Preparation And Modification Of LiNi_0.7Co_0.3O₂Lithium-ion Battery Cathode Materials

Lithium cobalt oxide is currently the most widely used cathode material forlithium-ion battery. However, an urgent need to find alternative materials arise dueto its high costs and scarce resources. Current study focus more on spinel lithiummanganese oxide and layer-structured lithium nickel oxide for cathode materialapplication. Nevertheless, lithium manganese oxide possess a low specific capacityand a tendency of capacity fading in cycling process while lithium nickel oxide ishard to synthesized with a certain stoichiometric ratio. Their applications are greatlylimited. Lithium cobalt nickel oxides occupy the advantages of the both: relativelyhigh charge-discharge capacity and good cycling stability. But its rapid capacityfading during cycling restrain the commercial use. In this paper, solid-phasesynthesis method and coprecipitation synthesis method are employed to prepareLiNi_0.7Co_0.3O₂. Mg-doping and Mg, F-doping are exploited to improve its capacitydecay and enhance the electrochemical performance.Firstly, solid-phase synthesized LiNi_0.7Co_0.3O₂cathode materials are Explorethe temperature and calcination duration synthesis process, the study found that thesintering temperature of900℃, sintering time was16h synthesis of cathodematerials for the initial discharge capacity in the0.1C for182mAh·g^-1capacity after50cycles there160mAh·g^-1, for the first time,87.91%of capacity.Secondly, the Coprecipitation prepared by LiNi_0.7Co_0.3O₂of cathode materials.The study found that the best synthesis process of the electrode material wasprepared by coprecipitation as follows: the precipitating agent and the mother liquorplus, complexing agents, NH₄·H₂O concentration of0.4M, the sintering temperatureof800℃and sintering time8h. Active substances for the first time in the0.1Cdischarge capacity of202mAh·g^-1, after40cycles, there are still170mAh·g^-1. Thefirst time under high magnification of the1C discharge capacity is130mAh·g^-1after40cycles there100mAh·g^-1Last Mg-doped and Mg, F double-doped LiNi_0.7Co_0.3O₂LiNi_0.7Co_0.25Mg_0.05O_1.95F_0.05the first time under the0.1C discharge capacity of165mAh·g^-1, the study found, with cycle capacity has increased, the maximumcapacity of181mAh·g^-1has a high capacity retention rate after100cycles capacityof175mAh·g^-1.