正极纳米添加剂对MH/Ni电池性能的改善

【作者】 吕骥；

【导师】 涂江平；

【作者基本信息】 浙江大学 ， 材料学， 2004， 硕士

【摘要】 本文以改善高功率MH／Ni电池性能为应用背景，通过对MH／Ni电池正极物理添加CNTs、纳米CoO两种纳米添加剂，研究了正极纳米添加剂对Ni（OH）₂／NiOOH正极和对高功率MH／Ni电池性能的影响，并讨论了纳米添加剂对改善镍正极和MH／Ni电池性能的作用机理。 利用化学气相沉积法（CVD）制备了多壁纳米碳管（CNTs），并对纳米碳管进行纯化和球磨的处理。采用透射电子显微镜（TEM）对纳米碳管的微观结构进行了观察。 利用液相反应制备超细的碳酸钻中间体，加热分解后得到纳米CoO。采用激光粒度测试仪测量了试验制备的碳酸钻和氧化亚钻的粒度大小，并利用透射电子显微镜（TEM）观察了纳米碳酸钻和纳米氧化亚钻的形貌。 利用DC-5型电池测试仪研究了正极纳米添加剂对Ni（OH）₂／NiOOH正极电化学性能的影响。结果表明：添加剂为纳米CoO的电极的活化性能最好，纳米CoO相对于普通CoO能更加均匀的分布在镍电极内，也更易溶解、反应生成CoOOH导电网路，从而加快了镍电极的活化进程；添加纳米CoO和添加CNTs的极片具有较高的放电电位和较大的放电容量，纳米添加剂能有效提高镍正极活性物质的放电效率和利用率；纳米添加剂可以有效地提高镍正极片的容量密度，其中添加纳米CoO的极片体积容量密度达到784 mAh／cm³，质量容量密度达到224 mAh／g；添加CNTs的极片体积容量密度达到778 mAh／cm³，质量容量密度达到223 mAh／g。 利用BS-9365二次电池性能检测仪、BS-GF电池内阻测试仪研究了正极纳米添加剂对MH／Ni电池各方面性能的改善。结果表明：在高倍率放电的条件下，正极中添加少量CNTs的Ni／MH电池具有更好的循环稳定性、更高的放电平台以及更好的高倍率性能；正极中添加少量CNTs制成的MH／Ni电池在高倍率放电的循环过程中内阻升高较小；正极添加0.5 wt.％CNTs的电池具有理想的高倍率性能和综合性能，过多的加入CNTs无益于电池性能的提高。浙江人学硕十学位论文摘要 正极添加纳米COO的Ni/MH电池具有较好的活化性能，纳米COO更好地增强了镍正极的导电性，进一步减小了电池的内阻;正极添加纳米CoO的Ni/MH电池还具有较高的放电平台;由于纳米CoO的纳米结构，以及相对于普通C00更大的比表面积，会在碱液中溶解形成更均匀致密的Co0OH导电网络，从而提高了放电效率，对电池的高倍率性能也有积极的影响。更多还原

【Abstract】 In order to improving the performance of high-power Ni/MH batteries, nano-scale additives including CNTs and nano-scale CoO were added into the positive electrode of the batteries. The overall characteristics of Ni(OH)2/NiOOH electrode and Ni/MH batteries were investigated at different charge-discharge conditions at room temperature.Multi-walled carbon nanotubes were synthesized by chemical vapor deposition (CVD). Then the CNTs were purified by nitric acid and shortened by ball milling. The microstructure of carbon nanotubes was observed using transmission electron microscope (TEM).Nano-scale CoO was obtained by the decomposition of CoCO3, which synthesized by the liquid reaction. The grain-size of CoCO3 and CoO were measured by laser diffraction grain-size analysis. The microstructure of the samples was observed using transmission electron microscope (TEM).The electrochemical characteristics of the Ni(OH)2/NiOOH electrode were tested by DC-5 battery testing instrument. The results shows: the electrode with nano-scale CoO has best active properties. Nano-sacle CoO is apt to dissolve in the electrode homogeneously, and better conductive net of CoOOH come into being, thus contribute a lot to the procedure of the activation. The electrode with nano-scale CoO and CNTs shows higher discharge voltage and higher discharge capacity. Nano-scale additives can improve the specific capacity of the electrode, the volume specific capacity and the mass specific capacity of the electrode with nano-scale CoO are 784mAh/cm3 and 224mAh/g, respectively. That dates of the electrode with CNTs are 778mAh/cm3 and 223mAh/g.The improvement of overall characteristics of sealed MH/Ni batteries were investigated by BS-9365 rechargeable batteries and BS-GF internal-resistance testing instrument. The results shows: under high-rate discharge conditions, the batteries with CNTs added in the positive electrodes exhibited much better cycling stability, higher discharge voltage and high-rate capability. The increase in internal resistance of the batterieswith CNTs was lower than that of the batteries without CNTs during charge-discharge cycles. The addition of 0.5 wt.% CNTs was proved a desired amount to modify the batteries performance at the high discharge rates. Too much CNTs contributed no effect in the improvement of overall performance of the batteries.The batteries with nano-scale CoO shows better active properties, the addition of nano-scale CoO further the conductivity of the nickel electrode, thus lower the internal resistance of the batteries, higher discharge voltages are achieved accordingly. For the formation of the better conductive net of CoOOH, the effectivity of discharge rise, that contributes positive effect to the high rate capability of the batteries.更多还原