THE USE OF EQCM-D FOR IN-SITU CHARACTERIZATION OF DIMENSIONAL CHANGES AND MECHANICAL PROPERTIES IN CYCLED BATTERY ELECTRODES

Reversible Li-ions intercalation into battery electrode materials often results in significant dimensional changes during ions extraction/insertion. Those potential-dependent changes of the electrodes can present a severe problem for batteries performance: a large variety of undesirable mechanical effects, such as high-enough stresses, fatigue, fracture, and delamination from current collector is the part of the possible phenomena which causes degradation and eventually to short life of the device.

Development of the novel methodology to monitor dimensional and mechanical changes in the electrodes for energy storage and conversion will enable future developments and applications in the fields of batteries and supercapacitors research, especially for diagnostics of viscoelastic properties of the electrodes, runaway processes, and cycling life prediction.

Although existing techniques like EC-AFM and electrochemical dilatometry can provide in-situ nano-metrical scale measurements of vertical displacement changes, they lack the ability to track potential induced changes of the electrode porosity, which is an important factor of the stress relaxation in LIB electrodes. This emphasizes the need for non-invasive in-situ techniques enabling continuous monitoring of structural changes in cycled electrodes.

Here we demonstrate a new non-invasive EQCM-D-based method for characterization of composite battery electrodes, and the relevant hydrodynamic model describing solid liquid interactions between the porous electrode and the electrolyte. By applying this model to experimentally measured resonance frequency and dissipation factor changes for different overtone orders, we can easily quantize in-situ mechanical and morphological changes during charge/discharge processes.