A double-ion gradient-doped lithium-rich manganese-based layered transition metal oxide and a preparation method and application thereof

Abstract

The application belongs to the technical field of lithium ion batteries, and discloses a double-ion gradient doped lithium-rich manganese-based layered transition metal oxide and a preparation method and application thereof. 1‑y M y O2, TM is one or more of Mn, Ni, Co, Fe or Cr, M is one of Sn and Mg, Ba, Zn or Ce, 0.01<=x<=0.5, 0.01<=y<=0.3; the double-ion gradient doped lithium-rich manganese-based layered transition metal oxide has high initial coulombic efficiency, high capacity and excellent cycle performance. When the voltage window is 2-4.8V and the current density is 200mA / g, the specific capacity can reach 235mAh / g, and the capacity retention rate after 150 cycles is higher than 95.3%, so that the double-ion gradient doped lithium-rich manganese-based layered transition metal oxide can be applied as a positive electrode material in the fields of lithium ion batteries or power batteries.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and more specifically, relates to a lithium-rich manganese-based transition metal oxide with dual-ion gradient doping, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries possess advantages such as long lifespan, high specific energy, high charge / discharge efficiency, and strong safety performance, leading to their widespread application in mobile phones, laptops, cameras, electric vehicles, and energy storage grids. According to the National New Energy Development Plan Outline, the rapid development of new energy electric vehicles requires lithium-ion power batteries with high energy and power densities. However, the high cost of cathode materials in lithium-ion power batteries has always been a key factor restricting the improvement of energy density. Therefore, the key to promoting new energy vehicles in my country lies in improving the energy density of power batteries and driving their rapid development. The key to improving the energy density of power batteries lies in developing new cathode materials with high specific capacity or modifying existing cathode materials.

[0003] Currently, the energy densities of popular cathode materials on the market, such as lithium cobalt oxide, ternary materials, and lithium iron phosphate, fail to adequately meet the market's demand for high-energy-density cathode materials, hindering the promotion of electric vehicles and the advancement of the national new energy development plan. Lithium-rich layered transition metal oxides, due to their high specific capacity (theoretical capacity exceeding 250 mAh g⁻¹), offer a solution. -1 The high operating voltage and low cost of lithium-rich layered transition metal oxides have made them a hot topic in new energy research and development both domestically and internationally. However, lithium-rich layered transition metal oxides still have some problems to be solved as positive electrode active materials. During the first charge and discharge cycle, the Li2MnO3 component is activated, causing irreversible structural rearrangement of the material particles, resulting in a loss of reversible capacity. During cycling, spinel structure transformation occurs, also causing a loss of capacity. Oxidation of lattice oxygen in the material releases oxygen, causing the material structure to collapse. At high potentials, the material is susceptible to corrosion by the electrolyte. The combined effect of these factors leads to serious problems such as decreased cycle performance and voltage decay in lithium-ion batteries using lithium-rich layered transition metal oxides, severely limiting their commercial application. Currently, researchers generally use strategies such as doping, coating, and crystal surface manipulation to improve the initial coulombic efficiency and cycle performance of lithium-rich materials and alleviate voltage decay. However, it is difficult to achieve sufficiently good results by using any of the above strategies alone. Summary of the Invention

[0004] To address the aforementioned shortcomings and deficiencies, the primary objective of this invention is to provide a lithium-rich manganese-based transition metal oxide with dual-ion gradient doping. This dual-ion gradient doped lithium-rich manganese-based transition metal oxide exhibits high initial coulombic efficiency, high capacity, and excellent cycling performance. When the voltage window is 2–4.8 V and the current density is 200 mA / g, the specific capacity can reach 235 mAh / g, and the capacity retention after 150 cycles is higher than 95.3%.

[0005] Another objective of this invention is to provide a method for preparing the aforementioned lithium-rich manganese-based layered transition metal oxide with dual ion gradient doping. This method involves doping the lithium-rich layered transition metal oxide by incorporating a metal element M to replace one or more of Mn and Ni at their respective positions.

[0006] Another object of the present invention is to provide the application of the above-mentioned dual-ion gradient doped lithium-rich manganese-based layered transition metal oxide.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A lithium-rich manganese-based transition metal oxide with dual ion gradient doping has the chemical formula xLi₂MnO₃·(1-x)LiTM. 1-y M y O2, TM = one or more of Mn, Ni, Co, Fe or Cr, M = one of Sn and Mg, Ba, Zn or Ce, 0.01≤x≤0.5, 0.01≤y≤0.3.

[0009] Furthermore, the lithium-rich manganese-based layered transition metal oxide is prepared by uniformly mixing a transition metal compound precursor with a metal compound solution, adjusting the pH of the mixture to 8-10 using an alkaline solution and continuously stirring, and then washing, filtering, and drying to obtain a powder. The powder is then heated to 500-800°C, naturally cooled to room temperature, and a lithium source is added and mixed uniformly. The mixture is then heated to 800-1000°C and naturally cooled to room temperature.

[0010] Preferably, the metal compound solution is a mixed aqueous solution of Na2SnO4 and one of MgSO4, BaSO4, ZnSO4, and CeSO4.

[0011] Preferably, the transition metal compound precursor is a transition metal carbonate or a transition metal hydroxide; the particle size of the transition metal compound precursor is 5–10 μm.

[0012] More preferably, the transition metal carbonate is one or more of MnCO3, NiCO3, CoCO3, FeCO3 or CrCO3; and the transition metal hydroxide is one or more of Mn(OH)2, Ni(OH)2, Co(OH)2, Fe(OH)2 or Cr(OH)2.

[0013] Preferably, the lithium source is one or more of lithium carbonate, lithium hydroxide, lithium acetate, lithium fluoride, lithium chloride, or lithium nitrate.

[0014] Preferably, the molar ratio of Li in the transition metal compound precursor and the lithium source is 1:(1-10); the molar ratio of the transition metal compound precursor and the metal compound solution is 100:(0.1-5).

[0015] Preferably, the alkaline solution is one or more of ammonia water, sodium carbonate aqueous solution, or sodium bicarbonate aqueous solution.

[0016] The method for preparing the lithium-rich manganese-based transition metal oxide with dual ion gradient doping includes the following specific steps:

[0017] S1. Mix the transition metal compound precursor with the metal compound solution evenly, and adjust the pH of the above mixture to 8-10 with an alkaline solution. Stir for 30-240 min, filter and wash, and dry at 100-150℃ to obtain the powder.

[0018] S2. Heat the powder to 500-800℃ and hold for 2-6 hours, then cool to room temperature, add lithium source and mix evenly, then heat the mixture to 800-1000℃ and hold for 10-16 hours to obtain a lithium-rich manganese-based transition metal oxide with dual ion gradient doping.

[0019] The application of the aforementioned lithium-rich manganese-based transition metal oxide with dual-ion gradient doping in the field of lithium-ion batteries or power batteries.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The lithium-rich manganese-based transition metal oxide doped with dual ion gradients of this invention exhibits slow capacity decay and excellent cycle performance, overcoming the shortcomings of current lithium-rich oxide cathode materials, which suffer from poor cycle performance and rapid capacity decay. When the voltage window is 2.0–4.8V and the current density is 200 mA / g, the specific capacity can reach 235 mAh / g, and the capacity retention rate after 150 cycles is higher than 95%, making it suitable as a cathode material for use in lithium-ion batteries or power batteries.

[0022] 2. The metal ion concentration of the lithium-rich manganese-based layered transition metal oxide doped with dual ion gradients of the present invention varies from the surface of the material particles to the center. This cathode material has advantages such as high specific capacity, simple synthesis process, easy control, and good reproducibility, and has great commercial prospects. Attached Figure Description

[0023] Figure 1 This is a SEM image of the lithium-rich manganese-based transition metal oxide powder with dual ion gradient doping in Example 1.

[0024] Figure 2 The X-ray diffraction patterns are those of the lithium-rich manganese-based transition metal oxide powders doped with dual ion gradients in Examples 1-3 and the lithium-manganese-based transition metal oxide in Comparative Example 1.

[0025] Figure 3 The lithium-rich manganese-based layered transition metal oxide powders of Examples 1-3 and the lithium-manganese-based layered transition metal oxide of Comparative Example 1 were used as positive electrodes at room temperature with a capacity of 20 mAg. -1 The initial charge-discharge curve at that time.

[0026] Figure 4 The lithium-rich manganese-based layered transition metal oxide powders of Examples 1-3 and the lithium-manganese-based layered transition metal oxide of Comparative Example 1 were used as positive electrodes at room temperature with a capacity of 200 mAg. -1 Capacity stability curve. Detailed Implementation

[0027] The present invention will be further described below with reference to specific embodiments, but these should not be construed as limiting the invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field.

[0028] Example 1

[0029] Weigh out 0.96g of the transition metal carbonate precursor (Mn). 0.75 Ni 0.25CO3 was dispersed in 50 mL of deionized water to obtain solution A; 0.0254 g of Na2SnO4 and 0.0111 g of MgSO4 were weighed and dissolved in 25 mL of deionized water respectively to obtain solutions B and C. Solutions B and C were slowly added dropwise to the stirred solution A, and the pH of the above mixed solution was adjusted to 8 with ammonia water. The mixture was then stirred for 30 min, washed, filtered, and dried in an oven at 120 °C to obtain powder D; powder D was heated to 500 °C and held for 3 h, and then 0.45 g of lithium carbonate was added. The mixture was heated at 800 °C for 12 h to obtain a magnesium-tin dual-ion gradient doped lithium-rich manganese base layer transition metal oxide, namely 0.5Li2MnO3·0.5LiMn 0.99 Ni 0.99 Mg 0.01 Sn 0.01 O2.

[0030] Figure 1 This is a SEM image of the target product powder in this embodiment. Figure 1 As can be seen, the synthesized powder particles are round and uniform, with an average sphere diameter of about 4 micrometers.

[0031] Example 2

[0032] Weigh out 0.96 g of the transition metal carbonate precursor (Mn). 0.75 Ni 0.25 CO3 was dispersed in 50 mL of deionized water to obtain solution A; 0.0254 g of Na2SnO4 and 0.0154 g of BaSO4 were weighed and dissolved in 25 mL of deionized water respectively to obtain solutions B and C. Solutions B and C were slowly added dropwise to the stirred solution A, and the pH of the above mixed solution was adjusted to 8.0 with ammonia water. The mixture was then stirred for 30 min, washed, filtered, and dried in an oven at 120 °C to obtain powder D; powder D was heated to 500 °C and held for 3 h, and then 0.45 g of lithium carbonate was added. The mixture was heated at 800 °C for 12 h to obtain a barium-tin dual-ion gradient doped lithium-rich manganese-based layered transition metal oxide, namely 0.5Li2MnO3·0.5LiMn 0.99 Ba 0.99 Sn 0.01 Mg 0.01 O2.

[0033] Example 3

[0034] Weigh out 0.96g of the transition metal carbonate precursor (Mn). 0.75 Ni 0.25CO3 was dispersed in 50 mL of deionized water to obtain solution A. 0.0254 g of Na2SnO4 and 0.0172 g of CeSO4 were weighed and dissolved in 25 mL of deionized water respectively to obtain solutions B and C. Solutions B and C were slowly added dropwise to the stirred solution A. The pH of the mixture was adjusted to 8 with ammonia, and then stirred for 30 min. After washing and filtration, the mixture was dried at 120 °C to obtain powder D. Powder D was heated to 600 °C and held for 2.5 h, then 0.45 g of lithium carbonate was added, and the mixture was heated at 1000 °C for 10 h to obtain a cerium-tin dual-ion gradient doped lithium-rich manganese-based layered transition metal oxide, namely 0.5Li2MnO3·0.5LiMnO4. 0.99 Ni 0.99 Ce 0.01 Sn 0.01 O2.

[0035] Comparative Example 1

[0036] Weigh out 0.96 g of the transition metal carbonate precursor (Mn). 0.75 Ni 0.25 CO3 was dispersed in 100 mL of deionized water to obtain solution A. The pH of solution A was adjusted to 8 with ammonia water, and then stirred for 30 min. After washing and filtration, the solution was dried in an oven at 120 °C to obtain powder D. Powder D was heated to 500 °C and kept at that temperature for 3 h. Then, 0.45 g of lithium carbonate was added, and the solution was heated at 800 °C for 12 h to obtain a lithium-rich manganese-based transition metal oxide, namely 0.5Li2MnO3·0.5LiMnNiO2.

[0037] Figure 2 The images show the X-ray diffraction patterns of the lithium-manganese-rich base-like transition metal oxide powders doped with dual ion gradients in Examples 1-3 and the lithium-manganese-based base-like transition metal oxide in Comparative Example 1. Figure 2 It can be seen that the powders obtained from the preparation of powders in Examples 1-3 are pure crystalline phases of lithium-rich oxides.

[0038] The test was conducted using coin cells. Electrodes were prepared by mixing the dual-ion gradient doped lithium-rich manganese-based transition metal oxide powder obtained in Examples 1-3 with conductive carbon black and polyvinylidene fluoride (PVDF) binder at a mass ratio of 8:1:1, using a lithium metal sheet as the counter electrode. (1 mol·L⁻¹) -1 The electrolyte was LiPF6 / EC+DMC+EMC (EC:DMC:EMC volume ratio 1:1:1), the separator was polypropylene, the battery testing system was Xinwei, the charge / discharge voltage window was 2.0–4.8V, and the charge / discharge current density was selected as 20mAg. -1 and 200mAg -1 . Figure 3The lithium-rich manganese-based layered transition metal oxide powders of Examples 1-3 and the lithium-manganese-based layered transition metal oxide of Comparative Example 1 were used as positive electrodes at room temperature with a capacity of 20 mAg. -1 The initial charge-discharge curve at that time. From Figure 3 It can be seen that after 100 charge-discharge cycles, the discharge specific capacity decay of the lithium-rich manganese-based transition metal oxides prepared in Examples 1-3, with dual-ion gradient doping, is very slow. At 20 mAg... -1 The charge / discharge current density at the current density is 221 mAh g, and the initial discharge specific capacity is 221 mAh g. -1 and 235mAhg -1 . Figure 4 The lithium-rich manganese-based layered transition metal oxide powders of Examples 1-3 and the lithium-manganese-based layered transition metal oxide of Comparative Example 1 were used as positive electrodes at room temperature with a capacity of 200 mAg. -1 Capacity stability curve. (From) Figure 4 It can be seen that after 150 charge-discharge cycles, the discharge specific capacity of the lithium-rich manganese-based transition metal oxide powder with dual ion gradient doping as the positive electrode decays slowly, retaining 95.3%. After 200 charge-discharge cycles, the discharge specific capacity of the lithium-rich manganese-based transition metal oxide powder with dual ion gradient doping as the positive electrode decays slowly, retaining 91.2%. This indicates that the material exhibits good electrochemical performance when used as the positive electrode of a lithium-ion battery.

[0039] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a lithium-rich manganese-based transition metal oxide with dual ion gradient doping, characterized in that, The specific steps include the following: S1. A transition metal compound precursor is mixed uniformly with a metal compound solution, and the pH of the mixed solution is adjusted to 8-10 with an alkaline solution. The mixture is then stirred for 30-240 min, filtered, washed, and dried at 100-150℃ to obtain a powder. The metal compound solution is a mixed aqueous solution of Na2SnO4 and one of MgSO4, BaSO4, ZnSO4, and CeSO4. The molar ratio of the transition metal compound precursor to the metal compound solution is 100:(0.1-5). The alkaline solution is one or more of ammonia, sodium carbonate aqueous solution, or sodium bicarbonate aqueous solution. The transition metal compound precursor is a transition metal carbonate or a transition metal hydroxide. The particle size of the transition metal compound precursor is 5-10 μm. S2. The powder is heated to 500-800℃ and held for 2-6 hours, then cooled to room temperature. A lithium source is added and mixed evenly. The mixture is then heated to 800-1000℃ and held for 10-16 hours to obtain a lithium-rich manganese-based transition metal oxide with dual ion gradient doping. The chemical formula of this transition metal oxide is xLi2MnO3·(1-x)LiTM. 1-y M y O2, TM = one or more of Mn, Ni, Co, Fe or Cr, M = one of Sn and Mg, Ba, Zn or Ce, 0.01≤x≤0.5, 0.01≤y≤0.3; the molar ratio of Li in the transition metal compound precursor and the lithium source is 1:(1~10); when the voltage window is 2.0~4.8V and the current density is 200mA / g, the capacity retention rate after 150 cycles is higher than 95%.

2. The method for preparing the lithium-rich manganese-based transition metal oxide with dual ion gradient doping according to claim 1, characterized in that, The transition metal carbonate mentioned in step S1 is one or more of MnCO3, NiCO3, CoCO3, FeCO3 or CrCO3; the transition metal hydroxide is one or more of Mn(OH)2, Ni(OH)2, Co(OH)2, Fe(OH)2 or Cr(OH)2.

3. The method for preparing lithium-rich manganese-based layered transition metal oxides with dual ion gradient doping according to claim 1, characterized in that, The lithium source in step S2 is one or more of lithium carbonate, lithium hydroxide, lithium acetate, lithium fluoride, lithium chloride, or lithium nitrate.

4. A lithium-rich manganese-based transition metal oxide with dual ion gradient doping, characterized in that, The layered transition metal oxide is prepared by the method described in any one of claims 1-3, and its chemical formula is xLi₂MnO₃·(1-x)LiTM. 1- y M y O2, TM = one or more of Mn, Ni, Co, Fe or Cr, M = one of Sn and Mg, Ba, Zn or Ce, 0.01≤x≤0.5, 0.01≤y≤0.

3.

5. The lithium-rich manganese-based transition metal oxide with dual ion gradient doping according to claim 4, characterized in that, The layered transition metal oxide is 0.5 Li₂MnO₃·0.5 LiMn 0.99 Ni 0.99 Mg 0.01 Sn 0.01 O2, 0.5Li2MnO3·0.5LiMn 0.99 Ni 0.99 Ce 0.01 Sn 0.01 O2.

6. The application of the lithium-rich manganese-based transition metal oxide with dual ion gradient doping as described in claim 4 or 5 in the field of lithium-ion batteries or power batteries.

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