Non-aqueous electrolyte secondary battery, electrode used for secondary battery, and method of manufacturing electrode
A non-aqueous electrolyte secondary battery includes an electrode body including a positive electrode and a negative electrode superimposed upon each other with a separator interposed therebetween. The negative electrode is superimposed upon the positive electrode in a state where a negative electrode active material layer, except the part on a proximal end part of a negative electrode tab, is positioned inside an outer edge of a positive electrode active material layer of the positive electrode. A width H 1 of the negative electrode active material layer including the part on the proximal end part of the negative electrode tab, width H 2 of the negative electrode active material layer or negative electrode current collector at a part other than the negative electrode tab, and width H 3 of the positive electrode active material layer are formed to satisfy the relationships of H 2 <H 3 , and (H 1 −H 2 )≧(H 3 −H 2 )÷2.
1. A non-aqueous electrolyte secondary battery comprising:
an exterior member; and
an electrode body and non-aqueous electrolyte liquid disposed in the exterior member,
wherein:
the electrode body comprises a positive electrode and a negative electrode superimposed upon each other with a separator interposed between the electrodes;
the positive electrode comprises (i) a positive electrode current collector having an outer edge, (ii) a positive electrode tab protruding from the outer edge of the positive electrode current collector and being continuous with the positive electrode current collector without a joint, and (iii) a positive electrode active material layer disposed on the positive electrode current collector over an entire width of the positive electrode current collector;
the negative electrode comprises (i) a negative electrode current collector having an outer edge, (ii) a negative electrode tab protruding from the outer edge of the negative electrode current collector and being continuous with the negative electrode current collector without a joint, and (iii) a negative electrode active material layer comprising lithium titanate, disposed on the negative electrode current collector over an entire width of the negative electrode current collector, and on a proximal end part of the negative electrode tab;
the negative electrode is superimposed upon the positive electrode such that the negative electrode active material layer, except a portion on the proximal end part of the negative electrode tab, is positioned inside an outer edge of the positive electrode active material layer; and
a width H 1 of the negative electrode active material layer including the portion disposed on the proximal end part of the negative electrode tab, a width H 2 of the negative electrode active material layer or negative electrode current collector at a location other than the negative electrode tab, and a width H 3 of the positive electrode current collector or positive electrode active material layer satisfy relationships of H 2 <H 3 , and (H 1 -H 2 )≧(H 3 -H 2 )÷2.
2. The battery of claim 1 , wherein the negative electrode active material layer disposed on the negative electrode tab extends to the outer edge of the positive electrode active material layer or to an outside beyond the outer edge of the positive electrode active material layer.
3. The battery of claim 1 , wherein the separator has an outer edge positioned outside the outer edge of the positive electrode active material layer, and positioned inside an extending end of the positive electrode tab and an extending end of the negative electrode tab.
4. The battery of claim 1 , wherein:
a weight per unit area of the positive electrode current collector is W1, a weight per unit area of the positive electrode tab is W2, and W1 and W2 satisfy a relationship of 0.995<W2/W1 <0.999; and
a weight per unit area of the negative electrode current collector is W1′, a weight per unit area of the negative electrode tab is W2′, and W1′ and W2′ satisfy a relationship of 0.995<W2′/W1′<0.999.
5. The battery of claim 1 , wherein at least one selected from the group consisting of the positive electrode current collector, the negative electrode current collector, the positive electrode tab, and the negative electrode tab, comprises a metallic foil.
6. The battery of claim 1 , wherein the positive electrode active material layer is disposed on two surfaces of the positive electrode current collector.
7. The battery of claim 1 , wherein the negative electrode active material layer is disposed on two surfaces of the negative electrode current collector, and on an area comprising the proximal end part of the negative electrode tab.
8. The battery of claim 7 , wherein a width of the area is 3 mm or less.
9. The battery of claim 1 , wherein:
(a) a plurality of the positive electrode tabs protrude from a long side of the positive electrode current collector;
(b) a plurality of the negative electrode tabs protrude from a long side of the negative electrode current collector; or
(c) both (a) and (b).
10. The battery of claim 9 , wherein each tab has two sides opposed to each other, and each of the two sides forms an angle equal to or greater than 90° with the long side of the current collector.
11. The battery of claim 5 , wherein the positive electrode current collector comprises:
an aluminum foil, or
a foil of an aluminum alloy comprising at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu and Si.
12. The battery of claim 5 , wherein the negative electrode current collector comprises:
an aluminum foil, or
a foil of an aluminum alloy comprising at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu and Si.
13. The battery of claim 1 , wherein the separator comprises polyethylene or polypropylene.
14. The battery of claim 1 , wherein the exterior member is a metallic container comprising aluminum.
15. The battery of claim 14 , wherein the metallic container comprises 1% or less of transition metals.