Lithium-Ion Batteries Assembled with Electrospun Hybrid Polymer Membrane Containing Reactive Silica Nanoparticles

Lithium-ion batteries have been rapidly expanding in portable electronic devices, electric vehicles (EVs) and energy storage systems. In lithium-ion batteries, a separator is a critical component which prevents physical contact of the positive and negative electrodes while permitting free ionic transport within the cell.  Most of the separators currently used in lithium-ion batteries are based on microporous polyolefin membranes.  Although these separators offer excellent mechanical strength and chemical stability, they shrink, soften and even melt at high temperature, which cause short circuiting between electrodes. Furthermore, the large difference in polarity between the non-polar polyolefin separator and the polar organic electrolyte leads to poor wettability. As a result, there is a high resistance when the pores in the separator are not completely filled with liquid electrolyte.  In our previous studies, we synthesized silica nanoparticles with vinyl groups, which permitted the surface reaction with vinyl monomers by radical polymerization [1-3]. With the goal of developing high performance separators with high thermal stability, good transport properties and enhanced wettability for non-aqueous liquid electrolytes, we prepared electrospun hybrid polymer membrane based on polyacrylonitrile (PAN) and reactive SiO₂ nanoparticles. Due to the presence of reactive silica particles, it could be thermally cross-linked, resulting in good thermal stability and improved wettability for liquid electrolyte. Using the cross-linked electrospun hybrid polymer membranes, we assembled lithium-ion cell composed of carbon anode and LiNi_0.6Co_0.2Mn_0.2O₂ cathode. The cycling performances of the cells with cross-linked hybrid polymer membrane were evaluated, and the results were compared to those obtained with a pristine PE separator.

References

1. Y.S.Lee, S.H.Ju, J.H.Kim, S.S.Hwang, J.M.Choi, Y.K.Sun, H.Kim, B.Scrosati, D.W.Kim, Electrochem. Commun., 17, 18, 2012.

2. S.H.Ju, Y.S.Lee, Y.K.Sun, D.W. Kim, J. Mater. Chem. A, 1, 395, 2013.

3. Y.S.Lee, J.H.Lee, J.A.Choi, W.Y.Yoon, D.W.Kim, Adv. Funct. Mater., 23, 1019, 2013.