锂-空气电池用一体化双功能碳复合正极的设计、合成及构效关系研究

Lithium-air batteries have been considered as the future breakthrough for secondary-batteries due to their extremely high theoretical energy densities. The development of lithium-air batteries is significant to solve the storage of sustainable energy and improve the mileage of electric vehicles. However, the drawbacks of present air cathodes limit the development of lithium-air batteries. So it is urgent and crucial to design and prepare novel air cathodes to improve the capacities, rate-performance and cycle stability of the batteries. According to the working principles of lithium-air batteries, this project will design and synthesis of novel free-standing hierarchical porous and bifunctional carbon-composite cathodes. The novel electrodes have two significant features: optimized free-standing porous structure greatly facilitates deposition of solid products, electrical conduction, and diffusion of molecular and ions; the bifunctional catalysis of oxygen reduction and oxygen evolution reactions effectively decreases the overpotential and solve the problem of kinetics of the electrochemical reactions in the batteries, and then, improve the stability of carbon and the cycle life of the batteries, enhancing the energy density and conversion efficiency. Furthermore, such novel carbon-composite air cathodes would be produced by once shaping and act as the cathode directly, which makes the preparation of cathodes simple and saves the conventional complex procedures. This project firstly puts forward integrating design thought of structure-function of air cathodes and will provide new scientific basis to accelerate the research and development of lithium-air batteries.

锂-空气电池因其超高的能量密度被视为跨越式提高二次电池比能量的未来突破点，研究和开发锂-空气二次电池对解决可再生能源存储和提高电动汽车续航里程具有重要的意义。目前，空气正极整体性能不足已严重阻碍锂-空气电池的发展，设计和制备高性能空气正极是进一步提高电池容量、倍率和循环性能，突破其发展瓶颈的关键和难点。本项目基于锂-空气电池工作特点，设计和合成同时具有一体化多孔结构和氧还原氧析出双功能催化能力的新型碳复合空气电极，合理的结构可促进电子传导和离子与氧气的扩散，解决电池的传质动力学问题；双功能催化能力可有效降低充放电过程中的过电位，解决电池的反应动力学问题，提高了碳材料的稳定性和电池的循环寿命。同时新型电极作为整体一次成型，省去了复杂的粉末电极制备过程。本项目首次提出的空气电极"结构-功能"一体化整体设计思想和构筑高性能空气电极的新途径，将为促进锂-空气电池的研究和开发提供新的科学依。

项目执行期间重点开展了锂空气电池关键材料与器件功能导向设计、可控合成、反应调控和构效关系等方面的工作：1)实现了催化剂活性位点、导电性、反应物传质与产物存储的协同调控，获得的系统电催化剂大幅提升了锂空气电池能量转化效率；2) 调控了过氧化锂与金属锂沉积与生长行为，大幅改善了锂空气电池循环稳定性，初步阐明了性能演化规律；3)研制了具有完全自主知识产权的高比能锂空气电池组(能量密度大于达到1000Wh/kg)和柔性锂空气电池；4）提出并实现了锂-氮气和锂钠合金-空气电池的概念。上述系列研究成果发表后得到了国内外学术界同行的关注，被Science和Nature期刊予以亮点介绍或专题评述，有关研究结论被本领域国内外知名科学家多次正面引用。