A Nonflammable and Thermally Stable Polyethylene/Glass Fiber−Magnesium Hydroxide/Polyethylene Composite Separator with High Mechanical Strength and Electrolyte Retention to Enhance the Performance of Lithium‐Ion Batteries

To overcome the shortcomings in the thermal stability and electrolyte wettability when a commercial polyethylene (PE) separator is used alone, a PE/glass fiber (GF)−Mg(OH) 2 /PE composite (PGMP) separator is developed, and the electrochemical and safety performance of lithium‐ion batteries is effectively enhanced. The PGMP separator is prepared by soaking a mixed dispersion solution of polyacrylate and Mg(OH) 2 into the GF fabric substrate and subsequently bonding the PE microporous film on both substrate sides. Compared with the PE separator, PGMP separator exhibits enhanced mechanical strength (≥250 MPa), ionic conductivity, and electrolyte wettability. Furthermore, there is almost no shrinkage when this PGMP is annealed at 350 °C for 30 min. The nail penetration, impact, overcharge, and adiabatic rate calorimeter tests of LiNi 0.5 Co 0.2 Mn 0.3 O 2 /graphite pouch cell with a nominal capacity of 2500 mAh show that the PGMP separator effectively improves the safety performance. The thermal runaway temperature of the pouch cells is increased from about 120 to 146 °C, and the electrolyte wettability ability of the PGMP separator gives the cell a capacity retention of 85% after 500 cycles at 1.0 C. Combined with the advantages, it is indicated that this PGMP separator has great potential in commercial applications.