Construction of Fire-Resistant Solid Polymer Electrolytes for Lithium Safety Batteries Based on Aluminum Phosphate-Coated Sepiolite Core–Shell Nanostructure

Composite polymer electrolyte (CPEs) that combine safety, excellent electrochemical performance, and thermal stability have garnered considerable attention as viable solutions to achieve lithium-ion batteries (LIBs). In this study, we investigated a method to modify polyethylene oxide (PEO)-based polymer electrolytes via the introduction of modified aluminum phosphate coated sepiolite (mSEP@AlPO4). First, aluminum phosphate coated sepiolite (SEP@AlPO4)was synthesized using the heterophase precipitation method with SEP, Al(OH)3, and H3PO4 as raw materials. Subsequently, calcium stearate (CaSt2) was used to modify SEP@AlPO4(mSEP@AlPO4), which was then incorporated as a filler into the PEO/lithium bis(trifluoromethanesulfonyl)imide (PEO/LiTFSI). The results shown that the addition of mSEP@AlPO4 inhibits crystallization in the composite films, improves compatibility, and enhances the flame-retardant properties of the electrolyte films. When the content of mSEP@AlPO4 is 15%, the peak heat release rate of PEO electrolyte is 385.9 W/g, and the flame retardant effect is the best. When the addition of mSEP@AlPO4 is 10%, the ionic conductivity of CPE is 13.25 × 10−5 S/cm, and the ion transference number is 0.86. This indicates that the addition of mSEP@AlPO4 improves the ion migration performance of the composite polymer electrolyte. The use of mSEP@AlPO4 to prepare composite polymer electrolyte provides new insights and methods for the development of LIBs.