石榴型FeF3@C-石墨烯气凝胶三维网络结构的可控构筑与储锂性能研究

FeF3 based on conversion reaction has been considered one of the most promising cathode materials for power lithium ion battery due to its high theoretical specific capacity of 712 mAh/g, which is 3-5 times higher than traditional cathode materials. However, FeF3 undergoes intrinsic poor electronic conductivity and low reversible conversion rate (Fe3+↔Fe2+↔Fe) during the electrochemical charge-discharge process, which leads to a limited actual specific capacity, poor cycling performance seriously hindering its commercial application. This proposal is based on the research of low-cost iron-based compounds, glucose and graphene oxide. A one-pot hydrothermal strategy and gas-solid reaction strategy will be developed in this project. The influence of iron-based compounds, carbonization rate of glucose, and hydrothermal condition will be investigated for the controllable synthesis of FeF3. A novel 3D cathode composite of pomegranate-structured FeF3@carbon nanospheres-doped graphene aerogel will be design and fabricated, which provides double protection for FeF3 and controls the complex conversion reaction (Fe3+↔Fe2+↔Fe) within a limited space, resulting in the much improved reversible conversion reaction rate and superior lithium storage properties. Finally, the relationship of size-composite structure-lithium storage properties will be proposed, which will supply new research approach on design of cathode material with high reversible capacity and good cycling performance.

三氟化铁的理论比容量高达712 mAh/g，是传统正极材料的3~5倍，成为动力锂离子电池正极材料的理想之选。但是，FeF3是通过转化反应机制实现储锂，存在储锂过程的转化反应可逆性差(Fe3+↔Fe2+↔Fe)的瓶颈性难题，导致实际比容量远小于理论值，严重阻碍了其商业化应用。本项目拟以廉价丰富的铁基化合物、葡萄糖和氧化石墨烯为原料，基于水热合成和气-固反应技术，系统研究不同铁源、葡萄糖碳化速度、水热条件对FeF3尺寸的影响规律，实现对 FeF3尺寸的精确调控；设计和构筑包裹多个FeF3纳米晶的石榴结构碳球、进一步包覆在石墨烯气凝胶中的三维网络结构，实现对FeF3双层保护。将FeF3与锂离子的复杂反应限制在有限的空间内进行，克服FeF3可逆转化率低的难题，有效提高FeF3的储锂性能，揭示“FeF3尺寸-复合结构-储锂性能”之间的关系，为设计和制备比容量高和循环性能好的正极材料提供新的研究思路。

三氟化铁的理论比容量高达712 mAh/g，是传统正极材料的3~5倍，成为动力锂离子电池正极材料的理想之选。但是，FeF3是通过转化反应机制实现储锂，存在储锂过程的转化反应可逆性差(Fe3+↔Fe2+↔Fe)的瓶颈性难题，导致实际比容量远小于理论值，严重阻碍了其商业化应用。本项目以廉价丰富的铁基化合物、葡萄糖和氧化石墨烯为原料，基于水热合成和气-固反应技术，系统研究不同铁源、葡萄糖碳化速度、水热条件对FeF3尺寸的影响规律，实现对 FeF3尺寸的精确调控；设计和构筑包裹多个FeF3纳米晶的石榴结构碳球、进一步包覆在石墨烯气凝胶中的三维网络结构，实现对FeF3双层保护。将FeF3与锂离子的复杂反应限制在有限的空间内进行，克服FeF3可逆转化率低的难题，在100mA/g 电流密度下，120 次循环比容量高达410 mAh/g，远远超过目前的商业化正极材料（＜220 mAh/g），这种简单的策略也可以拓展到其他金属氟化物正极材料，为下一代了高容量锂离子电池的研究奠定一定的基础。