Preparation And Electrochemical Performance Of Layered Double Hydroxide Composite Materials

Supercapacitor is a unique energy storage device with high power density,short charging time and good cycle stability.The performance of supercapacitors depends largely on the electrode material.At present,electrode materials are mainly concentrated in carbon materials,transition metal compounds and polymers.Among them,layered double hydroxide?LDH?has been widely used in the fields of catalysis,environmental protection,biology and energy due to its unique two-dimensional structure and its many derivatives.Among them,especially in the field of supercapacitors,due to their excellent electrochemical performance and device performance,therefore,layered bimetallic hydroxides show great potential for energy storage applications.Nevertheless,it is difficult for a single material to meet the development requirements of supercapacitors in terms of energy density and cycle stability.Therefore,people have been working to explore nanocomposites with improved or expanded properties.LDH has a high specific capacitance and abundant active sites,while nano-carbon materials have a high specific surface area and good conductivity,which are complementary to a certain extent and play a synergistic role with each other.This paper is based on the above two points to carry out the following work:?1?PPy/GO composites with different mass ratios were prepared by in-situ polymerization.First,the electrochemical properties of PPy/GO composites with different mass ratios are studied.The study found that when the mass ratio of PPy to GO is 98:2,the PPy/GO composite exhibits the best electrochemical performance.Secondly,a layered CoFe-LDH/PPy/GO composite material is successfully prepared by co-precipitation method to electrostatically attract CoFe-LDH on the surface of the best PPy/GO composite material.Various physical and chemical characterization and electrochemical performance tests results show that the best CoFe-LDH/PPy/GO composite electrode material has a high specific capacitance of 1276 F g^-11 at a current density of 1 A g^-1,the retention rate of specific capacitance after 4000 cycles is 85.55%.An all-solid state asymmetric supercapacitor is assembled with CoFe-LDH/PPy/GO composite electrode material,and the results show that the maximum energy density of the all-solid asymmetric supercapacitor CoFe-LDH/PPy/GO//AC device is 25.7 Wh kg^-1,the cycle stability after 10000 cycles is 83.51%,and the LED lamp can be lit,indicating that the CoFe-LDH/PPy/GO composite electrode material has great potential prospects in practical applications.?2?NiCoAl-LDH/N-GO composite electrode material was successfully prepared by two-step hydrothermal method.Various physical and chemical characterization and electrochemical performance tests results show that when the molar ratio of nickel nitrate to cobalt nitrate is 1:2,the NiCo₂Al-LDH/N-GO composite electrode material has the best electrochemical performance.At a current density of 1 A g^-1,the specific capacitance of NiCo₂Al-LDH/N-GO composite electrode material is 1136.67 F g^-1,and the specific capacitance retention of NiCo₂Al-LDH/N-GO composite electrode material after 5000 cycles is 90.10%.Therefore,the prepared NiCo₂Al-LDH/N-GO composite electrode material has good electrochemical performance and cycle performance.The NiCo₂Al-LDH/N-GO composite electrode material is assembled with an all-solid asymmetric supercapacitor.The results show that the maximum energy density of the all-solid asymmetric NiCo₂Al-LDH/N-GO//AC device is 28.53 Wh kg^-1,and the LED lamp can be lit,indicating that the NiCo₂Al-LDH/N-GO electrode material has broad application prospects in the field of supercapacitors.?3?CoNi-LDH/NiCo₂S₄/RGO ternary composite material was successfully prepared by a simple two-step hydrothermal method.CoNi-LDH/NiCo₂S₄/RGO ternary composites are tested for physical and chemical characterization and electrochemical performance by using XRD,SEM,TEMBET,XPS and electrochemistry.The results show that when the current density is 1 A g^-1,the specific capacitance of the CoNi-LDH/NiCo₂S₄/RGO ternary composite material can reach 1846.66 F g^-1,and the specific capacitance retention rate is 93.57%after 5000 cycles.The CoNi-LDH/NiCo₂S₄/RGO composite electrode material is assembled in an all-solid asymmetric supercapacitor.The results show that the all-solid asymmetric supercapacitor CoNi-LDH/NiCo₂S₄/RGO//AC device has high energy density(28.88Wh kg^-1)and good cycle stability?cycle stability after 10000 cycles is 80.52%?,and the LED lamp can be lit,indicating CoNi-LDH/NiCo₂S₄/RGO ternary composite materials have great application prospects.