黑磷储钠负极材料容量衰减机理研究及其二维纳米复合化微观结构调控

Due to the high theoretical specific capacity of 2596 mAh/g and high-rate capability, the black phosphorus with a puckered honeycomb structure similar to graphite have been considered as a potential anode material for sodium ion batteries (NIBs). However, the large volume change during the sodiation process results in electrode degradation and rapid capacity fading, which greatly limited practical applications. In this proposal, two types of 2D nanoscale phospherene-based anode materials will be carefully explored based on first-principle calculations combined with ab initio molecular dynamics simulations. To gain insight into the capacity fading mechanism of phospherene-based anode materials, the relationship between composition, structure, sodium storage property, kinetics characteristics, and dynamic structural evolution will be systematically investigated by theoretical simulation of the sodiation process. Furthermore, a strategy by constructing a sandwich-like phospherene-based anode materials with N-doped grapheme(NG) substrate is proposed to improve the cycling stablility and electrochemical performance of electrode materials, becauae of NG’s high electrical conductivity and numerous active sites. We expect that the fundamental findings from this computational works will lead to a better understanding of essential effect of nano-composite technologies to the electrochemical properties improvement and provide useful guidelines in further designing and developments of high-performance phosphorus-based anode materials for NIBs.

具有类似石墨褶皱蜂巢层状结构的黑磷储钠负极材料具有超高的比容量(2596mAh/g)和良好的大电流充放电性能，是一类极具潜力的钠离子电池负极材料。然而体相黑磷充放电过程会发生较大体积膨胀致使电极粉化，造成电池容量快速衰减，成为制约该类材料实用化的壁垒。本项目运用第一性原理计算结合从头算分子动力学模拟方法，对不同结构和组成的黑磷负极材料的微观结构和钠化过程进行理论模拟计算，从热力学和动力学角度对该类材料的组成-微结构-储钠性能-动力学特性-结构形变之间的构效关系进行系统研究，阐明二维磷烯主体的表面效应和夹层石墨烯载体的协同作用对材料热力学稳定性和动态结构演变的影响，获得黑磷储钠负极材料容量衰减机理；在此基础上，开展以氮掺杂石墨烯为载体的黑磷储钠材料的微观结构设计和性能调控研究，探明二维纳米复合化等微观结构调控手段对黑磷电化学性能提升的作用方式和本质，为高性能储钠负极材料的研发提供理论依据。

本项目对具有高比容量和良好大电流充放电性能的大储量黑磷负极材料进行优化设计，以解决该类材料在脱嵌钠过程中体积膨胀导致电极粉化失效这一实际应用中出现的关键问题为出发点，针对二维纳米黑磷基复合负极材料的微观结构及电化学反应过程的钠化机理等基础科学问题，结合第一性原理计算和从头算分子动力学模拟等手段对二维单原子层的石墨烯、磷烯，以及磷烯/石墨烯异质结的晶体结构、电子性质、力学等性能进行系统理论研究，并模拟其作为钠离子电池负极材料电化学反应过程，从分子和原子的微观层面获得二维磷烯基钠离子电池复合负极材料钠化过程的相关性质和钠化机理。研究结果表明，二维石墨烯载体和磷烯主体两种材料复合形成的异质结材料具有良好的热力学和动力学稳定性。石墨烯载体的引入在提高复合材料导电性的同时能大幅提升其力学性能以有效缓解电极材料充放电过程体积膨胀产生的巨大应力。因此，二维纳米化和石墨烯复合化是两种能有效解决黑磷基钠离子电池负极材料容量快速衰减问题的策略。此外，由于异种原子氮掺杂能有效增加本征石墨烯的导电性能同时增加钠离子吸咐活性位点，故以氮掺杂石墨烯为载体的复合异质结将比本征石墨烯为载体的异质结具有更好的电化学性能，其中相比石墨型氮掺杂石墨烯和吡咯型氮掺石墨烯载体，以吡啶型氮掺杂石墨烯为载体的二维复合异质结材料由于具有更好的导电性、更强的钠离子吸咐活性和更优异的力学性能被认为是更具应用前景的钠离子电池负极材料。本研究结果能够为钠离子电池用黑磷基负极材料的结构设计和性能优化提供理论指导和依据，并且为实验设计和开发能够实现大规模应用、具有高倍率性能和循环性稳定性能的高容量钠离子电池负极材料提供理论依据。