| With the development of wearable electronic devices,flexible energy storage devices have gradually attracted extensive attention.Currently,supercapacitors are the research focus in the field of energy storage,due to the higher power density,faster charge and discharge rates,and superior safety compared with traditional energy storage devices(e.g.,Lithium ion battery).All-solid-state supercapacitors based on thin films are one of the most promising research directions in the future because of their characteristics of low quality,physical stability,and good compatibility with wearable electronic devices.In the electrode material studied,cobalt trioxide(Co3O4)has a good first charge/discharge capacity,and the maximum charge and discharge capacities are 1100 and 1700 mAh/g,respectively,which implies it is an important energy storage electrode material.In this work,Co3O4 nanoflowers were synthesized by the hydrothermal method,and the effects of hydrothermal temperatures and pH values on the morphologies and phases of the products were studied.Subsequently,the products were composited with the reduced graphene oxide(rGO)via mechanical blending to obtain Co3O4/rGO composite electrode materials.Finally,based on the composite materials and the gel-like electrolytes(KOH-PAAK),an all-solid supercapacitor was assembled and its electrochemical performance was studied.The following results were obtained:1.CO3O4 nanoflowers with cubic phase and good crystallinity were obtained by hydrothermal method.The effects of hydrothermal temperature and pH value of solution on the morphologies were studied,which showed that the phase and crystallinity almost unchanged within the temperature range of 160-200 °C and pH value of 8.6-9.4.The incomplete nanoflowers with a diameter of about 2 ?m were obtained at pH = 9.0 and temperature of 160 °C.As the temperature increased,the diameters of the nanoflowers gradually became larger and the nanoflowers became more complete.The most complete nanoflowers with a diameter of 10 ?m were obtained at 180 °C.When the temperature is further increased,the nanoflowers start to break again,and the diameter is reduced.At 200 ?,nanoflowers are completely broken into pieces.At 180 ?,the pH value gradually increases from 8.6 to 9.4,similarly,the sizes of nanoflowers increased in the beginning and then decreased until the nanoflower disappeared,and the most complete nanoflower was exhibited at the largest size as the pH is 9.0.2.C03O4 nanoflowers/rGO composite materials were obtained by blending process,which were used as the electrode and KOH-PAAK as the all-solid-state electrolyte to assemble all-solid supercapacitors with sandwich-structured.The cyclic voltammetry(CV)curves are approximately rectangular in the voltage range of 0?1 V and sweep speed of 5 mV/s?2 V/s,exhibiting a fast electrical response rate.At charge-discharge rates of 0.5 A/g?20 A/g,the galvanostatic charge-discharge(GCD)curves are approximately triangular,corresponding to a rapid charge-discharge process;at the same time,a higher specific capacitance is calculated based on the GCD curve(?190 F/g),and after 1×104 cycles,90%capacitance still retains,indicatin,its good cycling stability.The electrochemical impedance spectroscopy(EIS)test shows that near-vertical point-line distribution is obtained in the low-frequency region,further confirming faster ion diffusion.Meanwhile,the low internal resistance(about 0.55 ?)is calculated at the inflection point of the curve,corresponding to faster Electronic transmission.3.When the device is gradually bent from 0° to 180°,the CV curve remains almost unchanged,maintaining a fast electrochemical response rate,which indicates that the device has good electrochemical stability.Then the device is connected in series,and GCD analysis shows the output voltage also becomes higher correspondingly,with good cycle stability.Finally,the assembled devices can maintain the electronic watch(?5 ?W),LED Lamps(-0.06 W)and electronic scales(-0.1 W)work for 30 min,5 min,and 2 min,respectively. |
PDF Full Text Request