P.I.: K. AmineL. Curtiss, Jun Lu

Argonne National LaboratoryDOE merit review

June 10 , 2016

This presentation does not contain any proprietary, confidential, or otherwise restricted information.

Development of Novel Electrolytes and Catalysts for Li-Air Batteries

Project ID# ES286

2

Start: 2014 Finish: 2018 60%

Barriers addressed– Cycle life– Capacity– Efficiency

• Total project funding– DOE share: 1200– Contractor 0

• FY 14: $ 400 K• FY 15: $ 400 K• FY 16: $ 400 K

Timeline

Budget

Barriers

• Interactions/ collaborations• Y K. Sun, Korea• S. Vajda, ANL• S. Al-Hallaj, UIC• D. Miller, ANL• Y. Wu, Ohio State University

Partners

Overview

3

Project Objectives and Relevance

Development of Li-air batteries with increased capacity, efficiency, and cycle life through use of new electrolytes that act in conjunction with new cathode architectures

Use an integrated approach based on experimental synthesis and state-of-the-art characterization combined with high level computational studies focused on materials design and understanding

Li-air batteries have the potential for very high energy density and low cost

4

MilestonesMonth/Ye

ar Milestones

Dec/15Development of new cathode materials based on Pd nanoparticles and ZnOcoated carbon that can improve efficiency of Li-O2 batteries through control of morphology and oxygen evolution catalysis. Completed.

Mar/16Investigation of use of catholytes to control the lithium superoxide content of discharge products of Li-O2 batteries to help improve efficiency and cycling. On schedule.

Jun/16Computational studies of electrolyte stability with respect to superoxide species and salt concentrations for understanding and guiding experiment. On schedule.

Sep/16Investigations of mixed K/Li salts and salt concentration on the performance of Li-O2 batteries with goal of increasing cycle life. On schedule.

Strategy: an integrated experiment/theory approach that combines testing, understanding and design to develop cathodes and electrolytes for Li-O2

batteries

Test new Li-air battery cathode architectures (catalyst, supports)

Develop an understanding of the discharge and charge mechanism from theory and experiment

Cathode Development

Design of improved cathode for efficiency, cycle life, and capacity

Test new Li-air battery electrolytes

Develop an understanding of the reasons for electrolyte failure from theory and experiment

Design of improved cathode for efficiency, cycle life, and capacity

Electrolyte Development

Cathode development has been the major priority of the project so far as our strategy is to control charge overpotentials and then work on electrolytes

6

Experimental methods

Synthesis New catalyst materials New carbon materials Electrolytes

Characterization In situ XRD measurement (Advanced Photon Source) TEM imaging (ANL Electron Microspopy Center) FTIR, Raman SEM imaging

Testing Swagelock cells

7

Highly accurate quantum chemical modeling

Periodic, molecular, and cluster calculations using density functional calculations Static calculations Ab initio molecular dynamics simulations Assessment with high level theories (e.g. G4 theory)

Understanding discharge products Li2O2 structure and electronic properties LiO2 structure and electronic properties

Design of electrolytes Reaction energies and barriers for stability screening Ion pair formation Electrolyte/surface interface simulations

Design of oxygen reduction and oxygen evolution catalysts Density of states Adsorption energies

8

Technical AccomplishmentsCathode materials I. Lithium peroxide based discharge products: discovered cathode materials

with improved catalysts for Li2O2 formation and decomposition with improved efficiency and longer cycle life

II. Lithium peroxide/superoxide discharge products: Discharge product characterization has led to cathode materials that stabilize LiO2 in the discharge product, which provides a new way to reduce charge overpotential Has led to the first lithium superoxide based battery

ElectrolytesIII. Screening methods for finding electrolytes with greater stability that will

be used in future electrolyte developmentIV. Enhanced Li anode lifetime in Li-O2 batteries through mixed K/Li salts

New cathode materials: Characterization of Pdnanoparticles on ZnO-passivated carbon

• Transmission electron microscopy (TEM) show crystalline nanoparticles decorating the surface of the ZnO-passivated porous carbon support in which the size can be controlled in the range of 3–6 nm, depending on the number of Pd Atomic Layer Deposition (ALD) cycles.

• The ZnO-passivated layer effectively blocks the defect sites on the carbon surface, minimizing the electrolyte decomposition

TEM

SEM images

1c-Pd/2c-ZnO/C 3c-Pd/2c-ZnO/C 10c-Pd/2c-ZnO/C

New cathode materials: Discharge results for Pdnanoparticles on ZnO-passivated carbon

Discharge performance

XRD of discharge product

• Oxygen reduction reaction during discharge in the Li-O2 cell is significantly altered when Pdnanoparticles on ZnO-passivated carbon are used as the electrocatalyst as evidenced by the higher capacity in the case of 3c and 10c ALD-Pd samples

• Also leads to a different morphology of the discharge products

2c-ZnO/C 1c-Pd/2c-ZnO/C

3c-Pd/2c-ZnO/C 10c-Pd/2c-ZnO/C 3c-Pd/5c-ZnO/C

New cathode materials: Voltage profile of Pdnanoparticles on ZnO-passivated carbon

• Compared to the ZnO/C cathode, the ZnO-passivated greratly reduces the charge overpotential!

12

0

　

0 100 200 300 400 5000.00.51.01.52.02.53.03.54.04.55.0

Mo2C/CNT

Voltag

e (V

)

Specific capacity (mAh gtotal-1)

1st cycle 10th cycle 30th cycle 50th cycle 70th cycle 100th cycle

b

0 30 60 90 120 1500

100200300400500

Spec

ific

cap

acity

(mA

h g

tota

l-1)

Number of cycles (#)

discharge charge

2Li++O2+2e- → Li2O2 (Eo = 2.96 V)

C-K edgeLi-K edge

Mo-M edge

b

50 nm

0 100 200 300 400 5002.0

2.5

3.0

3.5

4.0

4.5

(b) cycle 1 cycle 2 cycle 3 cycle 4 cycle 5 cycle 6 cycle 7 cycle 8 cycle 9 cycle10

Vol

tage

(V)

Specific Capacity (mAh/g)

Pd/Al2O3/CLu et al, Nature Communications, 2013

Mo2C/CNTKwak et al, ACSNano, 2015

• Nanocrystalline discharge products promotes electronic conductivity and lower charge overpotentials

• Small Li2O2 particles promotes low charge potentials, longer cycle life

New cathode materials: Other cathode materials we have found that give low charge potentials

New cathode materials: Explanation for Pd results

e-

Grain boundary: amorphous LiO2 or Li2O2(spin, short O-O distances, conducting)

Grains: crystalline Li2O2

DFT calculations for a model of nanocrystalline Li2O2

Li2O2 grain

Li2O2 grain boundary

e-

Carbon cathode

• Nanocrystalline lithium peroxide discharge product may provide good electronic conductivity for charge

• Can LiO2 be incorporated into discharge product to increase electronic conductivity?

13

14

In a series of papers1-3 we have shown that a Li-O2 battery based on an activated carbon cathode can result in a discharge product containing both lithium peroxide and lithium superoxide.

Faster discharge rate and slow disproportionation kinetics more LiO2-component (lower charge overpotential)

1. Zhai, D. et al., J. Phys. Chem. Lett. (2014).2. Zhai, D. et al., J. Am. Chem. Soc. (2013).3. Yang, J. et al., Phys. Chem. Chem. Phys.

(2013)

Stabilization of LiO2: Background

Raman peak at 1125 cm-1 (S1) is evidence for more LiO2-like component at faster discharge current densities

~1 μma

~1.5 μm

c

b

200 nm

d

200 nm

f

200 nm200 600 1000 1400 1800

200 600 1000 1400 1800

c 0.05 mA/cm2 GD

S2S1

P2

Raman shift /cm-1

Inte

nsity

/ a.

u.

P1

b 0.1 mA/cm2

a 0.2 mA/cm2

30 40 50 60 70

30 40 50 60 70

(110

)

(101

)

d 0.2 mA/cm2

(100

)

e 0.1 mA/cm2Li2O2

Carbon paper

Inte

nsity

/ (a.

u.)

f 0.05 mA/cm2

2θ

15

In our latest paper1 on this topic we have found that interfacial effects can suppress disproportionation of a LiO2 component in the discharge product.

High-intensity X-ray diffraction and transmission electron microscopy measurements are first used to show that there is a LiO2 component along with Li2O2 in the discharge product

Stabilization of LiO2: Evidence for LiO2 in discharge product

h

20 1/nm

TEM image of toroid from activated carbon cathode

Electron diffraction pattern of toroid showing LiO2 crystal structure

16

The stability of the discharge product was then probed by investigating the dependence ofthe charge potential and Raman intensity of the superoxide peak with time.

The results indicate that the LiO2 component can be stable for possibly up to days when anelectrolyte is left on the surface of the discharged cathode

Stabilization of LiO2: Ageing of discharge product from activated carbon

17

Density functional calculations on amorphous LiO2 reveal that the disproportionation process will be slower at an electrolyte/LiO2 interface compared to a vacuum/LiO2 interface.

Stabilization of LiO2: Effect of electrolyte from DFT calculations

(C)

Ab initio molecular dynamics simulations: fast desorption of O2 occurs from amorphous surface in vacuum (left); presence of electrolyte slows down desorption of O2 (right)

Templated nucleation and growth of crystalline LiO2

LiO2

Ir3Li

Stabilization of LiO2: Templated growth

1. Lu et al, Nature, 2016, 529 377-382.

Our studies1 have revealed an approach to electrochemically synthesize LiO2 The lattice match of crystalline LiO2 with a Ir3Li intermetallic component of

the cathode can act as a template for electrochemical nucleation/growth ofcrystalline LiO2

Stabilization of the LiO2 is due to formation of crystalline LiO2 and the presence of an electrolyte at the interface

Performance of LiO2 in a Li-O2 battery was as good (efficiency, cycle life) as Li2O2 based Li-O2 batteries and opens up new opportunities

0 200 400 600 800 10002.0

2.5

3.0

3.5

4.0

4.5

5.0

1 5 10 20 30 39

Vol

tage

[V]

Specific Capacity [mAh/g]

0 5 10 15 20 25 30 35 40700

800

900

1000

Capa

city

[mAh

/g]

Cycle Number

Charge Capacity Discharge Capacity

Voltage profile for Ir-rGO cathode

Characterization of Ir-rGO discharge product from experiment and theory

EPR spectrum consistent with LiO2

XRD shows LiO2 peaks and no Li2O2

2.5 3.0 3.5 4.0 4.5

Ir (2

00),

Li2O 2 (0

04)

Li2O 2 (1

01)

LiO 2 (0

20)

Ir (1

11),

Li2O 2 (1

02)

Li2O 2 (1

10)

C Ir (2

20)

Rela

tive I

nten

sity

[a.u

.]

2θ [degree]

20th discharge 2nd discharge - after 7 days 2nd discharge - after 12 hrs 1st discharge - after 7 days 1st discharge - after 12 hrs

Li2O 2 (1

03)

CLi

O 2 (120

)Li

O 2 (111

)

200 400 600 800 1000 1200 1400 1600 1800

(LiO2)1123

Wavenumber [cm-1]

Ir-rGO -- 1st discharge(LiO2-C)1505

(LiO2-C)1505

Coun

t

Ir-rGO -- 2nd discharge (LiO2)1123

Raman shows LiO2 peaks

Differential electrochemical mass spectrometry (DEMS) shows 1 e per O2 on charge and discharge

• Much evidence for LiO2 (and no Li2O2) for the Ir-rGO cathode19

• Solvent molecules require ~4.5 V oxidative stability and ~1.0 V reductive stability

H3CO

CH2

H2C

OCH3

Dimethoxy Ethane (18)

Hydrogen abstraction reactions by OH radical, (Li2O2)4, (LiO2)4, and superoxide arethermodynamically favorable in solution

Predictions of electrolyte stability: examples of computational screening

Rajeev Assary

Electrolyte: TEGDME + salt mixtures • 1K : 1 M KCF3SO3• 0.8K0.2Li: 0.8 M KCF3SO3 + 0.2 M LiCF3SO3• 0.5K0.5Li: 0.5 M KCF3SO3 + 0.5 M LiCF3SO3• 0.2K0.8Li: 0.2 M KCF3SO3 + 0.8 M LiCF3SO3• Li: 1 M LiCF3SO3Cathode: Graphitized Carbon Black (no catalysts)Anode: Li metal

0 100 200 300 400 500

2.5

3.0

3.5

4.0

4.5 1 3 5 10 15

Volta

ge [V

]

Specific Capacity [mAh/g]

1K

0 2 4 6 8 10 12 14 16300

400

500

600

Spec

ific C

apac

ity [m

Ah/g

]

Cycle Number

Charge Discharge

0 100 200 300 400 500

2.5

3.0

3.5

4.0

4.5

1 2 3 4 5 6

Volta

ge [V

]

Specific Capacity [mAh/g]

1Li

0 1 2 3 4 5 6300

400

500

600

Spec

ific C

apac

ity [m

Ah/g

]

Cycle Number

Charge Discharge

0 100 200 300 400 500

2.5

3.0

3.5

4.0

4.5 1 3 5 10 15 19

Volta

ge [V

]

Specific Capacity [mAh/g]

0.2K0.8Li

0 5 10 15 20300

400

500

600

Spec

ific C

apac

ity [m

Ah/g

]

Cycle Number

Charge Discharge

0 100 200 300 400 500

2.5

3.0

3.5

4.0

4.5 1 3 5 10 20 26

Volta

ge [V

]

Specific Capacity [mAh/g]

0.5K0.5Li

0 5 10 15 20 25300

400

500

600

Spec

ific C

apac

ity [m

Ah/g

]

Cycle Number

Charge Discharge

0 100 200 300 400 500

2.5

3.0

3.5

4.0

4.5

1 3 5 10 20 30 37

Volta

ge [V

]

Specific Capacity [mAh/g]

0.8K0.2Li

0 5 10 15 20 25 30 35300

400

500

600

Spec

ific C

apac

ity [m

Ah/g

]

Cycle Number

Charge Discharge

Capacity-controlled cycles (500 mAh/g) • Cyclabilities and coulombic efficiencies are increased!

• 0.8K0.2Li has the best cyclability (37 cycles vs. 5 cycles for 1Li)• Charge potentials are slightly reduced

• Catalysts are still necessary

Mixed K/Li salts: The effect of salts on the performance of a Li-O2battery

Response to last year reviewer’s comments

The comments needing responses are listed below:

Comment: “Palladium (Pd) and molybdenum carbide (Mo2C) catalysts are expensive, the reviewer observed, recommending that cheaper alternatives be developed and the result be demonstrated in a full cell configuration.”

Response: Once we have achieved cathodes materials with good cycle life and low charge potential we will work on cheaper alternative

Comment: “Noting that development of new electrolytes and cathodes was proposed, the reviewer saw no strategy explained for developing materials nor what sort of materials were envisioned.”

Response: Our strategy might not have been well explained in the previous review. On slide 5 we have clarified our strategy. We note that this strategy has resulted in new cathode materials with reduced charge overpotentials and longer cycle life.

Collaborations with other institutions and companies

23

• S. Vajda, ANL• Development of new cathode materials based on supported size-selected

metal cluster• S. Al-Hallaj, UIC

• Characterization of discharge products and cathode materials • D. Miller, ANL

• TEM characterization of discharge products and catalysts• Y. Wu, Ohio State University

• Development of electrolytes for Li-air batteries.• Y K. Sun, Korea

Development of new cathode materials based on metal nanoparticles and novel carbons

24

New catalysts developed in this project provide the basis for improvement of efficiency, cycle life, and capacity of Li-air batteries using a combined experiment/theory approach Determine the cause of degradation of the electrolytes and

catalysts in these cathode materials that seems to limit performance

Design new electrolytes that are more stable in the Li-O2batteries

Synthesize, test, and evaluate new electrolytes and catalysts for Li-air batteries

Design new cathode materials that do not degrade in the Li-O2 batteries

Proposed Future Work

25

SummaryCathode materials I. Lithium peroxide based discharge products: discovered cathode materials

with improved catalysts for Li2O2 formation and decomposition with improved efficiency and longer cycle life

II. Lithium peroxide/superoxide discharge products: Discharge product characterization has led to cathode materials that stabilize LiO2 in the discharge product, which provides a new way to reduce charge overpotential Has led to the first lithium superoxide based battery

ElectrolytesIII. Screening methods for finding electrolytes with greater stability that will

be used in future electrolyte developmentIV. Enhanced Li anode lifetime in Li-O2 batteries through mixed K/Li salts