Effect of Hierarchical Porous Media on Specific Capacity and Energy Density of Li-O2 Battery

Transport and electrochemistry in porous cathodes of Li-O2 battery with uniform and hierarchical initial porosity are modeled using the lattice Boltzmann method. Compared to a uniformly porous cathode, the hierarchical porous cathode is found to be delivering a higher energy density. The energy density for the hierarchical cathode is higher than that of uniform porous cathode by 346% for low initial porosity and by 6.23% for high initial porosity. While comparing the specific capacity offered by the hierarchical porous cathode, the value is 1244% higher than that of the low porosity uniform porous cathode but 19.97% lower than that of the high porosity uniform porous cathode. The reason for this reduction in specific capacity is found to be the increase in density of the hierarchical cathode compared to the uniform porous cathode due to the addition of porous layers with low porosity. The hierarchical porous cathode is found to be the space-efficient, and hence, it is a better option where there are strict space constraints.