CN116230880A - Positive electrode material, preparation method thereof and lithium ion battery - Google Patents

Positive electrode material, preparation method thereof and lithium ion battery Download PDF

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CN116230880A
CN116230880A CN202211658413.XA CN202211658413A CN116230880A CN 116230880 A CN116230880 A CN 116230880A CN 202211658413 A CN202211658413 A CN 202211658413A CN 116230880 A CN116230880 A CN 116230880A
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positive electrode
electrode material
lithium
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张万圣
宋雄
张金龙
吴小珍
杨顺毅
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Better Jiangsu New Material Technology Co ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
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    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/523—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron for non-aqueous cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
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Abstract

The application relates to a positive electrode material, a preparation method thereof and a lithium ion battery, wherein the positive electrode material comprises a matrix and a coating layer coated on at least part of the surface of the matrix, and the chemical general formula of the matrix is shown as formula (I): li (Li) a Ni x Co y M 1‑x‑y O 2 In the formula (I), M comprises at least one of Mn and Al, a is more than or equal to 0.95 and less than or equal to 1.05,0.8 and x is more than or equal to 0.95, and y is more than or equal to 0.05 and less than or equal to 0.2; the material of the coating layer comprises oxide, and the metal element in the oxide comprises at least one of W, al, co, zr, Y and Ti; in the XRD pattern of the positive electrode materialDiffraction peak intensity ratio I between (001) and (101) planes 001 /Ⅰ 101 Less than or equal to 1.10; (003) Diffraction peak intensity ratio I between facets (104) 003 /Ⅰ 104 ≥1.70。

Description

Positive electrode material, preparation method thereof and lithium ion battery
Technical Field
The invention belongs to the technical field of positive electrode materials, and particularly relates to a positive electrode material, a preparation method thereof and a lithium ion battery.
Background
In recent years, with the increasing demands of people on new energy automobiles and the vigorous development of new energy power battery markets at home and abroad, the demands of consumers on the endurance mileage of electric automobiles are continuously improved, and the layered LiNi with the characteristics of high discharge capacity, good cycle life and low cost is provided 1-x-y Co x MyO 2 Ternary positive electrode materials have been developed. Positive electrode materials (Ni.gtoreq.80%) such as LiNi 0.8 Co 0.1 Mn 0.1 O 2 And LiNi 0.8 Co 0.15 Al 0.05 O 2 The material has high reversible specific capacity (more than 200 mAh/g) and good cycle stability, and is suitable for being used as a positive electrode material for a high specific energy power battery.
Although the ternary positive electrode material has a larger advantage in energy density than other positive electrode materials, the disadvantages of poor cycle performance and rate capability prevent the ternary positive electrode material from being applied to the field of power batteries on a large scale. Current research considers that the unstable surface crystal structure of the material is a main cause of rapid capacity decay, and crystal defects are an important cause of unstable crystal structure. On one hand, the ternary material is mostly prepared by adopting a coprecipitation method, primary particles are randomly distributed due to intense stirring in the process of synthesizing a precursor by coprecipitation, and a large number of crystal defects (especially on the surface layer of particles) are left in the subsequent sintering process, including grain boundaries, micropores and the like. On the other hand, ni element in the ternary positive electrode material particle mainly exists in the form of +3, and Ni is used as Ni on the surface layer 2+ Mainly. More Ni 2+ A large number of crystal defects can be caused in the surface layer structure of the material, including serious cation mixing, niO non-active impurity phase, spinel and the like. The crystal defects not only prevent the rapid deintercalation of lithium ions, but also increase the polarization of the battery and reduce the electrochemical activity.
Therefore, in order to promote the wide application of ternary materials in power batteries, a positive electrode material for improving the cycle performance and the rate performance is urgently needed.
Disclosure of Invention
The invention aims to provide a positive electrode material, a preparation method thereof and a lithium ion battery, wherein the surface crystal structure of the positive electrode material is stable, so that the positive electrode material has excellent capacity, cycle performance and multiplying power performance.
In a first aspect, an embodiment of the present application provides a positive electrode material, where the positive electrode material includes a substrate and a coating layer coated on at least a portion of a surface of the substrate, and a chemical general formula of the substrate is shown in formula (i):
Li a Ni x Co y M 1-x-y O 2 (Ⅰ)
in the formula (I), M comprises at least one of Mn and Al, a is more than or equal to 0.95 and less than or equal to 1.05,0.8 and x is more than or equal to 0.95, and y is more than or equal to 0.05 and less than or equal to 0.2;
the material of the coating layer comprises oxide, and the metal element in the oxide comprises at least one of W, al, co, zr, Y and Ti;
in the XRD pattern of the positive electrode material, the diffraction peak intensity ratio I between the (001) plane and the (101) plane 001 /Ⅰ 101 Less than or equal to 1.10; (003) Diffraction peak intensity ratio I between facets (104) 003 /Ⅰ 104 ≥1.70；
The nucleation rate k of the positive electrode material is more than or equal to 90%, wherein:
Figure SMS_1
in the formula (II), H β(300) Is the characteristic diffraction peak intensity of beta crystal (300) crystal face of the positive electrode material in XRD pattern, H α(110) ，H α(040) And H α(130) The characteristic diffraction peak intensities of alpha crystal (110), (040) and (130) crystal faces of the positive electrode material in an XRD spectrum are respectively corresponding.
In some embodiments, the material comprises at least one of the following features (1) - (3):
(1) The oxygen isThe chemical compound comprises WO 3 、WO 2 、Al 2 O 3 、CoO、Co 2 O 4 、B 2 O 3 、ZrO 2 、Y 2 O 3 And TiO 2 At least one of (a) and (b);
(2) The thickness of the coating layer is 4 nm-11 nm;
(3) Ni in the surface layer of the positive electrode material 3+ Mass of (c) and Ni in the positive electrode material 2+ And Ni 3+ The ratio of the total mass of the positive electrode material to the total mass of the positive electrode material is more than or equal to 0.9, wherein the surface layer of the positive electrode material refers to a part of the surface of the positive electrode material extending to the inside of the positive electrode material by a thickness of 0 nm-20 nm.
In some embodiments, the positive electrode material includes at least one of the following features (1) - (5):
(1) The median particle diameter of the positive electrode material is 3.5-4.5 mu m;
(2) The specific surface area of the positive electrode material is 0.4m 2 /g～0.8m 2 /g；
(3) The moisture content of the positive electrode material is less than or equal to 300ppm;
(4) Li in the positive electrode material 2 CO 3 The mass content of (2) is less than or equal to 0.3%;
(5) The mass content of LiOH in the positive electrode material is less than or equal to 0.4%.
In a second aspect, an embodiment of the present application provides a method for preparing a positive electrode material, including the following steps:
performing heat treatment on a mixture containing a lithium source, a nickel source, a cobalt source, a metal source, a polyoxometallate and a beta nucleating agent to obtain a positive electrode material, wherein the metal source comprises at least one of a manganese source and an aluminum source, and the polyoxometallate comprises Na 5 CoW 12 O 40 、Na 5 BW 12 O 40 、Na 5 AlW 12 O 40 、Na 5 TiW 12 O 40 、Na 5 YW 12 O 40 And Na (Na) 5 ZrW 12 O 40 At least one of them.
In some embodiments, the method comprises at least one of the following features (1) - (12):
(1) The lithium source comprises at least one of lithium carbonate, lithium hydroxide, lithium acetate, lithium oxalate, lithium sulfate, lithium chloride and lithium nitrate;
(2) The median particle diameter of the lithium source is 3-5 mu m;
(3) The nickel source comprises at least one of nickel acid, nickel acetate, nickel oxalate, nickel nitrate, nickel chloride and nickel nitrate;
(4) The median particle diameter of the nickel source is 3-5 mu m;
(5) The cobalt source comprises at least one of cobalt carbonate, cobalt acetate, cobalt oxalate, cobalt sulfate, cobalt chloride and cobalt nitrate;
(6) The median particle diameter of the cobalt source is 3-5 mu m;
(7) The manganese source comprises at least one of manganese carbonate, manganese acetate, manganese oxalate, manganese sulfate, manganese chloride and manganese nitrate;
(8) The median particle diameter of the manganese source is 3-5 mu m;
(9) The aluminum source comprises at least one of aluminum carbonate, aluminum acetate, aluminum oxalate, aluminum sulfate, aluminum chloride and aluminum nitrate;
(10) The median particle diameter of the aluminum source is 3-5 mu m;
(11) The lithium source, the nickel source, the cobalt source and the metal source are added according to the stoichiometric ratio shown in the following chemical formula: li (Li) a Ni x Co y M 1-x-y O 2 Wherein M is a metal source, a is more than or equal to 0.95 and less than or equal to 1.05,0.8, x is more than or equal to 0.95, and y is more than or equal to 0.05 and less than or equal to 0.2;
(12) The mass ratio of the polyoxometallate in the mixture is 1-5%;
in some embodiments, the method comprises at least one of the following features (1) - (6):
(1) The mixture containing a lithium source, a nickel source, a cobalt source, a metal source and polyoxometalate also comprises a dispersing agent;
(2) The mixture containing a lithium source, a nickel source, a cobalt source, a metal source and polyoxometallate also comprises a dispersing agent, wherein the dispersing agent comprises at least one of polyethylene glycol-2000 and imidazole ionic liquid;
(3) The mixed material containing the lithium source, the nickel source, the cobalt source, the metal source and the polyoxometallate also comprises a dispersing agent, wherein the mass ratio of the dispersing agent in the mixed material is 0.1-0.3%;
(4) The mixture containing a lithium source, a nickel source, a cobalt source, a metal source and polyoxometallate also comprises a solvent;
(5) The mixture containing the lithium source, the nickel source, the cobalt source, the metal source and the polyoxometallate also comprises a solvent, wherein the solvent comprises at least one of water and ethanol;
(6) The mixture containing a lithium source, a nickel source, a cobalt source, a metal source and polyoxometallate also comprises a solvent, and the solid content of the mixture is 20-70%.
In some embodiments, the beta nucleating agent comprises at least one of benzene p-cyclohexylamide carboxylate, zinc adipate, supported calcium pimelate, zinc phthalate, and liquid crystalline polyesters.
In some embodiments, the beta nucleating agent comprises 0.05 to 0.5 percent by mass of the mixture.
In some embodiments, the method comprises at least one of the following features (1) - (3):
(1) The heat treatment is performed in an air or oxygen atmosphere;
(2) The temperature of the heat treatment is 500-800 ℃;
(3) The feeding rate of the mixture containing the lithium source, the nickel source, the cobalt source, the metal source and the polyoxometallate is 20-80 mL/min.
In a third aspect, embodiments of the present application provide a lithium ion battery, where the lithium ion battery includes the positive electrode material according to the first aspect or the positive electrode material prepared by the method according to the second aspect.
Compared with the prior art, the invention has the following beneficial effects:
the positive electrode material disclosed by the application meets the following relation through XRD measurement: i 001 /Ⅰ 101 ≤1.10，Ⅰ 003 /Ⅰ 104 Not less than 1.70, wherein I 001 /Ⅰ 101 Less than or equal to 1.10, the surface of the matrix of the positive electrode material has a more complete crystal structure, which is favorable for improving the cycle performance and capacity of the positive electrode material, and simultaneously, the more complete crystal structure is favorable for removing and inserting lithium ions and improving the multiplying power performance of the positive electrode material; i 003 /Ⅰ 104 More than or equal to 1.70, the positive electrode material has a good layered structure, and NiO rock salt is smaller, so that lithium nickel mixed discharge can be reduced, the impedance of the material is further reduced, the occurrence of interface side reaction is facilitated to be reduced, and the capacity and the multiplying power performance of the material are improved; the application positive electrode material still includes to cover the metal oxide coating who establishes at the base member surface, and the existence of metal oxide coating can reduce the production of material grain boundary crackle, improves the granule intensity of material, promotes positive electrode material's electrochemical performance, and the nucleation rate of this application can reach 90%, carries out lattice matching with lattice spacing mismatch rate low between the base member crystal to reduce the lithium nickel mixed degree of material, improve positive electrode material's multiplying power performance.
In the preparation method, the precursor is generated in the heat treatment process through the lithium source, the nickel source, the cobalt source and the metal source, the polyoxometallate is used as the oxidant, and part of the polyoxometallate can be used for preparing Ni on the surface of the precursor in the heat treatment process 2+ Oxidation to generate NiOOH (the chemical valence of Ni in the NiOOH is +3), wherein the NiOOH can react with lithium element to generate lithium nickelate, so that crystal defects on the surface of the material can be eliminated, and the capacity, the multiplying power performance and the cycle performance of the positive electrode material are improved; the other part of polyoxometalate is reduced into corresponding oxide in the heat treatment process, and the corresponding oxide is coated on the surface of the matrix to form a coating layer, so that the generation of material grain boundary cracks can be reduced, the grain strength of the material is improved, the electrochemical performance of the material is improved, the beta nucleating agent in the mixture can be lattice matched with the matrix crystal at a lattice spacing mismatch rate lower than 15%, the nucleation rate of the material is improved, the lithium nickel mixing degree of the material is reduced, and the multiplying power performance of the positive electrode material is improved. The application enables polyoxometallate to be used as a dopant and a coating material pair simultaneously through in-situ reaction and heat treatment The electrochemical performance of the material can be improved by double modification of the material.
Drawings
For a clearer description of embodiments of the present application or of the prior art, the drawings that are used in the description of the embodiments or of the prior art will be briefly described, it being apparent that the drawings in the description that follow are only some embodiments of the present application, and that other drawings may be obtained from these drawings by a person of ordinary skill in the art without inventive effort.
FIG. 1 is a flow chart of the preparation of the positive electrode material of the present application;
FIG. 2 is a graph showing the discharge capacity curves of the materials prepared in example and comparative example 1;
FIG. 3 is a SEM comparison of the materials prepared in example 1 and comparative example 1;
FIG. 4 is a DSC curve comparison of the material prepared in example 1 and comparative example 1.
Detailed Description
For a better understanding of the technical solutions of the present application, embodiments of the present application are described in detail below with reference to the accompanying drawings.
It should be understood that the described embodiments are merely some, but not all, of the embodiments of the present application. All other embodiments, based on the embodiments herein, which would be apparent to one of ordinary skill in the art without making any inventive effort, are intended to be within the scope of the present application.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature.
For ease of understanding the present invention, specific terms are defined appropriately in the present application. Unless defined otherwise herein, scientific and technical terms used herein have the meanings commonly understood by one of ordinary skill in the art to which this invention belongs.
As described in the background art, the existing ternary positive electrode material has the disadvantage of poor cycle performance and rate capability, and large-scale application of the ternary positive electrode material in the field of power batteries is hindered. In order to improve the problems, at present, one of the important points of research is to carry out ion doping and coating on the material to improve the structural stability and stabilize the surface layer crystal structure of the ternary material in the charge and discharge process, but the crystal defect of the ternary material is not fundamentally eliminated, and the common coating material has different degrees of blocking effects on lithium ion deintercalation and can reduce the specific capacity of the material. In addition, researchers use spray pyrolysis to synthesize ternary positive electrode materials, so that the mixing medium of impurities can be greatly reduced, and small liquid drops formed after atomizing a metal solution can lead the components of metal ions to be more uniform, but the materials prepared by the method have the defects of poor crystallinity and the like.
Therefore, the application provides a positive electrode material, which comprises a matrix and a coating layer coated on at least part of the surface of the matrix, wherein the chemical general formula of the matrix is shown as the formula (I):
Li a Ni x Co y M 1-x-y O 2 (Ⅰ)
in the formula (I), M comprises at least one of Mn and Al, a is more than or equal to 0.95 and less than or equal to 1.05,0.8 and x is more than or equal to 0.95, and y is more than or equal to 0.05 and less than or equal to 0.2;
the material of the coating layer comprises oxide, and the metal element in the oxide comprises at least one of W, al, co, zr, Y and Ti;
diffraction peak intensity ratio I between (001) plane and (101) plane in XRD pattern of positive electrode material 001 /Ⅰ 101 Less than or equal to 1.10; (003) Diffraction peak intensity ratio I between facets (104) 003 /Ⅰ 104 ≥1.70。
The nucleation rate k of the positive electrode material is more than or equal to 90%, wherein:
Figure SMS_2
in the formula (II), H β(300) Is a characteristic diffraction peak of beta crystal (300) crystal face of the positive electrode material in XRD patternStrength, H α(110) ，H α(040) And H α(130) The characteristic diffraction peak intensities of alpha crystal (110), (040) and (130) crystal faces of the positive electrode material in the XRD spectrum are respectively corresponding.
In the above scheme, the positive electrode material of the present application satisfies the following relationship as measured by XRD: i 001 /Ⅰ 101 ≤1.10，Ⅰ 003 /Ⅰ 104 Not less than 1.70, wherein I 001 /Ⅰ 101 Less than or equal to 1.10, the surface of the matrix of the positive electrode material has a more complete crystal structure, which is favorable for improving the cycle performance and capacity of the positive electrode material, and simultaneously, the more complete crystal structure is favorable for removing and inserting lithium ions and improving the multiplying power performance of the positive electrode material; i 003 /Ⅰ 104 More than or equal to 1.70, the positive electrode material has a good layered structure, and NiO rock salt is smaller, so that lithium nickel mixed discharge can be reduced, the impedance of the material is further reduced, the occurrence of interface side reaction is facilitated to be reduced, and the capacity and the multiplying power performance of the material are improved; the application positive electrode material still includes to cover the oxide coating who establishes at the base member surface, and the existence of oxide coating can reduce the production of material grain boundary crackle, improves the granule intensity of material, promotes positive electrode material's electrochemical performance, and the nucleation rate of this application can reach 90%, carries out lattice matching with low lattice spacing mismatch rate between the base member crystal to reduce the lithium nickel of material and mix the row degree, improve positive electrode material's multiplying power performance.
In the present application, I 001 /Ⅰ 101 Less than or equal to 1.10, exemplary, I 001 /Ⅰ 101 May be 1.00, 1.01, 1.03, 1.05, 1.07, 1.08, 1.10, etc., but may be other values within the above range, the application is not limited thereto, if I 001 /Ⅰ 101 If the ratio is greater than 1.10, the matrix can have more crystal defects, which is unfavorable for forming a complete crystal structure. I 003 /Ⅰ 104 1.70, exemplary, I 003 /Ⅰ 104 May be 1.70, 1.73, 1.75, 1.78, 1.80, etc., but may be other values within the above range, the application is not limited thereto, if I 003 /Ⅰ 104 Less than 1.70, willThe surface lithium nickel of the positive electrode material is seriously mixed and discharged, which is unfavorable for the formation of the layered structure material.
Specifically, the nucleation rate k of the positive electrode material may be, for example, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or the like, and may be any other value within the above range, and is not limited thereto. In the above range, the positive electrode material has higher nucleation rate, and the lattice spacing mismatch rate of the crystals in the material is smaller, so that the crystallization rate of the positive electrode material is improved, and the preparation period of the material is shortened.
In some embodiments, the oxide includes WO 3 、WO 2 、Al 2 O 3 、CoO、Co 2 O 4 、B 2 O 3 、ZrO 2 、Y 2 O 3 And TiO 2 At least one of them. Exemplary, WO 3 、WO 2 、CoO、Co 2 O 4 And B 2 O 3 The existence of the oxide coating layer can improve the capacity of the positive electrode material; al (Al) 2 O 3 And ZrO(s) 2 The existence of the oxide coating layer can improve the cycle performance of the material, Y 2 O 3 The presence of the oxide coating layer can reduce gas production and TiO 2 The existence of the oxide coating layer can solve the side reaction of free lithium on the surface of the positive electrode material.
In some embodiments, the thickness of the coating layer is 4nm to 11nm, specifically, the thickness of the coating layer is 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 11nm, etc., but other values within the above range are also possible, and the present invention is not limited thereto.
In some embodiments, ni in the surface layer of the positive electrode material 3+ Mass of Ni in positive electrode material 2+ And Ni 3+ The ratio of the total mass of the positive electrode material is more than or equal to 0.9, wherein the surface layer of the positive electrode material refers to a part of the surface of the positive electrode material extending to the inside of the positive electrode material by a thickness of 0 nm-20 nm. Exemplary, ni in the surface layer of the cathode material 3+ Mass of Ni in positive electrode material 2+ And Ni 3+ The ratio of the total mass of (C) may be 0.9, 0.92, 0.95, 0.96, 0.98 and 0.99And the like, but of course, other values within the above range are also possible, and are not limited thereto. Within the above limit, it is shown that Ni is present on the surface of the positive electrode material of the present application 3+ More Ni 3+ The existence of the catalyst can improve the crystal structure of the surface of the positive electrode material, further reduce the lithium nickel mixing degree, enhance the conductivity of the material and improve the cycle performance of the material.
In some embodiments, the median particle diameter of the positive electrode material is 3.5 μm to 4.5 μm, specifically, the median particle diameter of the positive electrode material is 3.5 μm, 3.7 μm, 3.9 μm, 40 μm, 4.3 μm, 4.5 μm, etc., but other values within the above range are also possible, and are not limited thereto.
In some embodiments, the specific surface area of the positive electrode material is 0.4m 2 /g～0.8m 2 Specific surface area of the positive electrode material may be 0.4m 2 /g、0.5m 2 /g、0.6m 2 /g、0.7m 2 /g and 0.8m 2 Of course, the values of the ratio/g and the like may be other values within the above-mentioned range, and are not limited thereto.
In some embodiments, the moisture content of the positive electrode material is 300ppm or less, specifically, the moisture content of the positive electrode material may be 50ppm, 100ppm, 150ppm, 200ppm, 250ppm, 300ppm, or the like, but other values within the above range are also possible, and are not limited thereto.
In some embodiments, the surface alkaline impurities of the positive electrode material are primarily Li 2 CO 3 And LiOH, li in the cathode material 2 CO 3 The mass content of (2) is 0.3% or less, specifically, li in the positive electrode material 2 CO 3 The mass content of (a) may be 0.05%, 0.1%, 0.2%, 0.3%, etc., but may be other values within the above range, and is not limited thereto.
In some embodiments, the mass content of LiOH in the positive electrode material is 0.4% or less, specifically, the mass content of LiOH in the positive electrode material may be 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, or the like, but may be other values within the above range, which is not limited thereto.
Li is mixed with 2 CO 3 And the mass content of LiOH in the positive electrode materialThe amount is controlled within the above range, which is advantageous for improving the processability of the positive electrode material and reducing the gas production of the battery prepared from the positive electrode material.
The embodiment of the application provides a preparation method of a positive electrode material, as shown in fig. 1, comprising the following steps:
heat treatment is carried out on a mixture containing a lithium source, a nickel source, a cobalt source, a metal source, a polyoxometallate and a beta nucleating agent to obtain a positive electrode material, wherein the metal source comprises at least one of a manganese source and an aluminum source, and the polyoxometallate comprises Na 5 CoW 12 O 40 、Na 5 BW 12 O 40 、Na 5 AlW 12 O 40 、Na 5 TiW 12 O 40 、Na 5 YW 12 O 40 And Na (Na) 5 ZrW 12 O 40 At least one of them.
In the scheme, the lithium source, the nickel source, the cobalt source and the metal source generate a precursor in the heat treatment process, the polyoxometalate is used as an oxidant, and a part of the polyoxometalate can be used for preparing Ni on the surface of the precursor in the heat treatment process 2+ Oxidation to generate NiOOH (the chemical valence of Ni in the NiOOH is +3), wherein the NiOOH can react with lithium element to generate lithium nickelate, so that crystal defects on the surface of the material can be eliminated, and the capacity, the multiplying power performance and the cycle performance of the positive electrode material are improved; the other part of polyoxometalate is reduced into corresponding oxide in the heat treatment process, and the polyoxometalate is coated on the surface of the matrix to form a coating layer, so that the generation of cracks of grain boundaries of the material can be reduced, the particle strength of the material is improved, and the electrochemical performance of the material is improved. According to the method, the polyoxometallate is used as the doping agent and the coating material to carry out double modification on the material through in-situ reaction and heat treatment, so that the electrochemical performance of the material can be improved. The heat treatment of the application is carried out by adopting spray pyrolysis equipment, namely, mixed solution containing lithium source, nickel source, cobalt source, metal source, polyoxometallate, dispersing agent, solvent and beta nucleating agent is sprayed into high-temperature atmosphere in a mist form, so that each material in the mixed solution is thermally decomposed, and then solid phase is separated out due to supersaturation, and in the process of spray pyrolysis treatment, as the travel of the spray pyrolysis equipment is shorter, And the temperature control precision is low, so that the lattice matching degree of the material in the heat treatment process is low, and the crystallinity of the prepared positive electrode material is low.
The following describes the preparation method of the present application in detail with reference to examples:
heat treatment is carried out on a mixture containing a lithium source, a nickel source, a cobalt source, a metal source, a polyoxometallate and a beta nucleating agent to obtain a positive electrode material, wherein the metal source comprises at least one of a manganese source and an aluminum source, and the polyoxometallate comprises Na 5 CoW 12 O 40 、Na 5 BW 12 O 40 、Na 5 AlW 12 O 40 、Na 5 TiW 12 O 40 、Na 5 YW 12 O 40 And Na (Na) 5 ZrW 12 O 40 At least one of them.
In some embodiments, the lithium source comprises at least one of lithium carbonate, lithium hydroxide, lithium acetate, lithium oxalate, lithium sulfate, lithium chloride, and lithium nitrate.
In some embodiments, the median particle diameter of the lithium source is 3 μm to 5 μm, and specifically, the median particle diameter of the lithium source may be 3 μm, 4 μm, 5 μm, etc., but may be other values within the above range, without limitation.
In some embodiments, the nickel source comprises at least one of nickel acid, nickel acetate, nickel oxalate, nickel nitrate, nickel chloride, and nickel nitrate.
In some embodiments, the median particle size of the nickel source is 3 μm to 5 μm, and specifically, the median particle size of the nickel source may be 3 μm, 4 μm, 5 μm, etc., but may be other values within the above range, without limitation.
In some embodiments, the cobalt source comprises at least one of cobalt carbonate, cobalt acetate, cobalt oxalate, cobalt sulfate, cobalt chloride, and cobalt nitrate.
In some embodiments, the median particle size of the cobalt source is 3 μm to 5 μm, and specifically, the median particle size of the cobalt source may be 3 μm, 4 μm, 5 μm, etc., but may be other values within the above range, and is not limited thereto.
In some embodiments, the manganese source comprises at least one of manganese carbonate, manganese acetate, manganese oxalate, manganese sulfate, manganese chloride, and manganese nitrate.
In some embodiments, the median particle size of the manganese source is 3 μm to 5 μm, and specifically, the median particle size of the manganese source may be 3 μm, 4 μm, 5 μm, etc., but may be other values within the above range, without limitation.
In some embodiments, the aluminum source comprises at least one of aluminum carbonate, aluminum acetate, aluminum oxalate, aluminum sulfate, aluminum chloride, and aluminum nitrate.
In some embodiments, the median particle diameter of the aluminum source is 3 μm to 5 μm, and specifically, the median particle diameter of the aluminum source may be 3 μm, 4 μm, 5 μm, etc., but may be other values within the above range, without limitation.
In some embodiments, the lithium source, nickel source, cobalt source, and metal source are added in a stoichiometric ratio as shown in the chemical formula: li (Li) a Ni x Co y M 1-x-y O 2 Wherein M is a metal source, a is more than or equal to 0.95 and less than or equal to 1.05,0.8, x is more than or equal to 0.95, and y is more than or equal to 0.05 and less than or equal to 0.2.
In some embodiments, the mass ratio of the polyoxometalate in the mixture is 1% -5%, specifically, the mass ratio of the polyoxometalate in the mixture may be 1%, 2%, 3%, 4% and 5%, and the like, and of course, other values within the above range may be also possible, where the mass ratio of the polyoxometalate is not limited herein, and if the mass ratio of the polyoxometalate is greater than 5%, the coating amount of oxide on the surface of the mixture is excessive, which negatively affects the electrochemical performance of the cathode material; if the mass ratio of the polyoxometalate is less than 1%, the precursor surface layer Ni 2+ Failure to fully oxidize to Ni 3+ The improvement of surface crystal structure defects is not obvious.
In some embodiments, a dispersant is also included in the mixture comprising the lithium source, the nickel source, the cobalt source, the metal source, and the polyoxometalate.
In some embodiments, the dispersing agent comprises at least one of polyethylene glycol-2000 and imidazole-based ionic liquids, although the dispersing agent may be any other conventional dispersing agent in the art, and the present application is not limited thereto.
In some embodiments, the mass ratio of the dispersant in the mixture is 0.1% to 0.3%, specifically, the mass ratio of the dispersant in the mixture may be, for example, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, etc., but may be other values within the above range, which is not limited thereto.
In some embodiments, the mixture containing the lithium source, the nickel source, the cobalt source, the metal source and the polyoxometallate further comprises a solvent, namely the positive electrode material is prepared by a wet process, specifically, the positive electrode material comprises the following steps:
mixing a lithium source, a nickel source, a cobalt source, a metal source, a polyoxometallate, a dispersing agent and a solvent, and then performing heat treatment to obtain the anode material.
In some embodiments, the solvent comprises at least one of water and ethanol.
In some embodiments, the solid content of the mixture is 20% -70%, specifically, the solid content of the mixture may be, for example, 20%, 30%, 40%, 50%, 60%, 70%, etc., and of course, other values within the above range may be used, which is not limited herein.
In some embodiments, the mixing is performed under ultrasonic agitation.
In some embodiments, the beta nucleating agent comprises at least one of benzene p-cyclohexylamide carboxylate, zinc adipate, supported calcium pimelate, zinc phthalate, and a liquid crystalline polyester, wherein the liquid crystalline polyester is a backbone liquid crystalline polyester.
In some embodiments, the β nucleating agent may be present in the mixture at a mass ratio of 0.05% to 0.5%, specifically, the β nucleating agent may be present in the mixture at a mass ratio of 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, etc., although other values within the above range are also possible, and the present invention is not limited thereto. If the mass ratio of the beta nucleating agent in the mixture is less than 0.05%, the addition amount is too small to effectively improve the nucleation rate of the material; if the mass ratio of the beta nucleating agent in the mixture is more than 0.5%, the material nucleating efficiency is not obviously improved, and the cost is increased.
In some embodiments, the sample injection rate of the spray pyrolysis apparatus is 20mL/min to 80mL/min, specifically, the sample injection rate of the spray pyrolysis apparatus may be, for example, 20mL/min, 30mL/min, 40mL/min, 50mL/min, 60mL/min, 70mL/min, 80mL/min, etc., and of course, other values within the above range may be also used, which is not limited herein.
In some embodiments, the heat treatment is performed in an air or oxygen atmosphere.
In some embodiments, the temperature of the heat treatment is 500 ℃ to 800 ℃, specifically, the temperature of the heat treatment may be, for example, 500 ℃, 550 ℃, 600 ℃, 650 ℃, 700 ℃, 750 ℃, 800 ℃, etc., but may also be other values within the above range, without limitation. In the temperature range, the polyoxometalate oxidizes the precursor to ensure that Ni on the surface of the precursor 2+ Oxidation to Ni 3+ The surface of the precursor is subjected to structural recombination, and the crystallization defect on the surface of the material is eliminated.
In some embodiments, the heating rate of the heat treatment is 1 ℃/min to 5 ℃/min, specifically, the heating rate of the heat treatment may be, for example, 1 ℃/mi, 2 ℃/mi, 3 ℃/mi, 4 ℃/mi, 5 ℃/mi, and the like, and other values within the above range are of course also possible, and the present invention is not limited thereto.
The embodiment of the application also provides a lithium ion battery, which comprises a positive electrode plate, a negative electrode plate, a diaphragm, nonaqueous electrolyte and a shell, wherein the positive electrode plate comprises a current collector and the positive electrode material coated on the current collector or prepared by the preparation method of the positive electrode material.
In some embodiments, a positive electrode slurry containing a material (positive electrode material of the present invention), a conductive agent, a binder, and NMP is prepared, and the positive electrode mixture is supported on a positive electrode current collector, whereby a positive electrode sheet of a secondary battery can be manufactured.
The embodiments of the present invention have been described, but the present invention is not limited to these examples as long as the gist of the present invention is not exceeded.
Example 1
(1) According to stoichiometric ratio LiNi 0.8 Co 0.1 Mn 0.1 O 2 21.20g of lithium chloride, 129.60g of nickel chloride, 129.84g of cobalt chloride, 125.84g of manganese chloride and 2.60g of Na are weighed 5 CoW 12 O 40 0.20g of benzene p-cyclohexylamide carboxylate and 0.41g of polyethylene glycol-2000.
(2) And (3) putting the mixture into a reaction kettle, adding 1000mL of deionized water, ultrasonically stirring for 3 hours, and then pumping the mixture into spray pyrolysis equipment by a peristaltic pump to react to obtain the ternary cathode material, wherein the pyrolysis temperature is 700 ℃, and the feeding rate is 20mL/min.
The positive electrode material prepared by the application comprises LiNi 0.8 Co 0.1 Mn 0.1 O 2 Base body and coating layer on LiNi 0.8 Co 0.1 Mn 0.1 O 2 Coating layer on the surface of the substrate, wherein the material of the coating layer comprises CoO and WO 2 And WO 3 。
Example 2
(1) According to stoichiometric ratio LiNi 0.8 Co 0.1 Mn 0.1 O 2 21.20g of lithium chloride, 129.60g of nickel chloride, 129.84g of cobalt chloride, 125.84g of manganese chloride and 2.60g of Na are weighed 5 CoW 12 O 40 0.41g of zinc adipate and 0.41g of polyethylene glycol-2000, to give a mixture.
(2) And (3) putting the mixture into a reaction kettle, adding 1000mL of deionized water, ultrasonically stirring for 3 hours, and then pumping the mixture into spray pyrolysis equipment by a peristaltic pump to react to obtain the ternary cathode material, wherein the pyrolysis temperature is 700 ℃, and the feeding rate is 20mL/min.
The positive electrode material prepared by the application comprises LiNi 0.8 Co 0.1 Mn 0.1 O 2 Base body and coating layer on LiNi 0.8 Co 0.1 Mn 0.1 O 2 Coating layer on the surface of the substrate, wherein the material of the coating layer comprises CoO and WO 2 And WO 3 。
Example 3
(1) According to stoichiometric ratio Li 1.05 Ni 0.85 Co 0.05 Mn 0.1 O 2 21.20g of lithium chloride, 129.60g of nickel chloride, 129.84g of cobalt chloride, 125.84g of manganese chloride and 2.60g of Na are weighed 5 CoW 12 O 40 0.82g of zinc phthalate and 0.41g of polyethylene glycol-2000, to give a mixture.
(2) And (3) putting the mixture into a reaction kettle, adding 1000mL of deionized water, ultrasonically stirring for 3 hours, and then pumping the mixture into spray pyrolysis equipment by a peristaltic pump to react to obtain the ternary cathode material, wherein the pyrolysis temperature is 700 ℃, and the feeding rate is 20mL/min.
The positive electrode material prepared by the application comprises LiNi 0.8 Co 0.1 Mn 0.1 O 2 Base body and coating layer on LiNi 0.8 Co 0.1 Mn 0.1 O 2 Coating layer on the surface of the substrate, wherein the material of the coating layer comprises CoO and WO 2 And WO 3 。
Example 4
Unlike example 1, the amount of benzene p-cyclohexylamide carboxylic acid added in step (1) was 2.05g.
The positive electrode material prepared by the application comprises LiNi 0.8 Co 0.1 Mn 0.1 O 2 Base body and coating layer on LiNi 0.8 Co 0.1 Mn 0.1 O 2 Coating layer on the surface of the substrate, wherein the material of the coating layer comprises CoO and WO 2 And WO 3 。
Example 5
Unlike example 1, na in step (1) was added 5 CoW 12 O 40 The substitution is as follows: na (Na) 5 BW 12 O 40 。
The positive electrode material prepared by the application comprises LiNi 0.8 Co 0.1 Mn 0.1 O 2 Base body and coating layer on LiNi 0.8 Co 0.1 Mn 0.1 O 2 A coating layer on the surface of the substrate, wherein the material of the coating layer comprises B 2 O 3 、WO 2 And WO 3 。
Example 6
Unlike example 1, the procedure was followed(1) Middle Na 5 CoW 12 O 40 The substitution is as follows: na (Na) 5 AlW 12 O 40 。
The positive electrode material prepared by the application comprises LiNi 0.8 Co 0.1 Mn 0.1 O 2 Base body and coating layer on LiNi 0.8 Co 0.1 Mn 0.1 O 2 Coating layer on the surface of the substrate, wherein the material of the coating layer comprises Al 2 O 3 、WO 2 And WO 3 。
Example 7
(1) According to stoichiometric ratio LiNi 0.8 Co 0.1 Mn 0.1 O 2 21.20g of lithium chloride, 129.60g of nickel chloride, 129.84g of cobalt chloride, 125.84g of manganese chloride and 2.60g of Na are weighed 5 CoW 12 O 40 And 0.41g of polyethylene glycol-2000, to obtain a mixture.
(2) And (3) putting the mixture into a reaction kettle, adding 1000mL of deionized water, ultrasonically stirring for 3 hours, and then pumping the mixture into spray pyrolysis equipment by a peristaltic pump to react to obtain the ternary cathode material, wherein the pyrolysis temperature is 700 ℃, and the feeding rate is 20mL/min.
The positive electrode material prepared by the application comprises LiNi 0.8 Co 0.1 Mn 0.1 O 2 Base body and coating layer on LiNi 0.8 Co 0.1 Mn 0.1 O 2 Coating layer on the surface of the substrate, wherein the material of the coating layer comprises CoO and WO 2 And WO 3 。
Comparative example 1
(1) According to stoichiometric ratio LiNi 0.8 Co 0.1 Mn 0.05 Mg 0.05 O 2 21.20g of lithium chloride, 129.60g of nickel chloride, 129.84g of cobalt chloride, 125.84g of manganese chloride, 0.15g of cobalt oxide, 0.20g of tungsten oxide and 0.41g of polyethylene glycol-2000 were weighed out to obtain a mixture.
(2) And (3) putting the mixture into a reaction kettle, adding 1000mL of deionized water, ultrasonically stirring for 3 hours, and then pumping the mixture into spray pyrolysis equipment by a peristaltic pump to react to obtain the ternary cathode material, wherein the pyrolysis temperature is 700 ℃, and the feeding rate is 20mL/min.
Comparative example 2
(1) According to stoichiometric ratio LiNi 0.8 Co 0.1 Mn 0.1 O 2 21.20g of lithium chloride, 129.60g of nickel chloride, 129.84g of cobalt chloride, 125.84g of manganese chloride, 0.20g of benzene p-cyclohexylamide carboxylate and 0.41g of polyethylene glycol-2000 were weighed out to obtain a mixture.
(2) And (3) putting the materials into a reaction kettle, adding 1000mL of deionized water, ultrasonically stirring for 3 hours, and then pumping the materials into spray pyrolysis equipment by a peristaltic pump to react to obtain the ternary anode material, wherein the pyrolysis temperature is 700 ℃, and the feeding rate is 20mL/min.
Comparative example 3
(1) According to stoichiometric ratio LiNi 0.8 Co 0.1 Mn 0.1 O 2 21.20g of lithium chloride, 129.60g of nickel chloride, 129.84g of cobalt chloride, 125.84g of manganese chloride, 2.94g of potassium dichromate and 0.41g of polyethylene glycol-2000 are weighed out to obtain a mixture.
(2) And (3) putting the mixture into a reaction kettle, adding 1000mL of deionized water, ultrasonically stirring for 3 hours, and then pumping the mixture into spray pyrolysis equipment by a peristaltic pump to react to obtain the ternary cathode material, wherein the pyrolysis temperature is 700 ℃, and the feeding rate is 20mL/min.
Comparative example 4
(1) According to stoichiometric ratio LiNi 0.8 Co 0.1 Mn 0.1 O 2 21.20g of lithium chloride, 129.60g of nickel chloride, 129.84g of cobalt chloride, 125.84g of manganese chloride, 18.70g of nano titanium dioxide and 0.41g of polyethylene glycol-2000 are weighed out to obtain a mixture.
(2) And (3) putting the mixture into a reaction kettle, adding 1000mL of deionized water, ultrasonically stirring for 3 hours, and then pumping the mixture into spray pyrolysis equipment by a peristaltic pump to react to obtain the ternary cathode material, wherein the pyrolysis temperature is 700 ℃, and the feeding rate is 20mL/min.
Performance test:
(1) DSC test method of material: the sample is firstly heated to 300 ℃ at a speed of 10 ℃/min at a constant temperature of 50 ℃ for 2min, the heat history is eliminated after the sample is kept at the constant temperature of 300 ℃ for 5min, then the temperature is reduced to 50 ℃ at a speed of 10 ℃/min, the crystallization curve of the sample is obtained, finally the sample is kept at the constant temperature of 50 ℃ for 2min, the temperature is heated to 300 ℃ at a speed of 10 ℃/min, and the melting curve of the sample is recorded.
(2) Nucleation rate test of materials: adopting an X-ray powder diffractometer for characterization, wherein the scanning speed is 10 degrees/min, and the 2 theta angle testing range is 10-70 degrees; calculating the nucleation rate k of the material according to a Turner-Jones formula;
Figure SMS_3
wherein H is β(300) Characteristic diffraction peak intensity of beta crystal (300) crystal face, H α(110) ，H α(040) And H α(130) The characteristic diffraction peak intensities of the alpha crystal (110), (040) and (130) crystal faces are respectively corresponding.
(3) Ni on surface layer of positive electrode material 3+ Content of Ni in cathode material 2+ And Ni 3+ The content was tested using XPS.
(4) Median particle size of material: an appropriate amount of sample was taken and added to a 100ml beaker, three drops of 3% sodium hexametaphosphate reagent were added, and then 20ml water was added. The beaker was placed in an ultrasonic apparatus and stirred ultrasonically for 30s. Adding the prepared sample into a dispersing cup of the instrument, and keeping the added sample to enable the shading degree of the instrument to be 8-12%. Clicking to start measurement, waiting for the test to finish, and recording data.
(5) Specific surface area test of the material: and weighing the sample, placing the sample in a cleaned and dried sample tube, and assembling the sample bubble tube after degassing treatment. After the assembled sample bubble tube is placed on a corresponding analysis station, liquid nitrogen is added into the Dewar flask, then the Dewar flask is placed on a lifting table, a cabin door is closed, and test software is opened for analysis.
(6) Moisture test of materials: accurately adding 1g of sample (accurate to 0.0001 g) into a clean and dried sample bottle, and recording sample quality data after the value is stable. The weighed sample was capped with a rubber cap. Manufacturing two empty bottles, and sequentially placing the empty bottles on a rotary table of a sample converter of a Stromboli karst furnace to drift the positions of the bottles and blank bottles; the sample bottles were placed sequentially behind the blank bottles. Clicking to start measurement, waiting for the test to finish, and recording data.
(7) The buckling test method of the material comprises the following steps: weighing 0.8g of material, 0.1g of conductive carbon black and 0.1g of polyvinylidene fluoride into ballsAnd (3) adding 15mL of N-methyl pyrrolidone into a grinding tank, ball-milling to form uniform slurry, uniformly coating the slurry on aluminum foil, and vacuum-drying at 80 ℃ for 12 hours to obtain the positive electrode plate. The pole pieces were clamped into 12mm discs using a tablet press and were then placed in a glove box (H 2 O、O 2 Less than 0.1 ppm), the 2016 battery is assembled, the positive pole piece is taken as the positive pole, the metal lithium piece is taken as the counter electrode, the diaphragm is a PP diaphragm, and the electrolyte is 1M LiPF 6 EC: DEC (1:1). The assembled cell was allowed to stand for 12 hours and then tested for electrochemical performance (voltage interval 3-4.3V, temperature 25 ℃) on a blue electrical system.
The test results are shown in tables 1 and 2.
TABLE 1 Performance parameters of the cathode materials prepared in examples and comparative examples
Figure SMS_4
TABLE 2 electrochemical Performance test of the cathode materials prepared in examples and comparative examples
Figure SMS_5
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Figure SMS_6
From the data in tables 1 and 2, it can be seen that: the positive electrode materials prepared in examples 1 to 7 of the present application satisfy the following relationship as measured by XRD: i 001 /Ⅰ 101 ≤1.10，Ⅰ 003 /Ⅰ 104 More than or equal to 1.70, the surface of the prepared precursor has a relatively complete crystal structure, which is beneficial to the deintercalation of lithium ions and improves the multiplying power performance of the material; the anode material has a layered structure, which is beneficial to reducing the lithium nickel mixed discharge of cations on the surface of the material and reducing the occurrence of interface side reaction, thereby improving the capacity of the material; the application positive electrode material further comprises an oxide coating layer which is coated on the surface of the substrate, so that the generation of material grain boundary cracks can be reduced, the particle strength of the material is improved, and the electrochemical performance of the material is improved.
Example 1 in comparison with comparative example 1, comparative example 1 is a positive electrode material prepared without the polyoxometallate and nucleating agent of the present application, as can be seen from the data of table 2: the electrochemical performance of the example 1 is obviously better than that of the comparative example 1, and the electrochemical performance of the material is obviously improved after the precursor generated by the lithium source, the nickel source, the cobalt source and the metal source is pre-oxidized by the polyoxometallate, so that the capacity and the cycle efficiency after modification are obviously improved. The materials prepared in example 1 and comparative example 1 are shown in the graph of fig. 2, and as can be seen from fig. 2: the rate performance of the positive electrode material of the embodiment 1 of the application is obviously better than that of the positive electrode material prepared in the comparative example 1.
The XRD data for example 1 and comparative example 1 are shown in Table 1, and it can be seen that the polyoxometalate of example 1 is subjected to a thermal oxidation treatment to give a material I as compared with the XRD data for comparative example 1 001 /Ⅰ 101 The peak intensity ratio is reduced, which indicates that the heat treatment generates beta-NiOOH on the surface of the material; i 003 /Ⅰ 104 The ratio becomes larger, which shows that the cation mixing degree of the crystal structure of the surface layer of the material is reduced, in addition, the nucleation rate of the material of comparative example 1 is 70.3%, the nucleation rate of the material of example 1 is 90.8%, and shows that the p-cyclohexylamide carboxylic acid benzene nucleating agent of example 1 can obviously improve the heterogeneous nucleation efficiency of the material; therefore, the lithium nickel mixed discharge degree of the modified material in the embodiment 1 of the application is obviously reduced, the nucleation rate is obviously improved, and the electrochemical performance is improved.
Fig. 3 is an SEM image of the material prepared in example 1 and comparative example 1, fig. 3 (a) is an SEM image of the material of example 1, and fig. 3 (b) is an SEM image of the material of comparative example 1, and it can be seen from fig. 3 (a) and 3 (b) that the surface coating of the material prepared in example 1 is more uniform than that of the positive electrode material prepared in comparative example 1.
The DSC melting curves of the positive electrode materials prepared in example 1 and comparative example 1 are shown in FIG. 4, and it can be seen from FIG. 4 that example 1 shows characteristic melting peaks of beta crystal form at about 150 ℃, which indicates that p-cyclohexylamide carboxylic acid benzene is an effective beta nucleating agent and can induce the formation of beta crystal.
The nucleating agent is added in comparative example 2, but the crystal structure of the surface of the material cannot be improved without adding polyoxometallate, so that the capacity, the first efficiency and the rate capability of the prepared positive electrode material are low.
In comparative example 3, no nucleating agent was added, and a potassium dichromate oxidant was added to prepare a positive electrode material, which failed to form a relatively complete surface lattice structure, and the crystallinity of the material was low, so that the capacity, first efficiency and rate performance of the prepared positive electrode material were low.
In comparative example 4, polyoxometallate is not added, and nano titanium dioxide nucleating agent is added to prepare a positive electrode material, so that a relatively complete surface lattice structure cannot be formed, and the crystallinity of the material is low, so that the capacity, the first efficiency and the rate capability of the prepared positive electrode material are low.
The foregoing description is only of the preferred embodiments of the present application and is not intended to limit the same, but rather, various modifications and variations may be made by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims (10)

1. The positive electrode material is characterized by comprising a matrix and a coating layer coated on at least part of the surface of the matrix, wherein the chemical general formula of the matrix is shown in the formula (I):
Li a Ni x Co y M 1-x-y O 2 (Ⅰ)
in the formula (I), M comprises at least one of Mn and Al, a is more than or equal to 0.95 and less than or equal to 1.05,0.8 and x is more than or equal to 0.95, and y is more than or equal to 0.05 and less than or equal to 0.2;
the material of the coating layer comprises metal oxide, and the metal element in the metal oxide comprises at least one of W, al, co, zr, Y and Ti;
in the XRD pattern of the positive electrode material, the diffraction peak intensity ratio I between the (001) plane and the (101) plane 001 /Ⅰ 101 Less than or equal to 1.10; (003) Diffraction peak intensity ratio I between facets (104) 003 /Ⅰ 104 ≥1.70；
The nucleation rate k of the positive electrode material is more than or equal to 90%, wherein:
Figure FDA0004012561980000011
in the formula (II), H β(300) Is the characteristic diffraction peak intensity of beta crystal (300) crystal face of the positive electrode material in XRD pattern, H α(110) ，H α(040) And H α(130) The characteristic diffraction peak intensities of alpha crystal (110), (040) and (130) crystal faces of the positive electrode material in an XRD spectrum are respectively corresponding.
2. The positive electrode material according to claim 1, characterized in that the material comprises at least one of the following features (1) to (3):
(1) The metal oxide comprises WO 3 、WO 2 、Al 2 O 3 、CoO、Co 2 O 4 、B 2 O 3 、ZrO 2 、Y 2 O 3 And TiO 2 At least one of (a) and (b);
(2) The thickness of the coating layer is 4 nm-11 nm;
(3) Ni in the surface layer of the positive electrode material 3+ Mass of (c) and Ni in the positive electrode material 2+ And Ni 3+ The ratio of the total mass of the positive electrode material to the total mass of the positive electrode material is more than or equal to 0.9, wherein the surface layer of the positive electrode material refers to a part of the surface of the positive electrode material extending to the inside of the positive electrode material by a thickness of 0 nm-20 nm.
3. The positive electrode material according to claim 1, characterized in that the positive electrode material comprises at least one of the following features (1) to (5):
(1) The median particle diameter of the positive electrode material is 3.5-4.5 mu m;
(2) The specific surface area of the positive electrode material is 0.4m 2 /g～0.8m 2 /g；
(3) The moisture content of the positive electrode material is less than or equal to 300ppm;
(4) Li in the positive electrode material 2 CO 3 The mass content of (2) is less than or equal toAt 0.3%;
(5) The mass content of LiOH in the positive electrode material is less than or equal to 0.4%.
4. The preparation method of the positive electrode material is characterized by comprising the following steps:
Performing heat treatment on a mixture containing a lithium source, a nickel source, a cobalt source, a metal source, a polyoxometallate and a beta nucleating agent to obtain a positive electrode material, wherein the metal source comprises at least one of a manganese source and an aluminum source, and the polyoxometallate comprises Na 5 CoW 12 O 40 、Na 5 BW 12 O 40 、Na 5 AlW 12 O 40 、Na 5 TiW 12 O 40 、Na 5 YW 12 O 40 And Na (Na) 5 ZrW 12 O 40 At least one of them.
5. The method according to claim 4, wherein the method comprises at least one of the following features (1) to (12):
(1) The lithium source comprises at least one of lithium carbonate, lithium hydroxide, lithium acetate, lithium oxalate, lithium sulfate, lithium chloride and lithium nitrate;
(2) The median particle diameter of the lithium source is 3-5 mu m;
(3) The nickel source comprises at least one of nickel acid, nickel acetate, nickel oxalate, nickel nitrate, nickel chloride and nickel nitrate;
(4) The median particle diameter of the nickel source is 3-5 mu m;
(5) The cobalt source comprises at least one of cobalt carbonate, cobalt acetate, cobalt oxalate, cobalt sulfate, cobalt chloride and cobalt nitrate;
(6) The median particle diameter of the cobalt source is 3-5 mu m;
(7) The manganese source comprises at least one of manganese carbonate, manganese acetate, manganese oxalate, manganese sulfate, manganese chloride and manganese nitrate;
(8) The median particle diameter of the manganese source is 3-5 mu m;
(9) The aluminum source comprises at least one of aluminum carbonate, aluminum acetate, aluminum oxalate, aluminum sulfate, aluminum chloride and aluminum nitrate;
(10) The median particle diameter of the aluminum source is 3-5 mu m;
(11) The lithium source, the nickel source, the cobalt source and the metal source are added according to the metering ratio shown in the following chemical formula:
Li a Ni x Co y M 1-x-y O 2 wherein M is a metal source, a is more than or equal to 0.95 and less than or equal to 1.05,0.8, x is more than or equal to 0.95, and y is more than or equal to 0.05 and less than or equal to 0.2;
(12) The mass ratio of the polyoxometallate in the mixture is 1-5%.
6. The method according to claim 4, wherein the method comprises at least one of the following features (1) to (6):
(1) The mixture containing a lithium source, a nickel source, a cobalt source, a metal source and polyoxometalate also comprises a dispersing agent;
(2) The mixture containing a lithium source, a nickel source, a cobalt source, a metal source and polyoxometallate also comprises a dispersing agent, wherein the dispersing agent comprises at least one of polyethylene glycol-2000 and imidazole ionic liquid;
(3) The mixed material containing the lithium source, the nickel source, the cobalt source, the metal source and the polyoxometallate also comprises a dispersing agent, wherein the mass ratio of the dispersing agent in the mixed material is 0.1-0.3%;
(4) The mixture containing a lithium source, a nickel source, a cobalt source, a metal source, polyoxometallate and a beta nucleating agent also comprises a solvent;
(5) The mixture containing a lithium source, a nickel source, a cobalt source, a metal source, a polyoxometallate and a beta nucleating agent also comprises a solvent, wherein the solvent comprises at least one of water and ethanol;
(6) The mixed material containing the lithium source, the nickel source, the cobalt source, the metal source, the polyoxometallate and the beta nucleating agent also comprises a solvent, and the solid content of the mixed material is 20-70%.
7. The method of claim 4, wherein the beta nucleating agent comprises at least one of benzene p-cyclohexylamide carboxylate, zinc adipate, supported calcium pimelate, zinc phthalate, and liquid crystalline polyesters.
8. The preparation method according to claim 4, wherein the mass ratio of the beta nucleating agent in the mixture is 0.05% -0.5%.
9. The method according to claim 4, wherein the method comprises at least one of the following features (1) to (3):
(1) The heat treatment is performed in an air or oxygen atmosphere;
(2) The temperature of the heat treatment is 500-800 ℃;
(3) The feeding rate of the mixture containing the lithium source, the nickel source, the cobalt source, the metal source and the polyoxometallate is 20-80 mL/min.
10. A lithium ion battery, characterized in that the lithium ion battery comprises the positive electrode material according to any one of claims 1 to 3 or the positive electrode material prepared by the preparation method according to any one of claims 4 to 9.
CN202211658413.XA 2022-12-22 2022-12-22 Positive electrode material, preparation method thereof and lithium ion battery Pending CN116230880A (en)

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