Concentrated Laminate Structure in Dense MXene Monoliths Promises High‐Capacity Sodium Storage

Abstract

MXenes have great potential as fast‐charging anodes for sodium storage due to their excellent electrical conductivity, high pseudocapacitive charge storage, and large interlayer distance. The intercalation pseudocapacitance provided by the active sites within the laminate MXene nanosheets is generally the major contributor to their sodium‐storage capacity. Thus, it is highly preferred to construct porous materials with abundant laminate structures to overcome the ion‐diffusion limitation in MXene multilayer films and increase the accessible interlayer sites. Herein, the enhancement of laminate structures in a pre‐assembled Ti3C2Tx network is achieved, under the effects of interlayer slipping of MXene nanosheets during capillary densification, and finally obtained a dense monolith with both high density (2.37 g cm−3) and high porosity (87.3 m2 g−1). This MXene anode material delivers a high capacity of 185 mAh g−1 and a superior rate performance of 55 mAh g−1 (5 A g−1). With improvement of both density and gravimetric capacity, this monolith has a high volumetric capacity of up to 200 mAh cm−3 at 1 A g−1 even after 2000 cycles. Herein, new insights are provided into the design of high‐capacity MXene anodes for sodium‐ion batteries and control of different 2D materials in compact structures.