Electrospun PEO/PVDF blend solid polymer electrolytes with improved electrochemical performances for lithium metal batteries

Solid polymer electrolytes (SPEs) are routinely regarded as potential candidates to replace conventional lithium-ion liquid electrolytes due to their high safety and energy density. Poly(ethylene oxide)/poly(vinylidene fluoride)/lithium bis(trifluoromethanesulfonyl)imide (PVDF/PEO/LiTFSi) SPEs were prepared by a one-step electrospinning process and utilized in lithium metal batteries in this study. The electrospinning process enhanced the compatibility between PEO and PVDF, and induced the alpha to beta-phase crystalline transition of PVDF. Consequently, the continuity of the conductive phase, the solubility and the migration ability of lithium ions within the polymer matrix were improved. Compared to PEO/PVDF/LiTFSi SPE prepared by a solution casting method, the electrospun SPE exhibited superior electrochemical performances at the same composition, achieving a lithium-ion transference number of 0.64 at room temperature and 0.60 at 60 degrees C. The assembled LiFePO4/SPE/Li cell shows a stable capacity of 112 mAh g-1 with a retaining capacity of 105 mAh g-1 after 400 cycles at the current density of 1 C at 60 degrees C, and the Coulombic efficiency is 100%.