Investigation of lithium electrodeposits formed in practical rechargeable Li-Li_xMnO₂ batteries based on LiAsF₆/1,3-dioxolane solutions

Li deposits, which are formed in practical rechargeable Li-Li_0.3MnO₂ batteries, were studied. The relationship of surface morphology, grain size, microstructure, and texture to the operation conditions was characterized by scanning electron microscopy and X-ray diffraction. Lithium grains consist of relatively large textured crystallites. Two directions (110) and (211) are preferred in the crystal growth process. X-ray and element analysis were used for investigating the composition of the Li surface layer. Our results show that the surface films that appear on the Li deposits formed at low current density, contain a smaller amount of LiF as compared to surface films on Li deposits formed at high current density. Accumulation of insoluble products, formed as a result of reduction of solution species by the active metal, takes place more quickly as the current density is higher. The major cause of the failure of these batteries is depletion of the solvent (by reactions with the Li deposits) and not the salt.