Modeling of Lithium-Ion Battery Degradation for Cell Life Assessment

TLDR

Rechargeable lithium‑ion batteries are promising for grid‑level storage due to their high energy and power density, low discharge rate, and falling cost, yet accurate aging‑cost modeling is essential for energy‑storage planning, especially under irregular cycling. The study proposes a semi‑empirical lithium‑ion battery degradation model to assess cell life loss from operating profiles. The model integrates fundamental degradation theories with empirical aging test data, is adaptable to various lithium‑ion chemistries, includes manufacturer‑based coefficient tuning, and uses a cycle‑counting method to identify stress cycles in irregular operations. The model’s usefulness is shown by evaluating degradation of a battery‑energy‑storage system providing frequency control in the PJM regulation market.

Abstract

Rechargeable lithium-ion batteries are promising candidates for building grid-level storage systems because of their high energy and power density, low discharge rate, and decreasing cost. A vital aspect in energy storage planning and operations is to accurately model the aging cost of battery cells, especially in irregular cycling operations. This paper proposes a semi-empirical lithium-ion battery degradation model that assesses battery cell life loss from operating profiles. We formulate the model by combining fundamental theories of battery degradation and our observations in battery aging test results. The model is adaptable to different types of lithium-ion batteries, and methods for tuning the model coefficients based on manufacturer's data are presented. A cycle-counting method is incorporated to identify stress cycles from irregular operations, allowing the degradation model to be applied to any battery energy storage (BES) applications. The usefulness of this model is demonstrated through an assessment of the degradation that a BES would incur by providing frequency control in the PJM regulation market.