A quasi-solid-state self-healing flexible zinc-ion battery using a dual-crosslinked hybrid hydrogel as the electrolyte and Prussian blue analogue as the cathode material

Abstract

Due to their excellent safety and lower cost, aqueous Zn-ion batteries (AZIBs) have garnered extensive interest among various energy-storage systems. Here we report a quasi-solid-state self-healing AZIB by using a hybrid hydrogel which consists of dual-crosslinked polyacrylamide and polyvinyl alcohol as a flexible electrolyte and a cobalt hexacyanoferrate (K_3.24Co₃[Fe(CN)₆]₂·12.6H₂O) Prussian blue analogue as the cathode material. The obtained hybrid hydrogel showed a superhigh fracture strain of up to 1490%, which was almost 15 times higher than that of the original size. Due to the fast formation of hydrogen bonds, the self-healed hydrogel from two pieces still displayed 1165% strain upon failure. As a result, the self-healed battery delivered stable capacities of 119.1, 108.6 and 103.0 mA h g⁻¹ even after being completely cut into 2, 3 and 4 pieces, respectively. The battery capacity recovery rates for each bending cycle exceeded 99.5%, 99.8%, 98.6% and 98.9% during four continuous bending cycles (30 times bending at 90° for each cycle), which indicates outstanding flexibility and self-healing capability. In parallel, the hydrogel electrolyte displayed a broader electrochemically stable window of 3.37 V due to the suppression of water splitting and low overvoltage during the 500 h cycling in a symmetric cell. Zinc dendrites were also suppressed as evidenced in symmetric cell measurements. The assembled AZIB exhibited an initial capacity of 176 mA h g⁻¹ upon vertical bending. The battery showed a reliable capacity of 140.7 mA h g⁻¹ at 0.2 A g⁻¹ after 100 cycles along with a coulombic efficiency of >99%. A reliable capacity of nearly 100 mA h g⁻¹ was retained after 300 cycles at 1.0 A g⁻¹. The highly flexible and self-healing AZIB demonstrates great potential in various wearable electronic devices.