Modified lithium-rich manganese-based positive electrode material and preparation method thereof

Abstract

The invention discloses a modified lithium-rich manganese-based positive electrode material and a preparation method thereof, and relates to the technical field of lithium ion battery positive electrode materials. On the basis of a traditional metal modified lithium-rich manganese-based material, boride and MBene are further introduced for synergistic modification, so that the conductivity can be remarkably improved, the specific capacity and rate capability of the battery can be improved, the spinel structure of the lithium-rich manganese-based positive electrode material can be stabilized, the cycle performance of the material can be improved, and the service life of the battery can be prolonged.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery cathode materials technology, and in particular to a modified lithium-rich manganese-based cathode material and its preparation method. Background Technology

[0002] Lithium-ion batteries boast advantages such as high voltage, high capacity, and lightweight design, leading to their rapid development in recent years. However, commonly used lithium-ion battery cathode materials, such as LiFePO4, LiMnO2, and ternary materials, suffer from low battery capacity utilization, limiting the development of lithium-ion batteries. Lithium-rich manganese-based cathode materials (chemical formula xLi2MnO3·(1-x)LiMO2, where M represents Ni, Co, or Mn) have become a very popular cathode material in recent years, achieving a specific capacity of up to 300mAh. -1 The energy density of lithium-rich manganese-based cathode materials is significantly higher than that of other materials, and they offer advantages such as lower cost and superior safety compared to common lithium cobalt oxide and ternary materials. Therefore, lithium-rich manganese-based cathode materials are highly suitable as cathode materials for novel high-energy-density power batteries and are currently considered one of the most promising cathode materials. However, current lithium-rich manganese-based cathode materials still suffer from drawbacks such as short lifespan and unresolved cycle stability issues. Further research is necessary to improve the energy density and extend the lifespan of lithium-rich manganese-based materials. Summary of the Invention

[0003] Based on the technical problems existing in the background technology, this invention proposes a modified lithium-rich manganese-based cathode material and its preparation method.

[0004] The present invention proposes a method for preparing a modified lithium-rich manganese-based cathode material, comprising: adding a lithium-rich manganese-based material, an MBene material, a boride and a metal hydroxide to a hydrazine hydrate solution under a protective atmosphere and mixing them evenly, then heating to carry out a reduction reaction, separating the solid and liquid after the reaction is completed, and washing and drying the obtained solid to obtain the modified lithium-rich manganese-based cathode material.

[0005] Preferably, the molar ratio of the lithium-rich manganese-based material, MBene material, boride, and metal hydroxide is 1:0.005–0.05:0.005–0.08:0.005–0.06. By controlling the ratio of the lithium-rich manganese-based material, MBene material, boride, and metal hydroxide, the synergistic effect among the components in the boride / MBene / metal composite coating layer can be better utilized, further improving the material's cycle performance, rate performance, and energy density.

[0006] Preferably, the preparation method of the MBene material includes: mixing the MAB phase material with a 5%–30% (w / w) HF solution, stirring and reacting at 60–80°C for 20–30 h, then centrifuging, washing and drying the resulting precipitate to obtain the MBene material. The MAB phase material refers to a ternary layered transition metal boride, a material similar to the MAX phase (ternary layered transition metal nitride / carbide / carbonitride), except that the X element (carbon or nitrogen) is replaced by the B element (boron). The MAB phase has an orthorhombic structure, with an Al layer between the M and B layers. The MBene material is obtained by chemically etching away the Al layer. The MBene material prepared by the above method has more active sites and better dispersibility, which is beneficial for further improving the material's cycling performance, rate performance, and energy density.

[0007] In the preparation of MBene materials, the specific washing steps can be as follows: wash the obtained precipitate with deionized water until the pH is 6-8; the drying method can be a conventional method, such as vacuum drying.

[0008] Preferably, the MAB phase material is selected from at least one of Mn2AlB2, CrAlB4, Cr4AlB6, WAlB, and Fe2AlB2. By selecting the above-mentioned MAB phase materials as raw materials for preparing MBene materials, it is both economical and readily available, and the prepared MBene materials can have excellent layered structure and conductivity.

[0009] Preferably, the boride is selected from at least one of TiB2, ZrB2, FeB, and AlB2. By selecting the above-mentioned borides, both good economic efficiency and availability are achieved, and the stability of lithium-rich manganese-based materials can be significantly improved.

[0010] Preferably, the metal hydroxide is at least one of the hydroxides of Co, Rh, Fe, Ru, and Ag. By selecting the above-mentioned metal hydroxides, both good economic efficiency and availability are achieved, and uniform metal nanoparticles can be formed under the reduction of hydrazine hydrate, thereby improving the stability and conductivity of lithium-rich manganese-based materials.

[0011] Preferably, the chemical formula of the lithium-rich manganese-based material is xLi2MnO3·(1-x)LiMO2, where M is at least one of Ni, Co, and Mn, and 0 < x < 0.5.

[0012] In this invention, the preparation method of lithium-rich manganese-based materials is not particularly limited; conventional methods are acceptable, such as:

[0013] Soluble manganese salt and soluble salt of element M were weighed according to stoichiometric ratio and dissolved in deionized water to obtain a mixed salt solution. The mixed salt solution was then mixed with an aqueous carbonate solution and ammonia solution for a co-precipitation reaction. The pH of the solution was controlled at 11.5–12.8 during the reaction. After the reaction, the solution was filtered, and the resulting filter cake was washed and dried to obtain a precursor material. The precursor material was then mixed with a lithium compound and sintered to obtain a lithium-rich manganese-based material. The total concentration of metal ions in the mixed salt solution was 1–2 mol / L. The concentration of the carbonate aqueous solution is 1–3 mol / L; the concentration of the ammonia solution is 0.1–5 mol / L; the ratio of the total molar amount of metal elements in the precursor material to the molar amount of lithium elements in the lithium compound is 1:1.2–1.35; the sintering temperature is 700–900℃, the time is 15–20 h, and the sintering atmosphere is an oxygen atmosphere; the lithium compound is selected from at least one of lithium carbonate, lithium hydroxide, and lithium sulfate; the carbonate is selected from at least one of sodium carbonate, ammonium carbonate, lithium carbonate, and potassium carbonate.

[0014] Preferably, the total mass ratio of the lithium-rich manganese-based material, MBene material, borides, and metal hydroxides to the mass ratio of the hydrazine hydrate solution is 1:10 to 150.

[0015] Preferably, the hydrazine hydrate solution has a mass fraction of 10% to 50%.

[0016] Preferably, the temperature for heating the reduction reaction is 55–85°C, and the time is 0.5–4 hours.

[0017] By controlling the concentration and amount of hydrazine hydrate solution, as well as the temperature and time of the reduction reaction, the reduction reaction can be carried out fully and uniformly, thereby improving the uniformity of the boride / MBene / metal composite coating layer formed on the surface of lithium-rich manganese-based materials. This is beneficial for further improving the material's cycle performance, rate performance, and energy density.

[0018] In this invention, a protective atmosphere refers to an atmosphere formed by a protective gas. The protective gas may be, for example, nitrogen, helium, or argon.

[0019] A modified lithium-rich manganese-based cathode material is prepared by the method described above.

[0020] The beneficial effects of this invention are as follows:

[0021] This invention involves adding lithium-rich manganese-based materials, MBene materials, borides, and metal hydroxides to a hydrazine hydrate solution. The hydrazine hydrate reduces the metal hydroxides to form elemental metal nanoparticles, which then adhere to the lithium-rich manganese-based material, forming a boride / MBene / metal composite coating layer. Some of the metal elements and boron from the borides are doped into the lithium-rich manganese-based material, stabilizing the spinel phase on the surface, stabilizing the material interface structure, and maintaining the ordered structure of the material. This increases redox reversibility and improves cycle performance. The elemental metals and MBene increase the material's electronic conductivity, improving rate performance. Furthermore, MBene possesses... The two-dimensional layered structure of metal vacancies, in synergy with metal, can effectively conduct lithium ions, increase lithium ion diffusion paths, and improve the energy density of the material. The presence of elemental metal nanoparticles can also alleviate interfacial stress, further improving the cycle stability of the material. Boride coating can also improve the air stability of the material and react with harmful HF generated in the electrolyte to form BF compounds, inhibiting the occurrence of harmful side reactions and thus extending the battery's lifespan. In summary, this invention, through the synergistic effect of the boride / MBene / metal composite coating layer formed on the surface of lithium-rich manganese-based materials, can effectively stabilize the material structure and significantly improve its cycle performance, rate performance, and energy density. The modified lithium-rich manganese-based cathode material prepared by this invention can significantly improve conductivity, increase the battery's specific capacity and rate performance, stabilize the spinel structure of lithium-rich manganese-based cathode materials, improve the material's cycle performance, and extend the battery's lifespan. Attached Figure Description

[0022] Figure 1 This is a SEM image of the modified lithium-rich manganese-based cathode material prepared in Example 1.

[0023] Figure 2 SEM image of the modified lithium-rich manganese-based cathode material prepared in Comparative Example 1.

[0024] Figure 3 SEM image of the modified lithium-rich manganese-based cathode material prepared in Comparative Example 2.

[0025] Figure 4 The results are the rate performance test results of the modified lithium-rich manganese-based cathode materials prepared in Example 1 and Comparative Examples 1-2.

[0026] Figure 5 The results are the cycle performance test results of the modified lithium-rich manganese-based cathode materials prepared in Example 1 and Comparative Examples 1-2. Detailed Implementation

[0027] The technical solution of the present invention will now be described in detail through specific embodiments.

[0028] In the following examples and comparative examples, the MAB phase material is CrAlB4MAB phase material.

[0029] Example 1

[0030] Preparation of lithium-rich manganese-based materials:

[0031] According to Li 1.2 Mn 0.56 Ni 0.12 Co 0.12 The stoichiometric ratio of O2 is determined by weighing manganese nitrate, cobalt nitrate, and nickel nitrate and dissolving them in deionized water to obtain a manganese-nickel-cobalt salt solution, wherein the total concentration of manganese ions, nickel ions, and cobalt ions is 1.6 mol / L.

[0032] A coprecipitation reaction was carried out by mixing a manganese nickel cobalt salt solution with a sodium carbonate aqueous solution of 2 mol / L and an ammonia solution of 1 mol / L. The pH of the solution was controlled at 11.5-12.8 during the reaction. After the reaction was completed, the solution was filtered, and the resulting filter cake was washed and dried to obtain the precursor material.

[0033] The precursor material was mixed with lithium hydroxide and sintered at 800°C for 18 hours in an oxygen atmosphere to obtain a lithium-rich manganese-based material. The ratio of the total molar amount of manganese, nickel and cobalt in the precursor material to the molar amount of lithium in the lithium hydroxide was 1:1.05.

[0034] Preparation of MBene materials:

[0035] 1 g of MAB phase material was mixed with 20 mL of 20% wt HF solution and stirred at 65 °C for 24 h. The mixture was then centrifuged, and the resulting precipitate was washed with deionized water until the pH was 6-8. The precipitate was then vacuum dried for 24 h to obtain MBene material.

[0036] Preparation of modified lithium-rich manganese-based cathode materials:

[0037] Under a nitrogen atmosphere, lithium-rich manganese-based material, MBene material, aluminum boride, and cobalt hydroxide were added to a 20% (w / w) aqueous solution of hydrazine hydrate and mixed thoroughly. The mixture was then heated in a water bath at 65°C for 3 hours. After filtration, the resulting solid was washed with deionized water and dried at 100°C for 5 hours to obtain the modified lithium-rich manganese-based cathode material. The molar ratio of lithium-rich manganese-based material, MBene material, aluminum boride, and cobalt hydroxide was 1:0.01:0.02:0.02, and the ratio of the total mass of lithium-rich manganese-based material, MBene material, aluminum boride, and cobalt hydroxide to the mass of the hydrazine hydrate aqueous solution was 1:40.

[0038] Example 2

[0039] Preparation of MBene materials:

[0040] 1 g of MAB phase material was mixed with 20 mL of 5% wt HF solution and stirred at 60 °C for 30 h. The mixture was then centrifuged, and the resulting precipitate was washed with deionized water until the pH was 6-8. The precipitate was then vacuum dried for 24 h to obtain MBene material.

[0041] Preparation of modified lithium-rich manganese-based cathode materials:

[0042] Under a nitrogen atmosphere, lithium-rich manganese-based material, MBene material, titanium boride, and iron hydroxide were added to a 10% (w / w) aqueous solution of hydrazine hydrate and mixed thoroughly. The mixture was then heated in a water bath at 55°C for 4 hours. After filtration, the resulting solid was washed with deionized water and dried at 100°C for 5 hours to obtain the modified lithium-rich manganese-based cathode material. The molar ratio of lithium-rich manganese-based material, MBene material, titanium boride, and iron hydroxide was 1:0.005:0.005:0.005, and the ratio of the total mass of lithium-rich manganese-based material, MBene material, titanium boride, and iron hydroxide to the mass of the hydrazine hydrate aqueous solution was 1:10.

[0043] In Example 2, the preparation method of the lithium-rich manganese-based material is the same as in Example 1.

[0044] Example 3

[0045] Preparation of MBene materials:

[0046] 1 g of MAB phase material was mixed with 20 mL of 30% wt HF solution and stirred at 80 °C for 20 h. The mixture was then centrifuged, and the resulting precipitate was washed with deionized water until the pH was 6-8. The precipitate was then vacuum dried for 24 h to obtain MBene material.

[0047] Preparation of modified lithium-rich manganese-based cathode materials:

[0048] Under a nitrogen atmosphere, lithium-rich manganese-based material, MBene material, iron boride, and silver hydroxide were added to a 50% (w / w) aqueous solution of hydrazine hydrate and mixed thoroughly. The mixture was then heated in a water bath at 85°C for 0.5 h. After filtration, the resulting solid was washed with deionized water and dried at 100°C for 5 h to obtain the modified lithium-rich manganese-based cathode material. The molar ratio of lithium-rich manganese-based material, MBene material, iron boride, and silver hydroxide was 1:0.05:0.08:0.06, and the ratio of the total mass of lithium-rich manganese-based material, MBene material, iron boride, and silver hydroxide to the mass of the aqueous solution of hydrazine hydrate was 1:150.

[0049] In Example 3, the preparation method of the lithium-rich manganese-based material is the same as in Example 1.

[0050] Comparative Example 1

[0051] Preparation of modified lithium-rich manganese-based cathode materials:

[0052] Under a nitrogen atmosphere, lithium-rich manganese-based material, aluminum boride, and cobalt hydroxide were added to a 20% (w / w) aqueous solution of hydrazine hydrate and mixed thoroughly. The mixture was then heated in a water bath at 65°C for 3 hours. After filtration, the resulting solid was washed with deionized water and dried at 100°C for 5 hours to obtain the modified lithium-rich manganese-based cathode material. The molar ratio of lithium-rich manganese-based material, aluminum boride, and cobalt hydroxide was 1:0.02:0.02, and the mass ratio of the total mass of lithium-rich manganese-based material, aluminum boride, and cobalt hydroxide to the mass of the hydrazine hydrate aqueous solution was 1:40.

[0053] In Comparative Example 1, the preparation method of the lithium-rich manganese-based material is the same as in Example 1.

[0054] Comparative Example 2

[0055] Preparation of modified lithium-rich manganese-based cathode materials:

[0056] Under a nitrogen atmosphere, lithium-rich manganese-based material, MBene material, and cobalt hydroxide were added to a 20% (w / w) aqueous solution of hydrazine hydrate and mixed thoroughly. The mixture was then heated in a water bath at 65°C for 3 hours. After filtration, the resulting solid was washed with deionized water and dried at 100°C for 5 hours to obtain the modified lithium-rich manganese-based cathode material. The molar ratio of lithium-rich manganese-based material, MBene material, and cobalt hydroxide was 1:0.01:0.02, and the mass ratio of the total mass of lithium-rich manganese-based material, MBene material, and cobalt hydroxide to the mass of the aqueous solution of hydrazine hydrate was 1:40.

[0057] In Comparative Example 2, the preparation methods for lithium-rich manganese-based materials and MBene materials are the same as in Example 1.

[0058] Test case

[0059] The modified lithium-rich manganese-based cathode materials prepared in Example 1 and Comparative Examples 1-2 were subjected to SEM testing, and the obtained SEM images are shown below. Figures 1-3 As shown. From Figures 1-3 As can be seen, the modified material particles of the present invention have many fine particles distributed on their surface, and the particles are tightly arranged, that is, the porosity is significantly lower; while Comparative Example 1 and Comparative Example 2 have significantly higher porosity, indicating that the coating effect of the modified material of the present invention is better.

[0060] The modified lithium-rich manganese-based cathode materials prepared in Example 1 and Comparative Examples 1-2 were subjected to electrochemical performance tests, and the test results are as follows: Figures 4-5 As shown. The rate performance test conditions are 0.1 / 0.2 / 0.33 / 0.5 / 1 / 2 / 3C rate charge and discharge tests, and the cycle performance test conditions are 1C / 1C cycle at room temperature, with test voltages ranging from 2.0 to 4.8V. Figure 4 These are the rate performance test results of the modified lithium-rich manganese-based cathode materials prepared in Examples 1 and 1-2. Figure 5These are the results of the cyclic performance test. (By...) Figure 4 The initial discharge specific capacities of Example 1, Comparative Example 1, and Comparative Example 2 were 281.5 mAh / g, 252 mAh / g, and 278 mAh / g, respectively. Example 1 showed a slight improvement in initial discharge specific capacity compared to Comparative Example 2, and an improvement of nearly 30 mAh / g compared to Comparative Example 1. Furthermore, the discharge data at different rates also showed that Example 1 was slightly better than Comparative Example 2, and showed a significant improvement compared to Comparative Example 1, indicating that the synergistic modification of elemental metal nanoparticles and MBene can improve rate performance and charge / discharge capacity. Figure 5 The modified lithium-rich manganese-based cathode material of Example 1 still has a capacity of 235 mAh / g after 50 cycles at 1C rate. Its cycle performance is significantly better than that of Comparative Example 1 without MBene material and Comparative Example 2 without borides. This shows that the boride / MBene / metal composite coating layer formed on the surface of the lithium-rich manganese-based material in this invention can effectively stabilize the material structure and significantly improve its cycle performance.

[0061] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a modified lithium-rich manganese-based cathode material, characterized in that, The preparation method includes: under a protective atmosphere, adding lithium-rich manganese-based material, MBene material, boride and metal hydroxide to a hydrazine hydrate solution and mixing them evenly, then heating to carry out a reduction reaction, after the reaction is completed, separating the solid and liquid, and washing and drying the obtained solid to obtain the modified lithium-rich manganese-based cathode material.

2. The method for preparing the modified lithium-rich manganese-based cathode material according to claim 1, characterized in that, The molar ratio of the lithium-rich manganese-based material, MBene material, boride and metal hydroxide is 1:0.005~0.05:0.005~0.08:0.005~0.

06.

3. The method for preparing the modified lithium-rich manganese-based cathode material according to claim 1, characterized in that, The preparation method of the MBene material includes: mixing the MAB phase material with an HF solution of 5% to 30% by mass, stirring and reacting at 60 to 80°C for 20 to 30 hours, then centrifuging, and washing and drying the obtained precipitate to obtain the MBene material.

4. The method for preparing the modified lithium-rich manganese-based cathode material according to claim 3, characterized in that, The MAB phase material is selected from at least one of Mn2AlB2, CrAlB4, Cr4AlB6, WAlB, and Fe2AlB2.

5. The method for preparing the modified lithium-rich manganese-based cathode material according to claim 1, characterized in that, The boride is selected from at least one of TiB2, ZrB2, FeB, and AlB2.

6. The method for preparing the modified lithium-rich manganese-based cathode material according to claim 1, characterized in that, The metal hydroxide is at least one of the hydroxides of Co, Rh, Fe, Ru, and Ag.

7. The method for preparing the modified lithium-rich manganese-based cathode material according to claim 1, characterized in that, The chemical formula of the lithium-rich manganese-based material is xLi2MnO3·(1-x)LiMO2, where M is at least one of Ni, Co, and Mn, and 0 < x < 0.

5.

8. The method for preparing the modified lithium-rich manganese-based cathode material according to claim 1, characterized in that, The total mass ratio of the lithium-rich manganese-based material, MBene material, boride, and metal hydroxide to the hydrazine hydrate solution is 1:10 to 150; the mass fraction of the hydrazine hydrate solution is 10% to 50%.

9. The method for preparing the modified lithium-rich manganese-based cathode material according to claim 1, characterized in that, The reduction reaction is carried out at a temperature of 55–85°C for 0.5–4 hours.

10. A modified lithium-rich manganese-based cathode material, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 9.

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