Ion- and air-tailored micro-honeycomb structures for superior Na-ion storage in coir-derived hard carbon

Bio-carbon is currently being widely explored for use in Na-ion battery anodes due to its abundance and facile fabrication process. However, the desire for higher energy density and reduced cost still calls for optimized precursors, together with suitable post-treatment. To that end, we present here the fabrication of typical carbon, featuring rich nanopore-decorated side-by-side holes, obtained from natural coir via a simple secondary air-activation method. As a result, a reversible capacity of 408 mA h g(-1) at 20 mA g(-1) is achieved. Attractively, even at a current density of 500 mA g(-1), a specific capacity of 181 mA h g(-1) and remarkable capacity retention of 93% after 500 cycles still can be achieved, thus highlighting the material's great potential for assisting the future realization of commercialized SIBs.