Scrutiny of the LiCoO₂ Composite Electrode/Electrolyte Interface by Advanced Electrogravimetry and Implications for Aqueous Li-Ion Batteries

Abstract

Recent tendency in the battery field towards the use of aqueous electrolytes stimulated several studies searching for compatible electrode materials and charge carriers. Still, another aspect to forge ahead is the fundamental understanding of interfacial processes occurring at electrode/electrolyte interface. To this end, we investigated interfacial properties of a model LiCoO2 composite electrode, in Li2SO4 aqueous electrolyte through extensively exploiting operando Electrochemical Quartz Crystal Microbalance (EQCM) and its coupling with Electrochemical Impedance Spectroscopy (acelectrogravimetry). EQCM revealed a global cation-exchange behavior, which is decoded by acelectrogravimetry into multi-species contribution with different proportions/kinetics, benefited from the capacity of the latter to study interfacial dynamics. Li + plays the major role in charge-compensation mechanism but a strong interaction with H2O has been revealed with close interfacial transfer kinetics, which provides experimental evidence on the essential character of H2O assisting the Li + insertion in 2 layered materials, due to the weakened charge density by screening the electrostatic interactions between the Li + ions and the host lattice of cathode materials.

A Method for Deconvoluting and Quantifying the Real‐Time Species Fluxes and Ionic Currents Using In Situ Electrochemical Quartz Crystal Microbalance

“…[ 4b ] In contrast to classical EQCM, ac‐electrogravimetry coupled QCM and electrochemical impedance spectroscopy were developed to detect contributions from either charged or uncharged species, while separating the anionic, cationic and free solvent contributions. [ 5 ] In addition, EQCM with dissipation monitoring (EQCM‐D) has been proposed to probe the viscoelastic and mechanical properties of electrodes. [ 6 ]…”

Aqueous Multivalent Charge Storage Mechanism in Aromatic Diamine-Based Organic Electrodes

“…The term “gravimetric regime” is used to describe the conditions where the frequency changes can be converted to the mass changes, according to the Sauerbrey equation, which is applicable to thin dense films with flat surfaces rigidly attached to the quartz resonators’ surfaces (in the absence of solid–liquid hydrodynamic interactions and without any changes in the viscoelastic properties). , The beginning and end of the frequency variation overlap in Figure a,c indicates the reversibility of the process. The hysteresis in frequency response is assumed to be due to the differences between the kinetic rates of the interfacial species transfer which occur during the discharge/charge process. , The stability of the film has been probed with the frequency, charge, and current variations with time (Figure b); no significant decay was observed except a slight upward trend in the frequency profile. Figure a shows the respective data after stabilization of the current.…”

“…The hysteresis in frequency response is assumed to be due to the differences between the kinetic rates of the interfacial species transfer which occur during the discharge/charge process. 65,66 The stability of the film has been probed with the frequency, charge, and current variations with time (Figure 4b); no significant decay was observed except a slight upward trend in the frequency profile. Figure 4a shows the respective data after stabilization of the current.…”

Understanding Electrochemical Intercalation of Al3+ Cation into the WO3 Electrochromic Electrode from Solid Electrolyte Interphase and Mass Changes

“…For instance, a composite electrode model in the Li-ion electrolyte has been investigated by EQCM. 9 By using EQCM technology, it has been verified that the desolvation of the monovalent Na-ion still should be required during the discharge process. 10 Commonly, redox reactions are easily hindered by the formation of a complicated interface known as the solid electrolyte interphase (SEI).…”