钒酸钠与铁氰化铁钠离子电池正极材料的合成及性能研究

发布时间：2018-06-26 03:16

本文选题：钠离子电池 + NaV_6O_(15)　；参考：《合肥工业大学》2017年硕士论文

【摘要】：钠离子电池(SIBs)因具有原料储量丰富,价格低廉,安全性高等优点而备受青睐。其中寻找一种无毒、低成本、高比容量、结构稳定的正极材料是发展SIBs必经之路。本论文以此为出发点,对钒酸钠及铁氰化铁两种SIBs正极材料进行研究。氧化物型正极材料钒酸钠(NaV_6O_(15))因具备较大的Na+脱嵌空隙和优异的电子电导而受到广泛关注。为了进一步改善其电化学性能,本研究一方面通过PVP调控形貌合成NaV_6O_(15)纳米棒,另一方面采用一步水热法制备NaV_6O_(15)/C复合电极材料。另一种含氰根配位的普鲁士蓝类似物(FeFe(CN)_6)因具有独特的三维开放式框架结构,较高的理论比容量,合成方法简单等优势而成为新型SIBs正极材料。本研究对比了溶液共沉淀法和单一源沉淀法制备不同质量的FeFe(CN)_6电化学性能,并探讨Na+浓度对其影响。主要取得如下研究成果:1.采用PVP辅助水热法成功制备NaV_6O_(15)纳米棒,探讨了 PVP含量对NaV_6O_(15)形貌及性能的影响。其中添加0.1 g PVP可获得长1～2um,宽～100 nm尺寸均一的纳米棒,且电化学性能最佳:在20mAg-1、1.5-3.8V下,首次放电比容量为157 mAh g-1,20次循环后的容量保持率为71.38%,即使在200 mA g-1高倍率下,仍能释放121mAhg-1。此外,降低放电深度,在2.0-3.8V内测得2.69/2.40V氧化/还原峰,且样品的放电比容量为113 mAh g-1,循环50次后的容量保持率为86.55%,表现出较好的倍率循环性和高比容量性。交流阻抗法计算Na+循环前后的扩散速率分别为3.46× 10-12和2.71 × 10-12 cm2 s-1,并结合NaV_6O_(15)的态密度计算,结果表明NaV_6O_(15)具有较好的离子电导和电子电导。2.以葡萄糖为碳源,采用一步水热法制备500 nmNaV_6O_(15)/C纳米棒复合材料,探讨了C含量对材料性能的影响。电化学性能随C含量的增加先增后减,当添加15.67%C时性能最佳:样品包覆一层4 nm均匀厚度的无定型碳层,该碳层不仅抑制了 NaV_6O_(15)晶粒的长大,还提高了它的电子电导率。在20、200 mA g-1下,首次放电比容量分别为169.03、145.8 mAh g-1,且库伦效率均在80%以上。3.以FeCl_3、K_3Fe(CN)_6为原料,采用溶液共沉淀法制备500 nm FeFe(CN)_6纳米颗粒。尽管在高倍率(≥5 C)下的容量仅为理论比容量的19%,但0.1 C倍率时的首次放电比容量为115.467 mA h g-1 200次循环后的容量保持率为63%,表现出优异的循环性能。而以K_3Fe(CN)_6为单离子源,Na2S203辅助合成150-250nm,晶格较完美的FeFe(CN)_6纳米立方块,在0.1 C下的充/放电比容量为125.12/124.72 mA h g-1,首次库伦效率高达95.6%,且以0.5C倍率循环100次后的容量保持率为94%。5 C、10C及20 C倍率下的比容量分别为103.24、100.81和85.87 mAh g-1,表现出优良的倍率循环性能。此外增大Na+浓度有利于提高FeFe(CN)_6的放电容量,低倍率下最高可达134.689 mAh g-1。4.采用第一性原理和非原位XRD探讨Fe_3+在3d轨道的充放电机制。循环伏安曲线中3.68/3.46 V氧化还原峰对应与C相邻的低自旋FeLS2+/FeLs3+嵌钠反应:FeHS3+[FeLS3+(CN)_6|(?)NaFeHS3+[FeLS2+(CN)_6],而 3.08/2.81 V 峰则对应与 N 相连的高自旋 FeHS2+/FeHS3+嵌钠反应:NaFeHS3+[FeLS2+(CN)_6](?)Na2FeHS2+[FeLS2+(CN)_6]。非原位XRD结果表明在充放电过程中材料的结构很稳定,有利于Na+的可逆脱嵌。
[Abstract]:Sodium ion battery (SIBs) is favored because of its rich material reserves, low price and high safety. It is a necessary way to find a nontoxic, low cost, high specific capacity, and stable structure. This paper is the starting point for the study of two SIBs positive materials of sodium vanadate and ferricyanide. Sodium vanadate (NaV_6O_ (15)) of the type cathode material has been widely concerned for its large Na+ inlay gap and excellent electronic conductance. In order to further improve its electrochemical performance, this study on the one hand synthesis of NaV_6O_ (15) nanorods by PVP morphology, on the other hand, uses one step hydrothermal method to prepare NaV_6O_ (15) /C composite electrode material. The Prussian blue analogue containing cyanogen ligand (FeFe (CN) _6) has become a new SIBs cathode material for its unique three-dimensional open frame structure, higher theoretical ratio and simple synthesis method. This study compared the electrochemical properties of FeFe (CN) _6 with different mass by solution co precipitation and single source precipitation, and discussed Na. The main results are as follows: 1. the NaV_6O_ (15) nanorods were successfully prepared by PVP assisted hydrothermal method, and the effect of PVP content on the morphology and properties of NaV_6O_ (15) was investigated. The addition of 0.1 g PVP can obtain a nanoscale rod with a length of 1 to 2um and a wide to 100 nm, and the electrochemical performance is the best: under 20mAg-1,1.5-3.8V, the first The capacity retention rate of the secondary discharge ratio of 157 mAh g-1,20 was 71.38%. Even at the high rate of 200 mA g-1, 121mAhg-1. could still be released, and the discharge depth was reduced. The 2.69/2.40V oxidation / reduction peak was measured in 2.0-3.8V, and the discharge ratio of the sample was 113 mAh g-1, and the capacity retention rate after 50 cycles was 86.55%. The diffusion rate of the Na+ cycle was 3.46 * 10-12 and 2.71 x 10-12 cm2 S-1 respectively before and after the AC impedance method. The results showed that NaV_6O_ (15) had better ionic conductance and electron conductance.2. with glucose as carbon source, and 500 nm was prepared by one step hydrothermal method. NaV_6O_ (15) /C nanorod composite was used to investigate the effect of C content on the properties of materials. The electrochemical performance increased first and then decreased with the increase of C content. When 15.67%C was added, the performance was the best: the sample coated an amorphous carbon layer with a uniform thickness of 4 nm. The carbon layer not only inhibited the growth of NaV_6O_ (15) grain, but also increased its electronic conductivity. At the same time, the electron conductivity was increased. Under 200 mA g-1, the initial discharge specific capacity is 169.03145.8 mAh g-1, and the efficiency of Kulun is more than 80%.3. with FeCl_3, K_3Fe (CN) _6 as raw material and the solution co precipitation method is used to prepare 500 nm FeFe nanoparticles. Although the capacity of the high ratio (> 5) is only 19% of the theoretical specific capacity, the capacity of the first discharge ratio at the 0.1 ratio is the first discharge capacity. The capacity retention rate of 115.467 mA h g-1 200 cycles is 63%, showing excellent cycling performance. With K_3Fe (CN) _6 as a single ion source, Na2S203 assisted synthesis of 150-250nm, and the perfect lattice of FeFe (CN) _6 nano cubic block in lattice, and the capacity of charge / discharge ratio of 125.12 under 0.1 C. The first Kulun efficiency is up to 95.6% After 100 cycles, the capacity retention rate is 94%.5 C, the specific capacity of 10C and 20 C multiplier is 103.24100.81 and 85.87 mAh g-1, respectively, showing excellent multiplier cycle performance. In addition, increasing Na+ concentration is beneficial to improve the discharge capacity of FeFe (CN) _6, and the highest rate of 134.689 mAh is up to the first principle and non in situ exploration. The redox peak of the 3.68/3.46 V in the cyclic voltammetry curve corresponds to the low spin FeLS2+/FeLs3+ sodium reaction adjacent to the C: FeHS3+[FeLS3+ (CN) _6| (?) NaFeHS3+[FeLS2+ (CN) _6]. The results of FeLS2+ (CN) _6]. in situ XRD show that the structure of the material is stable during charging and discharging, which is conducive to the reversible deintercalation of Na+.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM912

【相似文献】