“…To address these issues, many efforts have been made to boost the basic electrochemical performance, especially for poly(ethylene oxide) (PEO)-based hybrid solid polymer electrolytes. − Commonly, two types of fillers, active- and inner-inorganic ceramics, could be introduced into the PEO matrix to improve the ionic conductivities by orders of magnifications. − Thanks to recent advances, the ionic conductivities of PEO-based solid electrolytes already reached up to 10 –4 to 10 –5 S/cm. − However, it is still a big challenge to improve the comprehensive performance of the solid composite polymer electrolytes simultaneously, such as high ionic conductivities, wide electrochemical voltage windows, excellent mechanical properties, good interfacial affinity with electrodes, superior heat resistance, and thermal/mechanical stabilities at high temperatures. − Very recently, Hu et al reported that a hydroxyapatite (HAP) nanowire membrane could be employed as a separator, especially for high-temperature lithium-ion battery applications. As is known to all, HAP is the main inorganic component of human or animal bones and teeth. − It is also a renewable biomass material with nontoxic biocompatibility, good mechanical strength, and excellent thermal stability. − What is more, the surface functional groups of HAP would be expected to interact with anions of lithium salts, further increase the concentration of free Li ions, and improve the ionic conductivities.…”