Tailoring natural anthracite carbon materials towards considerable electrochemical properties with exploration of ester/ether-based electrolyte

Abstract

Carbon, as a promising commercial material, has captured a lot of attention for use in sodium-ion batteries (SIBs). But, their energy-storage mechanism is still confusing, especially the effect of an ester/ether-based electrolyte. Attractive because of its rich resources and low cost, natural coal has been regarded as an important candidate. Through optimization of pyrolysis temperature, a series of significant traits towards improvements in energy-storage ability were tailored, including graphitization degree, interlayer distance and hetero-atoms (oxygen, sulfur). As an SIB anode, the optimized sample delivers a capacity of 252 mA h g⁻¹ in an ester-based electrolyte and 325 mA h g⁻¹ in ether-based systems. Through detailed analysis, it could be confirmed that the relatively small energy of dissolution would induce an enhancement in adsorption behavior. The flexible Na-solvation shells weaken the combining energy in a graphitized interlayer and compact ring-structure, resulting in improved capacity. More significantly, with the assistance of an ether-based solvation shell, the strong force between quasi-metallic Na and carbon atoms is reduced, facilitating the stabilization of the low-voltage capacity contribution even at high current density. Given this, the results are anticipated to provide an in-depth understanding of Na-ion diffusion with a solvation shell, and an effective strategy for natural coal-based carbon materials.