10⁵ Cyclable Pseudocapacitive Na-Ion Storage of Hierarchically Structured Phosphorus-Incorporating Nanoporous Carbons in Organic Electrolytes

Despite the significant impact of sodium (Na) storage systems in terms of natural abundance and environmental friendliness, high-performance pseudocapacitive mterials in organic electrolytes remain challenging. Here, we demonstrate the pseudocapacitive Na-ion storage of hierarchically structured, phosphorus-incorporating steam-activated nanoporous carbons (P-aCNs) with improved rate and cyclic capabilities in organic electrolytes. The P-aCNs with a hierarchical honeycomb structure are derived from lignocellulosic biomass via a proposed synthetic process. The prominent pseudocapacitive behaviors of the P-containing groups in organic Na-ion electrolytes are confirmed by the surface area-independent and surface-confined capacitances, distinctive redox waves, and strong binding with Na-ions. In particular, the P-aCN demonstrates the cyclic stability of 96.0% over 100 000 cycles in the full cell, achieving a high capacitance of 265.43 F g^-1 and rate capability of 75%. These Na-ion pseudocapacitive features of P-aCNs arising from the hierarchical interconnected porosity and the redox-active P=O bonds are comprehensively investigated by experimental and computational analyses.