The Preparation Of Porous Materials @ Sulfur And MOFs @Sulfur Composites As Well As Their Electrochemical Performance Of The Li-S Batteries

Currently, lithium-sulfur battery has attracted more and more attention due to its high energy density and low cost of sulfur. However, there are still some technical problems, such as the medium products produced in the discharge and charge reactions are soluble in the electrolyte, low sulfur utilization and low coulombic efficiency resulted from the poor conductivity of sulfur element, which has limited the development of lithium-sulfur battery.In our report, an N-doped dopamine sphere PDA-C is chosen as the host materials. The specific surface area of PDA-CS、PDA-CM and PDA-CL is 1723、1878�'� 2105 m2 g-1, and the average pore width is 9.89、12.54 and 22.12 ?, respectively. Moreover, PDA-CS has the highest graphitization degree. And the average sulfur content is 52~59 wt%. The electrochemical performanceresults show that PDA-CS, which has the smallest pore size, has the strongest affinity with sulfur. The initial discharge specific capacity is 1026.4 m A h g-1 of PDA-CS@S cathode, and the capacity remains to 893.5 m A h g-1 after 100 cycles. The capacity retention is 87.1 % and the coulombic efficiency keeps at 96 %.Besides, another material MIL-53(Cr) was also investigated as the sulfur host to produce the MIL-53(Cr)@S composites as the cathode of lithium-sulfur batteries. The XPS results show that Cr-S bond is formed during the discharge process, thus, the dissolve of polysulfur ions in electrolyte is decreased and the sulfur utilization is then improved. The electrochemical performance results show that the initial specific capacity is 597 m A h g-1, and then becomes 465 m A h g-1 and 386 m A h g-1 respectively after 100 and 300 cycles. The coulombic efficiency reaches 98%, which shows a high level among the MOFs cathodes.