有机电极材料在非水系金属镁二次电池中的研究进展

Recent Progress on Organic Electrode Materials for Nonaqueous Magnesium Secondary Batteries

由于镁资源储量丰富、成本低廉,且金属镁具有理论体积比容量高(3833m Ah/cm^(3)),沉积/溶解过程中不易形成枝晶等优点,金属镁二次电池受到了研究者的广泛关注.然而,Mg^(2+)较大的极性导致其在多数锂离子电池正极材料中无法实现可逆脱嵌.主流无机电极材料普遍存在只能在较小电流密度下循环、动力学缓慢、制备工艺复杂等问题.相较而言,有机电极材料具有理论比容量高、结构多样易调控、资源丰富、环境友好、受离子半径和电荷影响小等优点,被认为是一种有潜力的电极材料.综述了近年来用于非水系镁二次电池有机正极材料的研究进展,讨论了不同类型有机正极材料的电荷存储机制及电化学性能,并总结了其面临的挑战、解决策略以及未来的发展方向.

Nonaqueous magnesium secondary batteries have attracted tremendous attention owing to their natural abundance,low cost,high theoretical volumetric specific capacities of 3833 mAh/cm^(3),and free of dendrite formation.However,the high polarity of Mg^(2+)ion results in the strong electrostatic interaction between Mg^(2+)ions and the anions of cathode materials,which makes it difficult to realize reversible insertion and de-insertion of Mg^(2+)ion in most cathode materials used in lithium ion batteries.At present,the research of cathode materials for magnesium secondary batteries is mainly focused on inorganic compounds.Unfortunately,such cathode materials suffer from problems of working at low current density,slow reaction kinetics,and complicated synthesis process.In comparison,organic electrode materials have been recognized as promising electrode materials for electrochemical energy storage systems because organic materials composed of naturally abundant chemical elements of C,H,O,N,S,etc.,can be easily synthesized from renewable resources with low-cost at mild conditions.More importantly,organic materials with chemical diversity and structural flexibility can be purposefully synthesized.What’s more,the capacity,oxidation/reduction potentials,solubility,electron transfer rates,and mechanical properties can be regulated by introducing various groups or heteroatoms.Furthermore,compared to inorganic electrode materials with sluggish kinetics,organic electrode materials usually store ions through ion coordination mechanism,which is not limited by the type and size of ions and can be applied to different energy storage systems such as lithium ion batteries,sodium ion batteries,potassium ion batteries,multivalent-ion batteries,and supercapacitors.Herein,the recent progress of various organicbased materials for nonaqueous magnesium secondary batteries is summarized and the general redox mechanism is presented.Finally,the problems and challenges,resolution strategies and future development directions of organic electrode materials are briefly summarized and discussed.