KR20080016047A - Rechargeable battery - Google Patents

Abstract

A secondary battery is provided to increase a flow of an electric current by forming embossing on a current collector of an electrode assembly to increase a contact area upon contact with a case. A secondary battery includes: an electrode assembly(10) formed by rolling a positive electrode plate, a negative electrode plate, and a separator interposed between the positive electrode plate and negative electrode plate, wherein the positive electrode plate has a positive active material-uncoated part at one end thereof and the negative electrode plate has a negative active material-uncoated part at one end thereof; a case(20) which accommodates the electrode assembly; a cap assembly which combines with the upper part of the case; and a positive electrode current collector and a negative electrode current collector which face each other with the electrode assembly interposed between the positive electrode current collector and negative electrode current collector and are electrically connected with the electrode assembly. The negative electrode current collector to be joined to the inner bottom(20b) of the case has many contact parts(53) protruded toward the bottom.

Description

Rechargeable Battery

1 is a perspective view illustrating a rechargeable battery according to an exemplary embodiment of the present invention.

FIG. 2 is a cross-sectional view of the rechargeable battery of FIG. 1.

3 is a perspective view illustrating a state in which the electrode assembly is stacked before being wound in the secondary battery of FIG. 2.

4 is a perspective view illustrating a state in which a bottom surface of a negative electrode current collector plate of the secondary battery of FIG. 2 faces upward.

5 is a perspective view illustrating a state before the electrode assembly of FIG. 2 is inserted into a case.

FIG. 6 is a cross-sectional view taken along the line A-A of a state in which the bottom surface of the negative electrode current collector plate and the bottom surface of the case when the electrode assembly is coupled to the case in FIG.

<Brief Description of Major Codes in Drawings>

10: electrode assembly 11: bipolar plate

11a: positive electrode current collector 11b: positive electrode active material layer

11c: positive electrode uncoated portion 12: negative electrode plate

12a: negative electrode current collector 12b: negative electrode active material layer

12c: negative electrode uncoated portion 13: separator

20: case 20a: cylindrical surface

20b: bottom surface 30: cap assembly

31: gasket 32: cap plate

32a: external terminal 33: band plate

35: lead wire 40: positive electrode current collector plate

41: central hole 50: negative electrode collector plate

50a: when 50b: when

51: first welded portion 52: second welded portion

53: contact part 100: secondary battery

The present invention relates to a secondary battery, and more particularly, to a secondary battery capable of increasing the flow of current by forming an embossing on the current collector plate of the electrode assembly to increase the contact area upon contact with the electrode assembly and the case.

A rechargeable battery is a battery that can be charged and discharged unlike a primary battery that cannot be charged. In the case of a low-capacity battery in which one battery cell is packed in a pack form, a rechargeable battery is used in portable electronic devices such as mobile phones and camcorders. In the case of a large capacity battery in a battery pack unit in which dozens of battery cells are connected, the battery is widely used as a power source for driving a motor of a hybrid vehicle.

Secondary batteries are manufactured in various shapes. Representative shapes include cylindrical and rectangular shapes, and an electrode assembly (or jelly) wound around a vortex through a separator, which is an insulator, between the two bands and the negative electrode plate. A roll) is installed in a case, and a cap assembly in which an external terminal is formed is installed in the case to constitute a battery.

In low-capacity batteries applied to small electronic devices among secondary batteries, positive and negative plates mainly serve to collect current generated when the battery is operated, and conductive tabs are attached to the positive and negative electrodes, respectively. It is attached to the negative electrode non-coated portion of the negative electrode plate by welding or the like to induce currents generated in the positive and negative electrode plates to the positive and negative terminals.

When the structure of the low capacity battery configured as described above is applied to a large capacity battery as it is, it does not satisfy the operation characteristics of the large capacity battery, that is, the characteristics that allow a large current to flow in one instant, so that a large amount of current flows. Instead, a structure in which a current collector plate with a large current passing area is applied has been disclosed in US Pat. No. 6,091,765.

In a large-capacity battery employing a conventional electrode assembly having a current collector plate, the current collector plate has a planar shape, and a central portion of the current collector plate protrudes toward the bottom surface of the case for welding with the case serving as one electrode. Consists of Coupling the electrode assembly having the current collector plate to the case is performed by inserting the electrode assembly having the current collector plate located below into the case and welding the current collector plate to the bottom surface of the case by a welding process such as resistance welding. However, in this case, the current collector plate is formed in a structure in which only the center portion is protruded, and the remaining portion is flat, so that only the protrusions of the center portion of the current collector plate and the inner bottom portion of the case are in close contact with the inner bottom surface of the case. The contact is made and the contact between the remaining flat portion of the current collector plate and the bottom surface of the case is poor. As a result, the contact area between the current collector plate and the case is small as a protruding portion of the current collector plate, and as a result, the area through which the current flowing between the electrode plate and the case of the electrode assembly passes is narrow. When the contact area between the current collector, which is a passage of current flow, and the case is small, the flow of current is small. Therefore, the internal resistance of a large-capacity battery, for example, a hybrid electric vehicle (HEV) battery, which requires a large current flow at a moment. Will become large. Accordingly, there is a problem in that the heat generation of the battery is increased and the efficiency of the battery is lowered.

The present invention has been made to solve the above problems, an object of the present invention is to form an embossing on the current collector plate of the electrode assembly to increase the flow of current by increasing the contact area in contact with the case secondary secondary It is to provide a battery.

A secondary battery according to the present invention for achieving the above object is a positive electrode plate is formed on the positive electrode non-coating portion is not coated with a positive electrode active material at one end, a negative electrode plate is formed on the negative electrode non-coated active material is coated on one end, the negative plate and the positive plate An electrode assembly formed by winding a separator interposed therebetween; A case accommodating the electrode assembly; A cap assembly coupled to the upper case; And a positive electrode current collector plate and a negative electrode current collector plate electrically connected to the electrode assembly while facing each other with the electrode assembly interposed therebetween, and the negative electrode current collector plate coupled to the inner bottom surface of the case has a bottom surface at a portion thereof. It characterized in that it comprises a plurality of contact portions formed to protrude toward.

The negative electrode current collector plate may further include a first welding part protruding toward an inner bottom surface of the case at a central portion of a lower surface thereof.

The first welding part and the inner bottom surface of the case may be coupled to each other by resistance welding.

The negative electrode current collector plate may have a plurality of second welding parts protruding toward the electrode assembly in a cross-shaped area around the first welding part.

The second welding portion and the negative electrode non-coating portion may be coupled to each other by welding.

The contact portion may be formed at a portion formed between the plurality of second welding portions.

The contact portion may be formed in an embossed shape.

The embossing may be formed in a shape selected from any one of circular, elliptical, and polygonal.

The contact part may protrude from the lower surface of the negative electrode current collector plate to be equal to the height from which the first weld part protrudes.

The circular embossing may have a diameter of 5 to 20 mm in plan view.

The secondary battery may be a cylindrical battery.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

1 is a perspective view illustrating a secondary battery according to an embodiment of the present invention, FIG. 2 is a cross-sectional view illustrating the secondary battery of FIG. 1, and FIG. 3 is stacked before the electrode assembly is wound in the secondary battery of FIG. 2. It is a perspective view which shows the state.

1 and 2, the secondary battery 100 according to an embodiment of the present invention is manufactured as a cylindrical secondary battery having high energy density per unit weight, which is advantageous in terms of large capacity, and includes an electrode assembly 10 and an electrode assembly. 10 and the case 20 in which the electrolyte (not shown) is accommodated, the cap assembly 30 blocking the upper portion of the case 20, the electrode assembly 10 electrically between the electrode assembly 10, It includes a positive electrode collector plate 40 and the negative electrode collector plate 50 to be connected.

The electrode assembly 10 is formed by winding or overlapping a laminate of the positive electrode plate 11, the separator 13, and the negative electrode plate 12 formed in a thin plate shape or a film shape. In addition, the electrode assembly 10 may further include a positive electrode current collector plate 40 and a negative electrode current collector plate 50 electrically connected to the positive electrode plate 11 and the negative electrode plate 12.

The positive electrode plate 11 includes a positive electrode current collector 11 a and a positive electrode active material layer 11 b coated on both surfaces of the positive electrode current collector 11 a. In addition, the positive electrode collector 11a is provided with a positive electrode non-coating portion 11c not coated with a positive electrode active material.

The positive electrode current collector 11a is generally made of aluminum (Al) in the form of a foil collecting current, and the positive electrode active material layer 11b generates electricity, and is a transition metal oxide (eg, LiCoO ₂ , LiNiO). _{2 ,} LiMn ₂ O ₄ ) and the like. The positive electrode non-coating portion 11c is formed at an upper end of the positive electrode current collector to become a passage for current flow between the positive electrode plate 11 and the outside of the positive electrode plate 11.

The negative electrode plate 12 includes a negative electrode current collector 12a and a negative electrode active material layer 12b coated on both surfaces of the negative electrode current collector 12a. In addition, the negative electrode current collector 12a is provided with a negative electrode non-coating portion 12c not coated with the positive electrode active material.

The negative electrode current collector 12a is generally made of nickel or copper (Cu) in the form of a foil for collecting current, and the negative electrode active material generates electricity and is made of, for example, graphite or carbon. The negative electrode non-coating portion 12c is formed at the lower end of the negative electrode current collector 12a to serve as a passage for current flow between the negative electrode plate 12 and the outside of the negative electrode plate 12.

The positive electrode plate 11 and the negative electrode plate 12 may be arranged with different polarities.

The separator 13 is positioned between the positive electrode plate 11 and the negative electrode plate 12 to prevent shorting and to move only lithium ions, and is composed of polyethylene, polypropylene, or a composite film of polyethylene and polypropylene. have.

As described above, the positive electrode plate 12 may be an aluminum (Al) foil, the negative electrode plate 11 may be a copper (Cu) foil, and the separator 13 may be polyethylene (PE) or polypropylene (PP). It does not limit the material.

As illustrated in FIG. 3, the electrode assembly 10 as described above includes a positive electrode plate 11 such that the positive electrode non-coating portion 11c and the negative electrode non-coating portion 12c come out of the upper and lower ends of the electrode assembly 10 during winding. And the separator 13 and the negative electrode plate 12 are disposed and wound up. As a result, the positive and negative electrode portions 11c and the negative and negative electrode portions 12c protrude outward from both the upper and lower ends of the electrode assembly 10. In addition, the electrode assembly 10 may have a laminated structure in addition to the positive electrode plate 11, the separator 13, and the negative electrode plate 12 wound in a vortex as described above. Here, the electrode assembly 10 is wound in a circular shape.

The upper and lower ends of the electrode assembly 10 are coupled to the positive electrode collector plate 40 and the negative electrode collector plate 50 to be electrically connected to the positive electrode plate 11 and the negative electrode plate 12, respectively.

The positive electrode current collector plate 40 is made of a conductive material and is in contact with the positive electrode uncoated portion 11c protruding to the upper end of the electrode assembly 10, thereby being electrically connected to the positive electrode plate 11. The positive electrode current collector plate 40 and the positive electrode non-coating portion 11c are combined by a welding method or the like. Here, for easy welding of the positive electrode non-coating portion 11c and the positive electrode current collecting plate 40, the positive electrode non-coating portion 11c may be in contact with the positive electrode current collecting plate 40 in a bent form. This is because it is difficult to directly weld with the positive electrode current collector plate 40 in a state where the positive electrode non-coated portion 11c is perpendicular to the positive electrode current collector plate 40. Therefore, when the positive electrode non-coating portion 11c is bent, the area where the positive electrode non-coating portion 11c comes into contact with the positive electrode current collector plate 40 increases, so that the positive electrode current collector plate 40 and the positive electrode non-coating portion 11c are welded per unit area. The area to be increased can be easily welded. On the other hand, the center hole 41 for injecting the electrolyte, etc. may be formed in the center of the positive electrode current collector plate (40).

The negative electrode current collector plate 50 is also made of a conductive material and is in contact with the negative electrode uncoated portion 12c protruding to the lower end of the electrode assembly 10, thereby being electrically connected to the negative electrode plate 11. The negative electrode current collector plate 50 and the negative electrode uncoated portion 12c are combined by a welding method or the like. Here, the negative electrode non-coating portion 12c may be in contact with the negative electrode current collector plate 50 in a bent form for easy welding between the negative electrode non-coating portion 12c and the negative electrode current collector plate 50. This is because welding with the negative electrode current collector plate 50 is difficult in a state in which the negative electrode non-coating portion 12c is placed perpendicular to the negative electrode current collector plate 50. Therefore, when the negative electrode non-coating portion 12c is bent, the area where the negative electrode non-coating portion 12c comes into contact with the negative electrode current collector plate 50 increases, so that the negative electrode current collector plate 50 and the negative electrode non-coating portion 11c are welded per unit area. The area can be increased to facilitate welding.

The positive electrode collector plate 40 and the negative electrode collector plate 50 as described above are formed in a wide disc shape according to the shape of the circular electrode assembly 10, and thus a large amount of current is compared with a tap, which is a passage of current flow having a small area. It is a passage that can flow, and is advantageous for application to a large capacity battery, for example, a hybrid electric vehicle (HEV) battery. Thus, the positive electrode current collector plate 40 and the negative electrode current collector plate 50 formed in a disc shape may be formed in one or two layers.

The case 20 has a substantially cylindrical shape, a cylindrical surface 20a having a predetermined diameter is formed, a bottom surface 20b having a substantially disk shape is formed at the lower portion of the cylindrical surface 20a, and the upper portion is open. . Thus, the electrode assembly 10 can be inserted directly through the open top of the cylindrical case 20 to the bottom. The case 20 may be formed of a conductive metal such as aluminum, an aluminum alloy, or nickel plated steel to serve as an electrode having one polarity. In the present invention, the negative electrode current collector plate 50 electrically connected to the negative electrode plate 12 is in contact with the bottom surface 20b of the case 20, the case 20 serves as a negative electrode.

On the other hand, the cylindrical case 20 is formed with a beading portion (23) recessed in the lower portion of the center around the cap assembly 140 so that the cap assembly 30 is not separated to the outside, the upper portion A crimping part 24 bent inward is formed. The beading part 23 and the crimping part 24 serve to firmly fix and support the cap assembly 30 to the cylindrical case 20, and also to prevent leakage of the electrolyte to be described later. In addition, the beading part 23 also serves to prevent the electrode assembly 10 from flowing up and down inside the case 20. Although not shown in the drawings, an insulating plate may be provided between the beading unit 23 and the positive electrode current collector plate 40 to prevent electrical short circuits.

In addition, an electrolyte solution (not shown) is injected into the cylindrical case 20, and lithium ions generated by the electrochemical reaction in the positive electrode plate 11 and the negative electrode plate 12 inside the battery during charge and discharge are injected. It serves to make it mobile. The electrolyte may be a non-aqueous organic electrolyte that is a mixture of lithium salts and high purity organic solvents. In addition, the electrolyte may be a polymer using a polymer electrolyte, and the type of the electrolyte is not limited thereto.

The cap assembly 30 includes a cap plate 32 having an external terminal 32a and a gasket 31 that insulates the case 20 from the cap plate 32 to be broken under a set pressure condition to release gas. Thereby, it may further include a vent plate 33 for preventing the explosion of the battery, the vent plate 33 is electrically connected to the positive electrode current collector plate 40 via the lead wire 35. The vent plate 33 is not limited to the illustrated shape as long as it can block electrical connection between the electrode assembly 10 and the external terminal 32a through the lead wire 35 under a set pressure condition. Can be. The external terminal 32a is connected to the positive electrode current collector plate 40 electrically connected to the positive electrode plate 11 through the bent plate 33 and the lead wire 35, and the external terminal 32a serves as a positive electrode.

After the electrode assembly 10 having the above configuration is inserted into the case 20 through the open upper portion of the case 20, the electrolyte is injected, and the like, the cap assembly 30 is the case 20. The secondary battery is completed by covering the open top of the package).

Next, the structure of the negative electrode current collector plate 50 and the structure in which the negative electrode current collector plate 50 contacts the inner bottom surface of the case 20 will be described in detail with reference to FIGS. 4 to 6.

4 is a perspective view illustrating a state in which the bottom surface of the negative electrode current collector plate of the secondary battery of FIG. 2 faces upward, FIG. 5 is a perspective view illustrating a state before the electrode assembly of FIG. 2 is inserted into a case, and FIG. When the electrode assembly is coupled to the case is a cross-sectional view according to AA of the bonding state of the bottom surface of the negative electrode current collector plate and the bottom surface of the case.

4 and 5, the negative electrode current collector plate 50 connected to the electrode assembly 10 according to an embodiment of the present invention is made of a copper plate, the bottom of the case 20 in the center of the lower surface A first weld portion 51 protruding toward the surface 20b, a plurality of second weld portions 52 protruding toward the electrode assembly 10 in a cross-shaped area about the first weld portion 51, and a second A portion formed between each of the welding portions 52 includes a plurality of contact portions 53 protruding toward the bottom surface 20b of the case 20.

The first welding part 51 formed at the center portion of the negative electrode current collector plate 50 protrudes from the lower surface 50a of the negative electrode current collector plate 50 toward the bottom surface 20b of the case 20, thereby forming a negative electrode current collector plate. It serves as a welding part to fix 50 to the bottom surface 20b of the case 20 by welding processes, such as resistance welding.

The plurality of second welding portions 52 formed in the cross-shaped area around the first welding portion 51 protrude from the upper surface 50b of the negative electrode current collector plate 50 toward the electrode assembly 10, thereby forming the plurality of second welding portions 52. It is a part which comes into contact with the negative electrode plain part 12c, and is welded by a method, such as welding.

 The plurality of contact portions 53 formed at portions between each of the second welding portions 52 protrude toward the bottom surface 20b of the case 20. As shown in FIG. 6, the plurality of contact parts 53 are portions in which the negative electrode current collector plate 50 is in contact with the bottom surface 20b of the case 20. Except for the case where the remaining portion is formed in a flat surface and only the protruding center portion contacts the bottom surface of the case, the contact area between the negative electrode current collector plate 50 and the case 20 may be increased. Here, the contact portion 53 has an embossed shape, and the first welding portion 51 is formed to protrude by a height protruding from the lower surface 50a of the negative electrode current collector plate 53. This is because when the contact portion 53 protrudes to a height lower than the height at which the first welding portion 51 protrudes from the lower surface 50a of the negative electrode current collector plate 53, the contact portion 53 does not touch the inner bottom surface 20b of the case 20 in close contact. If the contact area with the case 20 cannot be increased, and the contact portion 53 protrudes to a height higher than the height at which the first welding portion 51 protrudes from the lower surface 50a of the negative electrode current collector plate 53, the case 20 is used. This is because it is difficult to weld since the first weld part 51 does not contact the inner bottom surface 20b during welding in close contact with the inner bottom surface 20b. In addition, the embossing is made into a circular shape of 5 to 20mm in diameter on the plane. If the diameter of the embossing is 5 mm or less, the size is small, the contact area with the case is too small, and the efficiency of increasing the flow path of the current is too small. If the diameter is 20 mm or more, the space for forming the second welding portion 52 becomes small, so that the negative electrode is uncoated. This is because the negative electrode current collector plate 50 can be separated from the negative electrode non-coating portion 12c when the welding area between the 12c and the negative electrode current collector plate 50 becomes small and an external impact is applied. In the present invention, the form of the embossing is formed in a circular shape, but it is also possible to form one of an ellipse, a polygon including a triangle, a square, and a pentagon.

As described above, the secondary battery according to the present invention can increase the flow of current by forming a plurality of contact portions of a plurality of embossed forms on the current collector plate of the electrode assembly to increase the contact area when the electrode assembly is in contact with the case. . Accordingly, the secondary battery according to the present invention can be efficiently applied to a battery for a hybrid electric vehicle (HEV) that requires a large amount of current at one time.

As described above, the present invention is not limited to the specific preferred embodiments described above, and any person having ordinary skill in the art to which the present invention pertains without departing from the gist of the present invention claimed in the claims. Various modifications are possible, of course, and such changes are within the scope of the claims.

Claims (11)

An electrode assembly formed by winding a separator interposed between the cathode plate and the anode plate on which one end of the cathode non-coating portion is formed, the cathode non-coating portion of which is not coated with the cathode active material; A case accommodating the electrode assembly; A cap assembly coupled to the upper case; And In the secondary battery comprising a positive electrode collector plate and a negative electrode collector plate electrically connected to the electrode assembly while facing each other with the electrode assembly therebetween, The negative electrode current collector coupled to the inner bottom surface of the case is a secondary battery, characterized in that it comprises a plurality of contact portions formed to protrude toward the bottom surface from a portion of the lower surface. The method of claim 1, The negative electrode current collector plate further includes a first welding part protruding toward an inner bottom surface of the case at a central portion of a lower surface thereof. The method of claim 2, Secondary battery, characterized in that the first welding portion and the inner bottom surface of the case are coupled to each other by resistance welding. The method of claim 2, The negative electrode current collector plate has a plurality of second welding parts protruding toward the electrode assembly in a cross-shaped area around the first welding part. The method of claim 4, wherein And the second welding portion and the negative electrode non-coating portion are joined to each other by welding. The method of claim 4, wherein And the contact portion is formed at a portion formed between the plurality of second welding portions. The method of claim 2, The secondary battery, characterized in that the contact portion is formed in an embossed shape. The method of claim 7, wherein The embossing is a secondary battery, characterized in that formed in a shape selected from any one of circular, oval and polygon. The method of claim 7, wherein And the contact portion protrudes from a lower surface of the negative electrode current collector plate to be equal to a height protruding from the first weld portion. The method of claim 9, The circular embossing secondary battery, characterized in that the planar diameter of 5 to 20mm.  The method of claim 1, The secondary battery is a secondary battery, characterized in that the cylindrical battery.

Images