Page - 114 - in Emerging Technologies for Electric and Hybrid Vehicles

Energies 2017,10, 1314 Table5.Overviewof thecell chemistriesusedforcostcalculations. Thefirstonewillbereferredtoas theNMCbatteryandthesecondoneas thesiliconbasedlithium-ionbattery. BatteryI BatteryII Positiveelectrode NMC(6:2:2) NMC(6:2:2) Negativeelectrode Graphite SiliconAlloy[50] Packenergydensity 155Wh/kg 205Wh/kg 3.4. BatteryCellManufacturing Severalarchitecturesanddesignsofbatterycellsexist suchascylindrical cells,pouchcells,hard casingwithavarietyofpositions for the tabs [51].However inall thesedesigns threemainprocesses canbe identifiedasdescribed inTable6 [33].Also in this table thematerial inputs (+)andoutputs (−) areshownsincematerial cost is themaincostofabattery,whichwillbedemonstrated inSection3.5. Thefirst step iselectrodemanufacturing inwhichtheelectrodes themselvesarebeingprepared. Theactivematerial, conductiveagents, solventsandbinderaremixedtoaslurrywhich iscoatedonto acurrentcollector (aluminiumfor thepositive tabandcopper for thenegativeone).Afterwhichthe cellsaredried, inorder tovaporise thesolvents. Toensureagoodelectrical connectionbetweenthe slurryandcurrentcollector theelectrodesarecalendared,whichconsistsofpressingthe twofirmly together.Asa last step in thiselectrodemanufacturingtheelectrodesarecut to theircorrect size. Thesecondstep is tomakeacellsassemblyoramultilayercombinationofapositiveelectrode, separatorandnegativeelectrode. Thesemultilayerscanbecreatedthroughstackingorwindingto createrespectivelypouchandcylindrical cells.Afterwards thecellsarepackaged(hardcasing/soft casing/...) andtemporarilysealed. Thecellsundergoadryingprocedure toensurenosolvents remain afterwhichtheyarefilledwithelectrolyteandpermanentlysealed. Thebatterycell isnowreadytouse,however toensurestableandgoodqualityof it itshas to undergosomeelectrical formationcycles. These formationcyclesare critical for the lifetimeof the cell since its stabilizes the chemical structureof the cell. Thefinal step is to test the cell’s electrical performance tomaintainagoodqualitycontrol. Table6.Batterycellmanufacturingprocesssummary includingmaterial in-andoutflow. ManufacturingProcess Material ElectrodeManufacturing SlurryMixing +ActiveMaterial +Conductiveagent +Solvents +Binder Coating +Al/Cufoil Drying −Solvents Calendaring Cutting +Remainingal/Cufoil CellAssembly Stacking/Winding +Separator +AdhesiveTape +Al/Cutabs Packaging(Pouch/Case) +PouchFoil/casing Temporarysealing +Solvents Drying Filling −Remainingal/Cufoil PermanentSeal Formation FormationCellTesting 114