Secondary battery
A secondary battery is disclosed. The secondary battery includes an electrode assembly a positive electrode and a negative electrode including an electrode portion in which an electrode mixture layer containing an electrode active material is formed on a portion of an electrode current collector, and an electrode uncoated portion not including the electrode mixture layer. The electrode assembly comprises a converging portion in which an end of the electrode uncoated portion is collected and a bonding portion in which at least a portion of the converging portion and an electrode lead are joined, and a portion of the electrode lead protrudes to an outside of the battery case. At least one of the positive electrode and the negative electrode includes a polymer compound layer on at least a portion of one surface or both surfaces of the electrode uncoated portion.
1 . A secondary battery comprising:
an electrode assembly including positive electrodes and negative electrodes alternately stacked in a battery case and separators interposed between the positive and negative electrodes,
wherein each of the positive electrodes and each of the negative electrodes include an electrode portion in which an electrode mixture layer containing an electrode active material is formed on a portion of an electrode current collector, and an electrode uncoated portion not including the electrode mixture layer,
wherein the electrode assembly comprises a converging portion in which ends of the electrode uncoated portions are collected and a bonding portion in which at least a portion of the converging portion and an electrode lead are joined, and a portion of the electrode lead protrudes to an outside of the battery case,
at least one of the positive electrodes and the negative electrodes includes a polymer compound layer on at least a portion of one surface or both surfaces of the electrode uncoated portion,
wherein the polymer compound layer is formed on a portion of the electrode uncoated portion between the electrode portion and the converging portion and
the polymer compound layer includes an expandable polymer compound of a composite of a hydroxyl group-containing compound and silica,
wherein the expandable polymer compound is a composite of polyurethane and silica.
2 . The secondary battery of claim 1 , wherein electrode uncoated portions of the negative electrodes and the positive electrodes located on outermost portions among the electrode uncoated portions include the polymer compound layer on a surface facing an inner surface of the electrode assembly.
3 . The secondary battery of claim 1 , wherein the polymer compound layer increases in volume by 30 to 4,000 times at 80° C. or higher compared to a volume at room temperature.
4 . The secondary battery of claim 1 , wherein the polymer compound layer has a thickness of 3 to 25 μm.
5 . The secondary battery of claim 1 , wherein the polymer compound is in a form of beads, pillars, flakes, or powder.
6 . The secondary battery of claim 1 , wherein the polymer compound comprises expanded graphite filled inside of the polymer compound.
7 . The secondary battery of claim 1 , wherein the polymer compound layer is biased toward the converging portion.
8 . The secondary battery of claim 7 , wherein a ½ point of a total length of the polymer compound layer is located on a side of the converging portion with a ½ point of a length of the electrode uncoated portion between the electrode portion and the converging portion as a center.
9 . The secondary battery of claim 1 , wherein the polymer compound layer is biased toward the electrode portion.
10 . The secondary battery of claim 1 , wherein a ½ point of a total length of the polymer compound layer is the same as a ½ point of a length of the electrode uncoated portion between the electrode portion and the converging portion.
11 . The secondary battery of claim 1 , wherein the electrode leads of the positive electrodes and the negative electrodes protrude in opposite directions of the battery case.
12 . The secondary battery of claim 1 , wherein the electrode leads of the positive electrodes and the negative electrodes protrude in the same direction of the battery case.