Flexible Fast Lithium Ion Conducting Ceramic Electrolyte
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Flexible Fast Lithium Ion Conducting Ceramic Electrolyte Koichi Hamamoto1, Danila Matveev2, Toshiaki Yamaguchi1, Hirofumi Sumi1, Toshio Suzuki1, Sergey Bredikhin2 and Yoshinobu Fujishiro1 1 Advanced Manufacturing Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 2266-98 Shimoshidami Moriyama-ku Nagoya 463-8687 JAPAN 2 Institute of Solid State Physic Russian Academy of Science, 142432 Chernogolovka, Russia ABSTRACT Large-area fast lithium ion conducting ceramic thin freestanding sheets was successfully prepared using a sheet forming technique. This ceramic sheet contains the crystalline phase of Li1+x+yAlxTi2-xSiyP3-yO12 with the NASICON type structure. The ceramic sheet showed maximum overall conductivity over 10−3 S cm−1 at room temperature. And, the developed thin ceramic sheet has sufficient flexibility against bending stress. Because a thin large-area ceramic electrolyte sheet was prepared using less energy compared with a conventional glass casting method, it is suitable for practical use. INTRODUCTION With increasing demand for large-scale and high-energy density rechargeable batteries, the securing of additional safety is becoming a critical issue. Solid lithium ion conducting ceramic electrolytes continues to attract great interest, especially for application in high- energy density lithium-ion batteries. Because, lithium-ion conducting ceramic electrolytes present potential advantages, such as a large electrochemical stability window and thermal stability, which are important for a safety improvement, absence of leakage, and the improvement of volumetric energy density by a bipolar battery stack configuration. Additionally, it shows high lithium-ion conductivity with negligible electronic conductivity at operating temperature. In particular, Many researchers focused on LiTi2(PO4)3 (LTP) -based ceramic electrolyte having a NASICON type crystal structure. The LTP -based ceramic electrolyte exceptionally has high water-resistant, though general lithium-ion conducting electrolytes are unstable with water. It is therefore expected as a possible material for lithium-air batteries [1-5], which have an energy density theoretically far greater than that of lithium ion batteries as well as to all-solid lithium ion batteries. The synthesis of LTP -based glass-ceramics with a high ionic conductivity has been reported by Aono et al. [6, 7] and subsequently by other investigators [8-14]. In LTP based materials, the lithium ion conductivity is greatly enhanced when Ti4+ is partially replaced by trivalent cations (Al, Ga, Sc, In, Y). The maximum conductivity (1.3×10−3 S/cm−1 at 298 K) was achieved at x ≈ 0.3 in the Li1+x AlxTi2−x P3O12 (LATP) series. However, the total conductivity due to the high grain-boundary resistance is substantially decreased [7]. Therefore, a negligibly small grain-boundary resistance is important if polycrystalline ceramic-type materials are used. In conventional processing, the row material of LATP-based glass-ceramic electrolyte is melted at over 1400°C
