JPH03276578A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PURPOSE:To improve the cycle characteristic without reducing the battery capacity by specifying the ratio between the diameter of an alloy section and the diameter of a base metal section and the ratio between the diameter of a positive electrode and the diameter of the alloy section. CONSTITUTION:A negative electrode 2 constituted of an alloy section 2a made of a lithium-aluminum alloy and a base metal section 2b made of aluminum is pressed to the inner face of a negative electrode current collector 7, the negative current collector 7 is fixed to the inner bottom face of a negative electrode can 5 with a nearly U-shaped cross section made of stainless, a positive electrode current collector 6 is fixed to the inner bottom face of a positive electrode can 4, and a positive electrode 1 is fixed to the inner face of the positive electrode current collector 6. The diameter of the alloy section 2a is set to 80-98% of that of the base metal section 2b, and the diameter of the positive electrode 1 is set to 83-100% of that of the alloy section 2a. The current concentration to peripheral sections of electrodes at the time of alloying, charging and discharging is suppressed, and the cycle characteristic can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention utilizes a positive electrode made of a rechargeable active material such as molybdenum trioxide, vanadium pentoxide, manganese dioxide, or titanium sulfide, and a lithium activated material. The present invention relates to a non-aqueous electrolyte secondary battery having a negative electrode made of a substance, and a separator interposed between the positive and negative electrodes and containing a non-aqueous electrolyte.

The problem with this type of battery is that the lithium, which is the negative electrode active material, grows in a dendritic form on the surface of the negative electrode during charging and comes into contact with the positive electrode, causing an internal short circuit, or it precipitates in a mossy pattern and falls off. Therefore, the charge/discharge cycle is extremely short.

Therefore, as shown in Japanese Unexamined Patent Publication No. 52-5423, a negative electrode using a lithium-aluminum alloy has been proposed. This is because in the case of lithium alone, when lithium is ionized and eluted during discharge, the negative electrode surface becomes uneven, and during subsequent charging, lithium is deposited intensively on the convex parts and grows like a tree. This is because, in the case of a lithium-aluminum alloy, lithium restores itself to form an alloy with aluminum, which serves as the base of the negative electrode, during charging, so that the dendritic growth of lithium can be suppressed.

The alloying method is 1, Special Publication No. 61-46
As shown in Japanese Patent No. 947, the properties of electrochemical alloys are good.

By the way, when electrochemically alloying as described above, the current tends to concentrate around the electrode, so alloying progresses faster at the electrode periphery than at the electrode center. In addition, when charging and discharging the above-mentioned battery, the electrode reaction concentrates on the periphery due to the edge effect.As a result, the periphery of the electrode deteriorates faster than the center, and as a result, the battery life is shortened. We had the challenge of becoming.

The present invention has been made in view of the current situation, and provides a non-aqueous electrolyte secondary battery that can improve cycle characteristics by suppressing current concentration around electrodes during alloying and charging/discharging. The purpose is to

In order to achieve the above object, the present invention includes a negative electrode comprising a base metal part and an alloyed part made of an alloy of the base metal and lithium, a positive electrode, and a separator interposed between these positive and negative electrodes. In the nonaqueous electrolyte secondary battery, the diameter of the alloyed portion is 80% or more and 98% or less of the diameter of the base metal portion, and the diameter of the positive electrode is 83% or more and 100% of the diameter of the alloyed portion. It is characterized by being configured as follows.

In order to prevent the peripheral part of the anal electrode from deteriorating faster than the central part, the diameter of the alloyed part should be made smaller than the diameter of the base metal part, and the diameter of the positive electrode should be made smaller than the diameter of the alloyed part. It is necessary to make it smaller. However, if the alloyed portion or the positive electrode is made too small, there is a problem in that the battery capacity decreases.

However, with the above structure (if the diameter of the alloyed part and the diameter of the positive electrode are specified), the diameter of the alloyed part and the positive electrode is not too small, so the battery capacity does not decrease, and the charging and discharging time during alloying and charging/discharging are Since it is possible to suppress current concentration from occurring around the electrode at times, cycle characteristics can be improved.

] One embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

[Example ■]

As shown in FIG. 1, an alloyed part 2a made of lithium-aluminum alloy and a base metal part 2 made of aluminum
The negative electrode 2 composed of the components b is crimped to the inner surface of a negative electrode current collector 7, and this negative electrode current collector 7 is fixed to the inner bottom surface of a negative electrode can 5 made of stainless steel and having a substantially U-shaped cross section. The peripheral edge of the negative electrode can 5 is covered with an insulating backing 8 made of polypropylene.
A positive electrode can 4 made of stainless steel and having a substantially U-shaped cross section in the opposite direction to the negative electrode can 5 is fixed to the outer periphery of the insulating backing 8.

A positive electrode current collector 6 is fixed to the inner bottom surface of the positive electrode can 4, and a positive electrode 1 is fixed to the inner surface of this positive electrode current collector 6. A separator 3 made of a porous polypropylene membrane impregnated with a non-aqueous electrolyte is interposed between the positive electrode 1 and the negative electrode 2.

The non-aqueous electrolyte is a mixed solvent of sulfolane and 1°3-dioxolane containing 1 mol/mol of lithium perchlorate.
A solution dissolved at a ratio of 1 liter is used. Also, the battery dimensions are 24mm in diameter. 0mm, thickness 3゜0㎬.

By the way, the diameter 12 of the alloyed part 2a is the same as that of the base metal part 2.
98% of the diameter l of b, and the diameter 13 of the positive electrode 1 is the diameter of the base metal portion 2b! ! , I (ie, the same as 12 above).

Next, a non-aqueous electrolyte secondary battery having the above structure was produced as follows.

First, the positive electrode 1 is produced as follows.

After adding 10 parts by weight of acetylene black as a conductive agent and 10 parts by weight of fluororesin powder as a binder to 80 parts by weight of manganese dioxide as an active material and thoroughly mixing the mixture, this positive electrode mixture was pressurized. Manufactured by molding.

In parallel with this, a metal lithium plate and an aluminum plate are produced by punching sheet-like lithium and aluminum into predetermined dimensions. At this time, the diameter 14 of the metal lithium shown in FIG. 2 is the diameter of the alloyed portion 2a! □Made smaller. This is done in consideration of the fact that metallic lithium expands when alloyed.

Thereafter, as shown in FIG. 2, an aluminum plate 9, a lithium plate 10, a separator 3, a cathode 1, and a cathode 1 are placed in order from the anode can 5 side in the space constituted by the cathode can 4 and the anode can 5. Attach. Thereafter, the spare battery thus produced was left for one week. Thereby, lithium and aluminum are alloyed, and a non-aqueous electrolyte secondary battery is produced.

The battery thus produced is hereinafter referred to as (A1) battery.

[Examples ■～■]

As shown in Table 1 below, a battery was produced in the same manner as in Example 2 above, except that the diameter 12 of the alloyed portion 2a and the diameter 23 of the positive electrode 1 were changed. However, also in this example,
Diameter of positive pjil! , are configured to be the same as the diameter 12 of the alloyed portion 2a.

The batteries produced in this way are shown below (At).
1iike~(A,)! It is called a pond.

[Margin below]

Table 1 [Comparative Examples ■ to ■] As shown in Table 1 above, the diameter Xt of the alloyed part 2a
A battery was produced in the same manner as in Example I above, except that (lithium diameter ffi) and the diameter 13 of the positive electrode 1 were changed. However, even in this comparative example, the diameter of positive electrode 1! , is configured to be the same as the diameter j22 of the alloyed portion 2a.

The batteries produced in this way are shown below (X,).
Battery ~(X3) Referred to as battery.

〔experiment〕

The cycle characteristics of the battery (A,) of the present invention to (A,)':a cell and the battery (X,) to (Xi)ii of the comparative example were investigated, and the results are shown in FIG. The experimental conditions are as follows:
After charging for 6 hours at a current of 12mA, the discharge current is 12mA.
The condition is to discharge at A to a final voltage of 2.0 .

As shown in Figure 3, all of the (A,) and (A,) batteries have a cycle life of 400 cycles or more, whereas all of the (XI) and (XI) batteries have a cycle life of 400 cycles or more. It is recognized that the cycle time is 400 cycles or less. Therefore, the diameter of the alloyed part 2a! 2 is the diameter 2 of the base metal portion 2b. It can be seen that it is preferable that the ratio is 80% or more and 98% or less.

In particular, the diameter l of the alloyed portion 2a! is the diameter of the base metal part 2b! , was set to be 90% of (A4)! It is recognized that the pond is excellent.

One embodiment of the present invention will be described below with reference to FIG.

[Example ■~m]

As shown in Table 2 below, the diameter of positive electrode 1! A battery was produced in the same manner as in Example 2 of the first example (the diameter 12 of the alloyed part 2a was set to be 90% of the diameter 11 of the base metal part 2b), except that . did.

The batteries produced in this way are shown below (B,).
Battery ~ (B3) Referred to as battery.

[Margin below]

Table 2 [Comparative Examples I to m] As shown in Table 2 above, the diameter of positive electrode 1! A battery was produced in the same manner as in Example 2 of the first example above, except that , and were changed.

The batteries produced in this way are shown below (Y,).
The battery is called a (yz) battery.

〔experiment〕

(B,') battery to (B3) battery of the present invention, the (A
4) The cycle characteristics of the battery, the comparative example (Y,) battery, and the (y8) battery were investigated, and the results are shown in FIG. The experimental conditions were the same as those of the first embodiment.

As shown in Figure 4, the (B1) battery to (B3) battery and the (A4) battery all have a cycle life of 400 cycles or more, while the (Y,) battery and (Y battery) all have a cycle life of 400 cycles or more. It is recognized that the cycle life is 400 cycles or less. Therefore, the diameter of the positive electrode 1 (3 is the alloyed part 2a
It can be seen that it is preferable that the diameter is 83% or more and IOθ% or less of the diameter 2□.

Note that in the above two examples, aluminum and lithium are alloyed inside the battery, but the same effect as described above cannot be achieved even if the alloy is alloyed outside the battery and then loaded into the battery. Of course.

Further, the base metal is not limited to aluminum, and one or more metals or alloys selected from the group consisting of lead, tin, cadmium, bismuth, silicon, indium, zinc, or magnesium may be used. .

Furthermore, the base metal contains manganese, chromium, and iron.

4゜ Silicon, tungsten, molybdenum, cobalt.

Nickel, zirconium, magnesium, titanium.

Alternatively, one to which one or more metals selected from vanadium is added may be used.

As explained above, according to the present invention, cycle characteristics can be improved without reducing battery capacity.

As a result, the performance of the non-aqueous electrolyte secondary battery can be dramatically improved.

[Brief Description of the Drawings] Fig. 1 is a sectional view showing a non-aqueous electrolyte secondary battery of the present invention, Fig. 2 is a sectional view showing a method for manufacturing the battery of Fig. 1, and Fig. 3 is a sectional view showing a method for manufacturing the battery of the present invention. (A,) Battery ~ (A,) Battery and Comparative Example (X
l) Battery ~ (X,) Graph showing the cycle life of the battery,
Figure 4 shows (Bl) battery to (B,) battery, (A
4) It is a graph showing the cycle life of a battery, a (Y+) battery, and a (yz) battery as comparative examples. ■... Positive electrode, 2... Negative electrode, 2a... Alloyed part, 2 b... Base metal part, 3... Separator.

Claims (1)

[Claims] (1) A non-aqueous electrolyte secondary battery having a negative electrode comprising a base metal part and an alloyed part made of an alloy of the base metal and lithium, a positive electrode, and a separator interposed between these positive and negative electrodes, The diameter of the alloyed portion is 80% or more and 98% or less of the diameter of the base metal portion, and the diameter of the positive electrode is configured to be 83% or more and 100% or less of the diameter of the alloyed portion. A non-aqueous electrolyte secondary battery.