基于金属镁负极和嵌锂正极材料的新型可充镁锂混合离子电池

The two-electron nature and intrinsic low cost of magnesium compared with lithium, potential benefit of the safety to handle in ambient atmosphere, highly reversible and dendrite-free deposition/dissolution enables metallic Mg as a high-capacity and safe anode. Rechargeable magnesium batteries are receiving growing attention in recent years. However, the strong coulombic interaction between an intercalation host and the bivalent Mg2+ makes the solid-state diffusion of Mg2+ rather sluggish, thus leading to low capacity, large polarization during charge/discharge, and poor rate performance for cathode materials. The absence of an Mg2+ intercalation cathode with high voltage, high capacity, and fast kinetics has severely hindered the development of the rechargeable magnesium batteries. One potential approach is to circumvent the intercalation of clumsy Mg2+. In this project, a rechargeable hybrid Mg2+/Li+ battery is designed by coupling a mature LIB (lithium-ion batteries) cathode with a dendrite-free magnesium anode in a mixed Mg2+/Li+ electrolyte with reversible Mg deposition/dissolution. Due to simultaneous combination of the high-capacity/high-voltage LIB cathode, fast Li ion diffusion, with the high-capacity/dendrite-free Mg anode, the novel battery will demonstrate good electrochemical performance in terms of specific capacity, voltage, rate capability, and cycling stability.

与金属锂相比，金属镁能提供两个电子，价格便宜，且在空气中稳定，特别是，Mg2+能高度可逆沉积-溶出且无枝晶生成，这些优势使镁成为安全、高容量的电池负极。可充镁电池近年来引起越来越多的关注。然而，Mg2+的二价电荷使其在嵌入式电极中的固相扩散非常缓慢，从而导致可充镁电池正极充放电容量低、电压极化大、倍率性能不佳，成为制约可充镁电池发展的瓶颈。本项目提出将锂电池中成熟的正极材料和镁电池中的金属镁负极结合起来，电解液为能可逆沉积-溶出镁、含有Li+和Mg2+混合离子的有机电解液，组成高能量密度的新型镁锂混合离子电池。绕开镁离子嵌入正极存在的问题，利用锂电正极中Li+快速扩散、高电压和大容量的优点，以及金属镁负极无枝晶和高容量的特点，提高电池的充放电容量、工作电压、倍率性能和循环稳定性。

由于体积比容量高、成本低、安全性高等优点，以镁为负极的可充镁电池近年来引起越来越多的关注。然而，Mg2+的二价电荷产生的库伦作用使其固相扩散非常缓慢，从而导致可充镁电池正极充放电容量低、电压极化大、倍率性能不佳，成为制约可充镁电池发展的瓶颈。鉴于可充镁电池存在Mg2+在正极材料中扩散速度缓慢造成的循环性能和倍率性能不佳的问题，本项目提出将锂电池中成熟的正极材料和镁电池中的金属镁负极结合起来，电解液为能可逆沉积-溶出镁、含有Li+和Mg2+混合离子的有机电解液，组成镁锂混合离子电池。绕开镁离子反应正极存在的问题，利用锂电正极中Li+快速扩散、高电压和大容量的优点，以及金属镁负极无枝晶和高容量的特点，提高电池的充放电容量、工作电压、倍率性能和循环稳定性。研究了发生嵌入、转化和置换反应的几种正极材料，制备简便的有机镁盐或（和）无机镁盐和锂盐/混合醚的新型电解液，调控电解液的结构、组成和配比，提高镁沉积-溶出性能和与正极的相容性。通过分析电极/电解液界面的组成，探讨形成和变化机理，研究界面性质与电池综合性能的内在联系，建立电解液与正极材料的相容机制。组成的镁锂混合电池在400 mA/g的速率下，在800次长循环后可逆放电容量达到118.3 mAh/g，相较第二次放电容量衰减仅为16.8%。