Research On Preparation And Electrochemical Performance Of New Carbon Materials For Beyond Lithium Battery

Today, with traditional energy reserves of coal, gasoline and natural gas becoming to be decreased and the enhancing of people’s awareness for environmental protection, the research for new electrochemical energy storage become more and more urgent Currently, lithium-sulfur batteries and sodium-ion batteries have become to be a promising electrochemical energy storage. Porous carbon possess a lot of characteristics, such as low price, environment-friendly, high specific surface area and adjustable pore structure, which can be used as an ideal electrode material of lithium-sulfur batteries and sodium-ion battery energy storage system. In this paper, the synthesis of porous carbon and electrochemical properties of lithium-sulfur batteries and sodium-ion batteries with the porous carbon were studied, this dissertation mainly completed the following work:Firstly, we tested and analyzed three composites of sulfur with different morphologies of carbon. The results showed, S/KB exhibited excellent electrochemical properties with a large specific surface area and pore volume. High surface area provides more reactive sites for sulfur, leading to increase the utilization rate of sulfur, reduce the polarization and improve the high-rate capability. Large pore volume can effectively capture the polysulfide species and improve easy passages for ion transport, which promotes the long-term cycling stability.Secondly, we prepared asp halt-based hard carbon by adjusting the mesophase modulation temperature and carbonization temperature and studied the effect on the electrochemical properties of the asphalt-based hard carbon in sodium ion batteries. The results show that the asphalt-based hard carbon by the adjusting mesophase modulation temperature of 220℃ and carbonization temperature of 900℃ can significantly improved the first coulomb efficiency and reversible discharge capacity. Its first coulombic efficiency reached 73%. After 50 cycles, the discharge capacity remained 227mAhg’1, the asphalt-based hard carbon showed a good property of sodium storage.Finally, we tested and analyzed the chemical properties of the pitch-based hard carbon (HC-P) glucose-based hard carbon prepared by hydrothermal method (HC-G) and sucrose-based hard carbon (HC-S) in lithium-ion batteries and sodium-ion batteries. The results showed, the first coulombic efficiency of HC-G and HC-S were 44%and 52%in lithium-ion batteries and were reduced to 31%and 39%in sodium ion batteries. The reason could be owed to their smaller graphite layer spacing which is difficult to insert sodium ion. While the first coulombic efficiency of HC-P increased from 60%to 73%in sodium batteries, and the capacity still maintained 220mAhg-1 after 100 cycles, which is due to the turbostratic graphite layer structure of HC-P. This structure is beneficial to the insertion of sodium ions, while the lithium ion with the smaller size is adsorbed on both surfaces of the graphite layer. So that, HC-P showed a higher first coulombic efficiency in sodium batteries.