Expander degradation

One of the irreversible processes that influence battery performance is the degradation of expander organic component during LAB operation. Expander degradation has been investigated in this laboratory.

Effect of hydrogen and oxygen on expander stability. Expanders operate under constant hydrogen and oxygen attack at high negative potentials, as a result of which they undergo degradation. This leads to changes in negative plate capacity, which may limit battery life. Expander stability depends on its structure. The influence of six different expanders on the electrochemical characteristics and the life of negative battery plates have been investigated. It has been established that structural groups of the pyrocatechin type have effective expander action. It has been found that pyrocatechin structural groups are easily oxidized than hydrogened. The most effective expander should be a combination of several compounds with different stabilities to oxidation and reduction.

Influence of temperature on expander stability. The temperature of cycling exerts strong influence on the cycle life performance of negative plates by affecting both expander stability and rate of disintegration as well as NAM structure, which in turn determines the capacity of the plate. It has been established that plates containing a mixture of Vanisperse A and Indulin and U-393, an expander material designed by LABD and Borregaard Ligno-Tech (Norway), ensure the longest cycle life at 40^oC. When the battery is cycled at 60^oC, the expander containing lignin and its derivatives disintegrates, which results in a two-fold decrease in battery cycle life.

References

Keywords: degradation of organic expander, chemical stability of expander, pyrocatechin structural groups