Development of Biomass‐Derived Hard Carbon for Sodium‐Ion Batteries: Optimizing Microstructure and Electrochemical Performance

The development of sodium‐ion batteries (SIBs) as a sustainable alternative to lithium‐ion batteries has garnered considerable attention, mainly due to the abundant supply and economic viability of sodium sources. In this study, we present the synthesis and characterization of hard carbon (HC) derived from biomass coconut shells, with the objective of optimizing its performance as an anode material for SIBs. A series of HC samples (denoted as YHC‐T) were prepared via carbonization at 1000°C, 1100°C, 1200°C, 1300°C, and 1400°C. The YHC‐1200 sample, exhibiting an expanded interlayer spacing of approximately 0.384 nm, demonstrated superior sodium storage properties, achieving a high reversible specific capacity of 350 mA h g −1 and an initial Coulombic efficiency of 92.9% at a current density of 0.1 A g −1 . Moreover, YHC‐1200 exhibited excellent cycling stability, retaining a capacity of 198 mAh g −1 after 1000 cycles at 1 A g −1 .