Lithium ion battery

Abstract

The invention provides a lithium ion battery, which comprises a negative electrode, a positive electrode and an electrolyte, the negative electrode comprises a negative electrode active layer, the negative electrode active layer comprises a negative electrode active material, and the negative electrode active material comprises silicon carbide; the electrolyte comprises an organic solvent, a lithium salt and an additive, and the additive comprises an impregnating compound; in the negative electrode active material, the mass percentage of silicon carbide is 5-30%; based on 100% of the total mass of the electrolyte, the mass percentage of the impregnating compound A is 1%-15%; the impregnating compound comprises a compound as shown in a formula 1 and / or a fluoroether compound; the compound shown in the formula 1 is shown in the specification, and A, B, C, X, Y and Z can be independently selected from H, F or CH3. According to the lithium ion battery provided by the invention, the compound shown in the formula 1 and / or the fluoroether compound are / is added into the electrolyte as the impregnating compound, so that the surface tension of the electrolyte and the pole piece can be reduced, the problem of poor infiltration of the pole piece is improved, and the interface stability and the ion transmission efficiency can be balanced by further regulating and controlling the mass percentage content of the impregnating compound and the negative active material.

Description

Technical Field

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

[0002] In the consumer electronics sector, both prismatic and cylindrical wound batteries are employing high-compaction processes for their negative electrodes and continuously increasing the proportion of silicon carbide (SiC) doping in pursuit of high energy density (ED). However, the corner areas of prismatic wound batteries and the head of cylindrical wound batteries often suffer from poor electrolyte wetting due to the expansion and breathing effect of the SiC negative electrode. This leads to lithium plating during cycling, accelerates electrolyte consumption, and ultimately deteriorates the battery's cycle performance. Summary of the Invention

[0003] To address the problem of poor electrolyte wetting caused by the expansion of the SiC negative electrode due to the high proportion of SiC in the negative electrode in existing batteries, a lithium-ion battery is provided.

[0004] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: On one hand, the present invention provides a lithium-ion battery, including a negative electrode, a positive electrode and an electrolyte, wherein the negative electrode includes a negative electrode active layer, the negative electrode active layer includes a negative electrode active material, and the negative electrode active material includes silicon carbide; The electrolyte includes an organic solvent, a lithium salt, and additives, the additives including a wetting agent; In the negative electrode active material, the mass percentage of silicon carbide is 5%-30%; Based on the total mass of the electrolyte being 100%, the mass percentage of the wetting agent A is 1%-15%; The wetting agent includes compounds represented by Formula 1 and / or fluoroether compounds; The compound represented by Formula 1 is shown below: , Among them, A, B, C, X, Y, and Z can each be independently selected from H, F, or CH3.

[0005] Optionally, the compound represented by Formula 1 is selected from one or more of the following compounds: the compound represented by Formula 1 includes one or more of fluorobenzene, 1,2,3-trifluorotoluene, 1,3,5-trifluorotoluene and methylbenzene.

[0006] Optionally, the fluoroether compound includes one or more of 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, methyl nonafluorobutyl ether, and bis(2,2,2-trifluoroethyl) ether.

[0007] Optionally, the lithium salt includes a first lithium salt, which includes one or more of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide. Based on the total mass of the electrolyte being 100%, the mass percentage of the first lithium salt is 10%-30%.

[0008] Optionally, the lithium salt further includes a second lithium salt, which includes one or more of lithium difluorooxalate borate, lithium difluorodioxalate phosphate, lithium tetrafluoroborate, lithium difluorophosphate, and lithium bis(oxalate borate). Based on the total mass of the electrolyte being 100%, the mass percentage of the second lithium salt is 0-7%.

[0009] Optionally, the organic solvent includes one or more of the following: ethylene carbonate, propylene carbonate, diethyl carbonate, methyl ethyl carbonate, dimethyl carbonate, ethyl propionate, propyl propionate, ethyl fluorocarbonate, methyl ethyl fluorocarbonate, dimethyl fluorocarbonate, propylene fluorocarbonate, γ-butyrolactone, sulfolane, methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, n-butyl acetate, isobutyl acetate, n-amyl acetate, isoamyl acetate, methyl propionate, methyl butyrate, ethyl butyrate, methyl acrylate, and ethyl acrylate. Based on the total mass of the electrolyte being 100%, the mass percentage of the organic solvent is 20%-80%.

[0010] Optionally, the additive further includes other additives, including one or more of the following: fluoroethylene carbonate, vinylene carbonate, 1,3-propanesulfonate lactone, vinyl sulfate, succinate, adiponitrile, 1,3,6-hexanetrionitrile, propenesulfonate lactone, methanedisulfonate, ethylene glycol bis(propionitrile) ether, pentafluoroethoxyphosphazene, dicyclohexylcarbonyl, trimethyl imide phosphate, and hexamethylene diisocyanate. Based on the total mass of the electrolyte being 100%, the mass percentage of the other additives is 10%-30%.

[0011] Optionally, the positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material, which includes at least one of lithium cobalt oxide, nickel-cobalt-manganese ternary materials, lithium iron phosphate, and lithium manganese oxide.

[0012] Optionally, the negative electrode active material further includes at least one of graphite, silicon, and silicon oxides.

[0013] Optionally, the lithium-ion battery includes a square wound battery or a cylindrical wound battery.

[0014] The beneficial effects of this application are as follows: The lithium-ion battery provided in this application adds a compound of Formula 1 and / or a fluorinated ether-based wetting agent to the lithium-ion battery electrolyte. Because the wetting agent contains fluorine atoms and / or specific groups, it can reduce the surface tension between the electrolyte and the electrode, allowing the electrolyte to spread and penetrate into the electrode more quickly. This is particularly beneficial for square and cylindrical wound batteries where the electrode pore structure changes due to high compaction and expansion of silicon carbide in the negative electrode active material, effectively improving the problem of poor electrolyte wetting in the bends and head positions of the wound battery. The molecular structure of the wetting agent makes it compatible with the negative electrode active material, and it can form a stable interface layer on the electrode surface, reducing the interface rupture caused by the volume expansion of silicon-based materials during cycling, thereby inhibiting lithium plating, reducing the electrolyte consumption rate, and ultimately optimizing the cycle performance of the battery. In addition, further adjusting the mass percentage of the wetting agent (1%-15%) and the mass percentage of the negative electrode active material (5%-30%) can fully exert its wetting effect while ensuring the overall performance of the electrolyte, and balance the interface stability and ion transport efficiency. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the negative electrode of a square wound battery provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the negative electrode of a square wound battery provided as a comparative example of the present invention; Figure 3 This is a schematic diagram of the negative electrode of a cylindrical wound battery provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the negative electrode of a cylindrical wound battery provided as a comparative example of the present invention. Detailed Implementation

[0016] 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 the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0017] The present invention provides a lithium-ion battery, comprising a negative electrode, a positive electrode and an electrolyte, wherein the negative electrode comprises a negative electrode active layer, the negative electrode active layer comprises a negative electrode active material, and the negative electrode active material comprises silicon carbide; The electrolyte includes an organic solvent, a lithium salt, and additives, the additives including a wetting agent; In the negative electrode active material, the mass percentage of silicon carbide is 5%-30%; Based on the total mass of the electrolyte being 100%, the mass percentage of the wetting agent A is 1%-15%; The wetting agent includes compounds represented by Formula 1 and / or fluoroether compounds; The compound represented by Formula 1 is shown below: , Among them, A, B, C, X, Y, and Z can each be independently selected from H, F, or CH3.

[0018] Specifically, the lithium-ion battery provided in this application adds a compound of Formula 1 and / or a fluorinated ether-based wetting agent to the lithium-ion battery electrolyte. Because the aforementioned wetting agent contains fluorine atoms and / or specific groups, it can reduce the surface tension between the electrolyte and the electrode, allowing the electrolyte to spread and penetrate into the electrode more quickly. This is particularly beneficial for square and cylindrical wound batteries (such as cylindrical button batteries) where changes in the electrode pore structure caused by high compaction and expansion of silicon carbide in the negative electrode active material can effectively improve the problem of poor electrolyte wetting in the bends and head areas of the wound battery. On the one hand, the molecular structure of the wetting agent makes it compatible with the negative electrode active material, and it can form a stable interface layer on the electrode surface, reducing the interface rupture caused by the volume expansion of the negative electrode active material during cycling, thereby inhibiting lithium plating, reducing the electrolyte consumption rate, and ultimately optimizing the cycle performance of the battery. In addition, further adjusting the mass percentage of the wetting agent (1%-15%) and the mass percentage of the negative electrode active material (5%-30%) can fully exert its wetting effect while ensuring the overall performance of the electrolyte, and balance the interface stability and ion transport efficiency.

[0019] In the negative electrode active material, the mass percentage of silicon carbide can be 5%, 8%, 10%, 15%, 20%, 25%, or 30%. Based on the total mass of the electrolyte as 100%, the mass percentage of the wetting agent A can be 1%, 3%, 5%, 8%, 10%, 12%, or 15%. In some embodiments, the compound represented by Formula 1 is selected from one or more of the following compounds: the compound represented by Formula 1 includes one or more of fluorobenzene, 1,2,3-trifluorotoluene, 1,3,5-trifluorotoluene and methylbenzene.

[0020] Specifically, the fluorine atoms or methyl groups contained in the compound shown in Formula 1 can further reduce the interfacial tension between the electrolyte and the electrode by adjusting the molecular polarity and surface energy, thereby enhancing the electrolyte's ability to penetrate the pore structure of the expanded silicon-based negative electrode. For example, the introduction of fluorine-containing groups can optimize intermolecular forces, enabling the formation of a more uniform adsorption layer on the electrode surface, and improving the wetting uniformity in complex structures such as the bends and heads of square or cylindrical batteries. Methyl groups and other functional groups can regulate molecular flexibility, adapting to interfacial deformation caused by volume changes in silicon-based materials, and reducing electrolyte consumption due to interfacial damage during cycling. The combined use of multiple compounds can also optimize the ion conduction pathway of the electrolyte through synergistic effects, reducing surface tension while maintaining interfacial stability, thus more effectively suppressing lithium plating and improving battery cycle life.

[0021] In some embodiments, the fluoroether compound includes one or more of 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether (TTE), methyl nonafluorobutyl ether, and bis(2,2,2-trifluoroethyl) ether (BTFE).

[0022] Specifically, the aforementioned compounds are rich in fluorine atoms. Fluorine's high electronegativity significantly reduces the surface tension of the electrolyte, accelerating its spread on the electrode surface. This is particularly beneficial for improving the uniformity of electrolyte wetting in areas such as bends and tips of the silicon-based anode after expansion. Simultaneously, the molecular chains of fluorinated ether compounds exhibit good flexibility and chemical stability. During the volume expansion of silicon-based materials, the dynamic adjustment of the molecular chains maintains interfacial integrity, reducing electrolyte consumption and lithium plating caused by interfacial breakage. Furthermore, these compounds demonstrate excellent compatibility with organic solvents and lithium salts in the electrolyte. They form a stable, low-interfacial-resistance layer on the electrode surface without affecting ion conduction efficiency, thereby improving wetting performance and further optimizing battery cycle life and rate performance. The combined use of multiple fluorinated ether compounds can also synergistically regulate the surface tension and interfacial compatibility of the electrolyte, adapting to the wetting requirements of different silicon-based anode contents and achieving a comprehensive improvement in battery performance.

[0023] In some embodiments, the lithium salt includes a first lithium salt, which includes one or more of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide. Based on the total mass of the electrolyte being 100%, the mass percentage of the first lithium salt is 10%-30%.

[0024] Specifically, among the aforementioned first lithium salts, lithium hexafluorophosphate is used as an example. It exhibits excellent dissociation ability in organic solvents, providing sufficient lithium-ion carriers for the electrolyte and ensuring ion transport efficiency during battery charging and discharging. This concentration range allows the electrolyte's ionic conductivity to remain at a high level, avoiding viscosity increases caused by insufficient ion concentration due to excessively low lithium salt concentration or excessively high concentration. Simultaneously, the synergistic effect of the first lithium salt with the wetting agent and silicon-based anode optimizes interface stability. For instance, the dissociated lithium ions interact with wetting agent molecules to form a uniform SEI film on the electrode surface, suppressing interfacial side reactions caused by silicon-based material expansion and reducing electrolyte consumption and lithium plating. In addition, the mass percentage of the first lithium salt in this range can balance the electrochemical stability and ion conduction performance of the electrolyte. Under the premise of ensuring that the lithium salt does not decompose during battery cycling, it ensures the rapid migration of lithium ions in the pores of the silicon-based negative electrode, thereby improving the cycle life and rate performance of the battery.

[0025] The mass percentage of the first lithium salt is 10%, 15%, 20%, 25%, or 30%.

[0026] In some embodiments, a second lithium salt may be added to the lithium salt in the electrolyte. If a second lithium salt is added, the second lithium salt may include one or more of lithium difluorooxalate borate, lithium difluorodioxalate phosphate, lithium tetrafluoroborate, lithium difluorophosphate, and lithium bis(oxalate borate). Specifically, the lithium difluorooxalate borate can form a stable SEI film rich in LiF and Li2CO3 on the surface of the silicon-based anode, which can suppress interface rupture caused by the volume expansion of silicon-based materials, reduce electrolyte penetration and consumption, and improve battery rate performance.

[0027] Based on the total mass of the electrolyte as 100%, the mass percentage of the second lithium salt is 0-7%. In addition, the content range of the second lithium salt of 0-7% can be adapted to the interface requirements of different silicon-based anode contents (5%-30%). By precisely controlling the composition and thickness of the SEI film, the electrolyte consumption and lithium plating phenomenon during the cycling process are reduced, thereby achieving synergistic optimization of battery cycle performance and energy density.

[0028] In some embodiments, the organic solvent includes one or more of ethylene carbonate, propylene carbonate, diethyl carbonate, methyl ethyl carbonate, dimethyl carbonate, ethyl propionate, propyl propionate, ethyl fluorocarbonate, methyl ethyl fluorocarbonate, dimethyl fluorocarbonate, propylene fluorocarbonate, γ-butyrolactone, sulfolane, methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, n-butyl acetate, isobutyl acetate, n-amyl acetate, isoamyl acetate, methyl propionate, methyl butyrate, n-ethyl butyrate, methyl acrylate, and ethyl acrylate. Based on the total mass of the electrolyte being 100%, the mass percentage of the organic solvent is 20%-80%.

[0029] Specifically, the aforementioned organic solvents, when properly proportioned, can form a solvent system that combines low viscosity and high dielectric constant. For example, when ethylene carbonate and dimethyl carbonate are combined, the high dielectric constant of ethylene carbonate can promote the dissociation of lithium salts, while dimethyl carbonate can reduce the viscosity of the system and enhance the permeability of the electrolyte in the pore structure after the expansion of the silicon-based negative electrode, especially improving the wetting uniformity of the bend area and head of square or cylindrical batteries. The introduction of fluorinated organic solvents such as fluoromethyl ethyl carbonate can reduce the surface tension of the electrolyte through the electronegativity of fluorine atoms, and synergistically enhance the wetting effect of the electrode interface with the wetting agent, while improving the antioxidant stability of the electrolyte.

[0030] An organic solvent content of 20%-80% by mass can balance the ion conductivity and chemical stability of the solvent, avoiding problems such as insufficient solubility of lithium salt due to too low organic solvent content or increased viscosity due to too high organic solvent content, thus ensuring rapid migration of lithium ions in the pores of silicon-based anodes.

[0031] In some embodiments, the additive further includes other additives, including one or more of the following: fluoroethylene carbonate, vinylene carbonate, 1,3-propanesulfonate lactone, vinyl sulfate, succinate, adiponitrile, 1,3,6-hexanetrionitrile, propylene sulfonate lactone, methanedisulfonate, ethylene glycol bis(propionitrile) ether, pentafluoroethoxyphosphazene, dicyclohexylcarbonyl, trimethyl imide phosphate, and hexamethylene diisocyanate. Based on the total mass of the electrolyte being 100%, the mass percentage of the other additives is 10%-30%.

[0032] The aforementioned additives can synergistically optimize electrolyte performance with wetting agents and lithium salts. Specifically, for example, fluoroethylene carbonate can form a stable SEI film containing LiF on the surface of silicon-based anodes, inhibiting interfacial rupture caused by the volume expansion of silicon-based materials and reducing electrolyte permeation consumption; vinylene carbonate can participate in the initial construction of the SEI film, improving the interfacial mechanical strength to adapt to the expansion deformation of silicon-based materials; nitrile additives such as succinate can reduce electrolyte viscosity and improve its wetting and permeation efficiency in complex structures such as electrode bends and heads, while accelerating ion migration through coordination with lithium ions; the combined use of different additives can exert a synergistic effect. For example, when vinyl sulfate is compounded with 1,3-propanesulfonate lactone, it can enhance the ion conductivity of the SEI film and suppress side reactions by forming a dense protective layer.

[0033] In some embodiments, the positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material, which includes at least one of lithium cobalt oxide, nickel-cobalt-manganese ternary materials, lithium iron phosphate, and lithium manganese oxide.

[0034] In some embodiments, the negative electrode active material further includes at least one of graphite, silicon, and silicon oxides.

[0035] When any one or more of the above-mentioned anode active materials are selected, the energy density of the battery can be improved by taking advantage of the high theoretical specific capacity of these materials, while the volume expansion problem can be optimized by the composite structure with silicon carbide. Specifically, silicon oxides can adjust the lattice spacing through oxygen atoms, thus alleviating the volume expansion stress during silicon lithium intercalation. In addition, these materials have a significant synergistic effect with the wetting agents in the electrolyte. Fluorine-containing wetting agents can quickly penetrate into the pores of the expanded silicon-based materials to form a stable interface layer, inhibiting the rupture of the SEI film and electrolyte consumption caused by volume changes. The combined use of different negative electrode active materials can also improve the overall performance through complementary advantages, achieving a balance between high specific capacity and structural stability.

[0036] In some embodiments, the lithium-ion battery includes a square wound battery or a cylindrical wound battery.

[0037] Specifically, when the lithium-ion battery provided in this application is a square wound battery or a cylindrical wound battery, the square wound structure is easy to set according to different device sizes, has high space utilization, and by optimizing the electrode winding tension, the dead corner of electrolyte wetting caused by the expansion of silicon negative electrode in the bend area can be reduced. Combined with the role of the wetting agent in the electrolyte in this application, the wetting uniformity of this area can be further improved. The cylindrical wound structure, thanks to the mechanical strength of the steel shell encapsulation, can alleviate the stress caused by the expansion of the silicon anode in the head region through structural design. When working in synergy with fluorinated ether wetting agents, it can reduce the wetting resistance at the complex structure of the head and reduce the phenomenon of lithium plating during cycling.

[0038] The present invention will be further illustrated by the following examples.

[0039] Table 1 Example 1 This embodiment illustrates the lithium-ion battery disclosed in this invention, and includes the following operational steps: Preparation of positive electrode The positive electrode active material lithium cobalt oxide (LCO), conductive agent CNT, and non-fluorinated binder PVDF are thoroughly mixed in NMP solvent in a certain proportion. This slurry is coated onto aluminum foil with a safety primer. After drying, cold pressing, slitting, sheet forming, welding of tabs, and adhesive bonding, a positive electrode that meets the winding requirements is produced.

[0040] Preparation of negative electrode A negative electrode slurry is prepared by adding the negative electrode active material (graphite and carbon-coated silicon material), binder (SBR-CMC), and conductive agent (carbon black) to water as a solvent. This slurry is then coated onto a Cu foil negative electrode current collector. After drying, cold pressing, slitting, sheet forming, welding of tabs, and adhesive bonding, a negative electrode that meets the winding requirements is produced. The compaction density of the negative electrode sheet is 1.75 g / cm³. 3 .

[0041] Preparation of electrolyte In an argon-filled glove box (moisture <1 ppm, oxygen <1 ppm), ethylene carbonate (EC), diethyl carbonate (DEC), and propyl propionate (PP) are mixed in a ratio of 2:3:5 to form a homogeneous solvent. Then, LiPF6, 1% AND, 2% SN, 3% HTCN, 12% FEC, and 4% PS (based on the total mass of the electrolyte) and a wetting agent are slowly added and stirred until homogeneous to obtain the desired lithium-ion battery electrolyte.

[0042] Manufacturing of lithium-ion batteries The above-mentioned positive electrode sheet, separator, and negative electrode sheet are wound to obtain a bare cell. The bare cell is then placed in a pre-punched aluminum-plastic film to complete the top and side sealing. After high-temperature baking, electrolytes from different experimental groups are injected, followed by processes such as settling, formation, capacity testing, and detection to complete the manufacturing of the lithium-ion battery.

[0043] Examples 2-16 This embodiment is used to illustrate the lithium-ion battery disclosed in this invention, including most of the following operating steps in Embodiment 1, with the difference being: The types of wetting agents, percentage content of wetting agents, percentage content of silicon carbide in the negative electrode active material, percentage content of the first lithium salt, and percentage content of the second lithium salt in Examples 2-16 are all based on the corresponding parameters set in Table 1.

[0044] Comparative Examples 1-4 Comparative Examples 1-4 are used to illustrate the lithium-ion battery disclosed in this invention, including most of the following operational steps in Example 1, with the following differences: The types of wetting agents, percentage content of wetting agents, percentage content of silicon carbide in the negative electrode active material, percentage content of the first lithium salt, and percentage content of the second lithium salt in Comparative Examples 1 to 4 are all based on the corresponding parameters set in Table 1.

[0045] Performance testing The following performance tests were performed on Examples 1-16 and Comparative Examples 1-4 prepared above: The aged full cells obtained from the above examples and comparative examples were placed in a 25-degree constant temperature chamber for 1C charge-discharge cycles, with a charge-discharge voltage range of 4.53V-3.0V. The cycle capacity after 500 cycles was recorded. The electrode was disassembled after 500 cycles to observe its lithium plating. The lithium plating levels are ranked from 1 to 10, with level 1 being no lithium plating at all and level 10 being severe lithium plating. The higher the level, the more severe the lithium plating.

[0046] The test results are entered into Table 2.

[0047] Figure 1-4 The figures show the disassembled electrode sheets of Embodiment 1 and Comparative Example 1 of this application. Figure 1 and Figure 3 No lithium plating issues were observed in any of the samples provided in this application, whereas the comparative samples provided in this application... Figure 2 and Figure 4 Lithium plating problems of varying degrees were observed in the negative electrode sheets of all of them.

[0048] Table 2 As can be seen from the test results in Table 2, the test results of Examples 1-16 are all better than those of Comparative Examples 1-4. In Examples 1-16, the compound shown in Formula 1 and / or fluorinated ether compounds were added as wetting agents, and the dosage of the wetting agent and the content of silicon carbide in the negative electrode active material were within the limits of this application. That is, it is beneficial to improve the cycle performance of lithium-ion batteries and suppress lithium plating. In Examples 1-3, different wetting agents were used. The test results of Examples 1-3 show that, whether the wetting agent is used alone or in combination, it can effectively reduce the surface tension between the electrolyte and the electrode and improve the problem of poor electrode wetting under the above parameter conditions, thereby ensuring the battery cycle performance and inhibiting lithium plating. In Examples 4-9, different amounts of wetting agent were added. The test results from Examples 4-9 show that when the wetting agent content was 3%-12% (Examples 5-8), the capacity retention rate reached 91.4%-92.3%, and the lithium plating grade was Grade 1 (no lithium plating at all), indicating optimal performance. When the wetting agent content was 1% (Example 4) and 15% (Example 9), the capacity retention rate slightly decreased to 89.7% and 88.9%, respectively, and the lithium plating grade increased to Grade 2 (slight lithium plating), but it was still far superior to Comparative Examples 1-2 (capacity retention rate 62.5%-65.7%, lithium plating grade 8-9) with a wetting agent content exceeding 15%. This indicates that the amount of wetting agent added within the range of 1%-15% can effectively improve wetting and ensure battery performance. In Examples 10-13, different amounts of silicon carbide were added. When the silicon carbide content was 5%-20% (Examples 10-12), the capacity retention rate reached 91.9%-93.4%, and the lithium plating grade was 1-2, showing excellent performance. This indicates that silicon carbide in this range can play a role without causing poor wetting due to excessive expansion. When the silicon carbide content increased to 30% (Example 13), the capacity retention rate dropped to 89.9%, and the lithium plating grade increased to 3 (slight lithium plating). Although the performance declined slightly, it was still far better than the comparative examples without the wetting agent specified in this application. This shows that under the specified wetting agent system, the basic performance of the battery can be guaranteed when the silicon carbide content is controlled within the range of 5%-30%. Among them, 5%-20% silicon carbide can be regarded as a further preferred range. In Examples 14-16, different amounts of lithium salt were added. Compared to Examples 14-15, Example 16 also added various wetting agents. The test results show that, under the condition of 10% silicon carbide content in the negative electrode, Example 14 (20% first lithium salt + 0.5% second lithium salt) and Example 15 (30% first lithium salt + 7% second lithium salt) achieved capacity retention rates of 90.5% and 88.5% respectively after 500 cycles at 25°C, with lithium plating grades of 1-2. Example 16 used a 5% wetting agent composed of 1,2,3-trifluorotoluene (compound of formula 1) + BTFE (fluoroether compound), 10% silicon carbide in the negative electrode, 10% first lithium salt, and no second lithium salt. The capacity retention rate was 89.2%, with a lithium plating grade of 1. The performance of all three examples in Examples 14-16 is at a high level. Although there are slight differences compared to some examples with low lithium salt content or single wetting agent, they are still superior to the comparative examples. The results above show that the lithium-ion battery provided in this application can effectively reduce the surface tension between the electrolyte and the electrode when the compound shown in Formula 1 and / or fluorinated ether compounds are added as wetting agents in the electrolyte, thereby improving the problem of poor electrode wetting. By further adjusting the mass percentage content of the wetting agent and the negative electrode active material, the interface stability and ion transport efficiency can be balanced.

[0049] 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 negative electrode, a positive electrode, and an electrolyte. The negative electrode includes a negative electrode active layer, the negative electrode active layer includes a negative electrode active material, and the negative electrode active material includes silicon carbide. The electrolyte includes an organic solvent, a lithium salt, and additives, the additives including a wetting agent; In the negative electrode active material, the mass percentage of silicon carbide is 5%-30%; Based on the total mass of the electrolyte being 100%, the mass percentage of the wetting agent A is 1%-15%; The wetting agent includes compounds represented by Formula 1 and / or fluoroether compounds; The compound represented by Formula 1 is shown below: ， Among them, A, B, C, X, Y, and Z can each be independently selected from H, F, or CH3.

2. The lithium-ion battery according to claim 1, characterized in that, The compounds represented by Formula 1 include one or more of fluorobenzene, 1,2,3-trifluorotoluene, 1,3,5-trifluorotoluene, and methylbenzene.

3. The lithium-ion battery according to claim 1, characterized in that, The fluoroether compounds include one or more of 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, methyl nonafluorobutyl ether, and bis(2,2,2-trifluoroethyl) ether.

4. The lithium-ion battery according to claim 1, characterized in that, The compacted density of the negative electrode sheet is 1.65~1.85 g / cm³. 3 .

5. The lithium-ion battery according to claim 1, characterized in that, The lithium salt includes a first lithium salt, which includes one or more of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide. Based on the total mass of the electrolyte being 100%, the mass percentage of the first lithium salt is 10%-30%.

6. The lithium-ion battery according to claim 1, characterized in that, The lithium salt further includes a second lithium salt, which includes one or more of lithium difluorooxalate borate, lithium difluorodioxalate phosphate, lithium tetrafluoroborate, lithium difluorophosphate, and lithium dioxalate borate. Based on the total mass of the electrolyte being 100%, the mass percentage of the second lithium salt is 0-7%.

7. The lithium-ion battery according to claim 1, characterized in that, The organic solvent includes one or more of the following: ethylene carbonate, propylene carbonate, diethyl carbonate, methyl ethyl carbonate, dimethyl carbonate, ethyl propionate, propyl propionate, ethyl fluorocarbonate, methyl ethyl fluorocarbonate, dimethyl fluorocarbonate, propylene fluorocarbonate, γ-butyrolactone, sulfolane, methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, n-butyl acetate, isobutyl acetate, n-amyl acetate, isoamyl acetate, methyl propionate, methyl butyrate, n-ethyl butyrate, methyl acrylate, and ethyl acrylate. Based on the total mass of the electrolyte being 100%, the mass percentage of the organic solvent is 20%-80%.

8. The lithium-ion battery according to claim 1, characterized in that, The additives also include other additives, including one or more of the following: fluoroethylene carbonate, vinylene carbonate, 1,3-propanesulfonate lactone, vinyl sulfate, succinate, adiponitrile, 1,3,6-hexanetrionitrile, propylene sulfonate lactone, methanedisulfonate, ethylene glycol bis(propionitrile) ether, pentafluoroethoxyphosphazene, dicyclohexylcarbonyl, trimethyl imide phosphate, and hexamethylene diisocyanate. Based on the total mass of the electrolyte being 100%, the mass percentage of the other additives is 10%-30%.

9. The lithium-ion battery according to claim 1, characterized in that, The positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material, which includes at least one of lithium cobalt oxide, nickel-cobalt-manganese ternary materials, lithium iron phosphate, and lithium manganese oxide.

10. The lithium-ion battery according to claim 1, characterized in that, The negative electrode active material also includes at least one of graphite, silicon, and silicon oxides.

11. The lithium-ion battery according to claim 1, characterized in that, The lithium-ion battery includes a square wound battery or a cylindrical wound battery.

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