2026-04-17T05:45:09Zhttps://recercat.cat/oai/request
oai:recercat.cat:2117/1215282026-01-16T06:09:29Zcom_2072_1033col_2072_452950
RECERCAT author Ovejas Benedicto, Victòria Júlia author Cuadras Tomàs, Àngel 2018-09-10 Currently, Li-ion cells are the preferred candidates as energy sources for existing portable applications and for those being developed. Thus, a proper characterization of Li-ion cells is required to optimize their use and their manufacturing process. In this study, the transport phenomena and electrochemical processes taking place in LiCoO2-Li(NiMnCo)O2/graphite (LCO-NMC/graphite) cells are identified from half-cell measurements by means of impedance spectroscopy. The results are calculated from current densities, instead of absolute values, for the future comparison of this data with other cells. In particular, impedance spectra are fitted to simple electrical models composed of an inductive part, serial resistance, and various RQ networks—the parallel combination of a resistor and a constant phase element—depending on the cell. Thus, the evolution of resistances, capacitances, and the characteristic frequencies of the various effects are tracked with the state-of-charge (SoC) at two aging levels. Concretely, two effects are identified at the impedance spectrum; one is clearly caused by the charge transfer at the positive electrode, whereas the other one is presumably caused by the transport of lithium ions across the solid electrolyte interphase (SEI) layer. Moreover, as the cells age, the characteristic frequency of the charge transfer is drastically reduced by a factor of around 70%.Postprint (published version) Open Access Àrees temàtiques de la UPC::Energies::Energia elèctrica Àrees temàtiques de la UPC::Enginyeria elèctrica Electric batteries Lithium cells impedance Electrochemical impedance spectroscopy (EIS) aging half-cells equivalent circuit lithium ion NMC solid electrolyte interphase (SEI) charge transfer Bateries d'ió liti Piles de de liti Bateries elèctriques Impedance characterization of an LCO-NMC/graphite cell: ohmic conduction, SEI transport and charge-transfer phenomenon Article