Sustainable porous carbon microspheres from calcium lignosulfonate: Tuning carbonization temperature to synergistically optimize porosity and electrochemical energy storage performance

Driven by the dual carbon goals and large-scale grid integration of renewable energy, developing electrode materials that integrate resource sustainability and high-efficiency energy storage has become a central focus in electrochemical energy storage. Lignin is an excellent precursor for low-cost carbon-based energy storage materials. However, lignin-derived carbon materials often face challenges in pore structure control and synergistic optimization of active site-conductivity performance, which restricts their practical applications. This study employs industrial-grade calcium lignosulfonate as a precursor and adopts a coupled process of “spray-drying with precisely controlled parameters followed by high-temperature carbonization for structural regulation”. This approach successfully produces lignin-derived porous carbon microspheres (CSL) with uniform morphology and controllable pore structures. To elucidate the structure-performance relationship between material structure and electrochemical properties during carbonization, the regulation mechanisms of CSL's microstructure, pore evolution, surface chemistry, and energy storage performance were systematically investigated at three carbonization temperatures (700, 800, and 900 °C). The study revealed that the 800 °C carbonization treatment (CSL-800) constructed a synergistic structure featuring “high-specific-surface-area hierarchical pores + suitable defect active sites + excellent conductivity”, exhibiting optimal energy storage characteristics. In a three-electrode system with 1 M KOH electrolyte, the CSL-800 electrode achieved a high specific capacitance of 345 F g −1 at a current density of 1 A g −1 . It maintained a capacitance retention of 58% when the current density was increased from 1 to 10 A g −1 , demonstrating good rate capability. When assembled into a symmetric supercapacitor, CSL-800 exhibited a remarkable 97.54% capacitance retention after 10,000 charge-discharge cycles under stringent conditions at 10 A g −1 . The device achieved an energy density of 17.13 Wh kg −1 at a power density of 270.4 W kg −1 . This study establishes quantitative relationships among carbonization temperature, structure, and properties, providing theoretical support for optimizing lignin-based carbon materials and promoting the high-value utilization of biomass resources.