化学交联聚酰亚胺隔膜增强锂离子电池性能研究

Study on chemically crosslinked polyimide separators for lithium-ion batteries with enhanced performance

隔膜作为锂离子电池的重要组成部分,用于阻隔阴极和阳极直接接触,同时为锂离子在电极间的传输提供有效通道。聚酰亚胺隔膜因其具有充放电循环寿命长、机械强度适中、良好的电绝缘性能以及自熄能力等优点,而受到广泛关注。以对苯二甲胺作为交联剂,将聚酰亚胺隔膜进行化学交联,研究了交联时间与隔膜形貌、结构及性能之间的构效关系。随着交联时间的增加,隔膜的孔隙率和吸液率逐渐降低,电解液接触角和机械强度逐渐增大。电化学测试表明,随着交联时间的增加,隔膜的本体阻抗逐渐增大,进而离子电导率逐渐降低,而交联隔膜的界面阻抗均远小于未交联隔膜,且交联隔膜的电化学窗口也均大于未交联隔膜。通过组装半电池测试发现,交联隔膜所组装电池的倍率性能和循环性能均优于未交联隔膜,当交联时间为48 h时,电池性能表现最优,循环100次以后,放电比容量为130.2 mA·h/g,容量保留率为91.1%。

As an important part of lithium-ion batteries,separators are used to block the direct contact between cathode and anode and provide an effective channel for lithium ion transmission between electrodes.Polyimide separators have been widely concerned because of their long charge-discharge cycle life,moderate mechanical strength,good electrical insulation and self extinguishing ability.Polyimide separators were chemically crosslinked by using p-dimethylamine as crosslinking agent,the structure-activity relationship between the crosslinking time and the morphology,structure and properties of separators was studied.With the increase of crosslinking time,the porosity and liquid absorption rate of separators decreased,and the contact angle of the electrolyte and mechanical strength increased gradually.Electrochemical tests showed that with the increase of crosslinking time,the bulk impedance of separators increased gradually and the ionic conductivity decreased gradually.The interfacial resistance of crosslinked separators was much lower than that of uncrosslinked separators,and the electro chemical window of crosslinked separators was also broader than that of uncrosslinked separators.The test result of assembling half cell showed that the rate performance and cycle performance of battery assembled by crosslinked separators were better than those of uncrosslinked separators.When the crosslinking time was 48 h,the performance of battery was best.After 100 charge-discharge cycles,the specific discharge capacity was 130.2 mA·h/g and the capacity retention rate was 91.1%.