Positive electrode material, positive electrode plate and battery

Abstract

The invention provides a positive electrode material, a positive electrode plate and a battery, the positive electrode material comprises ternary positive electrode particles, first lithium manganate particles and second lithium manganate particles, the first lithium manganate particles have an octahedral crystal structure, and the second lithium manganate particles have a spinel crystal structure. Through the synergistic effect of the ternary positive electrode particles, the first lithium manganate particles and the second lithium manganate particles, the compaction of the positive electrode material is improved, the compaction density, the energy density and the high temperature resistance of the positive electrode plate are further improved, and the cycle performance and the high-temperature storage performance of the battery are improved.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a positive electrode material, a positive electrode sheet, and a battery. Background Technology

[0002] In recent years, lithium-ion batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, as well as in power banks, power tools, electric bicycles, electric motorcycles, electric cars, military equipment, aerospace and many other fields.

[0003] Among the active materials for the cathode of lithium-ion batteries, lithium-rich manganese-based materials have attracted much attention due to their high specific capacity (>250 mAh / g). However, lithium-rich manganese-based materials suffer from poor battery cycle stability and high-temperature storage performance.

[0004] Therefore, there is an urgent need for a cathode material that enables batteries to have both high temperature resistance and high cycle stability. Summary of the Invention

[0005] This application provides a positive electrode material, a positive electrode sheet, and a battery, aiming to improve the cycle stability and thermal stability of existing batteries.

[0006] In a first aspect, this application provides a cathode material, including ternary cathode particles, a first lithium manganese oxide particle, and a second lithium manganese oxide particle, wherein the first lithium manganese oxide particle has an octahedral crystal structure and the second lithium manganese oxide particle has a spinel crystal structure.

[0007] Optionally, the volume average particle size of the ternary cathode particles is Dv150, the volume average particle size of the first lithium manganese oxide particles is Dv250, and the volume average particle size of the second lithium manganese oxide particles is Dv350. Among them, Dv150 < Dv350 < Dv250.

[0008] Optionally, the positive electrode material satisfies the following relationship: A=W1*K1+W2*K2+W3*K3, 1.3≤A≤2.6; Wherein, W1 is the mass content of the ternary cathode particles in the cathode material; W2 is the mass content of the first lithium manganese oxide particles in the cathode material; W3 represents the mass content of the second lithium manganese oxide particles in the cathode material; K1 is the particle size distribution span of the ternary cathode particles, 0.7≤K1≤1.94; K2 is the particle size distribution span of the first lithium manganese oxide particle, 1.44≤K2≤2.44; K3 is the particle size distribution span of the second lithium manganese oxide particles, 1.23≤K3≤2.25.

[0009] Optionally, K1 = (Dv190 - Dv110) / Dv150, where the Dv110 of the ternary cathode particles is 1.7-2.5 μm, the Dv150 is 3.3-4.3 μm, and the Dv190 is 5.5-8.1 μm; K2 = (Dv290 - Dv210) / Dv250, where the Dv210 of the first lithium manganese oxide particle is 2.5-5.5 μm, the Dv250 is 13.3-16.3 μm, and the Dv290 is 29-35 μm; K3 = (Dv390 - Dv310) / Dv350, where the Dv310 of the second lithium manganese oxide particle is 4-7 μm, the Dv350 is 8-13 μm, and the Dv390 is 20-25 μm.

[0010] Optionally, based on the mass of the cathode material being 100%, the mass content W1 of the ternary cathode particles is 5%-15%.

[0011] Optionally, based on the mass of the cathode material as 100%, the mass content W2 of the first lithium manganese oxide particles is 80%-90%.

[0012] Optionally, based on the mass of the cathode material as 100%, the mass content W3 of the second lithium manganese oxide particles is 5%-15%.

[0013] Optionally, the first lithium manganese oxide particles are block-shaped secondary particles, and the second lithium manganese oxide particles are spherical secondary particles.

[0014] Secondly, this application provides a positive electrode sheet, including a positive current collector and a positive active material layer, wherein the positive active material layer is disposed on at least one side of the positive current collector, and the positive active material layer includes the positive electrode material as described in any of the above.

[0015] Thirdly, this application provides a battery including the positive electrode sheet as described above.

[0016] In this application, the cathode material incorporates ternary cathode particles to improve the compaction and electrical performance of the cathode sheet. Simultaneously, the ternary cathode particles are alkaline, allowing them to preferentially react with HF in the electrolyte during battery formation, mitigating the Mn dissolution problem of lithium manganese oxide particles and ensuring subsequent cycle life and high-temperature storage performance. The first lithium manganese oxide particle is prepared using manganese dioxide as one of the raw materials, resulting in an octahedral crystal structure, high compaction, and high specific capacity. Furthermore, the first lithium manganese oxide particle has low cost, reducing the overall cost of the cathode material. The second lithium manganese oxide particle is prepared using manganese tetroxide as one of the raw materials. Its spinel-type crystal structure belongs to the cubic crystal system and possesses a three-dimensional tunnel structure. Lithium ions can reversibly intercalate and deintercalate from the spinel lattice without causing structural collapse, exhibiting excellent rate performance and stability. By leveraging the synergistic effect of ternary cathode particles, lithium manganese oxide first particles, and lithium manganese oxide second particles, the compaction of the cathode material is improved, further enhancing the compaction density, energy density, and high-temperature resistance of the cathode sheet, thereby improving the battery's cycle performance and high-temperature storage performance. Attached Figure Description

[0017] Figure 1 This is an electron microscope image of ternary cathode particles in a cathode material provided in an embodiment of this application; Figure 2 This is an electron microscope image of the first lithium manganese oxide particle in a cathode material provided in an embodiment of this application; Figure 3 This is an electron microscope image of a second lithium manganese oxide particle in a cathode material provided in an embodiment of this application; Figure 4 This is an electron microscope image of a positive electrode sheet after the coating process provided in Embodiment 1 of this application; Figure 5 This is an electron microscope image of a positive electrode sheet after the rolling process provided in Embodiment 1 of this application. Detailed Implementation

[0018] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0019] One embodiment of this application provides a cathode material, including ternary cathode particles, a first lithium manganese oxide particle, and a second lithium manganese oxide particle. The first lithium manganese oxide particle has an octahedral crystal structure, and the second lithium manganese oxide particle has a spinel crystal structure.

[0020] In this embodiment, the cathode material incorporates ternary cathode particles to improve the compaction and electrical performance of the cathode sheet. Simultaneously, the ternary cathode particles are alkaline, allowing them to preferentially react with HF in the electrolyte during battery formation, mitigating the Mn dissolution problem of lithium manganese oxide particles and ensuring subsequent cycle life and high-temperature storage performance. The first lithium manganese oxide particle is prepared using manganese dioxide as one of the raw materials, resulting in an octahedral crystal structure, high compaction, and high specific capacity. Furthermore, the first lithium manganese oxide particle has low cost, reducing the overall cost of the cathode material. The second lithium manganese oxide particle is prepared using manganese tetroxide as one of the raw materials. Its spinel-type crystal structure belongs to the cubic crystal system and has a three-dimensional tunnel structure. Lithium ions can reversibly intercalate and deintercalate from the spinel lattice without causing structural collapse, exhibiting excellent rate performance and stability. By leveraging the synergistic effect of ternary cathode particles, lithium manganese oxide first particles, and lithium manganese oxide second particles, the compaction of the cathode material is improved, further enhancing the compaction density, energy density, and high-temperature resistance of the cathode sheet, thereby improving the battery's cycle performance and high-temperature storage performance.

[0021] In one embodiment, the ternary cathode particles have a volume average particle size of Dv150, the first lithium manganese oxide particles have a volume average particle size of Dv250, and the second lithium manganese oxide particles have a volume average particle size of Dv350. Wherein, Dv150 < Dv350 < Dv250. The average particle size of the second lithium manganese oxide particles is larger than that of the ternary cathode particles but smaller than that of the first lithium manganese oxide particles. This allows the second lithium manganese oxide particles to fill the pores of the ternary cathode particles and the first lithium manganese oxide particles, enabling the ternary cathode particles, the first lithium manganese oxide particles, and the second lithium manganese oxide particles to work synergistically to improve the compaction and electrical properties of the cathode material, further increasing the compaction density and energy density of the cathode sheet, and improving the cycle performance of the battery.

[0022] In one embodiment, the positive electrode material satisfies the following relationship: A=W1*K1+W2*K2+W3*K3, 1.3≤A≤2.6; Wherein, W1 is the mass content of the ternary cathode particles in the cathode material; W2 is the mass content of the first lithium manganese oxide particles in the cathode material; W3 represents the mass content of the second lithium manganese oxide particles in the cathode material; K1 is the particle size distribution span of the ternary cathode particles, 0.7≤K1≤1.94; K2 is the particle size distribution span of the first lithium manganese oxide particle, 1.44≤K2≤2.44; K3 is the particle size distribution span of the second lithium manganese oxide particles, 1.23≤K3≤2.25.

[0023] The values ​​of W1*K1, W2*K2, and W3*K3 reflect the breadth of particle distribution. Their sum comprehensively reflects the breadth of particle distribution and filling efficiency in the cathode material. When 1.3 ≤ A ≤ 2.6, sufficient particle gradation is ensured, improving the compaction density of the cathode sheet while avoiding excessively wide distribution that could lead to porosity imbalance and affect cycle performance. When A is less than 1.3, the packing structure between the ternary cathode particles, the first lithium manganese oxide particles, and the second lithium manganese oxide particles is loose, resulting in lower cathode sheet compaction density and reduced battery cycle performance. When A is greater than 2.6, the cathode material is packed too tightly, leading to porosity imbalance and reduced battery cycle performance.

[0024] In one embodiment, K1 = (Dv190 - Dv110) / Dv150, where the ternary cathode particles have a Dv110 of 1.7-2.5 μm, a Dv150 of 3.3-4.3 μm, and a Dv190 of 5.5-8.1 μm. Specifically, Dv110 includes, but is not limited to, 1.7μm, 1.8μm, 1.9μm, 2.0μm, 2.1μm, 2.2μm, 2.3μm, 2.4μm, or 2.5μm. Dv150 includes, but is not limited to, 3.3μm, 3.4μm, 3.5μm, 3.6μm, 3.7μm, 3.8μm, 3.9μm, 4.0μm, 4.1μm, 4.2μm, or 4.3μm. Dv190 includes, but is not limited to, 5.5μm, 5.7μm, 5.9μm, 6.1μm, 6.3μm, 6.5μm, 6.7μm, 6.9μm, 7.1μm, 7.3μm, 7.5μm, 7.7μm, 7.9μm, or 8.1μm.

[0025] K2 = (Dv290 - Dv210) / Dv250, where the Dv210 of the first lithium manganese oxide particle is 2.5-5.5 μm, the Dv250 is 13.3-16.3 μm, and the Dv290 is 29-35 μm; Specifically, Dv210 includes, but is not limited to, 2.5μm, 2.8μm, 3.1μm, 3.4μm, 3.7μm, 4.0μm, 4.3μm, 4.7μm, 5.0μm, 5.3μm, or 5.5μm. Dv250 includes, but is not limited to, 13.3μm, 13.6μm, 13.9μm, 14.2μm, 14.5μm, 14.8μm, 15.1μm, 15.4μm, 15.7μm, 16.1μm, or 16.3μm. Dv290 includes, but is not limited to, 29μm, 29.5μm, 30μm, 30.5μm, 31μm, 31.5μm, 32μm, 32.5μm, 33μm, 33.5μm, 34μm, 34.5μm, or 35μm.

[0026] K3 = (Dv390 - Dv310) / Dv350, where the Dv310 of the second lithium manganese oxide particle is 4-7 μm, the Dv350 is 8-13 μm, and the Dv390 is 20-25 μm.

[0027] Specifically, Dv310 includes, but is not limited to, 4μm, 4.3μm, 4.6μm, 4.9μm, 5.2μm, 5.5μm, 5.8μm, 6.1μm, 6.4μm, 6.7μm, or 7μm. Dv350 includes, but is not limited to, 8μm, 8.5μm, 9μm, 9.5μm, 10μm, 10.5μm, 11μm, 11.5μm, 12μm, 12.5μm, or 13μm. Dv390 includes, but is not limited to, 20μm, 20.5μm, 21μm, 21.5μm, 22μm, 22.5μm, 23μm, 23.5μm, 24μm, 24.5μm, or 25μm.

[0028] By limiting the particle size range of the above-mentioned particles, the particle size distribution span is controlled within a reasonable range to ensure the uniformity of the particles.

[0029] In one embodiment, based on the mass of the cathode material being 100%, the mass content W1 of the ternary cathode particles is 5%-15%.

[0030] Specifically, W1 includes, but is not limited to, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%.

[0031] In one embodiment, based on the mass of the cathode material as 100%, the mass content W2 of the first lithium manganese oxide particles is 80%-90%.

[0032] Specifically, W2 includes, but is not limited to, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, or 90%.

[0033] In one embodiment, based on the mass of the positive electrode material as 100%, the mass content W3 of the second lithium manganese oxide particles is 5%-15%.

[0034] Specifically, W3 includes, but is not limited to, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%.

[0035] In one embodiment, the first lithium manganese oxide particle is a blocky secondary particle, and the second lithium manganese oxide particle is a spherical secondary particle. Specifically, the ternary cathode particle is a lithium nickel cobalt manganese oxide particle with a blocky structure and a smaller particle size than the first lithium manganese oxide particle. That is, the ternary cathode particle, the first lithium manganese oxide particle, and the second lithium manganese oxide particle, through the combination of shape and particle size, make the cathode material densely packed and improve the compaction density of the cathode sheet.

[0036] An embodiment of this application also provides a positive electrode sheet, including a positive current collector and a positive active material layer, wherein the positive active material layer is disposed on at least one side of the positive current collector, and the positive active material layer includes the positive electrode material as described in any of the above claims.

[0037] In one embodiment, the positive electrode active material layer further includes a conductive agent and an additive.

[0038] In some embodiments, the conductive agent includes at least one of graphite, hard carbon, soft carbon, carbon nanotubes, graphene, porous carbon, superconducting carbon black (Super P), acetylene black, and furnace black.

[0039] In some embodiments, the additives include at least one selected from polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), silicone rubber, styrene-butadiene rubber (SBR), hydrogenated nitrile butadiene rubber (HNBR), boronized polyethylene glycol, cellulose, cellulose ester, cellulose ether, nitrocellulose, carboxyalkyl cellulose, cellulose salt, sodium carboxymethyl cellulose and cellulose salt derivatives, polyacrylic acid (PAA), polyamide (PAI), polyvinyl alcohol (PVA), polyethyleneimine (PEI), and polyimide (PI).

[0040] In some embodiments, the mass percentage of each component in the positive electrode active material layer is: 96%-99% positive electrode material, 0.5%-1.6% conductive agent, and 1%-1.7% additives.

[0041] When the mass percentage of the positive electrode material in the positive electrode active material layer is within the above range, the positive electrode sheet can have a high specific capacity and compaction density, which can fully utilize the rate performance of the battery and meet the battery's fast charging and discharging requirements and high-temperature storage performance.

[0042] In some embodiments, the positive current collector is selected from a metallic material that can conduct electrons. Preferably, the positive current collector includes at least one of aluminum, copper, nickel, tin, copper, and stainless steel. In more preferred embodiments, the positive current collector is selected from aluminum foil or carbon-coated aluminum foil.

[0043] The preparation of the positive electrode sheet includes the following steps: S1. Premix the ternary cathode particles, lithium manganese oxide particles, SP, and NMP (N-methylpyrrolidone). SP and NMP have good wettability, and premixing them with the ternary cathode particles and lithium manganese oxide particles in advance can improve dispersibility. The stirring equipment for premixing is set to rotate at 13-17 rpm, the stirring time is 8-12 minutes, and the temperature of the equipment is controlled between 20-50℃.

[0044] S2. Add carbon nanotubes and stir. Set the stirring equipment to rotate at 28-32 rpm and stir for 50-70 minutes. Control the temperature of the equipment between 20 and 50 degrees Celsius.

[0045] S3. Add PVDF adhesive and mix the adhesive by stirring. In the third step, the stirring equipment should be set to rotate at 25-35 rpm for 15-25 minutes. The temperature of the equipment should be controlled between 20-50℃. At the same time, the equipment should be vacuumed to remove air bubbles.

[0046] S4. Add the first lithium manganese oxide particles, first stir slowly, then stir at high speed to ensure thorough mixing of the positive electrode material, conductive agent, and PVDF adhesive. For slow stirring, set the stirring speed to 12-18 rpm and the stirring time to 7-13 minutes, maintaining the equipment temperature between 20-50°C. For high-speed stirring, set the stirring speed to 27-33 rpm and the stirring time to 130-170 minutes, maintaining the equipment temperature between 20-50°C and applying vacuum.

[0047] S4. Adjust the viscosity of the slurry by adding NMP to control the solid content at 66%±1% and the viscosity at 5000±1000 mPa·s. After meeting the requirements for solid content and viscosity, perform vacuum degassing. After the slurry is prepared, it undergoes coating and rolling processes to obtain the positive electrode sheet.

[0048] One embodiment of this application also provides a battery, including the positive electrode sheet as described above. It should be noted that the battery can be a stacked, wound, or cylindrical battery.

[0049] In one embodiment, the battery further includes a negative electrode sheet, which includes a negative current collector and a negative active material layer. The negative active material layer is disposed on at least one side of the negative current collector, and the negative active material layer includes primary particulate graphite, silicon-carbon, silicon, lithium metal, or lithium alloy.

[0050] The negative electrode sheet can be prepared according to conventional methods in the art. For example, the negative electrode active material layer is typically formed by coating a negative electrode slurry, consisting of a negative electrode active material, a negative electrode conductive agent, a negative electrode binder, and any other components, onto a negative electrode current collector, followed by drying and cold pressing. The solvent can be an aqueous solvent, but is not limited to it.

[0051] In some embodiments, the battery further includes a separator and an electrolyte. The separator includes a base membrane, which includes at least one of PE separator, PP separator, non-woven separator, and PI separator.

[0052] In some embodiments, the base film has a coating on at least one side; the coating includes an adhesive and ceramic.

[0053] The electrolyte includes organic solvents, lithium salts, and additives. The solvents include, but are not limited to, PC (propylene carbonate), EC (ethylene carbonate), DMC (dimethyl carbonate), EMC (ethyl methyl carbonate), DEC (diethyl carbonate), and DME (ethylene glycol dimethyl ether).

[0054] Lithium salts include, but are not limited to, lithium hexafluorophosphate (LiPF6), lithium hexafluoroarsenate (LiAsF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroantimonyate (LiSbF6), lithium bis(trifluoromethanesulfonate imide) (LiTFSI or LiN(SO2CF2)2), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(fluorosulfonyl)imide (LiFSI or LiN(SO2CF3)2), lithium perchlorate (LiClO4), lithium iodide (LiI), and lithium bis(fluorosulfonyl)imide magnesium (Li2Mg(N(SO2CF3)2)2).

[0055] In some embodiments, the positive electrode tab of the positive electrode is located in the middle of the positive electrode. During battery discharge, the main bottleneck is on the positive electrode side. Therefore, designing the positive electrode as a centrally located structure can improve the dynamics of the positive electrode, reduce internal resistance, and increase the discharge rate.

[0056] The negative electrode is a conventional electrode head with a negative electrode tab to avoid scraping or laser cleaning processes.

[0057] One embodiment of this application provides an electrical device including the battery described above. Exemplary examples include, but are not limited to, mobile devices (e.g., power banks, mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, aircraft, and robots.

[0058] The present application will be further illustrated by the following examples.

[0059] Example 1 This embodiment illustrates the positive electrode material, positive electrode sheet, and battery disclosed in this application, and includes the following operational steps: 1. Cathode material The cathode material consists of 15% lithium nickel cobalt manganese oxide (NCM), 80% lithium first manganese oxide particles, and 5% lithium second manganese oxide particles.

[0060] The NCM has a Dv110 of 2 μm, a Dv150 of 3.5 μm, a Dv190 of 7 μm, and a K1 of 1.43.

[0061] The first lithium manganese oxide particles have a Dv210 of 4 μm, a Dv250 of 15 μm, a Dv290 of 33 μm, and a K2 of 1.93.

[0062] The second lithium manganese oxide particles have a Dv310 of 5 μm, a Dv350 of 10 μm, a Dv390 of 23 μm, and a K3 of 1.8.

[0063] 2. Preparation of the positive electrode sheet The obtained positive electrode material, CNT, Super-P, and PVDF binder are mixed in a mass ratio of 96.7:0.5:1.1:1.7. The mixture is thoroughly stirred in NMP solvent to form a uniform positive electrode slurry. This slurry is coated onto at least one side of the positive electrode current collector aluminum foil, and after drying, rolling, and die-cutting processes, a satisfactory positive electrode sheet is obtained.

[0064] 3. Preparation of negative electrode sheet One-time granular artificial graphite, SBR (styrene-butadiene rubber): CMC-Na sodium carboxymethyl cellulose were uniformly mixed at a mass ratio of 97.3:1.5:1.2, with deionized water as the solvent. After stirring evenly to obtain a slurry, it was coated onto a copper foil current collector, dried, cold-pressed, and cut into negative electrode sheets for later use.

[0065] The particle sizes of primary artificial graphite particles are 6 μm for DV410, 11 μm for DV450, and 21 μm for DV490.

[0066] 4. Preparation of electrolyte Electrolyte for liquid batteries: Lithium salt LiPF6 is dissolved in organic solvent EC-DMC (ethylene carbonate-dimethyl carbonate, 1:1 volume ratio) to obtain a liquid electrolyte at a concentration of 1M.

[0067] 5. Battery manufacturing The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. Then, one end of each of the positive electrode, separator, and negative electrode is wound around the separator to form a core. The wound core is then placed in a pre-formed aluminum-plastic film bag. The electrolyte prepared above is injected into the baked and dried cell. After vacuum sealing, settling, and formation processes, a 1Ah battery is obtained.

[0068] Example 2-25 Examples 2-25 are used to illustrate the positive electrode material, positive electrode sheet and battery disclosed in this application, including most of the operation steps in Example 1 above, the difference being that the formulation in Table 1 is used.

[0069] Comparative Examples 1-3 Comparative Examples 1-3 are used to illustrate the positive electrode material, positive electrode sheet and battery disclosed in this application, including most of the operation steps in Example 1, the difference being that the formulation in Table 1 is used.

[0070] Table 1 Performance testing I. The following performance tests were performed on the positive electrode sheets and batteries prepared in the above embodiments and comparative examples: 1. Compacted density of the positive electrode sheet: Compacted density = surface density / (electrode thickness - current collector thickness). After testing the surface density of the coated electrode sheet, roll the coated and dried electrode sheet according to different thickness requirements. Take samples from the left, center and right sides of the rolled electrode sheet, fold it 180° and 360°, use a 1kg metal block, apply pressure for 1 minute, turn on the backlight to observe the light transmission effect. The thickness of the electrode sheet with less than 3 light-transmitting micropores is used as the limit of the electrode sheet for calculation, and the thickness of the electrode sheet that is just opaque is used as the standard of the material for compaction. Substitute this electrode sheet thickness into the above formula: Compacted density = surface density / (electrode thickness - current collector thickness) to calculate the compaction of the positive electrode sheet.

[0071] 2. Cyclic performance test standard: The cell is fully charged to 4.2V at 0.5C, with a cutoff current of 0.05C, and discharged to 3.0V at 1C, and cycled 300 times. The battery capacity retention rate after the cycle must be ≥80%. The cycle test environment is room temperature 25℃.

[0072] 3. Discharge performance test standard: 1. Charge the cell to 4.2V at 0.2C, cut off current is 0.02C, discharge to 3.0V at 0.2C and 1C respectively, record the discharge capacity. The discharge capacity at 0.2C is recorded as 100%, and the discharge capacity at 1C needs to be ≥88% of the discharge capacity at 0.2C.

[0073] 4. High-temperature storage performance test: The battery is stored at 60℃ for 7 days, and then charged to 4.2V at 25℃ and 0.5C with a cutoff current of 0.05C, and discharged to 3.0V at 0.2C. The cycle is repeated 3 times, and the capacity retention rate (%) is measured.

[0074] The test results are shown in Table 2.

[0075] Table 2 In terms of compaction density, the compaction density of ternary cathode material > that of lithium manganese oxide first material > that of lithium manganese oxide second material. Regarding cycle performance and storage performance, the order is: ternary cathode material > lithium manganese oxide second material > lithium manganese oxide first material. In terms of cost, the order is: ternary cathode material > lithium manganese oxide second material > lithium manganese oxide first material. Furthermore, the test results from the examples and comparative examples in Table 2 show that when the content and particle size of ternary cathode particles, lithium manganese oxide first particles, and lithium manganese oxide second particles are appropriately matched, the compaction density and contact area between particles of the cathode material can be improved, reducing the internal resistance of the electrode sheet and improving the battery's cycle performance, high-temperature storage performance, and rate charging and discharging capabilities. When the cathode material does not contain ternary cathode particles, the compaction density of the cathode sheet decreases, and the battery's cycle performance, rate performance, and high-temperature storage performance decrease. When the cathode material does not contain lithium manganese oxide first particles, the battery's rate performance and high-temperature storage performance decrease. When the cathode material does not contain lithium manganese oxide particles, the battery's cycle performance, rate performance, and high-temperature storage performance decrease.

[0076] The test results from Examples 1 and 2 show that when the particle sizes of the ternary cathode particles, the first lithium manganese oxide particles, and the second lithium manganese oxide particles satisfy Dv150 < Dv350 < Dv250, the second lithium manganese oxide particles can fill the pores of the ternary cathode particles and the first lithium manganese oxide particles, which can increase the compaction density of the cathode sheet and further improve the battery's cycle performance, rate performance, and high-temperature storage performance. In Example 2, Dv350 > Dv250, and the first lithium manganese oxide particles have a small particle size, which is beneficial for rate discharge, but the large specific surface area leads to a violent reaction with the electrolyte at high temperatures, resulting in a decrease in the battery's high-temperature storage performance.

[0077] The test results from Examples 1 and 3-25 show that when the positive electrode material satisfies the conditions 1.3≤W1*K1+W2*K2+W3*K3≤2.6, 0.7≤K1≤1.94, 1.44≤K2≤2.44, and 1.23≤K3≤2.25, the positive electrode sheet has a suitable compaction density, resulting in good cycle performance of the battery. When W1*K1+W2*K2+W3*K3<1.3 or W1*K1+W2*K2+W3*K3>2.6, the cycle performance, rate performance, and high-temperature storage performance of the battery decrease. Furthermore, as shown in the test results of Examples 15-23, when the cathode material satisfies the following conditions: 1.3≤W1*K1+W2*K2+W3*K3≤2.6, 0.7≤K1≤1.94, 1.44≤K2≤2.44, 1.23≤K3≤2.25, W1 is 5%-15%, W2 is 80%-90%, and W3 is 5%-15%, the battery exhibits good cycle performance, rate performance, and high-temperature storage performance, while also having a lower production cost. In Example 18, the content of ternary cathode particles is higher than 15%, resulting in better cycle performance and storage performance, but also increasing the production cost.

[0078] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A positive electrode material, characterized in that, It includes ternary cathode particles, first lithium manganese oxide particles, and second lithium manganese oxide particles. The first lithium manganese oxide particles have an octahedral crystal structure, and the second lithium manganese oxide particles have a spinel crystal structure.

2. The cathode material according to claim 1, characterized in that, The ternary cathode particles have a volume average particle size of Dv150, the first lithium manganese oxide particles have a volume average particle size of Dv250, and the second lithium manganese oxide particles have a volume average particle size of Dv350. Among them, Dv150 < Dv350 < Dv250.

3. The cathode material according to claim 1, characterized in that, The cathode material satisfies the following relationship: A=W1*K1+W2*K2+W3*K3, 1.3≤A≤2.6; Wherein, W1 is the mass content of the ternary cathode particles in the cathode material; W2 is the mass content of the first lithium manganese oxide particles in the cathode material; W3 represents the mass content of the second lithium manganese oxide particles in the cathode material; K1 is the particle size distribution span of the ternary cathode particles, 0.7≤K1≤1.94; K2 is the particle size distribution span of the first lithium manganese oxide particle, 1.44≤K2≤2.44; K3 is the particle size distribution span of the second lithium manganese oxide particles, 1.23≤K3≤2.

25.

4. The cathode material according to claim 3, characterized in that, K1 = (Dv190 - Dv110) / Dv150, where the Dv110 of the ternary cathode particles is 1.7-2.5 μm, the Dv150 is 3.3-4.3 μm, and the Dv190 is 5.5-8.1 μm; K2 = (Dv290 - Dv210) / Dv250, where the Dv210 of the first lithium manganese oxide particle is 2.5-5.5 μm, the Dv250 is 13.3-16.3 μm, and the Dv290 is 29-35 μm; K3 = (Dv390 - Dv310) / Dv350, where the Dv310 of the second lithium manganese oxide particle is 4-7 μm, the Dv350 is 8-13 μm, and the Dv390 is 20-25 μm.

5. The positive electrode material according to claim 3, characterized in that, Based on the mass of the cathode material being 100%, the mass content W1 of the ternary cathode particles is 5%-15%.

6. The cathode material according to claim 3, characterized in that, Based on the mass of the cathode material being 100%, the mass content W2 of the first lithium manganese oxide particles is 80%-90%.

7. The cathode material according to claim 3, characterized in that, Based on the mass of the cathode material being 100%, the mass content W3 of the second lithium manganese oxide particles is 5%-15%.

8. The positive electrode material according to claim 1, characterized in that, The first lithium manganese oxide particle is a block-shaped secondary particle, and the second lithium manganese oxide particle is a spherical secondary particle.

9. A positive electrode sheet, characterized in that, It includes a positive current collector and a positive active material layer, wherein the positive active material layer is disposed on at least one side of the positive current collector, and the positive active material layer includes the positive electrode material according to any one of claims 1-8.

10. A battery, characterized in that, Including the positive electrode sheet as described in claim 9.

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