碳载“双功能”催化剂正极的可控构筑及锂空气电池性能研究

To optimize and select high-performance bifunctional catalysts and carbon active materials, and then to fabricate cathodes with effective microstructure is the critical issue for the development of lithium-air batteries using organic electrolyte. This project aims to develop an electrochemical route for controllable preparation of carbon-supported bifunctional catalysts for the synthesis of cathodes. The N-doped carbon-based materials including graphene,carbon nanohorns and carbon black have been investigated as carbon active materials; and single- or multi- walled carbon nanotubes have been using as enhanced conductance network for electrodes. MnO2 supplemented by other metal oxides or noble metals have been used to improve the performance of catalysts. The morphology and dispersion of catalysts have been controlled by adjusting the deposition conditions, such as voltage, current density, composition of solution and temperature, magnetic field, ultrasonic treatment and other deposited factors; and then the cathodes with an effective controlled-framework have been prepared. The mechanism of electrodeposition for fabricating these carbon-supported catalysts have been studied detailedly. The mechanism of which the microstructure and size-effect of catalysts can improve the efficiency of oxygen reduction and promote the rate of oxygen evolution, have been revealed in this project. This study is expected to obtain the high-performance electrode materials for lithium-air batteries, which is of vital importance for promoting the development of lithium-air batteries.

优选高效"双功能"催化剂，构筑有效微结构的正极是开发有机系锂空气电池中的关键所在。本项目拟发展电沉积法可控构筑碳载"双功能"催化剂复合电极技术作为解决之道。利用掺氮处理的石墨烯、碳纳米角、碳黑为碳正极活性物，辅以单/多壁碳纳米管作为电极电导网络；以二氧化锰为"双功能"主催化剂，辅以其他金属氧化物或贵金属为增强催化剂；通过调节电沉积条件- - 电压、电流密度、镀液参数及温度、磁场、超声等因素来调控催化剂的晶相形貌及其分散性，实现有效微结构复合电极的可控构筑。探讨碳载"双功能"催化剂复合电极的电沉积可控构筑机制；系统考察复合电极的锂空气电池电化学性能；揭示电极和催化剂微结构及尺寸效应对提高氧还原效率和促进氧析出速率的"双功能"催化的作用机制。此研究有望实现高性能锂空气电池电极材料的研发，为推动锂空气电池的开发进程有重要意义。

当今，能源环境危机日益严峻，锂空气电池因其具备高容量被认为是未来高能量密度储能装置的理想选择。实现有效结构碳基电极的构筑是研制锂空气电池的关键。本项目将石墨烯、碳管等碳材料进行异原子N掺杂、功能化及负载催化剂等综合处理，并以此作为原料，辅以泡沫镍为集流体，发展湿化学法、电纺丝法、气相沉积法及电泳法构筑电极材料。首先，通过湿化学方法制备了多壁碳纳米管负载纳米梭型的FeOOH的复合材料，并用此材料研究其锂空气电池的性能；其次，利用水热方法在多壁碳纳米管负载三元尖晶石MFe2O4（M = Co，Ni）纳米粒子，形成催化剂复合物MFe2O4（M = Co，Ni）/CNTs，并详细研究复合物MFe2O4/CNTs的锂空电池的电化学性能。最后，采用电纺丝方法合成一种新型的Fe/Fe3C-CNFs复合材料，并用于锂空气电池正极催化剂的性能研究；该Fe/Fe3C-CNFs催化剂在锂空气电池中应用时能表现出优良的性能：在200 mA/g测试报有容量6250 mAh/g，并在定容量为1200 mAh/g时循环稳定20个周期，定容量为600 mAh/g时循环稳定40次。另外，通过化学气相沉积法结合磁控溅射路径，设计并制备出无粘结剂的泡沫镍负载Pt /碳纳米管的复合自支撑电极（Pt/CNTs-NF），并直接用于锂空气电极的研究。结果表明，所制备的电极具有更合适的微空间结构，具备如下的电极优势——高比表面积、良好的导电性和催化剂的高分散型及电催化活性，所组装的锂空气电池可以提供优异的电化学性能。特别是，在400 mA/ g且定容量为1500 mAh /g的充放电循环可达80次，相对应地，电极材料的能量密度约为3000 Wh/kg，显示了优异的循环稳定性。总之，实验获得的正极整体表现出良好的锂空气电池性能。本项目对锂空气电池研究和改进具有重要的意义。