Analysis and Testing of Lithium-Ion Battery Materials

Importance of the Topic

As global CO2 emissions from transportation grow, lithium-ion secondary batteries play a critical role in enabling electric and hybrid vehicles. To meet demands for longer driving ranges, faster charging, reduced costs, and enhanced safety, comprehensive evaluation and optimization of battery materials and components are essential. Advanced analytical and testing methods support research and quality control, helping manufacturers and researchers improve performance and reliability.

Objectives and Study Overview

This work presents a multifaceted suite of analytical and measurement techniques for lithium-ion battery development and quality assurance. It covers methods for monitoring chemical state changes in electrode materials, non-destructive imaging of commercial cells, evaluation of electrolytes and gases, assessment of binder morphology, characterization of separator thermal and mechanical properties, and analysis of all-solid-state electrolyte films and powders.

Methodology and Instrumentation

Key approaches include chemical bond analysis (Xspecia) and X-ray absorption fine structure (XAFS) for valence state monitoring; micro-focus X-ray CT for internal structure imaging; gas chromatograph–mass spectrometry (GC-MS) and ion chromatography for electrolyte and gas analysis; scanning probe microscopy (SPM) and force-curve measurements for binder morphology and stiffness; differential scanning calorimetry (DSC) and thermomechanical analysis (TMA) for separator thermal transitions and shrinkage; universal testing machines for tensile and puncture tests; X-ray photoelectron spectroscopy (XPS) with monoatomic and cluster Ar sputtering for depth profiling of LiPON films; dynamic particle image analysis for solid electrolyte powders; and micro-compression testing for powder strength.

Key Results and Discussion

• Electrode Chemistry: Ternary Ni-Co-Mn cathodes exhibited Ni valence shifts from +3 to +3.6 during charge/discharge, with minor Co changes and static Mn states. Li-rich cathodes showed reversible Mn and Ni valence variations.
• Internal Imaging: X-ray CT resolved electrode deformation and separator layers in 18650 cells, large automotive modules, and flexible polymer cells.
• Electrolyte/Gas Analysis: GC-MS identified carbonate solvents and additives in fresh electrolyte; thermally aged cells released organic degradation products and fluoride species. Ion chromatography detected F⁻ and PO₂F₂⁻ in electrolytes after accelerated cycling.
• Binder Properties: SPM imaging in actual electrolyte revealed gelation differences among polyacrylic acid binders. Force-curve data quantified indentation and rigidity, guiding binder selection for silicon anodes.
• Separator Evaluation: DSC measured polyethylene melting peaks (100–150 °C) and crystallinities; TMA demonstrated directional shrinkage under load. Puncture tests showed strength retention at 60 °C but significant softening at 90 °C.
• Solid Electrolyte Films and Powders: XPS depth profiling with Ar clusters provided stoichiometric Li distributions in LiPON films, avoiding lithium implantation artifacts seen with monoatomic Ar. Dynamic image analysis characterized powder size (~5 µm) and shape distribution. Micro-compression testing distinguished particle fracture strengths, correlating with formability.

Benefits and Practical Applications

These analytical techniques enable rapid, quantitative evaluation of battery materials and components throughout R&D and production. Understanding chemical states, structural integrity, thermal and mechanical behaviors, and degradation pathways helps optimize material formulations, improve safety, ensure quality control, and accelerate the development of next-generation cells.

Future Trends and Opportunities

Emerging directions include operando characterization under realistic cycling conditions, integration of machine-learning for pattern recognition, development of advanced solid electrolytes with tailored nanostructures, expanded use of cluster-ion sputtering for depth profiling, and high-throughput imaging methods for industrial production monitoring. Continued innovation in analytical instrumentation will support the transition to safer, higher-energy, and longer-lived battery systems.

Conclusion

A comprehensive suite of advanced analytical and testing methods addresses the key challenges in lithium-ion battery development and manufacturing. By combining chemical, structural, thermal, and mechanical evaluations, researchers and engineers can achieve targeted improvements in performance, longevity, and safety, driving progress toward sustainable electric mobility.

References

No references were provided in the original document.