Biomimetic N-doped sea-urchin-structured porous carbon for the anode material of high-energy-density potassium-ion batteries

Abstract

Sea urchin is one of the oldest echinoderms in the ocean, because its osmotic effect of the cell membranes to sodium/potassium seawater and a porous spinous structure like a hydraulic pump. Herein, inspired by the structure of sea urchins and their ability to absorb and transport K+, we developed N-doped sea-urchin-structured porous carbon (N-SPC) with porous siphon effect and enhanced kinetics, and successfully applied them to advance potassium-ion batteries (KIBs). The biomimetic N-SPC possess high specific surface area, hierarchical micro/mesopores, moderate N-doped defect sites, and suitable K+ diffusion barrier energy, hence contributing to outstanding cyclability (296 mAh•g−1 at 1 A•g−1 after 2000 cycles) and excellent rate performance (116 mAh•g−1 at 20 A•g−1) for KIBs. The density functional theory (DFT) theoretical investigation further confirms that the boosted potassium storage performance of the N-SPC benefits from the plentiful N-doped active sites and fast reaction kinetics after the optimized N-doping. More impressively, the N-SPC//Prussian-blue full cells could exhibit high discharge specific capacity of 113 mAh•g−1 at about 0.47 A•g−1 after 100 cycles. The rational construction of sea-urchin-structured carbon in this work guides the KIBs to a more rapid development and application direction.