Battery cells, battery packs, electrical devices and energy storage devices

Abstract

This application provides a battery cell, a battery device, an electrical device, and an energy storage device. The battery cell includes an electrode assembly and an electrolyte; the positive electrode active material includes lithium-containing transition metal oxide particles and lithium-containing transition metal phosphate particles; the lithium-containing transition metal oxide particles include nickel, cobalt, and X1 elements, where X1 elements include manganese and / or aluminum; the lithium-containing transition metal phosphate particles include manganese and iron; based on the total molar number of manganese and iron in the lithium-containing transition metal phosphate particles, the molar percentage of manganese is 40%-75%; in the cross-section of the positive electrode active material layer along the thickness direction of the electrode sheet, the Dn50 of the lithium-containing transition metal phosphate particles is 100nm-300nm, and the Dn90 of the lithium-containing transition metal phosphate particles is 250nm-500nm; the electrolyte includes a first component, which includes one or more of lithium difluorophosphate, lithium difluorooxalate borate, tris(trimethylsilyl)phosphate, and lithium bis(oxalate borate).

Description

Cross-reference to related applications

[0001] This application claims priority to PCT patent application PCT / CN2026 / 090920, filed on April 16, 2026, entitled “Battery cell, battery device, power consumption device and energy storage device”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of battery technology, and in particular to a battery cell, battery device, power supply device, and energy storage device. Background Technology

[0003] Energy conservation and emission reduction are key to sustainable social development. Rechargeable batteries, with their ability to store and release energy as needed, are widely used in various electrical devices and energy storage systems, and are an important component in promoting energy transition and sustainable development. For the new energy industry, battery technology is a crucial factor in its development.

[0004] As the market demands increased battery capacity and lifespan, higher requirements are being placed on battery energy density and cycle stability. However, current technologies struggle to simultaneously improve these performance characteristics, making it crucial to address this critical technical challenge. Summary of the Invention

[0005] This application aims to at least address one of the technical problems existing in the background art. Therefore, one objective of this application is to provide a battery cell with low cost and good cycle performance.

[0006] This application provides a battery cell, including an electrode assembly and an electrolyte; the electrode assembly includes a positive electrode and a negative electrode, 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 layer, the positive electrode active material layer includes a positive electrode active material, the positive electrode active material includes lithium-containing transition metal oxide particles and lithium-containing transition metal phosphate particles; the lithium-containing transition metal oxide particles include nickel, cobalt, and X1 elements, the X1 element includes manganese and / or aluminum; the lithium-containing transition metal phosphate particles include manganese and iron; based on the manganese content in the lithium-containing transition metal phosphate particles... The total molar number of manganese and iron elements accounts for 40%-75% of the total molar number of manganese elements. In the cross-section of the positive electrode active material layer along the thickness direction of the electrode sheet, the Dn50 of lithium transition metal phosphate particles is 100nm-300nm, and the Dn90 of lithium transition metal phosphate particles is 250nm-500nm. Here, Dn50 and Dn90 refer to the particle size corresponding to 50% and 90% of the cumulative number of particles in the particle size distribution curve. The electrolyte includes a first component, which includes one or more of lithium difluorophosphate, lithium difluorooxalate borate, tris(trimethylsilyl)phosphate, and lithium bis(oxalate borate).

[0007] Using a mixture of lithium transition metal phosphate particles and lithium transition metal oxide particles as the positive electrode active material helps to balance the manufacturing cost and energy density of the battery cell. To fully utilize the specific capacity of the lithium transition metal oxide particles and improve the energy density of the battery cell, the charging cutoff voltage of the battery cell needs to be set to around 4.25V. The main discharge voltage range of the lithium transition metal oxide particles is significantly higher than that of the lithium transition metal phosphate particles. This means that the lithium transition metal phosphate particles mainly bear the main lithium-ion supply in the low-voltage range, while the lithium transition metal oxide particles mainly bear the main lithium-ion supply in the high-voltage range. This results in both materials experiencing an equivalent rate load much higher than the apparent rate in their corresponding operating ranges, i.e., load shunting. Therefore, even at low rates of charge and discharge, the load shunting phenomenon in the hybrid battery cell still causes rapid lithium-ion insertion / extraction within the positive electrode active material. The structural stability of the lithium transition metal oxide is poor, and it is easily affected by load shunting during cycling, which is significantly detrimental to its structural integrity. Sustained current overload can easily trigger irreversible phase transitions in lithium-containing transition metal oxide particles. Simultaneously, the rapid and non-uniform insertion / extraction of lithium ions at high current densities leads to a severe mismatch between the surface and bulk lattice parameters of the lithium-containing transition metal oxide particles, generating enormous internal stress within the particles. This triggers the initiation and propagation of grain boundary microcracks, ultimately causing particle breakage and surface structure collapse, resulting in decreased cycle stability of the hybrid battery cells. Therefore, reducing the current loaded by lithium-containing transition metal oxides has become crucial for improving the cycle stability of hybrid systems.

[0008] Compared to lithium iron phosphate, lithium transition metal phosphate particles, which contain both manganese and iron, can mitigate the voltage mismatch between the two materials by utilizing two voltage platforms. However, when the molar proportion of manganese in lithium transition metal phosphate particles is less than 40%, the capacity of these particles in the high-voltage range is reduced, hindering their compatibility with lithium transition metal oxide particles at high voltages and failing to effectively alleviate load shunting. While a molar proportion of manganese in lithium transition metal phosphate particles greater than 75% improves voltage platform compatibility, significant manganese ion dissolution still negatively impacts the cycle stability of the hybrid battery cells.

[0009] By controlling the molar proportion of manganese in lithium transition metal phosphate particles to 40%-75%, the matching degree between manganese and lithium transition metal oxide particles under high voltage is relatively high. This can reduce the current load of lithium transition metal oxide particles under high voltage, and at the same time, control the degree of manganese ion dissolution within a reasonable range.

[0010] However, lithium-containing transition metal phosphate particles have low electronic conductivity and lithium-ion diffusion coefficient, resulting in poor intrinsic kinetic performance. Furthermore, when the molar proportion of manganese is 40%-75%, manganese ions will cause a significant degree of lattice distortion, leading to the distortion of lithium-ion diffusion channels and further reducing the kinetic performance of lithium-containing transition metal phosphate particles.

[0011] During the charging and discharging process of a hybrid battery cell, lithium-containing transition metal phosphate particles with slow lithium-ion diffusion cannot complete charge transfer and lithium-ion intercalation / deintercalation in time. This causes the charging and discharging current to concentrate on lithium-containing transition metal oxide particles with better kinetics. As a result, lithium-containing transition metal phosphate particles still cannot effectively share the current, causing lithium-containing transition metal oxide particles to bear a high rate of current density even at a higher voltage than 3.7V.

[0012] By employing lithium transition metal phosphate particles containing iron and manganese, and controlling the molar ratio of manganese in the lithium transition metal phosphate particles to 40%-75%, and simultaneously matching the particles with a Dn50 of 100nm-300nm and a Dn90 of 250nm-500nm, the kinetic performance of the lithium transition metal phosphate particles and the voltage plateau matching with the lithium transition metal oxide particles can be balanced, thus alleviating the load shunting phenomenon and improving the cycle stability of the hybrid battery system.

[0013] It is worth mentioning that the applicant discovered that the content of small particles in the positive electrode active material layer has a crucial impact on alleviating the load shunting phenomenon. When the Dn50 of the lithium transition metal phosphate particles is 100nm-300nm but the Dn90 is greater than 500nm, it means that the lithium transition metal phosphate particles still contain a lot of large particles with insufficient kinetic performance. Most of the charge and discharge current still tends to concentrate in the lithium transition metal oxide particles with better kinetics, and cannot effectively alleviate the load shunting phenomenon.

[0014] However, small-sized lithium-containing transition metal phosphate particles have a large specific surface area, which can exacerbate the dissolution of manganese ions. The manganese ions further dissolve in the electrolyte and are reduced and precipitated at the negative electrode, which can easily damage the solid electrolyte interphase (SEI) membrane. As a result, more active lithium is consumed during the SEI membrane repair process, which has an adverse effect on the cycle stability of the hybrid battery cells.

[0015] In this embodiment, the first component mentioned above is further introduced into the electrolyte, which helps to form a dense and stable CEI film (positive electrode electrolyte interface film), blocks the dissolution of manganese ions in the positive electrode active material, inhibits the damage of the SEI film and the consumption of active lithium, thereby significantly improving the cycle stability of the hybrid system battery cell.

[0016] In summary, this application improves the cycle performance of hybrid battery cells by controlling the molar percentage of manganese in lithium transition metal phosphate particles, the range of Dn50 and Dn90, and further introducing a first component into the electrolyte, thereby reducing costs and increasing energy density.

[0017] In any implementation, the mass percentage of the first component is 0.2%-6% based on the total mass of the electrolyte.

[0018] Within the aforementioned range, the first component helps to further block the dissolution of manganese ions, reduce their damage to the SEI film and the consumption of active lithium, and improve the cycle performance of the hybrid system battery cells.

[0019] In any implementation, the mass percentage of the first component is 0.5%-5% based on the total mass of the electrolyte.

[0020] In any implementation, the mass percentage of the first component is 2%-4% based on the total mass of the electrolyte.

[0021] Within the aforementioned range, the first component not only helps to block the dissolution of manganese ions, reduce their damage to the SEI film and the consumption of active lithium, but also helps to form a CEI film with appropriate thickness and moderate impedance, thereby taking into account both the cycle performance and rate performance of the hybrid battery cells.

[0022] In any embodiment, the first component comprises lithium difluorophosphate.

[0023] In any embodiment, the Dn50 of the lithium transition metal phosphate particles in the cross-section of the positive electrode active material layer along the electrode thickness direction is 100nm-250nm.

[0024] The Dn50 of lithium transition metal phosphate particles within the above range helps to further shorten the lithium-ion diffusion path and improve its kinetic performance, thereby further increasing its reaction participation with lithium transition metal phosphate particles, alleviating the problem of lithium transition metal oxide particles being prone to particle breakage and surface structure collapse due to current overload, and improving the cycle performance of hybrid system battery cells.

[0025] In any embodiment, the Dn90 of the lithium transition metal phosphate particles in the cross-section of the positive electrode active material layer along the electrode thickness direction is 270nm-400nm.

[0026] The Dn90 of lithium transition metal phosphate particles within the above range helps to further shorten the lithium-ion diffusion path and improve its kinetic performance, thereby further increasing its reaction participation with lithium transition metal phosphate particles, alleviating the problem of lithium transition metal oxide particles being prone to particle breakage and surface structure collapse due to current overload, and improving the cycle performance of hybrid system battery cells.

[0027] In any embodiment, in the cross section of the positive electrode active material layer along the thickness direction of the electrode sheet, the Dn10 of the lithium transition metal phosphate particles is 70nm-130nm, where Dn10 refers to the particle size corresponding to the cumulative number of particles of 10% in the cumulative number distribution curve of particle size.

[0028] The Dn10 of lithium transition metal phosphate particles is within the above range, indicating that it contains a certain amount of small-sized particles, which helps to further improve the kinetic performance of lithium transition metal phosphate particles, alleviate the structural collapse caused by excessive deintercalation of lithium transition metal oxide particles, and further improve the cycle performance of hybrid battery cells.

[0029] In any embodiment, based on the total molar number of manganese and iron in the lithium transition metal phosphate particles, the molar number of manganese accounts for 40%-60%.

[0030] The manganese content in lithium transition metal phosphate particles within the above-mentioned range helps to improve the matching of their working voltage range with lithium transition metal oxide particles while taking into account the kinetic performance of lithium transition metal phosphate particles, thereby further improving the cycle performance of the battery cell.

[0031] In any embodiment, the electrolyte further includes lithium hexafluorophosphate and a second component, the second component including one or more of lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, and lithium bis(trifluoromethanesulfonyl)imide.

[0032] Electrolytes typically require a certain ion concentration to maintain good rate performance of individual battery cells. Lithium hexafluorophosphate (LiPF6) has advantages such as low cost, good solubility, and the ability to passivate current collectors to improve their stability; therefore, the electrolyte in this application also includes LiPF6.

[0033] The applicant further discovered that small-diameter lithium transition metal phosphate particles have a large specific surface area, significantly increasing residual water during battery manufacturing. This readily triggers the hydrolysis of electrolyte salts in the electrolyte, generating highly corrosive hydrofluoric acid, which damages the surface structure of the positive electrode active material and affects the cycle performance of the battery cells. In the embodiments of this application, a second component that is not easily hydrolyzed is further introduced, which can replace part of the easily hydrolyzed lithium hexafluorophosphate to reduce the generation of hydrofluoric acid, thereby further improving the cycle performance of the hybrid system battery cells.

[0034] In any embodiment, based on the total mass of the electrolyte, lithium hexafluorophosphate accounts for 5%-10% of the mass, and the second component accounts for 0.1%-8% of the mass.

[0035] Controlling the mass ratio of lithium hexafluorophosphate within the above range helps to maintain the ionic conductivity of the electrolyte while reducing the amount of hydrofluoric acid generated, mitigating damage to the structure of the positive electrode active material, and further improving the cycle performance of the hybrid battery cell.

[0036] The mass percentage of the second component within the above range helps to reduce the mass percentage of conventional electrolyte salts (such as lithium hexafluorophosphate), thereby reducing the amount of hydrofluoric acid generated, inhibiting its damage to the surface structure of the positive electrode active material, and improving the cycle performance of the hybrid system battery cells.

[0037] In any implementation, the mass percentage of the second component is 0.5%-8% based on the total mass of the electrolyte.

[0038] In any implementation, the second component accounts for 3%-8% of the total mass of the electrolyte.

[0039] The mass percentage of the second component is further within the above range, which helps to further reduce the amount of hydrofluoric acid generated, suppress its damage to the surface structure of the positive electrode active material, and improve the cycle performance of the hybrid system battery cells.

[0040] In any embodiment, the second component includes lithium bisfluorosulfonylimide, which accounts for 0.1%-8% of the total mass of the electrolyte.

[0041] In any embodiment, the second component includes lithium bisfluorosulfonylimide, which accounts for 2%-5% of the total mass of the electrolyte.

[0042] If the mass percentage of lithium bis(fluorosulfonyl)imide is too low, its effect on reducing hydrofluoric acid formation is limited; if its content is too high, it easily corrodes the current collector. Maintaining the mass percentage of lithium bis(fluorosulfonyl)imide within the range of 2%-5% helps to balance reducing hydrofluoric acid formation with its destructive effect on the current collector, thereby further improving the cycle performance of the battery cells.

[0043] In any embodiment, the electrolyte includes cyclic carbonate compounds, and the cyclic carbonate compounds account for 20%-45% of the total mass of the electrolyte.

[0044] The presence of cyclic carbonate compounds in the electrolyte, with their mass percentage falling within the aforementioned range, helps to increase the degree of lithium salt dissociation in the electrolyte, increase the lithium ion concentration, and thus improve the ionic conductivity of the electrolyte, thereby contributing to improving the rate performance of the battery cell.

[0045] In any embodiment, the electrolyte includes cyclic carbonate compounds, and the cyclic carbonate compounds account for 20%-35% of the total mass of the electrolyte.

[0046] In any embodiment, the cyclic carbonate compound includes one or more of ethylene carbonate, propylene carbonate, and butene carbonate.

[0047] In any embodiment, the cyclic carbonate compound includes ethylene carbonate.

[0048] In any embodiment, the electrolyte includes chain carbonate compounds, and the chain carbonate compounds account for 40%-75% of the total mass of the electrolyte.

[0049] Chain carbonate compounds have low viscosity. Including chain carbonate compounds in the electrolyte and controlling their mass percentage within the above range helps to reduce the viscosity of the electrolyte, thereby improving the ionic conductivity of the electrolyte and improving the rate performance of the battery cells.

[0050] In any embodiment, the electrolyte includes chain carbonate compounds, and the chain carbonate compounds account for 50%-70% of the total mass of the electrolyte.

[0051] In any embodiment, the chain carbonate compound includes one or more of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and methyl propyl carbonate.

[0052] In any embodiment, the chain carbonate includes methyl ethyl carbonate and diethyl carbonate.

[0053] Ethyl methyl carbonate and dimethyl carbonate have good high-voltage resistance, which helps to reduce the degree of side reactions of the electrolyte under high voltage, improve the stability of the electrolyte, and further improve the cycle performance of the hybrid battery cells.

[0054] In any embodiment, the electrolyte includes ethyl methyl carbonate, and the mass percentage of ethyl methyl carbonate is 35%-55% based on the total mass of the electrolyte.

[0055] In any embodiment, the electrolyte includes diethyl carbonate, and the mass percentage of diethyl carbonate is 10%-20% based on the total mass of the electrolyte.

[0056] In any embodiment, the electrolyte further includes a third component, which includes one or more of vinylene carbonate, fluoroethylene carbonate, 1,3-propane sulpholactone, and vinyl sulfate.

[0057] As mentioned above, the transition metals can easily damage the SEI film after dissolving from the positive electrode. In this application, a third component is further introduced, which helps to improve the stability of the SEI film, reduce the probability of SEI film rupture and regeneration, reduce electrolyte consumption, and further improve the cycle performance of the hybrid system battery cells.

[0058] In any implementation, the mass percentage of the third component is 0.08%-5% based on the total mass of the electrolyte.

[0059] The mass ratio of the third component within the above range helps to improve the strength of the SEI film, further improve the cycle performance of the hybrid battery cells, and also helps to obtain an SEI film of suitable thickness, taking into account both the cycle performance and rate performance of the battery cells.

[0060] In any implementation, the mass percentage of the third component is 0.1%-5% based on the total mass of the electrolyte.

[0061] In any implementation, the mass percentage of the third component is 1%-5% based on the total mass of the electrolyte.

[0062] In any embodiment, the Dn50 of the lithium transition metal oxide particles in the cross-section of the positive electrode active material layer along the electrode thickness direction is 1μm-4μm.

[0063] Compared to lithium transition metal phosphate particles, lithium transition metal oxide particles have a higher specific capacity. As a result, the area where lithium transition metal oxide particles are located in the positive electrode active material layer will release a large number of lithium ions per unit time. This requires the corresponding negative electrode side to bear a high concentration of lithium ion insertion, and may even cause local lithium plating, affecting the cycle performance of the battery cell.

[0064] In the embodiments of this application, the Dn50 of the lithium transition metal oxide particles is within the above range, indicating that they have a smaller particle size, which helps to improve the uniformity of the distribution of lithium transition metal oxide particles, improve the uniformity of the specific capacity in different regions of the positive electrode active material layer, reduce the probability of excessively high local lithium ion concentration, improve the local lithium plating phenomenon on the negative electrode side, and further improve the cycle performance of the hybrid system battery cell.

[0065] In any embodiment, the Dn50 of the lithium transition metal oxide particles in the cross-section of the positive electrode active material layer along the electrode thickness direction is 1μm-3μm.

[0066] In any embodiment, the Dn50 of the lithium transition metal oxide particles in the cross-section of the positive electrode active material layer along the electrode thickness direction is 1.5 μm-2.5 μm.

[0067] In any embodiment, the particle size distribution concentration of lithium transition metal oxide particles (Dn90-Dn10) / Dn50 in the cross section along the thickness direction of the positive electrode active material layer is 0.6-2.

[0068] The particle size distribution concentration (Dn90-Dn10) / Dn50 of lithium-containing transition metal oxide particles is 0.6-2, which indicates that the particle size of lithium-containing transition metal oxide particles is relatively uniform. This reduces the risk of individual large lithium-containing transition metal oxide particles appearing in the positive electrode active material layer, helps to improve the uniformity of specific capacity in different regions of the active material layer, thereby reducing the probability of excessively high local lithium-ion concentration, improving the local lithium plating phenomenon on the negative electrode side, and further improving the cycle performance of the hybrid system battery cell.

[0069] In any embodiment, the particle size distribution concentration (Dn90-Dn10) / Dn50 of the lithium transition metal oxide particles in the cross section along the thickness direction of the positive electrode active material layer is 0.8-1.8.

[0070] The particle size distribution concentration (Dn90-Dn10) / Dn50 of lithium-containing transition metal oxide particles is 0.8-1.8, which helps to further improve the uniformity of the particle size of lithium-containing transition metal oxide particles, improve the uniformity of the specific capacity in different regions of the active material layer, thereby reducing the probability of excessively high local lithium-ion concentration, improving the local lithium plating phenomenon on the negative electrode side, and further improving the cycle performance of the hybrid system battery cell.

[0071] In any embodiment, the Dn10 of the lithium transition metal oxide particles in the cross-section of the positive electrode active material layer along the electrode thickness direction is 0.5 μm-2 μm.

[0072] In any embodiment, the Dn10 of the lithium transition metal oxide particles in the cross-section of the positive electrode active material layer along the electrode thickness direction is 0.5 μm-1.5 μm.

[0073] In any embodiment, the Dn90 of the lithium transition metal oxide particles in the cross-section of the positive electrode active material layer along the electrode thickness direction is 2.5 μm-5 μm.

[0074] The Dn90 of lithium transition metal oxide particles within the above range helps to further reduce the content of large particles in lithium transition metal oxide particles, reduce the local lithium-ion concentration, alleviate the local lithium plating phenomenon, and further improve the cycle performance of hybrid system battery cells.

[0075] In any embodiment, the Dn90 of the lithium transition metal oxide particles in the cross-section of the positive electrode active material layer along the electrode thickness direction is 3μm-4μm.

[0076] In any embodiment, the molar percentage of nickel is 50%-80% based on the total molar number of nickel, cobalt and X1 elements in the lithium transition metal oxide particles.

[0077] The molar percentage of nickel within the above range helps to balance the specific capacity of lithium-containing transition metal oxide particles and the degree of side reaction with the electrolyte, thereby balancing the energy density and cycle performance of the hybrid battery cell.

[0078] In any embodiment, the molar percentage of cobalt is 5%-20% based on the total molar number of nickel, cobalt and X1 elements in the lithium transition metal oxide particles.

[0079] In any embodiment, the molar percentage of the element X1 is 15%-40% based on the total molar number of nickel, cobalt and X1 elements in the lithium transition metal oxide particles.

[0080] In any embodiment, the lithium-containing transition metal oxide particles are lithium-containing transition metal oxide single crystal particles.

[0081] The presence of lithium-containing transition metal oxide particles, specifically single-crystal lithium-containing transition metal oxide particles, helps to reduce the size of the lithium-containing transition metal oxide particles, thereby improving the uniformity of the specific capacity of the positive electrode active material layer. This reduces the probability of excessively high local lithium-ion concentration, improves the local lithium plating phenomenon on the negative electrode side, and further improves the cycle performance of the hybrid system battery cell.

[0082] In any embodiment, the mass percentage of lithium transition metal oxide particles is 50%-90% based on the total mass of the positive electrode active material.

[0083] In positive electrode active materials, a mass ratio of lithium transition metal oxide particles within the above-mentioned range helps to balance the cost and energy density of hybrid battery cells.

[0084] In any embodiment, the mass percentage of lithium transition metal oxide particles is 60%-80% based on the total mass of the positive electrode active material.

[0085] In any embodiment, the lithium-containing transition metal oxide particles include one or more of lithium-containing nickel-cobalt-manganese oxides and their doped and / or coated modified materials, and lithium-containing nickel-cobalt-aluminum oxides and their doped and / or coated modified materials.

[0086] In any embodiment, the lithium-containing transition metal phosphate particles include a particle body and a carbon material disposed on at least a portion of the surface of the particle body.

[0087] The lithium-containing transition metal phosphate particles include carbon material disposed on at least part of the particle body surface, which helps to improve their kinetic performance, thereby increasing the reaction participation of the lithium-containing transition metal phosphate particles, alleviating the structural degradation problem caused by over-reaction of lithium-containing transition metal oxide particles, and further improving the cycle performance of hybrid system battery cells.

[0088] In any embodiment, the average thickness of the carbon material is 2nm-25nm.

[0089] In any implementation, the carbon material accounts for 0.5%-3% of the total mass of the lithium transition metal phosphate particles.

[0090] In any embodiment, the lithium transition metal phosphate particles comprise the components represented by the following general formula I: Li m1 Fe x1 Mn y1 M1 b1 P z1 Q1 c1 O n1 N1 d1 Formula I; Wherein, 0.8≤m1≤1.2, 0<x1<1, 0<y1<1, 0.9≤x1+y1≤1, 0.95≤z1≤1, 3.5≤n1≤4, 0≤b1≤0.1, 0≤c1≤0.1, 0≤d1≤0.1; wherein, M1 includes one or more of Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, and Ti, Q1 includes one or more of B, S, Si, and N, and N1 includes one or more of F, Cl, and Br.

[0091] In any embodiment, the positive electrode active material layer includes a first conductive agent, which includes a dotted conductive agent, and the dotted conductive agent includes one or more of Super P, Ketjen Black, acetylene black, and conductive graphite.

[0092] In any embodiment, based on the total mass of the positive electrode active material layer, the mass percentage of the dotted conductive agent is 0.2%-2.0%.

[0093] In any embodiment, the first conductive agent further includes a linear conductive agent, which includes one or more of carbon nanotubes and carbon nanofibers.

[0094] In this application, carbon nanofibers include, but are not limited to, one or more of vapor-grown carbon fibers and graphite carbon fibers.

[0095] Compared to lithium transition metal oxide particles, lithium transition metal phosphate particles have smaller particle sizes. The large difference in particle size between the two leads to a reduction in the degree of contact, which in turn affects the continuity of the electron transport network in the positive electrode active material layer and is prone to polarization, thus affecting the cycle performance of the battery cell.

[0096] In this embodiment, the first conductive agent includes a linear conductive agent, which helps to enhance the electrical contact between two positive electrode active materials with significant differences in particle size through bridging, thereby improving the electronic conductivity of the positive electrode active material layer. At the same time, the linear conductive agent is used in conjunction with the dotted conductive agent to synergistically construct a good electronic transport network that takes into account both long-range and short-range conductivity, thereby alleviating polarization and further improving the cycle performance of the hybrid system battery cell.

[0097] In any embodiment, the linear conductive agent includes carbon nanotubes.

[0098] In any embodiment, the mass percentage of the linear conductive agent is 0.05%-1.5% based on the total mass of the positive electrode active material layer.

[0099] In any embodiment, the positive electrode active material layer further includes a first polymer.

[0100] In any embodiment, the first polymer includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0101] In any embodiment, the positive electrode film layer further includes a positive electrode undercoating layer disposed on the positive electrode active material layer near the positive electrode current collector side, the positive electrode undercoating layer including a second polymer and a second conductive agent.

[0102] On the one hand, the positive electrode undercoat layer helps to improve the adhesion between the positive electrode film and the positive electrode current collector, reducing the probability of separation between the positive electrode film and the positive electrode current collector during cycling; on the other hand, it also helps to improve the electrical contact between the positive electrode active material and the positive electrode current collector, thereby improving the dynamic performance of the battery cell.

[0103] In any embodiment, the thickness of the positive electrode undercoat is 0.5 μm-5 μm.

[0104] In any embodiment, the compaction density of the positive electrode film is 2.60 g / cm³. 3 -3.4g / cm 3 .

[0105] In this embodiment, smaller lithium transition metal phosphate particles fill the gaps between lithium transition metal oxide particles, which helps to increase the compaction density of the positive electrode film, thereby increasing the energy density of the battery cell.

[0106] In any embodiment, the negative electrode sheet 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, which includes graphite, and the volume distribution particle size Dv50 of the negative electrode active material is 7μm-15μm.

[0107] The volume distribution particle size Dv50 of the negative electrode active material is within the above range, which helps to increase the number of lithium-ion insertion ports and shorten the lithium-ion diffusion path, thereby improving the lithium-ion insertion rate, improving the local lithium plating phenomenon on the negative electrode side, and further improving the cycle performance of the hybrid system battery cell.

[0108] In any embodiment, the volume distribution particle size Dv50 of the negative electrode active material is 8μm-13μm.

[0109] When the volume distribution particle size Dv50 of the negative electrode active material is within the above range, it is more conducive to increasing the number of lithium-ion insertion ports and shortening the lithium-ion diffusion path, thereby improving the lithium-ion insertion rate, improving the local lithium plating phenomenon on the negative electrode side, and further improving the cycle performance of the hybrid system battery cell.

[0110] In any embodiment, the specific surface area of ​​the negative electrode active material is 0.5 m². 2 / g-3.0m 2 / g.

[0111] In any embodiment, the specific surface area of ​​the negative electrode active material is 0.8 m². 2 / g-2.0m 2 / g.

[0112] In any embodiment, the electrode assembly further includes a separator disposed between the positive electrode and the negative electrode, the separator comprising a base film and a coating disposed on at least one side of the base film, the coating comprising a first coating comprising a third polymer.

[0113] In any embodiment, the coating further includes a second coating disposed between the first coating and the base film, the second coating comprising inorganic particles and a fourth polymer.

[0114] Inorganic materials have good chemical stability, which helps to improve the stability of the separator. At the same time, they have good liquid retention capacity, which helps to improve the ion transport capacity of the separator, reduce the polarization phenomenon during the charging and discharging process of the battery cell, and thus improve the cycle performance and rate performance of the hybrid system battery cell.

[0115] In any embodiment, the coating further includes a second coating disposed between the first coating and the base film, the second coating comprising inorganic particles and a fourth polymer, the coating being disposed on the base film near the positive electrode plate.

[0116] Placing the second coating on the side of the base film close to the positive electrode helps reduce the direct contact between the base film and the positive electrode active material, reduces the damage to the base film caused by byproducts generated by the electrolyte at the positive electrode active material, thereby improving the stability of the separator and further improving the cycle stability of the hybrid battery cell.

[0117] In any embodiment, the inorganic particles include one or more of alumina, boehmite, silicon dioxide, cerium oxide, magnesium aluminate, zirconium oxide, and titanium dioxide.

[0118] In any embodiment, the third polymer and the fourth polymer each independently include one or more of fluoropolymers and acrylate polymers.

[0119] In any embodiment, the fluoropolymer includes a vinylidene fluoride polymer, which includes one or more of vinylidene fluoride homopolymers, copolymers of vinylidene fluoride and tetrafluoroethylene, copolymers of vinylidene fluoride and hexafluoropropylene, and copolymers of vinylidene fluoride and trifluoroethylene.

[0120] In any embodiment, the thickness of the base film is 5 μm-12 μm.

[0121] In any embodiment, the thickness of the coating on one side is 1µm-4µm.

[0122] In any embodiment, the thickness of the separator is 8 μm-15 μm.

[0123] In any embodiment, the air permeability of the separator at 25°C is 400s / 100cc-600s / 100cc.

[0124] When the permeability of the separator is within the above range, it can, to a certain extent, prevent the transition metal dissolved from the positive electrode from migrating to the negative electrode side, alleviate the problem of it being reduced to metal at the negative electrode and damaging the SEI film, or even causing local micro-short circuits, and further improve the cycle performance of the hybrid system battery cell.

[0125] In any embodiment, the porosity of the separator is 35%-55%.

[0126] In any embodiment, the thickness of the positive current collector is 9 μm-15 μm.

[0127] The thickness of the positive electrode current collector is within the above range, which helps to reduce the thickness and mass ratio of the positive electrode current collector in the battery cell and improve the energy density of the battery cell.

[0128] In any embodiment, the thickness of the negative electrode current collector is 3μm-7μm.

[0129] The thickness of the negative electrode current collector is within the above range, which helps to reduce the thickness and mass ratio of the negative electrode current collector in the battery cell and improve the energy density of the battery cell.

[0130] In any embodiment, the rated cutoff voltage of the battery cell is 4.25V-4.45V.

[0131] In any embodiment, the positive electrode includes a first main body and a first tab. The first main body includes a first straight section, which includes a positive current collector and a positive film layer. The first straight section is stacked along the thickness direction X of the battery cell. The ratio of the number of first tabs to the number of first straight sections is 0.5-1.

[0132] The applicant further discovered that high temperature conditions exacerbate manganese ion dissolution. In this application embodiment, the ratio of the number of first tabs to the number of first straight sections is 0.5-1, with a relatively large number of first tabs. This, combined with the above-mentioned hybrid system, reduces the impedance and heat generation at the tabs, reduces the heat at the maximum heat generation point of the battery cell, improves the temperature distribution uniformity of the positive electrode active material layer, reduces the temperature rise of the positive electrode sheet, thereby reducing the probability of manganese ion dissolution from lithium transition metal phosphate particles, reducing the damage of manganese ions to the SEI film, reducing the consumption of active lithium ions, and further improving the cycle stability of the hybrid system battery cell.

[0133] In any embodiment, the ratio of the number of first tabs to the number of first straight segments is 0.75-1.

[0134] The ratio of the number of first tabs to the number of first straight sections is within a reasonable range, which can further increase the number of first tabs, reduce the impedance and heat generation at the tabs, reduce the heat at the maximum heat generation point of the battery cell, improve the temperature distribution uniformity of the positive electrode active material layer, reduce the temperature rise of the positive electrode sheet, thereby reducing the probability of manganese ion dissolution from lithium transition metal phosphate particles, reducing the damage of manganese ions to the SEI film, reducing the consumption of active lithium ions, and further improving the cycle stability of the hybrid system battery cell.

[0135] In any embodiment, the ratio of the size of the first tab to the size of the electrode assembly is 12%-40% along the width direction of the battery cell.

[0136] Along the width direction of the battery cell, the ratio of the size of the first tab to the size of the electrode assembly is within the above-mentioned range. This is beneficial to increase the welding area between the first tab and the electrode assembly, reduce the contact resistance between the first tab and the electrode assembly, reduce the heat generation at the first tab, improve the temperature distribution uniformity of the positive electrode active material layer, reduce the temperature rise of the positive electrode sheet, thereby reducing the probability of manganese ion dissolution from lithium transition metal phosphate particles, reducing the damage of manganese ions to the SEI film, reducing the consumption of active lithium ions, and improving the cycle stability of the hybrid battery cell.

[0137] In any embodiment, the ratio of the size of the first electrode tab to the size of the electrode assembly is 24%-40%.

[0138] Along the width direction of the battery cell, the ratio of the size of the first tab to the size of the electrode assembly is within a reasonable range. This is beneficial for further increasing the welding area between the first tab and the electrode assembly, further reducing the contact resistance between the first tab and the electrode assembly, reducing the heat generation at the first tab, improving the temperature distribution uniformity of the positive electrode active material layer, reducing the temperature rise of the positive electrode sheet, thereby reducing the probability of manganese ion dissolution from lithium transition metal phosphate particles, reducing the damage of manganese ions to the SEI film, reducing the consumption of active lithium ions, and further improving the cycle stability of the hybrid system battery cell.

[0139] In any embodiment, the size of the first tab is 25mm-60mm along the width direction of the battery cell.

[0140] Along the width direction of the battery cell, if the size of the first tab is within the above range, it can increase the welding area between the first tab and the electrode assembly, reduce the contact resistance between the first tab and the electrode assembly, and reduce the heat generation at the first tab.

[0141] In any embodiment, the size of the electrode assembly is 140mm-390mm along the width direction of the battery cell.

[0142] In any embodiment, the negative electrode sheet includes a second main body and a second tab. The second main body includes a second straight section, which includes a negative current collector and a negative electrode film layer. The second straight section is stacked along the thickness direction of the battery cell. The ratio of the number of second tabs to the number of second straight sections is 0.5-1.

[0143] When the ratio of the number of second tabs to the number of second straight sections is within the above range, the number of second tabs can be increased, the impedance and heat generation at the second tabs can be reduced, the temperature distribution uniformity of the negative electrode active material layer can be improved, the temperature rise of the negative electrode sheet can be reduced, and the total heat generation of the battery cell can be reduced.

[0144] In any embodiment, the ratio of the number of second tabs to the number of second straight segments is 0.75-1.

[0145] The ratio of the number of second tabs to the number of second straight sections is within a reasonable range. Further increasing the number of second tabs reduces the impedance and heat generation at the second tabs, improves the temperature distribution uniformity of the negative electrode active material layer, reduces the temperature rise of the negative electrode sheet, and further reduces the total heat generation of the battery cell.

[0146] In any embodiment, the electrode assembly includes a wound electrode assembly.

[0147] A second aspect of this application provides a battery device, including the battery cell provided in the first aspect of this application.

[0148] A third aspect of this application provides an electrical device, including the battery device provided in the second aspect of this application, wherein the battery device is used to provide electrical energy.

[0149] The fourth aspect of this application provides an energy storage device, including the battery device provided in the second aspect of this application, the battery device being used to store electrical energy.

[0150] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0151] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the various drawings denote the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings depict only some embodiments disclosed in this application and should not be construed as limiting the scope of this application.

[0152] Figure 1 This is a state-of-charge (SOC-V) curve of a single battery cell under charging according to an embodiment of this application; Figure 2 This is a schematic diagram of a battery cell according to one embodiment of this application; Figure 3 yes Figure 2 An exploded view of a battery cell according to one embodiment of this application is shown. Figure 4 This is a schematic diagram of the electrode assembly of a battery cell according to one embodiment of this application; Figure 5 This is a schematic diagram of a battery pack according to one embodiment of this application; Figure 6 yes Figure 5 The diagram shown is a structural schematic of a battery module according to one embodiment of this application; Figure 7 This is a schematic diagram of an electrical device in which a single battery cell is used as a power source according to one embodiment of this application.

[0153] Figure label: M, length direction of battery module; X, thickness direction of battery cell; E, first direction; F, second direction; 2, battery pack; 5, housing; 5a, first housing section; 5b, second housing section; 5c, storage space; 6, battery module; 7, battery cell; 70, first battery pack; 10, electrode assembly; 11, positive electrode plate; 111, first tab; 112, first straight section; 113, first bent section; 12, negative electrode plate; 122, second straight section; 123, second bent section; 121, second tab; 13, separator; 20, outer shell; 21, housing; 22, end cap; 31, first electrode terminal; 32, second electrode terminal. Detailed Implementation

[0154] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0155] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0156] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0157] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. In the description of the embodiments of this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0158] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0159] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0160] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0161] 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.

[0162] 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 mention that the method may also include step (c) indicates 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.

[0163] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0164] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0165] Unless otherwise stated, the terms used in this application have the common meanings as commonly understood by those skilled in the art.

[0166] 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.

[0167] Battery cells using a mixture of lithium transition metal oxide particles and lithium transition metal phosphate particles as the positive electrode active material (hereinafter referred to as hybrid battery cells) offer the advantages of both high energy density and low cost. However, experimental results show that compared to single-system battery cells, hybrid battery cells exhibit a deteriorated cycle life, making it difficult to meet the growing market demand. Therefore, improving the cycle performance of battery cells while maintaining low cost and high energy density has become a pressing technical problem to be solved in this field.

[0168] To address the aforementioned problems, the first aspect of this application provides a battery cell, including an electrode assembly and an electrolyte; the electrode assembly includes a positive electrode and a negative electrode, the positive electrode includes a positive current collector and a positive electrode film disposed on at least one side of the positive current collector, the positive electrode film includes a positive active material layer, the positive active material layer includes a positive active material, the positive active material includes lithium-containing transition metal oxide particles and lithium-containing transition metal phosphate particles; the lithium-containing transition metal oxide particles include nickel, cobalt, and X1 elements, the X1 element includes manganese and / or aluminum; the lithium-containing transition metal phosphate particles include manganese and iron; based on the lithium-containing transition metal phosphate particles... The total molar number of manganese and iron in the particles is 40%-75%; in the cross section along the thickness direction of the positive electrode active material layer, the Dn50 of the lithium transition metal phosphate particles is 100nm-300nm, and the Dn90 of the lithium transition metal phosphate particles is 250nm-500nm. Here, Dn50 and Dn90 refer to the particle size corresponding to 50% and 90% of the cumulative particle size distribution curve, respectively; the electrolyte includes a first component, which includes one or more of lithium difluorophosphate, lithium difluorooxalate borate, tris(trimethylsilyl)phosphate, and lithium bis(oxalate borate).

[0169] Using a mixture of lithium transition metal phosphate particles and lithium transition metal oxide particles as the positive electrode active material helps to balance the manufacturing cost and energy density of the battery cell. To fully utilize the specific capacity of the lithium transition metal oxide particles and improve the energy density of the battery cell, the charging cutoff voltage of the battery cell needs to be set to around 4.25V. The main discharge voltage range of the lithium transition metal oxide particles is significantly higher than that of the lithium transition metal phosphate particles. This means that the lithium transition metal phosphate particles mainly bear the main lithium-ion supply in the low-voltage range, while the lithium transition metal oxide particles mainly bear the main lithium-ion supply in the high-voltage range. This results in both materials experiencing an equivalent rate load much higher than the apparent rate in their corresponding operating ranges, i.e., load shunting. Therefore, even at low rates of charge and discharge, the load shunting phenomenon in the hybrid battery cell still causes rapid lithium-ion insertion / extraction within the positive electrode active material. The structural stability of the lithium transition metal oxide is poor, and it is easily affected by load shunting during cycling, which is significantly detrimental to its structural integrity. Sustained current overload can easily trigger irreversible phase transitions in lithium-containing transition metal oxide particles. Simultaneously, the rapid and non-uniform insertion / extraction of lithium ions at high current densities leads to a severe mismatch between the surface and bulk lattice parameters of the lithium-containing transition metal oxide particles, generating enormous internal stress within the particles. This triggers the initiation and propagation of grain boundary microcracks, ultimately causing particle breakage and surface structure collapse, resulting in decreased cycle stability of the hybrid battery cells. Therefore, reducing the current loaded by lithium-containing transition metal oxides has become crucial for improving the cycle stability of hybrid systems.

[0170] Compared to lithium iron phosphate, lithium transition metal phosphate particles, which contain both manganese and iron, can mitigate the voltage mismatch between the two materials by utilizing two voltage platforms. However, when the molar proportion of manganese in lithium transition metal phosphate particles is less than 40%, the capacity of these particles in the high-voltage range is reduced, hindering their compatibility with lithium transition metal oxide particles at high voltages and failing to effectively alleviate load shunting. While a molar proportion of manganese in lithium transition metal phosphate particles greater than 75% improves voltage platform compatibility, significant manganese ion dissolution still negatively impacts the cycle stability of the hybrid battery cells.

[0171] like Figure 1 As shown, controlling the molar proportion of manganese in lithium transition metal phosphate particles to 40%-75% results in a high degree of matching between manganese and lithium transition metal oxide particles under high voltage, which can reduce the impact of high voltage ( Figure 1 The discharge voltage range under medium and high voltage conditions is used to control the current of lithium transition metal oxide loads, while also controlling the degree of manganese ion dissolution within a reasonable range.

[0172] However, lithium-containing transition metal phosphate particles have low electronic conductivity and lithium-ion diffusion coefficient, resulting in poor intrinsic kinetic performance. Furthermore, when the molar proportion of manganese is 40%-75%, manganese ions will cause a significant degree of lattice distortion, leading to the distortion of lithium-ion diffusion channels and further reducing the kinetic performance of lithium-containing transition metal phosphate particles.

[0173] During the charging and discharging process of a hybrid battery cell, lithium-containing transition metal phosphate particles with slow lithium-ion diffusion cannot complete charge transfer and lithium-ion intercalation / deintercalation in time. This causes the charging and discharging current to concentrate on lithium-containing transition metal oxide particles with better kinetics. As a result, lithium-containing transition metal phosphate particles still cannot effectively share the current, causing lithium-containing transition metal oxide particles to bear a high rate of current density even at a higher voltage than 3.7V.

[0174] By employing lithium transition metal phosphate particles containing iron and manganese, and controlling the molar ratio of manganese in the lithium transition metal phosphate particles to 40%-75%, and simultaneously matching the particles with a Dn50 of 100nm-300nm and a Dn90 of 250nm-500nm, the kinetic performance of the lithium transition metal phosphate particles and the voltage plateau matching with the lithium transition metal oxide particles can be balanced, thus alleviating the load shunting phenomenon and improving the cycle stability of the hybrid battery system.

[0175] It is worth mentioning that the applicant discovered that the content of small particles in the positive electrode active material layer has a crucial impact on alleviating the load shunting phenomenon. As shown in Table 3, when the Dn50 of the lithium transition metal phosphate particles is 100nm-300nm but the Dn90 is greater than 500nm, it means that the lithium transition metal phosphate particles still contain a lot of large particles with insufficient kinetic performance. Most of the charge and discharge current still tends to concentrate in the lithium transition metal oxide particles with better kinetics, and cannot effectively alleviate the load shunting phenomenon.

[0176] However, small-sized lithium-containing transition metal phosphate particles have a large specific surface area, which can exacerbate the dissolution of manganese ions. The manganese ions further dissolve in the electrolyte and are reduced and precipitated at the negative electrode, which can easily damage the solid electrolyte interphase (SEI) membrane. As a result, more active lithium is consumed during the SEI membrane repair process, which has an adverse effect on the cycle stability of the hybrid battery cells.

[0177] In this embodiment, the first component mentioned above is further introduced into the electrolyte, which helps to form a dense and stable CEI film (positive electrode electrolyte interface film), blocks the dissolution of manganese ions in the positive electrode active material, inhibits the damage of the SEI film and the consumption of active lithium, thereby significantly improving the cycle stability of the hybrid system battery cell.

[0178] In summary, this application improves the cycle performance of hybrid battery cells by controlling the molar percentage of manganese in lithium transition metal phosphate particles, the range of Dn50 and Dn90, and further introducing a first component into the electrolyte, thereby reducing costs and increasing energy density.

[0179] In some embodiments, the lithium-containing transition metal oxide particles include nickel, cobalt, and X1, wherein the X1 element includes manganese.

[0180] In some embodiments, the lithium-containing transition metal oxide particles include nickel, cobalt, and X1, wherein the X1 element includes aluminum.

[0181] In this application, lithium-containing transition metal oxide particles include, but are not limited to, nickel-cobalt-manganese-based lithium-containing oxides and their doped and / or coated modified materials, and nickel-cobalt-aluminum-based lithium-containing oxides and their doped and / or coated modified materials. Lithium-containing transition metal phosphate particles referred to in this application include lithium manganese iron phosphate and its doped and / or coated modified materials.

[0182] In this application, the type of positive electrode active material can be detected by any method known in the art. For example, it can be detected by combining an X-ray diffractometer (XRD) with an energy dispersive spectroscopy (EDS) analyzer or an inductively coupled plasma mass spectrometer (ICP-MS).

[0183] It is worth noting that the positive electrode sheet, positive electrode film layer, positive electrode active material layer, positive electrode active material, negative electrode sheet, negative electrode film layer, and negative electrode active material used for testing in this application can be freshly prepared or obtained by disassembling, washing, drying (and scraping off powder) from the battery.

[0184] In this application, based on the total molar number of manganese and iron in the lithium transition metal phosphate particles, the molar percentage of manganese can be tested using methods and equipment known in the art. A specific test method example is as follows: Disassemble the battery cell to obtain the positive electrode sheet. Cut the positive electrode sheet into 6mm × 6mm samples using ceramic scissors, and attach them to a sample stage coated with paraffin wax, ensuring the sample protrudes slightly (<1mm) from the edge of the sample stage. Then turn on the argon ion cross-section polisher (JEOL IB-09010 CP type argon ion cross-section polisher, Japan) and perform vacuuming (10... -7Adjusting the parameters, the positive electrode test film layer was cut along the thickness direction of the sample using a polishing instrument. After exposing the cut surface, a scanning electron microscope (SEM) was used to observe the cross-section of the positive electrode sheet along the thickness direction. The positive current collector and the positive active material layer set on both sides of the positive current collector were observed under the SEM. The field of view was then adjusted to the positive active material layer, and the field of view area was taken as the test area. An electron microscope image was taken to obtain a scanning electron microscope image of the cross-section of the positive active material layer along the thickness direction of the positive electrode sheet. An energy dispersive spectroscopy (EDS) surface scan was performed on the test area. Based on the distribution spectrum of the P element in the test area, the area where the P element was clearly displayed was magnified. The particle composition was determined by the energy dispersive spectroscopy, and it was identified as lithium transition metal phosphate particles. The lithium transition metal phosphate particles were selected for EDS testing to obtain the molar percentage of each element in the particles. The molar percentage of manganese was calculated based on the total molar number of manganese and iron in the lithium transition metal phosphate particles. At least 10 particles were measured, and the average value was taken as the test result.

[0185] In some embodiments, based on the total number of moles of manganese and iron in the lithium transition metal phosphate particles, the molar percentage of manganese can be 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, or any value range between the two.

[0186] When the molar percentage of manganese in lithium transition metal phosphate particles is less than 40%, the capacity of lithium transition metal phosphate particles in the high voltage range is low, which is not conducive to matching the voltage platform of lithium transition metal oxide particles. The two types of materials are prone to load shunting due to step charge and discharge. When the molar percentage of manganese in lithium transition metal phosphate particles is greater than 75%, the degree of manganese ion dissolution is large. Manganese ions dissolve in the electrolyte and are reduced and precipitated at the negative electrode, which easily damages the solid electrolyte interphase (SEI) film. As a result, more active lithium is consumed in the process of SEI film repair, which will deteriorate the cycle stability of the hybrid system battery cells.

[0187] In this application, the term "particle" refers to a particle in the positive electrode active material layer that has a recognizable complete boundary in the field of view at a certain magnification, such as 10,000x. Defects and scratches may exist inside the particle, but a complete boundary sufficient to divide the particle cannot be identified inside the particle.

[0188] In this application, the specific method for particle identification and classification is as follows: The positive electrode active material layer is cut along the thickness direction of the electrode sheet using an argon ion beam (for example, a Leica EMTIC3XCP device can be used, operating voltage: 6kV, operating time: 6h). After exposing the cut surface, a scanning electron microscope (for example, a Hitachi SU8230 device can be used, operating voltage: 3kV, beam current: high, probe model: U (LA100), working distance <5mm) is used to observe the cut surface of the positive electrode active material layer along the thickness direction of the electrode sheet. Based on the energy dispersive spectroscopy (EDS) spectrum of the phosphorus element in the test area, particles that do not clearly show phosphorus are identified as lithium-containing transition metal oxide particles, while particles that clearly show phosphorus are identified as lithium-containing transition metal phosphate particles. Images were acquired using a field emission scanning electron microscope (FESEM) at non-edge locations within a cross-section of the positive electrode active material layer (after observing the electrode edge under the SESEM, the field of view was adjusted to the center of the sample) in secondary electron mode. Electron micrographs were taken at 10kx magnification, and the particles in the electron micrographs were analyzed using ImageJ software (1.46r, Win64 version). The specific steps for using ImageJ are as follows: load the SESEM image to be analyzed; use the Cellpose plugin to identify particles, and perform manual corrections; use ImageJ to read and analyze data. The specific method for identifying particles using the Cellpose plugin is as follows: set the segmentation diameter parameter (diameter in the Segmentation module) to 15 pixels, click "runcyto3" to identify particles; manually mark particles in the image that were not identified by the software, were not fully identified by the software, or had identification errors. The particles in the image that were not recognized by the software, were not fully recognized by the software, or were recognized with errors mainly include the following: 1. Due to the particle being too large or having scratches on its surface, the particle cannot be recognized or cannot be fully recognized; 2. During the argon ion beam cutting process, scratches will be generated on the particle surface. The software may misjudge the scratches as particle boundaries during the recognition process, thus causing recognition errors; 3. Due to the particle being too small, it was not successfully recognized; 4. The particle is located at the edge of the electron microscope field of view, and the interior of the particle is penetrated by the edge, so the morphology cannot be fully displayed. The part is recognized instead of the whole, resulting in recognition errors.For the unidentified or misidentified particles mentioned above, manual calibration is performed. The specific process is as follows: 1. Delete large particles located around the edges of the scanning electron microscope that are not fully displayed. 2. Determine if any unidentified or misidentified particles have internal cracks or scratches. If no cracks or scratches are found, classify it as a single particle and manually mark it based on the observed particle boundary. 3. If cracks or scratches are found inside the particle, determine if they penetrate the particle. If not, classify it as a single particle and manually mark it. 4. If cracks or scratches penetrate the particle, determine if they are linear or irregular. 5. If the cracks or scratches are irregular, classify them as the boundary between particles and divide the particles along this boundary. 6. If the cracks or scratches are linear, perform contrast comparison. 7. If the contrast is not obvious and there is no crack-like appearance, classify it as a scratch and mark it as a single particle. 8. If the contrast is strong and there is a crack-like appearance, classify it as the boundary between particles and mark it as two particles. After manual marking, delete information irrelevant to the particles from the automatic image processing, thus completing the particle identification and marking in the image.

[0189] In existing technologies, laser particle size analyzers are typically used to statistically analyze the particle size of cathode active materials using Malvern laser diffraction. However, studies have shown that lithium-containing transition metal phosphate particles are prone to agglomeration. Therefore, the test results obtained using Malvern laser diffraction, based on the principle of laser scattering, often only reflect the particle size of these agglomerates and cannot accurately reflect the particle size within the cathode active material. Furthermore, it cannot reflect the dispersion state of the cathode active material in the film layer, as the dispersion of the cathode active material in the film layer increases during slurry preparation and film rolling. The test results obtained by Malvern laser diffraction are affected by the particle size, specific surface area, and degree of agglomeration of the cathode active material. Compared to the actual dispersion in the electrode sheet, the number of large particles obtained by this test is lower than the actual value, while the number of small particles is higher. Therefore, the particle size obtained by Malvern laser diffraction cannot be equated with or analogized to the particle size statistically obtained in the embodiments of this application.

[0190] In this application, the Dn50 and Dn90 of the lithium transition metal phosphate particles in the cross-section along the thickness direction of the positive electrode active material layer can be tested using methods and instruments known in the art. As an example, referring to the method described above, lithium transition metal phosphate particles in the positive electrode active material layer are identified and determined. The images after particle identification and labeling are imported into ImageJ software for analysis. The scale is set based on the scanning electron microscope image, and the particle size in the cross-section along the thickness direction of the positive electrode active material layer is statistically analyzed using the "Feret diameter" and analysis functions. According to the software manual (ImageJ User Guide IJ 1.46r), the "Feret" parameter obtained from the analysis represents the maximum spacing between all parallel lines in the two-dimensional projection of the particle, thus characterizing the particle size. Since particles with a diameter less than 50 nm have a large error in the statistical process and are difficult to accurately identify, and the particle size of conductive agents is generally less than 50 nm, which will produce a large error in the statistical results, particles with a diameter less than 50 nm are not counted in the particle size statistics process of this application. Following the above method, to ensure a statistically significant sample size, at least 10 non-overlapping scanning electron microscope (SEM) images were acquired for each electrode, and the particle size of at least 1000 lithium transition metal phosphate (LiMT) particles was statistically analyzed. The obtained LiMT particles were sorted from smallest to largest size, and a cumulative number distribution curve was obtained with particle size as the horizontal axis and cumulative number (the total number of particles) as the vertical axis. In the cumulative number distribution curve, the particle sizes corresponding to 50% and 90% of the cumulative number are the Dn50 and Dn90 of the LiMT particles in the cross-section along the electrode thickness direction of the positive electrode active material layer, respectively, in nm.

[0191] In some embodiments, the Dn50 of the lithium transition metal phosphate particles in the cross-section of the positive electrode active material layer along the electrode thickness direction can be 100nm, 105nm, 110nm, 115nm, 120nm, 125nm, 130nm, 135nm, 140nm, 145nm, 150nm, 155nm, 160nm, 165nm, 170nm, 175nm, 180nm, 185nm, 190nm, 195nm, 200nm, 205nm, 210nm, 215nm, 220nm, 225nm, 230nm, 235nm, 240nm, 245nm, 250nm, 255nm, 260nm, 265nm, 270nm, 275nm, 280nm, 285nm, 290nm, 295nm, 300nm, or any value range between the two.

[0192] When the Dn50 of lithium transition metal phosphate particles in the cross-section along the thickness direction of the positive electrode active material layer is less than 100 nm, it means that the particle size of the lithium transition metal phosphate particles is small. Their large specific surface area intensifies the dissolution of manganese ions, which further dissolve in the electrolyte and are reduced and precipitated at the negative electrode. This easily damages the solid electrolyte interphase (SEI) film, causing more active lithium to be consumed during the SEI film repair process. When the Dn50 of lithium transition metal phosphate particles in the cross-section along the thickness direction of the positive electrode active material layer is greater than 300 nm, it means that the particle size of lithium transition metal phosphate particles is large. The lithium ion transport path increases, but the improvement of the kinetic performance of lithium transition metal phosphate particles is insufficient. It cannot effectively match the kinetic performance of lithium transition metal oxide particles. Lithium transition metal oxide particles are prone to particle breakage and surface structure collapse due to current overload, which will adversely affect the cycle stability of the hybrid battery cells.

[0193] In some embodiments, the Dn90 of the lithium transition metal phosphate particles in the cross-section of the positive electrode active material layer along the electrode thickness direction can be 250nm, 255nm, 260nm, 265nm, 270nm, 275nm, 280nm, 285nm, 290nm, 295nm, 300nm, 305nm, 310nm, 315nm, 320nm, 325nm, 330nm, 335nm, 340nm, 345nm, 350nm, 355nm, or 360nm. nm, 365nm, 370nm, 375nm, 380nm, 385nm, 390nm, 395nm, 400nm, 405nm, 410nm, 415nm, 420nm, 425nm, 430nm, 435nm, 440nm, 445nm, 450nm, 455nm, 460nm, 465nm, 470nm, 475nm, 480nm, 485nm, 490nm, 495nm, 500nm, or any range between two of these values.

[0194] When the Dn50 of lithium transition metal phosphate particles in the cross-section along the thickness direction of the positive electrode active material layer is 100nm-300nm, but the Dn90 is less than 250nm, it means that there is an excessive amount of small particles in the lithium transition metal phosphate particles. This increases the specific surface area of ​​most lithium transition metal phosphate particles, leading to accelerated manganese ion dissolution. The manganese ions further dissolve in the electrolyte and are reduced and precipitated at the negative electrode, easily damaging the solid electrolyte interphase (SEI) film, resulting in more active lithium being released into the SEI. It is consumed during the membrane repair process; when the Dn50 of lithium transition metal phosphate particles in the cross section along the thickness direction of the positive electrode active material layer is 100nm-300nm, but the Dn90 of lithium transition metal phosphate particles is greater than 500nm, it means that there are still many large particles with insufficient kinetic performance in the lithium transition metal phosphate particles. Most of the charge and discharge current is still concentrated in the lithium transition metal oxide particles with better kinetics, which cannot effectively alleviate the load shunting phenomenon and is not conducive to improving the cycle stability of the hybrid system battery cell.

[0195] In this application, the types and mass contents of each component in the electrolyte can be obtained by detecting the electrolyte using any method known to those skilled in the art. For example, the composition and content of the electrolyte can be characterized using one or more of the following methods: gas chromatography-mass spectrometry (GC-MS), ion chromatography (IC), liquid chromatography (LC), nuclear magnetic resonance spectroscopy (NMR), and gas chromatography-mass spectrometry (GC-MS). For example, referring to GB / T-9722-2023 "General Rules for Gas Chromatography of Chemical Reagents" and / or GB / T6041-2020 "General Rules for Mass Spectrometry Analysis Methods", gas chromatography and mass spectrometry are coupled. After gas chromatography separates the components in the sample, the components are broken into ion fragments in mass spectrometry and separated according to mass-to-charge ratio (m / z) to form specific mass spectra, obtaining qualitative analysis of each organic component in the electrolyte. Then, the organic components in the electrolyte are separated in the chromatographic column, and detection signal spectra of each component are generated. The retention time is used for component qualitative analysis, and the peak area is corrected by standardization to achieve quantification, obtaining quantitative analysis of the organic components in the electrolyte. Referring to JY / T-020, the types of anions of electrolyte salts in the electrolyte are detected by ion chromatography and quantitatively analyzed. Referring to JY / T0578-2020, nuclear magnetic resonance spectroscopy (NMR) is used to obtain qualitative and quantitative analysis of the components in the electrolyte.

[0196] In this application, the electrolyte can be either fresh electrolyte or electrolyte obtained by disassembling a battery cell. The electrolyte obtained by disassembling a battery cell can be either the free electrolyte in the battery casing or the electrolyte obtained by centrifugation from the electrodes.

[0197] In some implementations, the mass percentage of the first component is 0.2%-6% based on the total mass of the electrolyte.

[0198] In some implementations, based on the total mass of the electrolyte, the mass percentage of the first component can be 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%. 2.9%, 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%, or any range of two.

[0199] Within the aforementioned range, the first component helps to further block the dissolution of manganese ions, reduce their damage to the SEI film and the consumption of active lithium, and improve the cycle performance of the hybrid system battery cells.

[0200] In some implementations, the mass percentage of the first component is 0.5%-5% based on the total mass of the electrolyte.

[0201] In some implementations, the first component accounts for 2%-4% of the total mass of the electrolyte.

[0202] Within the aforementioned range, the first component not only helps to block the dissolution of manganese ions, reduce their damage to the SEI film and the consumption of active lithium, but also helps to form a CEI film with appropriate thickness and moderate impedance, thereby taking into account both the cycle performance and rate performance of the hybrid battery cells.

[0203] In some embodiments, the first component includes lithium difluorophosphate.

[0204] In some embodiments, the Dn50 of lithium transition metal phosphate particles in the cross-section of the positive electrode active material layer along the electrode thickness direction is 100nm-250nm.

[0205] The Dn50 of lithium transition metal phosphate particles within the above range helps to further shorten the lithium-ion diffusion path and improve its kinetic performance, thereby further increasing its reaction participation with lithium transition metal phosphate particles, alleviating the problem of lithium transition metal oxide particles being prone to particle breakage and surface structure collapse due to current overload, and improving the cycle performance of hybrid system battery cells.

[0206] In some embodiments, the Dn90 of lithium transition metal phosphate particles in the cross-section of the positive electrode active material layer along the electrode thickness direction is 270nm-400nm.

[0207] The Dn90 of lithium transition metal phosphate particles within the above range helps to further shorten the lithium-ion diffusion path and improve its kinetic performance, thereby further increasing its reaction participation with lithium transition metal phosphate particles, alleviating the problem of lithium transition metal oxide particles being prone to particle breakage and surface structure collapse due to current overload, and improving the cycle performance of hybrid system battery cells.

[0208] In some embodiments, in the cross section of the positive electrode active material layer along the thickness direction of the electrode sheet, the Dn10 of the lithium transition metal phosphate particles is 70nm-130nm, where Dn10 refers to the particle size corresponding to the cumulative number of particles of 10% in the cumulative number distribution curve of particle size.

[0209] In this application, the Dn10 of lithium transition metal phosphate particles in the cross-section of the positive electrode active material layer along the electrode thickness direction can be tested by referring to the test methods for Dn50 and Dn90 of lithium transition metal phosphate particles in the cross-section of the positive electrode active material layer along the electrode thickness direction described above.

[0210] In some embodiments, the Dn10 of the lithium transition metal phosphate particles in the cross-section of the positive electrode active material layer along the thickness direction of the electrode sheet can be 70nm, 72nm, 74nm, 76nm, 78nm, 80nm, 82nm, 84nm, 86nm, 88nm, 90nm, 92nm, 94nm, 96nm, 98nm, 100nm, 102nm, 104nm, 106nm, 108nm, 110nm, 112nm, 114nm, 116nm, 118nm, 120nm, 122nm, 124nm, 126nm, 128nm, 130nm, or any value range between the two.

[0211] The Dn10 of lithium transition metal phosphate particles is within the above range, indicating that it contains a certain amount of small-sized particles, which helps to further improve the kinetic performance of lithium transition metal phosphate particles, alleviate the structural collapse caused by excessive deintercalation of lithium transition metal oxide particles, and further improve the cycle performance of hybrid battery cells.

[0212] In some embodiments, the molar percentage of manganese is 40%-60% based on the total molar number of manganese and iron in the lithium transition metal phosphate particles.

[0213] The manganese content in lithium transition metal phosphate particles within the above-mentioned range helps to improve the matching of their working voltage range with lithium transition metal oxide particles while taking into account the kinetic performance of lithium transition metal phosphate particles, thereby further improving the cycle performance of the battery cell.

[0214] In some embodiments, the electrolyte further includes lithium hexafluorophosphate and a second component, the second component including one or more of lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, and lithium bis(trifluoromethanesulfonyl)imide.

[0215] Electrolytes typically require a certain ion concentration to maintain good rate performance of individual battery cells. Lithium hexafluorophosphate (LiPF6) has advantages such as low cost, good solubility, and the ability to passivate current collectors to improve their stability; therefore, the electrolyte in this application also includes LiPF6.

[0216] The applicant further discovered that small-diameter lithium transition metal phosphate particles have a large specific surface area, significantly increasing residual water during battery manufacturing. This readily triggers the hydrolysis of electrolyte salts in the electrolyte, generating highly corrosive hydrofluoric acid, which damages the surface structure of the positive electrode active material and affects the cycle performance of the battery cells. In the embodiments of this application, a second component that is not easily hydrolyzed is further introduced, which can replace part of the easily hydrolyzed lithium hexafluorophosphate to reduce the generation of hydrofluoric acid, thereby further improving the cycle performance of the hybrid system battery cells.

[0217] In some implementations, based on the total mass of the electrolyte, lithium hexafluorophosphate accounts for 5%-10% of the mass, and the second component accounts for 0.1%-8% of the mass.

[0218] In some implementations, the mass percentage of lithium hexafluorophosphate, based on the total mass of the electrolyte, can be 5%, 5.1%, 5.2%, 5.3%, 5.4%, 5.5%, 5.6%, 5.7%, 5.8%, 5.9%, 6%, 6.1%, 6.2%, 6.3%, 6.4%, 6.5%, 6.6%, 6.7%, 6.8%, 6.9%, 7%, 7.1%, 7.2%, 7.3%, 7.4%, 7.5%, 7.6%, 7.7%, 7.8%, 7.9%, 8%, 8.1%, 8.2%, 8.3%, 8.4%, 8.5%, 8.6%, 8.7%, 8.8%, 8.9%, 9%, 9.1%, 9.2%, 9.3%, 9.4%, 9.5%, 9.6%, 9.7%, 9.8%, 9.9%, 10%, or any value between the two.

[0219] Controlling the mass ratio of lithium hexafluorophosphate within the above range helps to maintain the ionic conductivity of the electrolyte while reducing the amount of hydrofluoric acid generated, mitigating damage to the structure of the positive electrode active material, and further improving the cycle performance of the hybrid battery cell.

[0220] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the second component can be 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%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 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%, 6.1%, 6.2%, 6.3%, 6.4%, 6.5%, 6.6%, 6.7%, 6.8%, 6.9%, 7%, 7.1%, 7.2%, 7.3%, 7.4%, 7.5%, 7.6%, 7.7%, 7.8%, 7.9%, 8%, or any range of two.

[0221] The mass percentage of the second component within the above range helps to reduce the mass percentage of conventional electrolyte salts, thereby reducing the amount of hydrofluoric acid generated, inhibiting its damage to the surface structure of the positive electrode active material, and improving the cycle performance of the hybrid system battery cells.

[0222] In some implementations, the second component accounts for 0.5%-8% of the total mass of the electrolyte.

[0223] In some implementations, the second component accounts for 3%-8% of the total mass of the electrolyte.

[0224] The mass percentage of the second component is further within the above range, which helps to further reduce the amount of hydrofluoric acid generated, suppress its damage to the surface structure of the positive electrode active material, and improve the cycle performance of the hybrid system battery cells.

[0225] In some embodiments, the second component includes lithium bisfluorosulfonylimide, which accounts for 0.1%-8% of the total mass of the electrolyte.

[0226] In some embodiments, the second component includes lithium bisfluorosulfonylimide, and the mass percentage of lithium bisfluorosulfonylimide based on the total mass of the electrolyte can be 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%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, or 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%, 6.1%, 6.2%, 6.3%, 6.4%, 6.5%, 6.6%, 6.7%, 6.8%, 6.9%, 7%, 7.1%, 7.2%, 7.3%, 7.4%, 7.5%, 7.6%, 7.7%, 7.8%, 7.9%, 8%, or any range of values ​​between the two.

[0227] In some embodiments, the second component includes lithium bisfluorosulfonylimide, which accounts for 2%-5% of the total mass of the electrolyte.

[0228] If the mass percentage of lithium bis(fluorosulfonyl)imide is too low, its effect on reducing hydrofluoric acid formation is limited; if its content is too high, it easily corrodes the current collector. Maintaining the mass percentage of lithium bis(fluorosulfonyl)imide within the range of 2%-5% helps to balance reducing hydrofluoric acid formation with its destructive effect on the current collector, thereby further improving the cycle performance of the battery cells.

[0229] In some embodiments, the electrolyte includes cyclic carbonate compounds, and the cyclic carbonate compounds account for 20%-45% of the total mass of the electrolyte.

[0230] In some embodiments, the electrolyte includes cyclic carbonate compounds, and the mass percentage of the cyclic carbonate compounds, based on the total mass of the electrolyte, can be 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, or any range between the two.

[0231] The presence of cyclic carbonate compounds in the electrolyte, with their mass percentage falling within the aforementioned range, helps to increase the degree of lithium salt dissociation in the electrolyte, increase the lithium ion concentration, and thus improve the ionic conductivity of the electrolyte, thereby contributing to improving the rate performance of the battery cell.

[0232] In some embodiments, the electrolyte includes cyclic carbonate compounds, and the cyclic carbonate compounds account for 20%-35% of the total mass of the electrolyte.

[0233] In some embodiments, the cyclic carbonate compound includes one or more of ethylene carbonate, propylene carbonate, and butene carbonate.

[0234] In some embodiments, cyclic carbonate compounds include ethylene carbonate.

[0235] In some embodiments, the electrolyte includes chain carbonate compounds, and the chain carbonate compounds account for 40%-75% of the total mass of the electrolyte.

[0236] In some embodiments, the electrolyte includes a chain carbonate compound, and the mass percentage of the chain carbonate compound, based on the total mass of the electrolyte, can be 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, or any range between the two.

[0237] Chain carbonate compounds have low viscosity. Including chain carbonate compounds in the electrolyte and controlling their mass percentage within the above range helps to reduce the viscosity of the electrolyte, thereby improving the ionic conductivity of the electrolyte and improving the rate performance of the battery cells.

[0238] In some embodiments, the electrolyte includes chain carbonate compounds, and the chain carbonate compounds account for 50%-70% of the total mass of the electrolyte.

[0239] In some embodiments, the chain carbonate compound includes one or more of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and methyl propyl carbonate.

[0240] In some embodiments, the chain carbonate includes methyl ethyl carbonate and diethyl carbonate.

[0241] Ethyl methyl carbonate and dimethyl carbonate have good high-voltage resistance, which helps to reduce the degree of side reactions of the electrolyte under high voltage, improve the stability of the electrolyte, and further improve the cycle performance of the hybrid battery cells.

[0242] In some embodiments, the electrolyte includes ethyl methyl carbonate, and the mass percentage of ethyl methyl carbonate is 35%-55% based on the total mass of the electrolyte.

[0243] In some embodiments, the electrolyte includes ethyl methyl carbonate, and the mass percentage of ethyl methyl carbonate based on the total mass of the electrolyte can be 35%, 35.5%, 36%, 36.5%, 37%, 37.5%, 38%, 38.5%, 39%, 39.5%, 40%, 40.5%, 41%, 41.5%, 42%, 42.5%, 43%, 43.5%, 44%, 44.5%, 45%, 45.5%, 46%, 46.5%, 47%, 47.5%, 48%, 48.5%, 49%, 49.5%, 50%, 50.5%, 51%, 51.5%, 52%, 52.5%, 53%, 53.5%, 54%, 54.5%, 55%, or any value between the two.

[0244] In some embodiments, the electrolyte includes diethyl carbonate, which accounts for 10%-20% of the total mass of the electrolyte.

[0245] In some embodiments, the electrolyte includes diethyl carbonate, and the mass percentage of diethyl carbonate based on the total mass of the electrolyte can be 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, 18.5%, 19%, 19.5%, 20%, or any value between the two.

[0246] In some embodiments, the electrolyte further includes a third component, which includes one or more of vinylene carbonate, fluoroethylene carbonate, 1,3-propane sulpholactone, and vinyl sulfate.

[0247] As mentioned above, the transition metals can easily damage the SEI film after dissolving from the positive electrode. In this application, a third component is further introduced, which helps to improve the stability of the SEI film, reduce the probability of SEI film rupture and regeneration, reduce electrolyte consumption, and further improve the cycle performance of the hybrid system battery cells.

[0248] In some implementations, the third component accounts for 0.08%-5% of the total mass of the electrolyte.

[0249] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the third component is 0.08%, 0.1%, 0.12%, 0.14%, 0.16%, 0.18%, 0.2%, 0.22%, 0.24%, 0.26%, 0.28%, 0.3%, 0.32%, 0.34%, 0.36%, 0.38%, 0.4%, 0.42%, 0.44%, 0.46%, 0.48%, 0.5%, 0.52%, 0.54%, 0.56%, 0.58%, 0.6%, 0.62%, 0.64%, 0.66%, 0.68%, 0.7%, 0.72%, 0.74%, 0.76%, 0.78%, 0.8%, 0.82%, 0. 84%, 0.86%, 0.88%, 0.9%, 0.92%, 0.94%, 0.96%, 0.98%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5%, or any range of two.

[0250] The mass ratio of the third component within the above range helps to improve the strength of the SEI film, further improve the cycle performance of the hybrid battery cells, and also helps to obtain an SEI film of suitable thickness, taking into account both the cycle performance and rate performance of the battery cells.

[0251] In some implementations, the third component accounts for 0.1%-5% of the total mass of the electrolyte.

[0252] In some implementations, the third component accounts for 1%-5% of the total mass of the electrolyte.

[0253] In some embodiments, the Dn50 of lithium transition metal oxide particles in the cross-section of the positive electrode active material layer along the electrode thickness direction is 1μm-4μm.

[0254] In this application, the Dn50 of lithium transition metal oxide particles in the cross-section of the positive electrode active material layer along the electrode thickness direction can be tested by referring to the test methods of Dn50 and Dn90 of lithium transition metal phosphate particles in the cross-section of the positive electrode active material layer along the electrode thickness direction mentioned above, with appropriate adjustment of the magnification.

[0255] In some embodiments, the Dn50 of the lithium transition metal oxide particles in the cross-section of the positive electrode active material layer along the electrode thickness direction can be 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm, 3.5 μm, 3.6 μm, 3.7 μm, 3.8 μm, 3.9 μm, 4 μm, or any value range between the two.

[0256] Compared to lithium transition metal phosphate particles, lithium transition metal oxide particles have a higher specific capacity. As a result, the area where lithium transition metal oxide particles are located in the positive electrode active material layer will release a large number of lithium ions per unit time. This requires the corresponding negative electrode side to bear a high concentration of lithium ion insertion, and may even cause local lithium plating, affecting the cycle performance of the battery cell.

[0257] In the embodiments of this application, the Dn50 of the lithium transition metal oxide particles is within the above range, indicating that they have a smaller particle size, which helps to improve the uniformity of the distribution of lithium transition metal oxide particles, improve the uniformity of the specific capacity in different regions of the positive electrode active material layer, reduce the probability of excessively high local lithium ion concentration, improve the local lithium plating phenomenon on the negative electrode side, and further improve the cycle performance of the hybrid system battery cell.

[0258] In some embodiments, the Dn50 of lithium transition metal oxide particles in the cross-section of the positive electrode active material layer along the electrode thickness direction is 1μm-3μm.

[0259] In some embodiments, the Dn50 of the lithium transition metal oxide particles in the cross-section of the positive electrode active material layer along the electrode thickness direction is 1.5 μm-2.5 μm.

[0260] In some embodiments, the particle size distribution concentration of lithium transition metal oxide particles (Dn90-Dn10) / Dn50 in the cross section along the thickness direction of the positive electrode active material layer is 0.6-2.

[0261] In this application, the Dn10 and Dn90 of lithium transition metal oxide particles in the cross-section of the positive electrode active material layer along the electrode thickness direction can be tested by referring to the test method of the Dn50 and Dn90 of lithium transition metal phosphate particles in the cross-section of the positive electrode active material layer along the electrode thickness direction mentioned above, with appropriate adjustment of the magnification.

[0262] In some embodiments, the particle size distribution concentration (Dn90-Dn10) / Dn50 of the lithium transition metal oxide particles in the cross-section along the electrode thickness direction of the positive electrode active material layer can be 0.6, 0.62, 0.64, 0.66, 0.68, 0.7, 0.72, 0.74, 0.76, 0.78, 0.8, 0.82, 0.84, 0.86, 0.88, 0.9, 0.92, 0.94, 0.96, 0.98, 1, 1.02, 1.04, 1.06, 1.08, 1.1, 1.12, 1.14, 1.16, or 1.1. 8, 1.2, 1.22, 1.24, 1.26, 1.28, 1.3, 1.32, 1.34, 1.36, 1.38, 1.4, 1.42, 1.44, 1.46, 1.48, 1.5, 1.52, 1.54, 1.56, 1.58, 1.6, 1.62, 1.64, 1.66, 1.68, 1.7, 1.72, 1.74, 1.76, 1.78, 1.8, 1.82, 1.84, 1.86, 1.88, 1.9, 1.92, 1.94, 1.96, 1.98, 2, or any range of values ​​between two of these.

[0263] The particle size distribution concentration (Dn90-Dn10) / Dn50 of lithium-containing transition metal oxide particles is 0.6-2, which indicates that the particle size of lithium-containing transition metal oxide particles is relatively uniform. This reduces the risk of individual large lithium-containing transition metal oxide particles appearing in the positive electrode active material layer, helps to improve the uniformity of specific capacity in different regions of the active material layer, thereby reducing the probability of excessively high local lithium-ion concentration, improving the local lithium plating phenomenon on the negative electrode side, and further improving the cycle performance of the hybrid system battery cell.

[0264] In some embodiments, the particle size distribution concentration (Dn90-Dn10) / Dn50 of lithium-containing transition metal oxide particles in the cross section along the thickness direction of the positive electrode active material layer is 0.8-1.8.

[0265] The particle size distribution concentration (Dn90-Dn10) / Dn50 of lithium-containing transition metal oxide particles is 0.8-1.8, which helps to further improve the uniformity of the particle size of lithium-containing transition metal oxide particles, improve the uniformity of the specific capacity in different regions of the active material layer, thereby reducing the probability of excessively high local lithium-ion concentration, improving the local lithium plating phenomenon on the negative electrode side, and further improving the cycle performance of the hybrid system battery cell.

[0266] In some embodiments, the Dn10 of the lithium transition metal oxide particles in the cross-section of the positive electrode active material layer along the electrode thickness direction is 0.5 μm-2 μm.

[0267] In some embodiments, the Dn10 of the lithium transition metal oxide particles in the cross-section of the positive electrode active material layer along the thickness direction of the electrode can be 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm or any value range between the two.

[0268] In some embodiments, the Dn10 of the lithium transition metal oxide particles in the cross-section of the positive electrode active material layer along the electrode thickness direction is 0.5 μm-1.5 μm.

[0269] In some embodiments, the Dn90 of the lithium transition metal oxide particles in the cross-section of the positive electrode active material layer along the electrode thickness direction is 2.5 μm-5 μm.

[0270] In some embodiments, the Dn90 of the lithium transition metal oxide particles in the cross-section of the positive electrode active material layer along the thickness direction of the electrode sheet can be 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm, 3.5 μm, 3.6 μm, 3.7 μm, 3.8 μm, 3.9 μm, 4 μm, 4.1 μm, 4.2 μm, 4.3 μm, 4.4 μm, 4.5 μm, 4.6 μm, 4.7 μm, 4.8 μm, 4.9 μm, 5 μm, or any value range between the two.

[0271] The Dn90 of lithium transition metal oxide particles within the above range helps to further reduce the content of large particles in lithium transition metal oxide particles, reduce the local lithium-ion concentration, alleviate the local lithium plating phenomenon, and further improve the cycle performance of hybrid system battery cells.

[0272] In some embodiments, the Dn90 of the lithium transition metal oxide particles in the cross-section of the positive electrode active material layer along the electrode thickness direction is 3μm-4μm.

[0273] In some implementations, the molar percentage of nickel is 50%-80% based on the total molar number of nickel, cobalt and X1 elements in the lithium transition metal oxide particles.

[0274] In this application, the molar percentage of nickel, cobalt, and X1 elements in the lithium transition metal oxide particles is determined by methods and equipment known in the art. A specific testing method is illustrated below: Disassemble the battery cell to obtain the positive electrode sheet. Cut the positive electrode sheet into 6mm x 6mm samples using ceramic scissors and attach them to a sample stage coated with paraffin wax, ensuring the sample protrudes slightly (<1mm) from the edge of the sample stage. Then, turn on the argon ion cross-section polisher (JEOL IB-09010 CP type argon ion cross-section polisher) and perform vacuuming (10... -7 Adjusting the parameters, the positive electrode test film layer was cut along the thickness direction of the sample using a polishing instrument. After exposing the cut surface, a scanning electron microscope (SEM) was used to observe the cross-section of the positive electrode sheet along the thickness direction. The positive current collector and the positive active material layer set on both sides of the positive current collector were observed under the SEM. The field of view was then adjusted to the positive active material layer, and the field of view area was taken as the test area. An SEM image was taken to obtain a cross-section of the positive active material layer along the thickness direction of the positive electrode sheet. An energy dispersive spectroscopy (EDS) surface scan was performed on the test area. Based on the distribution spectrum of P element in the test area, the area where P element was not clearly displayed was magnified. The particle composition was determined by the EDS, and it was identified as lithium-containing transition metal oxide particles. The lithium-containing transition metal oxide particles were selected for EDS testing to obtain the molar percentage of each element in the particles. The molar percentage of nickel was calculated based on the total molar number of nickel, cobalt, and X1 elements in the lithium-containing transition metal oxide particles. Measure at least 10 particles and take the average value as the test result.

[0275] In some embodiments, based on the total number of moles of nickel, cobalt, and X1 in the lithium transition metal oxide particles, the molar percentage of nickel can be 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, or any value between the two.

[0276] The molar percentage of nickel within the above range helps to balance the specific capacity of lithium-containing transition metal oxide particles and the degree of side reaction with the electrolyte, thereby balancing the energy density and cycle performance of the hybrid battery cell.

[0277] In some implementations, the molar percentage of cobalt is 5%-20% based on the total molar number of nickel, cobalt and X1 elements in the lithium transition metal oxide particles.

[0278] In some embodiments, based on the total molar number of nickel, cobalt, and X1 elements in the lithium transition metal oxide particles, the molar percentage of cobalt can be 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, 18.5%, 19%, 19.5%, 20%, or any value between the two.

[0279] In some implementations, the molar percentage of the element X1 is 15%-40% based on the total molar number of nickel, cobalt and X1 elements in the lithium transition metal oxide particles.

[0280] In some embodiments, based on the total molar number of nickel, cobalt, and X1 elements in the lithium transition metal oxide particles, the molar percentage of X1 element can be 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, 18.5%, 19%, 19.5%, 20%, 20.5%, 21%, 21.5%, 22%, 22.5%, 23%, 23.5%, 24%, 24.5%, 25%, 25.5%, 26%, 26.5%, 27%, 27.5%, 28%, 28.5%, 29%, 29.5%, 30%, 30.5%, 31%, 31.5%, 32%, 32.5%, 33%, 33.5%, 34%, 34.5%, 35%, 35.5%, 36%, 36.5%, 37%, 37.5%, 38%, 38.5%, 39%, 39.5%, 40%, or any value between the two.

[0281] In some embodiments, the lithium-containing transition metal oxide particles are lithium-containing transition metal oxide single crystal particles.

[0282] The presence of lithium-containing transition metal oxide particles, specifically single-crystal lithium-containing transition metal oxide particles, helps to reduce the size of the lithium-containing transition metal oxide particles, thereby improving the uniformity of the specific capacity of the positive electrode active material layer. This reduces the probability of excessively high local lithium-ion concentration, improves the local lithium plating phenomenon on the negative electrode side, and further improves the cycle performance of the hybrid system battery cell.

[0283] In some implementations, the mass percentage of lithium transition metal oxide particles is 50%-90% based on the total mass of the positive electrode active material.

[0284] In this application, the "mass percentage of lithium transition metal oxide particles based on the total mass of the positive electrode active material" can be obtained by any method known in the art. For example, inductively coupled plasma atomic emission spectrometry (ICP) or X-ray diffraction (XRD) can be used for detection. Taking ICP as an example, the battery cell is disassembled to obtain the positive electrode sheet, and the positive electrode active material powder is obtained by scraping. The powder is then completely digested with acid (such as HNO3-HCl mixed acid) under isothermal conditions, so that all Ni, Co, M (Mn and / or Al), Fe, and P elements in the sample enter the solution. The elemental concentrations of Ni, Co, M, Fe, and P elements in the solution are measured by inductively coupled plasma atomic emission spectrometry (ICP-OES) or inductively coupled plasma mass spectrometry (ICP-MS). The mass of lithium transition metal oxide particles is calculated based on the molar ratio of Ni, Co, and M elements and the molar mass of each element in the lithium transition metal oxide particles. Then, the mass of lithium transition metal phosphate particles is calculated by combining the Fe and P elements. The mass percentage of lithium transition metal oxide particles is obtained based on the total mass of both.

[0285] In some implementations, based on the total mass of the positive electrode active material, the mass percentage of lithium transition metal oxide particles can be 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, or any value between the two.

[0286] In positive electrode active materials, a mass ratio of lithium transition metal oxide particles within the above-mentioned range helps to balance the cost and energy density of hybrid battery cells.

[0287] In some implementations, the mass percentage of lithium transition metal oxide particles is 60%-80% based on the total mass of the positive electrode active material.

[0288] In some embodiments, the lithium-containing transition metal oxide particles include one or more of lithium-containing nickel-cobalt-manganese oxides and their doped and / or coated modified materials, and lithium-containing nickel-cobalt-aluminum oxides and their doped and / or coated modified materials.

[0289] In some embodiments, the lithium transition metal phosphate particles include a particle body and a carbon material disposed on at least a portion of the surface of the particle body.

[0290] The lithium-containing transition metal phosphate particles include carbon material disposed on at least part of the particle body surface, which helps to improve their kinetic performance, thereby increasing the reaction participation of the lithium-containing transition metal phosphate particles, alleviating the structural degradation problem caused by over-reaction of lithium-containing transition metal oxide particles, and further improving the cycle performance of hybrid system battery cells.

[0291] In some implementations, the average thickness of the carbon material is 2 nm to 25 nm.

[0292] In this application, the thickness of the carbon material can be tested using methods and instruments known in the art. As an example, referring to the method described above, an electron microscope image of the positive electrode active material layer is taken and lithium-containing transition metal phosphate particles are identified. Then, ImageJ software is used to test the thickness of the carbon material.

[0293] In some embodiments, the average thickness of the carbon material can be 2 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm, 5 nm, 5.5 nm, 6 nm, 6.5 nm, 7 nm, 7.5 nm, 8 nm, 8.5 nm, 9 nm, 9.5 nm, 10 nm, 10.5 nm, 11 nm, 11.5 nm, 12 nm, 12.5 nm, 13 nm, 13.5 nm, 14 nm, 14.5 nm, 15 nm, 15.5 nm, 16 nm, 16.5 nm, 17 nm, 17.5 nm, 18 nm, 18.5 nm, 19 nm, 19.5 nm, 20 nm, 20.5 nm, 21 nm, 21.5 nm, 22 nm, 22.5 nm, 23 nm, 23.5 nm, 24 nm, 24.5 nm, 25 nm, or any value between the two.

[0294] In some implementations, the carbon material accounts for 0.5%-3% of the total mass of the lithium transition metal phosphate particles.

[0295] In some implementations, the mass percentage of carbon material, based on the total mass of lithium transition metal phosphate particles, can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, or any range between the two.

[0296] In some embodiments, the lithium transition metal phosphate particles comprise the components represented by the following general formula I: Li m1 Fe x1 Mn y1 M1b1 P z1 Q1 c1 O n1 N1 d1 Formula I; Wherein, 0.8≤m1≤1.2, 0<x1<1, 0<y1<1, 0.9≤x1+y1≤1, 0.95≤z1≤1, 3.5≤n1≤4, 0≤b1≤0.1, 0≤c1≤0.1, 0≤d1≤0.1; wherein, M1 includes one or more of Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, and Ti, Q1 includes one or more of B, S, Si, and N, and N1 includes one or more of F, Cl, and Br.

[0297] In some implementations, m1 can be 0.8, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.1, 1.11, 1.12, 1.13, 1.14, 1.15, 1.16, 1.17, 1.18, 1.19, 1.2, or any value range between the two.

[0298] In some implementations, x1 can be 0.01, 0.04, 0.07, 0.1, 0.13, 0.16, 0.19, 0.22, 0.25, 0.28, 0.31, 0.34, 0.37, 0.4, 0.43, 0.46, 0.49, 0.52, 0.55, 0.58, 0.61, 0.64, 0.67, 0.7, 0.73, 0.76, 0.79, 0.82, 0.85, 0.88, 0.91, 0.94, 0.97, 0.98, 0.99, or any value range between the two.

[0299] In some implementations, y1 can be 0.01, 0.04, 0.07, 0.1, 0.13, 0.16, 0.19, 0.22, 0.25, 0.28, 0.31, 0.34, 0.37, 0.4, 0.43, 0.46, 0.49, 0.52, 0.55, 0.58, 0.61, 0.64, 0.67, 0.7, 0.73, 0.76, 0.79, 0.82, 0.85, 0.88, 0.91, 0.94, 0.97, 0.98, 0.9, or any value range between the two.

[0300] In some implementations, x1+y1 can be 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1, or any range between the two.

[0301] In some implementations, z1 can be a value range of 0.95, 0.96, 0.97, 0.98, 0.99, 1, or any two of these values.

[0302] In some implementations, n1 can be 3.5, 3.51, 3.52, 3.53, 3.54, 3.55, 3.56, 3.57, 3.58, 3.59, 3.6, 3.61, 3.62, 3.63, 3.64, 3.65, 3.66, 3.67, 3.68, 3.69, 3.7, 3.71, 3.72, 3.73, 3.74, 3.75, 3.76, 3.77, 3.78, 3.79, 3.8, 3.81, 3.82, 3.83, 3.84, 3.85, 3.86, 3.87, 3.88, 3.89, 3.9, 3.91, 3.92, 3.93, 3.94, 3.95, 3.96, 3.97, 3.98, 3.99, 4, or any range of two.

[0303] In some implementations, b1 can be 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, or any value range between the two.

[0304] In some implementations, c1 can be 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, or any value range between the two.

[0305] In some implementations, the value can be 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, or any range between the two.

[0306] In some embodiments, the positive electrode active material layer includes a first conductive agent, which includes a dotted conductive agent, and the dotted conductive agent includes one or more of Super P, Ketjen Black, acetylene black, and conductive graphite.

[0307] In some implementations, the mass percentage of the dot-shaped conductive agent is 0.2%-2.0% based on the total mass of the positive electrode active material layer.

[0308] In some embodiments, based on the total mass of the positive electrode active material layer, the mass percentage of the dot-shaped conductive agent can be 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, 1%, 1.05%, 1.1%, 1.15%, 1.2%, 1.25%, 1.3%, 1.35%, 1.4%, 1.45%, 1.5%, 1.55%, 1.6%, 1.65%, 1.7%, 1.75%, 1.8%, 1.85%, 1.9%, 1.95%, 2%, or any value between the two.

[0309] In some embodiments, the first conductive agent further includes a linear conductive agent, which includes one or more of carbon nanotubes and carbon nanofibers.

[0310] In this application, carbon nanofibers include, but are not limited to, one or more of vapor-grown carbon fibers and graphite carbon fibers.

[0311] Compared to lithium transition metal oxide particles, lithium transition metal phosphate particles have smaller particle sizes. The large difference in particle size between the two leads to a reduction in the degree of contact, which in turn affects the continuity of the electron transport network in the positive electrode active material layer and is prone to polarization, thus affecting the cycle performance of the battery cell.

[0312] In this embodiment, the first conductive agent includes a linear conductive agent, which helps to enhance the electrical contact between two positive electrode active materials with significant differences in particle size through bridging, thereby improving the electronic conductivity of the positive electrode active material layer. At the same time, the linear conductive agent is used in conjunction with the dotted conductive agent to synergistically construct a good electronic transport network that takes into account both long-range and short-range conductivity, thereby alleviating polarization and further improving the cycle performance of the hybrid system battery cell.

[0313] In some implementations, the linear conductive agent includes carbon nanotubes.

[0314] In some implementations, the mass percentage of the linear conductive agent is 0.05%-1.5% based on the total mass of the positive electrode active material layer.

[0315] In some embodiments, based on the total mass of the positive electrode active material layer, the mass percentage of the linear conductive agent can be 0.05%, 0.1%, 0.12%, 0.14%, 0.16%, 0.18%, 0.2%, 0.22%, 0.24%, 0.26%, 0.28%, 0.3%, 0.32%, 0.34%, 0.36%, 0.38%, 0.4%, 0.42%, 0.44%, 0.46%, 0.48%, 0.5%, 0.52%, 0.54%, 0.56%, 0.58%, 0.6%, 0.62%, 0.64%, 0.66%, 0.68%, 0.7%, 0.72%, 0.74%, 0.76%, 0.78%, 0.8%, 0.82%, 0.84%, 0.86%, 0.88%, 0.9%, 0.92%, 0.94%, 0.96%, 0.98%, or 1%. 1.01%, 1.02%, 1.03%, 1.04%, 1.05%, 1.06%, 1.07%, 1.08%, 1.09%, 1.1%, 1.11%, 1.12%, 1.13%, 1.14%, 1.15%, 1.16%, 1.17%, 1.18%, 1.19%, 1.2%, 1.21%, 1.22%, 1.23%, 1.24%, 1.25%, 1.26 %, 1.27%, 1.28%, 1.29%, 1.3%, 1.31%, 1.32%, 1.33%, 1.34%, 1.35%, 1.36%, 1.37%, 1.38%, 1.39%, 1.4%, 1.41%, 1.42%, 1.43%, 1.44%, 1.45%, 1.46%, 1.47%, 1.48%, 1.49%, 1.5%, or any range between the two.

[0316] In some embodiments, the positive electrode active material layer further includes a first polymer.

[0317] In some embodiments, the first polymer includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0318] In some embodiments, the positive electrode film layer further includes a positive electrode undercoating layer disposed on the positive electrode active material layer near the positive electrode current collector side, the positive electrode undercoating layer comprising a second polymer and a second conductive agent.

[0319] On the one hand, the positive electrode undercoat layer helps to improve the adhesion between the positive electrode film and the positive electrode current collector, reducing the probability of separation between the positive electrode film and the positive electrode current collector during cycling; on the other hand, it also helps to improve the electrical contact between the positive electrode active material and the positive electrode current collector, thereby improving the dynamic performance of the battery cell.

[0320] In some implementations, the thickness of the positive electrode undercoat is 0.5 μm to 5 μm.

[0321] In this application, the thickness of the positive electrode undercoat can be tested using methods and instruments known in the art. As an example, an electron microscope image of a cross-section of the positive electrode film along the electrode thickness direction can be taken and imported into ImageJ software for testing.

[0322] In some embodiments, the thickness of the positive electrode undercoat can be 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7μm, 2.8μm, 2.9μm, 3μm, 3.1μm, 3.2μm, 3.3μm, 3.4μm, 3.5μm, 3.6μm, 3.7μm, 3.8μm, 3.9μm, 4μm, 4.1μm, 4.2μm, 4.3μm, 4.4μm, 4.5μm, 4.6μm, 4.7μm, 4.8μm, 4.9μm, 5μm, or any range of two.

[0323] In some embodiments, the compaction density of the positive electrode film is 2.60 g / cm³. 3 -3.4g / cm 3 .

[0324] In this application, the compaction density of the positive electrode film can be tested using methods known in the art. For example, the battery cell is placed at 25°C and discharged at a constant current of 0.05C to 2.0V. The fully discharged electrode is then disassembled, and residual electrolyte is cleaned using an organic solvent (the organic solvent can be any solvent commonly used in the art capable of cleaning electrolytes, including but not limited to dimethyl carbonate). After removing the residual electrolyte, the electrode is dried. An electrode sample with an area of ​​S is weighed using an electronic balance, and the weight is recorded as W. The thickness T of the positive electrode film is then measured (for example, by cutting the positive electrode with an ion beam and then observing the cross-section of the positive electrode film using a scanning electron microscope to obtain the thickness of the positive electrode film). The compaction density of the positive electrode film can be calculated using the formula W / (T×S), with units of g / cm³. 3 .

[0325] In some embodiments, the compaction density of the positive electrode film can be 2.6 g / cm³. 3 2.65g / cm 3 2.7g / cm 3 2.75g / cm3 2.8g / cm 3 2.85g / cm 3 2.9g / cm 3 2.95g / cm 3 3g / cm 3 3.05g / cm 3 3.1g / cm 3 3.15g / cm 3 3.2g / cm 3 3.25g / cm 3 3.3g / cm 3 3.35g / cm 3 3.4g / cm 3 Or the range of values ​​between any two.

[0326] In this embodiment, smaller lithium transition metal phosphate particles fill the gaps between lithium transition metal oxide particles, which helps to increase the compaction density of the positive electrode film, thereby increasing the energy density of the battery cell.

[0327] In some embodiments, the negative electrode sheet 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, which includes graphite, and the volume distribution particle size Dv50 of the negative electrode active material is 7μm-15μm.

[0328] In this application, Dv50 has a well-known meaning in the art, representing the particle size corresponding to a cumulative volume distribution percentage of 50%, which 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 / T19077-2016 Particle Size Distribution Laser Diffraction Method. The testing instrument can be a Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0329] In some embodiments, the volumetric particle size distribution Dv50 of the negative electrode active material can be 7 μm, 7.2 μm, 7.4 μm, 7.6 μm, 7.8 μm, 8 μm, 8.2 μm, 8.4 μm, 8.6 μm, 8.8 μm, 9 μm, 9.2 μm, 9.4 μm, 9.6 μm, 9.8 μm, 10 μm, 10.2 μm, 10.4 μm, 10.6 μm, 10.8 μm, 1 1μm, 11.2μm, 11.4μm, 11.6μm, 11.8μm, 12μm, 12.2μm, 12.4μm, 12.6μm, 12.8μm, 13μm, 13.2μm, 13.4μm, 13.6μm, 13.8μm, 14μm, 14.2μm, 14.4μm, 14.6μm, 14.8μm, 15μm, or any range of two.

[0330] The volume distribution particle size Dv50 of the negative electrode active material is within the above range, which helps to increase the number of lithium-ion insertion ports and shorten the lithium-ion diffusion path, thereby improving the lithium-ion insertion rate, improving the local lithium plating phenomenon on the negative electrode side, and further improving the cycle performance of the hybrid system battery cell.

[0331] In some embodiments, the volume distribution particle size Dv50 of the negative electrode active material is 8 μm-13 μm.

[0332] When the volume distribution particle size Dv50 of the negative electrode active material is within the above range, it is more conducive to increasing the number of lithium-ion insertion ports and shortening the lithium-ion diffusion path, thereby improving the lithium-ion insertion rate, improving the local lithium plating phenomenon on the negative electrode side, and further improving the cycle performance of the hybrid system battery cell.

[0333] In some embodiments, the specific surface area of ​​the negative electrode active material is 0.5 m². 2 / g-3.0m 2 / g.

[0334] In this application, the specific surface area of ​​graphite can be measured using methods and instruments known in the art. As an example, the method can be based on GB / T19587-2017, employing the nitrogen adsorption specific surface area analysis method, and calculated using the BET (Brunauer Emmett Teller) method. The nitrogen adsorption specific surface area analysis can be performed using a Tri-Star 3020 specific surface area and pore size analyzer from Micromeritics, Inc.

[0335] In some embodiments, the specific surface area of ​​the negative electrode active material can be 0.5 m². 2 / g, 0.55m 2 / g, 0.6m 2 / g, 0.65m2 / g, 0.7m 2 / g, 0.75m 2 / g, 0.8m 2 / g, 0.85m 2 / g, 0.9m 2 / g, 0.95m 2 / g, 1m 2 / g, 1.05m 2 / g, 1.1m 2 / g, 1.15m 2 / g, 1.2m 2 / g, 1.25m 2 / g, 1.3m 2 / g, 1.35m 2 / g, 1.4m 2 / g, 1.45m 2 / g, 1.5m 2 / g, 1.55m 2 / g, 1.6m 2 / g, 1.65m 2 / g, 1.7m 2 / g, 1.75m 2 / g, 1.8m 2 / g, 1.85m 2 / g, 1.9m 2 / g, 1.95m 2 / g、2m 2 / g, 2.05m 2 / g、2.1m 2 / g, 2.15m 2 / g, 2.2m 2 / g, 2.25m 2 / g, 2.3m 2 / g, 2.35m 2 / g, 2.4m 2 / g, 2.45m 2 / g, 2.5m 2 / g, 2.55m 2 / g, 2.6m 2 / g, 2.65m 2 / g, 2.7m 2 / g, 2.75m 2 / g, 2.8m 2 / g, 2.85m 2 / g, 2.9m 2 / g, 2.95m 2 / g、3m 2 / g or any value between the two.

[0336] In some embodiments, the specific surface area of ​​the negative electrode active material is 0.8 m². 2 / g-2.0m 2 / g.

[0337] In some embodiments, the electrode assembly further includes a separator disposed between the positive electrode and the negative electrode, the separator comprising a base film and a coating disposed on at least one side of the base film, the coating comprising a first coating comprising a third polymer.

[0338] In some embodiments, the coating further includes a second coating disposed between the first coating and the base film, the second coating comprising inorganic particles and a fourth polymer.

[0339] Inorganic materials have good chemical stability, which helps to improve the stability of the separator. At the same time, they have good liquid retention capacity, which helps to improve the ion transport capacity of the separator, reduce the polarization phenomenon during the charging and discharging process of the battery cell, and thus improve the cycle performance and rate performance of the hybrid system battery cell.

[0340] In some embodiments, the coating further includes a second coating disposed between the first coating and the base film, the second coating comprising inorganic particles and a fourth polymer, the coating being disposed on the base film near the positive electrode side.

[0341] Placing the second coating on the side of the base film close to the positive electrode helps reduce the direct contact between the base film and the positive electrode active material, reduces the damage to the base film caused by byproducts generated by the electrolyte at the positive electrode active material, thereby improving the stability of the separator and further improving the cycle stability of the hybrid battery cell.

[0342] In some embodiments, the inorganic particles include one or more of alumina, boehmite, silicon dioxide, cerium oxide, magnesium aluminate, zirconium oxide, and titanium dioxide.

[0343] In some embodiments, the third polymer and the fourth polymer each independently include one or more of fluoropolymers and acrylate polymers.

[0344] In some embodiments, the fluoropolymer includes a vinylidene fluoride polymer, which includes one or more of vinylidene fluoride homopolymers, copolymers of vinylidene fluoride and tetrafluoroethylene, copolymers of vinylidene fluoride and hexafluoropropylene, and copolymers of vinylidene fluoride and trifluoroethylene.

[0345] In some implementations, the thickness of the base film is 5 μm-12 μm.

[0346] In some embodiments, the thickness of the base film can be 5 μm, 5.2 μm, 5.4 μm, 5.6 μm, 5.8 μm, 6 μm, 6.2 μm, 6.4 μm, 6.6 μm, 6.8 μm, 7 μm, 7.2 μm, 7.4 μm, 7.6 μm, 7.8 μm, 8 μm, 8.2 μm, 8.4 μm, 8.6 μm, 8.8 μm, 9 μm, 9.2 μm, 9.4 μm, 9.6 μm, 9.8 μm, 10 μm, 10.2 μm, 10.4 μm, 10.6 μm, 10.8 μm, 11 μm, 11.2 μm, 11.4 μm, 11.6 μm, 11.8 μm, 12 μm, or any value between the two.

[0347] In some implementations, the coating thickness on one side is 1µm-4µm.

[0348] In some embodiments, the thickness of one side of the coating can be 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm, 3.5 μm, 3.6 μm, 3.7 μm, 3.8 μm, 3.9 μm, 4 μm, or any value range between the two.

[0349] In some implementations, the thickness of the separator is 8 μm-15 μm.

[0350] In some embodiments, the thickness of the separator can be 8 μm, 8.1 μm, 8.2 μm, 8.3 μm, 8.4 μm, 8.5 μm, 8.6 μm, 8.7 μm, 8.8 μm, 8.9 μm, 9 μm, 9.1 μm, 9.2 μm, 9.3 μm, 9.4 μm, 9.5 μm, 9.6 μm, 9.7 μm, 9.8 μm, 9.9 μm, 10 μm, 10.1 μm, 10.2 μm, 10.3 μm, 10.4 μm, 10.5 μm, 10.6 μm, 10.7 μm, 10.8 μm, 10.9 μm, 11 μm, 11.1 μm, 11.2 μm, 11.3 μm, 11.4 μm, 11.5 μm, 11. 6μm, 11.7μm, 11.8μm, 11.9μm, 12μm, 12.1μm, 12.2μm, 12.3μm, 12.4μm, 12.5μm, 12.6μm, 12.7μm, 12.8μm, 12.9μm, 13μm, 13.1μm, 13.2μm, 13.3μm, 13.4μm, 13.5μm, 13.6μm, 13.7μm, 13.8μm, 13.9μm, 14μm, 14.1μm, 14.2μm, 14.3μm, 14.4μm, 14.5μm, 14.6μm, 14.7μm, 14.8μm, 14.9μm, 15μm, or any range between the two.

[0351] In some embodiments, the air permeability of the separator at 25°C is 400s / 100cc-600s / 100cc.

[0352] In this application, the air permeability of the separator at 25°C can be tested using methods and instruments known in the art. As an example: at a temperature of 25°C and humidity of less than 80%, a test sample of 4cm × 4cm is prepared, and the air permeability value is directly obtained by measuring it using the Gurley test (100cc) method with an Air-permeability-tester.

[0353] In some embodiments, the air permeability of the separator at 25°C can be 400s / 100cc, 410s / 100cc, 420s / 100cc, 430s / 100cc, 440s / 100cc, 450s / 100cc, 460s / 100cc, 470s / 100cc, 480s / 100cc, 490s / 100cc, 500s / 100cc, 510s / 100cc, 520s / 100cc, 530s / 100cc, 540s / 100cc, 550s / 100cc, 560s / 100cc, 570s / 100cc, 580s / 100cc, 590s / 100cc, 600s / 100cc, or any value between the two.

[0354] When the permeability of the separator is within the above range, it can, to a certain extent, prevent the transition metal dissolved from the positive electrode from migrating to the negative electrode side, alleviate the problem of it being reduced to metal at the negative electrode and damaging the SEI film, or even causing local micro-short circuits, and further improve the cycle performance of the hybrid system battery cell.

[0355] In some implementations, the porosity of the separator is 35%-55%.

[0356] In this application, porosity refers to the percentage of the volume of the pores in the separator to the total volume of the separator, expressed as porosity ε = (V1 - V2) / V1 × 100%, where V1 is the apparent volume of the sample and V2 is the actual volume of the sample. Porosity can be determined using methods known in the art. As an example, it can be tested according to the standard GB / T 36363-2018 "Polyolefin Separators for Battery Cells". It should be noted that the actual testing process may differ slightly from the standard due to differences in testing instruments, testing errors, and to minimize the influence on porosity testing, in order to obtain more accurate test values.

[0357] In some embodiments, the porosity of the separator can be 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, or any value between the two.

[0358] In some implementations, the thickness of the positive current collector is 9 μm-15 μm.

[0359] In this application, the thickness of the positive electrode current collector can be tested using methods and instruments known in the art. As an example, a high-precision micrometer can be used, or a cross-section of the positive electrode film along the electrode thickness direction can be photographed and imported into ImageJ for testing.

[0360] In some embodiments, the thickness of the positive electrode current collector can be 9 μm, 9.1 μm, 9.2 μm, 9.3 μm, 9.4 μm, 9.5 μm, 9.6 μm, 9.7 μm, 9.8 μm, 9.9 μm, 10 μm, 10.1 μm, 10.2 μm, 10.3 μm, 10.4 μm, 10.5 μm, 10.6 μm, 10.7 μm, 10.8 μm, 10.9 μm, 11 μm, 11.1 μm, 11.2 μm, 11.3 μm, 11.4 μm, 11.5 μm, 11.6 μm, 11.7 μm, 11.8 μm, 11.9 μm, or 12 μm. m,12.1μm,12.2μm,12.3μm,12.4μm,12.5μm,12.6μm,12.7μm,12.8μm,12.9μm,13μm,13.1μm,13.2μm,13.3μm,13.4μm,13.5μm,13. 6μm, 13.7μm, 13.8μm, 13.9μm, 14μm, 14.1μm, 14.2μm, 14.3μm, 14.4μm, 14.5μm, 14.6μm, 14.7μm, 14.8μm, 14.9μm, 15μm or any numerical range between the two.

[0361] The thickness of the positive electrode current collector is within the above range, which helps to reduce the thickness and mass ratio of the positive electrode current collector in the battery cell and improve the energy density of the battery cell.

[0362] In some implementations, the thickness of the negative electrode current collector is 3μm-7μm.

[0363] In this application, the thickness of the negative electrode current collector can be tested by referring to the test method for the thickness of the positive electrode current collector.

[0364] In some embodiments, the thickness of the negative electrode current collector can be 3 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm, 3.5 μm, 3.6 μm, 3.7 μm, 3.8 μm, 3.9 μm, 4 μm, 4.1 μm, 4.2 μm, 4.3 μm, 4.4 μm, 4.5 μm, 4.6 μm, 4.7 μm, 4.8 μm, 4.9 μm. μm, 5μm, 5.1μm, 5.2μm, 5.3μm, 5.4μm, 5.5μm, 5.6μm, 5.7μm, 5.8μm, 5.9μm, 6μm, 6. 1μm, 6.2μm, 6.3μm, 6.4μm, 6.5μm, 6.6μm, 6.7μm, 6.8μm, 6.9μm, 7μm or any numerical range between the two.

[0365] The thickness of the negative electrode current collector is within the above range, which helps to reduce the thickness and mass ratio of the negative electrode current collector in the battery cell and improve the energy density of the battery cell.

[0366] In some implementations, the rated cutoff voltage of a single battery cell is 4.25V-4.45V.

[0367] In this application, the rated cutoff voltage of a battery cell refers to the charging cutoff voltage of the battery cell, that is, the highest voltage that the battery cell is allowed to reach during charging. The rated cutoff voltage of a battery cell can be obtained in the following ways: for example, from the nameplate of the battery device, power consumption device, or energy storage device; from the charging cutoff voltage of the corresponding positive electrode active material described in the literature; or it can be determined by performing a standard charging test on the battery cell and recording the charging curve. As an example, when charging a battery cell using the rated current, the voltage corresponding to the highest charging plateau in the charging curve is taken as the rated cutoff voltage of the battery cell.

[0368] In some implementations, the rated cutoff voltage of a single battery cell can be 4.25V, 4.26V, 4.27V, 4.28V, 4.29V, 4.3V, 4.31V, 4.32V, 4.33V, 4.34V, 4.35V, 4.36V, 4.37V, 4.38V, 4.39V, 4.4V, 4.41V, 4.42V, 4.43V, 4.44V, 4.45V, or any value between the two.

[0369] In some implementations, such as Figure 4 As shown, the positive electrode 11 includes a first main body and a first tab 111. The first main body includes a first straight section 112. The first straight section 112 includes a positive current collector and a positive film layer. The first straight section 112 is stacked along the thickness direction X of the battery cell. The ratio of the number of first tabs 111 to the number of first straight sections 112 is 0.5-1.

[0370] In some embodiments, the ratio of the number of first tabs to the number of first straight segments can be selected as 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, or any value range between the two.

[0371] The applicant further discovered that high temperature conditions exacerbate manganese ion dissolution. In this application embodiment, the ratio of the number of first tabs to the number of first straight sections is 0.5-1, with a relatively large number of first tabs. This, combined with the above-mentioned hybrid system, reduces the impedance and heat generation at the tabs, reduces the heat at the maximum heat generation point of the battery cell, improves the temperature distribution uniformity of the positive electrode active material layer, reduces the temperature rise of the positive electrode sheet, thereby reducing the probability of manganese ion dissolution from lithium transition metal phosphate particles, reducing the damage of manganese ions to the SEI film, reducing the consumption of active lithium ions, and further improving the cycle stability of the hybrid system battery cell.

[0372] In some implementations, the ratio of the number of first tabs to the number of first straight segments is 0.75-1.

[0373] The ratio of the number of first tabs to the number of first straight sections is within a reasonable range, which can further increase the number of first tabs, reduce the impedance and heat generation at the tabs, reduce the heat at the maximum heat generation point of the battery cell, improve the temperature distribution uniformity of the positive electrode active material layer, reduce the temperature rise of the positive electrode sheet, thereby reducing the probability of manganese ion dissolution from lithium transition metal phosphate particles, reducing the damage of manganese ions to the SEI film, reducing the consumption of active lithium ions, and further improving the cycle stability of the hybrid system battery cell.

[0374] In some implementations, the ratio of the size of the first tab to the size of the electrode assembly is 12%-40% along the width direction of the battery cell.

[0375] In some embodiments, the ratio of the size of the first tab to the size of the electrode assembly along the width direction of the battery cell can be selected as 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, or any value range between the two.

[0376] Along the width direction of the battery cell, the ratio of the size of the first tab to the size of the electrode assembly is within the above-mentioned range. This is beneficial to increase the welding area between the first tab and the electrode assembly, reduce the contact resistance between the first tab and the electrode assembly, reduce the heat generation at the first tab, improve the temperature distribution uniformity of the positive electrode active material layer, reduce the temperature rise of the positive electrode sheet, thereby reducing the probability of manganese ion dissolution from lithium transition metal phosphate particles, reducing the damage of manganese ions to the SEI film, reducing the consumption of active lithium ions, and improving the cycle stability of the hybrid battery cell.

[0377] In some implementations, the ratio of the size of the first tab to the size of the electrode assembly is 24%-40%.

[0378] Along the width direction of the battery cell, the ratio of the size of the first tab to the size of the electrode assembly is within a reasonable range. This is beneficial for further increasing the welding area between the first tab and the electrode assembly, further reducing the contact resistance between the first tab and the electrode assembly, reducing the heat generation at the first tab, improving the temperature distribution uniformity of the positive electrode active material layer, reducing the temperature rise of the positive electrode sheet, thereby reducing the probability of manganese ion dissolution from lithium transition metal phosphate particles, reducing the damage of manganese ions to the SEI film, reducing the consumption of active lithium ions, and further improving the cycle stability of the hybrid system battery cell.

[0379] In some implementations, the size of the first tab is 25mm-60mm along the width direction of the battery cell.

[0380] In some embodiments, the size of the first tab along the width direction of the battery cell can be selected as 25mm, 26mm, 27mm, 28mm, 29mm, 30mm, 31mm, 32mm, 33mm, 34mm, 35mm, 36mm, 37mm, 38mm, 39mm, 40mm, 41mm, 42mm, 43mm, 44mm, 45mm, 46mm, 47mm, 48mm, 49mm, 50mm, 51mm, 52mm, 53mm, 54mm, 55mm, 56mm, 57mm, 58mm, 59mm, 60mm or any value range between the two.

[0381] Along the width direction of the battery cell, if the size of the first tab is within the above range, it can increase the welding area between the first tab and the electrode assembly, reduce the contact resistance between the first tab and the electrode assembly, and reduce the heat generation at the first tab.

[0382] In some implementations, the electrode assembly has a size of 140mm-390mm along the width direction of the battery cell.

[0383] In some embodiments, the dimensions of the electrode assembly along the width direction of the battery cell can be selected as 140mm, 145mm, 150mm, 155mm, 160mm, 165mm, 170mm, 175mm, 180mm, 185mm, 190mm, 195mm, 200mm, 205mm, 210mm, 215mm, 220mm, 225mm, 230mm, 235mm, 240mm, 245mm, 250mm, 255mm. 260mm, 265mm, 270mm, 275mm, 280mm, 285mm, 290mm, 295mm, 300mm, 305mm, 310mm, 315mm, 320mm, 325mm, 330mm, 335mm, 340mm, 345mm, 350mm, 355mm, 360mm, 365mm, 370mm, 375mm, 380mm, 385mm, 390mm, or any range of two.

[0384] In some implementations, such as Figure 4As shown, the negative electrode 12 includes a second main body and a second tab 121. The second main body includes a second straight section 122. The second straight section 122 includes a negative current collector and a negative electrode film layer. The second straight section 122 is stacked along the thickness direction of the battery cell. The ratio of the number of second tabs 121 to the number of second straight sections 122 is 0.5-1.

[0385] In some embodiments, the ratio of the number of second tabs to the number of second straight segments can be selected as 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1 or any value range between the two.

[0386] When the ratio of the number of second tabs to the number of second straight sections is within the above range, the number of second tabs can be increased, the impedance and heat generation at the second tabs can be reduced, the temperature distribution uniformity of the negative electrode active material layer can be improved, the temperature rise of the negative electrode sheet can be reduced, and the total heat generation of the battery cell can be reduced.

[0387] In some implementations, the ratio of the number of second tabs to the number of second straight segments is 0.75-1.

[0388] The ratio of the number of second tabs to the number of second straight sections is within a reasonable range. Further increasing the number of second tabs reduces the impedance and heat generation at the second tabs, improves the temperature distribution uniformity of the negative electrode active material layer, reduces the temperature rise of the negative electrode sheet, and further reduces the total heat generation of the battery cell.

[0389] In some embodiments, the housing can be of various shapes, such as a cylinder, a cuboid, etc. The shape of the housing can be determined according to the specific shape of the electrode assembly. For example, if the electrode assembly is a cylindrical structure, the housing can be a cylindrical structure. If the electrode assembly is a cuboid structure, the housing can be a cuboid structure. Optionally, the electrode assembly is a cuboid structure.

[0390] The outer shell can be made of various materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, etc., and the embodiments of this application do not impose any special restrictions on this.

[0391] In some implementations, such as Figure 3 As shown, the outer casing 20 includes a housing 21 and an end cap 22.

[0392] In some implementations, such as Figure 3 As shown, the end cap 22 includes electrode terminals, which include a first electrode terminal 31 and a second electrode terminal 32. The first electrode terminal 31 is the positive terminal and the second electrode terminal 32 is the negative terminal.

[0393] In some implementations, such as Figure 3 As shown, the shell 21 has a cuboid structure.

[0394] In some implementations, the thickness of the battery cell is 15 mm to 30 mm. Figure 2 T0 shown in the figure represents the thickness of the battery cell 7.

[0395] In some implementations, the thickness of the battery cell can be selected as 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, 21mm, 22mm, 23mm, 24mm, 25mm, 26mm, 27mm, 28mm, 29mm, 30mm or any value between the two.

[0396] In some embodiments, the dimensions of the battery cell along the second direction are 150 mm to 400 mm. Figure 2 W0 shown in the figure represents the dimension of the battery cell 7 along the second direction F, wherein the second direction F is parallel to the width direction of the battery cell.

[0397] In some embodiments, the dimensions of the battery cell along the second direction can be selected as 200mm, 205mm, 210mm, 215mm, 220mm, 225mm, 230mm, 235mm, 240mm, 245mm, 250mm, 255mm, 260mm, 265mm, 270mm, 275mm, 280mm, 285mm, 290mm, 295mm, 300mm, 305mm, 310mm, 315mm, 320mm, 325mm, 330mm, 335mm, 340mm, 345mm, 350mm, 355mm, 360mm, 365mm, 370mm, 375mm, 380mm, 385mm, 390mm, 395mm, 400mm, or any value range between the two.

[0398] In some implementations, the height of the battery cell is 80mm-250mm.

[0399] In some embodiments, the height of the battery cell can be selected as 80mm, 85mm, 90mm, 95mm, 100mm, 105mm, 110mm, 115mm, 120mm, 125mm, 130mm, 135mm, 140mm, 145mm, 150mm, 155mm, 160mm, 165mm, 170mm, 175mm, 180mm, 185mm, 190mm, 195mm, 200mm, 205mm, 210mm, 215mm, 220mm, 225mm, 230mm, 235mm, 240mm, 245mm, 250mm, or any value between the two.

[0400] In this embodiment, the first direction is parallel to the height direction of the battery cell, and the second direction, the first direction, and the thickness direction X of the battery cell are perpendicular to each other.

[0401] In some embodiments, the electrode assembly is a wound electrode assembly. One or more electrode assemblies may be housed within the housing.

[0402] like Figure 4 As shown, in some embodiments, the electrode assembly 10 includes a positive electrode 11, a negative electrode 12, and a separator 13.

[0403] Continue to refer to Figure 4 The positive electrode 11 includes a first main body and a first tab 111. The first main body includes a first straight section 112. The first straight section 112 includes a positive current collector and a positive active material layer disposed on at least one side of the positive current collector. The first tab 111 is connected to the positive current collector of the first straight section 112 and extends out of the positive current collector.

[0404] Continue to refer to Figure 4 The negative electrode 12 includes a second main body and a second tab 121. The second main body includes a second straight section 122. The second straight section 122 includes a negative current collector and a negative active material layer disposed on at least one side of the negative current collector. The second tab 121 is connected to the negative current collector of the second straight section 122 and extends out of the negative current collector.

[0405] Continue to refer to Figure 4 In the case of a wound structure for the electrode assembly 10, structurally, the positive electrode 11 can be a single piece, the negative electrode 12 can be a single piece, and the separator 13 can be a single piece. The separator 13 is disposed between the positive electrode 11 and the negative electrode 12. The positive electrode 11, the separator 13, and the negative electrode 12 are wound in one direction to form the electrode assembly 10. The positive electrode 11 includes a first main body and a plurality of first tabs 111. The negative electrode 12 includes a second main body and a plurality of second tabs 121.

[0406] Continue to refer to Figure 4After the electrode assembly 10 is formed by winding, the first main body of the positive electrode 11 may include a plurality of first straight segments 112 and a plurality of first bent segments 113. The first bent segments 113 and the first straight segments 112 are arranged along the winding direction of the electrode assembly 10, and the first bent segments 113 are connected to the first straight segments 112. The first straight segment 112 includes a positive current collector and an active material layer disposed on at least one side of the positive current collector. The first bent segment 113 includes a positive current collector and an active material layer disposed on at least one side of the positive current collector. During the winding process of the electrode assembly 10, the positive electrode 11 can form a first straight segment 112 by winding half a turn. If the beginning end of the positive electrode 11 is too short, it is considered that the beginning end is not a complete first straight segment. When counting the number of first straight segments 112, the short beginning end may not be counted as a first straight segment. For example, the beginning of the negative electrode (i.e., the innermost ring) does not have to be a complete first straight section, and it does not have to have a negative electrode tab; of course, the beginning can also have a negative electrode tab.

[0407] The second main body of the negative electrode sheet 12 may include a plurality of second straight sections 122 and a plurality of second bent sections 123. The second bent sections 123 and the second straight sections 122 are arranged along the winding direction of the electrode assembly 10, and the second bent sections 123 are connected to the second straight sections 122. The first straight sections 112 and the second straight sections 122 are alternately stacked in the thickness direction X of the battery cell 7. The first bent sections 113 and the second bent sections 123 are alternately stacked. The second straight section 122 includes a negative current collector and a negative active material layer disposed on at least one side of the negative current collector. The second bent section 123 includes a negative current collector and a negative active material layer disposed on at least one side of the negative current collector.

[0408] like Figure 5 As shown, in some embodiments, the battery device may be a battery pack 2, which includes a housing 5 and one or more battery cell assemblies housed in the housing 5.

[0409] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0410] As an example, such as Figure 5 As shown, the housing 5 includes a first housing portion 5a and a second housing portion 5b. The housing 5 has an accommodating space 5c. The first housing portion 5a and the second housing portion 5b are fastened together to form a closed space inside the housing 5 to accommodate the battery cell assembly. Here, "closed" refers to covering or closing, which can be either sealed or unsealed. The first housing portion 5a can be a top cover or a bottom plate.

[0411] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0412] In some implementations, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0413] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module to the housing.

[0414] like Figure 6 As shown, the battery module 6 includes multiple battery cells 7. For example, the battery module 6 includes multiple first battery packs 70 arranged along the length direction M of the battery module 6, and each first battery pack 70 includes multiple battery cells 7. Optionally, the battery module 6 includes four first battery packs 70 arranged along the length direction M of the battery module 6.

[0415] A second aspect of this application provides a battery device, including the battery cell provided in the first aspect of this application.

[0416] The battery device disclosed in this application can be used in electrical devices that use the battery device as a power source or in various energy storage systems that use the battery device as an energy storage element. Besides vehicles, the battery device can also be used in, but is not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0417] A third aspect of this application provides an electrical device that uses a battery as a power source. The electrical device includes at least one of the battery cell, battery module, or battery pack provided in this application. The battery cell, battery module, or battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. As an electrical device, the battery cell, battery module, or battery pack can be selected according to its usage requirements.

[0418] Figure 7This is an example of an electrical device. The electrical device disclosed in this application can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A battery device is installed inside the vehicle, and the battery device can be located at the bottom, front, or rear of the vehicle. The battery device can be used to power the vehicle; for example, the battery device can serve as the vehicle's operating power source. The vehicle may also include a controller and a motor. The controller is used to control the battery device to supply power to the motor, for example, for the vehicle's starting, navigation, and operating power needs. In some embodiments of this application, the battery device can not only serve as the vehicle's operating power source but also as the vehicle's drive power source, replacing or partially replacing gasoline or natural gas to provide driving power for the vehicle.

[0419] The fourth aspect of this application provides an energy storage device that uses a battery device as a power source. The energy storage device can be, but is not limited to, an energy storage container, an energy storage cabinet, an energy storage power station, an energy storage battery pack, or a portable energy storage system.

[0420] Example The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0421] I. Preparation Method 1. Preparation of Example 1 (1) Positive electrode plate ① Preparation of lithium-containing transition metal phosphate particles S1. Take 35.6 kg of manganese tetroxide, 56.1 kg of ferric phosphate, 41.6 kg of lithium dihydrogen phosphate, 15.7 kg of lithium carbonate, 0.75 kg of titanium dioxide, and 6.7 kg of glucose into a ball mill jar, add ultrapure water to form a raw slurry with a solid content of 40%. Pour the mixture into a ball mill and mix thoroughly, then transfer it to a sand mill at 800 rpm. When the slurry particle size reaches 0.51 μm, transfer it to a centrifugal spray tower for spray drying, controlling the inlet air temperature at 250℃ and the outlet air temperature at 90℃ to obtain the first spray-dried material. Sinter the spray-dried material at 550℃ under a nitrogen atmosphere for 8 hours to obtain a first-burnt sample.

[0422] S2. Take 100 kg of the above-mentioned first-burned sample, 4.8 kg of glucose, and 5.2 kg of polyethylene glycol (Polyethylene Glycol 6000) and pour them into a ball mill jar. Add ultrapure water to disperse the mixture, controlling the solid content of the slurry to 40%. Transfer the slurry to a sand mill and mill until the particle size is 0.34 μm. Then, transfer the slurry to a centrifugal spray tower for spray drying, controlling the inlet air temperature to 250℃ and the outlet air temperature to 90℃ to obtain the second spray-dried material. Sinter the second spray-dried material at 760℃ under a nitrogen atmosphere for 10 hours to obtain the second-burned sample.

[0423] S3. Place the calcined sample in an air jet mill, control the air pressure to 0.24 MPa and the grading frequency to 72 Hz to obtain air-jet material; then sieve and demagnetize the air-jet material to obtain lithium transition metal phosphate particles LMFP-1.

[0424] The lithium-containing transition metal phosphate particles comprise a particle body and carbon material disposed on at least a portion of the surface of the particle body. Based on the total mass of the lithium-containing transition metal phosphate particles, the carbon material accounts for 1.45% of the total mass. The chemical formula of the particle body of the lithium-containing transition metal phosphate particles is LiMn. 0.594 Fe 0.396 Ti 0.005 PO4.

[0425] ② Preparation of the positive electrode film Preparation of positive electrode undercoat: Preparation of positive electrode undercoat: The conductive agent Super P and the binder polyvinylidene fluoride are mixed evenly at a total mass ratio of 55%:45%, and coated onto a 15μm positive electrode current collector aluminum foil. After drying, a positive electrode current collector coated with the positive electrode undercoat is obtained.

[0426] Preparation of positive electrode active material layer: Positive electrode active material, conductive agent, and binder polyvinylidene fluoride were mixed in a mass ratio of 96.0:2.5:1.5 in the solvent N-methylpyrrolidone. The mixture was thoroughly stirred and dispersed in a mixing tank to form a slurry for the positive electrode active material layer. After stirring, the slurry was transferred and coated onto a current collector aluminum foil, then dried, compacted, slit, and sheeted to obtain the positive electrode sheet. The one-sided density of the positive electrode active material layer was 310 mg / 1540 cm³. 2 .

[0427] The positive electrode active material includes lithium-containing transition metal oxide particles (LiNi) with a mass ratio of 7:3. 0.6 Co 0.2 Mn 0.2 O2 single crystal particles and lithium-containing transition metal phosphate particles prepared above; the conductive agent is carbon nanotubes and Super P in a mass ratio of 1:1.

[0428] When the battery cell is at 0% SOC, in the cross-section along the thickness direction of the positive electrode active material layer, the Dn10 of the lithium transition metal oxide particles is 0.95 μm, Dn50 is 2.0 μm, and Dn90 is 3.65 μm, and the compaction density of the positive electrode film is 3.0 g / cm³. 3 .

[0429] (2) Negative electrode plate A negative electrode slurry was prepared by mixing graphite (anode active material), conductive carbon black (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC) (thickener) in deionized water at a mass ratio of 97:0.8:1.2:1. The slurry was then coated onto a 6 μm thick copper current collector foil, dried, compacted, slit, and sheeted to obtain the negative electrode sheet. The one-sided density of the negative electrode film was 170 mg / 1540.25 cm³. 2 .

[0430] The negative electrode active material has a Dv50 of 14 μm and a specific surface area of ​​1.8 m². 2 / g.

[0431] (3) Separating membrane Inorganic material boehmite, binder polyvinylidene fluoride (PVDF), acrylic emulsion, and deionized water were mixed uniformly in a mass ratio of 40%:2%:4.5%:53.5% to prepare a second coating slurry. This second coating slurry was applied to the base membrane near the positive electrode and dried. PVDF was then dissolved in water to prepare a first coating slurry, which was sprayed onto both sides of the base membrane bearing the second coating. After drying and slitting, a separator membrane was obtained. Specifically, the base membrane has both a first and second coating on the side facing the positive electrode, and a second coating on the side facing the negative electrode. The base membrane is a 7 μm thick polypropylene membrane, the second coating is 3 μm thick, and the first coating on each side is 0.5 μm thick.

[0432] The air permeability of the separator at 25°C is 550s / 100cc, and the porosity of the separator is 45%.

[0433] (4) Electrolyte The electrolyte composition in Example 1 is detailed in Table 1.

[0434] (5) Battery cell The positive electrode, separator, and negative electrode are stacked in sequence. The separator must be able to isolate the anode and cathode. The bare cell is obtained by winding. The bare cell is placed in the casing, the top cover assembly is closed, electrolyte is injected, and the cell undergoes processes such as encapsulation, formation, and venting to obtain a single battery cell. The rated cutoff voltage of the single battery cell is set to 4.4V.

[0435] like Figure 4 As shown, the ratio of the number of first electrodes to the number of first straight segments is 1; the ratio of the number of second electrodes to the number of second straight segments is 1.

[0436] Along the thickness direction of the battery cell, the size of the first tab is 34mm, the size of the electrode assembly is 225mm, and the ratio of the size of the first tab to the size of the electrode assembly is 15%.

[0437] 2. Preparation of other embodiments The preparation methods of Examples 2-5 and Comparative Examples 1-2 are basically the same as those of Example 1, except that the amount of manganese tetroxide and iron phosphate added in the preparation S1 of lithium transition metal phosphate particles is adjusted so that the molar ratio of manganese is different based on the total molar number of manganese and iron in the lithium transition metal phosphate particles, as detailed in Table 2.

[0438] Examples 6-9 and Comparative Example 3 are prepared in basically the same way as Example 1, except that the fractionation frequency in the preparation of lithium transition metal phosphate particles S3 is adjusted.

[0439] The preparation method of Example 10 is basically the same as that of Example 1, except that the lithium transition metal phosphate particles include lithium transition metal phosphate LMFP-10.1 and lithium transition metal phosphate LMFP-10.2 in a mass ratio of 3:7. The preparation methods of lithium transition metal phosphates LMFP-10.1 and LMFP-10.2 are basically the same as those of lithium transition metal phosphate LMFP-1, with the difference being: when preparing LMFP-10.1, the grinding in S2 is controlled to 0.3 μm and the grading frequency in S3 is adjusted; when preparing LMFP-10.2, the grinding in S2 is controlled to 0.4 μm and the grading frequency in S3 is adjusted.

[0440] The preparation methods of Comparative Example 4 and Example 10 are basically the same, except that the lithium-containing transition metal oxide particles include lithium-containing transition metal oxide LMFP-10.1 and lithium-containing transition metal oxide LMFP-10.2 with a mass ratio of 2.5:7.5. The preparation methods of Examples 11-22 are basically the same as those of Example 1, except that the electrolytes are different. Specifically, the electrolytes of Examples 11-22 and Example 1 all include 15% diethyl carbonate, 20% ethylene carbonate and 4.2% vinylene carbonate by mass. The remaining components are detailed in Table 1.

[0441] Table 1

[0442] Among them, LiFSI is lithium difluorosulfonylimide, PS is 1,3-propanesulfonyl lactone, LiPF6 is lithium hexafluorophosphate, LiPO2F2 is lithium difluorophosphate, LiDFOB is lithium difluorooxalate borate, TMSP is tris(trimethylsilyl) phosphate, LiBOB is lithium dioxalate borate, and DTD is vinyl sulfate.

[0443] The preparation method of Example 23 is basically the same as that of Example 1, except that the conductive agent in the preparation of the positive electrode active material layer is Super P.

[0444] II. Testing Methods 1. Capacity retention test At 45℃, the battery cells are charged at a constant current of 1C to 4.4V, then allowed to stand for 10 minutes. Next, they are charged at a constant voltage of 4.4V until the current reaches 0.05C, at which point charging is stopped. After the battery cells are allowed to stand at 45℃ for 1 hour, they are discharged at 1C at 45℃ until the discharge cutoff voltage of 2.5V is reached. This constitutes one cycle, and the discharge capacity Q1 of the first cycle is recorded. The above steps are repeated for 1400 cycles, and the discharge capacity Q2 after each cycle is recorded. The capacity retention rate is calculated as Q2 / Q1 × 100%.

[0445] 2. Current distribution test of lithium transition metal oxide particles and lithium transition metal phosphate particles in battery cells The areal loading of lithium transition metal oxide particles and lithium transition metal phosphate particles in a single battery cell is determined. The bifacial loading of the positive electrode of the battery cell is denoted as A, and the mass percentages of lithium transition metal oxide particles and lithium transition metal phosphate particles are denoted as a1 and a2, respectively. The bifacial loading of lithium transition metal oxide particles is calculated using the formula: areal loading = A·a1, and the bifacial loading of lithium transition metal phosphate particles is calculated using the formula: areal loading = A·a2. The lithium transition metal oxide particles and lithium transition metal phosphate particles are then combined with the negative electrode according to their respective areal loadings to prepare pouch cells. After connecting these pouch cells in parallel, the current magnitude of each pouch cell and the total positive and negative terminal voltages are collected under preset energizing conditions.

[0446] At 25℃, the total capacity of the independent cells containing lithium transition metal oxide particles and lithium transition metal phosphate particles was taken as the total capacity. The parallel cells were charged with a constant current of 2C of the total capacity to 4.35V, then left to stand for 10 minutes. Then, constant voltage charging was performed at 4.25V until the current was 0.05C of the total capacity. The charging was then stopped. The total positive and negative terminal voltages during the charging process, as well as the current flowing through the soft-pack cells containing lithium transition metal oxide particles and lithium transition metal phosphate particles, were recorded.

[0447] III. Test Results and Analysis The test results of the above embodiments and comparative examples are detailed in Tables 2-5.

[0448] As shown in Tables 2-5, 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 active material layer, which includes a positive active material. The positive active material includes lithium-containing transition metal oxide particles and lithium-containing transition metal phosphate particles. The lithium-containing transition metal oxide particles include nickel, cobalt, and X1 elements, where X1 elements include manganese and / or aluminum. The lithium-containing transition metal phosphate particles include manganese and iron. Based on the total molar number of manganese and iron in the lithium-containing transition metal phosphate particles, the molar percentage of manganese is 40%- 75%; In the cross-section of the positive electrode active material layer along the thickness direction of the electrode sheet, the Dn50 of the lithium transition metal phosphate particles is 100nm-300nm, and the Dn90 of the lithium transition metal phosphate particles is 250nm-500nm. Among them, Dn50 and Dn90 refer to the particle size corresponding to 50% and 90% of the cumulative particle size distribution curve, respectively; The electrolyte includes a first component, which includes one or more of lithium difluorophosphate, lithium difluorooxalate borate, tris(trimethylsilyl)phosphate, and lithium bis(oxalate borate). The mixed system battery cell has good cycle performance.

[0449] Table 2

[0450] As can be seen from the comparison between Examples 1-5 and Comparative Examples 1-2, based on the total molar number of manganese and iron elements in lithium transition metal phosphate particles, the molar proportion of manganese is 40%-75%, which helps to improve the cycle performance of battery cells.

[0451] As can be seen from the comparison between Examples 6-10 and Comparative Example 3, the Dn50 of lithium transition metal phosphate particles in the cross-section of the positive electrode active material layer along the electrode thickness direction is 100nm-300nm, which helps to improve the cycle performance of the battery cell.

[0452] As can be seen from the comparison between Examples 6-10 and Comparative Example 4, the Dn90 of lithium transition metal phosphate particles in the cross-section of the positive electrode active material layer along the electrode thickness direction is 250nm-500nm, which helps to improve the cycle performance of the battery cell.

[0453] Table 3

[0454] As can be seen from Example 1 and Comparative Example 4, the Dn50 of lithium transition metal phosphate is in the range of 100nm-300nm, but when Dn90 is greater than 500nm, the current proportion of lithium transition metal oxide particles in the battery cell is relatively high in the range of 3.95V-4.15V, and the capacity retention rate of the battery cell is only 77%. Further controlling the Dn90 of lithium transition metal phosphate particles to less than or equal to 500nm reduces the current proportion of lithium transition metal oxide particles by at least 7.9%, and significantly improves the capacity retention rate of the battery cell (increasing by 12%).

[0455] Table 4

[0456] As can be seen from the comparison of Examples 1, 11-14 and Comparative Example 5, the electrolyte includes a first component, which includes one or more of lithium difluorophosphate, lithium difluorooxalate borate, tris(trimethylsilyl)phosphate, and lithium bis(oxalate borate), which helps to improve the cycle performance of the battery cell.

[0457] As can be seen from the comparison between Example 11 and Examples 12-14, the first component includes lithium difluorophosphate, which helps to further improve the cycle performance of the battery cell.

[0458] As can be seen from the comparison between Examples 1 and 18 and Example 17, based on the total mass of the electrolyte, the mass ratio of the first component is 2%-4%, which helps to further improve the cycle performance of the battery cell.

[0459] As can be seen from the comparison between Example 1 and Example 15, the electrolyte includes 1,3-propanesulfonyl lactone, which helps to further improve the cycle performance of the battery cell.

[0460] As can be seen from the comparison between Example 16 and Example 15, the electrolyte includes a second component, which includes lithium bisfluorosulfonylimide, which helps to further improve the cycle performance of the battery cell.

[0461] As can be seen from the comparison between Examples 1, 20, and 21 and Examples 19 and 22, based on the total mass of the electrolyte, the mass ratio of lithium difluorosulfonylimide is 2%-5%, which helps to further improve the cycle performance of the battery cell.

[0462] Table 5

[0463] As can be seen from the comparison between Example 1 and Example 23, the conductive agent includes a linear conductive agent, which helps to further improve the cycle performance of the battery cell.

[0464] 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

1. A battery cell, characterized in that, Includes electrode components and electrolyte; The electrode assembly includes a positive electrode and a negative electrode. 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 layer, which includes a positive electrode active material comprising lithium-containing transition metal oxide particles and lithium-containing transition metal phosphate particles. The lithium-containing transition metal oxide particles include nickel, cobalt, and X1 elements, where X1 elements include manganese and / or aluminum. The lithium-containing transition metal phosphate particles include manganese and iron. Based on the total molar number of manganese and iron in the lithium-containing transition metal phosphate particles, the molar percentage of manganese is 40%-75%. In the cross-section of the positive electrode active material layer along the thickness direction of the electrode sheet, the Dn50 of the lithium transition metal phosphate particles is 100nm-300nm, and the Dn90 of the lithium transition metal phosphate particles is 250nm-500nm. Here, Dn50 and Dn90 refer to the particle size corresponding to 50% and 90% of the cumulative particle size distribution curve. The electrolyte includes a first component, which includes one or more of lithium difluorophosphate, lithium difluorooxalate borate, tris(trimethylsilyl)phosphate, and lithium bis(oxalate borate); the first component accounts for 0.2%-6% of the total mass of the electrolyte.

2. The battery cell according to claim 1, characterized in that, Based on the total mass of the electrolyte, the mass percentage of the first component is 0.5%-5%.

3. The battery cell according to claim 1, characterized in that, Based on the total mass of the electrolyte, the first component accounts for 2%-4% of the total mass.

4. The battery cell according to any one of claims 1-3, characterized in that, The first component includes lithium difluorophosphate.

5. The battery cell according to claim 4, characterized in that, In the cross-section of the positive electrode active material layer along the thickness direction of the electrode sheet, the Dn50 of the lithium transition metal phosphate particles is 100nm-250nm.

6. The battery cell according to claim 5, characterized in that, The Dn90 of the lithium-containing transition metal phosphate particles is 270nm-400nm.

7. The battery cell according to claim 1, characterized in that, In the cross-section of the positive electrode active material layer along the thickness direction of the electrode sheet, the Dn10 of the lithium transition metal phosphate particles is 70nm-130nm, where Dn10 refers to the particle size corresponding to the cumulative number of particles being 10% in the cumulative distribution curve of particle number.

8. The battery cell according to claim 1, characterized in that, Based on the total number of moles of manganese and iron in the lithium-containing transition metal phosphate particles, the molar percentage of manganese is 40%-60%.

9. The battery cell according to claim 1, characterized in that, The electrolyte also includes lithium hexafluorophosphate and a second component, the second component including one or more of lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, and lithium bis(trifluoromethanesulfonyl)imide.

10. The battery cell according to claim 9, characterized in that, Based on the total mass of the electrolyte, the lithium hexafluorophosphate accounts for 5%-10% of the mass, and the second component accounts for 0.1%-8% of the mass. And / or, the second component includes lithium bisfluorosulfonamide, which accounts for 0.1%-8% of the total mass of the electrolyte.

11. The battery cell according to claim 10, characterized in that, Based on the total mass of the electrolyte, the second component accounts for 0.5%-8% of the total mass.

12. The battery cell according to claim 11, characterized in that, Based on the total mass of the electrolyte, the second component accounts for 3%-8% of the total mass.

13. The battery cell according to claim 10, characterized in that, Based on the total mass of the electrolyte, the mass percentage of the lithium difluorosulfonamide is 2%-5%.

14. The battery cell according to claim 1, characterized in that, The electrolyte comprises cyclic carbonate compounds, and the cyclic carbonate compounds account for 20%-45% of the total mass of the electrolyte.

15. The battery cell according to claim 14, characterized in that, Based on the total mass of the electrolyte, the cyclic carbonate compound accounts for 20%-35% of the total mass.

16. The battery cell according to claim 14 or 15, characterized in that, The cyclic carbonate compounds include one or more of ethylene carbonate, propylene carbonate, and butene carbonate.

17. The battery cell according to claim 16, characterized in that, The cyclic carbonate compounds include ethylene carbonate.

18. The battery cell according to claim 1, characterized in that, The electrolyte comprises chain carbonate compounds, and the chain carbonate compounds account for 40%-75% of the total mass of the electrolyte.

19. The battery cell according to claim 18, characterized in that, Based on the total mass of the electrolyte, the chain carbonate compound accounts for 50%-70% of the mass.

20. The battery cell according to claim 18 or 19, characterized in that, The chain carbonate compounds include one or more of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and methyl propyl carbonate.

21. The battery cell according to claim 20, characterized in that, The chain carbonates include methyl ethyl carbonate and diethyl carbonate.

22. The battery cell according to claim 1, characterized in that, The electrolyte includes ethyl methyl carbonate, and the ethyl methyl carbonate accounts for 35%-55% of the total mass of the electrolyte. And / or, the electrolyte includes diethyl carbonate, and the mass percentage of diethyl carbonate is 10%-20% based on the total mass of the electrolyte.

23. The battery cell according to claim 1, characterized in that, The electrolyte further includes a third component, which includes one or more of vinylene carbonate, fluoroethylene carbonate, 1,3-propane sulpholactone, and vinyl sulfate.

24. The battery cell according to claim 23, characterized in that, Based on the total mass of the electrolyte, the mass percentage of the third component is 0.08%-5%.

25. The battery cell according to claim 24, characterized in that, Based on the total mass of the electrolyte, the mass percentage of the third component is 0.1%-5%.

26. The battery cell according to claim 25, characterized in that, Based on the total mass of the electrolyte, the mass percentage of the third component is 1%-5%.

27. The battery cell according to claim 1, characterized in that, In the cross-section of the positive electrode active material layer along the thickness direction of the electrode sheet, the Dn50 of the lithium-containing transition metal oxide particles is 1μm-4μm.

28. The battery cell according to claim 27, characterized in that, In the cross-section of the positive electrode active material layer along the thickness direction of the electrode sheet, the Dn50 of the lithium-containing transition metal oxide particles is 1μm-3μm.

29. The battery cell according to claim 28, characterized in that, In the cross-section of the positive electrode active material layer along the thickness direction of the electrode sheet, the Dn50 of the lithium-containing transition metal oxide particles is 1.5μm-2.5μm.

30. The battery cell according to claim 1, characterized in that, In the cross-section of the positive electrode active material layer along the thickness direction of the electrode sheet, the particle size distribution concentration of the lithium-containing transition metal oxide particles (Dn90-Dn10) / Dn50 is 0.6-2.

31. The battery cell according to claim 30, characterized in that, In the cross-section of the positive electrode active material layer along the thickness direction of the electrode sheet, the particle size distribution concentration of the lithium-containing transition metal oxide particles (Dn90-Dn10) / Dn50 is 0.8-1.

8.

32. The battery cell according to claim 1, characterized in that, In the cross-section of the positive electrode active material layer along the thickness direction of the electrode sheet, the Dn10 of the lithium-containing transition metal oxide particles is 0.5μm-2μm; And / or, in the cross-section of the positive electrode active material layer along the electrode thickness direction, the Dn90 of the lithium-containing transition metal oxide particles is 2.5μm-5μm.

33. The battery cell according to claim 32, characterized in that, In the cross-section of the positive electrode active material layer along the thickness direction of the electrode sheet, the Dn10 of the lithium-containing transition metal oxide particles is 0.5μm-1.5μm.

34. The battery cell according to claim 32, characterized in that, In the cross-section of the positive electrode active material layer along the thickness direction of the electrode sheet, the Dn90 of the lithium-containing transition metal oxide particles is 3μm-4μm.

35. The battery cell according to claim 1, characterized in that, Based on the total molar number of nickel, cobalt and X1 elements in the lithium-containing transition metal oxide particles, the molar percentage of nickel is 50%-80%.

36. The battery cell according to claim 1, characterized in that, Based on the total molar number of nickel, cobalt and X1 elements in the lithium-containing transition metal oxide particles, the molar percentage of cobalt is 5%-20%.

37. The battery cell according to claim 1, characterized in that, Based on the total molar number of nickel, cobalt and X1 elements in the lithium-containing transition metal oxide particles, the molar percentage of X1 element is 15%-40%.

38. The battery cell according to claim 1, characterized in that, The lithium-containing transition metal oxide particles are lithium-containing transition metal oxide single crystal particles.

39. The battery cell according to claim 1, characterized in that, Based on the total mass of the positive electrode active material, the mass percentage of the lithium-containing transition metal oxide particles is 50%-90%.

40. The battery cell according to claim 39, characterized in that, Based on the total mass of the positive electrode active material, the mass percentage of the lithium-containing transition metal oxide particles is 60%-80%.

41. The battery cell according to claim 1, characterized in that, The lithium-containing transition metal oxide particles include one or more of lithium-containing nickel-cobalt-manganese oxides and their doped and / or coated modified materials, and lithium-containing nickel-cobalt-aluminum oxides and their doped and / or coated modified materials.

42. The battery cell according to claim 1, characterized in that, The lithium-containing transition metal phosphate particles include a particle body and a carbon material disposed on at least a portion of the surface of the particle body.

43. The battery cell according to claim 42, characterized in that, The average thickness of the carbon material is 2nm-25nm; And / or, based on the total mass of the lithium transition metal phosphate particles, the carbon material accounts for 0.5%-3% of the total mass.

44. The battery cell according to claim 1, characterized in that, The lithium-containing transition metal phosphate particles comprise the components represented by the following general formula I: Li m1 Fe x1 Mn y1 M1 b1 P z1 Q1 c1 O n1 N1 d1 Formula I; Wherein, 0.8≤m1≤1.2, 0<x1<1, 0<y1<1, 0.9≤x1+y1≤1, 0.95≤z1≤1, 3.5≤n1≤4, 0≤b1≤0.1, 0≤c1≤0.1, 0≤d1≤0.1; wherein, M1 includes one or more of Cu, Cr, Zn, Pb, Ca, Co, Ni, Sr, Nb, V, and Ti, Q1 includes one or more of B, S, Si, and N, and N1 includes one or more of F, Cl, and Br.

45. The battery cell according to claim 1, characterized in that, The positive electrode active material layer includes a first conductive agent, which includes a dotted conductive agent, and the dotted conductive agent includes one or more of Super P, Ketjen Black, acetylene black, and conductive graphite.

46. ​​The battery cell according to claim 45, characterized in that, Based on the total mass of the positive electrode active material layer, the mass percentage of the dotted conductive agent is 0.2%-2.0%.

47. The battery cell according to claim 45 or 46, characterized in that, The first conductive agent further includes a linear conductive agent, which includes one or more of carbon nanotubes and carbon nanofibers.

48. The battery cell according to claim 47, characterized in that, The linear conductive agent includes carbon nanotubes.

49. The battery cell according to claim 47, characterized in that, Based on the total mass of the positive electrode active material layer, the mass percentage of the linear conductive agent is 0.05%-1.5%.

50. The battery cell according to claim 1, characterized in that, The positive electrode film layer further includes a positive electrode undercoating layer disposed on the positive electrode active material layer near the positive electrode current collector side, the positive electrode undercoating layer comprising a second polymer and a second conductive agent.

51. The battery cell according to claim 50, characterized in that, The thickness of the positive electrode undercoat is 0.5μm-5μm.

52. The battery cell according to claim 1, characterized in that, The compaction density of the positive electrode film is 2.60 g / cm³. 3 -3.4g / cm 3 .

53. The battery cell according to claim 1, characterized in that, The negative electrode sheet 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, which includes graphite, and the volume distribution particle size Dv50 of the negative electrode active material is 7μm-15μm.

54. The battery cell according to claim 53, characterized in that, The volume distribution particle size Dv50 of the negative electrode active material is 8μm-13μm.

55. The battery cell according to claim 53 or 54, characterized in that, The specific surface area of ​​the negative electrode active material is 0.5 m². 2 / g-3.0m 2 / g.

56. The battery cell according to claim 55, characterized in that, The specific surface area of ​​the negative electrode active material is 0.8 m². 2 / g-2.0m 2 / g.

57. The battery cell according to claim 1, characterized in that, The electrode assembly further includes a separator membrane disposed between the positive electrode and the negative electrode, the separator membrane comprising a base film and a coating disposed on at least one side of the base film, the coating comprising a first coating comprising a third polymer.

58. The battery cell according to claim 57, characterized in that, The coating further includes a second coating disposed between the first coating and the base film, the second coating comprising inorganic particles and a fourth polymer.

59. The battery cell according to claim 58, characterized in that, The coating is applied to the base film near the positive electrode sheet.

60. The battery cell according to claim 58, characterized in that, The inorganic particles include one or more of alumina, boehmite, silicon dioxide, cerium oxide, magnesium aluminate, zirconium oxide, and titanium dioxide.

61. The battery cell according to claim 58, characterized in that, The third polymer and the fourth polymer each independently include one or more of fluoropolymers and acrylate polymers.

62. The battery cell according to claim 61, characterized in that, The fluoropolymer includes vinylidene fluoride polymers, which include one or more of the following: vinylidene fluoride homopolymers, copolymers of vinylidene fluoride and tetrafluoroethylene, copolymers of vinylidene fluoride and hexafluoropropylene, and copolymers of vinylidene fluoride and trifluoroethylene.

63. The battery cell according to any one of claims 57-59, characterized in that, The thickness of the base film is 5μm-12μm.

64. The battery cell according to any one of claims 57-59, characterized in that, The coating has a single-sided thickness of 1µm-4µm.

65. The battery cell according to any one of claims 57-59, characterized in that, The thickness of the isolation membrane is 8μm-15μm.

66. The battery cell according to claim 57, characterized in that, The air permeability of the isolation membrane at 25°C is 400s / 100cc-600s / 100cc.

67. The battery cell according to claim 57, characterized in that, The porosity of the isolation membrane is 35%-55%.

68. The battery cell according to claim 1, characterized in that, The thickness of the positive electrode current collector is 9μm-15μm.

69. The battery cell according to claim 53, characterized in that, The thickness of the negative electrode current collector is 3μm-7μm.

70. The battery cell according to claim 1, characterized in that, The rated cutoff voltage of the battery cell is 4.25V-4.45V.

71. The battery cell according to claim 1, characterized in that, The positive electrode includes a first main body and a first tab. The first main body includes a first straight section, which includes the positive current collector and the positive film layer. The first straight section is stacked along the thickness direction of the battery cell. The ratio of the number of first tabs to the number of first straight segments is 0.5-1.

72. The battery cell according to claim 71, characterized in that, The ratio of the number of first tabs to the number of first straight segments is 0.75-1.

73. The battery cell according to claim 71, characterized in that, Along the width direction of the battery cell, the ratio of the size of the first tab to the size of the electrode assembly is 12%-40%.

74. The battery cell according to claim 73, characterized in that, Along the width direction of the battery cell, the ratio of the size of the first tab to the size of the electrode assembly is 24%-40%.

75. The battery cell according to claim 73 or 74, characterized in that, Along the width direction of the battery cell, the size of the first tab is 25mm-60mm.

76. The battery cell according to claim 73 or 74, characterized in that, Along the width direction of the battery cell, the size of the electrode assembly is 140mm-390mm.

77. The battery cell according to claim 53, characterized in that, The negative electrode sheet includes a second main body and a second tab. The second main body includes a second straight section, which includes the negative current collector and the negative electrode film layer. The second straight section is stacked along the thickness direction of the battery cell. The ratio of the number of the second electrode tabs to the number of the second straight segments is 0.5-1.

78. The battery cell according to claim 77, characterized in that, The ratio of the number of the second electrode tabs to the number of the second straight segments is 0.75-1.

79. The battery cell according to claim 1, characterized in that, The electrode assembly includes a wound electrode assembly.

80. A battery device, characterized in that, Includes the battery cell according to any one of claims 1-79.

81. An electrical appliance, characterized in that, Includes the battery device of claim 80, the battery device being used to provide electrical energy.

82. An energy storage device, characterized in that, Includes the battery device of claim 80, the battery device being used for storing electrical energy.

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