Sodium-ion batteries offer an economic advantage over Li-ion batteries, as they can achieve similar performance using naturally abundant sodium (Na). Additionally, solid-state Na batteries (SSNBs) that use solid Na-ion conductors instead of liquid electrolytes improve device safety and are applicable to mid- and large-scale energy storage systems such as electric vehicles and utility grids. In this project, sulfide solid electrolytes (SEs) will be investigated for their superior ionic conductivity. However, for sulfide-based SSNBs, high interfacial resistance remains a challenge to maximizing performance and commercialization. This research project will systematically investigate structural changes at the two main interfaces in sulfide-based SSNBs to fundamentally understand the sodium ion transport across those interfaces. The investigators aim to address critical interface issues preventing high battery performance. This research will be integrated with outreach and education efforts such as creating Women Engineering Network program and a collaboration with Kentucky Science Center. These initiatives will encourage more students from underrepresented minority groups such as K-12 Girls to enroll in the science, technology, engineering and mathematics (STEM) majors, as well as increase the public’s scientific awareness on electrochemical energy storage and its role in using clean energy sources.
The technical goal of this project is to fundamentally understand the origins of interfacial resistance at both Na anode/sulfide SEs and cathode/sulfide SEs interfaces. The investigators will use this fundamental knowledge to engineer sulfide SEs with reduced resistance across interface and achieve advanced SSNBs with high energy density and stability. The first objective is to investigate the compatibility of halide doped sulfide solid electrolyte with electrodes (both Na anode and cathodes) to elucidate the halide doping effects on interface resistance. The second objective aims to understand Na-ion transport mechanisms in sulfide-polymer composite solid electrolytes (CSEs) as well as across the interfaces of CSE/electrodes in Na symmetric cells and SSNBs. The third objective focuses on study the cycling performance of sulfide based SSNBs that use metal-sulfide cathodes with different levels of volume change, aiming to determine the volume expansion /contraction effects on the interface resistance in SSNBs during their repeated charge/discharge cycling process. The fundamental knowledge obtained from this project will give insights into engineering interface design to reduce the interfacial resistance, overcome an important roadblock to achieve advanced solid-state Na batteries with high capacities and long lifetimes.
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.
