Abstract
The pursuit of more efficient carbon-based anodes for sodium-ion batteries (SIBs) prepared from facile and economical methods is a very important endeavor. Based on the crystallinity difference within carbon materials, herein, a low-temperature selective burning method is developed for preparing oxygen and nitrogen codoped holey graphene aerogel as additive-free anode for SIBs. By selective burning of a mixture of graphene and low-crystallinity carbon at 450 degrees C in air, an elastic porous graphene monolith with abundant holes on graphene sheets and optimized crystallinity is obtained. These structural characteristics lead to an additive-free electrode with fast charge (ions and electrons) transfer and more abundant Na+ storage active sites. Moreover, the heteroatom oxygen/nitrogen doping favors large interlayer distance for rapid Na+ insertion/extraction and provides more active sites for high capacitive contribution. The optimized sample exhibits superior sodium-ion storage capability, i.e., high specific capacity (446 mAh g(-1) at 0.1 A g(-1)), ultrahigh rate capability (189 mAh g(-1) at 10 A g(-1)), and long cycle life (81.0% capacity retention after 2000 cycles at 5 A g(-1)). This facile and economic strategy might be extended to fabricating other superior carbon-based energy storage materials.