Spent Graphene Oxide With Hydrogel Polymer Electrolyte for Zn‐Ion Batteries: Insights From Computational and Experimental Correlation of Zn‐Ion Storage

ABSTRACT To mitigate dendrite growth in Zn‐ion batteries (ZIBs), herein, aqueous electrolyte is replaced by polyvinyl alcohol (PVA)—ZnSO ₄ ‐based hydrogel polymer electrolyte (HPE). The Zn//Zn symmetric cell with PVA‐ZnSO ₄ HPE achieved an appreciable lifespan exceeding 200 h and maintained a stable overpotential at a current density of 0.25 mA/cm ² . A Zn‐ion full cell was fabricated using graphene oxide (GO) cathode upcycled from an end‐of‐life Li‐ion battery (LIB) using the PVA‐ZnSO ₄ HPE to evaluate the practical application. The Zn//Spent graphite GO (SG‐GO) full cell exhibited an initial discharge capacity of 206 mAh/g and a capacity retention of 72% even after cycling at a current density of 1 A/g over 1000 cycles. The coupling–decoupling mechanism of Zn interacting with carbonyl groups on graphene oxide bilayer is captured through our computational analysis, revealing an associated energy cost of approximately −1.5 eV. This interaction also leads to a pronounced disruption of the Dirac cone symmetry, driven by strong hybridization between Zn states and carbonyl oxygen states as the Zn ion migrates across the graphene oxide interface.