Core-shell MoS₂ Supercrystals:Controllable Synthesis,growth Mechanism And Electrochemical Performance

MoS₂,as a tapical transition metal sulfide with graphene-like structure and wider band gap,which can be applied for the next generation electron devices,has been a new research focus,recently.The research based on the forcus of controlable structure-function play a decisive role in the field of energy storage.However,controllable synthesie of well-difined MoS₂ and especially hollow and core-shell MoS₂,remain a great challenge,with a low cost and high efficiency process.In this paper,the core-shell MoS₂ and MoS₂/RGO composites with well-difined structures are controllably produced and applied for the supercapacitor and lithium batteries.The detailes are as follows:?1?The optimum condition synthesis of MoS₂,through controlled reverse micelle by adjusting the reaction parameters such as volume ratio of solvent,the concentration and temperature of reactant in the experiment to make different structures of micromicelles resulting in regulating and controlling the size,structure and composion,can be obtained.Based on the optimum condition,we can produce a series of MoS₂ supercystal materials assembled with oriented nanosheets by adjusting the reaction temperature.?2?The core-shell MoS₂ supercystal materials droped by O atoms homogeneous have been verified by numorous and in-depth characterizations.At the same time,abundant defects can be generated on the surface of nanosheets during process of nanosheets bended forming sphere,the novel core-shell MoS₂ supercystal materials with rich-dopants and defects can be therefore produced successfully.The CTAB can decouple the atomic layers forming superlattices structures,at high reaction temperature.Based on the change of structures and composions along with the increasing of reaction temperature,we have proposed and verified a fresh mechanism of embryonic development for the synthesis of core-shell supercystal materials.The novel embryonic development will provide a new method to produce core-shell materials.?3?The S160,S180,S200 and S220 materials are applied to fabricate supercapacitors and investigated their structure-performance both in three-electrode system.The S220electrode fabricated with special structure and composion exhibites outstanding electrochemical performance.In the three-electrode system,the S220 supercapacitor shows the specific capacitance of 986 and 529 F g^-1 at the currents detensities of 0.5 and 16 A g^-1and keep the 92%of the initial capacitor after cycling for 2500 numbers at 4 A g^-1.Based on the density functional theory?DFT?,we investigate the charge density distribution and band gap after droped O atoms and lacked S atoms with the Dmol3.The results show that droped and lacked couple atoms have more effect on the band gap,and the effect from defects are greater than dopants.Compared with the reports related to supercapacitor,the simulated calculation about band gap give the reason why S220 electrode shows the most excellent capacitance performance.?4?We produce RGO/MoS₂ composites based on the 2H-MoS₂ obtained with an annealed process in N₂,GO solution and ethylene glycol reductant by hydrothermal process.The weight contents of 0%,1.0%,3.5%,7.0%,8.5%and 15.9%can be produced through change the addition of GO,designed as MSA,MSA-1,MSA-2,MSA-3,MSA-4 and MSA-5,respectively.The MSA-3 electrode possess initial charge-discharge of 1045 and1363 mAh g^-1,and the corresponding colum efficient of⁷6.7%,exhibiting best initial charge and maximum colum efficient.The capacitance can remain 88.8%of the second capacity after cycle 100 numbers at 0.2 A g^-1,showing excellent cycle stability.Compared with the pure MoS₂ and other composites,MSA-3 possess 1134,1017,904,739 and 458mAh g^-1 at the current densities of 0.1,0.2,0.5,1 and 2 A g^-1,revealing the best rate-capacitance.What is more,the capacitance can still reach to¹011 mAh g^-1 at 0.1 A g^-1 after large current charge-discharge at 2 A g^-1,which also indicate the MSA-3 electrode owns the most outstanding rate-capacitance and best recovery after big current charge-discharge.?5?Porous and uniform Mn₂O₃ microspheres that are coated with amorphous carbon can be produced by annealing MnCO₃ precursors at 400,500 and 600°C for 8 h,with biomass glycerol in-situ encapsulated inside the voids of the particles.In the three electorde system,the Mn₂O₃-500 microspheres show specific capacitances of 383.87 F g^-1 at current density of 0.5 A g^-1,and excellent cycling stability of 90.47%of its initial value after cycling for 5000 times(4 A g^-1).The asymmetric supercapacitors assembled with C@Mn₂O₃ microspheres after annealed at 500°C and activated carbon?AC?show an energy density of up to 77.8 Wh kg^-1 at power density of 500.00 W kg^-1,and a maximum power density of 20.14 kW kg^-1 at energy density of 46.8 Wh kg^-1.