3D core-shell nanofibers framework and functional ceramic nanoparticles synergistically reinforced composite polymer electrolytes for high-performance all-solid-state lithium metal battery

Satisfactory ionic conductivity, excellent mechanical stability, and high-temperature resistance are the prerequisites for the safe application of solid polymer electrolytes (SPEs) in all-solid-state lithium metal batteries (ASSLMBs). In this study, a novel poly-m-phenyleneisophthalamide (PMIA)-core/poly (ethylene oxide) (PEO)-shell nanofiber membrane and the functional Li6.4La3Zr1.4Ta0.6O12 (LLZTO) ceramic nanoparticle are simultaneously introduced into the PEO-based SPEs to prepare composite polymer electrolytes (CPEs). The core PMIA layer of composite nanofibers can greatly improve the mechanical strength and thermal stability of the CPEs, while the shell PEO layer can provide the 3D continuous transport channels for lithium ions. In addition, the introduction of functional LLZTO nanoparticle not only reduces the crystallinity of PEO, but also promotes the dissociation of lithium salts and releases more Li+ ions through its interaction with the Lewis acid-base of anions, thereby overall improving the transport of lithium ions. Consequently, the optimized CPEs present high ionic conductivity of 1.38×10−4 S/cm at 30°C, significantly improved mechanical strength (8.5 MPa), remarkable thermal stability (without obvious shrinkage at 150°C), and conspicuous Li dendrites blocking ability (> 1800 h). The CPEs also both have good compatibility and cyclic stability with LiFePO4 (> 2000 cycles) and high-voltage LiNi0.8Mn0.1Co0.1O2 (NMC811) (>500 cycles) cathodes. In addition, even at low temperature (40°C), the assembled LiFePO4/CPEs/Li battery still can cycle stably. The novel design can provide an effective way to exploit high-performance solid-state electrolytes.