A simple and recyclable molten-salt route to prepare superthin biocarbon sheets based on the high water-absorbent agaric for efficient lithium storage

Due to its sustainability, biomass materials shows great potential in replacing mineral carbon source to fabricate high-energy electrode materials, and efficient routes have been explored to synthesize and regulate biomass-derived carbonaceous materials with rational structures to enable their applications. Herein, a simple and recyclable molten-salt route is used to synthesize porous ultrathin biocarbon nanosheets from biomass (agaric). Due to the excellent adsorption ability of agaric for molten-salt ions, the interior and exterior of the agaric was fully exposed to the molten-salts, the fluidity and thermal motion of the high-temperature ionic solution promoted the complete exfoliation of biomass. The obtained superthin porous 2D carbon nanosheets provided more active sites and shortened the diffusion distance for lithium ion insertion/deinsertion, and formed a continuous conducting network for electron transport. Consequently, when used as the anodic material for lithium storage, the electrode displayed a higher specific capacity (∼795 mAh g−1 at 0.1 A g−1), outstanding rate performance (∼382 and ∼331 mAh g−1 at 5 and 10 A g−1), and superior cyclic stability (no capacity decay after 1000 cycles at 1 A g−1). Therefore, the preparation of sustainable biocarbon materials by the recyclable, molten-salt-assisted method described in this paper will enable the practical application of such materials in various energy storage devices.