【作者】 王盎然；

【导师】 翁志学； 包永忠；

【作者基本信息】 浙江大学 ， 化学工艺， 2010， 博士

【摘要】 锂离子电池和质子交换膜燃料电池是二次电池和燃料电池的典型代表,具有绿色环保、可再生、使用效率高等优点。具有锂离子和质子传导特性的聚合物电解质膜分别是锂离子电池和质子交换膜燃料电池的重要组件,对电池使用性能和寿命有重大影响。针对锂离子传导固体聚合物电解质膜电导率偏低、常用质子交换膜—全氟磺酸膜阻醇性偏差等不足,论文开展聚合物电解质的共聚和纳米复合改性基础研究。论文以丙烯腈（AN）为主单体,分别与N-[4-（磺酰胺）苯基]丙烯酰胺（ASPAA）和对苯乙烯磺酸钠（SSNa）共聚,制备锂离子和质子传导聚合物电解质膜。进一步采用层状双金属氢氧化物（LDH）进行聚合物电解质的纳米复合改性,以期利用LDH纳米层板的带正电性和亲水性,形成有利于电解质阳离子解离和传输的环境,提高锂离子和质子传导聚合物电解质的导电性能。以合成组成均匀的锂离子传导电解质基体AN-ASPAA共聚物为目标,开展AN-ASPAA共聚规律研究,得到以N,N-二甲基甲酰胺为溶剂的AN-ASPAA共聚竞聚率为:r_AN=0.60,r_ASPAA=1.76,两种单体以接近理想共聚方式形成无规共聚物。AN-ASPAA共聚物与20wt%（相对聚合物）的LiClO₄复合制得锂离子传导电解质膜,通过交流阻抗谱和电路分析建立了等效电路模型,计算得到包括电解质膜电阻在内的各个电路元件参数,拟合的交流阻抗谱与实验结果相吻合。由于ASPAA的引入有助于Li⁺与聚合物的缔合,但同时使链节运动能力下降,共聚物电解质膜电导率、介电常数和介电损耗随共聚物中ASPAA摩尔分率的增加呈现先增大后减小的趋势,由ASPAA摩尔分率为32.6%的共聚物制备的电解质膜的电导率达到最大值1.54×10^-2S/m（30℃）。提出了AN-ASPAA共聚物中Li⁺传输机理:在共聚物中引入ASPAA链节增加了亲核基团与Li⁺的结合力,Li⁺在电场力和浓度梯度作用下,主要以与共聚物亲核基团缔合-解缔合的方式跳跃传递。为了提高LDH在AN聚合物基体中的分散均匀性和剥离程度,对不同有机阴离子插层LDH在有机介质的分散和原位溶液聚合行为进行了研究。根据对苯乙烯磺酸根、10-十一烯酸根、α-丙烯基烷基酚聚氧乙烯醚（10）硫酸根（HS10）插层LDH在不同介质的分散行为,提出了以插层剂疏水端和溶剂的Hansen三维溶度参数为依据,判别LDH分散性和剥离程度的方法。实验发现HS10插层LDH在二甲基亚砜中分散稳定,分散粒径最小,并达到部分剥离;在此基础上,进行原位溶液聚合,得到LDH剥离程度高、分散均匀的PAN/LDH和AN-ASPAA共聚物/LDH纳米复合材料。研究了AN-ASPAA共聚物/LDH纳米复合材料和LDH改性AN-ASPAA共聚物/LiClO₄电解质的性能。发现AN-ASPAA共聚物/LDH纳米复合材料热稳定性随LDH含量增加而提高。加入少量LDH能提高纳米复合电解质膜的电导率,LDH含量为1wt%时复合电解质膜电导率达到最高值（5℃）,进一步增加LDH含量使复合电解质膜的电导率下降。提出了LDH改性AN-ASPAA复合电解质膜等效电路模型,分析了复合电解质膜中LDH的作用机理:带正电的LDH层板在膜中相当于若干个串联电容,络合少量ClO₄^-,促进Li⁺传递,但同时LDH层板的阻隔作用会阻碍离子传递,在此两种相反作用的影响下,复合电解质膜在合适的LDH含量时出现电导率最大值。采用磺化单体-对苯乙烯磺酸钠（SSNa）与AN半连续沉淀聚合制备了组成均匀、磺化度可控的AN-SSNa共聚物。发现酸化得到的AN-对苯乙烯磺酸（SSA）共聚物质子交换膜的吸水率、离子交换容量、电导率和甲醇渗透率均随共聚物中SSA摩尔分率增大而增加;当SSA摩尔分率小于3.12%时,吸水率、电导率和甲醇渗透率缓慢增加;当SSA摩尔分率大于3.12%时,吸水率、电导率和甲醇渗透率急剧上升。SSA摩尔分率为3.12%时,质子交换膜的电导率与甲醇渗透率之比最大。通过交流阻抗谱图和电路分析建立了等效电路模型,计算得到的质子交换膜中H⁺扩散系数随共聚物中SSA摩尔分率增加先增后减,在SSA摩尔分率为3.12%时达到最大值（5℃）。在对苯乙烯磺酸根插层LDH（MgAl-SS LDH）存在下,采用原位沉淀共聚方法制备了AN-SSNa共聚物/LDH纳米复合材料,酸化得到AN-SSA共聚物/LDH复合质子交换膜。发现复合质子交换膜的甲醇渗透率随LDH含量增加而下降,离子交换容量和吸水率随LDH含量增加而增大。AN-SSA共聚物/LDH复合质子交换膜的电导率、介电常数和介电损耗随LDH含量增加先增后减。提出了LDH改善质子交换膜电性能的机理:LDH层板的亲水性使水化质子在膜中有更多质子通道,而其阻隔性又给水化质子的传输造成阻碍,两种机制共同作用导致复合质子交换膜的电导率在LDH含量为4wt%时达到最大值,为1.04×10^-3S/m（30℃）。更多还原

【Abstract】 Secondary lithium battery and proton-conducting membrane fuel cell （PCMFC） are typical representitives of the secondary battery and fuel cell, respectively, which exhibit envionment-friendly, renewable and high efficient characteristics. Lithium ion and proton-conducting polymer electrolytes are the main components of lithium ion battery and PCMFC, respectively, which significantly influence the performances of cells. In view of the low ion conductivity of solid lithium polymer electrolytes and high methanol crossover of common proton-conducting membrane, such as perfluorosulfonate membrane, the modification of polymer electrolytes by copolymerization and compositing with nanometer material were carried out in this thesis. Acrylonitrile-N-[4-（aminosulfonyl） phenyl] acrylamide （AN-ASPAA） copolymers were synthesized through the solution copolymerization and composited with lithium salt to obtain lithium ion polymer electrolyte. AN-sodium 4-sulphonate styrene （AN-SSNa） were synthesized through precipitation copolymerization and treated with acid to obtain proton-conducting polymer membranes. A novel layered nanometer material-layered double hydroxide （LDH） was further composited with AN copolymers to improve the properties of polymer electrolyte membranes. The influences of copolymer composition and LDH content on the properties of polymer electrolyte were investigated, and the mechanism of ion transportation in the modified polymer electrolytes was discussed.In order to obtain a new host for lithium ion polymer electrolyte, the synthesis of AN-ASPAA copolymer with homogeneous composition was carried out at first. It was found that the reactivity ratios of AN-ASPAA copolymerization in DMF were r_AN=0.60 and r_ASPAA=1.76, which indicated the ideal copolymerization behavior of two monomers and the formation of random copolymer.Lithium ion polymer electrolyte membrane was obtained by combining of AN-ASPAA copolymer with 20wt% （based on polymer） LiClO₄. An equivalent circuit model was proposed based on AC impendance spectra and practical circuit analysis. The element parameters of the equivalent circuit model, including resistance of polymer electrolyte, were calculated, and the simulated AC impendance spectra were fitted well with experimental data. It was considered that the addition of ASPAA unit was a favor to the association between Li⁺ and polymer chains, but reduced the local mobility of polymer chains. As a result, the conductivity, the dielectric constant and dielectric loss of copolymer electrolyte were increased with the increase of ASPAA content initially, and decreased when the molar fraction of ASPAA was greater than 32.6%. The membrane exhibited a maximum conductivity of 1.54×10^-2S/m （30℃） when ASPAA molar fraction was 32.6%. The ion transportation mechanism of AN-ASPAA copolymer/LiClO₄ composite was proposed as follows: the introduction of ASPAA unit into copolymer would provided more nucleophilic groups to complex with Li⁺, and lithium ions transported mainly through association-disassociation with the nucleophilic groups under the electric field force and concentration gradient.In order to improve the dispersion and exfoliation of LDH in AN polymer matrix, the dispersion behavior and in-situ solution polymerization of LDH intercalated with different organic anions in organic mediums were studied. According to the dispersion behavior of 4-styrene sulfonate intercalated LDH, 10-undecylenate intercalated LDH and polyoxyethyleneα-propenyl alkylphenyl ether sulfate intercalated LDH （MgAl-HS10 LDH） in different solvents, Hansen’s solubility parameters of the intercalated hydrophobic groups and that of the solvents were adopted to judge the dispersing ability and exfoliation of LDH. It was found that MgAl-HS10 LDH could be stably dispersed and partially exfoliated in DMSO. Thus, in-situ polymerization of AN and copolymerization of AN-ASPAA were carried out in the presence of MgAl-HS10 LDH to obtain PAN/LDH and AN-ASPAA copolymer/LDH nanocomposite with well dispersed and exfoliated LDH layers.The properties of AN-ASPAA copolymer/LDH nanocomposite and AN-ASPAA copolymer/LDH/LiClO4 nanocomposite electrolyte were investigated. It was found that the thermal stability of AN-ASPAA copolymer/LDH nanocomposite was increased as LDH content increased. The ion conductivity of nanocomposite electrolyte was also increased when the weight fraction of added LDH was lower, and reached a maximum （5℃） when the weight fraction of LDH was 1%. Further increase of LDH content would lead the decrease of ion conductivity of nanocomposite electrolyte. A new equivalent circuit model for AN-ASPAA copolymer /LDH/UClO₄ nanocomposite electrolyte was proposed, and the role of LDH played in the nanocomposite electrolyte was analyzed. It was considered that LDH layers with positive charges acted as capacitances in the nanocomposite electrolyte, which would associated with ClO₄^- and enhanced the transportation of Li⁺. However, LDH layers also hindered the transportation of Li⁺.AN-（sodium 4-styrene sulfonated） （AN-SSNa） copolymers with different composition were prepared through semi-continuous precipitation polymerization, and protonated to obtain AN-4-styrene sulfonic acid （AN-SSA） copolymer proton-conducting membrane with different sulfonation degree. It was found that the water uptake, ion exchange capacity, proton conductivity and methanol permeation were all increased as the molar fraction of SSA in copolymer increased. The water uptake, proton conductivity and methanol permeation coefficient of AN-SSA copolymer proton-conducting membrane were increased slowly when the molar fraction of SSA ranged from 0 to 3.12%, and increased rapidly when the molar fraction of SSA was greater than 3.12%. The selectivity of membrane defined as the ratio of the proton conductivity to methanol permeation coefficient reached a maximum value for the membrane prepared from AN-SSA copolymer with 3.12mol% of SSA. The proton diffusion coefficient in the proton-conducting membrane obtained through simulation of equivalent circuit model and fitting of AC impedance spectra also reached a maximum （5℃） when the molar fraction of SSA in copolymer was 3.12%.AN-SSNa copolymer/LDH nanocomposites were prepared by in-situ aqueous precipitation copolymerization of AN and SSNa in the presence of sodium 4-styrene sulfonated intercalated LDH（MgAl-SS LDH） and transferred to AN-SSA copolymer/LDH nanocomposites as a proton-conducting polymer electrolyte. It was found that the methanol permeation coefficient of the proton-conducting nanocomposite membrane was decreased as the weight fraction of LDH in nanocomposite increased, while the ion exchange capacity and water uptake were increased as the weight fraction of LDH increased. The ion conductivity, dielectric content and dielectric loss of proton-conducting nanocomposite membrane showed an increasing trend at the lower content of LDH, and a decreasing trend when the weight fraction of LDH was greater than 4%. It was considered that the incorporated LDH layers would lead the formation of more proton conducting channels in the membrane due to its hydrophilicity, while they would also hinder the transportation of protons due to their barrier property. As a result, the proton conductivity of nanocomposite membrane showed a maximum of 1.04×10^<sup>-3S/m （30℃） when the LDH content was 4wt%.更多还原