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Hard carbons (HCs) prepared from renewable precursors are promising cost-effective electrodematerial candidates for the application in Na-ion battery. Usually these materials are derived from cellulose. Here, however, we demonstrate that other polysaccharides, such as chitin and chitosan, can be as well up-and-coming parent materials of HCs. Despite structural similarities, thermal decomposition of these two biopolymers proceeds differently, contributing to the discrepancies in physicochemical properties of resulting HCs. Although chitin-and chitosan-derived HCs have comparable d-spacings and crystallite sizes, solid state pyrolysis of the former biopolymer leads to micro-mesoporous material with significant specific surface area, while that of chitosan yields non-porous carbon. Despite that, both materials deliver similar initial specific charge of 280 mAh g-1 (at C/10 rate) and their electrochemical performance starts to diverge only upon longer cycling at higher rate. With time, inorganic contaminants present in chitosan-derived HC presumably delay the diffusion of Na-ions to and within the electrode, and slow down the rate of electrochemical reactions, eventually triggering polarization build-up. Further optimization of the chitosan-derived HC through acid-treatment enables unblocking some of the micropores and increasing the carbon content in this material, therefore enhancing its active surface area and suppressing continuous fading of the specific charge.

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