JPS6086760A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PURPOSE:To obtain a negative electrode which has a great charge-and-discharge capacity per its unit weight and exhibits a stable performance since the active material does not pulverize even when charge and discharge are repeated by using as a negative material either an aluminum-magnesium alloy or an alloy prepared by adding silicon, zinc, tin or silver to an aluminum-magnesium alloy. CONSTITUTION:An aluminum-magnesium alloy is used as a negative material, so that the negative material does not pulverize and has a stable form due to the existence of magnesium and so that the quantity of electricity for charge and discharge increases due to the existence of aluminium. When at least one element selected from the group consisting of silicon, tin, zinc and silver is added to an aluminum-magnesium alloy and the thus obtained alloy is used as a negative material, the quantity of electricity for charge and discharge further increases. Here, when the content of magnesium in the aluminum-magnesium alloy is lower than 15wt%, the active material significantly pulverizes and separates from the plate as charge-and-discharge cycle proceeds. When the content of magnesium in the alloy exceeds 65wt%, the quantity of electricity for charge and discharge reduced due to a decreased amount of aluminum.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a non-aqueous electrolyte secondary battery VC.
The present invention relates to an improvement in an electrode absorber having the function of occluding alkali metals during charging and releasing alkali metal ions during discharge.

The structure of the conventional example and its problems At present 1, as a non-aqueous electrolyte j + high quality secondary '1b7 with an alkali modern style such as lithium and strium as the negative electrode (d2, for example, titanium disulfide (Ti52) is f) (Using intercalation compounds of various families as positive electrode active materials,
As for q'l, the development of batteries using a J4 electrolyte prepared by dissolving 1N lithium oxide in an organic solvent such as propylene carbonate has been actively pursued. A feature of this secondary battery is that by using lithium for the negative electrode, the electrolyte voltage increases, resulting in a secondary battery with high energy density.

However, this type of secondary battery is currently not in practical use. The main reason is that the number of charging and discharging times is life-threatening.
The charging and discharging efficiency during charging and discharging is extremely low.

The cause of this is extremely likely to be due to the deterioration of the lithium negative electrode. In other words, current lithium-negative IUHA-nickel or other screen-shaped current collectors are generally used once a month with plate-shaped metal lithium crimped to them, but during discharge, the metal lithium is converted into lithium ions in Ryukaku It qa. However, it is difficult to charge this and precipitate it into a plate-like lithium like before discharging, and it becomes dendrite-like (
Phenomena occur, such as dendritic (dendritic) lithium occurring and breaking off from the base and falling off, or small spherical (moss-like) lithium deposits falling sharply from the current collector. This results in a battery that cannot be charged or discharged. The dendrite-like metallic lithium that is generated often penetrates the separator that separates the positive and negative electrodes and comes into contact with the positive electrode, causing a short circuit and causing the battery to lose its function.

Various methods have been tried in the past to improve these drawbacks of negative electrodes. In general, the material of the negative electrode current collector is changed to improve adhesion to the precipitated lithium, or additives are added to prevent the formation of tentrite. However, these methods are not necessarily effective.In other words, with regard to current collector materials, they are effective for lithium deposited directly on the current collector material, but it is effective for lithium that is deposited directly on the current collector material, but it is effective for lithium that is deposited directly on the current collector material. If this continues, lithium will precipitate onto the precipitated lithium, and the effect of the monthly current collector will disappear.As for additives, they are effective at the beginning of the charge/discharge cycle, but as the cycle progresses, oxidation inside the battery will disappear. Reduction reaction: Most of the substances decompose and lose their effectiveness.

Furthermore, it has been proposed to use an alloy with lithium as a negative electrode. A well-known example of this is lithium-aluminum alloy. In this case, a homogeneous alloy is formed, but when charging and discharging are repeated, this uniformity disappears, and especially when the amount of lithium is increased, the electrode becomes atomized and collapses. It has also been proposed to use a solid projectile of alkali metal and alkali metal (4.1
-7386). In this case, it is said that there is no disintegration like in alloying with aluminum, but the amount of lithium that alloys quickly enough is small, and metallic lithium may precipitate without alloying. The use of porous materials is recommended to prevent this.

(Thus, the charging effect of large currents is poor, and in alloys with a large amount of lithium, micronization due to charging and discharging is gradually accelerated, resulting in a sharp decrease in cycle life.

In addition, the idea of using a lithium-mercury alloy (Japanese Unexamined Patent Publication No. 5
7-98978), a device using lithium-lead alloy (q
,' is published in 1987-141869). However, in the case of a lithium-mercury alloy, due to discharge, the negative electrode no longer retains the overall shape of the liquid particle mercury stain. In the case of a lithium-lead alloy, the fineness of the powder due to charging and discharging the electrode is greater than that of a silver solid solution.

Recently, it has been proposed to use a fusible metal such as tin or cadmium as a negative electrode material. By using this fusible alloy, the negative electrode does not become finely pulverized, and stable charging and discharging can be performed. Among the fusible metals, tin,
Because the total bending of atoms such as cadmium, bismuth, and lead is large, the charge/discharge fi' of 9, which is a unit weight, is small.

Purpose of the Invention The present invention has a large charging/discharging field f11 per unit weight,
It is also an object of the present invention to provide a negative electrode that exhibits stable performance without causing pulverization of the electrode even after repeated charging and discharging.

Components of the Invention The secondary battery of the present invention is characterized in that an aluminum-magnesium alloy or an aluminum-magnesium alloy to which at least one selected from the group consisting of silicon, tin, zinc, and silver is added is used as a negative electrode material. By charging, lithium is occluded in the form of a lithium-aluminum intermetallic compound in the alloy used in December, and by discharging, it is released as lithium ions into the electrolytic bamboo.

As mentioned above, in the secondary battery of the present invention, the negative electrode material alloy is charged to absorb an alkali metal, such as d[lithium, and discharged to release lithium into the electrolytic bamboo. An alloy of lithium will be produced.

Here, the negative electrode material refers to the material that is alloyed with lithium.
It is an alloy of +.

For example, an alloy (Al (70) - Mg (30
)] The charging/discharging reaction of /Koki is as shown in the following equation.

CAl (70) -Mg (30)')+XL1+
In the xe formula [A1 (completed o) -Mg (30)] Li
X is atubenium-magnesium- produced by charging
Indicates a lithium alloy.

In addition, as for the range of charging and discharging, it is not necessary to discharge until lithium is completely removed from the negative electrode as in equation (1), but it is necessary to change the amount of lithium occluded in the negative electrode as in equation (2). Therefore, it is natural that it can be charged and discharged0 (Al (70) Mg (30) ) Lix +YL
L+Ye The inventors have discovered that even when an aluminum-magnesium alloy is used as a negative electrode material and charged and discharged in an electric current containing lithium ions, the electrode does not become finely pulverized, and the negative electrode material becomes small. It was also found that the charge/discharge per unit weight (I:) is also large.

When aluminum alone is used as the negative electrode material, t/(ijl,
Due to repeated charging and discharging, it becomes fine powder and the electrode shape cannot be maintained. On the other hand, when magnesium alone is used as the negative electrode removal material, charging and discharging are repeated in 1. -C also has a stable pole shape, but it is small to the extent of one charge/discharge charge.

In other words, by using an aluminum-magnesium alloy, even after repeated charging and discharging, the presence of Magne/Ram prevents pulverization and stabilizes the shape, and the presence of aluminum increases the amount of electricity charged and discharged. . The living substance that performs the 7M charge is aluminum, which is thought to act as a binder along with magnesium.

Furthermore, silicon,
In alloys to which at least one selected from the group consisting of tin, zinc, and silver is added, the amount of gas released becomes even larger. By adding these metals, many phases are added to the alloy. This is thought to be due to the fact that the lithium absorbed at the phase interface becomes more easily diffused.

Explanation of practical example No. 1: Configuring this cell and examining its characteristics as a negative electrode for non-aqueous electrolyte secondary batteries made of various metals and alloys.
In the figure, 1 is a test electrode made of metal or alloy placed on the side, 2
3 is a positive electrode made of TiS2, and 3 is a lithium plate as a reference electrode. Nickel metal was used for each electrode lead. Test electrode 1 was a metal or alloy with a size of 1×1 cm and a thickness of 1 mm, and a nickel ribbon was attached as a lead.

'1l) TPT substance 4 contains 1 mol/l (7) L
iC10, i-molded propylene carbonate was used. The liquid tank 5 of the test electrode 1 and the liquid tank 6 of the reference electrode 3 are connected through a communication pipe 7.

In order to measure the characteristics of a non-aqueous electrolyte secondary battery made of metal or alloy as a negative electrode, the test electrode 1 was charged in the cathode direction with a constant current of 5 mA in a trench such that the potential of the test electrode 1 was OmV with respect to the lithium reference electrode 3. . Under these conditions, lithium does not precipitate on the test electrode but enters the alloy. After the potential of the test electrode reaches OmV, 1. 5mA at oV
The battery was discharged toward the anode at a constant current of , and then charging and discharging were repeated under the same conditions.

The table shows the amount of electricity charged per unit weight of the negative electrode material in the 1st cycle and the 10th cycle of the alloy size or metal used for test electrode 1, the amount of electricity discharged, and the efficiency of the amount of electricity discharged as the amount of charged electricity. The first cycle characteristic is
The amount of discharged electricity in the 0th cycle divided by the discharged electricity in the 1st cycle is shown. Charge per unit weight of negative electrode material,
It can be said that the negative electrode has good values for the amount of electricity, amount of discharged electricity, efficiency, and cycle characteristics.

From the results in the table, negative electrode for non-aqueous electrolyte secondary battery *): Ki
In addition, compared to conventionally used aluminum, magnesium, and fusible alloys, the aluminum-magnesium alloy of the present invention further contains silicon.

By using an alloy to which silver (zinc, tin) is added as the negative electrode material, it is possible to obtain a secondary battery with a higher charge/discharge capacity per unit weight and a higher number of cycles.

Next, the results of studying the composition of the alloy used for the negative electrode material will be explained. FIG. 2 is a plot of the discharged energy and the amount of electricity in the 10th cycle per unit weight of the negative electrode material when the magnesium content in the aluminum-magnesium alloy is changed. In addition, the test method is the same as the above fll. From the figure, it can be seen that the alloy composition exhibits good negative electrode characteristics when the aluminum/magnesium weight ratio is from 86/i5 to 35/6s.

Magnesium in aluminum-magnesium alloy is 1
When the weight ratio was less than 5, the electrode plate became finely powdered and fell off as the charge/discharge cycle progressed. Further, when the weight exceeds 65, the amount of aluminum decreases and the amount of electricity charged and discharged decreases.

As an electrolyte, you can use not only organic electrolytes as shown in the examples, but also Li3N (lithium nitride) and LiI (
Even when using a solid electrolyte such as lithium iodide,
The aluminum-magnesium alloy of the present invention exhibits better characteristics than conventional negative electrode materials.Advantageous Effects of the Invention 1: As shown above, according to the present invention, the amount of electricity charged and discharged per unit weight is large, A nonaqueous electrolyte secondary battery with excellent cycle characteristics can be obtained.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a cell used for examining negative electrode characteristics, and FIG. 2 is a diagram showing the relationship between the composition of the alloy and the amount of discharged electricity.

Claims (3)

[Claims] (1) A nonaqueous electrolyte containing alkali metal ions, a rechargeable positive electrode, and a negative electrode material that occludes alkali metals during charging and releases alkaline metal ions in the electrolyte during discharge, wherein the negative electrode material is aluminum and A non-aqueous electrolyte secondary battery characterized by being made of a magnesium alloy. (2) Gravity 1 of aluminum/magnesium of the above alloy
The non-aqueous electrolyte secondary battery according to claim 1, wherein the ratio is in the range of 85/15 to 35/es. (3) A non-aqueous electrolyte containing alkali metal ions, a rechargeable positive electrode, and a negative electrode material that occludes alkali metals during charging and releases alkali metal ions in the electrolyte during discharge, wherein the negative electrode material is tin, A non-aqueous electrolyte secondary battery comprising an alloy of at least one selected from the group consisting of silicon, zinc and silver and aluminum and magnesium.