Na0.44MnO2颗粒尺寸对其作为水系钠离子电池正极性能的影响

水溶性钠离子电池是一种与锂离子电池相辅相成的技术，因其相对较低的成本、改善的安全性和环境友好的电解液而备受青睐。然而，较低的电极容量限制了这种电池的应用。Na_0.44MnO₂是一种用于钠离子电池的高容量阴极材料，其理论容量为121 mAh/g。文章研究了Na_0.44MnO₂的尺寸效应对阴极性能的影响。纳米棒通过热处理MnO₂纳米片前驱体制备而成，其尺寸通过CTAB和KMnO₄的比例进行调控。然后，Na_0.44MnO₂纳米棒被用作水溶性钠离子电池的活性材料。纳米棒阴极在1 C的初始循环中提供了60 mAh/g的容量，并在经过200个循环后保持了55 mAh/g，比Na_0.44MnO₂块状阴极高出37.5%。在高倍率的5 C下，该阴极在经过200个循环后仍能提供47 mAh/g的高容量。容量的增加归因于减小的电荷传递阻抗和纳米棒具有较高比表面积所带来的改善的钠离子扩散性能。

Li-ion battery materials: present and future

Aqueous sodium-ion battery is a complementary technique to lithium-ion battery because of its comparatively low cost, improved safety, and environmentally friendly electrolyte. However, the lower electrode capacity limits the application of this kind of batteries. Na_0.44MnO₂ is a high capacity cathode for Na-ion batteries. Its theoretical capacity is 121 mAh/g. In this article, we investigate the size effect of Na_0.44MnO₂ on cathode performance. The nanorods are prepared by heat treatment of a MnO₂ nanoflake precursor, of which the size is tuned by the ratio of CTAB and KMnO₄. The Na_0.44MnO₂ nanorods are then used as the active material of cathode for aqueous sodium-ion batteries. The nanorod cathode delivers 60 mAh/g in the initial cycle at 1 C and retains 55 mAh/g after 200 cycles, which is 37.5% higher than Na_0.44MnO₂ bulk cathode. This cathode gives a high capacity of 47 mAh/g after 200 cycles at a high rate of 5 C. The increased capacity is attributed to diminishing charge transfer resistance and improved Na-ion diffusivity caused by the higher specific surface area of the nanorod.