Effect of phase inversion on microporous structure development of Al2O3/poly(vinylidene fluoride-hexafluoropropylene)-based ceramic composite separators for lithium-ion batteries

To improve the thermal shrinkage of the separators that are essential to securing the electrical isolation between electrodes in lithium-ion batteries, we develop a new separator based on a ceramic composite membrane. Introduction of microporous, ceramic coating layers onto both sides of a polyethylene (PE) separator allows such a progress. The ceramic coating layers consist of nano-sized alumina (Al2O3) powders and polymeric binders (PVdF-HFP). The microporous structure of the ceramic coating layers is observed to be crucial to governing the thermal shrinkage as well as the ionic transport of the ceramic composite separators. This microporous structure is determined by controlling the phase inversion, more specifically, nonsolvent (water) contents in the coating solutions. To provide a theoretical basis for this approach, a pre-investigation on the phase diagram for a ternary mixture comprising PVdF-HFP, acetone, and water is conducted. On the basis of this observation, the effect of phase inversion on the morphology and air permeability (i.e. Gurley value) of ceramic coating layers is systematically discussed. In addition, to explore the application of ceramic composite separators to lithium-ion batteries, the influence of the structural change in the coating layers on the thermal shrinkage and electrochemical performance of the separators is quantitatively identified.

[1]  K. Abraham,et al.  Polymer Electrolytes Reinforced by Celgard® Membranes , 1995 .

[2]  Z. Jia,et al.  Polyvinylidene fluoride membrane by novel electrospinning system for separator of Li-ion batteries , 2009 .

[3]  Soon Ho Chang,et al.  Characteristics of PVdF-HFP/TiO2 composite membrane electrolytes prepared by phase inversion and conventional casting methods , 2006 .

[4]  Takashi Nishimura,et al.  A powder particle size effect on ceramic powder based separator for lithium rechargeable battery , 2005 .

[5]  Kew-Ho Lee,et al.  Preparation of asymmetric polyacrylonitrile membrane with small pore size by phase inversion and post-treatment process , 2002 .

[6]  K. Abraham,et al.  Highly Conductive PEO-like Polymer Electrolytes , 1997 .

[7]  Hu Jian,et al.  Wet-laid non-woven fabric for separator of lithium-ion battery , 2009 .

[8]  Kang Xu,et al.  An inorganic composite membrane as the separator of Li-ion batteries , 2005 .

[9]  Marcel Mulder,et al.  Basic Principles of Membrane Technology , 1991 .

[10]  Shengbo Zhang.  A review on the separators of liquid electrolyte Li-ion batteries , 2007 .

[11]  Volker Hennige,et al.  Ceramic but flexible: new ceramic membrane foils for fuel cells and batteries , 2002 .

[12]  Kang Li,et al.  Isothermal phase diagrams and phase-inversion behavior of poly(vinylidene fluoride)/solvents/additives/water systems , 2003 .

[13]  Li Wang,et al.  Rapid communicationPreparation of P(AN–MMA) microporous membrane for Li-ion batteries by phase inversion , 2006 .

[14]  Kee Suk Nahm,et al.  Poly(vinylidene fluoride-hexafluoropropylene)-based membranes for lithium batteries , 2008 .

[15]  K. Abraham,et al.  Studies of some poly(vinylidene fluoride) electrolytes , 1997 .

[16]  Tatsuo Nakamura,et al.  Battery performances and thermal stability of polyacrylonitrile nano-fiber-based nonwoven separators for Li-ion battery , 2008 .