Precast solid electrolyte interface film on Li metal anode toward longer cycling life

In this paper, a precast solid electrolyte interface (SEI) film strategy was explored for Li metal anode with longer cycling life. At the current density of 0.5 mA cm⁻² for 0.5 mAh cm⁻² of Li, electrochemical performance tests showed that the half cell with optimized precast SEI film had a coulombic efficiency of more than 99.0% after 620 cycles. Cyclic voltammetry, electrochemical impedance spectrum, mechanical properties, ionic conductivity, scanning electron microscopy, infrared spectroscopy, thermogravimetry, etc., were used to analyze the performance of SEI film. The results showed that when 0.04 mol of lithium bis(oxalato)borate was added into 7.0 g of the poly(vinylidene fluoride-co-hexafluoropropylene) matrix as the components of SEI film, the half cell with the precast SEI film showed the best cycling performance. When different kinds of lithium salts were added into the matrix, the morphology and property after curing were different, which affected the tensile strength, elongation, ionic conductivity, electrolyte absorption rate, and thermal decomposition temperature. Moreover, it had also been found that the strength and ionic conductivity were the main factors in determining the performance of the precast SEI film. [Figure not available: see fulltext.].