Investigation of Lithium Superoxide-Based Batteries

P.I.: K. Amine L. Curtiss Argonne National Laboratory DOE merit review June 1-4, 2020

Project ID# BAT-431 This presentation does not contain any proprietary, confidential, or otherwise restricted information. Overview

Timeline Barriers ▪ Start: 2019 ▪ Barriers addressed ▪ Finish: 2023 – Cycle life ▪ 60 % – Capacity – Efficiency

Budget Partners • Total project funding • Interactions/ collaborations – DOE share: $ 1280 K • M. Asadi, IIT – Contractor 0 • S. Al-Hallaj and B. Chaplin, UIC • FY 18: $ 400 K • J. G. Wen, ANL • FY 19: $ 450 K • K. C. Lau University of • FY 20: $ 430 K California-Northridge • M. Asadi, IIT 2 Project Objectives and Relevance

▪ Investigation of Li-O2 batteries based on lithium superoxide to achieve understanding of discharge chemistry and how to enhance cycle life. ▪ 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 based on lithium superoxide have the potential for being the basis for closed systems

without need for an external O2 source

3 Milestones

Month/ Milestones Year

Characterization of electronic properties of high temperature Jun/20 synthesized Ir3Li, (Completed)

Voltage profiles and characterization of discharge product by titration Sep/20 and other techniques in an Ir3Li cell, (Completed)

TEM studies of large LiO particles, investigation of stability and Dec/21 2 formation mechanism, (Completed)

Investigate performance of Li-O battery using cathode based on bulk Mar/21 2 high temperature synthesized IrLi particles on rGO support, (Initiated)

4 Strategy: an integrated experiment/theory approach that combines testing, understanding and design to develop

lithium superoxide based Li-O2 batteries

Synthesize, test, and Evaluate solvents, salts, and characterize cathode additives architectures

Develop Develop understanding of understanding of the the synergies between discharge and charge electrolyte components mechanisms and cathode

Design of improved cathodes/electrolytes for efficiency, cycle life, and capacity Experimental methods

Synthesis ▪ New catalyst materials ▪ Electrolytes

Characterization ▪ In situ XRD measurement (Advanced Photon Source) ▪ TEM imaging ▪ FTIR, Raman ▪ SEM imaging ▪ Impedance measurements ▪ Titration

Testing ▪ Swagelok cells 6 Highly accurate quantum chemical modeling

▪ Periodic, molecular, and cluster calculations using density functional calculations ▪ Static calculations ▪ Ab initio molecular dynamics simulations (AIMD) ▪ Understanding discharge products

▪ Li2O2 structure and electronic properties

▪ LiO2 structure and electronic properties ▪ Design of electrolytes ▪ Reaction energies and barriers for stability screening ▪ Electrolyte/surface interface simulations

7 Background

▪ Previous studies of lithium superoxide based Li-O2 batteries have been based on Ir nanoparticles on a reduced graphene oxide (rGO)

cathode that partially form Ir3Li during cycling, which act as templates for growth of LiO2 instead of the more stable Li2O2 product – Ir nanoparticles and different sizes : Lu, Amine, Curtiss, et al Nature 529, 377 (2016).

– Size selected Ir clusters (Irn, n = 2-8) Lu, Vajda, Amine, Curtiss et al J. Phys. Chem A 123, 10047 (2019). – In both cases Li is partially incorporated into Ir particles during discharge ▪ In this work we have synthesized (at high temperatures) and

characterized bulk IrLi3 and IrLi alloys using a high temperature method to use in LiO2 batteries

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1. Characterization of electronic properties of Ir3Li particles relevant to use as catalysts in Li-O2 cells

– Bulk Ir3Li was found to have comparable conductivity to iridium metal – Possess metal-like magnetic properties, and have an affinity toward

O2.

2. Micron sized Ir3Li particles are used to stabilize large LiO2 particles of over 200 nm for first time

– Use of large Ir3Li particles in a Li-O2 cell promotes a nucleation and growth mechanism that results in large ultra-nanocrystalline LiO2 particles in the discharge product

– The large LiO2 particles are more stable than previously grown small LiO2 particles in Li-O2 cells

3. IrLi alloy found to give good cycling performance in a Li-O2 cell with LiO2 as the discharge product

– 100 cycles with confirmation of LiO2 as a product a * Ir * * Ir3Li *

100 150 200 250

* * Relative Intensity

100 200 300 400 500 600 Raman Shift (cm-1)

a * Ir b * * Ir3Li -1 ~128 cm ~138 cm-1 ~433 cm-1 ~435 cm-1 (A ) (A ) (A ) * 1 2 (B1) 1 Ir-Li coupled Li 100 150 200 250 vibration modes

Characterization of Bulk Ir* 3Li Synthesized* at High

Phonon Phonon Density of States (PDOS) Temperatures (500 nm toRelative Intensity 5 microns): Raman spectroscopy

and100 stability200 300 400 500 600 0 100 200 300 400 500 600 -1 Raman Shift (cm ) Phonon Frequency (cm-1) a * Ir b c Initial Test * * Ir3Li 12 hr Air Exposure 96 hr Air Exposure ~128 cm-1 -1 -1 -1 ~138 cm ~433 cm ~435 cm 4 Week Air Exposure * (A ) (A ) (A ) 1 2 (B1) 1 Ir-Li coupled Li 100 150 200 250 vibration modes

* *

Phonon DensityPhonon

Relative Intensity

of States (PDOS) Relative Intensity

100 200 300 400 500 600 0 100 200 300 400 500 600 200 400 600 800 Raman Shift (cm-1) -1 Phonon Frequency (cm-1) Raman Shift (cm ) b (a) Raman shift of Ir starting materialc and synthesized Initial Test Ir3Li. 12 hr Air Exposure (b) Calculated phonon density of states of Ir3Li with Ir-Li coupled modes (red trace) and vibration -1 96 hr Air Exposure ~128 cm ~138 cm-1 ~433 cm-1 ~435 cm-1 (A ) modes(A ) dominated(A ) by Li (green trace). 4 Week Air Exposure 1 2 (B1) 1 (c) RamanIr-Li coupled spectra ofLi Ir3Li powder during extended exposure to air. vibration modes

• These results show that Raman spectroscopy can be used to

Phonon Phonon Density

of States (PDOS) Relative Intensity differentiate Ir3Li from Ir.

0 100 200 300 400 500 600 200 400 600 800 -1 • RamanPhonon Frequency measurements (cm-1) performedRaman on Shiftthe (cm sample) after 12 hr, 96 hr and 4

c weeks of Initial exposure Test found that the Raman spectra was similar in all cases 12 hr Air Exposure indicating 96 hrthat Air Exposure bulk Ir3Li is stable in air for extended periods. 4 Week Air Exposure Go to ”Insert (View) | Header and Footer" to add your organization, sponsor, meeting name here; then, click "Apply to All"

10 Relative Intensity

200 400 600 800 Raman Shift (cm-1) Characterization of Bulk Ir3Li (500 nm to 5 microns): Magnetic susceptibility, heat capacity, and EPR

2.5 60

] -1 50

oe a b ) -1 2.0

-1 40 (a) Magnetic susceptibility of Ir3Li (black

K -1

-2 0.015

1.5 30 K -1 trace) with fitted curve (red trace) 0.010

(J mol 20

p 0.005

emu mol(f.u.)

1.0 /T (J mol p -4 (b) heat capacity of Ir3Li 10 C 0.000

10 0 25 50 [ 2 2

c T (K ) 0.5 0 (c) EPR spectrum of iridium powder in O 0 20 40 60 80 100 120 0 50 100 150 200 250 2 T (K) T (K) atmosphere at 200 K 1x104 c g = 2.0008 g = 1.9797 d 4 O2 1x10 (d) Ir Li and Ir EPR spectrum in O 1x104 3 2

0 atmosphere at 100 K and 200K, 0

Intensity 0 g = 2.0394 Intensity respectively. 4 g = 2.0238 Intensity -1x10 Ir + O2

g = 1.9746 Ir3Li + O2 -1x104 -1x104 -2x104 3000 3200 3400 3600 3800 3000 3200 3400 3600 3800 Field G Field G

• The magnetic susceptibility measurement together with heat capacity

indicate that the temperature dependent behavior of Ir3Li is metallic, which is support for the ORR/OER properties of Ir3Li.

• The EPR results suggest that both Ir and Ir3Li attract oxygen.

Go to ”Insert (View) | Header and Footer" to add your organization, sponsor, meeting name here; then, click "Apply to All" 11 Characterization of Bulk Ir3Li (500 nm to 5 microns): XPS and AFM a b

Ir 4f5/2 Ir 4f7/2 Intensity

70 68 66 64 62 60 58 56 Binding Energy (eV)

(c) XPS spectra of Ir3Li powders showing three components of a Ir 4f7/2 peak at binding energy - (BE) 59.95 eV [Ir3 blue trace], 60.89 eV [Ir(0) green trace], and 63.99 eV [unknown impurity], respectively. (d) 5 x 5 μm current image of conductive AFM scan indicating high conductivity in bright color throughout the sample. • This XPS analysis suggests a charge distribution of Li ~ +0.81e and Ir ~ -0.25e. The negative Ir charge provides a higher tendency to donate electrons. The ORR reaction may be more facile when occurring on Ir3Li compared to IR.

7 • From AFM measurements the Ir3Li conductivity was determined as 2.5·10 S/m, which is similar to that of Ir metal. These results demonstrate the highly

conductive nature of Ir3Li needed for a cathode material. Go to ”Insert (View) | Header and Footer" to add your organization, sponsor, meeting name here; then, click "Apply to All" 12 Li-O2 cell performance with micron size Ir3Li particles

5 5 a ba 1 2 cb 1 2 3 4 3 4

4 5 4 5

Voltage Voltage 3 3

2 2 0 200 400 600 800 1000 0 200 400 600 800 1000 Capacity (mAh/g) Capacity (mAh/g) 5 (a) SEM image of Ir3Li powders post grinding with mortar and pestle. Scaled bar is 10Spot μm. 1 c * LiO2 (b) The first five cycles of a Li-O cell with rGO/GDL cathode, 1 M Li triflate in TEGDME Spot 2 electrolyte and 2 4 Spot 3 2 * current density 0.05 mA/cm , showing a two-plateau charge profile *

(c) The first five cycles of a Li-O2 cell withVoltage Ir3Li-rGO/GDL cathode showing an initial high charge potential toward the end of the 1st charge cycle which3 tapered down and reached a charge potential below 3.5 V by the fourth cycle. Same electrolyte and current density as in (b) were applied.Relative Intensity 2 0 500 1000 1500 800 1000 1200 1400 1600 1800 Capacity (mAh/g) Raman Shift (cm-1) • Ir3Li particles used in the cathode of the Li-O2 cell ranged from 200 nm to 5 microns

• Voltage profiles show low charge potentials similar to previous Li-O2 cells based on much smaller Ir nanoparticles that gave LiO2 discharge product

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4 5 4 5

Voltage Voltage 3 3 Characterization of the Ir3Li- based Li-O2 cell 2 2 discharge0 product200 400 600 by800 Raman1000 0 200and400 titration600 800 1000 Capacity (mAh/g) Capacity (mAh/g) 5 b Spot 1 ca d * LiO Spot 2 2 Spot 3 4 *

* Voltage

3 Relative Intensity

2 0 500 1000 1500 800 1000 1200 1400 1600 1800 Capacity (mAh/g) Raman Shift (cm-1)

(a) Deep discharge of Ir3Li-rGO cathode in a Li-O2 cell showing the discharge potential ~2.75 V for use in characterization

(b) Raman spectra of deep discharged Ir3Li-rGO cathode in a Li-O2 cell showing strong LiO2 peaks at different areas.

• Raman spectra were collected on several different areas and

demonstrated strong LiO2 characteristic peaks at 1125 and 1505 cm-1, along with the characteristic rGO/graphitic peaks at 1328 and 1596 cm-1

• Titration analysis with Ti(IV)OSO4 followed by UV-Vis of the titrant indicated that the presence of Li2O2 was negligible on the discharged cathode consistent with the presence of LiO2 14 Characterization of the LiO2 discharge product by TEMa b c

(a) Low resolution TEM image of discharge product particles of a representative ~80x 100 nm large raspberry shaped discharge product that was attached to the cathode surface (b) electron diffraction pattern of discharge product particle in (a) (c) Low resolution TEM image of discharge product particles of a representative ~200 nm large raspberry shaped discharge product that was attached to the cathode surface

• The discharge product morphology is made up of small primary particles (~5 nm) that appear to be connected together via amorphous regions to formd much larger secondarye particles (100-200 nm)

• Selected area electron diffraction (SAED) was performed on the raspberry shaped particle. The diffraction pattern of the particle is

consistentd with that of (ī10), (101),e and (211) LiO2 surfaces. Go to ”Insert (View) | Header and Footer" to add your organization, sponsor, meeting name here; then, click "Apply to All" 15 Conversion of large ultra-nanocrystalline LiO2 particles to Li2O particles c (c) TEM image snapshots during electron beam irradiation of discharge product particle (d) high resolution image of particle formed during electron beam irradiation of discharge product (cubic particle circled in green in last video tile) d e (e) Electron diffraction pattern of particle formed during electron beam irradiation of initial discharge product

showing that LiO2 is converted to Li2O (cubic particle)

• The LiO2 particles show no change under low electron beam accelerating voltage (80 kV), however, they undergo reaction during a high voltage electron beam (200 kV)

• The LiO2 is converted to Li2O during irradiation, further evidence for the LiO2 in the discharge product. Summary: Stability and Growth

Mechanism of LiO2 Ultrananocrystalline Particles

• First time such large LiO2 particles have been found in discharge products • Remarkably stable compared to previous LiO2 found in discharge products, which have a relatively short lifetime from disproportionation. • Evidence for stability is that the 80 kV electron beam doesnot change them; and time between discharge and the TEM experiments

• The growth of these large particles may be due to the use of large (up to 2

micron size) Ir3Li particles for the cathode that results in ORR as well as nucleation/growth on the same substrate. • This is in contrast to previous studies where cathodes have been based on small Ir nanoparticles loaded onto an rGO support where ORR and nucleation/growth are probably occurring on separate surfaces

• Mechanism probably involves the primary nucleation and growth of crystalline particles from solution, and subsequent diffusion-controlled agglomeration of these primary particles or ‘secondary nucleation’ of new particles on primary particles a b

IrLi particles synthesized at high temperature: characterization c IrLi Nanopowder a d (b)e (a) Pristine IrLi Nanopowderb IrLi Standard IrLi nanopowder post

Ir Standard 2 week air exposure

RelativeIntensity Relativeintensity

1 2 3 4 5 6 7 200 400 600 800 2Theta Raman Shift (1/cm)

ca) SEM and (b) IrLi TEM Nanopowder images of IrLi nanopowderd Pristinesynthesized IrLi Nanopowder by thermal etreatment of Ir nanopowder and IrLi StandardLi foil. TEM inset shows electron IrLi diffractionnanopowder postof IrLi particle. Scale bars Ir Standard

in a and e are 500 nm and 2 nm, respectively 2 week air exposure

RelativeIntensity Relativeintensity • SEM and TEM used to identify IrLi particles and their size (100- 5001 nm)2 3 4 5 6 7 200 400 600 800 2Theta Raman Shift (1/cm)

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used in a Li-O2 battery with a rGO support a 0.4 c 5.0 e 5.0 Ar a 1 25 c 1 5 4.5 4.5 O 50 75 10 (a) galvanostatic cycling of IrLi-rGO cathode ) 0.2 2 2 4.0 100 4.0 in Li-O2 cell at a current density of 100 mA/g

0.0 3.5 3.5 and a capacity of 1000 mAh/g

(mA/cm

Voltage(V) Voltage(V) WE 3.0 3.0 I -0.2 2.5 2.5 (b) galvanostatic cycling of IrLi-rGO cathode in Li-O cell at a current density of 200 mA/g -0.4 2.0 2.0 2 1 2 3 4 5 0 200 400 600 800 1000 0 200 400 600 800 1000 and a capacity of 500 mAh/g. EWE (V) Capacity (mAh/g) Capacity (mAh/g) 1.5 5.0 2.5 (c) galvanostatic cycling of rGO cathode in d 100 mA/g current density b ORR OER db 1 25 f 2.0

) 4.5 50 75 IrLi - rGO Li-O cell at a current density of 100 mA/g

2 2 1.0 1.5 100 rGO

4.0 1.0 and a capacity of 1000 mAh/g.

A/cm m

( 0.5 3.5 0.5 2.5 WE (d) maximum charge polarization

Voltage(V) 3.0 2.0 200 mA/g current density log log I 0.0 overpotentials calculated from IrLi-rGO and 1.5 IrLi - rGO 2.5 Gap (V) Polarization rGO 1.0 rGO cathode cycling at 100 mA/g and 200 -0.5 2.0 0.5 -0.2 -0.1 0.0 0.1 0.2 0 100 200 300 400 500 0 25 50 75 100 mA/g current densities. Overpotential (V) Capacity (mAh/g) Cycles

• Pre-formed IrLi3 particles (<1μm in size) are found to result in LiO2 discharge product with low charge potentials during cycling

Go to ”Insert (View) | Header and Footer" to add your organization, sponsor, meeting name here; then, click "Apply to All" 19 Characterization of Li-O2 battery based on cathodes with synthesized IrLi particles: DEMS and Raman a b

(a) molar quantiles of the evolved O2 at the 10th charge cycle in three-time intervals (first 30 minutes, mid 30 minutes, and last 30 minutes) calculated from In-situ DEMS experiment of IrLi-rGO cell.

(b) Raman spectra of discharged IrLi-rGO cathode directly after removal from cell, and after ageing in Ar atmosphere for 24 hr and 4 months, post removal from cell. • DEMS measurements are consistent with 1 electron/O2 reaction

consistent with LiO2 formation

• Raman shows LiO2 peaks that are present still after 24 hours, disappear after 4 months due to disproportionation.

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Two epitaxial growth interfaces of

crystalline LiO2 on IrLi facets.

(a) Crystalline LiO2 in (111) orientation on a (111) facet of IrLi with the electronic density of states (DOS) shown by c.

• Based on DFT calculations on the interface between LiO2 and IrLi, we find some crystalline faces have good lattice matches, as

would be required for epitaxial growth of crystalline LiO2. Go to ”Insert (View) | Header and Footer" to add your organization, sponsor, meeting name here; then, click "Apply to All" 21 Accomplishment: LiO2 battery with long cycle life using IrLi nanoparticles

▪ IrLi nanoparticle synthesis was carried out by high temperature synthesis

▪ Li-O2 batteries employing IrLi-rGO cathodes were cycled up to 100 cycles at moderate current densities with sustained low charge potentials (<3.5 V). ▪ Various techniques including SEM, DEMS, TEM, Raman, and titration were

implemented to demonstrate a film-like LiO2 discharge product and an absence of Li2O2.

▪ The formation of crystalline LiO2 can be stabilized by epitaxial growth on IrLi facets of IrLi nanoparticles on the cathode surface based on first-principles calculation.

▪ These results demonstrate that by finding appropriate surfaces in alloys

lithium superoxide can be stabilized and efficiently cycled in Li-O2 batteries

– This is the second cathode material that has been shown to stabilize LiO2

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No comments from last year. Proposed Future Work ▪ Stability of large lithium superoxide nanoparticles

– Our preliminary results show that the large raspberry shaped LiO2 particles may be quite stable

– Investigate optimization of Li-O2 cell cathode material to increase size and stability of the particles

▪ Closed Li-O2 battery based on lithium superoxide, i.e. no external source of O2 – Investigate the possibility of using these large nanoparticles in a closed system – Examine coatings from electrolyte additives on the particles to extend life and enable a closed system

▪ Search for lower cost materials to template lithium superoxide in Li-O2 batteries – Use computational simulations to find materials with good lattice matches with lithium superoxide – Synthesize or purchase the materials for testing in cathodes 24 Collaborations with other institutions and companies

S. Al-Hallaj, B. Chaplin UIC • Characterization of discharge products and cathode materials J. G Wen ANL • TEM characterization of discharge products and catalysts K. C. Lau, California State University, Norridge • Computations M. Asadi, IIT • Characterization of gaseous products

25 Remaining Challenges and Barriers

▪ Discovery of new electrolytes for lithium

superoxide Li-O2 batteries that can extend the lifetime of the discharge product for longer cycle life ▪ Investigation of additives to electrolytes for protection of the lithium anode for longer cycle life ▪ Search for lower cost materials to template

lithium superoxide in Li-O2 batteries Summary of Technical Accomplishments