Electrolytes and silicon-carbon batteries

Abstract

This application provides an electrolyte and a silicon-carbon battery. The electrolyte, by weight percentage, comprises: 0.1–3% bis(1,2-cycloglycerite) oxalate, 0.1–3% tetraethoxysilane, 0.1–3% bis(trimethylsilyl)sulfate, and the balance being an organic solvent and a lithium salt. In the electrolyte of this application, the tetraethoxysilane and bis(trimethylsilyl)sulfate readily react with the natural silanol groups on the surface of the silicon-carbon anode, forming a Si-O-Si bonded cross-polymer network on the anode surface. This helps improve the mechanical strength and flexibility of the SEI film, thereby stabilizing the charged interface and improving the electrochemical performance of the battery. The combination of bis(1,2-cycloglycerite) oxalate and bis(trimethylsilyl)sulfate, with their synergistic effect, can form a protective layer with a three-dimensional network on the anode of the battery, helping to balance various battery performance aspects, thereby improving the battery's cycle performance and high-temperature storage performance.

Description

Technical Field

[0001] This application relates to the field of battery technology, and more specifically, to an electrolyte and a silicon-carbon battery. Background Technology

[0002] High-capacity anode materials are a key breakthrough for improving the energy density of lithium-ion batteries. Compared with graphite anodes, silicon-carbon anodes have significant advantages in both compaction density and specific capacity. It is difficult to further improve the capacity of graphite anode materials. Moreover, the theoretical energy density of 372 mAh / g is far lower than that of silicon anode materials, which have a theoretical energy density of up to 4200 mAh / g. Silicon anode materials have suitable discharge potential and relatively abundant reserves in nature, and are considered to be the most likely anode material to replace graphite.

[0003] However, the commercial application of elemental silicon in lithium-ion batteries faces numerous challenges. Firstly, the lithium-ion insertion / extraction process generates internal stress within the silicon material, leading to volume expansion and structural damage. This can result in issues such as active particle breakage, electrode pulverization, and active material detachment. Secondly, changes in silicon volume cause the solid electrolyte interphase (SEI) film to rupture. Newly exposed silicon produces a new SEI film, continuously consuming lithium ions in the electrolyte and reducing the initial coulombic efficiency. Finally, during cycling, volume changes in the electrode material cause repeated growth and rupture of the SEI film at the silicon anode interface, rapid lithium source depletion, and other issues, all contributing to rapid capacity decay and significantly impacting cycle stability.

[0004] Classic film-forming additives such as fluoroethylene carbonate (FEC), vinylene carbonate (VC), propylene sulfite (PS), and ethylene sulfate (DTD) play important roles in lithium-ion batteries. However, with the increasing proportion of silicon doping and the continuous development of high-voltage materials, conventional additives cannot meet the requirements of long-cycle and wide-temperature operating environments. From the current commercial application perspective, DTD can significantly improve the high-temperature storage and high-temperature cycling performance of batteries and is the most effective additive among sulfate compounds. However, DTD is relatively expensive, and its low-temperature storage requirements cause inconvenience for electrolyte transportation and storage. After film formation, VC has oxidation stability issues under high-temperature and high-voltage systems, leading to a series of side decompositions. Although PS performs well in suppressing gas production, it is prone to continuous oxidation with the positive electrode, resulting in increased film impedance and rapid increase in DC internal resistance (DCR) during long cycles. Furthermore, PS has drawbacks such as significant health hazards. Summary of the Invention

[0005] The main objective of this application is to provide an electrolyte and a silicon-carbon battery to solve the problem of poor high-temperature storage stability of silicon-carbon batteries in the prior art.

[0006] To achieve the above objectives, according to one aspect of this application, an electrolyte is provided, comprising, by weight percentage: 0.1 to 3% bis(1,2-cycloglyceride) oxalate, 0.1 to 3% tetraethoxysilane, 0.1 to 3% bis(trimethylsilyl) sulfate, and the balance being an organic solvent and a lithium salt.

[0007] Further, the mass content of the above-mentioned bis(1,2-cycloglyceride) oxalate is 0.3-3%; and / or, the mass content of tetraethoxysilane is 0.3-3%; and / or, the mass content of bis(trimethylsilyl) sulfate is 0.5-3%.

[0008] Furthermore, the mass ratio of the above-mentioned bis(1,2-cycloglycerite) oxalate, tetraethoxysilane and bis(trimethylsilyl) sulfate is (0.3-1):(0.3-1):(0.5-1).

[0009] Furthermore, the electrolyte further includes 1.1% to 18% additives; further, the additives are selected from any one or more of fluoroethylene carbonate, succinic acid, adiponitrile, glutaronitrile, 1,3,6-hexanetrionitrile, vinylene carbonate and ethylene ethylene carbonate.

[0010] Furthermore, the above-mentioned additive is a combination of fluoroethylene carbonate and succinic acid, and the mass ratio of fluoroethylene carbonate to succinic acid is (5-15):(0.1-1).

[0011] Further, the mass content of the above lithium salt is 10-27%; further, the lithium salt is selected from any one or more of LiPF6, lithium difluorooxalate borate, LiPO2F2, lithium tetrafluoroborate, lithium bis(oxalate borate), lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethylsulfonyl)imide.

[0012] Furthermore, the lithium salt is a combination of LiPF6, lithium difluorooxalate borate and LiPO2F2, and the mass ratio of LiPF6, lithium difluorooxalate borate and LiPO2F2 is (10-14):(1-5):(0.5-5).

[0013] Furthermore, the organic solvent mentioned above is selected from any one or more of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, butylene carbonate, ethyl propionate, ethyl acetate, and propyl propionate.

[0014] Furthermore, the organic solvent is a combination of ethylene carbonate, propylene carbonate, diethyl carbonate and ethyl propionate, and the mass ratio of ethylene carbonate, propylene carbonate, diethyl carbonate and ethyl propionate is (5-15):(15-25):(10-45):(15-60).

[0015] According to another aspect of this application, a silicon-carbon battery is provided, comprising a positive electrode, an electrolyte, and a silicon-carbon negative electrode, wherein the electrolyte is the aforementioned electrolyte.

[0016] Applying the technical solution of this application, the tetraethoxysilane and bis(trimethylsilyl)sulfate in the electrolyte readily react with the natural silanol groups on the surface of the silicon-carbon anode, forming a cross-polymerized network of Si-O-Si bonds on the anode surface. This helps improve the mechanical strength and flexibility of the SEI film, thereby stabilizing the charged interface and improving the electrochemical performance of the battery. Otherwise, Li + It will react with silanol to generate Li₂O and LiOH; the combination of bis(1,2-cycloglycerite) oxalate and bis(trimethylsilyl) sulfate can, on the one hand, form sulfur-containing compounds in the positive electrode protective film, and on the other hand, help inhibit the further decomposition of the SEI of organic polymers, thus modifying the SEI. The synergistic effect of the two can form a three-dimensional network protective layer on the anode of the battery, providing cross-linking protective layers and forming an SEI with high conductivity and high thermal stability, which helps to balance the various performances of the battery, thereby improving the battery's cycle performance and high-temperature storage performance. Controlling the mass content of bis(1,2-cycloglycerite) oxalate, tetraethoxysilane, and bis(trimethylsilyl) sulfate in the electrolyte within the above range helps to further enhance the synergistic effect among the three, thereby further improving the battery's cycle performance and high-temperature storage performance. Detailed Implementation

[0017] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present application will now be described in detail with reference to the embodiments.

[0018] As analyzed in the background section of this application, silicon-carbon batteries in the prior art have poor high-temperature storage stability. In order to solve this problem, this application provides an electrolyte and a silicon-carbon battery.

[0019] In a typical embodiment of this application, an electrolyte is provided, comprising, by mass percentage: 0.1-3% bis(1,2-cycloglyceride) oxalate, 0.1-3% tetraethoxysilane, 0.1-3% bis(trimethylsilyl) sulfate, and the balance being an organic solvent and a lithium salt.

[0020] In this application, tetraethoxysilane and bis(trimethylsilyl)sulfate in the electrolyte readily react with the natural silanol groups on the surface of the silicon-carbon anode, forming a cross-polymerized network of Si-O-Si bonds on the anode surface. This helps improve the mechanical strength and flexibility of the SEI film, thereby stabilizing the charged interface and improving the electrochemical performance of the battery. Otherwise, Li+ It will react with silanol to generate Li₂O and LiOH; the combination of bis(1,2-cycloglycerite) oxalate and bis(trimethylsilyl) sulfate can, on the one hand, form sulfur-containing compounds in the positive electrode protective film, and on the other hand, help inhibit the further decomposition of the SEI of organic polymers, thus modifying the SEI. The synergistic effect of the two can form a three-dimensional network protective layer on the anode of the battery, providing cross-linking protective layers and forming an SEI with high conductivity and high thermal stability, which helps to balance the various performances of the battery, thereby improving the battery's cycle performance and high-temperature storage performance. Controlling the mass content of bis(1,2-cycloglycerite) oxalate, tetraethoxysilane, and bis(trimethylsilyl) sulfate in the electrolyte within the above range helps to further enhance the synergistic effect among the three, thereby further improving the battery's cycle performance and high-temperature storage performance.

[0021] In one embodiment of this application, the mass content of the above-mentioned bis(1,2-cycloglycerite) oxalate is 0.3-3%; and / or, the mass content of tetraethoxysilane is 0.3-3%; and / or, the mass content of bis(trimethylsilyl)sulfate is 0.5-3%.

[0022] Controlling the mass content of bis(1,2-cycloglycerite) oxalate, tetraethoxysilane, and bis(trimethylsilyl) sulfate within the above range helps to further improve the mechanical strength and flexibility of the SEI film, inhibit the further decomposition of the SEI of organic polymers, and thus help to improve the cycle performance and high-temperature storage performance of the battery.

[0023] In one embodiment of this application, the mass ratio of the above-mentioned bis(1,2-cycloglycerite) oxalate, tetraethoxysilane and bis(trimethylsilyl) sulfate is (0.3-1):(0.3-1):(0.5-1).

[0024] Controlling the mass ratio of bis(1,2-cycloglycerite) oxalate, tetraethoxysilane, and bis(trimethylsilyl) sulfate within the above range helps to further optimize the SEI film and suppress the generation of side reactions, thereby helping to improve the cycle performance and high-temperature storage performance of the battery.

[0025] In one embodiment of this application, the electrolyte further includes 1.1% to 18% additives; in one embodiment of this application, the additives are selected from any one or more of fluoroethylene carbonate, succinic acid, adiponitrile, glutaronitrile, 1,3,6-hexanetrionitrile, vinylene carbonate and ethylene ethylene carbonate.

[0026] The addition of additives helps to further optimize the performance of the SEI film, improve the cycle stability, high temperature adaptability and first coulombic efficiency of the battery, while reducing gas production and expansion.

[0027] In one embodiment of this application, the additive is a combination of fluoroethylene carbonate and succinic acid, and the mass ratio of fluoroethylene carbonate to succinic acid is (5-15):(0.1-1).

[0028] The addition of fluoroethylene carbonate effectively improves the stability of the SEI film on silicon-based anodes, especially under high voltage and wide temperature range conditions. The decomposition of fluoroethylene carbonate on the electrode surface forms a fluorine-rich SEI film, which exhibits better electronic insulation, ionic conductivity, and thermal stability. This effectively suppresses side reactions of the electrode material during charge and discharge, extending the battery's cycle life. The addition of succinic anionylene helps promote the dynamic balance of the SEI film during charge and discharge, reducing film rupture and regeneration, thereby lowering the battery's internal resistance and improving cycle performance. The addition of succinic anionylene helps maintain good stability and continuity of the SEI film during cycling, reducing the loss of active material and optimizing the battery's coulombic efficiency. Controlling the mass ratio of fluoroethylene carbonate to succinic anionylene within the aforementioned range helps enhance their synergistic effect, further improving the battery's cycle performance and high-temperature storage performance.

[0029] In one embodiment of this application, the mass content of the lithium salt is 10-27%; in another embodiment of this application, the lithium salt is selected from any one or more of lithium hexafluorophosphate (LiPF6), lithium difluorooxalate borate (LiODFB), LiPO2F2, lithium tetrafluoroborate (LiBF4), lithium bis(oxalate borate) (LiBOB), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI).

[0030] Lithium salts are the primary source of lithium ions in electrolytes. Controlling the mass content of lithium salts within the aforementioned range helps to ensure good electrolyte conductivity, improve ion transport efficiency, enhance the chemical stability of the electrolyte, and reduce lithium plating and side reactions. Controlling the types of lithium salts within the aforementioned range further helps to improve the conductivity and stability of the electrolyte.

[0031] In one embodiment of this application, the lithium salt is a combination of LiPF6, lithium difluorooxalate borate and LiPO2F2, and the mass ratio of LiPF6, lithium difluorooxalate borate and LiPO2F2 is (10-14):(1-5):(0.5-5).

[0032] The addition of LiPF6 helps improve the conductivity and electrochemical stability of the electrolyte. Lithium difluorooxalate borate and LiPO2F2 can participate in the formation of the SEI film, optimizing its composition and structure. Lithium difluorooxalate borate promotes the formation of a stable SEI film under high-temperature conditions, while LiPO2F2 helps form a fluorine-rich SEI film, improving its thermal stability and mechanical strength, and reducing the volume change of the electrode during charge and discharge, thereby contributing to improved battery cycle stability and energy efficiency. Controlling the mass ratio of LiPF6, lithium difluorooxalate borate, and LiPO2F2 within the aforementioned range helps to fully leverage their synergistic effects, thereby improving the electrolyte conductivity, electrochemical window, and SEI film performance, ultimately enhancing battery cycle stability, energy efficiency, wide temperature adaptability, and overall safety.

[0033] To further improve the chemical stability of the electrolyte, in one embodiment of this application, the organic solvent is selected from any one or more of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, butylene carbonate, ethyl propionate, ethyl acetate, and propyl propionate.

[0034] In one embodiment of this application, the organic solvent is a combination of ethylene carbonate, propylene carbonate, diethyl carbonate, and ethyl propionate, and the mass ratio of ethylene carbonate, propylene carbonate, diethyl carbonate, and ethyl propionate is (5-15):(15-25):(10-45):(15-60).

[0035] Controlling the mass ratio of ethylene carbonate, propylene carbonate, diethyl carbonate, and ethyl propionate within the above range helps to fully utilize the synergistic effect between the components, thereby improving the conductivity and stability of the electrolyte.

[0036] In one embodiment of this application, the electrolyte comprises, by mass percentage, 14% LiPF6, 1% lithium difluorooxalate borate, 0.5% LiPO2F2, 5% fluoroethylene carbonate, 1% succinic anionyl, 0.3% bis(1,2-cycloglyceride) oxalate, 0.3% tetraethoxysilane, 0.5% bis(trimethylsilyl) sulfate, and the balance being an organic solvent, wherein the organic solvent is a combination of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), and ethyl propionate (EP), and the mass ratio of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), and ethyl propionate (EP) is 10:20:15:55.

[0037] In one embodiment of this application, the electrolyte comprises, by mass percentage, 10% LiPF6, 5% lithium difluorooxalate borate, 5% LiPO2F2, 15% fluoroethylene carbonate, 0.1% succinic anionyl, 0.5% bis(1,2-cycloglyceride) oxalate, 0.3% tetraethoxysilane, 0.5% bis(trimethylsilyl) sulfate, and the balance being an organic solvent, wherein the organic solvent is a combination of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), and ethyl propionate (EP), and the mass ratio of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), and ethyl propionate (EP) is 10:20:15:55.

[0038] In another typical embodiment of this application, a silicon-carbon battery is provided, including a positive electrode, an electrolyte, and a silicon-carbon negative electrode, wherein the electrolyte is the aforementioned electrolyte.

[0039] Because the battery contains the electrolyte of this application, it has good cycle stability and high-temperature storage performance.

[0040] The beneficial effects of this application will be further illustrated below with reference to the embodiments.

[0041] Examples 1-14, Comparative Examples 1-4

[0042] In a glove box filled with nitrogen / argon (H2O < 0.5 ppm), ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), and ethyl propionate (EP) were mixed in a mass ratio of 10:20:15:55 to obtain an organic solvent. Then, LiPF6, lithium difluorooxalate borate, LiPO2F2, fluoroethylene carbonate, and succinate were slowly added to the organic solvent. Finally, bis(1,2-cycloglycerite) oxalate, tetraethoxysilane, and bis(trimethylsilyl) sulfate were added, and the mixture was stirred until homogeneous to obtain the electrolyte. By mass percentage, the electrolyte contains 14% LiPF6, 1% lithium difluorooxalate borate, 0.5% LiPO2F2, 5% fluoroethylene carbonate, 1% succinate, and the mass contents of bis(1,2-cycloglyceride) oxalate, tetraethoxysilane, and bis(trimethylsilyl) sulfate are shown in Table 1. The remainder is organic solvent.

[0043] Table 1

[0044]

[0045]

[0046] Example 15

[0047] The difference from Example 1 is that the mass content of fluoroethylene carbonate is 15% and the mass content of succinic acid is 0.1%, resulting in an electrolyte.

[0048] Example 16

[0049] The difference from Example 1 is that the mass content of fluoroethylene carbonate is 4% and the mass content of succinic acid is 2%, resulting in an electrolyte.

[0050] Example 17

[0051] The difference from Example 1 is that the mass content of LiPF6 is 10%, the mass content of lithium difluorooxalate borate is 5%, and the mass content of LiPO2F2 is 5%, resulting in an electrolyte.

[0052] Example 18

[0053] The difference from Example 1 is that the mass content of LiPF6 is 17%, the mass content of lithium difluorooxalate borate is 1%, and the mass content of LiPO2F2 is 0.5%, resulting in the final electrolyte.

[0054] Example 19

[0055] The difference from Example 1 is that the mass ratio of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), and ethyl propionate (EP) is 5:25:10:60 to obtain the final electrolyte.

[0056] Example 20

[0057] The difference from Example 1 is that the mass ratio of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), and ethyl propionate (EP) is 4:26:9:61, resulting in the final electrolyte.

[0058] Comparative Example 5

[0059] The difference from Example 1 is that bis(1,2-cycloglyceride) oxalate, tetraethoxysilane and bis(trimethylsilyl) sulfate were replaced with vinylene carbonate to obtain the final electrolyte.

[0060] Preparation of the positive electrode: The positive electrode active materials lithium cobalt oxide (LCO), carbon nanotubes (CNT), conductive carbon black SP, and polyvinylidene fluoride (PVDF) are thoroughly mixed in a mass ratio of 98:0.5:0.5:1.0, coated on aluminum foil, dried, and cold-pressed to obtain the positive electrode sheet.

[0061] Preparation of the negative electrode: Silicon-carbon negative electrode material (SiC), conductive carbon black (SP), single-walled carbon nanotubes (SWCNT) and binder polyacrylic acid (PAA) are mixed in a mass ratio of 80:9:1:10 and added to deionized water as a solvent. After being mixed evenly, the mixture is coated on copper foil, dried, and cold-pressed to obtain the negative electrode sheet.

[0062] Battery fabrication: The positive electrode, negative electrode and separator prepared above are wound into a square cell, packaged with polymer, and filled with the electrolyte prepared in the above examples and comparative examples.

[0063] Electrical performance testing

[0064] Cyclic performance test: Under conditions of 25℃ or 45℃, the lithium-ion battery is charged at a 1C rate with constant current and constant voltage to 4.5V, with a cutoff current of 0.05C, and allowed to rest for 10 minutes. Then, the lithium-ion battery is discharged at a 1C rate with constant current to 3.0V, and allowed to rest for 10 minutes. This constitutes one charge-discharge cycle. The capacity retention rate (%) of the lithium-ion battery after N cycles = (discharge capacity of the Nth cycle / initial discharge capacity) × 100%, where N is the number of cycles of the lithium-ion battery.

[0065] High-temperature storage performance test: First, the formed battery was charged and discharged at 1.0C to 3.0V at room temperature, and the initial thickness was recorded; then it was charged at 0.2C constant current and constant voltage to 4.5V, and cut off at 0.02C; then discharged at 0.2C constant current to 3.0V; this was recorded as the initial capacity; then it was charged at 0.2C constant current and constant voltage to 4.5V, and cut off at 0.02C; after the battery was placed in a 60℃ constant temperature chamber for 14 days, the battery was removed, the hot thickness was measured (the hot thickness was recorded at the temperature chamber), and after resting for 2 hours, it was discharged at 0.2C constant current to 3.0V, which was recorded as the residual capacity; then it was charged at 0.2C constant current and constant voltage to 4.5V, and cut off at 0.02C; after resting for 10 minutes, it was discharged at 0.2C constant current to 3.0V; the recovered capacity was recorded.

[0066] Battery thermal expansion rate after 14 days of storage at 60℃ = (Hot thickness - Initial thickness) / Initial thickness * 100% Battery capacity retention rate after 14 days of storage at 60℃ = (Residual capacity / Initial capacity) * 100%

[0067] Battery capacity recovery rate after 14 days of storage at 60℃ = (recovered capacity / initial capacity) * 100%

[0068] The results of the cycle performance test and high-temperature storage performance test of the above batteries are shown in Table 2.

[0069] Table 2

[0070]

[0071] As can be seen from the above description, the embodiments of this application achieve the following technical effects:

[0072] In this application, tetraethoxysilane and bis(trimethylsilyl)sulfate in the electrolyte readily react with the natural silanol groups on the surface of the silicon-carbon anode, forming a cross-polymerized network of Si-O-Si bonds on the anode surface. This helps improve the mechanical strength and flexibility of the SEI film, thereby stabilizing the charged interface and improving the electrochemical performance of the battery. Otherwise, Li + It will react with silanol to generate Li₂O and LiOH; the combination of bis(1,2-cycloglycerite) oxalate and bis(trimethylsilyl) sulfate can, on the one hand, form sulfur-containing compounds in the positive electrode protective film, and on the other hand, help inhibit the further decomposition of the SEI of organic polymers, thus modifying the SEI. The synergistic effect of the two can form a three-dimensional network protective layer on the anode of the battery, providing cross-linking protective layers and forming an SEI with high conductivity and high thermal stability, which helps to balance the various performances of the battery, thereby improving the battery's cycle performance and high-temperature storage performance. Controlling the mass content of bis(1,2-cycloglycerite) oxalate, tetraethoxysilane, and bis(trimethylsilyl) sulfate in the electrolyte within the above range helps to further enhance the synergistic effect among the three, thereby further improving the battery's cycle performance and high-temperature storage performance.

[0073] The above are merely embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An electrolyte, characterized by, The electrolyte comprises, in mass percentage, 0.1-3% of bis(1,2-cyclosulfite) oxalate, 0.1-3% of tetraethoxysilane, 0.1-3% of bis(trimethylsilyl) sulfate, and the rest of organic solvent and lithium salt; the mass ratio of the bis(1,2-cyclosulfite) oxalate, the tetraethoxysilane and the bis(trimethylsilyl) sulfate is (0.3-1):(0.3-1):(0.5-1).

2. The electrolyte according to claim 1, characterized in that, The mass content of the bis(1,2-cyclosulfite) oxalate is 0.3-3%; and / or, the mass content of the tetraethoxysilane is 0.3-3%; and / or, the mass content of the bis(trimethylsilyl) sulfate is 0.5-3%.

3. The electrolyte of claim 1, wherein, The electrolyte further comprises 1.1-18% of an additive.

4. The electrolyte according to claim 3, characterized in that, The additive is selected from any one or more of fluoroethylene carbonate, butanedinitrile, hexanedinitrile, pentanedinitrile, 1,3,6-hexanetricarbonitrile, vinylidene carbonate and vinyl ethylene carbonate.

5. The electrolyte according to claim 4, characterized in that, The additive is a combination of the fluoroethylene carbonate and the butanedinitrile, and the mass ratio of the fluoroethylene carbonate and the butanedinitrile is (5-15):(0.1-1).

6. The electrolyte according to any one of claims 1 to 5, characterized in that, The mass content of the lithium salt is 10-27%.

7. The electrolyte according to claim 6, characterized in that The lithium salt is selected from any one or more of LiPF6, lithium difluoro(oxalato)borate, LiPO2F2, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium bisfluorosulfonylimide and lithium bis(trifluoromethylsulfonyl)imide.

8. The electrolyte of claim 7, wherein, The lithium salt is a combination of the LiPF6, the lithium difluoro(oxalato)borate and the LiPO2F2, and the mass ratio of the LiPF6, the lithium difluoro(oxalato)borate and the LiPO2F2 is (10-14):(1-5):(0.5-5).

9. The electrolyte according to any one of claims 1 to 5, characterized in that, The organic solvent is selected from any one or more of vinyl carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, butylene carbonate, ethyl propionate, ethyl acetate and propyl propionate.

10. The electrolyte of claim 9, wherein, The organic solvent is a combination of the vinyl carbonate, the propylene carbonate, the diethyl carbonate and the ethyl propionate, and the mass ratio of the vinyl carbonate, the propylene carbonate, the diethyl carbonate and the ethyl propionate is (5-15):(15-25):(10-45):(15-60).

11. A silicon-carbon battery comprising a positive electrode sheet, an electrolyte, and a silicon-carbon negative electrode sheet, characterized by, The electrolyte is the electrolyte of any one of claims 1-10.

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