State Analysis of Lithium-Ion Batteries Using Discharge Curves

Abstract

It is essential to derive and quantitatively evaluate the parameters of capacity fade in order to understand degradation mechanisms of lithium-ion batteries. Capacity is directly connected with the discharge curve, and it can be reproduced from cathode and anode specific discharge curves. The states of lithium-ion cell cathodes and anodes were accurately estimated using nondestructive state analysis. The cell discharge curve was well reproduced for both the initial and deteriorated states from the specific cathode and anode discharge curves, the amounts of accessible active materials in each electrode, and the alignment between cathode and anode discharge curves. This method was used in a calendar-life test to separately evaluate the decrease in the amounts of active materials in each electrode and the increase in irreversible lithium loss.