Characterization of Cylindrical Lithium-Ion Batteries with Varying Electrolyte Amounts at Beginning of Life

Abstract

This study investigates the impact of the electrolyte amount on the electrical performance at beginning of life in high energy cylindrical lithium-ion batteries. We investigate cylindrical 4695 prototype cells with varying pore filling ratios (PFRs), defined as the ratio of electrolyte volume to pore volume within anode, cathode, and separator. The PFR ranges from roughly half-filled pore volume to completely filled pore volume with additional free electrolyte. It is found that the energy and resistance remain constant as long as the PFR 100 (at 100% SoC) > 1.00. As soon as the PFR 100 < 1.00, the cell energy decreases, and the resistance increases with decreasing PFR. We also demonstrate the application of moment of inertia (MoI) measurements as a complementary technique to validate PFR calculations. Additionally, an analytical equation is developed to describe the relation between the electrolyte mass expelled from the jelly roll vs measured MoI change, isolating the contribution of electrolyte motion. This work lays the foundation for a subsequent study on the influence of PFR on the aging of cylindrical cells.