Speaker
Description
Two commercial LFP|C cells of 26650-type were investigated non-destructively using a combination of electrochemical measurements, X-ray computed tomography (CT), diffraction and differential thermal analysis (DTA) to assess structural uniformity, lithium distribution, and aging behavior.
Despite identical cell chemistry and form factor, significant differences between the two cell types were noticed. Variations in charging profiles were attributed to differences in mobile lithium availability and cell balancing. Both cells employed a multi-tab electrode connection scheme with eight current collectors in total; however, distinct wiring layouts were revealed by X-ray CT, directly affecting lithium distribution and electrochemical performance. Notably, one cell exhibited severe electrode deformation and shorter lifetime, while the other displayed minor housing deformation but longer durability. Cycling data indicated heterogeneous lithium distribution as a critical factor for accelerated aging in the short-lived cell, whereas electrolyte degradation followed similar pathways in both cells, as suggested by DTA results.
The study highlights that external cell geometry does not necessarily reflect internal structural changes, underscoring the need for advanced, spatially resolved, non-destructive diagnostic tools. Beyond the current 26650 format, these insights are directly relevant to the development and evaluation of emerging large-format cylindrical cells (e.g., 4680, 4895), where uniformity and reliability are crucial for safe and efficient electric vehicle integration. Overall, this work emphasizes the role of internal connection schemes, lithium distribution, and mechanical integrity in determining Li-ion battery lifetime, and advocates for realistic cycling protocols in future investigations to better capture automotive-use aging phenomena.
