Enhancement of Thermal Stability and Cycling Performance of Lithium-Ion Battery at High Temperature by Nano-ppy/OMMT-Coated Separator

Nanopolypyrrole/organic montmorillonite- (nano-ppy/OMMT-) coated separator is prepared by coating nano-ppy/OMMT on the surface of polyethylene (PE). Nano-ppy/OMMT-coated separator with three-dimensional and multilayered network structure is beneficial to absorb more organic electrolyte, enhancing the ionic conductivity (reach 4.31 ). Meanwhile, the composite separator exhibits excellent thermal stability and mechanical properties. The strong covalent bonds (Si-F) are formed by the nucleophilic substitution reaction between F− from the thermal decomposition and hydrolysis of LiPF6 and the covalent bonds (Si-O) of nano-ppy/OMMT. The Si-F can effectively prevent the formation of HF, POF3, and LiF, resulting in the inhibition of the disproportionation of Mn3+ in LiNi1/3Co1/3Mn1/3O2 material as well as reducing the internal resistance of the cell. Therefore, the nano-ppy/OMMT-coated separator exhibits outstanding capacity retention and cycling performance at 80°C.