JP5420938B2 - Nonaqueous secondary battery separator and nonaqueous secondary battery - Google Patents

Description

  The present invention relates to a separator for a non-aqueous secondary battery, and more particularly to a technique for improving the safety and battery characteristics of a non-aqueous secondary battery.

  Non-aqueous secondary batteries represented by lithium ion secondary batteries have a high energy density and are widely used as main power sources for portable electronic devices such as mobile phones and laptop computers. This lithium ion secondary battery is required to have a higher energy density, but ensuring safety is a technical issue.

  The role of the separator is important in ensuring the safety of the lithium ion secondary battery, and from the viewpoint of having a shutdown function, polyolefins, particularly polyethylene microporous membranes are currently used. Here, the shutdown function refers to a function of blocking pores in the microporous membrane when the temperature of the battery rises, and blocking the current, and has a function of preventing thermal runaway of the battery.

  On the other hand, lithium ion secondary batteries have been increased in energy density year by year, and heat resistance has been required in addition to a shutdown function to ensure safety. However, the shutdown function is contrary to heat resistance because the operating principle is to close the hole by melting polyethylene. For this reason, if the battery continues to be exposed to a temperature higher than the temperature at which the shutdown function is activated after the shutdown function is activated, the separator may be melted (so-called meltdown). As a result of this meltdown, a short circuit occurs inside the battery, and as a result, a large amount of heat is generated, and the battery is exposed to dangers such as smoke, ignition, and explosion. For this reason, in addition to the shutdown function, the separator is required to have sufficient heat resistance so that meltdown does not occur near the temperature at which the shutdown function operates.

  In this regard, conventionally, in order to achieve both heat resistance and a shutdown function, a technique has been proposed in which one or both surfaces of a polyolefin microporous membrane are covered with a heat resistant porous layer or a nonwoven fabric made of heat resistant fibers is laminated. ing. For example, a nonaqueous electrolyte battery separator is known in which a heat-resistant porous layer made of a heat-resistant resin such as polyamide or polyimide is laminated on one side or both sides of a polyethylene microporous membrane (see Patent Documents 1 to 5).

  By the way, in terms of increasing the capacity of lithium ion batteries, in recent years, various high capacity type positive electrode materials and negative electrode materials have been developed. However, such high-capacity positive and negative electrode materials often have large volume changes during charging and discharging, and thus a problem arises in that battery characteristics deteriorate due to large volume changes in electrodes. .

  That is, since the separator is disposed between the positive electrode and the negative electrode in the battery, when the battery is charged / discharged, a compressive force or a restoring force acts in the thickness direction of the separator due to the expansion / contraction of the electrode. . In the case of conventional low-capacity positive and negative electrode materials such as lithium cobaltate and hard carbon, since the volume change of the electrode is small, the deformation in the thickness direction of the separator is small, and the battery characteristics are not particularly affected. However, when an electrode material having a large volume change rate during charge / discharge, such as a high-capacity positive / negative active material, is used, the acting force applied from the electrode to the separator also increases. If the separator cannot follow the volume change of the electrode, the separator may be locally folded or wrinkled, or a gap may be formed between the electrode and the separator. In particular, in a cylindrical or flat cylindrical battery in which an electrode and a separator are wound, since a shearing force is likely to be generated between the separator and the electrode, problems such as breakage of the separator become more serious. Furthermore, in the case of conventional heat-resistant separators as described in Patent Documents 1 to 3, since the heat-resistant porous layer is formed of a heat-resistant resin having poor slip properties, problems such as breakage of the separator are more likely to occur. It can be said. Such breakage of the separator or the like eventually leads to deterioration of the cycle characteristics of the battery.

  In this regard, the techniques described in the conventional patent documents 4 and 5 are configured to include an inorganic filler in the heat-resistant porous layer, and therefore, a slight improvement is expected with respect to a decrease in slipperiness of the heat-resistant resin. However, the problem of electrode volume change remains unresolved.

JP 2002-355938 A JP 2005-209570 A JP 2005-285385 A JP 2000-030686 A JP 2008-300362 A

  In view of the above problems, the present invention provides a separator that can suitably follow the volume change of an electrode even when an electrode having an excellent shutdown function and heat resistance and having a large volume change rate during charge and discharge is used. The purpose is to provide.

In order to solve the above problems, the present invention adopts the following configuration.
1. A separator for a non-aqueous secondary battery comprising a polyolefin porous substrate and a heat-resistant porous layer containing a heat-resistant resin coated on one or both surfaces of the porous substrate, the contact bottom surface having a diameter Using a contact-type film thickness meter having a circular contact terminal of 0.5 cm, the film thickness measured at an applied load of 36 g / cm ² is L1, and the film thickness measured at an applied load of 1.2 kg / cm ² is A separator for a non-aqueous secondary battery, wherein L1−L2 = 2.0 to 10 μm when L2.
2. 2. The separator for a non-aqueous secondary battery according to 1 above, wherein the separator has a static friction coefficient of 0.3 to 1.0.
3. 3. The non-aqueous secondary layer according to 1 or 2 above, wherein the heat-resistant porous layer has a porosity of 50 to 80% and an average pore diameter measured by a BET method of 50 to 300 nm. Battery separator.
4). Any of the above 1-3, wherein the heat-resistant resin is at least one selected from the group consisting of aromatic polyamide, polyimide, polyamideimide, polyethersulfone, polysulfone, polyetherketone, polyetherimide. A separator for a non-aqueous secondary battery according to 1.
5. About the said porous base material, when the film thickness measured with the applied load of 36 g / cm < ² > using the said contact-type film thickness meter is set to L3, and the film thickness measured with the applied load of 1.2 kg / cm < ² > is set to L4 L3-L4 = 0.1 to 2.0 μm, The separator for a non-aqueous secondary battery according to any one of 1 to 4 above.
6). 6. The separator for a non-aqueous secondary battery according to 5 above, wherein the porous substrate has a porosity of 30 to 70% and an average pore diameter measured by a BET method of 10 to 400 nm. .
7). The non-aqueous secondary battery separator according to any one of 1 to 6, wherein the heat-resistant porous layer contains an inorganic filler.
8). 8. The separator for a non-aqueous secondary battery as described in 7 above, wherein the inorganic filler comprises at least one of a metal hydroxide and a metal oxide.
9. 9. The separator for a non-aqueous secondary battery as described in 7 or 8 above, wherein the inorganic filler has an average particle size of 0.1 to 1 μm.
10. The separator for a nonaqueous secondary battery according to any one of 7 to 9, wherein the content of the inorganic filler is 0.4 to 4 times the volume of the heat resistant resin.
11. A non-aqueous secondary battery for obtaining an electromotive force by doping and dedoping of lithium, a positive electrode having a positive electrode current collector and a positive electrode active material layer, a negative electrode having a negative electrode current collector and a negative electrode active material layer, and A non-aqueous secondary battery comprising the separator for a non-aqueous secondary battery according to any one of 1 to 10 and a non-aqueous electrolyte disposed between electrodes.
12 12. The non-aqueous secondary battery as described in 11 above, wherein the positive electrode active material has a volume change rate of 1% or more in the process of dedoping lithium.
13. 13. The nonaqueous secondary battery as described in 12 above, wherein the negative electrode active material has a volume change rate of 3% or more in the process of doping lithium.

  ADVANTAGE OF THE INVENTION According to this invention, the separator excellent in the shutdown function, heat resistance, and the followable | trackability to the volume change of an electrode can be provided. Such a separator is very useful as a technique for improving the safety and battery characteristics of a non-aqueous secondary battery.

Hereinafter, embodiments of the present invention will be described in detail.
[Separator for non-aqueous secondary battery]
A separator for a non-aqueous secondary battery according to the present invention comprises a non-aqueous two-layer battery comprising a polyolefin porous substrate and a heat-resistant porous layer containing a heat-resistant resin coated on one or both surfaces of the porous substrate. Using a contact film thickness meter having a circular contact terminal with a contact bottom surface of 0.5 cm in diameter, which is a separator for a secondary battery, the film thickness measured at an applied load of 36 g / cm ² is L1, and the applied load When the film thickness measured at 1.2 kg / cm ² is L2, L1−L2 = 2.0 to 10 μm, which is a non-aqueous secondary battery separator.

  According to the separator for a non-aqueous secondary battery of the present invention, a shutdown function is obtained by the polyolefin porous substrate, and heat resistance that does not melt even at a temperature higher than the shutdown temperature is obtained by the heat-resistant porous layer. Can do. In the separator of the present invention, the relationship between the film thickness L1 when the contact pressure to the separator is relatively weak and the film thickness L2 when the contact pressure is relatively strong is L1-L2 = 2. Since the flexibility is large so as to be 0 to 10 μm, it is possible to suitably follow the volume change of the electrode. Therefore, even when an electrode having a large volume change rate at the time of charging / discharging is used, it is possible to prevent problems such as local folding or wrinkling of the separator or a gap between the electrode and the separator. it can. For this reason, according to the separator of this invention, the battery excellent in safety | security and cycling characteristics can be provided, and it can use suitably for the battery especially using the high capacity | capacitance type electrode material.

The separator for a non-aqueous secondary battery of the present invention has a film thickness difference when the film thickness measured at an applied load of 36 g / cm ² is L1, and the film thickness measured at an applied load of 1.2 kg / cm ² is L2. It is necessary to set it as the range of L1-L2 = 2.0-10micrometer. A more preferable film thickness difference (L1-L2) is in the range of 2.0 to 5.0 μm. Here, the film thickness difference (L1-L2) referred to in the present invention represents an index of “flexibility” of the separator. In addition, when the film thickness difference (L1-L2) is less than 2.0 μm, it becomes difficult for the separator to follow the volume change of the electrode, and there is a possibility that the above-described problems such as breakage of the separator may occur. On the other hand, when the film thickness difference (L1-L2) exceeds 10 μm, it is not preferable because the thickness of the entire separator becomes too large or the strength is lowered and becomes impractical. In order to obtain the relationship between the film thickness differences (L1-L2), it is important to control factors such as the material, porosity, pore diameter, film thickness, and inorganic filler particle diameter and content of the heat-resistant porous layer. It is also important to control factors such as the above-described materials in the polyolefin porous substrate.

  In the present invention, the static friction coefficient of the separator is preferably 0.3 to 1.0, more preferably 0.3 to 0.7. Even if the separator is applied to a cylindrical or flat cylindrical battery, even if the electrode is greatly deformed during charging and discharging, the separator slides against the electrode. Problems such as breakage can be more suitably prevented. In addition, since the separator is slippery, there is an advantage in manufacturing such that winding can be performed smoothly even in the process of stacking the electrode and the separator into the battery. In addition, when the static friction coefficient of a separator is less than 0.3, it is not preferable because slippage is too good and end face deviation is likely to occur, which may cause manufacturability problems. On the other hand, if the coefficient of static friction exceeds 1.0, the problem of electrode volume change during charging / discharging becomes noticeable. The method of adjusting the static friction coefficient is not particularly limited, but can be adjusted by appropriately adding a lubricant such as an inorganic filler or a silicone resin to the heat resistant porous layer, for example.

In addition, the film thickness of the separator of the present invention is preferably 25 μm or less from the viewpoint of improving the energy density and output characteristics of the battery. As the physical properties of the separator for non-aqueous secondary batteries, the Gurley value (JIS P8117) is 10 to 1000 sec / 100 cc, the membrane resistance is 0.5 to 10 ohm · cm ² , and the puncture strength is 10 to 1000 g. It is preferable.

  The polyolefin porous substrate in the present invention is a substrate having pores or voids therein, and examples thereof include a microporous film, a nonwoven fabric, a paper sheet, and other sheets having a three-dimensional network structure. Among these, a microporous film is preferable from the viewpoints of easy adjustment of the thickness difference (L1-L2) of the separator within the scope of the present invention, handling properties, and strength. A microporous membrane means a membrane that has a large number of micropores inside and has a structure in which these micropores are connected, allowing gas or liquid to pass from one surface to the other. To do.

  Examples of the polyolefin resin constituting the porous substrate include polyethylene, polypropylene, polymethylpentene, and the like. Among these, polyethylene is preferable in that a good shutdown function can be obtained, and high-density polyethylene or a mixture of high-density polyethylene and ultrahigh molecular weight polyethylene is particularly preferable. As for the molecular weight of polyethylene, it is suitable that the weight average molecular weight is 100,000 to 10,000,000. For example, in addition to polyethylene, other polyolefins such as polypropylene and polymethylpentene may be mixed and used.

The polyolefin porous substrate according to the present invention has a film thickness measured at an applied load of 36 g / cm ² using the contact-type film thickness meter as L3, and a film thickness measured at an applied load of 1.2 kg / cm ² as L4. In this case, L3−L4 = 0.1 to 2.0 μm is preferable. A more preferable thickness difference (L3−L4) of the applied load is 0.5 to 1.8 μm. Since such a porous substrate is a portion that is relatively difficult to deform in the entire separator, the shape of the entire separator can be maintained satisfactorily and appropriate strength can be imparted, and handling properties are good. It becomes. In addition, since it becomes difficult to adjust the thickness difference (L1-L2) of the whole separator in the range of this invention when the thickness difference (L3-L4) of an applied load is less than 0.1 micrometer, it is unpreferable. On the other hand, when the thickness difference (L3-L4) of the applied load exceeds 2 μm, the handling property is lowered, which is not preferable.

The polyolefin porous substrate in the present invention preferably has a porosity of 30 to 70% and an average pore diameter measured by the BET method of 10 to 400 nm. If it is this range, it is suitable for adjusting the thickness difference (L1-L2) of the whole separator in the range of the present invention. In addition, when the porosity of the porous substrate is less than 30% or the average pore diameter is less than 10 nm, it is not preferable because the membrane resistance becomes too high and the porous substrate becomes too difficult to deform. On the other hand, when the porosity of the porous substrate exceeds 70% or the average pore diameter exceeds 400 nm, the thermal contraction rate of the separator becomes too high, which is not preferable.
In addition, it is preferable that the film thickness of the polyolefin porous base material in this invention is 5-20 micrometers. The Gurley value (JIS P8117) of the porous substrate is preferably 10 to 500 sec / 100 cc.

  The heat-resistant porous layer in the present invention includes a heat-resistant resin, and has a porous structure in which a large number of micropores are connected to each other and these micropores are connected to each other. Such a heat-resistant porous layer is preferably coated in a state of being directly fixed to one or both surfaces of the polyolefin porous substrate by a coating method.

  As the heat resistant resin, a resin having a melting point of 200 ° C. or higher, or a resin having a melting point of 200 ° C. or higher can be suitably used for a resin having substantially no melting point. Examples of such a heat resistant resin include at least one of wholly aromatic polyamide, polyimide, polyamideimide, polysulfone, polyethersulfone, polyketone, polyetherketone, polyetherimide, and cellulose. In particular, wholly aromatic polyamides are preferable from the viewpoint of durability, and meta-type aromatic polyamides are preferable from the viewpoint of easily forming a porous layer and excellent redox resistance.

  The heat-resistant porous layer is preferably formed on both the front and back surfaces of the polyolefin porous substrate from the viewpoints of handling properties, durability, and the effect of suppressing heat shrinkage. When the heat-resistant porous layer is formed on both surfaces of the polyolefin porous substrate, the total thickness of the heat-resistant porous layer is preferably 3 μm or more and 12 μm or less, When the heat resistant porous layer is formed only on one side, it is preferably 3 μm or more and 12 μm or less.

  The heat-resistant porous layer preferably has a porosity of 50 to 80% and an average pore diameter measured by the BET method of 50 to 300 nm. If it is this range, it is suitable for adjusting the thickness difference (L1-L2) of the whole separator in the range of the present invention. When the porosity of the heat-resistant porous layer is less than 50% or the average pore diameter is less than 50 nm, the membrane resistance becomes too high, and the thickness difference (L1-L2) of the entire separator is within the scope of the present invention. Since it becomes difficult to adjust, it is not preferable. On the other hand, when the porosity of the heat resistant porous layer exceeds 80% or the average pore diameter exceeds 300 nm, the thermal contraction rate of the separator becomes too high, which is not preferable.

  In the present invention, the heat-resistant porous layer preferably contains an inorganic filler. Appropriately adding an inorganic filler improves the shutdown characteristics, suppresses thermal contraction of the separator in the high temperature range exceeding the melting point of polyolefin, reduces film resistance, and reduces the friction coefficient Can do. As the material of the inorganic filler, metal oxides such as alumina, zirconia, yttria, ceria, magnesia, titania and silica, metal carbides such as aluminum carbide, titanium carbide and tungsten carbide, metal nitrides such as boron nitride and aluminum nitride, Examples thereof include salts such as calcium carbonate and barium sulfate, metal hydroxides such as aluminum hydroxide, boehmite and magnesium hydroxide, or combinations of two or more thereof. Moreover, these may have a porous shape, and may be either amorphous or crystalline. Especially, it is preferable to consist of at least 1 sort (s) among a metal hydroxide and a metal oxide from a viewpoint of suppression of the thermal contraction of the separator under high temperature. In particular, metal hydroxides such as aluminum hydroxide and boehmite are preferable because they are softer than metal oxides such as alumina and do not damage the separator manufacturing apparatus or the battery manufacturing apparatus.

  In the present invention, the content of the inorganic filler is preferably 0.4 to 4 times the volume of the heat resistant resin. When the content of the inorganic filler is lower than 0.4 times, it is difficult to obtain the effect of improving the slipperiness, and the characteristics related to heat resistance such as dimensional stability at high temperatures may be insufficient. On the other hand, when the content of the inorganic filler exceeds 4 times, the heat-resistant porous layer is excessively densified, and it is difficult to adjust the thickness difference (L1-L2) of the entire separator within the range of the present invention.

  In the present invention, the average particle size of the inorganic filler is preferably in the range of 0.1 to 1 μm. When the average particle diameter of the inorganic filler exceeds 1 μm, it becomes difficult to form the heat-resistant porous layer with an appropriate thickness, and the thickness difference (L1-L2) of the entire separator is adjusted within the range of the present invention. Since it becomes difficult, it is not preferable. Moreover, when the average particle diameter of an inorganic filler becomes smaller than 0.1 micrometer, since the effect of a slip improvement is hard to be acquired, it is unpreferable.

[Production method of polyolefin microporous membrane]
The polyolefin microporous membrane that can be used as the porous substrate in the present invention can be produced, for example, by the method shown below. That is, (I) a polyolefin composition is dissolved in a solvent such as paraffin, liquid paraffin, paraffin oil, mineral oil, castor oil, tetralin, ethylene glycol, glycerin, decalin, toluene, xylene, diethyltriamine, ethyldiamine, dimethylsulfoxide, hexane, etc. A step of preparing a solution, (II) a step of extruding the solution from a die at a temperature not lower than the melting point of the polyolefin composition and not higher than a melting point + 60 ° C., and cooling to form a gel-like composition, (III) the gel-like composition It is manufactured by a series of steps including a step of stretching a product, (IV) a step of heat-setting the stretched gel-like composition, (V) a step of removing the solvent, and (VI) a step of annealing.
Here, the stretching step is preferably biaxial stretching, and any method of sequential biaxial stretching, longitudinal stretching, and lateral stretching simultaneously performing longitudinal stretching and transverse stretching separately can be suitably used. It is.

  The polyolefin microporous membrane used in the present invention is, for example, a mixed solvent composed of liquid paraffin and decalin as the solvent, the concentration of the polyolefin composition is 15 to 35% by weight, and the stretch ratio is 50 to 100 times (longitudinal stretch ratio). X transverse stretching ratio), a heat setting temperature of 110 to 140 ° C., and an annealing temperature not higher than the heat setting temperature, but is not limited thereto.

  In addition, when the density | concentration of a polyolefin composition is made low or a draw ratio is enlarged, there exists a tendency for an average hole diameter to become large. Moreover, when the density | concentration of polyolefin composition is made high or a draw ratio is made low, there exists a tendency for an average hole diameter to become small. Further, when the heat setting temperature is increased, the average pore diameter may be increased. Conversely, when the heat setting temperature is decreased, the average hole diameter may be excessively decreased. If the annealing temperature is set higher than the heat setting temperature, or if the annealing temperature is greatly deformed during annealing, the average pore diameter may be increased. If the concentration of the polyolefin composition is 35% by weight or more, the heat setting temperature is higher than 140 ° C., or the annealing is performed at a temperature higher than the heat setting temperature, the porosity may be too low. Further, even if there is a large deformation during annealing, the porosity may be too low. If the concentration of the polyolefin composition is lower than 15% by weight, the porosity may become too high.

[Method for producing separator for non-aqueous secondary battery]
Although the manufacturing method of the separator for non-aqueous secondary batteries of this invention is not specifically limited, For example, it can manufacture with the manufacturing method containing the process of the following (i)-(iv). That is, (i) a step of producing a slurry for coating containing a heat-resistant resin and a water-soluble organic solvent, and (ii) a step of coating the obtained coating slurry on one or both sides of a polyolefin porous substrate. And (iii) a step of coagulating the heat-resistant resin in the coated slurry, and (iv) a step of washing and drying the sheet after the coagulation step.

  In the step (i), the water-soluble organic solvent is not particularly limited as long as it is a good solvent for the heat-resistant resin, and specifically, for example, N-methylpyrrolidone, dimethylacetamide, dimethylformamide, dimethyl Polar solvents such as sulfoxide can be used. Further, in the slurry, a solvent that becomes a poor solvent for the heat-resistant resin can be partially mixed and used. By applying such a poor solvent, a microphase separation structure is induced and the formation of a heat-resistant porous layer is facilitated. As the poor solvent, alcohols are preferred, and polyhydric alcohols such as glycol are particularly preferred. In addition, in order to obtain the separator of the aspect which includes an inorganic filler in a heat resistant porous layer, what is necessary is just to mix an appropriate amount of inorganic fillers in the said slurry. The concentration of the heat resistant resin in the slurry is preferably 4 to 9% by weight.

In step (ii), the amount of slurry applied to the polyolefin porous substrate is preferably about ² to 3 g / m ² . Examples of the coating method include a knife coater method, a gravure coater method, a screen printing method, a Meyer bar method, a die coater method, a reverse roll coater method, an ink jet method, a spray method, and a roll coater method. Among them, the reverse roll coater method is preferable from the viewpoint of uniformly applying the coating film. Moreover, a heat resistant porous layer can be stably obtained by adjusting the slurry temperature at the time of coating. Here, the slurry temperature is not particularly limited, but a range of 5 ° C to 40 ° C is preferable.

  In step (iii), the heat-resistant resin in the slurry can be coagulated by spraying a coagulating liquid on the polyolefin porous substrate after coating, or a bath containing the coagulating liquid (coagulating bath). For example, a method of immersing the base material therein. The coagulation liquid is not particularly limited as long as it can coagulate the heat-resistant resin, but water or a mixed liquid in which an appropriate amount of water is contained in a good solvent used in the slurry is preferable. Here, the mixing amount of water is preferably 40 to 80% by weight with respect to the coagulation liquid. Further, it is preferable that the difference between the temperature of the coagulation liquid and the slurry temperature in the step (ii) is small. For example, the temperature difference is preferably within 30 ° C. Further, a method of immersing in these coagulation baths and then immediately immersing in the second coagulation bath is also desirable for obtaining the film thickness difference (L1-L2) in the separator of the present invention. The second coagulation bath is preferably water or a mixed solution in which an appropriate amount of water is contained in the good solvent used for the slurry. Here, the mixing amount of water is preferably 40% by weight or more with respect to the coagulating liquid.

  In the step (iv), the drying method is not particularly limited, but the drying temperature is suitably 50 to 80 ° C. In the case of applying a high drying temperature, it is preferable to apply a method of contacting the roll in order to prevent dimensional change due to heat shrinkage.

[Non-aqueous secondary battery]
The non-aqueous secondary battery of the present invention is a non-aqueous secondary battery that obtains an electromotive force by doping and dedoping lithium, and includes a positive electrode having a positive electrode current collector and a positive electrode active material layer, a negative electrode current collector, and a negative electrode A non-aqueous secondary battery comprising: a negative electrode having an active material layer; the separator of the present invention disposed between these electrodes; and a non-aqueous electrolyte. Such a non-aqueous secondary battery of the present invention is excellent in safety and durability at high temperatures, and is excellent in cycle characteristics and the like.

In the present invention, the positive electrode active material preferably has a volume change rate of 1% or more in the process of dedoping lithium. Examples of the positive electrode active material include LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , LiCo _0.5 Ni _0.5 O ₂ , LiAl _0.25 Ni _0.75 O ₂ , or a combination of two or more of these. The thing etc. can be mentioned. In addition, when the volume change rate of a positive electrode active material is less than 1%, since the discharge capacity of a battery becomes small and the advantage of the separator of this invention is not utilized, it is unpreferable.

  Such a positive electrode active material exists in the positive electrode layer laminated on the positive electrode current collector. The positive electrode layer can include a positive electrode active material, a binder, and a conductive auxiliary. Such a positive electrode layer can be prepared by kneading a positive electrode active material, a binder, a conductive additive, and a solvent to prepare a slurry, coating this on a positive electrode current collector, drying and pressing. . In this case, when the total weight of the positive electrode active material, the binder and the conductive auxiliary is 100%, the positive electrode active material has a weight of 80 to 98% by weight, the binder has a weight of 2 to 20%, and the conductive auxiliary has a weight of 0 to 10%. % Range is preferred. As the binder, polyvinylidene fluoride is preferably used. As the conductive additive, graphite powder, acetylene black, ketjen black, vapor grown carbon fiber, and the like are preferably used. For the current collector, aluminum foil, stainless steel or the like is suitable.

In the present invention, the negative electrode active material preferably has a volume change rate of 3% or more in the process of doping lithium. Examples of the negative electrode active material include Sn, SnSb, Ag ₃ Sn, artificial graphite, graphite, Si, SiO, V ₅ O _4, or combinations of two or more thereof. In addition, when the volume change rate of a negative electrode active material is less than 3%, since the discharge capacity of a battery becomes small and the advantage of this invention separator is not utilized, it is unpreferable.

  Such a negative electrode active material is present in the negative electrode layer laminated on the negative electrode current collector. The negative electrode layer can include a negative electrode active material, a binder, and a conductive additive. Such a negative electrode layer can be prepared by kneading a negative electrode active material, a binder, a conductive additive, and a solvent to prepare a slurry, coating this on a negative electrode current collector, drying and pressing. . In this case, when the total weight of the negative electrode active material, the binder, and the conductive auxiliary agent is 100%, the negative electrode active material weight is 80 to 98% by weight, the binder is 2 to 20% by weight, and the conductive auxiliary agent is 0 to 10% by weight. % Range is preferred. Examples of the binder include polyvinylidene fluoride and carboxymethyl cellulose. As the conductive additive, graphite powder, acetylene black, ketjen black, vapor grown carbon fiber, and the like are preferably used. The current collector is preferably copper foil, stainless steel, or the like.

As the electrolytic solution, a non-aqueous electrolytic solution in which a lithium salt is dissolved in a non-aqueous solvent is used. As the lithium salt, LiPF ₆ , LiBF ₄ , LiClO _{4 and the} like are preferably used. Examples of the non-aqueous solvent include propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). These lithium salts and non-aqueous solvents may be used alone or in combination of two or more. The concentration of the lithium salt is preferably in the range of 0.5 to 2.0M. In addition, it is preferable from the viewpoint of durability that vinylene carbonate is added to the electrolytic solution.

  In the non-aqueous secondary battery of the present invention, the battery element composed of the positive electrode, the negative electrode, and the separator is wound in a cylindrical shape or a flat shape, or is laminated in a package structure. The exterior can be applied in any form such as a metal case or an aluminum laminated film case.

The measuring methods of various physical properties in the examples and comparative examples of the present invention are as follows.
[Measurement of film thickness and film thickness difference (L1-L2)]
A separator as a sample was collected in a size of 15 cm in the length direction and 50 cm in the width direction. About this sample, it measured about arbitrary 20 points | pieces using the contact-type film thickness meter. As the film thickness meter, a contact-type film thickness meter (manufactured by Mitutoyo Corporation), a cylindrical one having a contact terminal bottom of 0.5 cm in diameter was used. In the measurement, first, 20 points were measured with an applied load of 36 g / cm ² , and an average value L1 was obtained. At this time, the measurement location was marked with a marker. Next, the film thickness was measured at an applied load of 1.2 kg / cm ² at 20 points marked earlier, and an average value L2 was obtained. And the film thickness difference (L1-L2) which is the difference of L1 and L2 was calculated | required. Note that the film thickness difference (L3-L4) of the polyolefin porous substrate is obtained in the same manner as described above. In this case, the above L1 may be read as L3 and the above L2 may be read as L4. Further, when there is no specific designation in the “film thickness” of the present invention, a numerical value at a load of 36 g / cm ² was used.

[Porosity]
The constituent materials are a, b, c..., N, and the weights of the constituent materials are Wa, Wb, Wc..., Wn (g · cm ² ), and their true densities are da, db, dc. g / cm ³ ), where the thickness of the layer of interest is t (cm), the porosity ε (%) was obtained from the following formula (1).
ε = {1− (Wa / da + Wb / db + Wc / dc +... + Wn / dn) / t} × 100 (1)
In addition, the porosity under load shows the porosity at the time of measuring by applying a load to material. In addition, when simply referred to as porosity, the porosity at a load of 36 g / cm ² is shown.

[Pore diameter of heat-resistant porous layer]
First, the nitrogen gas adsorption amount of each of the separator, the base material, and the filler as a sample was determined by a nitrogen gas adsorption method according to JIS Z 8830. The measurement was performed by a three-point method using NOVA-1200 (manufactured by Yuasa Ionics). And the specific surface area of each separator, a base material, and a filler was calculated | required from the obtained nitrogen gas adsorption amount based on following formula (2).
1 / [W · {(P ₀ / P) −1}] = {(C−1) / (Wm · C)} (P / P ₀ ) (1 / (Wm · C) (2)
Here, P is the gas pressure of the adsorbate in the adsorption equilibrium, P ₀ is the saturated vapor pressure of the adsorbate in the adsorption equilibrium, W is the adsorption amount at the adsorption equilibrium pressure P, Wm is the single molecule adsorption amount, and C is the BET constant. is there.
Then, assuming that the pore structure in the sample was all cylindrical, the average pore diameter was calculated from the measurement results of the pore volume and surface area. Specifically, the specific surface area of the separator is St, the specific surface area of the substrate is Ss, the specific surface area of the inorganic filler is Sf, and the surface area of the constituent material in the sample is obtained by multiplying the specific surface area by the weight constituting the sample. be able to. That is, when the weight of the heat resistant resin is Wa, the weight of the inorganic filler is Wf, and the weight of the polyolefin microporous film of the substrate is Ws, the surface area of the heat resistant resin is St · (Wa + Wf + Ws) − (Ss · Ws + Sf · Wf). The surface area of the polyolefin microporous membrane of the substrate is Ss · Ws.
When the total pore volume is Vt2, the diameter of the cylindrical pore is Rt2, and the total length of the cylindrical pore is Lt2, the following equations (3) to (5) are established.
St · (Wa + Wf + Ws) −Ss · Ws = π · Rt2 · Lt2 (3)
Vt2 = π (Rt2 / 2) ² · Lt2 (4)
Vt2 = ε · (Wa / da + Wf / df + Vt2) (5)
Here, Wf is the weight of the inorganic filler, and df is the density of the inorganic filler. From the formulas (3) to (5), the average pore diameter Rt2 of the pores in the heat resistant porous layer was determined. Note that the average pore diameter can be determined by the same method for the nonwoven fabric laminated with the heat resistant porous layer.

[Porosity of polyolefin microporous membrane]
It is assumed that the polyolefin microporous membrane of the substrate is composed of fibrillar fibers and the pores are cylindrical pores. The total volume of fibril fiber is Vs1, and the total pore volume is Vs2. When the diameter of the fibril is Rs1, the diameter of the cylindrical hole is Rs2, the total length of the fibril is Ls1, and the total length of the cylindrical hole is Ls2, the following equations (6) to (10) are established.
Ss · Ws = π · Rs1 · Ls1 = π · Rs2 · Ls2 (6)
Vs1 = π · (Rs1 / 2) ² · Ls1 (7)
Vs2 = π · (Rs / 2) ² · Ls2 (8)
Vs2 = ε · (Vs1 + Vs2) (9)
Vs1 = Ws / ds (10)
Here, ε is the porosity, and ds is the specific gravity of the polyolefin. From the above formulas (6) to (10), the average pore diameter Rs2 of the pores of the polyolefin microporous membrane of the substrate was determined. It should be noted that the average pore diameter can be similarly determined for the nonwoven fabric.

[Average particle size of inorganic filler]
Measurement was performed using a laser diffraction particle size distribution analyzer (manufactured by Sysmex Corporation, Mastersizer 2000). Water was used as a dispersion medium, and a small amount of nonionic surfactant “Triton X-100” was used as a dispersant. The central particle size (D50) in the volume particle size distribution was taken as the average particle size.

[Coating amount of heat-resistant porous layer]
The basis weight of the separator coated with the heat resistant porous layer and the polyethylene microporous film used therefor was measured, and the coating amount of the heat resistant porous layer was determined from the difference between them. The basis weight was obtained by cutting a sample into 10 cm × 10 cm, measuring this weight, and converting this to a weight per 1 m ² .

[Gurley value]
The Gurley value (second / 100 cc) was measured according to JIS P8117.

[Example 1]
(1) Production of polyethylene microporous membrane Ticona's GUR2126 (weight average molecular weight 4150,000, melting point 141 ° C) and GURX143 (weight average molecular weight 560,000, melting point 135 ° C) were used as polyethylene powder. A polyethylene solution was prepared by dissolving GUR2126 and GURX143 in a mixed solvent of liquid paraffin and decalin such that the polyethylene concentration was 30% by weight so that the ratio was 1: 9 (weight ratio). The composition of the polyethylene solution is polyethylene: liquid paraffin: decalin = 30: 45: 25 (weight ratio). This polyethylene solution was extruded from a die at 148 ° C., cooled in a water bath, and dried at 60 ° C. for 8 minutes and at 95 ° C. for 15 minutes to produce a gel tape (base tape). The base tape was stretched by biaxial stretching, which was sequentially performed with longitudinal stretching and lateral stretching. Here, the longitudinal stretching was 5.5 times, the stretching temperature was 90 ° C., the transverse stretching was 11.0 times the stretching ratio, and the stretching temperature was 105 ° C. After transverse stretching, heat setting was performed at 125 ° C. Next, this was immersed in a methylene chloride bath to extract liquid paraffin and decalin. Then, it dried at 50 degreeC and obtained the polyethylene microporous film by annealing at 120 degreeC. The physical properties of this polyethylene microporous film are as follows: film thickness L3 is 10.3 μm, film thickness L4 measured at an applied load of 1.2 kg / cm ² is 9.5 μm, film thickness difference (L3−L4) is 0.8 μm, empty The porosity was 50%, the Gurley value was 268 seconds / 100 cc, the membrane resistance was 2.641 ohm · cm ² , the puncture strength was 443 g, and the average pore diameter measured by the BET method was 42.1 nm.

(2) Production of Separator Conex (registered trademark; manufactured by Teijin Techno Products), which is polymetaphenylene isophthalamide, was used as a meta-type wholly aromatic polyamide. Aluminum hydroxide (manufactured by Showa Denko; H-43M) having an average particle diameter of 0.8 μm was used as the inorganic fine particles.
Conex and aluminum hydroxide were adjusted so that the weight ratio was 23:77 (volume ratio was 34:66), and these were adjusted so that Conex was 5.5% by weight, dimethylacetamide (DMAc) and tripropylene. Glycol (TPG) was mixed with a mixed solvent having a weight ratio of 50:50 to prepare a coating solution.
Two Meyer bars (counter 6) face each other, the clearance between the Mayer bars is adjusted to 30 μm, and the coating liquid adjusted to 20 ° C. is supplied from both sides of these Mayer bars, and the polyethylene microporous between the Mayer bars The coating solution was applied to both the front and back surfaces of the polyethylene microporous membrane by passing the membrane while pulling.
This was immersed in a coagulation liquid having a weight ratio of water: the mixed solvent = 50: 50 and 40 ° C., then immersed in a second coagulation bath adjusted to water: the mixed solvent = 90: 10, Washing with water and drying were performed, and heat-resistant porous layers made of Conex and aluminum hydroxide were formed on both surfaces of the polyethylene microporous membrane.
The characteristics of the separator for a non-aqueous secondary battery of the present invention produced by the method as described above were as follows. The film thickness L1 is 18.2 μm, the film thickness L2 measured at an applied load of 1.2 kg / cm ² is 15.9 μm, the film thickness difference (L1−L2) is 2.3 μm, and the coating amount is 6.08 g / m ^2. The Gurley value was 380 seconds / 100 cc. The heat-resistant porous layer had a thickness of 7.9 μm, a coating amount of 6.08 g / m ² , a porosity of 65%, and a BET method average pore diameter of 151 nm. These physical properties are shown in Table 1. In addition, Examples 2 to 3 described below , Reference Example 1 and Comparative Examples 1 to 4 are also shown in Table 1 in the same manner.

[Example 2]
The same polyethylene microporous membrane and meta-type wholly aromatic polyamide as in Example 1 were used. Further, α-alumina (manufactured by Showa Denko; AL160SG-3) having an average particle diameter of 0.8 μm was used as the inorganic fine particles.
Conex and alumina were adjusted so that the weight ratio was 15:85 (volume ratio was 34:66), and these were adjusted so that Conex was 5.5% by weight, dimethylacetamide (DMAc) and tripropylene glycol ( TPG) was mixed with a mixed solvent having a weight ratio of 50:50 to prepare a coating solution. Two Mayer bars were opposed to each other, and an appropriate amount of the coating solution adjusted to 25 ° C. was placed between them. The polyethylene microporous film was passed between Mayer bars on which the coating liquid was placed, and the coating liquid was applied to both sides of the polyethylene microporous film. Here, the clearance between the Mayer bars was adjusted to 30 μm, and the number of the Mayer bars used was 6.
This was immersed in a coagulation liquid having a weight ratio of water: the mixed solvent = 50: 50 and 40 ° C., then immersed in a second coagulation bath adjusted to water: the mixed solvent = 99: 1, Washing with water and drying were performed to form heat-resistant porous layers on both sides of the polyethylene microporous membrane.
The characteristics of the separator for a non-aqueous secondary battery of the present invention produced by the method as described above were as follows. The film thickness L1 was 17.5 μm, the film thickness L2 measured at an applied load of 1.2 kg / cm ² was 15.5 μm, the film thickness difference (L1−L2) was 2.0 μm, and the Gurley value was 390 seconds / 100 cc. . The heat-resistant porous layer had a thickness of 7.2 μm, a coating amount of 7.58 g / m ² , a porosity of 70%, and a BET method average pore diameter of 217 nm.

[Example 3]
The same polyethylene microporous membrane as in Example 1 was used. Polyethersulfone (PES, Sumika Excel PES4800P manufactured by Sumitomo Chemical Co., Ltd.) was used as the heat resistant resin. Α-alumina (manufactured by Showa Denko KK; AL160SG-3) having an average particle diameter of 0.8 μm was used as the inorganic fine particles.
The weight ratio of PES and alumina was adjusted to 15:85 (volume ratio was 34:66), and these were adjusted so that PES was 5.5% by weight, dimethylacetamide (DMAc) and tripropylene glycol (TPG). Was mixed with a mixed solvent having a weight ratio of 50:50 to prepare a coating solution.
Two Meyer bars were confronted. Here, the clearance between the Mayer bars was adjusted to 30 μm, and the number of the Mayer bars used was 6. The coating liquid adjusted to 25 ° C. is supplied from both sides of these Mayer bars, and the coating liquid is applied to both the front and back surfaces of the polyethylene microporous film by passing the polyethylene microporous film between the Mayer bars while pulling. did.
This was immersed in a coagulation liquid having a weight ratio of water: the mixed solvent = 50: 50 and 40 ° C., then immersed in a second coagulation bath adjusted to water: the mixed solvent = 61: 39, Washing with water and drying were performed, and a porous layer made of PES and alumina was formed on both the front and back surfaces of the polyethylene microporous membrane.
The characteristics of the separator for a non-aqueous secondary battery of the present invention produced by the method as described above were as follows. The film thickness L1 was 21 μm, the film thickness L2 measured at an applied load of 1.2 kg / cm ² was 18 μm, the film thickness difference (L1−L2) was 3.0 μm, and the Gurley value was 410 seconds / 100 cc. The heat-resistant porous layer had a thickness of 10.7 μm, a coating amount of 12.08 g / m ² , a porosity of 68%, and a BET method average pore diameter of 185 nm.

[ Reference Example 1 ]
In the preparation of the coating solution in Example 1, except that CONEX aluminum hydroxide was adjusted to 80:20 (volume ratio 88:12) in a weight ratio in the same manner as in Example 1, the non A separator for an aqueous secondary battery was obtained.
The physical properties of this separator are as follows: the film thickness L1 is 21 μm, the film thickness L2 measured at an applied load of 1.2 kg / cm ² is 18 μm, the film thickness difference (L1-L2) is 3.0 μm, and the Gurley value is 388 seconds / 100 cc. there were. The heat-resistant porous layer had a thickness of 10.7 μm, a coating amount of 6.08 g / m ² , a porosity of 64%, and a BET method average pore diameter of 124 nm.

[Comparative Example 1]
As the porous substrate, a nonwoven fabric (manufactured by Teijin Fibers Limited) made of polyethylene terephthalate (PET) was used. This nonwoven fabric has a basis weight of 7 g / m ² , a film thickness L3 of 15.0 μm, a film thickness L4 measured at an applied load of 1.2 kg / cm ² of 14.6 μm, a film thickness difference (L3−L4) of 0.4 μm, The porosity was 67%, the average pore diameter measured by the BET method was 90 nm, the Gurley value was 120 seconds / 100 cc, and the puncture strength was 320 g. The same coating solution as in Example 1 was used.
A PET nonwoven fabric was fixed on a glass plate, and the coating liquid adjusted to 25 ° C. using a Meyer bar of No. 6 was applied to both surfaces of the PET nonwoven fabric. Here, the clearance between the Meyer bar and the PET nonwoven fabric was 40 μm. The PET nonwoven fabric coated with the coating liquid was immersed in a coagulating liquid at 40 ° C. in a weight ratio of water: the mixed solvent = 50: 50, and then adjusted to water: the mixed solvent = 98: 2. 2 It was immersed in a coagulation bath, then washed with water and dried to form heat-resistant porous layers on both sides of the PET nonwoven fabric.
The characteristics of the separator for a non-aqueous secondary battery produced by the method as described above were as follows. The film thickness L1 was 20.8 μm, the film thickness L2 measured at an applied load of 1.2 kg / cm ² was 18.3 μm, the film thickness difference (L1−L2) was 2.5 μm, and the Gurley value was 381 seconds / 100 cc. . The heat-resistant porous layer had a thickness of 5.8 μm, a coating amount of 5.0 g / m ² , a porosity of 76%, and a BET method average pore diameter of 238 nm.

[Comparative Example 2]
The same polyethylene microporous film and coating solution as those shown in Example 1 were used.
Two Meyer bars were confronted. Here, the clearance between the Mayer bars was adjusted to 60 μm, and the number of the Mayer bars used was 6. The coating liquid adjusted to 9 ° C. is supplied from both sides of these Mayer bars, and the coating liquid is applied to both the front and back surfaces of the polyethylene microporous film by passing the polyethylene microporous film between the Mayer bars while pulling it. did. This was immersed in a coagulation liquid having a water ratio of water: the mixed solvent = 50: 50 at 40 ° C., then washed with water and dried, and the porous layer composed of Conex and aluminum hydroxide was microporous in polyethylene. Formed on both sides of the membrane.
The characteristics of the separator for a non-aqueous secondary battery produced by the method as described above were as follows. The film thickness L1 was 27.0 μm, the film thickness L2 measured at an applied load of 1.2 kg / cm ² was 16.5 μm, the film thickness difference (L1−L2) was 10.5 μm, and the Gurley value was 410 seconds / 100 cc. . The heat-resistant porous layer had a thickness of 16.7 μm, a coating amount of 12.08 g / m ² , a porosity of 80%, and a BET method average pore diameter of 110 nm.

[Comparative Example 3]
The same polyethylene microporous film and coating solution as those shown in Example 1 were used.
Two Meyer bars were confronted. Here, the clearance between the Mayer bars was adjusted to 30 μm, and the number of the Mayer bars used was 6. The coating liquid adjusted to 0 ° C. is supplied from both sides of these Mayer bars, and the coating liquid is applied to both the front and back sides of the polyethylene microporous film by passing the polyethylene microporous film between the Mayer bars while pulling. did. This was immersed in a coagulating liquid at 40 ° C. with water: the mixed solvent = 70: 40 by weight ratio, then washed with water and dried, and the porous layer made of Conex and aluminum hydroxide was microporous in polyethylene. Formed on both sides of the membrane.
The characteristics of the separator for a non-aqueous secondary battery produced by the method as described above were as follows. The film thickness L1 was 25.0 μm, the film thickness L2 measured at an applied load of 1.2 kg / cm ² was 14.0 μm, the film thickness difference (L1−L2) was 11.0 μm, and the Gurley value was 405 seconds / 100 cc. . The heat-resistant porous layer had a thickness of 14.7 μm, a coating amount of 9.08 g / m ² , a porosity of 83%, and a BET method average pore diameter of 280 nm.

[Comparative Example 4]
The same polyethylene microporous film and coating solution as those shown in Example 1 were used.
Two Meyer bars were confronted. Here, the clearance between the Mayer bars was adjusted to 20 μm, and the number of the Mayer bars used was 6. The coating liquid adjusted to 4 ° C. is supplied from both sides of these Mayer bars, and the coating liquid is applied to both the front and back surfaces of the polyethylene microporous film by passing the polyethylene microporous film between the Mayer bars while pulling. did. This was immersed in a coagulation liquid having a water ratio of water: the mixed solvent = 50: 50 at 40 ° C., then washed with water and dried, and the porous layer composed of Conex and aluminum hydroxide was microporous in polyethylene. Formed on both sides of the membrane.
The characteristics of the separator for a non-aqueous secondary battery produced by the method as described above were as follows. The film thickness L1 was 12 μm, the film thickness L2 measured at an applied load of 1.2 kg / cm ² was 11 μm, the film thickness difference (L1−L2) was 1.0 μm, and the Gurley value was 385 seconds / 100 cc. The heat-resistant porous layer had a thickness of 1.7 μm, a coating amount of 2.08 g / m ² , a porosity of 66%, and a BET method average pore diameter of 179 nm.

[Membrane resistance]
Membrane resistance was measured for each of the separators of Examples 1 to 3, Reference Example 1 and Comparative Examples 1 to 4 produced as described above. Specifically, first, a separator as a sample was cut into a size of 2.6 cm × 2.0 cm. The cut sample was immersed in a methanol solution in which 3% by weight of a nonionic surfactant (manufactured by Kao Corporation; Emulgen 210P) was dissolved, and air-dried. A 20 μm thick aluminum foil was cut into 2.0 cm × 1.4 cm, and a lead tab was attached. Two aluminum foils were prepared, and a separator cut between the aluminum foils was sandwiched between the aluminum foils so that the aluminum foils were not short-circuited. As the electrolytic solution, a solution in which 1M LiBF ₄ was dissolved in a solvent in which propylene carbonate and ethylene carbonate were mixed at a weight ratio of 1: 1 was used, and the separator was impregnated with the electrolytic solution. This was sealed in an aluminum laminate pack under reduced pressure so that the tabs came out of the aluminum pack. Such cells were prepared so that there were one, two, and three separators in the aluminum foil, respectively. The cell was placed in a constant temperature bath at 20 ° C., and the resistance of the cell was measured by an AC impedance method at an amplitude of 10 mV and a frequency of 100 kHz. The measured resistance value of the cell was plotted against the number of separators, and this plot was linearly approximated to obtain the slope. The inclination was multiplied by the electrode area of 2.0 cm × 1.4 cm to determine the membrane resistance (ohm · cm ² ) per separator. The results are summarized in Table 2.

[Static friction coefficient]
In order to evaluate the slipperiness of the separator, the friction coefficient of the separator was measured using a card friction tester manufactured by Toyo Seiki Co., Ltd. Specifically, a separator was attached to a weight with a load of 1 kg, the surface on which the separator was attached was brought into contact with a SUS stage surface in a testing machine, and the force required to push the weight was measured. And the friction coefficient was calculated | required from this force and normal force. The surface on which the weight separator was affixed was a 7 cm × 7 cm square plane. The results are summarized in Table 2.

[Shutdown (SD) characteristics]
SD characteristics were evaluated for the separators of Examples 1 to 3, Reference Example 1 and Comparative Examples 1 to 4 produced as described above. Specifically, first, the separator is punched to Φ19 mm, dipped in a 3% by weight methanol solution of a nonionic surfactant (manufactured by Kao Corporation; Emulgen 210P), and air-dried. Then, the separator was impregnated with the electrolytic solution and sandwiched between SUS plates (Φ15.5 mm). Here, 1 M LiBF ₄ propylene carbonate / ethylene carbonate (1/1 weight ratio) was used as the electrolytic solution. This was enclosed in a 2032 type coin cell. I took the lead from the coin cell, put a thermocouple, and put it in the oven. The cell resistance was measured by raising the temperature at a rate of temperature increase of 1.6 ° C./min and simultaneously applying alternating current with an amplitude of 10 mV and a frequency of 1 kHz. As a result, when the resistance value increased to 1.0 × 10 ³ ohm · cm ² or more at the time of temperature rise, it was considered that the shutdown function was exhibited. The results are summarized in Table 2.

[Heat-resistant]
In the evaluation of the above SD characteristics, if the resistance value continues to maintain a level of 1.0 × 10 ³ ohm · cm ² or higher even at a temperature of 150 to 190 ° C. after the shutdown function is exhibited, Was not generated and the heat resistance was excellent, and therefore, the heat resistance was judged to be good (◯). On the other hand, when the resistance value at 150 to 190 ° C. was lower than 1.0 × 10 ³ ohm · cm ² , the heat resistance was judged to be poor (×). The results are summarized in Table 2.

[Examples 5 to 7, Reference Example 2 , Comparative Examples 5 to 8]
Using the separators of Examples 1 to 3, Reference Example 1 and Comparative Examples 1 to 4, 18650 type cylindrical batteries were prepared as follows, and the cycle characteristics were evaluated.
(1) Production of negative electrode N-methylpyrrolidone was prepared by adding 100 parts by weight of tin powder (manufactured by Mitsubishi Materials) classified to an average particle size of 10 m, 5 parts by weight of acetylene black, and 10 parts by weight of polyvinylidene fluoride. A negative electrode agent paste dissolved and dispersed in was prepared. In this negative electrode paste, the concentration of polyvinylidene fluoride was 6% by weight. The obtained paste was applied onto a copper foil having a thickness of 18 μm, dried and pressed to prepare a negative electrode so that the total thickness was 100 μm. This was slit to a width of 52 mm, and a tab was joined to the end to produce a negative electrode. The volume change rate of tin of the negative electrode active material was 370%.

(2) Production of Positive Electrode 89.5 parts by weight of lithium cobaltate (LiCoO ₂ ; manufactured by Nippon Chemical Industry Co., Ltd.) powder of the positive electrode active material, acetylene black (Denka Black; manufactured by Electrochemical Industry Co., Ltd.) powder in terms of dry weight A positive electrode paste in which these materials were dissolved in N-methylpyrrolidone was prepared so as to be 5 parts by weight and 6 parts by weight of polyvinylidene fluoride (manufactured by Kureha Chemical Industry Co., Ltd.). In this positive electrode paste, the concentration of polyvinylidene fluoride was 6% by weight. The obtained paste was applied onto an aluminum foil having a thickness of 20 μm, dried and pressed to produce a positive electrode so that the total thickness was 100 μm. This was slit to a width of 55 mm, and a tab was joined to the end to produce a positive electrode. The volume change rate of LiCoO _{2 as} the positive electrode active material was 1.8%.

(3) Production of electrode group The positive electrode and the negative electrode obtained above were connected to the positive electrode current collector and the negative electrode current collector at both ends through the separators of Examples 1 to 3, Reference Example 1 and Comparative Examples 1 to 4, respectively. The electrode was wound into a cylindrical shape in an exposed manner to produce a wound electrode group (diameter 17 mm, length 60 mm).

(4) Production of Cylindrical Battery Each wound electrode group obtained above was inserted into a bottomed cylindrical battery case having a diameter of 18 mm and a height of 65 mm. At the same time, the other end of the positive electrode lead was connected to the sealing plate, and the other end of the negative electrode lead was connected to the bottom of the battery case. After this battery case is inserted into a cylindrical plastic casing, 5.2 ml of non-aqueous electrolyte is injected into the battery case, the opening end of the battery case is crimped to fix the sealing plate, and the battery case is fixed. The nonaqueous electrolyte secondary battery (Examples 5-7 , Reference Example 2 , Comparative Examples 5-8) of this invention was produced by sealing. Here, as the non-aqueous electrolyte, a solution obtained by dissolving LiPF ₆ at a concentration of 1 M in a mixed solution in which ethylene carbonate and ethyl methyl carbonate were mixed at a weight ratio of 3 to 7 was used.

(5) Cylindrical battery cycle characteristic evaluation Cylindrical batteries prepared using the separators of Examples 1 to 3, Reference Example 1 and Comparative Examples 1 to 4 (Examples 5 to 7, Reference Example 2 and Comparative Examples 5 to 5) For 8), a 4.0 V constant current / constant voltage charge and a 2.75 V constant current discharge were repeated 100 cycles, and then the discharge capacity was measured.
The evaluation of the cycle characteristics was performed by discharge capacity retention rate (%) = discharge capacity after 100 cycles / discharge capacity after 3 cycles. When the discharge capacity retention rate was over 80%, it was evaluated as good (◯), when it was 70 to 80%, it was evaluated as Δ, and when it was less than 70%, it was evaluated as defective (×). The results are shown in Table 3. The following Examples 9 to 13 are also shown in Table 3 in the same manner.

[Example 9]
A nonaqueous secondary battery of the present invention was produced in the same manner as in Example 5 except that the negative electrode material in Example 5 was changed to SiO powder (manufactured by Wako Pure Chemical Industries, Ltd., reagent). The volume change rate of SiO of the negative electrode active material was 120%.

[Example 10]
A nonaqueous secondary battery of the present invention was produced in the same manner as in Example 5 except that the negative electrode material in Example 5 was changed to Si. The volume change rate of Si of the negative electrode active material was 200%.

[Example 11]
A non-aqueous secondary battery of the present invention was produced in the same manner as in Example 5 except that the negative electrode material in Example 5 was changed to hard carbon (manufactured by Showa Denko KK). In addition, the volume change rate of the hard carbon of the negative electrode active material was 5%.

[Example 12]
A non-aqueous secondary battery of the present invention was produced in the same manner as in Example 5 except that the negative electrode material in Example 5 was changed to natural graphite (manufactured by Graphtec). The volume change rate of natural graphite as the negative electrode active material was 5%.

[Example 13]
A nonaqueous secondary battery of the present invention was produced in the same manner as in Example 5 except that the negative electrode material in Example 5 was changed to SnSb. The volume change rate of SnSb of the negative electrode active material was 20%.

Claims (6)

A non-aqueous secondary battery comprising a porous base material, which is a microporous membrane made of polyolefin, and a heat-resistant porous layer containing a heat-resistant resin coated on one or both sides of the porous base material A separator,
The non-aqueous secondary battery separator uses a contact-type film thickness meter having a circular contact terminal with a contact bottom surface of 0.5 cm in diameter, and the film thickness measured at an applied load of 36 g / cm ² is L1, the film thickness measured at an applied load of 1.2 kg / cm ² in the case of the L2, becomes L1-L2 = 2.0~10μm,
The porous substrate has a thickness measured with an applied load of 36 g / cm ² using the contact film thickness meter as L3, and a thickness measured with an applied load of 1.2 kg / cm ² as L4. L3-L4 = 0.5 to 1.8 μm, the film thickness is 5 to 20 μm, the porosity is 30 to 70%, and the average pore diameter measured by the BET method is 10 to 400 nm,
The heat-resistant porous layer has a film thickness of 3 to 12 μm, a porosity of 50 to 80%, and an average pore diameter measured by the BET method of 50 to 300 nm,
The heat resistant resin is at least one selected from the group consisting of aromatic polyamide, polyimide, polyamideimide, polyethersulfone, polysulfone, polyetherketone, polyetherimide,
The heat-resistant porous layer contains an inorganic filler, the average particle diameter of the inorganic filler is 0.1 to 1 μm, and the content of the inorganic filler is 0.4 to 4 with respect to the volume of the heat-resistant resin. The separator for non-aqueous secondary batteries characterized by being doubled .   The separator for a non-aqueous secondary battery according to claim 1, wherein the separator has a static friction coefficient of 0.3 to 1.0.   The said inorganic filler consists of at least 1 sort (s) among a metal hydroxide and a metal oxide, The separator for non-aqueous secondary batteries of Claim 1 or Claim 2 characterized by the above-mentioned.   A non-aqueous secondary battery for obtaining an electromotive force by doping and dedoping of lithium, a positive electrode having a positive electrode current collector and a positive electrode active material layer, a negative electrode having a negative electrode current collector and a negative electrode active material layer, and A non-aqueous secondary battery comprising the non-aqueous secondary battery separator according to claim 1 and a non-aqueous electrolyte disposed between the electrodes.   The non-aqueous secondary battery according to claim 4, wherein the positive electrode active material has a volume change rate of 1% or more in a process of dedoping lithium.   The non-aqueous secondary battery according to claim 4 or 5, wherein the negative electrode active material has a volume change rate of 3% or more in the process of doping lithium.