3D 3D-Elect Electroch ochemist emistry Designin igning g and resolving olving the microstru ostructure ture of an electr ctrod ode Gaëta tan Dambla mblanc nc
Ext xten ension sion to the Development lopment Additi tion on of a 3D electr ctroch ochem emist stry y mode del Applies to idealised or ‘real’ geometries Increasing Length Scale Battery Cell Battery modules/packs In Situ MicroStructure Modeling Battery tery Simulation ulation Module
Agenda da Motiv ivat ations ions What is a Li Li-ion ion Batt tter ery? y? Designin igning g the microst ostructure: cture: The 3D approac oach STAR-C -CCM+ CM+ Li Li-ion ion Batt tter ery y Cell ll Model Exam ample ple of a 3D Numeric erical al model el Future ure developments opments and conclusion usion
Motiv ivat ations ions Cost st reduc educti tion on for the e design ign – Minimise the number of tests and experiments – Identify at the early stages of the development potential problems Process cess and resear search ch speed ed up up – Parameterisation and optimisation methods Impr mprovem emen ent t of the e un under derst stand anding ng of the e phenome nomena na taking ing place – Performance – Ionic and electronic transport – Ageing – Short circuit
What is a Lithium hium -ion n Batt tter ery? Posit itive e and d nega gativ tive half reacti tions ons for a LiCoO CoO 2 cathode hode: 𝑴𝒋𝑫𝒑𝑷 𝟑 𝑴𝒋 𝟐−𝒚 𝑫𝒑𝑷 𝟑 + 𝒚𝑴𝒋 + + 𝒚𝒇 − 𝒚𝑴𝒋 + + 𝒚𝒇 − + 𝟕𝐃 𝑴𝒋 𝒚 𝑫 𝟕
What is inside ide a Li Li-ion ion Electr ectrod ode? e? The e elec ectr trode des s are made de of porou ous s activ tive e materi erials als placed ed in a liqui uid non-aqueo eous us electr ectroly olyte - +
Advanta ntages ges of the 3D approac oach Geom ometrical trically ly resol olved electr ectrode ode – Interfacial surface area – Volume/porosity fraction – Tortuosity Tortuosity Local cal interac eractions tions – Voltage distribution – Li-ion pathways – Li-ion concentration – Short circuiting – Thermodynamic effects – SEI growth Materia erial int nteractions eractions – Active material – Liquid or Solid Electrolyte – Binders, conductive additives Contract traction on and Expansi ansion on During the intercalation process – SEI
The Li Li-ion ion Batt tter ery y Cell l model el Solid particles structure is to be resolved or represented by a simpler, regular structure (e.g. cylinders, grid etc.) Section across a typical Li-ion cell Geometry-resolved model
The Li Li-ion ion Batt tter ery y Cell l model el We suggest est to discreti tize ze separat ratel ely y solid and d fluid regions ons within in an electr trod ode, e, with the desired d level of comp mple lexi xity ty Within in solid struc ucture ture, one can n accou count t for acti tive and d passive e mater eria ials (e.g. activ ive e mater eria ial and condu duct cting ing aid). Chemical cal react ctions ions take e place ce at the solid-elect electrol olyt yte e inter erpha hase (SEI): ): standar ndard d form of equa uations tions can an be used, with special al cond nditi ition ons at inter erface ces. The model of a Li Li-ion n batter ery y requi uires res solution ion of the following ing equa uations: tions: – Salt concentration in electrolyte; – Concentration of Li in solid part of electrodes; – Potential in solid; – Potential in electrolyte; – Thermal energy. Flow will initia tiall lly y be neglect ected ed, but may y be included luded in the future ure (as well as volume me chan ange ge during ing charging rging and d discharging harging to accou ount nt for expansi ansion on/c /cont ontra ract ction). on). Crucia cial: l: cond nditions itions at the inter erfac aces.. s...
The main n equati tions ons Lith thium m (Li + ) ) is transp nspor orted ed into o and out ut of particles cles by diffusi sion on: We assume here a binary electrolyte and express the conservation equation for Li-salt in the liquid phase as follows The potential in the solid phase, Φ 1 , is computed from the following equation: The e pot otenti ential al in liqui uid, , Φ 2 , can be comput puted d from om the follo lowing wing equa uati tion on:
Interface ce Condition itions Local l curre rrent t density ity at solid activ ive surfac face e is modelled lled as (Butt ttler ler-Vol olmer er relati tion on): with c s – Site concentration of solid phase (maximum possible value of c 1 ). k – Rate constant R sei – Solid-electrolyte-interface resistance U eq – Equilibrium potential of the active material
The 3D Numeri rical al Model l Definition nition • Cathod hode Colle llector or – Alumin minum m foil 10µm m thick ( δ k p ), , • Cathod hode activ ive e mater erial ial – LiMn 2 O 4 80µm thick ( δ p) p), , partic ticle le diame ameter er 10µm, m, target porosity osity 40% • Separ arator or - 10µm m thick ( δ s) s), , porosity osity 40%, , Mac acMull Mullin in number ber 5 • Anode ode activ ive mater erial ial – Grap aphit hite e 96µm m thick ( δ n) n), , particle icle diame ameter er 20µm, m, target t porosit osity 40% Anode ode Colle llector or – Copper er foil 10µm m thick ( δ k n ) • • Elec ectr trolyte – et ethylene lene car arbonat onate/e e/eth thyl l met ethyl l car arbo bonat ate e 50:50 mix, , salt t - LiFP 6 • Over erall all unit cell ell dimen mensions sions - 25 µm by 25 µm by 206 µm 15 15
Model l De Definit nition ion - Catho thode de Polyhedral mesh 2.8 million cells Solid & electrolyte resolved STAR-CCM+ CAD tool 40% Porosity 16 16
Model l De Definit nition ion - Ano node Polyhedral mesh 1.2 million cells Solid & electrolyte resolved Anode Active Material - Graphite STAR-CCM+ CAD tool 40% Porosity 17 17
Mesh Det etails ails Ele lectroly trolyte te Active Ac ive Materi erial al Conf nform ormal l Mes esh Prism ism Layer yer at th the SEI 18 18
The full electr ctrod ode e to be resolv solved ed – Mesh view Symmetrical boundaries on all external walls
The Physic sics s set et-up up and Butler tler-Volm olmer er relat ation The e proper perti ties es of the e Active Material rial are defined ined in the e physics sics continu ntinua – Electrical conductivity – Diffusion coefficient – The parameter can also account for a dependence on the Temperature and Li-Ion Concentration The e But utler er-Volm lmer er relat elations ions parame meter ers are define ined d in a panel el un under er the e relevant ant Liquid/So uid/Soli lid d phases ses inter erface ces
Report Re rt for r Batt ttery ery Ce Cell ll state ate Open questions: • After setup: cell capacity (Ah / coulomb) • During simulation: State Of Charge (SOC) and corresponding Open Circuit Voltage (OCV) • Additional: average electrode concentrations to reinitialize at different SOC / OCV Provide only: • Initial Setup (electrode regions & initial conditions) • (Open Circuit) Voltages where cell is defined as fully charged / discharged Report computes amount of Li+ which can be shuttled between electrodes until upper / lower voltage attained
Re Report rt for r Batt ttery ery Ce Cell ll state ate Resu sult lts: s: C/10 full dischar harge ge rest
Resu sults lts during ing Charge rge Lith thium m salt conc ncentra ntrati tion on at 3 transient nsient points nts throu ough gh a charge ge 3D model 1D model 24 24
Solid lid Phase ase Concen entr trat ation ion – Liquid uid Phase se Electric ctric Poten enti tial al 1 min 2 min 3 min
Li Li-ion ion Concen entration tration diffusion usion in solid id phase
Elect ectric ic Poten enti tial al in Elect ectrolyt olyte
Next xt Steps ps and Conclusion clusion Initia itial l results ts prese sent nted ed Pub ublicat cation ion of valida dati tion on paper Begi gin n workin king g with h externa ernal l us users s Available able in STAR AR-CC CCM+ M+ 7.06 06 Fut uture ure developme elopments nts • Impr mprove e the e mode del bui uild ld process cess • Extend work to “real” geometries • Model del half-elect electrod ode e to focus on the e Catho hode de or An Anode de desi sign gn • Measure sure SEI EI overpo poten ential tial 28 28
Aknowled wledgem gement nt Many y thanks anks to my colleagues leagues who ho actively ely work on this s inno novat ative e topic – Dr Robert Spotnitz from Battery Design LLC – Milovan Peric – Steve Hartridge – Boris Kaludercic – Christian Walchshofer THANK YOU!
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