We will describe our work on the development of techniques for assessment of Li-ion batteries and battery materials via magnetic resonance imaging (MRI). The goal of these studies is to analyze battery degradation and energy storage mechanisms in situduring charging or discharging conditions by imaging changes in both the electrolyte and the electrodes in a noninvasive fashion.

In situ NMR/MRI have proven to be a useful tool to probe the structure of Li-ion batteries during real-time charge and discharge.  Ex situ studies of batteries are limited by self-relaxation of the electrode materials before a measurement can be obtained. The application of advanced magnetic resonance techniques, such as MRI and complex NMR experiments, in situ has the potential to monitor dynamics and visually monitor changes in functioning electrochemical systems in real time. The functionality of some energy storage devices where only the electrolyte is involved in the electrochemical process (such as supercapacitors) can only be studied in situ, as the electrolyte concentration gradients will relax as a potential is removed from the cell. Here we present techniques for in situ MRI of batteries and supercapacitors and discuss findings obtained from these studies [1,2]. It will be discussed how the rf field is perturbed by the presence of conducting materials in the probe [2], how susceptibility shifts can be used for assessing the morphology of microstructure buildup on electrodes [3]. The location and concentration of both cations and anions can be followed separately [4]. Figure 1 shows 3D images of Li metal obtained from an intact cell, at different times after initiation of charging, and Figure 2 shows both electrolyte and electrode 7Li images which are used to test dendrite growth models such as the Chazalviel model [5].

1.         S. Chandrashekar, N. M. Trease, H. J. Chang, L.-S. Du, C. P. Grey, A. Jerschow, Nat. Mater., 2012, 11, 311-315.

2.         A. J. Ilott, S. Chandrashekar, A. Klöckner, H. J. Chang, N. M. Trease, C. P. Grey, L. Greengard, A. Jerschow, J. Magn. Reson. 2014, 245, 143–149.

3.         H. J. Chang , N. M. Trease , A. J. Ilott , D. Zeng , L.-S. Du , A. Jerschow, C. P. Grey, J. Phys. Chem. C, 2015, 119, 16443−16451.

4.         A. J. Ilott, N. M. Trease, C. P. Grey, A. Jerschow, Nat. Comm. 5, 2014, 4536.

5.         H. J. Chang, A. J. Ilott, N. M. Trease, M. Mohammadi, A. Jerschow, C. P. Grey, J. Am. Chem. Soc. 2015, 137, 15209−15216.