Method for preparing positive electrode material, positive electrode material, positive electrode sheet, battery, and electric device

Abstract

Provided are a method for preparing a positive electrode material, a positive electrode material, a positive electrode sheet, a battery, and an electric device. The method comprises: mixing a lithium source with a phosphoric acid solution, so as to obtain a first mixture; mixing the first mixture with manganese hydrogen phosphate, an iron source and a source of an optional M element, so as to obtain a second mixture; and drying and sintering the second mixture, so as to obtain a lithium manganese iron phosphate positive electrode material, wherein the M element comprises one or more of transition metal elements other than manganese and iron, metal elements of group IIA, metal elements of group IIIA, metal elements of group IVA, and metal elements of group VIIA. The method reduces side reaction gases and byproducts, improves the compaction density of a positive electrode material, decreases the resistivity of the positive electrode material, and improves the specific capacity and rate performance of a battery.

Description

Method for preparing positive electrode material, positive electrode material, positive electrode sheet, battery and electric device

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application No. 202311599356.7, filed on November 27, 2023, entitled “Method for preparing positive electrode materials, positive electrode materials, positive electrode sheets, batteries and electrical devices,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates to the technical field of secondary 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 scope of secondary batteries has become increasingly broad. 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, rate performance, and other aspects.

[0005] Summary of the Invention

[0006] This application is made in response to the above-mentioned problems and aims to provide a method for preparing a positive electrode material, the resulting positive electrode material, a positive electrode sheet, a battery, and an electrical device. The method of this application reduces side reaction gases and byproducts during the preparation process, increases the compaction density of the positive electrode material, and reduces the resistivity of the positive electrode material, thereby improving the specific capacity and rate 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] mixing a lithium source with a phosphoric acid solution to obtain a first mixture;

[0009] Mixing the first mixture with manganese hydrogen phosphate, an iron source, and an optional source of an M element to obtain a second mixture; wherein the M element comprises one or more transition metal elements other than manganese and iron, Group IIA metal elements, Group IIIA metal elements, Group IVA metal elements, and Group VIIA elements;

[0010] The second mixture is dried and sintered to obtain a lithium manganese iron phosphate positive electrode material.

[0011] Therefore, the present application is beneficial to improving the lithium ion conductivity of the material and reducing the generation of side reaction gases and by-products by first reacting the lithium source with the phosphoric acid solution and then reacting with other raw materials, thereby increasing the compaction density of the positive electrode material, reducing the resistivity of the material, and improving the specific capacity and rate performance of the battery.

[0012] In any embodiment, the positive electrode material includes a compound Li a Mn x Fe y M b PO4; wherein, x is selected from 0.5-0.9, y is selected from 0.1-0.5, the sum of x and y is 0.96-1, a is selected from 1.01-1.05, and b is selected from 0-0.05, and can be selected from 0.01-0.05; M includes one or more transition metal elements other than manganese and iron, Group IIA metal elements, Group IIIA metal elements, Group IVA metal elements, and Group VIIA elements, and can be selected from one or more elements selected from titanium, vanadium, chromium, copper, magnesium, aluminum, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, europium, and fluorine.

[0013] The second invention of this application provides a method for preparing a positive electrode material, comprising the following steps:

[0014] mixing a lithium source with a phosphoric acid solution to obtain a third mixture;

[0015] Mixing the third mixture with manganese hydrogen phosphate, an iron source, a carbon source, and an optional source of an M element to obtain a fourth mixture; wherein the M element comprises one or more transition metal elements other than manganese and iron, Group IIA metal elements, Group IIIA metal elements, Group IVA metal elements, and Group VIIA elements;

[0016] The fourth mixture is dried and sintered to obtain a lithium manganese iron phosphate positive electrode material.

[0017] Therefore, adding a carbon-containing coating layer is beneficial to improving the conductivity of the positive electrode material and further reducing the resistivity of the positive electrode material, thereby improving the specific capacity and rate performance of the battery.

[0018] In any embodiment, the positive electrode material includes a core and a coating layer covering the core, wherein the core includes the compound Li a Mn x Fe y M bPO4; wherein, x is selected from 0.5-0.9, y is selected from 0.1-0.5, the sum of x and y is 0.96-1, a is selected from 1.01-1.05, and b is selected from 0-0.05, and can be optionally 0.01-0.05; M includes one or more transition metal elements other than manganese and iron, Group IIA metal elements, Group IIIA metal elements, Group IVA metal elements, and Group VIIA elements, and can be optionally one or more elements selected from titanium, vanadium, chromium, copper, magnesium, aluminum, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, europium, and fluorine; and the coating layer includes carbon.

[0019] In any embodiment, the M element includes one or more elements selected from titanium, vanadium, chromium, copper, magnesium, aluminum, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, europium, and fluorine.

[0020] In any embodiment, the sintering temperature is 620° C.-780° C., optionally 650° C.-750° C.; and / or,

[0021] The sintering time is 6-14 hours, optionally 6-12 hours; and / or,

[0022] The sintering is carried out in an inert atmosphere, optionally in a nitrogen atmosphere; and / or,

[0023] The temperature is raised to the sintering temperature at a rate of 1-15°C / min, and optionally at a rate of 2-10°C / min.

[0024] Therefore, adopting the above-mentioned calcination temperature, time and / or other calcination conditions is beneficial to reducing the resistivity of the positive electrode material and improving the specific capacity and rate performance of the battery.

[0025] In any embodiment, the carbon source includes one or more of an inorganic carbon source and an organic carbon source, and can be selected from one or more of glucose, sucrose, polyethylene glycol, polyvinyl alcohol, citric acid, hydroxypropyl beta-cyclodextrin, polyvinyl pyrrolidone, polyacrylic acid, polyvinylidene fluoride, polystyrene, polypropylene, and ethylene glycol, and can be selected from hydroxypropyl beta-cyclodextrin; and / or,

[0026] The weight of the carbon source is 4%-7% of the total weight of the manganese hydrogen phosphate and the iron source.

[0027] Therefore, the use of the above-mentioned carbon source is conducive to forming nanoparticles of the positive electrode material and increasing the specific surface area of ​​the positive electrode material.

[0028] In any embodiment, the Dv50 particle size of the insoluble matter in the second mixture and the fourth mixture is independently 0.2-1.0 μm, optionally 0.2-0.6 μm.

[0029] In any embodiment, the molar ratio of phosphorus in the phosphoric acid solution to manganese hydrogen phosphate is 0.02-0.07, optionally 0.02-0.04; and / or,

[0030] The molar ratio of the lithium element in the lithium source to the total phosphorus element in the phosphoric acid solution and the manganese hydrogen phosphate is 1.01-1.05; and / or,

[0031] The molar ratio of the iron element in the iron source to the total phosphorus element in the phosphoric acid solution and the manganese hydrogen phosphate is 0.1-0.5; and / or,

[0032] The molar ratio of the M element in the source of the M element to the total phosphorus element in the phosphoric acid solution and the manganese hydrogen phosphate is 0.01-0.05; and / or,

[0033] The concentration of the phosphoric acid solution is 75% to 85% by weight; and / or,

[0034] In the steps of preparing the first mixture and the third mixture, the mixing time is independently 15-20 minutes; and / or,

[0035] In the steps of preparing the second mixture and the fourth mixture, mixing is performed sequentially by stirring and ball milling; and / or,

[0036] The drying is performed by a spray dryer; optionally, the air inlet temperature of the spray dryer is 200°C-250°C, and the air outlet temperature is 100°C-120°C.

[0037] In any embodiment, the lithium source includes one or more of an inorganic acid salt, an organic acid salt, an oxide, and a hydroxide of lithium, and may be selected from one or more of lithium carbonate, lithium hydroxide, lithium acetate, lithium oxalate, lithium citrate, lithium dihydrogen phosphate, and lithium phosphate; and / or,

[0038] The iron source includes one or more of an inorganic acid salt, an organic acid salt, an oxide, and a hydroxide of iron, and can be selected from one or more of ferrous oxalate, ferrous acetate, ferrous carbonate, ferric phosphate, and ferric hydrogen phosphate; and / or,

[0039] The source of the M element includes one or more of an inorganic acid salt, an organic acid salt, an oxide, and a hydroxide of the M element, and can optionally include one or more of an oxalate, an acetate, a carbonate, a phosphate, an oxide, and a hydroxide of the M element.

[0040] The third aspect of the present application also provides a positive electrode material, including a compound Li a Mn x Fe y M bPO4; wherein, x is selected from 0.5-0.9, y is selected from 0.1-0.5, the sum of x and y is 0.96-1, a is selected from 1.01-1.05, and b is selected from 0-0.05, and can be selected from 0.01-0.05; M includes one or more transition metal elements other than manganese and iron, Group IIA metal elements, Group IIIA metal elements, Group IVA metal elements, and Group VIIA elements, and can be selected from one or more elements selected from titanium, vanadium, chromium, copper, magnesium, aluminum, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, europium, and fluorine.

[0041] Therefore, the positive electrode material of the present application contains fewer by-products, the compaction density of the positive electrode material is improved, and the resistivity of the positive electrode material is reduced, thereby improving the specific capacity and rate performance of the battery.

[0042] The fourth aspect of the present application also provides a positive electrode material, comprising a core and a coating layer covering the core; the core comprises the compound Li a Mn x Fe y M b PO4; wherein, x is selected from 0.5-0.9, y is selected from 0.1-0.5, the sum of x and y is 0.96-1, a is selected from 1.01-1.05, and b is selected from 0-0.05, and can be selected from 0.01-0.05; M includes one or more transition metal elements other than manganese and iron, group IIA metal elements, group IIIA metal elements, group IVA metal elements, and group VIIA elements, and can be selected from one or more elements selected from titanium, vanadium, chromium, copper, magnesium, aluminum, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, europium, and fluorine; and the coating layer includes carbon;

[0043] Optionally, the average thickness of the coating layer is 6-12 nm, more preferably 8-12 nm;

[0044] Optionally, the weight of the carbon is 1.1%-2% of the total weight of the positive electrode material, and more optionally 1.3%-1.5%.

[0045] Therefore, adding a carbon-containing coating layer is beneficial to improving the conductivity of the positive electrode material and further reducing the resistivity of the positive electrode material, thereby improving the specific capacity and rate performance of the battery.

[0046] In any embodiment, the compaction density of the positive electrode material at 294.2 MPa is 2.09-2.48 g / cm 3 , optional 2.1-2.3g / cm 3 and / or,

[0047] The Dv50 particle size of the primary particles of the positive electrode material is 100-600 nm, optionally 100-300 nm; and / or,

[0048] The BET specific surface area of ​​the positive electrode material at liquid nitrogen temperature is 6-20 m 2 / g, optional 14-19.87m 2 / g; and / or,

[0049] The powder resistivity of the positive electrode material at 7.85 MPa is 10.8-870.6 Ω·cm, optionally 48.5-205.1 Ω·cm; and / or,

[0050] The positive electrode material is prepared by the method of the first or second aspect of the present application.

[0051] The fifth aspect of the present application provides a positive electrode plate, comprising the positive electrode material of the third or fourth aspect of the present application or the positive electrode material prepared according to the method of the first or second aspect of the present application.

[0052] The sixth aspect of the present application provides a battery, comprising the positive electrode material of the third or fourth aspect of the present application, the positive electrode material prepared according to the method of the first or second aspect of the present application, or the positive electrode sheet of the fifth aspect of the present application.

[0053] The seventh aspect of the present application provides an electrical device comprising the battery of the sixth aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] FIG1 is a schematic diagram of a battery cell according to an embodiment of the present application.

[0055] FIG. 2 is an exploded view of the battery cell according to the embodiment of the present application shown in FIG. 1 .

[0056] FIG3 is a schematic diagram of a battery module according to an embodiment of the present application.

[0057] FIG4 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0058] FIG. 5 is an exploded view of the battery pack shown in FIG. 4 according to an embodiment of the present application.

[0059] 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.

[0060] FIG7 is a SEM photograph of the positive electrode material of Example 1 of the present application.

[0061] Description of reference numerals:

[0062] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 battery cell; 51 shell; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0063] Below, with appropriate reference to the accompanying drawings, the embodiments of the positive electrode material and its preparation method, positive electrode sheet, battery cell, battery module, battery pack and electric device of the present application are specifically disclosed in detail. 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 structure 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.

[0064] " 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.

[0065] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0066] 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.

[0067] 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.

[0068] Unless otherwise specified, the Dv50 particle size in this application refers to the particle size when the cumulative value of the volume distribution of the particles is 50%.

[0069] [Battery Cell]

[0070] 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.

[0071] 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.

[0072] [Method for preparing positive electrode material]

[0073] One embodiment of the present application provides a method for preparing a positive electrode material, comprising the following steps:

[0074] mixing a lithium source with a phosphoric acid solution to obtain a first mixture;

[0075] Mixing the first mixture with manganese hydrogen phosphate, an iron source, and an optional source of an M element to obtain a second mixture; wherein the M element comprises one or more transition metal elements other than manganese and iron, Group IIA metal elements, Group IIIA metal elements, Group IVA metal elements, and Group VIIA elements;

[0076] The second mixture is dried and sintered to obtain a lithium manganese iron phosphate positive electrode material.

[0077] When the lithium source, manganese hydrogen phosphate, iron source, and optional other transition metal sources react with the phosphoric acid solution, side reactions are likely to occur, producing a large amount of side reaction gases and by-products, resulting in a decrease in the compaction density of the positive electrode material and an increase in the resistivity, resulting in a decrease in the yield of the preparation method, thereby adversely affecting the energy density and rate performance of the battery.

[0078] Although the mechanism is still unclear, the applicant unexpectedly discovered that by first reacting the lithium source with a phosphoric acid solution and then reacting with other raw materials, the generation of side reaction gases and by-products is reduced, and the lithium ion conductivity of the material is also improved, thereby increasing the compaction density of the positive electrode material, reducing the resistivity of the material, and improving the specific capacity and rate performance of the battery.

[0079] In some embodiments, the cathode material includes a compound Li a Mn x Fe y M b PO4; wherein, x is selected from 0.5-0.9, and can be selected from 0.58-0.6, such as 0.52, 0.53, 0.55, 0.56, 0.58, 0.59, 0.6, 0.63, 0.65, 0.67, 0.7, 0.72, 0.74, 0.76, 0.8, 0.83, 0.85, 0.87, 0.9 or a range consisting of any of the above values, and y is selected from 0.1-0.5, and can be selected from 0.38-0.4, such as 0.1, 0.12, 0.15, 0.16, 0.18, 0.2, 0.23, 0.25, 0.27, 0.29, 0.3, 0.32, 0.35, 0.36, 0.37, 0.38, 0.39, 0.4, 0.43, 0.45, 0.46, 0.5 or any of the above values, the sum of x and y is 0.96-1, for example, 0.96, 0.98, 0.99, 1 or any of the above values, a is selected from 1.01-1.05, optionally 1.01-1.04, for example 1.01, 1.02, 1.03, 1.04, 1.05 or any of the above values, b is selected from 0-0.05, optionally 0.01-0.05, more optionally The range of M is 0.015-0.03, for example, 0.005, 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.045, 0.05 or any of the above values; the M includes one or more transition metal elements other than manganese and iron, Group IIA metal elements, Group IIIA metal elements, Group IVA metal elements, and Group VIIA elements, and can be optionally one or more elements including titanium, vanadium, chromium, copper, magnesium, aluminum, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, europium, and fluorine.

[0080] Another embodiment of the present application provides a method for preparing a positive electrode material, comprising the following steps:

[0081] mixing a lithium source with a phosphoric acid solution to obtain a third mixture;

[0082] Mixing the third mixture with manganese hydrogen phosphate, an iron source, a carbon source, and an optional source of an M element to obtain a fourth mixture; wherein the M element comprises one or more transition metal elements other than manganese and iron, Group IIA metal elements, Group IIIA metal elements, Group IVA metal elements, and Group VIIA elements;

[0083] The fourth mixture is dried and sintered to obtain a lithium manganese iron phosphate positive electrode material.

[0084] Therefore, adding a carbon-containing coating layer is beneficial to improving the conductivity of the positive electrode material and further reducing the resistivity of the positive electrode material, thereby improving the specific capacity and rate performance of the battery.

[0085] In some embodiments, the positive electrode material includes a core and a coating layer covering the core, wherein the core includes the compound Li a Mn x Fe y M b PO4; wherein, x is selected from 0.5-0.9, optionally 0.58-0.6, such as 0.52, 0.53, 0.55, 0.56, 0.58, 0.59, 0.6, 0.63, 0.65, 0.67, 0.7, 0.72, 0.74, 0.76, 0.8, 0.83, 0.85, 0.87, 0.9 or a range consisting of any of the above values, and y is selected from 0.1-0.5, optionally 0 0.38-0.4, for example, 0.1, 0.12, 0.15, 0.16, 0.18, 0.2, 0.23, 0.25, 0.27, 0.29, 0.3, 0.32, 0.35, 0.36, 0.37, 0.38, 0.39, 0.4, 0.43, 0.45, 0.46, 0.5 or any range thereof, and the sum of x and y is 0.96-1, for example, 0.96, 0.98, 0 0.99, 1 or any range consisting of the above values, the a is selected from 1.01-1.05, optionally 1.01-1.04, for example 1.01, 1.02, 1.03, 1.04, 1.05 or any range consisting of the above values, the b is selected from 0-0.05, optionally 0.01-0.05, more optionally 0.015-0.03, for example 0.005, 0.01, 0.015, 0.02, 0.025 , 0.03, 0.035, 0.04, 0.045, 0.05 or a range consisting of any of the above values; the M includes one or more transition metal elements other than manganese and iron, group IIA metal elements, group IIIA metal elements, group IVA metal elements, and group VIIA elements, and can be optionally one or more elements including titanium, vanadium, chromium, copper, magnesium, aluminum, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, europium, and fluorine; the coating layer includes carbon.

[0086] In some embodiments, the M element includes one or more elements selected from the group consisting of titanium, vanadium, chromium, copper, magnesium, aluminum, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, europium, and fluorine.

[0087] In some embodiments, the sintering temperature is 620°C-780°C, optionally 650°C-750°C, for example, 620°C, 630°C, 640°C, 650°C, 670°C, 690°C, 700°C, 720°C, 740°C, 750°C, 770°C, 780°C or a range consisting of any of the above values; and / or,

[0088] The sintering time is 6-14 hours, and can be 6-12 hours, for example, 6, 7, 8, 9, 10, 11, 12, 13, 14 hours or a range consisting of any of the above values; and / or,

[0089] The sintering is carried out in an inert atmosphere, optionally in a nitrogen atmosphere; and / or,

[0090] The temperature is raised to the sintering temperature at a rate of 1-15°C / min, and can be optionally raised to the sintering temperature at a rate of 2-10°C / min, for example, at a rate of 1°C / min, 2°C / min, 4°C / min, 5°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min, 12°C / min, 13°C / min, 14°C / min, 15°C / min or a range of any of the above values.

[0091] Therefore, adopting the above-mentioned calcination temperature, time and / or other calcination conditions is beneficial to reducing the resistivity of the positive electrode material and improving the specific capacity and rate performance of the battery.

[0092] In some embodiments, the carbon source includes one or more of an inorganic carbon source and an organic carbon source, and may be selected from the group consisting of glucose, sucrose, polyethylene glycol, polyvinyl alcohol, citric acid, hydroxypropyl β-cyclodextrin, polyvinyl pyrrolidone, polyacrylic acid, polyvinylidene fluoride, polystyrene, polypropylene, and ethylene glycol, and may be selected from the group consisting of hydroxypropyl β-cyclodextrin; and / or,

[0093] The weight of the carbon source is 4%-7% of the sum of the weight of the manganese hydrogen phosphate and the iron source, for example, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7% or a range consisting of any of the above values.

[0094] Therefore, the use of the above-mentioned carbon source is conducive to forming nanoparticles of the positive electrode material and increasing the specific surface area of ​​the positive electrode material.

[0095] In some embodiments, the Dv50 particle size of the insoluble matter in the second mixture and the fourth mixture is independently 0.2-1.0 μm, optionally 0.2-0.6 μm, such as 0.2 μm, 0.23 μm, 0.25 μm, 0.27 μm, 0.28 μm, 0.3 μm, 0.32 μm, 0.34 μm, 0.36 μm, 0.38 μm, 0.4 μm, 0.42 μm, 0.44 μm, 0.45 μm, 0.47 μm, 0.49 μm, 0.5μm, 0.53μm, 0.55μm, 0.57μm, 0.6μm, 0.62μm, 0.64μm, 0.65μm, 0.67μm, 0.7μm, 0.73μm, 0.75μm, 0 .78μm, 0.8μm, 0.83μm, 0.85μm, 0.87μm, 0.9μm, 0.92μm, 0.95μm, 0.97μm, 0.99μm, 1.0μm or a range consisting of any of the above values.

[0096] In some embodiments, the molar ratio of phosphorus in the phosphoric acid solution to manganese hydrogen phosphate is 0.02-0.07, optionally 0.02-0.04, for example, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07 or any range thereof; and / or,

[0097] The molar ratio of the lithium element in the lithium source to the total phosphorus element in the phosphoric acid solution and the manganese hydrogen phosphate is 1.01-1.05, for example, 1.01, 1.02, 1.03, 1.04, 1.05 or any range thereof; and / or,

[0098] The molar ratio of the iron in the iron source to the total phosphorus in the phosphoric acid solution and the manganese hydrogen phosphate is 0.1-0.5, for example, 0.13, 0.15, 0.18, 0.2, 0.22, 0.24, 0.25, 0.27, 0.29, 0.3, 0.32, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.4, 0.42, 0.44, 0.45, 0.47, 0.48, 0.49, 0.5 or any range thereof; and / or,

[0099] The molar ratio of the M element in the source of the M element to the total phosphorus element in the phosphoric acid solution and the manganese hydrogen phosphate is 0.01-0.05, for example, 0.01, 0.02, 0.03, 0.04, 0.05 or any range thereof; and / or,

[0100] The concentration of the phosphoric acid solution is 75 wt % to 85 wt %, for example, 75 wt %, 78 wt %, 80 wt %, 82 wt %, 84 wt %, 85 wt % or any range thereof; and / or,

[0101] In the steps of preparing the first mixture and the third mixture, the mixing time is independently 15-20 minutes, for example, 15, 16, 17, 18, 19, 20 minutes or a range consisting of any of the above values; and / or,

[0102] In the steps of preparing the second mixture and the fourth mixture, mixing is performed sequentially by stirring and ball milling; and / or,

[0103] The drying is carried out by a spray dryer; optionally, the inlet air temperature of the spray dryer is 200°C-250°C, for example, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C or a range consisting of any of the above values, and the outlet air temperature is 100°C-120°C, for example, 100°C, 105°C, 110°C, 115°C, 120°C or a range consisting of any of the above values.

[0104] In this application, the Dv50 particle size of the insoluble matter in the mixture is measured using conventional methods in the art, such as taking an appropriate amount of the mixture, adding deionized water, ultrasonically treating the sample to completely disperse it, and measuring it using a laser particle size analyzer.

[0105] In some embodiments, the lithium source includes one or more of an inorganic acid salt, an organic acid salt, an oxide, and a hydroxide of lithium, and may be selected from one or more of lithium carbonate, lithium hydroxide, lithium acetate, lithium oxalate, lithium citrate, lithium dihydrogen phosphate, and lithium phosphate; and / or

[0106] The iron source includes one or more of an inorganic acid salt, an organic acid salt, an oxide, and a hydroxide of iron, and can be selected from one or more of ferrous oxalate, ferrous acetate, ferrous carbonate, ferric phosphate, and ferric hydrogen phosphate; and / or,

[0107] The source of the M element includes one or more of an inorganic acid salt, an organic acid salt, an oxide, and a hydroxide of the M element, and can optionally include one or more of an oxalate, an acetate, a carbonate, a phosphate, an oxide, and a hydroxide of the M element.

[0108] [Cathode material]

[0109] One embodiment of the present application provides a positive electrode material, including a compound Li a Mn x Fe y M bPO4; wherein, x is selected from 0.5-0.9, optionally 0.58-0.6, such as 0.52, 0.53, 0.55, 0.56, 0.58, 0.59, 0.6, 0.63, 0.65, 0.67, 0.7, 0.72, 0.74, 0.76, 0.8, 0.83, 0.85, 0.87, 0.9 or a range consisting of any of the above values, and y is selected from 0.1-0.5, optionally is 0.38-0.4, for example, 0.1, 0.12, 0.15, 0.16, 0.18, 0.2, 0.23, 0.25, 0.27, 0.29, 0.3, 0.32, 0.35, 0.36, 0.37, 0.38, 0.39, 0.4, 0.43, 0.45, 0.46, 0.5 or any range thereof, and the sum of x and y is 0.96-1, for example, 0.96, 0 0.98, 0.99, 1 or any of the above values, the a is selected from 1.01-1.05, optionally 1.01-1.04, for example 1.01, 1.02, 1.03, 1.04, 1.05 or any of the above values, the b is selected from 0-0.05, optionally 0.01-0.05, more optionally 0.015-0.03, for example 0.005, 0.01, 0.015, 0.0 2, 0.025, 0.03, 0.035, 0.04, 0.045, 0.05 or any range consisting of the foregoing values; wherein M includes one or more transition metal elements other than manganese and iron, Group IIA metal elements, Group IIIA metal elements, Group IVA metal elements, and Group VIIA elements, and can be optionally one or more elements selected from titanium, vanadium, chromium, copper, magnesium, aluminum, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, europium, and fluorine.

[0110] Therefore, the positive electrode material of the present application contains fewer by-products, the compaction density of the positive electrode material is improved, and the resistivity of the positive electrode material is reduced, thereby improving the specific capacity and rate performance of the battery.

[0111] Another embodiment of the present application provides a positive electrode material, comprising a core and a coating layer covering the core; the core comprises the compound Li a Mn x Fe y M bPO4; wherein, x is selected from 0.5-0.9, optionally 0.58-0.6, such as 0.52, 0.53, 0.55, 0.56, 0.58, 0.59, 0.6, 0.63, 0.65, 0.67, 0.7, 0.72, 0.74, 0.76, 0.8, 0.83, 0.85, 0.87, 0.9 or a range consisting of any of the above values, and y is selected from 0.1-0.5, optionally 0 0.38–0.4, for example, 0.1, 0.12, 0.15, 0.16, 0.18, 0.2, 0.23, 0.25, 0.27, 0.29, 0.3, 0.32, 0.35, 0.36, 0.37, 0.38, 0.39, 0.4, 0.43, 0.45, 0.46, 0.5 or any range thereof, and the sum of x and y is 0.96-1, for example, 0.96, 0.98, 0 0.99, 1 or any range consisting of the above values, the a is selected from 1.01-1.05, optionally 1.01-1.04, for example 1.01, 1.02, 1.03, 1.04, 1.05 or any range consisting of the above values, the b is selected from 0-0.05, optionally 0.01-0.05, more optionally 0.015-0.03, for example 0.005, 0.01, 0.015, 0.02, 0.025 , 0.03, 0.035, 0.04, 0.045, 0.05 or any range thereof; the M includes one or more transition metal elements, Group IIA metal elements, Group IIIA metal elements, Group IVA metal elements, and Group VIIA elements other than manganese and iron, and can be optionally one or more elements selected from titanium, vanadium, chromium, copper, magnesium, aluminum, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, europium, and fluorine; the coating layer includes carbon;

[0112] Optionally, the average thickness of the coating layer is 6-12 nm, more preferably 8-12 nm, for example, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm or a range consisting of any of the above values;

[0113] Optionally, the weight of the carbon is 1.1%-2% of the total weight of the positive electrode material, and more optionally 1.3%-1.5%, for example, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0% or a range consisting of any of the above values.

[0114] Therefore, adding a carbon-containing coating layer is beneficial to improving the conductivity of the positive electrode material and further reducing the resistivity of the positive electrode material, thereby improving the specific capacity and rate performance of the battery.

[0115] In the present application, the average thickness of the coating layer is tested by conventional methods in the field; for example, the primary particles of the positive electrode material (particle size is Dv50 particle size ± 0.3 μm) are scanned by a SEM-EDS combination instrument to determine the boundary line between the core and the coating layer, and the distance from the core to the boundary line and the distance from the core to the outermost edge of the coating layer are measured in the scanning electron microscope image. The measurements are randomly oriented multiple times, and then the above test is repeated on multiple primary particles of the positive electrode material. The average value of the difference between the distance from the core to the outermost edge of the coating layer and the distance from the core to the boundary line is the average thickness of the coating layer.

[0116] In the present application, the weight percentage of carbon in the positive electrode material is tested using conventional methods in the art; for example, flux metal tungsten particles are added to the positive electrode material, mixed, placed in a high-frequency infrared carbon-sulfur analyzer for sintering, and the weight percentage of carbon in the positive electrode material is tested.

[0117] In some embodiments, the cathode material has a compaction density of 2.09-2.48 g / cm at 294.2 MPa. 3 , optional 2.1-2.3g / cm 3 , for example 2.09 g / cm 3 , 2.1g / cm 3 , 2.13g / cm 3 , 2.16g / cm 3 , 2.18g / cm 3 , 2.2g / cm 3 , 2.22g / cm 3 , 2.25g / cm 3 , 2.27g / cm 3 , 2.29g / cm 3 , 2.3g / cm 3 , 2.32g / cm 3 , 2.35g / cm 3 , 2.36g / cm 3 , 2.38g / cm 3 , 2.4g / cm 3 , 2.42g / cm 3 , 2.44g / cm 3 , 2.45g / cm 3 , 2.46g / cm 3 , 2.48g / cm 3 or a range consisting of any of the above values; and / or,

[0118] The primary particles of the positive electrode material have a Dv50 particle size of 100-600 nm, optionally 100-300 nm, for example, 100 nm, 150 nm, 200 nm, 230 nm, 250 nm, 280 nm, 300 nm, 330 nm, 350 nm, 380 nm, 400 nm, 450 nm, 480 nm, 500 nm, 530 nm, 550 nm, 580 nm, 600 nm or a range consisting of any of the above values; and / or,

[0119] The BET specific surface area of ​​the positive electrode material at liquid nitrogen temperature is 6-20 m 2 / g, optional 14-19.87m 2 / g, for example 6m 2 / g、8m 2 / g、9m 2 / g、10m 2 / g、11m 2 / g、12m 2 / g、13m 2 / g、15m 2 / g, 15.5m 2 / g、16m 2 / g, 16.3m 2 / g, 16.7m 2 / g、17m 2 / g, 17.3m 2 / g、18m 2 / g、19m 2 / g, 20m 2 / g or any range consisting of the above values; and / or,

[0120] The powder resistivity of the positive electrode material at 7.85 MPa is 10.8-870.6 Ω·cm, which can be 48.5-205.1 Ω·cm, such as 10.8 Ω·cm, 15 Ω·cm, 20 Ω·cm, 30 Ω·cm, 35 Ω·cm, 40 Ω·cm, 45 Ω·cm, 48 Ω·cm, 50 Ω·cm, 55 Ω·cm, 56 Ω·cm, 60 Ω·cm, 65 Ω·cm, 68 Ω·cm, 70 Ω·cm, cm, 75Ω·cm, 80Ω·cm, 85Ω·cm, 90Ω·cm, 95Ω·cm, 100Ω·cm, 110Ω·cm, 120Ω·cm, 150Ω·cm, 160Ω·cm, 18 0Ω·cm, 190Ω·cm, 200Ω·cm, 205Ω·cm, 210Ω·cm, 250Ω·cm, 270Ω·cm, 300Ω·cm, 350Ω·cm, 400Ω·cm, 450 Ω·cm, 500Ω·cm, 550Ω·cm, 600Ω·cm, 650Ω·cm, 700Ω·cm, 750Ω·cm, 800Ω·cm, 820Ω·cm, 840Ω·cm, 850Ω·cm, 860Ω·cm, 870Ω·cm, 870.6Ω·cm, or a range consisting of any of the above values; and / or,

[0121] The positive electrode material is prepared by the method described above in this application.

[0122] In the present application, the compaction density of the material is tested using conventional methods in the art; for example, the method is: weigh the sample powder and place it in a compaction density mold, put it into a compaction density machine, and test the compaction density after compaction with a certain pressure.

[0123] In this application, the Dv50 particle size of the primary particles of the material is tested using conventional methods in the field; for example, the method is: testing the positive electrode material by SEM, observing the primary particles based on the SEM photos and randomly taking multiple primary particles to measure the particle size, and statistically calculating to obtain the Dv50 particle size of the primary particles of the positive electrode material.

[0124] In this application, the BET specific surface area of ​​the material at liquid nitrogen temperature is tested using conventional methods in the art; for example, the method is: the sample is placed in a specific surface area test tube, the liquid nitrogen cup is filled with liquid nitrogen, and the specific surface area test tube is placed in it, and the specific surface area analyzer is used for testing.

[0125] In this application, the powder resistivity of the material at 7.85 MPa is tested using conventional methods in the art; for example, the method is: the sample is placed in a mold, and then the mold is placed in a four-probe resistivity tester, the pressure is adjusted to 7.85 MPa, 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.

[0126] [Positive electrode]

[0127] The positive electrode sheet generally includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector. The positive electrode film layer includes the aforementioned positive electrode material or the positive electrode material prepared by the aforementioned method.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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.).

[0132] In some embodiments, the positive electrode material may further include positive electrode active materials for batteries that are well known in the art. As an example, the positive electrode material may include at least one of the following materials: lithium transition metal oxides and modified compounds thereof. 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 ), LiNi0.5 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.

[0133] 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.

[0134] 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.

[0135] 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.

[0136] [Negative electrode]

[0137] 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.

[0138] 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.

[0139] 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.).

[0140] 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.

[0141] 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).

[0142] 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.

[0143] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0144] 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.

[0145] [Electrolytes]

[0146] 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.

[0147] In some embodiments, the electrolyte is liquid and includes an electrolyte salt and a solvent.

[0148] 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.

[0149] 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.

[0150] 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.

[0151] [Isolation film]

[0152] 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.

[0153] 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.

[0154] 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.

[0155] In some embodiments, the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0156] 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.

[0157] 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.

[0158] 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.

[0159] 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.

[0160] 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.

[0161] 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.

[0162] 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.

[0163] 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.

[0164] 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.

[0165] As an electrical device, a battery cell, battery module or battery pack can be selected according to its usage requirements.

[0166] 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.

[0167] [Example]

[0168] 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.

[0169] Example 1

[0170] (1) Preparation of positive electrode materials:

[0171] 45.4g of Li2CO3 (purity ≥99.5%) was added to a 75% by weight phosphoric acid solution and mixed for 15 minutes under stirring; then FePO4 (purity ≥99%), MnHPO4 (purity ≥99%), hydroxypropyl β-cyclodextrin, titanium dioxide and 4.8g of PEG4000 was mixed a second time; the molar ratio of lithium in Li2CO3 to the total phosphorus in the phosphoric acid solution and MnHPO4 was 1.02, the molar ratio of phosphorus in the phosphoric acid solution to MnHPO4 was 0.03, the molar ratio of FePO4 to the total phosphorus in the phosphoric acid solution and MnHPO4 was 0.392, the molar ratio of titanium dioxide to the total phosphorus in the phosphoric acid solution and MnHPO4 was 0.02, and the weight of hydroxypropyl β-cyclodextrin was 6% of the total weight of MnHPO4 and FePO4. The mixture was transferred to a ball mill and ground using a planetary ball mill until the final mixture (slurry) had an insoluble matter Dv50 particle size of 0.38 μm. The slurry was spray dried using a 10L centrifugal spray dryer with an inlet air temperature of 200°C, an outlet air temperature of 105°C, and a peristaltic feed pump frequency of 20 Hz. The dried powder was sintered in a box furnace in a nitrogen atmosphere with a nitrogen flow rate of 6 L / min, a heating rate of 2°C / min, a sintering temperature of 730°C, a sintering time of 12 hours, and cooled to obtain a positive electrode material.

[0172] (2) Preparation of positive electrode sheet:

[0173] Weigh 0.3g of polyvinylidene fluoride (PVDF) binder into 10.8g of N-methylpyrrolidone (NMP) and stir until completely dissolved. Then, add 2.4g of the aforementioned cathode material and 0.3g of carbon black conductive agent (SP) and stir until a paste is formed. Use an applicator to evenly coat the paste on aluminum foil and dry it 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.

[0174] (3) Negative electrode: Metal lithium sheet is used.

[0175] (4) Isolation film: PE-PP composite film.

[0176] (5) Preparation of electrolyte:

[0177] 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.

[0178] (6) Preparation of button batteries:

[0179] The positive electrode sheet, separator, negative electrode sheet and electrolyte were assembled into a CR2032 button battery.

[0180] The secondary battery preparation methods of Examples 2-30 and Comparative Examples 1-2 are similar to those of Example 1, and the different parameters are detailed in Table 1-2.

[0181] Comparative Example 1-2

[0182] Various raw materials were mixed and stirred together according to the proportions in Table 1 for 15 minutes, and then dried and sintered according to the parameters in Table 1 to obtain a positive electrode material; the rest was the same as in Example 1.

[0183] Material testing and battery testing

[0184] (1) Test of core chemical formula and carbon content:

[0185] Weigh the positive electrode 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 h, and dilute to volume with a 100 mL volumetric flask; use a pipette to transfer 1 mL to a 100 mL volumetric flask and dilute to volume to obtain the test solution.

[0186] An inductively coupled plasma optical emission spectrometer (ICP-OES, instrument brand: Agilent 5800) was used to determine the contents of lithium, manganese, iron, phosphorus, oxygen, and doping elements in the test solution, calculate the element ratio in the material, and determine the chemical formula.

[0187] Weigh 0.1g of positive electrode material, add 1.5g of flux metal tungsten particles and mix, put it into a high-frequency infrared carbon-sulfur analyzer for sintering and test the weight percentage of carbon in the positive electrode material.

[0188] (2) Test of average thickness of coating layer of positive electrode material:

[0189] The primary particles of the positive electrode material (particle size is Dv50 particle size ± 0.3 μm) are scanned by a SEM-EDS combination instrument to determine the boundary line between the inner core and the coating layer. The distance from the inner core to the boundary line and the distance from the inner core to the outermost edge of the coating layer are measured in the scanning electron microscope image. The random orientation measurement is repeated 50 times. Then, a total of 50 primary particles of the positive electrode material are taken to repeat the above test. The average value of the difference between the distance from the inner core to the outermost edge of the coating layer and the distance from the inner core to the boundary line is the average thickness of the coating layer.

[0190] (3) Test of the Dv50 particle size of the insoluble matter in the mixture and the Dv50 particle size of the primary particles of the positive electrode material:

[0191] An appropriate amount of the mixture was added with 20 mL of deionized water and ultrasonically treated for 5 minutes (53 KHz, 120 W) to completely disperse the sample. The Dv50 particle size of the material was measured using a laser particle size analyzer (MasterSizer 2000).

[0192] Dv50 particle size test of primary particles of positive electrode materials:

[0193] The positive electrode material was tested by SEM. The primary particles were observed based on the SEM photos and 100 primary particles were randomly selected to measure the particle size, and the Dv50 particle size of the primary particles of the positive electrode material was calculated.

[0194] (4) Compaction density test:

[0195] Weigh 1g of sample powder and place it in a compaction density mold, put it into a compaction density machine, and test the compaction density after compaction at a pressure of 294.2MPa.

[0196] (5) BET specific surface area test:

[0197] Weigh 1 g of sample and place it in a specific surface area test tube. Fill a liquid nitrogen cup with liquid nitrogen and place it in the specific surface area test tube. Place the sample in a temperature environment of -200°C and use a specific surface area analyzer (Beijing Jingwei Gaobo, JWBK-112) for testing.

[0198] (6) Test of powder resistivity:

[0199] 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.

[0200] (7) Micromorphology evaluation:

[0201] The microscopic morphology of the positive electrode material of Example 1 was observed using a scanning electron microscope (SEM, instrument brand: ZEISS sigma 300), as shown in FIG7 .

[0202] (8) Test method for battery capacity in grams:

[0203] After assembling the button cell, let it sit for 3 hours, charge it at 0.1C (1C, 2C, or 3C) to 4.3V, then charge it at a constant voltage at 4.3V until the current is less than or equal to 0.02C. Let the battery sit for 5 minutes, then discharge it at 0.1C (1C, 2C, or 3C) to 2V. Record the discharge capacity D1 at this point. Divide the discharge capacity D1 by the mass of the positive electrode material to obtain the battery's capacity in grams.

[0204] Table 3: Performance test results of Examples 1-30 and Comparative Examples 1-2

[0205] According to the above results, we can know that:

[0206] Compared with comparative example 1-2 in which the raw materials are mixed together, the battery of example 1-27 of the present application has a higher gram capacity and better rate performance;

[0207] Compared with the lower sintering temperature used in Example 22, the battery in Example 19 of the present application has a higher gram capacity and better rate performance;

[0208] Compared with the higher sintering temperature used in Example 28, the battery in Example 8 of the present application has a higher gram capacity and better rate performance;

[0209] Compared with the higher molar ratio of phosphorus element to manganese hydrogen phosphate in the phosphoric acid solution in Example 23, the batteries in Examples 1, 9, 12, and 20 of the present application have higher gram capacities and better rate performance;

[0210] Compared with the positive electrode materials of Examples 24-25, which have a higher primary particle Dv50 particle size and a lower powder resistivity, the batteries of Examples 1, 5, 9-12, 17, and 20 of the present application have a higher gram capacity and better rate performance;

[0211] Compared with the lower powder resistivity of the positive electrode material of Example 26, the battery of Example 8 of the present application has a higher gram capacity and better rate performance;

[0212] Compared with the thinner average thickness of the coating layer in Example 27, the batteries in Examples 1, 8, 9, 12, 19, and 20 of the present application have higher gram capacities and better rate performance;

[0213] Compared with the larger particle size Dv50 of the insoluble matter in the final mixture of Example 29, the batteries of Examples 1, 5, 9, 10, 11, 12, 17, and 20 of the present application have higher gram capacities and better rate performance;

[0214] Compared with Example 21 using glucose as the carbon source, the battery of Example 19 of the present application has higher 1C, 2C, and 3C gram capacities and better rate performance;

[0215] 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: mixing a lithium source with a phosphoric acid solution to obtain a first mixture; The first mixture is mixed with manganese hydrogen phosphate, an iron source, and an optional source of the M element to obtain a second mixture; wherein, The M element includes one or more of transition metal elements other than manganese and iron, group IIA metal elements, group IIIA metal elements, group IVA metal elements, and group VIIA elements; The second mixture is dried and sintered to obtain a lithium manganese iron phosphate positive electrode material.

2. The method according to claim 1, wherein: The positive electrode material includes a compound Li a Mn x Fe y M b PO4; wherein, the x is selected from 0.5-0.9, the y is selected from 0.1-0.5, the sum of x and y is 0.96-1, the a is selected from 1.01-1.05, and the b is selected from 0-0.05, and can be selected from 0.01-0.05; the M includes one or more of transition metal elements other than manganese and iron, group IIA metal elements, group IIIA metal elements, group IVA metal elements, and group VIIA elements, and can be selected to include one or more elements of titanium, vanadium, chromium, copper, magnesium, aluminum, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, europium, and fluorine.

3. A method for preparing a positive electrode material, comprising the following steps: mixing a lithium source with a phosphoric acid solution to obtain a third mixture; The third mixture is mixed with manganese hydrogen phosphate, an iron source, a carbon source, and an optional source of the M element to obtain a fourth mixture; wherein, The M element includes one or more of transition metal elements other than manganese and iron, group IIA metal elements, group IIIA metal elements, group IVA metal elements, and group VIIA elements; The fourth mixture is dried and sintered to obtain a lithium manganese iron phosphate positive electrode material.

4. The method according to claim 3, wherein: The positive electrode material comprises a core and a coating layer covering the core, wherein the core comprises the compound Li a Mn x Fe y M b PO4; wherein, the x is selected from 0.5-0.9, the y is selected from 0.1-0.5, the sum of x and y is 0.96-1, the a is selected from 1.01-1.05, the b is selected from 0-0.05, and can be selected from 0.01-0.05; the M includes one or more of transition metal elements, IIA group metal elements, IIIA group metal elements, IVA group metal elements, and VIIA group elements other than manganese and iron elements, and can be selected to include one or more elements of titanium, vanadium, chromium, copper, magnesium, aluminum, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, europium, and fluorine; the coating layer includes carbon.

5. The method according to any one of claims 1 to 4, wherein: The M element includes one or more elements selected from titanium, vanadium, chromium, copper, magnesium, aluminum, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, europium, and fluorine.

6. The method according to any one of claims 1 to 5, wherein: The sintering temperature is 620°C-780°C, and can be 650°C-750°C; and / or, The sintering time is 6-14 hours, and can be 6-12 hours; and / or, The sintering is carried out in an inert atmosphere, and may be carried out in a nitrogen atmosphere; and / or, The temperature is raised to the sintering temperature at a rate of 1-15°C / min, and can be optionally raised to the sintering temperature at a rate of 2-10°C / min.

7. The method according to claim 3 or 4, wherein: The carbon source includes one or more of an inorganic carbon source and an organic carbon source, and may be selected from one or more of glucose, sucrose, polyethylene glycol, polyvinyl alcohol, citric acid, hydroxypropyl β-cyclodextrin, polyvinyl pyrrolidone, polyacrylic acid, polyvinylidene fluoride, polystyrene, polypropylene, and ethylene glycol, and may be selected from hydroxypropyl β-cyclodextrin; and / or, The weight of the carbon source is 4%-7% of the sum of the weight of the manganese hydrogen phosphate and the iron source.

8. The method according to any one of claims 1 to 7, wherein: The Dv50 particle sizes of the insoluble matter in the second mixture and the fourth mixture are independently 0.2-1.0 μm, and optionally 0.2-0.6 μm.

9. The method according to any one of claims 1 to 8, wherein: The molar ratio of phosphorus in the phosphoric acid solution to manganese hydrogen phosphate is 0.02-0.07, and can be 0.02-0.04; and / or, The molar ratio of the lithium element in the lithium source to the total phosphorus element in the phosphoric acid solution and the manganese hydrogen phosphate is 1.01-1.05; and / or, The molar ratio of the iron element in the iron source to the total phosphorus element in the phosphoric acid solution and the manganese hydrogen phosphate is 0.1-0.5; and / or, The molar ratio of the M element in the source of the M element to the total phosphorus element in the phosphoric acid solution and the manganese hydrogen phosphate is 0.01-0.05; and / or, The concentration of the phosphoric acid solution is 75 wt%-85 wt%; and / or, In the steps of preparing the first mixture and the third mixture, the mixing time is independently 15-20 minutes; and / or, In the step of preparing the second mixture and the fourth mixture, mixing is performed sequentially by stirring and ball milling; and / or, The drying is performed by a spray dryer; optionally, the air inlet temperature of the spray dryer is 200°C-250°C, and the air outlet temperature is 100°C-120°C.

10. The method according to any one of claims 1 to 9, wherein: The lithium source includes one or more of an inorganic acid salt, an organic acid salt, an oxide, and a hydroxide of lithium, and may be selected from one or more of lithium carbonate, lithium hydroxide, lithium acetate, lithium oxalate, lithium citrate, lithium dihydrogen phosphate, and lithium phosphate; and / or, The iron source includes one or more of an inorganic acid salt, an organic acid salt, an oxide, and a hydroxide of iron, and can be selected from one of ferrous oxalate, ferrous acetate, ferrous carbonate, ferrous phosphate, and ferric hydrogen phosphate. one or more; and / or, The source of the M element includes one or more of an inorganic acid salt, an organic acid salt, an oxide, and a hydroxide of the M element, and may optionally include one or more of an oxalate, an acetate, a carbonate, a phosphate, an oxide, and a hydroxide of the M element.

11. A positive electrode material comprising a compound Li a Mn x Fe y M b PO4; among them, The x is selected from 0.5-0.9, the y is selected from 0.1-0.5, the sum of x and y is 0.96-1, the a is selected from 1.01-1.05, and the b is selected from 0-0.05, and can be selected from 0.01-0.05; the M includes one or more transition metal elements other than manganese and iron, group IIA metal elements, group IIIA metal elements, group IVA metal elements, and group VIIA elements, and can be selected to include one or more elements of titanium, vanadium, chromium, copper, magnesium, aluminum, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, europium, and fluorine.

12. A positive electrode material, comprising a core and a coating layer coating the core; the core comprising the compound Li a Mn x Fe y M b PO4; among them, The x is selected from 0.5-0.9, the y is selected from 0.1-0.5, the sum of x and y is 0.96-1, the a is selected from 1.01-1.05, the b is selected from 0-0.05, and can be selected from 0.01-0.05; the M includes one or more transition metal elements, ⅡA group metal elements, ⅢA group metal elements, ⅣA group metal elements, and VIIA group elements other than manganese and iron elements, and can be selected to include one or more elements of titanium, vanadium, chromium, copper, magnesium, aluminum, zinc, cobalt, nickel, tin, niobium, tungsten, zirconium, tantalum, cerium, europium, and fluorine; the coating layer includes carbon; Optionally, the average thickness of the coating layer is 6-12 nm, more preferably 8-12 nm; Optionally, the weight of the carbon is 1.1%-2% of the total weight of the positive electrode material, and more optionally 1.3%-1.5%.

13. The positive electrode material according to claim 11 or 12, wherein The compaction density of the positive electrode material at 294.2 MPa is 2.09-2.48 g / cm 3 , optional: 2.1-2.3g / cm 3 and / or, The primary particles of the positive electrode material have a Dv50 particle size of 100-600 nm, and may be 100-300 nm; and / or, The BET specific surface area of ​​the positive electrode material at liquid nitrogen temperature is 6-20 m 2 / g, optional: 14-19.87m 2 / g; and / or, The powder resistivity of the positive electrode material at 7.85 MPa is 10.8-870.6 Ω·cm, and can be 48.5-205.1 Ω·cm; and / or, The positive electrode material is prepared by the method according to any one of claims 1 to 9. 14 . 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 11 . 15 . A battery comprising a positive electrode material prepared by the method of claim 1 , a positive electrode material of claim 11 , or a positive electrode sheet of claim 14 .

16. An electrical device comprising the battery according to claim 15.

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