TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Components: The cathode comprises current collector, and cathodic active material layer on current collector capable of absorbing and discharging lithium ions. The electrolyte comprises lithium salts in organic solvent.    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The polyolefin copolymer is ethylene- alpha -olefin copolymer having melting peak of less than or equal to 130.0 (preferably 122.0-126.0) degrees C, weight average molecular weight of 9.0x 105 (preferably 1.0x 104-1.0x 105), molecular weight distribution of less than or equal to 10.0 (preferably 2.5-4.5), and comonomer content of 1.0-5.0 mol%; or copolymer of ethylene and second alpha -olefin. The membrane further comprises second polyethylene having melting peak of 131.0 degrees C and weight average molecular weight of 1.0x 105-9.0x 105 or less than or equal to 1.0x 106, and third polyethylene having weight average molecular weight of 1.0x 106. The membrane's shutdown activation energy is 3.60x 103-5.50x 103 J/mol. The polyolefin copolymer has melting peak of 122.0-126.0 degrees C. The second alpha -olefin comprises propylene, butene-1, pentene-1, hexene-1,4-methylpentene-1, octene-1, vinyl acetate, methyl methacrylate, styrene and/or other comonomer. The first, second and third polyolefins are polyethylenes. Preferred Method: The copolymer is produced by process using single site catalyst. The method further comprises stretching membrane in planar direction(s) following third step; subjecting membrane to thermal treatment following third step; and cooling extrudate before second step. The stretching step is conducted biaxially to magnification factor of 9-fold to 49-fold in area, while exposing extrudate to temperature of less than or equal to 10 degrees C. Any remaining volatile species are removed from membrane after third step. Preferred Composition: The membrane comprises 8.0-13.0 wt.% polyolefin copolymer. The polyolefin copolymer is present in amount of 1.0-20.0 wt.% in polymer-diluent mixture. The second polyethylene is present in amount of 25.0-99.0 wt.%; and the third polyethylene is present in amount of 0-74.0 wt.%. EXAMPLE - No suitable example given.