Triggering Zn~(2+) Unsaturated Hydration Structure via Hydrated Salt Electrolyte for High Voltage and Cycling Stable Rechargeable Aqueous Zn Battery

摘要

Ocean-like free water in conventional aqueous electrolytes limits operatingvoltage and induces parasitic reactions in rechargeable Zn metal batteries(AZMBs). Herein, a hydrated salt electrolyte (HSE), which suppresses thepresence of free water and triggers an unsaturated hydration structure(Zn(H_2O)n~(2+), n < 6), is proposed to circumvent the parasitic reactionsoccurring on the zinc anode and cathode and elevate the decompositionvoltage (to ≈2.55 V vs Zn~(2+)/Zn). In a full cell with a transition metal oxidecathode, the parasitic reactions of dissolution and diffusion of dischargeproducts are inhibited, and high discharge capacity retention above 80% at500 mA g~(-1) and super-stable Coulombic efficiency (average value ≈99.97%)are delivered. Moreover, when applied in a high-voltage AZMB with zinchexacyanoferrate cathode, the full cell yields an average output voltageabove 1.8 V together with a 132.3 Wh kg~(-1) energy density at 10 mA g~(-1) and1.78 V output voltage combining high energy density and power density(88.5 Wh kg~(-1)/106.2 W kg~(-1)). The exceptional electrochemical performanceof HSE indicates rosy prospects for the prevention of parasitic reactions inAZMBs, a key step on the road to further commercialization of AZMBs.