Nonhomogeneous In Situ Polymerization of Poly(1,3-dioxolane) Electrolytes for High Stable Polymer Lithium Batteries

Homogeneous in situ polymerization is a green and common method to prepare polymer electrolytes and improve interfacial contact effectively. However, it is difficult to balance high mechanical properties, good interfacial flexible contact, and controlled polymerization processes under different initiator conditions. In this work, a nonhomogeneous in situ polymerization process was proposed to prepare a gradient structural poly(1,3-dioxolane) (PDOL) solid electrolyte. By preloading the aluminum trifluoromethanesulfonate (Al(OTf)3) initiator on the porous skeleton, the polymerization rate is controlled to form a gel–solid–gel rigid–flexible composite structure. This nonhomogeneous design significantly reduces sensitivity to initiator dosage/activity, enabling controllable and easy-to-operate processes. Simultaneously, this gradient structure maintains high ionic conductivity while retaining high mechanical properties characteristic of solid electrolytes and favorable interfacial soft bonding properties typical of gel electrolytes. The prepared NPDOL-3 + 1 electrolyte possesses an electrochemical stabilization window of 5.5 V, an ionic conductivity of 3.29 × 10–4 S·cm–1, and a high lithium-ion migration number of 0.71 with a tensile strength of 175 MPa. The Li/NPDOL/Li cell could be cycled for up to 1000 h at 0.3 mA cm–2 without significant changes, indicating the NPDOL-3 + 1 electrolyte possesses good interfacial stability with the lithium electrode. These features enable the developed electrolyte to be used in LiFePO4 and NCM622 high-voltage batteries while maintaining stable cycle performance and excellent rate performance. This nonhomogeneous polymerization provides a green and practical method for the development of solid polymer electrolytes and solid-state batteries.