MXene‐Derived Na+‐Pillared Vanadate Cathodes for Dendrite‐Free Potassium Metal Batteries

Abstract

AbstractCation‐intercalated vanadates, which have considerable promise as the cathode for high‐performance potassium metal batteries (PMBs), suffer from structural collapse upon K+ insertion and desertion. Exotic cations in the vanadate cathode may ease the collapse, yet their effect on the intrinsic cation remains speculative. Herein, a stable and dendrite‐free PMB, composed of a Na+ and K+ co‐intercalated vanadate (NKVO) cathode and a liquid NaK alloy anode, is presented. A series of NKVO with tuneable Na/K ratios are facilely prepared using MXene precursors, in which Na+ is testified to be immobilized upon cycling, functioning as a structural pillar. Due to stronger ionic bonding and lower Fermi level of Na+ compared to K+, moderate Na+ intercalation could reduce K+ binding to the solvation sheath and favor K+ diffusion kinetics. As a result, the MXene‐derived Na+‐pillared NKVO exhibits markedly improved specific capacities, rate performance, and cycle stability than the Na+‐free counterpart. Moreover, thermally‐treated carbon paper, which imitates the microscopic structure of Chinese Xuan paper, allows high surface tension liquid NaK alloy to adhere readily, enabling dendrite‐free metal anodes. By clarifying the role of foreign intercalating cations, this study may lead to a more rational design of stable and high‐performance electrode materials.