【作者】 李为立；

【导师】 杨慕杰；

【作者基本信息】 浙江大学 ， 高分子化学和物理， 2007， 博士

【摘要】 本论文着重研究锂离子电池用凝胶聚合物电解质。设计制备了四种体系共十种凝胶聚合物电解质，其四个体系分别为膜支撑凝胶聚合物电解质、改性两相凝胶聚合物电解质、semi-IPN凝胶聚合物电解质、以及改性PVdF多孔凝胶聚合物电解质等。采用FTIR、NMR、DSC、TGA、XRD、SEM等物理和化学测试手段，以及交流阻抗谱和线性扫描伏安法等电化学测试手段，研究凝胶聚合物电解质的化学结构、膜表面形态、热性能和电化学性能。分析不同工艺制备条件和原料组成比例对产物性能的影响，以实现体系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有实际应用前景。1．设计制备了膜支撑凝胶聚合物电解质，分别为“PPEGMA／PMMA膜支撑凝胶聚合物电解质”、“HBP／PEO膜支撑凝胶聚合物电解质”、以及“MAPTMS／MMA膜支撑凝胶聚合物电解质”。研究发现交联预聚物的涂覆固化并不破坏PE微孔膜的结晶度，PE膜在体系中依然保持较好的力学支撑性能。极性交联组分在微孔膜上固化后呈现多孔状形态，由于其化学结构和极性与液体电解质的相似性，有利于吸附液体电解质于其内并凝胶化，使体系具有较高的离子导电率。此外，涂覆的极性交联聚合物有利于提高微孔膜和金属锂电极之间的接触性能，使对金属锂片的电化学稳定性较好。体系室温离子导电率在10^-3S cm^-1数量级。电化学稳定窗口＞4.5V，且其与金属锂片的接触较为稳定，降低了液体电解质和锂金属反应的可能性，防止金属锂的钝化而失效。2．制备改性两相凝胶聚合物电解质：“PMMA-g-NBR／PMMA改性两相凝胶聚合物电解质”、以及“PMMA-g-PVC／PMMA改性两相凝胶聚合物电解质”。通过接枝聚合对聚合物母体NBR和PVC进行改性，两者分别与PMMA共混后，吸附液体电解质以制备改性两相凝胶聚合物电解质。PMMA的链段接枝可提高共混两相聚合物的相间相容性，通过光学显微镜和扫描电镜观察，得到均相透明的共混两相聚合物薄膜。PMMA组分在体系中吸附大量液体电解质形成离子导电通道，使得体系在室温下离子导电率达到10^-3S cm^-1数量级，而接枝共聚物组分在体系中保持较好的力学强度。3．通过热聚合或紫外光辐照聚合的方法，分别制备了如“（PPEG200MA-co-MMA／NBR）半互穿凝胶聚合物电解质”、“MAPTMA-co-PEGDMA／NBR半互穿凝胶聚合物电解质”，以及“XPEG／PMMA半互穿凝胶聚合物电解质”。制备得到的聚合物薄膜表面均一，未发现由于相分离而出现的卷曲或者裂痕。通过DSC或XRD观察证明，整个体系呈现无定形态。整个semi-IPN薄膜的力学性能随着共混聚合物的比例而变化。与普通的共混型凝胶聚合物电解质相比，semi-IPN凝胶电解质体系相间相容性好，体系不仅保持较好力学性能，而且极性交联组分可吸附大量液体电解质，交联网状结构也有利于液体电解包覆于其内凝胶化，以实现较高的室温离子导电率。体系的室温离子导电率达到10^-3S cm^-1数量级，且电化学稳定窗口超过4.5V。4．通过两种方法改性PVdF多孔膜，制备改性PVdF多孔凝胶聚合物电解质。第一种手段通过将水解交联的预聚物涂覆于PVdF多孔膜表面，紫外光固化后，再吸附液体电解质凝胶化，以制备复合PVdF多孔凝胶聚合物电解质；第二种手段溶利用分散聚合方法合成带有PEG支链的极性共聚物，将其共混PVdF，制备共混改性PVdF多孔凝胶聚合物电解质。所涂覆的交联聚合物溶液浓度以及共混聚合物的添加量均影响PVdF多孔膜表面的孔隙大小（1-5μm）和孔隙率。在体系中，PVdF保持较好的力学强度和电化学稳定性；涂覆或共混的共聚物组分有利于吸附液体电解质以凝胶化，此外，共聚物极性较强，易于将液体电解质吸附其内，且其链段中极性基团与锂离子有络合作用，可促进锂盐离解，增加锂离子含量，提高室温离子导电率，以达到实用的10^-3S cm^-1水平。此外，改性PVdF多孔膜凝胶聚合物电解质电化学窗口均超过4.5V，电化学稳定性好。上述设计的凝胶聚合物电解质，制备方法简便，性能良好，具有实际应用价值。更多还原

【Abstract】 The novel gel polymer electrolytes （GPEs） for Secondary Lithium-ion Battery have been investigated. Four kinds of gel polymer electrolyte were prepared, including membrane supporting gel polymer electrolyte （MSGPE）, modified dual-phase polymer electrolyte （DPE）, semi-IPN gel polymer electrolyte and modified PVdF microporous gel polymer electrolyte. The chemical characteristics, surface morphology, thermal behavior, ionic conductivity, interfacial stability between lithium metal electrode have been investigated by using of FT-IR, Differential Scanning Calorimetry （DSC）, Scanning Electron Microscopy （SEM）, Optical microscopic images, Alternating Current Impedance （AC Impedance） and Linear Sweep Voltammetry （LSV）, respectively. Analysis the effects of preparation conditions and the proportions of raw materials on the properties of obtained GPEs, the aim of the paper is to develop the high ionic conductivity GPE with good mechanical strength.1. The membrane supporting gel polymer electrolytes （MSGPE）, such as MSGPE-PPEGMA/PMMA, MSGPE-HBP/PEO and MSGPE-MAPTMS-MMA were prepared and investigated. For the polar prepolymers coated and cured PE membrane, the crystallinity property of PE, which imparted the mechanical strength to MSGPE was found to be almost maintenance. The coated polar copolymer presented a microporous structure, the absorbed liquid electrolyte could be trapped in the pores and formed gel polymer electrolyte due to good compatibility between them. In addition, the coated copolymer could increase the surface area in contact with the electrode, which would be benefit to the electrochemical stability between them. The ionic conductivity at room temperature reached 10^-3S cm^-1 and the electrochemical stability window was more than 4.5V.2. Dual-phase polymer electrolytes （DPEs） with enhanced phase compatibility, such as DPE-PMMA-g-NBR/PMMA and DPE-PMMA-g-PVC/PMMA were prepared. The polymer host NBR and PVC were modified with MMA by solution grafting polymerization. The grafted copolymer was first blend with PMMA and then absorbed the liquid electrolyte to prepare a new type DPE with enhanced phase compatibility. The films of DPE so obtained were homogeneous and transparent. In the DPE systems, the blending PMMA absorbed vastliquid electrolyte and formed ionic conduction channel to make the ionic conductivity at room temperature reach 10^-3S cm^-1 scale, while the PMMA-g-NBR or PMMA-g-PVC component kept excellent mechanical properties.3. Semi-IPN gel electrolytes such as SIN-（PPEG200MA-co-MMA/NBR）, SIN-（MAPTMS -co-PEGDMA/NBR） and SIN-（XPEG/PMMA） were prepared by means of thermal polymerization or ultraviolet （UV） radiation. The surfaces of the semi-IPN polymer films were uniform and homogeneous, and hardly any cracks were observed. In the semi-IPN systems, the blending polymer chains tend to tangle with each other. The results of DSC and XRD analysis confirmed that the prepared hosts present amorphous state. The mechanical properties of the semi-IPN hosts varied with the proportion of the polymer blends. The phase compatibility of the semi-IPN gel electrolytes so obtained was better than the former blending type gel polymer electrolyte. This gel polymer electrolyte could not only retain the good mechanics, but also absorb a mass of liquid electrolyte to withstand a highly ionic conductivity. The ionic conductivity of gel polymer electrolyte reached 10^-3S cm^-1 and the electrochemical stability window was more than 4.5V.4. Modified PVdF microporous gel polymer electrolytes with enhanced properties were prepared by two methods. For the first method, PVdF microporous membranes were coated with polar cross-linked copolymer by means of UV radiation. For the second method, PVdF was blent with the polar copolymer which was prepared by means of dispersion polymerization, to prepare the microporous membrane. The images of the vacuum-dried films showed that micropores of 1-5μm were formed, which were influenced by concentration of the coated and the blending copolymer, respectively. PVdF kept good mechanical property and electrochemical stability in the GPE system. The addition of coated or blending copolymers helped to absorb the liquid electrolyte and gelatinize. In addition, the complexation effect of the copolymer and Li⁺ ion could promote the dissociation of the Li salt, which eventually increased the number of conductive ions and enhanced the ionic conductivities. The prepared microporous gel polymer electrolyte reached 10^-3S cm^-1 and the electrochemical stability window exceeded 4.5V.In a word, the above preparation methods of gel polymer electrolytes （GPEs） are quitesimple. GPEs so prepared have good properties, which made it possible to be used for secondary Lithium-ion battery in practice.更多还原