Operando characterization of cathodic reactions in a liquid-state lithium-oxygen micro-battery by scanning transmission electron microscopy

Pan Liu,Shoucong Ning,Akihiko Hirata,Takeshi Fujita,Xianwei Guo,Chuchu Yang,Yoshikazu Ito,Jiuhui Han,Mingwei Chen

doi:10.1038/s41598-018-21503-w

Abstract

Rechargeable non-aqueous lithium-oxygen batteries with a large theoretical capacity are emerging as a high-energy electrochemical device for sustainable energy strategy. Despite many efforts made to understand the fundamental Li-O2 electrochemistry, the kinetic process of cathodic reactions, associated with the formation and decomposition of a solid Li2O2 phase during charging and discharging, remains debate. Here we report direct visualization of the charge/discharge reactions on a gold cathode in a non-aqueous lithium-oxygen micro-battery using liquid-cell aberration-corrected scanning transmission electron microscopy (STEM) combining with synchronized electrochemical measurements. The real-time and real-space characterization by time-resolved STEM reveals the electrochemical correspondence of discharge/charge overpotentials to the nucleation, growth and decomposition of Li2O2 at a constant current density. The nano-scale operando observations would enrich our knowledge on the underlying reaction mechanisms of lithium-oxygen batteries during round-trip discharging and charging and shed lights on the strategies in improving the performances of lithium-oxygen batteries by tailoring the cathodic reactions.

Highlights

Lithium-oxygen (Li-O2) batteries have recently attracted enormous research attention as a new generation of high energy storage devices for all electric vehicles and other high-energy-demanded applications because of the high theoretical capacity[1]
The direct correspondence of Li2O2 nucleation, growth and decomposition to electrochemical discharge/charge in the liquid-state Li-O2 system has not been well established owing to the lack of operando characterization with real-space visualization
The state-of-the-art spherical aberration corrected scanning transmission electron microscopy (STEM) with enhanced contrast by a high angle annular dark field (HAADF) detector is a promising technique for characterizing basic electrochemical reactions in liquid-state at a high spatial resolution of ~1 nm[19]

Summary

Introduction

Lithium-oxygen (Li-O2) batteries have recently attracted enormous research attention as a new generation of high energy storage devices for all electric vehicles and other high-energy-demanded applications because of the high theoretical capacity[1]. In this study we employ in situ EC HAADF-STEM to investigate the nucleation, growth and decomposition of Li2O2 in a basic liquid-state Li-O2 system during discharging and charging at a constant current density, together with synchronized electrochemical measurements.

Results

Conclusion