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

Abstract

A prefabricated matrix is normally used as cathode host for lithium-sulfur batteries to address the shuttle effect problem. Being out of the ordinary, herein we show a non-shaped matrix for sulfur cathode enabling a better lithium-sulfur battery. La2Mo2O9 as a fast oxide-ion conductor is introduced for the first time to sulfur cathodes. Specially, 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, completely different from the conventional model. The non-shaped matrix provides an enormous surface contact with sulfur and high catalytic ability for conversion of polysulfides to deliver a high discharge capacity and satisfactory cycle stability. LMO-in-S with a high tap density delivers a high gravimetric capacity of 1374.1 mAh g−1 corresponding to volumetric capacity of 2294.8 mA h cm−3 at 0.1C rate. Especially, LMO-in-S exhibits satisfactory cycle stability with low fading rate of 0.07% per cycle over 400 cycles at 1C rate. Furthermore, it allows ultra-high sulfur content (92.6 wt%), delivering high capacity of 1076.5 mA h g−1 at 0.1C rate. Objectively, this work breaks through the original concept of sulfur cathode structure and provides a novel possibility for developing high-performance lithium-sulfur batteries.