Magnesium-sulfur (Mg-S) battery cells represent one of the more promising alternatives to existing lithium-ion technologies, as they combine high theoretical energy density with low cost and safety of the materials used. In this master’s thesis, we focused on the development and optimization of Mg-S cells using composite cathodes based on sulfur and porous carbon (C-S), a conductivity additive (C65), and a binder (PTFE).
With galvanostatic discharge, we found that the choice of cathode composition has a crucial influence on the performance of Mg-S battery cells, as it determines the mass of the active material and the wetting of this material by the electrolyte. Another great influence on the performance of the Mg–S system is exerted by the choice of electrolyte. Cells with DIGLYME showed a higher average working voltage, a more distinct two-step polysulfide conversion, and higher specific capacity – even with a lower sulfur mass. The HPLC analysis results showed that higher concentration of polysulfides was present in the separator, confirming the dissolution and migration of reaction products from the cathode. The concentration of polysulfide species mostly increased during the first part of the discharge and then decreased to an almost zero value in the second part. During the discharge, longer-chain polysulfide species are formed first, followed by shorter-chain ones.
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