Development of Li-based Garnet Electrolytes for All-Solid-State Li Batteries
Date
2021-04-26
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Abstract
All-solid-state Li batteries employing a ceramic solid electrolyte are considered as the nextgeneration energy storage devices due to their advantages in safety and potentially high energydensity. Garnet-type Li6.5La3-xAxZr1.5-xTax+0.5O12 (A = Ca, Sr, Ba; x = 0, 0.1, 0.3, 0.5) solidelectrolytes were prepared by conventional solid-state synthesis and spark plasma synthesis (SPS).The effect of doping of alkaline earth metals and sintering methods on the structural andelectrochemical properties of the solid electrolytes were investigated in this thesis. Powder X-raydiffraction (PXRD) studies have confirmed the cubic garnet-type structure of the solid electrolytes.Microstructure of the solid electrolytes were analysed by scanning electron microscopy (SEM).The samples prepared by SPS process exhibited higher density than the samples prepared byconventional solid-state route. The AC electrochemical impedance spectroscopy (EIS) was usedto measure the impedance of solid electrolytes. All garnet electrolytes prepared in this thesisshowed bulk conductivity in the range of 10-4 S/cm. Among the alkaline earth metal-doped solidelectrolytes, x = 0.1 (Ca and Sr) members prepared by SPS route showed highest conductivity atroom temperature (4.8 x 10-4 S/cm). Li6.5La2.9Sr0.1Zr1.4Ta0.6O12 prepared by SPS process showedan excellent Li-ion charge transfer resistance of 3.5 ? cm2 at 25 °C and the highest critical currentdensity of 0.6 mA/cm2 among all other samples.X-ray photoelectron spectroscopy (XPS) analyses were conducted on SPS-processedLi6.5La3-xAxZr1.5-xTax+0.5O12 (A = Ca, Sr, Ba; x = 0, 0.1) garnet electrolytes to quantify the impuritylayers on garnet surface. XPS analyses revealed that the surface of these electrolytes is covered byLiOH and Li2CO3-based compounds with a thickness of 4?6 nm within 30 minutes as a result ofthe reaction with traces of H2O and CO2 in an Ar-filled glovebox. Chemical compatibility ofLi7La2.75Ca0.25Zr1.75Ta0.25O12 (LLCZT) with commercial cathode materials and liquid Li-ion electrolytes (LLEs) was investigated using PXRD, SEM and EIS analysis. Hybrid cell consistingof Li metal, LLEs, LLCZT and LiNi0.8Co0.15Al0.05O2 or LiNi0.6Mn0.2Co0.2O2 cathode wereassembled in a coin cell and electrochemical performance was evaluated.
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Keywords
Li batteries, solid-state electrolytes, Li garnets
Citation
Palakkathodi Kammampata, S. (2021). Development of Li-based Garnet Electrolytes for All-Solid-State Li Batteries (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.