Battery cell, battery device, and electric device

Abstract

The invention discloses a battery monomer, a battery device and a power utilization device. Each battery monomer comprises a positive pole piece, a negative pole piece and an electrolyte; the electrolyte comprises an organic solvent and an additive, and the organic solvent comprises a carboxylic ester solvent; the additive comprises an ethylene sulfate compound, and the ethylene sulfate compound comprises a compound as shown in the following formula: the # imgabs0 # negative electrode plate comprises a negative electrode current collector and a negative electrode film layer arranged on at least one side of the negative electrode current collector, and the negative electrode film layer comprises a negative electrode active material; the negative electrode active material comprises a core part and a coating layer at least partially coating the surface of the core part, the core part comprises graphite, and in an R value cumulative distribution curve obtained by the negative electrode active material in a surface scanning mode of a laser microscopy confocal Raman spectrometer, an R value R50 with cumulative distribution of 50% is 0.15-0.50. The battery monomer provided by the invention has good dynamic performance and long cycle life.

Description

[0001] This divisional application is based on an invention titled "Battery Cell, Battery Device, and Electrical Device" with the application number 202411606003.X, the filing date of November 12, 2024, the applicant Contemporary Amperex Technology Co., Limited. Technical Field

[0002] This application relates to the technical field of battery cells, and particularly to a battery cell, a battery device, and an electrical device. Background Art

[0003] In recent years, battery cells have been widely used in energy storage power systems such as hydroelectric, thermal, wind, and solar power stations, as well as in multiple fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace.

[0004] With the increasing market demand for the driving range, cycle life, and charging efficiency of electrical devices, higher requirements have also been put forward for the energy density, fast charging performance, cycle life, etc. of battery cells. However, it is difficult to simultaneously improve the above-mentioned performances in the existing technology, which has become a technical problem urgently to be solved in this field. Summary of the Invention

[0005] This application is made in view of the above problems, and its purpose is to provide a battery cell with high energy density, high cycle life, and good fast charging performance.

[0006] In a first aspect of this application, a battery cell is provided. The battery cell includes a positive electrode plate, a negative electrode plate, and an electrolyte; the lithium ion conductivity of the electrolyte is greater than or equal to 10 mS / cm; the negative electrode plate includes a negative electrode current collector and a negative electrode film layer provided on at least one side of the negative electrode current collector. The negative electrode film layer includes a negative electrode active material. The negative electrode active material includes a core and a coating layer at least partially covering the surface of the core. The core includes graphite, and in the R-value cumulative distribution curve obtained in the surface scanning mode of a laser confocal Raman spectrometer for the negative electrode active material, the R-value R50 with a cumulative distribution of 50% is 0.15 - 0.50; among the R-values of the obtained negative electrode active material, the proportion of the R-values less than or equal to 0.11 is less than or equal to 15%.

[0007] The negative electrode active material with the R-value R50 with a cumulative distribution of 50% being 0.15 - 0.50 can not only improve the charge exchange ability of lithium ions on the surface of the negative electrode active material in a high-conductivity electrolyte, making the liquid-phase transport rate and solid-phase transport rate of lithium ions match, improving the kinetic performance of the battery, but also keep the side reactions on the surface of the negative electrode active material at a low level, while taking into account the cycle life of the battery cell.

[0008] In any embodiment, among the R values of the obtained negative electrode active material, the proportion of the number of R values less than or equal to 0.11 is less than or equal to 15%, optionally less than or equal to 10%, and further optionally less than or equal to 6%.

[0009] The R value R50 with a cumulative distribution of 50% of the core graphite generally does not exceed 0.11. Therefore, among all the R values of the obtained negative electrode active material, the proportion of the number of R values less than or equal to 0.11 can be used to represent the degree of uncoating of the negative electrode active material. The smaller this value is, the smaller the degree of uncoating of the negative electrode active material, the higher the surface coating degree of the negative electrode active material, the improvement of the isotropy of ion intercalation, the improvement of the charge exchange ability of ions on the surface of the negative electrode active material, and then the improvement of the solid-liquid transport rate of lithium ions, so as to match with the high-conductivity electrolyte and improve the kinetic performance of the battery. In addition, the small degree of uncoating of the negative electrode active material can also reduce the co-intercalation phenomenon of the electrolyte solvent during the cycle, and then make the battery have better cycle performance.

[0010] In any embodiment, in the R value cumulative distribution curve obtained by the negative electrode active material in the surface scanning mode of a laser confocal Raman spectrometer, the R value R50 with a cumulative distribution of 50% is 0.15 - 0.30, and among the R values of the obtained negative electrode active material, the proportion of the number of R values less than or equal to 0.11 is less than or equal to 10%.

[0011] The negative electrode active material in this embodiment enables the battery cell to have better fast charging performance. The speculated reason may be that the surface disorder degree of the negative electrode active material is in the above range and the coating rate is high, indicating that the isotropy degree on the surface of the negative electrode active material is high, which is beneficial to the uniform intercalation of lithium ions into the core graphite from all directions and is beneficial to the further improvement of the fast charging performance of the battery cell.

[0012] In any embodiment, in the R value cumulative distribution curve obtained by the negative electrode active material in the surface scanning mode of a laser confocal Raman spectrometer, the R value R50 with a cumulative distribution of 50% is 0.30 - 0.50, and among the R values of the obtained negative electrode active material, the proportion of the number of R values less than or equal to 0.11 is less than or equal to 15%.

[0013] The negative electrode active material in this embodiment takes into account low cost, good cycle stability, and improved fast charging performance.

[0014] In any embodiment, the electrolyte includes an organic solvent, and the organic solvent includes one or more of carboxylic ester solvents, nitrile solvents, and carbonate solvents.

[0015] In any embodiment, the carboxylic ester solvent includes one or more of ethyl acetate, methyl acetate, methyl formate, butyl acetate, methyl propionate, ethyl propionate, methyl butyrate, propyl butyrate, butyl butyrate, isopropyl acetate, and isoamyl acetate, and may be one or several of ethyl acetate and methyl acetate; and / or the nitrile solvent includes one or several of acetonitrile, monofluoroacetonitrile, difluoroacetonitrile, and trifluoroacetonitrile; and / or the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0016] The carboxylic ester solvent and / or the nitrile solvent can improve the lithium ion conductivity of the electrolyte and enhance the fast charging performance of the battery cell. The carbonate solvent easily forms a solvation structure with the lithium ions in the lithium-containing electrolyte salt to increase the dissociation rate of the lithium ions and anions in the lithium-containing electrolyte salt, thereby improving the fast charging performance of the battery cell.

[0017] In any embodiment, the organic solvent includes dimethyl carbonate. Based on the total mass of the organic solvent, the mass content of dimethyl carbonate is greater than or equal to 20%, and may be 30%-90%.

[0018] In any embodiment, the organic solvent includes one or more of ethyl acetate and methyl acetate and a carbonate solvent.

[0019] Ethyl acetate and methyl acetate have high conductivity and low gas generation. The combination of ethyl acetate and / or methyl acetate and the carbonate solvent enables the lithium ions in the electrolyte to have both a high dissociation rate and a fast lithium ion transport rate, which is beneficial to improving the kinetic performance of the battery cell while reducing battery gas generation and taking into account the cycle life of the battery.

[0020] In any embodiment, based on the total mass of the organic solvent, the total mass ratio of ethyl acetate and methyl acetate is 5%-80%, and the mass ratio of the carbonate solvent is 5%-90%.

[0021] In any embodiment, the organic solvent includes methyl acetate. Based on the total mass of the organic solvent, the mass content of methyl acetate is 5%-70%, and may be 5%-50%.

[0022] Methyl acetate has higher activity than ethyl acetate. Although the addition of a small amount of it in the electrolyte will slightly sacrifice the life of the battery cell, it can further improve the kinetic performance of the battery cell and further improve the fast charging performance of the battery cell while maintaining the high cycle life of the battery cell.

[0023] In any embodiment, the electrolyte includes an electrolyte salt, and the electrolyte salt includes lithium bis(fluorosulfonyl)imide (LiFSI). Based on the total mass of the electrolyte, the mass content of lithium bis(fluorosulfonyl)imide is 3% - 10%.

[0024] Lithium bis(fluorosulfonyl)imide is prone to dissociation in the electrolyte solvent, which is beneficial to improving the kinetics of the battery cell, reducing the internal resistance of the battery, and improving the fast charging performance of the battery. However, lithium bis(fluorosulfonyl)imide is prone to 6 undergoing side reactions with LiC formed during the deep lithium insertion process at the negative electrode, reducing the reversible lithium capacity, and being unfavorable for maintaining the capacity of the battery cell during cycling. When the mass content of lithium bis(fluorosulfonyl)imide (LiFSI) in the electrolyte is within the above range, the cycle life of the battery cell can be further improved on the basis of considering the fast charging performance of the battery cell.

[0025] In any embodiment, based on the total mass of the electrolyte salt, the mass content of lithium bis(fluorosulfonyl)imide (LiFSI) is 20% - 80%, and may be optionally 30% - 70%.

[0026] The electrolyte with lithium bis(fluorosulfonyl)imide within the above mass range can not only improve the fast charging performance of the battery, but also keep the side reaction with the negative electrode material at a reasonable level, comprehensively improving the cycle life of the battery.

[0027] In any embodiment, the battery cell includes a stacked electrode cell. The positive electrode plate includes a positive current collector, and the positive current collector includes a positive current collecting portion and positive electrode tabs provided on at least one side of the side surface of the positive current collecting portion. The width of the positive current collecting portion is 60 mm - 110 mm, and may be optionally 62 mm - 98 mm.

[0028] The width of the positive current collecting portion within the above range is beneficial to reducing the maximum distance between the tab and the edge of the positive current collecting portion, which can not only reduce the electron transmission distance, improve the fast charging performance of the battery, but also reduce the phenomenon of inconsistent temperature rise of the current collecting portion during fast charging, reduce the temperature gradient on the current collecting portion, and reduce the probability of the active material at the high-temperature rise part being inactivated first, improving the fast charging cycle life of the battery, and also taking into account the energy density of the battery.

[0029] In any embodiment, the length of the positive current collecting portion in the stacked electrode cell is 100 mm - 700 mm, and may be optionally 200 mm - 600 mm.

[0030] The length of the positive current collecting portion in the stacked electrode cell within the above range can further reduce the electron transmission distance on the current collector, improve the phenomenon of inconsistent temperature rise during the fast charging process of the battery cell, and improve the fast charging cycle life of the battery cell.

[0031] In any embodiment, the electrolyte includes a first additive, and the first additive includes one or more of fluorophosphates and borates.

[0032] In any embodiment, the fluorophosphate includes one or more of monofluorophosphate and difluorophosphate; the fluorophosphate includes an alkali metal, and may be one or more of lithium salt, sodium salt, and potassium salt.

[0033] In any embodiment, the borate includes at least one of tetrafluoroborate, bis(oxalato)borate, and fluorinated oxalato borate; the borate includes an alkali metal, and may be one or more of lithium salt, sodium salt, and potassium salt.

[0034] In any embodiment, the electrolyte includes a second additive, and the second additive includes one or more of sulfonate compounds and vinylene sulfate compounds.

[0035] In any embodiment, the vinylene sulfate compound includes

[0036] one or more of; and / or the sulfonate compound includes at least one of.

[0037] The second additive in the electrolyte is liable to form a film on the negative electrode, can simultaneously generate inorganic components and organic components in the SEI film, reduce the degree of side reactions of carboxylate solvents on the negative electrode, and improve the cycle life of the battery.

[0038] In any embodiment, the air oxidation temperature T 0 of the negative electrode active material is 630°C to 730°C, where the air oxidation temperature T 0 is the temperature corresponding to the intersection of two tangents at two points corresponding to 500°C and T 1 temperature on the thermogravimetric curve of the negative electrode active material, and the T 1 temperature is the peak temperature of the maximum area peak in the differential thermogravimetric curve of the negative electrode active material. The thermogravimetric curve and the differential thermogravimetric curve can be obtained by thermogravimetric analysis under the following conditions: sample mass 10 ± 0.05 mg, purge gas is air, gas flow rate is 60 mL / min, heating rate is 5°C / min, and test temperature range is 35°C to 950°C.

[0039] Air oxidation temperature T 0The negative electrode active material at 630 °C to 730 °C has an appropriate number of surface defects, provides sufficient end faces for the insertion of active ions, matches the lithium ion transport rate of the electrolyte, and keeps the side reaction degree of the battery cell within a controllable range. Therefore, the battery cell can have improved fast charging performance while maintaining high energy density and cycle life.

[0040] In any embodiment, the core of the negative electrode active material is a secondary particle formed by the aggregation of primary graphite particles, the coating layer of the negative electrode active material includes amorphous carbon, and the negative electrode active material further includes kinetic carbon material; the layer spacing d of the (002) crystal plane of the kinetic carbon material 002 > 0.335 nm, and can be selected from 0.3355 nm to 0.337 nm.

[0041] In any embodiment, the kinetic carbon material includes one or more of hard carbon, expanded graphite, and graphene.

[0042] In any embodiment, the kinetic carbon material is located in the core and / or the coating layer.

[0043] The negative electrode active material including the above kinetic carbon material can improve the insertion and extraction rates of active ions, thereby enhancing the transport performance of active ions and electrons, and further improving the fast charging performance of the battery cell on the basis of maintaining high energy density. At the same time, amorphous carbon has high hardness, so it also has good compressive resistance, has a strong ability to maintain the pore structure of the negative electrode film layer during cycling, and has better electrolyte wettability of the negative electrode sheet. Therefore, it is also beneficial to improve the cycle performance of the battery cell.

[0044] In any embodiment, based on the total mass of the negative electrode active material, the mass percentage of the kinetic carbon material is 1% to 30%, and can be selected from 8% to 15%.

[0045] When the mass percentage of the kinetic carbon material is within a suitable range, the negative electrode active material can have a high specific capacity, a high solid-phase transport ability of active ions, and a high charge exchange rate of active ions and electrons. Furthermore, the battery cell can have improved fast charging performance on the premise of high energy density. At the same time, when the mass percentage of the kinetic carbon material is within a suitable range, it has a better ability to maintain the pore structure of the negative electrode film layer during cycling, better electrolyte wettability of the negative electrode sheet, and the battery cell can also have good cycle performance.

[0046] In any embodiment, the negative electrode active material includes secondary particles formed by the aggregation of primary particles, and the volume distribution particle size Dv50 of the negative electrode active material is 8 μm - 18 μm.

[0047] On the one hand, the negative electrode active material with a volume distribution particle size Dv50 within the above range can utilize a certain number of primary particles in the secondary particles to endow the negative electrode active material with a suitable embedding surface, and the solid-phase transmission rate and solid-liquid transmission rate of active ions in the negative electrode active material can match the liquid-phase transmission rate of lithium ions in the electrolyte, improving the fast charging performance of the battery; on the other hand, it can also have the advantages of large secondary particle size, high tap density, and large capacity, taking into account the energy density of the battery cell while improving the fast charging performance of the battery.

[0048] In any embodiment, the negative electrode active material includes unagglomerated primary particles, and the volume distribution particle size Dv50 of the negative electrode active material is 5 μm - 13 μm.

[0049] The negative electrode active material with a volume distribution particle size Dv50 within the above range has higher interfacial stability compared to small particle size particles, but at the same time has a larger ionic solid-phase transmission distance. By size design, the two can be balanced to achieve both the fast charging performance and cycle life of the battery cell.

[0050] In any embodiment, the core of the negative electrode active material includes artificial graphite.

[0051] Artificial graphite has few defects and high capacity, can reduce the degree of side reactions with the electrolyte, give full play to the high-capacity characteristics of graphite, reduce gas generation, and enable the battery cell to have both high energy density and good cycle performance.

[0052] In any embodiment, the mass of the coating layer is 0.3% - 5% of the mass of the core; and / or the average thickness of the coating layer is 100 nm - 300 nm.

[0053] When the mass ratio or thickness of the coating layer is within the above range, the uniformity of the coating layer can be better, thereby improving the charge exchange ability of ions on the surface of the negative electrode active material; when the mass ratio or thickness of the coating layer is within the above range, the side reactions on the surface of the negative electrode active material particles can also be at a low level, enabling the negative electrode active material to have a high specific capacity. Therefore, when the mass ratio of the coating layer is within the above range, it is beneficial for the battery to have both high energy density, good kinetic performance, and long cycle life.

[0054] In any embodiment, the coating layer is disposed on 90% - 100% of the surface of the core.

[0055] Coating a coating layer on most of the surface of the core can not only provide an end face for the embedding of active ions, but also reduce the contact between the core and the electrolyte, thereby reducing the co-embedding phenomenon of electrolyte solvents during the cycle, and thus taking into account the fast charging performance and cycle performance of the battery cell.

[0056] In any embodiment, the negative electrode film layer includes a first negative electrode film layer disposed on the surface of the negative electrode current collector and a second negative electrode film layer disposed on the side of the first negative electrode film layer away from the negative electrode current collector, and the porosity of the second negative electrode film layer is greater than that of the first negative electrode film layer.

[0057] In the embodiment of the present application, a high-conductivity electrolyte is adopted, and the ion transport rate of the electrolyte is high. By designing that the second negative electrode film layer close to the electrolyte has a relatively large porosity, the transport rate of lithium ions in the electrode plate is matched with the liquid-phase transport rate in the electrolyte, improving the fast charging performance of the battery and reducing the risk of lithium plating; at the same time, a low-porosity design is adopted near the current collector of the negative electrode film layer to take into account the energy density of the battery cell.

[0058] In any embodiment, the first negative electrode film layer includes a first negative electrode active material, and the particle size consistency of the first negative electrode active material is 0.4 to 0.6; the second negative electrode film layer includes a second negative electrode active material, and the particle size consistency of the second negative electrode active material is 0.25 to 0.45.

[0059] The negative electrode active material with a particle size consistency of 0.4 - 0.6 can achieve close packing through the grading of large and small particles, making the first negative electrode film layer have a relatively low porosity; the negative electrode active material with a particle size consistency of 0.25 - 0.45 has a relatively low particle size consistency between particles and is difficult to form an effective match, making the second negative electrode film layer have a relatively high porosity, thereby realizing the hierarchical design of the porosity of the electrode plate.

[0060] In any embodiment, the negative electrode film layer includes a first negative electrode film layer disposed on the surface of the negative electrode current collector and a second negative electrode film layer disposed on the side of the first negative electrode film layer away from the negative electrode current collector, and the powder compaction density of the negative electrode active material in the second negative electrode film layer under a pressure of 50000N is less than the powder compaction density of the negative electrode active material in the first negative electrode film layer under a pressure of 50000N.

[0061] The small powder compaction density of the negative electrode active material in the second negative electrode film layer close to the electrolyte is beneficial to maintaining the pore structure on the side of the negative electrode film layer close to the electrolyte and improving the fast charging performance of the battery cell; at the same time, the large powder compaction density of the negative electrode active material in the first negative electrode film layer far from the electrolyte is beneficial to increasing the compaction density of the negative electrode film layer and taking into account the energy density of the battery cell.

[0062] In any embodiment, the single-sided areal density of the negative electrode film layer is 0.08 g / 1540.25 mm 2 - 0.20 g / 1540.25 mm 2 , and may be optionally 0.10 g / 1540.25 mm 2 - 0.16 g / 1540.25 mm2 .

[0063] The battery cell with the single-sided areal density of the negative electrode film layer within the above range can reduce the transport distance of lithium ions in the negative electrode film layer, which is beneficial to improving the fast charging performance of the battery cell.

[0064] In any embodiment, the negative electrode active material further includes a silicon-based material, and the single-sided areal density of the negative electrode film layer is 0.06 g / 1540.25 mm 2 -0.15 g / 1540.25 mm 2 .

[0065] The silicon-based material has a high specific capacity. The addition of the silicon-based material in the negative electrode film layer further reduces the thickness of the negative electrode film layer corresponding to the battery with the same capacity, that is, the single-sided areal density of the negative electrode film layer is further reduced, which is beneficial to reducing the transport distance of lithium ions in the negative electrode film layer and further improving the fast charging performance of the battery cell.

[0066] In any embodiment, the tap density of the negative electrode plate is 1.2 g / cm 3 -1.9 g / cm 3 , and can be optionally 1.2 g / cm 3 -1.65 g / cm 3 .

[0067] The negative electrode plate with the tap density within the above range has a suitable porosity, can match with the electrolyte having a high conductivity, improve the diffusion rate of lithium ions in the negative electrode, reduce the concentration polarization generated during fast charging of the battery cell, and is beneficial to improving the fast charging performance of the battery cell while taking into account the energy density of the battery cell.

[0068] In any embodiment, the average thickness of the single side of the negative electrode film layer is 30 μm - 150 μm, and can be optionally 30 μm - 80 μm.

[0069] The negative electrode film layer with the average thickness within the above range has a suitable lithium ion diffusion distance, can match with the electrolyte having a high conductivity, improve the diffusion rate of lithium ions in the negative electrode film layer, and improve the fast charging performance of the battery cell while taking into account the energy density of the battery cell.

[0070] In any embodiment, the negative electrode active material further includes a silicon-based material, and the average thickness of the single side of the negative electrode film layer is 30 μm - 80 μm.

[0071] The silicon-based material has a high specific capacity. The addition of the silicon-based material in the negative electrode film layer further reduces the thickness of the negative electrode film layer corresponding to the battery with the same capacity, which is beneficial to reducing the transport distance of lithium ions in the negative electrode film layer and further improving the fast charging performance of the battery cell.

[0072] In any embodiment, the porosity of the negative electrode plate is 20%-60%, and may be optionally 25%-40%.

[0073] The negative electrode plate with the porosity within the above range can be matched with an electrolyte having high conductivity, facilitating the transport of lithium ions at the negative electrode, reducing the concentration polarization generated during fast charging of the battery cell, and being beneficial to improving the fast charging performance of the battery cell while taking into account the energy density of the battery cell.

[0074] In any embodiment, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer provided on at least one side of the positive electrode current collector. The positive electrode film layer includes a positive electrode active material. The positive electrode active material includes a lithium-containing phosphate. The positive electrode active material includes unagglomerated primary particles; and the positive electrode active material satisfies at least one of the following conditions:

[0075] (1) The volume distribution particle size Dv50 of the positive electrode active material 正1 satisfies: 0.3 μm ≤ Dv50 正1 ≤ 2 μm;

[0076] (2) The average particle size of the primary particles of the positive electrode active material satisfies: 50 nm ≤ D 正1 ≤ 300 nm.

[0077] The lithium-containing phosphate with the average particle size of the primary particles within the above range has both a short ion transport path, low lithium ion transport impedance, and low moisture absorption. It can not only match the liquid-phase transport rate of lithium ions in the electrolyte, but also reduce the temperature rise during fast charging of the battery cell, and can also take into account the cycle life of the battery cell by controlling the moisture absorption.

[0078] In any embodiment, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer provided on at least one side of the positive electrode current collector. The positive electrode film layer includes a positive electrode active material. The positive electrode active material contains a lithium-containing transition metal oxide, and the volume distribution particle size Dv50 of the positive electrode active material 正2 satisfies: 2 μm ≤ Dv50 正2 ≤ 15 μm.

[0079] The lithium-containing transition metal oxide of the positive electrode active material with the volume distribution particle size Dv50 正2 within the above range has both a short ion transport path, low lithium ion transport impedance, and a low degree of side reactions. It can not only match the liquid-phase transport rate of lithium ions in the electrolyte, but also reduce the temperature rise during fast charging of the battery cell, and can also take into account the cycle life of the battery cell by reducing the degree of side reactions.

[0080] In any embodiment, the positive electrode active material includes a lithium nickel cobalt manganese oxide, and the Dv50 of the positive electrode active material正2 is 6 μm - 15 μm, optionally 8 μm - 12 μm. The positive electrode active material includes secondary particles formed by aggregation of primary particles, and the average particle size of the primary particles in the secondary particles is 0.1 μm - 1.5 μm.

[0081] In this embodiment, the positive electrode active material mainly includes secondary particles, that is, a powder mainly composed of secondary particles. The secondary particles include many primary particles with small particle sizes, resulting in short lithium ion transmission paths and many embedding end faces, which can match the electrolyte with a relatively high lithium ion transmission rate, and is beneficial to improving the power performance of the battery cell.

[0082] In any embodiment, the positive electrode active material includes lithium nickel cobalt manganese oxide, and the Dv50 of the positive electrode active material 正2 is 2 μm - 5 μm, optionally 2.5 μm - 4.5 μm. The positive electrode active material includes unaggregated primary particles.

[0083] In this embodiment, the positive electrode active material mainly includes unaggregated primary particles, that is, a powder mainly composed of unaggregated primary particles. The side reaction degree of this positive electrode active material with a carboxylic ester solvent with high activity is low, which is beneficial to further improving the cycle life of the battery cell.

[0084] In any embodiment, the positive electrode active material includes lithium nickel cobalt manganese oxide. The particle size distribution curve of the positive electrode active material shows a bimodal distribution, with the peak positions located at 2 μm - 5 μm and 7 μm - 20 μm respectively. The positive electrode active material includes unaggregated primary particles and secondary particles formed by aggregation of primary particles, and the average particle size of the secondary particles is greater than that of the unaggregated primary particles.

[0085] The above positive electrode active material forms a grading through secondary particles mainly with large particle sizes and primary particles mainly with small particle sizes, which further improves the energy density of the battery while taking into account the cycle life and power performance of the battery cell.

[0086] In any embodiment, the positive electrode active material includes lithium nickel cobalt manganese oxide. Based on the total molar amount of transition metals in the positive electrode active material, the molar content ratio of cobalt is less than or equal to 20%, and the Dv50 of the positive electrode active material 正2 is 2 μm - 5 μm. The positive electrode active material includes unaggregated primary particles.

[0087] A molar content ratio of cobalt less than or equal to 20% is beneficial to reducing the cost of the cathode active material, but is not conducive to improving the kinetic performance of the cathode active material. By using relatively small-sized unagglomerated primary particles, the side reaction between the carboxylic acid ester and the cathode active material can be reduced, the cycle life of the single battery can be improved, and at the same time, the kinetic performance of the cathode active material can be improved, and the power performance of the single battery can be improved.

[0088] In any embodiment, the cathode active material includes lithium nickel cobalt manganese oxide. Based on the total molar number of transition metals in the cathode active material, the molar content ratio of nickel is less than 80%. The Dv50 正2 of the cathode active material is 2 μm - 5 μm, and the cathode active material includes unagglomerated primary particles.

[0089] A molar content ratio of nickel less than 80% is beneficial to reducing the nickel dissolution probability of the cathode active material at a high voltage (charging cut-off voltage ≥ 4.3 V) and improving the withstand voltage of the cathode active material. Combining a low-nickel component with unagglomerated primary particles can further reduce the degree of side reaction between the cathode active material and the carboxylic acid ester solvent, reduce the probability of cracking of the cathode active material during high-voltage charge and discharge, and improve the cycle performance of the single battery.

[0090] In any embodiment, the cathode active material includes lithium nickel cobalt manganese oxide. Based on the total molar number of transition metals in the cathode active material, the molar content ratio of nickel is greater than or equal to 80%. The Dv50 正2 of the cathode active material is 6 μm - 15 μm, and the cathode active material includes secondary particles formed by agglomeration of primary particles. The average particle size of the primary particles in the secondary particles is 0.1 μm - 1.5 μm.

[0091] Shaping the high-nickel material into large-sized secondary particles is beneficial to simultaneously improving the specific capacity of the cathode active material and the grading of the cathode electrode sheet, and improving the energy density of the battery. At the same time, the secondary particles are composed of small-sized primary particles, which can shorten the transmission distance of lithium ions, increase the number of insertion end faces, reduce the DC impedance of the single battery, and improve the power performance of the single battery.

[0092] In any embodiment, the cathode active material includes cobalt element. In the particles of the cathode active material, the mass ratio of cobalt element near the particle surface is greater than the mass ratio of cobalt element near the center of the cathode active material particle.

[0093] In any embodiment, the ratio of the mass percentage of cobalt element near the surface of the positive electrode active material to the mass percentage of cobalt element near the center of the positive electrode active material particle is in the range of (1.2 - 5.0):1, and can be optionally (1.4 - 2.0):1; wherein, the region near the surface of the particle is the region between the surface of the particle and a depth of 200 nm in the direction towards the geometric center of the particle, and the region near the center of the positive electrode active material particle is a spherical region with a diameter of 200 nm centered on the geometric center of the cross-section of the particle.

[0094] Although the highly conductive electrolyte is beneficial to improving the liquid-phase transport rate of lithium ions, at the same time, the components in the highly conductive electrolyte have relatively high electrochemical activity. For example, the carboxylic esters in the highly conductive electrolyte are prone to side reactions with the oxygen-releasing structure after the phase change on the surface of the positive electrode active material, increasing gas generation and deteriorating the cycle life of the battery. The relatively high cobalt element content on the surface of the positive electrode active material helps to improve the ionic conductivity of the positive electrode active material, improve the problem of excessive delithiation on the surface of the positive electrode active material during charge and discharge, reduce the cation mixing between the Li layer and the transition metal layer, stabilize the layered structure of the positive electrode active material, and reduce the risk of structural phase change on the surface of the positive electrode active material, thereby reducing the degree of side reactions of the battery cell and improving the cycle life of the battery cell. And the relatively low cobalt content at the center of the positive electrode active material can simultaneously reduce the cost of the positive electrode active material.

[0095] In any embodiment, the positive electrode active material includes lithium-containing phosphate, and the single-sided areal density of the positive electrode film layer is 0.2 g / 1540.25 mm 2 - 0.35 g / 1540.25 mm 2 。

[0096] In any embodiment, the positive electrode active material includes lithium-containing transition metal oxide, and the single-sided areal density of the positive electrode film layer is 0.13 g / 1540.25 mm 2 - 0.24 g / 1540.25 mm 2 。

[0097] The positive electrode film layer with an areal density within the above range has a suitable thickness, which is beneficial to the diffusion of active ions in the electrode sheet, can more effectively improve the fast charging performance of the battery cell; at the same time, it can reduce heat generation, reduce the reaction activity of the electrolyte and the probability of side reactions, and take into account the cycle performance of the battery cell.

[0098] In any embodiment, the porosity of the positive electrode film layer is 22% - 35%.

[0099] The positive electrode film layer with a porosity within the above range is beneficial to the diffusion of active ions in the electrode sheet, and can more effectively improve the fast charging performance of the battery cell; at the same time, it can reduce heat generation, reduce the reaction activity of the electrolyte and the probability of side reactions, and take into account the cycle performance of the battery cell.

[0100] In any embodiment, the lithium ion conductivity of the electrolyte is 10 mS / cm - 20 mS / cm.

[0101] The increase in the lithium ion conductivity of the electrolyte often means that a relatively high content of highly conductive solvent needs to be added. While the highly conductive solvent has a high transmission rate for lithium ions, it also has high chemical reaction activity and is prone to side reactions with the negative electrode active material, reducing the cycle life of the battery. The electrolyte with a lithium ion conductivity within the above range has a suitable lithium ion conduction rate and reaction activity, and can better balance the fast charging performance and cycle life of the battery cell.

[0102] In any embodiment, the lithium ion conductivity of the electrolyte is 12 mS / cm - 20 mS / cm, and can be optionally 10 mS / cm - 15 mS / cm.

[0103] In any embodiment, the positive electrode active material includes lithium iron phosphate, and the single-sided areal density of the positive electrode film layer is 0.2 g / 1540.25 mm 2 - 0.35 g / 1540.25 mm 2 ; the conductivity of the electrolyte is 12 mS / cm - 20 mS / cm.

[0104] Lithium iron phosphate has a relatively low specific capacity. Therefore, the positive electrode film layer of a battery cell with the same capacity often requires a relatively high coating areal density. Matching the electrolyte with a conductivity within the above range is beneficial to improving the loss of the kinetic performance of the battery cell caused by the coating areal density required for the lithium iron phosphate battery, and taking into account the power performance of the battery cell while meeting the battery energy density requirements.

[0105] In any embodiment, the positive electrode active material includes lithium nickel cobalt manganese oxide, and the single-sided areal density of the positive electrode film layer is 0.13 g / 1540.25 mm 2 - 0.24 g / 1540.25 mm 2 ; the conductivity of the electrolyte is 10 mS / cm - 15 mS / cm.

[0106] Lithium nickel cobalt manganese oxide has a relatively high specific capacity. Therefore, the coating areal density of the positive electrode film layer of a battery cell with the same capacity is relatively low, and an electrolyte with a relatively low conductivity can meet the fast charging performance requirements of the battery cell. The above battery cell can take into account the cycle life of the battery while meeting the power performance of the battery.

[0107] The second aspect of the present application further provides a battery device, which includes the battery cell provided by the first aspect, and the battery device includes one or more of a battery module, a battery pack, and an energy storage battery.

[0108] The third aspect of the present application further provides an electrical device, which includes the battery cell provided by the first aspect of the present application or the battery device provided by the second aspect of the present application, and the battery cell or the battery device is used to provide electrical energy. Description of the Drawings

[0109] To more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required to be used in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and those of ordinary skill in the art can obtain other drawings according to the drawings without creative efforts.

[0110] Figure 1 It is a schematic diagram of a battery cell provided by some embodiments of the present application;

[0111] Figure 2 It is a schematic diagram of a battery module provided by some embodiments of the present application;

[0112] Figure 3 It is a schematic diagram of a battery pack provided by some embodiments of the present application;

[0113] Figure 4 is Figure 3 An exploded schematic diagram of the battery pack shown;

[0114] Figure 5 It is an exploded schematic diagram of a battery cell provided by some embodiments of the present application;

[0115] Figure 6 It is a schematic diagram of an electrical device provided by some embodiments of the present application;

[0116] Figure 7 It is a schematic diagram of a positive electrode plate provided by some embodiments of the present application.

[0117] In the drawings, the drawings are not necessarily drawn to actual scale.

[0118] The description of the reference numerals is as follows: 1. Battery pack; 2. Upper box body; 3. Lower box body; 4. Battery module; 5. Battery cell; 51. Shell; 52. Electrode assembly; 53. Cover plate; 101. Positive electrode plate; 1011. Positive current collector; 1012. Positive film layer; 10111. Positive current collecting part; 10112. Positive electrode tab. Detailed Embodiments

[0119] Hereinafter, embodiments of the battery cell, battery device, and electrical device of the present application will be specifically disclosed in detail with reference to the accompanying drawings as appropriate. However, there may be cases where unnecessary details are omitted. For example, there are cases where details of well-known matters are omitted and repeated descriptions of actually identical structures are omitted. This is to prevent the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0120] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a specific range. The range defined in this way can include the end values or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In the present application, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" have been fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0121] If there is no special instruction, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution, and such a technical solution should be considered to be included in the disclosure of the present application.

[0122] If there is no special instruction, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution, and such a technical solution should be considered to be included in the disclosure of the present application.

[0123] Unless otherwise specified, all steps of this application can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out sequentially, or can also include steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b) and (c), or can also include steps (a), (c) and (b), or can also include steps (c), (a) and (b), etc.

[0124] In this application, the terms "a plurality of" and "multiple types" refer to two or more than two.

[0125] Unless otherwise specified, the terms used in this application have the well-known meanings commonly understood by those skilled in the art.

[0126] Unless otherwise specified, the numerical values of the various parameters mentioned in this application can be measured by various commonly used testing methods in the art. For example, they can be measured according to the testing methods given in the embodiments of this application. Unless otherwise specified, the testing temperature of each parameter is 25 °C.

[0127] The battery mentioned in the embodiments of this application can be a single physical module including one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in this application can include battery cells, battery modules or battery packs, etc.

[0128] A battery cell is the smallest unit that makes up a battery and can independently perform the functions of charging and discharging. The battery cell can be in the shape of a cylinder, a cuboid or other shapes, etc., and the embodiments of this application do not limit this. For example, Figure 1 is a battery cell 5 in the shape of a cuboid structure as an example.

[0129] When there are multiple battery cells, the multiple battery cells are connected in series, parallel or in a hybrid connection through a busbar component. In some embodiments, the battery can be a battery module; when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module. In some embodiments, the battery can be a battery pack, and the battery pack includes a box body and battery cells, and the battery cells or battery modules are accommodated in the box body. In some embodiments, the box body can be part of the chassis structure of a vehicle. For example, part of the box body can become at least part of the vehicle floor, or part of the box body can become at least part of the crossbeam and longitudinal beam of the vehicle.

[0130] In some embodiments, the battery can be an energy storage device. The energy storage device includes an energy storage container, an energy storage cabinet, etc.

[0131] In some embodiments, battery cells can be assembled into a battery module. The number of battery cells included in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module. Figure 2 is a schematic diagram of a battery module 4 as an example. As Figure 2 shown, in the battery module 4, multiple battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other way. Further, the multiple battery cells 5 can be fixed by fasteners.

[0132] Optionally, the battery module 4 can further include a housing having an accommodation space, and the multiple battery cells 5 are accommodated in the accommodation space.

[0133] In some embodiments, the above battery module can be further assembled into a battery pack, and the number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0134] Figure 3 and Figure 4 are schematic diagrams of a battery pack 1 as an example. As Figure 3 and Figure 4 shown, the battery pack 1 can include a box body and multiple battery modules 4 arranged in the box body. The box body includes an upper box body 2 and a lower box body 3. The upper box body 2 is used to cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in the box body in any way.

[0135] The battery provided by the embodiments of the present application can include a lithium-ion battery.

[0136] The battery cell includes an electrode assembly and an electrolyte. The electrode assembly can be a wound structure or a stacked structure, and the embodiments of the present application do not limit this.

[0137] The battery cell can further include an outer package, and the outer package can be used to encapsulate the electrode assembly and the electrolyte. The outer package can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package can also be a soft package, such as a bag-type soft package. The material of the soft package can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0138] In some embodiments, as Figure 5 shown, the outer package can include a housing 51 and a cover plate 53. The housing 51 can include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose an accommodation cavity. The housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 is used to cover the opening to close the accommodation cavity. The electrode assembly 52 is encapsulated in the accommodation cavity. The number of electrode assemblies 52 included in the battery cell 5 can be one or more, and can be adjusted according to requirements.

[0139] An electrode assembly generally includes a positive electrode plate and a negative electrode plate. The negative electrode plate is the electrode where the reaction of absorbing or lithiating lithium ions occurs during battery charging and releasing or delithiating lithium occurs during discharging. The positive electrode plate is the electrode where the reaction of releasing or delithiating lithium ions occurs during battery charging and absorbing or lithiating lithium occurs during discharging.

[0140] The key to improving the fast charging performance of a battery cell lies in enhancing the transport rate of active ions in the battery cell. To increase the transport rate of active ions in the liquid phase, a highly conductive electrolyte is often used in the battery cell. However, if the rapidly transported lithium ions cannot be rapidly embedded on the surface of the negative active material in the electrode plate, polarization will occur, which will then lead to lithium deposition, causing the battery cycle life to drop significantly. To balance the energy density of the battery, high-capacity negative active material graphite is usually used in the prior art. However, the kinetic performance of graphite is not excellent enough, and it is difficult to effectively cooperate with the highly conductive electrolyte to achieve a coordinated improvement in the rates of lithium ion transport in the liquid phase and liquid-solid transport. Therefore, a coating layer with a certain degree of disorder is provided on the surface of graphite to cooperate with the highly conductive electrolyte to improve the fast charging performance of the battery cell. Although the high degree of disorder on the surface of the coating layer will improve the kinetic performance of the battery cell, it will also increase the degree of side reactions between the negative active material and the highly conductive electrolyte, having a negative impact on the cycle life of the battery cell.

[0141] In a first aspect of the present application, a battery cell is provided, including a positive electrode plate, a negative electrode plate, and an electrolyte; the lithium ion conductivity of the electrolyte is greater than or equal to 10 mS / cm; the negative electrode plate includes a negative current collector and a negative electrode film layer provided on at least one side of the negative current collector. The negative electrode film layer includes a negative active material. The negative active material includes a core portion and a coating layer at least partially covering the surface of the core portion. The core portion includes graphite. In the R value cumulative distribution curve obtained by the laser confocal Raman spectrometer in the surface scanning mode of the negative active material, the R value R50 with a cumulative distribution of 50% is 0.15 - 0.50; among the R values of the obtained negative active material, the proportion of the number of R values less than or equal to 0.11 is less than or equal to 15%.

[0142] In the present application, the lithium-ion conductivity of the electrolyte is the ability to describe the conductive process formed by the directional movement of the dissociated ions in the electrolyte solution in an electric field, and can be tested by any well-known method in the art. As an example, disassemble the battery cell, take about 100 mL of the electrolyte sample with a dry, clean and corrosion-resistant sample bottle, seal it and place it in a constant temperature water bath, shake the sample from time to time, and keep the temperature constant at 25 °C (deviation ±0.5 °C). After the temperature of the sample is constant, use a commercially available conductivity meter to test its conductivity. After wiping the conductivity meter clean with the calibration solution, vertically place it into the liquid to be tested, click to start the test, and record the test result after the data is stable for more than 10 s. It can be understood that the lithium-ion conductivity of the electrolyte is closely related to its components and formulations such as solvents, lithium-containing electrolyte salts, and additives.

[0143] In some embodiments, the lithium-ion conductivity of the electrolyte can be selected as 10 mS / cm, 11 mS / cm, 12 mS / cm, 13 mS / cm, 14 mS / cm, 15 mS / cm, 16 mS / cm, 17 mS / cm, 18 mS / cm, 19 mS / cm, 20 mS / cm, 21 mS / cm, 22 mS / cm, 23 mS / cm, 24 mS / cm, 25 mS / cm or the numerical range between any two of them.

[0144] In the present application, the R value R50 of the negative electrode active material can be obtained by the surface scanning mode of a laser confocal Raman spectrometer. As an example, specifically, use a laser confocal Raman spectrometer (such as a high-precision Renishaw laser confocal Raman spectrometer), select a laser wavelength of 532 nm, take an appropriate amount of the sample and perform a full-range surface scan on its surface. The scanning area is 100 μm × 100 μm, the step size is 2 μm, and the total number of scanning points is 2500 points, thereby obtaining the R values at different sites and the cumulative distribution curve of the R values in the surface scan area. The negative electrode active material in the present application can be either the prepared negative electrode active material or the negative electrode material scraped from the negative electrode plate.

[0145] The R value of the negative electrode active material refers to the ratio of the peak height of the D peak (D-band) and the G peak (G-band) in its Raman spectrum. The position of the D peak is 1350 ± 50 cm -1 , and the position of the G peak is 1585 ± 50 cm -1 . The R value can characterize the defect degree and disorder degree of the negative electrode active material. The larger this value is, the greater the surface defect degree and the higher the surface disorder degree of the negative electrode active material.

[0146] The R value cumulative distribution curve means that the obtained 2500 R values are arranged in ascending order, and R50 is the R value corresponding to the 50% quantity arranged in order.

[0147] In some embodiments, in the cumulative distribution curve of the R value obtained in the surface scanning mode of a laser confocal Raman spectrometer for the negative electrode active material, the R value R50 with a cumulative distribution of 50% can be selected from 0.15, 0.18, 0.20, 0.22, 0.24, 0.26, 0.28, 0.30, 0.32, 0.34, 0.36, 0.38, 0.40, 0.42, 0.44, 0.46, 0.48, 0.50, or a numerical range between any two of them.

[0148] The R value R50 with a cumulative distribution of 50% for the negative electrode active material is related to the R value with a cumulative distribution of 50% for the core part, the R value with a cumulative distribution of 50% for the coating layer, the thickness of the coating layer, the uniformity of the coating layer, etc. For example, when other conditions are the same, if the R value with a cumulative distribution of 50% for the core part is large, the R value R50 with a cumulative distribution of 50% for the negative electrode active material is large; if the thickness of the coating layer is large, the R value R50 with a cumulative distribution of 50% for the negative electrode active material is large.

[0149] The negative electrode active material with an R value R50 with a cumulative distribution of 50% in the range of 0.15 - 0.50 can not only improve the charge exchange ability of lithium ions on the surface of the negative electrode active material in a highly conductive electrolyte, making the liquid-phase transport rate of lithium ions match the solid-phase transport rate and improving the kinetic performance of the battery, but also keep the side reactions on the surface of the negative electrode active material at a low level, while taking into account the cycle life of the battery monomer.

[0150] In some embodiments, the R value R50 with a cumulative distribution of 50% for the core part is 0.06 - 0.11.

[0151] In some embodiments, the R value R50 with a cumulative distribution of 50% for the core part can be selected from 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, or a range composed of any of the above numerical values.

[0152] In some embodiments, the R value R50 with a cumulative distribution of 50% for the core part can be 0.07 - 0.11.

[0153] When the R value R50 with a cumulative distribution of 50% for the core part is large, the kinetic performance of the negative electrode active material is good; when the R value R50 with a cumulative distribution of 50% for the core part is small, the specific capacity per gram of the negative electrode active material is higher. When the R value R50 with a cumulative distribution of 50% for the core part is within the above range, the battery can have both high energy density and good kinetic performance.

[0154] The core part of the negative electrode active material includes graphite, which is beneficial for the battery cell to maintain good energy density. However, the graphite surface has a high degree of order and a low defect content, which makes lithium ions need to be inserted directionally between the graphite layers, resulting in low kinetic performance of the battery cell. By providing a coating layer with a certain degree of disorder on the graphite surface, on the one hand, the number of lithium ion insertion channels of the negative electrode active material increases, and the insertion efficiency of lithium ions in the negative electrode active material is improved. Furthermore, it forms a cooperation with the lithium ions that are rapidly transported in the high-conductivity electrolyte, synergistically enhancing the charge transport ability of lithium ions in the liquid phase and liquid-solid phase in the battery cell, so that the fast charging performance of the battery cell is comprehensively improved; on the other hand, it controls the degree of side reaction between the negative electrode active material and the high-conductivity electrolyte, taking into account the cycle life of the battery.

[0155] In some embodiments, among the R values of the obtained negative electrode active material, the proportion of the number of R values less than or equal to 0.11 is less than or equal to 15%, optionally less than or equal to 10%, and further optionally less than or equal to 6%.

[0156] In some embodiments, among the R values of the obtained negative electrode active material, the proportion of the number of R values less than or equal to 0.11 can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15% or any numerical range between any two of them.

[0157] As described above, the R value R50 with a cumulative distribution of 50% of the core graphite generally does not exceed 0.11. Therefore, among all the R values of the obtained negative electrode active material, the proportion of the number of R values less than or equal to 0.11 can be used to represent the uncoated degree of the negative electrode active material. The smaller this value is, the smaller the uncoated degree of the negative electrode active material, the higher the surface coating degree of the negative electrode active material, the improvement of the isotropy degree of ion insertion, the improvement of the charge exchange ability of ions on the surface of the negative electrode active material, and further the improvement of the solid-liquid transport rate of lithium ions, so as to match with the high-conductivity electrolyte and improve the kinetic performance of the battery.

[0158] In addition, when the uncoated degree of the negative electrode active material is small, the co-insertion phenomenon of the electrolyte solvent during the cycle can also be reduced, and further the battery has better cycle performance.

[0159] In some embodiments, among the R values of the obtained negative electrode active material, the proportion of the number of R values less than or equal to 0.11 is less than or equal to 10%, optionally less than or equal to 6%.

[0160] Among all the R values obtained for the negative electrode active material, when the proportion of the number of R values less than or equal to 0.11 is within the above range, the kinetic performance and cycle performance of the battery can be further improved.

[0161] In some embodiments, in the R-value cumulative distribution curve obtained by the laser confocal Raman spectrometer in the area scanning mode for the negative electrode active material, the R-value R50 with a cumulative distribution of 50% is 0.15 - 0.30, and among the R-values of the obtained negative electrode active material, the proportion of the number of R-values less than or equal to 0.11 is less than or equal to 10%.

[0162] The negative electrode active material in this embodiment enables the battery cell to have better fast charging performance. The speculated reason may be that the surface disorder degree of the negative electrode active material is within the above range and the coating rate is high, indicating a high degree of isotropy on the surface of the negative electrode active material, which is conducive to the uniform insertion of lithium ions into the core graphite from all directions and is conducive to the further improvement of the fast charging performance of the battery cell.

[0163] In some embodiments, in the R-value cumulative distribution curve obtained by the laser confocal Raman spectrometer in the area scanning mode for the negative electrode active material, the R-value R50 with a cumulative distribution of 50% is 0.30 - 0.50, and among the R-values of the obtained negative electrode active material, the proportion of the number of R-values less than or equal to 0.11 is less than or equal to 15%.

[0164] The negative electrode active material in this embodiment takes into account low cost, good cycle stability, and improved fast charging performance.

[0165] In some embodiments, the electrolyte includes an organic solvent, and the organic solvent includes one or more of carboxylic ester solvents, nitrile solvents, and carbonate solvents.

[0166] The carboxylic ester solvent is an organic solvent including a carboxylic ester group. The nitrile solvent refers to an organic solvent including a cyano group. The carbonate solvent refers to an organic solvent including a carbonate group, including cyclic carbonates and chain carbonate compounds.

[0167] In some embodiments, the carboxylic ester solvent is a chain carboxylic ester solvent. The chain carboxylic ester solvent refers to a linear carboxylic ester solvent, rather than a cyclic structure.

[0168] In some embodiments, the carboxylic ester solvent includes one or more of ethyl acetate, methyl acetate, methyl formate, butyl acetate, methyl propionate, ethyl propionate, methyl butyrate, propyl butyrate, butyl butyrate, isopropyl acetate, and isoamyl acetate, and can be one or more of ethyl acetate and methyl acetate; and / or the nitrile solvent includes one or more of acetonitrile, monofluoroacetonitrile, difluoroacetonitrile, and trifluoroacetonitrile; and / or the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0169] Carboxylate solvents and / or nitrile solvents can increase the lithium-ion conductivity of the electrolyte and improve the fast charging performance of the battery cell. Carbonate solvents are prone to form a solvation structure with lithium ions in the lithium-containing electrolyte salt to increase the dissociation rate of lithium ions and anions in the lithium-containing electrolyte salt, thereby improving the fast charging performance of the battery cell.

[0170] In some embodiments, the organic solvent includes dimethyl carbonate. Based on the total mass of the organic solvent, the mass content of dimethyl carbonate is greater than or equal to 20%, and can be optionally 30%-90%.

[0171] In some embodiments, based on the total mass of the organic solvent, the mass content of dimethyl carbonate can be optionally 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90% or any value range between any two of them.

[0172] In some embodiments, the organic solvent includes one or more of ethyl acetate and methyl acetate and a carbonate solvent.

[0173] Ethyl acetate and methyl acetate have high conductivity and low gas generation. The combination of ethyl acetate and / or methyl acetate and a carbonate solvent enables lithium ions in the electrolyte to have both a high dissociation rate and a fast lithium-ion transport rate, which is beneficial to improving the kinetic performance of the battery cell, reducing battery gas generation, and taking into account the cycle life of the battery.

[0174] In some embodiments, based on the total mass of the organic solvent, the total mass ratio of ethyl acetate and methyl acetate is 5%-80%, and the mass ratio of the carbonate solvent is 5%-90%.

[0175] In some embodiments, based on the total mass of the organic solvent, the total mass ratio of ethyl acetate and methyl acetate can be optionally 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80% or any value range between any two of them, and the mass ratio of the carbonate solvent can be optionally 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or any value range between any two of them.

[0176] In some embodiments, the organic solvent includes methyl acetate. Based on the total mass of the organic solvent, the mass content of methyl acetate is 5%-70%.

[0177] In some embodiments, based on the total mass of the organic solvent, the mass content of methyl acetate can be optionally 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, or a numerical range between any two of them. Methyl acetate has higher activity compared to ethyl acetate. Although the addition of a small amount of it in the electrolyte will slightly sacrifice the life of the battery cell, it can further improve the kinetic performance of the battery cell, and further improve the fast charging performance of the battery cell while maintaining the high cycle life of the battery cell.

[0178] In some embodiments, based on the total mass of the organic solvent, the mass content of methyl acetate is 5% - 50%.

[0179] In some embodiments, the organic solvent includes one or more of ethyl acetate and methyl acetate and dimethyl carbonate solvent.

[0180] Ethyl acetate and methyl acetate have higher activity compared to carbonate solvents and are prone to side reactions with ternary cathode materials. It is found that the side reaction of methyl acetate solvent is more intense, but methyl acetate has a lower molecular weight and lower viscosity. When the electrolyte reaches the same conductivity, its addition amount in the electrolyte can be much smaller than that of ethyl acetate; especially when used in combination with dimethyl carbonate, the addition amount of methyl acetate can be further reduced. For a high-rate fast-charging battery system, through the combination of methyl acetate and dimethyl carbonate, a small amount of methyl acetate added can effectively increase the conductivity of the electrolyte. At the same time, compared with the electrolyte system with a large amount of ethyl acetate added, the degree of battery side reaction decreases instead, which is beneficial to taking into account the cycle stability of the battery at the same time.

[0181] In some embodiments, the electrolyte includes an electrolyte salt, and the electrolyte salt includes lithium bis(fluorosulfonyl)imide LiFSI. Based on the total mass of the electrolyte, the mass content of lithium bis(fluorosulfonyl)imide is 3% - 10%.

[0182] In some embodiments, based on the total mass of the electrolyte, the mass content ratio of the lithium bis(fluorosulfonyl)imide LiFSI can be optionally 3%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5%, 5.1%, 5.2%, 5.3%, 5.4%, 5.5%, 5.6%, 5.7%, 5.8%, 5.9%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, or a numerical range between any two of them.

[0183] Lithium bis(fluorosulfonyl)imide is prone to dissociation in the electrolyte solvent, which is beneficial to improving the kinetics of the battery cell, reducing the internal resistance of the battery, and improving the fast charging performance of the battery. However, lithium bis(fluorosulfonyl)imide is prone to react with LiC formed during the deep lithium intercalation process of the negative electrode, reducing the reversible lithium capacity and being unfavorable for maintaining the capacity of the battery cell during cycling. When the mass content of lithium bis(fluorosulfonyl)imide LiFSI in the electrolyte is within the above range, the cycle life of the battery cell can be further improved on the basis of taking into account the fast charging performance of the battery cell. 6 When the mass content of lithium bis(fluorosulfonyl)imide LiFSI in the electrolyte is within the above range, the cycle life of the battery cell can be further improved on the basis of taking into account the fast charging performance of the battery cell.

[0184] In some embodiments, based on the total mass of the electrolyte salt, the mass content of lithium bis(fluorosulfonyl)imide LiFSI is 20%-80%, and can be optionally 30%-70%.

[0185] In some embodiments, based on the total mass of the electrolyte salt, the mass content of lithium bis(fluorosulfonyl)imide can be optionally 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80% or the numerical range between any two of them.

[0186] The electrolyte with lithium bis(fluorosulfonyl)imide within the above mass range can not only improve the fast charging performance of the battery, but also keep the side reaction with the negative electrode material at a reasonable level, comprehensively improving the cycle life of the battery.

[0187] In some embodiments, the battery cell includes a stacked cell, the positive electrode plate includes a positive current collector, the positive current collector includes a positive current collecting portion and a positive tab provided on at least one side of the side of the positive current collecting portion, and the width of the positive current collecting portion is 60 mm - 110 mm, and can be optionally 62 mm - 98 mm.

[0188] In some embodiments, the width of the positive current collecting portion can be optionally 60 mm, 62 mm, 64 mm, 66 mm, 68 mm, 70 mm, 72 mm, 74 mm, 76 mm, 78 mm, 80 mm, 82 mm, 84 mm, 86 mm, 88 mm, 90 mm, 92 mm, 94 mm, 96 mm, 98 mm, 100 mm, 102 mm, 104 mm, 106 mm, 108 mm, 110 mm or the numerical range between any two of them.

[0189] The material of the positive current collector is not particularly limited as long as it does not cause chemical changes in the battery cell and has electrical conductivity. The current collector includes metal foils with a pure metal content of more than 95%, such as at least one of copper foil, aluminum foil, stainless steel foil, titanium foil, and nickel foil, and also includes alloy foils of at least two main metals. For example, alloy foils made of at least two main elements among copper, aluminum, nickel, titanium, and iron can be used. It can also include copper, aluminum cadmium alloy, iron, or stainless steel, etc. surface-treated with carbon, nickel, titanium, silver, copper, etc. In addition, the bonding force with the negative active material can be enhanced by forming fine concavities and convexities on the surface, and it can be used in various forms such as films, sheets, foils, meshes, porous bodies, foams, and non-woven fabrics.

[0190] A laminated battery cell refers to a battery cell formed by stacking a positive electrode plate, a separator, and a negative electrode plate together.

[0191] Please refer to Figure 7 , the width L1 of the positive current collector portion 10111 refers to the dimension of the positive current collector portion 10111 in the direction perpendicular to the rolling direction of the positive electrode film layer 1012 in the positive electrode plate 101, and also refers to the dimension of the positive current collector portion 10111 in the direction perpendicular to the connection portion between the positive electrode tab 10112 and the positive current collector portion 10111 (i.e., Figure 7 the X direction in

[0192] During high-rate fast charging, due to the need to use a large current, the temperature rise rate of the battery cell is fast and the temperature rise amplitude is large. During the battery charging process, the current first converges at the tab and then is transmitted to the current collector portion of the current collector. Research shows that there is a difference in the current density between the tab and the current collector portion, and the difference in the current density between the sites on the current collector portion with different distances from the tab and the tab is also different. Generally speaking, the difference in the current density between the current collector portion and the tab increases with the increase in the distance between the current collector portion and the tab, and also increases with the increase in the current density. That is, the phenomenon of inconsistent current density on the current collector portion is more significant during high-rate charge and discharge, that is, during fast charging. According to Joule's law, the inconsistency of the current density at different sites on the current collector portion will further lead to inconsistent temperature rises in different positions of the battery, uneven transmission rates of lithium ions inside the battery cell, increasing the risk of battery polarization and local lithium deposition, and reducing the cycle life of the battery cell.

[0193] The width of the positive current collector portion within the above range is beneficial to reducing the maximum distance between the tab and the edge of the positive current collector portion, which can not only reduce the electron transmission distance, improve the fast charging performance of the battery, but also reduce the phenomenon of inconsistent temperature rise of the current collector portion during fast charging, reduce the temperature gradient on the current collector portion, reduce the probability of the active material at the high-temperature site deactivating first, improve the fast charging cycle life of the battery, and also take into account the energy density of the battery. In some embodiments, the length of the positive current collector portion in the laminated battery cell is 100 mm - 700 mm, and can be optionally 200 mm - 600 mm.

[0194] In some embodiments, the length of the positive current collector portion in the laminated battery cell may be selected from 100 mm, 150 mm, 200 mm, 250 mm, 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, 550 mm, 600 mm, 650 mm, 700 mm, or a numerical range between any two of them.

[0195] When the length of the positive current collector portion in the laminated battery cell is within the above range, it can further reduce the electron transfer distance on the current collector, improve the phenomenon of inconsistent temperature rise during the fast charging process of the battery cell, and increase the fast charging cycle life of the battery cell. In some embodiments, the electrolyte includes a first additive, and the first additive includes one or more of fluorophosphate and borate.

[0196] In some embodiments, the fluorophosphate includes one or more of monofluorophosphate and difluorophosphate; the fluorophosphate includes an alkali metal, and may be selected from one or more of lithium salt, sodium salt, and potassium salt.

[0197] In some embodiments, the borate includes at least one of tetrafluoroborate, bis(oxalato)borate, and fluorinated oxalato borate; the borate includes an alkali metal, and may be selected from one or more of lithium salt, sodium salt, and potassium salt.

[0198] In some embodiments, the first additive includes one or more of lithium monofluorophosphate, sodium monofluorophosphate, potassium monofluorophosphate, lithium difluorophosphate, sodium difluorophosphate, potassium difluorophosphate, lithium tetrafluoroborate, sodium tetrafluoroborate, potassium tetrafluoroborate, lithium bis(oxalato)borate, sodium bis(oxalato)borate, potassium bis(oxalato)borate, lithium fluorinated oxalato borate, sodium fluorinated oxalato borate, and potassium fluorinated oxalato borate.

[0199] In some embodiments, the positive electrode active material includes a lithium-containing transition metal oxide, and the electrolyte includes a first additive.

[0200] The first additive in the electrolyte can combine with metal ions on the surface of the lithium-containing transition metal oxide in the positive electrode active material to form a stable scaffold, thereby greatly reducing the probability of irreversible phase change of the positive electrode active material at a high lithium deintercalation amount, reducing the degree of side reaction between the electrolyte and the positive electrode side, and improving the cycle stability of the battery.

[0201] In some embodiments, the positive electrode active material includes a lithium-containing phosphate, and the electrolyte includes a first additive.

[0202] When the positive electrode active material includes a lithium-containing phosphate, the first additive in the electrolyte preferentially forms a film on the negative electrode, which is beneficial to the formation of inorganic components, improves the thermal stability and cycle stability of the solid electrolyte interface (SEI) film on the negative electrode, and improves the cycle life and high-temperature storage stability of the battery.

[0203] In some embodiments, the electrolyte includes a second additive, and the second additive includes one or more of sulfonate compounds and vinylene sulfate compounds.

[0204] Vinylene sulfate compounds refer to vinylene sulfate and its derivatives.

[0205] Sulfonate compounds refer to compounds including a sulfonate group.

[0206] In some embodiments, the sulfonate compounds include cyclic sulfonate compounds.

[0207] In some embodiments, the vinylene sulfate compounds include at least one of

[0208] In some embodiments, the sulfonate compounds include at least one of

[0209] The second additive in the electrolyte is prone to form a film on the negative electrode, can simultaneously generate inorganic and organic components in the SEI film, reduce the degree of side reactions of carboxylate solvents on the negative electrode, and improve the cycle life of the battery.

[0210] In some embodiments, the air oxidation temperature T 0 of the negative electrode active material is 630 °C to 730 °C, wherein the air oxidation temperature T 0 is the temperature corresponding to the intersection of two tangents at two points corresponding to 500 °C and T 1 temperature on the thermogravimetric curve of the negative electrode active material, and the T 1 temperature is the peak temperature of the maximum area peak in the differential thermogravimetric curve of the negative electrode active material. The thermogravimetric curve and the differential thermogravimetric curve can be obtained by thermogravimetric analysis under the following conditions: sample mass 10 ± 0.05 mg, purge gas is air and the gas flow rate is 60 mL / min, heating rate is 5 °C / min, and test temperature range is 35 °C to 950 °C.

[0211] The air oxidation temperature T 0 can be determined according to the thermogravimetric analysis including the following steps: performing thermogravimetric test on the negative electrode active material under the conditions of weighing mass 10 ± 0.05 mg, purge gas is air and the gas flow rate is 60 mL / min, heating rate is 5 °C / min, and test temperature range is 35 °C to 950 °C to obtain a thermogravimetric curve (also called a TG curve) and a differential thermogravimetric curve (also called a DTG curve), reading the peak temperature T 1 of the maximum area peak from the differential thermogravimetric curve, and determining on the thermogravimetric curve the temperatures corresponding to 500 °C and T 1The intersection of two tangents at two points of temperature, and the temperature corresponding to this intersection on the thermogravimetric curve is the air oxidation temperature T of the composite graphite material 0 。

[0212] The oxidation of the negative electrode active material in air often starts from surface defects. Therefore, the temperature corresponding to the intersection of two tangents at two points on the thermogravimetric curve corresponding to 500 °C and the peak temperature T of the peak with the largest area respectively, that is, the air oxidation temperature T of the negative electrode active material 1 can accurately represent the temperature at which weight loss starts during air oxidation and can reflect the number of surface defects of the negative electrode active material. 0

[0213] In some embodiments, the air oxidation temperature T of the negative electrode active material 0 can be selected as 630 °C, 640 °C, 650 °C, 660 °C, 670 °C, 680 °C, 690 °C, 700 °C, 710 °C, 720 °C, 730 °C or the numerical range between any two of them.

[0214] The air oxidation temperature T 0 of the negative electrode active material with a temperature range of 630 °C to 730 °C has a suitable number of surface defects, provides sufficient end faces for the insertion of active ions, matches the lithium ion transmission rate of the electrolyte, and at the same time keeps the side reaction degree of the battery monomer within a controllable range. Therefore, the battery monomer can have improved fast charging performance while maintaining high energy density and cycle life.

[0215] In some embodiments, the core of the negative electrode active material is a secondary particle formed by the aggregation of primary graphite particles, the coating layer of the negative electrode active material includes amorphous carbon, and the negative electrode active material also includes kinetic carbon materials; the interlayer spacing d of the (002) crystal plane of the kinetic carbon materials 002 > 0.335 nm, and can be selected as 0.3355 nm to 0.337 nm.

[0216] In some embodiments, the kinetic carbon materials include one or more of hard carbon, expanded graphite, and graphene.

[0217] In some embodiments, the kinetic carbon materials are located in the core and / or the coating layer.

[0218] In this application, a primary particle refers to the smallest unit of a particle within a certain observation range. There may be any form of defects inside the primary particle, but it is impossible to define smaller particles within the primary particle. The primary particles may aggregate under physical actions such as van der Waals forces, but this aggregation is easily depolymerized under external forces such as ultrasonic waves, stirring, and rolling, so that the main composition form of the active material in the film layer is still primary particles.

[0219] In the present application, the secondary particles are formed by the aggregation of primary particles. Here, the aggregation is a hard aggregation caused by chemical bonding of the primary particles, so that the secondary particles have a definite surface and boundary and are not easily dispersed under external forces such as ultrasound. However, after cross-section cutting of the secondary particles, it can be seen that the secondary particles are formed by the aggregation of numerous primary particles.

[0220] In this embodiment, the core part is secondary particles formed by the aggregation of primary graphite particles.

[0221] Amorphous carbon refers to a carbon material with a very low degree of graphitization, approximately in an amorphous form (or without a fixed shape and periodic structural rules). In the structure of amorphous carbon, the carbon atoms are not arranged regularly. Therefore, amorphous carbon can be characterized by transmission electron microscopy (TEM) testing. By cutting a thin slice with a thickness of about 100 nm from the middle of the negative electrode active material particles using a focused ion beam (FIB), and then performing TEM testing on the thin slice, it can be observed that the surface layer region includes a coating layer. The lattice fringes in the coating layer show long-range disorder and short-range order, and the electron diffraction pattern shows a halo shape, indicating that the coating layer includes amorphous carbon.

[0222] In some embodiments, the layer spacing d of the (002) crystal plane of the kinetic carbon material 002 can be selected as 0.3351 nm, 0.3352 nm, 0.3353 nm, 0.3354 nm, 0.3355 nm, 0.3356 nm, 0.3357 nm, 0.3358 nm, 0.3359 nm, 0.3360 nm, 0.3361 nm, 0.3362 nm, 0.3363 nm, 0.3364 nm, 0.3365 nm, 0.3366 nm, 0.3367 nm, 0.3368 nm, 0.3369 nm, 0.337 nm, 0.34 nm, 0.35 nm, 0.36 nm or the numerical range between any two of them.

[0223] In the present application, the layer spacing d of the material 002 has the meaning well-known in the art and can be measured by the instruments and methods well-known in the art. For example, reference can be made to JIS K 0131-1996 and JB / T 4220-2011, and the X-ray powder diffractometer (such as PANalytical X’pert PRO) can be used to measure d 002 .

[0224] The layer spacing d of conventional graphite 002 is generally 0.335 nm, and the layer spacing d of the above-mentioned kinetic carbon materials 002 are all greater than that of conventional graphite.

[0225] The negative electrode active material including the above kinetic carbon material can improve the insertion and extraction rates of active ions, thereby enhancing the transport performance of active ions and electrons, and further improving the fast charging performance of the battery cell on the basis of maintaining a high energy density. At the same time, amorphous carbon has a high hardness, so it also has good compressive resistance, has a strong ability to maintain the pore structure of the negative electrode film layer during the cycling process, and has better electrolyte wettability of the negative electrode plate, so it is also beneficial to improve the cycling performance of the battery cell.

[0226] In some embodiments, the kinetic carbon material includes one or more of hard carbon, expanded graphite, and graphene.

[0227] The hard carbon material has a trace amount of crystallite disordered arrangement and cannot be transformed into a graphite structure even after high-temperature heat treatment. The hard carbon material has no long-range ordered lattice structure, and the arrangement of atoms is only short-range ordered, lying between the graphite and diamond structures. There is basically no parallel graphite sheet structure with more than 3-4 layers in the hard carbon material, which is mainly composed of disordered arrangement of single-layer graphite sheet structures. Therefore, there are a large number of micropores with a diameter less than 1 nm in the material.

[0228] Expanded graphite refers to the expansion of the flake crystal of graphite at a certain temperature. The expanded graphite is in the shape of fibrous worms, and the layer spacing of the expanded graphite along the C-axis direction is dozens to hundreds of times that of conventional graphite.

[0229] In some embodiments, the kinetic carbon material is located in the core and / or the coating layer.

[0230] In some embodiments, based on the total mass of the negative electrode active material, the mass percentage of the kinetic carbon material is 1% to 30%, and can be optionally 8% to 15%.

[0231] In some embodiments, based on the total mass of the negative electrode active material, the mass percentage of the kinetic carbon material can be optionally 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30% or the numerical range between any two of them.

[0232] When the mass percentage of the kinetic carbon material is within a suitable range, the negative electrode active material can have a high specific capacity, a high solid-phase transport ability of active ions, and a high charge exchange rate of active ions and electrons. Furthermore, the battery cell can have improved fast charging performance on the premise of having a high energy density. At the same time, when the mass percentage of the kinetic carbon material is within a suitable range, it has a better ability to maintain the pore structure of the negative electrode film layer during the cycling process, better electrolyte wettability of the negative electrode plate, and the battery cell can also have good cycling performance.

[0233] In some embodiments, the negative electrode active material includes secondary particles formed by aggregation of primary particles, and the volume-based median diameter Dv50 of the negative electrode active material is 8 μm - 18 μm.

[0234] The volume-based median diameter Dv50 of the material represents the particle diameter corresponding to when the cumulative volume distribution percentage of the material reaches 50%, and can be measured by instruments and methods known in the art. For example, it can be conveniently measured by referring to GB / T 19077-2016 Laser diffraction method for particle size distribution and using a laser particle size analyzer. The test instrument can be the Mastersizer 3000 type laser particle size analyzer of Malvern Instruments Limited, UK.

[0235] In some embodiments, the negative electrode active material includes secondary particles formed by aggregation of primary particles, and the volume-based median diameter Dv50 of the negative electrode active material can be selected from 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm or the numerical range between any two of them.

[0236] In some embodiments, the negative electrode active material including secondary particles formed by aggregation of primary particles means that the negative electrode active material mainly includes secondary particles formed by aggregation of primary particles. That is, more than 85% of the particles in the negative electrode active material are secondary particles. This can be judged by observing the particle morphology of the cross-section in the thickness direction of the negative electrode plate.

[0237] On the one hand, the negative electrode active material with the volume-based median diameter Dv50 within the above range can make the negative electrode active material have a suitable embedding surface by means of a certain number of primary particles in the secondary particles, and the solid-phase transport rate and solid-liquid transport rate of active ions in the negative electrode active material can match the liquid-phase transport rate of lithium ions in the electrolyte, improving the fast charging performance of the battery; and it can also have the advantages of large secondary particle size, high tap density and large capacity, taking into account the energy density of the battery cell while improving the fast charging performance of the battery.

[0238] In some embodiments, the negative electrode active material includes unaggregated primary particles, and the volume-based median diameter Dv50 of the negative electrode active material is 5 μm - 13 μm.

[0239] In some embodiments, the negative electrode active material includes unaggregated primary particles, and the volume-based median diameter Dv50 of the negative electrode active material can be selected from 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm or the numerical range between any two of them.

[0240] In some embodiments, the negative electrode active material mainly comprises unagglomerated primary particles. That is, more than 85% of the particles in the negative electrode active material are unagglomerated primary particles. This can be judged by observing the particle morphology of the cross-section in the thickness direction of the negative electrode sheet.

[0241] The negative electrode active material with a volume distribution particle size Dv50 within the above range has higher interfacial stability compared to small particle size particles, but at the same time has a larger ionic solid-phase transport distance. By size design, the two can be balanced to achieve both the fast charging performance and cycle life of the battery cell.

[0242] In some embodiments, the core of the negative electrode active material comprises artificial graphite.

[0243] Artificial graphite refers to the material that can be easily graphitized and is treated under high temperature and other conditions to form a regular graphitized lamellar structure. Artificial graphite has obvious differences in morphology compared to natural graphite. By observing the cross-section of graphite with a scanning electron microscope, natural graphite has more layered structures and a large number of pores between the lamellar structures; while the crystals of artificial graphite are strictly arranged in ABAB, with a dense interior, no gaps or only a small number of gaps. There are also differences in the crystal structure between artificial graphite and natural graphite. Natural graphite not only has a hexagonal phase but also a rhombohedral phase (3R phase); while only the hexagonal phase exists in artificial graphite. Artificial graphite has few defects and high capacity, can reduce the degree of side reactions with the electrolyte, give full play to the high-capacity characteristics of graphite, reduce gas generation, and enable the battery cell to have both high energy density and good cycle performance.

[0244] In some embodiments, the mass of the coating layer is 0.3% - 5% of the mass of the core; and / or, the average thickness of the coating layer is 100 nm - 300 nm.

[0245] In some embodiments, the mass of the coating layer can be selected as 0.3%, 0.4%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% of the mass of the core or the numerical range between any two of them.

[0246] The mass of the coating layer affects the thickness of the coating layer and also affects the R value R50 at which the cumulative distribution of the negative electrode active material is 50%.

[0247] In some embodiments, the average thickness of the coating layer can be selected as 100 nm, 150 nm, 200 nm, 250 nm, 300 nm or the numerical range between any two of them.

[0248] The thickness of the coating layer can be characterized by transmission electron microscopy (TEM) testing. The negative electrode active material is observed by transmission electron microscopy. Based on the difference in lattice fringes, the coating layer coated on the core surface can be clearly observed. Five locations in the coating layer are randomly selected for testing, and the average value is calculated as the average thickness of the coating layer.

[0249] When the mass ratio of the coating layer or the thickness of the coating layer is within the above range, the consistency of the coating layer can be better, thereby improving the charge exchange capacity of ions on the surface of the negative electrode active material; when the mass ratio of the coating layer or the thickness of the coating layer is within the above range, the side reactions on the surface of the negative electrode active material particles can be kept at a lower level, so that the negative electrode active material has a higher gram capacity. Therefore, when the mass ratio of the coating layer is within the above range, it is beneficial for the battery to have high energy density, good kinetic performance and long cycle life.

[0250] In some embodiments, the coating is disposed on 90%-100% of the surface of the core.

[0251] The coating layer is disposed on 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100% or any range of values ​​therebetween on the surface of the core.

[0252] A coating layer is coated on most of the surface of the core, which can not only provide an end surface for the embedding of active ions, but also reduce the contact between the core and the electrolyte, thereby reducing the co-embedding phenomenon of the electrolyte solvent during the cycle process, thereby taking into account both the fast charging performance and the cycle performance of the battery cell.

[0253] In some embodiments, the negative electrode film layer includes a first negative electrode film layer disposed on the surface of the negative electrode current collector and a second negative electrode film layer disposed on a side of the first negative electrode film layer away from the negative electrode current collector, and the porosity of the second negative electrode film layer is greater than the porosity of the first negative electrode film layer.

[0254] In the present application, the porosity of the negative electrode film layer can be measured by methods known in the art, such as observing the longitudinal cross section of the negative electrode film layer under a scanning electron microscope, and judging the packing density and porosity of the negative electrode active material through the image.

[0255] It is understood that the porosity of the first negative electrode film layer and the second negative electrode film layer can be adjusted by any known method in the art. As an example, the porosity of the negative electrode film layer can be adjusted by adjusting the particle size consistency of the negative electrode active material. The particle size consistency of the negative electrode active material refers to the degree of dispersion of the particle size of the negative electrode active material particles in different film layers from the average particle size, which can reflect the uniformity of the particle size distribution of the negative electrode active material.

[0256] In the embodiments of the present application, a highly conductive electrolyte is adopted. The electrolyte has a high ion transport rate. By designing the second negative electrode film layer close to the electrolyte to have a relatively large porosity, the transport rate of lithium ions in the electrode plate is matched with the liquid-phase transport rate in the electrolyte, improving the fast charging performance of the battery and reducing the risk of lithium plating. At the same time, a low-porosity design is adopted at the part of the negative electrode film layer close to the current collector to take into account the energy density of the battery cell.

[0257] In some embodiments, the first negative electrode film layer includes a first negative electrode active material, and the particle size uniformity of the first negative electrode active material is 0.4 - 0.6; the second negative electrode film layer includes a second negative electrode active material, and the particle size uniformity of the second negative electrode active material is 0.25 - 0.45.

[0258] In the present application, the particle size uniformity of the negative electrode active material has the meaning well-known in the art. It can characterize the degree of dispersion of the particle sizes of all particles in the negative electrode active material deviating from the volume distribution particle size Dv50, and can reflect the uniformity of the particle size distribution of the negative electrode active material. The particle size uniformity of the negative electrode active material has the meaning well-known in the art and can be tested by methods known in the art. For example, it can be directly tested with reference to Standard GB / T 19077.1-2016 using a Malvern Mastersizer 3000 laser diffraction particle size distribution measuring instrument, and its specific calculation formula can refer to the user manual of this instrument.

[0259] In some embodiments, the particle size uniformity of the first negative electrode active material can be selected as 0.40, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.5, 0.51, 0.52, 0.53, 0.54, 0.55, 0.56, 0.57, 0.58, 0.59, 0.6 or the numerical range between any two of them.

[0260] In some embodiments, the particle size uniformity of the second negative electrode active material can be selected as 0.25, 0.26, 0.27, 0.28, 0.29, 0.3, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.4, 0.41, 0.42, 0.43, 0.44, 0.45 or the numerical range between any two of them.

[0261] The negative electrode active material with a particle size uniformity of 0.4 - 0.6 can achieve close packing through the grading of large and small particles, making the first negative electrode film layer have a relatively low porosity; the negative electrode active material with a particle size uniformity of 0.25 - 0.45 has a relatively low particle size uniformity between particles and is difficult to form an effective match, making the second negative electrode film layer have a relatively high porosity.

[0262] In some embodiments, the volume distribution particle size DV50 of the first negative electrode active material is 13.7 μm to 20.7 μm; the volume distribution particle size DV50 of the second negative electrode active material is 10 μm to 18 μm.

[0263] In some embodiments, the volume distribution particle size DV50 of the first negative electrode active material can be selected from 13.7 μm, 14.7 μm, 15.7 μm, 16.7 μm, 17.7 μm, 18.7 μm, 19.7 μm, 20.7 μm or the numerical range between any two of them; the volume distribution particle size DV50 of the second negative electrode active material is 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm or the numerical range between any two of them.

[0264] In some embodiments, the volume distribution particle size D V 10 of the first negative electrode active material is 4.8 μm to 8.0 μm, and the volume distribution particle size D V 10 of the second negative electrode active material is 6.0 μm to 9.5 μm.

[0265] In some embodiments, the volume distribution particle size DV10 of the first negative electrode active material can be selected from 4.8 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm or the numerical range between any two of them; the volume distribution particle size DV10 of the second negative electrode active material is 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm or the numerical range between any two of them.

[0266] When the negative electrode active materials of the first film layer and the second film layer meet this design condition, the pores of the second negative electrode film layer tend to be linear, which is beneficial to the liquid-phase conduction of active ions in the low SOC (State of charge) state at the initial stage of charging. At the same time, there are more small-particle active substances and smaller particle sizes in the second negative electrode film layer, which is beneficial to the charge exchange of active ions in the high SOC state at the end stage of charging, thereby further improving the fast charging performance of the battery.

[0267] In some embodiments, the second negative electrode active material includes artificial graphite, and the first negative electrode active material includes one or more of artificial graphite and natural graphite.

[0268] In some embodiments, the negative electrode film layer includes a first negative electrode film layer disposed on the surface of the negative electrode current collector and a second negative electrode film layer disposed on the side of the first negative electrode film layer away from the negative electrode current collector. The powder compaction density of the negative electrode active material in the second negative electrode film layer under a pressure of 50000 N is less than the powder compaction density of the negative electrode active material in the first negative electrode film layer under a pressure of 50000 N.

[0269] In the present application, the powder compaction density of the material has the meaning well-known in the art and can be measured by instruments and methods known in the art. For example, it can be measured by referring to the standard GB / T 24533-2009 using an electronic pressure testing machine (such as the UTM7305 type). An exemplary test method is as follows: Weigh 1 g of the material and add it to a mold with a bottom area of 1.327 cm 2 , apply pressure up to 5000 kg (equivalent to 50000 N), hold the pressure for 30 s, then release the pressure and keep it for 10 s, and then record and calculate the powder compaction density of the material under a force of 50000 N.

[0270] The small powder compaction density of the negative electrode active material in the second negative electrode film layer close to the electrolyte side is beneficial to maintaining the pore structure of the negative electrode film layer close to the electrolyte side and improving the fast charging performance of the battery cell; at the same time, the large powder compaction density of the negative electrode active material in the first negative electrode film layer far from the electrolyte side is beneficial to increasing the compaction density of the negative electrode film layer and taking into account the energy density of the battery cell.

[0271] In some embodiments, the powder compaction density ρ of the negative electrode active material in the second negative electrode film layer under a pressure of 50000 N 2 satisfies: 1.50 g / cm 3 ≤ρ 2 ≤2.00 g / cm 3 .

[0272] In some embodiments, the powder compaction density ρ of the negative electrode active material in the second negative electrode film layer under a pressure of 50000 N 2 satisfies: 1.55 g / cm 3 ≤ρ 2 ≤1.95 g / cm 3 .

[0273] In some embodiments, the powder compaction density ρ of the negative electrode active material in the second negative electrode film layer under a pressure of 50000 N 2 can be selected as 1.50 g / cm 3 , 1.55 g / cm 3 , 1.60 g / cm 3 , 1.65 g / cm 3 , 1.70 g / cm 3 , 1.75 g / cm 3 , 1.80 g / cm 3 , 1.85 g / cm 3 , 1.90 g / cm 3 , 1.95 g / cm 3 , 2.00 g / cm 3 or any numerical range between any two of them.

[0274] In some embodiments, the powder compaction density ρ of the negative electrode active material in the first negative electrode film layer under a pressure of 50,000 N 1 satisfies: 1.70 g / cm 3 ≤ρ 1 ≤2.05 g / cm 3 .

[0275] In some embodiments, the powder compaction density ρ of the negative electrode active material in the first negative electrode film layer under a pressure of 50,000 N 1 can be optionally 1.70 g / cm 3 , 1.72 g / cm 3 , 1.74 g / cm 3 , 1.76 g / cm 3 , 1.80 g / cm 3 , 1.82 g / cm 3 , 1.84 g / cm 3 , 1.86 g / cm 3 , 1.88 g / cm 3 , 2.00 g / cm 3 , 2.02 g / cm 3 , 2.04 g / cm 3 , 2.05 g / cm 3 or any numerical range between any two of them.

[0276] In some embodiments, the powder compaction density ρ of the negative electrode active material in the first negative electrode film layer under a pressure of 50,000 N 1 satisfies: 1.80 g / cm 3 ≤ρ 1 ≤2.05 g / cm 3 .

[0277] In some embodiments, the areal density of the negative electrode film layer is 0.08 g / 1540.25 mm 2 -0.20 g / 1540.25 mm 2 , and can be optionally 0.10 g / 1540.25 mm 2 -0.16 g / 1540.25 mm 2 .

[0278] In this application, the areal density of the film layer has the meaning well known in the art, and can be tested by methods known in the art. For example, take a single-sided coated and cold-pressed electrode sheet (if it is a double-sided coated electrode sheet, the film layer on one side can be wiped off first), punch it into small round pieces with an area of S 1 , weigh it, and record it as M 1 . Then wipe off the film layer of the above-mentioned weighed electrode sheet, weigh the weight of the current collector, and record it as M0 。The single-sided density of the film layer = (M 1 - M 0 ) / S 1 。To ensure the accuracy of the test results, multiple groups (e.g., 10 groups) of samples to be tested can be tested, and the average value can be calculated as the test result.

[0279] In some embodiments, the single-sided density of the negative electrode film layer can be selected as 0.08 g / 1540.25 mm 2 , 0.09 g / 1540.25 mm 2 , 0.10 g / 1540.25 mm 2 , 0.11 g / 1540.25 mm 2 , 0.12 g / 1540.25 mm 2 , 0.13 g / 1540.25 mm 2 , 0.14 g / 1540.25 mm 2 , 0.15 g / 1540.25 mm 2 , 0.16 g / 1540.25 mm 2 , 0.17 g / 1540.25 mm 2 , 0.18 g / 1540.25 mm 2 , 0.19 g / 1540.25 mm 2 , 0.20 g / 1540.25 mm 2 or any value range between any two of them.

[0280] It can be understood that the single-sided density of the negative electrode film layer is measured on the negative electrode plate, and the single-sided density of the positive electrode film layer is measured on the positive electrode plate.

[0281] The battery cell with the single-sided density of the negative electrode film layer within the above range can reduce the transmission distance of lithium ions in the negative electrode film layer, which is beneficial to improving the fast charging performance of the battery cell.

[0282] In some embodiments, the negative electrode active material further includes a silicon-based material, and the single-sided density of the negative electrode film layer is 0.06 g / 1540.25 mm 2 - 0.15 g / 1540.25 mm 2 。

[0283] In some embodiments, the silicon-based material includes one or more of nano-silicon, silicon-carbon material, silicon-oxygen material, silicon-nitrogen material, and alloy silicon.

[0284] In some embodiments, the negative electrode active material further includes a silicon-based material, and the single-sided density of the negative electrode film layer can be selected as 0.06 g / 1540.25 mm 2 , 0.07 g / 1540.25 mm2 、0.08 g / 1540.25 mm 2 、0.09 g / 1540.25 mm 2 、0.10 g / 1540.25 mm 2 、0.11 g / 1540.25 mm 2 、0.12 g / 1540.25 mm 2 、0.13 g / 1540.25 mm 2 、0.14 g / 1540.25 mm 2 、0.15 g / 1540.25 mm 2 or the numerical range between any two of them.

[0285] Silicon-based materials have a high specific capacity. The addition of silicon-based materials to the negative electrode film layer further reduces the thickness of the negative electrode film layer corresponding to a battery with the same capacity, that is, the areal density of the single side of the negative electrode film layer is further reduced, which is beneficial to reducing the transmission distance of lithium ions in the negative electrode film layer and further improving the fast charging performance of the battery monomer.

[0286] In some embodiments, the compaction density of the negative electrode sheet is 1.2 g / cm 3 -1.9 g / cm 3 , and can be optionally 1.2 g / cm 3 -1.65 g / cm 3 .

[0287] In this application, the compaction density of the negative electrode sheet has the meaning well-known in the art and can be tested by methods known in the art. Remove the negative electrode sheet from the lithium-ion battery, take a certain area of the electrode sheet, and measure the mass and thickness of the electrode sheet and the current collector after removing the film layer respectively. According to the following formula, calculate the compaction density of the electrode sheet. Compaction density of the electrode sheet = (electrode sheet mass - current collector mass) / [(electrode sheet thickness - current collector thickness) × electrode sheet area].

[0288] In some embodiments, the compaction density of the negative electrode sheet can be optionally 1.2 g / cm 3 、1.3 g / cm 3 、1.4 g / cm 3 、1.5 g / cm 3 、1.6 g / cm 3 、1.65 g / cm 3 、1.7 g / cm 3 、1.8 g / cm 3 、1.9 g / cm 3 or the numerical range between any two of them.

[0289] The negative electrode plate with a compaction density within the above range has an appropriate porosity, can match with the electrolyte having a high conductivity, improve the diffusion rate of lithium ions in the negative electrode, reduce the concentration polarization generated by the battery cell during fast charging, and is beneficial to improving the fast charging performance of the battery cell while taking into account the energy density of the battery cell.

[0290] In some embodiments, the average thickness of one side of the negative electrode film layer is 30μm - 150μm, and can be selected as 30μm - 80μm.

[0291] In some embodiments, the average thickness of one side of the negative electrode film layer can be selected as 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 90μm, 95μm, 100μm, 105μm, 110μm, 115μm, 120μm, 125μm, 130μm, 135μm, 140μm, 145μm, 150μm or the numerical range between any two of them.

[0292] The negative electrode film layer with an average thickness within the above range has an appropriate lithium ion diffusion distance, can match with the electrolyte having a high conductivity, improve the diffusion rate of lithium ions in the negative electrode film layer, and improve the fast charging performance of the battery cell while taking into account the energy density of the battery cell.

[0293] In some embodiments, the negative electrode active material further includes a silicon-based material, and the average thickness of one side of the negative electrode film layer is 30μm - 80μm.

[0294] In some embodiments, the negative electrode active material further includes a silicon-based material, and the average thickness of one side of the negative electrode film layer can be selected as 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm or the numerical range between any two of them.

[0295] The silicon-based material has a high specific capacity. The addition of the silicon-based material in the negative electrode film layer further reduces the thickness of the negative electrode film layer corresponding to a battery with the same capacity, which is beneficial to reducing the transmission distance of lithium ions in the negative electrode film layer and further improving the fast charging performance of the battery cell.

[0296] In some embodiments, the porosity of the negative electrode plate is 20% - 60%, and can be selected as 25% - 40%.

[0297] In this application, the porosity of the negative electrode sheet can be tested by methods known in the art. For example, it can be tested based on the national standard GB / T24586-2009. The electrode sheet is immersed in ethyl methyl carbonate (EMC) for cleaning, and a true density meter, a testing instrument, is used to measure based on the gas displacement method. Among them, the percentage of the pore volume in the total volume of the electrode sheet is the porosity of the electrode sheet, and the calculation formula is: porosity = (V - V0) / V × 100%, where V0 is the true volume and V is the apparent volume.

[0298] In some embodiments, the porosity of the negative electrode sheet can be selected as 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60% or any value range between any two of them.

[0299] The negative electrode sheet with porosity within the above range can match with the electrolyte having high conductivity, facilitate the transmission of lithium ions in the negative electrode, reduce the concentration polarization generated during fast charging of the battery cell, and is beneficial to improving the fast charging performance of the battery cell while taking into account the energy density of the battery cell.

[0300] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one side of the positive electrode current collector. The positive electrode film layer includes a positive electrode active material. The positive electrode active material includes a lithium-containing phosphate, and the positive electrode active material includes unagglomerated primary particles; the volume distribution particle size Dv50 of the positive electrode active material 正1 satisfies: 0.3μm ≤ Dv50 正1 ≤ 2μm.

[0301] The volume distribution particle size Dv50 of the positive electrode active material 正 can be tested with reference to the volume distribution particle size of the negative electrode active material above. It can be understood that the unagglomerated primary particles here refer to that the primary particles do not form secondary particles through granulation, which does not mean that the primary particles will not spontaneously aggregate. Due to the small particle size and large specific surface area of the lithium-containing phosphate primary particles, aggregation will inevitably occur during the process of testing the volume distribution particle size by the Malvern scattering method, resulting in the particle size of the primary particle aggregates obtained by the Malvern laser particle size analyzer, making the volume distribution particle size of the positive electrode active material larger than the particle size of the primary particles in the positive electrode active material. In some embodiments, the volume distribution particle size Dv50 of the lithium-containing phosphate in the positive electrode active material 正1 can be selected as 0.3μm, 0.4μm, 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm, 1.6μm, 1.7μm, 1.8μm, 1.9μm, 2μm or any value range between any two of them.

[0302] In some embodiments, the lithium-containing phosphate cathode active material includes unagglomerated primary particles, and the average particle size of the primary particles of the lithium-containing phosphate cathode active material satisfies: 50 nm ≤ D 正1 ≤ 300 nm.

[0303] In some embodiments, the average particle size of the primary particles of the lithium-containing phosphate cathode active material can be selected from 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, 260 nm, 270 nm, 280 nm, 290 nm, 300 nm or the numerical range between any two of them.

[0304] The statistics of the particle size of the primary particles of the cathode active material can be carried out in the following manner. As an example, disassemble the battery to obtain the cathode electrode sheet, peel off the cathode film layer of the cathode electrode sheet, wash the cathode film layer thoroughly with acetone, filter and dry it to obtain a powder. Take 0.05 g of the uniformly mixed powder and dissolve it in 40 mL of absolute ethanol, then add an appropriate amount of dispersant and stir evenly to obtain a suspension. Take 2 mL of the suspension and mix it with 2 mL of absolute ethanol, and then perform ultrasonic treatment. The ultrasonic power is 480 W and the ultrasonic time is 5 min to obtain a uniformly dispersed suspension. Take an appropriate amount of the middle-layer suspension for transmission electron microscopy (TEM) testing to obtain a TEM image. Select 5 - 10 TEM images with the number of particles ranging from 50 to 100 as the sampling areas, ensuring that at least 500 particles are tested. Then, through the Avizo 3D software image processing software, the projected area of each primary particle in each sampling area can be statistically obtained, which is the cross-sectional area S of the primary particle. Among them, when identifying the primary particles, for the particles with obvious adhesion, manual identification and software identification can be combined to determine whether the particle belongs to a single primary particle or two secondary particles. The equivalent circle diameter of the primary particle is obtained by the equivalent circle method, which is the particle size d of the primary particle.

[0305] The lithium-containing phosphate with the average particle size of the primary particles within the above range has both a short ion transport path, low lithium ion transport impedance and low moisture absorption. It can not only match the liquid-phase transport rate of lithium ions in the electrolyte, but also reduce the temperature rise during fast charging of the battery cell, and can also take into account the cycle life of the battery cell by controlling the moisture absorption.

[0306] In some embodiments, the general formula of the composition of the lithium-containing phosphate is shown in Formula VI,

[0307] Li x1 A y1 Mea1 M b1 P 1-c1 X c1 Y z1 Formula VI

[0308] Wherein, 0.5 ≤ x1 ≤ 1.3, 0 ≤ y1 ≤ 1.3, and 0.7 ≤ x1 + y1 ≤ 1.3; 0.9 ≤ a1 ≤ 1.5, 0 ≤ b1 ≤ 0.5, and 0.9 ≤ a1 + b1 ≤ 1.5; 0 ≤ c1 ≤ 0.5; 3 ≤ z1 ≤ 5; A includes one or more of Na, K, Mg; Me includes one or more of Mn, Fe, Co, Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, Ce; X includes one or more of S, Si, Cl, B, C, N; Y includes one or more of O, F.

[0309] In some embodiments, x1 can be selected from 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3 or the numerical range between any two of them, y1 can be selected from 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3 or the numerical range between any two of them, x1 + y1 can be selected from 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3 or the numerical range between any two of them, a1 can be selected from 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5 or the numerical range between any two of them, b1 can be selected from 0, 0.1, 0.2, 0.3, 0.4, 0.5 or the numerical range between any two of them, a1 + b1 can be selected from 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5 or the numerical range between any two of them, c1 can be selected from 0, 0.1, 0.2, 0.3, 0.4, 0.5 or the numerical range between any two of them, z1 can be selected from 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5 or the numerical range between any two of them.

[0310] The lithium-containing phosphate with the above components has good structural stability and low irreversible loss during fast charging, thereby improving the cycle stability of the battery cell.

[0311] In some embodiments, the lithium-containing phosphate has an olivine structure, including but not limited to one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, and their respective doped modification materials, coated modification materials, and composite modification materials. In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector. The positive electrode film layer includes a positive electrode active material. The positive electrode active material contains a lithium-containing transition metal oxide, and the volume distribution particle size Dv50 of the positive electrode active material 正2 satisfies: 2 μm ≤ Dv50 正2 ≤ 15 μm.

[0312] In some embodiments, the lithium-containing transition metal oxide may include but not limited to one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds.

[0313] In some embodiments, the general formula of the lithium-containing transition metal oxide includes Li a Ni b Co c M d O e A f , where 0 < a ≤ 1.2; 0.8 ≤ b < 1; 0 < c < 1; 0 < d < 1; 1 ≤ e ≤ 2; 0 ≤ f ≤ 1; M includes but not limited to one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, and B; A includes but not limited to one or more of N, F, S, and Cl. Thereby, the energy density of the battery cell can be further improved. Optionally, the lithium transition metal oxide may include but not limited to LiNi 0.8 Co 0.1 Mn 0.1 O 2 , LiNi 0.80 Co 0.15 Al 0.05 O 2 , LiNi 0.9 Co 0.06 Mn 0.04 O 2 , LiNi 0.92 Co 0.06 Mn 0.02 O 2 , LiNi 0.96 Co 0.02 Mn 0.02 O 2 , LiNi 0.55 Co 0.07 Mn 0.38 O 2 , LiNi0.55 Co 0.12 Mn 0.33 O 2 、LiNi 0.65 Co 0.1 Mn 0.25 O 2 、LiNi 0.7 Co 0.1 Mn 0.2 O 2 、LiNi 0.6 Co 0.1 Mn 0.3 O 2 One or more of the above.

[0314] In some embodiments, the volume distribution particle size Dv50 of the lithium-containing transition metal oxide of the positive electrode active material 正2 May be 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm or the numerical range between any two of them.

[0315] Volume distribution particle size Dv50 正2 The lithium-containing transition metal oxide of the positive electrode active material within the above range has both a short ion transport path, low lithium ion transport impedance and a low degree of side reactions, can both match the liquid-phase transport rate of lithium ions in the electrolyte and reduce the temperature rise during fast charging of the battery cell, and can also take into account the cycle life of the battery cell by reducing the degree of side reactions.

[0316] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganese oxide, and the Dv50 of the positive electrode active material 正2 Is 6μm - 15μm, may be 8μm - 12μm, and the positive electrode active material includes secondary particles agglomerated from primary particles, and the average particle size of the primary particles in the secondary particles is 0.1μm - 1.5μm.

[0317] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganese oxide, and the Dv50 of the positive electrode active material 正2 May be 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm or the numerical range between any two of them.

[0318] In some embodiments, the positive electrode active material lithium nickel cobalt manganese oxide includes secondary particles formed by agglomeration of primary particles. The average particle size of the primary particles in the secondary particles can be selected from 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm or the numerical range between any two of them.

[0319] The average particle size of the primary particles in the secondary particles can be tested by any well-known method in the art. As an example, a cross-section in the thickness direction of the positive electrode sheet is obtained, and 10 particles in the same scanning electron microscope image (SEM) with the same size and shape at a magnification of 10 kv and 30 k are observed. Then, each of the 10 regions is further divided into 5 positions including four corners and the center. The average particle size of any one primary particle at each position at this magnification is selected, and the average values of the particle sizes at the 5 positions of the four corners and the center are averaged to obtain the average particle size of the primary particles in this region. Then, the average values of the particle sizes of the primary particles obtained from the 10 regions are averaged again to obtain the average particle size of the primary particles. Specifically, the average value of the major axis and the minor axis of each particle is taken as the average particle size of the particle.

[0320] In this embodiment, the positive electrode active material mainly includes secondary particles, that is, a powder material with secondary particles as the main body. The secondary particles include many primary particles with small particle sizes, resulting in short lithium ion transmission paths and many embedding end faces, which can match the electrolyte with a relatively high lithium ion transmission rate and is beneficial to improving the power performance of the battery cell.

[0321] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganese oxide, and the Dv50 of the positive electrode active material 正2 is 2 μm - 5 μm, and can be selected from 2.5 μm - 4.5 μm. The positive electrode active material includes unagglomerated primary particles.

[0322] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganese oxide, and the Dv50 of the positive electrode active material 正2 can be selected from 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm or the numerical range between any two of them.

[0323] In this embodiment, the positive electrode active material mainly includes unagglomerated primary particles, that is, a powder material with unagglomerated primary particles as the main body. The side reaction degree of this positive electrode active material with a carboxylic ester solvent with high activity is low, which is beneficial to further improving the cycle life of the battery cell.

[0324] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganese oxide. The particle size distribution curve of the positive electrode active material shows a bimodal distribution, with the peak positions located at 2 μm - 5 μm and 7 μm - 20 μm respectively. The positive electrode active material includes unagglomerated primary particles and secondary particles formed by the agglomeration of primary particles, and the average particle size of the secondary particles is larger than that of the unagglomerated primary particles.

[0325] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganese oxide. The particle size distribution curve of the positive electrode active material shows a bimodal distribution, with the peak positions located at 2 μm, 3 μm, 4 μm, 5 μm or the numerical range between any two of them and 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm or the numerical range between any two of them.

[0326] The above positive electrode active material forms a grading through secondary particles mainly with large particle sizes and primary particles mainly with small particle sizes, which can further improve the energy density of the battery while taking into account the cycle life and power performance of the battery cell.

[0327] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganese oxide. Based on the total molar number of transition metals in the positive electrode active material, the molar content ratio of cobalt is less than or equal to 20%. The Dv50 of the positive electrode active material 正2 is 2 μm - 5 μm, and the positive electrode active material includes unagglomerated primary particles.

[0328] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganese oxide. Based on the total molar number of transition metals in the positive electrode active material, the molar content ratio of cobalt can be selected from 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20% or the numerical range between any two of them.

[0329] The molar content ratio of cobalt being less than or equal to 20% is beneficial to reducing the cost of the positive electrode active material, but is not conducive to improving the kinetic performance of the positive electrode active material. By using relatively small-sized unagglomerated primary particles, it is possible to reduce the side reaction between the carboxylic acid ester and the positive electrode active material, improve the cycle life of the battery cell, and at the same time improve the kinetic performance of the positive electrode active material and the power performance of the battery cell.

[0330] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganese oxide. Based on the total molar number of transition metals in the positive electrode active material, the molar content ratio of nickel is less than 80%. The Dv50 of the positive electrode active material 正2 is 2 μm - 5 μm, and the positive electrode active material includes unagglomerated primary particles.

[0331] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganese oxide. Based on the total molar number of transition metals in the positive electrode active material, the molar content ratio of nickel can be selected as 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 79% or any value range between any two of them.

[0332] A molar content ratio of nickel less than 80% is beneficial to reducing the nickel dissolution probability of the positive electrode active material at high voltages (charging cut-off voltage ≥ 4.3V) and improving the withstand voltage of the positive electrode active material. Combining a low nickel component with unagglomerated primary particles can further reduce the degree of side reactions between the positive electrode active material and the carboxylic ester solvent, reduce the probability of cracking of the positive electrode active material during high voltage charge and discharge, and improve the cycle performance of the battery cell.

[0333] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganese oxide. Based on the total molar number of transition metals in the positive electrode active material, the molar content ratio of nickel is greater than or equal to 80%, and the Dv50 正2 of the positive electrode active material is 6 μm - 15 μm. The positive electrode active material includes secondary particles formed by agglomeration of primary particles, and the average particle size of the primary particles in the secondary particles is 0.1 μm - 1.5 μm.

[0334] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganese oxide. Based on the total molar number of transition metals in the positive electrode active material, the molar content ratio of nickel is 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or any value range between any two of them.

[0335] Shaping the high nickel material into large-sized secondary particles is beneficial to simultaneously improving the specific capacity of the positive electrode active material and the grading of the positive electrode sheet, and improving the energy density of the battery. At the same time, the secondary particles are composed of primary particles with small particle sizes, which can shorten the transmission distance of lithium ions, increase the number of embedding end faces, reduce the DC impedance of the battery cell, and improve the power performance of the battery cell.

[0336] In some embodiments, the positive electrode active material includes cobalt element. In the particles of the positive electrode active material, the mass ratio of cobalt element near the particle surface is greater than the mass ratio of cobalt element near the center of the positive electrode active material particle.

[0337] The mass percentage of cobalt element in the cathode active material particles can be obtained by measuring the percentage of the mass of cobalt element relative to the mass of all elements at different positions of the cross-section of the cathode active material particles. As an example, an argon ion cross-section polisher (model JEOL IB-19530CP) and a scanning electron microscope (model Zeiss sigma 300) (equipped with an energy dispersive spectrometer (EDS, model Oxford Energy Spectrometer OXFord X-Max-50mm2)) can be used in combination for the determination. The longitudinal cross-section of the cathode film layer is obtained by using the ion cross-section polisher, and the line scan of Co element is performed on the cross-section of the cathode active material particles using the scanning electron microscope. The mass percentage of cobalt element near the particle surface is greater than that near the center of the cross-section of the cathode active material particles.

[0338] In some embodiments, the ratio of the mass percentage of cobalt element near the particle surface of the cathode active material to the mass percentage of cobalt element near the center of the cathode active material particles is in the range of (1.2 - 5.0):1, and can be optionally (1.4 - 2.0):1.

[0339] The ratio of the mass percentage of cobalt element at the particle surface of the cathode active material to the mass percentage of cobalt element at the center can be calculated by the ratio of the mass of cobalt element at different sites in the line scan. Among them, the region near the particle surface is the region between the surface of the particle and a depth of 200 nm in the direction towards the geometric center of the particle, and the region near the center of the cathode active material particles is the spherical region with a diameter of 200 nm centered on the geometric center of the particle cross-section.

[0340] In some embodiments, the ratio of the mass percentage of cobalt element at the particle surface of the cathode active material to the mass percentage of cobalt element at the center can be optionally 1.2:1, 1.3:1, 1.4:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5.0:1 or any value within the range between any two of them.

[0341] Although the highly conductive electrolyte is beneficial to improving the liquid-phase transport rate of lithium ions, at the same time, the components in the highly conductive electrolyte have relatively high electrochemical activity. For example, the carboxylic ester in the highly conductive electrolyte is prone to side reactions with the oxygen-releasing structure after the phase change on the surface of the cathode active material, increasing gas production and deteriorating the cycle life of the battery. The cathode active material surface has a relatively high cobalt element content, which helps to improve the ionic conductivity of the cathode active material, improve the problem of excessive delithiation on the surface of the cathode active material during charge and discharge, reduce the cation mixing of the Li layer and the transition metal layer, stabilize the layered structure of the cathode active material, and reduce the risk of structural phase change on the surface of the cathode active material, thereby reducing the degree of side reactions of the battery cell and improving the cycle life of the battery cell. And the relatively low cobalt content at the center of the cathode active material can synchronously reduce the cost of the cathode active material.

[0342] In some embodiments, the positive electrode active material includes lithium-containing phosphate, and the single-sided density of the positive electrode film layer is 0.2 g / 1540.25 mm 2 -0.35 g / 1540.25 mm 2 .

[0343] In some embodiments, the positive electrode active material includes lithium-containing phosphate, and the single-sided density of the positive electrode film layer can be selected from 0.2 g / 1540.25 mm 2 , 0.21 g / 1540.25 mm 2 , 0.22 g / 1540.25 mm 2 , 0.23 g / 1540.25 mm 2 , 0.24 g / 1540.25 mm 2 , 0.25 g / 1540.25 mm 2 , 0.26 g / 1540.25 mm 2 , 0.27 g / 1540.25 mm 2 , 0.28 g / 1540.25 mm 2 , 0.29 g / 1540.25 mm 2 , 0.3 g / 1540.25 mm 2 , 0.31 g / 1540.25 mm 2 , 0.32 g / 1540.25 mm 2 , 0.33 g / 1540.25 mm 2 , 0.34 g / 1540.25 mm 2 , 0.35 g / 1540.25 mm 2 or any numerical range between any two of them.

[0344] In some embodiments, the positive electrode active material includes lithium-containing transition metal oxide, and the single-sided density of the positive electrode film layer is 0.13 g / 1540.25 mm 2 -0.24 g / 1540.25 mm 2 ;

[0345] In some embodiments, the positive electrode active material includes lithium-containing transition metal oxide, and the single-sided density of the positive electrode film layer can be selected from 0.13 g / 1540.25 mm 2 , 0.14 g / 1540.25 mm 2 , 0.15 g / 1540.25 mm 2 , 0.16 g / 1540.25 mm 2 , 0.17 g / 1540.25 mm 2 , 0.18 g / 1540.25 mm2 、0.19 g / 1540.25 mm 2 、0.20 g / 1540.25 mm 2 、0.21 g / 1540.25 mm 2 、0.22 g / 1540.25 mm 2 、0.23 g / 1540.25 mm 2 、0.24 g / 1540.25 mm 2 or a numerical range between any two of them.

[0346] The positive electrode film layer with areal density within the above range has a suitable thickness, which is beneficial to the diffusion of active ions in the electrode sheet, and can more effectively improve the fast charging performance of the battery cell; at the same time, it can reduce heat generation, reduce the reaction activity of the electrolyte and the probability of side reactions, and take into account the cycle performance of the battery cell.

[0347] In some embodiments, the porosity of the positive electrode film layer is 22%-35%.

[0348] In some embodiments, the porosity of the positive electrode film layer can be selected as 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35% or a numerical range between any two of them.

[0349] The positive electrode film layer with porosity within the above range is beneficial to the diffusion of active ions in the electrode sheet, and can more effectively improve the fast charging performance of the battery cell; at the same time, it can reduce heat generation, reduce the reaction activity of the electrolyte and the probability of side reactions, and take into account the cycle performance of the battery cell.

[0350] In some embodiments, the lithium ion conductivity of the electrolyte is 10 mS / cm - 20 mS / cm.

[0351] The increase in the lithium ion conductivity of the electrolyte often means that a higher content of highly conductive solvent needs to be added. While the highly conductive solvent has a high transmission rate for lithium ions, it also has high chemical reaction activity and is prone to side reactions with the negative electrode active material, reducing the cycle life of the battery. The electrolyte with lithium ion conductivity within the above range has a suitable lithium ion conduction rate and reaction activity, and can better balance the fast charging performance and cycle life of the battery cell.

[0352] In some embodiments, the lithium ion conductivity of the electrolyte is 12 mS / cm - 20 mS / cm, and can be selected as 10 mS / cm - 15 mS / cm.

[0353] In some embodiments, the positive electrode active material includes lithium iron phosphate, and the areal density of the single side of the positive electrode film layer is 0.2 g / 1540.25 mm 2-0.35 g / 1540.25 mm 2 ; The conductivity of the electrolyte is 12 mS / cm - 20 mS / cm.

[0354] It can be understood that the positive electrode active material includes lithium iron phosphate in lithium iron phosphate, which may be a salt having a lithium iron phosphate structure, or a doped modified material, a coated modified material of lithium iron phosphate, or a mixture of lithium iron phosphate and other active materials.

[0355] Lithium iron phosphate has a relatively low specific capacity. Therefore, the positive electrode film layer of a battery cell with the same capacity often requires a relatively high coating areal density. An electrolyte with a conductivity within the above range is beneficial to improving the loss of the coating areal density required for a lithium iron phosphate battery on the kinetic performance of the battery cell, while taking into account the power performance of the battery while meeting the battery energy density requirements.

[0356] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganese oxide, and the single-sided areal density of the positive electrode film layer is 0.13 g / 1540.25 mm 2 -0.24 g / 1540.25 mm 2 ; The conductivity of the electrolyte is 10 mS / cm - 15 mS / cm.

[0357] Lithium nickel cobalt manganese oxide has a relatively high specific capacity. Therefore, the coating areal density of the positive electrode film layer of a battery cell with the same capacity is relatively low, and an electrolyte with a relatively low conductivity can meet the fast charging performance requirements of the battery cell. The above battery cell can take into account the cycle life of the battery while meeting the power performance of the battery.

[0358] In some embodiments, the negative electrode current collector may include a metal foil, a three-dimensional porous current collector, or a composite current collector. As an example of the metal foil, copper foil, copper alloy foil, nickel foil, nickel alloy foil, aluminum foil, or aluminum alloy foil can be used. As an example of the three-dimensional porous current collector, copper mesh, nickel mesh, copper foam, nickel foam, or aluminum foam can be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include, but is not limited to, one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, aluminum, aluminum alloy, silver, and silver alloy. As an example, the polymer material base layer may include, but is not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0359] In some embodiments, the negative electrode film layer may further include other negative electrode active materials well known in the art. For example, the other negative electrode active materials include, but are not limited to, one or more of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate.

[0360] In some embodiments, the negative electrode film layer may further optionally include a negative electrode conductive agent. As an example, the negative electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0361] In some embodiments, the negative electrode film layer may further optionally include a negative electrode binder. As an example, the negative electrode binder may include, but is not limited to, one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0362] In some embodiments, the negative electrode film layer may further optionally include other additives. As an example, the other additives may include, but are not limited to, thickeners such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.

[0363] The negative electrode film layer is generally formed by coating a negative electrode slurry on a negative electrode current collector and then drying and cold pressing. The negative electrode slurry is generally formed by dispersing a negative electrode active material, a negative electrode conductive agent, a negative electrode binder, and other optional additives in a solvent and stirring evenly. The solvent may be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

[0364] The negative electrode plate does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode plate may further include a conductive bottom layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector; in some embodiments, the negative electrode plate may further include a protective layer covering the surface of the negative electrode film layer.

[0365] In some embodiments, the positive electrode film layer may further optionally include a positive electrode conductive agent. As an example, the positive electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0366] In some embodiments, the positive electrode film layer may optionally further include a positive electrode binder. As an example, the positive electrode binder may include, but is not limited to, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride - tetrafluoroethylene - propylene terpolymer, vinylidene fluoride - hexafluoropropylene - tetrafluoroethylene terpolymer, tetrafluoroethylene - hexafluoropropylene copolymer, fluorinated acrylate resin, styrene - butadiene rubber (SBR), water - soluble unsaturated resin SR - 1B, water - based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), carboxymethyl chitosan (CMCS), or one or more of them.

[0367] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. As an example of the metal foil, aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include, but is not limited to, one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy. As an example, the polymer material base layer may include, but is not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE).

[0368] The positive electrode film layer is usually formed by coating a positive electrode slurry on the positive electrode current collector and then drying and cold - pressing. The positive electrode slurry is usually formed by dispersing a positive electrode active material, a positive electrode conductive agent, a positive electrode binder, and any other components in a solvent and stirring evenly. The solvent may be N - methylpyrrolidone (NMP), but is not limited thereto.

[0369] In some embodiments, the battery cell includes an electrolyte. The present application does not specifically limit the type of the electrolyte, and it can be selected according to requirements. For example, the electrolyte may include one or more of a solid electrolyte and a liquid electrolyte (i.e., an electrolyte solution).

[0370] In some embodiments, as an example, the electrolyte salt may include, but is not limited to, lithium hexafluorophosphate (LiPF 6 )、lithium tetrafluoroborate (LiBF 4 )、lithium perchlorate (LiClO 4 )、lithium hexafluoroarsenate (LiAsF 6 )、lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluorophosphate (LiPO 2 F 2) one or more of lithium difluoro(oxalato)phosphate (LiDFOP) and lithium tetrafluoro(oxalato)phosphate (LiTFOP).

[0371] In some embodiments, the solvent further includes, but is not limited to, one or more of ester solvents, sulfone solvents, and ether solvents. By way of example, the solvent may include, but is not limited to, one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0372] In some embodiments, the electrolyte may optionally further include other additives.

[0373] In some embodiments, the battery cell further includes a separator. The separator is disposed between the positive electrode plate and the negative electrode plate, mainly functioning to prevent internal short circuit.

[0374] This application does not particularly limit the type of the separator, and any well-known porous structure separator with good chemical stability and mechanical stability can be selected.

[0375] In some embodiments, the material of the separator may include, but is not limited to, one or more of glass fiber, non-woven fabric, polyethylene (PE), polypropylene (PP), and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer may be the same or different.

[0376] The preparation method of the battery cell in the battery cell is well-known. In some embodiments, the positive electrode plate, the separator, the negative electrode plate, and the electrolyte may be assembled to form a battery cell. By way of example, the positive electrode plate, the separator, and the negative electrode plate may be formed into an electrode assembly through a winding process and / or a stacking process, the electrode assembly is placed in an outer package, dried, and then the above-mentioned electrolyte is injected, and after processes such as encapsulation, standing, and formation, a battery cell is obtained. A plurality of battery cells may further be combined in series or in parallel or in a hybrid connection to form a battery module. A plurality of battery modules may further form a battery pack through series or parallel or hybrid connection. In some embodiments, a plurality of battery cells may also directly form a battery pack.

[0377] The embodiments of this application further provide a preparation method of a negative electrode active material, which can prepare the negative electrode active material provided by the embodiments of this application.

[0378] The preparation method comprises the following steps: providing graphite; fusing the graphite with a coating agent; subjecting the fused product to carbonization treatment under a protective gas atmosphere so that the coating agent is carbonized into a coating layer at least covering the surface of the graphite to obtain the negative electrode active material. The negative electrode active material comprises a core part and a coating layer at least partially covering the surface of the core part. The core part comprises graphite, and in the cumulative distribution curve of the R value obtained in the surface scanning mode of a laser confocal Raman spectrometer for the negative electrode active material, starting from the lower limit, the R value R50 with a cumulative distribution of 50% is 0.15 - 0.50.

[0379] In some embodiments, the method of providing graphite comprises the following steps: providing a coke raw material; performing crushing treatment, shaping treatment and grading treatment on the coke raw material to obtain aggregates; mixing the obtained aggregates with a binder and sequentially performing granulation treatment and graphitization treatment to obtain graphite.

[0380] The particle size of the coke raw material is generally relatively large, and the particle size of the coke raw material can be reduced through crushing treatment. Optionally, the crushing treatment may include two steps of coarse crushing and pulverization. Coarse crushing can crush the coke raw material into millimeter-sized blocky particles. Pulverization can crush the particle size from the millimeter level to the tens of micrometer level. After the crushing treatment, the surface of the coke raw material is uneven, and the shaping treatment can make the coke raw material particles themselves more round. The grading treatment can reduce the content of particles with too large and too small particle sizes, and can further adjust the particle size and particle size distribution of the coke raw material.

[0381] The coke raw material may include one or more of petroleum-based needle coke and coal-based needle coke. These coke raw materials are anisotropic materials, which are beneficial to reducing the disorder degree of the inner core material, increasing the specific capacity of the inner core material and the overall specific capacity of the negative electrode active material, and are also beneficial to increasing the energy density of the battery. Optionally, the mass of the binder may be 6% - 12% of the mass of the aggregates obtained by the grading treatment, and may be optionally 8% - 10%. Thereby, the graphite can have a good secondary particle morphology.

[0382] Optionally, the binder may include pitch.

[0383] The equipment used for the granulation treatment may include any one of a horizontal reaction kettle or a vertical reaction kettle.

[0384] Optionally, the granulation treatment may adopt a stepped temperature rise and heat preservation process. Thereby, the graphite can have a good secondary particle morphology and high capacity.

[0385] Optionally, 2 - 4 programmed temperature rise platforms may be set during the temperature rise process.

[0386] Generally, the surfaces of coke raw materials from different batches and with different raw materials are uneven and have many defects. Graphitization treatment can also significantly repair the surface defects of the materials, thereby making the Raman values in the surface scanning mode of the core material have good concentration, and further improving the consistency of the properties of the graphite products.

[0387] The equipment used for graphitization treatment can include any one of Acheson graphitization furnace, box furnace or internal flash furnace.

[0388] Optionally, the temperature of graphitization treatment can be 2800°C - 3800°C, for example, it can be 2800°C, 2850°C, 2900°C, 3000°C, 3100°C, 3200°C, 3300°C, 3400°C, 3500°C, 3600°C, 3700°C, 3800°C, or the range composed of any of the above values. More optionally, the temperature of graphitization treatment can be 2850°C - 3300°C. The specific time of graphitization treatment can be reasonably selected according to the equipment used.

[0389] When the graphitization temperature is high and the graphitization treatment time is long, the specific capacity of graphite is high, the degree of disorder is small, and the R value R50 with a cumulative distribution of 50% of graphite is small.

[0390] By selecting an appropriate graphitization treatment temperature, the battery can have both high energy density and good kinetic performance.

[0391] In some embodiments, the coating agent includes a hard carbon coating agent and / or a soft carbon coating agent.

[0392] Hard carbon refers to carbon that is difficult to be graphitized and is the thermal decomposition of high molecular polymers. Common hard carbons include resin carbon, organic polymer pyrolysis carbon, carbon black, etc.

[0393] Soft carbon refers to amorphous carbon that can be graphitized at a high temperature above 2500 degrees Celsius. Common soft carbons include one or more of petroleum coke, needle coke, carbon fiber, carbon microsphere, by-products of coking, and residues from crude oil distillation.

[0394] In some embodiments, the coating agent includes a solid-phase coating agent, and the fusion is solid-solid fusion.

[0395] The solid-phase coating agent has advantages such as low cost and relatively simple process, and is easy to be popularized industrially.

[0396] In some embodiments, the coating agent includes a liquid-phase coating agent, and the fusion is solid-liquid fusion.

[0397] In some embodiments, the coking value of the liquid-phase hard carbon coating agent can be 35% - 50%, and can be optionally 38% - 48%.

[0398] The coking value of the liquid-phase hard carbon coating agent is the percentage of the residual carbon mass left after heating a specified amount of the liquid-phase hard carbon coating agent sample under specified conditions to the mass of the liquid-phase hard carbon coating agent sample, and the test can be carried out with reference to GB / T 8727-2008.

[0399] In some embodiments, the mass of the liquid-phase hard carbon coating agent can be 0.7%-10% of the mass of graphite, for example, it can be 0.7%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range composed of any of the above values. Optionally, the mass of the liquid-phase hard carbon coating agent can be 3%-7% of the mass of graphite.

[0400] As the mass ratio of the liquid-phase hard carbon coating agent increases, the R value R50 with a cumulative distribution of 50% of the negative electrode active material increases, and the degree of disorder on the surface of the negative electrode active material particles increases.

[0401] When the mass ratio of the liquid-phase hard carbon coating agent is within the above range, the uncoated degree of the negative electrode active material can be within a small range, so that both the charge exchange ability of ions on the surface of the prepared negative electrode active material can be improved, the side reactions on the surface of the prepared negative electrode active material particles can be at a low level, and the prepared negative electrode active material can have a high specific capacity, which is beneficial to the battery having both a high energy density, good kinetic performance, and a long cycle life.

[0402] In some embodiments, the liquid-phase soft carbon coating agent includes petroleum or coal-based by-products such as liquid-phase asphalt and liquid tar.

[0403] In some embodiments, the liquid-phase hard carbon coating agent includes liquid resin, and the liquid resin is a hard carbon precursor material. When the coating layer includes hard carbon, the negative electrode active material and the battery can have better kinetic performance.

[0404] The liquid resin can be obtained commercially, or synthesized according to methods known in the art, or obtained by mixing and stirring resin powder with a solvent evenly.

[0405] In some embodiments, the viscosity of the liquid resin at 25 °C can be 150 mPa·s - 2500 mPa·s. For example, it can be 150 mPa·s, 200 mPa·s, 300 mPa·s, 400 mPa·s, 500 mPa·s, 600 mPa·s, 700 mPa·s, 800 mPa·s, 850 mPa·s, 950 mPa·s, 1050 mPa·s, 1200 mPa·s, 1400 mPa·s, 1600 mPa·s, 1800 mPa·s, 2000 mPa·s, 2250 mPa·s, 2500 mPa·s, or a range composed of any of the above values. Optionally, the viscosity of the liquid resin at 25 °C can be 300 mPa·s - 950 mPa·s.

[0406] The viscosity of the liquid resin can be tested with reference to GB / T 14074-2017. The test temperature is 25 °C, and the test equipment can be an NDJ-1 type rotational viscometer.

[0407] When the viscosity of the liquid resin is within the above range, the liquid resin can have both good fluidity and diffusivity, as well as good curing and coating effects. Thus, the liquid resin can be evenly dispersed on the surface of graphite particles, which is beneficial to improving the coating effect, reducing the uncoated degree, and can also improve the coating uniformity on the surface of graphite particles, thereby being beneficial to the battery having both good kinetic performance and long cycle life.

[0408] In some embodiments, the solid content of the liquid resin can be 50% - 88%, and can be optionally 60% - 85%.

[0409] The solid content of the liquid-phase hard carbon coating agent can be tested by the drying method with reference to GB / T 14074-2017. The free components and moisture in the liquid-phase hard carbon coating agent will volatilize at high temperature. The solid content of the liquid-phase hard carbon coating agent refers to the percentage of the remaining mass after drying under specified conditions to the total mass. The oven temperature is set at 150 °C and baked until constant weight.

[0410] When the solid content of the liquid resin is within the above range, the liquid resin can have both good fluidity and diffusivity, as well as good curing and coating effects. Thus, the liquid resin can be evenly dispersed on the surface of graphite particles, which is beneficial to improving the coating effect, reducing the uncoated degree, and can also adjust the R value R50 of the cumulative distribution of the negative electrode active material to 50%, increase the disorder degree on the surface of the negative electrode active material particles, and enhance the charge exchange ability of ions on the surface of the negative electrode active material, thereby being beneficial to the battery having both good kinetic performance and long cycle life.

[0411] In some embodiments, the liquid resin may include at least one of a liquid phenolic resin, a liquid epoxy resin, a liquid vinyl ester resin, a liquid unsaturated polyester resin, a liquid furan resin, and their respective derivatives. Derivatives generally refer to products derived from the substitution of hydrogen atoms or atomic groups in a polymer by other atoms or atomic groups.

[0412] The above liquid resin is a good hard carbon precursor material. As a liquid-phase hard carbon coating agent, it can better improve the kinetic performance of the battery and endow the battery with good cycling performance.

[0413] In some embodiments, the liquid-phase hard carbon coating agent includes a liquid phenolic resin, and the solid content of the liquid phenolic resin can be 60%-82%, and the weight-average molecular weight can be 300-800.

[0414] Optionally, the solid content of the liquid phenolic resin can be 68%-78%, and the weight-average molecular weight can be 450-700.

[0415] Compared with other liquid resins, the hard carbon formed by the carbonization and coking of the liquid phenolic resin itself has better performance.

[0416] By further adjusting the solid content and weight-average molecular weight of the liquid phenolic resin within the above ranges, the hard carbon formed by its carbonization can have better kinetic performance, can also improve the coating effect, reduce the uncoated degree, thereby improving the charge exchange ability of ions on the surface of the negative active material, and further improving the kinetic performance of the negative active material.

[0417] The weight-average molecular weight of the liquid phenolic resin can be tested by gel permeation chromatography. The test instrument can be an Agilent 1290 Infinity II GPC system. The eluent can be tetrahydrofuran, and polystyrene standards are used for calibration.

[0418] The liquid phenolic resin can be formed by the polycondensation of phenolic compounds, aldehyde compounds, etc. in the presence of an alkali catalyst. The polycondensation reaction initially generates a liquid. The liquid phenolic resin mentioned in the embodiments of the present application is a resole phenolic resin.

[0419] The phenolic compounds may include one or more of phenol, cresol, dimethylphenol, nonylphenol, bisphenol A, bisphenol F, resorcinol, propylphenol, ethylphenol, and cardanol, and phenol is optional. The aldehyde compounds may include one or more of formaldehyde, acetaldehyde, butyraldehyde, paraformaldehyde, and furfural, and formaldehyde is optional. The alkali catalyst may include one or more of sodium hydroxide, potassium hydroxide, barium hydroxide, calcium hydroxide, magnesium hydroxide, ammonia water, sodium carbonate, and tertiary amines.

[0420] In some embodiments, the equipment for solid-liquid fusion of graphite and the liquid-phase hard carbon coating agent can be a fusion machine.

[0421] Optionally, the stirring speed of the fusion machine can be 300 r / min - 1000 r / min. For example, it can be 300 r / min, 350 r / min, 400 r / min, 450 r / min, 500 r / min, 550 r / min, 600 r / min, 650 r / min, 700 r / min, 750 r / min, 800 r / min, 850 r / min, 900 r / min, 1000 r / min, or any range composed of the above values. More optionally, the stirring speed of the fusion machine can be 450 r / min - 850 r / min.

[0422] Increasing the stirring speed of the fusion machine is beneficial to improving the coating effect and reducing the uncoated degree. Thereby, the charge exchange ability of ions on the surface of the negative electrode active material can be enhanced, and further the kinetic performance of the negative electrode active material can be improved. However, if the stirring speed of the fusion machine is too large, the outer surface structure of the core will be damaged, and strong centrifugal force will also cause mass loss of the liquid-phase hard carbon coating agent.

[0423] Optionally, the stirring time for solid-liquid fusion can be 4 min - 10 min. For example, it can be 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, or any range composed of the above values. More optionally, the stirring time for solid-liquid fusion can be 6 min - 8 min.

[0424] Increasing the stirring time for solid-liquid fusion is beneficial to improving the coating effect and reducing the uncoated degree. Thereby, the charge exchange ability of ions on the surface of the negative electrode active material can be enhanced, and further the kinetic performance of the negative electrode active material can be improved. However, if the stirring time is too long, the gain in improving the coating effect is not obvious, and at the same time, the energy consumption will increase.

[0425] In some embodiments, the equipment for carbonization treatment can be a track kiln.

[0426] In some embodiments, the heat preservation temperature for carbonization treatment can be 900°C - 1500°C. For example, it can be 900°C, 1000°C, 1050°C, 1100°C, 1150°C, 1200°C, 1250°C, 1300°C, 1350°C, 1400°C, 1500°C, or any range composed of the above values. Optionally, the heat preservation temperature for carbonization treatment can be 1050°C - 1350°C.

[0427] In some embodiments, the heat preservation time for carbonization treatment can be 2h - 10h, for example, it can be 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, or a range composed of any of the above values. Optionally, the heat preservation time for carbonization treatment can be 5h - 8h. The heat preservation time for carbonization treatment refers to the residence time at the heat preservation temperature.

[0428] In some embodiments, the preparation method may further include the steps of depolymerizing, screening, and demagnetizing the material after carbonization treatment.

[0429] Depolymerization can be carried out in a depolymerizer. Depolymerization can eliminate the weak adhesiveness on the surface of the coating layer and reduce the problem of excessive agglomeration of the obtained finished product particles. Screening can reduce the content of large particles and fine powder in the obtained finished product, thereby facilitating the obtaining of the desired particle size and particle size distribution. Demagnetization can reduce the content of magnetic impurities in the obtained finished product. Magnetic impurities will increase the self-discharge of the battery and reduce the battery performance.

[0430] In another embodiment, the present application also provides a preparation method for a negative electrode active material in which the core is secondary particles aggregated by primary graphite particles and the coating layer includes amorphous carbon. For the convenience of description, this negative electrode active material is referred to as composite graphite material.

[0431] The method includes the steps of: S10, providing coke powder or coke powder added with kinetic carbon material raw material powder, and performing graphitization treatment on the coke powder or coke powder added with kinetic carbon material raw material powder to obtain body particles. The body particles are secondary particles aggregated by two or more primary particles, and the body particles include artificial graphite; S20, mixing the body particles with an organic carbon source, or mixing the body particles with an organic carbon source and kinetic carbon material raw material powder, and forming a coating layer including amorphous carbon on at least a part of the surface of the body particles after carbonization treatment to obtain a composite graphite material, that is, a negative electrode active material with a core of body particles and a coating layer including amorphous carbon.

[0432] Among them, kinetic carbon material raw material powder is added in at least one of steps S10 and S20. The kinetic carbon material raw material is selected from one or more of hard carbon, expanded graphite, and graphene. The interlayer spacing d002 of the (002) crystal plane of the kinetic carbon material raw material > 0.335nm.

[0433] It can be understood that the product of the kinetic carbon material after graphitization treatment and / or carbonization treatment is the kinetic carbon material.

[0434] The air oxidation temperature T of the obtained composite graphite material 0 is 630°C to 730°C, and the air oxidation temperature T 0It is the temperature corresponding to the intersection point of two tangents at two points on the thermogravimetric curve of the composite graphite material corresponding to 500 °C and T1 temperature respectively. The T1 temperature is the peak temperature of the peak with the largest area in the differential thermogravimetric curve of the composite graphite material. The thermogravimetric curve and the differential thermogravimetric curve can be obtained through thermogravimetric analysis carried out under the following conditions: sample mass 10 ± 0.05 mg, purge gas is air and the gas flow rate is 60 mL / min, heating rate is 5 °C / min, and the test temperature range is 35 °C to 950 °C.

[0435] Specifically, the air oxidation temperature T 0 can be determined according to the thermogravimetric analysis including the following steps: subject the composite graphite material to thermogravimetric test under the conditions of weighing mass 10 ± 0.05 mg, purge gas is air and the gas flow rate is 60 mL / min, heating rate is 5 °C / min, and the test temperature range is 35 °C to 950 °C to obtain the thermogravimetric curve and the differential thermogravimetric curve, read the peak temperature T1 of the peak with the largest area from the differential thermogravimetric curve, and determine the intersection point of two tangents at two points on the thermogravimetric curve corresponding to 500 °C and T1 temperature respectively. The temperature corresponding to this intersection point on the thermogravimetric curve is the air oxidation temperature T of the composite graphite material 0 .

[0436] The preparation method of the composite graphite material of the present application is simple in operation and controllable in cost, and can be used for large-scale industrial production.

[0437] In some embodiments, the method for providing coke powder includes the steps of: coking the coke raw material to obtain coke, and performing crushing, shaping, and grading on the obtained coke to obtain coke powder.

[0438] In some embodiments, the coke can be directly obtained by commercial purchase.

[0439] Optionally, the coke raw material can be selected from one or more of petroleum-based raw materials and coal-based raw materials. As an example, the petroleum-based raw materials are selected from one or more of heavy oil, residue oil, and vacuum residue oil, and the coal-based raw materials are mainly selected from coal tar pitch. Among them, heavy oil, residue oil, and vacuum residue oil are usually produced in the petroleum refining process, and coal tar pitch is usually produced in the coal carbonization process.

[0440] In some embodiments, the coke includes one or more of petroleum-based non-needle coke, petroleum-based needle coke, coal-based non-needle coke, and coal-based needle coke. Optionally, the coke includes one or more of petroleum-based non-needle coke (such as petroleum calcined coke, petroleum-based green coke) and petroleum-based needle coke. In particular, the coke includes petroleum-based green coke. Using a suitable coke can make the prepared composite graphite material have an appropriate number of end faces and defects, and thus have better active ion and electron transport performance and higher structural stability, so that the fast charging performance, low-temperature power performance, and cycle performance of the battery can be improved.

[0441] Optionally, the coking treatment of the coke raw material is carried out in a delayed coking unit. The delayed coking unit includes a heating furnace and a coke drum. The delayed coking process refers to quickly heating the coke raw material to the required coking treatment temperature in the heating furnace first, and then entering the coke drum, and generating coke through processes such as preheating and coke quenching in the coke drum.

[0442] The coke can be crushed by using equipment and methods known in the art, such as a jet mill, a mechanical mill, a roller press mill or other crushing equipment.

[0443] The morphology of the coke powder obtained after crushing may include one or several of blocky, spherical and quasi-spherical. After crushing is completed, shaping is carried out to polish the edges and corners of the coke powder. The greater the degree of shaping, the closer the powder particles are to a spherical shape, which can increase the deintercalation active ion sites on the surface of the composite graphite material. The shaping treatment is also beneficial to the subsequent granulation process, so that the secondary particles in the obtained composite graphite material have higher structural stability.

[0444] The coke powder can be shaped by using equipment and methods known in the art, such as a shaping machine or other shaping equipment.

[0445] During the crushing and shaping processes, a large number of too small particles are often generated, and sometimes there are also too large particles. Therefore, classification treatment can be carried out according to requirements to remove the too small particles and too large particles in the powder. After classification treatment, coke powder with a better particle size distribution can be obtained, which is convenient for subsequent granulation and coating processes. The classification treatment can be carried out by using equipment and methods known in the art, such as a sieve shaker, a gravity classifier, a centrifugal classifier, etc.

[0446] In some embodiments, the volume average particle size Dv50 of the coke powder is 6 μm to 12 μm. Optionally, the volume average particle size Dv50 of the coke powder is 8 μm to 10 μm.

[0447] In some embodiments, the method for providing the kinetic carbon material raw material powder includes the steps of: crushing, shaping, and classifying the kinetic carbon material raw material to obtain the kinetic carbon material raw material powder. Among them, the methods of crushing, shaping, and classifying are the same as those of the above-mentioned coke crushing, shaping, and classifying.

[0448] In some embodiments, the volume average particle size Dv50 of the kinetic carbon material raw material powder is 3 μm to 12 μm. Optionally, the volume average particle size Dv50 of the kinetic carbon material raw material powder is 4 μm to 9 μm.

[0449] In some embodiments, the ratio of the volume average particle size Dv50 of the coke powder to the volume average particle size Dv50 of the kinetic carbon material raw powder is 1.05 to 1.75. Optionally, the ratio of the volume average particle size Dv50 of the coke powder to the volume average particle size Dv50 of the kinetic carbon material raw powder is 1.2 to 1.5. When the ratio of the volume average particle size Dv50 of the coke powder to the volume average particle size Dv50 of the kinetic carbon material raw powder is within a suitable range, the primary particles of the composite graphite material can have a good degree of secondary particles.

[0450] In some embodiments, in the coke powder added with the kinetic carbon material raw powder, the mass ratio of the coke powder to the kinetic carbon material raw powder is 1 to 20:99 to 80. Optionally, the mass ratio of the coke powder to the kinetic carbon material raw material is 3 to 12:97 to 88. When the mass ratio of the coke powder to the kinetic carbon material raw powder is within a suitable range, it is beneficial to obtain a composite graphite material with moderate end face and defect content. Furthermore, on the premise of high energy density, the battery cell can also have significantly improved fast charging performance and low-temperature power performance.

[0451] In some embodiments, based on the total mass of the obtained composite graphite material, the total mass percentage of the kinetic carbon material raw powder added in steps S10 and S20 is 1% to 30%. For example, 3% to 30%, 3% to 25%, 3% to 20%, 3% to 15%, 5% to 30%, 5% to 25%, 5% to 20%, 5% to 15%, 8% to 30%, 8% to 25%, 8% to 20%, 8% to 15%, or 8% to 12%.

[0452] In some embodiments, the method further includes the step of adding a binder in S10. The binder is mixed with the coke powder and then granulated, and then graphitized to obtain primary particles, or the binder is mixed with the coke powder added with the kinetic carbon material raw powder and then granulated, and then graphitized to obtain primary particles.

[0453] Adding a binder can make the primary particles of the composite graphite material have a good degree of secondary particles, which is beneficial to improving the active ion and electron transport performance of the composite graphite material while making it have high structural stability.

[0454] Optionally, based on the total mass of the obtained composite graphite material, the mass percentage of the binder is 3% to 12%. Further optionally, the mass percentage of the binder is 5% to 8%. When the content of the binder is within a suitable range, excessive particle agglomeration can be avoided, and the primary particles of the composite graphite material can have a good degree of secondary particles.

[0455] Optionally, the binder is selected from pitch. Optionally, the softening point of the pitch is above 200 °C.

[0456] Optionally, the asphalt is selected from one or more of coal tar pitch and petroleum asphalt.

[0457] Optionally, the volume average particle size Dv50 of the particles obtained after granulation is 8 μm to 14 μm. In particular, the volume average particle size Dv50 of the particles obtained after granulation is 9.5 μm to 12 μm.

[0458] Granulation can be carried out using equipment and methods known in the art, such as a granulator. The granulator generally includes a stirring reaction kettle and a module for controlling the temperature of the reaction kettle. By regulating the stirring speed, heating rate, granulation temperature, cooling rate, etc. during the granulation process, the degree of granulation and the structural strength of the particles can be regulated, and the volume average particle size Dv50 of the bulk particles of the finally prepared composite graphite material can be within the required range.

[0459] In some embodiments, in S10, the graphitization temperature can be 2800 °C to 3200 °C. Optionally, the graphitization temperature can be 2900 °C to 3100 °C. Graphitization can make the bulk particles have a suitable degree of graphitization, and then the composite graphite material has a higher specific capacity. Graphitization also makes the lattice expansion of the bulk particles lower during the process of intercalating and deintercalating active ions. Graphitization can also effectively eliminate the bulk phase structure defects of the bulk particles and improve the cycle performance of the single battery.

[0460] In some embodiments, in S10, the graphitization time is 10 days to 15 days.

[0461] Graphitization can be carried out using equipment and methods known in the art, such as a graphitization furnace, particularly an Acheson graphitization furnace. After the graphitization treatment, a small amount of oversize particles formed by agglomeration of the granulation product during the graphitization process can also be removed by screening, which can prevent the oversize particles from affecting the processing performance of the composite graphite material, such as the stability and coating performance of the negative electrode slurry.

[0462] In some embodiments, in S10, the volume average particle size Dv50 of the obtained bulk particles is 7.5 μm to 13.5 μm. Optionally, the volume average particle size Dv50 of the obtained bulk particles is 9.0 μm to 11.5 μm.

[0463] In some embodiments, in S20, the organic carbon source is selected from one or more of coal tar pitch, petroleum asphalt, phenolic resin, and coconut shell. Optionally, the organic carbon source is selected from petroleum asphalt. Optionally, the softening point of coal tar pitch and petroleum asphalt is below 250 °C.

[0464] In some embodiments, based on the total mass of the obtained composite graphite material, the addition amount of the organic carbon source is such that the mass percentage of the amorphous carbon obtained after carbonization of the organic carbon source is 1% to 8%. Optionally, the addition amount of the organic carbon source is such that the mass percentage of the amorphous carbon obtained after carbonization of the organic carbon source is 2% to 5%. When the addition amount of the organic carbon source is within a suitable range, the composite graphite material can have a high specific capacity while also having a high active ion solid-phase transport capacity.

[0465] In some embodiments, in S20, the carbonization treatment temperature is 700°C to 1800°C. Optionally, the carbonization treatment temperature is 1000°C to 1300°C. When the carbonization treatment temperature is within a suitable range, the organic carbon source (and optionally the kinetic carbon material raw material) can be carbonized, and a coating layer containing amorphous carbon can be formed on at least a part of the surface of the artificial graphite.

[0466] In some embodiments, in S20, the carbonization treatment time is 1 h to 6 h.

[0467] In some embodiments, the method for preparing the composite graphite material includes the steps of: S10, providing coke powder and kinetic carbon material raw material powder, mixing a binder with the coke powder and the kinetic carbon material raw material powder, granulating, and then performing graphitization treatment to obtain body particles, where the body particles are secondary particles formed by aggregation of two or more primary particles, and the body particles include artificial graphite; S20, mixing the body particles with an organic carbon source, and after carbonization treatment, forming a coating layer containing amorphous carbon on at least a part of the surface of the body particles to obtain the composite graphite material.

[0468] In some embodiments, the method for preparing the composite graphite material includes the steps of: S10, providing coke powder, mixing a binder with the coke powder, granulating, and then performing graphitization treatment to obtain body particles, where the body particles are secondary particles formed by aggregation of two or more primary particles, and the body particles include artificial graphite; S20, mixing the body particles with an organic carbon source and kinetic carbon material raw material powder, and after carbonization treatment, forming a coating layer containing amorphous carbon on at least a part of the surface of the body particles to obtain the composite graphite material.

[0469] In some embodiments, the method for preparing the composite graphite material includes the steps of: S10, providing coke powder and kinetic carbon material raw material powder, mixing a binder with the coke powder and the kinetic carbon material raw material powder, granulating, and then performing graphitization treatment to obtain body particles, where the body particles are secondary particles formed by aggregation of two or more primary particles, and the body particles include artificial graphite; S20, mixing the body particles with an organic carbon source and kinetic carbon material raw material powder, and after carbonization treatment, forming a coating layer containing amorphous carbon on at least a part of the surface of the body particles to obtain the composite graphite material.

[0470] In the preparation method of the present application, the coke powder or the coke powder added with the raw material powder of the kinetic carbon material is graphitized to obtain the body particles, and the body particles are secondary particles aggregated by two or more primary particles. Among them, the coke powder obtained after being crushed, shaped and other treatments is mainly single particles. From the morphology, the coke powder is primary particles (or primary particles); the body particles obtained after granulation and graphitization of the coke powder or the coke powder added with the raw material powder of the kinetic carbon material are aggregates of multiple above-mentioned primary particles. Therefore, from the morphology, the body particles are secondary particles.

[0471] In the preparation method of the present application, by adjusting the volume average particle size Dv50 and its addition amount of the coke powder, the volume average particle size Dv50 and its addition amount of the raw material powder of the kinetic carbon material, the addition amount of the binder, the addition amount of the organic carbon source, etc., a composite graphite material with different air oxidation temperatures T can be obtained. 0 of the composite graphite material.

[0472] Battery device

[0473] The embodiment of the present application also provides a battery device. The battery device includes the battery monomer provided by the embodiment of the present application, and the battery monomer is used to provide electric energy. The battery device includes one or more of a battery module, a battery pack, and an energy storage battery.

[0474] Electrical device

[0475] The embodiment of the present application also provides an electrical device. The electrical device includes the battery monomer provided by the embodiment of the present application or the battery device provided by the embodiment of the present application, and the battery monomer or the battery device is used to provide electric energy. The battery can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device can be but is not limited to mobile devices (such as mobile phones, tablet computers, laptop computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc.

[0476] The electrical device can select the specific type of battery according to its usage requirements, such as a battery monomer, a battery module or a battery pack.

[0477] Figure 6 is a schematic diagram of an electrical device as an example. The electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirements of the electrical device for high power and high energy density, a battery pack or a battery module can be used.

[0478] Another example of an electrical device can be a mobile phone, a tablet computer, a laptop computer, etc. This electrical device usually requires being thin and light, and a battery cell can be used as the power source.

[0479] Example

[0480] The following embodiments more specifically describe the content disclosed in the present application. These embodiments are only for illustrative purposes, because various modifications and changes within the scope of the content disclosed in the present application are obvious to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and all instruments used in the embodiments are commercially available.

[0481] Example 1

[0482] (1) Preparation of the negative electrode active material

[0483] The petroleum-based acicular coke is subjected to crushing treatment, shaping treatment, and grading treatment to obtain aggregates; the obtained aggregates are mixed with binder pitch at a mass ratio of 100:8 and placed in a horizontal reactor for granulation treatment. During heating, a stepped temperature rise and insulation process is adopted, and the programmed temperature rise platforms are set at 200°C, 300°C, and 600°C respectively, with a constant temperature of 1 h at 200°C, 2 h at 300°C, and 2 h at 600°C, and then taken out of the furnace after cooling for 3 h; the granulated material is placed in an Acheson graphitization furnace for graphitization treatment at 2900°C for 50 h to obtain graphite.

[0484] The graphite and the liquid-phase hard carbon coating agent are subjected to solid-liquid fusion at a mass ratio of 100:5 using a fusion machine. The stirring speed of the fusion machine is 600 r / min, and the stirring time is 7 min. The liquid-phase hard carbon coating agent is a commercially available liquid phenolic resin with a weight-average molecular weight of 600, a viscosity of 680 mPa·s at 25°C, and a solid content of 73%-74%; the solid-liquid fused product is placed in a track kiln and heated to 1150°C in a nitrogen atmosphere for carbonization treatment, with a holding time of 370 min. After completion, it is cooled to 50°C and then taken out of the furnace, and then subjected to depolymerization, screening, and demagnetization treatment to obtain the negative electrode active material. The specific capacity of the negative electrode active material is 357.0 mAh / g, and the powder compaction density of the negative electrode active material is 1.75 g / cm 3 . The air oxidation temperature of the negative electrode active material is 730°C. The thickness of the coating layer of the negative electrode active material is 150 nm.

[0485] (2) Preparation of the negative electrode plate

[0486] Mix the above-mentioned negative electrode active material, thickener sodium carboxymethyl cellulose, negative electrode binder styrene-butadiene rubber (SBR), and negative electrode conductive agent Super P according to a mass ratio of 96.9:1.1:1.5:0.5, add the solvent deionized water, and stir evenly under the action of a vacuum mixer to prepare a negative electrode slurry.

[0487] Coat the negative electrode slurry evenly on both surfaces of the negative electrode current collector copper foil. After air-drying the coated negative electrode current collector at room temperature, transfer it to an oven for drying, and then obtain a negative electrode sheet through cold pressing and slitting. The thickness of the negative electrode film layer on one side of the negative electrode current collector is 53 μm, and the areal density of the single side of the negative electrode film layer is 0.131 g / 1540.25 mm 2 , and the tap density of the negative electrode sheet is 1.6 g / cm 3 , and the porosity of the negative electrode sheet is 30%.

[0488] (3) Preparation of the positive electrode sheet

[0489] Mix the positive electrode active material LiNi 0.65 Co 0.1 Mn 0.25 O 2 , positive electrode conductive agent Super P, and positive electrode binder polyvinylidene fluoride (PVDF) according to a mass ratio of 96:2:2, add the solvent N-methylpyrrolidone (NMP), and stir under the action of a vacuum mixer until the system becomes homogeneous and transparent to obtain a positive electrode slurry; coat the positive electrode slurry evenly on both surfaces of the positive electrode current collector aluminum foil; after air-drying the coated positive electrode current collector at room temperature, transfer it to an oven for drying, and then obtain a positive electrode sheet through cold pressing and slitting. The volume distribution particle size Dv50 正2 of the positive electrode active material is 3.5 μm, and the main composition is primary particles; the areal density of the single side of the positive electrode film layer is 0.23 g / 1540.25 mm 2 ; the porosity of the positive electrode film layer is 25%.

[0490] (4) Preparation of the electrolyte

[0491] Ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl acetate (EA) are mixed in a mass ratio of 3:2:5, and lithium difluoro(oxalato)borate LiDFOB as the first additive, methylene methanedisulfonate (MMDS, formula V), the additive shown in formula III, and a third additive are slowly added. The third additive includes fluoroethylene carbonate FEC, 1,3-propane sultone PS, and vinylene sulfate DTD. Based on the total mass of the electrolyte, the mass content of the first additive is 1%, the total mass content of the second additive is 2%, where the mass content of MMDS in the electrolyte is 0.5%, the mass content of the additive shown in formula III in the electrolyte is 1.5%, and the total mass content of the third additive is 3.2%, where the mass content of FEC in the electrolyte is 1%, the mass content of PS in the electrolyte is 0.7%, and the mass content of DTD in the electrolyte is 1.5%.

[0492]

[0493] Then, the fully dried lithium salt LiPF 6 is dissolved in the mixed solvent in a certain proportion to prepare an electrolyte. The mass content of LiPF 6 in the electrolyte is 12.5%, and the conductivity of the electrolyte is 13.5 mS / cm.

[0494] (5) Preparation of the separator

[0495] A 12-micron polyethylene film is selected.

[0496] (6) Preparation of the battery (full cell)

[0497] The above positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an insulating role, and then wound to obtain an electrode assembly; the electrode assembly is placed in an outer package, and the prepared electrolyte is injected into the dried electrode assembly. After processes such as vacuum packaging, standing, formation, and shaping, a battery containing a wound battery core is obtained.

[0498] The battery preparation methods of Examples 2 - 4 are basically the same as those of Example 1, except that the coating method of the negative electrode active material is adjusted. The specific preparation method is as follows:

[0499] Example 2

[0500] (1) Preparation of the negative electrode active material

[0501] The petroleum-based needle coke is subjected to crushing treatment, shaping treatment and grading treatment to obtain aggregates; the obtained aggregates are mixed with binder pitch in a mass ratio of 100:8 and placed in a horizontal reactor for heating and granulation treatment. During heating, a stepped temperature rise and heat preservation process is adopted, and the programmed temperature rise platforms are set at 200 °C, 300 °C and 600 °C respectively. It is kept at 200 °C for 1 h, 300 °C for 2 h, and 600 °C for 2 h, and then taken out of the furnace after cooling for 3 h; the granulated material is placed in an Acheson graphitization furnace for graphitization treatment at 2900 °C for 50 h to obtain graphite.

[0502] The graphite and the liquid-phase hard carbon coating agent are subjected to solid-liquid fusion in a mass ratio of 100:3 by using a fusion machine. The stirring speed of the fusion machine is 600 r / min, and the stirring time is 7 min. The liquid-phase hard carbon coating agent is a commercially available liquid phenolic resin with a weight-average molecular weight of 580, a viscosity of 550 mPa·s at 25 °C, and a solid content of 70%-71%; the product after solid-liquid fusion is placed in a track kiln and heated to 1150 °C in a nitrogen atmosphere for carbonization treatment. The heat preservation time is 6 h, and then it is cooled to 50 °C and taken out of the furnace. After depolymerization, screening and demagnetization treatment, the negative electrode active material is obtained.

[0503] Example 3

[0504] (1) Preparation of negative electrode active material

[0505] The petroleum-based needle coke is subjected to crushing treatment, shaping treatment and grading treatment to obtain aggregates; the obtained aggregates are mixed with binder pitch in a mass ratio of 100:8 and placed in a horizontal reactor for heating and granulation treatment. During heating, a stepped temperature rise and heat preservation process is adopted, and the programmed temperature rise platforms are set at 200 °C, 300 °C and 600 °C respectively. It is kept at 200 °C for 1 h, 300 °C for 2 h, and 600 °C for 2 h, and then taken out of the furnace after cooling for 3 h; the granulated material is placed in an Acheson graphitization furnace for graphitization treatment at 2900 °C for 50 h to obtain graphite.

[0506] The graphite and the liquid-phase hard carbon coating agent are subjected to solid-liquid fusion in a mass ratio of 100:0.7 by using a fusion machine. The stirring speed of the fusion machine is 600 r / min, and the stirring time is 7 min. The liquid-phase hard carbon coating agent is a commercially available liquid phenolic resin with a weight-average molecular weight of 580, a viscosity of 550 mPa·s at 25 °C, and a solid content of 70%-71%; the product after solid-liquid fusion is placed in a track kiln and heated to 1150 °C in a nitrogen atmosphere for carbonization treatment. The heat preservation time is 6 h, and then it is cooled to 50 °C and taken out of the furnace. After depolymerization, screening and demagnetization treatment, the negative electrode active material is obtained.

[0507] Example 4

[0508] (1) Preparation of negative electrode active material

[0509] The petroleum coke is subjected to crushing treatment, shaping treatment and classification treatment to obtain aggregate; the obtained aggregate is mixed with binder asphalt in a mass ratio of 100:8 and placed in a horizontal reactor for heating for granulation treatment. During heating, a stepped heating and heat preservation process is adopted, and the programmed temperature rising platforms are set at 200°C, 300°C and 600°C respectively, with a constant temperature of 200°C for 1 h, a constant temperature of 300°C for 2 h, and a constant temperature of 600°C for 2 h. After cooling for 3 h, it is taken out of the furnace; the granulated material is placed in an Acheson graphitization furnace for graphitization treatment at 2900°C for 50 h to obtain graphite.

[0510] The graphite and the solid-phase coating agent are subjected to solid-solid stirring by a fusion machine in a mass ratio of 100:3. The solid-phase coating agent is asphalt with a softening point of 270°C; the solid-solid stirring product is placed in a track kiln, heated to 1150°C in a nitrogen atmosphere for carbonization treatment, with a heat preservation time of 6 h, and then cooled to 50°C and taken out of the furnace. After depolymerization, screening and demagnetization treatment, the negative electrode active material is obtained.

[0511] Example 5

[0512] The battery preparation method of Example 5 is basically the same as that of Example 1, except that the preparation method of the negative electrode active material is adjusted: the specific preparation method is as follows:

[0513] (1) Preparation of negative electrode active material

[0514] The petroleum resid is subjected to delayed coking treatment at 490°C - 510°C to obtain petroleum non-needle coke green coke; the green coke is crushed, shaped and classified to obtain coke powder with a volume average particle size Dv50 of 9.5 μm as the main raw material of the composite graphite material.

[0515] For the expanded graphite with an interlayer spacing d 002 of 0.3363 nm (expansion multiple is 180), it is crushed, shaped and classified to obtain expanded graphite powder with a volume average particle size Dv50 of 7.5 μm.

[0516] The coke powder and the expanded graphite powder are mixed, then mixed with binder coal tar pitch, and then granulated. The volume average particle size Dv50 of the obtained granules is about 13 μm. The granulated product is placed in a graphite crucible, and then the graphite crucible is placed in an Acheson graphitization furnace. Resistance material is filled around the graphite crucible, and an electric current is passed through the resistance material to generate heat energy, and graphitization treatment is carried out at about 3000°C to obtain the main body particles.

[0517] The obtained main body particles are mixed with organic carbon source petroleum asphalt and then carbonized in a track kiln. The highest temperature zone is about 1150°C, and the running time of the highest temperature zone is about 4 h to form a coating layer on at least a part of the surface of the main body particles to obtain the composite graphite material.

[0518] Among them, based on the total mass of the obtained composite graphite material, the mass percentage of the expanded graphite powder added is 8%, the mass percentage of the binder added is 6%, and the mass of the organic carbon source added is such that the mass percentage of the amorphous carbon obtained after carbonization of the organic carbon source is 3%. The powder compaction density of the composite graphite material is 1.64 g / cm 3 , and the specific capacity is 355.8 mAh / g. The volume distribution particle size Dv50 of the composite graphite material is 13 μm, the volume distribution particle size Dv50 of the primary particles in the secondary particles is 8 μm, and the air oxidation temperature T 0 of the negative electrode active material is 694 °C.

[0519] Example 6

[0520] The battery preparation method of Example 6 is basically the same as that of Example 1, except that the preparation method of the negative electrode active material is adjusted: the specific preparation method is as follows:

[0521] (1) Preparation of the negative electrode active material

[0522] The petroleum-based needle coke is subjected to crushing treatment, shaping treatment and classification treatment to obtain aggregates; the obtained aggregates and binder pitch are mixed in a mass ratio of 100:8 and placed in a horizontal reaction kettle for granulation treatment. During heating, a stepped heating and heat preservation process is adopted, and the programmed heating platforms are set at 200 °C, 300 °C, and 600 °C respectively. The temperature is kept constant at 200 °C for 1 h, 300 °C for 2 h, and 600 °C for 2 h, and then it is taken out of the furnace after cooling for 3 h; the granulated material is placed in an Acheson graphitization furnace for graphitization treatment at 2850 °C for 45 h to obtain graphite.

[0523] The graphite and the solid-phase coating agent are subjected to solid-solid stirring in a mass ratio of 100:5 by using a fusion machine; the solid-phase coating agent is pitch with a softening point of 270 °C; the solid-solid stirring product is placed in a track kiln and heated to 1150 °C in a nitrogen atmosphere for carbonization treatment, and the heat preservation time is 6 h, and then it is taken out of the furnace after cooling to 50 °C. After depolymerization, screening and demagnetization treatment, the negative electrode active material is obtained.

[0524] The battery preparation methods of Examples 7-8 are basically the same as that of Example 1, except that the preparation method of the negative electrode plate is adjusted: the specific preparation method is as follows:

[0525] Example 7

[0526] Preparation method of the negative electrode plate:

[0527] The first negative electrode active material, binder SBR, thickener sodium carboxymethyl cellulose (CMC-Na), conductive agent carbon black (Super-P) and deionized water were added to a stirring tank in a certain order according to a mass ratio of 96.2:1.8:1.2:0.8 for mixing to prepare negative electrode slurry 1;

[0528] The second negative electrode active material, binder SBR, thickener sodium carboxymethyl cellulose (CMC-Na), conductive agent carbon black (Super-P) and deionized water were added to a stirring tank in a certain order according to a weight ratio of 96.2:1.8:1.2:0.8 for mixing to prepare negative electrode slurry 2;

[0529] Among them, the preparation methods of the first negative electrode active material and the second negative electrode active material are basically the same as the preparation method of the negative electrode active material in Example 1, except that the particle size consistency is different. By adjusting the granulation parameters, the particle size consistency of the first negative electrode active material is 0.43, and the particle size consistency of the second negative electrode active material is 0.35, so that the porosity of the first negative electrode film layer is less than that of the second negative electrode film layer.

[0530] Through a double-chamber coating device, negative electrode slurry 1 and negative electrode slurry 2 were simultaneously extruded. Negative electrode slurry 1 was coated on a copper foil current collector to form a first negative electrode film layer, and negative electrode slurry 2 was coated on the first negative electrode film layer to form a second negative electrode film layer.

[0531] The single-sided surface density of the negative electrode film layer is 0.13 mg / 1540.25 mm 2 。

[0532] Example 8

[0533] Preparation method of negative electrode plate:

[0534] Based on the preparation method of the negative electrode active material in Example 1, the first negative electrode active material was prepared by selecting raw materials and adjusting the material preparation process. The powder compaction density of the first negative electrode active material under a pressure of 50000 N is 1.98 g / cm 3 。Taking the negative electrode active material prepared in Example 1 as the second negative electrode active material, its powder compaction density under a pressure of 50000 N is 1.75 g / cm 3 。The powder compaction density of the first negative electrode active material is greater than that of the second negative electrode active material.

[0535] The first negative electrode active material, binder SBR, thickener sodium carboxymethyl cellulose (CMC-Na), conductive agent carbon black (Super-P) and deionized water were added to a stirring tank in a certain order according to a mass ratio of 96.2:1.8:1.2:0.8 for mixing to prepare negative electrode slurry 1;

[0536] The second negative electrode active material, binder SBR, thickener sodium carboxymethyl cellulose (CMC-Na), conductive agent carbon black (Super-P) and deionized water were added to a stirring tank in a weight ratio of 96.2:1.8:1.2:0.8 in a certain order for mixing to prepare negative electrode slurry 2;

[0537] Through a double-chamber coating device, negative electrode slurry 1 and negative electrode slurry 2 were simultaneously extruded. Negative electrode slurry 1 was coated on a copper foil current collector to form a first negative electrode film layer, and negative electrode slurry 2 was coated on the first negative electrode film layer to form a second negative electrode film layer.

[0538] The single-sided areal density of the negative electrode film layer is 0.13 g / 1540.25 mm 2 。

[0539] Example 9

[0540] The battery preparation method of Example 9 was basically the same as that of Example 1, except that the positive electrode active material and the preparation method of the positive electrode plate were adjusted. Specifically, the preparation method of the positive electrode active material is as follows:

[0541] 1) Preparation of the positive electrode active material precursor

[0542] Nickel sulfate, manganese sulfate and cobalt sulfate were added to deionized water to prepare a mixed solution, in which the molar ratio of nickel element, cobalt element and manganese element was Ni:Co:Mn = 55.6:11:33.4; 0.4 mol / L ammonia water and 1 mol / L sodium hydroxide aqueous solution were added to the mixed solution to adjust the pH of the reaction system to 11.3, and the reaction was carried out under the conditions of stirring at 40 °C and 600 rpm. During the reaction, inert gas nitrogen was introduced for protection. After the reaction was completed, the solid-phase product was washed with deionized water, and after the washing was completed, it was dried at 100 °C to obtain the positive electrode active material precursor Ni 0.556 Co 0.11 Mn 0.334 (OH) 2 。

[0543] 2) Preparation of the precursor 1 of the active substance particles

[0544] Lithium carbonate Li 2 CO 3 、positive electrode active material precursor Ni 0.556 Co 0.11 Mn 0.334 (OH) 2 and zirconia ZrO 2The mixture is mixed and then mechanically mixed. Based on the total molar amount of metal elements (nickel, cobalt and manganese, i.e., Me=Ni+Co+Mn) of the positive electrode active material precursor, the amount of lithium carbonate added is such that the molar ratio of lithium to Me is Li:Me=1.06:1; the amount of zirconium oxide added is such that the molar ratio of zirconium to Me is Zr:Me=2.031×10 -3 :1.

[0545] The mixed material was placed in a tube furnace and heated to 940°C at 5°C / min in air atmosphere for 13 h. It was then cooled to room temperature and pulverized in a jet mill (Shenfei (40m 3 )), with a crushing gas pressure of 0.35 MPa and a feeding rate of 300 Kg / h, the 2 mm particles are crushed to obtain active material particle precursor 1.

[0546] 3) Preparation of active material particle precursor 2

[0547] Cobalt hydroxide was added to the precursor 1 of the active material particles obtained above. Based on the total molar amount of the metal elements (nickel, cobalt and manganese, i.e., Me = Ni + Co + Mn) of the positive electrode active material precursor, the amount of cobalt hydroxide added was such that the molar ratio of the cobalt element to Me was 1.14×10 -2 :1, after being fully mixed, the temperature was raised to 700°C at 5°C / min in an air atmosphere and sintered for 5 hours, and then cooled to room temperature in the furnace to obtain an active material particle precursor 2.

[0548] 4) Preparation of low-cobalt positive electrode active materials

[0549] The obtained active material particle precursor 2 was subjected to tempering treatment at a temperature of 500° C. for 5 h to obtain a positive electrode active material, wherein the general formula of the positive electrode active material includes Li 1.03 (Ni 0.55 Co 0.12 Mn 0.33 ) 0.998 Zr 0.002 O 2 .

[0550] The prepared positive electrode active material, conductive carbon black SP and binder polyvinylidene fluoride (PVDF) are dispersed in a solvent N-methylpyrrolidone (NMP) in a weight ratio of 18:1:1, mixed evenly, and a positive electrode slurry is obtained; the positive electrode slurry is evenly coated on the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet is obtained.

[0551] The battery preparation methods of Examples 10-13 are basically the same as that of Example 1, except that the components and ratios of the electrolyte are adjusted, thereby adjusting the lithium-ion conductivity of the electrolyte.

[0552] Example 10

[0553] The preparation method of the electrolyte is as follows: Ethylene carbonate (EC) and methyl acetate (MA) are mixed according to a mass ratio of 3:7. Then, the fully dried lithium salt LiPF 6 is dissolved in the mixed solvent at a ratio of 1 mol / L, and additives are added with reference to Example 1 to prepare an electrolyte, such that the lithium-ion conductivity of the electrolyte is 20 mS / cm.

[0554] Example 11

[0555] The difference in the preparation method of the electrolyte from that of Example 1 is that the first additive is not added to the electrolyte.

[0556] Example 12

[0557] The difference in the preparation method of the electrolyte from that of Example 1 is that the second additive is not added to the electrolyte.

[0558] Example 13

[0559] The preparation method of the electrolyte is basically the same as that of the electrolyte solvent in Example 1, except that the ratio of the solvents in the electrolyte is that the mass ratio of ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl acetate (EA), and methyl acetate is 3:2:2.5:2.5.

[0560] Example 14

[0561] The preparation method of Example 14 is basically the same as that of Example 1, except that the cathode active material is different. The cathode active material is LiNi 0.8 Co 0.12 Mn 0.08 O 2 , whose Dv50 is 8 um, mainly consists of secondary particles aggregated by primary particles, and the average particle size of the primary particles is 200 nm.

[0562] Example 15

[0563] The preparation method of Example 15 is basically the same as that of Example 1, except that the type and mass content of the electrolyte salt in the electrolyte are changed. Based on the total mass of the electrolyte, the mass content of lithium hexafluorophosphate is 8.75%, and the mass content of lithium bis(fluorosulfonyl)imide is 4.62%.

[0564] The preparation methods of Examples 16 and 17 are basically the same as that of Example 1, except that the preparation method of the battery monomer is different:

[0565] Example 16

[0566] Preparation of battery (full battery):

[0567] Stack the positive electrode plate (the width of the positive current collector part is 87 mm and the length is 240 mm), the separator, and the negative electrode plate in sequence, so that the separator is between the positive and negative electrode plates to play an isolation role, and an electrode assembly is obtained; place the electrode assembly in the outer package, inject the prepared electrolyte into the dried electrode assembly, and through processes such as vacuum packaging, standing, formation, and shaping, a battery containing a stacked cell is obtained.

[0568] Example 17

[0569] Preparation of battery (full battery):

[0570] Stack the positive electrode plate (the width of the positive current collector part is 102 mm and the length is 240 mm), the separator, and the negative electrode plate in sequence, so that the separator is between the positive and negative electrode plates to play an isolation role, and an electrode assembly is obtained; place the electrode assembly in the outer package, inject the prepared electrolyte into the dried electrode assembly, and through processes such as vacuum packaging, standing, formation, and shaping, a battery containing a stacked cell is obtained.

[0571] The battery preparation method of Comparative Examples 1-2 is basically the same as that of Example 1, except that the coating method of the negative active material is adjusted. The specific preparation method is as follows:

[0572] Comparative Example 1

[0573] Except for the different preparation processes of the negative active material, the battery preparation process is the same as that of Example 1.

[0574] (1) Preparation of negative active material

[0575] Crush, shape, and classify petroleum-based needle coke to obtain aggregates; mix the obtained aggregates with binder pitch in a mass ratio of 100:8 and place them in a horizontal reaction kettle for granulation treatment. During heating, a stepped temperature rise and heat preservation process is adopted, and the programmed temperature rise platforms are set at 200 °C, 300 °C, and 600 °C respectively, with a constant temperature of 1 h at 200 °C, 2 h at 300 °C, and 2 h at 600 °C. After cooling for 3 h, take out of the furnace; place the granulated material in an Acheson graphitization furnace for graphitization treatment at 2900 °C for 50 h, and then through screening and demagnetization treatment, graphite is obtained as the negative active material.

[0576] Comparative Example 2

[0577] Except for the different preparation processes of the negative active material, the battery preparation process is the same as that of Example 1.

[0578] (1) Preparation of the negative electrode active material

[0579] The petroleum-based needle coke is subjected to crushing treatment, shaping treatment and grading treatment to obtain aggregates; the obtained aggregates and binder pitch are mixed at a mass ratio of 100:8 and placed in a horizontal reactor for granulation treatment. During heating, a stepped temperature rise and insulation process is adopted, and the programmed temperature rise platforms are set at 200 °C, 300 °C and 600 °C respectively, with a constant temperature of 200 °C for 1 h, 300 °C for 2 h, 600 °C for 2 h, and then cooled for 3 h before discharging; the granulated material is placed in an Acheson graphitization furnace for graphitization treatment at 2850 °C for 45 h to obtain graphite.

[0580] The graphite and the solid-phase coating agent are subjected to solid-solid stirring by a mixer at a mass ratio of 100:6.3, and the solid-phase coating agent is pitch with a softening point of 270 °C; the solid-solid stirring product is placed in a track kiln and heated to 1150 °C in a nitrogen atmosphere for carbonization treatment, with a holding time of 6 h, then cooled to 50 °C and discharged, and after depolymerization, screening and demagnetization treatment, the negative electrode active material is obtained.

[0581] The battery preparation method of Comparative Example 3 is basically the same as that of Example 1, except that the electrolyte formulation is adjusted, specifically:

[0582] Comparative Example 3

[0583] Except for the different preparation of the electrolyte, the battery preparation process is the same as that of Example 1.

[0584] (1) Preparation of the electrolyte

[0585] Ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed at a volume ratio of 1:1:1 to obtain an organic solvent; LiPF 6 is uniformly dissolved in the above organic solvent to obtain an electrolyte, wherein the concentration of LiPF 6 is 1 mol / L and the conductivity of the electrolyte is 8 mS / cm.

[0586] Performance test

[0587] 10%-80% SOC charging time test

[0588] The batteries of the examples and comparative examples were first charged and discharged at a current of 1C (i.e., the current value that completely discharges the theoretical capacity within 1 h). Specifically, at 35 °C, the battery was charged at a constant current of 1C rate until the voltage reached 4.4V, then charged at a constant voltage until the current ≤ 0.05C, rested for 5 min, and then discharged at a constant current of 0.33C rate until the voltage reached 2.5V. The actual capacity was recorded as C0. Then the battery was successively charged at constant currents of 1.0C0, 1.3C0, 1.5C0, 1.8C0, 2.0C0, 2.3C0, 2.5C0, 3.0C0, 3.5C0, 4C0, 4.5C0, 5C0 until the full-battery charge cut-off voltage of 4.4V or the 0V negative electrode cut-off potential (whichever reached first). After each charge was completed, it was discharged at 1C0 until the full-battery discharge cut-off voltage of 2.5V. The negative electrode potential corresponding to 10%, 20%, 30%, ……, 80% SOC (State of Charge, when "SOC = 0" it means the battery is fully discharged, when "SOC = 100%" it means the battery is fully charged) at different charging rates was recorded, and the charging rate-negative electrode potential curve at different SOC states was plotted. After linear fitting, the charging rate corresponding to the negative electrode potential of 0V at different SOC states was obtained. This charging rate is the charging window at this SOC state, denoted as C(10% SOC), C(20% SOC), C(30% SOC), C(40% SOC), C(50% SOC), C(60% SOC), C(70% SOC), C(80% SOC) respectively, and the maximum charging rate at the corresponding state of charge, i.e., the fast charging window, was obtained. The charging time from 10% to 80% is 6 / C(20% SOC) + 6 / C(30% SOC) + 6 / C(40% SOC) + 6 / C(50% SOC) + 6 / C(60% SOC) + 6 / C(70% SOC) + 6 / C(80% SOC).

[0589] Test of the initial DC internal resistance (DCR) of the battery cell:

[0590] At 25 °C, the battery was charged at a constant current of 0.5C to 4.4V, and then charged at a constant voltage until the current was 0.05C; the battery was discharged at a constant current of 0.5C for 30 minutes to adjust the battery to 50% SOC, and the voltage of the battery at this time was recorded as U1; the battery was discharged at a constant current of 4C for 30 seconds, with sampling every 0.1 second, and the voltage at the end of discharge was recorded as U2. The initial DCR of the battery was represented by the discharge DCR at 50% SOC of the battery, and the initial DCR of the battery = (U1 - U2) / 4C.

[0591] High-temperature cycle life test

[0592] At 45 °C, the batteries of the examples and comparative examples were charged at a constant current of 1C to 4.4V, then charged at a constant voltage of 4.4V until the current dropped to 0.05C. After standing for 5 minutes, they were discharged at a constant current of 1C to 2.5V. This was the first charge / discharge cycle of the battery, and the discharge capacity at this time was recorded as the discharge capacity (C1) of the first cycle of the battery. The above steps were repeated for the same battery. After the nth cycle, the process capacity (Cn) of the battery was obtained, and the capacity retention rate after n cycles = Cn / C1×100%. The number of cycles when the cycle capacity retention rate was 80% was recorded.

[0593] Fast charge cycle life test

[0594] First, the fast charge window needs to be obtained: The batteries of the above examples and comparative examples were charged and discharged for the first time at a current of 1C (i.e., the current value that completely discharges the theoretical capacity within 1 hour). Specifically, at 35 °C, the battery was charged at a constant current of 1C rate until the voltage reached 3.65V, then charged at a constant voltage until the current ≤ 0.05C, stood for 5 minutes, and then discharged at a constant current of 0.33C rate until the voltage reached 2.5V. Its actual capacity was recorded as C0. Then, the battery was successively charged at a constant current of 1.0C0, 1.3C0, 1.5C0, 1.8C0, 2.0C0, 2.3C0, 2.5C0, 3.0C0, 3.5C0, 4C0, 4.5C0, 5C0 to the full battery charge cut-off voltage of 3.65V or the 0V negative electrode cut-off potential (whichever reached first). After each charge was completed, it was discharged at 1C0 to the full battery discharge cut-off voltage of 2.1V. The negative electrode potentials corresponding to 10%, 20%, 30%, ……, 80% SOC (State of Charge, when "SOC = 0", it means the battery is fully discharged, and when "SOC = 100%", it means the battery is fully charged) at different charge rates were recorded, and the charge rate - negative electrode potential curve at different SOC states was plotted. After linear fitting, the charge rate corresponding to the negative electrode potential of 0V at different SOC states was obtained. This charge rate was the charge window at this SOC state, which was respectively recorded as C(10% SOC), C(20% SOC), C(30% SOC), C(40% SOC), C(50% SOC), C(60% SOC), C(70% SOC), C(80% SOC), and the maximum charge rate at the corresponding state of charge was obtained, that is, the fast charge window.

[0595] At 25°C, charging is carried out using the obtained fast-charging window distribution. Charge to 10% SOC at C(10% SOC), 20% SOC at C(20% SOC), 30% SOC at C(30% SOC), 40% SOC at C(40% SOC), 50% SOC at C(50% SOC), 60% SOC at C(60% SOC), 70% SOC at C(70% SOC), 80% SOC at C(80% SOC), and 100% SOC at 0.33C. After standing for 10 min, charge to 2.1V at 0.33C DC, record the discharge capacity at this time as C1, monitor the temperature rise at the tab during this charging process, repeat the above process, record the discharge capacity of each cycle as Cn, and the cycle capacity retention rate = Cn / C1. Record the number of cycles when the cycle capacity retention rate drops to 80% SOH.

[0596] The fast-charging time, DCR, and cycle life test methods in Example 14 are basically the same as the above methods, except that the upper limit of the charging cut-off voltage in Example 14 is adjusted to 4.25V.

[0597] Experimental results

[0598] Table 1

[0599] R50 Lithium ion conductivity mS / cm 10 - 80% SOC charging time @ 35°C / min Number of high - temperature cycles Example 1 0.25 13.5 10.5 1600 Example 2 0.2 13.5 11.3 1680 Example 3 0.15 13.5 12.2 1780 Example 4 0.3 13.5 11.8 1740 Example 5 0.35 13.5 11.6 1440 Example 6 0.45 13.5 11.2 1650 Comparative example 1 0.08 13.5 14.0 1790 Comparative example 2 0.55 13.5 12.3 860 Comparative example 3 0.25 8 15.2 1710

[0600] From the comparison between the examples and the comparative examples, it can be seen that when the lithium-ion conductivity of the electrolyte is greater than or equal to 10 mS / cm and the R value R50 at the cumulative distribution of 50% in the cumulative distribution curve of the R values obtained by the laser microscopic confocal Raman spectrometer in the area scanning mode of the negative electrode active material is 0.15 - 0.50, it is beneficial to balance the fast-charging performance and cycle life of the battery cell.

[0601] Table 2

[0602] R50 Uncoated rate Lithium ion conductivity mS / cm 10 - 80% SOC charging time @ 35°C / min Number of high - temperature cycles Example 1 0.25 6％ 13.5 10.5 1600 Example 2 0.2 8％ 13.5 11.3 1680 Example 3 0.15 10％ 13.5 12.2 1780 Example 6 0.45 15％ 13.5 11.2 1650

[0603] From the comparison between Examples 1 - 3 and Example 6, it can be seen that when the lithium-ion conductivity of the electrolyte is greater than or equal to 10 mS / cm and the R value R50 at the cumulative distribution of 50% in the cumulative distribution curve of the R values obtained by the laser microscopic confocal Raman spectrometer in the area scanning mode of the negative electrode active material is 0.15 - 0.50, and the proportion of the R values less than or equal to 0.11 in the R values of the negative electrode active material is less than or equal to 10%, it is possible to optimize another performance while maintaining a good fast-charging level or cycle performance of the battery.

[0604] Table 3

[0605]

[0606] As can be seen from the comparison between Example 1 and Example 7, the porosity of the first negative electrode film layer provided on the surface of the negative electrode current collector is less than that of the second negative electrode film layer provided on the side of the first negative electrode film layer away from the negative electrode current collector, which is beneficial to simultaneously improving the fast charging performance and the cycling performance.

[0607] Table 4

[0608]

[0609] As can be seen from the comparison between Example 1 and Example 8, a greater compaction density of the lower-layer powder than that of the upper-layer powder is beneficial to simultaneously improving the fast charging performance and the cycling performance.

[0610] Table 5

[0611]

[0612] As can be seen from the comparison between Example 9 and Example 1, a relatively high cobalt element content on the surface of the positive electrode active material helps to further improve the cycle life of the battery cell while maintaining the high charging performance of the battery.

[0613] Table 6

[0614]

[0615] As can be seen from the comparison between Example 13 and Examples 1 and 10, the simultaneous inclusion of ethyl acetate and methyl acetate in the electrolyte can further improve the fast charging performance of the battery while maintaining a good cycle life of the battery.

[0616] As can be seen from the comparison between Example 1 and Examples 11 and 12, the simultaneous inclusion of a first additive and a second additive in the electrolyte can further improve the cycle performance of the battery while maintaining a good fast charging performance of the battery.

[0617] Table 7

[0618]

[0619] As can be seen from the comparison between Example 5 and Example 4, the negative electrode active material further includes a kinetic carbon material with an interlayer spacing d 002 > 0.335 nm, which is beneficial to improving the kinetic performance of the battery.

[0620] Table 8

[0621]

[0622] As can be seen from the comparison between Example 1 and Example 14, the positive electrode active material includes a low-nickel lithium-containing oxide, the Dv50 of the positive electrode active material is 2 μm - 5 μm, and the positive electrode active material mainly includes unagglomerated primary particles, which is beneficial to improving the fast charging performance of the battery cell while improving the cycle life of the battery cell.

[0623] As can be seen from the comparison between Example 14 and Example 1, the positive electrode active material includes a high-nickel lithium-containing oxide, the Dv50 of the positive electrode active material is 6 μm - 15 μm, the positive electrode active material mainly includes secondary particles formed by agglomeration of primary particles, and the average particle size of the primary particles in the secondary particles is 0.1 μm - 1.5 μm, which is beneficial to improving the fast charging performance of the battery cell while reducing the DC impedance of the battery cell and improving the power performance of the battery cell.

[0624] Table 9

[0625]

[0626] As can be seen from the comparison between Example 1 and Example 15, the electrolyte salt in the electrolyte includes lithium bis(fluorosulfonyl)imide, which is beneficial to improving the fast charging performance of the battery cell while improving the cycle life of the battery cell.

[0627] Table 10

[0628]

[0629] As can be seen from the comparison between Example 1 and Examples 16 and 17, the battery cell includes a stacked electrode core and the width of the positive electrode current collector part is 60 mm - 110 mm, which is beneficial to improving the fast charging cycle life of the battery cell.

[0630] It should be noted that this application is not limited to the above embodiments. The above embodiments are only examples, and embodiments with the same structure and the same function and effect as the technical idea within the technical solution scope of this application are all included in the technical scope of this application. In addition, within the scope of not departing from the gist of this application, various deformations that those skilled in the art can think of applied to the embodiments, and other ways constructed by combining some constituent elements in the embodiments are also included in the scope of this application.

Claims

1. A battery cell, characterized in that: Including positive electrode sheet, negative electrode sheet and electrolyte; The electrolyte includes an organic solvent and an additive, wherein the organic solvent includes a carboxylic acid ester solvent; The additive includes a vinyl sulfate compound, and the vinyl sulfate compound includes a compound described in the following formula: The negative electrode plate includes a negative electrode current collector and a negative electrode film layer arranged on at least one side of the negative electrode current collector, the negative electrode film layer includes a negative electrode active material, the negative electrode active material includes a core portion and a coating layer at least partially coated on the surface of the core portion, the core portion includes graphite, and in the R value cumulative distribution curve of the negative electrode active material obtained under the surface scanning mode of a laser microscopic confocal Raman spectrometer, the R value R50 with a cumulative distribution of 50% is 0.15-0.

50.

2. The battery cell according to claim 1, characterized in that: The carboxylic acid ester solvent includes one or more of ethyl acetate, methyl acetate, methyl formate, butyl acetate, methyl propionate, ethyl propionate, methyl butyrate, propyl butyrate, butyl butyrate, isopropyl acetate, and isoamyl acetate.

3. The battery cell according to claim 1, characterized in that: The carboxylic acid ester solvent includes one or more of ethyl acetate and methyl acetate.

4. The battery cell according to any one of claims 1 to 3, characterized in that: The organic solvent also includes one or more of nitrile solvents and carbonate solvents.

5. The battery cell according to claim 4, characterized in that: The nitrile solvent includes one or more of acetonitrile, monofluoroacetonitrile, difluoroacetonitrile and trifluoroacetonitrile; and / or The carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

6. The battery cell according to any one of claims 1, characterized in that: The organic solvent includes dimethyl carbonate, and the mass content of dimethyl carbonate is greater than or equal to 20% based on the total mass of the organic solvent.

7. The battery cell according to claim 6, characterized in that: Based on the total mass of the organic solvent, the mass content of dimethyl carbonate is 30%-90%.

8. The battery cell according to claim 1, characterized in that: The organic solvent includes one or more of ethyl acetate, methyl acetate and a carbonate solvent.

9. The battery cell according to claim 8, characterized in that: Based on the total mass of the organic solvent, the total mass of ethyl acetate and methyl acetate accounts for 5%-80%, and the mass of the carbonate solvent accounts for 5%-90%.

10. The battery cell according to claim 1, characterized in that: The organic solvent comprises methyl acetate, and the mass content of methyl acetate is 5%-70% based on the total mass of the organic solvent.

11. The battery cell according to claim 10, characterized in that: Based on the total mass of the organic solvent, the mass content of methyl acetate is 5%-50%.

12. The battery cell according to any one of claims 1 to 11, characterized in that: The electrolyte solution further includes an electrolyte salt, wherein the electrolyte salt includes lithium bis(fluorosulfonyl)imide, and the mass content of the lithium bis(fluorosulfonyl)imide is 3%-10% based on the total mass of the electrolyte solution.

13. The battery cell according to claim 12, characterized in that: The mass content of lithium bis(fluorosulfonyl)imide is 20%-80% based on the total mass of the electrolyte salt in the electrolyte.

14. The battery cell according to claim 13, characterized in that: The mass content of lithium bis(fluorosulfonyl)imide is 30%-70% based on the total mass of the electrolyte salt in the electrolyte.

15. The battery cell according to any one of claims 1 to 14, characterized in that: The additive also includes a sulfonate compound, and the sulfonate compound includes At least one of .

16. The battery cell according to any one of claims 1 to 15, characterized in that: The vinyl sulfate compound also includes One or more of .

17. The battery cell according to any one of claims 1 to 16, characterized in that: The additives also include one or more of fluorine-containing phosphates and borates.

18. The battery cell according to claim 17, characterized in that: The fluorophosphate includes one or more of monofluorophosphate and difluorophosphate; the fluorophosphate includes an alkali metal.

19. The battery cell according to claim 18, characterized in that: The fluorophosphate includes one or more of lithium salt, sodium salt and potassium salt.

20. The battery cell according to claim 17, characterized in that: The borate comprises at least one of tetrafluoroborate, bisoxalatoborate and fluorine-containing oxalatoborate; and the borate comprises an alkali metal.

21. The battery cell according to claim 20, characterized in that: The borate includes one or more of lithium salt, sodium salt and potassium salt.

22. The battery cell according to any one of claims 1 to 21, characterized in that: Among the R values ​​of the obtained negative electrode active materials, the number of R values ​​less than or equal to 0.11 accounts for less than or equal to 15%.

23. The battery cell according to any one of claims 1 to 21, characterized in that: Among the R values ​​of the obtained negative electrode active materials, the number of R values ​​less than or equal to 0.11 accounts for less than or equal to 10%.

24. The battery cell according to any one of claims 1 to 21, characterized in that: Among the R values ​​of the obtained negative electrode active materials, the number of R values ​​less than or equal to 0.11 accounts for less than or equal to 6%.

25. The battery cell according to any one of claims 1 to 21, characterized in that: In the R value cumulative distribution curve of the negative electrode active material obtained in the surface scanning mode of the laser microscopic confocal Raman spectrometer, the R value R50 with a cumulative distribution of 50% is 0.15-0.30, and among the R values ​​of the negative electrode active material obtained, the number of R values ​​less than or equal to 0.11 accounts for less than or equal to 10%.

26. The battery cell according to any one of claims 1 to 21, characterized in that: In the R value cumulative distribution curve of the negative electrode active material obtained in the surface scanning mode of the laser microscopic confocal Raman spectrometer, the R value R50 with a cumulative distribution of 50% is 0.30-0.50, and among the R values ​​of the negative electrode active material obtained, the number of R values ​​less than or equal to 0.11 accounts for less than or equal to 15%.

27. The battery cell according to any one of claims 1 to 26, characterized in that: The battery cell comprises a laminated cell, the positive electrode sheet comprises a positive current collector, the positive current collector comprises a positive current collecting portion and a positive electrode tab disposed on at least one side of the positive current collecting portion, and the width of the positive current collecting portion is 60 mm-110 mm.

28. The battery cell according to claim 27, characterized in that: The width of the positive electrode current collecting portion is 62 mm-98 mm.

29. The battery cell according to claim 27 or 28, characterized in that: The length of the positive electrode current collecting part in the laminated battery core is 100mm-700mm.

30. The battery cell according to claim 29, characterized in that The length of the positive electrode current collecting part in the laminated battery core is 200mm-600mm.

31. The battery cell according to any one of claims 1 to 30, characterized in that: The air oxidation temperature T0 of the negative electrode active material is 630°C to 730°C, wherein the air oxidation temperature T0 is the temperature corresponding to the intersection of two tangents at two points corresponding to 500°C and T1 temperatures on the thermogravimetric curve of the negative electrode active material, respectively, and the T1 temperature is the peak top temperature of the maximum area peak in the differential thermogravimetric curve of the negative electrode active material. The thermogravimetric curve and the differential thermogravimetric curve can be obtained by thermogravimetric analysis under the following conditions: sample mass 10±0.05 mg, purge gas is air and the airflow rate is 60 mL / min, the heating rate is 5°C / min, and the test temperature range is 35°C to 950°C.

32. The battery cell according to any one of claims 1 to 30, characterized in that: The core of the negative electrode active material is a secondary particle formed by agglomeration of graphite primary particles, the coating layer of the negative electrode active material includes amorphous carbon, and the negative electrode active material also includes a kinetic carbon material; the interlayer spacing d of the (002) crystal plane of the kinetic carbon material is 002 >0.335nm.

33. The battery cell according to claim 32, characterized in that: The interlayer spacing of the (002) crystal plane of the kinetic carbon material is 0.3355 nm to 0.337 nm.

34. The battery cell according to claim 32 or 33, characterized in that: The kinetic carbon material includes one or more of hard carbon, expanded graphite and graphene.

35. The battery cell according to claim 34, characterized in that: The kinetic carbon material is located in the core and / or the coating layer.

36. The battery cell according to any one of claims 32 to 35, characterized in that: Based on the total mass of the negative electrode active material, the mass percentage of the kinetic carbon material is 1% to 30%.

37. The battery cell according to claim 36, characterized in that: Based on the total mass of the negative electrode active material, the mass percentage of the kinetic carbon material is 8% to 15%.

38. The battery cell according to any one of claims 1 to 37, characterized in that: The negative electrode active material includes secondary particles formed by agglomeration of primary particles, and the volume distribution particle size Dv50 of the negative electrode active material is 8 μm-18 μm.

39. The battery cell according to any one of claims 1 to 37, characterized in that: The negative electrode active material includes unagglomerated primary particles, and the volume distribution particle size Dv50 of the negative electrode active material is 5 μm-13 μm.

40. The battery cell according to any one of claims 1 to 39, characterized in that: The core portion of the negative electrode active material includes artificial graphite.

41. The battery cell according to any one of claims 1 to 40, characterized in that: The negative electrode active material satisfies one or more of the following conditions: (1) The mass of the coating layer is 0.3% to 5% of the mass of the core; (2) The average thickness of the coating layer is 100nm-300nm; (3) The coating layer is disposed on 90% to 100% of the surface of the core portion.

42. The battery cell according to any one of claims 1 to 41, characterized in that: The negative electrode film layer includes a first negative electrode film layer arranged on the surface of the negative electrode current collector and a second negative electrode film layer arranged on a side of the first negative electrode film layer away from the negative electrode current collector, and the porosity of the second negative electrode film layer is greater than that of the first negative electrode film layer.

43. The battery cell according to claim 42, characterized in that The first negative electrode film layer includes a first negative electrode active material, and the particle size consistency of the first negative electrode active material is 0.4-0.6; the second negative electrode film layer includes a second negative electrode active material, and the particle size consistency of the second negative electrode active material is 0.25-0.

45.

44. The battery cell according to any one of claims 1 to 41, characterized in that: The negative electrode film layer includes a first negative electrode film layer arranged on the surface of the negative electrode current collector and a second negative electrode film layer arranged on a side of the first negative electrode film layer away from the negative electrode current collector, and the powder compaction density of the negative electrode active material in the second negative electrode film layer under a pressure of 50000N is less than the powder compaction density of the negative electrode active material in the first negative electrode film layer under a pressure of 50000N.

45. The battery cell according to any one of claims 1 to 41, characterized in that: The negative electrode active material also includes a silicon-based material, and the single-side density of the negative electrode film layer is 0.06g / 1540.25mm 2 -0.15g / 1540.25mm 2 .

46. ​​The battery cell according to any one of claims 1 to 41, characterized in that: The negative electrode active material further comprises a silicon-based material, and the average thickness of a single side of the negative electrode film layer is 30 μm-80 μm.

47. The battery cell according to any one of claims 1 to 46, characterized in that: The negative electrode sheet satisfies at least one of the following conditions: (1) The single-side density of the negative electrode film layer is 0.08 g / 1540.25 mm 2 -0.20g / 1540.25mm 2 ; (2) The compaction density of the negative electrode sheet is 1.2 g / cm 3 -1.9g / cm 3 ; (3) The average thickness of the negative electrode film layer on one side is 30 μm-150 μm; (4) The porosity of the negative electrode plate is 20%-60%.

48. The battery cell according to any one of claims 1 to 46, characterized in that: The negative electrode sheet satisfies at least one of the following conditions: (1) The single-side density of the negative electrode film layer is 0.10 g / 1540.25 mm 2 -0.16g / 1540.25mm 2 ; (2) The compaction density of the negative electrode sheet is 1.2 g / cm 3 -1.65g / cm 3 ; (3) The average thickness of the negative electrode film layer on one side is 30 μm-80 μm; (4) The porosity of the negative electrode plate is 25%-40%.

49. The battery cell according to any one of claims 1 to 48, characterized in that: The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector, the positive electrode film layer includes a positive electrode active material, the positive electrode active material includes a lithium-containing phosphate, and the positive electrode active material includes unagglomerated primary particles; and the positive electrode active material satisfies at least one of the following conditions: (1) Volume distribution particle size Dv50 of the positive electrode active material 正1 Satisfy: 0.3μm≤Dv50 正1 ≤2μm; (2) The average particle size of the primary particles of the positive electrode active material satisfies: 50 nm ≤ D 正1 ≤300nm.

50. The battery cell according to any one of claims 1 to 48, characterized in that: The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material, wherein the positive electrode active material includes a lithium-containing transition metal oxide, and the volume distribution particle size Dv50 of the positive electrode active material is 正2 Meet: 2μm≤Dv50 正2 ≤15μm.

51. The battery cell according to claim 50, characterized in that The positive electrode active material comprises lithium nickel cobalt manganese oxide, and the Dv50 of the positive electrode active material 正2 The positive electrode active material includes secondary particles formed by agglomeration of primary particles, and the average particle size of the primary particles in the secondary particles is 0.1 μm-1.5 μm.

52. The battery cell according to claim 51, characterized in that The Dv50 of the positive electrode active material is 8 μm-12 μm.

53. The battery cell according to claim 50, characterized in that The positive electrode active material comprises lithium nickel cobalt manganese oxide, and the Dv50 of the positive electrode active material 正2 The positive electrode active material has a diameter of 2 μm to 5 μm, and the positive electrode active material includes unagglomerated primary particles.

54. The battery cell according to claim 53, characterized in that The Dv50 of the positive electrode active material is 2.5 μm-4.5 μm.

55. The battery cell according to claim 50, characterized in that The positive electrode active material includes lithium nickel cobalt manganese oxide, and the particle size distribution curve of the positive electrode active material presents a bimodal distribution, with peaks located at 2μm-5μm and 7μm-20μm, respectively. The positive electrode active material includes unagglomerated primary particles and secondary particles formed by agglomeration of primary particles, and the average particle size of the secondary particles is greater than the average particle size of the unagglomerated primary particles.

56. The battery cell according to claim 50, characterized in that The positive electrode active material comprises lithium nickel cobalt manganese oxide, and the molar content of cobalt is less than or equal to 20% based on the total molar number of transition metals in the positive electrode active material. The Dv50 正2 The positive electrode active material has a diameter of 2 μm to 5 μm, and the positive electrode active material includes unagglomerated primary particles.

57. The battery cell according to claim 50, characterized in that The positive electrode active material comprises lithium nickel cobalt manganese oxide, based on the total molar number of transition metals in the positive electrode active material, the molar content of nickel accounts for less than 80%, and the Dv50 of the positive electrode active material is 正2 The positive electrode active material has a diameter of 2 μm to 5 μm, and the positive electrode active material includes unagglomerated primary particles.

58. The battery cell according to claim 50, characterized in that The positive electrode active material comprises lithium nickel cobalt manganese oxide, based on the total molar number of transition metals in the positive electrode active material, the molar content of nickel accounts for greater than or equal to 80%, and the Dv50 of the positive electrode active material 正2 The positive electrode active material includes secondary particles formed by agglomeration of primary particles, and the average particle size of the primary particles in the secondary particles is 0.1 μm-1.5 μm.

59. The battery cell according to claim 1, characterized in that The positive electrode plate includes a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector, the positive electrode film layer includes a positive electrode active material, the positive electrode active material includes a cobalt element, and in the particles of the positive electrode active material, the mass proportion of the cobalt element near the surface of the particle is greater than the mass proportion of the cobalt element near the center of the positive electrode active material particle.

60. The battery cell according to claim 59, characterized in that The ratio of the mass proportion of the cobalt element near the particle surface of the positive electrode active material to the mass proportion of the cobalt element near the center of the positive electrode active material particle is in the range of (1.2-5.0):1; wherein, the area near the particle surface is the area from the surface of the particle to a depth of 200nm in the direction toward the geometric center of the particle, and the area near the center of the positive electrode active material particle is a spherical area with a diameter of 200nm and the geometric center of the particle cross section as the center of the circle.

61. The battery cell according to claim 60, characterized in that The ratio of the mass proportion of the cobalt element near the particle surface of the positive electrode active material to the mass proportion of the cobalt element near the center of the positive electrode active material particle is in the range of (1.4-2.0):

1.

62. The battery cell according to claim 1, characterized in that The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector, the positive electrode film layer includes a positive electrode active material, the positive electrode active material includes a lithium-containing phosphate, and the single-side density of the positive electrode film layer is 0.2g / 1540.25mm 2 -0.35g / 1540.25mm 2 .

63. The battery cell according to claim 1, characterized in that The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one side of the positive electrode current collector, the positive electrode film layer includes a positive electrode active material, the positive electrode active material includes a lithium-containing transition metal oxide, and the single-side density of the positive electrode film layer is 0.13g / 1540.25mm 2 -0.24g / 1540.25mm 2 .

64. The battery cell according to claim 1, characterized in that The positive electrode plate comprises a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector. The positive electrode film layer comprises a positive electrode active material, and the porosity of the positive electrode film layer is 22%-35%.

65. The battery cell according to any one of claims 1 to 64, characterized in that: The lithium ion conductivity of the electrolyte is greater than or equal to 10 mS / cm.

66. The battery cell according to any one of claims 1 to 64, characterized in that: The lithium ion conductivity of the electrolyte is 10mS / cm-20mS / cm.

67. The battery cell according to any one of claims 1 to 64, characterized in that: The lithium ion conductivity of the electrolyte is 12mS / cm-20mS / cm.

68. The battery cell according to any one of claims 1 to 64, characterized in that: The lithium ion conductivity of the electrolyte is 10mS / cm-15mS / cm.

69. The battery cell according to claim 49, characterized in that The positive electrode active material includes lithium iron phosphate, and the single-side density of the positive electrode film layer is 0.2g / 1540.25mm 2 -0.35g / 1540.25mm 2 ; The conductivity of the electrolyte is 12mS / cm-20mS / cm.

70. The battery cell according to claim 50, characterized in that The positive electrode active material includes lithium-containing nickel-cobalt-manganese oxide, and the single-side density of the positive electrode film layer is 0.13 g / 1540.25 mm 2 -0.24g / 1540.25mm 2 ; The conductivity of the electrolyte is 10mS / cm-15mS / cm.

71. A battery device, characterized in that: Comprising the battery cell described in any one of claims 1-70, the battery device comprises one or more of a battery module, a battery pack, and an energy storage battery.

72. An electrical device, characterized in that: The battery cell comprises the battery cell according to any one of claims 1 to 70 or the battery device according to claim 71, wherein the battery cell or the battery device is used to provide electrical energy.

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