An integrated strategy based on Schiff base reactions to construct unique two-dimensional nanostructures for intrinsic pseudocapacitive sodium/lithium storage

Abstract

Combining electrode materials with low-dimensional carbonaceous materials such as graphene is an effective way to improve the electrochemical performance of sodium/lithium-ion batteries (SIBs/LIBs). A common drawback of these recombinant hybrids is the weak interaction between the active component and graphene, resulting in poor structural stability and high resistance to diffusion of Na+/Li+ and electrons diffusing between phase boundaries during charging and discharging, thus leading to capacity decay and low rate capability of these hybrids. Here, a facile integrated construction strategy based on Schiff base reactions is developed to build a nitrogen and sulfur co-doped flexible lotus-leaf-like carbon and FeS nanosheets (FeS@N,S-CNSs). This structure takes full advantage of the high conductivity and mechanical flexibility of carbon nanosheets, and the high theoretical capacity of FeS. Together with the co-doping effects, the nanoscale size of FeS, and the robust connection between the in-situ generated FeS nanocrystals and carbon nanosheets, the FeS@N,S-CNSs outputs excellent electrochemical performance in both of SIBs and LIBs. Impressively, experimental results and Density functional theory (DFT) calculations indicate that the charging/discharging process is essentially dominated by pseudocapacitive behavior, this intrinsic feature gives FeS@N,S-CNSs electrode exceptional rate capability (∼50% capacity retention even at 100 A g−1 in SIBs).