Non-aqueous electrolyte and lithium ion battery

Abstract

In order to overcome the problems of the existing silicon-based negative electrode battery, the linear carbonate solvent used does not contain fluorine elements, is easy to be reduced to generate gas at high temperature, the film forming additive such as vinylene carbonate is insufficient in stability at high temperature, the high-temperature gas production of the battery is increased, and the high-temperature cycle performance is reduced, the application provides a non-aqueous electrolyte and a lithium ion battery; the non-aqueous electrolyte comprises a non-aqueous organic solvent, an additive and a lithium salt; the additive comprises a compound shown in structural formula 1 and a compound shown in structural formula 2; the non-aqueous organic solvent comprises fluorine-containing substituted carbonate solvents, and the fluorine-containing substituted carbonate solvents comprise fluorine-containing substituted linear carbonate solvents and fluorine-containing substituted cyclic carbonate solvents; wherein R1 and R3 are each independently selected from alkenyl with 2-4 carbon atoms and alkynyl with 2-4 carbon atoms. The non-aqueous electrolyte provided by the application can effectively improve the high-temperature cycle performance and high-temperature storage performance of the battery.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a non-aqueous electrolyte and a lithium-ion battery. Background Technology

[0002] In modern electronic devices, electric vehicles, and energy storage systems, lithium-ion batteries are the mainstream energy storage solution, and their performance and safety are of great concern. With the continuous expansion of application scenarios, the performance requirements for batteries under high-temperature conditions are becoming increasingly stringent. For example, in scenarios such as electric vehicle operation in hot climates and outdoor energy storage equipment operation, batteries need to have good high-temperature performance to ensure their safe and stable operation and lifespan.

[0003] Existing lithium-ion batteries use silicon-based anodes, which exhibit high activity and are more prone to catalyzing solvent reduction at high temperatures. Traditional lithium-ion battery electrolytes mainly consist of organic carbonate solvents, lithium salts, and necessary additives. However, conventional electrolyte systems suffer from the following problems under high-temperature conditions: 1) Commonly used fluorine-free linear carbonate solvents, such as ethylene carbonate (EC) and propylene carbonate (PC), while EC can participate in SEI film formation, are easily over-reduced at high temperatures to generate gases such as CO, exacerbating battery gas production and capacity decay, and increasing the risk of battery thermal runaway. At the same time, the volume expansion of the silicon-based anode will compress the electrolyte channels, increasing concentration polarization at the anode interface and affecting lithium-ion transport; 2) Film-forming additives in traditional electrolytes (such as vinylene carbonate) lack stability at high temperatures, making it difficult to effectively suppress side reactions between the electrode and the electrolyte. This makes the solid electrolyte interphase (SEI) film on the electrode surface unstable at high temperatures, further exacerbating battery capacity loss and reducing the battery's high-temperature cycle performance. Summary of the Invention

[0004] In response to the problems of existing silicon-based anode batteries using fluorine-free linear carbonate solvents that are easily reduced to generate gas at high temperatures, and the insufficient stability of film-forming additives such as vinylene carbonate at high temperatures, resulting in increased gas generation and reduced high-temperature cycle performance, this application provides a non-aqueous electrolyte and a lithium-ion battery.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0006] On one hand, the present invention provides a non-aqueous electrolyte, comprising a non-aqueous organic solvent, an additive, and a lithium salt; the additive comprises compounds shown in structural formula 1 and compounds shown in structural formula 2; the non-aqueous organic solvent comprises fluorinated substituted carbonate solvents, which include fluorinated substituted linear carbonate solvents and fluorinated substituted cyclic carbonate solvents.

[0007]

[0008] R1 and R3 are each independently selected from alkenyl groups with 2 to 4 carbon atoms and alkynyl groups with 2 to 4 carbon atoms.

[0009] Preferably, R1 and R3 are each independently selected from straight-chain alkenyl groups with 2 to 4 carbon atoms, branched alkenyl groups with 2 to 4 carbon atoms, straight-chain alkynyl groups with 2 to 4 carbon atoms, and branched alkynyl groups with 2 to 4 carbon atoms.

[0010] Preferably, the compound shown in structural formula 1 is selected from one or both of diallyl-2,2,2-trifluoroethyl phosphate and diargynyl-2,2,2-trifluoroethyl phosphate.

[0011] Preferably, in the non-aqueous electrolyte, the mass content of the compound shown in structural formula 1 is 1-3%;

[0012] And / or, in the non-aqueous electrolyte, the mass content of the compound shown in structural formula 2 is 1~5%.

[0013] Preferably, in the non-aqueous electrolyte, the mass content of the compound shown in structural formula 1 is 1-2%;

[0014] And / or, in the non-aqueous electrolyte, the mass content of the compound shown in structural formula 2 is 1~3%.

[0015] Preferably, in the non-aqueous electrolyte, the mass ratio of the compound shown in structural formula 1 to the compound shown in structural formula 2 is (0.35~1.5):1;

[0016] And / or, the mass ratio of the compound shown in structural formula 1 to the fluorocarbonate solvent is 0.015 to 0.05.

[0017] Preferably, the fluorinated substituted linear carbonate solvent includes one or more of methyltrifluoroethyl carbonate and bis(2,2,2-trifluoroethyl) carbonate, and the mass content of the fluorinated substituted linear carbonate solvent in the non-aqueous electrolyte is 20-50%.

[0018] The fluorinated substituted cyclic carbonate solvent includes fluoroethylene carbonate, and in the non-aqueous electrolyte, the mass content of the fluorinated substituted cyclic carbonate solvent is 15-30%.

[0019] And / or, the additive further includes auxiliary additives, which include at least one of cyclic sulfate compounds, sulfonyl lactone compounds, cyclic carbonate compounds, phosphate compounds, borate compounds and nitrile compounds; in the non-aqueous electrolyte, the mass content of the auxiliary additive is 0.01~30%.

[0020] On the other hand, this application provides a lithium-ion battery, including a positive electrode, a negative electrode, and the non-aqueous electrolyte described above.

[0021] Preferably, the negative electrode includes a negative electrode material layer, the negative electrode material layer includes a negative electrode active material, and the negative electrode active material includes silicon; the specific capacity of the negative electrode material layer is 800~1500 mAh / g.

[0022] Preferably, the negative electrode active material includes silicon-based materials and carbon materials, wherein the silicon-based materials include one or more of silicon materials, silicon oxides, silicon-carbon composite materials, and silicon alloys;

[0023] The silicon material includes nano-silicon materials;

[0024] The silicon-carbon composite material includes one of the following: a composite material composed of silicon oxide and carbon materials, and a composite material composed of elemental silicon and carbon materials;

[0025] The carbon material is selected from one or more of artificial graphite, natural graphite, composite graphite, graphene, and hard carbon.

[0026] The silicon oxide includes SiO x Compounds, where 0 < x < 2.

[0027] The non-aqueous electrolyte provided in this application has the following effects: The compound shown in structural formula 1, together with fluorinated linear carbonate solvent and fluorinated cyclic carbonate solvent, synergistically generates a composite film containing LiF, Li3PO4, and CC conjugated polymers, improving the mechanical modulus of the SEI film, enabling it to withstand the stress generated by the expansion of the silicon system, and reducing repeated rupture of the film; The compound shown in structural formula 2 contains sulfate groups, which, after reduction at the silicon anode, can combine with components such as Li2CO3 and LiF generated by fluorinated cyclic carbonate solvent to fill the pores of the SEI film, forming an "inorganic-organic" mixed film, improving the ion conductivity and anti-swelling ability of the SEI film; The compounds shown in structural formula 1 and structural formula 2 synergistically allow the polar groups (S=O) in the phosphate ester group (P=O) and sulfate ester group to adsorb Li through dipole interaction. +This forms an "ion conduction channel," reduces concentration polarization, and inhibits lithium dendrite formation. The non-aqueous electrolyte provided in this application improves the electrode interface film from multiple dimensions, including "interface protection, thermal runaway suppression, and ion conduction," through the synergistic effect of the compound shown in structural formula 1 and the compound shown in structural formula 2, the fluorinated substituted linear carbonate solvent, and the fluorinated substituted cyclic carbonate solvent. It constructs a "bi-stable interface film" on the positive and negative electrode surfaces of the silicon-carbon battery: the negative electrode forms an anti-expansion SEI film rich in LiF / phosphate ester, and the positive electrode forms a sulfur oxide-containing anti-dissolution CEI film. At the same time, the fluorinated substituted linear carbonate solvent and the fluorinated substituted cyclic carbonate solvent enhance the thermal stability of the electrolyte.

[0028] The non-aqueous electrolyte provided in this application, when used in batteries, can effectively improve the high-temperature cycle performance and high-temperature storage performance of batteries. Detailed Implementation

[0029] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0030] This invention provides a non-aqueous electrolyte, comprising a non-aqueous organic solvent, an additive, and a lithium salt; the additive comprises compounds shown in structural formula 1 and compounds shown in structural formula 2; the non-aqueous organic solvent comprises fluorinated substituted carbonate solvents, which include fluorinated substituted linear carbonate solvents and fluorinated substituted cyclic carbonate solvents.

[0031]

[0032] R1 and R3 are each independently selected from alkenyl groups with 2 to 4 carbon atoms and alkynyl groups with 2 to 4 carbon atoms.

[0033] Specifically, introducing fluorinated substituted linear carbonate solvents into the electrolyte improves the ion conductivity of the electrolyte, increases the lithium-ion transference number of the electrolyte, and compensates for the increased diffusion resistance caused by the high viscosity of fluorinated substituted cyclic carbonate solvents. The two work synergistically to adjust the composition of the SEI film, increase the LiF / LiOCOCF3 ratio, and form an SEI film with a gradient structure of an outer layer rich in LiF and an inner layer rich in organic esters, thus balancing the mechanical strength and ion permeability of the SEI film.

[0034] The non-aqueous electrolyte provided in this application has the following effects: The compound shown in structural formula 1, together with the fluorinated linear carbonate solvent and the fluorinated cyclic carbonate solvent, synergistically forms a composite film containing LiF, Li3PO4, and CC conjugated polymers at the negative electrode interface, improving the mechanical modulus of the SEI film, enabling it to withstand the stress generated by the expansion of the silicon system, and reducing repeated rupture of the SEI film; The compound shown in structural formula 2 contains sulfate groups, which, after reduction at the silicon negative electrode, can combine with components such as Li2CO3 and LiF generated by the fluorinated cyclic carbonate solvent to fill the pores of the SEI film, forming an "inorganic-organic" mixed film, improving the ion conductivity and anti-swelling ability of the SEI film; The compounds shown in structural formula 1 and structural formula 2 synergistically allow the polar groups (S=O) in the phosphate ester group (P=O) and sulfate ester group at the negative electrode interface to adsorb Li through dipole interaction. + This forms an "ion conduction channel," reduces concentration polarization, and inhibits lithium dendrite formation. The non-aqueous electrolyte provided in this application improves the electrode interface film from multiple dimensions, including "interface protection, thermal runaway suppression, and ion conduction," through the synergistic effect of the compound shown in structural formula 1 and the compound shown in structural formula 2, the fluorinated substituted linear carbonate solvent, and the fluorinated substituted cyclic carbonate solvent. It constructs a "bi-stable interface film" on the positive and negative electrode surfaces of the silicon-carbon battery: the negative electrode forms an anti-expansion SEI film rich in LiF / phosphate ester, and the positive electrode forms a sulfur oxide-containing anti-dissolution CEI film. At the same time, the fluorinated substituted linear carbonate solvent and the fluorinated substituted cyclic carbonate solvent enhance the thermal stability of the electrolyte.

[0035] The non-aqueous electrolyte provided in this application, when used in batteries, can effectively improve the high-temperature cycle performance and high-temperature storage performance of batteries.

[0036] In some embodiments, R1 and R3 are each independently selected from straight-chain alkenyl groups with 2 to 4 carbon atoms, branched alkenyl groups with 2 to 4 carbon atoms, straight-chain alkynyl groups with 2 to 4 carbon atoms, and branched alkynyl groups with 2 to 4 carbon atoms.

[0037] Specifically, alkenyl groups with 2 to 4 carbon atoms include straight-chain alkenyl groups or branched alkenyl groups, such as vinyl, propynyl, isopropynyl, 1-butenyl, 2-butenyl, 2-methyl-1-propenyl, 3-methyl-1-propenyl, etc. Alkynyl groups with 2 to 4 carbon atoms include straight-chain alkynyl groups or branched alkynyl groups, such as ethynyl, propynyl, 1-butynyl, 2-butynyl, 3-methyl-1-propynyl, etc.

[0038] In some embodiments, the compound represented by structural formula 1 is selected from one or both of diallyl-2,2,2-trifluoroethyl phosphate and diargynyl-2,2,2-trifluoroethyl phosphate.

[0039] Specifically, the compound shown in structural formula 1 is selected from the above-mentioned types, which is beneficial for synergistic effects with fluorinated substituted carbonate solvents to improve the mechanical modulus of the SEI film and reduce repeated rupture of the SEI film; and synergistic effects with the compound shown in structural formula 2 to effectively reduce concentration polarization; and effectively improve the high-temperature cycle performance and high-temperature storage performance of the battery.

[0040] In some embodiments, the mass content of the compound represented by structural formula 1 in the non-aqueous electrolyte is 1-3%;

[0041] And / or, in the non-aqueous electrolyte, the mass content of the compound shown in structural formula 2 is 1~5%.

[0042] Specifically, in the non-aqueous electrolyte, the compound shown in structural formula 1 is added. The PO bond in the compound shown in structural formula 1 can form a chemical bond with the hydroxyl groups (-OH) on the silicon surface, improving the adhesion between the SEI film and the electrode. The polarity of the phosphate ester group can promote the adhesion of Li... + Uniform conduction and reduced SEI film interfacial impedance: Trifluoroethyl, through its strong electron-withdrawing effect, can suppress the thermal decomposition of the additive itself, reducing electrolyte side reactions at high temperatures. Simultaneously, fluorine (F) can form a LiF-rich SEI film, enhancing its ionic conductivity and chemical stability. In non-aqueous electrolytes, a mass content of the compound shown in Structural Formula 1 within the range of 1% to 3% is beneficial for the synergistic effect of the compound shown in Structural Formula 1 with the compound shown in Structural Formula 2, fluorinated linear carbonate solvents, and fluorinated cyclic carbonate solvents to form a structurally stable SEI film at the silicon-based anode interface at high temperatures. This effectively suppresses SEI film rupture caused by silicon anode expansion, improves the mechanical modulus of the SEI film, and adsorbs Li through dipole interactions. + The SEI film formed has "ion conduction channels", which reduces concentration polarization and inhibits lithium dendrite formation. When used in batteries, it can improve the high-temperature storage performance and high-temperature cycle performance of batteries, and improve the high-temperature stability of batteries.

[0043] If the mass content of the compound shown in Formula 1 is less than 1%, the resulting SEI film is thin and has low mechanical strength, failing to effectively suppress the SEI film rupture caused by the expansion of the silicon anode. This reduces the battery's high-temperature stability and deteriorates its high-temperature cycle and storage performance. If the mass content of the compound shown in Formula 1 is greater than 3%, the excessive content of this compound results in a thicker SEI film, increasing the lithium-ion conduction distance, increasing the impedance of the SIE film, increasing polarization, and reducing the battery's high-temperature cycle and storage performance.

[0044] Specifically, in non-aqueous electrolytes, the mass content of the compound shown in structural formula 1 can be 1%, 1.2%, 1.3%, 1.5%, 1.6%, 1.8%, 1.9%, 2.0%, 2.2%, 2.4%, 2.5%, 2.8%, 3.0%, etc., as long as the mass content of the compound shown in structural formula 1 is within the range of 1% to 3%.

[0045] In some embodiments, the mass content of the compound represented by structural formula 2 in the non-aqueous electrolyte is 1-5%.

[0046] Specifically, in the non-aqueous electrolyte, the compound shown in structural formula 2 is added. This compound contains sulfate groups. After reduction at the silicon anode, it can combine with components such as Li₂CO₃ and LiF generated from fluorine-substituted cyclic carbonate solvents to fill the pores of the SEI membrane, forming an "inorganic-organic" mixed membrane. This improves the ion conductivity and anti-swelling ability of the SEI membrane. The compounds shown in structural formulas 1 and 2 work synergistically; the polar groups (S=O) in the phosphate ester group (P=O) and sulfate ester group can adsorb Li through dipole interactions. + This forms an "ion conduction channel," reduces concentration polarization, and inhibits the formation of lithium dendrites.

[0047] The compound shown in structural formula 2, with a mass content ranging from 1% to 5%, works synergistically with the compound shown in structural formula 1, the fluorinated linear carbonate solvent, and the fluorinated cyclic carbonate solvent to form a LiF / phosphate-rich, anti-expansion SEI film at the negative electrode. This effectively inhibits the rupture of the SEI film caused by the expansion of the silicon negative electrode and adsorbs Li through dipole interaction. + The SEI film formed has an "ion conduction channel", which reduces concentration polarization and inhibits the formation of lithium dendrites; the positive electrode forms a sulfur oxide-containing anti-dissolution CEI film; when used in batteries, it can improve the high-temperature storage performance and high-temperature cycle performance of batteries, and improve the high-temperature stability of batteries.

[0048] If the mass content of the compound shown in Formula 2 is less than 1%, the resulting SEI film is thin and has low mechanical strength, failing to effectively suppress the rupture of the SEI film caused by the expansion of the silicon anode. Simultaneously, it affects the formation of the CEI film at the cathode, reducing the battery's high-temperature stability and deteriorating its high-temperature cycle and storage performance. If the mass content of the compound shown in Formula 2 is greater than 5%, the excessive content results in a thicker SEI film, increasing the lithium-ion conduction distance, increasing the impedance of the SIE film, increasing polarization, and reducing the battery's high-temperature cycle and storage performance. Simultaneously, the increased thickness of the CEI film formed at the cathode interface increases battery impedance, further reducing the battery's high-temperature cycle and storage performance.

[0049] Specifically, in non-aqueous electrolytes, the mass content of the compound shown in structural formula 2 can be 1%, 1.2%, 1.3%, 1.5%, 1.6%, 1.8%, 1.9%, 2.0%, 2.2%, 2.4%, 2.5%, 2.8%, 3.0%, 3.2%, 3.5%, 3.8%, 4.0%, 4.3%, 4.5%, 4.7%, 5.0%, etc., as long as the mass content of the compound shown in structural formula 1 is within the range of 1% to 3%.

[0050] In some preferred embodiments, the mass content of the compound represented by structural formula 2 in the non-aqueous electrolyte is 1% to 3%.

[0051] Specifically, in the non-aqueous electrolyte, the compound shown in structural formula 2 has a mass content in the range of 1% to 3%. In combination with the compound shown in structural formula 1, the fluorinated linear carbonate solvent, and the fluorinated cyclic carbonate solvent, the resulting SEI film and CEI film have moderate thickness and low concentration polarization. This effectively suppresses the SIE film rupture caused by the expansion of the silicon-based negative electrode. The resulting SEI film has good high-temperature stability, and the battery has higher high-temperature cycle capacity retention and better high-temperature storage performance.

[0052] In some preferred embodiments, the mass content of the compound represented by structural formula 1 in the non-aqueous electrolyte is 1-2%.

[0053] Specifically, in the non-aqueous electrolyte, the mass content of the compound shown in structural formula 1 is in the range of 1% to 2%. Together with the compound shown in structural formula 2, the fluorinated linear carbonate solvent, and the fluorinated cyclic carbonate solvent, the SEI film formed at the silicon-based anode interface has a moderate thickness. The lithium ions adsorbed through the dipole effect form short ion conduction channels in the SIE film with low concentration polarization. At the same time, it can effectively suppress the SIE film rupture caused by the expansion of the silicon-based anode. The formed SEI film has good high-temperature stability, and the battery has a higher high-temperature cycle capacity retention rate and better high-temperature storage performance.

[0054] In some embodiments, in the non-aqueous electrolyte, the mass ratio of the compound shown in structural formula 1 to the compound shown in structural formula 2 is (0.35~1.5):1;

[0055] And / or, the mass ratio of the compound shown in structural formula 1 to the fluorinated substituted carbonate solvent is 0.015 to 0.05.

[0056] Specifically, the mass ratio of the compound shown in structural formula 1 to the compound shown in structural formula 2 is in the range of (0.35~1.5):1. The compounds shown in structural formula 1 and structural formula 2 work synergistically, and the polar groups (S=O) in the phosphate ester group (P=O) and sulfate ester group can adsorb Li through dipole interaction. +This forms an "ion conduction channel," which reduces concentration polarization at the positive and negative electrode interfaces, effectively suppressing lithium dendrite formation and improving the battery's high-temperature cycle performance.

[0057] Specifically, the mass ratio of the compound shown in structural formula 1 to the fluorinated substituted carbonate solvent is in the range of 0.015~0.05. The added compound shown in structural formula 1, together with the fluorinated substituted linear carbonate solvent and the fluorinated substituted cyclic carbonate solvent, synergistically generates a composite film containing LiF, Li3PO4, and CC conjugated polymers. The SEI film has a higher mechanical modulus and a greater ability to withstand the stress generated by the expansion of the silicon system, further reducing repeated rupture of the film and improving the thermal stability of the electrolyte.

[0058] In some embodiments, the fluorinated substituted linear carbonate solvent includes one or more of methyltrifluoroethyl carbonate and bis(2,2,2-trifluoroethyl) carbonate, and the mass content of the fluorinated substituted linear carbonate solvent in the non-aqueous electrolyte is 20-50%.

[0059] The fluorinated substituted cyclic carbonate solvent includes fluoroethylene carbonate, and the mass content of the fluorinated substituted cyclic carbonate solvent in the non-aqueous electrolyte is 15-30%.

[0060] Specifically, in the non-aqueous electrolyte, the mass content of fluorinated substituted linear carbonate solvents ranges from 20% to 50%, and the mass content of fluorinated substituted cyclic carbonate solvents ranges from 15% to 30%. The addition of fluorinated substituted linear carbonate solvents improves the ionic conductivity of the electrolyte, increases the lithium-ion transference number of the electrolyte, and compensates for the increased diffusion resistance caused by the high viscosity of fluorinated substituted cyclic carbonate solvents. This is beneficial to the synergistic effect of the compounds shown in structural formula 1 and structural formula 2 with the fluorinated substituted linear carbonate solvents and fluorinated substituted cyclic carbonate solvents, further improving the high-temperature cycle performance and high-temperature storage performance of the battery.

[0061] In non-aqueous electrolytes, the mass content of fluorinated substituted linear carbonate solvents can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc.; the mass content of fluorinated substituted cyclic carbonate solvents can be 15%, 17%, 20%, 22%, 25%, 27%, 30%, etc.

[0062] In some preferred embodiments, the fluorinated substituted linear carbonate solvent has a mass content of 20-40% in the non-aqueous electrolyte.

[0063] Specifically, adding fluorinated substituted linear carbonate solvents in the non-aqueous electrolyte at a mass content of 20-40% helps to enhance the synergistic effect of fluorinated substituted linear carbonate solvents, fluorinated substituted cyclic carbonate solvents, and the compound shown in structural formula 1, thereby improving the mechanical strength of the SEI film and effectively suppressing the SEI film rupture caused by the expansion of the silicon-based anode.

[0064] In some embodiments, the non-aqueous organic solvent further includes at least one of carboxylic acid ester solvents, sulfone solvents, ether solvents, and nitrile solvents.

[0065] In some embodiments, the ether solvent includes cyclic ethers or chain ethers, preferably chain ethers with 3 to 10 carbon atoms and cyclic ethers with 3 to 6 carbon atoms. The cyclic ether may be, but is not limited to, at least one of 1,3-dioxolane (DOL), 1,4-dioxolane (DX), crown ethers, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH3-THF), and 2-trifluoromethyltetrahydrofuran (2-CF3-THF). The chain ether may be, but is not limited to, at least one of dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether, 1,3-dioxolane, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether. Because chain ethers have high solvation ability with lithium ions and can improve ion dissociation, dimethoxymethane, diethoxymethane, and ethoxymethoxymethane, which have low viscosity and can impart high ionic conductivity, are particularly preferred. One ether compound can be used alone, or two or more can be used in any combination and ratio. There are no particular restrictions on the amount of ether compound added; it is arbitrary as long as it does not significantly impair the lithium-ion battery effect of the present invention. Typically, the volume ratio is 1% or more, preferably 2% or more, and more preferably 3% or more, when the non-aqueous solvent volume ratio is 100%. Furthermore, the volume ratio is typically 30% or less, preferably 25% or less, and more preferably 20% or less. When two or more ether compounds are used in combination, the total amount of ether compounds should meet the above-mentioned range. When the amount of ether compound added is within the above-mentioned preferred range, it is easy to ensure the improved ionic conductivity effect resulting from the increased lithium-ion dissociation degree and reduced viscosity of the chain ether. In addition, when the negative electrode active material is a carbon material, the phenomenon of co-intercalation between chain ethers and lithium ions can be suppressed, thus enabling the input-output characteristics and charge-discharge rate characteristics to reach an appropriate range.

[0066] In some embodiments, the nitrile solvent may specifically include, but is not limited to, at least one of acetonitrile and malononitrile.

[0067] In some embodiments, the organic solvent further includes unfluorinated carbonate solvents, which include unfluorinated cyclic carbonate solvents and unfluorinated linear carbonate solvents. Unfluorinated cyclic carbonate solvents further include at least one of vinylene carbonate, ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (GBL), butylene carbonate (BC), and butene carbonate.

[0068] In some embodiments, the unfluorinated linear carbonate solvents also include at least one of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and dipropyl carbonate (DPC).

[0069] There are no particular restrictions on the content of the unfluorinated cyclic carbonate solvent, and it can be arbitrary within a range that does not significantly impair the performance of the lithium-ion battery of this invention. However, when using a single solvent, its lower limit relative to the total volume of the non-aqueous electrolyte is typically 3% or more, preferably 5% or more. By setting this range, a decrease in conductivity due to a decrease in the dielectric constant of the non-aqueous electrolyte can be avoided, making it easier to achieve good high-current discharge characteristics, stability relative to the negative electrode, and cycle characteristics of the non-aqueous electrolyte battery. Furthermore, the upper limit is typically 90% or less, preferably 85% or less, and more preferably 80% or less. By setting this range, the oxidation / reduction resistance of the non-aqueous electrolyte can be improved, thereby contributing to improved stability during high-temperature storage.

[0070] The content of unfluorinated linear carbonate solvents is not particularly limited, but relative to the total amount of solvent in the non-aqueous electrolyte, it is typically 15% or more by volume, preferably 20% or more, and more preferably 25% or more. Furthermore, it is typically 90% or less by volume, preferably 85% or less, and more preferably 80% or less. By keeping the content of the linear carbonate solvent within the above range, it is easy to achieve an appropriate viscosity for the non-aqueous electrolyte, suppressing the decrease in ionic conductivity, and thus helping to achieve a good range of output characteristics for the non-aqueous electrolyte battery. When using two or more linear carbonate solvents in combination, it is sufficient to ensure that the total amount of the linear carbonate solvent meets the above range.

[0071] In some embodiments, the number of fluorine atoms in the fluorinated substituted linear carbonate solvent is not particularly limited as long as it is 1 or more, but is generally 6 or less, preferably 4 or less. When the fluorinated substituted linear carbonate solvent has multiple fluorine atoms, these fluorine atoms may be bonded to the same carbon atom or to different carbon atom groups. Other fluorinated substituted linear carbonate solvents include dimethyl fluoride derivatives, methyl ethyl fluoride derivatives, and diethyl fluoride derivatives.

[0072] Carboxylic acid ester solvents include cyclic carboxylic acid esters and / or chain carbonates. Examples of cyclic carboxylic acid esters include at least one of γ-butyrolactone, γ-valerolactone, and δ-valerolactone. Examples of chain carbonates include at least one of methyl formate, methyl acetate (MA), ethyl acetate (EA), propyl acetate (EP), butyl acetate, propyl propionate (PP), butyl propionate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, methyl trimethylacetate, and ethyl trimethylacetate.

[0073] In some embodiments, the sulfone solvent includes cyclic sulfones and chain sulfones. Preferably, in the case of cyclic sulfones, it is typically a compound with 3 to 6 carbon atoms, more preferably 3 to 5 carbon atoms; in the case of chain sulfones, it is typically a compound with 2 to 6 carbon atoms, more preferably 2 to 5 carbon atoms. There are no particular limitations on the amount of sulfone solvent added, and it is arbitrary within a range that does not significantly impair the performance of the lithium-ion battery of the present invention. Relative to the total amount of solvent in the non-aqueous electrolyte, it is typically 0.3% or more by volume, preferably 0.5% or more by volume, more preferably 1% or more by volume. Furthermore, it is typically 40% or less by volume, preferably 35% or less by volume, more preferably 30% or less by volume. When using two or more sulfone solvents in combination, the total amount of sulfone solvent should satisfy the above range. When the amount of sulfone solvent added is within the above range, a non-aqueous electrolyte with excellent high-temperature storage stability is tended to be obtained.

[0074] In a preferred embodiment, the solvent is a mixture of cyclic carbonate solvents and linear carbonate solvents.

[0075] In some embodiments, the non-aqueous electrolyte further includes auxiliary additives, which include at least one of cyclic sulfate compounds, sulfonyl lactone compounds, cyclic carbonate compounds, phosphate compounds, borate compounds, and nitrile compounds;

[0076] In the non-aqueous electrolyte, the mass content of the auxiliary additive is 0.01~30%.

[0077] In some embodiments, the cyclic sulfate compounds include at least one of vinyl sulfate, propylene sulfate, and methyl vinyl sulfate;

[0078] The sulfonyl lactone compounds include at least one of 1,3-propanesulfonyl lactone, 1,4-butanesulfonyl lactone, 1,3-propenesulfonyl lactone, and methylene disulfonate.

[0079] The cyclic carbonate compound is selected from at least one of vinylene carbonate (VC), ethylene ethylene carbonate, fluoroethylene carbonate, or the compound shown in structural formula 4:

[0080]

[0081] Structural Formula 4

[0082] In structural formula 4, R 21 R 22 R 23 R 24 R 25 R 26 Each is independently selected from one of the following: hydrogen atom, halogen atom, or C1-C5 group;

[0083] The phosphate ester compound is selected from tris(trimethylsilane) phosphites;

[0084] The borate esters are selected from tri(triethylsilane) borate esters.

[0085] The nitrile compounds include at least one of butadionitrile, glutaronitrile, ethylene glycol bis(propionitrile) ether, hexanetrionitrile, adiponitrile, heptacyanide, octadionitrile, nonadionitrile, and sebaconitol.

[0086] In other embodiments, the additive may also include other additives that can improve battery performance: for example, additives that improve battery safety performance, such as flame retardant additives like fluorophosphates, or overcharge prevention additives like tert-amylbenzene and tert-butylbenzene.

[0087] It should be noted that, unless otherwise specified, the amount of any one of the optional substances in the additives in the non-aqueous electrolyte is generally less than 10%, preferably 0.1-5%, and more preferably 0.1% to 2%. Specifically, the amount of any one of the optional substances in the additives can be 0.05%, 0.08%, 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 7.8%, 8%, 8.5%, 9%, 9.5%, or 10%.

[0088] In some embodiments, the lithium salt in the non-aqueous electrolyte includes LiPF6, LiBF4, LiAsF6, LiClO4, LiBOB, LiDFOB, LiFSI, LiTFSI, LiPO2F2, LiCH3SO3, LiSbF6, LiCF3SO3, LiC(SO2CF3)3, LiN(SO2C2F5)2, LiCl, LiBr, LiI, and LiB. 10 Cl 10At least one of the following: LiAlCl4, lithium chloroborane, lithium difluorodioxane phosphate, lithium lower aliphatic carboxylic acids having four or fewer carbon atoms, lithium tetraphenylborate, and lithium imino.

[0089] In the non-aqueous electrolyte, the molar concentration of the lithium salt is 0.9~1.5 mol.

[0090] Specifically, the lithium salt is selected from the above-mentioned types, and the molar concentration of the lithium salt is 0.9~1.5 mol. The lithium salt is used to provide lithium ions and improve the ionic conductivity of the electrolyte. The ionized lithium ions, together with the compound shown in structural formula 1, the compound shown in structural formula 2, the fluorinated substituted linear carbonate solvent, and the fluorinated substituted cyclic carbonate solvent, participate in the formation of the SEI film and improve the electrical performance of the battery.

[0091] On the other hand, this application provides a lithium-ion battery, including a positive electrode, a negative electrode, and the non-aqueous electrolyte described above.

[0092] The lithium-ion battery provided in this application uses the aforementioned non-aqueous electrolyte. Through the synergistic effect of the compound shown in structural formula 1 and the compound shown in structural formula 2, the fluorinated substituted linear carbonate solvent, and the fluorinated substituted cyclic carbonate solvent, the electrode interface film is improved from multiple dimensions of "interface protection, thermal runaway suppression, and ion conduction". A "bi-stable interface film" is constructed on the positive and negative electrode surfaces of the silicon-carbon battery: the negative electrode forms an anti-expansion SEI film rich in LiF / phosphate ester, which effectively suppresses the repeated rupture of the SEI film caused by the expansion of the silicon-based negative electrode; the positive electrode forms a sulfur oxide-containing anti-dissolution CEI film. At the same time, the fluorinated substituted linear carbonate solvent and the fluorinated substituted cyclic carbonate solvent improve the thermal stability of the electrolyte; this is beneficial to improving the high-temperature cycle performance and high-temperature storage performance of the battery.

[0093] In some embodiments, the negative electrode includes a negative electrode material layer, the negative electrode material layer includes a negative electrode active material, the negative electrode active material contains silicon, and the specific capacity of the negative electrode material layer is 800~1500 mAh / g.

[0094] Specifically, the lithium-ion battery provided in this application contains silicon as the negative electrode active material, which has a high specific capacity. The higher the silicon content, the higher the specific capacity in the negative electrode material layer. At the same time, due to the volume expansion of silicon, the battery's electrical performance is affected. The specific capacity in the negative electrode material layer is limited to the range of 800~1500 mAh / g, resulting in a battery with a high specific capacity. Furthermore, using the non-aqueous electrolyte of this application, a "dual-stable interface film" is constructed on the positive and negative electrode surfaces of the silicon-carbon battery: a LiF / phosphate ester-rich anti-expansion SEI film is formed on the negative electrode, and a sulfur oxide-containing anti-dissolution CEI film is formed on the positive electrode. The formed SEI film has a high mechanical modulus, effectively suppressing the expansion of the silicon-based negative electrode. The SEI film has good stability at high temperatures, effectively improving the battery's electrical performance.

[0095] In some embodiments, the negative electrode active material includes silicon-based materials and carbon materials, wherein the silicon-based materials include one or more of silicon materials, silicon oxides, silicon-carbon composite materials, and silicon alloys;

[0096] The silicon material includes nano-silicon materials;

[0097] The silicon-carbon composite material includes one of the following: a composite material composed of silicon oxide and carbon materials, and a composite material composed of elemental silicon and carbon materials;

[0098] The carbon material is selected from one or more of artificial graphite, natural graphite, composite graphite, graphene, and hard carbon.

[0099] The silicon oxide includes SiO x Compounds, where 0 < x < 2

[0100] Specifically, silicon materials are elemental silicon materials, including nano-silicon materials, which include amorphous silicon and vapor-deposited silicon-carbon.

[0101] Further preferably, the carbon material is selected from artificial graphite.

[0102] In some preferred embodiments, the silicon-carbon composite material comprises a composite material consisting of silicon oxide and carbon materials.

[0103] Furthermore, composite materials composed of elemental silicon and carbon materials include composites of nano-silicon materials deposited with hard carbon as a framework and artificial graphite.

[0104] In some embodiments, the positive electrode includes a positive electrode material layer, which is obtained by blending a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder.

[0105] In some embodiments, the positive electrode active material includes at least one of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, and ternary materials.

[0106] Furthermore, positive electrode active materials include LiNi x Co y Mn z L (1-x-y-z) O2, LiCo x＇ L (1-x´) O2, LiNi x＇＇ L' y＇ Mn (2-x＇＇-y＇) O4, Li z＇At least one of MPO4, where L is at least one of Al, Sr, Mg, Ti, Ca, Zr, Zn, Si or Fe, 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1, 0 < x + y + z ≤ 1, 0 < x' ≤ 1, 0.3 ≤ x'' ≤ 0.6, 0.01 ≤ y' ≤ 0.2, L' is at least one of Co, Al, Sr, Mg, Ti, Ca, Zr, Zn, Si, Fe; 0.5 ≤ z' ≤ 1, and M is at least one of Fe, Mn, Co.

[0107] The positive electrode conductive agent includes at least one of conductive carbon black, conductive carbon spheres, conductive graphite, SP, conductive carbon fibers, carbon nanotubes, graphene or reduced graphene oxide. Preferred are carbon nanotubes, SP, and conductive graphite.

[0108] The positive electrode binder includes at least one of polyvinylidene fluoride, copolymers of vinylidene fluoride, polytetrafluoroethylene, copolymers of vinylidene fluoride - hexafluoropropylene, copolymers of tetrafluoroethylene - hexafluoropropylene, copolymers of tetrafluoroethylene - perfluoroalkyl vinyl ether, copolymers of ethylene - tetrafluoroethylene, copolymers of vinylidene fluoride - tetrafluoroethylene, copolymers of vinylidene fluoride - trifluoroethylene, copolymers of vinylidene fluoride - trichloroethylene, copolymers of vinylidene fluoride - fluoroethylene, copolymers of vinylidene fluoride - hexafluoropropylene - tetrafluoroethylene, thermoplastic polyimides, thermoplastic resins such as polyethylene and polypropylene; acrylic resins; sodium carboxymethyl cellulose; polyvinyl butyral; ethylene - vinyl acetate copolymer; polyvinyl alcohol; and styrene - butadiene rubber.

[0109] In some embodiments, the positive electrode further includes a positive electrode current collector, and the positive electrode material layer is formed on the surface of the positive electrode current collector.

[0110] The positive electrode current collector is selected from metal materials that can conduct electrons. Preferably, the positive electrode current collector includes at least one of Al, Ni, tin, copper, and stainless steel. In a more preferred embodiment, the positive electrode current collector is selected from aluminum foil.

[0111] In some embodiments, the negative electrode material layer further includes a negative electrode binder and a negative electrode conductive agent, and the negative electrode active material, the negative electrode binder, and the negative electrode conductive agent are blended to obtain the negative electrode material layer.

[0112] The selectable ranges of the negative electrode binder and the negative electrode conductive agent are the same as those of the positive electrode binder and the positive electrode conductive agent respectively, and will not be elaborated here.

[0113] In some embodiments, the negative electrode sheet further includes a negative electrode current collector, and the negative electrode material layer is formed on the surface of the negative electrode current collector.

[0114] The negative electrode current collector is selected from a metallic material that can conduct electrons. Preferably, the negative electrode current collector includes at least one of Al, Ni, tin, copper, and stainless steel. In a more preferred embodiment, the negative electrode current collector is selected from copper foil.

[0115] In some embodiments, the diaphragm includes a substrate layer and a surface coating disposed on at least one side of the substrate layer. The substrate layer includes, but is not limited to, single-layer PP (polypropylene), single-layer PE (polyethylene), double-layer PP / PE, double-layer PP / PP, and triple-layer PP / PE / PP.

[0116] It should be noted that lithium-ion batteries include lithium-ion batteries.

[0117] The present invention will be further illustrated by the following examples.

[0118] Example 1

[0119] This embodiment is used to illustrate a non-aqueous electrolyte and lithium-ion battery disclosed in this invention.

[0120] 1) Preparation of positive electrode sheet

[0121] High-nickel ternary cathode active material NCM811, conductive carbon black, and binder polyvinylidene fluoride were mixed in a mass ratio of 97:1.5:1.5 and dispersed in N-methyl-2-pyrrolidone to obtain a cathode slurry. The cathode slurry was uniformly coated on both sides of an aluminum foil, and after drying, rolling, and vacuum drying, aluminum leads were welded on using an ultrasonic welder to obtain the cathode sheet. The thickness of the cathode sheet was between 120-150 μm. The compaction density of the cathode material was controlled to be 3.45 g / cm³ by the areal density and rolling thickness of the cathode material. 3 ;

[0122] 2) Preparation of negative electrode sheet

[0123] A negative electrode active material (theoretical specific capacity of 1200 mAh / g), conductive carbon black, binder polyacrylic acid, and carboxymethyl cellulose were mixed in a mass ratio of 94.2:1.2:3.0:1.5 and dispersed in deionized water to obtain a negative electrode slurry. The negative electrode slurry was coated on both sides of a copper foil, and after drying, rolling, and vacuum drying, nickel leads were soldered on using an ultrasonic welding machine to obtain a negative electrode sheet. The thickness of the negative electrode sheet was between 120-150 μm. The compaction density of the negative electrode material was controlled to be 1.65 g / cm³ by the areal density and rolling thickness of the negative electrode material. 3 The negative electrode active material is a mixture of silicon-carbon composite material and graphite, which is obtained through purchase.

[0124] 3) Preparation of electrolyte

[0125] The electrolyte preparation steps are as follows: An organic solvent is obtained by mixing FEC:EC:FEMC:EMC in a mass ratio of 20:10:30:50. LiPF6, 1.5 wt% of the compound shown in Structural Formula 1, and 2 wt% of the compound shown in Structural Formula 2 are added to the organic solvent. The compound shown in Structural Formula 1 added in Example 1 is diallyl-2,2,2-trifluoroethyl phosphate. FEC is fluoroethylene carbonate, EMC is methyl ethyl carbonate, and FEMC is methyl trifluoroethyl carbonate. The mass content of FEC in the electrolyte is 15%, and the mass content of FEMC in the electrolyte is 22.5%. The molar concentration of lithium salt LiPF6 is 1 mol / L, and the mass content of LiPF6 in the tested electrolyte is 14%.

[0126] The specific contents of the organic solvent FEMC, the organic solvent FEC, the compound shown in structural formula 1, the compound shown in structural formula 2, the types of auxiliary additives and their mass contents in the electrolyte, and the mass ratio of the compound shown in structural formula 1 to the compound shown in structural formula 2 are shown in Table 1.

[0127] Table 1 shows the calculation of the mass content of fluorinated substituted linear carbonate solvent and fluorinated substituted cyclic carbonate solvent in the electrolyte. The calculation method is as follows: The mass content of organic solvent in the electrolyte is calculated as 100% - 14% - 1.5% - 2% = 82.5%. The mass content of fluorinated substituted linear carbonate solvent FEMC in the electrolyte is calculated as 30 / (20+10+30+50)*82.5% = 22.5%. The corresponding mass content of FEC is calculated as 20 / (20+10+30+50)*82.5% = 15%.

[0128] The diaphragm is a three-layer membrane composed of polypropylene, polyethylene, and polypropylene, with a thickness of 20μm.

[0129] 4) Battery assembly

[0130] The battery assembly steps are as follows: a three-layer separator with a thickness of 20μm is placed between the positive electrode and the negative electrode. Then, the sandwich structure composed of the positive electrode, the negative electrode and the separator is wound up. The wound body is flattened and placed in an aluminum-plastic shell. After welding the tabs, the aluminum-plastic shell is sealed to obtain the cell to be injected with electrolyte. The electrolyte prepared above is cut and injected into the cell. After standing for 1 hour, it is sealed. After sealing, the battery is aged at 45°C for 48 hours.

[0131] Then, perform the first charge routine formation as follows: 0.05C constant current charging for 3 hours, 0.1C constant current charging for 2 hours, 0.2C constant current charging for 2 hours, rest for 1 hour, age at 45℃ for 48 hours, and then further charge at 0.2C constant current to 4.35V, and discharge at 0.2C constant current to 2.75V.

[0132] Examples 2-27 and Comparative Examples 1-11

[0133] Examples 2-27 and Comparative Examples 1-11 illustrate the non-aqueous electrolyte and lithium-ion battery disclosed in this invention. They include most of the operational steps in Example 1, but differ in the types and corresponding mass ratios of organic solvents in the electrolyte, the mass content of fluorinated linear carbonate solvents in the electrolyte, the mass content of fluorinated cyclic carbonate solvents in the electrolyte, the mass content of the compound shown in structural formula 1 in the electrolyte, the mass content of the compound shown in structural formula 2 in the electrolyte, the types of auxiliary additives and their mass content in the electrolyte, and the mass ratio of the compound shown in structural formula 1 to the compound shown in structural formula 2, as detailed in Table 1. The calculation method for the mass content of FEMC and FEC in the electrolyte is the same as in Example 1.

[0134] In Example 23, the organic solvent consisted of FEC, EC, FDEC, and EMC, where FDEC was di(2,2,2-trifluoroethyl) carbonate, and the specific mass ratios are shown in Table 1. In Example 24, the compound represented by structural formula 1 was dipropyne-2,2,2-trifluoroethyl phosphate, and in Comparative Example 9, the compound represented by structural formula 1 was... The compounds selected for the remaining examples and comparative examples are the same as those in Example 1, as shown in Structural Formula 1.

[0135] Battery performance testing

[0136] The batteries prepared in the above embodiments and comparative examples were subjected to the following performance tests.

[0137] 1) High-temperature cycling performance test:

[0138] The formed battery was charged to 4.35V using a 1C constant current and constant voltage method at 45℃, and then discharged to 2.75V using a 1C constant current method. The capacity retention after 800 charge / discharge cycles was calculated. The calculation formula is as follows:

[0139] Capacity retention rate after 800 cycles (%) = (Discharge capacity after 800 cycles / Discharge capacity after the first cycle) × 100%;

[0140] 2) High-temperature storage performance: After formation, the battery was charged to 4.35V at room temperature using a 1C constant current and constant voltage method. The initial volume of the battery was measured using the water displacement method. It was then discharged to 2.75V using a 1C constant current method, and the initial discharge capacity was recorded. It was then charged again to 4.35V using a 1C method. After storing the battery at 60℃ for 30 days, the battery was allowed to cool to room temperature, and the final volume was measured again using the water displacement method. The battery volume expansion rate was calculated. Afterward, the battery was discharged to 2.75V using a 1C method, then charged again to 4.35V using a 1C constant current and constant voltage method, and finally discharged to 2.75V using a 1C method. The battery recovery discharge capacity (2.75~4.35V) was measured and recorded after discharge. The calculation formula is as follows:

[0141] Battery capacity recovery rate (%) = recovered capacity / initial capacity × 100%.

[0142] Battery volume expansion rate (%) = (final volume - initial volume) / initial volume × 100%;

[0143] The test results are shown in Table 2.

[0144] Table 1

[0145]

[0146]

[0147]

[0148] Table 2

[0149]

[0150]

[0151] As shown in Tables 1 and 2, comparing Example 1 with Comparative Examples 1-3, without the compound shown in Structure 1 in the electrolyte, changing the content of the compound shown in Structure 2 resulted in an initial increase followed by a decrease in high-temperature cycling capacity as the content of the compound shown in Structure 2 increased. Comparing Example 1 with Comparative Examples 4-6, without the compound shown in Structure 2 in the electrolyte, changing the content of the compound shown in Structure 1 resulted in poor high-temperature cycling and storage performance of the battery. Comparing Example 1 with Comparative Example 7, without the fluorine-substituted linear carbonate solvent FEMC in the organic solvent, the battery exhibited a low high-temperature cycling capacity retention rate and a high high-temperature storage volume expansion rate. Comparing Example 1 with Comparative Example 8, the organic solvent... The fluorine-free cyclic carbonate solvent FEC results in poorer high-temperature cycle performance and lower high-temperature storage capacity recovery rate in the battery. Through comparison of Example 1 and Comparative Examples 1-8, it is shown that the synergistic effect of the compound shown in Structural Formula 1 and the compound shown in Structural Formula 2, the fluorine-substituted linear carbonate solvent, and the fluorine-substituted cyclic carbonate solvent can construct a "bi-stable interface film" on the positive and negative electrode surfaces of silicon-carbon batteries: a LiF / phosphate-rich anti-expansion SEI film is formed on the negative electrode, and a sulfur oxide-containing anti-dissolution CEI film is formed on the positive electrode. At the same time, the fluorine-substituted linear carbonate solvent and the fluorine-substituted cyclic carbonate solvent improve the thermal stability of the electrolyte, thus synergistically improving the high-temperature cycle performance and high-temperature storage performance of the battery.

[0152] Comparing Examples 1-3 and Examples 4-5, when the FEC content in the electrolyte is higher than 30%, the battery's high-temperature storage gas production increases; when the FEC content is lower than 15%, the battery's high-temperature cycle capacity retention decreases. This indicates that in the electrolyte, a fluorinated cyclic carbonate solvent content in the range of 15-30% is beneficial for synergistic effects with the compounds shown in Structural Formulas 1 and 2, and fluorinated linear carbonate solvents, thereby improving the battery's high-temperature cycle performance and high-temperature storage performance. Comparing Examples 1, 6-9 and Examples 10-11, when the FEMC mass content in the electrolyte is lower than 20%, the battery's high-temperature cycle capacity retention and high-temperature storage capacity recovery rate are low; when the FEMC mass content in the electrolyte is higher than 50%, the battery's high-temperature storage capacity recovery rate decreases. This indicates that in the electrolyte, a fluorinated linear carbonate solvent content in the range of 20-50% is beneficial for synergistic effects with the compounds shown in Structural Formulas 1 and 2, and fluorinated cyclic carbonate solvents, thereby improving the battery's high-temperature cycle performance and high-temperature storage performance. Comparing Examples 1 and 23, changing the type of fluorinated linear carbonate solvent both improve the battery's high-temperature cycle performance and high-temperature storage performance.

[0153] A comparison of Examples 1, 12-14, and 15-16 demonstrates that a mass content of the compound shown in Structural Formula 1 in the electrolyte within the range of 1-3% is beneficial for synergistic effects with the compound shown in Structural Formula 2, fluorinated substituted cyclic carbonate solvents, and fluorinated substituted linear carbonate solvents, thereby improving the high-temperature cycle performance and high-temperature storage performance of the battery. A comparison of Examples 1, 17-20, and 21-22 demonstrates that a mass content of the compound shown in Structural Formula 2 within the range of 1-5% results in a battery with higher high-temperature cycle capacity retention and high-temperature storage performance.

[0154] Comparing Examples 1, 24, and Comparative Example 9, Comparative Example 9 contains a phosphite group, and R1 and R3 are selected from propyl groups. The high-temperature cycle capacity retention rate of the battery is less than 80%, the high-temperature storage capacity recovery rate is low, and there is a lot of gas generation during high-temperature storage. This indicates that adding the compound shown in structural formula 1 provided in this application, where R1 and R3 are selected from alkenyl groups with 2 to 4 carbon atoms or alkynyl groups with 2 to 4 carbon atoms, can improve the high-temperature cycle capacity retention rate of the battery and improve the high-temperature storage performance of the battery.

[0155] Compared with Examples 26 and 27 and Comparative Examples 10 and 11, Comparative Examples 10 and 11 did not contain the compound shown in Structural Formula 2. The addition of auxiliary additives such as sulfonates and phosphates to the electrolyte resulted in a low high-temperature storage capacity recovery rate and increased gas production during high-temperature storage. This indicates that the compound shown in Structural Formula 2 added to the electrolyte can work synergistically with the compound shown in Structural Formula 1, the fluorinated linear carbonate solvent, and the fluorinated cyclic carbonate solvent to improve the high-temperature cycle performance and high-temperature storage performance of the battery.

[0156] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A lithium-ion battery, characterized in that, It includes a positive electrode, a negative electrode, and a non-aqueous electrolyte. The non-aqueous electrolyte includes a non-aqueous organic solvent, additives, and a lithium salt. The additives include compounds shown in structural formula 1 and compounds shown in structural formula 2. The non-aqueous organic solvent includes fluorinated substituted carbonate solvents, which include fluorinated substituted linear carbonate solvents and fluorinated substituted cyclic carbonate solvents. Among them, R1 and R3 are each independently selected from alkenyl groups with 2 to 4 carbon atoms and alkynyl groups with 2 to 4 carbon atoms; The negative electrode includes a negative electrode material layer, the negative electrode material layer includes a negative electrode active material, and the negative electrode active material includes silicon; the specific capacity of the negative electrode material layer is 800~1500 mAh / g; In the non-aqueous electrolyte, the mass content of the compound represented by structural formula 1 is 1-3%; And / or, in the non-aqueous electrolyte, the mass content of the compound shown in structural formula 2 is 1-5%; In the non-aqueous electrolyte, the mass ratio of the compound shown in structural formula 1 to the compound shown in structural formula 2 is (0.35~1.5):

1.

2. The lithium-ion battery according to claim 1, characterized in that, R1 and R3 are each independently selected from straight-chain alkenyl groups with 2 to 4 carbon atoms, branched alkenyl groups with 2 to 4 carbon atoms, straight-chain alkynyl groups with 2 to 4 carbon atoms, and branched alkynyl groups with 2 to 4 carbon atoms.

3. The lithium-ion battery according to claim 1, characterized in that, The compound shown in structural formula 1 is selected from one or both of diallyl-2,2,2-trifluoroethyl phosphate and diargynyl-2,2,2-trifluoroethyl phosphate.

4. The lithium-ion battery according to claim 1, characterized in that, In the non-aqueous electrolyte, the mass content of the compound represented by structural formula 1 is 1-2%; And / or, In the non-aqueous electrolyte, the mass content of the compound shown in structural formula 2 is 1-3%.

5. The lithium-ion battery according to claim 1, characterized in that, In the non-aqueous electrolyte, the mass ratio of the compound shown in structural formula 1 to the fluorinated substituted carbonate solvent is 0.015~0.

05.

6. The lithium-ion battery according to claim 1, characterized in that, The fluorinated substituted linear carbonate solvent includes one or more of methyltrifluoroethyl carbonate and bis(2,2,2-trifluoroethyl) carbonate, and the mass content of the fluorinated substituted linear carbonate solvent in the non-aqueous electrolyte is 20-50%. The fluorinated substituted cyclic carbonate solvent includes fluoroethylene carbonate, and in the non-aqueous electrolyte, the mass content of the fluorinated substituted cyclic carbonate solvent is 15-30%. And / or, the additive further includes auxiliary additives, which include at least one of cyclic sulfate compounds, sulfonyl lactone compounds, cyclic carbonate compounds, phosphate compounds, borate compounds and nitrile compounds; in the non-aqueous electrolyte, the mass content of the auxiliary additive is 0.01~30%.

7. The lithium-ion battery according to claim 1, characterized in that, The negative electrode active material includes silicon-based materials and carbon materials, wherein the silicon-based materials include one or more of silicon materials, silicon oxides, silicon-carbon composite materials, and silicon alloys; The silicon material includes nano-silicon materials; The silicon-carbon composite material includes one of the following: a composite material composed of silicon oxide and carbon materials, and a composite material composed of elemental silicon and carbon materials; The carbon material is selected from one or more of artificial graphite, natural graphite, composite graphite, graphene, and hard carbon. The silicon oxide includes SiO x Compounds, where 0 < x < 2.

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