Electrospun heterocycle aramid nanofiber separator with MOF-supported porous structure enabled excellent cycling stability for lithium metal batteries with high LiFePO4 loading

Recently, para-aramid nanofiber separators have attracted more attention in lithium metal batteries (LMBs); however, the balance between safety and electrochemical performance remains challenging. Herein, a robust, porous, and thermotolerant separator (ZPBIA) is proposed based on electrospun heterocycle aramid nanofibers and in-situ grown metal-organic framework (MOF). First, introducing H2SO4 enables improved electrospinnability of rigid-chain poly(p-phenylene -benzimidazole-terephthalate) (PBIA) due to hierarchical hydrogen bonds crosslinking network formation. Next, zeolitic imidazolate framework-67 (ZIF-67) nanosheets anchored in situ on PBIA nanofibers confer high porosity (91%) and good electrolyte wettability to the ZPBIA separator. As a result, the assembled LFP/ZPBIA/Li cell with a high LiFePO4 (LFP) loading (12 mg cm−2) delivers excellent rate capacity at 5.0 C (76 mAh g−1) and impressive long-term cycling stability at 1.0 C (a minor capacity decay of 0.031% per cycle after 500 cycles). Benefiting from the intrinsic properties of PBIA, the ZPBIA separator possesses high mechanical strength to prevent Li dendrites puncture. Moreover, the open circuit voltage stabilizes at ∼3.4 V from 30 to 150 ℃ for LFP/ZPBIA/Li cell, which is probably applied in high-temperature conditions. This work provides a novel fabrication of functional separators to balance the safety and electrochemical property of LMBs.