N-doped graphene wrapped SnP2O7 for sodium storage with high pseudocapacitance contribution

Abstract

Developing advanced electrode materials for sodium storage is hindered by the sluggish Na+ diffusion kinetics and terrible structure damage. Pseudocapacitance is believed as a promising solution to supply fast, large and stable sodium storage via surface-controlled behavior. Herein, a hybrid material approach is implemented to pursue pseudocapacitance contributed sodium storage by constructing nitrogen-doped graphene nanosheets packed SnP2O7 particles. The rationally selected components and specific structure also provide advantages for electrolyte penetration and Na+ diffusion, fast charge transfer, and structure stability. Hence, the developed composite delivers anode performances for sodium storage with high capacity of 423 mAh g−1 at 0.1 A g−1, good rate performance of 206 mAh g−1 at 2 A g−1, and stable cyclic property (retention rate of ∼95% after 1000 cycles at 1 A g−1). Pseudocapacitance contribution is vital for the composite electrode, especially at high rate, dedicating a percentage as high as 89% to the total capacity at a sweep rate of 1 mV s−1. This work demonstrates the promising potential of compositing graphene and conversion reaction material as pseudocapacitive electrode for sodium ion batteries.