Thickness‐Dependent Impedance of Composite Battery Electrodes Containing Ionic Liquid‐Based Electrolytes. Issue 7 (18th March 2020)

• Record Type: Journal Article
• Authors: Cronau, Marvin; Kroll, Moritz; Szabo, Marvin; Sälzer, Fabian; Roling, Bernhard
• Is Part Of: Batteries & supercaps. Volume 3:Issue 7(2020)
• Page Start: 611
• Page End: 618
• Publication Date: 2020-03-18
• Subjects: Li-ion batteries -- composite electrodes -- ionic liquids -- solvate ionic liquids -- transference number -- electrochemical impedance spectroscopy; Electrochemistry -- Periodicals; Electrodes -- Periodicals; Electric batteries -- Periodicals; 621.31242
• DOI: 10.1002/batt.202000023
• Languages: English
• ISSNs: 2566-6223

Abstract

Abstract: Lithium‐ion battery models often neglect the salt concentration polarization inside the electrolyte‐filled pores of the composite electrodes. However, this concentration polarization causes a significant impedance, in particular in the case of electrolytes with low Li + transference numbers. Here, we analyze in detail measured and calculated impedance spectra of composite electrodes containing a solvate ionic liquid‐based electrolyte and an ionic liquid‐based electrolyte, respectively, in comparison to a conventional carbonate‐based electrolyte. For calculating spectra, we use a recently published model by Huang and Zhang. We find that the impedance at 10 −4 Hz, which is relevant for battery cycling rates around 1 C to 2 C, increases in the order carbonate‐based electrolyte<ionic liquid‐based electrolyte<solvate ionic liquid‐based electrolytes, but exhibits a remarkably weak thickness dependence, when the electrode thickness exceeds 50–100 μm. This suggests that electrodes considerably thicker than the conventional 80 μm can be used in batteries without significantly deteriorating battery power. Abstract : Thicker electrodes : Salt concentration polarization inside the electrolyte‐filled pore space of composite electrodes causes a considerable battery impedance, in particular when ionic‐liquid‐based electrolytes are used. In this study, the influence of the electrolyte on the composite electrode impedance is investigated through experiments and through impedance calculations in the framework of an analytical model by Huang and Zhang. We find that the impedance exhibits a remarkably weak dependence on the electrode thickness, suggesting that thicker electrodes in batteries are feasible.