CN116722135A - Double-layer coated positive electrode material, preparation method thereof, lithium ion battery and vehicle - Google Patents

Double-layer coated positive electrode material, preparation method thereof, lithium ion battery and vehicle Download PDF

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CN116722135A
CN116722135A CN202310500618.3A CN202310500618A CN116722135A CN 116722135 A CN116722135 A CN 116722135A CN 202310500618 A CN202310500618 A CN 202310500618A CN 116722135 A CN116722135 A CN 116722135A
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positive electrode
electrode active
coating layer
active material
coating
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沈伟
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Beijing CHJ Automobile Technology Co Ltd
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Beijing CHJ Automobile 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection 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
    • 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
    • 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
    • H01M4/525—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
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a double-layer coated positive electrode material and a preparation method thereof. The double-layer coated positive electrode material comprises a positive electrode active material, wherein a first coating layer and a second coating layer are sequentially arranged on the surface of the positive electrode active material, and the first coating layer comprises PO 4 3‑ The coating material of the first coating layer comprises phosphate which does not contain transition metal and does not contain lithium titanium aluminum phosphate; the second cladding layer includes lithium aluminum titanium phosphate. The positive electrode material of the invention contains PO 4 3‑ Can avoid the second coating layer containing lithium aluminum titanium phosphate from being directly connected with the positive electrode active materialContact is carried out, the interdiffusion among elements in the high-temperature calcination process during coating is avoided, meanwhile, the strong oxidative decomposition of the positive electrode active material during charging is avoided, the crystal structure stability of the positive electrode active material and the aluminum titanium lithium phosphate is improved, and the multiplying power performance and the cycle performance of the positive electrode material are further improved.

Description

Double-layer coated positive electrode material, preparation method thereof, lithium ion battery and vehicle
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a double-layer coated positive electrode material and a preparation method thereof, and further relates to a lithium ion battery and a vehicle.
Background
Power lithium ion batteries are currently the most promising energy storage technology for electric vehicles and have been widely used. The main disadvantages of the power lithium ion battery are high cost, insufficient energy density and poor cycling stability, which is limited by the positive electrode material to a great extent. Therefore, development of a positive electrode material having high energy density and good cycle stability is urgently required to improve the performance of a power lithium ion battery. The common positive electrode materials in the current power battery are mainly lithium iron phosphate and ternary positive electrode active materials, wherein the lithium iron phosphate is difficult to meet the requirement of battery energy density due to lower specific capacity, and the ternary positive electrode active materials are poor in cycle life and high-rate performance due to poor stability. Therefore, further development of the lithium ion battery anode material with high energy density, long cycle life and high rate performance is of great importance to the development of the electric automobile industry.
The ternary positive electrode active material has higher specific capacity and is receiving more and more attention and application. However, as the nickel content in the system is continuously improved, the structural stability of the material is also poorer and poorer. The main reason is that: (1) The material forms a large amount of Ni with strong oxidability in the charging process 4+ The side reaction with the electrolyte is more severe; (2) High nickel positive electrode material in higher charging state>4.15V), with the release of more lithium ions, the structure of the material undergoes H2-H3 phase transition, thereby causing anisotropic volume expansion of primary particles, resulting in an increase in the gaps between primary particles in secondary particles, and during repeated charge and discharge, as the gaps increase, more positive electrode active material is in direct contact with the electrolyte, side reactions increase continuously, causing more serious structural deterioration. At present, the surface of the positive electrode active material is subjected to cladding modification by mainly adopting measures in the related art, so that the precipitation of oxygen in the lattice material can be reduced, the phase transition is inhibited, the first coulomb efficiency of the material is improved, the capacity attenuation and other effects of the material are relieved, and the high-rate discharge performance and the cycling stability of the material are improved.
In the coating material, LATP (Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 ) Namely lithium titanium aluminum phosphate with three-dimensional lithiumThe ion migration channel has higher ion conductivity, and can reach 10 at room temperature -3 S/cm, the lithium aluminum titanium phosphate is used as a coating layer of the positive electrode active material, so that the interface ion conductivity of the positive electrode and the electrolyte can be improved. However, when the LATP and the positive electrode active material are co-sintered in the coating process, mutual diffusion is easy to occur between elements, so that the LATP structure is damaged, new impurity phases are generated, the ionic conductivity of the coating layer is reduced, the interface impedance is increased, and the coating effect is affected. Therefore, improvement of the anode material coated with the LATP is needed to effectively protect the LATP coating layer and improve the comprehensive performance of the anode material.
Disclosure of Invention
The present invention aims to solve at least one of the technical problems in the related art to some extent. For this reason, the embodiment of the invention provides a double-layer coated positive electrode material and a preparation method thereof, wherein the positive electrode material is provided with PO 4 3- The inner coating layer can avoid direct contact between the titanium aluminum lithium phosphate coating layer and the positive electrode active material, effectively inhibit mutual diffusion between LATP and positive electrode active material elements, and simultaneously is favorable for avoiding strong oxidative decomposition of the positive electrode material to titanium aluminum lithium phosphate in a charged state, and is favorable for improving the stability of the crystal structures of the positive electrode active material and the titanium aluminum lithium phosphate, thereby improving the cycle stability and the multiplying power performance of the battery.
The embodiment of the invention provides a double-layer coated positive electrode material, which comprises a positive electrode active material, wherein a first coating layer and a second coating layer are sequentially arranged on the surface of the positive electrode active material,
the first coating layer comprises PO 4 3- The coating material of the first coating layer comprises phosphate which does not contain transition metal and does not contain lithium titanium aluminum phosphate;
the second cladding layer includes lithium aluminum titanium phosphate.
The double-layer coated positive electrode material of the embodiment of the invention has the advantages and technical effects that 1, in the embodiment of the invention, PO is sequentially arranged on the surface of the positive electrode active material 4 3- And a second coating layer containing lithium aluminum titanium phosphate, due to the first coating layerThe coating material does not contain transition metal, does not generate element interdiffusion with the positive electrode active material, is favorable for the positive electrode material to obtain a stable crystal structure, and meanwhile, the transition metal element in the positive electrode active material and PO in the first coating layer 4 3- The coating interface of the positive electrode active material and the first coating layer can easily form a stable TM-P-O bond (TM refers to transition metal, TM is transition metal element in the positive electrode active material), and the structural stability of the first coating layer is improved; 2. in the embodiment of the invention, the first coating layer can be used as a transition layer between the positive electrode active material and the second coating layer containing the titanium aluminum lithium phosphate, so that the direct contact between the positive electrode active material and the second coating layer containing the titanium aluminum lithium phosphate is avoided, the mutual diffusion between elements of the positive electrode active material and the second coating layer in the calcination of the coating process is avoided, meanwhile, the oxidative decomposition of the titanium aluminum lithium phosphate by the strong oxidizing property of the positive electrode in a charging state is also avoided, and the stability of the crystal structures of the positive electrode active material and the titanium aluminum lithium phosphate is improved; 3. in the embodiment of the invention, the surface of the positive electrode active material is provided with the double-layer coating layer, so that the side reaction of the positive electrode active material and the electrolyte is effectively avoided; 4. in the embodiment of the invention, the active material of the positive electrode material, the first coating layer and the second coating layer all have stable structures, so that the lithium ion conductivity between the titanium aluminum lithium phosphate and the electrolyte is effectively improved, the impedance is reduced, and meanwhile, the side reaction between the positive electrode material and the electrolyte is further reduced due to the excellent stable structure of the second coating layer containing the titanium aluminum lithium phosphate, so that the positive electrode material has excellent multiplying power performance and cycle stability.
In some embodiments, the positive electrode active material comprises a ternary positive electrode active material having the formula LiNi x Co y Mn 1-x-y O 2 Wherein x is more than or equal to 0.5 and less than or equal to 0.96,0.02, and y is more than or equal to 0.2.
In some embodiments, the cladding material of the first cladding layer comprises Li 3 PO 4 、NH 4 H 2 PO 4 Or (NH) 4 ) 2 HPO 4 At least one of them.
In some embodiments, the first cladding layer has a thickness of 5nm to 30nm, and/or the second cladding layer has a thickness of 6nm to 50nm.
The embodiment of the invention also provides a preparation method of the double-layer coated positive electrode material, which comprises the following steps:
(1) Adding a positive electrode active material and a coating material of a first coating layer into an organic solvent, stirring and evaporating the organic solvent, and calcining to obtain a first product;
(2) And mixing the first product with lithium aluminum titanium phosphate, and calcining to obtain the double-layer coated positive electrode material.
The preparation method of the double-layer coated positive electrode material of the embodiment of the invention has the advantages and technical effects that 1, the method of the embodiment of the invention forms the material containing PO on the positive electrode active material through wet coating 4 3- The first coating layer is favorable for forming a more uniform first coating layer on the outer surface of the positive electrode active material, effectively inhibiting side reaction between the positive electrode active material and electrolyte, and continuously coating a second coating layer containing lithium aluminum titanium phosphate on the first coating layer, and simultaneously effectively avoiding contact between the positive electrode active material and the second coating layer containing lithium aluminum titanium phosphate, thereby avoiding side reaction between the positive electrode active material and the lithium aluminum titanium phosphate; 2. the first coating layer of the anode material prepared by the method of the embodiment of the invention contains PO 4 3- Stable TM-P-O bonds are easy to form at the coating interface of the positive electrode active material and the first coating layer, so that the structural stability of the first coating layer is improved; 3. the method of the embodiment of the invention has the advantages that the second coating layer of the prepared anode material contains the aluminum titanium lithium phosphate, the formation of the first coating layer avoids the direct contact between the second coating layer containing the aluminum titanium lithium phosphate and the anode active material, thereby avoiding the mutual diffusion of elements between the anode active material and the aluminum titanium lithium phosphate in the high-temperature calcination process during the coating, simultaneously being beneficial to avoiding the strong oxidative decomposition of the aluminum titanium lithium phosphate of the anode in the charging state, being beneficial to improving the stability of the crystal structures of the anode active material and the aluminum titanium lithium phosphate, improving the lithium ion conductivity between the aluminum titanium lithium phosphate and the electrolyte and reducing the resistanceThe second coating layer containing the lithium aluminum titanium phosphate has excellent structural stability, and can reduce side reaction between the positive electrode active material and electrolyte; 4. the method provided by the embodiment of the invention has the advantages of low energy consumption and simple process, and the prepared positive electrode material is uniform in size and has excellent multiplying power performance and cycle performance.
In some embodiments, in step (1), the molar ratio of the positive electrode active material to phosphate in phosphate is 100:0.05 to 0.3; and/or, in the step (2), the molar ratio of the positive electrode active material to sulfate radical in the lithium aluminum titanium phosphate is 100:0.05 to 0.4.
In some embodiments, in the step (1), the organic solvent includes at least one of ethanol and methanol, and/or the mass ratio of the positive electrode active material and the organic solvent is 1 to 3:3.
in some embodiments, in step (1) and/or step (2), the calcination is performed at a temperature of 400 to 700 ℃, for a time of 2 to 10 hours, and/or in an air or oxygen atmosphere.
The embodiment of the invention also provides a lithium ion battery, which comprises the double-layer coated positive electrode material of the embodiment of the invention or the double-layer coated positive electrode material prepared by the method of the embodiment of the invention.
The lithium ion battery provided by the embodiment of the invention has all technical characteristics of the double-layer coated positive electrode material provided by the embodiment of the invention, so that the lithium ion battery provided by the embodiment of the invention has all advantages and technical effects provided by the double-layer coated positive electrode material provided by the embodiment of the invention, and the description is omitted herein.
The embodiment of the invention also provides a vehicle comprising the lithium ion battery.
The vehicle in the embodiment of the present invention has all the technical features of the lithium ion battery in the embodiment of the present invention, so that all the advantages and technical effects of the lithium ion battery in the embodiment of the present invention are provided, and are not described herein.
Drawings
FIG. 1 is a flow chart of a double coated positive electrode material prepared in example 1;
fig. 2 is a scanning electron microscope image of the double-coated positive electrode material prepared in example 1.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings. The embodiments described below by referring to the drawings are illustrative and intended to explain the present invention and should not be construed as limiting the invention.
The embodiment of the invention provides a double-layer coated positive electrode material, which comprises a positive electrode active material, wherein a first coating layer and a second coating layer are sequentially arranged on the surface of the positive electrode active material,
the first coating layer comprises PO 4 3- The coating material of the first coating layer comprises phosphate which does not contain transition metal and does not contain lithium titanium aluminum phosphate;
the second cladding layer includes lithium aluminum titanium phosphate.
The double-layer coated positive electrode material of the embodiment of the invention is characterized in that PO is sequentially arranged on the surface of the positive electrode active material 4 3- The first coating layer and the second coating layer containing the lithium aluminum titanium phosphate can not generate element interdiffusion with the positive electrode active material because the coating material of the first coating layer does not contain transition metal, thereby being beneficial to the positive electrode material to obtain stable crystal structure, and meanwhile, the transition metal element in the positive electrode active material and PO in the first coating layer 4 3- The coating interface of the positive electrode active material and the first coating layer can easily form a stable TM-P-O bond (TM refers to transition metal, TM is transition metal element in the positive electrode active material), and the structural stability of the first coating layer is improved; in the embodiment of the invention, the first coating layer can be used as a transition layer between the positive electrode active material and the second coating layer containing the titanium aluminum lithium phosphate, so that the direct contact between the positive electrode active material and the second coating layer containing the titanium aluminum lithium phosphate is avoided, and the positive electrode active material and the second coating layer in the calcination of the coating process are avoidedThe mutual diffusion among the elements of the layers, meanwhile, the oxidative decomposition of the titanium aluminum lithium phosphate by the strong oxidizing property of the positive electrode in a charged state is avoided, and the stability of the positive electrode active material and the crystal structure of the titanium aluminum lithium phosphate is improved; in the embodiment of the invention, the surface of the positive electrode active material is provided with the double-layer coating layer, so that the side reaction of the positive electrode active material and the electrolyte is effectively avoided; in the embodiment of the invention, the active material of the positive electrode material, the first coating layer and the second coating layer all have stable structures, so that the lithium ion conductivity between the titanium aluminum lithium phosphate and the electrolyte is effectively improved, the impedance is reduced, and meanwhile, the side reaction between the positive electrode material and the electrolyte is further reduced due to the excellent stable structure of the second coating layer containing the titanium aluminum lithium phosphate, so that the positive electrode material has excellent multiplying power performance and cycle stability.
In some embodiments, the positive electrode active material comprises a ternary positive electrode active material having the formula LiNi x Co y Mn 1-x-y O 2 Wherein 0.5.ltoreq.x.ltoreq.0.96, e.g. 0.5, 0.6, 0.7, 0.8, 0.9, 0.96 etc., 0.02.ltoreq.y.ltoreq.0.2, e.g. 0.02, 0.05, 0.10, 0.15, 0.2 etc. In the embodiment of the invention, the types of the positive electrode active materials are optimized, and the nickel-cobalt-manganese ternary positive electrode active material has higher reversible capacity, structural stability and thermal stability, and can be used for preparing the positive electrode material to further improve the performance of the positive electrode material.
In some embodiments, the cladding material of the first cladding layer comprises Li 3 PO 4 、NH 4 H 2 PO 4 Or (NH) 4 ) 2 HPO 4 At least one of them. In the embodiment of the invention, the type of phosphate is optimized, and the coating raw material has no transition metal, does not generate element interdiffusion with the positive electrode active material, and is favorable for stabilizing the crystal structure of the positive electrode active material.
In some embodiments, the first cladding layer cladding thickness is 5nm to 30nm and the second cladding layer cladding thickness is 6nm to 50nm. In the embodiment of the invention, the thickness of the coating layer is optimized, if the first coating layer is too thick, the duty ratio of the active positive electrode material can be reduced, the capacity exertion is influenced, the lithium ion conductivity of the coating layer can be reduced, and the impedance is increased; if the first coating layer is too thin, the effect is limited, which is unfavorable for effectively isolating the positive electrode active material from the second coating layer containing titanium aluminum lithium phosphate; if the second coating layer is too thin, the interfacial stability between the second coating layer and the electrolyte is not improved, and if the second coating layer is too thick, the duty ratio of the active positive electrode material is reduced, and the capacity exertion is affected.
The embodiment of the invention also provides a preparation method of the double-layer coated positive electrode material, which comprises the following steps:
(1) Adding a positive electrode active material and a coating material of a first coating layer into an organic solvent, stirring and evaporating the organic solvent, and calcining to obtain a first product;
(2) And mixing the first product with Lithium Aluminum Titanium Phosphate (LATP), and performing calcination treatment to obtain the double-layer coated cathode material.
According to the preparation method of the double-layer coated positive electrode material, disclosed by the embodiment of the invention, PO is formed on the positive electrode active material through wet coating 4 3- The first coating layer is favorable for forming a more uniform first coating layer on the outer surface of the positive electrode active material, effectively inhibiting side reaction between the positive electrode active material and electrolyte, and continuously coating a second coating layer containing lithium aluminum titanium phosphate on the first coating layer, and simultaneously effectively avoiding contact between the positive electrode active material and the second coating layer containing lithium aluminum titanium phosphate, thereby avoiding side reaction between the positive electrode active material and the lithium aluminum titanium phosphate; the first coating layer of the anode material prepared by the method of the embodiment of the invention contains PO 4 3- Stable TM-P-O bonds are easy to form at the coating interface of the positive electrode active material and the first coating layer, so that the structural stability of the first coating layer is improved; the method of the embodiment of the invention has the advantages that the second coating layer of the prepared anode material contains the aluminum titanium lithium phosphate, and the formation of the first coating layer avoids the direct contact between the second coating layer containing the aluminum titanium lithium phosphate and the anode active material, thereby avoiding the mutual diffusion of elements between the anode active material and the aluminum titanium lithium phosphate in the high-temperature calcination process during the coating, and being beneficial to avoiding the charging stateThe strong oxidative decomposition of the positive electrode is beneficial to improving the stability of the positive electrode active material and the crystal structure of the aluminum titanium lithium phosphate, improving the lithium ion conductivity between the aluminum titanium lithium phosphate and the electrolyte, reducing the impedance, and simultaneously forming a second coating layer containing the aluminum titanium lithium phosphate, which has excellent structural stability and can reduce the side reaction of the positive electrode active material and the electrolyte; the method provided by the embodiment of the invention has the advantages of low energy consumption and simple process, and the prepared positive electrode material is uniform in size and has excellent multiplying power performance and cycle performance.
In some embodiments, preferably, in the step (1), the molar ratio of the positive electrode active material to phosphate in phosphate is 100:0.05 to 0.3, for example 100:0.05, 100:0.10, 100:0.15, 100:0.20, 100:0.25, 100:0.30, etc. In the embodiment of the invention, the molar ratio of the positive electrode active material to the phosphate radical is optimized, which is favorable for forming PO with proper thickness, uniformity and integrity on the surface of the positive electrode active material 4 3- If the amount of phosphate is too small, the coating layer is insufficient to form a complete PO on the surface of the positive electrode active material 4 3- The coating layer has very limited improvement in performance, and if the amount of phosphate is excessive, PO is formed on the surface of the positive electrode active material 4 3- The coating layer is too thick, which is unfavorable for the transmission of ions, increases the impedance and reduces the performance of the anode material.
In some embodiments, preferably, in the step (1), the organic solvent includes at least one of ethanol and methanol. Further preferably, in the step (1), the solution temperature is controlled to be 60 to 90 ℃, for example, 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃ or the like during the stirring to accelerate the evaporation of the organic solvent. In the embodiment of the invention, the types of organic solvents are optimized, the sources of the organic solvents are wide, the cost can be reduced, the organic solvents are easy to volatilize, the volatilization is easier in the subsequent heating and evaporating process, and the treatment efficiency is improved.
In some embodiments, preferably, in the step (1), the mass ratio of the positive electrode active material to the organic solvent is 1 to 3:3, for example 1: 3. 1.5: 3. 2: 3. 2.5: 3. 3:3, etc. In the embodiment of the invention, the dosage of the organic solvent is optimized, which is favorable for fully dispersing the anode active material and the coating raw material, so that the surface of the anode active material can form a more uniform first coating layer; if the amount of the organic solvent is too large, unnecessary waste is caused, the evaporation time is prolonged, and if the amount of the organic solvent is too small, uniform dispersion of the coating raw material and the positive electrode active material is not facilitated.
In some embodiments, preferably, in the step (2), the molar ratio of the positive electrode active material to phosphate in Lithium Aluminum Titanium Phosphate (LATP) is 100:0.05 to 0.4, for example, 100:0.05, 100:0.15, 100:0.2, 100:0.25, 100:0.3, 100:0.35, 100:0.4, etc. In the embodiment of the invention, the LATP is preferably used in an amount that can contain PO 4 3- The outer surface of the first coating layer is further formed with a uniform LATP coating layer, so that the interface ionic conductivity of the positive electrode material and the electrolyte can be improved, if the dosage of LATP is too large, the duty ratio of the active positive electrode material can be reduced, the capacity exertion is affected, and if the dosage of LATP is too small, the interface stability of the LATP and the electrolyte is not improved.
In some embodiments, preferably, in the step (1) and/or the step (2), the calcination temperature is 400 to 700 ℃, for example, 400 ℃, 450 ℃, 500 ℃, 550 ℃, 600 ℃, 650 ℃, 700 ℃, etc., and the calcination time is 2 to 10 hours, for example, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, etc.; the calcination is performed in an air or oxygen atmosphere. Further preferably, the temperature rising rate at the time of calcination is 1 to 10℃per minute, for example, 1℃per minute, 2℃per minute, 3℃per minute, 4℃per minute, 5℃per minute, 6℃per minute, 7℃per minute, 8℃per minute, 9℃per minute, 10℃per minute, etc. In the embodiment of the invention, the calcination treatment is carried out in the two coating processes, the calcination treatment conditions are optimized, and the calcination is carried out at a proper calcination temperature, thereby being beneficial to improving PO 4 3- The structural stability of the coating layer and the LATP coating layer, and the heating rate is optimized, so that the cracking problem caused by the too high heating rate is avoided.
The embodiment of the invention also provides a lithium ion battery, which comprises the double-layer coated positive electrode material of the embodiment of the invention or the double-layer coated positive electrode material prepared by the method of the embodiment of the invention. The lithium ion battery provided by the embodiment of the invention has all advantages and technical effects brought by the double-layer coated positive electrode material provided by the embodiment of the invention, and is not repeated here.
The embodiment of the invention also provides a vehicle comprising the lithium ion battery. The vehicle of the embodiment of the present invention has all advantages and technical effects brought by the lithium ion battery of the embodiment of the present invention, and will not be described herein.
The technical scheme of the present invention is described in detail below with reference to specific embodiments and drawings.
Example 1
The flow of the preparation of the double-layer coated cathode material in this example is shown in fig. 1.
(1) 100g of positive electrode active material LiNi 0.5 Co 0.2 Mn 0.3 O 2 Adding into 300g ethanol, stirring and heating to 60deg.C, and then according to LiNi 0.5 Co 0.2 Mn 0.3 O 2 ：PO 4 3- The molar ratio of (2) is 100:0.05 addition of Li 3 PO 4 Stirring uniformly, and volatilizing ethanol continuously to obtain powdery coating materials; heating the coating material to 400 ℃ at a heating rate of 1 ℃/min under an air atmosphere, preserving heat for 10 hours, naturally cooling to room temperature, and crushing to obtain a first product;
(2) According to LiNi 0.5 Co 0.2 Mn 0.3 O 2 ：PO 4 3- The molar ratio of (2) is 100:0.3 adding LATP into the first product, mixing uniformly, heating to 400 ℃ at a heating rate of 1 ℃/min under air atmosphere, preserving heat for 10 hours, naturally cooling to room temperature, and crushing to obtain the double-layer coated LiNi 0.5 Co 0.2 Mn 0.3 O 2 And the ternary positive electrode material is characterized in that the thickness of the first coating layer is 5nm, and the thickness of the second coating layer is 40nm. The positive electrode material prepared in the embodiment is subjected to scanning electron microscope characterization, and the result is shown in fig. 2, and the graph shows that the prepared positive electrode material has good sphericity and no agglomeration phenomenon among spherical particles.
Example 2
(1) 300g of positive electrode active material LiNi 0.6 Co 0.2 Mn 0.2 O 2 Adding into 300g of methanol, stirring and heating to 90 ℃, and then according to LiNi 0.6 Co 0.2 Mn 0.2 O 2 ：PO 4 3- The molar ratio of (2) is 100:0.3 adding NH 4 H 2 PO 4 Stirring uniformly, and volatilizing methanol continuously to obtain powdery coating material; heating the coating material to 700 ℃ at a heating rate of 10 ℃/min under an air atmosphere, preserving heat for 2 hours, naturally cooling to room temperature, and crushing to obtain a first product;
(2) According to LiNi 0.6 Co 0.2 Mn 0.2 O 2 ：PO 4 3- The molar ratio of (2) is 100:0.05 adding LATP into the first product, mixing uniformly, heating to 700 ℃ at a heating rate of 10 ℃/min under air atmosphere, preserving heat for 2h, naturally cooling to room temperature, and pulverizing to obtain bisphosphonate gradient coated LiNi 0.6 Co 0.2 Mn 0.2 O 2 And the ternary positive electrode material comprises a first coating layer, a second coating layer and a third coating layer, wherein the thickness of the first coating layer is 30nm, and the thickness of the second coating layer is 6nm.
Example 3
(1) 200g of positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O 2 Adding into 300g of methanol, stirring and heating to 70deg.C, and then according to LiNi 0.8 Co 0.1 Mn 0.1 O 2 ：PO 4 3- The molar ratio of (2) is 100:0.2 addition (NH) 4 ) 2 HPO 4 Stirring uniformly, and volatilizing methanol continuously to obtain powdery coating material; heating the coating material to 600 ℃ at a heating rate of 5 ℃/min under an oxygen atmosphere, preserving heat for 7 hours, naturally cooling to room temperature, and crushing to obtain a first product;
(2) According to LiNi 0.8 Co 0.1 Mn 0.1 O 2 ：PO 4 3- The molar ratio of (2) is 100:0.1 adding LATP into the first product, mixing, heating to 600deg.C at a heating rate of 5 ℃/min under oxygen atmosphere, and maintaining for 7hNaturally cooling to room temperature, and pulverizing to obtain bisphosphonate gradient coated LiNi 0.8 Co 0.1 Mn 0.1 O 2 And the ternary positive electrode material is characterized in that the thickness of the first coating layer is 20nm, and the thickness of the second coating layer is 15nm.
Example 4
The preparation method of this example is the same as that of example 3, except that: in the step (1), liNi is used 0.8 Co 0.1 Mn 0.1 O 2 Replaced by LiNi 0.9 Co 0.05 Mn 0.05 O 2 。
Example 5
The preparation method of this example is the same as that of example 3, except that: in the step (1), liNi is used 0.8 Co 0.1 Mn 0.1 O 2 Replaced by LiNi 0.96 Co 0.02 Mn 0.02 O 2 。
Comparative example 1
100g of positive electrode active material LiNi 0.5 Co 0.2 Mn 0.3 O 2 Adding into 300g ethanol, stirring and heating to 60deg.C, and then according to LiNi 0.5 Co 0.2 Mn 0.3 O 2 ：PO 4 3- The molar ratio of (2) is 100:0.05 addition of Li 3 PO 4 Stirring uniformly, and volatilizing ethanol continuously to obtain powdery coating materials; heating the coating material to 400 ℃ at a heating rate of 1 ℃/min under an air atmosphere, preserving heat for 10 hours, naturally cooling to room temperature, and crushing to obtain single-layer phosphate-coated LiNi 0.5 Co 0.2 Mn 0.3 O 2 Ternary positive electrode material.
Comparative example 2
At 100g of positive electrode active material LiNi 0.5 Co 0.2 Mn 0.3 O 2 Middle according to LiNi 0.5 Co 0.2 Mn 0.3 O 2 ：PO 4 3- The molar ratio of (2) is 100:0.3 adding LATP, mixing uniformly, heating to 400 ℃ at a heating rate of 1 ℃/min under air atmosphere, preserving heat for 10 hours, naturally cooling to room temperature, and pulverizing to obtain single-layer phosphate coated LiNi 0.5 Co 0.2 Mn 0.3 O 2 Ternary positive electrode material.
Comparative example 3
200g of positive electrode active material LiNi 0.96 Co 0.02 Mn 0.02 O 2 Adding into 300g of methanol, stirring and heating to 70deg.C, and then according to LiNi 0.96 Co 0.02 Mn 0.02 O 2 ：PO 4 3- The molar ratio of (2) is 100:0.2 addition (NH) 4 ) 2 HPO 4 Stirring uniformly, and volatilizing methanol continuously to obtain powdery coating material. Heating the coating material to 600 ℃ at a heating rate of 5 ℃/min in an oxygen atmosphere, preserving heat for 7 hours, naturally cooling to room temperature, and crushing to obtain single-layer phosphate-coated LiNi 0.96 Co 0.02 Mn 0.02 O 2 Ternary positive electrode material.
Comparative example 4
The same procedure as in example 1 was followed except that the positive electrode active material LiNi 0.5 Co 0.2 Mn 0.3 O 2 、Li 3 PO 4 And (3) uniformly mixing the composite coated ternary anode material with LATP, preserving heat for 10 hours at 400 ℃, and naturally cooling to room temperature to obtain the composite coated ternary anode material.
The positive electrode materials prepared in examples 1 to 5 and comparative examples 1 to 4 were assembled into lithium ion batteries, and the performance of the lithium ion batteries was tested.
(1) The prepared positive electrode material is taken as a sample, N-methyl pyrrolidone is taken as a dispersing agent, sample powder, conductive carbon black and polyvinylidene fluoride are uniformly stirred according to the mass ratio of 90:5:5, and then the mixture is coated on the surface of clean aluminum foil, and a film is formed by blade coating. And (3) drying by blowing to obtain an electrode slice, blanking into a circular slice with the diameter of 8mm, and further drying in a vacuum oven at 120 ℃ for 6 hours to remove water. The prepared electrode plate is used as a working electrode of a half battery, the metal lithium is used as a counter electrode, and 1mol/L LiPF is used 6 Ethylene Carbonate (EC) -dimethyl carbonate (DMC) (mass ratio of EC to DMC 1:1) was used as an electrolyte, and assembled into a battery in a glove box.
(2) The assembled battery is charged and discharged, and the voltage range is 2.5-4.3V (LiNi x Co y Mn 1-x-y O 2 Wherein, when x is more than or equal to 0.5 and less than 0.8, the voltage range is 2.5-4.4V; when x is more than or equal to 0.8 and less than or equal to 0.96, the voltage range is 2.5-4.3V); the charge-discharge current densities were 0.1C, 1C and 4C, and the test results are shown in table 1.
TABLE 1
From the data in table 1, it is clear that the batteries prepared from the double-layer coated cathode materials prepared in examples 1 to 5 have a charge capacity retention rate of higher than 87.0% and an impedance growth rate of lower than 47.0% after 100 cycles, and have very good cycle stability; and the battery has higher rate capability and lower impedance.
Compared with the example 1, the positive electrode material adopted in the comparative example 1 only coats the first coating layer containing phosphate, so that the capacity retention rate is reduced, meanwhile, the impedance growth rate is greatly increased after 100 circles of circulation, the stability of the battery is poor, the specific capacity of the battery at 4C charge-discharge current density is only 157mAh/g, and the rate performance is reduced. Comparative example 2 compared with example 1, the positive electrode material used only coated the LATP coating layer, and the cell showed a 9% increase in the rate of increase in resistance after 100 cycles compared with example 1, a significant decrease in cycle performance, and a decrease in rate capability.
Compared with the example 5, the cathode material adopted in the comparative example 3 is a first coating layer only coated with phosphate, after 100 cycles, the capacity retention rate of the battery is reduced to 81.2%, the impedance growth rate is as high as 73.0%, the cycle stability is obviously reduced, and the specific capacity of the battery at 4C charge-discharge current density is 170mAh/g, and the rate capability is reduced.
In comparative example 4, a composite coating layer containing two mixed phosphates was formed on the surface of the positive electrode active material, and although good cycle performance could be maintained, the resistance increased significantly, and after 100 cycles, the resistance increase rate increased significantly as compared with example 1, and the rate performance also showed a significant decrease.
For purposes of this disclosure, the terms "one embodiment," "some embodiments," "example," "a particular example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.
While the above embodiments have been shown and described, it should be understood that the above embodiments are illustrative and not to be construed as limiting the invention, and that variations, modifications, alternatives, and variations of the above embodiments may be made by those of ordinary skill in the art without departing from the scope of the invention.

Claims (10)

1. The double-layer coated positive electrode material is characterized by comprising a positive electrode active material, wherein a first coating layer and a second coating layer are sequentially arranged on the surface of the positive electrode active material,
the first coating layer comprises PO 4 3- The coating material of the first coating layer comprises phosphate which does not contain transition metal and does not contain lithium titanium aluminum phosphate;
the second cladding layer includes lithium aluminum titanium phosphate.
2. The double-coated positive electrode material according to claim 1, wherein the positive electrode active material comprises a ternary positive electrode active material having a chemical formula LiNi x Co y Mn 1-x-y O 2 Wherein x is more than or equal to 0.5 and less than or equal to 0.96,0.02, and y is more than or equal to 0.2.
3. The double-coated positive electrode material according to claim 1, wherein the coating material of the first coating layerThe material comprises Li 3 PO 4 、NH 4 H 2 PO 4 Or (NH) 4 ) 2 HPO 4 At least one of them.
4. The double-coated positive electrode material according to any one of claims 1 to 3, wherein the first coating layer has a coating thickness of 5nm to 30nm and the second coating layer has a coating thickness of 6nm to 50nm.
5. A method for preparing the double-layer coated positive electrode material according to any one of claims 1 to 4, comprising the steps of:
(1) Adding a positive electrode active material and a coating material of a first coating layer into an organic solvent, stirring and evaporating the organic solvent, and calcining to obtain a first product;
(2) And mixing the first product with lithium aluminum titanium phosphate, and calcining to obtain the double-layer coated positive electrode material.
6. The method according to claim 5, wherein in the step (1), the molar ratio of phosphate groups in the positive electrode active material to the coating material is 100:0.05 to 0.3;
and/or, in the step (2), the molar ratio of the positive electrode active material to phosphate radical in the lithium aluminum titanium phosphate is 100:0.05 to 0.4.
7. The production method according to claim 5 or 6, wherein in the step (1), the organic solvent includes at least one of ethanol and methanol, and/or the mass ratio of the positive electrode active material and the organic solvent is 1 to 3:3.
8. The method according to claim 5 or 6, wherein in the step (1) and/or the step (2), the calcination is performed at a temperature of 400 to 700 ℃, for a time of 2 to 10 hours, and/or in an air or oxygen atmosphere.
9. A lithium ion battery comprising the positive electrode material according to any one of claims 1 to 4 or the positive electrode material produced by the method according to any one of claims 5 to 8.
10. A vehicle comprising the lithium-ion battery of claim 9.
CN202310500618.3A 2023-05-05 2023-05-05 Double-layer coated positive electrode material, preparation method thereof, lithium ion battery and vehicle Pending CN116722135A (en)

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