功能化离子液体的制备及其电化学性能研究

发布时间：2018-09-17 13:19

【摘要】：传统锂离子电池有机电解液有挥发、易燃等缺点，给锂离子电池带来安全性能上的隐患。离子液体液体具有不挥发、不易燃的优点，且在一定温度范围内，电导率较高。功能化离子液体是在离子液体的基础上进一步通过引入功能化基团改造离子液体的相关性能，本文从功能化离子液体电解质及功能化离子液体凝胶聚合物电解质的物理化学性能及其与电极材料的相容性等方面研究了其作为锂离子电池电解质的可能性。制备了两种离子液体N-甲基-N-乙酸甲酯基哌啶双三氟甲磺酰亚胺(PPO2TFSI)和N-甲基-N-烯丙基吡咯双三氟甲磺酰亚胺(PyrMeATFSI)，PPO2TFSI和PyrMeATFSI都具有较宽的电化学窗口，即有较好的电化学稳定性，电化学窗口均大于4.5V，分别为5.8V和5.0V。对电化学窗口的分析说明，离子液体PPO2TFSI和PyrMeATFSI可以应用于锂离子电池中。其热稳定性优于有机电解液，室温离子电导率达到10-4数量级，电解液PPO2TFSI+0.1mol/L LiTFSI和电解液PyrMeATFSI+0.8mol/L LiTFSI具有较高的tLi+，，分别为0.56和0.72。 LiFePO4正极在电解液PPO2TFSI+0.1mol/L LiTFSI中的循环伏安曲线对称性好，LiFePO4在该电解液中表现出良好的循环性能，20个循环，电池容量基本没有衰减，在110mAh·g-1左右，除首次库仑效率较低为92.4%，库仑效率一直保持在100%附近。 LiFePO4在电解液PyrMeATFSI+0.8mol/L LiTFSI中的循环性能比较好，经过20次循环后其容量几乎无衰减，一直为110mAh·g-1左右。首次库仑效率较低，为87%，经多次循环后，库仑效率则接近100%。进一步制备了离子液体凝胶聚合物电解质应用于常用电极材料。正极材料LiFePO4在离子液体凝胶聚合物电解质中表出了良好的循环性能：室温0.1C倍率下，LiFePO4的首次充电比容量均能达到100mAh·g-1以上，放电库仑效率在80%左右；20次循环后比容量无明显衰减，循环性能好。电化学阻抗谱和SEM显示，充放电循环后，在LiFePO4电极表面均生成了某种物质，提高了电池的充放电稳定性。
[Abstract]:The organic electrolyte of traditional lithium ion battery has the disadvantages of volatilization and flammability, which brings hidden trouble to the safety of lithium ion battery. Ionic liquids have the advantages of nonvolatile, non-flammable, and high conductivity in a certain temperature range. Functionalized ionic liquids are based on ionic liquids to further transform the correlation energy of ionic liquids by introducing functional groups. In this paper, the possibility of functionalized ionic liquid electrolyte and functionalized ionic liquid gel polymer electrolyte as lithium-ion battery electrolyte was studied in terms of its physical and chemical properties and its compatibility with electrode materials. Two ionic liquids, N-methyl-methyl piperidine bisfluoromethyl sulfonimide (PPO2TFSI) and N-methyl-N-allyl pyrrolidine bisfluoromethyl sulfonimide (PyrMeATFSI) (PPO2TFSI) and PyrMeATFSI, have been prepared, which show good electrochemical stability. The electrochemical windows were larger than 4.5 V, 5.8V and 5.0V, respectively. The analysis of electrochemical window shows that ionic liquid PPO2TFSI and PyrMeATFSI can be used in lithium ion battery. Its thermal stability is superior to that of organic electrolyte. The ionic conductivity reaches 10-4 orders of magnitude at room temperature. The electrolyte PPO2TFSI 0.1mol/L LiTFSI and electrolyte PyrMeATFSI 0.8mol/L LiTFSI have higher tLi. The cyclic voltammetric curves of the LiFePO4 positive electrode in the electrolyte PPO2TFSI 0.1mol/L LiTFSI were symmetrical. LiFePO4 showed good cycling performance in the electrolyte. Twenty cycles showed no attenuation of the battery capacity, and the cell capacity was about 110mAh g ~ (-1). Except for the low Coulomb efficiency of 92.4% for the first time, the Coulomb efficiency has been kept around 100%. The LiFePO4 has good cycling performance in the electrolyte PyrMeATFSI 0.8mol/L LiTFSI. After 20 cycles, the capacity of the Coulomb has almost no attenuation and has been about 110mAh g-1. The first Coulomb efficiency is relatively low, 87. After several cycles, the Coulomb efficiency is close to 100. Ionic liquid gel polymer electrolytes were further prepared and used as electrode materials. The cathode material LiFePO4 shows good cycling performance in ionic liquid gel polymer electrolyte. The initial charge specific capacity of LiFePO4 can reach above 100mAh g -1 at room temperature 0.1 C ratio, and the discharge Coulomb efficiency is about 80%. After 20 cycles, the specific capacity has no obvious attenuation, and the cycle performance is good. Electrochemical impedance spectroscopy (EIS) and SEM showed that some substance was formed on the surface of LiFePO4 electrode after charge and discharge cycle, which improved the charge and discharge stability of the battery.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM912

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