Bamboo-derived flake-layer hierarchically porous carbon coupling nano-Si@porous carbon for advanced high-performance Li-ion capacitor

Abstract

Lithium-ion capacitors (LICs) are increasingly being developed for energy storage as a consequence of their high power/energy density and ultra-long cycle lifetime. Herein, flake-layer hierarchically porous carbon (FPC) was obtained from bamboo liquid converted from bamboo powder using flake-layer Mg(OH)2 as template combined with KOH activation. Meanwhile, FPC-Si was obtained via loading nano-Si on the FPC surface through magnesiothermic reduction strategy. FPC has a high-specific surface area (SSA) of 1430.1 m2 g−1 and total pore volume of 2.84 cm3 g−1 with 90 % of mesopores. The high-SSA and mesopore volume contribute to superb capacitance and enhanced rate performance when used as the cathode in LIC. FPC-Si anode presents a rate capability of 720.5 mAh g−1 at 5 A g−1 with good cyclability. Therefore, the assembled LIC composed of FPC-Si anode and FPC cathode presents high energy/power density (179 Wh kg−1, 27.5 kW kg−1) and protracted lifetime of 8000 cycles (82.3 % capacitance retention). The current research indicates that the cathode requires not only high-SSA but also high mesopore volume. The mesopores as ions spreading highways can advance the ions transport and enhance the ions storage, causing high capacity and fine rate performance. The scalable methods offer a novel pathway for synthesizing biochar-based high-performance LICs.