Porous membrane host-derived in-situ polymer electrolytes with double-stabilized electrode interface enable long cycling lithium metal batteries

Abstract

The application of solid polymer electrolytes (SPEs) has been impeded by the low ionic conductivity, narrow oxidation potential and poor mechanical strength. Herein, we designed a novel in-situ PVDF-HFP/Poly 1,3-dioxolane (PDOL) polymer electrolyte with dual-salts and functional plasticizers of succinonitrile (SN)/fluoroethylene carbonate (FEC). One of the dual-salts, Lithium difloro(oxalato)borate (LiDFOB), could initiate the polymerization of DOL in-situ in the porous PVDF-HFP host to improve the interfacial compatibility. SN is beneficial to the improvement of ionic conductivity and the stability of high voltage cathodes, while the FEC can generate the LiF-rich SEI on Li metal anode. The PVDF-HFP host can further restrict the motion of anion and increase the strength of the SPE. Therefore, the as-obtained SPE exhibits a thin thickness of ∼ 32 μm, high ionic conductivity of 1.06 × 10⁻⁴ S cm⁻¹ at room temperature, an enlarged electrochemical window of 5.86 V versus Li/Li⁺ and high lithium-ion transference number t_Li+ of 0.72. Benefited from the synergetic effect, the Li/LiFePO₄ cell delivers a high initial capacity of 141.7 mAh g⁻¹ at 2C with a capacity retention of 94.99% after 1000 cycles. This three-dimensional porous film-derived in-situ polymer electrolytes provide a new sight and simple strategy for designing polymer electrolytes, exhibiting attractive potential in flexible and high-energy–density solid-state batteries.