3D Microstructrue Electrochemistry Model

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<ul><li><p>8/13/2019 3D Microstructrue Electrochemistry Model</p><p> 1/1</p><p>THREE-DIMENSIONALLY RESOLVED SIMULATIONS OF ALICOO2 ELECTRODE STRUCTURE OBTAINED VIA FIB/SEM</p><p>CHRISTIANWALCHSHOFER1, TOBIASHUTZENLAUB2, SIMONT HIELE2,BORISKALUDERCIC1, ROBERTS POTNITZ3</p><p>1CD-adapco (christian.walchshofer@cd-adapco.com), 3 Battery Design LLC (rspotnitz@batdesign.com)2 Department of Microsystems Engineering - IMTEK, Laboratory for MEMS Applications (tobias.hutzenlaub@hsg-imit.de)</p><p>PREFACEEstablished simulation models for Li-ion batter-</p><p>ies are formulated in 0D or 1D (Dualfoil), and relyon assumptions, e.g. well defined particle shapes</p><p>and absence of diffusion between such particles.Fitted solid conductivities have to be applied tomatch experiments. The 3D Micro-Structural Elec-trochemistry model implemented in STAR-CCM+extends the well known Dualfoil model to 3D [1] toaccurately predict spatial phenomena.</p><p>SETUPA VARTA LIC 18650 WC lithium-ion battery</p><p>was segmented by FIB-SEM in [2] and recon-structed (right box). The reconstructed porous elec-trode block was contacted with a current collector,separator andnegativefoil (carbon) to form a carte-sian mesh simulation setup comprising 21 M cells.</p><p>Detailed model parametrization was conducted</p><p>by applying LiCoO2 equilibrium potentials from[3] and electrolyte parameters from [4].</p><p>LiPF6 in EC-EMC-DMC (1:1:1, vol.); 20C</p><p>The setup assumed an aluminum current col-lector, a perfectly porous (= 1) separator and acarbon anode foil. A 1C charge was applied.</p><p>CONCLUSIONSModeling electrically conductive pathways ac-</p><p>curately by introducing a third phase, which rep-resents conductive aid and binder, allows for us-ing physically measured conductivities for activematerials in simulations. The third modeled phaseleads to stronger gradients in electrolyte concentra-tion, affecting cell performance.</p><p>GEOMETRYGENERATION</p><p>The image stack provided by [2] was read into Scilab using the ScilabImage Processing toolbox (SIP), and coarsened (2x) by a majority wins</p><p>algorithm. Small regions of minor impactwere removed by applying asmoothing algorithm. A mesh was generated using pro-STAR and im-ported into STAR-CCM+. No transport was assumed between binderand electrolyte phases. A Java-macro was used therefore to removeelectrolyte regions purely contacting binder and vice-versa, thereby re-moving 0.390% of electrolyte and 0.015% of binder cells.</p><p>MODELF ORMULATIONTransport equations</p><p>Solid Liquid</p><p>J= J=+2RuT </p><p>F</p><p>1t0+</p><p> 1 +</p><p>d(ln f)</p><p>d(ln c)</p><p> (ln c)</p><p>S</p><p>dS= 0 S</p><p>dS= S</p><p>d (ln c)dS</p><p>t</p><p>V</p><p>cdV =</p><p>S</p><p>D cdS </p><p>t</p><p>V</p><p> c dV =</p><p>S</p><p>D cdS</p><p>V</p><p>J t0+F</p><p> dV</p><p>D= D0 </p><p>1</p><p>d (ln c0)</p><p>d (ln c)</p><p>Butler-Volmer kinetics</p><p>Jn,s= J0</p><p>e</p><p>a F </p><p>R Te</p><p>cF </p><p>R T</p><p>+C</p><p>t(sl) J0 = F k</p><p> cs</p><p>cs,max</p><p>11</p><p> cs</p><p>cs,max</p><p>2 clcl,ref</p><p>3</p><p>RESULTS</p><p>t = 8 (s) t = 360 (s) t = 3600 (s)</p><p>SOC = 0 SOC = 0.1 SOC = 1</p><p>REFERENCES</p><p>[1] Spotnitz et al. 2012 Geometry-resolved electro-chemistrymodel of li-ion batteries SAE Technical Paper2012-01-0663</p><p>[2] Hutzenlaub et al. 2012 Three-Dimensional Reconstructionofa LiCoO2 Li-Ion Battery Cathode Electrochemical and Solid-</p><p>State Letters, 15 (3), A33A36[3] Karthikeyan, Sikha, White, 2008 Thermodynamic modeldevelopment for lithium intercalation electrodes. Journal ofPower Sources185 (2), 1398 1407.</p><p>[4] Gering, K. L. 2006 Prediction of electrolyte viscosity foraqueous and non-aqueous systems: Results from a molec-ular model based on ion solvation and a chemical physicsframework.Electrochimica Acta51 (15), 3125 3138.</p><p>[5] Hutzenlaub et al. 2013 Electrochemical modelling in aFIB/SEM based three-phase reconstruction of a LiCoO2 Li-ion battery cathode to appear</p></li></ul>