Batteries are important storage devices that can enable renewable energy integration into the grid. However, they need to meet certain requirements like safety, low cost, high cycle life and high energy densities for use in grid applications. Manganese dioxide (MnO₂)/Zinc (Zn) alkaline batteries have the aforementioned safety and cost attributes including very high volumetric energy densities of >400Wh/L (1) because of the high gravimetric capacities of its electroactive materials – 617mAh/g for MnO₂ and 820mAh/g for Zn based on 2 electron reactions. However, their use has been restricted to primary applications like common household appliances because rechargeability has been an issue due to the fundamental nature of MnO₂ and Zn (2). The cathode, MnO₂, has been known to undergo lattice expansion and crystal structure breakdown beyond a certain depth-of-discharge (DOD). Prior work has concentrated on limiting the DOD of MnO₂ (5-10% of 617mAh/g) to make the battery rechargeable (3); however, this has resulted in low energy densities. Accessing the 2^nd electron capacity (617mAh/g) of MnO₂ reversibly has been the holy grail of MnO₂/Zn batteries to obtain very high energy dense batteries for use as low cost safe aqueous batteries in grid and electric vehicle applications (4).

In this presentation, we report the breakthrough of reversibly accessing the 2^nd electron capacity of MnO₂ by using its layered polymorph called birnessite mixed with bismuth oxide (Bi-birnessite) and intercalating the layers with Cu ions (5). Bi-birnessite undergoes conversion reactions in alkaline electrolyte and ultimately forms electro-inactive hausmannite (Mn₃O₄) because of its poor charge transfer characteristics. Intercalating the layers of Bi-birnessite with Cu ions is shown to improve its charge transfer characteristics dramatically and regenerate its layered structure reversibly for thousands of cycles. We also present a case of Cu-intercalated Bi-birnessite’s applicability in practical batteries by cycling the material at high areal capacities (10-29mAh/cm²) for thousands of cycles at C-rates that are of interest in the battery community. Finally, a Cu-intercalated Bi-birnessite/Zn battery is shown to reversibly cycle at 140 Wh/L for over 90 cycles.

References:

1] Gallaway, J. W.; Hertzberg, B. J.; Zhong, Z.; Croft, M.; Turney, D. E.; Yadav, G. G.; Steingart, D. A; Erdonmez; C. K.; Banerjee, S. “Operando identification of the point of [Mn₂]O₄ spinel formation during γ-MnO2 discharge within batteries” Journal of Power Sources 321, 135-142 (2016).

2] Wei, X.; Desai, D.; Yadav, G. G.; Turney, D. E.; Couzis, A.; Banerjee, S. “Impact of anode substrates on electrodeposited zinc over cycling in zinc-anode rechargeable alkaline batteries”. Electrochimica Acta 212, 603-613 (2016)

3] Ingale, N. D.; Gallaway, J. W.; Nyce, M.; Couzis, A.; Banerjee, S., “Rechargeability and economic aspects of alkaline zinc­manganese dioxide cells for electrical storage and load leveling,” Journal of Power Sources 276, 7­18 (2015)

4] Dzieciuch, M. A.; Gupta, N.; Wroblowa, H. S. “Rechargeable cells with modified MnO₂ cathodes.” J. Electrochem. Soc. 135, 2415–2418 (1988)

5] Yadav, G. G.; Gallaway, J. W.; Turney, D. E.; Nyce, M.; Huang, J.; Wei, X.; Banerjee, S. “Regenerable Cu-intercalated MnO₂ layered cathode for highly cyclable energy dense batteries” Nat. Commun. 8, 14424 (2017).