Table Of ContentElectrochemical Power
Sources: Fundamentals,
Systems, and Applications
Metal-Air Batteries:
Present and Perspectives
Edited by
Hajime Arai
Tokyo Institute of Technology, Yokohama, Japan
Ju¨rgen Garche
Ulm University, Ulm, Germany
Luis Colmenares
CIDETEC Energy Storage, Donastia-San Sebastia´n, Spain
Elsevier
Radarweg29,POBox211,1000AEAmsterdam,Netherlands
TheBoulevard,LangfordLane,Kidlington,OxfordOX51GB,UnitedKingdom
50HampshireStreet,5thFloor,Cambridge,MA02139,UnitedStates
Copyright©2021ElsevierB.V.Allrightsreserved.
Nopartofthispublicationmaybereproducedortransmittedinanyformorbyanymeans,electronicor
mechanical,includingphotocopying,recording,oranyinformationstorageandretrievalsystem,without
permissioninwritingfromthepublisher.Detailsonhowtoseekpermission,furtherinformationaboutthe
Publisher’spermissionspoliciesandourarrangementswithorganizationssuchastheCopyrightClearance
CenterandtheCopyrightLicensingAgency,canbefoundatourwebsite:www.elsevier.com/permissions.
ThisbookandtheindividualcontributionscontainedinitareprotectedundercopyrightbythePublisher
(otherthanasmaybenotedherein).
Notices
Knowledgeandbestpracticeinthisfieldareconstantlychanging.Asnewresearchandexperiencebroadenour
understanding,changesinresearchmethods,professionalpractices,ormedicaltreatmentmaybecome
necessary.
Practitionersandresearchersmustalwaysrelyontheirownexperienceandknowledgeinevaluatingandusing
anyinformation,methods,compounds,orexperimentsdescribedherein.Inusingsuchinformationor
methodstheyshouldbemindfuloftheirownsafetyandthesafetyofothers,includingpartiesforwhomthey
haveaprofessionalresponsibility.
Tothefullestextentofthelaw,neitherthePublishernortheauthors,contributors,oreditors,assumeany
liabilityforanyinjuryand/ordamagetopersonsorpropertyasamatterofproductsliability,negligenceor
otherwise,orfromanyuseoroperationofanymethods,products,instructions,orideascontainedinthe
materialherein.
LibraryofCongressCataloging-in-PublicationData
AcatalogrecordforthisbookisavailablefromtheLibraryofCongress
BritishLibraryCataloguing-in-PublicationData
AcataloguerecordforthisbookisavailablefromtheBritishLibrary
ISBN:978-0-444-64333-9
ForinformationonallElsevierpublicationsvisitourwebsite
athttps://www.elsevier.com/books-and-journals
Publisher:SusanDennis
AcquisitionsEditor:KostasMarinakis
EditorialProjectManager:DevlinPerson
ProductionProjectManager:SruthiSatheesh
CoverDesigner:GregHarris
TypesetbyTNQTechnologies
Contributors
Francisco Alcaide-Monterrubio
Laboratory ofElectrochemistry ofMaterials and theEnvironment, MaterialsScience and
Physical Chemistry,Universitat de Barcelona,Barcelona, Spain; CIDETEC,Donostia-San
Sebastia´n,Spain
StefanAndersson
SINTEF Industry,Process Metallurgy and Raw Materials, Trondheim, Norway
Hajime Arai
Department of Chemical Science and Engineering,School ofMaterials and Chemical
Technology,TokyoInstituteofTechnology,Yokohama, Japan
Pere L. Cabot iJulia`
CIDETEC,Donostia-San Sebastia´n, Spain
SimonClark
SINTEF Industry,New Energy Solutions,Trondheim,Norway
David Fuchs
Department of Energy Technology,University Duisburg-Essen,Duisburg,Germany
AngelikaHeinzel
Department of Energy Technology,University Duisburg-Essen,Duisburg,Germany
TatsumiIshihara
InternationalInstituteforCarbon-NeutralEnergyResearch,KyushuUniversity,Fukuoka,Japan
Kaushik Jayasayee
New Energy Solutions,SINTEF Industry,Trondheim,Norway
Ingvild Julie Thue Jensen
SINTEF Industry,Materials Physics, Oslo, Norway
LudwigJo¨rissen
Znetrumfu¨rSonnenenergie-undWasserstoff-ForschungBaden-Wu¨rttemberg,Ulm,Germany
MariJuel
New Energy Solutions,SINTEF Industry,Trondheim,Norway
HackhoKim
InternationalInstituteforCarbon-NeutralEnergyResearch,KyushuUniversity,Fukuoka,Japan
MartinKrebs
Innovative Projects R&D VARTA Microbattery, Ellwangen,Germany
FalkoMahlendorf
Department of Energy Technology,University Duisburg-Essen,Duisburg,Germany
MarcelMeeus
Sustainable Energy Services Consulting, SUSTESCO,Flanders, Belgium
xi
xii Contributors
Kohei Miyazaki
Department ofEnergy &Hydrocarbon Chemistry,GraduateSchool ofEngineering, Kyoto
University, Kyoto, Japan
Christoph Mueller
Department ofEnergy Technology, University Duisburg-Essen,Duisburg,Germany
Linda Nazar
Chemistry, University ofWaterloo,Waterloo,ON, Canada
Ponce deLeo´n
Electrochemical Engineering Laboratory,University ofSouthampton, Southampton,
United Kingdom
Hans-Ulrich Reichardt
DC Instituteof Electrochemistry, Clausthal University ofTechnology,Bochum, Germany
Reiner Sojka
Accurec Recycling GmbH,Krefeld, Germany
Philippe Stevens
EDF R&D, GwenaelleToussaint,France
XiaWei
ZPower LLC, Camarillo, CA,UnitedStates
Gautam G.Yadav
Urban Electric Power,Pearl River,NY,UnitedStates
Series overview
Manydecarbonizationtechnologieswhichhelptosolveglobalenvironmentalandresourcesproblems
arebasedonElectrochemicalPowerSources(ECPS).TheimportanceofECPShasincreasedrecently,
even though their principles were known since more than 150 years. Forecasts value the worldwide
batterymarketatabout$150bill/yand1000GWh/yfor2025.Themainreasonisthestronggrowth
ofboth,theelectricvehiclemarketandthetransformationoftheenergysystems,towardaCO -neutral
2
powersupply bymeansof renewable energies. Bothrequire significantenergy-storage capacities.
Asaconsequence,anincreasingnumberofbookshavebeenpublishedinthepastyears.Mostofthem
are related to the favored Li-ion battery technology and less to other battery chemistries. This is
understandable on the one hand, since the Li-ion system is at present the main battery chemistry
forEVsandstationarystorage,butontheotherhand,thistechnologyhasamarketshareofonlyabout
40%yet.Inaddition,togiveacomprehensiveoverview,othercurrentandfuturetechnologiesneedto
be discussed. Furthermore, a CO -neutral energy world requires a strong sector coupling to serve
2
mobility, industry, and the heating systems with CO -free gases or fuels. This leads automatically
2
to a huge demand in hydrogen production by means of electrolyzers and efficient use of hydrogen
with fuelcells for power and heat productionin mobile andstationary applications.
ThisserieswillissuebooksconsideringthecurrentR&Dstatus,challenges,opportunities,andthreats
of ECPS and their applications. We focus on the value chain toward system applications invarious
fields(verticalapproach),butalsodiscussspecialtechnologyissuesalongthevaluechain(horizontal
approach).Intheverticalapproach,mainlyrechargeablebatteries(Li-ion,lead-acid,alkaline,metal-
air,postLi-systems),fuelcells,electrochemicalcapacitors,andphoto-electrochemicalcells,aswellas
electrolyzers,willbediscussed.Thehorizontalapproachcoverstopicssuchascellandbatterydesign,
productiontechnologies,batterysafety,modeling,batterymanagementsystems,andrecycling.With
regard to applications, the focus will be on the mobility sector, stationary storage systems in in-grid
and off-grid applications, consumer products, medical healthcare devices, and military and space
applications.
Ju¨rgen Garche
AndreasJossen
Dirk Uwe Sauer
xiii
CHAPTER
1
Introductiondgeneral features of
metal-air batteries
Hajime Arai
DepartmentofChemicalScienceandEngineering,SchoolofMaterialsandChemicalTechnology,TokyoInstituteof
Technology,Yokohama,Japan
Chapter outline
1.1 Concept...........................................................................................................................................1
1.1.1 Basics.........................................................................................................................1
1.1.2 Classification...............................................................................................................2
1.2 Maincomponents.............................................................................................................................3
1.2.1 Metalelectrode............................................................................................................3
1.2.2 Electrolyte...................................................................................................................5
1.2.3 Airelectrode................................................................................................................7
1.2.4 Separator.....................................................................................................................9
1.2.5 Subsystem...................................................................................................................9
1.3 Performances.................................................................................................................................10
References............................................................................................................................................10
1.1 Concept
1.1.1 Basics
Ametal-airbattery(MAB)isanelectrochemicalcellthathasametalnegativeelectrode,anairpositive
electrode,andanelectrolyte.Theuseofoxygeninairasanactivematerialforthepositiveelectrode
bringsaboutvarietyofmeritsinthebattery.Oxygen,theactivematerial,islightinweighttoproduce
hugespecificcapacity(3.35Ahg(cid:1)1)andhashighredoxpotential(1.23Vvs.RHE).Oxygeninairis
availableeverywhereonearth,freeandenvironmentallybenign.Sincetheaircomesfromoutofthe
cell,theMABisessentiallyfreefromthespaceforthepositiveelectrodeactivematerial(onlyathin
catalyst layer is needed) and can contain the negativeelectrode activematerial as much as possible.
Basemetalswithstrongreducingpowerarewidelyusedasthenegativeelectrodeactivematerials.As
illustratedinFig.1.1,thisisincontrasttothesituationinotherbatteriessuchaslithiumionbatteries
(LIBs), inwhich space is needed for both negativeandpositiveelectrodes.
The MAB can supply electricity until the negative metal is all consumed, owing to the inex-
haustible nature of oxygen (see Section 1.2.2 for cases where the accommodation of the discharge
1
ElectrochemicalPowerSources:Fundamentals,Systems,andApplications.https://doi.org/10.1016/B978-0-444-64333-9.00001-1
Copyright©2021ElsevierB.V.Allrightsreserved.
2 Chapter 1 Introductiondgeneral features of metal-air batteries
FIGURE1.1
Configurationsof(A)metal-airand(B)lithiumionbatteries.
products limits the utilization). This ideal feature has long been recognized and offers practical ap-
plicationsaslong-lastingpowersources,particularlyasprimarybatteries.Thoughtheairelectrodeis
similartothatinfuelcells,theMABisessentiallyastoragebatterywhereasthefuelcellisapower
generator with no functionof power storage.
1.1.2 Classification
TheMABs can be classifiedinto severalcategories asshown inFig. 1.2.
ThevastmajorityofMABcellstodaybelongtotheprimarytypes.Theelectrolyteisusuallysetin
thecelltobereadytouse,butisoccasionallyseparatedfromthenegativemetaltopreventitscorrosion
(self-discharge),whichiscalledreservebattery.Theotherwaytopreventtheself-dischargeistoseal
airholesbeforeuse.
Secondary MABs can be categorized into two by theway of charging, electrically and mechani-
cally rechargeable. Electrically rechargeable MABs are (re-)charged by electricity. Bifunctional air
electrodes function both in discharging (with oxygen reduction reaction, ORR) and charging (with
oxygen evolution reaction, OER), whereas some electrically rechargeable MABs have two air
electrodes; one is for discharging and the other (the third electrode) for charging, as described in
Section 1.2.3.
FIGURE1.2
Classificationofmetal-airbatteries.
1.2 Main components 3
MechanicallyrechargeableMABsarerechargedbymechanicallyreplacingtheusednegativemetal
(andelectrolytes)withthefreshone,whichessentiallytakesmuchshorterperiodoftimethanelectrical
recharging.MechanicalrechargingisaspecialfeatureofMABsthatutilizeinexhaustibleoxygenasthe
activematerial.Theusednegativemetal(compound)isregeneratedinadifferentelectrolysiscellwith
acounterelectrodeexclusivelyforcharging(OERelectrode).ThemechanicallyrechargeableMABs
can further be classified into the solid metal type and the hydraulic/flow type with the active metal
dispersed or dissolved in the electrolyte. The mechanical recharging of the hydraulic/flow type is
employed with a pump. The advantage of using the third electrode, as well as the mechanical
recharging,isthattheairelectrodemostsuitable totheORRcan beapplied fordischarging.
1.2 Main components
1.2.1 Metal electrode
The configuration of the MABs significantly depends on the metal used for the negative electrode,
because the kind of metal chiefly determines the kind of the electrolyte and also of the air electrode
design.
Generally, the requirements for the negative metal are strong reducing power, lightness, and
compactness.Itshouldbeinexpensivesincethecostofthebatterysignificantlydependsonthemetal
intheMABwithcost-freeoxygeninthepositiveside.Basemetalelementsarecommonlyusedforthis
purposesuchaslithium,aluminum,magnesium,iron,andzinc.Inaddition,metalhydride(hydrogen
asanactivematerial),alloys,organicmaterialssuchassugarandotherreducingagentscanbeusedas
the activematerials for the negativeelectrode.
ThedischargeproductsoftheconventionalMABsaregenerallymetaloxides,whicharesimplythe
combination ofthe metal andoxygen.
M þ n=4O2/MOn=2 (1.1)
Metalperoxides/superoxidesandmetalhydroxidesareoccasionallyformedasdischargeproducts.
Wateris consumed on discharging,in addition tooxygen, when the hydroxides are formed.
M þ nO /MO (1.2)
2 2n
M þ n=2O /MO (1.3)
2 n
M þ n=4O þn=2H O/MðOHÞ (1.4)
2 2 n
Fig. 1.3 shows the theoretical specific energy and energy density of several MABs based on the
metals to form oxides. These values are much larger than those of a primary lithium/MnO battery
2
(assumingitsvoltageof3V),whichcanbeestimatedas0.86Whg(cid:1)1and2.6Whcm(cid:1)3,showingthe
significant advantage ofthe MABs.
For secondary batteries, it is fair to compare the data based on the discharged states because the
discharged products are generally heavier and bulkier than the charged products. The theoretical
specificenergyandenergydensitybasedonthepossibledischargeproductsareshowninFig.1.4.The
specific energy and energy density will be decreased when the discharge products are dissolved in
the electrolyte.
4 Chapter 1 Introductiondgeneral features of metal-air batteries
FIGURE1.3
Theoretical(A)specificenergy(Whg(cid:1)1)and(B)energydensity(Whcm(cid:1)3)ofmetal-airbatteriesbasedonthe
metalmassandvolume.
FIGURE1.4
Theoretical(A)specificenergy(Whg(cid:1)1)and(B)energydensity(Whcm(cid:1)3)ofmetal-airbatteriesbasedonthe
massandvolumeofcorrespondingdischargeproducts.
The corresponding theoretical specific energy and energy density of LIBs (2LiCoO þC ¼
2 6
2Li CoO þLiC )are,respectively,0.78Whg(cid:1)1and2.9Whcm(cid:1)3,againshowingthegreatadvan-
0.5 2 6
tages of the MABs in terms of energy. On the other hand, the volume increase during discharging is
generallylargeofseveraltensofpercent,incontrasttoafewpercentforLIBelectrodes,whichcanbe
1.2 Main components 5
disadvantageousastotherechargeability.ItispossibletofabricatesomeMABsinthefullydischarged
state(e.g.,withmetaloxideasthenegativeactivematerial)andtoactivatethecellsbycharging.
ThevoltageprofileofMABsisgenerallyflat,correspondingtoasimplebiphasicreactionbetween
themetalandthedischargedproduct.Thedischargeproductsareoftennonconductive,incontrastto
the highlyconductivemetals,which causes thevoltagedrop inthe courseof discharging.
1.2.2 Electrolyte
Theelectrolyteisrequiredtohavegoodionicconductivity,electricallyinsulatingnature,andsufficient
stability against the reducing potential of the negative metal, as well as the oxidizing potential of
oxygen. For aqueous systems, alkaline electrolytes are widely employed owing to its low proton
activity to prevent hydrogen evolution reaction (HER) as the side reaction. The HER causing self-
discharge to consume the negative metal, as shown in Eq. (1.5), can be severe in neutral and acidic
aqueous electrolytes.
M þ n=2H2O/MOn=2þn=2H2 (1.5)
For particular combination of the negative metal and the electrolyte, such as aluminum or mag-
nesiuminbrineelectrolytes,thenegativemetalisimmersedintheelectrolyteonlywhenthebatteryis
operated topreventself-discharge (reservebattery).
For base metals that are incompatiblewith the aqueous electrolytes, variety of nonaqueous elec-
trolytesareemployedincludingorganicelectrolytes,polymerelectrolytes,inorganicsolidelectrolytes,
andmoltensalts(ionicliquid).Thoughmostofthemhavewidepotentialwindowstobestableforboth
negativemetalsandoxygen,somesolvents,suchascarbonatesoftenusedinLIBs,arevulnerableto
oxidation.Sometimesacombinationofelectrolytesisapplied.AnexampleisshowninFig.1.5,where
metallic lithium covered by a lithium ion conductive solid electrolyte is immersed in the aqueous
electrolyte. The air electrode is operated in the aqueous media whereas the negative metal can be
operated withoutdirect contact withthe aqueouselectrolyte.
Thevaporpressureoftheliquidelectrolyteisoftenanimportantissue,sincetheairelectrodeinthe
MABs is semi-opened for air suction. Water uptake (or release) through the air electrode leads to
FIGURE1.5
Configurationoflithium-airbatteryusingaqueouselectrolyte.
