Effect of poly(acrylic acid) binder on the stability of sulfur-enriched crystalline Mo3S13 clusters for high capacity of Li-ion batteries

Abstract

Molybdenum sulfide (MoSx)-based materials have been extensively studied as a potential alternative of low-capacity graphite anode, owing to their remarkable capacity through intercalation and conversion reactions. However, these materials should be electrochemically activated at a low potential in first discharge and simultaneously degrade, owing to their inert basal plane and unstable sulfur configuration, respectively, leading to unexpectedly low performance. Hence, it is necessary to apply sulfur-enriched crystalline Mo3S13 clusters as an anode material to increase the number of active sites and energy densities. Unlike MoS2 possessing only terminal sulfur, Mo3S13 clusters have higher sulfur content with various and stable configuration in their structure, which can act as additional active sulfur sites. To realize an electrode with high energy density, we used the Mo3S13 clusters without any carbon supports as active materials. In the electrode preparation, we confirmed that employing poly(acrylic acid) and isopropyl alcohol as a binder and solvent, respectively, was appropriate for retaining the cluster crystallinity, resulting in the enhanced cycling stability. The Mo3S13 cluster-based electrode as a carbon-free electrode exhibited capacity of 1192 mAh g(-1) at 0.1 A g(-1) and good C-rate capability. The significant capacity variation with the selective removal of sulfur configuration in Mo3S13 clusters indicates that the increased sulfur contents were provided as additional sources for (de)lithiation.