Levelized Electrode Utilization of Silicon-Enriched Pouch-Type Lithium-Ion Batteries from External Stress-Induced Overpotential Modulation

The sectional utilization of the Si negative electrode resulted from the appropriate physical treatment of the pouch cell based on the distribution of electrical resistance. Active materials loaded near the tab have low electrical resistance, leading to a higher degree of lithiation in the Si near the tab. This localized utilization in large pouch cells causes significant polarization growth of the electrode due to mechanical and interphasial degradation. In contrast, the active material loaded farther from the tab does not participate in the electrochemical reaction due to its high electrical resistance. Li plating on near-tab-loaded particles arises from the inhomogeneous failure of the Si negative electrode in a large electrode, causing abrupt discharge capacity fading after cycling. However, the application of external pressure increases the overpotential of near-tab-loaded active materials by constraining their volumetric expansion. Therefore, applying external pressure equalizes the Si utilization across the pouch cell footprint through external stress-induced overpotential modulation, thereby mitigating the sectional failure of the Si negative electrode.