Porous-carbon aerogels with tailored subnanopores 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 to carbon, increasing interlayer spacing or creating amorphous region in graphite have been investigated. Here, we studied the effect of subnanopores in a porous-carbon aerogel with a centered pore size distribution 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 subnanopores lead to substantially low barrier for K-ion transport and storage, with ultrasmall diffusion energy and negligible lattice change. Subnanopore 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.