Highly compressible lignin hydrogel electrolytes via double-crosslinked strategy for superior foldable supercapacitors

Abstract

Employing renewable, earth-abundant, low-cost natural materials to fabricate highly compressible, foldable and high-performance energy storage devices can greatly promote the sustainable development and wide applications of compression-resistant electronics. Herein, a hybrid double-crosslinked (DC) lignin hydrogel electrolyte with superior compressibility is firstly developed by postformation of lignin hydrophobic aggregation via simple treatment of single chemical crosslinked (SC) lignin hydrogel using H2SO4 solution. This synthetic DC lignin hydrogel exhibits significant improvement of mechanical strength, excellent shape recovery property and high ionic conductivity (0.08 S cm−1). The compression stress at fracture is 4.74 MPa, which is 40 times compared to that of SC lignin hydrogel. Exploiting this DC lignin hydrogel as electrolyte and PANI deposited carbon cloth as electrode, a flexible supercapacitor is constructed, which possesses high specific capacitance of 190 F g−1 and excellent energy density. Remarkably, this supercapacitor retains high specific capacitance after 500 cycle numbers of 180° bending, or 80% compression strain. Thus, this presented work opens a new avenue of lignin as a prominent candidate for potential application in compression-resistant and foldable energy storage devices.