The Batteries’ New Clothes: Li and H Dynamics in Poorly Conducting Li<sub>2</sub>OHCl Directly Probed by Nuclear Spin Relaxation
Jonas Spychala, Alexandra Wilkening, Martin Wilkening
Abstract
High Resolution Image Download MS PowerPoint Slide Li 2 OHCl is considered to act as a suitable Li + ionic conductor that is, excluding Li, solely composed of rather abundant elements. Its low meting point allows rather easy synthesis methods to prepare Li 2 OHCl in large quantities. So far, only few studies tackled the problem to deliver a clear-cut picture of Li + self-diffusion. Li + hopping in Li 2 OHCl is suggested to be coupled to OH – rotational dynamics. Proving such an interdependent coupling beyond any doubt remains, however, challenging. Here, we observed diffusion-induced 7 Li and 1 H NMR spin–lattice relaxation in both the laboratory and rotating frame of reference to find out (i) whether Li + displacements are caused by fast OH – motions or (ii) whether anisotropic rotational OH – dynamics is a consequence of the rapid Li + translational processes. By considering 7 Li and 1 H NMR line shapes and comparing our results with those obtained from conductivity spectroscopy as well as from recent ab initio molecular dynamics simulations and 2 H NMR by Dawson et al., Energy. Environ. Sci. 2018, 11, 2993–3002, we propose that OH – rotational dynamics could also be a consequence rather than the trigger for fast Li + self-diffusion (0.41 eV) on the NMR time scale.