Facile Fabrication of Co9S8 Embedded in a Boron and Nitrogen Co-Doped Carbon Matrix as Sodium-Ion Battery Anode

A unique composite (Co9S8@BNC) consisting of cobalt sulfide (Co9S8) embedded in a boron and nitrogen co-doped carbon matrix (BNC) is successfully synthesized as anode material for sodium-ion batteries (SIBs). The BNC matrix was demonstrated to improve the electronic and ion diffusion speed, as well as help buffer the dramatic volumetric expansion during the repeated cycling processes. Benefited from the advantages of BNC matrix, Co9S8@BNC delivered a high initial reversible capacity of 494mAhg(-1) at 100mAg(-1) and could remain 388mAhg(-1) after 100 cycles. Apart from that, it exhibited an excellent rate performance (258mAhg(-1) at the current density of 2Ag(-1)) and was demonstrated as pseudocapacitive charge storage. As a consequence, the as-prepared Co9S8@BNC possesses an exceptional electrochemical performance and could be utilized as a potential anode material candidate for SIBs.