Abstract

Garnet-type Li7-xLa3Zr2-xTaxO12 (LLZT) is considered a good candidate for the solid electrolyte in all-solid-state lithium batteries because of its reasonably high conductivity around 10−3 S cm−1 at room temperature and stability against lithium (Li) metal with the lowest redox potential. In this study, we synthesized LLZT with a tantalum (Ta) content of 0.45 via a conventional solid-state reaction process and constructed a Li/LLZT/Li symmetric cell by attaching Li metal foils on the polished top and bottom surfaces of an LLZT pellet. We investigated the influence of heating temperatures and times on the interfacial charge-transfer resistance between LLZT and the Li metal electrode. In addition, the effect of the interface resistance on the stability for Li deposition and dissolution was examined using a galvanostatic cycling test. The lowest interfacial resistance of 25 Ω cm2 at room temperature was obtained by heating at 175 °C (5 °C lower than the melting point of Li) for three to five hours. We confirmed that the current density at which the short circuit occurs in the Li/LLZT/Li cell via the propagation of Li dendrite into LLZT increases with decreasing interfacial charge transfer resistance.

Highlights

  • A high performance electrical energy storage device is a key technology in the sustainable development of a ubiquitous and clean energy society

  • The development of middle- or large-scale lithium-ion batteries (LIBs) has accelerated for use in automotive propulsion and stationary load-leveling for intermittent power generation from solar or wind energy [1,2,3]

  • The use of Li metal with extremely large gravimetric specific capacity (3860 mAh g−1 ) with the lowest redox potential as an anode leads to the high energy density of a battery, but the formation of a solid-solid interface among garnet-type solid electrolyte (SE) and Li metal electrodes is another challenging issue in achieving better electrochemical performance in solid-state batteries [32,33,34]

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Summary

Introduction

A high performance electrical energy storage device is a key technology in the sustainable development of a ubiquitous and clean energy society. Rechargeable lithium-ion batteries (LIBs), using graphite as the anode and organic liquid electrolyte and lithium transition-metal oxide as the cathode, were commercialized in 1991 and have since been widely used worldwide as a power source for mobile electronic devices, such as cell phones and laptop computers because of their high-energy density and reasonably good cycling performance. The use of Li metal with extremely large gravimetric specific capacity (3860 mAh g−1 ) with the lowest redox potential as an anode leads to the high energy density of a battery, but the formation of a solid-solid interface among garnet-type SE and Li metal electrodes is another challenging issue in achieving better electrochemical performance in solid-state batteries [32,33,34]. The effect of the interface resistance on the stability of Li deposition and dissolution reactions at the Li/LLZT interface was systematically investigated using a galvanostatic cycling test

Synthesis and Characterization of LLZT
2.2.Evaluation
Results and Discussion
Interfacial
25 Ω cm at
Stability against Li Deposition and Dissolution Reaction at the Interface
Galvanostatic cells with different
We the pellet removed from into the cell with
25 ΩmA cm2cm and their cycle stabilities
Galvanostatic
Conclusions
Full Text
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