C14H6O4Na2/graphene composite as a high performance sodium storage cathode

Quinone molecules hold the promise as electrodes for sodium ion batteries (SIBs). Made of earth abundant elements, these organic materials offer rapid multi-electron redox reaction at high theoretical specific capacities. However, they often display poor cycle life and low rate of performance due to a low electrical conductivity and a high solubility in an organic electrolyte. In this work, we report a 1,5-dihydroxy anthraquinone sodium salt (DHAQNa) synthesized by using simple neutralization and its composite with graphene (DHAQNa/G) prepared through a simple ball-milling and dispersed-deposition process. Compared with DHAQNa, DHAQNa/G exhibit higher capacity (176 mAh g−1 vs. 159 mAh g−1) and better cycling performance (~151 mAh g−1 vs ~90 mAh g−1 after 100 cycles at 0.1C), which are attributed to the suppressed dissolution and the enhanced electrical conductivity owing to the formation of oxygen‑sodium bonds and the introduction of graphene, respectively. Also, the excellent electrical conductivity of DHAQNa/G is confirmed by density of states calculations. The strategy demonstrated here should be widely applicable to other organic electrode materials.