Accessing the second electron capacity of MnO2 by exploring complexation and intercalation reactions in energy dense alkaline batteries. (26th April 2018)

• Record Type: Journal Article
• Authors: Yadav, Gautam G.; Wei, Xia; Huang, Jinchao; Turney, Damon; Nyce, Michael; Banerjee, Sanjoy
• Is Part Of: International journal of hydrogen energy. Volume 43:Number 17(2018)
• Page Start: 8480
• Page End: 8487
• Publication Date: 2018-04-26
• Subjects: Batteries -- Alkaline -- Manganese dioxide -- Zinc; Hydrogen as fuel -- Periodicals; Hydrogène (Combustible) -- Périodiques; Hydrogen as fuel; Periodicals; 665.81
• DOI: 10.1016/j.ijhydene.2018.03.061
• Languages: English
• ISSNs: 0360-3199

Abstract

Abstract: MnO2 is one of the safest and most abundant electrochemical materials available. It exhibits polymorphism, which has been exploited in many applications especially batteries. In alkaline batteries, γ-MnO2 is widely used because its proton insertion reaction yields one e − (1st) per Mn at high voltages. It also gives a second (2nd) e − during dissolution-precipitation reactions that occur at lower voltages than the proton insertion; however, these 2nd e − reactions are highly irreversible. In this communication, we explore the reversibility of the 2nd e − reactions with bismuth oxide (Bi2 O3 ) and copper (Cu) additives, and cycling in specific potential regions where δ-MnO2 is the polymorph synthesized electrochemically in-situ from γ-MnO2 . The use of Bi2 O3 and Cu add complexation and intercalation reactions, where presence and/or electrochemical activation of both are essential for reversibility and for capacity retention (50–100%). Attaining 300–610Wh kg −1 against a zinc anode is possible for these batteries, which could promote its use for many applications. Graphical abstract: Highlights: Cycling potentials affect reversibility of MnO2 with Bi2 O3 and Cu. Complexation reactions take place even when activation potentials are not reached. Cu as a lone additive unlocks high capacity retention and reversibility of MnO2 . Cu and Bi2 O3 together allow for rapid attainment of MnO2 's theoretical capacity. Attaining 300–610Wh.kg −1 against a Zn anode is possible with additives.