Cathode

● Simulations for the study were conducted using smooth particle hydrodynamics (sph)● Each case study changed the geometry of the separator

○ tortuosity ■ Ratio of path length to thickness of the separator

○ porosity (not pictured)● Success in suppressing dendrite growth was measured by analyzing:

○ Breakthrough time (BT)■ the time taken for a dendrite to reach a separator channel

● The 6 tests run were:1. Single channel with low tortuosity2. Two adjacent channels with low tortuosity3. Two channels with low tortuosity separated by a channel of high tortuosity4. Channels with tortuosity in a parabolic pattern5. Randomized tortuosity for all channels6. Randomized tortuosity for all channels

Skyline High School, 1122 228th Avenue SE, Sammamish, WA1, Computational Energy Lab, Department of Mechanical Engineering, 110 Cummington Mall, Boston, MA2

Interestingly, tortuosity has a much more significant impact on dendrite growth than porosity. Evidenced in all graphs, the first dendritic growth to reach the separator would always occur in the channel of the lowest tortuosity, shown prominently in test cases 1 and 4. These results suggest that in the channels with the highest tortuosity, the Li ion gradient is larger and causes the ions to diffuse into the surrounding channels, leading to an increased Li ion transport into adjacent channels and in turn accelerated dendritic growth.

These findings imply that new separator designs could possibility force dendrites to grow in a uniform manner by creating a separator that allows homogenous mass transport, where a balance of varying tortuosities would need to be struck. For future studies, the specific impacts of a low tortuosity channel on its adjacent channels can be looked at to see exactly how the excess Li ions flow once a channel fills up. Once the dendritic growth is controlled into a more uniform growth pattern, Li-Air batteries can be closer to reaching the marketplace.

The Effects of Varying Separator Structures on Dendritic Growth in Lithium-Air Batteries

Nithin Tamilselvan1,2, Andrew Cannon2, and Emily Ryan2

Results

References Acknowledgements

Conclusions

MethodsIntroduction

● Lithium-air batteries have:

○ an extreme capacity for energy storage

○ dendrite growth issues that are a safety concern and

reduce battery life

● Without controlling dendrite growth in the battery, possibilities

○ of a battery rupture

○ of short circuiting

○ of accelerated deterioration of the battery’s performance

● Research conducted by testing potential solutions through

changing geometry of separator

○ Changing porosity and tortuosity by adjusting the

dimensions of the blocks in channels

● A battery separator:

○ is a porous polymer membrane between anode and cathode

○ prevents contact between electrodes whilst allowing ionic

flow

Tan, Jinwang, and Emily M. Ryan. “Structured Electrolytes to Suppress Dendrite Growth in High Energy Density Batteries: Structured Electrolytes to Suppress Dendrite Growth.” International Journal of Energy Research, vol. 40, no. 13, Oct. 2016, pp. 1800–10. DOI.org (Crossref), doi:10.1002/er.3560.Albertus, Paul, et al. “Status and Challenges in Enabling the Lithium Metal Electrode for High-Energy and Low-Cost Rechargeable Batteries.” Nature Energy, vol. 3, no. 1, Jan. 2018, pp. 16–21. DOI.org (Crossref), doi:10.1038/s41560-017-0047-2.Yoo, Kisoo, et al. “A Review of Lithium-Air Battery Modeling Studies.” Energies, vol. 10, no. 11, Nov. 2017, p. 1748. DOI.org (Crossref), doi:10.3390/en10111748.Recent Progresses in the Suppression Method Based on the Growth Mechanism of Lithium DendriteSuppressing Dendritic Lithium Formation Using Porous Media in Lithium Metal-Based BatteriesTechnique to suppress dendrite growth in lithium metal batteries

My greatest thanks to Andrew Cannon and Dr. Emily Ryan for guiding me through such a positive research experience. Thank you to the RISE Program for this research opportunity.

Visualization of 1st Test Case Parabolic Tortuosity Spread

Visualization of 5th Test Case Random Tortuosities

Visualization of 6th Test Case Random Tortuosities

= Dendrite Growth

= Separator

Anode Anode

Cathode

Anode

Cathode

= Liquid Electrolyte

= Test Case 4

= Test Case 1

= Test Case 6

Combustion Behavior of Large Scale Lithium Titanate Battery - Huang and Wang