Carbons derived from resole-type phenolic resins for use in lithium–sulfur batteries: templating the resins with sulfur leads to enhanced cell performance

Abstract

Pyrolysed resole-type phenol-formaldehyde resins were used as carbonaceous sulfur-hosts in the cathodes of lithium–sulfur batteries. Porosity was added through sulfur-depositing, via acidification of ammonium thiosulfate, within the polymerisation reaction. Micellar-templated and untemplated carbons were also synthesised as comparisons. The carbons that had been subjected to the lowest extremes of pyrolysis (600 °C) retained higher amounts of functional groups and greater pore volumes when characterised by IR and nitrogen sorption studies, respectively. The three carbon types behaved similarly giving performances of circa 500 mA h g_sulfur⁻¹ (by the 40th cycle at 0.05C) when melt-loaded with sulfur into cathode films. In contrast, when sulfur was deposited onto the same carbons, via thiosulfate acidification, the different porous designs led to changes in battery performance of between 500–800 mA h g_sulfur⁻¹ (after the 40th cycle at 0.05C). The structures afforded by the different sulfur-loading methods were analysed using SEM-EDS and Raman spectroscopy.