▎ 摘　　要

Graphene is a promising material for energy conversion and storage applications. However, the production of graphene is limited by their complicated and high-cost processing. Here we have shown that graphene could be synthesized by a simple magnesiothermic reduction reaction from eggshell, a sustainable precursor of bio-calcite produced at a rate of tens of millions of tons annually. Due to their intrinsic structure (e.g., porous structure, high crystallinity), the synthesized graphene could be used as a promising electrodematerial with high-capacity, high-rate capability and long cyclability. At a specific current of 100 mA g(-1), they exhibited a reversible capacity of 678.4mA h g(-1). Even at an extremely high discharge/charge current of 20 A g(-1) (about 27 s to full charge), it retained a capacity of 149.9mA h g(-1) after 1000 charge/discharge cycles. At such rate, it could exhibit a specific energy density of 253.9Wh kg(-1) and a specific power density of 32.6 kW kg(-1). The results suggested that bio-calcite derived from eggshell could be a sustainable and ample resource to synthesize graphene for energy storage.