Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan.
Department of Applied Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa 223-8522, Japan.
ACS Nano. 2023 Feb 14;17(3):3135-3142. doi: 10.1021/acsnano.2c12392. Epub 2023 Jan 20.
Magnesium rechargeable batteries (MRBs) promise to be the next post lithium-ion batteries that can help meet the increasing demand for high-energy, cost-effective, high-safety energy storage devices. Early prototype MRBs that use molybdenum-sulfide cathodes have low terminal voltages, requiring the development of oxide-based cathodes capable of overcoming the sulfide's low Mg conductivity. Here, we fabricate an ultraporous (>500 m g) and ultrasmall (<2.5 nm) cubic spinel MgMnO (MMO) by a freeze-dry assisted room-temperature alcohol reduction process. While the as-fabricated MMO exhibits a discharge capacity of 160 mAh g, the removal of its surface hydroxy groups by heat-treatment activates it without structural change, improving its discharge capacity to 270 mAh g─the theoretical capacity at room temperature. These results are made possible by the ultraporous, ultrasmall particles that stabilize the metastable cubic spinel phase, promoting both the Mg insertion/deintercalation in the MMO and the reversible transformation between the cubic spinel and cubic rock-salt phases.
镁可充电池有望成为下一代锂离子电池之后的又一新型电池，它有助于满足对高能量、高性价比、高安全性储能设备日益增长的需求。早期使用硫化物作为正极材料的镁可充电池原型的端电压较低，需要开发能够克服硫化物低镁电导率的基于氧化物的正极材料。在此，我们通过冷冻干燥辅助室温醇还原法制备了超多孔 (>500 m g) 和超小 (<2.5 nm) 的立方尖晶石 MgMnO (MMO)。所制备的 MMO 表现出 160 mAh g 的放电容量，而通过热处理去除其表面羟基基团而不改变结构，将其放电容量提高到 270 mAh g——这是室温下的理论容量。这些结果是通过超多孔、超小的颗粒实现的，这些颗粒稳定了亚稳的立方尖晶石相，促进了 MMO 中的 Mg 插入/脱插和立方尖晶石与立方岩盐相之间的可逆转变。
