Curly hard carbon derived from pistachio shells as high-performance anode materials for sodium-ion batteries

Sodium-ion batteries (SIBs) have drawn more attention to serve as one of the promising energy storage devices owing to the abundance of sodium resources and similar characters with lithium element. Hard carbon materials derived from biomass or biomass waste have been considered to act as candidate anode materials for SIBs. In this paper, we have successfully prepared curly hard carbon materials using pistachio shells as biomass template via a two-step approach including hydrothermal treatment and following a pyrolysis process at various temperatures. Physical properties of pistachio shell-derived hard carbons (PSHCs) including microstructure, morphology and pore size distribution are evaluated by X-ray diffraction, Raman spectrum and N2 sorption analysis. The PSHCs carbonized at 1000 °C (PSHC-1000) with average micropores of 0.7398 nm and larger interlayer space of the (002) crystal plane deliver the highest reversible capacity of 317 mAh g−1 at 0.1C, also show the excellent long-term cycling and rate performances. Electrochemical impedance spectroscopy technology is introduced to study the kinetics parameters during the first sodiation process of PSHC-1000 electrode, and also to compare the resistance of the charge transfer process for all the PSHCs. Results exhibit PSHC-1000 electrode with the symmetry factor of 0.1352 has the smallest charge transfer resistance, leading to more easily transportation of electrons and ions. This work can provide a simple and green route for preparation of hard carbon materials derived from biomass waste with unique morphology and microstructure which can exhibit an excellent electrochemical performance.