Determining the oxidation states of dissolved transition metals in battery electrolytes from solution NMR spectra.

Dissolved transition metal ions can induce peak shifts in the NMR spectra of degraded battery electrolytes. Here, we exploit this staightforward, accessible method to calculate magnetic moments for dissolved Ni 2+ , Mn 2+ , Co 2+ , and Cu 2+ ; subsequent analysis of dissolution from LiMn 2 O 4 , LiNiO 2 , and LiNi 0.5 Mn 1.5 O 4 shows that the dissolved metals are exclusively divalent.