Very High Specific Area Lithium-Air Battery

Abstract

Unlike traditional batteries, the lithium-air cell is an open system by definition, since it needs to have access to oxygen from the surrounding air to work. This has important implications on the cell design. The traditional lithium-ion or LMP (lithium metal polymer) sealed designs can no longer be applied and completely new architectures need to be developed. For example, very large, very thin electrodes tightly wound into cylindrical cells or folded into prismatic cells will be difficult to use since they would lead to air starvation. Positive and negative compartments with high specific surface area capacities therefore need to be developed in order to reduce the size of the electrodes packed into a cell. As a consequence, the negative electrode needs to be able cycle over much greater lithium thicknesses than a lithium battery in order to limit its size. Large amounts of the discharge product per geometrical area unit also have to be stored in the positive electrode. In the aqueous lithium-air design developed by EDF and its partners, the areal capacity of the positive electrode is not limited since the product of the reaction is stored as solid LiOH.H2O in the aqueous electrolyte compartment, and not in the air electrode as in the anhydrous design. The precipitation of LiOH in the aqueous compartment have little impact on the performance of the cell, even up 80% solid LiOH.H2O by volume. Cells that can be charged to more than 100 mAh/cm² on the negative electrode have been obtained.