Separator modified by Y2O3 nanoparticles-Ketjen Black hybrid and its application in lithium-sulfur battery

The shuttle effect of soluble lithium polysulfides (LiPSs) during the charging/discharging processes is one of the most difficult obstacles for the practical application of lithium-sulfur batteries (LSBs). In order to confine the LiPSs in the cathode area, Y2O3 nanoparticles-Ketjen Black (KB) hybrid prepared by wet impregnation followed by freeze drying and heat treatment was used as the main coating material of the separator in LSB. Transmission electron microscope (TEM) images showed that the Y2O3 nanoparticles are approximately 5 nm and distributed uniformly in the KB matrix. The Y2O3-KB hybrid was coated on the surface of the common separator, working as a physical shield to restrain the shuttle phenomenon of LiPSs and an upper current collector to promote the charge transportation. LSB using this modified separator displays an initial discharge capacity of 1054 mAh g(-1) at 1 C (1675 mA g(-1)) and remains 816 mAh g(-1) after 200 cycles. Moreover, the discharge capacity of Y2O3-KB-modified separator sample reaches 846 mAh g(-1) at 2 C in the rate test which suggests an excellent rate capability. Meanwhile, electrochemical impedance spectroscopy (EIS) shows that the Y2O3-KB-modified separator sample owns low charge transfer resistance, indicating a fast electrochemical kinetics, which is also proved by the cyclic voltammogram (CV) results.