Improved supercapacitor performances by adding carbonized C-based nanospheres to PVA/TEMPO-cellulose hydrogel-based electrolyte.

With the emergence of the energy crisis and the development of flexible electronics, there is an urgent need to develop new reliable energy supply devices with good flexibility, stable energy storage, and efficient energy transfer. Porous carbon materials have been proven to enhance the efficiency of ion transport, as the nanospaces within them serve as pathways for mass transport. However, they have been mainly investigated in the electrodes of supercapacitors and batteries. To elucidate their function in the solid electrolytes, we introduced C-based carbonized nanospheres into PVA/TEMPO-cellulose-based hydrogels by exploiting the electrostatic interaction between the carboxyl groups of TEMPO-cellulose and the carbonized nanospheres. The obtained hydrogels were further utilized as the solid electrolytes for the supercapacitors. Through a comprehensive investigation, we found that the carbonized nanospheres can act as physical crosslinking points and increase the maximum stress of the hydrogel from 0.12 to 0.31 MPa without affecting the maximum strain. In addition, the nanospaces of the carbonized nanospheres provided a pathway for ion transport, improving the capacitance of the supercapacitor from 344.83 to 369.18 mF cm at 0.5 mA cm. The capacitance retention was also improved from 53% to 62% at 10 mA cm. Collectively, this study provides new insights into the application of carbonized materials to solid electrolytes.