二硫化钼的制备改性及在混合电容器中的应用研究

发布时间：2018-02-26 19:36

本文关键词： 锂离子电容器二硫化钼水热法碳氮复合　出处：《哈尔滨工业大学》2017年硕士论文　论文类型：学位论文

【摘要】：碳材料是目前广泛使用的商用锂离子电池负极材料,但其放电容量低、易产生锂枝晶,无法满足高功率、高能量、高容量等需求。二硫化钼是一种类石墨烯的层状化合物,其二维结构方便锂离子的嵌入与脱出。同时,二硫化钼制作工艺相对简单,且其作为储能器件负极时具有较高容量,目前受到广泛关注。本文对制备的二硫化钼进行了XRD、SEM、XPS等物理表征和循环伏安、交流阻抗、充放电等电化学测试,从结构、形貌、电化学性能等方面对二硫化钼进行研究。采用水热法合成二硫化钼,通过对硫源、钼源的比例,添加剂的使用、反应温度、反应时间等条件进行工艺优化,制得具有规则形貌的二硫化钼。电化学测试结果表明:二硫化钼电极在1 A g-1的电流密度下,首次放电比容量可以达到337mAhg~(-1),1000次循环过后保留比容量为57mAhg~(-1),明显优于商业碳材料。电池比容量的提高与二硫化钼具有规则的立方体结构相关,层状结构和较大的比表面积有利于电解液与电极的充分接触,降低了电池内阻、提高了倍率性能以及循环性能。以活性炭为正极、二硫化钼为负极、1 mol L-1的Li PF6-PC作为有机电解液,组装成混合电容器。组装后Mo S2/AC锂离子混合电容器工作电压为0-3.4 V,功率密度与能量密度较高,容量保持率较好。尽管二硫化钼具有规则形貌和相对稳定的电化学性能,但是随着充电截止电压的升高,电池循环性能逐渐变差;且在高电流密度下极化增加,容量衰减加快。通过煅烧聚吡咯制备了二硫化钼与碳氮复合材料,并对包覆后的材料进行电化学测试。测试结果表明:经过复合后的材料,不仅电池容量有所提高,且在充放电过程中的稳定性也明显增强。在大电流密度1 A g-1的条件下,经500次循环后容量仍能达到230mAhg~(-1);未经包覆二硫化钼经过500次循环后,剩余容量仅有65mAhg~(-1)。碳氮包覆层增强了材料的导电性以及结构稳定性,进而保证了材料较好的电化学性能。
[Abstract]:Carbon materials are widely used as anode materials for commercial lithium-ion batteries at present, but their discharge capacity is low and lithium dendrites are easily produced, which can not meet the needs of high power, high energy, high capacity, etc. Molybdenum disulfide is a layered compound of graphene. The two-dimensional structure facilitates the intercalation and removal of lithium ions. At the same time, the fabrication process of molybdenum disulfide is relatively simple, and it has a high capacity as a negative electrode for energy storage devices. The preparation of molybdenum disulfide has been characterized by XRDX SEM XPS and electrochemical measurements such as cyclic voltammetry, AC impedance, charge / discharge, etc. The electrochemical properties of molybdenum disulfide were studied in this paper. Molybdenum disulfide was synthesized by hydrothermal method. The conditions such as sulfur source, proportion of molybdenum source, additive, reaction temperature and reaction time were optimized. Molybdenum disulfide with regular morphology was prepared. The electrochemical measurement results showed that the current density of molybdenum disulfide electrode was 1 A g ~ (-1). The specific discharge capacity of the first discharge can reach 337mAhgGN ~ (-1) ~ (-1). After 1000 cycles, the reserved specific capacity is 57m Ahg ~ (-1), which is obviously superior to that of commercial carbon materials. The increase of the specific capacity of the battery is related to the regular cubic structure of molybdenum disulfide (MoS _ 2). The layered structure and large specific surface area are beneficial to the full contact between electrolyte and electrode, reduce the internal resistance of the battery, improve the performance of the rate and cycle. The active carbon is the positive electrode. Li PF6-PC, with 1 mol L-1 molybdenum disulfide as organic electrolyte, was assembled into a hybrid capacitor. The operating voltage of Mo S 2 / AC lithium ion hybrid capacitor was 0-3.4 V, and the power density and energy density were high. Although molybdenum disulfide has regular morphology and relatively stable electrochemical performance, the cycle performance of the battery becomes worse with the increase of charging cutoff voltage, and polarization increases at high current density. After calcination of polypyrrole, molybdenum disulfide and carbon nitrogen composites were prepared, and the coated materials were tested by electrochemical test. The results showed that the composite material not only increased the capacity of the battery, but also increased the battery capacity. Under the condition of high current density of 1 A g ~ (-1), after 500 cycles, the capacity of molybdenum disulfide can still reach 230 m 路g ~ (-1), and after 500 cycles without coating, the capacity of molybdenum disulfide can reach 230m 路g ~ (-1). The residual capacity is only 65 m 路g ~ (-1). The carbon and nitrogen coating enhances the electrical conductivity and structural stability of the material, thus ensuring the better electrochemical performance of the material.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ136.12;TM53

【参考文献】