CN108598400B - Three-layer core-shell structure cathode material, preparation method and lithium ion battery - Google Patents

Three-layer core-shell structure cathode material, preparation method and lithium ion battery Download PDF

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CN108598400B
CN108598400B CN201810322221.9A CN201810322221A CN108598400B CN 108598400 B CN108598400 B CN 108598400B CN 201810322221 A CN201810322221 A CN 201810322221A CN 108598400 B CN108598400 B CN 108598400B
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cathode material
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CN108598400A (en
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靳岩
娄忠良
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Soundon New Energy 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
    • H01M4/366—Composites as layered products
    • 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
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • 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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    • H01M4/36—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
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    • 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
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    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, 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
    • 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
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    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention relates to a three-layer core-shell structure cathode material, which comprises a three-layer structure: the anode material comprises a ternary anode material core, an alumina layer coating the ternary anode material core, and a fast ion conductor layer coating the alumina layer. The invention also discloses a preparation method of the anode material with the three-layer core-shell structure. Because the fast ion conductor coated by the outer layer of the anode material with the three-layer core-shell structure has super strong ion conductivity, the Al can be improved2O3The ion conductivity of the whole coated anode material reduces the electric energy loss and improves the cycle performance of the battery. And the aluminum oxide layer and the ternary cathode material core form a Li-Al-Co-O eutectic body by high-temperature calcination in the preparation process, so that the ionic conductivity of the material can be further enhanced, the conductivity and the micro stability of the composite material are increased, the corrosion of electrolyte to the ternary cathode material core can be reduced by the three-layer core-shell structure, and the safety of the battery is improved.

Description

Three-layer core-shell structure cathode material, preparation method and lithium ion battery
Technical Field
The invention relates to a battery anode material, a preparation method thereof and a lithium ion battery containing the anode material.
Background
Lithium ion batteries have the characteristics of high energy density, long cycle life, no memory effect, no environmental pollution and the like, and are widely applied to portable electronic equipment and power automobiles. Therefore, lithium ion batteries and related materials thereof become hot spots of current research. The most widely used positive electrode materials of commercial lithium ion batteries at present are lithium cobaltate, lithium manganate, lithium iron phosphate, layered nickel cobalt manganese ternary materials, nickel cobalt aluminum ternary materials and the like. Lithium cobaltate is the earliest to realize industrial production, but the cobalt resource is expensive, so the material cost is high, and the environment is influenced to a certain extent. Although the lithium manganate material is low in price, Jahn-Teller effect is easy to occur, so that the battery capacity is low, and the cycling stability is poor. The safety performance of the lithium iron phosphate is good, but the theoretical capacity of the lithium iron phosphate is low, so that the requirement of high energy density cannot be met.Nickel-cobalt-manganese ternary material LiNiaCobMncO2(wherein 0)<a,b,c<1, a + b + c is 1) fully utilizes the synergistic effect of three materials of Ni, Co and Mn and integrates LiNiO2、LiCoO2、LiMnO2The performance of the three lithium ion battery anode materials is superior to that of a single-component anode material, and the three lithium ion battery anode materials are considered to be the lithium ion battery anode materials with the most development prospect at present. And nickel cobalt aluminum ternary material LiNiaCobAlcO2(0.7 & lt a & lt 0.9 & gt, 0.05 & lt b & lt 0.2 & gt, and a + b + c & lt 1 & gt) also has electrochemical properties similar to those of the nickel-cobalt-manganese ternary material.
Although the nickel-cobalt-manganese ternary material LiNiaCobMncO2[ also denoted as Li (NiCoMn) ]1O2]Or the nickel-cobalt-aluminum ternary material has the advantages, but has serious defects, such as cation mixed discharging effect in the charging and discharging process, and change of the microstructure of the material, so that the first coulomb efficiency and the cycle stability in the first charging and discharging process are low; the lithium ion diffusion coefficient and the electronic conductivity are low, and the rate capability of the material is poor; in the charging and discharging processes, the ternary material and the electrolyte have serious side reaction, poor cycle performance and low coulombic efficiency; and the material is easy to have high-temperature flatulence phenomenon, so that serious potential safety hazard exists. The main means for solving the above problems include atom doping, surface coating, and mixing with other active materials. At present, the ternary anode material is coated by alumina, such as Chinese patent application CN 103618064B, CN106784837A, which firstly obtains Al (OH)3And mixing and grinding the coated ternary material precursor with lithium acetate or lithium carbonate, and finally calcining at high temperature to obtain the ternary material. However, since alumina is an ion/electron insulator, coating alumina on the surface of the ternary cathode material has a certain effect of inhibiting the transmission of lithium ions, and is not beneficial to the charge and discharge process at high rate, specifically, the discharge capacity of the battery at high rate is attenuated more rapidly, and the capacity retention rate is low. Secondly, powder blending and grinding are not favorable for the uniformity of the material.
In view of the above reasons, the present invention aims to improve the microstructure and the preparation method of a ternary cathode material coated with alumina, to improve the overall ionic conductivity of the material, and to reduce the inhibition effect of alumina on lithium ion transmission, thereby slowing down the decay rate of the battery discharge capacity at high rate, and improving the capacity retention rate of the battery.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a three-layer core-shell structure cathode material, which is characterized in that a layer of fast ion conductor is further coated outside a ternary cathode material with the surface coated with aluminum oxide, so that the overall ionic conductivity of the material is improved, the attenuation speed of the battery discharge capacity under high rate is slowed, and the cycle performance and the safety of the battery are improved. The invention also provides a method for preparing the three-layer core-shell structure cathode material and application.
In order to achieve the purpose, the invention adopts the main technical scheme that:
a three-layer core-shell structure cathode material comprises a three-layer structure: the anode material comprises a ternary anode material core, an aluminum oxide layer coating the ternary anode material core, and a fast ion conductor layer coating the aluminum oxide layer.
Wherein the fast ion conductor is Li1+xAlxTi2-x(PO4)3(0＜x≤0.5)、Li1+xAlxGe2-x(PO4)3(0＜x≤0.5)、LiA2(PO4)3(A＝Ti，Zr，Hf)、Li2+2xZn1-xGeO4(0 < x < 1) or Li4-xGe(Si,P)1-yMyS4(M is a metal cation with a valence of 3 or 5, x is more than 0 and less than 1, y is more than 0 and less than 1) and the like. Wherein the ternary cathode material is nickel-cobalt-manganese cathode material LiNiaCobMncO2(0<a,b,c<1, a + b + c ═ 1) or nickel cobalt aluminum positive electrode material LiNiaCobAlcO2(0.7≤a≤0.9，0.05≤b≤0.2,a+b+c＝1)。
According to the invention, the fast ion conductor layer is coated outside the anode material coated by the aluminum oxide, and partial impedance brought by the aluminum oxide is counteracted by virtue of the super-strong ion conductivity of the fast ion conductor layer, so that the ion conductivity of the anode material with the three-layer core-shell structure is integrally improved. In addition, compared with a two-layer core-shell composite structure, the three-layer core-shell composite structure has the advantages that the contact area between the ternary cathode material and the electrolyte can be effectively reduced by the outermost fast ion conductor layer, the corrosion of the electrolyte to the cathode material is prevented, and the service life of the lithium ion battery is prolonged.
Preferably, the fast ion conductor is Li1+xAlxTi2-x(PO4)3(x is more than 0 and less than or equal to 0.5). This is because when the fast ion conductor is Li1+xAlxTi2-x(PO4)3And when x is more than 0 and less than or equal to 0.5, the fast ion conductor and the middle alumina layer have the same chemical element Al and can form chemical bonds, and a eutectic of Li-Al-Co-O is formed between the alumina layer and the inner core of the ternary cathode material. Therefore, interactive structures or chemical bonds are respectively formed between the middle layer and the inner core, and between the middle layer and the outer layer of the three-layer core-shell structure cathode material, and through the related actions between the layers, on one hand, the ion conductivity can be further increased, and the ion conductivity can be improved; on the other hand, the stability of the composite material microstructure and the safety of the battery can be improved.
In the application, the eutectic body means that aluminum oxide and a ternary cathode material are changed into liquid at a high temperature, and are mutually dissolved (mutually dissolved), and the mutually dissolved parts form uniform and consistent substances after cooling.
Preferably, the mass ratio of the ternary positive electrode material core to the aluminum oxide layer to the fast ion conductor layer is 50-100: 1-10: 1 to 10.
Fast ionic conductors (fast ionic conductors) are also called solid electrolytes. In the present application, a lithium super-ion conductor or a lithium fast ion conductor is mainly referred to. The most basic features of fast ion conductors that are distinguished from general ion conductors are: has an ionic conductivity (1 x 10) comparable to that of a liquid electrolyte over a certain temperature range-6S·cm-1) And low ion conductivity activation energy (less than 0.40eV), and the ion conductivity of the fast ion conductor is high and the electron conductivity is very low (less than 1% of the total conductivity). For being transmittedThe types of the conductive ions are different, and the conductive ions comprise positive ion fast conductors such as a lithium fast ion conductor and a sodium fast ion conductor, and negative ion fast conductors such as an oxygen fast ion conductor and a chlorine fast ion conductor.
The technical scheme of the invention also comprises a preparation method of the three-layer core-shell structure cathode material, wherein the method comprises the following steps:
preparing sol: preparing a lithium source, a titanium source, an aluminum source and phosphate into sol in a solvent;
preparing gel: coating the sol with Al (OH)3Coated ternary positive electrode material precursor or Al2O3Coating a ternary cathode material, and processing the sol into gel;
and (3) gel calcination: calcining the gel in an oxygen-containing atmosphere to obtain a three-layer core-shell structure anode material; the three-layer core-shell structure anode material sequentially comprises a ternary anode material core, an aluminum oxide layer coating the ternary anode material core and a fast ion conductor layer coating the aluminum oxide layer from inside to outside, wherein the fast ion conductor is Li1+xAlxTi2-x(PO4)3(0＜x≤0.5)。
Wherein the ternary cathode material is nickel-cobalt-manganese cathode material LiNiaCobMncO2(0<a,b,c<1, a + b + c ═ 1) or nickel cobalt aluminum positive electrode material LiNiaCobAlcO2(0.7≤a≤0.9，0.05≤b≤0.2,a+b+c＝1)。
Preferably, the Al2O3The coated ternary positive electrode material is either purchased directly or prepared by any one of the existing methods, for example according to the methods of chinese patent application CN 103618064B or CN 106784837A.
Preferably, in the step of preparing the sol, a certain amount of soluble lithium source, a certain amount of soluble titanium source, a certain amount of soluble aluminum source and a certain amount of soluble phosphate are dissolved in water or an organic solvent, a certain amount of gelling agent is added, and the pH value is adjusted to 6-8 to obtain the sol.
It is noted that in the sol preparation step, soluble lithium sources, soluble titanium sources, soluble aluminum sourcesThe mass or amount of substance added by the phosphate and the fast ion conductor Li to be obtained1+xAlxTi2-x(PO4)3The value of x is related, and the amount of the lithium source, the titanium source, the aluminum source and the phosphate can be determined by the skilled in the art according to the expression of the fast ion conductor obtained as required.
Preferably, the lithium source is any one of lithium acetate, lithium hydroxide or lithium carbonate; preferably, the titanium source is any one of tetrabutyl titanate, isopropyl titanate, tetrabutyl titanate, ethyl titanate or n-butyl titanate; preferably, the aluminum source is one capable of producing Al in water3+、AlO2 -、[Al(OH)4]-Or [ Al (OH) ]4(H2O2)]-Any one of the aluminum salts of (a); preferably, the phosphate is capable of generating PO in water4 3-、HPO4 2-、H2PO4 -Any one of the phosphate salts of (1).
Preferably, the gelling agent is selected from citric acid, gelatin, carrageenan, xanthan gum, sodium alginate, konjac flour, agar, etc.
In the context of the present invention, the gelling agent is preferably citric acid, which on the one hand can be used for pH adjustment and also as complexing agent for forming the colloid. Citric acid is used as a complexing agent, the dosage of the citric acid is related to the stability of colloid, and the precipitation phenomenon can be caused when the dosage is too small. The sol was left for a sufficient time to just avoid the occurrence of metal salt precipitates as a minimum amount of citric acid to be used.
Preferably, the organic solvent is a proton donating solvent such as ethylene glycol, methanol, ethanol, propanol, butanol, pentanol, hexanol, or a polar aprotic solvent such as diethyl ether, tetrahydrofuran, dimethyl sulfoxide, dimethylformamide, or hexamethylphosphoramide. The aforementioned solvents can be used to disperse and dilute the sol.
Preferably, the step of preparing the gel comprises: mixing Al (OH)3Coated ternary positive electrode material precursor or Al2O3The coated ternary cathode material is put into the sol to enable the sol to wrap the solAl(OH)3Coated ternary positive electrode material precursor or Al2O3And heating the coated ternary cathode material to 170-180 ℃ to volatilize the solvent in the sol to obtain the gel.
In one embodiment of the present invention, the Al (OH)3The coated ternary positive electrode material precursor is prepared by the following method: adding a precursor of a ternary cathode material into Al3+The precursor suspension of the ternary anode material is formed in the participating double hydrolysis reaction system, and Al (OH) is generated by double hydrolysis reaction3Depositing by taking the ternary cathode material precursor suspended particles as a carrier to obtain Al (OH)3And (3) coating the ternary cathode material precursor precipitate.
Preferably, the alloy consists of Al3+The participated double hydrolysis reaction system refers to an aqueous solution simultaneously containing soluble aluminum salt and bicarbonate radical or carbonate radical; or an aqueous solution comprising both soluble aluminium salts and sulphide ions or hydrogensulphide; or Al2S3Or an aqueous solution of AlN. The double hydrolysis reaction makes full use of the reaction materials and the reaction is more thorough. The raw materials used in the double hydrolysis, especially aluminum salt and bicarbonate, are common reagents, so that the cost is low, and the environment is not polluted. In the prior art, aluminum metaaluminate and ammonia water are generated into aluminum hydroxide coagulation sediment in an alkaline environment, the surface residual alkali quantity is higher, and negative effects are generated on the prepared electrode active material.
Al mentioned above3+The reaction process of the participating double hydrolysis reaction system is as follows:
Al3++3HCO3 －＝Al(OH)3↓+3CO2either or not at either ≈ or ≈
Al2S3+6H2O＝2Al(OH)3↓+3H2S ↓or
AlN+3H2O＝Al(OH)3↓+NH3Either or not at either ≈ or ≈
2Al3++3CO32-+3H2O＝2Al(OH)3↓+3CO2Either or not at either ≈ or ≈
2Al3++3S2-+6H2O＝2Al(OH)3↓+3H2S ↓or
Al3++3HS-+3H2O＝Al(OH)3↓+3H2S↑。
In one embodiment of the invention, the alloy is made of Al3+The participated double hydrolysis reaction system is that HCO3 is dripped into water-soluble aluminum salt－Solution of Al3+With HCO3－The double hydrolysis reaction is carried out to continuously generate Al (OH)3Formation of Al (OH)3Depositing and coating the ternary positive electrode material precursor to form a precipitate, and separating to obtain Al (OH)3And (3) a coated ternary cathode material precursor.
In the application, the precursor of the ternary cathode material is nickel-cobalt-manganese hydroxide NiaCobMnc(OH)2，(0<a,b,c<1, a + b + c ═ 1); or nickel cobalt aluminum hydroxide NiaCobAlc(OH)2(0.7. ltoreq. a.ltoreq.0.9, 0.05. ltoreq. b.ltoreq.0.2, and a + b + c 1); the former ternary anode material precursor is prepared by taking nickel salt, cobalt salt and manganese salt as raw materials; the latter precursor is prepared from nickel salt, cobalt salt and aluminum salt. Wherein the proportion (a: b: c) can be adjusted according to actual needs. Wherein, the nickel-cobalt-manganese ternary cathode material LiNiaCobMncO2The application is most extensive, and the adaptability is better, so that the precursor of the ternary cathode material is preferably nickel-cobalt-manganese hydroxide NiaCobMnc(OH)2。
In addition, Al (OH)3The coated ternary cathode material precursor can be prepared by any one of the existing methods, such as the method according to the Chinese patent application CN 103618064B or CN 106784837A.
In one embodiment of the invention, the ternary cathode material precursor NiaCobMnc(OH)2(0<a,b,c<1, a + b + c is 1) dissolving soluble Ni salt, Co salt and Mn salt in a certain mass ratio in alcohol solution, adjusting the solution to be alkalescent by adopting weak base, then carrying out solvothermal reaction for 5-20 h at 150-180 ℃, and filtering to obtain the precursor of the ternary cathode material. It should be noted that, in the following description,the ternary precursor may also be made by any other existing method or directly from commercial purchase. Preferably, the soluble Ni salt is any one of nickel nitrate, nickel sulfate and nickel chloride; preferably, the soluble Co salt is any one of cobalt nitrate, cobalt sulfate and cobalt chloride; preferably, the soluble Mn salt is any one of manganese nitrate, manganese sulfate, and manganese chloride. Preferably, the alcohol is lower alcohol such as isopropanol, propanol, methanol, ethanol, butanol, pentanol, hexanol, etc. Preferably, the weak base is any one of ammonia water, ammonium bicarbonate, sodium carbonate, potassium bicarbonate, and the like. Preferably, the weak alkalinity is pH 10-12.
In one embodiment of the invention, the gel calcination step is performed under the conditions of 600-950 ℃ for 3-10 hours.
The technical scheme of the invention also comprises a lithium ion battery manufactured by the three-layer core-shell structure cathode material and the three-layer core-shell structure cathode material obtained by the preparation method.
In this application, soluble means soluble with respect to the solvent specifically used.
The beneficial technical effects of the invention are as follows:
(1) according to the three-layer core-shell structure cathode material, the fast ion conductor is coated outside the aluminum oxide layer, and the fast ion conductor has high lithium ion conductivity, so that Al can be offset2O3The ionic conductivity of the whole positive electrode material is improved due to the ionic conduction hindering effect. In addition, the fast ion conductor can weaken the corrosivity of liquid electrolyte to the ternary cathode material, and the battery safety is improved.
(2) The fast ion conductor is Li1+xAlxTi2-x(PO4)3(x is more than 0 and less than or equal to 0.5), the fast ion conductor Li has the function of a common fast ion conductor1+xAlxTi2-x(PO4)3Also due to the intermediate Al2O3The layer has the same metal element Al and can form chemical bonds, and the middle alumina layer and the ternary cathode material core form Li-Al-Co-O eutectic. By this means of this, the first and second,on one hand, the ionic conductivity of the anode material can be improved, the blocking effect of aluminum oxide on lithium ion conduction is weakened, the retention rate of the battery discharge capacity under high rate is improved, and the cycle performance and the safety of the battery are improved; on the other hand, the core-shell structure of the material can be stabilized, and the stability of the microstructure of the material is further enhanced.
(3) According to the preparation method of the three-layer core-shell structure cathode material, only one-step calcination treatment is needed, so that the precursor of the ternary cathode material is converted into the ternary cathode material, and Al (OH) coated on the outer layer of the ternary cathode material3The aluminum oxide is converted, the outermost layer forms a coating structure of the fast ion conductor, and the preparation cost is low by a one-step calcining method. Meanwhile, in the calcining process, the alumina layer and the ternary cathode material kernel form Li-Al-Co-O eutectic, namely the fast ion conductor Li1+xAlxTi2-x(PO4)3(x is more than 0 and less than or equal to 0.5) and intermediate Al2O3The layers form a chemical bond, and the connection and support effect among the layers strengthens the stability of the three-layer core-shell structure anode material structure and improves the ionic conductivity of the material.
(4) In the preparation method of the three-layer core-shell structure cathode material, Al (OH) is prepared3The process of the coated ternary anode material precursor is to put the ternary anode material precursor into Al3+The participating double hydrolysis reaction system leads the precursor of the ternary cathode material to be dispersed into granular suspension in water, and Al (OH) is continuously generated by double hydrolysis reaction3Insoluble Al (OH) generated by continuously slowly depositing in the solution and taking ternary anode material precursor suspended particles as deposition carriers3Gradually depositing and wrapping the ternary cathode material precursor suspension particles to enlarge and weigh the particles, and generating Al (OH) in a reaction solution3And (3) coating the ternary cathode material precursor precipitate. Compared with the prior art, Al (OH)3As for the coated ternary positive electrode material precursor and lithium carbonate or lithium acetate blending grinding method, the method of the invention enables the Li ions and the ternary positive electrode material precursor to be more uniformly assembled, and can effectively ensure that Al (OH)3Uniformity of the coated ternary positive electrode material precursor.
(5) The preparation method of the three-layer core-shell structure cathode material comprises the steps of coating a ternary cathode material by adopting a wet method and a sol-gel method to form a three-layer core-shell structure, and specifically, dissolving a soluble lithium source, a soluble titanium source, a soluble aluminum source and a soluble phosphate in water or a mixed solvent of water and an organic solvent to form sol, and then adding Al (OH)3Coated ternary positive electrode material precursor powder (or Al)2O3A coated ternary positive electrode material) is dispersed in the sol, and is coagulated by heat treatment, thereby causing al (oh)3Li, Ti, Al and phosphate radicals are wrapped outside the wrapped ternary cathode material precursor, and lithium ions in the solution also penetrate into the ternary cathode material precursor on the inner layer. Compared with the solid phase system in the prior art, the reaction process of the wet reaction system can ensure the structural uniformity of the target product.
Drawings
Fig. 1 is a schematic structural diagram of a three-layer core-shell structure cathode material of the invention.
Fig. 2 is an SEM scanning electron micrograph of the al (oh) 3-coated ternary positive electrode material precursor coated with the intermediate product of example 2 according to the present invention.
FIG. 3 is a TEM transmission electron microscope image of a final product of the anode material with a three-layer core-shell structure in example 2.
10-ternary positive pole material kernel, 20-alumina layer and 30-fast ion conductor layer.
Detailed Description
For the purpose of better explaining the present invention and to facilitate understanding, the present invention will be described in detail by way of specific embodiments with reference to the accompanying drawings.
As shown in fig. 1, the three-layer core-shell structure cathode material of the present invention comprises a three-layer structure: the cathode material comprises a ternary cathode material core 10, an alumina layer 20 coated on the ternary cathode material core, and a fast ion conductor layer 30 coated on the alumina layer, wherein the fast ion conductor is Li1+xAlxTi2-x(PO4)3(x is more than 0 and less than or equal to 0.5). The mass ratio of the ternary positive electrode material inner core 10, the alumina layer 20 and the fast ion conductor layer 30 is (50-100):(1-10): (1-10). A eutectic of Li-Al-Co-O is formed between the alumina layer 20 and the ternary positive electrode material core 10; a chemical bond is formed between the fast ion conductor layer 30 and the alumina layer 20.
The method for preparing the three-layer core-shell structure cathode material mainly comprises the steps of coating a ternary cathode material by adopting a wet method and a sol-gel method to form a three-layer core-shell structure, dissolving a soluble lithium source, a soluble titanium source, a soluble aluminum source and soluble phosphate in a solvent, forming sol under the promotion of a gelling agent, and then adding Al (OH)3Coated ternary positive electrode material precursor powder or Al2O3The coated ternary anode material is dispersed in the sol and subjected to coagulation through heating treatment, Li, Ti, Al and phosphate radical gel is coated outside, and some lithium ions can also penetrate into the interior and be embedded on the precursor of the ternary anode material or the anode material; and finally, calcining the gel in a high-temperature oxygen-containing atmosphere to obtain the three-layer core-shell structure anode material.
Preferably, the ternary positive electrode material precursor is nickel cobalt manganese hydroxide NiaCobMnc(OH)2Or nickel cobalt aluminum hydroxide NiaCobAlc(OH)2The former precursor is prepared from nickel salt, cobalt salt and manganese salt as raw materials, and the latter precursor is prepared from nickel salt, cobalt salt and aluminum salt as raw materials. Wherein the ratio (a: b: c) can be adjusted according to actual needs. In addition, the ternary cathode material precursor can be obtained by any one of the existing methods.
In the present invention, Al (OH)3The precursor of the coated ternary cathode material is prepared by adding the precursor of the ternary cathode material into Al3+Forming ternary positive electrode material precursor suspension in the participating double hydrolysis reaction system to make Al (OH) produced by double hydrolysis reaction3Continuously taking ternary anode material precursor suspended particles as a carrier to deposit to obtain Al (OH)3And (3) coating the ternary cathode material precursor precipitate.
According to the above thought, the preparation method of the three-layer core-shell structure cathode material can be designed as the following experimental operation steps:
step S1: weighing a certain amount of soluble Ni, Co and Mn salts, adding the soluble Ni, Co and Mn salts into an alcohol solution, and then dropwise adding a certain amount of ammonium bicarbonate solution into the alcohol solution until the solution is in a weakly alkaline environment. And then placing the mixture in a reaction kettle for solvothermal reaction at 150-180 ℃ for 5-20 h, and then filtering and washing to obtain the ternary cathode material precursor.
Preferably, the soluble Ni salt is any one of nickel nitrate, nickel sulfate and nickel chloride; preferably, the soluble Co salt is any one of cobalt nitrate, cobalt sulfate and cobalt chloride; preferably, the soluble Mn salt is any one of manganese nitrate, manganese sulfate, and manganese chloride. Preferably, the alcohol is lower alcohol such as isopropanol, propanol, methanol, ethanol, butanol, pentanol, hexanol, etc. Preferably, the ammonium bicarbonate can be replaced by any weak base of ammonia, sodium carbonate, potassium bicarbonate, etc. Preferably, the weak alkaline environment is pH 10-12.
The solvothermal reaction time is preferably 12 h. The solvothermal method is developed on the basis of a hydrothermal method, and refers to a synthetic method in which an original mixture is reacted in a closed system such as an autoclave by using an organic or non-aqueous solvent as a solvent at a certain temperature and under the autogenous pressure of the solution. It differs from hydrothermal reactions in that the solvent used is organic rather than water.
Step S2: adding the ternary positive electrode material precursor into 0.1-1 mol/L aluminum sulfate solution, stirring to form uniform ternary positive electrode material precursor particle suspension dispersion, then slowly dripping sodium bicarbonate solution into the ternary positive electrode material precursor particle suspension dispersion while stirring until no gas is generated, and then washing and filtering to obtain Al (OH)3And (3) a coated ternary cathode material precursor. The process generates a chemical expression Al3++3HCO3 －＝Al(OH)3↓+3CO2And (4) performing double hydrolysis reaction of ≈ er.
Providing Al from aluminum sulfate solution3+Dropwise addition of sodium bicarbonate solution to provide HCO3 －The two components are subjected to double hydrolysis reaction in aqueous solution to generate water-insoluble Al (OH)3And CO2Gases, and the like. Thus the above-mentioned reactantIs replaced by any other material capable of producing Al (OH)3The double hydrolysis reaction system. The following reaction processes are also possible, for example:
Al3++3HCO3 －＝Al(OH)3↓+3CO2either or not at either ≈ or ≈
Al2S3+6H2O＝2Al(OH)3↓+3H2S ↓or
AlN+3H2O＝Al(OH)3↓+NH3Either or not at either ≈ or ≈
2Al3++3CO32-+3H2O＝2Al(OH)3↓+3CO2Either or not at either ≈ or ≈
2Al3++3S2-+6H2O＝2Al(OH)3↓+3H2S ↓or
Al3++3HS-+3H2O＝Al(OH)3↓+3H2S↑。
Step S3: respectively adding a certain amount of Li source, titanium source, Al source, phosphate and citric acid (serving as a gelling agent) into water, then adjusting the pH value to 6-8 to obtain sol, then adding glycol into the sol to properly dilute the sol, and continuously stirring. Then, the above-mentioned Al (OH) was added thereto3And (3) heating the coated ternary cathode material precursor at 170-180 ℃, and performing coagulation on the sol to obtain the gel.
The lithium source is any lithium salt or alkali which can provide lithium ions in water, such as any one of lithium acetate, lithium hydroxide or lithium carbonate; preferably, the titanium source is a hydrated ion that provides hexavalent titanium in water ([ Ti (OH))3O2]-) For example, it is any one of tetrabutyl titanate, isopropyl titanate, tetrabutyl titanate, ethyl titanate or n-butyl titanate; preferably, the aluminum source is one capable of generating AlO in water2 -、[Al(OH)4]-Or [ Al (OH) ]4(H2O2)]-Any one of the aluminum salts of (a); preferably, the phosphate is one that produces PO in water4 3-、HPO4 2-、H2PO4 -OfMeaning a phosphate.
Preferably, the gelling agent is selected from citric acid, gelatin, carrageenan, xanthan gum, sodium alginate, konjac flour, agar, etc. The gelling agent is preferably citric acid, which on the one hand can be used for pH adjustment and also as a complexing agent for forming a colloid. Citric acid is used as a complexing agent, the dosage of the citric acid is related to the stability of colloid, and the precipitation phenomenon can be caused when the dosage is too small. The sol was left for a sufficient time to just avoid the occurrence of metal salt precipitates as a minimum amount of citric acid to be used.
Preferably, the organic solvent is a proton donating solvent such as ethylene glycol, methanol, ethanol, propanol, butanol, pentanol, hexanol, isopropanol, or a polar aprotic solvent such as diethyl ether, tetrahydrofuran, dimethyl sulfoxide, dimethylformamide, or hexamethylphosphoramide. The aforementioned solvents can be used to disperse and dilute the sol.
Step S4: and calcining the gel at 600-950 ℃ for 3-10 h to obtain the composite three-layer core-shell structure.
The following description will be given, with reference to specific examples, of the preparation method of the three-layer core-shell structure positive electrode material of the present invention and electrochemical properties exhibited by the application of the prepared three-layer core-shell structure positive electrode material in a battery.
Example 1
In the three-layer core-shell composite cathode material of the embodiment, the inner core is LiNi0.6Co0.2Mn0.2O2The shell layer comprises an intermediate layer Al2O3And an outer layer Li1.3Al0.3Ti1.7(PO4)3Wherein LiNi0.6Co0.2Mn0.2O2With Al2O3And Li1.3Al0.3Ti1.7(PO4)3In a mass ratio of 50: 1: the preparation method of the core-shell structure comprises the following steps:
s1 LiNi lithium nickel cobalt manganese0.6Co0.2Mn0.2O2The precursor preparation:
109.620g of nickel nitrate Ni (NO)3)258.211g of cobalt Co nitrate (N)O3)2·6H2O, 35.790g manganese nitrate Mn (NO)3)2Adding the mixture into 700ml of butanol, and then dropwise adding 1mol/L ammonium bicarbonate solution into the mixture until the pH value of the solution is 10-12. Then placing the mixture into a polytetrafluoroethylene reaction kettle for solvothermal reaction at 150 ℃ for 12h, and then filtering and washing the mixture to obtain the precursor of the cathode material.
S2, adding the spherical precursor into 42.0ml of 0.01mol/L aluminum sulfate solution, stirring to form uniform dispersion, then slowly dropwise adding sodium bicarbonate solution into the mixture while stirring until no gas is generated, and then washing and filtering to obtain Al (OH)3And (3) a coated ternary cathode material precursor.
S3 preparation of 6.071g of lithium acetate, 0.636g of tetrabutyl titanate and 0.124g of aluminum nitrate (Al (NO)3)3·9H2O), 0.879g of tributyl phosphate and 2g of citric acid are added into water, the pH is adjusted to 6-8, and then an ethylene glycol solution is added into the water, and the mixture is continuously stirred. Then, the above-mentioned Al (OH) was added thereto3And (3) heating the coated ternary cathode material precursor at 180 ℃ to obtain the gel.
And S4, calcining the gel at 900 ℃ for 4 hours to obtain the anode material compounded with the three-layer core-shell structure.
And (2) mixing the synthesized composite material with a conductive agent Super and a binder PVDF according to the mass ratio of 9: 0.5: 0.5, preparing slurry, preparing an electrode through the processes of coating, drying, rolling and the like, assembling the electrode, the graphite electrode, the diaphragm and the electrolyte into the soft package battery, and testing the cycle performance of the soft package battery.
Example 2
In the three-layer core-shell composite cathode material of the embodiment, the inner core is LiNi0.6Co0.2Mn0.2O2The shell layer comprises an intermediate layer Al2O3And an outer layer Li1.3Al0.3Ti1.7(PO4)3Wherein LiNi0.6Co0.2Mn0.2O2With Al2O3And Li1.3Al0.3Ti1.7(PO4)3The mass ratio of (A) to (B) is 80: 1:1, itThe preparation method of the core-shell structure comprises the following steps:
s1 LiNi lithium nickel cobalt manganese0.6Co0.2Mn0.2O2The precursor preparation: 109.620g of nickel nitrate Ni (NO)3)258.211g of cobalt nitrate Co (NO)3)2·6H2O, 35.790g manganese nitrate Mn (NO)3)2Adding the mixture into 700ml of isopropanol, and then dropwise adding 1mol/L ammonium bicarbonate solution into the isopropanol until the pH value of the solution is 10-12. Then placing the mixture into a polytetrafluoroethylene reaction kettle for solvothermal reaction at 150 ℃ for 12h, and then filtering and washing the mixture to obtain the precursor of the cathode material.
S2, adding the spherical precursor into 26.2ml of 0.01mol/L aluminum sulfate solution, stirring to form uniform dispersion, slowly dropwise adding sodium bicarbonate solution into the dispersion while stirring until no gas is generated, washing and filtering to obtain Al (OH)3And (3) a coated ternary cathode material precursor. Detected by SEM with Al (OH)3The SEM atlas of the coated ternary cathode material precursor is shown in figure 2, and then EDS (electron-ray diffraction) energy spectrum analysis is assisted to obtain that Al elements are uniformly distributed on the surface of particles, so that the actual existence of the coating layer is verified.
S3 preparation of 5.941g of lithium acetate, 0.397g of tetrabutyl titanate and 0.077g of aluminum nitrate (Al (NO)3)3·9H2O), 0.624g of tributyl phosphate and 2g of citric acid are added into water, the pH is adjusted to 6-8, and then an ethylene glycol solution is added into the water, and the mixture is continuously stirred. Then, the above-mentioned Al (OH) was added thereto3And (3) heating the coated ternary cathode material precursor at 180 ℃ to obtain the gel.
And S4, calcining the gel at 900 ℃ for 4h to obtain the anode material compounded with the three-layer core-shell structure, wherein a TEM image of the material is shown by a transmission electron microscope. As shown in fig. 3, the fast ion conductor Li with the outermost layer at the leftmost side1+ xAlxTi2-x(PO4)3Intermediate layer of Al2O3And the rightmost side is an inner core LiNi0.6Co0.2Mn0.2O2。
And (2) mixing the synthesized composite material with a conductive agent Super and a binder PVDF according to the mass ratio of 9: 0.5: 0.5, preparing slurry, preparing electrodes through the processes of coating, drying, rolling and the like, assembling the electrodes, the graphite electrodes, the diaphragm and the electrolyte into the soft package battery, wherein the test results of the cycle performance are shown in the following table 1.
Example 3
In the three-layer core-shell composite cathode material of the embodiment, the inner core is LiNi0.6Co0.2Mn0.2O2The shell layer comprises an intermediate layer Al2O3And an outer layer Li1.3Al0.3Ti1.7(PO4)3Wherein LiNi0.6Co0.2Mn0.2O2With Al2O3And Li1.3Al0.3Ti1.7(PO4)3The mass ratio of (A) to (B) is 100: 1: the preparation method of the core-shell structure comprises the following steps:
s1 LiNi lithium nickel cobalt manganese0.6Co0.2Mn0.2O2Preparing a precursor: 109.62g (0.6mol) of nickel nitrate Ni (NO)3)258.21g (0.2mol) cobalt nitrate Co (NO)3)2·6H2O, 35.79g (0.2mol) manganese nitrate Mn (NO)3)2Adding the mixture into 700ml of propanol, and then dropwise adding 1mol/L ammonium bicarbonate solution into the mixture until the pH of the solution is 10-12. Then placing the mixture into a polytetrafluoroethylene reaction kettle for solvothermal reaction at 150 ℃ for 12h, and then filtering and washing the mixture to obtain the precursor of the cathode material.
S2, adding the spherical precursor into 21ml of 0.01mol/L aluminum sulfate solution, stirring to form uniform dispersion, then slowly dripping sodium bicarbonate solution into the mixture while stirring until no gas is generated, and then washing and filtering to obtain Al (OH)3And (3) a coated ternary cathode material precursor.
S3 preparation of 5.984g of lithium acetate, 0.318g of tetrabutyl titanate and 0.062g of aluminum nitrate (Al (NO)3)3·9H2O), 0.439g of tributyl phosphate and 2g of sodium alginate are added into water, the pH is adjusted to 6-8, and then an ethylene glycol solution is added into the water, and the mixture is continuously stirred. Then, the above-mentioned Al (OH) was added thereto3Coating ofThe precursor of the ternary anode material is heated at 180 ℃ to obtain the gel.
And S4, calcining the gel at 900 ℃ for 4 hours to obtain the composite three-layer core-shell structure.
And (2) mixing the synthesized composite material with a conductive agent Super and a binder PVDF according to the mass ratio of 9: 0.5: 0.5, preparing slurry, preparing an electrode through the processes of coating, drying, rolling and the like, assembling the electrode, the graphite electrode, the diaphragm and the electrolyte into the soft package battery, and testing the cycle performance of the soft package battery.
Example 4
In the three-layer core-shell composite cathode material of the embodiment, the inner core is LiNi0.8Co0.1Mn0.1O2The shell layer comprises an inner layer Al2O3And an outer layer Li1.5Al0.5Ti1.5(PO4)3Wherein LiNi0.8Co0.1Mn0.1O2With Al2O3And Li1.5Al0.5Ti1.5(PO4)3The mass ratio of (A) to (B) is 100: 1: the preparation method of the core-shell structure comprises the following steps:
s1 LiNi lithium nickel cobalt manganese0.8Co0.1Mn0.1O2Preparing a precursor: 146.16(0.8mol) nickel nitrate Ni (NO)3)229.10g (0.1mol) of cobalt nitrate Co (NO)3)2·6H2O, 17.90g (0.1mol) manganese nitrate Mn (NO)3)2Adding the mixture into 700ml of ethanol, and then dropwise adding 1mol/L ammonium bicarbonate solution into the mixture until the pH value of the solution is 10-12. Then placing the mixture into a polytetrafluoroethylene reaction kettle for solvothermal reaction at 150 ℃ for 12h, and then filtering and washing the mixture to obtain the precursor of the cathode material.
S2, adding the spherical precursor into 21ml of 0.01mol/L aluminum sulfate solution, stirring to form uniform dispersion, then slowly dripping sodium bicarbonate solution into the mixture while stirring until no gas is generated, and then washing and filtering to obtain Al (OH)3And (3) a coated ternary cathode material precursor.
S3 preparation of 6.905g of lithium acetate and 0.281g of tetra-titanic acidButyl ester, 0.103g of aluminum nitrate (Al (NO)3)3·9H2O), 0.439g of tributyl phosphate and 2g of gelatin are added into water, then the pH is adjusted to 6-8, and then an ethylene glycol solution is added into the mixture, and the mixture is continuously stirred. Then, the above-mentioned Al (OH) was added thereto3And (3) heating the coated ternary cathode material precursor at 180 ℃ to obtain the gel.
And S4, calcining the gel at 900 ℃ for 4 hours to obtain the composite three-layer core-shell structure cathode material.
The synthesized three-layer core-shell structure anode material is mixed with a conductive agent Super and a binder PVDF according to the mass ratio of 9: 0.5: 0.5, preparing slurry, preparing an electrode through the processes of coating, drying, rolling and the like, assembling the electrode, the graphite electrode, the diaphragm and the electrolyte into the soft package battery, and testing the cycle performance of the soft package battery.
Example 5
In the embodiment 5, basically the same as the embodiment 2, the inner core of the three-layer core-shell composite cathode material is Li Ni0.75Co0.1Mn0.15O2The shell layer comprises an inner layer Al2O3And an outer layer Li1.3Al0.3Ti1.7(PO4)3In which Li Ni0.75Co0.1Mn0.15O2With Al2O3And Li1.3Al0.3Ti1.7(PO4)3The mass ratio of (A) to (B) is 80: 1: 1. except that Al (OH) is prepared therein3When the precursor of the coated ternary cathode material is a commercial layered nickelic material Ni which is directly purchased0.75Co0.1Mn0.15(OH)2(precursor) Al (OH) was obtained according to the conventional technique described in Chinese patent application CN106784837A3And (3) a coated ternary positive electrode precursor.
6.905g of lithium acetate, 0.281g of tetrabutyl titanate, 0.103g of aluminum nitrate (Al (NO)3)3·9H2O), 0.439g of tributyl phosphate and 2g of gelatin are added into water, then the pH is adjusted to 6-8, and then an ethylene glycol solution is added into the mixture, and the mixture is continuously stirred. Then adding thereto Al (OH) prepared according to the above process3And (3) heating the coated ternary cathode material precursor at 180 ℃, and performing sol coagulation to obtain gel. And calcining the gel at 900 ℃ for 4h to obtain the composite three-layer core-shell structure.
The synthesized three-layer core-shell structure anode material is mixed with a conductive agent Super and a binder PVDF according to the mass ratio of 9: 0.5: 0.5, preparing slurry, preparing an electrode through the processes of coating, drying, rolling and the like, assembling the electrode, the graphite electrode, the diaphragm and the electrolyte into the soft package battery, and testing the cycle performance of the soft package battery.
Example 6
Example 6 the same as example 5, the core of the three-layer core-shell composite cathode material is Li Ni0.75Co0.1Mn0.15O2The shell layer comprises an inner layer Al2O3And an outer layer Li1.3Al0.3Ti1.7(PO4)3In which Li Ni0.75Co0.1Mn0.15O2With Al2O3And Li1.3Al0.3Ti1.7(PO4)3The mass ratio of (A) to (B) is 80: 1: 1. except that in the step of preparing the sol, Al was obtained by directly using the method of example 1 described in Chinese patent application CN106784837A2O3Coated ternary positive electrode material LiNi0.75Co0.1Mn0.15O2The material is dispersed in the reaction system to form suspended particles.
Specifically, 6.905g of lithium acetate, 0.281g of tetrabutyl titanate, 0.103g of aluminum nitrate (Al (NO)3)3·9H2O), 0.439g of tributyl phosphate and 2g of gelatin are added into water, the pH is adjusted to 6-8, then an ethylene glycol solution is added into the mixture, and the Al is added into the mixture under continuous stirring2O3Coated ternary positive electrode material LiNi0.75Co0.1Mn0.15O2Then heating at 180 deg.C, and coagulating to obtain gel.
And calcining the gel at 900 ℃ for 4h to obtain the composite three-layer core-shell structure.
The synthesized three-layer core-shell structure anode material is mixed with a conductive agent Super and a binder PVDF according to the mass ratio of 9: 0.5: 0.5, preparing slurry, preparing an electrode through the processes of coating, drying, rolling and the like, assembling the electrode, the graphite electrode, the diaphragm and the electrolyte into the soft package battery, and testing the cycle performance of the soft package battery.
Comparative example 1
The material synthesized by the comparative example was LiNi0.6Co0.2Mn0.2O2With Al2O3The composite material is formed by a core LiNi0.6Co0.2Mn0.2O2Outer shell Al2O3Wherein LiNi is0.6Co0.2Mn0.2O2With Al2O3The mass ratio of (A) to (B) is 80: the preparation method of the core-shell structure comprises the following steps:
s1 LiNi lithium nickel cobalt manganese0.6Co0.2Mn0.2O2Preparing a precursor: 109.620g of nickel nitrate Ni (NO)3)258.211g of cobalt nitrate Co (NO)3)2·6H2O, 35.790g manganese nitrate Mn (NO)3)2Adding the mixture into 700ml of isopropanol, and then dropwise adding 1mol/L ammonium bicarbonate solution into the isopropanol until the pH value of the solution is 10-12. Then placing the mixture into a polytetrafluoroethylene reaction kettle for solvothermal reaction at 150 ℃ for 12h, and then filtering and washing the mixture to obtain the precursor of the cathode material.
S2, adding the precursor into 26.2ml of 0.01mol/L aluminum sulfate solution, stirring to form uniform dispersion, slowly dropwise adding sodium bicarbonate solution into the dispersion while stirring until no gas is generated, washing and filtering to obtain Al (OH)3And (3) a coated ternary cathode material precursor.
S3, mixing and grinding the ternary positive electrode material precursor and 5.900g of lithium acetate, and then calcining the mixture at 900 ℃ for 4 hours to obtain the lithium iron oxide/lithium manganese oxide ternary positive electrode material0.6Co0.2Mn0.2O2With Al2O3The formed ternary anode material coated by the alumina.
The aluminum oxide-coated ternary positive electrode composite material obtained by the method is mixed with a conductive agent Super and a binder PVDF according to the mass ratio of 9: 0.5: 0.5, preparing slurry, preparing an electrode through the processes of coating, drying, rolling and the like, and assembling the electrode, the graphite electrode, the diaphragm and the electrolyte into the soft package battery.
Comparative example 2
With commercial layered nickelic material Ni0.75Co0.1Mn0.15(OH)210g of ternary positive electrode precursor Ni is used as a coating object0.75Co0.1Mn0.15(OH)280ml of deionized water are used for dispersion, stirring is assisted in this process, and stirring is stopped after 30 min.
Dissolving 0.5184g of sodium metaaluminate with 20ml of deionized water according to the coating amount of 3 wt% of the aluminum oxide by mass, mixing with the precursor slurry dispersed previously, introducing CO2 into the system, stirring for 120min at 70 +/-5 ℃, washing, filtering, and drying in a blast drying oven at 80 ℃ for 12-15h to obtain Al (OH)3And (3) a coated ternary positive electrode precursor.
Mixing lithium with the obtained precursor powder according to the molar ratio Li/(Ni + Co + Mn) of 1.05:1, namely mixing and grinding the calculated lithium acetate with the Al (OH) 3-coated ternary positive electrode precursor. Two-stage heating in oxygen atmosphere at 480 deg.c for 300min, further heating to 750 deg.c for 900min, and naturally cooling to obtain LiNi0.75Co0.1Mn0.15O2With Al2O3The formed ternary anode material coated by the alumina.
The aluminum oxide-coated ternary positive electrode material obtained by the method is mixed with a conductive agent Super and a binder PVDF according to the mass ratio of 9: 0.5: 0.5, preparing slurry, preparing an electrode through the processes of coating, drying, rolling and the like, and assembling the electrode, the graphite electrode, the diaphragm and the electrolyte into the soft package battery.
The three-layer core-shell cathode materials prepared in examples 1-6 above were prepared into cathodes, and graphite, LiPF6(EC/DEC ═ 1:1) electrolyte is assembled into a soft package battery, and the soft package battery is subjected to electrochemical performance test and test with the soft package battery assembled by the aluminum oxide coated ternary cathode material prepared in comparative example 1-2The results are shown in the following table:
Figure BDA0001625587790000181
Figure BDA0001625587790000191
from the above examples, it can be seen that, in the high-rate charge and discharge, the discharge capacities of examples 1 to 6 are significantly higher than those of comparative examples 1 to 2 for 300 times, and the retention rates are all higher than 95%, and particularly, the high-rate cycle stability and the capacity retention rate are shown in the high-rate discharge at 1.0C and 2.0C; in the case where the rate was increased several times, the variation in the capacity retention rate of the batteries obtained in examples 1 to 6 of the present invention was small.

Claims (5)

1. A preparation method of a three-layer core-shell structure cathode material is characterized by comprising the following steps:
preparing sol: preparing a lithium source, a titanium source, an aluminum source and phosphate into sol in a solvent;
preparing gel: coating the sol with Al (OH)3Coated ternary positive electrode material precursor or Al2O3Coating the ternary anode material, and processing the sol into gel;
and (3) gel calcining step: calcining the gel in an oxygen-containing atmosphere to obtain a three-layer core-shell structure anode material;
the three-layer core-shell structure anode material sequentially comprises the following components from inside to outside: the ternary cathode material comprises a ternary cathode material core, an aluminum oxide layer coating the ternary cathode material core, and a fast ion conductor layer coating the aluminum oxide layer, wherein the aluminum oxide layer is made of aluminum oxide, the fast ion conductor layer is made of a fast ion conductor, and the fast ion conductor is Li1+ x Al x Ti x2-(PO4)3 ，0＜x ≤ 0.5。
2. The preparation method according to claim 1, wherein in the sol preparation step, a certain amount of soluble lithium source, a soluble titanium source, a soluble aluminum source, and a soluble phosphate are dissolved in water or an organic solvent, a certain amount of a gelling agent is added, and the pH is adjusted to 6 to 8 to prepare the sol.
3. The method according to claim 1, wherein in the step of preparing the gel, Al (OH)3Coated ternary positive electrode material precursor or Al2O3The coated ternary positive electrode material is put into the sol so that the sol coats the Al (OH)3Coated ternary positive electrode material precursor or Al2O3And heating the coated ternary cathode material to volatilize the solvent in the sol to obtain the gel.
4. The method according to claim 1, wherein the Al (OH)3The coated ternary positive electrode material precursor is prepared by the following method:
the precursor of the ternary anode material is added into Al3+The precursor suspension of the ternary anode material is formed in the participating double hydrolysis reaction system, and Al (OH) is generated by double hydrolysis reaction3Depositing by taking the ternary cathode material precursor suspended particles as a carrier to obtain Al (OH)3And (3) coating the ternary cathode material precursor precipitate.
5. The production method according to claim 4, wherein the ternary positive electrode material precursor is: Ni-Co-Mn positive electrode material precursor NiaCobMnc(OH)2Wherein 0 is<a,b,c<1, a + b + c = 1; or Ni-Co-Al positive electrode material precursor NiaCobAlc(OH)2Wherein a is more than or equal to 0.7 and less than or equal to 0.9, b is more than or equal to 0.05 and less than or equal to 0.2, and a + b + c = 1.
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