自支撑膨胀石墨-碳纳米管微/纳尺度复合柔性锂离子电池电极研究

The development of lightweight, super-thin, flexible and wearable electronics is an important goal for next-generation portable electronic devices. However, the heavy and inflexible electrode structure of current Li-ion battery system has great gap with the practical demand of flexible electronics. Herein, novel metal oxide nanoparticles/carbon nanotube (CNT)-exfoliated graphite (EG) hybrid free-standing flexible anodes have been proposed. To overcome the defects of EG, a gas phase route is designed to prepare the composite. Firstly, the catalyst nanoparticles (Fe/Co/Ni) were homogeneously loaded on the surface of EG by the gas diffusion-pyrolysis of ferrocene, cobaltocene or nickelocene. Then the CNTs are in-site grown on the surface of EG by catalytic chemical vapor deposition (CVD). Finally, oxygen oxidation method is employed to realize the conversion of catalyst nanoparticles from metal phase to their corresponding metal oxide phase. After a simple roll-in treatment, the hybrid flexible anodes can be prepared. In view of the nanosheets of EG are easy to form serious π-π stack under the inducement of solvent removal and pressure, the above mentioned gas-phase strategy can effectively avoid the structural destruction of EG during the preparation process. Furthermore, the CNTs and metal oxide particles can improve the electrolyte diffusion to the inner of electrode structure. By the control of the loading of nanoparticles and the modification of CNTs, it is expected to improve the initial Coulombic efficiency, specific capacity and rate capability of the hybrid electrode. This research will provide some theoretical and experimental references for Li-ion batteries with low cost, scalable size and superior combination performance.

下一代消费类电子产品正朝着轻薄、柔性、可穿戴性发展，但现有锂离子电池厚重、不可弯折的电极结构难以满足柔性电子器件的使用要求。本项目拟利用膨胀石墨（EG）优良的自粘结性、高的导电性和多孔性，通过二茂（铁、钴、镍）的弥散-热解在EG表面担载催化剂纳米颗粒，然后用化学气相沉积法将碳纳米管（CNT）在EG表面修饰得到纳-微尺度复合的CNT/EG载体；利用热氧化法将催化剂原位转变为活性纳米颗粒，再经辊压得到柔性电极。本思路针对EG的石墨纳米片在溶剂脱除和压力作用下π-π堆叠严重的问题，设计气相途径来避免传统溶液方法对EG微观结构的破坏，利用CNT对EG纳米片层所产生的适度阻隔来改善电解液向电极内部的扩散，同时期望通过对纳米颗粒的担载和CNT的修饰过程的控制来提高电极的首次效率、比容量和倍率性能。本项目的开展将为低成本的、尺寸可控的、综合储锂性能优良的柔性电极的发展提供理论和实践参考。

随着柔性电子产品、电动汽车和大规模储能的快速发展，对锂离子电池提出更高要求。负极材料作为决定电池性能的关键部分，当前面临如何具有柔性以及更高的比容量和倍率性能等问题，而这也是目前电化学能源存储领域的研究热点。针对这些问题，本研究致力于以膨胀石墨为载体，通过气相法实现高容量的过渡金属化合物的均匀担载，同时尝试碳纳米管的修饰以及柔性电极材料的构建。研究结果发现，以二茂（铁、钴、镍）为原料，在密闭反应器中通过升温机制的控制分别可以实现碳包覆的铁、钴和镍在膨胀石墨表面的均匀分散。而进一步的气相硫化反应分别得到碳包覆Fe1-xS/膨胀石墨、CoS/碳纳米空腔/膨胀石墨以及NiS2/多孔膨胀石墨复合材料。这三类材料都具有高的储锂/储钾比容量、优良的循环稳定性和倍率性能。在利用化学气相沉积法进行碳纳米管的原位生长后，再经气相硒化反应得到过渡金属硒化物/碳纳米管/膨胀石墨复合材料，发现具有稳定的储钾性能。受上述气相法的启示，我们尝试了气相法制备氧化铁/碳纳米管复合材料，结果证明该材料具有优异的储锂性能。此外，我们利用辊压法开发了一种倍率性能优良的石墨类柔性电极材料。