JPH0477425B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a thin film solid secondary battery comprising a conductive solid electrolyte such as lithium, silver, or copper ions, and a reversible positive electrode and negative electrode. More specifically, the present invention relates to a solid secondary battery having a reversible positive electrode and negative electrode in which the positive electrode and/or negative electrode reaction involves dissolution and precipitation of metal.

Conventional technology Solid secondary batteries, in which all battery components are solid materials, can be repeatedly charged and discharged, and have a battery outer diameter of 100 μm or less, are used as power sources for small electronic devices, such as backup power sources for semiconductor memories and solar cells. It is useful as These devices have the advantage that they can be formed together on a silicon substrate on which a semiconductor device is formed, or they can be used as a hybrid in the same package. This is extremely difficult in conventional batteries in which the battery components are liquid substances, which require a container of a certain size to prevent the liquid from flowing out of the battery.

As solid-state secondary batteries having the above-mentioned advantages, for example, the following ones have been proposed so far. That is, metallic lithium or lithium alloy is used as the negative electrode, Li ₄ SiO ₄ −Li ₃ PO ₄ solid electrolyte, Li−βAl ₂ O ₃ solid electrolyte, polymer electrolyte made of polyethylene oxide doped with ClO ₄ etc. as the electrolyte, etc., and the positive electrode is used as the negative electrode. Lithium-based solid state secondary batteries using polymeric materials such as TiS ₂ , NbS ₂ , polyacene and polythiophene Negative electrodes mainly made of metallic silver;
Solid electrolytes such as RbAg ₄ I ₅ and AgI−Ag ₂ MO ₄ glass, pre-doped with TiS ₂ or Ag
Silver-based solid-state secondary battery composed of positive electrode of AgxTiS ₂ Negative electrode mainly made of metallic copper, Rbcl−CuCl−
There are copper-based solid-state secondary batteries that are composed of a CuI-based solid electrolyte and a Cu _x TiS ₂ positive electrode pre-doped with TiS ₂ or copper. Each battery has a three-layer structure in which a negative electrode layer is placed on one side of the solid electrolyte layer (membrane) and a positive electrode layer is placed on the other side of the membrane so as to face each other.

Problems to be solved by the invention Many of these solid-state secondary batteries are
It uses a reversible negative electrode mainly made of metal, and involves an electrochemical precipitation and dissolution reaction of the metal during the charging and discharging process of the battery.

At this time, particularly in the precipitation reaction, there is a problem that the negative electrode metal grows and precipitates in a dendritic shape, and the negative electrode metal that has developed in a dendritic shape reaches the positive electrode through the solid electrolyte membrane, causing an internal short circuit. In particular, the larger the current flowing through the battery during discharging or charging, or the thinner the solid electrolyte membrane, the more likely internal short circuits will occur. Attempts have been made to alleviate these problems by making the solid electrolyte membrane thicker, but since thinness is a major feature of thin-film solid-state secondary batteries, it is necessary to make the solid electrolyte membrane thicker to alleviate this problem. It is not a good idea to do so.

Means for Solving the Problems In the present invention, a negative electrode and a positive electrode, which involve dissolution and precipitation of metal, are arranged so as not to face each other with a solid electrolyte membrane interposed therebetween. In this case, parts of the current collectors of the negative electrode and the positive electrode may face each other. As a further improvement, the negative electrode and the positive electrode are shaped like a calyx and are placed on both sides of the electrode with a solid electrolyte membrane in between so as not to face each other.

Effect According to the present invention, by arranging the negative electrode and the positive electrode so that they do not face each other through the solid electrolyte membrane, dendritic metal deposition on the negative electrode or the positive electrode occurs along the electrode during the battery charging and discharging process. It can be done. Therefore, the dendritic metal grown from one electrode will not reach the other electrode and cause an internal short circuit.

However, if the negative and positive electrodes are arranged so that they do not face each other, depending on the shape and area of the electrodes,
For example, in the case of a square electrode with a side of about 5 mm, the battery reaction will be concentrated in the part closest to the other electrode, and it is inevitable that the electrode will be uneven within the electrode plane, and the current efficiency will be lower than when the electrodes are facing each other. Deteriorate.
However, by forming the electrode into a comb shape, this non-uniformity can be very effectively reduced.
Since the teeth of one of the combs are placed between the two teeth of the other comb-shaped electrode, the area where the electrode reaction is concentrated is distributed to two locations on both sides of the teeth of the comb, which causes the aforementioned non-uniformity. is reduced. If the number of teeth on the comb is N, they will be distributed in (2XH-1) locations.
In general, considering the line width that allows easy patterning of electrodes using normal photolithography, the line width is 1 mm.
Electrodes having about 10 comb teeth can be easily obtained. As a solid electrolyte, RbCu ₄ I _1.
5 Cl _3.5 , a Cu ⁺ ion conductive solid electrolyte membrane with a thickness of 1μ is used, and a metal copper with a thickness of 3000Å is used as the negative electrode.
A battery composed of a Cu ₂ S film with a thickness of 4800 Å on the positive electrode has a comb tooth length of 5 mm, with 4 or more comb teeth per 1 mm, which is about the same level as a battery with a negative electrode and a positive electrode facing each other. Current efficiency can be obtained.

Examples Example 1 Cu ⁺ ion conductive solid electrolyte membrane 1 with a thickness of 1 μ expressed by RbCu ₄ l _1.5 Cl _3.5 , negative electrode 2 made of metallic copper with a thickness of 3000 Å, Cu ₂ with a thickness of 4800 Å A thin-film solid-state secondary battery having the structure shown in FIGS. 1 and 2 was fabricated, consisting of a positive electrode 3 made of an S film. According to the present invention, the negative electrode 2 and the positive electrode 3 are formed and arranged in a comb shape so that they do not face each other with the solid electrolyte membrane 1 in between. The length of each tooth of the comb is 5mm and the width is 100μ.
It is. 4 and 5 are negative electrode and positive electrode current collectors made of Au-Cr with a thickness of 1000 Å. 6 is a glass substrate, and 7 is a resin coating layer. After forming the positive electrode current collector 5 on the glass substrate 6 by a vacuum evaporation method using resistance heating, the positive electrode 3 is formed by a sputtering method.
A film was formed using a Cu ₂ S target (Ar gas pressure:
3.0Pa, board temperature: 200℃, RF power: 400W).
Next, a solid electrolyte membrane 1 is deposited by vacuum evaporation method by resistance heating using a mixture of RbCl-CuI-CuCl as an evaporation source, a metal copper negative electrode 2 is deposited, and then Au
-Cr negative electrode current collector 4 was vacuum deposited.

Comparative Example 1 Cu ⁺ ion conductive solid electrolyte membrane 8 with a thickness of 1 μ expressed by RbCu ₄ I _1.5 Cl _3.5 , negative electrode 9 made of metallic copper with a thickness of 3000 Å, Cu ₂ S film with a thickness of 4800 Å FIG. 3 (plan view and cross-sectional view) consisting of a positive electrode 10 consisting of
We created a thin-film solid-state secondary battery with the structure shown below. The long side of the negative electrode 9 and the positive electrode 10 is 5 mm, and the short side is 0.4 mm.
They were made in the same manner as in Example 1, except that they were rectangular in size and were arranged to face each other with the solid electrolyte membrane 8 in between. Reference numerals 11 and 12 denote a negative electrode and a positive electrode current collector made of an Au-Cr vapor deposited film, and the same numbers as in FIGS. 1 and 2 indicate the same parts as in Example 1.

After discharging the batteries produced in Example 1 and Comparative Example 1 at constant currents of 0.2, 0.5, 1.0, 2.0, 5.0, 10.0, and 20.0 μA for 2.0 μA at 20°C (at this time, the metal copper of the negative electrode was Cu When charging at the same current value as when discharging (Cu ⁺ ions become metallic copper and precipitate on the negative electrode ⁾ , the battery voltage increases rapidly or
When an internal short circuit occurred, current efficiency was evaluated by measuring the charging capacity Qch (μAh) until it suddenly decreased, and the critical current value at which an internal short circuit occurred was determined. The results are shown in FIG. Fourth
As is clear from the figure, the battery of Example 1 according to the present invention provides approximately the same current efficiency as the battery of Comparative Example 1 in which the negative electrode and the positive electrode face each other, and the battery of Comparative Example 1 has a charging current value of An internal short circuit occurs when the voltage exceeds 10 μA, whereas in the battery of Example 1, the voltage exceeds 20 μA.
However, no internal short circuit occurs.

Example 2 Consisting of a 2 μ thick Ag ⁺ ion conductive solid electrolyte membrane represented by Ag ₅ I ₃ MoO ₄ , a 4500 Å thick negative electrode made of metallic silver, and a 6000 Å thick positive electrode made of an Ag ₂ Se film. A silver-based thin film solid state secondary battery having the same structure as in Example 1 was manufactured. Both films were formed by a vacuum evaporation method using resistance heating. As the substrate, a polyimide film having a thickness of 20 μm was used in place of the glass substrate of Example 1.

Comparative Example 2 Comprised of a 2 μ thick Ag ⁺ ion conductive solid electrolyte membrane represented by Ag ₅ I ₃ MoO ₄ , a 4500 Å thick negative electrode made of metallic silver, and a 6000 Å thick positive electrode made of an Ag ₂ Se film. A silver-based thin film solid state secondary battery having the same structure as Comparative Example 1 was manufactured.

Both films were formed by a vacuum evaporation method using resistance heating. For the substrate, a polyimide film with a thickness of 20 μm was used in place of the glass substrate of Comparative Example 1.

The batteries made in Example 2 and Comparative Example 2 were subjected to the same charging and discharging tests as were conducted on the batteries in Example 1 and Comparative Example 1. As shown in FIG. 5, the results were as follows. The battery of Example 2 according to the present invention provides almost the same current efficiency as the battery of Comparative Example 2 in which the negative and positive electrodes face each other, and while the battery of Comparative Example 2 suffers from an internal short circuit when the voltage exceeds 5 μA. On the other hand, in the battery of Example 2, no internal short circuit occurs even at 20 μA.

Example 3 Li _3.6 Si _0.6 P _0.4 O ₄ with a thickness of 5000 Å
A lithium-based thin-film solid-state secondary battery with the same structure as Example 1, consisting of a Li ⁺ ion conductive solid electrolyte membrane, a negative electrode made of metallic lithium with a thickness of 2000 Å, and a positive electrode made of a TiS ₂ film with a thickness of 5000 Å. I made it.

The solid electrolyte film was an amorphous amorphous film formed by a sputtering method, the negative electrode was formed by a resistance heating vacuum evaporation method, and the positive electrode was formed by a plasma CVD method using H ₂ S and TiCl ₄ as source gases. A glass substrate with a thickness of 1.0 mm was used as the substrate.

Comparative Example 3 A lithium-based thin film solid state secondary battery was produced in the same manner as in Example 3, except that it had the same structure as Comparative Example 1. For the batteries made in Example 3 and Comparative Example 3, the current values were 0.05, 0.1, 0.2, 0.5, 1.0,
The batteries of Example 1 and Comparative Example 1 were subjected to the same charging and discharging tests as the same except that the voltage was set at 2.0 μA. As shown in FIG. 6, the battery of Example 3 according to the present invention gives almost the same current efficiency as the battery of Comparative Example 3 in which the negative and positive electrodes face each other, and while the battery of Comparative Example 3 suffers from an internal short circuit when the voltage exceeds 1 μA, the battery of Example 3 Well then
Internal short circuit does not occur even at 2μA.

Note that polarizable Cu ₂ S, which involves a charge transfer reaction across two solid phases, was used as the positive electrode of the battery in the example of the present invention.
Ag ₂ Se and TiS ₂ were used, but in addition to these, non-polarizable electrodes such as Au, Pt, carbon, ITO, etc., which involve charge transfer, are used to form an electric double layer at the interface between this electrode and the solid electrolyte. Thin-film solid-state secondary batteries according to the present invention also include batteries in which one pole of the battery is .

Effects of the Invention As described above, by arranging the positive electrode and the negative electrode on the solid electrolyte membrane so that they do not face each other through the solid electrolyte membrane, dissolution and precipitation of the electrode metal can be prevented during battery charging and discharging. A thin-film solid-state secondary battery that is unlikely to cause internal short circuits can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the structure of a battery according to an embodiment of the present invention, FIG. 2 is a sectional view of the same battery, and FIGS. 4 to 6 are characteristic diagrams showing current efficiency. 1... Solid electrolyte membrane, 2... Negative electrode, 3... Positive electrode, 8... Solid electrolyte membrane, 9... Negative electrode, 10...
Positive electrode.

Claims (1)

[Claims] 1. Consisting of a positive electrode on one side of the solid electrolyte membrane and a negative electrode on the other side of the membrane, and arranged so that the positive electrode and the negative electrode do not face each other. A solid-state secondary battery featuring: 2. The solid secondary battery according to claim 1, wherein the positive electrode and the negative electrode are arranged in a comb shape.