Bio-mimicking organic-inorganic hybrid ladder-like polysilsesquioxanes as a surface modifier for polyethylene separator in lithium-ion batteries

The ladder-like polysilsesquioxanes containing both the bio-mimicking adhesive polycatechol and polyethylene oxide (CA-PEO-LPSQ) were synthesized as an organic-inorganic hybrid material and applied as a surface modifier for the preparation of a compatible polyethylene (PE) separator in high performing lithium ion batteries (LIBs). The dip-coating of CA-PEO-LPSQ onto PE (PE-M) separator was optimized at different alkaline pH values. The PE-M separator contained an inorganic ladder-like polysilsesquioxane-based backbone chain with organic moieties PEO and catechol acting as functional groups for enhancing the surface wettability, lithium ion conductivity, and thermal and electrochemical stability. The LIBs fabricated using PE-M as the separator, LiCoO2 as the cathode, and Li metal foil as the anode showed excellent capacity retention of 96% and 82% after the first cycle and 300th cycle at 0.5C rate, respectively, when compared to bare a PE separator exhibiting 95% and 15%, respectively.