Preparation of lignite-based porous carbon/CoNi₂S₄ composite materials and their capacitance performance

A lignite-based porous carbon was prepared by KOH solution extraction and subsequently by an activation of the extractant with Baoqing lignite as the raw material, and the composite capacitive materials combining the porous carbon with CoNi₂S₄ were fabricated by a facile hydrothermal method. The effect of different carbon material ratios on the electrochemical performance of lignite-based porous carbon/CoNi₂S₄ composites was investigated. The results indicate that too high or too low carbon content is not conducive to an improvement in the specific capacitance of the composites, while the lignite-based porous carbon/CoNi₂S₄ composites with 37% of carbon have higher specific capacitance and better cycling performance. The specific capacitance of the composites is as high as 1318.2 F/g at a current density of 4 A/g, and the capacitance retention is 80.9% after 4000 cycles.