PEO/LiClO_4纳米SiO_2复合聚合物电解质的电化学研究

STUDIES ON COMPOSITE POLYMER ELECTROLYTE PEO/LiClO_4/NANO-SiO_2

将实验室制备的纳米二氧化硅和市售纳米二氧化硅粉末与PEO LiClO4复合 ,制得了复合PEO电解质 .它们的室温离子电导率可比未复合的PEO电解质提高 1～ 2个数量级 ,最高可以达到 1 2 4× 10 - 5S cm .离子电导率的提高有两方面的原因 :一是无机二氧化硅粉末的加入抑制了PEO的结晶 ,是二氧化硅粉末和聚合物电解质之间形成的界面对电导率的提高也有一定的作用 .在进一步加入PC EC(碳酸丙烯酯 碳酸乙烯酯 )混合增塑剂后制得的复合凝胶PEO电解质 ,可使室温离子电导率再提高 2个数量 ,达到 2× 10 - 3 S cm .用这种复合凝胶PEO电解质组装了Li|compositegelelectrolyte|Li半电池 ,并测量了该半电池的交流阻抗谱图随组装后保持时间的变化 ,实验观察到在保持时间为 144h以内钝化膜的交流阻抗迅速增大 ,但在随后的时间内逐渐趋于平稳 。

In order to enhance the ionic conductivity of PEO based polymer electrolytes and improve the stability of the interface between the lithium electrode and the polymer electrolyte, PEO/LiClO4/nano-SiO2 composite polymer electrolytes were prepared by adding self-synthesized nanometric SiO2 ( NMSIO) or commercial nanometric SiO2 (MN1P and modified MN1P) powder into the PEO/LiClO4 complex. There was 1 similar to 2 orders of magnitude increase in the ionic conductivities for these composite PEO electrolytes. It could reach as high as 1.24 x 10(-5) S/cm at room temperature. There are two reasons of the increase in ionic conductivity. First, the addition of SiO2 powder can suppress the crystallization of PEO. Secondly, the interface between the SiO2 powder and polymer electrolyte also makes a contribution to the increase in ionic conductivity. PEO based composite gel electrolytes were prepared by the addition of plasticizer PC(propylene carbonate) /EC (ethylene carbonate) into the PEO based composite electrolytes. The ionic conductivity was increased by another two orders of magnitude. The highest one reached 2 x 10(-3) S/cm at room temperature. A half-cell of Li \ composite gel electrolyte \ Li was assembled with the above mentioned composite gel PEO electrolyte. The variation of the AC impedance spectra with post-preparing time of the half-cell was measured. It was found that the AC impedance of the passivation layer increased quickly within 144 h, but stabilized gradually in the following time. It revealed that SiO2 powder could suppress the growth of the passivation layer between the composite gel PEO electrolyte and the lithium electrode.