A high-temperature fast-charging lithium-ion battery

Abstract

This invention belongs to the field of lithium-ion battery technology, specifically relating to a high-temperature fast-charging lithium-ion battery, comprising a positive electrode, a negative electrode, an electrolyte, and a separator. The negative electrode comprises graphite, conductive carbon black, conductive slurry, a thickener, and a binder; the graphite is a composite of isoprismatic coke secondary particles and coal-based needle coke single particles, with the isoprismatic coke secondary particles accounting for 30-70% of the total weight of the composite, and the isotropic ratio of the isoprismatic coke secondary particles being 20-80%. At least one component of the isoprismatic coke secondary particles and the coal-based needle coke single particles is surface-coated with carbon. This invention addresses both the negative electrode and the electrolyte, and through the synergistic effect of the negative electrode and the electrolyte, significantly improves the high-temperature fast-charging performance of the lithium-ion battery, while also improving its kinetic performance and cycle life.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a high-temperature fast-charging lithium-ion battery. Background Technology

[0002] Under pressure from the energy crisis and environmental pollution, safety, environmental protection, and energy conservation have become the themes of automotive development. New energy vehicles, due to their energy-saving, environmentally friendly, and pollution-free advantages, have received high attention and strong support from transportation and energy departments. The power battery, as a key component of new energy vehicles, plays a crucial role. As the power source for electric vehicles, the power battery is a critical component. In recent years, the high price and short driving range of power batteries have made improving energy density, fast charging performance, high-temperature safety performance, and cost reduction the goals of the lithium battery industry. Currently, the fast charging performance and high-temperature performance of lithium-ion batteries cannot be perfectly balanced, which remains one of the constraints on the industry's development. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a high-temperature fast-charging lithium-ion battery.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A high-temperature fast-charging lithium-ion battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. The negative electrode comprises graphite, conductive carbon black, conductive slurry, thickener, and binder. The weight ratio of the graphite, conductive carbon black, conductive slurry, thickener, and binder is 93–98:0.2–0.5:0.2–0.5:0.5–1.5:1–2.

[0006] The graphite is a composite of isoprismatic coke secondary particles and coal-based needle coke single particles. The weight of the isoprismatic coke secondary particles accounts for 30-70% of the total weight of the composite, and the isotropic ratio of the isoprismatic coke secondary particles is 20-80%. At least one component of the isoprismatic coke secondary particles and the coal-based needle coke single particles is coated with carbon on its surface.

[0007] In a preferred example, the surface carbon coating is an organic polymer liquid phase coating.

[0008] In a preferred example, the conductive carbon black has an oil absorption value greater than 350 ml·g. -1 The specific surface area of ​​the conductive carbon black is greater than 100 μm. 2 ·g -1 ;

[0009] In a preferred embodiment, the conductive paste is a paste formed by mixing carbon nanotubes and graphene.

[0010] In a preferred example, the thickener is surface hemiacetal-modified carboxymethyl cellulose-Li.

[0011] In a preferred embodiment, the adhesive comprises lithium acrylate and styrene-butadiene rubber, wherein the lithium acrylate accounts for 30-70% of the total weight of the adhesive.

[0012] In a preferred embodiment, the electrolyte comprises a solvent, an electrolyte lithium salt, and additives, wherein the solvent comprises EC, DMC, PP, and EMC, and the sum of the volumes of DMC and PP accounts for 10-40% of the total volume of the solvent.

[0013] In a preferred example, the electrolyte lithium salt is a mixture of LiPF6 and LiFSI, wherein the weight of LiFSI accounts for 10-50% of the total weight of the mixture, and the concentration of the electrolyte lithium salt in the electrolyte is 1-1.2 mol / L.

[0014] In a preferred embodiment, the additive is a blend of VC, FEC, MMDS, DTD, LiPO2F2 and FB, wherein the weight of VC accounts for 1.5 to 2.5% of the total weight of the blend, the sum of the weights of FEC, MMDS, DTD and LiPO2F2 accounts for 1 to 5% of the total weight of the blend, and the weight of FB accounts for 0.5 to 2% of the total weight of the blend.

[0015] Compared with existing technologies, this invention addresses both the negative electrode and the electrolyte, significantly improving the high-temperature fast-charging performance of lithium-ion batteries through the synergistic effect of the two components, while also enhancing kinetic performance and cycle life. Specifically, it utilizes isotropic coke and coal-based needle coke, combining single and secondary particles with a surface organic polymer liquid phase coating, thereby improving both kinetic and cycle performance. The use of CMC-Li reduces internal resistance, improving kinetic performance and reducing polarization, thus further enhancing cycle performance. Modified lithium acrylate and styrene-butadiene rubber composites improve both kinetic and binding properties. The electrolyte enhances liquid absorption and reduces SEI impedance, while maintaining high-temperature performance, thereby improving the cell's rate performance and high-temperature cycle performance. The combined action of graphite, binder, and electrolyte improves the high-temperature fast-charging performance of lithium-ion batteries. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is further described in conjunction with specific embodiments. However, this invention is not limited to these embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments. In this invention, unless otherwise specified, all parts and percentages are units of mass, and the equipment and raw materials used are commercially available or commonly used in the art. Unless otherwise specified, the methods in the following embodiments are conventional methods in the art.

[0017] The terms “comprising,” “including,” “containing,” or any other variations thereof, as used herein, are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0018] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1 to 5” is disclosed, the described range should be interpreted as including the ranges “1 to 4”, “1 to 3”, “1 to 2”, “1 to 2 and 4 to 5”, “1 to 3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0019] Example 1

[0020] A high-temperature fast-charging lithium-ion battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. The negative electrode comprises graphite, conductive carbon black, conductive slurry, thickener, and binder, wherein the weight ratio of the graphite, conductive carbon black, conductive slurry, thickener, and binder is 95.6:0.38:0.35:1:1.5.

[0021] The graphite is a composite of isogonal coke secondary particles and coal-based needle coke single particles. The weight of the isogonal coke secondary particles accounts for 50% of the total weight of the composite. The isotropic ratio of the isogonal coke secondary particles is 50%. The isogonal coke secondary particles and coal-based needle coke single particles are respectively coated with surface carbon. The surface carbon coating is an organic polymer liquid phase coating.

[0022] The conductive carbon black has an oil absorption value of 380 ml·g. -1 The specific surface area of ​​the conductive carbon black is 125 μm. 2 ·g -1 ;

[0023] The conductive paste is a paste formed by mixing carbon nanotubes and graphene;

[0024] The thickener is surface-modified hemiacetal carboxymethyl cellulose-Li;

[0025] The adhesive comprises lithium acrylate and styrene-butadiene rubber, wherein the weight of lithium acrylate accounts for 50% of the total weight of the adhesive;

[0026] The electrolyte includes a solvent, an electrolyte lithium salt, and additives. The solvent is a mixture of EC, DMC, PP, and EMC, wherein the sum of the volumes of DMC and PP accounts for 25% of the total volume of the solvent.

[0027] The electrolyte lithium salt is a mixture of LiPF6 and LiFSI, wherein the weight of LiFSI accounts for 30% of the total weight of the mixture, and the concentration of the electrolyte lithium salt in the electrolyte is 1.1 mol / L;

[0028] The additive is a blend of VC, FEC, MMDS, DTD, LiPO2F2 and FB, wherein the weight of VC accounts for 2.2% of the total weight of the blend, the sum of the weights of FEC, MMDS, DTD and LiPO2F2 accounts for 3% of the total weight of the blend, and the weight of FB accounts for 1.2% of the total weight of the blend.

[0029] The positive electrode uses existing technology, coating the surface of a 20μm aluminum foil with lithium iron phosphate slurry, and forming a positive electrode sheet through rolling and die cutting. The lithium iron phosphate slurry is made by mixing lithium iron phosphate, Ketjen black, single-walled carbon nanotubes and binder PVDF with solvent NMP in a ratio of 98:0.5:1:1. Celgard 2400 membrane is selected as the separator. The positive and negative electrode sheets are rolled and laser-cut, and then wound, assembled, baked, injected with electrolyte, formed and capacity tested with the separator to obtain a 25Ah soft-pack thick electrode lithium-ion battery. The electrolyte used for injection is prepared by dissolving LiPF6 (1.2mol / L concentration) and additive VC (1%) in a mixed solvent of PC (propylene carbonate) / EC (ethylene carbonate) / DMC (dimethyl carbonate) = 3:1:2 (volume ratio) to form the electrolyte.

[0030] For ease of description, C represents the rated capacity of the battery (Ah), and I represents the current, with the value of I equal to C (A). A battery in its empty state is charged at a constant current of 0.5I (A) to the upper limit voltage (V), and then charged at that voltage at a constant voltage until the cutoff current (A) is less than or equal to 0.05I. The resulting charging capacity (Ah) is J. A battery in its empty state is charged at a constant current of 3I (A) to the upper limit voltage (V), and then charged at that voltage at a constant voltage until the cutoff current (A) is less than or equal to I. The resulting charging capacity (Ah) is K. A battery in its empty state is charged at a constant current of 3I (A) to the upper limit voltage (V), and then charged at that voltage at a constant voltage until the upper limit voltage is reached. This charging process lasts for 20 minutes, followed by constant current discharge at I (A) to the lower limit voltage (V). This process is considered one cycle.

[0031] The test results are as follows:

[0032] (1) The mass energy density of a single cell is 282Wh / kg, and the volumetric energy density of a single cell is 529Wh / L.

[0033] (2) The temperature probe is placed at the geometric center of the largest surface of the battery. The battery is charged from an empty state with a constant current of 3I (A) to the upper limit voltage (V). After reaching the upper limit voltage, it is charged with a constant voltage of that voltage. The charging process lasts for 20 minutes. During this period, the difference between the highest temperature of the probe and the starting temperature at which the recording begins is 15℃.

[0034] (3) In the first cycle, K / J > 0.858;

[0035] (4) In the 10th cycle, K / J > 0.846;

[0036] (5) In the 100th cycle, K / J > 0.834;

[0037] (6) In the 200th cycle, K / J > 0.822;

[0038] (7) In the 300th cycle, K / J>0.811.

[0039] Example 2

[0040] A high-temperature fast-charging lithium-ion battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. The negative electrode comprises graphite, conductive carbon black, conductive slurry, thickener, and binder, wherein the weight ratio of the graphite, conductive carbon black, conductive slurry, thickener, and binder is 98:0.2:0.5:0.5:2.

[0041] The graphite is a composite of isogonal coke secondary particles and coal-based needle coke single particles. The weight of the isogonal coke secondary particles accounts for 70% of the total weight of the composite. The isotropic ratio of the isogonal coke secondary particles is 20%. The isogonal coke secondary particles are coated with carbon on their surface. The carbon coating is an organic polymer liquid phase coating.

[0042] The conductive carbon black has an oil absorption value of 420 ml·g. -1 The specific surface area of ​​the conductive carbon black is 135 μm. 2 ·g -1 ;

[0043] The conductive paste is a paste formed by mixing carbon nanotubes and graphene;

[0044] The thickener is surface-modified hemiacetal carboxymethyl cellulose-Li;

[0045] The adhesive comprises lithium acrylate and styrene-butadiene rubber, wherein the weight of lithium acrylate accounts for 70% of the total weight of the adhesive;

[0046] The electrolyte includes a solvent, an electrolyte lithium salt, and additives. The solvent is a mixture of EC, DMC, PP, and EMC, wherein the sum of the volumes of DMC and PP accounts for 10% of the total volume of the solvent.

[0047] The electrolyte lithium salt is a mixture of LiPF6 and LiFSI, wherein the weight of LiFSI accounts for 50% of the total weight of the mixture, and the concentration of the electrolyte lithium salt in the electrolyte is 1 mol / L;

[0048] The additive is a blend of VC, FEC, MMDS, DTD, LiPO2F2 and FB, wherein the weight of VC accounts for 2.5% of the total weight of the blend, the sum of the weights of FEC, MMDS, DTD and LiPO2F2 accounts for 1% of the total weight of the blend, and the weight of FB accounts for 2% of the total weight of the blend.

[0049] The positive electrode uses existing technology, coating the surface of a 20μm aluminum foil with lithium iron phosphate slurry, and forming a positive electrode sheet through rolling and die cutting. The lithium iron phosphate slurry is made by mixing lithium iron phosphate, Ketjen black, single-walled carbon nanotubes and binder PVDF with solvent NMP in a ratio of 98:0.5:1:1. Celgard 2400 membrane is selected as the separator. The positive and negative electrode sheets are rolled and laser-cut, and then wound, assembled, baked, injected with electrolyte, formed and capacity tested with the separator to obtain a 25Ah soft-pack thick electrode lithium-ion battery. The electrolyte used for injection is prepared by dissolving LiPF6 (1.2mol / L concentration) and additive VC (1%) in a mixed solvent of PC (propylene carbonate) / EC (ethylene carbonate) / DMC (dimethyl carbonate) = 3:1:2 (volume ratio) to form the electrolyte.

[0050] For ease of description, C represents the rated capacity of the battery (Ah), and I represents the current, with the value of I equal to C (A). A battery in its empty state is charged at a constant current of 0.5I (A) to the upper limit voltage (V), and then charged at that voltage at a constant voltage until the cutoff current (A) is less than or equal to 0.05I. The resulting charging capacity (Ah) is J. A battery in its empty state is charged at a constant current of 3I (A) to the upper limit voltage (V), and then charged at that voltage at a constant voltage until the cutoff current (A) is less than or equal to I. The resulting charging capacity (Ah) is K. A battery in its empty state is charged at a constant current of 3I (A) to the upper limit voltage (V), and then charged at that voltage at a constant voltage until the upper limit voltage is reached. This charging process lasts for 20 minutes, followed by constant current discharge at I (A) to the lower limit voltage (V). This process is considered one cycle.

[0051] The test results are as follows:

[0052] (1) The mass energy density of a single cell is 281Wh / kg, and the volumetric energy density of a single cell is 527Wh / L.

[0053] (2) The temperature probe is placed at the geometric center of the largest surface of the battery. The battery is charged from an empty state with a constant current of 3I (A) to the upper limit voltage (V). After reaching the upper limit voltage, it is charged with a constant voltage of that voltage. The charging process lasts for 20 minutes. During this period, the difference between the highest temperature of the probe and the starting temperature at which the recording begins is 15℃.

[0054] (3) In the first cycle, K / J > 0.858;

[0055] (4) In the 10th cycle, K / J > 0.846;

[0056] (5) In the 100th cycle, K / J > 0.834;

[0057] (6) In the 200th cycle, K / J > 0.822;

[0058] (7) In the 300th cycle, K / J>0.811.

[0059] Example 3

[0060] A high-temperature fast-charging lithium-ion battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. The negative electrode comprises graphite, conductive carbon black, conductive slurry, thickener, and binder, wherein the weight ratio of the graphite, conductive carbon black, conductive slurry, thickener, and binder is 93:0.5:0.2:1.5:2.

[0061] The graphite is a composite of isoprismatic coke secondary particles and coal-based needle coke single particles. The weight of the isoprismatic coke secondary particles accounts for 30% of the total weight of the composite. The isotropic ratio of the isoprismatic coke secondary particles is 80%. The coal-based needle coke single particles are coated with surface carbon, and the surface carbon coating is an organic polymer liquid phase coating.

[0062] The conductive carbon black has an oil absorption value of 360 ml·g. -1 The specific surface area of ​​the conductive carbon black is 105 μm. 2 ·g -1 ;

[0063] The conductive paste is a paste formed by mixing carbon nanotubes and graphene;

[0064] The thickener is surface-modified hemiacetal carboxymethyl cellulose-Li;

[0065] The adhesive comprises lithium acrylate and styrene-butadiene rubber, wherein the weight of lithium acrylate accounts for 30% of the total weight of the adhesive;

[0066] The electrolyte includes a solvent, an electrolyte lithium salt, and additives. The solvent is a mixture of EC, DMC, PP, and EMC, wherein the sum of the volumes of DMC and PP accounts for 40% of the total volume of the solvent.

[0067] The electrolyte lithium salt is a mixture of LiPF6 and LiFSI, wherein the weight of LiFSI accounts for 10% of the total weight of the mixture, and the concentration of the electrolyte lithium salt in the electrolyte is 1.2 mol / L;

[0068] The additive is a blend of VC, FEC, MMDS, DTD, LiPO2F2 and FB, wherein the weight of VC accounts for 1.5% of the total weight of the blend, the sum of the weights of FEC, MMDS, DTD and LiPO2F2 accounts for 5% of the total weight of the blend, and the weight of FB accounts for 0.5% of the total weight of the blend.

[0069] The positive electrode uses existing technology, coating the surface of a 20μm aluminum foil with lithium iron phosphate slurry, and forming a positive electrode sheet through rolling and die cutting. The lithium iron phosphate slurry is made by mixing lithium iron phosphate, Ketjen black, single-walled carbon nanotubes and binder PVDF with solvent NMP in a ratio of 98:0.5:1:1. Celgard 2400 membrane is selected as the separator. The positive and negative electrode sheets are rolled and laser-cut, and then wound, assembled, baked, injected with electrolyte, formed and capacity tested with the separator to obtain a 25Ah soft-pack thick electrode lithium-ion battery. The electrolyte used for injection is prepared by dissolving LiPF6 (1.2mol / L concentration) and additive VC (1%) in a mixed solvent of PC (propylene carbonate) / EC (ethylene carbonate) / DMC (dimethyl carbonate) = 3:1:2 (volume ratio) to form the electrolyte.

[0070] For ease of description, C represents the rated capacity of the battery (Ah), and I represents the current, with the value of I equal to C (A). A battery in its empty state is charged at a constant current of 0.5I (A) to the upper limit voltage (V), and then charged at that voltage at a constant voltage until the cutoff current (A) is less than or equal to 0.05I. The resulting charging capacity (Ah) is J. A battery in its empty state is charged at a constant current of 3I (A) to the upper limit voltage (V), and then charged at that voltage at a constant voltage until the cutoff current (A) is less than or equal to I. The resulting charging capacity (Ah) is K. A battery in its empty state is charged at a constant current of 3I (A) to the upper limit voltage (V), and then charged at that voltage at a constant voltage until the upper limit voltage is reached. This charging process lasts for 20 minutes, followed by constant current discharge at I (A) to the lower limit voltage (V). This process is considered one cycle.

[0071] The test results are as follows:

[0072] (1) The mass energy density of a single cell is 280Wh / kg, and the volume energy density of a single cell is 526Wh / L.

[0073] (2) The temperature probe is placed at the geometric center of the largest surface of the battery. The battery is charged from an empty state with a constant current of 3I (A) to the upper limit voltage (V). After reaching the upper limit voltage, it is charged with a constant voltage of that voltage. The charging process lasts for 20 minutes. During this period, the difference between the highest temperature of the probe and the starting temperature at which the recording begins is 15℃.

[0074] (3) In the first cycle, K / J > 0.858;

[0075] (4) In the 10th cycle, K / J > 0.846;

[0076] (5) In the 100th cycle, K / J > 0.834;

[0077] (6) In the 200th cycle, K / J > 0.822;

[0078] (7) In the 300th cycle, K / J>0.811.

[0079] As can be seen from the above, the mass energy density of the single battery cell in this invention is not less than 280Wh / kg, and the volumetric energy density is greater than 525Wh / L.

[0080] The battery can be charged to more than 85% of its rated capacity in 20 minutes when it is in a depleted state. The battery is charged from a depleted state with a constant current of 3I (A) to the upper limit voltage (V). After reaching the upper limit voltage, it is charged with a constant voltage of that voltage for 20 minutes. The maximum temperature rise of the battery surface during the entire process is less than 30°C. When the battery has undergone 300 20-minute fast charging cycles, the battery capacity can still reach more than 75% of its initial capacity. The battery's 20-minute fast charging cycle life is more than 1000 cycles.

[0081] This demonstrates that the present invention has good fast charging capability and maintains good cycle stability even under fast charging conditions.

[0082] Comparative Example 1

[0083] Unlike Example 1, the weight of the iso-square coke secondary particles accounts for 28% of the total weight of the composite.

[0084] Comparative Example 2

[0085] Unlike Example 1, this one does not contain a thickener; the negative electrode comprises graphite, conductive carbon black, conductive slurry, and a binder, wherein the weight ratio of the graphite, conductive carbon black, conductive slurry, and binder is 96.8:0.5:05:2.2.

[0086] Comparative Example 3

[0087] Unlike Example 1, the binder is styrene-butadiene rubber (SBR); the negative electrode includes graphite, conductive carbon black, conductive slurry, thickener, and binder, with a weight ratio of 96.8:0.5:05:1.2:1.

[0088] Comparative Example 4

[0089] The oil absorption value of conductive carbon black is 350 ml·g -1 The conductive carbon black has a specific surface area of ​​100 μm. 2 ·g -1 Other factors are the same as in Example 1.

[0090] Comparative Example 5

[0091] The difference from Example 1 is the preparation of the electrolyte:

[0092] LiPF6 (1 mol / L concentration) and additive VC (1%) were dissolved in a mixed solvent of PC (propylene carbonate) / EC (ethylene carbonate) / DMC (dimethyl carbonate) = 1:1:1 (volume ratio) to form an electrolyte.

[0093] Test case

[0094] (1) Room temperature cycling performance test

[0095] At 25℃, the capacity-balanced lithium-ion battery was charged to 3.65V using a 1C constant current and constant voltage method, with a cutoff current of 0.05C, and then discharged to 2.5V using a 1C constant current method. The capacity retention rate was calculated after 1000 charge / discharge cycles. The calculation formula is as follows:

[0096] Capacity retention rate at week 1000 = (Cyclic discharge capacity at week 1000 / Cyclic discharge capacity at week 1) × 100%

[0097] (2) 55℃ high temperature cycling performance test

[0098] The lithium-ion battery, after capacity gradation, was placed in a 55℃ environment and charged at a constant current and constant voltage of 1C to 3.65V, with a cutoff current of 0.05C. Then, it was discharged at a constant current of 1C to 2.5V. The capacity retention rate was calculated after 500 charge / discharge cycles. The calculation formula is as follows:

[0099] Capacity retention rate at week 500 (%) = Week 500 cycle discharge capacity / Week 1 cycle discharge capacity × 100%

[0100] (3) Fast charging performance test

[0101] The test results of the lithium-ion battery cycle performance and thermal insulation rate performance of each embodiment and comparative example are as follows:

[0102] Table 1. Battery cycle performance test results of Examples 1-3 and Comparative Examples 1-5

[0103]

[0104] Table 2. Battery thermal insulation rate performance test results of Examples 1-3 and Comparative Examples 1-5

[0105]

[0106]

[0107] Among them, the higher the discharge platform, the lower the temperature rise, and the better the rate discharge performance; the lower the charging platform, the lower the temperature rise, the better the rate charging performance, and the stronger the fast charging effect.

[0108] This invention addresses two main aspects: the negative electrode and the electrolyte. Through the synergistic effect of the negative electrode and the electrolyte, it significantly improves the high-temperature fast-charging performance of lithium-ion batteries, while also enhancing kinetic performance and cycle life. Specifically, it utilizes isotropic coke and coal-based needle coke, combining single and secondary particles with a surface organic polymer liquid phase coating, thereby improving both kinetic and cycle performance. The use of CMC-Li reduces internal resistance, improving kinetic performance and reducing polarization, thus further enhancing cycle performance. Modified lithium acrylate and styrene-butadiene rubber composites improve both kinetic and binding properties. The electrolyte enhances liquid absorption and reduces SEI impedance, while maintaining high-temperature performance, thereby improving the cell's rate performance and high-temperature cycle performance. The combined effect of graphite, binder, and electrolyte improves the high-temperature fast-charging performance of lithium-ion batteries.

[0109] The above embodiments are merely preferred embodiments of the present invention. Any simple modifications, alterations, and substitutions made to the above embodiments based on the technical essence of the present invention shall fall within the scope of the technical solution of the present invention.

Claims

1. A high-temperature fast-charging lithium-ion battery, characterized in that, The device includes a positive electrode, a negative electrode, an electrolyte, and a separator. The negative electrode comprises graphite, conductive carbon black, conductive slurry, a thickener, and a binder, wherein the weight ratio of the graphite, conductive carbon black, conductive slurry, thickener, and binder is 93–98:0.2–0.5:0.2–0.5:0.5–1.5:1–2. The graphite is a composite of isoprismatic coke secondary particles and coal-based needle coke single particles. The weight of the isoprismatic coke secondary particles accounts for 30-70% of the total weight of the composite. The isotropic ratio of the isoprismatic coke secondary particles is 20-80%. At least one component of the isoprismatic coke secondary particles and the coal-based needle coke single particles is coated with surface carbon. The thickener is surface-modified hemiacetal carboxymethyl cellulose-Li; The electrolyte includes a solvent, an electrolyte lithium salt, and additives. The solvent includes EC, DMC, PP, and EMC, wherein the sum of the volumes of DMC and PP accounts for 10-40% of the total volume of the solvent.

2. The high-temperature fast-charging lithium-ion battery according to claim 1, characterized in that, The surface carbon coating is an organic polymer liquid phase coating.

3. A high-temperature fast-charging lithium-ion battery according to claim 1, characterized in that, The conductive carbon black has an oil absorption value greater than 350 ml·g. -1 The specific surface area of ​​the conductive carbon black is greater than 100 μm. 2 ·g -1 .

4. A high-temperature fast-charging lithium-ion battery according to claim 1, characterized in that, The conductive paste is a paste formed by mixing carbon nanotubes and graphene.

5. A high-temperature fast-charging lithium-ion battery according to claim 1, characterized in that, The adhesive comprises lithium acrylate and styrene-butadiene rubber, wherein the weight of lithium acrylate accounts for 30-70% of the total weight of the adhesive.

6. A high-temperature fast-charging lithium-ion battery according to claim 1, characterized in that, The electrolyte lithium salt is a mixture of LiPF6 and LiFSI, wherein the weight of LiFSI accounts for 10-50% of the total weight of the mixture, and the concentration of the electrolyte lithium salt in the electrolyte is 1-1.2 mol / L.

7. A high-temperature fast-charging lithium-ion battery according to claim 1, characterized in that, The additive is a blend of VC, FEC, MMDS, DTD, LiPO2F2 and FB, wherein the weight of VC accounts for 1.5 to 2.5% of the total weight of the blend, the sum of the weights of FEC, MMDS, DTD and LiPO2F2 accounts for 1 to 5% of the total weight of the blend, and the weight of FB accounts for 0.5 to 2% of the total weight of the blend.

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