Method for coating nickel cobalt lithium manganate positive electrode material with calcium fluorophosphate

Abstract

The invention discloses a method for coating a nickel cobalt lithium manganate positive electrode material with calcium fluorophosphate, and belongs to the technical field of lithium batteries. According to the technical scheme, the method comprises the following steps: (1) providing a nickel cobalt lithium manganate positive electrode material, (2) stirring a lanthanum source and a titanium source in an alcohol solvent to form sol, then adding the nickel cobalt lithium manganate positive electrode material into the sol system, stirring for 1-8 hours at room temperature, then carrying out evaporation and vacuum drying, and then carrying out heat treatment for 1-6 hours at 300-600 DEG C in a muffle furnace to obtain the lithium ion battery positive electrode material. And finally obtaining the lanthanum-titanium composite oxide coated nickel cobalt lithium manganate positive electrode material. The lithium vanadium phosphate can provide good ion transmission performance, the carbon material can provide good electron transmission performance, the ionic conductivity and the electron conductivity of the single-crystal-morphology lithium nickel cobalt manganese oxide material can be effectively improved through organic combination of the lithium vanadium phosphate and the carbon material, and the chemical activity of the material is improved; therefore, the gram volume and the rate capability of the single-crystal nickel cobalt lithium manganate positive electrode material are greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium ions, and in particular relates to a method for coating a positive electrode material of lithium nickel cobalt manganate with calcium fluorophosphate. Background Art

[0002] As an important energy storage device, lithium-ion batteries have been widely used in electronic products such as mobile phones and computers. Traditional lithium-ion batteries mainly use lithium cobalt oxide as the positive electrode material, but due to the high price and low energy density of lithium cobalt oxide, there is an urgent need to find a positive electrode material with high energy density. At present, the positive electrode materials that are studied more are mainly layered ternary positive electrode materials, lithium-rich manganese-based materials, lithium manganese oxide and lithium iron phosphate. Among them, nickel cobalt manganese oxide ternary positive electrode materials are favored by people due to their high energy density, especially high nickel-based ternary materials, whose specific capacity can reach 200mAh / g. However, nickel cobalt manganese oxide positive electrode materials face problems such as poor structural stability and rapid capacity decay during the cycle, which limits their commercial application. In view of the problems faced by nickel cobalt manganese oxide materials, there are currently two main ways to improve them, namely ion doping and surface coating. Summary of the invention

[0003] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a method for coating a positive electrode material of lithium nickel cobalt manganese oxide with calcium fluorophosphate.

[0004] The technical solution of the present invention is: The method for coating a positive electrode material of lithium nickel cobalt manganese oxide with calcium fluorophosphate comprises a single crystal lithium nickel cobalt manganese oxide precursor and a coating layer coated on the surface of the single crystal lithium nickel cobalt manganese oxide, wherein the coating layer is composed of lithium vanadium phosphate and a carbon material.

[0005] Preferably, the weight ratio of single crystal lithium nickel cobalt manganese oxide, lithium vanadium phosphate and carbon material is: 50: (0.05-1): (0.05-0.5).

[0006] Preferably, the carbon material is a combination of one or more of carbon black, carbon nanotubes and graphene.

[0007] A method for preparing a nickel-cobalt-lithium manganese oxide composite material, comprising: The lithium nickel cobalt manganese oxide precursor, the lithium source, and the doping compound are mixed to obtain a first mixture, and then the mixture is calcined for the first time; The product of the first calcination is mixed with the coating compound to obtain a second mixture, and then calcined for a second time to obtain a nickel-cobalt-lithium manganese oxide composite material; Dissolve nickel salt, cobalt salt and manganese salt in water to prepare a mixed solution, then add a precipitant and a complexing agent to the mixed solution for reaction, filter, wash and dry after the reaction to obtain a nickel cobalt manganese oxide lithium precursor. The precipitant can be sodium hydroxide, disodium ethylenediaminetetraacetic acid, sodium citrate, sodium lactate, etc., and the complexing agent can be ammonia water, etc.

[0008] The lithium nickel cobalt manganese oxide precursor comprises a first precursor and a second precursor, wherein the first precursor is Ni 1 / 3Co 1 / 3 Mn 1 / 3 (OH)2, the second precursor includes Ni 0.5 Co 0.2 Mn 0.3 (OH)2、Ni 0.6 Co 0.2 Mn 0.2 (OH)2 and Ni 0.8 Co 0.1 Mn 0.1 One or more of (OH)2.

[0009] Preferably, the mass ratio of the first precursor to the second precursor is (2-5):(1-4).

[0010] Preferably, the doping compound includes one or more of Mg oxides and hydroxides, Ti oxides and hydroxides, Zr oxides and hydroxides, and Al oxides and hydroxides.

[0011] Compared with the prior art, the present invention has the following beneficial effects: 1. The nickel cobalt lithium manganese oxide positive electrode material of the present invention, lithium vanadium phosphate can provide good ion transmission performance, and the carbon material can provide good electron transmission performance. The organic combination of the two can effectively improve the ion conductivity and electronic conductivity of the single crystal nickel cobalt lithium manganese oxide material, improve its chemical activity, and thus greatly improve the single crystal nickel cobalt lithium manganese oxide positive electrode material The gram capacity and rate performance.

[0012] 2. Two nickel cobalt manganese oxide precursors with complementary electrochemical properties are selected as raw materials. The second precursor makes up for the defects of the first precursor, such as low specific capacity, high cobalt content and high price, and can be compounded with part of the first precursor, which increases the capacity of the material and keeps the cycle performance normal. After the two precursors are mixed and sintered by lithium, it is easier to form a concentration gradient material, which plays a great role in improving the overall performance of the battery cell. Doping compounds improve the rate performance of ternary materials and improve power performance; coating compounds improve the cycle performance and storage performance of ternary materials; element doping and coating improve the structural stability and thermal stability of the material. DETAILED DESCRIPTION

[0013] Example 1 A nickel-cobalt-manganese-oxide positive electrode material comprises a single-crystal nickel-cobalt-manganese-oxide precursor and a coating layer coated on the surface of the single-crystal nickel-cobalt-manganese-oxide, wherein the coating layer is composed of lithium vanadium phosphate and a carbon material.

[0014] The weight ratio of single crystal lithium nickel cobalt manganese oxide, lithium vanadium phosphate, and carbon material is 50:0.05:0.05.

[0015] The carbon material is a combination of one or more of carbon black, carbon nanotubes and graphene.

[0016] A method for preparing a nickel-cobalt-lithium manganese oxide composite material, comprising: The lithium nickel cobalt manganese oxide precursor, the lithium source, and the doping compound are mixed to obtain a first mixture, and then the mixture is calcined for the first time; The product of the first calcination is mixed with the coating compound to obtain a second mixture, and then calcined for a second time to obtain a nickel-cobalt-lithium manganese oxide composite material; Dissolve nickel salt, cobalt salt and manganese salt in water to prepare a mixed solution, then add a precipitant and a complexing agent to the mixed solution for reaction, filter, wash and dry after the reaction to obtain a nickel cobalt manganese oxide lithium precursor. The precipitant can be sodium hydroxide, disodium ethylenediaminetetraacetic acid, sodium citrate, sodium lactate, etc., and the complexing agent can be ammonia water, etc.

[0017] The lithium nickel cobalt manganese oxide precursor comprises a first precursor and a second precursor, wherein the first precursor is Ni 1 / 3Co 1 / 3 Mn 1 / 3 (OH)2, the second precursor is Ni 0.5 Co 0.2 Mn 0.3 (OH)2.

[0018] The mass ratio of the first precursor to the second precursor is 2:1.

[0019] The doping compound is Mg oxide and Mg hydroxide.

[0020] Example 2 A nickel-cobalt-manganese-oxide positive electrode material comprises a single-crystal nickel-cobalt-manganese-oxide precursor and a coating layer coated on the surface of the single-crystal nickel-cobalt-manganese-oxide, wherein the coating layer is composed of lithium vanadium phosphate and a carbon material.

[0021] The weight ratio of single crystal lithium nickel cobalt manganese oxide, lithium vanadium phosphate, and carbon material is 50:1:0.5.

[0022] The carbon material is a combination of carbon black, carbon nanotubes and graphene.

[0023] A method for preparing a nickel-cobalt-lithium manganese oxide composite material, comprising: The lithium nickel cobalt manganese oxide precursor, the lithium source, and the doping compound are mixed to obtain a first mixture, and then the mixture is calcined for the first time; The product of the first calcination is mixed with the coating compound to obtain a second mixture, and then calcined for a second time to obtain a nickel-cobalt-lithium manganese oxide composite material; Nickel salt, cobalt salt and manganese salt are dissolved in water to prepare a mixed solution, and then a precipitant and a complexing agent are added to the mixed solution for reaction, and after the reaction, the lithium nickel cobalt manganese oxide precursor is obtained by filtering, washing and drying. The precipitant is disodium ethylenediaminetetraacetate.

[0024] The lithium nickel cobalt manganese oxide precursor comprises a first precursor and a second precursor, wherein the first precursor is Ni 1 / 3Co 1 / 3 Mn 1 / 3 (OH)2, the second precursor is Ni 0.8 Co 0.1 Mn 0.1 One or more of (OH)2.

[0025] The mass ratio of the first precursor to the second precursor is 5:4.

[0026] The doping compounds are oxides and hydroxides of Ti.

[0027] Although the present invention has been described in detail by reference and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions shall be within the scope of the present invention. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, and all of these shall be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

[0028] Although the present invention has been described in detail by combining the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions shall be within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for coating a positive electrode material of lithium nickel cobalt manganese oxide with calcium fluorophosphate, characterized in that: The steps include: (1) Providing a nickel cobalt manganese oxide positive electrode material, wherein the chemical formula of the nickel cobalt manganese oxide positive electrode material is LiNixCoyMnzO2, wherein x = 0.3, y = 0.05, z = 0.05; (2) A lanthanum source and a titanium source are stirred in an alcohol solvent to form a sol, and then a nickel cobalt manganese oxide positive electrode material is added to the sol system, stirred at room temperature for 1-8 hours, evaporated, vacuum dried, and then heat treated in a muffle furnace at 300-600°C for 1-6 hours to finally obtain a lanthanum-titanium composite oxide-coated nickel cobalt manganese oxide positive electrode material.

2. The method for coating a positive electrode material of lithium nickel cobalt manganese oxide with calcium fluorophosphate according to claim 1, characterized in that: The mass ratio of calcium fluorophosphate to the nickel cobalt manganese oxide positive electrode material is 0.01 to 0.1:

1.

3. The method for coating a positive electrode material of lithium nickel cobalt manganese oxide with calcium fluorophosphate as claimed in claim 2, characterized in that: The mass ratio of calcium fluorophosphate to the nickel cobalt manganese oxide lithium positive electrode material is 0.01-0.05:

1.

4. The method for coating a positive electrode material of lithium nickel cobalt manganate with calcium fluorophosphate according to claim 1 or 2, characterized in that: The titanium source is one or more of tetraisopropyl titanate and tetrabutyl titanate.

5. The method for coating a positive electrode material of lithium nickel cobalt manganate with calcium fluorophosphate according to claim 1 or 2, characterized in that: The alcohol solvent is one or more of ethanol, isopropanol, n-propanol and n-butanol.

6. The method for coating a positive electrode material of lithium nickel cobalt manganate with calcium fluorophosphate according to claim 1 or 2, characterized in that: The temperature of the evaporation operation is 50-80°C.

7. The method for coating a positive electrode material of lithium nickel cobalt manganate with calcium fluorophosphate according to claim 1 or 2, characterized in that: The vacuum drying time is 2-10 hours.