(366s) Towards Practical High-Loading Lithium-Sulfur Batteries

My research studies lithium sulfur (Li-S) batteries from both an engineering and theoretical perspective. On the engineering side, my research covers the improvement and fabrication of all three major battery components: cathode, electrolyte/separator, and anode. On the theoretical side, my research focuses on the in situ observation of sulfur nucleation and gas generation, as well as DFT calculations.

Research experience

In recent years, renewable energy storage technologies have garnered significant attention due to the boom in household portable electronics, the urgent need to address climate change, and the emergence of new technologies. Lithium batteries, in particular, have become a primary focus in both academia and industry. Among these, lithium-sulfur (Li-S) batteries have been recognized as one of the most promising alternatives to the state-of-art lithium-ion batteries (LIB), because of their low cost and high theoretical specific energy (~2510 Wh/kg, roughly 10 times of LIB). The most viable applications of Li-S batteries are in electric vehicles (EVs), aerospace, and drones, where they can provide long driving/flying range and lightweight benefits due to their high energy density.

However, sulfur cathodes in Li-S batteries face several challenges, including low conductivity, severe polysulfide shuttle effects, high electrolyte amount required, and low sulfur mass loading, etc. My research seeks to overcome these challenges through various engineering approaches: (1) designing and fabricating an adsorption-enhanced layer-on-layer sulfur cathode via air-assisted electrospray (AAES), to mitigate the shuttle effects and increase mass loading by 5 times; (2) discovering that reduced LiFePO4 can catalyze sulfur conversion kinetics & enable high sulfur loading by improving slurry rheology; (3) building a mathematical model to predict initial discharge capacity based on sulfur loading and E/S ratio.

As my research progressed, it became clear that, in order to address the aforementioned challenges, understanding the reaction mechanisms within sulfur cathodes is as crucial as engineering the cathode for higher capacities. Therefore, in the latter half of my PhD, I shifted my focus to unveil the interfacial reactions in Li-S batteries, by (1) studying the spatial inhomogeneity of sulfur nucleation via synchrotron X-ray imaging and XANES imaging and (2) analyzing gas products from electrolyte decomposition via DEMS.

Beyond sulfur cathodes, my PhD research also encompassed other components of Li-S batteries, and extended to other battery systems (LIB, Zn-aqueous batteries, etc.), to align with broader applications in the field of energy storage: (1) designing an artificial SEI for lithium metal anodes, (2) fabricating PEO-LLZTO solid-state electrolytes via air-assisted electrospray (AAES), and (3) performing ab initio DFT calculations of polymer-electrolyte interactions and lithium diffusion in metal lattices. These comprehensive research efforts aim to advance Li-S battery technology, with implications for other battery systems and future energy solutions.

I sincerely hope my work can contribute to the development of next-generation energy storage solutions essential for a sustainable future.

Internship & Career Plan

My experience in lithium batteries is reinforced by three internships, providing me with hands-on knowledge in the large-scale manufacturing of state-of-the-art lithium-ion batteries. Before starting my PhD, I worked as a research assistant at the Lawrence Livermore National Laboratory (LLNL) for a year, focusing on ceramic solid-state electrolyte (LLZTO). There, we optimized ball-milling conditions, achieving minimal lithium loss and lower sintering temperatures. In the spring of 2022, I interned at the Watt Lab of the 2012 Research Institute at Huawei, where I developed surface protection of lithium metal. My protection layer was successfully scaled up from coin cells to pouch cells, giving me insight into the ampere-hour-scale production of multi-layer pouch cells. During the summer of 2023, I interned at the Cell Development Lab of Tesla, responsible for the quality check and failure analysis of mass-produced 2170 cylindrical cells via over 100 cell dissections. I performed root cause analysis on more than 15 identified issues and prepared standard operating protocols (SOPs).

Having graduated with my PhD, I am now seeking full-time positions as a battery cell engineer, preferably with R&D components, and ideally in the Bay Area. Given my PhD research and internship experiences, I am confident in my abilities in cathode, electrolyte, and anode materials development, cell testing, cell failure analysis, and more.

Publications

1. S. Jin, X. Gao, S. Hong, Y. L. Joo, L. Archer. “Design Principles of metallic interphases for fast-charge, long-duration lithium metal batteries.”, Science, in prep.
2. X. Gao, Z. Yuan, Y. Shao, H. Wang, X. Feng, Y. L. Joo, S. Lang, H. D. Abruña. “Operando gas generation from electrolyte decomposition in Li-S pouch cells using differential electrochemical mass spectroscopy (DEMS)”, Proc. of the National Academy of Sciences, in prep.
3. Z. Gao*, X. Gao* (co-first author), R. Sinha, V. R. Shah, Y. Shao, P. Chen, Y. L. Joo. “Lithiophobic-lithiophilic organic-inorganic gradient protection to lithium metal anode", Advanced Functional Materials, in prep.
4. X. Gao, Y. Shao, P. Chen, Y. Wang, Z. Gao, S. Lang, Y. L. Joo. “Quantifying the impact of E/S ratio on initial discharge capacity in lean-electrolyte Li-S batteries”, Nature Communications, in prep.
5. S. Lang*, X. Gao* (co-first author), Y. Wang, Y. Shao, Z. Gao, L. M. Smieska, Y. Du, Y. L. Joo, H. D. Abruña. “Nucleation, growth and aggregation of sulfur clusters in lithium-sulfur pouch cells”, Nature Nanotechnology, 2024, submitted.
6. X. Gao, Y. Joshi, V. R. Shah, Y. Shao, C. Yi, Y. L. Joo. “Layer-on-layer high sulfur loading cathodes for lithium sulfur batteries via air-controlled electrospray”, Small, 2024, submitted.
7. Z. Gao, N. Utomo, X. Gao, Y. Joshi, V. R. Shah, M. A. Aziz, Y. Shao, S. Jin, Y. L. Joo. “Tailoring assembly of lithiated graphene by air-controlled electrospray for lithium metal battery anode”, Journal of Materials Chemistry A, 2024, submitted.
8. V. R. Shah, R. Sinha, X. Gao, W. Cesarski, S. F. Yuk, Y. L. Joo. “Facile Fabrication of Modality-Tunable Exfoliated N-doped Graphene as An Effective Electrolyte Additive for High-Performance Lithium-Sulfur Batteries”, Advanced Functional Materials, 2024, submitted.
9. S. Jin*, X. Gao* (co-first author), Y. Deng, P. Chen, S. Hong, R. Yang, Y. L. Joo, L. Archer. “Fast-charge, long-duration storage in lithium batteries”, Joule, 2023, https://doi.org/10.1016/j.joule.2023.12.022.
10. L. Archer, S. Jin, S. Hong, Y. Deng, X. Gao, Y. L. Joo. “Self-sufficient metal-air battery systems enabled by solid-ion conductive interphases”, Faraday Discussions, 2023, https://doi.org/10.1039/D3FD00112A.
11. X. Gao, C. Zheng, Y. Shao, V. R. Shah, S. Jin, J. Suntivich, Y. L. Joo. “Lithium Iron Phosphate Enhances the Performance of High-Areal-Capacity Sulfur Composite Cathodes”, ACS Applied Materials & Interfaces, vol. 15, no. 15, 2023, https://doi.org/10.1021/acsami.3c01515.
12. S. Jin, Y. Shao, X. Gao, P. Chen, J. Zheng, J. Yin, Y. L. Joo, L. A. Archer. “Designing interphases for practical aqueous Zinc flow battery with high power density and high areal capacity”, Science Advances, vol. 8, no. 39, 2022, https://doi.org/10.1126/sciadv.abq4456.
13. S. Jin, J. Yin, X. Gao, A. Sharma, P. Chen, Q. Zhao, J. Zheng, Y. Deng, Y. L. Joo, L. A. Archer, “Production of fast-charge Zn-based aqueous batteries via interfacial adsorption of ion-oligomer complexes”, Nature Communications, vol. 13, no. 1, 2022, https://doi.org/10.1038/s41467-022-29954-6.
14. M. Wood*, X. Gao* (co-first author), R. Shi, T. W. Heo, J. A. Espitia, E. B. Duoss, B. C. Wood, J. Ye, “Exploring the relationship between solvent-assisted ball milling, particle size, and sintering temperature in garnet-type solid electrolytes”, Journal of Power Sources, vol. 484, 2021, p. 229252, https://doi.org/10.1016/j.jpowsour.2020.229252.
15. E. Zhao, O. Borodin, X. Gao, D. Lei, Y. Xiao, X. Ren, W. Fu, A. Magasinski, K. Turcheniuk, G. Yushin, “Lithium-Iron (III) Fluoride Battery with Double Surface Protections”, Adv. Energy Mat., 2018, 1800721. https://doi.org/10.1002/aenm.201800721.

Presentations

1. X. Gao, S. Tiwari, A. Pandey, Y. Shao, Z. Gao, Y. L. Joo. “Threshold and Excess Electrolyte-to-Sulfur (E/S) Ratios in Lean-Electrolyte Li-S Batteries”, the 2023 AIChE Annual Meeting, 670803, November 2023, Orlando FL.
2. X. Gao, C. Zheng, Y. Shao, J. Suntivich, Y. L. Joo. “Lithium Iron Phosphate Reconstruction Facilitates Kinetics in High-Areal-Capacity Sulfur Composite Cathodes”, the 241^st Electrochemical Society Meeting, June 2022, Vancouver BC Canada.
3. X. Gao, C. Yi, S. Zamani, Y. Shao, Y. L. Joo. “Layer-on-Layer High Sulfur-Loading Cathodes for Lithium Sulfur Batteries Via Air-Controlled Electrospray”, the 2021 AIChE Annual Meeting, November 2021, Boston MA.
4. X. Gao, S. S. Yu, M. Grover, F. J. Schork, “Organic Micro-Environment to Promote Prebiotic Polymerization”, 2016 Annual Meeting of the Center for Chemical Evolution, May 2016, Atlanta, GA, USA.