Rational Design of Nanostructured Polymer Electrolytes and Solid–Liquid Interphases for Lithium Batteries

239 Pages·2019·13.766 MB·English

by  Snehashis Choudhury

Springer Theses
Recognizing Outstanding Ph.D. Research
Snehashis Choudhury

Rational Design
of Nanostructured
Polymer Electrolytes
and Solid–Liquid
Interphases for
Lithium Batteries
Springer Theses
Recognizing Outstanding Ph.D. Research
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Snehashis Choudhury
Rational Design
of Nanostructured Polymer
Electrolytes and Solid–
Liquid Interphases
for Lithium Batteries
Doctoral Thesis accepted by Cornell University,
Ithaca, NY, USA
Snehashis Choudhury
Department of Chemical Engineering
Stanford University
Stanford, CA, USA
ISSN 2190-5053 ISSN 2190-5061 (electronic)
Springer Theses
ISBN 978-3-030-28942-3 ISBN 978-3-030-28943-0 (eBook)
https://doi.org/10.1007/978-3-030-28943-0
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“The important thing is not to stop questioning. Curiosity has its own reason for existing. One
cannot help but be in awe when he contemplates the mysteries of eternity, of life, of the marvelous
structure of reality. It is enough if one tries merely to comprehend a little of this mystery every
day.” – Albert Einstein
v
Dedicated to my family and my mentees
and to all those who live with a passion
Supervisor’s Foreword
I am very pleased to introduce the PhD thesis work of my former student,
Dr. Snehashis Choudhury. Snehashis’ doctoral thesis focuses on the development of
design rules for electrolytes and interphases in electrochemical cells that use reac-
tive metals such as Li and Na as anodes. Such cells are of contemporary interest
because they offer substantially higher charge storage capacity per unit mass or
volume than state-of-the-art Lithium-ion battery technology. They are scientifically
interesting because they present opportunities for chemical and materials engineer-
ing science research on transport and ion-matter field interactions on length scales
ranging from the few molecule-thick interfacial phases that form spontaneously on
and passivate reactive metal anodes to micron length scale phases associated with
morphological instability and dendritic electrodeposition at the metal electrode.
Ultimately, these physics manifest on macroscopic length scales in the form of
metal dendrites that proliferate in the interelectrode space to produce catastrophic
battery failure when they bridge the electrodes, short-circuiting the cell.
Until recently, it was taught that only a solid electrolyte with modulus that
exceeds that of the metal could be effective in stopping the cascade of instabilities
that lead to dendritic deposition. As a consequence, all serious efforts to create prac-
tical secondary batteries that utilize Li or Na metal anodes placed priority on what
has so far been an insurmountable design objective – find a suitable solid electrolyte
that is chemically stable in extended contact with the metal, which has a high-
enough mechanical modulus to block dendrites and which enables fast enough ion
transport to enable battery operation at temperatures close to ambient. Dr.
Choudhury’s thesis is a tour de force exploration of clever materials design and
metrology strategies that lead to a rather different set of design rules. His work
shows that electrolytes formed by tethering Li-ion conducting polyethers to inor-
ganic nanoparticles are able to suppress metal dendrite formation by forming a
nanoporous, tortuous network with pore sizes below a theory-defined critical value
at which surface tension forces are effective in retarding the morphological instabil-
ity that produces dendrites. As significant is the discovery that these effects are
largely agnostic to the configuration of the polymer-grafted nanoparticle electro-
lytes – free-standing membranes formed by covalently cross-linking the structures,
ix
x Supervisor’s Foreword
solvent-free soft glassy electrolytes formed when the tethered chains interpenetrate
to jam the material, and nanoparticle-rich interphases formed on the metal by spon-
taneous absorption of grafted particles have all been shown to be effective. This
indicates that the design principle developed in the thesis, stabilizing metal electro-
deposition by confining the deposition to nanometer length scales, is quite general.
With an eye towards practical application in batteries where the metal anode is
paired with a cathode, the thesis also considers design rules for anode and cathode
electrolyte interphase that, respectively, limit reductive and oxidative degradation of
polyether-based electrolytes. By means of detailed experimental and computational
studies, Dr. Choudhury has shown that purpose-built interphases composed of salts
or polymer thin films which promote de-solvation of metal ions are effective in
stabilizing reductive and oxidative degradation of polyether electrolytes.
James A Friend Family Distinguished Lynden A. Archer
Professor of Engineering
David Croll Director of the Cornell
Energy Systems Institute
Deputy Editor, Science Advances
Robert Frederick Smith School of Chemical
and Biomolecular Engineering
Cornell University
Ithaca, NY, USA
Acknowledgments
I have to apologize as my words will not do justice to all the help and support I have
received from everyone in my PhD journey and in my life. I would like to firstly
thank Prof. Lynden Archer for his help not only in my PhD work but also in my
career counseling. His knowledge in a wide spectrum of subjects and his passion for
science have always driven me to improve every single day I spent at Cornell. I
greatly appreciate the help from my committee members, Prof. Yong Joo and Prof.
Geoffrey Coates. I greatly enjoyed the discussions with them on my research.
Perhaps, one of the most satisfying and inspiring experiences at Cornell was my
teaching assistant responsibilities. Overall, I served as a TA for four different times
in the Chemical Engineering and Physics Department. I want to thank every student
in these classes who have inspired me and helped me in discovering my love for
teaching. I am grateful to Prof. Julius Lucks, Prof. William Olbricht, and Prof. Chris
Alabi for providing me guidance and independence in conducting lectures and reci-
tations in my TA classes.
Thanks to all the former and current members of Archer group. I am greatly
thankful to Rajesh for being my mentor in my first year at Cornell as a Master of
Engineering student. I have to say, I wouldn’t have been in the PhD program with-
out Rajesh’s guidance. I am sincerely grateful to Akanksha who have been a great
friend, mentor, and collaborator. I will always miss our long conversations about
research, people, and life with her while simultaneously working long hours in the
lab. Also, in the course of my PhD, I met a great human being and researcher,
Zhengyuan, whose dedication towards research was extraordinary. I thank him for
making my life so easy in handling different projects and serving as a great partner
in everything I worked on in my PhD. Over the 5 years at Cornell, I have worked
with several undergraduate and master’s students who have been more of my men-
tor than vice versa. I am thankful to Charles, Dylan, and Sanjuna for their constant
support in research and making my experience in the group so memorable.
A big thanks to Himanshu, Prayag, Samanvaya, Sanjuna, Dylan, Ritesh, Pooja,
Zhengyuan, Anubhav, Yue, Alex, Kaihang, Nijam, Rohit, Prajwal, Rahul, Mun Sek,
and Sampson for their strong support in my research and life. I am greatly obliged
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