Operando 7 Li NMR Reveals Lithium Plating and Recovery in Commercial Grade NMC811||Graphite Cells

Fast charging of lithium‐ion batteries can induce lithium plating on graphite, compromising safety and lifetime. We use operando 7 Li NMR to detect metallic lithium and intercalation stages in NMC811||graphite full cells with an anode‐to‐cathode capacity ratio (N/P) of 1.1, reflecting a commercial energy‐dense design. During formation, a metallic Li signal at a Knight shift of 270 ppm appeared above 4.1 V, whereas LiC 6 /LiC 12 resonances near 50 ppm emerged above 33% state‐of‐charge (SOC), consistent with LiC 12 . Upon discharge, both the metallic Li and LiC 6 /LiC 12 signals vanished, restoring the initial state, though a small fraction of dead Li may remain. After two formation cycles, cells were charged at up to 4 C and temperatures down to 5°C. In low N/P full cells, fast charging quickly advanced the upper cutoff, promoting plating at moderate SOC. No plating was detected below 4.2 V. Warming charged cells to 20°C reduced plated Li slightly, indicating kinetically limited transport. However, Li plated during 4 C pulses at room temperature was reabsorbed by the graphite after prolonged rest (4 days). Operando 7 Li NMR sensitively probes plating and recovery in commercially relevant cells and highlights voltage control and postcharge rest as practical levers to limit irreversible lithium.