Letno poročilo 2005

1 objavljeni znanstveni prispevek na
konferenci (vabljeno predavanje)
5 objavljenih znanstvenih prispevkov na
konferencah
15 objavljenih povzetkov znanstvenih
prispevkov na konferencah
1 patentna prijava
3 kon~na poro~ila o rezultatih raziskav
3 elaborati, pred{tudije, {tudije
2 diplomi
GLAVNI DOSE@KI V LETU 2005
- Sinteza in karakterizacija novega materiala z
bistveno ve~jo teoreti~no kapaciteto od doslej
znanih materialov za pozitivne baterijske
elektrode
V doslej znanih materialih za pozitivne elektrode
v litijevih baterijah smo lahko za shranjevanje
energije izkoristili najve~ 1 litij na
molekulsko enoto materiala – ~eprav je ta
enota na~eloma lahko vsebovala ve~ kot 1
litij. S tem je bila specifi~na kapaciteta pozitivnih
elektrod omejena na vrednosti med 150
in 170 mAh/g. V laboratoriju pa nam je uspelo
sintetizirati povsem nov anorganski
material, Li 2 MnSiO 4 , v katerem lahko za
shranjevanje naboja teoreti~no izrabimo oba
litija, kar pomeni, da zna{a teoreti~na kapaciteta
okoli 320 mAh/g. @al v praksi zaenkrat
te kapacitete nismo uspeli izkoristiti – pri
praznjenju/polnjenju dobimo podobne vrednosti
kapacitete kot v prej omenjenih klasi~nih
materialih. Vzrok so takoreko~ izolatorske
elektri~ne lastnosti silikatov (elektronska
prevodnost za Li 2 MnSiO 4 denimo zna{a okoli
10 -12 S/cm), kar upo~asni kinetiko do te mere,
da v realnem ~asu lahko izkoristimo le del
razpolo`ljivega naboja. Glede na pretekle
izku{nje s podobnimi izolatorskimi materiali
pa obstaja realna mo`nost, da bomo z ustreznimi
modifikacijami (zmanj{evanjem
povpre~ne velikosti delcev, dodajanjem
prevodnih faz, morda celo z dopiranjem)
precej izbolj{ali povpre~no prevodnost elektrodnega
kompozita ter posledi~no izkoristili
znatno ve~ kot 1 litij na molekulsko enoto
Laboratorij za elektrokemijo materialov
Laboratory for Materials Electrochemistry
1 Published Scientific Conference Contribution
(Invited Lecture)
5 Published Scientific Conference Contributions
15 Published Scientific Conference Contribution
Abstracts
1 Patent Application
3 Final Research Reports
3 Treatises, Preliminary Studies, Studies
2 Undergraduate Theses
IMPORTANT ACHIEVEMENTS IN 2005
- Synthesis and characterization of a new material
with a considerably higher theoretical
capacity than in present materials for Li battery
positive electrodes
In all existing materials for positive Li electrodes
it is only possible to reversibly exchange
up to 1 lithium per formula unit – even if the
formula contains more than 1 lithium. This
has limited the specific capacity of positive
electrodes to values between 150 and 170
mAh/g. Recently we have synthesized a completely
new inorganic compound, Li 2 MnSiO 4 ,
in which both lithium ions can in principle
be exchanged so that the theoretical reversible
capacity amounts as high as 320 mAh/
g. Unfortunately, in practice we have not
been able to exploit this huge capacity. In
fact, upon material cycling we have obtained
similar values of capacity as reported for other
materials. The reason is the huge electrode
polarization resulting from the insulating
nature of silicates (for example, the electronic
conductivity of Li 2 MnSiO 4 is in the range of
10 -12 S/cm) which limits the exploitation of
available charge. However, based on our experience
with other insulating active particles,
we hope that in future we will be able
to improve the average conductivity of electrode
composites, either by particle size minimization,
addition of conductive phases or
even by heterogeneous doping. It can be
claimed that eventual practical exploitation
of more than 1 Li per formula unit will open
a new chapter in search for high-energy density
storage materials.
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