In situ mineralized Ca₃(PO₄)₂ inorganic coating modified polyethylene separator for high-performance lithium-ion batteries

The organic–inorganic composite separator possesses great thermal stability and electrolyte wettability, which is normally prepared via the slurry containing binder. However, this preparation is involved with large amounts of organic solvent that is harmful to health. In this paper, we design a novel method that combines the crosslinking technology and biomimetic mineralization process to prepare a Ca₃(PO₄)₂ inorganic coating modified polyethylene separator (CaP@PE). The obtained composite separator exhibits stronger affinity to electrolyte, and its porous coating structure can store more liquid electrolyte, thus the ionic conductivity is promoted from 0.27 mS cm⁻¹ to 0.52 mS cm⁻¹ and the lithium-ion transference number is increased from 0.26 to 0.36. Compared with PE separator, CaP@PE separator shows better thermal stability at high temperature. Due to the improved ionic transport performance and reduced charge transfer impedance, LiCoO₂/Li half-cell employing CaP@PE separator displays superior cycle stability and capacity retention ability after 150 cycles at a current density of 1C. Even at a high rate of 5C (7.5 mA cm⁻²), the cell with CaP@PE separator still exhibits a discharge capacity of 0.80 mAh. This work provides a promising separator to optimize the electrochemical performance and safety performance in lithium-ion battery.