Conductive graphene oxide-polyacrylic acid (GOPAA) binder for lithium-sulfur battery

Lithium-sulfur batteries have high cathode theoretical energy density, but the poor conductivity of sulfur and polysulfide shuttling result in serious polarization and low sulfur utilization. Moreover, the addition of insulating binder in the electrode increases the internal resistance, reducing specific capacity and rate performance. Herein, we develop a composite binder with higher electronic conductivity, superior mechanical property and strong adsorption of polysulfides that imparts it some electrocatalytic activity. The reduced graphene oxide-polyacrylic acid (GOPAA) binder is prepared via a simple solution process. At constant loading fraction of 10 wt%, using GOPAA binder induces a 30% enhancement in the cathode capacity, better cycle life and rate capability compared to using PAA binder, reducing both the local charge-transfer resistance and the global electronic resistance before and after cycling. These are attributed to the enhanced binding strength and synergistic effect of reduced graphene oxide and PAA forming well-dispersed conductive bridges to promote rapid electron transfer. Additionally, GOPAA provides active sites for adsorption of lithium polysulfides and electrocatalytic activity, shifting redox peaks in cyclic voltammetry and improving roundtrip efficiency.