TW201640715A - Non-woven fabric base material, and battery separator - Google Patents

Abstract

The objective of the present invention is to provide a non-woven fabric base material and a battery separator with which it is possible to prevent the occurrence of internal short circuits, without causing a deterioration in discharge capacity under large currents or low temperatures. In a non-woven fabric base material 11 used in a battery separator 10, if an initial thickness measured using a micrometer is T0 ([mu]m), a minimum theoretical thickness obtained using the following formula A is Tmin ([mu]m), and a difference between an amount of displacement Dmax ([mu]m) under maximum loading and an amount of displacement Dmin ([mu]m) under minimum loading, when a loading-unloading test is performed using a plane indenter having a diameter of 200 [mu]m under the following conditions, namely a maximum load of 1.96 x 10-3 N, a minimum load of 0.0196 x 10-3 N, a holding time of 2 seconds, and a loading speed of 0.142 x 10-3 N/second, is a recovery amount R ([mu]m), a compression change ratio calculated using the following formula B is at least equal to 30%, and a shape recovery ratio calculated using the following formula C is at least equal to 60%.

Description

Non-woven substrate and battery separator

The present invention relates to a non-woven substrate for a separator of a battery and a battery separator using the non-woven substrate, and more particularly to a non-woven substrate for a non-aqueous electrolyte rechargeable battery for a lithium ion secondary battery or the like Battery separator.

In the nonaqueous electrolyte rechargeable battery which is a lithium ion secondary battery, the electrode material expands and contracts during charge and discharge, which is one of the causes for shortening the battery life (see Non-Patent Document 1). For example, when the active material expands or contracts with the charge and discharge of the battery, the mixture constituting the electrode expands and contracts, and an internal short circuit due to breakage of the separator occurs. Therefore, in the past, in order to prevent the occurrence of a conventional internal short circuit, it has been proposed to provide a battery in a space where a mixture is fixed (see Patent Document 1).

Further, in the non-aqueous electrolyte rechargeable battery, in addition to the breakage of the separator due to expansion and contraction of the electrode material, an internal short circuit occurs due to heat generation in the battery, shrinkage or melting of the separator, formation of dendrites, and the like. Therefore, a method of increasing the void ratio of the separator has been proposed as a technique for preventing internal short-circuiting (see Patent Document 2).

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] JP-A-9-213366

[Patent Document 2] JP-A-2009-123399

[Non-patent literature]

[Non-Patent Document 1] Peter Ruegg, "Why lithium-ion-batteries fail", [online], October 17, 2013, Swiss Federal Institute of Technology Zürich, ETH Life, [Searched on January 23, 2015], URL <URL: https://www.ethlife.ethz.ch/archive_articles/131017_li-ion-battery_per/index_EN>

Non-aqueous electrolyte rechargeable batteries are required to be "resistant to use at higher currents" or "tolerant to use over a wider temperature range" as their applications expand. However, as described in Patent Document 1, in the mixture installation space, the conduction between the current collector and the mixture or between the active material containing the mixture and the conductive agent is lowered, and the internal resistance of the battery is raised, so that at a higher current or a lower temperature. Sufficient discharge capacity cannot be obtained when used.

On the other hand, the lithium ion secondary battery described in Patent Document 2 improves the void ratio of the separator for the purpose of improving the discharge characteristics while preventing the occurrence of an internal short circuit, but the air resistance is high, and the ratio characteristics of the battery are low. The problem.

The present invention is to solve the above problems, and to provide a device that does not reduce the discharge capacity and can suppress A non-woven substrate and a battery separator that cause internal short-circuiting.

In the nonaqueous electrolyte rechargeable battery, the active material expands or contracts during charge and discharge, but it is presumed that a gap is formed between the active material and the current collector or the active material and the electrolyte. When such a void occurs in the battery, localized spots of charge and discharge occur due to a decrease in conduction, and an internal short circuit easily occurs at a position where electric charges are concentrated. Accordingly, the present inventors focused on the review of the separator to find out that the use of a specific non-woven substrate can follow the expansion and contraction of the active material, thereby suppressing the generation of voids between the current collector or the electrolyte and the mixture, and preventing the charge. The internal short circuit generated collectively, thereby completing the present invention.

That is, the nonwoven fabric substrate of the present invention is used for a nonwoven fabric substrate for a battery separator, and the initial thickness measured by the micrometer is T ₀ (μm), and the minimum theoretical thickness is T _min (the following formula 1). Μm), using a planar indenter with a diameter of 200 μm, a maximum load of 1.96 × 10 ^-3 N, a minimum load of 0.0196 × 10 ^-3 N, a holding time of 2 seconds, and a load speed of 0.142 × 10 ^-3 N / sec carried out under the conditions of the load - displacement amount of the difference D _max (μm) with the maximum load bearing test when the displacement amount in addition to the D _min (μm) is the time of minimum load recovery amount R (μm), by the The compression variation rate calculated by the above formula 2 is 30% or more, and the shape recovery ratio calculated by the following formula 3 is 60% or more.

In the nonwoven fabric substrate of the present invention, when the compression variation rate and the shape recovery ratio are at a specific value or more, and the active material expands or contracts, the separator also follows the expansion and contraction. Therefore, in the case of using the rechargeable battery of the nonwoven substrate of the present invention, the electrode and the nonwoven substrate can be brought into contact without gap even in the case where the active material accompanying charging and discharging is expanded or shrunk.

[Formula 1] Minimum theoretical thickness T _min (μm) = {weight per unit area (g/m ² )} / {density of raw material material (g/cm ³ )}

[Equation 2] Compression variation rate (%) = {(T _{0 -} T _min ) / T ₀ } × 100

[Equation 3] Shape recovery rate (%) = {(R + T _min ) / T ₀ } × 100

In the nonwoven fabric substrate, at least one of the raw material fibers is a composite fiber formed of a low melting point component composed of a polyolefin resin and a high melting point component composed of a thermoplastic resin having a melting point higher than the low melting point component by 20° C. or more. It is better.

In this case, for the high melting point component, for example, either or both of polypropylene and polyester can be used.

In the battery separator of the present invention, the nonwoven substrate is used.

In such a battery separator, it is preferable to provide an insulating layer containing at least one kind of inorganic particles on at least one side of the nonwoven substrate.

In this case, Bob particles, alumina particles, or the like can be used as the inorganic particles constituting the insulating layer.

The battery separator having the insulating layer is, for example, an air resistance of 100 sec/100 ml or less and a maximum pore diameter of 1.0 μm or less as measured by a Gurley tester method prescribed in JIS P8117. The initial thickness of the micro-device measurement is T' ₀ (μm), and the minimum theoretical thickness is T' _min (μm), the planar indenter with a diameter of 200 μm, and the maximum load of 1.96×10 ^-3 N are obtained by the following formula 4. The displacement amount D' _max at the maximum load at the load-de-loading test under the conditions of a minimum load of 0.0196 × 10 ^-3 N, a holding time of 2 seconds, and a load speed of 0.142 × 10 ^-3 N / sec. When the difference between the (μm) and the displacement amount D' _min (μm) at the minimum load is the recovery amount R' (μm), the compression variation rate calculated by the following Equation 5 is 20% or more, and the following formula 6 The calculated shape recovery rate is 60% or more.

[Formula 4] Minimum theoretical thickness T' _min (μm) = {weight per unit area (g/m ² )} / {density of raw material (g/cm ³ )} + total thickness of insulating layer t (μm)

[Equation 5] Compression variation rate (%) = {(T' _{0 -} T' _min ) / T' ₀ } × 100

[Equation 6] Shape recovery rate (%) = {(R' + T' _min ) / T' ₀ } × 100

According to the present invention, the separator can follow the expansion or contraction of the active material without lowering the discharge capacity, and can suppress the occurrence of an internal short circuit.

1~3‧‧‧Composite fiber

4‧‧‧low melting point ingredients

5‧‧‧High melting point ingredients

10‧‧‧Separator

11‧‧‧Nonwoven substrate

12‧‧‧Insulation

Fig. 1A to C are cross-sectional views showing a structural example of a composite fiber.

Fig. 2 is a standard cross-sectional view showing a configuration example of a battery separator having an insulating layer.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Further, the present invention is not limited to the embodiments described below.

(First embodiment)

First, the nonwoven fabric substrate according to the first embodiment of the present invention will be described. The nonwoven fabric substrate of the present embodiment can be used for a battery separator, and has a compression variation rate of 30% or more and a shape recovery ratio of 60% or more.

[compression rate]

The compression variation rate is a value indicating the compression difficulty of the nonwoven fabric substrate, and can be calculated by the following formula 7. Here, T ₀ (μm) in the following formula 7 is the thickness of the nonwoven fabric substrate in an uncompressed initial state as measured by a micrometer. Further, T _min (μm) is the minimum theoretical thickness, and it is assumed that the non-woven substrate is completely crushed, and the resin (material) block or film constituting the raw material fiber is calculated based on the following formula 8.

[Equation 7] Compression variation rate (%) = {(T _{0 -} T _min ) / T ₀ } × 100

[Equation 8] Minimum theoretical thickness T _min (μm) = {weight per unit area (g/m ² )} / {density of raw material (g/cm ³ )}

In addition, when a plurality of raw material fiber materials are used, the density of the raw material fiber material in the above formula 8 may be calculated from the ratio of the density of the resin (material) constituting the raw material fiber to the respective raw material fibers. Further, when a composite fiber composed of two or more kinds of components having different melting points is used, the density of the raw material fiber material may be calculated from the ratio of the area of each component. For example, when a sheath fiber having a sheath core structure formed of a resin having a different melting point is used for the sheath portion and the core portion, the density of the raw material fiber material can be calculated from the ratio of the area of the sheath portion to the core portion.

When the compression variation rate of the nonwoven fabric substrate is less than 30%, when the battery separator is used, the expansion of the active material cannot be followed, and an internal short circuit is likely to occur. On the other hand, in the nonwoven fabric substrate of the present embodiment, the compression variation rate is 30% or more, and the active material may be swollen even when charged.

The compression variation rate of the nonwoven fabric substrate can be adjusted by, for example, changing the component ratio of the composite fibers constituting the raw material fibers, adjusting the composition ratio of the raw material fibers, and the heating and pressing conditions at the time of production, and changing the density of the nonwoven fabric substrate. At the same time, the compression variation rate of the nonwoven fabric substrate of the present embodiment is 30% or more, and the raw material fiber is a low melting point component composed of a polyolefin resin and a thermoplastic resin having a melting point higher than the melting point of the low melting point component by 20 ° C or more. The composite fiber formed of the high melting point component is preferably a composite fiber.

The composite fiber is composed of a sheath portion formed of a low melting point component and a core portion formed of a high melting point component, and the ratio of the area of the sheath portion to the core portion is a sheath portion (low melting point). Ingredients: core (high melting point component) = 60:40~5:95 in the range of composite fibers, using sheath (low melting point component): core (high melting point component) = 50:50~15: 85 composite fibers are better.

Further, the density of the nonwoven fabric substrate is preferably such that the density of the raw material fiber material is in the range of 15 to 70%. The density of the nonwoven fabric substrate is in this range. For example, when the composite fiber of the sheath core structure is used as the raw material fiber, the heating temperature is higher than the melting point of the low melting point component constituting the sheath portion and lower than the melting point of the high melting point component constituting the core portion. It can be heated and pressurized under the conditions of 0.01 to 3.00 MPa. Further, by setting the ratio of the low melting point component of the raw material fibers to 5 to 50% by mass, the density of the nonwoven fabric substrate can be within the above range.

[shape recovery rate]

The shape recovery ratio is a value indicating the recovery property when the nonwoven fabric substrate is compressed, and can be calculated by the following formula 9. Here, in the following formula 9, R (μm) is the recovery amount of the nonwoven fabric substrate, and the displacement amount D _max (μm) at the maximum load measured by the load-and-load test is used, and the minimum load is used. The time shift amount D _min (μm) is calculated by the following formula 10. In addition, the load-de-loading test system uses a planar indenter with a diameter of 200 μm, a maximum load of 1.96 × 10 ^-3 N, a minimum load of 0.0196 × 10 ^-3 N, a holding time of 2 seconds, and a load speed of 0.142 × 10 ^-3 N / sec.

[Equation 9] Shape recovery rate (%) = {(R + T _min ) / T ₀ } × 100

[Equation 10] R=D _max -D _min

When the shape recovery rate of the nonwoven fabric substrate is less than 60%, the shrinkage of the active material accompanying the discharge cannot be followed, and an internal short circuit is likely to occur. On the other hand, in the nonwoven fabric substrate of the present embodiment, since the shape recovery ratio is 60% or more, even if the volume of the mixture is reduced by discharge, it can be followed. Further, from the viewpoint of improving the followability of the shrinkage of the active material, the shape recovery ratio of the nonwoven fabric substrate is preferably 70% or more.

The shape recovery ratio of the nonwoven fabric substrate, for example, when the composite fiber of the sheath fiber structure is used as the raw material fiber, can be adjusted by changing the ratio of the low melting point component and the high melting point component in the composite fiber or the ratio of the raw fiber to the composite fiber. Further, in order to make the shape recovery ratio of the nonwoven fabric substrate of the present embodiment 60% or more, the raw material fiber uses a low melting point component composed of a polyolefin resin and a thermoplasticity higher than a melting point of the low melting point component by 20 ° C or more. A composite fiber formed of a high melting point component composed of a resin is preferred.

In the composite fiber, the sheath portion composed of a low melting point component and a core portion composed of a high melting point component are used, and the ratio of the area of the sheath portion to the core portion is a sheath portion (low melting point component): core Part (high melting point component) = 60:40~5:95 in the range of composite fibers, using sheath (low melting point component): core (high melting point component) = 50:50~15:85 composite fiber Better. In addition, when the ratio of the conjugate fiber contained in the raw material fiber is adjusted, the ratio of the conjugate fiber formed by the low-melting component and the high-melting component contained in the raw material fiber is preferably 60% by volume or more.

[raw fiber]

In the raw material fiber of the nonwoven fabric substrate of the present embodiment, for example, a low melting point component composed of a polyolefin resin and a thermoplastic resin having a melting point higher than a melting point of the low melting point component by 20 ° C or more can be used. A composite fiber formed by a high melting point component. 1A to 1C are cross-sectional views showing a structural example of a composite fiber. The structure of the composite fiber used for the raw material fiber is not particularly limited, and a sheath-core composite type as shown in FIG. 1A, an eccentric sheath core type as shown in FIG. 1B, and a side-by-side type as shown in FIG. 1C can be used. Various structures such as a core type (island type).

In the case of the sheath-core composite type composite fiber 1 shown in Fig. 1A, the eccentric sheath-core type composite fiber 2 and the multi-core type (island type) composite fiber shown in Fig. 1A, the sheath portion (sea portion) has a low melting point component. 4 is formed, and the core (island portion) is formed with a high melting point component 5. On the other hand, in the case of the side-by-side type composite fiber 3 shown in Fig. 1C, the ratio of the low melting point component 4 and the high melting point component 5 is in the sectional area ratio, and the low melting point component: high melting point component = 1:9 to 9:1. It is better.

By using the composite fiber having such a constitution in the raw material, the compression variation rate of the nonwoven fabric substrate can be 30% or more, and the shape recovery ratio can be 60% or more. Further, when a plurality of types of fibers are used as the raw material, at least one type of composite fiber of the above resin may be used.

On the other hand, the nonwoven fabric substrate for the separator for a nonaqueous electrolyte secondary battery is preferably formed of a material that does not contain water from the viewpoint of preventing internal short circuit. Specifically, the raw material fiber is preferably formed of a polyolefin resin or a polyester resin. Further, when the raw material fiber is a composite fiber formed of the low melting point component and the high melting point component, it is preferred that the high melting point component contains either or both of polypropylene and polyester. Thereby, the drying time of the battery manufacturing step can be shortened, and the occurrence of a failure such as a short circuit can be reduced by moisture absorption.

As described above, in the nonwoven fabric substrate of the present embodiment, since the compression variation rate and the shape recovery ratio are at a specific value or more, the cushioning property is good, and the expansion and contraction of the active material accompanying the charge and discharge can be followed. Further, when the nonwoven fabric substrate of the present embodiment is used for a battery separator, it is possible to suppress voids between the current collector and the mixture due to expansion and contraction of the active material, and thus it is not possible to The localized spot of charge and discharge due to the decrease in conduction can prevent the occurrence of an internal short circuit due to charge concentration. In other words, by using the non-woven substrate of the present embodiment, it is possible to suppress the occurrence of an internal short circuit without reducing the discharge characteristics of the nonaqueous electrolyte secondary battery such as a lithium ion secondary battery.

(Second embodiment)

Next, a battery separator according to a second embodiment of the present invention will be described. The battery separator (hereinafter simply referred to as a separator) of the present embodiment is a nonwoven fabric substrate according to the first embodiment.

[non-woven substrate]

The thickness of the nonwoven fabric substrate used in the battery separator of the present embodiment is not particularly limited, and may be appropriately set depending on the type, performance, size, and the like of the battery. However, from the viewpoint of preventing internal short circuit and increasing battery capacity, non-woven fabric is used. The thickness of the substrate is preferably from 5 to 200 μm. When the thickness of the nonwoven substrate is less than 5 μm, the insulation between the electrodes may not be sufficiently ensured. Further, when the thickness of the nonwoven substrate exceeds 200 μm, the proportion of the separator is too high in a limited battery volume, resulting in a decrease in battery capacity. .

The configuration of the battery separator of the present embodiment is not particularly limited. For example, one or both surfaces of the nonwoven fabric substrate may be provided with an insulating layer containing at least one type of inorganic particles. 2 is a standard cross-sectional view showing a configuration example of a battery separator having an insulating layer.

[insulation layer 12]

The inorganic particles contained in the insulating layer 12 provided in the separator 10 may have insulating properties. For example, aluminum hydroxide, aluminum oxide, cerium oxide, zirconium oxide, aluminum silicate, or citric acid may be used. A metal oxide such as magnesium, titanium oxide or zinc oxide, or a particle composed of a poorly soluble salt such as barium sulfate or a general inorganic particle such as cerium oxide particles. However, the electrolyte is containing fluorine In the case of a substance, the use of cerium oxide particles may cause hydrogen fluoride to erode the insulating layer. Therefore, it is preferred to use boomer particles or alumina particles.

The size of the inorganic particles is not particularly limited, and when the maximum pore diameter of the separator 10 is 1.0 μm or less, it is preferred to use inorganic particles having a weight average particle diameter of 2.0 μm or less as measured by a light scattering method. Further, the maximum pore diameter and the average particle diameter of the separator 10 can be measured using a commercially available measuring device (the boundary potential ‧ particle diameter measuring system, etc.).

The thickness of the insulating layer 12 is also not particularly limited and may be appropriately set depending on the type, performance, size, and the like of the battery. However, the thicker the insulating layer 12, the lower the air resistance, and the thinner the insulating layer 12, the easier the dendrite is. Short circuit. Therefore, from the viewpoint of improving the air resistance and preventing the occurrence of an internal short circuit, the thickness of the insulating layer 12 is preferably 2 to 20 μm, and more preferably 4 to 8 μm.

Further, the insulating layer 12 may be formed on the surface of the nonwoven fabric substrate 11 in the state in which the inorganic particles are laminated in the form of a binder resin or the like; or, in the state in which the inorganic particles are infiltrated in a portion of the nonwoven substrate 11 . When the inorganic particles infiltrate in a portion of the nonwoven substrate 11, the thickness of the insulating layer 12 means the range in which the inorganic particles exist.

[Characteristics of separators for insulating layer batteries]

In the battery separator of the present embodiment, the insulating layer 12 is preferably one having a gas impermeability of 100 sec/100 ml or less and a maximum pore diameter of 1.0 μm or less as measured by a Gurley tester method prescribed in JIS P8117. Thereby, it is possible to suppress a decrease in battery ratio characteristics or an occurrence of an internal short circuit. Further, when the maximum pore diameter of the separator exceeds 1.0 μm, the dendrite penetrates the separator to cause an internal short circuit.

Further, in the battery separator of the present embodiment, the insulating layer 12 is provided, and it is preferable that the compression variation rate is 20% or more by the following formula 11. Here, T' ₀ (μm) in the following formula 11 is the thickness of the separator in the initial state of uncompression measured by the micrometer. Further, T' _min (μm) is the minimum theoretical thickness of the separator calculated from the following formula 12, which is the minimum theoretical thickness T _min (μm) of the nonwoven fabric substrate calculated by the above formula 8 plus the total thickness of the insulating layer t The value of (μm). As described above, the compressive variation rate of the separator is 20% or more, and the non-woven substrate can maintain the followability to the expansion of the active material.

[Equation 11] Compression variation rate (%) = {(T' _{0 -} T' _min ) / T' ₀ } × 100

[Equation 12] Minimum theoretical thickness T' _min (μm) = {weight per unit area (g/m ² )} / {density of raw material (g/cm ³ )} + total thickness of insulating layer t (μm)

Further, in the battery separator of the present embodiment, it is preferable that the shape recovery ratio calculated by the following formula 13 is 60% or more. Here, in the following formula 13, R' is the recovery amount of the separator, which is the displacement amount D' _max (μm) at the maximum load measured by the load-loading test and the displacement amount D at the minimum load. ' _min (μm), the value calculated by the following formula 14. In addition, the diaphragm load-de-loading test system uses a planar indenter with a diameter of 200 μm, a maximum load of 1.96 × 10 ^-3 N, a minimum load of 0.0196 × 10 ^-3 N, a holding time of 2 seconds, and a load. The speed is 0.142 × 10 ^-3 N / sec.

[Equation 13] Shape recovery rate (%) = {(R' + T' _min ) / T' ₀ } × 100

[Equation 14] R'=D' _max -D' _min

Thus, by the shape recovery ratio of the separator of 60% or more, it is possible to maintain the shrinkage of the material of the nonwoven fabric substrate and the followability of the volume reduction of the accompanying mixture.

As described in detail above, the battery separator of the present embodiment has a good cushioning property, and the nonwoven fabric substrate which can follow the expansion and contraction of the active material accompanying the charge and discharge can suppress the expansion and contraction of the active material. The gap between the body and the mixture. Therefore, when the battery separator of the present embodiment is used, the discharge characteristics are not lowered, and the occurrence of an internal short circuit due to breakage of the separator can be suppressed. The battery separator of the present embodiment can be applied to various types of batteries, and is particularly suitable for a nonaqueous electrolyte rechargeable battery such as a lithium ion secondary battery.

2 shows a configuration example in which the insulating layer 12 is provided on one surface of the nonwoven fabric substrate 11. However, the present invention is not limited thereto, and the insulating layer 12 may be provided on both surfaces of the nonwoven substrate 11, and in this case, the same can be obtained. The effect. Further, the configuration and effect of the nonwoven substrate in the battery separator of the present embodiment are the same as those of the first embodiment.

Hereinafter, the effects of the present invention will be specifically described by way of examples and comparative examples.

(First embodiment)

First, in the first embodiment of the present invention, the nonwoven fabric substrates of the examples and the comparative examples were produced by the methods described below, and the properties were evaluated.

(1) Production of non-woven fabric

The raw material fiber is a composite fiber composed of a low melting point component composed of polyethylene (PE) and a high melting point component composed of polypropylene (PP) or polyethylene terephthalate (PET), and polypropylene ( A single fiber composed of PP) was prepared as shown in Table 1 below to prepare a nonwoven fabric roll A to S of a nonwoven fabric substrate. Further, the nonwoven fabric rolls A, C, E, and F were formed in a ratio of 75.1% by volume of the composite fibers in the raw material fibers.

【Table 1】

Specifically, first, each raw material fiber was cut into short fibers of 3 mm, and uniformly dispersed in 15 L of water to which a viscosity adjusting agent was added to prepare a dispersion liquid. Next, the dispersion Paper was made on a mesh of dimensions of 250 mm in length and 200 mm in width to make a wet web. The obtained wet web was sandwiched between two rubber heating plates, and dried under pressure at a temperature of 140 ° C and a pressure of 0.049 MPa for 1 minute using a general-purpose heating press. Thereby, the low melting point component of the short fiber is melt-bonded between the short fibers to obtain the original fiber A to S for the nonwoven fabric substrate.

(2) Production of evaluation samples

Next, using the original fiber A to S, the No. was produced by the method shown below. Non-woven substrate of 1~17, 19~23. In addition, for comparison, prepare No. 18 PET film. In addition, the following No. The non-woven substrate of 1~16, 19~23 is an embodiment of the invention, No. 17 non-woven substrate and No. The film substrate of 18 is a comparative example of the present invention.

<No. 1>

The original fiber A produced by the above method was sandwiched between two rubber heating plates, and the surface was flattened by pressurizing for 5 minutes under the conditions of a temperature of 120 ° C and a pressure of 20 MPa using a general-purpose heating press. , making No. 1 non-woven substrate.

<No. 2>

Except for the use of the original fiber B, and the aforementioned No. 1 under the same method and conditions, making No. 2 non-woven substrate.

<No. 3>

Except for the use of the original fiber C, and the aforementioned No. 1 under the same method and conditions, making No. 3 non-woven substrate.

<No. 4>

The surface of the original fiber D is not formed by the flattening of the surface by pressurization. 4 non-woven substrate.

<No. 5>

The original fiber D was used, except that the temperature of the press machine was changed to 130 ° C, and the aforementioned No. 1 under the same method and conditions, making No. 5 non-woven substrate.

<No. 6>

Except for the use of the original fiber E, with the aforementioned No. 1 under the same method and conditions, making No. 6 non-woven substrate.

<No. 7>

Except for the use of the original fiber F, with the aforementioned No. 1 under the same method and conditions, making No. 7 non-woven substrate.

<No. 8>

The surface of the original fiber G is not formed by the flattening of the surface by pressurization. 8 non-woven substrate.

<No. 9>

The surface of the original fiber H is not formed by the flattening of the surface by pressurization. 9 non-woven substrate.

<No. 10>

The surface of the original fiber I is not formed by the flattening of the surface by pressurization. 10 non-woven substrate.

<No. 11>

The laminated original fiber A and the original fiber B are sandwiched between two rubber heating plates in their state. In the meantime, a general-purpose heating presser was used, and the temperature was raised at a temperature of 120 ° C and a pressure of 20 MPa for 5 minutes to prepare No. 11 non-woven substrate.

<No. 12>

Except for the use of the original fiber J, with the aforementioned No. 1 under the same method and conditions, making No. 12 non-woven substrate.

<No. 13>

Except for the use of the original fiber K, with the aforementioned No. 1 under the same method and conditions, making No. 13 non-woven substrate.

<No. 14>

Except for the use of the original fiber L, and the aforementioned No. 1 under the same method and conditions, making No. 14 non-woven substrate.

<No. 15>

Except for the use of the original fiber M, with the aforementioned No. 1 under the same method and conditions, making No. 15 non-woven substrate.

<No. 16>

Except for the use of the original fiber N, with the aforementioned No. 1 under the same method and conditions, making No. 16 non-woven substrate.

<No. 17>

The original fiber D was used, except that the temperature of the press machine was changed to 145 ° C, and the aforementioned No. 1 under the same method and conditions, making No. 17 non-woven substrate.

<No. 18>

PET film with a thickness of 100 μm as No. 18 substrate.

<No. 19>

Except for the use of the original fiber R, with the aforementioned No. 1 under the same method and conditions, making No. 19 non-woven substrate.

<No. 20>

Except for the use of the original fiber S, with the aforementioned No. 1 under the same method and conditions, making No. 20 non-woven substrates.

<No. 21>

The surface of the original fiber O is not formed by the flattening of the surface by pressurization. 21 non-woven substrate.

<No. 22>

The surface of the original fiber P is not formed by the flattening of the surface by pressurization. 22 non-woven substrate.

<No. 23>

Except for the use of the original fiber Q, and the aforementioned No. 1 under the same method and conditions, making No. 23 non-woven substrate.

(3) Evaluation

Next, the No. produced by the aforementioned method. Non-woven substrate of 1~17, 19~23 and No. The film substrate of 18 was evaluated by the method shown below.

[weight per unit area]

The weight per unit area of each of the five points of the substrate was measured in accordance with the method specified in JIS P8124. Next, the average value was calculated as the weight per unit area of each base material.

〔thickness〕

The thickness of any three points was measured using a micrometer (anti-freezing agent micrometer MDC-25MJ manufactured by Mitsutoyo Co., Ltd.), and the average value was the thickness of each substrate.

〔density〕

The weight per unit area measured by the method specified in JIS P8124, divided by the individual thickness, is the density of each substrate.

[Air impermeability]

The air impermeability of each of the substrates was measured using an airtightness tester (G-B2, manufactured by Toyo Seiki Co., Ltd.) in accordance with JIS P8117. At this time, each of the substrates was placed on a test stand of the airtightness tester, and a load of 567 g of mass was applied to the cylindrical members of the respective substrates, and the fields in the cylinders of the respective substrates (diameter 28.6 mm) were used. Area: 645 mm ² ) The average time was measured by measuring the time required for 100 ml of air to pass at 3 points.

[compression rate]

Each compression rates of change of substrate, 7, each of the substrates by the beginning of the value obtained by subtracting the thickness T ₀ of the theoretical minimum thickness T _min Based on the foregoing equation, divided by the initial thickness T ₀ of each substrate was calculated. Further, the minimum theoretical thickness T _{min is} calculated by dividing the weight per unit area of the substrate by the density of the raw material fiber material based on the above formula 8. In this case, the resin material constituting the fiber density of each of the (material) of, PP was 0.905g / cm ^3, PE was 0.915g / cm ^3, PET was 1.38g / cm ^3, and all these values with the raw material fibers The ratio of the composite fiber to the sheath core structure is calculated from the ratio of the area of the sheath to the core.

[buffering]

The cushioning properties of the respective substrates were evaluated by the value of the shape recovery rate. Specifically, each substrate was set on a test stand of a micro compression tester, a flat press head having a diameter of 200 μm was used for the upper press ram, and a KSK plate was used for the lower press plate, and a load-de-load test was performed to measure the recovery amount R. At this time, the maximum load was 1.96 × 10 ^-3 N, the minimum load was 0.0196 × 10 ^-3 N, the maintenance time was 2 seconds, and the load speed was 0.142 × 10 ^-3 N / sec.

The shape recovery rate (%) of each substrate is the sum of the recovery amount R (μm) and the minimum theoretical thickness T _min (μm) measured by the aforementioned load-and-load test, divided by the initial thickness T ₀ of each substrate. Calculated. Further, the cushioning property can be evaluated in the following two stages according to the shape recovery ratio (%) calculated by the above method.

○: The substrate was compressed, and the shape recovery rate was 60% or more.

×: The shape recovery rate was less than 60% or the substrate was not compressed (unmeasurable).

The above results are shown in Tables 2 and 3 below.

【Table 2】

As shown in Table 3 above, No. of Comparative Example of the Present Invention. The 17 non-woven base material had a compression change rate of 5% and a low value, and the force was not crushed by the application of force, so the shape recovery rate could not be measured. Similarly, the No. of the comparative example. The PET film of 18 could not be compressed and could not be crushed, so the shape recovery rate could not be measured. Further, these No. 17 and No. The substrate of 18 does not easily pass through the air, so the discharge characteristics are lowered, and it is not suitable for the battery separator.

On the other hand, as shown in the above Table 2 and Table 3, the embodiment of the present invention is No. The non-woven fabrics of 1~16 and 19~23 have a compression rate of 30% or more and a high value, and the shape recovery rate is also 60% or more, and the cushioning property is good.

(Second embodiment)

Next, in the second embodiment of the present invention, the battery separators of the examples and the comparative examples were produced by the methods described below, and the properties thereof were evaluated.

(1) Production of samples

In the present embodiment, an insulating layer containing inorganic particles is provided on one surface of the nonwoven fabric substrate produced in the first embodiment, and No. is produced. 31~36 battery separator. In addition, the following No. The diaphragm of 31 to 35 is an embodiment of the present invention, No. The separator of 36 is a comparative example of the present invention.

<No. 31>

To 59.75 parts by mass of water, 31.5 parts by mass of Boom (alumina-water-based) particles (average particle diameter: 1.0 μm) as inorganic particles were dispersed. In the dispersion, 8.75 parts by mass of an anthranone acrylic resin to which an adhesive was added was mixed by stirring, and a coating liquid having a solid content concentration of 35% by mass was obtained.

Then, No. 2 non-woven fabric is cut into the specified size, after the non-woven fabric The surface of the substrate was spray coated with a water-repellent agent, which was dried at 80 ° C for 10 minutes. Next, one side of the nonwoven fabric substrate was hydrophilized by a corona surface treatment apparatus with a condition of 0.10 kW, a speed of 3.0 m/min, and a path number of 1. Then the surface of the hydrophilization treatment, using No. 8 line rod (made by Matsuo Industry Co., Ltd.), coated with coating liquid. It was dried at a temperature of 100 ° C for 2 minutes to form an insulating layer, and No. was obtained. 31 diaphragm. The No. The thickness of the insulating layer of the separator of 31 was 4 μm.

<No. 32>

Except using No. In addition to the line rod of 12 (made by Matsuo Industry Co., Ltd.), the aforementioned No. No. 31 under the same method and conditions, making No. 32 diaphragm. The No. The insulating layer of the separator of 32 has a thickness of 7 μm.

<No. 33>

Except using No. In addition to the 16-line bar (made by Matsuo Industry Co., Ltd.), the aforementioned No. No. 31 under the same method and conditions, making No. 33 diaphragm. The No. The insulating layer of the separator of 33 has a thickness of 10 μm.

<No. 34>

Using a 0.1% aqueous solution of a commercially available hydrophilic agent (sodium dodecyl sulfate), a spray coating was applied to the surface of the nonwoven fabric roll A, and then dried at 80 ° C for 10 minutes to obtain a hydrophilic nonwoven fabric. Volume A'. Further, a commercially available water repellent was applied, and a spray coating was applied to the surface of the nonwoven fabric roll B, followed by drying at 80 ° C for 10 minutes to obtain a hydrophobic nonwoven fabric roll B'. Then, the laminated non-woven fabric roll A' and the non-woven fabric roll B' are sandwiched between two rubber heating plates in a state thereof, and a general-purpose heating presser is used at a temperature of 120 ° C and a pressure of 20 MPa. Pressurize for 5 minutes to form a non-woven substrate.

On the hydrophilic surface (non-woven fabric roll A' side) of such a nonwoven substrate, No. is used. 8 line rod (made by Matsuo Industry Co., Ltd.) coated with No. 31 modulated coating solution. This was dried at a temperature of 100 ° C for 2 minutes to form an insulating layer, and No. was made. 34 diaphragm. The No. The insulating layer of the separator of 34 has a thickness of 4 μm.

<No. 35>

In No. 1 non-woven substrate, except No. In addition to the coating liquid prepared by coating the 16-bar rod (made by Matsuo Industry Co., Ltd.), the aforementioned No. No. 31 under the same method and conditions, making No. 35 diaphragm. The No. The thickness of the insulating layer of 35 is 10 μm.

<No. 36>

Except using No. In addition to the 17 non-woven substrate, the aforementioned No. No. 31 under the same method and conditions, making No. 36 diaphragm. The No. The insulating layer of the separator of 36 has a thickness of 4 μm.

(3) Evaluation

Next, the No. produced by the aforementioned method. The separator of 31 to 36 was evaluated by the method shown below. Further, the weight per unit area, the thickness, the air resistance, the compression change rate, the shape recovery ratio, and the cushioning property of each separator were measured in the same manner as in the above-described first embodiment.

[maximum aperture]

The maximum pore size of each of the battery separators of the examples and the comparative examples was measured using a pore size distribution measuring instrument (manufactured by Quantachrome ‧ Japan Co., Ltd., Porometer 3G zh).

The above results are summarized as shown in Table 4 below. Further, in the separator structure shown in Table 4 below, the "layered" system indicates the shape of the insulating layer containing inorganic particles on the nonwoven fabric substrate. In the state of "filling", the state in which the inorganic particles constituting the insulating layer are infiltrated in one of the non-woven base materials.

As shown in Table 4 above, No. of the embodiment of the present invention. The 31~35 diaphragm has low air resistance and excellent cushioning properties. In contrast, the comparative example of the present invention is No. The diaphragm of 36, the air is not easy to pass, and the cushioning property is also poor.

From the above results, it has been confirmed that by using the nonwoven fabric substrate of the present invention, it is possible to realize a battery separator which can suppress the occurrence of an internal short circuit without lowering the discharge capacity.

10‧‧‧Separator

11‧‧‧Nonwoven substrate

12‧‧‧Insulation

Claims (7)

A non-woven substrate for a non-woven substrate for a battery separator, characterized in that the initial thickness measured by the micrometer is T ₀ (μm), and the minimum theoretical thickness obtained by the following formula A is T _min (μm) ), using a planar indenter with a diameter of 200 μm, a maximum load of 1.96 × 10 ^-3 N, a minimum load of 0.0196 × 10 ^-3 N, a holding time of 2 seconds, and a load speed of 0.142 × 10 ^-3 N / sec. for load conditions - when the difference between the displacement amount D _max (μm) with the maximum load bearing test when the displacement amount in addition to the D _min (μm) is the time of minimum load recovery amount R (μm), by the following The compression variation rate calculated by the equation B is 30% or more, and the shape recovery ratio calculated by the following formula C is 60% or more, and the minimum theoretical thickness T _min (μm) = {weight per unit area (g/m ² )} /{Density of raw fiber material (g/cm ³ )} (A) Compression variation rate (%) = {(T _{0 -} T _min ) / T ₀ } × 100 (B) Shape recovery rate (%) = {(R+T _min )/T ₀ }×100...(C). The non-woven base material according to the first aspect of the invention, wherein at least one of the raw material fibers, the low melting point component composed of the polyolefin resin, and the thermoplastic resin having a melting point higher than the low melting point component by 20 ° C or more A composite fiber formed by a high melting point component. The non-woven base material according to claim 2, wherein the high-melting-point component contains either or both of polypropylene and polyester. A separator for a battery, characterized by using any one of items 1 to 3 of the patent application scope A non-woven substrate is loaded. The battery separator according to claim 4, wherein an insulating layer containing at least one type of inorganic particles is provided on at least one surface of the nonwoven substrate. The battery separator according to claim 5, wherein the inorganic particles are boomer particles or alumina particles. The battery separator according to the fifth aspect of the invention, wherein the airtightness measured by a Gurley tester method defined in JIS P8117 is 100 sec/100 ml or less, and the maximum pore diameter is 1.0 μm or less. The initial theoretical thickness measured by the micrometer is T' ₀ (μm), and the minimum theoretical thickness obtained by the following formula D is T' _min (μm), and a planar indenter with a diameter of 200 μm is used, and the maximum load is 1.96×10. ^-3 N, the minimum load is 0.0196 × 10 ^-3 N, the holding time is 2 seconds, and the load speed is 0.142 × 10 ^-3 N / sec. The displacement at the maximum load at the load-deload test is performed. When the difference between D' _max (μm) and the displacement amount D' _min (μm) at the minimum load is the recovery amount R' (μm), the compression variation rate calculated by the following formula E is 20% or more. The shape recovery rate calculated by the following formula F is 60% or more, and the minimum theoretical thickness _T'min (μm) = {weight per unit area of the nonwoven fabric substrate (g/m ² )} / {the density of the raw material material (g/) Cm ³ )}+Total thickness of insulating layer t(μm)...(D) Compression variation rate (%)={(T' ₀ -T' _min )/T' ₀ }×100...(E) Shape recovery rate ( %)={(R'+T' _min )/T' ₀ }×100...(F).