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

Abstract

The invention provides a method for preparing a positive electrode material, the positive electrode material, a positive electrode plate, a battery and an electric device. The method for preparing the positive electrode material comprises the following steps: mixing, drying and sintering precursor lithium manganese iron phosphate, a carbon source and a doped element source in a solvent to obtain the positive electrode material, the positive electrode material comprises an inner core and a coating layer coating the inner core, the inner core comprises LiMnxFe1-xPO4, and x is more than 0 and less than 1; the coating layer comprises carbon and doping elements; the doping elements comprise one or more of IIA group elements, IIIA group elements, IVA group elements and transition metal elements. According to the method, the powder resistivity and the specific surface area of the positive electrode material are reduced, and the gram volume and the cycle performance of the battery are improved.

Description

Technical Field

[0001] The present application relates to the technical field of lithium batteries, and particularly to a method for preparing a cathode material, a cathode material, a cathode electrode sheet, a battery, and an electrical device. Background Art

[0002] In recent years, with the increasingly wide application range of secondary batteries, secondary batteries are widely used in energy storage power systems such as hydraulic, thermal, wind, and solar power stations, as well as in multiple fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. Due to the great development of secondary batteries, higher requirements are put forward for the electrochemical performance of the batteries. Summary of the Invention

[0003] The present application is made in view of the above problems, and its purpose is to provide a method for preparing a cathode material, a cathode material, a cathode electrode sheet, a battery, and an electrical device. The method of the present application reduces the powder resistivity and specific surface area of the cathode material, increases the specific capacity of the cathode material, and improves the cycle performance of the battery.

[0004] To achieve the above object, a first aspect of the present application provides a method for preparing a cathode material, including:

[0005] Mixing a precursor lithium iron manganese phosphate, a carbon source, and a source of a doping element in a solvent, drying, and sintering to obtain a cathode material;

[0006] The cathode material includes a core and a coating layer covering the core; the core includes LiMn x Fe 1-x PO 4 , where 0 < x < 1; the coating layer includes carbon and a doping element; the doping element includes one or more of Group IIA elements, Group IIIA elements, Group IVA elements, and transition metal elements.

[0007] Thus, in the coating process of the present application, a carbon source and a source of a doping element are added simultaneously, which is beneficial to forming a tight structure between the coating layer and the surface of the core, and plays a stabilizing role in the crystal of the cathode material, reducing the powder resistivity of the cathode material, reducing the specific surface area of the cathode material within a reasonable range, and increasing the specific capacity and cycle performance of the battery.

[0008] In any embodiment, 0.1 ≤ x ≤ 0.9; and / or,

[0009] The doping element includes one or more of Mg, Ti, V, Si, Cr, Mn, Fe, Co, Ni, and B.

[0010] In any embodiment, the molar ratio of the precursor to the carbon element in the carbon source is 1:1.5 - 1:0.001, optionally 1:1.45 - 1:0.01; and / or,

[0011] The molar ratio of the precursor to the doping element in the doping element source is 1:0.25 - 1:0.00001, optionally 1:0.2 - 1:0.0001.

[0012] The precursor and the carbon element in the carbon source within the above ratio range are beneficial to forming an appropriate coating layer thickness, which is beneficial to improving the specific capacity and cycling performance of the battery.

[0013] The ratio of the precursor to the doping element within the above range is beneficial to the presence of the doping element between the core and the carbon element and within the coating layer, thereby improving the specific capacity and cycling performance of the battery.

[0014] In any embodiment, the mixing is carried out at 5°C - 70°C, optionally, the mixing is carried out at 10°C - 60°C; and / or,

[0015] The mixing time is 0.5 - 12 hours; and / or,

[0016] The mixing is carried out by grinding.

[0017] Thus, adopting the above mixing temperature and time is beneficial to the uniform distribution of the doping element within the coating layer and at the boundary between the core and the coating layer, and is also beneficial to the uniform distribution of the carbon element within the coating layer, thereby improving the specific capacity and cycling performance of the battery.

[0018] In any embodiment, the sintering temperature is 350°C - 950°C, optionally 400°C - 900°C; and / or,

[0019] The sintering time is 2 - 20 hours; and / or,

[0020] The sintering is carried out in an inert atmosphere.

[0021] Thus, adopting the above sintering temperature and sintering time when preparing the positive electrode material is beneficial to the reaction proceeding more completely, forming a tight structure on the surface of the coating layer and the core, thereby improving the specific capacity and cycling performance of the battery.

[0022] In any embodiment, the drying temperature is 150°C - 400°C; and / or,

[0023] The drying is carried out by spray drying or baking; and / or,

[0024] The method further includes screening the mixture before the drying and collecting the sieved part; and / or,

[0025] The method further includes crushing after the sintering, and optionally sieving; and / or,

[0026] The carbon source includes one or more of an organic carbon source and an inorganic carbon source, and is optionally one or more of citric acid, glucose, sucrose, polyvinyl alcohol, polypyrrole, polyethylene glycol, pitch, anthracene, aniline; and / or,

[0027] The source of the doping element includes one or more of a hydroxide of the doping element, an oxide of the doping element, an acid of the doping element, a salt of the doping element; and / or,

[0028] The solvent includes one or more of water and an organic solvent. Optionally, the solvent includes one or more of water, ethanol, methanol, acetone, ethylene glycol, isopropanol.

[0029] In any embodiment, the precursor is obtained by the following steps:

[0030] React a lithium source, a manganese source, an iron source, and a phosphorus source in a solvent, perform solid-liquid separation, and collect the solid phase;

[0031] Dry and sinter the solid phase to obtain a precursor.

[0032] In any embodiment, the precursor includes LiMn x Fe 1-x PO 4 , where 0 < x < 1, and optionally, 0.1 ≤ x ≤ 0.9;

[0033] Optionally, in the steps of preparing the precursor, the molar ratio of lithium element in the lithium source, manganese element in the manganese source, iron element in the iron source, and phosphorus element in the phosphorus source is 1:x:(1 - x):1.

[0034] The elements in the precursor of the present application are evenly distributed and have good batch consistency. The elements in the positive electrode material prepared using the precursor material of the present application are evenly distributed and have good batch consistency, thereby improving the specific capacity and cycle performance and other electrical properties of the battery prepared.

[0035] In any embodiment, in the steps of preparing the precursor, the reaction is carried out at 5°C - 60°C, and optionally, the reaction is carried out at 10°C - 50°C; and / or,

[0036] The reaction time is 10 minutes to 8 hours, and is optionally 10 minutes to 6 hours; and / or,

[0037] The drying temperature is 50°C - 250°C; and / or,

[0038] The drying time is 10 minutes to 12 hours; and / or,

[0039] The sintering temperature is 150°C - 800°C, optionally 200°C - 700°C; and / or,

[0040] The sintering time is 1 - 12 hours; and / or,

[0041] The sintering is carried out in an inert atmosphere.

[0042] Adopting the above reaction temperature and time during the preparation of the precursor is beneficial to reducing side reactions, so as to obtain a precursor material with uniform composition and good batch consistency, thereby improving the specific capacity and cycling performance of the battery.

[0043] Adopting the above sintering temperature and time during the preparation of the precursor is beneficial to the growth of crystallites, so as to reduce the proportion of amorphous particles, thereby obtaining a precursor with better crystallinity, and thus the specific capacity and cycling performance of the battery.

[0044] In any embodiment, in the step of preparing the precursor, the solid-liquid separation is carried out by filtration or centrifugation; and / or,

[0045] Before the drying, the solid phase is ball-milled; optionally, the rotation speed of the ball-milling is 100 - 600 rpm, optionally 200 - 500 rpm, and the ball-milling time is 1 - 12 hours, optionally 2 - 10 hours; and / or,

[0046] Before the drying, the solid phase is washed; and / or,

[0047] Between the drying and the sintering, the solid phase is crushed; and / or,

[0048] The lithium source includes one or more of hydroxides, oxides, inorganic acid salts, and organic acid salts of lithium element, optionally including one or more of lithium hydroxide, lithium oxide, lithium carbonate, lithium acetate, lithium oxalate, lithium phosphate, and lithium chloride; and / or,

[0049] The manganese source includes one or more of organic acid salts, inorganic acid salts, oxides, and hydroxides of manganese element; and / or,

[0050] The iron source includes one or more of organic acid salts, inorganic acid salts, oxides, and hydroxides of iron element; and / or,

[0051] The phosphorus source includes one or more of phosphoric acid, phosphates, hydrogen phosphates, and dihydrogen phosphates, optionally including one or more of phosphoric acid, iron phosphate, ferrous phosphate, ammonium ferrous phosphate, ammonium dihydrogen phosphate, ammonium hydrogen phosphate, ammonium phosphate, lithium hydrogen phosphate, lithium dihydrogen phosphate, and lithium phosphate; and / or,

[0052] A carbon source is added during the reaction process.

[0053] Adopting the above-mentioned ball milling rotation speed and time during the preparation of the precursor is beneficial to improving the degree of solid-solid reaction, making the reaction more complete, thereby improving the specific capacity and cycling performance of the battery.

[0054] The second aspect of the present application further provides a cathode material, including a core and a coating layer covering the core. The core includes LiMn x Fe 1-x PO 4 , where 0 < x < 1, optionally, 0.1 ≤ x ≤ 0.9; the coating layer includes carbon and doping elements; the doping elements include one or more of Group IIA elements, Group IIIA elements, Group IVA elements, and transition metal elements, and may be selected from one or more elements including Mg, Ti, V, Si, Cr, Mn, Fe, Co, Ni, B;

[0055] Optionally, the molar ratio of manganese element to iron element in the core is 1:9 - 9:1.

[0056] Therefore, in the coating process of the present application, a carbon source and a source of doping elements are added simultaneously, which is beneficial to forming a tight structure between the coating layer and the surface of the core, stabilizing the crystal of the cathode material, reducing the powder resistivity of the cathode material, reducing the specific surface area of the cathode material within a reasonable range, and improving the specific capacity and cycling performance of the battery.

[0057] In any embodiment, the molar ratio of LiMn x Fe 1-x PO 4 in the core to the carbon element in the coating layer is 1:1.5 - 1:0.001, optionally 1:1.45 - 1:0.01; and / or,

[0058] the molar ratio of LiMn x Fe 1-x PO 4 in the core to the doping element in the coating layer is 1:0.25 - 1:0.00001, optionally 1:0.2 - 1:0.0001.

[0059] In any embodiment, the Dv50 particle size of the cathode material is 0.1 - 13 μm; and / or,

[0060] the BET specific surface area of the cathode material is 10 - 27 m² / g, optionally 10 - 25 m² / g; and / or,

[0061] The powder resistivity of the positive electrode material is ≤ 1200 Ω·cm, optionally, the powder resistivity of the positive electrode material is ≤ 300 Ω·cm; and / or,

[0062] The positive electrode material is prepared by the method of the first aspect of the present application.

[0063] The third aspect of the present application further provides a positive electrode sheet, including 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.

[0064] The fourth aspect of the present application further provides a battery, including the positive electrode material prepared by the method of the first aspect of the present application, the positive electrode material of the second aspect of the present application, or the positive electrode sheet of the third aspect of the present application.

[0065] The fifth aspect of the present application further provides an electrical device, including the battery of the fourth aspect of the present application. Description of the Drawings

[0066] Figure 1 It is a schematic diagram of a battery cell of an embodiment of the present application.

[0067] Figure 2 is Figure 1 The exploded view of the battery cell of an embodiment of the present application shown.

[0068] Figure 3 It is a schematic diagram of a battery module of an embodiment of the present application.

[0069] Figure 4 It is a schematic diagram of a battery pack of an embodiment of the present application.

[0070] Figure 5 is Figure 4 The exploded view of the battery pack of an embodiment of the present application shown.

[0071] Figure 6 It is a schematic diagram of an electrical device using the battery cell of an embodiment of the present application as a power source.

[0072] Figure 7 It is a TEM photograph of the positive electrode material of Example 1 of the present application.

[0073] Figure 8 It is a TEM photograph of the positive electrode material of Comparative Example 3 of the present application.

[0074] Description of the Reference Numerals:

[0075] 1 Battery pack; 2 Upper box body; 3 Lower box body; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed Description of the Embodiments

[0076] Hereinafter, embodiments of the negative electrode active material, its manufacturing method, the positive electrode sheet, the negative electrode sheet, the battery cell, the battery module, the battery pack, and the electrical device of the present application specifically disclosed will be described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary details are omitted. For example, there are cases where the detailed description of well-known matters and the repeated description of actually identical structures are omitted. This is to prevent the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the accompanying 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 recited in the claims.

[0077] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a particular range. The range defined in this way can include the end values or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In the present application, unless otherwise stated, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" have been fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0078] If there is no special instruction, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0079] If there is no special instruction, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0080] Unless otherwise specified, all steps of this application can be carried out sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) carried out sequentially, or may also include steps (b) and (a) carried out sequentially. For example, if it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may also include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0081] Unless otherwise specified, the Dv50 particle size in this application refers to the particle size when the cumulative volume distribution value is 50%.

[0082] [Battery cell]

[0083] A battery cell, also known as a rechargeable battery or a storage battery, refers to a battery that can be activated by charging after discharging so that the active material can be reused.

[0084] Under normal circumstances, a battery cell includes a positive electrode plate, a negative electrode plate, a separator and an electrolyte. During the charge and discharge process of the battery, active ions (such as lithium ions) are embedded and extracted back and forth between the positive electrode plate and the negative electrode plate. The separator is arranged between the positive electrode plate and the negative electrode plate, mainly to prevent short circuit between the positive and negative electrodes, and at the same time allows active ions to pass through. The electrolyte is between the positive electrode plate and the negative electrode plate, mainly to conduct active ions.

[0085] [Method for preparing a positive electrode material]

[0086] An embodiment of this application provides a method for preparing a positive electrode material, including:

[0087] Mixing a precursor lithium iron manganese phosphate, a carbon source, and a source of a doping element in a solvent, drying, and sintering to obtain a positive electrode material;

[0088] The positive electrode material includes a core and a coating layer covering the core; the core includes LiMn x Fe 1-x PO 4 , where 0 < x < 1, such as 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 or a range composed of any of the above values; the coating layer includes carbon and a doping element; the doping element includes one or more of Group IIA elements, Group IIIA elements, Group IVA elements, and transition metal elements.

[0089] The lithium iron manganese phosphate material has poor electrical conductivity, with an insulator having a spin exchange band gap of 0.2 eV and a semiconductor having a crystal field band gap of 0.3 eV in its structure. Although the usual carbon coating can solve the problem of the relatively large powder resistance of the lithium iron manganese phosphate material, it still cannot improve the electrochemical performance of the battery made of the material.

[0090] Although the mechanism is not yet clear, the applicant unexpectedly found that: adding a carbon source and a source of doping elements simultaneously during the coating process in this application is beneficial to forming a tight structure between the coating layer and the surface of the core, stabilizing the crystal of the cathode material, reducing the powder resistivity of the cathode material, reducing the specific surface area of the cathode material within a reasonable range, and improving the gram capacity and cycling performance of the battery.

[0091] In some embodiments, 0.1 ≤ x ≤ 0.9; and / or,

[0092] The doping element includes one or more elements of Mg, Ti, V, Si, Cr, Mn, Fe, Co, Ni, B.

[0093] In some embodiments, the molar ratio of the carbon element in the precursor to the carbon source is 1:1.5 - 1:0.001, optionally 1:1.45 - 1:0.01, such as 1:1.5, 1:1.45, 1:1.4, 1:1.35, 1:1.3, 1:1.25, 1:1.2, 1:1.15, 1:1.1, 1:1.05, 1:1, 1:0.95, 1:0.9, 1:0.8, 1:0.7, 1:0.6, 1:0.5, 1:0.4, 1:0.3, 1:0.2, 1:0.1, 1:0.09, 1:0.07, 1:0.06, 1:0.05, 1:0.04, 1:0.03, 1:0.02, 1:0.01, 1:0.009, 1:0.007, 1:0.005, 1:0.003, 1:0.002, 1:0.001 or a range composed of any of the above values; and / or,

[0094] The molar ratio of the precursor to the doping element in the source of the doping element is 1:0.25 - 1:0.00001, optionally 1:0.2 - 1:0.0001, for example 1:0.25, 1:0.2, 1:0.15, 1:0.1, 1:0.05, 1:0.01, 1:0.009, 1:0.007, 1:0.005, 1:0.003, 1:0.001, 1:0.0009, 1:0.0007, 1:0.0005, 1:0.0003, 1:0.0002, 1:0.0001, 1:0.00009, 1:0.00007, 1:0.00005, 1:0.00003, 1:0.00002, 1:0.00001 or a range composed of any of the above values.

[0095] The carbon element in the precursor and the carbon source within the above proportion range is beneficial to forming an appropriate coating layer thickness, and is beneficial to improving the specific capacity and cycling performance of the battery.

[0096] The ratio of the precursor to the doping element within the above range is beneficial to the presence of the doping element between the inner core and the carbon element and within the coating layer, thereby improving the specific capacity and cycling performance of the battery.

[0097] In some embodiments, the mixing is carried out at 5°C - 70°C. Optionally, the mixing is carried out at 10°C - 60°C. For example, the mixing is carried out at 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C or a range composed of any of the above values; and / or,

[0098] The mixing time is 0.5 - 12 hours, for example 0.5 hour, 1 hour, 2.5 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 9.5 hours, 10 hours, 10.5 hours, 11 hours, 11.5 hours, 12 hours or a range composed of any of the above values; and / or,

[0099] The mixing is carried out by grinding.

[0100] Thus, adopting the above mixing temperature and time is beneficial to the uniform distribution of the doping element within the coating layer and at the boundary between the inner core and the coating layer, and is also beneficial to the uniform distribution of the carbon element within the coating layer, thereby improving the specific capacity and cycling performance of the battery.

[0101] In some embodiments, the sintering temperature is 350°C - 950°C, optionally 400°C - 900°C, such as 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C or a range composed of any of the above values; and / or,

[0102] the sintering time is 2 - 20 hours, such as 2 hours, 3 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours or a range composed of any of the above values; and / or,

[0103] the sintering is carried out in an inert atmosphere.

[0104] Thus, when preparing the cathode material, adopting the above sintering temperature and sintering time is beneficial to the reaction proceeding more completely, forming a tight structure between the coating layer and the surface of the core, thereby improving the specific capacity and cycling performance of the battery.

[0105] In some embodiments, the drying temperature is 150°C - 400°C, such as 150°C, 180°C, 200°C, 220°C, 250°C, 270°C, 300°C, 330°C, 350°C, 380°C, 400°C or a range composed of any of the above values; and / or,

[0106] the drying is carried out by spray drying or baking; and / or,

[0107] the method further includes sieving the mixture before the drying and collecting the sieved part; and / or,

[0108] the method further includes crushing after the sintering and optionally sieving; and / or,

[0109] the carbon source includes one or more of an organic carbon source and an inorganic carbon source, optionally including one or more of citric acid, glucose, sucrose, polyvinyl alcohol, polypyrrole, polyethylene glycol, pitch, anthracene, aniline; and / or,

[0110] the source of the doping element includes one or more of a hydroxide of the doping element, an oxide of the doping element, an acid of the doping element, a salt of the doping element; and / or,

[0111] the solvent includes one or more of water and an organic solvent. Optionally, the solvent includes one or more of water, ethanol, methanol, acetone, ethylene glycol, isopropanol.

[0112] In some embodiments, the precursor is prepared by the following steps:

[0113] React a lithium source, a manganese source, an iron source, and a phosphorus source in a solvent, perform solid-liquid separation, and collect the solid phase;

[0114] Dry and sinter the solid phase to obtain a precursor.

[0115] In some embodiments, the precursor includes LiMn x Fe 1-x PO 4 , where 0 < x < 1, optionally, 0.1 ≤ x ≤ 0.9, for example, x is 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 or a range composed of any of the above values;

[0116] Optionally, in the steps of preparing the precursor, the molar ratio of lithium element in the lithium source, manganese element in the manganese source, iron element in the iron source, and phosphorus element in the phosphorus source is 1:x:(1 - x):1.

[0117] The elements in the precursor of the present application are evenly distributed and have good batch consistency. The elements in the positive electrode material prepared using the precursor material of the present application are evenly distributed and have good batch consistency, thereby improving the specific capacity and cycle performance and other electrical properties of the prepared battery.

[0118] In some embodiments, in the steps of preparing the precursor, the reaction is carried out at 5°C - 60°C, optionally, the reaction is carried out at 10°C - 50°C, for example, the reaction is carried out at 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C or a range composed of any of the above values; and / or,

[0119] The reaction time is 10 minutes to 8 hours, optionally 10 minutes to 6 hours, for example, 10 minutes, 20 minutes, 30 minutes, 50 minutes, 60 minutes, 1.5 hours, 2 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, 8 hours or a range composed of any of the above values; and / or,

[0120] The drying temperature is 50°C - 250°C, for example, 60°C, 70°C, 80°C, 90°C, 100°C, 120°C, 140°C, 150°C, 160°C, 180°C, 200°C, 220°C, 230°C, 240°C, 250°C or a range composed of any of the above values; and / or,

[0121] The drying time is from 10 minutes to 12 hours, such as 10 minutes, 20 minutes, 30 minutes, 50 minutes, 60 minutes, 1.5 hours, 2 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours or the range composed of any of the above values; and / or,

[0122] The sintering temperature is 150°C - 800°C, optionally 200°C - 700°C, such as 150°C, 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C; and / or,

[0123] The sintering time is 1 - 12 hours, such as 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours or the range composed of any of the above values; and / or,

[0124] The sintering is carried out in an inert atmosphere.

[0125] Adopting the above reaction temperature and time when preparing the precursor is beneficial to reducing side reactions, so as to obtain a precursor material with uniform composition and good batch consistency, thereby improving the specific capacity and cycle performance of the battery.

[0126] Adopting the above sintering temperature and time when preparing the precursor is beneficial to the growth of crystallites, so as to reduce the proportion of amorphous particles, thereby obtaining a precursor with better crystallinity, and thus the specific capacity and cycle performance of the battery.

[0127] In some embodiments, in the step of preparing the precursor, the solid-liquid separation is carried out by filtration or centrifugation; and / or,

[0128] Before the drying, the solid phase is ball-milled; optionally, the rotation speed of the ball milling is 100 - 600 rpm, optionally 200 - 500 rpm, such as 100 rpm, 200 rpm, 300 rpm, 400 rpm, 500 rpm, 600 rpm or the range composed of any of the above values, and the time of the ball milling is 1 - 12 hours, optionally 2 - 10 hours, such as 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours or the range composed of any of the above values; and / or,

[0129] Before the drying, the solid phase is washed; and / or,

[0130] Between the drying and the sintering, the solid phase is crushed; and / or,

[0131] The lithium source includes one or more of hydroxides, oxides, inorganic acid salts, and organic acid salts of lithium element, and may optionally include one or more of lithium hydroxide, lithium oxide, lithium carbonate, lithium acetate, lithium oxalate, lithium phosphate, and lithium chloride; and / or,

[0132] The manganese source includes one or more of organic acid salts, inorganic acid salts, oxides, and hydroxides of manganese element; and / or,

[0133] The iron source includes one or more of organic acid salts, inorganic acid salts, oxides, and hydroxides of iron element; and / or,

[0134] The phosphorus source includes one or more of phosphoric acid, phosphates, hydrogen phosphates, and dihydrogen phosphates, and may optionally include one or more of phosphoric acid, iron phosphate, ferrous phosphate, ammonium ferrous phosphate, ammonium dihydrogen phosphate, ammonium hydrogen phosphate, ammonium phosphate, lithium hydrogen phosphate, lithium dihydrogen phosphate, and lithium phosphate; and / or,

[0135] A carbon source is added during the reaction process.

[0136] Adopting the above ball milling speed and time when preparing the precursor is beneficial to improving the solid-solid reaction degree, making the reaction more complete, thereby improving the specific capacity and cycling performance of the battery.

[0137] [Cathode material]

[0138] An embodiment of the present application provides a cathode material, including a core and a coating layer covering the core. The core includes LiMn x Fe 1-x PO 4 , where 0 < x < 1, optionally, 0.1 ≤ x ≤ 0.9, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 or a range composed of any of the above values; the coating layer includes carbon and doping elements; the doping elements include one or more of Group IIA elements, Group IIIA elements, Group IVA elements, and transition metal elements, and may optionally include one or more elements of Mg, Ti, V, Si, Cr, Mn, Fe, Co, Ni, and B;

[0139] Optionally, the molar ratio of manganese element to iron element in the core is 1:9 - 9:1, such as 1:8, 1:7.5, 1:7, 1:6.5, 1:6, 1:5.5, 1:5, 1:4.5, 1:4, 1:3.5, 1:3, 1:2.5, 1:2, 1:1.5, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1 or the range composed of any of the above values.

[0140] Therefore, in the coating process of this application, a carbon source and a source of doping elements are added simultaneously, which is conducive to forming a tight structure between the coating layer and the surface of the core, stabilizing the crystal of the cathode material, reducing the powder resistivity of the cathode material, reducing the specific surface area of the cathode material within a reasonable range, and improving the gram capacity and cycle performance of the battery.

[0141] In some embodiments, the LiMn x Fe 1-x PO 4 in the core and the carbon element in the coating layer have a molar ratio of 1:1.5 - 1:0.001, and can be optionally 1:1.45 - 1:0.01, such as 1:1.5, 1:1.45, 1:1.4, 1:1.35, 1:1.3, 1:1.25, 1:1.2, 1:1.15, 1:1.1, 1:1.05, 1:1, 1:0.95, 1:0.9, 1:0.8, 1:0.7, 1:0.6, 1:0.5, 1:0.4, 1:0.3, 1:0.2, 1:0.1, 1:0.09, 1:0.07, 1:0.06, 1:0.05, 1:0.04, 1:0.03, 1:0.02, 1:0.01, 1:0.009, 1:0.007, 1:0.005, 1:0.003, 1:0.002, 1:0.001 or the range composed of any of the above values; and / or,

[0142] the LiMn x Fe 1-x PO 4The molar ratio to the doping element in the coating layer is 1:0.25 - 1:0.00001, optionally 1:0.2 - 1:0.0001, such as 1:0.25, 1:0.2, 1:0.15, 1:0.1, 1:0.05, 1:0.01, 1:0.009, 1:0.007, 1:0.005, 1:0.003, 1:0.001, 1:0.0009, 1:0.0007, 1:0.0005, 1:0.0003, 1:0.0002, 1:0.0001, 1:0.00009, 1:0.00007, 1:0.00005, 1:0.00003, 1:0.00002, 1:0.00001 or a range composed of any of the above values.

[0143] In some embodiments, the Dv50 particle size of the positive electrode material is 0.1 - 13 μm, such as 0.1 μm, 1 μm, 2 μm, 3 μm, 5 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm or a range composed of any of the above values; and / or,

[0144] The BET specific surface area of the positive electrode material is 10 - 27 m² / g, optionally 10 - 25 m² / g, such as 10 m² / g, 11 m² / g, 12 m² / g, 13 m² / g, 14 m² / g, 15 m² / g, 16 m² / g, 17 m² / g, 18 m² / g, 19 m² / g, 20 m² / g, 21 m² / g, 22 m² / g, 23 m² / g, 24 m² / g, 25 m² / g, 26 m² / g, 27 m² / g or a range composed of any of the above values; and / or,

[0145] The powder resistivity of the positive electrode material is ≤ 1200 Ω·cm. Optionally, the powder resistivity of the positive electrode material is ≤ 300 Ω·cm, such as 10 Ω·cm, 15 Ω·cm, 20 Ω·cm, 30 Ω·cm, 40 Ω·cm, 50 Ω·cm, 60 Ω·cm, 70 Ω·cm, 80 Ω·cm, 100 Ω·cm, 120 Ω·cm, 130 Ω·cm, 150 Ω·cm, 170 Ω·cm, 180 Ω·cm, 200 Ω·cm, 220 Ω·cm, 250 Ω·cm, 280 Ω·cm, 300 Ω·cm, 350 Ω·cm, 400 Ω·cm, 500 Ω·cm, 600 Ω·cm, 700 Ω·cm, 800 Ω·cm, 850 Ω·cm, 900 Ω·cm, 1000 Ω·cm, 1100 Ω·cm, 1200 Ω·cm or a range composed of any of the above values; and / or,

[0146] The positive electrode material is prepared by the method described above in this application.

[0147] In this application, the Dv50 particle size is tested by conventional methods in the art; for example, a sample is added to water to completely disperse the sample, and a laser particle size analyzer is used to measure the Dv50 particle size of the material.

[0148] In this application, the BET specific surface area is the BET specific surface area at -200 °C and is tested by conventional methods in the art. For example, a sample is weighed and placed in a specific surface area test tube. The liquid nitrogen cup is filled with liquid nitrogen and placed in the specific surface area test tube to allow the sample to be in a temperature environment of -200 °C, and a specific surface area analyzer is used for testing.

[0149] In this application, the powder resistivity is the powder resistivity at 7.85 MPa and is tested by conventional methods in the art. For example, 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. After the height and pressure of the mold are both stable, the forward resistivity and reverse resistivity of the sample are measured respectively, and the average value of the two is taken as the powder resistivity of the sample.

[0150] [Positive electrode plate]

[0151] The positive electrode plate 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.

[0152] During the charge and discharge process of the battery, the insertion and extraction and consumption of Li will occur, and the molar content of Li is different when the battery is discharged to different states. In the listing of the positive electrode material in this application, the molar content of Li is the initial state of the material, that is, the state before feeding. When the positive electrode material is applied to the battery system, the molar content of Li will change after charge and discharge cycles.

[0153] In the listing of the positive electrode material in this application, the molar content of O is only the theoretical state value, and the release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.

[0154] As an example, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode film layer is provided on either or both of the two opposite surfaces of the positive electrode current collector.

[0155] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (such as 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.).

[0156] In some embodiments, it may further include a cathode material for a battery well-known in the art. As an example, the cathode material may include at least one of the following materials: lithium transition metal oxides and their modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as the cathode active material of the battery may also be used. These cathode active materials may be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO 2 ), lithium nickel oxide (such as LiNiO 2 ), lithium manganese oxide (such as LiMnO 2 , LiMn 2 O 4 ), 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 O 2 (which can also be abbreviated as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (which can also be abbreviated as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (which can also be abbreviated as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (which can also be abbreviated as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (which can also be abbreviated as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O 2 ) and at least one of their modified compounds, etc.

[0157] In some embodiments, the cathode film layer may optionally further include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0158] In some embodiments, the positive electrode film layer may further optionally include a conductive agent. As an 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.

[0159] In some embodiments, the positive electrode plate can be prepared by the following method: dispersing the components for preparing the positive electrode plate, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on the positive electrode current collector, and after processes such as drying and cold pressing, the positive electrode plate can be obtained.

[0160] [Negative electrode plate]

[0161] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material.

[0162] As an example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode film layer is provided on any one or both of the two opposite surfaces of the negative electrode current collector.

[0163] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, copper foil can be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (such as copper, copper 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.).

[0164] In some embodiments, the negative electrode active material can be a negative electrode active material for batteries 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, etc. The silicon-based materials can be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based materials can 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 conventional materials that can be used as the negative electrode active material of the battery can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0165] In some embodiments, the negative electrode film layer may further optionally include a binder. As an 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).

[0166] In some embodiments, the negative electrode film layer may further optionally include a conductive agent. As an 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.

[0167] In some embodiments, the negative electrode film layer may further optionally include other additives, such as a thickening agent (such as sodium carboxymethyl cellulose (CMC-Na)), etc.

[0168] In some embodiments, the negative electrode plate can be prepared in the following manner: dispersing the components for preparing the negative electrode plate, such as the negative electrode active material, conductive agent, binder, and any other components, in a solvent (such as deionized water) to form a negative electrode slurry; coating the negative electrode slurry on the negative electrode current collector, and after processes such as drying and cold pressing, the negative electrode plate can be obtained.

[0169] [Electrolyte]

[0170] The electrolyte functions to conduct ions between the positive electrode plate and the negative electrode plate. There is no specific limitation on the type of electrolyte in this application, and it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or all-solid-state.

[0171] In some embodiments, the electrolyte is liquid and includes an electrolyte salt and a solvent.

[0172] 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 difluorooxalate borate, lithium bis(oxalato)borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0173] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl 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, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0174] In some embodiments, the electrolyte may further optionally include additives. As an example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain performance of the battery, such as additives for improving the overcharge performance of the battery, additives for improving the high-temperature or low-temperature performance of the battery, and the like.

[0175] [Separator membrane]

[0176] In some embodiments, the battery cell further includes a separator membrane. The present application does not particularly limit the type of the separator membrane, and any well-known porous structure separator membrane with good chemical stability and mechanical stability can be selected.

[0177] In some embodiments, the material of the separator membrane may be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator membrane may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator membrane is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0178] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator membrane can be made into an electrode assembly by a winding process or a stacking process.

[0179] In some embodiments, the battery cell may include an outer package. The outer package can be used to encapsulate the above-mentioned electrode assembly and electrolyte.

[0180] In some embodiments, the outer package of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the battery cell can also be a soft package, such as a pouch soft package. The material of the soft package can be plastic. As plastics, polypropylene, polybutylene terephthalate, and polybutylene succinate can be listed, etc.

[0181] The present application does not particularly limit the shape of the battery cell, and it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 is a battery cell 5 with a square structure as an example.

[0182] In some embodiments, referring to Figure 2 , the outer package may include a housing 51 and a cover plate 53. Among them, the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity. The housing 51 has an opening communicating with 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 separator membrane can form an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte infiltrates into the electrode assembly 52. The number of the electrode assemblies 52 included in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0183] In some embodiments, battery cells can be assembled into a battery module. The number of battery cells included in the battery module can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery module.

[0184] Figure 3 is a battery module 4 as an example. Referring to Figure 3 , in the battery module 4, a plurality of battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other manner. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0185] Optionally, the battery module 4 can further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0186] In some embodiments, the above battery module can be further assembled into a battery pack. The number of battery modules included in the battery pack can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery pack.

[0187] Figure 4 and Figure 5 is a battery pack 1 as an example. Referring to Figure 4 and Figure 5 , the battery pack 1 can include a battery box and a plurality of battery modules 4 arranged in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0188] In addition, the present application further provides an electrical device. The electrical device includes at least one of the battery cell, battery module, or battery pack provided by the present application. The battery cell, battery module, or battery pack can be used as the power supply of the electrical device or as the energy storage unit of the electrical device. The electrical device can 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, satellites, energy storage systems, etc., but are not limited thereto.

[0189] As the electrical device, the battery cell, battery module, or battery pack can be selected according to its usage requirements.

[0190] Figure 6 is an electrical device as an example. The electrical device is a pure electric vehicle, hybrid electric vehicle, or plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the electrical device for the battery cell, a battery pack or battery module can be used.

[0191] [Embodiment]

[0192] The embodiments of the present application will be described below. The embodiments described below are exemplary and are only used to explain the present application and should not be construed as a limitation to the present application. For those techniques or conditions not specified in the embodiments, they shall be carried out according to the techniques or conditions described in the literature in the art or according to the product specifications. For reagents or instruments whose manufacturers are not specified, they are all conventional products that can be obtained through commercial purchases.

[0193] Embodiment 1

[0194] (1) Preparation of the precursor:

[0195] 1182 g of Li 2 CO 3 , 3325 g of NH 4 H 2 PO 4 , 2899 g of MnSO 4 , 1945 g of FeSO 4 were put into 14 kg of pure water, stirred and reacted at 25°C for 60 minutes, and the precipitate was collected by filtration; the precipitate was washed and filtered with pure water, ball-milled at a speed of 350 rpm for 120 minutes, dried at 100°C for 120 minutes, crushed, and the obtained dry powder was then placed in a nitrogen atmosphere sintering furnace and sintered at a constant temperature of 500°C for 3 hours to obtain the precursor.

[0196] (2) Preparation of the positive electrode material:

[0197] 5000 g of the precursor was put into 14 kg of glucose aqueous solution (containing 1 kg of glucose), and 19 g of Mg(OH) 2 , 26 g of TiO 2 , 37 g of NH 4 VO 3 , 25 g of H 2 SiO 3 , 6 g of Cr 2 O 3 , 28 g of MnO 2 , 6 g of Fe 2 O 3 , 29 g of CoO 2 , 24 g of NiO and 20 g of H 3 BO 3, it was ground in a sand mill at 25 °C for 3 hours to obtain a slurry; a part of the slurry passing through a 400-mesh sieve was collected and spray-dried at 300 °C to obtain a dry powder; the dry powder was placed in a nitrogen atmosphere furnace at 800 °C and sintered for 6 hours, then cooled and taken out, and crushed to completely pass through an 800-mesh sieve to obtain a cathode material with a Dv50 particle size of 12 μm.

[0198] (3) Preparation of the cathode electrode sheet:

[0199] The cathode material, polyvinylidene fluoride, conductive carbon black, and N-methylpyrrolidone were dissolved in the solvent N-methylpyrrolidone (NMP) according to a weight ratio of 95:2.5:2.5:100, and after being fully stirred and mixed evenly, a cathode slurry was prepared; the cathode slurry was evenly coated on the cathode current collector aluminum foil, and then dried, cold-pressed, and slit to obtain the cathode electrode sheet.

[0200] (4) Preparation of the anode electrode sheet:

[0201] The anode active material artificial graphite, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC-Na) were dissolved in deionized water according to a weight ratio of 95.5:1.5:1.8:1.2, and after being fully stirred and mixed evenly, an anode slurry was prepared; the anode slurry was coated on the anode current collector copper foil, and then dried, cold-pressed, and slit to obtain the anode electrode sheet.

[0202] (5) Separator: A polypropylene membrane was used.

[0203] (6) Preparation of the electrolyte:

[0204] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1, and then LiPF 6 was uniformly dissolved in the above solution to obtain an electrolyte. In this electrolyte, the concentration of LiPF 6 was 1 mol / L.

[0205] (7) Preparation of the coin cell:

[0206] The above-mentioned cathode electrode sheet, separator, and anode electrode sheet were stacked and wound in sequence to obtain an electrode assembly; the electrode assembly was placed in an outer package, the prepared electrolyte was added, and after processes such as encapsulation, standing, formation, and aging, a secondary battery was obtained.

[0207] The preparation methods of the secondary batteries in Examples 2-46 and Comparative Example 3 were similar to that of Example 1, but the parameters were adjusted. See Tables 1-2 for details. The preparation methods of Comparative Examples 1-2 are as follows:

[0208] Comparative Example 1

[0209] Put 1182 g of Li 2 CO 3 、3325 g of NH 4 H 2 PO 4 、2899 g of MnSO 4 、1945 g of FeSO 4、 into 14 kg of pure water, stir and react at 25 °C for 60 minutes, then continue to add 19 g of Mg(OH) 2 、26 g of TiO 2 、37 g of NH 4 VO 3 、25 g of H 2 SiO 3 、6 g of Cr 2 O 3 、28 g of MnO 2 、6 g of Fe 2 O 3 、29 g of CoO 2 、24 g of NiO and 20 g of H 3 BO 3 , wash and collect the precipitate after mixing, microwave dry for 25 min, heating power 800 W, crush, obtain the dry powder, then place the dry powder in a nitrogen atmosphere sintering furnace, sinter at 650 °C for 6 hours at a constant temperature to obtain the precursor.

[0210] Mix 5000 g of the precursor and 1 kg of glucose, grind at 300 rpm for 1 hour, sinter in a nitrogen atmosphere furnace at 800 °C for 5 hours, then cool down and take out, and crush to completely pass through an 800-mesh sieve to obtain the cathode material.

[0211] Comparative Example 2

[0212] Put 1182 g of Li 2 CO 3 、3325 g of NH 4 H 2 PO 4 、2899 g of MnSO 4 、1945 g of FeSO 4 、into 14 kg of pure water, stir and react at 25 °C for 60 minutes, then continue to add 28 g of MnO 2 、6 g of Fe 2 O 3 、6 g of Cr 2 O 3 、29 g of CoO 2, Wash and collect the precipitate after mixing, microwave dry for 25 min at a heating power of 800 W, crush, and obtain the dry powder. Then place the dry powder in a nitrogen atmosphere sintering furnace and sinter at 650 °C for 6 hours to obtain the precursor.

[0213] Mix 5000 g of the precursor and 1 kg of glucose, grind at 300 rpm for 1 hour, sinter in a nitrogen atmosphere furnace at 800 °C for 5 hours, then cool down and take out, and crush until it can completely pass through an 800-mesh sieve to obtain the cathode material.

[0214]

[0215]

[0216]

[0217]

[0218]

[0219]

[0220]

[0221]

[0222] Table 3: Cathode material parameters of Examples 1 - 46 and Comparative Examples 1 - 3

[0223]

[0224]

[0225]

[0226] Testing of materials and batteries

[0227] (1) Testing of the precursor chemical formula, coating layer composition and element ratio of the cathode material:

[0228] Weigh 0.2 g of the precursor 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 hour, then make up the volume to 100 mL with a volumetric flask; then use a pipette to transfer 1 mL and make up the volume to 100 mL with a volumetric flask to obtain the test solution.

[0229] The mass fractions of lithium, manganese, iron, phosphorus, doping elements, etc. in the solution to be measured were determined using an inductively coupled plasma optical emission spectrometer (ICP-OES, instrument brand: Agilent 5800); the molar ratios of the elements in the precursor were calculated based on the mass fractions of the elements in the solution to be measured of the precursor, so as to determine the chemical formula and element molar ratio of the precursor; the molar ratios of the elements in the cathode material were calculated based on the mass fractions of the elements in the solution to be measured of the cathode material, and the molar ratios of the elements in the precursor were deducted to obtain the element composition of the coating layer, thereby calculating the element molar ratio;

[0230] Weigh 0.1 g of the cathode material, add 1.5 g of the flux metal tungsten granules for mixing, put them into a high-frequency infrared carbon-sulfur analyzer for sintering and testing the mass ratio of carbon in the cathode material and convert it into a molar ratio.

[0231] (2) Measurement of Dv50 particle size:

[0232] Take an appropriate amount of the sample, add 20 mL of deionized water, and ultrasonically treat it 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.

[0233] (3) Measurement of BET specific surface area:

[0234] Weigh 1 g of the sample and place it in a specific surface area test tube. Fill the liquid nitrogen cup with liquid nitrogen and put it into the specific surface area test tube to make the sample in a temperature environment of -200 °C. Use a specific surface area analyzer (Beijing Jingwei Gaobo, JWBK-112) for testing.

[0235] (4) Measurement of the powder resistivity of the cathode material:

[0236] Weigh 1 g of the sample and place it in a mold, then put the mold into a four-probe resistivity tester, adjust the pressure to 7.85 MPa. Wait until the height and pressure of the mold are both stable, and respectively test the forward resistivity and reverse resistivity of the sample. Take the average of the two as the powder resistivity of the sample.

[0237] (5) TEM test of the cathode material:

[0238] The cathode materials of Example 1 and Comparative Example 3 were subjected to TEM tests, and the results are as Figures 7-8 shown. By comparison, it can be seen that the coating layer of the cathode material of Example 1 of the present application is more complete, the structure is more compact, and the texture of the cathode material is more uniform and stable.

[0239] (6) Tests of the charging and discharging specific capacities of the battery:

[0240] Using the Shenzhen Neware battery testing system, the coin-type battery was cycled for charge and discharge at a charge-discharge rate of 0.1C. The test temperature was 25.0 °C, and the charge-discharge voltage was 2.0V - 4.3V. The charge capacity per gram was obtained by dividing the charge capacity of the first cycle by the mass of the cathode material, and the discharge capacity per gram was obtained by dividing the discharge capacity of the first cycle by the mass of the cathode material.

[0241] (7) Test of the capacity retention rate of the battery at 25 °C:

[0242] Using the Shenzhen Neware battery testing system, the coin-type battery was cycled for charge and discharge at a charge-discharge rate of 1C for 2000 cycles. The test temperature was 25.0 °C, and the charge-discharge voltage was 2.0V - 4.3V. The capacity retention rate was obtained by dividing the discharge capacity of the last cycle by the discharge capacity of the first cycle.

[0243] The above results are shown in Table 3-4.

[0244] Table 4: Performance test results of Examples 1-46 and Comparative Examples 1-3

[0245]

[0246]

[0247] It can be seen from the above results that:

[0248] Compared with Comparative Example 1 where the doping element was added to the core, the cycle capacity retention rates of the batteries of Examples 1-13, 15-18, 20-29, 33-40, 43-44 of the present application were significantly higher, and the charge capacity per gram and discharge capacity per gram of the batteries of Examples 1-13, 15-18, 20-29, 39-40, 43-44 of the present application were significantly higher;

[0249] Compared with Comparative Example 2 where the doping element was added to the core, the charge and discharge capacities per gram of the battery of Example 14 of the present application were significantly higher, and the cycle capacity retention rate was significantly higher;

[0250] Compared with Comparative Example 3 where no doping element was added to the core and the shell, the cycle capacity retention rates of the batteries of Examples 1, 14, 17-18, 41-42 of the present application were significantly higher, and the charge and discharge capacities per gram of Examples 1, 14, 17-18 of the present application were significantly higher;

[0251] Compared with Example 33 where a lower reaction temperature and a longer reaction time were used to prepare the precursor, and Example 34 where a higher reaction temperature was used to prepare the precursor, the charge and discharge capacities per gram and the cycle capacity retention rate of the batteries of Examples 1-4 of the present application were significantly higher;

[0252] Compared with Example 35 where a lower ball milling speed was used to prepare the precursor and Example 36 where a higher ball milling speed was used to prepare the precursor, the charge and discharge specific capacities of the batteries of Examples 1, 5 - 7 of the present application are significantly higher, and the cycle capacity retention rate is significantly higher;

[0253] Compared with Example 37 where a lower sintering temperature was used to prepare the precursor and Example 38 where a higher sintering temperature was used to prepare the precursor, the charge and discharge specific capacities of the batteries of Examples 1, 11 - 13 of the present application are significantly higher, and the cycle capacity retention rate is significantly higher;

[0254] Compared with Example 39 where a lower molar ratio of precursor to carbon element was used to prepare the positive electrode material, the charge and discharge specific capacities of the batteries of Examples 1, 15 - 16 of the present application are significantly higher, and the cycle capacity retention rate is significantly higher; compared with Example 40 where a higher molar ratio of precursor to carbon element was used to prepare the positive electrode material, the charge and discharge specific capacities of the batteries of Examples 1, 15 - 16 of the present application are significantly higher;

[0255] Compared with Example 41 where a lower molar ratio of precursor to doping element was used to prepare the positive electrode material and Example 42 where a higher molar ratio of precursor to doping element was used to prepare the positive electrode material, the charge and discharge specific capacities of the batteries of Examples 1, 17 - 18 of the present application are significantly higher, and the cycle capacity retention rate is significantly higher;

[0256] Compared with Example 43 where a lower grinding temperature was used to prepare the positive electrode material and Example 44 where a higher grinding temperature was used to prepare the positive electrode material, the charge and discharge specific capacities of the batteries of Examples 1, 20 - 22 of the present application are significantly higher, and the cycle capacity retention rate is significantly higher;

[0257] Compared with Example 45 where a lower sintering temperature was used to prepare the positive electrode material and Example 46 where a higher sintering temperature was used to prepare the positive electrode material, the charge and discharge specific capacities of the batteries of Examples 1, 26 - 28 of the present application are significantly higher, and the cycle capacity retention rate is significantly higher.

[0258] It should be noted that the present application is not limited to the above - mentioned embodiments. The above - mentioned embodiments are only examples, and embodiments having the same constitution as the technical idea in essence and achieving the same effect within the technical solution scope of the present application are all included in the technical scope of the present application. In addition, within the scope not departing from the gist of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other ways constructed by combining some constituent elements of the embodiments are also included in the scope of the present application.

Claims

1. A method for preparing a cathode material, comprising: mixing a precursor lithium iron manganese phosphate, a carbon source, and a source of a doping element in a solvent, drying, and sintering to obtain the cathode material; The positive electrode material includes a core and a coating layer that coats the core; the core includes LiMn x Fe 1-x PO 4 , where 0 < x < 1; the coating layer includes carbon and a doping element; the doping element includes one or more of Group IIA elements, Group IIIA elements, Group IVA elements, and transition metal elements.

2. The method according to claim 1, wherein, 0.1 ≤ x ≤ 0.9; and / or, the doping element includes one or more elements selected from Mg, Ti, V, Si, Cr, Mn, Fe, Co, Ni, and B.

3. The method according to claim 1 or 2, wherein, the molar ratio of the carbon element in the precursor to the carbon element in the carbon source is 1:1.5 - 1:0.001, optionally 1:1.45 - 1:0.01; and / or, the molar ratio of the precursor to the doping element in the source of the doping element is 1:0.25 - 1:0.00001, optionally 1:0.2 - 1:0.0001.

4. The method according to any one of claims 1 to 3, wherein, the mixing is carried out at 5°C - 70°C, optionally, the mixing is carried out at 10°C - 60°C; and / or, the mixing time is 0.5 - 12 hours; and / or, the mixing is carried out by grinding.

5. The method according to any one of claims 1 to 4, wherein, the sintering temperature is 350°C - 950°C, optionally 400°C - 900°C; and / or, the sintering time is 2 - 20 hours; and / or, the sintering is carried out in an inert atmosphere.

6. The method according to any one of claims 1 to 5, wherein, the drying temperature is 150°C - 400°C; and / or, the drying is carried out by spray drying or baking; and / or, the method further includes sieving the mixture before the drying and collecting the sieved part; and / or, the method further includes crushing after the sintering, optionally followed by sieving; and / or, the carbon source includes one or more of an organic carbon source and an inorganic carbon source, optionally including one or more of citric acid, glucose, sucrose, polyvinyl alcohol, polypyrrole, polyethylene glycol, pitch, anthracene, and aniline; and / or, the source of the doping element includes one or more of a hydroxide of the doping element, an oxide of the doping element, an acid of the doping element, and a salt of the doping element; and / or, the solvent includes one or more of water and an organic solvent, optionally, the solvent includes one or more of water, ethanol, methanol, acetone, ethylene glycol, and isopropanol.

7. The method according to any one of claims 1 to 6, wherein, the precursor is obtained by the following steps: reacting a lithium source, a manganese source, an iron source, and a phosphorus source in a solvent, separating the solid and liquid phases, and collecting the solid phase; drying and sintering the solid phase to obtain the precursor.

8. The method according to claim 7, wherein, The precursor includes LiMn x Fe 1-x PO 4 , where 0 < x < 1, optionally, 0.1 ≤ x ≤ 0.9; optionally, in the steps of preparing the precursor, the molar ratio of the lithium element in the lithium source, the manganese element in the manganese source, the iron element in the iron source, and the phosphorus element in the phosphorus source is 1:x:(1 - x):

1.

9. The method according to claim 7 or 8, wherein, In the step of preparing the precursor, the reaction is carried out at 5°C - 60°C, optionally, the reaction is carried out at 10°C - 50°C; and / or, the reaction time is 10 minutes to 8 hours, optionally 10 minutes to 6 hours; and / or, the drying temperature is 50°C - 250°C; and / or, the drying time is 10 minutes to 12 hours; and / or, the sintering temperature is 150°C - 800°C, optionally 200°C - 700°C; and / or, the sintering time is 1 - 12 hours; and / or, the sintering is carried out in an inert atmosphere.

10. The method according to any one of claims 7 to 9, wherein, in the step of preparing the precursor, the solid-liquid separation is carried out by filtration or centrifugation; and / or, before the drying, the solid phase is ball-milled; optionally, the rotation speed of the ball-milling is 100 - 600 rpm, optionally 200 - 500 rpm, and the ball-milling time is 1 - 12 hours, optionally 2 - 10 hours; and / or, before the drying, the solid phase is washed; and / or, between the drying and the sintering, the solid phase is crushed; and / or, the lithium source includes one or more of hydroxides, oxides, inorganic acid salts, and organic acid salts of lithium element, optionally including one or more of lithium hydroxide, lithium oxide, lithium carbonate, lithium acetate, lithium oxalate, lithium phosphate, and lithium chloride; and / or, the manganese source includes one or more of organic acid salts, inorganic acid salts, oxides, and hydroxides of manganese element; and / or, the iron source includes one or more of organic acid salts, inorganic acid salts, oxides, and hydroxides of iron element; and / or, the phosphorus source includes one or more of phosphoric acid, phosphates, hydrogen phosphates, and dihydrogen phosphates, optionally including one or more of phosphoric acid, iron phosphate, ferrous phosphate, ammonium ferrous phosphate, ammonium dihydrogen phosphate, ammonium hydrogen phosphate, ammonium phosphate, lithium hydrogen phosphate, lithium dihydrogen phosphate, and lithium phosphate; and / or, a carbon source is added during the reaction process.

11. A cathode material, comprising a core and a coating layer coating the core, the core comprising LiMn x Fe 1-x PO 4 , wherein, 0 < x < 1, optionally, 0.1 ≤ x ≤ 0.9; the coating layer includes carbon and doping elements; the doping elements include one or more of Group IIA elements, Group IIIA elements, Group IVA elements, and transition metal elements, optionally including one or more elements such as Mg, Ti, V, Si, Cr, Mn, Fe, Co, Ni, and B; optionally, the molar ratio of manganese element to iron element in the core is 1:9 - 9:

1.

12. The positive electrode material according to claim 11, wherein, The LiMn x Fe 1-x PO 4 in the core has a molar ratio to the carbon element in the coating layer of 1:1.5 - 1:0.001, optionally 1:1.45 - 1:0.01; and / or, The LiMn in the core x Fe 1-x PO 4 has a molar ratio to the doping element in the coating layer of 1:0.25 to 1:0.00001, and may be optionally 1:0.2 to 1:0.0001.

13. The positive electrode material according to claim 11 or 12, wherein, the Dv50 particle size of the positive electrode material is 0.1 - 13 μm; and / or, the BET specific surface area of the positive electrode material is 10 - 27 m² / g, optionally 10 - 25 m² / g; and / or, the powder resistivity of the positive electrode material ≤ 1200 Ω·cm, optionally, the powder resistivity of the positive electrode material ≤ 300 Ω·cm; and / or, the positive electrode material is prepared by the method according to any one of claims 1 to 10.

14. A positive electrode sheet, comprising a positive electrode material prepared by the method according to any one of claims 1 to 10 or a positive electrode material according to any one of claims 11 to 13.

15. A battery, comprising a positive electrode material prepared by the method according to any one of claims 1 to 10, a positive electrode material according to any one of claims 11 to 13, or the positive electrode sheet according to claim 14.

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

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