understanding the stability of positive electrode

Understanding the stability of positive electrode materials for aqueous organic

redox flow batteries

Sri Narayan

Bo Yang, Advaith Murali, Vinayak Krishnamurthi and G.K. Surya Prakash

University of Southern California, Los Angeles, CA

Presentation ID# 405

Session Topic : Flow Batteries

DoE Office of Electricity

Peer Review Meeting

October 27, 2021

1

Goals and Objectives

Overall Goal

Advance the understanding of an All-Organic Water-based RFBs for cost-effective large-scale energy storage.

Specific Objectives

• Understand the mechanisms of degradation to formulate design rules for new molecules

• Design and demonstrate inexpensive positive side organic molecules that can be cycled repeatedly without degradation

2

Advances Made at USC in RFBs

• First ever aqueous all-organic redox flow batteries based on quinone derivatives (BQDS/AQDS) in acidic media.

• Mitigated crossover by molecular design and symmetrical cycling.

• Demonstrated cycling of Michael-Reaction resistant positive side materials (DHDMBS)

• Scale up and demonstration (ITN) of 1kW/2KWh all-organic redox flow batteries (DHDMBS/AQDS) 4000 Ah/ 4.5 h per cycle with <0.01% loss/hour.

• Developed Iron sulfate/AQDS system for stable cycling over 1000 cycles with < 8 x10-6

%/hour. 3

Capacity Degradation Modes and Rates

4

(5x 10-4 %/ hour)

• For realizing LCOS of < 5 cents/kWh degradation rates must be < 5x10-4

%/hour (<500 ppm %/hour)

Michael Reaction (1,4-addition) with a nucleophile such as water, hydroxide ion or phenoxide ion. • Loss of capacity• Decrease of cell voltage

Desulfonation or loss of the sulfonic acid group• Loss of solubility • Decrease of cell voltage

• Capacity loss in water-based organic systems arises from two major processes: 1. Chemical transformations

2. Molecular crossover

Michael Reaction or 1,4-Addition

• Occurs more readily on electron-deficient systems

5

In Acid

In Alkali

Desulfonation Processes (acid medium)

6

Proto-desulfonation in Acid: Loss of sulfonic acid group

Desulfonation Processes (alkaline medium)

7

• Oxidative Hydroxy-desulfonation

• Nucleophilic (SNAR) Hydroxy-desulfonation

Technical Approach

• To reduce the propensity for Desulfonation and Michael Reactions

- Examine the effect of substitution by alkyl and phenyl groups on benzoquinone rings

- Examine these reactivities in bi-functional molecules

• Adding functional groups to increase solubility without increasing reactivity.

• Developing procedures for in-house synthesis of compounds

• Follow the stability changes by NMR and GC-MS to determine effects of long-term cycling

• Electrochemical kinetics testing using RDE and CV on glassy carbon/graphite

• Establishing solubility in charged and discharged state

• Establish decay rates by extended cycling in symmetric cell configuration in flow cells (25 cm2)

8

Tasks to Address Challenges

• Task 1. Synthesis, purification and scale-up of materials.

• Task 2. Electrochemical characterization of charge/discharge reversibility and electrode potential.

• Task 3. Characterization of solubility and diffusion coefficient

• Task 4. Crossover rate studies

• Task 5. Passive and active durability studies using flow cell and electrolysis

• Task 6. Reporting, Reviews and Publication

9

Accomplishments in the past year

• Several promising benzoquinone derivatives have been synthesized and tested in acid and alkaline media.

• Preliminary results show these molecules possess distinct reactivity and stability based on the substituent groups.

• Verified that anthraquinone-based molecules can be stabilized to make positive side materials and also allow for bifunctional activity to achieve high cell voltage.

• Verified the long-term cycling behavior of stabilized redox materials.

10

Three Classes of Benzoquinone-derivedPositive Side Materials

11

Alkyl-substituted

Aryl-substituted Anthraquinone–derived

Studies on 6-methyl hydroquinone-3-sulfonic acid (MMS)

12

MMS

Synthesis

• Cyclic voltammogramssuggest excellent reversibility.

• Slow chemical transformations are not captured in a CV.

Cycling studies on MMS

13

0

1

2

3

4

5

0 50 100 150 200 250

Cap

acit

y , A

h

Cycle #

Cycling of MMS/ AQDS cell in Acid Medium100 mA/cm2, 25 cm2 , Graphite Felts

Charge

Discharge

CV at 50 mV/s,Graphite Electrodein 1 M Sulfuric Acid

Starting Material

After 516 cycles

MMS-1 MMS-2

After 516 cycles: Significant Loss of the Aromatic Protons and appearance of multiple aliphatic peaks

NMR Analysis-Starting Material

Polymerization of MMS

• Shown: dimerization

• Process can continue (chain propagation) to form redox active oligomers

14

CV Characterization of O3MMS, O4MMS, O3MDS

15

-4.00E-05

-3.00E-05

-2.00E-05

-1.00E-05

0.00E+00

1.00E-05

2.00E-05

3.00E-05

4.00E-05

5.00E-05

6.00E-05

-1 -0.5 0 0.5 1

Cu

rren

t (A

)

Potential (V vs MSE)

O3MMS, 1M H2SO4, GC, 50mV/second

-2.00E-05

-1.50E-05

-1.00E-05

-5.00E-06

0.00E+00

5.00E-06

1.00E-05

1.50E-05

2.00E-05

2.50E-05

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1Cu

rren

t (A

)


O3MDS, 1M H2SO4, GC, 50mV/second

-3.00E-05

-2.00E-05

-1.00E-05

0.00E+00

1.00E-05

2.00E-05

3.00E-05

4.00E-05

-1 -0.5 0 0.5 1Cu

rren

t (A

)


O4MMS, 1M H2SO4, GC, 50mV/second

O3MMS

O3MDS

O4MMS

Tertiary-Butyl Substituted Orthobenzoquinonemonosulfonic acid (O4TBMS)

16

00.5

11.5

22.5

33.5

44.5

0 50 100 150 200

Cap

acit

y (A

h)

cycle number

Cha cap

Discha Cap

-8.00E-05

-6.00E-05

-4.00E-05

-2.00E-05

0.00E+00

2.00E-05

4.00E-05

6.00E-05

8.00E-05

1.00E-04

1.20E-04

-0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8

Cu

rren

t (A

)


O4TBMS, 1M H2SO4, GC, 50mV/second

Synthesis1M O4TBMS/ 1M AQDS cell cycled at 100 mA/cm2 in sulfuric acid

Potential shift to positive values upon sulfonation

NMR Analysis confirms fast single step hydroxylation

Aryl-Substituted benzoquinonesPHQS, PHQDS, Aryl sulfones

17

Aryl sulfones

0

0.5

1

1.5

2

2.5

3

0 50 100 150 200 250 300

Cap

acit

y (A

h)

cycle number

Positive 100mL 1M PHQS, 1M H2SO4, Negative 100mL 1M AQDS, 1M H2SO4, E750, felt, centrifugal pump, 100mA/cm2

charge cap

discha cap

OH

OH

SO3H

-4.00E-05

-2.00E-05

0.00E+00

2.00E-05

4.00E-05

6.00E-05

-0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1Cu

rre

nt

(A)


PHQS, 1M H2SO4, GC, 50mV/second

-4.00E-05

-3.00E-05

-2.00E-05

-1.00E-05

0.00E+00

1.00E-05

2.00E-05

3.00E-05

4.00E-05

5.00E-05

6.00E-05

-0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1Cu

rren

t (A

)


PHQDS, 1M H2SO4, GC, 50mV/second

PHQS

PHQDSCycling of PHQS /AQDS cell in 1M sulfuric acid at 100 mA/cm2

OH

OH

OH

SO3H

Bifunctional Anthraquinone –Derived Molecules-Alizarin Red in Alkaline Media

18

O

O

OH

OH

SO3H

O

O

OH

OH

SO3H

O

O

O

O

SO3H

Charge

Discharge

O

O

O

O

SO3H

O

O

OH

OH

SO3H

OH

Michael Reaction

O

O

OH

OH

SO3H

OH

O

O

OH

OH

OH

OH

KOH

-8.00E-05

-6.00E-05

-4.00E-05

-2.00E-05

0.00E+00

2.00E-05

4.00E-05

6.00E-05

8.00E-05

1.00E-04

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6Cu

rre

nt

(A)

Potential (V vs MMO)

Alizarin Red, 1M KOH, GC, 50mV/second

Hydroxydesulfonation of Alizarin Red

19

NMR Analysis of cycled Alizarin Red Confirms the formation of the tetrahydroxylatedproduct

Purpurin-a viable pathway to using anthraquinone derivatives

20

0

0.2

0.4

0.6

0.8

1

1.2

-0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.4

Ce

ll V

olt

age

(V

olt

s)

Capacity (Ah)

40mMPurpurin/200mM AQDS 1M NaOH, 200mA

O

O

OH

OH

OH

OH

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 5 10 15 20 25 30 35

Cap

acit

y (A

h)

Cycle number

40mMPurpurin/200mM AQDS 1M NaOH, 200mA, 400 mL on each side

Ch. Cap.

Disch. Cap.

HydroxylatedPurpurin can be cycled in alkali without noticeable degradation

O

O

OH

OH

SO3H

OH

O

O

OH

OH

OH

OH

KOH

Other Promising Bifunctional Molecules StudiedCompound Structure E1/2 (Volts) vs MMO Bi-functional Material

Potential

1,2,4-trihydroxy anthraquinone

O

O

OH

OH

OH

-0.84 V Yes, 840 mV difference

1,4-dihydroxy anthraquinone

O

O

OH

OH


1,2-dihydroxy anthraquinone

O

O

OH

OH

-0.73 V Yes, 1 V difference

1,2-dihydroxy, 3-sulfonic acid anthraquinone

O

O

OH

OH

SO3H


21

Potential to increase cell voltage by substitution

Next Steps

• Increase the solubility of stable redox molecules to ensure high concentrations.

• Develop methods of sulfonation for the non-participating ring.

• Complete the characterization in alkaline media

• Down-select molecules for full-cell testing

• Pursue further molecular designs to avoid oligomer formation.

• Explore the bifunctional nature of stabilized redox molecules in full cell.

22

Acknowledgements

• Dr. Imre Gyuk , DoE’s Office of Electricity.

• Drs. Wei Wang, David Reed and Vincent Sprenkle at PNNL

• University of Southern California, Loker Hydrocarbon Research Institute for post-doctoral fellow and graduate student support.

23

The USC Organic Flow Battery Team

Dr. Lena Hoober(past student)

Dr. Bo Yang

Dr. SankarganeshKrishnamoorthy(past student)

Advaith Murali

Dr. ArchithNirmalchandar(past student)

Prof. SuryaPrakash

Dr. Robert Aniszfeld

24

Sri Narayan

VinayakKrishnamurti

understanding the stability of positive electrode

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