9 and 10 directly contact the welding portion or the electrode terminal, and as a result, there is no concern about the damage to the welding portion as compared with the conventional welding quality inspection apparatus. Moreover, the welding quality inspection may be performed for the first electrode current collector 2 without disassembling the battery can A to overcome a limit of the conventional welding quality inspection apparatus. Accordingly, since the welding quality inspection may be completely performed for the secondary battery while the damage to the welding portion does not occur, the defect may be prevented by achieving maintenance or enhancement of the welding quality.

According to an additional embodiment, provided is the welding quality inspection apparatus in which the diameter of the second resistance measurement member is 70% or less with respect to the diameter of the winding hole.

Selectively, the diameter of the second resistance measurement member may be 70% or less, 60% or less, or 50% or less with respect to the diameter of the winding hole.

The welding quality inspection apparatus may prevent interference between the second resistance measurement member and the electrode assembly.

According to an additional implementation example, provided is the welding quality inspection apparatus which further includes a second electrode current collector provided on the end portion of the electrode assembly opposite to the first electrode terminal of the secondary battery,

- in which the second electrode current collector includes a hole of the second electrode current collector provided in a portion corresponding to the winding hole of the electrode assembly.

In regard to the implementation example, referring to FIG. 2, the second electrode current collector 7 is positioned on the end portion of the electrode assembly opposite to the first electrode terminal 1. Further, a hole 7a of the second electrode current collector is formed to correspond to the winding hole 5.

The hole 7a of the second electrode current collector enables an electrolyte to be injected into the center of the second electrode current collector 7, and allows the second resistance measurement member 10 to directly contact the second measurement point 12 which exists inside the secondary battery through the hole 7a of the second electrode current collector and the winding hole 5.

Selectively, the diameter of the second resistance measurement member may be 70% or less, 60% or less, or 50% or less with respect to the diameter of the hole of the second electrode current collector.

In regard to the implementation example, referring to FIG. 2, the diameter of the second resistance measurement member 10 is smaller than the hole 7a of the second electrode current collector.

The welding quality inspection apparatus according to the implementation example may prevent interference between the second resistance measurement member, and the electrode assembly and the electrode current collector.

According to an additional implementation example, a ratio between the diameter of the hole of the second electrode current collector and the diameter of the winding hole of the electrode assembly is 0.8 or more and 1.2 or less, but is not limited thereto. The ratio between the diameter of the hole of the second electrode current collector and the diameter of the winding hole of the electrode assembly may be selected as an appropriate range according to the need of those skilled in the art.

According to an additional implementation example, the hole of the second electrode current collector may have a shape such as a circular shape, an elliptical shape, a triangular shape, a rectangular shape, etc., but is not limited thereto.

According to an additional implementation example, provided is the welding quality inspection apparatus in which the first electrode current collector is connected to one or more tabs of the electrode assembly of the secondary battery.

In regard to the implementation example, referring to FIG. 2, the first electrode current collector 2 may be connected to one or more tabs (included in the non-coated portion 3) of the electrode assembly 4.

For example, the first electrode includes a first current collector and a first electrode active material layer provided on one surface of the first current collector, and the first current collector includes a non-coated portion not having the first active material layer on a peripheral portion provided on one end portion side of the electrode assembly. Herein, the tab is formed from the non-coated portion or the table is formed by connecting a material such as a foil to the non-coated portion.

In the welding quality inspection apparatus according to the implementation example, the tensile force is not also applied to the welding portions of one or more tabs of the electrode assembly 4 connected to the first electrode terminal 1 and the first electrode current collector 2, and the first and second resistance measurement members 9 and 10 directly contact the welding portion or the electrode terminal, and as a result, there is no concern about the damage to the tab in addition to the welding portion as compared with the conventional welding quality inspection apparatus.

According to an additional implementation example, provided is the welding quality inspection apparatus in which each of the first resistance measurement member and the second resistance measurement member includes a current probe applying current to the first measurement point and the second measurement point and a voltage probe measuring voltage at the first measurement point and the second measurement point.

In regard to the implementation example, referring to FIG. 2 and FIG. 4, the first resistance measurement member 9 and the second resistance measurement member 10 may include a current probe 1300 applying current to the first measurement point and the second measurement point and a voltage probe 1400 measuring voltage on both surfaces of the first measurement point and the second measurement point.

Accordingly, in the welding quality inspection apparatus according to the implementation example, since the welding quality inspection may be completely performed for the secondary battery while the damage to the welding portion does not occur, the defect may be prevented by achieving maintenance or enhancement of the welding quality, as compared with the conventional welding quality inspection apparatus. Further, the resistance value may be easily determined from the current probe 1300 and the voltage probe 1400.

According to an additional implementation example, provided is the welding quality inspection apparatus in which the first electrode terminal is a cathode terminal and the first electrode current collector is a cathode current collector.

In regard to the implementation example, referring to FIG. 2, the first electrode terminal 1 may be the cathode terminal and the first electrode current collector 2 may be the cathode current collector.

In the welding quality inspection apparatus according to the implementation example, since the welding quality inspection may be completely performed for the secondary battery while the damage to the welding portion does not occur, the defect may be prevented by achieving maintenance or enhancement of the welding quality, as compared with the conventional welding quality inspection apparatus.

According to an additional implementation example, provided is the welding quality inspection apparatus in which the cathode terminal includes aluminum having a purity of 95% or more or the cathode current collector includes aluminum having a purity of 95% or more.

Alternatively, according to an additional implementation example, provided is the welding quality inspection apparatus in which the cathode terminal includes aluminum having a purity of 95% or more or the cathode current collector includes aluminum having a purity of 95% or more.

In regard to the implementation example, referring to FIG. 2, each of the cathode terminal which is the first electrode terminal 1 and the cathode current collector which is the first electrode current collector 2 may independently include aluminum having a purity of 95% or more. Preferably, each of the cathode terminal and the cathode current collector may independently include aluminum having a purity of 96% or more, 97% or more, 98% or more, 99% or more, or 99.5% or more.

Further, the welding quality inspection apparatus according to the implementation example may achieve a constant welding quality or enhancement of the welding quality in spite of considering characteristics of the material constituting the secondary battery. Therefore, even though both the cathode terminal and the cathode current collector include aluminum having a high purity, it is easier to manage the welding quality, thereby providing an effect of reducing a defect rate.

According to an additional implementation example, provided is the welding quality inspection apparatus in which the cathode terminal is constituted by a rivet inserted by penetrating the bottom surface of the sealing portion of the secondary battery.

In regard to the implementation example, referring to FIG. 2, the first electrode terminal 1 in which the bottom surface of the sealing portion B of the secondary battery is riveted through the through-hole 13 is a rivet.

In particular, the implementation example is meaningful in that with the structural development of a secondary battery that achieves resistance reduction of a jelly-roll electrode assembly itself, the welding quality of the cylindrical secondary battery may be inspected more closely.

Further, a sealing property between the riveted first electrode terminal 1 and the battery can A may be remarkably enhanced.

According to an additional implementation example, the secondary battery provides the welding quality inspection apparatus which is the cylindrical secondary battery.

In regard to the implementation example, referring to FIG. 2, the first measurement point 11 is positioned on the first electrode terminal 1 exposed to the outside of the cylindrical secondary battery, and the second measurement point 12 is positioned on the welding portion of the first electrode current collector 2 inside the cylindrical secondary battery.

In the welding quality inspection apparatus according to the implementation example, since the welding quality inspection may be completely performed for the cylindrical secondary battery while the damage to the welding portion does not occur, the defect may be prevented by achieving maintenance or enhancement of the welding quality.

In particular, the implementation example is meaningful in that with the structural development of a cylindrical secondary battery that achieves resistance reduction of a jelly-roll electrode assembly itself, the welding quality of the cylindrical secondary battery may be inspected more closely.

Further, a sealing property between the riveted first electrode terminal 1 and the battery can A may be remarkably enhanced.

Further, production cost is small, mass production is easy, and energy density per volume is high.

According to an additional implementation example, provided is the welding quality inspection apparatus in which the second resistance measurement member includes a body portion, an elastic portion, and a tip portion,

- the elastic portion connects the body portion and the tip portion to each other, and adjusts a total length of the second resistance measurement member, and
- the tip portion is provided to contact a second measurement point.

In regard to the implementation example, referring to FIG. 3, an elastic portion 200 connects a body portion 100 and a tip portion 300 to each other.

Selectively, a member such as a spring may be installed in the elastic portion 200, and as a result, elasticity is granted when a total length of a second resistance measurement member is adjusted.

Selectively, the body portion 100 may include a head, plunger, a bearing, a collar, a sleeve, etc., but is not limited thereto.

The welding quality inspection apparatus according to the implementation example may inspect welding qualities of a first electrode terminal and a first electrode current collector regardless of a height of a battery can by adjusting the total length of the second resistance measurement member. Alternatively, the total length of the second resistance measurement member is adjusted to prevent damage to a second measurement point of a welding portion.

According to an additional implementation example, provided is the welding quality inspection apparatus in which the body portion and the tip portion include iron components, and

- at least one of the body portion and the tip portion is nickel-plated.

The welding quality inspection apparatus according to the implementation example may prevent corrosion from external factors such as air, moisture, etc.

According to an additional implementation example, provided is the welding quality inspection apparatus in which the elastic portion includes the iron component, and is gold-plated.

The welding quality inspection apparatus according to the implementation example provides a corrosion prevention effect and/or elasticity.

According to another implementation example of the present invention, provided is a welding quality inspection method for a welding portion of a secondary battery including an electrode assembly wound in which a first electrode, a separator, and a second electrode are stacked and wound and a first electrode current collector provided on one end portion of the electrode assembly, which includes:

- (A) measuring a resistance value by directly contacting a first resistance measurement member with a first measurement point;
- (B) measuring the resistance value by directly contacting a second resistance measurement member with a second measurement point; and
- (C) judging a welding quality by comparing the resistance values measured from steps (A) and (B) with a threshold resistance value,
- in which the first measurement point is positioned on a first electrode terminal exposed to the outside of the secondary battery,
- the second measurement point is positioned on the welding portion of the first electrode current collector provided inside the secondary battery, and
- the second resistance measurement member contacts the welding portion of the first electrode current collector which exists inside the secondary battery through a winding hole of the electrode assembly opposite to the first electrode terminal.

In regard to the implementation example, referring to FIG. 2, a welding quality inspection apparatus according to an embodiment of the present invention, which may be used for the welding quality inspection method is illustrated.

First, in step (A), the resistance value may be measured by directly contacting a first measurement point 11 by using a first resistance measurement member 9.

Further, in step (B), the resistance value may be measured by directly contacting a second measurement point 12 by using a second resistance measurement member 10.

Then, in step (C), the welding quality may be judged by comparing the resistance values measured from steps (A) and (B) with the threshold resistance value. Here, when the resistance values measured from steps (A) and (B) exceed the threshold resistance value, it is judged that a welding defect occurs to sort a defective item.

The first measurement point 11 is positioned on the first electrode terminal 1 exposed to the outside of the secondary battery, and the second measurement point 12 is positioned on the welding portion of the first electrode current collector which is provided inside the secondary battery.

Further, the resistance value is measured by directly contacting the second resistance measurement member 10 with the second measurement point 12 through a winding hole 5 of an electrode assembly 4 at an opening portion C of the secondary battery.

In the welding quality inspection method according to the implementation example, the tensile force is not applied to the welding portions of the first electrode terminal 1 and the first electrode current collector 2, and the first and second resistance measurement members 9 and 10 directly contact the welding portion or the electrode terminal, and as a result, there is no concern about the damage to the welding portion as compared with the conventional welding quality inspection method. Moreover, the welding quality inspection may be performed for the first electrode current collector 2 without disassembling the battery can A to overcome a limit of the conventional welding quality inspection method. Accordingly, since the welding quality inspection may be completely performed for the secondary battery while the damage to the welding portion does not occur, the defect may be prevented by achieving maintenance or enhancement of the welding quality.

According to an additional embodiment, provided is the welding quality inspection method in which the diameter of the second resistance measurement member is 70% or less with respect to the diameter of the winding hole.

According to an additional implementation example, provided is the welding quality inspection method which further includes a second electrode current collector provided on the end portion of the electrode assembly opposite to the first electrode terminal of the secondary battery,

- in which the second electrode current collector includes a hole of the second electrode current collector provided in a portion corresponding to the winding hole of the electrode assembly.

The welding quality inspection method according to the implementation examples is described above.

According to an additional implementation example, provided is the welding quality inspection method in which the first electrode current collector is connected to one or more tabs of the electrode assembly of the secondary battery.

In regard to the implementation example, referring to FIG. 2, the first electrode current collector 2 may be connected to one or more tabs included in the non-coated portion 3) of the electrode assembly 4.

The description of the tab is the same as the above description.

In the welding quality inspection method according to the implementation example, since the welding quality inspection may be completely performed for the secondary battery while the damage to the welding portion does not occur, the defect may be prevented by achieving maintenance or enhancement of the welding quality.

According to an additional implementation example, provided is the welding quality inspection method in which step (A) is

- a step in which a resistance value is measured through a current value and a voltage value by directly contacting a first resistance measurement member