A stretchable solid-state zinc ion battery based on a cellulose nanofiber-polyacrylamide hydrogel electrolyte and a Mg_0.23V₂O₅·1.0H₂O cathode

In comparison with well-protected rigid batteries with liquid electrolytes, solid-state batteries (ssBs) are more beneficial, offering high flexibility, high wearability and leakage prevention. Currently, ssBs with the capability of bending and twisting have been extensively studied. However, it remains a challenge to develop a highly stretchable ssB with the maintenance of high performance. Herein, we report a stable solid-state zinc ion battery (ssZIB) based on a cellulose nanofiber (CNF)-polyacrylamide (PAM) hydrogel electrolyte and a Mg_0.23V₂O₅·1.0H₂O cathode. The designed CNF-PAM hydrogel shows high stretchability and robust mechanical stability. Moreover, the porous CNF-PAM hydrogel electrolyte provides efficient pathways for the transportation of zinc ions. And the robust layered structure of V₂O₅·1.0H₂O pillared with Mg²⁺ions and water supports the fast insertion/extraction of zinc ions in the lattice. Therefore, the designed ssZIB shows unprecedented high capacity at high current with durable cycling life. At a current density of 5 A g⁻¹(charging time of around 3 minutes), the ssZIBs can deliver a high reversible capacity of 216 mA h g⁻¹after 2000 cycles and retain 98.6% of the initial capacity, showing a high capacity and long-life durability at high currents. Furthermore, the designed spring ssZIBs can work under stretching with the strain reaching 650%. And the designed ssZIBs are still operational even under repeated bending, freezing, and heating conditions. The ssZIBs show robust mechanical stability, high stretchability and impressive electrochemical performance, providing a potential pathway to expand the application of ZIBs to a broad range of practical energy storage devices.