Chapter 5 NMR Experiments in Ionic Conductors Nuclear Magnetic Resonance (NMR) has been shown to be a useful tool for the study of the structure [1–4] and dynamics [3, 5–11] of ionic conductors. While magic-angle spinning techniques are most often used for obtaining structural details, the dynamics of ion are usually explored by measuring spin-relaxation times [12]. Many of these NMR studies of ionically conducting materials have focused on lithium ion conductors. The reason is probably twofold: on one hand, the huge interest in these materials for their application in solid state batteries due to the usually high lithium mobility; and on the other hand, the existence of two stables isotopes, 6 Li and 7 Li, with different magnetic dipole and electrical quadrupole moments, that allow studying these ionic conductors from two different views since different NMR interactions are dominant for different probe nuclei [10, 11, 13, 14]. However, in many cases lithium NMR experiments are performed with the 7 Li (I ¼ 3/2) nucleus rather than 6 Li (I ¼ 1). This is because of the higher sensitivity of the former due to its higher natural abundance and gyromagnetic ratio, while 6 Li experiments require enrichment of the samples. Incidentally a series of ( 6 Li, 7 Li) 2 O- 2.88B 2 O 3 glasses had been studied for the Li isotope mass dependence of conduc- tivity by Downing et al. [15], and data were explained by the Coupling Model [16]. Recently, NMR spectroscopy has been also shown to be useful to probe the structural changes that occur in battery electrode materials during electrochemical cycling [17]. While most of these studies have been performed ex situ, providing considerable insight into the structural and dynamical processes that occur in battery materials at different (previously achieved) states of charge, in situ NMR now provides a non-invasive means to study the electrochemically-induced struc- tural changes that occur on cycling a lithium ion battery [18]. In this chapter we will focus in particular on how NMR experiments can be used to study the dynamics of mobile ions in electrolytes, showing examples on different crystalline and glassy lithium ion conductors, and we will also show how the data obtained from these experiments can be compared to electrical conductivity relax- ation (ECR) measurements. © Springer International Publishing Switzerland 2017 J. Habasaki et al., Dynamics of Glassy, Crystalline and Liquid Ionic Conductors, Topics in Applied Physics 132, DOI 10.1007/978-3-319-42391-3_5 251