中国科学院过程工程研究所机构知识库

目前，锂离子电池由于存在价格昂贵、能量密度低和安全性差等问题，作为替代品的镁离子电池引起了广泛关注。而镁离子电池中因二价镁离子在扩散过程中的强极化作用，很难实现镁离子的可逆脱嵌，从而导致正极材料循环稳定性较差，阻碍了其商业化应用。针对这一问题，本课题采用镁锂复合双盐电解液，将能够快速可逆脱嵌Li+的正极和安全稳定、无枝晶、低成本的Mg负极相结合，组成镁锂混合电池，提出以钒氧系化合物作为镁锂混合电池正极材料，并研究其制备方法与电化学性能。主要研究结果如下：（1）采用水热法制备颗粒大小均一的微花状NH4V4O10正极材料。系统分析了反应物浓度和反应时间对产物结构形貌的影响规律，用奥斯沃尔德熟化机制阐述了NH4V4O10材料由生长成片、络合成块、熟化分裂成花的生长过程；考察了反应温度对产物电化学性能的影响。结果表明，当水热温度为180℃时，NH4V4O10材料具有较为优异的电化学性能，在电流密度为100 mA g-1、电压范围为0.5~2 V的条件下，初始放电比容量为228.9 mAh g-1，100次充放电循环后，容量保留率为72.3%，能量密度达412 Wh kg-1。（2）对比分析NH4V4O10在镁锂混合电池体系和锂离子电池体系中的电化学性能，发现镁锂混合电池体系结合了镁锂二者的优势，在镁负极无枝晶产生的同时正极可达到与其在锂电中相当的容量性能。通过对比两种电池体系中循环伏安和充放电特性曲线，发现正极仅有锂离子发生脱嵌，未发现镁离子脱嵌特征，两种体系工作电压差异来自于对电极电势的不同。（3）采用水热法制备出VO2(B)正极材料。系统考察pH值对产物电化学性能的影响，当pH值为2.25时得到具有较高容量的VO2(B)材料通过与石墨烯复合改性，提高了二氧化钒正极材料的容量，在电流密度为100 mA g-1、电压范围为0.5~2 V的条件下，石墨烯复合改性后的VO2(B)材料首次放电比容量从229.2 mAh g-1提高到268.1 mAh g-1，能量密度从391 Wh kg-1提高到450 Wh kg-1。;Recently, due to the problems of high price, low energy density and poor safety in lithium ion batteries (LIBs), magnesium ion batteries (MIBs) as substitutes have attracted extensive attention. However, it is difficult to achieve reversible de-intercalation of Mg2+ due to the strong polarization of divalent magnesium ions in the diffusion process, which results in poor cyclic stability of cathode materials and hinders the commercial application of MIBs. In order to solve this problem, the hybrid magnesium-lithium-ion batteries (MLIBs) was designed to combine the cathode which can rapidly and reversibly de-intercalate Li+ and Mg anode with safety, stability, dendrite-free and low-cost by using magnesium-lithium dual-salt electrolyte. Vanadium oxides were proposed as its cathode materials and their preparation methods and electrochemical performance were studied. The main research results are as follows:(1) NH4V4O10 cathode material was obtained by hydrothermal synthesis method preparation. The effects of reactant concentration and reaction time on the structure and morphology of the product were systematically studied. The growth process of NH4V4O10 micro-flowers from growing, complexing and ripening was described by Oswald ripening mechanism. The effect of reaction temperature on product performance was investigated. The results showed that NH4V4O10 cathode material had excellent electrochemical performance when the hydrothermal temperature was 180℃. At the current density of 100 mA g-1 and the voltage window of 0.5~2 V, the initial discharge specific capacity was 228.9 mAh g-1. After 100 cycles, the specific capacity kept at 165.6 mAh g-1, and the capacity retention rate was 72.3%. The energy density reached 412 Wh kg-1.(2) By analyzing the electrochemical performances of NH4V4O10 cathode material in MLIBs and LIBs, it was found that the MLIBs combines the advantages of Mg and Li. It can achieve the same capacity performance as LIBs while using dendrite-free Mg as anode. Based on the characteristic of cyclic voltammetry and charge-discharge curves in the two systems, it was found that there was no electrochemical reaction of magnesium on cathode, but only the de-intercalation of lithium. And it was concluded that the difference of working voltage between the two systems was mainly affected by the anode potential.(3) VO2(B) cathode material was prepared by hydrothermal method. The effect of pH on the electrochemical performance of the product was investigated. VO2(B) material with high specific capacity was obtained when the pH is at 2.25. The capacity of VO2(B) cathode material was improved by composite modification with graphene. After modification, the first discharge specific capacities of the materials was 229.2 mAh g-1and 268.1 mAh g-1, and the energy densities reached 391 Wh kg-1 and 450 Wh kg-1 at the current density of 100 mA g-1 and the voltage window of 0.5~2 V.