Discrete carbon nanotubes promote resistance to corrosion in lead-acid batteries by altering the grid-active material interface

Abstract

In lead-acid battery cycling tests, addition of discrete carbon nanotubes (dCNT) to Positive Active Material (PAM) extends life. Despite this observation, dCNT are undetectable in PAM following formation. This paradox led us to examine aspects of the positive electrode that are established prior to or during formation and the role dCNT play in their evolution. One such aspect is the corrosion layer, the protective boundary between current collector and PAM, which provides lasting benefits to the positive plate without the persistent need for any components that may have assisted in its development.Here, we detail physical and electrical differences identified in dCNT-modified positive plates and confirm the absence of dCNT following formation via scanning electron microscopy. When compared to control samples, we find the corrosion layer constructed in dCNT-modified positive electrodes to be thinner and more uniform following formation and after high-temperature cycling in a variety of grid alloys. Mechanistic theories are also discussed.We present evidence that dCNT alter the structure of the corrosion layer in a dose-responsive fashion, thus providing an original hypothesis for the observed dCNT-based enhancements for corrosion-intensive cycling.