Engineering the Future: Unveiling the Mysteries of Solid Electrolyte Ionic Conductivity

Significance 

All-solid-state batteries (SSBs) use solid materials for both the electrolyte and electrodes. This is a significant shift from traditional batteries, which typically use liquid or gel electrolytes. For example, in SSBs, the liquid or polymer gel electrolytes found in conventional lithium-ion batteries are replaced with solid electrolytes. These solid electrolytes can be made from ceramics, glass, or sulfides. The electrodes in SSBs are also solid (lithium, nickel, cobalt, and manganese) and are similar to those in regular batteries. Like in traditional batteries, lithium ions move from the negative electrode (anode) to the positive electrode (cathode) during discharge and back when charging. The solid electrolyte facilitates this ion transport without the need for a liquid medium. SSBs are considered much safer with reduced risk of fires and explosions because it does not contain flammable liquid electrolytes. Solid electrolytes can potentially allow for closer packing of materials, leading to higher energy densities. Moreover, SSBs are expected to have a longer life due to less degradation of materials compared to liquid electrolyte batteries. They can also operate effectively across a broader range of temperatures and are more stable over time. Furthermore, SSBs could enable faster charging times due to better ion conductivity of some solid materials.

SSBs are considered an important technological advancement because SSBs could significantly improve the range and safety of EVs, addressing one of the major barriers to their adoption. They are also seen as key to efficient storage solutions for solar and wind energy, facilitating a transition to renewable energy sources. They also may offer more sustainable and environmentally friendly options compared to traditional batteries. However, creating solid materials that can transport ions as effectively as liquids is challenging. Additionally, producing these batteries with consistent quality and performance is currently more complex and costly than traditional batteries. There is also the limitation of lithium dendrites which can still form and penetrate solid electrolytes, potentially causing short circuits. Solid electrolytes, while offering increased mechanical strength and reduced flammability, pose their own unique challenges. The core issue lies in their relatively low Li-ion conductivity, a factor critical to the performance of SSBs. This conductivity is influenced by two primary mechanisms: lattice diffusion within the solid phase and the limited contact area between electrolyte particles. There is extensive research to overcoming current technical and manufacturing challenges.

To address some of these challenges, a collaborative effort between NASA Langley and NASA Glenn Research Centers provided a new study published in the journal ACS Applied Materials & Interfaces led by Dr. Vesselin Yamakov explored the impact of pressure on the ionic conductivity of solid electrolytes in SSBs, crucial for safe, reliable, and high-capacity energy storage. His co-authors include April Rains, Jin Ho Kang, Lopamudra Das, Rehan Rashid, Ji Su, Rocco Viggiano, John Connell, and Yi Lin. The article investigates the interaction between particle dynamics and ionic conductivity, particularly focusing on the influence of pressurization on lithium-ion (Li-ion) conductivity. The study contrasts low and high grain boundary conductivity scenarios, providing insights into the mechanical and structural challenges posed by solid electrolytes. The research employs both theoretical modeling and experimental approaches to analyze these dynamics, aiming to enhance the performance of SSBs.

The authors employed both theoretical modeling and experimental methods to investigate the pressure dependence of ionic conductivity in solid electrolytes. The theoretical model was based on linear elastic theory and particle dynamics, predicting a power-law dependence of conductivity on pressure, differing for bulk-dominant and grain boundary-dominant conductivity. Particle dynamics simulations were used to test these predictions, modeling solid electrolyte particles under various pressure conditions. Experimentally, they measured ionic conductivity of lithium phosphorus sulfide chloride (LPSC) solid electrolyte under different fabrication pressures. These measurements were conducted using electrochemical impedance spectroscopy (EIS), with LPSC sandwiched between holey graphene layers. The experimental results qualitatively agreed with the theoretical predictions, demonstrating increased ionic conductivity with higher fabrication pressures and confirming the power-law dependence of conductivity on pressure. This work provides insights into optimizing solid electrolyte properties for improved performance in solid-state batteries.

Dr. Vesselin Yamakov and colleagues advanced our understanding of how pressure affects SE ionic conductivity. By exploring scenarios with varying grain boundary conductivities, the research unveils the scaling dependence of conductivity on pressure. This dependence is not linear; different regimes of conductivity behavior emerge based on the relationship between bulk and grain boundary conductivity. The authors’ findings suggest that electrolytes with specific particle sizes and shapes, subjected to controlled pressurization during fabrication of SSBs, could exhibit significantly enhanced ionic conductivities and enhanced performance. This insight is invaluable for engineers and researchers striving to overcome the conductivity limitations that have long hampered the broader adoption of SSBs. In conclusion, the exploration of pressure dependence in solid electrolyte ionic conductivity paves the way for the next generation of battery technologies.

About the author

Dr. Vesselin I. Yamakov is Research Scientist Lead at Analytical Mechanics Associates in Hampton, Virginia, and works as a NASA contractor at the NASA Langley Research Center (LaRC) in support of the computational materials effort. He received M.S. (1991) from the University of Sofia, Bulgaria, and spent four years (1999-2003) as a post-doctoral researcher at Argonne National Laboratory, Chicago, IL before joining NASA (LaRC) as a contractor. He is a recipient of two NASA Group Achievements Awards (2015, 2020), the Administrator’s Gears of Government Team Award (2019), and the NASA Exceptional Scientific Achievement Medal (2021). His current research interest is in developing computational models to investigate new materials and structures that are of interest for aero and space applications.

About the author

April A Rains is a Chemistry PhD student at the University of Georgia, Athens. She has had multiple internships with NASA Langley Research Center and is a two-time recipient of the Exceptional Contribution Award from NASA Langley Research Center (2020, 2021).   She has earned two bachelor’s degrees, one from the University of Wisconsin and one from Florida International University.  Her research interests are in materials for energy storage and direct recycling of Li-Ion batteries.

About the author

Dr. Jin Ho Kang is an Aerospace Material Research Engineer, in the Advanced Materials and Processing Branch at NASA Langley Research Center. His role is fundamental and applied research in the structure, property, durability relationships of aerospace materials for deployable and inflatable space structures such as solar sails, payload booms and Mars/Moon habitats, and energy harvesters/storages. He received his B.S. from Sogang University and M.S. and Ph.D. from POSTECH (Pohang University and Science and Technology), South Korea in 2004. He has received the Richard T. Whitcomb and Paul F. Holloway Technology Transfer Award and the NASA Exceptional Technology Achievement Medal.

About the author

Dr. Lopamudra Das is a materials research scientist working as a contractor at the Advanced Materials and Processing Branch at NASA Langley Research Center. She holds a B.Tech in Electronics and Instrumentation Engineering from Kalyani University, India, and a M.Tech in Materials Engineering from Jadavpur University, India. She received a M.S in Electrical & Computer Engineering from Virginia Commonwealth University, U.S.A, (2010) and earned her doctorate in Applied Science from The College of William and Mary, Virginia (2017). Dr. Das has experience in a diverse range of materials and surfaces development and characterization, including semiconductor device fabrication and polymer surface modification. She has worked on developing materials for lunar dust adhesion mitigation and researched materials for energy storage devices. She is enthusiastic about bio-inspired materials and efficient energy storage solutions.

About the author

Rehan Rashid is a U.S./Canadian senior mechanical engineering student at York University (Toronto, ON). He previously interned at the NASA Johnson Space Center’s Energy Systems Test Branch, NASA Langley Research Center’s Advanced Materials and Processing Branch, and NASA Kennedy Space Center’s Exploration Research Technology and Programs Branch. His research interests lie in energy storage and conversion processes, thermofluids and heat transfer research, and plasma physics for space applications.

About the author

Ji Su is a research materials engineer in the Advanced Materials and Processing Branch at NASA Langley Research Center (LaRC). He received B.S. (1982) from Harbin Institute of Technology and M.S. (1990) and Ph.D. (1995) from the Rutgers-the State University of New Jersey.   He is a recipient of Best Technology Development of Energy Harvesting at International Energy Conference (2011) and NASA Exceptional Technology Achievement Medal (2019).  His current research interests include active polymer materials and their applications in energy technologies and composite materials for aerospace applications.

About the author

Dr. Rocco Viggiano graduated with a Ph.D. in Macromolecular Science and Engineering from Case Western Reserve University in 2015 under the direction of Dr. David Schiraldi.  Dr. Viggiano specializes in polymer chemistry and synthesis.  Since joining the NASA Glenn Research center in 2015, he has focused on the synthesis of polyimide based aerogels for high temperature insulation applications.  In 2018, Dr. Viggiano has pursued investigations into solid-state electrolytes for all solid-state batteries. Currently, Dr. Viggiano is the PI and the lead of the Solid-state Architecture Batteries for Enhanced Rechargeability and Safety (SABERS) project which is developing novel solid-state batteries and solid-state electrolytes.

About the author

Yi Lin is a research materials engineer in the Advanced Materials and Processing Branch at NASA Langley Research Center (LaRC). He received B.S. (1996) and M.S. (1999) degrees from the University of Science and Technology of China and a Ph.D. (2004) from Clemson University. He is a recipient of the NASA Technology Achievement Medal (2017) and NASA Langley Research Center’s H. J. E. Reid Award (2018). His current research interest is energy storage materials for aeronautics and space applications.

Reference

Vesselin I. Yamakov,* April A. Rains, Jin Ho Kang, Lopamudra Das, Rehan Rashid, Ji Su, Rocco P. Viggiano, John W. Connell, and Yi Lin. Pressure Dependence of Solid Electrolyte Ionic Conductivity: A Particle Dynamics Study. ACS Appl. Mater. Interfaces 2023, 15, 27243−27252.

Go to ACS Appl. Mater. Interfaces

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