Design,Assembly And Performances Of Asymmetric Supercapacitors Based On Metal Oxide Nanomaterials

The problem of environment and energy is becoming more and more serious.Supercapacitor has become one of the hotspots of new energy storage devices because of its high energy density,high power density and long cycle life.But in practical applications,the energy density will always be unable to meet the demand with the increase of current.In order to solve this technology bottleneck,asymmetric supercapacitor?ASC?came into being.According to the theoretical calculation formula of energy density,by selecting manganese and vanadium metal oxides as positive and negative electrodes,the potential windows are expanded,and they are combined with carbon materials and conductive polymers to achieve the synergistic coupling of pseudo capacitance and double layer capacitor,so as to improve the specific surface area and conductivity.The specific work is as follows:?1?The hydrothermal method and microemulsion method were used to prepare the nano?-MnO₂ with sea urchin-like morphology and a novel nano?-MnO₂ with the flocculus morphology.On this basis,the well dispersed graphene/CNT/MnO₂ hybrids were prepared by the high energy ball milling.The performance of?-MnO₂ after wet milling for two hours,adding 7%PEG4000 as dispersing agent and material mass ratio of 8:1:1 was better,which the specific capacitance was 206 F/g at the scanning speed was 2 mV/s.The synergistic effect of three-phase composite was proved by the improved of conductivity,and the specific surface area was increased to 180%of?-MnO₂.MnO₂/PANI composites were prepared by ultrasonic assisted in situ method.When Potassium Permanganate was adding as oxidant and the mass ratio of?-MnO₂ to aniline was 1:5,polyaniline nanorods were interspersed in the hive?-MnO₂ with the best electrochemical performance.The specific capacitance reached524 F/g at the current density of 0.5 A/g by constant current charge discharge.The microemulsion method was used to synthesized Gr/CNT/MnO₂ composites in situ.The specific capacitance of the composites was 270 F/g at the scanning speed of 2 mV/s.?2?The nano V₂O₅ with different morphologies was prepared by hydrothermal method combined with calcining,NH₄VO₃ as mother salt,ethanol and oxalic acid as reducing agent,carbon sphere and glucose as template and the calcination temperature between 350-500?.Six side plate V₂O₅ was prepared by ethanol,lamellar self assembled flower balls was prepared by oxalic acid,and the multi layer square rose structure was prepared by carbon sphere.It was found that glucose can be used as reducing agent as well as a template to form V₂O₅ hollow microspheres.CNT/Gr/V₂O₅ nanomaterials were synthesized in sute by adding graphene and carbon nanotubes in the hydrothermal process.When the glucose content was 1M,the electrochemical performance was the best,which the specific surface area was 382.7m²/g,and the specific capacitance reaches 274 F/g at the 2 mV/s scanning speed.?3?Using MnO₂ hybrids as the positive pole,V₂O₅ hybrids was used as the negative electrode,the membrane was added between two electrode,and the electrolyte was dripped into it.The sandwich structure was wrapped up with the film and assembled into asymmetric supercapacitor devices.Among them,the electrochemical performance of ASC which assembled with 1 M LiCl as the electrolyte,the CNT/Gr/MnO₂ hybrids prepared by microemulsion as the positive electrode,the CNT/Gr/V₂O₅ hybrids prepared by 1 M glucose as the negative electrode,was the best one of these ASC devices,the potential window was-0.6-0.8 V,expanded to 1.4 V,and the specific capacitance reached 326.6 F/g at the scanning speed of 2 mV/s,higher than the positive and negative single electrode.It has a power density of 36.5 Wh/kg and a power density of 1460 W/kg at 1 A/g current density.