Boosting high-rate Zn-ion storage capability of α-MnO2 through Tri-ion co-intercalation

Abstract

Aqueous rechargeable zinc-ion batteries (ARZIBs) have become a research hotspot in recent years because of their high energy density, low cost, rich zinc resources, and high safety. However, defects in the electrochemical performance of cathode materials become a stumbling block for the practical application of ARZIBs. The α-MnO2 cathode material is attracted attention due to its high theoretical capacity and scalable industrial manufacturing, but inherently low electron conduction and poor ion mobility affect transport kinetics, resulting in low capacity and rate capabilities. Here, for the first time, a new α-MnO2 cathode is prepared with co-intercalation of K+, Co2+ and Al3+ through a one-step solution co-precipitation strategy. Taking advantage of the synergistic effect of alkali metal ions and transition metal ions, modified α-MnO2 shows superior high-rate performance (a capacity of 100 mAh g−1 after 800 cycles at 5.0 A g−1) and stable crystal structure. This result is attributed to the enlarged tunnel structure brought about by multi-ion intercalation, which promotes the rapid migration of Zn2+ and improves the transport kinetics. On the basis of the new design of tri-ion co-intercalation, it is hoped that this research will provide theoretical guidance for the preparation of high-capacity Mn-based cathode active materials for ARZIBs.