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The activation entropy for ionic conduction and critical current density for Li charge transfer in novel garnet-type Li6.5La2.9A0.1Zr1.4Ta0.6O12 (A = Ca, Sr, Ba) solid electrolytes

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Abstract

In this paper, we report the activation entropy (ΔS) values for Li-stuffed Li6.5La2.9A0.1Zr1.4Ta0.6O12 (A = Ca, Sr, Ba) garnets using a statistical mechanical approach and the role of ceramic processing in Li ion charge transfer between elemental Li and Li-stuffed Li6.5La2.9A0.1Zr1.4Ta0.6O12 garnets. The investigated solid electrolytes were prepared by a solid-state reaction and a spark plasma sintering method. The formation of the garnet-type structure was confirmed by powder X-ray diffraction. The homogeneous distribution of the elements in the prepared compositions was investigated using electron probe micro analyzer coupled with a wavelength-dispersive X-ray spectrometer. Li ion conductivity was determined using electrochemical ac impedance spectroscopy. The calculated ΔS value for garnet-type Li6.5La2.9A0.1Zr1.4Ta0.6O12 is found to be one order of magnitude higher than that of other solid electrolytes such as Li4SiO4 (Li+), Na3ZrMgP3O12 (Na+), AgI (Ag+) and Ag-β-alumina (Ag+) and comparable to that of the polymer Li ion electrolyte (PEO)10-LiClO4. SPS-processed Li6.5La2.9A0.1Zr1.4Ta0.6O12 samples showed a bulk Li ion conductivity of 5.5 × 10−4 S cm−1 at 22 °C. Among all the samples investigated in this work, Li6.5La2.9Sr0.1Zr1.4Ta0.6O12 showed an impressive Li ion charge transfer resistance (RCT) of 3.5 Ω cm2 at 25 °C without any surface coating of metal oxides, such as Al2O3 and ZnO, and exhibited a critical current density of 0.6 mA cm−2.

Graphical abstract: The activation entropy for ionic conduction and critical current density for Li charge transfer in novel garnet-type Li6.5La2.9A0.1Zr1.4Ta0.6O12 (A = Ca, Sr, Ba) solid electrolytes

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Article information


Submitted
06 Nov 2019
Accepted
22 Dec 2019
First published
14 Jan 2020

J. Mater. Chem. A, 2020, Advance Article
Article type
Paper

The activation entropy for ionic conduction and critical current density for Li charge transfer in novel garnet-type Li6.5La2.9A0.1Zr1.4Ta0.6O12 (A = Ca, Sr, Ba) solid electrolytes

S. Palakkathodi Kammampata, H. Yamada, T. Ito, R. Paul and V. Thangadurai, J. Mater. Chem. A, 2020, Advance Article , DOI: 10.1039/C9TA12193E

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