Low-cost and long-life Zn/Prussian blue battery using a water-in-ethanol electrolyte with a normal salt concentration

Although rechargeable aqueous Zn-ion batteries (ZIBs) are very attractive as one of the most promising energy storage systems with merits of low cost, environmental friendliness, high power density and high safety, practical applications of ZIBs are largely limited by Zn corrosion, Zn dendrite growth and cathode dissolution. In this work, a cost-effective water/ethanol hybrid (WEH) electrolyte with a normal salt concentration was proposed to solve the above issues in Daniell-type zinc/manganese Prussian blue (MnPB) battery with MnPB cathode and Zn anode. The unique WEH electrolyte endows the batteries with a high specific capacity of ∼80 mAh g–1, superior rate capability with 90.4% capacity yielded at 50 C relative to 0.5 C, and an extremely stable cycling with 91.6% capacity retained after 20000 cycles at 5 C (the cycling time lasts as long as ∼ 1 year). Dendrite-free Zn stripping/deposition is confirmed by in situ optical microscopy and first-principles calculation. Pouch-type batteries were assembled which exhibit stable cycling and easy scale up in capacity and voltage by connecting cells in series and parallel. A low-cost strategy was further demonstrated by using low-concentration salt, cheap salt (Na2SO4) and waste liquor. This work provides a practical strategy to design low-cost, environmentally friendly and high-performance Zn-based batteries.