Advanced solid-state NMR for cathode materials: Insights into local structure and ionic dynamics mechanisms in lithium- and sodium-ion batteries

Abstract

This review synthesizes the pivotal role of advanced solid-state nuclear magnetic resonance (SSNMR) in characterizing high-performance lithium- and sodium-ion battery cathodes. While diffraction-based techniques are often constrained by long-range order requirements, SSNMR leverages the unique chemical shift and hyperfine interactions to resolve the local atomic and electronic landscapes of paramagnetic cathode materials. We examine critical methodological innovations, such as ultrafast magic angle spinning and multi-dimensional experiments, which are essential for mitigating paramagnetic broadening and achieving high-resolution spectra. Furthermore, we discuss the integration of operando SSNMR as a powerful tool for the real-time observation of electrochemical pathways and structural evolution under realistic cycling conditions. The review systematically explores applications across layered oxides (oxygen redox and structural evolution), disordered rock-salts (lattice fluorination), and polyanionic frameworks (multi-electron transfer and ion dynamics). Finally, we outlook the future potential of dynamic nuclear polarization and DFT-integrated machine learning in decoding complex interfacial phenomena and structural heterogeneities.