Biomass-Derived Carbon Electrodes with Optimized Defects and Porosity via Regulated Carbonization Temperature for Supercapacitors

Biomass-derived carbons hold substantial promise for sustainable electrochemical energy storage due to their low cost, wide availability, and intrinsic heteroatom- and mineral-rich nature. However, the fundamental influence of carbonization temperature on the structural evolution of non-activated biomass-derived carbons remains insufficiently understood. In this work, corn straw-derived carbon (CS) is produced without any chemical additives to isolate the intrinsic effects of carbonization temperature on its physicochemical properties. Systematic temperature variation from 600 to 1000°C reveals pronounced changes in micro-morphology, pore development, defect density, and the ordering of the carbon matrix, all strongly governed by the inherent mineral content of corn straw. Electrochemical evaluation in alkaline electrolyte demonstrates that CS-800 delivers the highest specific capacitance of 53.8 F g⁻ ¹ at 1 A g⁻ ¹ in a three-electrode configuration and maintains favorable rate capability in a symmetric supercapacitor device. The symmetric coin cell supercapacitor device assembled with CS-800 as the electrodes achieved an energy density of 3.64/5.8 Wh kg⁻ ¹ and power density 5200/750 W kg⁻ ¹ , along with remarkable cycling stability over 30000 cycles with negligible capacitance loss. Overall, this study provides mechanistic insight into temperature-driven structural evolution in non-activated biomass carbons, offering a baseline understanding that can guide rational design and future activation strategies for high-performance, sustainable carbon electrodes.