Covalent Organic\nFramework/Aluminum Oxide Composite\nNanosheets as a Separator for High-Performance Lithium–Sulfur\nBatteries

Abstract

With\nthe depletion of fossil energy and increasingly serious environmental\npollution, the development of renewable sources of energy is imminent.\nExploration of high-efficiency energy storage and transformation materials\nhas become the focus in the field of energy research. Covalent organic\nframeworks (COFs), as a kind of porous and crystalline polymer, have\nattracted extensive attention. In this work, we developed a composite\nmaterial (Al₂O₃-G-COF_SO₃) using COFs and alumina, which can serve as an efficient separator\nin lithium–sulfur (Li–S) batteries. In the composite,\nalumina can improve the transport ability of Li⁺ and thus\nimprove conductivity and SO₃–COF can effectively\nrestrain the shuttle of polysulfides by electrostatic repulsion. At\na current density of 0.05C, the composite-based battery exhibited\na high capacity of 1404 mAh g^–1, which ranks as\none of the highest values among all of the COF-based Li–S batteries.\nEven at a discharge rate of 1C, it can also achieve a high experimental\ncapacity of 999 mAh g^–1 with a low decay rate of\n0.061% over 500 cycles. Moreover, the battery also showed a high electrochemical\nstability and long-term performance stability.