高性能锂-空气二次电池用双功能金属催化剂研究

Rechargeable lithium-air (Li-air) battery has recently attracted a great deal of attentions because it can theoretically store 10-100 times more energy than current lithium-ion batteries, which is vital for electric vehicles, future clean energy storage, and other high energy applications. However, to enable Li-air battery for practical applications, numerous scientific challenges are urgently need to be surmounted, especially poor round-trip efficiency and rate capability due to the terribly sluggish oxygen reduction reaction (ORR, during discharging) and oxygen evolution reaction (OER, during charging) kinetics, which should be enhanced by two orders of magnitude to ensure Li-air batteries viable for electrical vehicle applications. Therefore, there is an urgent need to design and fabricate high efficient catalyst for Li-air battery. To this end, in this project, based on the working principle of Li-air battery, novel metal-based bifounctional catalysts will be designed and fabricated to enhance and balance the catalytic activity of ORR and OER. In addition, the underlying relationships between the electrochemical performances (rate capability, energy efficiency, and stability) and the properties of metal-based catalysts such as composition, porosity, size, and morphology, etc. will be investigated in detail. Finally, integrated air electrode of Li-air battery will be fabricated using the optimized metal-based bifunctional catalyst to improve the electrochemical performance of Li-air battery, which would provide new scientific basis to accelerate the research and development of Li-air battery.

锂-空气二次电池因具有超高的能量密度，其研究和开发对解决可再生能源存储和大幅提高电动汽车续航里程等问题具有重要的科学意义和实用价值。但锂-空气电池的研究尚处于初级阶段，高性能空气电极催化剂的缺乏导致目前锂-空气电池的性能特别是能量效率和倍率性能离实用化尚有很大差距。本项目拟针对锂-空气电池的工作原理，设计和制备一系列金属基双功能催化剂，实现氧还原/氧析出催化性能的双向平衡，提高电池充放电效率和倍率性能；阐明催化剂成分、纳米多孔性、尺寸效应、形貌特征等因素对锂-空气电池性能的影响规律；筛选出高效双功能催化剂并制成一体化空气电极，提升锂-空气电池的能量密度、倍率和循环稳定性，为锂-空气电池的研究和开发提供科学依据。

金属空气电池因为其超高的能量密度在长续航动力电池领域中有巨大的应用前景，其中锂空气电池和钠空气电池的研究最为广泛。对于金属空气电池而言目前存在循环寿命短、充放电能量效率低以及容量不足的问题，而空气正极和催化剂的设计对以上问题至关重要。1）项目首先制备了表层包埋金属钴纳米粒子的氮掺杂型碳纤维用于钠空气电池的正极和催化剂，这种无粘结剂型的正极显著提高了电池循环稳定性和比容量，同时降低了充电过电位。通过研究分析表明掺杂型碳和钴纳米粒子氧化物存在协同作用，起到了调控固态放电产物结构和形貌作用，从而改善了充电过程的热力学和动力学。2）另外，在碳纸上制备了一种四氧化三钴纳米线阵列作为一体化无粘结剂空气电极并用于钠空气电池，获得4687mAh/g的电池比容量，循环寿命达62次。3）合成了结构优化的氮掺杂的多孔碳材料用作空气电极催化剂，钠空气电池容量提升到6905mAh/g，循环寿命从8次提升到66次，研究结果表明氮掺杂在金属空气电池正极材料中协同作用的重要性。