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Author:Vara, Vilja
Title:Fabrication of Li4Ti5O12 negative electrodes using water-based binders
Negatiivisen Li4Ti5O12 -elektrodin valmistaminen vesipohjaisten sideaineiden avulla
Publication type:Master's thesis
Publication year:2010
Pages:vii + 70      Language:   eng
Department/School:Kemian laitos
Main subject:Epäorgaaninen kemia   (Kem-35)
Supervisor:Karppinen, Maarit
Instructor:Räsänen, Samuli ; Kuusivaara, Juha
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark Aalto  3520   | Archive
Keywords:lithium-ion battery
lithium titanate
negative electrode
binder
litiumioniakku
litiumtitanaatti
negatiivinen elektrodi
sideaine
Abstract (eng): Lithium-ion battery was developed to replace hazardous rechargeable metallic lithium battery.
Most widely used materials for the negative and the positive electrode materials have been graphite and LiCoO2, respectively.
These materials are constantly developed to find more efficient materials especially for high power density applications such as electric vehicles.
Li4Ti5O12 is a very promising material for the negative electrode and possesses many advantages over conventionally used graphite: it is faster to charge, possesses longer life time, is environmentally friendlier and undergoes no volume change during charging and discharging which would otherwise lead to mechanical degradation of the battery.

In the literature part discussed are the binding agents used in the Lithium-ion batteries.
Binding agent binds electrode particles together and to the current collectors and brings mechanical stability to the electrode.
Conventionally used fluorinated binders, PVDF (polyvinylidene fluoride) and Teflon, require hazardous and expensive organic solvents.
On this account, water-based binders have drawn interest in the manufacturing of lithium-ion batteries.
They are environmentally benign, non-toxic, and of low cost.
Also, less amount of binder is required for sufficient battery performance than in the case of conventional binders, which leads to higher active material contents and the capacity of the battery increases.

In the experimental part, the behaviour of Li4Ti5O12 negative electrodes prepared with water-based binders was studied.
Different binder systems, including acryl, styrene butadiene latex and carboxyl methyl cellulose, and their amounts were investigated to find properly functioning batteries.
The adhesion to aluminium current collector and the stability towards the electrolyte were studied.
Electrodes with PVDF binder were fabricated for reference.
The coin cells were cycled at different current rates to obtain their specific capacities.
The best capacity results were obtained with acryl binders, whose amount in the electrode was 3 wt. %.
Abstract (fin): Perinteisesti negatiivisina ja positiivisina elektrodimateriaaleina litiumioniakuissa on käytetty grafiittia ja LiCoO2 :a.
Näitä materiaaleja kehitetään jatkuvasti, jotta saataisiin yhä tehokkaampia korkean tehotiheyden omaavia akkuja.
Sovelluskohteina tällaisille entistä tehokkaammille litiumioniakuille ovat muun muassa sähköautot.
Li4Ti5O12 on erittäin lupaava negatiivielektrodimateriaali ja edut grafiittiin verrattuna ovat huomattavat.
Li4Ti5O12 -elektrodit ovat turvallisia, pitkäikäisiä ja kestävät korkeita lataus- ja purkuvirtoja.
Lisäksi ne ovat mekaanisesti kestäviä, koska akun purkauksen ja latauksen aikana Li4Ti5O12 :n tilavuus ei muutu.

Kirjallisuusosassa tarkastellaan elektrodien sideaineita, joiden tehtävänä on sitoa elektrodimateriaalien partikkelit toisiinsa sekä virrankerääjään.
Sideaineet parantavat myös akun mekaanista kestävyyttä.
Perinteisesti sideaineina on käytetty kalliita ja haitallisia fluoripitoisia sideaineita, polyvinylideenifluoridia (PVDF) ja Teflonia, jotka vaativat liuottimikseen ongelmallisia orgaanisia yhdisteitä.
Vesipohjaisia sideaineita on tutkittu paljon, jotta päästäisiin eroon haitallisista ja kalliista liuottimista.
Vesipohjaiset sideaineet ovat ympäristöystävällisiä ja halpoja.
Lisäksi niitä tarvitaan pienempi määrä, jolloin aktiivisen aineen määrä akussa kasvaa.
Tällöin akun kapasiteetti kasvaa.

Työn kokeellisessa osassa tutkittiin eri sideaineita ja niiden määriä Li4Ti5O12 -elektrodien valmistuksessa.
Sideaineina käytettiin muun muassa akryylejä, styreenibutadieenilateksia sekä selluloosaa.
Työssä tutkittiin vesipohjaisten elektrodien adheesiota virrankerääjiin ja stabiiliutta käytettävässä elektrolyyttiliuoksessa.
Sähköiset ominaisuudet mitattiin syklaamalla kennoja eri virrannopeuksilla, jolloin saatiin selville spesifiset kapasiteetit.
Vertailuksi valmistettiin PVDF -pohjaisia vertailuelektrodeja.
Parhaimmat spesifiset kapasiteetit saavutettiin akryylisideaineilla, joiden määrä elektrodissa oli 3 painoprosenttia.
ED:2010-10-12
INSSI record number: 41052
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