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Energies 2017,10, 1314
3.1. State of theArt—Anode
Twentyyearsagographite (372mAh/g[34])wasfirst commercialized[35]asanodematerial ina
lithium-ionbatteryanduptonowit is stillbeingused inmost lithium-ionbatteries. Its lowcost,good
electrochemicalperformance, lowvolumeexpansionduringcharginganddischargingaswellas that
it isabundantlyavailable,explains thewidelyaccepteduseofgraphiteasanodematerial [33,35,36].
Manyresearcheffortsallowedtooptimize thismaterial resulting it isalmost reaching itsmaximum
theoretical capacityandonly incremental improvementscanbeexpected[29].However,byadding
small amountsofmetalswithhigh theoretical energydensities, suchas silicon (4200mAh/g [37]),
the overall energydensity can be increased [38]. Addinghigh concentrations of these additional
components causenumerousproblemssuchasvolumeexpansionsup to300%aswell as reduced
lifetimedespite thecurrentnumerousresearchefforts, forexampleusingsiliconasnano-particlessuch
as in [37].
OtheroftenusedanodesmaterialsusedarelithiumalloyedmetalswithasmostpopularLi4Ti5O12
LTO(175mAh/g[35]).Morenoblemetalsareusedresulting inahigherprice thangraphite.Other
disadvantagesare its lowerenergycapacityandreducedcellvoltagecomparedtographite.However
itsexceptionalgoodstabilityover its lifetimemakes it the idealanodes inspecificcasesexplaining its
wideusage.
Anoverviewof the twomostusedanodematerials is showninTable3 [34,35].
Table3.Anodematerials—Overviewincludingspecificenergydensity, costandlifetime.
AnodeMaterial EnergyDensity Cost
Lifetime(mAh/g)
Graphite 372 Medium Medium
Li4Ti5O12 (LTO) 175 High High
3.2. State of theArt—Cathode
Theselectionof themostsuitedcathodematerial is stronglydependentontheapplication itself.
Aselectionhas tobemadeofwhichkeyproperty is themost important foranapplication. Thekey
propertiesofabatteryare: energydensity,powerdensity, costandlifetime.Anoverviewof themost
usedcathodematerialscanbefoundinTable4 [29,33,36,38–45].
Table4.Cathodematerials—Overviewincludingenergydensitycostandlifetime.
CathodeMaterial EnergyDensity Cost
Lifetime(Wh/kg)
LiCoO2 (LCO) 546 Medium Medium
LiMn2O4 (LMO) 410–492 Low Low
LiNiMnCoO2 (NMC) 610–650 High High
LiFePO4 (LFP) 518–587 Medium High
LiNiCoAlO2 (NCA) 680–760 High Medium
TheoldestcommerciallyusedelectrodesareLiMn2O4 (LMO)dueto the lowcost,however the
lifetime is limitedwhich is considered tobe thebiggest disadvantagebut they are still frequently
used. LiCoO2 (LCO)anotheroldelectrode,characterizedwithamediumcostandhighenergy,has
somesafetydrawbacksbut is stillusedfrequently. LiNiMnCoO2 (NMC),acombinationofLCO,LMO
andnickel, isgainingpopularitydueto itshigh lifetimeaswellas itshighenergydensity. Theexact
mixtureofNi,MnandCowill define thepropertyof the cathodeofwhichavariety exist suchas
NMC(1:1:1),NMC(5:3:2), ... The trend is touseNi richNMCsince thisgivesan increasedenergy
density. It ismainlyusedwherecost is less important. LiFePO4 (LFP)hasexcellent lifetimeproperties
andis frequentlyused incombinationwithanLTOanodetogetanexcellentoverall lifetimeof the
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Emerging Technologies for Electric and Hybrid Vehicles
- Title
- Emerging Technologies for Electric and Hybrid Vehicles
- Editor
- MDPI
- Location
- Basel
- Date
- 2017
- Language
- English
- License
- CC BY-NC-ND 4.0
- ISBN
- 978-3-03897-191-7
- Size
- 17.0 x 24.4 cm
- Pages
- 376
- Keywords
- electric vehicle, plug-in hybrid electric vehicle (PHEV), energy sources, energy management strategy, energy-storage system, charging technologies, control algorithms, battery, operating scenario, wireless power transfer (WPT)
- Category
- Technik