Pillared Structure Design of MXene with Ultralarge Interlayer Spacing for High-Performance Lithium-Ion Capacitors

Abstract

Two-dimensional transition-metal carbide materials (termed MXene) have attracted huge attention in the field of electrochemical energy storage due to their excellent electrical conductivity, high volumetric capacity, etc. Herein, with inspiration from the interesting structure of pillared interlayered clays, we attempt to fabricate pillared Ti₃C₂ MXene (CTAB-Sn(IV)@Ti₃C₂) via a facile liquid-phase cetyltrimethylammonium bromide (CTAB) prepillaring and Sn⁴⁺ pillaring method. The interlayer spacing of Ti₃C₂ MXene can be controlled according to the size of the intercalated prepillaring agent (cationic surfactant) and can reach 2.708 nm with 177% increase compared with the original spacing of 0.977 nm, which is currently the maximum value according to our knowledge. Because of the pillar effect, the assembled LIC exhibits a superior energy density of 239.50 Wh kg^-1 based on the weight of CTAB-Sn(IV)@Ti₃C₂ even under higher power density of 10.8 kW kg^-1. When CTAB-Sn(IV)@Ti₃C₂ anode couples with commercial AC cathode, LIC reveals higher energy density and power density compared with conventional MXene materials.