钒系正极材料的制备及其储钠性能的研究

发布时间：2018-01-14 14:42

本文关键词：钒系正极材料的制备及其储钠性能的研究　出处：《南开大学》2016年硕士论文　论文类型：学位论文

【摘要】：近年来,钠离子电池因钠元素分布广泛和价格低廉而受到越来越多的关注。但是,由于钠离子的半径较大,使其难以在循环过程中快速的脱嵌。缺少性能优异的储钠材料,尤其是正极材料是钠离子电池发展和商业化的瓶颈。目前钠离子电池正极材料的研究主要集中在过渡金属氧化物,聚阴离子型化合物等材料上,但是,这些材料的容量较低,一般限制在90-130 mAh g-1。因此,寻找新型高性能的钠离子电池正极材料极为重要。钒基氧化物及其衍生物以其多变的结构,较高的容量,丰富的资源和便宜的价格受到越来越多的关注。但是钒系材料存在导电性差,钒易在有机电解液中溶解等问题,造成其循环稳定性和高倍率性能不足。本文针对以上问题,利用包覆导电聚合物,合理设计结构等手段对钒系材料进行了改性研究,具体内容和研究成果如下:1.采用化学氧化聚合的方法合成了聚吡咯(PPy)包覆的NaV3O8纳米片。首次将NaV3O8@PPy纳米复合材料用作钠离子电池的正极,与纯NaV3O8相比,表现出明显提高的循环与倍率性能。进一步对PPy包覆量进行了优化,发现NaV3O8@10%PPy的样品具有最优异的储钠性能。在1.5-4.0 V,80 mA g-1的条件下,该电极循环60周后,仍能保持99 mAh g-1的放电容量,远远大于纯NaV3O8样品的放电容量52 mAh g-1。利用电化学和XPS技术,对NaV3O8的储钠机理进行研究,结果表明放电中的两个平台都对应着V5+向V4+的转变。2.采用静电纺丝的方法制备了一维多孔的V2O5纳米纤维(F-V2O5)。对煅烧条件进行了优化,确定最佳煅烧条件为:在Ar中,煅烧温度500℃,升温速率1℃/min,预煅烧时间2 h,使材料结构稳定;然后在空气中,煅烧温度400℃,升温速率1℃/min,煅烧时间30 min,使纺丝前驱体充分氧化为V2O5。当将F-V2O5纳米纤维用作钠离子电池正极时,其表现出优异的电化学性能。与商业化的B-V2O5相比,F-V2O5的循环稳定性和倍率性能都有了明显的提升。在1.5-4.0 V,40 mA g-1的条件下,F-V2O5电极循环50次后,仍能保持89.5 mAh g-1的放电比容量,远远大于B-V2O5的32.7 mAh g-1的放电容量。
[Abstract]:In recent years, the sodium ion battery has attracted more and more attention because of Na wide distribution and low price. However, the sodium ion radius is larger, making it difficult to quickly in the circulation process. The lack of deintercalate sodium storage material with excellent properties, especially the cathode materials of sodium ion battery is the bottleneck of the development and commercialization of at present the study of cathode materials of sodium ion battery is mainly concentrated in transition metal oxide, poly anionic compounds and other materials, but these materials lower capacity is generally limited to 90-130 mAh g-1. so, looking for a new high performance cathode materials of sodium ion battery is very important. Vanadium oxide and its derivatives with its varied the structure, high capacity, rich resources and cheap prices has attracted more and more attention. But the vanadium material has poor conductivity, easy to dissolve in organic electrolyte of vanadium and other problems caused by The cycle stability and high rate performance. Aiming at the above problem, the use of coated conductive polymer, reasonable structure design method research on modification of vanadium materials, concrete contents and results are as follows: 1. by chemical oxidative polymerization of polypyrrole synthesized (PPy) NaV3O8 nanosheets coated NaV3O8@PPy cathode for the first time. Nano composite materials used for sodium ion batteries, compared with pure NaV3O8, showed the cycle and rate performance significantly improved. Further PPy coating amount were optimized, found that the NaV3O8@10%PPy sample has the best performance of sodium storage. In 1.5-4.0 V, 80 mA g-1 under the condition of the electrode after 60 cycles, the discharge the capacity can still maintain 99 mAh g-1 52 mAh g-1., the discharge capacity of the electrochemical and XPS technology is far greater than that of the pure NaV3O8 samples, study of sodium storage mechanism of NaV3O8, the discharge of The two platforms are corresponding to V5+ transition to the.2. V4+ by electrospinning V2O5 nanofiber porous synthesized (F-V2O5). The calcination conditions were optimized to determine the best conditions for calcination in Ar, calcination temperature of 500 DEG C, the heating rate of 1 DEG /min, pre calcination time 2 h the material, the structure is stable; and in the air, the calcination temperature is 400 degrees centigrade, the heating rate of 1 DEG /min, calcination time 30 min, the spinning precursor fully oxidized to V2O5. when the F-V2O5 nano fiber as cathode sodium ion batteries, which exhibit excellent electrochemical performance. Compared with commercial B-V2O5, cycle stability and the rate performance of F-V2O5 has been significantly improved. In 1.5-4.0 V, 40 mA g-1, the F-V2O5 electrode after 50 cycles, still can maintain 89.5 mAh g-1 discharge capacity, discharge capacity is far greater than that of B-V2O5 32.7 mAh g-1.

【学位授予单位】：南开大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TQ343.5;TM912

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