Advanced Performance of Janus Separators Fabricated from PAF-56-SO₃Li and SFPEEKK-Li with Sulfonic Acid Groups

In this work, sulfonated lithium-rich porous aromatic frameworks (PAF-56-SO3Li) and poly(ether ether ketone ketone) (SFPEEKK-Li) were synthesized, introducing a large number of Li+ ions while retaining the electrostatic repulsion effect of the sulfonic acid group. The carbon material Super P was applied to enhance the redox kinetics. They were solution-compounded and scraped onto a PE separator to produce Janus separator LSP-PAF-56-SO3Li with a coated layer thickness of about 1 μm, which can successfully suppress the “shuttle effect” and ensure the stability of lithium stripping and plating at high current densities. LSP-PAF-56-SO3Li exhibited an impressive Li+ transfer number, reaching a maximum of 0.85, which endowed it with a substantial initial specific capacity of 1153 mA h g–1 at a current rate of 0.5 C. The initial specific capacities reached 1053 and 955 mA h g–1 at 1 and 2 C, respectively, and when returned to 0.2 C, the capacity can still achieve 1198 mA h g–1 with a recovery rate of 97%. This work provided a concept that LSP-PAF-56-SO3Li can restrain the “shuttle effect” and elevate the uniform deposition of Li+, which was of significance in the field of lithium–sulfur battery (LSB) separators.