Lead-Acid Battery: Electrochemical Compatibility of Plastics

l.i Materials Selection The general problem of materials selection for battery use is divided into two areas: (i) the test material must meet some specified physical property requirements and maintain them over a period of long exposure to battery electrolyte (usually a strong corrosive acid or base solution), and (ii) the material must not introduce any solute into the electrolyte which will upset the electrochemical behavior of the cell. During the early history of lead-acid battery development, the cell was placed in a container made of a material which experience had shown resistant to the sulfuric acid. Since a wide range of polymeric materials was unavailable, glass and lead-lined containers predominated. During the 1930s, hard rubber containers for lead-acid cells were introduced. There was no compatibility testing of this material but, in retrospect, it can be seen that none was needed since: 1377 1378 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1970 (i) cell lifetimes were short due to failure mechanisms which were faster operating than cell contamination by the container material; (ii) cells were generally cycled, which tended to decompose organic contaminants due to the high charge potentials; (Hi) a lead-antimony alloy was used in the grids and the antimonycaused negative overvoltage lowering was so large that it swamped the much smaller increases caused by organic contaminants. These cells required much higher float currents due to this shift and lead-calcium cells which float at much lower currents are preferred for Bell System use.