【作者】 陈亚；

【导师】 陈白珍；

【作者基本信息】 中南大学 ， 冶金物理化学， 2008， 博士

【摘要】 铅酸电池至今仍然是世界上应用最为广泛的一种可充电电池,但与其他新型电池相比,却存在比能量低等问题。为此,采用炭泡沫集流体材料代替铅合金板栅的研究倍受注目。然而,由于受自身结构和制备成本的限制,发泡法制备的炭泡沫材料在作为铅酸电池集流体的推广应用方面尚面临诸多的困难。本论文的目的即是开发一种适合于铅酸电池集流体用途的新型炭泡沫材料制备技术,并系统考察该炭泡沫集流体对组装的铅酸电池性能的影响。采用木素磺酸铵为分散剂制备水基沥青浆料,研究了该分散剂对沥青浆料分散稳定性的影响,以及pH值、固含量、分散剂用量对浆料流变特性的影响,发现沥青颗粒对木素磺酸铵具有较强的的吸附能力,沥青悬浮液中加入1wt%的木素磺酸铵就能使其Zeta电位发生明显变化,在pH=8附近,含木素磺酸铵分散剂的沥青粉体颗粒悬浮液的沉降体积最小。在固含量低于60%的范围内,pH值为8,分散剂用量为1.2%的沥青浆料粘度最低,流动性最好。提出了采用有机多孔模板浸渍水基沥青浆料成型来制备沥青基炭泡沫的新方法,筛选出了一种RPC表面活性剂,采用该表面活性剂对模板进行改性处理能够提高模板的挂浆量;选择木素磺酸铵为分散剂,聚乙二醇为粘结剂,羧甲基纤维素为触变剂配制沥青粉体浆料,当浆料固含量和流变剂用量分别为55%和1.5%,模板挤压应变为75%时,所制备的沥青多孔素坯具有良好的三维开口结构和合适的孔筋厚度。该沥青多孔素坯经350℃氮气氛中预处理30分钟,950℃炭化180分钟后得到了具有三维连通开口网络结构的沥青基炭泡沫。循环伏安测试发现,在H₂SO₄溶液中,上述炭泡沫在-1.2～0V处于电化学稳定状态,可作为理想的铅酸电池负极集流体材料,但其表面析氧电位大约在0.8V左右,远低于铅酸电池正极在充电过程中发生电化学反应时的电位（＞1.4V）,难以直接用作铅酸电池正极集流体材料。研究了炭泡沫作为铅酸电池负极集流体对电池性能的影响,发现采用炭泡沫作为负极集流体不仅能够提高电池的充电接受能力和负极活性物质利用率,而且还能改善电池的部分荷电循环性能。在放电电流为1/20C和1/10C条件下,炭泡沫负极的活性物质利用率比铅板栅负极分别提高15%和27%;在部分荷电状态窗口为40%～70%的情况下,经50次循环的炭泡沫电池放电截止电压仍高于2V,而铅板栅电池只能完成30次循坏。计算发现该炭泡沫集流体具有较低的设计参数,其γ参数大约为传统铅板栅的1/40～1/100。考察了炭泡沫作为集流体材料对铅酸电池负极阻抗特性的影响,提出了描述铅酸电池负极交流阻抗的数学模型和等效电路模型。交流阻抗谱测试和等效电路拟合结果表明,两种电极无论在充电或放电状态下均由电化学极化和浓度极化混合控制,但处在完全充电状态时,浓度极化起主导作用,而处于完全放电状态时电化学极化起主要作用。无论处于完全充电或完全放电状态,炭泡沫电极均具有比铅板栅电池更高的交换电流密度和双电层电容。初步研究了炭泡沫表面改性对其电化学特性的影响,循环伏安和SEM测试发现,采用循环伏安法电沉积的聚苯胺致密性较差,靠单一的聚苯胺涂层很难提高炭泡沫表面的氧析出电位,而经表面电沉积铅后的炭泡沫（Pb/CFM）具有较高的氧析出电位。以Pb/CFM为正极集流体的铅酸电池能够改善正极活性物质利用率,在放电电流为1/25C和1/10C时,Pb/CFM电池正极活性物质利用率比铅板栅电极高24.8%和40%。计算发现Pb/CFM电池的Peuker系数达到1.18,远低于目前铅酸电池1.33的水平。更多还原

【Abstract】 Lead acid batteries are still the most prevalent rechargeable batteries in today’s application markets.However,compared to other advanced rechargeable batteries,lead acid batteries have some drawbacks such as lower specific energy etc.To overcome these disadvantages,carbon foams attract much attention as substitutes for conventional lead-alloy grids in lead acid batteries.But due to the structure and production costs of carbon foams prepared by foaming method,these materials still face many difficulties in commercial application as current collectors in lead acid batteries.The aim of this paper is to develop a new method for preparation of carbon foams suitable for use as current collectors in lead acid batteries,and investigate the effects of the carbon foams as current collectors on properties of lead acid batteries.A water-based pitch powder slurry was prepared using ammonium lignosulfonate as the dispersant,and influence of the dispersant on the stability and fluidity of the slurry was investigated.The results show that pitch particles have good adsorbability for ammonium lignosulfonate.The Zata potential of pitch powder suspension varies obviously when 1wt%of ammonium lignosulfonate is added to the suspension,and the lowest sendimental volume can be observed in the suspension at pH=8.Slurries with 1.2%of dispersant and less than 60%of solid content at pH=8 exhibite the lowest viscosity and best fluidity.A new method for preparation of carbon foams using porous organic templates to form green pitch foam bodies was proposed.Pitch powder slurries were prepared using ammonium lignosulfonate as the dispersant,polyglycol as the binder and sodium carboxy methyl cellulose as the thickener.It was found that suface modification of polyurethane foam templates with a surfactant RPC can improve the loading of pitch powder slurry on the templates.The effects of the solid content,dosage of thickener and compressive strain of templates on the structure of green porous pitch bodies were evaluated.The results show that the obtained pitch bodies have 3D open-pore structure and suitable lignament thickness when the solid content,dosage of thickener and compressive strain are 55%,1.5%and 75%,respectively.The bodies can convert to carbon foams by preheating at 350℃in nitrogen for 30 minutes and then carbonizing at 1000℃for 3 hours.Cyclic voitamethy were performed on the pitch-based carbon foams.The results show that the carbon foam is electrochemically stable in the voltage range from -1.2 V to 0 V,while oxygen evolution at the foam occurs at ca.0.8 V which is below the voltage related to the oxidation of PbSO₄ to PbO₂（＞1.4V）.As a result,it is proposed that the carbon foam is suitable for use as the negative current collectors but can not be directly used as the positive current collectors in lead acid batteries.The effect of carbon foam negative current collectors on the properties of lead acid batteries was also investigated.It was found that using pitch-based carbon foams as negative current collectors can improve not only the charge acceptance and negative mass utilization efficiencies but also partial-state-of-charge（PSoC） cyclibilities of lead acid batteries.Comparative charge-discharge tests show that the utilization efficiencies of the active material on the carbon foam negative current collector are 15%and 27% higher than those of the material on a lead grid at 1/20 C and 1/10 C,respectively. Through a PSoC window of 70%～40%,lead acid batteries with carbon foam negative current collectors can experience 50 cycles,and the end-of-discharge voltage is still above 2 V at the end of 50^th cycle,while the batteries with lead grids as the negative current collectors can only experience 30 cycles.Calculation shows that carbon foam current collectors have lowerαandγparameters when compared to conventional lead grids.Theγparameter of carbon foam collectors is 1/40～1/100 of conventional lead grids.The effect of carbon foams as negative current collectors on the impedance characteristics of lead acid batteries was evaluated.A mathematic model and an equivalent circuit model were proposed to describe the faradic and total impedance of lead acid battery negative electrodes,respectively.The obtained impedance spectrascopes and fitting results show that whether at fully charged or discharged state,both electrochemical reaction and diffusion steps play roles in determining the polarization of lead acid battery negative electrodes.The diffusion step plays a much more important role in determining the polarization of the electrodes at fully charged state,while the electrochemical reaction step is much more important at fully discharged state.At both states,carbon foam electrodes have much higher exchange current densities and double-layer capacities than lead grid ones.To use these carbon foams as positive current collectors in lead acid batteries,initial surface modification of the foam material was carried out.The CV and SEM test results show that electroplated polyaniline（PANI） is not compact,and thus it is difficult to increase the oxygen evolution potential at the carbon foams by electroplating a single layer of PANI on the surfaces of carbon foams.On the other hand,electroplating a lead layer on the lignment surfaces of carbon foams can increase the oxygen evolution potential effectively.Charge-discharge test results show that lead acid batteries using carbon foams electroplated with lead as the positive current collectors can improve the utilization efficiencies of positive active materials.The utilization efficiencies of the active material on lead coated carbon foam positive current collectors are 24.8%and 40%higher than those on lead grids at 1/25 C and 1/10 C,respectively.Calculation shows that Peuker coefficient for batteries with lead coated carbon foams as the positive current collectors is 1.18,which is much lower than 1.33 for today’s commercial lead acid batteries.更多还原