Self-standing reduced graphene oxide/Nb2C MXene paper electrode with three-dimensional open structure for high-rate potassium ion storage

Potassium ion battery (PIBs) is in the primary stage of development, exploring appropriate electrode materials is the key to obtain high performance and practical application. Herein, we design a self-standing reduced graphene (rGO) and Nb2C MXene (3D-rGO/Nb2C) composite paper electrode with three-dimensional porous conductive network by electrostatic absorption self-assembly method. Compared with the compact structure of L-rGO/Nb2C paper electrode via layer-by-layer vacuum filtration approach, the structure design in which the wrinkled rGO is applied as the framework provides a large number of surface active sites and promotes the rapid transfer of K+ to improve the storage capacity and kinetics of potassium ions. Moreover, the 3D-rGO/Nb2C hybrid paper with large specific surface area can effectively accommodate the volume expansion during charging and discharging process and ensure the cycle stability. At current density of 500 mA g−1, the 3D-rGO/Nb2C hybrid paper electrode delivers an initial capacity of 207 mAh·g−1, which is maintained at 139 mAh·g−1 after 1000 cycles. The 3D-rGO/Nb2C hybrid paper combines both diffusion mechanism and pseudo-capacitance mechanism, which significantly improves its electrochemical performance in K-ion storage. These results show the good potential of the 3D-rGO/Nb2C hybrid paper as a high-performance electrode.