JP3507926B2 - Solid-state battery - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid type battery having an ion conductive solid electrolyte provided between a positive electrode and a negative electrode. More specifically, the present invention relates to a solid-state battery in which, as a solid electrolyte, at least two layers of solid electrolytes having different potential windows are provided on the positive electrode side and the negative electrode side, respectively, to suppress decomposition of the solid electrolyte and reduce internal resistance. .

[0002]

2. Description of the Related Art A small battery using a light metal such as lithium, sodium or aluminum for its negative electrode can generate a high voltage and has a high energy density, and is widely used as a power source for consumer electronic devices. Recently, research and development of making these batteries into secondary batteries have been actively conducted.
Further, such a battery can be roughly classified into an electrolyte solution type battery in which an electrolyte solution is interposed between a positive electrode and a negative electrode and a solid type battery in which a solid electrolyte is interposed. Solid-state batteries have attracted attention because there is no risk of leakage of the contents inside the batteries, the safety and reliability of the batteries can be improved, and the batteries can be made thinner and stacked.

The solid electrolyte used in this solid-state battery can be roughly classified into two types, that is, an inorganic material and an organic material. Among them, the solid electrolyte made of an inorganic material has a relatively high ionic conductivity, but since it is a crystalline body, it has poor mechanical strength and is difficult to be processed into a flexible film. On the other hand, a polymer solid electrolyte made of an organic polymer can be formed into a thin film having flexibility, and the formed thin film has excellent mechanical properties due to its inherent flexibility. It is possible to add properties. Therefore, the polymer solid electrolyte is regarded as a particularly promising solid electrolyte material for thin high energy density batteries, and its research and development is being conducted. As such a solid polymer electrolyte, a composite of polyethylene oxide having a polyether structure and an alkali metal salt such as Li salt or Na salt has been known so far.

[0004]

However, all of the conventional solid electrolytes are prone to oxidative decomposition or reductive decomposition due to the reaction with the electrode, which causes a problem of deterioration of battery performance such as increase of internal resistance.

Further, when the solid-state battery is configured as a secondary battery, a high voltage including an overvoltage is applied between both electrodes at the time of charging, so that the decomposition of the solid electrolyte is further promoted. there were. For example, in a secondary battery using a lithium metal, a lithium alloy, or a carbonaceous material that can be doped or dedoped with lithium or lithium ions for the negative electrode and a lithium-containing composite oxide such as LiCoO _{2 for} the positive electrode, the applied voltage during charging May exceed 4V.

Also, the overvoltage increases as the charging speed increases. Therefore, with the recent demand for increasing the battery capacity and shortening the charging time, as the demand for increasing the charging speed becomes stronger, it is necessary to develop a solid electrolyte material that is electrically stable against overvoltage. Was being strongly desired.

By the way, the electrochemical stability of the electrolyte is
Generally, the concept of the potential window is evaluated as an index. Here, the potential window of the solid electrolyte is defined as a potential range in which an irreversible current is not observed in the cyclic voltammogram.

However, in practice, it is difficult to distinguish between an irreversible current and a reversible current, and since the absolute value of the current is small, it is difficult to precisely define the potential window. For example, the potential window of a solid electrolyte composed of a complex of LiClO ₄ and polyethylene oxide is set to 0 to 4.2 V based on the Li electrode (M. Armand, Solid State Io).
nics, 9 & 10 , 749 (1983)), actually, when this solid electrolyte is brought into contact with Li metal (0 V VS Li / Li ⁺ ), the decomposition reaction proceeds and a resistance film is formed at the interface between the electrode and the solid electrolyte. (T.Ichino, BDCahan, DAScherson, J.Elec
trochem.Soc., 138 (11) , 159 (1991), Z.Takehara, Z.Ogum
i, Y.Uchimoto, E.Endo, Y.Kanamori, J.Electrochem.So
c., 138 (6) , 1574 (1991)). From these, it is understood that the decomposition reaction of the solid electrolyte proceeds near the threshold value even within the range of the potential window.

FIG. 3 shows a non-aqueous electrolyte type lithium ion secondary battery (positive electrode: lithium-cobalt composite oxide,
(Negative electrode: pitch coke) represents a general potential change between the positive electrode and the negative electrode during the charging / discharging process. If the resistance in each electrode is ignored, the solid-state secondary battery electrode-solid electrolyte interface It is considered that the electric potential is changing as well.
Therefore, also from this fact, in order to prevent the solid electrolyte from undergoing oxidative decomposition and reductive decomposition in the charging / discharging process, FIG.
As shown in (a), the potential window of the solid electrolyte needs to include the potential range of both electrodes. Further, in consideration of overvoltage, in order to prevent a slight decomposition of the solid electrolyte,
As shown in FIG. 6B, it is found that it is desired to have a wider potential window.

However, it is difficult to obtain a solid electrolyte having such a wide potential window as a single material.

The present invention is intended to solve the problems of the prior art as described above, and the decomposition due to the reaction with the electrode is prevented in a wide potential range including the overvoltage, and stable high ionic conductivity is exhibited. An object of the present invention is to make it possible to construct a solid-state battery using a solid electrolyte.

[0012]

The present inventors suppress the decomposition of the solid electrolyte by providing at least two layers of solid electrolyte having different potential windows on the positive electrode side and the negative electrode side, respectively, as the solid electrolyte. The inventors have found that the resistance can be reduced and have completed the present invention.

That is, the present invention provides a solid-state battery including a positive electrode, a negative electrode, and a solid electrolyte provided between both electrodes,
The solid electrolyte is composed of at least a first solid electrolyte in contact with the positive electrode and a second solid electrolyte in contact with the negative electrode, and
The first solid electrolyte has a wide potential window in the noble direction with respect to the second solid electrolyte, and the second solid electrolyte has a wide potential window in the base direction with respect to the first solid electrolyte. The solid-state battery is characterized in that the ions involved in charging and discharging are lithium ions . Further, the present invention is a positive electrode
A solid-state battery comprising a negative electrode and a solid electrolyte provided between both electrodes, wherein the solid electrolyte comprises a laminate of at least a first solid electrolyte in contact with the positive electrode and a second solid electrolyte in contact with the negative electrode, the first solid electrolyte Has a wide potential window in the noble direction with respect to the second solid electrolyte, the second solid electrolyte has a wide potential window in the base direction with respect to the first solid electrolyte, and the first solid electrolyte is ester-based. A polymer solid electrolyte, the second solid electrolyte is an ether polymer solid electrolyte, or the first solid electrolyte is an ester polymer solid electrolyte and the second solid electrolyte is an ether polymer Provided is a solid-state battery characterized by being a polymer solid electrolyte.

The present invention will be described in detail below.

The solid-state battery of the present invention uses, as a solid electrolyte interposed between both electrodes, a laminate of at least two solid electrolytes having different potential windows. For example, as shown in FIG. 1, as the first solid electrolyte 1 in contact with the positive electrode, one having a wide potential window in the noble potential direction and excellent in oxidation resistance is used, while the second solid electrolyte 1 in contact with the negative electrode is used. As the solid electrolyte 2,
Use a wide potential window in the base direction and excellent reduction resistance. By using a solid electrolyte laminate having different potential windows in this way, the potential window (composite potential window) of the entire laminate can be set to a wide range that cannot be obtained with a single material. Therefore, not only in the potential range of both poles, but in a wide potential range including overvoltage,
It is possible to prevent the solid electrolyte from decomposing at the electrode interface.

In FIG. 1, as the first solid electrolyte 1 in contact with the positive electrode, the limit value of the potential window in the base direction overlaps with the potential range of the negative electrode. Although the example in which the potential window of the solid electrolyte 2 of No. 2 overlaps is shown, the laminated body of the solid electrolyte used in the present invention is not limited to this example. The potential window of the first solid electrolyte in contact with the positive electrode and the potential window of the second solid electrolyte in contact with the negative electrode may include the potential ranges of the positive electrode and the negative electrode, respectively, and preferably have a wider potential range. Just do it. Further, the potential window of the first solid electrolyte 1 and the potential window of the second solid electrolyte 2 do not have to be deeply overlapped as shown in FIG. 1 and may be in contact with each other.

FIG. 1 shows an example in which two layers of a first solid electrolyte 1 in contact with the positive electrode and a second solid electrolyte 2 in contact with the negative electrode are laminated as the solid electrolyte used in the present invention. As the solid electrolyte used in the present invention, the potential window of the first solid electrolyte in contact with the positive electrode is wider in the noble direction than the potential window of the second solid electrolyte in contact with the negative electrode, and the second solid electrolyte is in contact with the negative electrode. As long as the potential window of the solid electrolyte is wider in the base direction than the potential window of the first solid electrolyte in contact with the positive electrode, another layer can be further provided between both layers.

As described above, the material of the individual solid electrolytes constituting the laminated body of solid electrolytes may be composed of an inorganic material or an organic material. As the laminated body, an inorganic material and an organic material are laminated. You can also use the
It is preferable to use an organic material from the viewpoint of film forming property on a thin film, mechanical properties such as flexibility, and the like.

Among the organic materials, the preferred solid electrolyte as the first solid electrolyte in contact with the positive electrode or the second solid electrolyte in contact with the negative electrode can be appropriately determined depending on the type of the battery, the constituent material of the positive electrode or the negative electrode, and the like. But,
For example, in the case of forming a lithium battery, examples of a preferred solid electrolyte as the first solid electrolyte in contact with the positive electrode include a complex of an ester polymer such as poly-β-propiolactone and polyethylene succinate, and a metal salt. be able to. Further, as a solid electrolyte preferable as the second solid electrolyte in contact with the negative electrode, a complex of an ether polymer such as polyethylene oxide and polypropylene oxide and a metal salt can be cited.

When the solid electrolyte is formed of an organic material, the metal salt used with the polymer may be either the first solid electrolyte or the second solid electrolyte.
What was used for the conventional polymer solid electrolyte can be used. For example, LiBr, LiCl, Li
I, LiSCN, LiBF ₄ , LiAsF ₆ , LiCl
O ₄ , CH ₃ COOLi, CF ₃ COOLi, LiCF
₃ SO ₃ , LiPF ₆ , LiN (CF ₃ SO ₂ ) ₂ , L
Lithium salts such as iC (CF ₃ SO ₂ ) ₃ can be used. It is also possible to use salts of these lithium salt anions with alkali metals other than lithium, such as potassium and sodium. As the metal salt, a single type may be used, or a plurality of types of salts may be used at the same time.

When both the first solid electrolyte and the second solid electrolyte are composed of a composite of an organic polymer and a metal salt, the method for producing the laminate is, for example, the first
The solid electrolyte and the second solid electrolyte may be separately formed on the positive electrode or the negative electrode by a casting method or the like, and then both may be superposed and heated to thermally diffuse both polymer chains.

The laminated body of the first solid electrolyte and the second solid electrolyte is usually provided as a thin film between the positive electrode and the negative electrode. The same can be applied to the solid polymer electrolyte. That is, from the viewpoint of reducing the internal resistance of the battery, it is preferable that the thickness of the polymer solid electrolyte is thin, but if it is too thin, during the production of a solid battery, or during the charge / discharge reaction of the battery in which the volume change of the electrode occurs Since the internal short circuit in which the positive electrode and the negative electrode contact each other is likely to occur, the thickness of the laminated body of the first solid electrolyte and the second solid electrolyte is usually preferably 20 to 200 μm.

The solid-state battery of the present invention is characterized by using the above laminated body as a solid electrolyte, and there is no particular limitation on the other battery elements. Further, it can be configured as either a primary battery or a secondary battery.

For example, when the solid-state battery of the present invention is constructed as a lithium primary battery, TiS ₂ , MnO ₂ , graphite, FeS ₂ or the like can be used as the positive electrode active material in the positive electrode. Further, when the solid-state battery of the present invention is configured as a lithium secondary battery, Ti is used as the positive electrode active material.
Lithium-free metal sulfides or oxides such as S ₂ , MoS ₂ , NbSe ₂ , V ₂ O ₅ , and Li _x MO ₂
(In the formula, M represents one or more transition metals, and is usually 0.05
It is possible to use a lithium composite oxide mainly composed of ≦ x ≦ 1.10). As the transition metal M constituting the lithium composite oxide, Co, Ni, Mn and the like are preferable. Specific examples of such a lithium composite oxide include LiCoO ₂ , LiNiO ₂ , and Li _x Ni _y Co.
(Wherein, x, y vary according to charge and discharge state of the battery, usually a 0 <x <1,0.7 <y < 1.02) 1-y O 2, and the like LiMn ₂ O _4, etc. it can. These lithium composite oxides can generate a high voltage and become a positive electrode active material excellent in energy density.

For the positive electrode, plural kinds of these positive electrode active materials may be mixed and used. Further, when forming a positive electrode using the positive electrode active material as described above, a known conductive agent, binder or the like can be added. When a polymer solid electrolyte is used as the first solid electrolyte, the polymer solid electrolyte can be used as a binder for the positive electrode. This allows ions to easily reach from the electrode surface to the deep part, and the internal resistance of the battery is lowered, which is preferable.

On the other hand, as the constituent material of the negative electrode when the solid-state battery of the present invention is constituted as a lithium primary battery or a secondary battery, a lithium metal, a lithium alloy, or a carbonaceous material capable of being doped or dedoped with lithium or lithium ions. Can be used. Of these, materials that can be doped or dedoped with lithium or lithium ions include, for example, pyrolytic carbons, cokes (pitch coke, needle coke, petroleum coke, etc.), graphites, glassy carbons, organic polymer compound firing. Carbonaceous materials such as body (phenolic resin, furan resin, etc., fired at an appropriate temperature to carbonize), carbon fiber, activated carbon, etc.
Alternatively, polymers such as polyacetylene and polypyrrole can be used. As the lithium alloy, lithium-aluminum alloy or the like can be used.

When forming the negative electrode from such a carbon material, a known binder or the like can be added. When a polymer solid electrolyte is used as the second solid electrolyte, the polymer solid electrolyte can be used as a binder for the negative electrode. This allows ions to easily reach from the electrode surface to the deep part, and the internal resistance of the battery is lowered, which is preferable.

In addition, the negative electrode of the solid-state battery of the present invention includes
Light metals other than lithium and light metal compounds can be used, and examples of such light metals include sodium, potassium, cesium, and aluminum.

As a method of assembling the solid-state battery of the present invention using the positive electrode and the negative electrode as described above, for example, first, a mixture containing a positive electrode active material, a conductive agent, and a binder is collected from an aluminum foil. It is applied to an electric body and dried to form a positive electrode. On the other hand, the organic polymer forming the first solid electrolyte and the metal salt are dissolved in a casting solvent at a predetermined ratio to form a casting solution. Then, the cast solution is directly applied onto the positive electrode and desolvated to form a first solid electrolyte membrane. Similarly, a second solid electrolyte membrane is formed on the negative electrode. Then, the first solid electrolyte membrane and the second solid electrolyte membrane are superposed on each other and heated to bond the first solid electrolyte membrane and the second solid electrolyte membrane.
Then, this is sealed in a predetermined exterior material to obtain a battery.

The battery shape of the battery of the present invention is not particularly limited. Various shapes such as a cylindrical shape, a square shape, a coin shape, and a button shape can be used.

[0031]

In the solid-state battery of the present invention, the solid electrolyte interposed between the positive electrode and the negative electrode is a laminate of at least two layers of a first solid electrolyte in contact with the positive electrode and a second solid electrolyte in contact with the negative electrode. The potential window of the first solid electrolyte is wider in the noble direction than that of the second solid electrolyte, and the second solid electrolyte is wider in the noble direction of the potential window of the first solid electrolyte. Therefore, the first solid electrolyte can be provided with a potential window that sufficiently covers the potential range of the positive electrode, including the range that fluctuates due to overvoltage, and the second solid electrolyte also similarly has the negative electrode. It is possible to provide a potential window that sufficiently covers the potential range of (3) including the range that varies due to overvoltage. Therefore, it is possible to prevent decomposition of the solid electrolyte at the electrode interface on both the positive electrode side and the negative electrode side, thereby reducing the internal resistance of the battery.

In this case, since the first solid electrolyte and the second solid electrolyte are formed from separate solid electrolytes, the solid electrolyte having a potential window suitable for contacting the positive electrode and the negative electrode is made into a single solid electrolyte. Compared with the case where it is composed of materials,
It is possible to easily select a solid electrolyte having a potential window suitable for making contact with the positive electrode and a solid electrolyte having a potential window suitable for making contact with the negative electrode.

[0033]

EXAMPLES The present invention will be specifically described below based on examples. The solid electrolyte used in the following examples is 1
0% LiClO ₄ / polyethylene oxide, 10% Li
ClO ₄ / polypropylene oxide or 10% LiCl
O ₄ / poly-β-propiolactone, and the potential windows of these were 0.2 to 4.0 V on the basis of Li / Li ⁺ standard, respectively, as determined by cyclic voltammetry.
It was 0.4-4.0V and 1.0-5.0V.

Example 1 [Production of Lithium Primary Battery] A lithium primary battery having a cross-sectional structure shown in FIG. 4 was produced as follows.

First, in producing the positive electrode 3, 91 parts by weight of commercially available TiS ₂ as a positive electrode active material, 6 parts by weight of graphite as a conductive agent, and 3 parts by weight of polyvinylidene fluoride as a binder were mixed, and N- was added. It was kneaded with methyl-2-pyrrolidone to form a paste. And 1x1 of this paste
cm aluminum plate coated on one side (thickness 50 μm)
Then, a plate-shaped positive electrode 3 was obtained.

Next, poly-β having a molecular weight of about 100,000
-90 parts by weight of propiolactone and 10 parts of lithium perchlorate
The first solid electrolyte 1 was deposited on the positive electrode 3 by coating the positive electrode 3 in a thickness of about 50 μm by mixing 1 part by weight with dimethylformamide to form a paste.

On the other hand, a lithium foil having a thickness of 1 mm and a size of 1 × 1 cm was used as the negative electrode 4, and the second solid electrolyte 2 was formed on the negative electrode 4 as follows. First, molecular weight 1
90 parts by weight of polyethylene oxide of about 00000 and 10 parts by weight of lithium perchlorate are mixed in dimethylformamide to form a paste, and about 50 parts of this is placed on the negative electrode 4.
The second solid electrolyte 2 was formed into a film on the negative electrode 4 by applying it in a thickness of μm.

After that, the first solid electrolyte 1 formed on the positive electrode 3 and the second solid electrolyte 2 formed on the negative electrode 4 were laminated and held at 60 ° C. for 24 hours to obtain a polymer at the interface. The chains were joined by thermal diffusion of the chains to produce an all-solid-state primary battery.

Example 2, Comparative Example 1 and Comparative Example 2 In forming the first solid electrolyte and the second solid electrolyte, Example 1 was repeated except that the polymer shown in Table 1 was used. A battery was made. In addition, Table 1 also shows the range of the potential window (composite potential window) of the laminated body in which the first solid electrolyte and the second solid electrolyte are combined.

[0040]

[Table 1] First Solid Electrolyte Second Solid Electrolyte Complex Potential Window Polymer of Impedance Polymer (V vs. Li ^/ Li ⁺ ) (ohm) Example 1 Poly-β-fluoroiolactone Polyethylene oxide 0.2-5.0 1000 Example 2 Poly-β-fluoro-iolactone 0.4-5.0 1300 Comparative Example 1 Poly-propylene oxide O-poly 0.4-4.0 1400 Comparative example 2 Poly-β-fluoro-iolactone 1.0-5.0 1-5.0 Cell impedance and discharge characteristics of the all-solid-state primary batteries of Evaluation Examples 1 and 2 and Comparative Examples 1 and 2 were measured as follows.

(I) The cell impedance of each battery immediately after preparation was measured by the AC impedance method in order to examine the degree of decomposition of the solid electrolyte. The results are shown in Table 1. From these results, it can be seen that the cell impedance of the battery of the example immediately after fabrication is suppressed lower than that of the battery of the comparative example.

After measuring the cell impedance, each battery was disassembled and visually observed, and it was found that the solid electrolyte was clouded in all the batteries, but the degree of cloudiness was
The batteries of Examples 1 and 2 were extremely smaller than the batteries of Comparative Examples 1 and 2.

It is considered that such white turbidity is caused by the decomposition of the solid electrolyte in contact with the electrode. Therefore, the degree of white turbidity of the solid electrolyte in the battery of the example was small,
Because the potential window was wide enough for the electrode potential,
This is probably because the decomposition reaction hardly proceeded.

(Ii) Discharge characteristics For each battery, a constant current discharge of 30 μA was applied and the battery voltage was 1
It carried out until it became V, and calculated | required the relationship between each discharge capacity and battery voltage. The result is shown in FIG.

From FIG. 5, it can be seen that the batteries of Examples 1 and 2 have a larger discharge capacity than the batteries of Comparative Examples 1 and 2. Further, the order of magnitude of the discharge capacity matches the order of the width of the potential window shown in Table 1, and also the order of the small cell impedance. Therefore, also from this fact, the decomposition of the solid electrolyte due to the contact of the solid electrolyte with the electrode increases the internal resistance of the battery and causes the decrease of the discharge capacity, and thus the electrode is contacted as in the present invention. It can be seen that the internal resistance of the battery can be reduced and the discharge capacity can be increased by making the potential window of the solid electrolyte sufficiently wider than the potential of the electrode.

Example 3 [Preparation of lithium secondary battery] First, a positive electrode was prepared as follows. Commercially available lithium carbonate and cobalt carbonate were mixed so that the composition ratio was Li / Co = 1: 1, and the mixture was baked in air at 900 ° C. for 5 hours to obtain a lithium-cobalt composite oxide. Lithium obtained
91 parts by weight of cobalt composite oxide as a positive electrode active material, 6 parts by weight of graphite as a conductive agent, and 3 parts by weight of polyvinylidene fluoride as a binder were mixed and further kneaded with N-methyl-2-pyrrolidone to form a paste. . And this 1 × 1
cm aluminum plate coated on one side (thickness 50 μm)
Then, a plate-shaped positive electrode was obtained.

Next, poly-β having a molecular weight of about 100,000 is used.
-90 parts by weight of propiolactone and 10 parts of lithium perchlorate
Part by weight was mixed with dimethylformamide to form a paste, which was applied to the above positive electrode to a thickness of about 50 μm to form a first solid electrolyte film on the positive electrode.

On the other hand, a negative electrode was prepared as follows. 90 parts by weight of crushed pitch course and 10 parts by weight of polyvinylidene fluoride as a binder were mixed and further kneaded with N-methyl-2-pyrrolidone to form a paste. Then, apply this to one side of a 1 × 1 cm copper plate (thickness 50 μm)
Then, a plate-shaped negative electrode was obtained.

Next, 90 parts by weight of polyethylene oxide having a molecular weight of about 100,000 and 10 parts by weight of lithium perchlorate are mixed in dimethylformamide to form a paste, which is applied on the negative electrode to a thickness of about 50 μm. Thus, a second solid electrolyte was formed on the negative electrode.

Thereafter, the first solid electrolyte 1 formed on the positive electrode and the second solid electrolyte 2 formed on the negative electrode were laminated and held at 60 ° C. for 24 hours to remove the polymer chains at the interface. Both were joined by thermal diffusion, and the all-solid-state secondary battery was produced.

Example 4, Comparative Example 3 and Comparative Example 4 In forming the first solid electrolyte and the second solid electrolyte, Example 3 was repeated except that the polymers shown in Table 2 were used. A secondary battery was produced.

[0052]

[Table 2] First solid Second solid Charge capacity Discharge capacity Impedance Electrolyte polymer Electrolyte polymer (mAh) (mAh) (ohm) Example 3 Poly-β-Propylolactone Polyethylene oxide 1.05 0.90 1000 Example 4 Poly- β-Propolyoline lactone 1.10 0.80 1100 Comparative Example 3 Polyproloxylene Oxide Polypropylene Oxido 1.30 0.50 5000 Comparative Example 4 Poly-β-Proploolactone 1.60 0.30 6000 The charge / discharge characteristics (charge capacity and discharge capacity) of the all-solid-state secondary batteries of Evaluation Examples 3 and 4 and Comparative Examples 3 and 4 were measured as follows, and the cell impedance was the same as in Example 1. It was measured. The results are shown in Table 2.

Method for measuring charge / discharge characteristics: Since the batteries immediately after fabrication were in a discharged state, first, 30 μA was measured for each battery.
3. By constant current charging and subsequent constant voltage charging.
The battery was charged to 2V and then discharged at a constant current of 30 μA until the battery voltage reached 2.5V, and the charge capacity and discharge capacity in this case were determined.

From Table 2, it can be seen that the batteries of Examples 3 and 4 exhibited a large discharge capacity with a smaller charge capacity than the batteries of Comparative Examples 3 and 4. Also, regarding the cell impedance, the batteries of Examples 3 and 4 are smaller than the batteries of Comparative Examples 3 and 4 and have excellent battery characteristics.

Further, after measuring the charge / discharge characteristics and cell impedance, each battery was disassembled and visually observed.
In the batteries of Comparative Examples 3 and 4, the solid electrolyte was observed to be cloudy, but in Examples 3 and 4, discoloration of the solid electrolyte was not observed.

From the above, in the batteries of Comparative Examples 3 and 4, a part of the charging current was spent on the decomposition reaction of the solid electrolyte, whereby a film was formed at the electrode interface, the internal resistance increased, and the discharge Although the capacity also decreased, it is considered that in the batteries of Examples 3 and 4, the decomposition reaction of the solid electrolyte at the electrode interface hardly proceeded, and therefore the internal resistance was low and the discharge capacity was large.

[0057]

According to the present invention, in a wide potential range including overvoltage, decomposition of the solid electrolyte at the electrode interface is largely prevented, the internal resistance is small, and the discharge capacity is extremely large. You can get a battery.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a potential window of a first solid electrolyte and a second solid electrolyte and a potential range of electrodes in a solid-state battery of the present invention.

FIG. 2 is a relationship diagram between a potential window of a solid electrolyte and a potential range of electrodes in a conventional solid-state battery.

FIG. 3 is a diagram showing a potential change of an electrode during a charge / discharge process of a lithium ion secondary battery.

FIG. 4 is a cross-sectional view of a laminate of an electrode and a solid electrolyte of a battery of an example.

FIG. 5 is a relationship diagram between the discharge capacity and the battery voltage of the batteries of Examples and Comparative Examples.

[Explanation of symbols]

1 First solid electrolyte 2 Second solid electrolyte 3 positive electrode 4 Negative electrode

Continuation of front page (56) Reference JP-A-4-115472 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01M 6/18 H01M 10/40

Claims (9)

(57) [Claims] 1. A solid-state battery comprising a positive electrode, a negative electrode, and a solid electrolyte provided between both electrodes, wherein a solid electrolyte is a laminate of at least a first solid electrolyte in contact with the positive electrode and a second solid electrolyte in contact with the negative electrode. The first solid electrolyte has a wide potential window in the noble direction relative to the second solid electrolyte, and the second solid electrolyte has a wide potential window in the noble direction relative to the first solid electrolyte. A solid-state battery characterized in that the ions involved in charging and discharging in the negative electrode are lithium ions . 2. The primary battery, wherein the negative electrode comprises a lithium metal, a lithium alloy, or a carbonaceous material that can be doped or dedoped with lithium or lithium ions.
The solid-state battery described. 3. The secondary battery, wherein the negative electrode comprises a lithium metal, a lithium alloy, or a carbonaceous material that can be doped or dedoped with lithium or lithium ions.
The solid-state battery described. 4. A solid-state battery comprising a positive electrode, a negative electrode, and a solid electrolyte provided between both electrodes, wherein the solid electrolyte comprises a laminate of at least a first solid electrolyte in contact with the positive electrode and a second solid electrolyte in contact with the negative electrode. , The first solid electrolyte has a wider potential window in the noble direction than the second solid electrolyte,
A solid-state battery, wherein the second solid electrolyte has a wider potential window in the base direction than the first solid electrolyte, and the first solid electrolyte is an ester-based polymer solid electrolyte. 5. The solid-state battery according to claim 4, wherein the ester-based polymer solid electrolyte forming the first solid electrolyte contains poly-β-propiolactone. 6. A solid-state battery comprising a positive electrode, a negative electrode, and a solid electrolyte provided between both electrodes, wherein the solid electrolyte comprises a laminate of at least a first solid electrolyte in contact with the positive electrode and a second solid electrolyte in contact with the negative electrode. , The first solid electrolyte has a wider potential window in the noble direction than the second solid electrolyte,
A solid-state battery, wherein the second solid electrolyte has a wider potential window in the base direction than the first solid electrolyte, and the second solid electrolyte is an ether polymer solid electrolyte. 7. The solid-state battery according to claim 6 , wherein the ether polymer solid electrolyte forming the second solid electrolyte contains polyethylene oxide. 8. A solid-state battery comprising a positive electrode, a negative electrode, and a solid electrolyte provided between both electrodes, wherein the solid electrolyte comprises a laminate of at least a first solid electrolyte in contact with the positive electrode and a second solid electrolyte in contact with the negative electrode. , The first solid electrolyte has a wider potential window in the noble direction than the second solid electrolyte,
The second solid electrolyte has a wider potential window in the base direction than the first solid electrolyte, the first solid electrolyte is an ester-based polymer solid electrolyte, and the second solid electrolyte is an ether-based polymer solid. A solid-state battery characterized by being an electrolyte. 9. The ester-based polymer solid electrolyte forming the first solid electrolyte contains poly-β-propiolactone, and the ether-based polymer solid electrolyte forming the second solid electrolyte contains polyethylene oxide. The solid-state battery according to claim 8 .