High-valence cation doped high-nickel lithium-rich manganese-based positive electrode material and preparation method thereof

Abstract

The invention belongs to the technical field of positive electrode materials for lithium ion secondary batteries, and particularly discloses a high-valence cation doped high-nickel lithium-rich manganese-based positive electrode material and a preparation method thereof, the chemical formula of the high-valence cation doped high-nickel lithium-rich manganese-based positive electrode material is Li < 1.13 > (Mn < 0.522 > Ni < 0.261 > Co < 0.087 >) < 1-x > Nb < x > O < 2 >, and x is greater than or equal to 0 and less than or equal to 0.005. According to the high-valence cation doped high-nickel lithium-rich manganese-based positive electrode material and the preparation method thereof, by doping the Nb doped high-nickel lithium-rich manganese-based positive electrode material, the voltage attenuation is effectively reduced, the long cycle performance of the material is improved, the rate capability of the material is improved, in addition, a firm Nb-O bond can effectively stabilize an oxygen lattice frame, and the high-valence cation doped high-nickel lithium-rich manganese-based positive electrode material is prepared. Phase change is slowed down, so that irreversible release of oxygen is inhibited, and the structural stability of the material is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of positive electrode materials for lithium ion secondary batteries, and particularly relates to a high-valence cation doped high-nickel lithium-rich manganese-based positive electrode material and a preparation method thereof. BACKGROUND

[0002] The practical application of lithium ion batteries (LIBs) in portable electronic devices and electric vehicles (EVs) has had a significant impact on energy storage systems. With the rapid growth in demand for high-energy density lithium ion batteries, there is an increasing demand for high-performance battery electrode materials. In particular, the positive electrode material plays a key role in determining the energy density and cost of lithium ion batteries.

[0003] The currently commonly used commercial positive electrode materials such as layered LiMO2 (M = Mn, Co, Ni) and LiFePO4 (specific capacity of 120-200 mAh g -1 ) have not been able to meet the growing demand for energy and power density. Lithium-rich manganese-based positive electrode materials (LLOs) have been widely studied in recent years due to their high reversible capacity (> 250 mAh g -1 ), environmental friendliness and low cost. LLOs are mainly composed of Li2MnO3 and LiMO2 (M = Mn, Co, Ni), both of which have a layered structure similar to that of alpha-NaFeO2.

[0004] The high capacity of LLOs is due to the activation of the Li2MnO3 phase at high pressure, with an anion redox reaction providing charge compensation. Due to the problem of irreversible release of oxygen, LLOs face serious challenges. For example, low first coulombic efficiency, poor capacity retention, severe voltage decay, kinetic lag, TM metal dissolution, etc. In order to solve these problems, various strategies have been proposed, including surface coating, ion doping, chemical composition optimization, and control of particle size and morphology. Increasing the Ni content in lithium-rich manganese-based positive electrode materials to obtain high-nickel lithium-rich manganese-based positive electrode materials is considered to be an effective way to solve this problem, but is usually accompanied by a decrease in capacity and poor cycle stability.

[0005] Therefore, there is a need in the art to develop a high-valence cation doped high-nickel lithium-rich manganese-based positive electrode material and a preparation method thereof, which can effectively solve the above problems. SUMMARY

[0006] The purpose of the present application is to provide a high-valence cation doped high-nickel lithium-rich manganese-based positive electrode material and a preparation method thereof. The method dopes a high-nickel lithium-rich manganese-based positive electrode material with Nb, effectively reducing voltage decay and improving the long cycle performance of the material. In addition, the strong Nb-O bond can effectively stabilize the oxygen lattice framework and slow down the phase transition, thereby inhibiting the irreversible release of oxygen and improving the structural stability of the material.

[0007] To achieve the above objectives, the present invention provides a high-valence cation-doped high-nickel lithium-rich manganese-based cathode material, wherein the chemical formula of the high-valence cation-doped high-nickel lithium-rich manganese-based cathode material is Li. 1.13 (Mn 0.522 Ni 0.261 Co 0.087 ) 1-x Nb x O2, 0≤x≤0.005.

[0008] This invention also provides a method for preparing a high-valent cation-doped high-nickel lithium-rich manganese-based cathode material, which is prepared by co-precipitation and high-temperature solid-state methods, specifically including the following steps: Step S1: Preparation of hydroxide precursor Mn 0.6 Ni 0.3 Co 0.1 (OH)2; Step S2: Preparation of high-nickel, lithium-rich manganese-based cathode material Li 1.13 Mn 0.522 Ni 0.261 Co 0.087 O2; Step S3: Preparation of high-nickel lithium-rich manganese-based cathode material Li doped with high-valence cations 1.13 (Mn 0.522 Ni 0.261 Co 0.087 ) 1-x Nb x O2, 0≤x≤0.005.

[0009] Preferably, step S1 specifically involves: Step S11, according to the hydroxide precursor Mn 0.6 Ni 0.3 Co 0.1 To determine the stoichiometric ratio of elements in (OH)₂, weigh out manganese, nickel, and cobalt salts, add them to deionized water, and mix thoroughly to obtain a concentration of 1.5–4 mol / L. -1 A mixed solution; Step S12: The mixed solution, precipitant solution, and buffer solution are simultaneously added to the reaction vessel using a constant flow pump to carry out a coprecipitation reaction and obtain a coprecipitate. Step S13: The coprecipitate is sequentially filtered, washed with deionized water, and dried at 50-500℃ for 1-20 hours to obtain the hydroxide precursor Mn. 0.6 Ni 0.3 Co 0.1 (OH)2.

[0010] Preferably, in step S11, the manganese salt is one or a combination of manganese chloride, manganese sulfate monohydrate, manganese nitrate, and manganese acetate; the nickel salt is one or a combination of nickel chloride, nickel sulfate hexahydrate, nickel nitrate, and nickel acetate; and the cobalt salt is one or a combination of cobalt chloride, cobalt sulfate heptahydrate, cobalt nitrate, and cobalt acetate.

[0011] Preferably, in step S12, the buffer solution is one or a combination of ethylenediamine, ammonia, hydroxylammonium chloride, sodium sulfosalicylate, sodium phosphate, ethylenediaminetetraacetic acid (EDTA), hydroxyethylenediaminetriacetic acid (HEDTA), ethyleneglycolbis(2-aminoethylether)tetraacetic acid (EGTA), diethylenetriaminepentaacetic acid (DTPA), and 1,2-cyclohexanediaminetetraacetic acid (DCyTA); and the precipitant solution is sodium hydroxide.

[0012] Preferably, in step S12, the pH of the co-precipitation reaction is 10-11, the temperature of the co-precipitation reaction is 50-80°C, and the time of the co-precipitation reaction is 8-16h.

[0013] Preferably, step S2 is specifically, In step S21, the lithium source compound is weighed in an amount of 0.5-1.5 times the molar mass of the hydroxide precursor Mn 0.6 Ni 0.3 Co 0.1 (OH)2, and the hydroxide precursor Mn 0.6 Ni 0.3 Co 0.1 (OH)2are mixed uniformly to obtain a mixture. In step S22, the mixture is heated to 200-500°C at a heating rate of 0.5-10°C / min under an air atmosphere, and then heated to 600-1200°C at a heating rate of 0.5-10°C / min, and calcined for 2-60h. In step S23, the temperature is lowered, and a high-nickel lithium-rich manganese-based positive electrode material Li 1.13 Mn 0.522 Ni 0.261 Co 0.087 O2is obtained.

[0014] Preferably, in step S21, the lithium source compound is one or a combination of lithium carbonate, lithium hydroxide, lithium nitrate, and lithium sulfate.

[0015] Preferably, step S3 is specifically, In step S31, the high-nickel lithium-rich manganese-based positive electrode material Li 1.13 (Mn 0.522 Ni 0.261 Co 0.087 )1-x Nb x O2, 0≤x≤0.005 1.13 Mn 0.522 Ni 0.261 Co 0.087 O2 and niobium compound are placed in a ball mill jar, and ball mill mixing is performed to obtain a mixture; Step S32, drying the mixture at a temperature of 50-200℃ for 1-20h; Step S33, heating to 500-700℃ at a temperature rising speed of 0.5-10℃ / min, calcining for 2-30h, and cooling, to obtain the high-valence cation doped modified high-nickel lithium-rich manganese-based positive electrode material Li 1.13 (Mn 0.522 Ni 0.261 Co 0.087 ) 1-x Nb x O2, 0≤x≤0.005.

[0016] Preferably, in step S31, the niobium compound is one or a combination of niobium oxide, hydrated niobium oxalate, and niobium chloride; The ball-to-material ratio of the ball mill mixing is 1:(2-10), the ball mill rotation speed of the ball mill mixing is 100-300r / min, and the ball mill mixing time is 6-12h.

[0017] The above-mentioned high-valence cation doped high-nickel lithium-rich manganese-based positive electrode material and the preparation method thereof have the following beneficial effects: (1) The high-nickel lithium-rich manganese-based positive electrode material is obtained by increasing the Ni content in the lithium-rich manganese-based positive electrode material. Since the Ni-O bond is stronger, the activation of Li2MnO3 can be inhibited, which stabilizes the oxidation and reduction of anions and the oxygen loss. In the delithiation / lithiation process, the nickel ions tend to reversibly migrate between the TM layer and the intermediate layer, which can inhibit the formation of spinel phases and improve the cycle stability of the material.

[0018] (2) A small amount of high-valence cation Nb is doped in the present application, which has a strong Nb-O bond, can reduce the covalence of TM─O bond, thereby stabilizing the Li-TM-O main structure framework and inhibiting the release of oxygen in the electrochemical cycle process; at the same time, since the high-valence Nb 5+ ion has a large ionic radius, the interlattice spacing of the crystal is increased, the electrochemical reaction kinetics and rate performance of the high-nickel lithium-rich manganese-based positive electrode material are improved; in addition, the columnar effect of the high-valence cation Nb 5+ further inhibits the migration of TM ions and the capture of Li + ions in tetrahedral sites, thereby improving the stability of the structure.

[0019] (3) The high valence cation doped high-nickel lithium-rich manganese-based positive electrode material Li 1.13 (Mn 0.522 Ni 0.261 Co 0.087 ) 1-x Nb x O2, 0≤x≤0.005 when applied to a lithium ion battery, the lithium ion battery can maintain 94.86% of the capacity after 200 cycles at 1.0C (1.0C=250 mA g -1 ) rate when charged and discharged in the voltage range of 2.5-4.6V at room temperature, the median voltage only attenuates 0.160V after 200 cycles at 1.0C (1.0C=250 mA g -1 ) rate, and has a discharge specific capacity of 158 mAh g -1 ) at 5.0C (1.0C=250 mA g -1 ) rate. Therefore, the high valence cation doped high-nickel lithium-rich manganese-based positive electrode material prepared by the present application has excellent cycle and rate performance.

[0020] The technical solutions of the present application are further described in detail below through the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 Figure 1 is an XRD pattern of the high-nickel lithium-rich manganese-based positive electrode material prepared in Example 2 of the experimental example of the high valence cation doped high-nickel lithium-rich manganese-based positive electrode material and the preparation method thereof of the present application. Figure 2 Figure 2 is a first charge-discharge curve of the high-nickel lithium-rich manganese-based positive electrode material prepared in Example 2 and the comparative example of the experimental example of the high valence cation doped high-nickel lithium-rich manganese-based positive electrode material and the preparation method thereof of the present application. Figure 3 Figure 3 is a rate performance graph of the high-nickel lithium-rich manganese-based positive electrode material prepared in Example 2 and the comparative example of the experimental example of the high valence cation doped high-nickel lithium-rich manganese-based positive electrode material and the preparation method thereof of the present application. Figure 4 Figure 4 is a cycle performance graph of the high-nickel lithium-rich manganese-based positive electrode material prepared in Example 2 and the comparative example of the experimental example of the high valence cation doped high-nickel lithium-rich manganese-based positive electrode material and the preparation method thereof of the present application. DETAILED DESCRIPTION

[0022] The technical solutions of the present application are further described in detail below through the drawings and examples.

[0023] Unless otherwise defined, the technical terms or scientific terms used in the present application shall have the usual meaning understood by a person with ordinary skill in the art to which the present application belongs.

[0024] Example 1 A preparation method of a high-valence cation doped high-nickel lithium-rich manganese-based positive electrode material, comprising the following steps: Step S1, preparing a hydroxide precursor Mn 0.6 Ni 0.3 Co 0.1 (OH)2.

[0025] Step S11, according to the stoichiometric ratio of elements in the hydroxide precursor Mn 0.6 Ni 0.3 Co 0.1 (OH)2, 201.7g of manganese sulfate monohydrate, 160.8g of nickel sulfate hexahydrate, and 57.1g of cobalt sulfate heptahydrate are weighed, and the manganese sulfate monohydrate, the nickel sulfate hexahydrate, and the cobalt sulfate heptahydrate are mixed uniformly in deionized water to obtain a mixed solution with a concentration of 2mol / L. -1

[0026] Step S12, the mixed solution, 169.7g of sodium hydroxide, and 100mL of ammonia water are simultaneously added to the reaction kettle for co-precipitation reaction by using a constant flow pump, and the co-precipitate is obtained under the conditions of a temperature of 55℃, a pH value of 10.0, and a stirring speed of 500rpm for 12 hours.

[0027] Step S13, the co-precipitate is sequentially filtered, washed with deionized water, and dried at a temperature of 200℃ for 10h to obtain the hydroxide precursor Mn 0.6 Ni 0.3 Co 0.1 (OH)2.

[0028] Step S2, preparing a high-nickel lithium-rich manganese-based positive electrode material Li 1.13 Mn 0.522 Ni 0.261 Co 0.087 O2.

[0029] Step S21, 10g of the hydroxide precursor Mn 0.6 Ni 0.3 Co 0.1 (OH)2, and 6g of lithium carbonate are weighed, and the lithium carbonate and the hydroxide precursor Mn 0.6 Ni 0.3 Co 0.1 (OH)2 are put into a ball milling jar, 20mL of ethanol is added as a dispersant, the bead-to-material ratio in the ball milling jar is 1:3, the ball milling speed is set to 180r / min, and the ball milling time is 10 hours to obtain a mixture.

[0030] ​Step S22, the mixture is heated to 450℃ at a temperature rising rate of 3℃ / min under air atmosphere, and kept for 6h. Then it is heated to 850℃ at a temperature rising rate of 3℃ / min, and calcined for 16h.

[0031] Step S23, natural cooling, to obtain the high-nickel lithium-rich manganese-based positive electrode material Li 1.13 Mn 0.522 Ni 0.261 Co 0.087 O2.

[0032] Step S3, preparation of the high-valence cation doped modified high-nickel lithium-rich manganese-based positive electrode material Li 1.13 (Mn 0.522 Ni 0.261 Co 0.087 ) 1-x Nb x O2, 0≤x≤0.005.

[0033] Step S31, according to the stoichiometric ratio of the elements in the high-valence cation doped modified high-nickel lithium-rich manganese-based positive electrode material Li 1.13 (Mn 0.522 Ni 0.261 Co 0.087 ) 1-x Nb x O2, 0≤x≤0.005, 3g of the high-nickel lithium-rich manganese-based positive electrode material Li 1.13 Mn 0.522 Ni 0.261 Co 0.087 O2 and 0.03g of the hydrated niobium oxalate compound are weighed into a ball mill jar, 20mL of ethanol is added as a dispersant, the ball mill jar has a bead-to-material ratio of 1:3, the ball mill rotation speed is set to 180r / min, and the ball milling time is 10 hours, to obtain a mixture.

[0034] Step S32, the mixture is dried at a temperature of 100℃ for 10h.

[0035] Step S33, heating to 600℃ at a temperature rising rate of 3℃ / min under air atmosphere, and calcining for 10h, and natural cooling, to obtain the high-valence cation doped modified high-nickel lithium-rich manganese-based positive electrode material Li 1.13 (Mn 0.522 Ni 0.261 Co 0.087 ) 0.999 Nb 0.001 O2, denoted as LLMO-Nb1.

[0036] Example 2 A preparation method of a high-valence cation doped high-nickel lithium-rich manganese-based positive electrode material, comprising the following steps: Step S1, preparing hydroxide precursor Mn 0.6 Ni 0.3 Co 0.1 (OH)2.

[0037] Step S11, according to the stoichiometric ratio of elements in the hydroxide precursor Mn 0.6 Ni 0.3 Co 0.1 (OH)2, 201.7g of manganese sulfate monohydrate, 160.8g of nickel sulfate hexahydrate, and 57.1g of cobalt sulfate heptahydrate are weighed, and the manganese sulfate monohydrate, nickel sulfate hexahydrate, and cobalt sulfate heptahydrate are added to deionized water and mixed uniformly to obtain a mixed solution with a concentration of 2mol / L. -1

[0038] Step S12, the mixed solution, 169.7g of sodium hydroxide, and 100mL of ammonia water are simultaneously added to the reaction kettle by a constant flow pump for co-precipitation reaction, and the reaction is stirred for 12 hours under the conditions of a temperature of 55°C, a pH value of 10.0, and a stirring speed of 500rpm to obtain a co-precipitate.

[0039] Step S13, the co-precipitate is sequentially filtered, washed with deionized water, and dried at a temperature of 200°C for 10h to obtain the hydroxide precursor Mn 0.6 Ni 0.3 Co 0.1 (OH)2.

[0040] Step S2, preparing high-nickel lithium-rich manganese-based positive electrode material Li 1.13 Mn 0.522 Ni 0.261 Co 0.087 O2.

[0041] Step S21, 10g of hydroxide precursor Mn 0.6 Ni 0.3 Co 0.1 (OH)2, and 6g of lithium carbonate are weighed, and the lithium carbonate and the hydroxide precursor Mn 0.6 Ni 0.3 Co 0.1 (OH)2are placed in a ball milling jar, 20mL of ethanol is added as a dispersant, the bead-to-material ratio in the ball milling jar is 1:3, the ball milling speed is set to 180r / min, and the ball milling time is 10 hours to obtain a mixture.

[0042] Step S22, the mixture is heated to 450°C at a heating rate of 3°C / min under an air atmosphere, and then heated to 850°C at a heating rate of 3°C / min and calcined for 16h.

[0043] Step S23, natural cooling, to obtain the high-nickel lithium-rich manganese-based positive electrode material Li​1.13 Mn 0.522 Ni 0.261 Co 0.087 O2.

[0044] Step S3: Preparation of high-nickel lithium-rich manganese-based cathode material Li doped with high-valence cations 1.13 (Mn 0.522 Ni 0.261 Co 0.087 ) 1-x Nb x O2, 0≤x≤0.005.

[0045] Step S31: Modify high-nickel lithium-rich manganese-based cathode material Li according to high-valence cation doping. 1.13 (Mn 0.522 Ni 0.261 Co 0.087 ) 1-x Nb x The stoichiometric ratio of elements in O2, 0≤x≤0.005 is used to weigh 3g of high-nickel lithium-rich manganese-based cathode material Li. 1.13 Mn 0.522 Ni 0.261 Co 0.087 O2 and 0.09 g of niobium oxalate hydrate were placed in a ball mill jar, and 20 mL of ethanol was added as a dispersant. The ball mill ratio in the jar was 1:3. The ball mill speed was set to 180 r / min and the ball milling time was 10 hours to obtain a mixture.

[0046] Step S32: Dry the mixture at 100℃ for 10 hours.

[0047] Step S33: Heat to 600℃ in air at a heating rate of 3℃ / min, calcine for 10 hours, and then allow to cool naturally to obtain the high-valence cation-doped modified high-nickel lithium-rich manganese-based cathode material Li. 1.13 (Mn 0.522 Ni 0.261 Co 0.087 ) 0.997 Nb 0.003 O2, denoted as LLMO-Nb3.

[0048] Example 3 A method for preparing a high-valent cation-doped high-nickel lithium-rich manganese-based cathode material includes the following steps: Step S1: Preparation of hydroxide precursor Mn 0.6 Ni 0.3 Co 0.1 (OH)2.

[0049] Step S11, according to the hydroxide precursor Mn 0.6 Ni 0.3Co 0.1 The stoichiometric ratio of elements in (OH)₂ was determined by weighing 201.7 g of manganese sulfate monohydrate, 160.8 g of nickel sulfate hexahydrate, and 57.1 g of cobalt sulfate heptahydrate. These components were then added to deionized water and mixed thoroughly to obtain a solution with a concentration of 2 mol / L. -1 A mixed solution.

[0050] Step S12: The mixed solution, 169.7g sodium hydroxide, and 100mL ammonia water are simultaneously added to the reaction vessel using a constant flow pump to carry out a coprecipitation reaction. The reaction is carried out at a temperature of 55℃, a pH value of 10.0, and a stirring speed of 500rpm for 12 hours to obtain the coprecipitate.

[0051] Step S13: The coprecipitate is sequentially filtered, washed with deionized water, and dried at 200℃ for 10 hours to obtain the hydroxide precursor Mn. 0.6 Ni 0.3 Co 0.1 (OH)2.

[0052] Step S2: Preparation of high-nickel, lithium-rich manganese-based cathode material Li 1.13 Mn 0.522 Ni 0.261 Co 0.087 O2.

[0053] Step S21: Weigh 10g of hydroxide precursor Mn 0.6 Ni 0.3 Co 0.1 (OH)2, 6g lithium carbonate, lithium carbonate, hydroxide precursor Mn 0.6 Ni 0.3 Co 0.1 (OH)2 was placed in a ball mill jar, and 20 mL of ethanol was added as a dispersant. The ball mill ratio in the jar was 1:3. The ball mill speed was set to 180 r / min and the ball milling time was 10 hours to obtain a mixture.

[0054] Step S22: In an air atmosphere, heat the mixture to 450°C at a heating rate of 3°C / min and hold for 6 hours. Then heat it to 850°C at a heating rate of 3°C / min and calcine for 16 hours.

[0055] Step S23: Natural cooling yields the high-nickel, lithium-rich manganese-based cathode material Li. 1.13 Mn 0.522 Ni 0.261 Co 0.087 O2.

[0056] Step S3: Preparation of high-nickel lithium-rich manganese-based cathode material Li doped with high-valence cations 1.13 (Mn0.522 Ni 0.261 Co 0.087 ) 1-x Nb x O2, 0≤x≤0.005.

[0057] Step S31: Modify high-nickel lithium-rich manganese-based cathode material Li according to high-valence cation doping. 1.13 (Mn 0.522 Ni 0.261 Co 0.087 ) 1-x Nb x The stoichiometric ratio of elements in O2, 0≤x≤0.005 is used to weigh 3g of high-nickel lithium-rich manganese-based cathode material Li. 1.13 Mn 0.522 Ni 0.261 Co 0.087 O2 and 0.15g of niobium oxalate hydrate were placed in a ball mill jar, and 20mL of ethanol was added as a dispersant. The ball mill ratio in the jar was 1:3. The ball mill speed was set to 180r / min and the ball milling time was 10 hours to obtain a mixture.

[0058] Step S32: Dry the mixture at 100℃ for 10 hours.

[0059] Step S33: Heat to 600℃ in air at a heating rate of 3℃ / min, calcine for 10 hours, and then allow to cool naturally to obtain the high-valence cation-doped modified high-nickel lithium-rich manganese-based cathode material Li. 1.13 (Mn 0.522 Ni 0.261 Co 0.087 ) 0.995 Nb 0.005 O2, denoted as LLMO-Nb5.

[0060] Comparative Example A method for preparing a high-nickel, lithium-rich manganese-based cathode material includes the following steps: Step S1: Preparation of hydroxide precursor Mn 0.6 Ni 0.3 Co 0.1 (OH)2.

[0061] Step S11, according to the hydroxide precursor Mn 0.6 Ni 0.3 Co 0.1 The stoichiometric ratio of elements in (OH)₂ was determined by weighing 201.7 g of manganese sulfate monohydrate, 160.8 g of nickel sulfate hexahydrate, and 57.1 g of cobalt sulfate heptahydrate. These components were then added to deionized water and mixed thoroughly to obtain a solution with a concentration of 2 mol / L. -1 A mixed solution.

[0062] Step S12: The mixed solution, 169.7g sodium hydroxide, and 100mL ammonia water are simultaneously added to the reaction vessel using a constant flow pump to carry out a coprecipitation reaction. The reaction is carried out at a temperature of 55℃, a pH value of 10.0, and a stirring speed of 500rpm for 12 hours to obtain the coprecipitate.

[0063] Step S13: The coprecipitate is sequentially filtered, washed with deionized water, and dried at 200℃ for 10 hours to obtain the hydroxide precursor Mn. 0.6 Ni 0.3 Co 0.1 (OH)2.

[0064] Step S2: Preparation of high-nickel, lithium-rich manganese-based cathode material Li 1.13 Mn 0.522 Ni 0.261 Co 0.087 O2.

[0065] Step S21: Weigh 10g of hydroxide precursor Mn 0.6 Ni 0.3 Co 0.1 (OH)2, 6g lithium carbonate, lithium carbonate, hydroxide precursor Mn 0.6 Ni 0.3 Co 0.1 (OH)2 was placed in a ball mill jar, and 20 mL of ethanol was added as a dispersant. The ball mill ratio in the jar was 1:3. The ball mill speed was set to 180 r / min and the ball milling time was 10 hours to obtain a mixture.

[0066] Step S22: In an air atmosphere, heat the mixture to 450°C at a heating rate of 3°C / min and hold for 6 hours. Then heat it to 850°C at a heating rate of 3°C / min and calcine for 16 hours.

[0067] Step S23: Natural cooling yields the high-nickel, lithium-rich manganese-based cathode material Li. 1.13 Mn 0.522 Ni 0.261 Co 0.087 O2, denoted as LLMO.

[0068] Experimental Example (1) As Figure 1 As shown, the structure of the high-valent cation-doped high-nickel lithium-rich manganese-based cathode material prepared in Example 2 was characterized by XRD.

[0069] (2) The high-nickel lithium-rich manganese-based cathode materials prepared in Examples 1-3 and the comparative example were weighed and mixed with conductive carbon black Super and PVDF in a ratio of 8:1:1. N-methylpyrrolidone solution (NMP) was added to homogenize the mixture. The slurry was then uniformly coated on aluminum foil and dried in a vacuum drying oven at 120°C for 12 hours. The lithium battery cathode sheet was obtained by rolling and cutting.

[0070] A coin cell was assembled in an argon-filled glove box using a lithium metal sheet as the counter electrode, a 1 mol / L LiPF6 solution of ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) (volume ratio 1:1:1) as the electrolyte, and polyethylene as the separator.

[0071] The assembled button cells were tested on the Newway testing system, with a voltage window of 2.5V-4.6V and 1C=250mAg. -1 All test results are shown in Table 1. Figures 2-4 As shown.

[0072] Table 1. Test results of charge-discharge performance of Examples 1-3 and comparative examples. ;

[0073] The test results above show that, compared with the comparative examples, the appropriate amount of high-valence cation Nb doping in Examples 1-3 is beneficial to improving the discharge specific capacity, rate performance and cycle performance of the material. This indicates that the doping of a small amount of high-valence cation Nb has a strong Nb-O bond, which can reduce the covalent of the TM-O bond, thereby stabilizing the Li-TM-O main structural framework and inhibiting oxygen release during electrochemical cycling.

[0074] Meanwhile, due to the high price of Nb 5+ The ions have a large ionic radius, which increases the lattice interlayer spacing and improves the electrochemical reaction kinetics and rate performance of high-nickel lithium-rich manganese-based cathode materials. In addition, the high-valence cation Nb... 5+ The columnar effect further inhibited the migration of TM ions and Li + The trapping of ions at tetrahedral sites improves structural stability.

[0075] Therefore, the present invention adopts the above-mentioned high-valence cation-doped high-nickel lithium-rich manganese-based cathode material and its preparation method. The method effectively reduces voltage decay, improves the long-cycle performance of the material, improves the rate performance of the material, and enhances the stability of the material structure by Nb-doping the high-nickel lithium-rich manganese-based cathode material.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A high-valent cation-doped, high-nickel, lithium-rich manganese-based cathode material, characterized in that: The chemical formula of the high-valent cation-doped high-nickel lithium-rich manganese-based cathode material is Li. 1.13 (Mn 0.522 Ni 0.261 Co 0.087 ) 1-x Nb x O2, 0≤x≤0.

005.

2. The method for preparing a high-valent cation-doped high-nickel lithium-rich manganese-based cathode material as described in claim 1, characterized in that, Includes the following steps: Step S1: Preparation of hydroxide precursor Mn 0.6 Ni 0.3 Co 0.1 (OH)2; Step S2: Preparation of high-nickel, lithium-rich manganese-based cathode material Li 1.13 Mn 0.522 Ni 0.261 Co 0.087 O2; Step S3: Preparation of high-nickel lithium-rich manganese-based cathode material Li doped with high-valence cations 1.13 (Mn 0.522 Ni 0.261 Co 0.087 ) 1- x Nb x O2, 0≤x≤0.

005.

3. The method for preparing a high-valent cation-doped high-nickel lithium-rich manganese-based cathode material according to claim 2, characterized in that: Step S1 specifically involves: Step S11, according to the hydroxide precursor Mn 0.6 Ni 0.3 Co 0.1 To determine the stoichiometric ratio of elements in (OH)₂, weigh out manganese, nickel, and cobalt salts, add them to deionized water, and mix thoroughly to obtain a concentration of 1.5–4 mol / L. -1 A mixed solution; Step S12: The mixed solution, precipitant solution, and buffer solution are simultaneously added to the reaction vessel using a constant flow pump to carry out a coprecipitation reaction and obtain a coprecipitate. Step S13: The coprecipitate is sequentially filtered, washed with deionized water, and dried at 50-500℃ for 1-20 hours to obtain the hydroxide precursor Mn. 0.6 Ni 0.3 Co 0.1 (OH)2.

4. The method for preparing a high-valent cation-doped high-nickel lithium-rich manganese-based cathode material according to claim 3, characterized in that: In step S11, the manganese salt is one or a combination of manganese chloride, manganese sulfate monohydrate, manganese nitrate, and manganese acetate; the nickel salt is one or a combination of nickel chloride, nickel sulfate hexahydrate, nickel nitrate, and nickel acetate; and the cobalt salt is one or a combination of cobalt chloride, cobalt sulfate heptahydrate, cobalt nitrate, and cobalt acetate.

5. The method for preparing a high-valent cation-doped high-nickel lithium-rich manganese-based cathode material according to claim 3, characterized in that: In step S12, the buffer solution is one or a combination of several of the following: ethylenediamine, ammonia, hydroxyammonium hydrochloride, sodium sulfosalicylate, sodium phosphate, ethylenediaminetetraacetic acid, hydroxyethylethylenediaminetriacetic acid, ethylene glycol bis(2-aminoethyl ether)tetraacetic acid, diethyltriaminepentaacetic acid, and 1,2-cyclohexanediaminetetraacetic acid; the precipitant solution is sodium hydroxide.

6. The method for preparing a high-valence cation-doped high-nickel lithium-rich manganese-based cathode material according to claim 3, characterized in that: In step S12, the pH of the coprecipitation reaction is 10-11, the temperature of the coprecipitation reaction is 50-80℃, and the time of the coprecipitation reaction is 8-16h.

7. The method for preparing a high-valence cation-doped high-nickel lithium-rich manganese-based cathode material according to claim 2, characterized in that: Step S2 specifically involves: Step S21, using the hydroxide precursor Mn obtained in step S1 0.6 Ni 0.3 Co 0.1 Weigh out 0.5-1.5 times the molar mass of the lithium source compound (OH)₂, and combine the lithium source compound and the hydroxide precursor Mn. 0.6 Ni 0.3 Co 0.1 (OH)2 is mixed evenly to obtain a mixture; Step S22: In an air atmosphere, heat the mixture to 200-500℃ at a heating rate of 0.5-10℃ / min and hold for 2-30h; then heat it to 600-1200℃ at a heating rate of 0.5-10℃ / min and calcine for 2-60h. Step S23: Cooling down yields the high-nickel, lithium-rich manganese-based cathode material Li. 1.13 Mn 0.522 Ni 0.261 Co 0.087 O2.

8. The method for preparing a high-valence cation-doped high-nickel lithium-rich manganese-based cathode material according to claim 7, characterized in that: In step S21, the lithium source compound is one or a combination of lithium carbonate, lithium hydroxide, lithium nitrate, and lithium sulfate.

9. The method for preparing a high-valent cation-doped high-nickel lithium-rich manganese-based cathode material according to claim 2, characterized in that: Step S3 specifically involves: Step S31: Modify high-nickel lithium-rich manganese-based cathode material Li according to high-valence cation doping. 1.13 (Mn 0.522 Ni 0.261 Co 0.087 ) 1-x Nb x Weigh the high-nickel, lithium-rich manganese-based cathode material Li obtained in step S2 according to the stoichiometric ratio of elements in O2, 0≤x≤0.

005. 1.13 Mn 0.522 Ni 0.261 Co 0.087 O2 and niobium compounds were placed in a ball mill jar and mixed by ball milling to obtain a mixture. Step S32: Dry the mixture at a temperature of 50-200℃ for 1-20 hours; Step S33: Heat to 500-700℃ at a heating rate of 0.5-10℃ / min, calcine for 2-30 hours, and then cool down to obtain the high-valence cation-doped modified high-nickel lithium-rich manganese-based cathode material Li. 1.13 (Mn 0.522 Ni 0.261 Co 0.087 ) 1-x Nb x O2, 0≤x≤0.

005.

10. The method for preparing a high-valence cation-doped high-nickel lithium-rich manganese-based cathode material according to claim 9, characterized in that: In step S31, the niobium compound is one or a combination of niobium oxide, niobium oxalate hydrate, and niobium chloride; The ball-to-material ratio for ball milling is 1:(2-10), the ball milling speed is 100-300 r / min, and the ball milling time is 6-12 h.

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