Li2S/carbon nanocomposite strips from a low-temperature conversion of Li2SO4 as high-performance lithium–sulfur cathodes†
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 °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 °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 CC and CO bonds derived from the carbonization of PVA can promote the conversion of Li2SO4 at such a low temperature.