Revisiting High-Frequency Impedance in Li-Ion Batteries: Decoupling Solid Electrolyte Interphase Resistance from Pore...

Area of Science:

• Electrochemistry
• Materials Science
• Battery Technology

Background:

• Electrochemical impedance spectroscopy (EIS) is crucial for analyzing lithium-ion battery (LIB) kinetics.
• High-frequency impedance analysis in porous electrodes is complicated by coupled ionic diffusion resistance (R_ion) and solid electrolyte interphase (SEI) resistance (R_SEI).
• This coupling leads to significant errors in R_SEI estimation.

Purpose of the Study:

• To quantitatively evaluate the influence of R_ion-to-R_SEI coupling on high-frequency impedance in LIBs.
• To develop a robust methodology for accurate R_SEI quantification.
• To advance the interpretation of high-frequency impedance data.

Main Methods:

• Utilized a LiFePO4//graphite three-electrode system.
• Integrated experimental measurements with numerical simulations.
• Employed a transmission line model (TLM) to decouple and determine R_ion under a quasi-blocking electrode state.
• Applied mathematical inverse transformation to remove R_ion effects from impedance spectra.

Main Results:

• The transformed impedance spectrum showed significantly improved fitting accuracy.
• The transformed spectrum demonstrated better adherence to the Arrhenius relationship.
• TLM simulations elucidated the coupling dynamics between R_ion and R_SEI, quantifying R_ion's dominant impact.

Conclusions:

• Accurate R_ion correction is essential for reliable R_SEI determination in LIBs.
• The developed methodology enables precise R_SEI quantification.
• This work enhances high-frequency impedance interpretation for LIB analysis.