Influence of MXene/MXene-Oxide Heterostructure Chemistry and Structure on Lithium-Ion Battery Anodes and Supercapacitor Electrodes

The global decarbonisation strategy has accelerated the shift toward renewable energy and electric transport, demanding advanced electrochemical energy storage systems. Conventional anodes such as graphite and silicon composites face challenges in conductivity, stability and cycling performance. MXenes, a class of two-dimensional (2D) materials, offer promising alternatives owing to their metallic conductivity, tunable surface chemistry and high theoretical capacity. Here, we synthesise and characterise Mo2TiC2Tx and V2CTx (T = O, OH, F and/or Cl) MXenes for lithium-ion battery anodes and supercapacitors. Unlike Ti3C2Tx, which stores charge via intercalation and surface redox reactions, Mo2TiC2Tx and V2CTx exhibit conversion-type mechanisms. We also identify novel V2C–VOx heterostructures, achieving a specific capacitance of 532.4 F g−1 at 2 mV s−1 and an initial capacity of 493.3 mAh g−1 at 50 mA g−1 in lithium half-cells, with a low decay rate of 0.071% per cycle over 200 cycles. Pristine Mo2TiC2Tx shows 391.7 mAh g−1 at 50 mA g−1, decaying by 0.109% per cycle. These results experimentally validate theoretical predictions, revealing how MXene structure and transition metal chemistry govern electrochemical behaviour, thus guiding electrode design for next-generation batteries and supercapacitors.