JP2014003071A - Load-resistant insulation evaluation apparatus for nonwoven fabric separator for electrochemical element and load-resistant insulation evaluation method for unwoven fabric separator for electrochemical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a load-resistant insulation evaluation apparatus for an unwoven fabric separator for an electrochemical element capable of easily evaluating insulation of an unwoven fabric separator for an electrochemical element in the state approximate to a real system, even without performing complicated work such as assembling the electrochemical element, in load-resistant insulation evaluation for the separator, and a load-resistant insulation evaluation method for an unwoven fabric separator for an electrochemical element employing the apparatus.SOLUTION: The load-resistant insulation evaluation apparatus for an unwoven fabric separator for an electrochemical element comprises: two conductive elastic plate electrodes holding a separator to be tested therebetween; an approximately columnar metallic hard member and a metallic hard member larger than the approximately columnar metallic hard member further holding therebetween the conductive elastic plate electrodes which hold the separator to be tested therebetween; a pressing device for applying a load from both sides of the two metallic hard members; a load measuring device for measuring the load applied to the separator to be tested; and an ammeter for measuring current which flows to the separator to be tested. The evaluation method employs the evaluation apparatus.

Description

  TECHNICAL FIELD The present invention relates to an apparatus for evaluating load resistance insulation of a nonwoven fabric separator for electrochemical devices and a load resistance insulation evaluation method for nonwoven fabric separators for electrochemical devices.

  As a separator for an electrochemical element used for a battery or a capacitor (hereinafter sometimes abbreviated as “separator”), a nonwoven fabric separator for an electrochemical element using a nonwoven fabric (hereinafter abbreviated as “nonwoven fabric separator”) And a film separator for electrochemical devices using a porous film (hereinafter sometimes abbreviated as “film separator”). The separator is required to have a level of insulation that does not short-circuit between electrodes even under pressure. On the other hand, since the separator is also a path for ions and electrons between the electrodes, if the insulating property is too high, there is a problem that the internal resistance is increased and the performance as an electrochemical element is lowered.

  When evaluating the insulating properties of the separator, there is a method of actually assembling an electrochemical element and performing a test, but there is a problem that the work becomes complicated and a long time is required. As a test method for evaluating the load resistance insulation of the film separator, there is a method of measuring a resistance value between the mounting table and the contact terminal while placing a film separator on the mounting table and applying a load by moving the contact terminal up and down. It is disclosed (for example, see Patent Document 1). However, since the contact terminal for applying a load has a small radius of curvature of 0.05 mm to 4.00 mm, the load is applied at a point. What is the state in the electrochemical element that applies the load to the entire separator? There was a problem of being different. In addition, since the film separator was destroyed during conduction, it was closer to a test for perforation resistance than load-bearing insulation characteristics. When the nonwoven fabric separator is evaluated by the load bearing insulation evaluation method in this film separator, the load of the nonwoven fabric separator is moved by opening the eyes by applying a load with a contact terminal, so that in the actual system called an electrochemical device There arises a problem that the deviation from the evaluation result of the insulating property becomes larger than that of the film separator.

JP 2009-243929 A

  The present invention has been made in view of the above circumstances, and in a load-proof insulation evaluation of a nonwoven fabric separator for electrochemical elements, it is in a state close to an actual system without performing a complicated operation such as assembling an electrochemical element. An object of the present invention is to provide a load-resistant insulation evaluation apparatus for a non-woven fabric separator for electrochemical elements that can easily evaluate the insulation of the separator, and a load-resistant insulation evaluation method for a non-woven separator for electrochemical elements using the apparatus.

As a result of earnest research to solve the above problems,
(1) A load-resistant insulation evaluation device for an electrochemical device nonwoven fabric separator,
Two conductive elastic plate electrodes sandwiching the separator under test,
A substantially cylindrical metal hard member that further sandwiches a conductive elastic plate electrode that sandwiches a separator under test, and a metal hard member that is larger than the substantially cylindrical metal hard member,
A pressure device for applying a load from both sides of two metal hard members,
A load measuring device for measuring the load applied to the separator under test,
An ammeter for measuring the current flowing through the separator under test,
A load-resistant insulation evaluation apparatus for a nonwoven fabric separator for electrochemical devices, comprising:
(2) The apparatus for evaluating load resistance insulation of the nonwoven fabric separator for electrochemical elements according to (1), wherein the conductive elastic plate electrode is a conductive elastic plate electrode having a thickness of 1 mm or more and 5 mm or less,
(3) The apparatus for evaluating load insulation of the nonwoven fabric separator for electrochemical elements according to (1) or (2), wherein the diameter of the substantially cylindrical metal hard member is 10 mm to 50 mm,
(4) In the load resistance insulation evaluation method for a non-woven fabric separator for electrochemical devices using the device for evaluating the load resistance insulation of the non-woven fabric separator for electrochemical devices according to any one of (1) to (3), two sheets A non-woven fabric separator for electrochemical devices, characterized in that a separator to be tested is sandwiched between two conductive elastic plate electrodes and the time change of the load applied to both conductive elastic plate electrodes and the current flowing between the separators is measured simultaneously. Load insulation evaluation method,
I found.

  With the load-resistant insulation evaluation device for the non-woven fabric separator for electrochemical elements of the present invention and the load-proof insulation evaluation method for the non-woven fabric separator for electrochemical devices using the evaluation device, without much labor and time, It is possible to evaluate the insulation of the separator against the load in a short time with a simple operation.

It is the schematic which shows an example of the part in the apparatus for load-proof insulation evaluation of the separator in this invention. It is the schematic which shows an example of the apparatus for load-proof insulation evaluation of the separator in this invention. It is a figure which shows the correlation with the voltage drop two weeks after charge in the load-bearing insulation evaluation (1) by cell assembly, and the load-bearing insulation evaluation in this invention. It is a figure which shows the correlation with the voltage drop two weeks after charge in the load-bearing insulation evaluation (2) by cell assembly, and the load-bearing insulation evaluation in this invention.

  FIG. 1 is a schematic view showing an example of an electrode set which is a part of a load-resistant insulation evaluation apparatus (hereinafter, may be referred to as “evaluation apparatus”) of a nonwoven fabric separator for electrochemical devices in the present invention. In the present invention, the electrode set sandwiches two conductive elastic plate electrodes 2 and 3 sandwiching a separator under test (nonwoven separator for test) 1, and the separator under test 1 and conductive elastic plate electrodes 2 and 3. It consists of a substantially cylindrical metal hard member 4 and a metal hard member 5 larger than the substantially cylindrical metal hard member 4.

  FIG. 2 is a schematic view of an apparatus for evaluating load resistance insulation of a nonwoven fabric separator for electrochemical elements in the present invention. In addition to the electrode set, a load measuring device 7 for measuring a load applied to the separator to be tested, a pressurizing device 8 for applying a load from both sides of the metal hard members 4 and 5, and a current flowing through the separator to be tested. It has an ammeter 9 for measuring. Thick arrows indicate the direction of pressurization during evaluation.

  The thickness of the conductive elastic plate electrodes 2 and 3 is preferably 500 μm to 10 mm, and more preferably 1 mm to 5 mm. If the thickness of the conductive elastic plate electrode is too thin, the mechanical strength may be low and test operation may be difficult.

  Various conductive rubbers can be used as the material of the conductive elastic plate electrodes 2 and 3. Examples thereof include natural rubber, synthetic rubber, silicon rubber and the like in which conductive carbon black or metal powder is blended. By using the elastic plate electrode, the conductive elastic plate electrode enters into the pores of the nonwoven fabric separator, which is the separator to be tested, under load, and comes into contact with the conductive elastic plate electrode on the opposite side, thereby increasing the current value. It is considered possible to evaluate When an inelastic electrode is used, no increase in current value is observed even when the same load is applied.

  Metal, hard members (hereinafter sometimes referred to as “hard members”) 4 and 5 are preferably iron, copper, aluminum, stainless steel, gun metal, brass, etc., because they can maintain stable strength over a long period of time. It is done. When the flatness of the hard member is low, the pressure distribution becomes non-uniform and the evaluation result may become unstable. In particular, the surface that contacts the elastic plate electrode is preferably polished flat. As such a polishing method, it is possible to use a method such as polishing one surface with a polishing paper placed on a glass plate. The abrasive paper is preferably finer than # 180. By attaching a metal hard member having high conductivity and small dimensional change due to a load to the conductive elastic plate electrode, a more stable result can be obtained than in the case of measuring only with the conductive elastic electrode.

  In the present invention, the diameter 6 of the substantially cylindrical metal hard member 4 is preferably 10 mm to 50 mm. If the diameter 6 is too small, the test operation becomes difficult, and the test area may be too small to give a test result representing the entire separator. If the diameter 6 is too large, a larger pressure device may be required to apply the load, which is inefficient.

  In the present invention, “the hard member 5 is larger than the substantially cylindrical hard member 4” indicates that both hard members can be overlapped so that the substantially cylindrical hard member 4 does not protrude.

  As the load measuring device 7 used in the present invention, various load cells can be used. In particular, a load cell using a strain resistor is preferably used because it has good resolution and responsiveness in the vicinity of a load (conduction load) when the insulation of the separator under test is lowered. The rated load of the load measuring device used in the evaluation device of the present invention (showing the maximum load that can be applied without damaging or degrading the evaluation device) is preferably 1 to 5 kN. This is because if the rated load is too small, a measurement value regarding a highly insulating separator may not be obtained, and if the rated load is too large, the resolution of the measurement value may be insufficient.

  As the pressurizing device 8 used in the evaluation apparatus of the present invention, a vise and other instruments can be used in addition to a load device using an air cylinder and a hydraulic cylinder. When the pressurizing device is made of a conductive material such as metal, the metal hard members 4 and 5 may be short-circuited through the pressurizing device. In that case, it is necessary to sandwich an insulating member made of rubber, resin or the like between the pressure device and at least one of the electrodes.

  The load resistance insulation evaluation method using the evaluation apparatus of the present invention is as follows. First, the tested separator 1 is sandwiched between the conductive elastic plate electrodes 2 and 3. At this time, the tested separator 1 is cut out larger than the conductive elastic plate electrodes 2 and 3 so that the conductive elastic plate electrodes 2 and 3 are not in direct contact with each other. This is sandwiched by the hard members 4 and 5 from both sides, and an electrode set is assembled. The assembled electrode set is sandwiched by the pressurizing device 8 and pressed from the surface of the hard members 4 and 5 opposite to the conductive elastic plate electrodes 2 and 3. A load measuring device 7 such as a load cell is disposed between the pressurizing device 8 and the hard member 4 or 5. As a result, the load applied to the separator under test by 1 can be measured. Furthermore, by connecting the ammeter 9 to the hard members 4 and 5, it is possible to observe the change in the insulation of the separator under test 1 due to the load.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a present Example.

  Table 1 shows the basis weight, thickness, density, air permeability, and maximum pore diameter of the nonwoven fabric separator used as the test separator 1 used in the test. The basis weight of the separator means a value measured by a method defined in JIS P8124. Thickness and density mean values measured by the method defined in JIS P8118. The air permeability was measured according to JIS P8117 using a Gurley air permeability meter having a circular hole with an outer diameter of 28.6 mm. The maximum pore size was measured using a Porsimeter II manufactured by Coulter in accordance with the bubble point method defined in JIS K3832.

<Evaluation of Load Insulation According to the Present Invention (Example)>
A 50 mm square conductive rubber (thickness 1.0 mm, hardness Shore A 50 °) was placed as the conductive elastic plate electrode 3 on an aluminum cylinder having a diameter of 40 mm and a height of 25 mm, which is the hard member 5. A 60 mm square separator to be tested 1 was installed at a substantially center on the conductive elastic plate electrode 3. Further, on this separator 1 to be tested, an elastic plate electrode 2 similar to the conductive elastic plate electrode 3, and an aluminum cylinder having a diameter of 30 mm and a height of 25 mm as a substantially cylindrical hard member 4 were placed in order.

  An insulating plate made of glass epoxy was attached to the surface of the jaw (jaw) of the vise (pressurizing device 8), and a load cell (load measuring device 7) having a rated load of 2224N was fixed to the other jaw. The test apparatus 1, the conductive elastic plate electrodes 2, 3 and the hard members 4, 5 were sandwiched between them, and an evaluation apparatus having the configuration shown in FIG. 2 was assembled. While applying a voltage of 2.5 V between both electrodes and measuring the current flowing between both electrodes with an ammeter 9, the handle of the vise was tightened and the pressure was gradually increased. When the current flowing between the two electrodes became 10 μA or more, it was determined that the insulation of the separator was lowered (conduction), and the load (conduction load) at that time was measured. A 9 V DC power source was used as the power source for the load measuring device 7 and the ammeter 9. The test was performed at N = 10 and the average value was recorded.

<Weight-proof insulation evaluation by cell assembly (1)>
Lithium manganate as the positive electrode active material, artificial graphite as the negative electrode active material, ethylene carbonate: diethyl carbonate mixed solvent (3: 7 v / v) solution (1M) of lithium hexafluorophosphate as the electrolyte, and pouch type with a capacity of 100 mAh A lithium ion battery was assembled and charged at 4.2V. Thereafter, the whole cell was left standing with or without pressurization at a constant pressure (1 kN or 3 kN), the voltage drop after 2 weeks was measured at N = 10, and the average value was recorded. It can be said that the higher the insulation of the separator, the smaller the voltage drop after 2 weeks and the better the self-discharge characteristics.

<Weight-proof insulation evaluation by cell assembly (2)>
Using a activated carbon as the electrode active material and a propylene carbonate solution of triethylammonium tetrafluoroborate (1M) as the electrolyte, a pouch-type electric double layer capacitor having a capacity of 3F was assembled and charged at 2.7V. Then, the whole cell was left still in a state where it was pressurized at a constant pressure (1 kN or 3 kN) or not, a voltage drop after 24 hours was measured at N = 10, and an average value was recorded. It can be said that the higher the insulation of the separator, the smaller the voltage drop after 24 hours and the better the self-discharge characteristics.

  Table 2 shows the results when each separator under test was tested by the above evaluation method. In the load-bearing insulation evaluation according to the present invention, the load when the current flowing between both electrodes becomes 10 μA or more, and in the load-bearing insulation evaluation (1) by cell assembly, the voltage drop after 2 weeks of charging is determined by cell assembly. In the load-bearing insulation evaluation (2), the voltage drop after 24 hours of charging is described. In the nonwoven fabric separator D, since the interelectrode current did not become 10 μA or more in the measurement range (˜2224N) of the present invention, no numerical value is described.

  FIG. 3 is a correlation diagram of the results of the load-bearing insulation evaluation according to the present invention and the results of the load-bearing insulation evaluation (1) by cell assembly, and FIG. 4 is the load-bearing insulation evaluation according to the present invention and the load-bearing insulation by cell assembly. It is a correlation diagram of the result of evaluation (2). As apparent from FIGS. 3 and 4, the separator insulation in the load-resistant insulation evaluation by cell assembly and the separator insulation in the load-proof insulation evaluation according to the present invention showed a good correlation. That is, when evaluated by the evaluation apparatus and evaluation method of the present invention, it can be said that the separator whose insulating property is lowered by a smaller load is deteriorated in self-discharge characteristics when it is incorporated in a cell and applied with the load.

(Comparative Example 1)
Instead of the conductive elastic plate electrode, a load-resistant insulation test was conducted in the same manner as in the example except that an electrode for an electric double layer capacitor in which the electrode active material was activated carbon and the current collector was aluminum was used. In any case of the nonwoven fabric separators A to D, the current value did not become 10 μA or more, and the load resistance insulation could not be evaluated. This seems to be because the electrodes used do not have elasticity, so that some of the electrodes enter the pores of the nonwoven fabric due to the load and the electrodes do not contact each other.

(Comparative Example 2)
A load insulation test was conducted in the same manner as in the example except that a contact terminal having a spherical stainless steel tip having a radius of curvature of 2 mm was attached to the metal hard member 4 and the conductive elastic plate electrode was not used. The load when the current value was 10 μA or more had a variation of 100% or more in any of the nonwoven fabric separators A to D. The variation mentioned here refers to a value obtained by dividing the difference between the maximum value and the minimum value when tested at N = 10 by the average value and multiplying by 100. The variation when measured by the method of the examples was within 20% for any nonwoven fabric separator. This is presumably because the load on the nonwoven fabric separator is applied with a point, and the resulting fluctuation increases when the contact point hits the pore and when it hits the fiber.

  As an application example of the present invention, load-resistant insulation evaluation in production / development of a nonwoven fabric separator for electrochemical elements is suitable.

DESCRIPTION OF SYMBOLS 1 Separator to be tested 2 Conductive elastic plate electrode 3 Conductive elastic plate electrode 4 A substantially cylindrical metal hard member 5 A metal hard member larger than a substantially columnar metal hard member 6 A substantially columnar metal hard member Diameter 7 Load measuring device 8 Pressurizing device 9 Ammeter

Claims (4)

A device for evaluating load-bearing insulation of a nonwoven fabric separator for electrochemical devices,
Two conductive elastic plate electrodes sandwiching the separator under test,
A substantially cylindrical metal hard member that further sandwiches a conductive elastic plate electrode that sandwiches a separator under test, and a metal hard member that is larger than the substantially cylindrical metal hard member,
A pressure device for applying a load from both sides of two metal hard members,
A load measuring device for measuring the load applied to the separator under test,
An ammeter for measuring the current flowing through the separator under test,
A load-resistant insulation evaluation apparatus for a nonwoven fabric separator for electrochemical devices, comprising:   2. The apparatus for evaluating load resistance insulation of a nonwoven fabric separator for an electrochemical element according to claim 1, wherein the conductive elastic plate electrode is a conductive elastic plate electrode having a thickness of 1 mm to 5 mm.   The apparatus for evaluating load resistance insulation of a nonwoven fabric separator for an electrochemical element according to claim 1 or 2, wherein the substantially cylindrical metal hard member has a diameter of 10 mm to 50 mm.   In the method for evaluating the load-bearing insulation of the nonwoven fabric separator for electrochemical devices using the apparatus for evaluating the load-bearing insulation of the nonwoven fabric separator for electrochemical devices according to any one of claims 1 to 3, two conductive elastic plate electrodes Evaluation of load insulation of a non-woven separator for electrochemical devices, characterized by simultaneously measuring the time applied to the load applied to both conductive elastic plate electrodes and the time variation of the current flowing between the separators to be tested by sandwiching the separator to be tested between them. Method.