Battery electrode, battery, and battery electrode manufacturing method
A battery electrode which is one example of an embodiment is provided with a core and an active material layer disposed on the surface of the core. The core has a based part where the core surface is covered by the active material layer and a tab part projecting from the based part. Notches are formed on the core from the base of the tab part to the base part, or at positions where the base part adjoins the tab part. The edge of each notch is formed from a first curve comprising a first arc and either a second curve comprising a second arch having a smaller curvature than the first arc or a straight line. This allows a battery electrode to be provided such that the occurrence of cracks at the base of the tab part of the core and in the vicinity thereof can be sufficiently suppressed.
1. A battery electrode comprising an electrode current collector, and an active material layer provided on a surface of the electrode current collector, wherein:
the electrode current collector has a based portion in which the electrode current collector surface is covered by the active material layer and a tab portion projecting from the based portion;
a pair of cutouts are formed in the electrode current collector, wherein each of the pair of cutouts is formed in the based portion from a corresponding one of opposite end portions of a root of the tab portion in a width direction of the tab portion, or in a corresponding one of opposed parts of the based portion respectively adjacent to the corresponding one of the opposite end portions of the root of the tab portion in the width direction;
an edge of said each of the pair of cutouts consists of a single curve and a single straight line,
the edge of said each of the pair of cutouts has a first end thereof on the tab portion side and a second end thereof on the based portion side, wherein the single curve is formed from the first end and the single straight line is formed from the second end; and
a portion of the electrode current collector surface interposed between the pair of cutouts in the width direction is covered by the active material layer formed thereon.
2. The battery electrode according to claim 1 , wherein:
said each of the pair of cutouts is formed from the root of the tab portion to the based portion; and
a width of the tab portion is smaller in the root than in a distal end.
3. The battery electrode according to claim 1 , wherein the single straight line is formed so as to have a length from the second end, the length preventing the single straight line from extending across a line that is an extension of a side edge of the tab portion.
4. The battery electrode according to claim 1 , wherein the first curve is an arc of an ellipse.
5. The battery electrode according to claim 1 , wherein a packing density of the active material layer is no less than 3.65 g/cm 3 .
6. The battery electrode according to claim 1 , further comprising a protection layer provided on the root of the tab portion,
wherein a part of said each of the pair of cutouts is formed in a part in which the protection layer is provided.
7. A battery comprising the battery electrode according to claim 1 .
8. The battery according to claim 7 , wherein the battery electrode is a positive electrode.
9. A method for manufacturing a battery electrode comprising an electrode current collector and an active material layer provided on a surface of the electrode current collector, the electrode current collector having a based portion in which the electrode current collector surface is covered by the active material layer and a tab portion projecting from the based portion, the method comprising:
providing the active material layer on at least a surface of the based portion or a part that is to be the based portion;
forming a pair of cutouts in the electrode current collector, each of the pair of cutouts being formed in the based portion from a corresponding one of opposite end portions of the root of the tab portion in a width direction of the tab portion, or in a corresponding one of opposed parts of the based portion respectively adjacent to the corresponding one of the opposite end portions in the width direction,
wherein an edge of said each of the pair of cutouts consists of a single curve and a single straight line,
the edge of said each of the pair of cutouts has a first end thereof on the tab portion side and a second end thereof on the based portion side, wherein the single curve is formed from the first end and the single straight line is formed from the second end; and
compressing the active material layer after the formation of the cutout, wherein
a portion of the electrode current collector surface interposed between the pair of cutouts in the width direction is covered by the active material layer formed thereon.
10. The battery electrode according to claim 1 , wherein
an angle formed by the single straight line and an edge of the based portion connected to the second end of the edge of said each of the cutouts is 100° to 160°.
11. The battery electrode according to claim 10 , wherein
the angle formed by the single straight line and the edge of the based portion is 110° to 150°.
12. The method according to claim 9 , wherein:
an angle formed by the single straight line and an edge of the based portion connected to the second end of the edge of said each of the cutouts is 100° to 160°.
13. The battery electrode according to claim 12 , wherein
the angle formed by the single straight line and the edge of the based portion is 110° to 150°.