EQCM-D: a Versatile Technique for In-Situ Characterization of Energy Storage and Conversion Electrodes

Netanel Shpigel, Chemistry, Bar Ilan University, Ramat Gan, Israel (nshpigel@gmail.com)
Mikhael D. Levi, Chemistry, Bar Ilan University, Ramat Gan, Israel
Vadim Dargel, Chemistry, Bar Ilan University, Ramat Gan, Israel
Leonid Daikhin, School Of Chemistry, Faculty Of Exact Sciences, Tel-aviv University
Doron Aurbach, Chemistry, Bar Ilan University, Ramat Gan, Israel

QCM (quartz crystal microbalance) is a well-known analytical technique based on the acoustic response of the piezoelectric sensor, which provides nano-scale gravimetric information. EQCM (electrochemical QCM) is an electroanalytic method which is adjusted to monitoring of the changes in the quartz sensor response during the occurrence of electrochemical reactions. Usually, the upper metallic contact of the quartz sensor is deposited with an electro-active material serving as a working electrode in the electrochemical cell. While the traditional use of this technique is to provide in-situ monitoring of ions fluxes during electrochemical processes, in the recent years we have been developing an advanced EQCM-D (QCM with dissipation monitoring) approach based on recording and theoretical   simulation (modeling)  of multiple resonance frequencies modes (also referred to as overtones) of quartz crystal oscillator loaded by electrode coatings. The changes in the measured frequencies and dissipation of the oscillation energy in different environments (i.e. gas and electrolyte solutions) under the selected operating conditions (different modes of charging) are treated by suitable analytical models to extract unique information about the intercalation induced electrode's volume changes, binder - particles mechanical interactions, viscoelastic state of the electrode's surface films (SEI), etc.

Two demonstrative and practical examples will be discussed: implication of the hydrodynamic models to retrieve structural information about operated LiMn₂O₄ (LMO) electrode, and the use of viscoelastic modeling to extract mechanical characteristics related to the passivation film (SEI) formed on Li₄Ti₅O₁₂ (LTO) anode.

References:

1.        Shpigel, N. et al. In situ hydrodynamic spectroscopy for structure characterization of porous energy storage electrodes. Nat. Mater. 1–13 (2016).

2.        Dargel, V. et al. In situ real-time gravimetric and viscoelastic probing of surface films formation on lithium batteries electrodes. Nat. Commun. 8, 1389 (2017).