Cold neutron depth protiling of lithium-ion battery materials

We report the characterization of two thin-film battery materials using neutron techniques. Neutron depth profiling (NDP) has been employed to determine the distribution of lithium and nitrogen simultaneously in lithium phosphorous oxynitride (UPON) deposited by ion beam assisted deposition (IBAD). The depth profiles are based on the measurement of the energy of the charged particle products from the Li-6(n,alpha)H-3 and N-14(n,p) C-14 reactions for lithium and nitrogen, respectively. Lithium at the level of 10(22) atoms/cm(3) and N of 10(21) atoms/cm(3), distributed in the film thickness on the order of I gm, have been determined. This information provides insights into nitrogen incorporation and lithium concentration in the films under various fabrication conditions. NDP of lithium has also been performed on IBAD LiCoO2 films, in conjunction with instrumental neutron activation analysis (INAA) to determine the cobalt concentration. The Li/Co ratio thus obtained serves as an ex situ control for the thin-film evaporation process. The non-destructive nature of the neutron techniques is especially suitable for repeated analysis of these materials and for actual working devices. Published by Elsevier Science B.V.