Ultrathin and Non-Flammable Dual-Salt Polymer Electrolyte for High-Energy-Density Lithium-Metal Battery

Rechargeable batteries with Li-metal anodes and Ni-rich LiNixMnyCozO2 (x + y + z = 1, NMC) cathodes promise high-energy-density storage solutions. However, commercial carbonate-based electrolytes (CBEs) induce deteriorative interfacial reactions to both Li-metal and NMC, leading to Li dendrite formation and NMC degradation. Moreover, CBEs are thermally unstable and flammable, demonstrating severe safety risks. In this study, an ultrathin and non-flammable dual-salt polymer electrolyte (DSPE) is proposed via lightweight polytetrafluoroethylene scaffold, poly(vinylidene fluoride-co-hexafluoropropylene) polymeric matrix, dual-salt, and adiponitrile/fluoroethylene carbonate functional plasticizers. The as-obtained DSPE exhibits an ultralow thickness of 20 µm, high room temperature ionic conductivity of 0.45 mS cm−1, and a large electrochemical window (4.91 V versus Li/Li+). The dual-salt synergized with functional plasticizers is used to fabricate a stable interface layer on both anode and cathode. In-depth experimental and theoretical analyses have revealed the formation of stable interfaces between the DSPE and the anode/cathodes. As a result, the DSPE effectively prevents Li/DSPE/Li symmetric cell from short-circuiting after 1200 h, indicating effective suppression of Li dendrites. Moreover, the Li/DSPE/NMC cell delivers outstanding cyclic stability at 2 C, maintaining a high capacity of 112 mAh g−1 over 1000 cycles.