Development of metal hydride surface structures for high power NiMH batteries Also extended cycle-life and lead to more effective recycling methods

50 Pages·2018·1.584 MB·English

by  Yang Shen

Development of metal hydride surface structures
for high power NiMH batteries
Also extended cycle-life and lead to more effective recycling
methods
Yang Shen
Academic dissertation for the Degree of Doctor of Philosophy in Inorganic Chemistry at
Stockholm University to be publicly defended on Monday 10 December 2018 at 13.00 in
Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B.
Abstract
By combining alkaline etching of hydrogen storage alloys or their hydrides with a controlled oxidation, it was possible to
improve reaction kinetics and accelerate activation of MH-electrodes. Both AB and AB alloys were studied where A is
5 2
mixtures of rare earth elements for AB alloys and titanium and/or vanadium, zirconium for AB alloys; nickel contributes
5 2
the major part of B. With SEM and TEM studies the surface could be described as consisting of several phases where
an interphase with active Ni-containing cluster protected the inner metallic hydrogen storage part of the powder particles.
These catalytic Ni-clusters presumably lead to the fast activation and high discharge capacity of alloy.
This interphase was observed to be stable enough to allow us to develop a method, where we could add pure oxygen to
a NiMH battery pack in order to regenerate the amount of electrolyte that was lost during long time cycling of the battery.
Meanwhile, the method will rebalance the electrodes mitigating excessive pressures during over charge. Therefore, the
internal resistance of cells can be reduced and cycle life will increase.
It was also shown that the stable interphase could survive a mild ball milling or sonication which enabled us to upcycle
material from spent NiMH batteries into a better working MH-electrodes with improved kinetics and activation properties.
Reuse of ball-milled or sonicated material could serve as a simple recycling alternative to energy-demanding metallurgical
smelting methods and chemical consuming hydrometallurgical recycling processes, where the possibilities of up-scaling
further favour the less complex mechanical treatments. The stable but catalytic interphase protecting the inner particles
indicates that the MH-electrode material may perform better in its second life in a new NiMH battery.
Keywords: Metal hydrides, NiMH batteries, Surface treatment, Ni clusters, Rare earths hydroxides, Oxygen, Hydrogen.
Stockholm 2018
http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-154581
ISBN 978-91-7797-218-1
ISBN 978-91-7797-219-8
Department of Materials and Environmental
Chemistry (MMK)
Stockholm University, 106 91 Stockholm

DEVELOPMENT OF METAL HYDRIDE SURFACE STRUCTURES
FOR HIGH POWER NIMH BATTERIES 

Yang Shen

Development of metal hydride
surface structures for high
power NiMH batteries 

Also extended cycle-life and lead to more effective recycling methods

Yang Shen
©Yang Shen, Stockholm University 2018

ISBN print 978-91-7797-218-1
ISBN PDF 978-91-7797-219-8

Printed in Sweden by Universitetsservice US-AB, Stockholm 2018
Distributor: Department of Materials and Environmental Chemistry
Development of metal hydride surface structures for high power NiMH batteries also
extendedcycle-lifeandleadtomoreeffectiverecyclingmethods.
Tomyparents
Tomygrandma
致我亲爱的父母
致我已逝的奶奶
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Abstract
Bycombiningalkalineetchingofhydrogenstoragealloysortheirhydrideswithacontrolledoxidation,
itwaspossibletoimprovereactionkineticsandaccelerateactivationofMH-electrodes.BothAB5and
AB2alloyswerestudiedwhereAismixturesofrareearthelementsforAB5alloysandtitaniumand/or
vanadium, zirconium for AB2 alloys; nickel contributes the major part of B. With SEM and TEM
studiesthesurfacecouldbedescribedasconsistingofseveralphaseswhereaninterphasewithactive
Ni-containingclusterprotectedtheinnermetallichydrogenstoragepartofthepowderparticles.These
catalyticNi-clusterspresumablyleadtothefastactivationandhighdischargecapacityofalloy.
Thisinterphasewasobserved to bestableenough toallowustodevelop amethod, wherewe could
addpureoxygentoaNiMHbatterypackinordertoregeneratetheamountofelectrolytethatwaslost
during long time cycling of the battery. Meanwhile, the method will rebalance the electrodes
mitigating excessive pressures during over charge. Therefore, the internal resistance of cells can be
reducedandcyclelifewillincrease.
It was also shown that the stable interphase could survive a mild ball milling or sonication which
enabledustoupcyclematerialfromspentNiMHbatteriesintoabetterworkingMH-electrodeswith
improvedkineticsandactivationproperties. Reuseofball-milledorsonicatedmaterialcouldserveas
a simple recycling alternative to energy-demanding metallurgical smelting methods and chemical
consuminghydrometallurgicalrecyclingprocesses,wherethepossibilitiesofup-scalingfurtherfavour
the less complex mechanical treatments. The stable but catalytic interphase protecting the inner
particlesindicatesthattheMH-electrodematerialmayperformbetterinitssecondlifeinanewNiMH
battery.
Keywords:Metalhydrides,NiMHbatteries,Surfacetreatment,Niclusters,Rareearthshydroxides,
Oxygen,Hydrogen.
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ListofPapers
Thisthesisisbasedonthefollowingpapers,whicharereferredtotheromannumbers.
PaperI:ShenY,PengF,KontosS,NoréusD.ImprovedNiMHperformancebyasurfacetreatment
thatcreatesmagneticNi-clusters.InternationalJournalofHydrogenEnergy2016;41:9933-9938.
My contribution: I planned and executed all experimental work. I wrote the manuscript. I did most
characterizationsexpecttheTEMpartwasperformedbythesecondauthorandthemagnetizationpart
wasdonebythethirdauthor.
PaperII:TanS,ShenY,Şahin,EO,NoréusD,ÖztürkT.ActivationbehaviorofanAB2typemetal
hydridealloyforNiMHbatteries.InternationalJournalofHydrogenEnergy2016;41:9948–9953.
Mycontribution:IplannedtheworkwithfirstauthoranddidtheKOHtreatmentpart.Iwasinvolved
inthewritinganddiscussionsaboutthemanuscript.
Paper III: Shen Y, Noréus D, Starborg S. Increasing NiMH battery cycle life with oxygen.
InternationalJournalofHydrogenEnergy2018;43:18626-18631.
My contribution: I planned and executed all experimental work. I did all characterizations. I wrote
mostofthemanuscript.
PaperIV:ShenY,GrapeE,NoréusD,WidenkvistE,StarborgS.UpcyclingofspentNiMHbattery
material-Reconditionedbatteryalloysshowfasteractivationandreactionkineticsthanpristinealloys
aswellaslongercyclelifeduetolowercorrosionrates.InManuscript.
My contribution: I planned and executed the experimental work together with the second author. I
wrotethemanuscript.
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