Skip to content Skip to navigation
University of Warwick
  • Study
  • |
  • Research
  • |
  • Business
  • |
  • Alumni
  • |
  • News
  • |
  • About

University of Warwick
Publications service & WRAP

Highlight your research

  • WRAP
    • Home
    • Search WRAP
    • Browse by Warwick Author
    • Browse WRAP by Year
    • Browse WRAP by Subject
    • Browse WRAP by Department
    • Browse WRAP by Funder
    • Browse Theses by Department
  • Publications Service
    • Home
    • Search Publications Service
    • Browse by Warwick Author
    • Browse Publications service by Year
    • Browse Publications service by Subject
    • Browse Publications service by Department
    • Browse Publications service by Funder
  • Help & Advice
University of Warwick

The Library

  • Login
  • Admin

Ageing analysis and asymmetric stress considerations for small format cylindrical cells for wearable electronic devices

Tools
- Tools
+ Tools

Tan, Chaou C., Walker, Marc, Remy, Guillaume , Kourra, Nadia, Maddar, Faduma, Dixon, Steve M., Williams, Mark A. and Loveridge, Melanie (2020) Ageing analysis and asymmetric stress considerations for small format cylindrical cells for wearable electronic devices. Journal of Power Sources, 472 . 228626. doi:10.1016/j.jpowsour.2020.228626

[img] PDF
WRAP-Ageing-analysis-asymmetric-stress-considerations-Williams-2020.pdf - Accepted Version
Embargoed item. Restricted access to Repository staff only until 18 July 2021. Contact author directly, specifying your specific needs. - Requires a PDF viewer.
Available under License Creative Commons Attribution Non-commercial No Derivatives 4.0.

Download (3029Kb)
Official URL: http://dx.doi.org/10.1016/j.jpowsour.2020.228626

Request Changes to record.

Abstract

Performance assessments on miniature cylindrical cells used in Fitbit Flex 2 fitness trackers have been performed to understand the dominant ageing modes and small format implications. We utilise electrochemical testing, x-ray photoelectron Spectroscopy (XPS), x-ray computed tomography (XCT) and scanning electron microscopy (SEM), to reveal device and component structural features and changes. The cell maintains 82% cell capacity retention after 500 continuous charging and discharging cycles at 3.0–4.35 V, 0.75C rate at 20 °C. The anode shows severe delamination due to high bending stress exerted on the cell components, however this seemingly has minimum impact on the electrochemical performance if the coating is sufficiently compressed in the jelly roll with a good electrical contact. After ageing, the surface layers continue to grow, with more LiF found on the cathode and anode. The formation of LiF is discussed and we suggest the main ageing mechanism of the Fitbit cell is related to increasing charge transfer resistance due to the transportation of Li+ ions being inhibited by the thicker surface layer, which contains LiF. That preferential delamination on the inner sides of the electrode coatings was observed consistently opens up an interesting avenues for advances in cylindrical cell manufacturing at large.

Item Type: Journal Article
Subjects: T Technology > TK Electrical engineering. Electronics Nuclear engineering
Divisions: Faculty of Science > Physics
Faculty of Science > WMG (Formerly the Warwick Manufacturing Group)
Library of Congress Subject Headings (LCSH): Lithium ion batteries, Lithium ion batteries -- Deterioration, Strains and stresses, Wearable technology
Journal or Publication Title: Journal of Power Sources
Publisher: Elsevier S.A.
ISSN: 0378-7753
Official Date: 1 October 2020
Dates:
DateEvent
1 October 2020Published
18 July 2020Available
6 July 2020Accepted
Date of first compliant deposit: 30 July 2020
Volume: 472
Article Number: 228626
DOI: 10.1016/j.jpowsour.2020.228626
Status: Peer Reviewed
Publication Status: Published
Access rights to Published version: Restricted or Subscription Access
RIOXX Funder/Project Grant:
Project/Grant IDRIOXX Funder NameFunder ID
UNSPECIFIEDHigh Value Manufacturing CatapultUNSPECIFIED
EP/S003053/1The Faraday InstitutionUNSPECIFIED

Request changes or add full text files to a record

Repository staff actions (login required)

View Item View Item
twitter

Email us: wrap@warwick.ac.uk
Contact Details
About Us