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Technology

This invention generates an ion conducting film on lithium electrodes by reacting the metal with one of the following: nitrous oxide, nitrogen trifluoride, or sulfur hexafluoride. Reaction of nitrous oxide with lithium surfaces at temperatures below melting (<180.5 °C) for 24 hours results in the incorporation of oxygen into the surface film, which can be as thick as 1µm. Upon ambient air exposure, these nitrous-oxide-coated lithium electrodes do not visibly react or discolor in contrast to untreated lithium surfaces that rapidly discolor and blacken due to the formation of lithium oxide. They also exhibit stable cycling over 150 hours, with lowered overpotentials at current densities of 1 mA/cm2 and capacities of 1 mAh/cm2. Reaction of nitrogen trifluoride and sulfur hexafluoride with lithium electrodes at 175 °C and 150 °C respectively result in the incorporation of fluorine into the surface film. Lithium-fluorine-coated films exhibit up to 5-fold improvement (~50 hrs) in cell lifetime before dendrite formation and growth led to short circuiting.