JPH0637569Y2 - Negative electrode current collector for lithium battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION << Industrial Application Field >> The present invention relates to improvement of a negative electrode current collector for a lithium battery.

<Prior art> Generally, in a spiral lithium battery, a lithium sheet as a negative electrode and a sheet-shaped positive electrode are sandwiched between separators and spirally wound to form a cylindrical power generation element, which is housed in a cylindrical case. It is assembled by injecting a non-aqueous electrolyte and then sealing the inside of the case. Further, the bobbin type lithium battery is assembled by arranging a lithium sheet and a positive electrode in a bobbin shape in a cylindrical case via a separator, and then performing the same steps as the spiral type lithium battery.

For example, in a spiral lithium battery, the battery case and the negative electrode are electrically connected to each other by pressing the negative electrode current collector onto the lithium sheet and projecting the end of the negative electrode current collector from the power generating element into the inner bottom portion of the case. It is done by spot welding.

Also, on the positive electrode side as well, the electrical connection is secured by spot welding the positive electrode current collector to the sealing plate.

The negative electrode current collector is composed of a stainless thin plate or the like,
Conventionally, the shapes shown in FIGS. 4 and 5 have been adopted in order to increase the adhesion effect on the pressure-bonded surface to the lithium sheet.

In the current collector 1 shown in FIGS. 4 (A) and 4 (B), the lead portion 1b projecting from the widthwise edge of the lithium sheet 2 is integrally formed at one end of the rectangular crimp portion 1a. The crimping portion 1a has a large number of rectangular openings 1c arranged regularly.
Punching out and projecting on the edge of each opening 1c.
1d is erected and projected toward the crimping surface.

According to this configuration, when the crimp portion 1a is crimped to the lithium sheet 2, the protrusion 1d bites into the lithium sheet 2, and the lithium sheet 2 positioned inside the opening 1c corresponds to the biting amount. Is raised on the surface of the opening 1c, and the crimp portion 1a is brought into close contact with the lithium sheet 2.

In the figure, reference numeral 3 is a separator laminated on the back surface of the lithium sheet 2, and 4 is a positive electrode laminated on the back surface of the separator 3.

The current collector 5 shown in FIGS. 5 (A) and 5 (B) has a crimped portion 5a.
A lead portion 5b is formed in a straight rectangular shape on the upper part of the above, and a plurality of circular holes 5c are formed in the crimp portion 5a.

In this example, when the pressure-bonding portion 5a is pressure-bonded to the lithium sheet 2, the portion of the lithium sheet 2 located inside the circular hole 5c rises, so that an adhesion effect is obtained.

However, the lithium battery using the negative electrode current collectors 1 and 5 having these shapes has the following technical problems.

<< Problems to be Solved by the Invention >> That is, in the lithium battery, since lithium on the negative electrode side moves to the positive electrode side by the discharge reaction, lithium is consumed as the discharge reaction proceeds, and the plate thickness of the lithium sheet 2 becomes thin. Conversely, the positive electrode side 4 expands and becomes thicker.

Therefore, in the former structure, the lithium sheet 2
The protrusion 1d penetrates the lithium sheet 2 and comes into contact with the separator 3 due to the consumption of, while the separator 3 is pressed against the tip of the protrusion 1d by the expansion pressure on the positive electrode 4 side and touches the sharp edge of the tip of the protrusion 1d. It could be breached, causing an internal short circuit, which could lead to explosion and ignition.

As a material for the separator 3, polypropylene non-woven fabric or the like has been conventionally used, but recently, a porous thin film is often used to improve the performance of the battery. Since it is about 25 μm, which is extremely thin compared to the non-woven fabric, when a thin film is used, it is easy for a breakthrough accident due to the protrusion 1d to occur frequently.

Further, in the latter circular hole structure, since there is no protrusion, the effect of sticking to the lithium sheet 2 is small, peeling occurs during the manufacturing process, and there is variation in discharge performance due to reduced adhesion.

Further, even with this circular hole structure, punching burrs 5d may occur in the circumferential circle of the circular hole 5c as shown in an enlarged view of a part of the figure. When a film is used, the separator 3 may be pierced by touching the sharp edge of the punching burr 5d.
After all, there was a fear of causing an internal short circuit.

The present invention solves the above problems, and an object thereof is to provide a negative electrode current collector for a lithium battery, which can secure the adhesion of the negative electrode current collector to the lithium sheet and which does not break through the separator. To do.

<< Means for Solving the Problems >> In order to achieve the above-mentioned object, the negative electrode current collector of the present invention has a plurality of dish-shaped projections formed so as to project toward a pressure-bonding surface against a lithium sheet, and each of these dish-shaped projections. It is provided with a hole that is bored and an edge portion that rises toward the inner side of the dish-shaped projection at the peripheral edge of the hole.

<< Operation >> According to the above configuration, when the current collector is pressure-bonded to the lithium sheet, the dish-shaped protrusions dig into the lithium sheet, and the portion of the lithium sheet located in the hole portion repelled by the lithium sheet becomes a hole. Rises inside the dish-shaped projection through
Cut into the edge of the edge.

When the lithium sheet is consumed by the discharge, the tip of the dish-shaped protrusion comes into surface contact with the separator, so that the separator is prevented from being pierced.

<< Embodiment >> An embodiment of the present invention will be described below in detail with reference to the drawings. However, the same or corresponding portions as in the conventional case will be denoted by the same reference numerals for description.

1 and 2 show a spiral type lithium battery according to the present invention, 2 is a lithium sheet constituting a negative electrode, 3 is a separator laminated on the front and back of the lithium sheet 2, and 4 is a back surface side separator. The sheet-shaped positive electrode is laminated on the back surface, and the cylindrical power generation element A is formed by spirally winding the positive electrode 4 inside with the positive electrode 4 in the direction of the arrow.

On the winding start end side of the positive electrode 4, a positive electrode current collector 10 is pressure-bonded in a buried state.

Further, the pressure-bonding portion 12a of the negative electrode current collector 12 is pressure-bonded to the end of winding of the surface of the lithium sheet 2, and the power generating element A is placed in the case 14 with the lead portion 12b protruding to the lower portion thereof bent.
The negative electrode current collector 12 and the case 14 are connected by being housed inside, inserting a spot welding electrode from the center hole of the power generating element A, and spot welding the lead portion 12b to the inner bottom surface of the case 14.

Further, the lead portion 10a of the positive electrode current collector 10 is a sealing gasket 16
Is spot-welded to the sealing plate 18 through, through the spot welding the electrolyte is injected into the inside of the case 14, then fit the positive electrode terminal plate 19 through the sealing gasket 16 to the inner circumference of the opening of the case 14, By caulking the opening edge of the case 14, the inside is sealed and the spiral lithium battery is completed.

In the above configuration, the negative electrode current collector 12 is a strip-shaped product in which the lead portion 12b is straightly integrated with the crimping portion 12a, and is made of a stainless thin plate or the like as in the conventional case.

A large number of dish-shaped projections 20 are formed on the pressure-bonding portion 12a toward the lithium sheet 2.

As shown in FIG. 3, the dish-shaped projection 20 has a trapezoidal cross section, a projecting tip 20a is formed in a flat shape, and a hole 20b is formed in the center thereof. An edge portion 20c that rises toward the inside of the dish-shaped projection 20 is formed at the peripheral edge of the hole 20b.

Note that these shapes can be easily formed depending on the press punching die.

In the above structure, when the pressure-bonding portion 12a of the negative electrode current collector 12 is pressure-bonded to the lithium sheet 2, the respective dish-shaped projections 20 bite into the lithium sheet 2 and the holes 20b corresponding to the volume relieved by the holes 20b. The portion of the lithium sheet 2 located in the portion flows, deforms into a mushroom shape inside the dish-shaped projection 20 through the hole 20b and rises, and the peripheral edge of the raised portion bites into the edge of the edge portion 20c.

Therefore, the edge portion 20 of the mushroom-shaped deformed portion
Due to the sticking effect on c, the adhesion of the negative electrode current collector 12 to the lithium sheet 2 is maintained, discharge performance is secured, and peeling of the current collector 12 during the assembly process is prevented in advance.

When the lithium sheet 2 becomes thin due to the progress of the discharge reaction, the tip 20a of the dish-shaped projection 20 is exposed and the positive electrode 4 expands to come into contact with the separator 3.

However, since this tip portion is flat, it makes surface contact, and since the edge portion 20c at the periphery of the hole 20b projects toward the inside of the dish-shaped projection 20, it does not directly contact the separator 3. The breakthrough of the separator 3 can be prevented.

In addition, the number of each dish 20 is 10 to 2 for CR14 and CR20 type batteries.
About 0 is desirable, and the diameter, the amount of protrusion, and the like can be appropriately set according to the number of formed sheets and the thickness of the lithium sheet 2.

Furthermore, the negative electrode current collector having this structure can be applied to a bobbin type lithium battery.

<Effects of the Invention> As described in detail with reference to the embodiments above, in the negative electrode current collector for a lithium battery according to the present invention, the adhesion to the lithium sheet is secured, the discharge performance is improved, and Since there is no fear of peeling or the like, there is an advantage that the yield is improved, and at the same time, accidents such as breakthrough of the separator and internal short circuit, rupture, or ignition accompanying it can be prevented.

[Brief description of drawings]

FIG. 1 is an exploded explanatory view of a power generating element when the present invention is applied to a spiral lithium battery, FIG. 2 is a sectional view showing an assembled state of the lithium battery, and FIG. 3 is a crimping portion of a negative electrode current collector. Enlarged sectional views, FIGS. 4 (A) and 4 (B) are explanatory views of a conventional negative electrode current collector, and FIGS. 5 (A) and 5 (B) are explanatory views of other conventional negative electrode current collectors. Is. 2 ... Lithium sheet 3 ... Separator 4 ... Positive electrode 12 ... Negative electrode current collector 12a ... Crimping part, 12b ... Lead part 20 ... Dish-shaped projection 20a ... Tip, 20b ... Hole, 20c ... Edge part A ... Power generation element

Claims (1)

[Scope of utility model registration request] 1. A negative electrode current collector, which is pressure-bonded to the surface of a lithium sheet constituting a negative electrode, and a positive electrode laminated on the back surface of the lithium sheet via a separator, and the lithium sheet, the separator and the positive electrode are laminated. In a lithium battery in which a cylindrical power generation element is configured by winding in a state: the negative electrode current collector has a plurality of dish-shaped projections formed to project toward a pressure-bonding surface of the lithium sheet, and each dish-shaped projection. A negative electrode current collector for a lithium battery, comprising: a hole formed in the protrusion; and an edge portion at the periphery of the hole that rises toward the inside of the dish-shaped protrusion.