Crystal Phase-Controlled Modulation of Binary Transition Metal Oxides for Highly Reversible Li-O<sub>2</sub> Batteries.

Cao, Dong; Zheng, Lumin; Li, Qiaojun; Zhang, Junfan; Dong, Ying; Yue, Jiasheng; Wang, Xinran; Bai, Ying et al. · Nano Lett · 2021

basic_science · Level V

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Abstract

Reducing charge-discharge overpotential of transition metal oxide catalysts can eventually enhance the cell efficiency and cycle life of Li-O<sub>2</sub> batteries. Here, we propose that crystal phase engineering of transition metal oxides could be an effective way to achieve the above purpose. We establish controllable crystal phase modulation of the binary Mn<sub><i>x</i></sub>Co<sub>1-<i>x</i></sub>O by adopting a cation regulation strategy. Systematic studies reveal an unprecedented relevancy between charge overpotential and crystal phase of Mn<sub><i>x</i></sub>Co<sub>1-<i>x</i></sub>O catalysts, whereas a dramatically reduced charge overpotential (0.48 V) via a rational optimization of Mn/Co molar ratio = 8/2 is achieved. Further computational studies indicate that the different morphologies of Li<sub>2</sub>O<sub>2</sub> should be related to different electronic conductivity and binding of Li<sub>2</sub>O<sub>2</sub> on crystal facets of Mn<sub><i>x</i></sub>Co<sub>1-<i>x</i></sub>O catalysts, finally leading to different charge overpotential. We anticipate that this specific crystal phase engineering would offer good technical support for developing high-performance transition metal oxide catalysts for advanced Li-O<sub>2</sub> batteries.