hubert gasteiger at basf science symposium 2015

03/10/2015 Hubert Gasteiger — Chair of Technical Electrochemistry page 1

Electromobility – Batteries or Fuel Cells?

battery electric vehicles (BEVs) BEV constraints Li-ion battery projections Li-O2 batteries

fuel cell electric vehicles (FCEVs) performance attributes catalyst performance / aging

BEVs vs. FCEVs

Technical Electrochemistry, Chemistry DepartmentTechnische Universität München

H.A. Gasteiger


Electromobility = car + … + … demand: lowered/zero fossil fuel consumption

significant reduction of CO2 emissions

life-cycle CO2 savings × market-penetration = societal benefit

generationdistribution& storage

electricityhydrogen

use

Electromobility


BEV Battery Weight & Cost

projected performance of today’s LiB technology: - 0.20 kWh/kgbattery-pack*)

- 95% discharge efficiency- 80% state-of-charge range- 250 €/kWhname-plate

**)

**) “Transitions to Alternative Transportation Technologies – Plug-In Hybrid Electric Vehicles”, National Research Council (2010); see: www.nap.edu/catalog/12826.html

*) F.T. Wagner, B. Lakshmanan, M.F. Mathias; J. Phys. Chem. Lett. 1 (2010) 2204

energy required for small 4-passenger car: - 0.10 kWh/km*)


BEV Battery Weight & Cost

projected performance of today’s LiB technology: - 0.20 kWh/kgbattery-pack*)

- 95% discharge efficiency- 80% state-of-charge range- 250 €/kWhname-plate

**)

**) “Transitions to Alternative Transportation Technologies – Plug-In Hybrid Electric Vehicles”, National Research Council (2010); see: www.nap.edu/catalog/12826.html

*) F.T. Wagner, B. Lakshmanan, M.F. Mathias; J. Phys. Chem. Lett. 1 (2010) 2204

energy required for small 4-passenger car: - 0.10 kWh/km*)

150 km range 500 km range

required net energy: 15 kWhnet 50 kWhnet

required name-plate energy: 20 kWhname-plate 66 kWhname-plate

battery weight: 100 kg 330 kgbattery cost: 5000 € 16500 €

currently: ≈250-300 €/kWhname-plate & 0.15 kWh/kgbattery-pack

→ market penetration limited by “range anxiety” ?


Range Extension – Approaches

multiple potential pathways within different disciplines

multi-variate problem with many inter-dependencies !

Vehicle Components & Design

Energy Conversion& Storage

post-LiBs

light-weight matls. adv. cooling/heating electric drive effic.

Wh ↑Management & MobilityConcepts

integrated mobilityconcepts

Energy Management

rapid charging

Wh/km ↓range ↓

“range” ↑



post-LiBs




Energy Management

rapid charging

Wh/km ↓range ↓

“range” ↑

H2-fuel cells


Commercial Approach premium cars → ≈150 km range & 150 km/h (150 PS; 0 → 100 km/h in 7s)

→ technical data: - carbon-composite chassis (enables 0.13 kWh/km)- 19 kWh lithium-ion battery- charging: - possible in 0.5 hours (40 kW))

- ≈6-8 hours (3 kW)

limited range also for premium cars





post-LiBs




Energy Management

rapid charging

Wh/km ↓range ↓

“range” ↑



post-LiBs




Energy Management

rapid charging

Wh/km ↓range ↓

“range” ↑

H2-fuel cells


Rapid Charging

charging time:

from:E.ON presentationat the IAS Openingby J. Eckstein (Oct., 2010)

rapid charging: - reduced charging efficiency (iR-drop, etc.) & durability issue- questionable business case for electric utilities→ 5 min. re-charge not feasible

tcharging = kWhbattery / kWsupply → ≈66 kWh in 5 mins. ≡ 0.8 MW !





post-LiBs




Energy Management

rapid charging

Wh/km ↓range ↓

“range” ↑



post-LiBs




Energy Management

rapid charging

Wh/km ↓range ↓

“range” ↑

H2-fuel cells




BEVs vs. FCEVs


Li-Ion Battery Limits

F.T. Wagner, B. Lakshmanan, M.F. Mathias; J. Phys. Chem. Lett. 1 (2010) 2204

specific energy [Wh/kg] of LiNi1/3Mn1/3Co1/3O2 / Graphite (+/-)→ active-materials: ≈0.45 kWh/kgactive-materials

NMC/Graphite limit of ≈0.20 kWh/kgbattery-system

through engineering design & product development

specific energy of the battery system→ battery managements, sensors, cooling, …

specific energy of cells→ includes weight of:

- separator (porous electrolyte-filled polymer)- electrolyte (organic solvents + Li-salt)- negative current collector (copper)- positive current collector (aluminum)

≈0.3 kWh/kgcell


Advanced LiB Materials

from: K.G. Gallagher, S. Goebel, T. Greszler, M. Mathias, W. Oelerich, D. Eroglu, V. Srinivasan; Energy Environ. Sci. 7 (2014) 1555

Si-anodes & HV/HE-cathodes:up to 0.25 kWh/kgbattery-pack projected

Li-anodes & HV/HE-cathodes:up to 0.30 kWh/kgbattery-pack projected

advanced LiBs: ≈1.5-fold gainover current 0.2 kWh/kg benchmark

→ cycle-life with Li & Si anodes ?→ stability of HV-electrodes ?


4/21/2015

- EC-only electrolyte [1] → low signal background in mass spec- 13C labeled EC (E13C) → C and EC corrosion at different m/z

conductive carbon (“SuperC65”) stability study via on-line mass-spectrometry:

TO OEMS [2] →

CELL INLETCELL OUTLET

TWO-COMPARTMENT CELL

NORMAL ELECTROLYTE

CO2

ELECTRODE

CARBON

13C-LABELED ELECTROLYTE

H2O IN ELECTROLYTE

HIGH VOLTAGE

PHENOMENON

[1] M. Nie, B.L. Lucht; J. Electrochem. Soc. 161 (2014) A1001

E13C + H2O → 13CO2 + …ELECTROLYTE OXIDATION

12C + 2H2O → 12CO2 + 4H+ + 4e- [3]CARBON CORROSION

[3] L.M. Roen, C.H. Paik, T.D. Jarvi; Electrochem. & Solid-State Lett. 7 (2004) A19[2] N. Tsiouvaras, S. Meini, I. Buchberger, H.A. Gasteiger; J. Electrochem. Soc. 160 (2013) A471

CALIBRATED CAPILLARY LEAK (1 µl/min)

Carbon Stability in HV-Cathodes


SuperC65 & EC Stability at 5.0 VLi

from: M. Metzger, C. Marino, J. Sicklinger, D. Haering, H.A. Gasteiger; J. Electrochem. Soc. (2015) in press.

oxidation rates of C ( ≡ 12CO2 + 12CO)& EC ( ≡ 13CO2 + 13CO)

→ anodic oxidation enhanced by H2O(via initial contamination or permeation)

at ≥40ºC: insufficient long-term stabilityof EC & conductive carbon

→ C-coatings less durable

→ improved electrolyte and/or additives

C & EC weight-loss over 100h at 5.0V:




BEVs vs. FCEVs


Energy Density Projections

from: K.G. Gallagher, S. Goebel, T. Greszler, M. Mathias, W. Oelerich, D. Eroglu, V. Srinivasan; Energy Environ. Sci. 7 (2014) 1555

system-based energy densities:- closed system: O2 pressure vessel- open system: air clean-up

no gain in Wh/L if compared toSi/LMRNMC (Li-rich NMC, HE-NMC)& maximum 1.5x gain in Wh/kg (Li/O2 assumes stable Limetal-anode)


Li-Air Cycle Life

from: M.M.O. Thotiyl, S.A. Freunberger, Z. Peng, Y. Chen, Z. Liu, P.G. Bruce; Nature Materials 12 (2013) 1050

100’s of cycles in several literature report → usually limited to partial discharge

long cycle-life & high capacities, but sometimes difficult to reproduce → need more fundamental insights

TiC cathode:in DMSO + 0.5M LiClO4

SuperP/C-Paper:LiCF3SO3 in TEGDME (1:4)from: H.-g. Jung, J. Hassoun, J.-B. Park, Y.-K. Sun, B. Scrosai; Nature Chemistry 4 (2012) 579


Discharge (O2 reduction)

Li+

Li+

O2 + e− O2•−

e-

e-

electrolyte degradation products

Li2O2Li2O

Li2CO3

LiOH ?

O2

CO2, C

H2O

Li-O2 Discharge/Charge Reactions


Discharge (O2 reduction)

Li+

Li+

O2 + e− O2•−

e-

e-

electrolyte degradation products

Li2O2Li2O

Li2CO3

LiOH ?

O2

CO2, C

H2O

Li-O2 Discharge/Charge Reactions

Charge (O2 evolution)

O2

ideally: O2, evolved ≡ O2, consumed

→ no parasitic reactions

Li2O2

Li2OLiOHLi2CO3

O2

see: S. Meini, N. Tsiouvaras, K.U. Schwenke,M. Piana, H. Beyer, L. Lange, H.A. Gasteiger;Phys. Chem. Chem. Phys. 15 (2013) 11478


Li/O2 Charge/Discharge: O2 Recovery

from: N. Tsiouvaras, S. Meini, I. Buchberger,H.A. Gasteiger, J. Electrochem. Soc. 160 (2013) 471

2.0

2.5

3.0

3.5

4.0

0 1 2 3 4 5 cycle number

elec

tron

s/O

2

50

55

60

65

70

75

80

85

90

95

100

O2 r

ecov

ery

[%]

via on-line mass-spectrometry:

≈20-30% „missing“ O2 due toside reactions during charge/discharge→ reaction with electrolyte/carbon

from: B.D. McCloskey, D.S. Bethune, R.M. Shelby, T. Mori, R. Scheffler, A. Speidel, M. Sherwood, A.C. Luntz; J. Phys. Chem. Lett. 3 (2012) 3043

→ similarly high e-/O2 in most studies:- in NMP and DMSO

(C.J. Bondue, A.A. Abd-El-Latif, P. Hegemann, H. Baltruschat;J. Electrochem. Soc. 162 (2015) A479)

- with Pt, Au, or MnO2 cathodes (DME/LiTFSI)(B.D. McCloskey et al., JACS 133 (2011) 18038& C. Kavakli et al., ChemCatChem 5 (2013) 1)


recently proposed new electrolyte:

Alternative Electrolytes: DMDMB

(B.D. Adams, R. Black, Z. Williams, R. Fernandes, M. Cuisinier, E.J. Berg, P. Novak, G.K. Murphy,L.F. Nazar; Adv. Energy Mater. (2014) 1400867)

→ CH3-groups prevent β-H abstraction

→ cycle-life & 1H-NMR suggest improved stability

→ OEMS (0.25 mA charge): ≈3.9 e-/O2

no O2 reversibility, despite high cycle-life→ stable electrolyte/cathode critical for Li-O2




BEVs vs. FCEVs


Fuel Cell Electric Vehicle Constraintssince ≈2008: 500 km range 70 MPa H2 (4-6 kgH2 at 5%wt) with refuelling <5 mins.

catalyst cost & supply (100kW car):current: ≈0.5 gPt/kW ≡ 50gPt/car

→ >10x vs. automotive emission catalysts

long-term: <0.1gPt/kW ≡ <10gPt/car → large-scale commercial viability

H2 generation & distribution infrastructure...

catalyst durability:≈4000 h vs. 5000 h target → advanced catalysts & controls

challenge: improved Pt catalysts or non-Pt catalystsfrom: Fuel Cell Technology Status AnalysisProject; Fact Sheet (Dec. 2014);http://www.nrel.gov/docs/fy15osti/62944.pdf


H2/Air PEMFC – Processes / Electrodes

→ 60% void volume(dpore ≈50-100nm)


H2/Air PEMFC Performance

0.60

0.65

0.70

0.75

0.80

0.85

0.90

0.0 0.3 0.6 0.9 1.2 1.5 [A/cm2]

Vol

tage

(V)

Ecell

ηHFR=90 mV (ηmem=30 mV)

ST19-S0559 (Nano-x coating) RC FCPM op-line

MEA: Gore 5720 (18 µm, 0.2/0.3 mgPt/cm2, I/C=1.2)DM/MPL: Pre-compressed SGL 25BC

ηtx,O2(dry)=26 mV

ηORR=410 mV

ηtx,H+ =18 mV

ηtx,O2(wet)=18 mV

H2/air (s=1.5/2), 150kPaabs, <50% RHinlet≈25µm membrane and ≈0.05/0.4mgPt/cm2

MEA

( 60 mV Rcontact)

from: W. Gu, D.R. Baker, Y. Liu, H.A. Gasteiger, in: Handbook of Fuel Cells, Wiley (2009): vol. 6, pp. 631.

( ηHOR < 5 mV*) )

undefined losses, ηtx,O2(wet), of only ≈20mV→ improvements require new materials


H2/Air PEMFC Performance

0.60

0.65

0.70

0.75

0.80

0.85

0.90

0.0 0.3 0.6 0.9 1.2 1.5 [A/cm2]

Vol

tage

(V)

Ecell

ηHFR=90 mV (ηmem=30 mV)

ST19-S0559 (Nano-x coating) RC FCPM op-line

MEA: Gore 5720 (18 µm, 0.2/0.3 mgPt/cm2, I/C=1.2)DM/MPL: Pre-compressed SGL 25BC

ηtx,O2(dry)=26 mV

ηORR=410 mV

ηtx,H+ =18 mV

ηtx,O2(wet)=18 mV

kWg

cmW

cmmg

Pt

MEA

MEA

Pt

5.09.0

45.0

2

2

=

→ at 1.5 A/cm2:

H2/air (s=1.5/2), 150kPaabs, <50% RHinlet≈25µm membrane and ≈0.05/0.4mgPt/cm2

MEA

( 60 mV Rcontact)

from: W. Gu, D.R. Baker, Y. Liu, H.A. Gasteiger, in: Handbook of Fuel Cells, Wiley (2009): vol. 6, pp. 631.

( ηHOR < 5 mV*) )

undefined losses, ηtx,O2(wet), of only ≈20mV→ improvements require new materials

need 10x better ORR catalysts to reach 0.05/0.04 mgPt/cm2MEA → ≈0.1 gPt/kW


Pt Savings through High-Power Density

Toyota Mirai (2015): increase of power density from ≈0.9 to ≈1.5 W/cm2

→ decrease gPt/kW by ≈1.5-fold

requires improved mass-transport concepts (cascaded bipolar plate)




BEVs vs. FCEVs


Fuel Cell Cathode Catalyst Options

high mass activity [A/mgPt ] of Pt-based catalysts: → cost limited: need ultra-high TOF to meet gPt/kW

high volumetric activity [A/cm3electrode ] of non-Pt catalysts:

→ electrode thickness limited: need Pt-like turnover frequency (TOF)

TOF at 0.8V RHE 5)

(80°C, 100kPa O2)

4) H.A. Gasteiger & N.M. Marković, Science 324 (2009) 48

→ Fe/N/C based catalysts1)

→ nano-structured thin-films2)

& de-alloyed Pt-alloys3)

1) M. Lefèvre, E. Proietti, F. Jaouen, J.-P. Dodelet, Science 324 (2009) 71

→ shape-controlled Pt-alloys4)

3) K.C. Neyerlin, R. Srivasta, C. Yu, P.Strasser, J. Power S. 186 (2009) 261

2) M.K. Debe, A.K. Schmoeckel, G.D. Vernstrom, R. Atanasoski,

J. Power S. 161 (2006) 1002


Pt-Based ORR Catalysts – Status de-alloyed Pt-alloys (e.g., Strasser group TUB)1)

1) M. Oezaslan, F. Hasché, P. Strasser; J. Phys. Chem. Lett. 4 (2013) 3273

→ ≈5-fold mass-activity enhancement for core/shell-type nanoparticles

shape-controlled Pt-alloys (e.g., Markovic/Stamenkovic group at ANL)2

2) C.Chen, Y. Kang, Z. Huo, Z. Zhu, W. Huang, H.L. Xin, et al., Science (2014), doi: 10.1126/science.1249061

Pt3Ni octahedra → Pt3Ni nanoframes

→ highest A/mgPt for C-supported catalysts so far


Aging: Pt-Dissolution / Particle Growth

E/RHE [V]

Pt-foil, 196°C (H3PO4)

Pt/C, 80°C (H2SO4)

80°C Pourbaix (est.)

25°C Pourbaix

Pt dissolution during voltage cycling1)

1) P.J. Ferreira. G.J. la O’, Y. Shao-Horn, D. Morgan, R. Makharia, S.S. Kocha, H.A. Gasteiger, J. Electrochem. Soc. 152 (2005) A2256

→ Ostwald-ripening (nm) & diffusion (µm)

H2 + Pt2+

↓Pt + 2H+

membrane

carbonsupport

Pt Pt

Pt PtPt

Pt

Pt

Pt

PtPt

carbonsupport

Pt Pt

PtPt

PtPt

carbonsupport

PtPt

Pt2+

Pt Pt

H2

anod

e

Pt

Pt

≈10µm

timetime

cathode/DM interfacememb./cath. interf.

Diff

usio

n M

ediu

m (D

M)

cathode

Ptcarbonsupport

H2 + Pt2+

↓Pt + 2H+

membrane

H2 + Pt2+

↓Pt + 2H+

membrane

carbonsupport

PtPt PtPt

PtPt PtPtPtPt

PtPt

PtPt

PtPt

PtPtPtPt

carbonsupport

Pt Pt

PtPt

PtPt

carbonsupport

PtPt

PtPt PtPt

PtPtPtPt

PtPtPtPt

carbonsupport

PtPtPtPt

Pt2+

PtPt PtPt

H2

anod

e

PtPt

PtPt

≈10µm

timetimetimetime

cathode/DM interfacememb./cath. interf.

Diff

usio

n M

ediu

m (D

M)

cathode

PtPtcarbonsupportcarbonsupport

µm-scale Pt diffusion into ionomer

µm-scale Pt diffusion into ionomer

nm-scale Pt sintering on carbon

nm-scale Pt sintering on carbon

→ similar process for Pt-alloys ?


processes: - Pt dissolution → re-deposition on particles or in membrane- Co dissolution → re-deposition thermodynamically not possible

from: S. Chen, H.A. Gasteiger, K. Hayakawa, T. Tada,Y. Shao-Horn; J. Electrochem. Soc. 157 (2010) A82

hybridization with high-power battery to minimize Pt-dissolution

Aging: Pt-Dissolution / Particle Growth


Aging: Carbon Support Oxidation “start/stop” induced carbon-support oxidation: C + 2 H2O → CO2 + 4 H+ + 4 e-

air (O2)

air (O2)H2 start-upstart-up shutdownshutdown

≈1.4 - 1.6V≈1.4 - 1.6V≈1V≈1V air (O2)

anode

cathode

H2/air front at τ = 1.3s(80°C/66%RHin & 150kPaabs)

carbon-support instability largely addressed by system mitigation

e.g., T.A. Greszler, G.M. Robb, J.P. Salvador, B. Lakshmanan, H.A. Gasteiger; US 8,580,445 (2013)

200 nm

200 nm

new cathode: after start/stop:

→ 10-100x improvements:- short front times (≈0.1s)- partial stack-shorting at start/stop

→ 40,000 projected start/stops !

→ slow H2 bleed & recirculation→ <400 start/stops with H2/air-front

from: R.N. Carter, W. Gu, B. Brady, P.T. Yu, K. Subramanian, H.A. Gasteiger; Handbook of Fuel Cells; Wiley (2009) p. 829




BEVs vs. FCEVs


for >200 km range: BEVs with advanced batteries or FCEVs

Fuel Cells or Batteries ? comparison of the storage/conversion system mass

- battery: 0.20 kWh/kgbattery-system (80% battery utilization; 95% efficiency)- fuel cell: 70 MPa H2 and hybrid-battery

BEV

FCEV

BEV

FCEV

BEV

FCEV

150 km 500 km

from: F.T. Wagner, B. Lakshmanan, M.F. Mathias; J. Phys. Chem. Lett. 1 (2010) 2204


Summary & Acknowledgements

• fuel cell electric vehicles offer large range → requires improved catalysts→ renewable H2 generation & distribution infrastructure…

• battery electric vehicles → ≈150-200 km range with today’s LiB technology, ≈300 km feasible long-term→ 5 minute charging likely not feasible


Backup Slides


H2

H2O

O2H+

fast kinetics,1

≤ 0.05 mgPt/cm2slow kinetics

≈ 0.4 mgPt/cm2

H2-ox (HOR) @ anode

O2-red. (ORR) @ cathode

1) K.C. Neyerlin, W.B. Gu, J. Jorne, H.A. Gasteiger, J. Electrochem. Soc. 154 (2007) B631

Improved HOR catalyst for AMFCs!

mechanistic differences ?

2) W. Sheng, H.A. Gasteiger, and Y. Shao-Horn, J. Electrochem. Soc. 157 (2010) B1529

slow kinetics,inexpensive catalysts

slow kinetics,2

>> 0.05 mgPt/cm2

H2

H2O

OH− O2

Kinetics in PEMFCs and AMFCs


H2 Oxidation/Evolution: Acid vs. Base

1) J. Durst, A. Siebel, C. Simon, F. Hasché, J. Herranz, H.A. Gasteiger; Energy Environ. Sci. 7 (2014) 2255

HOR/HER on C-supported metals:→ ≈100-fold activity loss in base for all Pt-metals

→ analysis suggests increased M-H bond strength1)


HOR Mechanism: Acid vs. Base

1) D. Strmcnik, M. Uchimura, C. Wang, R. Subbaraman, N. Danilovic, D. Van der Vliet, A.P. Paulikas, V. Stamenkovic, N. Markovic; Nat. Chem. 5 (2013) 300

acid: H2 ↔ 2H+ + 2e-

base: H2 + 2OH- ↔ 2H2O + 2e-

overall reaction:

e.g., Tafel-Volmer mechanism:

Tafel: H2 ↔ 2Had

Volmer-acid: Had ↔ H+ + e-

Volmer-base: Had + OH- ↔ H2O + e-

→ acid/base differences rationalized by additional OH-nucleation step in base→ more hydrophilic surfaces suggested to be more active (e.g., Ir > Pt)1)


HOR Mechanism: Acid vs. Base

1) D. Strmcnik, M. Uchimura, C. Wang, R. Subbaraman, N. Danilovic, D. Van der Vliet, A.P. Paulikas, V. Stamenkovic, N. Markovic; Nat. Chem. 5 (2013) 300

acid: H2 ↔ 2H+ + 2e-

base: H2 + 2OH- ↔ 2H2O + 2e-

dissoc.: 2H+ + 2OH- ↔ 2H2O

overall reaction:

e.g., Tafel-Volmer mechanism:

Tafel: H2 ↔ 2Had

Volmer-acid: Had ↔ H+ + e-

dissoc.: H+ + OH- ↔ H2OVolmer-base: Had + OH- ↔ H2O + e-

→ acid/base differences rationalized by additional OH-nucleation step in base→ more hydrophilic surfaces suggested to be more active (e.g., Ir > Pt)1)

→ no obvious reason, why fundamental steps in acid and base should be different


→ carbon blacks (e.g., Super C65) as conductive additives

Example: LiCoPO4Spinel Oxides [2]Olivine Phosphates [1]

LiMPO4 (M = Fe, Co, Mn)High voltage spinel:

LiNi0.5Mn1.5O4 (LNMO)

[1] S. Wittingham, Chem. Rev. 104 (2004) 4271[2] D. Liu, RCS Adv. 4 (2014) 156

HV-Materials

stability of carbon-blacks & carbon-coatings at 5 VLi and effect of T and cH2O ?


(K. U. Schwenke et al., PCCP 15 (2013) 11830)C-electrode: 0.2 M LiTFSI in glymes

enhanced discharge capacity by contaminated/oxidized solvents and/or water

Effect of Contaminants

various contaminants avoid/delay surface passivation during discharge→ in pure electrolytes: passivating ≈2 ML thick films (≈500 µC/cm2

carbon )

0 500 1000 1500 2000 2500 30002.0

2.1

2.2

2.3

2.4

2.5

2.6

2.7

2.8

2.9

DME

PC/DME 2/1

1000 ppm H2O cont. DME

Cel

l Vol

tage

/ V

vs.

Li+ /L

i

Specific Capacity / mAhg-1carbon

H2O saturated O2 (2-3% vol. at RT)

0.1 M LiClO4 in DME, DME+H2O, and PC/DME( S. Meini et al., Electrochem. Solid-State Lett. 15 (2012) A45)

(S. Meini et al., J. Electrochem. Soc. 159 (2012) A2135)


(S. Meini et al., Electrochem. Solid-State Lett. 15 (2012) A45)

4000 3500 2000 1500 1000

0.2 M LiTFSI in diglyme

0.01 Abs

0.2 M LiTFSI in diglyme with water

0.001 Abs

Li2CO3 contamination LiOH

Abso

rban

ce

Wavenumber (cm-1)

Li2O2

10 11 12 13 14 15 16 17 18 19

LiOH*H2O

Li2O2

Al

Inte

nsity

/ a.

u.2θ / degree

0.2 M LiTFSI in diglymewith water

→ XRD & FTIR analysis of electrodes reveal Li2O2 and no/little LiOH

water effect in Li-O2 cells ?

initially assumed LiOH formation with H2O: 4Li+ + 4e– + H2O + O2 → 4LiOH

Li/O2 Discharge with 1% H2O


photometric titration using yellow [Ti(O2)]2+ complex

Li2O2 Discharge Yield with H2O

water substantially increases Li2O2 yield→ higher yield at faster rates ( ≡ shorter exposure time)

from: K.U. Schwenke et al., J. Electrochem. Soc. (2015) in press


previous observations: large Li2O2 crystals at low discharge rates


Li/O2 Discharge: Li2O2 Morphology

(B.D. Adams et al., Energy Environ. Sci. 6 (2013) 1772)





Li2O2 crystal growth only with H2O or H+



Fuel Options for Low-T Fuel Cells

• liquid fuels- direct methanol oxidation: low power density & high gnoble-metal/kW - hydrocarbon/alcohol reforming: low efficiency, startup energy loss

• H2+tank storage capacitykWh/kg kWh/l

*) based on the density of liquefied gas(from: P. Piela and P. Zelenay, Fuel Cell Review 1 (2004) 17)

(A. Bouza et al., DOE Annual Hydrogen Program Review (2004))

→ for 500km range (≈5 kgH2): ≈100 kg/≈150 l tank

+ tank

- 1.9 kWh/kgH2+tank ≡ ≈5%wt. H2 → 20 kg/kgH2

- 1.3 kWh/lH2+tank → 30 l/kgH2

70 MPa H2 tank:


Formation of Core/Shell Particles voltage-cycled Pt0.5Co0.5 particles

→ rPt increases by ≈1.5 nm: ≈1.5 nm Pt-skin ?→ spot-resolved EDS (dsampling ≈ 2.5nm)

× × × ×× × × ×

10 nm 10 nm

a) near membrane interface b) in cathode center

× × × ×× × × ×

10 nm 10 nm

a) near membrane interface b) in cathode center

→ formation of Pt(-rich) skins

Pt-alloys become more Pt-like

→ loss of specific activity

from: S. Chen, H.A. Gasteiger, K. Hayakawa, T. Tada,Y. Shao-Horn; J. Electrochem. Soc. 157 (2010) A82

hubert gasteiger at basf science symposium 2015

Science

charge range

limited range

range anxiety

plate energy

kwhnameplatebattery

libs lightweight matls

s technical data

passenger car