In Situ Investigation of Expansion during the Lithiation of Pillared MXenes with Ultralarge Interlayer Distance

Abstract

Pillared Ti3C2T z MXene with a large interlayer spacing (1.75 nm) is shown to be promising for high-power Li-ion batteries. Pillaring dramatically enhances the electrochemical performance, with superior capacities, rate capability, and cycling stability compared to the nonpillared material. In particular, at a high rate of 1 A g–1, the SiO2-pillared MXene has a capacity over 4.2 times that of the nonpillared material. For the first time, we apply in situ electrochemical dilatometry to study the volume changes within the MXenes during (de)­lithiation. The pillared MXene has superior performance despite larger volume changes compared to the nonpillared material. These results give key fundamental insights into the behavior of Ti3C2T z electrodes in organic Li electrolytes and demonstrate that MXene electrodes should be designed to maximize interlayer spacings and that MXenes can tolerate significant initial expansions. After 10 cycles, both MXenes show nearly reversible thickness changes after the charge–discharge process, explaining the stable long-term electrochemical performance.