Solid Polymer Electrolytes Based on Cross-Linked Polybenzoxazine Possessing Poly(ethylene oxide) Segments Enhancing Cycling Performance of Lithium Metal Batteries

Abstract

Solid polymer electrolytes (SPEs) are suitable materials for safety enhancements of high-energy-density lithium metal batteries. Low ionic conductivity and poor interfacial compatibility could be the major issues to be addressed for SPEs. In this work, a cross-linked polybenzoxazine polymer with poly(ethylene oxide) (PEO) segments (CR-PEO-PBz) has been synthesized and used as a polymeric matrix for preparation of SPEs. The cross-linked structure contributes to suppression of PEO crystallization. PEO-PBz is also used as a binder to reduce the interfacial resistance between the electrode and the electrolyte. The features enhance the lithium ion transportation and increase the ionic conductivity of the corresponding SPE (5.32 × 10–¹ mS cm–¹ at 60 °C). CR-PEG-PBz also exhibits the ability to prevent lithium dendrite growth with promotion of uniform lithium deposition. The LiFePO₄/Li coin cells made with the SPEs demonstrate a high initial capacity of 142 mAh g–¹ at 0.2C and 60 °C and a 93% initial capacity after a 100-cycle test. The cells could be operated at 30, 40, and 50 °C, thus proving the capability of the SPE at various temperatures.