We present a NMR investigation of 6Li7−xHxLa3Zr2O12 (0 ≤ x ≤ 5) garnets to study the distribution of Li ions. The facile H+/Li+ exchange alters the relative population of Li sites, and allows the identification of 3 different bands ascribed to Li in different environments. Variable temperature measurements indicated the presence of dynamic processes between octahedral and tetrahedral Li sites.

H2V3O8 (HVO) is a promising high-capacity cathode material for lithium-ion batteries (LIBs). It allows reversible two-electron transfer during electrochemical lithium cycling processes, yielding a very attractive theoretical capacity of 378 mAh g–1. While an abundant number of research works exclusively proved the outstanding electrochemical lithium storage properties of H2V3O8, structural changes during the intercalation process have not been scrutinized, and the crystallographic positions occupied by the guest species have not been revealed yet. However, an in-depth understanding of structural changes of cathode materials is essential for developing new materials and improving current materials. Aimed at providing insights into the storage behavior of HVO, in this work, we employed a combination of high-resolution synchrotron X-ray and neutron diffraction to accurately describe the crystal structures of both pristine and lithiated H2V3O8. In HVO, hydrogen is located on one single-crystallographic site in a waterlike arrangement, through which bent asymmetric hydrogen bonds across adjacent V3O8 2– chains are established. The role played by water in network stabilization was further examined by density functional theory (DFT) calculations. Easy hydrogen-bonding switch of structural water upon lithium intercalation not only allows better accommodation of intercalated lithium ions but also enhances Li-ion mobility in the crystal host, as evidenced by magic-angle spinning (MAS) NMR spectroscopy. Facile conduction pathways for Li ions in the structure are deduced from bond valence sum difference mapping. The hydrogen bonds mitigate the volume expansion/contraction of vanadium layers during Li intercalation/deintercalation, resulting in improved long-term structural stability, explaining the excellent performance in rate capability and cycle life reported for this high-energy cathode in LIBs. This study suggests that many hydrated materials can be good candidates for electrode materials in not only implemented Li technology but also emerging rechargeable batteries.

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Ti/Ge distribution in rhombohedral LiTi2-xGex(PO4)3 NASICON series has been analyzed by (31)P magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy and first-principles density functional theory (DFT) calculations. Nuclear magnetic resonance is an excellent probe to follow Ti/Ge disorder, as it is sensitive to the atomic scale environment without long-range periodicity requirements. In the samples considered here, PO4 units are surrounded by four Ti/Ge octahedra, and then, five different components ascribed to P(OTi)4, P(OTi)3(OGe), P(OTi)2(OGe)2, P(OTi)(OGe)3, and P(OGe)4 environments are expected in (31)P MAS NMR spectra of R3̅c NASICON samples. However, (31)P MAS NMR spectra of analyzed series display a higher number of signals, suggesting that, although the overall symmetry remains R3̅c, partial substitution causes a local decrement in symmetry. With the aid of first-principles DFT calculations, 10 detected (31)P NMR signals have been assigned to different Ti4-nGen arrangements in the R3 subgroup symmetry. In this assignment, the influence of octahedra of the same or different R2(PO4)3 structural units has been considered. The influence of bond distances, angles and atom charges on (31)P NMR chemical shieldings has been discussed. Simulation of the LiTi2-xGex(PO4)3 series suggests that detection of 10 P environments is mainly due to the existence of two oxygen types, O1 and O2, whose charges are differently affected by Ge and Ti occupation of octahedra. From the quantitative analysis of detected components, a random Ti/Ge distribution has been deduced in next nearest neighbor (NNN) sites that surround tetrahedral PO4 units. This random distribution was supported by XRD data displaying Vegard's law.