JPH10270068A - Rectangular battery and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an active layer from cracking or falling and eliminate electric short between positive and negative electrode sheets, by winding a both-electrode sheet which includes a positive sheet and a negative sheet having lack part of active material to provide a flat wound assembly, and positioning the lack part of active material at a turn end of the most inside of the winding. SOLUTION: The assembling sheet A consists of a positive electrode sheet 1 which includes a positive electrode collector 11 and positive electrode active materials 12, 12' placed respectively on its both surfaces, a negative electrode sheet 2 which includes a negative electrode collector 21 and negative electrode active materials 22, 22' placed respectively on its both surfaces, and separators 3, 3', and is wound such that the separator is inside. The positive electrode active materials 12, 12' and the negative electrode active materials 22, 22' in part of the assembly sheet A which is positioned at the turn end B of the most inside of the winding are lacked so that the positive electrode collector 11 and the negative electrode collector 21 are unwrapped. Because no active material layer exists at the turn end B even when the flat wound assembly is compressed to remove a space S, problem of electric short does not occur.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prismatic battery and a method of manufacturing the same, and more particularly, to a prismatic battery suitable as a prismatic secondary battery having a nonaqueous liquid electrolyte, for example, a prismatic lithium secondary battery, and the like. It relates to a manufacturing method.

[0002]

2. Description of the Related Art Various electric devices, especially portable personal computers and telephones, are required to be further reduced in weight and size, and from this requirement, batteries used for them can be accommodated in a compact small storage space. The development of prismatic batteries is needed.

FIG. 7 is a perspective view of an electrode element used in a conventional prismatic lithium secondary battery. In FIG.
1 is a positive electrode sheet and 2 is a negative electrode sheet. Although not shown, a separator is interposed between the positive and negative bipolar sheets 1 and 2 in the electrode element, and three layers of the positive and negative bipolar sheets 1 and 2 and the separator are formed as one set, and further between each pair. The positive electrode sheet 1 and the negative electrode sheet 2 have a structure in which a large number of sets are laminated with one layer of separator interposed therebetween.
Are electrically connected to each other. In a secondary battery such as a lithium secondary battery, the battery capacity is proportional to the amount of the positive electrode active material of the positive electrode sheet. Therefore, when the thickness of the positive electrode active material layer of the positive electrode sheet is increased, the amount of the positive electrode active material per unit area of the positive electrode sheet is increased. Capacity can be secured. However, in practice, a normal positive electrode active material layer is poor in electric conductivity, so that when it is made thick, the electric resistance becomes excessively large, and the battery action is adversely reduced. For this reason, a method of increasing the number of stacks in order to ensure a required battery capacity in an electrode area by making the positive electrode active material layer thinner is employed. However, when the number of stacked sets is increased, the number of electrical connections by the connection wires 4 which requires a lot of work is increased, and mass production of batteries becomes difficult.

FIG. 8 is a perspective view of another electrode element used in a conventional prismatic lithium secondary battery, wherein the electrode element is a long assembly comprising a positive electrode sheet, a negative electrode sheet, and a separator. Body sheet A is a flat core (not shown)
It is a flat-shaped wound body obtained by winding it up and then removing the core. In this wound body, the necessary electrode area and the battery capacity can be secured by increasing the number of windings, so that there is no problem with the laminate shown in FIG. However, since the flat wound body is manufactured by winding the above-mentioned aggregate sheet A on a flat core body and removing the core body after winding, a space S corresponding to the core volume is provided at the center thereof. However, due to the presence of the space S, the space factor of the positive electrode sheet and the negative electrode sheet in the flat wound body decreases, and as a result, there is a problem that the volume energy density of the flat wound body decreases.

The inventor of the present invention compressed the flat wound body from both sides in the direction shown by the arrow in FIG. 8 in order to improve the volume energy density of the flat wound body, and reduced the space at the center thereof. Attempted to erase. 9 is an enlarged cross-sectional view of the innermost part of the flat wound body before compression, that is, a portion indicated by B in FIG. 8, and FIG. 10 is an enlarged cross-sectional view of the same portion after compression. 9 and 10, the aggregate sheet A
Are a positive electrode sheet 1 composed of a positive electrode current collector 11 and positive electrode active material layers 12 and 12 ′ provided on both surfaces thereof, and a negative electrode current collector 2.
1 and negative electrode active material layers 22 and 22 'provided on both surfaces thereof, and a negative electrode sheet 2 and separators 3 and 3', which are wound with the separator 3 inside. S
Is a space existing at the center of the flat wound body before compression.
After the compression shown in FIG. 10, the space S has disappeared, and the inner surfaces of the separator 3 are in contact with each other.

By eliminating the space S, the volume energy density of the flat wound body is improved. However, due to the compression for eliminating the space S, the positive electrode sheet 1 and the negative electrode sheet 2 are extremely bent at the position indicated by B, which is the innermost position, in other words, at the position located at the innermost turn end of the winding. A new problem arises in that the active material layers are cracked, some of the active material layers are dropped, and the positive and negative bipolar sheets are electrically short-circuited. In some cases, such cracking or falling off of the positive electrode active material layer may occur on B, that is, at the position located at the turn end shown by C in FIG.

[0007]

However, according to the present invention, even when the flat wound body is compressed, the active material layer is cracked or dropped at a location located at the innermost end of the wound body or at a turn end in the vicinity thereof. It is an object of the present invention to provide a prismatic battery in which the problem of an electrical short circuit between the positive and negative electrode sheets caused by the problem is solved and a method of manufacturing the same.

[0008]

The present invention has the following features. (1) A flat wound body formed by winding positive and negative bipolar sheets including a positive electrode sheet and / or a negative electrode sheet having an active material lacking portion in which an active material layer is missing over the entire length in a direction orthogonal to the longitudinal direction of the sheet. And the active material lacking portion is located at least at the innermost turn end of the winding. (2) The prismatic battery according to the above (1), wherein the flat wound body is subjected to a compression treatment so as to narrow or eliminate a space at the center of the wound. (3) Positive and negative bipolar sheets including a positive electrode sheet and / or a negative electrode sheet having an active material lacking portion in which an active material layer is missing over the entire length in a direction orthogonal to the longitudinal direction of the sheet are wound on a flat core to form an active material. Obtain a wound body where the missing part is located at least at the innermost turn end of the winding, then remove the flat core to compress the wound body, and remove the space remaining after removing the flat core. A method for manufacturing a prismatic battery, comprising erasing to obtain a flat wound body.

[0009]

The active material layer in at least the portion of the flat wound body located at the turn end of the innermost positive electrode sheet and / or the negative electrode sheet has been removed in advance, for example, in the form of a slit. Even if it is compressed to eliminate the space existing in the center thereof, the problem of cracking or falling off of the active material layer and the resulting electrical short circuit between the positive and negative electrode sheets can be solved.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the drawings. FIG. 1 is a partial cross-sectional view of an embodiment of the present invention, FIG. 2 is a partial cross-sectional view after compressing the embodiment shown in FIG. 1, and FIGS. 3 and 4 are a positive electrode sheet and a negative electrode sheet used in the manufacturing method of the present invention. Top view of FIG. 5 (a)
FIG. 5B is an enlarged sectional view taken along the line XY in FIG. 4, and FIG.
4 is an enlarged sectional view taken along line YZ in FIG. 4, and FIG. 6 is a partial sectional view of another embodiment of the present invention.

FIG. 1 is an enlarged sectional view of the innermost part of the flat wound body before compression, corresponding to FIG.
Is an enlarged sectional view of the same part after compression. 1 and 2
9, the aggregate sheet A includes a positive electrode current collector 11 and positive electrode active material layers 12 provided on both surfaces thereof, as in FIG.
12 ′, a negative electrode sheet 2 composed of a negative electrode current collector 21 and negative electrode active material layers 22 and 22 ′ provided on both surfaces thereof, and separators 3 and 3 ′, with the separator 3 inside. It is wound. S is a space existing at the center of the flat wound body before compression. After the compression shown in FIG. 2, the space S has disappeared, and the inner surfaces of the separator 3 are in contact with each other.

FIGS. 1 and 2 show a conventional example shown in FIGS.
The difference from 0 is that the positive electrode active material layers 12, 12 'and the negative electrode active material layers 22, 22' in the aggregate sheet A located at the innermost turn end B of the winding are missing, and the positive electrode That is, the current collector 11 and the negative electrode current collector 21 are exposed. Due to the partial lack of the positive and negative active material layers, even if the flat wound body is compressed to eliminate the space S and the state shown in FIG. The electrical shorting problem often seen in the examples does not arise. In the present invention, the positive electrode active material layer 1
It is preferable that both of the negative electrode active material layers 2 and 12 ′ and the negative electrode active material layers 22 and 22 ′ are missing at the innermost turn end B, but even if at least one of the positive and negative electrode active material layers is missing. effective.

The manufacturing method of the present invention will be described with reference to FIGS. 3 to 6, reference numeral 1 denotes a positive electrode sheet, 11 denotes a positive electrode current collector, 12 and 12 ′ denote positive electrode active material layers provided on the surface thereof, and 13 denotes a positive electrode provided on the winding start end of the positive electrode sheet 1. The positive electrode lead is welded onto the positive electrode current collector 11 in the active material non-applied portion. 2 is a negative electrode sheet,
Reference numeral 21 denotes a negative electrode current collector, 22 and 22 ′ denote negative electrode active material layers provided on the surface thereof, and 23 denotes a negative electrode active material non-applied portion provided at the end of the negative electrode sheet 1 where the negative electrode active material is not applied. A negative electrode lead welded on top.

The positive and negative bipolar sheets 1 and 2 shown in FIG.
It may be the same as that conventionally used for a lithium secondary battery or the like. The positive / negative bipolar sheet 1 shown in FIG.
Numeral 2 is obtained by processing both sheets of FIG. 3, and the positive and negative bipolar sheets 1 and 2 shown in FIG. 3 are placed at three places defined as described later from their winding start ends. Active material lacking portions 14, 14 ′ to 16, 16 ′ and 2 in which the active material layer is missing over the entire length in the direction orthogonal to the longitudinal direction of each sheet, in other words, between both ends in the width direction of each sheet.
4, 24 'to 26, 26' are formed. FIG. 4
In the active material missing portions 14 'to 16' and 24 'to
26 'is not shown as it is behind the page. Since these active material lacking portions have the same structure,
The representation of 6 'and 26, 26' is shown in FIG.

Each of the active material missing portions shown in FIG. 4 is formed by winding the above-mentioned positive and negative active material missing portions 14 to 14 ′ when an aggregate sheet composed of the positive and negative bipolar sheets 1 and 2 is wound on a flat core. And 24 to 24 ', 15 to 15' and 25 to 25 ', and 1
6-16 'and 26-26' are provided so as to come together and come to the end of the winding turn. The installation positions of these active material missing portions can be determined in consideration of the circumference of the flat core used and the total thickness of the aggregate sheet. Each time the aggregate sheet is wound, an interval for providing the active material lacking portion is increased by twice the total thickness of the aggregate sheet.

FIG. 6 shows a partially enlarged cross section of the flat wound body used in the present invention manufactured using the positive and negative bipolar sheets 1 and 2 shown in FIGS. The flat wound body is composed of an aggregate sheet A obtained by laminating three sheets of a positive electrode sheet 1, a separator 3 ', and a negative electrode sheet 2 in that order, and a separator 3,
The separator 3 is wound on a flat core (not shown) with the lower side facing down, then the flat core is removed, and finally the wound body thus obtained is compressed to eliminate the central space. It is manufactured by

In FIG. 6, B is the innermost turn end of the winding, C is a second turn end located just above the innermost turn end B, and D is just above the second turn end C. The third turn end located. Of course, at each turn end BD
Each of the current collectors of the positive and negative bipolar sheets 1 and 2 is present, but is indicated by a blank in that part.
Means that the active material layer is missing. Then
The lack of the active material layer at the turn end B is shown in FIG.
14 'and 24 to 24', the loss of the active material layer at the turn end C is 15 to 15 'and 25 to 25', and the loss of the active material layer at the turn end D is 16 to 16 'and 2
6 to 26 '.

The radius of curvature of the positive / negative active material layer at each turn end of the winding gradually increases from the innermost turn end B to C, D,..., And the space S increases as the radius of curvature increases. The frequency of crack generation is also reduced by compression at the time of erasing. Therefore, the formation of the active material lacking portion is usually
In some cases, only the innermost turn end is sufficient, and if the above-described second and third turn ends are also performed, it is more effective in preventing the occurrence of cracks. Depending on the flexibility of the material forming the positive / negative active material layer, for example, in the case of a material commonly used for a lithium secondary battery having a non-aqueous liquid electrolyte, the positive / negative active material layer under compression applied at the time of erasing the space S Let R be the radius of curvature of the active material layer and t be the thickness of the active material layer.
It is preferable that the active material lacking portion be present at all of the turn ends where t is 10 or less, particularly 5 or less. For example, when t is 0.1 mm, R is 1 mm or less, particularly 0.5 mm.
The following turn ends correspond to the above.

The width of the active material lacking portion (for example, 1 in FIG. 5)
The width W of 6 to 16 'or 26 to 26' does not need to be as wide as 180 degrees as the center radius as illustrated in FIG. In this case, only the turn ends (generally, the tops of the turn ends and the vicinity thereof) where the radius of curvature of the positive and negative active material layers is in the above range are sufficient.

[0020]

According to the present invention, it is possible to form a flat wound body without cracking or falling off of the active material layer at a location located at the innermost end of the flat wound body or in the vicinity of the turn end. Since the volume energy density can be increased by compression, a high-capacity square battery with excellent safety can be obtained. In addition, the compression for increasing the volume energy density increases the degree of adhesion between the positive and negative electrode sheets, and the improvement in the degree of adhesion also has the effect of improving the battery capacity.

[Brief description of the drawings]

FIG. 1 is a partial sectional view of an embodiment of the present invention.

FIG. 2 is a partial sectional view after compressing the embodiment shown in FIG. 1;

FIG. 3 is a top view of a positive electrode sheet and a negative electrode sheet used in the production method of the present invention.

FIG. 4 is a top view of a positive electrode sheet and a negative electrode sheet used in the production method of the present invention.

5A is an enlarged sectional view taken along line XY in FIG. 4, and FIG. 5B is an enlarged sectional view taken along line YZ in FIG.

FIG. 6 is a partial sectional view of another embodiment of the present invention.

FIG. 7 is a perspective view of an electrode element used in a conventional prismatic lithium secondary battery.

FIG. 8 is a perspective view of another electrode element used in a conventional prismatic lithium secondary battery.

FIG. 9 is a partially enlarged sectional view of a conventional flat wound body as an electrode element.

FIG. 10 is a partially enlarged sectional view of a flat wound body as another conventional electrode element.

[Explanation of symbols]

 A aggregate sheet 1 positive electrode sheet 11 positive electrode current collector 12, 12 'positive electrode active material layer 2 negative electrode sheet 21 negative electrode current collector 22, 22' negative electrode active material layer 3, 3 'separator

Claims (3)

[Claims] 1. A flat wound body obtained by winding positive and negative bipolar sheets including a positive electrode sheet and / or a negative electrode sheet having an active material lacking portion in which an active material layer is missing over the entire length in a direction orthogonal to the longitudinal direction of the sheet. Wherein the active material lacking portion is located at least at the innermost turn end of the winding. 2. The flat wound body is subjected to a compression treatment so as to narrow or eliminate a space at the center of the wound.
The prismatic battery as described. 3. A positive / negative bipolar sheet including a positive electrode sheet and / or a negative electrode sheet having an active material lacking portion in which an active material layer is missing over the entire length in a direction orthogonal to the longitudinal direction of the sheet is wound on a flat core. Obtain a wound body in which the active material lacking portion is located at least at the innermost turn end of the wound, then remove the flat core and compress the wound body, and remain after removing the flat core. A method for manufacturing a prismatic battery, wherein a flat wound body is obtained by eliminating a space.