Developing high-performance Zn-pre-inserted MnO electrodeposition for aqueous Zn-ion batteries.

Rechargeable aqueous zinc-ion batteries (AZIBs) are considered to be a promising alternative to lithium-ion batteries (LIBs), because they are more environmentally friendly, cheaper and safer than LIBs. Although manganese dioxide (MnO) has many advantages as a cathode material for use in AZIBs, its structural degradation and slow ion diffusion seriously hinder its electrochemical performance. Herein, Zn-pre-inserted MnO (Zn-MnO) was prepared by a simple electrodeposition method. The specific capacity and cycling performance of AZIBs based on Zn-MnO cathodes were significantly improved compared to those of AZIBs with original MnO cathodes. The capacity decay of a Zn//Zn-MnO cell was only 0.029% per cycle at a current density of 1 A g for 1000 cycles. The pre-inserted Zn not only reinforces the structure of MnO, but it also reduces the voltage difference between the charge and discharge curves. In addition, the mechanism of the co-insertion of H and Zn during the discharge of AZIBs was elucidated based on the galvanostatic intermittent titration technique (GITT). This work will inspire and promote the development of aqueous zinc-ion batteries.