Flexible TiVCTx MXene film for high-performance magnesium-ion storage device

Magnesium-based battery system has emerged as the potential candidate to beyond Li-ion battery system due to the numerous advantageous of magnesium anode, such as natural abundance, high capacity and dendrites free. However, the selection of cathode materials and the intercalation of magnesium-ions in the cathode host material remains a challenge due to the strong interaction of highly polar divalent magnesium ions with the cathode material, making the diffusion of magnesium ions relatively difficult. Herein, the flexible TiVCT_x MXene film was developed via a facile and economical approach. As the cathode host material for magnesium-ion storage, the freestanding TiVCT_x MXene film displays a high specific capacity of 111 and 135 mAh g^-1 at a current density of 0.05 A g^-1 for magnesium-ion batteries (MIB) and Mg/Li hybrid batteries (MLHB). Furthermore, a long-term cycling stability over 1000 cycles was demonstrated and a detailed investigation of the unique long activation phenomenon of MXene films during cycling. More importantly, the reaction mechanism of magnesium-ion storage was validated, i.e., the MXene interlayer spacing variation with the reversible Mg²⁺ diffusion behavior. This work reveals the magnesium storage mechanism of MXene materials and provides a new pathway for high-performance storage of magnesium-ion cathode materials.