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 °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.