Quantitative Delineation of the Low Energy Decomposition Pathway for Lithium Peroxide in Lithium–Oxygen Battery
Arghya Dutta, Kimihiko Ito, Akihiro Nomura, Yoshimi Kubo
Abstract
Abstract Identification of a low‐potential decomposition pathway for lithium peroxide (Li 2 O 2 ) in nonaqueous lithium–oxygen (Li–O 2 ) battery is urgently needed to ameliorate its poor energy efficiency. In this study, experimental data and theoretical calculations demonstrate that the recharge overpotential ( η RC ) of Li–O 2 battery is fundamentally dependent on the Li 2 O 2 crystallization pathway which is intrinsically related to the microscopic structural properties of the growing crystals during discharge. The Li 2 O 2 grown by concurrent surface reduction and chemical disproportionation seems to form two discrete phases that have been deconvoluted and the amount of Li 2 O 2 deposited by these two routes is quantitatively estimated. Systematic analyses have demonstrated that, regardless of the bulk morphology, solution‐grown Li 2 O 2 shows higher η RC (>1 V) which can be attributed to higher structural order in the crystal compared to the surface‐grown Li 2 O 2 . Presumably due to a cohesive interaction between the electrode surface and growing crystals, the surface‐grown Li 2 O 2 seems to possess microscopic structural disorder that facilitates a delithiation induced partial solution‐phase oxidation at lower η RC (<0.5 V). This difference in η RC for differently grown Li 2 O 2 provides crucial insights into necessary control over Li 2 O 2 crystallization pathways to improve the energy efficiency of a Li–O 2 battery.