The Research On Preparation And Electrochemical Properties Of Cobalt-based Perovskite-type Oxide Composite Electrode Materials

Supercapacitors have become a research hotspot in the field of new energy storage with its high power density,long cycle life and green environmental protection.The most important factor affecting the performance of supercapacitors is the electrode material.The transition metal oxide exhibits strong tantalum capacitance characteristics and high specific capacity.It has become the research focus of tantalum capacitors.A single electrode material cannot meet the high power density of supercapacitors.And the need for high energy density density.However,its poor conductivity,small potential window and poor cycle stability limit its practical application,and it is necessary to improve the electrochemical performance of transition metal oxides by compounding with highly conductive materials.The perovskite-type oxide having the ABO₃ structure is structurally stable,and can produce higher ionic conductivity and electron conductivity as well as surface oxygen exchange kinetics.The conductivity is several orders of magnitude higher than that of the trans-group metal oxide at room temperature(La_0.7Sr_0.3CoO_3-?room temperature conductivity is 10²–10³S cm^-1).Therefore,the preparation of a perovskite-type oxide and a transition metal oxide composite electrode material can effectively improve the insufficiency of the electrode material.Therefore,a novel transition metal oxide and LSC composite electrode material was designed and synthesized based on the perovskiteoxideLa_0.7Sr_0.3CoO_3-??LSC?.Thecomposition,morphologyand electrochemical properties of the composite electrode materials were investigated.And using composite electrode material as cathode material and activated carbon?AC?material as anode material,the electrochemical performance of asymmetric capacitor was assembled and studied.The main findings are as follows:?1?Sr element was doped at the A site of LaCoO₃,and LSC nanofibers with hollowporousstructurewerepreparedbyelectrospinning.Theoptimal electrospinning process parameters were studied.On this basis,a series of LSC/Co₃O₄composite electrode material with different LSC content were prepared by electrospinning,and their microstructure and electrochemical properties were studied.The results show that the optimal content of LSC?20 wt%?/Co₃O₄ composite has a hollow porous structure,which is conducive to the diffusion of electrolyte ions and the transfer of electrons.LSC as a"bridge"of Co₃O₄ nanoparticles forms a good conductive network,and the synergistic mechanism of LSC and Co₃O₄ energy storage,LSC?20 wt%?/Co₃O₄ electrode material has good electrochemical performance.The specific capacitance is 430 Fg^-1 at a current density of 1 A g^-1,while the specific capacitance of a single LSC and Co₃O₄ electrode is only 85 F g^-1 and 240 F g^-1.The capacitance retention rate remained above 95.3%after 5000 cycles at a current density of 1 A g^-1.?2?The LSC@MnO₂ nanorod composite electrode material was prepared by usingLSCnanofibersastheconductive substrate.Themorphologyand electrochemical properties of LSC@MnO₂ composites were studied.The results show that the prepared LSC@MnO₂ nanorods have a core-shell heterostructure with a specific surface area of 159.29 m² g^-1(LSC specific surface area of 26.02 m² g^-1).Such a structure facilitates the transport of electrons and ions and increases the position of the electrochemical reaction site.At a current density of 1 A g^-1,the specific capacitance of the LSC@MnO₂ electrode reaches 570 F g^-1,while the specific capacitance of a single MnO₂ electrode is only 228 F g^-1.When the current density was increased from 0.5 A g^-1 to 10 A g^-1,the electrode capacity retention ratio was61.9%.And it has excellent cycle stability,and the capacitance retention rate remains above 97.2%after 5000 cycles at a current density of 1 A g^-1.?3?The LSC/Co₃O₄ composite material is used as the positive electrode material,the AC for commercial application is the negative electrode material,and the 6 M KOH is the electrolyte.The electrochemical performance of the LSC/Co₃O₄//AC asymmetric capacitor is assembled and studied,the potential window reaches 1.5V.The specific capacitance at a density of 0.5 A g^-1 is 70 F g^-1,and its specific capacitance can reach 46 F g^-1 when the current density is 10 A g^-1.At a current density of 1 A g^-1,the capacitance retention of the capacitor is as high as 86.3%after5000 cycles.The LSC/Co₃O₄//AC asymmetric capacitor exhibits the highest energy density of 21.9 W h kg^-1 at a power density of 358.4 W kg^-1 and 14.37 W h kg^-1at a power density of 7392 W kg^-1.The energy density of W h kg^-1.?4?The LSC@MnO₂ nanorod electrode is used as the positive electrode,the commercial AC is the negative electrode material,and the 6 M KOH is the electrolyte.The electrochemical performance of the LSC@MnO₂//AC asymmetric capacitor is assembled and studied,the potential window can reach 1.5V.The specific capacitance at a current density of 0.5 A g^-1 is 120.3 F g^-1,and when the current density is 10 A g^-1,its specific capacitance can reach 74.7 F g^-1.The asymmetric supercapacitor device displayed a desirable energy density of 37.6 W h kg^-1 at 375 W kg^-1,and still remains at 23.3 W h kg^-1 at a high power density of 7489.3 W kg^-1.After 5000 cycles,the capacitance retention rate is as high as 92.6%.It indicating that the LSC@MnO₂nanorods are an outstanding pseudo-capacitive electrode material,with significant potential for application in high-performance supercapacitors.