A comparative mathematical study on the influence of electrolyte and separator variations on lithium-ion battery performance

This study systematically investigates LiFePO₄ (LFP) and graphite half-cells using different separator-electrolyte configurations to explain their effects on lithium-ion transport and electrochemical performance. The electrodes are prepared from commercially available powders and characterized using XRD and SEM. Electrochemical analysis is performed using cyclic voltammetry (CV), galvanostatic intermittent titration technique (GITT), and electrochemical impedance spectroscopy (EIS). Lithium diffusion coefficients (D_Li+) are determined from both CV and GITT data, allowing for comparison of transport kinetics. The results indicate that electrolyte viscosity and separator porosity are critical determinants of ion transport. The LFP and graphite cell configuration containing Electrolyte-B (1.08 M LiPF₆ in 1:3 EC:EMC) consistently provides the highest D_Li+ values and the lowest charge transfer resistance. In graphite half-cells, the Electrolyte-B and Separator-2 (three-layer, PP, 54% porosity, 20 μm) configuration exhibits superior anodic kinetics, low polarization, and excellent capacity retention. Similarly, the same electrolyte and Separator-1 (single-layer, PP, 55% porosity, 25 μm) cell configuration exhibits the highest diffusion coefficient and specific discharge capacity among LFP systems. These results confirm a strong correlation between lithium-ion diffusion and long-term electrochemical stability.