Covalent grafting interface engineering to prepare highly efficient and stable polypropylene/mesoporous SiO2 separator for Li-ion batteries

Abstract Due to the deficiency of low melting point and poor wettability of commercial polyolefin separators, the design and development of ceramic coating separators have been received more and more attention in Li-ion batteries recently. However, it is challenging to solve the disadvantageous exfoliation issue of ceramic coating during charge/discharge cycles and needs to be addressed urgently. Herein, a covalent grafting interface engineering strategy has been proposed to prepare a highly efficient and stable polypropylene/mSiO2 separator (PP-g-mSiO2) by the nanoscale mSiO2 layer anchoring on the surface of PP separator with covalent bonding. As expected, the covalent bonding force increase the interfacial stability of PP-g-mSiO2 separator and the mSiO2 NPs facilitate more storage of electrolyte, which results in high thermal stability, high electrolyte affinity and swift lithium-ion diffusion. When used as the separator in LIBs, the Li/LiFePO4 cell with PP-g-mSiO2 separator exhibits excellent rate capability with a discharge capacity of 101 mA h/g at 5 C and remains high capacity retention of 93% after 1000 continuous charge–discharge cycles, which suggests that the PP-g-mSiO2 separator possesses a stable and covalent grafting ceramic surface and have greater affinity to electrolyte, resulting in quicker lithium-ion diffusion and excellent cycling stability. Therefore, the covalent grafting interface modification has confirmed an effective strategy to block exfoliation issues of ceramic coating and developed the high-performance ceramic separators for LIBs.