Enhanced mechanical strength and improved Li+ transport in PEO-based electrolytes via scalable bicontinuous PMIA porous membrane

The low ionic conductivity and poor mechanical strength of polyethylene oxide (PEO)-based electrolytes severely restrict their practical application. To address this problem, this work designs a scalable, high-strength (24.3 MPa) bicontinuous porous poly (m-phthaloyl-m-phenylenediamine) (PMIA) membrane integrated into PEO/LiTFSI (PL), thus forming a PMIA/PEO/LiTFSI (PPL) composite electrolyte. Compared to the PL electrolyte, the PPL electrolyte reinforced by a bicontinuous porous PMIA membrane exhibits significantly enhanced mechanical strength, reaching 13.4 MPa. In addition, the amide groups on PMIA strongly coordinate with LiTFSI and form hydrogen bonds with PEO, promoting Li salt dissociation and reducing the Li⁺ migration barrier. This creates efficient, fast Li⁺ transport channels at the PMIA/PL interfaces, effectively promoting the uniform Li⁺ deposition and minimizing lithium dendrite formation. The PPL electrolyte achieves high ionic conductivity (1×10⁻⁴ S cm⁻¹ at 30 °C) and Li⁺ transference number (t_Li⁺=0.43). The assembled LiFePO₄/Li battery demonstrates excellent cycling stability, retaining 80% capacity after 2000 cycles at 2 C, while the Li/Li symmetric cell operates stably for over 900 h at 0.3 mA cm⁻². Therefore, the scalable porous PMIA membrane effectively enhances both the mechanical strength and Li⁺ transport in PEO-based electrolytes, offering a viable strategy for their commercial-scale implementation.