Kajihara Koichi, Takahashi Daisuke, Kobayashi Hiroaki, Mandai Toshihiko, Imai Hiroaki, Kanamura Kiyoshi
Department of Applied Chemistry for Environment, Graduate School of Urban Environmental Sciences, Tokyo Metropolitan University 1-1 Minami-Osawa Hachioji Tokyo 192-0397 Japan
Institute of Multidisciplinary Research for Advanced Materials, Tohoku University 2-1-1 Katahira, Aoba-ku Sendai Miyagi 980-8577 Japan.
RSC Adv. 2021 May 26;11(31):19076-19082. doi: 10.1039/d1ra02598h. eCollection 2021 May 24.
Spinel-type MgMnO, prepared by a propylene-oxide-driven sol-gel method, has a high surface area and structured bimodal macro- and mesopores, and exhibits good electrochemical properties as a cathode active material for rechargeable magnesium batteries. However, because of its hydrophilicity and significant water adsorption properties, macroscopic aggregates are formed in composite slurry-coated cathodes when 1-methyl-2-pyrrolidone (NMP) is used as a non-aqueous solvent. Functionalising the surface with phenylphosphonate groups was found to be an easy and effective technique to render the structured MgMnO hydrophobic and suppress aggregate formation in NMP-based slurries. This surface functionalisation also reduced side reactions during charging, while maintaining the discharge capacity, and significantly improved the coulombic efficiency. Uniform slurry-coated cathodes with active material fractions as high as 93 wt% can be produced on Al foils by this technique employing carbon nanotubes as an electrically conductive support. A coin-type full cell consisting of this slurry-coated cathode and a magnesium alloy anode delivered an initial discharge capacity of ∼100 mA h g at 25 °C.
通过环氧丙烷驱动的溶胶-凝胶法制备的尖晶石型MgMnO具有高比表面积和结构化的双峰大孔与介孔，作为可充电镁电池的阴极活性材料表现出良好的电化学性能。然而，由于其亲水性和显著的水吸附特性，当使用1-甲基-2-吡咯烷酮（NMP）作为非水溶剂时，在复合浆料涂覆的阴极中会形成宏观聚集体。发现用苯基膦酸酯基团对表面进行功能化是一种简单有效的技术，可使结构化的MgMnO疏水并抑制基于NMP的浆料中聚集体的形成。这种表面功能化还减少了充电过程中的副反应，同时保持放电容量，并显著提高了库仑效率。通过采用碳纳米管作为导电载体的该技术，可以在铝箔上制备活性材料分数高达93 wt%的均匀浆料涂覆阴极。由这种浆料涂覆阴极和镁合金阳极组成的硬币型全电池在25°C下的初始放电容量约为100 mA h g。
