Single-Crystal 31P and 7Li NMR of the Ionic Conductor LiH2PO4

Abstract

The electronic surroundings of phosphorus and lithium atoms in the ionic conductor lithium dihydrogen phosphate (LDP) have been studied by single-crystal nuclear magnetic resonance (NMR) spectroscopy at room temperature. From orientation-dependent NMR spectra of a large homegrown LDP single crystal, the full 31 P chemical shift (CS) and 7 Li quadrupole coupling (QC) tensor was determined, using a global fit over three rotation patterns. The resulting CS tensor is characterized by its three eigenvalues: δ PAS 11 = (67.0 ± 0.6) ppm, δ PAS 22 = (13.9 ± 1.5) ppm, and δ PAS 33 = (−78.7 ± 0.9) ppm. All eigenvalues have also been verified by magic-angle spinning NMR on a polycrystalline sample, using Herzfeld-Berger analysis of the rotational side band pattern. The resulting 7 Li QC tensor is characterized by its quadrupolar coupling constant χ = Q PAS 33 = (−71 ± 1) kHz and the two eigenvalues Q PAS 11 = (22.3 ± 0.9) kHz, and Q PAS 22 = (48.4 ± 0.8) kHz. The initially unknown orientation of the mounted crystal, expressed by the orientation of the rotation axis in the orthorhombic crystal frame, was included in the global data fit as well, thus obtaining it from NMR data only.Crystals 2020, 10, 302 2 of 12 with four formula units per unit cell [6]. The PO 4 tetrahedra build a three-dimensional framework connected by two different types of hydrogen bonds. The LiO 4 coordination tetrahedra are linked by their vertices forming [100] isolated chains and share each edge with the PO 4 units. All atoms in the unit cell are located at Wyckoff position 4a with the general site symmetry 1 − C 1 [7]. As a result, no symmetry constraints affect the algebraic form of the NMR interaction tensors, as will be explained in the following.Abstract: Last thing to be done...

Water‐Soluble Inorganic Binders for Lithium‐Ion and Sodium‐Ion Batteries

“…However, this conductivity is predominantly due to the conduction of protons (H + ) as confirmed by 1 H NMR investigations. [ 97 ] A recent study reported an IC of 2×10 −5 S cm −1 at 200 °C and 1.6 × 10 −8 S cm −1 at 60 °C, which was much lower than previously reported values. [ 43 ] This might be attributed to the fact that the LHPO pellet was first dried at 200 °C before recording the impedance.…”