Electrochemical-Thermal Modelling and Optimisation of Lithium-Ion Battery Design Parameters Using Analysis of Variance

A 1D electrochemical-thermal model of an electrode pair of a lithium ion battery is developed in Comsol Multiphysics. The mathematical model is validated against the literature data for a 10 Ah lithium phosphate (LFP) pouch cell operating under 1 C to 5 C electrical load at 25 degrees C ambient temperature. The validated model is used to conduct statistical analysis of the most influential parameters that dictate cell performance; i.e., particle radius (r(p)); electrode thickness (L-pos); volume fraction of the active material (epsilon(s,pos)) and C-rate; and their interaction on the two main responses; namely; specific energy and specific power. To achieve an optimised window for energy and power within the defined range of design variables; the range of variation of the variables is determined based on literature data and includes: r(p): 30-100 nm; L-pos: 20-100 mu m; epsilon(s,pos): 0.3-0.7; C-rate: 1-5. By investigating the main effect and the interaction effect of the design variables on energy and power; it is observed that the optimum energy can be achieved when (r(p) < 40 nm); (75 mu m < L-pos < 100 mu m); (0.4 < epsilon(s,pos) < 0.6) and while the C-rate is below 4C. Conversely; the optimum power is achieved for a thin electrode (L-pos < 30 mu m); with high porosity and high C-rate (5 C).