In situ high-energy synchrotron X-ray diffraction studies and first principles modeling of α-MnO2 electrodes in Li–O2 and Li-ion coin cells

Author(s): Zhenzhen Yang ¹ ^, ² ^, ³ ^, ⁴ , Lynn Trahey ¹ ^, ² ^, ³ ^, ⁴ , Yang Ren ⁵ ^, ⁶ ^, ² ^, ³ ^, ⁴ , Maria K. Y. Chan ⁷ ^, ² ^, ³ ^, ⁴ , Chikai Lin ¹ ^, ² ^, ³ ^, ⁴ , John Okasinski ⁵ ^, ⁶ ^, ² ^, ³ ^, ⁴ , Michael M. Thackeray ¹ ^, ² ^, ³ ^, ⁴

Publication date (Electronic): 2015

Journal: Journal of Materials Chemistry A

Publisher: Royal Society of Chemistry (RSC)

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Abstract

In situ synchrotron diffraction and first principles modeling shows structural changes in α-MnO ₂ during cycling in Li–O ₂ battery cells, as lithium and oxygen are incorporated into and removed from tunnels in the structure.

Abstract

Despite their technological challenges, non-aqueous rechargeable lithium–oxygen cells offer extremely high theoretical energy densities and are therefore attracting much attention in a rapidly emerging area of electrochemical research. Early results have suggested that, among the transition metal oxides, alpha manganese dioxide (α-MnO ₂) appears to offer electrocatalytic properties that can enhance the electrochemical properties of Li–O ₂ cells, particularly during the early cycles. In this study, we have investigated the hybrid Li-ion/Li–O ₂ character of α-MnO ₂ electrodes in Li–O ₂ coin cells by in situ high-energy synchrotron X-ray diffraction, and compared the results with conventional Li/α-MnO ₂ coin cells assembled under argon. Complementary first principles density functional theory calculations have been used to shed light on competing lithium insertion and lithium and oxygen insertion reactions within the α-MnO ₂ tunnel structure during discharge, relative to lithium peroxide or lithium oxide formation.