The Effects of Defects on Localized Plating in Lithium-Ion Batteries

This work investigates how local cell defects can induce local lithium deposition and dendrite growth in a lithium-ion cell that appears to otherwise be performing correctly. Using local pore closure in the battery separator as a model defect, we experimentally demonstrate the occurrence of local lithium deposition during cycling in coin cells containing deliberately manufactured local regions of separator pore closure. We further investigate the local plating phenomena observed in these experiments using an axisymmetric finite element model of the defect-containing coin cell geometry. Our simulations show that the pore closure acts as an "electrochemical concentrator," creating locally high currents and overpotentials in the adjacent electrodes. This leads to lithium plating if the local overpotential exceeds equilibrium potential in the negative electrode. We examine the sensitivity of the local plating behavior to various materials, geometric, and operating parameters to identify mitigation strategies. The results of this work can be generalized to any defect that creates spatially non-uniform current distributions.