Polymer-Derived Ceramic Aerogels to Immobilize Sulfur for Li-S Batteries

Lithium-sulfur batteries are among the promising high-capacity candidates owing to the superior theoretical capacity of sulfur, when compared with conventional cathodes such as LiCoO2. However, several issues must be addressed before these batteries can be considered fully operational. Major issues regard the insulating nature of sulfur and the so-called shuttle effect of soluble polysulfides, which dramatically reduces the cathode capacity upon cycling. Herein, three carbon-containing polymer-derived ceramic aerogels are characterized belonging to the Si-C-O and Si-C-N systems, infiltrated with sulfur to work as cathodes for Li-S batteries. The electrochemical performances are evaluated in relation to the microstructural and chemical features of such materials. In particular, the effect of the pore size of the ceramic matrices on the shuttling behavior of polysulfides is investigated. Despite the high initial specific capacities exceeding hundreds of mAh g-1, all types of cathodes show stable capacities in the 60-120 mAh g-1 range after 100 cycles. In this work, the polymer-derived ceramic route is systematically employed to synthesize macro-to-mesoporous SiOC and SiCN scaffolds for the containment of sulfur as storage medium for lithium-sulfur batteries. The chemistry and morphology of the scaffolds is put in relation to the performances of the Li-S batteries.image & COPY; 2023 WILEY-VCH GmbH