Nonwoven support material for improved separators in Li-polymer batteries

In the present paper, a nonwoven material is presented, which improves the mechanical behaviour and safety of current polymer electrolytes/separators in Li-polymer batteries. The nonwoven material thereby acts as a support material of the separating polymer electrolytes. It helps to improve mechanical properties, safety and processibility of the current polymers. The presented nonwoven material consists of fine polyester fibres and has a thickness of below 20 mu m. The mechanical strength values are in the range of 20 N/5 cm with low values of elongation at tension values, which are relevant in battery production. It is electrochemically stable against a Li battery environment and can tolerate temperatures up to 180 degrees C with low values of thermal shrinkage. The wet-laid material is homogeneous regarding pore size distribution. Average pore sizes are in the range of 20-30 mu m. On the other hand, the material's porosity is in the range of 55-65%, which is high enough to be filled with gel electrolytes also of increased viscosity. Due to the labyrinth-like structure of the nonwoven material, pin-holes do not occur. An outlook is given, how such a material could also improve separators for proton exchange membrane (PEM) fuel cells. (c) 2006 Elsevier B.V. All rights reserved.