Jake Christensen
Robert Bosch, LLC

Li-metal based cells, including Li/air, are attractive due to their high gravimetric energy density, but safely recharging Li metal over hundreds of cycles remains a significant challenge.  This is due in part to the fact that Li metal electrodes are chemically and morphologically unstable in most, if not all, liquid electrolytes and must be protected with a solid electrolyte, for which there are few working prototypes.  Here we examine the principle requirements of such a protection layer from a systems perspective.  In addition to possessing high ionic conductivity, mechanical strength, and chemical stability against both lithium and the positive electrode constituents, these materials must be thin (< 50 µm,) cheap (< $100/m2), and defect free.  We conclude that further fundamental materials and processing research and development are needed to attain these objectives.

Paul Albertus
Robert Bosch, LLC

For a Li/O2 battery system to achieve a high energy per mass and volume and thereby enable long-range electric vehicles, a technology is needed to handle the gases entering and exiting the cell.  Such a technology should be light weight and compact and both supply contaminant-free O2 during discharge and prevent the loss of any volatile cell components during charge.  While the highest energy per mass and volume may ultimately be obtained with a technology that allows the use of ambient air, another option is the use of an oxygen tank, which would create a completely closed system. In this talk I will give an overview of the requirements for gas handling in a Li/O2 battery system, including acceptable mass and volume as well as energy use.  Calculations for an oxygen tank will be presented.

Shuye Ping Ong
MIT

The lithium-air battery is a promising alternative to existing rechargeable batteries. However, there are substantial challenges, such as poor reversibility, cyclability, rate capability, and energy efficiency, which limit commercialization. Currently, the charge and discharge mechanisms and their relationship to the battery parameters are not clearly understood.

In this talk, we present our study of the mechanisms of the oxygen evolution reaction (OER) and electronic conduction in lithium peroxide (Li2O2) using first-principles calculations. Li2O2, the primary product during discharging, is an insulator and is suspected to increase the charging overpotential, thereby deteriorating the Li-air battery performance. We show that i) the OER process on low-index surfaces of Li2O2 is kinetically limited by the oxygen evolution, not by the extraction of Li+ ions and/or electrons, and that ii) the formation and migration of hole polaron VLi+ pairs is a possible electronic conduction mechanism in Li2O2.

John Newman
University of California, Berkeley

Renewable fuels are a long-term solution to the world’s energy needs.  It is a significant challenge to find efficient ways to harness solar and wind energy that are cost-competitive with fossil fuels.  Because renewable sources are intermittent, energy storage is essential to renewable fuel production.  In this work, we discuss modular approaches to making solar fuels.  We use back-of-the-envelope calculations to evaluate production schemes, including energy storage with batteries.  A relationship that predicts the required sales price of energy storage is also discussed.

Nobuyuki Imanishi
Mie University, Japan

Lithium-air secondary batteries with a lithium metal anode and an air cathode are an attractive energy storage system because they have high theoretical energy density. Two types of lithium-air batteries have been developed, namely, non-aqueous and aqueous types. We have studied aqueous type of lithium-air batteries, which consist of a lithium electrode, an aqueous electrolyte with LiCl, and an air electrode. A protected lithium electrode, Li/PEO18LiTFSI/Li1+xTi2-xAlx(PO4)3 was stable in a saturated LiOH with 10 M LiCl aqueous electrolyte, which showed a pH value of ca. 9.

In this study, applicability of air electrodes in this moderately alkaline aqueous solution were examined. Carbon electrodes with perovskite-type oxide catalysts were used as air electrodes. The catalytic activity for oxygen reduction and evolution, and chemical, electrochemical stabilities were evaluated for these perovskites. Various carbon materials are studied for the long term polarization in the LiOH-LiCl electrolyte. The effect of ion exchange membranes is also investigated which are applied to avoid direct deposition of solid LiOH on the air electrode.