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

7Li and 1 H magic-angle spinning (MAS) NMR spectra were recorded for Li(Ni.Co,Al)O 2 samples. The 7 Li MAS NMR signal of the layer on the pristine material is close to that of Li 2 CO 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 2 CO 3 . Upon hydration, this layer grows, while 1 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 7 Li and 1 H NMR signatures, showing its largely organic nature.