Deciphering the Double-Layer Structure and Dynamics on a Model LiMoO₃ Interface by Advanced Electrogravimetric...

Area of Science:

• Electrochemistry
• Materials Science
• Physical Chemistry

Background:

• The electrical double layer (EDL) at the electrolyte/electrode interface (EEI) is crucial for charge storage in lithium-ion batteries.
• Existing experimental methods for probing EDL structure are often limited by electrical field and redox reaction disturbances.
• The EDL's structuration is frequently overlooked due to these experimental challenges.

Purpose of the Study:

• To introduce and validate an advanced electrochemical quartz crystal microbalance (EQCM)-based method, ac-electrogravimetry, for probing EDL structure.
• To investigate the influence of solvent properties (dipole moment, polarity) and salt characteristics on EDL formation at the Li$_{}$MoO$_{3}$ EEI.
• To demonstrate the capability of ac-electrogravimetry in elucidating ion solvation and dynamics within the EDL.

Main Methods:

• Utilized ac-electrogravimetry, an advanced EQCM-based technique, to analyze the EDL at the Li$_{}$MoO$_{3}$ electrolyte/electrode interface.
• Systematically varied solvent/salt combinations to study their impact on EDL structure and ion behavior.
• Employed classical EQCM in conjunction with ac-electrogravimetry for comprehensive interface analysis.

Main Results:

• Demonstrated that solvated lithium ions and anions significantly contribute to charge compensation at the interface.
• Provided experimental evidence linking ion solvation and solvent polarity by comparing cyclic and noncyclic solvents.
• Observed a cessation of anionic motion in less polar solvents, suggesting the formation of contact ion pairs and agglomerates at the EDL.

Conclusions:

• Ac-electrogravimetry, combined with EQCM, offers a powerful and elegant experimental approach to assess EDL chemical structure and dynamics.
• The findings highlight the direct relationship between ion solvation, solvent polarity, and EDL behavior.
• This technique holds promise for advancing the engineering of interfaces in electrochemical energy storage devices.