Potentiostatic Intermittent Titration Technique (PITT)

Importance of the Topic

Lithium-ion batteries are central to modern energy storage due to their high energy density and long cycle life. Understanding the kinetics of Li-ion migration within electrode materials is vital for improving charge/discharge rates, capacity retention and overall battery performance.

Goals and Study Overview

This study demonstrates how the potentiostatic intermittent titration technique (PITT) can be applied to a commercial Li-ion cell to extract the chemical diffusion coefficient of lithium within electrode materials. The objective is to outline an experimental workflow, data interpretation and diffusion coefficient calculation.

Methodology and Instrumentation

The PITT protocol comprises:

• Recording open circuit potential (OCP).
• Applying 15-minute OCP pulses followed by 15-minute relaxation periods.
• Imposing successive +20 mV steps until the upper voltage limit is reached, each pulse lasting 15 minutes with 15 minutes relaxation.
• Reversing the sequence with −20 mV steps down to the lower voltage limit under identical timing.

Used Instrumentation

Autolab PGSTAT302N potentiostat/galvanostat controlled by NOVA software. Test cell: 2.2 Ah Li-ion battery (3.75 V nominal, 8.25 Wh energy) from Enix Energies.

Main Results and Discussion

Voltage and current transients during each pulse show characteristic exponential decays. Initial current peaks correspond to rapid intercalation/de-intercalation followed by diffusion-limited decay. Plotting ln(current/area) versus time yields linear segments. The slope of these segments, in conjunction with electrode geometry and Faraday’s constant, allows calculation of the chemical diffusion coefficient D.

Benefits and Practical Applications of the Method

PITT provides:

• Quantitative determination of Li diffusion coefficients under near-equilibrium conditions.
• Insights into rate-limiting processes in electrodes.
• Data to guide material selection and electrode design for high-power batteries.

Future Trends and Opportunities

Advances may include:

• Integration of in situ spectroscopic or imaging techniques with PITT for real-time observation of phase changes.
• High-throughput PITT screening of novel electrode materials.
• Modeling-driven optimization combining experimental diffusion data with multi-scale simulations.

Conclusion

The presented PITT procedure on a commercial Li-ion cell, using controlled potential steps and relaxation, effectively yields the diffusion coefficient of lithium in electrode materials. This information is essential for improving battery performance and guiding future material development.

Reference

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[5] Y. Zhu and C. Wang, J. Phys. Chem., 114(6), 2830 (2010)