Gelatin‐Derived Hard Carbon Achieves Effective Control of Microstructure toward Fast and Durable Sodium Storage

Abstract Hard carbon (HC) is the most promising anode material for commercial sodium‐ion batteries (SIBs). However, the complex composition of biomass‐derived HC precursors often requires great efforts to impart controlled structures and desired performance. Effective control of the microstructure is still highly desirable for HC anodes. Herein, gelatin is employed as a precursor to regulating the HC structure, including defect concentration, average interlayer spacing, and the pore structure. This provides insights into systematic improvement strategies of sodium‐ion transfer kinetics toward fast and durable sodium storage. Gelatin, as a bio‐precursor, contains abundant ─COOH and ─NH₂ groups that promote metal cross‐linking and facilitate the control of the structural evolution of HC. By reasonably controlling the defect content and pore structure, the electrochemical performance can be tailored with enhanced kinetics of sodium‐ion storage. The optimized HC shows a high reversible capacity of 400 mAh g⁻¹, outstanding rate performance, and structural stability over 10 000 cycles with a capacity retention of 77.8%. This work leads to the development of high‐performance HC materials from biomass, which is essential for advancements in battery technology.