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• The capacities achieved 0.08 mAh/cm2 for thin-film electrolytic MnO 2 -Zn batteries. • Over 200 cycles were demonstrated for batteries with electrolyte of 25 µL/cm2. • The shuttle reactions caused by iodide mediators were revealed experimentally. Whilst electrolytic MnO 2 with a high capacity draws great attention recently, the shuttle reactions between the mediator additives in the electrolytes with zinc and MnO 2 are often overlooked. In this work, neutral acetate electrolytes with iodide mediator are tested for electrolytic MnO 2 -Zn system on thin-film batteries. With a limited amount of electrolyte, the shuttle reactions caused by iodide mediator becomes more obvious, which results in low Coulombic efficiencies and shortens shelf-life. [ABSTRACT FROM AUTHOR]

We propose an electrode-free zinc manganese battery, where both zinc and MnO2 are electro-deposited from the electrolyte via a charging process onto carbon current collectors. The electrode-free batteries show an improved cycling performance of thin-film batteries than the ones with a zinc anode and a facilitated fabrication process for fiber batteries. [ABSTRACT FROM AUTHOR]

Manganese oxide (MnO 2) is proven to be an efficient cathode material in zinc-ion batteries (ZIBs). However, its poor electronic conductivity strongly limits the performance of Zn–MnO 2 batteries. In order to improve performance beyond typical graphitic carbon additives, a binary conductive additive, a combination of carbon nanohorns (CNHs) and carbon nanotubes (CNTs), is added into the MnO 2 electrode to establish high-speed electron-channels in the CNTs/CNHs network with an efficient "line-to-surface-to-point" microstructure. In this electrode, the high aspect-ratio CNTs create a conducting highway for the collected charges, while the CNHs provide extra surface area for electron transfer. Moreover, the specific surface area of the electrode increases due to the introduction of CNHs, which increases the Zn2+ diffusion coefficient. As a result, the corresponding battery reaches a high specific capacity (343 mAh g−1 at 0.3 A g−1), excellent rate performance (191.3 mAh g−1 at 3 A g−1) and long-life cycle. Moreover, it achieves an admirable specific energy density of 466 W h kg−1, together with a peak power density of 9.4 kW kg−1 (normalized to the weight of MnO 2), the performance of which is among the best reported ZIBs. This work reveals new pathways to improve the performance of MnO 2 cathodes for ZIBs. Image 1 [ABSTRACT FROM AUTHOR]