Grafted MXenes Based Electrolytes for 5V‐Class Solid‐State Batteries

Abstract Polymer blends based solid polymer electrolytes (SPEs), combining the advantages of multiple polymers, are promising for the utilization of 5 V‐class cathodes (e.g., LiCoMnO₄ (LCMO)) with enhanced safety. However, severe macro‐phase separation with defects and voids in polymer blends restrict the electrochemical stability and ionic migration of SPEs. Herein, inorganic compatibilizer polyacrylonitrile grafted MXene (MXene‐g‐PAN) is exploited to improve the miscibility of the poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVHF)/PAN blends and suppress the consolidation of phase particles. The resulting SPE exhibits a high anodic stability with an ionic conductivity of 2.17 × 10⁻⁴ S cm⁻¹, enabling a stable and reversible Li platting/stripping (over 2500 h). The fabricated solid Li‖LCMO cell delivers a 5.1 V discharge voltage with a decent capacity (131 mAh g⁻¹) and cycling performance. Subsequently, the solid all‐in‐one graphite‖LCMO battery is also constructed to extend the application of MXene based SPEs in flexible batteries. Benefiting from the interface‐less design, outstanding mechanical flexibility and stability is achieved in the battery, which can endure various deformations with a low‐capacity loss (< ≈10%). This study signifies a significant development on solid flexible lithium ion batteries with enhanced performance, stability, and reliability by investigating the miscibility of polymer blends, benefiting for the design of high‐performance SPEs.