【作者】 罗丹；

【导师】 杨慕杰； 李扬；

【作者基本信息】 浙江大学 ， 高分子化学与物理， 2010， 博士

【摘要】 本文设计制备了半互穿网络(semi-IPN)凝胶聚合物电解质,两亲性网络凝胶聚合物电解质,聚醚胺改性网络凝胶聚合物电解质,碳纳米管复合凝胶聚合物电解质以及静电纺丝多孔纤维凝胶聚合物电解质等五种类型的电解质体系。采用FTIR、NMR、DSC、TGA、XRD、SEM,拉伸测试等表征手段,以及交流阻抗谱测试,研究凝胶聚合物电解质膜的化学结构、凝胶含量、形貌、热性能,力学性能和电化学性能。分析不同聚合物基体,组分组成比例对电解质膜性能的影响,以实现力学性能和电化学性能的统一,使制备的凝胶聚合物电解质具有实际应用前景。本文首先将聚氧化乙烯(PEO)与聚(丙烯腈-甲基丙烯酸缩水甘油酯)(P(AN-GMA))共混,采用二乙烯三胺(DETA)做交联剂,制备semi-IPN型凝胶聚合物电解质。XRD和DSC分析结果表明DETA与共聚物中环氧基团交联后,体系中PEO组分的结晶受到明显抑制,有利于锂离子在聚合物基体中的传导。拉伸性能测试结果显示,semi-IPN结构的聚合物膜拉伸强度提高。并且随着PEO组分含量的增加,semi-IPN结构的聚合物膜对液体电解质的吸附量增大,体系的离子电导率增加。当P(AN-GMA)/PEO质量比为1/1时,室温离子电导率为1.25×10-4 S/cm。研究制备了新型的两亲性网络(聚乙二醇200-甲基丙烯酸缩水甘油酯)-甲基丙烯酸甲酯(PEG200-b-GMA)-co-MMA和(PEG2000-b-GMA)-co-MMA聚合物电解质膜。DSC分析发现其具有两个玻璃化转变温度。接触角测试表明聚合物膜具有两亲性,平衡接触角大小与共聚物两亲性网络聚合物中PEG-b-GMA的分子量以及PEG-b-GMA与MMA摩尔组成的变化有关。两亲性共网络聚合物凝胶聚合物中,MMA组分越少,PEG-b-GMA组分含量越高,体系的交联度越大,离子电导率越高。并且(PEG2000-b-GMA)-co-MMA由于所含的EO基团链段长于(PEG200-b-GMA)-co-MMA体系,其离子电导率较高。研究制备了不同分子量的聚醚胺(Jeffamine D400, Jeffamine D2000)做交联剂,分别与P(AN-GMA)及聚(甲基丙烯酸缩水甘油酯-甲基丙烯酸聚乙二醇单甲醚酯)(P(GMA-PEGMA))交联的网络聚合物电解质体系。FTIR分析表明随着Jeffamine D400和Jeffamine D2000用量的增加,环氧基团反应程度提高。拉伸测试结果表明聚醚胺用量的增加会使交联体系的拉伸强度降低,断裂伸长率提高。所制备的凝胶聚合物电解质的DSC分析表明Jeffamine与P(AN-GMA)之间的相容性差于P(GMA-PEGMA)。分子量较大的Jeffamine所含的PPO链段较长,且Jeffamine用量越多,越有利于交联聚合物体系的链运动,体系的室温离子电导率较高。进一步研究将不同分子量的聚醚胺接枝到多壁碳纳米管表面,分别与P(AN-GMA)和P(GMA-PEGMA)两种聚合物复合,得到具有化学交联结构的杂化聚合物膜。SEM表征发现表面接枝的多壁碳纳米管在两种聚合物中被完全包裹,分散均匀。拉伸测试结果表明碳纳米管与聚合物之间的化学交联作用,提高了两者之间的结合力,体系的拉伸强度大大提高,且较长链段聚醚胺接枝的碳纳米管与聚合物之间的结合更加紧密,拉伸强度相对更高。由于P(GMA-PEGMA)的柔韧性高于P(AN-GMA),体系的断裂伸长率相对较大。多壁碳纳米管表面接枝的聚醚胺,有利于提高复合体系与锂离子的亲和力,离子电导率提高。且Jeffamine D400接枝的碳纳米管复合体系的离子电导率高于Jeffamine D2000接枝的碳纳米管复合体系。由于P(GMA-PEGMA)体系的玻璃化温度低于P(AN-GMA)体系,离子电导率更加优异。最后,采用静电纺丝法制备了PVdF/PEO和纳米SiO2复合PVdF/PMMA多孔纤维聚合物膜。SEM表征发现两种膜纤维表面比较光滑,纤维之间相互交织,形成大量尺寸不一的孔洞结构。纳米SiO2在PVdF/PMMA纤维表面分散比较均匀；含量较高时,部分纳米粒子出现团聚现象。XRD和DSC分析证明PVdF/PEO多孔纤维膜中随着PEO组分含量的增加,PVdF的结晶度降低,而PEO组分的结晶度提高。PVdF/PEO质量比为3/1时,体系的室温离子电导率最大。纳米SiO2粒子分散性越好,PVdF组分的结晶度越低。当纳米SiO2的添加量为6%时,体系的室温离子电导率最高,达2.55×10-3S/cm。更多还原

【Abstract】 Novel gel polymer elelctrolytes (GPEs) for secondary lithium-ion batteries have been investigated. Five kinds of gel polymer electrolytes were prepared, i.e. semi-interpenetrating (semi-IPN) GPEs, amphiphilic conetwork GPEs, network-structured GPEs with polyetheramine as crosslinking agent, multiwall carbon nanotube/GPE hybrids and electrospun fibrous GPEs. The chemical structure and composition, morphology, thermal behavior, mechanical strength and ionic conductivity of these GPE membranes have been investigated by Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), X-ray diffraction pattern (XRD), stess-strain test and alternating current impedance (AC Impedance). The influences of the structure and compositions of the polymers on the properties of resulting GPEs were studied, aiming at obtaining GPEs with both good ionic conductivity at room temperature and good mechanical strength for practical application.Novel semi-IPN GPEs based on poly(acrylonitrile-co-glycidyl methacrylate)/poly(ethylene oxide) (P(AN-GMA)/PEO) crosslinked by diethylenetriamine (DETA) were synthesized. DSC and XRD measurements showed that the crystallization of PEO fraction in the semi-IPN polymer electrolyte was greatly impeded by the crosslinking of DETA with epoxy group, which facilitated the transportation of lithium ion. The tensil tests revealed that the critical strength of the membrane was enhanced. Moreover, the semi-IPN GPEs exhibited better absorptive ability of liquid electrolyte and higher ionic conductivity with the increased in the content of PEO. The ionic conductivity of the GPE at room temperature reached 1.25×10-4S/cm when the weight ration of P(AN-GMA)/PEO was 1/1.Novel amphiphilic conetwork GPEs based on (PEG200-b-GMA)-co-methyl methacrylate (MMA) and (PEG2000-b-GMA)-co-MMA have been investigated. Two glass transition temperatures were observed in the DSC curves. The measurements of the static contact angle of the polymer membranes revealed the amphiphilic nature of the polymers, and the contact angles were found to vary with the molecular weight of PEG-b-GMA and the mole ratio of PEG-b-GMA and MMA. With the increase of weight ratio of PEG-b-GMA, both the crosslinking degree and the ionic conductivity of the amphiphilic conetwork copolymer increased. And the ionic conductivity of (PEG2000-b-GMA)-co-MMA is higher than that of (PEG200-b-GMA)-co-MMA because of its longer ethylyne oxide (EO) chains.Crosslinked GPEs based on P(AN-GMA) and poly(glycidyl methacrylate-polyethylene glycol methyl ether methacrylate) (P(GMA-PEGMA)) with polyetheramine (Jeffamine D400, Jeffamine D2000) as crosslinking agents were prepared. The reaction degree of the epoxy group increased with the increase in the content of Jeffamine D400 and Jeffamine D2000 as indicated in FT-IR analysis. The stress-strain tests revealed that the critical strength of the crosslinked polymer membranes decreased with the weight content of polyetheramine, while their elongation at break increased accordingly. The DSC analysis of the resulting GPEs suggested that the compatibility between Jeffamine and P(AN-GMA) was worse than that between Jeffamine and P(GMA-PEGMA). The ionic conductivity of the crosslinked GPEs exhibited enhanced ionic conductivity with the increase in the molecular weight and weight ratio of Jeffamine, which is due to the fact that more PPO segments involved in the system facilitated the segment mobility of the crosslinked polymer.GPEs based on multiwall carbon nanotubes (MWCNTs)/polymer hybrids were prepared based on the blending of MWCNTs grafted with Jeffamine of different molecular weights with P(AN-GMA) and P(GMA-PEGMA), respectively. SEM images of the composite membranes showed that the MWCNTs were completely wrapped with polymers and dispersed finely in the polymer matrix. The stress-strain test revealed that the hybrids exhibited enhanced critical strength, which might be related to stronger binding force between MWCNTs and copolymer resulting from the chemical covalent crosslinking. Moreover the critical strength of the hybrids in which MWCNTs grafted with PPO of longer chains was higher due to stronger linkage between MWCNTs and copolymers. The elongation at break of P(GMA-PEGMA)/MWCNTs was higher than that of P(AN-GMA)/MWCNTs due to the different flexibility of the copolymers.higher content of Jeffamine grafted MWCNTs enhanced the ionophilicity of the hybrid GPEs and led to higher ionic conductivity. The GPEs based on Jeffamine D400 grafted MWCNTs exhibit higher ionic conductivity than that based on Jeffamine D2000 grafted MWCNTs. In contrast, the ionic conductivity of P(GMA-PEGMA)/MWCNTs was higher than that of P(AN-GMA)/MWCNTs due to its lower glass transition temperature of the former system. Electrospun PVdF/PEO and the composite of PVdF/PMMA and nano-SiO2 were fabricated. The resulting membranes were composed of fibers with smooth surface and large number of cavities of different sizes as indicated in SEM images. Moreover, it was found that the nano-SiO2 dispersed uniformly in PVdF/PMMA fiber. However, the nano particles tended to aggregate with the increase in its weight ratio. XRD and DSC results revealed that the crystallinity of PVdF decreased and the crystallinity of PEO increased with the increase in PEO in the PVdF/PEO fibrous membrane. The electrospun PVdF/PEO (3/1) exhibited the highest ionic conductivity. Better dispersity of nano-SiO2 led to lower crystallinity of PVdF. The electrospun composite of PVdF/PMMA and 6wt% of nano SiO2 showed the highest ionic conductivity of 2.55×10-3 S/cm at room temperature.更多还原