Degradation in parallel-connected lithium-ion battery packs under thermal gradients

Degradation in parallel-connected lithium-ion battery packs under thermal gradients

(2024)3:2 | Max Naylor Marlow, Jingyi Chen & Billy Wu
This study investigates the impact of thermal gradients on the degradation of parallel-connected lithium-ion battery packs. The researchers conducted experiments on 1S2P battery packs (1 cell in series, 2 cells in parallel) under controlled thermal conditions (20-45°C) and identified two main operational modes: convergent degradation with homogeneous temperatures and divergent degradation driven by thermal gradients. The divergent mode is attributed to cathode impedance growth, which is often overlooked but negatively correlates with temperature and can cause positive feedback, leading to increasing heterogeneous current and state-of-charge (SOC) distributions. The study uses current distribution measurements, decoupled impedance measurements, and degradation mode analysis to support these conclusions. The findings highlight the critical role of capturing cathode degradation in parallel-connected batteries, providing key insights for battery pack developers. The research also discusses the implications of thermal gradients on battery pack lifetime and the need to minimize thermal gradients to maximize energy availability.This study investigates the impact of thermal gradients on the degradation of parallel-connected lithium-ion battery packs. The researchers conducted experiments on 1S2P battery packs (1 cell in series, 2 cells in parallel) under controlled thermal conditions (20-45°C) and identified two main operational modes: convergent degradation with homogeneous temperatures and divergent degradation driven by thermal gradients. The divergent mode is attributed to cathode impedance growth, which is often overlooked but negatively correlates with temperature and can cause positive feedback, leading to increasing heterogeneous current and state-of-charge (SOC) distributions. The study uses current distribution measurements, decoupled impedance measurements, and degradation mode analysis to support these conclusions. The findings highlight the critical role of capturing cathode degradation in parallel-connected batteries, providing key insights for battery pack developers. The research also discusses the implications of thermal gradients on battery pack lifetime and the need to minimize thermal gradients to maximize energy availability.
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