Alkaline zinc-manganese dioxide batteries are the most common non-rechargable batteries on the market. They are cheap, safe, and easy to manufacture. A rechargeable variant of this type of battery would be useful. However, when using alkaline electrolytes, the capacity of rechargable Zn-MnO₂ batteries is limited and their cycling performance is insufficient. This is caused by the irreversible formation of discharged species.

To solve these problems, Fangyi Cheng, Jun Chen, Nankai University, Tianjin, China, and colleagues have developed a rechargeable zinc-manganese dioxide battery with an aqueous, mildly acidic zinc triflate electrolyte with a manganese triflate additive. The team studied the reactions of the electrode materials using electrochemical measurements, X-ray diffraction analysis (XRD), elemental analysis, transmission electron microscopy (TEM), and synchrotron X-ray absorption spectroscopy (XAS).

The researchers found that during the first discharge cycle, the manganese dioxide cathode undergoes a phase transition to a layered zinc-buserite, which then allows the reversible intercalation of zinc cations in further cycles. The electrolyte causes the formation of a layer of manganese oxide nanosheets on the cathode, which helps to protect the electrode. A battery based on this approach has a reversible capacity of 1550 mAh with a total energy density of 75.2 Wh kg⁻¹ after 50 cycles. According to the researchers, the system is promising for applications in large-scale energy storage.

• Rechargeable aqueous zinc-manganese dioxide batteries with high energy and power densities,
  Ning Zhang, Fangyi Cheng, Junxiang Liu, Liubin Wang, Xinghui Long, Xiaosong Liu, Fujun Li, Jun Chen,
  Nat. Commun. 2017.
  DOI: 10.1038/s41467-017-00467-x