论文标题:锂离子电池中PAN基聚合物电解质特性研究
Study on the Properties of PAN-based Polymer Electrolytes for Lithium-ion Batteries
论文作者 高卫东
论文导师 莫育俊；王兆翔,论文学位 硕士,论文专业 光学
论文单位 河南大学,点击次数 1040,论文页数 62页File Size2832k
2002-06-01论文网 http://www.lw23.com/lunwen_415072/ 锂离子电池;聚合物电解质;拉曼光谱;红外光谱;复阻抗谱;缔合;离子传导机制
Lithium-ions Batteries;Raman;IR;AC impedance spectroscopy;Polymer electrolyte;association;the transport mechanism of lithium ions
聚合物锂离子电池既保持了液体电解质锂离子固有的优势，即高能量和长循环寿命，也将聚合物结构优点、易装配性和高安全性融入了锂离子电池。聚合物电解质取代常规的液态电解质是一种革命! 研究聚合物电解质中各组分之间的相互作用和微观结构，对于了解Li~+离子在聚合物电解质中的传导机制，从而探索性能更为优良的聚合物电解质具有重要的意义。在本论文中，我们利用拉曼(Raman)光谱、红外(IR)光谱和电化学复阻抗谱等手段，研究了以聚丙烯腈(polyacrylontrile，简写为PAN)为基，以双氟磺酰亚胺锂(bis-(trifluoromethanesuphone)imide，简写为LiTFSI)为锂离子源，以丙烯碳酸酯(propylene carbonate，简写为PC)为增塑剂的聚合物电解质体系中各组分间的相互作用和离子存在状态。以此为基础，提出了不同类型PAN基聚合物电解质的可能离子输运机理，并对于聚合物在聚合物电解质中的作用进行重新的评价。具体工作如下： 实验发现，在LiTFSI\PC电解液内，Li+和PC溶剂分子间的缔合以及PC对TFSI-阴离子结构的影响从而导致了在电解液内溶剂化离子对的形成。 在配制聚合物电解质的过程中，在所有的PC分子和Li+发生缔合之前，PAN极难溶于PC中，而一旦PAN开始溶于PC，电解质内与PC相关的微结构保持恒定，而盐和PAN的相互作用则显得尤为强烈。 利用电化学复阻抗谱对该体系的电导率的测试发现，体系的电导率对Li+与电子施主PAN之间的缔合有强烈的依赖性，并在较高的盐的浓度下(PC:PAN:LiTFSI=1:1:5)，观测到了该体系从“Salt-in-Polymer"’向“Polymer-in-Salt”的转变。 在以上实验结果的基础上，我们对聚合物在传统的“Salt-in-Polymer”型聚合物电解质和“Polymer-in-Salt”型聚合物电解质中的作用进行了解释，并提出了不同类型的PAN基聚合物电解质的可能的传导机制。
Polymer Lithium-ion batteries retain the inherent superiority of their counterparts with liquid electrolyte, that is high energy density and long cycling life; meantime, They contain the virtue of the structural properties of polymer, easier packing properties and high electrochemical and chemical stability. It is a revolution that polymer electrolytes replace conditional liquid electrolytes!It is interesting to find out if there are interactions between the components and how the components interact with each other. These questions are important because they are relevant to the transport mechanism of lithium ions in the solid electrolytes, which have not been fully understood to date, and the synthesis of gel electrolytes with better properties. In this paper, a novel PAN-based polymer electrolyte has been studied by Raman, IR and AC impedance spectroscopy. Based on our experimental facts, the ion conductivity mechanism of different polymer electrolytes has been put forward, at the same time; the role and the function of polymer have been re-evaluated.Detailed work as follows:The interactions between propylene carbonate (PC) and bis-(trifluoromethanesuphone)imide (LiTFSI) have been studied by Fourier transform (FT) Raman and infrared (IR) spectroscopy. It is found that the coordination of the Li"1" ions with the solvent PC and the influence of PC upon the structure of the TFSF anion lead to the formation of solvent-shared ion pairs in this liquid electrolyte.When PC,PAN and LiTFSI are mixed to prepare for Polymer electrolyte, the polymer can not be dissolved in PC before all the PC molecules are associated with the salt. As long as the polymer is dissolved in PC, the microstructure related to PC does not vary with the salt content in the polymer electrolyte while the interaction between the Li+ ion and the polymer is striking.The microstructure evolution of polymer electrolyte composed of PC, PAN and LiTFSI has been characterized by Raman spectroscopy and the conductivity of the electrolytes have been evaluate by AC impedance spectroscopy. It is found that the conductivity of the electrolyte depends strongly on the association of the lithium ions with the electron donor of the polymer and a transition from "Salt-in-Polymer" to "Polymer-in-Salt" electrolyte has been observed when the salt content is very high (PC:PAN:LiTFSI=1:1:5).Based on these facts, the distinct effects of the polymer are proposed on the transportation of ionic species in conventional "Salt-in-Polymer" electrolyte and in the "Polymer-in-Salt" electrolyte.
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