Dual cation doping enabling simultaneously boosted capacity and rate capability of MnO₂ cathodes for Zn//MnO₂ batteries

Aqueous rechargeable Zn//MnO₂ batteries show promising prospects for grid-scale energy storage due to their intrinsic safety, abundant resource, and potential high performance. Unfortunately, the real capability of these devices is far from satisfactory thanks to the low capacity and sluggish kinetics of the MnO₂ cathode. Herein, we report a dual cation doping strategy by synthesis of MnO₂ in the presence of Ti₃C₂X MXenes and Ni²⁺ ions to essentially address these drawbacks. Such a process contributes to a Ti,Ni co-doped α-MnO₂ anchored on MXenes. The Ti³⁺ ions incorporated in the framework allow a partial multivalent variation for a large capacity while the Ni²⁺ ions promote the H⁺ transfer within the MnO₂ matrix via the Grotthuss proton transport manner. As a result, the optimal dual cation doped MnO₂ exhibits a large reversible capacity of 378 mAh·g⁻¹ at 0.1 C and a high rate capability. Moreover, capacity retention as high as 92% is observed after cycling at 4 C for 1000 times, far superior to many of the previously reported results. This facile strategy demonstrated here may shed new insight into the rational design of electrodes based on high-performance Zn//MnO₂ batteries.