Zheng Qifeng, Miura Shota, Miyazaki Kasumi, Ko Seongjae, Watanabe Eriko, Okoshi Masaki, Chou Chien-Pin, Nishimura Yoshifumi, Nakai Hiromi, Kamiya Takeshi, Honda Tsunetoshi, Akikusa Jun, Yamada Yuki, Yamada Atsuo
Department of Chemical System Engineering, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, 113-8656, Tokyo, Japan.
Department of Chemistry and Biochemistry, Waseda University, 3-4-1, Okubo, Shinjuku-ku, Tokyo, 169-8555, Japan.
Angew Chem Int Ed Engl. 2019 Oct 1;58(40):14202-14207. doi: 10.1002/anie.201908830. Epub 2019 Aug 30.
Aqueous Na- or K-ion batteries could virtually eliminate the safety and cost concerns raised from Li-ion batteries, but their widespread applications have generally suffered from narrow electrochemical potential window (ca. 1.23 V) of aqueous electrolytes that leads to low energy density. Herein, by exploring optimized eutectic systems of Na and K salts with asymmetric imide anions, we discovered, for the first time, room-temperature hydrate melts for Na and K systems, which are the second and third alkali metal hydrate melts reported since the first discovery of Li hydrate melt by our group in 2016. The newly discovered Na- and K- hydrate melts could significantly extend the potential window up to 2.7 and 2.5 V (at Pt electrode), respectively, owing to the merit that almost all water molecules participate in the Na or K hydration shells. As a proof-of-concept, a prototype Na V (PO ) F |NaTi (PO ) aqueous Na-ion full-cell with the Na-hydrate-melt electrolyte delivers an average discharge voltage of 1.75 V, that is among the highest value ever reported for all aqueous Na-ion batteries.
水系钠或钾离子电池实际上可以消除锂离子电池引发的安全和成本问题，但它们的广泛应用通常受到水系电解质较窄的电化学势窗（约1.23 V）的困扰，这导致能量密度较低。在此，通过探索具有不对称酰亚胺阴离子的钠和钾盐的优化共晶体系，我们首次发现了用于钠和钾体系的室温水合物熔体，这是自2016年我们小组首次发现锂水合物熔体以来报道的第二和第三种碱金属水合物熔体。新发现的钠和钾水合物熔体可以将势窗分别显著扩展至2.7和2.5 V（在铂电极上），这得益于几乎所有水分子都参与钠或钾水合壳层这一优点。作为概念验证，采用钠水合物熔体电解质的原型Na V (PO ) F |NaTi (PO )水系钠离子全电池的平均放电电压为1.75 V，这是所有水系钠离子电池报道过的最高值之一。
