Understanding and Controlling Electrolyte Motion induced Salt Inhomogeneity in Cylindrical Lithium-ion Batteries

Abstract

Electrolyte motion induced salt inhomogeneity (EMSI) is a failure mechanism that can occur in lithium-ion batteries. This mechanism can occur when volume changes in the electrodes induce movement of liquid electrolyte, leading to a re-distribution of the conducting lithium salt inside of the cell. This leads to increases in cell resistance, rapid capacity loss, and potentially lithium plating and cell failure. This thesis investigates the effects of cell design parameters such as anode chemistry and electrolyte fill volume on the EMSI effect. This is done using CT imaging and operando rotational inertia measurements to track electrolyte motion, and electrochemical impedance spectroscopy to quantify the generation and relaxation of salt gradients. EMSI is seen to be more severe in cells containing silicon, due to this material’s large volume change upon cycling. Electrolyte underfilling is presented as a strategy to avoid EMSI, though this has consequences for the cell’s long-term cycle life.