【作者】 苏耿；

【导师】 贺跃辉； 刘开宇；

【作者基本信息】 中南大学 ， 材料科学与工程， 2012， 博士

【摘要】 镍氢电池是近期和中期的首选动力电池,但其性能依然需要进一步提高,而目前主要是要提高贮氢合金电极性能,为了提高贮氢合金电极和镍氢电池的性能,本文进行了通过低温烧结、采用C0304作为添加剂、贮氢合金粉末的表面处理以及粘合剂和导电剂配方的优化等途径来提高贮氢合金电极性能的研究,并研制出了性能优异的HEV6Ah和40Ah方形动力电池。采用XRD、SEM、TEM、EDX、 BET、ICP、FTIR等测试技术对材料、电极进行了表征和分析；采用循环伏安、线性极化、阳极极化、电位阶跃、交流阻抗等测量方法对电极或电池进行了测试分析；采用恒流充放电对电极和电池进行了充放电性能研究,有效地提高了贮氢合金电极和电池的性能,并分析了其机理。通过将贮氢合金电极在300℃下进行烧结1h显著提高了电极的动力学性能,相对未烧结电极,烧结电极的极化电阻(Rp)、接触电阻(Rpp)和电荷迁移电阻(Rct)大幅度降低,交换电流密度(I0)、极限电流密度(IL)、氢扩散系数(D)都明显提高；从而有效地提高了电极的高倍率放电性能和循环寿命,当以1500mA·g-1电流密度放电时,烧结电极的容量已经高于未烧结电极53.0mAh·g-1和27.95%,HRD值较未烧结电极提高了14.87%,不同放电电流密度下的放电中值电位和放电平台也都高于未烧结电极,1C充放电循环时的容量衰减速度明显比未烧结电极缓慢,这应该是因为电极的致密化、合金晶格畸变和应力的消除或者减小和合金颗粒表面产生了微裂纹。通过对不同的C0304添加量对贮氢合金电极性能的影响研究得出了C0304作为添加剂应用于实际电极时的合适添加量,并采用该电极制备了AA(额定容量为1500mAh)圆柱型电池,结果表明,适量的C0304可以有效地提高电池的倍率性能、高低温性能、耐过充性能、循环寿命,可以降低电池的内阻、内压和温升；通过各种测试手段对材料、电极和电池进行了C0304的影响机制分析,结果表明,C0304对贮氢合金电极和镍氢电池性能的影响应该是因为其良好的电催化活性和电容性能、一定的贮氢性能、低的电导率、Co3O4-Co(OH)2-Co可逆反应的存在以及能抑制电极合金的氧化、提高电池内部气体复合反应的速度和氧气的电化学还原比例。通过采用新的碱处理方法对贮氢合金粉末进行了处理,去除了合金粉末表面的氧化层并在表面形成了具有高电催化活性的Ni和Co富集层(其中NaOH碱液处理的合金原子百分含量为92.91%,KOH碱液处理合金的原子百分含量为90.68%,分别比未处理合金提高了26.62%、24.39%),提高了合金粉末的比表面积,从而提高了电催化活性、氢扩散能力、导电性和抗氧化腐蚀能力,降低了吸放氢的平台斜率,进而有效地改善了贮氢合金电极的活化性能、高倍率充放电性能、高低温性能、充放电电压平台和循环寿命。通过贮氢合金电极的粘合剂和导电剂配方优化提高了HEV用6Ah方形镍氢动力电池用贮氢合金电极的充电效率、大电流放电性能、放电电压平台和低温性能。综合采用本文研究结果研制了HEV用6Ah方形镍氢动力电池,测试结果表明,该电池具有很好的充放电倍率性能、高低温性能、循环寿命,80%SOC下45C放电效率达81.8%,放电0.1S时,电池电压为0.9797V,比功率高达1422W／Kg；-20℃下的80%SOC3C放电效率达83.73%;80%SOC下的3C充放电循环寿命达4224次；经电池检测机构检测,性能达国际先进水平。在项目产业化时,采用本文部分研究结果制备了混合动力大巴用40Ah方形镍氢动力电池,经国内车用电池权威检测机构测试,电池各项指标均符合国家标准,且倍率放电能力、高低温性能、荷电保持能力、循环寿命和贮存等性能均远优于国家标准。更多还原

【Abstract】 MH/Ni battery is the preference of prismatic batteries in the near future and medium-term and its performance need to be improved stilly. The performance of Ni-MH battery mainly depends on the capability of hydrogen storage alloy electrode. In order to improve the performances of hydrogen storage alloy electrode and MH/Ni battery, the performance improvements of hydrogen storage alloy electrode by low-temperature sintering of alloy electrode, Co3O4used as additive, pretreatment of AB5-type hydrogen storage alloy powders and the improvement of adhesive and conductive agent were investigated. By using the above results, the prismatic traction batteries with the capacities of6Ah and40Ah for HEVs which had excellent performances were prepared. The materials and electrodes were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy with energy dispersive X-ray detector (TEM-EDX), inductively coupled plasma-atomic emission spectroscopy (ICP), Fourier transform infrared spectroscopy (FTIR) and BET method, et al. The electrodes or batteries were studied by electrochemical measurement methods such as:cyclic voltammogram (CV), linear polarization, anodic polarization, potential step method and electrochemical impedance spectroscopy (EIS). The charge/discharge performances of electrodes and batteries were measured by galvanostatic charge-discharge. The performances of electrodes and batteries were significantly improved and the influencing mechanisms were investigated.The kinetic properties of MH electrode were improved significantly by being sintered for1h at300℃. Compared with the untreated one, the polarization resistance (Rp), contact resistances(Rpp) and charge-transfer resistance (Rct) of sintered electrode decreased significantly, while the exchange current density(I0), hydrogen diffusion coefficient (D) and limiting current density (IL) of sintered electrode increased apparently. The high-rate discharge performance and cycle lifetime of sintered electrode were improved effectively. The capacity of sintered electrode at the discharge current density of1500mA·g-1was53.0mAh·g-1and27.95%more than that of the untreated one, and the value of HRD was14.87%more than that of the untreated one. The discharge voltage plateau at different discharge current density was higher and more horizontal for the sintered electrode. The decrease speed of capacity of sintered electrode was obviously slower than that of untreated one during cycling. These results should be due to the densification of electrode, the elimination or decrease of micro-stress and lattice distortion of alloy powders and the formation of micro-cracks on alloy powder surfaces.The proper amounts of Co3O4as additive in practical MH electrode was acquired by the investigation of effects of different contents of Co3O4additive on MH electrode. AA size cylindrical Ni-MH battery (with the rated capacity of1500mAh) was prepared from the electrode with proper amounts of Co3O4as additive. The performance measurement results proved that proper amounts of Co3O4can effectively improve the high-rate discharge ability, overcharge endurance capability, high-and-low temperature performance and cycle lifetime, and decrease the internal resistance, inner pressure and temperature-rising during the charge process of the battery. The influencing mechanism of Co3O4on the performance of MH electrode and MH/Ni battery was investigated via to the analysis of materials, electrodes and battery by some test methods. The effects of Co3O4on the performances of MH electrode and MH/Ni battery should be attributed to good electrochemical catalytic activity and capacitance performance, extended capability of hydrogen storage and low conductivity of Co3O4and the existing of conversion reaction of Co3O4-Co(OH)2-Co, and that Co3O4can restrain the oxidation of electrode alloys, increase gas consumption ability and the electro-reduction of oxygen among side-reactions.The electrocatalytic activity, diffusion rate of hydrogen, surface electric conductivity and oxidation resistance of alloy powders were significantly enhanced due to the removal of oxide film, the enriched Ni and Co metal layers on the alloy surface (the contents of Ni and Co on the alloy surface treated in NaOH and KOH solutions are92.91at%and90.68at%, and are26.62%,24.39%higher than that of untreated alloy, respectively) and the increase of specific surface area, and the slope of hydriding and dehydriding plateau of alloy powders was decreased by using new alkaline-treatment method. Hence, the activation, high-rate charge/discharge performance, high-and-low temperature performance, charging/discharging voltage plateau and cycle lifetime of MH electrode were improved effectively.The charge efficiency, high-rate discharge capability, discharge voltage plateau and low-temperature performance of MH electrode for HEV6Ah prismatic traction battery were enhanced by the improvement of adhesive and conductive agent. The prepared6Ah prismatic traction battery for HEV had good high-rate charge/discharge performance, high-and-low temperature performance and long cycle lifetime. The discharge efficiency of80%of SOC at45C was81.8%and the voltage was0.9797V when the battery was discharged for0.1S. The specific power was1422W/Kg. The discharge efficiency of80%of SOC at3C at-20℃was83.73%. The cycle lifetime at3C of SOC of80%was4424. The test results from testing institution proved that the prepared6Ah prismatic traction battery for HEV had international advanced performance. The test results from testing institution proved the performances of40Ah prismatic traction battery for HEV accorded with national standard, and the high-rate discharge ability, high-and-low temperature performance, charge retention, cycle lifetime and storage performance were significantly superior to national standard.更多还原