Received: from mx01.ecn.purdue.edu (mx01.ecn.purdue.edu [128.46.154.8]) by mailbag.ecn.purdue.edu (8.14.4/8.14.4) with ESMTP id q3GCc8Sd003181 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NOT); Mon, 16 Apr 2012 08:38:08 -0400 (EDT) Received: from mailhub130.itcs.purdue.edu (mailhub130.itcs.purdue.edu [128.210.5.130]) by mx01.ecn.purdue.edu (8.14.4/8.14.4) with ESMTP id q3GCbBC8011359 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NOT); Mon, 16 Apr 2012 08:37:11 -0400 Received: from WPPEXHUB01F.purdue.lcl (wppexhub01f.itap.purdue.edu [172.21.6.90]) by mailhub130.itcs.purdue.edu (8.14.4/8.14.4/mta-nopmx.smtp.purdue.edu) with ESMTP id q3GCbA1t021954; Mon, 16 Apr 2012 08:37:11 -0400 Received: from VPEXCH02.purdue.lcl ([169.254.2.132]) by WPPEXHUB01F.purdue.lcl ([::1]) with mapi; Mon, 16 Apr 2012 08:37:10 -0400 From: "Stacey, Lisa A" To: "'msefaculty-list@ecn.purdue.edu'" , "'msepostdoc-list@ecn.purdue.edu'" , "'msegradstudent-list@ecn.purdue.edu'" Date: Mon, 16 Apr 2012 08:37:09 -0400 Subject: REMINDER SEMINAR - B. Vijayaraghavan Mon. 4/16/12-2:30 PM Thread-Topic: REMINDER SEMINAR - B. Vijayaraghavan Mon. 4/16/12-2:30 PM Thread-Index: Ac0WWFyPLLsSem77TXSMWKLFIOhzXgFdQxxA Message-ID: <92F872D971E7AA498CF64DD847E5594D89C36E822A@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_92F872D971E7AA498CF64DD847E5594D89C36E822AVPEXCH02purdu_"; 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_92F872D971E7AA498CF64DD847E5594D89C36E822AVPEXCH02purdu_ Content-Type: multipart/alternative; boundary="_000_92F872D971E7AA498CF64DD847E5594D89C36E822AVPEXCH02purdu_" --_000_92F872D971E7AA498CF64DD847E5594D89C36E822AVPEXCH02purdu_ 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_92F872D971E7AA498CF64DD847E5594D89C36E822AVPEXCH02purdu_ 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 ENGINEERING

S= EMINAR

 

Three-Dimensional Mode= ling of Commercial Battery Anode Microstructures

 

by

 

Bharath P. Vijayaraghavan

Purdue MS Final Exam

 

Advisor

Prof. E. Garcia

 

ABSTRACT

&n= bsp;

=  

A t= hree-dimensional theoretical and numerical framework was developed to under= stand the processing-induced randomness and microstructural interactions of= rechargeable lithium-ion batteries. By starting from graphite anode micros= tructures extracted from X-ray tomography data the effects of the individua= l features on the electrochemical and mechanical reliability during galvano= static recharge are quantified. Spatially resolved electrochemical calculat= ions show that for dense porous electrodes: a) spatially connected porosity= combined with internal surface roughness increases the macroscopic capacit= y of the cell; b) isolated porosity decreases the local conductivity, diffu= sivity, and charge capacity of the system; and c) fully dense regions are e= ffective obstacles for charge transport at large C-rates. A combined statis= tical and visualization analysis identifies surface morphological features = with a small radius of curvature and porosity bundles as favorable location= s for dendritic growth. Simulations also show that lithium accumulation ind= uces low electrochemical potential values and compressive stresses in those= surfaces exposed to spatially connected porosity, while tensile stresses d= evelop in surfaces exposed to electrochemically isolated porosity and fully= dense regions, which in turn, favor crack initiation. The crystallographic= anisotropy of graphite favors stress localization at grain corners and bou= ndaries, particularly for large grain boundary misorientations. Simulations= demonstrate that battery reliability can be improved by controlling the ra= dius of curvature of features and the minimization of the occurrence of por= e bundles. The acquired scientific experiences were abstracted into an anal= ytical framework to validate and extend widely accepted porosity-tortuosity= relations. The proposed framework enables the derivation of analytical exp= ressions by starting from the volume fractions of the constitutive componen= ts.

Exper= imentally measured tortuosities are rationalized through the relation devel= oped herein,          &nb= sp;     in the Bruggemann limit.

 

 

Date:   Monday, April 16, 2012

Time:   2:30 P.M.

Place:  ARMS Rm. 1028

=  

 

 

 

Lisa Stacey

= Secretary/Development Ass= istant

Purdue University

School of Materi= als Engineering

765/494-4100

 

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