Effect of Lithium Salt Concentration on Materials Characteristics and Electrochemical Performance of Hybrid Inorganic/Polymer Solid Electrolyte for Solid-State Lithium-Ion Batteries

Lithium-ion batteries are popular energy storage devices due to their high energy density. Solid electrolytes appear to be a potential replacement for flammable liquid electrolytes in lithium batteries. This inorganic/hybrid solid electrolyte is a composite of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt, (poly(vinylidene fluoride-hexafluoro propylene) (PVDF-HFP) polymer and sodium superionic conductor (NASICON)-type Li1+xAlxTi2-x(PO4)(3) (LATP) ceramic powder. The structure, morphology, mechanical behavior, and electrochemical performance of this composite solid electrolyte, based on various amounts of LiTFSI, were investigated. The lithium-ion transfer and conductivity increased as the LiTFSI lithium salt concentration increased. However, the mechanical strength apparently decreased once the percentage of LITFSI was over 60%. The hybrid electrolyte with 60% LiTFSI content showed high ionic conductivity of 2.14 x 10(-4) S cm(-1), a wide electrochemical stability window (3-6 V) and good electrochemical stability. The capacity of the Li|60% LiTFSI/PVDF-HFP/LATP| LiFePO4 solid-state lithium-metal battery was 103.8 mA h g(-1) at 0.1 C, with a high-capacity retention of 98% after 50 cycles.

Automated summary

This study investigates the potential of using a solid electrolyte as a replacement for flammable liquid electrolytes in lithium batteries. The composite solid electrolyte, composed of LiTFSI salt, PVDF-HFP polymer, and LATP ceramic powder, shows increased lithium-ion transfer and conductivity with higher LiTFSI salt concentration. However, the mechanical strength decreases when the percentage of LiTFSI exceeds 60%. The hybrid electrolyte with 60% LiTFSI content exhibits high ionic conductivity, wide electrochemical stability window, and good electrochemical stability.