Electrode material preparation method, electrode material, electrode plate, battery, and electrical apparatus

Abstract

An electrode material preparation method, an electrode material, an electrode plate, a battery, and an electrical apparatus. The preparation method comprises: mixing a transition metal oxide with raw materials of a lithium iron manganese phosphate material, and performing first calcination, to obtain a first material; mixing the first material, an inner core, and a first conductive agent, to obtain a second material, the second material comprising the inner core and a first coating layer coated on the exterior of the inner core; and forming a second coating layer on the exterior of the first coating layer, the second coating layer comprising a conductive agent.

Description

Preparation method of electrode material, electrode material, electrode sheet, battery and electric device

[0001] This application claims priority to Chinese Patent Application No. 202410869507.4, filed on June 28, 2024, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0002] The present disclosure relates to the technical field of batteries, and in particular to a preparation method of electrode material, electrode material, electrode sheet, battery and electric device. BACKGROUND

[0003] With the rapid development of electrochemical energy storage devices, high-safety and high-stability lithium ion energy storage systems such as lithium ion batteries are an inevitable choice for the development of the power industry. Lithium ion batteries are a kind of secondary batteries, which include electrode materials and mainly work by the reciprocal movement of lithium ions in the electrode materials between the positive electrode and the negative electrode. SUMMARY

[0004] The present disclosure provides a new technical solution for a preparation method of electrode material.

[0005] In a first aspect, a preparation method of electrode material is provided. The preparation method includes: mixing a transition metal oxide and raw materials of a lithium manganese iron phosphate material, and performing a first calcination to obtain a first material; mixing the first material, an inner core, and a first conductive agent to obtain a second material, the second material including the inner core and a first coating layer coated outside the inner core; and forming a second coating layer outside the first coating layer, the second coating layer including a conductive agent.

[0006] In some embodiments, the forming of the second coating layer outside the first coating layer, the second coating layer including a conductive agent, includes:

[0007] mixing a second carbon-containing organic matter and the second material, and performing a second calcination to obtain the electrode material, the electrode material including the inner core, the first coating layer coated outside the inner core, and the second coating layer coated outside the first coating layer.

[0008] In some embodiments, the raw materials of the lithium manganese iron phosphate material include: a lithium source, a manganese source, an iron source, and a phosphorus source.

[0009] In some embodiments, in the manganese source and the iron source, the molar ratio of manganese to iron is x:(1-x), x being any value in 0.3 to 0.9.

[0010] In some embodiments, the mixing the transition metal oxide with the raw material of the lithium iron manganese phosphate material and performing the first calcination to obtain the first material comprises: adding a lithium source, a manganese source, an iron source, and a phosphorus source into a first solvent to dissolve to obtain a first mixed solution; dissolving a transition metal oxide and a first carbon-containing organic matter in the first mixed solution to obtain a second mixed solution; and performing the first calcination on the second mixed solution to obtain the first material.

[0011] In some embodiments, a molar ratio of the transition metal oxide to the lithium iron manganese phosphate is a, a molar ratio of the first carbon-containing organic matter to the lithium iron manganese phosphate is a / 3, and a is any value in a range from 0.03 to 0.2.

[0012] In some embodiments, the first calcination is performed at a temperature in a range from 400°C to 950°C, and the temperature is maintained for 1 hour to 3 hours when the temperature rises to an integer multiple of the temperature.

[0013] In some embodiments, the mixing the first material, the core, and the first conductive agent to obtain the second material comprises: dissolving a part of the first material, a nickel-cobalt-manganese material, and a first conductive agent in a second solvent to obtain a third mixed solution; and drying the third mixed solution after the mixing.

[0014] In some embodiments, the method further comprises: mixing another part of the first material, a product after the drying of the third mixed solution, and a second conductive agent in a third solvent to obtain a fourth mixed solution; and drying the fourth mixed solution after the mixing to obtain a second material.

[0015] In some embodiments, in the mixing the second carbon-containing organic matter and the second material and performing the second calcination to obtain the electrode material, a molar ratio of the second carbon-containing organic matter to the second material is b, and b is any value in a range from 0.01 to 0.15.

[0016] In some embodiments, the second calcination is performed at a temperature in a range from 700°C to 1000°C, and the temperature is maintained for 0.5 hours to 1.5 hours when the temperature rises to an integer multiple of the temperature.

[0017] In a second aspect, an electrode material is provided. The electrode material is prepared according to the preparation method described above.

[0018] In a third aspect, an electrode sheet is provided. The electrode sheet comprises a sheet body and the electrode material described above, and the electrode material is arranged on a surface of the sheet body.

[0019] In a fourth aspect, a battery is provided. The battery comprises the electrode sheet described above.

[0020] In a fifth aspect, a power consuming device is provided. The power consuming device comprises one of the battery, the electrode sheet, or the electrode material.

[0021] According to some embodiments of the present disclosure, the preparation method is simple in operation, and the electrode material formed has stable properties. The electrode material prepared by the preparation method comprises a core and two coating layers coated outside the core. The two coating layers can effectively reduce the contact between the electrolyte and the nickel-cobalt-manganese material, improve the surface stability of the electrode material, and effectively inhibit the exothermic reaction between the electrolyte and the nickel-cobalt-manganese material under abuse conditions such as overcharge, short circuit, heating, and needle puncture, thereby improving the cycle stability and safety performance of the electrode material. The conductive agent can improve the conductivity of the electrode material and reduce the internal resistance of the battery.

[0022] Other features of the present disclosure, and their advantages, will become apparent in the non-limiting description of some embodiments of the present disclosure, given for the purpose of explanation only, and not of limitation. BRIEF DESCRIPTION OF DRAWINGS

[0023] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate some embodiments of the present disclosure and together with the description, serve to explain the principles of the present disclosure.

[0024] FIG. 1 is a schematic structural diagram of a positive electrode material according to some embodiments.

[0025] FIG. 2 is a partial enlarged view of FIG. 1.

[0026] Reference signs: 1, core; 2, first coating layer; 2-1, high-concentration layer; 2-2, low-concentration layer; 2-3, carbon material; 3, second coating layer. DETAILED DESCRIPTION

[0027] Some embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. Note that the relative arrangement, numerical expressions, and numerical values of the components and steps set forth in these embodiments are not limiting to the scope of the present disclosure unless otherwise specified.

[0028] The following description of at least one embodiment is merely exemplary in nature and is in no way intended to limit the present disclosure or its application or uses.

[0029] Techniques, methods, and devices known to those of ordinary skill in the relevant art can not be discussed in detail herein. However, where appropriate, such techniques, methods, and devices can be viewed as part of the specification.

[0030] In all examples shown and discussed herein, any value should be interpreted as merely exemplary and not as a limitation. Thus, other examples in some embodiments can have different values.

[0031] It should be noted that like numerals and letters refer to like items throughout the several views, as such, once an item is defined in one view, it need not be discussed further in subsequent views.

[0032] In the related art, the positive electrode of a lithium ion battery generally includes nickel-cobalt-manganese ternary materials, which have poor stability during use and are prone to failure, and the nickel-cobalt-manganese ternary materials have a large internal resistance.

[0033] Based on this, some embodiments of the present disclosure provide a preparation method of an electrode material. The preparation method includes: mixing a transition metal oxide and raw materials of a manganese iron phosphate material, and performing first calcination to obtain a first material; mixing the first material, an inner core, and a first conductive agent to obtain a second material, the second material including the inner core and a first coating layer 2 coated outside the inner core; and forming a second coating layer 3 outside the first coating layer 2, the second coating layer including a conductive agent.

[0034] In some embodiments of the present disclosure, as shown in FIG. 1, the inner core 1 is a ternary material, such as a nickel-cobalt-manganese material.

[0035] In some embodiments, the ternary material includes at least one of NCM111, NCM523, NCM622, and NCM811. The inner core 1 is a powder, and the particle size of the inner core 1 is microns.

[0036] In some embodiments, the particle size of the inner core 1 is less than or equal to 5 μm. For example, the particle size of the inner core 1 is 0.5 μm to 1 μm. For example, the particle size of the inner core 1 is 0.5 μm, 0.6 μm, 0.8 μm to 1 μm.

[0037] It can be understood that within this range, the inner core 1 has high activity and high electrochemical stability.

[0038] The first coating layer 2 is coated outside the inner core 1 and the second coating layer 3 is coated outside the first coating layer 2 by physical coating. The transition metal-doped manganese iron phosphate (LiMnPO4, referred to as LMP) material combines the stability of the olivine phosphate structure and the high-voltage characteristics. By doping different transition metal oxides, the manganese iron phosphate material can obtain better electrochemical performance, such as high structural stability, conductivity, and cycle performance.

[0039] The second coating layer 3 is a conductive agent. The conductive agent is used for conduction, can increase the electron conduction path inside the electrode material, reduce the internal resistance of the battery, improve the charge and discharge efficiency of the battery, and also can improve the rate performance and cycle stability of the battery. The conductive agent helps to reduce the polarization of the electrode reaction, reduces energy loss, and improves the working voltage of the battery. The preparation method has a simple process and can form an electrode material with stable properties.

[0040] In some embodiments, the first coating layer 2 formed outside the core 1 comprises a transition metal-doped lithium manganese iron phosphate material, comprising: mixing a transition metal oxide with raw materials of the lithium manganese iron phosphate material, and performing a first calcination to obtain a first material; and mixing the first material, the core 1 and a first conductive agent to obtain a second material, wherein the second material comprises the core 1 and the first coating layer 2 coated outside the core 1.

[0041] In some embodiments, the raw materials of the lithium manganese iron phosphate material comprise a lithium source, a manganese source, an iron source and a phosphorus source.

[0042] In some embodiments, the lithium source comprises at least one of lithium hydroxide, lithium carbonate, lithium chloride and lithium oxide. The manganese source comprises at least one of manganese dioxide, trimanganese tetroxide and manganese sulfate. The iron source comprises at least one of ferrous sulfate, ferric nitrate, iron oxide, iron powder, ferrous oxalate and ferric phosphate. The phosphorus source comprises at least one of phosphoric acid, ammonium dihydrogen phosphate or dihydrogen ammonium phosphate.

[0043] It can be understood that the transition metal oxide is used to provide transition metal elements. The transition metal oxide is introduced in the process of preparing the lithium manganese iron phosphate material. The transition metal oxide can play a role of doping and modification on the lithium manganese iron phosphate material, and improve the ionic conductivity of the lithium manganese iron phosphate material.

[0044] In addition, the transition metal oxide can also form a nano metal oxide on the surface of the lithium manganese iron phosphate material. During the annealing process, the transition metal oxide reacts with residual lithium carbonate, lithium hydroxide and other substances on the surface of the lithium manganese iron phosphate material to form a lithium ion conductor, thereby reducing the residual alkali content of the lithium manganese iron phosphate material, improving the ability of the lithium manganese iron phosphate material to conduct lithium ions, and enhancing the binding force between the first coating layer 2 and the second coating layer 3. After the first calcination, the transition metal-doped lithium manganese iron phosphate material, i.e. the first material, can be formed.

[0045] In the coating process, the first material, the core 1 and the first conductive agent are mixed to obtain a second material, wherein the second material comprises the core 1 and the first coating layer 2 coated outside the core 1.

[0046] It should be noted that the particle size of the core 1 is less than or equal to 5 μm. For example, the particle size of the core 1 is 0.5 μm to 1 μm. The first material is a granular material, and the particle size of the first material is in the nanometer level, for example, the particle size of the first material is less than or equal to 100 μm. Since the particle size of the core 1 is larger than the particle size of the first material, the first material can be attached to the surface of the core 1 during the mixing process. For example, the particle size of the first material is greater than or equal to 40 μm. The particle size range is not only conducive to the coating of the first coating layer 2 on the core, but also conducive to the coating of the second coating layer 3 on the first coating layer 2.

[0047] For example, in order to improve the conductivity of the first material, the raw material of the lithium manganese iron phosphate material further comprises a first carbon-containing organic matter. The first carbon-containing organic matter comprises at least one of glucose, sucrose, fructose, cellulose, starch, etc. In order to mix uniformly, the raw material of the lithium manganese iron phosphate material is added into a first solvent. The first solvent comprises at least one of ketone, alcohol, water, etc. The ketone comprises acetone, methyl ethyl ketone, butanone, cyclohexanone, etc. The alcohol comprises methanol, ethanol, propanol, ethylene glycol, etc. When preparing, the above-mentioned materials are added into the first solvent and mixed. For example, the mixing is performed by ultrasonic dispersion, mechanical stirring, etc.

[0048] Finally, the mixed liquid is subjected to the first calcination in a muffle furnace. For example, the calcination atmosphere is nitrogen or inert gas. After the calcination, the first material is obtained.

[0049] In some embodiments, the second coating layer 3 is formed outside the first coating layer 2, and the second coating layer 3 comprises a conductive agent, comprising: mixing a second carbon-containing organic matter and a second material, and performing the second calcination to obtain the electrode material, wherein the electrode material comprises the core 1, the first coating layer 2 coated outside the core 1, and the second coating layer 3 coated outside the first coating layer 2.

[0050] In some embodiments, the second carbon-containing organic matter comprises at least one of glucose, sucrose, fructose, cellulose, starch, etc. The above-mentioned substances can form a package for the second material. After the second calcination, the second carbon-containing organic matter forms the conductive agent, the conductive agent forms the second coating layer 3, and the second coating layer 3 is coated outside the first coating layer 2. The conductive agent is a granular material. The particle size of the conductive agent is 20 μm to 35 μm. The particle size of the conductive agent is smaller than the particle size of the first material, so that the second coating layer 3 can be coated outside the first coating layer 2.

[0051] In some embodiments, in the manganese source and the iron source, the molar ratio of manganese to iron is x:(1-x), and x is any value in the range of 0.3 to 0.9. For example, x is 0.3, 0.5, 0.75, or 0.9.

[0052] In some embodiments, the general formula of the lithium manganese iron phosphate material is LiMn x Fe 1-x PO4. For example, x is 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9. Within this range, the manganese content in the first coating layer 2 is further reduced, the amount of manganese dissolution is reduced, and the performance stability of the first coating layer 2 is ensured.

[0053] In some embodiments, the mixing of the lithium source, the manganese source, the iron source, the phosphorus source, the transition metal oxide, and the first carbon-containing organic compound in the first solvent and the first calcination to obtain the first material comprises: dissolving the lithium source, the manganese source, the iron source, and the phosphorus source in the first solvent to obtain a first mixed solution; dissolving the transition metal oxide and the first carbon-containing organic compound in the first mixed solution to obtain a second mixed solution; and calcining the second mixed solution to obtain the first material.

[0054] In some embodiments, the plurality of raw materials are added step by step. For example, in the dissolving of the lithium source, the manganese source, the iron source, and the phosphorus source in the first solvent to obtain the first mixed solution, the dispersion of the above-mentioned materials in the first solvent is easier, and thus the lithium source, the manganese source, the iron source, and the phosphorus source are added in the first solvent at room temperature for dissolving.

[0055] In the dissolving of the lithium source, the manganese source, the iron source, and the phosphorus source in the first solvent to obtain the first mixed solution, the transition metal oxide and the first carbon-containing organic compound are not easy to disperse in the first mixed solution, and thus the transition metal oxide and the first carbon-containing organic compound are dispersed in the first mixed solution under heating to obtain the second mixed solution.

[0056] For example, the heating temperature is 60°C. The time for ultrasonic dispersion is 0.5 hours to 1 hour. Of course, the heating temperature is not limited to 60°C, and can also be 50°C, 70°C, 80°C, etc. Those skilled in the art can set it according to actual needs.

[0057] Finally, the second mixed solution is added into a muffle furnace for the first calcination.

[0058] Through the multi-step dispersion mixing, the quality of the obtained first material is uniform.

[0059] In some embodiments, the molar ratio of the transition metal oxide, the first carbon-containing organic compound, and the manganese iron lithium phosphate is 3a:a:3, for example, a is any value in 0.03 to 0.2 (for example, 0.03, 0.05, 0.1, 0.15, or 0.2).

[0060] Within this range, the transition metal oxide can effectively dope and modify the manganese iron lithium phosphate, and the first carbon-containing organic compound can make the transition metal-doped manganese iron lithium phosphate material form a nanomaterial.

[0061] In some embodiments, the temperature of the first calcination is 400°C to 950°C (for example, 400°C, 500°C, 600°C, 700°C, 800°C, or 900, etc.), and the temperature is kept at the whole hundred temperature for 1 hour to 3 hours (for example, 1 hour, 2 hours, or 3 hours, etc.).

[0062] For example, the first sintering temperature is in the range, so that the transition metal doped lithium manganese iron phosphate material can form a nanomaterial. The muffle furnace is heated to a temperature of 800°C, and the temperature is kept for 1-3 hours when the temperature is increased to the whole hundred temperature.

[0063] It can be understood that the heat preservation can ensure that the transition metal oxide, the first carbon-containing organic matter and the lithium manganese iron phosphate have sufficient time to fully react at a high temperature to form the required compound phase. The heat preservation can promote the growth of the crystal lattice of the transition metal doped lithium manganese iron phosphate material, improve the crystallinity of the material, and the high crystallinity helps the rapid diffusion of lithium ions. In addition, the heat preservation helps to form a more stable crystal structure, which can effectively improve the electrochemical performance and cycle stability of the material. The heat preservation can also reduce the thermal stress caused by rapid cooling, reduce the microstructure defects of the crystal structure, reduce the thermal decomposition of the material at high temperature, and maintain the chemical stability of the material. The length of the heat preservation time can control the microstructure of the material, including the size and shape of the crystal grains. The heat preservation also helps to improve the density of the sintered body, reduce the pores, and improve the energy density and power density of the battery.

[0064] For example, the temperature of the first sintering is 800°C. During the sintering process, the temperature is increased to 800°C at a rate of 5°C / min under a nitrogen atmosphere. After natural cooling, the first material is obtained. For example, the temperature is increased in steps at whole hundred temperatures of 200°C, 400°C, etc., and the heat preservation is performed in multiple steps.

[0065] For example, the room temperature is 25°C→200°C→400°C→600°C→800°C. Each step is kept constant for 2 hours. That is, the temperature is kept constant for 2 hours at 200°C, 400°C, 600°C and 800°C. In this way, the transition metal doped lithium manganese iron phosphate material generated has good crystal form, few defects, small thermal stress, high material density, good chemical stability, high energy density and high power density.

[0066] For example, the heat preservation can also be performed at 100°C, 300°C, 500°C, 700°C and 800°C. The heat preservation can also be performed at 200°C, 300°C, 600°C, 700°C and 800°C. The heat preservation temperature can be set according to actual needs.

[0067] Of course, the temperature of the first calcination and the heat preservation process are not limited to the above examples, and those skilled in the art can set them according to actual needs.

[0068] In some embodiments, the mixing of the first material, the core 1 and the first conductive agent to obtain the second material comprises: dissolving a part of the first material, the nickel-cobalt-manganese material and the first conductive agent in a second solvent, and mixing by ultrasonic dispersion to obtain a third mixed solution; ball milling the third mixed solution; and spray drying the third mixed solution after ball milling.

[0069] In some embodiments, the nickel-cobalt-manganese material comprises at least one of NCM111, NCM523, NCM622 and NCM811. The first conductive agent can be, but is not limited to, carbon material 2-3. The second solvent comprises at least one of ketone, alcohol and water.

[0070] After the first material, the nickel-cobalt-manganese material and the first conductive agent are added to the second solvent, they are mixed by mechanical stirring, ultrasonic dispersion, etc. The mixed solution is dried by spray drying, heating drying, etc. The second material is obtained after drying.

[0071] In the step of dissolving a part of the first material, the nickel-cobalt-manganese material and the first conductive agent in a second solvent, and mixing by ultrasonic dispersion to obtain a third mixed solution, the second solvent is ethanol. A part of the first material, the nickel-cobalt-manganese material and the first conductive agent are dissolved in ethanol. For example, at 60°C, ultrasonic dispersion is performed for 0.5 to 1 hour, and finally a third mixed solution is obtained.

[0072] In the step of ball milling the third mixed solution, the third mixed solution is ball milled. For example, the third mixed solution is added to a ball mill tank and ball milled for 2 hours. The ball milling speed is 300 to 600 rpm (for example, 300 rpm, 400 rpm, 500 rpm or 600 rpm). The ball milling times is 2 or 3 times.

[0073] Ball milling reduces the particle size of the above-mentioned raw material powder by mechanical force, forming fine primary particles, which helps to increase the specific surface area of the material, thereby increasing the diffusion rate of lithium ions and improving the charge and discharge rate of the battery. Ball milling can promote the occurrence of solid-state reaction, especially in the second calcination, ball milling can increase the reaction rate, which helps to synthesize electrode materials with specific structure and performance. Ball milling can improve the compaction density of the electrode material, reduce the inter-particle voids, and help to improve the energy density of the battery. By ball milling, more defects and grain boundaries can be introduced, which can serve as fast diffusion channels for lithium ions, improving the electrical conductivity of the electrode material.

[0074] Finally, the third mixed solution after ball milling is subjected to spray drying. By adjusting the parameters of spray drying, such as spray speed, hot air temperature, drying rate, etc., the particle morphology and size of the obtained electrode material powder can be controlled, thereby affecting the charge and discharge performance of the electrode material. The particles produced by spray drying usually have small size and high specific surface area, which helps to improve the diffusion rate of lithium ions, thereby improving the charge and discharge efficiency of the battery. Spray drying can prepare electrode materials with good electrochemical performance, such as high capacity, high rate performance and excellent cycle stability.

[0075] In some embodiments, the method further comprises: adding another portion of the first material, the second material, and a second conductive agent to a third solvent, mixing by ultrasonic dispersion to obtain a fourth mixed solution; subjecting the fourth mixed solution to ball milling; and subjecting the fourth mixed solution after ball milling to spray drying.

[0076] For example, the second conductive agent comprises carbon material 2-3. The third solvent comprises at least one of ketone, alcohol, and water. After the other portion of the first material, the second material, and the second conductive agent are added to the third solvent, they are mixed by mechanical stirring, ultrasonic dispersion, etc. The mixed solution is dried by spray drying, heating drying, etc. After drying, the second material is obtained.

[0077] In the process of adding the other portion of the first material, the second material, and the second conductive agent to the third solvent and mixing by ultrasonic dispersion to obtain the fourth mixed solution, the third solvent is ethanol. The first material, the second material, and the second conductive agent are dissolved in ethanol. Under the condition of 60°C, ultrasonic dispersion is performed for 1-2 hours, and finally the fourth mixed solution is obtained.

[0078] In the process of subjecting the fourth mixed solution to ball milling, the fourth mixed solution is subjected to ball milling. For example, the fourth mixed solution is added to a ball milling tank and subjected to ball milling for 2 hours. The ball milling speed is 300-600 rpm, and the ball milling times are 2 or 3.

[0079] In the process of subjecting the fourth mixed solution after ball milling to spray drying, the fourth mixed solution after ball milling is subjected to spray drying to obtain the second material.

[0080] In some embodiments, as shown in FIG. 2, by adding the first material twice, the second coating layer 3 can form a high-concentration layer 2-1 and a low-concentration layer 2-2.

[0081] Of course, more times of adding the first material can be used to form more gradient concentration layers.

[0082] In some embodiments, the second carbon-containing organic matter and the second material are mixed, and a second calcination is performed to obtain the electrode material, wherein a molar ratio of the second carbon-containing organic matter to the second material is b, and b is any value in a range from 0.01 to 0.15.

[0083] For example, the second carbon-containing organic matter includes at least one of glucose, sucrose, fructose, cellulose, starch, and the like. The fourth solvent includes at least one of a ketone, an alcohol, and water. The ketone includes acetone, methyl ethyl ketone, butanone, cyclohexanone, and the like. The alcohol includes methanol, ethanol, propanol, ethylene glycol, and the like.

[0084] After the second material and the second carbon-containing organic matter are added to the fourth solvent, mixing is performed by mechanical stirring, ultrasonic dispersion, or the like. The mixed solution is added to a muffle furnace, and a second calcination is performed in an inert gas or nitrogen gas atmosphere. The electrode material in some embodiments of the present disclosure is obtained after the second calcination.

[0085] For example, the second carbon-containing organic matter is glucose. The fourth solvent is ethanol. For example, the solution after mixing of the second material, the second carbon-containing organic matter, and the fourth solvent is ultrasonically dispersed at 60°C for 1 hour to 2 hours. Then, the ultrasonically dispersed solution is placed in a muffle furnace to perform the second calcination.

[0086] In some embodiments, a molar ratio of the second carbon-containing organic matter to the second material is b, and b is any value in a range from 0.01 to 0.15. For example, a molar ratio of glucose to the second material is 0.01 to 0.15. The glucose is converted into a carbon material 2-3 in a high-temperature calcination process.

[0087] The carbon material 2-3 serves as a conductive agent, i.e., a second coating layer 3. In this range, the second coating layer 3 has a uniform thickness and few defects. For example, the thickness is in the above-mentioned thickness range, and the second coating layer 3 significantly improves the electrical conductivity of the electrode material, thereby reducing the internal resistance of the battery. The second coating layer 3 can serve as a protective layer, reducing side reactions of the electrode material with the electrolyte during charging and discharging, thereby improving the cycle stability of the battery.

[0088] The second coating layer 3 helps to form a stable chemical and electrochemical reaction interface on the surface of the electrode material, reducing the decomposition of the electrolyte. The second coating layer 3 can also buffer the volume change of the electrode material during charging and discharging, reduce the structural stress, and improve the structural stability of the electrode material.

[0089] In some embodiments, the second calcination is performed at a temperature of 700°C to 1000°C (for example, 700°C, 800°C, 900°C, or 1000°C, and the like), and the temperature is maintained for 0.5 hours to 1.5 hours (for example, 0.5 hours, 1 hour, or 1.5 hours, and the like) at an integer multiple of 100 of the temperature.

[0090] For example, the calcination atmosphere of the muffle furnace is nitrogen, and the temperature is increased to 700°C at a rate of 5°C / min. The temperature is kept at 700°C. After natural cooling, the electrode material is obtained. In the second calcination process, for example, the room temperature is 25°C. The temperature is increased to 700°C at a rate of 25°C→100°C→200°C→300°C→400°C→500°C→600°C. At each step, i.e. 100°C, 200°C, 300°C, 400°C, 500°C, 600°C, 700°C, the temperature is kept constant for 1 hour, and finally the electrode material is obtained.

[0091] It can be understood that, through the second calcination, the electrode material with a core-shell structure is finally obtained, which contains a core 1 of a nickel-cobalt-manganese material, a first coating layer 2 of a transition metal-doped lithium manganese iron phosphate material, and a second coating layer 3 of a conductive agent.

[0092] Of course, in the above steps, when performing ultrasonic dispersion, the heating temperature is not limited to 60°C, and can also be 50°C, 70°C, 80°C, etc. Those skilled in the art can set it according to actual needs.

[0093] In some embodiments of the present disclosure, the lithium source, the manganese source, the iron source, the phosphorus source, the transition metal oxide, and the first carbon-containing organic matter are subjected to the first calcination to prepare nano-sized lithium manganese iron phosphate, for example, manganese and iron exist in the form of divalent ions. The anion is phosphate. In the sintering process, there is no need to perform a reduction process, which reduces the structural defects of the electrode material caused by the reduction of Mn and Fe in the electrode material preparation process.

[0094] The transition metal oxide is introduced in the preparation of the lithium manganese iron phosphate material. The transition metal oxide can play a role of doping and modification on the lithium manganese iron phosphate material, and improve the ionic conductivity of the lithium manganese iron phosphate material.

[0095] In addition, the transition metal oxide also forms a nano metal oxide on the surface of the lithium manganese iron phosphate material. During the annealing process, the transition metal oxide reacts with residual lithium carbonate, lithium hydroxide, and other substances on the surface of the lithium manganese iron phosphate material to form a lithium ion conductor, thereby reducing the residual alkali content of the lithium manganese iron phosphate material, improving the ability of the lithium manganese iron phosphate material to conduct lithium ions, and enhancing the bonding force between the first coating layer 2 and the second coating layer 3.

[0096] The gap between the transition metal oxide-doped lithium manganese iron phosphate material and the nickel-cobalt-manganese material is filled with a conductive agent. The conductive agent can improve the ionic conductivity of the electrode material, and can effectively avoid the direct contact between the transition metal oxide-doped lithium manganese iron phosphate material and the nickel-cobalt-manganese material, prevent spontaneous oxidation-reduction reaction between the two, and improve the interface structure stability of the electrode material.

[0097] Meanwhile, the structure can isolate moisture, so that the sensitivity of the nickel-cobalt-manganese material to environmental humidity is reduced, and the storage and processing performance of the electrode material during use is improved.

[0098] In addition, the first coating layer 2 and the second coating layer 3 can effectively reduce the contact between the electrolyte and the nickel-cobalt-manganese material, improve the stability of the surface structure of the electrode material, effectively inhibit the exothermic reaction between the electrolyte and the nickel-cobalt-manganese material under overcharge, short circuit, heating, and needle puncture, and the like, thereby improving the cycle and safety performance of the electrode material.

[0099] In addition, the secondary coating is performed in a mechanical processing manner, which can form a uniform and tight coating of the transition metal oxide doped manganese iron phosphate material on the surface of the nickel-cobalt-manganese material. The preparation method is simple, efficient, and suitable for industrial production.

[0100] According to some embodiments of the present disclosure, an electrode material is provided. The electrode material is prepared according to the preparation method described above. As shown in FIGS. 1 and 2, the electrode material includes an inner core 1 containing a nickel-cobalt-manganese material, a first coating layer 2 coated outside the inner core 1, and a second coating layer 3 coated outside the first coating layer 2, the first coating layer 2 includes a transition metal doped manganese iron phosphate material, and the second coating layer 3 includes a conductive agent.

[0101] The electrode material is used as a positive electrode material. The electrode material has a core-shell structure. The inner core 1 is a ternary material, i.e., a nickel-cobalt-manganese material.

[0102] In some embodiments, the ternary material includes at least one of NCM111, NCM523, NCM622, and NCM811. The first coating layer 2 is coated outside the inner core 1.

[0103] The transition metal doped manganese iron phosphate (LiMnPO4, referred to as LMP) material combines the stability of the olivine type phosphate structure and the high voltage characteristics. By doping different transition metal oxides, the manganese iron phosphate material can obtain better electrochemical performance, such as high structural stability, conductivity, and cycle performance. The second coating layer 3 is a conductive agent.

[0104] The conductive agent is used for conduction, which can increase the electron conduction path inside the electrode material, reduce the internal resistance of the battery, improve the charge and discharge efficiency of the battery, and also improve the rate performance and cycle stability of the battery. The conductive agent helps to reduce the polarization of the electrode reaction, reduce energy loss, and improve the working voltage of the battery.

[0105] The electrode material is in the form of particles. The average particle size of the core-shell structure is less than or equal to 10 pm. Within this range, the core-shell structure has high structural strength and excellent electrochemical performance. For example, the average particle size is 200 nm to 2 pm, and within this range, the electrode material has even better electrochemical performance.

[0106] The first coating layer 2 has a thickness of 1 nm to 100 nm, for example, 10 nm to 80 nm. The second coating layer 3 has a thickness of 10 nm to 50 nm, for example, 20 nm to 35 nm. Within the above ranges, the two coating layers provide good protection for the core 1.

[0107] In some embodiments of the present disclosure, the electrode material includes a core 1 and two coating layers covering the core 1. The two coating layers can effectively reduce the contact between the electrolyte and the nickel-cobalt-manganese material, improve the surface stability of the electrode material, and effectively inhibit the exothermic reaction between the electrolyte and the nickel-cobalt-manganese material under abuse conditions such as overcharging, short circuiting, heating, and needle pricking, thereby improving the cycle stability and safety performance of the electrode material. The conductive agent can improve the conductivity of the electrode material and reduce the internal resistance of the battery.

[0108] In some embodiments, the first coating layer 2 includes a conductive agent, and the transition metal-doped manganese iron lithium phosphate material is mixed with the conductive agent.

[0109] In some embodiments, the transition metal-doped manganese iron lithium phosphate material forms particles. The gaps between the particles are filled with a conductive agent. This conductive agent can further increase the electron conduction path inside the electrode material, reduce the internal resistance of the battery, improve the charge and discharge efficiency of the battery, and improve the rate performance and cycle stability of the battery.

[0110] For example, the nickel-cobalt-manganese material as the core 1 forms particles. The gaps between the particles are also filled with a conductive agent. This arrangement can further reduce the internal resistance of the battery, improve the charge and discharge efficiency of the battery, and improve the rate performance and cycle stability of the battery.

[0111] In some embodiments, the conductive agent includes a carbon material 2-3. The carbon material 2-3 has good conductivity and can form good bonds with the nickel-cobalt-manganese material and the transition metal-doped manganese iron lithium phosphate material.

[0112] Of course, the conductive agent is not limited to the carbon material 2-3 and can also be a conductive polymer, etc. Those skilled in the art can make settings according to actual needs.

[0113] In some embodiments, the carbon material 2-3 includes at least one of a point-shaped carbon material 2-3 and a line-shaped carbon material 2-3.

[0114] In some embodiments, the point-like carbon material 2-3 includes at least one of carbon black, acetylene black, ketjen black, and conductive graphite. The line-like carbon material 2-3 includes at least one of carbon fiber and carbon nanotube. The line-like carbon material 2-3 has high strength and toughness, which can improve the mechanical properties of the electrode material and prevent deformation or breakage of the electrode material during charging and discharging. The addition of the point-like carbon material 2-3 can further enhance the structural stability of the electrode material.

[0115] For example, the carbon material 2-3 includes the point-like carbon material 2-3 and the line-like carbon material 2-3. Since the line-like carbon material 2-3 and the point-like carbon material 2-3 have excellent electrical conductivity, mixing them together can effectively reduce the internal resistance of the electrode material, improve the charging and discharging efficiency of the battery, and increase the energy density of the battery.

[0116] Of course, the carbon material 2-3 is not limited to the above embodiments, and those skilled in the art can make settings according to actual needs.

[0117] In some embodiments, along the thickness direction of the electrode material, the concentration of the transition metal-doped lithium iron manganese phosphate material in the first coating layer 2 gradually decreases from the side close to the inner core 1 to the side close to the second coating layer 3.

[0118] In some embodiments, the concentration of the transition metal-doped lithium iron manganese phosphate material in the first coating layer 2 gradually decreases from the inside to the outside. The concentration of the conductive agent in the first coating layer 2 gradually increases from the inside to the outside. In this way, the closer the first coating layer 2 is to the outer layer, the better the electron transport performance, thereby effectively improving the electrical conductivity of the electrode material. The closer the first coating layer 2 is to the inner layer, the higher the concentration of the lithium iron manganese phosphate material, and the higher the energy density. In this way, the electrode material can effectively balance high energy density and high electrical conductivity.

[0119] For example, as shown in FIGS. 1-2, the portion of the first coating layer 2 close to the inner core 1 forms a high-concentration layer 2-1, and the portion close to the second coating layer 3 forms a low-concentration layer 2-2. The concentration of the transition metal-doped lithium iron manganese phosphate material in the high-concentration layer 2-1 is high. The concentration of the transition metal-doped lithium iron manganese phosphate material in the low-concentration layer 2-2 is low. The electrode material can more effectively balance high energy density and high electrical conductivity.

[0120] In some embodiments, the transition metal oxide includes a divalent transition metal oxide.

[0121] In some embodiments, the divalent transition metal oxide introduced into the lithium iron manganese phosphate material can play a doping modification role on the lithium iron manganese phosphate material, significantly improving the ion conductivity of the lithium iron manganese phosphate material.

[0122] In addition, the divalent transition metal doped lithium manganese iron phosphate material can form nanoscale metal oxides, such as nanoscale divalent transition metal oxides, on the surface of the lithium manganese iron phosphate material. During the annealing process, the nanoscale divalent transition metal oxides react with residual lithium carbonate, lithium hydroxide, and other materials on the surface of the lithium manganese iron phosphate material to form lithium ion conductors, thereby reducing the residual alkali content of the lithium manganese iron phosphate material, improving the ability of the lithium manganese iron phosphate material to conduct lithium ions, and enhancing the binding force between the first coating layer 2 and the second coating layer 3.

[0123] In some embodiments, the divalent transition metal oxides include at least one of beryllium oxide, magnesium oxide, and calcium oxide.

[0124] In some embodiments, the above-mentioned materials have good stability, can effectively reduce the residual alkali content of the lithium manganese iron phosphate material, improve the ability of the lithium manganese iron phosphate material to conduct lithium ions, and enhance the binding force between the first coating layer 2 and the second coating layer 3.

[0125] In some embodiments, the molar ratio of manganese to iron is x:(1-x), for example, x is any value in the range of 0.3 to 0.9.

[0126] For example, the general formula of the lithium manganese iron phosphate material is LiMn x Fe 1-x PO4. For example, x is 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9. Within this range, the manganese content in the first coating layer 2 is further reduced, the amount of manganese elution is reduced, and the performance stability of the first coating layer 2 is ensured.

[0127] In some embodiments, the molar ratio of the transition metal to the lithium manganese iron phosphate material in the transition metal doped lithium manganese iron phosphate material is any value in the range of 0.1% to 10%.

[0128] Within this range, the divalent transition metal oxides can effectively reduce the residual alkali content of the lithium manganese iron phosphate material, improve the ability of the lithium manganese iron phosphate material to conduct lithium ions, and enhance the binding force between the first coating layer 2 and the second coating layer 3.

[0129] According to some embodiments of the present disclosure, an electrode sheet is provided. The electrode sheet includes a sheet body and the electrode material described above, and the electrode material is arranged on the surface of the sheet body.

[0130] The sheet body is a metal foil. The material of the sheet body is copper, aluminum, nickel, etc. The electrode material of some embodiments of the present disclosure is coated on the surface of the metal foil by coating. The physical and chemical properties of the electrode sheet are stable.

[0131] According to some embodiments of the present disclosure, a battery is provided. The battery includes the electrode sheet described above.

[0132] For example, the electrode sheet is a positive electrode sheet. In use, the electrode active material of the negative electrode sheet is graphite. A separator is arranged between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet, the separator and the negative electrode sheet are combined together in a laminated manner or a wound manner.

[0133] The battery has the characteristics of stable performance, high energy density and long service life.

[0134] According to some embodiments of the present disclosure, a power consuming device is provided. The power consuming device comprises the battery as described above, or the electrode sheet as described above, or the electrode material as described above.

[0135] The power consuming device has the characteristics of stable performance and long service life.

[0136] In some embodiments described above, the differences between various embodiments are mainly described. The optimization features different between various embodiments can be combined to form new embodiments as long as they are not contradictory. In view of the brevity of the writing, they will not be described here.

[0137] Although some embodiments of the present disclosure have been described in detail by examples, those skilled in the art should understand that the above examples are only for illustration, not for limiting the scope of the present disclosure. Those skilled in the art should understand that the above embodiments can be modified without departing from the scope and spirit of the present disclosure. The scope of the present disclosure is defined by the appended claims.

Claims

1. A method for preparing an electrode material, comprising: The transition metal oxide is mixed with the raw material of lithium manganese iron phosphate material and subjected to a first calcination to obtain the first material; The first material, the core, and the first conductive agent are mixed to obtain a second material; wherein the second material includes the core and a first coating layer covering the core. as well as A second coating layer is formed outside the first coating layer, the second coating layer comprising a conductive agent.

2. The preparation method according to claim 1, wherein, The second coating layer is formed outside the first coating layer, and the second coating layer includes a conductive agent, comprising: The second carbon-containing organic compound and the second material are mixed and then calcined a second time to obtain the electrode material; wherein the electrode material includes the core, a first coating layer covering the core, and a second coating layer covering the first coating layer.

3. The preparation method according to claim 1 or 2, wherein, The raw materials for the lithium manganese iron phosphate material include: lithium source, manganese source, iron source and phosphorus source.

4. The preparation method according to claim 3, wherein, In the manganese source and the iron source, the molar ratio of manganese to iron is x:(1-x), where x is any value from 0.3 to 0.

9.

5. The preparation method according to claim 3 or 4, wherein, The process of mixing transition metal oxides with lithium manganese iron phosphate material raw materials and then subjecting them to a first calcination to obtain a first material includes: The lithium source, the manganese source, the iron source and the phosphorus source are added to a first solvent and dissolved to obtain a first mixed solution; The transition metal oxide and the first carbon-containing organic compound are dissolved in the first mixed solution to obtain a second mixed solution; and The second mixed solution is subjected to the first calcination to obtain the first material.

6. The preparation method according to claim 5, wherein, The molar ratio of the transition metal oxide to the lithium manganese iron phosphate is a, and the molar ratio of the first carbon-containing organic compound to the lithium manganese iron phosphate is a / 3, wherein a is any value from 0.03 to 0.

2.

7. The preparation method according to any one of claims 1-6, wherein, The temperature of the first calcination is 400°C to 950°C; the temperature is held for 1 to 3 hours after reaching the whole number of 100°C.

8. The preparation method according to any one of claims 1-7, wherein, The step of mixing the first material, the core, and the first conductive agent to obtain the second material includes: A portion of the first material, the nickel-cobalt-manganese material, and the first conductive agent are dissolved and mixed in a second solvent to obtain a third mixed solution; and The third mixed solution is then dried.

9. The preparation method according to claim 8, further comprising: Another portion of the first material, the dried product of the third mixed solution, and the second conductive agent are added to the third solvent and mixed to obtain a fourth mixed solution; as well as The fourth mixed solution is dried to obtain the second material.

10. The preparation method according to any one of claims 2-9, wherein, In the process of mixing the second carbon-containing organic compound and the second material, and then calcining them a second time to obtain the electrode material, the molar ratio of the second carbon-containing organic compound to the second material is b; wherein b is any value from 0.01 to 0.

15.

11. The preparation method according to any one of claims 2-10, wherein, The second calcination temperature is 700°C to 1000°C; when the temperature increases by an integer multiple of 100°C, the temperature is held for 0.5 to 1.5 hours.

12. An electrode material prepared by the preparation method according to any one of claims 1 to 11.

13. An electrode sheet comprising a sheet body and an electrode material according to claim 12, the electrode material being disposed on the surface of the sheet body.

14. A battery comprising the electrode sheet according to claim 13.

15. An electrical appliance, comprising one of the following: The battery according to claim 14; The electrode sheet according to claim 13; or The electrode material according to claim 12.

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