Biomass activated carbon (AC), produced from the pyrolysis of biomass waste feedstock (wood, agricultural residues, etc.) has been studied as low cost Electrochemical Double Layer Capacitor (EDLC) electrodes. Their parent biomass materials also lead biomass ACs with different natural porous templates which can be further tuned or modified via chemical activation techniques. We have investigated several waste biomass ACs ranging from corn cobs, pine cones, to chitosan and found that, while all inherited porous structures from nature, they displayed quite different surface chemical compositions and pore structures. For example, the surfaces area of these biomass AC were in around 570 m²/g, 2400 m²/g and 3300 m²/g, respectively. These differences, especially in surface area, morphology and pore size distribution, have direct impact on the electrochemical performance of these biomass ACs in both liquid and solid electrolytes. Among the three biomass materials, chitosan-based carbon has demonstrated a high level of hierarchical meso-pore structure and the highest specific energy density.

Solid-state supercapacitors, enabled by polymer electrolytes, are ideal solutions for future energy storage applications that require high performance, safe operation, light-weight, thin and flexible form factors. We have developed a series of aqueous-based polymer electrolytes that are proton-conducting, hydroxide ion-conducting or neutral salt ion-conducting to match various cell chemistries. Many electrolytes exhibited ionic conductivities >10^-2mS/cm and maintained stable performance under ambient conditions (i.e. room temperature and 45% relative humidity).

In this talk, we will present the development of solid EDLC devices leveraging biomass ACs and aqueous based polymer electrolytes. The performance of solid EDLC devices using chitosan AC carbon and polymer electrolyte containing Li₂SO₄ will be compared with their liquid counterpart (Fig. 1) as well as with the commercial baselines.