Electrospun vanadium sulfide / carbon hybrid fibers obtained via one-step thermal sulfidation for use as lithium-ion battery electrodes

Abstract

Many metal sulfides present a layered structure with large interlayer space and a high theoretical capacity for lithium-ion battery applications. Compared to other transition metal dichalcogenides, vanadium sulfides remain little explored. Vanadium sulfides are commonly obtained by hydrothermal synthesis, which requires further post-processing and coating with binder and carbon additives. Here, we introduce a route to obtain free-standing vanadium sulfide fiber mats with in-built carbon. The combination of electrospinning and thermal sulfidation with H2S produces homogeneous vanadium sulfide particles embedded in carbon fibers that provide electrical conductivity and mechanical resistance for the electrode. The fibers were tested as a binder-free lithium-ion battery cathode within different potential ranges to evaluate insertion and conversion mechanisms and contributions to the overall capacity. Between 1.2 V and 3.5 V vs. Li/Li+, lithium intercalation provides a specific capacity up to 138 mAh∙g−1 at 0.01 A g−1 with good rate handling. When operating in a larger potential range between 0.1 V and 3.0 V vs. Li/Li+, the contribution by conversion reactions increases the capacity to 790 mAh∙g−1, but there is a fast capacity fading.