An electron microprobe has been utilized to examine the LiI electrolyte layer that forms in Li / I 2 (P2VP) batteries with pelletized cathodes. Carbon x‐ray maps were generated to determine the distribution of reacted P2VP that becomes incorporated into the LiI layer as it grows into the cathode. It was found that a carbon‐containing derivative of P2VP was uniformly incorporated into the LiI formed during low rate discharges (cells discharged across constant 20 and 40 kΩ loads, approximately 20–40 μA/cm 2 ). The conductivity of these layers is similar to those reported for LiI containing dispersed particles of Al 2 O 3 and SiO 2 . On the other hand, LiI layers formed at high rates (cells discharged across constant 1 and 2 kΩ loads, approximately 200–300 μA/cm 2 ) contained large chunks (greater than 10 μm) of reacted P2VP. The resistivity of electrolyte layers formed at high rates is consequently nearly an order of magnitude greater than those formed at low rates. Evidence is presented suggesting that the cathode material is inhomogeneous and that at high rates regions that are iodine rich discharge preferentially, leaving chunks of reacted P2VP trapped in the layer.
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Streinz et al. (1990) studied this question.