Ion Intercalation into 2D Titanium Carbide Based MXenes: Applications for Electrochemical Capacitors

We recently produced a new 2-D material, viz. Ti₃C₂, by selectively etching aluminium from a MAX phase Ti₃AlC₂ and labelled it MXene. MXenes represents a large family of transition metal carbides and carbonitrides, not just a single phase. Unlike graphene, whose chemistry is restricted to carbon, MXenes allow a variety of chemical compositions and are establishing themselves as a new class of two-dimensional materials. MXenes possess good in-plane conductivity, which in combination with the rich surface chemistry makes them attractive for electrical energy storage applications. However while potential of MXenes as anode materials for Li-ion batteries has already been shown, their use in electrochemical capacitors has not been explored.

Herein, we report on the intercalation of Li⁺, Na⁺, Mg²⁺, K⁺, NH₄⁺, and Al³⁺ ions between the 2D Ti₃C₂T_x layers. In most cases, the cations intercalated spontaneously. The intercalation of some ions, notably Al³⁺, can be promoted electrochemically. We also report on intercalation-induced high volumetric capacitance of flexible Ti₃C₂T_x paper electrodes. This study provides a basis for exploring a large family of 2D carbides and carbonitrides in electrochemical energy storage applications using single- and multivalent ions.

References.

Lukatskaya, M.R., et al., Cation Intercalation and High Volumetric Capacitance of Two-Dimensional Titanium Carbide. Science, 2013. 341(6153): p. 1502-1505.