Battery-material characterisation usually falls into three layers. Diffraction and electron microscopy read structure and morphology. Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) read chemical state. In-situ diffraction and absorption read the charge–discharge process. In an all-solid-state cell the interface reactions often sit inside the sample, so that part leans on synchrotron X-ray diffraction (SXRD) and X-ray absorption spectroscopy (XAS), which can penetrate the cell. Specific electrolyte and interface cases belong with their own experiments. This note only keeps the question each method can answer.

Structure: XRD and electron microscopy

X-ray diffraction measures coherent scattering and is used for phase, lattice parameters, and strain. A laboratory diffractometer turns the diffraction angle into a lattice spacing through Bragg’s law. In batteries it is used to check whether a synthesis is clean and to follow structural change during charge and discharge. The example in the source is the phase change of $\mathrm{LiFePO_4}$. SXRD is brighter, so it can do micro-beam and in-situ work, and it is used for crystal structure, phase, and lattice parameters of solid electrolytes and electrodes.

Optical path of a laboratory X-ray diffractometer

Transmission electron microscopy (TEM) uses transmitted electrons to look at atomic arrangement and layered structure. Scanning electron microscopy (SEM) uses secondary electrons for surface morphology: particles, pores, and detached active material. Selected-area electron diffraction and electron backscatter diffraction can add crystal orientation. Samples usually go into vacuum, and TEM needs a very thin specimen. Too high an accelerating voltage or beam current damages the sample.

Length scales seen by TEM and SEM

Surface and bonding: Raman and XPS

Raman spectroscopy separates elastic Rayleigh scattering from inelastic Raman scattering and is used for chemical bonds and functional groups. The uses listed in the source are the D/G intensity ratio of carbon as a guide to graphitisation and defects, characteristic MXene structure, and the composition of an electrode–electrolyte interphase. In-situ Raman can follow bonds during charge and discharge, but the source does not show a specific battery spectrum for that part.

Raman scattering compared with Rayleigh scattering

XPS measures photoelectron binding energies and is used to identify surface elements and chemical states: transition-metal valence, oxygen-containing groups, and interphase films. The measurement is in vacuum. The energy scale is commonly set with $\mathrm{C,1s} = 284.8\ \mathrm{eV}$. The source writes the XPS analysis depth as 0.4 mm to 0.6 mm and calls that an atomic layer. That length does not match the nanometre depth usually quoted for surface-sensitive XPS, so it is left unchecked and is not treated here as the probing depth.

XPS turns photoelectron energy into a surface chemical state

In-situ diffraction, combined setups, and XAS

In-situ XRD on a synchrotron gives a stronger signal, makes low-concentration elements easier to see, and suits fast processes. The penetration also helps micro-region structure work in multiphase samples. One combined setup puts small-angle X-ray scattering (SAXS), XRD, and X-ray absorption fine structure (XAFS) together: SAXS for nanoscale inhomogeneity, XRD for long-range crystals, XAFS for the neighbours of a chosen element.

In-situ diffraction used to follow structure while a cell is working

A combined SAXS, XRD, and XAFS setup

XAS splits into the near edge (XANES) and the extended region (EXAFS). The near edge reads valence, for example how the edge moves as ions are inserted and removed. The extended region gives bond length, coordination number, and disorder. It is also used for products of interfacial side reactions, such as the local environment after a transition metal dissolves.

Where XANES and EXAFS sit on one absorption spectrum

How the methods sit together

Method Main information Limit stated in the source
XRD / SXRD phase, lattice, strain a laboratory source is weak for faint signals and buried interfaces
TEM / SEM morphology, atomic arrangement, orientation vacuum is required; a strong beam can damage the sample
Raman bonds, defects, interphase films no specific in-situ battery spectrum is shown
XPS surface chemical state vacuum is required; the millimetre probing-depth figure is unchecked
In-situ XRD, XAS structure and valence during charge and discharge the data sets are large, and quantitative accounts of degradation are still scarce

One method covers one side. The combination in the source is in-situ XRD for the crystal structure, microscopy for morphology, and XPS for the surface chemical state. The vacuum of SEM and XPS is not the working condition of a real cell. Lithium-dendrite growth and interphase rupture have no separate measurement in this methods overview.

The source title mentions infrared spectroscopy. The body has no infrared experiment or spectrum, so no infrared conclusion is added here.