Open AccessWetting and Inductivity in the Impedance Behavior of Large Lithium-Ion Cells
Author(s) -
Florian J. Günter,
Josef Keilhofer,
Viktor Böhm,
Rüdiger Daub,
Gunther Reinhart
Publication year - 2022
Publication title -
journal of the electrochemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.258
H-Index - 271
eISSN - 1945-7111
pISSN - 0013-4651
DOI - 10.1149/1945-7111/ac6aec
Subject(s) - wetting , materials science , electrical impedance , equivalent circuit , electrode , inductance , nyquist plot , separator (oil production) , dielectric spectroscopy , composite material , optoelectronics , electrical engineering , chemistry , voltage , electrochemistry , physics , engineering , thermodynamics
The wetting of the porous electrodes and the separator is crucial in the production of lithium ion cells. Electrochemical impedance spectroscopy is able to measure and characterize the wetting. This paper presents an equivalent circuit for commercial high-capacity cells and shows a method to analyze the wetting of these cells. The equivalent circuit includes an external inductance, a transmission line model (TLM) for the description of the pore impedance and, additionally, a TLM for the impedance of substrate foil inductance and contact resistance. Based on symmetric and full laboratory cells, the superposition of the impedance is discussed. Furthermore, the method to adjust the impedance and analyze the wetting is demonstrated on 22Ah hard case cells. In addition to inductance for cables and electrode-external contacts, high-capacity lithium-ion cells build up inductance due to the electrode area in combination with the substrate foil. This inductance, together with the contact resistance, result in a characteristic hook in the Nyquist plot. A TLM describes and explains this behaviour. The impedance of the cell is adjustable so that it corresponds to a laboratory cell in blocking conditions. Thus, the wetting of the separator and the wetting of the electrode become separately evaluable.