Evaluation method and evaluation system for separator for battery, production method for separator for battery, production method for electrode unit, and production method for battery

Abstract

A test material is prepared by placing a separator on the surface of a substrate. In the test material, a piercing device is inserted into the separator from the opposite side of the substrate, along the thickness direction of the separator. The electrical resistance between the piercing device and the substrate is measured. The separator is evaluated based on the magnitude of the load applied to the piercing device when the electrical resistance decreases to a predetermined value. The substrate and the piercing device each possess conductivity.

Description

Technology Field

[0001] The present disclosure relates to a method for evaluating a separator for a battery, an evaluation system, a method for manufacturing a separator for a battery, a method for manufacturing an electrode unit, and a method for manufacturing a battery. Background Technology

[0002] Japanese Patent Publication No. 2014-32173 discloses a puncture strength measuring device.

[0003] Hereinafter, in this specification, “separator,” “electrode,” and “electrode body” refer to a “separator for a battery,” a “electrode for a battery,” and an “electrode body for a battery,” respectively, unless specifically stated otherwise. Additionally, “electrode” may be used as a general term for a “positive electrode” and a “negative electrode.”

[0004] The separator is in the form of a film. Within the battery, the separator electrically insulates the positive electrode and the negative electrode. For example, during the battery manufacturing process, it is assumed that foreign substances (such as small metal fragments) may be mixed between the separator and the electrodes. Within the battery, these foreign substances can apply a local load to the separator. As the separator becomes locally deformed, the insulation resistance decreases, and voltage defects may occur.

[0005] Conventionally, the "puncture strength test" described in "JIS Z 1707 General Rules for Plastic Films for Food Packaging" has been used as a method for evaluating separators.

[0006] Figure 1 is an explanatory diagram of a puncture strength test.

[0007] A test specimen (1) (film) is loaded onto a hole-drilling stage (2). A hole (3) is drilled in the hole-drilling stage (2). The test specimen (1) is placed over the hole (3). The tip of the needle (4) is hemispherical. The needle (4) has a diameter of 1.0 mm and a tip shape radius of 0.5 mm. The needle (4) is pierced into the test specimen (1). The test speed is 50 ± 5 mm / min. The maximum force until the needle (4) penetrates the test specimen (1) is measured. This maximum force (the maximum load applied to the needle (4)) is considered as the piercing strength [unit N] of the test specimen (1). The greater the piercing strength, the stronger the film is against local deformation and the less likely it is to break.

[0008] In a conventional puncture strength test, the test specimen (1) can be stretched in the direction of movement (Z-axis direction) of the needle (4). Therefore, films that are easy to stretch tend to have higher puncture strength. In an actual battery, it can be assumed that there is almost no space for the separator to stretch. Therefore, puncture strength can be considered unsuitable as an indicator of the strength of the separator in an actual battery.

[0009] In addition, there are cases where an electrode unit is manufactured by, for example, coupling a separator to an electrode. For instance, a separator coupled to an electrode can be formed by applying an insulating material to the surface of the electrode. Evaluating the strength of the separator included in the electrode unit is difficult. That is, it is difficult to distinguish between the strength of the base (electrode) and the strength of the separator. An evaluation method applicable to the separator included in the electrode unit is required.

[0010] The object of the present disclosure is to provide a method for evaluating a separator for a battery.

[0011] The technical configuration and effects of the present disclosure are described below. However, the mechanisms of operation described herein include presumptions. The mechanisms of operation do not limit the technical scope of the present disclosure.

[0012] 1. A method for evaluating a battery separator includes the following (a) to (d).

[0013] (a) A test material is prepared by placing a separator on the surface of a substrate.

[0014] (b) In the test material, a piercing device is inserted into the separator from the opposite side of the material, along the thickness direction of the separator.

[0015] (c) Measure the electrical resistance between the piercing device and the material while piercing the separator.

[0016] (d) The separator is evaluated based on the magnitude of the load applied to the piercing mechanism when the electrical resistance is reduced to a predetermined value.

[0017] The material and the piercing mechanism each have conductivity.

[0018] In the test material of the present disclosure, a separator is supported by a substrate. The substrate may, for example, be a simulated electrode. The substrate may, for example, be an actual electrode. The separator may, for example, simply be placed on the substrate. The separator may, for example, be adhered to the substrate.

[0019] In the evaluation method of the present disclosure, a piercing mechanism is pierced into the front of the separator while the back of the separator is supported by a substrate. That is, the piercing mechanism is pierced into the separator while the separator is in a state where it is difficult to extend. Therefore, it can be assumed that the deformation behavior of the separator within an actual battery can be simulated.

[0020] The piercing mechanism is conductive. The piercing mechanism may be, for example, a metal needle. The piercing mechanism moves along the thickness direction of the separator. During the movement of the piercing mechanism, the electrical resistance between the piercing mechanism and the substrate is monitored. The electrical resistance can be considered to correspond to the insulation resistance when foreign matter is mixed between the separator and the electrode. As the piercing mechanism moves, the electrical resistance decreases.

[0021] As the piercing mechanism moves, the load applied to the piercing mechanism increases. In the present disclosure, the load [unit N] is measured when the electrical resistance decreases to a predetermined value. Hereinafter, the predetermined value of the electrical resistance is also referred to as "short-circuit resistance." The load in the short-circuit resistance is also referred to as "short-circuit load." Short-circuit resistance can be determined, for example, by referring to the insulation resistance required between electrodes within a battery. By the short-circuit load, it can be evaluated whether the separator can maintain insulation without breaking, for example, when foreign matter is mixed between the electrodes. It can be considered that the short-circuit load can serve as a useful indicator in the design, development, and manufacture of the separator.

[0022] The short-circuit load of the present disclosure can be measured before the piercing mechanism penetrates the separator. Additionally, the test material corresponds to an electrode unit in which the separator is coupled to an electrode. Accordingly, it is also possible to evaluate the strength of the separator included in the electrode unit.

[0023] 2. The evaluation method for a battery separator may further include, for example, the following (e).

[0024] (e) The separator is evaluated based on the amount of displacement of the piercing mechanism when the electrical resistance is reduced to a predetermined value.

[0025] Hereinafter, the displacement amount is also referred to as "short-circuit displacement amount." The amount of indentation of the separator can be derived from the displacement amount of the puncture mechanism and the initial thickness of the separator. The short-circuit displacement amount can be considered to correspond to the limit of indentation amount in which the separator can maintain insulation within the battery. The short-circuit displacement amount can also be considered to serve as a useful indicator in the design, development, and manufacturing of the separator.

[0026] 3. The material may include, for example, an electrode for a battery.

[0027] It can be assumed that the load applied to foreign substances and separators within an actual battery may change depending on the mechanical properties of the electrode (e.g., hardness). Since the substrate is an actual electrode, it is expected to closely approximate the environment inside an actual battery.

[0028] 4. The description may include, for example, an electrode body for a battery. The electrode body for a battery includes a plurality of electrodes for a battery.

[0029] Generally, a battery includes an electrode body. An electrode body is an assembly of electrodes. It can be assumed that the load applied to foreign substances and separators within an actual battery may vary depending on the structure and mechanical properties of the electrode body. Since the substrate is an actual electrode body, it is expected to closely approximate the environment inside an actual battery.

[0030] 5. The evaluation system includes a stage, a driving device, a resistance measuring device, and a load measuring device. The stage is configured to load a test material.

[0031] The driving device is configured to move the piercing mechanism along the thickness direction of the separator toward the test material loaded on the stage.

[0032] The resistance measuring device is configured to measure the electrical resistance between the piercing mechanism and the substrate.

[0033] The load measuring device is configured to measure the load applied to the piercing mechanism.

[0034] In the evaluation system of "5" above, the evaluation method of the battery separator of "1" above can be implemented.

[0035] 6. The evaluation system may further include, for example, a displacement measuring device.

[0036] The displacement measuring device is configured to measure the amount of displacement of the piercing mechanism.

[0037] In the evaluation system of "6" above, the evaluation method of the battery separator of "2" above can be implemented.

[0038] 7. The stage may be conductive. The resistance measuring device may be configured to measure the electrical resistance between the piercing mechanism and the stage.

[0039] When the substrate and the stage are in a conductive state, the electrical resistance between the piercing mechanism and the stage can be considered to include the electrical resistance between the piercing mechanism and the substrate. By measuring the electrical resistance between the piercing mechanism and the stage, the electrical resistance between the piercing mechanism and the substrate can be measured indirectly. Depending on the shape of the test material (substrate), measuring the electrical resistance between the piercing mechanism and the stage may make the work easier.

[0040] 8. A method for manufacturing a separator for a battery comprises the following (A1) and (A2).

[0041] (A1) Manufacture a separator.

[0042] (A2) The separator is evaluated according to the evaluation method for battery separators.

[0043] The evaluation method for battery separators may be used, for example, in the design development of separators. For example, the design of separators may be reviewed based on the magnitude of the short-circuit load. The evaluation method for battery separators may be used, for example, in the quality control of separators. For example, in the manufacturing process of separators, sample inspection may be performed using the evaluation method for battery separators. For example, the quality of a manufacturing lot may be determined based on the magnitude of the short-circuit load.

[0044] 9. A method for manufacturing an electrode unit comprises the following (B1) and (B2).

[0045] (B1) An electrode unit is manufactured by placing a separator on the surface of a battery electrode.

[0046] (B2) Using the electrode unit as a test material, the separator is evaluated according to the evaluation method for battery separators.

[0047] In the electrode unit, a separator is coupled to the electrode. In the evaluation method for a battery separator, the electrode unit can serve as a test material. In the evaluation method for a battery separator, even when the separator is coupled to the electrode, the strength of the separator can be evaluated independently.

[0048] The evaluation method for battery separators may be used, for example, in the design development of electrode units. For example, the design of the separator may be reviewed based on the magnitude of the short-circuit load. For example, the design of the electrode may be reviewed based on the magnitude of the short-circuit load. The evaluation method for battery separators may be used, for example, in the quality control of electrode units. For example, in the manufacturing process of electrode units, a sample inspection may be performed using the evaluation method for battery separators. For example, the quality of a manufacturing lot may be determined based on the magnitude of the short-circuit load.

[0049] 10. The separator may be bonded to the surface of the electrode for the battery.

[0050] When a separator is coupled to an electrode, it is difficult to separate the separator from the electrode. Furthermore, there is a possibility that the separator may be damaged as it is separated from the electrode. If the separator is damaged, it is assumed that its strength cannot be properly evaluated. In the evaluation method for battery separators, the separator can be evaluated while it remains coupled to the electrode.

[0051] 11. A method for manufacturing a battery comprises the following (C1) and (C2).

[0052] (C1) An electrode unit is manufactured by the method of manufacturing an electrode unit.

[0053] (C2) Manufacture a battery including an electrode unit.

[0054] For example, an electrode body can be formed by stacking a plurality of electrode units. A battery can be manufactured by housing the electrode body in a case. A method for manufacturing an electrode unit includes a method for evaluating a separator for a battery. The battery is expected to have short-circuit resistance according to the short-circuit load of the separator.

[0055] 12. A method for manufacturing a battery comprises the following (D1) and (D2).

[0056] (D1) The separator is evaluated according to the evaluation method for battery separators.

[0057] (D2) Manufacture a battery including a separator.

[0058] The evaluation method for battery separators may be used, for example, in the design and development of batteries. For example, the magnitude of the separator short-circuit load may be adjusted to match the battery specifications. The evaluation method for battery separators may be used, for example, in the quality control of batteries. For example, batteries may be manufactured using separators with a short-circuit load greater than or equal to a reference value.

[0059] The above and other objects, features, aspects, and advantages of the present disclosure will become clear from the following detailed description of the present disclosure as understood in conjunction with the accompanying drawings. Brief explanation of the drawing

[0060] Figure 1 is an explanatory diagram of a puncture strength test. FIG. 2 is a conceptual diagram showing an evaluation system in the present embodiment. FIG. 3 is a schematic flowchart of the evaluation method for a battery separator in the present embodiment. Figure 4 is a conceptual diagram showing an example of a test material. Figure 5 is a schematic flowchart of the first manufacturing method. Figure 6 is a schematic flowchart of the second manufacturing method. Figure 7 is a schematic flowchart of the third manufacturing method. Figure 8 is a graph showing the relationship between the puncture strength and the thickness of the separator in the first evaluation example. Figure 9 is a conceptual diagram showing a second evaluation example. Figure 10 is a conceptual diagram showing a third evaluation example. FIG. 11 is a schematic diagram showing a piercing mechanism in the fourth evaluation example. Figure 12 is a graph showing the relationship between the short-circuit load and the thickness of the separator in the fourth evaluation example. FIG. 13 is a schematic diagram showing the piercing mechanism in the fifth evaluation example. Figure 14 is a graph showing the relationship between the short-circuit load and the thickness of the separator in the fifth evaluation example. Specific details for implementing the invention

[0061] Definition of Terms, etc.

[0062] Hereinafter, embodiments of the present disclosure (which may be abbreviated as “present embodiments”) and examples of the present disclosure (which may be abbreviated as “present embodiments”) are described. However, the present embodiments and the present embodiments do not limit the technical scope of the present disclosure.

[0063] In this specification, descriptions of "comprising," "including," "having," and variations thereof (e.g., "consisting of," etc.) are in an open-ended format. An open-ended format may include additional elements in addition to essential elements, or it may not include them. A description of "consists of" is in a closed format. However, even in a closed format, impurities that are incidental in ordinary practice or additional elements unrelated to the present disclosure are not excluded. A description of "substantially consisting of ..." is in a semi-closed format. In a semi-closed format, the addition of elements that do not substantially affect the basic and novel characteristics of the present disclosure is permitted.

[0064] In the method described herein, the execution order of a plurality of steps, operations, and the like is not limited to the order described unless specifically stated otherwise. For example, a plurality of steps may proceed simultaneously. For example, a plurality of steps may be performed sequentially.

[0065] In this specification, expressions such as “may” and “can” are used not in the obligatory sense of “must do,” but in the permissive sense of “having the possibility to do.”

[0066] Geometric terms used in this specification (e.g., "parallel," "perpendicular," "orthogonal," etc.) should not be interpreted in a strict sense. For example, "parallel" may deviate somewhat from "parallel" in the strict sense. Geometric terms used in this specification may include tolerances, errors, etc., such as those arising from design, operation, or manufacturing. The dimensional relationships in the drawings may not correspond to actual dimensional relationships. To aid in understanding the technology disclosed herein, dimensional relationships (length, width, thickness, etc.) in the drawings may be altered. Additionally, some components may be omitted.

[0067] In this specification, numerical ranges, such as "m to n%", include upper and lower limits unless specifically stated otherwise. That is, "m to n%" indicates a numerical range of "m% or more and n% or less." Furthermore, "m% or more and n% or less" includes "greater than m% and less than n%." Additionally, a numerical value arbitrarily selected from within the numerical range may serve as a new upper or lower limit. For example, a new numerical range may be established by arbitrarily combining a numerical value within the numerical range with a numerical value described in other parts of this specification, tables, drawings, etc.

[0068] In this specification, all numerical values ​​are modified by the term "approximately." The term "approximately" may mean, for example, ±5%, ±3%, ±1%, etc. All numerical values ​​may be approximations that may vary depending on the form of use of the technology disclosed herein. All numerical values ​​may be expressed in significant figures. A measurement value may be an average value obtained from multiple measurements. The number of measurements may be three or more, five or more, or ten or more. Generally, it is expected that the reliability of the average value improves as the number of measurements increases. A measurement value may be rounded to the nearest whole number based on the number of significant figures. A measurement value may include errors, for example, due to the detection limit of a measuring device.

[0069] In this specification, "having conductivity" means that at least a part of the object is 10 7 It indicates having an electrical resistivity of Ω·cm or less. The entire object is 10 7 It may have an electrical resistivity of Ω·cm or less, and a part of the object is 10 7 It may have an electrical resistivity of Ω·cm or less. For example, when the object is a single material such as metal foil, the entire object is 10 7 It can have an electrical resistivity of Ω·cm or less. For example, when the object is a composite material such as an electrode or an electrode body, a part of the object is 10 7 It can have an electrical resistivity of Ω·cm or less.

[0070] In this specification, "air permeability" refers to "air resistance" as defined in "JIS P 8117 Paper and cardboard - Air permeability and air resistance test method (intermediate range) Gurley test". Air permeability is measured by the Gurley test.

[0071] The present embodiment may be applied to any battery separator. The present embodiment may be applied, for example, to a lithium-ion battery separator.

[0072] Evaluation System

[0073] FIG. 2 is a conceptual diagram showing an evaluation system in the present embodiment.

[0074] Hereinafter, the “evaluation system in this embodiment” may be abbreviated as “this evaluation system”.

[0075] The evaluation system (100) can be used to evaluate the strength of a separator. The evaluation system (100) includes a stage (101), a driving device (102), a resistance measuring device (103), and a load measuring device (104). The evaluation system (100) may further include, for example, a displacement measuring device (105), etc.

[0076] The evaluation system (100) may further include, for example, a control device, a computing device, a recording device, a display device (all not shown), etc.

[0077] For example, each device may be independent. For example, some or all of the devices may be integrated. For example, the present evaluation system (100) may include a texture analyzer, a precision universal test (autograph), etc. The texture analyzer may include, for example, a stage (101), a driving device (102), a load measuring device (104), and a displacement measuring device (105).

[0078] Stage

[0079] The stage (101) is configured to load a test material (10). The test material (10) includes a substrate (11) and a separator (12). Details of the test material (10) will be described later. The stage (101) may be equipped with, for example, a jig for fixing the test material (10). The surface of the stage (101) may be, for example, flat. Flatness indicates that no holes, irregularities, etc. are substantially formed. The stage (101) may be formed from any material. The stage (101) may be electrically insulating, for example. The stage (101) may include, for example, a resin plate. The stage (101) may have, for example, conductivity. The stage (101) may include, for example, a metal plate. The stage (101) may be, for example, made of stainless steel (SUS), aluminum (Al) alloy, etc.

[0080] "drive"

[0081] The driving device (102) is configured to move the piercing mechanism (20) along the thickness direction of the separator (12) toward the test material (10) loaded on the stage (101). The driving device (102) can move the piercing mechanism (20) by any driving principle. The driving device (102) may include, for example, a servo motor, a ball screw, a crosser head, etc. The driving device (102) may be configured to move the piercing mechanism (20) in a direction perpendicular to the surface of the stage (101) (the Z-axis direction in FIG. 2), for example. The driving device (102) may be configured to move the piercing mechanism (20) at a sufficiently low speed. The driving device (102) may be configured to move the piercing mechanism (20) at, for example, a test speed of 0.01 to 100 mm / min.

[0082] 《Stabbing device》

[0083] The piercing mechanism (20) is mounted on the driving device (102). The piercing mechanism (20) may be replaceable, for example. The piercing mechanism (20) may be needle-shaped, for example. The piercing mechanism (20) is conductive. The piercing mechanism (20) may be made of iron (Fe), stainless steel, etc. For example, a needle used in conventional piercing strength tests may be used as the piercing mechanism (20). The size and tip shape of the piercing mechanism (20) may be appropriately selected, for example, according to the expected foreign substance, problem mode, etc. The piercing mechanism (20) may have a diameter of, for example, 0.1 to 10 mm. The diameter indicates the maximum diameter of the body (part other than the tip). The piercing mechanism (20) may have a hemispherical tip shape, for example. The piercing mechanism (20) may, for example, have a tapered R-shaped tip. The angle of the taper may, for example, be 30 to 90°. The radius of the tip shape may, for example, be 0.01 to 1 mm. For example, it can be thought that the sharper the tip shape becomes, the more severe the evaluation under strict conditions.

[0084] Resistance measuring device

[0085] The resistance measuring device (103) is configured to measure the electrical resistance between the piercing mechanism (20) and the substrate (11). The resistance measuring device (103) may include, for example, a commercially available tester, an insulation resistance meter, etc. The measurement range of the resistance measuring device (103) may be appropriately selected, for example, according to the assumed foreign substance, problem mode, etc. The upper limit of the measurement range may be, for example, 0.1 to 100 MΩ or 10 to 50 MΩ.

[0086] The resistance measuring device (103) may be connected to the piercing mechanism (20) and the substrate (11) by means of, for example, a lead wire and a clip. When the stage (101) is conductive and the stage (101) and the substrate (11) are in a conductive state, the electrical resistance between the piercing mechanism (20) and the stage (101) may be measured. Depending on the shape of the test material (10) (substrate (11)), measuring the electrical resistance between the piercing mechanism (20) and the stage (101) may make the work easier.

[0087] Load measuring device

[0088] The load measuring device (104) is configured to measure the load applied to the piercing mechanism (20). The load measuring device (104) may include, for example, a load cell. The measurement range and measurement precision of the load measuring device (104) may be appropriately selected, for example, according to the strength, thickness, etc. of the separator (12). The measurement range of the load measuring device (104) may be, for example, 0.1 to 1000 N.

[0089] Displacement measuring device

[0090] The evaluation system (100) may further include a displacement measuring device (105). The displacement measuring device (105) is configured to measure the amount of displacement of the piercing mechanism (20). The displacement measuring device (105) may measure the amount of displacement of the piercing mechanism (20) by any method. For example, the displacement measuring device (105) may calculate the amount of displacement from the movement speed (test speed) and the movement time of the piercing mechanism (20).

[0091] Display device

[0092] The evaluation system (100) may further include, for example, a display device (not shown). The display device may include, for example, a liquid crystal panel. The display device may be configured to display at least one selected from the group consisting of, for example, test speed, load (test force), displacement amount, and electrical resistance.

[0093] Recording device

[0094] The evaluation system (100) may further include, for example, a recording device (not shown). The recording device may include, for example, a data logger. The recording device may be configured to record at least one selected from the group consisting of electrical resistance, load, and displacement amount. The recording device may record the temporal trend of the target value (e.g., load, displacement amount, etc.).

[0095] "controller"

[0096] The evaluation system (100) may further include, for example, a control device (not shown). The control device may, for example, control the operation of each device, the linkage of each device, etc. The control device may, for example, have a calculation function. The control device may, for example, be configured to acquire the temporal trend of electrical resistance and load from a recording device and to calculate the load at a specified electrical resistance. The control device may also calculate the displacement amount of the piercing mechanism (20).

[0097] Evaluation Method

[0098] FIG. 3 is a schematic flowchart of an evaluation method for a battery separator in the present embodiment. Hereinafter, "evaluation method for a battery separator in the present embodiment" may be abbreviated as "the present evaluation method." The present evaluation method may be performed in the present evaluation system (100). The present evaluation method includes "(a) preparation of a test material," "(b) piercing," "(c) measurement of electrical resistance," and "(d) measurement of load." The present evaluation method may further include "(e) measurement of displacement amount." Furthermore, the order of (a) to (e) in FIG. 3 is for convenience. For example, (b) to (e) may be performed substantially simultaneously.

[0099] (a) Preparation of test material

[0100] The present evaluation method includes preparing a test material (10) (test work) by placing a separator (12) on the surface of a substrate (11) (see FIG. 2).

[0101] For example, depending on the size of the stage (101), the separator (12) is cut to a predetermined size. For example, the test material (10) may be prepared by simply placing the separator (12) on the substrate (11). For example, the test material (10) may be prepared by adhering the separator (12) to the surface of the substrate (11).

[0102] For example, an electrode unit may be manufactured. The electrode unit includes an electrode and a separator (12). The separator (12) is bonded to the surface of the electrode. A test material (10) may be prepared by cutting the electrode unit to a predetermined size. In this case, the electrode is considered to be a substrate (11).

[0103] Separator

[0104] The separator (12) is in the form of a film. The separator (12) may have a thickness of, for example, 10 to 50 μm or 10 to 20 μm. The separator (12) is electrically insulating. The separator (12) may include, for example, resin, ceramic, etc.

[0105] The separator (12) may be porous, for example. The separator (12) may have a permeability of, for example, 100 to 500 s / mL. The separator (12) may be for, for example, a liquid battery. A liquid battery contains an electrolyte. The electrolyte can penetrate into the pores of the separator (12).

[0106] The separator (12) may include, for example, polyolefin, etc. The separator (12) may include, for example, polyethylene (PE), polypropylene (PP), etc. The separator (12) may have a single-layer structure. The separator (12) may, for example, substantially consist of a PE layer. The separator (12) may, for example, have a multi-layer structure. The separator (12) may, for example, include a three-layer structure. For example, a three-layer structure may be formed by stacking a PP layer, a PE layer, and a PP layer in this order.

[0107] The separator (12) may be, for example, a composite material of resin and ceramic. For example, the ceramic may be in the form of particles. For example, a slurry may be prepared by mixing ceramic, a binder, and a dispersion medium. A ceramic layer may be formed by applying the slurry to the surface of a resin film. The ceramic may include, for example, alumina, boehmite, titania, zirconia, silica, etc. The binder may include, for example, polyvinylidene fluoride (PVdF), etc.

[0108] The separator (12) can be manufactured by any method. The separator (12) may be manufactured by a dry method or by a wet method. The separator (12) may be manufactured by, for example, a stretching method, a phase separation method, etc. The separator (12) may be, for example, a "self-supporting film." A self-supporting film refers to a film that can maintain its shape on its own. The separator (12) may be, for example, a "non-self-supporting film." A non-self-supporting film refers to a film that requires a support to maintain its shape. For example, a non-self-supporting film may be formed on the surface of an electrode by coating a particle-shaped resin, a particle-shaped ceramic, etc., onto the surface of the electrode.

[0109] The separator (12) may be, for example, non-porous. The separator (12) may be, for example, for an all-solid-state battery. For example, the solid electrolyte may be in the form of particles. For example, a slurry may be prepared by mixing the solid electrolyte, a binder, and a dispersion medium. The separator (12) (solid electrolyte layer) may be formed by applying the slurry to the surface of the electrode. The solid electrolyte layer may be densified by compressing the solid electrolyte layer. The solid electrolyte may include, for example, Li2S-P2S5.

[0110] <Information>

[0111] The substrate (11) may be, for example, in the shape of a sheet or a plate. The thickness of the substrate (11) may be set so that, for example, the separator (12) has a suitable deformation value. The substrate (11) may, for example, have a thickness of 1 μm or more, may have a thickness of 10 μm or more, or may have a thickness of 100 μm or more. The substrate (11) is conductive. The substrate (11) may include, for example, a metal foil, a metal plate, etc. The substrate (11) may include, for example, a copper (Cu) foil, an Al foil, etc.

[0112] The substrate (11) may include, for example, an electrode. Since the substrate (11) is an electrode, it is expected to be closer to the actual internal environment of the battery. The electrode may be a positive electrode or a negative electrode. For example, in a lithium-ion battery, the negative electrode tends to be softer than the positive electrode. In a lithium-ion battery, if foreign substances are mixed in, the foreign substances tend to enter the negative electrode side. For example, since the substrate (11) is a negative electrode, it can be thought that the mixing of foreign substances in the lithium-ion battery is easily simulated.

[0113] The electrode may include, for example, an active material layer and a current collector. The active material layer is disposed on the surface of the current collector. The active material layer may be disposed on only one side of the current collector, or on both the front and back sides of the current collector.

[0114] The current collector may have a thickness of, for example, 5 to 50 μm or 5 to 20 μm. The current collector may include, for example, a metal foil. The current collector may include, for example, a Cu foil, a Cu alloy foil, an Al foil, an Al alloy foil, a nickel (Ni) foil, a Ni alloy foil, a titanium (Ti) foil, a Ti alloy foil, etc.

[0115] The active material layer may have a thickness of, for example, 10 to 200 μm. The active material layer includes a positive electrode active material or a negative electrode active material. The positive electrode active material may include, for example, lithium nickel-cobalt-manganese, lithium nickel-cobalt-aluminum, lithium iron phosphate, etc. The negative electrode active material may include, for example, graphite, silicon, silicon oxide, tin, tin oxide, lithium titanate, metallic lithium, etc. The active material layer may further include a conductive material, a binder, etc. The conductive material may include, for example, carbon black, etc. The amount of conductive material may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of the active material. The binder may include, for example, PVdF, carboxymethylcellulose (CMC), styrene-butadiene rubber (SBR), etc. The amount of binder may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of active material.

[0116] Figure 4 is a conceptual diagram showing an example of a test material.

[0117] The substrate (11) may include, for example, an electrode body (13). The electrode body (13) includes a plurality of electrodes. The electrode body (13) may have any shape. The electrode body (13) may be, for example, a wound type or a stacked type. By the substrate (11) being an electrode body (13), it is expected to be closer to the actual internal environment of a battery.

[0118] (b) thrust

[0119] The present evaluation method includes, in the test material (10), inserting a piercing mechanism (20) into the separator (12) along the thickness direction of the separator (12) from the opposite side of the substrate (11).

[0120] For example, the present evaluation system (100) and the piercing mechanism (20) are prepared (see FIG. 2). The details of the present evaluation system (100) and the piercing mechanism (20) are as described above. The piercing mechanism (20) is mounted on a driving device (102). A resistance measuring device (103) is connected to the piercing mechanism (20). The resistance measuring device (103) is connected to a substrate (11) (or a stage (101)). The electrical resistance between the piercing mechanism (20) and the substrate (11) is measured. At this point, the electrical resistance may exceed the upper limit of the measurement range of the resistance measuring device (103). That is, the displayed value of the electrical resistance may be, for example, infinite.

[0121] For example, the piercing mechanism (20) can descend to just before the separator (12) at any test speed. It can be assumed that the test speed does not affect the evaluation result while the piercing mechanism (20) is not in contact with the separator (12). By moving the piercing mechanism (20) to just before the separator (12) at a relatively high test speed, the test time can be shortened.

[0122] Next, a test speed (piercing speed) is set. The piercing mechanism (20) is inserted into the separator (12) at a substantially constant test speed. The test speed can be appropriately adjusted according to the thickness of the separator (12), and the sampling frequency of the load and electrical resistance, etc. For example, regarding the thickness of the separator (12) and the sampling frequency, if the test speed is too fast, it may be considered difficult to obtain the load at the time of short circuit occurrence. The test speed may be, for example, 0.001 to 10 mm / min, 0.01 to 1 mm / min, or 0.1 to 0.5 mm / min.

[0123] The direction of movement (the direction of piercing) of the piercing mechanism (20) may be parallel to the thickness direction of the separator (12). In this evaluation method, it can be assumed that the separator (12) is difficult to extend in the direction of piercing. This is because the back surface of the separator (12) is supported by the substrate (11). Because the separator (12) is difficult to extend, it is expected to approximate the actual internal environment of the battery.

[0124] (c) Measurement of Electric Resistance

[0125] The evaluation method comprises measuring the electrical resistance between the piercing device (20) and the substrate (11) while piercing the piercing device (20) into the separator (12). The electrical resistance can be measured, for example, by a resistance measuring device (103) (see FIG. 2).

[0126] (d) Measurement of Load

[0127] The evaluation method includes evaluating the separator (12) by the magnitude of the load (short-circuit load) applied to the piercing mechanism (20) when the electrical resistance is reduced to a predetermined value (short-circuit resistance).

[0128] The load applied to the piercing mechanism (20) can be measured, for example, by a load measuring device (104) (see FIG. 2). The short-circuit resistance can be determined, for example, by referring to the insulation resistance required between electrodes within the battery. The short-circuit resistance may, for example, be the upper limit value of the measurement range of the resistance measuring device (103). For example, it may be determined that the electrical resistance has reached the short-circuit resistance at the point when the displayed value of the resistance measuring device (103) changes from infinity (∞) to a numerical value. A numerical value displayed on the resistance measuring device (103) can be thought of as indicating that a minute current has flowed between the piercing mechanism (20) and the material (11). That is, a numerical value displayed on the resistance measuring device (103) can be thought of as indicating the occurrence of a minute short circuit. The short-circuit resistance may be set to, for example, 0.1 to 100 MΩ, 1 to 100 MΩ, 5 to 50 MΩ, or 30 to 50 MΩ.

[0129] In this evaluation method, the load (short-circuit load) at the point when the electrical resistance reaches the short-circuit resistance is measured. The piercing mechanism (20) may be stopped at the point when the electrical resistance reaches the short-circuit resistance. The short-circuit load may be measured after the piercing mechanism (20) is stopped. The movement of the piercing mechanism (20) may continue even after the electrical resistance reaches the short-circuit resistance. For example, the load at the time of the short-circuit resistance may be determined from the temporal progression of the electrical resistance and the load. The temporal progression of the electrical resistance and the load may be accumulated, for example, in a recording device.

[0130] Depending on the short-circuit load, for example, whether the separator can maintain insulation without breaking when foreign matter is mixed between the electrodes can be evaluated. For example, the separator (12) can be evaluated based on the magnitude of the short-circuit load. For example, the greater the short-circuit load, the better the short-circuit resistance of the separator (12) may be evaluated.

[0131] After measuring the short-circuit load, the movement of the piercing mechanism (20) and the measurement of electrical resistance and load may be continued or stopped. The piercing mechanism (20) may be stopped at the point where it penetrates the separator (12), or it may be stopped before it penetrates the separator (12).

[0132] (e) Measurement of displacement

[0133] The present evaluation method may include evaluating the separator (12) based on the amount of displacement (short-circuit displacement) of the piercing mechanism (20) when the electrical resistance is reduced to a predetermined value (short-circuit resistance). The amount of displacement of the piercing mechanism (20) may be measured by a displacement measuring device (105) (see FIG. 2). For example, the amount of compression of the separator (12) may be derived from the amount of displacement of the piercing mechanism (20) and the initial thickness of the separator (12). By doing so, for example, it can be evaluated how much the separator (12) is compressed within the battery to cause a short circuit.

[0134] <First Manufacturing Method>

[0135] Figure 5 is a schematic flowchart of the first manufacturing method.

[0136] The first manufacturing method is a method for manufacturing a separator. The first manufacturing method includes “(A1) manufacturing of a separator” and “(A2) evaluation of a separator”.

[0137] (A1) Manufacture of Separator

[0138] The first manufacturing method includes manufacturing a separator (12). In the first manufacturing method, the separator (12) is a self-standing film. The separator (12) can be manufactured by any method. For example, a mass-produced product may be manufactured. For example, a prototype may be manufactured.

[0139] (A2) Separator Evaluation

[0140] The first manufacturing method includes evaluating the separator by the present evaluation method.

[0141] This evaluation method may be used, for example, for the design and development of a separator (12). For example, the short-circuit load of a prototype of the separator (12) may be measured. The separator (12) may be improved so that the short-circuit load increases.

[0142] This evaluation method may be used, for example, for quality control of a separator (12). For example, a sample inspection may be performed during the manufacturing process of the separator (12). The quality of the manufacturing lot may be determined by the magnitude of the short-circuit load.

[0143] <Second Manufacturing Method>

[0144] Figure 6 is a schematic flowchart of the second manufacturing method.

[0145] The second manufacturing method includes a method for manufacturing an electrode unit. The second manufacturing method includes “(B1) manufacturing of an electrode unit” and “(B2) evaluation of a separator”. The second manufacturing method also includes a method for manufacturing a battery. That is, the second manufacturing method may include “(C1) manufacturing of an electrode unit” and “(C2) manufacturing of a battery”.

[0146] (B1) Manufacture of electrode unit

[0147] The second manufacturing method includes manufacturing an electrode unit by placing a separator (12) on the surface of the electrode.

[0148] The electrode unit is a component for a battery. For example, an electrode body may be formed by stacking electrode units. In the electrode unit, a separator (12) is coupled to the electrode.

[0149] The electrode unit can be manufactured by any method. For example, an active material is prepared. The active material may be in the form of particles, for example. A current collector is prepared. The current collector may include, for example, a metal foil. For example, a slurry may be prepared by mixing an active material, a binder, and a dispersion medium. An active material layer may be formed by applying the slurry to the surface of the current collector. An electrode may be manufactured by compressing the active material layer.

[0150] For example, a polymer film may be formed on the surface of the electrode by applying, for example, a polymer solution to the surface of the electrode. For example, open pores may be formed in the polymer film by a phase separation method. By doing so, a separator (12) coupled to the electrode can be formed. That is, an electrode unit can be manufactured.

[0151] For example, an electrode unit may be manufactured by attaching a separator (12) (self-supporting film) to the surface of an electrode. For example, the separator (12) may be attached to the electrode by an adhesive. The adhesive may include, for example, PVdF. For example, the separator (12) may be attached to the electrode by applying at least one of heat and pressure to the laminate of the separator (12) and the electrode. The separator (12) may be attached to the electrode entirely or partially.

[0152] (B2) Separator Evaluation

[0153] The second manufacturing method includes using an electrode unit as a test material (10) and evaluating a separator (12) by the present evaluation method. For example, the test material (10) can be manufactured by cutting the electrode unit to a predetermined size. In the present evaluation method, the separator (12) can be evaluated while the separator (12) is coupled to the electrode. The present evaluation method is suitable for evaluating a separator (12) included in an electrode unit.

[0154] This evaluation method may be used, for example, in the design and development of an electrode unit. For example, in a prototype of an electrode unit, the short-circuit load of the separator (12) may be measured. The electrode unit may be improved so that the short-circuit load increases.

[0155] This evaluation method may be used, for example, for quality control of electrode units. For example, in the manufacturing process of electrode units, a sample inspection may be performed. The quality of a manufacturing lot may be determined based on the magnitude of the short-circuit load.

[0156] (C1) Manufacture of electrode unit

[0157] In “(C1) manufacturing of the electrode unit,” the electrode unit is manufactured and the separator (12) is evaluated by the aforementioned “(B1) manufacturing of the electrode unit” and “(B2) evaluation of the separator.”

[0158] (C2) Manufacturing of batteries

[0159] The second manufacturing method comprises manufacturing a battery including electrode units. The battery may be manufactured by any method. For example, an electrode body may be formed by stacking electrode units. A battery may be manufactured by encapsulating the electrode body and the electrolyte in a case. The case may be, for example, a metal container, or a pouch made of a metal foil laminate film.

[0160] The battery includes a separator (12) for which a short-circuit load is evaluated. The battery may have short-circuit resistance according to the short-circuit load of the separator (12).

[0161] <Third Manufacturing Method>

[0162] Figure 7 is a schematic flowchart of the third manufacturing method.

[0163] The third manufacturing method is a method for manufacturing a battery. The third manufacturing method includes “(D1) evaluation of a separator” and “(D2) manufacturing of a battery”.

[0164] (D1) Separator Evaluation

[0165] The third manufacturing method includes evaluating the separator (12) by the present evaluation method. The separator (12) may be prepared by any method. For example, a ready-made separator (12) may be obtained from the market. For example, the separator (12) may be manufactured. The separator (12) is evaluated by the present evaluation method. For example, the quality of the separator (12) may be determined by the magnitude of the short-circuit load.

[0166] (D2) Manufacturing of Batteries

[0167] The third manufacturing method includes manufacturing a battery including a separator (12).

[0168] For example, a positive electrode, a separator (12), and a negative electrode are prepared. For example, the positive electrode, the separator (12), and the negative electrode may all be strip-shaped sheets. For example, a laminate may be formed by stacking the positive electrode, the separator (12), and the negative electrode. The separator (12) is placed between the positive electrode and the negative electrode. A wound electrode body may be formed by winding the laminate in a spiral shape. The electrode body may be molded into a flat shape.

[0169] For example, the positive electrode, the separator (12), and the negative electrode may all be sheets in the shape of a single sheet. For example, a stacked electrode body may be formed by alternately stacking the positive electrode and the negative electrode with the separator (12) in between.

[0170] For example, a battery can be manufactured by enclosing an electrode body and an electrolyte in a case. The battery includes a separator (12) for which a short-circuit load is evaluated. The battery may have short-circuit resistance according to the short-circuit load of the separator (12). For example, the design of the battery may be reviewed by comparing the result of a short-circuit test of the battery with the short-circuit load of the separator (12).

[0171] [Example]

[0172] A separator was evaluated according to the first to fifth evaluation examples. This embodiment includes the fourth and fifth evaluation examples. This embodiment does not include the first to third evaluation examples.

[0173] Preparation of Exam Materials

[0174] A separator was prepared. The separator was a porous film made of polyolefin. The separator was manufactured by the dry method (stretching method).

[0175] An electrode (negative electrode) was prepared. The electrode had a thickness of 66 μm. The electrode included an active material layer and a current collector. The active material layer was placed on both the front and back sides of the current collector. The active material layer had a basis weight of 3.30 mg / cm² per side. The active material layer contained graphite, CMC, and SBR. The current collector contained Cu foil.

[0176] In the first evaluation example, a separator unit was used as the test material. In the second to fifth evaluation examples, the test material was produced by placing a separator on the surface of an electrode (active material layer).

[0177] 《First Evaluation Example》

[0178] In the first evaluation example, the puncture strength (maximum force) of a separator unit was measured in accordance with the “JIS Z 1707 General Rules for Plastic Films for Food Packaging.”

[0179] FIG. 8 is a graph showing the relationship between the piercing strength and the thickness of the separator in the first evaluation example. In the first evaluation example, there is a tendency for the correlation between the thickness of the separator and the piercing strength to be weak. In the first evaluation example, the separator can extend in the piercing direction. It can be assumed that a separator that is easy to extend has a higher piercing strength. Therefore, it can be assumed that the correlation between the thickness of the separator and the piercing strength is weak.

[0180] In an actual battery, it can be assumed that there is almost no space for the separator to expand. The puncture strength in the first evaluation example can be considered inappropriate as an indicator of the strength of the separator in an actual battery.

[0181] 《2nd Evaluation Example》

[0182] Figure 9 is a conceptual diagram showing a second evaluation example.

[0183] A piercing mechanism (20) was pierced into a test material (10) (separator (12)). During the piercing, the displacement of the piercing mechanism (20) and the load were measured. A stress-strain curve was obtained.

[0184] It was considered to extract the peak of the separator (12) from the stress-strain curve of the test material (10). The separator (12) has a relatively lower strength compared to the substrate (11). Therefore, the peak of the separator (12) is buried in the peak of the substrate (11), making it difficult to extract the peak of the separator (12). That is, in the second evaluation example, it was difficult to evaluate the strength of the separator (12).

[0185] 《Third Evaluation Example》

[0186] Figure 10 is a conceptual diagram showing a third evaluation example.

[0187] A simulated foreign material (30) was prepared. The simulated foreign material (30) was a Cu wire (diameter 100 μm). The simulated foreign material (30) was placed on the surface of the separator (12). The simulated foreign material (30) was pushed into the separator (12) by a push jig (35). During the push, the displacement of the push jig (35) and the load were measured. A stress-strain curve was obtained.

[0188] In the third evaluation example, the deviation in the measurement results was large. Factors contributing to the deviation include the surface properties (burrs, etc.) of the simulated foreign substance (30), and the fact that the contact method between the simulated foreign substance (30) and the test material (10) is not stable.

[0189] 《4th Evaluation Example》

[0190] FIG. 11 is a schematic diagram showing a piercing mechanism in the fourth evaluation example.

[0191] As a piercing device, a needle having a hemispherical tip shape was prepared. The tip shape radius (SR) of the needle was 0.5 mm. The diameter (φ) of the needle was 1 mm.

[0192] The fourth evaluation example was performed by the present evaluation system (see Fig. 2).

[0193] A test material (10) (separator (12), material (11)) was placed on a stage (101). The stage (101) was conductive. A piercing mechanism (20) was mounted on a driving device (102). A tester was prepared as a resistance measuring device (103). The measurement range of the tester was 419.9Ω to 41.99MΩ. The resistance measuring device (103) was connected to the stage (101) and the piercing mechanism (20). At this point, the display value of the tester was infinity.

[0194] At the point where the piercing mechanism (20) descended just before the separator (12), the piercing mechanism (20) stopped. Subsequently, the piercing mechanism (20) descended at a test speed of 0.5 mm / min, and the piercing mechanism (20) was pierced into the separator (12).

[0195] At the point when the display value of the tester changed from infinity to 40 MΩ (i.e., when the electrical resistance decreased to the short-circuit resistance), the piercing mechanism (20) stopped. The load at this point (short-circuit load) was measured by the load measuring device (104).

[0196] Figure 12 is a graph showing the relationship between the short-circuit load and the thickness of the separator in the fourth evaluation example. The short-circuit load is correlated with the thickness of the separator. This can be attributed to the fact that the separator is difficult to elongate in the piercing direction. The short-circuit load can be thought to accurately represent the strength of the separator when foreign substances are mixed between the electrodes within the battery.

[0197] 《5th Evaluation Example》

[0198] FIG. 13 is a schematic diagram showing the piercing mechanism in the fifth evaluation example.

[0199] As a piercing device, a needle having a tapered R-shaped tip was prepared. The tip shape radius (SR) of the needle was 0.1 mm. The diameter (φ) of the needle was 1 mm. The angle of taper (θ) was 60°. A separator was evaluated in the same manner as in the fourth evaluation example, except that the piercing device of FIG. 13 was used.

[0200] FIG. 14 is a graph showing the relationship between the short-circuit load and the thickness of the separator in the fifth evaluation example. In the fifth evaluation example (Fig. 14), the absolute value of the short-circuit load is smaller compared to the fourth evaluation example (Fig. 12). The fifth evaluation example can be considered to be an evaluation under stricter conditions compared to the fourth evaluation example. In the fifth evaluation example, a piercing mechanism having a sharp tip is used compared to the fourth evaluation example (see FIG. 11 and 13). In this evaluation method, it can be considered that various problem modes within the battery can be simulated by adjusting the shape of the piercing mechanism.

[0201] The present embodiments and examples are illustrative in all respects. The present embodiments and examples are not limiting. The technical scope of the present disclosure includes all modifications within the meaning and scope equivalent to the description in the claims. For example, any configuration may be derived from the present embodiments and examples, and any combination thereof is also intended from the outset.

Claims

Claim 1 (a) preparing a test material by placing a separator on the surface of a substrate; (b) in the test material, inserting a piercing device into the separator along the thickness direction of the separator from the opposite side of the substrate; (c) measuring the electrical resistance between the piercing device and the substrate while inserting the piercing device into the separator; (d) evaluating the separator by the magnitude of the load applied to the piercing device when the electrical resistance is reduced to a predetermined value; and (e) evaluating the separator by the amount of displacement of the piercing device when the electrical resistance is reduced to the predetermined value, wherein the substrate and the piercing device each have conductivity, and the substrate includes an electrode for a battery. Claim 2 delete Claim 3 delete Claim 4 A method for evaluating a battery separator according to claim 1, wherein the above description comprises an electrode body for a battery, and the electrode body for a battery comprises a plurality of electrodes for the battery. Claim 5 An evaluation system for carrying out the evaluation method of a battery separator described in claim 1, comprising a stage, a driving device, a resistance measuring device, and a load measuring device, wherein the stage is configured to load the test material, the driving device is configured to move the piercing mechanism along the thickness direction of the separator toward the test material loaded on the stage, the resistance measuring device is configured to measure the electrical resistance between the piercing mechanism and the material, and the load measuring device is configured to measure the load applied to the piercing mechanism. Claim 6 An evaluation system according to claim 5, further comprising a displacement measuring device, wherein the displacement measuring device is configured to measure the displacement amount of the piercing mechanism. Claim 7 An evaluation system according to claim 5 or 6, wherein the stage has conductivity, and the resistance measuring device is configured to measure the electrical resistance between the piercing mechanism and the stage. Claim 8 (A1) manufacturing a separator, and, (A2) evaluating the separator by the method for evaluating a separator for a battery described in claim 1 or 4, a method for manufacturing a separator for a battery. Claim 9 (B1) manufacturing an electrode unit by placing a separator on the surface of an electrode for a battery, and (B2) evaluating the separator by the method for evaluating a separator for a battery described in claim 1 using the electrode unit as a test material, a method for manufacturing an electrode unit. Claim 10 In claim 9, the method of manufacturing an electrode unit wherein the separator is coupled to the surface of the electrode for the battery. Claim 11 (C1) manufacturing an electrode unit by the method for manufacturing an electrode unit described in claim 9 or 10, and, (C2) manufacturing a battery comprising said electrode unit. A method for manufacturing a battery. Claim 12 (D1) evaluating a separator by the method for evaluating a separator for a battery described in claim 1 or 4, and, (D2) manufacturing a battery comprising said separator. A method for manufacturing a battery.

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