CN111490241A - Lithium phosphate in-situ coated lithium-rich manganese-based positive electrode material and preparation method thereof - Google Patents

Lithium phosphate in-situ coated lithium-rich manganese-based positive electrode material and preparation method thereof Download PDF

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CN111490241A
CN111490241A CN202010301667.0A CN202010301667A CN111490241A CN 111490241 A CN111490241 A CN 111490241A CN 202010301667 A CN202010301667 A CN 202010301667A CN 111490241 A CN111490241 A CN 111490241A
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lithium
phosphate
rich manganese
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程方益
刘九鼎
刘芳名
李海霞
严振华
陈军
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Nankai University
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    • H01M4/50Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
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    • H01M4/525Selection 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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Abstract

Lithium phosphate in-situ coated lithium-rich manganese-based positive electrode material and preparation method thereof, wherein the chemical formula of the material is x L i2MnO3·(1‑x)LiMO2@Li3PO4Wherein x is more than or equal to 0.3 and less than or equal to 0.7, M is Ni or at least one of Ni, Co and Mn, and the mass fraction of lithium phosphate is 0.1-5%. The preparation method comprises the steps of adding a mixed solution of ammonia water and sodium carbonate and a mixed solution of nickel, cobalt and manganese into a reaction kettle in a concurrent flow manner, and carrying out coprecipitation reaction to obtain a precursor. Adding the precursor into a solution containing phosphate ions, stirring, precipitating, converting, filtering, washing and drying, and mixing with lithiumAnd mixing the sources, and calcining in an air atmosphere to obtain the lithium phosphate coated lithium-rich manganese-based positive electrode material. According to the invention, the lithium phosphate in-situ coating modification of the lithium-rich manganese-based anode material in the calcining process is realized by a precursor precipitation conversion method, the coating process is simplified, the cycle life and the rate capability of the lithium-rich manganese-based material are improved, and the lithium-rich manganese-based anode material has a prospect of large-scale production and application.

Description

Lithium phosphate in-situ coated lithium-rich manganese-based positive electrode material and preparation method thereof
Technical Field
The invention belongs to the technical field of lithium ion battery anode materials, and particularly relates to a lithium-rich manganese-based anode material precursor and a preparation method of a lithium phosphate-coated anode material.
Background
In recent years, with the rapid development of mobile devices such as mobile phones and tablet computers and electric automobiles, people have made demands on lithium ion batteries such as higher specific capacity, higher energy density, longer service life and lower cost2、LiFePO4、LiMn2O4And L iNi1-x-yCoxMnyO2The limited specific capacity is a bottleneck for limiting the further development of the lithium ion battery, and the lithium-rich manganese-based material (x L i)2MnO3·(1-x)LiMO2M ═ Mn, Co, Ni, etc.) has a g of more than 250mAh-1And the specific capacity and the theoretical energy density of nearly 1000Wh/kg, and the low cost of the main element component, namely manganese, attract the attention of many researchers and are considered to be the most promising next-generation high-specific-energy lithium ion battery cathode material. However, the lithium-rich manganese-based material has the problems of low coulombic efficiency in the first cycle, serious capacity and voltage attenuation, poor rate capability and the like, and practical application of the lithium-rich manganese-based material is restricted.
The main reasons for the problems of low coulombic efficiency and voltage attenuation in the first cycle are the side reaction between the surface of the positive electrode material and the electrolyte during charging and discharging and the dissolution of the transition metal element in the material, and in order to solve the problems, a cladding strategy is often adopted to improve the stability of the material. For example, chinese patent No. CN 110364713 a discloses a method for preparing a composite conductive agent coated single crystal lithium-rich manganese-based positive electrode material, in which graphene, carbon nanotubes and conductive carbon black are dispersed on the surface of a lithium-rich material by liquid phase ultrasound, and further sintered to obtain the composite conductive agent coated single crystal lithium-rich manganese-based positive electrode material, and a good conductive network enables the material to have good electrochemical properties. Chinese patent No. CN 110890541 a discloses a method for preparing a surface-modified lithium-rich manganese-based positive electrode material, in which a coating solution such as hydrogen phosphate, pyrophosphate, and meta-aluminate is used to treat a lithium-rich material, and a material coated with a fast ion conductor is obtained by subsequent sintering.
However, the current cladding process still has drawbacks. The preparation of the lithium-rich manganese-based material is divided into two steps of precursor synthesis and high-temperature calcination, the precursor is stable in property and easy to store, and the lithium-rich manganese-based material obtained by sintering is sensitive to conditions such as environmental humidity, atmosphere and the like. In a common strategy based on coating after preparation, a lithium-rich manganese-based material is generally required to be placed in an aqueous solution for treatment, the surface structure of the material is easily damaged, such as lithium ion loss, hydrogen ion intercalation, surface layer structure phase change and the like, so that secondary calcination is required to improve the crystallinity of the material, and the secondary high-temperature heating process generates energy consumption and additionally increases the complexity of the process. In order to avoid the coating treatment after the synthesis of the lithium-rich manganese-based material, the development of the in-situ uniform coating technology of the precursor is a necessary and challenging subject, and has important significance for simplifying the process flow, enhancing the preparation controllability and reducing the production cost.
Disclosure of Invention
The invention aims to solve the technical problems of low first-cycle coulombic efficiency, serious capacity and voltage attenuation, poor rate capability and the like of a lithium-rich manganese-based material, provides a strategy for coating the lithium-rich manganese-based anode material by using lithium phosphate, and adopts a simple precursor precipitation conversion in-situ coating technology, so that the high-efficiency, uniform and stable coating in the synthesis process of the lithium-rich manganese-based material is realized, and the first-cycle coulombic efficiency, the cycle performance and the rate capability of the material are improved. The method has the advantages of obvious modification effect, low cost and simple and convenient operation, and is suitable for large-scale production.
The technical scheme of the invention is as follows:
lithium phosphate in-situ coated lithium-rich manganese-based positive electrodeMaterial of the formula composition x L i2MnO3·(1-x)LiMO2@Li3PO4Wherein x is more than or equal to 0.3 and less than or equal to 0.7, M is Ni or at least one of Ni, Co and Mn, the mass fraction of lithium phosphate is 0.1-5%, and the thickness of the coating layer is less than 30 nm.
The preparation method of the lithium-rich manganese-based positive electrode material coated with lithium phosphate in situ comprises the following steps:
firstly, preparing a salt solution A with metal ion concentration of 1-5 mol/L, a mixed solution B with 0.5-2 mol/L of sodium carbonate and 0.05-5 mol/L of ammonia water and a soluble phosphate solution C with concentration of 0.01-0.5 mol/L from one or more of nickel soluble salt, cobalt soluble salt and manganese soluble salt according to the stoichiometric ratio in the chemical formula;
step two: adding deionized water into a reaction kettle, adding the solution A and the solution B into the reaction kettle in a concurrent flow manner, mechanically stirring for reaction, controlling the temperature of a reaction solution to be constant, and controlling the pH to be constant by adjusting the flow rate of the solution B; after the reaction is finished, filtering, washing and vacuum drying the obtained precipitate to obtain the lithium-rich manganese-based material precursor TMCO3TM is a transition metal;
step three: subjecting the obtained precursor TMCO3Dispersing in the solution C, stirring at normal temperature for reaction, filtering, washing and drying in vacuum to obtain a precursor coated by nickel phosphate;
step four: and D, uniformly mixing the precursor coated with the nickel phosphate obtained in the step three and a lithium source according to the stoichiometric excess of 0-10% (preferably 5%) of lithium, and calcining in an air atmosphere according to a set heating program to obtain the lithium phosphate in-situ coated lithium-rich manganese-based positive electrode material.
Further, in the first step, the soluble metal salt is one or more of sulfate, nitrate and chloride, the total metal concentration is 1-5 mol/L, preferably 2 mol/L, the sodium carbonate concentration is 0.5-5 mol/L, preferably 2 mol/L, the ammonia water concentration is 0.05-5 mol/L, preferably 0.5 mol/L, and the soluble phosphate is one or more of lithium, sodium, potassium and ammonium phosphate, hydrogen phosphate and dihydrogen phosphate, and the concentration is 0.01-0.5 mol/L, preferably 0.1 mol/L.
Further, in the second step, the metal salt solution A is injected into the reaction kettle at a constant speed of 1-2m L/min, the solution B is injected into the reaction kettle at a speed of 0.5-2.5m L/min, the pH of the reaction kettle is controlled to be 7.3-8.3, preferably 7.8, the mechanical stirring speed is 300-900rpm/min, preferably 800rpm/min, the reaction temperature of the reaction kettle is 40-70 ℃, preferably 55 ℃, and the reaction time is 10-40 h.
Further, the precursor TMCO in the third step3The reaction time in the soluble phosphate solution C is 1min-24h, preferably 40 min.
Furthermore, the dosage ratio of the lithium source in the fourth step is 100-110% of the stoichiometric ratio, preferably 105% of the stoichiometric ratio, the lithium source is L iOH and L i2CO3Preferably L i, preferably2CO3
Further, the calcination procedure in the fourth step is to firstly preserve heat at 550 ℃ for 4-6h, preferably at 500 ℃ for 5h, and then raise the temperature to 900 ℃ for sintering at 750 ℃ for 10-25h, preferably at 800 ℃ for sintering for 20h, in an air atmosphere.
The invention has the advantages and effects that:
1. different from coating after material synthesis, the method carries out coating treatment on the lithium-rich manganese-based material precursor, so that the lithium phosphate coated lithium-rich manganese-based material can be generated by subsequent calcining, the lithium-rich material which is relatively sensitive to water washing in the traditional liquid phase coating process and the secondary calcining process are avoided, and the process flow is simplified.
2. The coating process of the precursor is based on the precipitation conversion reaction of insoluble salt, the surface of the carbonate precursor can be converted into a coating layer in situ, the solid-liquid reaction ensures the uniformity of coating, the operation is convenient, and the scale-up production is facilitated.
3. The lithium phosphate has a stable crystal structure and certain lithium ion conductivity, and the coating layer can reduce surface side reactions and simultaneously cannot block the transmission of lithium ions, so that the first-turn coulomb efficiency, the capacity retention rate and the rate capability of the material can be improved.
4. The prepared lithium phosphate in-situ coated lithium-rich manganese-based positive electrode material has a micron-sized spherical shape, is high in tap density and is convenient to process and apply.
Drawings
Fig. 1 is a schematic flow chart of a preparation process of the lithium phosphate coated lithium-rich manganese-based positive electrode material provided by the invention.
Fig. 2 is SEM images of the nickel phosphate coated carbonate precursor of example 3 and the carbonate precursor of the comparative example.
Fig. 3 is TEM images of lithium phosphate coated lithium rich manganese-based materials of example 3 and a lithium rich manganese-based material of a comparative example.
Fig. 4 is XRD patterns of the lithium-rich manganese-based material coated with lithium phosphate of example 3 and the lithium-rich manganese-based material of the comparative example.
Fig. 5 is a graph of the cycling performance of the button half cells of the materials of example 3 and comparative example 1.
Fig. 6 is a graph of the rate performance of button half cells of the materials of example 3 and comparative example 1.
Detailed Description
For a further understanding of the present invention, reference is made to the following further description taken in conjunction with the accompanying drawings, which are included, however, not to limit the scope of the invention.
Example 1
x is 0.3, and the synthetic target chemical formula is 0.3L i2MnO3·0.7LiNiO2@Li3PO4The preparation process of the material is shown in figure 1, and the specific parameters are as follows. 0.9mol of MnCl is respectively weighed2And 2.1molNiCl2Preparing solid, metal salt solution A with volume of 1.5L, weighing 3mol Na2CO3Weighing 65m L strong ammonia water (ammonia mass fraction is 27%), preparing 1.5L volume alkali liquor B from sodium carbonate and ammonia water, weighing 0.07mol K2HPO4Solid, make coating solution C with a volume of 1L.
Adding 1L deionized water into a reaction kettle as a base solution, wherein the reaction temperature is 70 ℃, the stirring speed is 900rpm/min, simultaneously adding a salt solution A and an alkali liquor B into the reaction kettle in a parallel flow manner through a peristaltic pump, the flow rate of the salt solution A is 1.5m L/min, the flow rate of the alkali liquor B is 1.3-1.8m L/min, controlling the pH to be 7.8 by using the alkali liquor, stopping the reaction for 14h, filtering the reaction solution, washing solids by using the deionized water, and performing vacuum drying at 80 ℃ to obtain a carbonate precursor.
1g of carbonate precursor was taken and dispersed in 30m LStirring and reacting the coating liquid C for 60min at normal temperature, filtering, washing and drying by the method to obtain a precursor coated by the nickel phosphate, and mixing the precursor coated by the nickel phosphate with L i2CO3Uniformly mixing the materials in a mortar according to the proportion of L i (Mn + Ni) 1.36:1, preserving heat for 6h at 500 ℃ in a muffle furnace in an air atmosphere, then raising the temperature to 850 ℃ and preserving heat for 15h, naturally cooling and grinding to obtain the lithium phosphate coated lithium-rich manganese-based material.
Example 2
x is 0.5, and the synthetic target chemical formula is 0.5L i2MnO3·0.5LiNi0.5Mn0.5O2@Li3PO4The preparation process of the material is shown in figure 1, and the specific parameters are as follows. 2.25mol of Mn (NO) are weighed out separately3)2And 0.75mol of Ni (NO)3)2Preparing solid, preparing metal salt solution A with volume of 1.5L, weighing 3mol Na2CO350m L concentrated ammonia water (ammonia mass fraction: 27%) is weighed, sodium carbonate and ammonia water are prepared into 1.5L volume of alkali liquor B, 0.01mol Na is weighed3PO4Solid, make coating solution C with a volume of 1L.
Adding 1L deionized water into a reaction kettle as a base solution, wherein the reaction temperature is 45 ℃, the stirring speed is 700rpm/min, simultaneously adding a salt solution A and an alkali liquor B into the reaction kettle in a parallel flow manner through a peristaltic pump, the flow rate of the salt solution A is 1.7m L/min, the flow rate of the alkali liquor B is 1.4-2.0m L/min, controlling the pH value to be 7.5 by using the alkali liquor, stopping the reaction for 12h, filtering the reaction solution, washing solids by using the deionized water, and performing vacuum drying at 80 ℃ to obtain a carbonate precursor.
Taking 1g of carbonate precursor, dispersing the carbonate precursor into 30m L coating liquid C, stirring and reacting at normal temperature for 20min, filtering, washing and drying by the method to obtain a nickel phosphate coated precursor, mixing the nickel phosphate coated precursor with L i2CO3Uniformly mixing the materials in a mortar according to the proportion of L i (Mn + Ni) ═ 1.57:1, preserving heat for 5h at 550 ℃ in a muffle furnace in an air atmosphere, then raising the temperature to 900 ℃ and preserving heat for 25h, naturally cooling and grinding to obtain the lithium phosphate coated lithium-rich manganese-based material.
Example 3
x is 0.5, and the target chemical formula is synthesized0.5Li2MnO3·0.5LiNi1/3Co1/3Mn1/3O2@Li3PO4The preparation process of the material is shown in figure 1, and the specific parameters are as follows. Respectively weighing 2mol of MnSO4、0.5mol CoSO4And 0.5mol of NiSO4Preparing solid, metal salt solution A with volume of 1.5L, weighing 3mol Na2CO3Weighing 55m L strong ammonia water (mass percent of ammonia is 27%), preparing alkali liquor B with the volume of 1.5L by sodium carbonate and ammonia water, and weighing 0.1mol of Na2HPO4Solid, make coating solution C with a volume of 1L.
Adding 1L deionized water into a reaction kettle as a base solution, wherein the reaction temperature is 55 ℃, the stirring speed is 800rpm/min, simultaneously adding a salt solution A and an alkali liquor B into the reaction kettle in a parallel flow manner through a peristaltic pump, the flow rate of the salt solution A is 1.5m L/min, the flow rate of the alkali liquor B is 1.3-1.7m L/min, controlling the pH to be 7.8 by using the alkali liquor, stopping the reaction for 16h, filtering the reaction solution, washing solids by using the deionized water, and performing vacuum drying at 80 ℃ to obtain a carbonate precursor.
Taking 1g of carbonate precursor, dispersing the carbonate precursor into 30m L coating liquid C, stirring and reacting at normal temperature for 40min, filtering, washing and drying by the method to obtain a nickel phosphate coated precursor, mixing the nickel phosphate coated precursor with L i2CO3Uniformly mixing the materials in a mortar according to the proportion of L i (Mn + Co + Ni) being 1.55:1, preserving heat for 5h at 500 ℃ in a muffle furnace in an air atmosphere, then raising the temperature to 800 ℃ and preserving heat for 20h, naturally cooling and grinding to obtain the lithium phosphate coated lithium-rich manganese-based material.
Example 4
x is 0.7, and the synthetic target chemical formula is 0.7L i2MnO3·0.3LiNi0.375Co0.25Mn0.375O2@Li3PO4The preparation process of the material is shown in figure 1, and the specific parameters are as follows. Respectively weighing 2.44mol of MnSO4、0.22mol CoSO4And 0.34mol of NiSO4Preparing solid, metal salt solution A with volume of 1.5L, weighing 3mol Na2CO3Weighing 35m L strong ammonia water (ammonia mass fraction is 27%), preparing 1.5L volume alkali liquor B from sodium carbonate and ammonia water, and weighingTaking 0.2mol (NH)4)2HPO4Solid, make coating solution C with a volume of 1L.
Adding 1L deionized water into a reaction kettle as a base solution, wherein the reaction temperature is 60 ℃, the stirring speed is 800rpm/min, simultaneously adding a salt solution A and an alkali liquor B into the reaction kettle in a parallel flow manner through a peristaltic pump, the flow rate of the salt solution A is 1.3m L/min, the flow rate of the alkali liquor B is 1.1-1.5m L/min, controlling the pH value to be 8.1 by using the alkali liquor, stopping the reaction for 18h, filtering the reaction solution, washing solids by using the deionized water, and performing vacuum drying at 80 ℃ to obtain a carbonate precursor.
Taking 1g of carbonate precursor, dispersing the carbonate precursor into 30m L coating liquid C, stirring at normal temperature for reaction for 180min, filtering, washing and drying by the method to obtain a nickel phosphate coated precursor, uniformly mixing the nickel phosphate coated precursor and L iOH according to the proportion of L i (Mn + Co + Ni) ═ 1.78:1 by a mortar, preserving heat for 6h at 550 ℃ in a muffle furnace in an air atmosphere, then heating to 850 ℃ and preserving heat for 20h, naturally cooling and grinding to obtain the lithium phosphate coated lithium-rich manganese-based material.
Comparative example
In order to prove the beneficial effect of the lithium-rich manganese-based positive electrode material coated with lithium phosphate in situ, a non-coated lithium-rich manganese-based contrast material is constructed.
x is 0.5, and the synthetic target chemical formula is 0.5L i2MnO3·0.5LiNi1/3Co1/3Mn1/3O2The material of (1). Respectively weighing 2mol of MnSO4、0.5mol CoSO4And 0.5mol of NiSO4Preparing solid, metal salt solution A with volume of 1.5L, weighing 3mol Na2CO3Weighing 55m L strong ammonia water (mass percent of ammonia is 27%), preparing alkali liquor B with the volume of 1.5L by sodium carbonate and ammonia water, and weighing 0.1mol of Na2HPO4Solid, make coating solution C with a volume of 1L.
Adding 1L deionized water into a reaction kettle as a base solution, wherein the reaction temperature is 55 ℃, the stirring speed is 800rpm/min, simultaneously adding a salt solution A and an alkali liquor B into the reaction kettle in a parallel flow manner through a peristaltic pump, the flow rate of the salt solution A is 1.5m L/min, the flow rate of the alkali liquor B is 1.3-1.7m L/min, controlling the pH to be 7.8 by using the alkali liquor, stopping the reaction for 16h, filtering the reaction solution, washing solids by using the deionized water, and performing vacuum drying at 80 ℃ to obtain a carbonate precursor.
Taking 1g of carbonate precursor and L i2CO3Uniformly mixing the materials in a mortar according to the proportion of L i (Mn + Co + Ni) being 1.55:1, preserving heat for 5h at 500 ℃ in a muffle furnace in an air atmosphere, then raising the temperature to 800 ℃ and preserving heat for 20h, naturally cooling and grinding to obtain the comparative lithium-rich manganese-based material.
Test example
(1) Material characterization by elemental analysis of the lithium phosphate coated lithium-rich manganese-based material prepared in example 3 using ICP-AES to determine L i3PO4The coating amount was 0.61%. SEM characterization of the lithium phosphate-coated lithium-rich manganese-based material prepared in example 3 and the comparative example material was performed, and the results are shown in FIG. 2, where both materials had a better spherical morphology. The lithium phosphate-coated lithium-rich manganese-based material prepared in example 3 and the comparative example material were subjected to TEM characterization, and as shown in fig. 3, a lithium phosphate coating layer of about 10nm was present on the surface of the example material, while the surface of the comparative example material was smooth. XRD characterization is carried out on the lithium phosphate-coated lithium-rich manganese-based material prepared in the embodiment 3 and a comparative example material, as shown in figure 4, the spectra of the two materials except a superlattice peak of 20-30 degrees accord with an R-3m space group structure, and no obvious impurity peak appears, which indicates that the lithium phosphate-coated lithium-rich manganese-based material synthesized by the invention has high purity.
(2) Assembling the battery: the lithium-rich manganese-based material coated with lithium phosphate prepared in example 3 and the comparative material were mixed with Super P and PVDF in a mass ratio of 8:1:1, respectively, slurried and coated, vacuum-dried and cut into disks with a diameter of 10mm, and a half-cell was assembled with a metal lithium sheet as the negative electrode.
(3) And (3) performance testing: at 0.5C (1C-250 mAh g)-1) The above-assembled half cell was subjected to a cycle test in a voltage interval of 2 to 4.8V, and as shown in fig. 5, the initial discharge capacity of the lithium phosphate-coated lithium-rich manganese-based material prepared in example 3 was 234mAh g at 0.5C-1After 200 cycles, the capacity is 189mAh g-1The capacity retention rate was 80.7%, and the initial discharge capacity of the comparative example material at 0.5C was 237mAh g-1Capacity after 200 cycles of 173mAh g-1The capacity retention rate is 72.9%, which shows that the lithium-rich material coated by the lithium phosphate prepared by the invention has better capacity retention rate and cycle performance compared with the uncoated lithium-rich material. Rate test As shown in FIG. 6, the discharge capacities of the lithium phosphate-coated lithium-rich manganese-based material prepared in example 3 at 0.1C, 1C, 5C, and 10C were 274mAh g, respectively-1、210mAh g-1、144mAh g-1And 108mAh g-1And comparative example materials respectively had discharge capacities of 271mAh g-1、189mAh g-1、118mAh g-1And 70mAh g-1This shows that the lithium-rich manganese-based material coated with lithium phosphate prepared by the invention has better rate performance than the uncoated lithium-rich material.
The above embodiments are merely illustrative of the principles and embodiments, and are not intended to limit the invention, and any modifications, equivalents, improvements and the like made without departing from the principles of the invention are intended to be included within the scope of the invention.

Claims (10)

1. The lithium phosphate in-situ coated lithium-rich manganese-based cathode material is characterized in that the chemical formula of the lithium phosphate coated lithium-rich manganese-based cathode material is shown as the formula (I):
xLi2MnO3·(1-x)LiMO2@Li3PO4(Ⅰ);
wherein x is more than or equal to 0.3 and less than or equal to 0.7, and M is selected from Ni or at least one element of Ni, Co and Mn.
2. The lithium phosphate in-situ coated lithium-rich manganese-based positive electrode material as claimed in claim 1, wherein the lithium phosphate mass fraction is 0.1-5%, and the coating thickness is less than 30 nm.
3. The preparation method of the lithium phosphate in-situ coated lithium-rich manganese-based positive electrode material as claimed in claim 1, characterized by comprising the following steps:
firstly, preparing a salt solution A with metal ion concentration of 1-5 mol/L, a mixed solution B with 0.5-2 mol/L of sodium carbonate and 0.05-5 mol/L of ammonia water and a soluble phosphate solution C with concentration of 0.01-0.5 mol/L from one or more of nickel soluble salt, cobalt soluble salt and manganese soluble salt according to the stoichiometric ratio in the chemical formula;
step two: adding deionized water into a reaction kettle, adding the solution A and the solution B into the reaction kettle in a concurrent flow manner, mechanically stirring for reaction, controlling the temperature of a reaction solution to be constant, and controlling the pH to be constant by adjusting the flow rate of the solution B; after the reaction is finished, filtering, washing and vacuum drying the obtained precipitate to obtain the lithium-rich manganese-based material precursor TMCO3TM is a transition metal;
step three: subjecting the obtained precursor TMCO3Dispersing in the solution C, stirring at normal temperature for reaction, filtering, washing and drying in vacuum to obtain a precursor coated by nickel phosphate;
step four: and D, uniformly mixing the precursor coated by the nickel phosphate obtained in the step three with a lithium source, and calcining in an air atmosphere according to a set heating program to obtain the lithium-rich manganese-based anode material coated by the lithium phosphate in situ.
4. The method for preparing the lithium-rich manganese-based cathode material coated with lithium phosphate in situ according to claim 3, wherein in the first step, the soluble metal salt is one or more of sulfate, nitrate and chloride, the total metal concentration is 1-5 mol/L, the sodium carbonate concentration is 0.5-5 mol/L, the ammonia water concentration is 0.05-5 mol/L, and the soluble phosphate is one or more of lithium, sodium, potassium and ammonium phosphate, hydrogen phosphate and dihydrogen phosphate, and the concentration is 0.01-0.5 mol/L, preferably 0.1 mol/L.
5. The method for preparing the lithium-rich manganese-based anode material coated with lithium phosphate in situ as claimed in claim 3, wherein in the second step, the metal salt solution A is injected into the reaction kettle at a constant speed of 1-2m L/min, the solution B is injected into the reaction kettle at a speed of 0.5-2.5m L/min to control the pH of the solution, the pH is controlled to be 7.3-8.3, and the mechanical stirring speed is 300-900 rpm/min.
6. The method for preparing the lithium-rich manganese-based positive electrode material coated with lithium phosphate in situ according to claim 3, wherein the reaction temperature of the reaction kettle in the second step is 40-70 ℃ and the reaction time is 10-40 h.
7. The method for preparing the lithium phosphate in-situ coated lithium-rich manganese-based cathode material as claimed in claim 3, wherein the precursor TMCO is obtained in step three3The reaction time in soluble phosphate is 1min-24h, preferably 40 min.
8. The method for preparing the lithium phosphate in-situ coated lithium-rich manganese-based cathode material as claimed in claim 3, wherein the lithium source in the fourth step is L iOH and L i2CO3One or two of them.
9. The method for preparing the lithium-rich manganese-based anode material coated in situ with lithium phosphate as claimed in claim 3, wherein the calcination procedure in step four is to firstly preserve heat at 550 ℃ for 4-6h in air atmosphere, then heat up to 900 ℃ at 750 ℃ for sintering for 10-25h, and then naturally cool to room temperature to obtain the lithium-rich manganese-based anode material coated in situ with lithium phosphate.
10. The method for preparing the lithium phosphate in-situ coated lithium-rich manganese-based cathode material according to claim 9, wherein the sintering temperature is 800 ℃ for 20 h.
CN202010301667.0A 2020-04-16 2020-04-16 Lithium phosphate in-situ coated lithium-rich manganese-based positive electrode material and preparation method thereof Pending CN111490241A (en)

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