APPLIED ELECTROCHEMISTRY Technion s Chemical Power Sources Research

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1 ה ט כ נ י ו ן מ כ ו ן ט כ נ ו ל ו ג י ל י ש ר א ל TECHNION - ISRAEL INSTITUTE OF TECHNOLOGY הפקולטה למדע והנדסה של חומרים DEPARTMENT OF MATERIALS SCIENCE & ENGINEERING - APPLIED ELECTROCHEMISTRY Technion s Chemical Power Sources Research Alexander Kraytsberg and Yair Ein-Eli Department of Materials Science & Engineering

2 Major Research Fields Silicon Electrochemistry: texturing, polishing, etc. Microelectronics Solar cells Copper electrochemistry: Passivity, CMP, Electro-deposition Electrochemical Catalysis Water cleaning Chemical Power Sources Department of Materials Engineering, Technion Applied Electrochemistry Research Group

3 Chemical Power Sources in our Lab Membrane Development Batteries PEM Fuel Cells Water Management Primary Batteries Secondary Batteries Corrosion issues Bipolar Plate contact resistance issue Li-thermal cells Metal-air Li-ion cathode materials

4 a1 PEM Fuel Cells - I Advanced Materials for PEM Fuel Cells In collaboration with Prof. B. Chmelka, UCSB, USA. Mesoporous Silica Films with cubic (Imm) structure: a) SEM and TEM (inset) micrographs showing a tilted cross-sectional view and cubic pore ordering, respectively, for a 190-nm-thick silica film prepared by dip-coating on a polished silicon wafer. b) SEM and TEM (inset) micrographs showing similar features for a 62-µmthick free-standing film.

5 Slide 4 a1 Please add some information about specific potential fuel-cell related implementation of these nice films. alexkra, 04/09/2012

6 PEM Fuel Cells - II PEM FC Water Management Alexander Kraytsberg, Yair Ein-Eli,Journal of Power Sources, vol. 160, pp , 2006

7 PEM Fuel Cells - III Construction and bipolar plates material corrosion I Iron, chromium, aluminum, other polyvalent ions fill SO - 3 sites. The result is the membrane conductivity degradation The ions come mostly from fluorine assisted bipolar plate and construction materials dissolution Copper & alloys: Cu + 2F - CuF 2- + e - Aluminum & alloys: HF + Al 2 O 3 = 2 AlF H 2 O Titanium & alloys: Ti 4+ {in passive film} + 2HF TiF H + SS & Fe-Cr-Ni - based alloys 6HF + Cr 2 O 3 3 H 2 O + 2 CrF 2 + F 2 2HF + NiO NiF 2 + H 2 O Fluoride ion release is generally related to NAFION TM decomposition.

8 PEM Fuel Cells - III Construction and bipolar plates corrosion prevention II Eliminate fluorides - reduce corrosion! The idea to incorporate a scavenger of fluorinerelated contaminations into the membrane The way to produce such a membrane: to cast or to extrude NAFION membranes using [anionite]/[nafion mix slurry or to extrude NAFION membranes using [anionite powder]/[nafion melt] precursors.

9 PEM Fuel Cells - IV The best way to couple bipolar plate and FC electrode A. Kraytsberg, M. Auinat, Y. Ein-Eli, Journal of Power Sources 164 (2007) The important parameter of fuel cell stack is conductivity of the contacts between electrode support (TORAY carbon paper) and bipolar plates. The enhancement of this conductivity receives the bulk of attention. Usually, a premium is placed upon the quality of bipolar plate surface. The common beliefs are that the contact conductivity of the mirror-like bipolar plate surface grows up with its flatness We have discovered that, contrary of these believes, flattening the surface of metal bipolar plates results in a steep drop of the contact conductivity. starting from some point.

10 PEM Fuel Cells - IV Coupling bipolar plate and FC electrode The explanation is that the contact conductivity depends on the nano-scale pressure. Too smooth contact interface offers more low pressurized nanoscale contacts and finally demonstrates lower conductivity. Schematics of electrical contact on nano-level

11 Batteries I - Primary Batteries α-cuv 2 O 6 cathode for lithium-thermal batteries

12 Batteries I - Primary Batteries Cu-V Materials for Li and Li-thermal batteries Voltage [V] vs Li/Li CuV 2 O 6 Cu 2 V 2 O 7 Cu 3 V 2 O 8 Cu 5 V 2 O 10 Voltage [V] vs Li/Li CuV 2 O ma/cm 2 g 310 ma/cm 2 g Specific Capacity [mah/g] Time [sec]

13 Batteries II - Advanced Metal-air Batteries MARC - Metal air Research Center Development of high energy density anode in metal-air fuel cells. Such anode materials are based on Zn, Al, Mg, Li and Si.

14 Batteries II - Advanced Metal-air Batteries Metal Air Couples o H R o G R Fuel Fuel cell reaction (kj/mol) (kj/mol) Specific energy (W hr/kg) Energy density (W hr/l) Al 2Al + 3/2O 2 Al 2 O Be Be + 1/2O 2 BeO H 2 H 2 + 1/2O 2 H 2 O (@ 1000atm) Li 2Li + 1/2O 2 Li 2 O Mg Mg + 1/2O 2 MgO Zn Zn + 1/2O 2 ZnO Si Si + O 2 SiO TECHNION, ISRAEL INSTITUTE OF TECHNOLOGY

15 Batteries II - Advanced Metal-air Batteries Silicon Air Cell Configuration G. Cohn and Y. Ein-Eli, J. Power Sources, 195, (2010) TECHNION, ISRAEL INSTITUTE OF TECHNOLOGY

16 Batteries II - Advanced Metal-air Batteries Si Air Discharge I n Voltage (V) µa/cm µa/cm 2 Current (µa/cm 2 ) Cell Voltage (V) Time (hr) G. Cohn et. al., Electrochem. Comm. 11 (2009) TECHNION, ISRAEL INSTITUTE OF TECHNOLOGY

17 Batteries II - Advanced Metal-air Batteries Si Air Discharge II n Voltage / V A cm -2 (53.4) (30.5) (25) (6 mahr cm -2 ) Time / hr TECHNION, ISRAEL INSTITUTE OF TECHNOLOGY

18 Batteries II - Advanced Metal-air Batteries Si Air Solid State Battery The use of gel polymer electrolyte (GPE) eliminates the need to handle liquid electrolyte, and simplifies technical issues. Gil Cohn, Anna Altberg, Digby D. Macdonald, Yair Ein-Eli, A silicon air battery utilizing a composite polymer electrolyte, Electrochimica Acta, Vol. 58, 2011, pp ,

19 Batteries II - the Next Tipping Point: Small Scale Batteries

20 Batteries II Si-air Battery On-chip Si-air cells perfectly fit the task: 32nm SoC technology, Claremont chip operates at 2 mw 1 cm 2 Si/air cell may provide 35 hours of operation time. Chemistry Si + O 2 SiO 2 Best current Li-ion 3D cells Voltage 2.21 V (1.2) 2-3 V Specific energy 8.47 Whg - 1 Capacity 12 wafer, Ah/mm Ah/mm 2 The next generation, 22nm tri-gate technology chip, will be able to work 70 hours with 1 cm 2 Si/air cell.

21 Battery II Zn-air discharge vs. temperature RT Potential (V) Potential (V) PEG DiAcid PEG Cell Capacity (Ah) PEG DiAcid PEG Cell Capacity (Ah) Potential (V) Potential (V) PEG DiAcid PEG Cell Capacity (Ah) PEG DiAcid PEG Cell Capacity (Ah)

22 Battery II Other Metal-Air Technologies that We Are Looking at... Li-air Non Aqueous. Mg-air Non Aqueous. and Al-air Aqueous...& Non Aqueous

23 Battery III Lithium/air cell improvement The organic electrolytes easily wet the air cathode pores in non- aqueous systems flooding air channels: Thus only dissolved O 2 is available for reduction. The ability of electrolyte to transport O 2 turns to be a crucial parameter, which determines the energy and power capacities of the cell. Common non-aqueous electrolytes have low O 2 -solubility and diffusivity The proprietary cathode design is addressing the issue and provides an adequate oxygen delivery rate toward catalytically active air cathode surface.

24 Battery III Advanced Metal Oxides in Li and Li-ion Batteries Development of novel cathode materials, based on ceramic compounds, capable of delivering high potential (above 4V) and high capacity.

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26 Applied Electrochemistry Lab Personnel Yair Ein-Eli (PI) 2 senior researchers (PhD) 2 engineers 1 technician 3 MSc students 7 PhD students Prof. Yair Ein Eli Dr. Alexander Kraytsberg Dr. David Starosvetsky

27 Ein-Eli s Research Group Publications & IP ( ) 100 Publications 8 Patents Ein-Eli s Research Group Funding ( in USD) From academic funding agencies: $2.25 M From industrial source: $3 M