Laminated battery cell comprising multilayer composite separator and methods for creating the same

1. An electrode/separator assembly, comprising:

an electrode comprising an electrode current collector and an electroactive material layer disposed on one or both sides of the electrode current collector; and

a porous multilayer composite separator layer disposed on one or both sides of the electrode,

wherein said multilayer composite separator layer comprises at least first and second layers, said first and second layers comprising inorganic particulate material(s) and organic polymer(s) having different inorganic particulate material/organic polymer weight ratios;

wherein the first layer of the multilayer composite separator layer having a first weight percent of polymer is disposed over the electrode; and the second layer containing a higher weight percentage of organic polymer than the first layer is disposed as the outermost layer of the multilayer composite separator; and

wherein the thickness of said first layer is at least 80% of the total thickness of the multilayer composite separator; said first layer comprises greater than 50% inorganic particulate material by weight; and said second layer comprises greater than 50% organic polymer by weight.

2. The electrode/separator assembly of claim 1 , wherein the thickness of said first layer is 80% to 90% of the total thickness of the multilayer composite separator.

3. The electrode/separator assembly of claim 2 , wherein the thickness of said first layer is 90% of the total thickness of the multilayer composite separator layer.

4. The electrode/separator assembly of claim 2 , wherein the thickness of said first layer is 80% of the total thickness of the multilayer composite separator layer.

5. The electrode/separator assembly of claim 2 , wherein said first layer has an inorganic particulate material/organic polymer weight ratio of about 60:40 to 80:20; and said second layer has an inorganic particulate material/organic polymer weight ratio of about 49:51 to 20:80.

6. The electrode/separator assembly of claim 2 , wherein said first layer has an inorganic particulate material/organic polymer weight ratio in the range of about 60:40 to 70:30; and said second layer has an inorganic particulate material/organic polymer weight ratio in the range of about 49:51 to about 40:60.

7. The electrode/separator assembly of claim 1 , wherein said organic polymer comprises a polymer which is electrochemically compatible with Li-ion cells.

8. The electrode/separator assembly of claim 1 , wherein the organic polymer is selected from the group consisting of polyvinylidene fluoride (PVDF)-based polymers, such as poly(vinylidene fluoride) (PVDF) and its co- and terpolymers with hexafluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene, poly(vinyl fluoride), polytetraethylene (PTFE), ethylene-tetrafluoroethylene copolymers (ETFE), polybutadiene, cyanoethyl cellulose, carboxymethyl cellulose and its blends with styrene-butadiene rubber, polyacrylonitrile, ethylene propylene diene terpolymers (EPDM), styrene-butadiene rubbers (SBR), polyimides, ethylene-vinyl acetate copolymers, polyacrylic acids and lithiated polyacrylic acids.

9. The electrode/separator assembly of claim 1 , wherein said inorganic particulate material is selected from the group consisting of silica, alumina, titania, natural and synthetic zeolites, metal carbonates, zirconia, silicon phosphates, silicates and other electrochemically stable inorganic particles.

10. The electrode/separator assembly of claim 1 , wherein the inorganic particulate material has a particle size in the range of 4 nm to about 500 nm.

11. The electrode/separator assembly of claim 1 , wherein the inorganic particulate material has a particle size in the range of about 10 nm to about 20 nm.

12. The electrode/separator assembly of claim 1 , wherein the inorganic particulate material has a particle size in the range of about 1 μm to about 6 μm.

13. A laminated electrochemical cell, comprising:

a positive electrode comprising a positive electrode current collector and a positive electrode active material layer disposed on one or both sides of the positive electrode current collector;

a negative electrode comprising a negative electrode current collector and a negative electrode active material layer disposed on one or both sides of the negative electrode current collector;

wherein at least one of the positive and negative electrodes comprises the electrode/separator assembly of claim 1 ;

and wherein the positive electrode and negative electrode are positioned in a facing relationship to form a laminate multilayer composite separator layer between the two opposite electrodes.

14. The laminated electrochemical cell of claim 13 , wherein said electrochemical cell is a prismatic cell.

15. The laminated electrochemical cell of claim 13 , wherein one of the positive or negative electrodes comprises the electrode/separator assembly of claim 1 .

16. The laminated electrochemical cell of claim 15 , wherein the other of the positive or negative electrode comprises a monolayer composite separator layer attached to one or both sides of the electrode.

17. The laminated electrochemical cell of claim 13 , wherein both of the electrodes comprise the electrode/separator assembly of claim 1 .

18. The laminated electrochemical cell of claim 13 , wherein the total thickness of a multilayer composite separator layer is in the range of about 2 to 40 μm.

19. The laminated electrochemical cell of claim 18 , wherein said laminate multilayer composite separator layer between the two opposite electrodes has a thickness of about 20 μm.