Uneven electrical current distribution in a parallel-connected lithium-ion battery pack can result in different degradation rates and overcurrent issues in the cells. Understanding the electrical current dynamics can enhance configuration design and battery management of parallel connections.
Parallel connection of lithium-ion batteries significantly aggravates the unbalanced discharging phenomenon between the cells. A simplified capacity loss model was proposed for the lithium-ion batteries and was used to assess the capacity degradation performances for the parallel-connected cells.
Parallel charging induces the imbalance discharge phenomenon between the cells in a battery pack, which potentially reduces the battery pack's performances, such as capacity degradation and overcurrent discharge. This can lead to uneven wear and tear among the cells.
Yang, N., Zhang, X., Shang, B. & Li, G. Unbalanced discharging and aging due to temperature differences among the cells in a lithium-ion battery pack with parallel combination. J. Power Sour.306, 733–741 (2016). Article Google Scholar
To meet the power and energy requirements of the specific applications, lithium-ion battery cells often need to be connected in series to boost voltage and in parallel to add capacity . However, as cell performance varies from one to another [2, 3], imbalances occur in both series and parallel connections.
The capacity degradation of a lithium-ion battery is caused by several mechanisms associated with unwanted side reactions. Unbalanced discharging and aging due to temperature differences among the cells are among the factors that induce phase changes in the inserted electrode materials, active material dissolution, passive film formation, electrolyte decomposition, and other negative effects.