Single-ion conductors functionalized graphene oxide enabling solid polymer electrolytes with uniform Li-ion transport toward stable and dendrite-free lithium metal batteries

The utilization of poly(ethylene oxide) (PEO)-based solid polymer electrolytes (SPEs) has long been deemed promising for the application of state-of-the-art lithium metal metals (LMBs), but still severely impeded by the insufficient Li-ion transporting channels and inhomogeneous Li deposition. Herein, the design of single-ion conductors (PSLi) modified graphene oxide nanosheets (GO-PSLi)-reinforced PEO-based SPEs to address these long-standing issues is proposed. The electronegative sulfonate-rich groups with lithiophilic features on GO-PSLi surface not only effectively enhance the dispersion of nanoparticles within the PEO matrix, but also provide fast Li-ion diffusion pathways. Meanwhile, introducing PSLi chains is also favorable to highly reducing the crystallization of composite SPEs through hydrogen interactions derived from the desired amide functional groups. This, in turn, facilitates segmental relaxation of the PEO backbone, leading to accelerates the Li-ion migration. As a proof of concept, the as-prepared composite SPEs demonstrate a good ionic conductivity of 2.2 × 10−4 S cm−1 and a high lithium transference number of 0.53, significantly outperforming the pure PEO SPEs (1.0 × 10−4 S cm−1 and 0.28, respectively) at 60 °C. In addition, the symmetrical Li||Li cells based on the composite SPEs show excellent reversible lithium plating/stripping performances with dendrite-free uniform lithium deposition over 1100 h under a current of 0.1 mA cm−2 at 60 °C. The Li||LiFePO4 batteries also achieve an impressive capacity of 120.2 mAh g−1 at a high current density of 4C and deliver remarkable cycling abilities with 84.6% retention after 250 cycles under 1C at 60 °C. This study offers a facile and practical strategy to develop advanced composite PEO-based SPEs for safe and dendrite-free solid-state LMBs.