Figure 4.

(a) TOF-SIMS chemical mapping of the organic electrolyte decomposition layer and dissolved transition-metal layer in the form of fluorides on an NMC cathode particle. (b) Comparison after 3,000 cycles of the amounts of transition-metal dissolution, forming metal fluorides (e.g., MnF₂), from an undoped and a 1 mol % Al-doped NMC cathode relative to that from a fresh electrode. (c) Comparison after 3,000 cycles of the amounts of dissolved transition metals and the calculated thickness of Li metal dendrites on graphite anodes that were paired with an undoped and a 1 mol % Al-doped NMC cathode. (d) Schematic illustrating the evolution of the SEI on graphite anode during cycling under the influence of dissolved transition-metal ion crossover from the cathode to the anode. Reproduced with permission from ref (37). Copyright 2017 American Chemical Society.