Investigation of solvation in lithium ion battery electrolytes by NMR spectroscopy

The solvation of LiPF6 by carbonate solvents (EC, DMC, and DEC) was investigated via 13C NMR chemical shift and 1H NMR diffusion coefficient experiments. The gradual addition of LiPF6 into a ternary solvent mixture results in a larger change in the chemical shift of EC than DMC or DEC suggesting that EC binds Li+ more strongly than DEC or DMC. The self diffusion coefficient of the carbonate solvents provides additional support for EC binding Li+ more strongly than DEC or DMC. Variable temperature NMR spectroscopic investigations support an increase in EC binding at low temperature and an enthalpic preference for the binding of EC to Li+.