Study Of Molybdenum Disulfide Composite Electrode For Zinc-based Batteries

Zinc-based batteries have wide range of application in wearable electronic devices due to the advantages of high theoretical capacity,low cost,safety,and non-pollution.Recently,the research of zinc-based batteries focuses on the cathode materials with high capacity and long cycling life.As we know,molybdenum disulfide（MoS₂）gets increasing attention in zinc-based batteries research,because of its large spacing of interlayers that is beneficial to the diffusion and transport of ions.However,its low conductivity and stackable layered structure limit the capacity and stability of batteries.Therefore,in this thesis,metal sulfides with good conductivity were used to modify MoS₂,and the MoS₂ composite electrodes were synthesized successfully,which can be used in flexible quasi-solid-state zinc batteries.And then,the capacity and stability of the battery are significantly improved.The main works of this thesis are as follows:（1）MoS₂ was modified by the metal sulfide Ni₃S₂ and the synthetic process of cathode materials was optimized,in order to improve the capacity of the electrode.The effects of cathode materials growth time on the electrochemical performances of MoS₂/Ni₃S₂ electrode were researched,and the optimal growth time for the composite electrode was obtained.The electrode with this growth time has the lowest contact resistance and charge transfer resistance,and the fabricated flexible quasi-solid-state zinc battery with this electrode has a capacity of 0.96 m Ah cm^-2 when the current density is 10 m A cm^-2.（2）After determining the growth time of MoS₂/Ni₃S₂,the effects of different concentrations of CS（NH₂）₂on the micromorphology and electrochemical performance of the electrode were researched when fixing the concentration of（NH₄）₆Mo₇O₂₄·4H₂O as 2 m M,and the optimal concentration ratio of（NH₄）₆Mo₇O₂₄·4H₂O to CS（NH₂）₂ was determined.The synthesized MoS₂/Ni₃S₂ electrode has a three-dimensional nanorod arrays structure so that it exhibits larger specific surface area and more active sites for redox reactions.The fabricated flexible quasi-solid-state zinc battery with this composite electrode has a capacity of 1.42 m Ah cm^-2 and high stability,the retention of capacity is 84.6%after 6000 cycles.In addition,the battery has a capacity of 0.53 m Ah cm^-2 at the current density of 80 m A cm^-2 and the retention of capacity is 52.3%after1000 cycles when it is bent at 90°.（3）MoS₂/Ni₃S₂ was further modified by Zn element,and ZnS/MoS₂/Ni₃S₂electrode was synthesized by one-step hydrothermal method.The influences of different Zn concentrations on the microstructure and electrochemical performance of MoS₂/Ni₃S₂ electrode were researched,and the optimal atomic ratio of Zn/Mo was determined.The obtained ZnS/MoS₂/Ni₃S₂ electrode has the sphere-like nanoflowers structure,which is beneficial to the charge transfer at the interface between the electrode and electrolyte,and the appropriate amount of ZnS makes the content of 1T phase MoS₂increase.The capacity of ZnS/MoS₂/Ni₃S₂ composite electrode is 1.4 times that of MoS₂/Ni₃S₂ at the current density of 40 m A cm^-2,and the flexible quasi-solid-state zinc battery with the ZnS/MoS₂/Ni₃S₂ electrode has a capacity of 0.86 m Ah cm^-2 at high current density of 80 m A cm^-2,which is about 2 times that of the zinc battery with MoS₂/Ni₃S₂ electrode at the same current density.It is evidenced that multicomponent metal sulfides have better electrochemical performance than that of bimetallic sulfides,and it is an effective method to improve the capacity of zinc-based batteries by modifying MoS₂ with metal sulfides.