investigation on additives to improve positive active material utilization in lead-acid batteries
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Investigation on additives to improve positive active material utilization in lead-acid batteries. Rubha Ponraj Research seminar October 23, 2007. Department of Chemistry. Outline. Introduction to Electric vehicle (EV) Our choice of battery in EV Goal of our project - PowerPoint PPT PresentationTRANSCRIPT
Investigation on additives to improve positive active material utilization in
lead-acid batteries
Rubha Ponraj Research seminar October 23, 2007
Department of ChemistryDepartment of Chemistry
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Outline
• Introduction to Electric vehicle (EV)• Our choice of battery in EV• Goal of our project• Working principle• Advantages and limitation• How to overcome the limitation?• Our effort• Results • Conclusion
Department of ChemistryDepartment of Chemistry
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Alternative fuel for vehicles
• Gas emissions and its ecology impact
• Electric vehicle
• California Air Resources Board (CARB) –Zero emission vehicle – 1995
Department of ChemistryDepartment of Chemistry
http://en.wikipedia.org/wiki/Electric_vehiclehttp://en.wikipedia.org/wiki/Electric_vehicle
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Battery powered electric vehicles
Batteries – Lead acid batteries, Nickel metal Hydride (Ni-MH) and Lithium-ion
• Problem of recharging (7-10 hours)• Limited range – type and weight• Batteries are bulky• Safety issues • High initial cost
http://www.naftc.wvu.edu/NAFTC/data/indepth/Electric/HybridElectric.HTML
Department of ChemistryDepartment of Chemistry
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Comparison between different batteries in electric vehicle
Lead–acid
Ni–MH
Li-ion
Safety + 0 Specific energy + ++
Specific power + ++ +
Specific cost + 0
Recycling ++ 0 0
Comparison between different batteries (++: very good, + : good, 0: satisfactory, : poor, : very poor)
Jürgen Garche, J. Phys. Chem. Chem. Phys., 3, (2001) 356-367
Specific energy - Wh/kg
Specific power - W/kg
Specific cost - $/Wh
Department of ChemistryDepartment of Chemistry
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Feasibility of lead acid batteries
Can lead acid battery compete in modern times?
Yes
• Dominant position due to low cost - automobile applications
• Cost efficient technologies – to improve the performance
Department of ChemistryDepartment of Chemistry
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Goal of our project
Advanced lead-acid battery for military electric vehicle
- high fuel economy
- provides power at remote location
- stealth operation
Department of ChemistryDepartment of Chemistry
Lead-acid batteries
Department of ChemistryDepartment of Chemistry
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History of lead-acid batteries
Inventor of first rechargeable battery - 1859
Gaston Plante (1834-1889)
http://www.geocities.com/bioelectrochemistry/plante.htm
Plante’s Lead–acid battery (1859)
Department of ChemistryDepartment of Chemistry
http://www.leadacidbatteryinfo.org/resources.htmhttp://www.leadacidbatteryinfo.org/resources.htm
1010
Reaction mechanism• Reaction at positive electrode:
• Reaction at negative electrode:
• Total cell reaction:
E0 – in 1.3 specific gravity H2SO4
H. Bode, Lead-Acid Batteries, translated by R.J. Brodd and K.V. Kordesch, Wiley
Interscience, New York, 1997, page 4.
Department of ChemistryDepartment of Chemistry
Pb(IV)O2 + HSO4- + 3H+ + 2e- discharge
charge Pb(II)SO4 + 2H2O Eo = 1.805 V
Pb(0) + HSO4- discharge
charge Pb(II)SO4 + H+ + 2e- Eo = -0.340 V
PbO2 + Pb + 2HSO4- + 4H+ discharge
charge 2PbSO4 + 2H2O Eocell = 2.145 V
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Working principle LAB
During discharge process:
Link
http://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/animations/PbbatteryV8web.html
Department of ChemistryDepartment of Chemistry
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Lead-acid battery construction
Department of ChemistryDepartment of Chemistry
Positive plate pack
Positive plate pack
Microporous separator
Positive plate
Grid plate
Negative plate
Negative pole
Positive cell connector
valve
terminal
casing
Negative cell connection
http://www.doitpoms.ac.uk/tlplib/batteries/batteries_lead_acid.php
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Advantages• Low cost. • Reliable.• Indefinite shelf life – compared to modern
batteries• Deliver high currents• Low self-discharge• Low maintenance requirements • Many suppliers world wide. • The world's most recycled product.
http://en.wikipedia.org/wiki/Lead-acid_battery http://www.lead-battery-recycling.com/lead battery-recycling.html
Department of ChemistryDepartment of Chemistry
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Limitation
• Low specific energy (energy to weight ratio)
Department of ChemistryDepartment of Chemistry
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Reasons for the reduction of the theoretical specific energy
Department of ChemistryDepartment of Chemistry
Specific energy of Plante’s battery- 9 Wh/kgSpecific energy of Plante’s battery- 9 Wh/kg
Jürgen Garche, J. Phys. Chem. Chem. Phys., 3, (2001) 356-367
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What is active material utilization?
• Positive electrode: lead dioxide
• Negative electrode: lead
- Ratio of ampere hours discharged to its stoichiometric capacity
Department of ChemistryDepartment of Chemistry
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Electrical conductivity
• Positive electrode:
PbO2 - 50 Ω-1cm-1
• Negative electrode: Pb - 5.3x104 Ω-1cm-1
• PbSO4 - Insulator
Department of ChemistryDepartment of Chemistry
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Positive electrode - reaction limiting
Positive plate reaction
Discharge capacity (Ah) depends on this reaction
To sustain this reaction:
• Supply of acid • Supply of electrons
P.T. Moseley, J. of Power Sources 64 (1997) 47-50
Department of ChemistryDepartment of Chemistry
Pb(IV)O2 + HSO4- + 3H+ + 2e- discharge
charge Pb(II)SO4 + 2H2O Eo = 1.805 V
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Methods to improve positive active material utilization
• Increasing energy – weight ratio• Increasing mass transport of H+ and HSO4 ֿ inside
active material• Increasing electrical conductivity of active material
H.Dietz, J.Garche, K.Weisner, J. Power Sources, 14 (1985) 305.D.B.Edwards, Song Zhang, J. Power Sources, 135 (2004) 297Tokunaga, M. Tsubota, K. Yonezu, K. Ando, J. Electrochem. Soc., 13 (1987) 525-529
Department of ChemistryDepartment of Chemistry
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Effect of discharge rates on active material utilization
• During discharge – permanent layer of PbSO4
• Fast discharge rate (50 mA/cm2)
- Positive active material utilization – 30%
- Not enough time (mass-transport limited)
- Porous non-conductive additives
• Slow discharge rate (10 mA/cm2)
- Positive active material utilization – 60%
(Electronic conduction limited)
- higher electrical conductive materials
Department of ChemistryDepartment of Chemistry
HSO4¯
HSO4¯
e ֿ
Grid
At positive electrode
PbO2
PbSO4
Electrically Electrically isolated PbOisolated PbO22
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Active material with mass transport enhancing additive
e ֿ
Illustration on the effect of porous additive
HSO4 ֿ
HSO4¯
HSO4¯
e ֿ
Grid
Active material without additive
PbO2
PbSO4
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Effect of electrically conductive additives
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Current collectorCurrent collector
(grid)(grid)
Active Active materialmaterial
Electrically conductive Electrically conductive materialmaterial
Electronic conducting matrix in active massElectronic conducting matrix in active mass
Jürgen Garche, J. Phys. Chem. Chem. Phys., 3, (2001) 356-367
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Survey on positive plate additives
Carboxymethyl cellulose (0.2 wt.%)• 9.9% increase in utilization (at 1 h discharge rate)• Initial capacity was high• Not stable – carbon oxidized
Carbon black (0.1 wt.%)• 3.3% increase in utilization (at 1 h discharge rate)• Not stable – carbon oxidized
H.Dietz, J.Garche, K.Weisner, J. Power Sources, 14 (1985) 305.
Department of ChemistryDepartment of Chemistry
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Survey on positive plate additivesGlass microspheres• Filler material • Utilization -11.4 % to 33.12% ( at 0.1 A/g discharge rate)• Optimum loading – 4.4 wt.%
Silica gel • Particle size - 30 to 150 nm • 0.2 wt.% addition• Increases utilization by 10% (high discharge rate)
D.B. Edwards, V.S.Srikanth, J. Power Sources, 34 (1991) 217Wang Qing, J. of Wuhan University of Technology--Materials Science Edition, 22 (2007) 174H.Dietz, J.Garche, K.Weisner, J. Power Sources, 14 (1985) 305
SEM image for glass microspheres (x 500)
Department of ChemistryDepartment of Chemistry
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Selection of additives
• Stable • Good adhesion to active material• Improve positive active material utilization• Cost effective• Light weight
Simon D. McAllister, Rubha Ponraj, I. Francis Cheng and Dean B. Edwards, J. of Power Sources Simon D. McAllister, Rubha Ponraj, I. Francis Cheng and Dean B. Edwards, J. of Power Sources 173173, 2 , 2 (2007)(2007)
Department of ChemistryDepartment of Chemistry
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Our choice of additive Diatomaceous earth particles
(SiO2)- Fossilized remains of diatoms, a type of hard-shelled algae
- Uses: filtration aid, insecticide, cat litter- It is stable, light weight, porous and cost
effective
5µm
http://en.wikipedia.org/wiki/Diatomaceous_earth
Department of ChemistryDepartment of Chemistry
EXPERIMENTAL
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Sorting of diatomaceous earth
- Diatomaceous earth particles -sorted using Nylon screen cloth
20-30 µm
30-53 µm
53-74 µm
74-90 µm
SEM of diatomites of different sizes: (A) 20–30 µm, (B) 53–74 µm, (C) >90 µm
BA
C
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Paste preparation
Curing
Zero valent Pb test
Formation
Conditioning
Satisfactory
Porosity test
Unsatisfactory
Unsatisfactory
Process of positive plate preparation
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Paste Composition• PbO-(11% Pb0), 0.5% Dynel fibers, additive - total 10 g
Mixed with H2SO4 and H2O - paste
• Density -
2.5 – 3.5 g/cm3
• Pasted into teflon rings
(volume 0.24 ml)
Department of ChemistryDepartment of Chemistry
Pb strip Paste inside teflon ring
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Curing
• 24 hrs hydroset – 250 °F pressure cooker
• Pb0→ PbO
• Some formation of PbSO4
• Dried overnight
• Each plate - 0.6 to 0.8 g
Department of ChemistryDepartment of Chemistry
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Testing
• Porosity by water absorption - >45%• Pb0 atomic absorption spectroscopy - <5wt.%
• SO42- by ion-conduction chromatography
If it passed the screen test….
Department of ChemistryDepartment of Chemistry
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Formation PbO + H2SO4 PbSO4 + H2O
PbSO4 PbO2 + 2e-
• 1.1 sp. gr. H2SO4
• commercial negative plate with polyethylene separator• Theoretical capacity - 0.2241 Ah/g• Charge positive plates to 125%
Calculation of theoretical capacity: 2F = 53.6 Ah
Berndt, D. Maintenance-Free Batteries. 2nd ed. 1997, p. 106
.
negative plate in between separators
Formation cell (side view)
polyethylene separator b/w negative andpositive plates
Glass mat with 90% porosity
Formation cell (cross-sectional view)
Positive plate
Department of ChemistryDepartment of Chemistry
oxidationoxidation
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Conditioning and cyclingChanged the electrolyte - 1.3 sp. gr. H2SO4
- Discharged at 10 mA/g
- Charged to 125% discharge
capacity
- 4 to 5 cyclesCounter Electrode 20-30 cm of Pt wire
Working Electrode – Positive plate Reference Electrode –
Ag/AgCl
Department of ChemistryDepartment of Chemistry
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Performance measurement• Capacity measurements are taken at a 50 mA cm-2
discharge and a 10 mA cm-2 discharge. • Diatomites - 20-30 µm, 30-53 µm, 53-74 µm and 74-90 µm, at 1 wt.%, 3 wt.% and 5 wt.% were tested.
• Our control – without additive
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RESULTS
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Discharge curve
Department of ChemistryDepartment of Chemistry
1.20E+00
1.30E+00
1.40E+00
1.50E+00
1.60E+00
1.70E+00
1.80E+00
0 1000 2000 3000 4000
Time (s)
Vo
ltag
e (V
)
PbOPbO2 2 + HSO+ HSO44- - + 3H+ 3H+ + + 2e+ 2e- - PbSOPbSO4 4 + H+ H22OO
dischargedischarge
• Fast discharge rate (50 mA/cm2)
• Discharge capacity (mAh)
• Utilization = Calculated capacity
• Theoretical capacity = 0.2241 Ah/g
Theoretical capacityTheoretical capacity
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Utilization at fast discharge rate
-4
-2
0
2
4
6
8
10
12
14
20-30 30-53 53-74 74-90Size (µm)
% c
han
ge in
uti
lizat
ion
3% loadings
5% loadings
Department of ChemistryDepartment of Chemistry
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Utilization at slow discharge rate
Department of ChemistryDepartment of Chemistry
-10
-5
0
5
10
15
20-30 30-53 53-74 74-90
Size (µm)
% c
hang
e in
uti
liza
tion
3% loadings
5% loadings
40
Specific capacity
-12
-10
-8
-6
-4
-2
0
2
4
6
8
20-30 30-53 53-74 74-90
Size (µm)
% c
hang
e in
spe
cifi
c ca
paci
ty
3% loadings
5% loadings
-10
-8
-6
-4
-2
0
2
4
6
8
10
12
20-30 30-53 53-74 74-90
Size (µm)
% c
hang
e in
spe
cifi
c ca
paci
ty
3% loadings
5% loadings
At fast discharge rate (50 mA/cm2) At slow discharge rate (10 mA/cm2)
Department of ChemistryDepartment of Chemistry
Specific capacity – mAh/g
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Diatomites’ structure A
B C
Scanning electron micrograph of diatomites: A) recovered from active material after the performance tests, B) 20-30 µm C) 53–74 µm.
• Diatomites are stable in the battery environment• Single diatomite elements did not perform as good as conglomerates
Department of ChemistryDepartment of Chemistry
Simon D. McAllister, Rubha Ponraj, I. Francis Cheng and Dean B. Edwards, J. of Power Sources Simon D. McAllister, Rubha Ponraj, I. Francis Cheng and Dean B. Edwards, J. of Power Sources 173173, 2 , 2 (2007)(2007)
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Conclusions
• Statistically significant increase in performance
• Specific energy – 12.69% increase relative to control
Department of ChemistryDepartment of Chemistry
Fast discharge rate
(50 mA/cm2)
Slow discharge rate (10 mA/cm2)
Control
(without diatomites)
33.65 ± 2.52%
58.00 ± 2.01 %
With diatomites particle size- (53-74 µm)
38 .04 ± 2.09%
58.96 ± 2.42%
Comparison of % utilization of best performed size of diatomites with control
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Summary
• Diatomites are an inexpensive filler material
• Utilization increases by 12.7% at a fast discharge rate.
• Specific capacity increases by 9.3% at a fast discharge rate
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The way forward
Department of ChemistryDepartment of Chemistry
• Test in Full sized plates
• Use electrically conductive additives
1cm1cm22 3.65 x 3.365 x 0.050 in3.65 x 3.365 x 0.050 in33
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Acknowledgements
• Dr. I. Francis Cheng• Dr. Dean B. Edwards• Simon D. McAllister• Kenichi Shimizu• Derek F. Laine• Dr. Song Zhang• Dr. and Mrs. Renfrew• Office of Naval Research Award Number: N00014-
04-1-0612
Department of ChemistryDepartment of Chemistry