Self-assembly of secondary-formed multilayer La/e-Ti3C2 as high performance supercapacitive material with excellent cycle stability and high rate capability

Abstract

MXenes are a new class of two-dimensional (2D) materials and have been considered as promising energy storage materials due to their high conductivity and unique layered structure. To improve the charge storage performance of these materials, it is crucial to prevent self-stacking and expand the interlayer spacing of MXenes since this will increase the transfer channels and accessible active sites for electrolyte ions and improve the dynamics of charge storage. This paper presents an effective approach to preventing self-stacking and expanding the interlayer spacing of Ti3C2 using electrostatic reassembly between lanthanum ions and exfoliated Ti3C2 sheets to obtain a secondary-formed multilayer-structured Ti3C2 (La/e-Ti3C2). An increased interlayer spacing and greater specific surface area were achieved and capacitive performance was improved compared with that of pure multilayer Ti3C2. The specific capacitance of La/e-Ti3C2 was found to be 233.3 F g−1 at a current density of 0.5 A g−1 and the capacitance retention under 2 A g−1 was as high as 94.3% after 10,000 cycles. An interesting result is presented, namely that a large interlayer spacing is beneficial for improving the rate capability of Ti3C2 at different current densities. The study paves the way for controllable tuning of the interlayer spacing, specific surface area, and pseudocapacitive performance of two-dimensional materials.