Building durable aqueous K-ion capacitors based on MXene family

Abstract

Obtaining stable aqueous K-ion capacitors is still challenging due to the cathode materials tended to structurally collapse after long-term cycling during large-radius K-ion insertion/extraction. In this work, three different typical MXene electrodes, i.e., Nb<inf>2</inf>C, Ti<inf>2</inf>C, and Ti<inf>3</inf>C<inf>2</inf> were individually investigated upon their electrochemical behaviors for potassium-ion (K-ion) storage. All these MXene materials exhibited pseudocapacitive-dominated behaviors, fast kinetics, and durable K-ion storage, delivering superior performance compared with other K-ion host materials. According to the experimental results, it could be ascribed to the intrinsically large interlayer distance for K-ion transport and the superb structural stability of MXene even subjected to long-term potassiation/depotassiation process.