Preparation and electrochemical performance of Na0.67Mn0.67Fe0.2Co0.1Cu0.03O2 cathode material for sodium-ion batteries☆

Mn-based layered oxides were considered one of the most promising cathode materials for sodium-ion batteries due to their high specific capacity and abundant resources. At present, they had the problems of low Na+ migration rate and poor phase transition during cycling, resulting in low cycle stability. In this paper, a Cu-O surface was introduced to construct Mn-Fe-Co-Cu system, and a new P2-type cathode material Na0.67Mn0.7xFe0.2Co0.1CuxO2 (P2-NaMFCCO-x) was prepared by combining complexation chemical precipitation with high temperature calcination to improve its cycling performance. The obtained materials were characterized by XRD, Raman and XPS. At the same time, their corresponding electrochemical performance were tested. The results showed that P2-NaMFCCO-0.03 could maintain P2 phase during the 2.0-4.2 V charging and discharging, and the undesirable phase transition (P2-O2/OP4 phase transition) could be effectively inhibited, showing high cycling stability and air stability. It exhibited a high initial discharge specific capacity of 217mAh g- 1 at 0.1C and maintained a capacity retention rate of about 90.3 % after 200 cycles at 5C. All these indicated that Mn-Fe-Co-Cu system was an effective way to obtain excellent electrochemical properties of cathode materials for sodium-ion batteries.