Preparation And Electrochemical Performances Of Intercalating Composite Electrode Materials

With the development and progress of society, the human desire for new energy sources is becoming more and more. The electrochemical energy storage as an important part of the new energy system, is regarded as alternative to fossil energy system for the sustainable development of energy system. Supercapacitor and lithium ion battery as an important part of electrochemical energy storage system has attracted a great deal of attention in recent years. Electrode material is an important component that affects the performance of supercapacitor and lithium ion battery. We synthesized vanadium oxides intercalated NiAl-LDH, NiCo-LDH and manganese oxides intercalated NiCo-LDH as the precursor of cathode material, and the energy storage properties of the composites has been investigated. The specific studies are as follows:1. We prepared NiAl-LDH by hydrothermal synthesis method. By using NiAl-LDH as a precursor, by adjusting the pH of the solution, we prepared vanadium oxides intercalated NiAl-LDH with different intercalating amount via ion exchange method. We investigated the effects of different molar ratio on the structure and properties. As the Ni:Al mole ratio decreases, vanadium oxides intercalated quantity increases gradually, hydrotalcite layer spacing as bigger.Then investigates that the pH of the reaction solution affects the quantity of intercalation, and found that the higher the pH, intercalating quantity is smaller. The experimental results show that:When the molar ratio of NiAl is 3:1 and pH 4.5, the structure and electrochemical performance are excellent. A specific capacitance of 990 F-g"1 was obtained in 6 M KOH solution at a current density of 1 A-g'1.2. The layer and spherical NiCo-LDH was directly prepared using Co(NO3)2 and Ni(NO3)2 as the raw material and urea as the source of OH" through mild reflux method. The molar ratio of metal nickel and cobalt elements is 4:1 and interlayer anion is carbonate ions. Then we studied the electrochemical properties as super capacitor materials. The experimental results show that a specific capacitance of 1873 F·g-1 was obtained in 6 M KOH solution at a current density of 1 A·g-1, after 1000 cycles the capacitance retention of the NiCo-LDH is up to 81%.3. By using NiCo-LDH as the precursor, swelling overnight, we obtained manganese oxide intercalated NiCo-LDH by ion exchange method. Intercalation of layered double hydroxides then mixed with LiOH and ground, roasted at different temperatures, and obtained LiNi0.7Co0.15Mn0.15O2 cathode materials. We characterized the structure and morphology that synthesised materials. And the electrochemical performances of the composites were investigated by electrochemical workstation and Land and other instruments system. Studies show that the mixed materials were calcined at 450? for 3 h in the first stage, and then calcined at 800? for 12 h at oxygen atmosphere in the second stage. At above situations synthesized the cathode materials LiNi0.7Co0.15Mn0.15O2 showed that the initial discharge capacity was 193 mAh·g-1 in 2.75?4.5V (vs.Li+Li) at 0.1 C rate. And then after 20 cycles the capacity retention rate was 91%.