context: ssZIBs are composed of four components including a cathode, an anode (zinc metal), a solid electrolyte and current collectors. The gel electrolyte is sandwiched between the cathode and anode. Each component has a significant effect on the performance of the whole battery. Currently, various gel electrolytes have been studied and have been applied in ZIBs. However, the performance of ssZIBs is still not comparable with that of the batteries using liquid electrolytes, especially high rate capability, due to the low ionic conductivities of gel electrolytes. To realize high ionic conductivity, an ideal gel electrolyte requires a high-water content and efficient ion migration channels, combined with reasonable mechanical properties. As one of the principal natural polymers, cellulose nanofibers (CNFs) are widely used as a sustainable reinforcing additive in various composites. In addition, the hydrophilic skeleton of CNFs and their three-dimensional fiber network with a large space can help stabilize the channels for charge transportation. Furthermore, due to the abundant hydroxyl groups on the surface of CNFs, it is facile to link the CNFs with polyacrylamide (PAM) molecular chains through hydrogen bonding. The combination of CNFs and PAM can serve as an effective solid electrolyte with good mechanical properties and high ionic conductivity. Due to the high thermal stability of hydrogel polymers, ssBs are also able to operate under both low and high temperature conditions, which is critical for the application of batteries in some harsh environments such as cold/frozen regions and flying airplanes in space.
answer: zinc metal