Li-S battery is widely considered as one of the most promising candidates for the next generation energy storage devices due to its high theoretical capacity and energy density. However, the actual performance of the whole Li-S battery is highly impacted by the structure of cathode materials and the amount of electrolyte.

In this talk, the performance of Li-S battery was studied based on different cathode porosities (40% ~ 70 %). It was shown that the two discharging plateaus were both affected as the porosity is lower than 50%. The capacity of the first plateau around 2.4 V was shortened while the voltage in the second plateau around 2.1 V was highly depressed, leading to a lower energy density.

To further understand the design limitations, a combined experimental and modeling approach was utilized to determine the limiting factor in each plateau and predict the relationship between energy density and porosity. It was revealed that the first plateau was mainly limited by the amount of soluble polysulfide while the second plateau was limited by the surface area of the carbon matrix. Since a decreased porosity would have a negative influence on both limiting factors, an optimal porosity is predicted for maximum energy density. A consistency between modeling prediction and experimental observation was obtained, suggesting the validation of this model.