Received: from mx04.ecn.purdue.edu (mx04.ecn.purdue.edu [128.46.117.252]) by mailbag.ecn.purdue.edu (8.14.4/8.14.4) with ESMTP id q39DtlU9024931 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NOT); Mon, 9 Apr 2012 09:55:48 -0400 (EDT) Received: from mailhub130.itcs.purdue.edu (mailhub130.itcs.purdue.edu [128.210.5.130]) by mx04.ecn.purdue.edu (8.14.4/8.14.4) with ESMTP id q39Dt4Dp028857 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NOT); Mon, 9 Apr 2012 09:55:04 -0400 Received: from WPPEXHUB02F.purdue.lcl (wppexhub02f.itap.purdue.edu [172.21.6.91]) by mailhub130.itcs.purdue.edu (8.14.4/8.14.4/mta-nopmx.smtp.purdue.edu) with ESMTP id q39Dt4fd007330; Mon, 9 Apr 2012 09:55:04 -0400 Received: from VPEXCH02.purdue.lcl ([169.254.1.4]) by WPPEXHUB02F.purdue.lcl ([::1]) with mapi; Mon, 9 Apr 2012 09:55:03 -0400 From: "Stacey, Lisa A" To: "'msefaculty-list@ecn.purdue.edu'" , "'msepostdoc-list@ecn.purdue.edu'" , "'msegradstudent-list@ecn.purdue.edu'" Date: Mon, 9 Apr 2012 09:55:03 -0400 Subject: SEMINAR NOTICE - B. Vijayaraghavan 4/16/12 Thread-Topic: SEMINAR NOTICE - B. Vijayaraghavan 4/16/12 Thread-Index: Ac0WWFyPLLsSem77TXSMWKLFIOhzXg== Message-ID: <92F872D971E7AA498CF64DD847E5594D83C438C19C@VPEXCH02.purdue.lcl> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: yes X-MS-TNEF-Correlator: acceptlanguage: en-US Content-Type: multipart/related; boundary="_005_92F872D971E7AA498CF64DD847E5594D83C438C19CVPEXCH02purdu_"; type="multipart/alternative" MIME-Version: 1.0 X-PMX-Version: 5.5.9.388399 X-PerlMx-Virus-Scanned: Yes X-ECN-MailServer-VirusScanned: by amavisd-new X-ECN-MailServer-Origination: mailhub130.itcs.purdue.edu [128.210.5.130] X-ECN-MailServer-SpamScanAdvice: DoNotScan --_005_92F872D971E7AA498CF64DD847E5594D83C438C19CVPEXCH02purdu_ Content-Type: multipart/alternative; boundary="_000_92F872D971E7AA498CF64DD847E5594D83C438C19CVPEXCH02purdu_" --_000_92F872D971E7AA498CF64DD847E5594D83C438C19CVPEXCH02purdu_ Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MATERIALS SCIENCE AND ENGINEERING SEMINAR Three-Dimensional Modeling of Commercial Battery Anode Microstructures by Bharath P. Vijayaraghavan Purdue MS Final Exam Advisor Prof. E. Garcia ABSTRACT A three-dimensional theoretical and numerical framework was developed to un= derstand the processing-induced randomness and microstructural interactions= of rechargeable lithium-ion batteries. By starting from graphite anode mic= rostructures extracted from X-ray tomography data the effects of the indivi= dual features on the electrochemical and mechanical reliability during galv= anostatic recharge are quantified. Spatially resolved electrochemical calcu= lations show that for dense porous electrodes: a) spatially connected poros= ity combined with internal surface roughness increases the macroscopic capa= city of the cell; b) isolated porosity decreases the local conductivity, di= ffusivity, and charge capacity of the system; and c) fully dense regions ar= e effective obstacles for charge transport at large C-rates. A combined sta= tistical and visualization analysis identifies surface morphological featur= es with a small radius of curvature and porosity bundles as favorable locat= ions for dendritic growth. Simulations also show that lithium accumulation = induces low electrochemical potential values and compressive stresses in th= ose surfaces exposed to spatially connected porosity, while tensile stresse= s develop in surfaces exposed to electrochemically isolated porosity and fu= lly dense regions, which in turn, favor crack initiation. The crystallograp= hic anisotropy of graphite favors stress localization at grain corners and = boundaries, particularly for large grain boundary misorientations. Simulati= ons demonstrate that battery reliability can be improved by controlling the= radius of curvature of features and the minimization of the occurrence of = pore bundles. The acquired scientific experiences were abstracted into an a= nalytical framework to validate and extend widely accepted porosity-tortuos= ity relations. The proposed framework enables the derivation of analytical = expressions by starting from the volume fractions of the constitutive compo= nents. Experimentally measured tortuosities are rationalized through the relation = developed herein, [cid:image003.png@01CD1636.CC2AE260] in th= e Bruggemann limit. Date: Monday, April 16, 2012 Time: 2:30 P.M. Place: ARMS Rm. 1028 Lisa Stacey Secretary/Development Assistant Purdue University School of Materials Engineering 765/494-4100 --_000_92F872D971E7AA498CF64DD847E5594D83C438C19CVPEXCH02purdu_ Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable = <= meta name=3DGenerator content=3D"Microsoft Word 12 (filtered medium)">

MATERIALS SCIENCE AND ENGINEERIN= G

<= span style=3D'font-size:14.0pt'>SEMINAR

&nbs= p;

Three-Dimensional Modeling of Commercial Battery Anode Microstru= ctures

 <= /b>

by

 

Bharath P. Vijayaraghav= an

Purdue MS Final Exam

 

Advisor

Prof. E. Garcia

=  

ABSTRACT

=

 

 

A three-dimensional theoretical and numerical = framework was developed to understand the processing-induced randomness and= microstructural interactions of rechargeable lithium-ion batteries. By sta= rting from graphite anode microstructures extracted from X-ray tomography d= ata the effects of the individual features on the electrochemical and mecha= nical reliability during galvanostatic recharge are quantified. Spatially r= esolved electrochemical calculations show that for dense porous electrodes:= a) spatially connected porosity combined with internal surface roughness i= ncreases the macroscopic capacity of the cell; b) isolated porosity decreas= es the local conductivity, diffusivity, and charge capacity of the system; = and c) fully dense regions are effective obstacles for charge transport at = large C-rates. A combined statistical and visualization analysis identifies= surface morphological features with a small radius of curvature and porosi= ty bundles as favorable locations for dendritic growth. Simulations also sh= ow that lithium accumulation induces low electrochemical potential values a= nd compressive stresses in those surfaces exposed to spatially connected po= rosity, while tensile stresses develop in surfaces exposed to electrochemic= ally isolated porosity and fully dense regions, which in turn, favor crack = initiation. The crystallographic anisotropy of graphite favors stress local= ization at grain corners and boundaries, particularly for large grain bound= ary misorientations. Simulations demonstrate that battery reliability can b= e improved by controlling the radius of curvature of features and the minim= ization of the occurrence of pore bundles. The acquired scientific experien= ces were abstracted into an analytical framework to validate and extend wid= ely accepted porosity-tortuosity relations. The proposed framework enables = the derivation of analytical expressions by starting from the volume fracti= ons of the constitutive components.

Experimentally measured tortuosities are rationa= lized through the relation developed herein,     &= nbsp;          i= n the Bruggemann limit.

 

 

= Date:   Monday, April 16, 201= 2

Time:   2:30 P.M= .

Place:  ARMS Rm. 1028

<= span style=3D'font-size:11.0pt'> 

 

=  

 

Lisa Stacey

Secretary/Development Assistant<= /span>

Purdue University

School of Materials Engineering

765/494-4100=

 

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