High Cycling Stability Sisal-Fiber-Derived Carbon Anode Materials with a Spiky Nanostructure for Sodium-Ion Batteries

Biomass hard carbon is commonly used as an anode material for sodium-ion batteries (SIBs); however, the lower cycling stability and capacity retention limit its large-scale application. In this study, polyaniline-modified spherical sisal fiber carbon (PAN@SSFC) was prepared by a surface coating method using sisal fiber as a precursor. And the effects of morphological conditions on cycling stability and capacity retention were also explored. The prepared PAN@SSFC composites have unique nanostructured protrusions, large crystal plane spacing, and moderate specific surface area, which facilitates the rapid transfer of sodium ions and large ion adsorption. Compared to SSFC, the PAN@SSFC shows a much better electrochemical performance with a reversible specific capacity up to 239 mAh g^–1 after 1000 long-term cycles at a current density of 0.1 A g^–1 and 77.4% high capacity retention. Through analysis of the capacity changes in the discharge curves, it can be explained that the sodium storage behavior of PAN@SSFC follows an “adsorption–insertion/filling” mechanism. This study paves the way to develop anode materials for sodium-ion batteries with outstanding cycling stability.