RECHARGEABLE THIN-FILM LITHIUM BATTERIES

Rechargeable thin-film batteries consisting of lithium metal anodes, a n amorphous inorganic electrolyte, and cathodes of lithium intercalati on compounds have been fabricated and characterized. These include Li- TiS2, Li-V2O5, and Li-LiMn2O4 cells with open circuit voltages at full charge of about 2.5 V, 3.7 V, and 4.2 V, respectively. The realizatio n of these robust cells, which can be cycled thousands of times, was p ossible because of the stability of the amorphous lithium electrolyte, lithium phosphorus oxynitride. This material has a typical compositio n of Li3.3PO3.8N0.22 and a conductivity at 25-degrees-C of 2 muS/cm. T he thin-film cells have been cycled at 100% depth of discharge using c urrent densities of 5 to 100 muA/cm2. Over most of the charge-discharg e range, the internal resistance appears to be dominated by the cathod e, and the major source of the resistance is the diffusion of Li+ ions from the electrolyte into the cathode. Chemical diffusion coefficient s were determined from ac impedance measurements.