An environmentally sustainable supercapacitor design combines the use of low‐cost alkali lignin as an active carbon‐based material and manganese dioxide nanoparticles to form lightweight and efficient electrodes.

Researchers from Texas A&M University and U.S. Lawrence Berkeley National Laboratory first treated lignin with a potassium permanganate disinfectant. High heat and pressure were then applied to initiate an oxidation reaction that breaks down the potassium permanganate and deposits manganese dioxide on lignin. After this mixture was used to coat an aluminum plate to form the electrode, the device was assembled by sandwiching a gel electrolyte between the lignin-manganese dioxide-aluminum electrode and another composed of aluminum and activated charcoal.

A higher surface packing density observed for the electrode with lignin relative to the device wth activated charcoal translates into a high energy density value. A literature-based comparison of performance with other advanced supercapacitor designs confirms that the lignin-manganese dioxide device was the top performer in terms of specific capacitance. At 40 mA/g current density, the peak value of areal specific capacitance achieved is 379 mF/cm2, or up to 900 times greater than that reported. The highest power and energy densities achieved were 355 W/kg and 6 Wh/kg, respectively.

The research published in Energy Storage demonstrated great potential to use alkali lignin as an active material to obtain high‐performance green electronics electrodes for supercapacitors. The sustainable design and fabrication process address the problem of achieving high specific capacitance and high electrode conductance at the same time for biomass‐derived electrodes.

Fabrication process of the lignin/manganese dioxide supercapacitor. Source: Swarn Jha et al.Fabrication process of the lignin/manganese dioxide supercapacitor. Source: Swarn Jha et al.

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