TUM CREATE Centre for Electromobility, Singapore The Importance of Electrochemistry for the Development of Sustainable Mobility Jochen Friedl, Ulrich Stimming DPG-Frühjahrstagung, Working Group on Energy, 18.03.2014 TUM CREATE TUM Department of Physics E19 TUM Institute for Advanced Study
Bridging East and West 18 March 2014 2
Outline Physical Background/ Operating Principle Outlook/ Perspectives State of the Art 18 March 2014 3
Electrochemical Double Layer Capacitor 18 March 2014 4
Electrochemical Double Layer Capacitor C pf 1 nf cm 2 + + + S.O. Kasap: Principles of Electrical Engineering Materials and Devices, McGraw-Hill Higher Education, 2000 Electrode - - - - φ φ C DL = dq dφ 10μF cm 2 φ NHE 4. 5 V vs. vacuum Q + Q - Electrolyte 0 x H x d Kolb DM. Angew Chem Int Ed Engl 2001;40:1162 81. Klaus J. Vetter: Electrochemical Kinetics, Academic Press Inc., 1967 18 March 2014 5 x
Electrochemical Double Layer Capacitor Béguin F et al. Adv Mater 2014:1 33. C +/ = dq du C act = 1 C + + 1 C 1 C E = 1 2 C U2 P = 1 4 ESR U2 Energy stored in Electrochemical Double Layer (inner & diffuse) 18 March 2014 6
Electrochemical Double Layer Capacitor Power Density U(t) = U 0 (1 exp t τ ) No charge transfer, no reaction: τ = C R s Small τ 10 kw kg -1 Simon P, Gogotsi Y. Nat Mater 2008;7:845 54. CAP-XX Supercapacitors for Micro-Hybrid Automotive Applications (2013). 18 March 2014 7
Electrochemical Double Layer Capacitor Energy Density E = 1 2 C(1 V)2 organic aqueous E = 1 2 C(U)2 C(2. 7 V)2 High Conductivity Electrochemical Stability High Surface Area Carbonaceous material: 5-20 μf cm -2 Pandolfo AG, Hollenkamp AF. J Power Sources 2006;157:11 27. Simon P, Gogotsi Y. Nat Mater 2008;7:845 54. CAP-XX Supercapacitors for Micro-Hybrid Automotive Applications (2013). 18 March 2014 8
Electrochemical Double Layer Capacitor High conductivity Electrochemical stability High surface area Carbon TEM of typical Disordered Microporous (<2 nm) Carbon S BET ~ 2000 m 2 g -1 Above S BET ~ 1200 m 2 g -1 gravimetric C DL exhibits plateau. Barbieri Béguin 18 March F O et et 2014 al. al. Adv Carbon Mater 2005;43:1303 10. 2014:1 33. Béguin F et al. Adv Mater 2014:1 33. 9 Simon P, Gogotsi Y. Nat Mater 2008;7:845 54.
Electrochemical Double Layer Capacitor Applications for Mobility: Simon P, Gogotsi Y. Nat Mater 2008;7:845 54. TOYOTA HYBRID: Hybrid at the Heart of Toyota Racing in 2014 (2014); CAP-XX Supercapacitors for Micro-Hybrid Automotive Applications (2013). 18 March 2014 10
Batteries 18 March 2014 11
Batteries Lead-Acid Battery U charged E = Q ΔU E 35 Wh kg 1 U/V vs. NHE PbO 2 /PbSO 4 1.69 Pb H + HSO 4 - PbO 2 U=2.04 V H + H 2 O Pb s + HSO 4 PbSO 4 s + H + + 2e Pb/PbSO 4-0.35 Bard et al: Standard Potentials in Aqueous Solution, CRC Press, 1985 PbO 2 s + HSO 4 + 3H + + 2e PbSO 4 s + 2H 2 O Energy stored in Electrodes 18 March 2014 12
Batteries Redox Flow Batteries E E = Q ΔU E eu 0 pos = -3.45 ev vs. vacuum VO 2+ E F,Me Energy stored in Electrolyte E F,Me D Me D El Negative Electrode V 3+ V 2+ eu 0 neg = - 4.75 ev vs. vacuum 18 March 2014 13 z D El Positive Electrode D Me
Batteries Redox Flow Batteries E E = Q ΔU E eu 0 pos = -3.45 ev vs. vacuum VO 2+ E F,Me E F,Me V 3+ V 2+ eu 0 neg = - 4.75 ev vs. vacuum η = (U U 0 ) D Me D El Negative Electrode I = I 0 (exp 18 March 2014 14 D El D Me z α af Positive RT η exp α cf Electrode RT η )
Batteries Lithium-Ion Battery E 200 Wh kg 1 U charged E = Q ΔU U/V vs. Li/Li + Li 1-x CoO 2 / Li x CoO 2 ~3.7 Li X C 6 + + + + Li + Li 1-x CoO 2 U ~ 3.6 V + + + PF 6 - Li x C 6 C 6 + xli + + xe Li x C 6 /C 6 ~0.1 Li 1 x CoO 2 + xli + + xe Li x CoO 2 18 March 2014 15
Batteries Battery: Electrical car designed as taxi for tropical megacities. 170 Wh kg -1 Pack: Lightweight CFRP body; Overhead air conditioning; 101 Seat Wh cooling; kg -1 200 Wh kg -1 United States Advanced Battery Consortium Battery Pack: 200 km range in 15 min charging; 50 kwh energy content; 300 kg battery weight; 495 kg pack weight; 216 Li-Ion NMC cells; 400 V nominal voltage; 360 A max. current. 18 March 2014 16 Christian Huber, TUM CREATE
Batteries Energy Density E = Q ΔU silicon x Li + MX y Li x MX y Insertion Scrosati B, Garche J. J Power Sources 2010;195:2419 30. x Li + MX y Li x X y + M Conversion/Alloying J.-M. Tarascon, M. Armand, Nature, 2001, 414, 359 18 March 2014 17
Batteries Alloying Anode: Silicon Full Discharge: Li 22 Si 5 4200 mah g -1 LiC 6 372 mah g -1 Problem: Extreme Volume change Capacity decay Possible Approach: Nanostructures with facile strain relaxation Nanostructured Si anodes are promising, but quantitative understanding is still missing and nature of SEI needs to be understood. 18 March 2014 18 Wu H, Cui Y. Nano Today 2012;7:414 29. McDowell et al. Adv Mater 2013;25:4966 85.
current-collector separator Batteries Novel Cathode: Li-O 2 Discharge Mechanism: 2 Li + O 2 Li 2 O 2 Up to 1200 mah g -1 e - e - c c c Li 2 O 2 / Li 2 O c Challenges: Li Li + O 2 (air) Li x O 2 ( H 2 O, CO 2 ) Li 2 CO 3 LiOH c c [ LiO 2 ] solv. c + e - Li-electrode porous air-electrode Electrolyte stability; Blockage of porous carbon cathode with discharge products ( clogging ); Slow kinetics for charging. Y.-C. Lu,et al, Electrochem. & Solid-State Lett., 2010, 13, A69 18 March 2014 19
Fuel Cells 18 March 2014 20
fuel Fuel Cells Pt Pt oxidant j 0 Pt 1mA cm -2 j 0 Pt 2.8 10-4 ma cm -2 electrolyte Direct conversion of chemical into electrical energy; Constant supply of fuel and oxidant. Energy Conversion j 0 = R T nf R f A j = j 0 (Exp α anf RT η Exp α cnf RT η ) 18 March 2014 21
Fuel Cells Complicated reaction mechanism Hydrogen related reactions: H 2 + 2 2 H ad H 2 + H ad + H + + e H ad + H + + e Tafel Heyrovsky Volmer j 0 Pt 1mA cm -2 Slow kinetics Increase Temperature. Computational studies. Low power; High cost. Model catalyst studies. Values from: DOE Strategic Analysis: Mass Production Cost Estimation of Direct H 2 PEM Fuel Cell System for Transportation Applications (2012) Friedl J, Stimming U. Electrochim. Acta 2013;101:41 58. 18 March 2014 22
Fuel Cells Characteristic Curve PEM Many possible fuels high energy kinetic losses evident Friedl J, Stimming U. Electrochim. Acta 2013;101:41 58. 18 March 2014 23
POWER: No faradaic reactions ENERGY: Double layer only CYCLE LIFE: Very high, no faradaic reaction 18 March 2014 24
POWER: Facile Charge transfer ENERGY: Stored in electrodes CYCLE LIFE: Low, electrode conversion 18 March 2014 25
POWER: Sluggish Charge Transfer ENERGY: Stored in electrolyte CYCLE LIFE: High, electrodes for charge transfer 18 March 2014 26
POWER: Intercalation reaction ENERGY: No conversion but intercalation CYCLE LIFE: High as strain small 18 March 2014 27
POWER: ENERGY: Very sluggish O 2 reduction High energy density fuels 18 March 2014 28
Thank you for your attention! 18 March 2014 29