以纤维素为前驱体构筑硬炭基复合电极材料及其储锂机制研究

硬炭的理论容量、倍率性能与低温性能均优于石墨，但较低的首次库伦效率和电压滞后现象限制了其应用。去除表面杂质组分、减少SEI膜对Li+的消耗以及降低H/C原子比是解决问题的关键。项目以多层级三维网络结构的纤维素为前驱体，深入研究其热解硬炭的储锂性能与机制：控制炭化反应以去除杂原子及调控微观结构，探讨其炭化机制；包覆软沥青或PVDF以形成高导电碳层，揭示电子与Li+在硬炭网络中的传输模式；将非金属元素修饰在硬炭表面以增加反应活性点，阐明此异质结构对于功能化炭材料的作用机理；以氧化石墨烯为桥梁，利用其丰富的含氧基团与金属离子形成共价键以构筑金属氧化物/硬炭复合材料，分析组分之间的界面交互作用，探明其作为锂离子电池负极的储锂反应机理。本项目旨在合理设计材料结构与组分以提高硬炭的储锂能力，揭示其结构、组分、储锂机制及电化学稳定性的内在联系，进而推动此类硬炭基复合电极其在锂离子动力电池领域的应用。

The theoretical capacity, rate capacity and low-temperature performance of hard carbon is much better than graphite. But hard carbon has defects of large irreversible capacity and hysteresis voltage when charge and discharge as anode material of lithium ion batteries. These are the main barriers of industrialization of it. The emphases and difficulties to solve the problems include the removal of surface impurities, reduction of lithium ion consumption for SEI and reduction of H/C atomic ratio. Cellulose with multi-level three-dimensional network structure is the research object of this project. The purpose is to improve the lithium storage performance of its derivative hard carbon. First, optimize the pyrolyzation process to remove the surface impurity and then discuss its carbonation mechanism. Second, coat coal pitch and PVDF on the surface to form the high conductive carbon layer and then reveal the transmission mode of electron and Li+. Third, connect non-metallic heteroatoms on surface of hard carbon by Van der Waals' force to increase the reactivity point, then clarify the influence mechanism of this hetero-structure to hard carbon. Finally, disperse graphene oxide among cellulose as “bridge” to construct metallic oxide/hard carbon composite. The oxygen-containing groups are used to form covalent bond with metallic ions. This project aims at designing hard carbon structure rationally to fill the gap of lithium storage, acquiring the inner link between composite structure and reaction activity/stability, and finally promoting the application of hard carbon based composite in the filed of lithium ion power battery.