secondary batteries

Abstract

This secondary battery comprises: a conductive exterior member having a through-hole; an electrode terminal disposed on the outside of the exterior member and shielding the through-hole; an insulating sealing member disposed between the exterior member and the electrode terminal; a battery element stored inside the exterior member; and an insulating member disposed between the exterior member and the battery element. The exterior member includes a recess where the through-hole is provided; and in the recess, the exterior member curves so as to be recessed inward. The recess has an opposing surface opposing the battery element, and the insulating member covers the opposing surface and is fixed to the opposing surface.

Description

[Technical Field]

[0001] The present technology relates to a secondary battery. [Background technology]

[0002] Due to the widespread use of various electronic devices such as mobile phones, secondary batteries have been developed as a power source that is small, lightweight, and has high energy density. These secondary batteries have battery elements (positive electrode, negative electrode, and electrolyte) inside an exterior member, and various studies have been conducted on the configuration of these secondary batteries.

[0003] Specifically, an electrode body is housed inside an exterior case, and a flat electrode terminal member is disposed on the outside of the case body via a sealing member (see, for example, Patent Document 1). The electrode body is housed inside an exterior body, and the exterior body has a laminate structure including a resin layer and a metal layer (see, for example, Patent Document 2). A power generating element is housed inside a battery case sealed with a sealing plate, and an electrode terminal is attached to the sealing plate via an insulator (see, for example, Patent Document 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-046639 [Patent Document 2] Japanese Patent Publication No. 2020-095904 [Patent Document 3] Japanese Patent Application Laid-Open No. 2001-143763 Summary of the Invention

[0005] Although various studies have been conducted on the configuration of secondary batteries, the capacity characteristics and operational stability of the secondary batteries are still insufficient, and there is room for improvement.

[0006] Therefore, there is a demand for a secondary battery that can achieve both excellent capacity characteristics and excellent operational stability.

[0007] A secondary battery according to an embodiment of the present technology includes a conductive exterior member having a through hole, an electrode terminal disposed on the outside of the exterior member and shielding the through hole, an insulating sealing member disposed between the exterior member and the electrode terminal, a battery element housed inside the exterior member, and an insulating member disposed between the exterior member and the battery element. It has a flat and columnar three-dimensional shape. The battery includes a recessed portion having a through hole, and the exterior member is bent in the recessed portion so as to be recessed inward. The recessed portion has a facing surface facing the battery element, and the insulating member covers the facing surface and is fixed to the facing surface.

[0008] According to a secondary battery of one embodiment of the present technology, a battery element is housed inside a conductive exterior member having a through hole, an electrode terminal arranged on the outside of the exterior member shields the through hole, an insulating sealing member is arranged between the exterior member and the electrode terminal, a recessed portion having a through hole is provided in the exterior member, and an insulating member covers the opposing surface of the recessed portion and is fixed to the opposing surface, thereby achieving both excellent capacity characteristics and excellent operational stability.

[0009] Note that the effects of the present technology are not necessarily limited to the effects described here, but may be any of a series of effects related to the present technology described below. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a perspective view illustrating a configuration of a secondary battery according to an embodiment of the present technology. [Figure 2] 2 is an enlarged cross-sectional view showing the configuration of the secondary battery shown in FIG. 1. FIG. [Figure 3] FIG. 3 is an enlarged cross-sectional view showing the configuration of the battery element shown in FIG. 2. [Figure 4] 3 is a plan view illustrating the configuration of a main part of the secondary battery illustrated in FIG. 2. FIG. [Figure 5] FIG. 2 is a cross-sectional view illustrating the operation of a secondary battery. [Figure 6] FIG. 2 is a perspective view illustrating a manufacturing process of a secondary battery. [Figure 7] 1 is an enlarged cross-sectional view showing the configuration of a secondary battery of Comparative Example 1. FIG. [Figure 8] 10 is an enlarged cross-sectional view showing the configuration of a secondary battery of Comparative Example 2. FIG. [Figure 9] 10 is an enlarged cross-sectional view showing the configuration of a secondary battery of Comparative Example 3. FIG. [Figure 10] 10 is an enlarged cross-sectional view showing the configuration of a secondary battery of Comparative Example 4. FIG. [Figure 11] 11 is a plan view illustrating the configuration of a main part of the secondary battery illustrated in FIG. [Figure 12] 10 is an enlarged cross-sectional view showing the configuration of a secondary battery according to Modification 1 (part 1). FIG. [Figure 13] 13 is a plan view illustrating the configuration of a main part of the secondary battery illustrated in FIG. 12. FIG. [Figure 14] 10 is an enlarged cross-sectional view showing the configuration of a secondary battery according to Modification 1 (part 2). FIG. [Figure 15] 15 is a plan view illustrating the configuration of a main part of the secondary battery illustrated in FIG. 14. FIG. [Figure 16] 10 is an enlarged cross-sectional view showing the configuration of a secondary battery according to Modification 2. FIG. [Figure 17] 10 is an enlarged cross-sectional view showing the configuration of a secondary battery according to a third modification. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present technology will be described in detail with reference to the drawings. The description will be made in the following order. 1. Secondary battery 1-1.Configuration 1-2.Operation 1-3. Manufacturing method 1-4. Action and effects 2. Variations

[0012] <1. Secondary battery> First, a secondary battery according to an embodiment of the present technology will be described.

[0013] The secondary battery described here is a so-called coin-type or button-type secondary battery.

[0014] As will be described later, this secondary battery includes a pair of bottoms facing each other and sidewalls connected to each of the pair of bottoms. The secondary battery also has an outer diameter and a height, and the height is smaller than the outer diameter. The "outer diameter" refers to the diameter (maximum diameter) of each of the pair of bottoms, and the "height" refers to the distance (maximum distance) from one bottom to the other.

[0015] The charge / discharge principle of a secondary battery is not particularly limited, but the following description will be given of a case where battery capacity is obtained by utilizing the absorption and release of an electrode reactant.

[0016] This secondary battery includes a positive electrode, a negative electrode, and an electrolyte, and the charge capacity of the negative electrode is larger than the discharge capacity of the positive electrode. That is, the electrochemical capacity per unit area of ​​the negative electrode is set to be larger than the electrochemical capacity per unit area of ​​the positive electrode. This is to prevent deposition of electrode reactants on the surface of the negative electrode during charging.

[0017] The type of electrode reactant is not particularly limited, but specifically includes light metals such as alkali metals and alkaline earth metals. Specific examples of alkali metals include lithium, sodium, and potassium, and specific examples of alkaline earth metals include beryllium, magnesium, and calcium.

[0018] In the following, we will take the case where the electrode reactant is lithium as an example. A secondary battery that obtains battery capacity by utilizing the absorption and desorption of lithium is called a lithium ion secondary battery. In this lithium ion secondary battery, lithium is absorbed and desorbed in the ionic state.

[0019] <1-1.Configuration> Fig. 1 shows a perspective view of a secondary battery. Fig. 2 shows an enlarged cross-sectional view of the secondary battery shown in Fig. 1. Fig. 3 shows an enlarged cross-sectional view of a battery element 40 shown in Fig. 2. Fig. 4 shows a plan view of the main part of the secondary battery shown in Fig. 2.

[0020] In the following description, for convenience, the upper side in FIG. 2 will be referred to as the upper side of the secondary battery, and the lower side in FIG. 2 will be referred to as the lower side of the secondary battery.

[0021] However, in order to simplify the illustration, the positive electrode 41, the negative electrode 42, the separator 43, the positive electrode lead 51, and the negative electrode lead 52 are each shown as a line in Fig. 2. In Fig. 3, only a portion of the battery element 40 is shown.

[0022] Fig. 4 shows only the lid portion 12, the battery element 40, and the insulating film 60. Fig. 4 also shows the lid portion 12 and the insulating film 60 as viewed from below, and indicates the outer edge and inner edge (winding center space 40K) of the battery element 40 with dashed lines.

[0023] The secondary battery described here is a button-type secondary battery, as shown in Figures 1 and 2, and has an outer diameter D and a height H. This secondary battery has a three-dimensional shape in which the height H is smaller than the outer diameter D, i.e., a flat and columnar three-dimensional shape. Here, the three-dimensional shape of the secondary battery is flat and cylindrical (columnar), and the ratio D / H of the outer diameter D to the height H is greater than 1.

[0024] Although the specific dimensions of the secondary battery are not particularly limited, an example is an outer diameter D of 3 mm to 30 mm and a height H of 0.5 mm to 70 mm. The ratio D / H is preferably 25 or less.

[0025] Specifically, as shown in Figures 1 to 4, the secondary battery includes an outer can 10, an external terminal 20, a gasket 30, a battery element 40, a positive electrode lead 51, a negative electrode lead 52, and an insulating film 60.

[0026] [Outer can] As shown in FIGS. 1 and 2, the exterior can 10 is a hollow exterior member that houses the battery element 40 and the like, and has a through-hole 10K.

[0027] Here, the exterior can 10 has a three-dimensional shape similar to that of a secondary battery, i.e., a flat, columnar (cylindrical) three-dimensional shape. This allows the exterior can 10 to have an upper base M1 and a lower base M2 that face each other, and a side wall M3. The side wall M3 is disposed between the upper base M1 and the lower base M2 and is connected to each of the upper base M1 and the lower base M2. Because the three-dimensional shape of the exterior can 10 is flat and cylindrical as described above, the planar shapes of the upper base M1 and the lower base M2 are each circular, and the surface of the side wall M3 is a curved surface that is convex outward.

[0028] The inner diameter of the through hole 10K may be the same as the inner diameter of the winding center space 40K described below, or may be different from the inner diameter of the winding center space 40K. Fig. 2 shows the case where the inner diameter of the through hole 10K is larger than the inner diameter of the winding center space 40K.

[0029] This exterior can 10 includes a recessed portion 10U, and the through-hole 10K is provided in the recessed portion 10U. In this recessed portion 10U, the exterior can 10 is bent so as to be recessed inward, and therefore a part of the exterior can 10 is bent so as to form a downward step.

[0030] As a result, the recessed portion 10U has a facing surface 10UM that faces the battery element 40. This facing surface 10UM is the bottom surface of the lid portion 12, that is, the bottom surface of the portion (recessed portion 10U) of the lid portion 12 that is closest to the battery element 40. However, since the recessed portion 10U does not exist in the through hole 10K, the area where the through hole 10K exists is excluded from the facing surface 10UM.

[0031] The shape of the recessed portion 10U, i.e., the shape defined by the outer edge of the recessed portion 10U when the secondary battery is viewed from above, is not particularly limited. Here, the shape of the recessed portion 10U is circular. The inner diameter and depth of the recessed portion 10U are not particularly limited and can be set arbitrarily.

[0032] Here, the outer can 10 includes a storage section 11 and a lid section 12, which are joined together. Specifically, the storage section 11 and the lid section 12 are welded together, and therefore the storage section 11 is sealed by the lid section 12.

[0033] The storage section 11 is a cylindrical, roughly container-shaped member (lower bottom M2 and side wall M3) that stores the battery element 40 and other components therein. Here, the storage section 11 has a structure in which the lower bottom M2 and the side wall M3 are integrated with each other. The storage section 11 has a hollow structure with an open top end and a closed bottom end, and therefore has an opening 11K at the top end.

[0034] The lid 12 is a substantially disk-shaped member (upper base M1) that closes the opening 11K and includes a recess 10U in which a through hole 10K is provided. As will be described later, this through hole 10K is used as a connection path for electrically connecting the battery element 40 and the external terminal 20 to each other.

[0035] As described above, in the completed secondary battery, lid portion 12 is already joined to storage portion 11, and therefore opening portion 11K is closed by lid portion 12. This means that it may not be possible to determine after the fact whether storage portion 11 had opening portion 11K by looking at the exterior of the secondary battery.

[0036] However, if the housing portion 11 and the lid portion 12 are welded together to join them in the manufacturing process of the secondary battery, weld marks should remain on the surface of the outer can 10, more specifically, at the boundary between the housing portion 11 and the lid portion 12. Therefore, based on the presence or absence of weld marks, it can be confirmed after the fact whether the housing portion 11 had the opening portion 11K.

[0037] That is, if welding marks remain on the surface of the outer can 10 and are visible, this means that the storage section 11 had an opening 11K. On the other hand, if welding marks do not remain on the surface of the outer can 10 and are not visible, this means that the storage section 11 did not have an opening 11K.

[0038] As described above, the outer can 10 is a can in which two components (the storage section 11 and the lid section 12) that were physically separate from each other are joined together, and is a so-called joined can. More specifically, when the storage section 11 and the lid section 12 are welded to each other, the outer can 10 is a so-called welded can. As a result, the outer can 10 after joining is physically a single component as a whole, and cannot be separated into the two components (the storage section 11 and the lid section 12) later.

[0039] The outer can 10, which is a bonded can, is a can that differs from a crimped can formed using a caulking process and is a so-called crimpless can. This is because the volumetric energy density increases because the spatial volume of the element increases inside the outer can 10. This "spatial volume of the element" refers to the volume (effective volume) of the internal space of the outer can 10 that can be used to store the battery element 40.

[0040] Furthermore, the outer can 10, which is a bonded can, does not have any overlapping portions, nor does it have any portion where two or more members overlap each other.

[0041] "Having no overlapping parts" means that the outer can 10 is not processed (folded) so that parts thereof are overlapping each other. Also, "having no overlapping parts of two or more components" means that the outer can 10 is physically a single component after the secondary battery is completed, and therefore the outer can 10 cannot be separated into two or more components afterward. In other words, the state of the outer can 10 in the completed secondary battery is not a state in which two or more components are combined while overlapping each other so that they can be separated afterward.

[0042] Since the outer can 10 is conductive, the storage section 11 and the lid section 12 are both conductive. As a result, the outer can 10 is connected to the battery element 40 (the negative electrode 42 described below) via the negative electrode lead 52, and is therefore electrically connected to the negative electrode 42. Therefore, the outer can 10 functions as an external connection terminal for the negative electrode 42. This is because the secondary battery does not need to have an external connection terminal for the negative electrode 42 separate from the outer can 10, and therefore a reduction in the element spatial volume due to the presence of the external connection terminal for the negative electrode 42 is suppressed. As a result, the element spatial volume increases, and the volumetric energy density increases.

[0043] Specifically, the exterior can 10 contains one or more types of conductive materials such as metal materials and alloy materials, and specific examples of the conductive materials include iron, copper, nickel, stainless steel, iron alloys, copper alloys, and nickel alloys. The type of stainless steel is not particularly limited, but specific examples include SUS304 and SUS316. However, the materials forming the storage portion 11 and the lid portion 12 may be the same or different from each other.

[0044] Among these, it is preferable that the outer can 10 is a so-called metal can, because this improves the rigidity of the outer can 10, thereby suppressing deformation of the outer can 10. This metal can is a can containing one or more of the above-mentioned metal materials and alloy materials.

[0045] As will be described later, the lid portion 12 is insulated via a gasket 30 from the external terminal 20 that functions as an external connection terminal for the positive electrode 41. This is because contact (short circuit) between the outer can 10 (external connection terminal for the negative electrode 42) and the external terminal 20 (external connection terminal for the positive electrode 41) is prevented.

[0046] [External terminal] 1 and 2, the external terminal 20 is an electrode terminal that is connected to an electronic device when the secondary battery is mounted in the electronic device. The external terminal 20 is disposed on the outside of the outer can 10 and shields the through hole 10K.

[0047] The external terminals 20 are supported by the exterior can 10 via the gasket 30. More specifically, as will be described later, the external terminals 20 are heat-welded to the lid portion 12 via the gasket 30. As a result, the external terminals 20 are fixed to the lid portion 12 via the gasket 30 while being insulated from the lid portion 12 via the gasket 30.

[0048] This external terminal 20 is connected to the battery element 40 (positive electrode 41) via the positive electrode lead 51, and is therefore electrically connected to the positive electrode 41. As a result, the external terminal 20 functions as an external connection terminal for the positive electrode 41. When the secondary battery is in use, the secondary battery is connected to an electronic device via the external terminal 20 (external connection terminal for the positive electrode 41) and the outer casing 10 (external connection terminal for the negative electrode 42), and therefore the electronic device can operate using the secondary battery as a power source.

[0049] The external terminal 20 is a substantially plate-shaped member. The three-dimensional shape of the external terminal 20 is not particularly limited, but specifically, it is a flat plate-like shape.

[0050] A part or the whole of the external terminals 20 is disposed inside the recessed portion 10U. Here, the whole of the external terminals 20 is disposed inside the recessed portion 10U, that is, inside the space surrounded by the recessed portion 10U. As a result, the external terminals 20 are accommodated inside the recessed portion 10U so as not to protrude outside (upper) the recessed portion 10U.

[0051] The reason why the exterior can 10 includes the recessed portion 10U and the external terminal 20 is housed inside the recessed portion 10U is that the volumetric energy density increases, thereby increasing the battery capacity.

[0052] Specifically, when the external terminal 20 is not housed inside the recessed portion 10U, a part of the external terminal 20 protrudes outward from the recessed portion 10U. In this case, the volume (the opposing area of ​​the positive electrode 41 and the negative electrode 42) of the battery element 40 housed inside the outer can 10 does not change, but the height H increases by the amount that the external terminal 20 protrudes outward from the recessed portion 10U. This reduces the volumetric energy density, and therefore the battery capacity.

[0053] In contrast, when the external terminal 20 is housed inside the recessed portion 10U, the external terminal 20 does not protrude outward from the recessed portion 10U. In this case, the volume of the battery element 40 housed inside the outer can 10 does not change, and the height H does not increase. This increases the volumetric energy density, and therefore the battery capacity.

[0054] Since the outer diameter of the external terminal 20 is smaller than the inner diameter of the recess 10U, the external terminal 20 is spaced apart from the lid 12. As a result, the gasket 30 is disposed in at least a portion of the space between the lid 12 and the external terminal 20 inside the recess 10U, and more specifically, is disposed in a location where the lid 12 and the external terminal 20 would come into contact with each other if the gasket 30 were not present.

[0055] The external terminals 20 include one or more types of conductive materials such as metal materials and alloy materials, and specific examples of the conductive materials include aluminum and aluminum alloys.

[0056] However, the external terminal 20 may also include a clad material. This clad material includes, in order from the side closest to the gasket 30, an aluminum layer and a nickel layer, and the aluminum layer and nickel layer are roll-bonded to each other. The clad material may also include a nickel alloy layer instead of the nickel layer. The clad material may also include, in order from the side closest to the gasket 30, an aluminum layer, a stainless steel (SUS) layer, and a nickel layer, and the aluminum layer, the stainless steel layer, and nickel layer are roll-bonded to each other.

[0057] In particular, the external terminal 20 functions as a terminal for external connection of the positive electrode 41, and also functions as a relief valve for releasing the internal pressure when the internal pressure of the outer can 10 rises excessively, as will be described later. The rise in internal pressure is caused by the generation of gas due to the decomposition reaction of the electrolyte during charging and discharging, and the decomposition reaction of the electrolyte is accelerated by an internal short circuit in the secondary battery, heating of the secondary battery, discharging of the secondary battery under large current conditions, and the like.

[0058] The operation of the external terminal 20 functioning as a release valve will be described in detail later (see FIG. 5).

[0059] [gasket] 2, the gasket 30 is an insulating sealing member disposed between the outer can 10 and the external terminal 20. Here, the gasket 30 is disposed between the lid portion 12 and the external terminal 20, and has a through hole 30K at a location that overlaps with the through hole 10K. As a result, the gasket 30 is disposed so as not to block the through hole 10K.

[0060] The gasket 30 contains one or more types of insulating and heat-fusible polymer compounds, and therefore, as described above, the external terminal 20 is heat-welded to the lid 12 via the gasket 30. The type of polymer compound is not particularly limited, but specific examples include polypropylene and polyethylene.

[0061] The installation area of ​​the gasket 30 is not particularly limited and can be set arbitrarily. Here, the gasket 30 is disposed inside the recess 10U, between the upper surface of the lid 12 and the lower surface of the external terminal 20. However, the installation area of ​​the gasket 30 may extend beyond the area between the upper surface of the lid 12 and the lower surface of the external terminal 20.

[0062] That is, the inner diameter of the through hole 30K may be the same as the inner diameter of the through hole 10K, or may be different from the inner diameter of the through hole 10K. Fig. 2 shows a case where the inner diameter of the through hole 30K and the inner diameter of the through hole 10K are the same.

[0063] [Battery element] 1 to 4, the battery element 40 is a power generating element that causes charge / discharge reactions to proceed, and is housed inside the exterior can 10. The battery element 40 includes a positive electrode 41 that is a first electrode, a negative electrode 42 that is a second electrode, a separator 43, and an electrolytic solution (not shown) that is a liquid electrolyte.

[0064] Here, the battery element 40 is a so-called wound electrode body, and therefore the element structure of the battery element 40 is a so-called wound type. In this case, the positive electrode 41 and the negative electrode 42 are stacked on top of each other with the separator 43 interposed therebetween, and the positive electrode 41, the negative electrode 42, and the separator 43 are wound together. As a result, the positive electrode 41 and the negative electrode 42 are wound while facing each other with the separator 43 interposed therebetween, and the battery element 40 has a winding center space 40K, which is a winding core portion. The extension direction (vertical direction) of this winding center space 40K coincides with the penetration direction (vertical direction) of the through-hole 10K, and therefore the winding direction (left-right direction) of the positive electrode 41, the negative electrode 42, and the separator 43 intersects with the penetration direction of the through-hole 10K.

[0065] The battery element 40 has a three-dimensional shape similar to that of the outer can 10, and therefore has a flat, cylindrical three-dimensional shape. Compared to a case where the battery element 40 has a three-dimensional shape different from that of the outer can 10, dead space (excess space between the outer can 10 and the battery element 40) is less likely to occur when the battery element 40 is housed inside the outer can 10, and the internal space of the outer can 10 is used effectively. This increases the spatial volume of the element, and therefore the volumetric energy density.

[0066] (positive electrode) As shown in FIGS. 2 and 3, the positive electrode 41 includes a positive electrode current collector 41A and a positive electrode active material layer 41B.

[0067] Positive electrode current collector 41A is a conductive support that supports positive electrode active material layer 41B, and has a pair of surfaces on which positive electrode active material layer 41B is provided. Positive electrode current collector 41A contains a conductive material such as a metal material, and a specific example of the conductive material is aluminum.

[0068] Here, the positive electrode active material layer 41B is provided on both sides of the positive electrode current collector 41A and contains one or more types of positive electrode active materials capable of absorbing and releasing lithium. However, the positive electrode active material layer 41B may be provided on only one side of the positive electrode current collector 41A, on the side where the positive electrode 41 faces the negative electrode 42. The positive electrode active material layer 41B may further contain one or more types of a positive electrode binder, a positive electrode conductive agent, and the like. The method for forming the positive electrode active material layer 41B is not particularly limited, but specifically includes a coating method, etc.

[0069] The positive electrode active material contains a lithium-containing compound because it can provide a high energy density. The lithium-containing compound is a compound containing lithium as a constituent element, more specifically, a compound containing lithium and one or more transition metal elements as constituent elements. However, the lithium-containing compound may further contain one or more other elements (elements other than lithium and transition metal elements).

[0070] The type of lithium-containing compound is not particularly limited, but specific examples include oxides, phosphate compounds, silicate compounds, and borate compounds. Specific examples of oxides include LiNiO2, LiCoO2, and LiMn2O4. Specific examples of phosphate compounds include LiFePO4 and LiMnPO4.

[0071] The positive electrode binder contains one or more of synthetic rubbers and polymer compounds, etc. A specific example of the synthetic rubber is styrene-butadiene rubber, and a specific example of the polymer compound is polyvinylidene fluoride.

[0072] The positive electrode conductive agent contains one or more conductive materials such as carbon materials, and specific examples of the conductive materials include graphite, carbon black, acetylene black, and ketjen black. However, the conductive material may also be a metal material or a polymer compound.

[0073] (Negative electrode) As shown in FIGS. 2 and 3, the negative electrode 42 includes a negative electrode current collector 42A and a negative electrode active material layer 42B.

[0074] The negative electrode current collector 42A is a conductive support that supports the negative electrode active material layer 42B, and has a pair of surfaces on which the negative electrode active material layer 42B is provided. The negative electrode current collector 42A contains a conductive material such as a metal material, and a specific example of the conductive material is copper.

[0075] Here, the anode active material layer 42B is provided on both sides of the anode current collector 42A and contains one or more types of anode active materials capable of absorbing and releasing lithium. However, the anode active material layer 42B may be provided on only one side of the anode current collector 42A, on the side where the anode 42 faces the positive electrode 41. The anode active material layer 42B may further contain one or more types of anode binders and anode conductors. Details regarding the anode binders and anode conductors are the same as those regarding the positive electrode binders and positive electrode conductors. The method for forming the anode active material layer 42B is not particularly limited, but specifically includes one or more types of a coating method, a vapor phase method, a liquid phase method, a thermal spraying method, and a firing method (sintering method).

[0076] The negative electrode active material contains one or more of a carbon material and a metal-based material. This is because a high energy density can be obtained. Specific examples of carbon materials include graphitizable carbon, non-graphitizable carbon, and graphite (natural graphite and artificial graphite). The metal-based material is a material containing, as a constituent element, one or more of a metal element and a metalloid element that can form an alloy with lithium. Specific examples of the metal element and the metalloid element include silicon and tin. However, the metal-based material may be a simple substance, an alloy, a compound, a mixture of two or more of these, or a material containing two or more of these phases. Specific examples of the metal-based material are TiSi2 and SiO x(0 <x≦2または0.2<x<1.4)などである。

[0077] (separator) 2 and 3, separator 43 is an insulating porous film interposed between positive electrode 41 and negative electrode 42, and allows lithium ions to pass through while preventing short-circuiting between positive electrode 41 and negative electrode 42. Separator 43 contains a polymer compound such as polyethylene.

[0078] (electrolyte) The electrolyte solution is impregnated into each of the positive electrode 41, the negative electrode 42, and the separator 43, and contains a solvent and an electrolyte salt.

[0079] Here, the solvent contains one or more types of non-aqueous solvents (organic solvents), and the electrolyte containing the non-aqueous solvent is a so-called non-aqueous electrolyte. The non-aqueous solvents include esters and ethers, more specifically, carbonate ester compounds, carboxylic acid ester compounds, and lactone compounds.

[0080] The carbonate ester compounds include cyclic carbonate esters and chain carbonate esters, etc. Specific examples of cyclic carbonate esters include ethylene carbonate and propylene carbonate, and specific examples of chain carbonate esters include dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

[0081] The carboxylic acid ester compound is a chain carboxylic acid ester, etc. Specific examples of the chain carboxylic acid ester include methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, ethyl trimethylacetate, methyl butyrate, and ethyl butyrate.

[0082] The lactone compound is a lactone, etc. Specific examples of lactones include γ-butyrolactone and γ-valerolactone.

[0083] The ethers may be 1,2-dimethoxyethane, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, etc., in addition to the lactone compounds mentioned above.

[0084] The electrolyte salt is a light metal salt such as lithium salt, including lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium trifluoromethanesulfonate (LiCFSO), lithium bis(fluorosulfonyl)imide (LiN(FSO)), lithium bis(trifluoromethanesulfonyl)imide (LiN(CFSO)), lithium tris(trifluoromethanesulfonyl)methide (LiC(CFSO)), lithium bis(oxalato)borate (LiB(CO)), and lithium difluoro(oxalato)borate (LiB(CO)F).

[0085] The content of the electrolyte salt is not particularly limited, but specifically, it is 0.3 mol / kg to 3.0 mol / kg relative to the solvent, because high ionic conductivity can be obtained.

[0086] [Positive lead] 2, the positive electrode lead 51 is a wiring member for electrically connecting the positive electrode 41 to the external terminal 20, and is housed inside the exterior can 10. The positive electrode lead 51 is connected to the external terminal 20 via the through hole 10K, and is also connected to the positive electrode current collector 41A of the positive electrode 41, and is therefore electrically connected to both the external terminal 20 and the positive electrode 41. Here, the positive electrode lead 51 is connected to the positive electrode 41 on the side closer to the lid portion 12, and is therefore connected to the upper end of the positive electrode 41.

[0087] Although the secondary battery includes one positive electrode lead 51, it may include two or more positive electrode leads 51. This is because the electrical resistance of the battery element 40 decreases as the number of positive electrode leads 51 increases.

[0088] The details regarding the material for forming the positive electrode lead 51 are the same as the details regarding the material for forming the positive electrode current collector 41A. However, the materials for forming the positive electrode lead 51 and the positive electrode current collector 41A may be the same as or different from each other.

[0089] The positive electrode lead 51 is physically separated from the positive electrode current collector 41A, and therefore is a member separate from the positive electrode current collector 41A. However, since the positive electrode lead 51 is physically continuous with the positive electrode current collector 41A, it may be a member integrated with the positive electrode current collector 41A.

[0090] [Negative lead] 2, the negative electrode lead 52 is a member for electrically connecting the negative electrode 42 to the outer can 10, and is housed inside the outer can 10. The negative electrode lead 52 is connected to the housing portion 11 (lower bottom portion M2) and also to the negative electrode current collector 42A of the negative electrode 42, and is therefore electrically connected to both the outer can 10 and the negative electrode 42. In this case, the negative electrode lead 52 is connected to the negative electrode 42 on the side farther from the lid portion 12, and is therefore connected to the lower end of the negative electrode 42.

[0091] Although the secondary battery includes one negative electrode lead 52, it may include two or more negative electrode leads 52. This is because the electrical resistance of the battery element 40 decreases as the number of negative electrode leads 52 increases.

[0092] The details regarding the material for forming the negative electrode lead 52 are the same as the details regarding the material for forming the negative electrode current collector 42A. However, the materials for forming the negative electrode lead 52 and the negative electrode current collector 42A may be the same as or different from each other.

[0093] The negative electrode lead 52 is physically separated from the negative electrode current collector 42A, and therefore is a member separate from the negative electrode current collector 42A. However, since the negative electrode lead 52 is physically continuous with the negative electrode current collector 42A, it may be a member integrated with the negative electrode current collector 42A.

[0094] [Insulating film] 2 and 4, the insulating film 60 is an insulating member disposed between the outer can 10 and the battery element 40. Here, the insulating film 60 is disposed between the lid portion 12 and the battery element 40, and has a through hole 60K at a location that overlaps with the through hole 10K. As a result, the insulating film 60 is disposed so as not to block the through hole 10K.

[0095] The inner diameter of the through hole 60K may be the same as or different from the inner diameter of the through hole 10K. Fig. 2 shows a case where the inner diameter of the through hole 60K and the inner diameter of the through hole 10K are the same.

[0096] The insulating film 60 covers the opposing surface 10UM and is fixed to the opposing surface 10UM. In Fig. 4, the insulating film 60 is shaded in a dark shaded area to make it easier to see the installation area of ​​the insulating film 60.

[0097] The secondary battery is provided with an insulating film 60 that covers the opposing surface 10UM and is fixed to the opposing surface 10UM, because this prevents a short circuit from occurring even if a part (recessed portion 10U) of the outer can 10 (lid portion 12) protrudes toward the battery element 40.

[0098] More specifically, since a portion of the exterior can 10 protrudes toward the battery element 40, the battery element 40 (positive electrode 41) and the exterior can 10 (external connection terminal of the negative electrode 42) come close to each other when the opposing surface 10UM is close to the battery element 40. This makes it easier for contact (short circuit) to occur between the positive electrode 41 and the exterior can 10, making it difficult for the secondary battery to operate stably.

[0099] Furthermore, even if the insulating film 60 is present between the battery element 40 and the outer casing 10, if the insulating film 60 does not cover the opposing surface 10UM, the positive electrode 41 and the outer casing 10 may come into contact with each other in part of the opposing surface 10UM (the area where the insulating film 60 is not present). This also makes it more likely that a short circuit will occur, making it difficult for the secondary battery to operate stably.

[0100] Furthermore, even if the insulating film 60 covers the opposing surface 10UM, if the insulating film 60 is not fixed to the opposing surface 10UM, the insulating film 60 is likely to shift position when the secondary battery is subjected to vibration, shock, etc., and the positive electrode 41 and the outer casing 10 may come into contact with each other at a part of the opposing surface 10UM. This also makes it easier for a short circuit to occur, as described above, making it difficult for the secondary battery to operate stably.

[0101] In contrast, when the insulating film 60 is present between the battery element 40 and the exterior can 10 and covers the opposing surface 10UM and is fixed to the opposing surface 10UM, the positive electrode 41 and the exterior can 10 are less likely to come into contact with each other over the entire opposing surface 10UM, and the insulating film 60 is less likely to shift position even if the secondary battery is subjected to vibrations, shocks, etc. This makes it less likely for a short circuit to occur, making it easier for the secondary battery to operate stably.

[0102] In addition, when the insulating film 60 is fixed to the opposing surface 10UM, as will be described later, the insulating film 60 does not get in the way when an electrolyte solution is poured into the storage section 11 storing the wound body 40Z in the manufacturing process of the secondary battery. This also has the advantage that the electrolyte solution can be easily impregnated into the wound body 40Z (see FIG. 6). The reasons for this will be described in detail later.

[0103] The insulating film 60 contains one or more types of insulating materials such as insulating polymer compounds, and a specific example of the insulating material is polyimide.

[0104] The insulating film 60 may be a non-adhesive member that does not include an adhesive layer, or may be an adhesive member (so-called adhesive tape) that includes an adhesive layer (not shown). The non-adhesive insulating film 60 is adhered to the opposing surface 10UM via an adhesive, and is therefore fixed to the opposing surface 10UM. The adhesive insulating film 60 is adhered to the opposing surface 10UM via an adhesive layer, and is therefore fixed to the opposing surface 10UM.

[0105] Since the insulating film 60 is fixed to the opposing surface 10UM, the insulating film 60 is disposed between the lid portion 12 and the positive electrode lead 51, and a portion of the positive electrode lead 51 is disposed between the insulating film 60 and the battery element 40.

[0106] [others] The secondary battery may further include one or more of other components not shown.

[0107] Specifically, the other component is a sealant. This sealant is an insulating coating member that coats the surface of the positive electrode lead 51, and the positive electrode lead 51 is insulated from the outer can 10 and the negative electrode 42 via the sealant. The sealant contains one or more insulating materials such as insulating polymer compounds, and a specific example of the insulating material is polyimide.

[0108] The other component is another insulating film. This other insulating film is an insulating member disposed between the storage section 11 (lower bottom portion M2) and the battery element 40, and the material forming the other insulating film is the same as the material forming the insulating film 60.

[0109] <1-2. Operation> To explain the operation of the secondary battery, Fig. 5 shows a cross-sectional configuration corresponding to Fig. 2. Below, the operation during charging and discharging will be explained first, followed by the operation when an abnormality occurs.

[0110] [Charge / discharge operation] During charging, lithium is released from the positive electrode 41 of the battery element 40 and is absorbed into the negative electrode 42 via the electrolyte. During discharging, lithium is released from the negative electrode 42 of the battery element 40 and is absorbed into the positive electrode 41 via the electrolyte. During charging and discharging, lithium is absorbed and released in an ionic state.

[0111] [Actions when an error occurs] As described above, the external terminal 20 is disposed on the outside of the lid portion 12 and is fixed to the lid portion 12 via the gasket 30. As a result, under normal conditions, the external terminal 20 seals the outer can 10, and the battery element 40 is enclosed inside the outer can 10.

[0112] In contrast, when an abnormality occurs, i.e., when the internal pressure of the outer can 10 rises excessively, the external terminal 20 is pushed outward (upward) through the through hole 10K in response to the rise in internal pressure. In this case, if the strength of the force pushing the external terminal 20 outward becomes greater than the fixing strength (so-called sealing strength) with which the external terminal 20 is fixed to the lid portion 12 via the gasket 30, the external terminal 20 will be partially or entirely separated from the lid portion 12.

[0113] 5, a gap G (a path for releasing the internal pressure) is formed between the lid portion 12 and the external terminal 20, and the internal pressure is released in the gap G. FIG. 5 shows a case where the external terminal 20 is partially separated from the lid portion 12.

[0114] As described above, the housing portion 11 is joined to the lid portion 12, while the external terminal 20 is fixed to the lid portion 12 via the gasket 30, and therefore the fixing strength (thermal welding strength) of the external terminal 20 to the lid portion 12 is smaller than the joining strength (welding strength) of the lid portion 12 to the housing portion 11. In this case, if the internal pressure of the outer can 10 rises excessively, the external terminal 20 will separate from the lid portion 12 before the lid portion 12 separates from the housing portion 11. As a result, the external terminal 20 functions as a release valve before the outer can 10 bursts, preventing the outer can 10 from bursting.

[0115] <1-3. Manufacturing method> Fig. 6 shows a perspective view corresponding to Fig. 1 in order to explain the manufacturing process of the secondary battery. However, Fig. 6 shows a state before the lid part 12 is joined to the storage part 11, and therefore the lid part 12 is separated from the storage part 11.

[0116] When manufacturing a secondary battery, positive electrode 41 and negative electrode 42 are fabricated and an electrolyte solution is prepared according to the procedure described below as an example, and then a secondary battery is assembled using positive electrode 41, negative electrode 42, and the electrolyte solution, and a stabilization treatment is performed on the assembled secondary battery. In the following description, FIG. 6 and already described FIGS. 1 to 4 are occasionally referenced.

[0117] 6, a housing section 11 and a lid section 12 that are physically separated from each other are used to form an outer can 10. As described above, the housing section 11 has an opening 11K, and the lid section 12 includes a recessed section 10U. Also, as described above, the external terminals 20 are heat-welded to the lid section 12 in advance via the gasket 30, and an insulating film 60, which is an adhesive tape, is adhered to the lid section 12.

[0118] [Preparation of positive electrode] First, a paste-like cathode mixture slurry is prepared by adding a cathode mixture, which is a mixture of a cathode active material, a cathode binder, and a cathode conductor, to a solvent. This solvent may be an aqueous solvent or an organic solvent. The details regarding the solvent described here will also apply hereinafter. Next, the cathode mixture slurry is applied to both sides of the cathode current collector 41A to form the cathode active material layer 41B. Finally, the cathode active material layer 41B is compression-molded using a roll press or the like. In this case, the cathode active material layer 41B may be heated, and compression-molding may be repeated multiple times. As a result, the cathode active material layer 41B is formed on both sides of the cathode current collector 41A, thereby producing the cathode 41.

[0119] [Preparation of negative electrode] First, a paste-like anode mixture slurry is prepared by adding an anode mixture, which is a mixture of an anode active material, an anode binder, and an anode conductor, to a solvent. The anode mixture slurry is then applied to both sides of an anode current collector 42A to form an anode active material layer 42B. Finally, the anode active material layer 42B is compression-molded using a roll press or the like. Details regarding the compression molding of the anode active material layer 42B are the same as those regarding the compression molding of the cathode active material layer 41B. As a result, the anode active material layers 42B are formed on both sides of the anode current collector 42A, thereby producing the anode 42.

[0120] [Preparation of electrolyte] An electrolyte salt is added to a solvent, whereby the electrolyte salt is dispersed or dissolved in the solvent, thereby preparing an electrolytic solution.

[0121] [Secondary battery assembly] First, the positive electrode lead 51 is connected to the positive electrode current collector 41A of the positive electrode 41 using a welding method or the like, and the negative electrode lead 52 is connected to the negative electrode current collector 42A of the negative electrode 42 using a welding method or the like.

[0122] Next, the positive electrode 41 and the negative electrode 42 are stacked together with the separator 43 interposed therebetween, and then the positive electrode 41, the negative electrode 42, and the separator 43 are wound together to produce a wound body 40Z having a winding central space 40K, as shown in Fig. 6. This wound body 40Z has a configuration similar to that of the battery element 40, except that the positive electrode 41, the negative electrode 42, and the separator 43 are not impregnated with an electrolyte solution. In Fig. 6, the positive electrode lead 51 and the negative electrode lead 52 are not shown.

[0123] Subsequently, the wound body 40Z is housed inside the housing portion 11 through the opening 11K. In this case, the negative electrode lead 52 is connected to the housing portion 11 by welding or the like.

[0124] Next, using the lid portion 12 on which the external terminal 20 and the insulating film 60 have been previously provided, the positive electrode lead 51 is connected to the external terminal 20 via the through hole 10K by welding or the like.

[0125] Next, the electrolyte is poured into the storage section 11 through the opening 11K. As a result, the wound body 40Z (positive electrode 41, negative electrode 42, and separator 43) is impregnated with the electrolyte, and the battery element 40, which is a wound electrode body, is produced.

[0126] In this case, as described above, since the insulating film 60 is fixed to the lid portion 12, the insulating film 60 does not get in the way when injecting the electrolyte into the storage portion 11, compared to when the insulating film 60 is adhered to the battery element 40. This makes it easier to inject the electrolyte into the storage portion 11, and therefore makes it easier to impregnate the wound body 40Z with the electrolyte.

[0127] In particular, when an electrolyte solution is injected into the storage section 11, a portion of the electrolyte solution is supplied into the winding central space 40K. This allows the winding central space 40K to be used as an impregnation path for the electrolyte solution, making it easier for the electrolyte solution to be impregnated into the wound body 40Z.

[0128] Next, the opening 11K is covered with the lid 12, and then the lid 12 is joined to the storage section 11 by a joining method such as welding. As a result, the outer can 10 is formed, and the battery element 40 and the like are housed inside the outer can 10, so that the secondary battery is assembled as shown in FIG.

[0129] [Secondary battery stabilization] The assembled secondary battery is charged and discharged. Various conditions, such as the ambient temperature, the number of charge / discharge cycles (number of cycles), and the charge / discharge conditions, can be set as desired. As a result, a coating is formed on the surface of each of the positive electrode 41 and the negative electrode 42 in the battery element 40, electrochemically stabilizing the state of the secondary battery.

[0130] Therefore, the battery element 40 and other components are sealed inside the exterior can 10, completing the secondary battery.

[0131] <1-4. Actions and Effects> In this secondary battery, a battery element 40 is housed inside a conductive outer can 10 having a through hole 10K, an external terminal 20 arranged on the outside of the outer can 10 shields the through hole 10K, and an insulating gasket 30 is arranged between the outer can 10 and the external terminal 20. In addition, a recess 10U having a through hole 10K is provided in the outer can 10, and an insulating film 60 covers an opposing surface 10UM of the recess 10U between the outer can 10 and the battery element 40 and is fixed to the opposing surface 10UM. Therefore, for reasons explained below, it is possible to achieve both excellent capacity characteristics and excellent operational stability.

[0132] Fig. 7 shows the cross-sectional structure of the secondary battery of Comparative Example 1 and corresponds to Fig. 2. Fig. 8 shows the cross-sectional structure of the secondary battery of Comparative Example 2 and corresponds to Fig. 2. Fig. 9 shows the cross-sectional structure of the secondary battery of Comparative Example 3 and corresponds to Fig. 2. Fig. 10 shows the cross-sectional structure of the secondary battery of Comparative Example 4 and corresponds to Fig. 2, and Fig. 11 shows the planar structure of the main part of the secondary battery shown in Fig. 10 and corresponds to Fig. 4.

[0133] As shown in FIG. 7, the secondary battery of Comparative Example 1 has the same configuration as the secondary battery of this embodiment (FIG. 2), except that it does not include the insulating film 60.

[0134] As shown in Fig. 8 and Fig. 9, each of the secondary batteries of Comparative Examples 2 and 3 includes an insulating film 60, and has a configuration similar to that of the secondary battery of this embodiment (Fig. 2) except that the insulating film 60 is fixed to the battery element 40. However, in the secondary battery of Comparative Example 2, the insulating film 60 covers the entire upper end surface 40M of the battery element 40, and an outlet 60Q for leading out the positive electrode lead 51 is provided in the insulating film 60. In the secondary battery of Comparative Example 3, the insulating film 60 covers only a portion of the upper end surface 40M.

[0135] 10 and 11, the secondary battery of Comparative Example 4 includes an insulating film 60, and has the same configuration as the secondary battery of this embodiment (FIGS. 2 and 4) except that the insulating film 60 covers only a portion of the opposing surface 10UM. In FIG. 11, the opposing surface 10UM is lightly shaded.

[0136] In the secondary battery of Comparative Example 1, as shown in FIG. 7, no insulating film 60 is interposed between the outer can 10 and the battery element 40. In this case, there is no insulating film 60 that would get in the way when injecting an electrolyte solution into the storage portion 11 through the opening 11K during the manufacturing process of the secondary battery. As a result, the step of injecting the electrolyte solution is not hindered by the insulating film 60, and the electrolyte solution is more easily impregnated into the wound body 40Z. This increases the amount of electrolyte solution held by the battery element 40, ensuring battery capacity.

[0137] However, a part of the outer can 10 (recessed portion 10U) protrudes toward the battery element 40. In this case, the opposing surface 10UM approaches the battery element 40, so that the battery element 40 (positive electrode 41) and the outer can 10 (external connection terminal of the negative electrode 42) approach each other. This makes it easier for contact (short circuit) to occur between the positive electrode 41 and the outer can 10, making it difficult for the secondary battery to operate stably.

[0138] For these reasons, the secondary battery of Comparative Example 1 ensures battery capacity but is less likely to operate stably, making it difficult to achieve both excellent capacity characteristics and excellent operational stability.

[0139] 8, in the secondary battery of Comparative Example 2, a portion of the exterior can 10 protrudes toward the battery element 40, and therefore, even if the opposing surface 10UM is close to the battery element 40, the insulating film 60 is interposed between the battery element 40 and the exterior can 10, and the insulating film 60 covers the entire upper end surface 40M. This makes it less likely that a short circuit will occur between the positive electrode 41 and the exterior can 10, making it easier for the secondary battery to operate stably.

[0140] However, because the insulating film 60 covers the entire upper end surface 40M, the insulating film 60 gets in the way when injecting electrolyte into the storage compartment 11 through the opening 11K during the manufacturing process of the secondary battery. This hinders the electrolyte injection process, making it difficult for the electrolyte to permeate the wound body 40Z. This reduces the amount of electrolyte held by the battery element 40, and therefore reduces the battery capacity.

[0141] For these reasons, the secondary battery of Comparative Example 2 tends to operate stably, but the battery capacity decreases, making it difficult to achieve both excellent capacity characteristics and excellent operational stability.

[0142] In the secondary battery of Comparative Example 3, as shown in FIG. 9 , even though the opposing surface 10UM is close to the battery element 40, an insulating film 60 is interposed between the battery element 40 and the outer can 10, and the insulating film 60 covers only a portion of the upper end surface 40M. As a result, when injecting electrolyte into the storage compartment 11 through the opening 11K during the manufacturing process of the secondary battery, there are areas where the insulating film 60 is not present, which would interfere with the injection of electrolyte. This makes it less likely that the insulating film 60 will interfere with the injection process of electrolyte, and the electrolyte can more easily penetrate into the wound body 40Z in areas where the insulating film 60 is not present. Therefore, the amount of electrolyte held by the battery element 40 increases, and the battery capacity also increases.

[0143] In this case, the electrolyte is more easily impregnated into the wound body 40Z in areas where the insulating film 60 is not present, whereas the electrolyte is less easily impregnated into the wound body 40Z in areas where the insulating film 60 is present. As a result, the battery capacity is increased compared to the secondary battery of Comparative Example 2, but the increase in battery capacity is not sufficient.

[0144] However, a part of the battery element 40 is exposed in the area where the insulating film 60 is not present. In this case, the opposing surface 10UM approaches the battery element 40, and the battery element 40 and the outer casing 10 approach each other. This makes it easier for a short circuit to occur between the positive electrode 41 and the outer casing 10, making it difficult for the secondary battery to operate stably.

[0145] In this case, particularly when the secondary battery is subjected to vibration, impact, or the like, if the position of the battery element 40 shifts inside the exterior can 10, the position of the insulating film 60 fixed to the battery element 40 also tends to shift. As a result, compared to the secondary battery of Comparative Example 2, a short circuit between the positive electrode 41 and the exterior can 10 tends to occur more easily.

[0146] For these reasons, the secondary battery of Comparative Example 2 does not have a sufficient increase in battery capacity and does not operate with sufficient stability, making it difficult to achieve both excellent capacity characteristics and excellent operational stability.

[0147] 10 and 11, in the secondary battery of Comparative Example 4, the insulating film 60 is fixed to the opposing surface 10UM, so that the insulating film 60 does not get in the way when the electrolyte is poured into the storage portion 11 from the opening 11K during the manufacturing process of the secondary battery. As a result, for the reasons described above, the amount of electrolyte held by the battery element 40 increases, thereby ensuring the battery capacity.

[0148] Furthermore, since the insulating film 60 is interposed between the battery element 40 and the outer casing 10, a short circuit between the positive electrode 41 and the outer casing 10 is less likely to occur in the area where the insulating film 60 is present.

[0149] However, since the insulating film 60 covers only a portion of the opposing surface 10UM, a short circuit between the positive electrode 41 and the outer can 10 is likely to occur in the area where the insulating film 60 is not present.

[0150] For these reasons, although the battery capacity is ensured in the secondary battery of Comparative Example 3, the secondary battery still has difficulty in stable operation, making it difficult to achieve both excellent capacity characteristics and excellent operational stability.

[0151] In contrast to this, in the secondary battery of this embodiment, as shown in FIGS. 2 and 4, the insulating film 60 is fixed to the opposing surface 10UM, and therefore, for the reasons described above, the battery capacity is guaranteed.

[0152] Furthermore, an insulating film 60 is interposed between the battery element 40 and the outer casing 10, and the insulating film 60 covers the entire opposing surface 10UM. This makes it difficult for a short circuit to occur between the positive electrode 41 and the outer casing 10 over the entire opposing surface 10UM, making it easier for the secondary battery to operate stably.

[0153] In this case, even if the battery element 40 is displaced inside the exterior can 10 when the secondary battery is subjected to vibration, impact, or the like, the insulating film 60 is less likely to be displaced. This makes it less likely that a short circuit will occur between the positive electrode 41 and the exterior can 10, making it easier for the secondary battery to operate continuously and stably.

[0154] For these reasons, the secondary battery of this embodiment ensures battery capacity and facilitates stable operation, thereby achieving both excellent capacity characteristics and excellent operational stability.

[0155] In particular, in the secondary battery of this embodiment, if the external terminal 20 is housed inside the recessed portion 10U, the volumetric energy density increases, and therefore the battery capacity increases further, thereby achieving a greater effect.

[0156] Furthermore, if the exterior can 10 includes the storage section 11 and the lid section 12, and the storage section 11 and the lid section 12 are joined together, the secondary battery is constructed using the exterior can 10, which is a so-called crimpless joined can, and therefore the volumetric energy density is further increased. As a result, the capacity characteristics are further improved, and greater effects can be obtained.

[0157] Furthermore, if the positive electrode 41 is electrically connected to the external terminal 20 and the negative electrode 42 is electrically connected to the outer can 10, the external terminal 20 functions as an external connection terminal for the positive electrode 41, and the outer can 10 functions as an external connection terminal for the negative electrode 42. This eliminates the need for the secondary battery to have an external connection terminal for the positive electrode 41 and an external connection terminal for the negative electrode 42 separate from the outer can 10 and external terminal 20, thereby further increasing the volumetric energy density. This further improves the capacity characteristics, thereby achieving greater effects.

[0158] Furthermore, if the outer can 10 has a flat, columnar, three-dimensional shape, excellent capacity characteristics and excellent operational stability can be obtained even in a small secondary battery in which the internal pressure of the outer can 10 is likely to increase, thereby achieving even greater effects.

[0159] Furthermore, if the exterior can 10 is a metal can, deformation of the exterior can 10 is suppressed. Therefore, from the viewpoint of the physical durability of the exterior can 10, the secondary battery tends to operate stably, and a greater effect can be obtained.

[0160] Furthermore, if the secondary battery is a lithium ion secondary battery, a sufficient battery capacity can be stably obtained by utilizing the absorption and desorption of lithium, and therefore a greater effect can be obtained.

[0161] <2. Modifications> The configuration of the secondary battery can be modified as appropriate, as described below, although any two or more of the series of modifications described below may be combined with each other.

[0162] [Variation 1] 2 and 4, the insulating film 60 covers the opposing surface 10UM. However, since it is only necessary for the insulating film 60 to cover the opposing surface 10UM, the installation area of ​​the insulating film 60 may be expanded beyond the opposing surface 10UM.

[0163] Specifically, as shown in Fig. 12 corresponding to Fig. 2 and Fig. 13 corresponding to Fig. 4, the installation area of ​​the insulating film 60 may extend inward from the opposing surface 10UM. However, the insulating film 60 is arranged so as not to block the through-hole 10K in order to ensure a connection path for the positive electrode lead 51 to the external terminal 20.

[0164] In this case, the same effect can be obtained because the battery capacity is ensured and the secondary battery operates more stably by using the insulating film 60. In this case, the positive electrode lead 51 and the outer can 10 (lid portion 12) are prevented from contacting each other by using the inwardly extending portion of the insulating film 60, and therefore, a greater effect can be obtained.

[0165] 2 and 4, the installation area of ​​the insulating film 60 may be extended outward from the opposing surface 10UM. The position of the outer edge of the insulating film 60 is not particularly limited and can be set arbitrarily.

[0166] In this case, the same effect can be obtained by using the insulating film 60 to ensure the battery capacity and facilitate stable operation of the secondary battery. In this case, the use of the portion of the insulating film 60 that extends outward can more easily prevent contact between the positive electrode 41 and the exterior can 10 (lid portion 12) even if the secondary battery is unintentionally deformed due to an impact such as when dropped, thereby obtaining a greater effect.

[0167] However, although not specifically illustrated here, it should be noted that if the insulating film 60 extends too far outward from the opposing surface 10UM, it may become difficult to stably form the outer can 10 during the manufacturing process of the secondary battery.

[0168] In detail, if the installation area of ​​the insulating film 60 is extended outward too much, when the lid portion 12 is joined to the storage portion 11, a part of the insulating film 60 is likely to be interposed between the storage portion 11 and the lid portion 12. This makes it difficult to join the lid portion 12 to the storage portion 11, which may make it difficult to stably form the outer can 10.

[0169] In contrast, if the installation area of ​​the insulating film 60 is appropriately expanded, it becomes difficult for a part of the insulating film 60 to be interposed between the storage section 11 and the lid section 12. This makes it easier to join the lid section 12 to the storage section 11, and therefore makes it easier to form the outer can 10 stably.

[0170] [Variation 2] In Fig. 2, the external terminals 20 are accommodated inside the recessed portion 10U, and therefore do not protrude outside the recessed portion 10U. However, as shown in Fig. 16 corresponding to Fig. 2, since a portion of the external terminals 20 is accommodated inside the recessed portion 10U, the remaining portion of the external terminals 20 may protrude outside the recessed portion 10U.

[0171] In this case, the same effect can be obtained by using the insulating film 60 to ensure the battery capacity and facilitate stable operation of the secondary battery. However, it should be noted that if the external terminals 20 protrude outside the recessed portion 10U, the height H increases, which reduces the volumetric energy density and therefore the battery capacity.

[0172] [Variation 3] 2, a positive electrode 41, which is a first electrode, is connected to an external terminal 20 via a positive electrode lead 51, and a negative electrode 42, which is a second electrode, is connected to a storage section 11 via a negative electrode lead 52. As a result, the external terminal 20 functions as an external connection terminal for the positive electrode 41, and the outer can 10 functions as an external connection terminal for the negative electrode 42.

[0173] 2, the positive electrode 41 as the second electrode may be connected to the storage section 11 via a positive electrode lead 51, and the negative electrode 42 as the first electrode may be connected to the external terminal 20 via a negative electrode lead 52. In this way, the outer can 10 may function as an external connection terminal for the positive electrode 41, and the external terminal 20 may function as an external connection terminal for the negative electrode 42.

[0174] In this case, the external terminal 20 contains one or more types of conductive metal and alloy materials to function as an external connection terminal for the negative electrode 42, and specific examples of the conductive material include iron, copper, nickel, stainless steel, iron alloys, copper alloys, and nickel alloys. The outer can 10, i.e., the storage portion 11 and the lid portion 12, each contain one or more types of conductive metal and alloy materials to function as an external connection terminal for the positive electrode 41, and specific examples of the conductive material include aluminum, aluminum alloys, and stainless steel.

[0175] Even in this case, the secondary battery can be connected to an electronic device via the external terminal 20 (external connection terminal of the negative electrode 42) and the outer casing 10 (external connection terminal of the positive electrode 41). Therefore, the insulating film 60 is used to ensure the battery capacity and facilitate stable operation of the secondary battery, thereby achieving the same effect.

[0176] [Variation 4] A porous film separator 43 was used. However, although not specifically shown here, a laminated separator including a polymer compound layer may be used instead of separator 43.

[0177] Specifically, the laminated separator includes a porous membrane having a pair of surfaces and a polymer compound layer provided on one or both surfaces of the porous membrane. This is because the separator improves adhesion to each of the positive electrode 41 and the negative electrode 42, thereby preventing miswinding of the battery element 40. This prevents swelling of the secondary battery even if a decomposition reaction of the electrolyte occurs. The polymer compound layer includes a polymer compound such as polyvinylidene fluoride. This is because polymer compounds such as polyvinylidene fluoride have excellent physical strength and are electrochemically stable.

[0178] One or both of the porous film and the polymer compound layer may contain one or more types of insulating particles. This is because the insulating particles promote heat dissipation when the secondary battery generates heat, thereby improving the safety (heat resistance) of the secondary battery. The insulating particles may be one or both of inorganic particles and resin particles. Specific examples of inorganic particles include particles of aluminum oxide, aluminum nitride, boehmite, silicon oxide, titanium oxide, magnesium oxide, and zirconium oxide. Specific examples of resin particles include particles of acrylic resin and styrene resin.

[0179] When fabricating a laminated separator, a precursor solution containing a polymer compound and a solvent is prepared, and then the precursor solution is applied to one or both sides of a porous membrane. In this case, instead of applying the precursor solution to the porous membrane, the porous membrane may be immersed in the precursor solution. In addition, multiple insulating particles may be added to the precursor solution.

[0180] Even when this laminated separator is used, the same effect can be obtained because lithium ions are able to move between the positive electrode 41 and the negative electrode 42. In this case, the safety of the secondary battery is particularly improved as described above, and therefore, even greater effects can be obtained.

[0181] [Variation 5] An electrolytic solution, which is a liquid electrolyte, was used. However, although not specifically shown here, an electrolyte layer, which is a gel electrolyte, may be used instead of the electrolytic solution.

[0182] In a battery element 40 using an electrolyte layer, a positive electrode 41 and a negative electrode 42 are stacked with a separator 43 and an electrolyte layer interposed therebetween, and the positive electrode 41, the negative electrode 42, the separator 43, and the electrolyte layer are wound together. The electrolyte layer is interposed between the positive electrode 41 and the separator 43, and also between the negative electrode 42 and the separator 43. However, the electrolyte layer may be interposed only between the positive electrode 41 and the separator 43, or may be interposed only between the negative electrode 42 and the separator 43.

[0183] Specifically, the electrolyte layer contains a polymer compound together with an electrolytic solution, and the electrolytic solution is held by the polymer compound. This is because leakage of the electrolytic solution is prevented. The composition of the electrolytic solution is as described above. The polymer compound contains polyvinylidene fluoride, etc. When forming the electrolyte layer, a precursor solution containing the electrolytic solution, the polymer compound, a solvent, etc. is prepared, and then the precursor solution is applied to one or both surfaces of each of the positive electrode 41 and the negative electrode 42.

[0184] Even when this electrolyte layer is used, the same effect can be obtained because lithium ions can move between the positive electrode 41 and the negative electrode 42 via the electrolyte layer. In this case, leakage of the electrolyte solution is prevented as described above, and therefore a greater effect can be obtained.

[0185] Although the present technology has been described above with reference to one embodiment, the configuration of the present technology is not limited to the configuration described in the one embodiment and can be modified in various ways.

[0186] Specifically, the battery element has been described as having a wound structure, but the element structure is not particularly limited and may be a stacked structure, a zigzag structure, etc. In the stacked structure, the positive and negative electrodes are alternately stacked with a separator interposed therebetween, and in the zigzag structure, the positive and negative electrodes are folded in a zigzag pattern with the separator interposed therebetween.

[0187] Although the electrode reactant is lithium in the above description, the electrode reactant is not particularly limited. Therefore, as described above, the electrode reactant may be other alkali metals such as sodium and potassium, or alkaline earth metals such as beryllium, magnesium, and calcium. In addition, the electrode reactant may be other light metals such as aluminum.

[0188] The effects described in this specification are merely examples, and the effects of the present technology are not limited to the effects described in this specification. Therefore, other effects may be obtained with respect to the present technology.

Claims

1. a conductive exterior member having a through hole; an electrode terminal disposed on the outer casing member and covering the through hole; an insulating sealing member disposed between the exterior member and the electrode terminal; a battery element housed inside the exterior member; an insulating member disposed between the exterior member and the battery element; Equipped with the exterior member has a flat, columnar, three-dimensional shape and includes a recessed portion in which the through-hole is provided, and the exterior member is bent in the recessed portion so as to be recessed inward, the recessed portion has a facing surface facing the battery element, The insulating member covers the opposing surface and is fixed to the opposing surface. Secondary battery.

2. The insulating member extends further inward than the opposing surface so as not to block the through hole. The secondary battery according to claim 1 .

3. The insulating member extends outward beyond the opposing surface. The secondary battery according to claim 1 .

4. The electrode terminal is accommodated inside the recess. The secondary battery according to claim 1 .

5. The exterior member is a storage section having an opening and storing the battery element therein; a lid portion that includes the recessed portion and closes the opening; Including, The lid portion and the storage portion are joined to each other. The secondary battery according to claim 1 .

6. the battery element includes a first electrode and a second electrode; the first electrode is electrically connected to the electrode terminal; The second electrode is electrically connected to the exterior member. The secondary battery according to claim 1 .

7. The exterior member is a metal can. The secondary battery according to any one of claims 1 to 6.

8. It is a lithium-ion secondary battery. The secondary battery according to any one of claims 1 to 6.

Images