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 lithium ion conductivity of the electrolyte is greater than or equal to 10mS / cm; the 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, 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 the coating layer comprises graphite. And in an R value cumulative distribution curve of the negative electrode active material obtained in a surface scanning mode of a laser microscopic confocal Raman spectrometer, the R value R50 with the 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 application is a divisional application based on the invention with application number 202411606003.X, application date November 12, 2024, applicant Contemporary Amperex Technology Co., Ltd., and invention name “Battery Cell, Battery Device and Electrical Device”. Technical Field

[0002] The present application relates to the technical field of battery cells, and in particular to a battery cell, a battery device and an electrical device. Background Art

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

[0004] As the market demands for the range, cycle life and energy replenishment efficiency of electric devices increase, higher requirements are also put forward for the energy density, fast charging performance and cycle life of battery cells. However, it is difficult to achieve the improvement of the above performances at the same time in the existing technology, which has become a technical problem that needs to be solved urgently in this field. Summary of the invention

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

[0006] The first aspect of the present application provides a battery cell, the battery cell comprising a positive electrode plate, a negative electrode plate and an electrolyte; the lithium ion conductivity of the electrolyte is greater than or equal to 10mS / cm; the 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, the negative electrode film layer comprises a negative electrode active material, the negative electrode active material comprises a core portion and a coating layer at least partially coated on the surface of the core portion, the core portion comprises graphite, and in the R value cumulative distribution curve obtained by the negative electrode active material in 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; 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%.

[0007] The negative electrode active material with a cumulative distribution of 50% R value R50 of 0.15-0.50 can not only improve the charge exchange capacity of lithium ions in the high-conductivity electrolyte on the surface of the negative electrode active material, so that the liquid phase transmission rate of lithium ions matches the solid phase transmission rate, improving the kinetic performance of the battery, but also can make the side reactions on the surface of the negative electrode active material have a lower 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 materials, the proportion 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 cumulative distribution of 50% of the R value R50 of the core graphite generally does not exceed 0.11. Therefore, among all the R values ​​of the obtained negative electrode active materials, the proportion of the number of R values ​​less than or equal to 0.11 can be used to indicate the degree of uncoating of the negative electrode active material. The smaller the value, 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 higher the isotropy of ion embedding, the better the charge exchange capacity of ions on the surface of the negative electrode active material, and the higher the solid-liquid transfer rate of lithium ions, so that it can 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-embedding phenomenon of the electrolyte solvent during the cycle, thereby making 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 the laser microconfocal 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%.

[0011] The negative electrode active material in this embodiment enables the battery cell to have better fast charging performance. The reason for this speculation may be that the surface disorder of the negative electrode active material is within the above range and the coverage is high, indicating that the surface isotropy of the negative electrode active material is high, which is conducive to the uniform embedding of lithium ions into the core graphite from all directions, and is conducive to further improving 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 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%.

[0013] The negative electrode active material in this embodiment has 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 a carboxylate solvent, a nitrile solvent, and a carbonate solvent.

[0015] In any embodiment, the carboxylate 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 selected from 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.

[0016] 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 and lithium ions in lithium-containing electrolyte salts can easily form a solvation structure to increase the dissociation rate of lithium ions and anions in lithium-containing electrolyte salts, thereby improving the fast charging performance of battery cells.

[0017] In any embodiment, the organic solvent includes dimethyl carbonate, and 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%.

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

[0019] Ethyl acetate and methyl acetate have high conductivity and low gas production. The combination of ethyl acetate and / or methyl acetate and carbonate solvents allows the lithium ions in the electrolyte to have both a high dissociation rate and a fast lithium ion transmission rate, which is beneficial to improving the dynamic performance of the battery monomer, while reducing the gas production of the battery 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 of ethyl acetate and methyl acetate accounts for 5%-80%, and the mass of the carbonate solvent accounts for 5%-90%.

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

[0022] Methyl acetate has higher activity than ethyl acetate. Although its small addition in the electrolyte will slightly sacrifice the life of the battery cell, it can further improve the dynamic 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, the electrolyte salt includes lithium bis(fluorosulfonyl)imide LiFSI, and the mass content of lithium bis(fluorosulfonyl)imide is 3%-10% based on the total mass of the electrolyte.

[0024] Lithium bis(fluorosulfonyl)imide is prone to dissociation in electrolyte solvents, which is beneficial to improving the dynamics of battery cells, reducing the internal resistance of the battery, and improving the fast charging performance of the battery. However, lithium bis(fluorosulfonyl)imide is prone to side reactions with LiC6 formed during the deep lithium insertion process of the negative electrode, reducing the reversible lithium capacity, which is not conducive to maintaining the capacity of the battery cell during the cycle. 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 while taking into account 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 optionally 30%-70%.

[0026] The electrolyte of 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, thereby comprehensively improving the cycle life of the battery.

[0027] In any embodiment, the battery cell includes a laminated battery cell, the positive electrode sheet includes a positive current collector, the positive current collector includes a positive current collecting portion and a positive electrode ear arranged on at least one side of the positive current collecting portion, and the width of the positive current collecting portion is 60mm-110mm, and can be optionally 62mm-98mm.

[0028] The width of the positive electrode current collecting part within the above range is conducive to reducing the maximum distance between the pole ear and the edge of the positive electrode current collecting part, which can not only reduce the electron transmission distance and improve the fast charging performance of the battery, but also reduce the phenomenon of inconsistent temperature rise of the current collecting part during fast charging, reduce the temperature gradient on the current collecting part, and reduce the probability of active materials being deactivated first at the place where the temperature rises, thereby improving the fast charging cycle life of the battery and taking into account the energy density of the battery.

[0029] In any embodiment, the length of the positive electrode current collecting portion in the laminated battery core is 100 mm-700 mm, and can be optionally 200 mm-600 mm.

[0030] The length of the positive electrode current collector in the laminated battery cell within the above range can further reduce the transmission distance of electrons on the current collector, improve the phenomenon of inconsistent temperature rise during fast charging of the battery cell, and increase 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 fluorine-containing phosphates and borates.

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

[0033] In any embodiment, the borate includes at least one of tetrafluoroborate, bisoxalatoborate, and fluorine-containing oxalatoborate; the borate includes an alkali metal, which can be one or more of a lithium salt, a sodium salt, and a potassium salt.

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

[0035] In any embodiment, the vinyl sulfate compound comprises One or more of; and / or the sulfonate compound includes At least one of .

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

[0038] In any embodiment, 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 temperature 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.

[0039] The negative electrode active material with an air oxidation temperature T0 of 630°C to 730°C has a suitable number of surface defects, which provide sufficient end surfaces for the embedding of active ions and match the lithium ion transfer rate of the electrolyte, while keeping the degree of side reactions 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 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, can be selected as 0.3355nm~0.337nm.

[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 cladding.

[0043] The negative electrode active materials including the above-mentioned kinetic carbon materials can increase the embedding and extraction rates of active ions, thereby improving the transmission performance of active ions and electrons, and further improving the fast charging performance of battery cells while maintaining high energy density. At the same time, amorphous carbon has a high hardness, so it also has good compressive resistance, a strong ability to maintain the pore structure of the negative electrode film layer during the cycle, and better electrolyte wettability of the negative electrode plate, so 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 optionally 8% to 15%.

[0045] When the mass percentage of the kinetic carbon material is within an appropriate range, the negative electrode active material can have a high solid-phase transport capacity of active ions and a high exchange rate of active ions and electrons while having a high gram capacity, and thus the battery cell can have improved fast charging performance while having a high energy density. At the same time, when the mass percentage of the kinetic carbon material is within an appropriate range, the ability to maintain the pore structure of the negative electrode film layer during the cycle is better, the electrolyte wettability of the negative electrode plate is better, and the battery cell can also have good cycle performance.

[0046] In any embodiment, 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.

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

[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] Compared with small-size particles, negative electrode active materials with a volume distribution particle size Dv50 within the above range have higher interface stability, but also have a larger ion solid phase transmission distance. The size design can balance the two and achieve a balance between 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 fewer defects and higher capacity, which can reduce the degree of side reactions with the electrolyte, give full play to the high capacity characteristics of graphite, reduce gas production, and enable the battery cells 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 portion; and / or the average thickness of the coating layer is 100nm-300nm.

[0053] 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.

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

[0055] 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.

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

[0057] The embodiment of the present application adopts a high-conductivity electrolyte with a high ion transfer rate. By designing the second negative electrode film layer close to the electrolyte to have a larger porosity, the transfer rate of lithium ions in the electrode and the liquid phase transfer rate in the electrolyte are matched with each other, thereby 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 in the negative electrode film layer close to the current collector 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 0.4-0.6; 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.

[0059] The negative electrode active material with a particle size consistency of 0.4-0.6 can be densely packed by grading large and small particles, so that the first negative electrode film layer has a relatively low porosity; the negative electrode active material with a particle size consistency of 0.25-0.45 is difficult to form an effective match due to the low particle size consistency between particles, so that the second negative electrode film layer has a relatively high porosity, thereby realizing a layered design of the electrode porosity.

[0060] In any embodiment, 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 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 powder compaction density of the negative electrode active material in the second negative electrode film layer close to the electrolyte side is small, which 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 powder compaction density of the negative electrode active material in the first negative electrode film layer away from the electrolyte side is large, which is beneficial to improving the compaction density of the negative electrode film layer while taking into account the energy density of the battery cell.

[0062] In any embodiment, the single-side density of the negative electrode film layer is 0.08g / 1540.25mm 2 -0.20g / 1540.25mm 2 , optional: 0.10g / 1540.25mm 2 -0.16g / 1540.25mm2 .

[0063] A battery cell having a single-side 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.

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

[0065] Silicon-based materials have 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 the battery with the same capacity, that is, the single-side density of the negative electrode film layer is further reduced, which is beneficial to reduce the transmission distance of lithium ions in the negative electrode film layer and further improve the fast charging performance of the battery cell.

[0066] In any embodiment, the compaction density of the negative electrode plate is 1.2 g / cm 3 -1.9g / cm 3 , optional 1.2g / cm 3 -1.65g / cm 3 .

[0067] The negative electrode sheet with a compaction density within the above range has a suitable porosity, can match the electrolyte with high conductivity, increase the diffusion rate of lithium ions in the negative electrode, and reduce the concentration polarization generated by the battery cell during fast charging, which is beneficial to improve 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 a single side of the negative electrode film layer is 30 μm-150 μm, and can be 30 μm-80 μm.

[0069] The negative electrode film layer with an average thickness within the above range has a suitable lithium ion diffusion distance, can match the electrolyte with high conductivity, increase the diffusion rate of lithium ions in the negative electrode film layer, 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 comprises a silicon-based material, and the average thickness of a single side of the negative electrode film layer is 30 μm-80 μm.

[0071] Silicon-based materials have 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 the battery with the same capacity, which is beneficial to reduce the transmission distance of lithium ions in the negative electrode film layer and further improve the fast charging performance of the battery cell.

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

[0073] The negative electrode plate with a porosity within the above range can be matched with an electrolyte with high conductivity, which facilitates the transmission of lithium ions in the negative electrode and reduces the concentration polarization generated in the battery cell during fast charging, which is 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 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:

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

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

[0077] Lithium-containing phosphates with an average particle size of primary particles within the above range have a shorter ion transmission path, low lithium ion transmission impedance and low moisture absorption, which can not only match the liquid phase transmission rate of lithium ions in the electrolyte, but also reduce the temperature rise of the battery cell during fast charging, 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 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 volume distribution particle size Dv50 of the positive electrode active material is 正2 Meet: 2μm≤Dv50 正2 ≤15μm.

[0079] Volume distribution particle size Dv50 正2 The positive electrode active material containing lithium transition metal oxide within the above range has a shorter ion transmission path, low lithium ion transmission impedance and low side reaction degree. It can not only match the liquid phase transmission rate of lithium ions in the electrolyte, but also reduce the temperature rise of the battery cell during fast charging, and 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 comprises lithium nickel cobalt manganese oxide, and the Dv50 of the positive electrode active material is正2 The positive electrode active material comprises 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.

[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 a large number of primary particles with small particle sizes, which makes the lithium ion transmission path short and the embedded end faces more, and can match the electrolyte with a high lithium ion transmission rate, which is beneficial to improve the power performance of the battery cell.

[0082] In any embodiment, the positive electrode active material comprises lithium nickel cobalt manganese oxide, 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 can be 2.5 μm to 4.5 μm. The positive electrode active material includes unagglomerated primary particles.

[0083] In this embodiment, the positive electrode active material mainly includes unagglomerated primary particles, that is, a powder mainly composed of unagglomerated primary particles. The positive electrode active material has a low degree of side reaction with the highly active carboxylate solvent, which is conducive 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, 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 larger than the average particle size of the unagglomerated primary particles.

[0085] The positive electrode active material is graded by secondary particles mainly having large particle sizes and primary particles mainly having small particle sizes, which not only takes into account the cycle life and power performance of the battery cell, but also further improves the energy density of the battery.

[0086] In any embodiment, the positive electrode active material comprises lithium nickel cobalt manganese oxide, 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, 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.

[0087] The molar content 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 non-agglomerated primary particles, the side reaction between the carboxylic acid ester and the positive electrode active material can be reduced, the cycle life of the battery cell can be increased, and the kinetic performance of the positive electrode active material can be improved, thereby improving the power performance of the battery cell.

[0088] In any embodiment, 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 is less than 80%, and the Dv50 of the positive electrode active material is 正2 The positive electrode active material has a particle size of 2 μm to 5 μm, and the positive electrode active material includes unagglomerated primary particles.

[0089] The molar content of nickel is less than 80%, which is beneficial to reduce the probability of nickel dissolution of the positive electrode active material under high voltage (charging cut-off voltage ≥ 4.3V) and improve the withstand voltage of the positive electrode active material. The combination of low nickel components and unagglomerated primary particles can further reduce the degree of side reactions between the positive electrode active material and the carboxylic acid ester solvent, reduce the probability of cracking of the positive electrode active material during high voltage charging and discharging, and improve the cycle performance of the battery cell.

[0090] In any embodiment, 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.

[0091] Forming high-nickel materials into large-sized secondary particles is beneficial to simultaneously increase the specific capacity of the positive electrode active material and the gradation of the positive electrode sheet, and improve 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 embedded end faces, reduce the DC impedance of the battery cell, and improve the power performance of the battery cell.

[0092] In any embodiment, the positive electrode active material includes cobalt element, and in particles of the positive electrode active material, the mass proportion of the cobalt element near the particle surface is greater than the mass proportion of the cobalt element near the center of the positive electrode active material particle.

[0093] In any embodiment, the ratio of the mass proportion of the cobalt element near the surface of the positive electrode active material particle 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, and can be optionally (1.4-2.0):1; wherein, the area close to the surface of the particle 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 close to the center of the positive electrode active material particle is a spherical area with a diameter of 200nm with the geometric center of the particle cross section as the center of the circle.

[0094] Although high-conductivity electrolyte is beneficial to improve the liquid phase transmission rate of lithium ions, the components in the high-conductivity electrolyte have high electrochemical activity. For example, the carboxylic acid ester in the high-conductivity electrolyte is easy to react with the oxygen-released structure after the phase change on the surface of the positive electrode active material, increasing gas production and deteriorating the cycle life of the battery. The surface of the positive electrode active material has a relatively high cobalt content, which helps to improve the ionic conductivity of the positive electrode active material, improve the problem of excessive lithium removal on the surface of the positive electrode active material during charging and discharging, reduce the cation mixing of 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. The relatively low cobalt content in 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 a lithium-containing phosphate, and the single-side density of the positive electrode film layer is 0.2 g / 1540.25 mm 2 -0.35g / 1540.25mm 2 .

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

[0097] The positive electrode film layer with a surface density within the above range has a suitable thickness, which is conducive to the diffusion of active ions in the electrode piece 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.

[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 conducive to the diffusion of active ions in the electrode piece, 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] Improving the lithium ion conductivity of the electrolyte often means that a higher content of high-conductivity solvent needs to be added. High-conductivity solvents have high chemical reactivity while having a high transfer rate for lithium ions, and are prone to side reactions with negative electrode active materials, reducing the cycle life of the battery. Electrolytes with lithium ion conductivity within the above range have suitable lithium ion conduction rate and reactivity, and can better balance the fast charging performance and cycle life of battery cells.

[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-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.

[0104] Lithium iron phosphate has a relatively low specific capacity, so the positive electrode film layer of the same capacity battery cell often requires a relatively high coating surface density. Using an electrolyte with a conductivity within the above range is conducive to improving the loss of the coating surface density required for lithium iron phosphate batteries to the battery cell dynamic performance, while meeting the battery energy density requirements and taking into account the battery power performance.

[0105] In any embodiment, 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.

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

[0107] The second aspect of the present application further provides a battery device, the battery device includes the battery cell provided in 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, comprising the battery cell provided in the first aspect of the present application or the battery device provided in the second aspect of the present application, wherein the battery cell or the battery device is used to provide electrical energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0109] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some implementation methods of the present application, and for ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

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

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

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

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

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

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

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

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

[0118] The reference numerals are as follows: 1. battery pack; 2. upper case; 3. lower case; 4. battery module; 5. battery cell; 51. shell; 52. electrode assembly; 53. cover plate; 101. positive electrode sheet; 1011. positive electrode current collector; 1012. positive electrode film layer; 10111. positive electrode current collecting part; 10112. positive electrode ear. DETAILED DESCRIPTION

[0119] Hereinafter, the battery cells, battery devices and power devices of the present application are specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0120] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0121] If not otherwise specified, all embodiments and optional embodiments of the present application may be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of the present application.

[0122] Unless otherwise specified, all technical features and optional technical features of the present application may be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of the present application.

[0123] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0124] In the present application, the terms "plurality" and "multiple" refer to two or more.

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

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

[0127] The battery mentioned in the embodiments of the present application may be a single physical module including one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in the present application may include a battery cell, a battery module or a battery pack.

[0128] A battery cell is the smallest unit of a battery, which can independently realize the functions of charging and discharging. The battery cell can be cylindrical, rectangular or in other shapes, etc., which is not limited in the embodiments of the present application. Figure 1 The battery cell 5 is a rectangular parallelepiped structure as an example.

[0129] When there are multiple battery cells, the multiple battery cells are connected in series, in parallel, or in mixed connection through a busbar. In some embodiments, the battery may 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 may be a battery pack, which includes a case and battery cells, and the battery cells or battery modules are accommodated in the case. In some embodiments, the case may serve as part of the chassis structure of the vehicle. For example, part of the case may become at least a part of the floor of the vehicle, or part of the case may become at least a part of the crossbeam and longitudinal beam of the vehicle.

[0130] In some embodiments, the battery may be an energy storage device, which includes an energy storage container, an energy storage cabinet, and the like.

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

[0132] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.

[0133] In some embodiments, the battery modules described above may also be assembled into a battery pack, and the number of battery modules contained in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0134] Figure 3 and Figure 4 FIG. 1 is a schematic diagram of a battery pack 1 as an example. Figure 3 and Figure 4 As shown, the battery pack 1 may include a box body and a plurality of battery modules 4 disposed in the box body. The box body includes an upper box body 2 and a lower box body 3, and 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 plurality of battery modules 4 may be arranged in the box body in any manner.

[0135] The battery provided in the embodiment of the present application may include a lithium-ion battery.

[0136] The battery cell includes an electrode assembly and an electrolyte. The electrode assembly can be a winding structure or a stacked structure, which is not limited in the present application.

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

[0138] In some embodiments, Figure 5 As shown, the outer package may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 is used to cover the opening to close the receiving cavity. The electrode assembly 52 is encapsulated in the receiving cavity. The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, which can be adjusted according to demand.

[0139] The electrode assembly usually includes a positive electrode plate and a negative electrode plate. The negative electrode plate is the electrode that absorbs or lithiates lithium ions when the battery is charged and releases or delithiates lithium when the battery is discharged. The positive electrode plate is the electrode that releases or delithiates lithium ions when the battery is charged and absorbs or lithiates lithium when the battery is discharged.

[0140] The key to improving the fast charging performance of battery cells is to improve the transmission rate of active ions in battery cells. In order to improve the transmission rate of active ions in the liquid phase, it is often necessary to use a high-conductivity electrolyte in the battery cell. However, if the rapidly transmitted lithium ions cannot be quickly embedded on the surface of the negative electrode active material in the electrode sheet, polarization will occur, which will lead to lithium precipitation, causing the battery cycle life to plummet. In order to take into account the energy density of the battery, high-capacity negative electrode active material graphite is usually used in the prior art, but the kinetic properties of graphite are not excellent enough, and it is difficult to form an effective combination with a high-conductivity electrolyte to achieve a coordinated increase in the rate of lithium ion transmission in the liquid phase and liquid-solid transmission. Therefore, a coating layer with a certain degree of disorder is set on the graphite surface to form a combination with a high-conductivity electrolyte to improve the fast charging performance of the battery cell. Although the high 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 electrode active material and the high-conductivity electrolyte, which will have a negative impact on the cycle life of the battery cell.

[0141] In a first aspect, the present application provides a battery cell, comprising 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 comprises 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 comprises a negative electrode active material, the negative electrode active material comprises a core portion and a coating layer at least partially coated on the surface of the core portion, the core portion comprises graphite, and in the R value cumulative distribution curve obtained by the negative electrode active material in 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; 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%.

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

[0143] In some embodiments, the lithium ion conductivity of the electrolyte may be selected to be 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 any range therebetween.

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

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

[0146] The R value cumulative distribution curve refers to arranging the 2500 R values ​​obtained in order from small to large, and R50 is the R value corresponding to the 50% number arranged in order.

[0147] In some embodiments, in the R value cumulative distribution curve obtained by the laser microconfocal Raman spectrometer surface scanning mode, the R value R50 with a cumulative distribution of 50% can be selected as 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 any numerical range therebetween.

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

[0149] The negative electrode active material with a cumulative distribution of 50% R value R50 of 0.15-0.50 can not only improve the charge exchange capacity of lithium ions in the high-conductivity electrolyte on the surface of the negative electrode active material, so that the liquid phase transmission rate of lithium ions matches the solid phase transmission rate, improving the kinetic performance of the battery, but also can make the side reactions on the surface of the negative electrode active material have a lower level, while taking into account the cycle life of the battery cell.

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

[0151] In some embodiments, the R value R50 at which the cumulative distribution of the core portion is 50% may be selected to be 0.06, 0.07, 0.08, 0.09, 0.10, 0.11 or a range consisting of any of the above values.

[0152] In some embodiments, the R value R50 at which the cumulative distribution of the core portion is 50% may be 0.07-0.11.

[0153] The larger the R value R50 of the cumulative distribution of the core is, the better the kinetic performance of the negative electrode active material is; the smaller the R value R50 of the cumulative distribution of the core is, the higher the gram capacity of the negative electrode active material is. When the R value R50 of the cumulative distribution of the core is within the above range, the battery can have both high energy density and good kinetic performance.

[0154] The inclusion of graphite in the core of the negative electrode active material is conducive to maintaining a good energy density of the battery cell, but the graphite surface has a high degree of order and a low defect content, which requires lithium ions to be inserted directionally from the graphite layer, 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 embedding channels of the negative electrode active material is increased, and the embedding efficiency of lithium ions in the negative electrode active material is improved, which in turn forms a coordination with the high-speed transmission of lithium ions in the high-conductivity electrolyte, synergistically improving the charge transmission capacity of lithium ions in the liquid phase and liquid-solid in the battery cell, so that the fast charging performance of the battery cell is comprehensively improved; on the other hand, the degree of side reactions between the negative electrode active material and the high-conductivity electrolyte is controlled, taking into account the cycle life of the battery.

[0155] In some embodiments, 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%, 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 negative electrode active material obtained, the proportion of R values ​​less than or equal to 0.11 can be selected as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15% or any numerical range therebetween.

[0157] As mentioned above, the cumulative distribution of the core graphite is 50% of the R value R50 generally does not exceed 0.11. Therefore, among all the R values ​​of the obtained negative electrode active materials, the proportion of the number of R values ​​less than or equal to 0.11 can be used to indicate the degree of uncoating of the negative electrode active material. The smaller the value, 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 higher the isotropy of ion embedding, the better the charge exchange capacity of ions on the surface of the negative electrode active material, and the higher the solid-liquid transmission rate of lithium ions, so that it can match with the high-conductivity electrolyte and improve the kinetic performance of the battery.

[0158] In addition, the degree of uncoating of the negative electrode active material is small, which can also reduce the co-embedding phenomenon of the electrolyte solvent during the cycle process, thereby making the battery have better cycle performance.

[0159] In some embodiments, 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%, and can be optionally less than or equal to 6%.

[0160] Among all the R values ​​obtained for the negative electrode active materials, the proportion of R values ​​less than or equal to 0.11 within the above range can further improve the kinetic performance and cycle performance of the battery.

[0161] In some embodiments, in the R value cumulative distribution curve obtained by the negative electrode active material in the surface scanning mode of the laser microconfocal 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%.

[0162] The negative electrode active material in this embodiment enables the battery cell to have better fast charging performance. The reason for this speculation may be that the surface disorder of the negative electrode active material is within the above range and the coverage is high, indicating that the surface isotropy of the negative electrode active material is high, which is conducive to the uniform embedding of lithium ions into the core graphite from all directions, and is conducive to further improving the fast charging performance of the battery cell.

[0163] In some embodiments, in the R value cumulative distribution curve obtained by the negative electrode active material in the surface scanning mode of the laser microconfocal 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%.

[0164] The negative electrode active material in this embodiment has 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 a carboxylate solvent, a nitrile solvent, and a carbonate solvent.

[0166] Carboxylate solvents are organic solvents that include carboxylate groups. Nitrile solvents refer to organic solvents that include cyano groups. Carbonate solvents refer to organic solvents that include carbonate groups, including cyclic carbonate and chain carbonate compounds.

[0167] In some embodiments, the carboxylate solvent is a linear carboxylate solvent, which refers to a linear carboxylate solvent rather than a cyclic structure.

[0168] In some embodiments, the carboxylate 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 selected from 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 and lithium ions in lithium-containing electrolyte salts can easily form a solvation structure to increase the dissociation rate of lithium ions and anions in lithium-containing electrolyte salts, thereby improving the fast charging performance of battery cells.

[0170] In some embodiments, the organic solvent includes dimethyl carbonate, and 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 selected to be 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90% or any numerical range therebetween.

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

[0173] Ethyl acetate and methyl acetate have high conductivity and low gas production. The combination of ethyl acetate and / or methyl acetate and carbonate solvents allows the lithium ions in the electrolyte to have both a high dissociation rate and a fast lithium ion transmission rate, which is beneficial to improving the dynamic performance of the battery monomer, while reducing the gas production of the battery 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 of ethyl acetate and methyl acetate accounts for 5%-80%, and the mass of the carbonate solvent accounts for 5%-90%.

[0175] In some embodiments, based on the total mass of the organic solvent, the total mass proportion of ethyl acetate and methyl acetate can be selected as 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80% or any range therebetween, and the mass proportion of the carbonate solvent can be selected as 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or any range therebetween.

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

[0177] In some embodiments, based on the total mass of the organic solvent, the mass content of methyl acetate can be selected as 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70% or any numerical range therebetween. Compared with ethyl acetate, methyl acetate has higher activity. Although a small amount of methyl acetate added to the electrolyte will slightly sacrifice the life of the battery cell, it can further improve the dynamic performance of the battery cell, and further improve the fast charging performance of the battery cell while maintaining a high cycle life of the battery cell.

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

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

[0180] Compared with carbonate solvents, ethyl acetate and methyl acetate are more active and prone to side reactions with ternary cathode materials. Studies have found that the side reactions of methyl acetate solvent are more violent, 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 less than ethyl acetate; especially when used with dimethyl carbonate, the addition amount of methyl acetate can be further reduced. For high-rate fast-charging battery systems, through the combination of methyl acetate and dimethyl carbonate, the addition of a small amount of methyl acetate can effectively improve 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 reactions is reduced, which is beneficial to take 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. The mass content of lithium bis(fluorosulfonyl)imide is 3%-10% based on the total mass of the electrolyte.

[0182] In some embodiments, based on the total mass of the electrolyte, the mass content of the lithium bis(fluorosulfonyl)imide LiFSI may be 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 any range between the two.

[0183] Lithium bis(fluorosulfonyl)imide is prone to dissociation in electrolyte solvents, which is beneficial to improving the dynamics of battery cells, reducing the internal resistance of the battery, and improving the fast charging performance of the battery. However, lithium bis(fluorosulfonyl)imide is prone to side reactions with LiC6 formed during the deep lithium insertion process of the negative electrode, reducing the reversible lithium capacity, which is not conducive to maintaining the capacity of the battery cell during the cycle. 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 while 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 optionally 30%-70%.

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

[0186] The electrolyte of 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, thereby comprehensively improving the cycle life of the battery.

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

[0188] In some embodiments, the width of the positive electrode current collector may be selected to be 60mm, 62mm, 64mm, 66mm, 68mm, 70mm, 72mm, 74mm, 76mm, 78mm, 80mm, 82mm, 84mm, 86mm, 88mm, 90mm, 92mm, 94mm, 96mm, 98mm, 100mm, 102mm, 104mm, 106mm, 108mm, 110mm or any range therebetween.

[0189] The material of the positive electrode current collector is not particularly limited, as long as it does not cause chemical changes in the battery cell and has conductivity. The current collector includes a metal foil 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 an alloy foil of at least two main elements, such as copper, aluminum, nickel, titanium, and iron. It can also include copper, aluminum-cadmium alloy, iron, or stainless steel that is surface-treated with carbon, nickel, titanium, silver, copper, etc. In addition, the binding force with the negative electrode active material can be enhanced by forming fine concave-convex on the surface, and it can be used in various forms such as film, sheet, foil, net, porous body, foam, non-woven fabric, etc.

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

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

[0192] During the high-rate fast charging process, the need to use a large current leads to a fast temperature rise rate and a large temperature rise range for the battery cell. During the battery charging process, the current first converges at the pole ear and then is transmitted to the current collector of the current collector. Studies have shown that there are differences in current density between the pole ear and the current collector, and the difference in current density between the pole ear and the site at a different distance from the pole ear on the current collector is also different. Generally speaking, the difference in current density between the current collector and the pole ear increases with the increase in the distance between the current collector and the pole ear, and also increases with the increase in current density. That is, the phenomenon of inconsistent current density on the current collector is more significant during high-rate charging and discharging, that is, fast charging. According to Joule's law, the inconsistency of current density at different sites on the current collector will further lead to inconsistent temperature rises in different positions of the battery, uneven lithium ion transmission rate inside the battery cell, increased battery polarization and the risk of local lithium precipitation, and reduced the cycle life of the battery cell.

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

[0194] In some embodiments, the length of the positive electrode current collecting portion in the laminated battery core may be selected to be 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 any range therebetween.

[0195] The length of the positive current collector in the laminated battery cell within the above range can further reduce the transmission distance of electrons on the current collector, improve the phenomenon of inconsistent temperature rise during fast charging 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 a fluorine-containing phosphate and a borate.

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

[0197] In some embodiments, the borate includes at least one of tetrafluoroborate, bisoxalatoborate, and fluorine-containing oxalatoborate; the borate includes an alkali metal, which can be one or more of a lithium salt, a sodium salt, and a 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 bisoxalatoborate, sodium bisoxalatoborate, potassium bisoxalatoborate, fluorine-containing lithium oxalatoborate, fluorine-containing sodium oxalatoborate, and fluorine-containing potassium oxalatoborate.

[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 the 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 under high lithium desorption, reducing the degree of side reactions 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 at the negative electrode, which is beneficial to the generation of inorganic components, improves the thermal stability and cycle stability of the negative electrode solid electrolyte membrane (SEI membrane), 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 vinyl sulfate compounds.

[0204] Vinyl sulfate compounds refer to vinyl sulfate and its derivatives.

[0205] The sulfonate compound refers to a compound including a sulfonate group.

[0206] In some embodiments, the sulfonate ester compound includes a cyclic sulfonate ester compound.

[0207] In some embodiments, the vinyl sulfate compound includes At least one of .

[0208] In some embodiments, the sulfonate compound includes At least one of .

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

[0210] In some embodiments, 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.

[0211] The air oxidation temperature T0 can be determined according to a thermogravimetric analysis comprising the following steps: the negative electrode active material is subjected to a thermogravimetric test under the conditions of a weighing mass of 10±0.05 mg, a purge gas of air and an air flow rate of 60 mL / min, a heating rate of 5°C / min, and a test temperature range of 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), the peak top temperature T1 of the maximum area peak is read from the differential thermogravimetric curve, and the intersection of two tangents at two points corresponding to the temperatures of 500°C and T1, respectively, is determined on the thermogravimetric curve, and the temperature corresponding to the intersection on the thermogravimetric curve is the air oxidation temperature T0 of the composite graphite material.

[0212] The oxidation of negative electrode active materials in the air often starts from surface defects. Therefore, the temperature corresponding to the intersection of two tangents at two points corresponding to 500°C and the peak temperature T1 of the maximum area peak on the thermogravimetric curve, that is, the air oxidation temperature T0 of the negative electrode active material, can accurately indicate the temperature when it starts to lose weight due to air oxidation, and can reflect the number of surface defects of the negative electrode active material.

[0213] In some embodiments, the air oxidation temperature T0 of the negative electrode active material may be 630°C, 640°C, 650°C, 660°C, 670°C, 680°C, 690°C, 700°C, 710°C, 720°C, 730°C or any range therebetween.

[0214] The negative electrode active material with an air oxidation temperature T0 of 630°C to 730°C has a suitable number of surface defects, which provide sufficient end surfaces for the embedding of active ions and match the lithium ion transfer rate of the electrolyte, while keeping the degree of side reactions 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.

[0215] In some embodiments, 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 002 >0.335nm, can be selected as 0.3355nm~0.337nm.

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

[0217] In some embodiments, the kinetic carbon material is located in the core and / or the cladding.

[0218] In this application, primary particles refer to the smallest unit of particles within a certain observation range. Primary particles may contain defects of any form, but it is impossible to define smaller particles in primary particles. Primary particles may aggregate under physical effects such as van der Waals forces, but such aggregation is easily deagglomerated under external forces such as ultrasound, stirring, and rolling, so that the main component form of the active material in the membrane layer is still primary particles.

[0219] In the present application, secondary particles are formed by the agglomeration of primary particles. The agglomeration here is a hard agglomeration caused by chemical bonding of primary particles, so that the secondary particles have a clear surface and boundary, and are not easily dispersed under external forces such as ultrasound; however, after cutting the cross section of the secondary particles, it can be seen that the secondary particles are formed by the agglomeration of many primary particles.

[0220] In this embodiment, the core portion is a secondary particle formed by agglomeration of primary graphite particles.

[0221] Amorphous carbon refers to carbon materials with a very low degree of graphitization and a nearly amorphous form (or no fixed shape and periodic structural regularity). There is no regular arrangement between the carbon atoms in the amorphous carbon structure. Therefore, amorphous carbon can be characterized by transmission electron microscopy (TEM) testing. By cutting a thin slice of about 100nm thickness from the middle of the negative electrode active material particles using a focused ion beam (FIB), and then performing a TEM test on the slice, it can be observed that the surface area includes the coating layer. The lattice fringes in the coating layer show long-range disorder and short-range order, and the electron diffraction pattern is halo-shaped, indicating that the coating layer includes amorphous carbon.

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

[0223] In this application, the interlayer distance d of a material is 002 The meaning is well known in the art and can be measured by instruments and methods well known in the art. For example, d can be measured by using an X-ray powder diffractometer (such as PANalyticalX'pert PRO) according to JIS K 0131-1996 and JB / T 4220-2011. 002 .

[0224] The interlayer spacing d of conventional graphite 002 Generally, it is 0.335 nm. The interlayer spacing d of the above-mentioned kinetic carbon materials is 002 Both are larger than conventional graphite.

[0225] The negative electrode active materials including the above-mentioned kinetic carbon materials can increase the embedding and extraction rates of active ions, thereby improving the transmission performance of active ions and electrons, and further improving the fast charging performance of battery cells while maintaining high energy density. At the same time, amorphous carbon has a high hardness, so it also has good compressive resistance, a strong ability to maintain the pore structure of the negative electrode film layer during the cycle, and better electrolyte wettability of the negative electrode plate, so it is also beneficial to improve the cycle 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] Hard carbon materials have a small amount of disordered crystallites, and cannot be transformed into graphite structures even after high-temperature heat treatment. Hard carbon materials do not have a long-range ordered lattice structure, and the arrangement of atoms is only short-range ordered, which is between the graphite and diamond structures. There are basically no parallel graphite sheet structures with more than 3-4 layers in hard carbon materials, and they are mainly composed of disordered single-layer graphite sheet structures. Therefore, there are a large number of micropores with a diameter of less than 1nm in the material.

[0228] Expanded graphite refers to graphite flake crystals that expand at a certain temperature. The expanded graphite is in the shape of a filamentous worm. The interlayer spacing of expanded graphite along the C-axis direction is tens to hundreds of times that of conventional graphite.

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

[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 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 selected as 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 any numerical range therebetween.

[0232] When the mass percentage of the kinetic carbon material is within an appropriate range, the negative electrode active material can have a high solid-phase transport capacity of active ions and a high exchange rate of active ions and electrons while having a high gram capacity, and thus the battery cell can have improved fast charging performance while having a high energy density. At the same time, when the mass percentage of the kinetic carbon material is within an appropriate range, the ability to maintain the pore structure of the negative electrode film layer during the cycle is better, the electrolyte wettability of the negative electrode plate is better, and the battery cell can also have good cycle performance.

[0233] In some embodiments, 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.

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

[0235] In some embodiments, 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 can be selected as 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm or any numerical range therebetween.

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

[0237] The negative electrode active material with a volume distribution particle size Dv50 within the above range can, on the one hand, make use of a certain number of primary particles in the secondary particles to make the negative electrode active material have a suitable embedding surface, and the solid phase transmission rate and solid-liquid transmission rate of the active ions in the negative electrode active material can match the liquid phase transmission rate of lithium ions in the electrolyte, thereby improving the fast charging performance of the battery; on the other hand, it can also have the advantages of large secondary particle size, high compaction density and large capacity, thereby improving the fast charging performance of the battery while taking into account the energy density of the battery cell.

[0238] In some embodiments, 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.

[0239] In some embodiments, the negative electrode active material includes unagglomerated primary particles, and the volume distribution particle size Dv50 of the negative electrode active material can be selected as 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm or any numerical range therebetween.

[0240] In some embodiments, the negative electrode active material mainly includes unagglomerated primary particles, which means that more than 85% of the particles in the negative electrode active material are unagglomerated primary particles. This can be determined by observing the particle morphology of the cross section in the thickness direction of the negative electrode sheet.

[0241] Compared with small-size particles, negative electrode active materials with a volume distribution particle size Dv50 within the above range have higher interface stability, but also have a larger ion solid phase transmission distance. The size design can balance the two and achieve a balance between the fast charging performance and cycle life of the battery cell.

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

[0243] Artificial graphite refers to materials that are easily graphitized and treated under high temperature and other conditions to form a regular graphitized lamellar structure. Artificial graphite is significantly different from natural graphite in morphology. Through scanning electron microscopy, the cross section of graphite is observed. Natural graphite has more layered structures, and there are a large number of pores between the lamellar structures; while the crystals of artificial graphite are strictly arranged according to ABAB, and the interior is dense, without gaps or only a small number of gaps. Artificial graphite and natural graphite also differ in crystal structure. Natural graphite not only has a hexagonal phase, but also an orthorhombic hexahedral phase (3R phase); while artificial graphite only has a hexagonal phase. Artificial graphite has fewer defects and higher capacity, which can reduce the degree of side reactions with the electrolyte, give full play to the high capacity characteristics of graphite, reduce gas production, and make the battery monomer 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 portion; and / or the average thickness of the coating layer is 100nm-300nm.

[0245] In some embodiments, the mass of the coating layer may be selected to be 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 any range therebetween.

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

[0247] In some embodiments, the average thickness of the coating layer may be 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, or any range therebetween.

[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] The embodiment of the present application adopts a high-conductivity electrolyte with a high ion transfer rate. By designing the second negative electrode film layer close to the electrolyte to have a larger porosity, the transfer rate of lithium ions in the electrode and the liquid phase transfer rate in the electrolyte are matched with each other, thereby 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 in 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 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.

[0258] In the present application, the particle size uniformity of the negative electrode active material has a meaning known in the art, which can characterize the degree of dispersion of the particle size of all particles in the negative electrode active material 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 a meaning known in the art and can be tested by methods known in the art. For example, it can be directly tested by referring to the 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 the instrument.

[0259] In some embodiments, the particle size consistency 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 any range therebetween.

[0260] In some embodiments, the particle size consistency 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 any range therebetween.

[0261] The negative electrode active material with a particle size consistency of 0.4-0.6 can be densely packed by grading large and small particles, so that the first negative electrode film layer has a relatively low porosity; the negative electrode active material with a particle size consistency of 0.25-0.45 is difficult to form an effective match due to the low particle size consistency between particles, so that the second negative electrode film layer has 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; and 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 as 13.7μm, 14.7μm, 15.7μm, 16.7μm, 17.7μm, 18.7μm, 19.7μm, 20.7μm or any numerical range therebetween; the volume distribution particle size DV50 of the second negative electrode active material is 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm or any numerical range therebetween.

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

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

[0266] When the negative electrode active materials of the first film layer and the second film layer meet the design conditions, 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 (State of charge) at the initial stage of charging. At the same time, there are more small-particle active substances in the second negative electrode film layer and the particle size is smaller, which is beneficial to the charge exchange of active ions in the high SOC state at the end 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, 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.

[0269] In this application, the powder compaction density of a material has a well-known meaning in the art and can be measured by instruments and methods known in the art. For example, it can be measured by an electronic pressure testing machine (such as UTM7305) with reference to the standard GB / T24533-2009. An exemplary test method is as follows: weigh 1g of material and add a bottom area of ​​1.327cm 2 The mold is pressurized to 5000kg (equivalent to 50000N), maintained for 30s, then released, maintained for 10s, and then the powder compaction density of the material under a force of 50000N is recorded and calculated.

[0270] The powder compaction density of the negative electrode active material in the second negative electrode film layer close to the electrolyte side is small, which 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 powder compaction density of the negative electrode active material in the first negative electrode film layer away from the electrolyte side is large, which is beneficial to improving the compaction density of the negative electrode film layer while taking into account the energy density of the battery cell.

[0271] In some embodiments, the powder compaction density ρ2 of the negative electrode active material in the second negative electrode film layer under a pressure of 50000N satisfies: 1.50 g / cm 3 ≤ρ2≤2.00g / cm 3 .

[0272] In some embodiments, the powder compaction density ρ2 of the negative electrode active material in the second negative electrode film layer under a pressure of 50000N satisfies: 1.55 g / cm 3 ≤ρ2≤1.95g / cm 3 .

[0273] In some embodiments, the powder compaction density ρ2 of the negative electrode active material in the second negative electrode film layer under a pressure of 50000N may be 1.50 g / cm 3 , 1.55g / cm 3 , 1.60g / cm 3 , 1.65g / cm 3 , 1.70g / cm 3 , 1.75g / cm 3 , 1.80g / cm 3 , 1.85g / cm 3 , 1.90g / cm 3 , 1.95g / cm 3 , 2.00g / cm 3 Or any range of values ​​in between.

[0274] In some embodiments, the powder compaction density ρ1 of the negative electrode active material in the first negative electrode film layer under a pressure of 50000N satisfies: 1.70 g / cm 3≤ρ1≤2.05g / cm 3 .

[0275] In some embodiments, the powder compaction density ρ1 of the negative electrode active material in the first negative electrode film layer under a pressure of 50000N may be 1.70 g / cm 3 , 1.72g / cm 3 , 1.74g / cm 3 , 1.76g / cm 3 , 1.80g / cm 3 , 1.82g / cm 3 、1.84g / cm 3 , 1.86g / cm 3 、1.88g / cm 3 , 2.00g / cm 3 , 2.02g / cm 3 , 2.04g / cm 3 , 2.05g / cm 3 Or any range of values ​​in between.

[0276] In some embodiments, the powder compaction density ρ1 of the negative electrode active material in the first negative electrode film layer under a pressure of 50000N satisfies: 1.80 g / cm 3 ≤ρ1≤2.05g / cm 3 .

[0277] In some embodiments, the single-side density of the negative electrode film layer is 0.08 g / 1540.25 mm 2 -0.20g / 1540.25mm 2 , optional: 0.10g / 1540.25mm 2 -0.16g / 1540.25mm 2 .

[0278] In the present application, the surface density of the film layer has a well-known meaning in the art and can be tested by methods known in the art. For example, take a pole piece that has been coated on one side and cold pressed (if it is a pole piece coated on both sides, the film layer on one side can be wiped off first), punch it into small discs with an area of ​​S1, weigh it, and record it as M1. Then wipe off the film layer of the pole piece after the above weighing, weigh the weight of the collector, and record it as M0. The single-side density of the film layer = (M1-M0) / S1. In order to ensure the accuracy of the test results, multiple groups (for example, 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-side density of the negative electrode film layer can be selected to be 0.08 g / 1540.25 mm 2 , 0.09g / 1540.25mm 2, 0.10g / 1540.25mm 2 , 0.11g / 1540.25mm 2 , 0.12g / 1540.25mm 2 , 0.13g / 1540.25mm 2 , 0.14g / 1540.25mm 2 , 0.15g / 1540.25mm 2 , 0.16g / 1540.25mm 2 , 0.17g / 1540.25mm 2 , 0.18g / 1540.25mm 2 , 0.19g / 1540.25mm 2 , 0.20g / 1540.25mm 2 Or any range of values ​​in between.

[0280] It can be understood that the single-side density of the negative electrode film layer is tested on the negative electrode sheet, and the single-side density of the positive electrode film layer is tested on the positive electrode sheet.

[0281] A battery cell having a single-side 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-side density of the negative electrode film layer is 0.06 g / 1540.25 mm 2 -0.15g / 1540.25mm 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-side density of the negative electrode film layer can be selected to be 0.06 g / 1540.25 mm 2 , 0.07g / 1540.25mm 2 , 0.08g / 1540.25mm 2 , 0.09g / 1540.25mm 2 , 0.10g / 1540.25mm 2 , 0.11g / 1540.25mm 2 , 0.12g / 1540.25mm 2 , 0.13g / 1540.25mm 2 , 0.14g / 1540.25mm 2, 0.15g / 1540.25mm 2 Or any range of values ​​in between.

[0285] Silicon-based materials have 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 the battery with the same capacity, that is, the single-side density of the negative electrode film layer is further reduced, which is beneficial to reduce the transmission distance of lithium ions in the negative electrode film layer and further improve the fast charging performance of the battery cell.

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

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

[0288] In some embodiments, the compaction density of the negative electrode sheet can be selected to be 1.2 g / cm 3 , 1.3g / cm 3 , 1.4g / cm 3 , 1.5g / cm 3 , 1.6g / cm 3 , 1.65g / cm 3 , 1.7g / cm 3 , 1.8g / cm 3 , 1.9g / cm 3 Or any range of values ​​in between.

[0289] The negative electrode sheet with a compaction density within the above range has a suitable porosity, can match the electrolyte with high conductivity, increase the diffusion rate of lithium ions in the negative electrode, and reduce the concentration polarization generated by the battery cell during fast charging, which is beneficial to improve 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 a single side of the negative electrode film layer is 30 μm-150 μm, and can be 30 μm-80 μm.

[0291] In some embodiments, the average single-sided thickness of the negative electrode film layer may be selected to be 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, 105 μm, 110 μm, 115 μm, 120 μm, 125 μm, 130 μm, 135 μm, 140 μm, 145 μm, 150 μm or any numerical range therebetween.

[0292] The negative electrode film layer with an average thickness within the above range has a suitable lithium ion diffusion distance, can match the electrolyte with high conductivity, increase the diffusion rate of lithium ions in the negative electrode film layer, 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 comprises a silicon-based material, and the average thickness of a single side of the negative electrode film layer is 30 μm-80 μm.

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

[0295] Silicon-based materials have 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 the battery with the same capacity, which is beneficial to reduce the transmission distance of lithium ions in the negative electrode film layer and further improve the fast charging performance of the battery cell.

[0296] In some embodiments, the porosity of the negative electrode sheet is 20%-60%, and optionally 25%-40%.

[0297] In the present application, the porosity of the negative electrode plate can be tested by methods known in the art. For example, the test is based on the national standard GB / T24586-2009, the plate is immersed in ethyl methyl carbonate (EMC) for cleaning; and the test instrument true density meter is used to measure based on the gas displacement method. Among them, the percentage of the pore volume in the plate to the total volume of the plate is the plate porosity, 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 may be 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60% or any range therebetween.

[0299] The negative electrode plate with a porosity within the above range can be matched with an electrolyte with high conductivity, which facilitates the transmission of lithium ions in the negative electrode and reduces the concentration polarization generated in the battery cell during fast charging, which 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 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; the volume distribution particle size Dv50 of the positive electrode active material 正1 Meet: 0.3μm≤Dv50 正1 ≤2μm.

[0301] Volume distribution particle size Dv50 of positive electrode active material 正 The test can be performed with reference to the volume distribution particle size of the negative electrode active material mentioned above. It can be understood that the unagglomerated primary particles here refer to the primary particles that have not been granulated to form secondary particles, and it does not mean that the primary particles will not spontaneously aggregate. Since the particle size of the primary particles containing lithium phosphate is small and the specific surface area is large, aggregation is inevitable in the process of testing the volume distribution particle size by the Malvern scattering method, so that the result obtained by the Malvern laser particle size analyzer test is the particle size of the primary particle aggregates, 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 phosphate-containing positive electrode active material 正1 The optional value may be 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 numerical range therebetween.

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

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

[0304] The statistics of the primary particle size of the positive electrode active material can be carried out in the following way. As an example, the battery is disassembled to obtain the positive electrode plate, the positive electrode film layer of the positive electrode plate is peeled off, the positive electrode film layer is fully washed with acetone, and the powder is filtered and dried. Take 0.05g of the uniformly mixed powder and dissolve it in 40mL of anhydrous ethanol, then add an appropriate amount of dispersant, stir evenly to obtain a suspension, take 2mL of the suspension and 2mL of anhydrous ethanol and mix them for ultrasonic treatment, the ultrasonic power is 480W, the ultrasonic time is 5min, and the uniformly dispersed suspension is obtained. Take an appropriate amount of the middle layer suspension for transmission electron microscopy test to obtain a transmission electron microscope image. Select 5-10 transmission electron microscope images with a number of 50 to 100 particles as the sampling area, ensure that at least 500 particles are tested, and then use Avizo 3D software image processing software to count the projected area of ​​each primary particle in each sampling area, that is, the primary particle cross-sectional area S. When performing primary particle identification, for particles with obvious adhesion, manual identification and software identification can be combined to determine whether the particle is a single primary particle or two secondary particles. The equivalent circle method is used to obtain the equivalent circle diameter of the primary particle, which is the primary particle diameter d.

[0305] Lithium-containing phosphates with an average particle size of primary particles within the above range have a shorter ion transmission path, low lithium ion transmission impedance and low moisture absorption, which can not only match the liquid phase transmission rate of lithium ions in the electrolyte, but also reduce the temperature rise of the battery cell during fast charging, and can also take into account the cycle life of the battery cell by controlling the moisture absorption.

[0306] In some embodiments, the lithium-containing phosphate has a general composition formula as shown in Formula VI,

[0307] Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1 Formula VI,

[0308] Among them, 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, and Mg; Me includes one or more of Mn, Fe, Co, and 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, and Ce; X includes one or more of S, Si, Cl, B, C, and N; Y includes one or more of O and F.

[0309] In some embodiments, x1 can be selected as 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3 or any range therebetween, y1 can be selected as 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 any range therebetween, x1+y1 can be selected as 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3 or any range therebetween, a1 can be selected as 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5 or any range therebetween, b 1 can be selected as 0, 0.1, 0.2, 0.3, 0.4, 0.5 or any range therebetween, a1+b1 can be selected as 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5 or any range therebetween, c1 can be selected as 0, 0.1, 0.2, 0.3, 0.4, 0.5 or any range therebetween, z1 can be selected as 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 any range therebetween.

[0310] The lithium-containing phosphate having 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 is an olivine structure, including but not limited to lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate and their respective doping modified materials, coating modified materials, composite modified materials or one or more thereof. 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 includes a lithium-containing transition metal oxide, and the volume distribution particle size Dv50 of the positive electrode active material is 正2Meet: 2μm≤Dv50 正2 ≤15μm.

[0312] In some embodiments, the lithium-containing transition metal oxide may include, but is 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 , wherein 0<a≤1.2; 0.8≤b<1; 0<c<1; 0<d<1; 1≤e≤2; 0≤f≤1; M includes but is not limited to one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B; A includes but is not limited to one or more of N, F, S and Cl. This can further improve the energy density of the battery cell. Optionally, the lithium transition metal oxide may include but is not limited to LiNi 0.8 Co 0.1 Mn 0.1 O2、LiNi 0.80 Co 0.15 Al 0.05 O2、LiNi 0.9 Co 0.06 Mn 0.04 O2、LiNi 0.92 Co 0.06 Mn 0.02 O2、LiNi 0.96 Co 0.02 Mn 0.02 O2、LiNi 0.55 Co 0.07 Mn 0.38 O2、LiNi 0.55 Co 0.12 Mn 0.33 O2、LiNi 0.65 Co 0.1 Mn 0.25 O2、LiNi 0.7 Co 0.1 Mn 0.2 O2、LiNi 0.6 Co 0.1 Mn 0.3 One or more of O2.

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

[0315] Volume distribution particle size Dv50 正2 The positive electrode active material containing lithium transition metal oxide within the above range has a shorter ion transmission path, low lithium ion transmission impedance and low side reaction degree. It can not only match the liquid phase transmission rate of lithium ions in the electrolyte, but also reduce the temperature rise of the battery cell during fast charging, and 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 is 正2 The positive electrode active material comprises 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.

[0317] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganese oxide, and the Dv50 of the positive electrode active material is 正2 The thickness can be selected as 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm or any numerical range therebetween.

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

[0319] The average particle size of the primary particles in the secondary particles can be tested by any known method in the art. As an example, a cross section in the thickness direction of the positive electrode sheet is obtained, and particles of any 10 areas of the same size and shape in the same scanning electron microscope image (SEM) under 10kv and 30k magnifications are observed. The 10 areas are then subdivided into 5 positions in the four corners and the center, and the mean particle size of any primary particle at each position under this magnification is selected, and the mean particle size results of the 5 positions in the four corners and the center are averaged to obtain the mean particle size of the primary particles in the area, and then the particle size of the primary particles obtained in the 10 areas is averaged as the average particle size of the primary particles. Specifically, the average of the major diameter and minor diameter of each particle is taken as the mean particle size of the particle.

[0320] 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 a large number of primary particles with small particle sizes, which makes the lithium ion transmission path short and the embedded end faces more, and can match the electrolyte with a high lithium ion transmission rate, which is beneficial to improve 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 is 正2 The positive electrode active material has a diameter of 2 μm to 5 μm, and can be optionally 2.5 μm to 4.5 μm, and 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 is 正2 The thickness can be selected as 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm or any range therebetween.

[0323] In this embodiment, the positive electrode active material mainly includes unagglomerated primary particles, that is, a powder mainly composed of unagglomerated primary particles. The positive electrode active material has a low degree of side reaction with the highly active carboxylate solvent, which is conducive 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, 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 larger than the average particle size of the unagglomerated primary particles.

[0325] In some embodiments, 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, 3μm, 4μm, 5μm or any numerical range between two thereof and 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm or any numerical range between two thereof.

[0326] The positive electrode active material is graded by secondary particles mainly having large particle sizes and primary particles mainly having small particle sizes, which not only takes into account the cycle life and power performance of the battery cell, but also further improves the energy density of the battery.

[0327] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganese oxide, 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, and the Dv50 of the positive electrode active material is less than or equal to 20%. 正2 The positive electrode active material includes unagglomerated primary particles.

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

[0329] The molar content 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 non-agglomerated primary particles, the side reaction between the carboxylic acid ester and the positive electrode active material can be reduced, the cycle life of the battery cell can be increased, and the kinetic performance of the positive electrode active material can be improved, thereby improving the power performance of the battery cell.

[0330] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganese oxide, the molar content of nickel is less than 80% based on the total molar number of transition metals in the positive electrode active material, and the Dv50 of the positive electrode active material is less than 10%. 正2 The positive electrode active material includes unagglomerated primary particles.

[0331] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganese oxide, and the molar content 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 range therebetween, based on the total moles of transition metals in the positive electrode active material.

[0332] The molar content of nickel is less than 80%, which is beneficial to reduce the probability of nickel dissolution of the positive electrode active material under high voltage (charging cut-off voltage ≥ 4.3V) and improve the withstand voltage of the positive electrode active material. The combination of low nickel components and unagglomerated primary particles can further reduce the degree of side reactions between the positive electrode active material and the carboxylic acid ester solvent, reduce the probability of cracking of the positive electrode active material during high voltage charging and discharging, and improve the cycle performance of the battery cell.

[0333] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganese oxide, the molar content of nickel is greater than or equal to 80% based on the total molar number of transition metals in the positive electrode active material, and the Dv50 of the positive electrode active material is greater than or equal to 80%. 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 0.1um-1.5um.

[0334] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganese oxide, and the molar content 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 range therebetween, based on the total moles of transition metals in the positive electrode active material.

[0335] Forming high-nickel materials into large-sized secondary particles is beneficial to simultaneously increase the specific capacity of the positive electrode active material and the gradation of the positive electrode sheet, and improve 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 embedded 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, and in particles of the positive electrode active material, the mass proportion of the cobalt element near the particle surface is greater than the mass proportion of the cobalt element near the center of the positive electrode active material particle.

[0337] The mass proportion of the cobalt element in the positive electrode active material particles can be obtained by measuring the percentage of the mass of the cobalt element relative to all elements at different positions of the cross section of the positive electrode 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) (configured with an X-ray energy spectrometer (EDS, model Oxford energy spectrometer OXFord X-Max-50mm2)) can be used for measurement. The longitudinal cross section of the positive electrode film layer is obtained by using an ion cross-section polisher, and a scanning electron microscope is used to perform a line scan of the Co element on the cross section of the positive electrode active material particles. 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 cross section of the positive electrode active material particle.

[0338] In some embodiments, the ratio of the mass fraction of cobalt elements near the surface of the positive electrode active material particles to the mass fraction of cobalt elements near the center of the positive electrode 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 proportion of the cobalt element at the particle surface of the positive electrode active material to the mass proportion of the cobalt element at the center can be calculated by the ratio of the mass of the cobalt element at different sites in the line scan. Wherein, the area close to 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 close to the center of the positive electrode active material particle is a spherical area with a diameter of 200nm with the geometric center of the particle cross section as the center.

[0340] In some embodiments, the ratio of the mass fraction of the cobalt element at the particle surface of the positive electrode active material to the mass fraction of the cobalt element at the center can be selected as 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 numerical range therebetween.

[0341] Although high-conductivity electrolyte is beneficial to improve the liquid phase transmission rate of lithium ions, the components in the high-conductivity electrolyte have high electrochemical activity. For example, the carboxylic acid ester in the high-conductivity electrolyte is easy to react with the oxygen-released structure after the phase change on the surface of the positive electrode active material, increasing gas production and deteriorating the cycle life of the battery. The surface of the positive electrode active material has a relatively high cobalt content, which helps to improve the ionic conductivity of the positive electrode active material, improve the problem of excessive lithium removal on the surface of the positive electrode active material during charging and discharging, reduce the cation mixing of 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. The relatively low cobalt content in the center of the positive electrode active material can simultaneously reduce the cost of the positive electrode active material.

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

[0343] In some embodiments, the positive electrode active material includes a lithium-containing phosphate, and the single-side density of the positive electrode film layer can be 0.2 g / 1540.25 mm 2 , 0.21g / 1540.25mm 2 , 0.22g / 1540.25mm 2 , 0.23g / 1540.25mm 2 , 0.24g / 1540.25mm 2 , 0.25g / 1540.25mm 2 , 0.26g / 1540.25mm 2 , 0.27g / 1540.25mm 2 , 0.28g / 1540.25mm 2 , 0.29g / 1540.25mm 2 , 0.3g / 1540.25mm 2 , 0.31g / 1540.25mm 2 , 0.32g / 1540.25mm 2 , 0.33g / 1540.25mm 2 , 0.34g / 1540.25mm 2 , 0.35g / 1540.25mm 2 Or any range of values ​​in between.

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

[0345] In some embodiments, the positive electrode active material includes a lithium-containing transition metal oxide, and the single-side density of the positive electrode film layer can be 0.13 g / 1540.25 mm 2 , 0.14g / 1540.25mm 2 , 0.15g / 1540.25mm 2 , 0.16g / 1540.25mm 2 , 0.17g / 1540.25mm 2 , 0.18g / 1540.25mm2 , 0.19g / 1540.25mm 2 , 0.20g / 1540.25mm 2 , 0.21g / 1540.25mm 2 , 0.22g / 1540.25mm 2 , 0.23g / 1540.25mm 2 , 0.24g / 1540.25mm 2 Or any range of values ​​in between.

[0346] The positive electrode film layer with a surface density within the above range has a suitable thickness, which is conducive to the diffusion of active ions in the electrode piece 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 may be selected to be 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35% or any range therebetween.

[0349] The positive electrode film layer with a porosity within the above range is conducive to the diffusion of active ions in the electrode piece, 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] Improving the lithium ion conductivity of the electrolyte often means that a higher content of high-conductivity solvent needs to be added. High-conductivity solvents have high chemical reactivity while having a high transfer rate for lithium ions, and are prone to side reactions with negative electrode active materials, reducing the cycle life of the battery. Electrolytes with lithium ion conductivity within the above range have suitable lithium ion conduction rate and reactivity, and can better balance the fast charging performance and cycle life of battery cells.

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

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

[0354] It can be understood that the positive electrode active material includes lithium iron phosphate, which may be a salt having a lithium iron phosphate structure, or may be 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, so the positive electrode film layer of the same capacity battery cell often requires a relatively high coating surface density. Using an electrolyte with a conductivity within the above range is conducive to improving the loss of the coating surface density required for lithium iron phosphate batteries to the battery cell dynamic performance, while meeting the battery energy density requirements and taking into account the battery power performance.

[0356] In some embodiments, 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.

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

[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 a metal foil, copper foil, copper alloy foil, nickel foil, nickel alloy foil, aluminum foil, and aluminum alloy foil may be used. As an example of a three-dimensional porous current collector, copper mesh, nickel mesh, foam copper, foam nickel, and foam aluminum 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 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 also include other negative electrode active materials known in the art, for example, 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, butadiene styrene 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 more.

[0362] In some embodiments, the negative electrode film layer may further 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, and the like.

[0363] The negative electrode film layer is usually formed by coating the negative electrode slurry on the negative electrode current collector, drying and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, negative electrode conductive agent, negative electrode binder, other optional additives, etc. in a solvent and stirring them evenly. The solvent can 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 also include a conductive primer 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 also include a protective layer covering the surface of the negative electrode film layer.

[0365] In some embodiments, the positive electrode film layer may also 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 also optionally 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 acrylic 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) One or more.

[0367] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. As an example of a 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, 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).

[0368] The positive electrode film layer is usually formed by coating the positive electrode slurry on the positive electrode current collector, drying and cold pressing. The positive electrode slurry is usually formed by dispersing the positive electrode active material, positive electrode conductive agent, positive electrode binder and any other components in a solvent and stirring them evenly. The solvent can 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 electrolyte, and it can be selected according to needs. For example, the electrolyte can include one or more of a solid electrolyte and a liquid electrolyte (ie, an electrolyte).

[0370] In some embodiments, as an example, the electrolyte salt may include, but is not limited to, one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalatophosphate) (LiDFOP), and lithium tetrafluorooxalatophosphate (LiTFOP).

[0371] In some embodiments, the solvent further includes, but is not limited to, one or more of an ester solvent, a sulfone solvent, and an ether solvent. As an 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), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE).

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

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

[0374] The present application has no particular limitation on the type of isolation membrane, and any known porous isolation membrane with good chemical stability and mechanical stability may be selected.

[0375] In some embodiments, the material of the isolation membrane may include, but is not limited to, one or more of glass fiber, non-woven fabric, polyethylene (PE), polypropylene (PP) and polyvinylidene fluoride. The isolation membrane may be a single-layer film or a multi-layer composite film. When the isolation membrane is a multi-layer composite film, the materials of each layer are 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 sheet, the separator, the negative electrode sheet and the electrolyte can be assembled to form a battery cell. As an example, the positive electrode sheet, the separator, and the negative electrode sheet can be formed into an electrode assembly through a winding process and / or a lamination process, and the electrode assembly is placed in an outer package, and the above-mentioned electrolyte is injected after drying. After packaging, standing, formation and other processes, a battery cell is obtained. Multiple battery cells can also be further connected in series, in parallel or in mixed connection to form a battery module. Multiple battery modules can also be connected in series, in parallel or in mixed connection to form a battery pack. In some embodiments, multiple battery cells can also directly form a battery pack.

[0377] The embodiment of the present application also provides a method for preparing a negative electrode active material, which can prepare the negative electrode active material provided in the embodiment of the present application.

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

[0379] In some embodiments, the method for providing graphite includes the following steps: providing coke raw material; crushing, shaping and grading the coke raw material to obtain aggregate; mixing the obtained aggregate with a binder and sequentially granulating and graphitizing to obtain graphite.

[0380] The particle size of the coke raw material is usually relatively large, and the particle size of the coke raw material can be reduced by crushing. Optionally, the crushing process can include two steps: coarse crushing and pulverizing. Coarse crushing can crush the coke raw material into millimeter-level block particles. Pulverizing can crush the particle size of the particles from the millimeter level to tens of micrometers. After the crushing process, the surface of the coke raw material is uneven, and the shaping process can make the coke raw material particles themselves more rounded. The grading process 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 of the core material, increasing the gram capacity of the core material and the gram capacity of the negative electrode active material as a whole, and are also beneficial to improving the energy density of the battery. Optionally, the mass of the binder can be 6%-12% of the mass of the aggregate obtained by graded treatment, and can be optionally 8%-10%. This can make the graphite have a good secondary particle morphology.

[0382] Alternatively, the binder may include asphalt.

[0383] The equipment used for the granulation process may include either a horizontal reactor or a vertical reactor.

[0384] Optionally, the granulation process can adopt a step-wise heating and heat preservation process, thereby making the graphite have good secondary particle morphology and high capacity.

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

[0386] Usually, the surface of coke raw materials from different batches and different raw materials is uneven and has many defects. Graphitization treatment can also significantly repair the surface defects of the material, thereby making the Raman value of the core material in the surface scanning mode more concentrated, and thus making the performance of the finished graphite product more consistent.

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

[0388] Optionally, the temperature of the graphitization treatment may be 2800°C-3800°C, for example, 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 a range of any of the above values. More optionally, the temperature of the graphitization treatment may be 2850°C-3300°C. The specific time of the graphitization treatment may be reasonably selected according to the equipment used.

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

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

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

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

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

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

[0395] Solid-phase coating agents have the advantages of low cost and relatively simple process, and are easy to promote industrially.

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

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

[0398] The coking value of a liquid hard carbon coating agent refers to the percentage of the residual carbon mass left after a quantitative liquid hard carbon coating agent sample is heated under specified conditions to the mass of the liquid hard carbon coating agent sample, and can be tested 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 the graphite, for example, 0.7%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range of any of the above values. Alternatively, the mass of the liquid-phase hard carbon coating agent can be 3%-7% of the mass of the graphite.

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

[0401] The mass proportion of the liquid phase hard carbon coating agent is within the above range, which can make the uncoated degree of the negative electrode active material within a smaller range, thereby not only improving the charge exchange capacity of ions on the surface of the prepared negative electrode active material, but also making the side reactions on the surface of the prepared negative electrode active material particles at a lower level, and also making the prepared negative electrode active material have a higher gram capacity, which is beneficial for the battery to have high energy density, good kinetic performance and long cycle life.

[0402] In some embodiments, the liquid soft carbon coating agent includes liquid asphalt, liquid tar, and other petroleum or coal byproducts.

[0403] In some embodiments, the liquid phase hard carbon coating agent includes a 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 purchased from the market, or synthesized according to methods known in the art, or can be obtained by mixing and stirring the resin powder with a solvent.

[0405] In some embodiments, the viscosity of the liquid resin at 25° C. may be 150 mPa·s-2500 mPa·s, for example, 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 consisting of any of the above values. Optionally, the viscosity of the liquid resin at 25° C. may 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 a NDJ-1 type rotational viscometer.

[0407] The viscosity of the liquid resin is within the above range, which can make the liquid resin have good fluidity and diffusibility, as well as good curing effect and coating effect. Therefore, the liquid resin can be evenly dispersed on the surface of the graphite particles, which is beneficial to improve the coating effect, reduce the degree of uncoating, and improve the coating uniformity of the surface of the graphite particles, which is beneficial to the battery to have both good dynamic performance and long cycle life.

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

[0409] The solid content of the liquid phase hard carbon coating agent can be tested by the drying method in accordance with GB / T 14074-2017. The free components and water in the liquid phase hard carbon coating agent will volatilize at high temperatures. The solid content of the liquid phase hard carbon coating agent refers to the percentage of the remaining mass to the total mass after drying under specified conditions. The oven temperature is set to 150°C and baked to 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 and good curing and coating effects. Thus, the liquid resin can be evenly dispersed on the surface of the graphite particles, which is beneficial to improving the coating effect and reducing the degree of uncoating. It can also adjust the cumulative distribution of the negative electrode active material to an R value R50 of 50%, increase the disorder of the surface of the negative electrode active material particles, and enhance the charge exchange capacity of ions on the surface of the negative electrode active material, which is beneficial for the battery to have both good kinetic performance and long cycle life.

[0411] In some embodiments, the liquid resin may include at least one of liquid phenolic resin, liquid epoxy resin, liquid vinyl ester resin, liquid unsaturated polyester resin, 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 liquid resin is a good hard carbon precursor material. As a liquid phase hard carbon coating agent, it can better improve the dynamic performance of the battery and also make the battery have good cycle performance.

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

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

[0415] Compared with other liquid resins, the hard carbon formed by carbonization and coking of 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 range, the hard carbon formed by carbonization can have better kinetic properties, and the coating effect can be improved and the degree of uncoating can be reduced, thereby enhancing the charge exchange capacity of ions on the surface of the negative electrode active material, thereby improving the kinetic properties of the negative electrode active material.

[0417] The weight average molecular weight of the liquid phenolic resin can be tested by gel permeation chromatography. The testing 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 a phenolic compound, an aldehyde compound, etc., which is formed by condensation in the presence of an alkaline catalyst. The condensation reaction begins to generate a liquid. The liquid phenolic resin mentioned in the embodiment of the present application is a resol phenolic resin.

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

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

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

[0422] Increasing the stirring speed of the fusion machine is beneficial to improving the coating effect and reducing the degree of uncoating, thereby improving the charge exchange capacity of ions on the surface of the negative electrode active material, and further improving the kinetic performance of the negative electrode active material; however, excessive stirring speed of the fusion machine will destroy the outer surface structure of the inner core, and strong centrifugation will also cause mass loss of the liquid hard carbon coating agent.

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

[0424] Increasing the stirring time of solid-liquid fusion is beneficial to improving the coating effect and reducing the degree of uncoating, thereby enhancing the charge exchange capacity of ions on the surface of the negative electrode active material, and further improving the kinetic properties of the negative electrode active material; however, if the stirring time is too long, the gain in improving the coating effect is not obvious, and energy consumption will also increase.

[0425] In some embodiments, the carbonization process equipment may be a track kiln.

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

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

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

[0429] Depolymerization can be carried out in a depolymerizer. Depolymerization can eliminate the weak adhesion of the coating surface and reduce the problem of excessive agglomeration of the finished product particles. Screening can reduce the content of large particles and fine powder in the finished product, which is conducive to obtaining the desired particle size and particle size distribution. Demagnetization can reduce the content of magnetic impurities in the 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 method for preparing a negative electrode active material having a core portion of secondary particles formed by agglomeration of primary graphite particles and a coating layer comprising amorphous carbon. For the convenience of description, this negative electrode active material is referred to as a 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, graphitizing the coke powder or the coke powder added with kinetic carbon material raw material powder to obtain main particles, the main particles are secondary particles formed by the aggregation of two or more primary particles, and the main particles include artificial graphite; S20, mixing the main particles with an organic carbon source, or mixing the main 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 portion of the surface of the main particles after carbonization treatment to obtain a composite graphite material, that is, a negative electrode active material whose core is the main particles and the coating layer includes amorphous carbon.

[0432] In which, 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, and the interlayer spacing d002 of the (002) crystal plane of the kinetic carbon material raw material is greater than 0.335nm.

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

[0434] The air oxidation temperature T0 of the obtained composite graphite material is 630°C to 730°C, 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 composite graphite material, respectively, the T1 temperature is the peak top temperature of the maximum area peak in the differential thermogravimetric curve of the composite graphite material, and 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.

[0435] Specifically, the air oxidation temperature T0 can be determined according to a thermogravimetric analysis comprising the following steps: the composite graphite material is subjected to a thermogravimetric test under the conditions of a weighing mass of 10±0.05 mg, a purge gas of air with an air flow rate of 60 mL / min, a heating rate of 5°C / min, and a test temperature range of 35°C to 950°C, to obtain a thermogravimetric curve and a differential thermogravimetric curve, the peak temperature T1 of the maximum area peak is read from the differential thermogravimetric curve, and the intersection of two tangents at two points corresponding to the temperatures of 500°C and T1, respectively, is determined on the thermogravimetric curve, and the temperature corresponding to the intersection on the thermogravimetric curve is the air oxidation temperature T0 of the composite graphite material.

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

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

[0438] In some embodiments, coke can be directly obtained commercially.

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

[0440] In some embodiments, the coke includes one or more of petroleum non-needle coke, petroleum needle coke, coal non-needle coke, and coal needle coke. Optionally, the coke includes one or more of petroleum non-needle coke (e.g., petroleum calcined coke, petroleum green coke), and petroleum needle coke. In particular, the coke includes petroleum green coke. The use of suitable coke can make the prepared composite graphite material have a suitable number of end faces and defects, and thus have better active ion and electron transport properties and higher structural stability, thereby improving the fast charging performance, low temperature power performance and cycle performance of the battery.

[0441] Optionally, the coking process of the coke raw material is carried out in a delayed coking device. The delayed coking device includes a heating furnace and a coke drum. The delayed coking process refers to the coke raw material being first quickly heated to the required coking process temperature in the heating furnace, and then entering the coke drum, and undergoing preheating, cooling and other processes in the coke drum to generate coke.

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

[0443] The morphology of the coke powder obtained after crushing may include one or more of block, spherical and quasi-spherical shapes. After crushing, the coke powder is shaped to polish the edges and corners. The greater the degree of shaping, the closer the powder particles are to spherical, which can increase the active ion sites for deintercalation on the surface of the composite graphite material. The shaping process 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 coked powder may be shaped using equipment and methods known in the art, such as a shaping machine or other shaping equipment.

[0445] During the crushing and shaping process, a large number of undersized particles and sometimes oversized particles are often produced. Therefore, classification treatment can be performed according to needs to remove undersized and oversized particles in the powder. After classification treatment, coke powder with a good particle size distribution can be obtained to facilitate subsequent granulation and coating processes. Classification treatment can be performed using equipment and methods known in the art, such as a classification screen, 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. Alternatively, the volume average particle size Dv50 of the coke powder is 8 μm to 10 μm.

[0447] In some embodiments, the method for providing a kinetic carbon material raw material powder comprises the steps of: crushing, shaping, and grading the kinetic carbon material raw material to obtain the kinetic carbon material raw material powder. The crushing, shaping, and grading methods are the same as the crushing, shaping, and grading of the coke described above.

[0448] In some embodiments, the volume average particle size Dv50 of the kinetic carbon material raw material powder is 3 μm to 12 μm. Alternatively, 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 material 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 material powder is 1.2 to 1.5. 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 material powder is within a suitable range, so that the bulk particles of the composite graphite material have a good degree of secondary particles.

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

[0451] In some embodiments, based on the total mass of the composite graphite material obtained, the total mass percentage of the kinetic carbon material raw material 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 comprises the step of: adding a binder in S10, mixing the binder with the coke powder, granulating the mixture, and then graphitizing the mixture to obtain bulk particles, or mixing the binder with the coke powder added with the kinetic carbon material raw material powder, granulating the mixture, and then graphitizing the mixture to obtain bulk particles.

[0453] Adding a binder can make the bulk particles of the composite graphite material have a better degree of secondary particles, which is beneficial to improving the active ion and electron transport properties of the composite graphite material while making it have a higher 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 agglomeration of particles can be avoided, so that the bulk particles of the composite graphite material have a good degree of secondary particles.

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

[0456] Optionally, the asphalt is selected from one or more of coal asphalt 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 performed using equipment and methods known in the art, such as a granulator. The granulator generally includes a stirred reactor and a module for controlling the temperature of the reactor. By regulating the stirring speed, heating rate, granulation temperature, cooling rate, etc. during the granulation process, the granulation degree and the structural strength of the particles can be regulated, and the volume average particle size Dv50 of the bulk particles of the composite graphite material finally prepared can be within the desired range.

[0459] In some embodiments, in S10, the graphitization temperature may be 2800° C. to 3200° C. Optionally, the graphitization temperature may be 2900° C. to 3100° C. The graphitization treatment can make the bulk particles have a suitable degree of graphitization, so that the composite graphite material has a higher gram capacity. The graphitization treatment also makes the lattice expansion of the bulk particles lower during the process of inserting and removing active ions. The graphitization treatment can also effectively eliminate the bulk structure defects of the bulk particles and improve the cycle performance of the battery cell.

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

[0461] Graphitization can be performed using equipment and methods known in the art, such as a graphitization furnace, especially an Acheson graphitization furnace. After the graphitization treatment is completed, a small amount of oversized particles formed by agglomeration of the granulated product during the graphitization treatment can be removed by screening, so as to prevent the oversized particles from affecting the processing properties of the composite graphite material, such as the stability of the negative electrode slurry, coating properties, etc.

[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. Alternatively, 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, petroleum tar, phenolic resin, and coconut shell. Optionally, the organic carbon source is selected from petroleum tar. Optionally, the softening point of coal tar and petroleum tar is below 250°C.

[0464] In some embodiments, based on the total mass of the obtained composite graphite material, the amount 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 1% to 8%. Alternatively, the amount 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 2% to 5%. When the amount of the organic carbon source added is within a suitable range, the composite graphite material can have a high gram capacity and a high active ion solid phase transport capacity.

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

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

[0467] In some embodiments, the preparation method of 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 the mixture, and then graphitizing the mixture to obtain body particles, wherein 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 forming a coating layer including amorphous carbon on at least a portion of the surface of the body particles after carbonization to obtain a composite graphite material.

[0468] In some embodiments, the preparation method of the composite graphite material includes the steps of: S10, providing coke powder, mixing a binder with the coke powder, granulating the mixture, and then graphitizing the mixture to obtain body particles, wherein the body particles are secondary particles formed by the 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 a kinetic carbon material raw material powder, and forming a coating layer including amorphous carbon on at least a portion of the surface of the body particles after carbonization to obtain a composite graphite material.

[0469] In some embodiments, the preparation method of 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 the mixture, and then graphitizing the mixture to obtain body particles, wherein the body particles are secondary particles formed by the 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 a kinetic carbon material raw material powder, and forming a coating layer including amorphous carbon on at least a portion of the surface of the body particles after carbonization to obtain a composite graphite material.

[0470] In the preparation method of the present application, the coke powder or the coke powder with the kinetic carbon material raw material powder is graphitized to obtain the main body particles, and the main body particles are secondary particles formed by the aggregation of two or more primary particles. Among them, the coke powder obtained after crushing, shaping and other treatments is mainly a single particle, and from the morphological point of view, the coke powder is a primary particle (or primary particle); the main body particles obtained after the coke powder or the coke powder with the kinetic carbon material raw material powder is granulated and graphitized are agglomerates of multiple above-mentioned primary particles, so from the morphological point of view, the main body particles are secondary particles.

[0471] In the preparation method of the present application, by adjusting the volume average particle size Dv50 of the coke powder and its addition amount, the volume average particle size Dv50 of the kinetic carbon material raw material powder and its addition amount, the binder addition amount, the organic carbon source addition amount, etc., a composite graphite material with different air oxidation temperatures T0 can be obtained.

[0472] Battery device

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

[0474] Electrical devices

[0475] The embodiments of the present application also provide an electrical device, which includes a battery cell provided in the embodiments of the present application or a battery device provided in the embodiments of the present application, and the battery cell or the battery device is used to provide electrical energy. The battery can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device. The electrical device can be, but is not limited to, a mobile device (such as a mobile phone, a tablet computer, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.

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

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

[0478] As another example, the electric device may be a mobile phone, a tablet computer, a notebook computer, etc. The electric device is usually required to be light and thin, and a battery cell may be used as a power source.

[0479] Example

[0480] The following examples describe the disclosure of the present application in more detail, and these examples are only for illustrative purposes, as it is obvious to those skilled in the art that various modifications and variations can be made within the scope of the disclosure of the present application. Unless otherwise stated, all parts, percentages and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and the instruments used in the examples are commercially available.

[0481] Example 1

[0482] (1) Preparation of negative electrode active materials

[0483] The petroleum needle coke is crushed, shaped and graded 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 and granulation. A step-by-step heating and insulation process is adopted during heating. The program temperature platforms are set to 200°C, 300°C, and 600°C, respectively. The temperature is kept constant at 200°C for 1h, 300°C for 2h, and 600°C for 2h. The material is taken out of the furnace after cooling for 3h. The granulated material is placed in an Acheson graphitization furnace for graphitization at 2900°C for 50h to obtain graphite.

[0484] A fusion machine is used to fuse graphite and liquid hard carbon coating agent in a mass ratio of 100:5. The stirring speed of the fusion machine is 600r / min, the stirring time is 7min, and the liquid hard carbon coating agent is a commercially available liquid phenolic resin with a weight average molecular weight of 600, a viscosity of 680mPa·s at 25°C, and a solid content of 73%-74%. The product after solid-liquid fusion is placed in a track kiln, heated to 1150°C for carbonization treatment under a nitrogen atmosphere, and the heat preservation time is 370min. After the carbonization treatment, the temperature is lowered to 50°C and then taken out of the kiln. After depolymerization, screening and demagnetization treatment, the negative electrode active material is obtained. The gram capacity of the negative electrode active material is 357.0mAh / g, and the compacted density of the negative electrode active material powder is 1.75g / 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 negative electrode sheet

[0486] The negative electrode active material, thickener sodium carboxymethyl cellulose, negative electrode binder styrene butadiene rubber (SBR), and negative electrode conductive agent Super P were mixed in a mass ratio of 96.9:1.1:1.5:0.5, deionized water was added as a solvent, and the mixture was stirred evenly under the action of a vacuum mixer to prepare a negative electrode slurry.

[0487] The negative electrode slurry is evenly coated on both surfaces of the negative electrode current collector copper foil, and the negative electrode current collector coated with the slurry is dried at room temperature and then transferred to an oven for drying, and then cold pressed and cut to obtain the negative electrode sheet. The thickness of the negative electrode film layer on one side of the negative electrode current collector is 53μm, and the single side density of the negative electrode film layer is 0.131g / 1540.25mm 2 The compaction density of the negative electrode is 1.6g / cm 3 , the porosity of the negative electrode sheet is 30%.

[0488] (3) Preparation of positive electrode sheet

[0489] The positive electrode active material LiNi 0.65 Co 0.1 Mn 0.25 O2, positive electrode conductive agent Super P, and positive electrode binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 96:2:2, and solvent N-methylpyrrolidone (NMP) is added. The system is stirred under the action of a vacuum mixer until it becomes uniform and transparent to obtain positive electrode slurry; the positive electrode slurry is evenly coated on both surfaces of the positive electrode current collector aluminum foil; the positive electrode current collector coated with the slurry is dried at room temperature and then transferred to an oven for drying, and then cold pressed and cut to obtain positive electrode sheets. Volume distribution particle size of positive electrode active material Dv50 正2 The single-side density of the positive electrode film is 0.23g / 1540.25mm 2 ; The porosity of the positive electrode film layer is 25%.

[0490] (4) Preparation of electrolyte

[0491] Ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl acetate (EA) are mixed in a mass ratio of 3:2:5, and a first additive, lithium difluorooxalate borate LiDFOB, a second additive, methylene disulfonate (MMDS, formula V), an additive shown in formula III, and a third additive are slowly added, wherein the third additive includes fluoroethylene carbonate FEC, 1,3-propyl sultone PS, and vinyl sulfate DTD, so that based on the total mass of the electrolyte, the mass content of the first additive is 1%, the mass content of the second additive is 2%, wherein 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 mass content of the third additive is 3.2%, wherein 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 LiPF6 is dissolved in a mixed solvent in a certain proportion to prepare an electrolyte. The mass content of LiPF6 in the electrolyte is 12.5%, and the conductivity of the electrolyte is 13.5 mS / cm.

[0494] (5) Preparation of isolation membrane

[0495] Choose 12 micron polyethylene film.

[0496] (6) Preparation of batteries (full batteries)

[0497] The positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, so that the separator is placed between the positive electrode sheet and the negative electrode sheet to play an isolating 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 vacuum packaging, standing, forming, shaping and other processes, a battery containing a wound cell 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 methods are as follows:

[0499] Example 2

[0500] (1) Preparation of negative electrode active materials

[0501] The petroleum needle coke is crushed, shaped and graded 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 and granulation. A step-by-step heating and insulation process is adopted during heating. The program temperature platforms are set to 200°C, 300°C, and 600°C, respectively. The temperature is kept constant at 200°C for 1h, 300°C for 2h, and 600°C for 2h. The material is taken out of the furnace after cooling for 3h. The granulated material is placed in an Acheson graphitization furnace for graphitization at 2900°C for 50h to obtain graphite.

[0502] A fusion machine is used to fuse graphite and a liquid hard carbon coating agent in a mass ratio of 100:3. The stirring speed of the fusion machine is 600 r / min, the stirring time is 7 min, and the liquid 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, heated to 1150°C for carbonization treatment under a nitrogen atmosphere, and the heat preservation time is 6 hours. Then the product is cooled to 50°C and taken out of the kiln. After depolymerization, screening and demagnetization treatment, a negative electrode active material is obtained.

[0503] Example 3

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

[0505] The petroleum needle coke is crushed, shaped and graded 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 and granulation. A step-by-step heating and insulation process is adopted during heating. The program temperature platforms are set to 200°C, 300°C, and 600°C, respectively. The temperature is kept constant at 200°C for 1h, 300°C for 2h, and 600°C for 2h. The material is taken out of the furnace after cooling for 3h. The granulated material is placed in an Acheson graphitization furnace for graphitization at 2900°C for 50h to obtain graphite.

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

[0507] Example 4

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

[0509] The petroleum coke is crushed, shaped and graded 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 and granulation. A step-by-step heating and insulation process is adopted during heating. The program temperature platforms are set to 200°C, 300°C, and 600°C, respectively. The temperature is kept constant at 200°C for 1h, 300°C for 2h, and 600°C for 2h, and then taken out of the furnace after cooling for 3h; the granulated material is placed in an Acheson graphitization furnace for graphitization at 2900°C for 50h to obtain graphite.

[0510] A fusion machine is used to mix graphite and a solid-phase coating agent in a mass ratio of 100:3. The solid-phase coating agent is asphalt with a softening point of 270°C. The solid-solid mixing product is placed in a track kiln and heated to 1150°C for carbonization treatment under a nitrogen atmosphere for 6 hours. The kiln is then cooled to 50°C and taken out of the kiln. 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 materials

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

[0515] Interlayer spacing d 002 The expanded graphite (expansion factor of 180) with a particle size of 0.3363 nm was 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 expanded graphite powder are mixed, and then mixed with the binder coal tar, and then granulated. The volume average particle size Dv50 of the particles obtained after granulation is about 13μm. The granulated product is placed in a graphite crucible, and then the graphite crucible is placed in an Acheson graphitization furnace. Resistor material is filled around the graphite crucible, and electricity is turned on to make the current flow through the resistor material to generate heat energy, and graphitization treatment is performed at about 3000℃ to obtain bulk particles.

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

[0518] Among them, based on the total mass of the obtained composite graphite material, the mass percentage of the added expanded graphite powder is 8%, the mass percentage of the added binder is 6%, and the mass of the added organic carbon source 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 1.64g / cm 3 The gram 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 T0 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 negative electrode active materials

[0522] The petroleum needle coke is crushed, shaped and graded 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 and granulation. A step-by-step heating and insulation process is adopted during heating. The program temperature platforms are set to 200°C, 300°C, and 600°C, respectively. The temperature is kept constant at 200°C for 1h, 300°C for 2h, and 600°C for 2h. The material is taken out of the furnace after cooling for 3h. The granulated material is placed in an Acheson graphitization furnace for graphitization at 2850°C for 45h to obtain graphite.

[0523] A fusion machine is used to mix graphite and a solid-phase coating agent in a mass ratio of 100:5. The solid-phase coating agent is asphalt with a softening point of 270°C. The solid-solid mixing product is placed in a track kiln and heated to 1150°C for carbonization treatment under a nitrogen atmosphere for 6 hours. The kiln is then cooled to 50°C and taken out of the kiln. After depolymerization, screening and demagnetization treatment, the negative electrode active material is obtained.

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

[0525] Example 7

[0526] Preparation method of negative electrode sheet:

[0527] The first negative electrode active material, binder SBR, thickener sodium carboxymethyl cellulose (CMC-Na), conductive agent carbon black (Super-P) at a mass ratio of 96.2:1.8:1.2:0.8 and deionized water are added to a stirring tank in a certain order 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) in a weight ratio of 96.2:1.8:1.2:0.8 and deionized water are added to a stirring tank in a certain order for mixing to prepare negative electrode slurry 2;

[0529] Among them, the preparation method of the first negative electrode active material and the second negative electrode active material is basically the same as the preparation method of the negative electrode active material in Example 1, the difference is 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 the porosity of the second negative electrode film layer.

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

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

[0532] Example 8

[0533] Preparation method of negative electrode sheet:

[0534] Based on the preparation method of the negative electrode active material in Example 1, the first negative electrode active material was prepared by adjusting the raw material selection and material preparation process. The powder compaction density of the first negative electrode active material under a pressure of 50000N was 1.98g / cm 3 The negative electrode active material prepared in Example 1 is used as the second negative electrode active material, and its powder compaction density under a pressure of 50000N is 1.75g / cm 3 The powder compaction density of the first negative electrode active material is greater than the powder compaction density 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) at a mass ratio of 96.2:1.8:1.2:0.8 and deionized water are added to a stirring tank in a certain order 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) in a weight ratio of 96.2:1.8:1.2:0.8 and deionized water are added to a stirring tank in a certain order for mixing to prepare negative electrode slurry 2;

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

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

[0539] Example 9

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

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

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

[0543] 2) Preparation of active material particle precursor 1

[0544] Lithium carbonate Li2CO3, positive electrode active material precursor Ni 0.556 Co 0.11 Mn 0.334 (OH)2 and zirconium oxide ZrO2 are 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 element to Me is Li:Me=1.06:1; the amount of zirconium oxide added is such that the molar ratio of zirconium element 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 O2.

[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 substantially the same as those of Example 1, except that the components and proportions of the electrolyte are adjusted to thereby adjust the lithium ion conductivity of the electrolyte.

[0552] Example 10

[0553] The preparation method of the electrolyte is: ethylene carbonate (EC) and methyl acetate (MA) are mixed in a mass ratio of 3:7, and then the fully dried lithium salt LiPF6 is dissolved in the mixed solvent at a ratio of 1 mol / L, and additives are added according to Example 1 to prepare an electrolyte so that the lithium ion conductivity of the electrolyte is 20 mS / cm.

[0554] Embodiment 11

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

[0556] Example 12

[0557] The difference between the preparation method of the electrolyte and that of Example 1 is that no second additive is added to the electrolyte.

[0558] Embodiment 13

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

[0560] Embodiment 14

[0561] The preparation method of Example 14 is basically the same as that of Example 1, except that the positive electrode active material is different. The positive electrode active material is LiNi 0.8 Co 0.12 Mn 0.08 O2, with a Dv50 of 8um, is mainly composed of secondary particles formed by the agglomeration of primary particles, in which the average particle size of the primary particles is 200nm.

[0562] Embodiment 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 those of Example 1, except that the preparation methods of the battery cells are different:

[0565] Example 16

[0566] Preparation of battery (full battery):

[0567] The positive electrode sheet (the positive electrode current collecting part is 87mm wide and 240mm long), the isolation membrane, and the negative electrode sheet are stacked in order, so that the isolation membrane is between the positive and negative electrode sheets to play an isolating role, 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 vacuum packaging, standing, forming, shaping and other processes, a battery containing stacked cells is obtained.

[0568] Embodiment 17

[0569] Preparation of battery (full battery):

[0570] The positive electrode sheet (the positive electrode current collecting part is 102mm wide and 240mm long), the isolation membrane, and the negative electrode sheet are stacked in order, so that the isolation membrane is between the positive and negative electrode sheets to play an isolating role, 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 vacuum packaging, standing, forming, shaping and other processes, a battery containing stacked cells is obtained.

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

[0572] Comparative Example 1

[0573] The preparation process of the battery is the same as that of Example 1 except that the preparation process of the negative electrode active material is different.

[0574] (1) Preparation of negative electrode active materials

[0575] The petroleum needle coke is crushed, shaped and graded 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 and granulation. A step-by-step heating and insulation process is adopted during heating. The program temperature platforms are set to 200°C, 300°C, and 600°C, respectively. The temperature is kept constant at 200°C for 1h, 300°C for 2h, and 600°C for 2h, and then taken out of the furnace after cooling for 3h; the granulated material is placed in an Acheson graphitization furnace for graphitization at 2900°C for 50h, and then screened and demagnetized to obtain graphite as a negative electrode active material.

[0576] Comparative Example 2

[0577] The preparation process of the battery is the same as that of Example 1 except that the preparation process of the negative electrode active material is different.

[0578] (1) Preparation of negative electrode active materials

[0579] The petroleum needle coke is crushed, shaped and graded 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 and granulation. A step-by-step heating and insulation process is adopted during heating. The program temperature platforms are set to 200°C, 300°C, and 600°C, respectively. The temperature is kept constant at 200°C for 1h, 300°C for 2h, and 600°C for 2h. The material is taken out of the furnace after cooling for 3h. The granulated material is placed in an Acheson graphitization furnace for graphitization at 2850°C for 45h to obtain graphite.

[0580] A fusion machine is used to mix graphite and a solid-phase coating agent in a mass ratio of 100:6.3. The solid-phase coating agent is asphalt with a softening point of 270°C. The solid-solid mixing product is placed in a track kiln and heated to 1150°C for carbonization treatment under a nitrogen atmosphere for 6 hours. The kiln is then cooled to 50°C and taken out of the kiln. 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 formula of the electrolyte is adjusted, specifically:

[0582] Comparative Example 3

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

[0584] (1) Preparation of electrolyte

[0585] Ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent; LiPF6 is uniformly dissolved in the organic solvent to obtain an electrolyte, wherein the concentration of LiPF6 is 1 mol / L and the conductivity of the electrolyte is 8 mS / cm.

[0586] Performance Testing

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

[0588] The batteries of the embodiment and the comparative example were charged and discharged for the first time at a current of 1C (i.e., the current value at which the theoretical capacity is completely discharged within 1 hour), specifically comprising: at 35°C, the battery was charged at a constant current of 1C to a voltage of 4.4V, then charged at a constant voltage to a current of ≤0.05C, left to stand for 5 minutes, and then discharged at a constant current of 0.33C to a voltage of 2.5V, and its actual capacity was recorded as C0. Then the battery is charged with 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 in sequence to the full battery charge cut-off voltage of 4.4V or 0V negative electrode cut-off potential (whichever is reached first). After each charge is completed, it is necessary to discharge with 1C0 to the full battery discharge cut-off voltage of 2.5V. Record the SOC (State of Charge) at different charge rates to 10%, 20%, 30%, ..., 80% Charge, state of charge, when "SOC = 0" indicates that the battery is fully discharged, when "SOC = 100%" indicates that the battery is fully charged) the corresponding negative electrode potential, draw the charging rate-negative electrode potential curve under different SOC states, and obtain the charging rate corresponding to the negative electrode potential of 0V under different SOC states after linear fitting. The charging rate is the charging window under the SOC state, which are recorded as C(10% SOC), C(20% SOC), C(30% SOC), C(40% SOC), C(50% SOC), C(60% SOC), C(70% SOC), and C(80% SOC) respectively, and the maximum charging rate under the corresponding charge state, that is, the fast charging window, is 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] Initial DC internal resistance (DCR) test of battery cells:

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

[0591] High temperature cycle life test

[0592] At 45°C, the battery of the embodiment and comparative example is charged to 4.4V at a constant current of 1C, then charged at a constant voltage of 4.4V until the current drops to 0.05C, and after standing for 5 minutes, discharged to 2.5V at a constant current of 1C. This is the first charge / discharge cycle of the battery, and the discharge capacity of this time is recorded as the discharge capacity of the first cycle of the battery (C1); repeat the above steps for the same battery, and the process capacity of the battery after the nth cycle (Cn), the capacity retention rate after n cycles = Cn / C1×100%. Record the number of cycles at which the cycle capacity retention rate is 80%.

[0593] Fast charge cycle life test

[0594] First, the fast charging window must be obtained: the batteries of the above embodiments and comparative examples are 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 including: at 35°C, the battery is charged at a constant current rate of 1C to a voltage of 3.65V, then charged at a constant voltage to a current ≤0.05C, allowed to stand for 5 minutes, and then discharged at a constant current rate of 0.33C to a voltage of 2.5V, and its actual capacity is recorded as C0. Then the battery is charged with 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 in sequence to the full battery charge cut-off voltage of 3.65V or 0V negative electrode cut-off potential (whichever is reached first). After each charge is completed, it is necessary to discharge with 1C0 to the full battery discharge cut-off voltage of 2.1V. Record the SOC (State of Charge) at different charge rates to 10%, 20%, 30%, ..., 80% Charge, state of charge, when "SOC = 0" indicates that the battery is fully discharged, when "SOC = 100%" indicates that the battery is fully charged) the corresponding negative electrode potential, draw the charging rate-negative electrode potential curve under different SOC states, and obtain the charging rate corresponding to the negative electrode potential of 0V under different SOC states after linear fitting. The charging rate is the charging window under the SOC state, which are recorded as C(10% SOC), C(20% SOC), C(30% SOC), C(40% SOC), C(50% SOC), C(60% SOC), C(70% SOC), and C(80% SOC) respectively, and the maximum charging rate under the corresponding charge state, that is, the fast charging window, is obtained.

[0595] At 25°C, the obtained fast charging window distribution was used for charging, and C (10% SOC) was charged to 10% SOC, C (20% SOC) was charged to 20% SOC, C (30% SOC) was charged to 30% SOC, C (40% SOC) was charged to 40% SOC, C (50% SOC) was charged to 50% SOC, C (60% SOC) was charged to 60% SOC, C (70% SOC) was charged to 70% SOC, and C (80% SOC) was charged to 80% SOC. 0.33C was charged to 100% SOC. After standing for 10 minutes, it was charged to 2.1V with 0.33C DC. The discharge capacity at this time was recorded as C1. The temperature rise at the pole ear during this charging process was monitored. The above process was repeated, and the discharge capacity of each cycle was recorded as Cn. The cycle capacity retention rate = Cn / C1. The number of cycles when the cycle capacity retention rate dropped to 80% SOH was recorded.

[0596] The fast charge 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 charge 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℃ / min High temperature cycle number 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 embodiment and the comparative example, it can be seen that the lithium ion conductivity of the electrolyte is greater than or equal to 10 mS / cm and the R value R50 of 50% of the cumulative distribution in the R value cumulative distribution curve obtained under the surface scanning mode of the laser microscopic confocal Raman spectrometer is 0.15-0.50, which is beneficial to taking into account the fast charging performance and cycle life of the battery cell.

[0601] Table 2

[0602] R50 Uncovered rate Lithium ion conductivity mS / cm 10-80% SOC charging time @35℃ / min High temperature cycle number 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 the lithium ion conductivity of the electrolyte is greater than or equal to 10 mS / cm and the cumulative distribution curve of the R value obtained by the laser microscopy confocal Raman spectrometer in the surface scanning mode has an R value R50 of 50% of the cumulative distribution of 0.15-0.50, and among the R values ​​of the negative electrode active material, the number of R values ​​less than or equal to 0.11 accounts for less than or equal to 10%, which can achieve the optimization of another performance while maintaining a good fast charging level or cycle performance of the battery.

[0604] Table 3

[0605]

[0606] From the comparison between Example 1 and Example 7, it can be seen that the porosity of the first negative electrode film layer arranged on the surface of the negative electrode current collector is smaller than the porosity of the second negative electrode film layer arranged on the side of the first negative electrode film layer away from the negative electrode current collector, which is beneficial to simultaneously achieve improvement in fast charging performance and improvement in cycle performance.

[0607] Table 4

[0608]

[0609] From the comparison between Example 1 and Example 8, it can be seen that the compaction density of the lower layer powder is greater than the compaction density of the upper layer powder, which is beneficial to simultaneously achieve the improvement of fast charging performance and the improvement of cycle performance.

[0610] Table 5

[0611]

[0612]

[0613] From the comparison between Example 9 and Example 1, it can be seen that the surface of the positive electrode active material has a relatively high cobalt content, which helps to further improve the cycle life of the battery cell while maintaining the high charging performance of the battery.

[0614] Table 6

[0615]

[0616] From the comparison between Example 13 and Examples 1 and 10, it can be seen that the electrolyte includes ethyl acetate and methyl acetate at the same time, which can further improve the fast charging performance of the battery while maintaining a good cycle life of the battery.

[0617] From the comparison between Example 1 and Examples 11 and 12, it can be seen that the electrolyte includes both the first additive and the second additive, which can further improve the cycle performance of the battery while maintaining good fast charging performance of the battery.

[0618] Table 7

[0619]

[0620] From the comparison between Example 5 and Example 4, it can be seen that the negative electrode active material also includes the interlayer spacing d of the (002) crystal plane. 002 Kinetic carbon materials with a diameter of >0.335nm are beneficial to improving the kinetic performance of batteries.

[0621] Table 8

[0622]

[0623] From the comparison between Example 1 and Example 14, it can be seen that the positive electrode active material includes low-nickel lithium-containing oxide, the Dv50 of the positive electrode active material is 2μm-5μm, 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.

[0624] From the comparison between Example 14 and Example 1, it can be seen that the positive electrode active material includes high-nickel lithium-containing oxide, the Dv50 of the positive electrode active material is 6μm-15μm, and the positive electrode active material mainly includes secondary particles formed by agglomeration of primary particles. The average particle size of the primary particles in the secondary particles is 0.1μm-1.5μm, which is beneficial to reducing the DC impedance of the battery cell and improving the power performance of the battery cell while improving the fast charging performance of the battery cell.

[0625] Table 9

[0626]

[0627] From the comparison between Example 1 and Example 15, it can be seen that 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.

[0628] Table 10

[0629]

[0630] From the comparison between Example 1 and Examples 16 and 17, it can be seen that the battery cell includes a laminated battery core and the width of the positive electrode current collector is 60 mm-110 mm, which is beneficial to improving the fast charging cycle life of the battery cell.

[0631] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A battery cell, characterized in that: Including positive electrode sheet, negative electrode sheet and 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 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: 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%.

3. The battery cell according to claim 1, 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%.

4. The battery cell according to claim 1, 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%.

5. The battery cell according to claim 1, 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%.

6. The battery cell according to claim 1, 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%.

7. The battery cell according to any one of claims 1 to 6, characterized in that: The electrolyte includes an organic solvent, and the organic solvent includes one or more of a carboxylate solvent, a nitrile solvent, and a carbonate solvent.

8. The battery cell according to claim 7, characterized in that: The carboxylate 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 / 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.

9. The battery cell according to claim 7 or 8, characterized in that: The carboxylic acid ester solvent includes one or more of ethyl acetate and methyl acetate.

10. The battery cell according to claim 7, 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.

11. The battery cell according to claim 10, characterized in that: Based on the total mass of the organic solvent, the mass content of dimethyl carbonate is 30%-90%.

12. The battery cell according to claim 7, characterized in that: The organic solvent includes one or more of ethyl acetate, methyl acetate and a carbonate solvent.

13. The battery cell according to claim 12, 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%.

14. The battery cell according to claim 7, 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.

15. The battery cell according to claim 14, characterized in that: Based on the total mass of the organic solvent, the mass content of methyl acetate is 5%-50%.

16. The battery cell according to any one of claims 1 to 15, characterized in that: The electrolyte solution includes an electrolyte salt, and the electrolyte salt includes lithium bis(fluorosulfonyl)imide. The mass content of the lithium bis(fluorosulfonyl)imide is 3%-10% based on the total mass of the electrolyte solution.

17. The battery cell according to claim 16, 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.

18. The battery cell according to claim 17, 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.

19. The battery cell according to any one of claims 1 to 18, 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.

20. The battery cell according to claim 19, characterized in that: The width of the positive electrode current collecting portion is 62 mm-98 mm.

21. The battery cell according to claim 19 or 20, characterized in that: The length of the positive electrode current collecting part in the laminated battery core is 100mm-700mm.

22. The battery cell according to claim 21, characterized in that: The length of the positive electrode current collecting part in the laminated battery core is 200mm-600mm.

23. The battery cell according to any one of claims 1 to 22, characterized in that: The electrolyte includes a first additive, and the first additive includes one or more of fluorine-containing phosphates and borates.

24. The battery cell according to claim 23, characterized in that: The fluorophosphate includes one or more of monofluorophosphate and difluorophosphate; the fluorophosphate includes an alkali metal.

25. The battery cell according to claim 23 or 24, characterized in that: The fluorophosphate includes one or more of lithium salt, sodium salt and potassium salt.

26. The battery cell according to claim 23, characterized in that: The borate comprises at least one of tetrafluoroborate, bisoxalatoborate and fluorine-containing oxalatoborate; and the borate comprises an alkali metal.

27. The battery cell according to claim 26, characterized in that: The borate includes one or more of lithium salt, sodium salt and potassium salt.

28. The battery cell according to any one of claims 1 to 27, characterized in that: The electrolyte includes a second additive, and the second additive includes one or more of sulfonate compounds and vinyl sulfate compounds.

29. The battery cell according to claim 28, characterized in that: The vinyl sulfate compounds include One or more of; and / or the sulfonate compound includes At least one of .

30. The battery cell according to any one of claims 1 to 29, 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 temperature 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.

31. 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.

32. The battery cell according to claim 31, characterized in that: The interlayer spacing of the (002) crystal plane of the kinetic carbon material is 0.3355 nm to 0.337 nm.

33. The battery cell according to claim 31 or 32, characterized in that: The kinetic carbon material includes one or more of hard carbon, expanded graphite and graphene.

34. The battery cell according to any one of claims 31 to 33, characterized in that: The kinetic carbon material is located in the core and / or the coating layer.

35. The battery cell according to any one of claims 31 to 34, 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%.

36. The battery cell according to claim 35, 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%.

37. The battery cell according to claim 1, 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.

38. The battery cell according to claim 1, 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.

39. The battery cell according to any one of claims 1 to 38, characterized in that: The core portion of the negative electrode active material includes artificial graphite.

40. The battery cell according to any one of claims 1 to 39, 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.

41. The battery cell according to claim 1, 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.

42. The battery cell according to claim 41, 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.

43. The battery cell according to claim 1, 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.

44. The battery cell according to any one of claims 1 to 43, 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 .

45. The battery cell according to any one of claims 1 to 44, 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.

46. ​​The battery cell according to any one of claims 1 to 43, 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%.

47. The battery cell according to claim 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%.

48. The battery cell according to any one of claims 1 to 47, 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.

49. The battery cell according to any one of claims 1 to 47, 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.

50. The battery cell according to claim 49, 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.

51. The battery cell according to claim 50, characterized in that The Dv50 of the positive electrode active material is 8 μm-12 μm.

52. The battery cell according to claim 49, 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.

53. The battery cell according to claim 52, characterized in that The Dv50 of the positive electrode active material is 2.5 μm-4.5 μm.

54. The battery cell according to claim 49, 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.

55. The battery cell according to claim 49, 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.

56. The battery cell according to claim 49, 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.

57. The battery cell according to claim 49, 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.

58. 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.

59. The battery cell according to claim 58, 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.

60. The battery cell according to claim 58, 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.

61. 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 .

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 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 .

63. The battery cell according to any one of claims 1 to 62, 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%.

64. The battery cell according to any one of claims 1 to 63, characterized in that: The lithium ion conductivity of the electrolyte is 10mS / cm-20mS / cm.

65. The battery cell according to any one of claims 1 to 63, characterized in that: The lithium ion conductivity of the electrolyte is 12mS / cm-20mS / cm.

66. The battery cell according to any one of claims 1 to 63, characterized in that: The lithium ion conductivity of the electrolyte is 10mS / cm-15mS / cm.

67. The battery cell according to claim 48, 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.

68. The battery cell according to claim 49, 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.

69. The battery cell according to any one of claims 1 to 68, characterized in that: The charging time t of the battery cell from 10% SOC to 80% SOC at 35° C. satisfies: t≤14 min.

70. The battery cell according to any one of claims 1 to 69, characterized in that: The charging time t of the battery cell from 10% SOC to 80% SOC at 35° C. satisfies: 7.9 min≤t≤12.2 min.

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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