Abstract
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•CuCl2 activation mechanism is elucidated.•Lignin-derived porous carbon with high specific surface area.•Lignin-derived porous carbon with high yields up to 49.4%.•High-voltage electrochemical capacitors are fabricated.
The high energy storage cost is a crucial factor limiting the wide application of electrochemical capacitors. Herein, we proposed a comprehensive strategy to reduce the cost of electrochemical capacitors with aqueous electrolytes, i.e., reducing the cost of electrode materials and increasing the energy density of electrochemical capacitors. Low-cost lignin-derived porous carbon electrode materials with high specific surface area and hierarchical porous structure were prepared by CuCl2 activation. The CuCl2 activation agent was recycled and thus can be reused. What is more, we proposed that the mechanism of CuCl2 activation is a solid-phase reaction in which the chloride ions in copper chloride deprive the hydrogen atoms in lignin, resulting in the loss of hydrogen atoms and the formation of pores. High energy density C//C symmetric electrochemical capacitors, Zn//C and Pb//C asymmetric electrochemical capacitors based on lignin-derived porous carbon were fabricated using sulfate electrolytes which endow high working voltage window. This work provides a comprehensive strategy for designing electrochemical capacitors with high energy densities and low cost of energy storage, which is expected to promote the industrial application of electrochemical capacitors with aqueous electrolytes.