In Situ / Operando EM
Most electron microscopy captures only a frozen snapshot—a single moment in time. In situ and operando techniques break that constraint, letting us watch atoms and phases reorganize in real time as batteries charge and discharge. This reveals the dynamic mechanisms behind ion diffusion, phase boundary migration, and mechanical failure.
Techniques
Open-Cell In Situ TEM
Using a piezo-driven nanomanipulator inside the TEM column, we bring a Li or Na source into direct contact with individual nanostructures to trigger electrochemical reactions under controlled bias. This approach provides atomic-resolution observation of lithiation/sodiation fronts, phase boundary migration, and stress evolution in real time.
Closed-Cell Operando TEM
With Protochips Poseidon (liquid cell) and Atmosphere (gas cell) holders, we observe reactions under realistic electrochemical conditions — with flowing electrolyte or controlled gas atmosphere. Combined with heating capability (up to 1000 °C for gas, 100 °C for liquid), these setups enable studies of nucleation, growth, and corrosion in their native environments.
In Situ Heating
The Gatan 652 furnace holder and Protochips Fusion MEMS heater allow us to study thermally driven phase transformations, sintering, and diffusion processes up to 1200 °C with minimal drift.
Key Discoveries
- Dislocation-pipe diffusion of Na in Sn: We revealed that sodium ions preferentially diffuse along dislocations in crystalline Sn, bypassing the self-limiting diffusion barrier at the migrating phase boundary (Small, 2020).
- Isotropic sodiation of Sn crystals: Contrary to expectation, crystalline Sn undergoes isotropic volume expansion during sodiation due to the rapid formation of an amorphous Na-Sn shell (ACS AMI, 2018).
- Nanopore-mediated lithiation pathway: In Si-C composite anodes, lithiation proceeds preferentially through nanopore channels, fundamentally altering the stress distribution and cracking behavior (ACS Energy Letters, 2022).
- Ultrafast Na transport via dislocation pipes: Na⁺ transport into crystalline Sn is accelerated by orders of magnitude through dislocation networks (Small, 2021).
Representative Publications
- Y.-W. Byeon et al., “Diffusion along dislocations mitigates self-limiting Na diffusion in crystalline Sn,” Small (2020)
- Y.-W. Byeon et al., “Isotropic sodiation behavior of ultrafast-chargeable Sn crystals,” ACS Appl. Mater. Interfaces (2018)
- H.-J. Lee, Y.-W. Byeon et al., “Lithiation pathway mechanism of Si-C composite anode revealed by the role of nanopore,” ACS Energy Lett. (2022)
- J.-H. Park, Y.-W. Byeon et al., “Diffusion kinetics governing the diffusivity and diffusional anisotropy of alloying anodes,” Nano Energy (2019)
- J.-H. Kim et al., “Ultrafast Na transport into crystalline Sn via dislocation-pipe diffusion,” Small (2021)
Equipment
- Titan probe Cs-corrected S/TEM + Protochips AXON
- Protochips Atmosphere, Fusion, Poseidon holders
- Gatan 652 double tilt heating holder
- Spectra Ultra (under installation — will enable 4D-STEM operando studies)