Preparation Of Carbide-Derived Carbon-Based Composite Electrode Materials And Their Performance In Supercapacitors

As a common electrode material for supercapacitors,carbon materials often have the advantages of high rate performance and stable cycling charge and discharge.As one of the many carbon materials,derived carbon not only has many advantages of carbon materials,but also shows the characteristics of low production cost,large specific surface area and adjustable pore size.However,many factors such as its low specific capacitance and the need to use highly toxic substances in the preparation process have restricted the further development of derived carbon in practical applications.Therefore,how to optimize the preparation process and how to improve the electrochemical performance of the derived carbon has become the focus of current research.In this paper,a safe and green etching method was used to successfully prepare carbide-derived carbon（CDC）with a hierarchical porous structure.CDC was used as the research substrate,and the composite modification with TiO₂,MnO₂ and Fe₃O₄,the three transition metal oxides.Relying on electric double layer capacitance of the CDC and pseudocapacitance of the transition metal oxide have excellent synergy,effectively improve the electrochemical performance of composite materials as electrode materials.The feasibility of its practical application is further verified by assembling the corresponding high-performance supercapacitor,which provides an important reference for expanding the application of CDC-based composites in energy storage devices.Using the SiOC obtained by pyrolysis of commercial silicone resin as a carbon source,the CDC with large specific surface area and diverse pore structure was prepared by etching reaction with NaOH at high temperature.Then the TiO₂/CDC composites were prepared by a one-step hydrothermal method.Many TiO₂microspheres are scattered and grown on the surface of CDC.When the current density is 1 A g^-1,the composite exhibits a maximum specific capacitance of 173.2 F g^-1,which is higher than 106.8 F g^-1 of CDC,and only 18%of the capacitance decay after 2000cycles.This result successfully verified the feasibility of the experimental strategy of improving the electrochemical performance of CDC by compounding transition metal oxides on the surface.By adjusting the mass ratio of KMnO₄ to CDC in the reaction solution,a series of MnO₂/CDC composites were obtained by hydrothermal synthesis.Due to the spontaneous reaction between KMnO₄ and CDC,many MnO₂ nanoneedles grow on the surface of CDC.When the mass ratio of KMnO₄ to CDC is 1:6,the distribution of MnO₂ nanoneedles on the surface of the composite is the most uniform and exhibits excellent electrochemical performance.The composite can exhibit a specific capacitance of 255.8 F g^-1 at 1 A g^-1,and it can still maintain the initial specific capacitance of 85.5%after 2000 cycles.With this composite material as the positive and negative electrode,a coin symmetrical supercapacitor was successfully prepared,and the energy density can reach 20.1 Wh kg^-1 at the power density of 400.1W kg^-1.By increasing the proportion of NaOH in the etching process,a CDC with a larger specific surface area was obtained.Then the Fe₃O₄/CDC composite was successfully prepared by a chemical precipitation method,and a large number of Fe₃O₄ nanoparticles with a size of only 15×10 nm grew tightly on CDC.In order to explore the compatibility between electrode materials and electrolytes,three-electrode electrochemical tests were performed on Fe₃O₄/CDC composite in 1 M Na₂SO₄ neutral electrolyte and 1 M KOH alkaline electrolyte.The results showed that the composite could show the maximum specific capacitance in KOH electrolyte.However,the composite in Na₂SO₄ electrolyte has excellent rate performance and cycle stability,which is closer to the actual use requirements.The Fe₃O₄/CDC composite material and Na₂SO₄ electrolyte were used to assemble a symmetrical supercapacitor.The device also showed excellent cycle stability,and produced only 7.7%of capacitance loss after4000 cycles.