SUBJECT: Ph.D. Proposal Presentation
BY: Zhantao Liu
TIME: Friday, August 7, 2020, 1:00 p.m.
PLACE:, online
TITLE: Design and Development of High-Performance Solid Electrolyte for All-solid-state Lithium Ion batteries
COMMITTEE: Dr. Hailong Chen, Chair (ME)
Dr. Matthew T. McDowell (ME)
Dr. Angus Wilkinson (Chemistry)
Dr. Shuman Xia (ME)
Dr. Ting Zhu (ME)


All SOlid-state Lithium Ion Batteries (ALSOLIBs) offering high energy density and power density are considered as one of the next generation electrochemical energy storage technologies. It is in urgent need to develop high-performance solid electrolytes (SEs), which is the key component of ALSOLIBs, satisfying the requirements in multiple categories of properties, including high ionic conductivity at ambient temperature, good chemical and electrochemical stability, and good mechanical durability. Among various type of SEs, sulfide and halide electrolytes show promising ionic conductivity and favorable synthesizability, which are beneficial for the ALSOLIBs fabrication.
In my past and ongoing thesis work, a novel lithium chlorothiophosphate compound, Li15P4S16Cl3, was successfully discovered, synthesized, and tested. The crystal structure was solved with using synchrotron and neutron diffraction methods. The ionic conductivity was measured by electrochemical impedance spectroscopy. The Li+ transport in Li15P4S16Cl3 was also investigated with multiple solid-state NMR methods. In order to improve its ionic conductivity, aliovalent cation doping strategy was applied and its influence on crystal structure and ionic conductivity will be studied.
In another project on halide SEs, we used Li3YX6 (Y=Y, Er, X=Cl, Br) as the structural motif and studied the influence of anion mixing on the crystal structure and ionic conductivity. A new compound Li3YBr3Cl3 was designed and successfully synthesized. It was found that the lithium distribution at different lithium sites can be tuned by the chemistry of anions. New tetrahedral Li sites, which were previously rarely reported in this type of layer structured compounds, were identified, which have pronounced positive impact on Li+ diffusivity. A novel grain boundary structure that promotes the overall ionic transport was also identified and investigated. Rational design and synthesis of halides are proposed further optimizing and tuning the chemical compositions and processing conditions to achieve higher conductivity and to fabricate ALSOLIBs with higher performance and longer life.