Water‐Mediated Synthesis of a Superionic Halide Solid Electrolyte

By Xiaona Li, Jianwen Liang, N. Chen, Jing Luo, Keegan Adair, Changhong Wang, M. Banis, T. Sham, Li Zhang, Shangqian Zhao and 4 more. Angewandte Chemie, 2019

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To promote the development of solid-state batteries, polymer, oxide, and sulfide-based solid-state electrolytes (SSEs) have been extensively investigated. However, the disadvantages of these SSEs, such as high-temperature sintering of oxides, air instability of sulfides, and narrow electrochemical windows of polymers electrolytes, significantly hinder their practical application. Therefore, developing SSEs that spontaneously possesses high ionic conductivity (>10 S cm), good-air stability, wide electrochemical window, excellent electrode interface stability, low-cost mass production is highly demanded. Here we report a halide Li superionic conductor, Li3InCl6 that can be synthesized in water. Most importantly, the as-synthesized Li3InCl6 shows a high ionic conductivity of 2.04×10 3 S cm at 25 °C. Furthermore, the ionic conductivity can be totally recovered after dissolved in water. Combining with LiNi0.8Co0.1Mn0.1O2 cathode, solid-state lithium batteries shows astonishing cycling stability. The H2O-mediated synthesis of Li3InCl6 can significantly promote the advances of all-solid-state lithium batteries. All-solid-state lithium batteries (ASSLBs) using solid-state electrolytes (SSEs) are considered as promising next-generation energy storage systems with improved safety due to the elimination of the flammable liquid electrolyte in convention lithium ion batteries. Among the various types of electrolytes, oxide-based and sulfide-based SSEs are considered to be the most promising candidates for use in ASSLBs because of their high ionic conductivity over 10 S cm. 2] Despite the recent progress made in these SSEs, several serious obstacles are still hindering their practical applications, especially the manufacturing complexity and sensitivity. For the case of oxide-based SSEs, high sintering temperatures are required both during the synthesis of SSEs and in the subsequent steps to promote intimate contact between electrode materials and SSE, making the manufacturing costly and might cause interfacial reactions. For sulfide-based SSEs, their chemical instability in air and moisture inevitably cause deterioration of structure/composition, leading to a large decrease in ionic conductivity and the release of noxious H2S gas. Another serious challenge for sulfide SSEs is the unavoidable and detrimental side reactions with high-voltage oxide cathode materials (e.g. LiCoO2 and LiNixMnyCozO2). Direct contact between sulfide SSEs and oxide cathode materials results in the formation of a lithium deficient space-charge layer and the diffusion of transition metals from cathode to sulfide SSE which react to the electrolyte and form metal sulfides. In this context, interfacial protection layers between sulfide SSEs and oxide cathodes are necessary but introduce extra complexity and cost for the fabrication process. 8] To address these issues, halide SSEs, which were developed in the 1970s, have emerged as attractive alternatives. Unfortunately, the development of halide SSEs has been limited due to their relatively low ionic conductivity and structural instability of some species. 10] For example, the Li3YCl6 synthesized by H. D. Lutz et al. in 1992 only achieved an ionic conductivity of ~10 S cm at 200 °C. Although hightemperature phase Li3InBr6 has a high ionic conductivity of 10 S cm at 25 °C, the as-prepared Li3InBr6 shows quite low ionic conductivity of 10 S cm and its structure will be destroyed at 13 °C. In more recent times, the relatively stable Li3YCl6 and Li3YBr6 SSEs with high ionic conductivities of ~10 S cm were synthesized by Tetsuya Asano et al. using a high-energy ball milling and high-temperature annealing process. Nevertheless, these Li-conducting halide SSEs are still sensitive to moisture.

Subfields: Electrical and Electronic Engineering, Inorganic Chemistry, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/e563342ac01e20ed0717e8268c0e81a579c60cdf