Probe for operando in situ electrochemical nuclear magnetic resonance spectroscopy
Electrochemical devices with metal casings have been considered incompatible with nuclear magnetic resonance (NMR) spectroscopy because the oscillating magnetic fields (“rf fields”) responsible for excitation and detection of NMR active nuclei do not penetrate metals. According to the present invention, rf fields can still efficiently penetrate into nonmetallic layers of electrochemical cells (such as a coin cell battery configuration) provided the magnetic field is oriented tangentially to the electrochemical cell electrodes in a “skimming” orientation. As an example, noninvasive high field in situ 7 Li and 19 F NMR of an unmodified commercial off-the-shelf rechargeable coin cell was demonstrated using a traditional external NMR coil setup. The in operando NMR measurements revealed that irreversible physical changes accumulate at the anode during electrochemical cycling.
1. A probe for operando in situ electrochemical nuclear magnetic resonance spectroscopy, comprising:
a transmission line coil comprising two anti-parallel planar conductors for inserting an electrochemical cell therebetween, the electrochemical cell comprising substantially planar parallel electrodes with an electrically insulating gap therebetween, wherein the transmission line coil is configured to apply a rf magnetic field tangentially to the parallel electrodes of the electrochemical cell when a pulsed rf excitation signal from an NMR spectrometer is applied to the transmission line coil, thereby allowing the rf magnetic field to at least partially penetrate into the gap; and
a tuned circuit for matching the pulsed rf excitation signal from the NMR spectrometer to the transmission line coil.
2. The probe of claim 1 , wherein the electrochemical cell comprises a battery, fuel cell, supercapacitor, or electrochemical sensor.
3. The probe of claim 2 , wherein the battery comprises a coin cell, pouch cell, or prismatic cell battery.
4. The probe of claim 1 , wherein the transmission line coil comprises a folded ribbon resonator.
5. The probe of claim 1 , wherein the transmission line coil comprises a flattened solenoid coil.
6. The probe of claim 1 , wherein the gap comprises an electrolyte.
7. The probe of claim 1 , wherein the gap comprises a separator.
8. The probe of claim 1 , wherein the penetrating rf magnetic field excites one or more NMR active nuclei in the gap of the electrochemical cell.
9. The probe of claim 8 , wherein the one or more NMR active nuclei comprises 1 H, 2 H, 3 H, 6 Li, 7 Li, 10 B, 11 B, 13 C, 15 N, 19 F, 23 Na, 25 Mg, 27 Al, 31 P, 51 V, 17 O, or 133 Cs.
10. The probe of claim 1 , wherein the tuned circuit comprises a double resonance circuit.
11. The probe of claim 10 , wherein the double resonance circuit tunes a low-frequency mode and a high-frequency mode of a pair of NMR active nuclei.
12. The probe of claim 11 , wherein the pair of NMR active nuclei comprises [ 1 H, 7 Li], [ 1 H, 6 Li], [ 19 F, 6 Li], [ 19 F, 7 Li], [ 1 H, 31 P], [ 19 F, 31 P], [ 1 H, 11 B], or [ 19 F, 11 B].