CN116207254A

CN116207254A - Positive electrode active material, preparation method, positive electrode plate, battery and electric equipment

Info

Publication number: CN116207254A
Application number: CN202310301355.3A
Authority: CN
Inventors: 黄兴; 万宁; 李明露; 刘静; 盛杰; 杨红新
Original assignee: Svolt Energy Technology Co Ltd
Current assignee: Svolt Energy Technology Co Ltd
Priority date: 2023-03-24
Filing date: 2023-03-24
Publication date: 2023-06-02

Abstract

The application discloses an anode active material, a preparation method, an anode plate, a battery and electric equipment. The positive electrode active material includes: particulate material, carbon nanotubes and a composition containing a polymer of the general formula M _n+1 X _n T _z A lamellar substrate of the compound of (a). According to the method, the carbon nano tube and the particle material are attached to the surface of the lamellar substrate, so that a three-dimensional net surface structure which is jointly constructed by taking the particle material as a point, taking the carbon nano tube as a line and taking the lamellar substrate as a surface is formed, the defect that the electron/ion conductivity of the particle material is not high is overcome, and the multiplying power performance and the cycle stability of the battery are improved.

Description

Positive electrode active material, preparation method, positive electrode plate, battery and electric equipment

Technical Field

The application relates to the technical field of batteries, in particular to an anode active material, a preparation method, an anode plate, a battery and electric equipment.

Background

Lithium ion batteries are widely used in electronic devices, new energy automobiles and other electric equipment. In lithium ion batteries, the positive electrode material is a central factor that restricts the development of high-performance batteries. Lithium iron manganese phosphate, which is one of the positive electrode materials, has a high energy density, but has limited electron transport and ion diffusion capabilities, and limits electron/ion conductivity, thereby affecting rate performance.

Disclosure of Invention

The purpose of the application is to provide an anode active material, a preparation method, an anode plate, a battery and electric equipment. According to the method, the carbon nano tube and the particle material are attached to the surface of the lamellar substrate, so that a three-dimensional net surface structure which is jointly constructed by taking the particle material as a point, the carbon nano tube as a line and the lamellar substrate as a surface is formed, and the defect that the electron/ion conductivity of the particle material is low is overcome.

Embodiments of the present application provide a positive electrode active material, which includes: particulate material, carbon nanotubes, and platelet substrates.

In some embodiments, the particulate material comprises lithium manganese phosphate particles.

In some embodiments, the sheet substrate comprises: the general formula is M _n+1 X _n T _z A compound of (a); m is a transition metal element, X is one or two of C or N, T _z The value of n is selected from 1, 2 or 3 for the surface group.

In some embodiments, the transition metal element is selected from at least one of Ti, zr, hf, V, nb, ta, cr, mo or Sc.

In some embodiments, the surface groups are selected from O ^2- 、OH ^- 、F ^- 、Cl ^- Or NH ⁴⁺ At least one of them.

In some embodiments, the general formula is M _n+1 X _n T _z The compound of (2) is selected from Ti ₃ C ₂ T _z 、Ti ₂ CT _z 、(Ti _0.5 Nb _0.5 ) ₂ CT _z 、(V _0.5 Cr _0.5 ) ₃ C ₂ T _z 、Ti ₃ CNT _z 、Ta ₄ C ₃ T _z 、V ₂ CT _z 、V ₄ C ₃ T _z 、Nb ₂ CT _z 、Nb ₄ C ₃ T _z 、(Nb _0.8 Ti _0.2 ) ₄ C ₃ T _z 、(Nb _0.8 Zr _0.2 ) ₄ C ₃ T _z 、Mo ₂ TiC ₂ T _z 、Mo ₂ Ti ₂ C ₃ T _z And Cr (V) ₂ TiC ₂ T _z At least one of them.

In some embodiments, the carbon nanotubes are selected from one or both of single-walled carbon nanotubes or multi-walled carbon nanotubes.

In some embodiments, the particulate material and the carbon nanotubes are attached to at least a portion of the surface of the platelet substrate. In some embodiments, the weight percent of the platelet substrate is 5% to 10% based on the total weight of solids of the particulate material. In some embodiments, the weight percent of carbon nanotubes is from 0.001% to 0.005% based on the total weight of the solids of the particulate material.

In some embodiments, the average particle size of the particulate material is greater than the thickness of the platelet substrate. The average particle diameter in this application refers to the average of the diameters of the particulate material.

In some embodiments, the average particle size of the particulate material is less than the length of the platelet substrate.

In some embodiments, the average particle size of the particulate material is greater than the diameter of the carbon nanotubes.

The embodiment of the application provides a preparation method of an anode active material, which comprises the following steps:

by M _n+1 AX _n Removing the element A by adopting an acid etchant as a precursor to obtain first slurry containing a lamellar substrate; the lamellar substrate comprises a compound of the general formula M _n+1 X _n T _z A compound of (a);

adding the granular material into the first slurry, mixing, adding the second slurry containing the carbon nano tubes and the dispersing agent, and mixing to obtain a third slurry;

And separating solid matters from the third slurry, freeze-drying the solid matters, crushing, and sieving to obtain the positive electrode active material.

In some embodiments, a is Al.

In some embodiments, the acidic etchant is selected from hydrofluoric acid, or a mixture of hydrochloric acid and lithium fluoride.

In some embodiments, the dispersant is selected from cetyltrimethylammonium bromide.

In some embodiments, the particulate material has a formula of LiMn _y Fe _1-y PO ₄ ，0.3≤y＜1。

In some embodiments, the particulate material has an average particle size of 100nm to 5 μm.

In some embodiments, the mesh number of the screen is 100 mesh to 200 mesh.

In some embodiments, the laminar substrate is selected from a single layer of material or a multiple layer of material.

In some embodiments, the thickness of the platelet substrate is from 1nm to 5nm.

In some embodiments, the single-walled carbon nanotubes have a diameter of 0.5nm to 3nm. The length of the single-walled carbon nanotubes is 1 μm to 50 μm.

In some embodiments, the multiwall carbon nanotubes have a diameter of 2nm to 30nm. The length of the multiwall carbon nanotubes is 0.1 μm to 50 μm.

In some embodiments, the concentration of the platelet substrate in the first slurry is from 0.1 to 10mg/ml.

In some embodiments, the carbon nanotubes are present in the second slurry in an amount of 1 to 15wt%.

In some embodiments, the concentration of dispersant is 1 to 6mg/ml.

In some embodiments, the temperature of freeze drying is from-25 ℃ to-60 ℃.

In some embodiments, the time of lyophilization is from 6 hours to 12 hours.

The embodiment of the application also provides a positive plate, which comprises: positive electrode current collector and positive electrode material layer.

The positive electrode material layer is located on the surface of the positive electrode current collector, for example, the positive electrode material layer covers the whole positive electrode current collector, or the positive electrode material layer is located on two opposite surfaces of the positive electrode current collector. The positive electrode material layer includes the positive electrode active material in any of the above embodiments, or includes the positive electrode active material produced by the positive electrode active material production method in any of the above embodiments.

In some embodiments, the positive electrode active material is a powder material having a size of less than or equal to 150 μm.

In some embodiments, the positive electrode current collector comprises aluminum foil.

The present application provides a battery, which includes: the lithium ion battery comprises a positive plate, a negative plate, a diaphragm positioned between the positive plate and the negative plate and electrolyte.

The positive plate is any one of the positive plates in the embodiment.

In some embodiments, the electrolyte includes a lithium salt, an organic solvent, and a film-forming additive. The film forming additive accounts for 0.1 to 1 percent of the electrolyte by mass percent.

In some embodiments, the lithium salt comprises lithium hexafluorophosphate (LiPF ₆ ) Lithium tetrafluoroborate (LiBF) ₄ ) Or lithium bis (fluorosulfonyl) imide (LiFSI).

In some embodiments, the organic solvent includes one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), and Ethyl Methyl Carbonate (EMC).

In some embodiments, the film forming additive is selected from chlorosulfonyl isocyanate (CSI) or fluoroethylene carbonate (FEC).

In some embodiments, the surface of the negative electrode sheet has an interfacial film (SEI film) including one or more of lithium carbonate, lithium oxide, and lithium fluoride.

In some embodiments, the interfacial film has a thickness of 10 to 50nm.

The embodiment of the application provides electric equipment, which comprises the battery in any embodiment, wherein the battery is used as a power supply of the electric equipment.

The beneficial effects of this application lie in: the embodiment of the application provides an anode active material, a preparation method, an anode plate, a battery and electric equipment. According to the method, the carbon nano tube and the particle material are attached to the surface of the lamellar substrate, so that a three-dimensional net surface structure which is jointly constructed by taking the particle material as a point, taking the carbon nano tube as a line and taking the lamellar substrate as a surface is formed, and the electron/ion conductivity of the particle material is improved, so that the battery has good multiplying power performance and circulation stability.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the description of the embodiments will be briefly introduced below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic structural view of a positive electrode active material in an embodiment of the present application.

Detailed Description

The following description of the embodiments of the present application and the accompanying drawings will be made clear and complete, and it is apparent that the described embodiments are only some embodiments of the present application and not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments herein without making any inventive effort, are intended to be within the scope of the present application. Various embodiments of the present application may exist in a range of forms; it should be understood that the description in a range format is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the application; it is therefore to be understood that the range description has specifically disclosed all possible sub-ranges and individual values within that range. For example, it should be considered that a description of a range from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the ranges, such as 1, 2, 3, 4, 5, and 6, wherever applicable. In addition, whenever a numerical range is referred to herein, it is meant to include any reference number (fractional or integer) within the indicated range.

The positive active material of the lithium ion battery includes lithium manganese iron phosphate particles, which have a relatively high energy density but relatively low electron transport and ion diffusion capabilities, thereby affecting the rate performance and cycle stability of the battery.

In order to solve the defects, the embodiment of the application provides an anode active material, a preparation method, an anode plate, a battery and electric equipment.

Wherein the positive electrode active material includes: particulate material, platelet substrate, and carbon nanotubes. The particulate material and the carbon nanotubes are attached to the surface of the platelet substrate. The particle material is used as a dot material, the carbon nano tube is used as a line material, and the lamellar base material is used as a surface material, so that the material with a three-dimensional net surface structure is constructed by taking the particle material as a dot, the carbon nano tube as a line and the lamellar base material as a surface. As the sheet substrate, the carbon nano tube and the granular material all have conductive performance, compared with the pure granular material, the ionic/electronic conductivity of the material with the three-dimensional network structure is greatly improved, thereby improving the multiplying power performance and the cycle stability of the battery.

In some embodiments of the present application, the laminar substrate is a laminar material having conductive properties, which may also be referred to as a laminar conductive substrate. The sheet substrate includes: the general formula is M _n+1 X _n T _z Is a compound of (a). Wherein M is a transition metal element, X is one or two of C or N, T _z The value of n is selected from 1, 2 or 3 for the surface group.

Wherein the transition metal element M is selected from at least one of Ti, zr, hf, V, nb, ta, cr, mo or Sc. "at least one" means that the M element may be any one of Ti, zr, hf, V, nb, ta, cr, mo or Sc, or any two of them, or any three of them, etc. For example, in some embodiments, the general formula M _n+1 X _n T _z The compound of (2) may be selected from Ti ₃ C ₂ T _z 、Ti ₂ CT _z 、(Ti _0.5 Nb _0.5 ) ₂ CT _z 、(V _0.5 Cr _0.5 ) ₃ C ₂ T _z 、Ti ₃ CNT _z 、Ta ₄ C ₃ T _z 、V ₂ CT _z 、V ₄ C ₃ T _z 、Nb ₂ CT _z 、Nb ₄ C ₃ T _z 、(Nb _0.8 Ti _0.2 ) ₄ C ₃ T _z 、(Nb _0.8 Zr _0.2 ) ₄ C ₃ T _z 、Mo ₂ TiC ₂ T _z 、Mo ₂ Ti ₂ C ₃ T _z And Cr (V) ₂ TiC ₂ T _z At least one of them. The surface groups being selected from O ^2- 、OH ^- 、F ^- 、Cl ^- Or NH ⁴⁺ At least one of them.

The general formula is M _n+1 X _n T _z The compound of (C) has a lamellar structure similar to that of Graphene, and is called an MXene material. After the carbon nano tube and the particle material are attached, the MXene material can provide more channels for the movement of ions, so that the speed of the movement of the ions is greatly improved, and the ion/electron conductivity is improved.

Carbon nanotubes are tubular materials with conductive properties, which are hollow, and have a major axis with a dimension greater than the diameter, also known as linear conductive materials. The carbon nanotubes are attached to the platelet substrate to form a wire-face bonded network structure. The carbon nanotubes and the lamellar substrate are attached to each other by electrostatic attraction, thereby achieving electrostatic self-assembly. The term "attached" as used herein refers to a material in which three components are attracted to each other by electrostatic attraction to create electrostatic self-assembly and construct a three-dimensional network structure.

The particulate material being of electrically conductive nature, also known as particlesA particulate conductive material. In some embodiments, the particulate material comprises lithium manganese phosphate particles. The molecular formula of the lithium iron manganese phosphate particles is LiMn _y Fe _1-y PO ₄ Y is more than or equal to 0.3 and less than 1. For example, y has a value of 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9, etc. For example, the lithium iron manganese phosphate particles have a chemical formula selected from LiMn _0.8 Fe _0.2 PO ₄ 、LiMn _0.7 Fe _0.3 PO ₄ Or LiMn _0.6 Fe _0.4 PO ₄ Any one or more of the following.

In some embodiments, the weight percent of the platelet substrate is 5% to 10% based on the total weight of solids of the particulate material. For example, the weight percent of the sheet substrate may be any of 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10% or a range of any two values therein. For example, if the weight part of the particulate material in solid form is 100, the weight part of the sheet substrate is 5 to 10 parts. For example, the parts by weight of the sheet substrate may be any of 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10 parts or a range of any two of these.

In some embodiments, the weight percent of carbon nanotubes is from 0.001% to 0.005% based on the total weight of the solids of the particulate material. For example, the weight percent of carbon nanotubes may be any of 0.001%, 0.002%, 0.003%, 0.004%, or 0.005%, or a range of any two values therein. That is, if the weight part of the particulate material in the solid form is 100, the weight part of the carbon nanotube is any one of 0.001, 0.002, 0.003, 0.004, or 0.005 or a range of any two thereof.

In any of the above embodiments, the particulate material and the carbon nanotubes are attached to the surface of the platelet substrate, thereby forming a material with a three-dimensional network structure co-constructed with dotted lines and planes. Compared with the single particle material, the positive plate and the battery made of the material with the three-dimensional network structure have good ionic/electronic conductivity. Wherein, the lamellar substrate and the carbon nano tube are respectively attached to the surface of the particle material through electrostatic attraction, thereby realizing electrostatic self-assembly.

The embodiment of the application also provides a preparation method of the positive electrode active material, which comprises the following steps:

1. by M _n+1 AX _n Removing the element A by adopting an acid etchant as a precursor to obtain first slurry containing a lamellar substrate; the lamellar substrate comprises a compound of the general formula M _n+1 X _n T _z A compound of (a);

2. adding the particle material into the first slurry, then adding the second slurry containing the carbon nano tubes and the dispersing agent, and mixing to obtain a third slurry;

3. and separating solid matters from the third slurry, freeze-drying the solid matters, crushing, and sieving to obtain the positive electrode active material.

In step 1, a is a main group element, and may be, for example, al. In the precursor, M and X have stronger bond energy, A has more active chemical property, so that A can be removed from the MAX phase through etching action, thereby obtaining the MXene material (also called a lamellar substrate) with a graphene-like two-dimensional structure (2D structure).

In step 1, the acidic etchant for removing a may be selected from hydrofluoric acid, or a mixed solution of hydrochloric acid and lithium fluoride.

In step 1, the detailed steps of the removal include: adding lithium fluoride into hydrochloric acid solution, stirring at room temperature to dissolve lithium fluoride into hydrochloric acid solution, and slowly adding precursor M _n+1 AX _n And stirring was continued to obtain a mixed solution. The mixed solution was diluted with dilute hydrochloric acid by a certain multiple and then placed in a shaker to perform shaking so as to allow a sufficient reaction. The oscillated solution is placed in a centrifuge for centrifugation, and the precipitate is taken and added into dilute hydrochloric acid. After repeating the dilute hydrochloric acid treatment 2 to 3 times, the removal of impurities in the precipitate is substantially completed. Adding the precipitate after impurity removal into deionized water, sequentially oscillating, centrifuging and collecting the precipitate, repeating for 2 to 3 times until the pH value of the solution containing the precipitate is neutral, and finally collecting the precipitate and regulating the concentration by using deionized water to obtain the first slurry. In the first slurry, the concentration of the lamellar base material is 0.1-10 mg/ml . For example, the concentration of the platelet substrate in the first slurry may be any of 0.1, 0.2, 0.4, 0.5, 0.8, 1.0, 1.2, 1.5, 2, 2.4, 2.8, 3, 4, 5, 5.2, 5.5, 6, 7, 8, 9, or 10mg/ml or a range of any two values therein. The content of the lamellar base material is within the range, and the lamellar base material can be well combined with the particle material and the carbon nano tube, so that the material with the three-dimensional network structure is formed.

In the step 1, the amplitude of the oscillator is 2-5 mm, and the oscillating speed is 100-3000 rpm. In other embodiments, the oscillator amplitude may also be 2, 3, 4 or 5mm and the oscillation speed may also be 100, 200, 300, 500, 1000, 2000, 2500 or 3000rpm. The rotation speed of the centrifugal machine is 1000-5000 rpm. In some embodiments, the rotational speed of the centrifuge may also be 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000rpm, or the like. The amplitude and oscillation speed of the oscillator are within this range, and sufficient contact of the reaction components can be achieved, so that sufficient reaction occurs. The number of shaking or centrifugation may be 3 to 6.

In step 1, the resulting laminate substrate comprises a single layer of material or multiple layers of material. When the sheet substrate is a single layer material, the thickness of the sheet substrate is 1nm to 5nm. When the lamellar base material is a multi-layer material, the thickness of each layer of material is 1nm to 2nm, and the total thickness of the lamellar base material formed by overlapping the multi-layer materials is 2nm to 5nm.

In step 2, the dispersant is selected from cetyltrimethylammonium bromide.

In step 2, the concentration of the dispersant itself is 1 to 6mg/ml, for example, the concentration of the dispersant is 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5 or 6mg/ml. The concentration of the dispersant itself is defined as the ratio of the mass of solute in the dispersant to the total volume of the dispersant. The concentration of the dispersing agent is in the range, so that the particle material and the carbon nano tube can be fully dispersed, and the particle material and the carbon nano tube can be fully contacted with the lamellar base material, so that the particle material, the carbon nano tube and the lamellar base material can form a stable three-dimensional net surface structure.

In step 2, the carbon nanotubes contained in the second slurry are selected from one or both of single-walled carbon nanotubes or multi-walled carbon nanotubes.

In some embodiments, the single-walled carbon nanotubes have a diameter of 0.5nm to 3nm. For example, the diameter of the single-walled carbon nanotubes may be any of 0.5, 1, 1.2, 1.5, 1.6, 1.8, 2, 2.5, 3nm or a range of any two of these values. The length of the single-walled carbon nanotubes is 1nm to 50 μm. For example, the length of the single-walled carbon nanotubes may be any of 1, 1.1, 1.2, 1.4, 1.5, 2, 5, 10, 12, 16, 18, 20, 25, 30, 31, 38, 40, 42, 44, 45, 48, 50 μm or a range of any two of these values. The particulate material and the single-walled carbon nanotubes adhere to each other by electrostatic attraction.

In some embodiments, the multiwall carbon nanotubes have a diameter of 2nm to 30nm. For example, the multiwall carbon nanotubes have diameters of any of 2, 3, 5, 8, 10, 12, 15, 18, 20, 22, 25, 27, 28, 30nm or a range of any two of these values. The length of the multiwall carbon nanotubes is 0.1 μm to 50 μm. For example, the length of the multiwall carbon nanotubes is any value or a range of any two values of 0.1, 0.3, 0.5, 0.8, 1.2, 1.5, 1.8, 2.0, 5, 8, 10, 12, 16, 18, 20, 25, 30, 31, 38, 40, 42, 44, 45, 48, 50 μm. The particulate material and the multiwall carbon nanotubes adhere to each other by electrostatic attraction. The linear single-wall carbon nano tube or multi-wall carbon nano tube can connect dot-shaped lithium iron manganese phosphate particles and then together with MXene to construct a dot-line-surface three-dimensional conductive network structure.

In the step 2, the content of the carbon nano tube in the second slurry is 1-15 wt%. For example, the concentration of carbon nanotubes in the second slurry may be any of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15wt% or a range of any two values therein. The content of the carbon nano tube is within the range, and the carbon nano tube can be well combined with the particle material and the lamellar base material, so that the material with the three-dimensional network structure is formed.

In step 2, the particulate material is lithium manganese iron phosphate particles with a molecular formula of LiMn _y Fe _1-y PO ₄ Y is more than or equal to 0.3 and less than 1. For example, the lithium iron manganese phosphate particles have a chemical formula selected from LiMn _0.8 Fe _0.2 PO ₄ 、LiMn _0.7 Fe _0.3 PO ₄ Or LiMn _0.6 Fe _0.4 PO ₄ Any one or more of the following.

In step 2, the average particle size of the particulate material is from 100nm to 5 μm. In some embodiments, the average particle size of the particulate material may be any value or range of any two values of 100, 120, 150, 160, 180, 200, 210, 220, 240, 250, 270, 300, 500, 800, 900, or 1000nm, and may also be any value or range of any two values of 1.1, 1.2, 1.4, 1.5, 1.6, 1.8, 2.0, 2.2, 2.4, 2.5, 2.8, 3.0, 3.2, 3.5, 3.8, 3.9, 4.0, 4.2, 4.5, 4.8, or 5 μm. The particle size of the particulate material is within this range, which facilitates better adhesion to the carbon nanotubes and the platelet substrate. The average particle size of the particulate material is greater than the thickness of the platelet substrate. The average particle size of the particulate material is greater than the diameter of the carbon nanotubes.

In step 3, the temperature of freeze-drying is from-25℃to-60℃and may be, for example, any value or a range of any two values of-25, -30, -35, -40, -45, -50, -55, or-60 ℃.

In step 3, the time for freeze-drying is 6 hours to 12 hours, and may be, for example, any value or a range of any two values among 6, 7, 8, 9, 10, 11 or 12 hours.

In step 3, the pulverization is performed using a pulverizer and a grinder. The mill first pulverizes the freeze-dried material to a particle size or size of 30 to 50 μm and then the mill continues to grind to a particle size or size of less than 5 μm. The purpose of comminution and grinding is to reduce the size of the individual components in order to increase the contact area after mixing thereof and thereby increase the electrical conductivity.

In step 3, the mesh number of the screen used for sieving is 100 mesh to 200 mesh. The anode active material can be obtained after sieving, and can also be called as an anode material of a lithium ion battery of MXene and carbon nano tube co-modified lithium manganese iron phosphate. In some embodiments, the positive electrode active material is undersize that passes 100 mesh to 200 mesh, and thus, the positive electrode active material is a powder material having a size of less than or equal to 150 μm. The purpose of sieving is to screen out impurities with larger particle size, particles which are not crushed into the required particle size, or larger particles which are crushed and re-agglomerated.

The embodiment of the application provides a positive plate, which comprises: positive electrode current collector and positive electrode material layer.

Wherein the positive electrode current collector comprises aluminum foil.

The positive electrode material layer is positioned on the surface of the positive electrode current collector, and comprises the positive electrode active material or the positive electrode active material prepared by the preparation method of the positive electrode active material. The structure of the obtained positive electrode active material is schematically shown in fig. 1. The black particles in fig. 1 represent lithium manganese iron phosphate particles. The molecular formula of the lithium iron manganese phosphate particles is LiMn _y Fe _1-y PO ₄ Y is more than or equal to 0.3 and less than 1. The graph in fig. 1 shows Carbon Nanotubes (CNTs).

The embodiment of the application also provides a preparation method of the positive plate in the embodiment, which comprises the following steps:

and mixing the positive electrode active material, the conductive agent, the binder and the solvent to obtain positive electrode slurry, and arranging the positive electrode slurry on the surface of the positive electrode current collector to enable the positive electrode slurry to form a positive electrode material layer on the surface of the positive electrode current collector, thereby obtaining the positive electrode plate.

Wherein in some embodiments, the conductive agent is selected from carbon materials such as natural graphite, artificial graphite, conductive carbon black (Super P), acetylene black, needle coke, carbon nanotubes, graphene, and the like. The conductive agent is beneficial to regulating and controlling the transmission channel of electrons and ions in the positive plate, and increasing the solid-phase diffusion capacity of the positive plate so as to improve the conductivity.

In some embodiments, the binder is selected from polyethylene, polypropylene, polyvinylidene fluoride (PVDF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and the like.

In some embodiments, the positive electrode active material comprises 95% to 98% by mass of the solid matter of the positive electrode slurry, or any value or range of values of any two of 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%.

In some embodiments, the solvents are each independently selected from any one of aqueous solvents and organic solvents. Examples of aqueous media may include, but are not limited to: water, a mixed medium of alcohol and water, and the like. Examples of organic-based media may include, but are not limited to: hexane, benzene, toluene, xylene, pyridine, acetone, tetrahydrofuran (THF), N-methylpyrrolidone (NMP), and the like.

In some embodiments, the positive electrode slurry is coated to form a positive electrode material layer. The positive electrode slurry also needs to be subjected to a sieving treatment to remove impurities before coating. After the positive electrode material layer is formed, the positive electrode plate is manufactured through the procedures of rolling, slitting, cutting and the like.

Embodiments of the present application provide a battery, which includes: the lithium ion battery comprises a positive plate, a negative plate, a diaphragm positioned between the positive plate and the negative plate and electrolyte.

The positive plate is the positive plate of any embodiment or is prepared by the preparation method of any embodiment.

The electrolyte comprises lithium salt, an organic solvent and a film forming additive.

The lithium salt is selected from lithium hexafluorophosphate (LiPF) ₆ ) Lithium tetrafluoroborate (LiBF) ₄ ) Or lithium bis (fluorosulfonyl) imide (LiFSI). The lithium salt accounts for 10 to 15 percent of the electrolyte by mass. For example, the lithium salt may be present in the electrolyte in a range of any or any two of 10%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15% by mass.

The organic solvent is selected from more than one of dimethyl carbonate (DMC), diethyl carbonate (DEC) and Ethyl Methyl Carbonate (EMC).

The film forming additive is selected from chlorosulfonyl isocyanate (CSI) or fluoroethylene carbonate (FEC). The film forming additive accounts for 0.1 to 1 percent of the electrolyte by mass percent. For example, the film-forming additive may be present in the electrolyte in any of or in the range of 0.1%, 0.2%, 0.3%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1% by mass. The film forming additive is added into the electrolyte to control the content of inorganic components in the interface film, so that the conductivity of the interface film is improved. The thickness of the interfacial film can be controlled by controlling the addition amount of the film-forming additive, thereby obtaining an interfacial film having a thickness of 10 to 50nm and containing a large amount of inorganic components.

The surface of the negative plate is provided with an interfacial film, and the interfacial film comprises more than one inorganic component of lithium carbonate, lithium oxide and lithium fluoride. These inorganic components are beneficial to enhance the conductivity of the interfacial film. The thickness of the interface film is 10 to 50nm, and for example, the thickness of the interface film may be any one of 10, 12, 15, 16, 18, 20, 21, 25, 26, 28, 30, 31, 32, 35, 38, 40, 41, 45, 47, 49, 50nm or a range of any two of them. The negative electrode sheet includes a negative electrode current collector and a negative electrode material layer. After the negative electrode sheet is contacted with the electrolyte, an interfacial film (SEI film) is formed on the negative electrode material layer. The negative electrode active material used for the negative electrode material layer may be selected from graphite, hard carbon, soft carbon, or the like.

The separator may be a polyethylene film or a polypropylene film having a thickness of 9 to 18 μm. For example, the thickness of the separator may be selected from any of 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 μm or a range of any two values therein.

The embodiment of the application also provides electric equipment, which comprises the battery, wherein the battery is used as a power supply of the electric equipment. In some embodiments, the powered devices of the present application include, but are not limited to: standby power, motors, electric vehicles, electric motorcycles, moped, bicycles, electric tools, household large-sized storage batteries, and the like.

For the same features in the above embodiments as those in other embodiments, reference may be made to and the description in other embodiments is directly cited, and a detailed description is omitted here.

The present application is further illustrated below in conjunction with examples and comparative examples. The following examples and comparative examples are not to be construed as limiting the technical solutions of the present application.

Example 1

The present embodiment provides a positive electrode active material including a sheet substrate, carbon nanotubes, and a particulate material. The positive electrode active material is a screen lower of a 200 mesh screen, which is a powder material having a size of 150 μm or less.

Wherein the lamellar base material has a general formula of Ti ₃ C ₂ T _z The thickness of the MXene nanoplatelets ranges from 1nm to 5nm. In this example, the thickness of the MXene nanoplatelets is a range of values, meaning that the MXene nanoplatelets in this example do not have a uniform thickness, but a mixture of MXene nanoplatelets of different thicknesses, but only if the thickness of the MXene nanoplatelets falls within the above range.

The carbon nanotubes were single-walled carbon nanotubes having a diameter of 1.5nm and a length of 25 μm.

The granular material is lithium iron manganese phosphate, and the molecular formula of the granular material is LiMn _0.6 Fe _0.4 PO ₄ . The average particle size of the particulate material was 500nm.

The embodiment also provides a preparation method of the positive electrode active material, which comprises the following steps:

1. 3.2g of lithium fluoride (LiF) was slowly added to 30ml of hydrochloric acid solution, and stirring was continued at room temperature for 10min, and after LiF was sufficiently dissolved in the hydrochloric acid solution, an acidic etchant was obtained.

2. Slowly adding 2g Ti into the acid etchant ₃ AlC ₂ The ceramic material (precursor) was stirred for 24 hours to obtain a mixed solution.

3. The mixed solution was diluted with dilute hydrochloric acid, and then placed in a shaker to perform shaking so as to allow a sufficient reaction. The oscillator amplitude was 3mm and the speed was 2000rpm. The shaken solution was placed in a centrifuge and centrifuged at 3000rpm, and the precipitate was taken and added to dilute hydrochloric acid. After 2 repeated treatments with dilute hydrochloric acid, the impurities in the precipitate are substantially removed. Adding the precipitate after impurity removal into deionized water, sequentially oscillating, centrifuging and collecting the precipitate, repeating for 3 times until the pH value of the solution containing the precipitate is neutral, and finally collecting the precipitate and regulating the concentration by using deionized water to obtain the first slurry. In the first slurry, the concentration of the lamellar base material is 2mg/ml, and the lamellar base material contains Ti with the general formula of ₃ C ₂ T _z Is a compound of (a).

4. 0.5g of particulate material (LiMn _0.6 Fe _0.4 PO ₄ Adding 20ml of the first slurry (containing 0.04g of MXene nano-sheets) with the average particle size of 500nm, then adding the second slurry containing carbon nano-tubes (single-wall carbon nano-tubes) and a dispersing agent (10 mg of CTAB), and mixing to obtain a third slurry; the volume of the second slurry was 0.1ml, which contained single-walled carbon nanotubes in an amount of 10wt% and the mass of the single-walled carbon nanotubes was 0.01mg.

5. And filtering the third slurry to separate out solid matters, carrying out vacuum drying on the obtained solid matters for 10 hours at the temperature of-45 ℃, crushing and grinding after the vacuum drying is finished, and sieving the solid matters through a 200-mesh sieve to obtain the anode active material which is marked as LMFP@MXene/CNT. In the positive electrode active material, a three-dimensional mesh surface structure is constructed by using a granular material as a dot material, a carbon nanotube as a wire material, and a sheet substrate as a surface material.

The embodiment provides a positive plate, and the preparation method comprises the following steps:

mixing the positive electrode active material, a conductive agent (conductive carbon black) and a binder (polyvinylidene fluoride, PVDF) according to a mass ratio of 97:1.8:1.2, and then stirring and mixing the mixture with a solvent (1-methyl-2-pyrrolidone, NMP) in vacuum to obtain positive electrode slurry. And sieving the positive electrode slurry to remove impurities, uniformly coating the positive electrode slurry on two surfaces of a positive electrode current collector, airing at room temperature, transferring into an oven for baking, and drying to form a positive electrode material layer. The thickness of the positive electrode material layer was 80. Mu.m. Then, rolling (such as cold pressing), slitting, cutting and the like are carried out to obtain the positive plate. The positive plate has a compacted density of 2.10g/cm ³ 。

The embodiment also provides a preparation method of the battery, which comprises the following steps:

the positive plate, the diaphragm and the negative plate are stacked in sequence (according to the sequence of one positive plate, one diaphragm and one negative plate), so that the diaphragm is positioned between the positive plate and the negative plate. And winding to obtain the bare cell. And drying the bare cell, adding electrolyte, and performing vacuum packaging, standing, formation, capacity division and other procedures to obtain the battery.

The preparation method of the negative plate comprises the following steps: active cathodeMaterial (graphite), conductive agent (CNT), thickener (CMC) and binder (SBR) according to the mass ratio of 96.5:0.8:0.9:1.8, adding a solvent (deionized water), stirring in vacuum until the system is uniform, obtaining negative electrode slurry, uniformly coating the negative electrode slurry on the upper surface and the lower surface of the negative electrode current collector, airing at room temperature, transferring to an oven, continuously drying, cold pressing, and cutting to obtain a negative electrode plate. The compaction density of the negative plate is 1.5g/cm ³ 。

The electrolyte comprises lithium hexafluorophosphate (LiPF) ₆ ) Organic solvents and film forming additives. The mass percentage of lithium hexafluorophosphate was 12.5wt% based on the total mass of the electrolyte. The organic solvent is a mixture of dimethyl carbonate (DMC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) in a mass ratio of 20:30:30. The film forming additive is chlorosulfonyl isocyanate (CSI). The mass percent (M) of the film forming additive is 0.5w% based on the total mass of the electrolyte.

The separator was a polyethylene film having a thickness of 9 μm.

The parameter pairs for the various examples and comparative examples of the present application are shown in table 1. The performance tests are shown in tables 2 and 3.

Example 2

The embodiment provides a positive electrode active material and a preparation method thereof, a positive electrode plate, a battery and a preparation method thereof. Unlike example 1, this example does not add a dispersant in step 4, and the rest of the steps are the same as example 1. Thus, the positive electrode active material obtained in example 2 did not contain a dispersant (CTAB), designated LMFP@MXene/CNT-Free CTAB.

From the experimental results, when the dispersing agent is not added, the electron conductivity of the positive electrode sheet and the ion conductivity of the battery in the embodiment 2 are both reduced, and the specific discharge capacity and the cycle performance of the battery are reduced, which indicates that the dispersing agent can promote the combination of the sheet substrate, the carbon nano tube and the particle material to form a stable three-dimensional network structure.

Examples 3 to 10

Example 3 provides a positive electrode active material and a preparation method thereof, a positive electrode sheet, a battery and a preparation method thereof. Example 3 increased the content of single-walled carbon nanotubes compared to example 1. From the experimental results, if the content of the single-walled carbon nanotubes is increased within a certain range, the conductivity is improved, and the specific discharge capacity is reduced. This is because the carbon nanotubes as inactive materials, after being added, decrease the proportion of active materials (particulate materials) in the entire positive electrode active material, and thus the specific discharge capacity decreases, but still falls within a suitable range. In addition, after the addition of the carbon nanotubes, the capacity retention rate of the positive electrode active material may be increased.

Examples 4 and 5 provide a positive electrode active material and a method for preparing the same, a positive electrode sheet, a battery and a method for preparing the same. Example 4 increased the content of the platelet substrate compared to example 1, and example 5 decreased the content of the platelet substrate. From the experimental results, it is known that an increase in the content of the sheet base material within a certain range increases the conductivity to some extent.

Examples 6 and 7 provide a positive electrode active material and a method for preparing the same, a positive electrode sheet, a battery and a method for preparing the same. Examples 6 and 7 changed the kind of the sheet base material as compared with example 1. The type of the lamellar substrate used in example 6 is Ti ₂ CT _z The type of the lamellar substrate used in example 7 is Ti ₂ CT _z And Ti is ₃ C ₂ T _z . From the experimental results, it was found that although the types of these sheet substrates were different, a battery having appropriate conductivity could be obtained. After the types of the sheet base materials are changed, the conductivity changes within 1-2 orders of magnitude, and the requirements of the positive electrode sheet and the battery on the conductivity are met. Proved by other experiments, ti ₃ C ₂ T _z 、Ti ₂ CT _z 、(Ti _0.5 Nb _0.5 ) ₂ CT _z 、(V _0.5 Cr _0.5 ) ₃ C ₂ T _z 、Ti ₃ CNT _z 、Ta ₄ C ₃ T _z 、V ₂ CT _z 、V ₄ C ₃ T _z 、Nb ₂ CT _z 、Nb ₄ C ₃ T _z 、(Nb _0.8 Ti _0.2 ) ₄ C ₃ T _z 、(Nb _0.8 Zr _0.2 ) ₄ C ₃ T _z 、Mo ₂ TiC ₂ T _z 、Mo ₂ Ti ₂ C ₃ T _z Or Cr ₂ TiC ₂ T _z These materials are all suitable for use in the present application.

Example 8 provides a positive electrode active material and a preparation method thereof, a positive electrode sheet, a battery and a preparation method thereof. In example 8, multi-walled carbon nanotubes having a diameter of 5nm and a length of 30nm were used as compared to example 1. The experimental results show that the difference of the conductivities of the multi-wall carbon nanotubes and the single-wall carbon nanotubes within a certain content range is within a reasonable range, and the multi-wall carbon nanotubes and the single-wall carbon nanotubes can be replaced by each other according to different requirements on the conductivities.

Examples 9 and 10 provide a positive electrode active material and a method for preparing the same, a positive electrode sheet, a battery and a method for preparing the same. Examples 9 and 10 changed the kind of the particulate material as compared with example 1. The particulate material of example 9 is LiMn _0.7 Fe _0.3 PO ₄ I.e. a particulate material with a higher Mn content is used. The particulate material of example 10 is LiMn _0.6 Fe _0.4 PO ₄ And LiMn _0.7 Fe _0.3 PO ₄ Is a mixture of (a) and (b). From the experimental results and through other experiments, it is known that the particle material is used as a main material and an active substance, and the particle material is selected from LiMn although different particle materials can generate different conductivity differences _0.8 Fe _0.2 PO ₄ 、LiMn _0.7 Fe _0.3 PO ₄ Or LiMn _0.6 Fe _0.4 PO ₄ Time-wise can be applied to the present application.

Comparative example 1

The comparative example provides a positive electrode active material and a preparation method thereof, a positive electrode sheet, a battery and a preparation method thereof. Unlike example 1, this comparative example was conducted by adding only the dispersant (CTAB) in the 4 th step, and not adding the second slurry containing carbon nanotubes (single-walled carbon nanotubes), and the other steps were the same as in example 1. Thus, the positive electrode active material obtained in comparative example 1 did not contain single-walled carbon nanotubes, and was designated as lmfp@mxene.

According to experimental results, when the cathode active material of comparative example 1 does not contain carbon nanotubes, both the electron conductivity of the cathode sheet and the ion conductivity of the battery in comparative example 1 are reduced, and the specific capacity and cycle performance of the resulting battery are also reduced, indicating that the carbon nanotubes have a certain effect on improving the conductivity.

Comparative example 2

The comparative example provides a positive electrode active material and a preparation method thereof, a positive electrode sheet, a battery and a preparation method thereof. Unlike example 1, this comparative example only 0.5g of particulate material (LiMn _0.6 Fe _0.4 PO ₄ Average particle size 500 nm) was added to 20ml of deionized water, and the first slurry (containing 0.04g of mxene nanoplatelets) was not added, and the rest of the procedure was the same as in example 1. Thus, the positive electrode active material obtained in comparative example 2 did not contain MXene nanoplatelets, denoted lmfp@cnt.

From the experimental results, it is found that the conductivity is greatly reduced only by the carbon nanotubes but not by the MXene nanoplatelets, and it is presumed that the MXene nanoplatelets can play a role of supporting the carbon nanotubes and the particulate material, thereby forming a three-dimensional network structure with stable structure. The three-dimensional net surface structure can provide more channels for the movement of ions, so that the speed of the movement of the ions is greatly improved, and the ion/electron conductivity is improved.

Comparative example 3

The comparative example provides a positive electrode active material and a preparation method thereof, a positive electrode sheet, a battery and a preparation method thereof. Unlike example 1, this comparative example only 0.5g of particulate material (LiMn _0.6 Fe _0.4 PO ₄ The procedure of example 1 was repeated except that 20ml of deionized water was added, but the first slurry (containing 0.04g of mxene nanoplatelets), carbon nanotubes (single-walled carbon nanotubes), and a dispersant (10 mg of CTAB) were not added. Therefore, the positive electrode active material obtained in comparative example 3 does not contain MXene nanoplatelets, carbon nanotubes (single-walled carbon nanotubes) and dispersant CTAB, denoted LMFP. From the experimental results, it can be seen that if only the particulate material is present and notIf the MXene nano-sheets and the carbon nano-tubes cannot form a three-dimensional network structure, the conductivity of the battery and the positive electrode sheet which are made of the granular materials is lower than that of the battery and the positive electrode sheet which are made of the materials with the three-dimensional network structure.

The above examples and comparative examples were subjected to performance tests, the methods of which are as follows:

and (5) buckling and assembling: the negative electrode sheet, the positive electrode sheet and the electrolyte of the above examples and comparative examples were assembled into a button half cell in a vacuum glove box. The assembled button half cell is subjected to performance test:

1. the batteries prepared in examples 1 to 10 and comparative examples 1 to 3 were subjected to ion and electron conductivity tests at room temperature, and the data are shown in Table 2.

The electron conductivity and the ion conductivity are achieved by using a Chen-Hua electrochemical workstation, the model is CHI660E, the output potential range is +/-10V, the output current range is 3 nA-250 mA, and the alternating current impedance frequency range is 10 uHz-1 MHz.

The electron conductivity testing step comprises the following steps: the direct current four-probe method can be used for testing the electronic conductivity of the positive plate of the battery by constructing a four-electrode system and applying a direct current source by using an electrochemical workstation.

The ion conductivity testing step comprises the following steps: and testing the battery by using an alternating current impedance method, and processing the obtained Nyquist diagram to obtain the ion conductivity of the battery.

2. Testing the initial discharge specific capacity of the battery at 0.1C; the test method comprises the following steps:

the batteries prepared in examples 1 to 10 and comparative examples 1 to 3 were placed on a charge/discharge tester to conduct a charge/discharge capacity test: charging to 4.3V at 0.1C rate at room temperature, cutting off current to 0.01C, and discharging to 2.5V at 0.1C rate, the result is shown in Table 3;

3. 1C of the battery is subjected to a first discharge specific capacity test; the test method comprises the following steps:

the batteries prepared in examples 1 to 10 and comparative examples 1 to 3 were placed on a charge-discharge tester to perform a charge-discharge performance test, charged to 4.3V at a 0.1C rate, and discharged to 2.5V at a 1C rate, respectively, with a cutoff current of 0.01C, and the results are shown in table 3;

4. testing the 10C initial discharge specific capacity of the battery; the test method comprises the following steps:

5. Capacity retention test of the cell for 100 weeks at 1C cycle; the test method comprises the following steps:

the batteries prepared in examples 1 to 10 and comparative examples 1 to 3 were placed on a charge/discharge tester for charge/discharge performance test, charged to 4.3V at 1C magnification, and cut-off current was 0.01C, and then discharged to 2.5V at 1C magnification, respectively, and charge/discharge was repeated 100 times, with the results shown in table 3.

Table 1 parameters of each of examples and comparative examples table 1

Table 2 performance test tables of batteries of respective examples and comparative examples

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Table 3 performance test tables of batteries of respective examples and comparative examples

In the foregoing embodiments, the descriptions of the embodiments are emphasized, and for parts of one embodiment that are not described in detail, reference may be made to related descriptions of other embodiments.

In shortThe positive electrode active material provided in some embodiments of the present application includes: carbon nanotubes, particulate materials and compositions containing a polymer of the general formula M _n+1 X _n T _z A lamellar substrate of the compound of (a). According to the method, the carbon nano tube and the particle material are attached to the surface of the lamellar substrate, so that the three-dimensional net surface structure jointly constructed by the point, the line and the surface is formed by taking the particle material as the point, the carbon nano tube as the line and the lamellar substrate as the surface, the defect of low electron/ion conductivity of the particle material is overcome, and the rate performance and the cycle stability of the battery are improved.

In addition, even if MXene is partially oxidized into titanium dioxide and carbon in a long-cycle process, the product of the MXene can promote the diffusion of lithium ions, and the battery is ensured to have good rate capability and cycle stability. Meanwhile, the MXene and the carbon nano tube have excellent heat conductivity and heat stability, so that the material can ensure the high safety of a battery system under extreme conditions, the processing process is simpler, and the industrial production is easy to realize.

The foregoing has outlined rather broadly the more detailed description of embodiments of the present application, wherein specific examples are provided herein to illustrate the principles and embodiments of the present application, the above examples being provided solely to assist in the understanding of the methods of the present application and the core ideas thereof; meanwhile, those skilled in the art will have variations in the specific embodiments and application scope in light of the ideas of the present application, and the present description should not be construed as limiting the present application in view of the above.

Claims

1. A positive electrode active material, characterized by comprising:

a particulate material;

a carbon nanotube; and

a sheet substrate comprising: the general formula is M _n+1 X _n T _z A compound of (a); m is a transition metal element, X is one or two of C or N, T _z Is a surface group, n has a value selected from 1, 2 or 3;

wherein the particulate material and the carbon nanotubes are attached to the surface of the platelet substrate.

2. The positive electrode active material according to claim 1, wherein the transition metal element is selected from at least one of Ti, zr, hf, V, nb, ta, cr, mo or Sc; and/or

The surface groups are selected from O ^2- 、OH ^- 、F ^- 、Cl ^- Or NH ⁴⁺ At least one of (a) and (b);

alternatively, the general formula is M _n+1 X _n T _z The compound of (2) is selected from Ti ₃ C ₂ T _z 、Ti ₂ CT _z 、(Ti _0.5 Nb _0.5 ) ₂ CT _z 、(V _0.5 Cr _0.5 ) ₃ C ₂ T _z 、Ti ₃ CNT _z 、Ta ₄ C ₃ T _z 、V ₂ CT _z 、V ₄ C ₃ T _z 、Nb ₂ CT _z 、Nb ₄ C ₃ T _z 、(Nb _0.8 Ti _0.2 ) ₄ C ₃ T _z 、(Nb _0.8 Zr _0.2 ) ₄ C ₃ T _z 、Mo ₂ TiC ₂ T _z 、Mo ₂ Ti ₂ C ₃ T _z And Cr (V) ₂ TiC ₂ T _z At least one of them.

3. The positive electrode active material according to claim 1, wherein the carbon nanotubes are selected from one or both of single-walled carbon nanotubes or multi-walled carbon nanotubes; and/or

The particulate material comprises lithium iron manganese phosphate particles; and/or

The weight percent of the platelet substrate is 5% to 10% based on the total weight of solids of the particulate material; and/or

The weight percent of the carbon nanotubes is 0.001% to 0.005% by total weight of the solids of the particulate material; and/or

The average particle size of the particulate material is greater than the thickness of the platelet substrate; and/or

The average particle size of the particulate material is greater than the diameter of the carbon nanotubes.

4. A method for preparing a positive electrode active material, comprising the steps of:

by M _n+1 AX _n Removing the element A by adopting an acid etchant as a precursor to obtain first slurry containing a lamellar substrate; the sheet substrate comprises a polymer of the general formula M _n+1 X _n T _z A compound of (a);

adding a particle material into the first slurry, mixing, adding a second slurry containing carbon nano tubes and a dispersing agent, and mixing to obtain a third slurry;

5. The method of claim 4, wherein A is Al; and/or

The acid etchant is selected from hydrofluoric acid or mixed solution of hydrochloric acid and lithium fluoride; and/or

The dispersant is selected from cetyl trimethyl ammonium bromide; and/or

The molecular formula of the granular material is LiMn _y Fe _1-y PO ₄ Y is more than or equal to 0.3 and less than 1; and/or

The average particle size of the particulate material is from 100nm to 5 μm; and/or

The mesh number of the sieving is 100 to 200.

6. The method of claim 4, wherein the sheet substrate is selected from a single layer material or a multi-layer material; and/or

The carbon nanotubes are selected from one or two of single-wall carbon nanotubes or multi-wall carbon nanotubes;

optionally, the thickness of the platelet substrate is from 1nm to 5nm; and/or

The diameter of the single-walled carbon nanotube is 0.5nm to 3nm; and/or

The length of the single-walled carbon nanotubes is 1 to 50 μm; and/or

The diameter of the multi-wall carbon nano tube is 2nm to 30nm; and/or

The multi-walled carbon nanotubes have a length of 0.1 μm to 50 μm.

7. The method according to claim 4, wherein the concentration of the lamellar substrate in the first slurry is 0.1 to 10mg/ml; and/or

The content of the carbon nano tube in the second slurry is 1-15 wt%; and/or

The concentration of the dispersing agent is 1-6 mg/ml; and/or

The temperature of the freeze drying is between 25 ℃ below zero and 60 ℃ below zero; and/or

The freeze-drying time is 6 hours to 12 hours.

8. A positive electrode sheet, comprising:

a positive electrode current collector; and

a positive electrode material layer on a surface of the positive electrode current collector, the positive electrode material layer comprising the positive electrode active material according to any one of claims 1 to 3, or comprising the positive electrode active material produced by the positive electrode active material production method according to any one of claims 4 to 7;

Optionally, the positive electrode active material is a powder material having a size of 150 μm or less; and/or

The positive electrode current collector includes aluminum foil.

9. A battery, comprising: the lithium ion battery comprises a positive plate, a negative plate, a diaphragm positioned between the positive plate and the negative plate and electrolyte;

the positive electrode sheet is the positive electrode sheet according to claim 8;

optionally, the electrolyte comprises a lithium salt, an organic solvent, and a film-forming additive;

further alternatively, the lithium salt is selected from more than one of lithium hexafluorophosphate, lithium tetrafluoroborate or lithium bis (fluorosulfonyl) imide; and/or

The organic solvent is selected from more than one of dimethyl carbonate, diethyl carbonate and ethylmethyl carbonate; and/or

The film forming additive is selected from chlorosulfonyl isocyanate (CSI) or fluoroethylene carbonate (FEC); and/or

The surface of the negative electrode plate is provided with an interface film, and the interface film comprises more than one of lithium carbonate, lithium oxide and lithium fluoride;

still further alternatively, the interface film has a thickness of 10 to 50nm.

10. A powered device comprising the battery of claim 9 as a power supply for the powered device.