锂-空气二次电池用自支撑三维有序双孔道结构空气电极的设计、制备及性能调控研究

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 overcome, including poor round-trip efficiency (much more energy is required to charge the battery than is released during discharge) which is resulted from the terrible overpotentials for discharge and especially for charge. In addition, the sluggish oxygen reduction reaction (ORR, during discharging) and oxygen evolution reaction (OER, during charging) kinetics also cause low rate capability which should be enhanced by two orders of magnitude to make Li-air batteries viable for electrical vehicle applications. Furthermore, precipitation of insoluble discharge products (Li2O2) in the air electrode would gradually block the electrolyte and oxygen pathway and eventually also limits the rate capability, capacity, and cyclic life of the Li-air batteries. Therefore, there is an urgent need to design and synthesize porous air electrode catalyst to catalyze Li-air reactions while benefit rapid oxygen diffusion and prevent excessive growth of the discharge products that block the chemical pathways. To this end, in this project, we firstly propose the design and preparation of a novel free-standing three-dimensional ordered (3DOM) carbon material integrated with bi-functional ORR/OER catalyst and its application and performance optimization as high-performance air-electrode for Li-air battery. Its capabilities of mass transport, accommodate capacity of insoluble Li2O2, and catalytic activity will be achieved by finely tuning the pore structure, dispersion and volume of 3DOM carbon material as well as the composition, size/shape, and/or structure of the integrated catalyst, respectively, and thus would significantly improve the capacity, rate capability, round-trip efficiency, and cycle stability of Li-air battery. Furthermore, our proposed free-standing air electrode will be fabricated using a facile and simple controllable molding process to avoid the use of the binder and metal current collector, and the obtained all-in-one air electrode would overcome the instability and low electronic conductivity of the conventional air electrode and thus would improve the reliability and performance homogeneity of Li-air battery. Our research would provide insights into design principle of highly efficient air electrodes for rechargeable Li-air battery.

锂-空气二次电池因具有超高的能量密度（高出现有锂离子电池1～2个数量级），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，设计和制备高性能空气电极是进一步提高其能量转换效率、倍率性能和循环寿命，突破其发展和应用瓶颈的关键和难点。本项目针对锂-空气电池的特点，设计和合成新型自支撑三维有序双孔道结构的纳米晶催化剂/碳复合薄膜空气电极，通过对孔道结构和催化剂组成及形貌的调控，增强空气电极的传质，固体产物沉积和氧还原/析出反应能力，进而大幅提高电池的能量密度、能量转换效率、倍率性能和循环寿命。此复合空气电极采用一次成型工艺，省去了复杂的粉末电极制备过程，整体起到集流体的作用，可克服传统电极活性物质附着性和导电性差的缺点，提高电池可靠性和性能均一性。本项目提出的构筑高性能空气电极的新途径以及一体化设计思想，将为促进锂-空气电池的研究和开发提供科学依据。

锂-空气二次电池因具有超高的能量密度（高出现有锂离子电池 1～2 个数量级），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，设计和制备高性能空气电极是进一步提高其能量转换效率、倍率性能和循环寿命，突破其发展和应用瓶颈的关键和难点。本项目针对锂-空气电池的特点，设计和合成了新型自支撑三维有序双孔道结构的纳米晶催化剂/碳复合薄膜空气电极，通过对孔道结构和催化剂组成及形貌的调控，增强空气电极的传质，固体产物沉积和氧还原/析出反应能力，进而大幅提高电池的比容量（14000mAh/g）、能量转换效率(74%)、倍率性能和循环寿命(205次)。此复合空气电极采用一次成型工艺，省去了复杂的粉末电极制备过程，整体起到集流体的作用，可克服传统电极活性物质附着性和导电性差的缺点，提高电池可靠性和性能均一性。本项目提出的构筑高性能空气电极的新途径以及一体化设计思想，将为促进锂-空气电池的研究和开发提供科学依据。