Large-scaled covalent triazine framework modified separator as efficient inhibit polysulfide shuttling in Li-S batteries

The shuttling of polysulfides during discharging/charging processes is a major challenge that severely hinders the widespread use of lithium-sulfur batteries (LiSBs). Here, a group of scaled-up covalent triazine frameworks (CTFs) were explored under relatively mild reaction conditions to reduce reaction related interactions. Triazine shows good chemical compatibility with lithium polysulfide though its pyridinic and pyrrolic nitrogen groups, while hierarchical microporous structures interact physically as a blocking layer. Moreover, the dual chemical/physical functional CTFs act as an ionic sieves owing to their two-dimensional microporous structures that selectively sieve desired lithium ions, while effectively inhibiting soluble polysulfides reaching the lithium anode. As a result, the CTFs coated on commercial separator enhance battery performance, through improved active material utilization, high reversible specific capacity (1249 mA h g⁻¹ at 0.5 C), an ideal rate performance of 802 mA h g⁻¹ at 2 C, good cycling stability with a low capacity fade-rate of 0.052% per cycle over 800 cycles at 1 C, good anti-self-discharge behaviour and enhanced protection of the lithium anode.