Application of Polymer Electrolytes Incorporating Cerium Bromide in Lithium-Oxygen Batteries

Li-O₂ batteries have ultra-high theoretical energy density and they are promising to replace commercial Li-ion batteries in the future. Compared with liquid electrolytes, polymer electrolytes have the advantages of non-flammability and higher electrochemical and thermal stability. Polymer electrolytes containing cerium bromide (CeBr₃) additives were prepared, which greatly improved the reliability and stability of Li-O₂ batteries. Poly(vinylidene fluoride-co-hexafluopropylene) (PVDF-HFP) based polymer electrolyte containing CeBr₃ was prepared by solution casting method to improve its stability in Li-O₂ battery. The morphology and composition of the electrode and electrolyte after cycling of Li-O₂ battery were characterized by Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS) and Fourier Transform Infrared Spectroscopy (FT-IR). The electrochemical performance of lithium-oxygen battery was tested by electrochemical workstation and battery test system to study the enhancement effect of CeBr₃ on the stability of polymer electrolyte. The experimental results demonstrate the bifunctional effect of CeBr₃ in PVDF-HFP electrolyte by trapping superoxide radicals and reducing the charging overpotential. The ionic conductivity of the electrolyte at 25 ℃ is 5.87×10⁻⁴ S/cm. At a current density of 500 mA/g and specific capacity of 1000 mA·h/g, the Li-O₂ battery with traditional PVDF-HFP polymer electrolyte drops the voltage below 2 V after 47 cycles, while the Li-O₂ battery with PVDF-HFP-CeBr₃ polymer electrolyte can reach up to 112 cycles.