Preparation method and application of high-dispersion lithium-rich manganese-based positive electrode material

Abstract

The application belongs to the technical field of electrochemical materials, and particularly relates to a preparation method of a high-dispersion lithium-rich manganese-based positive electrode material and application thereof. A transition metal salt solution, a precipitant and a complexing agent are introduced into a reaction container to perform a co-precipitation reaction and then crystallization, so as to obtain a lithium-rich manganese-based positive electrode material precursor; the transition metal salt comprises manganese salt, nickel salt and cobalt salt; the precursor and a lithium source are mixed in a solvent according to a stoichiometric ratio, and the mixed slurry is spray-dried to remove the solvent; the mixture obtained by spray-drying is mixed with a fluxing agent, and then sintered in an air atmosphere, and the sintered product is washed and dried to obtain the lithium-rich manganese-based positive electrode material. The lithium-rich manganese-based positive electrode material prepared by the application has good stability, and the capacity retention rate is 94.1% after 100 cycles at a 1C rate current in a wide voltage range of 2.0-4.8 V.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical materials technology, specifically relating to a method for preparing a highly dispersed lithium-rich manganese-based cathode material and its application. Background Technology

[0002] Lithium-ion batteries have become the most widely used battery system in the new energy vehicle industry due to their advantages of high specific capacity, high operating voltage, and long cycle life. In lithium-ion batteries, the cathode material not only accounts for the majority of the total cost of the battery pack, but its capacity and lifespan are also crucial parameters limiting the performance of lithium-ion batteries. Currently, commercially available cathode materials mainly include ternary (NCM, NCA) systems, lithium iron phosphate (LFP) systems, and lithium manganese oxide systems. Compared to these, lithium-rich manganese-based cathode materials have a specific capacity exceeding 300 mAh / g, which can significantly improve the energy density of lithium-ion batteries. Lithium-rich manganese-based cathodes, as layered metal oxide cathodes containing small amounts of rare and expensive metal elements such as nickel and cobalt, have become one of the important development directions for next-generation cathode materials. Molten salt technology utilizes a liquid reaction medium to achieve atomic-level mixing of reactants, allowing crystals to uniformly nucleate and grow from the flux at relatively low temperatures, thereby reducing lithium loss during the synthesis process and improving sample uniformity and quality.

[0003] Patent CN116971021A discloses a hydrothermal-molten salt-assisted method for preparing doped single-crystal lithium-rich manganese-based cathode materials. The method involves weighing a carbonate precipitant in an amount 1-2 times the total molar amount of manganese, nickel, and cobalt salts and dissolving it thoroughly in water to obtain solution B. Solution B is then poured into solution A and stirred thoroughly to obtain a suspension containing the precipitate. The suspension is transferred to a hydrothermal reactor and subjected to hydrothermal treatment at a preset temperature for a predetermined time. After washing, a precursor is obtained. The precursor, lithium salt, flux, and dopant are mixed, ground, and sintered according to a preset ratio. The resulting sample is washed, filtered, and dried to obtain the doped single-crystal lithium-rich manganese-based cathode material. However, this method requires elemental doping to obtain lithium-rich manganese-based cathode materials with good capacity and cycle performance, and it requires a high-temperature hydrothermal reaction, resulting in high energy consumption. Therefore, it is necessary to provide an improved method for preparing lithium-rich manganese-based cathode materials to solve the above problems. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a highly dispersed lithium-rich manganese-based cathode material and its application. By optimizing the preparation process, a lithium-rich manganese-based cathode material with good dispersion and superior electrochemical performance and cycle stability is obtained.

[0005] To achieve the above objectives, the present invention provides a method for preparing a highly dispersed lithium-rich manganese-based cathode material, comprising the following steps:

[0006] S1. A transition metal salt solution, a precipitant, and a complexing agent are introduced into a reaction vessel to carry out a co-precipitation reaction, followed by crystallization to obtain a lithium-rich manganese-based cathode material precursor; the transition metal salt includes manganese salt, nickel salt, and cobalt salt.

[0007] S2. The precursor and lithium source are ball-milled and mixed in a solvent according to a stoichiometric ratio, and the mixed slurry is spray-dried to remove the solvent.

[0008] S3. The mixture obtained by spray drying is mixed evenly with a flux and then sintered in an air atmosphere. The sintered product is washed and dried to obtain a lithium-rich manganese-based cathode material.

[0009] Furthermore, the chemical formula of the lithium-rich manganese-based cathode material is Li 1.2 Mn x Ni y Co (0.8-x-y) O2, where 0.5 ≤ x ≤ 0.6, 0.1 ≤ y ≤ 0.2. Each raw material satisfies the condition that the product Li... 1.2 Mn x Ni y Co (0.8-x-y) The stoichiometric ratio of O2.

[0010] Furthermore, the pH value of the coprecipitation reaction is 7.5-8.5, and the reaction is continuously stirred at 40-60°C for 24-48 hours; in step S2, the inlet temperature of the spray dryer is 135-145°C.

[0011] Furthermore, in step S2, the lithium source is at least one of lithium carbonate, lithium hydroxide, and lithium oxide;

[0012] And / or, the solvent is at least one of water, ethanol, methanol, and isopropanol, and the solid content in the solvent is 10-20 wt%; the ball milling time is 5-12 h, preferably 8-10 h.

[0013] Furthermore, in step S3, the sintering includes: heating to 500℃-600℃ at a rate of 2-10℃ / min and holding for 4-6 hours; then heating to 800℃-900℃ at a rate of 2-10℃ / min and holding for 10-14 hours; preferably, finally cooling to 250℃-350℃ at a rate of 2-10℃ / min and holding for 2-4 hours, followed by natural cooling.

[0014] Furthermore, in step S1, the nickel salt is at least one of nickel sulfate and nickel acetate; the manganese salt is at least one of manganese sulfate and manganese acetate; the cobalt salt is at least one of cobalt sulfate and cobalt acetate, and the total concentration of metal ions is 1-3 mol / L.

[0015] Furthermore, in step S1, the precipitant is at least one of sodium carbonate, potassium carbonate, sodium hydroxide, and potassium hydroxide, with a concentration of 1.5–3 mol / L; the complexing agent is at least one of ammonium carbonate, ammonium sulfate, and ammonium bicarbonate, with a concentration of 0.5–2 mol / L.

[0016] Furthermore, in step S3, the flux is at least one of sodium chloride, potassium chloride, lithium chloride, and lithium nitrate, and the addition ratio is 3 to 8 times the mass of the spray-dried product.

[0017] The present invention also provides a highly dispersed lithium-rich manganese-based cathode material, which is prepared by any of the preparation methods described above.

[0018] This invention also provides an application of a highly dispersed lithium-rich manganese-based cathode material as a cathode for lithium-ion batteries.

[0019] In summary, compared with the prior art, the above-described technical solutions conceived by this invention mainly possess the following technical advantages:

[0020] 1. This invention provides a method for preparing a highly dispersed lithium-rich manganese-based cathode material. The raw material mixture with ultrafine particle size and good dispersibility is obtained by spray drying, so that the particle size of the final product is mainly distributed in 300-500 nm, and thus obtains superior electrochemical performance.

[0021] 2. This invention uses a suitable flux to provide a molten salt environment, reducing the energy required for the lithium source to overcome during calcination. The flux is completely removed in subsequent processing, without adversely affecting crystallinity and electrochemical performance. This preparation method uses an environmentally friendly flux that is easy to recycle, while also having a lower sintering temperature and lower cost, resulting in good economic benefits and facilitating industrial application. It also shows great promise for use in lithium-ion batteries.

[0022] 3. This invention requires only a relatively low temperature to prepare the precursor, resulting in mild reaction conditions, energy savings, and improved precursor homogenization. By optimizing the concentration of wet ball milling and the parameters of spray drying, the resulting mixture has a small and uniform particle size, which is more conducive to crystal formation during calcination and improves its electrochemical performance. Segmented heating and cooling further enhances crystallinity and improves the performance of lithium-rich manganese-based cathode materials.

[0023] 4. The preparation method of the present invention is simple and efficient. The lithium-rich manganese-based cathode material exhibits good stability and excellent capacity. It can provide a reversible capacity of 314 mAh / g at a current of 0.1C within a wide voltage range of 2.0 to 4.8V. After 100 cycles at a current of 1C, the capacity retention rate is 93.65%, and after 300 cycles, the capacity retention rate is 85.14%. Attached Figure Description

[0024] Figure 1 The images shown are scanning electron microscope images of the lithium-rich manganese-based material prepared in Example 1 of this invention, wherein (a) has a scale of 2 μm, (b) has a scale of 1 μm, and (c) has a scale of 500 nm.

[0025] Figure 2 The images shown are scanning electron microscope images of the lithium-rich manganese-based material prepared in Comparative Example 1 of the present invention, wherein (a) has a scale of 2 μm, (b) has a scale of 1 μm, and (c) has a scale of 500 nm.

[0026] Figure 3 The X-ray diffraction pattern of the lithium-rich manganese-based material prepared in Example 1 of this invention;

[0027] Figure 4 The graph shows the test results of the lithium-rich manganese-based materials prepared in Example 1 and Comparative Example 1 of this invention after 100 cycles at a current of 1C within a voltage range of 2-4.8V.

[0028] Figure 5 This is a test image of the lithium-rich manganese-based material prepared in Example 1 of the present invention, after 300 cycles at a 1C rate within a voltage range of 2-4.8V.

[0029] Figure 6 This is a voltage-capacity diagram of the first and second charge / discharge cycles of the lithium-rich manganese-based material prepared in Example 1 of this invention at a 0.1C rate within a voltage range of 2-4.8V. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0031] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0032] Example 1

[0033] Manganese sulfate, nickel sulfate, and cobalt sulfate were prepared into a solution with a total transition metal ion concentration of 2 mol / L according to the stoichiometric ratio of Mn:Ni:Co = 0.54:0.13:0.13. This solution was then added to a 1 mol / L ammonium bicarbonate complexing agent solution, and the mixture was heated to 55°C. The pH was adjusted to 8 by dropwise addition of a 2 mol / L sodium carbonate solution. The reaction vessel was kept sealed, and the mixture was continuously stirred and heated for 24 hours. After the reaction was completed, the precipitate was collected, washed with water several times, and dried.

[0034] The dried precursor was dispersed in ethanol with excess lithium carbonate (5 mol% excess) and ball-milled for 10 hours, with the solid content controlled at 20 wt%. The resulting slurry was spray-dried under nitrogen protection (inlet temperature of 140℃), and then mechanically mixed with 5 times the mass of potassium chloride. The mixture was then calcined in an air atmosphere in a muffle furnace. The furnace was first heated to 600℃ at a rate of 2℃ / min for 5 hours, then heated to 850℃ at a rate of 2℃ / min for 10 hours, and then cooled to 300℃ at a rate of 2℃ / min for 3 hours, followed by natural cooling. The calcined product was repeatedly washed with water and dried to obtain lithium-rich manganese-based cathode material Li. 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2.

[0035] like Figure 1 As shown, the lithium-rich manganese-based cathode material has uniform particles and good dispersion. Figure 3 This indicates that it has a good crystal form. From Figures 4-6 It can be seen that within a wide voltage range of 2.0 to 4.8V, the capacity retention rate is 93.65% after 100 cycles at a current of 1C, and the initial discharge specific capacity is 232.2mAh / g.

[0036] Example 2

[0037] Manganese sulfate, nickel sulfate, and cobalt sulfate were prepared into a solution with a total transition metal ion concentration of 2 mol / L according to the stoichiometric ratio of Mn:Ni:Co = 0.55:0.15:0.1. This solution was then added to a 1 mol / L ammonium carbonate complexing agent solution, and the mixture was heated to 55°C. The pH was adjusted to 8 by dropwise addition of a 2 mol / L sodium carbonate solution. The reaction vessel was kept sealed, and the mixture was continuously stirred and heated for 24 hours. After the reaction was completed, the precipitate was collected, washed with water several times, and dried.

[0038] The dried precursor was dispersed in ethanol with excess lithium carbonate (5 mol% excess) and ball-milled for 10 hours, with the solid content controlled at 20 wt%. The resulting slurry was spray-dried under nitrogen protection (inlet temperature of 140℃), and then mixed mechanically with potassium chloride at 5 times its mass. The mixture was then calcined in an air atmosphere in a muffle furnace. The furnace was first heated to 600℃ at a rate of 2℃ / min for 5 hours, then heated to 850℃ at a rate of 2℃ / min for 10 hours, followed by natural cooling. The calcined product was repeatedly washed with water and dried to obtain the lithium-rich manganese-based cathode material Li. 1.2 Mn 0.55 Ni 0.15 Co 0.1 O2.

[0039] Example 3

[0040] Manganese sulfate, nickel sulfate, and cobalt sulfate were prepared into a solution with a total transition metal ion concentration of 2 mol / L according to the stoichiometric ratio of Mn:Ni:Co = 0.54:0.13:0.13. This solution was then added to a 1 mol / L ammonium bicarbonate complexing agent solution, and the mixture was heated to 55°C. The pH was adjusted to 8 by dropwise addition of a 2 mol / L sodium carbonate solution. The reaction vessel was kept sealed, and the mixture was continuously stirred and heated for 24 hours. After the reaction was completed, the precipitate was collected, washed with water several times, and dried.

[0041] The dried precursor was dispersed in ultrapure water and ball-milled with excess lithium carbonate (5 mol% excess) for 10 hours, with the solid content controlled at 15 wt%. The resulting slurry was spray-dried (inlet temperature of 180℃), and then mechanically mixed with 5 times the mass of potassium chloride. The mixture was then calcined in an air atmosphere in a muffle furnace. The furnace was first heated to 600℃ at a rate of 2℃ / min for 5 hours, then heated to 850℃ at a rate of 2℃ / min for 10 hours, and then cooled to 300℃ at a rate of 2℃ / min for 3 hours, followed by natural cooling. The calcined product was repeatedly washed with water and dried to obtain lithium-rich manganese-based cathode material Li. 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2.

[0042] Comparative Example 1

[0043] Manganese sulfate, nickel sulfate, and cobalt sulfate were prepared into a solution with a total transition metal ion concentration of 2 mol / L according to the stoichiometric ratio of Mn:Ni:Co = 0.54:0.13:0.13. This solution was then added to a 1 mol / L ammonium bicarbonate complexing agent solution, and the mixture was heated to 55°C. The pH was adjusted to 8 by dropwise addition of a 2 mol / L sodium carbonate solution. The reaction vessel was kept sealed, and the mixture was continuously stirred and heated for 24 hours. After the reaction was completed, the precipitate was collected, washed with water several times, and dried.

[0044] The dried precursor was dispersed with lithium carbonate (5 mol% excess) in ethanol and ball-milled for 10 hours, with the solid content controlled at 20 wt%. The resulting slurry was dried in a forced-air drying oven, and then mechanically mixed with potassium chloride at 5 times its mass. The mixture was then calcined in a muffle furnace under air atmosphere. The furnace was first heated to 600℃ at a heating rate of 2℃ / min for 5 hours, then heated to 850℃ at a heating rate of 2℃ / min for 10 hours, and then cooled to 300℃ at a rate of 2℃ / min for 3 hours, followed by natural cooling. The calcined product was repeatedly washed with water and dried to obtain lithium-rich manganese-based cathode material Li. 1.2 Mn 0.54 Ni0.13 Co 0.13 O2.

[0045] Table 1 Performance test results of Example 1 and Comparative Example 1

[0046] 1C discharge specific capacity (mAh / g) Capacity retention after 100 cycles (%) Example 1 232.2 93.65 Comparative Example 1 224.9 56.11

[0047] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a highly dispersed lithium-rich manganese-based cathode material, characterized in that, Includes the following steps: S1. A transition metal salt solution, a precipitant, and a complexing agent are introduced into a reaction vessel to carry out a co-precipitation reaction, thereby obtaining a lithium-rich manganese-based cathode material precursor; the transition metal salt includes manganese salt, nickel salt, and cobalt salt; the precipitant is at least one of sodium carbonate, potassium carbonate, sodium hydroxide, and potassium hydroxide; the complexing agent is at least one of ammonium carbonate, ammonium sulfate, and ammonium bicarbonate; the temperature of the co-precipitation reaction is 40~60℃; S2. The precursor and lithium source are ball-milled and mixed in a solvent, and the mixed slurry is spray-dried to remove the solvent; the inlet temperature of the spray dryer is 135-145℃; the solid content of the mixed slurry is 10-20 wt%. S3. The mixture obtained by spray drying is mixed evenly with a flux and then sintered in an air atmosphere. The sintered product is washed and dried to obtain a lithium-rich manganese-based cathode material. The flux is at least one of sodium chloride, potassium chloride, lithium chloride, and lithium nitrate. The sintering process includes: heating to 500℃~600℃ at a rate of 2~10℃ / min and holding for 4~6 hours; then heating to 800℃~900℃ at a rate of 2~10℃ / min and holding for 10~14 hours; finally cooling to 250℃-350℃ at a rate of 2~10℃ / min and holding for 2~4 hours, followed by natural cooling.

2. The preparation method according to claim 1, characterized in that, The chemical formula of the lithium-rich manganese-based cathode material is Li 1.2 Mn x Ni y Co (0.8-x-y) O2, where 0.5≤x≤0.6, 0.1≤y≤0.2, and when x=0.6, 0.1≤y<0.2, and when y=0.2, 0.5≤x<0.

6.

3. The preparation method according to claim 1, characterized in that, In step S1, the pH value of the coprecipitation reaction is 7.5~8.5, and the reaction is continuously stirred for 24~48 hours.

4. The preparation method according to claim 1, characterized in that, In step S2, the lithium source is at least one of lithium carbonate, lithium hydroxide, and lithium oxide; And / or, the solvent is at least one of water, ethanol, methanol, and isopropanol; the ball milling time is 5-12 hours.

5. The preparation method according to claim 1, characterized in that, The ball milling time is 8-10 hours.

6. The preparation method according to claim 1, characterized in that, In step S1, the nickel salt is at least one of nickel sulfate and nickel acetate; the manganese salt is at least one of manganese sulfate and manganese acetate; and the cobalt salt is at least one of cobalt sulfate and cobalt acetate.

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