Lignin-containing hydrogel matrices with enhanced adhesion and toughness for all-hydrogel supercapacitors

Flexible supercapacitors are promising energy storage devices benefitting from their portability and long cycle life. However, the weak interfacial adhesion between contiguous layers of flexible supercapacitors limits their practical applications. Here, a hydrogel matrix by integrating Ag-Lignin nanoparticles into polyacrylamide network is reported. Due to the unique interwoven-microfibrils structure and non-covalent interactions, the obtained hydrogel matrix presents largely enhanced adhesion and mechanical toughness. The assembled all-hydrogel supercapacitor based on the hydrogel matrix has robust interfaces and shows high specific capacitance (298.6 F g−1 at 10 mV s−1), outstanding rate performance, delivering high energy density of 13.7 Wh kg−1 and high capacitance retention of 89.9% after 10,000 cycles. Remarkably, the all-polymer device shows superior capacitance retention after mechanical deformations of 5000 cycles without slippage happens between contiguous layers. This study proposes an effective approach to improving the interfacial adhesion in integrated supercapacitors and extending the application scope of flexible supercapacitors.