An Ecofriendly Gel Polymer Electrolyte Based on Natural Lignocellulose with Ultrahigh Electrolyte Uptake and Excellent Ionic Conductivity for Alkaline Supercapacitors

In view of the global development and use of environmentally friendly energy materials and devices, exploring natural polymer-based gel polymer electrolyte (GPE) for preparing supercapacitors (SCs) is highly desirable. Here an earth-abundant, renewable, biodegradable natural lignocellulose (LC) membrane with 3D network porous structure is synthesized by a simple solution-casting method. The synthesized LC membrane possesses a good thermal stability of 270 °C, a high porosity of 86.2%, and reasonable mechanical property. LC membrane soaked in potassium hydroxide solution is first used as a GPE (LC-GPE) and exhibits an ultrahigh liquid electrolyte uptake of 948 wt % and an excellent ionic conductivity of 32.6 mS cm –1. The solid-state electric double layer capacitor (EDLC) assembled with the LC-GPE and activated carbon electrodes demonstrates a high specific capacitance of 120 F g–1 at 1 A g–1 with a rate capacity of only 8.4% capacitance loss as the current density increases from 1 to 10 A g–1, and a long cycling life of 10 000 cycles with 92.5% capacitance retention and nearly 100% coulomb efficiency. More importantly, the planar soft EDLC composing of LC-GPE and activated carbon electrodes is easily bent to 180° without breaking and still remains good electrochemical performance. Those results indicate that this kind of LC-GPE not only meets the green/sustainable demand but also retains good electrochemical performance of SCs. Therefore, the prepared LC-GPE is a potential candidate for assembling green and wearable/portable SCs.