Preparation and performance of creeping vine-like structured NiCo-MOF@CNTs composite electrode materials
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 su-percapacitors 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 m2/g to 44.27 m2/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 1 569 F/g at a current density of 1 A/g,and the rate per-formance 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 5 000 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 den-sity of 41.94 Wh/kg is achieved even at an increased power density of 17.3 kW/kg.
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