JP7148222B2 - Battery Internal Short Circuit Test Method and Internal Short Circuit Test Equipment - Google Patents

Description

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

There are various methods and evaluation tests for evaluating the safety of batteries such as lithium-ion secondary batteries. It is extremely important for battery manufacturers to evaluate the behavior during an internal short circuit.

A nail penetration test has been widely used 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. There are no major barriers to testing.

On the other hand, although the nail penetration test has the advantage that it can be easily performed, it has long been regarded as a problem that it merely creates a state far from the internal short-circuit phenomenon normally seen inside the cell. In other words, a thick nail penetrates from the front to the back, and a hole is formed in the electrode. Internal short-circuits caused by actual conductive foreign matter are thought to be limited to one or two layers at most, even if the electrode itself breaks or the foreign matter penetrates the electrode. It is nearly impossible to control the number of short-circuited layers.

Therefore, in recent years, a forced internal short circuit test has been developed in which the laminate or wound body is taken out of the battery, a conductive foreign substance is actually inserted between the electrode plates, and an internal short circuit is generated by applying pressure to that part from the outside. A test method has been proposed that reproduces conditions closer to what actually occurs in the field.

The nail penetration test, which has been widely used for a long time, differs greatly from the actual internal short circuit due to conductive foreign matter in that the nail penetrates the battery to generate the internal short circuit.

In addition, the forced internal short-circuit test is a test that can reproduce conditions very similar to internal short-circuits caused by conductive foreign matter that are thought to occur in reality, but it is very time-consuming, such as disassembling the battery and inserting the foreign matter. In addition, it is difficult to pressurize the location of the foreign object correctly, and therefore the reproducibility is poor. In addition, the dry room (ultra-low humidity clean room) and the test site must be close to each other in relation to dismantling the battery, and the test site is subject to restrictions. In addition, since it is necessary to monitor a minute voltage drop, the device, such as an elaborate voltage measuring unit and a mechanism for stopping pressurization by feeding it back, becomes very complicated and expensive.

Patent No. 5060623 JP 2015-159017 A

Patent Literature 1 proposes a test method that reproduces a state closer to what 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 at a high level, it is necessary to have a pressurizing force measuring unit that detects the applied force, a pressurizer control unit that feeds it back to position control, a short circuit control unit, etc. There was a problem of becoming a complicated and expensive device.

Further, in the battery testing apparatus of Patent Document 2, FIGS. 2 and 3, (0042) to (0043) describe that a nail penetration test jig 44 is attached to the pressurizing section 42. FIG. The nail penetration test jig 44 has a nail portion 44a and a base portion 44c integrally formed at the base of the nail portion 44a. The drive unit 18 lowers the pressure member 42 to pierce the battery B with the nail 44a, but there is no description as to how far the nail 44a pierces the battery B or whether the base 44c presses the battery B. Therefore, as in Patent Document 1, it is considered that the lowering distance of the drive unit 18 is measured and fed back. However, in that case, there is a problem that the device becomes complicated and expensive as in Patent Document 1.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-described problems and to provide a method and an internal short-circuit testing apparatus for easily and highly reproducibly testing internal short-circuits occurring in batteries.

The present invention provides a battery internal short-circuit test method comprising a laminate in which a positive electrode plate and a negative electrode plate are laminated with a separator interposed therebetween, and the laminate being housed in an outer package,
The battery is pressurized by a pressurizing plate and a pressurizing part provided with a protrusion projecting from the pressurizing plate by a length corresponding to a predetermined number of internal short-circuit layers to generate an internal short circuit in the battery. A battery internal short circuit test method characterized by:

Further, the present invention includes a base on which a battery to be tested is placed, a leg portion provided on the base, a mechanism support portion provided on the leg portion, a delivery mechanism supported by the mechanism support portion, and the A pressurizing unit provided in a delivery mechanism, comprising a pressurizing plate and a pressurizing unit having a protruding portion fixed on the pressurizing plate so as to protrude by a length corresponding to a predetermined number of internal short-circuit layers and piercing the battery to be tested. An internal short-circuit testing device characterized by:

ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to reproduce the state of the internal short circuit desired to generate|occur|produce inside a battery by a simple method, and it becomes possible to perform a highly reproducible test.

1 is a cross-sectional view of a film-clad battery, which is an example of an object to be evaluated in an embodiment of the present invention; FIG. FIG. 4 is a schematic perspective view showing a pressurizing section of the embodiment of the present invention; 1 is a configuration diagram schematically showing the configuration of a testing device according to an embodiment of the present invention; FIG. FIG. 4 is a cross-sectional view of a film-clad battery under test condition to generate an internal short circuit according to the method of an embodiment of the present invention;

(First embodiment)
A first embodiment of the present invention will be described with reference to FIGS. 1 to 4. FIG.

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 this embodiment. A film-clad battery is, for example, a lithium ion secondary battery. It is indicated as test cell 1 in FIG. As shown in FIG. 1, a power generation element is housed inside an exterior body 3 made of a laminate film together with an electrolytic solution (not shown). The power generation element is formed by alternately laminating a laminate in which the positive electrode plate 41 and the negative electrode plate 42 are laminated with the separator 43 interposed therebetween. A separator 43 is also sandwiched between the laminates. The power generation element formed in this way is covered with the exterior body 3 except for the positive terminal and the negative terminal.

The positive electrode plate 41 is formed by applying a positive electrode active material on both sides of a positive current collector. Aluminum foil or the like is used as the positive electrode current collector. The positive electrode active material includes, for example, lithium nickel oxide (LiNiO ₂ ), lithium manganate (LiMnO ₂ ), or lithium composite oxide such as lithium cobalt oxide (LiCoO ₂ ), carbon black, and the like. and a binder are applied on the positive electrode current collector, dried and rolled. 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 on both sides of a negative electrode current collector. A copper foil or the like is used as the negative electrode current collector. As the negative electrode active material, for example, amorphous carbon, non-graphitizable carbon, graphitizable carbon, or graphite can be used as the negative electrode active material that occludes and releases lithium ions of the above positive electrode active material, and a binder is added to the negative electrode active material. is applied to the main surface of the negative electrode current collector, followed by drying and rolling. 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 portion 44 not provided with the negative electrode active material layer, and the tip thereof is joined to the negative electrode terminal (tab 2). Also, although not shown in FIG. 1, a part of the edge in the longitudinal direction of the positive electrode current collector similarly extends as an extension without the positive electrode active material layer, and the tip thereof is joined to the positive electrode terminal. It is

The separator 43 has the function of preventing a short circuit between the positive electrode plate 41 and the negative electrode plate 42 and at the same time retaining the electrolyte. The separator 43 is made of, for example, a microporous film made of polyolefin such as polyethylene (PE) or polypropylene (PP). have a function. The separator is not limited to a monolayer film of polyolefin or the like, and a three-layer structure in which a polypropylene film is sandwiched between polyethylene films, or a laminate of a polyolefin microporous film and an organic non-woven fabric can also be used. The material and structure of the separator 43 are not particularly limited.

In addition, the electrolyte to be used is not particularly limited, but as an electrolyte generally used in lithium ion secondary batteries, for example, a non-aqueous electrolyte in which a lithium salt is dissolved in an organic solvent can be used.

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

FIG. 2 shows a schematic diagram of the pressure unit 10 of the present embodiment.

The pressurizing unit 10 includes a rod 7 attached to the device, a pressurizing plate 6 attached perpendicularly to the rod 7 and pressurizing the surface of the cell to be evaluated, and a projection projecting from the cell surface into the inside of the cell for a specified length. 5. The projecting portion 5 is fixed to the pressing plate 6 so as to protrude from the pressing plate 6 by a length corresponding to the predetermined number of internal short-circuit layers. 2 is pierced into the test cell 1 shown in FIG. 1 as shown in FIG. 4 to generate an internal short circuit.

FIG. 3 is a diagram showing the configuration of an internal short-circuit testing device 20 used in the method of this embodiment. A pressurizing unit 10 shown in FIG. 2 for pressurizing the cell, and a sending mechanism unit for holding the pressurizing unit 10 and pressurizing the pressurizing flat plate 6 of the pressurizing unit 10 in the vertical direction against the surface of the test cell 1 to be evaluated. 21 and a pedestal 22 on which the test cell 1 is placed. Four legs 23 are provided on the frame 22 , and a mechanism support part 24 is installed on the four legs 23 . The delivery mechanism portion 21 is fixed to the center of the lower surface of the mechanism support portion 24 . A rod 7 is connected to the tip of the delivery mechanism portion 21, and the pressure portion 10 described with reference to FIG. 2 is fixed to the tip of the rod 7. The pressing plate 6 and the protrusion 5 are made of, for example, stainless steel, and the shape of the protrusion 5 is conical. Note that the delivery mechanism portion 21 and the rod 7 may be combined to form a delivery mechanism portion.

The feeding mechanism 21 may be applied with a pressure force that allows the protruding portion 5 of the pressure member 10 to fully enter the inside of the cell and the pressure flat plate 6 reaches the surface of the cell. (Newton) is enough. In addition, since it is only necessary to stop the delivery when the pressurizing plate 6 reaches the cell surface, accuracy of the delivery position is not required. At the internal short-circuit portion of the battery, the projecting portion 5 is always pierced into the cell by a specified length by the pressurizing portion 10 . Therefore, the piercing length is always stable, and it is possible to simulate an internal short circuit that actually occurs with good reproducibility. The projecting portion 5 is pointed like a nail to pierce the battery. The pressing plate 6 has dimensions sufficiently larger than the protrusion 5 so that only the protrusion 5 sticks into the battery.

When the pressure unit 10 pressurizes the surface of the cell, the protrusion 5 of the pressure unit 10 first reaches the surface of the cell and then pierces the inside of the cell. It is desirable that the applanation plate 6 is slow enough not to cause a large impact when it reaches the cell surface. Therefore, it is desirable to be 1mm/sec or less.

Since the pressurizing plate 6 serves as a stopper for the protruding portion 5 to stick into the cell by a specified length, the shape of the plate does not matter. It can be circular, oval, rectangular or square. However, it is desirable to be rotationally symmetrical with respect to the rod so that the load is not distributed during pressurization.

The protruding portion 5 of the pressurizing portion 10 sticks into the inside of the battery, thereby causing an internal short circuit of the battery. Therefore, it is desirable that the projecting portion 5 be made of a conductive material. Any material can be used for the pressurizing plate 6 as long as it can withstand the load sufficiently and the amount of deformation is as small as possible. Even in such a case, the dimensions and materials should be selected so that the amount of deformation of the projecting portion 5 itself is minimized. From this point of view, it is desirable that the pressure plate 6 is a square with a side of 10 mm or more and made of metal with a thickness of 10 mm or more.

The protruding length of the protruding portion 5 of the pressurizing portion 10 is desirably set by assuming the short circuit resistance of the internal short circuit to be generated. Further, in order to reduce the short-circuit resistance, it is possible to provide a plurality of pressure members 10 or to provide a plurality of projections 5 on the pressure plate 6 .

In the present embodiment, the cell surface is pressurized using a pressurizing member that protrudes from the pressurizing plate by a predetermined length and is fixed so as to reproduce a predetermined internal short-circuit state. Therefore, a predetermined internal short circuit state can always be reproduced, and the test equipment does not require a highly accurate control mechanism for position control, and there is no need to link cell voltage drop detection and pressurization operation, assuming that it actually occurs. It is possible to easily realize the internal short-circuit state with good reproducibility.

In addition, although the laminated type battery is described in the present embodiment, the present invention can also be applied to a wound type battery. In addition, although the lithium-ion battery is targeted in this embodiment, batteries using other battery materials can also be applied.

EXAMPLE 1 Example 1 of the present invention will be described below. In this example, the internal short-circuit testing device 20 shown in FIG. 3 was used. As an example, the pressurizing plate 6 of the pressurizing unit 10 is a cube with a side of 10 mm and a thickness of 10 mm, and the center is fixed to the rod 7 . The protruding portion 5 was fixed to the center of the surface of the pressing plate 6 facing the battery, and had a tip angle of 30° and two types of protruding length of the protruding portion 5 of 1.0 mm and 0.6 mm. The test cell 1 is fixed directly below the pressurizing section 10 on the pedestal 22 .

The pressure member 10 was pressed vertically from the direction perpendicular to the stacking direction of the electrode stacks of the laminate-sheathed battery at a moving speed of 0.1 mm/sec with a maximum load of 50N.

The voltage of the battery and the load applied to the pressurized part were measured under these conditions. When the battery voltage dropped by 30 mV or more, it was determined that an internal short circuit had occurred, and the test was stopped.

Also, two types of test cells 1 were prepared. The test cell A has a high safety cell specification that passes a normal nail penetration test, and the test cell B has a cell specification that smokes and ignites in a normal nail penetration test. They are abbreviated as cell A and cell B hereinafter. Although the cells A and B have the same cell structure as shown in FIGS. 1 and 4, the separators used are different. Cell A uses a separator with high heat resistance such as aramid, and cell B uses a normal separator such as PP (polypropylene) with low heat resistance.

Table 1 shows the test results.
Table 1

In Table 1, "◯" in the "result" column means that there was no smoke or fire, and "x" means that smoke and fire occurred. When the protrusion length was 1 mm, the number of layers with an internal short circuit was two, and Cell A had neither smoke nor fire, and a good result was obtained. On the other hand, cell B, which is less safe than cell A, had an internal short circuit between two layers, causing smoke and fire. On the other hand, when the projection length was 0.6 mm, neither the cells A nor B emitted smoke or caught fire. In other words, if the protrusion length is short, neither the high-safety cell nor the non-safety cell emits smoke or fire. Smoke and fire occurred in cells that were not highly resistant.

This test was repeated about ten times for cells A and B, and the number of short-circuit layers was the same each time, and the test results were reproducible.

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

REFERENCE SIGNS LIST 1 test cell 2 tab 3 exterior body 5 protruding portion 6 pressurizing plate 7 rod 10 pressurizing portion 20 internal short-circuit test device 21 delivery mechanism portion 22 base 23 leg portion 24 mechanism support portion 41 positive electrode plate 42 negative electrode plate 43 separator 44 extension portion

Claims (7)

An internal short circuit test method for a battery comprising a laminate in which a positive electrode plate and a negative electrode plate are laminated with a separator interposed therebetween, the laminate being housed in an outer package,
generating an internal short circuit in the battery by pressurizing the battery with a pressurizing plate and a pressurizing unit provided with a protruding part fixed by protruding from the pressurizing plate by a length corresponding to a predetermined number of internal short-circuit layers ; A battery internal short circuit test method characterized in that the feeding of the pressure unit is stopped when the pressure plate reaches the surface of the battery,
An internal short-circuit test method for a battery provided with a plurality of the pressurizing plates. 2. The internal short-circuit testing method according to claim 1, wherein said pressure plate is sufficiently larger than said projection so that only said projection penetrates said battery. 3. The internal short-circuit testing method according to claim 1, wherein the pressure plate is connected to a rod, and the shape of the pressure plate is rotationally symmetrical with respect to the rod. 4. The internal short-circuit testing method according to claim 1, wherein a plurality of said protrusions are provided on said pressure flat plate. a base on which a battery to be tested is mounted; legs provided on the base; a mechanism support provided on the legs; a delivery mechanism supported by the mechanism support; ,
A pressurizing plate, and a pressurizing part having a protruding part fixed on the pressurizing plate so as to protrude by a length corresponding to a predetermined number of internal short-circuit layers to pierce the battery to be tested. An internal short-circuit test device,
An internal short-circuit testing apparatus, wherein a plurality of said pressure plates are provided, and said delivery mechanism stops delivery of said pressure member when said pressure plates reach the surface of said battery . 6. The internal short-circuit testing apparatus according to claim 5, wherein said pressing plate is connected to a rod, and the shape of said pressing plate is rotationally symmetrical with respect to said rod. 7. The internal short-circuit testing apparatus according to claim 5, wherein a plurality of said protrusions are provided on said pressing flat plate.

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