Chemical Engineering associate professor Dr. Vilas Pol and graduate research assistant Ryan Adams prepare to assemble potassium-ion batteries for testing (Purdue University photo/Vincent Walter).

A team of Purdue Chemical Engineering researchers has been awarded funding from the National Science Foundation (NSF) to evaluate and improve the safety-related characteristics of potassium-ion batteries (KIBs).

Dr. Vilas Pol, associate professor of Chemical Engineering, and Dr. Arvind Varma, the R. Games Slayter Distinguished Professor of Chemical Engineering, will receive $346,000/3y starting in June 2018 for their proposal, “Mechanistic Elucidation of Thermal Runaway in Potassium-Ion Batteries.”

Potassium has recently been identified as a new metal-ion battery system with similar advantages to Na-ion batteries in terms of low cost, sustainability, and natural abundance. Furthermore, carbon anodes exhibit remarkable performance for KIBs through the reversible intercalation of K-ions into graphite, while Na is unable to. While many promising carbon structures and architectures have been explored in the literature over the past couple years, a fundamental lack of understanding remains for this novel electrochemistry, which Dr. Pol and Dr. Varma aim to change.

Despite their widespread application, LIBs have significant safety issues due to their use of metastable electrodes and flammable electrolyte, with numerous incidents having occurred worldwide resulting in battery combustion or explosion in electric vehicles and portable electronics. No prior studies have been reported regarding KIB safety and the behavior of KIBs at extreme temperatures remains unknown. The Purdue researchers initiated a project last year to study the mechanism of thermal runaway in KIBs using differential scanning calorimetry analysis of charged graphite electrodes, exploring the effect of solid electrolyte interphase (SEI), state of charge, electrolyte composition, carbon structure, and cycle number on heat generation.

Due to the large size of K-ions, graphite expands volumetrically by 61% during potassium insertion, causing SEI layer cracking and exposing graphite surface, which can intensify thermal runaway (Purdue University illustration/Ryan Adams).

Through this proposal, the Purdue researchers aim to expand this initial investigation, using accelerating rate calorimetry to probe the kinetics of the exothermic reactions that cause thermal runaway in KIBs. Additionally, the researchers hope to generate increased understanding of the KIB SEI layer and its relationship to battery safety. The team expects that these studies will elucidate novel design principles for KIBs, with the aim to manipulate carbon material properties and electrolyte composition to create safer batteries in the future. The early results of the KIB safety aspects are published in the Journal of Power Sources, which can be accessed here.