Microporous Multilayer Membrane, System And Process For Producing Such Membrane, And The Use Of Such Membrane
OwnerKotaro Takita, Yoichi Matsuda +1inventors
InventorsKotaro Takita, Yoichi Matsuda, Norimitsu Kaimai
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Abstract
The invention relates to a multilayer microporous membrane comprising polyethylene and polypropylene and having an improved balance of properties including improved thickness variation in at least one planar direction. The invention also relates to a system and method for producing such a membrane, the use of such a membrane as a battery separator film, and batteries containing such a membrane.
Claims25
A process for producing a multilayer microporous membrane, comprising the steps of:
- (a) combining a first polyolefin composition and a first diluent to prepare a first mixture, the polyolefin composition comprising at least a first polyethylene having a crystal dispersion temperature (Tcd) and polypropylene;
- (b) combining a second polyolefin composition and a second diluent to prepare a second mixture, the second polyolefin composition comprising at least a first polyethylene having a crystal dispersion temperature (Tcd);
- (b) extruding the first mixture to from a first extrudate and the second mixture to form a second extrudate;
- (c) cooling each extrudate to form a first cooled extrudate and a second cooled extrudate;
- (d) orienting each cooled extrudate in at least a first direction by about one to about ten fold at a temperature of about Tcd+/−15° C.;
- and
- (e) further orienting each cooled extrudate in at least a second direction by about one to about five fold at a temperature about 10° C. to about 40° C. higher than the temperature employed in step (d).
A multi-layer microporous membrane comprising polyethylene and polypropylene and having a thickness fluctuation standard deviation in at least one planar direction of ≦1.0 μm and a melt down temperature≧160° C.
A battery comprising an anode, a cathode, and electrolyte, and at least one separator located between the anode and the cathode, the separator being a multilayer separator comprising polyethylene and polypropylene and having a thickness fluctuation standard deviation in at least one planar direction of ≦1.0 μm and a melt down temperature≧150° C.
Dependencies are inferred from the claim text.