KR20140046614A - Electrode assembly having improved dropping impact stability - Google Patents

Abstract

The present invention relates to an electrode assembly which includes a positive electrode, a negative electrode, and a separator installed between the positive and negative electrodes, wherein a protection member surrounds the lower surface of the electrode assembly in a structure where a positive electrode terminal and a negative electrode terminal are protruding from the upper surface, and an outer surface contacting the lower surface, and more specifically, to an electrode assembly having improved drop impact stability.

Description

Electrode Assembly Having Improved Dropping Impact Stability}

The present invention relates to an electrode assembly constituting a lithium secondary battery, and more particularly, to an electrode assembly having improved 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 have been made to further develop conventional lithium secondary battery technology to expand application fields, such as electric power storage, as well as environment-friendly transportation systems such as electric vehicles, and the like.

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

In case of a short circuit between the anode and the cathode, there is a risk of rupture and ignition due to heat generation and temperature rise due to a large current discharge, and thus the role of the separator to isolate the anode and cathode is very important.

The inventors of the present application, the battery comprising an electrode assembly having a structure interposed between the positive electrode and the negative electrode and the electrode terminal protrudes on the upper surface, the lower surface of the electrode assembly free fall in the direction that collides with the ground In this case, it was confirmed that a problem occurs that the separator exposed to the outside is damaged on the bottom surface of the electrode assembly.

Accordingly, the inventors of the present application have completed the present invention based on the idea that the above problem can be solved when the protective member is formed at the lower end of the electrode assembly so as to minimize the damage of the separator due to the drop impact.

On the other hand, in the case of using a liquid electrolyte as the electrolyte, the boundary between the protective member and the electrode assembly is in contact with the liquid electrolyte, so that the liquid electrolyte can penetrate into a gap formed at such a boundary, which is a reason for the binding force of the protective member to the assembly. It may cause the deterioration.

In order to solve this 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 positive electrode includes a positive electrode sheet, a positive electrode plate, and a positive electrode plate, the following negative electrode includes a negative electrode sheet, a negative electrode plate, and a negative electrode plate, and the following separator is a concept including a separator sheet and a separator.

The positive electrode sheet, the negative electrode sheet, and the separator sheet mean a sheet-shaped anode, a sheet-type cathode, and a sheet-type separator, each of which is composed of one unit, and the anode plate, the cathode plate, and the separator are plate-shaped anodes cut into predetermined lengths, and plate-shaped. Means a negative electrode and a plate-shaped separator, respectively.

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 protective member is formed at its lower end, and the protective member surrounds the lower end so as to minimize the area of the boundary between the protective 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 a structure in which a separator is interposed between the positive electrode, the negative electrode, and the positive electrode and the negative electrode, and the positive electrode terminal and the negative electrode terminal protrude from the top surface.

In one embodiment, the electrode assembly according to the present invention is wound with the separator sheet positioned between the positive electrode sheet and the negative electrode sheet, the positive electrode terminal and the negative electrode terminal protrude from the upper surface, the lower surface and the lower surface The outer surface in contact with the surface may be a jelly-roll electrode assembly wrapped around the electrically insulating protective member.

Specifically, the jelly-roll electrode assembly is manufactured by stacking and winding them in the order of the positive electrode sheet, the separator sheet, and the negative electrode sheet so that the negative electrode is arranged at the winding center, and then attaching and fixing a sealing tape along the winding end line. . At this time, the anode sheet is located on the outermost side of the winding center. Therefore, in the above, the outer side surface becomes the outer side surface of the positive electrode sheet to which the positive electrode active material is not coated, and the protective member surrounds the outer side surface of the positive electrode sheet.

In general, since the size increases in the order of the positive electrode sheet, the negative electrode sheet, and the separator sheet size, the bottom surface has a structure in which the separator sheet having a larger size than the positive electrode sheet and the negative electrode sheet protrudes. Therefore, the corresponding portion of the protective member surrounding the bottom surface is in contact with or coupled to the separator sheet.

Since the shape of the top surface on which the electrode terminals are formed and the bottom surface on which the electrode terminals are not formed are not limited, the shape may be circular or polygonal. In addition, the protection member may be formed of one sheet-like unit to simultaneously wrap the bottom surface and the outer surface in contact with it, or two or more sheet-like units may be combined to wrap the bottom surface and the outer surface in contact with it.

The protective member having a structure consisting of one sheet-shaped unit and simultaneously surrounding the lower surface and the outer surface in contact with the lower surface may be, for example, a film coated with an adhesive or a pressure-sensitive adhesive on the substrate, but is not limited thereto. In this case, as described above, the separator sheet is adhered to one surface of the film. The substrate may be a polymer resin such as polypropylene, polypropylene sulfide, polyimide, and the like, but is not limited thereto.

In a specific embodiment, the top surface and the bottom surface has a curved edge or short side, the long side may be a rectangular shape consisting of a straight line, wherein the protective member is a sheet-shaped adhesive of one unit having the following development shape Or an adhesive film.

The unfolded shape of the sheet-like adhesive or dot film is a first rectangular portion corresponding to the shape of the bottom surface of the electrode assembly, a second rectangular portion sharing one long side of the first rectangular portion, and an opposite side of the first rectangular portion. Including a third rectangular region that shares the long side,

On both short sides of the second rectangular portion and the third rectangular portion, rectangular portions each having a length not exceeding the short side length of the first rectangular portion are respectively extended.

Both short sides of the first rectangular portion may have a shape in which a triangular portion having a height within a short side length of the second rectangular portion or the third rectangular portion is extended.

The protective member having the expanded shape includes the rectangular portions and the third rectangular portion, wherein the first rectangular portion surrounds the lower surface of the electrode assembly and extends on the short sides of the second rectangular portion and the second rectangular portion. The rectangular portions extending at the short sides of the third rectangular portions surround the outer surface contacting the bottom surface, and the outer surface wrapped with the rectangular portions are wrapped again with the triangular portions extending at the short sides of the first rectangular portion. Wrap the bottom surface and the outer surface in contact with it.

At this time, the triangular portion may overlap while covering all or part of the overlapping portions of the rectangular portions surrounding the outer surface. In addition, the triangular portions may overlap with each one of the rectangular portions in a state where the rectangular portions do not overlap 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. Similarly, 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 portion can be wrapped around the outer surface overlapping, the shape of the triangular portion and the rectangular portion is not limited to the triangle and the square. That is, the rectangular portion may be semicircular, polygonal or triangular, and the triangular portion may be rectangular, polygonal or semicircular.

Specifically, the lower end portion may be a portion corresponding to a height corresponding to 10 to 50% of the height between the lower surface and the upper surface, and thus, the protective member is 10 to 50 relative to the height between the lower surface and the upper surface. It may be bordered with the outer surface at a height corresponding to%. The boundary may form a single closed curve in plane along the outer surface. Thus, the area of the boundary in contact with the liquid electrolyte can be minimized.

In a specific embodiment, the boundary may have the same height or may be formed to have a height difference.

In another embodiment, an electrode assembly according to the present invention includes two or more unit electrodes in a stacked structure, and includes one unit between the first unit electrode and the second unit electrode that are adjacent to each other in the unit electrodes. The separator sheet is continuously interposed, the electrode plate of the first unit electrode and the electrode plate of the second unit electrode facing each other with the separator sheet interposed therebetween are arranged to have opposite polarities, and the positive electrode terminal and the negative electrode terminal have an upper surface. A stack-and-fold type electrode assembly protruding from the lower surface and the outer surface of the lower surface and the outer surface of the lower surface is surrounded by an electrically insulating protective member.

In the case of the stack-and-fold 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 interposed therebetween should be arranged to have opposite polarities. In the case of a single positive electrode plate, the second unit electrode may be a single electrode plate or a stacked 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 may be arranged such that the electrode plates facing each other with the separator sheet therebetween have polarities opposite to each other.

The stack-and-fold type electrode assembly is 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, a protective member is formed on the outer surface of the separator sheet. do. Except for this, it is the same as 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-fold type electrode assembly is housed in a case, impregnated with an electrolyte, and sealed. The lithium secondary battery may be a circular battery, a square battery, a pouch type battery, and specifically, the case may be a square battery having a rectangular can shape.

Since manufacturing methods or manufacturing methods of the positive electrode active material, the negative electrode active material, the positive electrode, the negative electrode, the separator, and the lithium secondary battery are already known in the art, a detailed description thereof will be omitted.

As described above, by wrapping the lower surface of the electrode assembly and the outer surface of the electrode assembly with a protective member having a structure that can minimize the area of the boundary in contact with the liquid electrolyte, the electrode assembly according to the present invention, There is an advantage that 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 protective member is mounted on a lower end of a jelly-roll electrode assembly;
FIG. 3 is a side view in the S direction of the electrode assembly of FIG. 2; FIG.
4 is a top view of the electrode assembly of FIG. 2;
FIG. 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 diagram schematically illustrating a case in which the protective member is separated from the electrode assembly in FIG. 5; FIG.
7 is a perspective view of an electrode assembly according to the present invention;
FIG. 8 is a side view in the S direction of the electrode assembly of FIG. 7; FIG.
9 is a top view of the electrode assembly of FIG. 7;
10 is an exploded view of a protection member according to an embodiment of the present invention.

Hereinafter, although described with reference to the drawings and experimental examples according to an embodiment of the present invention, this is for easier understanding of the present invention, the scope of the present invention is not limited thereto.

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

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

The jelly-roll electrode assembly 100 is wound such that the negative electrode sheet 30 is located at the winding center and the positive electrode sheet 10 is located at the outermost side from the winding center, and the sealing tape 50 is further removed to maintain the winding shape. It is attached to the side surface, and the negative terminal 43 and the positive terminal 47 protrude on the upper surface. At this time, the outer surface with the sealing tape 50 attached to the outer surface of the positive electrode sheet 10 is a surface 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 a lower surface of the jelly-roll electrode assembly 100 of FIG. 1 and a part of an outer surface of the jelly-roll electrode assembly 100. Since the size increases in the order of the positive electrode sheet 10, the negative electrode sheet 30, and the separator sheet 20, the separator sheet 20 is adhered to the adhesive tape 70 at the bottom surface of the jelly-roll electrode assembly 100. It is.

Referring to FIG. 3, when the jelly-roll electrode assembly 100 of FIG. 2 is viewed in the S direction, a portion of the outer surface of the jelly-roll electrode assembly 100 is not attached to the adhesive tape 70. You can check it. 4, which is a plan view of the jelly-roll electrode assembly 100 of FIG. 2, the adhesive tape 70 is not attached to the bottom surface of the jelly-roll electrode assembly 100 and a part of the outer surface thereof. Is shown more clearly.

The above-described 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 soaked in the adhesive force of the adhesive tape 70 It may cause the deterioration.

In this regard, referring to FIG. 6, in the cell 200 in which the jelly-roll electrode assembly 100 of FIG. 2 is housed together with a liquid electrolyte (not shown) in the case 110, the liquid electrolyte infiltrates into the liquid electrolyte. When the adhesive force of the adhesive tape 70 is lowered by this, the adhesive tape 70 is separated from the outer surface of the jelly-roll electrode assembly 100 and also falls from the separator sheet 20 adhered thereto. As a result, a phenomenon in which the separator sheet 20 is rolled up occurs.

FIG. 7 illustrates a jelly-roll electrode assembly 100 according to an embodiment of the present invention. The difference from the electrode assembly of FIG. 2 is that the bottom surface and all of the outer surfaces thereof contact the adhesive tape 70. It is wrapped.

Referring to FIGS. 8 and 9 together, unlike FIGS. 3 and 4, it can be clearly seen that all of the lower surface and the outer surface contacting the lower surface are wrapped with the adhesive tape 70. This means that the space through which the liquid electrolyte can penetrate is reduced compared to the structure of the conventional adhesive tape. In particular, the adhesive tape surrounding the outer surface is overlapped, that is, in the case of the jelly-roll electrode assembly 100 according to the present invention, the liquid electrolyte soaks only to the boundary 80 formed at a predetermined height from the lower surface. Can be mentioned.

FIG. 10 schematically illustrates a development of the adhesive tape 70 according to one embodiment. Referring to this, the adhesive tape 70 may include a first rectangular portion 65 corresponding to the shape of the bottom surface of the electrode assembly, a second rectangular portion 63 sharing one long side of the first rectangular portion 65, and a first rectangular portion 65. A third rectangular portion 68 sharing the opposite long side of the first rectangular portion 65, and both short sides of the second rectangular portion 63 and the third rectangular portion 68 have a first rectangular portion 65; Square portions 63a, 63b, 68a, and 68b each having a length not exceeding the short side length of) are extended, and both short sides of the first rectangular portion 65 have a second rectangular portion 63 or a third portion. The triangular portions 65a and 65b having a height within the short side length of the rectangular portion 68 have an expanded shape.

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 separator sheet is wound with the separator sheet positioned between the positive electrode sheet and the negative electrode sheet, the positive electrode terminal and the negative electrode terminal protrude from the upper surface, and an electrically insulating protective member surrounds the lower surface and the outer surface in contact with the lower surface. Jelly-roll type electrode assembly, characterized in that. The jelly-roll electrode assembly of claim 1, wherein the top and bottom surfaces are curved in corners or short sides, and the long sides are rectangular in shape. The jelly-roll type electrode assembly of claim 1, wherein the protection member is formed of one sheet-like unit, and simultaneously surrounds a lower surface and an outer surface of the lower surface. According to claim 3, The deployment shape of the protective member,
A first rectangular portion corresponding to the shape of the bottom surface of the electrode assembly, a second rectangular portion sharing one long side of the first rectangular portion, and a third rectangular portion sharing an opposite long side of the first rectangular portion; ,
Both short sides of the second rectangular portion and the third rectangular portion each extend a rectangular portion having a length not exceeding the short side length of the first rectangular portion;
Both sides of the first rectangular portion of the jelly-roll electrode assembly, characterized in that a triangular portion having a height within the short side length of the second rectangular portion or the third rectangular portion is extended. 5. The jelly-roll electrode assembly of claim 4, wherein the triangular portion covers all or a portion of the overlapping portion of the rectangular portions. The jelly-roll electrode assembly of claim 4, 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 electrode assembly of 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 and upper surfaces. 8. The jelly-roll electrode assembly of claim 7, wherein the boundary forms a single closed curve in plane along the outer surface. 8. The jelly-roll electrode assembly of claim 7, wherein the boundary has the same height. 8. A jelly-roll electrode assembly as recited in claim 7, wherein said 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 a pressure-sensitive adhesive is applied. The jelly-roll electrode assembly of claim 1, wherein the protection member surrounds an outer circumferential surface of the positive electrode sheet. The jelly-roll type electrode assembly of claim 12, wherein the cathode sheet is coated with a cathode material layer only on an inner surface of the cathode sheet in contact with the separator sheet. The jelly-roll type electrode assembly of claim 1, wherein the protection member is coupled to the separator sheet at the bottom surface. A lithium secondary battery, wherein the jelly-roll type electrode assembly according to claim 1 is housed in a case and impregnated with an electrolyte. The lithium secondary battery of claim 15, wherein the case has a rectangular can shape. Two or more unit electrodes form a stacked structure, and a separator sheet of one unit 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 separator sheet is interposed therebetween. The pole plate of the first unit electrode and the pole plate of the second unit electrode facing each other are arranged to have opposite polarities, and the positive electrode terminal and the negative electrode terminal protrude from the top surface, and the bottom surface and the outer surface in contact with the bottom surface. Stacking and folding electrode assembly characterized in that the electrically insulating protective member is wrapped. 18. The stack-and-fold electrode assembly of claim 17, wherein the first unit electrode is a single anode plate and the second unit electrode is a single cathode plate. 18. The stack-and-fold type electrode assembly of claim 17, wherein the first unit electrode and / or the second unit electrode is a stacked electrode body including a structure in which a separator is positioned between the positive electrode plate and the negative electrode plate. 20. The stack-and-fold electrode assembly according to claim 19, wherein the stacked electrode body is a D-type stacked electrode body laminated so that polarities of the uppermost electrode plate and the lowermost electrode plate are opposite to each other. 20. The stack-and-fold electrode assembly according to claim 19, wherein the stacked electrode body is an S-type stacked electrode laminated so that the polarities of the uppermost electrode plate and the lowermost electrode plate are the same.

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