Layered lithium-rich manganese-based cathode material with olivine structured LIMPO4 surface modification and preparation method thereof

1. A preparation method of a layered lithium-rich manganese-based cathode material with olivine structured LiMPO 4 surface modification, comprising steps of:

1) weighing a nickel salt, a cobalt salt and a manganese salt and dissolving the nickel salt, the cobalt salt and the manganese salt in deionized water respectively to formulate salt solutions of each having a concentration of 0.5-2 mol/L, wherein the nickel salt, the cobalt salt and the manganese salt are weighed based on a molar ratio of Ni, Co and Mn in a chemical formula of Li 1.2 Mn x Ni y Co 0.8-x-y O 2 , where 0.4≤x≤0.6, 0.1≤y≤0.2;

2) dissolving alkali and ammonia water in the deionized water to formulate a mixed alkali solution, wherein a concentration of the alkali is 2-10 mol/L, and a molar concentration of the ammonia water is 2-5 mol/L;

3) adding the mixed alkali solution obtained in step 2) into a reactor, wherein a volume of the mixed alkali solution accounts for 30% to 50% of a volume of the reactor, and controlling a pH value between 9 and 12, and controlling a temperature between 60° C. and 80° C.;

4) respectively adding the salt solutions of the nickel salt, the cobalt salt and the manganese salt formulated in step 1) into the reactor via a peristaltic pump at a constant speed, wherein in step 4), the pH value is between 9 and 12, and the temperature is between 60° C. and 80° C.;

5) after finished adding the salt solutions of the nickel salt, the cobalt salt and the manganese salt, standing still and aging for 12-20 hours, followed by filtering a precipitate, washing the precipitate and drying the precipitate;

6) uniformly mixing the precipitate with a lithium salt, presintering a mixture of the precipitate and the lithium salt at a presintering temperature of 450-550° C. for 3-5 hours, and then calcining the mixture of the precipitate and the lithium salt at a calcining temperature of 750-950° C. for 10-16 hours to obtain a pure-phase layered lithium-rich manganese-based cathode material; wherein a molar ratio of the precipitate to the lithium salt is 1:(1.05-1.1);

7) totally dissolving a lithium source, a transition metal source, a phosphorus source and an additive in the deionized water at a molar ratio of 1:1:1:(1-5), followed by adding the pure-phase layered lithium-rich manganese-based cathode material obtained in step 6), evaporating to dry at an evaporating temperature of 80-100° C. to form a gel; and

8) vacuum drying the gel obtained in step 7) at a vacuum drying temperature of 100-120° C., crushing the gel, and precalcining the gel at a precalcining temperature of 400 600° C. for 4-6 hours to obtain the layered lithium-rich manganese-based cathode material with olivine structured LiMPO 4 surface modification.

2. The preparation method according to claim 1 , wherein in step 1), the nickel salt is one or more of nickel sulfate, nickel nitrate and nickel acetate; the cobalt salt is one or more of cobalt sulfate, cobalt nitrate and cobalt acetate; the manganese salt is one or more of manganese sulfate, manganese nitrate and manganese acetate.

3. The preparation method according to claim 1 , wherein in step 2), the alkali is one or more of a sodium hydroxide solution and a potassium hydroxide solution, and the concentration of the alkali is 2-5 mol/L; a molar ratio of sodium hydroxide to the ammonia water is 2:1.

4. The preparation method according to claim 1 , wherein in step 6), the lithium salt is one or more of lithium hydroxide, lithium carbonate and lithium acetate.

5. The preparation method according to claim 1 , wherein in step 6), the presintering temperature is raised to 450 550° C. at a heating rate of 1-5° C./min and is maintained for 3-5 hours; and then the calcining temperature is raised to 750-950° C. at the heating rate of 1-5° C./min and is maintained for 10-16 hours.

6. The preparation method according to claim 1 , wherein in step 7), the lithium source is one or more of lithium hydroxide, lithium dihydrogen phosphate and lithium carbonate.

7. The preparation method according to claim 1 , wherein in step 7), the transition metal source is one or more of ferrous sulfate, ferrous nitrate, ferrous oxalate and ferrous acetate.

8. The preparation method according to claim 1 , wherein in step 7), the phosphorus source is one or more of ammonium dihydrogen phosphate, ammonium hydrogen phosphate and phosphoric acid; and the additive is one or more of citric acid, tartaric acid, glucose and sucrose, and an amount of the additive is controlled to be 20-50% of a mass of the transition metal source.

9. The preparation method according to claim 1 , wherein in step 8), the precalcining temperature is raised to 400° C. to 600° C. at a heating rate of 1-5° C./min and is maintained for 4-6 hours.

10. A layered lithium-rich manganese-based cathode material with olivine structured LiMPO 4 surface modification obtained by using a preparation method according to claim 1 , wherein the layered lithium-rich manganese-based cathode material has a chemical formula of Li 1.2 Mn x Ni y Co 0.8-x-y O 2 , wherein x and y are moles, 0.4≤x≤0.6 and 0.1≤y≤0.2; an olivine structured LiMPO 4 coating layer of the layered lithium-rich manganese-based cathode material is LiNiPO 4 , LiCoPO 4 , LiMnPO 4 , LiFePO 4 , LiCuPO 4 , LiAlPO 4 , LiMoPO 4 or LiMgPO 4 , and a mass of the olivine structured LiMPO 4 coating layer is controlled to be 1-10% of a mass of the layered lithium-rich manganese-based cathode material.

11. A layered lithium-rich manganese-based cathode material with olivine structured LiMPO 4 surface modification obtained by using a preparation method according to claim 2 , wherein the layered lithium-rich manganese-based cathode material has a chemical formula of Li 1.2 Mn x Ni y Co 0.8-x-y O 2 , wherein x and y are moles, 0.4≤x≤0.6 and 0.1≤y≤0.2; an olivine structured LiMPO 4 coating layer of the layered lithium-rich manganese-based cathode material is LiNiPO 4 , LiCoPO 4 , LiMnPO 4 , LiFePO 4 , LiCuPO 4 , LiAlPO 4 , LiMoPO 4 or LiMgPO 4 , and a mass of the olivine structured LiMPO 4 coating layer is controlled to be 1-10% of a mass of the layered lithium-rich manganese-based cathode material.

12. A layered lithium-rich manganese-based cathode material with olivine structured LiMPO 4 surface modification obtained by using a preparation method according to claim 3 , wherein the layered lithium-rich manganese-based cathode material has a chemical formula of Li 1.2 Mn x Ni y Co 0.8-x-y O 2 , wherein x and y are moles, 0.4≤x≤0.6 and 0.1≤y≤0.2; an olivine structured LiMPO 4 coating layer of the layered lithium-rich manganese-based cathode material is LiNiPO 4 , LiCoPO 4 , LiMnPO 4 , LiFePO 4 , LiCuPO 4 , LiAlPO 4 , LiMoPO 4 or LiMgPO 4 , and a mass of the olivine structured LiMPO 4 coating layer is controlled to be 1-10% of a mass of the layered lithium-rich manganese-based cathode material.

13. A layered lithium-rich manganese-based cathode material with olivine structured LiMPO 4 surface modification obtained by using a preparation method according to claim 4 , wherein the layered lithium-rich manganese-based cathode material has a chemical formula of Li 1.2 Mn x Ni y Co 0.8-x-y O 2 , wherein x and y are moles, 0.4≤x≤0.6 and 0.1≤y≤0.2; an olivine structured LiMPO 4 coating layer of the layered lithium-rich manganese-based cathode material is LiNiPO 4 , LiCoPO 4 , LiMnPO 4 , LiFePO 4 , LiCuPO 4 , LiAlPO 4 , LiMoPO 4 or LiMgPO 4 , and a mass of the olivine structured LiMPO 4 coating layer is controlled to be 1-10% of a mass of the layered lithium-rich manganese-based cathode material.

14. A layered lithium-rich manganese-based cathode material with olivine structured LiMPO 4 surface modification obtained by using a preparation method according to claim 5 , wherein the layered lithium-rich manganese-based cathode material has a chemical formula of Li 1.2 Mn x Ni y Co 0.8-x-y O 2 , wherein x and y are moles, 0.4≤x≤0.6 and 0.1≤y≤0.2; an olivine structured LiMPO 4 coating layer of the layered lithium-rich manganese-based cathode material is LiNiPO 4 , LiCoPO 4 , LiMnPO 4 , LiFePO 4 , LiCuPO 4 , LiAlPO 4 , LiMoPO 4 or LiMgPO 4 , and a mass of the olivine structured LiMPO 4 coating layer is controlled to be 1-10% of a mass of the layered lithium-rich manganese-based cathode material.

15. A layered lithium-rich manganese-based cathode material with olivine structured LiMPO 4 surface modification obtained by using a preparation method according to claim 6 , wherein the layered lithium-rich manganese-based cathode material has a chemical formula of Li 1.2 Mn x Ni y Co 0.8-x-y O 2 , wherein x and y are moles, 0.4≤x≤0.6 and 0.1≤y≤0.2; an olivine structured LiMPO 4 coating layer of the layered lithium-rich manganese-based cathode material is LiNiPO 4 , LiCoPO 4 , LiMnPO 4 , LiFePO 4 , LiCuPO 4 , LiAlPO 4 , LiMoPO 4 or LiMgPO 4 , and a mass of the olivine structured LiMPO 4 coating layer is controlled to be 1-10% of a mass of the layered lithium-rich manganese-based cathode material.

16. A layered lithium-rich manganese-based cathode material with olivine structured LiMPO 4 surface modification obtained by using a preparation method according to claim 7 , wherein the layered lithium-rich manganese-based cathode material has a chemical formula of Li 1.2 Mn x Ni y Co 0.8-x-y O 2 , wherein x and y are moles, 0.4≤x≤0.6 and 0.1≤y≤0.2; an olivine structured LiMPO 4 coating layer of the layered lithium-rich manganese-based cathode material is LiNiPO 4 , LiCoPO 4 , LiMnPO 4 , LiFePO 4 , LiCuPO 4 , LiAlPO 4 , LiMoPO 4 or LiMgPO 4 , and a mass of the olivine structured LiMPO 4 coating layer is controlled to be 1-10% of a mass of the layered lithium-rich manganese-based cathode material.

17. A layered lithium-rich manganese-based cathode material with olivine structured LiMPO 4 surface modification obtained by using a preparation method according to claim 8 , wherein the layered lithium-rich manganese-based cathode material has a chemical formula of Li 1.2 Mn x Ni y Co 0.8-x-y O 2 , wherein x and y are moles, 0.4≤x≤0.6 and 0.1≤y≤0.2; an olivine structured LiMPO 4 coating layer of the layered lithium-rich manganese-based cathode material is LiNiPO 4 , LiCoPO 4 , LiMnPO 4 , LiFePO 4 , LiCuPO 4 , LiAlPO 4 , LiMoPO 4 or LiMgPO 4 , and a mass of the olivine structured LiMPO 4 coating layer is controlled to be 1-10% of a mass of the layered lithium-rich manganese-based cathode material.

18. A layered lithium-rich manganese-based cathode material with olivine structured LiMPO 4 surface modification obtained by using a preparation method according to claim 9 , wherein the layered lithium-rich manganese-based cathode material has a chemical formula of Li 1.2 Mn x Ni y Co 0.8-x-y O 2 , wherein x and y are moles, 0.4≤x≤0.6 and 0.1≤y≤0.2; an olivine structured LiMPO 4 coating layer of the layered lithium-rich manganese-based cathode material is LiNiPO 4 , LiCoPO 4 , LiMnPO 4 , LiFePO 4 , LiCuPO 4 , LiAlPO 4 , LiMoPO 4 or LiMgPO 4 , and a mass of the olivine structured LiMPO 4 coating layer is controlled to be 1-10% of a mass of the layered lithium-rich manganese-based cathode material.