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Energy Storage: EDLC & Pseudo – Capacitors

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Energy Storage: EDLC & Pseudo – Capacitors Energy storage: EDLC & Pseudo – Capacitors Doron Aurbach Department of chemistry, Bar Ilan University Ramat-Gan 52900 Israel Email: [email protected] Energy is found everywhere we just need to harvest and store it We lack good storage technologies Supercapacitors can be used for load leveling applications We want to move ASAP to sustainable energy overview Material design Aqueous SC High voltage SC PsC Summery SuprecapacitorsBatteries are evaluated (EDLC) in fill terms the Energy of energy Vs. Power gap betweenand power batteries densities and capacitors 105 capacitor 1 s 1 min ECs (2008) ) ) 1 1 - - 104 Wkg Wkg Comm. Li-ion 5V. Li-ion 1h 103 Ni/MH Ni/Cd Primary Li 102 Specific Power ( Specific Power Specific Power ( Specific Power 10 Lead acid 1 10-2 10-1 1 10 102 103 Specific energy (Whkg-1) A typical Ragone plot, of common Faradaic electrochemical energy storage cells (time constants in red) overview Material design Aqueous SC High voltage SC PsC Summery What is Capacitor? • A capacitor (originally known as condenser) is a passive two- terminal electrical component used to store energy in an electric field. • When there is a potential difference across the conductors, a static electric field develops across the dielectric, causing positive charge to collect on one plate and negative charge to accumulate on the other plate. Energy is formed in terms of electrostatic field. overview Material design Aqueous SC High voltage SC PsC Summery What is Supercapacitor? Supercapacitor (SC) also known as electric double-layer capacitor (EDLC) or Ultracapacitor, is electrochemical capacitor. The capacitance value of an electrochemical capacitor is determined by two storage principles, which both contribute indivisibly to the total capacitance: • Double layer capacitor – Electrostatic storage achieved by separation of charge in a Helmholtz double layer at the interface between the surface of a conductive electrode and an electrolyte. The separation of charge is of the order of a few angstrom (0.3–0.8 nm), much smaller than in a conventional capacitor than in a conventional capacitor. • Pseudocapacitor - Faradaic electrochemical storage with electron charge transfer, achieved by redox interaction, intercalation or electrosorption. overview Material design Aqueous SC High voltage SC PsC Summery Up to 109 V/m potential fall exist on charged interfaces Electrical Double Layer (EDL) - - - - + + - - + + - - - + - - + - OHP Water molecule + Counter ion Outer Helmholtz plane - Co-ions overview Material design Aqueous SC High voltage SC PsC Summery The difference between More power is required for short time Constant but less power required for interval in 200m race long time in 20km race overview Material design Aqueous SC High voltage SC PsC Summery Charged species can be stored electrostaticly by the EDL C A 0 r d A = Surface area (very high in Activated carbon). d = Dielectric thickness, single solvent molecule. = limited by the solvent properties. εr Possible electrolytes: 1. Aqueous electrolyte, high rates small ions high ionic conductivity, limited voltage. 2. Organic electrolyte, moderate conductivity and capacity up to 3V. 3. Ionic liquids- Low conductivity, lower capacity, high voltage, safe. www.youtube.com/watch?v=FJZKm5khaAA overview Material design Aqueous SC High voltage SC PsC Summery From dead leaves till energy storage devices M. Biswal, A. Banerjee, M. Deo, S. Ogale, Energy & Environmental Science 2013, 6, 1249-1259. overview Material design Aqueous SC High voltage SC PsC Summery High capacitance graphene SC P. A. Basnayaka, M. K. Ram, E. K. Stefanakos, A. Kumar, Electrochimica Acta 2013, 92, 376-382 overview Material design Aqueous SC High voltage SC PsC Summery Increasing the electrochemical window using neutral electrolyte solutions Q. Gao, L. Demarconnay, E. Raymundo-Pinero, F. Beguin, Energy & Environmental Science 2012, 5, 9611-9617. overview Material design Aqueous SC High voltage SC PsC Summery Electrodeposition of Mn-Mo oxide film on CNT/ITO M. Nakayama, K. Okamura, L. Athouël, O. Crosnier, T. Brousse, ECS Transactions 2012, 41, 53-64. overview Material design Aqueous SC High voltage SC PsC Summery Activated carbons possess unique physicochemical properties: Carbon Carbon Carbon Activated precursor precursor material carbon M M M M Oxidizing M M M M Polymerization Carbonization M M M M under inert agent M M M M atmosphere Activated carbon (AC) General features: • Highly disordered • High surface area (up to ~3000m2/g) • Electrically conductive overview Material design Aqueous SC High voltage SC PsC Summery 300 400 350 250 300 200 250 150 200 cc/g cc/g 150 100 volumeadsorbed (ml/gr) volumeadsorbed (ml/gr) 100 50 50 0 Activation 0 0 0.2 0.4 0.6 0.8 1 1.2 0 0.2 0.4 0.6 0.8 1 1.2 RelativeRelative Pressure pressure (p/p0) RelativeRelative Pressurepressure (p/p 0) C C O C 150 100 CO2 CO+ CO+2 100 50 50 0 -50 0 (F/gr) C C (F/gr) C -100 -50 -150 -200 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 -100 E (volts) vs S.C.E E (volts) Vs S.C.E M. Noked, E. Avraham, A. Soffer, D. Aurbach, The Journal of Physical Chemistry C 2009, 113, 21319-21327. overview Material design Aqueous SC High voltage SC PsC Summery Using CNTs as a conductive additive and as a reinforcing agent in novel electrodes Rolling up a graphene sheet to form a tube. Properties: • Very strong and flexible molecular material due to the C-C covalent bonding and seamless hexagonal network architecture. •Thermal conductivity ~ 3000 W/m.K in the axial direction •Electric conductivity six orders of a b magnitude higher than copper CNTs grow methods: a) Arc-discharge b) Laser ablation c) Catalytic chemical vapor deposition (CCVD) overview Material design Aqueous SC High voltage SC PsC Summery Carbon precursor Carbon Activated material carbon Stirring Carbonization Oxidizing under inert 5µm agent atmosphere CNT 5µm CNT dispersion overview Material design Aqueous SC High voltage SC PsC Summery .
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