Flexible, Robust Sodium Alginate/PAAm Hydrogel for High‐Performance Supercapacitor

ABSTRACT The use of hydrogel electrolytes with excellent ion transport capability and robust mechanical properties for energy storage devices such as supercapacitors has developed rapidly in recent years. However, the preparation of hydrogel electrolytes is usually complicated, time consuming, and expensive, which limits the potential of hydrogel electrolytes in practical applications. Here, the natural polymer material sodium alginate and the common polymer polyacrylamide were selected for synthesizing the double cross‐linked network conductive hydrogel through a straightforward in situ polymerization, followed by ionic response. The hydrogel has a rich pore structure to provide structural support for ion transport, while the double cross‐linked structure provides excellent mechanical properties with an elongation at break of 229%. The area specific capacitance of the hydrogel‐based supercapacitor is as high as 642.5 mF/cm 2 , and its energy density reaches 89.2 μ Wh/cm 2 at a power density of 500.2 μ W/cm 2 . Due to the excellent flexibility and robust mechanical properties, the area specific capacitance maintained 83.6% after 500 bending cycles. In practical applications, it can drive small electronic devices to operate normally. This study opens up a simple approach for the preparation of conductive hydrogels in the field of green energy storage and sustainable use.