Bollore

Frederic Paulais

Philippe Azais

Lucien Tamic

Xavier Rohel

Andre Huitric

The invention relates to a separator film for a device used for storing electrical energy, the film being porous and oriented, and being obtained by stretching in a longitudinal direction and in a direction transverse to the longitudinal direction, the film containing a mixture comprising a polypropylene homopolymer, at least 10% of a copolymer obtained from monomers comprising at least propylene and ethylene, and at least one beta-nucleating agent. According to the invention, the ethylene content of the copolymer is &#x2267;1% but &#x3c;10% and a propylene content of the copolymer is &#x2267;90% for a film thickness of &#x2267;8 microns and &#x2266;30 microns, corresponding to a specified space factor according to the IEC-60674-3-1 standard greater than or equal to 145% and a density of the biaxially stretched film greater than or equal to 0.18 g/cmbut less than or equal to 0.41 g/cm.

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Quimper, France

Frederic Paulais