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Procedings
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e n e r g y + p r o c e e d i n g s 55 it is already clear that li-ion
batteries
of the type currently used worldwide in mobile-phones and lap- tops now stand poised also to become the battery of choice in future electric and
hybrid
electric vehicle (ev and hev) concepts, e.g., figure 4, and other even larger-scale battery applications. such an advance will significantly reduce the direct use of fossil fuels. current li-ion
batteries
generally have li(co,ni)o 2 as their active cathode
material
. up-scaled li-ion batter- ies must exploit a much cheaper transition metal than cobalt (co); ideally, the very cheapest – iron (fe) – in combination with a graphite(c)-based anode. this is a consequence of the massively greater quantities of
material
needed in the fabrication of larger li-ion
batteries
. while a mobile-phone battery consumes only a few grams of the relatively expensive active transition metal oxide (tmo) licoo 2 , an ev/hev battery unit will consume kilogram quantities of ac- tive cathode
material
per unit; see figure 5. page 77 of 122 greater quantities of
material
needed in the fabrication of larger li-ion
batteries
. while a mobile-phone battery consumes only a few grams of the relatively expensive active transition metal oxide (tmo) licoo 2 , an ev/hev battery unit will consume kilogram quantities of active cathode
material
per unit; see figure 5. a temporary solution . . . figure 4. the toyota
hybrid
system (ths). figure.4..the.toyota.
hybrid
.system.(ths). page 78 of 122 figure 5. common cathode
material
s of today’s li-ion
batteries
. in this context; we can expect a long-term development within the transport sector corresponding to: internal fuel-cell/ combustion ► electric
hybrid
► plug-in electric ► plug-in electric ► plug-in engine
hybrid
hybrid
electric we can get our first clue about which direction to look from the new perspectives opened up by the discovery of electrochemical activity in lithium iron phosphate (lifepo 4 ) [1, 2]. this
material
satisfies many of the demands placed on a potential cathode
material
for large-scale li-ion
batteries
. its strong covalent p-o bonds ensure intrinsic stability in a voltage domain where only minimal chemical instabilities arise. the
material
is also “green” and relatively cheap, thus fulfilling the basic requirements for successful commercialization in larger
batteries
. its main drawback, however, is its low electronic conductivity (10 -9 scm -1 at room temperature), but the effect of this can be minimized by reducing the conduction pathlength, e.g., by preparing nano-size or nano-porous particles, and by decorating them with a thin electronically conducting layer (generally carbon) [3]. however, one serious problem still remains: its theoretical specific capacity is only ca. 170 mah/g, and its lower specific gravity results in a 15-20% reduction in the practical energy density poor el. conductivity ! solutions: - doping - coating - ”nano”-sizing a) layered: licoo 2 -> li 0.5 coo 2 : ~3.9v, ~140 mah/g b) spinels: limn 2 o 4 -> mn 2 o 4 : ~3v or ~4.0v, 148 mah/g c) olivines: lifepo 4 -> fepo 4 , ~3.5v, ~170 ah/ d) orthosilicates li 2 fesio 4 -> lifesio 4 , ~2.85v, ~ 170 mah/g instabilitility ! solution: doping cathode
material
s: a comparison figure.5..common.cathode.
material
s.of.today’s.li-ion.
batteries
. in this context; we can expect a long-term develop- ment within the transport sector corresponding to: internal fuel-cell/ combustion electric plug-in plug-in plug-in engine
hybrid
hybrid
electric electric
hybrid
we can get our first clue about which direction to look from the new perspectives opened up by the discovery of electrochemical activity in lithium iron phosphate (lifepo 4 ) [1, 2]. this
material
satisfies many of the demands placed on a potential cathode
material
for large-scale li-ion
batteries
. its strong covalent p-o bonds ensure intrinsic stability in a volt- age domain where only minimal chemical instabilities arise. the
material
is also “green” and relatively cheap, thus fulfilling the basic requirements for successful commercialization in larger
batteries
. its main draw- back, however, is its low electronic conductivity (10 -9 scm -1 at room temperature), but the effect of this can be minimized by reducing the conduction pathlength, e.g., by preparing nano-size or nano-porous particles, and by decorating them with a thin electronically conducting layer (generally carbon) [3]. however, one serious problem still remains: its theoretical specific capacity is only ca. 170 mah/g, and its lower specific
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