The Influence of P2VP Incorporation into the LiI Electrolyte Layer on the Rate Capabilities of Li / I 2 (P2VP) Batteries

An electron microprobe has been utilized to examine the electrolyte layer that forms in (P2VP) batteries with pelletized cathodes. Carbon x‐ray maps were generated to determine the distribution of reacted P2VP that becomes incorporated into the layer as it grows into the cathode. It was found that a carbon‐containing derivative of P2VP was uniformly incorporated into the formed during low rate discharges (cells discharged across constant 20 and 40 kΩ loads, approximately 20–40 μA/cm2). The conductivity of these layers is similar to those reported for containing dispersed particles of and . On the other hand, layers formed at high rates (cells discharged across constant 1 and 2 kΩ loads, approximately 200–300 μA/cm2) 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.