Lithium ion battery

Abstract

The application discloses a lithium ion battery, which comprises a positive electrode sheet, a diaphragm, a negative electrode sheet and an electrolyte; the negative electrode sheet comprises a negative electrode active material, and the electrolyte comprises a solvent and a lithium salt; the negative electrode active material is graphite, the graphite surface sweep Raman value R50 is C; the solvent comprises an aliphatic carboxylic ester and a carbonate, the aliphatic carboxylic ester accounts for A in the mass fraction of the electrolyte, and the lithium salt comprises a fluorine-containing anion conductive lithium salt and a film-forming functional lithium salt, the film-forming functional lithium salt accounts for B in the mass fraction of the electrolyte. The film-forming functional lithium salt can form a CEI film and a SEI film rich in inorganic components on the surfaces of the positive electrode and the negative electrode, inhibit the continuous decomposition of the electrolyte, improve the high-temperature performance of the battery, and through the synergistic effect of the negative electrode and the electrolyte, the lithium ion battery has the 4C fast charging performance, and meanwhile, the high-temperature performance and the cycle stability are considered.

Description

Technical Field

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

[0002] To mitigate the impacts of climate change and air pollution, the widespread application of lithium-ion batteries in pure electric vehicles is accelerating. Compared to traditional gasoline vehicles, range anxiety and long charging times are major obstacles to the development of electric vehicles. Therefore, improving fast charging capabilities has become a common development goal for battery manufacturers and vehicle manufacturers, making the fast-charging performance of lithium-ion batteries a research hotspot. However, improving fast-charging performance often leads to a significant reduction in cycle life and high-temperature performance; that is, improving fast-charging performance often affects cycle and high-temperature performance, resulting in a shorter battery lifespan and impacting the user experience. To address this issue, existing technologies that address similar problems include:

[0003] The patent publication document CN119400932A discloses a fast-charging lithium-ion battery and its preparation method. The prepared lithium-ion battery has excellent rate capability and cycle capability. By modifying the negative electrode material, optimizing the formula, areal density, compaction optimization, and electrolyte optimization, a scientific match of material composition and ratio is established. The resulting fast-charging long-cycle lithium-ion battery has an energy density of 176Wh / Kg, a room temperature cycle capability of more than 5000 cycles, a rate capability of more than 2C, and a fast-charging cycle life of more than 3000 cycles, effectively improving the problem of insufficient rate capability and cycle capability of lithium iron phosphate batteries.

[0004] Patent publication CN118553914A discloses a fast-charging lithium-ion battery, its preparation method, and its application. The positive electrode of the lithium-ion battery includes lithium iron phosphate and a positive electrode additive; the positive electrode additive includes at least one of lithium iron phosphate, lithium oxalate, and lithium squaric acid; the electrolyte of the lithium-ion battery includes a solvent, a lithium salt, and an electrolyte additive; the solvent includes a low-viscosity solvent with a viscosity ≤0.5 cps; the electrolyte additive includes carbonate additives, sulfur-containing additives, and lithium salt additives, effectively improving the fast-charging performance and low-temperature performance of the lithium iron phosphate battery without causing a decrease in battery cycle performance and high-temperature performance.

[0005] The patent publication document with the publication number CN115148983A proposes to control the amorphous carbon coating amount Ta of the positive electrode active material to be 0.5% - 5%, and the amorphous carbon coating amount Tb of the negative electrode active material to be 0.5% - 10%, and satisfy the following relational expression: 0.05 ≤ Ta / Tb ≤ 10. By designing the appropriate amorphous carbon coating amounts on the surfaces of the positive and negative electrode materials, the lithium ions have better insertion and extraction capabilities during charge and discharge, and the appropriate carbon coating amount balances the kinetics and high-temperature performance of the materials, improving the fast charging and high-temperature performance of the overall material system. Summary of the Invention

[0006] The purpose of the present invention is to overcome the deficiencies and defects of the prior art and provide a lithium-ion battery that takes into account the cycle, high-temperature performance, and fast charging performance of the battery cell.

[0007] The present invention is realized through the following technical solutions:

[0008] A lithium-ion battery, the lithium-ion battery includes a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte; the negative electrode sheet includes a negative electrode active material, and the electrolyte includes a solvent, a lithium salt, and an additive; the negative electrode active material is graphite, and the Raman value R50 of the graphite surface scan is C; the solvent includes a first solvent and a second solvent, the first solvent uses an aliphatic carboxylic acid ester, the second solvent uses a carbonate, the mass fraction of the first solvent in the electrolyte is A, the lithium salt includes a first lithium salt and a second lithium salt, the first lithium salt uses a fluorine-containing anion conductive lithium salt, the second lithium salt uses a film-forming functional lithium salt, the mass fraction of the second lithium salt in the electrolyte is B, and the lithium-ion battery satisfies the conditions:

[0009] 0.1 * (0.1C + 0.02A) < B < 0.1 * (0.3C + 0.02A), and C is greater than 0.3.

[0010] In an optional solution, the graphite of the negative electrode active material is at least one of artificial graphite and natural graphite.

[0011] In an optional solution, the particle size of the negative electrode active material satisfies:

[0012] 3μm ≤ D10 ≤ 8μm, preferably 4μm ≤ D10 ≤ 7μm;

[0013] 8μm ≤ D50 ≤ 17μm, preferably, 9μm ≤ D50 ≤ 14μm;

[0014] 18μm ≤ D90 ≤ 40μm, preferably, 20μm ≤ D90 ≤ 35μm.

[0015] In an optional solution, the OI value of the negative electrode active material is between 1 and 9, preferably between 2 and 6.

[0016] In an optional embodiment, the graphitization degree of the negative electrode active material is 85%-95%, preferably 90%-93%.

[0017] In an optional scheme, the surface scan Raman value of the graphite is between 0.1 and 0.8, and the corresponding value R50 of the cumulative surface scan Raman distribution of the graphite powder is C.

[0018] In an optional embodiment, the first solvent is a C3-06 aliphatic carboxylic acid ester, selected from at least one of methyl formate, ethyl formate, ethyl acetate, methyl acetate, propyl formate, and methyl propionate; preferably, the second solvent is selected from at least one of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate; preferably, the first lithium salt is selected from at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethyl)sulfonyl)imide; preferably, the second lithium salt is selected from at least one of LiODFB, LiODFP, and LiPO2F2.

[0019] In an optional embodiment, the weight ratio of the solvent to the lithium salt is 100:(9-72), preferably 100:(21-49).

[0020] Preferably, the weight ratio of the first solvent to the second solvent is (30-70):(70-30);

[0021] Preferably, the weight ratio of the first lithium salt to the second lithium salt is 100:(0-25), and more preferably 100:(2-15);

[0022] In an optional embodiment, the content of the first lithium salt in the electrolyte is 8%-14%.

[0023] Preferably, the content of the second lithium salt in the electrolyte is 0.1%-2.0%, more preferably 0.3%-1.3%.

[0024] In an optional embodiment, the additive is selected from at least one of vinylene carbonate, fluoroethylene carbonate, vinyl sulfate, vinyl sulfite, methane disulfonate, tris(trimethylsilane) phosphate, and polystyrene; preferably, the additive content in the electrolyte is not higher than 8%.

[0025] The negative electrode active material disclosed in this invention has a strong ability to accept lithium ions, which helps to improve the lithium ion insertion and extraction rate in the positive and negative electrodes, reduce the occurrence of lithium plating side reactions, and improve the fast charging performance of the battery cell. The lithium salt additive in the electrolyte can improve the interface stability and kinetic performance of the battery, giving it better cycle stability and high-temperature performance, reducing the side reactions between carboxylic acid ester solvents and low OI value graphite, and improving the lifespan and high-temperature performance of the battery cell.

[0026] In the lithium-ion battery of the present invention, the second lithium salt can form CEI and SEI films rich in inorganic components on the surfaces of the positive and negative electrodes, inhibit the continuous decomposition of the electrolyte, improve the high-temperature performance of the battery, and through the synergistic effect of the negative electrode and the electrolyte, enable the lithium-ion battery to have 4C fast charging performance while taking into account high-temperature performance and cycle stability. Detailed Embodiments

[0027] The present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0028] In an exemplary embodiment of the present application, the lithium-ion battery includes a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte. The negative electrode sheet includes a negative electrode active material, a binder, a conductive agent, and a copper foil. The negative electrode active material is graphite, and the Raman value R50 of the graphite surface scan is C.

[0029] Among them, the electrolyte of the lithium-ion battery includes a solvent, a lithium salt, and an electrolyte additive. The electrolyte solvent includes a first solvent and a second solvent. The first solvent is an aliphatic carboxylic acid ester, and the second solvent is a carbonate. The mass fraction of the first solvent in the electrolyte is A. The lithium salt includes a first lithium salt and a second lithium salt. The first lithium salt is a fluorine-containing anion conductive lithium salt, and the second lithium salt is a film-forming functional lithium salt. The mass fraction of the second lithium salt in the electrolyte is B. The lithium-ion battery satisfies the condition: 0.1*(0.1C + 0.02A) < B < 0.1*(0.3C + 0.02A), and C is greater than 0.3. The second lithium salt can form CEI and SEI films rich in inorganic components on the surfaces of the positive and negative electrodes, inhibit the continuous decomposition of the electrolyte, improve the high-temperature performance of the battery, so that the lithium-ion battery of the present invention has both 4C fast charging performance, storage performance, and cycle stability.

[0030] In an optional embodiment, the first solvent is a C3-06 aliphatic carboxylic acid ester, including methyl formate, ethyl formate, ethyl acetate, methyl acetate, propyl formate, methyl propionate, etc. The second solvent includes ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, etc.; the mass fraction of the first solvent in the electrolyte is A.

[0031] In an optional embodiment, the first lithium salt includes lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, etc., and the second lithium salt includes LiODFB, LiODFP, LiPO2F2, etc. The mass fraction of the second lithium salt in the electrolyte is B.

[0032] In some optional embodiments, in the electrolyte, the weight ratio of the solvent to the lithium salt is 100:(9 - 72), preferably 100:(21 - 49).

[0033] In some optional embodiments, the weight ratio of the first solvent and the second solvent in the electrolyte is (30-70):(70-30).

[0034] In some optional embodiments, the weight ratio of the first lithium salt and the second lithium salt in the electrolyte is 100:(0-25), preferably 100:(2-15).

[0035] In some alternative embodiments, the content of the first lithium salt is 8%-14%.

[0036] In some alternative embodiments, the content of the second lithium salt is 0.1%-2.0%, preferably 0.3%-1.3%.

[0037] In some alternative embodiments, the additive is selected from any one or more of vinylene carbonate, fluoroethylene carbonate, vinyl sulfate, vinyl sulfite, methane disulfonate, tris(trimethylsilane) phosphate, and polystyrene. The electrolyte additive content shall not exceed 8%.

[0038] In some alternative implementations, the negative electrode active material is one or more of artificial graphite and natural graphite.

[0039] In some optional embodiments, the particle size of the negative electrode active material is 3μm≤D10≤8μm, preferably 4μm≤D10≤7μm, 8μm≤D50≤17μm, preferably 9μm≤D50≤14μm, 18μm≤D90≤40μm, and preferably 20μm≤D90≤35μm.

[0040] In some alternative embodiments, the OI value of the negative electrode active material is between 1 and 9, preferably between 2 and 6.

[0041] In some optional embodiments, the graphitization degree of the negative electrode active material is 85%-95%, preferably 90%-93%. The surface scan Raman value of the graphite surface is between 0.1 and 0.8, and the value R50 corresponding to 50% of the surface scan Raman cumulative distribution of the graphite powder is C, wherein the C value is greater than 0.3.

[0042] The negative electrode active material, conductive agent, and binder are mixed and uniformly coated onto copper foil, then dried to form a negative electrode sheet. In some optional embodiments, the coating amount of the negative electrode sheet is 15-18 mg / cm³. 2 The compacted density is 1.4-1.7 g / cm³. 3 The preferred concentration is 1.4-1.6 g / cm³. 3 .

[0043] In some optional embodiments, the positive electrode active material is lithium iron phosphate, with a particle size of 0.2 μm ≤ D10 ≤ 0.6 μm, preferably 0.3 μm ≤ D10 ≤ 0.4 μm; 0.6 μm ≤ D50 ≤ 1.8 μm, preferably 0.7 μm ≤ D50 ≤ 1.3 μm; a carbon content of 0.8%-1.7%, preferably 1%-1.5%; and a specific surface area of ​​9 m². 2 / g-16m 2 / g, preferably 11m 2 / g-14m 2 / g.

[0044] Preparation of lithium-ion batteries.

[0045] Preparation of positive electrode:

[0046] Lithium iron phosphate (LFP), conductive carbon black Super-P, carbon nanotubes (CNT), and polyvinylidene fluoride (PVDF) binder are mixed in NMP at a weight ratio of 90%:2%:3%:5% to form a lithium iron phosphate cathode slurry. After thorough stirring and viscosity adjustment, a uniformly mixed cathode slurry with a solid content of 65% is obtained. The lithium iron phosphate cathode slurry is coated on both sides of a current collector aluminum foil according to a set double-sided surface density to form an electrode sheet at a coating speed of 5 m / min. The electrode sheets are then placed in an oven for drying. The dried cathode sheets are then rolled according to the designed compaction density to obtain a lithium iron phosphate cathode electrode sheet.

[0047] Preparation of negative electrode:

[0048] A graphite slurry is formed by mixing graphite, conductive carbon black, CMC binder, and SBR binder in water at a weight ratio of 94%:2%:1.5%:2.5%. After thorough stirring and viscosity adjustment, a uniformly mixed negative electrode slurry with a solid content of 55% is obtained. The graphite slurry is then coated onto both sides of a current collector copper foil at a double-sided density to form an electrode sheet at a coating speed of 8 m / min. The electrode sheets are then sequentially placed in an oven for drying. After drying, the negative electrode sheets are rolled according to the designed compaction density to obtain a graphite negative electrode sheet.

[0049] The electrolyte contains organic solvents, lithium salts, and additives. The organic solvents in the electrolyte include a first solvent and a second solvent, with the organic solvent content being 80%. The lithium salts include a first lithium salt and a second lithium salt. The first lithium salt contains lithium hexafluorophosphate (LiPF6) and lithium difluorosulfonyl imide (LiFSI), and the second lithium salt is lithium difluorophosphate (LiPO2F2). The content of additives in the electrolyte is no more than 8%.

[0050] The diaphragm is a polyethylene diaphragm with ceramic coating on one side and adhesive on the other.

[0051] Battery manufacturing:

[0052] A dry cell is fabricated by stacking positive electrode plates, a separator, and a negative electrode plates, with the separator located between the positive and negative electrode plates. Electrolyte is injected into the dry cell according to a fixed injection ratio. After processes such as settling, formation, secondary sealing, and capacity testing, a lithium-ion battery is obtained.

[0053] Cell experiments were conducted on the prepared lithium-ion batteries, including high-temperature storage at 60℃, room temperature cycling, and room temperature fast charging cycling tests.

[0054] 60℃ High-Temperature Storage: The lithium-ion battery was charged and discharged three times at 0.33C at room temperature (25℃), with a voltage range of 2.0V-3.65V. The average of the three discharge capacities was recorded as the initial capacity C0 before high-temperature storage. The battery was then charged at a constant current of 0.33C to 3.65V and then at a constant voltage of 0.05C. The 100% SOC battery was then stored in a 60℃ high-temperature chamber for 30 days. After 30 days, the battery was removed and placed at room temperature for 8 hours. It was then discharged at 0.33C to 2V, and the discharge capacity was recorded as the residual capacity C1. The battery was then charged at 0.33C to 3.65V and then at a constant voltage of 0.05C. Finally, it was discharged at 0.33C to 2V, and the discharge capacity was recorded as the recovered capacity C2. The residual capacity rate is C1 / C0*100%, and the recovered capacity rate is C2 / C0*100%.

[0055] Room temperature cycling: The lithium-ion battery was charged at 25℃ at 1C to 3.65V, then switched to constant voltage charging with a cutoff current of 0.05C. After resting for 30 minutes, it was discharged at 1C constant current to 2V, and the discharge capacity was recorded as C0. The battery was cycled through 1C constant current and constant voltage charging to 3.65V, and constant current discharging to 2V, with the discharge capacity recorded as C1. The capacity retention rate during room temperature cycling was C1 / C0*100%.

[0056] Room temperature fast charging cycle: The lithium-ion battery is charged at 25℃ at an average of 4C to 3.65V, then switched to constant voltage charging with a cutoff current of 0.05C. After resting for 30 minutes, it is discharged at 1C constant current to 2V, and the discharge capacity is recorded as C0. The battery is cycled through 4C constant current and constant voltage charging to 3.65V, and constant current discharging to 2V, with the discharge capacity recorded as C1. The room temperature cycle capacity retention rate is C1 / C0*100%.

[0057] Based on the aforementioned battery fabrication, examples of different electrolyte and negative electrode active material combinations are provided.

[0058] Example 1

[0059] An electrolyte is provided, comprising a first solvent, a second solvent, a first lithium salt, and a second lithium salt, wherein the first solvent is ethyl acetate (EA) with a content of 40%, the second solvent is a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) in a 50%:50% ratio; the first lithium salt is LiPF6 and LiFSI, and the second lithium salt is LiPO2F2 with a content of 1.0%. A negative electrode active material, graphite, is also provided, with a Raman surface scan R50 of 0.45.

[0060] Example 2

[0061] An electrolyte is provided, comprising a first solvent, a second solvent, a first lithium salt, and a second lithium salt, wherein the first solvent is ethyl acetate (EA) with a content of 40%, the second solvent is a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) in a 50%:50% ratio; the first lithium salt is LiPF6 and LiFSI, and the second lithium salt is LiPO2F2 with a content of 1.3%; and a negative electrode active material, graphite, is provided with a Raman surface scan R50 of 0.45.

[0062] Example 3

[0063] An electrolyte is provided, comprising a first solvent, a second solvent, a first lithium salt, and a second lithium salt, wherein the first solvent is ethyl acetate (EA) with a content of 40%, the second solvent is a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) in a 50%:50% ratio; the first lithium salt is LiPF6 and LiFSI, and the second lithium salt is LiPO2F2 with a content of 0.7%; and a negative electrode active material, graphite, is provided with a Raman surface scan R50 of 0.45.

[0064] Example 4

[0065] An electrolyte is provided, comprising a first solvent, a second solvent, a first lithium salt, and a second lithium salt, wherein the first solvent is ethyl acetate (EA) with a content of 50%, the second solvent is a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) in a 50%:50% ratio; the first lithium salt is LiPF6 and LiFSI, and the second lithium salt is LiPO2F2 with a content of 1.0%; and a negative electrode active material, graphite, is provided with a Raman surface scan R50 of 0.45.

[0066] Example 5

[0067] An electrolyte is provided, comprising a first solvent, a second solvent, a first lithium salt, and a second lithium salt, wherein the first solvent is ethyl acetate (EA) with a content of 60%, the second solvent is a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) in a 50%:50% ratio; the first lithium salt is LiPF6 and LiFSI, and the second lithium salt is LiPO2F2 with a content of 1.0%; and a negative electrode active material, graphite, is provided with a Raman surface scan R50 of 0.45.

[0068] Comparative Example 1

[0069] An electrolyte is provided, comprising a first solvent, a second solvent, a first lithium salt, and a second lithium salt, wherein the first solvent is ethyl acetate (EA) with a content of 40%, the second solvent is a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) in a 50%:50% ratio; the first lithium salt is LiPF6 and LiFSI, and the second lithium salt is LiPO2F2 with a content of 1.00%; and a negative electrode active material, graphite, is provided with a Raman surface scan R50 of 0.15.

[0070] Comparative Example 2

[0071] An electrolyte is provided, comprising a first solvent, a second solvent, a first lithium salt, and a second lithium salt, wherein the first solvent is ethyl acetate (EA) with a content of 40%, the second solvent is a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) in a 50%:50% ratio; the first lithium salt is LiPF6 and LiFSI, and the second lithium salt is LiPO2F2 with a content of 1.00%; and a negative electrode active material, graphite, is provided with a Raman surface scan R50 of 0.25.

[0072] Comparative Example 3

[0073] An electrolyte is provided, comprising a first solvent, a second solvent, a first lithium salt, and a second lithium salt, wherein the first solvent is ethyl acetate (EA) with a content of 40%, the second solvent is a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) in a 50%:50% ratio; the first lithium salt is LiPF6 and LiFSI, and the second lithium salt is LiPO2F2 with a content of 0.4%; and a negative electrode active material, graphite, is provided with a Raman surface scan R50 of 0.45.

[0074] Comparative Example 4

[0075] An electrolyte is provided, comprising a first solvent, a second solvent, a first lithium salt, and a second lithium salt, wherein the first solvent is ethyl acetate (EA) with a content of 40%, the second solvent is a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) in a 50%:50% ratio; the first lithium salt is LiPF6 and LiFSI, and the second lithium salt is LiPO2F2 with a content of 1.6%; and a negative electrode active material, graphite, is provided with a Raman surface scan R50 of 0.45.

[0076] The experimental data are shown in the table below:

[0077] <![CDATA[B (% content of LiPO2F2)]]> A (EA content %) C (Negative electrode defect degree R50) Recovery rate of storage at 60℃ 25℃ cycle 25℃ 4C fast charging cycle Example 1 1.00% 0.4 0.45 95.02% 300 laps @ 99.10% 100 laps @ 98.53% Example 2 1.30% 0.4 0.45 95.28% 300 laps @ 99.42% 100 laps @ 98.79% Example 3 0.70% 0.4 0.45 94.85% 300 laps @ 98.78% 100 laps @ 98.25% Example 4 1.00% 0.5 0.45 94.83% 300 laps @ 98.60% 100 laps @ 98.65% Example 5 1.00% 0.6 0.45 94.65% 300 laps @ 98.42% 100 laps @ 98.72% Comparative Example 1 1.00% 0.4 0.15 94.89% 300 laps @ 98.26% 100 laps @ 95.04% Comparative Example 2 1.00% 0.4 0.25 94.75% 300 laps @ 97.89% 100 laps @ 95.83% Comparative Example 3 0.40% 0.4 0.45 94.10% 300 laps @ 96.68% 100 laps @ 96.75% Comparative Example 4 1.60% 0.4 0.45 94.87% 300 laps @ 97.13% 100 laps @ 96.56%

[0078] Adding lithium difluorophosphate to the electrolyte can improve the high-temperature performance of the battery and enhance cycle stability by increasing the inorganic components in the positive / negative electrode interface film. However, lithium difluorophosphate has low solubility in the electrolyte system; increasing the amount added leads to a sharp increase in electrolyte viscosity and a decrease in electrolyte conductivity, affecting fast-charging performance. Ethyl acetate solvent in the electrolyte has low viscosity and high conductivity, but it is easily reduced on the negative electrode side, resulting in poor high-temperature performance. Increasing the ethyl acetate content affects high-temperature storage and cycle stability. Increasing the Raman value of the graphite negative electrode can improve lithium-ion diffusion performance and enhance the high-current charge-discharge performance of graphite materials.

[0079] In summary, experimental data demonstrate that the lithium-ion battery proposed in this invention, through optimization of the negative electrode and electrolyte, meets the requirements of 4C and above fast charging cycles, with a fast charging cycle life exceeding 2500 cycles and a storage recovery rate of over 95% at 60℃. The fast charging and high-temperature performance of the lithium iron phosphate battery is improved by controlling the Raman value of the graphite negative electrode material, the first solvent of the electrolyte, and the lithium salt additive in the electrolyte, while ensuring the battery's cycle stability. Furthermore, by controlling the Raman value of the graphite negative electrode material, the first solvent of the electrolyte, and the lithium salt additive in the electrolyte, the kinetics and high-temperature performance of the materials are balanced, improving the overall fast charging and high-temperature performance of the material system while ensuring the battery's cycle stability.

[0080] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, the embodiments should be regarded as exemplary and non-limiting in all respects. The scope of the present invention is defined by the appended claims rather than the foregoing description, and therefore all changes falling within the meaning and scope of the equivalents of the claims are intended to be included within the present invention.

[0081] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A lithium-ion battery, comprising a positive electrode, a separator, a negative electrode, and an electrolyte; wherein the negative electrode comprises a negative electrode active material, and the electrolyte comprises a solvent, a lithium salt, and additives; characterized in that, The negative electrode active material is graphite, and the surface Raman value R50 of the graphite is C; the solvent includes a first solvent and a second solvent. The first solvent is an aliphatic carboxylic acid ester, and the second solvent is a carbonate. The mass fraction of the first solvent in the electrolyte is A. The lithium salt includes a first lithium salt and a second lithium salt. The first lithium salt is a lithium salt with a fluorine-containing anion conductor, and the second lithium salt is a film-forming functional lithium salt. The mass fraction of the second lithium salt in the electrolyte is B. The lithium-ion battery satisfies the condition: 0.1*(0.1C + 0.02A) < B < 0.1*(0.3C + 0.02A), and C is greater than 0.

3.

2. The lithium-ion battery according to claim 1, characterized in that, The graphite of the negative electrode active material is at least one of artificial graphite and natural graphite.

3. The lithium-ion battery according to claim 1, characterized in that, The particle size of the negative electrode active material satisfies: 3μm ≤ D10 ≤ 8μm, preferably 4μm ≤ D10 ≤ 7μm; 8μm ≤ D50 ≤ 17μm, preferably 9μm ≤ D50 ≤ 14μm; 18μm ≤ D90 ≤ 40μm, preferably 20μm ≤ D90 ≤ 35μm.

4. The lithium-ion battery according to claim 1, characterized in that, The OI value of the negative electrode active material is between 1 and 9, preferably 2 - 6.

5. The lithium-ion battery according to claim 1, characterized in that, The graphitization degree of the negative electrode active material is between 85% and 95%, preferably 90% - 93%.

6. The lithium-ion battery according to claim 1, characterized in that, The surface Raman value of the graphite is between 0.1 and 7. The lithium-ion battery according to claim 1, characterized in that, ​ 8. The lithium-ion battery according to claim 1, characterized in that, ​ 9. The lithium-ion battery according to claim 1, characterized in that, ​ ​ ​ ​ 10. The lithium-ion battery according to claim 1, characterized in that, ​