Understanding molecular interactions and dynamic properties of liquid electrolytes is an essential step for developing novel future materials in the electrochemical research field. Nuclear magnetic resonance (NMR) spectroscopy is a highly accurate and non-invasive experimental technique that has been used to determine the molecular structures and kinetic information of electrolytes such as ionic liquid complexes. Moreover, in-situ NMR techniques provide a better understanding of chemical reactions and physical processes occurring inside electrochemical cells, allowing real time investigations of the cells under operating conditions. In NMR spectroscopy, bulk chemical and physical properties are acquired from whole sample, however, heterogeneous mediums such as gels can change the molecular dynamics, and result in localized signals due to spatial distributions in density or relaxation times. Furthermore, reactions which are coupling with hydrodynamics or which are sensitive to perturbations (e.g. in temperature) can also result in inhomogeneous molecular distributions and kinetics. Hence, using a technique which can spatially map and quantify the chemical species and their physical environment is convenient to understand such phenomena. Magnetic resonance imaging (MRI) is able to spatially resolve NMR signals by applying magnetic field gradients. The gradients cause a frequency variation of spins with the position of a matrix and allow to construct images which are related to spin densities, molecular motions and relaxation times.
In this study, a series of electrolyte samples consisting of a Co2+/3+(bpy)3(NTf2)2/3 redox couple (where bpy = bipyridyl and NTf2 = bis(tri-fluoromethanesulfonyl)imide) and 3-methoxypropionitrile (MPN) solvent, as well as gel versions with Polyvinylidene fluoride (PVDF), have been investigated using both NMR and MRI techniques. Relaxation and diffusion measurements of the paramagnetic, non-paramagnetic and mixed samples were investigated as a function of temperature and alterations between paramagnetic and non-paramagnetic samples were significantly observed.