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 Ni(2+)ions to essentially address these drawbacks. Such a process contributes to a Ti,Ni co-doped alpha-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 center dot 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.