In-Situ SEM Study on Lithium Oxygen Battery

Rechargeable nonaqueous lithium-oxygen batteries have attracted wide attention recently due to its high theoretical energy density. Numerous challenges hinder its practical applications, including low round-trip efficiency, poor rate capability, cycle life on the side of the oxygen electrode, safety issue at lithium side, suitable and stable electrolytes. Among them, the reaction kinetics (ORR and OER) and the transport kinetics (ion transport and electron transport) are essential problems. Great efforts have been paid on fundamental understanding on the morphology, structure and composition of the products under various discharging and charging conditions. Obviously, direct in-situ investigation on the products during ORR and OER processes are desirable. Recently, a facile micro-scale solid state lithium-oxygen battery has been constructed in the environmental scanning electron microscope (ESEM). Based on the design, direct visualization of discharge and charge process of the lithium-oxygen battery has been achieved. Different discharge product morphology has been observed including sphere, conformal films and toroids. And the particles with the size up to 1.5 mm are formed upon discharge, while upon charge, the decomposition initiates at their surface and continues along certain direction. This new findings indicates that the transport kinetics of the electron and lithium ion seem faster on the surface than in the bulk of Li₂O₂, and the growth and decomposition process of Li₂O₂is supposed to be anisotropic.

Acknowledgement: Financial support from CAS project "Strategic Priority Research Program" of the Chinese Academy of Sciences (XDA01020304) and National project 973 (2014CB932300,2012CB932900) are appreciated.