Controllable Preparation Of Polypyrrole Based Electrodes And Investigation On Planar Micro-supercapacitive Properties

Recently,with the continuous development of technology,the popularity of portable,wearable and implantable intelligent electronic products has greatly promoted the progress of flexible miniaturized power supply.Due to its fast charging/discharging capability,high power output,long cycle life,portable manufacturing and integration,micro-supercapacitors（MSCs）have become one of the popular micro-energy storage devices that have been widely investigated.However,there are still several defects in MSCs that have been reported,such as poor mechanical properties,accumulation of materials,and low energy density.Therefore,the preparation of planar MSCs with good mechanical properties and high performance is still a huge challenge.Polypyrrole（PPy）with highlyπ-conjugated backbones not only has the pseudocapacitance behavior similar to that of metal or semiconductor but also inherits the excellent flexibility and conductivity of traditional polymers.However,it still has the disadvantages of limited area capacitance and poor cyclic stability caused by self-agglomeration and volume expansion of charge and discharge.Based on this,polypyrrole and its composite films with excellent properties were prepared by morphologic adjustment and composite with transition metal sulfides（TMDs）which have good pseudocapacitance and conductivity.Meanwhile,the performance of polypyrrole and its composite films in MSC was investigated as follows:（1）For the first time,the template was loaded on the collector by spraying method,and the porous PPy film was prepared directly on the gold collector by combining electrodeposition and etching template method.PPy with good conductivity and false capacitance is prepared into a three-dimensional hollow network film on the conductive collector,which not only avoids the application of binders,reduces the resistance of the thin film electrode,and the hollow network structure is conducive to the rapid diffusion of ions and also facilitate efficient transmission of electrons.By regulating the electrodeposition time,the growth status of hollow PPy is controlled.Porous PPy has an area capacity increasement of 95%and a 2500 cycles stability increasement of 16.3%compared with the PPy without templates.（2）Preparation of polypyrrole@cobalt sulfide heterostructure hollow spheres（PPy-hs@Co S）by etching template method and reflux condensation process.By adjusting the ratio of polypyrrole hollow spheres（PPy-hs）to cobalt source sulfur source,the coating degree of outer cobalt sulfide（Co S）can be effectively controlled.The coated Co S not only provides capacitive contribution but also inhibits the external volume expansion of polypyrrole during charge and discharge,effectively improving the specific capacitance and stability.Thanks to the high specific capacitance of PPy-hs@Co S（639.8 F/g@1A/g）and the large potential window（1V）of AC,the prepared asymmetric MSCs have an area capacity of 131.9 m F/cm² and a high volumetric energy density（25.6 m Wh/cm³@140.6 m W/cm³）as well as mechanical and integrated properties at a current density of 0.3 m F/cm².After 5000cycle tests,the MSC capacity can still retain 91.3%.（3）polypyrrole@Bimetallic cobalt tetrasulfide nickel/cobalt sulfide heterostructured hollow spheres（PPy-hs@Ni Co₂S₄/Co S）were prepared based on system two by introducing new Ni ions.Ni ions are introduced to increase capacity as well as magnification performance.The optimal degree of coating is explored by adjusting the ratio of nickel,cobalt,sulfur source and PPy-hs by adding nickel source to the reflux process.The introduction of nickel increased the defect of insufficient capacity of single metals,and the prepared PPy-hs@Ni Co₂S₄/Co S（PPy@NCS/Co S）reached 1487 F/g@1 A/g.The synthetic active material is sprayed to prepare symmetrical MSCs.It has an area capacity of 66.2 m F/cm²@0.3 m F/cm² and retains an initial capacity of 50.2%@2 m F/cm².The MSC can still retain 98.5%of the capacity after 3000 cycle tests.