二次电池用正极活性物质Ni（OH）₂的固相合成及其电性能

【作者】 许娟；

【导师】 周益明；

【作者基本信息】 南京师范大学 ， 物理化学， 2004， 硕士

【摘要】 电子器具如玩具、收录机、数码相机、电动车、手机、手提电脑等的发展，对电池的电性能的要求越来越高，它们不仅要求电池的使用时间更长，而且要求瞬时能进行较大的电流放电。镍系列二次电池的正极活性物质Ni（OH）₂的晶型和镍电极的制备工艺对电池的性能具有重大影响。α-Ni（OH）₂比β-Ni（OH）₂具有更高的放电电位、更大的放电容量而且克服了β-Ni（OH）₂电极充放电过程中产生的电极变形现象，所以我们致力于通过掺杂不同的添加剂来制备α-Ni（OH）₂，同时不断优化电极的制各工艺，以期得到电化学性能最好的镍电极；利用XRD谱图和IR谱图来判断制备出的样品的晶型结构，用TG-DTA谱图来判断活性物质的稳定性，用CV图来研究电极的可逆性和充电效率，用恒电流充放电曲线来研究充电电位和放电电位的高低，以及放电容量的大小。本论文通过研究，取得了如下进展： 一．采用固相反应方法，制得掺不同量的Al的Ni（OH）₂。由XRD数据得出：掺5％Al的Ni（OH）₂是β-Ni（OH）₂，从掺10％Al开始，制得α-Ni（OH）₂，且掺25％Al的Ni（OH）₂的结晶度最好。比较它们的电化学性能，可知：掺5％Al的样品具有最低的充电电位和最高的活性，掺25％Al的样品具有最高的放电电位，掺20％Al的样品具有最好的电极可逆性。掺20％、25％和30％Al的样品的质量比容量均大约为350mAh·g^-1，远大于掺5％、10％和15％Al的样品。 二．采用液相反应法合成了掺20％Al的α-Ni（OH）₂，粒径比固相反应法制备的样品的粒径要大一些，且晶体化程度更高。将β-Ni（OH）₂、液相反应法合成的掺20％Al的α-Ni（OH）₂和固相反应法合成的掺20％Al的α-Ni（OH）₂样品分别做成电极，作循环伏安实验和充放电实验。固相反应法制备的样品具有最小的△E_p，即具有最好的可逆性；固相法和液相法制备的样品比β-Ni（OH）₂的还原电位高，说明它们的放电电位高；而固相反应法制备的样品比液相反应法制备的样品具有更低的氧化峰电位、更高的还原峰电位，说明固相法制备的样品比液相法制备的样品更易氧化，其氧化产物更易还原，即具有更好的可逆性。固相反应法样品的放电容量达到336 mAhg^-1，放电平台达到415 mV左右，而液相反应法样品的放电容量只有220 mAhg^-1，放电平台也只有400 mV左右，β-Ni（OH）₂的放化学与环境科学学院硕士学位论文许娟南京师范大学20（）4电容量只有175 mA五g一，，放电平台只有33omv。可见，固相反应法制备的样品放电容量更大，放电平台更高。 三.采用固相反应方法，制备了掺杂不同量的Mn的Ni（oH）2。从实验结果可知，只有当Mn掺杂量达到一定量，且加入一定量的还原剂时，才能制备出仪一Ni（OH）20 四.采用固相反应方法，制得了掺杂不同量的Al、Mn、Zn和Fe的双掺杂的Ni（OH）:，从循环伏安实验筛选出电性能较好的电极。更多还原

【Abstract】 The development of electronic apparatuses such as toys, recorderes, digital camerals, electromotion cycles, mobile telephone, mobile compyter and so on, needs the rechargeable cells with higher performance. Both the longer discharge time and the capability of instantaneous discharge with greater current are called for. Alkaline rechargeable cells have been upheld for its high capacity, high discharge voltage, capability of charge and discharge with great current, low price, non pollution and so on. We studied the nickel electrode, which is the cathode of the alkaline batteries. Conductive inhibition of active material, expansion of nickel electrode and theoretical limit to specific capacity are three main problems of the nickel electrode.As it is well known, among the polymorphs of nickel hydroxide, the a form has better electrochemical properties than the (3 form. The a-Ni(OH)2/r-NiOOH couple is also known for exhibitting higher charge capacity and better reversibility compared to the B-Ni(OH)2/B-NiOOH couple. But the a-Ni(OH)2 can rapidly ages into p-Ni(OH)2 in strong alkaline solution, so the advantages of the a-Ni(OH)2/r-NiOOH couple have not been expoited in practical battery. So efforts to synthesize stabilized a-Ni(OH)2 and realize the proloned cycle life of the a-Ni(OH)2/r-NiOOH couple have been major endeavoures of battery scientists and technologists. We committed ourselves to the preparation of a-Ni(OH)2 with high electrochemical performances via intermingling different additives and increasingly optimizing the preparation craftworks of the nickel electrode in order to gain nickel electrode with best electrochemical performances.The crystal type of Ni(OH)2 has been judged by the XRD curves and the IR curves and the thermal stability of active materials has been estimated by TG-DTA charts. The properties of doped nickel thin film electrodes were investigated by cyclic voltammetry and galvanostatic charge and discharge experiments.In this work, the additive effects of different ions on nickel hydroxide were studied. Firstly, nickel hydroxides substituted with different contents of aluminiumwere prepared by solid-state reaction. The results reveal that nickel hydroxide substituted with 5% aluminum is p form and when the content of aluminum attains some extent, the nickel hydroxide substituted with aluminum is a form, which has better electrochemical performance than B form. Then, we synthesized nickel hydroxide doped with 20% aluminum from nickel and aluminum mixed metal solutions. We found the product is also a-Ni(OH)2, but its electrochemical performance is inferior to the a-Ni(OH)2 doped with 20% aluminum prepared by solid-state reaction. Secondly, nickel hydroxides substituted with different contents of manganese were prepared by solid-state reaction. The XRD curves show that all the products are 3-Ni(OH)2. Howerever, when some proportions of manganese and reducing agent were appended altogether, the a form comes forth. Thirdly, nickel hydroxides substituted with two kind of different additives at one time were synthesized because different additive has different advantages. The doped metal elements included Al, Zn, Co, Fe, Mn and so on. Our goal was to prepare nickel electrode with the best electrochemical performances.更多还原