Preparation And Modification Of Lithium-rich Manganese-based Cathode Material Li_1.2Ni_0.1Co_0.1Mn_0.6O₂

Lithium-rich manganese-based（LMR）cathode material has attracted much attention because of its high specific capacity(>250 m Ah·g^-1).However,the serious problems of discharge voltage attenuation,low coulomb efficiency and poor rate performance in the charge discharge process of LMR cathode materials have hindered their practical application.In this paper,the precursor of oxalate lithium-rich manganese-based cathode material was prepared by rapid co-precipitation method,and Li_1.2Ni_0.1Co_0.1Mn_0.6O₂cathode material was obtained by high temperature sintering.Firstly,a group of orthogonal experiments were designed to explore the temperature,solvent and amount of oxalic acid precipitant in the precursor preparation process.The results showed that the optimal combination is to maintain the preparation temperature at 55℃,distilled water as solvent and 5%excess precipitant.After mixing with Li₂CO₃,the discharge specific capacity of the material sintered at 850℃for 12 hours was 252.13 m Ah·g^-1at 0.1C.Then a group of orthogonal experiments were designed to explore the final sintering temperature,time and lithium source in the sintering process,and finally the optimal precursor preparation process was obtained.The results showed that the final firing temperature was 850℃,the time was 8h,and the lithium source was Li OH.The discharge specific capacity was 289.86 m Ah·g^-1at 0.1C.In order to improve the performance of LMR cathode materials,Zr O₂and Ta₂O₅coated cathode materials were obtained by simple solid-state mixed sintering.It was found that Zr O₂and Ta₂O₅coatings can effectively inhibit voltage attenuation,stabilize the structure,improve the electrochemical properties of traditional cathode materials,and make the cathode materials have better electrochemical properties and structural stability.Porous Zr O₂-coating improveed the capacity retention of the composite cathode by inhibiting the impedance growth of the electrode electrolyte interface.The electrochemical performance of Zr O₂-5%modified material was the best.The specific discharge capacity was 283.6 m Ah·g^-1at 0.1C,the first effect was85.2%,the capacity was 99.2 m Ah·g^-1at 10C,and 82.19%after 100 cycles at 2C.The Ta₂O₅ coating reduced the polarization of the positive electrode during charging and discharging by preventing the decomposition of the electrolyte,thereby improving the electrochemical performance of the LMR material.The electrochemical performance of Ta₂O₅-5%modified material was the best.The first cycle discharge specific capacity was 292.9 m Ah·g^-1at 0.1C,the coulomb efficiency was 80.16%,the capacity was 92 m Ah·g^-1at 10C,and 85.35% after 100 cycles at 2C.