Lithium-air (or Li-oxygen) batteries are attracting a great deal of research interest due their very high energy densities, and thus their potential application in electric vehicles.

In its most classical configuration, the Li/O₂ battery is formed by a lithium metal anode, a liquid organic electrolyte and a carbon-supported (with or without catalyst) air electrode. Recently, a new configuration, where the lithium metal is replaced by a lithium alloy silicon anode, has also been reported. Key parameters in assuring proper Li/O₂ battery behavior are (i) the optimization of the positive electrode structure, in terms of use of an adequate gas diffusion layer and of effective catalysts, and (ii) the choice of an electrolyte stable to superoxide attack.

It is in fact well-known that the basic electrochemical cell process, leading to the reversible formation and dissolution of lithium peroxide, involves an intermediate oxygen anion radical O^2−•, namely, a highly reactive base that readily attacks and decomposes conventional electrolytes, such as organic carbonate solutions. Dimethoxyethane (DME)-based and ionic liquid-based solutions have been proposed as alternative electrolyte media, however with little success.

Recent works demonstrated that the best results in terms of Li/O₂ battery stability and cycling may be obtained with the use of long chain, ether-based glymes, such as tetraethylene glycol dimethyl ether (TEGDME) electrolyte solutions. [Earlier post.] In a previous paper we have reported a detailed transmission electron microscopy (TEM) study showing that Li/O₂ batteries based on the TEGDME-LiCF₃SO₃ electrolyte indeed show a very promising behavior at room temperature. In this paper we extend the study by investigating the role of temperature on influencing the response of Li/TEGDME-LiCF₃SO₃/O₂ cells.

—Park et al.

The Li-air cells in the study were based on a specially developed gas diffusion layer (GDL) oxygen electrode and on a TEGDME-LiCF₃SO₃ electrolyte. The gas diffusion layer was coated with Super-P carbon as matrix to host the lithium oxygen reaction products (Li₂O₂ nanospheres and hollow nanospheres formed at the interface with the tetraglyme-based solution). All of the cycles were run under a fixed capacity regime of 1000 mAh g⁻¹_carbon.

Low temperatures resulted in a rate decrease, due to a reduced diffusion of the lithium ions from the electrolyte to the electrode interface. High temperatures resulted in a rate enhancement, due to the decreased electrolyte viscosity and consequent increased oxygen mobility.

They also showed that the temperature also influences the crystallinity of lithium peroxide formed during cell discharge.

Resources

• Jin-Bum Park, Jusef Hassoun, Hun-Gi Jung, Hee-Soo Kim, Chong Seung Yoon, In-Hwan Oh, Bruno Scrosati, and Yang-Kook Sun (2013) Influence of Temperature on Lithium–Oxygen Battery Behavior. Nano Letters doi: 10.1021/nl401439b