Chemical shift reference scale for Li solid state NMR derived by first-principles DFT calculations

Abstract

For studying electrode and electrolyte materials for lithium ion batteries, solid-state (SS) nuclear magnetic resonance (NMR) of lithium moves into focus of current research. Theoretical simulations of magnetic resonance parameters facilitate the analysis and interpretation of experimental Li SS–NMR spectra and provide unique insight into physical and chemical processes that are determining the spectral profile. In the present paper, the accuracy and reliability of the theoretical simulation methods of Li chemical shielding values is benchmarked by establishing a reference scale for Li SS–NMR of diamagnetic compounds. The impact of geometry, ionic mobility and relativity are discussed. Eventually, the simulation methods are applied to the more complex lithium titanate spinel (Li4Ti5O12, LTO), which is a widely discussed battery anode material. Simulation of the Li SS–NMR spectrum shows that the commonly adopted approach of assigning the resonances to individual crystallographic sites is not unambiguous.