Dielectric constant and electrical conductivity of carbon black as an electrically conductive additive in a manganese-dioxide electrochemical electrode, and their dependence on electrolyte permeation

The relative dielectric constant and electrical conductivity of electrochemical electrodes with manganese-dioxide (MnO₂) particles mixed with carbon black (CB, the most common electrically conductive additive) are reported, with unprecedented determination of the decoupled CB properties and their dependence on the MnO₂ volume fraction. The electrolyte is 15 vol.% sulfuric acid. As the CB proportion increases, the CB electrical conduction connectivity increases, while the CB dielectric connectivity decreases (due to decreasing squishing by the MnO₂). The minimum MnO₂ content for squishing the CB to the extent of enhancing the CB polarizability is 65 vol.%. The electrolyte enhances the CB conduction/dielectric connectivity. Without electrolyte permeation, as the CB proportion increases from 14 to 30 vol.% (the MnO₂ proportion correspondingly decreasing from 69 to 59 vol.%), the CB resistivity decreases from 236 to 165 Ω cm and the CB relative dielectric constant decreases from 53 to 12 (leveling-off below 65 vol.% MnO₂), suggesting decreasing CB polarizability as CB is less squished. With complete electrolyte permeation, as the CB proportion increases from 18 to 25 vol.%, the CB resistivity decreases from 49 to 34 Ω cm and the CB relative dielectric constant decreases from 29 to 22. Without MnO₂, the CB conduction connectivity is the highest.