JP2018152260A - Internal short circuit test method and internal short circuit test device of battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal short circuit test method and an internal short circuit test device capable of restraining internal short circuit, occurring in a battery, conveniently with high repeatability, while preventing the surrounding of a pressurizing part from damaging the cell surface.SOLUTION: In an internal short circuit test method of a battery including a laminate of a positive electrode plate and a negative electrode plate laminated via a separator, where the laminate is housed in an exterior coating, internal short circuit is generated in the battery by compressing the battery by a compression part including a compression plate having a relief shape at least around a compression surface for compressing the battery, and a protrusion protruding from the compression plate by a length corresponding to a prescribed number of internal short circuit layers and piercing the battery.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a battery internal short circuit test method and an internal short circuit test apparatus.

  There are various methods and evaluation tests for evaluating the safety of batteries such as lithium ion secondary batteries. Among them, conductive foreign matter is mixed inside the battery, which is caused by short-circuiting between the positive electrode and the negative electrode It is extremely important for battery manufacturers to evaluate the behavior of internal short circuits.

  A nail penetration test has been widely conducted as a test simulating such an internal short circuit. In the nail penetration test, an internal short circuit can be reliably generated by inserting and penetrating a conductive nail from the outside of the cell, so that a certain degree of high reproducibility is easily obtained, and a specially sophisticated device is also required. Because there is no, there is no big barrier to testing.

  Although the nail penetration test has a feature that it can be easily performed, it has been regarded as a problem from the past only to create a state far from the internal short-circuit phenomenon normally observed in a cell. That is, the internal short circuit caused by the actual conductive foreign matter such as a point where a thick nail penetrates from the front to the back and a point where a hole is formed in the electrode is greatly different. The internal short circuit caused by the actual conductive foreign material is considered to be limited to 1 or 2 layers at most even if the electrode itself is torn or the foreign material penetrates the electrode. It is almost impossible to control the number of short-circuited layers.

  Although the nail penetration test has been performed more widely than before, the state differs greatly from an internal short circuit caused by a conductive foreign substance that is considered to actually occur in that a nail for generating an internal short circuit penetrates the battery.

  Patent Document 1 proposes a test method that reproduces a state closer to a phenomenon that actually occurs by piercing only a minute portion such as the tip of a nail. However, even with this method, in order to control the position of the pressurizer to a high degree, a pressurizing force measuring unit that looks at the pressurizing force, a pressurizer control unit that feeds it back to position control, a short-circuiting control unit, etc. There was a problem of becoming a complicated and expensive device.

  In addition, in the battery testing apparatus of Patent Document 2, it is described in FIGS. 2, 3, and (0042) to (0043) that a nail penetration test jig 44 is attached to the pressing portion 42. The nail penetration test jig 44 has a nail portion 44a and a base portion 44c formed integrally with the base of the nail portion 44a. The driving unit 18 lowers the pressurizing unit 42 to pierce the battery B with the nail 44a. However, there is no description about how far the nail 44a is inserted into the battery B and how the base 44c pressurizes the battery B. Therefore, as in Patent Document 1, it is considered that the descending distance of the drive unit 18 is measured and performed while feedback. However, in that case, there is a problem that the device becomes complicated and expensive as in Patent Document 1.

Patent No. 5060623 JP 2015-159017

  Therefore, recently, a test method that reproduces a state closer to a phenomenon that actually occurs, such as a forced internal short circuit test, has been proposed. In this test, the laminate or wound body is taken out from the battery, and a conductive foreign object (a small piece of nickel) is actually inserted between the electrodes, reassembled into the battery, and the foreign object insertion part is pressurized from the outside and shorted internally. Is generated.

  The forced internal short circuit test is a test that can reproduce a state very close to an internal short circuit caused by a conductive foreign substance that is considered to actually occur. However, it takes much time to disassemble the battery and insert foreign matter, and it is difficult to pressurize the location of the foreign matter correctly, so that reproducibility is poor.

  Furthermore, even if the foreign object insertion point is correctly pressurized, the end of the pressure part of the test device has an angular shape. The surface is damaged and an internal short circuit occurs due to crushing. For this reason, it often happens that the assumed internal short-circuit state does not occur. If the normal of the surface to be pressed is not correctly parallel to the pressing direction, the corner portion may damage the cell surface. For example, the case where the battery is tilted when the battery is attached to the test apparatus or the entire cell is curled due to the curl of the electrode itself.

  In addition, the dry room (ultra-low-humidity clean room) and the test site need to be close to each other in order to disassemble the battery, and the test site is limited. In addition, since it is necessary to monitor a minute voltage drop, a sophisticated voltage measurement unit and a mechanism that feeds back and stops the pressurization are very complicated and expensive.

  An object of the present invention is to provide an internal short-circuit test method and an internal short-circuit test apparatus that are simple and highly reproducible for internal short-circuits generated in a battery, and that can suppress damage to the cell surface around the pressurized portion. It is to be.

The present invention is an internal short-circuit test method for a battery in which a laminate in which a positive electrode plate and a negative electrode plate are laminated via a separator is housed in an exterior body,
At least a pressure plate having a relief shape around a pressure surface that pressurizes the battery, a length corresponding to a predetermined number of internal short-circuit layers from the pressure plate, and a pressure portion including a protrusion portion that pierces the battery, the battery. The battery is subjected to an internal short circuit test method, wherein an internal short circuit is generated in the battery.

The present invention also includes a mount on which a battery to be tested is placed;
Legs provided on the mount;
A mechanism support provided on the leg,
A delivery mechanism supported by the mechanism support;
A test plate provided in the delivery mechanism and having a relief shape around at least a pressurization surface for pressurizing the battery, and a battery projecting to a length corresponding to a predetermined number of internal short-circuit layers and fixed on the test plate A pressurizing part with a protruding part
It is an internal short circuit test apparatus characterized by comprising.

  According to the present invention, it is possible to reproduce the internal short-circuit state necessary for evaluation to be generated inside the battery by a simple method, and it is possible to suppress damage around the cell surface to the cell surface.

It is sectional drawing of the film-clad battery which is an example of the evaluation object in embodiment of this invention. It is a schematic perspective view which shows an example of the pressurization part of embodiment of this invention. It is a lineblock diagram showing roughly the composition of the test equipment concerning the embodiment of the present invention. It is sectional drawing of the film-clad battery of the test state which generates an internal short circuit by the evaluation method of embodiment of this invention. It is a figure which shows cross-sectional shapes other than FIG. 2 of a pressurizing plate.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

  First, based on FIG. 1, an example of a film-clad battery will be described as an example of a battery to be evaluated in the present embodiment. The film-clad battery is, for example, a lithium ion secondary battery. In FIG. 1, the test cell 1 is indicated. As shown in FIG. 1, the power generation element is accommodated in an exterior body 3 made of a laminate film together with an electrolytic solution (not shown). The power generation element is formed by alternately stacking stacked bodies in which positive plates 41 and negative plates 42 are stacked with separators 43 interposed therebetween. A separator 43 is also sandwiched between the laminated bodies. The power generation element thus formed is covered with the exterior body 3 except for the positive electrode terminal and the negative electrode terminal.

The positive electrode plate 41 is formed by applying a positive electrode active material to both surfaces of the positive electrode current collector. An aluminum foil or the like is used as the positive electrode current collector. Examples of the positive electrode active material include a positive electrode active material body made of a lithium composite oxide such as lithium nickelate (LiNiO ₂ ), lithium manganate (LiMnO ₂ ), or lithium cobaltate (LiCoO ₂ ), and carbon black. It is formed by applying a mixture of a conductive additive such as a binder and a binder to both main surfaces of the positive electrode current collector, followed by drying and rolling. Note that the positive electrode current collector and the positive electrode active material are not particularly limited.

  The negative electrode plate 42 is formed by applying a negative electrode active material to both surfaces of a negative electrode current collector. A copper foil or the like is used as the negative electrode current collector. Further, as the negative electrode active material, for example, in the negative electrode active material main body that occludes and releases lithium ions of the positive electrode active material, such as amorphous carbon, non-graphitizable carbon, graphitizable carbon, or graphite, A mixture of binders is applied to both main surfaces of the negative electrode current collector, and dried and rolled. Note that the negative electrode current collector and the negative electrode active material are not particularly limited.

  A part of the edge in the longitudinal direction of the negative electrode current collector extends as an extension 44 that does not include the negative electrode active material layer, and the tip thereof is joined to the negative electrode terminal (tab 2). Although not shown in FIG. 1, similarly, a part of the longitudinal edge of the positive electrode current collector extends as an extended portion that does not include the positive electrode active material layer, and the tip thereof is joined to the positive electrode terminal. Has been.

  The separator 43 has a function of holding an electrolyte while preventing a short circuit between the positive electrode plate 41 and the negative electrode plate 42. The separator 43 is made of, for example, a microporous film made of polyolefin such as polyethylene (PE) or polypropylene (PP). When an overcurrent flows, the pores of the layer are blocked by the heat generation to block the current. It has a function. The separator is not limited to a single-layer film such as polyolefin, but may also be a three-layer structure in which a polypropylene film is sandwiched with a polyethylene film, or a laminate of a polyolefin microporous film and an organic nonwoven fabric. The material and structure of the separator 43 are not particularly limited.

  Moreover, although the electrolyte solution to be used is not particularly limited, for example, a non-aqueous electrolyte solution in which a lithium salt is dissolved in an organic solvent can be used as an electrolyte generally used in a lithium ion secondary battery.

  In the above-described embodiment, the electrolytic solution is used. However, a solid or gel electrolyte obtained by mixing or dissolving a solid electrolyte containing an electrolyte salt, a polymer electrolyte, a polymer compound, or the like may be used. it can. These can also serve as separators.

  In FIG. 2, the schematic of the pressurization part 10 of this embodiment is shown.

  The pressurizing unit 10 is a rod 7 attached to the apparatus, a pressurizing plate 6 that is perpendicularly attached to the rod 7 and pressurizes the surface of the cell to be evaluated, and a projecting portion 5 that stabs into the cell for a predetermined length from the cell surface. It has. The protrusion 5 protrudes from the pressure plate 6 for a length corresponding to a predetermined number of internal short-circuit layers and is fixed to the pressure plate 6. 2 is pierced in the normal direction as shown in FIG. 4 in the test cell 1 shown in FIG. 1 to generate an internal short circuit.

  The pressure plate 6 shown in FIG. 2 has a relief shape 200 formed around the side that pressurizes the cell. The relief shape is, for example, a shape in which the periphery is warped in the direction opposite to the piercing direction, or a shape in which a curved surface (R) is provided around the flat portion of the pressing portion. In FIG. 2, the pressure plate 6 has a shape in which a portion where the pressure surface 201 that pressurizes the cell is in direct contact with the cell is a flat surface, and the entire periphery of the pressure surface 201 is bent in a direction opposite to the tip of the protruding portion 5. . Note that the broken lines in FIG. 2 are used to clearly indicate R and do not mean corners. Therefore, even if the rod 7 is attached to be inclined with respect to the normal direction, even if the pressing surface is not correctly parallel to the pressed surface of the battery, the protruding portion of a predetermined length can be inserted into the cell. In addition, the cell surface is not damaged around the pressing surface. Therefore, it is possible to prevent occurrence of a short circuit due to crushing at that portion, and it is possible to generate only an assumed internal short circuit.

  The pressure plate 6 may have a cross-sectional shape as shown in FIGS. 5A, 5B, and 5C in addition to the shape shown in FIG. In other words, a rectangular cross section with an R formed at an angle (FIG. 5 (a)), a corner of a rectangular cross section material is chamfered to make the end cross section a triangle, and an R is formed at each corner. (FIG. 5B) may be used. Further, various shapes are possible, such as a chamfered corner portion of a material having a rectangular cross section so that a flat surface remains and R is formed at each of the two corner portions of the chamfered portion (FIG. 5C).

  As yet another example, the entire pressing surface 201 may be a spherical surface having a large radius or a convex surface on the side pressing the cell. In the case of a spherical shape, the radius of the spherical surface is desirably sufficiently larger than the protruding length of the protruding portion, and is preferably at least three times the protruding length.

  FIG. 3 is a diagram showing the configuration of the internal short-circuit test apparatus 20 used in the method of the present embodiment. A pressurizing unit 10 shown in FIG. 2 that pressurizes the cell, and a delivery mechanism 21 that holds the pressurizing plate 6 of the pressurizing unit 10 in a direction perpendicular to the surface of the test cell 1 to be evaluated, And a gantry 22 on which the test cell 1 is placed. Four legs 23 are provided on the gantry 22, and a mechanism support 24 is installed on the four legs 23. The delivery mechanism unit 21 is fixed to the center of the lower surface of the mechanism support unit 24. The rod 7 is connected to the distal end of the delivery mechanism portion 21, and the pressure portion 10 described in FIG. 2 is fixed to the distal end of the rod 7. The material of the pressure flat 6 and the protrusion 5 is, for example, stainless steel, and the shape of the protrusion 5 is a conical shape. The feed mechanism 21 and the rod 7 may be combined to form a feed mechanism.

  The delivery mechanism unit 21 may be applied with pressure so that the protruding portion 5 of the pressurizing unit 10 enters the inside of the cell and the pressurizing plate 6 reaches the cell surface. Newton) is enough. Further, since it is only necessary to stop the delivery when the pressure plate 6 reaches the cell surface, the accuracy of the delivery position is not required. In the internal short circuit portion of the battery, the protruding portion 5 is always stuck into the cell by a predetermined length by the pressurizing portion 10. Therefore, the piercing length is always stable, and an internal short circuit that actually occurs can be simulated with good reproducibility. The protrusion 5 is pointed like a nail tip to pierce the battery. The pressure plate 6 has a dimension sufficiently larger than the protrusion 5 so that only the protrusion 5 is stuck in the battery.

  When pressurizing the cell surface with the pressurizing unit 10, the protruding portion 5 of the pressurizing unit 10 first reaches the surface of the cell and then stabs into the inside of the cell. It is desirable that the pressure plate 6 is slow enough not to cause a large impact when it reaches the cell surface. Therefore, it is desirable that it is 1 mm / sec or less.

  Since the pressing plate 6 serves as a stopper for the protruding portion 5 to be stabbed into the cell by a specified length, the projected shape from the pressing direction of the plate is not limited. It can be round, oval, rectangular or square. However, it is desirable that it is rotationally symmetric with respect to the rod so that the load is not dispersed during pressurization.

  The protruding portion 5 of the pressurizing unit 10 pierces the inside of the battery, thereby generating an internal short circuit of the battery. For this reason, it is desirable that the protrusion 5 is made of a conductive material. Further, the pressure plate 6 can sufficiently withstand the load, and any material may be used as long as the deformation amount is as small as possible. However, the load was applied so that the protruding portion 5 can always protrude the specified length. Even in this case, it is preferable to select dimensions and materials so that the deformation amount of the protrusion 5 itself is minimized. From such a viewpoint, it is desirable that the pressure plate 6 is a square of 10 mm square or more as a projected shape from the pressing direction, and is made of metal having a thickness of 10 mm or more.

  The projecting length of the projecting portion 5 of the pressurizing unit 10 is desirably set assuming a short-circuit resistance of an internal short circuit to be generated. For example, the length can be determined by the number of layers in which a short circuit occurs. Moreover, in order to reduce the short-circuit resistance, it is possible to provide a plurality of pressure units 10.

  In the present embodiment, the cell surface is pressurized using a pressurizing portion that protrudes from the pressure plate by a length corresponding to the number of internal short-circuit layers so as to reproduce a predetermined internal short-circuit state. For this reason, the internal short circuit portion of the battery is able to simulate an internal short circuit that actually occurs with high reproducibility because the protruding portion always stabs into the cell by a predetermined length by the pressurizing portion. Further, the test apparatus does not require a high-precision control mechanism for position control, and it is not necessary to link cell voltage drop detection and pressurization operation.

  In the present embodiment, the stacked type battery is described, but the present invention can also be applied to a wound type battery. In this embodiment, a lithium ion battery is targeted, but a battery using other battery materials can also be applied.

  A plurality of protrusions 5 may be provided.

Example 1
Embodiment 1 of the present invention will be described below. In this example, an internal short-circuit evaluation apparatus as shown in FIG. 3 was used. Moreover, the pressurizing part 10 as shown in FIG. 2 was used. Specifically, the pressure plate 6 has a side of 10 mm, a thickness of 5 mm, the protrusion 5 has a tip angle of 30 °, the protrusion 5 has a protrusion length of 1.0 mm, and the pressure surface of the pressure plate has a radius of curvature of 50 mm. .

  The pressurizing unit 10 was pressed from the direction perpendicular to the stacking direction of the electrode laminate of the laminate-clad battery at a moving speed of 0.1 mm / sec and a maximum load of 50N.

  As the battery information, the voltage of the battery and the load related to the pressurizing part were measured. When the voltage of the battery dropped by 30 mV or more, it was determined that an internal short circuit occurred. However, this information was not used to determine test suspension during the test, but only as a result determination after the test.

  As a comparative example, a test using a method based on a forced internal short circuit test specified in JISC8715-2 was performed.

  Two types of test batteries were prepared. The cell A has a cell specification with high safety that passes a normal nail penetration test, and the cell B has a cell specification that generates smoke and ignition in a normal nail penetration test. Hereinafter, they are simply referred to as cell A and cell B. Cell A and cell B have the same cell structure and are the structures shown in FIGS. 1 and 4, but the separators used are different. The cell A uses a separator having high heat resistance such as aramid, and the cell B uses a normal separator such as PP (polypropylene) having low heat resistance.

表１で、結果欄の「○」は、発煙・発火ともに無し、「×」は発煙および発火が起こった事を示している。また、電圧低下観察欄は、試験中に取得したセル電圧データから、内部短絡が発生した時に発生するセルの電圧低下が観察されたかどうかを示している。セルの電圧が30mV以上低下していたら、内部短絡が発生していたと判断し、「有り」、電圧低下が30mV未満であったら「無し」とした。試験後のセルの短絡発生部分の観察を実施した結果が内部短絡発生欄であり、観察により判断された、内部短絡の層数を示した。本実施例の方法だと、安全性の高いセルAは、内部短絡が2層発生している場合でも発煙・発火ともに無しという結果になった。それに対し、安全性の低いセルBでは、内部短絡が発生し、その結果、発煙および発火に至った。同様に比較例では、セルAは発煙・発火ともに無しという結果になり、短絡層数も1層短絡していることが確認出来たが、セルの電圧低下はデータからは確認出来なかった。短絡部の電気的抵抗値が大きかったため、セルの電圧低下としては検出されなかったためと考えられる。また、安全性の低いセルBも同様の試験結果であったが、こちらは、試験後のセルを確認したところ、電極間に配置した導電性異物がセパレータを貫通しておらず、セルの内部短絡が発生していない状態であった。 The test results are shown in Table 1.
Table 1

In Table 1, “◯” in the result column indicates that neither smoke nor ignition occurred, and “×” indicates that smoke or ignition occurred. The voltage drop observation column indicates whether or not a cell voltage drop that occurs when an internal short circuit occurs is observed from the cell voltage data acquired during the test. If the cell voltage was reduced by 30 mV or more, it was judged that an internal short circuit had occurred, and “Yes” was determined. The result of having observed the short circuit occurrence part of the cell after a test was an internal short circuit generation column, and showed the number of layers of the internal short circuit judged by observation. According to the method of this example, the highly safe cell A resulted in no smoke or ignition even when two layers of internal short circuit occurred. On the other hand, in cell B with low safety, an internal short circuit occurred, resulting in smoke and fire. Similarly, in the comparative example, it was confirmed that cell A did not emit smoke or ignite, and it was confirmed that the number of short-circuit layers was short-circuited by one layer, but the cell voltage drop could not be confirmed from the data. This is probably because the voltage drop of the cell was not detected because the electrical resistance value of the short-circuit portion was large. Cell B, which is less safe, had the same test results, but here, after confirming the cell after the test, the conductive foreign matter placed between the electrodes did not penetrate the separator, and the inside of the cell There was no short circuit.

  When the same test was performed on cell A and cell B, the same number of short-circuit layers and results were obtained each time with the method of this example, but the internal short circuit could be confirmed with the method of the comparative example. The case where it was not possible occurred at random and high reproducibility was not obtained.

  As described above, according to the test method of the present embodiment, a test simulating an internal short circuit can be performed easily and with good reproducibility.

DESCRIPTION OF SYMBOLS 1 Test cell 2 Tab 3 Exterior body 41 Positive electrode plate 42 Negative electrode plate 43 Separator 44 Extension part 5 Protrusion part 6 Pressure plate 7 Rod 10 Pressurization part 20 Internal short-circuit test device 21 Delivery mechanism 22 Base 23 Leg part 24 Mechanism support part 200 Escape Shape 201 Pressurized surface

Claims (10)

An internal short circuit test method for a battery in which a laminate in which a positive electrode plate and a negative electrode plate are laminated via a separator is housed in an exterior body,
At least a pressure plate having a relief shape around a pressure surface that pressurizes the battery, a length corresponding to a predetermined number of internal short-circuit layers from the pressure plate, and a pressure portion including a protrusion portion that pierces the battery, the battery. The internal short circuit test method for a battery, wherein the internal short circuit is generated in the battery.   The battery internal short-circuit test method according to claim 1, wherein the relief shape is a shape in which the periphery is bent in a direction opposite to the piercing direction or a shape in which a curved surface is provided in the periphery.   The internal short-circuit test method according to claim 1, wherein the pressure plate has a flat portion in direct contact with the battery.   The internal short circuit test method according to claim 1, wherein the relief shape is such that the pressure surface is a spherical shape.   The internal short circuit test method according to any one of claims 1 to 4, wherein the pressure plate is connected to a rod, and the shape of the pressure plate is rotationally symmetric with respect to the rod.   The internal short circuit test method according to any one of claims 1 to 5, wherein a plurality of the protrusions are provided on the pressure plate.   The internal short circuit test method according to any one of claims 1 to 6, wherein a plurality of the pressure plates are provided. A platform on which the battery to be tested is placed;
Legs provided on the mount;
A mechanism support provided on the leg,
A delivery mechanism supported by the mechanism support;
A test plate provided in the delivery mechanism and having a relief shape around at least a pressurization surface for pressurizing the battery, and a battery projecting to a length corresponding to a predetermined number of internal short-circuit layers and fixed on the test plate A pressurizing part with a protruding part
An internal short-circuit test apparatus comprising:   The battery internal short circuit test device according to claim 8, wherein the escape shape is a shape in which the periphery is curved in a direction opposite to the piercing direction or a shape in which a curved surface is provided in the periphery.   The internal short circuit test apparatus according to claim 8 or 9, wherein the pressure plate has a flat portion in direct contact with the battery.

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