Improving Ionic Conduction in Solid State Batteries Via Bulk and Interface Structure Design

Abstract

All-solid-state Li-ion batteries feature higher energy density, wider operation temperature range and better safety properties1 than conventional Li-ion batteries. The search for high performance solid state ionic conductors as the solid electrolyte (SEs) is one of the focuses of the battery field. Design principles for SE have been raised based on computational or experimental explorations. In this work, we will present our material design practices focusing on two factors that we believe to be essential for the performance of SE in solid state batteries: carrier density and interface. Attempts of tuning the carrier and vacancy densities were implemented in selected model systems, including known material systems and new material families, such as Li15P4S16Cl3 2 and other thiophosphates. Drastic improvement on ionic conductivity at room temperature was realized by either increasing the vacancy density or increasing stabilized interstitial sites. Interface design and engineering were also attempted with model systems including oxides, sulfides and halides. The impact of interface on effective conductivity was investigated with electrochemical impedance spectroscopy and complementary crystal structural characterizations including synchrotron X-ray diffraction and pair distribution function analysis. Modeling of interface structure was also employed to further understand the ionic conduction in the solid electrolyte layer and composite electrodes. 1. Auvergniot, J.; Cassel, A.; Ledeuil, J.-B.; Viallet, V.; Seznec, V.; Dedryvère, R., Interface Stability of Argyrodite Li6PS5Cl toward LiCoO2, LiNi1/3Co1/3Mn1/3O2, and LiMn2O4 in Bulk All-Solid-State Batteries. Chemistry of Materials 2017, 29 (9), 3883-3890.2. Liu, ZT.; Zinkevich, T.; He, XF.; Indris, S.; Xiong, S.; Liu, J.; Xu, W.; Bai, J.; Mo, Yifei; Chen, HL., Li15P4S16Cl3, a new lithium chloro-thiophosphate as a solid state ionic conductor. Inorganic Chemistry, in press.