Fabrication and Characterization of Li7La3Zr2O12 Thin Films for Lithium Ion Battery

The last few decades have seen a drastic miniaturization of electronic devices following the famous Moore’s law predicted by Gordan Moore in 1971. These developments in the electronic industry have resulted in ultra-low-weight electronic devices such as palm-top computers, smart phones, tablet PCs etc. Batteries constitute one of the most important and essential components of these devices. At present, lithium ion batteries (LIBs) are considered the most suitable candidateforuseinportableelectronicdevices.However,thesebatteriesare available only in the bulk form and comprise a significant percentage of the overall weight of the device. As the miniaturization of electronic devices continues, we need more advanced batteries which are light weight, safe, and environment friendly. One possible solution is the development of thin film batteries (TFBs) which can be integrated onto the microprocessor chips themselves. For these applications, we would require solid-state (SS) electrolyte. Currently, a major obstacle in this field is the low ionic conductivity of SS electrolytes and high temperature needed to fabricate thin films of these materials. As far as the research in SS electrolyte materials is concerned, many different kinds of inorganic systems have been explored to date. These include Nasicon-type electrolytes, 1‐4 perovskite-type lithium lanthanum tantantes, 5,6 and garnet-type Li ion conductors. 7,8 Among all of them, garnet type Li7La3Zr2O12 (LLZO), synthesized lately by Weppner’s group 9 has been reported to possess very high ionic conductivity. What’s more, LLZO is electrochemically stable with a potential window wider than 0‐7 V, is environment friendly, and is relatively inexpensive. 9‐11 However, to our knowledge, LLZO has so far been synthesized in bulk form only; no work has been reported on the preparation of LLZO thin films. For realizing thin film batteries, it is essential to be able to grow thin films of solid electrolytes and preferably at low temperatures. In this paper, we are reporting the fabrication of LLZO thin films on SrTiO3 (100) and Sapphire (0001) substrates by pulsed laser deposition at room temperature. The effect of annealing was investigated by detailed characterization of thin film structures and properties. Studies were also performed to understand the influence of lithium loss during the deposition process.