Nanoparticle-coated Separators for Lithium-ion Batteries with Advanced Electrochemical Performance

We report a simple, scalable approach to improve the interfacial characteristics and, thereby, the performance of commonly used polyolefin based battery separators. The nanoparticle-coated separators are synthesized by first plasma treating the membrane in oxygen to create surface anchoring groups followed by immersion into a dispersion of positively charged SiO2 nanoparticles. The process leads to nanoparticles electrostatically adsorbed not only onto the exterior of the surface but also inside the pores of the membrane. The thickness and depth of the coatings can be fine-tuned by controlling the f-potential of the nanoparticles. The membranes show improved wetting to common battery electrolytes such as propylenecarbonate. Cells based on the nanoparticle-coated membranes are operable even in a simple mixture of EC/PC. In contrast, an identical cell based on the pristine, untreated membrane fails to be charged even after addition of a surfactant to improve electrolyte wetting. When evaluated in a Li-ion cell using an EC/PC/DEC/VC electrolyte mixture, the nanoparticle-coated separator retains 92% of its charge capacity after 100 cycles compared to 80 and 77% for the plasma only treated and pristine membrane, respectively.This material is based on work supported as part of the Energy Materials Center at Cornell, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001086. This publication is based on work supported in part by Award No. KUS-C1-018-02,made by King Abdullah University of Science and Technology (KAUST). The authors acknowledge financial support from the Ministry of Economic Affairs of the Republic of China and the assistance from the Materials and Chemical Research Laboratories of the Industrial Technology Research Institute. The authors thank Mr Fred Humiston, Celgard LCC for kindly supplying the separator