Functional, water-soluble binders for improved capacity and stability of lithium–sulfur batteries

• Simple cells of moderate sulfur loading exhibit capacities of over 1000 mAh g−1 with a PEO:PVP binder mixture.
• These capacities are over 200 mAh g−1 higher compared to our reference CMC:SBR system.
• High capacities of 800 mAh g−1 were retained at 1C.
• The increase is attributed to complementary functions of the binder with respect to their interactions with intermediates.
• Manipulation of binder functionality may be a promising strategy for improving capacity and stability in this system.

Binders based on mixtures of poly(ethylene oxide) (PEO) and poly(vinylpyrrolidone) (PVP) are here shown to significantly improve the reversible capacity and capacity retention of lithium– sulfur batteries compared to conventional binders. This mixed binder formulation combines the local improvement to the solvent system offered by PEO and the lithium (poly)sulfide-stabilising effect of PVP. Cells with cathodes made of simple mixtures of sulfur powder and carbon black with a binder of 4:1 PEO:PVP exhibited a reversible capacity of over 1000 mAh g−1 at C/5 after 50 cycles and 800 mAh g−1 at 1C after 200 cycles. Furthermore, these materials are water soluble, environmentally friendly and widely available, making them particularly interesting for large-scale production and applications in, for example, electric vehicles.