三维网状结构Ru/石墨烯/碳纳米管复合材料作为锂氧电池正极催化剂的性能

利用物理浸渍和冷冻干燥等方法制备了具有三维网状结构的Ru/石墨烯/碳纳米管复合材料, 对该材料的结构、 形貌及电化学性能进行了表征和研究. 结果表明, 当Ru含量为30%, 热处理温度为500 ℃时, 材料的催化性能最优. 将其用作锂氧电池的正极催化剂, 以50 mA/g电流密度进行首次充放电时, 放电比容量约为5800 mA·h/g, 且在放电比容量为4000 mA·h/g以内时, 其极化电压仅为0.9 V; 当以50 mA/g电流密度进行恒容(500 mA·h/g)充放电循环时, 在极化电压低于1.1 V时, 仍能稳定循环12周. 复合材料电催化机理的研究结果表明, 三维网状结构不仅提供了O₂和Li⁺的传输通道, 更增加了放电产物Li₂O₂的储存场所. 金属钌纳米粒子的负载既增加了复合材料的反应活性位点, 又促进了放电产物Li₂O₂的分解.

Performance of Ru/graphene/carbon Nanotube Composites with Three-dimensional Network Structure as Positive Electrode Catalysts for Lithium Oxygen Batteries†

Ru/graphene/carbon nanotube composites with three-dimensional network structure were prepared by physical impregnation and freeze drying. When the Ru content was 30%(mass fraction) and the heat treatment temperature was 500 ℃, the catalytic performance of the composite was optimal. When the composite was used as a cathode catalyst for lithium oxygen batteries, it exhibited excellent battery performance. When the first charge and discharge were performed at a current density of 50 mA/g, the discharge capacity density was about 5800 mA·h/g, and when the discharge capacity density was within 4000 mA·h/g, the polarization voltage was only was 0.9 V; when a constant-capacitance(500 mA·h/g) charge-discharge cycle was performed at a current density of 50 mA/g, the battery was stable for 12 cycles even when the polarization voltage was lower than 1.1 V. The three-dimensional network structure not only provided a transmission channel for O₂ and Li⁺, but also increased the storage location of the discharge product Li₂O₂. The loading of the metal ruthenium nanoparticles not only increased the reactive site of the composite, but also promoted the decomposition of the discharge product Li₂O₂.