Post-mortem analysis of cycle-tested batteries is a critical process for understanding degradation mechanisms and improving battery materials. This guide details systematic techniques for dismantling cycled cells, characterizing components, and correlating findings with failure modes to drive material advancements.

**Dismantling Procedures**
The first step in post-mortem analysis is the safe disassembly of cycled batteries under controlled conditions. For lithium-ion cells, this begins with discharging to a safe voltage, typically below 1.0 V, to minimize risks of short-circuiting or thermal events. The cell is then transferred to an argon-filled glovebox with oxygen and moisture levels below 0.1 ppm to prevent air-sensitive materials from reacting.

Mechanical tools are used to open the cell casing, with care taken to avoid damaging internal components. The jelly roll or stacked electrodes are unwound or separated layer by layer. Electrodes, separators, and other components are visually inspected for macroscopic defects such as delamination, cracks, or discoloration. Each component is labeled and stored in airtight containers to preserve their chemical state for further analysis.

**Electrode Characterization**
Scanning Electron Microscopy (SEM) is used to examine electrode morphology at high resolution. Cycled anodes often show particle cracking or pulverization in silicon-based materials, while graphite anodes may exhibit exfoliation or lithium plating. Cathodes are inspected for particle fracturing or transition metal dissolution. Energy-Dispersive X-Ray Spectroscopy (EDS) coupled with SEM provides elemental mapping to detect inhomogeneities or contamination.

X-Ray Diffraction (XRD) reveals crystallographic changes in electrode materials. For example, layered oxide cathodes may show peak broadening due to structural disorder, while spinel or olivine cathodes might undergo phase transitions. Anodes like graphite display shifts in peak positions corresponding to lithium intercalation stages. Quantitative phase analysis helps determine the extent of degradation.

Electrochemical Impedance Spectroscopy (EIS) measures interfacial resistance changes. A three-electrode setup isolates anode, cathode, and electrolyte contributions. Increased charge-transfer resistance at the anode suggests solid electrolyte interphase (SEI) growth, while cathode impedance spikes may indicate contact loss or surface passivation.

**Electrolyte Analysis**
The cycled electrolyte is extracted and analyzed for decomposition products. Gas chromatography-mass spectrometry (GC-MS) identifies organic species like ethylene carbonate derivatives or alkyl carbonates. Nuclear magnetic resonance (NMR) spectroscopy quantifies lithium salt depletion or acid formation.

The separator is examined for pore blockage or shrinkage. SEM imaging checks for mechanical damage, while infrared spectroscopy detects polymer degradation or binder migration. Ionic conductivity measurements assess whether separator aging contributes to performance loss.

**Failure Mode Correlation**
Combining characterization data allows correlation with specific failure modes. For instance, capacity fade in nickel-rich cathodes often links to microcracking and oxygen release, verified by SEM and XRD. Silicon anode failure frequently stems from volume expansion-induced electrode detachment, visible in cross-sectional SEM.

Lithium plating, a common fast-charging failure, is identified through metallic lithium deposits on anode surfaces via SEM-EDS. Correlating this with EIS data showing low-frequency impedance rise confirms kinetic limitations. Electrolyte depletion, indicated by NMR, exacerbates these effects by increasing cell polarization.

**Material Improvement Insights**
Post-mortem findings directly inform material design strategies. Cathode stability can be enhanced by doping to suppress phase transitions or coating particles to limit side reactions. Anode improvements may involve porous architectures to accommodate volume changes or artificial SEI layers to reduce parasitic reactions.

Electrolyte additives that mitigate decomposition or promote stable interphases are tailored based on identified breakdown products. Separator modifications, such as ceramic coatings, address thermal instability or mechanical weakness observed in aged samples.

**Conclusion**
Post-mortem analysis provides a comprehensive view of battery degradation, linking physical and chemical changes to performance loss. By systematically dismantling cells and applying advanced characterization techniques, researchers pinpoint failure mechanisms and guide targeted material optimizations. This approach is indispensable for developing next-generation batteries with extended cycle life and improved reliability.

The process must be methodical, with each step building toward a cohesive understanding of degradation pathways. Only through rigorous post-mortem analysis can meaningful advancements in battery materials be achieved.