Aqueous flexible all-solid-state NiCo-Zn batteries with high capacity based on advanced ion-buffering reservoirs of NiCo2O4

Aqueous rechargeable Ni//Zn batteries have recently attracted increasing attention in portable electronics due to their intrinsic high safety, high operating voltage, and low cost. In this context, we have prepared a new kind of dodecyl benzene sulfate (DBS−) ions doped hierarchical flower-like NiCo2O4 spheres (DBS-fNiCo2O4, f stands for flower-like) via a typical solvothermal method based on the DBS-intercalated NiCo2(OH)6 layered double hydroxide (LDH) structures (NiCo2(OH)6-LDH) as precursors. The DBS-fNiCo2O4 cathodes exhibit typical “ion-buffering reservoirs” structures with ultrathin nanosheets (2–4 nm) as cathodes for aqueous rechargeable NiCo-Zn batteries. A specific capacity of 165 mAh g−1 at 0.5 A g−1 can be achieved for the produced DBS-NiCo2O4. Furthermore, the NiCo-Zn batteries have been assembled with a wide operating potential window of 1.93 V and a specific capacity of 198.6 mAh g−1 at 0.5 A g−1. Moreover, the flexible all-solid-state NiCo-Zn batteries have been further fabricated with PVA-KOH membrane as the solid hydrogel electrolyte to avoid freezing even at low temperature, which display excellent electrochemical performance under different bending states and at different temperatures from −25 to 60 °C for further potential applications. Flexible all-solid-state NiCo-Zn batteries have been fabricated based on advanced typical “ion-buffering reservoir” of DBS-NiCo2O4 as cathode electrode materials with PVA-KOH membrane electrolyte and display excellent electrochemical performance.