Battery safety mechanism and battery

Abstract

A battery safety mechanism 10 comprises: a lid 1; a pressure release member 2 that is in contact with the lid 1 and that deforms to release gas inside the battery to the outside thereof when the battery internal pressure is increased; a current blocking member 3 that is disposed on the opposite side to the lid 1 with respect to the pressure release member 2, and is connected to the pressure release member 2 to block a current flow to the pressure release member 2 when the battery internal pressure is increased; and an insulating bonding layer 4 that is interposed between the pressure release member 2 and the current blocking member 3 and bonds the pressure release member 2 and the current blocking member 3 to each other.

Description

[Technical Field]

[0001] This invention relates to a battery safety mechanism and a battery. [Background technology]

[0002] With the widespread use of various electronic devices such as mobile phones and personal digital assistants (PDAs), there is a demand for smaller, lighter, and longer-lasting electronic devices. Therefore, development is underway on batteries, particularly rechargeable batteries that are small, lightweight, and capable of achieving high energy density, as power sources. Furthermore, rechargeable batteries equipped with safety mechanisms to release gases generated by electrolyte decomposition to the outside of the battery are known.

[0003] Patent Document 1 discloses a battery equipped with such a safety mechanism. Figure 16 is a schematic diagram showing the safety mechanism 200 and its surrounding configuration in the battery disclosed in Patent Document 1.

[0004] As shown in Figure 16, the battery safety mechanism 200 disclosed in Patent Document 1 comprises a battery cover 201, a disk plate 202 having a pressure release function that deforms when the internal pressure of the battery rises to release gas inside the battery to the outside, a current interruption member 203 that interrupts the current when the internal pressure of the battery rises, and an insulating disk holder 204 interposed between the disk plate 202 and the current interruption member 203. The current interruption member 203 has an interruption disk 203a and a sub-disk 203b. The disk plate 202 has a protrusion 202a that protrudes toward the current interruption member 203 side. The protrusion 202a is connected to the sub-disk 203b via a hole 203c provided in the interruption disk 203a. The disk holder 204, which is an insulating material, is made of molded resin.

[0005] In the safety mechanism 200 of this battery, when the internal pressure of the battery rises, the disk plate 202 is lifted toward the battery cover 201, and the protrusion 202a disengages from the sub-disk 203b connected to the positive electrode lead 210, thereby cutting off the current flowing to the disk plate 202 and the battery cover 201. Further, the disk plate 202 is provided with a groove, and by breaking at the position where the groove is provided, the gas generated inside the battery flows toward the battery cover 201 side and is discharged to the outside through the holes provided in the battery cover 201.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] The safety mechanism of the battery preferably has a thin structure. For example, when the size of the battery is fixed, by thinning the safety mechanism, the internal volume of the battery can be increased. Therefore, the sizes of the positive electrode and negative electrode etc. can be increased, so that the battery capacity can be made larger. The battery described in Patent Document 1 has a thin safety mechanism, but there is still room for improvement in further thinning.

[0008] The present invention solves the above problems, and an object thereof is to provide a thinner safety mechanism for a battery and a battery provided with such a safety mechanism.

Means for Solving the Problems

[0009] The safety mechanism of the battery of the present invention is a lid, a pressure relief member that is in contact with the lid and deforms when the internal pressure of the battery rises to release the gas inside the battery to the outside, An overcurrent protection member that is disposed on the side opposite to the lid with respect to the pressure relief member, is connected to the pressure relief member, and cuts off the current flowing to the pressure relief member when the internal pressure of the battery rises. An insulating adhesive layer that is interposed between the pressure relief member and the overcurrent protection member and adheres the pressure relief member and the overcurrent protection member. It is characterized by including the above.

Advantages of the Invention

[0010] According to the battery safety mechanism of the present invention, since the insulating material interposed between the pressure relief member and the overcurrent protection member is an insulating adhesive layer, the safety mechanism can be made thinner than when an insulating material made of a molding resin or the like is used.

Brief Description of the Drawings

[0011] [Figure 1] It is a cross-sectional view schematically showing the configuration of a battery provided with a battery safety mechanism according to a first embodiment of the present invention. [Figure 2] It is a cross-sectional view schematically showing the configuration of a battery safety mechanism according to a first embodiment of the present invention. [Figure 3] It is an exploded perspective view of a battery safety mechanism according to a first embodiment of the present invention. [Figure 4] It is a plan view when the pressure relief member is viewed in the stacking direction from the overcurrent protection member side. [Figure 5] It is a plan view when the pressure relief member in the case where the shapes of the first groove and the second groove are arc-shaped is viewed in the stacking direction from the overcurrent protection member side. [Figure 6] (a) is a diagram for schematically explaining the overcurrent blocking function of the overcurrent protection member, and (b) is a diagram for schematically explaining the pressure relief function of the pressure relief member. [Figure 7] (a) to (c) are plan views showing examples of adhesive layers having shapes other than an annular shape. [Figure 8] It is a diagram for explaining the process in which the adhesion between the pressure relief member and the adhesive layer of the battery safety mechanism in the second embodiment deteriorates. [Figure 9] This figure illustrates the process by which the adhesion between the pressure release member and the adhesive layer of the battery safety mechanism in the first embodiment deteriorates. [Figure 10] (a) is a diagram showing the relationship between the expected lifespan and adhesive strength of the adhesive layer of the battery safety mechanism in the first and second embodiments, and (b) is a diagram showing the relationship between the expected lifespan and adhesive strength of the adhesive layer of the battery safety mechanism in the second embodiment. [Figure 11] This figure shows the relationship between the number of roughening treatments performed on the pressure release member and the surface area ratio of the roughened surface of the pressure release member. [Figure 12] (a) is a diagram showing the surface condition of the pressure release member when no roughening treatment is performed, (b) is a diagram showing the surface condition of the pressure release member when roughening treatment is performed once, and (c) is a diagram showing the surface condition of the pressure release member when roughening treatment is performed twice. [Figure 13] This figure shows the relationship between the expected lifespan and adhesive strength when the number of roughening treatments is changed. [Figure 14] This is a diagram illustrating the configuration of the electrode body. [Figure 15] This is a schematic cross-sectional view showing the configuration of a battery safety mechanism when the pressure release member has a convex portion and a flat portion, and the current interruption member has a flat shape. [Figure 16] This is a schematic cross-sectional view showing the safety mechanism and its surrounding components in a battery disclosed in Patent Document 1. [Modes for carrying out the invention]

[0012] The features of the present invention will be specifically described below with reference to embodiments of the present invention.

[0013] <First Embodiment> Figure 1 is a schematic cross-sectional view showing the configuration of a battery 100 equipped with a battery safety mechanism 10 according to a first embodiment of the present invention. Figure 2 is a schematic cross-sectional view showing the configuration of the battery safety mechanism 10 according to a first embodiment of the present invention. Figure 3 is an exploded perspective view of the battery safety mechanism 10.

[0014] Here, we will assume that battery 100 is a cylindrical lithium-ion secondary battery. However, the type of battery 100 is not limited to a lithium-ion battery; it may be a manganese battery, nickel-metal hydride battery, nickel-cadmium battery, or other types of batteries. Furthermore, battery 100 is not limited to a secondary battery; it may be a primary battery. In addition, the shape of battery 100 is not limited to a cylindrical shape; it may be a rectangular or button-shaped battery, or other shapes.

[0015] The battery safety mechanism 10 comprises a cover 1, a pressure release member 2, a current interruption member 3, and an adhesive layer 4.

[0016] The lid 1 is a component for sealing the opening of the battery can 20, which will be described later. As shown in Figure 2, the lid 1 has a flat plate portion 1a and a protruding portion 1b located in the center of the lid 1, surrounded by the flat plate portion 1a, and protruding to the outside of the battery 100. Since the protruding portion 1b of the lid 1 has a shape that protrudes to the outside of the battery 100, the protruding portion 1b includes a bent portion 1b1 that extends from the flat plate portion 1a toward the outside of the battery 100. Of the protruding portion 1b of the lid 1, the portion other than the bent portion 1b1 has a flat plate shape, similar to the flat plate portion 1a.

[0017] The thickness of the lid 1 is, for example, 1.5 mm or more and 3.0 mm or less. In the battery 100 in this embodiment, the lid 1 functions as the positive terminal of the battery 100, and the battery case 20 functions as the negative terminal. The lid 1 and the battery case 20 are insulated from each other. The lid 1 is provided with an exhaust hole 1c for releasing gas generated inside the battery 100 to the outside of the battery 100. The lid 1 is made of a conductive material such as steel such as SPCC, stainless steel such as SUS430 and SUS304, nickel (Ni), aluminum (Al), or titanium (Ti).

[0018] The pressure release member 2 is in contact with the lid 1 and deforms when the internal pressure of the battery rises, releasing gas from inside the battery to the outside. As shown in Figure 3, the pressure release member 2 has a flat plate shape, and its thickness is, for example, 0.2 mm to 0.5 mm. The shape of the pressure release member 2 when viewed in the stacking direction of the lid 1, pressure release member 2, adhesive layer 4, and current interruption member 3 (hereinafter simply referred to as the stacking direction) is circular. However, the shape of the pressure release member 2 is not limited to a circular shape.

[0019] The pressure release member 2 is made of a conductive material such as aluminum (e.g., A1050, A3203, A5052), titanium, platinum (Pt), or gold (Au). By making the pressure release member 2 from at least one of aluminum, titanium, platinum, and gold, reaction decomposition within the lithium-ion secondary battery can be prevented.

[0020] The pressure release member 2 has at least one groove so as to deform when the internal pressure of the battery increases. In this embodiment, the pressure release member 2 has a first groove 21 and a second groove 22 located radially outward from the first groove 21. As shown in Figure 2, the first groove 21 and the second groove 22 are provided in a direction perpendicular to the stacking direction, between the connection point between the protrusion 3b of the current interruption member 3 (described later) and the pressure release member 2, and the position where the lid 1 and the pressure release member 2 are in contact.

[0021] In this embodiment, the first groove 21 and the second groove 22 of the pressure release member 2 each open towards the current interruption member 3. Because the first groove 21 and the second groove 22 each open towards the current interruption member 3, compared to a configuration where they open towards the lid 1, it is possible to break with a smaller displacement when the internal pressure of the battery rises.

[0022] However, the first groove 21 and the second groove 22 of the pressure release member 2 may each open towards the lid 1 side. Also, the pressure release member 2 may have only one groove, or it may have three or more grooves.

[0023] Figure 4 is a plan view of the pressure release member 2 as seen from the current interruption member 3 side in the stacking direction. As shown in Figure 4, in this embodiment, the shapes of the first groove 21 and the second groove 22 as seen in the stacking direction are both circular. Furthermore, the first groove 21 and the second groove 22 form concentric circles.

[0024] However, the shapes of the first groove 21 and the second groove 22 when viewed in the stacking direction are not limited to circular shapes. For example, as shown in Figure 5, the shapes of the first groove 21 and the second groove 22 when viewed in the stacking direction may be arc-shaped. Figure 5 shows an example in which there are three arc-shaped first grooves 21 and three arc-shaped second grooves 22, but the number is not limited to three.

[0025] The depths of the first groove 21 and the second groove 22 are different. Specifically, the first groove 21 is deeper than the second groove 22. Because the first groove 21 is deeper than the second groove 22, when the internal pressure of the battery increases, the pressure release member 2 breaks at the location where the first groove 21 is provided. The depth of the first groove 21 is, for example, 0.11 mm or more and 0.2 mm or less, and the depth of the second groove 22 is, for example, 0.1 mm or more and 0.19 mm or less.

[0026] As shown in Figure 2, the second groove 22 of the pressure release member 2 is located near the inner contact end of the region where the lid 1 and the pressure release member 2 are in contact. "Near the contact end" refers to the area within 1.5 mm radially inward from the contact end. As shown in Figure 2, the pressure release member 2 is in contact with the flat portion 1a of the lid 1, but not with the bent portion 1b1. It is preferable that the second groove 22 of the pressure release member 2 is located in a position that overlaps with the bent portion 1b1 of the protruding portion 1b of the lid 1 in the stacking direction.

[0027] The second groove 22 of the pressure release member 2 is located near the inner contact end of the area where the lid 1 and the pressure release member 2 are in contact. As described later, when the internal pressure of the battery increases, the pressure release member 2 is less likely to deform along the bent portion 1b1 of the lid 1 at the location where the second groove 22 is provided. This suppresses misalignment of the lid 1 and reduces the impact on manufacturing variations of the lid 1. The pressure release member 2 is more prone to breakage at the location where the first groove 21 is provided.

[0028] The current interruption member 3 is connected to the positive electrode lead 36 that is led out from the electrode body 30 of the battery 100, which will be described later. The current interruption member 3 is positioned on the opposite side of the lid 1 from the pressure release member 2 and is connected to the pressure release member 2. It is a member for interrupting the current that flows to the pressure release member 2 when the internal pressure of the battery rises. The current interruption member 3 has a flat plate shape overall. Specifically, as shown in Figures 2 and 3, the current interruption member 3 has a flat plate portion 3a that has a flat plate shape and a protrusion 3b that is located in the center of the current interruption member 3 in a manner surrounded by the flat plate portion 3a and protrudes toward the pressure release member 2 side relative to the flat plate portion 3a for connection with the pressure release member 2.

[0029] In this embodiment, when viewed in the stacking direction, the outer edge of the current-blocking member 3 is circular. Also, when viewed in the stacking direction, the protrusion 3b of the current-blocking member 3 is circular. The thickness of the flat portion 3a and the protrusion 3b of the current-blocking member 3 is, for example, 0.25 mm or more and 0.5 mm or less. The thickness of the protrusion 3b is approximately the same as the thickness of the adhesive layer 4 described later, for example, 0.05 mm or more and 0.4 mm or less. Because the current-blocking member 3 has a protrusion 3b, it is not a perfectly flat plate, but because the thickness of the protrusion 3b is thin, it can be considered as having a flat plate shape overall.

[0030] In this embodiment, the protrusion 3b of the current interruption member 3 is connected to the pressure release member 2.

[0031] As shown in Figure 3, the flat plate portion 3a of the current-blocking member 3 may be provided with a plurality of holes 3c for allowing gas generated inside the battery to pass through. In this embodiment, six holes 3c are provided around the protrusion 3b. However, the number of holes 3c is not limited to six, nor is their shape limited to the shape shown in Figure 3. The holes 3c are provided in positions that do not overlap with the first groove 21 and the second groove 22 of the pressure-relieving member 2 in the stacking direction, and are configured so that gas generated inside the battery 100 flows from the holes 3c to the pressure-relieving member 2 side.

[0032] Depending on the shape of the current-cutting member 3, it is also possible to have a configuration without the hole 3c. The hole 3c may be provided in a position that overlaps with the first groove 21 and / or the second groove 22 of the pressure-relieving member 2 in the stacking direction.

[0033] The current-blocking member 3 is made of a conductive material such as aluminum, titanium, platinum, or gold, for example, A1050, A3203, or A5052. By making the current-blocking member 3 from at least one of aluminum, titanium, platinum, and gold, reaction decomposition within the lithium-ion secondary battery can be prevented.

[0034] The current-cutting member 3 has a groove 3d that opens toward the pressure-relieving member 2, between the position where the current-cutting member 3 and the pressure-relieving member 2 are connected and the position where the current-cutting member 3 and the adhesive layer 4 are in contact, in a direction perpendicular to the lamination direction. The depth of the groove 3d is, for example, 0.2 mm or more and 0.46 mm or less. In this embodiment, the groove 3d is provided near the protrusion 3b of the current-cutting member 3 so as to surround the protrusion 3b. The shape of the groove 3d when viewed in the lamination direction is circular. However, the shape of the groove 3d is not limited to a circle, and may be other shapes such as an arc shape.

[0035] Figure 6(a) is a schematic diagram illustrating the current interruption function of the current interruption member 3, and Figure 6(b) is a schematic diagram illustrating the pressure release function of the pressure release member 2. When the internal pressure of the battery 100 rises due to an internal short circuit or external heating of the battery 100, as shown in Figure 6(a), the portion of the current interruption member 3 including the protrusion 3b is separated from the flat plate portion 3a at the position where the groove 3d is formed. As a result, the portion including the protrusion 3b that has been separated from the flat plate portion 3a is also separated from the positive electrode lead 36 (see Figure 1), and the current flowing from the positive electrode lead 36 to the pressure release member 2 via the current interruption member 3 is interrupted. Also, as shown in Figure 6(a), the portion of the pressure release member 2 connected to the protrusion 3b of the current interruption member 3 that is not in contact with the lid 1 deforms so as to bulge towards the lid 1.

[0036] Furthermore, if the internal pressure of the battery increases further due to gases generated inside the battery 100, the force pushing the pressure release member 2 toward the lid 1 increases, and as shown in Figure 6(b), the pressure release member 2 is cut at the position where the first groove 21 is provided. That is, the pressure release member 2 deforms so that the area near where the second groove 22 is provided follows the curved portion 1b1 of the lid 1, and is cut at the position where the first groove 21, which is deeper than the second groove 22, is provided. As a result, the gas generated inside the battery 100 flows toward the lid 1 and is discharged to the outside through a hole (not shown) provided in the lid 1.

[0037] The adhesive layer 4 is insulating and is interposed between the pressure release member 2 and the current interruption member 3, bonding the two together. More specifically, the adhesive layer 4 is located between the pressure release member 2 and the current interruption member 3, radially outward from the second groove 22 of the pressure release member 2. The presence of the insulating adhesive layer 4 between the pressure release member 2 and the current interruption member 3 provides insulation between the pressure release member 2, which is connected to the positive electrode lead 36, and the current interruption member 3 when the current interruption function of the current interruption member 3 is activated (see Figure 6(a)).

[0038] The adhesive layer 4 consists of one of the following: a thermosetting resin, a thermoplastic resin, a UV-curable resin, and an anaerobic adhesive. Specifically, the adhesive layer 4 can be an epoxy resin-based adhesive mainly composed of epoxy resin, an acrylic resin-based adhesive mainly composed of acrylic resin, a fluororesin-based adhesive mainly composed of fluororesin, a silicone resin-based adhesive mainly composed of silicone resin, a synthetic resin-based adhesive mainly composed of synthetic resin, a urethane resin-based adhesive mainly composed of urethane resin, etc.

[0039] When a thermosetting resin is used as the adhesive layer 4, the glass transition temperature Tg is preferably 100°C or higher, and more preferably 170°C or higher. An example of a thermosetting resin with a glass transition temperature Tg of 100°C or higher is epoxy resin. The viscosity of the epoxy resin, which is a thermosetting resin, is, for example, 80 Pa·s to 130 Pa·s. When a thermoplastic resin is used as the adhesive layer 4, the melting point Tm is preferably 200°C or higher, and more preferably 270°C or higher. When the adhesive layer 4 is made of a thermosetting resin with a glass transition temperature Tg of 100°C or higher, or a thermoplastic resin with a melting point Tm of 200°C or higher, the insulating adhesive layer 4 remains interposed between the pressure release member 2 and the current interruption member 3 even when the battery temperature reaches high temperatures such as several hundred degrees Celsius. Therefore, when the current interruption function of the current interruption member 3 is activated (see Figure 6(a)), the insulating state between the pressure release member 2 connected to the positive electrode lead 36 and the current interruption member 3 can be maintained, and the occurrence of a short circuit can be prevented.

[0040] In this embodiment, when viewed in the stacking direction, the adhesive layer 4 has an annular shape, as shown in Figure 3. The adhesive layer 4 can be formed, for example, using a dispenser. The thickness of the adhesive layer 4 is, for example, 0.05 mm to 0.4 mm. The area of ​​the adhesive layer 4 is, for example, 0.6 mm². 2 100mm or more 2 The following applies:

[0041] However, the shape of the adhesive layer 4 when viewed in the stacking direction is not limited to an annular shape. Figures 7(a) to 7(c) show examples of other shapes of the adhesive layer 4. The adhesive layer 4 shown in Figure 7(a) has a shape in which the annulus is divided. The adhesive layer 4 shown in Figure 7(a) has a shape in which the annulus is divided into three parts, but it may also be divided into two parts, or into four or more parts. The adhesive layers 4 shown in Figures 7(b) and 7(c) are composed of multiple dots of a predetermined size. In Figure 7(b), there are 10 dots, and in Figure 7(c), there are 3 dots, but the number of dots can be any number. Also, the size of a single dot can be any size. The adhesive layers 4 shown in Figures 7(a) to 7(c) can be formed by a method using a dispenser or by printing.

[0042] As shown in Figures 7(a) to 7(c), by arranging the adhesive layer 4 discontinuously in multiple locations, a portion of the pressure applied from the current-cutting member 3 to the pressure-relieving member 2 can be released through the gaps between adjacent adhesive layers 4, thereby allowing the pressure applied to the pressure-relieving member 2 to be adjusted. On the other hand, as shown in Figure 3, if the shape of the adhesive layer 4 is an annular shape, the adhesive force between the pressure-relieving member 2 and the current-cutting member 3 can be made stronger.

[0043] Thus, in this embodiment, the battery safety mechanism 10 uses an insulating adhesive layer 4 made of adhesive as the insulating material interposed between the pressure release member 2 and the current interruption member 3. Compared to the case where an insulating material made of molded resin or the like is used, the distance between the pressure release member 2 and the current interruption member 3 can be shortened, and the safety mechanism 10 can be made thinner.

[0044] Furthermore, in the battery safety mechanism disclosed in Patent Document 1, the pressure-relieving disc plate, the insulating disc holder, and the current-cutting disc constituting the current-cutting member are fixed by crimping, so the thickness of each member increases in order to obtain the rigidity required for crimping. In contrast, in the battery safety mechanism 10 of this embodiment, the pressure-relieving member 2 and the current-cutting member 3 are bonded together by an adhesive layer 4, so the rigidity required for crimping is unnecessary, and the battery safety mechanism 10 can be made thinner.

[0045] Furthermore, in the battery safety mechanism disclosed in Patent Document 1, the pressure-relieving disc plate, the insulating disc holder, and the current-cutting disc constituting the current-cutting member are fixed by crimping, so the fixing strength is not very strong. For this reason, the thickness of each component needs to be increased in order to obtain the rigidity required for assembly and transport. In contrast, in the battery safety mechanism 10 of this embodiment, the pressure-relieving member 2 and the current-cutting member 3 are bonded together by an adhesive layer 4, so the fixing strength is strong. For this reason, it is not necessary to increase the thickness of each component to obtain the rigidity required for assembly and transport, and as a result, the battery safety mechanism 10 can be made thinner.

[0046] Furthermore, in this embodiment, the battery safety mechanism 10 has a pressure release member 2 and a current interruption member 3 bonded together by an adhesive layer 4, which increases resistance to increases in internal battery pressure and impacts from outside the battery, thereby improving the safety of the battery 100.

[0047] <Second Embodiment> The battery safety mechanism 10 in the second embodiment differs from the battery safety mechanism 10 in the first embodiment in the structure of the pressure release member 2 and the current interruption member 3.

[0048] In this embodiment, the surface of the pressure release member 2 facing the current interruption member 3 is a roughened surface that has been subjected to a roughening treatment. Similarly, the surface of the current interruption member 3 facing the pressure release member 2 is a roughened surface that has been subjected to a roughening treatment. Fine irregularities exist on the roughened surfaces of the pressure release member 2 and the current interruption member 3. The roughening treatment can be performed, for example, by irradiating the surface to be roughened with laser light.

[0049] However, the roughening treatment may be applied only to the area of ​​the pressure release member 2 that is in direct contact with the adhesive layer 4, rather than to the entire surface of the pressure release member 2 that is facing the current interruption member 3. Similarly, the roughening treatment may be applied only to the area of ​​the current interruption member 3 that is in direct contact with the adhesive layer 4, rather than to the entire surface of the pressure release member 2.

[0050] Because the surface of the pressure release member 2 facing the current interruption member 3 is a roughened surface, not only are hydrogen bonds formed by the adhesive between the pressure release member 2 and the adhesive layer 4, but an anchoring effect is also generated by the fine irregularities present on the roughened surface, thereby further improving the adhesive strength between the pressure release member 2 and the adhesive layer 4.

[0051] Similarly, because the surface of the current-blocking member 3 facing the pressure-releasing member 2 is a roughened surface, not only hydrogen bonding by the adhesive but also an anchoring effect due to the fine irregularities on the roughened surface occurs between the current-blocking member 3 and the adhesive layer 4, thereby further improving the adhesive strength between the current-blocking member 3 and the adhesive layer 4.

[0052] Figure 8 illustrates the process by which the adhesion between the pressure release member 2 and the adhesive layer 4 of the battery safety mechanism 10 deteriorates in the second embodiment. Although the explanation using the figure is omitted, the process by which the adhesion between the current interruption member 3 and the adhesive layer 4 deteriorates is similar.

[0053] Figure 8(a) is an enlarged cross-sectional view of the boundary between the pressure release member 2 and the adhesive layer 4 before the electrolyte is permeated during the manufacturing process of the battery 100. In the state before the electrolyte is permeated, the pressure release member 2 is fixed to the adhesive layer 4 not only by hydrogen bonding with the adhesive that makes up the adhesive layer 4, but also by an anchoring effect caused by the adhesive that makes up the adhesive layer 4 getting into the gaps between the fine irregularities on the surface of the pressure release member 2.

[0054] As the electrolyte is allowed to penetrate from the state shown in Figure 8(a), hydrogen bonds begin to break from the side in contact with the electrolyte, as shown in Figure 8(b), and a gap begins to form between the pressure release member 2 and the adhesive layer 4. As more time passes and the electrolyte penetrates further, hydrogen bonds break at all locations where they were formed in the adhesive, as shown in Figure 8(c), and a gap forms between the pressure release member 2 and the adhesive layer 4. However, in the state shown in Figure 8(c), the adhesion between the pressure release member 2 and the adhesive layer 4 is maintained by the anchoring effect.

[0055] Subsequently, as time passes, the cohesive strength of the adhesive continues to decrease, causing the base of the anchor portion where the anchoring effect occurs to begin to break, as shown in Figure 8(d), and ultimately the adhesive layer 4 peels off from the pressure release member 2.

[0056] Figure 9 is a diagram illustrating the process by which the adhesion between the pressure release member 2 and the adhesive layer 4 of the battery safety mechanism 10 in the first embodiment deteriorates. In the battery safety mechanism 10 in the first embodiment, the surface of the pressure release member 2 facing the current interruption member 3, and the surface of the current interruption member 3 facing the pressure release member 2, are not roughened. Although the explanation using the diagram is omitted, the process by which the adhesion between the current interruption member 3 and the adhesive layer 4 deteriorates is similar.

[0057] Figure 9(a) is an enlarged cross-sectional view of the boundary between the pressure release member 2 and the adhesive layer 4 before the electrolyte is permeated during the manufacturing process of the battery 100. In the state before the electrolyte is permeated, the pressure release member 2 is fixed to the adhesive layer 4 by hydrogen bonds formed by the adhesive that makes up the adhesive layer 4.

[0058] As the electrolyte is allowed to penetrate from the state shown in Figure 9(a), hydrogen bonds begin to break from the side in contact with the electrolyte, as shown in Figure 9(b), and a gap begins to form between the pressure release member 2 and the adhesive layer 4. As more time passes and the electrolyte penetrates further, hydrogen bonds break at all locations where they were formed in the adhesive, as shown in Figure 9(c), and a gap forms between the pressure release member 2 and the adhesive layer 4. In the state shown in Figure 9(c), the adhesion between the pressure release member 2 and the adhesive layer 4 is not maintained, and the adhesive layer 4 has peeled off.

[0059] Here, the acceleration coefficient was determined using temperature and immersion in the electrolyte as acceleration conditions by following the procedure below, and the expected lifespan of the adhesive layer of the battery's safety mechanism 10 was determined by conducting an acceleration test.

[0060] Under conditions of 25°C and 85°C, the pressure release member 2 and current interruption member 3 of the battery's safety mechanism 10 were immersed in a non-aqueous electrolyte, and the adhesive strength was measured after several predetermined immersion periods. For adhesive strength, pressure was applied using a push-bull gauge (MX2-500N, manufactured by Imada Co., Ltd.), and the average value until the pressure release member 2 and current interruption member 3 were completely separated was defined as the adhesive strength. Furthermore, based on the adhesive strength obtained during multiple immersion periods under the conditions of 25°C and 85°C, the slope of deterioration of adhesive strength with respect to the immersion period was calculated, and a first predicted deterioration acceleration α1 was obtained from the calculated slope.

[0061] The adhesive strength was measured after a predetermined immersion period in two conditions: a first state in which the safety mechanism 10 of the battery in this embodiment was completely immersed in a non-aqueous electrolyte under an 85°C environment, and a second state in which the safety mechanism 10 was sealed in a container under a non-aqueous electrolyte atmosphere without being immersed in the non-aqueous electrolyte. The method for measuring the adhesive strength was the same as the measurement method described above. Based on the adhesive strengths obtained for multiple immersion periods in the first and second states, the slope of deterioration of the adhesive strength with respect to the immersion period was calculated, and a second predicted deterioration acceleration α2 was obtained from the calculated slope.

[0062] The acceleration coefficient was defined as α1 × α2, obtained by multiplying the first predicted deterioration acceleration α1 by the second predicted deterioration acceleration α2. Then, in the second state, where the material was sealed in a container under an 85°C environment and a non-aqueous electrolyte atmosphere, the expected lifespan was defined as the value obtained by multiplying the number of days until the adhesive strength became 0N by the acceleration coefficient.

[0063] Figure 10 shows the relationship between the expected lifespan and adhesive strength of the adhesive layer of the battery safety mechanism 10 in the second embodiment. The adhesive strength is the adhesive strength between the pressure release member 2 and the current interruption member 3. For comparison, Figure 10(a) also includes data showing the relationship between the expected lifespan and adhesive strength of the adhesive layer of the battery safety mechanism 10 in the first embodiment. In Figure 10, the data labeled "with roughening treatment" is the data for the battery safety mechanism 10 in the second embodiment, and the data labeled "without roughening treatment" is the data for the battery safety mechanism 10 in the first embodiment.

[0064] As shown in Figure 10(a), in the initial state where the assumed lifespan is 0, i.e., before the acceleration test is performed, the battery safety mechanism 10 in the second embodiment has higher adhesive strength than the battery safety mechanism 10 in the first embodiment. Furthermore, the rate of decrease in adhesive strength due to aging is slower in the battery safety mechanism 10 in the second embodiment compared to the battery safety mechanism 10 in the first embodiment. This is because, as described above, in the battery safety mechanism 10 in the second embodiment, the pressure release member 2 and the adhesive layer 4, and the current interruption member 3 and the adhesive layer 4 are fixed by hydrogen bonds and the anchoring effect, whereas in the battery safety mechanism 10 in the first embodiment, they are fixed only by hydrogen bonds.

[0065] The dashed line D1 shown in Figure 10(b) is a hypothetical line that indicates the relationship between the expected lifespan and adhesive strength when the hydrogen bonds break, in the battery safety mechanism 10 of the second embodiment, where the pressure release member 2 and the adhesive layer 4, and the current interruption member 3 and the adhesive layer 4, are fixed by hydrogen bonds and the anchoring effect.

[0066] The dashed line D2 shown in Figure 10(b) is a hypothetical line that shows the relationship between the assumed lifespan and adhesive strength when the hydrogen bonds between the pressure release member 2 and the adhesive layer 4, and between the current interruption member 3 and the adhesive layer 4, are broken and the battery is fixed only by the anchoring effect in the safety mechanism 10 of the second embodiment. The dashed line D2 shows the state in which the adhesive strength decreases as the adhesive in the adhesive layer 4 softens. The rate of decrease in adhesive strength shown by the dashed line D2 is slower than the rate of decrease in adhesive strength shown by the dashed line D1.

[0067] Here, the roughening treatment performed on the pressure release member 2 may be carried out multiple times. By performing the roughening treatment multiple times, the surface area ratio of the pressure release member 2 can be further increased. Similarly, the roughening treatment performed on the current interruption member 3 may also be carried out multiple times.

[0068] Figure 11 shows the relationship between the number of roughening treatments performed on the pressure release member 2 and the surface area ratio of the roughened surface of the pressure release member 2. Here, the surface area ratios were determined for multiple samples when the number of roughening treatments was 0, 1, and 3. In Figure 11, the data with black circles shows the surface area ratio for each of the multiple samples, and the data with white circles shows the average value of multiple surface area ratios when the number of roughening treatments is the same. Note that if the material of the current interruption member 3 and the material of the pressure release member 2 are the same, the figure showing the relationship between the number of roughening treatments performed on the current interruption member 3 and the surface area ratio of the roughened surface of the current interruption member 3 will be the same as in Figure 11.

[0069] The surface area ratio of the roughened surface of the pressure release member 2 is expressed by the following formula, where S1 is the surface area of ​​the roughened surface of the pressure release member 2 and S2 is the surface area when the pressure release member 2 is assumed to be a plane. Surface area ratio of the roughened surface of the pressure release member 2 = (S1 / S2-1) × 100

[0070] Similarly, the surface area ratio of the roughened surface of the current-blocking member 3 is expressed by the following formula, where S3 is the surface area of ​​the roughened surface of the current-blocking member 3 and S4 is the surface area when the current-blocking member 3 is assumed to be a plane. Surface area ratio of the roughened surface of the current interruption member 3 = (S3 / S4-1) × 100 For measuring the surface area of ​​the pressure release member 2 and the current interruption member 3, an optical surface texture measuring instrument NewView7300 (manufactured by Zygo) was used, and measurements were taken within a rectangular measurement area of ​​0.7 mm × 0.5 mm.

[0071] As shown in Figure 11, the more times the roughening treatment is performed, the more fine irregularities and depths the recesses become on the roughened surface, thus increasing the surface area ratio of the pressure release member 2. Similarly, for the current interruption member 3, the more times the roughening treatment is performed, the larger the surface area ratio of the current interruption member 3 becomes.

[0072] Figure 12(a) shows the surface condition of the pressure release member 2 when no roughening treatment is performed, Figure 12(b) shows the surface condition of the pressure release member 2 when roughening treatment is performed once, and Figure 12(c) shows the surface condition of the pressure release member 2 when roughening treatment is performed twice. Figures 12(a) to (c) are images observed with a microscope (VHX-8000, manufactured by Keyence Corporation, magnification 500x), with the upper image showing the surface condition and the lower image showing the cross-sectional condition.

[0073] Figure 13 shows the relationship between the expected lifespan and adhesive strength when the number of roughening treatments is changed. The adhesive strength is the adhesive strength between the pressure release member 2 and the current interruption member 3. The number of roughening treatments was set to 0, 1, and 3 times. As shown in Figure 13, when the number of roughening treatments is 1 and 3, the expected lifespan is longer compared to when no roughening treatment is performed. However, when the number of roughening treatments is set to 3, the expected lifespan is shorter compared to when the number of roughening treatments is set to 1. In other words, it can be seen that simply increasing the number of roughening treatments and increasing the surface area ratio does not necessarily increase the expected lifespan. This is thought to be because when the number of roughening treatments is increased, the depth of the recesses among the fine irregularities on the surface of the pressure release member 2 formed by the roughening treatment increases, and the number of recesses into which the adhesive does not penetrate increases.

[0074] As shown in Figure 13, it is preferable that the number of roughening treatments applied to the roughened surface of the pressure release member 2 be more than 0 times but less than 3 times, and that the number of roughening treatments applied to the roughened surface of the current interruption member 3 be more than 0 times but less than 3 times. In the example shown in Figure 11, the average surface area ratio of the roughened surface of the pressure release member 2 when the number of roughening treatments is 0 is 5.65%, the average surface area ratio of the roughened surface when the number of roughening treatments is 1 is 15.66%, and the average surface area ratio of the roughened surface when the number of roughening treatments is 3 is 26.10%. Therefore, it is preferable that the surface area ratio of the roughened surface of the pressure release member 2 be 6% or more and 26% or less. Similarly, it is preferable that the surface area ratio of the roughened surface of the current interruption member 3 be 6% or more and 26% or less.

[0075] [Manufacturing method for safety mechanisms] An example of a manufacturing method for the safety mechanism 10 described above will be explained.

[0076] First, the lid 1 and the pressure release member 2 are joined together. Specifically, the flat plate portion 1a of the lid 1 is joined to the pressure release member 2. The joining method is arbitrary and can be done by welding, such as ultrasonic welding.

[0077] Next, adhesive is applied to at least one of the surfaces of the pressure release member 2 opposite to the lid 1 and the surface of the current interruption member 3 on the protrusion 3b side, and the pressure release member 2 and the current interruption member 3 are bonded together with the applied adhesive sandwiched between them. As described above, epoxy resin adhesives, acrylic resin adhesives, fluororesin adhesives, silicone resin adhesives, synthetic resin adhesives, urethane resin adhesives, etc. can be used as the adhesive. The thickness of the adhesive to be applied is, for example, 0.1 mm to 0.4 mm, and the area to be applied is, for example, 0.6 mm. 2 100mm or more 2 The following occurs: As a result, an adhesive layer 4 is formed between the pressure release member 2 and the current interruption member 3.

[0078] Finally, the protrusion 3b of the current-cutting member 3 and the pressure-releasing member 2 are connected. The connection method is arbitrary and can be done by welding, such as laser welding.

[0079] Alternatively, the pressure release member 2 and the current blocking member 3 may be bonded together first using an adhesive, then the protrusion 3b of the current blocking member 3 and the pressure release member 2 may be connected, and finally, the lid 1 and the pressure release member 2 may be joined together.

[0080] [battery] Next, an example of the structure of a battery 100 equipped with the safety mechanism 10 of the present invention will be described. The battery 100 comprises the safety mechanism 10, a battery case 20, and an electrode body 30.

[0081] In this embodiment, the battery casing 20 has a hollow cylindrical shape with one end open and houses the electrode body 30. The battery casing 20 is made of, for example, iron (Fe) plated with nickel. Nickel, stainless steel, aluminum, titanium, etc. may be used as the material for the battery casing 20. The surface of the battery casing 20 may be plated with, for example, nickel, to prevent electrochemical corrosion caused by the non-aqueous electrolyte during charging and discharging of the non-aqueous electrolyte battery.

[0082] A safety mechanism 10 is attached to the open end of the battery can 20 so that the lid 1 faces outwards. Specifically, the safety mechanism 10 is attached to the battery can 20 by crimping it through a gasket 11 for insulating sealing. This seals the inside of the battery can 20.

[0083] Inside the battery casing 20 is an electrode body 30, which includes a positive electrode 31, a negative electrode 32, and a separator 33 provided between the positive electrode 31 and the negative electrode 32. In this embodiment, the electrode body 30 is a wound electrode body in which a pair of strip-shaped positive electrodes 31 and strip-shaped negative electrodes 32 are stacked with the separator 33 in between, and wound around a center pin 38. However, the electrode body 30 is not limited to a wound electrode body. In the battery 100 of the present invention, the configuration of the electrode body 30 can be any configuration.

[0084] A positive lead 36 is connected to the positive electrode 31, and a negative lead 37 is connected to the negative electrode 32. As described above, the positive lead 36 is connected to the current interruption member 3 of the battery's safety mechanism 10 and is electrically connected to the lid 1 via the pressure release member 2. The negative lead 37 is welded to the battery can 20 and is electrically connected to the battery can 20.

[0085] The battery can 20 contains an electrolyte solution, which is a liquid electrolyte. The electrolyte solution impregnates the positive electrode 31, the negative electrode 32, and the separator 33. In addition, a pair of insulating plates 34 and 35 are arranged perpendicular to the winding surface, sandwiching the electrode body 30.

[0086] The positive electrode 31, negative electrode 32, separator 33, and electrolyte that constitute the electrode body 30 will be described in order below with reference to Figure 14.

[0087] (positive electrode) The positive electrode 31 has a structure in which, for example, a positive electrode active material layer 31B is provided on both sides of a positive electrode current collector 31A. However, the positive electrode active material layer 31B may be provided on only one side of the positive electrode current collector 31A. The positive electrode current collector 31A is made of a metal foil such as aluminum foil, nickel foil, or stainless steel foil. The positive electrode active material layer 31B contains, for example, a positive electrode active material capable of intercalating and releasing lithium, which is an electrode reactant. The positive electrode active material layer 31B may further contain additives as needed. As additives, for example, at least one of a conductive agent and a binder can be used.

[0088] As a positive electrode material capable of occluding and releasing lithium, for example, lithium-containing compounds such as lithium oxides, lithium phosphates, lithium sulfides, or intercalation compounds containing lithium are suitable, and two or more of these may be mixed and used. To increase the energy density, it is preferable to use a lithium-containing compound containing lithium, a transition metal element, and oxygen (O). Examples of such lithium-containing compounds include lithium composite oxides having a layered rock salt structure represented by formula (A), lithium composite phosphates having an olivine structure represented by formula (B), and the like. As the lithium-containing compound, it is more preferable that the transition metal element contains at least one selected from the group consisting of cobalt (Co), nickel, manganese (Mn), and iron. Examples of such lithium-containing compounds include lithium composite oxides having a layered rock salt structure represented by formula (C), formula (D), or formula (E), lithium composite oxides having a spinel structure represented by formula (F), or lithium composite phosphates having an olivine structure represented by formula (G), and specifically, LiNi 0.50 Co 0.20 Mn 0.30 O2, Li a CoO2 (a ≒ 1), Li b NiO2 (b ≒ 1), Li c1 Ni c2 Co 1-c2 O2 (c1 ≒ 1, 0 < c2 < 1), Li d Mn2O4 (d ≒ 1) or Li e FePO4 (e ≒ 1), etc.

[0089] Li p Ni (1-q-r) Mn q M1 r O (2-y) X z …(A) (However, in formula (A), M1 represents at least one element selected from groups 2 to 15 excluding nickel and manganese. X represents at least one element selected from group 16 elements and group 17 elements other than oxygen. p, q, y, z are values within the ranges of 0 ≦ p ≦ 1.5, 0 ≦ q ≦ 1.0, 0 ≦ r ≦ 1.0, -0.10 ≦ y ≦ 0.20, 0 ≦ z ≦ 0.2.)

[0090] Li a M2 b PO4…(B) (However, in formula (B), M2 represents at least one element selected from Group 2 to Group 15. a and b are values within the range of 0 ≦ a ≦ 2.0 and 0.5 ≦ b ≦ 2.0.)

[0091] Li f Mn (1-g-h) Ni g M3 h O (2-j) F k …(C) (However, in formula (C), M3 represents at least one species selected from the group consisting of cobalt, magnesium (Mg), aluminum, boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron, copper (Cu), zinc (Zn), zirconium (Zr), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), and tungsten (W). f, g, h, j, and k are values within the ranges of 0.8 ≦ f ≦ 1.2, 0 < g < 0.5, 0 ≦ h ≦ 0.5, g + h < 1, -0.1 ≦ j ≦ 0.2, and 0 ≦ k ≦ 0.1. Note that the lithium composition varies depending on the charge / discharge state, and the value of f represents the value in the fully discharged state.)

[0092] Li m Ni (1-n) M4 n O (2-p) F q …(D) (However, in formula (D), M4 represents at least one species selected from the group consisting of cobalt, manganese, magnesium, aluminum, boron, titanium, vanadium, chromium, iron, copper, zinc, molybdenum, tin, calcium, strontium, and tungsten. m, n, p, and q are values within the ranges of 0.8 ≦ m ≦ 1.2, 0.005 ≦ n ≦ 0.5, -0.1 ≦ p ≦ 0.2, and 0 ≦ q ≦ 0.1. Note that the lithium composition varies depending on the charge / discharge state, and the value of m represents the value in the fully discharged state.)

[0093] Li rCo (1-s) M5 s O (2-t) F u …(E) (However, in formula (E), M5 represents at least one element from the group consisting of nickel, manganese, magnesium, aluminum, boron, titanium, vanadium, chromium, iron, copper, zinc, molybdenum, tin, calcium, strontium, and tungsten. r, s, t, and u are values ​​within the ranges of 0.8 ≤ r ≤ 1.2, 0 ≤ s < 0.5, -0.1 ≤ t ≤ 0.2, and 0 ≤ u ≤ 0.1. Note that the lithium composition varies depending on the charge / discharge state, and the value of r represents the value in the fully discharged state.)

[0094] Li v Mn 2-w M6 w O x F y …(F) (However, in formula (F), M6 represents at least one element from the group consisting of cobalt, nickel, magnesium, aluminum, boron, titanium, vanadium, chromium, iron, copper, zinc, molybdenum, tin, calcium, strontium, and tungsten. v, w, x, and y are values ​​within the ranges of 0.9 ≤ v ≤ 1.1, 0 ≤ w ≤ 0.6, 3.7 ≤ x ≤ 4.1, and 0 ≤ y ≤ 0.1. Note that the lithium composition varies depending on the charge / discharge state, and the value of v represents the value in the fully discharged state.)

[0095] Li z M7PO4…(G) (However, in formula (G), M7 represents at least one element from the group consisting of cobalt, manganese, iron, nickel, magnesium, aluminum, boron, titanium, vanadium, niobium (Nb), copper, zinc, molybdenum, calcium, strontium, tungsten, and zirconium. z is a value within the range of 0.9 ≤ z ≤ 1.1. Note that the lithium composition varies depending on the charge / discharge state, and the value of z represents the value in the fully discharged state.)

[0096] Other cathode materials capable of intercalating and releasing lithium include MnO2, V2O5, and V6O 13 Other examples include lithium-free inorganic compounds such as NiS and MOS.

[0097] The positive electrode material capable of intercalating and releasing lithium may be other than those described above. Furthermore, two or more of the positive electrode materials exemplified above may be mixed in any combination.

[0098] As a binder, at least one selected from, for example, resin materials such as polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), polyacrylonitrile (PAN), styrene-butadiene rubber (SBR), and carboxymethylcellulose (CMC), as well as copolymers mainly composed of these resin materials, can be used.

[0099] Examples of conductive agents include carbon materials such as graphite, carbon black, or Ketjenblack, and it is possible to use one or more of these in mixture form. In addition to carbon materials, conductive materials such as metallic materials or conductive polymer materials can also be used as conductive agents.

[0100] (Negative electrode) The negative electrode 32 has a structure in which a negative electrode active material layer 32B is provided on both sides of the negative electrode current collector 32A. However, the negative electrode active material layer 32B may be provided on only one side of the negative electrode current collector 32A. The negative electrode current collector 32A is made of a metal foil such as copper foil, nickel foil, or stainless steel foil.

[0101] The negative electrode active material layer 32B contains one or more negative electrode active materials capable of intercalating and releasing lithium. The negative electrode active material layer 32B may further contain additives such as binders and conductive agents as needed.

[0102] In the case of battery 100, which is a non-aqueous electrolyte battery, it is preferable that the electrochemical equivalent of the negative electrode 32 or the negative electrode active material is greater than the electrochemical equivalent of the positive electrode 31, so that, theoretically, lithium metal does not deposit on the negative electrode 32 during charging.

[0103] Examples of negative electrode active materials include carbon materials such as non-graphitizable carbon, easily graphitizable carbon, graphite, pyrolytic carbons, cokes, glassy carbons, calcined organic polymer compounds, carbon fibers, or activated carbon. Examples of cokes include pitch coke, needle coke, or petroleum coke. Calcined organic polymer compounds refer to polymer materials such as phenolic resins and furan resins that have been calcined at an appropriate temperature to carbonize them, and some of these are classified as non-graphitizable carbon or easily graphitizable carbon. These carbon materials are preferred because they exhibit very little change in crystal structure during charging and discharging, allowing for high charge-discharge capacity and good cycle characteristics. Graphite is particularly preferred because it has a large electrochemical equivalent and can provide high energy density. Non-graphitizable carbon is preferred because it provides excellent cycle characteristics. Furthermore, materials with low charge-discharge potentials, specifically those with charge-discharge potentials close to those of lithium metal, are preferred because they can easily achieve high energy density in battery 100.

[0104] Other anode active materials capable of increasing capacity include materials containing at least one of the metallic and metalloid elements as constituent elements (e.g., alloys, compounds, or mixtures). This is because high energy density can be obtained by using such materials. In particular, it is more preferable to use them together with carbon materials, as this allows for both high energy density and excellent cycle characteristics. Alloys include those composed of two or more metallic elements, as well as those containing one or more metallic elements and one or more metalloid elements. Nonmetallic elements may also be included in the anode active material. Their structures may include solid solutions, eutectic (eutectic mixtures), intermetallic compounds, or coexistence of two or more of these.

[0105] Examples of the negative electrode active materials mentioned above include metallic or metalloid elements capable of forming alloys with lithium. Specifically, these include magnesium, boron, aluminum, titanium, gallium (Ga), indium (In), silicon (Si), germanium (Ge), tin, lead (Pb), bismuth (Bi), cadmium (Cd), silver (Ag), zinc, hafnium (Hf), zirconium, yttrium (Y), palladium (Pd), or platinum. These may be crystalline or amorphous.

[0106] The negative electrode active material is preferably one that contains a metallic or metalloid element of Group 4B of the short-period periodic table as a constituent element, and more preferably one that contains at least one of silicon and tin as a constituent element. This is because silicon and tin have a large capacity to intercalate and release lithium, and can obtain a high energy density. Examples of such negative electrode active materials include elemental silicon, alloys or compounds of silicon, elemental tin, alloys or compounds of tin, or materials having at least one or more of these phases as part.

[0107] Examples of silicon alloys include those containing at least one element from the group consisting of tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony (Sb), and chromium as the second constituent element other than tin. Examples of tin alloys include those containing at least one element from the group consisting of silicon, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, and chromium as the second constituent element other than tin.

[0108] Examples of tin compounds or silicon compounds include those containing oxygen or carbon. In addition to tin or silicon, the second constituent element described above may also be included.

[0109] In particular, SnCoC-containing materials are preferred as Sn-based negative electrode active materials, which contain cobalt, tin, and carbon as constituent elements, with a carbon content of 9.9% to 29.7% by mass, and a cobalt ratio of 30% to 70% by mass relative to the total of tin and cobalt. This is because a high energy density can be obtained within the above composition range, as well as excellent cycle characteristics.

[0110] The SnCoC-containing material described above may contain other constituent elements as needed. Preferred other constituent elements include, for example, silicon, iron, nickel, chromium, indium, niobium, germanium, titanium, molybdenum, aluminum, phosphorus (P), gallium, or bismuth, and may contain two or more of these elements. The inclusion of these elements in the other constituent elements can further improve capacity or cycle characteristics.

[0111] Furthermore, the SnCoC-containing material described above has a phase containing tin, cobalt, and carbon, and it is preferable that this phase has a low crystallinity or amorphous structure. In addition, in this SnCoC-containing material, it is preferable that at least a portion of the constituent element carbon is bonded to other constituent elements, which are metallic or metalloid elements. The decrease in cycle properties is thought to be due to the aggregation or crystallization of tin, etc., but such aggregation or crystallization can be suppressed by carbon bonding with other elements.

[0112] One measurement method for investigating the bonding state of elements is X-ray photoelectron spectroscopy (XPS). In XPS, for graphite, in an instrument energy-calibrated so that the peak of the gold atom's 4f orbital (Au4f) is obtained at 84.0 eV, the peak of the carbon atom's 1s orbital (C1s) appears at 284.5 eV. In the case of surface contamination carbon, the peak appears at 284.8 eV. In contrast, when the charge density of the carbon element is high, for example, when carbon is bonded to a metallic or metalloid element, the C1s peak appears in a region lower than 284.5 eV. That is, if the peak of the composite wave of C1s obtained for SnCoC-containing material appears in a region lower than 284.5 eV, it means that at least some of the carbon contained in the SnCoC-containing material is bonded to other constituent elements, such as metallic or metalloid elements.

[0113] In XPS measurements, the C1s peak is used to correct the energy axis of the spectrum. Since surface contamination carbon is usually present on the surface, the C1s peak of surface contamination carbon is set to 284.8 eV and used as the energy reference. In XPS measurements, the waveform of the C1s peak is obtained as a form that includes the peak of surface contamination carbon and the peak of carbon in the SnCoC-containing material. Therefore, the peak of surface contamination carbon and the peak of carbon in the SnCoC-containing material are separated by analysis using commercially available software, for example. In waveform analysis, the position of the main peak located on the lowest binding energy side is used as the energy reference (284.8 eV).

[0114] Other negative electrode active materials include, for example, metal oxides or polymer compounds capable of intercalating and releasing lithium. Examples of metal oxides include lithium titanate (Li4Ti5O4). 12 Examples of polymer compounds include lithium titanium oxide containing titanium and lithium, iron oxide, ruthenium oxide, or molybdenum oxide. Examples of polymer compounds include polyacetylene, polyaniline, or polypyrrole.

[0115] As a binder, at least one selected from, for example, resin materials such as polyvinylidene fluoride, polytetrafluoroethylene, polyacrylonitrile, styrene-butadiene rubber, and carboxymethylcellulose, or copolymers mainly composed of the above resin materials, can be used. As a conductive agent, carbon materials similar to those used in the positive electrode active material layer 31B can be used.

[0116] (Separator) The separator 33 separates the positive electrode 31 and the negative electrode 32, preventing short circuits of current due to contact between the two electrodes while allowing lithium ions to pass through. The separator 33 is composed of a porous membrane made of a resin such as polytetrafluoroethylene, polypropylene, or polyethylene. The separator 33 may have a structure in which two or more of the above-mentioned porous membranes are laminated. Among these, a porous membrane made of polyolefin is preferred because it has an excellent short-circuit prevention effect and can improve the safety of the battery 100 through a shutdown effect. Polyethylene, in particular, is preferred as a material for the separator 33 because it can obtain a shutdown effect in the range of 100°C to 160°C and also has excellent electrochemical stability. In addition, as a material for the separator 33, a material obtained by copolymerizing or blending a chemically stable resin with polyethylene or polypropylene can be used. The porous membrane may have a structure of three or more layers in which a polypropylene layer, a polyethylene layer, and a polypropylene layer are sequentially laminated.

[0117] The separator 33 may have a resin layer provided on one or both sides of the porous membrane substrate. The resin layer is a porous matrix resin layer on which inorganic material is supported. Such a structure can provide oxidation resistance and suppress the deterioration of the separator 33. As the matrix resin, for example, polyvinylidene fluoride, hexafluoropropylene (HFP), polytetrafluoroethylene, etc., or copolymers thereof can be used.

[0118] Examples of inorganic materials include metals, semiconductors, or oxides or nitrides thereof. Examples of metals include aluminum and titanium, and examples of semiconductors include silicon and boron. Preferably, the inorganic material is substantially non-conductive and has a large heat capacity. A large heat capacity makes it useful as a heat sink during current generation, thus further suppressing thermal runaway of the battery. Examples of such inorganic materials include alumina (Al2O3), boehmite (alumina monohydrate), talc, boron nitride (BN), aluminum nitride (AlN), titanium dioxide (TiO2), and silicon dioxide (SiO2). x Examples include oxides or nitrides such as ).

[0119] The particle size of the inorganic material is preferably in the range of 1 nm to 10 μm. If the particle size of the inorganic material is smaller than 1 nm, it becomes difficult to obtain, and even if it can be obtained, it is not cost-effective. If the particle size of the inorganic material is larger than 10 μm, the distance between electrodes becomes large, and a sufficient amount of active material cannot be obtained in the limited space, resulting in a lower battery capacity.

[0120] The resin layer of the separator 33 can be formed, for example, by applying a slurry consisting of a matrix resin, a solvent, and an inorganic substance onto a substrate (porous membrane), passing it through a bath that is a poor solvent for the matrix resin and a good solvent for the solvent to separate the phases, and then drying it.

[0121] The puncture strength of the separator 33 is preferably in the range of 100 gf to 1000 gf. More preferably, the puncture strength of the separator 33 is between 100 gf and 480 gf. This is because a low puncture strength may cause a short circuit, while a high puncture strength will reduce ionic conductivity.

[0122] The air permeability of the separator 33 is preferably in the range of 30 sec / 100cc to 1000 sec / 100cc. More preferably, the air permeability of the separator 33 is between 30 sec / 100cc and 680 sec / 100cc. This is because if the air permeability of the separator 33 is too low, a short circuit may occur, and if it is too high, the ion conductivity will decrease.

[0123] Furthermore, the inorganic substances mentioned above may be contained in the porous membrane used as the substrate.

[0124] (electrolyte) The separator 33 is impregnated with an electrolyte, which is a liquid electrolyte. The electrolyte contains a solvent and an electrolyte salt dissolved in this solvent. To improve the characteristics of the battery 100, the electrolyte may contain known additives.

[0125] As a solvent, cyclic carbonate esters such as ethylene carbonate or propylene carbonate can be used, and it is preferable to use one or both of ethylene carbonate and propylene carbonate in combination. This is because the cycle characteristics can be improved.

[0126] Furthermore, it is preferable to use a mixture of the cyclic carbonate esters mentioned above as a solvent, along with chain-like carbonate esters such as diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate, or methylpropyl carbonate. This is because high ionic conductivity can be obtained in this case.

[0127] Furthermore, it is preferable to include 2,4-difluoroanisole or vinylene carbonate as a solvent. This is because 2,4-difluoroanisole can improve discharge capacity, and vinylene carbonate can improve cycle characteristics. Therefore, using a mixture of 2,4-difluoroanisole and vinylene carbonate is more preferable because it can improve both discharge capacity and cycle characteristics.

[0128] Other solvents include butylene carbonate, γ-butyrolactone, γ-valerolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, methyl acetate, methyl propionate, acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, 3-methoxypropironitrile, N,N-dimethylformamide, N-methylpyrrolidinone, N-methyloxazolidinone, N,N-dimethylimidazolidinone, nitromethane, nitroethane, sulfolane, dimethyl sulfoxide, or trimethyl phosphate.

[0129] Furthermore, compounds in which at least some of the hydrogen atoms in these non-aqueous solvents are replaced with fluorine may be preferable in some cases, as they can improve the reversibility of the electrode reaction depending on the type of electrode they are combined with.

[0130] Examples of electrolyte salts include lithium salts. Lithium salts may be used individually or in mixtures of two or more. Examples of lithium salts include LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiAlCl4, LiSiF6, LiCl, lithium difluoro[oxolato-O,O']borate, lithium bisoxalate borate, or LiBr. Among these, LiPF6 is preferred because it can provide high ionic conductivity and improve cycle characteristics.

[0131] [Battery operation] In the battery 100 having the above configuration, when charging occurs, for example, lithium ions are released from the positive electrode active material layer 31B and absorbed into the negative electrode active material layer 32B via the electrolyte. Also, when discharging occurs, for example, lithium ions are released from the negative electrode active material layer 32B and absorbed into the positive electrode active material layer 31B via the electrolyte.

[0132] [Battery manufacturing method] An example of a manufacturing method for the battery 100 described above is explained below.

[0133] First, a positive electrode mixture is prepared by mixing a lithium-doped and dedoped positive electrode material with a conductive agent and a binder. This positive electrode mixture is then dispersed in a mixed solvent to form a positive electrode mixture slurry. Next, the positive electrode mixture slurry is applied to a positive electrode current collector 31A, dried, and then compressed to produce the positive electrode 31. After that, the positive electrode lead 36 is connected to the positive electrode current collector 31A by ultrasonic welding or spot welding.

[0134] Furthermore, a negative electrode mixture is prepared by mixing a lithium-doped and dedoped negative electrode material with a binder, and this negative electrode mixture is dispersed in a mixed solvent to form a negative electrode mixture slurry. Next, the negative electrode mixture slurry is applied to the negative electrode current collector 32A and dried, and then compressed and molded to produce the negative electrode 32. After that, the negative electrode lead 37 is connected to the negative electrode current collector 32A by ultrasonic welding or spot welding or the like.

[0135] Next, the positive electrode 31 and the negative electrode 32 are stacked with a separator 33 in between and wound many times to create the electrode body 30. Then, the electrode body 30 is sandwiched between a pair of insulating plates 34 and 35 and housed inside the battery can 20. In addition, the positive electrode lead 36 is connected to the current interruption member 3 of the safety mechanism 10, and the negative electrode lead 37 is connected to the battery can 20.

[0136] Next, the electrolyte is prepared by dissolving the electrolyte salt in a solvent. Then, the electrolyte is injected into the battery can 20 and impregnates the separator 33. Subsequently, the safety mechanism 10 is attached to the open end of the battery can 20 by crimping it via the gasket 11.

[0137] The battery 100 is completed using the method described above. Alternatively, a resin ring washer may be attached to the lid 1, or the entire battery 100 may be covered with a resin tube.

[0138] The present invention is not limited to the embodiments described above, and various applications and modifications can be made within the scope of the present invention.

[0139] For example, in the battery 100 of the embodiment described above, the current interruption member 3 has a protrusion 3b for connecting to the pressure release member 2 and a flat plate portion 3a, and the pressure release member 2 has a flat plate shape. However, as shown in Figure 15, the pressure release member 2 may have a protrusion 2b for connecting to the current interruption member 3 and a flat plate portion 2a, and the current interruption member 3 may be configured to have a flat plate shape. In either case, since both the pressure release member 2 and the current interruption member 3 are flat or substantially flat and thin, the safety mechanism 10 of the battery can be made thinner. As a result, for example, when the size of the battery 100 is fixed, the sizes of the positive electrode 31 and the negative electrode 32 can be increased, thereby increasing the capacity of the battery 100.

[0140] Furthermore, in the battery 100 in the above-described embodiment, the pressure release member 2 has a flat plate shape, but it may also have a portion that is bent toward the current interruption member 3, as in the disc plate of the battery described in Patent Document 1. Similarly, the flat plate portion 3a of the current interruption member 3, which is a portion other than the convex portion 3b, has a flat plate shape, but it may also have a portion that is bent toward the electrode body, as in the interruption disc of the battery described in Patent Document 1. [Explanation of Symbols]

[0141] 1 lid 1a Flat part of the lid 1b Protrusion of the lid 1c Discharge hole in the lid 2. Pressure relief member 2a Flat plate portion of the pressure release member 2b Protrusion of the pressure release member 3 Current interruption member 3a Flat plate portion of the current interruption member 3b Protrusion of the current interrupting member 3c hole 3D current-blocking member groove 4 Adhesive layer 10. Battery safety mechanism 11 Gasket 20 Battery Cans 21 The first trench 22 The second groove 30 Electrode body 31 Positive electrode 32 negative electrode 33 Separator 34,35 Insulating board 36 Positive leads 37 Negative lead 38 Center Pin 100 batteries

Claims

1. The lid and A pressure release member is provided, which is in contact with the aforementioned lid and deforms when the internal pressure of the battery rises, in order to release gas from inside the battery to the outside. A current-cutting member is positioned on the opposite side of the lid from the pressure-relieving member and connected to the pressure-relieving member, and is used to interrupt the current flowing to the pressure-relieving member when the internal pressure of the battery rises. An insulating adhesive layer is interposed between the pressure release member and the current interruption member to bond the pressure release member and the current interruption member together, Equipped with, The surface of the pressure release member facing the current interruption member is a roughened surface that has been subjected to a roughening treatment. The surface of the current interrupting member facing the pressure release member is a roughened surface that has been subjected to a roughening treatment. The safety mechanism for a battery is characterized in that the adhesive layer is made of a thermoplastic resin having a melting point of 200°C or higher.

2. The surface area ratio of the roughened surface of the pressure release member is 6% or more and 26% or less. The battery safety mechanism according to claim 1, characterized in that the surface area ratio of the roughened surface of the current interrupting member is 6% or more and 26% or less.

3. The safety mechanism for a battery according to claim 1 or 2, characterized in that the adhesive layer is arranged discontinuously at multiple locations.

4. The safety mechanism for a battery according to claim 1 or 2, characterized in that the thickness of the adhesive layer is 0.05 mm or more and 0.4 mm or less.

5. The area of ​​the adhesive layer is 0.6 mm². 2 100mm or more 2 The battery safety mechanism according to claim 1 or 2, characterized in that it is as follows:

6. The current interruption member has a protrusion for connecting to the pressure release member and a flat plate portion with a flat plate shape. The safety mechanism for a battery according to claim 1 or 2, characterized in that the pressure release member has a flat plate shape.

7. The pressure release member has a protrusion for connecting to the current interruption member and a flat plate portion with a flat plate shape. The safety mechanism for a battery according to claim 1 or 2, characterized in that the current interruption member has a flat plate shape.

8. The safety mechanism for a battery according to claim 1 or 2, characterized in that the current interruption member is made of at least one of aluminum, titanium, platinum, and gold.

9. The safety mechanism for a battery according to claim 1 or 2, characterized in that the pressure release member is made of at least one of aluminum, titanium, platinum, and gold.

10. An electrode body including a positive electrode, a negative electrode, and a separator provided between the positive electrode and the negative electrode, A battery case containing the electrode body, A battery safety mechanism according to claim 1 or 2, attached to the battery can, A battery characterized by having the following features.

11. The battery according to claim 10, characterized in that it is a cylindrical lithium-ion secondary battery.

12. The lid and A pressure release member is provided, which is in contact with the aforementioned lid and deforms when the internal pressure of the battery rises, in order to release gas from inside the battery to the outside. A current-cutting member is positioned on the opposite side of the lid from the pressure-relieving member and connected to the pressure-relieving member, and is used to interrupt the current flowing to the pressure-relieving member when the internal pressure of the battery rises. An insulating adhesive layer is interposed between the pressure release member and the current interruption member to bond the pressure release member and the current interruption member together, Equipped with, The safety mechanism for a battery is characterized in that the adhesive layer is arranged discontinuously at multiple locations.

13. The lid and A pressure release member is provided, which is in contact with the aforementioned lid and deforms when the internal pressure of the battery rises, in order to release gas from inside the battery to the outside. A current-cutting member is positioned on the opposite side of the lid from the pressure-relieving member and connected to the pressure-relieving member, and is used to interrupt the current flowing to the pressure-relieving member when the internal pressure of the battery rises. An insulating adhesive layer is interposed between the pressure release member and the current interruption member to bond the pressure release member and the current interruption member together, Equipped with, The current interruption member has a protrusion for connecting to the pressure release member and a flat plate portion with a flat plate shape. The safety mechanism for a battery is characterized in that the pressure release member has a flat plate shape.

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