JP2003151534A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery in which life elongation by suppressing precipitation of dendrite can be aimed at. SOLUTION: A plural number of exposed parts 14 are installed at a positive electrode active substance layer 13, and these exposed parts 14 are arranged in a radial form with the center of a corner part 13A positioned on the diagonal line of a protruding position 11A of a positive electrode reed 11. Accordingly, as it goes farther from the positive electrode reed 11, the exposed area per unit area becomes larger and the existing amount of the positive electrode active substance decreases. Here, the utilization rate of the positive electrode active substance 13 becomes lower as it goes farther from the positive electrode lead 11. Therefore, by reducing the amount of the positive electrode active substance as it goes farther from the positive electrode lead 11, the utilization rate of the positive electrode active substance can be made equal in the whole positive electrode active substance layer 13 and deviation of current distribution can be prevented from occurring. By this, the dendrite can be prevented from precipitating.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a non-aqueous electrolyte secondary battery.

[0002]

2. Description of the Related Art In recent years, with the rapid miniaturization and weight reduction of electronic devices, communication devices, etc., development of batteries capable of miniaturization and high capacity has been advanced. Among them, lithium-ion secondary batteries (hereinafter sometimes simply referred to as "batteries")
Has a high operating voltage and a high energy density, and is expected to meet such demands.

In such a battery, for example, a sheet-shaped positive and negative electrode plate wound with a separator interposed between a power generating element and an electrolytic solution are housed in a metal battery can. Has become. Each electrode plate includes a current collector formed of a metal in a long strip shape, and the positive electrode active material layer or the negative electrode active material layer is formed on both surfaces of the current collector. A positive electrode lead and a negative electrode lead, which are connected to the positive electrode terminal and the negative electrode terminal of the battery, are attached to one end of the current collector.

[0004]

However, the resistance of each current collector is small in the region close to the lead and increases as the distance from the lead increases. Due to such a bias in the resistance distribution, the battery reaction becomes active near the lead, and the contribution rate of the active material to the battery reaction (active material utilization rate) increases. However, the utilization rate of the active material decreases as the distance from the lead increases.

Therefore, there is a problem in that the current distribution on the positive electrode active material layer is biased, and dendrites are likely to be deposited in the portion where the current concentrates and flows.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a non-aqueous electrolyte secondary battery capable of suppressing the deposition of dendrites and extending the life thereof.

[0007]

In order to solve the above problems, a nonaqueous electrolyte secondary battery according to the invention of claim 1 has a positive electrode active material layer formed on the surface of a positive electrode side current collector,
A positive electrode provided with a positive electrode side connecting portion that connects the positive electrode side current collector and the positive electrode terminal, and a negative electrode active material layer is formed on the surface of the negative electrode side current collector, and the negative electrode side current collector and the negative electrode A non-aqueous electrolyte secondary battery comprising a negative electrode provided with a negative electrode side connecting portion connecting to a terminal, wherein the current collector is provided in at least one of the positive electrode active material layer and the negative electrode active material layer. It is characterized in that a plurality of exposed portions where the body is exposed are formed in a radial pattern extending from the end portion on the side distant from the connection portion toward the connection portion in the active material layer.

The invention of claim 2 is the non-aqueous electrolyte secondary battery according to claim 1, characterized in that the exposed portion is formed in the positive electrode active material layer.

A third aspect of the present invention is the non-aqueous electrolyte secondary battery according to the first or second aspect, wherein the connecting portion is formed so as to project toward one end of the current collector. The exposed portion is formed in a radial pattern centering on a corner portion of the active material layer that is diagonal to the protruding position of the connection portion.

[0010]

According to the invention of claim 1, in the active material layer, a plurality of exposed portions spread in the direction of the connecting portion from the end of the active material layer on the side remote from the connecting portion. It is formed radially. According to such a configuration, the closer to the connecting portion, the wider the interval between the exposed portions, and the number of exposed portions decreases. In other words, as the distance from the connecting portion increases, the proportion of the exposed portion increases, and the amount of the positive electrode active material present decreases.

Here, the utilization rate of the active material decreases as the distance from the connection portion increases. Therefore, by increasing the proportion occupied by the exposed portion as the distance from the connecting portion increases and decreasing the amount of the active material, it is possible to make the utilization rate of the active material uniform in the entire active material layer, which causes uneven current distribution. Can be prevented. Accordingly, it is possible to prevent the dendrite from being deposited due to the concentration of the current in a part of the active material layer.

According to the second aspect of the invention, the exposed portion is formed in the positive electrode active material layer. As described above, by changing the amount of the active material on the positive electrode side where dendrites are likely to occur, the generation of dendrites can be effectively controlled.

According to the third aspect of the present invention, the exposed portion is formed in a radial shape centering on a corner portion located diagonally to the projecting position of the connection portion. With such a configuration, the region in which the amount of the positive electrode active material present is the smallest is arranged at the position farthest from the position where the positive electrode is connected to the positive electrode terminal. As a result, the utilization rate of the active material can be made more uniform in the entire active material layer, and dendrites can be prevented from precipitating.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the non-aqueous decomposable secondary battery of the present invention will be described in detail below with reference to FIGS.

In FIG. 1, a completed lithium-ion secondary battery 1 of this embodiment (corresponding to the non-aqueous electrolyte secondary battery of the present invention; hereinafter, simply referred to as “battery 1”) is broken. And show it. The lithium-ion secondary battery 1 is provided with a battery can 41 formed of, for example, a metal in a cylindrical shape, and an electrode body 40 housed therein.

The battery can 41 includes a metal negative electrode case 42 formed in a bottomed cylindrical container shape, and a metal positive electrode cap 43 formed in a substantially disc shape and sealing the opening of the negative electrode case 42. It consists of and. In the negative electrode case 42, the electrode body 40 is housed with the disc-shaped insulating plates 44 arranged above and below the electrode body 40. And this negative electrode case 4
At the opening of 2, the positive electrode cap 43 is provided with the sealing gasket 4
It is crimped through 5. In addition, inside the battery can 41, for example, 1 m in a mixed liquid obtained by mixing ethylene carbonate (EC), diethyl carbonate (DEC) and dimethyl carbonate (DMC) in a ratio of 2: 1: 2.
A non-aqueous electrolytic solution added with ol / l lithium hexafluorophosphate is injected.

The electrode body 40 is a strip-shaped positive electrode plate 10.
A spiral shape is formed by stacking (corresponding to the positive electrode of the present invention) and the electrode plate 20 for the negative electrode (corresponding to the negative electrode of the present invention) via the separator 30 and winding.

The negative electrode plate 20, as shown in FIG.
For example, the negative electrode active material layer 23 is formed on both surfaces of the negative electrode side current collector 22 made of a copper foil having a thickness of 12 μm.

The negative electrode active material layer 23 is formed on the entire surface of both surfaces of the negative electrode side current collector 22, excluding the region from one end in the length direction to a little inside. This negative electrode active material layer 2
3, the graphite powder is kneaded together with polyvinylidene fluoride as a binder to form a paste-like negative electrode mixture, which is applied to both surfaces of the negative electrode side current collector 22, dried, and rolled by a roll pressing machine. Is formed by.

The negative electrode lead 2 is formed on the negative electrode plate 20 in a region where the negative electrode active material layer 23 is not formed.
1 (corresponding to the connection part of the present invention) is connected. The tip portion 21A of the negative electrode lead 21 has a negative electrode plate 20.
And is connected to the bottom of the negative electrode case 42 which functions as a negative electrode terminal.

On the other hand, as shown in FIG. 2, the positive electrode plate 10 has a positive electrode active material layer 13 formed on a positive electrode side current collector 12 made of a strip-shaped aluminum foil having a thickness of 20 μm, for example. is there.

The positive electrode active material layer 13 is formed on the entire surface of both surfaces of the positive electrode side current collector 12 excluding a region from one end in the length direction to a little inside. This positive electrode active material layer 1
3 is a positive electrode mixture prepared by adding polyvinylidene fluoride as a binder and acetylene black as a conductive material to lithium cobalt oxide as a positive electrode active material to prepare a positive electrode mixture. It is formed by coating both surfaces of the electric body 12, drying, and rolling with a roll pressing machine.

Further, the positive electrode lead 1 is provided in a region of the positive electrode plate 10 where the positive electrode active material layer 13 is not formed.
1 (corresponding to the connection part of the present invention) is connected. The tip portion 11A of the positive electrode lead 11 has a positive electrode plate 10
And is connected to a positive electrode cap 43 that functions as a positive electrode terminal.

The positive electrode active material layer 13 is provided with a plurality of exposed portions 14 from which the positive electrode side current collector 12 is exposed. Each exposed portion 14 is formed from a corner portion 13A diagonally opposite to the protruding position of the positive electrode lead 11 on the positive electrode plate 10,
In the positive electrode active material layer 13, the end 13B on the side to which the positive electrode lead 11 is attached, or the end 13 in the length direction
It is formed in a stripe shape over the length range up to C.
Then, the plural pieces are arranged radially around the corner portion 13A. These exposed portions 14 are, for example, in a state where a masking tape is attached to the position where the exposed portions 14 are formed on the positive electrode side current collector 12, after applying the positive electrode mixture to form the positive electrode active material layer 13, It can be formed by peeling off the masking tape.

As described above, the positive electrode active material layer 13 is provided with a plurality of exposed portions 14, and the exposed portions 14 are
Corner portion 13A diagonally opposite to the protruding position of the positive electrode lead 11
Are arranged in a radial pattern centered on. Therefore, the closer to the positive electrode lead 11, the wider the interval between the exposed portions 14 becomes, and the number of the exposed portions 14 decreases. That is, in the positive electrode active material layer 13, the exposed portion 14 is formed in the region S farthest from the tip portion 11A of the positive electrode lead 11 which is the connection portion with the positive electrode terminal.
Are most often distributed. The exposed portion 14 decreases as it approaches the positive electrode lead 11, and the exposed portion 14 becomes the smallest in the region R closest to the positive electrode lead 11. Therefore, as the distance from the positive electrode lead 11 increases, the exposed area per unit area increases and the amount of the positive electrode active material present decreases.

Here, the utilization rate of the positive electrode active material 13 decreases as the distance from the positive electrode lead 11 increases. Therefore, by decreasing the amount of the positive electrode active material as the distance from the positive electrode lead 11 increases, the utilization rate of the positive electrode active material can be made uniform in the entire positive electrode active material layer 13, and uneven distribution of the current can be prevented. This can prevent dendrites from depositing.

The technical scope of the present invention is not limited to the above-described embodiments, and the following technical scope is also included in the technical scope of the present invention.
In addition, the technical scope of the present invention extends to an equivalent range. (1) Although the lithium-ion secondary battery 1 of the present embodiment has a cylindrical shape, the shape of the battery is not limited to that of the present embodiment according to the present invention, and may be, for example, a prismatic shape. (2) In the present embodiment, the exposed portion 14 is formed radially around the corner portion 13A, but according to the present invention, the central position of the exposed portion does not necessarily have to be the corner portion, One of the positions may be the center position. (3) In the present embodiment, the exposed portion 14 is formed only on the positive electrode active material layer 13, but according to the present invention, the exposed portion may be formed on the negative electrode active material layer. It may be formed on both of the negative electrode active material layers.

[Brief description of drawings]

FIG. 1 is a perspective view of the battery of the present embodiment, broken away.

FIG. 2 is a diagram showing an electrode plate of the present embodiment.

[Explanation of symbols]

1 ... Battery (non-aqueous electrolyte secondary battery) 10 ... Electrode plate for positive electrode (positive electrode) 11 ... Positive electrode lead (positive electrode side connecting portion) 12 ... Positive electrode side current collector 13 ... Positive electrode active material layer 13A ... Corner 14 ... Exposed part 20 ... Negative electrode plate (negative electrode) 21 ... Negative electrode lead (negative electrode side connection part) 22 ... Negative electrode side current collector 23 ... Negative electrode active material layer 42 ... Negative electrode case (negative electrode terminal) 43 ... Positive electrode cap (positive electrode terminal)

Claims (3)

[Claims] 1. A positive electrode in which a positive electrode active material layer is formed on the surface of the positive electrode side current collector, and a positive electrode side connecting portion for connecting the positive electrode side current collector and the positive electrode terminal is provided, and a negative electrode side current collector. A non-aqueous electrolyte secondary battery comprising a negative electrode active material layer formed on the surface of an electric body, and a negative electrode provided with a negative electrode side connecting portion for connecting the negative electrode side current collector and a negative electrode terminal, At least one of the positive electrode active material layer and the negative electrode active material layer has a plurality of exposed portions from which the current collector is exposed, from an end portion of the active material layer on the side remote from the connection portion. A non-aqueous electrolyte secondary battery, wherein the non-aqueous electrolyte secondary battery is formed in a radial shape extending in the direction of the connecting portion. 2. The non-aqueous electrolyte secondary battery according to claim 1, wherein the exposed portion is formed on the positive electrode active material layer. 3. The corner portion, wherein the connecting portion is formed so as to project toward one end side of the current collector, and the exposed portion is at a diagonal position in the active material layer that is diagonal to the protruding position of the connecting portion. The non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the non-aqueous electrolyte secondary battery is formed in a radial shape centering around.