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New Developments in Electrochemical Cells

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1 New Developments in Electrochemical Cells
2017/4/11 Science Update Programme New Developments in Electrochemical Cells Education Bureau, HKSAR & Department of Chemistry The University of Hong Kong June 2002

2 Electrochemical Cells, K.Y. Chan, HKU
References Batteries Fuel Cells chem..hku.hk/~fuelcell Books:  A.J. Bard, L. Faulkner, “Electrochemical Methods”, 2001, Wiley. Derek Pletcher and Frank C. Walsh, “Industrial Electrochemistry”, Chapman and Hall, 1990. C.A. Vincent and B. Scrosati, “Modern Batteries : An Introduction to Electrochemical Power Sources”, Butterworth-Heinemann, 1998. James Larminie and Andrew Dicks, “Fuel Cell Systems Explained”, Wiley, 2000. Capacitors Green Energy Electric Vehicles Evworld.com Utilities Portable Power Sources June 2002 Electrochemical Cells, K.Y. Chan, HKU

3 Electrochemical Cells, K.Y. Chan, HKU
Multidisciplinary and Integrated Science Electrochemistry, General Chemistry Physical Chemistry:Thermodynamics, Kinetics, Transport Organic Chemistry Inorganic, Solid State Chemistry Materials Science Basics Physics, Energy, Electricity Environmental Science and Ecological/Biological Issues Can be discussed with different emphasis, at different levels, and platforms. June 2002 Electrochemical Cells, K.Y. Chan, HKU

4 Electrochemical Cells, K.Y. Chan, HKU
Fundamental Theories and Concepts Batteries Fuel Cells Applications June 2002 Electrochemical Cells, K.Y. Chan, HKU

5 Electrochemical Cells, K.Y. Chan, HKU
Fundamentals Thermodynamics Relate Reactivity to Electrode Potential Nernst Equation accounts for concentration(activity) effects Calculate Electrode Potential from Free Energy June 2002 Electrochemical Cells, K.Y. Chan, HKU

6 Electrochemical Cells, K.Y. Chan, HKU
Electrochemical Activity Series V Al/Al Zn/Zn H2/H Cu/Cu H2O/O2 June 2002 Electrochemical Cells, K.Y. Chan, HKU

7 Electrochemical Cells, K.Y. Chan, HKU
Fundamentals Kinetics Current  Rate of reaction (Faraday’s law) Rate (current) described by Tafel Equation or Butler-Volmer Equation (Bard and Faulkner, Wiley 2001) June 2002 Electrochemical Cells, K.Y. Chan, HKU

8 Electrochemical Cells, K.Y. Chan, HKU
Fundamentals Kinetics from Absolute Rate Theory O* Free energy G  nF E O + n e- n F E R Reaction co-ordinate June 2002 Electrochemical Cells, K.Y. Chan, HKU

9 Electrochemical Cells, K.Y. Chan, HKU
Current into electrolyte Electrons out of electrode June 2002 Electrochemical Cells, K.Y. Chan, HKU

10 Electrochemical Cells, K.Y. Chan, HKU
Concentration or pH effect E June 2002 Electrochemical Cells, K.Y. Chan, HKU

11 Electrochemical Cells, K.Y. Chan, HKU
Ecell Anode Cathode June 2002 Electrochemical Cells, K.Y. Chan, HKU

12 Electrochemical Cells, K.Y. Chan, HKU
Ref. electrode E-Eref E Ecell Anode Cathode June 2002 Electrochemical Cells, K.Y. Chan, HKU

13 Electrochemical Cells, K.Y. Chan, HKU
Fundamentals Transport and Interfaces Rate of supply of raw materials : diffusion of active materials Rate of removal of: products including ions, electrons ionic vs ohmic resistance Change of solid interfaces: dentritic growth Wetting/non-wetting affects gas transport into electrolyte Selectivity of transport, e.g. cationic membrane June 2002 Electrochemical Cells, K.Y. Chan, HKU

14 Electrochemical Cells, K.Y. Chan, HKU
H2SO4 0.6 KOH ohm-1 cm-1 KCl CH3COOH 10 M concentration June 2002 Electrochemical Cells, K.Y. Chan, HKU

15 Electrochemical Cells, K.Y. Chan, HKU
June 2002 Electrochemical Cells, K.Y. Chan, HKU

16 Electrochemical Cells, K.Y. Chan, HKU
Activation Ohmic Mass-Transfer Current Density Ideal Voltage Cell Voltage June 2002 Electrochemical Cells, K.Y. Chan, HKU

17 Electrochemical Cells, K.Y. Chan, HKU
Some Terminologies Open Circuit Voltage Equilibrium potential, Standard Potential Overpotential, underpotential Polarization (activation, ohmic, concentration) Capacity mA hr Energy Density W hr kg-1 , W hr l-1 Power Density W kg-1 , W l-1 , W cm-2 Current Density mA cm-2 June 2002 Electrochemical Cells, K.Y. Chan, HKU

18 Electrochemical Cells, K.Y. Chan, HKU
Anode: Oxidation reaction, release electrons to external circuit, negative terminal (galvanic cell) Cathode: Reduction reaction, receive electrons from external circuit, positive terminal (galnanic cell) Current Collector: continuous electronic conducting solid phase to collect electrons (in anode) and to distribute electrons (in cathode) Electrolyte: ionic conducting but electronic insulating, transfer ions from/to electrodes Separator: hydrophilic porous sheet material to hold a thin layer of electrolyte, electronic insulation June 2002 Electrochemical Cells, K.Y. Chan, HKU

19 Electrochemical Cells, K.Y. Chan, HKU
Polymer Electrolyte: polymeric backbone with fixed charge to allow transport of either cation or anion Porous Matrix to hold electrolyte: Ceramic, asbestos, “polymers”. Gel/Paste electrolyte: immobilize electrolyte but allow ionic transport Molten Salt Electrolyte:e.g. Carbonates Solid Oxide Electrolyte: oxide ion mobiliity at elevated temperature June 2002 Electrochemical Cells, K.Y. Chan, HKU

20 2017/4/11 Batteries A. Volta, 1880

21 Electrochemical Cells, K.Y. Chan, HKU
Primary Batteries: Zn/C Alkaline Zn/HgO Li metal Secondary Batteries: Lead Acid (Rechargeable) Ni-Cd Ni-MH Li ion Hybrid of Battery and Fuel Cell: Zn-Air Al-Air (Regenerative Fuel Cells) June 2002 Electrochemical Cells, K.Y. Chan, HKU

22 Electrochemical Cells, K.Y. Chan, HKU
Batteries Zinc/Carbon (Leclanché 1880s) Cathode: 2 MnO2 + H2O + 2e-  Mn2O3 + 2OH- Anode: Zn  Zn2+ + 2e- Overall: 2 MnO2 + Zn + H2O  Mn2O3 + Zn2+ + 2OH- G=-257 kJ mol-1 , Eo = 1.55 V electrolyte: moist NH4Cl/ZnCl2/MnO2/C powder current collectors: graphite rod and zinc Capacity 6 A hr, energy density 80 Whr kg-1 June 2002 Electrochemical Cells, K.Y. Chan, HKU

23 Electrochemical Cells, K.Y. Chan, HKU
Batteries Zinc/Carbon (Leclanché 1880s) Carbon rod current collector (+ve) separator MnO2 based positive paste Zinc can anode (-ve) June 2002 Electrochemical Cells, K.Y. Chan, HKU

24 Electrochemical Cells, K.Y. Chan, HKU
Batteries Lead/Acid Discharge reactions Cathode: PbO2 + 4H+ +SO e-  2H2O + PbSO4 Anode: Pb + SO42-  PbSO4 + 2e- Overall: PbO2 + Pb + 4H+ + 2SO42-  2PbSO4 + 2H2O G= -394 kJ mol-1 , Eo = 2.05 V electrolyte: aqueous H2SO4 current collectors: both Pb Capacity: 2.7 Ahr, Energy density 30 Whr kg-1 cell voltage> 1.23 V, Electrolysis of water kinetically hindered June 2002 Electrochemical Cells, K.Y. Chan, HKU

25 Electrochemical Cells, K.Y. Chan, HKU
Possible Electrode Pairs? V Pb/PbSO H2/H H2O/O2 PbSO4/PbO2 June 2002 Electrochemical Cells, K.Y. Chan, HKU

26 Electrochemical Cells, K.Y. Chan, HKU
Batteries Nickel/Cadmium Cathode: 2NiO(OH) + 2H2O + 2e-  2Ni(OH)2 + 2OH- Anode: Cd + 2OH-  Cd(OH)2 + 2e- Overall: NiO(OH) + Cd + 2H2O  2Ni(OH)2 + Cd(OH)2 G= -283 kJ mol-1 , Eo = 1.48 V electrolyte: aqueous KOH current collectors: Ni foam and peforated nickel sheet Capacity: 4 Ahr, energy density: 33 Whr kg-1 June 2002 Electrochemical Cells, K.Y. Chan, HKU

27 Electrochemical Cells, K.Y. Chan, HKU
Batteries Nickel/Metal hydride Cathode: NiO(OH) + H2O + e-  Ni(OH)2 + OH- Anode: MH + OH-  M + H2O + 2e- Overall: MH + NiO(OH)  M + Ni(OH)2 Metal hydride: AB5 e.g. LaNi5 or AB2, e.g. TiMn2 , ZnMn2 electrolyte: aqueous KOH current collectors: Ni foam and peforated nickel sheet Capacity: 4 Ahr, energy density: 80 Whr kg-1 June 2002 Electrochemical Cells, K.Y. Chan, HKU

28 Electrochemical Cells, K.Y. Chan, HKU
Batteries Nickel/Metal Hydride Overcharging Cathode: 2 OH-  H2O + ½O2 + 2e- Anode: charge reserve M + H2O + 2e-  MH + OH- Oxygen dissolves to Anode: MH + ½ O2  2M + H2O Prevent gassing and build up of pressure June 2002 Electrochemical Cells, K.Y. Chan, HKU

29 Electrochemical Cells, K.Y. Chan, HKU
Batteries Lithium Ion Cathode: xLi+ + LiM2O4 + xe-  Li1+xM2O4 M=Mn,Ti xLi+ + LiMO2 + xe-  Li1+xMO2 M=Co, Ni Anode: LiC6  x Li+ + x e- + Li1-xC6 Overall: C6 + LiMO2  LixC6 + Li1-xMO2 LiMn2O4 G= -287 kJ mol-1 , Eo = 2.97 V Energy density > 100 Whr/kg June 2002 Electrochemical Cells, K.Y. Chan, HKU

30 Electrochemical Cells, K.Y. Chan, HKU
2017/4/11 Batteries Lithium Ion Anode Electrolyte Aprotic Solvent Gel Polymer (lower weight) Li in graphite lattice Lower activity but safer than Li metal Cathode Solid Structures for storing Li Spinels, Olivines, rhombohedral NASICON June 2002 Electrochemical Cells, K.Y. Chan, HKU

31 Batteries and Fuel Cells
ReFuel Continuous Open system Mostly Gas/Liquid Fuel High energy density Micro to Mega Watts Batteries Recharge Intermittent Closed system Mostly solid High power density June 2002 Electrochemical Cells, K.Y. Chan, HKU

32 Electrochemical Cells, K.Y. Chan, HKU
Fuel Cells Efficient conversion of Chemical Energy to useful energy (without losing to heat, mechanical linkages) Environmentally friendly Flexible: from micro to mega Materials and Nanotechnology June 2002 Electrochemical Cells, K.Y. Chan, HKU

33 Electrochemical Cells, K.Y. Chan, HKU
Fuel Cells Classification according to electrolyte Alkaline Fue Cells Proton Exchange Membrane (PEM) Phosphoric Acid Molten Carbonate Solid Oxide Electrolyte June 2002 Electrochemical Cells, K.Y. Chan, HKU

34 Electrochemical Cells, K.Y. Chan, HKU
燃料電池發電的原理 CxHyOz ===> CO2 + H2O + e- 負極﹕燃料(氫氣﹐酒精﹐ 葡萄糖等) 負極 電解液 電能 正極 正極 ﹕氧氣 ( 氧化劑 ) O2 + e- ===> H2O June 2002 Electrochemical Cells, K.Y. Chan, HKU

35 Electrochemical Cells, K.Y. Chan, HKU
Fuel Cells Chemical Energy Electrical Energy June 2002 Electrochemical Cells, K.Y. Chan, HKU

36 Electrochemical Cells, K.Y. Chan, HKU
Activation Ohmic Mass-Transfer Current Density Ideal Voltage Cell Voltage June 2002 Electrochemical Cells, K.Y. Chan, HKU

37 Diversity of Technology and Materials Problems in Fuel Cells
Oxidant Catalyst Container Control Transport Storage June 2002 Electrochemical Cells, K.Y. Chan, HKU

38 Electrochemical Cells, K.Y. Chan, HKU
Fuels: Hydrogen Metals Natural Gas Small Hydrocarbons (methanol, glucose) Oxidant: air oxygen halides oxides Catalysts: platinum metals metal oxides macrocycles Catalyst Support: Porous Carbon Ceramic Matrix Molecular Sieves Polymer Container and Movable Parts: Alloys Ceramic Polymers Transport/Electrolyte: Proton Exchange Membranes PTFE (Teflon) Solid Electrolyte Storage: Metal Hydride June 2002 Electrochemical Cells, K.Y. Chan, HKU

39 Electrochemical Cells, K.Y. Chan, HKU
Fuels Hydrogen H2+2OH- 2H2O +2e- 2e- +½ O2+H2O  2 OH- Methanol CH3OH + H2O  CO2 + 6H+ +6e- 6e- +1½ O2+6H+  3H2O Aluminium Al + 4OH- Al(OH)4- +3e- 4e- +O2+2H2O  4 OH- Borohydride NaBH4 + 8 OH-  NaBO2 + 6H2O + 8e- Methane (natural gas) Octane : demonstrated in SOFC half cell June 2002 Electrochemical Cells, K.Y. Chan, HKU

40 Electrochemical Cells, K.Y. Chan, HKU
Thermochemistry June 2002 Electrochemical Cells, K.Y. Chan, HKU

41 Micro and Nanostructured Electrodes:
Catalyst Support: High Surface Carbon Size Effects of Catalysts Controlled Porosity Controlled Wetting Maxinum Gas-Liquid-Solid Interface Minimize ohmic resistance Minimize ionic resistance June 2002 Electrochemical Cells, K.Y. Chan, HKU

42 Electrochemical Cells, K.Y. Chan, HKU
Scanning Tunneling Spectroscopy June 2002 Electrochemical Cells, K.Y. Chan, HKU

43 Electrochemical Cells, K.Y. Chan, HKU
Catalysts Platinum is the most important for both anode and cathode Platinum can be replaced by Ag, Mn, Co, only for oxygen reduction in alkaline medium Platinum subject to CO poisoning (impure H2) Binary/Ternary system, macrocycle, bifunctional Stability/Life of nanometals June 2002 Electrochemical Cells, K.Y. Chan, HKU

44 Electrochemical Cells, K.Y. Chan, HKU
Maximum peak current density at 52.5~77.6% Co, one order of magnitude higher than that of pure Pt particles. One possible role of cobalt in promoting the catalysis of platinum, is the removal of COad COOHad intermediates. Chi et al., Catalysis Letters, 71 (2001) 21. June 2002 Electrochemical Cells, K.Y. Chan, HKU

45 Electrochemical Cells, K.Y. Chan, HKU
Catalysts Oxygen Cathode is most limiting and is present in most fuel cells Non-platinum cathode catalyst can tolerant cross over effect. At high temperature, no precious metal or no catalysts is needed in MCFC and SOFC June 2002 Electrochemical Cells, K.Y. Chan, HKU

46 Performances of different air cathode
June 2002 Electrochemical Cells, K.Y. Chan, HKU

47 Gas Diffusion Electrodes
Electronic circuit: continuous solid phase Ionic circuit: Continuous electrolyte phase Materials flow circuit: feed of reactancts H2 H+ e- Chan et al. , Electrochimica Acta, 32 (1987), 1227;33 (1988) 1767. Tang and Chan, Electroanal. Chem. 334 (1992) 65. June 2002 Electrochemical Cells, K.Y. Chan, HKU

48 Electrochemical Cells, K.Y. Chan, HKU
Single air cathode June 2002 Electrochemical Cells, K.Y. Chan, HKU

49 Electrochemical Cells, K.Y. Chan, HKU
Electrolyte Alkaline electrolyte (first deployed for Apollo mission) Phosphoric Acid 180 C Polymer Electrolyte Cross Over Stability (CO2 removal in alkaline) Solid Oxide (YSZ, doped Ceria) Shunt Current / Leak Current June 2002 Electrochemical Cells, K.Y. Chan, HKU

50 Electrochemical Cells, K.Y. Chan, HKU
SOFC Electrolyte Ytrium Stabilized Zirconia Doped Ceria (Cerium Oxide) O2- conductivity at 600~800 C Zr Ce Y O2- June 2002 Electrochemical Cells, K.Y. Chan, HKU

51 Electrochemical Cells, K.Y. Chan, HKU
Stack Design Manifold for fuel feed Manifold for oxidant feed Electronic circuit Ionic circuit Water transport Temperature, humidity control June 2002 Electrochemical Cells, K.Y. Chan, HKU

52 Electrochemical Cells, K.Y. Chan, HKU
June 2002 Electrochemical Cells, K.Y. Chan, HKU

53 Electrochemical Cells, K.Y. Chan, HKU
Stack Design Applications Demonstrated: Radio(Voice of Glucose); Portable CD player; Mobile Phone(GSM). Product Name: Fuel Cell Stack Fuels usable: Glucose, methanol, ethanol,NaBH4 No. of Fuel Cells: 10 in Serial Open Circuit Voltage: V Power Output: W Application: Stationary or Portable ( Mobile phone or toy cars ) June 2002 Electrochemical Cells, K.Y. Chan, HKU

54 Electrochemical Cells, K.Y. Chan, HKU
Electronic circuit: continuous solid phase with minimum electrical resistance to electronically connect anode and cathode through external circuit. Ionic circuit: to complete the other half of the “charge circuit”. Continuous electrolyte phase connecting cathode and anode, but electronic insulating. Maintain balance of ions for anodic, cathodic reactions. Materials flow circuit: feed of reactancts to and removal of products from anode/cathode. Avoid shunt current, leak current in multiple cells Avoid short circuit of cathode and anode Avoid breaking electrochemical window of electrolyte June 2002 Electrochemical Cells, K.Y. Chan, HKU

55 Stationery Power Utilities
10~100 kW 100~500 kWhr ONSY (IFC), Fiji SOFC (Westing House, Honey Well) Load Levelling Power Distribution Life

56 Electrochemical Cells, K.Y. Chan, HKU
June 2002 Electrochemical Cells, K.Y. Chan, HKU

57 Electric Vehicles 10~100 kW 100~500 kWhr Battery vs Fuel Cells
Hybrid with ICE and capacitor Costs: 7 times normal costs Startup time Direct/Reformer Fueling Station Infrastructure

58 Electrochemical Cells, K.Y. Chan, HKU
Transportation Fuel Cell Ballard Power Systems 1st Generation Fuel Cell Transit Bus 2nd Generation Fuel Cell Transit Bus Chrysler Fuel Cell Vehicle Model. Coval H2 Parteners T-1000 Neighborhood Truck. Daimler-Benz The NECAR 3 Three Generations of NECAR Vehicles The NEBUS DaimlerChrysler Jeep Commander Hybrid Fuel Cell Concept Energy Partners The "Gator" Utility Vehicle The "Genesis" Golf Cart The "Green Car" June 2002 Electrochemical Cells, K.Y. Chan, HKU

59 Electrochemical Cells, K.Y. Chan, HKU
Ford Motor Company The P2000 Prodigy Hydrogen Fuel Cell Vehicle The P Platform for a Fuel Cell Vehicle. General Motors Fuel Cell Engine Model H Power Corporation Fuel Cell Bus 50w PEM Fuel Cell Fuel Cell Bicycle Fuel Cell Wheelchair Humboldt State University's Schatz Energy Research Center The Kewet (Danish 2-Seater) Fuel Cell Golf Carts International Fuel Cells The Georgetown University Fuel Cell Bus June 2002 Electrochemical Cells, K.Y. Chan, HKU

60 Electrochemical Cells, K.Y. Chan, HKU
Mazda The Fuel Cell Demio The Demio - On the Road Under the Hood of the Demio Opel The Fuel Cell Sintra The Fuel Cell Zafira Siemens AG PEM Fuel Cell Powered Forklift Toyota The Fuel Cell RAV 4 Volkswagen/Volvo The Fuel Cell Golf (coming soon) Zevco The Fuel Cell Taxi Cab (London) Updated January 8, 1999 June 2002 Electrochemical Cells, K.Y. Chan, HKU

61 Electrochemical Cells, K.Y. Chan, HKU
June 2002 Electrochemical Cells, K.Y. Chan, HKU

62 Portable Power Sources
10~100 kW 100~500 kWhr Battery vs Fuel Cells Safety (H2 , MeOH, caustic electrolyte), Open vs Closed System Volume vs Weight Refueling Vs Recharging

63 Special Applications Space/Defence Communication
Energy Storage for Solar Energy Vector Biomedical Enery Recovery from Waste Marine and Remote Power Sources

64 Electrochemical Cells, K.Y. Chan, HKU
Energy Vector June 2002 Electrochemical Cells, K.Y. Chan, HKU

65 Electrochemical Cells, K.Y. Chan, HKU
Fuel Cells Running on Biogas from Garbage (Kajima Co. Japan) 67% CH4 33% CO2 140kg/day June 2002 Electrochemical Cells, K.Y. Chan, HKU

66 Electrochemical Cells, K.Y. Chan, HKU
June 2002 Electrochemical Cells, K.Y. Chan, HKU

67 Demo Fuel Cells 0.02 ~ 10 W H2 , MeOH, Glucose, alcohols, NaBH4
PEM, Alkaline

68 Electrochemical Cells, K.Y. Chan, HKU
World’s first glucose FC Demonstration Kit (HKU-002, Version 3) June 2002 Electrochemical Cells, K.Y. Chan, HKU

69 Electrochemical Cells, K.Y. Chan, HKU
Typical Performance of HKU-001 June 2002 Electrochemical Cells, K.Y. Chan, HKU


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