藤蔓结构NiCo-MOF@CNTs复合电极材料制备及性能

Preparation and performance of creeping vine-like structured NiCo-MOF@CNTs composite electrode materials

超级电容器是一种高性能电化学储能装置,具有功率密度高、循环稳定性强、充放电速率快等特点,在可再生能源存储中发挥重要作用。为提高超级电容器性能,满足日益增长的能源储存需求,利用水热法制备NiCo-MOF@CNTs复合电极材料,通过改变碳纳米管(CNTs)添加量,使复合材料储能特性达到最优。CNTs不仅增加了材料的比表面积和导电性,还与NiCo-MOF形成独特的藤蔓结构,其中NiCo-MOF构成藤蔓的叶片,为电荷存储提供活性位点,而CNTs构成与叶片相连接的茎蔓,将电子源源不断传递至活性中心,改善电化学性能。与未添加CNTs相比,效果最好的NiCo-MOF@CNTs5的比表面积由25.65 m^(2)/g增至44.27 m^(2)/g,平均孔径由37.86 nm降至18.99 nm,孔径分布更有利于电解质离子的扩散与传输;在1 A/g电流密度下,比电容高达1569 F/g,电流密度增至20 A/g时,倍率性能高达74%,高于未加入CNTs的NiCo-MOF电极材料(42.6%)。组装成非对称超级电容器后,在1 A/g电流密度下比电容为194 F/g,电流密度增至20 A/g时比电容仍有147 F/g;在5 A/g电流密度下经5000次充放电循环后,比电容保有率91.2%;在759 W/kg功率密度下的能量密度高达50.63 Wh/kg,功率密度提至17.3 kW/kg仍能实现41.94 Wh/kg高能量密度。

Supercapacitors are a type of high-performance electrochemical energy storage device with high power density,strong cycling stability,and fast charge-discharge rates,which play a crucial role in the storage of renewable energy.To enhance the performance of supercapacitors and meet the growing demands for energy storage,NiCo-MOF@CNTs composite electrode materials were prepared using a hydrothermal method.By varying the amount of carbon nanotubes(CNTs),the energy storage properties of the composite material were optimized.CNTs not only increase the material′s specific surface area and conductivity,but also form a unique vine-like structure with NiCo-MOF.NiCo-MOF constitutes the leaves of the vine in this structure,providing active sites for charge storage,while CNTs form the stems connecting to the leaves,continuously transferring electrons to the active centers,thereby improving electrochemical performance.In comparison to the case without the addition of CNTs,the specific surface area of the most effective NiCo-MOF@CNTs5 increases from 25.65 m^(2)/g to 44.27 m^(2)/g and the average pore size decreases from 37.86 nm to 18.99 nm.The pore distribution is more favorable for the diffusion and transport of electrolyte ions.The specific capacitance reaches up to 1569 F/g at a current density of 1 A/g,and the rate performance reaches 74%at an increased current density of 20 A/g,which is higher than that of the NiCo-MOF electrode material without CNTs(42.6%).After assembling into an asymmetric supercapacitor,the specific capacitance remains at 194 F/g at a current density of 1 A/g and still maintains 147 F/g at a higher current density of 20 A/g.After 5000 charge-discharge cycles at 5 A/g current density,the capacitance retention rate is 91.2%.The energy density at a power density of 759 W/kg reaches 50.63 Wh/kg,and a high energy density of 41.94 Wh/kg is achieved even at an increased power density of 17.3 kW/kg.