Heterogeneity propagation and surface homogenization for pouch-cell-sized Li metal anodes

Li metal batteries are challenged by anode instability issues originating from Li surface utilization heterogeneities, which emerge during the earliest stages of cycling, propagate throughout operation, and ultimately drive cell-to-cell performance variations and failure. However, heterogeneity issues remain under-investigated due to mainstream studies' reliance on electrodes with small areas and few replicates. Here, we evaluated 32 Li || NMC811 pouch cells, using either as-purchased or mechanically homogenized Li via brushing. The brushed group exhibits narrower distributions of capacity trajectories and lifetimes, along with a 35% increase in median lifetime relative to the as-purchased group. Additionally, millimeter-scale variations in chemical compositions are observed on the as-purchased Li surface and result in localized utilization patterns after initial plating and stripping, whereas such inhomogeneity is eliminated after brushing. This work establishes a link between early-stage Li utilization and cell performance consistency, providing a pathway for evaluating and improving reliability in large-format battery production.