磷烯负极材料的气-液界面合成、传质机理及其储钾性能研究

The large interlayer spacing and high theoretical specific capacity of phosphorene make it be an important choice for anode material of potassium ion batteries. However, it exists several deficiency for the preparation phosphorene: the uncontrollable synthesis of size and thickness, abundant defects, time-consuming, and easy to be oxidized. To solve these problems, the project proposes constructing high quality phosphorene and its composites on the surface of liquid gallium metal through a chemical vapor deposition route. The innovation and merit of this program involves: (1) it can achieve the size- and thickness-controlled phosphorene and phosphorene composite on the surface of gallium metal; (2) the synthesized nanosheets are defects-free and well crystalline; (3) the composite counterpart can improve the conductivity of the phosphorene, reduce the volume change and enhance the structural stability again. By the synthesis of controllable phosphorene and phosphorene composite, a new method for constructing of two-dimensional phosphorene and its composites is to be established. In addition, in this project, we would elucidate the mass transfer mechanism between the vapor-liquid interface using molecular dynamics simulation combined with in-situ and ex-situ observation. Analyzing the volume change and potassium storage of phosphorene and phosphorene composites anodes, we intend to disclose the volume-confined mechanism, electrode dynamics processes and structure-electrochemical performance mechanisms of composite structures. The implementation of this project will provide experimental and theoretical support for the development of phosphorene anode materials.

磷烯层间距大、理论比容量高，是钾离子电池负极材料的重要选择。但其制备存在尺寸、厚度不可控、缺陷多、周期长、易被氧化等不足。针对这几个问题，本项目拟采用化学气相法在液态金属镓的表面沉积高质量的磷烯及其复合材料。该方案的创新和特色之处在于：（1）金属镓表面可合成尺寸、形貌、厚度可控的磷烯及其复合物；（2）合成的纳米片缺陷少，晶体稳定性高；（3）复合组份可提高磷烯的导电性、进一步提高结构稳定性和降低其体积变化。通过磷烯及其复合物的可控制备，建立二维磷烯及其复合物构筑的新方法。另外，本项目将采用分子动力学模拟结合原位/非原位观察，阐明磷烯气-液界面合成的传质机理；分析磷烯及其复合物电化学过程中的体积变化和储钾性能，揭示复合结构的体积限制机理、电极动力学过程和构效机制。本项目的实施将为磷烯负极材料的发展提供实验和理论支持。

磷烯具有层间距大、理论比容量高等优势，是一种非常具有发展潜力的钾离子电池负极材料。然而，磷烯制备存在尺寸、厚度不可控、缺陷多、在空气中易被氧化等问题。针对这些问题，本项目采用化学气相法，通过调控反应温度、时间、液态金属的种类成功制备了在液态金属镓的表面沉积高质量的磷烯及其复合材料。该方法可以实现磷烯及其复合物的可控制备。电池性能结果表明，相关磷烯复合材料在1.0 A g-1下具有约200 mAh g-1比容量和高电流密度10 A g-1下呈现45 mAh g-1。进一步，在此基础上，构筑了MoS2和黑磷（磷烯）异质结结构来实现高的可逆比容量（在1.0 A g-1下，比容量为435.5 mAh g-1）、快速的钠（钾）离子迁移动力学和良好的结构稳定性。此外，MoS2和黑磷异质结可以隔绝磷与氧气的接触，提高磷在氧气中的稳定性。与此同时，利用相近的异质结改性策略，开发出了同类结构的钠（钾）离子电池用Ga2O3@Ga2S3@C和具有化学键合作用的V5.45S8与碳纳米纤维复合物（CB-VS@NSCNFs）负极材料。Ga2O3@Ga2S3@C在0.1 A g-1的电流密度下循环100圈后在展现出680 mAh g-1的放电容量；在20.0 A g-1电流密度下则获得250 mAh g-1的倍率容量。长循环测试表明，在充/放电电流密度为0.5/20 A g-1条件下循环4000圈后，异质结构纳米颗粒保留的容量高达410 mAh g-1，展现了优异的倍率性能和循环稳定性。本项目发表SCI论文10余篇，完成了相关研究任务，达到了预期成果考核指标要求。