I-007

Vytautas Klimavičius

vytautas.klimavicius@ff.vu.lt

Matas Manionis, Aurimas Dubauskas, Jurgis Pilipavičius, Nadežda Traškina, Linas Vilčiauskas, En Zhang, Gerd Buntkowsky, Stefan Kaskel

 Institute of Chemical Physics, Vilnius University, Lithuania

Solid-state NMR of Energy Materials

Solid-state NMR is a powerful experimental technique based on detecting transitions between nuclear energy levels that appear at strong magnetic fields. Combined with magic angle spinning (MAS) and numerous pulse sequences, solid-state NMR provides information on various aspects of studied systems at the molecular level, such as chemical surroundings, connectivities, internuclear distances, quadrupolar parameters, etc. This makes solid-state NMR an excellent technique for studying energy materials and energy storage devices such as batteries and supercapacitors, both ex-situ and in-situ. During the presentation, recent advances in studying N-doped carbons specifically designed for supercapacitor applications [1] and NASICON-based batteries will be presented [2]. 

Porous carbons functionalized by heteroatoms show enhanced capacitive performance. Nevertheless, defining clear molecular structure-property relations is not easy. It is demonstrated at a molecular level that N-doping strongly influences the electroabsorption mechanism. Low-temperature 2D 1H-15N solid-state NMR was used to characterize N-doped mesoporous carbons at the molecular level. For the first time, the molecular structure of N species in a mesoporous carbon scaffold was related to increased capacitance; namely, the conversion from pyridinium to pyrrolic N gives rise to a slightly decreased capacitance.

NASICON-structured negative electrode was studied using multinuclear 31P, 23Na, 13C, 47,49Ti ex-situ solid-state NMR. NaTi2(PO4)3 aqueous electrochemical degradation and solid-electrolyte interphase formation were detected and monitored. The formed interphase consists of amorphous phases similar to TiO(OH)(H2PO4)·nH2O and carboxylic groups on carbonaceous phases. The formation of these interphases ultimately leads to capacity loss during charge-discharge cycling of the NaTi2(PO4)3 based electrochemical device. 

Acknowledgment:

Funding Research Council of Lithuanian (S-MIP-23-47) is gratefully acknowledged.

References:

[1] JACS, 2022, 144, 31, 14217–14225.

[2] ACS Appl. Energy Mater. 2024, 7, 24, 11665–11669.