MXene/N-Doped Carbon Foam with Three-Dimensional Hollow Neuron-like Architecture for Freestanding, Highly Compressible All Solid-State Supercapacitors.

Currently, the MXene-based flexible supercapacitors have caused much attention due to their excellent mechanical performance and novel electrical property. However, the aggregation and rearrangement of MXene nanosheets in the process of electrode preparation limit their electrochemical performance. Herein, a kind of novel MXene/N-doped carbon foam (MXene/NCF) compressible composite with three-dimensional (3D) hollow interconnected neuron-like architecture is directly prepared by one-step pyrolysis and used for the freestanding, highly compressible supercapacitors. The synergistic effect exists in the MXene/NCF composite when applied to supercapacitors: NCF can provide the additional pseudocapacitance by N atom doping and simultaneously supports the MXene nanosheets to construct the 3D hollow interconnected neuron-like architecture for supplying highly stable, efficient channels for ion diffusion/electron transport and more contact sites, and that the MXene enhances conductivity and hydrophilicity. Therefore, the freestanding MXene/NCF electrode shows a remarkable gravimetric capacitance of 332 F g-1 and volumetric capacitance of 3162 mF cm-3, superior rate performance of 64% (from 0.5 to 100 A g-1), and 99.2% capacity retention after 10,000 cycles. Significantly, the MXene/NCF-based all solid-state supercapacitors still show a high specific capacitance and a large rate performance. In addition, the device can be compressed arbitrarily under 60% strain with almost no change in morphology and electrochemical property. These excellent properties expect that the MXene/NCF composite has broad applications in the field of flexible supercapacitors.