Semi-coherent Cation-Rich Mn-Cu Oxides Heterostructures as Cathode for Novel Aqueous Potassium Dual-Ion Energy Storage Devices

Abstract In this work, combining both advantages of aqueous energy storage systems (ESS) and conventional dual-ion ESS, a novel aqueous dual-ion ESS is developed based on K+ and OH- electrochemistry by employing semi-coherent K1.33Mn8O16-CuO (sc–Mn–Cu) cathode. Profting from the elaborate design, the electrolyte and cathode simultaneously act as source of cations. In the novel aqueous dual-ion ESS configuration, the dependence of the performance on the electrolyte salt concentration is reduced and the sc–Mn–Cu cathode can host OH− with lower working potentials by conversion mechanism. Furthermore, based on the sc–Mn–Cu cathode and freestanding V2O3–VC (fs-V2O3–VC) anode, we developed a flexible quasi-solid-state device. Remarkably, it exhibits an ultrahigh energy density of ∼39.9 μW h cm-2 together with high power density of carbon-based devices, which outperforms most previously reported flexible storage devices to our knowledge. These results indicating that the unique mechanism of the sc–Mn–Cu cathode opens up a promising direction for low-cost and high-performance novel aqueous ESS.