A high-performance slurry-coated polysulfide cathode for lithium–sulfur battery

Highlights: • A high-performance lithium-polysulfide (PS) battery using inexpensive commercially available materials has been developed. • Specific capacities between 1220 and 1007 mAh g⁻¹ were achieved at charge rates of 0.2–2.0 C. • At higher sulfur loading, a practical areal capacity of > 4 mAh cm^-2 was achieved. • The differences between sulfur cathodes prepared via polysulfide addition and conventional melt-diffusion were examined. • The 3D interconnected porous structure of the PS cathode led to a better performance over the conventional sulfur cathode. -- Abstract: There has been tremendous progress in enhancing the electrochemical performance of lithium-sulfur batteries. For example, the use of dissolved polysulfide (PS) as cathode improves sulfur (S) utilization and redox kinetics. Notably, free-standing PS cathodes have exceptional performance, but their preparation is not scalable as compared to the slurry-coating process. However, the electrochemical performance of slurry-coated PS electrodes such as Pt/graphene, Super P, metal nitrides and hierarchical porous carbon, is not satisfactory. Herein, a high-performance lithium-PS battery using inexpensive commercially available materials has been developed. Specific capacities between 1220 and 1007 mAh g⁻¹ were achieved at charge rates of 0.2–2.0 C, having capacity fade of lower than 0.14% per cycle over 200 cycles. At higher S loading, a practical areal capacity of > 4 mAh cm^-2 was achieved. The difference between PS and melt-diffusion S cathodes was also examined. Remarkably, the PS cathode offered 48% higher specific capacity and 26% lower capacity fade than the melt-diffused S cathode due to differences in morphology, surface area and ohmic resistance of the cathodes. This work provides a strong case towards a paradigm shift away from conventional cathode preparation approaches to improve the electrochemical performance of lithium-S batteries.