1.7. Advanced Methods (AFM, XAS, NMR)
Advanced Methods
Technique
Conventional techniques provide essential information, but each has limitations. XRD mainly describes the average, long-range structure of crystalline material and may miss local disorder, amorphous regions and subtle changes around specific elements. XPS is highly surface-sensitive, typically probing only the outer few nanometres, and does not fully describe the bulk material. Electron microscopy provides direct images, but only from very small selected regions.
Advanced techniques such as AFM, XAS and solid-state NMR provide complementary information about nanoscale surfaces, element-specific atomic environments and local lithium behaviour. They are particularly useful when conventional measurements cannot fully explain differences in electrochemical performance or degradation.
Observation
Atomic force microscopy (AFM) maps surface topography and roughness at the nanoscale. Depending on the operating mode, it can also examine local mechanical, electrical and adhesive properties. This makes it useful for studying particle surfaces, coatings, cracking and mechanical changes that may not be resolved clearly using SEM or XPS alone.
X-ray absorption spectroscopy (XAS), including the XANES and EXAFS regions, probes selected elements individually. XANES provides information about oxidation state and local electronic structure, while EXAFS examines neighbouring atoms, bond distances and coordination. XAS is useful when XRD cannot resolve local structural changes or when XPS provides only surface-level oxidation-state information.
Solid-state nuclear magnetic resonance (NMR) probes the local chemical environments, site occupation and mobility of lithium and other selected nuclei. It can reveal lithium distributions, local disorder and amorphous environments that may be averaged out or invisible in XRD. NMR is therefore particularly useful for understanding lithium transport and local structural changes within the bulk material.
“These methods connect atomic-scale information with bulk electrochemical behaviour, bridging theory and performance.”
NCM v LFP
NCM: XAS can track transition-metal oxidation states and local structural changes, NMR can probe lithium environments and disorder, and AFM can examine particle surfaces, coatings and mechanical changes.
LFP: XAS can follow the Fe²⁺/Fe³⁺ redox response and local coordination, NMR can examine lithium occupation and mobility, and AFM can assess surface structure and coating behaviour.
Impact on Cell KPIs
Advanced techniques help explain redox behaviour, local structural changes, lithium transport and interfacial degradation. These insights can guide material optimisation and help identify likely causes of capacity loss, resistance growth and reduced cycle life, but they do not replace representative electrode and cell testing.
