【作者】 胡斌；

【导师】 毕可东；

【作者基本信息】 东南大学 ， 机械设计及理论， 2021， 硕士

【摘要】 目前,便携式电子设备与电动汽车技术的发展使得锂离子电池有着巨大的市场需求。然而,锂离子电池的循环寿命、快充能力、能量密度等性能仍然不能满足实际使用的要求,其中锂离子电池充放电循环过程中负极表面形成的不稳定的固态电解质界面膜是制约锂离子电池发展最重要的因素之一。锂离子电池的固态电解质界面膜在循环过程中容易破裂、脱落和再生,影响锂离子电池的库伦效率、循环寿命和安全性能。因此设计稳定的人工固态电解质界面膜是提高锂离子电池寿命和综合性能的重要方式。本文利用分子动力学模拟方法,研究聚噻吩和石墨负极（氧化石墨烯）之间的黏附,聚噻吩作为人工固态电解质界面膜的效用以及锂离子在聚噻吩链中扩散动力学的机理。首先,研究了聚噻吩和氧化石墨烯之间的黏附相互作用,分别计算了聚噻吩与不同表面官能团密度的羧基-氧化石墨烯（FG-COOH）、羟基-氧化石墨烯（FG-OH）、氨基-氧化石墨烯（FG-NH₂）和甲基-氧化石墨烯（FG-CH₃）之间的黏附相互作用。在相同的条件下,聚噻吩与附着不同官能团的氧化石墨烯之间的黏附作用主要是由官能团的电负性主导,其中官能团电负性最强的羧基功能化形成的羧基-氧化石墨烯（FG-COOH）与聚噻吩之间的黏附作用最强,而基团电负性最弱的甲基功能化形成的甲基-氧化石墨烯（FG-CH₃）与聚噻吩之间的黏附作用最弱。此外,黏附体系的黏附作用还受氧化石墨烯与聚噻吩接触界面的表面粗糙度影响。随着甲基-氧化石墨烯（FG-CH₃）表面官能团密度的增加,黏附体系的相互作用能逐渐增强并趋于稳定,这表明接触界面的表面粗糙度会削弱聚噻吩和氧化石墨烯之间的黏附作用。本文在证实了聚噻吩与氧化石墨烯之间存在较强的黏附性后,进一步构建了锂离子电池模型,探究聚噻吩作为人工固态电解质界面膜在锂离子电池中发挥的功效。模拟结果说明聚噻吩作为人工固态电解质界面膜隔绝锂离子电池中电解液溶剂分子碳酸乙烯酯（EC）与石墨负极的接触,降低了电解液溶剂分子被还原分解的概率。此外,通过计算锂离子穿过聚噻吩层的扩散率以及锂离子电池的离子电导率,进一步分析锂离子在聚噻吩链间的扩散动力学,证实了锂离子沿聚噻吩链有特殊的“跳跃”运动机制。因此,本文系统研究了聚噻吩与氧化石墨烯之间较强的黏附作用机理以及在锂离子电池中聚噻吩作为人工固态电解质界面膜的效用,为设计开发新型锂离子电池的人工固态电解质界面膜提供了新的设计思路。更多还原

【Abstract】 At present,the development of portable electronic equipment and electric vehicle makes lithium-ion battery have a huge market demand.However,especially for the application of electric vehicles,new challenges,such as the life cycle,capability,safety,and irreversible capacity have to be overcome.The unstable solid electrolyte interface（SEI）formed on the anode surface during the charge-discharge cycle of lithium-ion batteries is one of the most important factors restricting the development of lithium-ion batteries.The unstable SEI formed during the cycle of lithium-ion battery is easy to rupture and fall off,which affects the Columbic efficiency,cycle life and safety of lithium-ion battery.Therefore,the design of a stable artificial solid electrolyte interface（A-SEI）is an important way to improve the life and performance of lithium-ion batteries.In this paper,molecular dynamics simulation is used to study the adhesion between polythiophene（PTh）and graphite anode（graphene oxide）,the utility of polythiophene（PTh）as an A-SEI,and the diffusion dynamics of lithium ions in the polythiophene matrix.First,the adhesion interaction between polythiophene and graphene oxide is studied,and the polythiophene and different surface density of carboxyl-graphene oxide（FG-COOH）,hydroxyl-graphene oxide（FG-OH）,amino-graphene oxide（FG-NH₂）and methyl-graphene oxide（FG-CH₃）are calculated via direct energy method.The enhanced adhesion behavior between PTh and graphene oxide substituted with different functional groups is mainly dominated by the electronegativity of the functional groups.The adhesion between carboxyl-graphene（FG-COOH）and PTh is the strongest,and the methyl group with the weakest electronegativity have the weakest adhesion interaction behavior.In addition,the adhesion of the adjoining system is also affected by the surface roughness of the interface between graphene oxide and PTh.With the increase of the density of the surface functional groups of the methyl-graphene oxide（FG-CH₃）,the interaction energy of the adhesion system gradually strengthens and tends to be stable,which indicates that the surface roughness of the contact interface weakens the adhesion interaction between PTh and graphene oxide.After confirming the strong adhesion between PTh and graphene oxide,lithium-ion battery model is constructed to explore the effect of PTh as an A-SEI in lithium-ion battery.PTh is used as an artificial solid electrolyte interface（A-SEI）to isolate the electrolyte solvent molecules（EC）in the lithium-ion battery from contact with the graphite negative electrode,reducing the probability of the electrolyte solvent molecules being reduced and decomposed.In addition,a special hopping transport mechanism is verified by the diffusion rate of lithium ions through the PTh layer and the diffusion kinetics of lithium ions between PTh matrix.Therefore,this article confirms the strong adhesion between PTh and graphene oxide and the utility of PTh as an A-SEI in lithium-ion batteries.The results provide new insight to develop A-SEI for high-performance lithium-ion batteries.更多还原