Heterogeneity In All-Solid-State Li Batteries

Abstract: 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.

Bio: Joshua Gallaway 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.

Seminars are held on select Wednesdays from 12:00 noon-1pm, Eastern/New York time.

A light lunch is provided at 11:30 a.m. in the Bowen Hall Atrium immediately prior to the seminar.