Self-doped porous sorghum husk-derived carbon as anode for high performance sodium-ion batteries at low temperatures

Hard carbon (HC) is widely regarded as one of the most promising anode materials for sodium-ion batteries (SIBs), but it still faces several key challenges, including low capacity, poor rate capability, and low initial Coulombic efficiency. To address these issues, in current study, naturally N-doped biomass waste sorghum husk is utilized as a high-quality carbon source to fabricate porous HC materials as anodes for SIBs. This self-doped strategy facilitates electron/ion transport, enhances electrolyte wettability, and significantly improves sodium storage performance, particularly at low temperatures. The synthesized anode electrodes exhibit outstanding performance at −20 °C with a high specific capacity of 322 mA h g⁻¹ at 50 mA g⁻¹ and an initial Coulombic efficiency of 91 %. The abundant porous structure of the material ensures long-term cycling stability, maintaining a capacity of over 150 mA h g⁻¹ after 600 cycles at 1 A g⁻¹. Additionally, the cyclic voltammetry (CV) test results and galvanostatic intermittent titration technique (GITT) confirm that the sodium ion transport is primarily diffusion-controlled, indicating excellent rate capability.