Garnet-type Li 7 La 3 Zr 2 O 12 Electrolyte Prepared by a Solution-Based Technique for Lithium ion battery
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Garnet-type Li7La3Zr2O12 Electrolyte Prepared by a Solution-Based Technique for Lithium ion battery Jiajia Tan1 and Ashutosh Tiwari1 1 Nanomaterials Research Laboratory, Department of Materials Science and Engineering, University of Utah, Salt Lake City, UT 84112, U.S.A. ABSTRACT High quality garnet-type Li7La3Zr2O12 solid electrolyte was synthesized using a solutionbased technique. The electrolyte pellets were sintered at 900 oC, resulting in tetragonal phase, which then transformed to cubic phase after annealing at 1230 oC. The ionic conductivity of both phases was studied and revealed to be 3.67x10-7 S/cm and 1.67×10-4 S/cm, respectively. A prototype cell comprising of Li7La3Zr2O12 electrolyte, LiCoO2 cathode and lithium metal anode was assembled. The cell made with the cubic phase electrolyte exhibited superior performance than the one made with the tetragonal phase electrolyte. The former cell possessed a very promising gravimetric discharge capacity of 3.4 mAh/g, which is the highest value obtained among similar setups. INTRODUCTION Lithium ion batteries (LIBs) have attracted a lot of attention over recent decades and have become an essential part in many of our portable electronic devices. Recently, the field of LIBs is further stimulated by the development of novel electric automobiles, which depends on the achievement of reliable power sources. Such power suppliers should be able to deliver a high power in an extended period of time and be able to restore quickly; as well, they must be intrinsically safe, especially at high temperatures. However, current LIBs couldn’t satisfy those requirements very well, since they use liquid organic electrolytes, which are toxic, prone to leakage, and are highly flammable. To substitute the conventional organic liquids, various kinds of solid-state electrolytes have been investigated, mainly glass or glass ceramics consisting of oxides, sulphides or a mixture of both [1-4]. Unfortunately, they have either high ionic conductivity or good chemical stability, rather than having both. Lately, a garnet-type Li7La3Zr2O12 (LLZO) electrolyte was synthesized by Weppner’s group [5], which was a source of enthusiasm in the field of all-solid-state LIBs [6-8]. LLZO has practically high enough ionic conductivity, negligible electronic conductivity, and good chemical stability against possible electrode materials; in addition, it is environmentally benign, easy to fabricate and of low cost [9-10]. Till date, there have been many reports on synthesizing the LLZO electrolyte by solidstate method, which requires multiple grinding and sintering at high temperatures [8]. The method is not only energy and time consuming, but also can lead to severe lithium loss during multiple high temperature procedures. Here, we are reporting the synthesis of LLZO through a solution-based technique, where most of the processes were conducted at low temperatures. The structural features and electrical properties of LLZO are reported. Moreover, the electrochemical behavior of the LLZO pellet is described as
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