盐模板法原位制备石墨烯/纳米金属复合材料及其储能机制研究

The combination of carbon material and active metal is an effective way to solve the problems of high surface activity and large volume change during electrochemical cycling of metal-base anodes. Graphene with excellent physicochemical properties is undoubtedly one of the best carbon materials. However, the agglomeration and high energy surfaces exposure of metal nanoparticles as well as the poor interfacial bonding between metal and graphene seriously affect the electrochemical performance of graphene/metal composites. Aiming to prepare graphene/metal anodes with superior rate-performance and long lifespan, this project intends to synthesize three-dimensional graphene/nano-metal (germanium, aluminum, silicon, bismuth, magnesium, zinc) composites using the combination of salt template assisted in-situ chemical vapor deposition method and gas phase ion exchange method. This project also aims at revealing the kinetic and thermodynamic processes as well as the mechanisms of graphene growth in the confined-space between salt templates, disclosing the microstructure and interface regulation of three-dimensional graphene/nano-metal composite, discovering the energy storage mechanism of these composites, and establishing the structure-property relationship of metal-based anode materials. Expected results may not only provide a viable theoretical basis and technical approach for graphene enhanced metal energy storage materials but also be of great significance for the low-cost large-scale production and application of graphene/metal composite anodes with excellent electrochemical performance.

碳材料与活性金属复合是解决金属基负极材料表面活性高，充放电时体积变化大等问题的有效途径。具有优异物化性质的石墨烯无疑是最佳的碳材料之一，然而，石墨烯与金属材料复合过程中金属纳米颗粒团聚长大、高能表面暴露以及金属/石墨烯界面结合差等问题严重影响了复合物的电化学性能。针对以上问题，本项目以制备具有高倍率性能，长循环寿命的石墨烯/金属负极材料为目标，拟采用盐模板辅助化学气相沉积结合气相离子交换方法原位制备三维石墨烯/纳米金属（锗、铝、硅、铋、镁、锌）复合材料。探明盐模板限域空间内金属原位催化石墨烯生长动力学、热力学过程及机制，揭示三维石墨烯/纳米金属复合材料的微观结构和界面调控规律。探明复合材料的储锂/钠机理，建立金属基负极材料结构-性能关系。预期成果可为石墨烯增强金属储能材料提供可行的理论基础与技术途径，对推动具有优异电化学性能的石墨烯/金属复合材料的低成本规模化制备和应用具有重要意义。

锂资源日渐匮乏，新一代储能体系的开发迫在眉睫。本项目主要针对资源丰富、成本低廉的钠/钾离子电池体系，采用盐模板辅助空间限域催化结合气相/液相离子交换法设计制备了多种三维石墨烯/纳米金属（氧属化物）复合材料。首先探究了三维石墨烯基底的储能特质，发现其在储钠过程中表现出表面离子吸附诱导的电容型储能行为，而在储钾过程中表现出离子嵌入和表面吸附共同主导的混合储能行为；其次制备了三维石墨烯内嵌锑/锑铋合金复合材料，进一步完善盐模板空间限域催化合成机理，并且利用硒表面包覆提高电子/离子扩散速率，揭示了储能中间产物优化固相中离子扩散动力学机制。聚焦此现象，通过第一性原理计算验证其通用性，发现氧化物，硫化物/硒化物与碳材料在储钠过程中生成的异质界面具有优异的电子结构，可以促进离子扩散，进而制备了三维石墨烯内嵌氧化锡，三维石墨烯内嵌硫化锡/硒化锡异质结构证实了理论计算结果。同时发现加快离子扩散可以优化材料的储能特性，使法拉第反应显现出赝电容特性，基于此现象，设计制备了中空碳立方体内嵌氧化锰复合材料，将其与活性炭正极组装成钠离子超级电容器，发现其可以完美匹配正极材料的吸附/脱附储钠特征，全器件展现出统一的电容式储能行为，并且具有高能量密度与功率密度；最后，聚焦异质界面的特殊作用，通过晶面错配分析和第一性原理计算选定错配低的硒化铁/硒化钴，采用液相离子交换法制备了具有半共格异质界面的碳负载硒化铁/硒化钴异质结构，深入研究了不同储放能态势下材料的纳米结构与电化学行为演变，揭示了异质界面对能带结构、电子结构、离子吸附/扩散等优化作用。本研究为高性能钠/钾离子电池负极材料的设计与合成提供了理论参考与实验依据。