~7Li and ~1H MAS NMR Observation of Interphase Layers on Lithium Nickel Oxide Based Positive Electrodes of Lithium-Ion Batteries

摘要

~7Li and ~1H magic-angle spinning (MAS) NMR spectra were recorded for Li (Ni, Co, Al) O_2 samples. The ~7Li MAS NMR signal of the layer on the pristine material is close to that of Li_2CO_3 in close contact with it. Its lineshape, due to dipolar interaction with electron spins of the material, is drastically different from that of pure Li_2CO_3. Upon hydration, this layer grows, while H NMR suggests that some lithium in the material is replaced by protons. Upon electrochemical cycling, the original layer is replaced by a different one, the solid electrolyte interphase, with distinct ~7Li and ~1H NMR signatures, showing its largely organic nature.