钒氧化物正极材料的制备、掺杂及其电化学性能研究

发布时间：2018-03-23 02:27

本文选题：锂离子电池　切入点：正极材料　出处：《桂林理工大学》2014年硕士论文　论文类型：学位论文

【摘要】：与传统的锂离子电池正极材料（LiCoO2等）相比，层状结构V6O13和VO2(B)具有比容量大、能量密度高、合成方法简单、价格便宜等优点，，被越来越多的研究者认为是具有开发和应用潜力的新一代锂离子正极材料。钒氧化物的常用合成方法为固相法和水热法，但是较难制备出纯相的钒氧化物。而溶剂热具有容易生成特殊价态的化合物、能够控制产物的形貌、能够均匀掺杂等优点。本文采用水热法、固相法制备出了V6O13，用溶剂热法制备了V6O13、VO2(B)、MnV2O6。对不同方法合成钒氧化物进行了电化学性能对比后发现溶剂热法制备的钒氧化物电化学性能较好。本文主要研究了溶剂热合成过程，并分别对V6O13和VO2(B)的溶剂热合成工艺进行了探讨，主要研究了乙醇和水的配比、溶剂热保温温度、溶剂热保温时间、煅烧温度等条件对产物物相和电化学性能的影响，得到了溶剂热制备V6O13和VO2(B)的最佳工艺。为了提高V6O13和VO2(B)在脱嵌锂过程中的结构稳定性，对V6O13分别进行Mn2+、Ni2+掺杂，对VO2(B)分别进行Cu2+、Ti4+掺杂。同时用溶剂热合成了块状和管状MnV2O6，并对其充放电性能进行了初步探讨。对V6O13分别进行Mn2+、Ni2+掺杂后发现，Mn2+或Ni2+都能够进入到V6O13正极材料的晶格中。掺杂后的V6O13脱嵌锂离子时的结构稳定性能得到提高。CV和EIS测试表明部分Mn2+或Ni2+取代了的钒位置，在锂离子的脱出和嵌入过程中材料被破坏的程度降低，抑制了容量衰减，循环性能得到改善。对VO2(B)进行Cu2+掺杂后发现，Cu2+的加入使VO2(B)正极材料的脱嵌锂离子的能力和充放电稳定性都得到提高。当掺Cu2+量为1.03at.%时，VO2(B)在低倍率和高倍率的性能都得到提高，在0.132C放电首次放电比容量317.1mAh/g，51次循环后的放电比容量仍然保存在234.3mAh/g。对VO2(B)进行Ti4+掺杂后增强了脱嵌锂能力和结构稳定性，尤其会提高正极材料在高倍率下的充放电性能。当掺Ti4+量为0.68at.%时，VO2(B)在6.563C下具有171mAh/g的放电比容量，50次循环后容量保持率达到83.6%。块状MnV2O6在40mA/g的电流密度下具有409mAh/g的放电比容量，但是容量衰减较快。管状MnV2O6它能够减少锂离子扩散在界面的距离，从而影响MnV2O6在充放电过程形成非晶态，在40mA/g的电流密度下具有216mAh/g的放电比容量，循环过程中其结构有所破坏，性能也有所降低。
[Abstract]:Compared with traditional cathode materials such as LiCoO _ 2, layered V6O13 and VO2B) have many advantages, such as high specific capacity, high energy density, simple synthesis method and low price. More and more researchers consider it a new generation of lithium ion cathode materials with potential for development and application. The common synthesis methods of vanadium oxide are solid phase method and hydrothermal method. However, it is difficult to prepare pure vanadium oxides, and solvothermal has the advantages of easily forming special valence compounds, controlling the morphology of the products and doping them uniformly. The hydrothermal method is used in this paper. V6O13 was prepared by solid state method, and V6O13 VO2O2V2O6 was prepared by solvothermal method. After comparing the electrochemical properties of vanadium oxide synthesized by different methods, it was found that the electrochemical performance of vanadium oxide prepared by solvothermal method was better. In this paper, the process of solvothermal synthesis was studied. The effects of the ratio of ethanol and water, the temperature of solvothermal insulation, the time of solvothermal insulation and the calcination temperature on the phase and electrochemical properties of the product were studied. The optimum solvothermal preparation process of V6O13 and VO2 / B was obtained. In order to improve the structural stability of V6O13 and VO2B in the process of lithium deintercalation, V6O13 was doped with Mn2 and Ni2, respectively. VO _ 2 O _ 2 B) was doped with Cu2 / Ti _ 4. Bulk and tubular MNO _ 2 O _ 6 were prepared by solvothermal method, and their charge-discharge properties were preliminarily discussed. It was found that both MNO _ 2 and Ni2 could enter the V6O13 cathode material after V6O13 was doped with Mn2 ~ (2 +) Ni _ (2) respectively. In the lattice, the structure stability of the doped V6O13 is improved. CV and EIS measurements show that some Mn2 or Ni2 have replaced the vanadium position. During the removal and intercalation of lithium ions, the material is destroyed to a lesser extent, which inhibits the capacity decay. The cycling performance was improved. It was found that the ability and charge-discharge stability of the cathode material were improved with the addition of Cu2 + after Cu2 doping. When the Cu2 content was 1.03at.wt%, the properties of VO _ 2B) at low rate and high rate were improved. After the first discharge capacity of 0.132C discharge was 317.1mAh/ g ~ (-1) cycle, the discharge specific capacity was still preserved at 234.3 mAh/ g. The Ti4 doping of VO _ 2H _ (2) B enhanced the deintercalation capacity and structure stability of VO _ (2) O _ (2) O _ (2) O _ (2) O _ (2) B, In particular, the charge-discharge performance of cathode materials at high rate can be improved. When the content of Ti4 is 0.68 at.%, the specific discharge capacity of 171mAh/g at 6.563C can be increased to 83.6% after 50 cycles. Bulk MnV2O6 has the specific discharge capacity of 409mAh/g at the current density of 40mA/g, but the capacity decays rapidly. Tubular MnV2O6 can reduce the distance of lithium ion diffusion at the interface, thus affecting the formation of amorphous MnV2O6 during charge and discharge. Under the current density of 40mA/g, the specific discharge capacity of 216mAh/g is obtained. During the cycle, the structure is destroyed and the performance is decreased.
【学位授予单位】：桂林理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM912

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