(49a) Modeling the Effect of Mesoporous Carbon Cathodes in Li-S Batteries

Lithium sulfur (Li-S) batteries are a promising candidate for next-generation energy storage due to their high theoretical energy density. However, well-known challenges such as polysulfide crossover, large volume changes during cycling, and passivation of reaction sites limit the capacity and capacity retention of Li-S batteries. One approach to address these issues is to control the size of pores in the carbon cathode, which affects the transport of sulfur, surface area for reaction, and lithium sulfide deposition during cycling. In particular, mesopores (2-50nm diameter) have shown prior success in Li-S cathode materials due to their high surface area and their ability to retain polysulfide intermediates while still maintaining electrolyte access.

To investigate the effect of mesopores on Li-S battery performance, we have developed a 1-dimension + time numerical continuum model for the Li-S full cell. The model includes the electrochemical reactions and precipitation of sulfur and intermediate polysulfide species, multicomponent transport of species through the pore, polysulfide crossover, lithium sulfide nucleation, and passivation of the cathode. We use the model to predict optimal pore size distributions for different charge rates and sulfur loading, which are compared to results from experimental Li-S coin cells made with mesoporous carbon nanofiber cathodes.