Multi-layer, microporous membrane, battery separator and battery

1. A multi-layer microporous membrane, comprising:

a first layer material comprising a first polyethylene and a first polypropylene having a weight-average molecular weight of 3.0×10 5 to 1.40×10 6 and a second layer material comprising a second polyethylene and a second polypropylene consisting of a propylene homopolymer, the second polypropylene having a weight-average molecular weight of 0.90×10 6 to 2.69×10 6 and a heat of fusion of 95 J/g or more the fraction of the second polypropylene having a molecular weight of 1.8×10 6 or more being 10% or more by mass of the second polypropylene and the first and second polypropylenes have different weight-average molecular weights.

2. The multi-layer microporous membrane of claim 1 , wherein the multi-layer microporous membrane comprises a first layer containing the first layer material and a second microporous layer containing the second layer material, and at least one of the first layer material or the second layer material is present in a skin layer of the multi-layer microporous membrane.

3. The multi-layer microporous membrane of claim 1 , wherein the multi-layer membrane comprises:

a first microporous layer containing the first layer material, a third microporous layer containing the first layer material, and a second microporous layer containing the second layer material, the second microporous layer being located between the first and third microporous layers.

4. The multi-layer microporous membrane of claim 1 , wherein the multi-layer microporous membrane comprises:

a first microporous layer containing the second layer material, a third microporous layer containing the second layer material, and a second microporous layer containing the first layer material, the second microporous layer being located between the first and third microporous layers.

5. The multi-layer microporous membrane of claim 3 , wherein

the first polyethylene is present in the first layer material in a first polyethylene amount in the range of from about 50 wt. % to about 99 wt. % based on the weight of the first layer material,

the first polypropylene is present in the first layer material in a first polypropylene amount in the range of from about 1 wt. % to about 50 wt. % based on the weight of the first layer material,

the second polyethylene is present in the second layer material in a second polyethylene amount in the range of from about 5 wt. % to about 95 wt. % based on the weight of the second layer material, and

the second polypropylene is present in the second layer material in a second polypropylene amount in the range of from about 5 wt. % to about 95 wt. % based on the weight of the second layer material.

6. The multi-layer microporous membrane of claim 5 , wherein

(a) the first and/or second polyethylene comprises a polyethylene having a weight-average molecular weight ranging from about 1×10 4 to about 5×10 5 , a polyethylene having a weight-average molecular weight of at least about 1×10 6 , or both, wherein

(1) the first and/or second polyethylene has a weight-average molecular weight in the range of about 1×10 4 to about 1×10 7 ;

(2) the first and/or second polyethylene has it weight-average molecular weight in the range of about 1×10 4 to about 5×10 7 ;

(3) the polyethylene having a weight-average molecular weight ranging from about 1×10 4 to about 5×10 5 is one or more of a high-density polyethylene, a medium-density polyethylene, a branched low-density polyethylene, or a linear low-density polyethylene;

(4) the polyethylene having a weight-average molecular weight ranging from about 1×10 4 to about 5×10 5 is at least one of (i) an ethylene homopolymer or (ii) a copolymer of ethylene and a third a-olefin selected from the group of propylene, butene-1, hexene-1;

(5) the polyethylene having a weight-average molecular weight of at least 1×10 6 has a weight-average molecular weight of at least about 1×10 6 ;

(6) the polyethylene having a weight-average molecular weight of at least 1×10 6 is at least one of (i) an ethylene homopolymer or (ii) a copolymer of ethylene and a fourth α-olefin selected from the group of propylene, butene-1, hexene-1;

(7) the amount of the polyethylene having a weight-average molecular weight ranging from about 1×10 4 to about 5×10 5 in the first microporous layer material is in the range of from about 70 wt. % to about 90 wt. %, based on the weight of the first microporous layer material;

(8) the amount of the polyethylene having a weight-average molecular weight of at least about 1×10 6 in the first microporous layer material is in the range of from, about 0 wt. % to about 10 wt. %, based on the weight of the first microporous layer material;

(9) the amount of the polyethylene having a weight-average molecular weight ranging from about 1×10 4 to about 5×10 5 in the second microporous layer material is in the range of from about 40 wt. % to about 60 wt. %, based on the weight of the second microporous layer material;

(10) the amount of the polyethylene having a weight-average molecular weight of at least about 1×10 6 in the second microporous layer material is in the range of from about 0 wt. % to about 10 wt. %, based on the weight of the second microporous layer material;

(11) the first and/or second polyethylene has a molecular weight distribution (“Mw/Mn”) of about 5 to about 300;

(b) the first polypropylene has at least one characteristic selected from:

(1) the first polypropylene is one or more of (i) a propylene homopolymer or (ii) a copolymer of propylene and a fifth olefins selected from one or more of α-olefins such as ethylene, butene-1, pen hexane-1,4-methylpentene-1, octene-1, vinyl acetate, methyl methacrylate, styrene, butadiene, 1,5-hexadiene, 1,7-ortadiene and 1,9-decadiene;

(2) the first polypropylene has an Mw/Mn ranging from about 1.01 to about 100;

(3) the first polypropylene is isotactic;

(4) the first polypropylene has a heat of fusion of at least about 90 Joules/gram;

(5) the first polypropylene has a melting peak (second melt) of at least about 160° C.; and

(c) the second polypropylene has an Mw/Mn of 2.5 or less.

7. The multi-layer microporous membrane of claim 1 , wherein the first and/or second polyethylene has a weight-average molecular weight in the range of about 2×10 5 to about 3×10 6 .

8. The multi-layer microporous membrane of claim 1 , wherein the first and/or second polyethylene has a weight-average molecular weight in the range of 1×10 4 to 5×10 5 .

9. The multi-layer microporous membrane of claim 6 , wherein the polyethylene having a weight-average molecular weight ranging from about 1×10 4 to about 5×10 5 is high-density polyethylene and the polyethylene having a weight-average molecular weight of at least about 1×10 6 is ultra-high molecular weight polyethylene.

10. The multi-layer membrane of claim 6 , wherein the first and/or second polyethylene comprises 10 wt. % or less of the polyethylene having a weight-average molecular weight of at least about 1×10 6 and 90 wt. % or more of the polyethylene having a weight-average molecular weight ranging from about 1×10 4 to about 5×10 5 .

11. A battery comprising an anode, a cathode, an electrolyte, and the multi-layer microporous membrane of claim 1 , wherein the multi-layer microporous membrane separates at least the anode from the cathode.

12. The battery of claim 11 , wherein the electrolyte contains lithium ions and the battery is a secondary battery.

13. The battery of claim 11 , wherein the multi-layer membrane has a porosity of 25 to 80%, an air permeability of 20 to 700 seconds/100 cc (converted to the value at 20-μm thickness), a pin puncture strength of 2,000 mN/20 μm or more, a shut down temperature of 120 to 140° C., and a meltdown temperature of 170° C. or higher, and a battery capacity recovery ratio of 70% or more.

14. The battery of claim 11 used as a source or sink of electric charge.