Functionalizing the surface of polyetherimide (PEI)-based cross-linked separator by introducing the polyamide layer through interfacial polymerization and adding boric acid as electrolyte additive for boosted performance in lithium‑oxygen battery

Lithium‑oxygen battery is a very promising energy storage device for its ultrahigh specific capacity. However, due to the undecomposable insulating oxidation species accumulated on the cathode and the safety issues caused by dendrite penetration, the cycling performance of lithium‑oxygen battery is seriously restricted. Herein, through interfacial polymerization (IP) method, a polyetherimide (PEI)-based separator with dense polyamide thin layer was prepared. And the PEI-based separator is cross-linked with Polyethylene polyamines (PEPA) and undergoes 1,3,5-benzenetricarbonyl chloride (TMC) amidation. According to the SEM result, the obtained polyamide layer is well cross-linked with the PEI-based separator and at the same time it owns a dense micro-pore structure, which ensures a battery structure stability and a good electrochemical performance of the separator. Moreover, the increased IP layer amidated by TMC can not only greatly increase the ionic conductivity of the polyamide/polyetherimide (P/PEI) cross-linked separator to 1.0 mS cm−1, but also significantly decrease the interfacial impedance between the PEI and the electrode. With all these merits, the battery assembled with the representative P/PEI2 separator shows boosted cycling performance of over 90 cycles at a capacity of 1000 mAhg−1. Besides, the electrophilic boric acid was introduced to reduce the interaction between anions and cations, resulting in effectively promoted transport efficiency of lithium ions and the cycling life of the battery can be even prolonged to 108 cycles at a capacity of 1000 mAhg−1.