NMR spectroscopy of coin cell batteries with metal casings

Brennan J Walder; Mark S Conradi; John J Borchardt; Laura C Merrill; Eric G Sorte; Eric J Deichmann; Travis M Anderson; Todd M Alam; Katharine L Harrison

doi:10.1126/sciadv.abg8298

NMR spectroscopy of coin cell batteries with metal casings

Sci Adv. 2021 Sep 10;7(37):eabg8298. doi: 10.1126/sciadv.abg8298. Epub 2021 Sep 10.

Authors

Brennan J Walder¹, Mark S Conradi², John J Borchardt³, Laura C Merrill⁴, Eric G Sorte⁵, Eric J Deichmann⁶, Travis M Anderson⁶, Todd M Alam¹, Katharine L Harrison⁴

Affiliations

¹ Department of Organic Materials Science, Sandia National Laboratories, Albuquerque, NM 87185, USA.
² ABQMR, 2301 Yale Blvd SE, Suite C2, Albuquerque, NM 87106, USA.
³ RF and Electronic Systems Center, Sandia National Laboratories, Albuquerque, NM 87185, USA.
⁴ Department of Nanoscale Sciences, Sandia National Laboratories, Albuquerque, NM 87185, USA.
⁵ Applied Strategic Technologies, Sandia National Laboratories, Albuquerque, NM 87185, USA.
⁶ Power Sources Research and Development, Sandia National Laboratories, Albuquerque, NM 87185, USA.

Abstract

Battery cells with metal casings are commonly considered incompatible with nuclear magnetic resonance (NMR) spectroscopy because the oscillating radio-frequency magnetic fields (“rf fields”) responsible for excitation and detection of NMR active nuclei do not penetrate metals. Here, we show that rf fields can still efficiently penetrate nonmetallic layers of coin cells with metal casings provided “B₁ damming” configurations are avoided. With this understanding, we demonstrate noninvasive high-field in situ ⁷Li and ¹⁹F NMR of coin cells with metal casings using a traditional external NMR coil. This includes the first NMR measurements of an unmodified commercial off-the-shelf rechargeable battery in operando, from which we detect, resolve, and separate ⁷Li NMR signals from elemental Li, anodic β-LiAl, and cathodic Li_xMnO₂ compounds. Real-time changes of β-LiAl lithium diffusion rates and variable β-LiAl ⁷Li NMR Knight shifts are observed and tied to electrochemically driven changes of the β-LiAl defect structure.