可再生碳纳米管膜辅助制备大尺寸高能量密度石墨烯-硅网格纸及其储锂机理研究

Graphene paper，prepared by layer-by-layer densely restacking of graphene, is lightweight and exhibits excellent mechanical properties, electric and thermal conductivity. Dispense with current collector, conductive and adhesive additives, the freestanding graphene paper is one of the ideally high energy density flexible electrodes. However, the large-scale application of graphene-based papers as high volumetric energy density electrodes is limited by the problems of its limited size, long duration and high cost for preparation, as well as the poor lithium storage properties of large-size graphene thick papers which are caused by its special oriented dense structure. In this project, a carbon nanotube macroporous membrane (CNT-MPM) assisted flow-directed self-assembly method is proposed to prepare large size graphene and its composite papers in an efficient and cheap way. The preparation process assisted by the reproducible CNT-MPM will be systematically studied to reveal the correlation between the structure and properties of CNT-MPM and as-prepared graphene papers. The CNT-MPM assisted preparation mechanism of graphene papers will be obtained by comprehensive analysis of both simulation and experimental results. By using this newly developed technique, the graphene-Si composite grid paper (GSGP) will be prepared to highly enhance the energy and power density of graphene paper. Meanwhile, the mechanism to enhance the lithium storage properties of GSGP will also deeply investigated. Finally, the optimized high energy density flexible GSGP will be obtained in this project. The successfully implementation of this project will provide critical technique accumulation and scientific basis for promoting the industrial application of graphene and developing high performance new carbon-based materials for flexible energy storage.

石墨烯纸由石墨烯逐层密堆而成，质轻力优、导电导热性好，无需集流体、导电和粘结剂，是一类理想的高体积能量密度柔性电极。目前石墨烯纸仍面临着尺寸受限、制备过程耗时长和成本高等问题以及具有特别取向的致密结构的大面积石墨烯厚纸储锂性能较差等问题，这两个瓶颈严重制约了石墨烯纸作为高体积能量密度电极的实际应用。本项目提出了一种碳纳米管大孔膜辅助流体导向自组装方法高效、低价和大尺寸制备石墨烯及其复合纸，将通过系统地研究可再生碳纳米管大孔膜辅助的石墨烯纸流体导向自组装制备过程揭示大孔膜和石墨烯纸的结构与性能之间的内在关系，计算和实验相结合获得碳纳米管大孔膜辅助制备石墨烯纸的机理。利用该新技术研制石墨烯-硅复合网格纸以提升石墨烯纸的能量和功率密度，并研究其储锂性能提升机理，优化出高能量密度柔性锂离子电池电极。为推动石墨烯的工业化应用、研制高性能新型碳基柔性储能材料提供重要技术积累和科学依据。

本项目针对抑制硅颗粒体积激烈变化，石墨烯纸制备成本高、效率低和无法大规模制备，以及石墨烯基复合纸用于锂离子电池负极是存在储锂性能受电极尺寸限制等关键问题，开展了一系列广泛而深入的研究，获得了大量的研究成果。首先本项目以可再生的碳纳米管多孔膜改性的纤维素定性滤纸替代传统昂贵的阳极氧化铝膜和PTFE膜制备大尺寸石墨烯及其复合纸，设计并试制成功大尺寸抽滤装置。该装置的成功试制，不仅为本项目的提供了设备保证，而且为实现利用流体导向抽滤法大规模制膜技术生产各类膜材料提供了装置保证，为大尺寸石墨烯及其复合纸的潜在产业化生产提供了有力保证。利用现有各种不同尺寸的漏斗成功制备了不同厚度的氧化石墨烯及其复合纸，并实现了氧化石墨烯纸从碳纳米管多孔膜表面自剥离。理论与实际相结合的方式深入研究和分析了成功利用碳纳米管多孔膜制备氧化石墨烯及其复合纸的基本原理，其中氧化石墨烯之间强烈的相互作用和碳纳米管强烈的相互拉扯导致的巨大应力差和氧化石墨烯与碳纳米管之间微弱的相互作用是成功实现自剥离的关键原因。同时由于碳纳米管多孔膜可再生利用，从而能大大降低了组装过程中最关键的昂贵滤膜材料的适用和损耗，使石墨烯纸的制备成本降低了80%以上。此外，本项目还引入石墨烯基复合网格纸的概念，通过在石墨烯-碳纳米管-硅纳米复合纸厚度方向上预制通孔阵列，形成均匀网格结构，使得锂离子在石墨烯基复合纸中的迁移距离相较小而且稳定，不会随着复合纸尺寸和厚度的增加而明显增大，同时大幅提升了复合纸的倍率和循环稳定性。