The high value-added utilization of traditional coal resources is one of the important ways to achieve the strategic goals of carbon peaking and carbon neutrality. Simultaneously, coal-based carbon materials, noted for their cost-effectiveness, superior conductivity, and inherent stability, are emerging as promising candidates for next-generation capacitor technologies. This research presents a series of coal-derived porous carbon by pyrolysis using low rank lignite as raw material and KOH as activator, which are employed in symmetrical supercapacitors filled with liquid electrolytes. The physicochemical properties of the as-prepared electrode materials are characterized by means of scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and their supercapacitive performance are evaluated through cyclic voltammetry and galvanostatic charge–discharge tests. The coal-based porous carbon electrode prepared at an activation temperature of 800 °C (KOH-800) exhibits a specific capacitance of 142.2 F g− 1 at a current density of 1 A g− 1, and retaining 80% of its capacitance (114.0 F g− 1) even at 10 A g− 1. The fabricated liquid supercapacitor displays a power density of 999.8 W kg− 1 and an energy density of 19.4 Wh kg− 1 at a current density of 1 A g− 1. Undergoing 10,000 cycles at 2 A g− 1, the supercapacitor maintains nearperfect capacitance retention and coulombic efficiency close to 100%, demonstrating its excellent durability and stability for supercapacitor applications.

High-performance symmetrical supercapacitor based on coal-derived porous carbon materials prepared via pyrolysis and KOH activation
    Abstract
    1 Introduction
    2 Experimental
        2.1 Chemicals and solutions
        2.2 Preparation of coal-based porous carbon
        2.3 Preparation of electrode
        2.4 Assemble symmetrical supercapacitors
        2.5 Physical and chemical characterizations
        2.6 Electrochemical measurements
    3 Results and discussion
    4 Conclusion
    Acknowledgements 
    References

• Fuyang Ren(Research Group of Functional Materials for Electrochemical Energy Conversion, School of Chemical Engineering, University of Science and Technology Liaoning, Qianshan Middle Road 185, Anshan, Liaoning, China, Research Institute of Clean Energy and Fuel Chemistry, School of Chemical Engineering, University of Science and Technology Liaoning, Qianshan Middle Road 185, Anshan, China, Key Laboratory for Advanced Coal and Coking Technology of Liaoning Province, School of Chemical Engineering, University of Science and Technology Liaoning, Qianshan Middle Road 185, Anshan, China)
• Hongze Zhu(Research Group of Functional Materials for Electrochemical Energy Conversion, School of Chemical Engineering, University of Science and Technology Liaoning, Qianshan Middle Road 185, Anshan, Liaoning, China, Research Institute of Clean Energy and Fuel Chemistry, School of Chemical Engineering, University of Science and Technology Liaoning, Qianshan Middle Road 185, Anshan, China, Key Laboratory for Advanced Coal and Coking Technology of Liaoning Province, School of Chemical Engineering, University of Science and Technology Liaoning, Qianshan Middle Road 185, Anshan, China)
• Haoran Pan(Research Group of Functional Materials for Electrochemical Energy Conversion, School of Chemical Engineering, University of Science and Technology Liaoning, Qianshan Middle Road 185, Anshan, Liaoning, China, Research Institute of Clean Energy and Fuel Chemistry, School of Chemical Engineering, University of Science and Technology Liaoning, Qianshan Middle Road 185, Anshan, China, Key Laboratory for Advanced Coal and Coking Technology of Liaoning Province, School of Chemical Engineering, University of Science and Technology Liaoning, Qianshan Middle Road 185, Anshan, China)
• Xingxing Chen(Research Group of Functional Materials for Electrochemical Energy Conversion, School of Chemical Engineering, University of Science and Technology Liaoning, Qianshan Middle Road 185, Anshan, Liaoning, China, Research Institute of Clean Energy and Fuel Chemistry, School of Chemical Engineering, University of Science and Technology Liaoning, Qianshan Middle Road 185, Anshan, China, Key Laboratory for Advanced Coal and Coking Technology of Liaoning Province, School of Chemical Engineering, University of Science and Technology Liaoning, Qianshan Middle Road 185, Anshan, China) Corresponding author
• Lu Tian(Research Institute of Clean Energy and Fuel Chemistry, School of Chemical Engineering, University of Science and Technology Liaoning, Qianshan Middle Road 185, Anshan, China, Key Laboratory for Advanced Coal and Coking Technology of Liaoning Province, School of Chemical Engineering, University of Science and Technology Liaoning, Qianshan Middle Road 185, Anshan, China)
• Jinxiao Dou(Research Institute of Clean Energy and Fuel Chemistry, School of Chemical Engineering, University of Science and Technology Liaoning, Qianshan Middle Road 185, Anshan, China, Key Laboratory for Advanced Coal and Coking Technology of Liaoning Province, School of Chemical Engineering, University of Science and Technology Liaoning, Qianshan Middle Road 185, Anshan, China)
• Jianglong Yu(Research Institute of Clean Energy and Fuel Chemistry, School of Chemical Engineering, University of Science and Technology Liaoning, Qianshan Middle Road 185, Anshan, China, Suzhou Industrial Park Monash Research Institute of Science and Technology, Suzhou, China, Key Laboratory for Advanced Coal and Coking Technology of Liaoning Province, School of Chemical Engineering, University of Science and Technology Liaoning, Qianshan Middle Road 185, Anshan, China)
• Tao Wang(State Key Laboratory of Chemistry and Utilization of Carbon Based Energy Resources, College of Chemistry, Xinjiang University, Urumqi, Xinjiang, China)
• Dongling Wu(State Key Laboratory of Chemistry and Utilization of Carbon Based Energy Resources, College of Chemistry, Xinjiang University, Urumqi, Xinjiang, China)