Dense SnS2 nanoplates vertically anchored on a graphene aerogel for pseudocapacitive sodium storage

Abstract

Two-dimensional (2D) heterostructures that combine advantages of individual components and overcome the associated drawbacks show great prospects for electrochemical energy storage. However, the prevailing layer-by-layer horizontal 2D stacks with tortuous and lengthy ion transport paths dramatically slow the reaction kinetics. Herein, we reported a 2D heterostructure with dense SnS₂ nanoplates uniformly and vertically anchored on a graphene aerogel (SnS₂@GA) for high-performance sodium-ion batteries. A SnS₂ loading of 68 wt% without aggregation was achieved in the vertically aligned heterostructure via a controlled self-assembly process at low temperature, followed by an optimized in situ sulfidation treatment. The GA skeleton with interconnected pores effectively facilitates electron transfer, improves electrolyte wettability, and accommodates the volume expansion of SnS₂ upon sodiation. The SnS₂ is extensively exposed because of its 2D morphology and ion-accessible vertical channels. By synergizing these characteristics with the robust heterointerface, the composite exhibits boosted electrochemical reaction kinetics based on the pseudocapacitance-dominated charge storage mechanism and enhanced structural stability. As a result, the SnS₂@GA anode delivers a high reversible capacity of 690 mA h g⁻¹ at 0.2 A g⁻¹, superior rate performance (492 mA h g⁻¹ at 4 A g⁻¹) and long cycle life with 83% capacity retention after 1000 cycles.