AVS 70 Session TF1-TuA: Thin Films for Energy Applications II: Batteries
Session Abstract Book
(274KB, Jul 23, 2024)
Time Period TuA Sessions
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Abstract Timeline
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2:15 PM |
TF1-TuA-1 Unlocking High Volumetric Energy Densities in LCO Cathode Materials through Atomic Layer Deposition
Jaime DuMont, Madison Martinez, Meghan Herbert-Walters, Arrelaine Dameron, Barbara Hughes (Forge Nano) For the last 40+ years lithium cobalt oxide (LCO) batteries have reigned supreme in consumer electronics. This chemistry is attractive for its ability to provide top tier energy density in applications that require faster, lighter, and longer lasting cells. With the expectation of at least a doubling of the global market demand for consumer electronics over the next 10 years, LCO performance will need to rise to meet the demands of an ever-changing marketplace. Enhancements will rely heavily on the ability of materials scientists to tease out more and more of LCO’s available capacity without sacrificing stability and lifetime. In this work, we will highlight how protective coatings grown using the thin film deposition technique atomic layer deposition (ALD) can unlock high volumetric energy densities in LCO cathode materials not yet realized by other commercially available technologies. Electrochemical testing and differential capacity analysis of cathode half cells at progressively wider voltage windows illustrate that ALD protects and stabilizes LCO against detrimental side reactions that cause capacity fade and increase internal resistance. Post-cycling SEM-EDX characterization from full cells show that Co dissolution can be significantly reduced when an ALD coating is deposited on the cathode and that this effect becomes more pronounced at elevated cut off voltages. EIS analysis results demonstrate that ALD protects LCO surfaces from detrimental phase transitions above a 4.5V upper cut off voltage, suppressing the formation of a spinel layer and shielding the surface from harmful reactions with the electrolyte. Together, these enhancements lead to cycling performances that rival the best performing commercial material investigated in this work, showing that ALD can be a viable and affordable technology to meet the materials enhancement needs for the LCO cathode market. |
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2:30 PM |
TF1-TuA-2 Surface Chemistry of Plasma Exposure on Sulfide Solid Electrolytes
Alexander Kozen (University of Vermont); Yang Wang, Daniela Fontecha, Gary Rubloff, Sang Bok Lee (University of Maryland, College Park) Sulfide solid state electrolytes (SSEs) are considered one of the most promising materials to replace liquid electrolytes in next-generation batteries due SSEs astonishing ionic conductivities. However, the high reactivity of sulfide SSE materials precludes direct contact with Li metal anodes. One approach to stabilize the sulfide SSEs is passivating the sulfide interface with thin films of stable chemical species, forming an artificial solid electrolyte interphase (ASEI) layer. Ideal passivation materials for the anode/SSE interface are generally comprised of Li3N or LiF species, which are stable at Li metal potentials. Here, we investigate the impact of plasma treatment on sulfide SSEs, as well as deposition of plasma-based ASEI materials using atomic layer deposition (ALD). I will discuss the implications of Ar, N2, and NH3 plasma exposures on sulfide solid electrolytes (LGPS, LPSCl) and the resulting surface chemical changes as determined by in-vacuo x-ray photoelectron spectroscopy (XPS) measurements. N2 and NH3 plasma exposure can cleave Li2S surface bonds and replace them with Li3N surface species, however due to a lack of Li available at the surface this coverage is limited to ~30% and cannot form complete ASEI layers. Additionally, I will report the changes in electrochemical behavior of these pellets in Li/SSE/Li symmetric cells. Due to the incomplete surface coverage of Li3N species, the surface nitride passivation is reduced and still allows deleterious reactions to occur after contact with Li metal. These results indicate that for complete Li3N surface coverage, additional Li species must be available on the sulfide SSE surface before plasma treatment. I will also discuss the initial stages of ALD ASEI layer deposition on the sulfide SSE materials and evaluate their protection efficacy. |
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2:45 PM |
TF1-TuA-3 Tuning the Composition and Structure of High Mobility Nasicon-Type Thin Films Through Atomic Layer Deposition
Daniela R. Fontecha (University of Maryland College Park); Alexander C. Kozen (University of Vermont); David M. Stewart, Gary W. Rubloff, Keith E. Gregorczyk (University of Maryland College Park) Fast Li+ ion conducting thin film solid state electrolytes (SSEs) by atomic layer deposition (ALD) enable high power density, fast time constants, and high operating frequency regimes in solid state ionic devices. However, the ionic conductivity of thin film SSEs fabricated by ALD has been limited by material development challenges, phase purity concerns when dealing with tertiary and quaternary systems, and challenges related to crystallinity. These complexities require careful consideration of the material system, precursor selection, process parameters, and post-annealing conditions to realize ideal ALD thin-film SSE materials with ionic conductivities >10-6 S/cm. Bulk oxide SSEs, such as Li1+xAlxTi2-x(PO4)3 (LATP) have a NASICON-type crystal structure, show high ionic conductivity when crystalline (10-3 S/cm), demonstrate air & water stability, and a high voltage stability window. ALD synthesis of LATP can be broken down into well-known constituent processes (e.g., Li3PO4, Al2O3, TiP2O7) which can be combined with respect to stoichiometric ratios. LATP can be considered Al-doped LiTi2(PO4)3 (LTP), in which Al+3 ions partially replace Ti+4 ions in the NASICON-type structure. This facilitates fast Li+ ion conduction through the 3D network. With that in mind, an ALD process for LTP was first developed by alternating between Li2O and TiP2O7 sub-processes. The Li2O sub-process uses lithium tert-butoxide (LiOtBu) as the lithium source and water to complete the surface reaction. The TiP2O7 sub-process uses titanium (IV) isopropoxide (TTIP) as the titanium source, trimethyl phosphate (TMP) as the phosphorous source, and water. The growth rate of LTP was measured to be 0.4 Å/cycle at 300 oC. By adjusting the ratio between Li2O and TiP2O7 cycles, the Li concentration in LTP can be tuned between 8.4-34.3 at % Li. A NASICON-type crystalline structure is achieved by post-annealing the LTP films between 650 oC – 850 oC. The ideal annealing temperature was found to be a function of Li-ion concentration. The resulting measured ionic conductivity of partially crystalline LTP thin films is 3.6x10-5 S/cm at 80 oC. In this talk, we will discuss the complex issues related to process parameters, stochiometric tunability, and the resulting ionic conductivity when exploring ternary and quaternary LTP/LATP metal phosphates phase space. View Supplemental Document (pdf) |
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3:00 PM |
TF1-TuA-4 Unlocking Novel Chemistry in Atomic Layer Deposition: Transformative Insights from Trimethylaluminum Interactions with Battery Materials
Donghyeon Kang, Anil Mane, Jeffrey Elam (Argonne National Laboratory) Trimethylaluminum (TMA) stands as a keystone in atomic layer deposition (ALD), widely esteemed for its role in crafting aluminum-based coatings across diverse applications. Notably, TMA is used to produce Al2O3 with H2O, AlF3 with HF-pyridine, and Al2S3 with H2S, adhering to well-defined ALD mechanisms. These processes have permeated various substrates, leading to ultra-thin Al-based coating layers, particularly within the realm of energy storage materials such as battery cathodes, anodes, and solid electrolytes. Our research group has embarked on a profound exploration of TMA's ALD chemistry, unveiling captivating interactions with reactive metal substrates, solid-state electrolytes, and battery cathode materials. Interestingly, when subjected to Li-metal anodes, TMA deviates from conventional ALD pathways, engendering a carbon composite layer atop the Li metal. This unconventional behavior arises from the inherent reactivity of both TMA and Li metal, diverging from established ALD paradigms. Moreover, our investigations reveal TMA's propensity to engage with Li-based impurities on solid electrolyte and cathode surfaces, yielding protective layers with beneficial attributes. Astonishingly, despite TMA's extensive utilization, this phenomenon has eluded prior scrutiny. In this presentation, we unveil our findings on the intricate chemistry between TMA and battery materials (Li-metal, cathode, solid electrolytes) elucidated through in-situ quartz crystal microbalance (QCM), high-resolution X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Raman spectroscopy studies. Furthermore, we demonstrate the transformative potential of these discoveries in the realm of battery materials surface treatment, offering tantalizing prospects for streamlined industrial applications. |
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3:15 PM |
TF1-TuA-5 Mapping Lithium Diffusion in Thin-Film V2O5 using Raman Spectroscopy
Daniel MacAyeal (University of Vermont); Leopoldo Tapia-Aracayo, Spencer Caverly, David Stewart, Gary Rubloff (University of Maryland); Alexander Kozen (University of Vermont) Understanding lateral diffusion of lithium in thin-film solid-state battery (SSB) materials is critical to improving SSB performance, stability, lifespan, and architecture. Using model test structures of sputtered V2O5/W/LiPON, we use Raman spectroscopy peak shifts to map Lithium concentration in V2O5. We evaluate the diffusion of lithium from LiPON layers into thin-film V2O5, measure the impact of different sputter deposition process conditions on lateral lithium diffusion, and investigate the effects of post-annealing the fabricated test structures. We will discuss the benefits of front versus back-side Raman spectroscopy for analyzing masked devices and correlate Raman spectroscopy mapping to XPS data to confirm compositional accuracy. Additionally, we will discuss the impact of electrochemical cycling at C/10 on lateral Lithium diffusion for symmetric V2O5/LiPON/V2O5 devices. Lastly, we will discuss the important implications of the lateral spacing limitations of clustered SSB devices due to lateral diffusion and propose architectural design rules based on this diffusion behavior for optimized device performance. |
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3:30 PM | BREAK |