S-La₂Mo₂O₉ solid solution: a sulfur cathode with a non-shaped matrix enables a better lithium-sulfur battery

A prefabricated matrix is normally used as the cathode host for lithium-sulfur batteries to address the shuttle effect problem. Unconventionally, herein we present a non-shaped matrix for a sulfur cathode that enables a better lithium-sulfur battery. The fast oxide-ion conductor La₂Mo₂O₉ is introduced into the sulfur cathodes for the first time. Specifically, La₂Mo₂O₉ is highly dispersed in sulfur to form a solid solution (LMO-in-S), in which the two components are homogenously mixed to a molecular level, which is completely different from the conventional model. The non-shaped matrix provides enormous surface contact with sulfur and high catalytic ability for the conversion of polysulfides to deliver a high discharge capacity and satisfactory cycle stability. LMO-in-S, which exhibits a high tap density, delivers a high gravimetric capacity of 1374.1 mAh g^-1, corresponding to a volumetric capacity of 2294.8 mAh cm^-3 at a 0.1C rate. Notably, LMO-in-S exhibits satisfactory cycle stability with a low fade rate of 0.07% per cycle over 400 cycles at 1C rate. Furthermore, it allows an ultra-high sulfur content (92.6 wt%) to deliver a high capacity of 1076.5 mAh g^-1 at a 0.1C rate. Objectively, this work breaks through the original concept of sulfur cathode structures and provides a novel possibility for developing high-performance lithium-sulfur batteries.