Research Of Cobalt-nickel Coordination Polymer Derived Supercapacitor Electrode Materials And Their High Performance Devices

Facing the increasingly energy and climate crisis,the development of renewable and sustainable energy is considered to be an effective strategy to reduce the consumption of fossil fuels.As a kind of efficient and clean energy,electric energy has gradually become the mainstream.The rapid development of some high-performance electronic products has greatly changed our lifestyle and provided us with more convenience.At the same time,they put forward a higher requirement for their power source,the electric energy storage device.As a new type of energy storage device,supercapacitors have received extensive attention around the world in recent years,because of their fast charging speed,high power density and long cycle life.It is well known that the performance of supercapacitors mainly depends on the chemical composition and microstructure of the electrode materials.In addition,the rational design and assembly of high-performance hybrid supercapacitor devices is also an effect way to enhance the enengy density of supercapacitor,which is one of the direction of future development.Here,our goal is to prepare the high theoretical specific capacity species of transition metal phosphates and transition metal sulfide.Using coordination polymer as the precursor,we successfully construct a series of coordination polymer derived transition metal phosphates and transition metal sulfides through calcinating or etching methods.The hybrid supercapacitors are further fabricated by those electrode materials and excellent supercapacitor performances are achieved.The main research content is as follows:1.The fabrication of rose-shaped Co₂P₂O₇/C nanohybrid via coordination polymer and their supercapacitor application:Herein,a rose-shaped cobalt phenylphosphonate coordination polymer[Co(Ph PO₃)]is firstly constructed via the solvothermal method and further used as a precursor to prepare porous Co₂P₂O₇/C nanohybrid through a thermal transformation process in N₂.By controlling the calcination temperature,a series of polyporous rose-shaped Co₂P₂O₇/C-X(X=600,700,800,900 and 1000)are obtained successfully.The prepared Co₂P₂O₇/C-X materials present in-situ hybrid nanostructure and unique polyporous structure,which will provide rich electrochemical active centers and enough migration paths of electron and electrolyte for the fast and deeply faradic reaction.Utilizing as a supercapacitor electrode,the optimized Co₂P₂O₇/C-900 performs a specific capacitance of 349.6 F g^-1at 1 A g^-1and remarkable cycling performances(97.33%retention after 3000 cycles at 2 A g^-1).Moreover,using the porous rose-shaped Co₂P₂O₇/C-900 as a cathode with 3D porous graphene gel(3DPG)as an anode,an asymmetric supercapacitor Co₂P₂O₇/C-900//3DPG is fabricated.The device performs an energy density of 21.9 Wh kg^-1at a power density of 0.375 k W kg^-1and outstanding cycle stability of maintaining 106.25%initial capacity after 10000cycles at 3 A g^-1.2.The fabrication of multi-stage porous phosphate hydroxide microspheres with double anion co-doping for enhanced zinc-based hybrid supercapacitors:Due to the synergistic effect of metal species,bimetallic phosphate materials commonly perform better supercapacitor properties than single metal phosphate.In this work,using bimetallic precursor(Co₄/Ni₆-BTC)as template,a OH^-and PO₄^3-anions co-doped multistage pore phosphate microsphere Co₄/Ni₆(OH)(PO₄)-X was prepared by Na₃PO₄etching process.The ratio of OH^-and PO₄^3-anions can be adjusted by changing the type of etching agent to adjust the PH value.The optimized Co₄/Ni₆(OH)(PO₄)-150 microspheres present a OH^-and PO₄^3-anions ratio of 1:1,which display unique multistage pore structure to increase the active sites of electrochemical reaction and enhance the intercalation/deintercalation of electrolyte solutionforboostingelectrochemicalperformance.Therefore,Co₄/Ni₆(OH)(PO₄)-150 shows a high specific capacity of 1601.4 F g^-1at 1 A g^-1,and excellent cycle stability(3000 cycles,93.5%retention).Moreover,the as-fabricated Co₄/Ni₆(OH)(PO₄)-150//r GO-Zn zinc-based hybrid supercapacitor possess an energy density of 376.5 W h kg^-1at 1.66 k W kg^-1and outstanding cycle stability(92.1%capacitance retention after 3000 cycles).3.Chemically coupled 0D-3D hetero-structure of Co₉S₈-Ni₃S₄hollow spheres for boosted asymmetric and zinc-based hybrid supercapacitors:As one of the most promising supercapacitor electrode materials,transition metal sulfides(TMSs)with unique hollow structural features and multiple functional compositions have attracted tremendous interest in the scientific community.Herein,by rationally design a Ni-LDH@Co-BTC yolk-shelled-structure as a template,we successfully fabricate a chemically coupled 0D-3D hetero-structured of Co₉S₈-Ni₃S₄hollow spheres(Co₉S₈-Ni₃S₄HS)for dramatically boosting supercapacitor performance.During the sulfidation process,the free Co²⁺ions derived from the hydrolysis of Co-BTC core are anchored by S-rich hierarchical Ni₃S₄hollow microsphere shell and further reacted with emerging S^2-ion from the hydrolysis of TAA to form the chemically coupled Co₉S₈and Ni₃S₄based on coordination bonds.The optimized Co₉S₈-Ni₃S₄HS-13 shows prominent supercapacitor performance with a specific capacitance of 1723 F g^-1at 1 A g^-1and excellent cycling stability of maintaining94.7%initial capacitance after 3000 cycles.Meanwhile,the as-fabricated Co₉S₈-Ni₃S₄HS-13//r GO-Zn Zinc-based hybrid supercapacitor presented a high energy density of 381.63 Wh kg^-1at 1.67 k W kg^-1and excellent cycling durability(91.7%capacitance retention after 5000 cycles).Then,through the ex-situ XPS measurements,the energy storage mechanism of the as-fabricated Co₉S₈-Ni₃S₄HS-13//r GO-Zn Zinc-based hybrid supercapacitor is proved to be a novel double ions(Zn(?)and OH^-)intercalation/deintercalation reaction,which is further supported by density functional theory(DFT)calculations.It is also observed that the synthesis strategy is universal and can be extended to other element systems for preparing functional complex chemically coupled 0D-3D hetero-structure with extended applications.