Distinguish MnO <sub>2</sub> /Mn <sup>2+</sup> Conversion/ Zn <sup>2+</sup> Intercalation/ H <sup>+</sup> Conversion Chemistries at Different Potentials in Aqueous Zn||MnO <sub>2</sub> Batteries
Chuan Li, Haonan Yuan, Ying Liu, Rong Zhang, Jiaxiong Zhu, Huilin Cui, Yanbo Wang, Duanyun Cao, Duanyun Cao, Donghong Wang, Donghong Wang, Chunyi Zhi
Abstract
Abstract The rechargeable aqueous Zn||MnO 2 chemistry has been extensively explored, but its electrochemical reaction mechanisms, especially in the context of MnO 2 /Mn 2+ conversion and Zn 2+ /H + intercalation chemistry, remain not fully understood. Here, we designed an amphiphilic hydrogel electrolyte, which distinguished the MnO 2 /Mn 2+ conversion, Zn 2+ intercalation, and H + intercalation and conversion processes at three distinct discharge plateaus of an aqueous Zn||MnO 2 battery. The amphiphilic hydrogel electrolyte is featured with an extended electrochemical stability window up to 3.0 V, high ionic conductivity, Zn 2+ ‐selective ion tunnels, and hydrophobic associations with cathode materials. This specifically designed electrolyte allows the MnO 2 /Mn 2+ conversion reaction at a discharge plateau of 1.75 V. More interesting, the discharge plateaus of ~1.33 V, previously assigned as the co‐intercalation of Zn 2+ and H + ions in the MnO 2 cathode, are specified as the exclusive intercalation of Zn 2+ ions, leading to an ultra‐flat voltage plateau. Furthermore, with a distinct three‐step electrochemical energy storage process, a high areal capacity of 1.8 mAh cm −2 and high specific energy of 0.858 Wh cm −2 , even at a low MnO 2 loading mass of 0.5 mg cm −2 are achieved. To our knowledge, this is the first report to fully distinguish different mechanisms at different potentials in aqueous Zn||MnO 2 batteries.