A Two-Dimensional Heterogeneous Model of Lithium-Ion Battery and Application on Designing Electrode with Non-Uniform Porosity

In this work, a two-dimensional heterogeneous model of lithium-ion battery electrode is developed. The electrode is reconstructed using a non-volume-averaging approach, generating a heterogeneous structure in which solid and liquid phase are characterized separately with respective real spatial occupation and boundaries between them. The heterogeneous model is parameterized using voltage and temperature curves at multiple C-rates. Mass and charge transport in the generated electrodes, coupled with interfacial reactions, are numerically solved. Three cases with different porosity profiles are compared. Without changing the amount of active materials and its particle size distribution, an improvement of rate performance up to 50% is achieved in the case with larger electrode porosity near the electrode-separator interface. Using the heterogeneous model as the benchmark, the precision of the pseudo-two-dimension model of lithium-ion battery electrode, which has been widely adopted in literatures and commercial computational softwares, can be improved by proper parameterization, including using the volume-averaged rather than number-averaged diameter as the negative electrode particle size; using the generated electrode structure, rather than the Bruggeman relationship, to calculate the tortuosity of porous electrodes; and using the size of primary particle, rather than that of the agglomerate, as the particle size at the positive electrode.