Construction of hierarchical porous carbon based on vacuum drying process of lignin hydrogel for supercapacitors

In this work, a novel preparation strategy of lignin-derived hierarchical porous carbon is proposed. This strategy is based on the mesoporous structure-rich precursor obtained by drying lignin hydrogel, combined with the subsequent one-step carbonization-activation process, while regulating the derived carbon hierarchical porous structure by controlling the carbonization temperature. The research results show that the derived carbon obtained from the vacuum-dried lignin hydrogel precursor at a carbonization temperature of 800 °C has a hierarchical porous structure favorable for electrolyte diffusion and a suitable graphitization degree. Therefore, the derived carbon exhibits relatively ideal electrochemical performance, typically, it possesses the high specific capacitance (310 F g−1 at 0.5 A g−1) and rate performance (65.2% capacitance retention at 20 A g−1) in three-electrode systems. Simultaneously, the coin-type symmetric supercapacitors (with an ionic liquid electrolyte) based on the derived carbon also exhibit acceptable energy density (63.4 Wh kg−1 at 748 W kg−1) and cycling stability (8% loss over 5000 cycles). The preparation method of lignin-derived carbon proposed in this study can bring new ideas for the preparation of such carbon materials.