JP3304367B2 - Method for producing negative electrode alloy for lithium secondary battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION This invention relates to the production how the negative electrode alloys of the lithium secondary battery using an alloy such as lithium and aluminum in a negative electrode.

[0002]

2. Description of the Related Art As is well known, in a lithium secondary battery,
To prevent the charging of lithium to the negative electrode with the discharge grows into dendritic (de <br/> handler site), lithium alloy capable of absorbing lithium - a (lithium aluminum alloys are typical) as a negative electrode Used. As a method for producing this type of lithium alloy, there are a metallurgical method and an electrochemical method. In the production of a lithium secondary battery, an electrochemical method is generally employed.

A lithium-aluminum alloy as a negative electrode for a lithium secondary battery is produced, for example, by the following electrochemical method. A lithium metal plate and an aluminum metal plate having a predetermined thickness are overlapped, immersed in a non-aqueous organic solvent, and electrochemically lithium-aluminum alloyed. In the case of an ordinary coin-type lithium secondary battery, alloying of a lithium metal plate and an aluminum metal plate is performed in a state where the alloy is assembled in a battery case. That is, an aluminum metal plate is pressed on the inner surface of the negative electrode terminal plate of the coin-shaped battery case via a metal net as a current collector, and a lithium metal plate is pressed on the aluminum metal plate. When the battery is assembled normally, the above-described alloying reaction between lithium and aluminum occurs in the nonaqueous electrolyte filled in the battery case.

[0004]

As shown in FIG. 1A, when a lithium metal plate 1 and an aluminum metal plate 2 are stacked and alloyed in a non-aqueous organic solvent, the alloyed portion expands. However, expansion does not occur at the portion remaining as the aluminum metal (the side opposite to the joint surface with the lithium metal plate 1). Therefore, as shown in FIG. 1B, the alloy warps like a bimetal toward the side where the aluminum metal remains. If the warping due to this alloying occurs in the battery case, an expansion force acts inside the battery, which deforms the battery case and impairs the sealing performance, and the applied pressure between the electrodes becomes uneven, and the battery performance becomes poor. Problems such as deterioration occur. Also,
Even if the alloying of lithium and aluminum is performed in the state of parts before being assembled in the battery case, the warped alloy plate must be corrected with a press when assembled in the battery,
The process becomes complicated and the negative electrode alloy cracks when warping is corrected.

As a countermeasure against warpage of the negative electrode alloy, Japanese Utility Model Laid-Open Publication No. 2-119354 discloses a method in which a groove is formed on a surface of a lithium alloy where expansion occurs, so that expansion is absorbed by the groove so as not to cause warpage. Techniques are disclosed. As described above, in the measures for forming an appropriate groove in the lithium alloy, the capacity of the active material is reduced by the amount of the groove, which impairs the characteristics as a lithium secondary battery having a high energy density.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems. An object of the present invention is to hardly warp a plate-shaped negative electrode alloy when lithium and aluminum are alloyed by an electrochemical method. An object of the present invention is to provide a manufacturing method as described above.

[0007]

According to the present invention, a lithium metal plate is provided between two plates of metal a selected from at least one of aluminum, tin, zinc, lead, bismuth, silicon, antimony and magnesium. In a method for producing a negative electrode alloy of a lithium secondary battery in which a three-layer laminate is sandwiched and immersed in a non-aqueous organic solvent to alloy lithium with the metal a, two sheets of the metal a The thickness of one of the plates is about one-half the thickness of the lithium metal plate, and the thickness of the other plate is greater than the thickness of the one plate.

[0008]

The alloying reaction occurs in a state where the lithium metal plate is sandwiched between the two plates of metal a, and the alloyed portion expands. Because of the expansion of the alloy part, there is almost no warping to one side.

[0009]

FIG. 2 shows an embodiment of the present invention. Here, the lithium metal plate 1 is sandwiched between the two aluminum metal plates 2a and 2b, and the three-layer laminated plate is immersed in a non-aqueous organic solvent to cause an alloying reaction between lithium and aluminum. The thickness of the lithium metal plate 1 is 0.4 mm, the thickness of the thin aluminum metal plate 2b applied to the lower side thereof is 0.2 mm, and the aluminum metal plate 2a applied to the upper surface side is It is 0.3 mm thicker than this. Since the thicknesses of the upper and lower aluminum metal plates 2a and 2b are different from each other, as shown in FIG. 2B, at the stage where lithium-aluminum alloying has progressed, the lower aluminum plate is entirely alloyed. However, a layer of aluminum metal remains on the uppermost surface of the upper aluminum metal plate. Therefore, also in this embodiment, the aluminum metal layer remaining on the upper surface of the lithium alloy plate does not expand at all, as shown in FIG. Is extremely small.
Because, at the stage where alloying proceeds, the upper and lower portions of the three-layered laminated plate are aluminum metal plates, so even if the intermediate alloy portion sandwiched between them is trying to expand, it is restrained by the aluminum metal plates on both surfaces. Therefore, alloying proceeds with almost no warpage or curvature.

The above-described method for producing a negative electrode alloy is carried out as follows in the production process of a coin-shaped lithium secondary battery. FIG. 3 is a sectional view of the lithium secondary battery to which the present invention has been applied, immediately after assembly. Hereinafter, this embodiment will be described in the order of manufacturing steps.

In FIG. 3, first, a current collector 4 made of a metal net is welded to the inner surface of the negative electrode terminal plate 3, and an aluminum metal plate 2 a having a thickness of 0.3 mm is pressed on the current collector 4. A 0.4 mm thick lithium metal plate 1 is pressed on the aluminum metal plate 2a, and a 0.2 mm thick lithium metal plate 1 is further pressed thereon.
Is pressed. On the other hand, the positive electrode mixture 6 is loaded into the center of the positive electrode terminal plate 5, the separator 7 is set thereon, and the nonaqueous electrolyte is injected into the positive electrode can 5. Next, the negative electrode terminal plate 3 and the sealing gasket 8 obtained by pressing the sandwich laminate of the aluminum metal plates 2a and 2b and the lithium metal plate 1 are combined with the positive electrode terminal plate 5 to seal the battery case. This means that the aluminum metal plate 2a, the lithium metal plate 1, and the aluminum metal plate 2b are immersed in the organic electrolytic solution, and the above-described alloying reaction gradually proceeds. Then, a slight aluminum metal layer remains in a portion in contact with the current collector 4, and the other portion is made of a lithium-aluminum alloy. This completes the lithium secondary battery.

[0012] Incidentally. The present invention is not applied only to the coin-type lithium secondary battery as shown in FIG.
It can be applied to other various lithium secondary batteries. Further, the present invention is not limited to the embodiment in which the alloying reaction between lithium and aluminum or the like is caused in the state where the battery is assembled in the battery case. The effect of the present invention that warpage does not occur is beneficial in battery production or battery performance.

[0013]

As described in detail above, according to the present invention, a metal such as aluminum alloyed with lithium is used.
When a lithium metal plate is sandwiched between two plates to form a three-layer laminate, the laminate is immersed in a non-aqueous organic solvent to alloy lithium and aluminum, etc.
The thickness of one of the plates was about half the thickness of the lithium metal plate, and the thickness of the other plate was larger than the thickness of the one plate. In the state where a metal layer such as aluminum is present, alloying proceeds from the middle part, so even if the alloyed part tries to expand, it is constrained on both sides of the laminate, so that the whole curves and warps to one side The phenomenon hardly occurs. So if in a state of being incorporated in the battery case performing the alloying is inflated and characteristic deterioration of a battery warping of the negative electrode due to alloying causes are eliminated Ji live. When the alloying is performed before the battery is assembled into the battery case, it is not necessary to correct the warpage of the negative electrode alloy, and the process is simplified, and the problem of cracking of the negative electrode alloy when correcting the warp is eliminated.

[Brief description of the drawings]

FIG. 1 is a view showing a problem of a conventional method for producing a negative electrode alloy.

FIG. 2 is a view illustrating a method for manufacturing a negative electrode alloy according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view of a coin-type lithium secondary battery to which the present invention has been applied, immediately after assembly.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lithium metal plate 2a, 2b Aluminum metal plate 3 Negative terminal plate 4 Current collector 5 Positive terminal plate 6 Positive electrode mixture 7 Separator 8 Sealing gasket

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hidetoshi Tanaka 5-36-11 Shimbashi, Minato-ku, Tokyo Inside Fuji Electric Chemical Co., Ltd. (56) References JP-A-53-75434 (JP, A) (58) ) Surveyed field (Int.Cl. ⁷ , DB name) H04M 4/02-4/04 H04M 4/40 H04M 10/40

Claims (1)

(57) [Claims] A lithium metal plate is sandwiched between two plates of a metal a selected from at least one of aluminum, tin, zinc, lead, bismuth, silicon, antimony, and magnesium to form a three-layer laminate, In a method for producing a negative electrode alloy of a lithium secondary battery in which the laminate is immersed in a non-aqueous organic solvent to alloy lithium and the metal a,
The thickness of one of the two plates of the metal a is about half the thickness of the lithium metal plate, and the thickness of the other plate is greater than the thickness of the one plate A method for producing a negative electrode alloy for a lithium secondary battery, comprising: