Polyethylene oxide (PEO)-based electrolytes have obvious merits such as strong ability to dissolve salts (e.g.,LiTFSI) and high flexibility,but their applications in solid-state batteries is hindered by the low ion conductance and poor mechanical and thermal properties.Herein,poly(m-phenylene isophthalamide) (PMIA) is employed as a multifunctional additive to improve the overall properties of the PEO-based electrolytes.The hydrogen-bond interactions between PMIA and PEO/TFSI-can effectively prevent the PEO crystallization and meanwhile facilitate the LiTFSI dissociation,and thus greatly improve the ionic conductivity (two times that of the pristine electrolyte at room temperature).With the incorporation of the high-strength PMIA with tough amide-benzene backbones,the PMIA/PEO-LiTFSI composite polymer electrolyte (CPE) membranes also show much higher mechanical strength (2.96 MPa),thermostability (419 °C) and interfacial stability against Li dendrites (468 h at 0.10 mA cm-2) than the pristine electrolyte (0.32 MPa,364 °C and short circuit after 246 h).Furthermore,the CPE-based LiFePO4/Li cells exhibit superior cycling stability (137 mAh g-1 with 93％ retention after 100 cycles at 0.5 C) and rate performance (123 mAh g-1 at 1.0 C).This work provides a novel and effective CPE structure design strategy to achieve comprehensively-upgraded electrolytes for promising solid-state battery applications.