Non‐Invasive In Situ Dynamic Monitoring of Elastic Properties of Composite Battery Electrodes by EQCM‐D

Abstract

Reversible Li-ion intercalation into composite Liion battery (LIB) electrodes is often accompanied by significant dimensional electrode changes (deformation) resulting in significant deterioration of the cycling performance.V iscoelastic properties of polymeric binders affected by intercalation-induced deformation of composite LIB electrodes have never been probed in situ on operating electrochemical cells. Here,w ei ntroduce an ewly developed noninvasive method, namely electrochemical quartz-crystal microbalance with dissipation monitoring (EQCM-D), for in situ monitoring of elastic properties of polymeric binders during charging of LIB electrodes.A ss uch,w ef ind EQCM-D as au niquely suitable tool to trackthe binders structural rigidity/softness in composite Li insertion electrodes in real-time by the characteristic increase/decrease of the dissipation factor during the chargingdischarging process.T he binders partially swollen in aprotic solutions demonstrate intermediate viscoelastic charge-ratedependent behavior,r evealing rigid/soft behavior at high/low charging rates,r espectively.T he method can be adjusted for continuous monitoring of elastic properties of the polymeric binders over the entire LIB electrodes cycling life.Lithium-ion batteries (LIB) offer av ery broad spectrum of applications,from portable devices to larger scale all-electric vehicles. [1] Forl arge-scale applications,p orous composite LIBs electrodes are usually used, containing at least three components:e lectrode particles (e.g.,L iFePO 4 ), ab inder (commonly,p olyvinylidene fluoride,P VdF,a nd sodium carboxymethylcellulose,NaCMC), [2] and conductive additives such as carbon black, graphene,o rc arbon nanotubes.T he processes of ions extraction/insertion occurring in LIBs electrodes during their charge/discharge result in periodic potential-dependent changes of the electrodes volume (i.e., their deformation), bringing about av ariety of undesirable mechanical effects,s uch as high-enough stresses,f atigue, fracture,a nd delamination from current collector. [3] Current techniques for in situ monitoring of electrodes strains include atomic force microscopy (AFM) [4] and electrochemical dilatometry. [5] Ac ommon drawback of these techniques is that they do not provide direct information on the potentialinduced changes of the electrode porosity,w hich is an important factor of stress relaxation in LIB electrodes.It has been recently shown that electrochemical quartzcrystal microbalance (EQCM) has at remendous benefit of direct in situ gravimetric probing of ionic fluxes into composite nanoporous carbon electrodes during charging and discharging. [6] Later we have developed as elf-consistent in situ methodology for tracking dimensional changes of this electrode based on EQCM with dissipation monitoring (EQCM-D) and we demonstrated this methods potential for two systems:L iFePO 4 olivine as at ypical composite intercalation-type LIB cathodes material [7] and Ti 3 C 2 M x MXene as acomposite material with properties intermediate between b...

Water‐Soluble Binders for Lithium‐Ion Battery Graphite Electrodes: Slurry Rheology, Coating Adhesion, and Electrochemical Performance

“…All laboratory‐scale formulations display similar mean discharge potentials up to a rate of 1 C. The PVdF electrode displays the lowest overpotential at a rate of 2 C, which could be related to the formation of a polymer–electrolyte gel at the electrode–electrolyte interface, owing to extensive material swelling. Such swelling is not observed for CMC‐Na or PAA‐Na, and therefore, the polymer layer adds to the interfacial resistance of the electrode …”

Review of Local In Situ Probing Techniques for the Interfaces of Lithium‐Ion and Lithium–Oxygen Batteries

“…proposed an in situ AFM approach for the thickness determination of smooth films (up to a few micrometers). The electrochemical quartz‐crystal microbalance with dissipation monitoring addressed the thickness increase δ film in situ . SECM FB measurements have been used to determine δ film of pristine graphite composite electrodes without prior SEI formation (Figure ).…”

“…Thee lectrochemicalq uartz-crystal microbalance with dissipation monitoring addressed the thickness increase d film in situ. [123] SECM FB measurements have been used to determine d film of pristineg raphite composite electrodes withoutp rior SEI formation ( Figure 9). The swelling began immediately after electrolyte additiona se videncedb yt he changei nt he initial absolute position z of the composite (z 0 ) ( Figure 9, inset i).T he approachc urves show nearly diffusion-controlled positive feedback.…”

Electrochemical and viscoelastic evolution of dodecyl sulfate-doped polypyrrole films during electrochemical cycling

“…Another issue is that the CPEs experience inevitable structural changes in practical applications primarily due to the electrochemical aging of the polymer. The latter may aggravate the mechanical properties of CPEs which can be reflected in the viscoelastic variations of polymer electrodes during electrochemical cycling [11][12][13]. Many CPEs have been studied for their appealing electrochemical properties [14], such as poly(3,4-ethylenedioxythiophene) (PEDOT) [15,16], polypyrrole (PPy) [17][18][19], polyaniline (PANI) [8,20] and polythiophene (PHT) [21,22].…”