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Here, we report the rechargeable aqueous battery of Zn/K0.17MnO2 with multiple metal ions in the electrolyte based on K0.17MnO2 as the cathode and zinc as the anode. The microspheres of broccoli-like K0.17MnO2 made up of large rod particles with a size of about 200 nm in diameter are synthesized by hydrothermal method followed by calcination at 500 °C in air for 2 h. The cyclic voltammetry measurement demonstrates that it is easy to intercalate into the cathode for zinc ions with smaller radius compared with potassium ions. The galvanostatic charge/discharge test displays that it delivers the initial discharge capacity of 189.3 mAh g−1 at 100 mA g−1 after adding 0.05 mol L−1 MnSO4 into the hybrid electrolyte. Meanwhile, the discharge capacity retains still up to 78.4 mAh g−1 at a current density of 3200 mA g−1, indicating the much better cycle stability than that without additive and the superfast ion transport characteristic. [ABSTRACT FROM AUTHOR]

Aqueous battery has been gained much more interest for large-scale energy storage fields due to its excellent safety, high power density and low cost. Cryptomelane-type KMn8O16 confirmed by X-ray diffraction (XRD) was successfully synthesized by a modified hydrothermal method, followed by annealed at 400°C for 3 h. The morphology and microstructure of as-prepared KMn8O16 investigated by field-emission scanning electron microscopy (FE-SEM) with the energy spectrum analysis (EDS) and transmission electron microscopy (TEM) demonstrate that one-dimensional nano rods with the length of about 500 nm constitute the microspheres with the diameter about 0.5~2 μm. The cyclic voltammetry measurement displays that the abundant intercalation of zinc ions on the cathode takes place during the initial discharge process, indicating that cryptomelane-type KMn8O16 can be used as the potential cathode material for aqueous zinc ion batteries. The electrode shows a good cycling performance with a reversible capacity of up to 77.0 mAh/g even after 100 cycles and a small self-discharge phenomenon.