Nonaqueous electrolyte secondary battery

Abstract

To provide a nonaqueous electrolyte secondary battery that solves the problems of the prior art.SOLUTION: A nonaqueous electrolyte secondary battery includes an electrode body, a nonaqueous electrolyte solution, an electrode terminal, and a battery case that accommodates the electrode body and the nonaqueous electrolyte solution. The battery case is made of aluminum or an aluminum alloy. The battery case includes an outer can having an opening part, and a sealing plate for sealing the opening part. The electrode terminal is insulated from the sealing plate by an insulating resin member. The insulating resin member contains polyphenylene sulfide and a glass filler. At least a part of the insulating resin member is located in the battery case so as to be in contact with the nonaqueous electrolytic solution. The nonaqueous electrolytic solution contains a dehydrating agent as an additive.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a non-aqueous electrolyte secondary battery. [Background technology]

[0002] In recent years, non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries have been suitably used as portable power sources for personal computers, mobile terminals, etc., and as power sources for driving vehicles such as electric vehicles (BEVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs).

[0003] In one typical form of a non-aqueous electrolyte secondary battery, an electrode assembly and a non-aqueous electrolyte are housed in a battery case. The battery case is made of aluminum and includes an outer can with an opening and a sealing plate that closes the opening. An electrode terminal is attached to the sealing plate. An insulating resin member is disposed between the sealing plate and the electrode terminal. In order to obtain a structure in which an insulating resin member is disposed between the sealing plate and the electrode terminal, a technique has been developed in which the sealing plate and the electrode terminal are integrated via a resin material by insert molding (see, for example, Patent Document 1). Polyphenylene sulfide (PPS) is known as a resin material used for the insulating resin member (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2020 / 110888 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-187401 Summary of the Invention [Problem to be solved by the invention]

[0005] As a result of extensive research, the present inventors have discovered the following problem. Specifically, when an insulating resin member is formed between a sealing plate and an electrode terminal by insert molding using PPS, molding defects can occur. Research by the present inventors has shown that this molding defect can be reduced by blending a glass filler with PPS. However, blending a glass filler with PPS causes corrosion of the glass filler contained in the insulating resin member in nonaqueous electrolyte secondary batteries, resulting in deterioration of the insulating resin member.

[0006] Therefore, the present invention provides a non-aqueous electrolyte secondary battery that solves the problems of the prior art. [Means for solving the problem]

[0007] The nonaqueous electrolyte secondary battery disclosed herein comprises an electrode assembly, a nonaqueous electrolyte, an electrode terminal, and a battery case that accommodates the electrode assembly and the nonaqueous electrolyte. The battery case is made of aluminum or an aluminum alloy. The battery case comprises an outer can with an opening and a sealing plate that seals the opening. The electrode terminal is insulated from the sealing plate by an insulating resin member. The insulating resin member contains polyphenylene sulfide and a glass filler. At least a portion of the insulating resin member is located within the battery case and can come into contact with the nonaqueous electrolyte. The nonaqueous electrolyte contains a dehydrating agent as an additive.

[0008] This configuration makes it possible to provide a secondary battery that overcomes the problems of the prior art. That is, this configuration makes it difficult for molding defects to occur during insert molding of an insulating resin member using PPS. Furthermore, in a nonaqueous electrolyte secondary battery, corrosion of the glass filler contained in the insulating resin member is unlikely to occur. Therefore, deterioration of the insulating resin member is suppressed. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a partial cross-sectional view of a battery 10, which is an example of a nonaqueous electrolyte secondary battery according to this embodiment. [Figure 2] FIG. 2 is a partial cross-sectional view showing the portion of the battery of FIG. 1 where the internal terminal 42 and the external terminal 43 are attached to the battery case 41. As shown in FIG. [Figure 3] FIG. 3 is a partial cross-sectional view of a battery 10A according to another embodiment. [Figure 4] FIG. 4 is a partial cross-sectional view of a battery 10B according to another embodiment. [Figure 5] FIG. 5 is a partial cross-sectional view of a battery 10C according to still another embodiment. [Figure 6] FIG. 6 is a perspective view illustrating a method for fabricating the electrode terminal structure of the battery 10A. [Figure 7] FIG. 7 is a perspective view illustrating a method for fabricating the electrode terminal structure of the battery 10A. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Matters not mentioned in this specification but necessary for implementing the present invention can be understood as design matters for a person skilled in the art based on the prior art in the relevant field. The present disclosure can be implemented based on the contents disclosed in this specification and the technical common sense in the relevant field. Furthermore, in the following drawings, components and parts that perform the same function are denoted by the same reference numerals. Furthermore, the dimensional relationships (length, width, thickness, etc.) in each drawing do not reflect the actual dimensional relationships. In this specification, a numerical range expressed as "A to B" includes A and B.

[0011] In this specification, the term "secondary battery" refers to an electricity storage device that can be repeatedly charged and discharged. In addition, in this specification, the term "lithium ion secondary battery" refers to a secondary battery that uses lithium ions as charge carriers and achieves charging and discharging by the transfer of charge associated with the lithium ions between the positive and negative electrodes.

[0012] <<Battery 10>> 1 is a partial cross-sectional view of a battery 10, which is an example of a nonaqueous electrolyte secondary battery according to this embodiment. In this example, the battery 10 is a lithium-ion secondary battery. However, the nonaqueous electrolyte secondary battery disclosed herein may be a nonaqueous electrolyte secondary battery other than a lithium-ion secondary battery.

[0013] FIG. 1 depicts a state in which the interior of a substantially rectangular parallelepiped battery case 41 is exposed along one wide surface. FIG. 2 is a partial cross-sectional view showing a portion where an internal terminal 42 and an external terminal 43 are attached to the battery case 41. The battery 10 shown in FIGS. 1 and 2 is a so-called sealed battery. The battery 10 has an electrode assembly 20, a non-aqueous electrolyte (not shown), electrode terminals, and a battery case 41 that contains the electrode assembly 20 and the non-aqueous electrolyte. In this example, the electrode terminals are composed of the internal terminal 42 and the external terminal 43. The battery 10 also has an insulating resin member 44.

[0014] <Electrode body 20> The electrode assembly 20 is housed in a battery case 41 while being covered with an insulating film (not shown) or the like. The electrode assembly 20 includes a positive electrode sheet 21 as a positive electrode element, a negative electrode sheet 22 as a negative electrode element, and separator sheets 31 and 32 as separators. The positive electrode sheet 21, the first separator sheet 31, the negative electrode sheet 22, and the second separator sheet 32 ​​are each a long, strip-shaped member.

[0015] The positive electrode sheet 21 may have a known configuration. In this embodiment, the positive electrode sheet 21 has a positive electrode active material layer 21b formed on one or both sides (both sides in this example) of a positive electrode current collector foil 21a. The positive electrode sheet 21 also has an active material layer-free portion 21a1 set to a fixed width at one end of the positive electrode sheet 21 in the width direction. The positive electrode current collector foil 21a is, for example, an aluminum foil. The positive electrode active material layer 21b contains a positive electrode active material that is a material that can release lithium ions during charging and absorb lithium ions during discharging. Examples of the positive electrode active material include a lithium transition metal composite oxide and a lithium transition metal phosphate compound. The positive electrode active material layer 21b may further contain a conductive material (e.g., carbon black), a binder (e.g., polyvinylidene fluoride), and the like.

[0016] The negative electrode sheet 22 may have a known configuration. In this embodiment, the negative electrode sheet 22 has a negative electrode active material layer 22b formed on one or both sides (both sides in this example) of a negative electrode current collector foil 22a. The negative electrode sheet 22 also has an active material layer-free portion 22a1 set to a fixed width at one end of the width direction. The negative electrode current collector foil 22a is, for example, a copper foil. The negative electrode active material layer 22b contains a negative electrode active material that is a material that can occlude lithium ions during charging and release the occluded lithium ions during discharging. The negative electrode active material is, for example, a carbon material such as graphite or hard carbon. The negative electrode active material layer 22b may further contain a thickener (e.g., carboxymethyl cellulose and its salt), a binder (e.g., styrene butadiene rubber), etc.

[0017] The separator sheets 31 and 32 may have a known configuration. For example, a resin porous sheet (film) is used for the separator sheets 31 and 32. The resin constituting the resin porous sheet is, for example, polyethylene (PE), polypropylene (PP), etc. The resin porous sheet may have a single layer structure or a laminated structure of two or more layers. A heat-resistant layer (HRL) may be provided on the surface of the separator sheets 31 and 32.

[0018] Here, the width of the negative electrode active material layer 22b is, for example, wider than that of the positive electrode active material layer 21b. The width of the separator sheets 31 and 32 is wider than that of the negative electrode active material layer 22b. The active material layer-unformed portion 21a1 of the positive electrode current collector foil 21a and the active material layer-unformed portion 22a1 of the negative electrode current collector foil 22a are oriented on opposite sides of each other in the width direction. The positive electrode sheet 21, the first separator sheet 31, the negative electrode sheet 22, and the second separator sheet 32 ​​are aligned in the length direction and sequentially stacked and wound. The negative electrode active material layer 22b covers the positive electrode active material layer 21b with the separator sheets 31 and 32 interposed therebetween. The negative electrode active material layer 22b is covered by the separator sheets 31 and 32. The active material layer-free portion 21a1 of the positive electrode current collector foil 21a protrudes from one widthwise side of the separator sheets 31 and 32. The active material layer-free portion 22a1 of the negative electrode current collector foil 22a protrudes from the separator sheets 31 and 32 on the opposite widthwise side.

[0019] As shown in FIG. 1 , the electrode assembly 20 described above is flattened along a plane including the winding axis so that it can be housed in an outer can 41a of a battery case 41. Along the winding axis of the electrode assembly 20, the active material layer-unformed portion 21a1 of the positive electrode current collector foil 21a is disposed on one side, and the active material layer-unformed portion 22a1 of the negative electrode current collector foil 22a is disposed on the other side. The active material layer-unformed portion 21a1 of the positive electrode current collector foil 21a and the active material layer-unformed portion 22a1 of the negative electrode current collector foil 22a are attached to internal terminals 42 attached to both longitudinal sides of the lid 41b. The electrode assembly 20 is housed in the battery case 41 in this state attached to the internal terminals 42 attached to the lid 41b. Therefore, in the illustrated example, the electrode assembly 20 is a wound electrode assembly. However, the electrode assembly 20 is not limited to this, and may be a laminated electrode assembly in which a plurality of positive electrode sheets and a plurality of negative electrode sheets are alternately stacked with separators interposed therebetween.

[0020] <Battery case 41> As shown in FIGS. 1 and 2, in this embodiment, the battery case 41 includes an outer can 41a and a sealing plate 41b. The battery case 41 is made of aluminum (e.g., 1000-series aluminum) or an aluminum alloy (e.g., 3000-series aluminum), and is particularly made of aluminum. The outer can 41a has an opening. Specifically, the outer can 41a has a flat, approximately rectangular parallelepiped container shape, and one side consisting of the long and short sides is open. The sealing plate 41b is a plate-like member shaped according to the opening of the outer can 41a. The sealing plate 41b seals the opening of the outer can 41a. Terminal mounting holes 41c for mounting an internal terminal 42 and an external terminal 43 are formed on both longitudinal sides of the sealing plate 41b. Here, the terminal mounting holes 41c are formed in the sealing plate 41b.

[0021] <Internal terminal 42> As shown in FIGS. 1 and 2, the internal terminal 42 is disposed inside the battery case 41 at a distance from the battery case 41. In this embodiment, the internal terminal 42 is a plate-shaped member as shown in FIG. 2. The internal terminal 42 is disposed inside the battery case 41 at a distance from a sealing plate 41b having a terminal mounting hole 41c formed therein. The internal terminal 42 includes a base 42a, a current collecting portion 42b, and a protruding portion 42c. The base 42a extends along the sealing plate 41b of the battery case 41. The current collecting portion 42b extends from one end of the base 42a along one side in the winding axis direction of the electrode body 20. The protruding portion 42c is provided on the base 42a and fits into the terminal mounting hole 41c of the sealing plate 41b. The protruding portion 42c is recessed from the inside of the base 42a and protrudes outward. The tip of the protrusion 42c has a flat surface 42c1. The positive electrode side of the internal terminal 42 is made of aluminum, and the negative electrode side is made of copper, for example.

[0022] <External terminal 43> The external terminal 43 is a member disposed outside the battery case 41 at a distance from the battery case 41 and connected to the internal terminal 42 through the terminal mounting hole 41c. In this embodiment, as shown in FIG. 2, the external terminal 43 is a flat plate-like member disposed at a distance from the sealing plate 41b in which the terminal mounting hole 41c is formed. The external terminal 43 is placed on the flat surface 42c1 of the protruding portion 42c of the internal terminal 42 that is inserted into the terminal mounting hole 41c, and this portion is joined. Thus, in this embodiment, the internal terminal 42 is a plate-like member. The base 42a of the internal terminal 42 is recessed from the inside and inserted into the terminal mounting hole 41c, and has the protruding portion 42c with a flat tip. The flat portion (flat surface 42c1) at the tip of the protruding portion 42c is joined to the external terminal 43. For example, the positive electrode side of the external terminal 43 is made of aluminum, and the negative electrode side is made of copper.

[0023] The internal terminal 42 and the external terminal 43 may be joined by, for example, solid-state bonding. Solid-state bonding reduces the electrical resistance of the joint 45 where the internal terminal 42 and the external terminal 43 are joined. For example, ultrasonic bonding may be used for solid-state bonding. In ultrasonic bonding, the internal terminal 42 and the external terminal 43 are overlapped and clamped between a horn and anvil, and the horn is vibrated. This heats and softens the overlapped internal terminal 42 and external terminal 43 while they remain in a solid state (solid) without melting, and then pressurizes them to cause plastic deformation, thereby joining them. In addition to ultrasonic bonding, other solid-state bonding methods may include cold pressure welding, hot pressure welding, and friction welding. Note that the joining of the internal terminal 42 and the external terminal 43 is not limited to the examples given here, and various other methods may be used. For example, the internal terminal 42 and the external terminal 43 may be welded.

[0024] A roughened surface having an arithmetic mean roughness of 30 nm to 500 nm may be formed on at least a portion of the bonded portions of the insulating resin member 44 of the battery case 41 (in this embodiment, the sealing plate 41b), the internal terminal 42, and the external terminal 43 (i.e., the portions where the insulating resin member 44 is in contact with the battery case 41, the internal terminal 42, and the external terminal 43). The roughened surface formed on the bonded portions of the resin may be formed by roughening the surfaces with fine irregularities, for example, by laser irradiation or chemical etching. The roughened surfaces formed on the portions where the insulating resin member 44 is bonded improve the bond strength between the battery case 41 (in this embodiment, the sealing plate 41b), the internal terminal 42, and the external terminal 43, and the insulating resin member 44. From the viewpoint of improving the bond strength of the insulating resin member 44, the arithmetic mean roughness of the irregularities formed by the roughening process may be approximately 30 nm to 500 nm. The arithmetic mean roughness of the unevenness in the roughened surface is preferably 450 nm or less, more preferably 400 nm or less. On the other hand, the arithmetic mean roughness of the unevenness in the roughened surface is preferably 40 nm or more, more preferably 50 nm or more. Furthermore, for example, for a member made of copper, the arithmetic mean roughness is preferably about 60 nm to 240 nm. For a member made of aluminum, the arithmetic mean roughness is preferably about 48 nm to 435 nm. This process of roughening the surface of the portion to which the insulating resin member 44 is bonded can also be called a nano-anchor process.

[0025] <Insulating resin member 44> The insulating resin member 44 is disposed so as to fill the gap between the battery case 41 and the internal terminal 42 and the gap between the battery case 41 and the external terminal 43. The insulating resin member 44 is joined to the battery case 41, the internal terminal 42, and the external terminal 43. The insulating resin member 44 insulates the battery case 41 from the internal terminal 42 and also insulates the battery case 41 from the external terminal 43. In this embodiment, the insulating resin member 44 is typically formed by insert molding.

[0026] The insulating resin constituting the insulating resin member 44 contains polyphenylene sulfide (PPS) and a glass filler. PPS is excellent in heat resistance, chemical resistance, self-extinguishing properties, and the like. As described above, the inventors' investigations have revealed that forming the insulating resin member 44 by insert molding using PPS can result in the problem of molding defects. In contrast, when the insulating resin constituting the insulating resin member 44 contains a glass filler in addition to PPS, as in this embodiment, the linear expansion coefficients of the aluminum sealing plate and the insulating resin used in insert molding become closer, thereby reducing molding defects.

[0027] The amount of glass filler contained in the insulating resin constituting the insulating resin member 44 is not particularly limited as long as the effects of the present invention can be obtained. Typically, different materials are used for the electrode terminals (i.e., the internal terminal 42 and the external terminal 43) of the battery 10 for the positive and negative electrodes. For example, the positive electrode terminal is made of aluminum (Al), and the negative electrode terminal is made of copper (Cu). When the difference in thermal expansion between the insulating resin and the metal constituting the terminal is small, stress generated during heating and cooling can be reduced, and durability against thermal shock can be improved. For this reason, it is preferable to adjust the linear expansion coefficient of the insulating resin to be intermediate between that of the metal constituting the positive electrode terminal (e.g., Al) and the material constituting the negative electrode terminal (e.g., Cu). However, if the amount of glass filler contained in the insulating resin is too large, moldability will be reduced. For these reasons, the amount of glass filler in the insulating resin constituting the insulating resin member 44 is preferably 40% to 60% by mass.

[0028] The insulating resin constituting the insulating resin member 44 may contain components (for example, additives) other than PPS and glass filler.

[0029] In the embodiment shown in FIG. 2 , at the joint portion 45 between the internal terminal 42 and the external terminal 43, the inner surface of the internal terminal 42 facing the inside of the battery case 41 is covered with the insulating resin member 44. Therefore, the joint portion 45 is not exposed to the atmosphere or nonaqueous electrolyte inside the battery case 41 due to the portion 44a of the insulating resin 44 that covers the joint portion 45. This suppresses deterioration of the joint portion 45. However, the portion of the insulating resin member 44 that is disposed on the inner surface of the internal terminal 42 (e.g., portion 44a) is located within the battery case 41 and is in a position where it can come into contact with the nonaqueous electrolyte. In addition, the end of the portion of the insulating resin member 44 between the sealing plate 41b and the internal terminal 42 is also located within the battery case 41 and is in a position where it can come into contact with the nonaqueous electrolyte.

[0030] At least a portion of the insulating resin member 44 may be in contact with the electrode assembly 20. In the embodiment shown in Fig. 2, the insulating resin member 44 has a contact portion 44b that protrudes toward the inside of the battery case 41 at a portion of the insulating resin member 44 that covers the inner surface of the internal terminal 42. The electrode assembly 20 attached to the internal terminal 42 is pressed down by this contact portion 44b. This stabilizes the electrode assembly 20 within the battery case 41. The contact portion 44b is also located within the battery case 41 and in a position that allows it to come into contact with the non-aqueous electrolyte.

[0031] In this embodiment, the electrode body 20 is attached to the current collecting portion 42b of the internal terminal 42 fixed to the sealing plate 41b via the insulating resin member 44. This prepares an assembly in which the electrode body 20 is attached to the internal terminal 42 fixed to the sealing plate 41b. In this assembly, the electrode body 20 is housed in the outer can 41a.

[0032] Furthermore, in this embodiment, the insulating resin member 44 surrounds the outer periphery of the external terminal 43. This makes it difficult for the external terminal 43 to shift relative to the sealing plate 41b. Therefore, the insulating resin member 44 may include a restricting portion 44c that restricts the outer periphery of the external terminal 43. In this embodiment, the restricting portion 44c rises along the outer periphery of the external terminal 43 and surrounds the entire outer periphery of the external terminal 43. The restricting portion 44c may partially restrict the outer periphery of the external terminal 43 in the circumferential direction.

[0033] In the battery 10, the portions of the battery case 41 where the internal terminals 42 and external terminals 43 are attached are covered with an insulating resin member 44. Therefore, stress acting on the joints between the battery case 41, the internal terminals 42, and the external terminals 43 is borne by the entire insulating resin member 44. This reduces the number of defects in leak tests and resistance tests of the battery case 41, improving the yield rate. The number of parts at the portions of the battery case 41 where the internal terminals 42 and external terminals 43 are attached is reduced.

[0034] In the battery 10, the structure in which the insulating resin member 44 is disposed between the sealing plate 41b and the electrode terminal (hereinafter also referred to as the "electrode terminal structure") is not limited to the one shown in the drawings, as long as a part of the insulating resin member 44 is located in a position where it can come into contact with the nonaqueous electrolyte solution in the battery case 41. Other embodiments as modified electrode terminal structures will be described below.

[0035] For example, FIG. 3 is a partial cross-sectional view of a battery 10A according to another embodiment. FIG. 3 is a cross-sectional view taken parallel to the broad surface of the battery case 41. As shown in FIG. 3, the external terminal 43 of the battery 10A is a plate-shaped member having a protruding portion 43c with a flattened tip, recessed from the outside and inserted into the terminal mounting hole 41c. On the other hand, the base 42a of the internal terminal 42 is formed in a flat plate shape. The flattened portion 43c1 at the tip of the protruding portion 43c is overlapped and joined to the internal terminal 42. In the embodiment shown in FIG. 3, the inner surface of the internal terminal 42 is covered with an insulating resin member 44. In particular, the insulating resin member 44 includes a portion 44a that covers the joint portion 45 between the internal terminal 42 and the external terminal 43 inside the battery case 41. A contact portion 44b that protrudes toward the inside of the battery case 41 and contacts the electrode assembly 20 is provided at a portion of the insulating resin member 44. In this embodiment as well, a part of the insulating resin member 44 (for example, a part disposed on the inner surface of the internal terminal 42) is located within the battery case 41 in a position where it can come into contact with the nonaqueous electrolyte.

[0036] FIG. 4 is a partial cross-sectional view of a battery 10B according to another embodiment. FIG. 4 is a cross-sectional view parallel to the broad surface of the battery case 41. As shown in FIG. 4, the internal terminal 42 of the battery 10B is a plate-shaped member. It has a protruding portion 42c that is recessed from the inside and protrudes toward the terminal mounting hole 41c, and has a flattened tip. The external terminal 43 is a plate-shaped member. It has a protruding portion 43c that is recessed from the outside and protrudes toward the terminal mounting hole 41c, and has a flattened tip. The flattened portion 42c1 at the tip of the protruding portion 42c of the internal terminal 42 is joined to the flattened portion 43c1 of the protruding portion 43c of the external terminal 43. In the embodiment shown in FIG. 4, the inner surface of the internal terminal 42 is covered with an insulating resin member 44. In particular, the insulating resin member 44 includes a portion 44a that covers the joint portion 45 between the internal terminal 42 and the external terminal 43 inside the battery case 41. Furthermore, a part of the insulating resin member 44 is provided with a contact portion 44b that bulges toward the inside of the battery case 41 and contacts the electrode body 20. In this embodiment as well, a part of the insulating resin member 44 (for example, a portion disposed on the inner surface of the internal terminal 42) is located within the battery case 41 in a position where it can come into contact with the nonaqueous electrolyte.

[0037] FIG. 5 is a partial cross-sectional view of a battery 10C according to yet another embodiment. Unlike FIGS. 3 and 4, FIG. 5 is a cross-sectional view taken perpendicular to the broad surface of the battery case 41. In this embodiment, an electrode terminal 46 is used instead of the internal terminal 42 and the external terminal 43. The electrode terminal 46 functions as both the internal terminal 42 and the external terminal 43. The electrode terminal 46 of the battery 10C penetrates a terminal mounting hole 41c in the sealing plate 41b and protrudes from the inside to the outside of the battery case 41. The tip of the electrode terminal 46 is bent. An insulating resin member 44 is disposed around the electrode terminal 46, filling the terminal mounting hole 41c. Another insulating resin member 44 is disposed between the electrode terminal 46 and the sealing plate 41b. Another insulating resin member 44 is disposed on the inner surface of the sealing plate 41b. In this embodiment, too, a portion of the insulating resin member 44 (e.g., a portion disposed on the inner surface of the sealing plate 41b) is located within the battery case 41 and in a position where it can come into contact with the nonaqueous electrolyte.

[0038] <Method for manufacturing electrode terminal structure> A method for fabricating a structure (electrode terminal structure) in which an insulating resin member 44 is disposed between a sealing plate 41b and an electrode terminal will be described using the structure of a battery 10A (see FIG. 3) as an example. In the following example, an insert molding method is used. However, the method for fabricating the electrode terminal structure is not limited to the following method.

[0039] As shown in FIG. 6, first, a sealing plate 41b, an internal terminal 42, and an external terminal 43 are prepared. These components may be roughened by laser irradiation or chemical etching. In the illustrated example, the sealing plate 41b is a plate-shaped component. A terminal mounting hole 41c of a required size is provided in a predetermined position in the sealing plate 41b. The external terminal 43 is provided with a protrusion 43c that fits into the terminal mounting hole 41c. On the other hand, the base 42a of the internal terminal 42 is configured in the shape of a flat plate.

[0040] 6, in the terminal mounting hole 41c of the sealing plate 41b, the flattened portion 43c1 at the tip of the protruding portion 43c of the external terminal 43 is overlapped and joined to the internal terminal 42. For this joining, solid-state joining such as ultrasonic joining or welding may be used, as described above.

[0041] The sealing plate 41b, the internal terminals 42, and the external terminals 43 are arranged in a mold (not shown) so that gaps 50 (see FIG. 6) are formed between the sealing plate 41b and the internal terminals 42 and external terminals 43. The mold has walls that define an area (i.e., a cavity) into which the insulating resin member 44 is filled. The mold also has a spool, runners, gates, and the like for filling the cavity with insulating resin.

[0042] Separately, an insulating resin containing PPS and glass filler is prepared. This insulating resin is heated to or above the melting point of PPS and then injected into a mold. This fills the cavity space with the insulating resin. The insulating resin is then cooled in the mold, thereby insert-molding an insulating resin member 44. As a result, as shown in FIG. 7, the internal terminals 42 and external terminals 43 are bonded to the sealing plate 41b by the insulating resin member 44. Note that if the sealing plate 41b, internal terminals 42, and external terminals are surface-roughened, the insulating resin member 44 penetrates into the fine irregularities, providing an anchoring effect, thereby more firmly bonding the internal terminals 42 and external terminals 43 to the sealing plate 41b by the insulating resin member 44.

[0043] <Nonaqueous electrolyte> In this embodiment, the non-aqueous electrolyte contains a dehydrating agent, and typically contains a non-aqueous solvent and a supporting salt (electrolyte salt).

[0044] As described above, the inventors' investigations have newly discovered a problem in that when an insulating resin member containing PPS and a glass filler is formed, corrosion of the glass filler may occur. Further investigations by the inventors have identified the cause of this corrosion as follows: A portion of the insulating resin member 44 is located in a position where it can come into contact with the nonaqueous electrolyte in the battery case 41. If hydrogen fluoride (HF) is generated in the nonaqueous electrolyte due to a side reaction or the like, when this hydrogen fluoride comes into contact with the insulating resin member 44, it corrodes the SiO2 contained in the glass filler, as shown in the following reaction formula (1). This generates water, which then hydrolyzes lithium hexafluorophosphate (LiPF6) contained in the electrolyte, as shown in the following reaction formula (2). This generates additional hydrogen fluoride, further corroding the glass filler. Therefore, the chain reaction of glass filler corrosion leads to deterioration of the insulating resin member. SiO2+4HF → SiF4+2H2O ···(1) LiPF6+4H2O → LiF+5HF+H3PO4···(2)

[0045] Therefore, by adding a dehydrating agent to the non-aqueous electrolyte, the reaction represented by the above reaction formula (2) can be suppressed, and deterioration of the insulating resin member 44 due to the chain reaction of corrosion of the glass filler can be suppressed.

[0046] The dehydrating agent may be a material that adsorbs water or a compound that reacts with water to consume the water. Examples of the dehydrating agent include molecular sieves, sodium sulfate, silica gel, magnesium oxide, calcium oxide, calcium chloride, calcium hydride, potassium hydride, sodium hydride, lithium aluminum hydride, and acid anhydrides (e.g., succinic anhydride, glutaric anhydride, maleic anhydride, etc.).

[0047] The amount of dehydrating agent in the non-aqueous electrolyte may be selected appropriately depending on the type of dehydrating agent, and may be, for example, 0.1 to 20% by mass, 0.5 to 10% by mass, or 1 to 5% by mass.

[0048] As the nonaqueous solvent, various organic solvents such as carbonates, ethers, esters, nitriles, sulfones, and lactones that are commonly used in electrolytes for lithium ion secondary batteries can be used without any particular limitation. Among these, carbonates are preferred, and specific examples thereof include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and monofluoroethylene carbonate (MFEC). Such nonaqueous solvents can be used alone or in appropriate combinations of two or more.

[0049] As the supporting salt, for example, lithium salts such as LiPF6, lithium bis(fluorosulfonyl)imide (LiFSI) etc. The concentration of the supporting salt is preferably 0.7 mol / L or more and 1.3 mol / L or less.

[0050] The nonaqueous electrolyte may contain various additives other than the above-mentioned components, such as film-forming agents such as vinylene carbonate (VC) and oxalate complexes; gas generating agents such as biphenyl (BP) and cyclohexylbenzene (CHB); and thickeners, as long as the effects of the present invention are not significantly impaired.

[0051] Battery 10 can be used for a variety of purposes. Specific applications include portable power sources for personal computers, portable electronic devices, portable terminals, etc.; power sources for driving vehicles such as electric vehicles (BEVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); and storage batteries for small-sized power storage devices, with battery 10 being preferred as a power source for driving vehicles. Battery 10 can also be used in the form of a battery pack, typically consisting of a plurality of batteries connected in series and / or parallel.

[0052] Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above.

[0053] That is, the nonaqueous electrolyte secondary battery disclosed herein has the following items [1] to [9]. [1] An electrode body; a nonaqueous electrolyte; An electrode terminal; a battery case that accommodates the electrode assembly and the nonaqueous electrolyte; A non-aqueous electrolyte secondary battery comprising: the battery case is made of aluminum or an aluminum alloy; the battery case includes an outer can having an opening and a sealing plate that seals the opening, the electrode terminal is insulated from the sealing plate by an insulating resin member; the insulating resin member contains polyphenylene sulfide and a glass filler; at least a portion of the insulating resin member is located within the battery case and in a position where it can come into contact with the nonaqueous electrolyte; The nonaqueous electrolyte secondary battery comprises a dehydrating agent as an additive in the nonaqueous electrolyte. [2] The nonaqueous electrolyte secondary battery according to item [1], wherein the insulating resin member is integrated with the sealing plate and the electrode terminals by insert molding. [3] The nonaqueous electrolyte secondary battery according to item [1] or [2], wherein the insulating resin constituting the insulating resin member contains the glass filler in an amount of 40% by mass to 60% by mass. [4] The nonaqueous electrolyte secondary battery according to any one of items [1] to [3], wherein a roughened surface having an arithmetic mean roughness of 30 nm to 500 nm is formed on at least a portion of the portion of the insulating resin member that is in contact with the battery case and the electrode terminal. [5] The nonaqueous electrolyte secondary battery according to any one of items [1] to [4], wherein the dehydrating agent is a material that adsorbs water. [6] The nonaqueous electrolyte secondary battery according to any one of items [1] to [4], wherein the dehydrating agent is a compound that reacts with water and consumes the water. [7] The nonaqueous electrolyte secondary battery according to any one of items [1] to [6], which is a lithium ion secondary battery. [Explanation of symbols]

[0054] 10,10A,10B,10C battery 20 Electrode body 21 Positive electrode sheet 21a Positive electrode current collector foil 21a1 Active material non-formed area 21b Positive electrode active material layer 22 Negative electrode sheet 22a Negative current collector foil 22a1 Active material non-formed area 22b Negative electrode active material layer 31,32 Separator sheet 41 Battery case 41a Outer can 41b Sealing plate 41c Terminal mounting hole 42 Internal terminal 42a base 42b Current collecting part 42c protrusion 42c1 Flattened area (flat surface) 43 External terminal 43c Protrusion 43c1 Flattened area 44 Insulating resin material 44a Part covering the joint 44b Contact area 44c Regulatory site 45 Joint part 50 gap

Claims

1. An electrode body; a nonaqueous electrolyte; An electrode terminal; a battery case that accommodates the electrode assembly and the nonaqueous electrolyte; A non-aqueous electrolyte secondary battery comprising: the battery case is made of aluminum or an aluminum alloy; the battery case includes an outer can having an opening and a sealing plate that seals the opening, the electrode terminal is insulated from the sealing plate by an insulating resin member; the insulating resin member contains polyphenylene sulfide and a glass filler; at least a portion of the insulating resin member is located within the battery case and in a position where it can come into contact with the nonaqueous electrolyte; The nonaqueous electrolyte secondary battery comprises a dehydrating agent as an additive.

2. 2. The nonaqueous electrolyte secondary battery according to claim 1, wherein the insulating resin member is integrated with the sealing plate and the electrode terminals by insert molding.

3. 2. The nonaqueous electrolyte secondary battery according to claim 1, wherein the insulating resin constituting the insulating resin member contains the glass filler in an amount of 40% by mass to 60% by mass.

4. 2. The nonaqueous electrolyte secondary battery according to claim 1, wherein a roughened surface having an arithmetic mean roughness of 30 nm to 500 nm is formed on at least a portion of the portion of the insulating resin member that is in contact with the battery case and the electrode terminal.

5. 2. The nonaqueous electrolyte secondary battery according to claim 1, wherein the dehydrating agent is a material that adsorbs water.

6. 2. The nonaqueous electrolyte secondary battery according to claim 1, wherein the dehydrating agent is a compound that reacts with water and consumes the water.

7. 2. The nonaqueous electrolyte secondary battery according to claim 1, which is a lithium ion secondary battery.

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