Toward understanding of ion dynamics in highly conductive lithium ion conductors: Some perspectives by solid state NMR techniques

Solid state lithium ion conductors are promising to replace the organic liquid electrolytes for a safer and long cycle-life lithium battery. However, solid electrolytes are still not fully explored and need extensive basic studies to understand their intrinsic conducting mechanism and interfacial properties between electrodes and electrolytes. In this review, we highlight the latest progresses in the research of lithium ion conductors by using advanced solid state nuclear magnetic resonance(SS NMR) spectroscopy, i.e. Magic angle spinning (MAS) NMR, pulsed-field gradient (PFG) NMR, spin-lattice(SLR) as well as spin-spin relaxation NMR, spin alignment echo (SAE) NMR and two-dimensional exchange (2D EXSY) NMR, and briefly review the application of these solid NMR techniques in LISICON-, NASICON- and Garnet-type lithium ion conductors in the different time/length scales, as well as the measurement in the determination of ion occupancy, ion diffusion pathways, and diffusion coefficients.