Preparation method for positive electrode material, positive electrode material, positive electrode sheet, battery, and electric device

Abstract

A preparation method for a positive electrode material, a positive electrode material, a positive electrode sheet, a battery, and an electric device. The method comprises: mixing a precursor material, a lithium source, and an optional phosphorus source, and sintering to obtain an intermediate product, wherein the precursor material comprises a compound MnxFeyM(1-x-y)HPO4·nH2O, 0.9≤x+y<1, 0<x≤0.9, 0<y≤0.9, 0≤n≤6, and M comprises one or more of transition metal elements except manganese and iron elements, group IIA metal elements, group IIIA metal elements, and group IVA metal elements; and mixing the intermediate product, a carbon source, and a solvent, drying, and sintering to obtain the positive electrode material. The positive electrode material has uniform elemental distribution, good material stability, high compaction density, low powder resistivity, and good electron conductivity, improving the specific capacity and cycle performance of the battery.

Description

Preparation method of positive electrode material, positive electrode material, positive electrode sheet, battery and electrical device

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application No. 202311638192.4 filed on December 1, 2023, entitled “Method for preparing positive electrode material, positive electrode material, positive electrode sheet, battery and electrical device,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates to the technical field of lithium batteries, and in particular to a method for preparing a positive electrode material, a positive electrode material, a positive electrode sheet, a battery, and an electrical device. Background Art

[0004] In recent years, the application of secondary batteries has become increasingly widespread. They are widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power stations, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. As secondary batteries have achieved great development, higher requirements have been placed on their energy density, cycle performance, and safety performance.

[0005] Summary of the Invention

[0006] This application is made in light of the above-mentioned problems and aims to provide a method for preparing a positive electrode material, a positive electrode material, a positive electrode sheet, a battery, and an electrical device. The positive electrode material of this application has uniform element distribution, good material stability, high compaction density, low powder resistivity, and good electronic conductivity, thereby improving the specific capacity and cycle performance of the battery.

[0007] In order to achieve the above-mentioned object, the first aspect of the present application provides a method for preparing a positive electrode material, comprising the following steps:

[0008] The precursor material, lithium source and optional phosphorus source are mixed and sintered to obtain a pre-product; wherein the precursor material includes compound Mn x Fe y M (1-x-y) HPO4·nH2O; wherein 0.9≤x+y<1, 0<x≤0.9, 0<y≤0.9, 0≤n≤6; said M comprises one or more of transition metal elements other than manganese and iron, Group IIA metal elements, Group IIIA metal elements, and Group IVA metal elements;

[0009] The pre-product, carbon source and solvent are mixed, dried and sintered to obtain a positive electrode material.

[0010] Thus, the distribution of manganese, iron, phosphorus, and doping elements in the precursor material used in this application is uniform, the composition is stable, and element segregation is not prone to occur. Using the precursor material as a raw material can improve the element distribution uniformity and material stability of the positive electrode material, thereby improving the specific capacity and cycle performance of the battery. In addition, in the step of preparing the pre-product, after sintering, the burnable substance has volatilized to obtain a dense pre-product, and then a coating layer is prepared on the pre-product, which is beneficial to improving the density of the coating layer, reducing the micropores on the coating layer, increasing the compaction density of the material, and reducing the powder resistivity of the material, thereby further improving the specific capacity and cycle performance of the battery. At the same time, the improvement of the density of the coating layer is conducive to controlling the specific surface area of ​​the material from being too large to improve the processing performance of the material.

[0011] In any embodiment, the positive electrode material includes a core and a coating layer covering the core; the core includes a compound LiMn x Fe y M (1-x-y) PO4; wherein, 0.9≤x+y<1, 0<x≤0.9, 0<y≤0.9; the M comprises one or more of transition metal elements other than manganese and iron, Group IIA metal elements, Group IIIA metal elements, and Group IVA metal elements; the coating layer comprises carbon.

[0012] In any embodiment, 0.992≤x+y<0.995; and / or,

[0013] 0.513≤x≤0.658; and / or,

[0014] 0.336≤y≤0.479; and / or,

[0015] 0≤n≤1; and / or,

[0016] The M includes one or more elements selected from titanium, magnesium, aluminum, vanadium, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, and europium.

[0017] In any embodiment, the Dv50 particle size of the precursor material is 3-100 μm, optionally 5-50 μm, more optionally 8-20 μm; and / or,

[0018] The precursor material has a compaction density of 1.35-2.5 g / cm at 30 MPa. 3 , optional 1.5-2.5g / cm 3 and / or,

[0019] The compound Mn in the precursor material x Fe y M (1-x-y)The mass content of HPO4·nH2O is 98%-100%; and / or,

[0020] The precursor material includes primary crystal particles having a polyhedral morphology.

[0021] The Dv50 particle size of the precursor material of the present application is within the above-mentioned range. On the one hand, it is beneficial to the washing and filtering operations during the precursor preparation process, thereby improving the yield of the precursor material. On the other hand, when preparing the positive electrode material, it is beneficial to the suspension of the precursor particles and is not easy to settle, thereby improving the efficiency of the mixing and grinding processes.

[0022] The compaction density of the precursor material of the present application is within the above range, which is beneficial to increasing the compaction density of the positive electrode material, thereby improving the specific capacity of the battery.

[0023] The precursor material of the present application has a high compound content and a low impurity content, so the obtained positive electrode material has a low impurity content, and the specific capacity and cycle performance of the battery are improved.

[0024] The precursor material of the present application includes primary crystallized particles with a polyhedral morphology, whose crystal faces are flat and regular, and the interparticle gaps are smaller, which is conducive to improving the compaction density of the precursor material.

[0025] In any embodiment, the precursor material is prepared by the following steps:

[0026] dissolving a soluble manganese source, a soluble iron source, and a soluble source of the M element in a solvent to obtain a solution;

[0027] slowly adding the solution into a phosphoric acid solution to react, and optionally aging to obtain a reaction product;

[0028] The reaction product is filtered, and the obtained filter residue is dried to obtain a precursor material.

[0029] Therefore, the present application first prepares a soluble manganese source, a soluble iron source and a soluble M element source into a stable, homogeneous solution, and then slowly adds the solution to a phosphoric acid solution to control and reduce side reactions, and then obtains a precursor material with uniform composition, good batch consistency and low impurity content through optional aging and drying of the filtered residue. The elements in the positive electrode material prepared using the precursor material are evenly distributed and have good batch consistency, thereby improving the specific capacity and cycle performance of the battery.

[0030] In any embodiment, in the step of preparing the precursor material:

[0031] The soluble manganese source includes one or more of a soluble organic manganese source and a soluble inorganic manganese source, and can be selected from a soluble organic manganese source, and can be selected from one or more of soluble organic acid salts of manganese, and can further be selected from one or more of manganous acetate, manganous formate, manganous citrate, and manganous 2-hydroxypropionate; and / or,

[0032] The soluble iron source includes one or more of a soluble organic iron source and a soluble inorganic iron source, and can be selected from a soluble organic iron source, and can be selected from one or more of a soluble organic acid salt of iron, and can further be selected from one or more of ferrous acetate, ferrous formate, ferrous citrate, and ferrous 2-hydroxypropionate; and / or,

[0033] The source of the soluble M element includes one or more of an inorganic source of the soluble M element and an organic source of the soluble M element, and can optionally include one or more of a soluble organic acid salt and a soluble inorganic acid salt of the M element, and can further optionally include one or more of sulfates, nitrates, chlorides, formates, acetates, citrates, and 2-hydroxypropionates of the M element.

[0034] Among them, the use of a soluble organic manganese source and / or a soluble organic iron source is beneficial to reducing the impurity content in the precursor material, improving batch consistency, and thus improving the specific capacity and cycle performance of the battery.

[0035] In any embodiment, in the step of preparing the precursor material:

[0036] Slowly adding the solution to the phosphoric acid solution at 25° C.-95° C. for reaction, optionally slowly adding the solution to the phosphoric acid solution at 30° C.-90° C. for reaction; and / or,

[0037] The solution addition time is 10-300 min, optionally 15-300 min, more optionally 60-180 min; and / or,

[0038] The molar ratio of phosphoric acid in the phosphoric acid solution to the total metal elements in the solution is 0.4-1.5, optionally 0.5-1.5, more optionally 0.8-1.2; and / or,

[0039] The total concentration of the metal elements in the solution is 0.1-3.0 mol / L, optionally 0.5-2.5 mol / L, more optionally 1.0-1.6 mol / L; and / or,

[0040] The phosphoric acid concentration in the phosphoric acid solution is 0.1-3.0 mol / L, optionally 0.5-2.5 mol / L, more optionally 1.0-1.32 mol / L; and / or,

[0041] The molar amount of the M element in the solution accounts for 0.1% to 10% of the total molar amount of the metal elements; and / or,

[0042] The molar amount of the Mn element in the solution accounts for 30% to 85% of the total molar amount of the metal elements.

[0043] The present application reduces side reactions by controlling the ambient temperature when the mixed metal solution is added to the phosphoric acid solution, so as to obtain a precursor material with uniform composition, good batch consistency and low impurity content, thereby improving the specific capacity and cycle performance of the battery.

[0044] The present application controls the rate at which the solution is added to the phosphoric acid solution, thereby helping to control and reduce side reactions, thereby preparing a precursor material with uniform composition, good batch consistency, and low impurity content, thereby improving the electrical performance of the battery.

[0045] The present application can improve the specific capacity of the battery by controlling the molar ratio of phosphoric acid to total metal elements.

[0046] The present application can adjust the molar ratio of each metal element in the precursor product by controlling the concentration of each metal element in the solution.

[0047] In any embodiment, in the step of preparing the precursor material:

[0048] The aging temperature is 40°C-98°C, optionally 60°C-95°C; and / or,

[0049] The aging time is 10-500 min, optionally 30-300 min; and / or,

[0050] Reaction and / or aging are carried out at a pH of 1.5-4.5; and / or,

[0051] The reaction and / or aging is carried out under stirring conditions.

[0052] Aging is beneficial to the crystallization and growth of the precipitate, so as to reduce the proportion of amorphous particles in the precursor material, thereby obtaining a precursor material with better crystallinity and higher compaction density, thereby improving the specific capacity and cycle performance of the battery.

[0053] In any embodiment, in the step of preparing the precursor material:

[0054] Dissolving at 25°C-80°C, optionally at 25°C-40°C; and / or,

[0055] The solvent is water; and / or,

[0056] The filtration is negative pressure filtration, positive pressure filtration or centrifugal filtration; and / or,

[0057] Before drying, washing the filter residue, optionally by washing the filter residue with water; and / or,

[0058] The drying temperature is 80°C-500°C, optionally 120°C-400°C, more optionally 150°C-300°C; and / or,

[0059] The drying time is 10-300 minutes.

[0060] In any embodiment, in the step of preparing the pre-product:

[0061] The molar ratio of the precursor material to the lithium element in the lithium source is 0.9:1-1.1:1; and / or,

[0062] The molar ratio of phosphorus in the phosphorus source to lithium in the lithium source is 1:1-1.05:1; and / or,

[0063] The mixing time is 0.5-4h; and / or,

[0064] The sintering temperature is 350°C-900°C, optionally 450°C-800°C; and / or,

[0065] The sintering time is 3-10 hours.

[0066] The mixing operation is beneficial to increase the surface energy of the particles, improve the activity of the solid-solid reaction, shorten the diffusion path of lithium into the crystals of the precursor material, and make the reaction to generate the pre-product more complete, thereby improving the electrical performance of the battery.

[0067] The sintering temperature and sintering time adopted are conducive to volatilizing the burned-out substances and obtaining a dense pre-product.

[0068] In any embodiment, in the step of preparing the positive electrode material:

[0069] The weight ratio of the pre-product to the carbon source is 3:1-30:1, optionally 5:1-15:1; and / or,

[0070] The ratio of the weight of the solvent to the total weight of the carbon source and the pre-product is 1:1-10:1; and / or,

[0071] The mixing time is 2-8 hours; and / or,

[0072] The drying is performed by spray drying; and / or,

[0073] The inlet temperature of the spray drying is 100°C-280°C; and / or,

[0074] The outlet temperature of the spray drying is 50°C-180°C; and / or,

[0075] The sintering temperature is 500° C.-900° C., optionally 600° C.-800° C.; and / or,

[0076] The sintering time is 8-20 hours.

[0077] The sintering temperature and time employed are conducive to a complete reaction, forming a dense coating on the pre-product, reducing micropores in the coating, increasing the material's compaction density, and lowering the powder resistivity, thereby further improving the battery's specific capacity and cycle performance. Furthermore, the increased density of the coating helps control the material's specific surface area from being excessively large.

[0078] In any embodiment, the lithium source includes one or more of organic acid salts, inorganic acid salts, oxides, and hydroxides of lithium, and may optionally include one or more of lithium carbonate, lithium hydroxide, lithium acetate, and lithium oxide; and / or,

[0079] The phosphorus source includes one or more of phosphate, hydrogen phosphate, and dihydrogen phosphate, and can be selected from one or more of lithium phosphate, lithium dihydrogen phosphate, dilithium hydrogen phosphate, manganese hydrogen phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and manganese-iron hydrogen phosphate; and / or,

[0080] The carbon source includes one or more of an organic carbon source and an inorganic carbon source, and can be selected from one or more of methanol, ethanol, acetic acid, polyethylene glycol, polyvinyl alcohol, polyvinyl butyral, glucose, maltose, and polytetrafluoroethylene; and / or,

[0081] The solvent includes one or more of water, ethanol, and acetone.

[0082] The second aspect of the present application also provides a positive electrode material, comprising a core and a coating layer covering the core; the core comprises a compound LiMn x Fe y M (1-x-y) PO4; wherein, 0.9≤x+y<1, 0<x≤0.9, 0<y≤0.9; the M comprises one or more of transition metal elements other than manganese and iron, group IIA metal elements, group IIIA metal elements, and group IVA metal elements, and may be optionally one or more of titanium, magnesium, aluminum, vanadium, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, and europium; the coating layer comprises carbon.

[0083] Thus, the distribution of manganese, iron, phosphorus, and doping elements in the precursor material used in this application is uniform, the composition is stable, and element segregation is not prone to occur. Using the precursor material as a raw material can improve the element distribution uniformity and material stability of the positive electrode material, thereby improving the specific capacity and cycle performance of the battery. In addition, in the step of preparing the pre-product, after sintering, the burnable substance has volatilized to obtain a dense pre-product, and then a coating layer is prepared on the pre-product, which is beneficial to improving the density of the coating layer, reducing the micropores on the coating layer, increasing the compaction density of the material, and reducing the powder resistivity of the material, thereby further improving the specific capacity and cycle performance of the battery. At the same time, the improvement of the density of the coating layer is conducive to controlling the specific surface area of ​​the material from being too large to improve the processing performance of the material.

[0084] In any embodiment, the compaction density of the positive electrode material at 30 MPa is 1.88-2.52 g / cm 3 , optional 2.0-2.5g / cm 3 and / or,

[0085] The BET specific surface area of ​​the positive electrode material at liquid nitrogen temperature is 9.87-22.34 m 2 / g, optional 12-18m 2 / g; and / or,

[0086] The powder resistivity of the positive electrode material is 1-1893Ω·cm, optionally 12-1000Ω·cm; and / or,

[0087] The positive electrode material is prepared by the method of the first aspect of the present application.

[0088] The third aspect of the present application provides a positive electrode plate, comprising the positive electrode material prepared by the method of the first aspect of the present application or the positive electrode material of the second aspect of the present application.

[0089] The fourth aspect of the present application provides a battery, comprising the positive electrode sheet of the third aspect of the present application.

[0090] The fifth aspect of the present application provides an electrical device comprising the battery of the fourth aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0091] FIG1 is a schematic diagram of a battery cell according to an embodiment of the present application.

[0092] FIG. 2 is an exploded view of the battery cell according to the embodiment of the present application shown in FIG. 1 .

[0093] FIG3 is a schematic diagram of a battery module according to an embodiment of the present application.

[0094] FIG4 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0095] FIG. 5 is an exploded view of the battery pack shown in FIG. 4 according to an embodiment of the present application.

[0096] FIG6 is a schematic diagram of an electrical device using a battery cell as a power source according to an embodiment of the present application.

[0097] FIG7 is a SEM photograph of the precursor material prepared in Example 1 of the present application.

[0098] FIG8 is a SEM photograph of the positive electrode material prepared in Example 1 of the present application.

[0099] FIG9 shows the distribution of manganese, iron, phosphorus, and cobalt elements in the positive electrode material prepared in Example 1 of the present application.

[0100] Explanation of reference numerals: 1 battery pack; 2 upper case; 3 lower case; 4 battery module; 5 battery cell; 51 housing; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0101] Below, the embodiments of the negative electrode active material and its manufacturing method, positive electrode sheet, negative electrode sheet, battery cell, battery module, battery pack and electric device of the present application are described in detail with appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0102] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0103] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0104] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0105] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, a method includes steps (a) and (b), which indicates that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, a method may further include step (c), which indicates that step (c) may be added to the method in any order, for example, the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0106] Unless otherwise specified, the Dv50 particle size in this application refers to the particle size when the cumulative value of volume distribution is 50%.

[0107] [Battery Cell]

[0108] A battery cell, also known as a rechargeable battery or storage battery, refers to a battery that can be recharged to activate the active material after discharge and continue to be used.

[0109] Typically, a battery cell consists of a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte. During the charge and discharge process of the battery, active ions (such as lithium ions) are embedded and released back and forth between the positive and negative electrode sheets. The separator is set between the positive and negative electrode sheets, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing active ions to pass through. The electrolyte between the positive and negative electrode sheets mainly plays the role of conducting active ions.

[0110] [Method for preparing positive electrode material]

[0111] One embodiment of the present application provides a method for preparing a positive electrode material, comprising the following steps:

[0112] The precursor material, lithium source and optional phosphorus source are mixed and sintered to obtain a pre-product; wherein the precursor material includes compound Mn x Fe y M (1-x-y) HPO4·nH2O; wherein 0.9≤x+y<1 (for example, x+y is 0.9, 0.93, 0.95, 0.97, 0.98, 0.99, 0.991, 0.992, 0.993, 0.994, 0.995, 0.996, 0.997, 0.998, 0.999 or a range consisting of any of the above values), 0<x≤0.9 (for example, x is 0.1, 0.2, 0.3, 0.4, 0.5, 0.513, 0.52, 0.53, 0.55, 0.57, 0.59, 0.597, 0.6, 0.63, 0.65, 0.66, 0.68, 0.7, 0≤n≤6 (for example, n is 1, 2, 3, 4, 5, 6 or a range consisting of any of the above values); M comprises one or more of transition metal elements other than manganese and iron, Group IIA metal elements, Group IIIA metal elements, and Group IVA metal elements;

[0113] The pre-product, carbon source and solvent are mixed, dried and sintered to obtain a positive electrode material.

[0114] Although the mechanism is not yet clear, the applicant unexpectedly discovered that the manganese, iron, phosphorus, and doping elements in the precursor material used in this application are evenly distributed, the composition is stable, and element segregation is not prone to occur. The use of this precursor material as a raw material can improve the element distribution uniformity and material stability of the positive electrode material, thereby improving the specific capacity and cycle performance of the battery. In addition, in the step of preparing the pre-product, after sintering, the burnable substance has volatilized to obtain a dense pre-product, and then a coating layer is prepared on the pre-product, which is beneficial to improving the density of the coating layer, reducing the micropores on the coating layer, increasing the compaction density of the material, and reducing the powder resistivity of the material, thereby further improving the specific capacity and cycle performance of the battery. At the same time, the improvement of the density of the coating layer is conducive to controlling the specific surface area of ​​the material from being too large, so as to improve the processing performance of the material.

[0115] In some embodiments, the positive electrode material includes a core and a coating layer covering the core; the core includes a compound LiMn x Fe y M (1-x-y) PO4; wherein, 0.9≤x+y<1 (e.g., x+y is 0.9, 0.93, 0.95, 0.97, 0.98, 0.99, 0.991, 0.992, 0.993, 0.994, 0.995, 0.996, 0.997, 0.998, 0.999 or a range consisting of any of the above values), 0<x≤0.9 (e.g., x is 0.1, 0.2, 0.3, 0.4, 0.5, 0.513, 0.52, 0.53, 0.55, 0.57, wherein the M comprises one or more transition metal elements other than manganese and iron, group IIA metal elements, group IIIA metal elements, and group IVA metal elements; and the coating layer comprises carbon.

[0116] In some embodiments, 0.992≤x+y<0.995; and / or,

[0117] 0.513≤x≤0.658; and / or,

[0118] 0.336≤y≤0.479; and / or,

[0119] 0≤n≤1; and / or,

[0120] The M includes one or more elements selected from titanium, magnesium, aluminum, vanadium, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, and europium.

[0121] In some embodiments, the Dv50 particle size of the precursor material is 3-100 μm, optionally 5-50 μm, more optionally 8-20 μm, for example, 3 μm, 5 μm, 7 μm, 8 μm, 10 μm, 12 μm, 15 μm, 17 μm, 18 μm, 20 μm, 22 μm, 24 μm, 26 μm, 28 μm, 30 μm, 32 μm, 35 μm, 37 μm, 38 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 80 μm, 90 μm, 100 μm or a range consisting of any of the above values; and / or,

[0122] The precursor material has a compaction density of 1.35-2.5 g / cm at 30 MPa. 3 , optional 1.5-2.5g / cm 3 , for example 1.35 g / cm 3 , 1.4g / cm 3 , 1.5g / cm 3 , 1.6g / cm 3 , 1.7g / cm 3 , 1.8g / cm 3 , 1.9g / cm 3 , 2.0g / cm 3 , 2.1g / cm 3 , 2.2g / cm 3 , 2.3g / cm 3 , 2.4g / cm 3 , 2.5g / cm 3 or a range consisting of any of the above values; / or,

[0123] The compound Mn in the precursor material x Fe y M (1-x-y) The mass content of HPO4·nH2O is 98%-100%, for example, 98.5%, 99%, 99.1%, 99.3%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, 100% or any range thereof; and / or,

[0124] The precursor material includes primary crystal particles having a polyhedral morphology.

[0125] The Dv50 particle size of the precursor material of the present application is within the above-mentioned range. On the one hand, it is beneficial to the washing and filtering operations during the precursor preparation process, thereby improving the yield of the precursor material. On the other hand, when preparing the positive electrode material, it is beneficial to the suspension of the precursor particles and is not easy to settle, thereby improving the efficiency of the mixing and grinding processes.

[0126] The compaction density of the precursor material of the present application is within the above range, which is beneficial to increasing the compaction density of the positive electrode material, thereby improving the specific capacity of the battery.

[0127] The precursor material of the present application has a high compound content and a low impurity content, so the obtained positive electrode material has a low impurity content, and the specific capacity and cycle performance of the battery are improved.

[0128] The precursor material of the present application includes primary crystallized particles with a polyhedral morphology, whose crystal faces are flat and regular, and the interparticle gaps are smaller, which is conducive to improving the compaction density of the precursor material.

[0129] In some embodiments, the precursor material is prepared by the following steps:

[0130] dissolving a soluble manganese source, a soluble iron source, and a soluble source of the M element in a solvent to obtain a solution;

[0131] slowly adding the solution into a phosphoric acid solution to react, and optionally aging to obtain a reaction product;

[0132] The reaction product is filtered, and the obtained filter residue is dried to obtain a precursor material.

[0133] Therefore, the present application first prepares a soluble manganese source, a soluble iron source and a soluble M element source into a stable, homogeneous solution, and then slowly adds the solution to a phosphoric acid solution to control and reduce side reactions, and then obtains a precursor material with uniform composition, good batch consistency and low impurity content through optional aging and drying of the filtered residue. The elements in the positive electrode material prepared using the precursor material are evenly distributed and have good batch consistency, thereby improving the specific capacity and cycle performance of the battery.

[0134] In some embodiments, in the step of preparing the precursor material:

[0135] The soluble manganese source includes one or more of a soluble organic manganese source and a soluble inorganic manganese source, and can be selected from a soluble organic manganese source, and can be selected from one or more of soluble organic acid salts of manganese, and can further be selected from one or more of manganous acetate, manganous formate, manganous citrate, and manganous 2-hydroxypropionate; and / or,

[0136] The soluble iron source includes one or more of a soluble organic iron source and a soluble inorganic iron source, and can be selected from a soluble organic iron source, and can be selected from one or more of a soluble organic acid salt of iron, and can further be selected from one or more of ferrous acetate, ferrous formate, ferrous citrate, and ferrous 2-hydroxypropionate; and / or,

[0137] The source of the soluble M element includes one or more of an inorganic source of the soluble M element and an organic source of the soluble M element, and can optionally include one or more of a soluble organic acid salt and a soluble inorganic acid salt of the M element, and can further optionally include one or more of sulfates, nitrates, chlorides, formates, acetates, citrates, and 2-hydroxypropionates of the M element.

[0138] Among them, the use of a soluble organic manganese source and / or a soluble organic iron source is beneficial to reducing the impurity content in the precursor material, improving batch consistency, and thus improving the specific capacity and cycle performance of the battery.

[0139] In some embodiments, in the step of preparing the precursor material:

[0140] Slowly adding the solution to the phosphoric acid solution for reaction at 25°C-95°C, optionally at 30°C-90°C, for example, slowly adding the solution to the phosphoric acid solution for reaction at 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C or any range thereof; and / or,

[0141] The addition time of the solution is 10-300 min, optionally 15-300 min, more optionally 60-180 min, for example, 10 min, 15 min, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 120 min, 140 min, 150 min, 170 min, 180 min, 200 min, 220 min, 240 min, 250 min, 270 min, 280 min, 290 min, 300 min or a range consisting of any of the above values; and / or,

[0142] The molar ratio of phosphoric acid in the phosphoric acid solution to the total metal elements in the solution is 0.4-1.5, optionally 0.5-1.5, more optionally 0.8-1.2, for example, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5 or any range thereof; and / or,

[0143] The total concentration of the metal elements in the solution is 0.1-3.0 mol / L, optionally 0.5-2.5 mol / L, more optionally 1.0-1.6 mol / L, for example, 0.1 mol / L, 0.3 mol / L, 0.5 mol / L, 0.7 mol / L, 0.8 mol / L, 1.0 mol / L, 1.1 mol / L, 1.3 mol / L, 1.5 mol / L, 1.7 mol / L, 1.9 mol / L, 2.0 mol / L, 2.1 mol / L, 2.3 mol / L, 2.5 mol / L, 2.7 mol / L, 2.8 mol / L, 2.9 mol / L, 3.0 mol / L or a range consisting of any of the above values; and / or,

[0144] The phosphoric acid concentration in the phosphoric acid solution is 0.1-3.0 mol / L, optionally 0.5-2.5 mol / L, more optionally 1.0–1.32 mol / L, for example, 0.1 mol / L, 0.3 mol / L, 0.5 mol / L, 0.7 mol / L, 0.8 mol / L, 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.7 mol / L, 1.9 mol / L, 2.0 mol / L, 2.1 mol / L, 2.3 mol / L, 2.5 mol / L, 2.7 mol / L, 2.8 mol / L, 2.9 mol / L, 3.0 mol / L or a range consisting of any of the above values; and / or,

[0145] The molar amount of the M element in the solution accounts for 0.1%-10% of the total molar amount of the metal elements, for example, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 8%, 9%, 10% or any range thereof; and / or,

[0146] The molar amount of the Mn element in the solution accounts for 30% to 85% of the total molar amount of the metal elements, for example, 30%, 35%, 40%, 45%, 50%, 51%, 53%, 55%, 58%, 59%, 60%, 64%, 65%, 66%, 67%, 70%, 75%, 80%, 85% or a range consisting of any of the above values.

[0147] The present application reduces side reactions by controlling the ambient temperature when the mixed metal solution is added to the phosphoric acid solution, so as to obtain a precursor material with uniform composition, good batch consistency and low impurity content, thereby improving the specific capacity and cycle performance of the battery.

[0148] The present application controls the rate at which the solution is added to the phosphoric acid solution, thereby helping to control and reduce side reactions, thereby preparing a precursor material with uniform composition, good batch consistency, and low impurity content, thereby improving the electrical performance of the battery.

[0149] The present application can improve the specific capacity of the battery by controlling the molar ratio of phosphoric acid to total metal elements.

[0150] The present application can adjust the molar ratio of each metal element in the precursor product by controlling the concentration of each metal element in the solution.

[0151] In some embodiments, in the step of preparing the precursor material:

[0152] The aging temperature is 40°C-98°C, optionally 60°C-95°C, such as 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 98°C or any range thereof; and / or,

[0153] The aging time is 10-500 min, and can be optionally 30-300 min, for example, 10 min, 20 min, 30 min, 50 min, 60 min, 80 min, 100 min, 120 min, 150 min, 170 min, 190 min, 200 min, 230 min, 250 min, 270 min, 280 min, 300 min, 320 min, 340 min, 350 min, 380 min, 400 min, 430 min, 450 min, 470 min, 480 min, 500 min or a range consisting of any of the above values; and / or,

[0154] Reaction and / or aging are carried out at a pH of 1.5-4.5 (e.g., 1.5, 2, 3, 4, 4.5, or a range consisting of any of the above values); and / or,

[0155] The reaction and / or aging is carried out under stirring conditions.

[0156] Aging is beneficial to the crystallization and growth of the precipitate, so as to reduce the proportion of amorphous particles in the precursor material, thereby obtaining a precursor material with better crystallinity and higher compaction density, thereby improving the specific capacity and cycle performance of the battery.

[0157] In some embodiments, in the step of preparing the precursor material:

[0158] Dissolving at 25°C-80°C, optionally at 25°C-40°C, for example, at 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 60°C, 70°C, 80°C or any range thereof; and / or,

[0159] The solvent is water; and / or,

[0160] The filtration is negative pressure filtration, positive pressure filtration or centrifugal filtration; and / or,

[0161] Before drying, washing the filter residue, optionally by washing the filter residue with water; and / or,

[0162] The drying temperature is 80°C-500°C, optionally 120°C-400°C, more optionally 150°C-300°C, for example, 80°C, 90°C, 100°C, 120°C, 140°C, 150°C, 160°C, 170°C, 200°C, 230°C, 250°C, 270°C, 300°C, 320°C, 340°C, 360°C, 380°C, 400°C, 430°C, 450°C, 470°C, 480°C, 500°C or any range thereof; and / or,

[0163] The drying time is 10-300 min, for example, 10 min, 20 min, 30 min, 50 min, 60 min, 80 min, 100 min, 120 min, 140 min, 160 min, 180 min, 200 min, 220 min, 240 min, 250 min, 270 min, 290 min, 300 min or a range consisting of any of the above values.

[0164] In some embodiments, in the step of preparing the pre-product:

[0165] The molar ratio of the precursor material to the lithium element in the lithium source is 0.9:1 to 1.1:1, for example, 0.9:1, 0.93:1, 0.95:1, 0.97:1, 0.98:1, 0.99:1, 1.0:1, 1.03:1, 1.05:1, 1.07:1, 1.08:1, 1.09:1, 1.1:1 or any range thereof; and / or,

[0166] The molar ratio of the phosphorus element in the phosphorus source to the lithium element in the lithium source is 1:1-1.05:1, for example, 1:1, 1.01:1, 1.02:1, 1.03:1, 1.04:1, 1.05:1 or any range thereof; and / or,

[0167] The mixing time is 0.5-4 h, for example, 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h or any range thereof; and / or,

[0168] The sintering temperature is 350° C.-900° C., optionally 450° C.-800° C., for example, 350° C., 380° C., 400° C., 450° C., 470° C., 500° C., 550° C., 600° C., 650° C., 700° C., 750° C., 800° C., 850° C., 870° C., 900° C. or any range thereof; and / or,

[0169] The sintering time is 3-10 hours, for example, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours or any range thereof.

[0170] The mixing operation is beneficial to increase the surface energy of the particles, improve the activity of the solid-solid reaction, shorten the diffusion path of lithium into the crystals of the precursor material, and make the reaction to generate the pre-product more complete, thereby improving the electrical performance of the battery.

[0171] The sintering temperature and sintering time adopted are conducive to volatilizing the burned-out substances and obtaining a dense pre-product.

[0172] In some embodiments, in the step of preparing the positive electrode material:

[0173] The weight ratio of the pre-product to the carbon source is 3:1-30:1, optionally 5:1-15:1, for example, 3:1, 4:1, 5:1, 7:1, 8:1, 10:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 20:1, 22:1, 24:1, 25:1, 26:1, 27:1, 28:1, 30:1 or any range thereof; and / or,

[0174] The ratio of the weight of the solvent to the total weight of the carbon source and the pre-product is 1:1-10:1, for example, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1 or any range thereof; and / or,

[0175] The mixing time is 2-8 hours, for example, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours or any range thereof; and / or,

[0176] The drying is performed by spray drying; and / or,

[0177] The inlet temperature of the spray drying is 100°C-280°C, for example, 100°C, 150°C, 200°C, 250°C, 280°C or any range thereof; and / or,

[0178] The outlet temperature of the spray drying is 50°C-180°C, for example, 50°C, 70°C, 100°C, 130°C, 150°C, 170°C, 180°C or any range thereof; and / or,

[0179] The sintering temperature is 500°C-900°C, optionally 600°C-800°C, for example, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C or any range thereof; and / or,

[0180] The sintering time is 8-20 hours, for example, 8 hours, 9 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours or a range consisting of any of the above values.

[0181] The sintering temperature and time employed are conducive to a complete reaction, forming a dense coating on the pre-product, reducing micropores in the coating, increasing the material's compaction density, and lowering the powder resistivity, thereby further improving the battery's specific capacity and cycle performance. Furthermore, the increased density of the coating helps control the material's specific surface area from being excessively large.

[0182] In some embodiments, the lithium source includes one or more of organic acid salts, inorganic acid salts, oxides, and hydroxides of lithium, and may optionally include one or more of lithium carbonate, lithium hydroxide, lithium acetate, and lithium oxide; and / or,

[0183] The phosphorus source includes one or more of phosphate, hydrogen phosphate, and dihydrogen phosphate, and can be selected from one or more of lithium phosphate, lithium dihydrogen phosphate, dilithium hydrogen phosphate, manganese hydrogen phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and manganese-iron hydrogen phosphate; and / or,

[0184] The carbon source includes one or more of an organic carbon source and an inorganic carbon source, and can be selected from one or more of methanol, ethanol, acetic acid, polyethylene glycol, polyvinyl alcohol, polyvinyl butyral, glucose, maltose, and polytetrafluoroethylene; and / or,

[0185] The solvent includes one or more of water, ethanol, and acetone.

[0186] In some embodiments, in the phosphorus source, the hydrogen phosphate is not included in the precursor material.

[0187] [Cathode material]

[0188] One embodiment of the present application provides a positive electrode material, comprising a core and a coating layer covering the core; the core comprises a compound LiMn x Fe y M (1-x-y) PO4; wherein 0.9≤x+y<1 (e.g., x+y is 0.9, 0.93, 0.95, 0.97, 0.98, 0.99, 0.991, 0.992, 0.993, 0.994, 0.995, 0.996, 0.997, 0.998, 0.999, or any range thereof), 0<x≤0.9 (e.g., x is 0.1, 0.2, 0.3, 0.4, 0.5, 0.513, 0.52, 0.53, 0.55, 0.57, 0.59, 0.597, 0.6, 0.63, 0.65, 0.66, 0.68, 0.7, 0.8, 0.9, or any range thereof) wherein M comprises one or more transition metal elements, Group IIA metal elements, Group IIIA metal elements, and Group IVA metal elements other than manganese and iron, and may be optionally one or more elements selected from titanium, magnesium, aluminum, vanadium, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, and europium; and wherein the coating layer comprises carbon.

[0189] Thus, the distribution of manganese, iron, phosphorus, and doping elements in the precursor material used in this application is uniform, the composition is stable, and element segregation is not prone to occur. Using the precursor material as a raw material can improve the element distribution uniformity and material stability of the positive electrode material, thereby improving the specific capacity and cycle performance of the battery. In addition, in the step of preparing the pre-product, after sintering, the burnable substance has volatilized to obtain a dense pre-product, and then a coating layer is prepared on the pre-product, which is beneficial to improving the density of the coating layer, reducing the micropores on the coating layer, increasing the compaction density of the material, and reducing the powder resistivity of the material, thereby further improving the specific capacity and cycle performance of the battery. At the same time, the improvement of the density of the coating layer is conducive to controlling the specific surface area of ​​the material from being too large to improve the processing performance of the material.

[0190] In some embodiments, the cathode material has a compaction density of 1.88–2.52 g / cm at 30 MPa. 3 , optional 2.0-2.5g / cm 3 , for example 1.88 g / cm 3 , 1.9g / cm 3 , 2.0g / cm 3, 2.1g / cm 3 , 2.2g / cm 3 , 2.3g / cm 3 , 2.5g / cm 3 , 2.52g / cm 3 or a range consisting of any of the above values; and / or,

[0191] The BET specific surface area of ​​the cathode material at liquid nitrogen temperature is 9.87–22.34 m 2 / g, optional 12-18m 2 / g, for example 9.87m 2 / g、10m 2 / g、11m 2 / g、12m 2 / g, 13m 2 / g、15m 2 / g、18m 2 / g, 20m 2 / g, 21m 2 / g、22m 2 / g, 22.34m 2 / g or any range consisting of the above values; and / or,

[0192] The powder resistivity of the positive electrode material is 1-1893Ω·cm, and can be optionally 12-1000Ω·cm, for example, 1Ω·cm, 6Ω·cm, 10Ω·cm, 12Ω·cm, 15Ω·cm, 20Ω·cm, 23Ω·cm, 25Ω·cm, 27Ω·cm, 30Ω·cm, 33Ω·cm, 35Ω·cm, 38Ω·cm, 40Ω·cm, 50Ω·cm, 60Ω·cm, 70Ω·cm, 80Ω·cm, 100Ω·cm , 200Ω·cm, 300Ω·cm, 500Ω·cm, 600Ω·cm, 800Ω·cm, 900Ω·cm, 950Ω·cm, 1000Ω·cm, 1050Ω·cm, 1100Ω·cm, 1200Ω·cm, 1400Ω·cm, 1500Ω·cm, 1700Ω·cm, 1750Ω·cm, 1800Ω·cm, 1850Ω·cm, 1893Ω·cm or a range consisting of any of the above values; and / or,

[0193] The positive electrode material is prepared by the above method of the present application.

[0194] In the present application, the Dv50 particle size is tested using conventional methods in the art; for example, water is added to the sample to completely disperse the sample, and the Dv50 particle size of the material is measured using a laser particle size analyzer.

[0195] In this application, the compaction density is tested using conventional methods in the field; for example, the sample is placed in the mold of a compaction density tester, and the tester automatically applies a certain pressure to the powder until the powder is compacted. Based on the cross-sectional area of ​​the mold and the thickness of the powder at this time, the volume of the powder can be calculated. According to compaction density = mass / volume, the compaction density of the powder material can be measured.

[0196] In this application, the BET specific surface area is tested using conventional methods in the art; for example, the sample is placed in a specific surface area test tube, placed in a specific surface area meter, the liquid nitrogen cup is filled with liquid nitrogen, and the specific surface area test tube is inserted to test the BET specific surface area.

[0197] In this application, the powder resistivity is tested using conventional methods in the field; for example, the sample is placed in a mold, and then the mold is placed in a four-probe resistivity tester, adjusted to a certain pressure, and after the mold height and pressure are stable, the forward resistivity and reverse resistivity of the sample are tested respectively, and the average of the two is taken as the powder resistivity of the sample.

[0198] [Positive electrode]

[0199] The positive electrode sheet generally includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes the aforementioned positive electrode material.

[0200] The battery's charge and discharge processes involve the intercalation and deintercalation of lithium, leading to different molar Li contents at different discharge states. The molar Li contents listed in this application for cathode materials refer to the initial state of the material, i.e., the state before addition of the materials. When the cathode material is used in a battery system, the molar Li content will change after charge and discharge cycles.

[0201] In the list of positive electrode materials in this application, the molar content of O is only a theoretical value. Lattice oxygen release will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.

[0202] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0203] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0204] In some embodiments, positive electrode materials for batteries that are well known in the art may also be included. As an example, at least one of the following materials may be included: lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and at least one of its modified compounds, etc.

[0205] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0206] In some embodiments, the positive electrode film layer may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0207] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0208] [Negative electrode]

[0209] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0210] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0211] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0212] In some embodiments, the negative electrode active material may be a negative electrode active material for a battery that is well known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0213] In some embodiments, the negative electrode film layer may further include a binder. For example, the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0214] In some embodiments, the negative electrode film layer may further include a conductive agent. For example, the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0215] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0216] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0217] [Electrolytes]

[0218] The electrolyte conducts ions between the positive and negative electrodes. This application does not specify the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0219] In some embodiments, the electrolyte is liquid and includes an electrolyte salt and a solvent.

[0220] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0221] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0222] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0223] [Isolation film]

[0224] In some embodiments, the battery cell further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0225] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0226] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0227] In some embodiments, the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0228] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the battery cell may be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0229] The present application has no particular limitation on the shape of the battery cell, which can be cylindrical, square, or any other shape. For example, FIG1 shows a battery cell 5 with a square structure as an example.

[0230] In some embodiments, referring to Figure 2, the outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0231] In some embodiments, battery cells may be assembled into a battery module. The battery module may contain one or more battery cells. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0232] FIG3 shows an example battery module 4. Referring to FIG3 , within the battery module 4, multiple battery cells 5 may be arranged sequentially along the length of the battery module 4. Of course, they may also be arranged in any other manner. Furthermore, the multiple battery cells 5 may be secured together using fasteners.

[0233] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0234] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0235] Figures 4 and 5 illustrate an example battery pack 1. Referring to Figures 4 and 5 , the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be placed over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0236] In addition, the present application also provides an electrical device, which includes at least one of the battery cells, battery modules, or battery packs provided in the present application. The battery cells, battery modules, or battery packs can be used as power sources for the electrical device, or as energy storage units for the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0237] As an electrical device, a battery cell, battery module or battery pack can be selected according to its usage requirements.

[0238] Figure 6 shows an example of an electric device. This device is a pure electric vehicle, hybrid electric vehicle, or plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the battery cells, a battery pack or battery module can be used.

[0239] [Example]

[0240] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0241] Example 1

[0242] (1) Preparation of precursor materials:

[0243] According to the molar ratio of Mn:Fe:Co of 0.597:0.398:0.005, 2.866 mol of manganous acetate, 1.910 mol of ferrous acetate, and 0.024 mol of cobalt sulfate were added to a stirring tank, and pure water was added to stir and dissolve according to the total metal ion molar concentration of 1.60 mol / L. The stirring function and the water bath heating function were turned on, and the liquid was heated to 40°C for insulation. After the powder was completely dissolved, 3.0 L of metal salt solution was obtained for use.

[0244] According to the above-mentioned total metal ion to phosphorus molar ratio of 1:1.100, 5.280 mol of concentrated phosphoric acid with a solute mass concentration of 85% was placed in a stirring tank, and pure water was added according to the molar concentration of the phosphoric acid solution of 1.32 mol / L and stirred evenly. The water bath heating function was turned on and the feed liquid was heated to 60°C and kept warm to obtain 4.0 L of phosphoric acid solution for use.

[0245] Maintaining the phosphoric acid solution in a water bath at 60°C, the metal salt solution was uniformly added to the phosphoric acid solution using a metering pump while stirring, allowing mixing and reaction. The volumetric flow rate of the metal salt solution was set at approximately 0.03 L / min, and the time required for complete addition of the solution was controlled within 100 minutes. After the addition was completed, the solution was heated to 85°C while stirring and aged for 120 minutes to complete the reaction and obtain a slurry. The system pH during the addition, reaction, and aging processes was measured using an online pH meter and was found to be 2-3.

[0246] The slurry was transferred to a vacuum filtration device with a maximum vacuum pressure of -0.06 MPa, and the solid precipitate was collected by filtration; about 3.6 L of pure water was added for online washing to obtain a precursor filter cake; the precursor filter cake was transferred to a blast drying oven, the drying temperature was set to 150 ° C, and dried for 120 minutes. At this time, the material was basically constant weight, and the precursor material was obtained.

[0247] (2) Preparation of positive electrode materials:

[0248] Lithium carbonate and the precursor material were added to a coulter mixer and mixed for 30 minutes, maintaining a molar ratio of lithium to precursor of 1:1. The coulter spindle speed was 100 rpm, and the fly cutter speed was 1440 rpm. Chilled water was circulated through the equipment jacket to prevent excessive material temperature from causing iron and manganese oxidation. This yielded a first mixed powder with a mixing ratio of 99%. The first mixed powder was placed in a sagger, placed in a box furnace, and heated to 500°C at a heating rate of 5°C / min. Sintered for 5 hours, cooled, and removed to obtain a pre-product.

[0249] The pre-product was added to a stirring tank, glucose was added at 15% of the weight of the pre-product, and water was added to the stirring tank in an amount of 1.5 times the total weight of the pre-product and glucose. The stirring tank was turned on and the stirring rate was controlled at 200 rpm for 2 hours to obtain a slurry. The slurry was spray-dried in a spray dryer with an inlet temperature of 200°C and an outlet temperature of 120°C to obtain a second mixed powder. The second mixed powder was placed in a sagger, placed in a box furnace, heated to 650°C at 5°C / min, sintered for 8 hours, and taken out after cooling to obtain a cobalt manganese iron lithium phosphate positive electrode material.

[0250] (3) Preparation of positive electrode sheet:

[0251] Using an analytical balance (accuracy 0.0001g), weigh 0.3g of polyvinylidene fluoride (PVDF) binder in 10.8g of N-methylpyrrolidone (NMP) and stir until completely dissolved. Then, add 2.4g of the aforementioned positive electrode material and 0.3g of carbon black conductive agent (SP) and stir until a paste is formed. The paste is evenly coated onto aluminum foil using an applicator and dried in a vacuum oven to remove the NMP solvent. After rolling and punching, a 16.0mm diameter disc is obtained to serve as the positive electrode sheet.

[0252] (4) Negative electrode: Metal lithium sheet is used.

[0253] (5) Isolation film: PE-PP composite film.

[0254] (6) Preparation of electrolyte:

[0255] Ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed in a volume ratio of 1:1, and then LiPF6 was uniformly dissolved in the above solution to obtain an electrolyte solution. The concentration of LiPF6 in the electrolyte solution was 1 mol / L.

[0256] (7) Preparation of secondary batteries:

[0257] The positive electrode sheet, separator, negative electrode sheet and electrolyte were assembled into a CR2032 button battery.

[0258]

[0259] The secondary battery preparation methods of Examples 2-42 and Comparative Example 1 are similar to those of Example 1. The different preparation methods and product parameters are detailed in Tables 1-4.

[0260] Example 42

[0261] (1) Preparation of precursor materials:

[0262] According to the molar ratio of Mn:Fe:Co of 0.597:0.398:0.005, 2.866 mol of manganous acetate, 1.910 mol of ferrous acetate, and 0.024 mol of cobalt sulfate were added to the stirring tank, and pure water was added according to the total metal ion molar concentration of 1.60 mol / L. Stir and dissolve, and turn on the water bath heating function to heat the liquid to 40°C for insulation. After the powder is completely dissolved, 3.0 L of metal salt solution is obtained for use.

[0263] According to the above-mentioned total metal ion to phosphorus molar ratio of 1:1.100, 5.280 mol of concentrated phosphoric acid with a solute mass concentration of 85% was placed in a stirring tank, and pure water was added according to the molar concentration of the phosphoric acid solution of 1.32 mol / L and stirred evenly. The water bath heating function was turned on and the feed liquid was heated to 60°C and kept warm to obtain 4.0 L of phosphoric acid solution for use.

[0264] The water bath temperature of the phosphoric acid solution was maintained at 60°C. The metal salt solution was added to the phosphoric acid solution at once under stirring and mixed for reaction. The pH value of the mixed slurry during the addition and reaction was measured using an online pH meter and was 2-3.

[0265] The slurry was transferred to a vacuum filtration device with a maximum vacuum pressure of -0.06 MPa, and the solid precipitate was collected by filtration; about 3.6 L of pure water was added for online washing to obtain a precursor filter cake; the precursor filter cake was transferred to a blast drying oven, the drying temperature was set to 150 ° C, and dried for 120 minutes. At this time, the material was basically constant weight, and the precursor material was obtained.

[0266] Steps (2) to (7) are the same as steps (2) to (7) in Example 1.

[0267] Comparative Example 1

[0268] (1) Preparation of positive electrode materials

[0269] According to the molar ratio of Li:Mn:Fe:Co:PO4 of 1.000:0.597:0.398:0.005:1.000, 2.400 mol of lithium carbonate and 4.800 mol of concentrated phosphoric acid with a solute mass concentration of 85% were first added to 5945.63 g of pure water for mixed reaction to obtain a lithium dihydrogen phosphate solution, and then 2.866 mol of manganous oxalate, 1.910 mol of ferrous oxalate, 0.024 mol of cobaltous oxalate, and 61.23 g of glucose were added and mixed evenly. The mixture was placed in a ball mill and ground to a particle size Dv50 of 0.8 μm to obtain a slurry; the slurry was dried by spray drying with an air inlet temperature of 220°C and an air outlet temperature of 105°C to obtain a powder; the powder was sintered at 700°C for 12 hours in an atmosphere box furnace under a nitrogen atmosphere to obtain a positive electrode material.

[0270] Steps (2)-(6) are the same as steps (3)-(7) of Example 1.

[0271] Table 3: Performance parameters of the precursors of Examples 1-42

[0272] Table 4: Performance parameters of the positive electrode materials of Examples 1-42 and Comparative Example 1

[0273] Material testing and battery testing

[0274] (1) Testing of the mass fraction of each element and the chemical formula of the compound in the precursor and cathode material:

[0275] Weigh 0.2 g of precursor material or cathode material into a 100 mL beaker, add 10 mL of 10% w / w nitric acid solution, heat and digest at 120°C for 0.5 hours, and then dilute to volume with a 100 mL volumetric flask; then use a pipette to transfer 1 mL to a 100 mL volumetric flask and dilute to volume to obtain the test solution.

[0276] The mass fractions of lithium, manganese, iron, phosphorus, and doping elements in the test solution were determined using an inductively coupled plasma optical emission spectrometer (ICP-OES, instrument brand: Agilent 5800). Based on the mass fractions of each element, the molar ratio of each element in the precursor material or cathode material was calculated to determine the chemical formula of the compound.

[0277] The mass content of the compound in the precursor material is calculated based on the measured mass fraction of phosphorus in the precursor material in combination with the above chemical formula.

[0278] (2) Dv50 particle size test:

[0279] Take an appropriate amount of sample, add 20 mL of deionized water, and ultrasonically treat for 5 minutes (53 KHz, 120 W) to completely disperse the sample. Use a laser particle size analyzer (MasterSizer 2000) to measure the Dv50 particle size of the material.

[0280] (3) Evaluation of micromorphology and micro-area element distribution:

[0281] The microstructures of the precursor material and the cathode material of Example 1 were observed using a scanning electron microscope (SEM, instrument brand: ZEISS sigma 300).

[0282] As shown in FIG7 , the precursor material is a primary crystal particle with a polyhedral morphology, with flat and regular crystal faces and few amorphous, honeycomb, and dendritic crystals, indicating that the precursor material has a high degree of crystallinity.

[0283] As shown in FIG8 , the carbon coating layer of the positive electrode material has good coating density and is not prone to micropores.

[0284] The element distribution of manganese, iron, phosphorus and doping element cobalt in the micro area of ​​the positive electrode material obtained in Example 1 was characterized by an energy dispersive X-ray spectrometer (EDS).

[0285] As shown in FIG9 , the elements in the positive electrode material are distributed relatively evenly.

[0286] (4) Compaction density test:

[0287] Weigh 0.6000g of sample and place it in the compaction density tester mold. The tester automatically applies 30MPa of pressure to the powder until the powder is compacted. The volume of the powder can be calculated based on the cross-sectional area of ​​the mold and the thickness of the powder at this time. According to the compaction density = mass / volume, the compaction density of the powder material can be measured.

[0288] (5) BET specific surface area test:

[0289] Weigh 1g of sample and place it in a specific surface area test tube. Place it in a specific surface area meter. Fill the liquid nitrogen cup with liquid nitrogen and insert it into the specific surface area test tube. Maintain the sample at -200℃ to test the BET specific surface area.

[0290] (6) Test of powder resistivity and electronic conductivity:

[0291] Weigh 1g of sample and place it in a mold. Then place the mold in a four-probe resistivity tester and adjust the pressure to 7.85MPa. After the mold height and pressure are stable, test the forward resistivity and reverse resistivity of the sample respectively, and take the average of the two as the powder resistivity of the sample.

[0292] The electronic conductivity is inversely proportional to the powder resistivity.

[0293] (7) Battery discharge capacity test:

[0294] Shenzhen Xinweier battery testing system was used to cycle the button battery at a charge and discharge rate of 0.1C for 50 times. The test temperature was 25.0℃ and the charge and discharge voltage was 2.0V-4.3V. The discharge capacity of the last cycle was divided by the mass of the positive electrode material to obtain the discharge specific capacity at a charge and discharge rate of 0.1C.

[0295] (8) Test of battery cycle capacity retention rate:

[0296] Shenzhen Xinweier battery testing system was used to cycle button batteries at a charge and discharge rate of 1.0C for 100 cycles. The test temperature was 25.0℃, and the charge and discharge voltage was 2.0V~4.3V. The percentage of the 100th discharge capacity to the first discharge capacity is the cycle capacity retention rate.

[0297] The above results are shown in Tables 3-5.

[0298] Table 5: Electrical performance test results of Examples 1-42 and Comparative Example 1

[0299] According to the above results, we can know that:

[0300] Compared with Comparative Example 1 in which the positive electrode material is prepared without using a precursor material, the specific capacity of the batteries of Examples 1-38 and 40-42 of the present application is significantly higher.

[0301] Compared with the precursor material with lower compaction density used in Example 31, the specific capacity and cycle capacity retention rate of the batteries in Examples 1, 4-5 of the present application are significantly higher.

[0302] Compared with the higher addition and reaction temperature used in preparing the precursor material in Example 32, the specific capacity of the batteries in Examples 1, 8-9 of the present application is higher.

[0303] Compared with the lower molar ratio of phosphoric acid to the total amount of metal elements when preparing the precursor material in Example 33, the specific capacity and cycle capacity retention rate of the batteries in Examples 1 and 12-13 of the present application are higher.

[0304] Compared with the use of a lower aging temperature and a longer aging time when preparing the precursor material in Example 34, the specific capacity and cycle capacity retention rate of the batteries in Examples 1 and 14-15 of the present application are higher; compared with the use of a higher aging temperature and a shorter aging time when preparing the precursor material in Example 35, the specific capacity and cycle capacity retention rate of the batteries in Examples 1 and 14-15 of the present application are higher.

[0305] Compared with the use of a lower sintering temperature when preparing the pre-product in Example 36, the specific capacity of the batteries in Examples 1 and 21-22 of the present application is higher; compared with the use of a higher sintering temperature when preparing the pre-product in Example 37, the specific capacity and cycle capacity retention rate of the batteries in Examples 1 and 21-22 of the present application are higher.

[0306] Compared with the lower weight ratio of the pre-product to the carbon source when preparing the positive electrode material in Example 38, the specific capacity and cycle capacity retention rate of the batteries in Examples 1 and 23-24 of the present application are higher; compared with the higher weight ratio of the pre-product to the carbon source when preparing the positive electrode material in Example 39, the specific capacity of the batteries in Examples 1 and 23-24 of the present application is higher.

[0307] Compared with the lower sintering temperature used in Example 40 for preparing the positive electrode material and the higher sintering temperature used in Example 41 for preparing the positive electrode material, the specific capacity of the batteries in Examples 1 and 26-27 of the present application is higher.

[0308] Compared with Example 42 in which the metal salt solution is added once during the preparation of the precursor material without aging, the specific capacity and cycle capacity retention rate of the batteries in Examples 1, 5, 10-11, and 14-15 of the present application are significantly higher.

[0309] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for preparing a positive electrode material, comprising the following steps: Precursor materials, a lithium source and an optional phosphorus source are mixed and sintered to obtain a pre-product; wherein, The precursor material includes a compound Mn x Fe y M (1-x-y) HPO4·nH2O; wherein 0.9≤x+y<1, 0<x≤0.9, 0<y≤0.9, 0≤n≤6; said M comprises one or more of transition metal elements, ⅡA group metal elements, ⅢA group metal elements and ⅣA group metal elements except manganese and iron elements; The pre-product, carbon source and solvent are mixed, dried and sintered to obtain a positive electrode material.

2. The method according to claim 1, wherein: The positive electrode material comprises a core and a coating layer covering the core; the core comprises a compound LiMn x Fe y M (1-x-y) PO4; wherein, 0.9≤x+y<1, 0<x≤0.9, 0<y≤0.9; the M comprises one or more of transition metal elements other than manganese and iron, ⅡA group metal elements, ⅢA group metal elements, and ⅣA group metal elements; the coating layer comprises carbon.

3. The method according to claim 1 or 2, wherein: 0.992≤x+y<0.995; and / or, 0.513≤x≤0.658; and / or, 0.336≤y≤0.479; and / or, 0≤n≤1; and / or, The M includes one or more elements selected from titanium, magnesium, aluminum, vanadium, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, and europium.

4. The method according to any one of claims 1 to 3, wherein: The Dv50 particle size of the precursor material is 3-100 μm, optionally 5-50 μm, and more optionally 8-20 μm; and / or, The compacted density of the precursor material at 30 MPa is 1.35-2.5 g / cm 3 , optional 1.5-2.5g / cm 3 and / or, The compound Mn in the precursor material x Fe y M (1-x-y) The mass content of HPO4·nH2O is 98%-100%; and / or, The precursor material includes primary crystal particles having a polyhedral morphology.

5. The method according to any one of claims 1 to 4, wherein: The precursor material is prepared by the following steps: Dissolving a soluble manganese source, a soluble iron source and a soluble source of the M element in a solvent to obtain a solution; Slowly adding the solution into a phosphoric acid solution to react, and optionally aging to obtain a reaction product; The reaction product is filtered, and the obtained filter residue is dried to obtain a precursor material.

6. The method according to claim 5, wherein: In the step of preparing the precursor material: The soluble manganese source includes one or more of a soluble organic manganese source and a soluble inorganic manganese source, and may be a soluble organic manganese source, and may be one or more of a soluble organic acid salt of manganese, and may be one or more of manganous acetate, manganous formate, manganous citrate, and manganous 2-hydroxypropionate; and / or, The soluble iron source includes one or more of a soluble organic iron source and a soluble inorganic iron source, and may be a soluble organic iron source, and may be one or more of a soluble organic acid salt of iron, and may be one or more of ferrous acetate, ferrous formate, ferrous citrate, and ferrous 2-hydroxypropionate; and / or, The source of the soluble M element includes one or more of an inorganic source of the soluble M element and an organic source of the soluble M element, and can be optionally one or more of a soluble organic acid salt and a soluble inorganic acid salt of the M element, and can be further optionally one or more of sulfates, nitrates, chlorides, formates, acetates, citrates, and 2-hydroxypropionates of the M element.

7. The method according to claim 5 or 6, wherein: In the step of preparing the precursor material: Slowly adding the solution into a phosphoric acid solution at 25°C-95°C for reaction, and optionally slowly adding the solution into a phosphoric acid solution at 30°C-90°C for reaction; and / or, The solution addition time is 10-300 min, optionally 15-300 min, more optionally 60-180 min; and / or, The molar ratio of phosphoric acid in the phosphoric acid solution to the total amount of metal elements in the solution is 0.4-1.5, optionally 0.5-1.5, and more optionally 0.8-1.2; and / or, The total concentration of the metal elements in the solution is 0.1-3.0 mol / L, optionally 0.5-2.5 mol / L, more preferably 1.0-1.6 mol / L; and / or, The phosphoric acid concentration in the phosphoric acid solution is 0.1-3.0 mol / L, optionally 0.5-2.5 mol / L, more optionally 1.0-1.32 mol / L; and / or, The molar amount of the M element in the solution accounts for 0.1%-10% of the total molar amount of the metal elements; and / or, The molar amount of the Mn element in the solution accounts for 30%-85% of the total molar amount of the metal elements.

8. The method according to any one of claims 5 to 7, wherein: In the step of preparing the precursor material: The aging temperature is 40°C-98°C, and can be 60°C-95°C; and / or, The aging time is 10-500 min, and can be 30-300 min; and / or, Reaction and / or aging are carried out at a pH value of 1.5-4.5; and / or, The reaction and / or aging is carried out under stirring conditions.

9. The method according to any one of claims 5 to 8, wherein: In the step of preparing the precursor material: Dissolving at 25°C-80°C, optionally at 25°C-40°C; and / or, The solvent is water; and / or, The filtration is negative pressure filtration, positive pressure filtration or centrifugal filtration; and / or, Before drying, washing the filter residue, optionally by washing the filter residue with water; and / or, The drying temperature is 80°C-500°C, optionally 120°C-400°C, more preferably 150°C-300°C; and / or, The drying time is 10-300 min.

10. The method according to any one of claims 1 to 9, wherein: In the steps of preparing the pre-product: The molar ratio of the precursor material to the lithium element in the lithium source is 0.9:1-1.1:1; and / or, The molar ratio of the phosphorus element in the phosphorus source to the lithium element in the lithium source is 1:1-1.05:1; and / or, The mixing time is 0.5-4h; and / or, The sintering temperature is 350°C-900°C, and can be 450°C-800°C; and / or, The sintering time is 3-10h.

11. The method according to any one of claims 1 to 10, wherein: In the steps of preparing the positive electrode material: The weight ratio of the pre-product to the carbon source is 3:1-30:1, and can be 5:1-15:1; and / or, The ratio of the weight of the solvent to the total weight of the carbon source and the pre-product is 1:1-10:1; and / or, The mixing time is 2-8 hours; and / or, The drying is performed by spray drying; and / or, The inlet temperature of the spray drying is 100°C-280°C; and / or, The outlet temperature of the spray drying is 50°C-180°C; and / or, The sintering temperature is 500°C-900°C, and can be 600°C-800°C; and / or, The sintering time is 8-20h.

12. The method according to any one of claims 1 to 11, wherein: The lithium source includes one or more of organic acid salts, inorganic acid salts, oxides, and hydroxides of lithium, and may be one or more of lithium carbonate, lithium hydroxide, lithium acetate, and lithium oxide; and / or, The phosphorus source includes one or more of phosphate, hydrogen phosphate, and dihydrogen phosphate, and can be selected from one or more of lithium phosphate, lithium dihydrogen phosphate, dilithium hydrogen phosphate, manganese hydrogen phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and manganese-iron hydrogen phosphate; and / or, The carbon source includes one or more of an organic carbon source and an inorganic carbon source, and may be selected from one or more of methanol, ethanol, acetic acid, polyethylene glycol, polyvinyl alcohol, polyvinyl butyral, glucose, maltose, and polytetrafluoroethylene; and / or, The solvent includes one or more of water, ethanol and acetone.

13. A positive electrode material, comprising a core and a coating layer covering the core; the core comprising a compound LiMn x Fe y M (1-x-y) PO4; among them, 0.9≤x+y<1, 0<x≤0.9, 0<y≤0.9; the M includes one or more of transition metal elements other than manganese and iron, group IIA metal elements, group IIIA metal elements, and group IVA metal elements, and can be selected to include one or more elements of titanium, magnesium, aluminum, vanadium, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, and europium; the coating layer includes carbon.

14. The positive electrode material according to claim 13, wherein The compaction density of the positive electrode material at 30 MPa is 1.88-2.52 g / cm 3 , optional: 2.0-2.5g / cm 3 and / or, The BET specific surface area of ​​the positive electrode material at liquid nitrogen temperature is 9.87-22.34 m 2 / g, optional 12-18m 2 / g; and / or, The powder resistivity of the positive electrode material is 1-1893Ω·cm, and can be 12-1000Ω·cm; and / or, The positive electrode material is prepared by the method according to any one of claims 1 to 12. 15 . A positive electrode sheet, comprising the positive electrode material prepared by the method according to claim 1 or the positive electrode material according to claim 13 or 14.

16. A battery comprising the positive electrode sheet according to claim 15.

17. An electrical device comprising the battery according to claim 16.

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