JP2010251215A - Separator for battery, and the battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a separator which has a mechanical strength and elongation, as well as, superior punching characteristics with high liquid retention ratio and high liquid absorption properties and precision, and to provide a lithium primary battery that uses the separator. <P>SOLUTION: Lyocell of 1.7 dtex×4 mm and PP/PE core sheath composite fiber of 2.2 dtex×5 mm are blended by the following ratio and mixed by a cylindrical net paper machine, to manufacture a wet type nonwoven fabric, and it is made into a sheet as a separator to manufacture a battery. Lyocell (solvent spinning rayon): 30-50% weight ratio, PP/PE core sheath composite fiber: 35-65% weight ratio, PE synthetic pulp: 5-15% weight ratio. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a battery separator and a battery, for example, a separator made of solvent-spun rayon, a polyolefin composite fiber, and synthetic pulp, and a non-aqueous organic electrolyte battery using the separator.

  As a conventional cylindrical lithium primary battery, for example, a negative electrode using lithium as an active material described in Patent Document 1 and a positive electrode are stacked via a separator, or further wound. Generally, the electrode body is inserted into an outer can and the opening of the outer can is crimp sealed or laser sealed with a battery lid.

  Generally, a structure in which a negative electrode and a positive electrode are stacked via a separator is called an inside-out structure, and a wound structure is called a spiral structure.

  A primary battery having an inside-out structure is often used in applications in which capacity characteristics are more important than output characteristics because the electrode area is small. On the other hand, since the spiral structure has a larger electrode area, the spiral structure is often used in applications where output characteristics are more important than capacity characteristics. In addition, spiral structures are common in secondary batteries that require high output. It is the structure used for

  Also, as a coin-type battery, a negative electrode and a positive electrode made of lithium or the like as an active material are laminated via a separator, punched into a disk shape, inserted into an outer can (positive electrode can), and a battery lid (negative electrode can). The opening of the outer can was sealed with the gasket part.

  Examples of conventional separators used in this type of battery include a separator composed of a polyolefin-based synthetic fiber nonwoven fabric described in Patent Document 2, a glass fiber compounded separator, a solvent-spun rayon separator described in Patent Document 3, and the like.

  a. As the polyolefin-based synthetic fiber nonwoven fabric, a dry nonwoven fabric obtained by forming a sheet by a melt blow method using polypropylene (hereinafter referred to as “PP”) fiber is used.

  b. As the glass fiber blending separator, a wet nonwoven fabric obtained by blending synthetic pulp made of glass fiber, polyolefin-based composite fiber and polyethylene (hereinafter referred to as “PE”) and making paper is used.

  c. As the solvent-spun rayon separator, a cellulose fiber is dissolved in N-methylmorpholine oxide, and the precipitated fiber is fibrillated to a fiber diameter of 1 μm or less in a beating process, and then a paper machine is used to make a sheet. .

JP 2008-192524 A JP-A-8-32287 JP-A-8-306352

(1) However, as in Patent Document 1, when a separator using a polyolefin-based nonwoven fabric is used for a cylindrical battery with an inside-out structure, the melting point difference of the raw materials used is small. At the same time, the separator melted to form a film.

  Furthermore, if the fusion is too strong, there is a problem that the heat-sealing process cannot be performed well, such as a hole in the separator. In addition, the part formed into a film by melting loses its original ion permeability, and there is a concern about deterioration of electrical characteristics.

(2) Also, as in Patent Document 2, when a polyolefin-based synthetic fiber nonwoven fabric is used for a coin-type battery, only the bonded portion of the constituent fibers is stopped by thermal fusion, so the mechanical tensile strength is weak. There was a risk of peeling over time, and there was a problem in reliability.

  Polyolefin-based synthetic fiber nonwoven fabrics often have a substantially circular cross section. The electrolyte is easily released when stress is applied to the separator due to expansion of the active material during caulking or discharging after the electrolyte is impregnated. Therefore, liquid absorbency is also inferior.

(3) When a glass fiber-blended separator is used for a cylindrical battery, the specific gravity difference between the glass fiber and the synthetic fiber constituting the separator is large, and the formation is difficult to obtain at the time of manufacturing the separator. Further, since glass fiber has a large specific gravity, it has settled in a tank or the like in the production process, and there is a problem that it is difficult to control the blending ratio of the finished separator.

  Furthermore, the glass fiber is suspected to be carcinogenic like asbestos, and there is a concern that the glass fiber may pierce the lungs when the worker inhales.

(4) When a glass fiber compounded separator is used for a coin-type battery, in the same way as when used for a cylindrical battery, in addition to the problem of carcinogenicity at the time of manufacturing the separator, the separator can be punched into a coin shape. There is a problem that the separator cannot be punched well by being pushed by the punching blade.

  In order to solve this problem, when the force for pushing the punching blade is increased, there is a concern that the punching blade itself may be scraped or chipped due to the high rigidity of the glass fiber blended in the separator. In addition, the glass fiber itself has a problem that it is difficult to assemble the cell because it does not have mechanical strength and elongation.

(5) As described in Patent Document 3, the applicants provide a non-aqueous organic electrolyte battery separator using 10% by weight or more of a solvent-spun rayon beating raw material.

  When this non-aqueous organic electrolyte battery separator is used for a cylindrical battery or a coin-type battery of a conventional lithium primary battery, although the low ESR and high shielding properties are satisfied, the separator itself is thin, so that it can be used as a lithium primary battery. It was difficult to maintain a sufficient amount of electrolyte that satisfies the required increase in capacity.

  There is also a problem that heat fusion cannot be performed because there is no heat fusion component. In the coin-type battery, the solvent-spun rayon separator has mechanical strength but does not stretch, and thus may be broken during caulking.

(6) The thickness of the porous film can be reduced, and the cylindrical shape is more suitable for a battery having a spiral structure than an inside-out structure. However, the porous film has a high density, in other words, there are not many voids in the film, so the liquid retention rate of the electrolytic solution is low, and for the same reason, the capillary phenomenon does not work, so the liquid absorption is poor. The same applies to both cylindrical and coin batteries.

  The present embodiment has been made in view of the above problems, and provides a separator having sufficient mechanical strength, excellent heat resistance, and ensuring electrolyte absorbability, and a battery using the separator. The purpose is to do.

  The present invention has been made to solve the above-described problems and achieve the above-described object, and includes, for example, the following configuration as one means for achieving such an object.

  That is, a separator for a lithium primary battery that is interposed between a positive electrode and a negative electrode and is capable of holding an electrolyte-containing electrolyte solution, wherein the separator is obtained by spinning a solution obtained by dissolving cellulose in a solvent. It contains 30 to 50% by weight of possible solvent-spun rayon fiber and 50 to 70% by weight of composite fiber and synthetic pulp made of olefin resin.

  For example, the solvent-spun rayon is beaten to a value CSF 200 ml to 0 ml indicating the degree of beating prescribed in JIS P 8121.

  Further, for example, the composite fiber made of the olefin resin is characterized in that the component to be heat-sealed at 140 ° C. or lower is a polyethylene component and the other component is a polypropylene component.

Further, for example, the composite fiber is characterized in that the core part of the fiber cross section is a polypropylene component and the sheath part of the fiber cross section is a polyethylene component.
The synthetic pulp made of the olefin resin is a synthetic pulp made of polyethylene.

  Further, for example, the solvent-spun rayon is contained in a proportion of 30 to 50% by weight, a polypropylene component of 17.5 to 32.5% by weight, and a polyethylene component of 27.5 to 42.5% by weight.

  Further, for example, 30 to 50% by weight of the solvent-spun rayon, 35 to 65% by weight of a composite fiber in which the core of the fiber cross section is a polypropylene component, and the sheath of the fiber cross section is a polyethylene component, and 5 to 15 of polyethylene synthetic pulp It is characterized by being mixed at a weight percentage.

  Alternatively, a battery including any of the separators described above is used. The battery is a primary battery. Alternatively, the battery is a cylindrical battery, more preferably an inside-out structure. Furthermore, the battery is a coin-type battery.

  According to the present invention, a dense separator having good mechanical strength and elongation, good punching characteristics, high liquid retention, high liquid absorption, and a battery using the separator can be provided.

  In addition, it is possible to provide a dense separator having a liquid-absorbing property of a non-aqueous organic electrolyte, a high liquid retention rate, and a battery using the separator.

  Hereinafter, an embodiment of the invention according to the present invention will be described in detail with reference to tables and the like. According to the present embodiment, the same or better characteristics as those of the conventional separator are realized without using glass fiber or the like that may be harmful to the human body for the battery separator.

  As a result of conducting a test study on various materials and constituent ratios in addition to the embodiment examples and the examples shown in the examples, it was found that the separator was composed of solvent-spun rayon and PP / PE core-sheath composite fibers. It was found that a satisfactory result was obtained.

The battery using the separator according to the present embodiment is impregnated and held with a non-aqueous organic electrolyte in the separator portion, and contains a positive metal containing light metal such as lithium, lithium or lithium alloy, and manganese dioxide or fluorinated graphite. The negative electrode having a negative electrode mixture layer on both sides of the current collector is separated by the separator to form a non-aqueous organic electrolyte battery.
[Description of separator]

  The separator of the present embodiment is composed mainly of solvent-spun rayon and PP / PE core-sheath composite fiber. As the solvent spinning rayon, it is desirable to use a natural fiber material obtained by spinning a solution in which cellulose itself is dissolved in a solvent, such as acetate fiber, without going through a process of derivatization.

  Here, the composite fiber includes a side-by-side type composite fiber in which different components are arranged side by side, a multilayer type composite fiber in which a plurality of different components are arranged side by side, and a core part (center part) of the fiber cross section. Core-sheath type composite fiber covered with resin of different components, and sea-island type composite fiber having a plurality of core parts of the core-sheath fiber covered with resin of different components, radially from the core part of the fiber cross section There are split type composite fibers in which resins of different components are alternately arranged, and there are many types of composite fibers depending on the combination of resin components.

  Combining components with different melting points and softening points of the resin itself containing the composite fiber, the melting point is lower than the low melting point (low softening point) component and the lower melting point (high softening point) component. The resin is fused and a sheet can be formed while maintaining the fiber shape.

  The composite fiber is preferably a core-sheath type composite fiber or a sea-island type composite fiber in which the ratio of the low melting point (low softening point) component exposed on the fiber surface is large.

  In this embodiment, the composite fiber is a core-sheath type composite fiber (hereinafter referred to as “PP / PE core-sheath composite fiber”) in which the core part of the fiber cross section is made of PP resin and the sheath part is made of PE resin. Used.

  Synthetic pulp is a pulp-like multi-branched fiber. Spin-drawing method of preformed polymer, flash spinning method from solution or emulsion, strip fiber method by uniaxial stretching of preformed film, and so-called shear polymerization method of polymerizing monomers under shear stress. Manufactured by. Among these, polyethylene synthetic pulp acts as a binder by being mixed with other fibers and heat-treated. Moreover, it has heat seal adhesiveness.

  As the synthetic pulp, it is desirable to use a synthetic pulp containing PE as a component (hereinafter referred to as “PE synthetic pulp”). Further, by blending the solvent-spun rayon at a weight ratio of 30 to 50%, the separator can be provided with good electrolytic solution retention, electrical resistance reduction effect, mechanical strength and denseness.

  Also, by blending the PP / PE core-sheath composite fiber in a weight ratio of 35 to 65%, it is possible to form a separator sheet by thermal fusion with the PE component of the sheath part, and to lower the density of the separator by the PP component of the core part. I can do it.

  Moreover, by blending 5 to 15% by weight of PE synthetic pulp, it is possible to easily form a sheet during heat sealing function or separator paper making.

  Further, as a constituent component of the PP / PE core-sheath composite fiber and the synthetic pulp, it is desirable that 50% or more of a component to be heat-sealed at 140 ° C. is included.

  Further, it is desirable to blend the solvent-spun rayon at a ratio of 45% by weight, the PP / PE core-sheath composite fiber at a ratio of 45% by weight, and the PE synthetic pulp at a ratio of 10% by weight.

  Since such solvent-spun rayon does not undergo a process such as derivatization, the degree of polymerization of cellulose molecules is small and the strength can be improved.

  As the composite fiber mixed with the solvent-spun rayon, it is desirable to employ a composite fiber of PP resin and PE resin. The PP / PE core-sheath composite fiber is composed of PP fiber for the core part and PE fiber for the sheath part. For this reason, PE part of a sheath expresses a binder function like PE synthetic pulp. As the PP / PE core-sheath composite fiber of this embodiment, for example, “NBF (H)” manufactured by Daiwabo Co., Ltd. can be used.

  Since the solvent-spun rayon has heat resistance, it is possible to achieve the effect of preventing perforation and the like during the formation of the cylinder and the effect of ensuring the liquid absorption and liquid retention. This solvent-spun rayon is preferably one in which the degree of beating specified in JIS P 8121 is beaten to CSF 200 ml to 0 ml from the balance of the mechanical strength of the separator, the liquid absorbency of the non-aqueous organic electrolyte, and the liquid retention. .

  In this embodiment, as described above, the ease of papermaking on papermaking is ensured by blending paper with PE synthetic pulp. Furthermore, the PP / PE core-sheath composite fiber can have both a binder function and a heat seal function together with the PE part of the sheath.

  As the PE synthetic pulp of the present embodiment, for example, “SWP EST-8” manufactured by Mitsui Chemicals, Inc. can be used.

  As the solvent spinning rayon, “Lyocell” is preferably adopted. Lyocell is made from wood (eucalyptus etc.) as a raw material, and this raw material is dissolved in an aqueous solution of N-methylmorpholine-N-oxide to form a spinning stock solution (dope). In a dilute solution of N-methylmorpholine-N-oxide, Extruded, fiber.

  Since lyocell does not go through a process such as derivatization, the degree of polymerization of cellulose molecules is small and the strength is excellent, and the strength in the production process can be ensured.

  As a result of experimenting by changing the mixing ratio of each fiber or the like, a substantially satisfactory characteristic was obtained if the desirable range of the mixing ratio of each fiber or the like was the following range. A separator having the following composition has a good electrolyte solution retention ratio, mechanical strength and elongation, and can be heat-sealed (heat-sealed) at the outermost periphery when forming a cylinder, and when used as a coin shape The punching characteristics are also good. The lyocell material used was 1.7 dtex × 4 mm, and the PP / PE core-sheath composite fiber was 2.2 dtex × 5 mm.

[Evaluation method of separator]
The test method for the battery separator conforms to JIS C2111 (electrical insulating paper test method).
〔Test conditions〕

Unless otherwise specified, the test was conducted after the specimen reached equilibrium under the conditions of a temperature of 20 ± 5 ° C. and a relative humidity of 65 ± 2%.
〔thickness〕

Take a 500 mm long test piece with no wrinkles and fold it so that the crease is perpendicular to the vertical direction of the paper. From the inside 15 mm or more from the edge of the paper, the thickness is roughly 5 at regular intervals. The average value was measured and further divided by the number of folded sheets to obtain the thickness per sheet to obtain the paper thickness. Note that the measurement was performed using a dial thickness gauge G type (measurement reaction force 2N, probe: φ10 mm).
[Basis weight]

A test piece having an area of 1000 cm ² or more was taken, and the weight was measured with a scale having a sensitivity superior to 0.25% of the weight of the test piece, and converted to a weight (g) per 1 m ² .
〔Tensile strength〕

Take four test pieces with a size of 15 x 200 mm in the longitudinal direction of the separator, and use a universal tensile testing machine or something similar, pull the test piece at a speed of about 200 mm per minute with an interval of the knob of 180 mm, and pull it Strength was measured. This test was performed 4 times, the average value was calculated | required, and the unit was represented by N / 15mm.
[Elongation]

Elongation can be measured at the same time as the tensile strength measurement. At the time of tensile strength measurement, the length (mm) from the measurement start position to the fracture position of the test piece is obtained, and this is divided by the distance of 180 mm between the claws. , 100 minutes were obtained. This test was performed 4 times, the average value was calculated | required, and the unit was represented by%.
[Electrolytic solution absorption]

Three test pieces with a size of 15 × 200 mm are taken in the vertical direction of the paper, each is suspended vertically, and the lower end is immersed in propylene carbonate solution for 3 mm or more, and after 3 minutes, the portion where the liquid penetrates from the liquid surface of the test piece The maximum height was measured, and the average value was taken as the electrolyte solution absorption.
[Internal resistance (ESR)]

The separator was sampled to 38 mmφ, impregnated with a predetermined electrolytic solution, sandwiched between 38 mmφ electrodes, and measured with an LCR meter at a frequency of 20 ° C. and 1 kHz.
[Air density]

  According to the method prescribed in JIS P 8117, measurement was performed with a B-type tester (Gurley densometer). However, an adapter having a hole diameter of 6 mmΦ was used because measurement of a separator having a low air density was used.

In the measurement, a test piece was sandwiched between adapters and fixed to a measurement port portion of a B-type tester, and the time required for 100 ml of air to pass was measured. This test was performed 5 times, the average value was obtained, and the unit was sec. / 100 ml.
[Electrolytic solution retention ratio]

Take a 50 × 50 mm test piece and immerse it in propylene carbonate solution for 10 ± 1 minutes, then remove the end of the test piece with tweezers and leave it on a glass plate inclined at 45 degrees for 3 minutes. The droplets were removed and the weight was measured, and the liquid retention rate was determined by the following formula 1. The test was performed 4 times, and the average value was used as the liquid retention rate.
[Formula 1] Liquid retention ratio (%) = (W2−W1) / W1 × 100
{W1: Mass before immersion, W2: Mass after immersion}

[Production of battery using separator]
(1) An example in which the separator (lyocell + synthetic fiber) of this embodiment is applied to a non-aqueous organic electrolyte battery will be described below.

  As the positive electrode active material of the non-aqueous organic electrolyte battery of the present embodiment, for example, a positive electrode active material that can be doped with lithium ions, and manganese dioxide is generally used. Electrolytic manganese dioxide that has been mainly heat treated at 375 to 400 ° C. is used as the positive electrode active material.

As the negative electrode active material of the non-aqueous organic electrolyte battery of this embodiment, metal Li (97%) is generally used, but with other metals such as Pb, Al, Pt, Zn, Mg, etc. A lithium alloy is mentioned.
As the electrolyte of the electrolytic solution, it is preferable to use one or a mixture of two or more lithium salts such as LiClO4, LiAsF6, LiPF6, LiBF4, CH3SO3Li, CF3SO3Li, CF3SO3Li, and (CF3SO2) 2NLi.

  Further, as a solvent for the electrolytic solution, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, 繃 -butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran 1,3-dioxolane, sulfolane, methylsulfolane, acetonitrile, propionitrile, methyl formate, ethyl formate, methyl acetate, ethyl acetate, or a mixture of two or more thereof can be used.

Hereinafter, the manufacturing method of the non-aqueous organic electrolyte battery of the present embodiment will be described in more detail.
・ Manufacture of cylindrical battery (1) Method of making positive electrode

For example, a mixture of heat-treated manganese dioxide mixed with a conductive agent such as carbon powder and a binder such as a fluororesin, and a mixture obtained by adding a sticker to the mixture to form a slurry. Some of them are applied and dried after application. The former is called a molded electrode, and the latter is called a paste electrode. Most coin-type batteries and cylindrical batteries with an inside-out structure use molded electrodes, and cylindrical batteries with a spiral structure use paste-type electrodes.
(2) Preparation method of negative electrode

For example, sheet-like metallic lithium or lithium alloy is cut into a predetermined size to obtain a negative electrode material.
(3) Non-aqueous organic electrolyte battery assembly method For example, a positive electrode mixture pressure-molded in a hollow cylindrical shape is placed in close contact with the inner peripheral surface of the battery can, and the hollow inner surface of the positive electrode mixture is cylindrically formed. The formed separator is closely arranged.

  A negative electrode made by impregnating a mixed solution of propylene carbonate and 1,2-dimethoxyethane in 1: 1 (weight ratio) with LiClO4 dissolved until the separator is sufficiently wet, and cutting the inner peripheral surface of the separator to a predetermined size The agent is wound and placed in close contact.

  Or it is good also as a structure wound in the state which laminated | stacked the separator and the negative electrode agent. And it sealed by crimping through a gasket and manufactured the cylindrical battery (reference "Unexamined-Japanese-Patent No. 2000-315497", battery manual).

  Even in this case, the separator of the present embodiment has sufficient mechanical strength in the cylinder forming process, and breakage occurs even when the outermost periphery is heat-sealed (heat-sealed). In addition, there is a liquid-absorbing property of the non-aqueous organic electrolyte.

-Manufacture of coin-type non-aqueous organic electrolyte battery (1) For example, the above-described electrolysis is performed on a separator interposed in parallel between a pair of polarizable electrodes formed in a coin shape with the above-described positive electrode material and negative electrode material, for example. After impregnating the solution, it is housed in a metal case that also serves as an exterior material and a metal lid, and is sealed by caulking through a gasket to produce a coin-shaped lithium primary battery.
In the manufacturing process of the negative electrode, the cylindrical battery is slit to a predetermined width using a slitter, but the coin battery is punched into a coin shape by, for example, a press punching machine.

[Battery evaluation method]
[Discharge test]
The discharge capacity was determined from the duration when discharging to a final voltage of 2.0 V with a standard load current (cylindrical type 1.0 mA, coin type 0.2 mA) under a temperature condition of 20 ° C.
In the pulse discharge, the depth of discharge was set to 50%, the current value at which the voltage was 2.0 V was obtained at a pulse time of 15 seconds under the temperature condition of 20 ° C., and the maximum current value was compared.

[Preservation test]
The discharge capacity after the assembled battery was left for 100 days in an environment of 60 ° C. was measured. This condition was assumed to be stored at room temperature for about 5 years.

Specific examples relating to the separator according to the embodiment of the present invention described above will be described below.
The separator of this example was prepared by blending the above-mentioned lyocell, PP / PE core-sheath composite fiber, and PE synthetic pulp, and mixing them with a circular net paper machine to produce a wet nonwoven fabric, which was made into a sheet as a separator. That is, the separator was composed of a wet nonwoven fabric.
Here, blending with a circular paper machine is a method in which fibers and a binder are added to a solvent (water) and the fibers are scraped off in the manner of papermaking. can do.

[Example 1]
As a raw material for the separator, 30% by weight of lyocell having a CSF value of 200 ml + 60% by weight of PP / PE core-sheath composite fiber + 10% of PE synthetic pulp was mixed to obtain a separator having a thickness of 150 μm and a basis weight of 40 g / m ² .

[Example 2]
As a separator raw material, lyocell 45% by weight with a CSF value of 150 ml + PP / PE core-sheath composite fiber 45% by weight + PE synthetic pulp 10% was mixed to obtain a separator having a thickness of 150 μm and a basis weight of 40 g / m ² .

Example 3
As a separator raw material, 30% by weight of lyocell having a CSF value of 50 ml + 65% by weight of PP / PE core-sheath composite fiber + 5% of PE synthetic pulp was mixed to obtain a separator having a thickness of 150 μm and a basis weight of 40 g / m ² .

Example 4
As a separator raw material, 50% by weight of lyocell having a CSF value of 100 ml + 35% by weight of PP / PE core-sheath composite fiber + 15% of PE synthetic pulp was mixed to obtain a separator having a thickness of 150 μm and a basis weight of 40 g / m ² .

Example 5
As a raw material for the separator, 50% by weight of lyocell having a CSF value of 0 ml + 45% by weight of PP / PE core-sheath composite fiber + 5% of PE synthetic pulp was mixed to obtain a separator having a thickness of 150 μm and a basis weight of 40 g / m ² .

Example 6
As a separator raw material, lyocell 30 wt% with a CSF value of 200 ml + PP / PE core-sheath composite fiber 55 wt% + PE synthetic pulp 15% was mixed to obtain a separator having a thickness of 150 μm and a basis weight of 40 g / m ² .

[Comparative Example 1]
As a separator material, 40% by weight of lyocell having a CSF value of 200 ml + 30% by weight of PP / PE core-sheath composite fiber + 30% of PE synthetic pulp was mixed to obtain a separator having a thickness of 150 μm and a basis weight of 40 g / m ² .

[Comparative Example 2]
As a raw material of the separator, 55% by weight of lyocell having a CSF value of 150 ml + 20% by weight of PP / PE core-sheath composite fiber + 25% of PE synthetic pulp was mixed to obtain a separator having a thickness of 150 μm and a basis weight of 40 g / m ² .

[Comparative Example 3]
As a separator raw material, 150 ml of lyocell 70% by weight + PP / PE core-sheath composite fiber 25% by weight + PE synthetic pulp 5% were mixed to obtain a separator having a thickness of 150 μm and a basis weight of 40 g / m ² .

[Comparative Example 4]
As a raw material for the separator, 50% by weight of lyocell having a CSF value of 0 ml + 50% by weight of PP / PE core-sheath composite fiber was mixed to obtain a separator having a thickness of 150 μm and a basis weight of 40 g / m ² .
Since this separator does not contain synthetic pulp, the wet paper strength is weak, paper breakage occurs, and papermaking properties are not good.

[Comparative Example 5]
Wet paper making was performed using 100% by weight of glass fiber as a raw material for the separator. The basis weight was 40 g / m ² , and the sheet thickness was 300 μm, which was larger than the other examples and comparative examples. This was used as a separator.

[Comparative Example 6]
Using 100% by weight of lyocell having a CSF value of 70 ml as a raw material for the separator, paper was made with a long net paper machine. The basis weight was 40 g / m ² and the sheet thickness was 110 μm, resulting in a smaller thickness than the other examples and comparative examples. This was used as a separator.

[Comparative Example 7]
As a separator raw material, 30% by weight of lyocell having a CSF value of 250 ml + 60% by weight of PP / PE core-sheath composite fiber + 10% of PE synthetic pulp was mixed to obtain a separator having a thickness of 150 μm and a basis weight of 40 g / m ² .

[Comparative Example 8]
As a separator material, a separator having a thickness of 150 μm and a basis weight of 40 g / m ² was prepared with a circular paper machine using 100% by weight of lyocell having a CSF value of 350 ml.

[Comparative Example 9]
As a separator raw material, a separator having a thickness of 50 μm and a basis weight of 20 g / m ² was prepared with a long net paper machine using 100% by weight of lyocell having a CSF value of 40 ml.

[Comparative Example 10]
As a raw material of the separator, 50% by weight of lyocell having a CSF value of 150 ml + 50% by weight of PE synthetic pulp was mixed. The basis weight was 40 g / m ² and the sheet thickness was 130 μm, which was smaller than the other examples and comparative examples. This was used as a separator.

[Conventional example 1]
Using 100% by weight of PP resin, a dry nonwoven fabric was prepared by a melt blow method and subjected to a surfactant treatment to obtain a separator having a thickness of 150 μm and a basis weight of 40 g / m ² .

[Conventional example 2]
40% by weight of glass fiber + 30% by weight of PP / PE core / sheath composite fiber + 30% of PE synthetic pulp was mixed to obtain a separator having a thickness of 150 μm and a basis weight of 40 g / m ² . In this separator, since the specific gravity of the glass fiber is larger than that of other raw material fibers, it is difficult to control the raw material mixing ratio in the finished separator. As the glass fiber, Tempslan 108A manufactured by Jones Manville was used.

  Table 1 shows the measurement results of the separator of this embodiment, the separators of Comparative Examples 1 to 9, and the separators of Conventional Examples 1 and 2 having the above-described configuration.

表１に示すように、本実施の形態例のセパレータは、従来のガラス繊維配合のセパレータ等と同等あるいはそれ以上の特性を有しながら、更に優れた機械的強度を達成している。

As shown in Table 1, the separator according to the present embodiment achieves further excellent mechanical strength while having the same or higher characteristics as those of conventional separators containing glass fibers.

  The separators of Examples 1 to 6 have a sufficient electrolyte solution absorbency as compared with separators conventionally used (Conventional Examples 1 and 2). In addition, the internal resistance (ESR) is low, and there is no problem in air density and liquid retention.

The characteristics of the separators of Comparative Examples 1 and 2 were at a level with no problem.
Since the separator of Comparative Example 3 does not contain a polyolefin component as a constituent component, the elongation is low. Other characteristics were at a satisfactory level.
Since the separator of Comparative Example 4 does not contain a component that serves as a binder in the constituent components, the strength of the wet paper web is weak, the manufacturing is difficult, and there is a concern about the stable supply surface.

  The separators of Comparative Examples 5 to 6 had no problem in tensile strength, but the elongation was low. This is probably because the polyolefin component is not included in the constituent components of the separator. Since the elongation is low, there is a concern that the separator may be broken in the coin battery assembly process. Other characteristics were at a satisfactory level.

Since the separator of Comparative Example 7 has a low air density, it can be seen that the density of the separator itself is low. For this reason, there is a concern about short circuit when a battery is manufactured.
Since the separators of Comparative Examples 8 to 9 were prepared using 100% by weight of lyocell, the tensile strength and elongation were low, but the ESR was low. However, since the retention rate of the electrolytic solution is low, there is a concern that the discharge capacity may deteriorate when the battery is assembled.

In the separator of Comparative Example 10, satisfactory results were obtained in terms of tensile strength and elongation, but the ESR deteriorated, the air density increased, and the liquid retention rate decreased. This is thought to be because the PE component was included in the separator and the PE component extremely formed a film in the separator, thereby increasing the density of the separator. It is thought that the apparent density of the separator increased because the density of the separator was improved, and that the thickness became thinner when the basis weight was adjusted to 40 g / m ² .

  For comparison with the conventional example, batteries were manufactured using the separators of Examples 1 to 6, Comparative Examples 1 to 9, and Conventional Examples 1 and 2, and the characteristics were compared. Table 2 shows configurations and characteristics of the present example and the comparative example.

表２に示すように、円筒形電池を組み立て時において、本実施の形態例のセパレータは、筒形成時あるいはヒートシール時において破損などの不具合は発生しなかった。又、コイン形電池を組み立てたが、セパレータの打ち抜き時及びカシメ時においても破損などの不具合は発生しなかった。

As shown in Table 2, when assembling the cylindrical battery, the separator of the present embodiment did not suffer from problems such as breakage during tube formation or heat sealing. In addition, although a coin-type battery was assembled, no troubles such as breakage occurred when the separator was punched out and caulked.

  Also, good results were obtained even when the battery performance was compared with that using a conventional separator.

  The separators of Comparative Examples 1 and 2 had no problem in the assembly process of the cylindrical battery and the coin battery, but the battery performance was inferior to that of the conventional one in terms of battery performance. Although this is not clear in detail, there are many PE components contained in the separator, and it is expected that a film is formed in the separator. For this reason, it is considered that the liquid retention rate of the separator is low, and the amount of the electrolyte inside the battery is insufficient.

  When assembling a cylindrical battery, the separator of Comparative Example 3 had a defect that the heat seal part was peeled off. This is presumably because the PE component contained in the separator is as low as 17.5% in the separator composition ratio and the heat fusion component is small.

  The battery assembly process and battery performance using the separator of Comparative Example 4 were good, but the wet paper strength was weak and the papermaking properties were not good during the manufacture of the separator, making it difficult to supply the separator.

  Since the separator of Comparative Example 5 was composed of 100% by weight of glass fiber, it did not contain a fusion component, and in the assembly process of the cylindrical battery, heat sealing could not be performed during cylinder molding. In the coin battery assembly process, the punching blade was worn during punching. Even during subsequent caulking, when the separator was under pressure, the glass fibers were frequently dropped and the defect rate was as high as 45%. The battery performance test was not performed due to the high defect rate.

  Since the separator of Comparative Example 6 was composed of 100% by weight of lyocell, it did not contain a fusion component, and in the assembly process of the cylindrical battery, heat sealing could not be performed during cylinder molding. In the assembly process of the coin-type battery, there was no problem with punchability, but since the separator did not stretch when crimped, the separator was torn when pressed, and the defect rate increased to 39%. It was. The battery performance test was not performed due to the high defect rate.

  The separator of Comparative Example 7 was able to produce a battery without problems in the assembly process of the cylindrical and coin-shaped batteries, but a voltage drop occurred during the discharge test, and the discharge capacity and pulse discharge values deteriorated. . The results of the preservation test were also bad. Although the details are unknown, it is considered that the discharge characteristics deteriorated because the beating of the lyocell was insufficient and the airtightness was low and the short-circuit resistance was inferior.

  The separator of Comparative Example 8 is a lyocell of 100% by weight with a shallow beating and the thickness of the separator is equivalent to that of the other examples. However, heat sealing could not be performed during cylinder molding. In the assembly process of the coin-type battery, there was no problem with punching, but since the separator did not stretch when squeezed, when the separator was pressurized, tearing occurred and the defect rate increased to 28%. It was. The battery performance test was not performed due to the high defect rate.

  The separator of Comparative Example 9 has a configuration provided by the applicants in the past. However, as in Comparative Example 6 and Comparative Example 8, the constituent component does not include a fusion component, and in the assembly process of the cylindrical battery. , Heat sealing was not possible during tube molding.

  Also, in the assembly process of the coin-type battery, there was no problem with punching, but since the separator does not stretch when crimped, when the separator is pressurized, tearing occurs and the defect rate increases to 91%. It was. The battery performance test was not performed due to the high defect rate. Considering this result and Comparative Examples 6 and 8, it can be seen that a separator composed of 100% by weight of lyocell cannot be used as a cylindrical or coin-type lithium primary battery separator.

  The separator of Comparative Example 10 was able to produce a battery without any problems in the battery production process. However, in terms of battery performance, both discharge capacity and storage test were inferior to the conventional ones. This is thought to be due to the deterioration in ESR and the decrease in the liquid retention rate due to the improvement in the denseness of the separator due to the PE component being formed into a film.

  It became clear that when the lyocell content is less than 30.0% by weight, the liquid retention performance of the electrolyte solution deteriorates and the discharge characteristics deteriorate. If the lyocell content exceeds 50.0%, the thickness of the separator itself tends to be thin.

  Moreover, since the polyolefin component content in the separator becomes too low, in the assembly process of the cylindrical battery, the heat-sealing property at the time of cylinder forming is deteriorated, and defects such as peeling of the heat-sealed portion occur.

  As described above, it can be seen that a separator composed of 100% by weight of lyocell cannot be used as a cylindrical or coin-type lithium primary battery separator.

Therefore, the content of the solvent spinning rayon is preferably 30.0 to 50.0% by weight.
When the beating degree of lyocell is 200 ml or more, the airtightness of the separator is lowered. That is, the denseness of the separator itself is impaired, and the possibility of occurrence of a short circuit is increased. From this, it is preferable that the beating degree of the solvent-spun rayon is beaten in the range of 200 to 0 ml.

  Even if the PE component contained in the separator is 27.5%, the tensile strength can be secured by proceeding with the lyocell beating. However, if the PE component contained in the separator is less than 27.5%, the strength is not secured or the heat fusion component is insufficient even when the lyocell is beaten. In other words, the wet paper strength of the separator decreases during paper making, and troubles such as running out of paper occur.

  Moreover, when the PE component contained in the separator exceeds 42.5%, the PE component in the separator is formed into a film, the gap of the separator is crushed, the electrolyte retention rate is lowered, and the discharge characteristics are adversely affected. It will be.

  Therefore, the PE component contained in the separator is preferably in the range of 27.5 to 42.5% by weight.

  When the PE component is not included as a constituent component of the separator, the separator does not include a heat-sealing component, and it becomes impossible to maintain wet paper strength during papermaking. Further, in the assembly process of the cylindrical battery, heat sealing at the time of forming the cylinder becomes impossible. In the process of assembling the cylindrical battery, it is preferable that the PE component is contained in the separator for heat sealing.

  When the PP component is 17.5% or less as a constituent component of the separator, it is impossible to lower the density of the separator, the electrolyte solution retention performance is deteriorated, and the discharge capacity is deteriorated.

  When no PP component is contained, the separator is densified, leading to an increase in internal resistance. On the other hand, when the PP component is contained in the separator in excess of 32.5%, the separator is too low in density, the electrolytic solution holding power is reduced, and the discharge capacity and storage performance after assembling the battery are deteriorated. Become.

  Therefore, the PP component is an essential component as a component of the separator, and the content thereof is preferably 17.5 to 32.5% by weight.

  The reason why the PP / PE core-sheath composite fiber is necessary is that the core part of the fiber cross-sectional shape is composed of the PP component and the sheath part is composed of the PE component. The PE component to be heat-sealed makes it possible to maintain the wet paper strength of the separator. Moreover, in the assembly process of the cylindrical battery, the PP component constituting the separator also contributes to heat fusion during heat sealing.

  From this, it is preferable that PP / PE core-sheath composite fiber is contained in a separator component, and it is more preferable that the content is 35 to 65% by weight.

  As described above, it has been clarified that solvent-spun rayon, PP / PE core-sheath composite fiber, and PE synthetic pulp are necessary as constituent components when the separator is manufactured.

  Further, it is clear that 30-50% by weight of solvent-spun rayon, 17.5-32.5% by weight of PP component, and 27.5-42.5% by weight of PE component are necessary as constituent components of the separator. It was.

  According to this embodiment, when used in a cylindrical battery, it has sufficient mechanical strength in the cylinder forming step, and can be heat-sealed (heat-sealed) on the outermost periphery. In addition, a dense separator and a cylindrical battery using the separator can be provided.

  Also, according to this embodiment, when using a coin-type battery, it has mechanical strength and elongation that does not break when crimped, has good punching characteristics, has a high liquid retention rate, and a high liquid absorption. A dense separator and a coin battery using the separator can be provided.

  From the above, in this example, by mixing the solvent-spun rayon at a ratio of 30 to 50%, PP / PE core-sheath composite fiber at a ratio of 35 to 65% by weight, and PE synthetic pulp at a ratio of 5 to 15% by weight, It is possible to provide a dense separator having high strength and elongation, good punching characteristics, high liquid retention, high liquid absorption, and a lithium primary battery using the separator.

  In the above description, the separator of the present embodiment was described with respect to the battery, but a detailed description of the battery was omitted, but as a battery to which the separator can be applied, in the above-described cylindrical battery or coin-type battery, The material for the electrode material and the electrolytic solution is not particularly limited, and various materials can be used.

  The type of battery may be a primary battery or a secondary battery, and superiority or inferiority in performance does not occur depending on the type of battery.

  Furthermore, the separator can be applied not only to a battery but also to an electric double layer capacitor (EDLC). Even when applied to an electric double layer capacitor, it has sufficient mechanical strength, and even a non-aqueous organic electrolyte has sufficient liquid absorption, high liquid retention, high liquid absorption, and dense. The performance as a separator can be secured.

Claims (11)

A lithium primary battery separator that is interposed between a positive electrode and a negative electrode and is capable of holding an electrolyte solution containing an electrolyte,
The separator is 30-50% by weight of bevelable solvent-spun rayon fiber obtained by spinning a solution in which cellulose is dissolved in a solvent, and 50-70% by weight of composite fiber and synthetic pulp made of olefin resin. A separator for a lithium primary battery, comprising: 2. The separator according to claim 1, wherein the solvent-spun rayon fiber is beaten to a value CSF of 200 ml to 0 ml indicating a degree of beating defined in JIS P8121. 3. The separator according to claim 1, wherein the composite fiber made of the olefin resin has a polyethylene component as a component to be heat-sealed at 140 ° C. or lower and a polypropylene component as another component. The separator according to any one of claims 1 to 3, wherein the composite fiber has a core part of a fiber cross section being a polypropylene component and a sheath part of the fiber cross section being a polyethylene component. The separator according to claim 1 or 2, wherein the synthetic pulp made of the olefin resin is a synthetic pulp made of polyethylene. The solvent-spun rayon is contained in an amount of 30 to 50% by weight, polypropylene component 17.5 to 32.5% by weight, and polyethylene component 27.5 to 42.5% by weight. Item 6. The separator according to any one of Items 5. 30 to 50% by weight of the solvent-spun rayon, 35 to 65% by weight of a composite fiber in which a core part of a fiber cross section is a polypropylene component, and a sheath part of the fiber cross section is a polyethylene component, and 5 to 15% by weight of a polyethylene synthetic pulp The separator according to any one of claims 1 to 6, wherein the separator is mixed at a ratio. A lithium primary battery using the separator according to any one of claims 1 to 7. The lithium primary battery according to claim 8, wherein the outer shape is cylindrical. The lithium primary battery according to claim 9, which has an inside-out structure. 9. The lithium primary battery according to claim 8, wherein the outer shape is a coin shape.