Electrochemical Energy Storage Behavior of Na0.44MnO2 in Aqueous Zinc-Ion Battery

Recently, rechargeable aqueous zinc-ion batteries (AZIBs) have gradually attracted attentions due to their high specific capacity, environmental friendliness, and low cost. However, the uncertain reaction mechanism of AZIBs and the lack of suitable cathode materials still puzzled researchers. Therefore, further exploration of electrode reactions in batteries is still one of the challenges in the development of AZIBs. In this paper, Na0.44MnO2 with an improved specific surface area was applied as a cathode material of AZIBs, and multimechanism reactions were found during the charging and discharging process, including a Zn2+ insertion/extraction reaction, conversion reaction, and pseudocapacitive reaction. Benefiting from the unique tunnel structure and mentioned mechanisms, the NMO-CG electrode can release a specific capacity of 301.3 mAh g–1 at a current density of 100 mA g–1. After 800 cycles, at a high rate of 1 A g–1, it still has a capacity retention rate of 69.3%. Our work provides new ideas for the subsequent research on the electrode mechanism of AZIBs and offers a basis for high-performance AZIBs.