Resin‐silica composite nanoparticle grafted polyethylene membranes for lithium ion batteries

To avoid the peeling‐off of ceramic nanoparticles (NPs) from polyolefin membranes usually occurred in commercially available ceramic NPs coated polyolefin separators for lithium batteries, we propose a simple one‐pot in‐situ reaction method to modify commercial polyethylene (PE) separators by surface grafting 3‐Aminophenol/formaldehyde (AF)/silica (SiO2) composite NPs. The AF/SiO2 composite NPs form self‐supporting connected pores on the modified layer of the separator surface, which ensures the transportation of Li+. Moreover, the PE@AF/SiO2 separators has higher electrolyte wettability and compatibility than neat PE separators attributed to the plentiful polar functional groups in the AF/SiO2 layer and AF/SiO2 composite NPs, resulting in higher lithium ion transference number (tLi+= 0.62) and ionic conductivity (σ = 0.722 mS cm−1). More importantly, the discharge capacity, capacity retention rate and coulombic efficiency (136.2 mA h g−1, 87.9% and 99%, respectively) after 200 cycles of Li|NMC half batteries with PE@AF/SiO2 separators, are all more excellent than that with the pure PE separator (125 mA h g−1, 83.1% and 85%, respectively). Our results show that the PE@AF/SiO2 separators obtained by this modification method have higher electrochemical stability in the lithium battery system. A simple one‐step in‐situ polymerization method is used to prepare a composite polyethylene separator grafted with AF/SiO2 NPs. The results indicate that the strong Lewis acidity of SiO2 and the abundant polar functional groups in AF/SiO2 weaken the decomposition of the electrolyte, which will further improve the electrochemical stability of the batteries.