Flexible battery cell

Abstract

Disclosed herein is a battery cell having an electrode assembly including one or more unit cells mounted in a variable cell case in a state in which the electrode assembly is impregnated with an electrolyte, wherein at least one of the unit cells includes a flexible electrode that can be bent or curved, an electrode current collector of the flexible electrode includes a first surface, to which an electrode active material is applied, and a second surface, to which no electrode active material is applied, the second surface being opposite to the first surface, and the second surface is provided with a mesh for improving flexibility of the electrode.

Claims

1. A battery cell having an electrode assembly comprising two or more unit cells mounted in a variable cell case in a state in which the electrode assembly is impregnated with an electrolyte, wherein at least one of the unit cells comprises a flexible electrode that can be bent or curved, an electrode current collector of the flexible electrode comprises a first surface, to which an electrode active material is applied, and a second surface, to which no electrode active material is applied, the second surface being opposite to the first surface, and the second surface is provided with a pattern for improving flexibility of the electrode, wherein the pattern is a relief or an intaglio, wherein the relief or the intaglio is a polygon, wherein the flexible electrode is located at an outermost side of the electrode assembly such that the pattern of the second surface of the electrode current collector contacts an inner surface of the cell case, and wherein only the flexible electrode at the outermost side has a surface provided with a pattern.

2. The battery cell according to claim 1, wherein the electrode assembly is configured to have a structure in which two or more unit cells are sequentially stacked or a structure in which two or more unit cells are folded using a long sheet-type separation film.

3. The battery cell according to claim 1, wherein each of the unit cells is a full cell configured to have a structure in which a first electrode, a separator, and a second electrode are sequentially stacked or a bi-cell configured to have a structure in which a first electrode, a separator, a second electrode, a separator, and a first electrode are sequentially stacked.

4. The battery cell according to claim 3, wherein at least one of the unit cells is configured to have a structure in which the first electrode or the second electrode is a flexible electrode.

5. The battery cell according to claim 1, wherein the pattern is formed in a portion of the second surface.

6. The battery cell according to claim 5, wherein the portion of the second surface is a remaining portion of the second surface excluding an area of the second surface near one end of the second surface, at which electrode tabs of the flexible electrode are located, and the opposite end of the second surface, which is equivalent to 1% to 90% an entire area of the second surface.

7. The battery cell according to claim 1, wherein the cell case is a pouch-shaped case made of a laminate sheet comprising a metal layer and a resin layer.

8. A battery pack comprising a battery cell according to claim 1 as a unit battery.

9. A device comprising a battery pack according to claim 8 as a power source.

10. The device according to claim 9, wherein the device is selected from among a mobile phone, a portable computer, a smart phone, a smart pad, a tablet PC, and a netbook computer.

11. The battery cell according to claim 1, wherein the pattern is formed in a portion of the second surface excluding a non-patterned area of the second surface near one end of the second surface, at which electrode tabs of the flexible electrode are located, and the opposite end of the second surface, wherein the non-patterned area is 30% or more of the entire area of the second surface.

12. The battery cell according to claim 11, wherein the non-patterned area is 40% or more of the entire area of the second surface.

13. The battery cell according to claim 12, wherein the non-patterned area is 50% or more of the entire area of the second surface.

14. A battery cell having an electrode assembly comprising two or more unit cells mounted in a variable cell case in a state in which the electrode assembly is impregnated with an electrolyte, wherein at least one of the unit cells comprises a flexible electrode that can be bent or curved, an electrode current collector of the flexible electrode comprises a first surface, to which an electrode active material is applied, and a second surface, to which no electrode active material is applied, the second surface being opposite to the first surface, and the second surface is provided with a pattern for improving flexibility of the electrode, wherein the pattern is a porous mesh structure comprising a plurality of pores, and wherein the pores of the porous mesh structure are recesses formed in the electrode current collector so as to be depressed in a thickness direction without extending through the entire thickness direction of the electrode current collector, wherein the flexible electrode is located at an outermost side of the electrode assembly such that the pattern of the second surface of the electrode current collector contacts an inner surface of the cell case, and wherein only the flexible electrode at the outermost side has a surface provided with a pattern.

15. The battery cell according to claim 14, wherein the porous mesh structure is configured such that each of the pores has a diameter of 0.1 mm to 1 mm.

16. The battery cell according to claim 14, wherein the porous mesh structure is configured such that the pores are arranged at intervals equivalent to 300% to 1000% a diameter of each of the pores.

17. The battery cell according to claim 14, wherein the cell case is provided at a portion of an inner surface thereof with a porous pattern configured to be brought into tight contact with the pattern formed in the second surface.

Description

DESCRIPTION OF DRAWINGS

(1) The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

(2) FIGS. 1 and 2 are exploded perspective views showing a conventional representative pouch-shaped secondary battery;

(3) FIG. 3 is a typical view showing an example of a unit cell that constitutes a battery cell according to an embodiment of the present invention;

(4) FIG. 4 is a typical view showing a flexible electrode of the unit cell shown in FIG. 3;

(5) FIG. 5 is a typical view showing a second surface of an electrode current collector of the flexible electrode shown in FIG. 4 when viewed from above;

(6) FIG. 6 is a typical view showing a modification of the flexible electrode shown in FIG. 4;

(7) FIGS. 7 to 9 are typical views showing other examples of the flexible electrode; and

(8) FIG. 10 is a perspective view showing a battery case having a lower case and an upper case that has a pattern configured to be brought into tight contact with the porous pattern formed in the second surface of the flexible electrode.

BEST MODE

(9) Now, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted, however, that the scope of the present invention is not limited by the illustrated embodiments.

(10) FIG. 3 is a view typically showing an example of a unit cell that constitutes a battery cell according to an embodiment of the present invention, and FIGS. 4 to 6 are typical views showing a flexible electrode of the unit cell shown in FIG. 3 in detail.

(11) Referring to these figures, a unit cell 200 is configured to have a structure in which a first electrode 210, which is a flexible electrode, a separator 201, a second electrode 220, a separator 201, and a first electrode 230 are sequentially stacked.

(12) The first electrodes 210 and 230 have a polarity opposite to that of the second electrode 220. For example, the unit cell 200 may be configured to have a structure in which a first electrode, which is a positive electrode, a separator, a second electrode, which is a negative electrode, another separator, and another first electrode, which is a positive electrode, are sequentially stacked. On the other hand, the unit cell 200 may be configured to have a structure in which a first electrode, which is a negative electrode, a separator, a second electrode, which is a positive electrode, another separator, and another first electrode, which is a negative electrode, are sequentially stacked.

(13) In the following description, one of the first electrodes 210 and 230 that is located at the uppermost end of the unit cell 200, i.e. the first electrode 210, is a flexible electrode. However, the present invention is not limited thereto.

(14) The flexible electrode 210 is located at the uppermost end of the unit cell 200. The flexible electrode 210 includes an electrode current collector 240 and an electrode active material layer 280.

(15) The electrode current collector 240 of the flexible electrode 210 has a first surface 260, to which an electrode active material is applied, and a second surface 250, to which no electrode active material is applied. The electrode active material layer 280 is applied to the first surface 260 such that the electrode active material layer 280 has a predetermined thickness. A porous mesh including pores 270, which extend vertically through the electrode current collector 240, is formed in the second surface 250.

(16) Electrode tabs 290 and 290 are formed at one end of the electrode current collector 240. The pores 270 are formed in the remaining area of the second surface 250 excluding the area of the second surface 250 near one end 291 of the electrode current collector 240, at which the electrode tabs 290 and 290 are located, and the opposite end 292 of the electrode current collector 240, which is equivalent to about 30% the entire area of the second surface 250.

(17) The pores 270 are formed in the second surface 250 in consideration of mechanical rigidity of the electrode current collector 240. In a case in which the pores 270 are formed over the entire area of the second surface 250 of the electrode current collector 240, deformability of the flexible electrode 210 is improved. However, the electrode current collector 240 may be damaged by the deformation of the flexible electrode 210. Furthermore, the contact area between the electrode current collector 240 and the electrode active material layer 280 is reduced, with the result that the electrode active material layer 280 may be easily separated from the surface of the electrode current collector 240. In the present invention, therefore, the mesh is formed over a region to which stress is greatly applied in response to deformation, such as bending or curving, i.e. the middle part of the second surface 250, at which the flexible electrode 210 is mainly deformed.

(18) The flexible electrode may be deformed as shown in FIG. 6. For example, a flexible electrode 210a may be deformed such that the end 291 of the electrode current collector 240, from which the electrode tabs 290 and 290 protrude, and the opposite end 292 are bent upward. In another example, a flexible electrode 210b may be deformed such that the other ends of the flexible electrode 210b, excluding the end 291 of the electrode current collector 240, from which the electrode tabs 290 and 290 protrude, and the opposite end 292, are bent. Although not shown, the flexible electrode may be bent twice, or may be twisted.

(19) FIGS. 7 to 9 are typical views showing other examples of the flexible electrode.

(20) Referring first to FIG. 7, an flexible electrode 310 is configured such that electrode tabs 390 and 390 are formed at one end of an electrode current collector 340 and such that a plurality of intaglios 370 is formed in the remaining area of a second surface 350 excluding the area of the second surface 350 near one end of the electrode current collector 340, at which electrode tabs 390 and 390 are located, and the opposite end of the electrode current collector 340, which is equivalent to about 40% the entire area of the second surface 350.

(21) The intaglios 370, which form an intaglio pattern, are formed in the second surface 350 of the electrode current collector 340 in straight lines that cross the second surface 350 in a lateral direction (in an x-axis direction). Each of the intaglios 370 is formed in the second surface 350 of the electrode current collector 340 such that each of the intaglios 370 has a shape of V in vertical section of the electrode current collector 340. The intaglio pattern 370 enables the flexible electrode 310 to be bent or curved in a longitudinal direction (in a y-axis direction).

(22) Meanwhile, a flexible electrode 410 shown in FIG. 8 is configured such that a lattice-type intaglio pattern 470 is formed in the remaining area of a second surface 450 excluding the area of the second surface 450 near one end of the flexible electrode 410, at which electrode tabs 490 and 490 are located, and the opposite end of the flexible electrode 410, which is equivalent to about 50% the entire area of the second surface 450. The lattice-type intaglio pattern 470 is configured such that intaglios are formed in a portion of the second surface 450 while intersecting each other in the longitudinal direction (in the y-axis direction) and the lateral direction (in the x-axis direction). As compared with the intaglio pattern shown in FIG. 7, the lattice-type intaglio pattern 470 enables the flexible electrode 410 to be bent or curved not only in the longitudinal direction (in the y-axis direction) but also in the lateral direction (in the x-axis direction). Furthermore, the lattice-type intaglio pattern 470 enables the flexible electrode 410 to be bent or curved in a diagonal direction (in a z-axis direction).

(23) Meanwhile, a flexible electrode 510 shown in FIG. 9 is configured such that a polygonal relief pattern 570 is formed in the remaining area of a second surface 550 excluding the area of the second surface 550 near one end of the flexible electrode 510, at which electrode tabs 590 and 590 are located, and the opposite end of the flexible electrode 510, which is equivalent to about 50% the entire area of the second surface 550.

(24) The relief pattern 570 may enable the flexible electrode 510 to be easily bent or curved in the same manner as the patterns 370 and 470 shown in FIGS. 7 and 8.

(25) In FIG. 10, a battery case 50 includes a lower case 52 and an upper case 53 that has a pattern configured to be brought into tight contact with the porous pattern formed in the second surface of the flexible electrode.

(26) As described above with reference to the drawings, the battery cell according to the present invention includes a flexible electrode that exhibits high flexibility and deformability based on the structural features thereof as described above. Consequently, the battery cell may be easily deformed. For example, the battery cell may be easily bent or curved. In addition, it is possible to solve a safety-related problem, which may occur when the battery cell is deformed, base on other features thereof, which will be described hereinafter.

(27) Specifically, the battery cell according to the present invention is configured such that a flexible electrode is located at the outermost side of an electrode assembly and such that a second surface of an electrode current collector of the flexible electrode, in which a mesh is formed, is exposed on a variable cell case. As a result, the surface area of the cell case is larger than the area of the electrode. In a case in which the battery cell is deformed in response to various designs of a device, therefore, a portion of the cell case corresponds to the mesh formed in the second surface, thereby maximally preventing unintended wrinkles from being formed in the cell case.

(28) Consequently, it is possible to effectively prevent dielectric breakdown or electrolyte leakage due to the exposure of a metal layer that is caused by wrinkles formed in the cell case when the battery cell is deformed, thereby securing the safety of the battery.

(29) Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

INDUSTRIAL APPLICABILITY

(30) As is apparent from the above description, a battery cell according to the present invention includes a flexible electrode having an electrode current collector configured to have a pattern structure for improving flexibility of the electrode. Consequently, it is possible to easily bend or curve the battery cell, whereby the battery cell is capable of precisely corresponding to a device having various designs or a flexible device, in which the battery cell is mounted.

(31) In addition, the battery cell according to the present invention is configured such that a flexible electrode is located at the outermost side of an electrode assembly and such that a second surface of an electrode current collector of the flexible electrode, in which a pattern is formed, is exposed on a variable cell case. As a result, the surface area of the cell case is larger than the area of the electrode. In a case in which the battery cell is deformed in response to various designs of a device, therefore, it is possible to maximally prevent unintended wrinkles from being formed in the cell case.