JPH09180757A - High-molecular solid electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-molecular solid electrolyte battery, of which cycle characteristic is improved, by forming a battery of a negative electrode, a positive electrode and the high-molecular solid electrolyte, which contacts the negative electrode active material and which contains the heterocyclic compound including double-coupled element. SOLUTION: In a high-molecular solid electrolyte battery, which is formed of a negative electrode, a positive electrode and the high-molecular electrolyte, as the high-molecular solid electrolyte, polyethylene oxide, which contains the heterocyclic compound having a double-coupled element such as thiophene at 0.05-5% by weight and which contains the organic matter plasticizer such as ethylene carbonate at need, is used. The negative electrode is desirably made of lithium or the carbonaceous material, and the high-molecular solid electrolyte contacts this negative electrode active material. The high-molecular solid electrolyte is desirable formed integrally with the negative electrode and/or the positive electrode. Affinity of the high-molecular solid electrolyte to the active material is thereby improved, and the power generating ability and the battery cycle characteristic can be improved.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polymer solid electrolyte battery, and more particularly to improvement of a polymer solid electrolyte.

[0002]

2. Description of the Related Art Batteries using ion-conductive polymer solid electrolytes have the following problems: deterioration of battery performance due to leakage and evaporation loss;
Since there is no risk of equipment damage due to liquid leakage, etc., it is superior in reliability and safety compared to organic electrolyte type batteries, and since the electrolyte also functions as a separator, further downsizing of the battery can be achieved. It has features. In particular, a polymer solid electrolyte battery using lithium or a carbonaceous material having an extremely base potential as a negative electrode active material has the potential to be a battery with high output and high energy density in addition to long-term reliability. Therefore, with the recent development of portable electronic devices, they are promising as secondary batteries for their drive power supplies and backup power supplies, and research and development are being actively conducted at present.

However, since the negative electrode active material is generally highly reactive, it reacts with the polymer compound or the organic plasticizer forming the polymer solid electrolyte during charge / discharge of the battery to alter or decompose the solid electrolyte and There is a problem of degrading the function. Since the deterioration of the electrolyte function immediately leads to the deterioration of the battery performance, the conventional battery of this type does not have a sufficient cycle life.

[0004]

The present invention, in a polymer solid electrolyte battery using a highly reactive negative electrode active material such as lithium or carbonaceous material, suppresses the adverse effect of the negative electrode active material on the polymer solid electrolyte. By doing so, it is intended to provide a polymer solid electrolyte battery having excellent cycle characteristics, and particularly with the main purpose of improving the cycle characteristics of the polymer solid electrolyte battery having a lithium or carbonaceous material as a negative electrode. To do.

[0005]

To achieve the above object, the invention according to claim 1 comprises a negative electrode, a positive electrode, and a solid polymer electrolyte containing a heterocyclic compound having a double bond. It is characterized by being a polymer solid electrolyte battery as an element.

According to a second aspect of the invention, in the polymer solid electrolyte battery according to the first aspect, the polymer solid electrolyte is in contact with the negative electrode active material.

According to a third aspect of the present invention, in the solid polymer electrolyte battery of the second aspect, the solid polymer electrolyte is integrated with a negative electrode and / or a positive electrode.

According to a fourth aspect of the present invention, in the polymer solid electrolyte battery according to the first aspect, the second aspect, or the third aspect, the negative electrode is made of lithium or a carbonaceous material. .

According to a fifth aspect of the present invention, in the polymer solid electrolyte battery according to the fourth aspect, the polymer solid electrolyte contains 0.05 wt% to 5 wt% of the heterocyclic compound. And

According to a sixth aspect of the invention, in the polymer solid electrolyte battery according to the fifth aspect, the polymer solid electrolyte contains an organic plasticizer.

The polymer solid electrolyte battery is prepared by adding an electrolyte salt as a carrier to a polymer compound as a matrix, or by adding an organic plasticizer to the battery to further improve ionic conductivity, or other than this. Electrolyte membrane consisting of ion-conductive polymer solid electrolyte mainly composed of organic matter, and a negative electrode and a positive electrode closely arranged on each surface of the electrolyte membrane, respectively, in this type of battery, the ionic conductivity of the solid electrolyte And the adhesion between the solid electrolyte and the active material are factors that determine the battery performance. Thus, the negative electrode active material is a highly reactive material, and particularly lithium or carbonaceous materials have extremely high reactivity.
It acts on the electrolyte that is in direct contact during charging, and modifies or decomposes the polymer compound and organic plasticizer that make up the electrolyte. As a result, the ionic conductivity of the electrolyte is reduced, and the electrolyte membrane contracts and peels off from the electrode surface, and the decomposition gas impairs the electrical contact property of the electrode / solid electrolyte interface. The efficiency of the electrode reaction is reduced.

However, in the present invention having the above-mentioned constitution, since the heterocyclic compound having a double bond (hereinafter, simply referred to as a heterocyclic compound) is mixed in the solid polymer electrolyte, the heterocyclic compound is It chemisorbs to the negative electrode active material and acts to improve the affinity of the solid polymer electrolyte for the active material, and at the same time acts as a protective film to suppress the adverse effect of the active material on the solid polymer electrolyte. . Therefore, according to the present invention, the electrical contact property at the electrode / solid electrolyte interface can be improved, and the modification or decomposition of the polymer solid electrolyte can be prevented. Therefore, it is possible to improve the power generation capacity and the battery cycle characteristics.

Such a solid polymer electrolyte battery of the present invention is basically constructed by stacking a negative electrode and a positive electrode via a solid polymer electrolyte membrane, as in the conventional battery. However, each power generation element in the present invention does not necessarily mean that each power generation element is independently manufactured. That is, even a battery prepared by a manufacturing method in which a solid polymer electrolyte membrane containing a heterocyclic compound is prepared independently of the electrodes, and a positive electrode and a negative electrode are closely arranged on each surface of the electrolyte membrane Well, first, a so-called composite negative electrode and / or positive electrode in which an electrolyte containing a heterocyclic compound and an electrode are integrated is prepared,
After that, the battery may be manufactured by stacking these electrodes with the electrolyte surface inside. Furthermore, for example, on a composite negative electrode using an electrolyte containing a heterocyclic compound, an electrolyte layer containing no heterocyclic compound is formed, or on a composite positive electrode using an electrolyte containing no heterocyclic compound. A battery using an electrolyte layer containing a heterocyclic compound may be used. Furthermore, for example, a precursor electrolyte (prepolymer or the like) is applied to the respective electrolyte surfaces of a composite negative electrode and a composite positive electrode using an electrolyte containing a heterocyclic compound, and the precursor electrolyte is preheated by heating the whole. It is also possible to form an integral type battery by a manufacturing method in which a body electrolyte is thermally polymerized to form an electrolyte layer and, at the same time, positive and negative electrodes are bound.

In the present invention, it is preferable that the solid polymer electrolyte containing the heterocyclic compound is in direct contact with the negative electrode active material. This is because with such a configuration, the action and effect unique to the heterocyclic compound of adsorbing on the negative electrode active material and suppressing its adverse action can be easily exhibited. Incidentally, in a manufacturing method in which a positive electrode and a negative electrode are superposed on each other by using a composite negative electrode and the like, and a battery is formed at the same time, a polymer solid electrolyte membrane integrated with the electrode is formed. (Including an electrolyte layer containing a heterocyclic compound) may not be clearly distinguished.

By the way, according to the manufacturing method in which the electrolyte and the electrode are integrated to form a composite electrode, the adhesion between the electrode and the electrolyte can be improved and the electrical contact property of the electrode / solid electrolyte interface can be improved, but it is preferable. Increasing the adhesion with the electrolyte also means increasing the reactivity (bad action) between the active material and the electrolyte. Therefore, in the conventional battery using the composite negative electrode, although the initial power generation capacity can be increased, the power generation capacity is rapidly reduced as the cycle progresses. Therefore, sufficient cycle life was not obtained.

On the other hand, according to the present invention, the higher the adhesion between the electrode and the electrolyte is, the more remarkable the effect of the heterocyclic compound is. Therefore, since improvement in adhesion can be directly linked to improvement in battery performance, in the production of the battery of the present invention, a method of forming a composite electrode is preferable, and particularly when a carbonaceous material is used as the negative electrode active material, the composite negative electrode is used. It is good to say Because the carbonaceous material is a powder material, if the negative electrode is composed of only the carbonaceous material, sufficient ion conductivity cannot be obtained. It is necessary to add a solvent (the organic plasticizer referred to in the present invention also has this function) and the like to form a composite negative electrode. Here is a guess,
When the electrolyte contains a heterocyclic compound, it is considered that the hetero compound reacts with radicals on the surface of the carbonaceous material to form a protective film and suppresses adverse effects of the carbonaceous material on the ion conductive organic solvent and the like. To be Therefore, it is considered that the power generation capacity of the carbonaceous material will be suitably exerted over a long period of time.

The same applies to a composite negative electrode using granular lithium (including a lithium alloy) as a negative electrode active material.

As described above, the action and effect prescribed by the present invention due to the inclusion of the heterocyclic compound in the solid polymer electrolyte is as follows.
Since it has high reactivity, it is more remarkably exhibited in a negative electrode containing lithium or a carbonaceous material as an active material, but the present invention is not limited to the negative electrode containing these active materials as constituent elements. For example, a negative electrode using an inorganic substance such as TiO ₂ or MnO ₂ may be used, and these negative electrodes can also obtain the above-described effects of the present invention.

Examples of the above-mentioned heterocyclic compound which can be used in the battery of the present invention include thiophene, furan, pyrrole, 2-methylpyrrole, 2-methylfuran, pyran,
Examples thereof include thiopyran and pyridine. However, it is not limited to these (the same applies hereinafter).

As the polymer compound, a plastic polymer such as polyethylene oxide, polyethyleneimine, polyacrylonitrile or a mixture of these substances, or polyethylene glycol diacrylate, polyethylene glycol triacrylate, polyethylene glycol dimethacrylate, methoxy polyethylene glycol mono is used. Examples thereof include a polymer composed of a prepolymer such as methacrylate or a mixture thereof, or a curable substance composed of a mixture of the thermoplastic polymer and the prepolymer. The prepolymer is polymerized and cured by applying energy such as heat, electromagnetic waves, and electron beams.At this time, a polymerization initiator such as azoisobutyronitrile or benzyl dimethyl ketal is used together with the prepolymer to accelerate the polymerization reaction. It may be added.

Examples of the electrolyte salt used together with the above polymer compound include LiPF ₆ , LiCl ₄ , LiBF ₄ , and Li.
Such as CF ₃ SO ₃ can be exemplified. Then, in addition to these electrolyte salt and the polymer compound, a polymer solid electrolyte is formed by using an organic plasticizer capable of improving the adhesion between the electrolyte layer and the electrode and enhancing the ionic conductivity of the electrolyte. Is preferred. Examples of such organic plasticizers include organic solvents such as ethylene carbonate, vinylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, 1,2-diethoxyethane, ethoxymethoxyethane, and mixed solvents thereof. You can

Further, the "lithium" as the negative electrode active material includes Li metal, Li-Al alloy, Li-Mg.
Examples thereof include alloys and Li-Al-Ni alloys. Also,
Examples of the carbonaceous material include graphite, carbon black, coke, glassy carbon, carbon fiber, and a fired body thereof. On the other hand, preferable positive electrode active materials that can be used for the positive electrode include LiCoO ₂ and LiNiO ₂ .
₂ , lithium composite oxides such as LiMnO ₂ can be exemplified, and conductive polymers such as polyaniline and polypyrrole can also be used as the positive electrode active material. Needless to say, substances other than the above-exemplified substances can be used as long as the gist of the present invention is not impaired.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below through examples.
Will be specifically disclosed. [Invention Example 1] First, 6 g of propylene carbonate and chi
Offen 0.05g and LiCLO _FourMixture consisting of 1g
Polyethylene glycol dimethacrylate in the combined solution
(Number of oxyethylene units = 9; Nippon Resin Co., Ltd.
1.5 g) and methoxy polyethylene glycol mono
Methacrylate (Number of oxyethylene units = 9; Japan
(Made by Resin Co., Ltd.) and mixed with 1.5 g,
2,000 azobisisobutyronitrile mixed
Machine polymer solution [A₁] Was produced.

An organic polymer solution [A ₂ ] was prepared in the same manner as the organic polymer solution [A ₁ ] except that benzyl methyl ketal (2000 ppm) was used instead of azobisisobutyronitrile. .

Then, a mixture of LiCoO ₂ and Ketjenblack in a weight ratio of 90:10 and the organic polymer solution [A ₁ ] were mixed in a weight ratio of 3: 1, and this mixture was used as a positive electrode made of aluminum. The composite positive electrode according to the present invention example 1 was produced by coating and rolling on a current collector plate and further heating at 80 ° C. for 1 hour to heat-polymerize the polymerization components.

On the other hand, lithium metal (negative electrode active material) is pressure-bonded to a stainless steel current collector, the above-mentioned organic polymer solution [A ₂ ] is cast on the lithium metal using a doctor knife applicator, and then ultraviolet light is applied at room temperature. 6mW
Irradiation with a light amount of / cm ² for 20 minutes to polymerize the polymerization components,
A negative electrode according to the present invention example 1 having an ion conductive polymer solid electrolyte layer formed on the surface was produced.

Further, the composite positive electrode and the negative electrode were superposed with the ion conductive polymer solid electrolyte layer on the inner side to prepare an ion conductive polymer solid electrolyte battery of Inventive Example 1. The power generation area of this ion conductive polymer solid electrolyte battery is 10 cm ² , and the designed battery capacity is 20 mAh. The batteries of Inventive Example 2 and below are designed in the same manner.

[Inventive Example 2] Polyethylene glycol dimethacrylate (the number of oxyethylene units = 9) was added to a mixed solution of 6 g of an ethylene carbonate / diethyl carbonate solution having a volume ratio of 1: 1 and 0.05 g of pyrrole and 1 g of LiClO ₄ . Nippon Oil & Fat Co., Ltd.) 1.5
g and methoxypolyethylene glycol monomethacrylate (the number of oxyethylene units = 9; manufactured by NOF CORPORATION) were added and mixed, and then 2000 ppm of azobisisobutyronitrile was mixed into the organic polymer solution [ B ₁ ].

An organic polymer solution [B ₂ ] was prepared in the same manner as the organic polymer solution [B ₁ ] except that benzyl methyl ketal (2000 ppm) was used instead of azobisisobutyronitrile. And

A composite positive electrode according to Inventive Example 2 was prepared in the same manner as in Inventive Example 1 except that the above organic polymer solution [B ₁ ] was used instead of the above organic polymer solution [A ₁ ].

On the other hand, a composite negative electrode having an ion conductive polymer solid electrolyte formed on its surface was prepared as follows. Graphite powder and the above organic polymer solution [B ₁ ] were mixed with graphite powder: [B
₁ ] = 3: 1 (weight ratio), and the mixture is applied onto a negative electrode current collector plate made of copper and rolled, and further heated at 80 ° C. for 1 hour to polymerize the polymerization components to form a composite negative electrode. It was made. Further, the organic polymer solution [B ₂ ] was cast on the surface of the composite negative electrode (the surface opposite to the current collector plate) using a doctor knife applicator, and irradiated with ultraviolet light having a light amount of 6 mW / cm ² at room temperature for 20 minutes. To polymerize the polymerization component. In this way, a composite negative electrode according to Example 2 of the present invention having an ion conductive polymer solid electrolyte layer formed on the surface thereof was produced, and the composite negative electrode and the composite positive electrode were superposed with the solid electrolyte layer sandwiched therebetween. The ion conductive polymer solid electrolyte battery of Example 2 was produced.

[Invention Example 3] The amount of pyrrole added was 0.0
An organic polymer solution [C ₁ ] was produced in the same manner as the organic polymer solution [B ₁ ] in Inventive Example 2 except that the amount was 05 g. Also, instead of azobisisobutyronitrile, benzyl methyl ketal (2000ppm
An organic polymer solution [C ₂ ] was prepared in the same manner as the organic polymer solution [B ₂ ] except that (1) was used. Then, using these organic polymers, a composite positive electrode and a composite negative electrode having an ion-conducting polymer solid electrolyte layer formed on the surface thereof were produced in the same manner as in the above-mentioned Invention Example 2, and these were superposed on each other to prepare the composite material of Example 3 of the present invention. An ion conductive polymer solid electrolyte battery was produced.

[Invention Example 4] The amount of pyrrole added was 0.5.
An organic polymer solution [D ₁ ] was prepared in the same manner as the organic polymer solution [B ₁ ] in Inventive Example 2 except that the amount was changed to g. Also, instead of azobisisobutyronitrile, benzyl methyl ketal (2000ppm
An organic polymer solution [D ₂ ] was prepared in the same manner as the organic polymer solution [B ₂ ] except that Then, using these organic polymers, a composite positive electrode and a composite negative electrode having an ion-conducting polymer solid electrolyte layer formed on the surface were prepared in the same manner as in the above-mentioned Invention Example 2, and these were superposed to superimpose them on each other. An ion conductive polymer solid electrolyte battery was produced.

Comparative Example 1 The ion of Comparative Example 1 was prepared in the same manner as in Example 1 of the present invention except that thiophene (heterocyclic compound having a double bond) was not added in Example 1 of the present invention. A conductive polymer solid electrolyte battery was produced.

Comparative Example 2 The same as Example 2 of the present invention (Examples 3 and 4 of the present invention) except that pyrrole (heterocyclic compound having a double bond) was not added in Example 2 of the present invention. Then, an ion conductive polymer solid electrolyte battery of Comparative Example 2 was produced.

In order to make it easier to understand the difference between the various batteries produced as described above, Tables 1 and 2 list the organic polymer composition and the types of positive and negative active materials used in each battery. In Tables 1 and 2, EC is ethylene carbonate, DEC
Represents diethyl carbonate, PEG-DMAc represents polyethylene glycol dimethacrylate, and mtxy PEGmonoMAc represents methoxy polyethylene glycol monomethacrylate.

[0037]

[Table 1]

[0038]

[Table 2]

The batteries of Examples 1 to 4 of the present invention and Comparative Examples 1 and 2 were charged at a current value of 0.1 C with a battery capacity (20 mAh) until the battery voltage reached 4.2 V, and then a current of 0.1 C was applied. The cycle of discharging until the battery voltage reached 3.0 V in value was repeated, and the discharge capacity in each cycle was obtained. The results are shown in FIG. 1 as the relationship between the battery discharge capacity and the number of cycles.

As is apparent from FIG. 1, the cycle characteristics are, in order from good one, Inventive Example 1> Inventive Example 2> Inventive Example 4> Inventive Example 3> Comparative Example 2> Comparative Example 1. The present invention batteries 1 to 4 showed better cycle characteristics than the comparative batteries 1 and 2 containing no heterocyclic compound.

That is, the present invention example 1 and the comparative example 1 are different only in the presence or absence of the heterocyclic compound having a double bond, but the battery of the present invention example 1 is remarkably better than the comparative example 1. The cycle characteristics were shown, and similar results were obtained in the comparison between Inventive Example 2 and Comparative Example 2 (see Tables 1 and 2).

Further, in the results of the batteries of Examples 2 to 4 of the present invention and Comparative Example 2 in which the compounding amount of the heterocyclic compound was changed, the relationship between the content of the heterocyclic compound (% by weight with respect to the electrolyte) and the cycle characteristics. Looking at, the cycle characteristics are in order from good to good: 0.5% content battery> 5% content battery>
Batteries containing 0.05%> batteries containing 0% were in that order. From this result, the content of at least the heterocyclic compound was 0.0
It can be seen that when the content is 05% or more, better cycle characteristics can be obtained than the comparative battery (containing 0%). Further, it is understood that the relationship between the content of the heterocyclic compound and the effect of improving the cycle characteristics is not a linear one but a parabolic one having a maximum value. That is, the ratio (content) of the heterocyclic compound added to the polymer solid electrolyte is not too large or too small, and in order to efficiently improve the cycle characteristics, the content of the heterocyclic compound is Is preferably in the range of 0.005% to 5%.

The difference in cycle characteristics between Inventive Example 1 and Inventive Example 2 and Comparative Example 1 and Comparative Example 2 is considered to be mainly due to the difference in the negative electrode active material.

[0044]

As is apparent from the above, in the polymer solid electrolyte according to the present invention in which the heterocyclic compound having a double bond is an essential element, the heterocyclic compound is a negative electrode such as lithium or a carbonaceous material. It is adsorbed on the active material and acts to increase the affinity with the negative electrode active material and suppress the reaction between the electrolyte and the negative electrode active material. As a result, the efficiency of the electrode reaction is increased, and the deterioration of the ionic conductivity of the electrolyte and the poor electrical contact at the electrode / electrolyte interface are prevented even by the charge / discharge cycle. Therefore, according to the present invention, a polymer solid electrolyte battery having high output and long cycle life can be provided.

[Brief description of the drawings]

FIG. 1 is a graph showing cycle characteristics of an inventive battery and a comparative battery.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01M 4/02 H01M 4/02 D

Claims (6)

[Claims] 1. A polymer solid electrolyte battery comprising a negative electrode, a positive electrode, and a polymer solid electrolyte containing a heterocyclic compound having a double bond. 2. The polymer solid electrolyte battery according to claim 1, wherein the polymer solid electrolyte is in contact with a negative electrode active material. 3. The solid polymer electrolyte is a negative electrode and / or
3. The polymer solid electrolyte battery according to claim 2, which is integrated with a positive electrode. 4. The polymer solid electrolyte battery according to claim 1, 2 or 3, wherein the negative electrode is made of lithium or a carbonaceous material. 5. The polymer solid electrolyte battery according to claim 4, wherein the polymer solid electrolyte contains 0.05 wt% to 5 wt% of the heterocyclic compound. 6. The polymer solid electrolyte battery according to claim 5, wherein the polymer solid electrolyte contains an organic plasticizer.