Pulsed Field Gradient Nuclear Magnetic Resonance and Diffusion Analysis in Battery Research

Abstract

Pulsed-field gradient nuclear magnetic resonance (PFG-NMR) is a widely used method for determining the diffusion coefficient of ions and molecules both in the bulk and when confined (e.g., within porous materials). Due to the nature of diffusion phenomena and the correlation of these processes with the structures of isolated molecules or clusters, studies of diffusion can be used to extract both dynamic and structural information from complex mixtures, including battery electrolytes composed of cations, anions, and solvent molecules. PFG-NMR presents a powerful opportunity for battery scientists to quantify electrolyte properties, such as time scales for dynamics, transference numbers, and solvation structures of active ions that vary due to ion–ion and ion–solvent interactions. These measurements and the derived information about molecular interactions can ultimately be correlated with real battery performance. The purpose of this review is to provide readers with an overview of the basic principles and experimental considerations when undertaking PFG-NMR for battery electrolyte research. In this review, we will first (1) introduce basic PFG-NMR experiments, parameters, and the proper setup for acquiring accurate diffusion coefficients and (2) discuss artifacts that can arise in diffusion measurements, including their diagnosis and suppression. Second, we show the ultimate power of careful analyses of diffusion coefficients for extracting dynamic and structural properties of a wide range of electrolyte types (i.e., dilute, concentrated, polymer, and solid-state) through a review of selected literature. In addition, other NMR methods are briefly introduced, including relaxation measurements and Overhauser dynamic nuclear polarization (ODNP) NMR.

Metastable properties of a garnet type Li5La3Bi2O12 solid electrolyte towards low temperature pressure driven densification

“…Short-duration magnetic eld gradient pulses are introduced into the spin-echo sequence to detect particle displacement in PFG NMR experiments. 37 The resultant signal intensity (I) depends on the parameters of the applied gradients and the self-diffusion coefficient (D) of the observed species as the following equation: I = I 0 e −BD , where I 0 is the NMR signal intensity without gradient application and B represents experimental conditions as: B = g 2 g 2 d 2 (D − d/3) with ggyromagnetic ratio of the observed nuclei, g and dstrength and duration of the gradient pulses, and Ddelay between the encoding and the decoding gradients. An example of stacked 7 Li PFG NMR spectra of the LLBO sample collected at different gradient strengths (g varied from 100 G cm −1 to 2500 G cm −1 in 16 equidistant steps) is shown in Fig.…”

Influence of AlPO4 Impurity on the Electrochemical Properties of NASICON‐Type Li1.5Al0.5Ti1.5(PO4)3 Solid Electrolyte

“…The lithium diffusion in the analyzed samples was investigated using pulsed‐field gradient nuclear magnetic resonance (PFG NMR) technique [27,28] . Short‐duration magnetic field gradient pulses are introduced into spin‐echo sequence to detect particles displacement in PFG NMR experiments.…”

“…The lithium diffusion in the analyzed samples was investigated using pulsed-field gradient nuclear magnetic resonance (PFG NMR) technique. [27,28] Short-duration magnetic field gradient pulses are introduced into spin-echo sequence to detect particles displacement in PFG NMR experiments. The resulted signal intensity (I) depends on parameters of the applied gradients and the self-diffusion coefficient (D) of the observed species by the following equation (Eq.…”

Simulating open quantum dynamics on an NMR quantum processor using the Sz.-Nagy dilation algorithm

“…C. Simulating a magnetic field gradient pulse MFGP are extensively used in NMR and magnetic resonance imaging experiments, covering a wide range of applications, such as studies of molecular diffusion and spatial encoding for imaging [37][38][39]. Recently, a time and space discretization method was proposed to simulate shaped gradient pulses [40].…”