JPS61239561A - Manufacture of metal electrode - Google Patents

Abstract

PURPOSE:To obtain a convenient electrode having reduced grain field by providing a liquid layer onto fused metal then immersing the current correcting member into the fused metal to adhere metal to the current collecting member thus to integrate thereafter leading to the liquid layer and cooling/solidifying. CONSTITUTION:A current collector 4 wound over a roller 5 is guided by an inversion roller 6 to be immersed into fused metal 1 the led to the liquid layer 2 and wound over a roller 7. When employing sufficiently deep liquid layer 2, the temperature at the upper portion of the liquid layer is lower than the melting point of negative electrode material thus to solidify the integrated current collector/negative electrode material to be wound at this position. The roller 7 can move between the liquid layer 2 and the atmosphere or inert gas environment such as N2, Ar, etc. The integrated current collector/negative electrode material wound over the roller 7 is cleaned with water, ether, etc. then cut into specific dimension to produce an electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an improved method for manufacturing a non-aqueous electrolyte secondary battery, particularly its negative electrode.

Conventional technology Until now, alkali metals such as Li and Na have been used as negative electrode active materials, and Lick○4°L I B F 4 has been used as a solute in a solvent such as γ-butyrolactone, tetrahydrofuran, propylene carbonate, dimethoxyethane, etc.
+ So-called non-aqueous electricity in which L I C1 etc. are dissolved
i, gaya □i 6 yuke 1. circle. [Yacca 1. □、
ゎ5□Eh. ;However, this type of secondary battery has not yet been put into practical use. The reason for this is that the life of the number of charge and discharge cycles is short and the charge and discharge efficiency during charge and discharge is still low. This is a decrease in reversibility.

When an alkali metal such as Li is used as a negative electrode active material,
Due to charging and discharging, tendrite is generated in the form of a negative electrode plate,
This reduces charging and discharging efficiency, and sometimes causes an internal short circuit with the positive electrode through the separator, creating a risk of heat generation and fire.

In order to overcome these drawbacks of the negative electrode, it has been proposed to use a material M in the negative electrode, which absorbs alkali metal ions such as L1+ during charging and releases them during discharge, according to the following formula.

The negative electrode materials include Al, Bi, Cd, In, and Pb.

Fusible alloys containing Sn, ..., Zn, etc. are known, and electrodes using these metals and alloys (these have already been
A simple manufacturing method has been reported for alkali metals such as i, which may or may not be occluded. For example, there is Japanese Patent Application Laid-open No. 52-70333 for Al, and Japanese Patent Application Laid-open No. 59-186275 for fusible metals.

The method for manufacturing these electrodes is generally as follows. That is,
A porous current collector such as Ni is immersed in the melt of the negative electrode material metal, the current collector retains the negative electrode material, and by taking it out, the negative electrode material is cooled and solidified by the current collector. , as an electrode (this is called the immersion method).

Problems to be Solved by the Invention However, even if an electrode manufactured by such an electrode manufacturing method is applied to a non-aqueous electrolyte secondary battery, a battery having a sufficient cycle life cannot be obtained. This is due to the following reasons.

□ The metal negative electrode material here is held in a porous current collector and then taken out from the melt. The temperature of this melt varies depending on the material, but is approximately 300 to 70°C.
It is 0°C. Therefore, when the molten negative electrode particles used as the current collector are taken out from the melt, they are rapidly cooled and solidified. Therefore, the negative electrode material metal of current collector-1- becomes fine polycrystalline, and the number of grain boundaries increases. Soaking? When charging and discharging are repeated using an electrode obtained by the blue method, the metal electrode becomes finer and finer than the grain boundaries, and the shape of the electrode plate collapses.

Therefore, the charging/discharging → no-cycle life becomes shorter.

In order to reduce the grain boundaries in the electrode plate obtained by the immersion method,
The method used is to heat the electrode again to a temperature close to the melting point of the negative electrode material metal and then slowly cool it, but this requires a double process and is complicated from a manufacturing standpoint.

The present invention eliminates these conventional drawbacks, and uses a simple method for manufacturing electrodes with few grain boundaries to produce highly reliable non-aqueous electrolyte secondary electrodes whose plate shape remains stable even after repeated charging and discharging. The purpose is to provide batteries.

Means for solving the problem 5. The electrode manufacturing method of the present invention includes providing a liquid layer on a molten metal,
Dip the current collector into the molten metal and attach the metal to the current collector.
After integrating and guiding this into the liquid layer, cooling 1. Characterized by solidification.

For production The effect of this technical means is as follows.

That is, the current collector and the negative electrode material integrated in the metal melt form a liquid layer in the melt.
``Guided'' - Collected in a 0 liquid layer - Melt and: □ When the container containing the liquid layer above it is then cooled, the cooling rate is slow because this container has a large heat capacity, and therefore The combined current collector/negative electrode material in the liquid layer is slowly cooled to form an electrode with slightly narrower grain boundaries.

Alternatively, the current collector/negative electrode material integrated product may be introduced into the liquid layer and then immediately removed from the liquid layer without cooling the melt container. This is because the liquid is retained on the surface of the integrated current collector/negative electrode material, so it is not rapidly cooled.

Example Examples of the present invention will be shown below.

Wood alloy (Bi2O, Cd 12.5°Pb26.Sn 12.5% by weight each, melting point 70°C) was used as a negative electrode material capable of occluding and releasing alkali metal ions such as Li+, glycerin (boiling point 270°C) as a liquid layer, Further, an expanded Ni metal was used as a negative electrode material holding material (also serving as a current collector). FIG. 1 is a schematic diagram of an electrode manufacturing apparatus used in the present invention. The current collector 4 wound around the roller 6 is guided by the reversing roller 6, immersed in the molten metal 1, guided into the liquid layer 2, and then wound around the roller 7. At this time,
If the liquid layer 2 is deep enough, the temperature of the second part of the liquid layer is lower than the melting point of the negative electrode material, so the current collector/negative electrode material combination will solidify and can be wound up at this position. . Still, roller 7 with liquid layer 2 under atmosphere or N 2 ,
It is designed to be able to move between inert gas atmospheres such as Ar. The integrated current collector/negative electrode material wound around the roller 7 is washed with water, ethanol, etc., and then cut to a predetermined size to form an electrode.

An electrode obtained by winding a Ni current collector/wood alloy integrated product with a roller 7, spinning the roller with the roller placed in the glycerin layer 2, and cooling the entire container 3 is designated as A.

Next, the roller 7 is brought out from the glycerin layer 2 as indicated by the broken line, and at this position, the Ni current collector/wood alloy integrated product is wound up and cooled, and the obtained electrode is designated as B.

As a comparative example, an electrode without the glycerin layer 2, in which the Ni current collector/wood alloy integrated product was cooled while being exposed to the atmosphere, and could be wound around a roller 7, was designated as C.

Comparing electrodes A, B, and C thus obtained, the electrode surface of C was coarse and dense as a whole, covered with oxide, and had a pure color. In contrast, the electrode A of the present invention
The surface of B was smooth and had a metallic luster. In order to obtain an electrode with metallic luster in the electrode C, it is necessary to polish the electrode surface or manufacture it in an inert atmosphere such as N2゜Ar'; from this point of view, the production of the present invention is The supremacy of law is clear.

When we observe the metal structures of electrodes A, B, and C, we find that the crystal grains in electrode A are the largest, followed by B and C.
The order was However, in the manufacturing method of electrode B, the depth of the glycerin layer 2 is five times the thickness of the wood alloy layer 1.
-, an electrode having the same crystal grain metal structure as electrode A was obtained when the speed of the roller 7 for winding up the integrated material was the same.

Next, using the above electrodes A, B, and C, a charge/discharge test was conducted on a flat battery.

Electrodes A, B, and C were formed to have a diameter of 1 mm. The weight of the wood alloy layer was approximately 270 mg. These were spot welded to a sealing plate, and 27 times of metallic lithium foil was crimped onto each.

V2O5 is used as the positive electrode active material, and the weight ratio of this, carbon black, and tetrafluoroethylene resin is 100:5:10.
200 mg of the mixture was molded and pressed into a battery case to which a T1 expanded metal current collector was spot welded.

The electrolyte used was a mixture of propylene carbonate and dimethoxyethane in equal volumes, with LIC (lO4) dissolved at a ratio of 97, -7 1 mol/l, and a separator. A polypropylene nonwoven fabric was used.

In a battery configured in this way, at a constant current of ZmA, 2
．． Charging and discharging were performed in a voltage range of 2 to 3.6 .

Figure 2 shows the discharge capacity of each battery at each cycle. In the figure, A, B, and C are electrodes A.

Corresponds to B and C. From this, the electricity/ll2 of the present invention
A.

It can be seen that Comparative Example B has a cycle life superior to that of Comparative Example C.

In this example, Wood alloy was used as the negative electrode material metal that absorbs and releases Li+, and glycerin was used as the liquid layer, but the present invention is not limited to these.
A similar effect can be obtained by using a liquid layer made of an alloy or other fusible metal negative electrode material, an organic liquid such as dodecylbenzene, or an inorganic liquid such as water or water glass.

Furthermore, since the cooling rate can be changed by changing the liquid layer, there is also the effect that electrodes having crystal grains of various sizes can be adjusted.

Effects of the Invention As described above, according to the present invention, a simple electrode with few grain boundaries can be obtained, and a battery with a stable electrode plate shape and a long cycle life even after repeated charging and discharging can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the electrode manufacturing apparatus used in the present invention, and FIG. 2 is a plot of the discharge capacity in each cycle of the batteries of the example of the present invention and the comparative example. 1...Metal melt, 2...Liquid layer, 3
... Container, 4... Current collector. (''!A(Dff140Flf rl°7f'!''11
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Claims (1)

[Claims] A method for manufacturing a metal electrode that occludes and releases alkali metal ions by charging and discharging a battery, the current collector being produced by providing a liquid layer on a molten metal and immersing a current collector in the molten metal. A method for manufacturing a metal electrode, which comprises: attaching a metal to the current collector/metal integrated product, guiding the current collector/metal integrated product to the liquid layer, and then cooling and solidifying the current collector/metal integrated product.