Collaborative Research: Understanding Sulfur-Carbon-Solid Electrolyte Interface of Lithium/Sulfur Solid-State Batteries

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In recent years, there has been a significant movement towards using electric vehicles (EVs) as a more sustainable form of transportation. Continuous innovation of rechargeable batteries that supply power to an electric motor is required to boost the adoption of EVs since the battery significantly affects the driving range, safety, and cost of EVs. A lithium/sulfur (Li/S) battery consisting of a lithium metal anode and sulfur cathode is a promising candidate for EV applications as it has the potential for a five-times longer driving distance at a given weight of the EV battery compared to conventional lithium-ion batteries. The major challenges towards the development of reliable and safe Li/S batteries are 1) the need to mitigate problematic issues associated with chemical compounds called lithium polysulfides, which are formed in the organic liquid electrolyte during battery operation, and 2) the flammable ionic conductor used as electrolyte. A Li/S solid-state battery is a promising system for overcoming these issues because it uses a solid-state electrolyte which is non-flammable and can prevent polysulfide formation better than liquid electrolytes. However Li/S solid-state batteries suffer from poor energy storage/delivery performance due to an insufficient understanding of the electrode-solid electrolyte interface. This project will conduct fundamental studies on the interfaces in Li/S solid-state batteries, advanced materials characterization methods, and implement rational electrode design to address these challenges. The results from this project will create new knowledge that can enable energy storage solutions to meet the U.S.’s mission toward decarbonizing the global automotive sector and shaping the sustainable energy future. Comprehensive education and workforce development plans are laid out through a seamless partnership between Arizona State University and the University of Michigan Ann Arbor. Training graduate and undergraduate students via this research project will significantly contribute to the mission of both universities mission to become a hotbed of energy technologies.The overarching goal of this project is to improve the understanding of the electrochemical processes taking place in Li/S composite cathodes employing garnet-type lithium lanthanum zirconium oxide (Li7La3Zr2O12, LLZO) as a solid electrolyte. The research will focus on: 1) Obtaining an improved understanding of the reaction mechanisms in Li/S composite cathodes using model systems, electroanalytical techniques, and in operando/ex-situ X-ray analyses, 2) Elucidation of fundamental thermodynamic and kinetic parameters influential in the electrochemical processes of sulfur, and 3) Investigation of design parameters such as particle size, morphology, surface properties, and mass loading of components in the sulfur/solid state electrolyte composite cathode. Enabled by the collaborative research team’s expertise in Li/S cell chemistry, solid-state battery technology, and synchrotron-based in-situ/operando characterization, this project will result in a comprehensive methodology for investigating and designing sustainable, next-generation energy storage systems. The results of the project will lead to the innovative design of S-LLZO composite cathodes, which is favorable for fast and sustainable electrochemical processes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.