Influence of flexible gelatinous coating layer on electrochemical performance and fatigue failure of lithium battery separator

Abstract Recently, the battery security issue receives widespread attention. Investigating the compression performance and failure mode of the battery separator, and then simulating the internal soft short-circuit of the battery due to separator rupture becomes the current focus. In this work, commercial polyethylene separators are coated with a Al2O3 composite organic silicone - acrylic acid gel layer and the electrochemical performance are characterized. The coated battery separator (PEAE-5) exhibits the lowest charge transfer resistance and increases the electrochemical stability window to 5.3 V, since the silicone exhibits oxidation resistance and the acrylic provides flexibility in polar electrolyte solvents. Subsequently, the battery separator is punched in cycles to simulate fatigue failure of the separator under external compression. The results indicate that the separator (PEAE-5) coated with a 5% solid content of organic silicone - acrylic acid emulsion exhibits the best combined physical-mechanical and electrochemical properties, maintaining nearly 80% of the original cycling performance after 50 cycles of compression. The separator coated with the composite organic silicone - acrylic acid gel layer suffers the least from cycle fatigue. The existence of the flexible gelatinous coating layer affords an efficient method to protect the battery separator from destruction.