Green and tunable fabrication of graphene-like N-doped carbon on a 3D metal substrate as a binder-free anode for high-performance potassium-ion batteries

Porous carbon materials have a broad range of potential applications, such as in electrochemical energy storage, filtration, catalysis, sensors, hydrogen storage, automobile exhaust treatment and so on. In this work, morphology evolution of metal-organic frameworks on a 3D metal substrate is explored via a simple binary-solvent method. With this rationally designed precursor, a graphene-like N-doped hierarchical porous carbon array on a 3D metal substrate (NPC/Cu) is obtained by a green and one-step vacuum de-metal assisted carbonization process. In situ-produced low boiling-point zinc elements can be evaporated and recycled during this process. The unique architecture where an N-doped porous carbon array is grown on a 3D metal substrate favors the graphitization degree and areal capacities of carbon anodes. When NPC/Cu is applied as a self-standing and binder-free anode for potassium-ion batteries (KIBs) in various electrolytes, an eminent electrochemical performance with a high reversible capacity of 315 mA h g(-1) at 50 mA g(-1) after 500 cycles, a superior rate performance of 120 mA h g(-1) at 21C, and a relatively stable capacity of 129 mA h g(-1) at 2000 mA g(-1) after 20 000 cycles (corresponding to a capacity decay of only 0.0034% per cycle) can be obtained in a 5 M concentrated ether electrolyte. Furthermore, the superior electrochemical performance, outperforming that of most of the reported carbonaceous anodes for KIBs, can be attributed to the potassium storage mechanism dominated by capacitive-controlled behavior, proven by quantitative kinetics analysis. This work can shed some light on searching for carbon-based materials for KIBs and offer new insight to construct porous materials.