CN114613968A - Positive electrode material and battery comprising same - Google Patents

Positive electrode material and battery comprising same Download PDF

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Publication number
CN114613968A
CN114613968A CN202210324061.8A CN202210324061A CN114613968A CN 114613968 A CN114613968 A CN 114613968A CN 202210324061 A CN202210324061 A CN 202210324061A CN 114613968 A CN114613968 A CN 114613968A
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positive electrode
carbon
coated
tungsten oxide
lithium cobaltate
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曾家江
李素丽
李俊义
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Zhuhai Cosmx Battery Co Ltd
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Zhuhai Cosmx Battery 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
    • H01M4/362—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
    • H01M4/04—Processes of manufacture in general
    • H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • 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
    • H01M4/625—Carbon or graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
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    • 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
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    • 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

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Abstract

The invention belongs to the technical field of batteries, and particularly relates to a positive electrode material and a battery comprising the same. The positive electrode material comprises doped lithium cobaltate and carbon-coated niobium tungsten oxide coated on the surface of the lithium cobaltate. According to the invention, the lithium cobaltate material has higher rate performance under the conditions of high working voltage of 3.0-4.55V and 5C rate charge and discharge through doping of elements and surface coating of carbon-coated niobium tungsten oxide; the capacity retention rate is excellent even after 50 cycles under the working voltage of 3.0-4.6V and the multiplying power of 0.5C.

Description

Positive electrode material and battery comprising same
Technical Field
The invention belongs to the technical field of batteries, and particularly relates to a positive electrode material and a battery comprising the same.
Background
In consumer lithium ion batteries, lithium cobaltate has been the most successful cathode material in use for the last two decades. However, as the energy density is gradually increased, the operating voltage of lithium cobaltate is higher and higher, from the first 4.2V, 4.35V, 4.4V, to the present 4.45V and 4.48V, to the future 4.5V, 4.53V, and 4.55V, and even to 4.58V, 4.6V or higher. With higher and higher operating voltages, the following problems and challenges also need to be addressed: 1. irreversible phase change; 2. a surface side reaction with the electrolyte; 3. dissolving transition metal; 4. lattice oxygen participates in charge transfer.
In order to solve the problems, a series of negative electrode materials capable of being charged and discharged quickly are developed for the negative electrode materials of the lithium ion battery, but few positive electrode materials capable of realizing quick charging and discharging and stable circulation are available, especially under high voltage.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a positive electrode material and a battery comprising the same. The anode material has higher capacity, multiplying power and cycling stability under the conditions of high working voltage (3.0V-4.55V or 3.0V-4.6V) and high multiplying power (more than 5C) of charge and discharge.
In order to achieve the above object, the present invention provides the following technical solutions:
a positive electrode material comprising doped lithium cobaltate and a carbon-coated niobium tungsten oxide coating the surface of the lithium cobaltate.
According to the embodiment of the invention, the cathode material has a core-shell structure, the doped lithium cobaltate is used as a core material, and the carbon-coated niobium tungsten oxide is used as a shell material. In the cathode material, the core can be completely or partially coated by the shell layer.
According to an embodiment of the present invention, the carbon-coated niobium tungsten oxide has a core-shell structure, and niobium tungsten oxide is a core material and carbon is a shell material. In the carbon-coated niobium tungsten oxide, the core can be completely coated or partially coated by the shell layer.
According to an embodiment of the present invention, the carbon-coated niobium tungsten oxide has the properties of a fast ion conductor.
According to an embodiment of the present invention, the niobium tungsten oxide has a chemical formula of Nb12WO33I.e. the molar ratio of Nb, W and O in the niobium tungsten oxide is 12:1: 33. The niobium-tungsten oxide meeting the chemical formula is coated on the surface of doped lithium cobaltate after being subjected to carbon coating modification, and the prepared positive electrode material has higher capacity, multiplying power and cycling stability and also has higher compaction density.
According to an embodiment of the invention, the carbon is amorphous carbon.
According to an embodiment of the invention, the mass of carbon is 0.5 wt% to 5 wt%, such as 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt% or 5 wt% of the total mass of the carbon-coated niobium tungsten oxide.
According to an embodiment of the present invention, the mass of the carbon-coated niobium tungsten oxide accounts for 0.1 wt% to 0.5 wt%, for example, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, or 0.5 wt% of the total mass of the positive electrode material.
According to an embodiment of the present invention, the carbon-coated niobium tungsten oxide has a median particle diameter D50200nm to 400 nm. The carbon-coated niobium tungsten oxide with the nanoscale is easier to coat on the surface of the doped lithium cobaltate, the coating effect is better, and the cathode material with higher capacity, multiplying power and cycling stability is easier to obtain.
According to an embodiment of the present invention, in the carbon-coated niobium tungsten oxide, the coating layer formed of carbon has a thickness of 10 to 50nm, for example, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, or 50 nm.
According to an embodiment of the present invention, in the positive electrode material, a thickness of a coating layer formed of a carbon-coated niobium tungsten oxide is 100 to 500nm, for example, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, or 500 nm.
According to an embodiment of the invention, the doped lithium cobaltate has a median particle diameter D50Is 14-18 μm.
According to an embodiment of the present invention, the median particle diameter D of the positive electrode material5015 to 18.5 mu m.
According to an embodiment of the invention, the doping element in the doped lithium cobaltate comprises at least one of Al, Mg and Ti. Further, the doping element further includes at least one of Nb and W. Specifically, the doping elements include Al, Mg, Ti, Nb, and W.
According to an embodiment of the invention, the doping elements Al, Mg, Ti are bulk doping.
According to the embodiment of the present invention, the doping elements Nb and W are surface layer doping.
According to the embodiment of the present invention, the doping amount of the doping element Al is 5000 to 8000ppm (base is the total mass of lithium cobaltate), for example 5000ppm, 6000ppm, 7000ppm, 8000 ppm.
According to an embodiment of the present invention, the doping amount of the doping element Mg is 1500 to 2500ppm (base is the total mass of lithium cobaltate), for example, 1500ppm, 1800ppm, 2000ppm, 2200ppm, 2500 ppm.
According to the embodiment of the present invention, the doping amount of the doping element Ti is 800 to 1500ppm (base is the total mass of lithium cobaltate), for example, 800ppm, 900ppm, 1000ppm, 1200ppm, 1300ppm, 1500 ppm.
According to the embodiment of the present invention, the doping amount of the doping element Nb is 200 to 500ppm (base is the total mass of lithium cobaltate), for example, 200ppm, 300ppm, 400ppm, 500 ppm.
According to the embodiment of the present invention, the doping amount of the doping element W is 200 to 500ppm (base is the total mass of lithium cobaltate), for example, 200ppm, 300ppm, 400ppm, 500 ppm.
According to the embodiment of the invention, the cathode material can have higher cycling stability under higher working voltage and high-rate charge and discharge conditions.
The invention also provides a preparation method of the cathode material, which comprises the following steps:
a) preparing doped lithium cobaltate;
b) mixing the doped lithium cobaltate obtained in the step a) with carbon-coated niobium tungsten oxide, and sintering to obtain the cathode material.
According to an embodiment of the present invention, the preparation method specifically comprises the steps of:
(1) mixing soluble aluminum salt (such as aluminum sulfate), soluble cobalt salt (such as cobalt sulfate), water and ammonia water, and performing coprecipitation reaction to obtain Al-doped Co3O4；
(2) Doping the Al with Co3O4With Li2CO3、MgO、TiO2Mixing, and sintering for the first time to obtain Al, Mg and Ti co-doped LiCoO2；
(3) The obtained Al, Mg and Ti co-doped LiCoO2Mixing with niobium tungsten oxide coated with carbon, and sintering for the second time to obtain the cathode material.
According to an embodiment of the present invention, in step (1), the molar ratio n (co) of cobalt and aluminum in the soluble cobalt salt and soluble aluminum salt: n (Al) is 100: (0.2-0.3).
According to the embodiment of the invention, in the step (1), the mass ratio of the soluble cobalt salt to the water is (500-700): 1500.
according to an embodiment of the present invention, in the step (1), the concentration of the ammonia water is 10% to 15%.
According to an embodiment of the present invention, in step (1), the volume ratio of ammonia to water is 2: 1.
According to the embodiment of the invention, in the step (1), the coprecipitation reaction is carried out under the conditions of introducing nitrogen and stirring, the flow rate of the nitrogen is 20-40 mL/min, and the rotation speed of the stirring is 650-850 revolutions/min.
According to the embodiment of the invention, in the step (1), the pH value of the coprecipitation reaction is 11-12, the reaction temperature is 50-65 ℃, and the reaction time is 36-50 h.
According to an embodiment of the present invention, in step (2), Li2CO3And Al-doped Co3O4The molar ratio of lithium to cobalt is n (Li): n (Co) is 1.0-1.08: 1.
According to an embodiment of the present invention, in the step (2), the amount of magnesium added to MgO is 1500 to 2500ppm (the base is Al-doped Co)3O4Mass of); TiO 22The addition amount of the medium titanium is 800-1500 ppm (the base number is Co doped with Al)3O4Mass of);
according to the embodiment of the invention, in the step (2), the atmosphere of the first sintering is air atmosphere, the temperature of the first sintering is 1000-1100 ℃, and the time of the first sintering is 10-12 h.
According to an embodiment of the present invention, in step (3), the mixing process realizes mechanical coating, i.e. coating of carbon-coated niobium tungsten oxide on Al, Mg, Ti doped LiCoO2A surface.
According to an embodiment of the present invention, in the step (3), the carbon-coated niobium tungsten oxide is added in an amount of 0.1 to 0.5 wt%.
According to the embodiment of the invention, in the step (3), the atmosphere of the second sintering is inert atmosphere (such as nitrogen or argon), the temperature of the second sintering is 450-750 ℃, and the time of the second sintering is 6-10 h.
According to an embodiment of the present invention, in the step (3), the carbon-coated niobium tungsten oxide is prepared by:
(a) mixing Nb with2O5And WO3Mixing, and carrying out primary calcination;
(b) mixing the calcined product with an organic carbon source, and performing sand milling, spray drying, secondary calcination and air flow crushing to prepare the carbon-coated niobium-tungsten oxide; alternatively, the first and second electrodes may be,
and (3) performing sand milling and refining on the calcined product, performing spray drying, performing vapor phase carbon deposition coating through absolute ethyl alcohol, performing secondary calcination, and performing jet milling to prepare the carbon-coated niobium-tungsten oxide.
According to an embodiment of the present invention, Nb2O5And WO3Molar ratio n (Nb) of niobium to tungsten: n is(W) is 12: 1.
According to the embodiment of the invention, the atmosphere of the first calcination is air atmosphere, the temperature of the first calcination is 1150-1350 ℃, and the time of the first calcination is 1-5 h.
According to an embodiment of the invention, D is obtained after sanding refinement50Is a product with the particle size of 50-100 nm.
According to an embodiment of the invention, the organic carbon source is glucose.
According to the embodiment of the invention, the atmosphere of the second calcination is inert atmosphere (such as nitrogen or argon), the temperature of the second calcination is 600-800 ℃, and the time of the second calcination is 5-10 h.
The invention also provides a positive plate, which comprises the positive electrode material.
According to an embodiment of the present invention, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer coated on at least one side surface of the positive electrode current collector, and the positive electrode active material layer includes the above-described positive electrode material.
According to an embodiment of the present invention, the positive electrode active material layer further includes a conductive agent. In some embodiments, the conductive agent is selected from one or more of conductive carbon black, acetylene black, ketjen black, carbon fiber, graphene, single-walled carbon nanotubes, and multi-walled carbon nanotubes.
According to an embodiment of the present invention, the positive electrode active material layer further includes a binder. In some embodiments, the binder is selected from one or more of carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyethylene, polyvinyl alcohol, polyvinyl chloride, polyvinyl fluoride, polyvinyl pyrrolidone, polytetrafluoroethylene, polypropylene, styrene butadiene rubber, epoxy resin, butadiene-based rubber binder, and acrylonitrile-based binder.
According to the embodiment of the invention, the positive electrode active material layer comprises the following components in percentage by mass:
91-97.5 wt% of positive electrode material, 0.5-4 wt% of conductive agent and 2-5 wt% of binder.
The invention also provides a battery, which comprises the positive electrode material or the positive electrode sheet.
According to an embodiment of the invention, the battery is a lithium ion battery.
According to an embodiment of the present invention, the battery further includes a negative electrode tab.
According to an embodiment of the invention, the battery further comprises a separator. In some embodiments, the membrane is selected from one or more of polyethylene or polypropylene.
According to an embodiment of the invention, the battery further comprises an electrolyte. In some embodiments, the electrolyte is a nonaqueous electrolyte comprising a nonaqueous organic solvent and a lithium salt. In some embodiments, the non-aqueous organic solvent is selected from one or more of Ethylene Carbonate (EC), Propylene Carbonate (PC), diethyl carbonate (DEC), fluoroethylene carbonate (FEC), dimethyl carbonate (DMC), Ethyl Methyl Carbonate (EMC), ethylene carbonate, γ -butyrolactone, propyl methyl carbonate, ethyl propionate. In some embodiments, the lithium salt is selected from LiPF6、LiBF4、LiSbF6、LiClO4、LiCF3SO3、LiAlO4、LiAlCl4、Li(CF3SO2)2N, LiBOB and LiDFOB.
According to an embodiment of the present invention, the battery further comprises an aluminum plastic film.
The invention has the beneficial effects that:
1) the invention adopts doping elements Al, Mg and Ti to LiCoO2And bulk phase doping is carried out, wherein the Al element can effectively inhibit the ordered-disordered phase change and the phase change from O3 → H1-3 of the lithium cobaltate after the delithiation amount exceeds 50%, the Mg element can improve the electronic conductivity of the material and can assist the Al element to better improve the cycle performance of the material, and the Ti element can improve the specific capacity and the first coulombic efficiency of the material and adjust the activity of lattice oxygen on the surface of the material.
2) The carbon-coated niobium tungsten oxide coated on the surface of the lithium cobaltate is a substructure with layered steps, lithium ions can be rapidly diffused in the carbon-coated niobium tungsten oxide, the rapid transmission of the lithium ions can be promoted, and the electronic conductivity of the niobium tungsten oxide can be increased by introducing the carbon; meanwhile, the niobium-tungsten oxide is coated on the surface of the lithium cobaltate, so that the lithium cobaltate is prevented from generating side reaction with electrolyte under high voltage, and the dissolution of metal cobalt is inhibited, thereby improving the cycling stability under the high voltage; the above reasons combine to improve the cycling stability, electronic conductivity and lithium ion conductivity of lithium cobaltate materials at high voltages.
3) According to the invention, the lithium cobaltate material has higher rate performance under the conditions of high working voltage of 3.0-4.55V and 5C rate charge and discharge through doping of elements and surface coating of carbon-coated niobium tungsten oxide; the capacity retention rate is excellent even after 50 cycles under the working voltage of 3.0-4.6V and the multiplying power of 0.5C.
Drawings
Fig. 1 is a SME diagram of the positive electrode material of example 1 of the present invention.
Fig. 2 is XRD of the positive electrode materials of example 1 of the present invention and comparative example 1.
Detailed Description
The present invention will be described in further detail with reference to specific examples. It is to be understood that the following examples are only illustrative and explanatory of the present invention and should not be construed as limiting the scope of the present invention. All the technologies realized based on the above-mentioned contents of the present invention are covered in the protection scope of the present invention.
The experimental methods used in the following examples are all conventional methods unless otherwise specified; reagents, materials and the like used in the following examples are commercially available unless otherwise specified.
Example 1
(1) Weighing lithium carbonate and cobaltosic oxide with the Al content of 7000ppm according to the mol ratio n (Li) n (Co) 1.05:1, respectively weighing magnesium oxide and titanium dioxide with the Mg content of 1500ppm and the Ti content of 1000ppm, carrying out ball milling and mixing for 1h, then sintering in a high-temperature sintering furnace in the air atmosphere at the sintering temperature of 1065 ℃ for 12h, then naturally cooling, and crushing and sieving by a pair of rollers to obtain Al, Mg and Ti co-doped lithium cobaltate;
(2) weighing niobium pentoxide and tungsten trioxide according to the molar ratio of n (Nb) to n (W) of 12:1, ball-milling and mixing for 2h, placing in a high-temperature sintering furnace in air atmosphere for sintering at 1300 ℃ for 2h, and pressing Nb after sintering12WO33In a molar ratio of 1:0.02 with respect to carbon in glucose, adding Nb12WO33Adding into 1L deionized water, and sanding to refine to D50Spray drying at 100nm to obtain Nb12WO33The surface is attached with a dry material of glucose. Sintering the dried material in a sintering furnace in nitrogen atmosphere at 700 ℃ for 6h, and crushing by airflow after sintering to obtain nano-grade carbon-coated niobium tungsten oxide Nb12WO33/C；
(3) Co-doped Al, Mg and Ti lithium cobaltate and Nb12WO33Coating in a ball mill, wherein Nb12WO33The addition amount of the/C is 0.2 wt% of the total mass of the lithium cobaltate, and the lithium cobaltate is calcined for 6 hours in an inert atmosphere at the temperature of 600 ℃ to obtain the carbon-coated lithium cobaltate cathode material coated with the niobium tungsten oxide, wherein the morphology of the carbon-coated lithium cobaltate cathode material is shown in figure 1, and the XRD (X-ray diffraction) diagram is shown in figure 2.
Example 2
Step (1) and step (3) the production method of example 1 was referred to, except for step (2).
The concrete content of the step (2) is as follows: weighing niobium pentoxide and tungsten trioxide according to the molar ratio of n (Nb) to n (W) of 12:1, ball-milling and mixing for 2h, placing in a high-temperature sintering furnace in air atmosphere for sintering at 1300 ℃ for 2h, and sintering Nb12WO33Adding into 1L deionized water, and sanding to refine to D50Spray drying at 100nm to obtain Nb12WO33The dried material of (1). Before nitrogen is introduced, the nitrogen is subjected to absolute ethyl alcohol for one time, then the dried material is placed in a sintering furnace in the nitrogen atmosphere for vapor phase carbon deposition coating, the sintering temperature is 700 ℃, the sintering time is 6 hours, and after sintering, the carbon-coated niobium-tungsten oxide Nb at the nano level is obtained by airflow crushing12WO33/C。
Example 3
Referring to the preparation method of example 1, except that, in the step (3), the lithium cobaltate coated with niobium tungsten oxide was calcined at 700 ℃ for 6 hours in an inert atmosphere after coating, and the final carbon-coated lithium cobaltate cathode material coated with niobium tungsten oxide was obtained.
Example 4
Reference example 1 was prepared with the only difference that, in step (3), Nb12WO33The addition amount of/C was 0.1 wt% based on the total mass of lithium cobaltate.
Example 5
With reference to the production method of example 1, except that, in the step (3), Nb12WO33The addition amount of/C was 0.5 wt% based on the total mass of lithium cobaltate.
Comparative example 1
(1) Weighing lithium carbonate and cobaltosic oxide with the Al content of 7000ppm according to the mol ratio n (Li) n (Co) 1.05:1, respectively weighing magnesium oxide and titanium dioxide with the Mg content of 1500ppm and the Ti content of 1000ppm, carrying out ball milling and mixing for 1h, then sintering in a high-temperature sintering furnace in the air atmosphere at the sintering temperature of 1065 ℃ for 12h, then naturally cooling, and crushing and sieving by a pair of rollers to obtain Al, Mg and Ti co-doped lithium cobaltate;
(2) weighing niobium pentoxide and tungsten trioxide according to the molar ratio of n (Nb) to n (W) of 12:1, ball-milling and mixing for 2h, placing in a high-temperature sintering furnace in air atmosphere for sintering at 1300 ℃ for 2h, and sintering Nb12WO33Adding into 1L deionized water, and sanding to refine to D50Spray drying at 100nm to obtain Nb12WO33And (4) drying the material. Sintering the dried material in a sintering furnace in a nitrogen atmosphere at 700 ℃ for 6h, and crushing by airflow after sintering to obtain nano-grade niobium-tungsten oxide Nb12WO33；
(3) Co-doped Al, Mg and Ti lithium cobaltate and Nb12WO33Coating in a ball mill, wherein Nb12WO33The addition amount of (B) is 0.2 wt% of the total mass of lithium cobaltate, and the lithium cobaltate is calcined in inert atmosphere at the temperature of 600 DEG CAnd (4) sintering for 6h to obtain the niobium tungsten oxide coated lithium cobaltate cathode material, wherein XRD (X-ray diffraction) of the lithium cobaltate cathode material is shown in figure 2.
Comparative example 2
(1) Weighing lithium carbonate and cobaltosic oxide with Al content of 7000ppm according to the mol ratio of n (Li) to n (Co) of 1.05:1, respectively weighing magnesium oxide and titanium dioxide with Mg content of 1500ppm and Ti content of 1000ppm, ball-milling and mixing for 1h, sintering in a high-temperature sintering furnace in an air atmosphere at 1065 ℃ for 12h, naturally cooling, crushing by using a pair of rollers and sieving to obtain Al, Mg and Ti co-doped lithium cobaltate;
(2) and putting the Al, Mg and Ti co-doped lithium cobaltate into a nitrogen atmosphere of absolute ethyl alcohol, and sintering at the temperature of 600 ℃ for 6h to obtain the carbon-coated lithium cobaltate cathode material.
Test example
Dispersing the lithium cobaltate positive electrode material obtained in the above examples 1-5 and comparative examples 1-2, a conductive agent Super P and a binder polyvinylidene fluoride PVDF in a N-methylpyrrolidone NMP solvent according to a mass ratio of 97:1.5:1.5, uniformly stirring in a defoaming machine to obtain positive electrode slurry, uniformly coating the positive electrode slurry on the surface of an aluminum foil, baking in a vacuum oven at 100 ℃ for 12h, rolling and cutting to obtain a positive electrode sheet.
The positive plate and the negative plate of the lithium plate, a PP/PE/PP three-layer diaphragm, are arranged in a glove box by using 1mol/LLIPF6And (EC + DEC) electrolyte (volume ratio is 1:1), assembling the battery into a button cell for electrochemical test.
The prepared button cell is subjected to a rate performance test at a test temperature of 25 ℃ under the condition that a voltage interval is 3.0-4.55V, wherein the charging rate is 0.1C, the discharging rate is 0.1C, 0.2C, 0.5C, 1C, 2C and 5C in sequence, and the rate performance test is shown in Table 1. And then, carrying out cycle performance test under the conditions that the charge-discharge multiplying factor is 0.5C and the voltage interval is 3.0-4.6V, wherein the test results are shown in Table 1.
Table 1 performance test results of button cells of examples and comparative examples
Figure BDA0003571090710000101
As can be seen from the specific test results of the examples and the comparative examples in Table 1, the battery using the embodiment of the present invention shows excellent electrochemical performance in both rate performance at a high voltage of 3.0 to 4.55V and cycle performance at a high voltage of 3.0 to 4.6V, while the battery of the comparative example is inferior to the electrochemical performance of the battery of the examples in both rate performance and cycle performance.
The difference between example 1 and comparative examples 1-2 is mainly that: comparative example 1 is a niobium tungsten oxide coated on the surface of doped lithium cobaltate, which is inferior to the carbon-coated niobium tungsten oxide coated on the surface of doped lithium cobaltate in example 1 in rate capability and cycle performance at high voltage, but superior to the carbon-coated lithium cobaltate in comparative example 2. The improvement of the performance of the anode material is mainly achieved by the synergistic effect between niobium tungsten oxide and carbon coating, and the performance of the battery is enhanced.
Example 1 differs from example 2 mainly in the way the carbon-coated niobium tungsten oxide does, but does not have a great influence on the properties. The main difference between example 1 and example 3 is that the sintering temperature after coating is different, and the temperature has little effect on the performance in a suitable temperature range. The difference between example 1 and examples 4 to 5 is that the coating amount of the carbon-coated niobium tungsten oxide on the surface of the doped lithium cobaltate is different, and the performance of the battery increases and then decreases with the increase of the coating amount, because the coating amount is insufficient and only point-shaped coating is performed, and when the coating amount is excessive, the coating layer is too thick, and only a proper coating amount forms a thin and uniform coating layer, so that the coating effect is the best.
The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. The positive electrode material is characterized by comprising doped lithium cobaltate and carbon-coated niobium tungsten oxide coated on the surface of the lithium cobaltate.
2. The positive electrode material of claim 1, wherein the molar ratio of Nb, W, and O in the niobium tungsten oxygen compound is 12:1: 33.
3. The positive electrode material according to claim 1, wherein the mass of carbon is 0.5 to 5 wt% of the total mass of the carbon-coated niobium tungsten oxide; and/or the mass of the carbon-coated niobium tungsten oxide accounts for 0.1-0.5 wt% of the total mass of the cathode material.
4. The positive electrode material as claimed in claim 1, wherein the carbon-coated niobium tungsten oxide has a median particle diameter D50200nm to 400 nm; and/or in the carbon-coated niobium tungsten oxide, the thickness of a coating layer formed by carbon is 10-50 nm.
5. The positive electrode material according to claim 1, wherein a thickness of a coating layer formed of a carbon-coated niobium tungsten oxide is 100 to 500 nm; and/or the median particle diameter D of the cathode material5015 to 18.5 mu m.
6. The positive electrode material according to claim 1, wherein the doping element in the doped lithium cobaltate comprises at least one of Al, Mg and Ti;
and/or doping elements Al, Mg and Ti as bulk phase;
and/or the doping amount of the doping element Al is 5000-8000 ppm;
and/or the doping amount of the doping element Mg is 1500-2500 ppm;
and/or the doping amount of the doping element Ti is 800-1500 ppm.
7. The positive electrode material as claimed in claim 1 or 6, wherein the doping element further comprises at least one of Nb and W;
and/or doping elements Nb and W on the surface layer;
and/or the doping amount of the doping element Nb is 200-500 ppm;
and/or the doping amount of the doping element W is 200-500 ppm.
8. A positive electrode sheet, characterized in that it comprises the positive electrode material according to any one of claims 1 to 7.
9. The positive electrode sheet according to claim 8, comprising a positive electrode collector and a positive electrode active material layer coated on at least one surface of the positive electrode collector, wherein the positive electrode active material layer comprises the positive electrode material according to any one of claims 1 to 7.
10. A battery comprising the positive electrode material of any one of claims 1 to 7 or the positive electrode sheet of claim 8 or 9.
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