Information on the structure of the conference

Poster-No.

P1-050

Author:

Other authors:

Institution/company:

Due to its high specific capacity and availability, sulfur has long been the research focus as a promising cathode active material for high-energy cells. However, intrinsic problems like polysulfide shuttling and sulfur being an electrical insulator have held back its use. An alternative to classical electrodes with sulfur intruded in carbon is an electrode with sulfur-polyacrylonitrile (SPAN). In this material, chains of 2 to 5 sulfur atoms are bound to a backbone of partly aromatised PAN. This structure can successfully suppress the polysulfide shuttle while increasing the conductivity of the active material into the range of classical LIB cathode active materials. This material shows stable cycling behaviour in ether and carbonate-based electrolytes. On the other hand, the low sulfur content of <45 wt.-% within a largely inactive polymer backbone decreases the material's specific capacity and energy values. However, stability during cycling is one of many advantages of the material. SPAN also shows favourable behaviour during processing with classical production equipment for LIBs. For the water-based slurry production process, we found a significant impact of the mixing intensity on the electrode's performance. This is due to the advancing carbon black deagglomeration with increasing mixing intensity. However, carbon black agglomerates are needed within the SPAN-cathodes structure for good electrical percolation. A worse electrical percolation within the cathode leads to a decreased C-rate performance, especially in charge direction. For coating, the rheological properties of the slurry are most important. On the one hand, SPAN slurries show a high low-shear viscosity with a gel-like characteristic, which leads to a good sedimentation stability of the slurry. On the other hand, these slurries show a low high-shear viscosity with free-flowing behaviour, resulting in good coatability. So overall, the slurry properties are very beneficial for a stable coating performance. During calendering, SPAN cathodes show a quite elastic reaction to compression with a high springback. This leads to low compressibility, loss of percolation of the conductive network, and serious deterioration of the electrodes' performance. This elasticity is intrinsic to the used SPAN material, so the use of easily networking conductive additives like CNTs or the narrowing of the particle size distribution may lead to better calendering performance. Overall, SPAN shows very beneficial processing behaviour during water-based slurry mixing, coating, and drying. During coating, established process knowledge can be easily transferred from NCM-NMP cathodes due to their similar rheology. During drying, the behaviour is very similar to classical graphite anodes due to the same solvent-additive system. During calendering, however, SPAN shows new challenges.