am5b11175_si_002.avi (4.42 MB)
Creasable Batteries: Understanding Failure Modes through Dynamic Electrochemical Mechanical Testing
media
posted on 2016-01-07, 00:00 authored by Aaron J. Blake, Ryan R. Kohlmeyer, Lawrence F. Drummy, Jacob S. Gutiérrez-Kolar, Jennifer Carpena-Núñez, Benji Maruyama, Reza Shahbazian-Yassar, Hong Huang, Michael F. DurstockThin-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.