Two-Dimensional Titanium Carbide MXene As a Cathode Material for Hybrid Magnesium/Lithium-Ion Batteries

As an alternative to pure lithium-ion, Li⁺, systems, a hybrid magnesium, Mg²⁺, and Li⁺ battery can potentially combine the high capacity, high voltage, and fast Li⁺ intercalation of Li-ion battery cathodes and the high capacity, low cost, and dendrite-free Mg metal anodes. Herein, we report on the use of two-dimensional titanium carbide, Ti₃C₂T_x (MXene), as a cathode in hybrid Mg²⁺/Li⁺ batteries, coupled with a Mg metal anode. Free-standing and flexible Ti₃C₂T_x/carbon nanotube composite "paper" delivered ∼100 mAh g^-1 at 0.1 C and ∼50 mAh g^-1 at 10 C. At 1 C the capacity was maintained for >500 cycles at 80 mAh g^-1. The Mo₂CT_x MXene also demonstrated good performance as a cathode material in this hybrid battery. Considering the variety of available MXenes, this work opens the door for exploring a new large family of 2D materials with high electrical conductivity and large intercalation capacity as cathodes for hybrid Mg²⁺/Li⁺ batteries.