轻金属基复杂氢化物原子、电子结构与转换反应型储钠性质的第一性原理研究

The problems of environmental pollution and finite fossil fuel supply have stimulated the hot research on the relative cheap sodium-ion batteries (SIB) for large-scale and green energy storage applications around the world these years. Currently, the majority of the studies on SIB anode materials have focused on various carbon, the Ⅳ and Ⅴ group elements and metal oxides and sulfides. While, there has been very little research on metal hydrides as SIB anode materials. It is quite necessary to perform fundamental research on metal hydrides since this materials system has potentially high specific capacities. In this project, we will focus on the light-metal (Al, Mg, Ti) based complex hydrides and investigate theoretically their structures and sodium-storage properties based on the state-of-the-art first-principles (ab-initio) molecular dynamics method combined with hybrid functionals. The atomic and electronic structures of several light-metal based complex hydrides and the effects of doping will be revealed. The sodium-storage thermo-kinetic properties of intrinsic and doped light-metal complex hydrides and their relationship with the electronic structures of materials will be investigated. In addition, the conversion reaction process of the light-metal complex hydrides anodes will also be studied to theoretically predict the reaction paths and the reaction mechanisms. This fundamental research is proposed to supply computational quantatitive design on the usage of light metals in SIB anodes on one hand; on the other hand, the proposed theoretical study will lay an important foundation for the future experimental research and development.

近年来环境污染和化石能源短缺的双重倒逼引发了绿色、大规模储能用廉价钠离子电池材料的研究热潮。目前国内外关于储钠负极材料的研究多集中于各种碳材料、第Ⅳ和第Ⅴ主族单质或合金以及各种氧化物和硫化物，而对于金属基氢化物这一体系作为转换反应型储钠负极材料的研究则非常缺乏。考虑到轻金属氢化物潜在的容量密度，很有必要对其开展前瞻性理论研究。为此，本项目主要基于第一性原理从头算的分子动力学并结合杂化泛函等先进密度泛函理论方法，剖析Al、Mg、Ti基轻金属复杂氢化物的原子、电子结构及掺杂元素影响，获得本征及掺杂态各氢化物负极材料的储钠热、动力学性质并探索其与材料电子结构的关联规律，探究轻金属基复杂氢化物负极材料的电极反应过程，从理论上预测电极反应路径并初步阐释转换反应型储钠机理。预期该项研究不仅为后续实验研究奠定重要的理论基础，而且将为轻金属在钠离子电池转换反应型负极材料中的应用提供有效的材料设计方法。

近年来能源与环境问题的双重影响引起了具有较高资源丰度的储钠材料的研究热潮。本项目主要采用第一性原理计算方法探索了一系列轻金属基复杂氢化物作为储钠电极材料的原子尺度结构、电子结构和电化学性质。从理论计算层面揭示了所研究轻金属基复杂氢化物的微观原子、电子结构，获得了各轻金属氢化物电极材料的电化学储钠基本性质并阐明了各掺杂元素对钠离子扩散动力学的影响，从理论上理解了电极反应过程并初步阐释了转换反应型储钠的化学物理机制。钠离子在Li4Al4(N4H8)4晶格中的扩散能垒为0.45 eV，在改性Li4AlB3(N4H8)4材料中的扩散能垒可降至0.31 eV。Li-Mg1掺杂体系作为钠离子电池负极材料时，理论比容量可提升到1978.26 mAh/g，平均电压降低到0.408 V。钠离子在Mg7TiH16表面上的扩散需要克服0.04 eV的扩散能垒，而在Li-Mg1掺杂体系表面上扩散仅需要克服0.01 eV的能垒。发表SCI学术论文11篇，并得到德国亥姆霍兹乌尔姆研究所、韩国成均馆大学等单位的正面引用与评价。本项目的研究结果将为后续实验研究以及其它新型转换反应型储钠负极材料的理性设计提供有价值的基础理论指导。

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