External microbeam PIGE study of Li and F distribution in PVDF_HFP electrolyte gel/polymer for lithium battery application

Studies of Li and F distribution in a series of gel polymer electrolyte samples containing lithium salt solution have been performed by microbeam scanning of the sample cross-section using PIGE spectroscopy. In order to preserve gel polymer during experiment, all measurements have been performed with an external microbeam (in air), using a focused 4 MeV proton beam and a 50 μm thick Kapton exit foil. The main contribution to the deterioration of the beam spatial resolution comes from the ion multiple scattering in the vacuum-air interface foil and in atmosphere. Direct depth profiling of lithium and fluorine is not possible since the ion energy straggling in the foil and in atmosphere precludes the use of nuclear resonant reactions. Lateral scans over the sample cross-section were performed with PIGE spectroscopy used for the determination of fluorine and lithium distributions.