Design Optimization of Storage Life of Mercuric Oxide-Cadmium Battery for Use in Long Delay Fuzes

The objective of the work conducted under this contract was to extend the storage life of mercuric oxide-cadmium cells by determining the mechanism of mercury migration and find a barrier that would retard the migration process. By diffusion studies, material balances, and cell examinations, it was found that the major part of the mercury migrates as dissolved mercuric oxide with the diffusion to a reduction site as the rate-determining step. To slow down the diffusion process, several commercial barrier materials were characterized and evaluated in actual cells. The highly crosslinked polyethylene material, Permion 2291, gave the best charge retention, 87 percent of initial capacity after six months storage at +165F. This more than doubled the pre-contract performance. Pretreatment of the barrier materials permitted this increase in storage life without significant loss of performance at -65F. Aiming at additional improvements in shelf life, a polysulfide-type barrier was developed but was not tested in actual cells. (Author)