title: Creasable Batteries: Understanding Failure Modes through Dynamic Electrochemical Mechanical Testing.
abstract: Thin-film batteries that can be folded, bent, and even repeatedly creased with minimal or no loss in electrochemical performance have been demonstrated and systematically evaluated using two dynamic mechanical testing approaches for either controlled bending or creasing of flexible devices. The results show that mechanically robust and flexible Li-ion batteries (Li4Ti5O12//LiFePO4) based on the use of a nonwoven multiwalled carbon nanotube (MWNT) mat as a current collector (CC) exhibited a 14-fold decrease in voltage fluctuation at a bending strain of 4.2%, as compared to cells using traditional metal foil CCs. More importantly, MWNT-based full-cells exhibited excellent mechanical integrity through 288 crease cycles, whereas the foil full-cell exhibited continuously degraded performance with each fold and catastrophic fracture after only 94 folds. The enhancements due to MWNT CCs can be attributed to excellent interfacial properties as well as high mechanical strength coupled with compliancy, which allow the batteries to easily conform during mechanical abuse. These results quantitatively demonstrate the substantial enhancement offered in both mechanical and electrochemical stability which can be realized with traditional processing approaches when an appropriate choice of a flexible and robust CC is utilized.
authors.affiliation: Soft Materials Branch, Materials and Manufacturing Directorate, Air Force Research Laboratory , Wright Patterson Air Force Base, Ohio 45433, United States.|Department of Mechanical and Materials Engineering, Wright State University , Dayton, Ohio 45435, United States.
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Blake
authors.affiliation: Soft Materials Branch, Materials and Manufacturing Directorate, Air Force Research Laboratory , Wright Patterson Air Force Base, Ohio 45433, United States.|National Research Council , Washington, D.C. 20001, United States.
authors.forename: Ryan R
authors.initials: RR
authors.lastname: Kohlmeyer
authors.affiliation: Soft Materials Branch, Materials and Manufacturing Directorate, Air Force Research Laboratory , Wright Patterson Air Force Base, Ohio 45433, United States.
authors.forename: Lawrence F
authors.initials: LF
authors.lastname: Drummy
authors.affiliation: Department of Mechanical Engineering-Engineering Mechanics, Michigan Technological University , Houghton, Michigan 49931, United States.
authors.forename: Jacob S
authors.initials: JS
authors.lastname: Gutiérrez-Kolar
authors.affiliation: Soft Materials Branch, Materials and Manufacturing Directorate, Air Force Research Laboratory , Wright Patterson Air Force Base, Ohio 45433, United States.|National Research Council , Washington, D.C. 20001, United States.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Carpena-Núñez
authors.affiliation: Soft Materials Branch, Materials and Manufacturing Directorate, Air Force Research Laboratory , Wright Patterson Air Force Base, Ohio 45433, United States.
authors.forename: Benji
authors.initials: B
authors.lastname: Maruyama
authors.affiliation: Department of Mechanical Engineering-Engineering Mechanics, Michigan Technological University , Houghton, Michigan 49931, United States.
authors.forename: Reza
authors.initials: R
authors.lastname: Shahbazian-Yassar
authors.affiliation: Department of Mechanical and Materials Engineering, Wright State University , Dayton, Ohio 45435, United States.
authors.forename: Hong
authors.initials: H
authors.lastname: Huang
authors.affiliation: Soft Materials Branch, Materials and Manufacturing Directorate, Air Force Research Laboratory , Wright Patterson Air Force Base, Ohio 45433, United States.
authors.forename: Michael F
authors.initials: MF
authors.lastname: Durstock
keywords: Li-ion battery; bendable battery; carbon nanotube current collectors; creasable battery; in situ mechanical testing