Porous-Carbon Aerogels with Tailored Sub-Nanopores for High Cycling Stability and Rate Capability Potassium-Ion Battery Anodes.

Developing advanced electrode materials for potassium-ion batteries (PIBs) is an emerging research area in recent years; so far, several strategies such as heteroatom doping into carbon, increasing interlayer spacing, or creating amorphous region in graphite have been investigated. Here, we studied the effect of sub-nanopores in a porous-carbon aerogel with a pore size distribution centered at around 0.8 nm and achieved outstanding PIB performance including long cycling stability (particularly at small current densities for prolonged charge/discharge period) and high rate capability with enhanced retentions. Mechanism studies reveal very high contribution from surface capacitive potassium (K)-ion storage (more than 90%) to the total capacity, and theoretical calculations show that 0.8 nm sub-nanopores lead to substantially low barrier for K-ion transport and storage, with ultrasmall diffusion energy and negligible lattice change. Sub-nanopore engineering, as demonstrated here, may be adopted to develop highly efficient and stable porous-carbon-based structures for applications in advanced energy storage systems and electrochemical catalysis.