Li2S/carbon nanocomposite strips from a low-temperature conversion of Li2SO4 as high-performance lithium-sulfur cathodes

Abstract

The carbothermal conversion of Li2SO4 provides a cost-effective strategy to fabricate high-capacity Li2S cathodes; however, Li2S cathodes derived from Li2SO4 at high temperatures (>800 degrees C), having high crystallinity and large crystal size, result in a low utilization of Li2S. Here, we report Li2SO4/poly(vinyl alcohol)-derived Li2S/carbon nanocomposite (Li2S@C) strips at a record low temperature of 635 degrees C. These Li2S@C nanocomposite strips as a cathode show a low initial activation potential (2.63 V), a high initial discharge capacity (805 mA h g(-1) Li2S) and a high cycling stability (0.2C and 1C). These improved results could be ascribed to the nano-sized Li2S particles as well as their low crystallinity due to the PVA-induced carbon network and the low conversion temperature, respectively. An XPS analysis reveals that the C=C and C=O bonds derived from the carbonization of PVA can promote the conversion of Li2SO4 at such a low temperature.