Supercaps Fields of Application and Limits Dietmar Rahner TU Dresden Institut für Physikalische Chemie und Elektrochemie D-01062 Dresden Steffen Rahner Battery-Lab Rahner GmbH Dresden D-01217 Dresden www.battery-lab.de 1
1. Why Supercaps? 2. Comparison of a battery and a capacitor 3. Mode of action of electrochemical systems 4. Examples 5. Trends 2
Battery Change of the oxidation state of two Redox Systems Faraday-currents + mass transport long times short diffusion paths desired Host 1 D Li < 10-10 cm 2 s -1 Host 2 charge Li + Li + discharge LiCoO 2 (+) Graphite (-) 3
Li + (hostlattice 2) Li+ (hostlattice1) M.Winter, J.-O. Besenhard, Chemie in unserer Zeit 33 (1999) 4
Capacitor Change of the charge condition of surfaces capacitive currents short times, low energy large surfaces necessary C DL ~ 10-20 µf/cm 2 For 1000F we need ~10 4 m 2 www.udomi.de 5
Comparison: Capacitor - Battery Battery 12 V/44 Ah Ultracap 3600 F/2,5 V Energy density 40 Wh/kg 4,5 Wh/kg Power density 300 W/kg 5000 W/kg over 1s charge discharge slow fast www.udomi.de 6
Einsatzbereiche der Speichertechnologien 7 100 MW Hydro and large compressed air 10 MW Energy batteries 1 MW Power batteries 100 kw 10 kw 1-second storage Batteries for portable applications Redox-flow and reversible fuel cells 1 kw 100 W 1-minute storage 1-hour storage 1-day storage 1-week storage 1-month storage Supercapacitors SMES Flywheels 10 100 1000 10 100 1000 10 100 1000 Wh kwh MWh Compressed air Institut für Solare Energieversorgungstechnik Verein an der Universität Gesamthochschule Kassel Quelle: EU 2001
Electrochemical storage systems (selection) Battery /Accumulator Primary Secondary Hydrogen fuel cell Metal/air Zn/MnO2 Ni/MH H2/O2 Zn/O2 Li/FeS2 Ni/Cd Li/MnO2 Pb/PbO2 Li ion www.udomi.de 8
Battery size and application fields Battery type Button cells Mobile communication Home use Automotive Traction Stationary Load levelling Energy [Wh] 0.1 -- 5 2-100 2-100 10 2-10 3 10 4-10 6 10 4-10 6 10 7-10 8 Examples Clocks, computers, heat cost devices Mobile phones, laptops Mobile devices, camcorders Starter batteries, traction Electric vehicles Stand-by batteries, UPS Peak load compensation, reserves 9
Example :Ultracap www.epcos.de 10
Example: Activated carbon 1,5 V www.epcos.de 11
Materials for Supercaps Electrodes Activated carbon and pyrolysis products Ceramics and redox systems may be added Electrolyte Organic solvents adapted from the Li-Battery technology Quaternary salts with high solubility and stability Current collector mostly Aluminum 12
Construction in thin layer technics with high active surface I II III IV V d1 d2 d3 d4 d5 50-150 µm 13
Why these Materials for Supercaps? Activated carbon very high surface, cheap, common technology Organic Electrolyte The energy W is a function of the voltage of the capacitor with the capacitance C: W = C 2 U Aqueous system: U ~ 1.2 V Organic system: U ~ 2.3.2,5V 1 2 14
Experimental: UltraCap 100F/2.3 V UltraCap 100F/2.3V 135 2,5 300 capacitance C [F] 130 125 120 115 110 105 charge discharge U [ V ] 2,0 1,5 1,0 0,5 250 200 150 100 50 C D [ F ] 100 0 100 200 300 400 500 cycle # Epcos-100F.opj 0,0 0 0 20 40 60 80 100 120 140 160 180 t [min] EPCOS-2700F.opj Differential capacitance C D : C D = I 1 du dt 15
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Experimental: UltraCap 2700F/2.3 V UltraCap 2700F/2.3 V 6000 3060 2.25 3040 charge discharge 2.00 5000 capacitance C [F] 3020 3000 2980 U [ V ] 1.75 1.50 1.25 1.00 4000 3000 2000 C D [F] 2960 0 20 40 60 80 100 120 140 160 cycle # Epcos-2700F.opj 0.75 1000 0.50 0 0 1 2 3 4 5 t [h] EPCOS-2700F.opj Differential capacitance C D : C D = I 1 du dt 18
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Specific Energy and Power Density of Rechargeable Battery Systems 500 400 Li-Metall Polymer Specific Energy [Wh kg -1 ] Ragone-Batterien.opj 300 200 100 Li-Ion, Li-Ion Polymer Ni - Metallhydrid Ni-Zn RAM Pb Ni - Cd 0 0 100 200 300 400 500 SuperCaps Power density [Wh L -1 ] 20
Applications for Supercaps Automotive Traction Industrial Renewable Energy 21
Trends Nano-Nano Systems Smaller particles, larger surfaces Improvement and optimization of known systems Technology Flexible construction 22