Highly efficient Mn2+ deposition induced by H-vacancies of NiMn-LDH nanosheets for durable zinc ion batteries

Abstract

The dissolution of Mn-based oxides cathodes is an urgent issue, as it leads to electrochemically irreversible byproducts and, finally, battery failure. In this work, activated NiMn-LDHv nanosheets with H vacancies are proposed as the cathode material for durable zinc ion batteries. The H vacancies promote Mn²⁺ deposition by redistributing the electron density and building strong Mn-O bonds, as a result, endowing NiMn-LDHv with the ability of controllable back-deposition of Mn²⁺. It's verified that MnO₂ is deposited on the NiMn-LHDv substrate during charging, the dissolution and the Zn²⁺/H⁺ co-intercalation of MnO₂ have a combined contribution to the discharge capacity. The full battery with NiMn-LDHv cathode delivers rate capacity of 258 mAh g⁻¹ at 0.3 A g⁻¹, and even 90 mAh g⁻¹ at 11.0 A g⁻¹. Furthermore, the irreversible Mn-based byproducts are inhibited, resulting in durable cycling performance. After 2500 charge/discharge cycles, the initial capacity remains 91 %. This work provides an important strategy to utilize Mn²⁺ efficiently and develop a robust Mn-based cathode, which could greatly prompt the practical application of aqueous zinc ion batteries.