The structure of sulfur-poly(acrylonitrile)-based Li-sulfur batteries is elucidated and correlated with the electrochemical performance of such devices. Apart from the poly(acrylonitrile)-derived backbone, thioamide as well as poly(sulfide) structures are proposed. Furthermore, the intermediary formation of S8 during cycling and the role of the electrolyte in its reintegration during charging into are addressed. In summary, a comprehensive picture of the chemistry and electrochemistry of Li-sulfur batteries is presented.

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Sulfur-poly(acrylonitrile) (SPAN) composites were synthesized from different poly(acrylonitrile)- (PAN) sulfur mixtures. This way it was possible to increase the sulfur content and concomitantly the measured specific capacity of the final lithium-sulfur batteries from 300 mAh/gcathode to 440 mAh/gcathode (629 mAh/gcomposite, 1429 mAh/gsulfur). A maximum of 44 wt-% of covalently bound sulfur was reached using a PAN-sulfur ratio of 1:15 (wt/wt). Virtually no loss of capacity was observed during the first 40 cycles.

Intrinsically conducting polymer fibers are prepared from P3HT by melt spinning. High crystallinity is achieved by drawing the fibers after the spinning process, applying a draw ratio of 1:2. DSC and XRD measurements confirm the continuous increase of crystalline phases with drawing. For comparison, poly(ethylene terephthalate) fibers are coated with P3HT and drawn as well. Again, the drawing of the coated fiber results in a significant increase in crystallinity of the P3HT coating. The high amount of crystalline phases is associated with a dramatic increase in conductivity (350 S · cm−1) after doping with FeCl3 in nitromethane.magnified image

Naphthyridines have been identified as structural elements in sulfurized polyacrylonitrile, which is a common electrode material in lithium–sulfur batteries. Some dibenzonaphthyridine derivatives with a fused dithiolo moiety were prepared as model compounds for battery studies. These heterocyclic systems were prepared via the corresponding diphenyldicarbamide intermediate. Followed by naphthyridione formation, stepwise installation of the dithiolane subunit occurred in a straightforward manner. In the solid state, the heteroaromatic system is completely planar and was thoroughly characterized. Initial battery cycling tests indicated a potential use of such structural motifs in sulfur–lithium systems.