Battery cell, battery device, and electric device

Abstract

A battery cell, a battery device, and an electric device. The battery cell comprises a positive electrode sheet, a negative electrode sheet, and an electrolyte; the lithium-ion conductivity of the electrolyte is greater than or equal to 10 mS / cm; the negative electrode sheet comprises a negative electrode current collector and a negative electrode film layer provided on at least one side of the negative electrode current collector; the negative electrode film layer comprises a negative electrode active material; the negative electrode active material comprises a core portion and a coating layer at least partially covering the surface of the core portion; the core portion comprises graphite; in a cumulative distribution curve of R values obtained for the negative electrode active material in a surface scanning mode of a laser microscopic confocal Raman spectrometer, R50, the R value at the 50th percentile of the cumulative distribution, ranges from 0.15 to 0.50; and among the obtained R values of the negative electrode active material, the proportion of the R values less than or equal to 0.11 is less than or equal to 15%. The battery cell has good kinetic performance and a long cycle life.

Description

Battery cells, battery packs, and electrical devices

[0001] Cross-references

[0002] This application incorporates Chinese Patent Application No. 202411606003.X, filed on November 12, 2024, entitled “Battery cell, battery device and power consumption device”, which is incorporated herein by reference in its entirety. Technical Field

[0003] This application relates to the field of battery cell technology, and more particularly to a battery cell, a battery device, and an electrical device. Background Technology

[0004] In recent years, battery cells have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, as well as in many fields such as power tools, electric bicycles, electric motorcycles, electric cars, military equipment, and aerospace.

[0005] As the market demands for longer driving range, longer cycle life, and faster charging efficiency from electrical devices, higher requirements are being placed on the energy density, fast charging performance, and cycle life of individual battery cells. However, existing technologies struggle to simultaneously improve these performance characteristics, making this a critical technical problem that needs to be solved in this field. Summary of the Invention

[0006] This application is made in view of the above-mentioned issues, and its purpose is to provide a battery cell that combines high energy density, high cycle life and good fast charging performance.

[0007] The first aspect of this application provides a battery cell, which includes a positive electrode, a negative electrode, and an electrolyte; the electrolyte has a lithium-ion conductivity greater than or equal to 10 mS / cm; the negative electrode includes a negative current collector and a negative electrode film disposed on at least one side of the negative current collector, the negative electrode film includes a negative electrode active material, the negative electrode active material includes a core and a coating layer at least partially covering the surface of the core, the core includes graphite, and in the cumulative distribution curve of the R value obtained by laser microscopy confocal Raman spectroscopy in surface scanning mode, the cumulative distribution of the R value R50 of the negative electrode active material is 0.15-0.50; and the proportion of R values ​​less than or equal to 0.11 in the obtained R values ​​of the negative electrode active material is less than or equal to 15%.

[0008] Anode active materials with a cumulative distribution of 50% and an R value of R50 of 0.15-0.50 can enhance the charge exchange capacity of lithium ions in the highly conductive electrolyte on the surface of the anode active material, so that the liquid phase transport rate of lithium ions matches the solid phase transport rate, thereby improving the kinetic performance of the battery. At the same time, it can keep the side reactions on the surface of the anode active material at a low level, while also taking into account the cycle life of the battery cells.

[0009] In any embodiment, the proportion of R values ​​less than or equal to 0.11 in the obtained negative electrode active material is less than or equal to 15%, optionally less than or equal to 10%, and further optionally less than or equal to 6%.

[0010] The R-value R50, where the cumulative distribution of graphite in the core is 50%, generally does not exceed 0.11. Therefore, the percentage of R-values ​​less than or equal to 0.11 among all obtained R-values ​​of the negative electrode active material can be used to represent the degree of uncoated negative electrode active material. The smaller this value, the less uncoated the negative electrode active material, the higher the surface coating of the negative electrode active material, the improved isotropic ion intercalation, and the better the charge exchange capacity of ions on the surface of the negative electrode active material. This, in turn, increases the solid-liquid transport rate of lithium ions, allowing for better matching with highly conductive electrolytes and improving the kinetic performance of the battery. In addition, a smaller degree of uncoated negative electrode active material can also reduce the co-intercalation phenomenon of electrolyte solvent during cycling, thereby giving the battery better cycle performance.

[0011] In any embodiment, in the cumulative distribution curve of R value obtained by laser microscopy confocal Raman spectroscopy instrument scanning mode, the cumulative distribution of R value R50 of 50% is 0.15-0.30, and the proportion of R values ​​less than or equal to 0.11 in the obtained R values ​​of negative electrode active material is less than or equal to 10%.

[0012] 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-mentioned range and the coverage is high, indicating that the surface of the negative electrode active material has high isotropy. This is conducive to the uniform embedding of lithium ions into the core graphite from all directions, which is beneficial to further improving the fast-charging performance of the battery cell.

[0013] In any embodiment, in the cumulative distribution curve of R value obtained by laser microscopy confocal Raman spectroscopy instrument scanning mode, the cumulative distribution of R value R50 of 50% is 0.30-0.50, and the proportion of R values ​​less than or equal to 0.11 in the obtained R values ​​of the negative electrode active material is less than or equal to 15%.

[0014] The negative electrode active material in this embodiment combines low cost, good cycle stability, and improved fast charging performance.

[0015] In any embodiment, the electrolyte includes an organic solvent, which includes one or more of carboxylic acid ester solvents, nitrile solvents, and carbonate solvents.

[0016] In any embodiment, the carboxylic acid ester solvent includes one or more of ethyl acetate, methyl acetate, methyl formate, butyl acetate, methyl propionate, ethyl propionate, methyl butyrate, propyl butyrate, butyl butyrate, isopropyl acetate, and isoamyl acetate, and may be selected as 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 methyl ethyl carbonate.

[0017] Carboxylic acid ester solvents and / or nitrile solvents can improve the lithium-ion conductivity of the electrolyte and enhance the fast-charging performance of individual battery cells. Carbonate solvents readily form solvation structures with lithium ions in lithium-containing electrolyte salts, thereby increasing the dissociation rate of lithium ions and anions in the lithium-containing electrolyte salt and further improving the fast-charging performance of individual battery cells.

[0018] In any embodiment, 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, optionally 30%-90%.

[0019] In any embodiment, the organic solvent includes one or more of ethyl acetate, methyl acetate, and carbonate solvents.

[0020] Ethyl acetate and methyl acetate have high electrical conductivity while producing low gas content. The combination of ethyl acetate and / or methyl acetate with carbonate solvents allows lithium ions in the electrolyte to have both a high dissociation rate and a fast lithium ion transport rate, which is beneficial for improving the kinetic performance of the battery cells, while reducing battery gas production and balancing battery cycle life.

[0021] In any embodiment, based on the total mass of organic solvents, the total mass percentage of ethyl acetate and methyl acetate is 5%-80%, and the mass percentage of carbonate solvents is 5%-90%.

[0022] In any embodiment, the organic solvent includes methyl acetate, and the methyl acetate content is 5%-70% based on the total mass of the organic solvent, optionally 5%-50%.

[0023] Methyl acetate has higher activity than ethyl acetate. Although its addition in small amounts to the electrolyte may slightly reduce the lifespan of the battery cells, it can further improve the kinetic performance of the battery cells and improve their fast-charging performance while maintaining their high cycle life.

[0024] In any embodiment, the electrolyte comprises an electrolyte salt, which comprises 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.

[0025] Lithium difluorosulfonylimide (LiFSI) readily dissociates in the electrolyte solvent, which is beneficial for improving the kinetics of individual cells, reducing internal resistance, and enhancing fast-charging performance. However, LiFSI is prone to side reactions with LiC6 formed during deep lithium intercalation at the negative electrode, reducing reversible lithium capacity and negatively impacting the retention of cell capacity during cycling. Maintaining the LiFSI mass content within the aforementioned range in the electrolyte can further improve the cycle life of individual cells while ensuring fast-charging performance.

[0026] In any embodiment, the mass content of lithium bis(fluorosulfonyl)imide (LiFSI) is 20%-80% based on the total mass of the electrolyte salt, and optionally 30%-70%.

[0027] Lithium difluorosulfonylimide electrolytes within the aforementioned mass range can improve the battery's fast-charging performance while maintaining side reactions with the negative electrode material at a reasonable level, thus comprehensively improving the battery's cycle life.

[0028] In any embodiment, the battery cell includes a stacked cell, the positive electrode includes a positive current collector, the positive current collector includes a positive current collector portion and a positive electrode tab disposed on at least one side of the positive current collector portion, and the width of the positive current collector portion is 60mm-110mm, optionally 62mm-98mm.

[0029] The width of the positive current collector within the above range is beneficial to reduce the maximum distance between the tab and the edge of the positive current collector. This can reduce the electron transmission distance, improve the battery's fast charging performance, reduce the uneven temperature rise of the current collector during fast charging, reduce the temperature gradient on the current collector, reduce the probability of active materials inactive first at the temperature rise, improve the battery's fast charging cycle life, and also take into account the battery's energy density.

[0030] In any embodiment, the length of the positive current collector in the laminated cell is 100mm-700mm, and can be selected as 200mm-600mm.

[0031] Within the aforementioned range, the length of the positive current collector in the stacked cell can further reduce the electron transport distance on the current collector, improve the inconsistent temperature rise during fast charging of the battery cell, and increase the fast charging cycle life of the battery cell.

[0032] In any embodiment, the electrolyte includes a first additive, which includes one or more of fluorinated phosphates and borates.

[0033] In any embodiment, the fluorophosphate includes one or more of monofluorophosphate and difluorophosphate; the fluorophosphate includes an alkali metal, which may be one or more of lithium salt, sodium salt, and potassium salt.

[0034] In any embodiment, the borate includes at least one of tetrafluoroborate, bis(oxalate)borate, and fluorinated oxalateborate; the borate includes an alkali metal, optionally one or more of lithium, sodium, and potassium salts.

[0035] In any embodiment, the electrolyte includes a second additive, which includes one or more of sulfonate compounds and vinyl sulfate compounds.

[0036] In any embodiment, vinyl sulfate compounds include One or more of the following; and / or sulfonates include At least one of them.

[0037] The second additive in the electrolyte is easy to form a film on the negative electrode, and can simultaneously generate inorganic and organic components in the SEI film, reduce the degree of side reaction of carboxylic acid ester solvents on 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℃~730℃, where the air oxidation temperature T0 is the temperature corresponding to the intersection of two tangents at two points corresponding to 500℃ and T1 temperatures respectively on the thermogravimetric curve of the negative electrode active material, and the T1 temperature is the peak temperature of the maximum area peak in the differential thermogravimetric curve of the negative electrode active material. The thermogravimetric curve and the differential thermogravimetric curve can be obtained by thermogravimetric analysis under the following conditions: sample mass 10±0.05mg, purge gas is air with a flow rate of 60mL / min, heating rate is 5℃ / min, and test temperature range is 35℃~950℃.

[0039] Anode active materials with an air oxidation temperature (T0) of 630℃~730℃ have a suitable number of surface defects, providing sufficient end faces for active ion insertion and matching the lithium-ion transport rate of the electrolyte. At the same time, this keeps the degree of side reactions in the battery cell within a controllable range. Therefore, the battery cell can have improved fast-charging performance while maintaining high energy density and cycle life.

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

[0043] The aforementioned kinetic carbon materials, used as negative electrode active materials, can improve the insertion and extraction rates of active ions, thereby enhancing the transport performance of active ions and electrons, and thus improving the fast-charging performance of battery cells while maintaining high energy density. Simultaneously, amorphous carbon has high hardness, thus exhibiting good compressive strength and a strong ability to maintain the pore structure of the negative electrode film during cycling. This also results in better electrolyte wettability of the negative electrode sheet, further contributing to improved cycle performance of the battery cells.

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

[0045] When the mass percentage of kinetic carbon material is within a suitable range, the negative electrode active material can possess high specific capacity, as well as high active ion solid-phase transport capability and high active ion and electron charge exchange rate. Consequently, the battery cell can achieve high energy density while also exhibiting improved fast-charging performance. Furthermore, within a suitable mass percentage range, the negative electrode film pore structure is better maintained during cycling, resulting in better electrolyte wettability of the negative electrode sheet and improved cycle performance of the battery cell.

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

[0047] Negative electrode active materials with a volume distribution particle size Dv50 within the above range can, on the one hand, utilize a certain number of primary particles in the secondary particles to give the negative electrode active material a suitable intercalation surface, and the solid-phase transport rate and solid-liquid transport rate of active ions in the negative electrode active material can match the lithium-ion liquid-phase transport rate of the electrolyte, thus improving the fast charging performance of the battery; on the other hand, they can also have the advantages of large particle size, high compaction density, and large capacity of secondary particles, thus improving the fast charging performance of the battery while taking into account the energy density of the battery cells.

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

[0049] Negative electrode active materials with a volume distribution particle size (Dv50) within the aforementioned range exhibit higher interfacial stability compared to smaller particle sizes, while simultaneously possessing a greater ion solid-phase transport distance. These two aspects can be balanced through size design, achieving a balance between fast-charging performance and cycle life of individual battery cells.

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

[0051] Artificial graphite has fewer defects and higher capacity, which can reduce the degree of side reactions with electrolytes, fully utilize the high capacity of graphite, and reduce gas production so that battery cells can have both high energy density and good cycle performance.

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

[0053] When the mass percentage or thickness of the coating layer is within the aforementioned range, the uniformity of the coating layer is improved, thereby enhancing the charge exchange capacity of ions on the surface of the negative electrode active material. Furthermore, within this range, side reactions on the surface of the negative electrode active material particles are also kept at a low level, resulting in a higher specific capacity. Therefore, a coating layer mass percentage within this range is beneficial for batteries to possess 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 applied to most of the surface of the core, which can provide end faces for active ion insertion and reduce the contact between the core and the electrolyte. This reduces the co-intercalation of the electrolyte solvent during cycling, thus balancing the fast charging performance and cycle performance of the battery cell.

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

[0057] This application uses a highly conductive electrolyte with a high ion transport rate. By designing the second negative electrode film layer near the electrolyte to have a large porosity, the transport rate of lithium ions in the electrode is matched with the liquid phase transport rate in the electrolyte, 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 near the current collector to take into account the energy density of the battery cells.

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

[0059] Anode active materials with a particle size uniformity of 0.4-0.6 can achieve close packing through particle size gradation, resulting in a relatively low porosity for the first anode film layer. Anode active materials with a particle size uniformity of 0.25-0.45 have lower particle size uniformity, making it difficult to form an effective match, resulting in a relatively high porosity for the second anode film layer, thus achieving a layered design of electrode porosity.

[0060] In any embodiment, the negative electrode film layer includes a first negative electrode film layer disposed on the surface of the negative electrode current collector and a second negative electrode film layer disposed on the side of the first negative electrode film layer away from the negative electrode current collector. The powder compaction density of the negative electrode active material in the second negative electrode film layer under a pressure of 50,000 N is less than the powder compaction density of the negative electrode active material in the first negative electrode film layer under a pressure of 50,000 N.

[0061] The powder compaction density of the negative electrode active material in the second negative electrode film layer near the electrolyte side is small, which helps to maintain the pore structure of the negative electrode film layer near the electrolyte side and improve 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 far from the electrolyte side is large, which helps to improve the compaction density of the negative electrode film layer and take into account the energy density of the battery cell.

[0062] In any embodiment, the density of the negative electrode film layer on one side is 0.08 g / 1540.25 mm. 2 -0.20g / 1540.25mm 2 Available in 0.10g / 1540.25mm. 2 -0.16g / 1540.25mm 2 .

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

[0064] In any embodiment, the negative electrode active material further includes a silicon-based material, and the one-sided density of the negative electrode film is 0.06 g / 1540.25 mm². 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 for batteries with the same capacity, that is, further reduces the density of the one-sided side of the negative electrode film layer. This is beneficial to reduce the transport 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 sheet is 1.2 g / cm³. 3 -1.9g / cm3 1.2g / cm³ is an optional value. 3 -1.65g / cm 3 .

[0067] Negative electrode sheets with a compaction density within the above range have suitable porosity, which can match electrolytes with high conductivity, improve the diffusion rate of lithium ions in the negative electrode, reduce concentration polarization generated by the battery cell during fast charging, and help 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 the negative electrode film layer on one side is 30μm-150μm, and can be selected as 30μm-80μm.

[0069] Anode films with an average thickness within the above range have a suitable lithium-ion diffusion distance, which can be matched with electrolytes with high conductivity, improve the diffusion rate of lithium ions in the anode film, and improve the fast charging performance of battery cells while taking into account the energy density of battery cells.

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

[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 for batteries with the same capacity, which helps to reduce the transport distance of lithium ions in the negative electrode film layer and further improves the fast charging performance of the battery cell.

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

[0073] Negative electrode sheets with porosity within the above range can be matched with electrolytes with high conductivity, facilitating the transport of lithium ions in the negative electrode, reducing concentration polarization generated during fast charging of battery cells, and improving the fast charging performance of battery cells while taking into account the energy density of battery cells.

[0074] In any embodiment, the positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector. The positive electrode film layer includes a positive electrode active material, which includes lithium phosphate and non-agglomerated primary particles. The positive electrode active material satisfies at least one of the following conditions:

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

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

[0077] Lithium phosphates with an average particle size within the above range have a shorter ion transport path, lower lithium ion transport impedance, and lower moisture absorption. This not only matches the liquid phase transport rate of lithium ions in the electrolyte, but also reduces 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 current collector and a positive electrode film layer disposed on at least one side of the positive current collector. The positive electrode film layer includes a positive electrode active material, which comprises a lithium-containing transition metal oxide, and the volume distribution particle size Dv50 of the positive electrode active material is [missing value]. 正2 Satisfies: 2μm≤Dv50 正2 ≤15μm.

[0079] Volumetric particle size Dv50 正2 The positive electrode active material containing lithium transition metal oxides within the above range has a shorter ion transport path, lower lithium ion transport impedance, and lower degree of side reaction. It can match the liquid phase transport rate of lithium ions in the electrolyte, reduce the temperature rise of the battery cell during fast charging, and also improve the cycle life of the battery cell by reducing the degree of side reaction.

[0080] In any embodiment, the positive electrode active material includes lithium nickel cobalt manganese oxide, and the Dv50 of the positive electrode active material... 正2 The size ranges from 6μm to 15μm, with an optional range of 8μm to 12μm. The positive electrode active material includes secondary particles formed by the agglomeration of primary particles, with the average particle size of the primary particles in the secondary particles being 0.1μm to 1.5μm.

[0081] In this embodiment, the positive electrode active material mainly comprises secondary particles, that is, powder with secondary particles as the main component. The secondary particles include numerous small-diameter primary particles, resulting in a short lithium-ion transport path and multiple insertion faces, which can be matched with electrolytes with high lithium-ion transport rates, thus improving the power performance of the battery cell.

[0082] In any embodiment, the positive electrode active material includes lithium nickel cobalt manganese oxide, and the Dv50 of the positive electrode active material... 正2 The size ranges from 2μm to 5μm, with an optional range of 2.5μm to 4.5μm. The positive electrode active material includes unaggregated primary particles.

[0083] In this embodiment, the positive electrode active material mainly comprises unagglomerated primary particles, that is, a powder mainly composed of unagglomerated primary particles. This positive electrode active material exhibits low side reaction with highly reactive carboxylic acid ester solvents, which is beneficial for further improving the cycle life of the battery cell.

[0084] In any embodiment, the positive electrode active material includes lithium nickel cobalt manganese oxide. The particle size distribution curve of the positive electrode active material exhibits a bimodal distribution, with the 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. The average particle size of the secondary particles is larger than the average particle size of the unagglomerated primary particles.

[0085] The aforementioned positive electrode active material is graded by secondary particles with a predominantly large particle size and primary particles with a predominantly small particle size, which takes into account the cycle life and power performance of the battery cells while further improving the energy density of the battery.

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

[0087] A cobalt molar content of less than or equal to 20% is beneficial for reducing the cost of cathode active materials, but it is not conducive to improving the kinetic performance of cathode active materials. By using relatively small-sized, non-agglomerated primary particles, it is possible to reduce the side reactions between carboxylic esters and cathode active materials, improve the cycle life of battery cells, and improve the kinetic performance of cathode active materials, thereby increasing the power performance of battery cells.

[0088] In any embodiment, the positive electrode active material comprises lithium nickel cobalt manganese oxide, wherein 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... 正2 The size is 2μm-5μm, and the positive electrode active material includes unaggregated primary particles.

[0089] A nickel molar content of less than 80% helps reduce the probability of nickel dissolution in the positive electrode active material under high voltage (charging cutoff voltage ≥ 4.3V), thereby improving the withstand voltage of the positive electrode active material. Combining low-nickel components with non-agglomerated 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 charge and discharge, and improve the cycle performance of the battery cell.

[0090] In any embodiment, the positive electrode active material comprises lithium nickel cobalt manganese oxide, wherein 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... 正2 The positive electrode active material has a particle size of 6μm-15μm and consists of secondary particles formed by the agglomeration of primary particles. The average particle size of the primary particles in the secondary particles is 0.1μm-1.5μm.

[0091] Molding high-nickel materials into large-sized secondary particles is beneficial for simultaneously improving the specific capacity of the positive electrode active material and the gradation of the positive electrode sheet, thereby improving the energy density of the battery. At the same time, the secondary particles, composed of small-diameter primary particles, can shorten the lithium-ion transport distance, increase the number of intercalation 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, and the mass percentage of cobalt near the surface of the positive electrode active material particles is greater than the mass percentage of cobalt near the center of the positive electrode active material particles.

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

[0094] While highly conductive electrolytes are beneficial for improving the liquid-phase transport rate of lithium ions, their components also exhibit high electrochemical activity. For example, carboxylic acid esters in highly conductive electrolytes are prone to side reactions with the oxygen-releasing structures on the surface of the positive electrode active material after phase transition, increasing gas production and deteriorating the battery's cycle life. A relatively high cobalt content on the surface of the positive electrode active material helps improve its ionic conductivity, mitigates excessive delithiation during charge and discharge, reduces cation mixing between the Li layer and the transition metal layer, stabilizes the layered structure of the positive electrode active material, and reduces the risk of structural phase transitions on the surface, thereby reducing the degree of side reactions in the battery cell and improving its cycle life. Conversely, a relatively low cobalt content in the center of the positive electrode active material can simultaneously reduce its cost.

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

[0096] In any embodiment, the positive electrode active material comprises a lithium-containing transition metal oxide, and the one-sided density of the positive electrode film is 0.13 g / 1540.25 mm². 2 -0.24g / 1540.25mm 2 .

[0097] A positive electrode film with an areal density within the above range has a suitable thickness, which is conducive to the diffusion of active ions in the electrode and can more effectively improve the fast charging performance of the battery cell; at the same time, it can reduce heat generation, reduce the reactivity 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 is 22%-35%.

[0099] Porosity within the above-mentioned range of positive electrode film is conducive to the diffusion of active ions in the electrode, which can more effectively improve the fast charging performance of the battery cell; at the same time, it can reduce heat generation, reduce the reactivity 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] Increasing the lithium-ion conductivity of the electrolyte often necessitates the addition of a higher content of highly conductive solvents. While highly conductive solvents offer high lithium-ion transport rates, they also exhibit high chemical reactivity, making them prone to side reactions with the negative electrode active material and reducing battery cycle life. Electrolytes with lithium-ion conductivity within the aforementioned range possess suitable lithium-ion conduction rates and reactivity, better balancing the fast-charging performance and cycle life of individual battery cells.

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

[0103] In any embodiment, the positive electrode active material includes lithium iron phosphate, and the one-sided density of the positive electrode film is 0.2 g / 1540.25 mm². 2 -0.35g / 1540.25mm 2 The conductivity of the electrolyte is 12 mS / cm - 20 mS / cm.

[0104] Lithium iron phosphate (LFP) batteries have a relatively low specific capacity; therefore, the positive electrode film of a single cell with the same capacity often requires a relatively high coating density. Using an electrolyte with conductivity within the aforementioned range helps mitigate the losses to the cell's kinetic performance caused by the required coating density, thus meeting both energy density and power performance requirements.

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

[0106] Lithium-containing nickel-cobalt-manganese oxides have relatively high specific capacity. Therefore, for battery cells of the same capacity, the coating density of the positive electrode film is relatively low, and electrolytes with relatively low conductivity can meet the fast-charging performance requirements of the battery cells. These battery cells can meet both power performance and cycle life requirements.

[0107] The second aspect of this application also provides a battery device, which includes the battery cell provided in the first aspect, and the battery device includes one or more of the following: battery module, battery pack, and energy storage battery.

[0108] A third aspect of this application also provides an electrical device, including a battery cell provided in the first aspect of this application or a battery device provided in the second aspect of this application, wherein the battery cell or battery device is used to provide electrical energy. Attached Figure Description

[0109] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

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

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

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

[0113] Figure 4 is an exploded view of the battery pack shown in Figure 3;

[0114] Figure 5 is an exploded view of a single battery cell provided in some embodiments of this application;

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

[0116] Figure 7 is a schematic diagram of the positive electrode sheet provided in some embodiments of this application.

[0117] The accompanying drawings are not necessarily drawn to scale.

[0118] The reference numerals in the attached drawings are explained as follows: 1. Battery pack; 2. Upper casing; 3. Lower casing; 4. Battery module; 5. Battery cell; 51. Housing; 52. Electrode assembly; 53. Cover plate; 101. Positive electrode plate; 1011. Positive current collector; 1012. Positive electrode film; 10111. Positive current collector; 10112. Positive electrode tab. Detailed Implementation

[0119] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the battery cell, battery device, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0120] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0121] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

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

[0123] Unless otherwise specified, all steps in this application may 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 it 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 it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0124] In this application, the terms "multiple" or "various" refer to two or more kinds.

[0125] Unless otherwise stated, the terms used in this application have the common meanings as commonly understood by those skilled in the art.

[0126] Unless otherwise stated, the values ​​of the parameters mentioned in this application can be determined using various testing methods commonly used in the art, for example, according to the testing methods given in the embodiments of this application. Unless otherwise stated, the test temperature for each parameter is 25°C.

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

[0128] A battery cell is the smallest unit that makes up a battery, and it can independently perform the functions of charging and discharging. A battery cell can be cylindrical, cuboid, or other shapes, and the embodiments of this application are not limited to this. Figure 1 shows a cuboid battery cell 5 as an example.

[0129] When there are multiple battery cells, they are connected in series, parallel, or mixed via a busbar. In some embodiments, the battery can be a battery module; when there are multiple battery cells, they are arranged and fixed to form a battery module. In some embodiments, the battery can be a battery pack, which includes a housing and battery cells, with the battery cells or battery modules housed within the housing. In some embodiments, the housing can be part of the vehicle's chassis structure. For example, a portion of the housing can be at least part of the vehicle's floor, or a portion of the housing can be at least part of the vehicle's crossbeams and longitudinal beams.

[0130] In some embodiments, the battery can be an energy storage device. Energy storage devices include energy storage containers, energy storage cabinets, etc.

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

[0132] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

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

[0134] Figures 3 and 4 are schematic diagrams of a battery pack 1 as an example. As shown in Figures 3 and 4, the battery pack 1 may include a housing and multiple battery modules 4 disposed within the housing. The housing includes an upper housing 2 and a lower housing 3, with the upper housing 2 covering the lower housing 3 and forming a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the housing.

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

[0136] A single battery cell includes an electrode assembly and an electrolyte. The electrode assembly can be a wound structure or a stacked structure, and the embodiments of this application are not limited in this regard.

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

[0138] In some embodiments, as shown in FIG5, the outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates enclosing a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 is used to cover the opening to close the receiving cavity. Electrode assemblies 52 are encapsulated in the receiving cavity. The number of electrode assemblies 52 contained in the battery cell 5 may be one or more, and can be adjusted as needed.

[0139] Electrode assemblies typically include positive and negative electrodes. The negative electrode is the electrode that absorbs or lithiates lithium ions during battery charging and releases or delithiates lithium during discharge. The positive electrode is the electrode that releases or delithiates lithium ions during battery charging and absorbs or lithiates lithium during discharge.

[0140] The key to improving the fast-charging performance of a single battery cell lies in increasing the transport rate of active ions within the cell. To enhance this transport rate in the liquid phase, highly conductive electrolytes are often used. However, if rapidly transported lithium ions cannot quickly intercalate onto the surface of the negative electrode active material, polarization occurs, leading to lithium plating and a significant reduction in battery cycle life. To balance energy density, existing technologies typically use high-capacity graphite as the negative electrode active material. However, graphite's kinetic properties are not optimal, making it difficult to effectively combine with highly conductive electrolytes to achieve a coordinated increase in lithium ion transport rates in both the liquid and liquid-solid phases. Therefore, a coating layer with a certain degree of disorder is applied to the graphite surface to combine with the highly conductive electrolyte and improve the fast-charging performance of the battery cell. While the high degree of disorder on the coating layer surface improves the kinetic properties of the battery cell, it also increases the degree of side reactions between the negative electrode active material and the highly conductive electrolyte, negatively impacting the cycle life of the battery cell.

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

[0142] In this application, the lithium-ion conductivity of the electrolyte describes the ability of dissociated ions in the electrolyte solution to conduct electricity through the directional movement of these ions in an electric field, and can be tested using any method known in the art. As an example, a battery cell is disassembled, and approximately 100 mL of electrolyte sample is taken into a dry, clean, corrosion-resistant sample bottle. This sample is then sealed and placed in a constant-temperature water bath, with occasional shaking, until the temperature reaches 25°C (deviation ±0.5°C). After the sample temperature stabilizes, its conductivity is tested using a commercially available conductivity meter. The conductivity meter is thoroughly dried with calibration solution and then vertically immersed in the liquid to be tested. The test is started, and the results are recorded after the data has stabilized for at least 10 seconds. It is understood that the lithium-ion conductivity of the electrolyte is closely related to its solvent, lithium-containing electrolyte salt, additives, and other components and formulation.

[0143] In some embodiments, the lithium-ion conductivity of the electrolyte can be selected from 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 value range between the two.

[0144] In this application, the R-value R50 of the negative electrode active material can be obtained using a laser microconfocal Raman spectrometer in surface scanning mode. Specifically, a laser microconfocal Raman spectrometer (e.g., a high-precision Renishaw laser microconfocal Raman spectrometer) is used, with a laser wavelength of 532 nm. An appropriate amount of sample is taken and its surface is scanned in all directions. The scanning area is 100 μm × 100 μm, the step size is 2 μm, and the total number of scanning points is 2500. This yields the R-values ​​at different sites and the cumulative distribution curve of the R-values ​​over the surface scanning area. The negative electrode active material in this 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 a negative electrode active material refers to the ratio of the peak heights of the D-band and G-band peaks in its Raman spectrum. The D-band peak is located at 1350 ± 50 cm⁻¹. -1 The position of peak G is 1585±50cm. -1 The R value can characterize the degree of defect and disorder of the negative electrode active material. The larger the value, the greater the degree of surface defect and the higher the surface disorder of the negative electrode active material.

[0146] The cumulative distribution curve of R-values ​​refers to arranging the obtained 2500 R-values ​​in ascending order, with R50 being the R-value corresponding to the 50th percentile of the values ​​in that order.

[0147] In some embodiments, the R-value R50, which represents 50% of the cumulative distribution of the negative electrode active material in the laser microscopy confocal Raman spectroscopy instrument scanning mode, can be selected from 0.15, 0.18, 0.20, 0.22, 0.24, 0.26, 0.28, 0.30, 0.32, 0.34, 0.36, 0.38, 0.40, 0.42, 0.44, 0.46, 0.48, 0.50, or any value range between the two.

[0148] The R-value R50 for a 50% cumulative distribution of the negative electrode active material is related to the R-value for a 50% cumulative distribution in the core, the R-value for a 50% cumulative distribution in the coating layer, the thickness of the coating layer, and the uniformity of the coating layer. For example, under the same conditions, a larger R-value for a 50% cumulative distribution in the core results in a larger R-value R50 for a 50% cumulative distribution of the negative electrode active material; a larger coating layer thickness also results in a larger R-value R50 for a 50% cumulative distribution of the negative electrode active material.

[0149] Anode active materials with a cumulative distribution of 50% and an R value of R50 of 0.15-0.50 can enhance the charge exchange capacity of lithium ions in the highly conductive electrolyte on the surface of the anode active material, so that the liquid phase transport rate of lithium ions matches the solid phase transport rate, thereby improving the kinetic performance of the battery. At the same time, it can keep the side reactions on the surface of the anode active material at a low level, while also taking into account the cycle life of the battery cells.

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

[0151] In some embodiments, the R value R50, where the cumulative distribution of the core is 50%, can be selected as 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, or any range of the above values.

[0152] In some embodiments, the R value R50, where the cumulative distribution of the core is 50%, can be 0.07-0.11.

[0153] A large R-value (R50) with a 50% cumulative distribution in the core results in good kinetic performance of the negative electrode active material; a small R-value (R50) with a 50% cumulative distribution in the core results in higher specific capacity of the negative electrode active material. An R-value (R50) with a 50% cumulative distribution in the core within the above-mentioned range allows the battery to possess both high energy density and good kinetic performance.

[0154] The inclusion of graphite in the core of the negative electrode active material is beneficial for maintaining good energy density in the battery cell. However, the high orderliness and low defect content of the graphite surface require lithium ions to be directionally inserted from between the graphite layers, resulting in lower kinetic performance of the battery cell. By providing a coating layer with a certain degree of disorder on the graphite surface, on the one hand, the number of lithium ion insertion channels in the negative electrode active material is increased, improving the insertion efficiency of lithium ions in the negative electrode active material. This, in turn, cooperates with the high-speed transport of lithium ions in the highly conductive electrolyte, synergistically enhancing the charge transport capacity of lithium ions in the liquid and liquid-solid phases of the battery cell, thus comprehensively improving the fast-charging performance of the battery cell. On the other hand, it controls the degree of side reactions between the negative electrode active material and the highly conductive electrolyte, while also considering the cycle life of the battery.

[0155] In some embodiments, the proportion of R values ​​less than or equal to 0.11 in the obtained negative electrode active material is less than or equal to 15%.

[0156] In some embodiments, the proportion of R values ​​less than or equal to 0.11 in the obtained negative electrode active material is less than or equal to 10%.

[0157] In some embodiments, the proportion of R values ​​less than or equal to 0.11 in the obtained negative electrode active material is less than or equal to 6%.

[0158] In some embodiments, the percentage of R values ​​less than or equal to 0.11 in the obtained negative electrode active material can be selected as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or any value range between the two.

[0159] As mentioned above, the R-value R50 for a 50% cumulative distribution of graphite in the core generally does not exceed 0.11. Therefore, the percentage of R-values ​​less than or equal to 0.11 among all obtained R-values ​​of the negative electrode active material can be used to indicate the degree of uncoated negative electrode active material. The smaller this value, the less uncoated the negative electrode active material, the higher the surface coating degree of the negative electrode active material, the improved isotropic ion intercalation, and the improved charge exchange capacity of ions on the surface of the negative electrode active material. This, in turn, increases the solid-liquid transport rate of lithium ions, allowing for better matching with highly conductive electrolytes and improving the kinetic performance of the battery.

[0160] In addition, a smaller degree of uncoated negative electrode active material can reduce the co-intercalation of electrolyte solvent during cycling, thereby giving the battery better cycle performance.

[0161] In some embodiments, the proportion of R values ​​less than or equal to 0.11 in the obtained negative electrode active material is less than or equal to 10%, and optionally less than or equal to 6%.

[0162] Among all the R values ​​obtained by the negative electrode active material, 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.

[0163] In some embodiments, in the cumulative distribution curve of the R-value obtained by the laser microscopy confocal Raman spectroscopy instrument scanning mode, the cumulative distribution of 50% of the R-values ​​R50 is 0.15-0.30, and in the obtained R-values ​​of the negative electrode active material, the proportion of R-values ​​less than or equal to 0.11 is less than or equal to 10%.

[0164] 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-mentioned range and the coverage is high, indicating that the surface of the negative electrode active material has high isotropy. This is conducive to the uniform embedding of lithium ions into the core graphite from all directions, which is beneficial to further improving the fast-charging performance of the battery cell.

[0165] In some embodiments, in the cumulative distribution curve of R-values ​​obtained by laser microscopy confocal Raman spectroscopy instrument scanning mode, the cumulative distribution of R-values ​​R50, which is 50%, is 0.30-0.50, and in the obtained R-values ​​of the negative electrode active material, the proportion of R-values ​​less than or equal to 0.11 is less than or equal to 15%.

[0166] The negative electrode active material in this embodiment combines low cost, good cycle stability, and improved fast charging performance.

[0167] In some embodiments, the electrolyte includes an organic solvent, which includes one or more of carboxylic acid ester solvents, nitrile solvents, and carbonate solvents.

[0168] Carboxylic acid ester solvents are organic solvents that include carboxylic acid ester groups. Nitrile solvents are organic solvents that include cyano groups. Carbonate solvents are organic solvents that include carbonate groups, including cyclic carbonates and chain carbonate compounds.

[0169] In some embodiments, the carboxylic acid ester solvent is a linear carboxylic acid ester solvent. A linear carboxylic acid ester solvent refers to a linear carboxylic acid ester solvent, not a cyclic structure.

[0170] In some embodiments, carboxylic acid ester solvents include 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 nitrile solvents include one or more of acetonitrile, monofluoroacetonitrile, difluoroacetonitrile, and trifluoroacetonitrile; and / or carbonate solvents include one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate.

[0171] In some embodiments, the carboxylic acid ester solvent includes one or more of ethyl acetate and methyl acetate.

[0172] Carboxylic acid ester solvents and / or nitrile solvents can improve the lithium-ion conductivity of the electrolyte and enhance the fast-charging performance of individual battery cells. Carbonate solvents readily form solvation structures with lithium ions in lithium-containing electrolyte salts, thereby increasing the dissociation rate of lithium ions and anions in the lithium-containing electrolyte salt and further improving the fast-charging performance of individual battery cells.

[0173] In some embodiments, 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.

[0174] In some embodiments, the mass content of dimethyl carbonate is 30%-90% based on the total mass of the organic solvent.

[0175] In some embodiments, the mass content of dimethyl carbonate, based on the total mass of the organic solvent, can be selected as 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or any range between the two.

[0176] In some embodiments, the organic solvent includes one or more of ethyl acetate, methyl acetate, and carbonate solvents.

[0177] Ethyl acetate and methyl acetate have high electrical conductivity while producing low gas content. The combination of ethyl acetate and / or methyl acetate with carbonate solvents allows lithium ions in the electrolyte to have both a high dissociation rate and a fast lithium ion transport rate, which is beneficial for improving the kinetic performance of the battery cells, while reducing battery gas production and balancing battery cycle life.

[0178] In some embodiments, based on the total mass of organic solvents, ethyl acetate and methyl acetate account for 5%-80% of the total mass, and carbonate solvents account for 5%-90% of the total mass.

[0179] In some embodiments, based on the total mass of organic solvents, the total mass percentage of ethyl acetate and methyl acetate can be selected as 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or any range between the two, and the mass percentage of carbonate solvents can be selected as 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or any range between the two.

[0180] In some embodiments, the organic solvent includes methyl acetate, and the methyl acetate content is 5%-70% based on the total mass of the organic solvent.

[0181] In some embodiments, the mass content of methyl acetate, based on the total mass of the organic solvent, can be selected as 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, or any range between the two. Methyl acetate has higher activity than ethyl acetate. Although its addition in small amounts to the electrolyte may slightly sacrifice the lifespan of the battery cells, it can further improve the kinetic performance of the battery cells, thereby improving their fast-charging performance while maintaining a high cycle life.

[0182] In some embodiments, the methyl acetate content is 5%-50% based on the total mass of the organic solvent.

[0183] In some embodiments, the organic solvent includes one or more of ethyl acetate, methyl acetate, and dimethyl carbonate solvent.

[0184] Ethyl acetate and methyl acetate exhibit higher reactivity than carbonate solvents, making them more prone to side reactions with ternary cathode materials. Studies have shown that side reactions are more severe with methyl acetate solvents. However, methyl acetate has a lower molecular weight and viscosity, allowing for a significantly lower addition amount to the electrolyte while maintaining the same conductivity. This is especially true when used in combination with dimethyl carbonate, where the amount of methyl acetate can be further reduced. For high-rate fast-charging battery systems, the combination of methyl acetate and dimethyl carbonate allows for a significant improvement in electrolyte conductivity with a small amount of methyl acetate. Simultaneously, compared to electrolyte systems with a large addition of ethyl acetate, the degree of side reactions is reduced, which is beneficial for maintaining battery cycle stability.

[0185] In some embodiments, the electrolyte comprises an electrolyte salt, which comprises lithium bis(fluorosulfonyl)imide (LiFSI), wherein the mass content of lithium bis(fluorosulfonyl)imide is 3%-10% based on the total mass of the electrolyte.

[0186] In some embodiments, based on the total mass of the electrolyte, the mass content percentage of lithium bisfluorosulfonylimide (LiFSI) 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%, 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 value range between the two.

[0187] Lithium difluorosulfonylimide (LiFSI) readily dissociates in the electrolyte solvent, which is beneficial for improving the kinetics of individual cells, reducing internal resistance, and enhancing fast-charging performance. However, LiFSI is prone to side reactions with LiC6 formed during deep lithium intercalation at the negative electrode, reducing reversible lithium capacity and negatively impacting the retention of cell capacity during cycling. Maintaining the LiFSI mass content within the aforementioned range in the electrolyte can further improve the cycle life of individual cells while ensuring fast-charging performance.

[0188] In some embodiments, the mass content of lithium bis(fluorosulfonyl)imide (LiFSI) is 20%-80% based on the total mass of the electrolyte salt.

[0189] In some embodiments, the mass content of lithium bis(fluorosulfonyl)imide (LiFSI) is 30%-70% based on the total mass of the electrolyte salt.

[0190] In some embodiments, the mass content of lithium difluorosulfonamide, based on the total mass of the electrolyte salt, can be selected as 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or any range between the two.

[0191] Lithium difluorosulfonylimide electrolytes within the aforementioned mass range can improve the battery's fast-charging performance while maintaining side reactions with the negative electrode material at a reasonable level, thus comprehensively improving the battery's cycle life.

[0192] In some embodiments, the battery cell includes a stacked cell, the positive electrode includes a positive current collector, the positive current collector includes a positive current collector portion and a positive electrode tab disposed on at least one side of the positive current collector portion, and the width of the positive current collector portion is 60mm-110mm.

[0193] In some implementations, the width of the positive current collector is 62mm-98mm.

[0194] In some embodiments, the width of the positive current collector can be selected as 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 value range between the two.

[0195] 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 is conductive. Current collectors include metal foils with a pure metal content of 95% or higher, such as at least one of copper, aluminum, stainless steel, titanium, and nickel foils. They also include alloy foils with at least two main metals, for example, alloy foils made from at least two main elements of copper, aluminum, nickel, titanium, and iron. Furthermore, they can include copper, aluminum-cadmium alloys, iron, or stainless steel with surface treatments using carbon, nickel, titanium, silver, copper, etc. In addition, the bonding force with the negative electrode active material can be enhanced by forming micro-uneven surfaces, and they can be used in various forms such as films, sheets, foils, meshes, porous bodies, foams, and non-woven fabrics.

[0196] A laminated battery cell refers to a battery cell formed by stacking positive electrode plates, separator films, and negative electrode plates together.

[0197] Please refer to Figure 7. The width L1 of the positive current collector 10111 refers to the dimension of the positive current collector 10111 in the direction perpendicular to the rolling of the positive electrode film layer 1012 in the positive electrode sheet 101. It also refers to the dimension of the positive current collector 10111 in the direction perpendicular to the connection between the positive electrode tab 10112 and the positive current collector 10111 (i.e., the X direction in Figure 7).

[0198] During high-rate fast charging, the large current required results in rapid and significant temperature rise in the battery cell. During charging, the current first converges at the tabs and then flows to the current collector. Studies show a difference in current density between the tabs and the current collector, and the difference in current density also varies at different points on the current collector relative to the tabs. Generally, the difference in current density between the current collector and the tabs increases with both the distance between them and the current density. In other words, the inconsistency in current density on the current collector is more pronounced during high-rate charging and discharging, i.e., fast charging. According to Joule's law, this inconsistency in current density at different points on the current collector further leads to inconsistent temperature rises in different parts of the battery, resulting in uneven lithium-ion transport rates within the cell. This increases the risk of battery polarization and localized lithium plating, ultimately reducing the cycle life of the individual battery cells.

[0199] The width of the positive current collector within the above range is beneficial to reduce the maximum distance between the tab and the edge of the positive current collector. This can reduce the electron transmission distance, improve the battery's fast charging performance, reduce the uneven temperature rise of the current collector during fast charging, reduce the temperature gradient on the current collector, reduce the probability of active materials inactive first at the temperature rise, improve the battery's fast charging cycle life, and also take into account the battery's energy density.

[0200] In some embodiments, the length of the positive current collector in the laminated cell is 100mm-700mm.

[0201] In some embodiments, the length of the positive current collector in the laminated cell is 200mm-600mm.

[0202] In some embodiments, the length of the positive current collector in the laminated cell can be selected as 100mm, 150mm, 200mm, 250mm, 300mm, 350mm, 400mm, 450mm, 500mm, 550mm, 600mm, 650mm, 700mm or any value range between the two.

[0203] Within the aforementioned range, the length of the positive current collector in the laminated cell can further reduce the electron transport distance along the current collector, improve the inconsistent temperature rise during fast charging of individual battery cells, and increase the fast charging cycle life of individual battery cells. In some embodiments, the electrolyte includes a first additive, which includes one or more of fluorophosphates and borates.

[0204] In some embodiments, the fluorophosphate includes one or more of monofluorophosphate and difluorophosphate; the fluorophosphate includes an alkali metal, optionally one or more of lithium salt, sodium salt, and potassium salt.

[0205] In some embodiments, the borate includes at least one of tetrafluoroborate, bis(oxalate)borate, and fluoro(oxalate)borate; the borate includes an alkali metal, optionally one or more of lithium, sodium, and potassium salts.

[0206] In some embodiments, the first additive includes one or more of lithium monofluorophosphate, sodium monofluorophosphate, potassium monofluorophosphate, lithium difluorophosphate, sodium difluorophosphate, potassium difluorophosphate, lithium tetrafluoroborate, sodium tetrafluoroborate, potassium tetrafluoroborate, lithium bis(oxalate)borate, sodium bis(oxalate)borate, potassium bis(oxalate)borate, lithium fluorine oxalate borate, sodium fluorine oxalate borate, and potassium fluorine oxalate borate.

[0207] In some embodiments, the positive electrode active material includes a lithium-containing transition metal oxide, and the electrolyte includes a first additive.

[0208] The first additive in the electrolyte can combine with metal ions on the surface of lithium-containing transition metal oxides in the positive electrode active material to form a stable scaffold, thereby greatly reducing the probability of irreversible phase transition of the positive electrode active material under high delithiation, reducing the degree of side reactions between the electrolyte and the positive electrode side, and improving the cycle stability of the battery.

[0209] In some embodiments, the positive electrode active material includes a lithium phosphate, and the electrolyte includes a first additive.

[0210] When the positive electrode active material includes lithium phosphate, the first additive in the electrolyte preferentially forms a film on the negative electrode, which is beneficial for 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.

[0211] In some embodiments, the electrolyte includes a second additive, which includes one or more of sulfonate compounds and vinyl sulfate compounds.

[0212] Vinyl sulfate compounds refer to vinyl sulfate and its derivatives.

[0213] Sulfonate compounds are compounds that include sulfonate groups.

[0214] In some embodiments, sulfonate compounds include cyclic sulfonate compounds.

[0215] In some embodiments, vinyl sulfate compounds include At least one of them.

[0216] In some embodiments, sulfonate compounds include At least one of them.

[0217] The second additive in the electrolyte is easy to form a film on the negative electrode, and can simultaneously generate inorganic and organic components in the SEI film, reduce the degree of side reaction of carboxylic acid ester solvents on the negative electrode, and improve the cycle life of the battery.

[0218] In some embodiments, the air oxidation temperature T0 of the negative electrode active material is 630℃~730℃, wherein the air oxidation temperature T0 is the temperature corresponding to the intersection of two tangents at two points corresponding to 500℃ and T1 temperatures respectively on the thermogravimetric curve of the negative electrode active material, and the T1 temperature is the peak temperature of the maximum area peak in the differential thermogravimetric curve of the negative electrode active material. The thermogravimetric curve and the differential thermogravimetric curve can be obtained by thermogravimetric analysis under the following conditions: sample mass 10±0.05mg, purge gas is air with a flow rate of 60mL / min, heating rate is 5℃ / min, and test temperature range is 35℃~950℃.

[0219] The air oxidation temperature T0 can be determined by thermogravimetric analysis including the following steps: The negative electrode active material is subjected to thermogravimetric analysis under the following conditions: a weight of 10±0.05mg, purge gas is air with a flow rate of 60mL / min, heating rate is 5℃ / min, and test temperature range is 35℃~950℃. The thermogravimetric curve (also known as the TG curve) and the differential thermogravimetric curve (also known as the DTG curve) are obtained. The peak temperature T1 of the maximum area peak is read from the differential thermogravimetric curve. The intersection of the two tangents at two points corresponding to the temperatures of 500℃ and T1 is determined on the thermogravimetric curve. The temperature corresponding to the intersection point on the thermogravimetric curve is the air oxidation temperature T0 of the composite graphite material.

[0220] The oxidation of negative electrode active materials in air often begins with surface defects. Therefore, the temperature corresponding to the intersection of the two tangents on the thermogravimetric curve at the two points corresponding to 500℃ and the peak temperature T1 of the maximum area peak, respectively, is the air oxidation temperature T0 of the negative electrode active material. This temperature can accurately represent the temperature at which the air oxidation begins to lose weight and can reflect the number of surface defects of the negative electrode active material.

[0221] In some embodiments, the air oxidation temperature T0 of the negative electrode active material can be selected as 630°C, 640°C, 650°C, 660°C, 670°C, 680°C, 690°C, 700°C, 710°C, 720°C, 730°C or any range between the two.

[0222] Anode active materials with an air oxidation temperature (T0) of 630℃~730℃ have a suitable number of surface defects, providing sufficient end faces for active ion insertion and matching the lithium-ion transport rate of the electrolyte. At the same time, this keeps the degree of side reactions in 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.

[0223] In some embodiments, the core of the negative electrode active material is a secondary particle formed by the agglomeration of primary graphite particles, the coating layer of the negative electrode active material includes amorphous carbon, and the negative electrode active material also includes kinetic carbon material; the interlayer spacing d of the (002) crystal plane of the kinetic carbon material is... 002 >0.335nm.

[0224] In some embodiments, the interlayer spacing d of the (002) crystal plane of the kinetic carbon material 002 The wavelength ranges from 0.3355nm to 0.337nm.

[0225] In some embodiments, the kinetic carbon material includes one or more of hard carbon, expanded graphite, and graphene.

[0226] In some embodiments, the kinetic carbon material is located in the core and / or the coating layer.

[0227] In this application, a primary particle refers to the smallest unit of a particle within a certain observation range. A primary particle may contain defects of any form, but it is impossible to further define smaller particles within a primary particle. Primary particles may aggregate under physical forces such as van der Waals forces, but such aggregation is easily deaggregated under external forces such as ultrasound, stirring, and rolling, so that the main constituent morphology of the active material in the film layer is still primary particles.

[0228] In this application, the secondary particles are formed by the agglomeration of primary particles. The agglomeration here is a hard agglomeration caused by the chemical bonding of primary particles, which makes the secondary particles have a clear surface and boundary and are not easy to disperse 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.

[0229] In this embodiment, the core is a secondary particle formed by the agglomeration of primary graphite particles.

[0230] Amorphous carbon refers to carbon materials with a very low degree of graphitization, exhibiting an approximately amorphous morphology (or lacking a fixed shape and periodic structural regularity). The carbon atoms in amorphous carbon structures are not arranged in a regular pattern; therefore, amorphous carbon can be characterized by transmission electron microscopy (TEM). By using focused ion beam (FIB) to cut a thin slice approximately 100 nm thick from the middle of the negative electrode active material particles, and then performing TEM on the slice, it can be observed that the surface region includes a coating layer. The lattice fringes in the coating layer exhibit long-range disorder and short-range order, and the electron diffraction pattern shows a halo-like appearance, indicating that the coating layer contains amorphous carbon.

[0231] In some embodiments, the interlayer spacing d of the (002) crystal plane of the kinetic carbon material 002 The values ​​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 range between the two.

[0232] In this application, the interlayer spacing d of the material 002As is well known in the art, d can be determined using instruments and methods well known in the art. For example, JIS K 0131-1996 and JB / T 4220-2011 can be consulted, and an X-ray powder diffractometer (e.g., PANalytical X'pert PRO) can be used to determine d. 002 .

[0233] Interlayer spacing d of conventional graphite 002 Typically 0.335 nm, the interlayer spacing d of the aforementioned kinetic carbon material 002 Both are greater than those of conventional graphite.

[0234] The aforementioned kinetic carbon materials, used as negative electrode active materials, can improve the insertion and extraction rates of active ions, thereby enhancing the transport performance of active ions and electrons, and thus improving the fast-charging performance of battery cells while maintaining high energy density. Simultaneously, amorphous carbon has high hardness, thus exhibiting good compressive strength and a strong ability to maintain the pore structure of the negative electrode film during cycling. This also results in better electrolyte wettability of the negative electrode sheet, further contributing to improved cycle performance of the battery cells.

[0235] In some implementations, the kinetic carbon material includes one or more of hard carbon, expanded graphite, and graphene.

[0236] Hard carbon materials exhibit a trace amount of disordered crystallites, and even high-temperature heat treatment cannot transform them into a graphite structure. Hard carbon materials lack a long-range ordered crystal lattice structure; the atomic arrangement is only short-range ordered, falling between the structures of graphite and diamond. Hard carbon materials generally do not contain 3-4 layers or more of parallel graphite sheet structures; they are primarily composed of disordered single-layer graphite sheet structures, resulting in a large number of micropores with diameters less than 1 nm.

[0237] Expanded graphite refers to graphite flakes that expand at a certain temperature. The expanded graphite has a fibrous, worm-like shape, and the interlayer spacing of expanded graphite along the C-axis is tens to hundreds of times that of conventional graphite.

[0238] In some embodiments, the kinetic carbon material is located in the core and / or coating layer.

[0239] In some embodiments, the mass percentage of kinetic carbon material is 1% to 30% based on the total mass of the negative electrode active material.

[0240] In some embodiments, the mass percentage of kinetic carbon material is 8% to 15% based on the total mass of the negative electrode active material.

[0241] 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 range between the two.

[0242] When the mass percentage of kinetic carbon material is within a suitable range, the negative electrode active material can possess high specific capacity, as well as high active ion solid-phase transport capability and high active ion and electron charge exchange rate. Consequently, the battery cell can achieve high energy density while also exhibiting improved fast-charging performance. Furthermore, within a suitable mass percentage range, the negative electrode film pore structure is better maintained during cycling, resulting in better electrolyte wettability of the negative electrode sheet and improved cycle performance of the battery cell.

[0243] In some embodiments, the negative electrode active material includes secondary particles formed by the agglomeration of primary particles, and the volume distribution particle size Dv50 of the negative electrode active material is 8μm-18μm.

[0244] The volumetric distribution particle size Dv50 represents the particle size corresponding to a cumulative volumetric distribution percentage of 50% of the material, and can be determined using instruments and methods known in the art. For example, it can be conveniently determined using a laser particle size analyzer, referring to GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method. The testing instrument can be the Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0245] In some embodiments, the negative electrode active material includes secondary particles formed by the 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 value range between the two.

[0246] In some embodiments, the negative electrode active material comprising secondary particles formed by the agglomeration of primary particles means that the negative electrode active material mainly comprises secondary particles formed by the 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 a cross-section along the thickness direction of the negative electrode sheet.

[0247] Negative electrode active materials with a volume distribution particle size Dv50 within the above range can, on the one hand, utilize a certain number of primary particles in the secondary particles to give the negative electrode active material a suitable intercalation surface, and the solid-phase transport rate and solid-liquid transport rate of active ions in the negative electrode active material can match the lithium-ion liquid-phase transport rate of the electrolyte, thus improving the fast charging performance of the battery; on the other hand, they can also have the advantages of large particle size, high compaction density, and large capacity of secondary particles, thus improving the fast charging performance of the battery while taking into account the energy density of the battery cells.

[0248] In some embodiments, the negative electrode active material comprises unaggregated primary particles, and the volume distribution particle size Dv50 of the negative electrode active material is 5μm-13μm.

[0249] In some embodiments, the negative electrode active material comprises unaggregated primary particles, and the volume distribution particle size Dv50 of the negative electrode active material can be selected as 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm or any value range between the two.

[0250] In some embodiments, the negative electrode active material mainly comprises unaggregated primary particles. That is, more than 85% of the particles in the negative electrode active material are unaggregated primary particles. This can be determined by observing the particle morphology of a cross-section along the thickness direction of the negative electrode sheet.

[0251] Negative electrode active materials with a volume distribution particle size (Dv50) within the aforementioned range exhibit higher interfacial stability compared to smaller particle sizes, while simultaneously possessing a greater ion solid-phase transport distance. These two aspects can be balanced through size design, achieving a balance between fast-charging performance and cycle life of individual battery cells.

[0252] In some embodiments, the core of the negative electrode active material comprises artificial graphite.

[0253] Artificial graphite refers to materials that are easily graphitized, processed under high-temperature conditions to form a regular graphitized layered structure. Artificial graphite differs significantly from natural graphite in morphology. Scanning electron microscopy (SEM) observation of graphite cross-sections reveals that natural graphite exhibits a more layered structure with numerous pores between the layers; while artificial graphite crystals are arranged strictly according to an ABAB pattern, with a dense internal structure and few or no gaps. The crystal structures of artificial and natural graphite also differ. Natural graphite contains not only a hexagonal phase but also an orthorhombic hexahedral phase (3R phase); artificial graphite contains only the hexagonal phase. Artificial graphite has fewer defects and higher capacity, reducing side reactions with the electrolyte, fully utilizing the high capacity of graphite, and minimizing gas production, resulting in battery cells with both high energy density and good cycle performance.

[0254] In some embodiments, the mass of the coating layer is 0.3%-5% of the mass of the core; and / or, the average thickness of the coating layer is 100nm-300nm.

[0255] In some embodiments, the mass of the coating layer may be selected as 0.3%, 0.4%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% of the mass of the core, or any value between the two.

[0256] The quality of the coating layer affects its thickness and also the cumulative distribution of the negative electrode active material, which is the R value R50 at 50%.

[0257] In some implementations, the average thickness of the coating layer can be selected as 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, or any value range between the two.

[0258] The thickness of the coating layer can be characterized by transmission electron microscopy (TEM). By observing the negative electrode active material with TEM, the coating layer covering the core surface can be clearly observed based on the differences in lattice fringes. 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.

[0259] When the mass percentage or thickness of the coating layer is within the aforementioned range, the uniformity of the coating layer is improved, thereby enhancing the charge exchange capacity of ions on the surface of the negative electrode active material. Furthermore, within this range, side reactions on the surface of the negative electrode active material particles are also kept at a low level, resulting in a higher specific capacity. Therefore, a coating layer mass percentage within this range is beneficial for batteries to possess high energy density, good kinetic performance, and long cycle life.

[0260] In some embodiments, the coating layer is disposed on 90%-100% of the surface of the core.

[0261] The coating layer is disposed on the surface of the core at a value range of 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, or any two of these values.

[0262] A coating layer is applied to most of the surface of the core, which can provide end faces for active ion insertion and reduce the contact between the core and the electrolyte. This reduces the co-intercalation of the electrolyte solvent during cycling, thus balancing the fast charging performance and cycle performance of the battery cell.

[0263] 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, wherein the porosity of the second negative electrode film layer is greater than that of the first negative electrode film layer.

[0264] In this application, the porosity of the negative electrode film can be determined using methods known in the art. For example, the longitudinal cross-section of the negative electrode film can be observed under a scanning electron microscope, and the compactness and porosity of the negative electrode active material can be determined from the images.

[0265] It is understood that the porosity of the first and second negative electrode films can be adjusted in any manner known in the art. For example, the porosity of the negative electrode film can be adjusted by regulating the particle size uniformity of the negative electrode active material. The particle size uniformity of the negative electrode active material refers to the degree of dispersion of the particle size of the negative electrode active material in different film layers from the average particle size, and can reflect the uniformity of the particle size distribution of the negative electrode active material.

[0266] This application uses a highly conductive electrolyte with a high ion transport rate. By designing the second negative electrode film layer near the electrolyte to have a large porosity, the transport rate of lithium ions in the electrode is matched with the liquid phase transport rate in the electrolyte, 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 near the current collector to take into account the energy density of the battery cells.

[0267] In some embodiments, the first negative electrode film layer includes a first negative electrode active material with a particle size uniformity of 0.4 to 0.6; the second negative electrode film layer includes a second negative electrode active material with a particle size uniformity of 0.25 to 0.45.

[0268] In this application, the particle size uniformity of the negative electrode active material has a meaning known in the art. It 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 using methods known in the art. For example, it can be directly tested using a Malvern Mastersizer 3000 laser diffraction particle size distribution measuring instrument (referring to standard GB / T 19077.1-2016). The specific calculation formula can be found in the instrument's user manual.

[0269] In some embodiments, the particle size uniformity of the first negative electrode active material can be selected as 0.40, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.5, 0.51, 0.52, 0.53, 0.54, 0.55, 0.56, 0.57, 0.58, 0.59, 0.6 or any value range between the two.

[0270] In some embodiments, the particle size uniformity of the second negative electrode active material can be selected as 0.25, 0.26, 0.27, 0.28, 0.29, 0.3, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.4, 0.41, 0.42, 0.43, 0.44, 0.45 or any value range between the two.

[0271] Anode active materials with a particle size uniformity of 0.4-0.6 can achieve close packing through the gradation of large and small particles, resulting in a relatively low porosity in the first anode film layer; anode active materials with a particle size uniformity of 0.25-0.45 have low particle size uniformity, making it difficult to form an effective match, resulting in a relatively high porosity in the second anode film layer.

[0272] 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.

[0273] In some embodiments, the volume distribution particle size DV50 of the first negative electrode active material can be selected as 13.7 μm, 14.7 μm, 15.7 μm, 16.7 μm, 17.7 μm, 18.7 μm, 19.7 μm, 20.7 μm or any range between the two; the volume distribution particle size DV50 of the second negative electrode active material is 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm or any range between the two.

[0274] In some embodiments, the volume distribution particle size D of the first negative electrode active material V The particle size D of the second negative electrode active material ranges from 4.8 μm to 8.0 μm. V 10 ranges from 6.0 μm to 9.5 μm.

[0275] In some embodiments, the volume distribution particle size DV10 of the first negative electrode active material can be selected as 4.8 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm or any value range between the two; the volume distribution particle size DV10 of the second negative electrode active material is 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm or any value range between the two.

[0276] When the negative electrode active materials of the first and second films meet the design conditions, the pores of the second negative electrode film tend to be linear, which is conducive to the liquid phase conduction of active ions in the low SOC state (State of charge) at the beginning of charging. At the same time, the second negative electrode film contains more small-particle active materials with smaller particle size, which is conducive 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.

[0277] 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.

[0278] In some embodiments, the negative electrode film layer includes a first negative electrode film layer disposed on the surface of the negative electrode current collector and a second negative electrode film layer disposed on the side of the first negative electrode film layer away from the negative electrode current collector. The powder compaction density of the negative electrode active material in the second negative electrode film layer under a pressure of 50,000 N is less than the powder compaction density of the negative electrode active material in the first negative electrode film layer under a pressure of 50,000 N.

[0279] In this application, the powder compaction density of the material has a meaning known in the art and can be determined using instruments and methods known in the art. For example, it can be determined using an electronic pressure testing machine (e.g., UTM7305 type) according to standard GB / T24533-2009. An exemplary test method is as follows: Weigh 1g of material and add it to a container with a bottom area of ​​1.327cm². 2 In the mold, the pressure is increased to 5000 kg (equivalent to 50000 N), held for 30 seconds, then depressurized and held for 10 seconds. The compaction density of the powder under a force of 50000 N is then recorded and calculated.

[0280] The powder compaction density of the negative electrode active material in the second negative electrode film layer near the electrolyte side is small, which helps to maintain the pore structure of the negative electrode film layer near the electrolyte side and improve 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 far from the electrolyte side is large, which helps to improve the compaction density of the negative electrode film layer and take into account the energy density of the battery cell.

[0281] 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 / cm³ 3 ≤ρ2≤2.00g / cm 3 .

[0282] 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 / cm³ 3 ≤ρ2≤1.95g / cm 3 .

[0283] 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 can be selected as 1.50 g / cm³. 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 the range of values ​​between any two.

[0284] 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 / cm³ 3 ≤ρ1≤2.05g / cm 3 .

[0285] 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 can be selected as 1.70 g / cm³. 3 1.72g / cm 3 1.74 g / cm 3 1.76 g / cm 3 1.80g / cm 3 1.82g / cm 3 1.84 g / cm 3 1.86 g / cm 3 1.88g / cm 3 2.00g / cm 3 2.02 g / cm 3 2.04 g / cm 3 2.05g / cm 3Or the range of values ​​between any two.

[0286] 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 / cm³ 3 ≤ρ1≤2.05g / cm 3 .

[0287] In some embodiments, the one-sided density of the negative electrode film is 0.08 g / 1540.25 mm². 2 -0.20g / 1540.25mm 2 Available in 0.10g / 1540.25mm. 2 -0.16g / 1540.25mm 2 .

[0288] In this application, the areal density of the film layer has a meaning known in the art and can be tested using methods known in the art. For example, take an electrode sheet that has been coated on one side and cold-pressed (if it is a double-sided coated electrode sheet, the film layer on one side can be wiped off first), cut it into small circular pieces with an area of ​​S1, weigh them, and record their weight as M1. Then wipe off the film layer of the electrode sheet after weighing, weigh the current collector, and record it as M0. The areal density of the film layer on one side = (M1-M0) / S1. To ensure the accuracy of the test results, multiple groups (e.g., 10 groups) of samples can be tested, and the average value can be calculated as the test result.

[0289] In some embodiments, the single-sided density of the negative electrode film can be selected as 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 the range of values ​​between any two.

[0290] It is understandable that the density of the negative electrode film is tested on the negative electrode sheet, and the density of the positive electrode film is tested on the positive electrode sheet.

[0291] Battery cells with a single-sided density of the negative electrode film within the above range can reduce the transport distance of lithium ions in the negative electrode film, which is beneficial to improving the fast charging performance of the battery cells.

[0292] In some embodiments, the negative electrode active material further includes a silicon-based material, and the one-sided density of the negative electrode film is 0.06 g / 1540.25 mm². 2 -0.15g / 1540.25mm 2 .

[0293] In some embodiments, silicon-based materials include one or more of nano-silicon, silicon-carbon materials, silicon-oxygen materials, silicon-nitrogen materials, and alloy silicon.

[0294] In some embodiments, the negative electrode active material further includes a silicon-based material, and the single-sided density of the negative electrode film can be selected as 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 the range of values ​​between any two.

[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 for batteries with the same capacity, that is, further reduces the density of the one-sided side of the negative electrode film layer. This is beneficial to reduce the transport 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 compaction density of the negative electrode sheet is 1.2 g / cm³. 3 -1.9g / cm 3 1.2g / cm³ is an optional value. 3 -1.65g / cm 3 .

[0297] In this application, the compaction density of the negative electrode sheet has a meaning known in the art and can be tested using methods known in the art. The negative electrode sheet is removed from the lithium-ion battery, and a certain area of ​​the electrode sheet is taken. The mass and thickness of the electrode sheet and the current collector after the film layer has been removed are measured respectively. The compaction density of the electrode sheet is calculated according to the following formula: Compaction density of the electrode sheet = (Electrode sheet mass - Current collector mass) / [(Electrode sheet thickness - Current collector thickness) × Electrode sheet area].

[0298] In some embodiments, the compaction density of the negative electrode sheet may be selected as 1.2 g / cm³. 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 the range of values ​​between any two.

[0299] Negative electrode sheets with a compaction density within the above range have suitable porosity, which can match electrolytes with high conductivity, improve the diffusion rate of lithium ions in the negative electrode, reduce concentration polarization generated by the battery cell during fast charging, and help improve the fast charging performance of the battery cell while taking into account the energy density of the battery cell.

[0300] In some embodiments, the average thickness of the negative electrode film on one side is 30 μm-150 μm.

[0301] In some embodiments, the average thickness of the negative electrode film on one side is 30 μm-80 μm.

[0302] In some embodiments, the average thickness of one side of the negative electrode film can be selected as 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 90μm, 95μm, 100μm, 105μm, 110μm, 115μm, 120μm, 125μm, 130μm, 135μm, 140μm, 145μm, 150μm or any value range between the two.

[0303] Anode films with an average thickness within the above range have a suitable lithium-ion diffusion distance, which can be matched with electrolytes with high conductivity, improve the diffusion rate of lithium ions in the anode film, and improve the fast charging performance of battery cells while taking into account the energy density of battery cells.

[0304] In some embodiments, the negative electrode active material further includes a silicon-based material, and the average thickness of the negative electrode film on one side is 30 μm-80 μm.

[0305] In some embodiments, the negative electrode active material further includes a silicon-based material, and the average thickness of the negative electrode film layer on one side can be selected as 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm or any value range between the two.

[0306] 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 for batteries with the same capacity, which helps to reduce the transport distance of lithium ions in the negative electrode film layer and further improves the fast charging performance of the battery cell.

[0307] In some embodiments, the porosity of the negative electrode sheet is 20%-60%.

[0308] In some embodiments, the porosity of the negative electrode sheet is 25%-40%.

[0309] In this application, the porosity of the negative electrode sheet can be tested using methods known in the art. For example, based on the national standard GB / T24586-2009, the electrode sheet is immersed in ethyl methyl carbonate (EMC) for cleaning; the porosity is determined using a true density meter based on the gas displacement method. The porosity is the percentage of pore volume to the total volume of the electrode sheet, calculated using the formula: Porosity = (V - V0) / V × 100%, where V0 is the true volume and V is the apparent volume.

[0310] In some embodiments, the porosity of the negative electrode sheet can be selected as 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, or any value range between the two.

[0311] Negative electrode sheets with porosity within the above range can be matched with electrolytes with high conductivity, facilitating the transport of lithium ions in the negative electrode, reducing concentration polarization generated during fast charging of battery cells, and improving the fast charging performance of battery cells while taking into account the energy density of battery cells.

[0312] In some embodiments, the positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector. The positive electrode film layer includes a positive electrode active material, which includes lithium phosphate and consists of non-agglomerated primary particles. The volume distribution particle size Dv50 of the positive electrode active material is [missing information]. 正1 Satisfies: 0.3μm≤Dv50 正 1≤2μm.

[0313] Volume distribution particle size Dv50 of positive electrode active material正 The volume distribution particle size of the negative electrode active material can be tested with reference to the above description. It is understood that "unagglomerated primary particles" here refers to primary particles that have not undergone granulation to form secondary particles, and does not mean that primary particles will not spontaneously aggregate. Because the primary particles containing lithium phosphate have a small particle size and a large specific surface area, aggregation is inevitable during the Malvern scattering method for testing the volume distribution particle size. This results in the Malvern laser particle size analyzer measuring the particle size of the primary particle aggregate, 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 value can be selected as 0.3μm, 0.4μm, 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm, 1.6μm, 1.7μm, 1.8μm, 1.9μm, 2μm or any value range between the two.

[0314] In some embodiments, the positive electrode active material containing lithium phosphate comprises unaggregated 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.

[0315] In some embodiments, the average particle size of the primary particles containing lithium phosphate in the positive electrode active material can be selected as 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 value range between the two.

[0316] The particle size of primary particles in the positive electrode active material can be statistically analyzed as follows. For example, disassemble the battery to obtain the positive electrode sheet. Peel off the positive electrode film layer, thoroughly wash the film layer with acetone, filter, and dry to obtain powder. Dissolve 0.05g of the uniformly mixed powder in 40mL of anhydrous ethanol, then add an appropriate amount of dispersant and stir until a suspension is obtained. Mix 2mL of the suspension with 2mL of anhydrous ethanol and sonicate at a power of 480W for 5 minutes to obtain a uniformly dispersed suspension. Take an appropriate amount of the middle layer suspension for transmission electron microscopy (TEM) testing to obtain TEM images. Select 5-10 TEM images containing 50 to 100 particles as sampling areas, ensuring at least 500 particles are tested. Then, using Avizo 3D software, the projected area of ​​each primary particle in each sampling area can be statistically analyzed, which is the cross-sectional area S of the primary particle. In the primary particle identification process, for particles with obvious adhesion, a combination of manual and software identification can be used to determine whether the particle is a single primary particle or two secondary particles. The equivalent circle diameter of the primary particle is obtained using the equivalent circle method, which is the primary particle diameter d.

[0317] Lithium phosphates with an average particle size within the above range have a shorter ion transport path, lower lithium ion transport impedance, and lower moisture absorption. This not only matches the liquid phase transport rate of lithium ions in the electrolyte, but also reduces 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.

[0318] In some embodiments, the composition of the lithium phosphate is as shown in Formula VI.

[0319] Li x1 A y1 Me a1 M b1 P 1-c1 X c1 Y z1 Formula VI,

[0320] Wherein, 0.5≤x1≤1.3, 0≤y1≤1.3, and 0.7≤x1+y1≤1.3; 0.9≤a1≤1.5, 0≤b1≤0.5, and 0.9≤a1+b1≤1.5; 0≤c1≤0.5; 3≤z1≤5; A includes one or more of Na, K, 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.

[0321] In some embodiments, x1 can be selected as a numerical range of 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3 or any two of these values; y1 can be selected as a numerical range of 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 two of these values; x1+y1 can be selected as a numerical range of 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3 or any two of these values; a1 can be selected as a numerical range of 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5 or any two of these values; b 1 can be selected from 0, 0.1, 0.2, 0.3, 0.4, 0.5 or any value between two of them; a1+b1 can be selected from 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5 or any value between two of them; c1 can be selected from 0, 0.1, 0.2, 0.3, 0.4, 0.5 or any value between two of them; z1 can be selected from 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5 or any value between two of them.

[0322] Lithium phosphates containing the above components exhibit good structural stability and low irreversible loss during fast charging, thereby improving the cycle stability of individual battery cells.

[0323] In some embodiments, the lithium-containing phosphate has an olivine structure, including but not limited to one or more of lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, and their respective doped, coated, or composite modified materials. In some embodiments, the positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector. The positive electrode film layer includes a positive electrode active material, which comprises a lithium-containing transition metal oxide, and the volume distribution particle size Dv50 of the positive electrode active material is [missing information]. 正2 Satisfies: 2μm≤Dv50 正2 ≤15μm.

[0324] 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.

[0325] In some embodiments, the general formula for lithium-containing transition metal oxides includes Li a Ni b Co c M d Oe 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.

[0326] In some embodiments, the volume distribution particle size Dv50 of the positive electrode active material containing lithium transition metal oxides 正2 The value can be selected as 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm or any range between the two.

[0327] Volumetric particle size Dv50 正2 The positive electrode active material containing lithium transition metal oxides within the above range has a shorter ion transport path, lower lithium ion transport impedance, and lower degree of side reaction. It can match the liquid phase transport rate of lithium ions in the electrolyte, reduce the temperature rise of the battery cell during fast charging, and also improve the cycle life of the battery cell by reducing the degree of side reaction.

[0328] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganese oxide, and the Dv50 of the positive electrode active material... 正2 The positive electrode active material has a particle size of 6μm-15μm and consists of secondary particles formed by the agglomeration of primary particles. The average particle size of the primary particles in the secondary particles is 0.1μm-1.5μm.

[0329] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganese oxide, and the Dv50 of the positive electrode active material... 正2 The positive electrode active material has a particle size of 8μm-12μm and consists of secondary particles formed by the agglomeration of primary particles. The average particle size of the primary particles in the secondary particles is 0.1μm-1.5μm.

[0330] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganese oxide, and the Dv50 of the positive electrode active material... 正2 The value can be selected as 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm or any range between the two.

[0331] In some embodiments, the positive electrode active material lithium nickel cobalt manganese oxide includes secondary particles formed by the agglomeration of primary particles. The average particle size of the primary particles in the secondary particles can be selected from 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm or any value range between the two.

[0332] The average particle size of primary particles in secondary particles can be tested using any method known in the art. As an example, a cross-section along the thickness direction of the positive electrode sheet is obtained, and particles of the same size and shape from any 10 regions in the same scanning electron microscope (SEM) image at 10kV and 30k magnification are observed. Each of these 10 regions is then subdivided into five positions: the four corners and the center. The average particle size of any primary particle at each position is selected at this magnification, and the average particle size results from the five positions (corners and center) are averaged to obtain the average particle size of the primary particles in that region. Then, the average particle sizes obtained from the 10 regions are averaged again to obtain the average particle size of the primary particles. Specifically, the average of the major and minor axes of each particle is taken as the average particle size.

[0333] In this embodiment, the positive electrode active material mainly comprises secondary particles, that is, powder with secondary particles as the main component. The secondary particles include numerous small-diameter primary particles, resulting in a short lithium-ion transport path and multiple insertion faces, which can be matched with electrolytes with high lithium-ion transport rates, thus improving the power performance of the battery cell.

[0334] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganese oxide, and the Dv50 of the positive electrode active material... 正2 The size is 2μm-5μm, and the positive electrode active material includes unaggregated primary particles.

[0335] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganese oxide, and the Dv50 of the positive electrode active material... 正2 The size ranges from 2.5μm to 4.5μm, and the positive electrode active material includes unaggregated primary particles.

[0336] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganese oxide, and the Dv50 of the positive electrode active material... 正2 The value can be selected as 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm or any range between two of them.

[0337] In this embodiment, the positive electrode active material mainly comprises unagglomerated primary particles, that is, a powder mainly composed of unagglomerated primary particles. This positive electrode active material exhibits low side reaction with highly reactive carboxylic acid ester solvents, which is beneficial for further improving the cycle life of the battery cell.

[0338] 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 exhibits 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.

[0339] 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 exhibits a bimodal distribution, with the peak positions located in the numerical range of 2μm, 3μm, 4μm, 5μm or any two of them and the numerical range of 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm or any two of them.

[0340] The aforementioned positive electrode active material is graded by secondary particles with a predominantly large particle size and primary particles with a predominantly small particle size, which takes into account the cycle life and power performance of the battery cells while further improving the energy density of the battery.

[0341] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganese oxide, wherein 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2The size is 2μm-5μm, and the positive electrode active material includes unaggregated primary particles.

[0342] 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 value range between the two, based on the total number of moles of transition metals in the positive electrode active material.

[0343] A cobalt molar content of less than or equal to 20% is beneficial for reducing the cost of cathode active materials, but it is not conducive to improving the kinetic performance of cathode active materials. By using relatively small-sized, non-agglomerated primary particles, it is possible to reduce the side reactions between carboxylic esters and cathode active materials, improve the cycle life of battery cells, and improve the kinetic performance of cathode active materials, thereby increasing the power performance of battery cells.

[0344] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganese oxide, wherein 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... 正2 The size is 2μm-5μm, and the positive electrode active material includes unaggregated primary particles.

[0345] 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 value range between the two, based on the total number of moles of transition metals in the positive electrode active material.

[0346] A nickel molar content of less than 80% helps reduce the probability of nickel dissolution in the positive electrode active material under high voltage (charging cutoff voltage ≥ 4.3V), thereby improving the withstand voltage of the positive electrode active material. Combining low-nickel components with non-agglomerated 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 charge and discharge, and improve the cycle performance of the battery cell.

[0347] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganese oxide, wherein 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... 正2 The positive electrode active material has a particle size of 6μm-15μm and consists of secondary particles formed by the agglomeration of primary particles. The average particle size of the primary particles in the secondary particles is 0.1um-1.5um.

[0348] In some embodiments, the positive electrode active material includes lithium nickel cobalt manganese oxide, and the molar content of nickel, based on the total number of moles of transition metals in the positive electrode active material, is 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or any value between the two.

[0349] Molding high-nickel materials into large-sized secondary particles is beneficial for simultaneously improving the specific capacity of the positive electrode active material and the gradation of the positive electrode sheet, thereby improving the energy density of the battery. At the same time, the secondary particles, composed of small-diameter primary particles, can shorten the lithium-ion transport distance, increase the number of intercalation faces, reduce the DC impedance of the battery cell, and improve the power performance of the battery cell.

[0350] In some embodiments, the positive electrode active material includes cobalt, and the mass percentage of cobalt near the surface of the positive electrode active material particles is greater than the mass percentage of cobalt near the center of the positive electrode active material particles.

[0351] The mass percentage of cobalt in the cathode active material particles can be obtained by measuring the percentage of cobalt relative to all elements at different locations on the cross-section of the particles. As an example, this can be performed using an argon ion cross-section polisher (model JEOL IB-19530CP) and a scanning electron microscope (model Zeiss Sigma 300) (equipped with an X-ray energy dispersive spectrometer (EDS, model OXFord X-Max-50mm²)). The longitudinal cross-section of the cathode film is obtained using the ion cross-section polisher, and a line scan of the cobalt content is performed on the cross-section of the cathode active material particles using the scanning electron microscope. The mass percentage of cobalt near the particle surface is greater than that near the center of the cross-section of the cathode active material particles.

[0352] In some embodiments, the ratio of the mass percentage of cobalt near the particle surface to the mass percentage of cobalt near the center of the positive electrode active material particle is in the range of (1.2-5.0):1.

[0353] In some embodiments, the ratio of the mass percentage of cobalt near the surface of the positive electrode active material to the mass percentage of cobalt near the center of the positive electrode active material particles is (1.4-2.0):1.

[0354] The ratio of the mass percentage of cobalt at the surface of the positive electrode active material particle to the mass percentage of cobalt at the center can be calculated by the ratio of the mass percentage of cobalt at different sites during line scanning. Here, "near the particle surface" refers to the region from the particle surface to a depth of 200 nm in the direction towards the geometric center of the particle, and "near the center of the positive electrode active material particle" refers to a spherical region with a diameter of 200 nm centered on the geometric center of the particle's cross-section.

[0355] In some embodiments, the ratio of the mass percentage of cobalt at the surface of the positive electrode active material particles to the mass percentage of cobalt 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 value within the range of the two.

[0356] While highly conductive electrolytes are beneficial for improving the liquid-phase transport rate of lithium ions, their components also exhibit high electrochemical activity. For example, carboxylic acid esters in highly conductive electrolytes are prone to side reactions with the oxygen-releasing structures on the surface of the positive electrode active material after phase transition, increasing gas production and deteriorating the battery's cycle life. A relatively high cobalt content on the surface of the positive electrode active material helps improve its ionic conductivity, mitigates excessive delithiation during charge and discharge, reduces cation mixing between the Li layer and the transition metal layer, stabilizes the layered structure of the positive electrode active material, and reduces the risk of structural phase transitions on the surface, thereby reducing the degree of side reactions in the battery cell and improving its cycle life. Conversely, a relatively low cobalt content in the center of the positive electrode active material can simultaneously reduce its cost.

[0357] In some embodiments, the positive electrode active material includes lithium phosphate, and the one-sided density of the positive electrode film is 0.2 g / 1540.25 mm². 2 -0.35g / 1540.25mm 2 .

[0358] In some embodiments, the positive electrode active material includes lithium phosphate, and the one-sided density of the positive electrode film can be selected as 0.2 g / 1540.25 mm². 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 20.28g / 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 the range of values ​​between any two.

[0359] In some embodiments, the positive electrode active material comprises a lithium-containing transition metal oxide, and the one-sided density of the positive electrode film is 0.13 g / 1540.25 mm². 2 -0.24g / 1540.25mm 2 ;

[0360] In some embodiments, the positive electrode active material comprises a lithium-containing transition metal oxide, and the one-sided density of the positive electrode film can be selected as 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 / 1540.25mm 2 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 the range of values ​​between any two.

[0361] A positive electrode film with an areal density within the above range has a suitable thickness, which is conducive to the diffusion of active ions in the electrode and can more effectively improve the fast charging performance of the battery cell; at the same time, it can reduce heat generation, reduce the reactivity of the electrolyte and the probability of side reactions, and take into account the cycle performance of the battery cell.

[0362] In some embodiments, the porosity of the positive electrode film is 22%-35%.

[0363] In some embodiments, the porosity of the positive electrode film can be selected as 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, or any value range between the two.

[0364] Porosity within the above-mentioned range of positive electrode film is conducive to the diffusion of active ions in the electrode, which can more effectively improve the fast charging performance of the battery cell; at the same time, it can reduce heat generation, reduce the reactivity of the electrolyte and the probability of side reactions, and take into account the cycle performance of the battery cell.

[0365] In some embodiments, the lithium-ion conductivity of the electrolyte is 10 mS / cm-20 mS / cm.

[0366] Increasing the lithium-ion conductivity of the electrolyte often necessitates the addition of a higher content of highly conductive solvents. While highly conductive solvents offer high lithium-ion transport rates, they also exhibit high chemical reactivity, making them prone to side reactions with the negative electrode active material and reducing battery cycle life. Electrolytes with lithium-ion conductivity within the aforementioned range possess suitable lithium-ion conduction rates and reactivity, better balancing the fast-charging performance and cycle life of individual battery cells.

[0367] In some embodiments, the lithium-ion conductivity of the electrolyte is 12 mS / cm-20 mS / cm.

[0368] In some embodiments, the lithium-ion conductivity of the electrolyte is 10 mS / cm-15 mS / cm.

[0369] In some embodiments, the positive electrode active material includes lithium iron phosphate, and the one-sided surface area density of the positive electrode film is 0.2 g / 1540.25 mm². 2 -0.35g / 1540.25mm 2 The conductivity of the electrolyte is 12 mS / cm - 20 mS / cm.

[0370] It is understandable that the positive electrode active material, including lithium iron phosphate, may be a salt with a lithium iron phosphate structure, or it may be a doped or modified material of lithium iron phosphate, a coated or modified material, or a mixture of lithium iron phosphate and other active materials.

[0371] Lithium iron phosphate (LFP) batteries have a relatively low specific capacity; therefore, the positive electrode film of a single cell with the same capacity often requires a relatively high coating density. Using an electrolyte with conductivity within the aforementioned range helps mitigate the losses to the cell's kinetic performance caused by the required coating density, thus meeting both energy density and power performance requirements.

[0372] In some embodiments, the positive electrode active material includes lithium-containing nickel-cobalt-manganese oxide, and the one-sided density of the positive electrode film is 0.13 g / 1540.25 mm². 2 -0.24g / 1540.25mm 2 The conductivity of the electrolyte is 10 mS / cm - 15 mS / cm.

[0373] Lithium-containing nickel-cobalt-manganese oxides have relatively high specific capacity. Therefore, for battery cells of the same capacity, the coating density of the positive electrode film is relatively low, and electrolytes with relatively low conductivity can meet the fast-charging performance requirements of the battery cells. These battery cells can meet both power performance and cycle life requirements.

[0374] In some embodiments, the negative electrode current collector may include a metal foil, a three-dimensional porous current collector, or a composite current collector. Examples of metal foils include copper foil, copper alloy foil, nickel foil, nickel alloy foil, aluminum foil, and aluminum alloy foil. Examples of three-dimensional porous current collectors include copper mesh, nickel mesh, copper foam, nickel foam, and aluminum foam. The composite current collector may include a polymer material substrate and a metal material layer formed on at least one surface of the polymer material substrate. Examples of metal materials include, but are not limited to, one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, aluminum, aluminum alloys, silver, and silver alloys. Examples of polymer material substrates include, but are not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0375] In some embodiments, the negative electrode film layer may also include other negative electrode active materials known in the art, such as, but not limited to, one or more of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate.

[0376] In some embodiments, the negative electrode film layer may 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.

[0377] In some embodiments, the negative electrode film layer may optionally include a negative electrode binder. As an example, the negative electrode binder may include, but is not limited to, one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0378] In some embodiments, the negative electrode film may optionally include other additives. As an example, other additives may include, but are not limited to, thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.

[0379] The negative electrode film is typically formed by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is usually formed by dispersing negative electrode active materials, negative electrode conductive agents, negative electrode binders, and other optional additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0380] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet may also include a conductive undercoat layer (e.g., composed of a conductive agent and an adhesive) 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 sheet may also include a protective layer covering the surface of the negative electrode film layer.

[0381] In some embodiments, the positive electrode film may 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.

[0382] In some embodiments, the positive electrode film layer may optionally include a positive electrode binder. As an example, the positive electrode binder may include, but is not limited to, one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resins, styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0383] In some embodiments, the positive current collector may be a metal foil or a composite current collector. An example of a metal foil is aluminum foil. The composite current collector may include a polymeric material substrate and a metal material layer formed on at least one surface of the polymeric material substrate. As an example, the metal material may include, but is not limited to, one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymeric material substrate may include, but is not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0384] The positive electrode film is typically formed by coating a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is usually formed by dispersing positive electrode active materials, positive electrode conductive agents, positive electrode binders, and any other components in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP), but is not limited to this.

[0385] In some embodiments, the battery cell includes an electrolyte. This application does not specifically limit the type of electrolyte; it can be selected according to requirements. For example, the electrolyte may include one or more of solid electrolytes and liquid electrolytes (i.e., electrolyte solutions).

[0386] 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 difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0387] In some embodiments, the solvent includes, but is not limited to, one or more of ester solvents, sulfone solvents, and ether solvents. For example, the solvent may include, but is not limited to, ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0388] In some embodiments, the electrolyte may optionally include other additives.

[0389] In some embodiments, the battery cell further includes a separator. The separator is disposed between the positive electrode and the negative electrode, and its main function is to prevent internal short circuits.

[0390] This application does not impose any particular restrictions on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0391] In some embodiments, the material of the separator may include, but is not limited to, one or more of glass fiber, nonwoven fabric, polyethylene (PE), polypropylene (PP), and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer may be the same or different.

[0392] The methods for preparing individual battery cells are well known. In some embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte can be assembled to form a battery cell. As an example, the positive electrode, separator, and negative electrode can be wound and / or stacked to form an electrode assembly. The electrode assembly is then placed in an outer package, dried, and injected with the electrolyte. After encapsulation, settling, and formation processes, a battery cell is obtained. Multiple battery cells can further be connected in series, parallel, or a combination thereof to form a battery module. Multiple battery modules can also be connected in series, parallel, or a combination thereof to form a battery pack. In some embodiments, multiple battery cells can also be directly assembled into a battery pack.

[0393] This application also provides a method for preparing a negative electrode active material, which can prepare the negative electrode active material provided in this application.

[0394] The preparation method includes the following steps: providing graphite; fusing graphite with a coating agent; and carbonizing the fused product under a protective gas atmosphere to carbonize the coating agent into a coating layer that at least covers the surface of the graphite, thereby obtaining a negative electrode active material. The negative electrode active material includes a core and a coating layer that at least partially covers the surface of the core. The core includes graphite, and in the cumulative R-value distribution curve obtained by laser microscopy confocal Raman spectroscopy in instrument scanning mode, the R-value R50, from the lower limit to 50% cumulative distribution, is 0.15-0.50.

[0395] In some embodiments, the method of 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 performing granulation and graphitization treatments to obtain graphite.

[0396] Coking feedstock typically has a large particle size, which can be reduced through crushing. In some embodiments, crushing may include two steps: coarse crushing and pulverizing. Coarse crushing breaks the coking feedstock into millimeter-sized lumps. Pulverizing reduces the particle size from the millimeter level to the tens of micrometer level. After crushing, the surface of the coking feedstock is uneven; shaping treatment can make the coking feedstock particles more rounded. Grading treatment can reduce the content of excessively large and small particles and can further adjust the particle size and particle size distribution of the coking feedstock.

[0397] The coke feedstock may include one or more of petroleum-based needle coke and coal-based needle coke. These coke feedstocks are anisotropic materials, which is beneficial for reducing the disorder of the core material, increasing the specific capacity of the core material and the overall specific capacity of the negative electrode active material, and also for improving the energy density of the battery. In some embodiments, the mass of the binder can be 6%-12% of the mass of the aggregate obtained from the grading process. In some embodiments, the mass of the binder can be 8%-10% of the mass of the aggregate obtained from the grading process. This allows the graphite to have a good secondary particle morphology.

[0398] In some embodiments, the adhesive may include bitumen.

[0399] The equipment used for granulation can include either a horizontal reactor or a vertical reactor.

[0400] In some embodiments, the granulation process can employ a stepped heating and holding process. This allows the graphite to have good secondary particle morphology and high capacity.

[0401] In some embodiments, 2-4 programmed heating platforms can be set up during the heating process.

[0402] Coke raw materials from different batches and with different raw materials usually have uneven surfaces and many defects. Graphitization treatment can significantly repair the surface defects of the material, thereby improving the concentration of Raman values ​​in the core material surface scanning mode and resulting in better consistency of graphite product performance.

[0403] The equipment used for graphitization can include any one of the following: Atchison graphitization furnace, box furnace, or internal furnace.

[0404] In some embodiments, the graphitization temperature can be between 2800℃ and 3800℃, for example, 2800℃, 2850℃, 2900℃, 3000℃, 3100℃, 3200℃, 3300℃, 3400℃, 3500℃, 3600℃, 3700℃, 3800℃, or any range of the above values. In some embodiments, the graphitization temperature can be between 2850℃ and 3300℃. The specific time for the graphitization treatment can be reasonably selected according to the equipment used.

[0405] High graphitization temperature and long graphitization time result in high specific capacity and low disorder of graphite, with a small cumulative distribution of graphite and a low R value R50 of 50%.

[0406] By selecting an appropriate graphitization temperature, batteries can possess both high energy density and good kinetic performance.

[0407] In some embodiments, the coating agent includes hard carbon coating agent and / or soft carbon coating agent.

[0408] 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 pyrolysis carbon, and carbon black.

[0409] 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 the following: petroleum coke, needle coke, carbon fiber, carbon microspheres, coking by-products, and crude oil distillation residues.

[0410] In some embodiments, the coating agent includes a solid coating agent, which is fused to a solid-solid fusion.

[0411] Solid-phase coating agents have advantages such as low cost and relatively simple process, making them easy to promote in industrial applications.

[0412] In some embodiments, the coating agent includes a liquid-phase coating agent, which is fused into a solid-liquid fusion.

[0413] In some embodiments, the coking value of the liquid phase hard carbon coating agent can be 35%-50%.

[0414] In some embodiments, the coking value of the liquid phase hard carbon coating agent is 38%-48%.

[0415] The coking value of liquid phase hard carbon coating agent refers to the percentage of the mass of residual carbon left after heating a quantitative liquid phase hard carbon coating agent sample under specified conditions relative to the mass of the liquid phase hard carbon coating agent sample. It can be tested with reference to GB / T 8727-2008.

[0416] In some embodiments, the mass of the liquid-phase hard carbon coating agent can be 0.7%-10% of the mass of graphite, for example, it can be 0.7%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any range of the above values. In some embodiments, the mass of the liquid-phase hard carbon coating agent can be 3%-7% of the mass of graphite.

[0417] As the mass percentage of liquid-phase hard carbon coating agent increases, the cumulative distribution of negative electrode active material (R50) increases to 50%, and the disorder on the surface of negative electrode active material particles increases.

[0418] When the mass ratio of liquid-phase hard carbon coating agent is within the above range, the degree of uncoated negative electrode active material can be kept within a small range. This can improve the charge exchange capacity of ions on the surface of the prepared negative electrode active material, reduce the side reactions on the surface of the prepared negative electrode active material particles, and enable the prepared negative electrode active material to have a high specific capacity. This is beneficial for the battery to have high energy density, good kinetic performance and long cycle life.

[0419] In some embodiments, the liquid-phase soft carbon coating agent includes petroleum or coal-based byproducts such as liquid-phase pitch and liquid tar.

[0420] In some embodiments, the liquid-phase hard carbon coating agent comprises a liquid resin, which is a hard carbon precursor material. When the coating layer includes hard carbon, it can give the negative electrode active material and the battery better kinetic performance.

[0421] Liquid resins can be commercially available or synthesized using methods known in the art, or obtained by mixing resin powder with a solvent until homogeneous.

[0422] In some embodiments, the viscosity of the liquid resin at 25°C can be between 150 mPa·s and 2500 mPa·s, for example, it can be 150 mPa·s, 200 mPa·s, 300 mPa·s, 400 mPa·s, 500 mPa·s, 600 mPa·s, 700 mPa·s, 800 mPa·s, 850 mPa·s, 950 mPa·s, 1050 mPa·s, 1200 mPa·s, 1400 mPa·s, 1600 mPa·s, 1800 mPa·s, 2000 mPa·s, 2250 mPa·s, 2500 mPa·s, or any range of the above values. In some embodiments, the viscosity of the liquid resin at 25°C can be between 300 mPa·s and 950 mPa·s.

[0423] The viscosity of liquid resin can be tested according to GB / T 14074-2017. The test temperature is 25℃, and the test equipment can be an NDJ-1 rotational viscometer.

[0424] When the viscosity of the liquid resin is within the above range, it can have both good fluidity and diffusivity, as well as good curing and coating effects. As a result, the liquid resin can be uniformly dispersed on the surface of graphite particles, which is beneficial to improving the coating effect, reducing the degree of uncoated state, and improving the coating uniformity on the surface of graphite particles. This is conducive to the battery having both good kinetic performance and long cycle life.

[0425] In some embodiments, the solid content of the liquid resin can be 50%-88%.

[0426] In some embodiments, the solid content of the liquid resin is 60%-85%.

[0427] The solid content of liquid-phase hard carbon coating agents can be tested using the drying method according to GB / T 14074-2017. Free components and moisture 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 after drying under specified conditions. The oven temperature is set to 150℃, and baking is performed until constant weight is achieved.

[0428] When the solid content of the liquid resin is within the above range, it can have both good fluidity and diffusivity, as well as good curing and coating effects. As a result, the liquid resin can be uniformly dispersed on the surface of graphite particles, which is conducive to improving the coating effect, reducing the degree of uncoated coating, and can also adjust the cumulative distribution of the negative electrode active material to 50% R value R50, increase the disorder of the negative electrode active material particle surface, and enhance the charge exchange capacity of ions on the surface of the negative electrode active material, which is conducive to the battery having both good dynamic performance and long cycle life.

[0429] 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 derivatives thereof. Derivatives generally refer to products derived from polymers in which hydrogen atoms or groups of atoms are replaced by other atoms or groups of atoms.

[0430] The aforementioned liquid resin is a good precursor material for hard carbon. As a liquid-phase hard carbon coating agent, it can better improve the kinetic performance of the battery and also give the battery good cycle performance.

[0431] In some embodiments, the liquid phase hard carbon coating agent includes liquid phenolic resin, wherein the solid content of the liquid phenolic resin may be 60%-82% and the weight average molecular weight may be 300-800.

[0432] In some embodiments, the solid content of the liquid phenolic resin can be 68%-78%, and the weight-average molecular weight can be 450-700.

[0433] Compared to other liquid resins, liquid phenolic resins exhibit better performance in forming hard carbon through carbonization and coking.

[0434] 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 its carbonization can have better kinetic properties, and the coating effect can be improved, reducing the degree of uncoated material. This can enhance 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.

[0435] The weight-average molecular weight of liquid phenolic resin can be determined using gel permeation chromatography. The testing instrument can be an Agilent 1290 Infinity II GPC system. Tetrahydrofuran can be used as the eluent, and polystyrene standards are used for calibration.

[0436] Liquid phenolic resin can be phenolic compounds, aldehyde compounds, etc., which are polycondensed in the presence of an alkaline catalyst. The polycondensation reaction begins to generate a liquid. The liquid phenolic resin mentioned in the embodiments of this application is a methyl phenolic resin.

[0437] Phenolic compounds may include one or more of phenol, cresol, dimethylphenol, nonylphenol, bisphenol A, bisphenol F, resorcinol, propoxyphenol, ethylphenol, and cashew phenol. In some embodiments, the phenolic compound is phenol. Aldehyde compounds may include one or more of formaldehyde, acetaldehyde, butyraldehyde, paraformaldehyde, and furfural. In some embodiments, the aldehyde compound is formaldehyde. Alkali catalysts may include one or more of sodium hydroxide, potassium hydroxide, barium hydroxide, calcium hydroxide, magnesium hydroxide, ammonia, sodium carbonate, and tertiary amines.

[0438] In some embodiments, the apparatus for solid-liquid fusion of graphite and liquid-phase hard carbon coating agent can be a fusion machine.

[0439] In some embodiments, the stirring speed of the blender can be between 300 r / min and 1000 r / min, for example, it can be 300 r / min, 350 r / min, 400 r / min, 450 r / min, 500 r / min, 550 r / min, 600 r / min, 650 r / min, 700 r / min, 750 r / min, 800 r / min, 850 r / min, 900 r / min, 1000 r / min, or any range of the above values. In some embodiments, the stirring speed of the blender can be between 450 r / min and 850 r / min.

[0440] Increasing the stirring speed of the fusion machine can improve the coating effect and reduce the degree of uncoated material, thereby enhancing the charge exchange capacity of ions on the surface of the negative electrode active material and thus improving the kinetic performance of the negative electrode active material. However, excessive stirring speed of the fusion machine can damage the outer surface structure of the core, and strong centrifugation can also cause mass loss of liquid phase hard carbon coating agent.

[0441] In some embodiments, the stirring time for solid-liquid fusion can be 4 min to 10 min, for example, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, or any range of the above values. In some embodiments, the stirring time for solid-liquid fusion can be 6 min to 8 min.

[0442] Increasing the stirring time during solid-liquid fusion is beneficial for improving the coating effect and reducing the degree of uncoated material, thereby enhancing the charge exchange capacity of ions on the surface of the negative electrode active material and thus improving the kinetic performance 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 it will also increase energy consumption.

[0443] In some embodiments, the equipment for carbonization can be a track kiln.

[0444] In some embodiments, the holding temperature for carbonization can be 900℃-1500℃, for example, 900℃, 1000℃, 1050℃, 1100℃, 1150℃, 1200℃, 1250℃, 1300℃, 1350℃, 1400℃, 1500℃, or any range of the above values. In some embodiments, the holding temperature for carbonization can be 1050℃-1350℃.

[0445] In some embodiments, the holding time for carbonization treatment can be 2h-10h, for example, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, or any range of the above values. In some embodiments, the holding time for carbonization treatment can be 5h-8h. The holding time for carbonization treatment refers to the residence time at the holding temperature.

[0446] In some embodiments, the preparation method may further include the steps of: depolymerizing, sieving and demagnetizing the carbonized material.

[0447] Deagglomeration can be performed in a deagglomeration machine. Deagglomeration eliminates the weak adhesion of the coating surface, reducing the problem of excessive agglomeration of the resulting product particles. Sieving reduces the content of large particles and fine powder in the resulting product, thereby facilitating the acquisition of the desired particle size and particle size distribution. Demagnetization reduces the content of magnetic impurities in the resulting product. Magnetic impurities increase the battery's self-discharge and reduce battery performance.

[0448] In another embodiment, this application also provides a method for preparing a negative electrode active material whose core is composed of agglomerated primary graphite particles and whose coating layer includes amorphous carbon. For ease of description, this negative electrode active material is referred to as a composite graphite material.

[0449] The method includes the following steps: S10, providing coke powder or coke powder with added kinetic carbon material raw material powder, and graphitizing the coke powder or coke powder with added kinetic carbon material raw material powder to obtain bulk particles, wherein the bulk particles are secondary particles formed by the aggregation of two or more primary particles, and the bulk particles include artificial graphite; S20, mixing the bulk particles with an organic carbon source, or mixing the bulk particles with an organic carbon source and kinetic carbon material raw material powder, and after carbonization treatment, forming a coating layer including amorphous carbon on at least a portion of the surface of the bulk particles to obtain a composite graphite material, i.e., a negative electrode active material with a core of bulk particles and a coating layer including amorphous carbon.

[0450] In at least one of steps S10 and S20, kinetic carbon material raw material powder is added. The kinetic carbon material raw material is selected from one or more of hard carbon, expanded graphite, and graphene. The interlayer spacing d002 of the (002) crystal plane of the kinetic carbon material raw material is greater than 0.335 nm.

[0451] It can be understood that the product of kinetic carbon materials after graphitization and / or carbonization is kinetic carbon material.

[0452] The air oxidation temperature T0 of the obtained composite graphite material is 630℃~730℃. The air oxidation temperature T0 is the temperature corresponding to the intersection of the two tangents at two points corresponding to 500℃ and T1 on the thermogravimetric curve of the composite graphite material. The T1 temperature is the peak temperature of the largest area peak in the differential thermogravimetric curve of the composite graphite material. The thermogravimetric curve and the differential thermogravimetric curve can be obtained by thermogravimetric analysis under the following conditions: sample mass 10±0.05mg, purge gas is air with a flow rate of 60mL / min, heating rate is 5℃ / min, and test temperature range is 35℃~950℃.

[0453] Specifically, the air oxidation temperature T0 can be determined by thermogravimetric analysis including the following steps: The composite graphite material is subjected to thermogravimetric analysis under the following conditions: a weight of 10±0.05mg, air as the purging gas with a flow rate of 60mL / min, a heating rate of 5℃ / min, and a test temperature range of 35℃~950℃. The thermogravimetric curve and the differential thermogravimetric curve are obtained. The peak temperature T1 of the maximum area peak is read from the differential thermogravimetric curve. The intersection of the two tangents at two points corresponding to the temperatures of 500℃ and T1 is determined on the thermogravimetric curve. The temperature corresponding to the intersection point on the thermogravimetric curve is the air oxidation temperature T0 of the composite graphite material.

[0454] The method for preparing the composite graphite material of this application is simple to operate, cost-controllable, and can be used for large-scale industrial production.

[0455] In some embodiments, the method of providing coke powder includes the steps of: coking coke raw material to obtain coke, and crushing, shaping and classifying the obtained coke to obtain coke powder.

[0456] In some implementations, the coke can be obtained commercially.

[0457] In some embodiments, the coke feedstock may be selected from one or more of petroleum-based and coal-based feedstocks. For example, the petroleum-based feedstock may be selected from one or more of heavy oil, residual oil, and vacuum residue, while the coal-based feedstock may primarily be selected from coal tar pitch. Heavy oil, residual oil, and vacuum residue are typically produced in petroleum refining processes, while coal tar pitch is typically produced in coal dry distillation processes.

[0458] In some embodiments, the coke includes one or more of petroleum-based non-needle coke, petroleum-based needle coke, coal-based non-needle coke, and coal-based needle coke. In some embodiments, the coke includes one or more of petroleum-based non-needle coke (e.g., petroleum calcined coke, petroleum-based green coke) and petroleum-based needle coke. In particular, the coke includes petroleum-based green coke. Using a suitable coke can enable the prepared composite graphite material to have a suitable number of end faces and defects, thereby exhibiting better active ion and electron transport properties and higher structural stability, thus improving the fast-charging performance, low-temperature power performance, and cycle performance of the battery.

[0459] In some embodiments, the coking of the coking feedstock is carried out in a delayed coking unit. The delayed coking unit includes a heating furnace and a coking tower. The delayed coking process refers to the process of rapidly heating the coking feedstock to the required coking temperature in the heating furnace, and then feeding it into the coking tower, where it undergoes preheating, cooling, and other processes to produce coke.

[0460] The coke can be crushed using equipment and methods known in the art, such as air jet mills, mechanical mills, roller mills or other crushing equipment.

[0461] The morphology of the coke powder obtained after crushing can include one or more of the following: blocky, spherical, and near-spherical. After crushing, the coke powder is then shaped to smooth out its sharp edges. The greater the degree of shaping, the closer the powder particles are to spherical shapes, which increases the number of active ion insertion / extraction sites on the surface of the composite graphite material. Shaping also benefits the subsequent granulation process, giving the secondary particles in the resulting composite graphite material higher structural stability.

[0462] Coke powder can be shaped using equipment and methods known in the art, such as shaping machines or other shaping equipment.

[0463] Crushing and shaping processes often produce a large number of excessively small particles, and sometimes excessively large particles as well. Therefore, grading can be performed as needed to remove these excessively small and large particles from the powder. Grading results in coke powder with a better particle size distribution, which facilitates subsequent granulation and coating processes. Grading can be carried out using equipment and methods known in the art, such as grading sieves, gravity classifiers, and centrifugal classifiers.

[0464] In some embodiments, the volume average particle size Dv50 of the coke powder is 6 μm to 12 μm. In some embodiments, the volume average particle size Dv50 of the coke powder is 8 μm to 10 μm.

[0465] In some embodiments, the method for providing kinetic carbon material raw material powder includes the steps of: pulverizing, shaping, and classifying the kinetic carbon material raw material to obtain kinetic carbon material raw material powder. The pulverizing, shaping, and classifying methods are the same as those used for pulverizing, shaping, and classifying coke as described above.

[0466] In some embodiments, the volume average particle size Dv50 of the kinetic carbon material raw material powder is 3 μm to 12 μm. In some embodiments, the volume average particle size Dv50 of the kinetic carbon material raw material powder is 4 μm to 9 μm.

[0467] 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. In some embodiments, the ratio is 1.2 to 1.5. When the ratio of the volume average particle size Dv50 of the coke powder to the volume average particle size Dv50 of the kinetic carbon material raw material powder is within a suitable range, the bulk particles of the composite graphite material can have a better secondary particle size distribution.

[0468] In some embodiments, the mass ratio of coke powder to kinetic carbon material raw material powder in the coke powder is 1–20:99–80. In some embodiments, the mass ratio of coke powder to kinetic carbon material raw material is 3–12:97–88. A suitable mass ratio of coke powder to kinetic carbon material raw material powder is beneficial for obtaining composite graphite materials with moderate end-face and defect contents. Consequently, the battery cells can achieve high energy density while also exhibiting significantly improved fast-charging performance and low-temperature power performance.

[0469] In some embodiments, based on the total mass of the obtained composite graphite material, 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%.

[0470] In some embodiments, the method further includes the step of adding a binder in S10. The binder is mixed with coke powder and then granulated, followed by graphitization to obtain bulk particles; or the binder is mixed with coke powder containing kinetic carbon material raw material powder and then granulated, followed by graphitization to obtain bulk particles.

[0471] Adding a binder can give the bulk particles of the composite graphite material a better degree of secondary particle size, which is beneficial to improving the active ion and electron transport performance of the composite graphite material while giving it higher structural stability.

[0472] In some embodiments, the binder content by mass percentage is 3% to 12% based on the total mass of the obtained composite graphite material. In some embodiments, the binder content by mass percentage is 5% to 8%. A binder content within a suitable range can prevent excessive particle agglomeration and ensure that the bulk particles of the composite graphite material have a good degree of secondary particle size.

[0473] In some embodiments, the binder is selected from bitumen. In some embodiments, the bitumen has a softening point of 200°C or higher.

[0474] In some embodiments, the asphalt is selected from one or more of coal tar pitch and petroleum asphalt.

[0475] In some embodiments, 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.

[0476] Granulation can be performed using equipment and methods known in the art, such as granulators. Granulators typically include a stirred reactor and a module for temperature control of the reactor. By adjusting the stirring speed, heating rate, granulation temperature, and cooling rate during the granulation process, the degree of granulation and the structural strength of the particles can be controlled, ensuring that the volume average particle size Dv50 of the bulk particles of the final composite graphite material is within the desired range.

[0477] In some embodiments, the graphitization temperature in S10 can be 2800°C to 3200°C. In some embodiments, the graphitization temperature can be 2900°C to 3100°C. Graphitization can give the bulk particles a suitable degree of graphitization, thereby giving the composite graphite material a higher specific capacity. Graphitization also reduces lattice expansion of the bulk particles during the insertion / extraction of active ions, and can effectively eliminate bulk structural defects in the bulk particles, improving the cycle performance of the battery cell.

[0478] In some implementations, the graphitization process in S10 takes 10 to 15 days.

[0479] Graphitization can be performed using equipment and methods known in the art, such as graphitization furnaces, particularly the Atchison graphitization furnace. After graphitization, a small number of excessively large particles formed during the graphitization process can be removed by sieving. This prevents excessively large particles from affecting the processing performance of the composite graphite material, such as the stability of the negative electrode slurry and the coating performance.

[0480] In some embodiments, in S10, the volume average particle size Dv50 of the obtained bulk particles is 7.5 μm to 13.5 μm. In some embodiments, the volume average particle size Dv50 of the obtained bulk particles is 9.0 μm to 11.5 μm.

[0481] In some embodiments, in step S20, the organic carbon source is selected from one or more of coal tar pitch, petroleum asphalt, phenolic resin, and coconut shell. In some embodiments, the organic carbon source is selected from petroleum asphalt. In some embodiments, the softening point of coal tar pitch or petroleum asphalt is below 250°C.

[0482] In some embodiments, based on the total mass of the obtained composite graphite material, the amount of organic carbon source added is such that the mass percentage of amorphous carbon obtained after carbonization of the organic carbon source is 1% to 8%. In some embodiments, the amount of organic carbon source added is such that the mass percentage of amorphous carbon obtained after carbonization of the organic carbon source is 2% to 5%. When the amount of organic carbon source added is within a suitable range, the composite graphite material can have both high specific capacity and high active ion solid-phase transport capability.

[0483] In some embodiments, the carbonization temperature in S20 is 700°C to 1800°C. In some embodiments, the carbonization temperature is 1000°C to 1300°C. Within a suitable range, the carbonization temperature allows the organic carbon source (and optionally a kinetic carbon material raw material) to carbonize and form a coating layer containing amorphous carbon on at least a portion of the surface of the artificial graphite.

[0484] In some embodiments, the carbonization treatment time in S20 is 1h to 6h.

[0485] In some embodiments, the preparation method of composite graphite material includes the following steps: S10, providing coke powder and kinetic carbon material raw material powder, mixing the binder with the coke powder and kinetic carbon material raw material powder, granulating the mixture, and then graphitizing it to obtain bulk particles, wherein the bulk particles are secondary particles formed by the aggregation of two or more primary particles, and the bulk particles include artificial graphite; S20, mixing the bulk particles with an organic carbon source, and after carbonization, forming a coating layer including amorphous carbon on at least a portion of the surface of the bulk particles to obtain composite graphite material.

[0486] In some embodiments, the preparation method of composite graphite material includes the following steps: S10, providing coke powder, mixing a binder with the coke powder and then granulating it, followed by graphitization treatment to obtain bulk particles, wherein the bulk particles are secondary particles formed by the aggregation of two or more primary particles, and the bulk particles include artificial graphite; S20, mixing the bulk particles with an organic carbon source and a kinetic carbon material raw material powder, and after carbonization treatment, forming a coating layer including amorphous carbon on at least a portion of the surface of the bulk particles to obtain composite graphite material.

[0487] In some embodiments, the preparation method of composite graphite material includes the following steps: S10, providing coke powder and kinetic carbon material raw material powder, mixing the binder with the coke powder and kinetic carbon material raw material powder, granulating the mixture, and then graphitizing it to obtain bulk particles, wherein the bulk particles are secondary particles formed by the aggregation of two or more primary particles, and the bulk particles include artificial graphite; S20, mixing the bulk particles with an organic carbon source and kinetic carbon material raw material powder, and after carbonization treatment, forming a coating layer including amorphous carbon on at least a portion of the surface of the bulk particles to obtain composite graphite material.

[0488] In the preparation method of this application, coke powder or coke powder containing kinetic carbon material raw material is graphitized to obtain bulk particles, and the bulk particles are secondary particles formed by the aggregation of two or more primary particles. Specifically, the coke powder obtained after crushing, shaping, and other treatments is mainly composed of single particles; morphologically, the coke powder is a primary particle (or primary particle). The bulk particles obtained after granulation and graphitization of coke powder or coke powder containing kinetic carbon material raw material are aggregates of multiple of the aforementioned primary particles; therefore, morphologically, the bulk particles are secondary particles.

[0489] In the preparation method of this application, composite graphite materials with different air oxidation temperatures T0 can be obtained by adjusting the volume average particle size Dv50 of coke powder and its addition amount, the volume average particle size Dv50 of kinetic carbon material raw material powder and its addition amount, the amount of binder added, and the amount of organic carbon source added.

[0490] Battery device

[0491] This application also provides a battery device, which includes the battery cell provided in this application embodiment. The battery cell is used to provide electrical energy. The battery device includes one or more of the following: battery module, battery pack, and energy storage battery.

[0492] Electrical appliances

[0493] This application also provides an electrical device, which includes a battery cell or a battery device provided in this application embodiment. The battery cell or battery device is used to provide electrical energy. The battery can be used as a power source for the electrical device or as an energy storage unit of the electrical device. The electrical device can be, but is not limited to, mobile devices (e.g., mobile phones, tablets, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0494] Electrical devices can choose the specific type of battery according to their usage needs, such as individual battery cells, battery modules, or battery packs.

[0495] Figure 6 is a schematic diagram of an example electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0496] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0497] Example

[0498] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0499] Example 1

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

[0501] Petroleum needle coke is crushed, shaped, and graded to obtain aggregate. The obtained aggregate is mixed with binder asphalt at a mass ratio of 100:8 and placed in a horizontal reactor for granulation. A stepped heating and holding process is used during heating, with the programmed heating platforms set to 200℃, 300℃, and 600℃ respectively. The temperature is held at 200℃ for 1 hour, 300℃ for 2 hours, and 600℃ for 2 hours, and then cooled for 3 hours before being removed from the reactor. The granulated material is then placed in an Atchison graphitization furnace for graphitization at 2900℃ for 50 hours to obtain graphite.

[0502] Graphite and liquid hard carbon coating agent were fused at a mass ratio of 100:5 using a fusion machine. The stirring speed of the fusion machine was 600 r / min, and the stirring time was 7 min. The liquid hard carbon coating agent was a commercially available liquid phenolic resin with a weight-average molecular weight of 600, a viscosity of 680 mPa·s at 25℃, and a solid content of 73%-74%. The fused product was placed in a track kiln and carbonized at 1150℃ under a nitrogen atmosphere for 370 min. After carbonization, the temperature was lowered to 50℃ before removal from the kiln. The material then underwent depolymerization, sieving, and demagnetization to obtain the negative electrode active material. The specific capacity of the negative electrode active material was 357.0 mAh / g, and the powder compaction density was 1.75 g / cm³. 3 The air oxidation temperature of the negative electrode active material is 730℃. The thickness of the coating layer of the negative electrode active material is 150nm.

[0503] (2) Preparation of negative electrode sheet

[0504] The above-mentioned negative electrode active material, thickener sodium carboxymethyl cellulose, negative electrode binder styrene-butadiene rubber (SBR), and negative electrode conductive agent Super P were mixed in a mass ratio of 96.9:1.1:1.5:0.5, and deionized water was added as solvent. The mixture was stirred evenly under the action of a vacuum mixer to prepare a negative electrode slurry.

[0505] The negative electrode slurry was uniformly coated onto both surfaces of the copper foil of the negative electrode current collector. After drying the slurry-coated negative electrode current collector at room temperature, it was transferred to an oven for further drying. Then, it was cold-pressed and slit to obtain the negative electrode sheet. The thickness of the negative electrode film layer on one side of the negative electrode current collector was 53 μm, and the density of the negative electrode film layer on one side was 0.131 g / 1540.25 mm. 2 The compaction density of the negative electrode sheet is 1.6 g / cm³. 3 The porosity of the negative electrode sheet is 30%.

[0506] (3) Preparation of positive electrode sheet

[0507] LiNi, the positive electrode active material 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. N-methylpyrrolidone (NMP) solvent is added, and the mixture is stirred under vacuum until it becomes a homogeneous and transparent system, obtaining a positive electrode slurry. The positive electrode slurry is then uniformly coated onto both surfaces of the positive electrode current collector aluminum foil. After the slurry-coated positive electrode current collector is air-dried at room temperature, it is transferred to an oven for drying, and then cold-pressed and slit to obtain the positive electrode sheet. The volume distribution and particle size Dv50 of the positive electrode active material are shown. 正2The particle size is 3.5 μm, and the main component is primary particles; the one-sided density of the positive electrode film is 0.23 g / 1540.25 mm. 2 The porosity of the positive electrode film is 25%.

[0508] (4) Preparation of electrolyte

[0509] Ethyl carbonate (EC), dimethyl carbonate (DMC), and ethyl acetate (EA) were mixed in a mass ratio of 3:2:5. The first additive, lithium difluorooxalate borate (LiDFOB), the second additive, methylene disulfonate (MMDS, Formula V), and the additive shown in Formula III, as well as the third additive, which included fluoroethylene carbonate (FEC), 1,3-propylsulfonate lactone (PS), and ethylene sulfate (DTD), were slowly added. Based on the total mass of the electrolyte, the mass content of the first additive was 1%, the mass content of the second additive was 2%, of which the mass content of MMDS in the electrolyte was 0.5%, the mass content of the additive shown in Formula III in the electrolyte was 1.5%, and the mass content of the third additive was 3.2%, of which the mass content of FEC in the electrolyte was 1%, the mass content of PS in the electrolyte was 0.7%, and the mass content of DTD in the electrolyte was 1.5%.

[0510] Next, the fully dried lithium salt LiPF6 was dissolved in a mixed solvent in a certain proportion to prepare an electrolyte. The mass content of LiPF6 in the electrolyte was 12.5%, and the conductivity of the electrolyte was 13.5 mS / cm.

[0511] (5) Preparation of the separating membrane

[0512] A 12-micron polyethylene film was selected.

[0513] (6) Preparation of batteries (full cells)

[0514] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrode. The electrode assembly is then wound up. The electrode assembly is placed in an outer package, and the prepared electrolyte is injected into the dried electrode assembly. After vacuum sealing, settling, formation, and shaping, a battery containing a wound cell is obtained.

[0515] The battery preparation methods in Examples 2-4 are basically the same as those in Example 1, except that the coating method of the negative electrode active material is adjusted. The specific preparation methods are as follows:

[0516] Example 2

[0517] (1) Preparation of negative electrode active materials

[0518] Petroleum needle coke is crushed, shaped, and graded to obtain aggregate. The obtained aggregate is mixed with binder asphalt at a mass ratio of 100:8 and placed in a horizontal reactor for granulation. A stepped heating and holding process is used during heating, with the programmed heating platforms set to 200℃, 300℃, and 600℃ respectively. The temperature is held at 200℃ for 1 hour, 300℃ for 2 hours, and 600℃ for 2 hours, and then cooled for 3 hours before being removed from the reactor. The granulated material is then placed in an Atchison graphitization furnace for graphitization at 2900℃ for 50 hours to obtain graphite.

[0519] Graphite and liquid hard carbon coating agent were fused together at a mass ratio of 100:3 using a fusion machine. The stirring speed of the fusion machine was 600 r / min, and the stirring time was 7 min. The liquid hard carbon coating agent was a commercially available liquid phenolic resin with a weight average molecular weight of 580, a viscosity of 550 mPa·s at 25℃, and a solid content of 70%-71%. The fused product was placed in a track kiln and heated to 1150℃ under a nitrogen atmosphere for carbonization treatment. The temperature was held for 6 h, and then cooled to 50℃ before being removed from the kiln. After depolymerization, sieving, and demagnetization, the negative electrode active material was obtained.

[0520] Example 3

[0521] (1) Preparation of negative electrode active materials

[0522] Petroleum needle coke is crushed, shaped, and graded to obtain aggregate. The obtained aggregate is mixed with binder asphalt at a mass ratio of 100:8 and placed in a horizontal reactor for granulation. A stepped heating and holding process is used during heating, with the programmed heating platforms set to 200℃, 300℃, and 600℃ respectively. The temperature is held at 200℃ for 1 hour, 300℃ for 2 hours, and 600℃ for 2 hours, and then cooled for 3 hours before being removed from the reactor. The granulated material is then placed in an Atchison graphitization furnace for graphitization at 2900℃ for 50 hours to obtain graphite.

[0523] Graphite and liquid hard carbon coating agent were fused together using a fusion machine at a mass ratio of 100:0.7. The stirring speed of the fusion machine was 600 r / min, and the stirring time was 7 min. The liquid hard carbon coating agent was a commercially available liquid phenolic resin with a weight average molecular weight of 580, a viscosity of 550 mPa·s at 25℃, and a solid content of 70%-71%. The fused product was placed in a track kiln and heated to 1150℃ under a nitrogen atmosphere for carbonization treatment. The temperature was held for 6 h, and then cooled to 50℃ before being removed from the kiln. After depolymerization, sieving, and demagnetization, the negative electrode active material was obtained.

[0524] Example 4

[0525] (1) Preparation of negative electrode active materials

[0526] Petroleum coke is crushed, shaped, and graded to obtain aggregate. The obtained aggregate is mixed with binder asphalt at a mass ratio of 100:8 and placed in a horizontal reactor for granulation. A stepped heating and holding process is used during heating, with the programmed heating platforms set to 200℃, 300℃, and 600℃ respectively. The temperature is held at 200℃ for 1 hour, 300℃ for 2 hours, and 600℃ for 2 hours, and then cooled for 3 hours before being removed from the reactor. The granulated material is then placed in an Atchison graphitization furnace for graphitization at 2900℃ for 50 hours to obtain graphite.

[0527] Graphite and a solid coating agent were mixed in a fusion machine at a mass ratio of 100:3. The solid coating agent was asphalt with a softening point of 270℃. The mixed product was placed in a track kiln and heated to 1150℃ under a nitrogen atmosphere for carbonization treatment. The temperature was held for 6 hours, and then cooled to 50℃ before being removed from the kiln. After depolymerization, sieving, and demagnetization, the negative electrode active material was obtained.

[0528] Example 5

[0529] The battery preparation method in Example 5 is basically the same as that in Example 1, except that the preparation method of the negative electrode active material is adjusted: The specific preparation method is as follows:

[0530] (1) Preparation of negative electrode active materials

[0531] Petroleum residue oil was subjected to delayed coking at 490℃~510℃ to obtain petroleum non-needle coke raw coke; the raw coke was crushed, shaped and graded to obtain coke powder with a volume average particle size Dv50 of 9.5μm, which was used as the main raw material for composite graphite materials.

[0532] For the interlayer spacing d 002 Expanded graphite with a particle size of 0.3363 nm (expansion ratio of 180) was pulverized, shaped and classified to obtain expanded graphite powder with a volume average particle size Dv50 of 7.5 μm.

[0533] Coke powder and expanded graphite powder were mixed, then mixed with coal tar pitch as a binder, and then granulated. The resulting granules had a volume average particle size (Dv50) of approximately 13 μm. The granulated product was placed in a graphite crucible, which was then placed in an Atchison graphitization furnace. Resistance material was filled around the graphite crucible, and an electric current was passed through the resistance material to generate heat. Graphitization was then performed at approximately 3000°C to obtain bulk particles.

[0534] The obtained bulk particles are mixed with organic carbon source petroleum asphalt and then carbonized in a track kiln at a maximum temperature of about 1150°C for about 4 hours to form a coating layer on at least a portion of the surface of the bulk particles, thus obtaining a composite graphite material.

[0535] Based on the total mass of the obtained composite graphite material, the added expanded graphite powder accounted for 8% of the total mass, the binder accounted for 6%, and the organic carbon source accounted for 3% of the total mass of amorphous carbon obtained after carbonization. The compacted density of the composite graphite material powder was 1.64 g / cm³. 3 The specific capacity is 355.8 mAh / g. The volume distribution particle size Dv50 of the composite graphite material is 13 μm, the volume distribution particle size Dv50 of the primary particles in the secondary particles is 8 μm, and the air oxidation temperature T0 of the negative electrode active material is 694℃.

[0536] Example 6

[0537] The battery preparation method in Example 6 is basically the same as that in Example 1, except that the preparation method of the negative electrode active material is adjusted: The specific preparation method is as follows:

[0538] (1) Preparation of negative electrode active materials

[0539] Petroleum needle coke is crushed, shaped, and graded to obtain aggregate. The obtained aggregate is mixed with binder asphalt at a mass ratio of 100:8 and placed in a horizontal reactor for granulation. A stepped heating and holding process is used during heating, with the programmed heating platforms set to 200℃, 300℃, and 600℃ respectively. The temperature is held at 200℃ for 1 hour, 300℃ for 2 hours, and 600℃ for 2 hours, and then cooled for 3 hours before being removed from the reactor. The granulated material is then placed in an Atchison graphitization furnace for graphitization at 2850℃ for 45 hours to obtain graphite.

[0540] Graphite and a solid coating agent were mixed in a fusion machine at a mass ratio of 100:5. The solid coating agent was asphalt with a softening point of 270℃. The mixed product was placed in a track kiln and heated to 1150℃ under a nitrogen atmosphere for carbonization treatment. The temperature was held for 6 hours, and then cooled to 50℃ before being removed from the kiln. After depolymerization, sieving, and demagnetization, the negative electrode active material was obtained.

[0541] The battery preparation methods in Examples 7-8 are basically the same as those in Example 1, except that the preparation method of the negative electrode sheet is adjusted: the specific preparation methods are as follows:

[0542] Example 7

[0543] Method for preparing negative electrode sheet:

[0544] The first negative electrode active material, binder SBR, thickener sodium carboxymethyl cellulose (CMC-Na), conductive agent carbon black (Super-P) were added to a mixing tank in a certain order at a mass ratio of 96.2:1.8:1.2:0.8 and deionized water to prepare negative electrode slurry 1.

[0545] The second negative electrode active material, binder SBR, thickener sodium carboxymethyl cellulose (CMC-Na), conductive agent carbon black (Super-P) were added to a mixing tank in a certain order at a weight ratio of 96.2:1.8:1.2:0.8 and deionized water to prepare negative electrode slurry 2.

[0546] The preparation methods of the first negative electrode active material and the second negative electrode active material are basically the same as those of the negative electrode active material in Example 1. The difference lies in the particle size consistency. 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 is less than that of the second negative electrode film.

[0547] A negative electrode slurry 1 and negative electrode slurry 2 are simultaneously extruded using a dual-cavity coating device. Negative electrode slurry 1 is coated onto a copper foil current collector to form a first negative electrode film layer, and negative electrode slurry 2 is coated onto the first negative electrode film layer to form a second negative electrode film layer.

[0548] The single-sided density of the negative electrode film is 0.13 mg / 1540.25 mm. 2 .

[0549] Example 8

[0550] Method for preparing negative electrode sheet:

[0551] Based on the preparation method of the negative electrode active material in Example 1, a 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 50000N pressure was 1.98 g / cm³. 3 Using the negative electrode active material prepared in Example 1 as the second negative electrode active material, its powder compaction density under 50000N pressure is 1.75 g / cm³. 3 The compacted density of the first negative electrode active material is greater than that of the second negative electrode active material.

[0552] The first negative electrode active material, binder SBR, thickener sodium carboxymethyl cellulose (CMC-Na), conductive agent carbon black (Super-P) were added to a mixing tank in a certain order at a mass ratio of 96.2:1.8:1.2:0.8 and deionized water to prepare negative electrode slurry 1.

[0553] The second negative electrode active material, binder SBR, thickener sodium carboxymethyl cellulose (CMC-Na), conductive agent carbon black (Super-P) were added to a mixing tank in a certain order at a weight ratio of 96.2:1.8:1.2:0.8 and deionized water to prepare negative electrode slurry 2.

[0554] A negative electrode slurry 1 and negative electrode slurry 2 are simultaneously extruded using a dual-cavity coating device. Negative electrode slurry 1 is coated onto a copper foil current collector to form a first negative electrode film layer, and negative electrode slurry 2 is coated onto the first negative electrode film layer to form a second negative electrode film layer.

[0555] The single-sided density of the negative electrode film is 0.13 g / 1540.25 mm. 2 .

[0556] Example 9

[0557] The battery preparation method in Example 9 is basically the same as that in Example 1, except that the preparation methods of the positive electrode active material and the positive electrode sheet are adjusted. Specifically, the preparation method of the positive electrode active material is as follows:

[0558] 1) Preparation of precursors for positive electrode active materials

[0559] Nickel sulfate, manganese sulfate, and cobalt sulfate were added to deionized water to prepare a mixed solution, wherein the molar ratio of nickel, cobalt, and manganese was Ni:Co:Mn = 55.6:11:33.4. 0.4 mol / L ammonia and 1 mol / L sodium hydroxide aqueous solution were added to the mixed solution to adjust the pH of the reaction system to 11.3. The reaction was carried out at 40℃ and 600 rpm with stirring. Inert nitrogen gas was purged during the reaction for protection. After the reaction was complete, the solid product was washed with deionized water and then dried at 100℃ to obtain the positive electrode active material precursor Ni. 0.556 Co 0.11 Mn 0.334 (OH)2.

[0560] 2) Preparation of active substance particle precursor 1

[0561] Lithium carbonate (Li2CO3) and Ni, the precursor of the positive electrode active material, are used. 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) in the cathode active material precursor, the amount of lithium carbonate added is such that the molar ratio of lithium to Me is Li:Me = 1.06:1; the amount of zirconium oxide added is such that the molar ratio of zirconium to Me is Zr:Me = 2.031 × 10⁻⁶. -3:1.

[0562] The mixture was placed in a tube furnace and sintered for 13 hours at a programmed temperature increase of 5°C / min to 940°C under air atmosphere. It was then cooled to room temperature with the furnace and subsequently sintered in an air jet mill (Shenyang Aircraft Corporation, 40m³). 3 The 2mm particles were crushed at a crushing air pressure of 0.35MPa and a feeding speed of 300Kg / h to obtain active substance particle precursor 1.

[0563] 3) Preparation of active substance particle precursor 2

[0564] Cobalt hydroxide was added to precursor 1 of the above-obtained active material particles. 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 cobalt hydroxide added was such that the molar ratio of cobalt to Me was 1.14 × 10⁻⁶. -2 1. After thorough mixing, the mixture is sintered at 700°C for 5 hours in air at a programmed temperature of 5°C / min, and then cooled to room temperature in the furnace to obtain the active material particle precursor 2.

[0565] 4) Preparation of low-cobalt cathode active materials

[0566] The obtained active material particle precursor 2 was subjected to tempering treatment at a temperature of 500℃ for 5 hours to obtain the 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.

[0567] The prepared positive electrode active material, conductive carbon black SP and binder polyvinylidene fluoride (PVDF) were dispersed in solvent N-methylpyrrolidone (NMP) at a weight ratio of 18:1:1 and mixed evenly to obtain a positive electrode slurry. The positive electrode slurry was evenly coated on the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet was obtained.

[0568] The battery preparation methods in Examples 10-13 are basically the same as those in Example 1, except that the composition and ratio of the electrolyte are adjusted, thereby adjusting the lithium-ion conductivity of the electrolyte.

[0569] Example 10

[0570] The electrolyte was prepared by mixing ethylene carbonate (EC) and methyl acetate (MA) at a mass ratio of 3:7, then dissolving fully dried lithium salt LiPF6 in the mixed solvent at a ratio of 1 mol / L, adding additives as described in Example 1, and preparing an electrolyte with a lithium-ion conductivity of 20 mS / cm.

[0571] Example 11

[0572] The difference between the preparation method of the electrolyte and that in Example 1 is that the first additive was not added to the electrolyte.

[0573] Example 12

[0574] The difference between the preparation method of the electrolyte and that in Example 1 is that no second additive was added to the electrolyte.

[0575] Example 13

[0576] The preparation method of the electrolyte is basically the same as that of the electrolyte solvent in Example 1. The difference is that the ratio of solvent in the electrolyte is 3:2:2.5:2.5.

[0577] Example 14

[0578] 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 aggregation of primary particles, with the average particle size of the primary particles being 200nm.

[0579] Example 15

[0580] The preparation method of Example 15 is basically the same as that of Example 1, except that the types and mass contents of electrolyte salts 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 difluorosulfonylimide is 4.62%.

[0581] Examples 16 and 17 are prepared using methods basically the same as those in Example 1, the difference being in the preparation method of the battery cells:

[0582] Example 16

[0583] Battery (full cell) fabrication:

[0584] The positive electrode (87mm wide and 240mm long), separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation, thus obtaining an electrode assembly. The electrode assembly is placed in an outer packaging, and the prepared electrolyte is injected into the dried electrode assembly. After vacuum sealing, settling, formation, and shaping, a battery containing stacked cells is obtained.

[0585] Example 17

[0586] Battery (full cell) fabrication:

[0587] The positive electrode (positive current collector width 102mm, length 240mm), separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation, thus obtaining an electrode assembly. The electrode assembly is placed in an outer packaging, and the prepared electrolyte is injected into the dried electrode assembly. After vacuum sealing, settling, formation, and shaping processes, a battery containing stacked cells is obtained.

[0588] The battery preparation methods for Comparative Examples 1-2 are basically the same as those for Example 1, except that the coating method of the negative electrode active material is adjusted. The specific preparation methods are as follows:

[0589] Comparative Example 1

[0590] Except for the different preparation process of the negative electrode active material, the battery preparation process is the same as that in Example 1.

[0591] (1) Preparation of negative electrode active materials

[0592] Petroleum needle coke is crushed, shaped, and graded to obtain aggregate. The obtained aggregate is mixed with binder asphalt at a mass ratio of 100:8 and placed in a horizontal reactor for granulation. A stepped heating and holding process is used during heating, with the programmable heating platforms set to 200℃, 300℃, and 600℃ respectively. The temperature is held at 200℃ for 1 hour, 300℃ for 2 hours, and 600℃ for 2 hours, and then cooled for 3 hours before being removed from the reactor. The granulated material is placed in an Atchison graphitization furnace for graphitization at 2900℃ for 50 hours. After screening and demagnetization, graphite is obtained, which is used as the negative electrode active material.

[0593] Comparative Example 2

[0594] Except for the different preparation process of the negative electrode active material, the battery preparation process is the same as that in Example 1.

[0595] (1) Preparation of negative electrode active materials

[0596] Petroleum needle coke is crushed, shaped, and graded to obtain aggregate. The obtained aggregate is mixed with binder asphalt at a mass ratio of 100:8 and placed in a horizontal reactor for granulation. A stepped heating and holding process is used during heating, with the programmed heating platforms set to 200℃, 300℃, and 600℃ respectively. The temperature is held at 200℃ for 1 hour, 300℃ for 2 hours, and 600℃ for 2 hours, and then cooled for 3 hours before being removed from the reactor. The granulated material is then placed in an Atchison graphitization furnace for graphitization at 2850℃ for 45 hours to obtain graphite.

[0597] Graphite and a solid coating agent were mixed in a fusion machine at a mass ratio of 100:6.3. The solid coating agent was asphalt with a softening point of 270℃. The mixture was placed in a track kiln and heated to 1150℃ under a nitrogen atmosphere for carbonization treatment. The temperature was held for 6 hours, and then cooled to 50℃ before being removed from the kiln. After depolymerization, sieving, and demagnetization, the negative electrode active material was obtained.

[0598] The battery preparation method of Comparative Example 3 is basically the same as that of Example 1, except that the electrolyte formulation is adjusted, specifically:

[0599] Comparative Example 3

[0600] Except for the different preparation of the electrolyte, the battery manufacturing process is the same as in Example 1.

[0601] (1) Preparation of electrolyte

[0602] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent; LiPF6 was uniformly dissolved in the above organic solvent to obtain an electrolyte, wherein the concentration of LiPF6 was 1 mol / L and the conductivity of the electrolyte was 8 mS / cm.

[0603] Performance testing

[0604] 10%-80% SOC charging time test

[0605] The batteries of the examples and comparative examples 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, the batteries were charged at a constant current rate of 1C to a voltage of 4.4V at 35°C, then charged at a constant voltage rate to a current of ≤0.05C, left to stand for 5 minutes, and then discharged at a constant current rate of 0.33C to a voltage of 2.5V. The actual capacity was recorded as C0. Then, the battery was sequentially charged at constant current rates of 1.0C0, 1.3C0, 1.5C0, 1.8C0, 2.0C0, 2.3C0, 2.5C0, 3.0C0, 3.5C0, 4C0, 4.5C0, and 5C0 until the full battery charging cutoff voltage of 4.4V or the negative terminal cutoff potential of 0V (whichever comes first). After each charging, the battery was discharged at 1C0 until the full battery discharge cutoff voltage of 2.5V. The state of charge (SOC) was recorded at different charging rates until 10%, 20%, 30%, ..., 80%. Charge, or State of Charge, refers to the negative electrode potential at which the battery is fully discharged (SOC = 0) and fully charged (SOC = 100%). By plotting the charge rate-negative electrode potential curves for different SOC states and performing linear fitting, the charge rate corresponding to a negative electrode potential of 0V under different SOC states is obtained. This charge rate is the charging window for that SOC state, denoted as C(10% SOC), C(20% SOC), C(30% SOC), C(40% SOC), C(50% SOC), C(60% SOC), C(70% SOC), and C(80% SOC). The maximum charge rate corresponding to this state of charge is then obtained, i.e., the fast charging window. 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).

[0606] Initial DC internal resistance (DCR) test of individual battery cells:

[0607] At 25℃, the battery is charged at a constant current of 0.5C to 4.4V, and then charged at a constant voltage until the current is 0.05C. The battery is then discharged at a constant current of 0.5C for 30 minutes to adjust the battery to 50% SOC. The voltage of the battery at this time is recorded as U1. The battery is then discharged at a constant current of 4C for 30 seconds, with a sampling time of 0.1 seconds. The voltage at the end of the discharge is recorded as U2. The initial DCR of the battery is represented by the discharge DCR at 50% SOC. The initial DCR of the battery is (U1-U2) / 4C.

[0608] High temperature cycle life test

[0609] At 45°C, the batteries of the examples and comparative examples were charged to 4.4V with a constant current of 1C, then charged at a constant voltage of 4.4V until the current dropped to 0.05C. After resting for 5 minutes, they were discharged to 2.5V with a constant current of 1C. This was the first charge / discharge cycle of the battery, and the discharge capacity of this cycle was recorded as the discharge capacity (C1) of the battery in the first cycle. The above steps were repeated for the same battery. The process capacity (Cn) of the battery after the nth cycle was recorded. The capacity retention rate after n cycles was calculated as Cn / C1 × 100%. The number of cycles in which the capacity retention rate was 80% was recorded.

[0610] Fast charging cycle life test

[0611] First, a fast charging window needs to 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 at which the theoretical capacity is completely discharged within 1 hour). Specifically, 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 rate to a current ≤0.05C, left to stand for 5 minutes, and then discharged at a constant current rate of 0.33C to a voltage of 2.5V. Its actual capacity is recorded as C0. Then, the battery was sequentially charged at constant current rates of 1.0C0, 1.3C0, 1.5C0, 1.8C0, 2.0C0, 2.3C0, 2.5C0, 3.0C0, 3.5C0, 4C0, 4.5C0, and 5C0 until the full battery charging cutoff voltage of 3.65V or the negative terminal cutoff potential of 0V (whichever comes first). After each charging, the battery was discharged at 1C0 until the full battery discharge cutoff voltage of 2.1V. The state of charge (SOC) was recorded at different charging rates until 10%, 20%, 30%, ..., 80%. Charge, or State of Charge, refers to the negative electrode potential at which the battery is fully discharged (SOC = 0) and fully charged (SOC = 100%). By plotting the charge rate-negative electrode potential curves for different SOC states and performing linear fitting, the charge rate corresponding to a negative electrode potential of 0V under different SOC states is obtained. This charge rate is the charging window for that SOC state, denoted as C(10% SOC), C(20% SOC), C(30% SOC), C(40% SOC), C(50% SOC), C(60% SOC), C(70% SOC), and C(80% SOC). The maximum charge rate corresponding to this state of charge is then obtained, i.e., the fast charging window.

[0612] At 25℃, charging was performed using the obtained fast charging window distribution. The charging process involved charging at C(10% SOC) to 10% SOC, C(20% SOC) to 20% SOC, C(30% SOC) to 30% SOC, C(40% SOC) to 40% SOC, C(50% SOC) to 50% SOC, C(60% SOC) to 60% SOC, C(70% SOC) to 70% SOC, and C(80% SOC) to 80% SOC. The charge was then increased to 100% SOC at 0.33C. After resting for 10 minutes, the charge was increased to 2.1V at 0.33C DC. The discharge capacity at this point was recorded as C1. The temperature rise at the tab was monitored during this charging process. The above process was repeated, and the discharge capacity for each cycle was recorded as Cn. The cycle capacity retention rate was calculated as Cn / C1. The number of cycles when the cycle capacity retention rate dropped to 80% SOH was recorded.

[0613] The fast charging time, DCR and cycle life test methods in Example 14 are basically the same as those described above. The difference is that the upper limit of the charging cutoff voltage in Example 14 is adjusted to 4.25V.

[0614] Experimental results

[0615] Table 1

[0616] As can be seen from the comparison between the examples and the comparative examples, 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 of the negative electrode active material in the laser microscopy confocal Raman spectroscopy instrument scanning mode has an R value R50 of 0.15-0.50 with a cumulative distribution of 50%, which is beneficial to balance the fast charging performance and cycle life of the battery cell.

[0617] Table 2

[0618] As can be seen from the comparison between Examples 1-3 and Example 6, 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 of the negative electrode active material obtained in the laser microscopy confocal Raman spectroscopy instrument scanning mode shows that the cumulative distribution of 50% of the R values ​​R50 is 0.15-0.50. In addition, the proportion of R values ​​less than or equal to 0.11 in the R values ​​of the negative electrode active material is less than or equal to 10%. This can achieve optimization of another performance while maintaining the battery's good fast charging level or cycle performance.

[0619] Table 3

[0620] As can be seen from the comparison between Example 1 and Example 7, the porosity of the first negative electrode film layer disposed on the surface of the negative electrode current collector is less than that of the second negative electrode film layer disposed on the side of the first negative electrode film layer away from the negative electrode current collector, which is beneficial to simultaneously improve fast charging performance and cycle performance.

[0621] Table 4

[0622] As can be seen from the comparison between Example 1 and Example 8, the compaction density of the lower layer powder is greater than that of the upper layer powder, which is beneficial to simultaneously improving fast charging performance and cycle performance.

[0623] Table 5

[0624] As can be seen from the comparison between Example 9 and Example 1, 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.

[0625] Table 6

[0626] As can be seen from the comparison between Example 13 and Examples 1 and 10, the electrolyte contains both ethyl acetate and methyl acetate, which can further improve the fast charging performance of the battery while maintaining a good cycle life.

[0627] As can be seen from the comparison between Example 1 and Examples 11 and 12, the electrolyte contains both the first additive and the second additive, which can further improve the cycle performance of the battery while maintaining its good fast charging performance.

[0628] Table 7

[0629] As can be seen from the comparison between Example 5 and Example 4, the negative electrode active material also includes the interlayer spacing d of the (002) crystal plane. 002 Dynamic carbon materials with a wavelength greater than 0.335 nm are beneficial for improving the dynamic performance of batteries.

[0630] Table 8

[0631] As can be seen from the comparison between Example 1 and Example 14, the positive electrode active material includes low nickel lithium oxide, the Dv50 of the positive electrode active material is 2μm-5μm, and the positive electrode active material mainly includes non-agglomerated primary particles, which is beneficial to improve the fast charging performance of the battery cell while improving the cycle life of the battery cell.

[0632] As can be seen from the comparison between Example 14 and Example 1, the positive electrode active material includes a high-nickel lithium oxide, the Dv50 of the positive electrode active material is 6μm-15μm, and the positive electrode active material mainly includes secondary particles formed by the 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 improve the fast charging performance of the battery cell while reducing the DC impedance of the battery cell and improving the power performance of the battery cell.

[0633] Table 9

[0634] As can be seen from the comparison between Example 1 and Example 15, the electrolyte salt in the electrolyte includes lithium bisfluorosulfonylimide, which is beneficial to improve the fast charging performance of the battery cell while improving the cycle life of the battery cell.

[0635] Table 10

[0636] As can be seen from the comparison between Example 1 and Examples 16 and 17, the battery cell includes stacked cells and the width of the positive electrode current collector is 60mm-110mm, which is beneficial to improving the fast charging cycle life of the battery cell.

[0637] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

A battery cell characterized by The positive electrode sheet, the negative electrode sheet, and an electrolyte solution; The lithium ion conductivity of the electrolyte solution is greater than or equal to 10 mS / cm. The negative electrode sheet 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 coated on the surface of the core part, the core part comprises graphite, and the negative electrode active material has an R value cumulative distribution curve obtained by a laser microscopic confocal Raman spectrometer in a face scanning mode, wherein the R value R50 corresponding to a cumulative distribution of 50% is 0.15-0.

50. In the R values of the obtained negative electrode active material, the proportion of the number of R values less than or equal to 0.11 is less than or equal to 15%. The battery cell of claim 1, wherein In the R values of the obtained negative electrode active material, the proportion of the number of R value less than or equal to 0.11 is less than or equal to 10%. The battery cell of claim 1, wherein In the R values of the obtained negative electrode active material, the proportion of the number of the R values less than or equal to 0.11 is less than or equal to 6%. The battery cell of claim 1, wherein The negative electrode active material has an R value cumulative distribution curve obtained by a laser microscopic confocal Rama spectrometer in a face scanning mode, wherein the R value R50 corresponding to a cumulative distribution rate of 50% is 0.15-0.30, and in the R values of the obtained negative electrode active material, the proportion of the number of R values equal to or less than 0.11 is less than or equal to 10%. The battery cell of claim 1, wherein The negative electrode active material has an R value cumulative distribution curve obtained by a laser microscopic confomal Raman spectrometer in a face scanning mode, wherein the R value R50 corresponding to a cumulativedistribution rate of 50% is 0.30-0.50, and in the R values of the obtained negative electrode active material, the proportion of the numberof R values equal to or less than 0.11 is less than or equal to 15%. The battery cell of claim 1, wherein The electrolyte solution comprises an organic solvent, and the organic solvent comprises one or more of a carboxylic acid ester solvent, a nitrile solvent, and a carbonate solvent. The battery cell according to claim 6, characterized in that The carboxylic acid ester solvent comprises 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 comprises one or more of acetonitrile, monofluoroacetonitrile, difluoroacetonitrile, and trifluoroacetonitrile; and / or The carbonate solvent comprises one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. The battery cell according to claim 7, characterized in that The carboxylic acid ester solvent comprises one or more of ethyl acetate and methyl acetate. The battery cell according to claim 6, characterized in that The organic solvent comprises 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. The battery cell according to claim 9, characterized in that The mass content of dimethyl carbonate is 30%-90% based on the total mass of the organic solvent. The battery cell according to claim 6, characterized in that The organic solvent comprises one or more of ethyl acetate and methyl acetate and a carbonate solvent. The battery cell of claim 11, wherein The total mass content of ethyl acetate and methyl acetate is 5%-80%, and the mass content of the carbonate solvent is 5%-90% based on the total mass of the organic solvent. The battery cell according to claim 6, 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. The battery cell of claim 13, wherein The mass content of methyl acetate is 5%-50% based on the total mass of the organic solvent. The battery cell of claim 1, wherein The electrolyte comprises an electrolyte salt, and the electrolyte salt comprises lithium difluorophosphate, and the mass content of lithium difluorophosphate is 3%-10% based on the total mass of the electrolyte. The battery cell of claim 15, wherein The mass content of lithium difluorophosphate is 20%-80% based on the total mass of the electrolyte salt in the electrolyte. The battery cell of claim 16, wherein The mass content of lithium difluorophosphate is 30%-70% based on the total mass of the electrolyte salt in the electrolyte. The battery cell of claim 1, wherein The battery monomer comprises a laminated core, the positive electrode sheet comprises a positive electrode current collector, the positive electrode current collector comprises a positive electrode current collecting part and a positive electrode tab arranged on at least one side of the positive electrode current collecting part, and the width of the positive electrode current collecting part is 60 mm-110 mm. The battery cell of claim 18, wherein The width of the positive electrode current collecting part is 62 mm-98 mm. The battery cell according to claim 18 or 19, characterized in that The length of the positive electrode current collecting part in the laminated core is 100 mm-700 mm. The battery cell of claim 20, wherein The length of the positive electrode current collecting part in the laminated core is 200 mm-600 mm. The battery cell of claim 1, wherein The electrolyte comprises a first additive, and the first additive comprises one or more of fluorine-containing phosphate and borate. The battery cell of claim 22, wherein The fluorine-containing phosphate comprises one or more of monofluorophosphate and difluorophosphate; and the fluorine-containing phosphate comprises an alkali metal. The battery cell of claim 23, wherein The fluorine-containing phosphate comprises one or more of lithium salt, sodium salt and potassium salt. The battery cell of claim 22, wherein The borate comprises at least one of tetrafluoroborate, bisoxalate borate and fluorine-containing oxalate borate; and the borate comprises an alkali metal. The battery cell of claim 25, wherein The borate comprises one or more of lithium salt, sodium salt and potassium salt. The battery cell of claim 1, wherein The electrolyte comprises a second additive, and the second additive comprises one or more of sulfonate compound and ethylene sulfate compound. The battery cell of claim 27, wherein The vinyl sulfate compound includes One or more of the following; and / or the sulfonate compounds include The second additive comprises at least one of the following compounds: a sulfonate compound, an ethylene sulfate compound, a phosphonate compound, a borate compound, a halide compound, a carbonate compound, a nitrate compound, a sulfate compound, a phosphate compound, a carboxylate compound, a halide compound, a carbonate compound, a nitrate compound, a sulfate The battery cell of claim 1, wherein The air oxidation temperature T0 of the negative electrode active material is 630 ℃-730 ℃, wherein the air oxidation temperature T0 is the temperature corresponding to the intersection of two tangent lines at two points on the thermogravimetric curve of the negative electrode active material, the two points corresponding to 500 ℃ and T1 temperature respectively, the T1 temperature is the peak top temperature of the maximum area peak in the differential thermogravimetric curve of the negative electrode active 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, purging gas is air and gas flow rate is 60 mL / min, temperature rising rate is 5 ℃ / min, and test temperature range is 35 ℃-950 ℃. The battery cell of claim 1, wherein The core of the negative electrode active material is a secondary particle in which primary particles of graphite are aggregated, the coating layer of the negative electrode active material includes amorphous carbon, and the negative electrode active material further includes a kinetic carbon material; the interlayer spacing d 002 > 0.335 nm. The battery cell of claim 30, wherein The interlayer spacing of the (002) crystal plane of the kinetic carbon material is 0.3355 nm-0.337 nm. The battery cell of claim 30, wherein The kinetic carbon material comprises one or more of hard carbon, expanded graphite and graphene. The battery cell of claim 30, wherein The kinetic carbon material is located in the core and / or the coating layer. The battery cell of any one of claims 30-33, wherein The mass percentage content of the kinetic carbon material is 1%-30% based on the total mass of the negative electrode active material. The battery cell of claim 34, wherein The mass percentage content of the kinetic carbon material is 8%-15% based on the total mass of the negative electrode active material. The battery cell of claim 1, wherein The negative electrode active material comprises 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. The battery cell of claim 1, wherein The negative active material comprises un-agglomerated primary particles, and a volume distribution particle size Dv50 of the negative active material is 5-13 μm. The battery cell of claim 1, wherein The core of the negative active material comprises artificial graphite. The battery cell of claim 1, wherein The negative active material satisfies one or more of the following conditions: (1) a mass of the coating layer is 0.3%-5% of a mass of the core; (2) an average thickness of the coating layer is 100-300 nm; (3) the coating layer is arranged on 90%-100% of a surface of the core. The battery cell of claim 1, wherein The negative film layer comprises a first negative film layer arranged on a surface of the negative current collector and a second negative film layer arranged on a side of the first negative film layer away from the negative current collector, and a porosity of the second negative film layer is greater than a porosity of the first negative film layer. The battery cell of claim 40, wherein The first negative film layer comprises a first negative active material, and a particle size consistency of the first negative active material is 0.4-0.6; and the second negative film layer comprises a second negative active material, and a particle size consistency of the second negative active material is 0.25-0.

45. The battery cell of claim 1, wherein The negative film layer comprises a first negative film layer arranged on a surface of the negative current collector and a second negative film layer arranged on a side of the first negative film layer away from the negative current collector, and a powder compaction density of a negative active material in the second negative film layer under a pressure of 50,000 N is less than a powder compaction density of a negative active material in the first negative film layer under a pressure of 50,000 N. The battery cell of claim 1, wherein The negative active material further comprises a silicon-based material, the single-sided surface density of the negative electrode film layer is 0.06 g / 15 40.25 mm 2 -0.15 g / 15 40.25 mm 2 . The battery cell of claim 1, wherein The negative active material further comprises a silicon-based material, and a single-side average thickness of the negative film layer is 30-80 μm. The battery cell of claim 1, wherein The negative electrode sheet satisfies at least one of the following conditions: (1) the single side surface density of the negative electrode film layer is 0.08 g / 1540.25 mm 2 -0.20 g / 1540.25 mm 2 ; (2) the compaction density of the negative electrode plate is 1.2 g / cm 3 -1.9 g / cm 3 ; (3) a single-side average thickness of the negative film layer is 30-150 μm; (4) a porosity of the negative electrode sheet is 20%-60%. The battery cell of claim 45, wherein The negative electrode sheet satisfies at least one of the following conditions: (1) the single side surface density of the negative electrode film layer is 0.10 g / 15 40.25 mm 2 -0.16 g / 15 40.25 mm 2 ; (2) the compaction density of the negative electrode plate is 1.2 g / cm 3 -1.65 g / cm 3 ; (3) a single-side average thickness of the negative film layer is 30-80 μm; (4) a porosity of the negative electrode sheet is 25%-40%. The battery cell of claim 1, wherein The positive electrode sheet comprises a positive current collector and a positive film layer arranged on at least one side of the positive current collector, the positive film layer comprises a positive active material, the positive active material comprises lithium-containing phosphate, the positive active material comprises un-agglomerated primary particles, and the positive active material satisfies at least one of the following conditions: (1) the volume distribution particle size Dv50 of the positive electrode active material 正1 satisfies: 0.3 pm ≤ Dv50 正1 ≤ 2 pm; (2) the average particle diameter of primary particles of the positive electrode active material satisfies: 50 nm ≤ D 正1 ≤ 300 nm. The battery cell of claim 1, wherein The positive electrode tab 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 including a positive electrode active material, the positive electrode active material including a lithium-containing transition metal oxide, and the positive electrode active material having a volume distribution particle size Dv50 正2 satisfying: 2 pm ≤ Dv50 正2 ≤ 15 pm. The battery cell of claim 48, wherein The positive electrode active material includes lithium nickel cobalt manganese oxide, the Dv50 of the positive electrode active material is 6 μm-15 μm, the positive electrode active material includes secondary particles formed by agglomeration of primary particles, and the average particle size of the primary particles in the secondary particles is 0.1 μm-1.5 μm. 正2 The positive electrode active material includes lithium nickel cobalt manganese oxide, the Dv50 of the positive electrode active material is 6 μm-15 μm, the positive electrode active material includes secondary particles formed by agglomeration of primary particles, and the average particle size of the primary particles in the secondary particles is 0.1 μm-1.5 μm. The battery cell of claim 49, wherein A Dv50 of the positive active material is 8-12 μm. The battery cell of claim 48, wherein The positive electrode active material includes lithium nickel cobalt manganese oxide, the Dv50 of the positive electrode active material is 2 pm - 5 pm, and the positive electrode active material includes unagglomerated primary particles. 正2 The positive electrode active material includes lithium nickel cobalt manganese oxide, the Dv50 of the positive electrode active material is 2 pm - 5 pm, and the positive electrode active material includes unagglomerated primary particles. The battery cell of claim 51, wherein A Dv50 of the positive active material is 2.5-4.5 μm. The battery cell of claim 48, wherein The positive active material comprises lithium nickel cobalt manganese oxide, a particle size distribution curve of the positive active material presents a bimodal distribution, peak positions are respectively located at 2-5 μm and 7-20 μm, the positive active material comprises un-agglomerated primary particles and secondary particles formed by agglomeration of the primary particles, and an average particle size of the secondary particles is greater than an average particle size of the un-agglomerated primary particles. The battery cell of claim 48, wherein The positive electrode active material includes lithium nickel cobalt manganese oxide, a molar content of cobalt is less than or equal to 20% based on the total number of moles of transition metals in the positive electrode active material, and a Dv50 of the positive electrode active material is 2 μm-5 μm, the positive electrode active material including unagglomerated primary particles. 正2 2 μm-5 μm, the positive electrode active material including unagglomerated primary particles. The battery cell of claim 48, wherein The positive electrode active material includes lithium nickel cobalt manganese oxide, a molar content of nickel is less than 80% based on a total number of moles of transition metals in the positive electrode active material, a Dv50 of the positive electrode active material is 2 μm-5 μm, and the positive electrode active material includes unagglomerated primary particles. 正2 The positive electrode active material includes lithium nickel cobalt manganese oxide, a molar content of nickel is less than 80% based on a total number of moles of transition metals in the positive electrode active material, a Dv50 of the positive electrode active material is 2 μm-5 μm, and the positive electrode active material includes unagglomerated primary particles. The battery cell of claim 48, wherein The positive electrode active material includes lithium nickel cobalt manganese oxide, the molar content of nickel accounts for 80% or more based on the total moles of transition metals in the positive electrode active material, the Dv50 of the positive electrode active material is 6 μm-15 μm, the positive electrode active material includes secondary particles formed by agglomeration of primary particles, and the average particle size of the primary particles in the secondary particles is 0.1 μm-1.5 μm. 正2 The positive electrode active material includes lithium nickel cobalt manganese oxide, the molar content of nickel accounts for 80% or more based on the total moles of transition metals in the positive electrode active material, the Dv50 of the positive electrode active material is 6 μm-15 μm, the positive electrode active material includes secondary particles formed by agglomeration of primary particles, and the average particle size of the primary particles in the secondary particles is 0.1 μm-1.5 μm. The battery cell of claim 1, wherein The positive electrode tab 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 comprising a positive electrode active material, the positive electrode active material comprising cobalt elements, and the mass percentage of cobalt elements near the surface of the particles of the positive electrode active material is greater than the mass percentage of cobalt elements near the center of the positive electrode active material particles. The battery cell of claim 57, wherein The ratio of the mass percentage of cobalt elements near the surface of the particles of the positive electrode active material to the mass percentage of cobalt elements near the center of the positive electrode active material particles is in the range of (1.2-5.0):1; wherein the region near the surface of the particles is between the surface of the particles and a depth of 200nm in the direction towards the geometric center of the particles, and the region near the center of the positive electrode active material particles is a spherical region with a diameter of 200nm with the geometric center of the cross-section of the particles as the center. The battery cell of claim 58, wherein The ratio of the mass percentage of cobalt elements near the surface of the particles of the positive electrode active material to the mass percentage of cobalt elements near the center of the positive electrode active material particles is in the range of (1.4-2.0):

1. The battery cell of claim 1, wherein The positive electrode tab 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 including a positive electrode active material, the positive electrode active material including a lithium-containing phosphate, a single-sided area density of the positive electrode film layer being 0.2 g / 15 40.25 mm 2 -0.35 g / 15 40.25 mm 2 . The battery cell of claim 1, wherein The positive electrode tab 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 including a positive electrode active material, the positive electrode active material including a lithium-containing transition metal oxide, a single-sided area density of the positive electrode film layer being 0.13 g / 15 40.25 mm 2 -0.24 g / 15 40.25 mm 2 . The battery cell of claim 1, wherein The positive electrode tab 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 comprising a positive electrode active material, and the porosity of the positive electrode film layer is 22%-35%. The battery cell of claim 1, wherein The lithium ion conductivity of the electrolyte is 10mS / cm-20mS / cm. The battery cell of claim 63, wherein The lithium ion conductivity of the electrolyte is 12mS / cm-20mS / cm. The battery cell of claim 63, wherein The lithium ion conductivity of the electrolyte is 10mS / cm-15mS / cm. The battery cell of claim 47, wherein The positive electrode active material includes lithium iron phosphate, the single-sided surface density of the positive electrode film layer is 0.2 g / 15 40.25 mm 2 -0.35 g / 15 40.25 mm 2 ; the conductivity of the electrolyte is 12 mS / cm-20 mS / cm. The battery cell of claim 48, wherein The positive electrode active material includes lithium-containing nickel-cobalt-manganese oxide, the single-sided surface density of the positive electrode film layer is 0.13 g / 15 40.25 mm 2 -0.24 g / 15 40.25 mm 2 ; and the conductivity of the electrolyte is 10 mS / cm-15 mS / cm. A battery device characterized by comprising: The battery device comprises one or more of a battery module, a battery pack, and an energy storage battery. An electric power utilization device characterized by comprising: The battery cell or the battery device is used to provide electrical energy.

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