In situ interfacial polymerization of lithiophilic COF@PP and POP@PP separators with lower shuttle effect and higher ion transport for high-performance Li–S batteries

Lithium–sulfur batteries have been considered one of the most promising energy storage devices because of their high energy density (2600 W·h·kg−1), low cost, and the environmental friendliness of sulfur. However, the shuttle effect caused by the soluble polysulfide produced by the sulfur cathode in the redox process seriously affects the commercialization of the battery. To solve such problems, we designed and synthesized a lightweight covalent organic framework (COF)–based TpPa–SO3H@PP separator through in situ interfacial polymerization. Benefiting from the lithiophilic –SO3H groups, which are arranged in the nanochannels of the TpPa–SO3H COF, the TpPa–SO3H@PP separator not only suppresses the shuttle of polysulfide but also facilitates Li+ migration. Moreover, the good wettability of the electrolyte to the TpPa–SO3H@PP separator resulted in a lower interfacial resistance and higher ionic conductivity, ensuring a higher energy density. Based on the above advantages, cells with the TpPa–SO3H@PP separator showed an initial specific capacity of 863.97 mAh g−1 at 1C, and a capacity of 645.62 mAh g−1 after 500 cycles, and the average capacity decay rate of each cycle was only 0.05%, indicating superior cycling performance. Significantly, we extended the in situ interfacial polymerization to the preparation of a lithiophilic amorphous porous organic polymer (POP)–based TpPa–COOH@PP separator, which also has good performance, demonstrating the universality and effectiveness of in situ interfacial polymerization. This work opens a new route to prepare lithiophilic COF@PP and POP@PP separators with a lower shuttle effect and higher ion transport via in situ interfacial polymerization for high–performance Li–S batteries.