Generation of innovative Li2S@C active materials via plasma processes

Summary:

Batteries become increasingly important as energy storage devices for a sustainable energy economy. In comparison to Lithium-ion batteries, Lithium sulfide (Li2S) as cheap, non-toxic cathode material with a high theoretical energy density, attracted significant attention. Since Li2S suffers from low ionic and electric conductivity as well as from volume changes during cell operation, it is of interest to investigate new pathways for active materials. The ability to generate innovative surface modifications and coatings with plasma processes gained more attention in the last decade, due to strong adherence and stability properties. Plasma polymerization is a solvent-free layer formation process for depositing polymers directly onto the surfaces of the substrates without any processing or additional cross-linking chemicals.
In our current project we work on two novel routs for the generation of Li2S cathode materials via plasma processes. Route 1 comprises a plasma sputtering method for the integration of nano-scaled carbon into the Li2S powder (Li2S@C), whereby Route 2 describes the addition of carbon nanotubes (CNT´s), both carbon add-ons were designed to improve the conductivity. Additionally, plasma polymerization generates a polymer encapsulation around both type of powders Li2S@C to minimize the mechanical stress, which results in Li2S@C hybrids and Li2S@C composites as active materials for high-performance cathodes. Here we present the latest results of route 1 and it turned out that the active material utilization as well as the capacity retention was significantly enhanced by carbon and polymer modification of Li2S. Compared to pristine Li2S, the capacity at 1 C was increased by 10 % and the capacity retention after 200 cycles was improved by 13 %.