Recently groups have been trying to improve the wetability of the polyer separators by co-dopping the normal polyethylene separator with acrylonitrile.
With regard to inner sleeves, plastic polyethylene is purported to be better than the common paper sleeve and less bulky than the poly-lined paper variety.
The disk can be covered with a thin diffusion limiting membrane (e.g. low-density polyethylene, polyethersulphone) depending on the application the device is being used for.
