Pressed double-layer gel electrolyte enabling suppression of redox mediator crossover in lithium-O2 batteries

초록

The commercial use of Li-O2 batteries is limited by redox mediator (RM) crossover and the resulting cell degradation. To address this challenge, we develop a pressed double-layer polymer gel electrolyte (PDLPE), in which the electrolyte-electrode architecture is integratively engineered to suppress the crossover of a tris(4-(diethylamino)phenyl)amine (TDPA)-based RM. Incorporating h-BN fillers into the poly(vinylidene fluoride-co-hexafluoropropylene) matrix effectively retards the physical transport of TDPA while maintaining Li+ transport, and the pressed double-layer configuration mitigates interfacial resistance. In the H-cell permeability test, PDLPE delayed visible TDPA permeation for 2 days, whereas the commercial separator showed obvious color change within 6 h. The h-BN-free bottom layer facilitates the formation of an enlarged triple-phase interface, whereas the mechanically robust h-BN-containing top layer ensures long-term operational stability. In addition, a redox polymeric catalyst (RPC) with immobilized TDPA was introduced to maintain catalytic activity and suppress mediator dissolution. The PDLPE-based Li-O2cell delivered 55 cycles at 100 mu A cm-2 with a fixed capacity of 200 mu Ah cm-2, corresponding to an approximately 1.7-fold lifetime improvement compared with the conventional liquid-electrolyte cell. Furthermore, the RPC-PDLPE system maintained stable operation at current densities up to 400 mu A cm-2 and achieved 80 cycles under air-breathing conditions, compared with 30 cycles for the RPC-PE cell. Overall, this integrated design secures the stability of RM-based systems even in the presence of moisture and CO2, thereby demonstrating potential applicability of Li-air batteries.

키워드