Tungsten oxide hydrate/polyvinylpyrrolidone/sulfur core-shell hollow particles as LiS battery cathode materials: Synthesis and electrochemical characterization

Although lithium‑sulfur (LiS) batteries exhibit high specific energy densities and are, therefore, promising next-generation energy storage systems, their widespread use is hindered by the low electrical conductivity of sulfur, dissolution of intermediate polysulfides, and low capacity retention. To address these issues, we herein use simple colloidal coating followed by co-precipitation to prepare tungsten oxide hydrate/polyvinylpyrrolidone (PVP)/sulfur core-shell hollow particles and examine their performance as a LiS battery cathode material. Specifically, PVP-coated hollow sulfur particles were easily formed from sodium thiosulfate and PVP under acidic conditions, and the tungsten oxide hydrate shell was produced by the subsequent addition of ammonium metatungstate hydrate. At a current density of 100 mA g−1, the tungsten oxide-coated particles featured first discharge and charge capacities of 856 and 867 mAh g−1, respectively, together with a capacity retention of 70% over 50 cycles. This excellent performance was attributed to the synergistic effects of PVP and tungsten oxide hydrate shells, i.e., the former accommodated the volume expansion of sulfur, whereas the latter further alleviated the above volume expansion and minimized polysulfide dissolution.