Influence of morphology of monolithic sulfur–poly(acrylonitrile) composites used as cathode materials in lithium–sulfur batteries on electrochemical performance

Abstract

Solvent-induced phase separation (SIPS) and thermally-induced phase separation (TIPS) derived poly(acrylonitrile) (PAN) based monoliths with different morphology and specific surface area were prepared and thermally converted into monolithic sulfur–poly(acrylonitrile) (SPAN) materials for use as active cathode materials in lithium–sulfur batteries. During thermal processing, the macroscopic monolithic structure fully prevailed while significant changes in porosity were observed. Both the monomer content in the precursor PAN-based monoliths and the tortuosity of the final monolithic SPAN materials correlate with the electrochemical performance of the SPAN-based cathodes. Overall, percolation issues predominate. In percolating SPAN-based cathode materials, the specific capacity of the SPAN-based cells increases with decreasing tortuosity. All monolithic SPAN materials provided highly reversible and cycle stable cathodes reaching reversible discharge capacities up to 1330 mA h g_sulfur⁻¹ @ 0.25C, 900 mA h g_sulfur⁻¹ @ 2C and 420 mA h g_sulfur⁻¹ @ 8C.