(7fj) Designing Solid-Liquid Interphases and Polymer Composite Networks for Energy Storage and Carbon Capture

Advances in the basic science and engineering principles of electrochemical energy storage are imperative for significant progress in portable electronic devices. In this regard, metal based batteries comprising of a reactive metal (like Li, Na, Al) as anode have attracted remarkable attention due to their promise of improving the anode-specific capacity by as much as 10-fold, compared to the current state-of-art Li-ion battery that uses a graphitic anode. Perhaps their greatest advantage lies in the possibility of using of a Li-free high-capacity cathode like Oxygen that can improve the gravimetric energy density of batteries from ~0.3kWh/kg to ~12kWh/kg (i.e. comparable to the useful energy available from combustion of hydrocarbons). A persistent challenge with batteries based on metallic anodes, concerns their propensity to fail by short-circuits produced by dendrite growth during battery recharge, as well as by runaway of the cell resistance due to internal side reactions with liquid electrolytes. In my thesis research, I utilized multiscale transport modeling and experiments to fundamentally understand and to thereby develop rational designs for polymer electrolytes and electrode-electrolyte interphases that overcome these challenges (Tikekar, Choudhury et al. Nat. Energy 2016).

There have been several studies in literature dedicated to the prevention of dendrite growth by means of a high modulus physical barrier. However, electrolytes/separators with high mechanical strength tend to have low ionic conductivity, thus limiting their practical use. A recent theoretical study from our group reported a linear stability analysis of dendrite growth (Tikekar et al., Sci Adv. 2016) of metal electrodeposition and showed that the length-scale on which transport occurs near the electrodes could be as important as electrolyte modulus in stabilizing metals against dendrite formation. In a nutshell, this study concluded that dendrites can be prevented from crossing over to the counter electrode using battery separators with pore-diameter lower than critical (smallest) size of the dendritic nucleate. To evaluate this proposal, we designed cross-linked nanoparticle-polymer composite electrolytes with tunable pore size and quantified the stability of metal electrodeposition in these systems. In contrast to most previously reported polymer electrolytes, the crosslinked membrane simultaneously showed good mechanical strength (~1MPa) and high ionic conductivity at room temperature (~5mS/cm), which is a consequence of the high crosslinking node points in these membranes (Choudhury et al. Nat. Commn. 2015). Direct visualization experiments were performed to understand the effect of pore-size on dendrite growth, which showed remarkable agreement with the theoretical predictions. Furthermore, when operated in a battery, the crosslinked membrane showed the highest short circuit time compared to similar electrolytes reported in the literature.

Importantly, these studies showed that while the tendency for battery failure by dendrite-induced short-circuits can be reduced in polymer electrolytes, the issue of capacity-fading as a result of continuous reactions of the metal with liquid electrolyte persists. An additional striking fact in the electrodeposition literature not addressed by the linear stability analysis is that certain metals, including Magnesium, do not form dendrites. Further in my PhD thesis, I showed how multiscale analysis of transport at electrochemical interfaces enables design of stable solid-liquid interphases for reactive metal batteries. Recently, we used Density Functional Theory (DFT) calculations to quantify the diffusion energy barrier of ions on Mg, Li, Na surfaces and interestingly it seen that the diffusion barrier of Mg (0.02eV/atom) is several fold lower than Li (0.14eV/atom) or Na (0.16eV/atom) metals. In fact, the diffusion barrier of Li2CO3, Li2O (the commonly found compounds in lithium interface) is even higher, which is consistent with the dendritic electrodeposition in such batteries. However, in quest for finding stable interfaces, we observed that most metal halides (LiF, LiBr, NaF etc.) have much lower diffusion barrier. In other words, halide-rich interfaces on lithium or sodium can lead to stable electrodeposition similar to Mg deposition (Choudhury et al. Nat. Commn., in revision). We further utilized Classical Nucleation Theory (CNT) to understand implication of the ab-initio model in macroscopic metal deposition. The predictions from the coupled DFT-CNT model were validated using ex-situ scanning electron microscopy as well as in-situ optical microscopy. The nucleation pattern, indeed, showed a strike difference between usual (carbonate-rich) and halide-rich lithium interfaces. Based on these fundamental understanding, the solid electrolyte interphase in lithium metal batteries were artificially modified using organo-metallic reactions to enable enhanced reversibility in high energy density Lithium-Oxygen battery that demonstrated extended capacity retention and longer cycle life (Choudhury et al. Sci. Adv. 2017).

Research Interests:

The issues related to energy storage and climate change are often thought to be coupled. It is because, most renewable energy sources like solar or wind are intermittent, so they require efficient energy storage devices for full-time operation. On the other hand, although electric vehicles reduce vehicular emissions of carbon dioxide, the main sources of electricity generation are fossil fuel based. In this regard, a clever way to curb the CO2 emissions as well as store (and generate) electricity is designing a high energy density metal-CO2/O2 battery. In my future research career, I want to understand the fundamental barriers and find out clever solutions to successfully build high energy density batteries (or fuel cells) that provide multi-functional platform for energy harvesting and carbon capture, one example is aqueous Lithium-CO2 battery. There are at least three directions of research in the same broad area. (1) The first challenge is closely related to my PhD research, which is stabilizing the lithium metal under harsh conditions like aqueous media. This area of research will deal with strategies to reduce the chemical activity of the reactive fluids with lithium or sodium. It has been observed that the electrochemical stability window of water can be altered within a specific range by changing the salt concentration. It is hypothesized that excess salt in water forms a protective film on the electrode, thus changing the electric field at the interface. Another school of thought is the fact that excess salt binds the water molecule together, thus preventing their access to the electrode surface. Thus, a more detailed understanding is required to further push the limits of electrochemical activity in reactive conditions. I believe, my prior research work on understanding the surface diffusion of ions at the interface will provide me an important base to carry out my future work. Specifically, I will use techniques like in-situ AFM and Focussed Ion Beam milling, to understand the properties of the interface and based on that I will design the chemistry of electrolyte. Also, creating an artificial solid-electrolyte interphase using inert materials like Indium or Graphene can be a direction. (2) The second sub research area is on designing hybrid polymer membrane for separating the anode and cathode compartments in a secondary battery. Particularly, in a metal based battery, there are two major problems, one associated with the reactivity of the metal and dendrite formation, while the other is related to the cathode, involving high voltage stability or dissolution of reaction products by cathodic reactions. These two problems are decoupled and need to be solved using different electrolyte chemistries. I plan to synthesize polymeric composite membranes that can regulate the flow of ions, while restricting the solvent passage. Cylindrically aligned block copolymer or janus-particle films are some obvious approach, which can interact with solvent molecules differently from different sides. I would be interested in characterizing the structure of the membrane using cross-sectional scanning electron microscopy and in-situ optical microscopy. My previous experience in designing nanoporous crosslinked nanoparticle-based membranes for dendrite suppression can help me in this research area. (3) The third research area, I am going to focus on deals with the design of semi-solid cathode materials with high capacity loadings. Flow batteries are not suitable for consumer devices, owing to the requirement of a flow system and low volumetric density, while slurry-casted planar cathodes are limited in the active material loading due to the ion and electron transport-related issues in thick cathodes. I plan to synthesize gel-type building blocks of cathodes that can have good electron conductivity as well as high packing density. One pathway for this is synthesizing carbon based nanostructures, whose surface may be decorated with redox active species. The interconnected carbon structure can provide electron mobility, and a high grafting density of redox species on the carbon structure can improve the total loading capability. It will be important to understand the rheological characteristics as well as the self-assembly of the cathode building blocks using techniques like Rheo-SAXS, and Rheo-SANS. A major portion of my PhD research dealt with the understanding of structure and dynamics of polymer grafted hairy nanoparticles. I hope to bring in these experiences in my future research.

Experience in Grant writing:

Previously I have written at total of three grant proposals and six beamline proposals for doctoral advisor as well as for my graduate committee member. Successful proposal include Lithium metal battery interphases funded by ARPA-E of DOE and Polymer Battery Separators funded by NSF.

Teaching Interests:

I have prior experience of teaching two undergraduate level courses as a Teaching Assistant (TA) in Cornell University. The first course I served as a TA was for the junior year Chemical Engineering course – ‘Heat and Mass Transfer’ comprising of 96 students. My responsibilities in the course included a weekly recitation session, design of homework and exam questions as well as taking office hours and review sessions for students. My second TA appointment was in the Physics Department of Cornell University for the Freshman Level Course – ‘Mechanics and Heat’. My task in this course was to instruct discussion sessions, conduct Physics Lab and take office hours as well as grade homework and exam papers. In addition, in my research group, I have guided several junior graduate (three M.S. and 1M.Eng.) students as well as three undergraduate students. I was also invited to give research talks in several research groups and R&D companies. Based on my PhD research, I am comfortable giving lectures in different areas including Polymer Physics, Electrochemistry, and Surface Science.

Publications:

1. Tuning surface diffusion barriers for high reversibility of lithium metal anodes S. Choudhury, Z. Tu, K. Fawole, S. Stalin, D. Gunceler, R. Sundararaman and L. A. Archer. Langmuir, in revision

2. Designing Solid-liquid Interphases for Sodium Batteries S. Choudhury, S. Wei, Y. Ozhabes, D. Gunceler, M. J. Zachman, Z. Tu, J. H. Shin, P. Nath, A. Agrawal, L. F. Kourkoutis, T. A. Arias and L. A. Archer. Nature Communications, in revision

3. Designing artificial solid-electrolyte interphases for single-ion, high-efficiency transport in batteries Z. Tu*, S. Choudhury*, M. J. Zachman, S. Wei, K. Zhang, L. F. Kourkoutis, L. A. Archer. Joule, in press [* First authorship shared]

4. Self-suspended Polymer Grafted Nanoparticles. S. Srivastava, S. Choudhury, A. Agrawal. Current Opinion in Chemical Engineering, 2017

5. Designer Interphases for the Lithium-Oxygen Electrochemical Cell. S. Choudhury, C. T. Wan, W. I. Al Sadat, Z. Tu, S. Lau, M. J. Zachman, L. F. Kourkoutis and L. A. Archer. Science Advances, E1602809 (2017) †Highlighted in: Cornell Chronicle, Phys.org, Green Car Congress, Nanowerk Nanotechnology News

6. Highly stable sodium batteries enabled by functional ionic polymer membranes. S. Wei*, S. Choudhury*, J. Xu, P. Nath, Z. Tu, and L. A. Archer. Advanced Materials, 29, 1605512 (2017) [* First authorship shared] †Featured on the cover

7. Nanoporous Hybrid Electrolytes for High Energy Batteries Based on Reactive Metal Anodes. Z. Tu, M. J. Zachman, S. Choudhury, S. Wei, L. Ma, Y. Yang, L. F. Kourkoutis, L. A. Archer. Advanced Energy Materials, 1602367 (2017) †Featured on the cover

8. Design Principles for Electrolytes and Interfaces for Stable Lithium-metal Batteries. M. D. Tikekar, S. Choudhury, Z. Tu, and L. A. Archer. Nature Energy, 1:16114 (2016)

9. Lithium Fluoride Additives for Stable Cycling of Lithium Batteries at High Current Densities. S. Choudhury and L. A. Archer. Advanced Electronic Materials, 2, 1500246 (2016)

10. Hybrid Hairy Nanoparticles Stabilize Lithium Metal Batteries. S. Choudhury, A. Agrawal, S. Wei, E. Jeng and L. A. Archer. Chemistry of Materials, 28 (7), 2147-2157 (2016)

11. A Stable Room Temperature Sodium-sulfur Battery. S. Wei, S. Xu, A. Agrawral, S. Choudhury, Y. Lu, Z. Tu, L. Ma, L. A. Archer. Nature Communications, 7: 117222 (2016)

12. Molecular Origins of Temperature-Induced jamming in Self-Suspended Hairy Nanoparticles A. Agrawal, H.Y. Yu, A. Sagar, S. Choudhury, L. A. Archer. Macromolecules, 49 (22), 8738-8747 (2016)

13. Multifunctional Separator Coatings for High-Performance Lithium-Sulfur Batteries M. S. Kim, L. Ma, S. Choudhury, L. A. Archer. Advanced Materials Interfaces, 3 (22) (2016) †Featured on the cover

14. Fabricating Multifunctional Nanoparticle Membranes by a Fast Layer-by-Layer Langmuir-Blodgett Process: Application in Lithium-Sulfur Batteries M. S. Kim, L. Ma, S. Choudhury, S. S. Moganty, S. Wei, and L. A. Archer. Journal of Materials Chemistry A, 4, 14709-14719 (2016)

15. Interactions, Structure, and Dynamics of Polymer-Tethered Nanoparticle Blends A. Agrawal, B. M. Wenning, S. Choudhury. Langmuir 32 (34), 8698-8708 (2016)

16. Multiscale Dynamics of polymers in Particle-Rich Nanocomposites R. Mangal, Y. H. Wen, S. Choudhury, L. A. Archer. Macromolecules 49 (14), 5202-5212 (2016)

17. A Highly Reversible Room Temperature Lithium Metal Battery based on Cross-linked Hairy Nanoparticles. S. Choudhury, R. Mangal, A. Agrawal and L. A. Archer. Nature Communications, 6: 10101 (2015) †Highlighted in: Cornell Chronicle, Phys.org, IEEE Spectrum, Engineering.com

18. Self-suspended Suspensions of Covalently Grafted Hairy Nanoparticles. S. Choudhury, A. Agrawal, S A Kim, and L. A. Archer. Langmuir, 31 (10) 3222-3231 (2015)

19. A Highly Conductive, Non-flammable Polymer-nanoparticle Hybrid Electrolyte. A. Agrawal*, S. Choudhury*, and L. A. Archer. RSC Advances, 5, 20800-20809 (2015) [* First authorship shared]

20. Dynamics and yielding of binary self-suspended Nanoparticle Fluids. A. Agrawal, H. Y. Hsiu, S. Srivastava, S. Choudhury, S. Narayanan and L. A. Archer. Soft Matter, 11, 5224-5234 (2015)

21. Electronic and Chemical Properties of Germanene: The Crucial Role of Buckling. A. Nijamudheen, R. Bhattacharjee, S. Choudhury, and A. Datta. Journal Physical Chemistry C, 119 (7), pp 3802–3809 (2015)

Patents:

1. Dendrite Inhibiting Electrolytes for Metal-Based Batteries. L. A. Archer, T. A. Arias, Y. Lu, Z. Tu, D. Gunceler, S. Choudhury U.S. Patent Serial No. 15/128,635, Filed on September 23, 2016

2. Protective layers for Metal Electrode Batteries. Z. Tu, S. Choudhury, S. Wei, and L. A. Archer. U.S. Provisional Patent No. 62/436,248. Issued on December 19, 2016

3. Binder-Free and Multicomponent Layer-by-Layer Separator Coating for Lithium Batteries. M. S. Kim, S. Choudhury, L. Ma, and L. A. Archer U.S. Provisional Patent No. 62/265,539. Issued on December 10, 2015