TWI643223B - Composition for manufacturing a polymer electrolyte membrane and method for manufacturing the polymer electrolyte membrane - Google Patents

Abstract

A composition for preparing an electrolyte membrane for solving the problem that the electrolyte membrane of the conventional supercapacitor has low conductivity, low dissociation degree, and insufficient mechanical strength at high temperatures. The system comprises: 5 to 20% by weight of polyvinylidene fluoride, 25 to 70% of barium titanate and 15 to 65% of one ionic liquid.

Description

Composition for preparing electrolyte membrane and method for producing electrolyte membrane

The present invention relates to a composition, especially a composition for preparing an electrolyte membrane. The invention further relates to a method of producing an electrolyte membrane.

The supercapacitor is also called an electric double-layer capacitor (EDLC), which comprises an electrolyte solution, two electrodes and an isolation layer separating the two electrodes, and belongs to a wet capacitor due to the use of a liquid electrolyte solution. When the supercapacitor is used, the electrolyte solution is subjected to a potential difference, and the ions generated by the dissociation of the electrolyte in the electrolyte solution are affected by the electric field, and an electric double layer is formed at each of the electrodes, so the energy of the supercapacitor is compared with the conventional capacitor. Higher density and larger capacitance make it more suitable for storing electrical energy.

However, since the supercapacitor uses a liquid electrolyte solution, when the supercapacitor is manufactured, a complicated process is required for encapsulating the electrolyte solution, and the fabricated supercapacitor still implicates the possibility of leakage of the solution, damaging the The life of supercapacitors. Moreover, the high temperature during operation of the supercapacitor may damage the isolation layer and cause short circuit of the electrode, thereby causing a dangerous event such as a fire.

In order to solve the above problems caused by the electrolyte solution, there has been an electrolyte membrane formed by mixing an electrolyte solution and a polymer material, which can be used as a separator, and can provide an electrolyte itself, so that a liquid electrolyte solution can be avoided. However, such an electrolyte membrane The conductivity is not good, and the mechanical strength at high temperatures is insufficient, and there is still a problem of breakage.

In addition, some ions generated by the dissociation of the electrolyte in the above electrolyte solution aggregate due to Coulomb force to form an ion group, and when the electrolyte dissociation degree is low, that is, the ion group volume is large, the charge per unit area of the electrode is caused. The amount is reduced, which in turn reduces the amount of power that the supercapacitor can store.

In view of this, the conventional electrolyte membrane does have a need for improvement.

In order to solve the above problems, an object of the present invention is to provide a composition for preparing an electrolyte membrane which can be used for preparing an electrolyte membrane having good electrical conductivity, dissociation of an electrolyte, and mechanical strength at a high temperature.

It is still another object of the present invention to provide a composition for preparing an electrolyte membrane which can be applied to a supercapacitor to increase the amount of electricity that the supercapacitor can store.

Still another object of the present invention is to provide a method for producing an electrolyte membrane which can produce an electrolyte membrane having good electrical conductivity, dissociation of an electrolyte, and mechanical strength at a high temperature.

The composition for preparing an electrolyte membrane of the present invention comprises 5 to 20% by weight of polyvinylidene fluoride, 25 to 70% of barium titanate and 15 to 65% of one ionic liquid.

Accordingly, since the composition for preparing an electrolyte membrane of the present invention contains barium titanate, the electrolyte membrane can improve the mechanical strength at a high temperature and achieve the effect of "improving the safety of the electrolyte membrane". In addition, the composition for preparing an electrolyte membrane can improve the dissociation degree of the ionic liquid, so that the volume of the ion cluster generated by dissociation of the ionic liquid is reduced, the ion mobility is increased, and the conductivity is improved, so the electrolyte membrane can be applied. Used as a separator containing an electrolyte in a supercapacitor, it can isolate the electrodes in the supercapacitor while providing electrolytes, achieving the effect of "increasing the power of the supercapacitor".

Among them, the ionic liquid is EMI-TFSI or EMI-BF4. So, the system has Provides the efficacy of electrolytes.

Wherein, the weight ratio of polyvinylidene fluoride, barium titanate and the ionic liquid is 1:4:4. In this way, it has the effect of taking into account the conductivity of the electrolyte membrane and the cost of the raw material.

A method of producing an electrolyte membrane of the present invention, comprising: providing a composition for preparing an electrolyte membrane, the composition for preparing an electrolyte membrane being the composition for preparing an electrolyte membrane; and the method for preparing an electrolyte membrane The composition is formed into an electrolyte membrane.

Wherein the forming of the composition for preparing an electrolyte membrane into the electrolyte membrane comprises coating the composition for preparing an electrolyte membrane on a substrate, and drying the composition for preparing the electrolyte membrane to form the electrolyte film Electrolyte membrane.

Wherein, before the composition for preparing an electrolyte membrane is applied to the substrate, the composition for preparing an electrolyte membrane is mixed with a solvent to obtain a mixture, and the mixture is continuously applied to the substrate. .

Wherein the solvent is acetone. Thus, it has the effect of mixing a raw material component uniformly.

Figure 1: Measurement results of dissociation of ionic liquids in different electrolyte membranes.

Figure 2: Conductivity measurement results for different electrolyte membranes.

Figure 3: Measurement of the frequency characteristic curve of a supercapacitor using different electrolyte membranes.

The above and other objects, features and advantages of the present invention will become more <RTIgt; The composition may comprise polyvinylidene difluoride (PVDF), barium titanate (BaTiO ₃ ) and an ionic liquid, and the composition for preparing an electrolyte membrane may be further prepared to obtain an electrolyte membrane. The polyvinylidene fluoride can help shape the electrolyte membrane, which is understood by those of ordinary skill in the art to which the present invention pertains, and is not described herein.

By the addition of barium titanate, the high-temperature strength of the polyvinylidene fluoride film after film formation can be improved, and the electrolyte membrane is more durable, thereby improving the safety of the electrolyte membrane. In addition, since barium titanate is a ceramic material having a high dielectric constant (dielectric constant value is about 3000 to 8000), the dielectric constant of the electrolyte membrane can also be increased by the addition of barium titanate, thereby increasing the ion. The dissociation rate of the liquid is such that the volume of the ion cluster generated by dissociation of the ionic liquid is reduced, and the ion mobility is increased to increase the conductivity of the electrolyte membrane.

The ionic liquid itself is an electrolyte, so that when the composition for preparing an electrolyte membrane contains the ionic liquid, the electrolyte membrane can be used as a supercapacitor when it is used as a separator containing an electrolyte, and the supercapacitor is isolated. The electrolyte is provided simultaneously with the electrode. Further, the type of the ionic liquid is not particularly limited, and for example, EMI-TFSI (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) or EMI-BF4 (1-ethyl-3-methylimidazolium tetrafluoroborate) may be selected.

The composition for preparing an electrolyte membrane contains polyvinylidene fluoride in an amount of 5 to 20% by weight, in view of moldability and electrical conductivity when the composition for preparing an electrolyte membrane is formed into an electrolyte membrane, 25 ~70% of barium titanate and 15~65% of one ionic liquid, preferably the weight ratio of polyvinylidene fluoride, barium titanate and the ionic liquid is 1:4:4. If the content of barium titanate is too small, the dielectric constant of the electrolyte membrane cannot be effectively increased, and if the content of the barium titanate is too large, it is difficult to form polyvinylidene fluoride. Further, when the content of the ionic liquid is too small, the electrolyte membrane cannot exhibit sufficient conductivity. Further, after the content of the ionic liquid exceeds the above range of the weight ratio, even if the amount of the ionic liquid added is increased, the increase in the degree of conductivity is limited, which in turn causes an increase in the cost of the raw material.

The above composition for preparing an electrolyte membrane can form the electrolyte membrane by various conventional means, for example, polyvinylidene fluoride, barium titanate, the ionic liquid, and a solution can be formed. After the mixture is obtained to obtain a mixture, the electrolyte membrane is formed on a substrate by spraying or coating. Alternatively, in order to mix the components of the composition for preparing the electrolyte membrane more uniformly, the polyvinylidene fluoride, the barium titanate and the solvent may be first mixed to form a dispersion, and then the dispersion is added. The ionic liquid forms a raw material solution, and the raw material solution is applied to the substrate to form the electrolyte membrane.

The solvent is not particularly limited as long as it is soluble in polyvinylidene fluoride and disperses barium titanate. For example, acetone may be optionally used as the solvent. In addition, an ultrasonic wave can be applied when mixed with a solvent to help the above components to be uniformly mixed.

The type of the substrate is not particularly limited as long as it does not react with or dissolves in the components in the raw material solution, and for example, a glass substrate can be selected. Further, drying may be carried out when the electrolyte membrane is formed, and the means for drying is not particularly limited, and for example, it may be left at room temperature or dried using an oven to volatilize the solvent.

In order to confirm that the electrolyte membrane manufactured by the present invention can be used for supercapacitors, the storable electric quantity can be improved, and the following experiment is carried out.

First, an electrolyte membrane of each group is produced according to the distribution ratio of the composition for preparing an electrolyte membrane according to Table 1, and the method for producing the electrolyte membrane, wherein polyvinylidene fluoride, barium titanate, and the ionic liquid are produced. The content is a weight ratio when the content of polyvinylidene fluoride is 1 part, and the ionic liquid is EMI-TFSI.

(A) Effect of the addition amount of ionic liquid on conductivity

For the electrolyte membranes of Groups 1 to 3, the conductivity was measured at a temperature of 298 K. As can be seen from the results of the first table, as the weight ratio of the ionic liquid increases, the conductivity of the electrolyte membrane also increases, and in particular, the conductivity of the second group is significantly higher than that of the first group. 0.73, however, the increase in conductivity is less pronounced in Group 3 than in Group 2.

(B) The presence or absence of barium titanate on the degree of dissociation

The dissociation degree of the ionic liquid in each electrolyte membrane was measured for the electrolyte membranes of the second group and the fourth group, and the measurement results are shown in Fig. 1. As can be seen from Fig. 1, the degree of dissociation of the electrolyte membrane of the second group was significantly improved with respect to the electrolyte membrane of the fourth group.

(C) The presence or absence of barium titanate on the conductivity

For the electrolyte membranes of Groups 2 and 4, the conductivity was measured at a temperature of 240 K to 360 K, respectively, and the measurement results are shown in Fig. 2. As can be seen from Fig. 2, the conductivity of the electrolyte membrane of the second group was significantly improved with respect to the electrolyte membrane of the fourth group.

(D) Capacitor capacitance

Supercapacitors were fabricated using the electrolyte membranes of Groups 2 and 4, respectively, and the capacitance-frequency characteristics were measured at an operating temperature of 30 ° C. The measurement results are shown in Fig. 3. As can be seen from Fig. 3, the supercapacitor using the electrolyte membrane of the second group has a higher capacitance than the supercapacitor using the electrolyte membrane of the fourth group at the same operating temperature, so that a large amount of electric power can be stored.

As described above, since the composition for preparing an electrolyte membrane of the present invention contains barium titanate, the electrolyte membrane can improve the mechanical strength at a high temperature and achieve the effect of "improving the safety of the electrolyte membrane". In addition, the composition for preparing an electrolyte membrane can improve the dissociation degree of the ionic liquid, so that the volume of the ion cluster generated by dissociation of the ionic liquid is reduced, the ion mobility is increased, and the conductivity is improved, so the electrolyte membrane can be applied. Used as a separator containing an electrolyte in a supercapacitor, it can isolate the electrodes in the supercapacitor while providing electrolytes, achieving the effect of "increasing the power of the supercapacitor".

Although the present invention has been disclosed by the above-described preferred embodiments, it is not intended to limit the invention, and it is apparent to those skilled in the art without departing from the spirit and scope of the invention. The various modifications and variations of the embodiments are still within the technical scope of the invention. The scope of the invention is defined by the scope of the appended claims.

Claims (7)

A composition for preparing an electrolyte membrane comprising 5 to 20% by weight of polyvinylidene fluoride, 25 to 70% of barium titanate and 15 to 65% of an ionic liquid. The composition for preparing an electrolyte membrane according to claim 1, wherein the ionic liquid is EMI-TFSI or EMI-BF4. The composition for preparing an electrolyte membrane according to claim 1, wherein the weight ratio of the polyvinylidene fluoride, the barium titanate, and the ionic liquid is 1:4:4. A method for producing an electrolyte membrane, comprising: providing a composition for preparing an electrolyte membrane, wherein the composition for preparing an electrolyte membrane is used for preparing an electrolyte according to any one of claims 1 to 3. a composition of the film; and forming the composition for preparing the electrolyte membrane into an electrolyte membrane. The method for producing an electrolyte membrane according to claim 4, wherein the forming the composition for preparing an electrolyte membrane into the electrolyte membrane comprises coating the composition for preparing an electrolyte membrane on a substrate, And the composition for preparing an electrolyte membrane is dried to be formed into the electrolyte membrane. The method for producing an electrolyte membrane according to claim 5, wherein the composition for preparing an electrolyte membrane and a solvent are applied before the composition for preparing an electrolyte membrane is applied to the substrate. After mixing to obtain a mixture, the mixture is continuously applied to the substrate. The method for producing an electrolyte membrane according to claim 6, wherein the solvent is acetone.