How can Incremental Capacity Analysis (ICA) be used to identify specific degradation modes in a lithium-ion battery?

Incremental Capacity Analysis (ICA) is a powerful technique used to identify specific degradation modes in lithium-ion batteries by analyzing the derivative of the battery's capacity with respect to voltage (dQ/dV) during a slow, constant-current charge or discharge. This derivative reveals distinct peaks and valleys in the voltage range, each corresponding to specific phase transitions or electrochemical reactions within the battery. Changes in the position, height, and shape of these features over time provide valuable insights into the types and extent of degradation occurring within the battery. In a healthy lithium-ion battery, the ICA curve exhibits well-defined peaks associated with specific lithium intercalation/deintercalation processes at the positive and negative electrodes. As the battery degrades, these peaks shift, broaden, or diminish, indicating changes in the electrochemical behavior of the electrodes. For example, loss of active material (LAM) at either the positive or negative electrode will typically result in a decrease in the height of the corresponding peak in the ICA curve. LAM means that some of the electrode material is no longer participating in the electrochemical reactions, reducing the battery's capacity. Lithium plating, which is the formation of metallic lithium on the surface of the negative electrode, can also be identified using ICA. Lithium plating often occurs during charging at low temperatures or high current rates. It results in the appearance of new peaks or shoulders in the ICA curve at specific voltage ranges. These features are associated with the electrochemical reactions involving the plated lithium. Electrolyte decomposition, which leads to the formation of solid electrolyte interphase (SEI) layers on the electrode surfaces, can also be detected using ICA. Electrolyte decomposition typically causes a shift in the position of the peaks in the ICA curve, as well as a general broadening of the features. The SEI layer increases the internal resistance of the battery and hinders lithium-ion transport. Changes in the shape and position of the ICA peaks can also indicate changes in the stoichiometry of the electrode materials or the development of internal short circuits. By carefully analyzing the ICA curve and tracking changes in its features over time, it is possible to identify the dominant degradation modes occurring in the battery and to quantify the extent of degradation. This information can be used to improve battery management strategies, optimize charging protocols, and predict remaining useful life. For instance, if ICA reveals significant lithium plating, the charging strategy can be adjusted to reduce the charging current or increase the charging temperature to minimize further plating. ICA is a valuable diagnostic tool for understanding battery degradation mechanisms and improving battery performance and lifespan.