Post on 04-Apr-2018
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Lithium Iron Phosphate (LiFePO4)
Battery as Energy Storage Material
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Current World Energy Status
Oil and Gas Production Coal Mining
Etc
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Current World Oil Reserve
Source : http://en.wikipedia.org/wiki/Oil_reserves
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Side effect of fossil fuel Air pollution
Acid rain Global warming
Etc
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Alternative Energy Provide
Solution Solar Energy Wind Energy
Nuclear Energy
Tidal Energy
Etc
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Battery Material Parameter
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Lithium Ion Battery
Why Lithium as battery material?
1. Low density (0.534 g/cm3)
2. Large specific capacity
(3860 Ah/kg)
3. lowest electrochemical
potential (-3.01 V vs NHE)4. lower self discharge
5. No memory effect
6. Prolonged service-life
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Why LiFePO4?
Compare to LiCoO2 battery, LiFePO4 :
Advantages :
1. Superior in thermal and
chemical stability
2. Less expensive3. Environmentally benign
4. Non-toxic
5. Longer cycle-life
Disadvantages
1. Lower energy density relative
to LiCoO2 (170 mAh/g vs 274
mAh/g)
2. Low conductivity (~10-9 S/cm)
LiFePO4 Battery
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LiFePO4 Battery
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Charging /Discharging of LiFePO4 Battery
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Attempts to Higher the Conductivity ofLiFePO
4Battery by modifiying Cathode
LiFePO4 has a limitation that is low conductivity, which leads to
high impedance and low rate capability for batteries using this
material. Approaches to solve that problem include but not limited
to:
1. Doping LiFePO4 with supervalent cations that enhance thematerial conductivity at the crystal level
2. Surface modification of LiFePO4 with Silver
3. Decreasing the particle size of LiFePO4 in order to make the
diffusion path of lithium shorter
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The resulting doped LiFePO4 materials
have lithium storage capacities that are
near the theoretical limit of 170 mAh/g at
low charge/discharge rates, and retain
significant discharge capacity at rates as
high as 6,000 mA/g of material.
But, doped olivine also show high defect
concentrations on the M1 site.
In one case, the unit cell volume contracts
(Fe3+ doped LiMgPO4), and in the othercase (Fe3+ doped LiNiPO4) it expands.
Doping LiFePO4 with Supervalent Cations(i.e Mg2+, Al3+, Ti4+, Zr4+, Nb 5+ and W6+)
Source : Chung, S. Y., Bloking, J. T. and Chiang, Y. M., (2002):
Electr onically conductive phospho-olivines as lithium storage electrodes,
Nature Materials, No.1, pp.123-128.
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The capacity of the silver coated LiFePO4 is larger than that of the pure
LiFePO4 and the ratio of increase in the capacity by coating is about 10% inall current densities, and the electronic conductivity is increase by factor of
108. The increased capacities by the coating are maintained even after
many charge/discharge reactions
Surface modification of LiFePO4 with Silver
Source : KS Park, JT Son, HT Chung, SJ Kim, CH Lee, KT Kang, HG Kim :
Surface modification by silver coating for improving electrochemical properties of LiFePO4,
Solid State Communications 129 (2004) 311314
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Decreasing the particle size of LiFePO4 in order tomake the diffusion path of lithium shorter
Source : KS Park, JT Son, HT Chung, SJ Kim, CH Lee, KT Kang, HG Kim :
Surface modification by silver coating for improving electrochemical properties of LiFePO4,
Solid State Communications 129 (2004) 311314
By decreasing the particle size of
LiFePO4 by soft chemistry method
and the addition of Ketjen carbon
black, specific capacity of 145 mAh/g
is achived. No significant capacity
fade was observed, even after morethan 400 charge/discharge cycles. At
low charge/discharge rates, an
increase of thecarbon amount from 5
to 16.7% leads to a constant increase
of the specific capacity of ~15 mAh/g,
whatever the C-rate used
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Attempts to Higher the Conductivity ofLiFePO
4Battery by modifiying Anode
in addition to modifying the cathode, someattempts are also done to improve the
electronic conductivity of LiFePO4 by
modifying the anode materials.
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TiO2 Nanowires as an Improved AnodeMaterial
By changing the anode from
LixC6 to TiO2 nanowire, the
capacity of LiFePO4 battery
increase to 225 mAh/g.
But the overall cell potential
range is reduce to 1.5 V
Source : Graham Armstrong, A. Robert Armstrong, Peter G. Bruce,Priscilla Reale, and Bruno Scrosati :
TiO2 Nanowires as an Improved Anode Material for Lithium-Ion Batteries Containing LiFePO4 or
LiNi0.5Mn1.5O4 Cathodes and a Polymer Electrolyte
Advanced Materials, Vol.18 Issue 19
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Temperature Effect on LiFePO4 Battery
It is being reported that the capacity of a
LiFePO4/graphite cell with LiPF6
electrolyte fades rapidly at high
temperature 55C due to Fe dissolution
from cathode and subsequent
deposition of the Fe ions on the graphite
anode to form an unfavorable superficial
layer. Increasing the temperature
to 37 and 55 C, the cells show
significant capacity loss after 100 cycles
especially at 55 C. Similar capacity fade
was also reported when storing the cells
at 3.8 V for four weeks at 55 C.
Source : K. Amine, J. Liu, I. Belharouak :
High-temperature storage and cycling of C-LiFePO4/graphite Li-ion cells
Electrochemistry Communications 7 (2005) 669673
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Enhanced High Temperature ofLiFePO4 Battery
Addition of vinylene carbonate (VC) in
electrolyte solution has been found to
greatly improve the high-temperature
55C cycling performance of LiFePO4
based Li-ion batteries. It has been
established that the VC additive
remarkably suppresses Fe dissolution
from LiFePO4 cathode and hence,
subsequent Fe deposition on the anode
side.
Source : Hung-Chun Wu, Ching-Yi Su, Deng-Tswen Shieh, Mo-Hua Yang and Nae-Lih Wu :
Enhanced High-Temperature Cycle Life of LiFePO4-Based Li-Ion Batteries by Vinylene Carbonate as
Electrolyte Additive
Electrochemical and Solid-State Letters,9 (12 ) A537-A541
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Summary
1. LiFePO4 offer a safer battery technology especially for electric vehicle
application due to its thermal and chemical stability
2. LiFePO4 offer a more environment benign battery technology
3. A further attempt to increase the electronic conductivity of LiFePO4is needed
4. The development of anode material, cathode material, electrolyte
material and binder material is needed to improve the performance of
LiFePO4 battery for future application