Constructing interlayers with micro-nano particles to enhance the fire safety and polysulfide adsorption ability of polypropylene separators for lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) are widely accepted representatives of next-generation energy storage with high energy density. However, the high flammability of polypropylene (PP) separators and ether electrolytes deteriorates the safety of LSBs. Moreover, the severe shuttle effect of lithium polysulfides (LiPSs) induces the capacity degradation and poor cycle stability of LSBs. In this work, we unprecedentedly synthesize multifunctional micro-nano-sized particles (ACNP) that are constructed on PP separators to improve the safety and electrochemical performance of LSBs. The ACNP is obtained by the electrostatic assembly of ammonium polyphosphate and chitosan. The presence of ACNP decreases the burning process and improves the thermal stability of separators and electrolytes. Besides, the temperature of pouch cells during combustion is decreased after the addition of ACNP or ACNP@super-P(SP) interlayers. Moreover, the abundant N-containing and O-containing groups in the ACNP layer effectively inhibit the shuttle effect of LiPSs via chemical adsorption, increase the affinity to electrolytes, and facilitate the Li + diffusion and redox kinetics. The SP enhances the conductivity of the interlayer, thus enhancing the capacity and cycle stability of LSBs. It is expected that this work provides a universal strategy to enhance the safety of separators as well as the batteries. • Multifunctional particles ACNP are synthesized via electrostatic assembly. • The interlayer composed of ACNP chemisorbs LiPSs. • The interlayer enhances the cycle stability of LSBs under high sulfur loading. • The interlayer reduces the flammability of separators and ether electrolytes. • The interlayer reduces the fire hazard of LSBs pouch cells.