Li2MnO3: A Catalyst for a Liquid Cl2 Electrode in Low‐Temperature Aqueous Batteries

Li2MnO3 has been contemplated as a high‐capacity cathode candidate for Li‐ion batteries; however, it evolves oxygen during battery charging under ambient conditions, which hinders a reversible reaction. However, it is unclear if this irreversible process still holds under subambient conditions. Here, the low‐temperature electrochemical properties of Li2MnO3 in an aqueous LiCl electrolyte are evaluated and a reversible discharge capacity of 302 mAh g−1 at a potential of 1.0 V versus Ag/AgCl at −78 °C with good rate capability and stable cycling performance, in sharp contrast to the findings in a typical Li2MnO3 cell cycled at room temperature, is observed. However, the results reveal that the capacity does not originate from the reversible oxygen oxidation in Li2MnO3 but the reversible Cl2(l)/Cl−(aq.) redox from the electrolyte. The results demonstrate the good catalytic properties of Li2MnO3 to promote the Cl2/Cl− redox at low temperatures.