In-situ observation of cracking and self healing in Li-ion battery electrodes
Oya Okman (Beckman Institute), Elizabeth Jones (), Scott White (Department of Aerospace Engineering, University of Illinois), Nancy Sottos (Dept. of Materials Science and Eng., Univ. of Illinois at Urbana-Champaign)
Lithium ion batteries: When Chemistry meets Mechanics
Wed 10:45 - 12:15
Salomon 003
Battery lifetime relies on the electrical and mechanical integrity of its electrodes. In Li-ion batteries, the anode undergoes severe mechanical deformation in each electrochemical cycle, leading to crack initiation, subsequent local delamination, loss of conductive path, or even complete disassociation of the functional layer. In this study, we capture cracking of graphite based electrodes during cell operation and introduce a microcapsule based self healing approach to restore functionality of the electrode. We use a custom built cell, designed to allow optical access to the graphite electrode during the entire course of lithiation/delithiation cycles. We fabricate a composite electrode with graphite, carbon black and CMC binder, and use a high graphite content to amplify the volumetric expansion during lithiation. We enhance localized electrode cracking by including stress concentration zones in the electrode design, and thus, induce a capacity loss based on mechanical failure during the standard battery operation. Incorporating microcapsules with a conductive core in the electrode, we assess the self healing performance upon delivery of the core material to the crack zone in a complex electrochemical cell in operation.