A battery positive electrode material, a preparation method and application thereof

Abstract

The application provides a battery positive electrode material and a preparation method and application thereof, and comprises lithium iron manganese phosphate primary particles, wherein the particle size distribution dispersion degree of the lithium iron manganese phosphate primary particles is 1-4, the particle size distribution dispersion degree=D v 90-D v 10) / D v 50, D v 10, D v 50, D v 90 respectively represent particle sizes corresponding to 10%, 50% and 90% of the cumulative volume distribution of the lithium iron manganese phosphate primary particles, and the units are nm. The battery positive electrode material has high capacity and good rate performance, and also has good electrochemical performance under low temperature conditions, which is beneficial to the application of the battery positive electrode material in secondary batteries.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of secondary batteries, in particular to a battery positive electrode material and a preparation method and application thereof. BACKGROUND

[0002] Lithium secondary batteries have the advantages of high energy density, high voltage, long service life, environmental friendliness, etc., and are widely used in electronic devices, automobiles, aerospace, etc. As an important component of lithium secondary batteries, the selection of the positive electrode material directly affects the performance of lithium ion batteries. Lithium manganese iron phosphate has the advantages of high capacity, high safety and non-toxicity, and is an important positive electrode material for lithium ion batteries. However, compared with lithium iron phosphate material, lithium manganese iron phosphate has poor electronic and ionic conductivity, which is not conducive to the capacity of lithium manganese iron phosphate, and its low-temperature performance is also poor, thereby limiting the application of lithium manganese iron phosphate. SUMMARY

[0003] Therefore, the present application provides a battery positive electrode material, which has high capacity and good rate performance, and also has good electrochemical performance at low temperature, which is beneficial to its application in secondary batteries.

[0004] The first aspect of the present application provides a battery positive electrode material, comprising lithium manganese iron phosphate primary particles, wherein the particle size distribution dispersion degree of the lithium manganese iron phosphate primary particles is 1-4, and the particle size distribution dispersion degree = (D v 90-D v 10) / D v 50, D v 10, D v 50, D v 90 respectively represent the particle size corresponding to the cumulative volume distribution percentage of 10%, 50%, and 90% of the lithium manganese iron phosphate primary particles, and the unit is nm.

[0005] In the battery positive electrode material of the present application, the lithium manganese iron phosphate primary nanoparticles have small size and narrow particle size distribution, which is beneficial to shorten the distance of electron and ion transmission, improve the lithium deintercalation rate of the positive electrode material, promote the capacity of the material, and improve its low-temperature performance. When the lithium manganese iron phosphate primary nanoparticles are applied in batteries, the batteries have high charge and discharge capacity and rate performance.

[0006] Optionally, the D v 50 of the lithium manganese iron phosphate primary particles is 30-60 nm.

[0007] Optionally, the sphericity of the lithium manganese iron phosphate primary particles is greater than or equal to 0.7.

[0008] Optionally, the lithium manganese iron phosphate primary particles further comprise a doping ion selected from one or more of Mg, Al, Co, Zn, Ti, V, Ni, Cu.

[0009] Optionally, the lithium manganese iron phosphate primary particles have a chemical formula of LiMn x Fe 1-x M' y PO4, wherein 0.6≤x≤0.95, 0≤y≤0.05, and M' is selected from one or more of Mg, Al, Co, Zn, Ti, V, Ni, Cu.

[0010] Optionally, the battery cathode material has a tap density of 2.0 g / cc to 2.4 g / cc.

[0011] In a second aspect, the present application provides a preparation method of a battery cathode material, comprising:

[0012] mixing and grinding a lithium manganese iron phosphate, a lithium source, a carbon source, and a solvent to obtain a first slurry, aging the first slurry to obtain a second slurry, and drying, sintering, and crushing the second slurry to obtain the battery cathode material.

[0013] Optionally, the D50 of the particles in the first slurry is 0.2 μm to 0.5 μm. v 50 is 0.2 μm to 0.5 μm.

[0014] Optionally, the D50 of the particles in the second slurry is 1 μm to 10 μm. v 50 is 1 μm to 10 μm.

[0015] Optionally, the first slurry has a viscosity of 200 cp to 500 cp.

[0016] Optionally, the second slurry has a viscosity of 100 cp to 300 cp.

[0017] Optionally, the lithium manganese iron phosphate is obtained by reacting a phosphorus source, an iron source, and a manganese source; the phosphorus source comprises one or more of phosphoric acid, sodium phosphate, potassium phosphate, lithium dihydrogen phosphate, lithium monohydrogen phosphate, ammonium dihydrogen phosphate, and ammonium hydrogen phosphate; the iron source comprises one or more of ferric chloride, ferric nitrate, ferrous oxalate, ferrous sulfate, and iron oxide; and the manganese source comprises one or more of manganese hydroxide, manganese carbonate, manganese oxide, manganese sulfate, manganese nitrate, and manganese oxalate.

[0018] Optionally, the lithium source comprises one or more of lithium carbonate, lithium phosphate, lithium dihydrogen phosphate, lithium hydroxide, lithium nitrate, lithium oxalate, lithium acetate, lithium benzoate, lithium citrate, and lithium benzoate.

[0019] Optionally, the molar ratio of the lithium source to the lithium manganese iron phosphate is (0.95-1.03):1.

[0020] Optionally, the carbon source comprises one or more of glucose, sucrose, water-soluble phenolic resin, polyethylene glycol, hydroxymethyl cellulose, polyacrylamide, starch, polyvinyl alcohol, carbon tube, graphene.

[0021] Optionally, the solvent comprises one or more of water, methanol, ethanol or N-methyl pyrrolidone.

[0022] Optionally, the mass percentage of the solvent in the first slurry is 60% to 90%.

[0023] Optionally, the mass ratio of the carbon source to manganese iron phosphate in the first slurry is 0.15 to 0.25.

[0024] Optionally, the grinding comprises one or more of ball milling or sand milling; the linear speed of the grinding is 5 m / s to 15 m / s, and the grinding time is 0.5 h to 12 h.

[0025] Optionally, the ball milling comprises coarse milling and fine milling, the coarse milling uses a grinding ball with a diameter of 0.5 mm to 0.6 mm, and the fine milling uses a grinding ball with a diameter of 0.05 mm to 0.3 mm.

[0026] Optionally, the aging treatment is performed at a temperature of 50℃ to 90℃ for a time of 0.5 h to 3 h.

[0027] Optionally, the drying comprises one or more of oven drying, belt drying or spray drying.

[0028] Optionally, the sintering is performed at a temperature of 650℃ to 760℃ for a time of 5 h to 10 h.

[0029] Optionally, the sintering is performed in an inert atmosphere comprising one or more of nitrogen, argon, helium, neon, krypton, xenon, radon.

[0030] Optionally, the crushing comprises jet milling, and the jet milling is performed at a pressure of 0.5 MPa to 1 MPa.

[0031] In a third aspect, the present application provides a positive electrode tab, comprising a current collector and a positive electrode material layer disposed on the current collector, wherein the positive electrode material layer comprises the battery positive electrode material according to the first aspect.

[0032] In a fourth aspect, the present application provides a secondary battery, comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein the positive electrode comprises the positive electrode tab according to the third aspect. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1A preparation method of a battery positive electrode material provided in an embodiment of the present application;

[0034] Figure 2 A scanning electron microscope image of an electrode positive electrode material provided in Embodiment 1 of the present application;

[0035] Figure 3 A scanning electron microscope image of an electrode positive electrode material provided in Embodiment 2 of the present application. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0037] Although the lithium manganese iron phosphate has a higher theoretical energy density than the lithium iron phosphate, its electronic conductivity and lithium ion diffusion rate are lower than those of the lithium iron phosphate, which is not conducive to the capacity of the lithium manganese iron phosphate. In order to improve the electrochemical performance of the lithium manganese iron phosphate positive electrode material, the present application provides a battery positive electrode material, which comprises lithium manganese iron phosphate primary particles, and the particle size distribution span of the lithium manganese iron phosphate primary particles is 1-4. The battery positive electrode material has higher uniformity and fewer lattice defects, which is conducive to the transmission of ions and electrons, so that it has good electrical conductivity. In the present application, the particle size distribution span of the lithium manganese iron phosphate primary particles is D v 90-D v 10) / D v 50, wherein D v 10, D v 50, D v 90 respectively represent the particle size corresponding to the cumulative volume distribution percentage of 10%, 50%, and 90% of the lithium manganese iron phosphate primary particles, and the unit is nm. The particle size distribution span of the lithium manganese iron phosphate primary particles can be, but is not limited to, 1, 1.5, 2, 2.5, 3, 3.5, or 4. In the present application, the D v 50, D v 10, D v 90 of the lithium manganese iron phosphate primary particles can be obtained by SEM (Scanning Electron Microscope), and in some embodiments, the D v 50, D v 10, D v90The specific test method is: selecting a photo with a magnification of 30k or 50k in a scanning electron microscope image, and then counting the size of all primary particles by using Smile view software to obtain a particle size distribution diagram of the lithium manganese iron phosphate primary particles, and further obtaining D v 10, D v 50, and D v 90.

[0038] In some embodiments of the present application, D v 50 of the lithium manganese iron phosphate primary particles is 30nm to 60nm, D v 50 can be but is not limited to 30nm, 35nm, 40nm, 45nm, 50nm, 55nm or 60nm. The particle size of the lithium manganese iron phosphate primary particles of the present application is small, which is beneficial to shorten the transmission path of lithium ions and improve the rate performance and low-temperature performance of the lithium manganese iron phosphate. In some embodiments of the present application, D v 10 of the lithium manganese iron phosphate primary particles is 10nm to 20nm, D v 10 can be but is not limited to 10nm, 12nm, 14nm, 15nm, 17nm, 19nm or 20nm. In some embodiments of the present application, D v 90 of the lithium manganese iron phosphate primary particles is 80nm to 350nm, D v 90 can be but is not limited to 80nm, 100nm, 150nm, 200nm, 250nm, 300nm or 350nm. In some embodiments of the present application, the particle size of the lithium manganese iron phosphate primary particles ranges from 10nm to 100nm.

[0039] In the present application, the lithium manganese iron phosphate is a spherical primary nanoparticle. Compared with a secondary particle, the lithium manganese iron phosphate primary particle not only has a shorter lithium ion migration path, but also has a smoother and more flat electrode plate surface, which is beneficial to form a stable electrode plate. In some embodiments of the present application, the sphericity of the lithium manganese iron phosphate primary particle is greater than or equal to 0.7, and in some embodiments, the sphericity of the lithium manganese iron phosphate primary particle is 0.7 to 0.95. The sphericity of the lithium manganese iron phosphate can be but is not limited to 0.7, 0.75, 0.8, 0.85, 0.9 or 0.95. The lithium manganese iron phosphate primary particle of the present application has a high sphericity, which is beneficial to the accumulation of particles, and when the battery positive electrode material is used to prepare an electrode slurry, it helps to improve the fluidity of the electrode slurry and reduce the viscosity of the slurry, thereby promoting the improvement of the flatness and smoothness of the electrode plate surface, so that the electrode plate has good structural stability.

[0040] In the embodiments of the present application, the chemical formula of the lithium manganese iron phosphate is LiMn xFe 1-x M' y PO4, wherein 0.6≤x≤0.95, 0≤y≤0.05, M' is selected from one or more of Mg, Al, Co, Zn, Ti, V, Ni, Cu, LiMn x Fe 1-x M' y The value of x in PO4may be, but is not limited to, 0.6, 0.7, 0.8 or 0.95, and the value of y may be, but is not limited to, 0, 0.01, 0.02, 0.03 or 0.05. Controlling the value of x can ensure that the lithium manganese iron phosphate has high electrical conductivity and high energy density. In the present application, M' is a doping element, and the doping element in the lithium manganese iron phosphate can improve the diffusion channel of lithium ions, shorten the particle size and shorten the ion diffusion path, thereby improving the ion and electron conductivity of the battery anode material.

[0041] In some embodiments of the present application, the lithium manganese iron phosphate primary particles further contain carbon, which can be coated on the surface of the lithium manganese iron phosphate or doped in the interior of the particles. The carbon in the lithium manganese iron phosphate primary particles is beneficial to improving the conductivity of the battery anode material and achieving large-rate charging and discharging. In some embodiments of the present application, the mass percentage of carbon in the battery anode material is 1.0% to 2.5%. The mass percentage of carbon in the battery anode material may be, but is not limited to, 1.0%, 1.3%, 1.5%, 2% or 2.5%.

[0042] In some embodiments of the present application, the compacted density of the battery anode material is 2.0 g / cc to 2.4 g / cc. The compacted density of the battery anode material may be, but is not limited to, 2.0 g / cc, 2.1 g / cc, 2.2 g / cc, 2.3 g / cc or 2.4 g / cc. The battery anode material of the present application has a high compacted density, which is beneficial to improving the energy density of the battery.

[0043] The battery anode material provided by the present application exhibits high specific capacity, good low-temperature performance and good cycle performance. The high specific capacity refers to that the charging specific capacity is greater than or equal to 155 mAh / g and the discharging specific capacity is greater than or equal to 154 mAh / g under the condition of 0.1C charging and discharging at room temperature. The good low-temperature performance refers to that the discharging efficiency (discharging capacity / charging capacity) is greater than or equal to 48% under the condition of discharging at -20℃ / 1C. The good cycle performance refers to that the capacity retention rate is greater than or equal to 96% after 500 cycles at 1C rate. The application of the battery anode material in a battery can effectively improve the cycle performance and rate performance of the battery.

[0044] The present application also provides a preparation method of the battery anode material. Please refer to Figure 1 , Figure 1The preparation method of the battery positive electrode material provided in an embodiment of the present application comprises the following steps:

[0045] Step 100: mixing and grinding manganese iron phosphate, a lithium source, a carbon source and a solvent to obtain a first slurry;

[0046] Step 200: performing aging treatment on the first slurry to obtain a second slurry;

[0047] Step 300: performing drying, sintering and crushing on the second slurry to obtain the battery positive electrode material.

[0048] In step 100 of the present application, the manganese iron phosphate can be prepared by a coprecipitation method. In some embodiments, the preparation method of the manganese iron phosphate comprises: causing a phosphorus source, an iron source and a manganese source to undergo a coprecipitation reaction in a solvent, wherein the phosphorus source comprises a compound containing phosphate ions, and the phosphorus source specifically comprises one or more of phosphoric acid, sodium phosphate, potassium phosphate, lithium dihydrogen phosphate, lithium monohydrogen phosphate, ammonium dihydrogen phosphate and ammonium hydrogen phosphate; the iron source specifically comprises one or more of ferric chloride, ferric nitrate, ferrous oxalate, ferrous sulfate and iron oxide; and the manganese source specifically comprises one or more of manganese hydroxide, manganese carbonate, manganese oxide, manganese sulfate, manganese nitrate and manganese oxalate.

[0049] In some embodiments of the present application, the lithium source comprises inorganic lithium salts and organic lithium salts, wherein the inorganic lithium salts comprise one or more of lithium carbonate, lithium bicarbonate, lithium dihydrogen phosphate, lithium monohydrogen phosphate, lithium phosphate, lithium nitrate, lithium sulfate, lithium chromate and lithium hydroxide, and the organic lithium salts comprise one or more of lithium oxalate, lithium acetate, lithium benzoate, lithium citrate and lithium benzoate. In some embodiments of the present application, the molar ratio of the lithium source to the manganese iron phosphate is (0.95-1.02):1. Specifically but not limitedly, the molar ratio of the lithium source to the manganese iron phosphate can be 0.95:1, 0.98:1, 1:1, 1.01:1 or 1.02:1. Controlling the relative content of the lithium source and the manganese iron phosphate can form stable manganese iron lithium phosphate particles, reduce the probability of forming lithium phosphate due to excessive lithium source content, and improve the cycle stability of the battery positive electrode material.

[0050] In some embodiments of the present application, the solvent comprises one or more of water, methanol, ethanol or N-methyl pyrrolidone. In some embodiments, the mass percentage content of the solvent in the first slurry is 60%-90%. In some embodiments of the present application, the carbon source comprises one or more of glucose, sucrose, water-soluble phenol formaldehyde resin, polyethylene glycol, hydroxymethyl cellulose, polyacrylamide, starch, polyvinyl alcohol, carbon nanotubes or graphene, wherein the graphene can be single-layer graphene or multi-layer graphene. In some embodiments, the mass ratio of the carbon source to the manganese iron phosphate in the first slurry is 0.15-0.25.

[0051] In the present application, the manganese iron phosphate, lithium source, carbon source and solvent are mixed and ground to obtain a first slurry, wherein the grinding includes one or more of ball milling or sand milling, the linear speed of grinding is 5 m / s to 15 m / s, and the grinding time is 0.5 h to 12 h. In some embodiments, the grinding includes coarse grinding and fine grinding performed in sequence, the diameter of the grinding balls used in the coarse grinding is 0.5 mm to 0.6 mm, and the diameter of the grinding balls used in the fine grinding is 0.05 mm to 0.3 mm. In some embodiments of the present application, a certain doping source can be added during the grinding process, and the doping source can be a compound containing one or more of Mg, Al, Co, Zn, Ti, V, Ni, and Cu.

[0052] In the preparation method of the electrode material of the present application, the manganese iron phosphate, lithium source, carbon source and solvent are first mixed and ground, and then aged. During the mixing and grinding process, the defects of the particles increase and the surface activity of the particles is enhanced, so that the lithium source and the carbon source can be fully mixed with the manganese iron phosphate and form stable lithium manganese iron phosphate. During the aging process, the fine nanoparticles grow by aggregation, and the crystal lattice of the lithium manganese iron phosphate is continuously optimized. This method can make the structure of the particles more uniform and complete, and tend to be spherical structure, which is beneficial to shorten the lithium ion transmission path and improve the capacity and low temperature performance of the material. In the embodiments of the present application, the viscosity of the first slurry obtained after the manganese iron phosphate, lithium source, carbon source and solvent are mixed and ground is 200 cp to 500 cp, and the D v 50 of the particles in the first slurry is 0.2 pm to 0.5 pm. In the present application, the D v 50 of the particles in the first slurry is 0.2 pm to 0.5 pm. In the present application, the D v 50 of the particles in the first slurry is 0.2 pm to 0.5 pm. In the present application, the D v 50 of the particles in the first slurry is 0.2 pm to 0.5 pm. In the present application, the D

[0053] In step 200 of the present application, the first slurry is aged to obtain a second slurry. During the aging process, each component in the slurry can fully react, so that the irregular particle morphology after grinding is reshaped, the surface defects are continuously improved, and relatively stable lithium manganese iron phosphate particles are formed. At the same time, the viscosity of the slurry will also be reduced. In some embodiments of the present application, the aging treatment adopts high-temperature aging, the temperature of the aging treatment is 50-90°C, and the temperature of the aging treatment can be but is not limited to 50°C, 60°C, 70°C, 80°C or 90°C. The time of the aging treatment is 0.5-3h, and the time of the aging treatment can be but is not limited to 0.5h, 1h, 1.5h, 2h or 3h. Controlling the temperature and time of the aging treatment can promote the primary particle morphology to be more spherical (spherical structure is the most stable, and the surface energy is the smallest), thereby obtaining lithium manganese iron phosphate particles with relatively regular morphology. In the embodiments of the present application, the viscosity of the second slurry is 100-300cp. When the viscosity of the second slurry is 100-300cp, it indicates that the particles in the slurry are relatively stable. In some embodiments of the present application, the ratio of the viscosity of the first slurry to the viscosity of the second slurry is 1:(0.4-0.7). In some embodiments of the present application, the D v 50 of the secondary particles in the second slurry is 1-10μm. It should be noted that in the second slurry obtained after aging, the D v 50 of the secondary particles refers to the D v 50 of the secondary particle agglomerates, which can be obtained by Malvern laser particle size testing.

[0054] In step 300 of the present application, the second slurry is dried, sintered and crushed to obtain a battery positive electrode material. The drying temperature is 90-100°C, and the drying method can be one or more of oven drying, belt drying or spray drying. In some embodiments of the present application, the sintering temperature is 650-760°C, and the sintering time is 5-10h. In some embodiments of the present application, the sintering is carried out in an inert atmosphere, and the inert atmosphere includes one or more of nitrogen, argon, helium, neon, krypton, xenon and radon. In some embodiments, the inert gas includes one or more of nitrogen and argon.

[0055] In the embodiments of the present application, the product particles obtained after drying and sintering of the second slurry are secondary particles, and therefore the product needs to be crushed to obtain primary particles. In some embodiments of the present application, the crushing includes one or more of jet milling, mortar grinding or roll processing. In some embodiments, the product is processed by jet milling, the principle of which is that by applying a certain pressure of gas flow, the particles collide with each other, so that the secondary particles composed of primary particles become well-dispersed primary particles. The pressure of jet milling is 0.5 MPa to 1 MPa, and the pressure of jet milling can be specifically but not limited to 0.5 MPa, 0.6 MPa, 0.8 MPa or 1 MPa. Controlling the pressure of jet milling can make the primary particles fully dispersed, and the original morphology and structure of the primary particles are not easily damaged, and have good stability.

[0056] In some embodiments of the present application, the method for preparing the battery cathode material includes:

[0057] Step 100: preparing a manganese iron phosphate precursor by a coprecipitation method;

[0058] Step 200: mixing and grinding the manganese iron phosphate precursor, a lithium source, a carbon source and a solvent to obtain a first slurry;

[0059] Step 300: performing aging treatment on the first slurry to obtain a second slurry;

[0060] Step 400: performing drying treatment on the second slurry to obtain a precursor dry powder;

[0061] Step 500: sintering the precursor dry powder in a box furnace, and obtaining a battery cathode material after coarse crushing, sieving and air crushing.

[0062] The method for preparing the battery cathode material provided in the present application is simple and has strong operability. The lithium manganese iron phosphate particles prepared by the method present a spherical primary nanoparticle morphology feature, have small nanoparticle size, good dispersion uniformity and short lithium ion diffusion path, and when used as a lithium ion battery cathode material, the method is beneficial to improving the battery capacity and the battery has excellent low-temperature performance and cycle performance.

[0063] The application also provides a positive electrode sheet, which comprises a current collector and a positive material layer arranged on the current collector, wherein the positive material layer comprises the battery positive material of the application. In the embodiments of the application, the positive material layer can be prepared by mixing the battery positive material, a conductive agent, a binder and a solvent to form a positive electrode slurry, and then coating and drying the positive electrode slurry to obtain the positive material layer. When preparing the positive electrode slurry, the binder can be mixed with the solvent first, and then the conductive agent is added after sufficient stirring, and then the battery positive material is added after stirring, and the positive electrode slurry is obtained after sieving. The conductive agent, the binder and the solvent are conventional choices in the field of batteries. For example, the binder can be selected from one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), styrene butadiene rubber (SBR), polyacrylonitrile (PAN), polyimide (PI), polyacrylic acid (PAA), polyacrylate, polyolefin, sodium carboxymethyl cellulose (CMC) and sodium alginate. The conductive agent can be selected from one or more of carbon nanotubes, carbon black and graphene.

[0064] The application also provides a secondary battery, which comprises a positive electrode, a negative electrode, an electrolyte and a separator between the positive electrode and the negative electrode, wherein the positive electrode comprises the positive electrode sheet provided by the application.

[0065] In the application, the negative electrode of the secondary battery can be any negative electrode known in the art. In the embodiments of the application, the negative electrode can comprise one or more of a carbon-based negative electrode, a silicon-based negative electrode, a tin-based negative electrode and a lithium negative electrode. The carbon-based negative electrode can comprise graphite, hard carbon, soft carbon, graphene, etc.; the silicon-based negative electrode can comprise silicon, silicon-carbon, silicon-oxygen, silicon-metal compounds, etc.; the tin-based negative electrode can comprise tin, tin-carbon, tin-oxygen, tin-metal compounds; and the lithium negative electrode can comprise metallic lithium or a lithium alloy. The lithium alloy can be at least one of a lithium-silicon alloy, a lithium-sodium alloy, a lithium-potassium alloy, a lithium-aluminum alloy, a lithium-tin alloy and a lithium-indium alloy. In some embodiments of the application, the current collector of the negative electrode is a copper foil, the negative electrode active material comprises one or more of natural graphite, artificial graphite, hard carbon, soft carbon, lithium titanate, iron oxide, lithium titanium phosphate, titanium dioxide, silicon, silicon monoxide, tin and antimony; the binder comprises one or more of polyacrylic acid (PAA), polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR); and the conductive agent comprises one or more of acetylene black, ketjen black, Super-P, carbon nanotubes, carbon nanofibers, activated carbon and graphene. In the application, the negative electrode can be prepared by any method known in the art.

[0066] In the application, the separator of the secondary battery can be any separator known to those skilled in the art, for example, the separator can be one or more of a polyolefin microporous membrane, polyethylene terephthalate, polyethylene felt, glass fiber felt or ultra-fine glass fiber paper.

[0067] In the present application, the electrolyte of the secondary battery includes a solution of electrolyte lithium salt in a non-aqueous solvent. In the embodiments of the present application, the electrolyte lithium salt includes one or more of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium hexafluorosilicate (LiSiF6), lithium tetraphenylborate (LiB(C6H5)4), lithium chloride (LiCl), lithium bromide (LiBr), lithium chloroaluminate (LiAlCl4), lithium fluorohydrocarbylsulfonate (LiC(SO2CF3)3), LiCH3SO3, LiN(SO2CF3)2, and LiN(SO2C2F5)2. In some embodiments of the present application, the non-aqueous solvent includes one or more of chain acid esters and cyclic acid esters. In some embodiments of the present application, the chain acid esters include one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), methylpropyl carbonate (MPC), and dipropyl carbonate (DPC). In some embodiments of the present application, the chain acid esters include fluorine-containing, sulfur-containing, or unsaturated bond-containing chain organic esters. In some embodiments of the present application, the cyclic acid esters include one or more of ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate (VC), γ-butyrolactone (γ-BL), and sulfolactone. In some embodiments of the present application, the cyclic acid esters include fluorine-containing, sulfur-containing, or unsaturated bond-containing cyclic organic esters. In some embodiments of the present application, the non-aqueous solvent includes one or more of chain ether and cyclic ether solutions. In some embodiments of the present application, the cyclic ether includes one or more of tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF), 1,3-dioxolane (DOL), and 4-methyl-1,3-dioxolane (4-MeDOL). In some embodiments of the present application, the cyclic ether includes fluorine-containing, sulfur-containing, or unsaturated bond-containing cyclic organic ethers. In some embodiments of the present application, the chain ether includes one or more of dimethoxymethane (DMM), 1,2-dimethoxyethane (DME), 1,2-dimethoxypropane (DMP), and diethylene glycol dimethyl ether (DG). In some embodiments of the present application, the chain ether includes fluorine-containing, sulfur-containing, or unsaturated bond-containing chain organic ethers. In the embodiments of the present application, the concentration of the electrolyte lithium salt in the electrolyte is 0.1 mol / L-15 mol / L. In some embodiments of the present application, the concentration of the electrolyte lithium salt is 1 mol / L-10 mol / L.

[0068] In the embodiments of the present application, the preparation of the battery can use any one of the lamination process or the winding process. In some embodiments of the present application, the battery is prepared using the lamination process.

[0069] The secondary battery provided in the present application has good cycle performance and rate performance due to the use of the battery positive electrode sheet of the present application.

[0070] The technical solutions of the present application are further described below in multiple embodiments.

[0071] Embodiment 1

[0072] Iron nitrate, manganese sulfate and sodium phosphate were mixed in a molar ratio of 0.35:0.65:1 and added to water. After stirring to uniformity, the manganese iron phosphate precursor was obtained by filtration and drying. The manganese iron phosphate precursor, lithium carbonate and glucose were added to water (the molar ratio of lithium source to manganese iron phosphate precursor was 1, and the mass ratio of glucose to manganese iron phosphate precursor was 0.18), and after uniform dispersion, the slurry was added to a coarse grinding device through a diaphragm pump for coarse grinding. The particle size of the zirconium balls used for coarse grinding was 0.6 mm. After coarse grinding for 30 min, the slurry was poured into a fine grinding sand mill. The particle size of the zirconium balls used for fine grinding was 0.1 mm. The sand grinding was carried out at a linear speed of 10 m / s for 2 h to obtain a first slurry. The D50 particle size of the first slurry was 0.35 μm, and the viscosity of the first slurry was 320 cp. Then the first slurry was poured into an aging container, and the second slurry was obtained after aging at 60°C for 1 h. The D50 particle size of the second slurry was 3.6 μm, and the viscosity of the second slurry was 160 cp. The dry powder was obtained by spray drying the second slurry. The battery anode material was obtained by calcining the dry powder at 720°C for 10 h, followed by coarse grinding, sieving and air crushing. The pressure of the air crushing was 0.7 MPa. v v

[0073] Embodiment 2

[0074] Embodiment 2 differed from embodiment 1 in that iron nitrate, manganese sulfate and sodium phosphate were mixed in a molar ratio of 0.3:0.7:1 and added to methanol. The manganese iron phosphate precursor was obtained by co-precipitation, filtration and drying. The battery anode material was prepared by the same method as in embodiment 1.

[0075] Embodiment 3

[0076] Embodiment 3 used the same method as embodiment 1 to obtain a first slurry. The D50 particle size of the first slurry was 0.35 μm, and the viscosity of the first slurry was 320 cp. The difference was that the first slurry was poured into an aging container, and a second slurry was obtained after aging at 100°C for 1 h. The D50 particle size of the second slurry was 15 μm, and the viscosity of the second slurry was 128 cp. v v The dry powder was obtained by spray drying the second slurry. The battery anode material was obtained by calcining the dry powder at 720°C for 10 h, followed by coarse grinding, sieving and air crushing. The pressure of the air crushing was 0.7 MPa.

[0077] Embodiment 4

[0078] ​​​Example 4 v 50 was 0.35 μm, and the viscosity of the first slurry was 320 cp. The difference was that the first slurry was pumped into an aging vessel, and a second slurry was obtained after aging at 25 °C for 1 h. The D50 of the particles in the second slurry was 0.8 μm, and the viscosity of the second slurry was 245 cp. The second slurry was spray-dried to obtain a dry powder. The dry powder was calcined at 720 °C for 10 h, and then coarsely ground, sieved, and air-attacked to obtain a battery cathode material. The air-attacking was performed at a pressure of 0.7 MPa. v 50 was 0.35 μm, and the viscosity of the first slurry was 320 cp. The difference was that the first slurry was pumped into an aging vessel, and a second slurry was obtained after aging at 25 °C for 1 h. The D50 of the particles in the second slurry was 0.8 μm, and the viscosity of the second slurry was 245 cp. The second slurry was spray-dried to obtain a dry powder. The dry powder was calcined at 720 °C for 10 h, and then coarsely ground, sieved, and air-attacked to obtain a battery cathode material. The air-attacking was performed at a pressure of 0.7 MPa.

[0079] Example 5

[0080] Example 5 was performed in the same manner as Example 1 to obtain a manganese iron phosphate precursor. The manganese iron phosphate precursor, a lithium source, and glucose were added to water (the molar ratio of the lithium source to the manganese iron phosphate precursor was 1, and the mass ratio of the glucose to the manganese iron phosphate precursor was 0.18). After being uniformly dispersed, the mixture was pumped into a coarse grinding device for coarse grinding. Zirconium balls with a particle size of 0.6 mm were used for the coarse grinding. After coarse grinding for 30 min, the slurry was pumped into a fine grinding sand mill. Zirconium balls with a particle size of 0.1 mm were used for the fine grinding. The slurry was sand ground at a linear speed of 10 m / s for 0.5 h to obtain a first slurry. The D50 of the particles in the first slurry was 1 μm, and the viscosity of the first slurry was 230 cp. Then, the first slurry was pumped into an aging vessel, and a second slurry was obtained after aging at 60 °C for 1 h. The D50 of the particles in the second slurry was 8.5 μm, and the viscosity of the second slurry was 156 cp. The second slurry was spray-dried to obtain a dry powder. The dry powder was calcined at 720 °C for 10 h, and then coarsely ground, sieved, and air-attacked to obtain a battery cathode material. The air-attacking was performed at a pressure of 0.7 MPa. v 50 was 0.35 μm, and the viscosity of the first slurry was 320 cp. The difference was that the first slurry was pumped into an aging vessel, and a second slurry was obtained after aging at 25 °C for 1 h. The D50 of the particles in the second slurry was 0.8 μm, and the viscosity of the second slurry was 245 cp. The second slurry was spray-dried to obtain a dry powder. The dry powder was calcined at 720 °C for 10 h, and then coarsely ground, sieved, and air-attacked to obtain a battery cathode material. The air-attacking was performed at a pressure of 0.7 MPa. v 50 was 0.35 μm, and the viscosity of the first slurry was 320 cp. The difference was that the first slurry was pumped into an aging vessel, and a second slurry was obtained after aging at 25 °C for 1 h. The D50 of the particles in the second slurry was 0.8 μm, and the viscosity of the second slurry was 245 cp. The second slurry was spray-dried to obtain a dry powder. The dry powder was calcined at 720 °C for 10 h, and then coarsely ground, sieved, and air-attacked to obtain a battery cathode material. The air-attacking was performed at a pressure of 0.7 MPa.

[0081] Example 6

[0082] Example 6 was performed in the same manner as Example 1 to obtain a manganese iron phosphate precursor. The manganese iron phosphate precursor, a lithium source, and glucose were added to water (the molar ratio of the lithium source to the manganese iron phosphate precursor was 1, and the mass ratio of the glucose to the manganese iron phosphate precursor was 0.18). After being uniformly dispersed, the mixture was pumped into a coarse grinding device for coarse grinding. Zirconium balls with a particle size of 0.6 mm were used for the coarse grinding. After coarse grinding for 30 min, the slurry was pumped into a fine grinding sand mill. Zirconium balls with a particle size of 0.1 mm were used for the fine grinding. The slurry was sand ground at a linear speed of 10 m / s for 0.5 h to obtain a first slurry. The D50 of the particles in the first slurry was 1 μm, and the viscosity of the first slurry was 230 cp. Then, the first slurry was pumped into an aging vessel, and a second slurry was obtained after aging at 60 °C for 1 h. The D50 of the particles in the second slurry was 8.5 μm, and the viscosity of the second slurry was 156 cp. The second slurry was spray-dried to obtain a dry powder. The dry powder was calcined at 720 °C for 10 h, and then coarsely ground, sieved, and air-attacked to obtain a battery cathode material. The air-attacking was performed at a pressure of 0.7 MPa. v 50 was 0.35 μm, and the viscosity of the first slurry was 320 cp. The difference was that the first slurry was pumped into an aging vessel, and a second slurry was obtained after aging at 25 °C for 1 h. The D50 of the particles in the second slurry was 0.8 μm, and the viscosity of the second slurry was 245 cp. The second slurry was spray-dried to obtain a dry powder. The dry powder was calcined at 720 °C for 10 h, and then coarsely ground, sieved, and air-attacked to obtain a battery cathode material. The air-attacking was performed at a pressure of 0.7 MPa. vThe particle size of the second slurry was 11.5 μm, and the viscosity of the second slurry was 235 cp. The second slurry was spray-dried to obtain a dry powder, which was calcined at 720°C for 10 hours, and then coarsely ground, sieved, and gas-crushed to obtain the battery positive electrode material. The gas-crushing pressure was 0.7 MPa.

[0083] Example 7

[0084] In Example 7, a second slurry was prepared by the same method as in Example 1. The second slurry was spray-dried to obtain a dry powder. The dry powder was calcined at 720°C for 10 hours and then coarsely ground, sieved and gas-crushed to obtain a battery positive electrode material. The pressure of the gas-crushing treatment was 0.2 MPa.

[0085] Example 8

[0086] The difference between Example 8 and Example 1 is that ferric nitrate, manganese sulfate, and sodium phosphate are mixed in a molar ratio of 0.3:0.7:1 and added to methanol, and a ferromanganese phosphate precursor is obtained after coprecipitation, filtration, and drying. The ferromanganese phosphate precursor, a lithium source, glucose, and magnesium carbonate are added to water (the molar ratio of the lithium source to the ferromanganese phosphate precursor is 1, the mass ratio of glucose to the ferromanganese phosphate precursor is 0.18, and the mass ratio of the doping source to the ferromanganese phosphate precursor is 1.2%), and the battery positive electrode material is prepared by the same method as in Example 1.

[0087] Comparative Example 1

[0088] Comparative Example 1: The first slurry was obtained by the same method as in Example 1. The D of the particles in the first slurry was v The particle size of the first slurry is 0.35 μm, and the viscosity of the first slurry is 320 cp. The difference is that the first slurry is not aged, but directly spray-dried to obtain a dry powder. The dry powder is calcined at 720°C for 10 hours, and then coarsely ground, sieved, and gas-crushed to obtain the battery positive electrode material. The gas-crushing pressure is 0.7 MPa.

[0089] Comparative Example 2

[0090] Iron nitrate, manganese sulfate and sodium phosphate were mixed in a molar ratio of 0.35:0.65:1 and added to water, and after stirring to homogeneity, co-precipitation was performed to obtain a manganese iron phosphate precursor. The manganese iron phosphate precursor was aged at 60°C for 1 h, and then filtered and dried to obtain the manganese iron phosphate precursor. The manganese iron phosphate precursor was added to water with a lithium source and glucose (the molar ratio of the lithium source to the manganese iron phosphate precursor was 1, and the mass ratio of the glucose to the manganese iron phosphate precursor was 0.18), and after being uniformly dispersed, the mixture was added to a coarse grinding device by a diaphragm pump for coarse grinding. The coarse grinding used zirconium balls with a particle size of 0.6 mm, and after coarse grinding for 30 min, the slurry was poured into a fine grinding sand mill. Fine grinding used zirconium balls with a particle size of 0.1 mm, and sand grinding was performed at a linear speed of 10 m / s for 2 h to obtain a slurry. The D v 50 of the particles in the slurry was 0.35 μm. After spray drying, a dry powder was obtained. The dry powder was calcined at 720°C for 10 h, and then subjected to coarse grinding, sieving and air crushing to obtain a battery positive electrode material. The air crushing was performed at a pressure of 0.7 MPa.

[0091] Effect implementation examples

[0092] To verify the performance of the battery positive electrode material prepared in the present application, effect implementation examples are also provided.

[0093] 1) The particle size analyzer was used to characterize the electrode positive electrode materials of Examples 1-8 and Comparative Examples 1-2, and the particle size distribution of the particles in the electrode positive electrode materials of Examples 1-8 and Comparative Examples 1-2 was obtained. The D v 10 of the particles in the electrode positive electrode materials of Examples 1-8 and Comparative Examples 1-2 was calculated, and the D v 50 of the particles in the electrode positive electrode materials of Examples 1-8 and Comparative Examples 1-2 was calculated. v 90 of the particles in the electrode positive electrode materials of Examples 1-8 and Comparative Examples 1-2 was calculated, and the particle size distribution dispersion degree of the battery positive electrode material was calculated, where the particle size distribution dispersion degree = (D v 90-D v 10) / D v 50. The relevant experimental results are summarized in Table 1.

[0094] 2) The scanning electron microscope was used to characterize the morphology of the electrode positive electrode materials of Examples 1-8 and Comparative Examples 1-2. Please refer to Figure 2 and Figure 3 , Figure 2 which are scanning electron microscope images of the electrode positive electrode material provided in Example 1 of the present application, Figure 3 which is a scanning electron microscope image of the electrode positive electrode material provided in Example 2 of the present application. The short side and long side of the primary nanoparticles in the SEM image were measured using the Smile view software, and the ratio of the short side diameter to the long side diameter was calculated and counted. This ratio is the sphericity of the electrode positive electrode material. The size of all primary particles was counted by the Smile view software to obtain the particle size distribution graph of the lithium manganese iron phosphate primary particles, and further to obtain the D v 10 of the lithium manganese iron phosphate primary particles. v50 and D v 90, and the particle size distribution dispersion of the electrode positive material was calculated, and the experimental results were summarized in Table 1.

[0095] Table 1 Structure information table of electrode positive material of each example and comparative example

[0096] Experimental Group Sphericity D v 50]]> D v 10]]> D v 90]]> Particle size distribution dispersity Example 1 0.86 45 15 82.5 1.5 Example 2 0.81 41 12 85.8 1.8 Example 3 0.65 62 20 243.2 3.6 Example 4 0.72 61 18 170.5 2.5 Example 5 0.52 70 19 306 3.9 Example 6 0.78 55 15 142 2.4 Example 7 0.80 45 15 102.5 1.94 Example 8 0.89 42 13 75 1.48 Comparative Example 1 0.48 90 18 423 4.5 Comparative Example 2 0.50 88 18 396.4 4.3

[0097] As can be seen from Table 1, the lithium manganese iron phosphate precursor, lithium source and carbon source are ground together and then aged in the preparation method of the embodiments of the present application, and the particle morphology in the electrode positive material obtained after drying, sintering and crushing of the obtained slurry is more regular and the size is smaller, the particle sphericity is higher and the particle size distribution is narrower, which shows that the method can effectively improve the uniformity of the particles in the electrode positive material and obtain small size lithium manganese iron phosphate particles. In the preparation method of Example 3, the temperature of the aging is too high, the particle agglomeration is serious, the sphericity is reduced, and the particle size distribution is widened; in the preparation method of Example 4, the temperature of the aging is too low, the aging effect is not obvious, the sphericity is reduced, and the particle size distribution is wider; in the preparation method of Example 5, the grinding time of the mixture is shorter, the D v 50 of the particles in the obtained first slurry is larger, the surface activity of the primary particles is not high during aging, and the subsequent aging process is not good; in the preparation method of Example 6, the grinding time of the mixture is longer, the D v 50 of the particles in the obtained first slurry is smaller, the primary particles agglomerate seriously during aging, which causes subsequent agglomeration and growth, the sphericity is reduced, and the particle size distribution is widened; in the preparation method of Example 7, the pressure of the gas crushing is smaller, the secondary particles in the product after calcination cannot be fully dispersed into primary particles, the particle size is larger, and the particle size distribution dispersion is also larger.

[0098] 3) The electrode positive materials of Examples 1-8 and Comparative Examples 1-2 were mixed with a conductive agent and a binder, wherein the mass ratio of the electrode positive material, the conductive agent and the binder was 100:2:3, and after being uniformly mixed, drying was performed, then grinding was performed, and then a round sheet was pressed under 15 MPa, the thickness of the round sheet at three different positions was tested using a thickness gauge, the average value was taken, and finally the powder compaction density was obtained by dividing the mass of the round sheet by the volume of the round sheet, and the experimental results were summarized in Table 2.

[0099] Table 2 Compaction density table of electrode positive materials of Examples 1-8 and Comparative Examples 1-2

[0100] Experimental Group Compacted density g / cc Example 1 2.25 Example 2 2.28 Example 3 2.12 Example 4 2.16 Example 5 2.30 Example 6 2.14 Example 7 2.28 Example 8 2.18 Comparative Example 1 2.32 Comparative Example 2 2.29

[0101] 4) The electrode positive materials of Examples 1-8 and Comparative Examples 1-2 were used to prepare batteries by the following method: the prepared battery positive materials were dispersed in N-methyl pyrrolidone with a conductive agent and a binder in a mass ratio of 100:2:3 to obtain a positive electrode slurry, wherein the conductive agent was conductive carbon black and the binder was PVDF, the positive electrode slurry was coated on the surface of an aluminum foil, and after drying, rolling was performed to obtain an electrode positive electrode; the above prepared battery positive electrode, lithium negative electrode and polyolefin microporous membrane separator were wound to form a half battery, and after packaging, 1 mol / L lithium hexafluorophosphate electrolyte (solvent: 1:1 EC:EMC) was injected to obtain a battery.

[0102] The batteries of each example and comparative example were subjected to charge-discharge capacity retention rate testing, and the capacity retention rate testing conditions were as follows: the battery was charged to 4.3V at 0.1C rate CC-CV, the cutoff current was 0.02C, then discharged to 2.0V at 0.1C rate CC, and the charge capacity and discharge capacity were recorded. The test results are shown in Table 3.

[0103] Table 3 Charge-discharge capacity retention rate of batteries of Examples 1-8 and Comparative Examples 1-2

[0104]

[0105] As can be seen from Table 3, the batteries prepared using the battery positive materials of the examples of the present application have higher charge specific capacity and discharge specific capacity than the batteries of the comparative examples, which indicates that the battery positive materials of the structure of the present application can better develop capacity. For each example, the battery positive materials of Example 3 and Example 5 have lower sphericity and higher particle size distribution dispersion, the battery positive material of Example 4 has a larger particle size, and its electronic conductivity and lithium ion diffusion rate are relatively low, and the material performance is reduced, the battery positive materials of Example 6 and Example 7 have lower sphericity than Example 1 and higher particle size distribution dispersion, and their charge-discharge capacity is also lower than that of Example 1.

[0106] The batteries of each example and comparative example were subjected to charge-discharge capacity retention rate testing under low temperature conditions, and the low temperature capacity retention rate testing conditions were as follows: the battery was charged to 3.8V at room temperature at 0.1C rate, then cut off at 3.8V when the current was 0.1C, then discharged to 2.5V at 0.1C, then cycled again, then charged to 3.8V at 0.5C rate, then cut off at 3.8V when the current was 0.1C, and then discharged to 2.0V at 1C rate in a refrigerator at -20°C. The ratio of the discharge capacity at -20°C to the charge capacity at room temperature at 0.5C was the low temperature capacity retention rate of the battery, and the test results are shown in Table 4.

[0107] Table 4 Low temperature capacity retention rate of batteries of Examples 1-8 and Comparative Examples 1-2

[0108] Experimental Group -20 °C capacity retention (%) Example 1 62 Example 2 65 Example 3 51 Example 4 49 Example 5 48 Example 6 55 Example 7 60 Example 8 63 Comparative Example 1 36 Comparative Example 2 35

[0109] As can be seen from Table 4, the batteries prepared by using the battery positive electrode materials of the embodiments of the present application have better low-temperature performance than the batteries of the comparative examples. For each embodiment, the battery positive electrode material of Example 3 and Example 5 has lower sphericity and higher particle size distribution dispersion, the battery positive electrode material of Example 4 has larger particle size, and the electronic conductivity and lithium ion diffusion rate thereof are relatively low, and the material performance is reduced, the battery positive electrode material of Example 6 and Example 7 has lower sphericity than that of Example 1, and the particle size distribution dispersion is higher, and the low-temperature capacity retention rate thereof is also lower than that of Example 1.

[0110] The batteries of each embodiment and comparative example are subjected to cycle performance test, and the cycle performance test conditions are as follows: the batteries are subjected to 500 times of charge-discharge cycles at 1C rate at normal temperature, and the ratio of the capacity of the 500th cycle to that of the 1st cycle is the cycle capacity retention rate of the battery, and the test results are shown in Table 5.

[0111] Table 5 Cycle performance table of batteries of Examples 1-8 and Comparative Examples 1-2

[0112]

[0113] As can be seen from Table 5, the batteries prepared by using the battery positive electrode materials of the embodiments of the present application have better cycle performance than the batteries of the comparative examples. For each embodiment, the battery positive electrode material of Example 3 and Example 5 has lower sphericity and higher particle size distribution dispersion, the battery positive electrode material of Example 4 has larger particle size, and the electronic conductivity and lithium ion diffusion rate thereof are relatively low, and the material performance is reduced, the battery positive electrode material of Example 6 and Example 7 has lower sphericity than that of Example 1, and the particle size distribution dispersion is higher, and the capacity retention rate after cycle thereof is also lower than that of Example 1.

[0114] The above describes the preferred embodiments of the present application, but it should not be understood as a limitation on the scope of the present application. It should be noted that, for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements are also considered as the protection scope of the present application.

Claims

1. A battery positive electrode material, characterized in that The lithium manganese iron phosphate primary particles have a particle size distribution dispersion of 1 to 4, wherein the particle size distribution dispersion = (D v 90-D v 10) / D v 50, D v 10. D v 50. D v 90 represent the particle sizes corresponding to the cumulative volume distribution percentages of the lithium manganese iron phosphate primary particles reaching 10%, 50%, and 90%, respectively, and the unit is nm.

2. The battery positive electrode material according to claim 1, wherein The D of the lithium manganese iron phosphate primary particles v 50 is 30nm~60nm.

3. The battery positive electrode material according to claim 1 or 2, characterized in that The sphericity of the lithium manganese iron phosphate primary particles is greater than or equal to 0.

7.

4. The battery positive electrode material according to claim 1, wherein The lithium iron manganese phosphate primary particles further include doping ions, and the doping ions are selected from one or more of Mg, Al, Co, Zn, Ti, V, Ni, and Cu.

5. The battery positive electrode material according to claim 1, wherein The compaction density of the battery positive electrode material is 2.0 g / cc to 2.4 g / cc.

6. A method for preparing a positive electrode material for a battery, characterized in that: include: Ferromanganese phosphate, a lithium source, a carbon source and a solvent are mixed and ground to obtain a first slurry, the first slurry is aged to obtain a second slurry, and the second slurry is dried, sintered and crushed to obtain the battery positive electrode material according to any one of claims 1 to 5.

7. The method for preparing a positive electrode material for a battery according to claim 6, wherein: The D of the particles in the first slurry v 50 is 0.2μm~0.5μm; D of the particles in the second slurry v 50 is 1μm~10μm.

8. The method for preparing a positive electrode material for a battery according to claim 6 or 7, wherein: The viscosity of the first slurry is 200 cp~500 cp; the viscosity of the second slurry is 100 cp~300 cp.

9. The method for preparing a positive electrode material for a battery according to claim 6, wherein: The temperature of the aging treatment is 50° C. to 90° C., and the time of the aging treatment is 0.5 h to 3 h.

10. The method for preparing a positive electrode material for a battery according to claim 6, wherein: The crushing includes air flow crushing, and the pressure of the air flow crushing is 0.5Mpa~1Mpa.

11. A positive electrode plate, characterized in that: It comprises a current collector and a positive electrode material layer arranged on the current collector, wherein the positive electrode material layer comprises the battery positive electrode material according to any one of claims 1 to 5, or the positive electrode material layer comprises the battery positive electrode material prepared by the preparation method of the battery positive electrode material according to any one of claims 6 to 10.

12. A secondary battery, characterized in that: The invention comprises a positive electrode, a negative electrode, a separator and an electrolyte, wherein the positive electrode comprises the positive electrode sheet as claimed in claim 11.

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