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Facile synthesis of high performance hard carbon anode materials for sodium ion batteries

A highly reversible, resource-abundant and low-cost anode is indispensable to the future success of sodium ion batteries (SIBs) in large-scale energy storage application. In this work, we report the facile synthesis of a biomass-derived hard carbon for SIBs by one-step pyrolysis of shaddock peel under an inert atmosphere without activation or any further treatments. The pyrolytic carbon shows very high reversible sodium storage capacities up to 430.5 mA h g−1 at a current density of 30 mA g−1 and superior cycling stability with only 2.5% capacity loss over 200 charge–discharge cycles. The high capacity and excellent cycle performance, combined with the facile synthesis procedure make it a promising anode material for practical SIBs. The good Na-ion storage property of the shaddock peel-derived pyrolytic carbon is attributed to its unique honeycomb-like morphology with a shortened distance for Na-ion diffusion, and the large interlayer distance which is available for sodium insertion/extraction.