LiCoO2 electrode/electrolyte interface of Li-ion batteries investigated by electrochemical impedance spectroscopy

Abstract

The storage behavior and the first delithiation of LiCoO 2 electrode in 1 mol/L LiPF 6 -EC : DMC : DEC electrolyte were investigated by electrochemical impedance spectroscopy (EIS). It has found that, along with the increase of storage time, the thickness of SEI film increases, and some organic carbonate lithium compounds are formed due to spontaneous reactions occurring between the LiCoO 2 electrode and the electrolyte. When electrode potential is changed from 3.8 to 3.95 V, the reversible breakdown of the resistive SEI film occurs, which is attributed to the reversible dissolution of the SEI film component. With the increase of electrode potential, the thickness of SEI film increases rapidly above 4.2 V, due to overcharge reactions. The inductive loop observed in impedance spectra of the LiCoO 2 electrode in Li/LiCoO 2 cells is attributed to the formation of a Li 1-x CoO 2 /LiCoO 2 concentration cell. Moreover, it has been demonstrated that the lithium-ion insertion-deinsertion in LiCoO 2 hosts can be well described by both Langmuir and Frumkin insertion isotherms, and the symmetry factor of charge transfer has been evaluated at 0.5.Li-ion batteries, LiCoO 2 , EIS, SEI film, inductance

Ionic origin of a negative capacitance in lead halide perovskites

“…As it has been reported recently [21], negative capacitance appears as inductive loops in impedance spectroscopy, which are associated with complex multistep dynamics. Similar effect was observed in battery materials [22][23] where ionic conductivity is also present. Notably, according to the previous studies the appearance of the nega-tive capacitance can be associated with several factors: on one hand, it has been reported that the effect can be associated with an electrochemical reaction in the presence of oxygen [20], but on the other hand several papers have been published [24][25][26][27][28] reporting the assumption that the negative capacitance can be of ionic origin due to the dielectric relaxation.…”

“…Size of the crystal was 3.7 × 4.1 × 1.2 mm 3 , distance between Au electrodes 4.1 mm (capacitor thickness) and active area 4.44 mm. In this regard, we exclude the interfacial or defect origin on the negative capacitance, which was repeatedly observed at low frequencies during impedance spectroscopy analysis of perovskite solar cells . Monocrystalline perovskites were prepared by an inverse temperature crystallization technique (Fig.…”

Diagnosis of Electrochemical Impedance Spectroscopy in Lithium-Ion Batteries

“…Gnanaraj et al [34] suggested that a plausible explanation for the IL is the formation of an electromotive force superimposed on the lithium ion extraction. The inductive loop has been found in EIS in our previous studies about layered LiCoO 2 [128] and spinel LiMn 2 O 4 [127] for lithium ion batteries (see Figure 6-1). For layered LiCoO 2 electrode, when lithium ions are extracted from the LiCoO 2 electrode, isolation of Li-rich and Li-poor (deficient) regions in the electrode may be created by the SEI film due to disequilibrium with respect to electronic continuity, thus a concentration cell is established between LiCoO 2 and delithiation LiCoO 2 (Li 1-x CoO 2 , 0<x<0.5) separated by the SEI film.…”

“…By using Eq. (4-48), the symmetry factor of charge transfer of lithium-ion insertion-desertion in LiCoO 2 is determined as 0.5 in our previous studies [128], and that of lithium-ion insertion-desertion in graphite materials is determined as 0.56 by Holzapfel et al [36].…”

“…(4-53), the intercalation-deintercalation reaction active energies of LiCoO 2 are calculated in our previous studies [128] …”