JPS6123947B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an ionically conductive solid composition. In particular, it has excellent mechanical properties such as ease of processing and forming films into arbitrary shapes, which is inherent to polymers, and also has extremely high ionic conductivity of metals belonging to groups and groups of the periodic table. The present invention relates to an ionically conductive solid composition having the following properties. Conventionally, ion conductive materials have mainly been (a) so-called electrolyte solutions in which electrolytes are dissolved in water or organic solvents, (b) beta alumina β-Al ₂ O ₃ , lithium iodide alumina LiI-A ₂ O ₃ , Solid electrolyte materials made of inorganic substances such as silver rubidium iodide, RbAg ₄ I ₅ are known. Ion-conductive materials are used in a wide variety of industrial fields, but examples of their use as electronic components include primary batteries, secondary batteries, electrolytic capacitors, sensors, electrochromic display elements, and electrodes. It is widely used as a material for electronic parts, such as by depositing metal and detecting the integral value of electrical quantity, and using it as a time-limiting element or an integral memory element. In recent years, in the field of electronics industry, not only high performance and miniaturization of electronic devices, but also high performance, small size and thinness of electronic components, as well as high reliability as components are required. The first requirement for highly reliable electronic components is that the material used in the component must be a solid body, that is, an object that appears solid under the conditions in which the component is used, and that flows like a liquid (hereinafter referred to as a fluid). (hereinafter referred to as a solid body). This is because when a fluid material is used in an electronic component, fluid often leaks from the inside of the component to the outside of the component. This leads to a deterioration in the performance of the electronic component and has an adverse effect on other electronic components near the electronic component, which ultimately causes the electronic device to malfunction. Therefore, when used as an ion conductive material in an electronic component, it can be said that an electronic component using a solid ion conductive material is more reliable than a liquid one. Meanwhile, in order to obtain highly reliable parts using fluid ionically conductive materials,
Although there are ways to make the component completely airtight, the result is often an expensive electronic component that cannot be put to practical use. Among the above-mentioned ion conductive materials, the electrolyte solution (a) is a fluid and has high reliability for the reasons mentioned above, but has the disadvantage that it cannot be used for inexpensive electronic components. On the other hand, the solid electrolyte material (b) mentioned above is
Since it is a solid body, it has the advantage of being compatible with highly reliable electronic components. However, there are very few solid electrolyte materials that have high ionic conductivity, and most solid electrolyte materials have low ionic conductivity. Moreover, in order to obtain a solid electrolyte with high ionic conductivity using an inorganic compound, it is necessary to make full use of reaction operations that are considered extremely difficult, so there are currently very few practical examples. Furthermore, since the solid electrolyte material of Olowa is a composition of inorganic compounds, it is extremely difficult to mold it into an arbitrary shape or form it into a film.
That is, solid electrolytes made of inorganic compounds have the drawback of poor mechanical properties, such as ease of processing and the ability to form films into arbitrary shapes. For this reason, it has the disadvantage that the fields in which it can be used as an ion-conductive material are extremely limited. Electrolyte solution of the above-mentioned ion conductive material (a) and (b)
As an intermediate form of solid electrolyte,
For example, there is an ion conductive material that is used in dry batteries and is made by kneading an aqueous electrolyte solution with an aqueous starch solution to form a paste. Even though they are glue-like, they take on a form similar to that of a fluid under conditions of practical use. For example, in dry batteries, paper or non-woven fabric is used as a separator to prevent short circuits between the anode active material and the cathode active material. must be used. In reality, this separator separates the active materials of both electrodes, and since it contains a glue-like ion conductive material, its usage is no different from that of a fluid such as an electrolyte solution. Even with glue-like ion-conductive materials, (a) fluid leakage occurs frequently, as seen in normal dry batteries, and reliability is poor. (b) Furthermore, since it cannot be molded into any shape or formed into a film, it has the disadvantage that its applicable fields are extremely limited. If the water solvent is removed by evaporation to an extent that does not cause liquid leakage, molding and film formation will not be impossible, but in this case, the ionic conductivity will drop significantly and it cannot be put to practical use. Furthermore, when water is used as a solvent, there are the following drawbacks. (i) Water reacts electrochemically with most metals and corrodes them.
Therefore, when applied, there is a drawback that the metal materials that come into contact with the ion conductive material containing water, for example, the metal materials for the parts that seal electrode parts and electronic devices, are extremely limited. (ii) The decomposition voltage of water is approximately 1.2V, which is generally lower than that of organic solvents, and cannot be used at voltages higher than the decomposition voltage. (iii) Ion conductive materials containing water have a high and stable ionic conductivity whose use temperature is limited to a range near the freezing point (0°C) and boiling point (100°C) of water, and at other temperatures. unable to maintain. (iv)For ionic conductive materials containing water, it is generated by ion dissociation of water.
H ⁺ and OH ^- also function as conductive carriers, and if it is desired to use only metal ions as conductive carriers, not only will the number of carrier species increase, but they will also ionically bond with metal ions, resulting in an extremely complex conductive mechanism.
For this reason, the ionic conductivity becomes unstable, making it unsuitable for use in, for example, a timing element or an integral memory element to detect an integral value of capacitance. The object of the present invention is to create a new ion-conductive material that solves these conventional drawbacks, namely, an ion-conductive solid material that has both high ion conductivity and excellent mechanical properties such as ease of processing and forming films into arbitrary shapes. The objective is to provide body compositions. According to the present invention, the main components are an electrolyte made of metal ions belonging to a group of the periodic table and/or a group, an organic polymer compound with a dielectric constant of 4 or more, and an organic solvent with a dielectric constant of 10 or more. An ionically conductive solid composition is obtained. The first feature of the present invention is that the ionically conductive composition contains an organic solvent in order to eliminate the conventional drawbacks, particularly the many drawbacks mentioned above that appear when water is used as a solvent. If an organic solvent is used (), it will be stable as there will be very little chemical reaction with various metal materials. () The decomposition voltage of organic solvent is the decomposition voltage of water.
Higher than 1.2V. () If an appropriate solvent is selected, the usable temperature range will be wider than in the case of water.
() Very few organic solvents, like water, dissociate into H ⁺ and OH ^- ions and have a negative effect. For the above-mentioned reasons, the use of organic solvents has the advantage of making it possible to construct ion-conductive materials that are more stable and have a wider range of applications than conventional aqueous solvents.
On the other hand, the ionic conductivity σi tends to be lower than when a water solvent is used. Generally, σi increases in proportion to the product of the concentration ni of the carrier ion species and its mobility μi. Therefore, as an effective organic solvent for increasing σi, (A) is an organic solvent that dissolves electrolyte in high concentration.
An organic solvent that contributes to an increase in ni and (B) dissolves not only the electrolyte but also the organic polymer compound well, making the distribution of ions uniform and increasing the mobility of the ions is desirable. Therefore, the organic solvent is not limited to one type, and a mixed solvent of two or more types may be used. In this way, the organic solvent functions as a material that dissolves electrolytes and organic polymers to prepare the solid composition, and ultimately remains in the solid composition to express the function of ionic conductivity. is also an important constituent of ionically conductive solid compositions. From the above viewpoint, as a result of detailed study on organic solvents that are effective in the present invention, it was found that the dielectric constant ε of the organic solvent has a very large influence on the expression of ionic conductivity. A detailed study of the relationship between σi and ε for many types of organic solvents having different dielectric constants ε shows that σi tends to increase as the ε of the organic solvent increases. In particular, when the ε of the organic solvent is 10 or more, the effect on σi becomes remarkable, and the practical σi of at least 10 ^-9 S cm ^-1 or more may be reached, and depending on the combination of solid compositions, the effect on σi becomes remarkable. A very high σi value of about 10 ⁻⁴ S·cm ⁻¹ was obtained. From the above results, considering the possibility of application as an ion conductive material, and from the effectiveness of ε of the organic solvent on σi, if ε of the organic solvent is 10 or more,
It can be understood that the requirements for the organic solvent contained in the composition are met. If the ε of the organic solvent increases, the ionic dissociation of the electrolyte will be promoted and the dissolution ability of the electrolyte will increase, and the solubility for highly polar organic polymer compounds will also be excellent. Due to the dissolution, the distribution of ions in the composition becomes uniform, contributing to an increase in the mobility of ions. As a result, the larger the ε of the organic solvent, the more it satisfies the above-mentioned requirements (A) and (B) for the organic solvent to be effective in increasing σi. This effect is manifested when ε is 10 or more, particularly when ε is 30 or more, and compositions exhibiting extremely high σi of about 10 ⁻⁵ S·cm ⁻¹ were also obtained. Organic solvents with a large ε are generally used for highly polar bonding groups (which are called polar groups ), and the more this polar group is arranged in a molecular structure that is more easily polarized, the larger ε becomes. In the table of examples, compounds such as alcohols, ketones, amides, nitriles, and carbonates are shown as examples, but the compounds are not limited to these compounds, and ε
The effects of the present invention can be obtained with any organic solvent having a high polarity of 10 or more. The second feature of the present invention is that the ionically conductive composition contains an organic polymer compound. This is expected to result in the ability to form into arbitrary shapes and form films by imparting excellent mechanical processability inherent to organic polymer compounds. There is also a method of using an organic polymer compound simply as a binder, but in this case there is a certain limit to the improvement of ionic conductivity. In other words, the presence of an organic polymer acts as a steric hindrance when ions move, and tends to reduce the ion mobility μi. Therefore, in order to remove this obstacle to the movement of ions, the inventors came up with the idea of creating an excellent swollen state for organic polymer compounds. When organic polymers are in a swollen state, the distance between them is expanded, allowing ions to move freely. Furthermore, the interaction between ions and organic polymers is relaxed, and the mobility of ions is greatly improved. As the composition ratio of the organic solvent increases, the distance between the organic polymers becomes wider and the organic polymers are completely dissolved to reach a solution state. In a solution state, it becomes a fluid and cannot be molded into a certain shape. Therefore, in order to maintain a constant solid state,
It is necessary to specify the maximum composition ratio of the organic solvent contained in the solid body composition, but this maximum composition ratio depends on the solubility of the organic solvent to the organic polymer compound, as well as the molecular weight and molecular weight distribution of the organic polymer compound. It depends. As a result of examining various organic polymer compounds that are effective in the present invention, it was found that the ionic conductivity σi significantly influences the dielectric constant ε of the organic polymer compound. Therefore, as a result of using various organic polymer compounds with different dielectric constants ε and examining the relationship between the ionic conductivity σi and the dielectric constant ε of the composition, it was found that when the organic polymer compound has ε of 4 or more, it is practical. We have reached the conclusion that the method is effective as it expresses σi that can be used for. The dielectric constant ε of an organic polymer compound promotes ion dissociation in the electrolyte, and as a result, during conduction, the concentration of ion carriers ni increases, and the ion mobility μi increases.
It is thought that this contributes to an increase in the ionic conductivity σi. In the end, the organic polymer compound used in the present invention that has a dielectric constant ε of 4 or more and is soluble in various organic solvents gave good results. A third feature of the present invention resides in the composition of an ionically conductive solid composition containing, as an electrolyte, a salt consisting of ions of metals belonging to groups and/or groups of the periodic table. In order to exhibit high ionic conductivity, it is necessary for the metal salt to have low ionic dissociation energy and to have excellent solubility in organic solvents. As a result of examining effective electrolytes for the present invention from this point of view, it was concluded that salts consisting of ions of metals belonging to groups and/or groups of the periodic table are particularly effective. The fourth feature of the present invention is that an organic solvent having an ε of 10 or more and an organic polymer compound having an ε of 4 or more are combined as an ion-conductive solid composition. ε is
An organic solvent with an ε of 10 or more and an organic polymer compound with an ε of 4 or less, or an organic polymer compound with an ε of 4 or more and an ε
In the case of a solid composition system in combination with an organic solvent of 10 or less, a σi of only about 10 ⁻⁸ to ^{10 −7} S·cm ⁻¹ can be obtained. On the other hand, in a solid composition system that combines an organic polymer compound with ε of 4 or more and an organic solvent with ε of 10 ^or more, the maximum
A very high σi of 10 ⁻⁴ S·cm ⁻¹ was obtained. This seems to be because the effect of the organic solvent and the ε of the organic polymer compound was significantly synergistically expressed, resulting in extremely high ionic conductivity. This is the most significant feature of the invention. As the composition ratio of the electrolyte in the solid body composition increases, it contributes to an increase in electrical conductivity, but when a large amount is present, the composition becomes hard and brittle, and mechanical workability decreases. Further, the larger the amount of solvent contained in the solid composition, the greater the mobility of ions and the higher the electrical conductivity, but if the solvent is present in a large amount, the composition will soften and eventually become a fluid. Therefore, there is a practical maximum value for the composition ratio of the electrolyte and the solvent. In addition, although this maximum value cannot be uniformly defined depending on the type and physical properties of the compounds that make up the solid body composition, as a result of various experiments, the maximum value of the electrolyte composition ratio is determined by the repeating unit of the organic polymer compound. The maximum value of the organic solvent composition ratio was approximately 50 to 90 wt%. Examples of the present invention will be described below. In addition, the content of the electrolyte and organic solvent in the ion conductive solid composition was carried out on samples within a range that did not exceed the maximum values mentioned above. [Example 1] An electrolyte solution in which an electrolyte was dissolved in an organic solvent and a polymer solution in which an organic polymer compound was dissolved in an organic solvent were prepared. The prepared electrolyte solution and polymer solution were mixed and sufficiently stirred until uniform. If it is difficult to obtain a uniform solution, a predetermined uniform solution can be obtained by stirring the mixed solution while heating it. after that,
The mixed solution was decompressed and degassed using a rotary pump. Next, a certain amount of this mixed solution was poured into a Teflon container prepared in advance, and the organic solvent was gradually evaporated while flowing nitrogen gas at a temperature from room temperature to below the boiling point of the organic solvent. This operation was continued until the sample in the Teflon container changed from a solution state to a gel state. After the sample was in a gel state, the Teflon container containing the sample was transferred to a vacuum heating dryer and heated and dried under normal pressure at a temperature below the boiling point of the organic solvent used while flowing nitrogen gas. In addition, when the boiling point of the organic solvent was 100° C. or higher, it was dried by heating under reduced pressure. Heat drying is
The sample state continued until it changed from a gel state to a state that does not deform even if the container is tilted, that is, a solid state. After heating and drying, the Teflon container containing the sample was transferred into a glove box filled with nitrogen gas, and the sample was peeled from the Teflon container and cut into a certain shape. The cut sample piece was sandwiched between platinum black electrodes in a sandwich pattern, and the resistance value of the sample piece was measured using the AC two-terminal method. The measurement was performed in a nitrogen gas atmosphere using a measurement frequency of 1 KHz, and the conductivity σ of the sample was calculated from the resistance value, thickness, and area of the platinum black electrode of the sample piece. The combination of compounds constituting the ionically conductive solid composition sample, that is, an organic polymer compound, an organic solvent, and an electrolyte, conducted using the sample preparation procedure and measurement method described above, and the combination formed by this combination. The ionic conductivity σi of the solid composition
are shown in Table 1. In addition, among the composition combinations in Table 1, the organic polymer compound does not completely dissolve in the organic solvent, but partially dissolves or is partially insoluble, the organic polymer compound swells, or the metal salt of the electrolyte Although some of the organic solvents were not completely dissolved, some were partially dissolved, and some were not, but there were no problems with the effects of the present invention such as sample preparation, moldability, and conductivity, so they were applied in this example. . In addition, as a result of measuring the electronic conductivity of all samples, the electronic conductivity was less than 10 ^-14 S cm ^-1 , so the conductivity σ by the measurement method described above was replaced by the ionic conductivity σi
It is shown in Table 4 as follows.

[Example 2]

In a solid composition system in which the organic polymer compound is polyvinylidene fluoride and polyacrylonitrile, the composition ratios of the electrolyte LiCO ₄ and the organic solvents propylene carbonate, dimethylformamide, and ethylene carbonate are varied to improve the ionic conductivity of the solid composition. The relationship with the rate σi was examined in detail. Sample preparation of the solid composition was carried out in the same manner as in Example 1. The sample preparation method will be described in detail below using a representative example of a solid composition system in which the organic polymer compound is polyvinylidene fluoride, the organic solvent is dimethylformamide (hereinafter abbreviated as DMF), and the electrolyte is LiCO ₄ . Polyvinylidene fluoride was dissolved in DMF to prepare a 1 mo/DMF solution of polyvinylidene fluoride, and LiCO ₄ was dissolved in DMF to prepare LiCO _{4 DMF solutions with different concentrations of LiCO 4 .} DMF of polyvinylidene fluoride
The solution and the DMF solution of LiCO ₄ were mixed, and the mixed solution was poured into a Teflon container so that the solution was cast in an area of approximately 10 cm square. When this was dried at a temperature of approximately 80° C. for 12 hours while flowing an inert gas such as nitrogen gas or argon gas, the sample in the Teflon container changed from a solution state to a gel state. After the sample became a gel, it was dried under reduced pressure at a temperature of about 140°C for about 24 hours. By such treatment, a thin film of the solid composition with a thickness of 1 mm or less was formed on the Teflon. This thin film was peeled off from the Teflon. The peeled film exhibited relatively elastic film properties with high flexibility. This membrane was cut into disks with a diameter of 10 mm and used as measurement samples. For measurements, the diameter is 10
The resistance value of the sample was measured using a sandwich-shaped lithium electrode formed into a disc-shaped lithium electrode with a sandwich shape between the disc-shaped lithium electrodes using the AC two-terminal method. All sample preparation and measurements were performed in an argon gas atmosphere to prevent moisture from entering, and the ionic conductivity σi was calculated from the thickness, area, and resistance value of the sample piece. Table 2 shows the combination of components of the ionically conductive solid composition, the composition ratio of each component, and σi. The composition ratio of the electrolyte LiCO ₄ was expressed in mole percent (mo%) with respect to the repeating unit of the organic polymer compound, and was changed depending on the amount of LiCO ₄ charged. In addition, the composition ratio of the organic solvent is
It is expressed as a weight percent (wt%) in the solid composition, and was determined by analyzing the formed solid composition using a pyrolysis gas chromatograph analysis method. Based on the results of gas chromatograph analysis, water was found to have been mixed in despite precautions taken during processing.

[Table] Figure 1 shows the relationship between the composition ratio (mol%) of the electrolyte LiCO ₄ and the ionic conductivity σi when polyvinylidene fluoride is used as the organic polymer compound. When the organic solvent is DMF (a in Figure 1), σi is larger than in a composition system without DMF (b in Figure 1), and the organic solvent DMF with a large ε contributes to the increase in σi. Is recognized. In addition, as the composition ratio of LiCO ₄ increases, σ
i is increasing. In this example, although σi was measured only up to a LiCO ₄ composition ratio of approximately 50mo%, when the LiCO ₄ composition ratio was 70mo%,
If it exceeds the above range, the film properties of the solid composition will become hard and brittle, and the mechanical processability will decrease. The maximum value of the electrolyte content varies depending on properties such as the type, solubility, and composition ratio of the components of the solid body composition. Figures 2 and 3 show the composition ratio (wt%) of the organic solvent contained in the solid composition when the organic polymer compound is polyvinylidene fluoride and polyacrylonitrile, respectively, and the electrolyte is LiCO ₄ .
This shows the relationship between σi and σi. In Figure 2, the σi of propylene carbonate (e in Figure 2) is larger than that in the case where the organic solvent is DMF (Figure 2 c), and when propylene carbonate is 35 wt.
%, a thin film with excellent elasticity and flexibility was obtained, exhibiting a σi of approximately 10 ⁻⁴ S·cm ⁻¹ . From the results shown in Figure 3, although the electrolyte is LiO ₄ and the organic polymer compound is the same as polyacrylonitrile, the organic solvent is propylene carbonate (tertiary carbonate).
In case h) in the figure, σi of about 10 ^-3 S cm ^-1 and
DMF (f in Figure 3) and ethylene carbonate (g in Figure 3) showed the highest σi of about 10 ^-4 S·cm ^-1 . In all compositions, the resulting films exhibited excellent mechanical processability in both flexibility and elasticity. When the organic solvent is DMF, the composition ratio is approximately 50wt%
Above this, the composition begins to soften, but in the case of propylene carbonate, it can maintain its shape as a solid up to about 80wt%, and when it reaches about 90wt% or more, the composition begins to soften and cannot maintain a certain shape as a solid. It disappears. As described above, the maximum composition ratio of the organic solvent as a solid body also differs, like the electrolyte, depending on various properties such as the type, molecular weight, mutual solubility, etc. of the organic solvent, organic polymer compound, and electrolyte. The ion conductive solid composition system obtained by the present invention can be formed into any shape or formed into a film depending on the volume and concentration of the solution to be prepared and the shape of the container into which the solution is injected. by decreasing the thickness to 100
It was possible to form a thin film with a wide area and high flexibility of less than μm. If it can be made into a thin film,
The resistance in the cross-sectional direction of the film decreases in proportion to the film thickness and inversely to the area, so it can be used in a wide range of applications. If the film thickness and area are controlled based on σi in the table, the ionically conductive solid composition according to the present invention can be used in batteries, electrolytic capacitors, sensors, electrochromic devices, time devices, integral memory devices, etc. It goes without saying that the electrically conductive material can be used in electronic components for practical purposes.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the ionic conductivity σi of the ion conductive solid composition using polyvinylidene fluoride of the present invention and the composition ratio (mo%) of the electrolyte LiCO ₄ , and FIG. Figure 3 is a diagram showing the relationship between _{σi and the composition ratio (wt%) of an organic solvent for an ion-conductive solid composition composed of polyvinylidene fluoride and LiCO 4 .} FIG. 2 is a diagram showing the relationship between σi and the organic solvent composition ratio (wt%) of the ionically conductive solid composition obtained. a...Dimethylformamide (4-6wt%),
A solid composition system containing H ₂ O (3 to 5 wt%).
b...A solid composition system that does not contain H ₂ O (5 to 8 wt%) and an organic solvent. c...A solid composition system containing dimethylformamide. d...A solid composition system containing dimethylformamide and propylene carbonate. e... Solid composition system containing propylene carbonate. f... Solid composition system containing dimethylformamide. g...A solid composition system containing ethylene carbonate. H...
...A solid composition system containing propylene carbonate.

Claims (1)

[Claims] 1. An electrolyte consisting of an ion of a metal belonging to a periodic table group and/or group, an organic polymer compound with a dielectric constant of 4 or more, and a dielectric constant having excellent solubility in the electrolyte and the organic polymer compound. An ion conductive solid composition comprising 10 or more organic solvents, wherein the content of the organic solvent contained in the solid composition is at least an amount that causes the organic polymer compound to be in a swollen state, and 90 wt% or less of the solid composition, and the content of the electrolyte is selected to be at least an amount that provides an ionic conductivity of about 10 ^-8 S cm ^-1 or more and not more than 90 mo% of the solid composition. An ionically conductive solid composition comprising: