Interface Study of All-Solid-State Lithium Batteries with Garnet-like Structure Llzo Electrolyte

All-Solid-State Lithium battery, which is consist of solid electrolyte, is expected the most promising candidate for next generation energy storage devices for its high safety, high energy density and long cycle life 1-3]. Because all these advantages were attributed to the electrolyte materials, most of the studies are focused on the electrolyte materials themselves.

Among many other lithium ionic conductors, the Garnet-like structure LLZO (Li₇La₃Zr₂O₁₂) is the most promising candidate for its high ionic conductivity (~0.1mS/cm), non-reactivity with air, and high chemical stability both with lithium metal and oxide cathode materials. There are many reports about modification of LLZO with doping elements and structural changes of LLZO, however, there are less reports of manufacturing process of All-Solid-State lithium batteries with LLZO or interfacial properties between cathode and electrolyte.

In this study All-solid-state lithium batteries with two different types of LLZO electrolyte/cathode composite electrodes were manufactured. The first type was based on sputtering process and the second one was based on co-firing process. (1) type 1 : Electrolyte green sheets were casted by dry casting, then they were sintered in oxygen environment. Each electrode was polished by sand papers to get a flat surface, and it was installed in vacuum chamber for sputtering of LiCoO₂ layer. The thickness of sputtered LiCoO₂ cathode film was 1um. (2) type 2: the cathode and electrolyte composite green sheets were casted by dry casting method. Those composite green sheets were sintered simultaneously (co-firing) in oxygen environment. The Lithium metal anode layer was prepared on the surfaces of the electrolyte sides in those composite electrodes by thermal deposition method and a gold film was deposited by sputtering process on the surfaces of the cathode for current collection. The Electrochemical properties of composite electrodes were evaluated by charge-discharge cycle test and electrochemical impedance analysis method. The interfaces in composite electrodes between cathode and electrolyte were investigated by spectroscopic methods.

Referecnes

[1] Ramaswamy Murugan,et al. Angew. Chem. Int. Ed. 2007, 46, 7778 –7781.

[2] Ezhiyl Rangasamy, et al. Solid State Ionics 206 (2012) 28–32.

[3] Kai Chen, et al. Electrochimica Acta 80 (2012) 133– 139.