A Method to Determine Fast Charging Procedures by Operando Overvoltage Analysis

Münster, Patrick; Winter, Martin; Niehoff, Philip

Abstract

A method to determine threshold voltage conditions for Li plating in lithium ion battery cells is presented. Transferring open-circuit values determined in a 3-electrode electrochemical measurement onto a 2-electrode cell setup, the boundary conditions for Li plating can be assessed. In multi-layer pouch cells, these boundary conditions agree perfectly with the exact onset of Li plating as proven by post mortem analysis. By knowledge of the Li plating threshold voltage conditions, plating-free fast-charging procedures can be exercised leading to an increase in charging rate by 84% and 79% for two different cell systems, respectively. Cycling above or below the Li plating threshold voltage, Li plating occurrence can be deliberately controlled. Comparing plating and plating-free conditions, the applied charging voltage properties differ hardly. Hence, the applied analysis of overvoltage proves a more sensitive and specific operando method to predict Li plating.