Ti3C2Tx@K2Ti4O9 composite materials by controlled oxidation and alkalization strategy for potassium ion batteries

Abstract

Due to their adjustable surface functional groups and high conductivity, MXenes are considered as a promising electrode material, and have been studied extensively in potassium ions batteries. Because of the compact structure, however, the multilayer MXenes electrode can only supply the less active sites, which resulting in the limited contact area between the electrode active material with electrolyte, low storage capacity and degraded cycle life in their electrochemical reaction. Herein, Ti3C2Tx@K2Ti4O9 composites (referred to as the Ti3C2Tx@KTO) have been prepared by a simple controlled oxidation and alkalization method. Due to the formation of porous and coarse nano-framework structure on the surface, as-prepared Ti3C2Tx@KTO not only presents a large specific surface area, but also provides the sufficient K ion diffusion path. Furthermore, during the preparation process, K ion can pre-embed between layers, which leads to enlarged interlayer distance and stabilized layer structure of Ti3C2Tx. As expected, the obtained Ti3C2Tx@KTO electrode material presents the high specific capacity of 170.2 mA h g−1 under the current density of 100 mA g−1 and superior cyclic stability with exceeds 120.1 mA h g−1 retained after 2000 cycles at 200 mA g−1.