A Three-Dimensional Carbon Framework Constructed by N/S Co-doped Graphene Nanosheets with Expanded Interlayer Spacing Facilitates Potassium Ion Storage

Carbon nanomaterials show potential in achieving good potassium ion storage; however, the limited interlayer spacing in existing carbon nanomaterials greatly impacts the performance of potassium ion batteries (PIBs). Herein, we report a class of three-dimensional (3D) porous carbon framework materials constructed by S/N co-doping graphene nanosheets (CFM-SNG) with an ultralarge interlayer spacing (0.448 nm) and a rich edge defect as high-performance PIBs anodes. The resulting 3D CFM-SNG material achieves enhanced reversible capacity (348.2 mAh/g at 50 mA/g), cycling performance (188.8 mAh/g at 1000 mA/g after 2000 cycles), and rate capability (204.3 mAh/g at a high current density of 2000 mA/g). Density functional theory calculations further demonstrate that the S/N co-doping and formed edge defects not only favor the interlayer spacing expansion and the adsorption of K+ to the 3D CFM-SNG anode but also prevent variation in volume during the potassiation/depotassiation process.