Tailoring 2D Heteroatom-Doped Carbon Nanosheets with Dominated Pseudocapacitive Behaviors Enabling Fast and High-Performance Sodium Storage

2D carbon nanosheets are considered to be promising candidates for use as sodium ion battery (SIB) anodes due to their large specific surface area and excellent electronic conductivity. However, their applications are hampered by inferior cycling performance, insufficient storage capacity, and high cost. N, B co-doping carbon nanosheets (NBTs) are synthesized using biomass-based gelatin as carbon precursor and boric acid as template, and demonstrate their great potential as high-performance SIB anodes in practical applications. The synergistic effect of heteroatom doping and ultrathin 2D structure provides the NBTs with abundant defects, active sites, and short ion/electron transfer distance, which favors and improves the storage capabilities and rate performances. The optimized NBTs present a remarkable cyclability and superb rate capability (309 mAh g(-1) at 0.2 A g(-1) for 200 cycles; 225 mAh g(-1) at 1 A g(-1) for 2000 cycles). Meanwhile, the Na storage mechanism is proved to be a pseudocapacitive-controlled process, which accounts for the fast charge/discharge behaviors. This work demonstrates an effective template method to produce 2D heteroatoms co-doping carbon nanosheets to achieve excellent Na storage performances.