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

Abstract

The invention discloses a preparation method of a positive electrode material, the positive electrode material, a battery and an electric device, the preparation method of the positive electrode material comprises the following steps: adding a reaction base solution, a reaction solution and a complexing agent solution, regulating the pH value of the solution to a first range value, and reacting for a first time at a first stirring speed; regulating the pH value of the solution to be within a second range value, reacting at a second stirring rotating speed until a target particle size is generated, and the second range value is greater than the first range value; separating precipitates from the reacted slurry, and drying the precipitates; mixing the material precursor with a lithium salt and an auxiliary agent; and sintering the mixed material at high temperature to obtain the positive electrode material which comprises positive electrode material particles. According to the preparation method of the positive electrode material provided by the embodiment of the invention, the obtained positive electrode material particles are internally provided with hollow cavities, microcracks generated in the charging and discharging process are reduced, and the structural stability of the material is improved; moreover, the high-power performance of the battery is improved; the method is simple, controllable and low in cost.

Description

Technical Field

[0001] The present invention relates to the field of battery materials, and in particular to a method for preparing a positive electrode material, a positive electrode material, a battery and an electrical device. Background Art

[0002] The positive electrode material is an important component of the battery. During the charging and discharging process of the lithium-ion battery, lithium ions are intercalated and deintercalated in the positive electrode material. In the related art, the efficiency of the intercalation and deintercalation process of lithium ions in the positive electrode material particles of the battery is low, resulting in insufficient power performance of the battery; and the preparation method of the positive electrode material of the battery in the related art is relatively cumbersome, which is not conducive to cost control. Therefore, there is room for improvement. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, one purpose of the present invention is to propose a method for preparing a positive electrode material, by making the second range value of the solution pH value greater than the first range value, the particle arrangement in the generated core precursor can be relatively loose, which is more convenient for the subsequent physical decomposition of the core precursor, and the particle arrangement in the shell precursor can be relatively tight, so that the shell structure of the precursor is more stable and not easy to be physically decomposed; by sintering the mixed material at high temperature to obtain the positive electrode material, the obtained positive electrode material particles can have a radial hollow structure, reduce the microcracks generated inside the positive electrode precursor particles due to volume shrinkage and expansion during charging and discharging, and improve the structural stability of the material; and the migration path distance and diffusion migration resistance of lithium ions can be reduced, and the migration rate of lithium ions can be improved; the surface contact active sites can be increased to make lithium ions more smoothly deintercalated, improve the migration ability of lithium ions, and improve the high power performance of the battery; the positive electrode material prepared by this method is simple and controllable, low-cost, and suitable for large-scale industrial production.

[0004] The invention also provides a positive electrode material prepared by the above preparation method.

[0005] The present invention also provides a battery comprising the positive electrode material.

[0006] The present invention also provides an electrical device comprising the battery.

[0007] A method for preparing a positive electrode material according to an embodiment of the present invention includes: adding a reaction base liquid to a reactor; adding a reaction liquid to the reaction base liquid, wherein the reaction liquid includes a first reaction liquid, the first reaction liquid includes phosphoric acid, and the first reaction liquid also includes at least one of an iron salt and a manganese salt; adding a complexing agent solution to the reaction base liquid, and adjusting the pH value of the solution to a first range value, reacting for a first time at a first stirring speed to form a core precursor; adjusting the pH value of the solution to a second range value, reacting at a second stirring speed to generate a target particle size, so as to generate a shell precursor outside the core precursor, the core precursor and the shell together constitute a particle precursor, and the second range value is greater than the first range value; separating a precipitate from the reacted slurry and drying it to obtain the material precursor, the material precursor including the particle precursor; mixing the material precursor with a lithium salt and an auxiliary agent; and sintering the mixed material at a high temperature to obtain the positive electrode material, the positive electrode material including positive electrode material particles, and the positive electrode material particles have a hollow cavity.

[0008] According to the method for preparing the positive electrode material of the embodiment of the present invention, by making the second range value of the solution pH value greater than the first range value, the particle arrangement in the generated core precursor can be made relatively loose, which is more convenient for the subsequent physical decomposition of the core precursor, and the particle arrangement in the shell precursor can be made relatively tight, so that the shell structure of the precursor is more stable and not easy to be physically decomposed; by high-temperature sintering the mixed material to obtain the positive electrode material, the obtained positive electrode material particles can have a radial hollow structure, reducing the microcracks generated inside the positive electrode precursor particles due to volume shrinkage and expansion during charging and discharging, thereby improving the structural stability of the material; and the migration path distance and diffusion migration resistance of lithium ions can be reduced, thereby improving the migration rate of lithium ions; the surface contact active sites can be increased to make lithium ions more smoothly deintercalated and embedded, thereby improving the migration ability of lithium ions and improving the high-power performance of the battery; the preparation of positive electrode materials by this method is simple, controllable, low-cost, and suitable for large-scale industrial production.

[0009] According to some embodiments of the present invention, adding a reaction base liquid into a reactor includes: during the process of adding the reaction base liquid into the reactor, blowing nitrogen into the reaction base liquid to remove oxygen in the reaction base liquid.

[0010] According to some embodiments of the present invention, during the process of adding the reaction liquid into the reaction base liquid, the reaction temperature is controlled at 50-65° C., and the reaction stirring speed is 250-550 rpm.

[0011] According to some embodiments of the present invention, the iron salt comprises ferrous oxalate; and / or the manganese salt comprises manganese sulfate.

[0012] According to some embodiments of the present invention, the complexing agent solution is an aqueous solution of citric acid.

[0013] According to some embodiments of the present invention, the molar concentration of the solute in the first reaction solution is 0.25-1.25 mol / L; and / or the molar concentration of the complexing agent in the complexing agent solution is 0.1-0.5 mol / L.

[0014] According to some embodiments of the present invention, the first range value is pH1.8-pH2.4; and / or, the second range value is pH2.4-pH3.2.

[0015] According to some embodiments of the present invention, the first stirring speed is 250-500 rpm / min, the first reaction time is 12-16 h; and / or the second stirring speed is 150-350 rpm / min.

[0016] According to some embodiments of the present invention, the target particle size D50 reaches 3.0-12.0 μm.

[0017] According to some embodiments of the present invention, the density of the core precursor is less than the density of the shell precursor.

[0018] According to some embodiments of the present invention, the core precursor is composed of a plurality of agglomerated first particles, and the shell precursor is composed of a plurality of agglomerated second particles, wherein the size of the second particles is greater than the size of the first particles.

[0019] According to some embodiments of the present invention, the auxiliary agent includes diammonium phosphate; and / or the lithium salt includes lithium carbonate.

[0020] According to some embodiments of the present invention, the auxiliary agent includes diammonium phosphate, the molar ratio of the diammonium phosphate to the material precursor is 1:2, and the molar ratio of the lithium salt to the material precursor is 1:2.

[0021] According to some embodiments of the present invention, the material precursor is mixed with a lithium salt and an auxiliary agent, comprising:

[0022] Grinding and mixing the material precursor, lithium salt and auxiliary agent;

[0023] The ground and mixed materials are made into a slurry and spray dried.

[0024] According to some embodiments of the present invention, after the material precursor is mixed with the lithium salt and the auxiliary agent, and before the mixed material is subjected to high-temperature sintering, a carbon source is added to form a carbon coating layer on the outer surface of the particles during the high-temperature sintering stage, and the mass ratio of the carbon source to the material precursor is 3%-6%.

[0025] According to some embodiments of the present invention, the mixed material is subjected to high temperature sintering, comprising:

[0026] In a first sintering stage, the temperature is increased to a first sintering temperature at a first heating rate and sintered for a first sintering time;

[0027] In the second sintering stage, the temperature is increased to a second sintering temperature according to a second heating rate and sintered for a second sintering time, the second heating rate is greater than or equal to the first heating rate, the second sintering temperature is greater than the first sintering temperature, and the second sintering time is greater than the first sintering time.

[0028] According to some embodiments of the present invention, the first heating rate is 2-4°C / min, the first sintering temperature is 400-500°C, and the first sintering time is 3-5h; and / or the second heating rate is 3-5°C / min, the second sintering temperature is 700-800°C, and the first sintering time is 8-12h.

[0029] According to some embodiments of the present invention, the reaction solution includes a second reaction solution, and the second reaction solution includes magnesium sulfate and vanadium pentachloride.

[0030] According to some embodiments of the present invention, the Mg in the second reaction solution 2+ With V 5+ The molar ratio is 1:2.

[0031] According to the second aspect of the present invention, the positive electrode material comprises at least one of lithium iron phosphate, lithium manganese iron phosphate and lithium manganese phosphate, and the positive electrode material comprises positive electrode material particles, and the positive electrode material particles are spherical and have a hollow cavity.

[0032] According to the positive electrode material of the embodiment of the present invention, by making the positive electrode material particles spherical and having a hollow cavity, the generation of internal cracks caused by volume shrinkage and expansion during the charge and discharge process of the battery can be alleviated, and the structural stability of the positive electrode material particles can be improved; and the migration path distance and diffusion migration resistance of lithium ions can be reduced, the transmission efficiency of lithium ions can be improved, and the cycle performance and power performance of the battery can be improved.

[0033] According to some embodiments of the present invention, the positive electrode material particles include a plurality of spherical particles arranged along the radial direction.

[0034] According to some embodiments of the present invention, the chemical formula of the positive electrode active material is LiMn x Fe 1-x M y N z PO4; where M and N are co-doping elements, 0 <x<1,0≤y≤0.05,0≤z≤0.05。

[0035] According to some embodiments of the present invention, the positive electrode material is prepared by the preparation method described in the embodiment of the first aspect of the present invention.

[0036] A battery according to an embodiment of the third aspect of the present invention comprises: a positive electrode plate and a negative electrode plate, wherein the positive electrode plate comprises a positive electrode collector and a positive electrode material covering the positive electrode collector, and the positive electrode material is the positive electrode material according to an embodiment of the second aspect of the present invention.

[0037] According to the battery of the embodiment of the present invention, by including the positive electrode material according to the embodiment of the second aspect of the present invention, the structural stability of the positive electrode material particles can be improved; and the transmission efficiency of lithium ions can be improved, and the cycle performance and power performance of the battery can be improved.

[0038] An electrical device according to an embodiment of a fourth aspect of the present invention comprises: a battery according to an embodiment of the third aspect of the present invention.

[0039] According to the electric device of the embodiment of the present invention, by including the battery according to the embodiment of the third aspect of the present invention, the structural stability of the positive electrode material particles can be improved; and the transmission efficiency of lithium ions can be improved, and the cycle performance and power performance of the battery can be improved.

[0040] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0042] Figure 1 is a simple schematic diagram of positive electrode material particles of some positive electrode materials according to the present invention;

[0043] Figure 2 is the XRD structure diagram corresponding to the lithium manganese iron phosphate positive electrode material of Example 1;

[0044] Figure 3 This is a first charge and discharge curve diagram of a button cell corresponding to the lithium manganese iron phosphate positive electrode material of Example 1;

[0045] Figure 4 This is the button cell impedance EIS spectrum corresponding to the lithium manganese iron phosphate positive electrode material of Example 1.

[0046] Reference numerals:

[0047] 100. positive electrode material particles; 10. hollow cavity. DETAILED DESCRIPTION

[0048] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0049] Reference below Figure 1-Figure 4 A method for preparing a positive electrode material according to an embodiment of the present invention is described.

[0050] The method for preparing a positive electrode material according to an embodiment of the present invention comprises:

[0051] Adding a reaction base liquid into the reactor, the reaction base liquid can be used as a solvent for the reaction liquid to provide a solution environment for the entire reaction, for example, the reaction base solution is a mixed solvent of propylene glycol and deionized water, wherein the volume ratio of deionized water to propylene glycol can be 1:1;

[0052] Adding a reaction liquid to the reaction base liquid, the reaction liquid includes a first reaction liquid, the first reaction liquid includes phosphoric acid, the first reaction liquid also includes at least one of an iron salt and a manganese salt, the first reaction liquid can provide phosphorus element for the reaction to form the phosphorus element in the positive electrode material, and the first reaction liquid can also provide iron element and / or manganese element to form the iron element and / or manganese element in the positive electrode material, for example, the first reaction liquid can include phosphoric acid and an iron salt; for another example, the first reaction liquid can include phosphoric acid and a manganese salt; for another example, the first reaction liquid can include phosphoric acid, an iron salt and a manganese salt;

[0053] For example, iron salts include ferrous oxalate and ferrous sulfate;

[0054] For example, manganese salts include manganese sulfate and manganese acetate;

[0055] For example, the complexing agent solution is a citric acid aqueous solution or an oxalic acid aqueous solution;

[0056] Adding a complexing agent solution to the reaction base solution, adjusting the pH value of the solution to a first range, and reacting at a first stirring speed for a first time to form a core precursor;

[0057] The solution pH value is adjusted to a second range value, and the reaction is performed at a second stirring speed until a target particle size is generated, so as to generate a shell precursor outside the core precursor, and the core precursor and the shell together constitute a particle precursor, and the second range value is greater than the first range value;

[0058] Separating a precipitate from the slurry after the reaction and drying it to obtain a material precursor, wherein the material precursor includes a particle precursor;

[0059] Mixing the material precursor with the lithium salt and the auxiliary agent, for example, may include grinding and mixing the precursor, diammonium phosphate, and lithium carbonate;

[0060] For example, lithium salts include lithium carbonate, which can provide lithium ions for batteries;

[0061] The mixed material is sintered at high temperature to obtain a positive electrode material, for example, wherein the material precursor, lithium salt and auxiliary agent react with the precursor, when the first reaction liquid includes phosphoric acid and iron salt, the reaction generates lithium iron phosphate; when the first reaction liquid includes phosphoric acid and manganese salt, the reaction generates lithium manganese phosphate; when the first reaction liquid includes phosphoric acid, iron salt and manganese salt, the reaction generates lithium manganese iron phosphate, and the positive electrode material includes positive electrode material particles 100, and the positive electrode material particles 100 have a hollow cavity 10.

[0062] After adding the reaction liquid and the complexing agent solution to the reaction base liquid, the solution first reacts within a first pH range to generate a core precursor, and then reacts within a second pH range to generate a shell precursor. By making the second pH range of the solution greater than the first pH range, the particles in the generated core precursor can be arranged relatively loosely, making it easier to physically decompose the core precursor later, and the particles in the shell precursor can be arranged relatively tightly, making the shell structure of the precursor more stable and less prone to physical decomposition.

[0063] The mixed material is subjected to high-temperature sintering to obtain the positive electrode material. During the high-temperature sintering process, the particles in the core precursor are physically decomposed and broken due to the loose arrangement of the particles in the core precursor, so that the space where the core precursor is located is formed into a cavity. The core precursor after physical decomposition forms extremely small particles, some of which pass through the fine channels in the shell precursor and leave the particle precursor; some of which diffuse into the shell precursor. The positive electrode material particle 100 obtained in this way has a hollow cavity 10, which reduces the path for lithium ions to be transmitted from the inside to the outside of the positive electrode material particle 100, improves the lithium ion deintercalation efficiency, and improves the high-power performance of the battery.

[0064] Too high a calcination temperature and too long a calcination time will cause the primary grains to melt and grow, and then the grains to coarsen; the precursors with specific shapes and assembly methods will lose their structure during the high-temperature calcination process. The use of a step-by-step heat preservation method is conducive to the growth of the particle surface. During the stage heat preservation process, the temperature difference between the inside and outside of the particles is small, and the orderliness of the positive electrode grain assembly is regulated. The prepared lithium manganese iron phosphate particles are uniform and regular in morphology. At the same time, the grain size and assembly method of the radially ordered precursor are inherited during the high-temperature calcination stage.

[0065] According to the preparation method of the positive electrode material of the embodiment of the present invention, by making the second range value of the solution pH value greater than the first range value, the particle arrangement in the generated core precursor can be made relatively loose, which is more convenient for the subsequent physical decomposition of the core precursor, and the particle arrangement in the shell precursor can be made relatively tight, so that the shell structure of the precursor is more stable and not easy to be physically decomposed; by high-temperature sintering the mixed material to obtain the positive electrode material, the obtained positive electrode material particles 100 can have a radial hollow structure, reducing the microcracks generated inside the positive electrode precursor particles due to volume shrinkage and expansion during charging and discharging, thereby improving the structural stability of the material; and the migration path distance and diffusion migration resistance of lithium ions can be reduced, thereby improving the migration rate of lithium ions; the surface contact active sites can be increased to make lithium ions more smoothly deintercalated, thereby improving the migration ability of lithium ions and improving the high-power performance of the battery; the preparation of positive electrode materials by this method is simple, controllable, low-cost, and suitable for large-scale industrial production.

[0066] According to some embodiments of the present invention, adding the reaction base liquid to the reactor includes: during the process of adding the reaction base liquid to the reactor, blowing nitrogen into the reaction base liquid to remove oxygen in the reaction base liquid. Since the reaction liquid subsequently added to the reaction base liquid includes iron salt and / or manganese salt, the Fe 2+ and Mn 2+ It is easy to be oxidized. By blowing nitrogen into the reaction liquid to remove the oxygen in the reaction liquid, Fe 2+ and Mn 2+ Oxidation affects the final product.

[0067] According to some embodiments of the present invention, during the process of adding the reaction solution to the reaction base solution, the reaction temperature is controlled at 50-65°C, and the reaction stirring speed is 250-550rpm. For example, the reaction temperature can be controlled at 50°C, 55°C, 60°C, 65°C, etc., and the reaction stirring speed can be adjusted to 250rpm, 300rpm, 350rpm, 400rpm, 450rpm, 500rpm, 550rpm, etc. By controlling the reaction temperature at 50-65°C and the reaction stirring speed at 250-550rpm, the reaction solution can be evenly dispersed in the reaction base solution.

[0068] According to some embodiments of the present invention, the molar concentration of the solute in the first reaction solution is 0.25-1.25 mol / L. For example, the molar concentration of the solute in the first reaction solution can be 0.25 mol / L, 0.5 mol / L, 0.75 mol / L, 1 mol / L, 1.25 mol / L, etc. By making the molar concentration of the solute in the first reaction solution not less than 0.25 mol / L, sufficient phosphorus can be provided in the first reaction solution, and sufficient manganese ions and / or ferrous ions can be provided to react to generate positive electrode materials; by making the molar concentration of the solute in the first reaction solution not greater than 1.25 mol / L, it is possible to avoid waste of raw materials and control costs while ensuring that sufficient reactants can be provided.

[0069] According to some embodiments of the present invention, the molar concentration of the complexing agent in the complexing agent solution is 0.1-0.5 mol / L. For example, the molar concentration of the complexing agent in the complexing agent solution can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, etc. By making the molar concentration of the complexing agent in the complexing agent solution not less than 0.1 mol / L, the complex can be fully reacted to form a complex so as to be separated from the solution, and it is convenient to collect the precipitate for the next step of reaction; by making the molar concentration of the complexing agent in the complexing agent solution not more than 0.5 mol / L, the waste of the complexing agent can be avoided and the cost can be controlled while ensuring that the complex is fully reacted to form a complex so as to be separated from the solution.

[0070] According to some embodiments of the present invention, the first range value is pH1.8-pH2.4. For example, the first range value may be pH1.8, pH2.0, pH2.2, pH2.4, etc. By setting the first range value to pH1.8-pH2.4, the particles of the generated core precursor can be arranged more loosely, which is more convenient for physically decomposing the core precursor in subsequent steps to form a hollow shape of the positive electrode material particles 100.

[0071] According to some embodiments of the present invention, the second range value is pH2.4-pH3.2. For example, the second range value may be pH2.4, pH2.6, pH2.8, pH3.0, pH3.2, etc. By setting the second range value to pH1.8-pH2.4, the particles in the generated shell precursor can be arranged relatively tightly, making the shell structure of the precursor more stable and not easily physically decomposed.

[0072] For example, adjusting the pH of the solution from a first range of values ​​to a second range of values ​​may include: adding an acetic acid solution to the solution, wherein the pH of the acetic acid solution is ≥ 3.5.

[0073] According to some embodiments of the present invention, the first stirring speed is 250-500rpm / min, and the first reaction time is 12-16h. For example, the first stirring speed can be 250rpm / min, 300rpm / min, 350rpm / min, 400rpm / min, 450rpm / min, 500rpm / min. By making the first stirring speed 250-500rpm / min and the first reaction time 12-16h, the generation reaction of the core precursor can be more sufficient to form a crystal nucleus so as to facilitate the subsequent generation of a shell on the basis of the crystal nucleus.

[0074] According to some embodiments of the present invention, the second stirring speed is 150-350 rpm / min. For example, the second stirring speed may be 150 rpm / min, 200 rpm / min, 250 rpm / min, 300 rpm / min, 350 rpm / min, etc. By setting the second stirring speed to 150-350 rpm / min, the formation reaction of the shell precursor can be more complete.

[0075] According to some embodiments of the present invention, the target particle size D50 reaches 3.0-12.0 μm. For example, the target particle size D50 may be 3.0 μm, 4.0 μm, 5.0 μm, 6.0 μm, 7.0 μm, etc. By making the target particle size D50 range from 3.0-12.0 μm, the cycle durability and high rate performance of the positive electrode material can be taken into account.

[0076] According to some embodiments of the present invention, the density of the core precursor is less than that of the shell precursor. By making the density of the core precursor less than that of the shell precursor, the density of the core precursor can be made less than that of the shell precursor, and the particles in the generated core precursor are relatively loose, which can make it easier to physically decompose the core precursor in the subsequent steps, and can make the particles in the shell precursor relatively tight, so that the shell structure of the precursor is more stable and not easy to physically decompose, so that the obtained positive electrode material particles 100 have a hollow cavity 10, reducing the microcracks generated inside the positive electrode precursor particles due to volume shrinkage and expansion during charging and discharging, and improving the structural stability of the material; and, the migration path distance and diffusion migration resistance of lithium ions can be reduced, and the migration rate of lithium ions can be improved; the surface contact active sites can be increased to make lithium ions more smoothly deintercalated, improve the migration ability of lithium ions, and improve the high power performance of the battery.

[0077] According to some embodiments of the present invention, the core precursor is composed of a plurality of agglomerated first particles, and the shell precursor is composed of a plurality of agglomerated second particles, and the size of the second particles is larger than the size of the first particles. By making the size of the second particles larger than the size of the first particles, the first particles can be made smaller and easier to physically decompose in the subsequent sintering step to form the hollow cavity 10 of the positive electrode material particles 100; and the second particles can be made larger and less likely to physically decompose in the sintering step, thereby improving the structural stability of the positive electrode material particles 100.

[0078] According to some embodiments of the present invention, the auxiliary agent includes diammonium phosphate. By adding glucose to the material precursor and the lithium salt, the glucose can provide an organic carbon source to carbon-coat the particle precursor. After the subsequent sintering step, the glucose forms a carbon coating layer on the surface of the particle precursor. The carbon coating layer has a high conductivity, which can improve the conductivity of the positive electrode material particles 100 and improve the performance of the battery.

[0079] According to some embodiments of the present invention, the auxiliary agent includes ammonium dihydrogen phosphate, and the molar ratio of ammonium dihydrogen phosphate to the material precursor is 1:2, and the molar ratio of lithium salt to the material precursor is 1:2. By adding ammonium dihydrogen phosphate to the material precursor and the lithium salt, and controlling the molar ratio of ammonium dihydrogen phosphate to the material precursor to be 1:2, the iron-phosphorus ratio can be controlled to be 1:1, and the element ratio of iron to phosphorus in the resultant lithium iron manganese phosphate can be controlled.

[0080] According to some embodiments of the present invention, mixing a material precursor with a lithium salt and an auxiliary agent comprises:

[0081] Grinding and mixing the material precursor, lithium salt and auxiliary agent;

[0082] The ground and mixed materials are made into a slurry and spray dried.

[0083] By making a slurry out of the ground and mixed materials and then spray drying them, solutions and emulsions can be directly dried into powder or granular products, which can save the evaporation, crushing and other processes in related technologies, reduce process steps and improve production efficiency.

[0084] According to some embodiments of the present invention, after the material precursor is mixed with the lithium salt and the auxiliary agent, and before the mixed material is subjected to high-temperature sintering, a carbon source is added to form a carbon coating layer on the outer surface of the particles during the high-temperature sintering stage, and the mass ratio of the carbon source to the material precursor is 3%-6%. By adding the carbon source after the material precursor is mixed with the lithium salt and the auxiliary agent, and before the mixed material is subjected to high-temperature sintering, a coating layer composed of carbon can be coated on the surface of the finally obtained positive electrode material particles 100, and the carbon has a strong electrical conductivity, which can improve the electrical conductivity of the positive electrode material and increase the rate performance of the battery.

[0085] For example, the carbon source can include glucose.

[0086] According to some embodiments of the present invention, the mixed material is subjected to high temperature sintering, comprising:

[0087] In a first sintering stage, the temperature is increased to a first sintering temperature at a first heating rate and sintered for a first sintering time;

[0088] In the second sintering stage, the temperature is increased to a second sintering temperature according to a second heating rate and sintered for a second sintering time. The second heating rate is greater than or equal to the first heating rate, the second sintering temperature is greater than the first sintering temperature, and the second sintering time is greater than the first sintering time.

[0089] By making the high-temperature sintering include the first sintering stage, the material precursor can be preheated to avoid the precursor particles from breaking due to too fast a temperature rise. By making the high-temperature sintering include the second sintering stage, the core of the material precursor can be physically decomposed, so that the obtained positive electrode material particles 100 have a hollow cavity 10, reducing the microcracks generated inside the positive electrode precursor particles due to volume shrinkage and expansion during charging and discharging, and improving the structural stability of the material; and the migration path distance and diffusion migration resistance of lithium ions can be reduced, and the migration rate of lithium ions can be improved; the surface contact active sites can be increased to make lithium ions more smoothly deintercalated, improve the migration ability of lithium ions, and improve the high-power performance of the battery; glucose can also be more fully carbonized, improve the conductivity of the formed carbon coating layer, and improve the rate performance of the battery.

[0090] For example, during the high-temperature sintering process, the first particles in the core precursor are physically decomposed, including: the first particles are decomposed into extremely small particles, passing through the tiny channels between the second particles in the shell precursor and leaving the particle precursor.

[0091] For example, during the high-temperature sintering process, the first particles in the core precursor are physically decomposed, including: the first particles are decomposed into extremely small particles and diffused into the shell precursor.

[0092] According to some embodiments of the present invention, the first heating rate is 2-4°C / min, the first sintering temperature is 400-500°C, and the first sintering time is 3-5h. In the first sintering stage, the material precursor can be preheated to avoid the precursor particles from breaking due to too fast a temperature rise.

[0093] According to some embodiments of the present invention, the second heating rate is 3-5°C / min, the second sintering temperature is 700-800°C, and the first sintering time is 8-12h. In the second sintering stage, the core of the material precursor can be decomposed, so that the obtained positive electrode material particles 100 have a hollow cavity 10, reducing the path for lithium ions to be transmitted from the inside to the outside of the positive electrode material particles 100, and improving the high power performance of the battery.

[0094] According to some embodiments of the present invention, the reaction liquid includes a second reaction liquid, and the second reaction liquid includes magnesium sulfate (MgSO4) and vanadium pentachloride (VCl5). By making the second reaction liquid include magnesium sulfate and vanadium chloride, magnesium ions and vanadium ions can be provided for the reaction, and magnesium and vanadium can be used as doping elements to make the structure of the product more stable, and can promote the radial growth of fine particles in the particle precursor, so that the diffusion and migration resistance of lithium ions can be reduced, the migration rate of lithium ions can be increased, and the high power performance of the battery can be improved.

[0095] According to some embodiments of the present invention, Mg in the second reaction solution 2+ With V 5+ The molar ratio is 1:2. Among them, the magnesium ion has a smaller radius and can enter the inner side of the crystal, while the vanadium ion has a larger radius and can be enriched on the grain boundary surface, promoting the radial growth of spherical particles along the particle precursor, which can reduce the diffusion and migration resistance of lithium ions, increase the migration rate of lithium ions, and improve the high-power performance of the battery.

[0096] The positive electrode material according to the second embodiment of the present invention includes at least one of lithium iron phosphate, lithium manganese iron phosphate and lithium manganese phosphate. The positive electrode material includes positive electrode material particles 100. The positive electrode material particles 100 are spherical and have a hollow cavity 10.

[0097] According to the positive electrode material of the embodiment of the present invention, by making the positive electrode material particles 100 spherical and having a hollow cavity 10, the microcracks generated inside the positive electrode precursor particles due to volume shrinkage and expansion during charging and discharging are reduced, thereby improving the structural stability of the material; and the migration path distance and diffusion migration resistance of lithium ions can be reduced, thereby improving the migration rate of lithium ions; the surface contact active sites can be increased to make lithium ions more smoothly deintercalated, thereby improving the migration ability of lithium ions and improving the high power performance of the battery.

[0098] According to some embodiments of the present invention, the positive electrode material particles 100 include a plurality of spherical particles arranged radially. By making the positive electrode material particles 100 include a plurality of spherical particles arranged radially, the lithium ion channels in the positive electrode material particles 100 can be arranged radially, shortening the movement path of lithium ions during insertion and extraction on the positive electrode material particles 100, improving the migration ability of lithium ions. Moreover, by arranging the lithium ion channels in the positive electrode material particles 100 radially, a plurality of lithium ion channels in the central divergence direction can be formed, enabling lithium ions to diffuse and migrate between the inside and outside of the positive electrode material particles 100 from multiple directions, reducing the diffusion and migration resistance of lithium ions, and improving the migration ability of lithium ions.

[0099] According to some embodiments of the present invention, the chemical formula of the positive electrode active material is LiMn x Fe 1-x M y N z PO4; where M and N are co-doping elements, 0 < x < 1, 0 ≤ y ≤ 0.05, 0 ≤ z ≤ 0.05. By combining the advantages of various doped metal ions to synergistically improve the electrochemical performance of the material, and by making the whole machine active material include M and N co-doping elements, the structure of the product can be made more stable, and the radial order of fine particles in the particle precursor can be regulated.

[0100] For example, the co-doping elements may include at least two of niobium, cerium, tungsten, vanadium, molybdenum, magnesium, titanium, and aluminum.

[0101] According to some embodiments of the present invention, the positive electrode material is prepared by the preparation method according to the embodiments of the first aspect of the present invention. By making the positive electrode material be prepared by the preparation method according to the embodiments of the first aspect of the present invention, the preparation process is simple and conducive to cost control.

[0102] The battery according to the embodiments of the third aspect of the present invention includes: a positive electrode plate and a negative electrode plate. The positive electrode plate includes a positive electrode current collector and a positive electrode material covering the positive electrode current collector, and the positive electrode material is the positive electrode material according to the embodiments of the second aspect of the present invention.

[0103] For the battery according to the embodiments of the present invention, by including the positive electrode material according to the embodiments of the second aspect of the present invention, the structural stability of the positive electrode material particles 100 can be improved; and the transmission efficiency of lithium ions can be improved, enhancing the cycle performance and power performance of the battery.

[0104] The electrical device according to the embodiments of the fourth aspect of the present invention includes: the battery according to the embodiments of the third aspect of the present invention.

[0105] According to the electric device of the embodiment of the present invention, by including the battery according to the embodiment of the third aspect of the present invention, the structural stability of the positive electrode material particles 100 can be improved; and the transmission efficiency of lithium ions can be improved, and the cycle performance and power performance of the battery can be improved.

[0106] The preparation method of the positive electrode material and the positive electrode material according to the embodiments of the present invention are further described below in combination with multiple embodiments of the present invention and comparative examples.

[0107] 1. Button cell assembly: The prepared sample was weighed with conductive carbon black SP and polyvinylidene fluoride PVDF in a mass ratio of 90:5:5, and N-methylpyrrolidone (NMP) was added and stirred to obtain a battery slurry; the battery slurry was evenly coated on an aluminum foil and dried to obtain a positive electrode sheet; the dried positive electrode sheet was placed on a roller press and rolled, and the rolled sheet was cut into a disc with a diameter of 14 mm, and the disc was placed in a vacuum drying oven and baked at 90°C for 1 h, and assembled into a CR2032 button cell in a glove box filled with argon.

[0108] 2. Button capacity test: The assembled button battery is left at room temperature for 24 hours for activation, and then the button charge and discharge performance test is performed on the charge and discharge test cabinet. The temperature is set to 25±2℃, the test voltage range is 2.2-4.3V, and the charge and discharge rate is 0.1C;

[0109] 3. Rate discharge performance test: The activated button battery is placed on the charge and discharge test cabinet for rate performance test. The temperature is set to 25±2℃, the test voltage range is 2.2-4.25V, the charging step is set to 0.2C CC-CV to 0.05C cut-off, and the discharge step uses 0.2C, 0.33C, 0.5C, 1.0C, 2.0C constant current discharge rate in sequence;

[0110] 4. High and low temperature performance test: The activated button battery is placed in a charge and discharge test cabinet for rate performance test. The temperature is set to 25±2℃, the test voltage range is 2.2-4.25V, the charging step is set to 0.2C CC-CV to 0.05C cutoff, and the discharge step uses 0.2C constant current discharge to the cutoff voltage; then the button battery is placed at 0℃, -10℃, -20℃, and 45℃ in turn for the above charge and discharge step tests.

[0111] 5. Long cycle performance test: The activated button battery is placed on a charge and discharge test cabinet for rate performance test. The temperature is set to 25±2℃, the test voltage range is 2.2-4.25V, the charging step is set to 0.5C CC-CV to 0.05C cutoff, and the discharge step uses 0.5C constant current discharge to cutoff voltage; the battery cycle capacity retention rate is calculated after 200 cycles at 0.5C / 0.5C. The first cycle test capacity is recorded as A1, and the test capacity after 200 cycles is recorded as An. The capacity retention rate = An / A1×100%.

[0112] 6. Electrochemical impedance spectroscopy (EIS) test: Electrochemical impedance spectroscopy (EIS) measurements were performed on an electrochemical workstation using a button cell. The temperature was set to 25±2°C and the battery state was adjusted to 50% SOC. The voltage window was set to 2.0-4.5V, the amplitude was 10mV, and the frequency range was 10 -2 ~10 5 Hz.

[0113] Reference below Figure 2-Figure 4 Describe the relevant tests of the positive electrode materials according to some specific embodiments of the present invention, Figure 2-Figure 4 This is a related test spectrum of the positive electrode material according to Example 1 of the present invention, wherein the positive electrode material is lithium manganese iron phosphate.

[0114] Reference Figure 2 , Figure 2 It is the XRD structure diagram corresponding to the lithium manganese iron phosphate positive electrode material of Example 1. The characteristic peaks are obvious and there are no impurity peaks, indicating that the prepared material has high purity and crystallinity. At the same time, the XRD spectrum corresponds to lithium iron phosphate but there is a shift to a low angle, indicating that the prepared material is a solid solution material, corresponding to the olivine lithium manganese iron phosphate olivine structure of the Pnma space group.

[0115] Reference Figure 3 , Figure 3 This is the first charge and discharge curve of the button battery corresponding to the lithium manganese iron phosphate positive electrode material of Example 1; the first discharge capacity per gram is 160.2 mAh / g, and the first charge and discharge efficiency is 98.8%, which has a relatively high discharge capacity per gram and first charge and discharge efficiency.

[0116] Reference Figure 4 , Figure 4 This is the button cell impedance EIS spectrum corresponding to the lithium manganese iron phosphate positive electrode material of Example 1; it has a lower impedance value and is applied to lithium-ion batteries with better high-rate discharge performance and high and low temperature discharge performance.

[0117] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0118] In the description of the present invention, "first feature" or "second feature" may include one or more of the features.

[0119] In the description of the present invention, "plurality" means two or more.

[0120] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0121] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for preparing a positive electrode material, characterized in that: include: Adding reaction bottom liquid into the reactor; Adding a reaction solution to the reaction base solution, wherein the reaction solution includes a first reaction solution, the first reaction solution includes phosphoric acid, and the first reaction solution further includes at least one of an iron salt and a manganese salt; Adding a complexing agent solution to the reaction base solution, adjusting the pH value of the solution to a first range, and reacting at a first stirring speed for a first time to form a core precursor; The solution pH value is adjusted to a second range value, and the solution is reacted at a second stirring speed to generate a target particle size, so as to generate a shell precursor outside the core precursor, wherein the core precursor and the shell together constitute a particle precursor, and the second range value is greater than the first range value; Separating a precipitate from the slurry after the reaction and drying it to obtain the material precursor, wherein the material precursor includes the particle precursor; Mixing the material precursor with a lithium salt and an auxiliary agent; The mixed materials are sintered at high temperature to obtain the positive electrode material, which includes positive electrode material particles having a hollow cavity therein.

2. The method for preparing the positive electrode material according to claim 1, characterized in that: Add a reaction base solution to the reactor, including: During the process of adding the reaction base liquid into the reactor, nitrogen is blown into the reaction base liquid to remove oxygen in the reaction base liquid.

3. The method for preparing the positive electrode material according to claim 1, characterized in that: During the process of adding the reaction liquid into the reaction base liquid, the reaction temperature is controlled at 50-65° C. and the reaction stirring speed is 250-550 rpm.

4. The method for preparing the positive electrode material according to claim 1, characterized in that: The iron salt comprises ferrous oxalate; and / or, the manganese salt comprises manganese sulfate.

5. The method for preparing the positive electrode material according to claim 1, characterized in that: The complexing agent solution is a citric acid aqueous solution.

6. The method for preparing the positive electrode material according to claim 1, characterized in that: The molar concentration of the solute in the first reaction solution is 0.25-1.25 mol / L; and / or the molar concentration of the complexing agent in the complexing agent solution is 0.1-0.5 mol / L.

7. The method for preparing the positive electrode material according to claim 1, characterized in that: The first range value is pH1.8-pH2.4; and / or, the second range value is pH2.4-pH3.

2.

8. The method for preparing the positive electrode material according to claim 1, characterized in that: The first stirring speed is 250-500 rpm / min, the first reaction time is 12-16 h; and / or the second stirring speed is 150-350 rpm / min.

9. The method for preparing the positive electrode material according to claim 1, characterized in that: The target particle size D50 reaches 3.0-12.0 μm.

10. The method for preparing the positive electrode material according to claim 1, characterized in that: The density of the core precursor is less than that of the shell precursor.

11. The method for preparing the positive electrode material according to claim 10, characterized in that: The core precursor is composed of a plurality of agglomerated first particles, and the shell precursor is composed of a plurality of agglomerated second particles, wherein the size of the second particles is greater than that of the first particles.

12. The method for preparing the positive electrode material according to claim 1, characterized in that: The auxiliary agent includes diammonium phosphate; and / or the lithium salt includes lithium carbonate.

13. The method for preparing the positive electrode material according to claim 1, characterized in that: The auxiliary agent includes diammonium phosphate, the molar ratio of the diammonium phosphate to the material precursor is 1:2, and the molar ratio of the lithium salt to the material precursor is 1:

2.

14. The method for preparing a positive electrode material according to claim 1, characterized in that: The material precursor is mixed with a lithium salt and an auxiliary agent, including: Grinding and mixing the material precursor, lithium salt and auxiliary agent; The ground and mixed materials are made into a slurry and spray dried.

15. The method for preparing the positive electrode material according to claim 1, characterized in that: After the material precursor is mixed with lithium salt and auxiliary agent, and before the mixed material is subjected to high-temperature sintering, a carbon source is added to form a carbon coating layer on the outer surface of the particles during the high-temperature sintering stage. The mass ratio of the carbon source to the material precursor is 3%-6%.

16. The method for preparing a positive electrode material according to claim 1, characterized in that: The mixed materials are sintered at high temperature, including: In a first sintering stage, the temperature is increased to a first sintering temperature at a first heating rate and sintered for a first sintering time; In the second sintering stage, the temperature is increased to a second sintering temperature according to a second heating rate and sintered for a second sintering time, the second heating rate is greater than or equal to the first heating rate, the second sintering temperature is greater than the first sintering temperature, and the second sintering time is greater than the first sintering time.

17. The method for preparing the positive electrode material according to claim 16, characterized in that: The first heating rate is 2-4°C / min, the first sintering temperature is 400-500°C, and the first sintering time is 3-5h; and / or the second heating rate is 3-5°C / min, the second sintering temperature is 700-800°C, and the first sintering time is 8-12h.

18. The method for preparing a positive electrode material according to any one of claims 1 to 17, characterized in that: The reaction solution includes a second reaction solution, and the second reaction solution includes magnesium sulfate and vanadium pentachloride.

19. The method for preparing the positive electrode material according to claim 18, characterized in that: The Mg in the second reaction solution 2 + With V 5+ The molar ratio is 1:

2.

20. A positive electrode material, characterized in that The positive electrode material comprises at least one of lithium iron phosphate, lithium manganese iron phosphate and lithium manganese phosphate. The positive electrode material comprises positive electrode material particles. The positive electrode material particles are spherical and have a hollow cavity.

21. The positive electrode material according to claim 20, characterized in that The positive electrode material particles include a plurality of spherical particles arranged along a radial direction.

22. The positive electrode material according to claim 20, characterized in that The chemical formula of the positive electrode active material is LiMn x Fe 1-x M y N z PO4; where M and N are co-doping elements, 0 <x<1,0≤y≤0.05,0≤z≤0.05。 23. The positive electrode material according to any one of claims 20 to 22, characterized in that The positive electrode material is prepared by the method for preparing the positive electrode material according to any one of claims 1-18.

24. A battery, characterized in that: include: A positive electrode sheet and a negative electrode sheet, wherein the positive electrode sheet comprises a positive electrode collector and a positive electrode material covering the positive electrode collector, and the positive electrode material is the positive electrode material according to any one of claims 20-23.

25. An electrical device, characterized in that: include: A battery according to claim 24.

Images