Mixed Phase Solid-State Plastic Crystal Electrolytes Based on a Phosphonium Cation for Sodium Devices

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• 作者：Faezeh Makhlooghiazad ; Daniel Gunzelmann ; Matthias Hilder ; Douglas R. MacFarlane ; Michel Armand ; Patrick C. Howlett and Maria Forsyth
• 刊名：Advanced Energy Materials
• 出版年：2017
• 出版时间：January 25, 2017
• 年：2017
• 卷：7
• 期：2
• 全文大小：2155K
• ISSN：1614-6840

文摘

Na batteries are seen as a feasible alternative technology to lithium ion batteries due to the greater abundance of sodium and potentially similar electrochemical behavior. In this work, mixed phase electrolyte materials based on solid-state compositions of a trimethylisobutylphosphonium (P_111i4) bis(trifluromethanesulphonyl)amide (NTf₂) organic ionic plastic crystal (OIPC) and high concentration of NaNTf₂ that support safe, sodium metal electrochemistry are demonstrated. A Na symmetric cell can be cycled efficiently, even in the solid state (at 50 °C and 60 °C), for a 25 mol% (P_111i4NTf₂)–75 mol% NaNTf₂ composition at 0.1 mA cm⁻² for 100 cycles. Thus, these mixed phase materials can be potentially used in Na-based devices under moderate temperature conditions. It is also investigated that the phase behavior, conductivity, and electrochemical properties of mixtures of NaNTf₂ with this OIPC. It is observed that these mixtures have complex phase behavior. For high compositions of the Na salt, the materials are solid at room temperature and retain a soft solid consistency even at 50 °C with remarkably high conductivity, approaching that of the pure ionic liquid at 50 °C, i.e., 10⁻³–10⁻² S cm⁻¹.