Analysis of Electrolyte and Electrode in LIB Degraded by Overcharge and High Temperature

Significance of the Topic

The performance and lifetime of lithium-ion batteries used in electric vehicles and energy storage systems are strongly influenced by charging conditions and operating temperature. Understanding the chemical and elemental changes in both electrolyte and electrode materials under stress is essential to improve safety, optimize cell design, and extend service life.

Objectives and Study Overview

This study examined pouch cells aged under overcharge and high-temperature conditions. Five test conditions varied cutoff voltage (4.0–5.6 V) and ambient temperature (40–60 °C) across 100 charge–discharge cycles. Degraded cells were disassembled, and their electrolytes and electrodes were analyzed to correlate operating parameters with dissolution of active materials, formation of degradation products, and surface element redistribution.

Methodology and Instrumentation

• ICP-AES (Shimadzu ICPE-9820) quantified dissolved Ni, Co, and Mn in electrolyte samples after controlled dilution.
• GC-MS (Shimadzu GCMS-QP2050 with AOC-30i) identified and quantified nine organic decomposition products, including phosphates and dioxahexane dicarboxylates, by selected-ion monitoring.
• EDXRF (Shimadzu EDX-8100) provided direct, pretreatment-free analysis of transition metals, phosphorus, and fluorine deposited on cathode and anode surfaces.

Main Results and Discussion

• Higher cutoff voltages significantly increased transition metal concentrations in electrolyte (up to hundreds of mg kg⁻¹) and elevated levels of degradation compounds detected by GC-MS.
• Ambient temperature rise showed modest metal dissolution (<1 ppm) but promoted specific organic byproducts and increased phosphorus deposition.
• EDXRF mapping revealed that dissolved metals migrated from the cathode to deposit on the anode, matching ICP-AES trends. Fluorine decreased on cathodes and accumulated on anodes; phosphorus increased on both electrodes under stress.

Benefits and Practical Applications

This multifaceted analytical approach enables rapid assessment of battery degradation mechanisms. Accurate quantification of metal dissolution and organic byproducts informs electrolyte formulation, while surface-element profiling guides electrode material selection and protective coating design to mitigate capacity loss and safety risks.

Future Trends and Potential Applications

Advances in high-throughput ICP-AES, GC-MS, and X-ray fluorescence techniques will support real-time monitoring of cell health. Integration with machine-learning models may predict remaining useful life and optimize charging protocols. Emerging in-situ spectroscopic methods could further elucidate dynamic interfacial changes under operational stress.

Conclusion

Combining ICP-AES, GC-MS, and EDXRF offers a comprehensive toolkit for diagnosing lithium-ion battery degradation induced by overcharge and temperature stress. The correlation between operating conditions, chemical breakdown, and element migration provides actionable insights for enhancing cell resilience and safety.

Reference

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3. Grützke M., Weber W., Winter M., Nowak S. Structure determination of organic aging products in lithium-ion battery electrolytes with gas chromatography chemical ionization mass spectrometry. RSC Adv. 6 (2016) 57253.