锂离子电池新型负极材料一氧化铌及碳化硅的研究

发布时间：2018-01-16 08:23

本文关键词：锂离子电池新型负极材料一氧化铌及碳化硅的研究　出处：《中南大学》2014年硕士论文　论文类型：学位论文

【摘要】：摘要：立方结构的一氧化铌(NbO)材料和碳化硅(SiC)材料因其具有安全、稳定、环保、低价等优势,有望成为新型的锂离子电池负极材料。本论文采用高温固相还原法制备了NbO材料,采用直接购买的SiC粉末为原材料,用XRD、SEM,激光粒度测试、CV曲线、EIS曲线及充放电曲线等检测分析手段,研究了一氧化铌和碳化硅两种不同材料的理化性能和电化学性能,并初步探究了两种材料的嵌锂动力学过程。得出主要结论如下： (1)以铌粉和五氧化二铌粉末为原料,采用高温固相法,制备了纯相的NbO粉末。通过球磨处理,减小了粉末颗粒粒径,改变了颗粒的表明形貌,使得NbO粉末分布更加均匀,提高了材料的电化学性能；NbO电极材料在0.1C倍率下首次放电比容量高达355mAh·g-1,循环50次后,仍有2931nAh·g-1的可逆比容量保留；NbO负极材料的嵌锂平台大概在1.6V左右；NbO材料的对锂的插嵌机理为锂离子的直接脱嵌,是一个单相转变的过程。 (2)以直接购买的碳化硅为原料,通过球磨处理后,SiC电极材料首次以0.02C倍率条件下放电,比容量高达468mAh·g-1,循环50次后,仍有335mAh·g-1的可逆比容量保留,不可逆容量损失为28.4%；不同倍率条件下,SiC电极的容量保持率都较高；SiC负极材料的嵌锂平台大概在0.8V左右；采用原位X射线衍射的方法对SiC电极材料的嵌锂机理进行了初步的探究,推断SiC材料的对锂的插嵌机理为单相锂离子的直接脱嵌。 (3)采用恒电流滴定(PITT)、循环伏安(CV)和交流阻抗(EIS)三种不同方法对NbO和SiC电极材料在充放电反应中进行了锂离子扩散系数的研究,结果表明：恒电位间歇滴定法研究测定的NbO电极在充放电过程中的锂离子在固相中的扩散系数在2.09×10-10～5.33×10-11cm2·S-1的范围；循环伏安法研究NbO电极的界面过程中NbO电极在氧化和还原过程中的锂离子在固相中的扩散浓度系数Ds分别为1.56×10-12和1.25×10-12cm2·s-1,两种方法测试结果相差不大,NbO电极具有较好的锂离子脱嵌可逆性；交流阻抗法计算测得了SiC电极中的锂离子扩散系数在6.2×10-13～7.9×10-13cm2·S-1的范围,电荷转移电阻Rct在0.8V处有一个最小值265.4Ω,表明了SiC在电位平台附近最容易发生界面电荷的转移。研究结果表明NbO和SiC材料均可作为新型负极材料用于锂离子电池领域,并具有一定的产业化前景。
[Abstract]:Abstract: cubic niobium oxide (NbO) and silicon carbide (sic) materials have the advantages of safety, stability, environmental protection and low cost. It is expected to be a new cathode material for lithium ion battery. In this paper, NbO materials were prepared by high temperature solid state reduction method. The SiC powder purchased directly was used as raw material and SiC was used as raw material. The physical and chemical properties and electrochemical properties of niobium oxide and silicon carbide were studied by means of laser particle size measurement CV curve EIS curve and charge-discharge curve. The kinetic processes of lithium intercalation between the two materials are preliminarily investigated. The main conclusions are as follows: Using niobium powder and niobium pentoxide powder as raw materials, pure phase NbO powder was prepared by high temperature solid state method. The particle size was reduced and the morphology of particle was changed by ball milling. The distribution of NbO powder is more uniform, and the electrochemical performance of the material is improved. The initial discharge specific capacity of NbO electrode was 355mAh 路g-1 at 0.1C ratio, and the reversible specific capacity of 2931nAh 路g-1 remained after 50 cycles. The lithium intercalation platform of NbO anode material is about 1.6 V; The intercalation mechanism of lithium in NbO is the direct deintercalation of lithium ion, which is a single phase transition process. (2) the sic electrode material, which was directly purchased from silicon carbide, was discharged at 0.02C rate for the first time, with a specific capacity of 468mAh 路g ~ (-1) after ball-milling treatment. After 50 cycles, the reversible specific capacity of 335mAh 路g-1 was retained, and the irreversible capacity loss was 28.4kb. The capacity retention rate of sic electrode is higher than that of sic electrode under different ratio. The lithium intercalation platform of SiC anode material is about 0.8V; The mechanism of lithium intercalation in SiC electrode materials was preliminarily investigated by in situ X-ray diffraction. It was inferred that the intercalation mechanism of lithium in SiC materials was the direct deintercalation of single phase lithium ion. (3) using constant current titration (PITT). The diffusion coefficients of lithium ions in charge and discharge reactions of NbO and SiC electrode materials were studied by cyclic voltammetry (CV) and AC impedance spectroscopy (EIS). The results show that:. The diffusion coefficient of lithium ion in solid phase of NbO electrode studied by potentiostatic intermittent titration is in the range of 2.09 脳 10 ~ (-10) 10 ~ (-1) 5.33 脳 10 ~ (-11) cm ~ (2) 路s ~ (-1). ; Cyclic voltammetry study of the diffusion concentration coefficients of lithium ions in solid phase of NbO electrode during redox and reduction at the interface of NbO electrode were 1.56 脳 10 ~ (-12) and 1.25 脳 10 ~ (-1) 脳 10 ~ (-1), respectively. -12 cm 2 路s -1. The results of the two methods are similar to those of the NbO electrode, and the results show that the lithium ion deintercalation reversibility is better than that of the NbO electrode. The diffusion coefficient of lithium ion in SiC electrode was measured by AC impedance method in the range of 6.2 脳 10 ~ (-13) ~ 7.9 脳 10 ~ (-13) cm ~ (-2) 路S ~ (-1). The charge transfer resistance (Rct) has a minimum value of 265.4 惟 at 0.8 V, which indicates that SiC is the most prone to interfacial charge transfer near the potential platform. The results show that both NbO and SiC can be used as new anode materials for lithium ion batteries and have a certain industrial prospect.
【学位授予单位】：中南大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM912

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