KR101545885B1 - Electrode Assembly Having Improved Dropping Impact Stability - Google Patents

Abstract

The present invention relates to an electrode assembly including a positive electrode, a negative electrode, a separator interposed between an anode and a cathode, and a lower end surface of the electrode assembly having a structure in which a cathode terminal and a cathode terminal protrude from a top surface, And more particularly, to an electrode assembly having improved stability against drop impact.

Description

[0001] The present invention relates to an electrode assembly having improved drop impact stability,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an electrode assembly constituting a lithium secondary battery, and more particularly, to an electrode assembly improved in drop impact stability.

As information technology (IT) technology has developed remarkably, various portable information and communication devices have been spreading, so that the 21st century is being developed into a "ubiquitous society" capable of providing high quality information services regardless of time and place.

As a development base for such a ubiquitous society, a lithium secondary battery occupies an important position.

The lithium secondary battery has a higher operating voltage and energy density than other secondary batteries and can be used for a long time, so that it can meet the complex requirements for diversification and combination of devices.

In recent years, efforts to develop the conventional lithium secondary battery technology to expand application fields not only in environmentally friendly transportation systems such as electric vehicles but also in electric power storage have been actively promoted all over the world.

Among the components of the lithium secondary battery (hereinafter referred to as a battery), the electrode assembly has a structure in which a separator is interposed between the positive electrode and the negative electrode. The separator itself is an inert material that does not participate in an electrochemical reaction, but it also provides a path through which lithium ions migrate and separates the physical contact between the anode and the cathode.

If there is a short circuit between the anode and the cathode, there is a risk of heat generation due to large current discharge and rupture and ignition due to temperature rise. Therefore, the role of the separator for isolating the anode and the cathode is very important.

The inventors of the present application have found that a battery including an electrode assembly having a structure in which a separator is interposed between an anode and a cathode and electrode terminals protrude from an upper surface of the battery includes a case in which a bottom surface of the electrode assembly falls freely , It is confirmed that there is a problem that the separation film exposed to the outside from the lower end surface of the electrode assembly is damaged.

The present inventors have completed the present invention based on the idea that when the protection member is formed at the lower end of the electrode assembly to minimize the damage of the separation membrane due to the falling impact, the above problem can be solved.

On the other hand, when a liquid electrolyte is used as the electrolyte, since the boundary between the protection member and the electrode assembly contacts the liquid electrolyte, the liquid electrolyte can permeate into the gap formed at the boundary, It may cause degradation.

In order to solve such a problem, the inventors of the present application have devised a protective member having a structure in which the area of the boundary in contact with the liquid electrolyte can be minimized.

In the present specification, the following anode includes a cathode sheet, a cathode plate and an anode electrode plate, and the following cathode includes a cathode sheet, a cathode plate and a cathode plate, and the following separator includes a separator sheet and a separator.

Each of the positive electrode sheet, the negative electrode sheet and the separator sheet means a sheet-like positive electrode and a sheet-like negative electrode and sheet-like separator which are formed at one end. The positive electrode plate, Respectively, of the cathode and the plate.

The unit electrode is a concept including a plate-like electrode plate, an electrode plate, or a stacked structure thereof cut to a predetermined length. Therefore, the first unit electrode may be a single positive electrode plate or a single negative electrode plate, and may be a laminated electrode body including a structure in which a separation membrane is disposed between the positive electrode plate and the negative electrode plate.

The first unit electrode and the second unit electrode are arbitrarily divided into unit electrodes in order to facilitate understanding of the structure of the stack and folding type electrode assemblies described below. Therefore, like the first unit electrode, The electrode may be a single negative electrode plate, a single positive electrode plate, or a laminated electrode body including a structure in which a separation membrane is disposed between a positive electrode plate and a negative electrode plate.

At this time, the laminated electrode body is composed of the D-shaped laminated electrode body laminated so that the polarities of the uppermost electrode plate and the lowermost electrode plate are opposite to each other, or the S-shaped laminated electrode unit laminated so that the polarities of the uppermost electrode plate and the lowermost electrode plate are equal to each other .

The electrode assembly according to the present invention is characterized in that a protection member is formed at a lower end portion thereof and the protection member surrounds the lower end portion to minimize the area of the boundary between the protection member and the electrode assembly in contact with the liquid electrolyte.

The electrode assembly according to the present invention is not limited as long as it is an electrode assembly having an anode, a cathode, a separator interposed between the anode and the cathode, and a cathode terminal and a cathode terminal protruding from the upper surface.

In one embodiment, the electrode assembly according to the present invention is wound in a state in which a separator sheet is positioned between a positive electrode sheet and a negative electrode sheet, and a positive electrode terminal and a negative electrode terminal protrude from the top surface, And a jelly-roll electrode assembly in which an electrically insulating protective member encloses an outer surface in contact with the surface.

Specifically, the jelly-roll type electrode assembly is manufactured by laminating and winding up a positive electrode sheet, a separator sheet and a negative electrode sheet in this order so that the negative electrode is arranged at the winding center, and then attaching and fixing a sealing tape along the winding termination line . At this time, the positive electrode sheet is located at the outermost side from the winding center. Thus, the outer surface is the outer surface of the positive electrode sheet to which the positive electrode active material is not applied, and the protective member covers the outer surface of the positive electrode sheet.

Generally, the size of the anode sheet, the cathode sheet, and the separator sheet increases in the order of the size, so that the lower end surface of the separator sheet protrudes larger than the anode sheet and the cathode sheet. Thus, the corresponding portion of the protective member surrounding the bottom surface is in contact or bonding with the separator sheet.

The shape of the upper end surface on which the electrode terminals are formed and the lower end surface on which the electrode terminals are not formed is not limited and may be circular or polygonal. In addition, the protective member may be formed of one sheet-like unit, and may be wound around the lower end surface and the outer surface contacting with the lower end surface at the same time, or two or more sheet-like units may be combined to cover the lower end surface and the outer surface contacting therewith.

The protective member made of a sheet-like unit and simultaneously enclosing the bottom surface and the outer surface in contact with the bottom surface may be, for example, a film on which an adhesive or a pressure-sensitive adhesive is applied, but the present invention is not limited thereto. In this case, the separator sheet is bonded to one surface of the film as described above. The substrate may be a polymer resin such as polypropylene, polypropylene sulfide, or polyimide, but is not limited thereto.

In a specific embodiment, the upper end surface and the lower end surface may be in the shape of a rectangle having corners or short side curves and the long side being a straight line. At this time, the protective member may be a sheet- Or an adhesive film.

Wherein the deployed shape of the sheet-like adhesive or cladding film has a first rectangular portion corresponding to a bottom surface shape of the electrode assembly, a second rectangular portion sharing one side long side of the first rectangular portion, and a second rectangular portion corresponding to the opposite side of the first rectangular portion A third rectangular region sharing a long side,

A rectangular portion having a length not exceeding a short side length of the first rectangular portion is extended to both short sides of the second rectangular portion and the third rectangular portion,

A triangular portion having a height within a short side length of the second rectangular portion or the third rectangular portion may be formed on both short sides of the first rectangular portion.

The protective member having the deployed shape may include a rectangular portion and a third rectangular portion that surround the lower end surface of the electrode assembly and extend in a short side of the second rectangular portion and the second rectangular portion, The outer surface of the third rectangular portion extending in the short side of the third rectangular portion surrounds the outer surface in contact with the bottom surface, and the outer surface of the rectangular portion is surrounded by the triangular portions extended in the short side of the first rectangular portion. And covers the bottom surface and the outer surface in contact therewith.

At this time, the triangular portion may overlap all or a part of the overlapping portions of the rectangular portions surrounding the outer surface. In addition, the triangular portion may overlap with one square portion in a state where the rectangular portions do not overlap with each other.

At least one of the rectangular portions extending from both short sides of the second rectangular portion and the third rectangular portion may share a vertex with the short sides of the second rectangular portion and the third rectangular portion. Likewise, at least one of the triangular portions extending from both short sides of the first rectangular portion may share a vertex with the short side of the first rectangular portion.

If the triangular portion and the rectangular portions can be wrapped around the overlapping outer surface, the shapes of the triangular portion and the rectangular portion are not limited to the triangle and the square. That is, the rectangular area may be semicircular, polygonal, or triangular, and the triangular area may be rectangular, polygonal, or semicircular.

Specifically, the lower end may be a portion corresponding to a height corresponding to 10 to 50% of the height between the lower end face and the upper end face. Accordingly, the protection member may have a height of 10 to 50 % ≪ / RTI > at the corresponding height. The boundary may form a single closed curve in plan view along the outer surface. Thus, the area of the boundary in contact with the liquid electrolyte can be minimized.

In a specific embodiment, the boundaries may have the same height and be formed with a height difference.

In another embodiment, the electrode assembly according to the present invention has a structure in which two or more unit electrodes form a laminated structure, and between the first unit electrode and the second unit electrode which are adjacent to each other in the unit electrodes, And the electrode plate of the first unit electrode and the electrode plate of the second unit electrode facing each other with the separator sheet therebetween are arranged so as to have opposite polarities with each other, And the outer surface contacting the lower end surface and the lower end surface is surrounded by an electrically insulating protective member.

In the case of such a stack and folding type electrode assembly, the electrode plate of the first unit electrode and the electrode plate of the second unit electrode facing each other with the separator sheet therebetween must be arranged to have opposite polarities, In the case of a single positive electrode plate, the second unit electrode may be a single negative electrode plate or a laminated electrode body including a negative electrode plate facing the single positive electrode plate.

Even when the first unit electrode and the second unit electrode are laminated electrode bodies, they can be arranged so that the polar plates facing each other with the separator sheet therebetween have opposite polarities.

The stack and folding type electrode assemblies are manufactured by arranging the first unit electrode and the second unit electrode on the separator sheet and then winding the separator sheet. Thus, unlike the jelly-roll type electrode assembly, the protection member is formed on the outer surface of the separator sheet do. Except for this, it is the same as that already described in the jelly-roll type electrode assembly.

The present invention provides a lithium secondary battery in which the jelly-roll type electrode assembly or the stack and folding type electrode assembly described above is housed in a case, impregnated with an electrolyte, and then sealed. The lithium secondary battery may be a circular battery, a prismatic battery, or a pouch-type battery. Specifically, the lithium secondary battery may be a prismatic battery having a square can shape.

The manufacturing method or the manufacturing method of the cathode active material, the anode active material, the anode, the cathode, the separator, and the lithium secondary battery are already well known in the related art, and a detailed description thereof will be omitted.

As described above, by covering the lower end surface of the electrode assembly and the outer surface contacting with the lower surface of the electrode assembly with the protective member having a structure in which the area of the boundary contacting the liquid electrolyte can be minimized, the electrode assembly according to the present invention, The stability is improved. This has the effect of improving the stability of the battery.

1 is a perspective view of a conventional jelly-roll electrode assembly;
2 is a perspective view schematically showing a form in which a protection member is mounted on a lower end of a jelly-roll electrode assembly;
3 is a side view in the direction of S of the electrode assembly of FIG. 2;
Figure 4 is a plan view of the electrode assembly of Figure 2;
5 is a diagram schematically showing a state in which the electrode assembly of Fig. 2 is mounted in a case; Fig.
Fig. 6 is a view schematically showing the case where the protection member is detached from the electrode assembly in Fig. 5;
7 is a perspective view of an electrode assembly according to the present invention;
8 is a side view in S direction of the electrode assembly of Fig. 7;
Figure 9 is a plan view of the electrode assembly of Figure 7;
10 is an exploded view of a protective member according to one embodiment of the present invention.

Hereinafter, the present invention will be described with reference to the drawings and experimental examples. However, the present invention is not limited by the scope of the present invention.

Referring to FIGS. 1 and 5 together, the battery 200 has a structure in which a jelly-roll electrode assembly 100 and an electrolyte (not shown) are housed in a case 110.

The jelly-roll electrode assembly 100 includes a positive electrode sheet 10, a separator sheet 20, a negative electrode sheet 30, and a sealing tape 50.

In the jelly-roll electrode assembly 100, the negative electrode sheet 30 is positioned at the winding center, and the positive electrode sheet 10 is wound on the outermost side from the winding center. And a negative electrode terminal 43 and a positive electrode terminal 47 protrude from the top surface. At this time, the outer surface to which the sealing tape 50 is attached is the outer surface of the positive electrode sheet 10 on which the positive electrode active material is not coated. An insulating tape (60) is wound around the negative electrode terminal (43).

2 and 5, an adhesive tape 70 is attached to the lower end surface of the jelly-roll electrode assembly 100 of FIG. 1 and a part of the outer surface thereof. The separator sheet 20 is adhered to the adhesive tape 70 at the lower end surface of the jelly-roll electrode assembly 100 because the anode sheet 10, the cathode sheet 30 and the separator sheet 20 become larger in this order. .

Referring to FIG. 3, when the jelly-roll electrode assembly 100 of FIG. 2 is viewed from the S direction, the adhesive tape 70 is not attached to a part of the outer surface of the jelly- Can be confirmed. 4 showing a plan view of the jelly-roll electrode assembly 100 of FIG. 2, the adhesive tape 70 is not attached to the lower end surface of the jelly-roll electrode assembly 100, As shown in FIG.

The liquid electrolyte (not shown) may penetrate into a gap formed at the boundary between the jelly-roll electrode assembly 100 and the adhesive tape 70, and the liquid electrolyte thus impregnated may adhere to the adhesive tape 70 Which may be a cause for lowering the temperature.

In this regard, referring to FIG. 6, in the battery 200 in which the jelly-roll electrode assembly 100 of FIG. 2 is housed in a case 110 together with a liquid electrolyte (not shown), a liquid electrolyte The adhesive tape 70 is separated from the outer surface of the jelly-roll electrode assembly 100 and falls off from the separator sheet 20 adhered to the jelly-roll electrode assembly 100, As a result, the separator sheet 20 is rolled up.

7 shows a jelly-roll electrode assembly 100 according to one embodiment of the present invention. The difference from the electrode assembly of FIG. 2 is that the bottom surface and all of the outer surface in contact therewith are bonded to the adhesive tape 70 It is wrapped.

Referring to FIGS. 8 and 9, it can be clearly seen that, unlike in FIGS. 3 and 4, the bottom surface and all of the outer surface in contact with the bottom surface are covered with the adhesive tape 70. This means that the space through which the liquid electrolyte can permeate is reduced as compared with the structure of the conventional adhesive tape. In particular, in the case of the jelly-roll electrode assembly 100 according to the present invention, the liquid electrolyte seeps only at the boundary 80 formed at a predetermined height from the lower end surface, .

10 schematically shows a developed shape of the adhesive tape 70 according to one embodiment. Referring to this, the adhesive tape 70 includes a first rectangular portion 65 corresponding to the lower end surface shape of the electrode assembly, a second rectangular portion 63 sharing one side long side of the first rectangular portion 65, And a third rectangular region 68 that shares the opposing long side of the first rectangular region 65. The second rectangular region 63 and the third rectangular region 68 include the first rectangular region 65 63b, 68a, and 68b each having a length not exceeding the short side length of the first rectangular portion 65 and the second rectangular portion 63 or the third rectangular portion 63b are formed on both short sides of the first rectangular portion 65, And has a deployed shape in which the triangular portions 65a and 65b having a height within the short side length of the rectangular portion 68 are extended.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.

Claims (21)

The positive electrode terminal and the negative electrode terminal are protruded from the upper surface, and the outer surface contacting the lower end surface and the lower end surface is wrapped by an electrically insulating protective member ,
Wherein the protective member is formed of one sheet-like unit and simultaneously surrounds the lower surface and the outer surface contacting the lower surface,
The deployed shape of the protective member
A first rectangle portion corresponding to a bottom surface shape of the electrode assembly, a second rectangle portion sharing one side long side of the first rectangle portion, and a third rectangle portion sharing an opposite long side of the first rectangle portion ,
A rectangular portion having a length not exceeding a short side length of the first rectangular portion is extended to both short sides of the second rectangular portion and the third rectangular portion;
Wherein a triangular portion having a height within a short side length of the second rectangular portion or the third rectangular portion is extended to both short sides of the first rectangular portion. The jelly-roll type electrode assembly according to claim 1, wherein the upper surface and the lower surface of the jelly-roll type electrode assembly are curved at an edge or a short side, and the long side is a rectangle having a straight line. delete delete The jelly-roll type electrode assembly according to claim 1, wherein the triangular portion covers all or a part of the overlapping portion of the rectangular portions. The jelly-roll type electrode assembly according to claim 1, wherein at least one of the rectangular portions extending from both short sides of the second rectangular portion and the third rectangular portion shares a vertex with the short side. The jelly-roll type electrode assembly according to claim 1, wherein the protection member forms a boundary with the outer surface at a height corresponding to 10 to 50% of the height between the lower end surface and the upper end surface. The jelly-roll type electrode assembly according to claim 7, wherein the boundary forms a single closed curve in plan view along an outer surface. 8. The jelly-roll type electrode assembly of claim 7, wherein the boundaries have the same height. 8. The jelly-roll type electrode assembly of claim 7, wherein the boundary has a height difference. The jelly-roll type electrode assembly according to claim 1, wherein the protective member is a film on which an adhesive or an adhesive is applied. The jelly-roll type electrode assembly according to claim 1, wherein the protective member covers an outer circumferential surface of the positive electrode sheet. The jelly-roll type electrode assembly according to claim 12, wherein the positive electrode sheet is coated with a positive electrode layer only on an inner surface thereof in contact with the separator sheet. The jelly-roll type electrode assembly according to claim 1, wherein the protective member is coupled to a separator sheet at a bottom surface. A jelly-roll type electrode assembly according to claim 1, which is housed in a case, impregnated with an electrolyte, and then sealed. The lithium secondary battery according to claim 15, wherein the case has a rectangular can shape. Wherein two or more unit electrodes form a laminated structure and one unit of separator sheet is continuously interposed between the first unit electrode and the second unit electrode which are adjacent to each other in the unit electrodes, And the positive electrode terminal and the negative electrode terminal are protruded from the top surface, and the bottom surface and the bottom surface of the second unit electrode facing the bottom surface An electrically insulating protective member surrounds the side surface,
Wherein the protective member is formed of one sheet-like unit and simultaneously surrounds the lower surface and the outer surface contacting the lower surface,
The deployed shape of the protective member
A first rectangle portion corresponding to a bottom surface shape of the electrode assembly, a second rectangle portion sharing one side long side of the first rectangle portion, and a third rectangle portion sharing an opposite long side of the first rectangle portion ,
A rectangular portion having a length not exceeding a short side length of the first rectangular portion is extended to both short sides of the second rectangular portion and the third rectangular portion;
And a triangular portion having a height within a short side length of the second rectangular portion or the third rectangular portion is extended to both short sides of the first rectangular portion. 18. The stack and folding type electrode assembly of claim 17, wherein the first unit electrode is a single cathode plate and the second unit electrode is a single cathode plate. 18. The stacking and stacking method according to claim 17, wherein the first unit electrode or the second unit electrode, or the first unit electrode and the second unit electrode are stacked electrodes including a structure in which a separator is disposed between the anode and the cathode. A folding type electrode assembly. The stack and folding type electrode assembly according to claim 19, wherein the laminated electrode body is a D-shaped laminated electrode in which polarities of the uppermost electrode plate and the lowermost electrode plate are opposite to each other. 20. The stack and folding type electrode assembly according to claim 19, wherein the laminated electrode body is an S-shaped laminated electrode in which the uppermost electrode plate and the lowermost electrode plate have the same polarity.

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