The surface modification of electrode materials using gel polymer electrolytes for anode-free lithium metal batteries (AFLMB)

Low cycling performance of the anode-free lithium-metal battery is exacerbated by the low ionic conductivity and thermal instability. Surface modification by gel polymer electrolytes (GPE) with conductive fillers offers the advantages like high ionic conductivity, thermodynamical stability, and electrode materials to use an anode-free lithium metal battery (AFLMB). Herein, we employ an approach by using gel polymer electrolyte sandwiched on both the anode and cathode surfaces. The gel polymer electrolyte, fabricated by ionic-liquid-polymer gelation, is composed of 1-ethyl-3-methylimidazolium bis(trifluoromethyl sulfonyl)imide as ionic liquid and poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) as a host polymer. Li1.5Al0.33Sc0.17Ge1.5(PO4)3 (LASGP) serves as a ceramic filler. The GPE with the LASGP ceramic filler (F) delivers enhanced ion conductivity of 5.22 mS/cm with electrochemical stability up to 5.31 V versus Li+/Li at 25 °C and 50 °C, respectively. Both anode and cathode surface modifications allow lithium plating on copper with a high coulombic Coulombic efficiency of 98.24% and reversible capacity retention of 42.82% after the 65th cycle at 0.2 mA/cm2 and 50 °C without dendrites. Hence, this ceramic filler combined with GPE based on ionic liquids can facilitate the practical use of gel electrolytes in AFLMB.