Design of compressible flame retardant grafted porous organic polymer based separator with high fire safety and good electrochemical properties

Melamine-based porous organic polymer (POP) is a three-dimensional organic porous material with good thermal stability, large specific surface area, abundant polar groups and low crystallinity. Here, melamine-based POP and flame retardant grafted melamine-based POP (P-POP) is prepared. Compressible POP and P-POP based lithium battery separators with high fire safety and good electrochemical properties are reported first. The compressibility, cycle, rate, size stability and fire safety performances of samples are investigated. The mechanism for good electrochemical property and high fire performance of P-POP based separator is proved. The thick P-POP/polyolefin composite separator with more flame retardant forms a good intumescent protective char between anode and cathode during fire hazard, resulting in increasing internal resistance and preventing thermal runaway. However, the P-POP/polyolefin composite separator is compressible. P-POP/polyolefin composite separator can be compressed during assembly to guarantee the capacity of lithium ion battery.