In-Operando Imaging of Dendrites Using Nanoscale X-Ray Computed Tomography and Epoxy-Free Sample Assembly

Paul Choi and Shawn Litster Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, PA, USA

MOTIVATION [1] [2]

[3]

• Dendrites: Microscopic branch-like structures that grows on

battery anodes over charge/discharge cycles especially at fast

rates and when cold

• Dendrite growth may cause puncturing of cell or electrical short

between electrodes, which leads to battery failure

• Interested in gaining further understanding of dendrite for-

mation mechanisms of various metal anodes

• Nano-CT 3D (and 4D w/ time) scans allows for high-resolution

observation of dendrite formation

[4]

Prior Work

Nano-CT (Xradia UltraXRM-L200)

Epoxy-Free Sample Assembly

• 8keV Cu rotating anode X-ray source

• Non-destructive

• Dendrites can be imaged as-is-grown

• Allows for multi-stage in-operando imaging of same sample

• Ambient Environment

• No vacuum required

• In-operando experiment setup inside CT possible

• High Resolution & 3D

• HRES: 16.3μm FOV / 50nm Resolution

• LFOV: 65μm FOV / 100 ~ 150nm Resolution

• Allows material evolution observation with respect to all

three directions

• Stainless steel tubing connectors have

250µm thru holes and rated for up to

15,000psi of internal pressure

• OD: 360µm / ID: 160µm PEEK capillary

• OD: 350µm / ID: 300µm Kapton capillary

• Ø = 100µm Cu wires used as electrodes

• Post-assembly electrolyte infiltration through

the T-port using needle/syringe

Cylindrical Electrode Cell

• Sample consists of Kapton capillary (ID = 1mm), Li coated

Cu wires LiPF6 electrolyte, epoxy seal

• Imaging conducted at the Diamond Light Source

(Synchrotron) in Manchester, United Kingdom

• Pixel size: 450 nm / Spatial resolution: ~1µm

• Filtered back projection algorithm used to produce 3D vol-

umes of X-ray attenuation with 1800 projections collected

over 180° of rotation

• Study successfully distinguishes and segments mossy

metallic lithium microstructures from high surface area

lithium salt formations using X-ray

• Demonstrates the effectiveness of X-ray computed to-

mography as in-situ dendrite characterization technique

Three-dimensional characterization of electrodeposit-

ed lithium microstructures using synchrotron X-Ray

phase contrast imaging — David Eastwood et al. [5]

Detection of subsurface structures underneath den-

drites formed on cycled lithium metal electrodes

— Katherine J. Harry et al. [6]

• Lithium-polymer-lithium cell sample was cycled at various

currents at 90°C until short inside Synchrotron

• Advanced Light Source, Berkeley, CA

• Spatial resolution: ~1µm

• Figure shows radiographs and reconstruction of failed cell

which demonstrates formation of sub-electrode-

electrolyte interface features prior to dendrite propaga-

tion

• Mechanism by which said structures nucleate has not

yet been characterized

• requires higher resolution in-situ tomography

• ~100 nm nucleation sites

ASSEMBLY PROCESS

Planar Electrode Cell (in development)

Heat-Sealer Concept Design

Bottom View

Top View

Planar Electrode Cell Mount Concept Design

Wire management

Cu strip for

passing current

Planar Cell

Postmortem SEM Images of Copper Electrodeposition (Potentiostatic) Cathode (Positively Charged)

Anode (Negatively Charged)

In-Operando Copper Electrodeposi-tion Using Cylindrical Electrode Cell Potentiostatic (0.7V)

Galvanostatic (0.02mA)

Cell Cycling &

3D Reconstructions

Before Electrodeposition After Electrodeposition After Cell Reversal

[7]

Acknowledgements • The nano-CT instrument was acquired through the support of a Ma-

jor Research Infrastructure award from the National Science Foun-dation (Grant No. 1229090 / PI: Shawn Litster)

• This Master’s project was made possible with the guidance and help of the following current and graduated students from Carnegie Mellon University: Dr. Siddharth Komini Babu (ME), Dr. Pratiti Man-dal (ME), Sarah Frisco (MSE), Vinayak Kedlaya (ME).

References [1] Stibbe, Matthew. Japanese Airlines Dreamliner Battery Fire. Forbes. Web. <http://b-i.forbesimg.com/matthewstibbe/files/2013/05/Dreamliner_battery_fire-w480-h480_thumb.jpg>

[2] National Transportation Safety Board - <http://www.ntsb.gov/investigations/2013/boeing_787/photos/1-7-12_JAL787_APU_Battery_s.jpghttp://www.ntsb.gov/investigations/2013/boeing_787/boeing_787>

[3] Love, Corey. "Laboratory for Autonomous Systems Research." Processing and Characterization of Lithium-ion Batteries. Naval Research Lab, n.d. Web. 26 Feb. 2016.

[4] CNN Money. Web. “Samsung customer says his new Note 7 burst into flames.” <http://money.cnn.com/2016/09/27/technology/samsung-galaxy-note-7-fire-china/>

[5] Eastwood, David S., Paul M. Bayley, Hee Jung Chang, Oluwadamilola O. Taiwo, Joan Vila-Comamala, Daniel J. L. Brett, Christoph Rau, Philip J. Withers, Paul R. Shearing, Clare P. Grey, and Peter D. Lee. "Three-dimensional Characterization of Electrodeposited Lithium Microstructures Using Synchrotron X-ray Phase Contrast Imaging." Chem. Commun. 51.2 (2015): 266-68. Web.

[6] K. J. Harry, D. T. Hallinan, D. Y. Parkinson, A. A. MacDowell, and N. P. Balsara, Nat. Mater., 13, 69–73 (2014)

[7] Litster, Shawn E. "Nano-CT Instrument-X-ray Computed Tomography Facility - Carnegie Mellon University." Nano-CT Instrument-X-ray Com-puted Tomography Facility - Carnegie Mellon University. Carnegie Mellon University, n.d. Web. 26 Feb. 2016. <http://www.cmu.edu/me/xctf/facility/index.html>.