Systematic Study of O₂ Supply in Li–O₂ Batteries with High and Low Doner Number Solvents

Abstract

The Li–O2 battery is a promising technology due to its high theoretical specific energy. However, its practical capacity and cycling performance need further improvement. In this scenario, the influence of the electrolyte and the supply of air/O2 to the device are essential to enhance the performance and build a commercial prototype. This paper presents a study focusing on the influence of oxygen flow and pressure in the gravimetric capacity of Li–O2 batteries using two different electrolytes: dimethyl sulfoxide (DMSO/LiClO4) and tetraethylene glycol dimethyl ether (TEGDME/LiClO4). This study pointed out the negative influence of flow over the capacity when combined in an open cell. Due to electrolyte loss, the life cycle was also deeply affected using the open cell, especially for DMSO. However, DMSO leads to the best performance due to higher ionic conductivity, oxygen diffusivity, and absence of a direct reaction with the lithium anode. Thus, the closed cell reached a maximum discharge capacity of 22537 mAh g–1 with 26 cycles of 1000 mAh g–1 for DMSO and 8764 mAh g–1 with 13 cycles of 1000 mAh g–1 for TEGDME.

A lithium–air battery and gas handling system demonstrator

“…While increasing the flow rate increased the capacity, very high flow rates had the opposite effect. Post-cycling analysis of the cell suggested that this was due to loss of electrolyte solution from the air electrode, which has been observed previously, 37,38 reconfirming the need for a solvent-management system. 34…”

“…This will increase the need for saturation and capture of solvent from the gas stream. 37,38,45 For Li–air to become a commercially viable battery technology, we anticipate the need for a system-specific energy of >400 W h kg −1 . 3,33 Our calculations suggest that if a positive electrode capable of storing 40% vol.…”

“…34 No experimental data on the requirements of a practical gas purification system have been reported. Some work has probed the effects of parameters such as gas composition, 35 O 2 partial pressure 36 and gas flow 37,38 on the capacity of Li–air cells, but usually in cells operating at unrealistically low current densities (<100 μA cm −2 ) and large flow rates. Progress towards the development of a practical Li–air battery requires a holistic view of the challenges involved, including not only the chemical and electrochemical processes occurring within the cell, but also of the effects of the gas-handling parameters on device performance.…”