JPH08185887A - Totally solid lithium battery - Google Patents

Abstract

PURPOSE: To improve a sealing capability for a battery using aluminum or an alloy containing aluminum as a battery jar material by using a lithium ion conductive inorganic solid electolytic layer having only lithium ions as conductive media. CONSTITUTION: The powder of lithium ion conductive inorganic solid electrolyte is pressed and molded into plate type by use of dies to be a electrolytic disc 1. Regarding a positive electrode, various types of active materials and solid electrolyte powder are mixed to a prescribed ratio, and a positive electrode disc 2 is thereby prepared. Then, the discs 1 and 2 are superposed on top of each other and pressed for integration. Then, the negative electrode disc 3 is further integrated therewith to form a battery element. For the element so prepared, a cylindrical vessel 4 of aluminum is used as a jar, thereby forming a lithium battery. According to this construction, no ion migration takes place in an electrolyte and a light alloy jar material can be used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium battery in which a positive electrode and a negative electrode are in contact with a lithium ion conductive inorganic solid electrolyte layer, and more particularly to a battery cell case constituent material thereof.

[0002]

2. Description of the Related Art In recent years, a high energy density lithium secondary battery using an organic electrolytic solution has been actively put into practical use. As a battery case material for these lithium batteries, stainless steel or iron plated with nickel is often used. However, in order to improve the energy density per weight of these batteries, it is extremely desirable to use a light metal such as aluminum or titanium as a battery case material for the battery, and already use fluorinated graphite for the positive electrode and lithium for the negative electrode. Aluminum is used as the battery case material in a lithium primary battery that uses an electrolytic solution prepared by dissolving lithium borofluoride in an organic solvent such as γ-butyrolactone as an electrolyte. In this battery, the aluminum of the battery case is connected to the positive electrode, and a high potential is constantly applied to the battery case so that a weak nonconductive coating is formed on the aluminum surface in the organic electrolyte. This has been devised to prevent the occurrence of chemical and electrochemical corrosion. However, using a light metal such as aluminum metal as a battery case material for a lithium secondary battery is generally lacking in strength, or electrochemical corrosion is large and it cannot be used in the same way as a battery case for a primary battery. It is extremely difficult to put to practical use. This is because, in a lithium secondary battery used as an organic solvent and an electrolytic solution, solvated cations and anions enter and leave the electrode active material at the positive electrode and the negative electrode during charge or discharge of the battery. If the battery case is made of aluminum, which has a large mechanical strength and weak mechanical strength, the sealing property of the sealing part of the battery case tends to be impaired. Furthermore, since there is a liquid organic electrolytic solution in the battery case, the aluminum in the battery material and lithium ions in the electrolytic solution chemically react with each other to form an alloy or the metal in the battery case is left as it is. Aluminum dissolves in the electrolyte. Therefore, a special device was required to use it as a battery case material.

As a lithium secondary battery system in which such problems are relatively easy to solve, there is a lithium battery using a solid electrolyte layer which is not in a liquid state as an electrolyte layer. This is because the electrolyte layer is in a solid state, so that it is easy to avoid direct contact between the battery case and the electrolyte layer, and the battery case and the internal battery element portion can be easily separated. However, the actual situation of this idea also differs depending on what kind of solid electrolyte layer material is used in the battery. For example, a lithium primary battery, which is often used as a power source for a pacemaker, uses lithium iodide as a lithium ion conductive solid electrolyte layer, 2 vinylpyridine polyiodide as a positive electrode active material, and lithium as a negative electrode active material. .
In this battery, the positive and negative electrode terminals are hermetic terminals, and the battery case and the battery element are completely independent and separated, and the battery case is made of stainless steel. This is because iodine is used in the positive electrode active material and the solid electrolyte layer material used in this battery system, and during storage of the battery, iodine gas is generated particularly at high temperatures, and more iodine gas is generated. This is because it corrodes the battery case material, and light metals such as aluminum and titanium cannot be used.

As described above, in a lithium secondary battery, it is practically difficult to apply a light metal such as aluminum to a battery case of any battery system. In particular, an inorganic solid electrolyte layer under development is used. At present, it is not used as a battery case material for the all-solid-state lithium secondary battery used.

[0005]

In order to use aluminum, titanium, or these light metal materials as the battery case material of a lithium secondary battery, contact between the organic electrolytic solution in the battery case and aluminum must be avoided or otherwise. For example, it is necessary to prevent electrochemical corrosion at the time of charging / discharging the battery, reduce the large volume expansion / shrinkage change of the electrode at that time, and eliminate the chemical corrosion with the battery element constituent material.

The present invention is intended to solve the above problems and provide an all solid lithium secondary battery using aluminum metal or an alloy mainly containing aluminum as a battery case material.

[0007]

A lithium ion conductive inorganic solid electrolyte layer is used as a solid electrolyte layer interposed between a positive electrode and a negative electrode, and a battery case material of a battery contains aluminum or at least aluminum metal. It is a structure using an alloy. Furthermore, the lithium ion conductive inorganic solid electrolyte layer does not contain a halide.

[0008]

Function: Corrosion of many metals is such that, after being chemically or electrochemically oxidized, the oxide forms a complex with an anion in the electrolytic solution and is eluted in the liquid electrolyte. In order to use aluminum, an aluminum alloy, etc., which are particularly susceptible to oxidation, as the battery case constituent material of the battery, it is necessary to chemically stabilize the film formed on the surface of these metals. On the other hand, in an ideal lithium ion conductive solid electrolyte layer, the ion conductive species is only lithium ions, and anions do not move like other organic electrolytic solutions. Therefore, when aluminum or its light alloy is used as the battery case material, even if these metals are chemically or electrochemically oxidized, the anions necessary for complex formation do not exist, so the solid electrolyte It cannot be eluted into the layer, and even if a complex is formed due to some change, the solid electrolyte layer itself has an ion selectivity for moving only lithium ions, so a certain amount of complex is formed. The metal surface is kept stable by itself. Therefore, it can be stably used as a battery case material for a lithium secondary battery.

Further, both negative and positive ions are present in the electrolyte of a lithium secondary battery using an organic electrolytic solution. For example, in a case where lithium perchlorate is dissolved in an organic solvent such as propylene carbonate, lithium ions are used as positive ions. Perchlorate ions as anions exist in a state of being solvated with the organic solvent. As a result, when an ordinary electrolyte is electrochemically reduced using, for example, an electrode such as carbon, the solvated lithium ions in the electrolytic solution are reduced, and metallic lithium enters the carbon layer. At this time, a part of the organic solvent also enters. On the contrary, when this electrolyte is electrochemically oxidized, the anion in the solvated state (in this case,
(Perchlorate ion) is oxidized, and the decomposition of the organic solvent is accompanied, and depending on the electrode active material, the organic solvent enters and exits as in the reduction reaction. This phenomenon also occurs in many polyelectrolyte layers, although there are some differences. However, in the battery using the lithium ion conductive solid electrolyte layer, as described above, the reaction involves only lithium ions, so in a lithium secondary battery using this, when charging and discharging the battery, the lithium ion Only the particles enter and leave the crystal layer of the electrode active material, so that the expansion and contraction of the electrode itself is small. As a result, even if it is used as a battery case of a battery, it is not necessary to apply a large mechanical force to the caulking seal portion, and it becomes possible to use light metal as a battery case material very easily.

Since the electrolyte used in the battery of the present invention is a lithium ion conductive inorganic solid electrolyte layer containing at least a sulfur compound such as lithium sulfide and silicon sulfide, aluminum or titanium is not used as the battery case material. However, even if sulfur is released from the electrolyte, these light metals produce almost no sulfur compound. Therefore, the chemical corrosion of the battery case hardly progresses. For these reasons, a highly reliable lithium secondary battery using a light metal such as aluminum as the battery case of the present invention can be provided.

[0011]

EXAMPLE A lithium ion conductive solid electrolyte layer used in the lithium battery of the present invention is a'X.b'Li ₂ S.c '.
Y (provided that a ′ + b ′ + c ′ is 1 and X is Li ₂
O, Li ₃ PO ₄ , Li ₂ SO ₄ , Li ₄ SiO ₄ , LiBO
₂ such as lithium oxide or lithium oxyacid salt, Y
Is represented by SiS ₂ , GeS ₂ , P ₂ S ₅ , B ₂ S ₃ , and one or more sulfides selected from the group of Al ₂ S ₃ ), and in particular, a lithium ion conductive solid electrolyte layer containing no halide. To use. Further, lithium and an alloy containing lithium or lithium carbon is used as the negative electrode, and the positive electrode is titanium disulfide, iron sulfide, molybdenum disulfide, lithium chevrel intercalation compound or sulfide such as silver sulfide or lithium cobalt oxide, lithium nickel oxide, A transition metal oxide such as a lithium manganese compound is used as an electrode active material. In making a lithium secondary battery using these, as shown in FIG. 1, first, a lithium ion conductive solid electrolyte powder is pressure-molded into a plate shape using a mold, and here, a thickness of 200 μ and a diameter are used. The disk shape was 10 mmφ (FIG. 1-1). For the positive electrode, powder obtained by mixing the above-mentioned various active materials and solid electrolyte powder in a volume ratio of 60:40 was pressure-molded into a disk shape (Fig. 1-2) having a diameter of 10 mm.
Subsequently, these two disks were overlapped and integrated again under pressure. Then, the disk-shaped negative electrode material was further pressed and integrated into an integrated disk to integrate the battery element (Fig. 1-
3).

The battery element thus prepared was inserted together with an insulating ring (Fig. 2-5) into a cylindrical container (Fig. 2-4, diameter 12 mmφ, height 2 mm) made of light metal, and then the upper lid (Fig. 2- 6) the plastic ring (Fig. 2-
A lithium battery of the present invention was produced by sealing and crimping via 7).

Hereinafter, the present invention will be described in more detail with reference to specific examples. (Example 1) In this example, the solid electrolyte is 0.6 Li ₂ S.
An amorphous lithium ion conductive solid electrolyte layer made of 0.4SiS ₂ was used, which had a diameter of 10 mmφ and a thickness of 0.
A disc-shaped product having a diameter of 2 mm was used. The positive electrode uses LiCoO ₂ as an active material, and the active material and the solid electrolyte are mixed at a volume ratio of 6: 4 and the diameter is 10 mmφ.
Was pressed into a disk shape. Subsequently, a negative electrode was prepared by punching a plate (0.3 mm thick) of a lithium aluminum alloy (alloy composition 20:80 weight ratio) into a plate having a diameter of 10 mm.

The pair of electrode discs thus produced was pressed and integrated so as to form a sandwich with the solid electrolyte disc as the center to produce a battery element.

As shown in FIG. 2, the battery element thus prepared was used to prepare a battery according to the present invention using a cylindrical container (4) which was a battery case made of aluminum.

The battery thus prepared was subjected to a charge / discharge test in a high temperature bath of 80 ° C. at a constant current of 200 μA / cm ² , and
The corrosion state inside the battery after 000 cycles was examined.

As a result, the charge and discharge effect after 1000 cycles was almost 100%, and no corrosion was observed on the aluminum surface of the battery case material.

The charging / discharging efficiency after 1000 cycles was almost 100%, which means that the sealing condition between the upper lid of the battery and the battery container was not damaged and the caulking strength was sufficient. It turned out to be bearable.

Example 2 Instead of the solid electrolyte (0.6Li ₂ S.0.4SiS ₂ ) used in Example 1, 0.01Li ₃ PO ₄ .0.63Li ₂ S.0.36
A battery according to the present invention was prepared in exactly the same manner as in Example 1, except that the battery was constructed using an amorphous lithium ion conductive solid electrolyte layer made of SiS ₂ . When this battery was evaluated in the same manner as in Example 1, almost the same results as in Example 1 were obtained.

Example 3 Instead of the solid electrolyte (0.6Li ₂ S.0.4SiS ₂ ) used in Example 1, 0.01Li ₂ O.0.63Li ₂ S.0.36Si
A battery according to the present invention was prepared in exactly the same manner as in Example 1 except that the battery was constructed using the amorphous lithium ion conductive solid electrolyte layer made of S ₂ . When this battery was evaluated in the same manner as in Example 1, almost the same results as in Example 1 were obtained.

Example 4 Instead of the solid electrolyte (0.6Li ₂ S.0.4SiS ₂ ) used in Example 1, 0.01Li ₄ SiO ₄ .0.63Li ₂ S.0.3
A battery according to the present invention was prepared in exactly the same manner as in Example 1 except that the battery was constructed using an amorphous lithium ion conductive solid electrolyte layer made of 6SiS ₂ . When this battery was evaluated in the same manner as in Example 1, almost the same results as in Example 1 were obtained.

Example 5 Instead of the solid electrolyte (0.6Li ₂ S.0.4SiS ₂ ) used in Example 1, 0.01LiBO ₂ .0.63Li ₂ S.0.36S
A battery according to the present invention was prepared in exactly the same manner as in Example 1 except that the battery was constructed using an amorphous lithium ion conductive solid electrolyte layer made of iS ₂ . As a result of evaluating this battery in the same manner as in Example 1, almost all Example 1
And gave similar results.

[0023] (Example 6) Instead, the amorphous lithium ion conductive consisting 0.6Li ₂ S · 0.4GeS ₂ of the solid electrolyte used in Example _{1 (0.6Li 2 S · 0.4SiS 2} ) A battery according to the present invention was prepared in exactly the same manner as in Example 1 except that the battery was constituted by using an organic solid electrolyte layer. When this battery was evaluated in the same manner as in Example 1, almost the same results as in Example 1 were obtained.

[0024] Alternatively, amorphous lithium consisting 0.6Li ₂ S · 0.4P ₂ S ₅ of the solid electrolyte used in Example 7 Example _{1 (0.6Li 2 S · 0.4SiS 2} ) A battery according to the present invention was prepared in exactly the same manner as in Example 1 except that the battery was constructed using an ion conductive solid electrolyte. When this battery was evaluated in the same manner as in Example 1, almost the same results as in Example 1 were obtained.

(Embodiment 8) In this embodiment, except that an aluminum zinc alloy is used instead of the aluminum battery case,
A battery was prepared in exactly the same manner as in Example 1, and the battery evaluation test was conducted in the same manner. The evaluation results gave almost the same results as in Example 1.

Example 9 A battery according to the present invention was prepared in the same manner as in Example 1 except that the aluminum battery case material used in Example 1 was changed to an aluminum magnesium alloy. When this battery was evaluated in the same manner as in Example 1, almost the same results as in Example 1 were obtained.

(Example 10) A battery according to the present invention was prepared in the same manner as in Example 1 except that the aluminum battery material used in Example 1 was changed to an aluminum tin alloy. When this battery was evaluated in the same manner as in Example 1, almost the same results as in Example 1 were obtained.

In order to study the effect of the present invention, a battery using another solid electrolyte was prepared, and a comparative experiment was conducted to evaluate its characteristics.

(Comparative Experiment 1) In this comparative experimental example, 0.75 (0.6Li ₂ S.0.4SiS ₂ ).
A battery using aluminum in a battery case was prepared in the same manner as in Example 1 except that an amorphous lithium ion conductive solid electrolyte layer made of 0.25 (LiI) was used.

The battery thus prepared was subjected to a charge / discharge test in a high temperature bath at 80 ° C. at a constant current of 100 μA / cm ² , and
The corrosion state inside the battery after 000 cycles was examined.

As a result, the charge and discharge efficiency after 1000 cycles was about 85%, and significant corrosion was observed on the aluminum surface of the battery case material.

Further, after the test, the seal portion of the sealing portion between the battery upper lid and the battery case is discolored in black brown, and free iodine leaks from the inside of the battery to the outside of the battery through the seal portion, and the caulking portion Corrosion was also observed, caulking strength decreased,
It was not sufficiently durable as a practical battery.

(Comparative Experiment 2) In this comparative experimental example, 0.75 (0.6Li ₂ S.0.4GeS ₂ ).
A battery was made in the same manner as in Example 1 except that the amorphous lithium ion conductive solid electrolyte layer made of 0.25 (LiI) was used.

The battery thus prepared was subjected to a charge / discharge test in a high temperature bath of 80 ° C. at a constant current of ²⁰ μA / cm ² , and 10
The corrosion state inside the battery after the lapse of 00 cycles was examined.

As a result, the charge / discharge efficiency after 1000 cycles was 78%, and significant corrosion was observed on the aluminum surface of the battery case material.

Further, after the test, the seal portion of the sealing portion between the battery upper lid and the battery case is discolored to black brown, and free iodine leaks from the inside of the battery through the seal portion to the outside of the battery, and the caulking portion Corrosion was also observed, caulking strength decreased,
Similar to Comparative Experiment 1, it was not sufficiently durable as a practical battery.

(Comparative Experiment 3) In this comparative experiment example, 0.75 (0.6Li ₂ S.0.4P ₂ S ₅ ).
A battery was made in the same manner as in Example 1 except that the amorphous lithium ion conductive solid electrolyte layer made of 0.25 (LiI) was used.

The battery thus produced was subjected to a charge / discharge test in a high temperature bath at 80 ° C. at a constant current of ²⁰ μA / cm ² , and 10
The corrosion state inside the battery after the lapse of 00 cycles was examined.

As a result, the charge / discharge efficiency after 1000 cycles was 78%, and significant corrosion was observed on the aluminum surface of the battery case material.

Further, after the test, the sealing portion of the sealing portion between the upper lid of the battery and the battery container is discolored to black brown, and free iodine leaks from the inside of the battery to the outside of the battery through the sealing portion, and the caulking part Corrosion was also observed, caulking strength decreased,
Similar to Comparative Experiment 1, it was not sufficiently durable as a practical battery.

(Comparative Experiment 4) In this comparative experimental example, 0.75 (0.6Li ₂ S.0.4B ₂ S ₃ ).
A battery was made in the same manner as in Example 1 except that the amorphous lithium ion conductive solid electrolyte layer made of 0.25 (LiI) was used.

The battery thus prepared was subjected to a charge / discharge test in a high temperature bath of 80 ° C. at a constant current of ²⁰ μA / cm ² , and 10
The corrosion state inside the battery after the lapse of 00 cycles was examined.

As a result, the charge / discharge efficiency after 1000 cycles was 79%, and significant corrosion was observed on the aluminum surface of the battery case material.

Further, after the test, the sealing portion of the sealing portion between the battery upper lid and the battery case is discolored to black brown, and free iodine leaks from the inside of the battery to the outside of the battery through the sealing portion, and the caulking portion Corrosion was also observed, caulking strength decreased,
Similar to Comparative Experiment 1, it was not sufficiently durable as a practical battery.

(Comparative Experiment 5) In this comparative experimental example, 0.85 (0.6Li ₂ S.0.4SiS ₂ ).
A battery was made in the same manner as in Example 1 except that the amorphous lithium ion conductive solid electrolyte layer made of 0.15 (LiBr) was used.

The battery thus prepared was subjected to a charge / discharge test in a high temperature bath at 80 ° C. at a constant current of ²⁰ μA / cm ² , and 10
The corrosion state inside the battery after the lapse of 00 cycles was examined.

As a result, the charge / discharge efficiency after 1000 cycles was 79%, and significant corrosion was observed on the aluminum surface of the battery case material.

Further, after the test, the sealing portion of the sealing portion between the upper lid of the battery and the battery case is discolored to black brown, and free bromine leaks from the inside of the battery through the sealing portion to the outside of the battery, and the caulking portion Corrosion was also observed, caulking strength decreased,
Similar to Comparative Experiment 1, it was not sufficiently durable as a practical battery.

(Comparative Experiment 6) In this comparative experimental example, 0.80 (0.6Li ₂ S.0.4SiS ₂ ).
A battery was made in the same manner as in Example 1 except that an amorphous lithium ion conductive solid electrolyte layer made of 0.20 (LiCl) was used.

The battery thus prepared was subjected to a charge / discharge test in a high-temperature bath at 80 ° C. at a constant current of ²⁰ μA / cm ² , and 10
The corrosion state inside the battery after the lapse of 00 cycles was examined.

As a result, the charge / discharge efficiency after 1000 cycles was 79%, and significant corrosion was observed on the aluminum surface of the battery case material.

Further, after the test, the sealing portion of the sealing portion between the upper lid of the battery and the battery case is discolored to black brown, and the free chlorine leaks from the inside of the battery to the outside of the battery through the sealing portion, and Corrosion was also observed, caulking strength decreased,
Similar to Comparative Experiment 1, it was not sufficiently durable as a practical battery.

(Comparative Experiment 7) In this comparative experiment example, lithium perchlorate as an electrolyte was added to a solution of polyethylene oxide dissolved in acetonitrile, which was applied on a Teflon plate to evaporate acetonitrile. A battery was prepared in the same manner as in Example 1 except that the molecular electrolyte was used.

The battery thus produced was subjected to a charge / discharge test in a high temperature bath at 60 ° C. at a constant current of 10 μA / cm ² , and then 50
The corrosion state inside the battery after the cycle was examined.

As a result, the charge / discharge efficiency after 50 cycles was about 55%, and significant corrosion was observed on the aluminum surface of the battery case material.

Further, after the test, the sealing part of the sealing part between the upper lid of the battery and the battery case is slightly deformed, and the outside air, especially the moisture is intruded into the battery, and the caulking part is remarkably corroded. However, it was not sufficiently durable as a practical battery.

(Comparative Experiment 8) In this comparative experiment example, a battery was prepared in the same manner as in Example 1 except that an organic electrolytic solution prepared by dissolving lithium perchlorate in propylene carbonate was used as an electrolyte.

The battery thus prepared was subjected to a charge / discharge test in a high temperature bath at 60 ° C. at a constant current of 100 μA / cm ² , and 5
The corrosion state inside the battery after 0 cycles was examined.

As a result, the charge / discharge efficiency after 50 cycles was about 55%, and significant corrosion was observed on the aluminum surface of the battery case material.

Further, after the test, the sealing portion of the sealing portion between the upper lid of the battery and the battery container was slightly deformed, and the outside air, especially the moisture was intruded into the battery, and the caulking portion was remarkably corroded. However, it was not sufficiently durable as a practical battery.

In the examples of the present invention, only the battery using the lithium aluminum alloy as the negative electrode active material was described, but other examples of the negative electrode active material include:
It goes without saying that the same effect can be obtained when a substance other than those described in the examples such as a lithium-graphite compound is used, and the all-solid-state lithium battery of the present invention is used as a negative electrode active material in the practice of the present invention. It is not limited to those shown in the examples.

In the examples of the present invention, LiCoO ₂ was used as the positive electrode active material.
It goes without saying that similar effects can be obtained by using transition metal oxides such as O ₂ and LiMn ₂ O ₄ which are not explained in the examples, and transition metal sulfides such as TiS ₂ and the like. The invention is not limited to the positive electrode active materials listed in the examples.

[0063]

INDUSTRIAL APPLICABILITY The present invention uses a lithium ion conductive inorganic solid electrolyte layer in which only lithium ions are used as a conductive species, so that aluminum or a light alloy containing aluminum is used as a battery case material for sealing lithium batteries. It is clear from Comparative Examples 7 and 8 that the above is improved, and this is achieved by the fact that the expansion and contraction of the electrode is extremely small due to the charge and discharge of the battery. As a result, it was found that even a material having a low mechanical strength, such as aluminum, as a battery case material can be practically used.

On the other hand, it has been clarified that the state of corrosion with respect to aluminum can be prevented by using a solid electrolyte layer containing no halide such as iodine or bromine, whereby a light metal such as aluminum is used as an all-solid lithium battery cell battery. Batteries could be provided.

[Brief description of drawings]

FIG. 1 is a sectional view of a battery element according to an embodiment of the present invention.

FIG. 2 is a sectional view of a lithium battery according to an embodiment of the present invention.

[Explanation of symbols]

 1 Electrolyte Disc 2 Positive Electrode Disc 3 Negative Disc 4 Cylindrical Container 5 Insulating Ring 6 Top Lid 7 Plastic Ring

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazunori Takada 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] 1. An all-solid-state lithium battery having at least a pair of electrodes in contact with a solid electrolyte layer, wherein the solid electrolyte layer is a lithium ion conductive inorganic solid electrolyte layer,
And an all-solid-state lithium battery using aluminum or an alloy containing at least aluminum metal as a battery case material. 2. The all-solid-state lithium battery according to claim 1, wherein the lithium ion conductive inorganic solid electrolyte layer does not contain a halide. 3. The all-solid-state lithium battery according to claim 1, wherein the lithium ion conductive inorganic solid electrolyte layer contains at least lithium sulfide.