In Situ Fabrication of Poly(aryl ether ketone)-Based Hybrid Polymer Electrolytes for Lithium Metal Batteries

In this study, a hybrid polymer electrolyte based on functional poly(aryl ether ketone) nonwoven fabric (f-PAEKNW-HPE) with a 3D interpenetrating rigid-flexible network was synthesized by heat-initiated in situ polymerization to address the critical challenges such as battery safety, interfacial stability, and ionic conductivity in Li metal batteries (LMBs). The rigid PAEK framework reinforced the mechanical properties of HPE, and the tensile stress reached 12.3 MPa, while the flexible poly(ethylene glycol) dimethacrylate segments and fluorine ion clusters on the side chains facilitated efficient Li-ion transmission. The in situ polymerization ensured excellent interfacial integration between the electrolyte and electrode, contributing to a wide electrochemical window of 4.46 V, a high Li-ion transference number of 0.563, and ionic conductivity of 1.8 × 10–3 S cm–1 under ambient conditions. The flame retardancy and noncombustibility of PAEK significantly enhanced the fire resistance and thermal stability of f-PAEKNW-HPE. Even after physical damage, the battery retained functionality without liquid leakage or thermal runaway. Furthermore, the compatibility of f-PAEKNW-HPE with the Li anode is demonstrated by its stable Li∥Li symmetric cell cycling with a current density of 200 μA cm–2 for 1000 h. When applied to LMBs with a LiFePO4 cathode, the coin cells exhibited excellent cycle stability with a retention capacity of 87.2% (117.2 mAh g–1) after 400 cycles at a rate of 1 C. The SEM and EDX results revealed that no serious lithium dendrites could be observed after cycling. The Li|f-PAEKNW-HPE|NCM811 test cells also exhibited good cycling stability, and the capacity reached 152.3 mAh g–1 after 200 cycles at 0.5 C, retaining over 81.7% of the initial capacity. The fabrication of a multifunctional hybrid polymer electrolyte with high ionic conductivity, excellent fire-retardant performance, and good interfacial stability with electrodes is essential for LMBs. These exceptional characteristics of f-PAEKNW-HPE demonstrate its potential for enabling safe and high-performance LMBs.