode sheet is obtained after drying, rolling and die cutting.

[0040] (4) Preparation of lithium-ion batteries The positive electrode, separator, and negative electrode are stacked to form a square soft-pack battery cell, which is then packaged in a polymer aluminum-plastic film and filled with the silicon-based negative electrode non-aqueous electrolyte prepared above. After formation, capacity testing, and other processes, a lithium-ion battery with a capacity of 3000mAh is produced.

[0041] Example 2: Following the process described in Example 1, non-aqueous electrolytes were prepared according to the specific components listed in Table 1 and assembled into lithium-ion batteries.

[0042] Table 1

[0043] The control compound, Formula 2, has the Chinese name 1-methylpyrrolidine-2,4-dione, CAS number 37772-91-1, and its structural formula is as follows: Formula 2.

[0044] Experimental example: (1) High-temperature cycling performance test of lithium-ion batteries: 1. Place the lithium-ion battery in a 45℃ constant temperature chamber and let it stand for 24 hours to allow the lithium-ion battery to reach a constant temperature; At 2.25℃, charge at a constant current of 1C until the voltage is 4.2V, and then charge at a constant voltage of 4.2V until the current is 0.05C; 3. After resting for 10 minutes, discharge the battery at a constant current of 1C until the voltage reaches 2.5V. Record the first discharge capacity of the battery as C0. This is one charge-discharge cycle.

[0045] 4. Under 45℃ conditions, perform 500 cycles of 1C / 1C charge and discharge, and record the discharge capacity as C1; The capacity retention rate of a lithium-ion battery can be calculated using the following formula: Capacity retention rate after 500 cycles = (C1 / C0) × 100%.

[0046] (2) High-temperature storage performance test of lithium-ion batteries: 1. A lithium-ion battery is charged at a constant current of 0.5C to 4.2V at 25℃, and then charged at a constant voltage until the current reaches 0.05C. The volume of the battery is measured and recorded as V0. 2. After resting for 10 minutes, discharge at a constant current of 0.5C to 2.5V, and record the discharge capacity at this time as C0; 3. Charge the battery at a constant current of 0.5C to 4.2V, and then charge it at a constant voltage until the current reaches 0.05C; 4. Place the battery in a 60℃ constant temperature oven and leave it for 30 days before removing the battery; 5. After the battery is left in an environment of 25℃ for 24 hours, test the battery volume and record it as V1. Discharge it to 2.5V at a constant current of 0.5C in an environment of 25℃, and record the discharge capacity at this time as C1. 6. Charge at a constant current of 0.5C to 4.2V, then charge at a constant voltage to the cutoff current of 0.05C, and finally discharge at a constant current of 0.5C to 2.5V. Record the discharge capacity at this point as C2.

[0047] The capacity retention rate and capacity recovery rate of lithium-ion batteries can be calculated using the following formulas: Capacity retention rate = C1 / C0 × 100%; Capacity recovery rate = C2 / C0 × 100%.

[0048] The expansion rate of a lithium-ion battery can be calculated using the following formula: Expansion rate = (V1 - V0) / V0 × 100%.

[0049] (3) Room temperature cycling test: 1. At 25℃, charge at a constant current of 1C until the voltage is 4.2V, and then charge at a constant voltage of 4.2V until the current is 0.05C; 2. After resting for 10 minutes, discharge the battery at a constant current of 1C until the voltage reaches 2.5V. Record the first discharge capacity of the battery as C0. This is one charge-discharge cycle.

[0050] 3. Under 25℃ conditions, perform 500 cycles of 1C / 1C charging and discharging, and record the discharge capacity as C1; The capacity retention rate of a lithium-ion battery can be calculated using the following formula: Capacity retention rate after 500 cycles = (C1 / C0) × 100%.

[0051] The results are shown in Table 2 below; Table 2

[0052] As shown in Table 2, compared with the control groups 1-5, the addition of compound A, sulfur-containing compound B and trimethyl phosphite (TMP) additives to the non-aqueous electrolyte in experimental groups 1-13 can significantly improve the capacity retention rate after cycling, while also improving the capacity retention rate and recovery rate after high-temperature storage and alleviating battery swelling.

[0053] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A non-aqueous electrolyte, characterized in that, Including compound A, compound B, trimethyl phosphite, non-aqueous organic solvent, and electrolyte lithium salt; The compound A has the structure shown in Formula 1: Formula 1 R1 is selected from hydrogen and C1-C4 alkyl groups; R2 is selected from hydrogen, chloryl group, and C1-C3 alkyl group; R3, R4, R5, and R6 are each independently selected from hydrogen, C1-C4 alkyl groups, C2-C4 alkenyl groups, or halogens. Compound B includes sulfur-containing compounds.

2. The non-aqueous electrolyte according to claim 1, characterized in that, The mass percentage of compound A is 0.1-5%, the mass percentage of compound B is 0.1-4%, and the mass percentage of trimethyl phosphite is 0.05-2%.

3. The non-aqueous electrolyte according to claim 1 or 2, characterized in that, The mass ratio of compound A to compound B is (1~5):(1~3).

4. The non-aqueous electrolyte according to claim 1 or 2, characterized in that, Compound A includes any one or two of the following compounds: Equation 1-1 Equation 1-2.

5. The non-aqueous electrolyte according to claim 1 or 2, characterized in that, The sulfur-containing compounds include vinyl sulfate, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, vinyl sulfite, methylene disulfonate, 1,3-propanediol cyclosulfonate, and 1,4-propanediol cyclosulfonate. One or more of butyryl lactones.

6. The non-aqueous electrolyte according to claim 1, characterized in that, The non-aqueous organic solvents include ethylene carbonate, propylene carbonate, diethyl carbonate, methyl ethyl carbonate, dimethyl carbonate, butylene carbonate, methyl acetate, ethyl acetate, propyl acetate, propyl propionate, and γ-ray diethyl carbonate. Butyrolactone, 1,3 Dioxolane, crown ether, 1,1,2,2 Tetrafluoroethyl 2,2,3,3 One or more of tetrafluoropropyl ether, ethylene glycol dimethyl ether, and ethylene glycol diethyl ether.

7. The non-aqueous electrolyte according to claim 1, characterized in that, The electrolyte lithium salt includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium difluorophosphate, lithium methanesulfonate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(oxalate-borate), lithium difluorooxalate-borate, lithium difluorobis(oxalate-borate), lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide.

8. A silicon-based lithium-ion battery with a negative electrode, characterized in that, It includes a silicon-based anode and the non-aqueous electrolyte as described in any one of claims 1-7.

9. The lithium battery according to claim 8, characterized in that, The silicon-based anode includes one or more of the following: pure silicon anode, silicon-carbon anode, and silicon-oxygen anode.

10. An electrical appliance, characterized in that, Includes the lithium battery of claim 8 or 9, wherein the lithium battery provides electrical energy to the electrical device or serves as an energy storage unit for the electrical device.

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