Analysis and Testing of Lithium-Ion Battery Materials

Importance of Topic

Lithium-ion secondary batteries are critical to decarbonizing transport by powering electric and hybrid vehicles, which account for a growing share of the market and are essential to reducing CO₂ emissions. To meet demands for lower cost, higher energy density, faster charging, longer cycle life, and enhanced safety, comprehensive analytical evaluation of materials and components is required at every development and manufacturing stage.

Goals and Overview of the Study

This application note reviews a suite of analytical and testing methods that address material characterization, quality control, and degradation analysis across all battery elements: cathodes, anodes, separators, electrolytes, cells, modules, and emerging solid-state systems. The objective is to illustrate how advanced instrumentation can optimize performance and reliability in lithium-ion battery research and production.

Methodology and Used Instrumentation

The following techniques and instruments were employed:

• Chemical state and valence analysis of positive electrodes: Xspecia™ chemical bond analysis system and X-ray Absorption Fine Structure (XAFS) at SPring-8.
• Non-destructive imaging of cells and modules: inspeXio SMX-225CT micro focus X-ray CT scanner.
• Electrolyte and gas analysis: GCMS-QP2020 NX gas chromatograph-mass spectrometer; HIC-ESP suppressor ion chromatography for anion degradation products.
• Negative electrode binder evaluation: SPM-9700HT™ scanning probe microscope for in-solution morphology and force-curve nanomechanics.
• Separator thermal and mechanical testing: DSC-60Plus differential scanning calorimeter; TMA-60 thermomechanical analyzer; AGX™-V universal testing machine for high-temperature puncture strength.
• Solid electrolyte characterization: XPS depth profiling with monoatomic Ar⁺ and Ar cluster ions; iSpect DIA-10 dynamic particle image analysis for powder size and shape; MCT-510 micro-compression tester for individual particle strength.

Main Results and Discussion

• Positive electrodes (Ni-Co-Mn ternary and Li-rich cathodes) showed quantifiable valence shifts: Ni increased from +3.0 to +3.6 at full charge, Co varied slightly, and Mn remained stable. XAFS confirmed these trends and validated Xspecia measurements.
• X-ray CT revealed internal winding deformation, clear visualization of resin separators, and mechanical strain in both cylindrical 18650 cells and larger prismatic and pouch formats under operating conditions.
• GC-MS analysis of fresh electrolyte identified key carbonate solvents and additives; aged cells stored at 80 °C generated complex degradation products and fluoride-containing species detectable by library search.
• Ionic chromatography of accelerated-aged electrolytes detected fluoride (F⁻) and difluorophosphate (PO₂F₂⁻) ions, correlating with capacity fade under high-temperature cycling.
• SPM studies in real electrolyte environments showed binder variants with distinct nanostructures and stiffness; force-curve measurements identified the optimal binder for silicon anodes based on minimal deformation and uniform gelation.
• DSC and TMA characterized separator melting transitions (100–150 °C) and anisotropic shrinkage under load, while puncture testing revealed temperature-dependent strength loss above 60 °C.
• XPS depth profiling highlighted the importance of Ar cluster ions for accurate LiPON stoichiometry, avoiding lithium migration artifacts seen with monoatomic Ar⁺ sputtering.
• Particle imaging of solid electrolyte powders showed narrow size distributions around 5 µm and stable aspect ratios. Micro-compression testing differentiated powders by fracture strength (27–315 MPa), guiding formability assessments.

Benefits and Practical Applications

By integrating these analytical tools, researchers and manufacturers can achieve precise control over material properties, detect early signs of degradation, optimize component formulations, and improve cell assembly processes. This leads to enhanced cycle life, safety, and performance in commercial lithium-ion and next-generation solid-state batteries.

Future Trends and Potential Uses

• Development of in situ and operando techniques for real-time monitoring of electrode and electrolyte evolution.
• High-throughput screening coupled with machine learning to accelerate material discovery and failure prediction.
• Advanced imaging modalities (e.g., synchrotron X-ray tomography) for multiscale structural analysis.
• Enhanced characterization protocols for solid-state electrolytes, interfaces, and dendrite suppression strategies.
• Integration of combined thermal, mechanical, and chemical analytics in smart manufacturing and quality assurance workflows.

Conclusion

A comprehensive analytical platform that spans molecular to cell-level evaluation is essential for advancing lithium-ion battery technologies. The reviewed methods provide robust, quantitative data to guide material development, optimize manufacturing, and ensure safety. Continued innovation in instrumentation and data integration will drive the next leap in battery performance.

Reference

No external literature references were provided in the original text.