Biomass-derived N–P double-doped porous carbon spheres and their lithium storage mechanism

Biomass-derived carbon materials are widely studied and used in energy storage applications. Unfortunately, the disadvantages such as poor capacity and rate performance limit their development. Heteroatom doping can effectively improve the electrochemical properties of biomass-derived carbon materials. In this work, we designed and prepared environmentally friendly and cost-effective biomass (lotus root)-derived nitrogen-phosphorus (N–P) double-doped porous carbon spheres. When used as an anode material for a lithium-ion battery, the porous carbon spheres exhibited excellent stability performance (a reversible capacity of 739.6 mAh g−1 after 100 cycles at 0.1 A g−1 and 599.16 mAh g−1 after 215 cycles at 0.5 A g−1, respectively) and superior rate performance (a capacity of 187.22 mAh g−1 at 10 A g−1) due to the synergy of the heteroatomic doping and the layered porous spherical structure. The novel biomass-derived material based on N–P double-doped porous carbon spheres can serve as a cost-effective option for anode materials of lithium-ion batteries. Besides, an "adsorption-pore filling/intercalation" hybrid mechanism is proposed to understand the possible principle for superior lithium storage performance based on CV, ex-situ Raman and XRD results.