Cation-assisted self-assembled pillared V2CT MXene electrodes for efficient energy storage

Among the MXene family members vanadium carbide MXenes with high electrical conductivity and multiple available redox states emerged as prospective candidates for supercapacitors and batteries. However, it's reaggregation and unstable behavior hinder its application as electrode material in capacitive devices. Here we report the cation-assisted self-assembled flexible and stable V2CTx MXene electrodes for enhanced energy storage. Monovalent alkali (Li, Na, K) and divalent Mg ions are intercalated for pillaring of MXene sheets. The XRD analysis reflects the significant increase in d-spacing after cation intercalation from 0.987 nm to 1.29 nm. We observe the highest d-spacing of 1.228 nm in the case of Na- intercalated MXene for monovalent cations. These pillared electrodes were electrochemically tested in 3 M H2SO4 and surpassed 3-folds the capacitance of Ti3C2Tx MXene. A maximum of 900 Fg−1 gravimetric capacitance was achieved with 95 % capacitance retention for Li intercalated MXene @5 mVs−1 scan rate over 10,000 cycles. All the cation intercalated electrodes exhibit an excellent Coulombic efficiency (100%) for 10,000 GCD cycles at a current density of 2 A/g indicative of high-rate capability and reversibility. These self-assembled cation-intercalated electrodes open new horizons for MXene materials as prospective storage devices.