Research On Preparation And Energy Storage Performance Of Layered Niobate-based Electrode Materials

Supercapacitors have been widely researched in recent years,and their electrochemical performance is related to their specific surface area and mesoporous structure.Layered compound electrode materials have gradually become the research object for preparing new electrode materials because of their unique structure that is conducive to the construction of huge specific surface areas and pore volumes.Improving electrical conductivity is another important direction to improve the performance of electrode materials.Electrode materials with a perovskite-like structure have the advantage of high conductivity,so they have also become an important direction in the research field of supercapacitor electrode materials.In this thesis,we focused on the preparation of a new layered perovskite-like electrode material with good energy storage performance and its doping modification and composite researches.The main research results are summarized as follows:（1）The layered perovskite-like niobate was synthesized as the active material for supercapacitor through the high-temperature solid-phase reaction and polymerization-complexation,and its microscopic morphology has a large number of mesoporous structures.A series of Na Ca₂Nb₃O₁₀@CF electrode materials were prepared using layered niobate as the active material and carbon felt as the substrate.When the sintering temperature was controlled at 700℃,its specific capacity reached200.8Fg^-1;after 6,000 charge-discharge cycle tests,its capacity retention rate reached 85.5%.In addition,the material has good mechanical flexibility and is expected to become a positive electrode material for flexible wearable energy storage devices in the future.（2）The layered niobate was modified by chromium doping to prepare a series of chromium-doped layered niobates Na_1+2xCa₂Nb_3-xCr_xO₁₀（x=0,0.01,0.025,0.05）.As the doping ratio of chromium was adjusted to 0.025,the specific surface area of??the electrode material was measured to be 30.0m²g^-1.The active material was comfirmed to be Na_1+2xCa₂Nb_3-xCr_xO₁₀@CF by material characterization analysis.When the doping ratio of chromium was 0.025,the prepared electrode material had the optimum electrochemical performance:a high specific capacity of 262.4Fg^-1;and a capacity retention rate of 87.5% after 8,000 charge-discharge cycles,which realized the modification of the Na Ca₂Nb₃O₁₀@CF electrode material.（3）The layered niobate and lanthanum were composite modified to prepare a series of lanthanum based composites Na_1-xCa_2-xNb₃La_xO₁₀@CF（x=0,0.25,0.5,0.75）.When the lanthanum composite ratio was adjusted to 0.5,the prepared electrode material had the optimum electrochemical performance:a high specific capacity of 390.8Fg^-1;and a capacity retention rate of 86.8%after 8,000 charge-discharge cycle tests,which realized the modification of the NaCa₂Nb₃O₁₀@CF electrode material and obtained high specific capacity performance and cycle life.