Al含量对Al取代氢氧化镍振实密度及电化学性能的影响

Effect of Al Content on the Tap-Density and Electrochemical Performances of Al-Substituted Nickel Hydroxide

采用化学共沉淀法制备了Al^(3+)/Ni^(2+)摩尔分数分别为0%,5%,10%,15%和20%的Al取代Ni(OH)2样品。振实密度测试发现当Al含量低于10%时,随着Al含量的增加样品的振实密度急剧增大;当Al含量为10%时,样品具有最大的振实密度;继续增加Al含量,样品的振实密度开始降低。X射线衍射分析发现,当Al含量低于5%时,样品的晶型为β相;当Al含量在5%~10%时,样品的晶型为α/β混合相;当Al含量高于10%时,样品的晶型为α相。循环伏安(CV)、电化学交流阻抗(EIS)和充放电测试研究表明:掺Al样品比未掺Al样品具有更高的电化学活性。其中Al含量为15%的样品具有最好的电化学性能,在100 m A/g恒电流充放电下的稳定质量比容量和体积比容量分别高达324 m Ah/g和516m Ah/cm^3,并且具有优异的循环性能。

Al-substituted nickel hydroxides with the Al3＋/Ni2＋ molar ratio of 0%, 5%, 10%, 15% and 20% were prepared by a chemical co-precipitation method. Tap density tests demonstrate that the tap-density of samples increases obviously with the increasing of the A1 content when the Al content is less than 10%; the sample presents the highest tap-density when the A1 content is 10%; however, further increasing of Al content leads to the decrease of tap density. X-ray diffraction （XRD） analysis reveals that the sample shows β phase when the Al content is less than 5%, and α/β mixed phase when the AI content is between 5% and 10%, but when the Al content is higher than 10% the samples show a phase. The results of cyclic voltammetry （CV）, electrochemical impedance spectroscopy （EIS）, and charge-discharge tests indicate that Al-substituted nickel hydroxide has higher electrochemical activity and smaller electrochemical reaction resistance than the pure nickel hydroxide. In particular, the Al-substituted nickel hydroxide with Al3＋/Ni2＋ molar ratio of 15% exhibits the best electrochemical performance. For example, the stable specific discharge capacity is up to 324 mAh/g （516 mAh/cm3） at the charge-discharge current density of 100 mA/g. Meanwhile, the samples also possess excellent cycling performance.