A positive electrode material, a positive electrode sheet including the same, and a battery

Abstract

The application provides a positive electrode material, a positive electrode sheet comprising the positive electrode material and a battery, wherein the positive electrode material is a lithium-rich manganese-based positive electrode material coated with nanometer niobium tungsten oxide (Nb 12 WO 33 ) fast ion conductor; and the battery has excellent cycle performance and rate performance. The synthesis process of the positive electrode material is simple, no additional modification operation is needed, and the modified positive electrode material can be directly modified in a lithium mixing and sintering process of a precursor, has high purity, and can realize large-scale industrial production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of batteries, and particularly relates to a modified positive electrode material coated with niobium tungsten oxide and a positive electrode sheet and a battery comprising the positive electrode material. BACKGROUND

[0002] Lithium ion batteries are widely used in various aspects of new energy fields, such as 3C digital, power supply and energy storage system, due to their excellent electrochemical performance, environmental friendliness and other advantages. As the most important energy storage and conversion substance, the positive electrode material determines the energy density of the lithium ion battery. With the increasing requirement of the energy density of the positive electrode material of the lithium ion battery in the field of power batteries, the existing commercialized positive electrode material is difficult to meet the growing demand. Moreover, with the increasing cost of lithium resources, the difficulty of increasing energy density and reducing cost of the positive electrode material also increases.

[0003] The lithium-rich manganese-based positive electrode material is widely favored due to its high capacity (>250 mAh / g) and energy density (>860 Wh / kg), and low raw material cost. However, there are still some problems to be solved in its large-scale application: (1) low first cycle coulombic efficiency, resulting in loss of reversible lithium number; (2) poor cycle performance, serious voltage and capacity attenuation; (3) poor rate performance. Therefore, it has high practical significance and application value to propose a solution to any of the above problems.

[0004] At present, the main means to improve the performance of the lithium-rich manganese-based positive electrode material is element doping (such as metal elements such as Mg, Al, Zr and non-metal elements such as B and F) and surface coating (such as phosphate, oxide, conductive carbon, etc.), the main purpose of which is to improve the stability of the crystal structure of the lithium-rich manganese-based positive electrode material and reduce the contact between the lithium-rich manganese-based positive electrode material surface and the electrolyte. These methods have played a certain role, but often have single modification effect and complex process and high cost. SUMMARY

[0005] In order to improve the deficiencies of the prior art, the application provides a positive electrode material, a positive electrode sheet and a battery comprising the positive electrode material. The positive electrode material is a lithium-rich manganese-based positive electrode material coated with nanometer niobium tungsten oxide (Nb 12 WO 33 ) on the surface of the secondary particles of the lithium-rich manganese-based positive electrode material. The battery has excellent cycle performance and rate performance. The synthesis process of the positive electrode material is simple, no additional modification operation is needed, and the positive electrode material can be directly modified in the mixing and sintering process of the lithium-rich manganese-based positive electrode material precursor, niobium tungsten oxide and lithium source. The prepared positive electrode material has high purity and can realize large-scale industrial production.

[0006] The application aims to realize the following technical solutions:

[0007] A cathode material, the cathode material being a plurality of secondary particles formed of lithium-rich manganese-based primary particles of the chemical formula xLi2MnO3·(1-x)LiMO2, and the surface of the secondary particles having a coating region formed of niobium tungsten oxide of the chemical formula Nb 12 WO 33 ; wherein 0 < x < 1, M is a combination of Mn and at least one of the following elements: Ni, Co, Al, Mg, Zr, Ti, Nb, W, P, B.

[0008] According to embodiments of the present application, 0 < x < 1, for example x is 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9.

[0009] According to embodiments of the present application, the plurality is more than one.

[0010] According to embodiments of the present application, the cathode material is a plurality of spherical or spheroidal secondary particles formed of agglomeration of lithium-rich manganese-based primary particles of the chemical formula xLi2MnO3·(1-x)LiMO2, and the surface of the secondary particles having a coating region formed of niobium tungsten oxide of the chemical formula Nb 12 WO 33 .

[0011] According to embodiments of the present application, the median particle size of the plurality of secondary particles formed of lithium-rich manganese-based primary particles of the chemical formula xLi2MnO3·(1-x)LiMO2 is 6 μm to 15 μm, for example 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm or 15 μm.

[0012] According to embodiments of the present application, the mass of the niobium tungsten oxide of the chemical formula Nb 12 WO 33 is 0.1 to 5 wt.%, for example 0.1 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, 0.5 wt.%, 0.6 wt.%, 0.7 wt.%, 0.8 wt.%, 0.9 wt.%, 1.0 wt.%, 1.1 wt.%, 1.2 wt.%, 1.3 wt.%, 1.4 wt.%, 1.5 wt.%, 1.6 wt.%, 1.7 wt.%, 1.8 wt.%, 1.9 wt.%, 2.0 wt.%, 2.2 wt.%, 2.3 wt.%, 2.5 wt.%, 2.6 wt.%, 2.8 wt.%, 3 wt.%, 3.2 wt.%, 3.5 wt.%, 3.6 wt.%, 3.8 wt.%, 4 wt.%, 4.2 wt.%, 4.5 wt.%, 4.8 wt.%, 5 wt.% of the total mass of the cathode material. It has been found that when the mass of the niobium tungsten oxide of the chemical formula Nb 12 WO33 The large amount of niobium tungsten oxide coating will hinder the contact between the positive electrode material and the conductive agent, increase the resistance of the positive electrode sheet, and be detrimental to battery performance. 12 WO 33 The coating amount (0.1-5 wt.%) and coating structure of niobium tungsten oxide will not only not reduce the conductivity of the positive electrode sheet, but also improve the rate performance to a certain extent.

[0013] According to an embodiment of the present invention, the chemical formula is Nb 12 WO 33 The median particle size of the niobium tungsten oxide is 5 to 50 nm, for example, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm or 50 nm.

[0014] According to an embodiment of the present invention, the median particle size of the positive electrode material is 6 μm to 15 μm, for example, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm or 15 μm.

[0015] According to an embodiment of the present invention, the positive electrode material is a lithium-rich manganese-based positive electrode material with a surface coated with niobium tungsten oxide.

[0016] According to an embodiment of the present invention, the niobium tungsten oxide has high ionic conductivity, good structural stability, and a fast lithium ion diffusion rate. The large atomic gaps between Nb and WO allow lithium ions to pass through in a three-dimensional manner, increasing the rate performance of the positive electrode material and reducing the polarization of the battery during high-rate charge and discharge. When used as a coating for the positive electrode material, it can significantly improve the cycling stability and rate performance of the positive electrode material. In addition, niobium tungsten oxide has a hard and open structure that does not capture lithium ions during the intercalation and deintercalation process. When coated on the surface of a lithium-rich manganese-based positive electrode material, it can enhance the structural stability of the surface of the lithium-rich manganese-based positive electrode material, reduce cracks on the secondary particle surface caused by internal stress during long cycles, and prevent the electrolyte from penetrating the secondary particles and causing side reactions, thereby improving the cycling performance and safety of the positive electrode material.

[0017] The present invention also provides a method for preparing the above-mentioned positive electrode material, which comprises the following steps:

[0018] (1) mixing a soluble salt of element M with water, adding a precipitant and a complexing agent, and performing a coprecipitation reaction to prepare a precursor of a lithium-rich manganese-based positive electrode material;

[0019] (2) mixing a complexing agent, a niobium-containing compound, and a tungsten-containing compound to prepare a sol and a gel, drying, sintering, and ball milling to prepare niobium tungsten oxide;

[0020] (3) mixing the precursor of the lithium-rich manganese-based positive electrode material of step (1), the niobium tungsten oxide of step (2), and a lithium source to obtain a mixture;

[0021] (4) sintering the mixture of step (3) to obtain the positive electrode material.

[0022] According to the embodiment of the present application, step (1) specifically comprises the following steps:

[0023] The soluble salt of element M is dissolved in water in a desired molar ratio, and a precipitant solution and a complexing agent solution or a mixed solution of the two are prepared respectively, and all the prepared solutions are introduced into a reaction kettle with deionized water as a bottom liquid (the amount of the bottom liquid is 25% to 35% of the volume of the reaction kettle), and the temperature, pH, and stirring speed in the reaction kettle are controlled to perform a co-precipitation reaction; after the reaction is completed, the precipitate is washed and dried to obtain the precursor of the lithium-rich manganese-based positive electrode material.

[0024] According to the embodiment of the present application, the soluble salt is selected from a mixture of one or more of sulfates, nitrates, phosphates, oxalates, acetates, and citrates of element M.

[0025] According to the embodiment of the present application, the concentration of the soluble salt of element M in the mixed solution of step (1) is 0.5 to 4 mol / L.

[0026] According to the embodiment of the present application, in step (1), the precipitant is selected from at least one of sodium carbonate, sodium hydroxide, potassium carbonate, potassium hydroxide, ammonium carbonate, and ammonium bicarbonate.

[0027] According to the embodiment of the present application, the concentration of the precipitant in the mixed solution of step (1) is 0.5 to 8 mol / L.

[0028] According to the embodiment of the present application, in step (1), the complexing agent is selected from ammonia (aqueous solution of ammonia gas, chemical formula: NH3·H2O).

[0029] According to the embodiment of the present application, the concentration of the complexing agent in the mixed solution of step (1) is 0.01 to 8 mol / L.

[0030] According to the embodiment of the present application, in step (1), the temperature of the co-precipitation reaction is maintained at 45 to 65°C.

[0031] According to the embodiment of the present application, in step (1), the pH of the co-precipitation reaction is 7.0 to 12.0.

[0032] According to the embodiment of the present application, in step (1), the co-precipitation reaction is performed under stirring, and the stirring speed is 50 to 1500 rpm.

[0033] According to the embodiment of the present application, in step (1), the co-precipitation reaction is carried out under air or nitrogen condition. Preferably, it is carried out under nitrogen condition to prevent Mn 2+ from being oxidized.

[0034] According to the embodiment of the present application, in step (1), the reaction time of the co-precipitation reaction is 5h-50h.

[0035] According to the embodiment of the present application, in step (2), the niobium-containing compound is selected from niobium oxalate hydrate, niobium pentachloride, ammonium niobium oxalate hydrate, niobium pentoxide, niobium n-propoxide, niobium N-butyl alcohol and other niobium-containing organic and inorganic compounds.

[0036] According to the embodiment of the present application, in step (2), the tungsten-containing compound is selected from tungsten hexachloride, tungsten pentachloride, ammonium paratungstate, ammonium metatungstate and other tungsten-containing organic and inorganic compounds.

[0037] According to the embodiment of the present application, in step (2), the molar ratio of Nb and W in the niobium-containing compound and the tungsten-containing compound is 12:1.

[0038] According to the embodiment of the present application, in step (2), the method for preparing the sol and the gel comprises the following steps: mixing the complexing agent, the niobium-containing compound and the tungsten-containing compound, dissolving them thoroughly to form a sol, heating and evaporating and continuously stirring until a gel is formed.

[0039] According to the embodiment of the present application, in step (2), the complexing agent is selected from one or more of citric acid, EDTA, PVP and sucrose.

[0040] According to the embodiment of the present application, in step (2), the drying temperature is 100℃-150℃ and the drying time is 5h-10h.

[0041] According to the embodiment of the present application, in step (2), the sintering is two-stage sintering, the first-stage sintering temperature is 300℃-500℃ (such as 300℃, 350℃, 400℃, 450℃ or 500℃), the sintering time is 5h-8h (such as 5h, 6h, 7h or 8h) and the heating rate is 3℃ / min-5℃ / min; the second-stage sintering temperature is 1000℃-1300℃ (such as 1000℃, 1050℃, 1100℃, 1150℃, 1200℃, 1250℃ or 1300℃), the sintering time is 8h-15h (such as 8h, 9h, 10h, 11h, 12h, 13h, 14h or 15h) and the heating rate is 3℃ / min-5℃ / min.

[0042] According to an embodiment of the present application, in step (2), the ball milling time is 1-4 hours, and the ball-to-material mass ratio is 3-5:1.

[0043] According to an embodiment of the present application, in step (2), the median particle size of the niobium tungsten oxide is 5-50 nm.

[0044] According to an embodiment of the present application, in step (3), the lithium source is at least one selected from lithium carbonate and lithium hydroxide.

[0045] According to an embodiment of the present application, in step (3), the amount of the niobium tungsten oxide added is 0.1-2 wt.% of the total mass of the mixture of the lithium-rich manganese-based positive electrode material precursor and the lithium source in step (1).

[0046] According to an embodiment of the present application, in step (3), the molar ratio of Li:TM is 1.2-1.6 (e.g., 1.2, 1.3, 1.4, 1.5 or 1.6), and TM is the transition metal in the lithium-rich manganese-based positive electrode material precursor, i.e., Mn in Li2MnO3 and M in LiMO2, where M is defined as above.

[0047] According to an embodiment of the present application, in step (4), the sintering is two-stage sintering, the first-stage sintering temperature is 450-500°C (e.g., 450°C, 460°C, 470°C, 480°C, 490°C or 500°C), and the sintering time is 4-5 hours (e.g., 4 hours, 4.5 hours or 5 hours); the second-stage sintering temperature is 870-890°C (e.g., 870°C, 880°C or 890°C), and the sintering time is 12-18 hours (e.g., 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours or 18 hours).

[0048] According to an embodiment of the present application, in step (4), the sintering atmosphere is air or oxygen.

[0049] The present application provides a positive electrode material prepared by the above method.

[0050] The present application provides a positive electrode sheet comprising the above positive electrode material.

[0051] According to an embodiment of the present application, the compaction density of the positive electrode sheet is 1.5-4.5 g / cm 3 .

[0052] According to an embodiment of the present application, the positive electrode sheet has a higher discharge capacity than a positive electrode sheet of the same chemical formula Nb 12 WO 33The secondary particles formed by the lithium-rich manganese-based primary particles of several chemical formulas of xLi2MnO3·(1-x)LiMO2 can improve the compaction density of the positive electrode sheet by 0.1-0.3 g / cm2 compared with the positive electrode sheet of the same formula. 3 .

[0053] According to an embodiment of the present application, the positive electrode sheet comprises a current collector and a positive electrode active material layer located on at least one side surface of the current collector, wherein the positive electrode active material layer comprises the positive electrode material described above.

[0054] According to an embodiment of the present application, the current collector is a single-faced aluminum foil, a double-faced aluminum foil or a porous aluminum foil.

[0055] According to an embodiment of the present application, the mass of the positive electrode material accounts for 80-95 wt% of the total mass of the positive electrode active material layer, such as 80-90 wt%, for example 80 wt%, 81 wt%, 82 wt%, 83 wt%, 84 wt%, 85 wt%, 86 wt%, 87 wt%, 88 wt%, 89 wt%, 90 wt%, 91 wt%, 92 wt%, 93 wt%, 94 wt% or 95 wt%.

[0056] According to an embodiment of the present application, the positive electrode active material layer further comprises a binder and a conductive agent.

[0057] According to an embodiment of the present application, the binder is selected from at least one of PVDF, PTFE, polyacrylate and polyacrylic acid.

[0058] According to an embodiment of the present application, the conductive agent is selected from at least one of graphite, carbon black, acetylene black, graphene and carbon nanotube.

[0059] The present application provides a battery comprising the positive electrode material described above, or the battery comprising the positive electrode sheet described above.

[0060] According to an embodiment of the present application, the mass energy density of the battery is 300-420 Wh / kg.

[0061] The present application has the following beneficial effects:

[0062] The present application provides a positive electrode material, a positive electrode sheet comprising the positive electrode material and a battery, wherein the positive electrode material is a nano-niobium tungsten oxide (Nb 12 WO 33) fast ion conductor; the battery has the characteristics of excellent cycle performance and rate performance. The synthesis process of the positive electrode material of the application is simple, does not need additional modification operation, can be directly modified in the lithium mixing and sintering process of the precursor, avoids the influence of multiple sintering on the two-phase layered structure of the lithium-rich manganese-based material, and has high purity, low time period and cost of the prepared positive electrode material, and can realize large-scale industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0063] Figure 1 The scanning electron microscope graph of the positive electrode material synthesized in example 1 of the application.

[0064] Figure 2 The XRD graph of the positive electrode material synthesized in example 1 of the application.

[0065] Figure 3 The first charge-discharge curve of the half battery prepared by the positive electrode material synthesized in example 1 of the application under a charge-discharge current density of 20mA·g -1 .

[0066] Figure 4 The discharge specific capacity graph of the half battery prepared by the positive electrode material synthesized in example 1 and comparative example 1 of the application under a charge-discharge current density of 100mA·g -1 for 100 cycles.

[0067] Figure 5 The discharge specific capacity graph of the half battery prepared by the positive electrode material synthesized in example 1 and comparative example 1 of the application under different rates. DETAILED DESCRIPTION

[0068] The application will be further described in detail below in combination with specific examples. It should be understood that the following examples are only illustratively and explain the application, and should not be interpreted as limiting the scope of protection of the application. Any technology realized on the basis of the above description of the application is covered within the scope of the application intended to be protected.

[0069] The experimental methods used in the following examples are conventional methods unless otherwise specified; the reagents, materials, etc. used in the following examples can be obtained from commercial channels unless otherwise specified.

[0070] Example 1

[0071] (1) Prepare a mixed salt solution of NiSO4, CoSO4 and MnSO4 and a mixed alkali solution of NaCO3 and NH3·H2O for use, wherein the total concentration of metal ions in the salt solution is 2mol / L, Ni 2+ :Co 2+ :Mn 2+The molar ratio of Nb2O5, (NH4)2WO4, and citric acid is 0.13:0.13:0.54, the molar concentration of NaCO3 is 2 mol / L, and the molar concentration of NH3·H2O is 0.2 mol / L; a certain amount of deionized water is added into the reaction kettle, the above salt solution is pumped into the reaction kettle at a feeding speed of 175 ml / h by using a peristaltic pump, the stirring speed is controlled to be 1000 rpm, the circulating water temperature is 55°C, the feeding speed of the lye is adjusted by using a three-stage speed regulator, the pH of the solution system is controlled to be 7.5, and the feeding time lasts for 30 h; after the reaction is completed, the slurry is subjected to solid-liquid separation, then deionized water is used for centrifugal cleaning, and then the slurry is dried at 120°C for 24 h to obtain the carbonate precursor of the positive electrode material.

[0072] (2) Dissolve niobium oxalate hydrate, ammonium paratungstate, citric acid, and ethylene glycol in deionized water, wherein the molar ratio of Nb:W is 12:1, the molar ratio of citric acid, ethylene glycol, and metal ions (Nb and W) is 1:1:1, and after being fully dissolved, evaporate in a water bath at 80°C with constant stirring until a gel is formed. Dry the gel in a forced air oven at 120°C for 8 h, grind it, heat it to 400°C in a muffle furnace for 5 h to remove the organic matrix in the material, then continue to heat it to 1200°C and sinter it for 10 h, mechanically ball mill it for 2 h after cooling, and obtain Nb 12 WO 33 compound.

[0073] (3) Mix the carbonate precursor of the positive electrode material with Nb 12 WO 33 compound and Li2CO3, wherein the molar ratio of Li:TM is 12:8, TM is Ni, Co, and Mn; the amount of Nb 12 WO 33 compound added is 1.2 wt.% of the total mass of the mixture of the carbonate precursor and Li2CO3, mix them well in a mixer, place them in a muffle furnace, pre-burn them at 500°C for 5 h, then heat them to 880°C and keep them at this temperature for 15 h to obtain the positive electrode material. The positive electrode material is a secondary particle formed by a plurality of primary particles of lithium-rich manganese-based material with the chemical formula xLi2MnO3·(1-x)LiMO2, and the surface of the secondary particle has a coating region formed by Nb 12 WO 33 tungsten oxide.

[0074] (4) The positive material was mixed with conductive carbon black and PVDF at a mass ratio of 8:1:1, N-methyl pyrrolidone was used as the solvent, a homogenizer was used to make the slurry, then coated on the aluminum foil, dried in a 80℃ air oven for 2h, after taking out the aluminum foil, it was rolled and punched into a 12mm diameter circular electrode by a puncher. The positive electrode was transferred into a glove box, lithium sheet was used as the negative electrode, clegard-2400 was used as the separator, the electrolyte was 1mol / L LiPF6+EC:EMC:DEC=1:1:1vol%, a coin cell was assembled in the glove box and tested on a blue cell test system.

[0075] (5) The test temperature of the half-cell was 25℃, the voltage range of the specific capacity test was 2.0-4.8V, and the current density was 20mA·g -1 The initial specific discharge capacity was 280.4mAh·g -1 , and the test results are shown in Figure 3 ; the cycle test voltage range was 2.0-4.6V, and the current density was 100mA·g -1 , and the capacity retention rate after 100 cycles was 94.37%, and the test results are shown in Figure 4 ; the current density was 0.1C (20mA·g -1 ), 0.5C (100mA·g -1 ), 1C (200mA·g -1 ), 2C (400mA·g -1 ), and 5C (1000mA·g -1 ), and the voltage range was 0.1C at 2.0-4.8V, and the rest of the current density was 2.0-4.6V, and the test results are shown in Figure 5 , and the average discharge specific capacity at 0.1C, 0.5C, 1C, 2C and 5C was 279.5mAh·g -1 , 239.8mAh·g -1 , 212.3mAh·g -1 , 188.5mAh·g -1 , and 165.6mAh·g -1 .

[0076] Example 2

[0077] (1) The preparation method of the carbonate precursor is as described in Example 1.

[0078] (2) niobium pentachloride, tungsten hexachloride, citric acid, ethylene glycol were dissolved in deionized water, wherein the molar ratio of Nb:W was 12:1, the molar ratio of citric acid, ethylene glycol and metal ions (Nb and W) was 1:1:1, after being dissolved sufficiently, the mixture was heated and evaporated in a water bath at 80°C, and was continuously stirred until a gel was formed. The gel was dried in a blast oven at 120°C for 8h, then was heated to 400°C in a muffle furnace for 5h to remove the organic matrix in the material, and then was continuously heated to 1200°C for 10h to sinter, after being cooled, the material was mechanically ball-milled for 2h to obtain the Nb 12 WO 33 compound.

[0079] (3) the carbonate precursor of the positive electrode material was mixed with Nb 12 WO 33 compound and Li2CO3, wherein the molar ratio of Li:TM was 12:8, TM was Ni, Co, Mn, the amount of Nb 12 WO 33 compound added was 1.8wt.% of the total mass of the mixture of the carbonate precursor and Li2CO3, after being mixed uniformly in a mixer, the mixture was placed in a muffle furnace, was pre-fired at 500°C for 5h, and then was heated to 870°C for 15h to obtain the positive electrode material.

[0080] (4) the assembly process of the coin cell was the same as that in Example 1.

[0081] (5) the test temperature of the half cell was 25°C, the voltage range for the specific capacity test was 2.0-4.8V, the current density was 20mA·g -1 , and the initial specific discharge capacity was 281.2mAh·g -1 ; the voltage range for the cycle test was 2.0-4.6V, the current density was 100mA·g -1 , and the capacity retention rate after 100 cycles was 94.45%; the half cell was cycled for 5 times at a current density of 0.1C (20mA·g -1 ), 0.5C (100mA·g -1 ), 1C (200mA·g -1 ), 2C (400mA·g -1 ) and 5C (1000mA·g -1 ) respectively, the voltage range was 2.0-4.8V at 0.1C, and the voltage range was 2.0-4.6V at the other current densities, the average specific discharge capacities at 0.1C, 0.5C, 1C, 2C and 5C were 278.8mAh·g -1 , 239.2mAh·g -1 , 212.6mAh·g -1 and 187.8mAh·g-1 , 165.2 mAh·g -1 .

[0082] Example 3

[0083] (1) Preparation method of carbonate precursor Reference Example 1.

[0084] (2) Ammonium niobate oxalate hydrate, ammonium paratungstate, citric acid and ethylene glycol were dissolved in deionized water, wherein the molar ratio of Nb:W was 12:1, the molar ratio of citric acid to ethylene glycol to metal ions (Nb and W) was 1:1:1, and after sufficient dissolution, evaporation was carried out at 80°C water bath heating, and constant stirring until a gel was formed. The gel was dried in a forced air oven at 120°C for 8h, then ground and heated to 400°C in a muffle furnace for 5h to remove the organic matrix in the material, and then continued to heat to 1200°C for sintering for 10h, and after cooling, mechanical ball milling was carried out for 2h, to obtain Nb 12 WO 33 compound.

[0085] (3) The carbonate precursor of the positive electrode material was mixed with Nb 12 WO 33 compound and Li2CO3, wherein the molar ratio of Li:TM = 12:8, TM is Ni, Co, Mn, and the addition amount of Nb 12 WO 33 compound was 3.0wt.% of the total mass of the mixture of the carbonate precursor and Li2CO3, and after uniform mixing in a mixer, it was placed in a muffle furnace, first pre-fired at 500°C for 5h, and then heated to 890°C for 15h to obtain the positive electrode material.

[0086] (4) The assembly process of the coin cell was according to Reference Example 1.

[0087] (5) The test temperature of the half-cell was 25°C, the voltage range for the specific capacity test was 2.0-4.8V, and the current density was 20mA·g -1 , and the initial specific discharge capacity was 280.9mAh·g -1 ; the cycle test voltage range was 2.0-4.6V, and the current density was 100mA·g -1 , and the capacity retention rate after 100 cycles was 95.56%; at 0.1C (20mA·g -1 ), 0.5C (100mA·g -1 ), 1C (200mA·g -1 ), 2C (400mA·g -1 ), 5C (1000mA·g -1mAh·g-1, 240.2 mAh·g-1, 211.8 mAh·g-1, 188.2 mAh·g-1, 166.5 mAh·g-1, 145.8 mAh·g-1, 124.2 mAh·g-1, 103.6 mAh·g-1, 82.9 mAh·g-1, 63.3 mAh·g-1, 42.7 mAh·g-1, 22.1 mAh·g-1, 2.0 mAh·g-1, 0.1 mAh·g-1. -1 mAh·g-1 -1 mAh·g-1 -1 mAh·g-1 -1 mAh·g-1 -1 .

[0088] Example 4

[0089] (1) The preparation method of the carbonate precursor is as described in Reference Example 1.

[0090] (2) The niobium oxalate hydrate, ammonium metatungstate, citric acid and ethylene glycol are dissolved in deionized water, and are weighed according to the molar ratio of Nb:W of 12:1, and the molar ratio of citric acid to ethylene glycol to metal ions (Nb and W) is 1:1:1. After being fully dissolved, the mixture is heated and evaporated in a water bath at 80°C, and is continuously stirred until a gel is formed. The gel is dried in a blast oven at 120°C for 8h, and is ground after being taken out. The material is heated to 400°C in a muffle furnace for 5h to remove the organic matrix in the material, and then is continuously heated to 1200°C for sintering for 10h. After being cooled, the material is mechanically ball-milled for 2h to obtain the Nb 12 WO 33 compound.

[0091] (3) The carbonate precursor of the positive electrode material is mixed with the Nb 12 WO 33 compound and Li2CO3, and the molar ratio of Li:TM is 12:8, and TM is Ni, Co and Mn. The amount of the Nb 12 WO 33 compound added is 0.5wt.% of the total mass of the mixture of the carbonate precursor and Li2CO3. After being uniformly mixed in a mixer, the mixture is placed in a muffle furnace, and is pre-fired at 500°C for 5h, and then is heated to 870°C for 15h to obtain the positive electrode material.

[0092] (4) The assembly process of the coin cell is as described in Reference Example 1.

[0093] (5) The test temperature of the half-cell is 25°C, the voltage range for the specific capacity test is 2.0-4.8V, and the current density is 20mA·g -1 when the first discharge specific capacity is 279.6 mAh·g-1 -1 ; the voltage range for the cycle test is 2.0-4.6V, and the current density is 100mA·g -1The capacity retention rate was 90.06% after 100 cycles; the average discharge specific capacity at 0.1C (20 mA·g -1 -1), 0.5C (100 mA·g -1 -1), 1C (200 mA·g -1 -1), 2C (400 mA·g -1 -1), and 5C (1000 mA·g -1 -1) was 278.2 mAh·g -1 -1, 238.5 mAh·g -1 -1, 210.1 mAh·g -1 -1, 182.6 mAh·g -1 -1, and 153.4 mAh·g -1 -1, respectively.

[0094] Example 5

[0095] (1) The preparation method of the carbonate precursor was as described in Reference Example 1.

[0096] (2) Niobium chloride, ammonium metatungstate, citric acid, and ethylene glycol were dissolved in deionized water, and were weighed according to a molar ratio of Nb:W of 12:1, and a molar ratio of citric acid:ethylene glycol:metal ions (Nb and W) of 1:1:1. After being fully dissolved, the mixture was heated and evaporated in a water bath at 80°C, and was continuously stirred until a gel was formed. The gel was dried in a blast oven at 120°C for 8 h, was ground after being taken out, was heated to 400°C in a muffle furnace for 5 h to remove the organic matrix in the material, and was then continuously heated to 1200°C for sintering for 10 h. After being cooled, the mixture was mechanically ball-milled for 2 h to obtain a Nb 12 WO 33 compound with a median particle size of 5-50 nm.

[0097] (3) The carbonate precursor of the positive electrode material was fully mixed with a Nb 12 WO 33 compound and Li2CO3, and a molar ratio of Li:TM was 12:8, TM was Ni, Co, and Mn. The amount of the Nb 12 WO 33 compound added was 1.2 wt.% of the total mass of the mixture of the carbonate precursor and Li2CO3. After being fully mixed in a mixer, the mixture was placed in a muffle furnace, was pre-fired at 500°C for 5 h, and was then heated to 880°C for 15 h to obtain a lithium-rich manganese-based positive electrode material.

[0098] (4) The assembly procedure of the coin cell was as described in Reference Example 1.

[0099] (5) The test temperature of the half-cell was 25℃, the voltage range of the gram capacity test was 2.0-4.8V, and the current density was 20mA·g -1 The initial specific discharge capacity was 279.6mAh·g -1 ; the cycle test voltage range was 2.0-4.6V, and the current density was 100mA·g -1 After 100 cycles, the capacity retention rate was 94.37%; at a current density of 0.1C (20mA·g -1 ), 0.5C (100mA·g -1 ), 1C (200mA·g -1 ), 2C (400mA·g -1 ), and 5C (1000mA·g -1 ), the voltage range was 0.1C at 2.0-4.8V, and the voltage ranges of the rest were 2.0-4.6V, the average specific discharge capacities at 0.1C, 0.5C, 1C, 2C, and 5C were 279.2mAh·g -1 , 239.7mAh·g -1 , 212.9mAh·g -1 , 188.1mAh·g -1 , 165.2mAh·g -1 .

[0100] Comparative Example 1

[0101] (1) The preparation method of the carbonate precursor was as described in Reference Example 1.

[0102] (2) The carbonate precursor of the positive electrode material was mixed with Li2CO3, wherein the molar ratio of Li:TM was 12:8, TM was Ni, Co, and Mn, and after being uniformly mixed in a mixer, it was placed in a muffle furnace, pre-fired at 500℃ for 5h, and then heated to 880℃ for 15h to obtain the positive electrode material.

[0103] (3) The assembly process of the coin cell was as described in Reference Example 1.

[0104] (4) The test temperature of the half-cell was 25℃, the voltage range of the gram capacity test was 2.0-4.8V, and the current density was 20mA·g -1 The initial specific discharge capacity was 277.8mAh·g -1 ; the cycle test voltage range was 2.0-4.6V, and the current density was 100mA·g -1 After 100 cycles, the capacity retention rate was 89.57%; at a current density of 0.1C (20mA·g -1 ), 0.5C (100mA·g -1 ), 1C (200mA·g-1 ), 2C (400 mA·g -1 ), 5C (1000 mA·g -1 ) at 0.1C, 0.5C, 1C, 2C and 5C were 276.5 mAh·g -1 , 233.2 mAh·g -1 , 202.4 mAh·g -1 , 172.6 mAh·g -1 , 139.8 mAh·g -1 .

[0105] Comparative Example 2

[0106] (1) The preparation method of the carbonate precursor was the same as that in Reference Example 1.

[0107] (2) The niobium pentoxide and tungsten trioxide were mixed and pressed in a molar ratio of niobium to tungsten of 12:1, and then sintered in a muffle furnace at 1300°C for 10 h. After cooling, preliminary grinding and mechanical ball milling for 4 h were performed to obtain Nb 12 WO 33 compound.

[0108] (3) The carbonate precursor of the positive electrode material was mixed with the Nb 12 WO 33 compound and Li2CO3, and the molar ratio of Li:TM was 12:8, and TM was Ni, Co and Mn. The amount of the Nb 12 WO 33 compound was 1.2 wt.% of the total mass of the mixture of the carbonate precursor and Li2CO3. After being mixed in a mixer, the mixture was placed in a muffle furnace, pre-sintered at 500°C for 5 h, and then heated to 880°C for 15 h to obtain the positive electrode material. The positive electrode material was a secondary particle formed by a plurality of primary particles of lithium-rich manganese-based with the chemical formula xLi2MnO3·(1-x)LiMO2, and the surface of the secondary particle had a coating region formed by the niobium tungsten oxide with the chemical formula Nb 12 WO 33 .

[0109] (4) The assembly process of the coin cell was the same as that in Reference Example 1.

[0110] (5) The test temperature of the half-cell was 25°C, the voltage range for the specific capacity test was 2.0-4.8V, and the initial discharge specific capacity was 277.2 mAh·g -1 when the current density was 20 mA·g -1; the cycle test voltage range was 2.0-4.6V, and the current density was 100mA·g -1 ; the capacity retention rate was 87.25% after 100 cycles; the current density was 0.1C (20mA·g -1 ), 0.5C (100mA·g -1 ), 1C (200mA·g -1 ), 2C (400mA·g -1 ), and 5C (1000mA·g -1 ), and the voltage range was 0.1C 2.0-4.8V, and the rest was 2.0-4.6V; the average discharge specific capacity at 0.1C, 0.5C, 1C, 2C, and 5C was 276.4mAh·g -1 , 234.9mAh·g -1 , 205.5mAh·g -1 , 178.8mAh·g -1 , and 144.9mAh·g -1 .

[0111] The above describes embodiments of the present application. However, the present application is not limited to the above-described embodiments. Any modification, equivalent replacement, improvement, and the like within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A positive electrode material, characterized in that The positive electrode material is secondary particles formed by a number of primary particles of lithium-rich manganese-based with the chemical formula xLi2MnO3·(1-x)LiMO2, and the surface of the secondary particles has a coating region formed by niobium tungsten oxide with the chemical formula Nb 12 WO 33 ; wherein, 0 < x < 1, and M is a combination of Mn and at least one of the following elements: Ni, Co, Al, Mg, Zr, Ti, Nb, W, P, B; The chemical formula is Nb 12 WO 33 The median particle size of niobium tungsten oxide is 5nm~50nm; The chemical formula is Nb 12 WO 33 The mass of niobium tungsten oxide accounts for 0.5~5wt.% of the total mass of the positive electrode material.

2. The positive electrode material according to claim 1, characterized in that The positive electrode material is a spherical or ellipsoidal secondary particle formed by the agglomeration of several lithium-rich manganese-based primary particles with a chemical formula of xLi2MnO3·(1-x)LiMO2, and the surface of the secondary particle has a chemical formula of Nb 12 WO 33 The coating area is formed by niobium tungsten oxide.

3. The positive electrode material according to claim 2, characterized in that The median particle size of secondary particles formed by several lithium-rich manganese-based primary particles with the chemical formula xLi2MnO3·(1-x)LiMO2 is 6μm~15μm.

4. The positive electrode material according to claim 1, characterized in that The median particle size of the positive electrode material is 6 μm to 15 μm.

5. The method for preparing the positive electrode material according to any one of claims 1 to 4, characterized in that: The preparation method comprises the following steps: (1) Mixing a soluble salt of element M with water, adding a precipitant and a complexing agent, and performing a coprecipitation reaction to prepare a precursor of a lithium-rich manganese-based positive electrode material; (2) mixing a complexing agent, a niobium-containing compound, and a tungsten-containing compound to prepare a sol and a gel, drying, sintering, and ball milling to prepare niobium tungsten oxide; (3) mixing the precursor of the lithium-rich manganese-based positive electrode material of step (1), the niobium tungsten oxide of step (2) and the lithium source to obtain a mixed material; (4) Sintering the mixed material of step (3) to prepare the positive electrode material.

6. A positive electrode sheet, characterized in that: The positive electrode sheet comprises the positive electrode material according to any one of claims 1 to 4.

7. A battery, characterized in that: The battery comprises the positive electrode material according to any one of claims 1 to 4, or the battery comprises the positive electrode sheet according to claim 6.

8. The battery according to claim 7, characterized in that The mass energy density of the battery is 300-420Wh / kg.

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