JP5973052B1 - Electrochemical element separator, electrochemical element, automobile, electronic equipment - Google Patents

Abstract

The present invention provides a highly reliable separator for an electrochemical element that can not only prevent a short-circuit failure by increasing shielding but also withstand the high voltage of the electrochemical element. A separator for an electrochemical element interposed between a pair of electrodes and capable of holding an organic electrolyte containing an electrolyte is beaten with a thermoplastic synthetic fiber and an average fiber length of 0.2 to 2.0 mm. The two parts obtained by dividing the cross section of the separator into two equal parts in the thickness direction are a part with a small number of thermoplastic synthetic fibers (part A) and a part with a large number of thermoplastic synthetic fibers ( B part), and the value obtained by dividing the number of thermoplastic synthetic fibers in part A by the number of thermoplastic synthetic fibers in part B is 0.85 or less. [Selection] Figure 1

Description

  The present invention relates to a separator for an electrochemical element and an electrochemical element using the separator. The present invention is suitable for application to separators and electrochemical elements for electrochemical elements such as aluminum electrolytic capacitors, electric double layer capacitors, lithium ion capacitors, lithium primary batteries, and lithium ion secondary batteries. These electrochemical elements are suitable for application to automobiles and various electronic devices.

  Examples of the electrochemical element include a capacitor, a capacitor, and a battery. These electrochemical elements have been used in many fields in recent years, such as automobile-related equipment, renewable energy-related equipment such as wind power generation and solar power generation, and communication equipment such as smart meters. Expected.

For example, in the case of an automobile, a lithium ion secondary battery or an electric double layer capacitor is used for energy regeneration, an aluminum electrolytic capacitor or an electronic control unit (ECU) such as a fuel spray, a transmission, an electronic throttle, or an antilock brake system is used. An electric double layer capacitor is used. In electric vehicles and hybrid vehicles that have been attracting attention in recent years, lithium-ion secondary batteries are used as power sources, electric double layer capacitors are used for energy regeneration, motor control, battery control, HEV system control, and DC conversion from external AC power sources. Aluminum electrolytic capacitors are used in ECUs such as these.
As described above, various electrochemical elements are mounted on the most important parts of automobiles such as running, braking, and turning, regardless of whether or not they have an internal combustion engine.
In such electrochemical devices, high reliability is required because short-circuit defects are immediately related to human life. That is, it is required to withstand vibrations of the vehicle body, so that short-circuit failure does not occur even when used for a long time in a cold region or a high temperature region, and the deterioration in performance is small.

In addition, there is a great demand for circuit boards used in electronic devices, such as thinning and miniaturization of mounted electrochemical elements. Moreover, the electrochemical element used for the power supply of a portable device is also required to be usable for a long time by one charge.
For this reason, an electrochemical element such as an aluminum electrolytic capacitor mounted on a substrate is required to have a low profile and a small size for the purpose of supplying power to a chip or CPU and smoothing an alternating current. In addition, lithium ion secondary batteries that are often used as power sources for portable devices are required to have a high capacity so that they can be used for a long time while being small and thin. There is also a need for less performance degradation.

  With the expansion of these applications and the higher performance of equipment used, electrochemical elements have higher reliability and charge / discharge characteristics that can withstand long-term use than ever before. There is a need for improved performance such as output characteristics.

  In the electrochemical device, the main role of the separator is to isolate the pair of electrodes and hold the electrolyte solution. In order to isolate a pair of electrodes, the separator is required to have low resistance and high shielding properties. As the use of electrochemical devices expands, separators are further required to improve these performances.

In addition, the separator material is required to have electrical insulation, and is required to have lyophilic properties (lyophilic properties) in order to retain various types of electrolytes.
As a material satisfying the above-described performance, there is cellulose. By applying a shearing force to the cellulose fiber (beating), the fiber is refined, and a nonwoven fabric is formed from the refined fiber, thereby obtaining a very dense sheet.
The refined cellulose fiber has a fiber length shorter than that of a synthetic fiber or the like, easily fills the gap between sheets, and improves the shielding performance of the separator. For this reason, the separator which consists of a cellulose fiber excellent in shielding property is employ | adopted widely, and has contributed to the short defect reduction of an electrochemical element.

In recent years, in addition to the above-described shielding properties, attention is focused on reliability in harsh usage environments.
Electrochemical elements are polarized during use. Then, the anion collected in the vicinity of the electrode serving as the positive electrode reacts with water in the electrolytic solution, or the electrolytic solution decomposes, whereby the electrolytic solution in the vicinity of the positive electrode exhibits strong acidity. It has been found that, under severe use environments as recently requested, this acid may cause the separator to decompose, resulting in a short circuit of the electrochemical device.

As described above, the separator for an electrochemical element not only enhances the shielding property to prevent short circuit defects, but also has a long-term stability and reliability even in harsh usage environments such as high temperatures and high voltages. A high separator is required.
Furthermore, there are strong demands for electrochemical element separators such as miniaturization, high capacity, and large current of electrochemical elements, and in order to improve these performances, there is a great demand for thinning the separator and reducing resistance.

  In the separator for electrochemical devices, various configurations have been proposed for the purpose of improving characteristics such as shielding properties (see, for example, Patent Documents 1 to 3).

International Publication No. 2012/008559 JP 2000-3834 A International Publication No. 2008/007500

Patent Document 1 proposes a separator composed of solvent-spun cellulose fibers with controlled freeness and fiber length, and synthetic fibers.
The separator of Patent Document 1 is a separator in which a beaten solvent-spun cellulose fiber and a synthetic fiber are intertwined uniformly, and is excellent in separator strength.

However, in the separator of Patent Document 1, in order to maintain strength, it is necessary that the solvent-spun cellulose fiber has a length that can be entangled with the synthetic fiber. ) Is low. Therefore, it cannot be said that the shielding property of the separator is high, and when used as a separator, a short circuit may occur.
If the solvent-spun cellulose fiber is further beaten in order to improve the shielding performance of the separator of Patent Document 1, the solvent-spun cellulose fiber is not entangled with the solvent-spun cellulose fiber. By inhibiting the hydrogen bond between each other, the separator strength is significantly reduced.

  Patent Document 2 proposes a method of using beaten solvent-spun recycled cellulose fibers in order to improve the density of the separator and reduce the resistance. By beating the solvent-spun recycled cellulose fiber that can be beaten, fine fibrils of less than 1 μm can be obtained. For this reason, the separator composed of the beaten solvent-spun recycled cellulose is a highly porous microporous sheet, which is a good separator with excellent shielding properties as compared with the separator of Patent Document 1.

However, with the recent expansion of applications and performance improvements of electrochemical devices, there have been cases where separators are required to have higher performance. Specifically, it is resistant to an acidic environment in the vicinity of the positive electrode when the electrochemical element is used.
Electrolytes containing fluorine are widely used as electrolytes for electrochemical devices. This electrolyte is decomposed when water is present in the electrochemical device system to generate hydrofluoric acid. The pole material and the separator are used after being dried (preliminary drying) in advance, but since it is difficult to completely eliminate them, moisture may be brought into the system.
As a result of efforts to increase the voltage of electrochemical devices in recent years, when an electrochemical device is used at a high voltage, it is polarized more strongly than normal voltage, the acidity near the positive electrode is also increased, and cellulose is decomposed. Has been found.
For this reason, there is a demand for improvement in reliability such as physical and chemical stability that can withstand long-term use even at high voltages.

Patent Document 3 proposes a separator composed of a layer containing cellulose (separator layer) and a layer made of a synthetic resin and inhibiting the decomposition of cellulose (suppression layer).
In patent document 3, the lifetime of an electrochemical element is extended by arrange | positioning the suppression layer in the positive electrode side.

However, when the two layers of the separator layer and the suppression layer are overlapped or laminated, the thickness of the separator as a whole increases, the resistance value increases, and there is a possibility of causing problems due to delamination. .
Further, when the suppression layer is applied and formed after the separator layer is formed, there is a possibility that the suppression layer soaks into the separator layer, the two-layer structure cannot be maintained, and the degradation due to the acid cannot be sufficiently suppressed.
In addition, it is actually difficult to form a separator layer by coating and drying a dispersion of cellulose fibers after forming the suppression layer. Cellulose has hydroxyl groups and forms hydrogen bonds. On the other hand, the resin forming the deterrent layer disclosed in Patent Document 3 does not form a hydrogen bond with cellulose and bind firmly. For this reason, even if the dispersion liquid of the cellulose fiber is applied and dried on the surface of the suppression layer, it is easily peeled off.

Although the above is described about the separator which consists of a nonwoven fabric, as a separator for electrochemical elements, there exists a thing by which the synthetic resin microporous film is employ | adopted. Generally, it is a film made of polyolefin resin and has fine pores.
Such polyolefin resin films have a lower electrolyte holding capacity than separators made of non-woven fabric, so it is difficult to extend the lifetime of electrochemical devices, and the separator has a large resistance value. In most cases, the resistance value of the element also increases. In addition, since polyolefin resins have lower heat resistance than cellulose or the like, preliminary drying at high temperatures cannot be performed, and it is difficult to improve the productivity of electrochemical devices.

  The present invention has been made in view of the above-mentioned problems, and not only enhances the shielding property of the separator for electrochemical elements to prevent short circuit defects, but also can withstand the high voltage of the electrochemical elements and has a high reliability. It aims at providing the electrochemical element provided with the high separator and the separator. It is another object of the present invention to provide an automobile or an electronic device provided with a highly reliable electrochemical element.

As means for solving the above-described problems and achieving the above-described object, the present invention has the following configuration.
That is, the separator for an electrochemical element according to the present invention is a separator for an electrochemical element that is interposed between a pair of electrodes to separate the electrodes and can hold an electrolytic solution containing an electrolyte. It consists of a plastic synthetic fiber and a regenerated cellulose fiber beaten with an average fiber length of 0.2 to 2.0 mm, the thermoplastic synthetic fiber is a polyester fiber, and contains 10 to 50% by mass of the thermoplastic synthetic fiber, 50 to 90% by mass of regenerated cellulose fiber beaten, the thickness of the separator is 10 to 70 μm, the density of the separator is 0.25 to 0.90 g / cm ³ , and the cross section of the separator is The two parts divided in two in the thickness direction are a part with a small number of thermoplastic synthetic fibers (part A) and a part with a large number of thermoplastic synthetic fibers (part B). A part and B part are One layer in one It is formed, and wherein the value obtained by dividing the number of thermoplastic synthetic fibers A portion in number of thermoplastic synthetic fibers B portion is 0.85 or less.

The electrochemical element of the present invention has a configuration in which the above-described separator for an electrochemical element of the present invention is used.
As an electrochemical element of this invention, an aluminum electrolytic capacitor, an electrical double layer capacitor, a lithium ion primary battery, and a lithium ion secondary battery are preferable. And in these electrochemical elements, it is more preferable that the part (B part) with many thermoplastic synthetic fibers of a separator is arrange | positioned at the positive electrode side.

The automobile of the present invention has a configuration in which the electrochemical element of the present invention is mounted.
Examples of the automobile of the present invention include an electric vehicle or a hybrid vehicle equipped with a battery, various vehicles equipped with an electric double layer capacitor for energy regeneration, an electronic control unit (ECU) such as an electronic throttle, an anti-lock brake system, etc. Various automobiles equipped with electrolytic capacitors and electric double layer capacitors can be listed.

The electronic device of the present invention has a configuration in which the electrochemical device of the present invention is mounted.
Examples of the electronic device of the present invention include various electronic devices equipped with a battery as a power source, and various electronic devices equipped with a capacitor or a capacitor.

According to the separator for an electrochemical element of the present invention, it is possible to provide a separator that has high shielding properties, mechanical strength, and chemical stability and is effective in reducing short-circuit defects.
The electrochemical element of the present invention uses the electrochemical element separator of the present invention, thereby reducing the short-circuit defect rate and increasing the voltage of the electrochemical element.
Furthermore, the safety of an automobile using the electrochemical device of the present invention can be improved, and the electronic equipment using the electrochemical device of the present invention can be reduced in size and extended in life.

It is a schematic sectional drawing of one Embodiment of the separator for electrochemical elements of this invention. It is a figure explaining how to count the number of fibers in the configuration of FIG. It is a block diagram which shows one Embodiment of the motor vehicle of this invention. It is a block diagram which shows other embodiment of the motor vehicle of this invention. It is a block diagram which shows other embodiment of the motor vehicle of this invention. It is a block diagram which shows one Embodiment of the electronic device of this invention. It is a block diagram which shows other embodiment of the electronic device of this invention.

The separator for an electrochemical element of the present invention is a separator for an electrochemical element that is interposed between a pair of electrodes to separate the electrodes and can hold an electrolyte solution containing an electrolyte. 2 parts consisting of fibers and regenerated cellulose fibers beaten with an average fiber length of 0.2 to 2.0 mm, and the two parts obtained by dividing the cross section of the separator into two in the thickness direction have a small number of thermoplastic synthetic fibers The part (part A) and the part (part B) having a large number of thermoplastic synthetic fibers, the value obtained by dividing the number of thermoplastic synthetic fibers in part A by the number of thermoplastic synthetic fibers in part B is 0.85. It is characterized by the following.
That is, the separator for an electrochemical element of the present invention has a two-layer structure, and has a portion with a small number of thermoplastic synthetic fibers (A portion) and a portion with a large number of thermoplastic synthetic fibers (B portion). Exists. When the value (A / B value) obtained by dividing the number of thermoplastic synthetic fibers of part A by the number of thermoplastic synthetic fibers of part B (A / B value) is 0.85 or less, the parts A and B are It has a two-layer structure.

Moreover, the electrochemical element of this invention uses the separator for electrochemical elements of this invention which has the said structure as a separator, and interposed the separator between a pair of electrodes.
That is, the electrochemical element of the present invention is constituted by impregnating and holding an electrolytic solution in the electrochemical element separator of the present invention, and separating both electrodes by the separator.

The automobile of the present invention is configured to mount the above-described electrochemical element of the present invention. The vehicle of the present invention can be applied to any of engine vehicles, electric vehicles, and hybrid vehicles.
Examples of the automobile of the present invention include an electric vehicle or a hybrid vehicle equipped with a battery, various vehicles equipped with an electric double layer capacitor for energy regeneration, an electronic control unit (ECU) such as an electronic throttle, an anti-lock brake system, etc. Various automobiles equipped with electrolytic capacitors and electric double layer capacitors can be listed.

The electronic device of the present invention has a configuration in which the above-described electrochemical element of the present invention is mounted.
Examples of the electronic device of the present invention include various electronic devices equipped with a battery as a power source, and various electronic devices equipped with a capacitor or a capacitor.

As thermoplastic synthetic fibers usable in the separator of the present invention, among various thermoplastic synthetic resins, polyester fibers such as polyethylene terephthalate, and polyolefin fibers such as polyethylene and polypropylene, from the viewpoint of acid resistance / heat resistance and papermaking suitability. Acrylic fibers such as fibers and polyacrylonitrile are preferred.
And since the manufacturing method which forms in a layer form using the specific gravity difference with a cellulose mentioned later for details is simple, as a thermoplastic synthetic resin, a thing with smaller specific gravity than a cellulose is preferable. Specifically, a specific gravity of 1.45 or less is preferable.

  Examples of the regenerated cellulose fiber that can be used in the separator of the present invention include solvent-spun rayon represented by lyocell and polynosic rayon. However, it is not limited to these examples, and any regenerated cellulose fiber that can be beaten may be used.

  Examples of the electrochemical device of the present invention include an aluminum electrolytic capacitor, an electric double layer capacitor, a lithium ion capacitor, a lithium ion secondary battery, and a lithium primary battery. The electrochemical element of this invention can be comprised using the separator for electrochemical elements of this invention for these electrochemical elements.

The electrolytic solution used in the electrochemical device of the present invention is not limited to the combination of the solvent and the electrolyte taken up in the examples described later, and any electrolytic solution that is usually used may be used.
Also, the material for the electrode of the electrochemical element of the present invention is not limited to the combination described in the examples described later, and any material may be used as long as it is a commonly used electrode material for an electrochemical element.

In the separator for electrochemical devices of the present invention, the part A forms a very dense layer with many regenerated cellulose fibers beaten. Thereby, compared with the separator which was disclosed by patent document 1 and a cellulose fiber and a synthetic fiber are a homogeneous mixed state, shielding property can be improved.
Therefore, the electrochemical device using the separator for electrochemical devices of the present invention has a reduced short-circuit defect rate.

  In the separator for electrochemical devices of the present invention, the B part has more thermoplastic synthetic fibers than the A part. For this reason, many entanglement by thermoplastic synthetic fibers exists in a layer, and an entanglement point welds and crimps | bonds by the heating and compression in the manufacturing process of a separator. Therefore, the mechanical strength of the separator is greatly improved as compared with the separator disclosed in Patent Document 1 in which the strength is improved by entanglement between the synthetic fibers and the cellulose fibers in a homogeneous mixed state.

  Since the above effects can be obtained at the same time, the strength is sufficiently improved even if the synthetic fiber content is lower than that conventionally used. And reducing the synthetic fiber content rate is to increase the content rate of the regenerated cellulose fiber, thereby further improving the shielding property.

  In addition, the A part and the B part contain both regenerated cellulose fibers and thermoplastic synthetic fibers, although there are various ratios. And since the regenerated cellulose fiber and the thermoplastic synthetic fiber are entangled with each other, and the thermoplastic synthetic fiber is welded and crimped, there is no fear of peeling between the respective layers.

When the A / B value is 0.85 or less, the separator of the present invention has a two-layer structure, and the shielding properties and mechanical strength of the separator can be improved. And when A / B value is 0.75 or less, it can be said that it is more strongly divided into two layers, and is more preferable. When the A / B value is 0.6 or less, it is more preferably divided into two layers, which is more preferable.
When the A / B value exceeds 0.85, the effect of the present invention cannot be obtained.

The regenerated cellulose fiber also preferably has a two-layer structure in which the number of trunk portions of the regenerated cellulose fibers in part A is large and the number of trunk portions of the regenerated cellulose fibers in part B is small.
And when the value (B / A value) obtained by dividing the number of trunk parts of the regenerated cellulose fiber of part B by the number of trunk parts of the regenerated cellulose fiber of part A is 0.85 or less, that is, thermoplastic synthetic fiber When it has a bias opposite to that of the above, the denseness, which is a feature of the regenerated cellulose fiber beaten, is exhibited to the maximum.

Moreover, in the separator for an electrochemical element of the present invention, by placing the B part of the separator on the positive electrode side of the electrochemical element, it is possible to withstand the acidic conditions generated near the positive electrode when the electrochemical element is used. Become. For this reason, it contributes also to the high voltage of various electrochemical elements in which market needs are increasing in recent years.
Of the electrochemical elements, capacitors and capacitors have no distinction between the positive electrode and the negative electrode of the two electrodes in the operation principle, but the actual product distinguishes between the positive electrode and the negative electrode. When the electrochemical device separator of the present invention is applied to a capacitor or a capacitor, it is preferable to dispose the portion B of the separator on the positive electrode side of the capacitor or capacitor product.

By the way, in general, when a separator made of regenerated cellulose fibers is immersed in an electrolytic solution, the electrolytic solution penetrates between the fibers, so that the strength is reduced as compared with that during drying.
On the other hand, the strength of the separator of the present invention does not decrease. For this reason, it contributes also to the improvement of the vibration resistance of the electrochemical element using the separator of this invention.

  Furthermore, since the separator of this invention is excellent in shielding property, even if it is a separator whose thickness is thinner than a normal use, or a density is low, it has sufficient shielding property. For this reason, if the separator of this invention is used, the short defect reduction of an electrochemical element and long-term reliability will be improved. Further, the resistance and size can be reduced.

Since it is configured to include the separator of the present invention described above, the electrochemical element of the present invention is required for automobiles and various electronic devices, and has a demand that it can be used for a long time with a small size, a high capacity, and a high output. Can be met at the same time.
And it contributes to improving the safety and reliability of automobiles using the electrochemical device of the present invention, and reducing the size, extending the life and improving the reliability of electronic equipment using the electrochemical device of the present invention.

The two-layer structure of the separator for electrochemical devices of the present invention can be realized, for example, by the following method.
Highly beaten regenerated cellulose fibers and thermoplastic synthetic fibers are mixed, dispersed in water, and filtered from the mesh surface by a papermaking method to form a sheet. That is, it is set as a wet nonwoven fabric.

The specific gravity of the cellulose fiber is about 1.5. On the other hand, the specific gravity of the synthetic fiber is smaller than 1.5 although it varies depending on the resin type.
For this reason, by mixing these and making paper with slow filtered water, a sheet having a multilayer structure in which cellulose fibers are deposited at the bottom of the sheet and synthetic fibers are deposited at the top of the sheet is obtained. In the following embodiment of the present invention, the sheet is formed into a layer using this specific gravity difference.
However, in the present invention, any separator may be used as long as it has a multilayer structure composed of regenerated cellulose fibers and synthetic resin fibers, and is limited to a separator by a specific papermaking method shown in the embodiment of the present invention. is not.

Specifically, for example, the separator of the present invention is obtained by the following method.
First, the regenerated cellulose fiber beaten is used as a regenerated cellulose fiber. By beating the regenerated cellulose fiber, fine fibrils branched from the fiber in a dendritic form are obtained. Further beating will not only increase this branching, but also cause fibrils to fall off.

In the papermaking process, the regenerated cellulose fibers and thermoplastic synthetic fibers that have been beaten are mixed and dispersed in a large amount of water to obtain a dispersion, which is then filtered through a wire (papermaking net). Thus, a sheet is formed. When this dispersion liquid is supplied onto the wire, first, fibers with a large diameter (fiber trunk portion) having high drainage resistance and high specific gravity are deposited on the wire. Then, fine fibrils are gradually deposited on the deposited layer of the trunk portion of the fiber.
Compared to the wire generally used in paper machines, the layer formed by the trunk portion of the regenerated regenerated cellulose fiber deposited first is finer and therefore deposits on the trunk layer deposition layer. Even if the fibril is very fine, it can be prevented from falling off (slipping out) from the wire.

Even when the synthetic fiber is fed to the wire at the same time as the regenerated cellulose fiber beaten, the trunk portion of the regenerated cellulose fiber is first deposited on the wire due to the difference in specific gravity between the cellulose and the synthetic fiber.
Synthetic fibers do not generate hydrogen bonds, so the density of the beaten regenerated cellulose nonwoven fabric may be reduced and the denseness may be impaired. In the separator of the present invention, the fibrils that have fallen from the trunk portion leave gaps between them. Since it is buried so as to be stable, the denseness is not lowered.
That is, the degree of beating of the regenerated cellulose fiber needs to be balanced so that the trunk portion and the fibril coexist.

By heating and compressing the sheet (wet nonwoven fabric) having a two-layer structure, the thermoplastic synthetic fibers of part A are welded and pressed together, and the strength of the separator can be greatly improved.
In general, when a separator made of regenerated cellulose is immersed in an electrolyte solution, the electrolyte solution penetrates between the fibers and the strength is reduced as compared with the time of drying, but the synthetic fibers are welded and pressed together. The separator of the present invention does not cause a decrease in strength due to the immersion of the electrolytic solution. For this reason, the vibration resistance when the separator of the present invention is applied to an electrochemical element is also improved.

As a method for forming a wet nonwoven fabric, any means conventionally selected can be employed without any particular limitation.
In general, a long net paper machine, a circular net paper machine, a short net paper machine, and the like are widely used.
Among them, the short net paper machine and the long net paper machine in which the drainage time from the supply of the raw material slurry to the papermaking wire to the sheet formation is relatively long and the drainage direction is vertical is suitable for obtaining the configuration of the present invention. It is.

  In the paper making process of the separator of the present invention, additives that are usually used in the paper making process, for example, a dispersant, an antifoaming agent, a paper strength enhancer, and the like may be used as necessary. Moreover, you may perform the coating of the paper strength enhancer using polyacrylamide etc. as needed.

In this invention, the fiber length by JISP8226-2 is used for the average fiber length of the regenerated cellulose fiber beaten.
The average fiber length is gradually shortened as the beatable fibers are beaten. When the average fiber length is in the range of 0.2 to 2.0 mm, the aforementioned A / B value and B / A value can be set to preferable values.
If the average fiber length exceeds 2.0 mm, the generation of fibrils is insufficient, cannot contribute to the improvement of the shielding property, and the long fibers that are not miniaturized entangle the thermoplastic synthetic fibers and deposit on the wire at the same time. It is easy to do and it is hard to become small A / B value and B / A value.
If the average fiber length is less than 0.2 mm, the fiber becomes too fine and the trunk portion becomes too small, so that the dropout from the wire increases and the A / B value and B / A value are unlikely to decrease.
When the average fiber length is 0.4 to 1.0 mm, the A / B value is easily set to 0.75 or less, so it is more preferable. When the average fiber length is 0.5 to 1.0 mm, the A / B value is 0. .6 or less, which is more preferable.

And the average fiber length within the range mentioned above can be achieved by managing the beating degree of the regenerated cellulose fiber. The degree of beating of regenerated cellulose fiber is the freeness (CSF value) according to JISP8121-2. As the beatable fiber is beaten, the CSF value gradually decreases and reaches the lower limit. Here, when the beating is further advanced, the CSF value starts to increase.
And in order to achieve the A / B value and B / A value of the present invention, this CSF value is important. The degree of beating of the regenerated cellulose of the present invention is preferably in the range of 100 ml or less for the lowered CSF value and 700 ml or less for the raised CSF value.
If the lowered CSF value is larger than 100 ml, it is difficult to make the average fiber length 2 mm or less. Further, when the increasing CSF value further exceeds 700 ml, it is difficult to make the average fiber length 2 mm or less.

  The equipment used for beating the regenerated cellulose fiber used in the separator of the present invention may be any equipment as long as it is used for preparing a normal papermaking raw material. In general, a beater, a conical refiner, a disc refiner, a high-pressure homogenizer, and the like can be given.

In the separator of the present invention, the thermoplastic synthetic fiber preferably has a small fiber diameter.
When compared with the same specific gravity, synthetic fibers with small fiber diameters are slower to settle in water than thick synthetic fibers. For this reason, a sheet can be formed in a more layered form. Moreover, since the denser sheet can be formed as the fiber diameter is thinner, the shielding property of the separator is also improved.
For the above reasons, the fiber diameter of the synthetic fiber is preferably 0.5 to 10 μm.
If the fiber diameter is less than 0.5 μm, it is difficult to uniformly disperse the fibers in water, which is not preferable.

  Note that the two-layer structure in the separator of the present invention does not need to be separated so that the two layers can be said to be only each fiber, and the composition ratio of each fiber gradually changes from one surface to the other surface. It may be what you are doing.

The content of the regenerated cellulose fiber in the entire separator of the present invention is preferably 50 to 90% by mass, and the content of the synthetic fiber is preferably 10 to 50% by mass.
When the content of the regenerated cellulose fiber exceeds 90% by mass, that is, when the content of the synthetic fiber is less than 10% by mass, an improvement in strength cannot be expected.
Further, when the content of the synthetic fiber exceeds 50% by mass, that is, when the content of the regenerated cellulose fiber is less than 50% by mass, an improvement in shielding properties cannot be expected.

The separator of the present invention preferably has a thickness of 10 to 70 μm and a density of 0.25 to 0.90 g / cm ³ . In order to control to a desired thickness and density, a calendar process may be performed as necessary.
If the thickness is less than 10 μm or the density is lower than 0.25 g / cm ³ , the mechanical strength becomes weak, the separator is easily broken in the separator manufacturing process and the electrochemical element manufacturing process, and the electrochemical element is short-circuited. It becomes impossible to suppress the occurrence of defects. When the thickness is thicker than 70 μm or the density is higher than 0.90 g / cm ³ , the resistance value increases.

  Hereinafter, specific embodiments according to the present invention will be described.

FIG. 1 shows a schematic cross-sectional view of an embodiment of the separator for electrochemical devices of the present invention.
The separator 10 for electrochemical elements shown in FIG. 1 contains a regenerated cellulose fiber and a thermoplastic synthetic fiber inside a sheet-like separator. These fibers can be broadly classified into three parts: a trunk portion 11 of a regenerated cellulose fiber, a thermoplastic synthetic fiber 12, and a fibril 13 of a regenerated cellulose fiber in order from the fiber having the largest diameter.

In FIG. 1, the cross section of the electrochemical device separator 10 is divided into two equal parts in the thickness direction and divided into a lower half A portion 10A and an upper half B portion 10B, and the boundary line is indicated by a dotted line. Yes.
The lower half A portion 10A has a small number of thermoplastic synthetic fibers 12 and a large number of trunk portions 11 of regenerated cellulose fibers.
In the upper half B portion 10B, the thermoplastic synthetic fiber 12 is large, and the trunk portion 11 of the regenerated cellulose fiber is small.

  In the electrochemical separator 10 of the present embodiment, the value (A / B value) obtained by dividing the number of the thermoplastic synthetic fibers 12 of the A portion 10A by the number of the thermoplastic synthetic fibers 12 of the B portion 10B is 0.85. The configuration is as follows. A configuration in which the A / B value is 0.75 or less is more preferable, and a configuration in which the A / B value is 0.6 or less is further preferable.

  Preferably, the value (B / A value) obtained by dividing the number of the regenerated cellulose fiber trunk portions 11 of the B part 10B by the number of the regenerated cellulose fiber trunk parts 11 of the A part 10A is 0.85 or less. And

A method for calculating the number of thermoplastic synthetic fibers 12 and the number of trunk portions 11 of regenerated cellulose in the cross section of the separator 10 for electrochemical elements will be described with reference to FIG.
In FIG. 2, the arrangement of the regenerated cellulose fiber trunk portion 11, the thermoplastic synthetic fiber 12, and the regenerated cellulose fiber fibril 13 in the cross section of the electrochemical device separator 10 is the same as that in FIG. 1.

In FIG. 2, the fibers that are not on the central line and are present only in the A portion 10A or only in the B portion 10B are counted as one.
On the other hand, the number of fibers straddling the center line is counted as shown in FIG.
The fibers that are largely biased toward the A part 10A are counted as 0.75 A part and 0.25 B part.
The fibers uniformly contained in the A part 10A and the B part 10B are counted as 0.5 part A and 0.5 part B.
The fibers which are largely biased toward the B part 10B are counted as 0.25 A part and 0.75 B part.
In this way, the number of fibers in each of the A part 10A and the B part 10B in the cross section of the electrochemical element separator 10 is calculated.

  In the case of FIG. 2, the number of the thermoplastic synthetic fibers 12 is 7.75 for the A portion 10A and 16.25 for the B portion, and the number of the trunk portions 11 of the regenerated cellulose fiber is 7.5 for the A portion. Book B is 3.5. Therefore, the A / B value of the thermoplastic synthetic fiber 12 is 7.75 / 16.25 = 0.48, and the B / A value of the trunk portion 11 of the regenerated cellulose fiber is 3.5 / 7.5 = 0. 47. In this case, since the A / B value of the thermoplastic synthetic fiber 12 and the B / A value of the trunk portion 11 of the regenerated cellulose fiber are both 0.85 or less, the effect of the separator for an electrochemical element of the present invention is sufficiently obtained. It is done.

  Next, several embodiments will be described in which the automobile of the present invention, that is, the electrochemical element of the present invention (an electrochemical element using the separator of the present invention) is applied to an automobile.

FIG. 3 is a block diagram showing an embodiment of the automobile of the present invention.
FIG. 3 shows a case where the present invention is applied to an electric vehicle.

An automobile 20 shown in FIG. 3 includes a lithium ion secondary battery 21 as a power source of the electric vehicle, and the lithium ion secondary battery 21 moves a motor 22 to travel. A brake 23 is connected to the wheel W. Furthermore, a charger 24 and an external power source 25 for charging the lithium ion secondary battery 21 are provided.
A battery control ECU 26 is connected to the lithium ion secondary battery 21, and the lithium ion secondary battery 21 is controlled by the battery control ECU 26.
A motor control ECU 27 and an EPS control ECU 28 are connected to the motor 22, and the motor 22 is controlled by the motor control ECU 27. The EPS control ECU 28 controls EPS (electric power steering).
A regenerative brake control ECU 29 is provided between the lithium ion secondary battery 21 and the motor 22 and the brake 23, and the regenerative brake control ECU 29 controls the regenerative brake operation of the brake 23.

And in this Embodiment, the lithium ion secondary battery provided with the separator for electrochemical elements of this invention can be used for the lithium ion secondary battery 21. FIG.
In the present embodiment, the battery control ECU 26, the motor control ECU 27, the EPS control ECU 28, and the regenerative brake control ECU 29 can use a capacitor or an electric double layer capacitor provided with the electrochemical element separator of the present invention. .

Since the separator has sufficient shielding properties, mechanical strength, and chemical stability by using the lithium ion secondary battery, capacitor, and electric double layer capacitor provided with the separator for an electrochemical device of the present invention, lithium ion In secondary batteries, capacitors, and electric double layer capacitors, it is possible to reduce short-circuit defects, improve vibration resistance and temperature resistance, and stabilize characteristics after long-term use.
Thereby, the automobile 20 having high safety and high reliability can be realized.

FIG. 4 is a block diagram showing another embodiment of the automobile of the present invention.
FIG. 4 shows a case where the present invention is applied to an engine vehicle having a regeneration system.

An automobile 30 shown in FIG. 4 includes an engine 31 as a power source, and includes an accelerator 32 and a transmission 33 in a power system including the engine 31. In addition, a brake 35 is connected to the wheel W, and a regeneration unit 34 and an ABS unit 36 are connected to the brake 35. By the ABS unit 36, an ABS (anti-lock brake system) function can be activated. Furthermore, an air conditioner 37 for air conditioning the vehicle is provided.
A fuel spray ECU 38 is connected to the engine 31, and the fuel spray of the engine 31 is controlled by the fuel spray ECU 38. An electronic throttle ECU 39 is provided between the engine 31 and the accelerator 32, and a transmission ECU 40 is provided between the engine 31 and the transmission 33. A regenerative brake control ECU 41 is connected to the regenerative unit 34, and the regenerative brake operation of the revolving unit 34 is controlled by the regenerative brake control ECU 41. An ABS ECU 42 is connected to the ABS unit 36, and the operation of the ABS unit 35 is controlled by the ABS ECU 42.

In this embodiment, the fuel spray ECU 38, the electronic throttle ECU 39, the transmission ECU 40, the regenerative brake control ECU 41, and the ABS ECU 42 use a capacitor or an electric double layer capacitor provided with the electrochemical element separator of the present invention. be able to.
By using a capacitor or an electric double layer capacitor provided with the separator for an electrochemical element of the present invention, the separator has sufficient shielding properties, mechanical strength, and chemical stability. Short circuit defects can be reduced, vibration resistance and temperature resistance can be improved, and characteristics after long-term use can be stabilized.
Thereby, the automobile 30 having high safety and high reliability can be realized.

A block diagram showing another embodiment of the automobile of the present invention is shown in FIG.
FIG. 5 shows a case where the present invention is applied to a hybrid vehicle.

  Since the automobile 50 shown in FIG. 5 is a hybrid automobile, it includes a configuration common to the automobile 20 shown in FIG. 3 that is an electric automobile and a configuration common to the automobile 30 shown in FIG. Yes.

The automobile 50 shown in FIG. 5 has an engine 51 and a lithium ion secondary battery 52 as power sources. A brake 53 and a motor 57 are connected to the wheel W. Furthermore, a charger 54 and an external power supply 55 for charging the lithium ion secondary battery 52 are provided. In addition to the motor 57 for driving the wheels W, an EPS (electric power steering) motor 56 is provided.
A fuel spray ECU 58 and an electronic throttle ECU 59 are connected to the engine 51.
A battery control ECU 60 is connected to the lithium ion secondary battery 52, and the lithium ion secondary battery 52 is controlled by the battery control ECU 60.
An HEV system control ECU 61 is provided at the center of FIG. 5, and the HEV system control ECU 61 controls switching between the engine 51 and the lithium ion secondary battery 52.
A regenerative brake control ECU 62 is connected to the brake 53, and the regenerative brake operation of the brake 53 is controlled by the regenerative brake control ECU 62. A motor control ECU 63 is connected to the motor 57 connected to the wheel W, and the motor 57 is controlled by the motor control ECU 63. An EPS control ECU 64 is connected to the EPS motor 56, and the EPS control ECU 64 controls EPS (electric power steering).

And in this Embodiment, the lithium ion secondary battery provided with the separator for electrochemical elements of this invention can be used for the lithium ion secondary battery 52. FIG.
In the present embodiment, the fuel spray ECU 58, the electronic throttle ECU 59, the battery control ECU 60, the HEV system control ECU 61, the regenerative brake control ECU 62, the motor control ECU 63, and the EPS control ECU 64 are provided with the electrochemical element separator of the present invention. Capacitors and electric double layer capacitors can be used.

Since the separator has sufficient shielding properties, mechanical strength, and chemical stability by using the lithium ion secondary battery, capacitor, and electric double layer capacitor provided with the separator for an electrochemical element of the present invention, lithium ion secondary In secondary batteries, capacitors, and electric double layer capacitors, it is possible to reduce short-circuit defects, improve vibration resistance and temperature resistance, and stabilize characteristics after long-term use.
Thereby, the automobile 50 having high safety and high reliability can be realized.

  Note that the hybrid vehicle includes other types in which the role of the battery and the engine and the connection relationship between the units are different from the configuration illustrated in FIG. 5. The present invention can also be applied to such other types of hybrid vehicles to mount the electrochemical device of the present invention.

  Next, some embodiments in the case where the electronic device of the present invention, that is, the electrochemical device of the present invention (an electrochemical device using the separator of the present invention) is applied to an electronic device will be described.

FIG. 6 is a block diagram illustrating an embodiment of an electronic apparatus according to the invention.
FIG. 6 shows a case where the present invention is applied to an electronic device that performs power supply assist using an electric double layer capacitor.

The electronic device 70 shown in FIG. 6 includes a power source 71, a load (such as an LED) 72, and an electric double layer capacitor 73.
The electric double layer capacitor 73 can accumulate electricity from the power source 71 and can assist the power source 71 by discharging the accumulated electricity.

And in this Embodiment, the electric double layer capacitor provided with the separator for electrochemical elements of this invention can be used for the electric double layer capacitor 73. FIG.
By using the electric double layer capacitor provided with the separator for electrochemical elements of the present invention, the separator has sufficient shielding properties, mechanical strength, and chemical stability. The vibration resistance, the voltage resistance, and the resistance to temperature can be improved, the resistance can be reduced and the size can be reduced by reducing the thickness, and the characteristics after long-term use can be stabilized.
Thereby, the electronic device 70 which is small and has high reliability can be realized.

FIG. 7 is a block diagram showing another embodiment of the electronic device of the present invention.
FIG. 7 shows a case where the present invention is applied to an electronic device that performs backup of a main power source using an electric double layer capacitor.

An electronic device 80 shown in FIG. 7 includes a lithium ion secondary battery 81 or the like as a main power source, a load 82, and an electric double layer capacitor 83 as a backup power source.
The electric double layer capacitor 83 is connected between the main power source of the lithium ion secondary battery 81 or the like and the load 82. Then, as indicated by x in FIG. 7, when the main power source cannot be used, the main power source is backed up by the electric double layer capacitor 83.

And in this Embodiment, the lithium ion secondary battery etc. which were equipped with the separator for electrochemical elements of this invention can be used for the lithium ion secondary battery etc. 81. FIG.
Moreover, in this Embodiment, the electrical double layer capacitor provided with the separator for electrochemical elements of this invention can be used for the electrical double layer capacitor 73. FIG.

By using a lithium ion secondary battery or the like or an electric double layer capacitor equipped with the separator for an electrochemical device of the present invention, the separator has sufficient shielding properties, mechanical strength, and chemical stability. Reduces short-circuit defects in secondary batteries and electric double layer capacitors, improves vibration resistance, voltage resistance and temperature resistance, lowers resistance and downsizing by reducing thickness, and stabilizes characteristics after long-term use Can be planned.
Thereby, the electronic device 80 which is small and has high reliability can be realized.

Hereinafter, specific various examples, comparative examples, and conventional examples of the electrochemical element separator and the electrochemical element provided with the electrochemical element separator according to the present invention will be described in detail.
In the example shown below, a lithium ion secondary battery (cylindrical type and coin type) and an electric double layer capacitor were produced as electrochemical elements.
In addition, the separator for alkaline batteries of each Example of the present invention described below was obtained by a papermaking method using a long web paper machine, a long web paper machine, a short paper machine, or the like. That is, the separator was composed of a wet nonwoven fabric.

[Method for measuring separator properties]
The specific measurement of the characteristics of the electrochemical device separator of the present embodiment was performed under the following conditions and method.

[Average fiber length]
Length-weighted using Fiber Tester Code 912 (manufactured by Lorentzen & Wettre) according to “JIS P8226-2 Pulp-Fiber length measurement method by optical automatic analysis method-Part 2: Non-change method (ISO16065-2)” The average fiber length was measured and taken as the average fiber length.

[CSF value]
The CSF value was measured in accordance with “JIS P8121-2 Pulp-Freeness Test Method—Part 2: Canadian Standard Freeness Method”.

〔thickness〕
“5.1.1 Measuring instrument and measuring method a When using an external micrometer” as defined in “JIS C 2300-2“ Cellulose paper for electrical use-Part 2: Test method ”5.1 Thickness” Using a micrometer, the thickness of the separator was measured by the method of folding it into 10 sheets as described in “5.1.3 When measuring the thickness by folding paper”.

〔density〕
The density of the absolutely dried separator was measured by the method defined in Method B of “JIS C 2300-2“ Electric Cellulose Paper—Part 2: Test Method ”7.0 A Density”.

〔Tensile strength〕
The tensile strength in the longitudinal direction of the separator was measured by the method specified in “JIS C 2300-2“ Cellulose paper for electrical use—Part 2: Test method ”8. Tensile strength and elongation”.

[Cross-section structure]
Using a sharp blade, cut the separator in the transverse direction (CD direction), and using a scanning electron microscope (model number JSM-5600LV (manufactured by JEOL)) with a magnification of 1000 times (imaging area 100 μm × 130 μm) A cross section was taken.
In each part obtained by dividing the photographed separator into two equal parts in the thickness direction. The number of synthetic fibers was counted.
The fibers straddling the bisected central line were counted in the same manner as described with reference to FIG. That is, when the cross section of the synthetic fiber is largely biased to the A part, the A part is 0.75 and the B part is 0.25, and when the synthetic fiber cross section is largely biased to the B part, 0.25 in the part, 0.75 in the B part, and when the cross section of the synthetic fiber is uniform between the A part and the B part, 0.5 in the A part and 0.5 in the B part. .
The number of synthetic fibers in part A was divided by the number of synthetic fibers in part B to obtain a synthetic fiber ratio (A / B value).
Also for the trunk portion of the regenerated cellulose fiber, the number is calculated in the same manner as the number of synthetic fibers, the number of the trunk portion of the regenerated cellulose fiber of the B part is divided by the number of the trunk part of the regenerated cellulose fiber of the A part, The ratio (B / A value) of the trunk part of the regenerated cellulose fiber was used.
In addition, imaging | photography and count were performed in arbitrary 10 places for each example, and each ratio was calculated using the counted average value.

[Production of lithium ion secondary batteries using separators]
Hereinafter, a method for manufacturing a lithium ion secondary battery using the separator of this embodiment will be described. Specifically, two types of lithium ion secondary batteries were produced: a cylindrical lithium ion secondary battery and a coin-type lithium secondary battery.

The cylindrical lithium ion secondary battery was produced as follows.
A lithium cobalt oxide electrode for a lithium ion secondary battery was used as the positive electrode material, a graphite electrode was used as the negative electrode material, and wound with a separator to obtain a lithium ion secondary battery element. The element was housed in a bottomed cylindrical case, an electrolyte solution in which lithium tetrafluoroborate was dissolved as an electrolyte was injected into a propylene carbonate solvent, and sealed with a press to produce a lithium ion secondary battery. .

The coin-type lithium ion secondary battery was produced as follows.
A lithium cobalt oxide electrode for a lithium ion secondary battery was used as the positive electrode material, a graphite electrode was used as the negative electrode material, and the separators were interposed. Next, a mixed solvent of diethylene carbonate and ethylene carbonate was impregnated with an electrolytic solution in which lithium hexafluorophosphate was dissolved as an electrolyte, and caulked and sealed to produce a lithium ion secondary battery.

[Production of electric double layer capacitor using separator]
Hereinafter, a method for manufacturing an electric double layer capacitor using the separator of this embodiment will be described.
The activated carbon electrode and the separator of the present invention were alternately folded to obtain an electric double layer capacitor element. The device was housed in an aluminum case, and an electrolytic solution in which triethylmethylammonium hexafluorophosphate was dissolved in acetonitrile was injected. After vacuum impregnation, the device was sealed to produce an electric double layer capacitor.

  In addition, 1000 each electrochemical element was produced for each example, and was used for the following characteristic evaluation.

[Characteristic evaluation method of electrochemical device]
The characteristics evaluation of the electrochemical device of the present embodiment was performed under the following conditions and method.

[Short defect rate]
The short-circuit defect rate of electrochemical elements is considered as short-circuit defects when the charging voltage does not increase to the rated voltage, and the number of electrochemical elements that have been short-circuited is the number of electrochemical elements subjected to capacitance measurement. The percentage of short-circuit defects was taken as a percentage.

[Internal resistance]
The internal resistance of the lithium ion secondary battery is defined in “8.6.3“ Industrial Lithium Secondary Battery Cell and Battery System—Part 1: Performance Requirements ”defined in“ 8.6.3 ”. Measured according to “AC internal resistance”.
The internal resistance of the electric double layer capacitor is measured by the alternating current (ac) resistance method of “4.6 Internal Resistance” defined in “JIS C 5160-1“ Fixed Electric Double Layer Capacitor for Electronic Equipment ””. did.

[Discharge capacity]
The discharge capacity of the lithium ion secondary battery is specified in “JIS C 8715-1“ Industrial Lithium Secondary Battery Single Cell and Battery System—Part 1: Performance Requirements ””. Measured according to “Discharge performance test”.

[Capacitance]
The capacitance of the electric double layer capacitor was determined by a constant current discharge method of “4.5 capacitance” defined in “JIS C 5160-1“ Fixed Electric Double Layer Capacitor for Electronic Equipment ””.

[Long-term reliability test of electrochemical devices]
A long-term reliability test was carried out using the electrochemical elements of each example that passed the above measurement.
Specifically, a long-term reliability test was conducted as follows.
After applying the rated voltage for 500 hours at 70 ° C., the capacity change rate and the internal resistance change rate were measured. The rate of change in capacity was determined using the following formula 1, and the rate of change in internal resistance was determined using formula 2 below.
Capacity change rate (%) = (Ca−Cb) / Ca × 100 Formula 1
(Ca: capacity before voltage application, Cb: capacity after voltage application)
Internal resistance change rate (%) = (Rb−Ra) / Ra × 100 Expression 2
(Ra: internal resistance before voltage application, Rb: internal resistance after voltage application)
In addition, the number of electrochemical elements in which short-circuit defects occurred during the long-term reliability test was counted, and divided by the number of electrochemical elements subjected to the long-term reliability test, and the percentage was used as the short-circuit defect rate in the long-term reliability test. .

Hereinafter, specific examples according to the present invention, comparative examples, and conventional examples will be described.
In addition, the CSF value of each example shows the CSF value of the step which has fallen unless there is particular description.

[Example 1]
As the regenerated cellulose fiber beaten, the average fiber length is 0.68 mm, the solvent-spun rayon fiber (hereinafter referred to as lyocell fiber) having an increasing CSF value of 25 ml is 70% by mass, and the thermoplastic synthetic fiber is the average fiber length. 30% by mass of polyethylene terephthalate fiber (hereinafter referred to as PET fiber) having a diameter of 3 mm and a fiber diameter of 2 μm is mixed to make a long web paper, a separator having a thickness of 10.0 μm, a density of 0.27 g / cm ³ , and a tensile strength of 15 N. Got. The average fiber length of the lyocell fiber of this separator was 0.68 mm. Further, this separator had an A / B value of 0.37 and a B / A value of 0.51.
Using this separator, a coin-type lithium ion secondary battery of Example 1 was produced.

[Example 2]
As the regenerated cellulose fiber beaten, PET having an average fiber length of 0.65 mm, an increasing polynosic rayon fiber of 25 ml of CSF value of 70% by mass, and a thermoplastic synthetic fiber having an average fiber length of 3 mm and a fiber diameter of 2.5 μm 30% by mass of the fiber was mixed to make a long web paper to obtain a separator having a thickness of 25.0 μm, a density of 0.48 g / cm ³ , and a tensile strength of 25N. This separator had an A / B value of 0.45 and a B / A value of 0.50.
Using this separator, a coin-type lithium ion secondary battery of Example 2 was produced.

Example 3
As regenerated cellulose fiber beaten, PET fiber having an average fiber length of 0.68 mm and an increasing lyocell fiber of 25 ml of CSF value of 70% by mass, and a thermoplastic synthetic fiber having an average fiber length of 3 mm and a fiber diameter of 3.5 μm 30% by mass was mixed to make a short mesh paper to obtain a sheet. This sheet was calendered to obtain a separator having a thickness of 70.0 μm, a density of 0.86 g / cm ³ , and a tensile strength of 55N. This separator had an A / B value of 0.51 and a B / A value of 0.56.
Using this separator, a coin-type lithium ion secondary battery of Example 3 was produced.

[Comparative Example 1]
Using the same raw materials as in Example 1, paper was made into a long web to obtain a separator having a thickness of 8.0 μm, a density of 0.23 g / cm ³ , and a tensile strength of 10N. This separator had an A / B value of 0.50 and a B / A value of 0.54.
A coin-type lithium ion secondary battery of Comparative Example 1 was produced using this separator.

[Comparative Example 2]
Using the same raw material as in Example 3, papermaking was performed and calendering was performed to obtain a separator having a thickness of 75.0 μm, a density of 0.93 g / cm ³ , and a tensile strength of 60N. This separator had an A / B value of 0.59 and a B / A value of 0.52.
A coin-type lithium ion secondary battery of Comparative Example 2 was produced using this separator.

[Conventional example 1]
A coin-type lithium ion secondary battery of Conventional Example 1 was produced using a polyethylene microporous membrane as a separator.
This separator had a thickness of 25.0 μm, a density of 0.60 g / cm ³ , and a tensile strength of 40N.

Example 4
80% by mass of lyocell fiber having an average fiber length of 1.91 mm and a CSF value of 100 ml as the regenerated cellulose fiber beaten, and 20% by mass of PET fiber having an average fiber length of 3 mm and a fiber diameter of 2.5 μm as the thermoplastic synthetic fiber. A long web paper was made by mixing and a separator having a thickness of 30.0 μm, a density of 0.40 g / cm ³ and a tensile strength of 20 N was obtained. This separator had an A / B value of 0.84 and a B / A value of 0.81.
A cylindrical lithium ion secondary battery of Example 4 was produced using this separator.

Example 5
As the regenerated cellulose fiber beaten, PET fiber with an average fiber length of 0.77 mm and rising lyocell fiber with 3 ml CSF value of 75% by mass, and as a thermoplastic synthetic fiber, an average fiber length of 3 mm and a fiber diameter of 3.0 μm 25% by weight was mixed to make a long web paper to obtain a sheet. This sheet was calendered to obtain a separator having a thickness of 20.0 μm, a density of 0.70 g / cm ³ , and a tensile strength of 45N. This separator had an A / B value of 0.59 and a B / A value of 0.73.
A cylindrical lithium ion secondary battery of Example 5 was produced using this separator.

Example 6
80% by mass of lyocell fiber having an average fiber length of 0.89 mm and a CSF value of 0 ml is used as the regenerated cellulose fiber beaten, and 20% by mass of polyethylene fiber having an average fiber length of 3 mm and a fiber diameter of 5.0 μm is used as the thermoplastic synthetic fiber. The mixture was mixed to make a long web paper to obtain a sheet. This sheet was calendered to obtain a separator having a thickness of 15.0 μm, a density of 0.73 g / cm ³ , and a tensile strength of 30N. This separator had an A / B value of 0.59 and a B / A value of 0.78.
A cylindrical lithium ion secondary battery of Example 6 was produced using this separator.

Example 7
The regenerated cellulose fiber beaten is an average fiber length of 0.55 mm, the rising lyocell fiber of 50 ml with a CSF value of 50 ml, and the thermoplastic synthetic fiber is a polypropylene fiber having an average fiber length of 3 mm and a fiber diameter of 2.0 μm. Was mixed to make a long web paper to obtain a sheet. This sheet was calendered to obtain a separator having a thickness of 20.0 μm, a density of 0.68 g / cm ³ , and a tensile strength of 45N. This separator had an A / B value of 0.59 and a B / A value of 0.74.
Using this separator, a cylindrical lithium ion secondary battery of Example 7 was produced.

Example 8
As the regenerated cellulose fiber beaten, the average fiber length is 0.49 mm, the rising CSF value of 200 ml of lyocell fiber is 80% by mass, and the thermoplastic synthetic fiber is an average fiber length of 2.0 mm and a fiber diameter of 1.5 μm. 10% by mass of PET fiber and 10% by mass of polypropylene fiber having an average fiber length of 5.0 mm and a fiber diameter of 8 μm were mixed to make a long web paper, thickness 40.0 μm, density 0.40 g / cm ³ , tensile A separator with a strength of 30 N was obtained. This separator had an A / B value of 0.63 and a B / A value of 0.67.
Using this separator, a cylindrical lithium ion secondary battery of Example 8 was produced.

Example 9
As the regenerated cellulose fiber beaten, polyacrylonitrile having an average fiber length of 0.42 mm, rising lyocell fiber of 300 ml of CSF value of 80% by mass, and thermoplastic synthetic fiber having an average fiber length of 3.0 mm and a fiber diameter of 5 μm The paper was mixed with 20% by mass of the fiber and made into a long web paper to obtain a separator having a thickness of 50.0 μm, a density of 0.32 g / cm ³ , and a tensile strength of 32N. This separator had an A / B value of 0.74 and a B / A value of 0.74.
Using this separator, a cylindrical lithium ion secondary battery of Example 9 was produced.

Example 10
As regenerated cellulose fibers beaten, PET fibers with an average fiber length of 0.26 mm and an increasing lyocell fiber with a CSF value of 700 ml of 80% by mass, and thermoplastic synthetic fibers with an average fiber length of 3.0 mm and a fiber diameter of 8 μm It was mixed with 20% by mass to make a long paper, and a separator having a thickness of 60.0 μm, a density of 0.50 g / cm ³ and a tensile strength of 40 N was obtained. This separator had an A / B value of 0.79 and a B / A value of 0.83.
A cylindrical lithium ion secondary battery of Example 10 was produced using this separator.

[Comparative Example 3]
80% by mass of lyocell fiber having an average fiber length of 2.12 mm and a CSF value of 150 ml as the regenerated cellulose fiber beaten, and 20% by mass of PET fiber having an average fiber length of 3 mm and a fiber diameter of 2.5 μm as the thermoplastic synthetic fiber. A long web paper was made by mixing and a separator having a thickness of 30.0 μm, a density of 0.40 g / cm ³ and a tensile strength of 12 N was obtained. This separator had an A / B value of 0.87 and a B / A value of 0.83.
A cylindrical lithium ion secondary battery of Comparative Example 3 was produced using this separator.

[Comparative Example 4]
As the regenerated cellulose fiber beaten, PET fiber with an average fiber length of 0.18 mm and an increasing lyocell fiber with a CSF value of 750 ml is 80% by mass, and a thermoplastic synthetic fiber has an average fiber length of 3 mm and a fiber diameter of 8.0 μm. Was mixed to obtain a separator having a thickness of 60.0 μm, a density of 0.50 g / cm ³ , and a tensile strength of 30 N. This separator had an A / B value of 0.59 and a B / A value of 0.87.
A cylindrical lithium ion secondary battery of Comparative Example 4 was produced using this separator.

[Conventional example 2]
As the regenerated cellulose fiber beaten, PET fiber having an average fiber length of 0.77 mm, an increasing lyocell fiber of 3 ml of CSF value of 75% by mass, and a thermoplastic synthetic fiber having an average fiber length of 3 mm and a fiber diameter of 10.0 μm Was mixed to obtain a separator having a thickness of 30.0 μm, a density of 0.40 g / cm ³ , and a tensile strength of 12N. This separator had an A / B value of 0.88 and a B / A value of 0.88.
Using this separator, a cylindrical lithium ion secondary battery of Conventional Example 2 was produced.

Example 11
Using the same separator as in Example 7, a multilayer electric double layer capacitor of Example 11 was produced.

Example 12
As the regenerated cellulose fiber beaten, PET fiber having an average fiber length of 0.77 mm and an increasing lyocell fiber of 3 ml of CSF value of 90% by mass, and a thermoplastic synthetic fiber having an average fiber length of 3 mm and a fiber diameter of 8.0 μm 10% by mass was mixed to make a long web paper to obtain a separator having a thickness of 30.0 μm, a density of 0.40 g / cm ³ , and a tensile strength of 16N. This separator had an A / B value of 0.59 and a B / A value of 0.64.
Using this separator, a multilayer electric double layer capacitor of Example 12 was produced.

Example 13
As the regenerated cellulose fiber beaten, PET fiber with an average fiber length of 0.77 mm and rising lyocell fiber with 3 ml CSF value of 75% by mass, and as a thermoplastic synthetic fiber, an average fiber length of 1 mm and a fiber diameter of 0.6 μm Was mixed to make a long web paper to obtain a separator having a thickness of 35.0 μm, a density of 0.40 g / cm ³ , and a tensile strength of 30 N. This separator had an A / B value of 0.59 and a B / A value of 0.73.
Using this separator, a multilayer electric double layer capacitor of Example 13 was produced.

Example 14
As the regenerated cellulose fiber beaten, PET fiber having an average fiber length of 0.77 mm and an increasing lyocell fiber of 3 ml of CSF value of 60% by mass, and a thermoplastic synthetic fiber having an average fiber length of 3 mm and a fiber diameter of 10.0 μm 40% by mass was mixed to make a long net paper to obtain a separator having a thickness of 30.0 μm, a density of 0.40 g / cm ³ , and a tensile strength of 15N. This separator had an A / B value of 0.59 and a B / A value of 0.64.
Using this separator, a multilayer electric double layer capacitor of Example 14 was produced.

Example 15
As the regenerated cellulose fiber beaten, an average fiber length of 0.77 mm, an increasing lyocell fiber with a CSF value of 3 ml is 50 mass%, and a thermoplastic synthetic fiber is an PET fiber having an average fiber length of 3 mm and a fiber diameter of 3.0 μm. Was mixed to make a long web paper to obtain a separator having a thickness of 30.0 μm, a density of 0.40 g / cm ³ , and a tensile strength of 40N. This separator had an A / B value of 0.59 and a B / A value of 0.67.
Using this separator, a multilayer electric double layer capacitor of Example 15 was produced.

[Reference Example 1]
As the regenerated cellulose fiber beaten, the average fiber length of 0.77 mm, the rising lyocell fiber with a CSF value of 3 ml is 80% by mass, and the thermoplastic synthetic fiber has an average fiber length of 0.5 mm and a fiber diameter of 0.1 μm. 20% by mass of PET fiber was mixed to make a long web paper to obtain a separator having a thickness of 30.0 μm, a density of 0.40 g / cm ³ , and a tensile strength of 45N. This separator had an A / B value of 0.59 and a B / A value of 0.61.
Using this separator, a multilayer electric double layer capacitor of Reference Example 1 was produced.

[Comparative Example 5]
As the regenerated cellulose fiber beaten, the average fiber length is 0.77 mm, and the rising CSF value of 3 ml of lyocell fiber is 40% by mass. As the thermoplastic synthetic fiber, the average fiber length is 3.0 mm and the fiber diameter is 2.5 μm. 60% by mass of PET fiber was mixed to make a long web paper to obtain a separator having a thickness of 30.0 μm, a density of 0.40 g / cm ³ , and a tensile strength of 25N. This separator had an A / B value of 0.58 and a B / A value of 0.64.
Using this separator, a multilayer electric double layer capacitor of Comparative Example 5 was produced.

[Conventional example 3]
Using the same separator as that of Conventional Example 2, a multilayer electric double layer capacitor of Conventional Example 3 was produced.

[Conventional Example 4]
As a regenerated cellulose fiber beaten, paper was made using only lyocell fibers having an average fiber length of 0.72 mm and an increasing CSF value of 10 ml, a thickness of 20.0 μm, a density of 0.40 g / cm ³ , and a tensile strength. A 10N separator was obtained. This separator had a B / A value of 0.65.
Using this separator, a multilayer electric double layer capacitor of Conventional Example 4 was produced.

  Table 1 shows the evaluation results of the individual separators of Examples 1 to 3 described above, Comparative Examples 1 and 2, and Conventional Example 1, and the performance evaluation results of the lithium ion secondary battery. These are examples of a coin-type lithium ion secondary battery having a rated voltage of 3.6 V, a rated capacity of 30 mAh, a diameter of 20 mm, and a height of 3.2 mm.

  Table 2 shows the evaluation results of the separators of Examples 4 to 10, Comparative Examples 3 and 4, and Conventional Example 2, and the performance evaluation results of the lithium ion secondary battery. These are examples of a cylindrical lithium ion secondary battery having a rated voltage of 3.7 V, a rated capacity of 3000 mAh, a diameter of 18 mm, and a height of 65 mm.

  Table 3 shows the evaluation results of the separators of Examples 11 to 15, Reference Example 1, Comparative Example 5, Conventional Example 3 and Conventional Example 4, and the performance evaluation results of the electric double layer capacitor. These are examples of a multilayer electric double layer capacitor having a rated voltage of 2.5 V, a rated capacity of 3000 F, a width of 55 mm, a depth of 55 mm, and a height of 155 mm.

In Tables 1 to 3, “CSF value” indicates the CSF value of the regenerated cellulose fiber beaten in each example.
Hereinafter, evaluation results will be described in detail for each of the examples, comparative examples, and conventional examples.

The lithium ion secondary batteries manufactured using the separators of Examples 1 to 3 are good because no short-circuit defect occurs. Also, the internal resistance value and the internal resistance change rate after the long-term reliability test are below the conventional example and are sufficiently small. Also, the capacity change rate after the long-term reliability test is within 20% from the initial stage, which is not a problem. And the short defect rate after a long-term reliability test does not generate | occur | produce, but it is favorable.
Example 1 and Example 3 and Example 2 differ in the used regenerated cellulose fiber. From these examples, it can be seen that any type of regenerated cellulose fiber may be used.

Comparative Example 1 is a separator produced in the same manner as in Example 1 except that the thickness and density are different. The lithium ion secondary battery of Comparative Example 1 has a high short-circuit defect rate and a short-circuit defect rate after a long-term reliability test of 1% or more. This shows that the thickness of the separator is preferably 10 μm or more and the density is preferably 0.25 g / cm ³ or more.
Comparative Example 2 is a separator produced in the same manner as Example 2 except that the thickness and density are different. In the lithium ion secondary battery of Comparative Example 2, both the internal resistance and the rate of change in internal resistance are higher than those in Examples 1 to 3. This indicates that the thickness of the separator is preferably 70 μm or less and the density is preferably 0.90 g / cm ³ or less.

The lithium ion secondary batteries manufactured using the separators of Example 4 to Example 10 have a short defect rate and a short defect rate after a long-term reliability test of 0.5% or less, which are sufficiently low. Also, the internal resistance value is 70 mΩ or less, which is sufficiently small. The rate of change in internal resistance after the long-term reliability test is an increase rate of 100% or less, and there is no problem. Also, the capacity change rate after the long-term reliability test is within 20% from the initial stage, which is not a problem.
Examples 5 to 7 are separators subjected to heat calendering after sheet formation. Example 6 has a thickness of 15 μm but has the same tensile strength as Example 8 with a thickness of 40 μm, and Examples 5 and 7 have a thickness of 20 μm, but Example 10 with a thickness of 60 μm. Tensile strength is stronger than that of the separator. From this, it can be seen that the calendering, which is more pressure than the heating / compression in the paper machine drying process, is stronger in welding / bonding between the thermoplastic synthetic fibers and further improves the separator strength.
Further, the separator of Example 7 has a higher tensile strength than the separator of Conventional Example 1 which is a film made only of a polyethylene resin. Although the details are unknown, the following reasons can be considered.
Since the separator of Conventional Example 1 is a film, it stretches when pulled. For this reason, the pores formed in the film and on the film surface also stretch, deform and tear. Alternatively, a thin portion is locally generated by stretching, and the mechanical strength of the locally thin portion is reduced, and the portion is broken with the mechanical strength as a base point. On the other hand, in the separator of Example 7, synthetic resin fibers are welded and pressure-bonded, and the periphery thereof is filled with regenerated cellulose. For this reason, the elongation when pulled is small. Thereby, it is thought that the tensile strength is improving.

Comparative Example 3 is 150 ml on the side where the CSF value is decreasing, and the fiber length exceeds 2 mm, so the A / B value exceeds 0.85. The separator of Comparative Example 3 has a small A / B value compared to Conventional Example 2, does not have the two-layer structure of the present invention, and has a low tensile strength.
Comparative Example 3 is a separator produced in the same manner as in Example 4. However, the lithium ion secondary battery using the separator of Comparative Example 3 has both a short-circuit defect rate and a short-circuit defect rate after a long-term reliability test of 1. It became high with more than%. This is because the A / B value exceeds 0.85, and there is little welding and pressure bonding between thermoplastic synthetic fibers.
Comparative Example 4 is 750 ml on the side where the CSF value is increasing, and the fiber length is less than 0.2 mm. The A / B value is 0.85 or less, but the B / A value exceeds 0.85. For this reason, compared with the lithium ion secondary battery of Example 4 thru | or Example 10, both the short-circuit defect rate and the short-circuit defect rate after a long-term reliability test became high.
From the above, it is understood that the A / B value of the separator is preferably 0.85 or less, and the B / A value is further preferably 0.85 or less.
And in order to implement | achieve these, the average fiber length of the regenerated cellulose fiber beaten is preferably 0.2 to 2.0 mm, and the CSF value is lowered to a CSF value of 100 to 0 ml, or increased. It can be seen that a CSF value of 700 ml or less is preferable.

  In Examples 4 and 10, the A / B value is 0.85 or less and exceeds 0.75. On the other hand, in Examples 5 to 9, the A / B value is 0.75 or less. For this reason, the lithium ion secondary batteries using the separators of Examples 5 to 9 have a lower short-circuit defect rate than the lithium ion secondary batteries using the separators of Examples 4 and 10. From this, it is understood that the A / B value is more preferably 0.75 or less. And in order to implement | achieve A / B value 0.75 or less, it turns out that the average fiber length of the regenerated cellulose fiber beaten is 0.4-1.0 mm.

  In Example 8 and Example 9, the A / B value is 0.75 or less and exceeds 0.6. On the other hand, in Examples 5 to 7, the A / B value is 0.59. For this reason, the lithium ion secondary batteries using the separators of Examples 5 to 7 have a lower short-circuit defect rate than the lithium ion secondary batteries using the separators of Examples 8 and 9. From this, it is understood that the A / B value is more preferably 0.6 or less. And in order to implement | achieve A / B value 0.6 or less, it turns out that the average fiber length of the regenerated cellulose fiber beaten is 0.5-1.0 mm.

  Conventional Example 2 is a separator manufactured based on Patent Document 1. It can be seen that because of the homogeneous cross-sectional structure, the short-circuit defect rate is slightly high and the short-circuit defect rate after a long-term reliability test is high.

The electric double layer capacitors produced using the separators of Example 11 to Example 15 have a short defect rate and a short defect rate after a long-term reliability test of 0.5% or less, which are sufficiently low. Also, the internal resistance value is sufficiently low. The rate of change in internal resistance after the long-term reliability test is also below the conventional example and is sufficiently small. Also, the capacity change rate after the long-term reliability test is within 20%, which is not a problem.
Example 11 uses the same separator as Example 7, and shows that the separator used in the lithium ion secondary battery can also be applied to the electric double layer capacitor.
Example 12 is a separator containing 90% by mass of regenerated cellulose fiber. If the content ratio of the thermoplastic synthetic fiber is reduced from this, it is presumed that the tensile strength cannot be improved as compared with the conventional example.
In Example 14, the fiber diameter of the thermoplastic synthetic fiber is 10 μm. If the fiber diameter of the thermoplastic synthetic fiber is further increased, it is presumed that the tensile strength cannot be improved as compared with the conventional example, as in the case where the content ratio of the thermoplastic synthetic fiber is too small.
Example 15 is a separator containing 50% by mass of regenerated cellulose fiber. If the content ratio of the regenerated cellulose fiber is reduced from this, it is presumed that the short-circuit defect rate cannot be reduced.

Reference Example 1 uses a synthetic fiber having a fiber diameter of 0.1 μm as a synthetic fiber. Both separator performance and electric double layer capacitor performance were satisfactory, but the synthetic fibers were easily lifted in the separator manufacturing process (stock stage before being supplied to the wire), and the productivity of the separator was reduced.
Comparative Example 5 is a separator containing 40% by mass of regenerated cellulose fiber. The shielding of the separator was low, and the short circuit failure of the electric double layer capacitor slightly increased. From the comparison between Comparative Example 5 and Example 15, it can be seen that the content ratio of the regenerated cellulose fiber is preferably 50% by mass or more.
Conventional Example 3 uses the same separator as Conventional Example 2. Therefore, similarly to the lithium ion secondary battery of Conventional Example 2, the electric double layer capacitor of Conventional Example 3 has a slightly high short-circuit defect rate and a high short-circuit defect rate after a long-term reliability test.
Conventional Example 4 is a separator manufactured based on Patent Document 2. Since the sheet is made of only regenerated cellulose fibers and has a very high shielding property, no short circuit has occurred. However, since the tensile strength is low, handling in the electric double layer capacitor manufacturing process is difficult, and the productivity of the electric double layer capacitor is reduced. Moreover, since it consists only of regenerated cellulose fiber, the deterioration of various performances after a long-term reliability test was large.

  Since the separator of the present embodiment shows a good long-term reliability test result in any of the examples, a severe environment more than that shown in the present embodiment, for example, a high-voltage electrochemical element, It is considered that application to an electrochemical element operating in a high temperature environment is sufficiently possible.

In the above, the example which used the separator of this Embodiment about the lithium ion secondary battery and the electric double layer capacitor was demonstrated.
In addition, the description about the detail of the other structure of a lithium ion secondary battery and an electric double layer capacitor and a manufacturing method was abbreviate | omitted.

In the lithium ion secondary battery and the electric double layer capacitor according to the electrochemical device of the present invention, electrode materials, electrolyte materials, other members, etc. are not particularly limited, and various materials can be used. Can be used.
The separator for electrochemical elements of the present invention can also be applied to electrochemical elements other than those described in this embodiment, for example, electrochemical elements such as lithium ion capacitors, aluminum electrolytic capacitors, and lithium ion primary batteries. is there.

DESCRIPTION OF SYMBOLS 10 Separator for electrochemical elements, 10A A part, 10B B part, 11 trunk part of regenerated cellulose fiber, 12 thermoplastic synthetic fiber, 13 fibril of regenerated cellulose fiber, 20, 30, 50 automobile, 21,52 lithium ion secondary Battery, 22, 56, 57 Motor, 23, 35, 53 Brake, 24, 54 Charger, 25, 55 External power supply, 26, 60 Battery control ECU, 27, 63 Motor control ECU, 28, 64 EPS control ECU, 29 , 41, 62 Regenerative brake control ECU, 31, 51 Engine, 32 Accelerator, 33 Transmission, 34 Regeneration unit, 36 ABS unit, 37 Air conditioner, 38, 58 Fuel spray ECU, 39, 59 Electronic throttle ECU, 40 Transmission ECU 42 ABS ECU, 61 HEV system system ECU, 70, 80 electronic apparatus, 71 power source, 72 a load (LED, etc.), 73, 83 electric double layer capacitor, 81 lithium-ion secondary battery or the like, 82 load

Claims (7)

A separator for an electrochemical element that is interposed between a pair of electrodes and can hold an organic electrolyte containing an electrolyte,
The separator is composed of a thermoplastic synthetic fiber and a regenerated cellulose fiber beaten with an average fiber length of 0.2 to 2.0 mm,
The thermoplastic synthetic fiber is a polyester fiber, containing 10 to 50% by mass of the thermoplastic synthetic fiber,
Containing 50 to 90 mass% of the regenerated cellulose fiber beaten,
The thickness of the separator is 10 to 70 μm, the density of the separator is 0.25 to 0.90 g / cm ³ ,
Two portions obtained by equally dividing the cross section of the separator in the thickness direction are a portion having a small number of the thermoplastic synthetic fibers (A portion) and a portion having a large number of the thermoplastic synthetic fibers (B portion). ,
The A part and the B part are integrally formed with one layer,
The value obtained by dividing the number of the thermoplastic synthetic fibers in the A part by the number of the thermoplastic synthetic fibers in the B part is 0.85 or less. 2. The separator for an electrochemical element according to claim 1 , wherein a value obtained by dividing the number of the regenerated cellulose fibers in the B part by the number of the regenerated cellulose fibers in the A part is 0.85 or less. The electrochemical element separator of Claim 1 or Claim 2 is used, The electrochemical element characterized by the above-mentioned. The electrochemical element according to claim 3 , wherein the electrochemical element is any one of an aluminum electrolytic capacitor, an electric double layer capacitor, a lithium ion capacitor, a lithium ion secondary battery, and a lithium primary battery. 5. The electrochemical element according to claim 4 , wherein a portion (part B) of the electrochemical element separator having a large number of the thermoplastic synthetic fibers is disposed on a positive electrode side of the electrochemical element. The electronic device carrying the electrochemical element of any one of Claims 3 thru | or 5 . An automobile equipped with the electrochemical device according to any one of claims 3 to 5 .

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