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 phosphate particles include manganese and iron; the lithium-containing transition metal oxide particles include nickel, cobalt, and X1 elements, where X1 elements include manganese and / or aluminum; 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 1.0 μm-3.5 μm, and based on the total number of lithium-containing transition metal oxide particles, the proportion of lithium-containing transition metal oxide particles with a particle size greater than or equal to 4 μm is 2%-10%.

Description

Cross-references to related applications

[0001] This application claims priority to PCT patent application PCT / CN2026 / 090953, 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 disposed on at least one side of the positive current collector, the positive electrode film 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 phosphate particles include manganese and iron; the lithium-containing transition metal oxide particles contain... The material includes nickel, cobalt, and X1 elements, wherein the X1 element includes manganese and / or aluminum. 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 1.0 μm-3.5 μm. Based on the total number of lithium-containing transition metal oxide particles, the proportion of lithium-containing transition metal oxide particles with a particle size greater than or equal to 4 μm is 2%-10%. Wherein, Dn50 refers to the particle size corresponding to 50% of the cumulative number of particles in the cumulative number distribution curve of particle size.

[0007] In this embodiment, the positive electrode active material includes lithium transition metal oxide particles and lithium transition metal phosphate particles, which helps to balance the energy density and cost of the battery cell.

[0008] To fully utilize the specific capacity of lithium-containing transition metal oxide particles and improve the energy density of individual battery cells, the charging cutoff voltage of the battery cells needs to be set to around 4.25V. The main discharge voltage range of lithium-containing transition metal oxide particles is significantly higher than that of lithium-containing transition metal phosphate particles. This means that lithium-containing transition metal phosphate particles must bear the main lithium-ion supply in the low-voltage range, while lithium-containing transition metal oxide particles must 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 when charging and discharging at low rates, the load shunting phenomenon in the hybrid battery cell still causes rapid lithium-ion insertion / extraction in the positive electrode active material.

[0009] Compared to lithium iron phosphate, lithium transition metal phosphate particles containing both manganese and iron can mitigate the voltage mismatch with lithium transition metal oxides by utilizing two voltage platforms. Mixing lithium transition metal phosphates containing manganese and iron with lithium transition metal oxides can alleviate load shunting caused by voltage mismatch, thus improving the cycle life of individual cells in the hybrid battery system.

[0010] Lithium-containing transition metal oxides have poor structural stability and are susceptible to load shunting during cycling, making their structure more prone to deterioration. 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 cell.

[0011] Controlling the Dn50 of lithium-containing transition metal oxide particles to 1.0μm-3.5μm can improve the kinetics of lithium-containing transition metal oxides, reduce the mismatch between the surface and bulk lattice parameters of lithium-containing transition metal oxide particles, and improve the cycle stability of hybrid battery cells.

[0012] However, studies have shown that small lithium transition metal oxide particles reduce the effective current sharing of lithium transition metal phosphate in higher voltage ranges (e.g., around 3.7V), as shown in Table 4. Based on this, the embodiments of this application further control the proportion of lithium transition metal oxide particles with a particle size greater than or equal to 4μm to 2%-10%, that is, retaining a certain number of larger-sized transition metal oxide particles to improve the current shunting degree of lithium transition metal phosphate particles in higher voltage ranges, thereby alleviating the structural degradation problem caused by load shunting of lithium transition metal oxide particles, and thus improving the cycle stability of the hybrid battery cell.

[0013] In summary, this application balances the energy density and cost of battery cells by setting the positive electrode active material to include lithium transition metal oxide particles and lithium transition metal phosphate particles containing manganese and iron. Furthermore, by controlling the Dn50 of the lithium transition metal oxide particles and the proportion of lithium transition metal oxide particles with a particle size greater than or equal to 4 μm, the cycle performance of hybrid battery cells is improved while reducing costs and increasing energy density.

[0014] In any embodiment, in the cross-section of the positive electrode active material layer along the electrode thickness direction, the Dn50 of the lithium-containing transition metal oxide particles is 1.5μm-3μm.

[0015] The lithium transition metal oxide-containing Dn50 is further within the above range, which helps to balance the uniformity of the distribution of lithium transition metal oxide in the positive electrode active material layer and the degree of side reaction with the electrolyte, thereby further improving the cycle performance of the hybrid system battery cell.

[0016] In any embodiment, in the cross section of the positive electrode active material layer along the electrode thickness direction, the proportion of lithium-containing transition metal oxide particles with a particle size greater than or equal to 4 μm is 2%-8% based on the total number of lithium-containing transition metal oxide particles.

[0017] The proportion of lithium-containing transition metal oxide particles with a particle size of 4 μm or greater within the above range helps to improve the shunting degree of lithium-containing transition metal phosphate particles in the high voltage range, improve the problem of surface structure degradation caused by current overload of lithium-containing transition metal oxides, and further improve the cycle performance of hybrid system battery cells.

[0018] In any embodiment, in the cross-section of the positive electrode active material layer along the electrode thickness direction, the average particle size R1 of the lithium-containing transition metal oxide particles with a particle size greater than or equal to 4 μm is 4.0 μm-6 μm.

[0019] The average particle size of the lithium-containing transition metal oxide particles with a particle size greater than or equal to 4 μm is within the above range, which helps to balance the kinetics and current shunting degree of lithium-containing transition metal oxides, and to balance the problems of surface and bulk lattice parameter mismatch and surface structure degradation caused by current overload in the higher voltage range, thereby improving the cycle performance of the hybrid system battery cell.

[0020] In any embodiment, in the cross-section of the positive electrode active material layer along the electrode thickness direction, the average particle size R1 of the lithium-containing transition metal oxide particles with a particle size greater than or equal to 4 μm is 4.1 μm-5.6 μm.

[0021] In any embodiment, in the cross-section of the positive electrode active material layer along the electrode thickness direction, the average particle size R1 of the lithium-containing transition metal oxide particles with a particle size greater than or equal to 4 μm is 4.4 μm-5.1 μm.

[0022] The average particle size of the lithium-containing transition metal oxide particles with a particle size greater than or equal to 4 μm is within the above range, which helps to balance the kinetics and current shunting degree of lithium-containing transition metal oxides, and to balance the problems of particle breakage and structural degradation caused by surface and bulk lattice parameter mismatch and current overload in higher voltage ranges, thereby improving the cycle performance of hybrid system battery cells.

[0023] In any embodiment, in the cross-section of the positive electrode active material layer along the electrode thickness direction, the average particle size R2 of the lithium-containing transition metal oxide particles with a particle size greater than or equal to 1 μm and less than 4 μm is 1.2 μm-3.5 μm.

[0024] The average particle size of lithium-containing transition metal oxide particles with a particle size greater than or equal to 1 μm and less than 4 μm is within the above range, which helps to improve the kinetic performance of lithium-containing transition metal oxides and suppress particle breakage and structural degradation caused by mismatch of surface and bulk lattice parameters; at the same time, it also helps to take into account the degree of side reaction with electrolyte and improve the cycle performance of hybrid system battery cells.

[0025] In any embodiment, in the cross-section of the positive electrode active material layer along the electrode thickness direction, the average particle size R2 of the lithium-containing transition metal oxide particles with a particle size greater than or equal to 1 μm and less than 4 μm is 1.2 μm-3.1 μm.

[0026] In any embodiment, in the cross-section of the positive electrode active material layer along the electrode thickness direction, the average particle size R2 of the lithium-containing transition metal oxide particles with a particle size greater than or equal to 1 μm and less than 4 μm is 1.7 μm-2.9 μm.

[0027] The average particle size of lithium-containing transition metal oxide particles with a particle size greater than or equal to 1 μm and less than 4 μm is within the above range, which helps to further improve the kinetic performance of lithium-containing transition metal oxides and suppress particle breakage and structural degradation caused by mismatch of surface and bulk lattice parameters; at the same time, it also helps to take into account the degree of side reaction with electrolyte and improve the cycle performance of hybrid system battery cells.

[0028] In any embodiment, the proportion of nickel moles is 50%-80% based on the total number of moles of nickel, cobalt and X1 elements in the lithium-containing transition metal oxide particles.

[0029] 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.

[0030] In any embodiment, the proportion of cobalt moles is 5%-20% based on the total number of moles of nickel, cobalt and X1 elements in the lithium-containing transition metal oxide particles.

[0031] In any embodiment, the molar percentage of the X1 element is 15%-40% based on the total molar number of nickel, cobalt and X1 elements in the lithium-containing transition metal oxide particles.

[0032] In any embodiment, the lithium-containing transition metal oxide particles are lithium-containing transition metal oxide single crystal particles.

[0033] Lithium-containing transition metal oxide particles, being single-crystal particles, help reduce the size of lithium-containing transition metal oxide particles, thereby improving their kinetic performance, suppressing particle breakage and structural degradation caused by mismatch between surface and bulk lattice parameters, and further improving the cycle performance of hybrid battery cells.

[0034] In any embodiment, 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%.

[0035] In positive electrode active materials, a mass percentage of lithium transition metal oxide particles within the aforementioned range helps to balance the cost and energy density of hybrid battery cells.

[0036] In any embodiment, 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%.

[0037] 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.

[0038] The carbon material embedded in lithium transition metal phosphate particles at least partially on the surface of the particle body helps to improve its kinetic performance, thereby increasing its shunting degree in the higher voltage range, alleviating the structural degradation problem caused by over-reaction of lithium transition metal oxide particles, and further improving the cycle performance of hybrid battery cells.

[0039] In any embodiment, the average thickness of the carbon material is 2nm-25nm.

[0040] In any embodiment, the carbon material accounts for 0.5%-3% of the total mass of the lithium transition metal phosphate particles.

[0041] In any embodiment, 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%-75%.

[0042] To fully utilize the specific capacity of lithium transition metal oxide particles and improve the energy density of individual battery cells, the charging cutoff voltage of the battery cells needs to be set to approximately 4.25V. The main discharge voltage range of lithium transition metal oxide particles is higher than that of lithium transition metal phosphate particles. This means that lithium transition metal phosphate particles primarily supply lithium ions in the low-voltage range, while lithium transition metal oxide particles primarily supply lithium ions in the high-voltage range. This results in both materials experiencing an equivalent rate load higher than the apparent rate in their respective operating ranges, leading to load shunting. Therefore, even at low rates, load shunting in the hybrid battery cell still causes rapid lithium ion insertion / extraction within the positive electrode active material. Furthermore, lithium transition metal oxides have poor structural stability and are easily affected by load shunting during cycling, which is detrimental to maintaining their structural integrity.

[0043] In this embodiment, the molar percentage of manganese in the lithium transition metal phosphate particles is further controlled within the range of 40%-75% to increase its upper limit of working voltage, improve the shunting degree of lithium transition metal phosphate in the higher working voltage range, thereby improving the load shunting problem of the hybrid system battery cell and further improving the cycle performance of the hybrid system battery cell.

[0044] In any embodiment, in the cross-section of the positive electrode active material layer along the electrode thickness direction, the Dn50 of the lithium transition metal phosphate particles is 100nm-300nm.

[0045] The Dn50 of lithium transition metal phosphate particles is within the above range, indicating that the overall particle size is small, which helps to improve its kinetic performance, increase its shunting degree in the higher voltage range, further improve the structural degradation problem caused by excessive participation of lithium transition metal oxides in the reaction, and improve the cycle performance of hybrid battery cells.

[0046] In any embodiment, in the cross-section of the positive electrode active material layer along the electrode thickness direction, the Dn50 of the lithium transition metal phosphate particles is 100nm-250nm.

[0047] The Dn50 of lithium transition metal phosphate particles within the above range helps to further improve their kinetic performance, increase their shunting degree in the higher voltage range, further improve the structural degradation problem caused by excessive participation of lithium transition metal oxides in the reaction, and improve the cycle performance of hybrid battery cells.

[0048] In any embodiment, in the cross-section of the positive electrode active material layer along the thickness direction of the electrode sheet, the Dn90 of the lithium transition metal phosphate particles is 250nm-500nm; wherein, Dn90 refers to the particle size corresponding to the cumulative number of particles being 90% in the cumulative number distribution curve of particle size.

[0049] The Dn90 of lithium transition metal phosphate particles is within the above range, indicating that the size of lithium transition metal phosphate particles is small, which helps to improve their kinetic performance, increase their shunting degree in the higher voltage range, further improve the structural degradation problem caused by excessive participation of lithium transition metal oxides in the reaction, and improve the cycle performance of hybrid system battery cells.

[0050] In any embodiment, in the cross-section of the positive electrode active material layer along the electrode thickness direction, the Dn90 of the lithium transition metal phosphate particles is 270nm-400nm.

[0051] The Dn90 of lithium transition metal phosphate particles within the above range helps to further improve its kinetic performance, increase its shunting degree in the higher voltage range, further improve the structural degradation problem caused by excessive participation of lithium transition metal oxides in the reaction, and improve the cycle performance of hybrid battery cells.

[0052] 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; wherein, Dn10 refers to the particle size corresponding to the cumulative number of particles being 10% in the cumulative number distribution curve of particle size.

[0053] Studies have shown that when the particle size of lithium transition metal phosphate particles is reduced, their specific surface area increases, the residual water in the battery cell manufacturing process increases significantly, and further triggers the hydrolysis of electrolyte salts in the electrolyte to generate highly corrosive hydrofluoric acid, which easily damages and thus destroys the surface structure of the positive electrode active material, affecting the cycle performance of the battery cell.

[0054] In any embodiment, the electrolyte includes a first component, which includes one or more of lithium bis(fluorosulfonyl)imide, lithium difluorophosphate, lithium tetrafluoroborate, and lithium bis(trifluoromethanesulfonyl)imide.

[0055] In this embodiment, a first component that is not easily hydrolyzed is used to replace part of the conventional easily hydrolyzable electrolyte salt (e.g., lithium hexafluorophosphate) to reduce the generation of hydrofluoric acid, alleviate the problem of hydrofluoric acid damaging the surface structure of lithium transition metal oxide particles, and further improve the cycle performance of the hybrid system battery cells.

[0056] In any embodiment, the mass percentage of the first component is 0.1%-8% based on the total mass of the electrolyte.

[0057] When the mass percentage of the first component is within the above range, it 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 further improving the cycle performance of the hybrid system battery cells.

[0058] In any embodiment, the mass percentage of the first component is 0.5%-8% based on the total mass of the electrolyte.

[0059] In any embodiment, the mass percentage of the first component is 3%-8% based on the total mass of the electrolyte.

[0060] The mass percentage of the first 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.

[0061] In any embodiment, the first component includes one or more of lithium bis(fluorosulfonyl)imide and lithium difluorophosphate.

[0062] The first component includes one or more of lithium bis(fluorosulfonyl)imide and lithium difluorophosphate. On the one hand, it helps to reduce the amount of hydrofluoric acid generated and inhibit its damage to the surface structure of the positive electrode active material. On the other hand, the first component includes the above substances, which can generate a lithium fluoride-rich positive electrode electrolyte interface (CEI film), thereby improving the mechanical strength of the CEI film and further improving the cycle performance of the battery cell.

[0063] In any embodiment, the mass percentage of lithium bis(fluorosulfonyl)imide is 0.1%-8% based on the total mass of the electrolyte.

[0064] In any embodiment, the lithium difluorosulfonamide accounts for 2%-5% of the total mass of the electrolyte.

[0065] If the mass percentage of lithium bis(fluorosulfonyl)imide is too low, its effect on reducing hydrofluoric acid formation is limited; if its mass percentage is too high, it easily corrodes the current collector. Further reducing the mass percentage of lithium bis(fluorosulfonyl)imide to within the range of 2%-5% helps to balance reducing hydrofluoric acid formation and its damaging effect on the current collector, thereby further improving the cycle performance of the battery cells.

[0066] In any embodiment, the lithium difluorophosphate accounts for 0.5%-8% of the total mass of the electrolyte.

[0067] In any embodiment, the lithium difluorophosphate accounts for 1%-5% of the total mass of the electrolyte.

[0068] If the mass percentage of lithium difluorophosphate is too low, its effect on reducing hydrofluoric acid formation is limited; if its mass percentage is too high, the CEI film thickness increases, impedance increases, and polarization is easily induced. Maintaining the mass percentage of lithium difluorosulfonylimide within the range of 1%-5% helps to balance reducing hydrofluoric acid formation with a lower CEI film thickness, further improving the cycle performance of the battery cell.

[0069] In any embodiment, the electrolyte further includes lithium hexafluorophosphate, and the mass percentage of lithium hexafluorophosphate is 5%-10% based on the total mass of the electrolyte.

[0070] Electrolytes typically require a certain ion concentration to maintain good rate performance of individual battery cells. Lithium hexafluorophosphate (LiPF6) offers 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. Furthermore, controlling the mass percentage of LiPF6 within the aforementioned range helps to maintain the ionic conductivity of the electrolyte while reducing the formation of hydrofluoric acid, mitigating damage to the structure of the positive electrode active material, and further improving the cycle performance of the hybrid battery cell.

[0071] In any embodiment, the electrolyte further includes a second component, which includes one or more of lithium difluorooxalate borate, tris(trimethylsilyl) phosphate, and lithium bis(oxalate borate).

[0072] While introducing the first component into the electrolyte can significantly reduce the formation of hydrofluoric acid and improve the cycle performance of individual cells, a small amount of hydrofluoric acid can still cause some damage to the structure of lithium-containing transition metal oxide particles, thereby triggering the dissolution of transition metal elements from the positive electrode. The dissolved transition metal ions migrate to the negative electrode and are reduced to metals, damaging the solid electrolyte interphase (SEI) film of the negative electrode and affecting the cycle performance of the individual cells.

[0073] In this application, a second component is further introduced into the electrolyte. Its decomposition products participate in the formation of the CEI film and help improve the chemical stability of the CEI film, reduce the frequency of CEI film rupture and regeneration, thereby reducing the probability of continuous direct contact between small-diameter lithium transition metal phosphate particles and the electrolyte, and reducing the generation of hydrofluoric acid. At the same time, it also helps to reduce the structural damage of hydrofluoric acid to lithium transition metal oxide particles, further improving the cycle performance of the battery cell.

[0074] In any embodiment, the mass percentage of the second component is 0.2%-5% based on the total mass of the electrolyte.

[0075] Within the aforementioned range, the second component not only helps reduce the formation of hydrofluoric acid and its damage to the structure of the positive electrode active material, but also helps to form a CEI film with appropriate thickness and moderate impedance, thereby balancing the cycle performance and rate performance of the hybrid battery cells.

[0076] In any embodiment, the mass percentage of the second component is 0.5%-2% based on the total mass of the electrolyte.

[0077] In any embodiment, the electrolyte comprises a cyclic carbonate compound, and the cyclic carbonate compound accounts for 20%-45% of the total mass of the electrolyte.

[0078] The presence of cyclic carbonate compounds in the electrolyte, with their mass percentage falling within the aforementioned range, helps to improve the degree of lithium salt dissociation in the electrolyte, increase lithium-ion concentration, and improve the cycle performance of the battery cell.

[0079] In any embodiment, the electrolyte comprises a cyclic carbonate compound, and the cyclic carbonate compound accounts for 20%-35% of the total mass of the electrolyte.

[0080] In any embodiment, the cyclic carbonate compound includes one or more of ethylene carbonate, propylene carbonate, and butene carbonate.

[0081] In any embodiment, the cyclic carbonate compound includes ethylene carbonate.

[0082] In any embodiment, the electrolyte comprises a chain carbonate compound, and the chain carbonate compound accounts for 40%-75% of the total mass of the electrolyte.

[0083] 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 and improve the cycle performance of the battery cells.

[0084] In any embodiment, the electrolyte comprises a chain carbonate compound, and the chain carbonate compound accounts for 50%-70% of the total mass of the electrolyte.

[0085] In any embodiment, the chain carbonate compound includes one or more of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and methyl propyl carbonate.

[0086] In any embodiment, the chain carbonate comprises methyl ethyl carbonate and / or diethyl carbonate.

[0087] Ethyl methyl carbonate and dimethyl carbonate have both low viscosity and good high-voltage resistance, thus improving the local lithium plating problem on the negative electrode side of the battery cell, while also taking into account the degree of side reaction of the electrolyte under high voltage, improving the stability of the electrolyte, and further improving the cycle performance of the hybrid system battery cell.

[0088] In any embodiment, the electrolyte comprises ethyl methyl carbonate, and the mass percentage of ethyl methyl carbonate is 35%-55% based on the total mass of the electrolyte.

[0089] In any embodiment, the electrolyte comprises diethyl carbonate, and the mass percentage of diethyl carbonate is 10%-20% based on the total mass of the electrolyte.

[0090] 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.

[0091] When the positive electrode active material is damaged, the transition metal elements therein are easily dissolved from the positive electrode and migrate to the negative electrode to be reduced to metal, thereby damaging the SEI film. 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 cell.

[0092] In any embodiment, the mass percentage of the third component is 0.08%-5% based on the total mass of the electrolyte.

[0093] 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.

[0094] In any embodiment, the mass percentage of the third component is 0.1%-5% based on the total mass of the electrolyte.

[0095] In any embodiment, the mass percentage of the third component is 1%-5% based on the total mass of the electrolyte.

[0096] 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.

[0097] In any embodiment, 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.

[0098] 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.

[0099] In any embodiment, based on the total mass of the positive electrode active material layer, the mass percentage of the dot-shaped conductive agent is 0.2%-2.0%.

[0100] In any embodiment, the first conductive agent further includes a linear conductive agent, which includes one or more of carbon nanotubes and carbon nanofibers.

[0101] In this application, carbon nanofibers include, but are not limited to, one or more of vapor-grown carbon fibers and graphite carbon fibers.

[0102] 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.

[0103] 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.

[0104] In any embodiment, the linear conductive agent comprises carbon nanotubes.

[0105] In any embodiment, the mass percentage of the linear conductive agent is 0.1%-1.5% based on the total mass of the positive electrode active material layer.

[0106] In any embodiment, the positive electrode active material layer further includes a first polymer.

[0107] 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.

[0108] 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 comprising a second polymer and a second conductive agent.

[0109] 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.

[0110] In any embodiment, the thickness of the positive electrode undercoat is 0.5 μm-5 μm.

[0111] In any embodiment, the compaction density of the positive electrode film is 2.6 g / cm³. 3 -3.4g / cm 3 .

[0112] 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.

[0113] In the embodiments of this application, after the lithium-containing transition metal oxide particles have a lower particle size and improved kinetics, their corresponding negative electrode side also bears a larger lithium ion insertion / extraction density, increasing the probability of lithium plating problems.

[0114] 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.

[0115] In any embodiment, the volume distribution particle size Dv50 of the negative electrode active material is 8μm-13μm.

[0116] 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.

[0117] In any embodiment, the specific surface area of ​​the negative electrode active material is 0.5 m². 2 / g-3.0m 2 / g.

[0118] In any embodiment, the specific surface area of ​​the negative electrode active material is 0.8 m². 2 / g-2.0m 2 / g.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] 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 sheet.

[0123] 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.

[0124] In any embodiment, the inorganic particles include one or more of alumina, boehmite, silicon dioxide, cerium oxide, magnesium aluminate, zirconium oxide, and titanium dioxide.

[0125] In any embodiment, the third polymer and the fourth polymer each independently include one or more of fluoropolymers and acrylate polymers.

[0126] 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.

[0127] In any embodiment, the thickness of the base film is 5 μm-12 μm.

[0128] In any embodiment, the thickness of the coating on one side is 1µm-4µm.

[0129] In any embodiment, the thickness of the isolation membrane is 8μm-15μm.

[0130] In any embodiment, the air permeability of the separator at 25°C is 400s / 100cc-600s / 100cc.

[0131] 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.

[0132] In any embodiment, the porosity of the isolation membrane is 35%-55%.

[0133] In any embodiment, the thickness of the positive current collector is 9μm-15μm.

[0134] 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.

[0135] In any embodiment, the thickness of the negative electrode current collector is 3μm-7μm.

[0136] 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.

[0137] In any embodiment, the rated cutoff voltage of the battery cell is 4.25V-4.45V.

[0138] In any embodiment, the battery cell includes a casing and electrode terminals. A receiving cavity is formed inside the casing, and the electrode assembly and electrolyte are disposed in the receiving cavity. The casing has a through hole communicating with the inside and outside of the receiving cavity. The electrode terminal includes a first part and a second part. The first part is entirely located inside the receiving cavity, and the second part passes through the through hole and is partially located outside the receiving cavity. The first part and the second part are an integral structure. The electrode assembly also includes a tab, which is directly connected to the first part.

[0139] In this embodiment, the tabs on the electrode assembly are directly connected to the first part of the electrode terminal. Combined with the above-mentioned hybrid system, the impedance and heat generation at the tabs are reduced, the heat at the maximum heat generation point of the battery cell is reduced, the temperature distribution uniformity of the positive electrode active material layer is improved, the temperature rise of the positive electrode sheet is reduced, thereby reducing the probability of manganese ion dissolution of 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 system battery cell.

[0140] In any embodiment, the housing further includes an end cap, and the ratio of the size of the first portion to the size of the end cap is 0.35-0.80 along the thickness direction of the battery cell.

[0141] Along the thickness direction of the battery cell, the ratio of the size of the first part to the size of the end cap is within the above range, which is beneficial to increase the area of ​​the first part, thereby increasing the solderable area of ​​the tab and electrode terminal, reducing connection resistance, reducing heat generation, further improving the temperature distribution uniformity of the positive electrode active material layer, 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 system battery cell.

[0142] In any embodiment, the ratio of the size of the first portion to the size of the end cap is 0.50-0.80 along the thickness direction of the battery cell.

[0143] Along the thickness direction of the battery cell, the ratio of the size of the first part to the size of the end cap is within the above range, which is beneficial to further increase the area of ​​the first part, further increase the solderable area of ​​the tab and electrode terminal, reduce connection resistance, reduce heat generation, further improve the temperature distribution uniformity of the positive electrode active material layer, thereby reducing the probability of manganese ion dissolution of 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 system battery cell.

[0144] The second aspect of this application provides a battery device, which includes the battery cell provided in the first aspect, and the battery device includes one or more of the following: battery module, battery pack, and energy storage battery.

[0145] A third aspect of this application provides an electrical device, which includes the battery device provided in the second aspect, the battery device being used to provide electrical energy.

[0146] The fourth aspect of this application provides an energy storage device, which includes the battery device provided in the second aspect, the battery device being used to store electrical energy.

[0147] 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

[0148] 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.

[0149] Figure 1 This is a schematic diagram of a battery cell according to one embodiment of this application; Figure 2 yes Figure 1 An exploded view of a battery cell according to one embodiment of this application is shown. Figure 3 This is a schematic diagram of a battery pack according to one embodiment of this application; Figure 4 yes Figure 3 The diagram shown is a structural schematic of a battery module according to one embodiment of this application; Figure 5 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.

[0150] 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; 111, first tab; 121, second tab; 20, outer casing; 21, housing; 22, end cap; 31, first electrode terminal; 32, second electrode terminal. Detailed Implementation

[0151] 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.

[0152] 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.

[0153] 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.

[0154] 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.

[0155] 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).

[0156] 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.

[0157] 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.

[0158] 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.

[0159] 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.

[0160] 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.

[0161] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0162] Unless otherwise stated, the terms used in this application have the common meanings as commonly understood by those skilled in the art.

[0163] 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.

[0164] 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.

[0165] To address the aforementioned problems, a 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 including a positive current collector and a positive electrode film disposed on at least one side of the positive current collector, the positive electrode film including a positive active material layer, the positive active material layer including a positive active material, the positive active material including lithium transition metal oxide particles and lithium transition metal phosphate particles; the lithium transition metal phosphate particles including manganese and iron; the lithium transition metal oxide... The particles include nickel, cobalt, and X1 elements, wherein the X1 elements include manganese and / or aluminum. 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 1.0 μm-3.5 μm. Based on the total number of lithium-containing transition metal oxide particles, the proportion of lithium-containing transition metal oxide particles with a particle size greater than or equal to 4 μm is 2%-10%. Here, Dn50 refers to the particle size corresponding to 50% of the cumulative number of particles in the cumulative number distribution curve of particle size.

[0166] In this embodiment, the positive electrode active material includes lithium transition metal oxide particles and lithium transition metal phosphate particles, which helps to balance the energy density and cost of the battery cell.

[0167] To fully utilize the specific capacity of lithium-containing transition metal oxide particles and improve the energy density of individual battery cells, the charging cutoff voltage of the battery cells needs to be set to around 4.25V. The main discharge voltage range of lithium-containing transition metal oxide particles is significantly higher than that of lithium-containing transition metal phosphate particles. This means that lithium-containing transition metal phosphate particles must bear the main lithium-ion supply in the low-voltage range, while lithium-containing transition metal oxide particles must 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 when charging and discharging at low rates, the load shunting phenomenon in the hybrid battery cell still causes rapid lithium-ion insertion / extraction in the positive electrode active material.

[0168] Compared to lithium iron phosphate, lithium transition metal phosphate particles containing both manganese and iron can mitigate the voltage mismatch with lithium transition metal oxides by utilizing two voltage platforms. Mixing lithium transition metal phosphates containing manganese and iron with lithium transition metal oxides can alleviate load shunting caused by voltage mismatch, thus improving the cycle life of individual cells in the hybrid battery system.

[0169] Lithium-containing transition metal oxides have poor structural stability and are susceptible to load shunting during cycling, making their structure more prone to deterioration. 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 cell.

[0170] Controlling the Dn50 of lithium-containing transition metal oxide particles to 1.0μm-3.5μm can improve the kinetics of lithium-containing transition metal oxides, reduce the mismatch between the surface and bulk lattice parameters of lithium-containing transition metal oxide particles, and improve the cycle stability of hybrid battery cells.

[0171] However, studies have shown that small lithium transition metal oxide particles reduce the effective current sharing of lithium transition metal phosphate in higher voltage ranges (e.g., around 3.7V), as shown in Table 4. Based on this, the embodiments of this application further control the proportion of lithium transition metal oxide particles with a particle size greater than or equal to 4μm to 2%-10%, that is, retaining a certain number of larger-sized transition metal oxide particles to improve the current shunting degree of lithium transition metal phosphate particles in higher voltage ranges, thereby alleviating the structural degradation problem caused by load shunting of lithium transition metal oxide particles, and thus improving the cycle stability of the hybrid battery cell.

[0172] In summary, this application balances the energy density and cost of battery cells by setting the positive electrode active material to include lithium transition metal oxide particles and lithium transition metal phosphate particles containing manganese and iron. Furthermore, by controlling the Dn50 of the lithium transition metal oxide particles and the proportion of lithium transition metal oxide particles with a particle size greater than or equal to 4 μm, the cycle performance of hybrid battery cells is improved while reducing costs and increasing energy density.

[0173] In some embodiments, the lithium-containing transition metal oxide particles include nickel, cobalt, and X1, wherein the X1 element includes manganese.

[0174] In some embodiments, the lithium-containing transition metal oxide particles include nickel, cobalt, and X1, wherein the X1 element includes aluminum.

[0175] 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.

[0176] 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).

[0177] 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.

[0178] 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.

[0179] 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.

[0180] In this application, the Dn50 of the lithium transition metal oxide 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 100 transition metal oxide (LMO) particles was statistically analyzed. The obtained at least 100 LMO particles were sorted by particle size from smallest to largest, and a cumulative particle size distribution curve was obtained with particle size as the horizontal axis and cumulative number (the total number of particles) as the vertical axis. The particle sizes corresponding to 50% and 90% of the cumulative particle size distribution curve represent the Dn50 of the LMO particles in the cross-section along the electrode thickness direction of the positive electrode active material layer.

[0181] In some embodiments, the Dn50 of the lithium-containing transition metal oxide particles in the cross-section along the thickness direction of the positive electrode active material layer 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, or any value range between the two.

[0182] When the Dn50 of lithium-containing transition metal oxide particles is greater than 3.5 μm, the particle size is large, the kinetics cannot be effectively improved, and the mismatch between the surface and bulk lattice parameters is severe, affecting the cycle stability of the hybrid system battery cells.

[0183] In this application, the percentage of lithium-containing transition metal oxide particles with a diameter greater than or equal to 4 μm, based on the total number of such particles, can be tested using methods and instruments known in the art. As an example, referring to the method for testing the Dn50 of lithium-containing transition metal oxide particles in a cross-section along the electrode thickness direction of the positive electrode active material layer described above, the total number of lithium-containing transition metal oxide particles is α1, and the number of particles with a diameter greater than or equal to 4 μm is α2. α2 / α1 × 100% is the percentage of lithium-containing transition metal oxide particles with a diameter greater than or equal to 4 μm, based on the total number of such particles.

[0184] In some embodiments, based on the total number of lithium-containing transition metal oxide particles, the percentage of lithium-containing transition metal oxide particles with a particle size greater than or equal to 4 μm can be 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%, 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 range between the two.

[0185] When the proportion of lithium transition metal oxide particles with a particle size of 4 μm or greater is less than 2%, the current carrying capacity of lithium transition metal phosphate particles in the high voltage range is relatively small. Overload of lithium transition metal oxide particles is prone to structural degradation, which affects the cycle performance of the battery cell.

[0186] In some embodiments, the Dn50 of the lithium-containing transition metal oxide particles in the cross-section of the positive electrode active material layer along the electrode thickness direction is 1.5 μm-3 μm.

[0187] The lithium transition metal oxide-containing Dn50 is further within the above range, which helps to balance the uniformity of the distribution of lithium transition metal oxide in the positive electrode active material layer and the degree of side reaction with the electrolyte, thereby further improving the cycle performance of the hybrid system battery cell.

[0188] In some embodiments, in the cross section of the positive electrode active material layer along the electrode thickness direction, the proportion of lithium-containing transition metal oxide particles with a particle size greater than or equal to 4 μm is 2%-8% based on the total number of lithium-containing transition metal oxide particles.

[0189] The proportion of lithium-containing transition metal oxide particles with a particle size of 4 μm or greater within the above range helps to improve the shunting degree of lithium-containing transition metal phosphate particles in the high voltage range, improve the problem of surface structure degradation caused by current overload of lithium-containing transition metal oxides, and further improve the cycle performance of hybrid system battery cells.

[0190] In some embodiments, in the cross-section of the positive electrode active material layer along the electrode thickness direction, the average particle size R1 of the lithium-containing transition metal oxide particles with a particle size greater than or equal to 4 μm is 4.0 μm-6 μm.

[0191] In this application, the average particle size R1 of the lithium-containing transition metal oxide particles with a particle size greater than or equal to 4 μm in the cross-section of the positive electrode active material layer along the electrode thickness direction can be tested using methods and instruments known in the art. As an example, referring to the test method for Dn50 of the lithium-containing transition metal oxide particles in the cross-section of the positive electrode active material layer along the electrode thickness direction described above, the average particle size of particles with a particle size greater than or equal to 4 μm among at least 100 lithium-containing transition metal oxide particles obtained can be calculated. This average value is the average particle size R1 of the lithium-containing transition metal oxide particles with a particle size greater than or equal to 4 μm in the cross-section of the positive electrode active material layer along the electrode thickness direction.

[0192] In some embodiments, in the cross-section of the positive electrode active material layer along the electrode thickness direction, the average particle size R1 of the lithium-containing transition metal oxide particles with a particle size greater than or equal to 4 μm can be 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, 5.1 μm, 5.2 μm, 5.3 μm, 5.4 μm, 5.5 μm, 5.6 μm, 5.7 μm, 5.8 μm, 5.9 μm, 6 μm, or any value range between the two.

[0193] The average particle size of the lithium-containing transition metal oxide particles with a particle size greater than or equal to 4 μm is within the above range, which helps to balance the kinetics and current shunting degree of lithium-containing transition metal oxides, and to balance the problems of surface and bulk lattice parameter mismatch and surface structure degradation caused by current overload in the higher voltage range, thereby improving the cycle performance of the hybrid system battery cell.

[0194] In some embodiments, the average particle size R1 of the lithium-containing transition metal oxide particles with a particle size greater than or equal to 4 μm in the cross-section of the positive electrode active material layer along the electrode thickness direction is 4.1 μm-5.6 μm.

[0195] In some embodiments, the average particle size R1 of the lithium-containing transition metal oxide particles with a particle size greater than or equal to 4 μm in the cross-section of the positive electrode active material layer along the electrode thickness direction is 4.4 μm-5.1 μm.

[0196] The average particle size of the lithium-containing transition metal oxide particles with a particle size greater than or equal to 4 μm is within the above range, which helps to balance the kinetics and current shunting degree of lithium-containing transition metal oxides, and to balance the problems of particle breakage and structural degradation caused by surface and bulk lattice parameter mismatch and current overload in higher voltage ranges, thereby improving the cycle performance of hybrid system battery cells.

[0197] In some embodiments, the average particle size R2 of the lithium-containing transition metal oxide particles with a particle size greater than or equal to 1 μm and less than 4 μm in the cross-section of the positive electrode active material layer along the electrode thickness direction is 1.2 μm-3.5 μm.

[0198] In this application, the average particle size R1 of the lithium-containing transition metal oxide particles with a particle size greater than or equal to 4 μm in the cross-section of the positive electrode active material layer along the electrode thickness direction can be tested using methods and instruments known in the art. As an example, referring to the test method for Dn50 of the lithium-containing transition metal oxide particles in the cross-section of the positive electrode active material layer along the electrode thickness direction described above, the average particle size of particles with a particle size greater than or equal to 1 μm and less than 4 μm among at least 100 lithium-containing transition metal oxide particles obtained can be calculated. This average value is the average particle size R2 of the lithium-containing transition metal oxide particles with a particle size greater than or equal to 1 μm and less than 4 μm in the cross-section of the positive electrode active material layer along the electrode thickness direction.

[0199] In some embodiments, the average particle size R2 of the lithium-containing transition metal oxide particles with a particle size greater than or equal to 1 μm and less than 4 μm in the cross-section of the positive electrode active material layer along the electrode thickness direction can be 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 or any value range between the two.

[0200] The average particle size of lithium-containing transition metal oxide particles with a particle size greater than or equal to 1 μm and less than 4 μm is within the above range, which helps to improve the kinetic performance of lithium-containing transition metal oxides and suppress particle breakage and structural degradation caused by mismatch of surface and bulk lattice parameters; at the same time, it also helps to take into account the degree of side reaction with electrolyte and improve the cycle performance of hybrid system battery cells.

[0201] In some embodiments, the average particle size R2 of the lithium-containing transition metal oxide particles with a particle size greater than or equal to 1 μm and less than 4 μm in the cross-section of the positive electrode active material layer along the electrode thickness direction is 1.2 μm-3.1 μm.

[0202] In some embodiments, the average particle size R2 of the lithium-containing transition metal oxide particles with a particle size greater than or equal to 1 μm and less than 4 μm in the cross-section of the positive electrode active material layer along the electrode thickness direction is 1.7 μm-2.9 μm.

[0203] The average particle size of lithium-containing transition metal oxide particles with a particle size greater than or equal to 1 μm and less than 4 μm is within the above range, which helps to further improve the kinetic performance of lithium-containing transition metal oxides and suppress particle breakage and structural degradation caused by mismatch of surface and bulk lattice parameters; at the same time, it also helps to take into account the degree of side reaction with electrolyte and improve the cycle performance of hybrid system battery cells.

[0204] In some embodiments, the percentage of nickel moles is 50%-80% based on the total molar number of nickel, cobalt and X1 elements in the lithium-containing transition metal oxide particles.

[0205] In this application, the molar percentage of nickel, cobalt, and X1 elements in the lithium-containing transition metal oxide particles can be tested using methods and equipment known in the art. A specific test method is illustrated below: 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) 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 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.

[0206] In some embodiments, based on the total number of moles of nickel, cobalt, and X1 in the lithium-containing 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 range between the two.

[0207] 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.

[0208] In some embodiments, the molar percentage of cobalt is 5%-20% based on the total molar number of nickel, cobalt and X1 elements in the lithium-containing transition metal oxide particles.

[0209] In some embodiments, 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 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.

[0210] In some embodiments, the molar percentage of the X1 element is 15%-40% based on the total molar number of nickel, cobalt and X1 elements in the lithium-containing transition metal oxide particles.

[0211] In some embodiments, based on the total molar number of nickel, cobalt, and X1 elements in the lithium-containing transition metal oxide particles, the molar percentage of the 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.

[0212] In some embodiments, the lithium-containing transition metal oxide particles are lithium-containing transition metal oxide single crystal particles.

[0213] Lithium-containing transition metal oxide particles, being single-crystal particles, help reduce the size of lithium-containing transition metal oxide particles, thereby improving their kinetic performance, suppressing particle breakage and structural degradation caused by mismatch between surface and bulk lattice parameters, and further improving the cycle performance of hybrid battery cells.

[0214] In some embodiments, the lithium-containing transition metal oxide particles account for 50%-90% of the total mass of the positive electrode active material.

[0215] 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.

[0216] In some embodiments, based on the total mass of the positive electrode active material, the mass percentage of the 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.

[0217] In positive electrode active materials, a mass percentage of lithium transition metal oxide particles within the aforementioned range helps to balance the cost and energy density of hybrid battery cells.

[0218] In some embodiments, the lithium-containing transition metal oxide particles account for 60%-80% of the total mass of the positive electrode active material.

[0219] In some embodiments, 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.

[0220] The carbon material embedded in lithium transition metal phosphate particles at least partially on the surface of the particle body helps to improve its kinetic performance, thereby increasing its shunting degree in the higher voltage range, alleviating the structural degradation problem caused by over-reaction of lithium transition metal oxide particles, and further improving the cycle performance of hybrid battery cells.

[0221] In some embodiments, the average thickness of the carbon material is 2 nm to 25 nm.

[0222] 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.

[0223] In some embodiments, the average thickness of the carbon material can be 2nm, 2.5nm, 3nm, 3.5nm, 4nm, 4.5nm, 5nm, 5.5nm, 6nm, 6.5nm, 7nm, 7.5nm, 8nm, 8.5nm, 9nm, 9.5nm, 10nm, 10.5nm, 11nm, 11.5nm, 12nm, 12.5nm, 13nm, 13.5nm, 14nm, 14.5nm, 15nm, 15.5nm, 16nm, 16.5nm, 17nm, 17.5nm, 18nm, 18.5nm, 19nm, 19.5nm, 20nm, 20.5nm, 21nm, 21.5nm, 22nm, 22.5nm, 23nm, 23.5nm, 24nm, 24.5nm, 25nm, or any value between the two.

[0224] In some embodiments, the carbon material accounts for 0.5%-3% of the total mass of the lithium transition metal phosphate particles.

[0225] In some embodiments, based on the total mass of the lithium transition metal phosphate particles, the mass percentage of the carbon material 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 value between the two.

[0226] In some embodiments, the molar percentage of manganese is 40%-75%, based on the total molar number of manganese and iron in the lithium transition metal phosphate particles.

[0227] 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... -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 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 phosphorus element in the test area, the area where the phosphorus 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 elements in the lithium transition metal phosphate particles. At least 10 particles were measured, and the average value was taken as the test result.

[0228] In some embodiments, based on the total number of moles of manganese and iron in the lithium-containing 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.

[0229] To fully utilize the specific capacity of lithium transition metal oxide particles and improve the energy density of individual battery cells, the charging cutoff voltage of the battery cells needs to be set to approximately 4.25V. The main discharge voltage range of lithium transition metal oxide particles is higher than that of lithium transition metal phosphate particles. This means that lithium transition metal phosphate particles primarily supply lithium ions in the low-voltage range, while lithium transition metal oxide particles must supply lithium ions in the high-voltage range. This results in both materials experiencing an equivalent rate load higher than the apparent rate in their respective operating ranges, leading to load shunting. Therefore, even at low rates, load shunting in the hybrid battery cell still causes rapid lithium ion insertion / extraction within the positive electrode active material. Lithium transition metal oxides have poor structural stability and are easily affected by load shunting during cycling, which is detrimental to maintaining their structural integrity.

[0230] In this embodiment, the molar percentage of manganese in the lithium transition metal phosphate particles is further controlled within the range of 40%-75% to increase its upper limit of working voltage, improve the shunting degree of lithium transition metal phosphate in the higher working voltage range, thereby improving the load shunting problem of the hybrid system battery cell and further improving the cycle performance of the hybrid system battery cell.

[0231] 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 is 100nm-300nm.

[0232] In this application, the Dn50 of the lithium transition metal phosphate particles in a 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, the test method for the Dn50 of the lithium transition metal oxide particles in a cross-section along the thickness direction of the positive electrode active material layer described above can be used for testing.

[0233] In some embodiments, the Dn50 of the lithium transition metal phosphate particles in the cross-section along the thickness direction of the positive electrode active material layer 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.

[0234] The Dn50 of lithium transition metal phosphate particles is within the above range, indicating that the overall particle size is small, which helps to improve its kinetic performance, increase its shunting degree in the higher voltage range, further improve the structural degradation problem caused by excessive participation of lithium transition metal oxides in the reaction, and improve the cycle performance of hybrid battery cells.

[0235] 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 is 100nm-250nm.

[0236] The Dn50 of lithium transition metal phosphate particles within the above range helps to further improve their kinetic performance, increase their shunting degree in the higher voltage range, further improve the structural degradation problem caused by excessive participation of lithium transition metal oxides in the reaction, and improve the cycle performance of hybrid battery cells.

[0237] In some embodiments, in the cross-section of the positive electrode active material layer along the thickness direction of the electrode sheet, the Dn90 of the lithium transition metal phosphate particles is 250nm-500nm; wherein, Dn90 refers to the particle size corresponding to the cumulative number of particles being 90% in the cumulative number distribution curve of particle size.

[0238] In this application, the Dn90 of the lithium transition metal phosphate particles in a 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, the testing method for the Dn50 of the lithium transition metal phosphate particles in a cross-section along the thickness direction of the positive electrode active material layer described above can be used for testing.

[0239] In some embodiments, in the cross-section of the positive electrode active material layer along the thickness direction of the electrode sheet, the Dn90 of the lithium transition metal phosphate particles can be 250nm, 255nm, 260nm, 265nm, 270nm, 275nm, 280nm, 285nm, 290nm, 295nm, 300nm, 305nm, 310nm, 315nm, 320nm, 325nm, 330nm, 335nm, 340nm, 345nm, 350nm, 355nm, 3... 60nm, 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 the two.

[0240] The Dn90 of lithium transition metal phosphate particles is within the above range, indicating that the size of lithium transition metal phosphate particles is small, which helps to improve their kinetic performance, increase their shunting degree in the higher voltage range, further improve the structural degradation problem caused by excessive participation of lithium transition metal oxides in the reaction, and improve the cycle performance of hybrid system battery cells.

[0241] In some embodiments, the Dn90 of the lithium-containing transition metal phosphate particles in the cross-section of the positive electrode active material layer along the electrode thickness direction is 270nm-400nm.

[0242] The Dn90 of lithium transition metal phosphate particles within the above range helps to further improve its kinetic performance, increase its shunting degree in the higher voltage range, further improve the structural degradation problem caused by excessive participation of lithium transition metal oxides in the reaction, and improve the cycle performance of hybrid battery cells.

[0243] 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; wherein, Dn10 refers to the particle size corresponding to the cumulative number of particles being 10% in the cumulative number distribution curve of particle size.

[0244] In this application, the lithium transition metal phosphate particles Dn10 in the cross-section of the positive electrode active material layer along the electrode thickness direction can be tested using methods and instruments known in the art. As an example, the testing method for the lithium transition metal phosphate particles Dn50 in the cross-section of the positive electrode active material layer along the electrode thickness direction described above can be referred to.

[0245] 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 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.

[0246] Studies have shown that when the particle size of lithium transition metal phosphate particles is reduced, their specific surface area increases, the residual water in the battery cell manufacturing process increases significantly, and further triggers the hydrolysis of electrolyte salts in the electrolyte to generate highly corrosive hydrofluoric acid, which easily damages and thus destroys the surface structure of the positive electrode active material, affecting the cycle performance of the battery cell.

[0247] In some embodiments, the electrolyte includes a first component, which includes one or more of lithium bis(fluorosulfonyl)imide, lithium difluorophosphate, lithium tetrafluoroborate, and lithium bis(trifluoromethanesulfonyl)imide.

[0248] 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.

[0249] 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.

[0250] In this embodiment, a first component that is not easily hydrolyzed is used to replace part of the conventional easily hydrolyzable electrolyte salt in order to reduce the generation of hydrofluoric acid, alleviate the problem of hydrofluoric acid damaging the surface structure of lithium transition metal oxide particles, and further improve the cycle performance of the hybrid system battery cell.

[0251] In some embodiments, the mass percentage of the first component is 0.1%-8% based on the total mass of the electrolyte.

[0252] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the first 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%, or 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.

[0253] When the mass percentage of the first component is within the above range, it 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 further improving the cycle performance of the hybrid system battery cells.

[0254] In some embodiments, the first component accounts for 0.5%-8% of the total mass of the electrolyte.

[0255] In some embodiments, the first component accounts for 3%-8% of the total mass of the electrolyte.

[0256] The mass percentage of the first 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.

[0257] In some embodiments, the first component includes one or more of lithium bis(fluorosulfonyl)imide and lithium difluorophosphate.

[0258] The first component includes one or more of lithium bis(fluorosulfonyl)imide and lithium difluorophosphate. On the one hand, it helps to reduce the amount of hydrofluoric acid generated and inhibit its damage to the surface structure of the positive electrode active material. On the other hand, the first component includes the above substances, which can generate a lithium fluoride-rich positive electrode electrolyte interface (CEI film), thereby improving the mechanical strength of the CEI film and further improving the cycle performance of the battery cell.

[0259] In some embodiments, the lithium bis(fluorosulfonyl)imide accounts for 0.1%-8% of the total mass of the electrolyte.

[0260] In some embodiments, based on the total mass of the electrolyte, the mass percentage of lithium bisfluorosulfonylimide 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%, or 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.

[0261] In some embodiments, the lithium bisfluorosulfonamide accounts for 2%-5% of the total mass of the electrolyte.

[0262] If the mass percentage of lithium bis(fluorosulfonyl)imide is too low, its effect on reducing hydrofluoric acid formation is limited; if its mass percentage is too high, it easily corrodes the current collector. Further reducing the mass percentage of lithium bis(fluorosulfonyl)imide to within the range of 2%-5% helps to balance reducing hydrofluoric acid formation and its damaging effect on the current collector, thereby further improving the cycle performance of the battery cells.

[0263] In some embodiments, the lithium difluorophosphate accounts for 0.5%-8% of the total mass of the electrolyte.

[0264] In some embodiments, based on the total mass of the electrolyte, the mass percentage of lithium difluorophosphate 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%, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, or 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.

[0265] In some embodiments, the lithium difluorophosphate accounts for 1%-5% of the total mass of the electrolyte.

[0266] If the mass percentage of lithium difluorophosphate is too low, its effect on reducing hydrofluoric acid formation is limited; if its mass percentage is too high, the CEI film thickness increases, impedance increases, and polarization is easily induced. Maintaining the mass percentage of lithium difluorosulfonylimide within the range of 1%-5% helps to balance reducing hydrofluoric acid formation with a lower CEI film thickness, further improving the cycle performance of the battery cell.

[0267] In some embodiments, the electrolyte further includes lithium hexafluorophosphate, wherein the mass percentage of lithium hexafluorophosphate is 5%-10% based on the total mass of the electrolyte.

[0268] In some embodiments, the electrolyte further includes lithium hexafluorophosphate, and 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 range between the two.

[0269] Electrolytes typically require a certain ion concentration to maintain good rate performance of individual battery cells. Lithium hexafluorophosphate (LiPF6) offers 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. Furthermore, controlling the mass percentage of LiPF6 within the aforementioned range helps to maintain the ionic conductivity of the electrolyte while reducing the formation of hydrofluoric acid, mitigating damage to the structure of the positive electrode active material, and further improving the cycle performance of the hybrid battery cell.

[0270] In some embodiments, the electrolyte further includes a second component, which includes one or more of lithium difluorooxalate borate, tris(trimethylsilyl)phosphate, and lithium bis(oxalate borate).

[0271] While introducing the first component into the electrolyte can significantly reduce the formation of hydrofluoric acid and improve the cycle performance of individual cells, a small amount of hydrofluoric acid can still cause some damage to the structure of lithium-containing transition metal oxide particles, thereby triggering the dissolution of transition metal elements from the positive electrode. The dissolved transition metal ions migrate to the negative electrode and are reduced to metals, damaging the solid electrolyte interphase (SEI) film of the negative electrode and affecting the cycle performance of the individual cells.

[0272] In this application, a second component is further introduced into the electrolyte. Its decomposition products participate in the formation of the CEI film and help improve the chemical stability of the CEI film, reduce the frequency of CEI film rupture and regeneration, thereby reducing the probability of continuous direct contact between small-diameter lithium transition metal phosphate particles and the electrolyte, and reducing the generation of hydrofluoric acid. At the same time, it also helps to reduce the structural damage of hydrofluoric acid to lithium transition metal oxide particles, further improving the cycle performance of the battery cell.

[0273] In some embodiments, the second component accounts for 0.2%-5% of the total mass of the electrolyte.

[0274] In some embodiments, based on the total mass of the electrolyte, the mass percentage of the second 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%, or any value range between the two.

[0275] Within the aforementioned range, the second component not only helps reduce the formation of hydrofluoric acid and its damage to the structure of the positive electrode active material, but also helps to form a CEI film with appropriate thickness and moderate impedance, thereby balancing the cycle performance and rate performance of the hybrid battery cells.

[0276] In some embodiments, the second component accounts for 0.5%-2% of the total mass of the electrolyte.

[0277] In some embodiments, the electrolyte comprises cyclic carbonate compounds, wherein the cyclic carbonate compounds account for 20%-45% of the total mass of the electrolyte.

[0278] In some embodiments, the electrolyte comprises 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 value range between the two.

[0279] The presence of cyclic carbonate compounds in the electrolyte, with their mass percentage falling within the aforementioned range, helps to improve the degree of lithium salt dissociation in the electrolyte, increase lithium-ion concentration, and improve the cycle performance of the battery cell.

[0280] In some embodiments, the electrolyte comprises cyclic carbonate compounds, and the cyclic carbonate compounds account for 20%-35% of the total mass of the electrolyte.

[0281] In some embodiments, the cyclic carbonate compound includes one or more of ethylene carbonate, propylene carbonate, and butene carbonate.

[0282] In some embodiments, the cyclic carbonate compound includes ethylene carbonate.

[0283] In some embodiments, the electrolyte comprises chain carbonate compounds, and the chain carbonate compounds account for 40%-75% of the total mass of the electrolyte.

[0284] In some embodiments, the electrolyte comprises 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 value range between the two.

[0285] 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 and improve the cycle performance of the battery cells.

[0286] In some embodiments, the electrolyte comprises chain carbonate compounds, and the mass percentage of the chain carbonate compounds may be 50%-70% based on the total mass of the electrolyte.

[0287] In some embodiments, the chain carbonate compound includes one or more of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and methyl propyl carbonate.

[0288] In some embodiments, the chain carbonate includes ethyl methyl carbonate and / or diethyl carbonate.

[0289] Ethyl methyl carbonate and dimethyl carbonate have both low viscosity and good high-voltage resistance, thus improving the local lithium plating problem on the negative electrode side of the battery cell, while also taking into account the degree of side reaction of the electrolyte under high voltage, improving the stability of the electrolyte, and further improving the cycle performance of the hybrid system battery cell.

[0290] In some embodiments, the electrolyte includes ethyl methyl carbonate, and the ethyl methyl carbonate accounts for 35%-55% of the total mass of the electrolyte.

[0291] In some embodiments, the electrolyte comprises 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 range between the two.

[0292] In some embodiments, the electrolyte includes diethyl carbonate, and the mass percentage of diethyl carbonate is 10%-20% based on the total mass of the electrolyte.

[0293] In some embodiments, the electrolyte comprises 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.

[0294] 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.

[0295] When the positive electrode active material is damaged, the transition metal elements therein are easily dissolved from the positive electrode and migrate to the negative electrode to be reduced to metal, thereby damaging the SEI film. 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 cell.

[0296] In some embodiments, the third component accounts for 0.08%-5% of the total mass of the electrolyte.

[0297] 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 between the two.

[0298] 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.

[0299] In some embodiments, the third component accounts for 0.1%-5% of the total mass of the electrolyte.

[0300] In some embodiments, the third component accounts for 1%-5% of the total mass of the electrolyte.

[0301] 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.

[0302] In some embodiments, 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 Pz1 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.

[0303] 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.

[0304] 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.

[0305] 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.

[0306] 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.

[0307] 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.

[0308] 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.

[0309] 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.

[0310] 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.

[0311] 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.

[0312] 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.

[0313] In some embodiments, 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.

[0314] 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 range between the two.

[0315] In some embodiments, the first conductive agent further includes a linear conductive agent, which includes one or more of carbon nanotubes and carbon nanofibers.

[0316] In this application, carbon nanofibers include, but are not limited to, one or more of vapor-grown carbon fibers and graphite carbon fibers.

[0317] 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.

[0318] 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.

[0319] In some embodiments, the linear conductive agent includes carbon nanotubes.

[0320] In some embodiments, the linear conductive agent accounts for 0.1%-1.5% of the total mass of the positive electrode active material layer.

[0321] 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 0.1%, 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.

[0322] In some embodiments, the positive electrode active material layer further includes a first polymer.

[0323] 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.

[0324] 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.

[0325] 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.

[0326] In some embodiments, the thickness of the positive electrode undercoat is 0.5 μm-5 μm.

[0327] 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.

[0328] 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, or 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 between the two.

[0329] In some embodiments, the compaction density of the positive electrode film is 2.6 g / cm³. 3 -3.4g / cm 3 .

[0330] 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 .

[0331] 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 / cm 3 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.

[0332] 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.

[0333] 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.

[0334] In some embodiments, the volume distribution particle size 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, 11μm, 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.

[0335] In the embodiments of this application, after the lithium-containing transition metal oxide particles have a lower particle size and improved kinetics, their corresponding negative electrode side also bears a larger lithium ion insertion / extraction density, increasing the probability of lithium plating problems.

[0336] 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.

[0337] In some embodiments, the volume distribution particle size Dv50 of the negative electrode active material is 8 μm-13 μm.

[0338] 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.

[0339] In some embodiments, the specific surface area of ​​the negative electrode active material is 0.5 m². 2 / g-3.0m 2 / g.

[0340] 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.

[0341] 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, 0.65m 2 / 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, 2.85m2 / g, 2.9m 2 / g, 2.95m 2 / g、3m 2 / g or any value between the two.

[0342] In some embodiments, the specific surface area of ​​the negative electrode active material is 0.8 m². 2 / g-2.0m 2 / g.

[0343] 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.

[0344] 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.

[0345] 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.

[0346] 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 sheet.

[0347] 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.

[0348] In some embodiments, the inorganic particles include one or more of alumina, boehmite, silicon dioxide, cerium oxide, magnesium aluminate, zirconium oxide, and titanium dioxide.

[0349] In some embodiments, the third polymer and the fourth polymer each independently include one or more of fluoropolymers and acrylate polymers.

[0350] 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.

[0351] In some embodiments, the thickness of the base film is 5 μm-12 μm.

[0352] 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 range between the two.

[0353] In some embodiments, the coating has a single-sided thickness of 1µm-4µm.

[0354] In some embodiments, the thickness of the coating on one side 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.

[0355] In some embodiments, the thickness of the separator is 8 μm-15 μm.

[0356] In some embodiments, the thickness of the isolation membrane 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, 1 ... 0.6μm, 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.

[0357] In some embodiments, the air permeability of the separator at 25°C is 400s / 100cc-600s / 100cc.

[0358] 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.

[0359] In some embodiments, the air permeability of the separator 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.

[0360] 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.

[0361] In some embodiments, the porosity of the separator is 35%-55%.

[0362] 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.

[0363] In some embodiments, the porosity of the isolation membrane 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.

[0364] In some embodiments, the thickness of the positive current collector is 9 μm-15 μm.

[0365] 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.

[0366] 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, 12 μm, etc. μm, 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.

[0367] 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.

[0368] In some embodiments, the thickness of the negative electrode current collector is 3μm-7μm.

[0369] In this application, the thickness of the negative electrode current collector can be tested by referring to the test method for the positive electrode current collector.

[0370] 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. 9μm, 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 range between two of these.

[0371] 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.

[0372] In some embodiments, the rated cutoff voltage of the battery cell is 4.25V-4.45V.

[0373] 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.

[0374] In some embodiments, the rated cutoff voltage of the 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 range between the two.

[0375] In some implementations, such as Figure 2 As shown, the battery cell 7 includes a housing 20 and electrode terminals (first electrode terminal 31 and second electrode terminal 32). The housing 20 forms a cavity inside, and the electrode assembly 10 and electrolyte are disposed in the cavity. The housing 20 has a through hole connecting the inside and outside of the cavity. The first electrode terminal 31 and the second electrode terminal 32 include a first part and a second part. The first part is entirely located inside the cavity, and the second part passes through the through hole and is partially located outside the cavity. The first part and the second part are an integral structure. The electrode assembly 10 also includes tabs (first tab 111 and second tab 121), which are directly connected to the first part.

[0376] In this embodiment, the tabs on the electrode assembly are directly connected to the first part of the electrode terminal. Combined with the above-mentioned hybrid system, the impedance and heat generation at the tabs are reduced, the heat at the maximum heat generation point of the battery cell is reduced, the temperature distribution uniformity of the positive electrode active material layer is improved, the temperature rise of the positive electrode sheet is reduced, thereby reducing the probability of manganese ion dissolution of 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 system battery cell.

[0377] In some embodiments, the housing further includes an end cap, and the ratio of the size of the first portion to the size of the end cap is 0.35-0.80 along the thickness direction of the battery cell.

[0378] In some embodiments, the ratio of the size of the first portion to the size of the end cap along the thickness direction of the battery cell can be selected as 0.35, 0.36, 0.37, 0.38, 0.39, 0.40, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.50, 0.51, 0.52, 0.53, or 0.5. 4. 0.55, 0.56, 0.57, 0.58, 0.59, 0.60, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, or any value range between two of these.

[0379] Along the thickness direction of the battery cell, the ratio of the size of the first part to the size of the end cap is within the above range, which is beneficial to increase the area of ​​the first part, thereby increasing the solderable area of ​​the tab and electrode terminal, reducing connection resistance, reducing heat generation, further improving the temperature distribution uniformity of the positive electrode active material layer, 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 system battery cell.

[0380] In some embodiments, the ratio of the size of the first portion to the size of the end cap is 0.50-0.80 along the thickness direction of the battery cell.

[0381] Along the thickness direction of the battery cell, the ratio of the size of the first part to the size of the end cap is within the above range, which is beneficial to further increase the area of ​​the first part, further increase the solderable area of ​​the tab and electrode terminal, reduce connection resistance, reduce heat generation, further improve the temperature distribution uniformity of the positive electrode active material layer, thereby reducing the probability of manganese ion dissolution of 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 system battery cell.

[0382] like Figure 1 and Figure 2 As shown, in some embodiments, the battery cell 7 may include a housing 20 and an electrode assembly 10.

[0383] In some embodiments, the outer casing 20 can be of various shapes, such as a cylinder, a cuboid, etc. The shape of the outer casing 20 can be determined according to the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 is a cylindrical structure, the outer casing 20 can be a cylindrical structure. If the electrode assembly 10 is a cuboid structure, the outer casing 20 can be a cuboid structure. Optionally, the electrode assembly 10 is a cuboid structure.

[0384] The outer shell 20 can be made of various materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, etc. This application does not impose any special restrictions on this.

[0385] In some implementations, such as Figure 2 As shown, the outer casing 20 includes a housing 21 and an end cap 22.

[0386] In some implementations, the housing is a cuboid structure.

[0387] In some implementations, such as Figure 1 As shown, the thickness of the battery cell 7 is 15mm-30mm. Figure 1 T0 shown in the figure represents the thickness of the battery cell 7.

[0388] In some implementations, the thickness of the battery cell can be 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, 21mm, 22mm, 23mm, 24mm, 25mm, 26mm, 27mm, 28mm, 29mm, 30mm or any value between the two.

[0389] In some implementations, such as Figure 1 As shown, the dimensions of the battery cell 7 along the second direction F are 150mm to 400mm. Figure 1 W0 shown in the figure represents the dimension of the battery cell 7 along the second direction F.

[0390] 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.

[0391] In some implementations, the height of the battery cell is 80mm-250mm.

[0392] 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.

[0393] In the embodiments of this application, such as Figure 1 As shown, the first direction E is parallel to the height direction of the battery cell, and the second direction F, the first direction E, and the thickness direction X of the battery cell 7 are perpendicular to each other.

[0394] In some implementations, such as Figure 1 As shown, the battery cell 7 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.

[0395] In some embodiments, the first electrode terminal is disposed on the housing, which may be disposed on the housing or end cap.

[0396] In some embodiments, the second electrode terminal is disposed on the housing, which may be disposed on the housing or end cap.

[0397] The electrode assembly can be a wound structure or a stacked structure. There can be one or more electrode assemblies housed within the housing.

[0398] In some implementations, such as Figure 2 As shown, the electrode assembly includes tabs, which include a first tab 111 and a second tab 121. The first tab 111 is a positive tab, and the second tab 121 is a negative tab.

[0399] In some embodiments, the first tab is directly connected to the first part of the first electrode terminal, and the first tab can be directly connected to the first part of the first electrode terminal by means of welding or the like.

[0400] In some embodiments, the second tab is directly connected to the first part of the second electrode terminal, and the second tab can be directly connected to the first part of the second electrode terminal by means of welding or the like.

[0401] In some implementations, such as Figure 3 As shown, the battery device can be a battery pack 2, which includes a housing 5 and one or more battery cell assemblies, with the battery cell assemblies housed in the housing 5.

[0402] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0403] As an example, such as Figure 3 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.

[0404] 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.

[0405] 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.

[0406] 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.

[0407] In some implementations, such as Figure 4 As shown, the battery module 6 includes multiple battery cells 7.

[0408] In some implementations, such as Figure 4 As shown, the battery module 6 includes a plurality of first battery packs 70 arranged along the length direction M of the battery module 6, and each first battery pack 70 includes a plurality of 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.

[0409] A second aspect of this application provides a battery device, including the battery cell provided in the first aspect of this application.

[0410] 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.

[0411] A third aspect of this application provides an electrical device that uses a battery as a power source, the electrical device including 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 a power source for the electrical device, or as an energy storage unit for the electrical device. The battery cell, battery module, or battery pack can be selected as the electrical device according to its usage requirements.

[0412] Figure 5 This 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.

[0413] 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.

[0414] 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.

[0415] I. Preparation Method 1. Preparation of Example 1 (1) Positive electrode plate ① Preparation of lithium-containing transition metal oxide particles S1: Nickel sulfate, cobalt sulfate, and manganese sulfate were mixed in a molar ratio of 0.68:0.07:0.25 to prepare a sulfate solution. Under a nitrogen atmosphere, sodium hydroxide solution was added to adjust the pH of the sulfate solution to 10.2, and ammonia water with a concentration of 4.5 g / L was added. The mixture was reacted at 60 °C for 48 hours to prepare the precursor (Ni). 0.68 Co 0.07 Mn 0.25 The precursor of OH2 has a volumetric particle size Dn50 of 1.9 μm.

[0416] S2: Nickel sulfate, cobalt sulfate, and manganese sulfate were mixed in a molar ratio of 0.83:0.07:0.1 to prepare a sulfate solution. Under a nitrogen atmosphere, sodium hydroxide solution was added to adjust the pH of the sulfate solution to 9.8, and ammonia water with a concentration of 2.5 g / L was added. The mixture was reacted at 60 °C for 48 hours to prepare the precursor (Ni). 0.68 Co 0.07 Mn 0.25 The precursor of OH2 has a volumetric particle size Dn50 of 4.7 μm.

[0417] S3: The precursors obtained in steps S1 and S2 are mixed in a mass ratio of 9:1, and then thoroughly mixed with LiOH•H2O, ZrO2 and MoO3 in a molar ratio of 1:1.05:0.004:0.001. The mixture is then heated to 780℃ at a heating rate of 6℃ / min and reacted for 14h to obtain the first sintered product. The first sintered product is then subjected to air jet milling treatment. The air jet milling treatment has an inlet pressure of 0.5MPa, a feeding frequency of 15Hz and a milling frequency of 20Hz to obtain the milled first sintered product.

[0418] S4: Mix the first sintered product, Co3O4 and Al2O3 evenly. Taking the molar amount of the first sintered product as 1, the molar amounts of Co in Co3O4 and Al in Al2O3 are 0.006 and 0.002, respectively. Then, react at 550℃ for 4 hours to carry out the second sintering treatment to obtain the second sintered product. S5: Mix the second sintering product, Al2O3 and H3BO3 evenly. Taking the molar amount of the second sintering product as 1, the molar amounts of Al in Al2O3 and B in H3BO3 are 0.002 and 0.008, respectively. Then, react at 350℃ for 4 hours to carry out the third sintering treatment to obtain the final product.

[0419] 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.

[0420] 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 .

[0421] The conductive agent consists of carbon nanotubes and Super P in a 1:1 mass ratio; the positive electrode active material comprises lithium-containing transition metal oxide particles and lithium-containing transition metal phosphate particles prepared above in a 7:3 mass ratio; the lithium-containing transition metal phosphate particles include a particle body and carbon material disposed on at least a portion of the surface of the particle body, with the carbon material accounting for 1.45% of the total mass of the lithium-containing transition metal phosphate particles. 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.

[0422] 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 phosphate particles is 104 nm, Dn50 is 173 nm, and Dn90 is 356 nm, and the compaction density of the positive electrode film is 3.0 g / cm³. 3 .

[0423] (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 .

[0424] The negative electrode active material has a Dv50 of 14.3 μm and a specific surface area of ​​1.76 m². 2 / g.

[0425] (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.

[0426] The air permeability of the separator at 25°C is 550s / 100cc, and the porosity of the separator is 45%.

[0427] (4) Electrolyte The electrolyte composition in Example 1 is detailed in Table 1.

[0428] (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.

[0429] like Figure 1 As shown, the battery cell includes a first electrode terminal and a second electrode terminal, and the electrode assembly includes a first tab and a second tab. The first tab is directly connected to the first electrode terminal, and the second tab is directly connected to the second electrode terminal. The first electrode terminal is the positive electrode terminal, the first tab is the positive tab, the second electrode terminal is the negative electrode terminal, and the second tab is the negative tab.

[0430] Along the thickness direction of the battery cell, the ratio of the size of the first part of the electrode terminal to the size of the end cap is 0.74, where the size of the first part along the thickness direction of the battery cell is specifically 14 mm, and the size of the end cap is specifically 19 mm.

[0431] 2. Preparation of other embodiments Examples 2-10 and Comparative Examples 1-3 are prepared in basically the same way as Example 1, except that the preparation of lithium-containing transition metal oxides is slightly different. Specific differences are detailed in Table 1. Table 1

[0432] The preparation methods of Examples 11-23 are basically the same as those of Example 1, except that the electrolytes are different. Specifically, the electrolytes of Examples 11-23 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 2.

[0433] Table 2

[0434] Among them, LiFSI is lithium bis(fluorosulfonyl)imide, PS is 1,3-propanesulfonyl lactone, LiPF6 is lithium hexafluorophosphate, LiPO2F2 is lithium difluorophosphate, LiBF4 is lithium tetrafluoroborate, LiTFSI is lithium bis(trifluoromethanesulfonyl)imide, and EMC is methyl ethyl carbonate.

[0435] The preparation method of Example 24 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.

[0436] 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%.

[0437] 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.

[0438] 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.

[0439] III. Test Results and Analysis The test results of the above embodiments and comparative examples are detailed in Tables 3-6.

[0440] As shown in Tables 3-6, the positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector. The positive electrode film layer includes a positive electrode active material layer, which includes 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 phosphate particles include manganese and iron. The lithium-containing transition metal oxide particles include nickel, cobalt, and X1 elements. The X1 elements include manganese and / or aluminum. 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 1.0 μm-3.5 μm. Based on the total number of lithium-containing transition metal oxide particles, the proportion of lithium-containing transition metal oxide particles with a particle size greater than or equal to 4 μm is 2%-10%. The hybrid system battery cell has good cycle performance.

[0441] Table 3

[0442] Table 4

[0443] As can be seen from Example 1 and Comparative Example 2, the Dn50 of lithium transition metal oxide particles is in the range of 1.0 μm-3.5 μm. However, when the proportion of lithium transition metal oxide particles larger than or equal to 4 μm is less than 2%, 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 72.2%. Furthermore, by controlling the proportion of lithium transition metal oxide particles larger than or equal to 4 μm to a range of larger than or equal to 2%, the current proportion of lithium transition metal oxide particles decreases, and the capacity retention rate of the battery cell is significantly improved (increased by 17%).

[0444] Wherein, R1 is the average particle size of lithium transition metal oxide particles with a diameter greater than or equal to 4 μm in the cross-section of the positive electrode active material layer along the electrode thickness direction; R2 is the average particle size of lithium transition metal oxide particles with a diameter greater than or equal to 1 μm and less than 4 μm in the cross-section of the positive electrode active material layer along the electrode thickness direction.

[0445] As can be seen from the comparison between Examples 1-6 and Comparative Example 1, 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 1.0μm-3.5μm, and the hybrid system battery cell has good cycle performance.

[0446] As can be seen from the comparison between Examples 1 and 3-5 and Examples 2 and 6, 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 1.5μm-3μm, which helps to further improve the cycle performance of the hybrid system battery cell.

[0447] As can be seen from the comparison of Examples 1, 7-10 and Comparative Examples 2-3, based on the total number of lithium transition metal oxide particles, the proportion of lithium transition metal oxide particles with a particle size greater than or equal to 4 μm is 2%-10%, and the hybrid system battery cells have good cycle performance.

[0448] As can be seen from the comparison between Examples 1, 7-9 and Example 10, based on the total number of lithium transition metal oxide particles, the proportion of lithium transition metal oxide particles with a particle size greater than or equal to 4 μm is 2%-8%, which helps to further improve the cycle performance of the hybrid system battery cells.

[0449] Table 5

[0450] As can be seen from Examples 1 and 11-16, the electrolyte includes a first component, which includes one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium difluorophosphate, lithium tetrafluoroborate, and lithium bis(trifluoromethanesulfonyl)imide, and the battery cell has good cycle performance.

[0451] As can be seen from the comparison between Example 12 and Example 11, the electrolyte includes 1,3-propanesulfonyl lactone, which helps to further improve the cycle performance of the battery cell.

[0452] As can be seen from the comparison between Examples 1, 13, and 14 and Examples 15 and 16, the first component includes one or more of lithium difluorosulfonylimide and lithium difluorophosphate, which helps to further improve the cycle performance of the battery cell.

[0453] As can be seen from the comparison of Examples 11, 12, and 20 with other examples, based on the total mass of the electrolyte, the mass ratio of the first component is 3%-8%, which helps to further improve the cycle performance of the battery cell.

[0454] As can be seen from the comparison between Examples 1, 18, and 19 and Examples 13 and 17, based on the total mass of the electrolyte, the mass ratio of lithium difluorophosphate is 1%-4%, which helps to further improve the cycle performance of the battery cells.

[0455] As can be seen from the comparison of Examples 1, 21, and 22 with Examples 20 and 23, 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.

[0456] Table 6

[0457] As can be seen from the comparison between Example 1 and Example 24, the conductive agent includes a linear conductive agent, which helps to further improve the cycle performance of the battery cell.

[0458] 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 sheet and a negative electrode sheet. The positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector. The positive electrode film layer includes a positive electrode active material layer. The positive electrode active material layer includes a positive electrode active material, which includes lithium transition metal oxide particles and lithium transition metal phosphate particles. The lithium-containing transition metal phosphate particles include manganese and iron; the lithium-containing transition metal oxide particles include nickel, cobalt, and X1, wherein X1 includes manganese and / or aluminum. 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 1.0μm-3.5μm. Based on the total number of lithium-containing transition metal oxide particles, the proportion of lithium-containing transition metal oxide particles with a particle size greater than or equal to 4μm is 2%-10%. Wherein, Dn50 refers to the particle size corresponding to the cumulative number of particles being 50% in the cumulative number distribution curve of particle size.

2. 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 1.5μm-3μm.

3. 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, based on the total number of lithium-containing transition metal oxide particles, the proportion of lithium-containing transition metal oxide particles with a particle size greater than or equal to 4 μm is 2%-8%.

4. The battery cell according to claim 1, characterized in that, In the cross-section of the positive electrode active material layer along the electrode thickness direction, the average particle size R1 of the lithium-containing transition metal oxide particles with a particle size greater than or equal to 4 μm is 4.0 μm-6 μm.

5. The battery cell according to claim 4, characterized in that, In the cross-section of the positive electrode active material layer along the electrode thickness direction, the average particle size R1 of the lithium-containing transition metal oxide particles with a particle size greater than or equal to 4 μm is 4.1 μm-5.6 μm.

6. The battery cell according to claim 5, characterized in that, In the cross-section of the positive electrode active material layer along the electrode thickness direction, the average particle size R1 of the lithium-containing transition metal oxide particles with a particle size greater than or equal to 4 μm is 4.4 μm-5.1 μm.

7. The battery cell according to claim 1, characterized in that, In the cross-section of the positive electrode active material layer along the electrode thickness direction, the average particle size R2 of the lithium-containing transition metal oxide particles with a particle size greater than or equal to 1 μm and less than 4 μm is 1.2 μm-3.5 μm.

8. The battery cell according to claim 7, characterized in that, In the cross-section of the positive electrode active material layer along the electrode thickness direction, the average particle size R2 of the lithium-containing transition metal oxide particles with a particle size greater than or equal to 1 μm and less than 4 μm is 1.2 μm-3.1 μm.

9. The battery cell according to claim 8, characterized in that, In the cross-section of the positive electrode active material layer along the electrode thickness direction, the average particle size R2 of the lithium-containing transition metal oxide particles with a particle size greater than or equal to 1 μm and less than 4 μm is 1.7 μm-2.9 μm.

10. The battery cell according to any one of claims 1-9, characterized in that, The lithium-containing transition metal oxide satisfies at least one of the following conditions: (1) 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%; (2) 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%; (3) Based on the total number of moles of nickel, cobalt and X1 in the lithium-containing transition metal oxide particles, the molar percentage of X1 is 15%-40%.

11. 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.

12. 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%, and can be selected as 60%-80%.

13. 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.

14. The battery cell according to claim 13, characterized in that, The carbon material has an average thickness of 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.

15. 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%-75%.

16. 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 transition metal phosphate particles is 100nm-300nm.

17. The battery cell according to claim 16, characterized in that, The Dn50 of the lithium-containing transition metal phosphate particles is 100nm-250nm.

18. The battery cell according to claim 1, characterized in that, The Dn90 of the lithium-containing transition metal phosphate particles is 250nm-500nm; where Dn90 refers to the particle size corresponding to the cumulative number of particles at 90% in the cumulative number distribution curve of particle size.

19. The battery cell according to claim 18, characterized in that, The Dn90 of the lithium-containing transition metal phosphate particles is 270nm-400nm.

20. 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 of 10% in the cumulative number distribution curve of particle size.

21. The battery cell according to claim 1, characterized in that, The electrolyte includes a first component, which includes one or more of lithium bis(fluorosulfonyl)imide, lithium difluorophosphate, lithium tetrafluoroborate, and lithium bis(trifluoromethanesulfonyl)imide.

22. The battery cell according to claim 21, characterized in that, The first component includes one or more of lithium bis(fluorosulfonyl)imide and lithium difluorophosphate.

23. The battery cell according to claim 21 or 22, characterized in that, Based on the total mass of the electrolyte, the mass percentage of the first component is 0.5%-8%.

24. The battery cell according to claim 23, characterized in that, Based on the total mass of the electrolyte, the first component accounts for 3%-8% of the total mass.

25. The battery cell according to claim 21 or 22, characterized in that, Based on the total mass of the electrolyte, the mass percentage of lithium bis(fluorosulfonyl)imide is 0.1%-8%. And / or, the lithium difluorophosphate accounts for 0.5%-8% of the total mass.

26. The battery cell according to claim 25, characterized in that, Based on the total mass of the electrolyte, the mass percentage of lithium bis(fluorosulfonyl)imide is 2%-5%.

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

28. The battery cell according to claim 1, characterized in that, The electrolyte includes lithium hexafluorophosphate, and the mass percentage of lithium hexafluorophosphate is 5%-10% based on the total mass of the electrolyte.

29. The battery cell according to claim 1, characterized in that, The electrolyte includes a second component, which includes one or more of lithium difluorooxalate borate, tris(trimethylsilyl) phosphate, and lithium dioxalate borate.

30. The battery cell according to claim 29, characterized in that, Based on the total mass of the electrolyte, the mass percentage of the second component is 0.2%-5%.

31. The battery cell according to claim 30, characterized in that, Based on the total mass of the electrolyte, the mass percentage of the second component is 0.5%-2%.

32. 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.

33. The battery cell according to claim 32, characterized in that, Based on the total mass of the electrolyte, the cyclic carbonate compound accounts for 18%-35% of the total mass.

34. The battery cell according to claim 32 or 33, characterized in that, The cyclic carbonate compounds include one or more of ethylene carbonate, propylene carbonate, and butene carbonate.

35. The battery cell according to claim 34, characterized in that, The cyclic carbonate compounds include ethylene carbonate.

36. 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.

37. The battery cell according to claim 36, characterized in that, Based on the total mass of the electrolyte, the chain carbonate compound accounts for 50%-70% of the mass.

38. The battery cell according to claim 36 or 37, characterized in that, The chain carbonate compounds include one or more of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and methyl propyl carbonate.

39. The battery cell according to claim 38, characterized in that, The chain carbonates include methyl ethyl carbonate and diethyl carbonate.

40. The battery cell according to claim 39, 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.

41. 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.

42. The battery cell according to claim 41, characterized in that, Based on the total mass of the electrolyte, the mass percentage of the third component is 0.08%-5%.

43. The battery cell according to claim 42, characterized in that, Based on the total mass of the electrolyte, the mass percentage of the third component is 0.1%-5%.

44. The battery cell according to claim 43, characterized in that, Based on the total mass of the electrolyte, the mass percentage of the third component is 1%-5%.

45. 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.

46. ​​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.

47. 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.

48. 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 dotted conductive agent is 0.2%-2.0%.

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

50. The battery cell according to claim 49, characterized in that, The linear conductive agent includes carbon nanotubes.

51. The battery cell according to claim 49 or 50, 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%.

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

53. The battery cell according to claim 52, characterized in that, The thickness of the positive electrode undercoat is 0.5μm-5μm.

54. The battery cell according to claim 1, characterized in that, The compacted density of the positive electrode film layer is 2.6 g / cm 3 - 3.4 g / cm 3 .

55. 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.

56. The battery cell according to claim 55, characterized in that, The volume distribution particle size Dv50 of the negative electrode active material is 8μm-13μm.

57. The battery cell according to claim 55 or 56, characterized in that, The specific surface area of ​​the negative electrode active material is 0.5 m². 2 / g-3.0m 2 / g.

58. The battery cell according to claim 57, characterized in that, The specific surface area of ​​the negative electrode active material is 0.8 m². 2 / g-2.0m 2 / g.

59. 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.

60. The battery cell according to claim 59, 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.

61. The battery cell according to claim 60, characterized in that, The coating is applied to the base film near the positive electrode sheet.

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

63. The battery cell according to claim 60, characterized in that, The third polymer and the fourth polymer each independently include one or more of fluoropolymers and acrylate polymers.

64. The battery cell according to claim 63, 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; and / or, The acrylate polymers include acrylate-acrylonitrile-acrylamide-propylene copolymers.

65. The battery cell according to any one of claims 59-64, characterized in that, The thickness of the base film is 5μm-12μm.

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

67. The battery cell according to any one of claims 59-64, characterized in that, The thickness of the isolation membrane is 8μm-15μm.

68. The battery cell according to any one of claims 59-64, characterized in that, The air permeability of the isolation membrane at 25°C is 400s / 100cc-600s / 100cc.

69. The battery cell according to any one of claims 59-64, characterized in that, The porosity of the isolation membrane is 35%-55%.

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

71. The battery cell according to claim 55, characterized in that, The thickness of the negative electrode current collector is 3μm-7μm.

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

73. The battery cell according to claim 1, characterized in that, The battery cell also includes a housing and electrode terminals. The housing has an internal cavity, and the electrode assembly and the electrolyte are disposed within the cavity. The outer shell has a through hole connecting the inside and outside of the receiving cavity; the electrode terminal includes a first part and a second part, the first part is entirely located inside the receiving cavity, the second part passes through the through hole and is partially located outside the receiving cavity, and the first part and the second part are an integral structure; The electrode assembly also includes tabs, which are directly connected to the first part.

74. The battery cell according to claim 73, characterized in that, The housing also includes an end cap, and the ratio of the size of the first portion to the size of the end cap is 0.35-0.80 along the thickness direction of the battery cell.

75. The battery cell according to claim 74, characterized in that, Along the thickness direction of the battery cell, the ratio of the size of the first portion to the size of the end cap is 0.50-0.

80.

76. A battery device, characterized in that, Includes the battery cell according to any one of claims 1-75.

77. An electrical appliance, characterized in that, Includes the battery device of claim 76, the battery device being used to provide electrical energy.

78. An energy storage device, characterized in that, Includes the battery device of claim 76, the battery device being used for storing electrical energy.

Images