Design And Preparation Of High Performance Electrode Materials And Its Electrochemical Performance

Although lithium-ion batteries and supercapacitors are promising energy storage devices in the present study, they are still facing the same challenge:the electrode material with high performance. Therefore, it is very important to obtain the electrode materials with high performance for lithium-ion batteries and supercapacitors.In this study, electrode-materials with high performance were designed and prepared. And the techniques of XRD, SEM, and TEM were adopted to characterize the microstructure and morphology of the as-prepared materials. The electrochemical methods including cyclic voltammetry and galvanostatically discharged and charged test were used to investigate their electrochemical performance in depth:(1) For lithium ion batteries, porous nano-sized SnO2@C/graphene and Sn@C/graphene electrode materials with three-dimensional carbon conductive network were be designed and prepared.Porous SnO2@C/graphene with three-dimensional carbon conductive network was prepared by combining hydrothermal carbonization and hydrothermal self-assembly. It is found that the particle size of SnO2 nanoparticles in the nanocomposite is less than 6 nm, and the SnO2 nanoparticles distribute in the 3D carbon conductive network homogeneously. The Brunauer-Emmett-Teller (BET) surface area of the material is 196.4 m2 g-1, and the total pore volume is 0.15 cm3 g-1. The first reversible specific capacity of the as-prepared nanocomposite is as high as 1115 mAh g-1 at the current density of 100 mA g-1. Even at a high current density of 1000 mA g-1, the reversible specific capacity remains 50%of reversible specific capacity at the current density of 100 mA g-1. After 50 cycles, the reversible capacity is still kept above 1000 mAh g-1 at the current density of 100 mA g-1.The above method was applied to prepare porous Sn@C/graphene with three-dimensional carbon conductive network. It is found that the particle size of Sn nanoparticles in the nanocomposite is less than 10 nm, and the Sn nanoparticles distribute in the 3D carbon conductive network homogeneously. The Brunauer-Emmett-Teller (BET) surface area of the material is 598.1 m2 g-1, and the total pore volume is 0.38 cm3 g-1. The first reversible specific capacity of the as-prepared nanocomposite is as high as 928 mAh g-1 at a current density of 100 mA g-1. After 50 cycles, the reversible capacity is still kept at 602 mAh g-1 at the current density of 100 mA g-1.(2) For the supercapacitor system, Bi2O2CO3 nanosheets were prepared which show an excellent supercapacitance behavior.Bi2O2CO3 nanosheets were synthesized via a gas/liquid interface reaction firstly. The Bi2O2CO3 nanosheets are very thin, which is close to transparent. The specific capacitance calculated from the discharge curve at the specific current of 1 A g-1 is as high as 1045.3 F g-1. The decay of the specific capacitance is well below 6%in after 250 cycles at the specific current of 20 A g-1. Above all, we found that OH" can reversibly intercalate into and deintercalate from layered Bi2O2CO3 with valence conversions of bismuth and without obvious crystal structure variation during charge and discharge process, which made the Bi2O2CO3 possess high specific capacitance, good rate capability and cycling stability. It’s very possible that the other layered subcarbonate may also be applied as the electrode material for supercapacitors with a similar intercalation mechanism.