A Copolymer Microspheres-Coated Separator to Enhance Thermal Stability of Lithium-sulfur Batteries

Abstract To enhance the thermal stability of lithium-sulfur batteries, separators are coated by ethylene-vinyl acetate copolymer microspheres (EVAs) and the thermal response behavior of ethylene-vinyl acetate copolymer microspheres/polypropylene separator (EVAs/PP) in lithium-sulfur batteries are investigated. The EVAs have a suitable melting point and a fast kinetic rate of thermal reaction. Thermal safety tests show that the prepared EVAs/PP thermal shutdown separators can quickly respond to the temperature change inside the lithium-sulfur battery under overheating conditions (85°C), forming an insulating layer to protect the lithium-sulfur battery from thermal runaway hazards. In addition, EVAs/PP thermal shutdown separators have excellent porosity and electrolyte wettability compared to commercial PP separators. Conventional electrochemical performance tests indicate that EVAs/PP thermal shutdown separators applied in lithium-sulfur batteries exhibit electrochemical performance almost similar to that of PP separators. Due to the simple preparation and low cost, EVAs/PP thermal shutdown separator is expected to be a safe and excellent performance separator for lithium-sulfur battery applications.