CHE Seminar Series with Dr. Joshua Gallaway
Friday, April 14, 2023
Heterogeneity In All-Solid-State Li Batteries
April 25, 3:00pm
Engineering North 107
All-solid-state Li batteries hold the promise of improving both the safety and energy
density beyond that of current-day Li-ion batteries. Safety would be improved by replacement
of flammable liquid electrolyte by a solid material. Energy density would be improved
by enabling thinner electrolyte layers and allowing bipolar stacking of
cells within a single casing. However, the materials and cell engineering challenges
that must be overcome are not trivial. Reports of all-solid-state cells prepared with
many different electrolyte materials are common these days: oxides, phosphates, sulfides,
polymers, and composites, particularly composites between polymers and one of the
other electrolyte types. No universally accepted “best choice” has emerged, but research
continues on all of these. It is reasonable to expect that achieving high energy density
will require several qualities: (a) the ability to cycle a Li metal anode reversibly
without cell shorting due to dendrites; (b) a relatively thin electrolyte layer, probably
thinner than the electrolyte-soaked separator it is meant to replace; and (c) a relatively
thick cathode, which is required to balance the highly energy dense Li metal anode.
This talk will concern heterogeneity in all-solid-state Li batteries using two particular
electrolyte systems. The first is sulfide solid electrolytes, which are attractive
because extremely high conductivities can be achieved, sometimes in excess of standard
liquid electrolytes. This is of great importance because to achieve a thick cathode,
relatively small ion-conducting channels will have to efficiently carry current through
long distances within composite cathodes. Imbalance in the relative ion vs electron
conductivity in a composite will produce reaction heterogeneity, which must
be understood and controlled for design of all-solid-state Li batteries to be successful.
A second electrolyte system will be discussed, in which material heterogeneity is
introduced into the electrolyte itself, to make a tougher barrier to prevent Li dendrite
growth across the cell, causing short circuits and cell failure.
Joshua Gallaway, Ph.D. is the DiPietro Assistant Professor in Chemical Engineering at Northeastern University, where he founded the Analysis of Complex Electrochemical Systems Laboratory (ACES Lab). His lab is primarily focused on battery engineering, and recent research has used high energy synchrotron techniques to visualize non-uniform reactions within battery electrodes.
He received his PhD in chemical engineering from Columbia University in 2007. Working
with his advisor Prof. Scott Calabrese Barton, he characterized the electron transfer
rates of enzymes embedded in oxygen-reducing hydrogels. After his PhD work, he completed
a postdoctoral appointment with Prof. Alan West, also at Columbia, studying non-uniform
current distributions in sub-micron interconnect features for the semiconductor industry.
He then joined the newly-formed CUNY Energy Institute in a research position funded
by the Wallis Foundation. There he worked on an ARPA-E funded project headed by Distinguished
Professor Sanjoy Banerjee, which resulted in
the spin out company Urban Electric Power. He received the NSF CAREER Award in 2021.