| At present,the contradiction between the increasing energy demand and the exhaustion of non-renewable fossil energy is intensifying,and a large number of energy storage devices are urgently needed for the stable utilization of new energy.Lithium-ion batteries are widely used to solve new energy conversion and storage problems due to their higher energy density.In this paper,the development and research of high-performance lithium-ion battery anode materials are carried out.Transition metal sulfides have received great attention from researchers in recent years due to their much higher theoretical specific capacity than graphite.Among them,bimetallic sulfides can generate more redox active sites than single metal sulfides,but the problems of poor electrical conductivity and structural stability restrict their development.Constructing the coating structure of transition metal sulfides and carbon nanotubes(CNTs)can synergistically exert their effects to obtain composite electrode materials with excellent comprehensive electrochemical performance.In this paper,two different CNTs/bimetallic sulfide composites were synthesized by hydrothermal method to prepare lithium-ion battery anode materials with high specific capacitance,high rate performance and long cycle life.(1)CNTs@PDA(polydopamine)was prepared by in-situ polymerization of dopamine with CNTs as skeleton,and then CoMoS4 was in-situ deposited on it by hydrothermal method to obtain the CNTs@PDA/CoMoS4 composite that specific surface area achieved 148.9 m2/g and the content of CoMoS4 accounted for 64.2%.As the anode material for Li-ion batteries,the discharge specific capacity of CNTs@PDA/CoMoS4 can still be maintained at 1025.2 mAh/g after 100 cycles at 0.1 A/g.And it still has a reversible capacity of 490.3 mAh/g after 200 charge-discharge cycles at 1 A/g.In addition,the lithium storage performance study shows that the capacitance contribution of CNTs@PDA/CoMoS4 electrode is more than 57.8%.The good electrochemical performance is attributed to the enhanced compact deposition of CoMoS4 nanoparticles on PDA through hydroxyl groups.In this encapsulated ternary material,CNTs effectively reduce the agglomeration problem of CoMoS4 nanoparticles with high active sites,and realize the uniform growth of CoMoS4 nanoparticles on the surface of CNTs@PDA.In addition,the high conductivity of CNTs can promote the diffusion of Li+and effectively improve the ion transport efficiency,and the framework stability of CNTs can effectively alleviate the volume expansion effect of the composites.(2)CNTs@PDA was first constructed with CNTs as carbon base material,and then FeCo2S4 nanoparticles were attached and deposited on it through hydrothermal reaction.Finally,the CNTs@NC/FeCo2S4 composite that specific surface area of 75.3 m2/g and FeCo2S4 content of 55.5%were prepared by carbonization treatment.The charge-discharge cycle stability and rate performance of the obtained composites were significantly improved.The CNTs@NC/FeCo2S4 electrode still had a high rate of 884.6 mAh/g after 80 charge-discharge cycles at 0.1 A/g.And after 300 cycles at a high current density of 2 A/g,the composite electrode can still provide a specific capacity of 481.6 mAh/g.The studies of Li-storage kinetics show that the energy storage of CNTs@NC/FeCo2S4 is mainly contributed by capacitive processes.The reason for the good electrochemical performance of the CNTs@NC/FeCo2S4 electrode may be that PDA acts as a bridge to promote the tight and uniform coating between the FeCo2S4 and CNTs.The subsequent carbonization process further strengthens the stability of this coating structure,and further carbonizes the PDA into a carbon layer with higher conductivity,which not only greatly reduced the volume change of the active material during the intercalation and deintercalation of Li+,but also improved the electrical conductivity of the ternary composite CNTs@NC/FeCo2S4,and the cycle stability and rate performance of the composite were significantly improved. |
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