Improved graphene-based sodium-ion battery anodes using low surface area, low temperature reduced graphene oxide powders

Reduced graphene oxide (rGO) is a promising high-capacity anode material for sodium-ion batteries. However, in rGO-based electrodes, the typically high surface area of the rGO results from exfoliation during reduction. This, in turn, leads to excessive solid electrolyte interface formation yielding large irreversible capacities during initial cycles. To overcome this limitation, we report an approach to generate low surface area rGO powders through a combination of spray drying and slow thermal reduction to avoid excessive exfoliation. The performance of low surface area rGO electrodes, reduced at various temperatures (200–1000 °C) is compared to high surface area rGO electrodes. This comparison is used to decouple the effects of surface area and oxygen content on electrochemical performance. Low surface area powders, reduced at lower temperatures (400 °C) exhibited the best performance, with a desodiation capacity of 216 mAh g⁻¹ at 100 mA g⁻¹, and a capacity retention of 85 % (after 200 cycles). Moreover, the irreversible capacity loss was reduced by two- to three-fold compared to previous literature. While further improvements are necessary to make this system practical, these results highlight the need for improved granularization strategies that further reduce surface area, increase restacking order, and yield the optimal level of oxygen functionalization.