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With the development of electric vehicles, the traditional polyolefin separators can not meet the increasing requirements of lithium ion batteries with high power density, high energy density, and high safety performance. Herein, a novel water-based binder is synthesized by grafting carboxyl groups onto cellulose diacetate. When the polyethylene (PE) separator is coated by this binder and SiO 2 nanoparticles, the thermal shrinkage of the modified separator is observed to be almost 0% after exposure at 200°C for 30 min. The puncture strength significantly increase from 5.10 MPa (PE separator) to 7.64 MPa. More importantly, the capacity retention of the cells assembled with modified separators after 100 cycles at 0.5 C increase from 73.3% (cells assembled with PE separator) to 81.6%, owing to the excellent electrolyte uptake and the good compatibility with lithium electrode. Besides, the modified separator shows excellent surface stability after 100 cycles. Considering the above excellent properties, this composite separator shows high potential to be used in lithium ion batteries with high power density and safety.

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