JPS59163758A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PURPOSE:To obtain a nonaqueous electrolyte secondary battery having a high energy density and a long charge-and-discharge life and being excellently safe and reliable by causing lithium or the like to be absorbed by a negative electrode material during charging and causing the negative electrode material to discharge lithium ion or the like into electrolyte during discharging by using an alloy principally consisting of lead as the negative electrode material. CONSTITUTION:Either an alloy principally consisting of lead and containing at least one element chosen from among cadmium, bismuth and indium, or an alloy prepared by adding tin to the above alloy is used to form a negative electrode. Such a negative electrode absorbs alkali metal ion contained in electrolyte during charging and discharges alkali metal ion into the electrolyte during discharging.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an improvement of a negative electrode for a non-aqueous electrolyte secondary battery, and as a result of this improvement, it has a high energy density, a long charging/discharging life, safety, and This provides a highly reliable charging battery.

Structures of conventional examples and their problems Until now, non-aqueous electrolyte secondary batteries using alkali metals such as lithium and sodium as negative electrodes have been made using titanium disulfide (TIS2) and various other intercalary compounds. The development of batteries that use organic electrolytes such as lithium perchlorate (LICQ 04 ) dissolved in organic solvents such as propylene carbonate (hereinafter abbreviated as PC), which are used as positive electrode active materials, has been actively developed. . A feature of this secondary battery is that by using lithium for the negative electrode, the battery voltage increases and the secondary battery has high energy resistance.

However, this type of secondary pond has not yet been put into practical use. The main reason for this is that the life of the number of charging and discharging times (cycles) is short and the charging and discharging efficiency during charging and discharging is low. This is largely due to deterioration of the lithium negative electrode.

That is, current lithium negative electrodes are mainly made of plate-shaped metallic lithium crimped onto a screen-shaped current collector made of nickel or the like, or metallic lithium dissolves in the electrolyte as lithium ions during discharge. However, it is difficult to charge this and deposit it into the plate-shaped lithium that it was before discharging, and dendrite-like lithium may be generated and break off from the base and fall off.
Phenomena such as lithium deposited in a small spherical (convex shape) detaching from the current collector occur. This results in a battery that cannot be charged or discharged. Oh, the generated dendrite-like metallic lithium will damage the separator separating the positive and negative electrodes.
It often happens that the electrode comes in contact with the positive electrode and causes a short circuit, causing the electrode to lose its function.

Various methods have been tried in the past to improve these drawbacks of negative electrodes. In general, methods have been reported in which the material of the negative electrode assembly is changed to improve adhesion to precipitated lithium, or an additive to prevent dendrite formation is added to the electrolyte. However, these methods are not always effective. In other words, with regard to the current collector material, it is effective for lithium that is deposited directly on the current collector material, but if the charging (deposition) continues, helium and helium will be deposited on the precipitated lithium, and the current collector material will be The effect disappears. Furthermore, most additives are effective at the beginning of the charge/discharge cycle, but as the cycle progresses, they decompose due to oxidation-reduction reactions within the battery and lose their effectiveness. Furthermore, recently it has been proposed to use an alloy with lithium as a negative electrode. For this column,
Lithium-aluminum alloys are well known. In this case, a somewhat uniform alloy is formed, but this uniformity disappears when charging and discharging are repeated, and especially when the amount of lithium is increased, the electrode becomes atomized and collapses. Also,
It has also been proposed to use a solid solution of silver and an alkali metal (JP-A-66-7386).

In this case, it is said that there is no collapse like in alloying with aluminum, but the amount of lithium that alloys quickly enough is small, and metallic lithium may precipitate without being alloyed. To prevent this, it is recommended to use porous materials for toilet use. Therefore, charging efficiency at large currents is poor, and alloys containing a large amount of lithium gradually accelerate refinement due to charging and discharging, resulting in a rapid decrease in cycle life.

In addition to this, there are ideas using a lithium-mercury alloy (Japanese Unexamined Patent Publication No. 67-98978), and ideas using a lithium-lead alloy (
JP-A-57-141869).

However, in the case of a lithium-mercury alloy, the negative electrode becomes liquid particle mercury due to discharge and no longer maintains its electrode shape.

In addition, in the case of a lithium-lead alloy, the fine side transformation due to charging and discharging of the electrode is more than that of a silver surface solution, and therefore it is said that it is desirable to set the amount of lead in the alloy to a modulus of 80. This makes it impossible to realize high energy density batteries. As described above, it can be said that a practically satisfactory negative electrode for non-aqueous electrolyte secondary batteries has not been found.

Therefore, as a submerged negative electrode, it is desired to develop a negative electrode material that has a large amount of alkali metal occlusion and has a fast release and occlusion rate.

OBJECTS OF THE INVENTION The present invention provides a non-aqueous electrolyte secondary battery that exhibits good characteristics such as a large charge/discharge capacity per unit volume and a long charge/discharge life by specifying a negative electrode material.

Structure of the Invention The secondary battery of the present invention is characterized in that an alloy containing lead as a main component is used as the negative electrode material, and lithium is occluded in the alloy used as the negative electrode material by charging, and lithium is stored in the electrolyte by discharging. It releases ions.

Description of Examples As mentioned above, in the secondary battery of the present invention, lithium is occluded in the negative electrode material alloy by charging, and lithium ions are released into the electrolyte by discharging. There will be 8 alloys.

The negative electrode material described in the present invention is a lead alloy before forming an alloy with lithium.

For example, when using an alloy consisting of 70% lead and 30% tin by weight, the charge/discharge reaction is expressed by the formula (1).
) In the formula (1), (Pb(70)-8n(30))Li, represents a lead, tin, and lithium alloy produced by charging, and the negative electrode material defined in the present invention is Pb in the formula (1).
(yo)-8n (30 ns).

As for the range of charging and discharging, it is necessary to discharge until lithium completely disappears from the negative electrode as shown in equation (1), and it is necessary to discharge until lithium is completely removed from the negative electrode as shown in equation (2). )-5n(30)]Li...
(2) X+Y It goes without saying that charging and discharging can be done by changing the rudder. Also in equation (2), the negative electrode material is Pb(yo)-
It is obvious that 8n(30).

An alloy whose main component is lead is an alloy in which lead is the heaviest metal in the alloy.

The inventors have discovered that by using an alloy containing lead as the main component as the negative electrode material and performing △ completion in non-aqueous electrolysis containing alkali metal ions, alkali metal precipitation does not occur even during high rate charging. We have discovered that the alkali metal is occluded in the negative electrode material without any deterioration, and that when further discharge is performed, the occluded alkali metal is released as alkali metal ions into the disintegrate with high current efficiency.

It was also found that the negative electrode material did not become finely pulverized even after repeated charging and discharging, and exhibited good negative electrode characteristics of a non-aqueous electrolyte secondary battery.

When comparing lead metal and an alloy mainly composed of lead as negative electrode materials, the alloy showed better negative electrode characteristics. Bismuth, cadmium,
Many alloys are made by adding tin, indium, etc.
Microscopically, it consists of many phases such as various metal components and intermetallic compounds, and is not uniform. Alkali metals such as lithium absorbed by charging are thought to diffuse at a high rate along the interface between the alloy and the phase, and when high-rate charging and discharging is performed, alloys containing lead as a generating component are used. It was better. Therefore, compared to the case where metallic lead is used, both the amount of electricity charged and discharged and the cycle customization are improved.

The cell shown in FIG. 1 was constructed and the characteristics of the negative electrode of a non-aqueous electrolyte secondary battery made of various metals and alloys were investigated.

In Figure 1, A is a test electrode made of the two metal alloys studied, B is
is a positive electrode made of TI S2, and C is a lithium plate as a reference electrode. Leads of each electrode EA, E
B, Nickel wire was used for EC. As shown in FIG. 2, the test electrode A was a 1 cm x 1 m thick metal or alloy board with a nickel ribbon EA attached as a lead. The electrolyte contains 1 mol/2 L z C1l
PC in which O4 was dissolved was used. The liquid tank H of the test electrode A and the liquid tank G of the reference electrode C are connected by a communication pipe I. In order to measure the custom made metal or alloy as a negative electrode for a non-aqueous electrolyte secondary battery, the test electrode A was charged in the cathode direction with a constant current of 5 mA until the potential of the test electrode A became OmV with respect to the lithium reference electrode C. Under these conditions, lithium does not precipitate on the test electrode but enters the alloy. After the potential of test electrode A reaches OmV, 1. The battery was discharged toward the anode at a constant current of 5 m until o'VK, and then charging and discharging were repeated under the same conditions. The table shows the alloy used for test electrode A, the amount of electricity charged in the 1st cycle and the 10th cycle of the metal,
The amount of discharged electricity and the efficiency are shown as the amount of discharged electricity divided by the amount of charged electricity, and as a custom cycle, the amount of discharged electricity of the 10th cycle divided by the amount of discharged electricity of the first cycle is shown. It can be said that it is a negative electrode with good charging electricity amount, drowsiness, efficiency, and cycle characteristics. The charging curve and the discharging curve of test electrode A at the 10th cycle, indicated by symbols in the table, are shown in FIG. 3 and FIG. 4, respectively.

From the results shown in the margin below, aluminum has traditionally been used as a negative electrode material for non-aqueous electrolyte secondary batteries.

It has been found that the lead-based alloy of the present invention is better than silver, silver, and mercury.

Comparing raw lead and lead alloy, the alloy shows better properties. Table 1 also shows custom-made negative electrodes made of simple metals, which are other components used to make the lead alloy. As a result, the performance was improved by using an alloy rather than using individual metals of each component. Furthermore, as shown in Table 4 for lead-tin alloys, there was a tendency for the performance to improve as the other components increased.

Regarding the amount of lead, which is the main component in the alloy composition, -1#4
-As shown in Table 8, a weight percentage of 35 or higher seems appropriate.

In addition, when mercury is used as the negative electrode material, the reason why the charged and discharged mercury paper is small is related to the fact that the sodium content in the sodium amalgam in mercury salt electrolysis is only about 0.2%, but this is not surprising. .

In the above embodiment, an example was shown in which lithium was inserted into and released from the negative electrode material. It is also possible to construct a negative electrode that intercalates and desorbs alkali metals such as sodium and potassium in addition to lithium.

In addition, as an electrolyte, L i CQ O4 shown in the example
Conventional aluminum, lead, silver, even when using solid electrolytes such as L 13N (g lithium oxide) and LiI (lithium iodide), as well as PC dissolved in .

Compared to mercury, the use of bismuth or an alloy containing bismuth as a main component of the present invention as a negative electrode material was superior to that of 1.).

As described above, by using an alloy whose main component is lead as the negative electrode material, it has good cycle characteristics with many charge and discharge cycles.
In other words, a highly reliable non-aqueous electrolyte battery with a long charge/discharge life can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a cell used for examining negative electrode characteristics, FIG. 2 is a side view of a test electrode, and FIGS. 3 and 4 are charging and discharging curve diagrams. A...Test electrode, B...Positive electrode, C...
...J (6 combined electrodes. Fig. 1 Fig. 2 r 1981 Patent Application No. 36881-2 Title of Invention Nonaqueous Electrolyte Secondary Battery 3 Relationship with the Amendment Case Patent Application
Appointment Address: 1006 Kadoma, Kadoma City, Osaka Prefecture
Name (582) Matsushita Electric Industrial Co., Ltd. Representative Toshihiko Yamashita 4 Agent'571 Address 7, Matsushita Electric Industrial Co., Ltd., 1006 Kadoma, Kadoma City, Osaka Prefecture Contents of amendments (1) Patent in the specification Correct the scope of claims column as shown in the attached sheet. (2) The statement on page 6, lines 4 to 8 of the specification is corrected and omitted as follows. “The present invention provides a non-aqueous electrolyte containing alkali metal ions,
It is equipped with a reversible positive electrode and a negative electrode made of an alloy that has the function of occluding alkali metal ions in an electrolyte during charging and releasing the metal ions into the electrolyte during discharging, and uses a lead alloy as the alloy of the negative electrode. be. More specifically, the lead alloy is characterized by using an alloy containing lead as a main component and at least one selected from the group consisting of cadmium, bismuth, and indium as another component, or an alloy further containing tin. do. (3) The statement from page 6, line 17 to page 7, line 7 from the bottom is corrected as follows. [For example, when an alloy (Pb(7o)-Cd(3o)) consisting of 70% lead and 30% cadmium by weight is used, the charge/discharge reaction is as shown in equation (1). (Pb(70) -Cd(30)')+xLi ++X
8 charging (:Pb(7o) -cc+ (30), 1lLix
Discharge - Discharge (1) In the formula (Pb(70)-Cd(30),: ILix indicates a lead-cadmium-lithium alloy produced by charging, and the negative electrode material defined in the present invention is the formula (1) % formula % Also, as for the range of charging and discharging, it is not necessary to discharge until the lithium is completely exhausted from the negative electrode as in equation (1), but it is not necessary to discharge until the amount of lithium occluded in the negative electrode is determined as in equation (2). It is natural that charging and discharging can be performed by adjusting the .
+ya charge [:Pb (70) Cd (30) ) L lx+7
Discharge・(2) Also in equation (2), the negative electrode material is Pb(70)-cd(3
It is obvious that o). (4) Insert the following sentence between page 13, line 19 and line 20. ``Furthermore, we considered the mechanical stability of the negative electrode material. When charging and discharging at a constant current of 5 mA, no refinement occurred in any lead alloy.Next, assuming long-term, low-rate charging, The negative electrode material was short-circuited with metallic lithium in the electrolyte. By short-circuiting, the maximum amount of lithium was occluded in the negative electrode material. Among the alloys 1 to 90 shown in the table, 2 to 4 lead - Fine powdering of the alloy occurred in tin alloys, but not in other alloys. Even in alloys containing lead and tin, such as alloys 8 and 9, fine powdering occurs when other components are included. No pulverization occurred. Even in alloys composed only of lead and tin, the more tin there was, the smaller the degree of pulverization was. From the above, by using an alloy whose main component is lead,
A good negative electrode that absorbs and desorbs lithium can be obtained, and even in lead-tin alloys, where the electrode becomes finer when the amount of lithium absorbed increases, one of the other components cadmium, bismuth, and indium can be added. By doing so, it becomes a good negative electrode material. (6) [Bismuth or bismuth] on page 14, line 8.
Correct ``lead'' to 1. 2. Claimed secondary battery. When charging, it absorbs alkali metal ions in the electrolyte,
A negative electrode made of an alloy having a function of releasing the metal ions into the electrolyte during discharge, the alloy containing lead as a main component and at least one member selected from the group consisting of cadmium, bismuth, and indium as other components. A nonaqueous electrolyte secondary battery that is an alloy containing tin.

Claims (2)

[Claims] (1) It has the function of occluding alkali metal ions in the electrolyte during charging and releasing the listed metal ions into the electrolyte during discharging, and is characterized by using an alloy containing lead as the main component as the negative electrode material. Non-aqueous electrolyte secondary battery. (2) The main component of the negative electrode material is mixed): Odomira 4
,e:,'Smas, Susfin; ”) la f)
The non-aqueous electrolyte secondary electricity tm according to claim 1, characterized in that 5 t5' ((t 4-Weighing 47 "Aho Teishumeru").