Prof. Linda Nazar at BASF Science Symposium 2015

Ludwigshafen, Germany

BASF 150th Anniversary Symposium

Amiens

NEW VISTAS IN ELECTROCHEMICAL ENERGY

STORAGE

March 9, 2015

Prof. Linda Nazar, FRSC

Senior Canada Research Chair

Electrochemical Energy Materials Laboratory

BASF International Scientific Network for Electrochemistry and Batteries

• Power consumption worldwide 2012: ~17 terawatts -> 28 terawatts by 2050

currently ~ 85% from the combustion of fossil fuels

• Solar: 23,000 TWy/yearlow percentage of renewable energy in global energy portfolio

Urban pollution, CO2 emissions → climate change

Finding Sustainable Energy Solutions

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• potential flood regions, Boston

Electrochemical energy storage: a key enabler

EV ↔ Grid

EV ↔ Home

Storage ↔ Grid

Off-peak capture essential

More important today than at any time in history: new large-scale demands

Future Na-ion

Ultracapacitors

Na/Li sulfur

Redox flow

Li-ion

Li sulfur/air

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Electrochemical Energy Science– past and future

Outline

Storing electrons and ions:- Intercalation chemistry

Storing electrons and ions:- Chemical transformations

Li-Sulfur and Li-Air cells

Conclusions

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Waterloo Institute for Nanotechnology and the

Quantum-Nano Centre

Rechargeable Li-ion Cells: Intercalation Batteries

in·ter·ca·lateinˈtərkəˌlāt/verb1. interpolate (an intercalary period) in a calendar.2. insert (something) between layers in a crystal lattice, geological formation, or other structure.

Capacity: Electrons stored per mass (mAh/g)

or volume (mAh/L)

Light weight/dense

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LiMO2 ↔ Li+ + electron + Li1-xMO2 (M= Ni, Mn,Co)

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1990 Intercalation Batteries: Chemistry Between the Sheets!

positive electrode: specific capacity around 180 mA•h/g @ voltage 3.9 V

Li-ion Storage in a Typical Electric Car Battery

700 Wh/kg (+ ve)

200 Wh/kg (full cell)

(electrons)

+

-

110 Wh/kg (pack)

2014 Draper Prize in Engineering for Li-ion Batteries

John Goodenough pictured with fellow Draper Prize recipients Akira Yoshino, Yoshio Nishi and Rachid Yazami at the award reception in February, 2014.

John Goodenough Wins Engineering’s Highest Honor for Pioneering Lithium-Ion Battery

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• Poor accessibility of the world’s largest lithium reserves• remote locations• political factors (new Li sources: Bolivia; Afghanistan)

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vs

0.3V penalty vs Li; higher mass Greater volume change on during cycling

• Popular in the 80’s (before mobile tech)L.F. Nazar et al., Below Lithium-Ion: The Emerging Chemistry of Na-ion Batteries for Electrochemical Energy Storage, Angewandte Chemie, 2015

Below Li-ion: Coupling to Renewable Energy

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Below Li-ion: Sodium Metal Layered Oxides and Phosphates

Ellis, Nazar et al., Nature Mater., 6, 749 (2007);

Discharged(reduced)Na2FePO4F

Charged(oxidized)NaFePO4F

-Na+/e-Langrock et al., J.P.S., 223, 62 (2013)

Figure 1. Schematic presentation of the P2-

NaxMO2 crystal structure

Na2FePO4F

Na+Li+

0.36 eV, 2-D ion transport

Activation energy for Na+ mobility lower than in many Li-ion metal phosphates

Activation barrier: 0.67 eV 1-D ion transport

Comparisons of alkali-ion mobility

LiFePO4

Tripathi, Gardiner, Islam, Nazar. Energy. Environ. Sci., 6, 2257 (2013)

→ Na+ diffusion coefficient : equal to LiCoO2

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High Voltage Na-ion Batteries : Na4NiP2O7F2

Voltage: ~ 5V2160 Wh/L (+ ve)

5V vs Na → suitable negative electrode, electrolyte → high power

~ 600 Wh/L full cell

Measured: Ea = 0.32 eV

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Computation

Kundu, Tripathi, Nazar, Chem Mater, 2015

Enroute to a Solid State Battery

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From MRS Bulletin, Dec 2014:Solid State Batteries enter EV FrayToyota roadmap suggests all solid-state batteries are an important step in the evolution of batteries for electric vehicles, but are not the ultimate solution. Figure courtesy of H. Iba (Toyota Motor Corporation)

Schematic of an all-solid state battery

Na4NiP2O7F2

NaSICON

Source: P.G. Bruce et al., Nature Mater., 11, 19 (2012)

Gasoline: 12000 Wh/kg

Source: P.G. Bruce et al., Nature Mater., 11, 19 (2012)

not much has changed: not true!

no Moore’s law (# transistors on an IC doubles every 2 years): true!

Misconceptions About Energy Storage Batteries

Higher energy density - better EV range at lower cost - reduced dependence on fossil fuels - less CO2 emission

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25% efficient

> 90% efficient

"storage" via low-cost intercalation chemistry is limited

Potential Generation 3 (or 4) Batteries: Lithium-Sulfur; Lithium-Oxygen

Beyond Li-ion Intercalation: Chemical Transformations

oxygen

Li-O2 Batteryproduct: Li2O2

stored in host cathode

O2 + 2 Li+/e- ↔ Li2O2

Theoretical: 3500 Wh/kgPractical: ~ 1000 Wh/kg

H+

oxygen

Li-S Batteryproduct: Li2Sstored in host cathode

S2 + 4 Li+/e- ↔ 2Li2S

Theoretical: 2500 Wh/kgPractical: ~ 600 Wh/kg

Resources of elemental sulfur (volcanic deposits, sulfur associated with natural gas, petroleum, tar sands, and metal sulfides: about 5 billion tons.

http://minerals.usgs.gov

$170/ton

Sulfur: a low cost, abundant element

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Canada is the world’s largest exporter of sulfur

Lit

hiu

m

Se

pa

rato

r

Li+

2 Li+

Li+Li2S8

a(Li2S6) + b(Li2S4)

(Li2S)

e-e-

Discharge

—maintain active mass? Li2S

Li2Sx Li2Sx/2

Charge Polysulfide shuttle

internal “short circuit”

2Li + S Li2Sx Li2S theoretical capacity 1675 mAh/g @ 2V

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Beyond Li-ion Intercalation: The Li-S Battery

2500 Wh/kg (full cell)500 - 1000 mAh/g today

-> 350 Wh/kg

Lit

hiu

m

cheese milk cheese

Space is precisely tuned to accommodate swelling of S to Li2S

Electrical Conductivity: sulfur: negligiblecarbon/sulfur: 0.21 S/cm

Mesoporous carbon

Molten S within pores( incomplete Filling)

C/S – 70 wt%

Li2S formed in close electrical contact with carbon - enables recharge

Solidification

D. Ji, K T Lee, L.F. Nazar, Nature Mater., 8, 500 (2009)

Cathode: S (elemental) + 4 Li+ + 4 e- ↔ 2Li2S Anode: 4Li ↔ 4Li+ + 4e-

Revitalization of Li-S Battery Chemistry

How Li-S battery chemistry works

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Bimodal nanostructured carbon cathode hosts - Li-S cells

Schuster, He, Bein, Nazar; Angew Chemie, (2012)He, Schuster, Mandelbrot, Bein, Nazar, Chem. Mater (2014)He, Nazar; ACS Nano (2013)Cuisinier, Balasubramanian, Nazar, J. Phys. Chem Lett (2014)Cuisinier, Balasubramanian, Nazar, Adv. Energ. Mater (2014)

For 1000 mAh/g capacity:

1400 Wh/kg based on total mass of cathode (S + carbon + binder)

2330 Wh/l volumetric for cathode

600 – 800 Wh/kg for a full cell

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In situ cell: synchrotron

0 20 40 60 80 1000

200

400

600

800

1000

1200

1400

1600

Co

ulu

mb

ic E

ffic

ien

cy (

%)

Cap

acit

y (m

Ah

/g)

Cycle Number

0

20

40

60

80

100

C/20

C/5

C/2 1C

Stable cycling

Bimodal nanostructured carbon cathode hosts - Li-S cells

Discharge/charge in 5 hours

The Problem with Carbon Good interaction with sulfur

No interaction with lithium polysulfides OR Li2S

Li

Charge- +

Li X / solventLi2S

Shuttle MechanismLi

Discharge

Self discharge

X

LiX/ solvent

Li2Sn (polysulfide) intermediates:

Soluble in the electrolyte physical entrapment not sufficient

Sulfur

The Problem with Porous Carbon

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Cuisinier, Balasubramanian, Nazar, J. Phys. Chem Lett (2014)

Tailoring the Surface Interaction: Oxides

Yi Cui et al., Nature Commun., 4, 1331, 2012

Q. Pang, L.F. Nazar, et al., Nature Comm., 5:4759, 2014

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Ti4O7

Metallic Ti4O7 : 2-in-1 host

Half the capacity fade rate compared to carbon

High electronic conductivity delivers electrons to S and Li2S High surface area and pore volume bind sulfur/polysulfide Surface properties inhibit polysulfide diffusion into the electrolyte

Insulating SiO2 or TiO2

L.F Nazar et al., Nature Commun., 2:325, 2011; J. Phys. Chem.

C., 116, 19653 (2012); Adv. Energ. Mater., 2, 1490 (2012)

Conductive VOx

X.Y Tao, W.K. Zhang, Yi. Cui, et al., Nano Lett., 14, 5288, 2014

Bifunctional polysulfide sponges: High electronic conductivity (metallic) hydrophilic nature for binding lithium polysulfides

Ti4O7 crystals

carbon

200 nm

Nanocrystalline (10 -20 nm)

Ti4O7 - a metallic oxide with a hydrophilic surface

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During discharge: Much lower fraction of polysulfides at all stages (efficient trapping) Li2S precipitates earlier and more progressively

Solid: Ti4O7/SDash: C/S

Ti4O7-polysulfide interaction promotes charge transfer

Operando XANES: Ti4O7/S cathode shows strong interaction

Ti-Ox e- e- e- e-

S8 Li2Sx2-

Ti4O7

e- e-

Solvated Li+

“adsorbed” Li2S

e-

Sulfur reduces and adsorbs on metallic oxide surface → “adsorbed” Li2S

Sulfur reduced and dissolves to form solvated lithium polysulfides→ Li2S isolated from electron wiring

Carbon e- e- e- e-

S8

Solvated Li+

Li2Sx2-

Carbon

“disconnected”Li2S

disproportionationUpon electrochemical reduction (receiving e- and Li+):

• Uniform deposition of Li2S• Suppress polysulfide diffusion/shuttle• Improved capacity retention

Q. Pang, D. Kundu, M. Cuisinier, L. F. Nazar, Nature Comm, 5 : 4759 (2014)

Ti4O7 - surface enhanced electrochemistry

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Tuning the Sulfur-Host Interaction: Functional Layered Materials

X. Liang, L.F. Nazar, et al., Nature Comm., 5:5682, 2015

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δ-MnO2

Mn3+ Mn2+Mn3+ Mn2+

catenate

Longevity (> 1500 cycles) now attainableTailor surface properties to bind (poly)sulfide

Y. Qiu, Y. Zhang, et al., Nano. Lett., 4827, 2014

- graphene oxide- N-doped graphene

MnO2 nanosheet sulphur hosts: accomodate high sulfur loading

δ MnO2– birnessite – nanosheets 10 nm thin

100nm

75 wt % sulfur/ “inorganic graphene”

melt diffuse sulphur =>

S map Mn map

Glass cell: Visual evidence of polysulfide trapping by MnO2

Comparison with sulfur/carbon electrode with same sulfur loading

S/KB cell

S/MnO2 nanosheet cell

0 hr 0.5 hr 4 hr 8 hr 12

hr

Almost colorless solution for S/MnO2 electrode at point of max LiPS formation

Interaction between MnO2 and polysulfide

B. Catenation of sulfur to form polythionate complex

A. Formation of thiosulfate via oxidation of LiPS/ reduction of Mn4+:

S/KB cell

S/MnO2 nanosheet cell

0 hr 0.5 hr 4 hr 8 hr 12 hr

Interaction between polysulfide and MnO2 or graphene oxide

Li2S4

Li2S4/MnO2

Li2S4/Grapheneoxide

Li2S4/Graphene

At 2.3 V: partial reduction or oxidation

Li-S/MnO2 cell cathodeSB (0)

ST (-1)

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Polysulfide Adsorptivity of Sulfur Hosts

• Non-polar materials (carbons) adsorb much less Sn2- compared to

polar materials (metallic oxides etc)

C. Hart, M. Cuisinier, L. Nazar et al. Chem Comm, 2015, DOI: 10.1039/C4CC08980D

Electroanalytical determination of residual polysulfide

0 40 80 120 160 2000

200

400

600

800

1000

1200

1400

1600

Cap

ac

ity (

mA

h g

-1)

Cycle number

MnO2 nanosheets: long term cycling

Capacity fade rate = 0.04% per cycle over 2000 cycles

Equivalent to some“conventional” lithium metal oxide cells

Challenge remains: sulfur loading & Li negative electrode

X. Liang, A. Garsuch, T. Weiss, L.F. Nazar*, Nature Commun., 5:5682, 2015

Cycling in 5 hours

vv

0 200 400 600 800 1000 1200 1400 16000

200

400

600

800

1000

1200

1400

1600

Charge

Discharge

Ca

pa

cit

y (

mA

h g

-1)

Cycle number

C/2

Cycling in 2 hours….over 2/3 year

In collaboration with BASF

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A Roadmap for Li-S cell design

all solid state batteries

sulfur/polysulfides

chemical confinementstrong interactions of sulfides with conductive host

highly solvating

electrolytes

“Catholyte” cells*redox flow

Nazar, et al.,

Adv Energy Mater, 2015

non-solvent

electrolytes

*high capacity*interface challenges

Nazar, et al.,

Energy Environ Sci, 2014

Looking to the future

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All-solid-state batteries (Li, Na, Li-S, etc) have in common with Lithium-air the requirement of strict control of interfaces

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O2 + 2 Li+/e- ↔ 2 LiO2 → Li2O2 + O2

Many challenges in the Li-O2 cell

Eo = 2.96 V

2

2.5

3

3.5

4

4.5

5

0 500 1000 1500 2000 2500 3000

Po

ten

tia

l /

V

Capacity / mAh g-1

Δηa

ΔEOCP

Electrolyte reactivity

carbon

Poor round trip efficiency; poor cycling; sensitivity to CO2…

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Reactivity of the intermediate (equivalent to polysulfides) Need robust surface and electrolyte

Reactivity of the electrolyte with peroxide on charge Need a better electrolyte!

Reaction of lithium peroxide with carbon on charge C + Li2O2 + ½ O2 Li2CO3

Need a metallic, nanoporous, non-carbon catalytic surface

Many challenges in the Li-O2 cell

O2 + 2 Li+/e- ↔ 2 LiO2 → Li2O2 + O2

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Significant progress on cathode supports..

Nanostructured Ti4O7: Metallic Oxide Cathode Host

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Electrochemistry of a metallic Magnéli-phase Ti4O7 cathode in a Li-O2 cell onset of oxygen evolution at equilibrium potential (2.96 V vs Li/Li+)

D. Kundu, R. Black, B. Adams, Energy & Environ. Science, 2015

Ti4O7

On-line mass spectrometry: gas evolution during charge of a Li-O2 cell

Energy storage: one component of energy management

Battery materials/electrochemistry is remarkably multifaceted▪ Complex chemistry at both electrodes; in electrolyte/at interfaces▪ Sophisticated in-situ methods developed to peer into working cells

Not one energy storage battery that fits all needs ▪ transportation

- Li-ion; future: Li-S; Li-O2 (?)▪ grid/mini-grid

- Na-ion (non-aqueous, aqueous); Na-O2, Mg-ion

Energy management needed for the next decade: combination of▪ energy conversion (photovoltaics, solar fuels..)▪ energy storage ▪ energy efficiency via electrochromic windows, LED lighting, software control…

Infrastructure (smart grids) to network the system

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Brian Adams

Thank You!

BASF International Scientific Network for Electrochemistry and Batteries

Prof. M. Wagemaker, TU Delft (Netherlands)Dr. Mali Balasubramanian, Argonne NL, USA

Prof. M. Saiful Islam, Univ Bath, UKProf. T. Bein, LMU Munich, Germany

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THANKS TO:

Happy 150th Anniversary BASF! ….from Waterloo Institute of Nanotech

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