JP2003217664A - Gel electrolyte for secondary battery and secondary battery, and method of manufacturing gel electrolyte for secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve the conductivity and mechanical strength of a gel electrolyte at the same time. <P>SOLUTION: Two gel electrolytes with high conductivity and high ratio of the included electrolytic solution are manufactured (S10), and at the same time, a gel electrolyte with high mechanical strength and low ratio of the included electrolytic solution is manufactured (S12). After that, both gel electrolytes are pasted one after another (S14), and the gel electrolyte is completed. As a result, as the electrolytic solution in the gel electrolyte is moved from the electrolyte with the high ratio of the included electrolytic solution to the electrolyte with the low ratio of included electrolytic solution, the conductivity of the gel electrolyte can be high on the whole, and at the same time, a sufficient mechanical strength can be maintained on the whole by the gel electrolyte with high strength. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a gel electrolyte, a secondary battery including the same, and a method for producing a gel electrolyte.

[0002]

2. Description of the Related Art In recent years, with the development of the field of microdevices, further higher energy density of secondary batteries is required. For example, a lithium secondary battery includes a positive electrode, a negative electrode, and an electrolyte, and a gel electrolyte is often used as the electrolyte from the viewpoint of safety and the like.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In this gel electrolyte,
The mechanical strength and ionic conductivity are determined according to the ratio of the retained electrolytic solution. Therefore, when the ratio of the electrolytic solution in the electrolyte is increased, the ionic conductivity is improved, but the mechanical strength is insufficient and the function as the separator is not exhibited, which may cause a short circuit between the positive electrode and the negative electrode. . Therefore, the reliability of the secondary battery may be reduced. On the contrary, when the ratio of the electrolytic solution in the electrolyte is reduced, the mechanical strength is improved and the above-mentioned problem is solved, but the ionic conductivity is lowered and the contact electric resistance between the electrolyte and the electrode may be increased. . Therefore, the performance (output) of the secondary battery may be reduced.

It is an object of the gel electrolyte and the method for producing a gel electrolyte of the present invention to solve these problems and provide a gel electrolyte which has both reliability and performance as a secondary battery. Another object of the gel electrolyte and the method for producing a gel electrolyte of the present invention is to provide a gel electrolyte having both ionic conductivity and mechanical strength.

The secondary battery of the present invention has one of the purposes of achieving both reliability and performance. Another object of the secondary battery of the present invention is to provide a secondary battery using a gel electrolyte that has both ionic conductivity and mechanical strength.

[0006]

Means for Solving the Problems and Their Actions / Effects The gel electrolyte of the present invention, a secondary battery including the same, and a method for producing a gel electrolyte adopt the following means in order to achieve at least a part of the above objects. It was

The gist of the gel electrolyte for a secondary battery of the present invention is that at least two kinds of gel electrolytes having different ratios of contained electrolytic solutions are stuck together.

In the gel electrolyte for a secondary battery according to the present invention, at least two kinds of gel electrolytes having different ratios of the contained electrolytic solution are bonded together, that is, the ratio of the gel electrolyte to the electrolytic solution is high and the ratio of the electrolytic solution is low. Laminate with gel electrolyte. Thereby, since the electrolytic solution moves from the gel electrolyte having a high ratio of the electrolytic solution to the gel electrolyte having a low ratio of the electrolytic solution, the gel electrolyte having a high ion conductivity containing the electrolytic solution in a sufficient ratio as a whole may be obtained. At the same time, due to the high mechanical strength of the gel electrolyte having a low ratio of the electrolytic solution, a gel electrolyte having a sufficient mechanical strength as a whole can be obtained.

In the gel electrolyte for a secondary battery of the present invention, among the at least two kinds of gel electrolytes,
A gel electrolyte containing a low proportion of the electrolyte solution may be sandwiched between gel electrolytes containing a high proportion of the electrolyte solution.

Further, in the gel electrolyte for a secondary battery of the present invention, one of the at least two kinds of gel electrolytes is a gel electrolyte containing 40 to 60% by weight of an electrolytic solution. The other gel electrolyte of the at least two types of gel electrolyte may be a gel electrolyte containing 85 to 95% by weight of an electrolytic solution.
In the gel electrolyte for a secondary battery of the present invention in this aspect,
The one gel electrolyte may be a gel electrolyte containing approximately 50% by weight of the electrolytic solution, and the other gel electrolyte may be a gel electrolyte containing approximately 90% by weight of the electrolytic solution.

The gist of the secondary battery of the present invention is to include the gel electrolyte of the present invention in each of the above aspects.

In the secondary battery of the present invention, since the secondary battery contains an electrolyte solution in a sufficient ratio as a whole and incorporates a gel electrolyte having a sufficient mechanical strength, it is possible to achieve both reliability and performance. It can be the next battery.

The first method for producing a gel electrolyte for a secondary battery according to the present invention is a method for producing a gel electrolyte for a secondary battery containing an electrolytic solution at a predetermined ratio or more, and is less than the predetermined ratio. A first step of producing a first gel electrolyte containing a ratio of the electrolyte solution and a second gel electrolyte containing a proportion of the electrolyte solution in a ratio higher than the predetermined ratio; The gist is to include a second step of bonding the gel electrolyte and the second gel electrolyte.

According to the first method for producing a gel electrolyte for a secondary battery of the present invention, a first gel electrolyte containing an electrolytic solution at a ratio lower than a predetermined ratio is produced, and an electrolysis at a ratio higher than the predetermined ratio is performed. A second gel electrolyte containing a liquid is prepared and both gel electrolytes are adhered to each other to prepare a gel electrolyte containing an electrolytic solution at a predetermined ratio or more. Therefore, since the electrolytic solution moves from the second gel electrolyte having a high ratio of the electrolytic solution to the first gel electrolyte having a low ratio of the electrolytic solution, the high-conductivity gel electrolyte containing the electrolytic solution at a predetermined ratio or more as a whole. At the same time, the gel electrolyte having a sufficient mechanical strength as a whole can be provided due to the high mechanical strength of the first gel electrolyte having a low ratio of the electrolytic solution.

A second method for producing a gel electrolyte for a secondary battery according to the present invention is a method for producing a gel electrolyte for a secondary battery containing an electrolytic solution at a predetermined ratio or more, which is less than the predetermined ratio. Providing a first step of producing a gel electrolyte containing a ratio of the electrolytic solution, and a second step of refilling the produced gel electrolyte with the electrolytic solution to contain the electrolytic solution in the predetermined ratio or more. Is the gist.

In the second method for producing a gel electrolyte for a secondary battery according to the present invention, a gel electrolyte containing an electrolyte solution in a ratio smaller than a predetermined ratio is prepared, and the electrolyte solution is re-used in the prepared gel electrolyte. A gel electrolyte is prepared by filling and containing an electrolytic solution at a predetermined ratio or more. Therefore, since the electrolytic solution moves to the gel electrolyte having a low ratio of the electrolytic solution,
As a whole, a gel electrolyte having a high conductivity containing a predetermined ratio or more of an electrolytic solution can be produced, and at the same time, due to the high mechanical strength of the gel electrolyte having a low ratio of the electrolytic solution, it is sufficient even after refilling with the electrolytic solution. A gel electrolyte having mechanical strength can be provided.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described using examples. FIG. 1 is a configuration diagram showing an outline of the configuration of a secondary battery 20 which is an embodiment of the present invention.
The secondary battery 20 of the embodiment is configured as, for example, a lithium secondary battery, and as shown in the drawing, a film-like gel electrolyte 22 and a positive electrode active material 30 sandwiching the gel electrolyte 22,
Negative electrode active material 32, positive electrode active material 30, positive side current collecting electrode 34 attached to negative electrode active material 32, negative side current collecting electrode 3 respectively
6 and the positive side terminal 4 electrically connected to the positive side current collecting electrode 34 and the negative side current collecting electrode 36 via lead wires 38 and 40, respectively.
2, and a negative terminal 44. Secondary battery 2 of this embodiment
In the case of 0, a stacked secondary battery can be formed by stacking a plurality of unit cells each including a gel electrolyte 22, a positive electrode active material 30, and a negative electrode active material 32. It can also be a secondary battery.

The gel electrolyte 22 is composed of two kinds of film-shaped first and second gel electrolytes 2 having different ratios of contained electrolytic solutions.
4, 26, and more specifically, the two first gel electrolytes 24 having a high electrolytic solution content (for example, a content of 85 to 95% by weight, preferably about 90% by weight). The second gel electrolyte 26 having a low content (for example, 40 to 60% by weight, preferably about 50%) is sandwiched between the second gel electrolyte 26 and the second gel electrolyte 26. The gel electrolyte exhibits high ionic conductivity and low mechanical strength when the ratio of the contained electrolyte is high, and low ionic conductivity and high mechanical strength when the ratio of contained electrolyte is low. Is
Two first gel electrolytes 24 having high ionic conductivity and low mechanical strength sandwich a second gel electrolyte having low ionic conductivity and high mechanical strength. FIG. 2 is a process drawing showing an example of a manufacturing process of such a gel electrolyte 22. In the manufacturing process of the gel electrolyte 22, two first gel electrolytes 24 having a high electrolytic solution content are manufactured (step S10), and a second gel electrolyte 26 having a low electrolytic solution content is manufactured (step S12). , Both gel electrolytes 24, 2
This is completed by alternately laminating 6 (step S14).

Here, the gel electrolyte 24 having a high electrolytic solution content, that is, a high conductivity, is prepared by mixing, for example, ethylene carbonate and diethyl carbonate in a volume ratio of 3: 7 with L in an organic solvent.
An electrolytic solution in which 0.75 mol / l of i (CF ₃ SO ₂ ) ₂ was dissolved, a gel material of triacrylate of polyethylene oxide (PEO), and a stimulating polymerization initiator were mixed at a predetermined ratio (90: 10: 1). Of the mixed solution) is applied on the resin film by the doctor blade method, and then U
It can be produced as an electrolyte membrane by irradiating with V ray for a predetermined time (about 1 minute). As the electrolytic solution, various known ones may be used, and as the gel material, various ones which can be crosslinked by heat or ultraviolet rays after being mixed with the electrolytic solution may be used. The same applies to the gel electrolyte 26 having a low electrolytic solution content. The gel electrolyte 24 may be prepared as an electrolyte membrane or may be directly supported on the positive and negative electrode active materials 30 and 32.

On the other hand, the gel electrolyte 26 having a low content of the electrolytic solution, that is, having a high mechanical strength is, for example, Li (CF ₃ SO 4) in an organic solvent in which ethylene carbonate and diethyl carbonate are mixed in a volume ratio of 3: 7. ₂ ) An electrolyte solution in which 0.75 mol / l of ₂ is dissolved, a gel material of polyethylene oxide (PEO) triacrylate, and a stimulative polymerization initiator are mixed at a predetermined ratio (weight ratio of 50: 50: 1). It can be prepared by applying the mixed solution on a resin film by using a doctor blade method and then irradiating with UV rays for a predetermined time (about 2 minutes).

The gel electrolyte 22 produced by the above method
Table 1 shows the experimental results regarding the change in the conductivity of the.

[Table 1] As shown in Table 1, when the gel electrolyte 24 having a high electrolytic solution content, that is, high conductivity, and the gel electrolyte 26 having a low electrolytic solution content, that is, high strength, are bonded, the gel electrolyte before bonding (Gel Electrolyte 2 with low content of electrolyte solution)
(Depending on the conductivity of 6), the ionic conductivity is greatly improved (4 times), and the gel electrolyte 22 as a whole is
It can be seen that the ionic conductivity of 1 greatly exceeds the ionic conductivity of about 1 mS / cm required as a gel electrolyte for secondary batteries. At the same time, the gel electrolyte 22 can maintain sufficient mechanical strength due to the gel electrolyte 26 having high mechanical strength.

In the secondary battery 20 of the embodiment described above,
Gel electrolyte with high electrolyte content, that is, high conductivity 2
4 and the gel electrolyte 26 having a low electrolytic solution content, that is, a high mechanical strength, are bonded to each other to form the gel electrolyte 22, so that the gel electrolyte having a high ionic conductivity while maintaining the mechanical strength, that is, A secondary battery including a gel electrolyte having both mechanical strength and ionic conductivity can be provided. As a result, a secondary battery having both high reliability and performance can be obtained.

In the secondary battery 20 of the embodiment, the gel electrolyte 2
2 to the two first gel electrolytes 24 having a high electrolytic solution content.
Although the second gel electrolyte 26 having a low electrolytic solution content is sandwiched between the two, a gel electrolyte having a high electrolytic solution content and a gel electrolyte having a low electrolytic solution content are bonded together. If so, various modes can be adopted. Further, in the secondary battery 20 of the embodiment, the gel electrolyte 22 is formed by sticking together two types of gel electrolytes, that is, the first gel electrolyte 24 and the second gel electrolyte 26. The gel electrolyte may be formed by bonding three or more types of gel electrolyte having different ratios.

In the secondary battery 20 of the embodiment, the gel electrolyte 22 is formed by bonding the gel electrolyte 24 having a high electrolytic solution content and the gel electrolyte 26 having a low electrolytic solution content. A gel electrolyte having a low electrolytic solution content may be further charged with the electrolytic solution to form a final gel electrolyte. FIG. 3 is a manufacturing process diagram showing another example of the manufacturing process of the gel electrolyte. The gel electrolyte is completed by preparing a gel electrolyte having a low electrolytic solution content (high mechanical strength) (step S20) and refilling the prepared gel electrolyte with the electrolytic solution (step S22).

As the gel electrolyte having a low electrolytic solution content, the same gel electrolyte as the gel electrolyte 26 of the secondary battery 20 of the embodiment can be used. Also, the electrolyte to refill is
The same electrolyte solution or the same kind as the electrolyte solution contained in the gel electrolyte before refilling is used. Also, step S22
As a refilling method in, for example, as shown in FIG. 4, a gel electrolyte having a low electrolytic solution content is directly immersed in an electrolytic solution tank filled with an electrolytic solution in advance, or as shown in FIG. The gel electrolyte having a low electrolytic solution content may be assembled in advance as a secondary battery together with the positive and negative electrodes, and then the electrolytic solution may be filled.

The experimental results for the change in ionic conductivity before and after refilling the above-mentioned gel electrolyte with an electrolytic solution are shown below.

[Table 2] As shown in Table 2, when the gel electrolyte having a low electrolyte content (50 wt%) was refilled with the electrolyte, the ionic conductivity was greatly (5 times) improved (3 mS / cm), It can be seen that the minimum required ionic conductivity as a gel electrolyte for a battery greatly exceeds about 1 mS / cm. Moreover, since the gel electrolyte having a low electrolytic solution content has high mechanical strength, sufficient strength can be maintained even by refilling with the electrolytic solution.

Therefore, the secondary battery of the modified example can also achieve the same effect as the secondary battery 20 of the embodiment.

Although the embodiments of the present invention have been described with reference to the embodiments, the present invention is not limited to the embodiments of the present invention, and various embodiments are possible without departing from the gist of the present invention. Of course, it can be implemented in.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an outline of a configuration of a secondary battery 20 which is an embodiment of the present invention.

FIG. 2 is a manufacturing process chart showing an example of a manufacturing process of the gel electrolyte 22 of the secondary battery 20 of the example.

FIG. 3 is a manufacturing process diagram showing an example of a manufacturing process of a gel electrolyte of a secondary battery of a modified example.

FIG. 4 is a diagram showing an example of a state in which a gel electrolyte having a low electrolytic solution content is refilled with electrolytic solution.

FIG. 5 is a diagram showing another example of a state of refilling with an electrolytic solution of a gel electrolyte having a low electrolytic solution content.

[Explanation of symbols]

20 secondary battery, 22 gel electrolyte, 24 first gel electrolyte, 26 second gel electrolyte, 30 positive electrode active material, 32
Negative electrode active material, 34 Positive side current collecting electrode, 36 Negative side current collecting electrode, 38, 40 Lead wire, 42 Positive side terminal, 44 Negative side terminal.

Claims (7)

[Claims] 1. A gel electrolyte for a secondary battery, which is formed by bonding at least two types of gel electrolyte having different ratios of contained electrolytic solutions. 2. The gel electrolyte for a secondary battery according to claim 1, wherein the gel electrolyte having a low ratio of the electrolyte solution contained in the at least two types of gel electrolyte has a ratio of the electrolyte solution containing therein. A gel electrolyte for a secondary battery, which is sandwiched between high gel electrolytes. 3. The gel electrolyte for a secondary battery according to claim 1, wherein one of the at least two types of gel electrolyte contains 40 to 60% by weight of an electrolytic solution. A gel electrolyte for a secondary battery, which is a gel electrolyte, and the other gel electrolyte of the at least two types of gel electrolyte is a gel electrolyte containing 85 to 95% by weight of an electrolytic solution. 4. The gel electrolyte for a secondary battery according to claim 3, wherein the one gel electrolyte is a gel electrolyte containing approximately 50% by weight of an electrolytic solution, and the other gel electrolyte is A gel electrolyte for a secondary battery, which is a gel electrolyte containing approximately 90% by weight of an electrolytic solution. 5. A secondary battery comprising the gel electrolyte according to claim 1. 6. A method for producing a gel electrolyte for a secondary battery, which contains an electrolyte solution at a predetermined ratio or more, wherein a first gel electrolyte containing an electrolyte solution at a ratio lower than the predetermined ratio is produced. And a second gel electrolyte containing an electrolyte solution having a ratio higher than the predetermined ratio.
And a second step of adhering the produced first gel electrolyte and the second gel electrolyte to each other, a gel electrolyte manufacturing method for a secondary battery. 7. A method for producing a gel electrolyte for a secondary battery, which contains an electrolyte solution at a predetermined ratio or more, which is a first method for producing a gel electrolyte containing an electrolyte solution at a ratio lower than the predetermined ratio. A method for producing a gel electrolyte for a secondary battery, comprising: a step; and a second step in which the produced gel electrolyte is refilled with an electrolyte solution to contain the electrolyte solution in a predetermined ratio or more.