Amphoteric zinc-manganese dioxide aqueous battery exceeding 2V potential Ramona Durena, Anzelms Zukuls, Martins Vanags Institute of Materials and Surface Engineering, Riga Technical University, Latvia Over the past decade, research interest in zinc-manganese dioxide (Zn-MnO 2 ) batteries has increased substantially due to green policy implementation efforts. These batteries are a potential addition or replacement for Li-ion batteries where their use is too costly or not desirable due to safety concerns. Commercially available alkaline Zn-MnO 2 batteries have a low potential of 1.5 V and are generally non-rechargeable. Many studies have addressed rechargeability problems by modifying the MnO 2 cathode [1] and controlling the depth of discharge [2] . However, the issue of low potential and thus undesirable energy density still needs to be addressed [3-4]. Herein we have addressed these issues and developed high-potential rechargeable aqueous Zn-MnO 2 batteries. We have increased the open circuit potential (OCP) up to 2.4 V. This has been accomplished by using an amphoteric electrolyte and operating the Zn anode in an alkaline medium and the MnO 2 cathode in an acidic medium. To realize this design, we have constructed an aqueous battery consisting of: (1) Zn metal sheet as the anode; (2) alkaline (1M KOH) Pluronic F-127 hydrogel; (3) acidic (0.5 M H 2 SO 4 ) alkaline Pluronic F-127 hydrogel; (4) MnO 2 powder and carbon black (13:5) mixture as the cathode. No ion-selective membranes were used in this design. The electrode materials were analyzed with XRD, SEM, EDX and Raman spectroscopy before and after the battery cycling. Also, the electrochemical performance of the amphoteric battery was analyzed by potentiostat/ galvanostat Autolab PGSTAT302N and Agilent (34970A) data logger switch unit. In conclusion, our battery design showed more than 25-hour pH gradient stability. A high OCP of 2.4 V was reached. Also, 200 charge-discharge cycles were obtained with a charge-discharge current of +/- 1 mA/s with a discharge potential of 2.2 V - 2.3 V and a charge potential of 2.7 V while maintaining a stable OCP. Acknowledgement: Ramona Durena acknowledges this work has been supported by the European Social Fund within the Project No 8.2.2.0/20/I/008 «Strengthening of PhD students and academic personnel of Riga Technical University and BA School of Business and Finance in the strategic fields of specialization» of the Specific Objective 8.2.2 «To Strengthen Academic Staff of Higher Education Institutions in Strategic Specialization Areas» of the Operational Programme «Growth and Employment». References 1. Nat. Commun. 2017, 8, 14424 2. J. Power Sources. 2015, 276, 7-18
3. ACS Energy Lett. 2019, 4, 9, 2144–2146 4. Electrochim. Acta. 2022, 434, 141275
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