A separator modified by spray-dried hollow spherical cerium oxide and its application in lithium sulfur batteries

Abstract

Large-scale application of lithium sulfur batteries (LSBs) has been hindered by certain intrinsic obstacles, particularly the shuttle effect of lithium polysulfides (LiPSs) generated during the redox process. A separator modified with various materials was proposed and demonstrated as an effective method to handle these obstacles. In this study, hollow spherical cerium oxide (CeO₂) fabricated by a practical approach, spray granulation, served as the separator coating material. LSBs with this hollow spherical cerium oxide-coated separator presented excellent electrochemical performances compared with reference samples using a super P-coated separator or a routine separator. This CeO₂ layer can not only block and absorb lithium polysulfides (LiPSs), but also facilitate the transportation of electrons and ions as an upper current collector as well as a catalyst. The initial discharge capacity of this CeO₂-coated separator sample reaches 1004 mA h g⁻¹ at 1C (1675 mA h g⁻¹) and the reversible capacity is maintained at 625 mA h g⁻¹ after 500 cycles, implying an excellent capacity retention. The high rate discharge capacity at 2C is as high as 760 mA h g⁻¹, which demonstrates a promising rate performance. The elemental mappings of scanning electron microscopy (SEM) and transmission electron microscopy (TEM), as well as the testing results of cyclic voltammetry (CV), further confirm the function of this hollow spherical CeO₂-coated separator.