Seite - 113 - in Emerging Technologies for Electric and Hybrid Vehicles

Energies 2017,10, 1314 battery. LiNiCoAlO2 (NCA),arelativelynewcathode,hasaveryhighenergydensityhowever it is potentially thermallyunstablestability,meaningareducedsafety. 3.3. State of theArt—Roadmap Demandson lifetimeandenergy/powerdensityareever increasing toextendtheduration in which the battery canbeused. Hence, there is a continuousneed to further improve lithium-ion batteries [46]. Thissectionwill explainwhichfuture trendscanbeexpectedduringthenextdecades, an overview is given in Figure 4, which is limited to lithium-ion batteries. Other types, such as sodium-ion,zincair, lithium-airarestill inaveryearlyphaseandthusomittedfromthisoverview. Figure4.RoadmapofLithium-ionbasedbatteries frompresentupto>10years. Theworldofbatteries is changingveryrapidlywhich is thereasonwhyit isveryhardtopredict themostpromisingbattery chemistry. It canbedisruptedveryeasily if anovel type/chemistry is discovered inmaterial scienceswithsuperiorproperties. Howeversometrendsarealreadyvisible whenlimitingto lithium-ionbasedbatteries. The first clear trend is to use different electrodeswhich have a significant higher theoretical capacity such as sulfur (1672 mAh/g [47]), silicon (4200 mAh/g [37]) and lithium metal (3860mA/g[48]). Thiswill inherently increase theenergydensityof thecell since theelectrodes itself canstoremoreenergy.Asecondtrendis to increasethevoltage limitofasinglecell toaround5Vsince it isaharmonizedvoltagevalueusedin thefieldofelectronics. This trendwillalso increase thecells energydensitydueto itsdefinitionwhichcanbesimplyrepresentedas integralof theactual capacity multipliedwith theactualvoltage. The third trendis togotowardssolidstateelectrolytessinceusing liquidelectrolytescancausesafetyproblemswhenleaking. Ingeneral it canbeconcludedthat in the near future theenergydensityandsafetyare the twokeytopics, inwhichsignificant improvementcan beexpectedduringthenextdecade[32]. Tomakepredictions further thanadecade isextremelydifficultbut lithium-magnesiumisworth mentioning. It has superior energydensity and is abundantly available, but is still in averyearly phase [49]. In thispaper,asalreadymentioned, thegoal is toperformapriceestimationupto2030. Thebest overall chemistrynowin2015 isNMC(6:2:2) as cathodecombinedwithgraphite as anodedue to theirhighenergydensityandlifetime. It canbeseen in literaturemanyresearcheffortsorongoing onsiliconbasedcells. Therefore in2030namelyasilicon-alloyanodecombinedanickel richcathode (NMC(6:2:2)) tomaximize itsenergycontentwillbemost likelyonthemarket.Anoverviewof the twobatterychemistries,usedthis researchaswellas theirpackenergydensity is showninTable5. Throughout these twobattery typeswillbereferredtoasbattery Iandbattery II. 113