钛酸镧钠基陶瓷电解质制备与电学性能研究
发布时间：2018-01-14 12:29
本文关键词：钛酸镧钠基陶瓷电解质制备与电学性能研究 出处：《中国地质大学》2017年博士论文 论文类型：学位论文
更多相关文章： 钠离子陶瓷电解质 NLTO基陶瓷 掺杂改性 晶体结构 离子电导率
【摘要】：无论是在移动电脑、智能手机中,还是在电动汽车和混合动力汽车中,电池作为核心的储能器件,已经成为信息社会人们日常生活中不可或缺的一部分。与传统的锂离子电池相比,钠离子电池有原料资源丰富、成本低廉、分布广泛,可分解电势更低的电解质溶剂或电解质盐和相对稳定的电化学性能,从而使得其具有更为突出的使用价值。因此,钠离子电池是目前所使用锂离子电池的最佳替代品。然而,由于电池在使用过程中存在电解液易燃与泄露造成严重的安全隐患,因此开发无机固态钠离子电解质是当下解决电池安全问题的重要策略之一。在开发无机固态钠离子电解质的过程中发现:传统利用高温固相法合成电解质陶瓷容易产生杂相,且合成的粉体容易烧结、粒度分布广等降低其电性能的缺点。此外,由于钠离子半径过大,使得Na_(0.5)La_(0.5)TiO_3(NLTO)陶瓷电解质中存在钠离子在晶体结构中不易迁移,从而造成低离子电导率的弊端。针对以上问题,本论文主要是通过开发一种新型合成钙钛矿结构NLTO陶瓷电解质材料的方法,系统探究了合成条件对陶瓷电解质离子电导率的影响,确定NLTO陶瓷最佳制备工艺。然后,在此基础上对NLTO陶瓷进行A、B位掺杂改性,并探究了NLTO陶瓷晶粒晶界结构、物相组成、晶胞参数等的变化对NLTO陶瓷中Na离子迁移的影响机制。结果发现制备工艺及元素掺杂均对NLTO陶瓷离子电导率有显著的影响。以下是本论文所得到的初步结果:(1)本文通过共离子络合法成功制备出纯相钙钛矿结构的NLTO纳米粉体。与传统的固相法相比,本方法具备合成温度低、制备的样品纯度高、样品粒度分布均匀等优点。此外,将所得粉体进一步制成电解质陶瓷薄片,系统探究烧结工艺对其离子电导率影响。结果发现,在一定范围内,提高煅烧温度,延长煅烧时间对NLTO陶瓷晶粒晶界结构有明显的改善作用,并最终确定煅烧温度为1200 oC、煅烧时间为12 h时可获得晶粒尺寸为650 nm、相对致密度为74.7%的NLTO基陶瓷。此时,其具有最佳离子电导率为1.01x10-5 S cm~(-1)与文献中报道提高了近2个数量级。(2)在成功制备NLTO陶瓷电解质基础上,为了进一步解决由钠离子半径过大引起离子迁移困难,造成NLTO陶瓷电解质离子电导率较低的问题,本文设计了系列掺杂改性实验。首先在A位掺杂Al、Fe、Mg、Cu四种元素。由于这四种元素原子半径较小,在NLTO陶瓷中形成间隙掺杂。在一定的掺量范围内,这四种元素均有利于改善NLTO陶瓷的晶粒晶界结构,提高陶瓷的致密度。其中Mg、Cu元素还有利于在陶瓷与电极之间形成离子“过渡区”,这种离子“过渡区”有利于减小陶瓷界面电阻,从而提高其离子电导率。本文还系统探究了不同掺量对NLTO陶瓷离子电导率的影响,结果发现当Al掺量为0.15时,NLTO陶瓷致密度最高可达96%,总离子电导率为4.54x10-5 S cm~(-1);Cu掺量为0.15时,NLTO陶瓷致密度最高可达95.8%,总离子电导率最高为1.24×10-4 S cm~(-1)。较NLTO陶瓷电解质原样离子电导率有明显的提高。(3)进一步在A位掺杂原子半径较大的Ca、Ba元素,通过XRD分析发现,掺杂这2种元素使得NLTO陶瓷原本的特征衍射峰发生偏移,说明Ca、Ba元素与La元素形成替代掺杂。并且,掺杂Ca元素使得衍射峰向高角度偏移,说明NLTO陶瓷晶胞参数减小,从而使得钠离子迁移通道变窄,因而其离子电导率会降低;掺杂Ba元素时,使得衍射峰向低角度偏移,利于扩大NLTO基陶瓷晶胞参数,拓宽Na离子迁移通道,提升其离子电导率。说明掺杂大原子半径有利于优化NLTO陶瓷晶体结构,改善其离子迁移通道。当Ba掺量为0.2时可得到最佳离子电导率为3.21×10-5 S cm~(-1)。在上述A位单掺研究基础上结合Ba、Cu元素掺杂的优势,得到Na_(0.5)La_(0.37)Cu_(0.1)Ba_(0.1)TiO_3(NLBUTO)共掺型陶瓷。对NLBUTO陶瓷进行元素分布,XPS、Raman等分析,发现掺杂Ba、Cu同时继承了Ba元素调控其晶体结构和Cu元素改善其晶粒晶界结构的优势,使得NLBUTO致密度达到93.5%,同时其离子电导率增大到1.76×10-4 S cm~(-1),是目前得到最高离子电导率。(4)研究表明B位掺杂有利于调控钙钛矿结构中Ti-O八面体的体积和偏转,从而调控钠离子迁移通道。本文在NLTO基陶瓷的基础上,分别制备了Zr、Ce等B位掺杂NLTO基纳米粉体和Na_(0.5)La_(0.5)Ti_(1-x)Zr_xO_3(NLTZO,0.02≤x≤0.1)、Na_(0.5)La_(0.5)Ti_(1-x)Ce_xO_3(NLTCO,0.1≤x≤1.0)等NLTO基陶瓷。结果发现,掺杂Zr元素含量在0.1以内时,能保持NLTO陶瓷原本的立方相钙钛矿结构,且其晶胞参数随着掺量增大而增大,因此其Na离子迁移通道得到拓展,从而其离子电导率得到提高。当Zr掺量为0.08时有最高离子电导率为4.08×10-5 S cm~(-1)。而掺入不同含量Ce元素后,NLTO陶瓷原始的立方相会发生变化,并且形成CeO_2和四方相NLTO两种新物相。新物相的形成对NLTO陶瓷的晶粒晶界结构、物相组成有显著的影响。随着掺量的变化,所得样品中CeO_2、NLTOT、NLTOC三种物相的相对含量也发生变化。当掺量为0.7时,其三者相对含量比例为3:2:20有最佳离子电导率为2.67×10-5 S cm~(-1)。综上,本文以NLTO陶瓷电解质材料为研究对象,首先通过开发一种新型合成方法制备得到高质量的NLTO纳米粉体,然后系统探究制备NLTO陶瓷电解质的制备工艺,确定最佳合成条件。在得到NLTO陶瓷电解质的基础上,通过掺杂技术,对NLTO陶瓷晶粒晶界结构、物相组成、晶体结构进行优化,得到具有最佳离子电导率(1.76×10-4 S cm~(-1))的NLTO陶瓷电解质材料,该离子电导率是目前同类材料中报道最高。此外,本文系统研究了不同元素不同位置掺杂NLTO基陶瓷对其离子电导率的影响规律,可以为研究其它在无机固态钠离子电解质材料提供有价值的参考。
[Abstract]:Whether it is in the mobile computer, intelligent mobile phone, or in the electric and hybrid vehicles, battery energy storage device as the core, has become an integral part of the information society in people's daily life. Compared with the traditional lithium ion batteries, sodium ion batteries have abundant raw material resources, low cost, wide distribution, can lower decomposition potential of electrolyte solvent or electrolyte and the electrochemical performance is relatively stable, so that it has more prominent value. Therefore, the sodium ion battery is the best alternative to the use of lithium ion batteries. However, because the battery is in use in the process of flammable and electrolyte leakage caused by serious hidden troubles. Therefore the development of inorganic solid electrolyte sodium ion is one of the important strategies to solve the battery safety issues. Found in the development of inorganic solid electrolyte of sodium ion in the process: Based on the traditional high temperature solid phase synthesis method to produce ceramic electrolyte impurity phase, and the powder synthesized by easy sintering, particle size distribution etc. reduce the electrical properties of faults. In addition, the sodium ion radius is too large, the Na_ (0.5) La_ (0.5) TiO_3 (NLTO) ceramic electrolyte in the sodium ion in the crystal structure not easy to transfer, resulting in defects of low ionic conductivity. To solve the above problems, this paper is mainly through the development of a new synthesis method of NLTO perovskite ceramic electrolyte materials, to explore the synthesis conditions on the conductivity of ceramic electrolyte from the impact, to determine the best preparation process of NLTO ceramic. Then, on the basis of NLTO ceramic A, modification of B doping, and to explore the NLTO ceramic grain boundary structure, phase composition, change of lattice parameters on the influence mechanism of Na ion migration in NLTO ceramics. The results showed that the process and preparation All dopants have significant influence on the ionic conductivity of NLTO ceramics. The following is the preliminary results of this thesis are: (1) the total ion complexation prepared NLTO nano powders of pure perovskite structure. Compared with the traditional solid phase method, this method has low synthesis temperature, sample purity the preparation of high, the advantages of uniform size distribution of samples. In addition, the resulting powder made further electrolyte ceramic sheets, explore the effect of sintering process on the ionic conductivity of the system. The results showed that in a certain range, the increase of calcination temperature, calcination time prolonging has obvious improvement effect on NLTO ceramic grain boundary structure, and ultimately determine the calcination the temperature is 1200 oC, calcination time for grain size can be obtained for 650 nm and 12 h, the relative density of NLTO based ceramics 74.7%. At this time, it has the best ionic conductivity of 1.01x10-5 S cm ~ (-1) and Literature Reported increased by nearly 2 orders of magnitude. (2) in the preparation of NLTO ceramic electrolyte on the basis, in order to further solve the difficulties caused by ion migration by sodium ion radius, resulting in NLTO ceramic electrolyte ionic conductivity is low, this paper designs a series of doping experiments. Firstly, A doped Al Fe, Mg, Cu four elements. Because the four elements of the atomic radius is smaller, the formation of gap doping in NLTO ceramics. In a certain range of dosage, the four elements are beneficial to improve the grain boundary structure of NLTO ceramics, improve the density of ceramics. The Mg, Cu elements are conducive to the formation of the ion "transition zone" between the ceramic and electrode, the ion "transition zone" is beneficial to reduce the ceramic interface resistance, so as to improve the ionic conductivity system. This paper also explores the effects of different dosage on the ionic conductivity of NLTO ceramics, the results showed that when Al When the amount is 0.15, NLTO density of up to 96%, the total ionic conductivity of 4.54x10-5 S cm~ (-1); the content of Cu is 0.15, NLTO density of up to 95.8%, the total ionic conductivity up to 1.24 x 10-4 S cm~ (-1). Compared with NLTO ceramic electrolyte ion conductivity is obvious improved. (3) further doped with A larger atomic radius Ca, Ba element analysis by XRD shows that the doping of these 2 elements make NLTO ceramic characteristic diffraction peak of the original shift, Ca, Ba and La elements to form substitutional doping and doping Ca element makes the diffraction peaks shift to the high angle, indicating reduced NLTO ceramic cell parameters, so that the sodium ion transport channel narrows, and the ionic conductivity decreases; Ba doping, the diffraction peak shifts to the low angle, conducive to the expansion of NLTO based ceramic cell parameters, broadening the Na ion migration channel, enhance its The ionic conductivity of doped. Large atomic radius is optimized for the NLTO ceramic crystal structure, improve the ion migration channel. When the dosage of Ba is 0.2 can get the best ionic conductivity is 3.21 * 10-5 S cm~ (-1). The A based on single doped with Ba, the advantages of Cu doping, get Na_ (0.5) La_ (0.37) Cu_ (0.1) Ba_ (0.1) TiO_3 (NLBUTO) Co doped ceramics. On NLBUTO ceramic element distribution, XPS, Raman analysis, found that the doping of Ba, Cu and Ba elements inherit the regulation of its crystal structure and Cu elements to improve its grain boundary structure advantages, making the the density of NLBUTO reached 93.5%, while the ionic conductivity increases to 1.76 * 10-4 S cm~ (-1), is currently the highest ionic conductivity. (4) study shows that B doped with volume and deflection for Ti-O regulation of the perovskite structure with eight sides, thereby regulating the sodium ion transport channel in the NLTO based ceramic. 鐡风殑鍩虹涓，
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