High-Performance Flow Battery with Inexpensive

Reactants

James Saraidaridis, RTRCTeam Members: MIT, Penn State, Lawrence Berkeley Nat’l Lab,

U. Colorado-Boulder

Project Visions

Total project cost: $4.87M

Current Q / Total Project Qs ~9 / 13

1. A new flow battery system that uses simple, inexpensive reactants and

innovative performance recovery methods to deliver long duration storage.

2. Advancing flow battery chemistries using large ligands bound to inexpensive

metal centers to allow high aqueous cell voltages and reversible operation

DAYS

Annual Meeting

March 1 & 2, 2021

Approved for Public Release

Flow Batteries @ Raytheon Technologies Research Center“Breakthrough Flow-Battery Stack” developed by RTRC

Improvements due to RTRC’s advanced-RFB cell

designs

NASA’s Cr/Fe RFB

Early All-V RFB (VRFB)

SOA VRFB

RTRC’s sub-scale VRFB

RTRC’s full-size VRFB cell

Commercialization by VionX Energy, now Largo Clean Energy

*non-exclusive license

0.5 MW3 MW-hr

Approved for Public Release

RTRC’s VRFB cells use same material set as other VRFB cells

The Concepts

Alkaline Sulfur/Manganese1 chemistry

‣ Electrolyte Takeover Process (ETP)

Approved for Public Release1. H. Girault, et al. (2016). Chem. Comm. 52(97): p. 14039

2. M. Marshak, et al. (2019). Joule. 2019: p. 2503.

Coordination Complex Chemistries2

‣ High aqueous voltage in neutral pH

vs. Br2

The Team

‣ RTRC: FB design, performance, modelling, and commercialization

‣ Brushett Group (MIT): electrodes and cell performance, modelling

‣ Hickner Group (PSU): membrane synthesis, characterization

‣ Weber Group (LBL): modelling & membrane characterization

Approved for Public Release

‣ Marshak Group (CUB): chemical synthesis & characterization, cell & component testing

Sulfur-Manganese: Project Objectives

Q# Power Density(mW/cm2)

EE(%)

Energy Density(Wh/L)

ASR(Ω-cm2)

Performance Loss(%/cycle)

Cycles(#)

Cycle Duration(hours)

ETP Frequency(Cycles/ETP)

Q4 25 80 ≥ 30 < 3.0 < 0.4 25 5 NA

Q810 75 80 ≥ 40 < 1.0 < 0.1 200 5 5

Q11 100 80 ≥ 40 < 1.0 < 0.01 500/20 5/20 10

‣ High-power & durability to keep LCOS low

‣ Sub-scale performance with components that can be scaled up easily

Cell Performance Targets (20+ cm2)

Approved for Public Release

‣ ETP unnecessary on polysulfide negative electrode

‣ Alkaline flush clears residual solution

‣ Two positive electrode ETPs recover performance:

– Polysulfide (pS) ETP

– Dilute acidic peroxide ETP

Cycled membrane Cycled membraneafter pS ETP

Cycled membraneafter H2O2 ETP

Mn-rich band

50 um

Ex Situ Proof-of-Principle:Electrodes & Membrane Cross-Section SEM

S-Mn: Electrolyte Takeover Process (ETP)

Cycled PositiveElectrode

Ex SitupS ETP

Ex SituH2O2 ETP

Approved for Public Release

S-Mn: Electrolyte Takeover Process: in situ

Cell Stats:Energy Density: 40 Wh/L DoD: 60% Cycle Duration: 5 hoursEE Fade: 0.02%/cycle Power Density @ 80% EE: ~50 mW/cm2

Full Cell Testing: in situ Proof-of-Principle

Serial H2O2 ETP recoveryCycled at 28 mAcm-2 (~29 mWcm-2)

Approved for Public Release

Coordination Chemistry: Project Objectives

Cell Performance Targets (20+ cm2)Q# Power Density

(mW/cm2)EE(%)

Energy Density(Wh/L)

ASR(Ω-cm2)

Performance Loss(%/cycle)

Cycles(#)

Cycle Duration(hours)

H2 gen.(%/day)

Q9 75 80 ≥ 30 < 2.0 < 0.4 25 5 < 1%

Q13 200 80 ≥ 40 < 1.2 < 0.1 200 5 < 0.5 %

Approved for Public Release

‣ High cell voltages improve power and limit active material cost

‣ Mild pH electrolytes offer cost and safety advantages, but also introduce pH management concerns

‣ CUB delivering significant e’lyte volumes

‣ Preliminary results meeting Q9 metrics

– 90% EE @ 75 mWcm–2 over 125 hours

– < 1% cycled capacity attributable to H2

– 30 Wh/L achievable

Coordination Chemistry: Cr(PDTA)1/2– & Fe(CN)63/4–

Cycles 5-14 Cycles 141-150

Approved for Public Release

Challenges and Risks: S-Mn & Coordination Chemistries

Challenges:

‣ Polysulfide electrode:– Developed carbon paperelectrodes to outperform metallic foam early leaders

‣ Permanganate Self-Discharge: 2 proven mitigation strategies

‣ Low ASR Membranes: PFSAs as baseline, non-PFSAs have struggled in Mn e’lyte, but may succeed with coordination chemistries

‣ Non-technical needs: Markets that allow energy storage to capture its value

Collaboration opportunities:

‣ RTRC RFB work spans basic science to production systems – looking for partners with new ideas to manufacturer’s looking for the next generation system

UTRC CarbonPaper

Best Ni Foams

TraditionallyActivated CarbonPaper

Catalyst DecoratedCarbonPaper

Different axis scaling

Approved for Public Release

Technology-to-Market

‣ In closing months: Down-select for 5 kW/50 kWh prototype system

‣ Licensees and development partners interested in vanadium alternatives

‣ Focus on renewables integration & diurnal cycling applications (10+ hr discharge)

– Military – Utilities – Behind-the-meter commercial

De

c 2

01

0

No

v 2

011

≈ 25 cm2

≈ 820 cm2

1-step scale-up factor ≈ 820/23 = 36

Began sub-scale cell testing

GEN1-A stack

GEN1-B stack

First full-size cell testing

Total scale-up factor = 36 X 26 ≈ 1,000

Ja

n 2

00

9

UTRC’s Field Demonstration System

2012Historical Perspective: RTRC VRB Scale-up

Approved for Public Release

Summary

‣ Flow batteries can meet future long duration needs

– Active materials just need to be dirt-cheap

‣ Progressing through sub-scale milestones

– S/Mn with ETP has requisite durability, needs

last 50% of power gains

– CUB coordination complex is on track

‣ Keep hitting milestones, then prototype and

commercialization partners next!

‣ Contact me at James.Saraidaridis@rtx.com

VionX installed 0.5 MW3 MW-hr

The information, data, or work presented herein was funded in part by the Advanced Research ProjectsAgency-Energy (ARPA-E), U.S. Department of Energy, under Award Number DE-AR000994. The views andopinions of authors expressed herein do not necessarily state or reflect those of the United StatesGovernment or any agency thereof.

Approved for Public Release

https://arpa-e.energy.gov