(6eo) Reinforced Anion Exchange Membrane (AEM) Separators Based on Triblock Copolymers for Electrode-Decoupled Redox Flow Batteries (RFBs)

Reinforced anion exchange membrane
(AEM) Separators Based on Triblock Copolymers for Electrode-decoupled redox
flow batteries (RFBs)

Shrihari Sankarasubramanian

Postdoctoral
research associate

Department
of Energy, Environmental and Chemical Engineering, Washington University in St.
Louis, St. Louis, MO

Research motivation

            Energy
consumption is one of the barometers of economic and human well-being and the equitable
development of humankind requires sustainable energy equity. Achieving this
overarching goal requires us to address issues such as the intermittency of
ecologically non-disruptive renewable energy technologies (solar and wind),
decarbonize the transportation sector, and find alternative chemical pathways
for large scale, energy intensive industrial processes. I aim to help address these key issues by leveraging my training and
experience in multi-scale theoretical and experimental investigations of
electrochemical systems.

Postdoctoral
project – “Reinforced
anion exchange membrane (AEM) Separators Based on Triblock Copolymers for Electrode-decoupled
redox flow batteries (RFBs)”

Supervisor:
Prof. Vijay K. Ramani, Department of Energy, Environmental and Chemical Engineering,
Washington University in St. Louis

PhD dissertation –
“Investigation
of the oxygen reduction reaction at the lithium-oxygen cell cathode”

Supervisor:
Prof. Jai Prakash, Department of Chemical and Biological Engineering, Illinois
Institute of Technology

 Research Interests:

            My
research journey began with my undergraduate work on continuum scale modeling
of the capacity fade mechanisms in lithium-ion batteries with Prof. Balaji
Krishnamurthy. An internship at Tata Power Solar, where I assisted in
formulating a new silicon texturing bath composition (resulting in a ~1%
improvement in final cell efficiency), whetted my appetite for translational
research.

            During
my PhD research with Prof. Prakash at Illinois Institute of Technology, I: 1)
evaluated novel lithium-ion cell chemistries for use in sub-zero temperatures (in
conjunction with Hydro-Quebec), 2) performed the first ever accelerating rate
calorimetry study of the thermal safety of lithium-sulfur cells (again with
Hydro-Quebec), and 3) performed a multi-year theoretical and experimental investigation
of catalysts, solvents and kinetics of the oxygen reduction reaction (ORR) in
lithium-oxygen cells in collaboration with Toyota Motors. Over the course of
these projects, I extensively employed density functional theory (DFT)
simulations, continuum scale kinetic modeling, and classical electrochemical
and electroanalytical experimental techniques.    

As an integral part of my postdoctoral research project,
I am investigating anion exchange membranes for use in electrode-decoupled
redox flow batteries (RFBs). Herein, I am applying my knowledge of
electrochemistry and transport phenomena to understand the transport of ions
across a functionalized membrane. The final goal of this project, funded by
ARPA-E, is to develop selective membranes that allow for the deployment of
low-cost, electrode-decoupled RFBs such as the Fe-Cr system.  

Future research directions

            I plan to leverage my training and
experience in multi-scale theoretical and experimental investigations of
electrochemical systems to carry out transformative, translational research
into next generation, beyond lithium-ion batteries, grid scale energy storage
using redox flow batteries, and the electro-synthesis of bulk and fine
chemicals.

Project 1: Metal- (metal
superoxide) batteries – Lithium-oxygen batteries have been the holy grail
of next generation battery systems due to their unmatched theoretical specific
energy (3458
Wh kg^-1). Despite years of
extensive work on catalysts, redox mediators and ever-more-stable electrolytes,
a practical lithium-oxygen battery has not been realized. As part of this
project I will examine sodium- and potassium- oxygen batteries whose reduction
products are superoxides instead of the peroxides, allowing me to circumvent
the columbic efficiency and degradation problems of lithium-oxygen batteries. I
will combine insights from electrochemical kinetics studies with oxygen
impermeable membranes and water tolerant ionic liquids to demonstrate long life
alkali metal- (metal superoxide) batteries. The
end goal will be the development of a true metal-ambient air battery. 

Project 2: Low-cost, grid
scale energy storage – The adoption of intermittent renewable energy
sources calls for the large-scale deployment of energy storage solutions to
maintain grid reliability. The DOE estimates that $100/kWh is the cost at which
storage solutions become cost competitive. This cost target precludes both the
Li-ion battery and the all-vanadium redox-flow battery. I will investigate alternative,
low cost, earth abundant chemistries for redox-flow batteries. The use of
catalytic inhibitors to suppress the hydrogen evolution and oxygen evolution
reactions, in conjunction with electrolyte systems that increase the nominal
redox potential of the redox couple of choice, will pave the way for >2V
RFBs utilizing couples such as Cr-Ce and provide an unparalleled cost advantage
compared to existing technologies. Further, I will develop highly
perm-selective, high anion transference number anion-exchange membranes for
this system both in-house and in collaboration with polymer scientists and
material chemists. 

Project 3: Electro-synthetic
alternatives to energy intensive chemical production –

Ammonia production
– Ammonia is produced to the tune of
140 million tons a year via the energy intensive Haber-Bosch process with a
massive carbon footprint. Biomimetic or electro-catalytic ammonia production is
a low CO₂ alternative to this process that will allow for low
capital cost and distributed production of ammonia at the demand site. Further,
the elimination of steam reforming to produce hydrogen and the avoidance of
transportation costs and associated emissions makes this an extremely
tantalizing proposition. I will examine metal, metal oxide, carbide, nitride
and alloy catalysts for electrochemical ammonia synthesis from water and air.
Combining DFT screening of catalyst candidates (nitrides, carbides, Pt and Pd
alloys) with robust half-cell and device-level testing, I will identify
candidate catalysts at the top of the activity pyramid, evaluate their nitrogen
reduction kinetics and design, test and optimize larger-scale cells to produce
ammonia.      

CO₂
capture, concentration and conversion (C3)- Any
realistic timeline of a transition to renewables envisions significant
dependence on fossil fuels in the near-term. Thus, it is imperative that
efficient CO₂ capture technologies be developed. In collaboration
with other groups working on CO₂ capture, I will develop alkali
metal-O₂/CO₂ batteries for direct conversion of CO₂ to
electricity. An intriguing idea that will be investigated is a combined N₂
electro-reduction/ alkali metal-O₂/CO₂ system wherein the
ammonia produced is used to capture and concentrate the CO₂ before
use in the battery.

Teaching Interests:

            The
experience I have gained assisting in the teaching of 9 courses across the
spectrum of ChE, from the sophomore level to the advanced PhD level, has
prepared me well to serve as an instructor teaching the traditional chemical engineering
core. I have served as Assistant to instructor and Support to instructor
respectively for courses on Electrochemical Engineering and Energy Conversion
and Storage at Washington University, where I have been actively involved in
class planning and laboratory sessions in addition to traditional teaching
assistant roles. During my PhD, I served as a Teaching assistant for 7 courses including
thermodynamics, transport phenomena, undergraduate laboratory and electives in
energy technology. The experience of assisting in the teaching of
thermodynamics as an introductory first course, an intermediate course for 1^st
year master’s students and as an advanced course for PhD students provided
invaluable insights into the nuances of balancing depth and clarity without
sacrificing technical accuracy. The mentor-mentee relationships I formed with
high school, undergraduate and graduate students in the lab redoubled and
renewed my commitment to excellence in teaching and training. I look forward to
bringing this passion to my future role as a ChE faculty member.

Invention and technology translation
(1 patent issued, 3 disclosed)

            I have
always wanted to see my work changing society in a reasonable timeframe. My PhD
work on Pd and Pt alloy catalysts for lithium-oxygen batteries with Toyota
resulted in a patent and is the basis of their continued research in this
field. My on-going postdoctoral work on reinforced membranes for flow batteries
has already resulted in a $50,000 Leadership in Entrepreneurial Acceleration
Program (LEAP) grant from Washington University to serve as a pre-seed fund for
a start-up. My future independent research career will maintain that same
strong practical, inventive and translational emphasis.       

Selected Publications (10 published, 2 under review and 4 under preparation)

1.    
S.
Sankarasubramanian, and B. Krishnamurthy, A
Capacity Fade Model for Lithium ion batteries including kinetics and diffusion,
Electrochim. Acta 70, 248-254 (2012). 

2.    
S.
Sankarasubramanian*, N. Singh, F. Mizuno, J. Prakash, Ab initio investigation of the Oxygen Reduction Reaction activity
on noble metal (Pt, Au, Pd), Pt₃M (M=Fe, Co, Ni, Cu) and Pd₃M
(M=Fe, Co, Ni, Cu) alloy surfaces, for Li-O₂ cells, J.
Power Sources, 319, 202-209 (2016).

3.    
S.
Sankarasubramanian*, J. Seo, F. Mizuno, N. Singh, J. Prakash,
Rotating ring-disc electrode investigation of the aprotic superoxide radical
electrochemistry on multi-crystalline surfaces and correlation with Density
functional theory modeling – implications for Lithium-air cells, J.
Electrochem. Soc., 163(10), A2377-A2384 (2016).

4.    
S.
Sankarasubramanian*, J. Seo, F. Mizuno, N. Singh, K. Takechi, J. Prakash, Enhancement of oxygen reduction
reaction rate by addition of water to an oxidatively stable ionic liquid
electrolyte for lithium-air cells, Electrochem. Commun.,
73, 55-57 (2016).

5.    
S.
Sankarasubramanian*, J. Seo, F. Mizuno, N. Singh, J. Prakash,
Elucidating the Oxygen reduction reaction kinetics and the origins of the
anomalous Tafel behavior at the Li-O₂ cell cathode, J.
Phys. Chem. C, 121, 4789-4798 (2017).

6.     Y. Zhang, J.
Parrondo, S. Sankarasubramanian, V.
Ramani, Detection of Reactive Oxygen Species in AEM Fuel Cells using in situ Fluorescence Spectroscopy, ChemSusChem, 10, 3056-3062 (2017).