Lee, Boeun Seo, Hyo Ree Lee, Hae Ri Yoon, Chong Seung Kim, Jong Hak Chung, Kyung Yoon Cho, Byung Won Oh, Si Hyoung 2024-01-20T03:03:31Z 2024-01-20T03:03:31Z 2021-09-05 2016-10-20 1864-5631 https://pubs.kist.re.kr/handle/201004/123550 The reaction mechanism of -MnO2 having 2x2 tunnel structure with zinc ions in a zinc rechargeable battery, employing an aqueous zinc sulfate electrolyte, was investigated by insitu monitoring structural changes and water chemistry alterations during the reaction. Contrary to the conventional belief that zinc ions intercalate into the tunnels of -MnO2, we reveal that they actually precipitate in the form of layered zinc hydroxide sulfate (Zn-4(OH)(6)(SO4)5H(2)O) on the -MnO2 surface. This precipitation occurs because unstable trivalent manganese disproportionates and is dissolved in the electrolyte during the discharge process, resulting in a gradual increase in the pH value of the electrolyte. This causes zinc hydroxide sulfate to crystallize from the electrolyte on the electrode surface. During the charge process, the pH value of the electrolyte decreases due to recombination of manganese on the cathode, leading to dissolution of zinc hydroxide sulfate back into the electrolyte. An analogous phenomenon is also observed in todorokite, a manganese dioxide polymorph with 3x3 tunnel structure that is an indication for the critical role of pH changes of the electrolyte in the reaction mechanism of this battery system. English WILEY-V C H VERLAG GMBH CLUSTER CHALCOGENIDES MO6X8 HIGH-ENERGY DENSITY MANGANESE-DIOXIDE ION BATTERY MAGNESIUM BATTERIES CATHODE MATERIALS HIGH-PERFORMANCE PHASE-DIAGRAM MG BATTERIES TODOROKITE Critical Role of pH Evolution of Electrolyte in the Reaction Mechanism for Rechargeable Zinc Batteries Article 10.1002/cssc.201600702 1 CHEMSUSCHEM, v.9, no.20, pp.2948 - 2956 CHEMSUSCHEM 9 20 2948 2956 scie scopus 000386953500010 2-s2.0-84988422108 Chemistry, Multidisciplinary Green & Sustainable Science & Technology Chemistry Science & Technology - Other Topics Article CLUSTER CHALCOGENIDES MO6X8 HIGH-ENERGY DENSITY MANGANESE-DIOXIDE ION BATTERY MAGNESIUM BATTERIES CATHODE MATERIALS HIGH-PERFORMANCE PHASE-DIAGRAM MG BATTERIES TODOROKITE batteries conversion intercalation manganese dioxide zinc