The Application of Garnet Type Lithium Conductor in Lithium Ion Batteries

In this study, solid state electrolyte, aluminum doped lithium lanthanum zirconium oxide (Li7La3Zr2O12, LLZO) without doping any expensive element, such as Tantalum, was synthesized. X-ray diffraction spectroscopy (XRD) was conducted to confirm that LLZO synthesized is cubic phase. Cyclic voltammetry (CV) was used to enhance the ionic conductivity of LLZO and the samples were compared with the ones without CV treatment. The following analytical methods were conducted. Electronic impedance spectroscopy (EIS) was used to evaluate ionic conductivity; Arrhenius plots were conducted to deduce migration activation energy of lithium ions; X-ray adsorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS) were done to determine chemical states of different elements; scanning electron microscope (SEM) was used to evaluate density of LLZO pellets. The LLZO with CV treatment has conductivity of 1.3 x 10-3 S/cm, which is almost five times higher than the one without CV treatment (3.0 x 10-4 S/cm). Both XAS and XPS data reveal that there is a change of coordinate of lithium ions after CV treatment. Full solid state lithium ion battery was successfully assembled using the LLZO, along with Li2Ni0.5Co0.2Mn0.3O2 cathode material and Li metal anode, and acquired the capacity of 60 mAh g-1 under the current density of 0.21 mA cm-1. This proves the potential industrial applicability of solid state electrolytes.