A low-self-discharge high-loading polysulfide cathode design for lithium–sulfur cells

Abstract

Lithium–sulfur batteries are a promising energy storage system with high energy density. However, during prolonged storage, they are prone to rapid capacity-fade, which is caused by severe self-discharge. This significantly shortens batteries' shelf life and impairs their long-term performance. This self-discharge effect has rarely been discussed in the literature. In this study, we develop a low-self-discharge polysulfide cathode with a carbonized electrospun nanofiber substrate. This cathode design achieves a high areal sulfur loading (4.03 mg cm⁻²) and a high sulfur content (66.8 wt%), while maintaining a low capacity-fade rate (0.26% per day) over a long storage time (90 days). In addition to the high capacity retention, it also maintains high lithium-ion diffusion coefficients after long-term storage. As a result, the rested low-self-discharge polysulfide cathode achieves a long cycle life (200 cycles) with stable electrochemistry. We further evaluate the long-term low-self-discharge performance of our lithium–sulfur cell via a series of quantitative analyses and performance analyses of the self-discharge behavior of the high-loading polysulfide cathode. The results provide key insights into the electrochemistry that occurs during the long-term storage of lithium–sulfur cells and into the low-self-discharge behavior of our designed cathode.