With the rapid development of flexible supercapacitors (SCs), there is increasing demand for high-performance solid electrolyte to replace the conventional liquid electrolyte. Hydrogel electrolyte is one of the promising candidates, which possesses solid state but contains plenty of water within its highly porous structure. In this paper, a strong and sticky hydrogel has been synthesized using bacterial cellulose (BC) and poly (acrylic acid) (PAA). The results of attenuated total reflectance Fourier transform infrared (ATR–FTIR) spectroscopy shows that two components are well combined. Scanning electron microscopy (SEM) test shows that BC/PAA has a highly porous structure, which is modified by the interaction between BC nanofibers and acrylic acid monomer. Double network created by BC and PAA not only enhances the mechanical property of PAA but also improves the anti-compression ability of BC. Moreover, a sticky property is recognized within BC/PAA due to PAA, which can prevent the spilt of two flexible e...