Battery

Abstract

This battery comprises an exterior member having an outer diameter and a height, a battery element housed inside the exterior member, an insulating sealing member, and a terminal member supported by the exterior member with the sealing member therebetween. The ratio of the outer diameter to the height is not less than 0.1 but less than 1. The exterior member includes a housing member that has an opening and that houses the battery element therein, and a lid member that is welded to the housing member, that closes the opening, and that has a through-hole. The terminal member is fixed to the lid member via the sealing member and blocks the through-hole. The fixing strength of the terminal member with respect to the lid member is less than the weld strength of the lid member with respect to the housing member.

Description

[Technical field]

[0001] The present technology relates to batteries. [Background technology]

[0002] Batteries have been developed as power sources for electronic devices, and the batteries have battery elements inside an outer casing. Various studies have been conducted on the structure of these batteries in order to improve their various characteristics.

[0003] Specifically, in order to improve the volumetric energy density, a welded-seal type outer case is used in which a cover plate member is welded to the case body, and a flat electrode terminal member is fixed to the bottom surface of the case body via a sealing member (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-046639 A Summary of the Invention

[0005] Although various studies have been conducted on the structure of the battery, the battery capacity characteristics and safety of the battery are still insufficient, and there is room for improvement.

[0006] Therefore, there is a demand for a battery that can provide excellent battery capacity characteristics and excellent safety.

[0007] The battery according to an embodiment of the present technology includes an exterior member having an outer diameter and a height, a battery element housed inside the exterior member, an insulating sealing member, and a terminal member supported by the exterior member via the sealing member. The ratio of the outer diameter to the height is 0.1 or more and less than 1. The exterior member includes a housing member having an opening and housing the battery element inside, and a lid member welded to the housing member, closing the opening and having a through hole. The terminal member is fixed to the lid member via the sealing member and shields the through hole. The fixing strength of the terminal member to the lid member is smaller than the welding strength of the lid member to the housing member.

[0008] According to a battery of one embodiment of the present technology, a battery element is stored inside an exterior member having a ratio of outer diameter to height of 0.1 or more and less than 1, a lid member having a through hole is welded to a storage member in the exterior member, a terminal member is fixed to the lid member via an insulating sealing member, and the fixing strength of the terminal member to the lid member is smaller than the welding strength of the lid member to the storage member, so that excellent battery capacity characteristics and excellent safety can be obtained.

[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 description of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view illustrating a configuration of a secondary battery, which is an example of a battery according to an embodiment of the present technology. [Diagram 2] 2 is a cross-sectional view illustrating the configuration of the battery element shown in FIG. [Diagram 3] 4 is a cross-sectional view for explaining the operation of a secondary battery. FIG. [Figure 4] 1A to 1C are cross-sectional views illustrating a manufacturing process of a secondary battery. [Diagram 5] 1 is a cross-sectional view illustrating a configuration of a secondary battery of a first comparative example. [Figure 6] FIG. 11 is a cross-sectional view illustrating the configuration of a secondary battery of a second comparative example. [Figure 7] 1 is a cross-sectional view illustrating a configuration of a secondary battery according to a first modified example. [Figure 8] 11 is a cross-sectional view illustrating a configuration of a secondary battery according to Modification 2. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

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

[0013] The battery described here is an electrochemical device that generates battery capacity using an electrode reaction, and is used as a power source for using electronic devices. This battery may be a primary battery or a secondary battery. The discharge principle of the primary battery is not particularly limited, and the charge / discharge principle of the secondary battery is not particularly limited.

[0014] In the following, as an example of a battery, a secondary battery in which battery capacity is obtained by utilizing the occlusion and release of an electrode reactant (charge and discharge reaction) as an electrode reaction will be described. This secondary battery includes a positive electrode, a negative electrode, and an electrolyte solution, which is a liquid electrolyte.

[0015] However, in the secondary battery described below, 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.

[0016] The type of the electrode reactant is not particularly limited, but specifically, it is a light metal such as an alkali metal or an alkaline earth metal, etc. The alkali metal is lithium, sodium, potassium, etc., and the alkaline earth metal is beryllium, magnesium, calcium, etc.

[0017] Here, we take the case where the electrode reactant is lithium as an example. A secondary battery that obtains battery capacity by utilizing the absorption and release of lithium is a so-called lithium ion secondary battery. In this lithium ion secondary battery, lithium is absorbed and released in an ionic state.

[0018] <1-1. Configuration> Fig. 1 shows a cross-sectional configuration of a secondary battery, which is an example of a battery, and Fig. 2 shows a cross-sectional configuration of a battery element 40 shown in Fig. 1. However, Fig. 2 shows only a part of the battery element 40.

[0019] For convenience, the upper side in FIG. 1 will be described below as the upper side of the secondary battery, and the lower side in FIG. 1 will be described as the lower side of the secondary battery.

[0020] As shown in Fig. 1, this secondary battery has a cylindrical three-dimensional shape with an outer diameter D and a height H. The outer diameter D is the horizontal dimension in Fig. 1, which is the so-called maximum outer diameter, and the height H is the vertical dimension in Fig. 1, which is the so-called maximum height.

[0021] Here, the secondary battery has two circular bottoms facing each other, and therefore has a cylindrical three-dimensional shape. That is, the secondary battery shown in Fig. 1 is a so-called cylindrical secondary battery.

[0022] As described above, this secondary battery has a cylindrical three-dimensional shape, and therefore the ratio of the outer diameter D to the height H (aspect ratio = outer diameter D / height H) is 0.1 or more and less than 1. This is because, compared with a case where the aspect ratio is 1, the internal volume of the secondary battery capable of housing the battery element 40 increases, and therefore a high volumetric energy density can be obtained. Also, compared with a case where the aspect ratio is less than 0.1, as described below, this is because the electrode terminal 20 is more likely to function as an open valve.

[0023] The aspect ratio is not particularly limited as long as it is 0.1 or more and less than 1. In particular, the aspect ratio is preferably 0.1 or more and 0.6 or less, and more preferably 0.1 or more and less than 0.5. This is because the internal volume of the secondary battery is further increased, and the volumetric energy density is further increased.

[0024] Specifically, as shown in Figures 1 and 2, the secondary battery includes an outer can 10, an electrode terminal 20, a gasket 30, a battery element 40, a positive electrode lead 50, a negative electrode lead 60, a pair of insulating plates 71, 72, and a sealant 73.

[0025] [Outer can] 1, the exterior can 10 is an exterior member that houses the battery element 40 and the like, and has a cylindrical three-dimensional shape with an outer diameter D and a height H. In other words, the three-dimensional shape of the secondary battery is substantially determined based on the three-dimensional shape of the exterior can 10. Details regarding the aspect ratio defined by the outer diameter D and the height H are as described above.

[0026] The outer can 10 includes a storage section 11 and a lid section 12 which are welded together, and the storage section 11 is sealed by the lid section 12 .

[0027] The storage section 11 is a storage member that stores the battery element 40 and the like inside, and has a hollow cylindrical three-dimensional shape with one end open and the other end closed. Thus, the storage section 11 has an opening 11K, which is the open end.

[0028] The lid 12 is a lid member that closes the opening 11K and has a substantially plate-like three-dimensional shape. The lid 12 has a through hole 12K for connecting the electrode terminal 20 and the battery element 40 to each other, and is welded to the storage section 11 to close the opening 11K, as described above. The lid 12 supports the electrode terminal 20 via a gasket 30, as described below.

[0029] The inner diameter (maximum inner diameter) of the through hole 12K is not particularly limited, but is preferably larger than the inner diameter (maximum inner diameter) of the winding center space 40S described later. This is because the exposed area of ​​the electrode terminal 20 at the through hole 12K increases. As a result, when the internal pressure of the outer can 10 rises excessively, the electrode terminal 20 is easily pushed outward at the through hole 12K in response to the internal pressure, and as described later, the electrode terminal 20 is easily able to function as an opening valve. In addition, the connection area of ​​the positive electrode lead 50 to the electrode terminal 20 increases, so that the electrical connection state between the electrode terminal 20 and the positive electrode lead 50 is easily ensured.

[0030] As an example, the inner diameter of the through hole 12K is preferably 1 mm or more, because this not only provides the above-mentioned advantages but also makes it easier to connect the positive electrode lead 50 to the electrode terminal 20 using a welding method or the like.

[0031] Here, the lid portion 12 is bent so as to partially protrude toward the inside (downward) of the storage portion 11, and thus the lid portion 12 is partially recessed. That is, a part of the lid portion 12 is bent so as to form a step toward the center of the lid portion 12, and thus the lid portion 12 has a recessed portion 12U. The above-mentioned through hole 12K is provided in the lid portion 12 inside the recessed portion 12U.

[0032] Here, exterior can 10 is a can in which two members (storage section 11 and lid section 12) are welded together, that is, a so-called welded can. As a result, exterior can 10 after welding is physically a single member as a whole, and therefore cannot be easily separated into the two members (storage section 11 and lid section 12) afterwards.

[0033] The exterior can 10, which is a welded can, does not have any parts folded over each other, and does not have any parts where two or more members overlap each other.

[0034] "Having no overlapping parts" means that parts of the outer can 10 are not folded (folded) so as to overlap each other. Also, "having no parts where two or more components overlap each other" means that the outer can 10 is physically one component after the secondary battery is completed, and therefore the outer can 10 cannot be easily separated into two or more components. In other words, the state of the outer can 10 in the completed secondary battery is not in a state where two or more components are combined while overlapping each other so that they can be easily separated later.

[0035] The exterior can 10, which is a welded can, is a can that is different from a crimped can (a so-called crimp can) formed using a crimping process, and is a so-called crimpless can. This is because the element space volume increases inside the exterior can 10, and the energy density per volume increases. This "element space volume" refers to the volume (effective volume) of the internal space of the exterior can 10 that is available for storing the battery element 40.

[0036] The reason why exterior can 10 is a welded can (crimpless can) is that, compared to when exterior can 80 described below is a crimped can (see FIG. 5), it does not require a series of components (special mechanisms and elements) such as safety valve mechanism 92 and PTC element 93. As a result, when the height H of the secondary battery is constant, the element space volume increases by the amount that the above-mentioned special mechanisms and elements are no longer required, and the energy density per volume increases.

[0037] This exterior can 10 (storage section 11 and lid section 12) is conductive. Here, the storage section 11 of the exterior can 10 is connected to a negative electrode 42 (described later) of the battery element 40 via a negative electrode lead 60. As a result, the exterior can 10 is electrically connected to the negative electrode 42, and therefore 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 exterior can 10, and therefore a reduction in the element space volume due to the presence of the external connection terminal for the negative electrode 42 is suppressed. As a result, the element space volume increases, and the energy density per unit volume increases.

[0038] Specifically, the exterior can 10 contains one or more types of conductive materials such as metal materials and alloy materials, and the conductive materials are iron, stainless steel (SUS), aluminum, aluminum alloys, etc. The surface of the exterior can 10 may be plated with a metal material such as nickel. However, the material of the storage section 11 and the material of the lid section 12 may be the same as or different from each other.

[0039] The lid portion 12 is insulated via a gasket 30 from an electrode terminal 20 that functions as an external connection terminal for a positive electrode 41 (described later) of the battery element 40. This is because contact (short circuit) between the exterior can 10 (external connection terminal for the negative electrode 42) and the electrode terminal 20 (external connection terminal for the positive electrode 41) is prevented.

[0040] [Electrode terminal] The electrode terminal 20 is a plate-shaped terminal member that is connected to an electronic device when the secondary battery is mounted in the electronic device, and is supported by the exterior can 10 (lid portion 12) via a gasket 30, as shown in Fig. 1. That is, the electrode terminal 20 is supported by the lid portion 12 while being insulated from the lid portion 12 via the gasket 30.

[0041] As a result, the electrode terminal 20 is fixed to the cover portion 12 via the gasket 30. In addition, since the electrode terminal 20 covers the through hole 12K, a portion of the electrode terminal 20 is exposed at the through hole 12K.

[0042] Here, as described above, the electrode terminal 20 is connected to the positive electrode 41 via the positive electrode lead 50. As a result, the electrode terminal 20 is electrically connected to the positive electrode 41 and functions as an external connection terminal for the positive electrode 41. Therefore, when the secondary battery is used, the secondary battery is connected to an electronic device via the electrode terminal 20 (external connection terminal for the positive electrode 41) and the exterior can 10 (external connection terminal for the negative electrode 42), and the electronic device can operate using the secondary battery as a power source.

[0043] Furthermore, the electrode terminal 20 functions as a relief valve for releasing the internal pressure when the internal pressure of the outer can 10 rises excessively. The cause of this rise in internal pressure is the generation of gas due to the decomposition reaction of the electrolyte during charging and discharging, and the causes that accelerate the decomposition reaction of the electrolyte are an internal short circuit of the secondary battery, heating of the secondary battery, and discharging of the secondary battery under large current conditions.

[0044] Specifically, under normal circumstances, the electrode terminal 20 is fixed to the lid portion 12 via the gasket 30, and therefore the through hole 12K is blocked by the electrode terminal 20. As a result, the exterior can 10 is hermetically sealed, and the battery element 40 is enclosed inside the exterior can 10.

[0045] On the other hand, when an abnormality occurs, that is, when the internal pressure of the exterior can 10 rises excessively, the exposed surface of the electrode terminal 20 at the through hole 12K is strongly pressed outward (upward) in response to the internal pressure. In this case, when the internal pressure exceeds the fixing strength (so-called seal strength) of the electrode terminal 20 to the lid portion 12, the electrode terminal 20 is partially or entirely separated from the lid portion 12. As a result, a gap (a path for releasing the internal pressure) is formed between the lid portion 12 and the electrode terminal 20, and the internal pressure is released by utilizing the gap.

[0046] The electrode terminal 20 is disposed inside the recessed portion 12U via the gasket 30, and is therefore insulated from the lid portion 12 via the gasket 30, as described above. Here, the electrode terminal 20 is stored inside the recessed portion 12U so as not to protrude above the lid portion 12. This is because, compared to the case where the electrode terminal 20 protrudes above the lid portion 12, the height H of the secondary battery is smaller, and the energy density per volume increases.

[0047] Furthermore, since the electrode terminal 20 is disposed outside the lid portion 12, as described above, it is disposed inside the recessed portion 12U. This is because, compared to a case in which the electrode terminal 20 is disposed inside the lid portion 12, when the internal pressure of the outer casing can 10 rises excessively, the electrode terminal 20 is more likely to be separated from the lid portion 12 in response to the internal pressure, and therefore the internal pressure is more likely to be released.

[0048] Since the outer diameter of the electrode terminal 20 is smaller than the inner diameter of the recessed portion 12U, the electrode terminal 20 is separated from the lid portion 12 at its periphery. As a result, the gasket 30 is disposed in the gap between the electrode terminal 20 and the lid portion 12 inside the recessed portion 12U, and more specifically, is disposed at a location where the electrode terminal 20 and the lid portion 12 would come into contact with each other if the gasket 30 was not present.

[0049] The electrode terminal 20 includes one or more conductive materials such as metal materials and alloy materials, and the conductive materials are aluminum and aluminum alloys. However, the electrode terminal 20 may be formed of a clad material. The clad material includes an aluminum layer and a nickel layer in this order from the side closer to the gasket 30, and the aluminum layer and the nickel layer are roll-bonded to each other in the clad material.

[0050] As described above, the lid 12 is welded to the storage section 11, whereas the electrode terminal 20 is fixed to the lid 12 via the gasket 30. In this case, the fixing strength of the electrode terminal 20 to the lid 12 is smaller than the welding strength of the lid 12 to the storage section 11. In other words, the opening pressure (kgf / cm) of the electrode terminal 20, which is the pressure when the electrode terminal 20 is separated from the lid 12, 2 ) is the opening pressure (kgf / cm) of the outer can 10, which is the pressure when the cover 12 is separated from the container 11. 2 ) is smaller than

[0051] This is because, when the internal pressure of the exterior can 10 rises excessively, the electrode terminal 20 is likely to be separated from the lid portion 12 before the lid portion 12 is separated from the storage portion 11. This makes it easier for the electrode terminal 20 to function as an open valve before the secondary battery (exterior can 10) explodes, preventing the high-temperature battery element 40 from being unintentionally released from the inside of the exterior can 10 to the outside.

[0052] In this case, particularly when the aspect ratio is 0.1 or more, unlike when the aspect ratio is less than 0.1, the exposed surface of the electrode terminal 20 is easily pushed outward when the internal pressure rises, making it easier for the electrode terminal 20 to function stably as an open valve.

[0053] The fixing strength of the electrode terminal 20 to the lid portion 12 can be adjusted based on conditions such as the material of the gasket 30 and the fixing area of ​​the electrode terminal 20 to the lid portion 12. On the other hand, the welding strength of the lid portion 12 to the storage portion 11 can be adjusted based on conditions such as the welding method, welding time, and welding area.

[0054] The fixing strength can be specified by applying pressure to the inside of the secondary battery while measuring the internal pressure of the exterior can 10 in a room temperature environment (temperature = 23°C). In this case, the internal pressure when the electrode terminal 20 is separated from the lid portion 12, i.e., the pressure (opening pressure) at which the exterior can 10 is opened using the electrode terminal 20, is specified, and the opening pressure is taken as the fixing strength.

[0055] The welding strength can be determined by the same procedure as that for determining the fixing strength described above. That is, the inside of the secondary battery is pressurized while measuring the internal pressure of the outer can 10 in a room temperature environment, and then the internal pressure when the lid portion 12 is separated from the housing portion 11, i.e., the pressure (opening pressure) at which the outer can 10 is opened by using the lid portion 12, is determined, and the opening pressure is regarded as the welding strength.

[0056] The ratio of the outer diameter of the electrode terminal 20 to the inner diameter of the through hole 12K, i.e., the fixing ratio that determines the fixing area of ​​the electrode terminal 20 to the lid portion 12, is not particularly limited, but is preferably 1.13 to 3.37. This is because the connection ratio that affects the fixing strength of the electrode terminal 20 to the lid portion 12 is optimized, and therefore the balance between the sealing property and the openability of the outer can 10 and the lid portion 12 is optimized. That is, while the fixing strength of the electrode terminal 20 to the lid portion 12 is guaranteed under normal conditions, the electrode terminal 20 is more likely to function as a release valve when an abnormality occurs. However, the value of the fixing ratio is rounded off to two decimal places.

[0057] [gasket] 1, the gasket 30 is an insulating sealing member interposed between the exterior can 10 (lid portion 12) and the electrode terminal 20, and the electrode terminal 20 is fixed to the lid portion 12 via the gasket 30. Specifically, the gasket 30 is heat-sealed to each of the lid portion 12 and the electrode terminal 20, and therefore the electrode terminal 20 is thermally fixed to the lid portion 12 by utilizing the gasket 30. Here, the gasket 30 has a ring-shaped planar shape having a through hole at a position corresponding to the through opening 12K.

[0058] The gasket 30 includes one or more types of insulating materials such as insulating polymer compounds, and specific examples of the insulating materials include polypropylene and polyethylene.

[0059] Among these, it is preferable that the gasket 30 contains polypropylene, and that the melting point of the polypropylene is 130° C. to 250° C. This is because the physical properties of the gasket 30 are optimized, and therefore the balance between the sealing property and the openability of the outer can 10 and the electrode terminal 20 is optimized. As a result, the fixing strength of the electrode terminal 20 to the lid portion 12 is guaranteed under normal conditions, making it easier to seal the outer can 10, and in the event of an abnormality, the electrode terminal 20 is easily separated from the lid portion 12, making it easier to release the internal pressure.

[0060] When the secondary battery is discharged with a large current, the temperature of the secondary battery may rise to about 80° C. Therefore, when the internal pressure has not risen excessively to a level that may cause the exterior can 10 to burst, i.e., when the temperature of the secondary battery has only risen to about 80° C., in order to prevent the electrode terminal 20 from being unintentionally separated from the lid portion 12, it is preferable that the melting point of the gasket 30 be within the appropriate range described above.

[0061] The installation range of the gasket 30 is not particularly limited and can be set arbitrarily. Here, the gasket 30 is disposed between the upper surface of the lid portion 12 and the lower surface of the electrode terminal 20 inside the recessed portion 12U.

[0062] [Battery element] The battery element 40 is a power generating element that causes charge / discharge reactions to proceed, and is housed inside an exterior can 10, as shown in Figures 1 and 2. The battery element 40 contains a positive electrode 41, a negative electrode 42, a separator 43, and an electrolytic solution (not shown) that is a liquid electrolyte.

[0063] The battery element 40 described here is a so-called wound electrode body. That is, in the battery element 40, a positive electrode 41 and a negative electrode 42 are stacked with a separator 43 interposed therebetween, and the positive electrode 41, the negative electrode 42, and the separator 43 are wound.

[0064] As a result, the positive electrode 41 and the negative electrode 42 are wound facing each other with the separator 43 interposed therebetween, so that the battery element 40 has a winding center space 40S at the center where the positive electrode 41 and the negative electrode 42 are wound. This winding center space 40S is a space that penetrates the battery element 40 in the height direction, and the positive electrode 41, the negative electrode 42, the separator 43, etc. are not present inside the winding center space 40S.

[0065] The inner diameter of the winding center space 40S is not particularly limited, but is preferably smaller than the inner diameter of the through hole 12K, and more preferably as small as possible. This is because, when the outer diameter D of the secondary battery is constant, the number of windings of the positive electrode 41 and the negative electrode 42 increases, and the energy density per volume increases.

[0066] This winding central space 40S functions as a path for transmitting the internal pressure to the electrode terminal 20 via the through hole 12K when the internal pressure of the outer can 10 rises excessively. For this reason, it is preferable that the through hole 12K is disposed at a position overlapping a part or the whole of the winding central space 40S. This is because the internal pressure is easily transmitted to the electrode terminal 20, and the electrode terminal 20 is more likely to function as a release valve. Fig. 1 shows a case where the through hole 12K is disposed so as to overlap the whole of the winding central space 40S.

[0067] In addition, "the through hole 12K overlaps with the entire winding center space 40S" means that when the secondary battery is viewed from above, the through hole 12K and the winding center space 40S are positioned so that a portion of the through hole 12K and the entire winding center space 40S overlap with each other.

[0068] Here, the positive electrode 41, the negative electrode 42, and the separator 43 are wound so that the separator 43 is disposed on the outermost and innermost circumferences, respectively. The number of turns of the positive electrode 41, the negative electrode 42, and the separator 43 is not particularly limited and can be set arbitrarily.

[0069] This battery element 40 has a three-dimensional shape similar to that of the exterior can 10, and therefore has a cylindrical three-dimensional shape. This is because, compared to a case in which the battery element 40 has a three-dimensional shape different from that of the exterior can 10, dead space (surplus space between the exterior can 10 and the battery element 40) is less likely to occur when the battery element 40 is housed inside the exterior can 10, and the internal space of the exterior can 10 is effectively utilized. This increases the element space volume, and therefore increases the energy density per volume.

[0070] (positive electrode) As shown in FIG. 2, the positive electrode 41 includes a positive electrode current collector 41A and a positive electrode active material layer 41B.

[0071] Positive electrode current collector 41A 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 the metal material is aluminum or the like.

[0072] Here, the positive electrode active material layer 41B is provided on both sides of the positive electrode 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 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 a positive electrode binder, a positive electrode conductive agent, and the like. The method of forming the positive electrode active material layer 41B is not particularly limited, but specifically includes a coating method, etc.

[0073] The positive electrode active material contains a lithium compound. This lithium 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. This is because a high energy density can be obtained. However, the lithium compound may further contain one or more of other elements (elements other than lithium and transition metal elements). The type of lithium 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, and specific examples of phosphate compounds include LiFePO4 and LiMnPO4.

[0074] The positive electrode binder contains one or more of synthetic rubber and polymer compounds. The synthetic rubber is styrene butadiene rubber and the polymer compounds are polyvinylidene fluoride. The positive electrode conductive agent contains one or more of conductive materials such as carbon materials, and the carbon materials are graphite, carbon black, acetylene black, ketjen black, and the like. However, the conductive materials may be metal materials and polymer compounds.

[0075] (Negative electrode) As shown in FIG. 2, the negative electrode 42 includes a negative electrode current collector 42A and a negative electrode active material layer 42B.

[0076] The negative electrode current collector 42A 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 the metal material is, for example, copper.

[0077] Here, the negative electrode active material layer 42B is provided on both sides of the negative electrode collector 42A, and contains one or more types of negative electrode active materials capable of absorbing and releasing lithium. However, the negative electrode active material layer 42B may be provided only on one side of the negative electrode collector 42A on the side where the negative electrode 42 faces the positive electrode 41. The negative electrode active material layer 42B may further contain a negative electrode binder, a negative electrode conductor, and the like. Details regarding the negative electrode binder and the negative electrode conductor are the same as those regarding the positive electrode binder and the positive electrode conductor, respectively. The method of forming the negative electrode active material layer 42B is not particularly limited, and specifically, it is one or more types of a coating method, a gas phase method, a liquid phase method, a thermal spraying method, a firing method (sintering method), and the like.

[0078] The negative electrode active material contains one or both of a carbon material and a metal-based material. This is because a high energy density can be obtained. Carbon materials include graphitizable carbon, non-graphitizable carbon, and graphite (natural graphite and artificial graphite). The metal-based material is a material that contains, as a constituent element, one or more of metal elements and metalloid elements that can form an alloy with lithium, and the metal elements and metalloid elements are one or both of silicon and tin. However, the metal-based material may be a single element, an alloy, a compound, a mixture of two or more of them, or a material containing two or more of them. Specific examples of metal-based materials are TiSi2 and SiO x (0 <x≦2または0.2<x<1.4)などである。

[0079] Here, the height of the negative electrode 42 is greater than the height of the positive electrode 41. In this case, the negative electrode 42 protrudes upward from the positive electrode 41 and also protrudes downward from the positive electrode 41. This is to prevent lithium released from the positive electrode 41 from being deposited on the surface of the negative electrode 42.

[0080] (Separator) 2, the separator 43 is an insulating porous film interposed between the positive electrode 41 and the negative electrode 42, and allows lithium ions to pass through while preventing a short circuit between the positive electrode 41 and the negative electrode 42. The separator 43 contains a polymer compound such as polyethylene.

[0081] Here, the height of separator 43 is greater than the height of negative electrode 42. In this case, separator 43 protrudes upward from negative electrode 42 and also protrudes downward from negative electrode 42. This is to prevent positive electrode 41 and exterior can 10 (storage portion 11 and lid portion 12) from contacting each other.

[0082] (electrolyte) The electrolyte 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. The solvent contains one or more of non-aqueous solvents (organic solvents) such as carbonate ester compounds, carboxylate ester compounds, and lactone compounds, and the electrolyte containing the non-aqueous solvent is a so-called non-aqueous electrolyte. The electrolyte salt contains one or more of light metal salts such as lithium salt.

[0083] [Positive lead] 1, the positive electrode lead 50 is housed inside the exterior can 10 and is a wiring member that connects the positive electrode 41 of the battery element 40 to the electrode terminal 20. Specifically, the positive electrode lead 50 is connected to the positive electrode current collector 41A of the positive electrode 41, and is connected to the electrode terminal 20 via a through hole 12K provided in the lid portion 12.

[0084] Here, the secondary battery includes one positive electrode lead 50. However, the secondary battery may include two or more positive electrode leads 50. As the number of positive electrode leads 50 increases, the electrical resistance of the battery element 40 decreases.

[0085] The details regarding the material of the positive electrode lead 50 are similar to the details regarding the material of the positive electrode current collector 41 A. However, the materials of the positive electrode lead 50 and the positive electrode current collector 41 A may be the same as or different from each other.

[0086] The connection position of the positive electrode lead 50 to the positive electrode 41 is not particularly limited and can be set arbitrarily. That is, the positive electrode lead 50 may be connected to the positive electrode 41 at the outermost circumference, may be connected to the positive electrode 41 at the innermost circumference, or may be connected to the positive electrode 41 midway through winding between the outermost circumference and the innermost circumference. FIG. 1 shows a case where the positive electrode lead 50 is connected to the positive electrode 41 at the outermost circumference.

[0087] Here, the positive electrode lead 50 is physically separated from the positive electrode current collector 41A, and is therefore separate from the positive electrode current collector 41A. As a result, the positive electrode lead 50 is connected to the positive electrode current collector 41A using a welding method or the like. However, since the positive electrode lead 50 is physically continuous with the positive electrode current collector 41A, it may be integrated with the positive electrode current collector 41A.

[0088] There is no particular limitation on the way in which the positive electrode lead 50 is routed between the positive electrode 41 and the electrode terminal 20. In particular, the positive electrode lead 50 is preferably bent between the positive electrode 41 and the electrode terminal 20, and more preferably folded back once or more midway between the positive electrode 41 and the electrode terminal 20.

[0089] In other words, it is preferable that the positive electrode lead 50 does not extend from the positive electrode 41 to the electrode terminal 20 via the shortest route between the positive electrode 41 and the electrode terminal 20, but rather extends from the positive electrode 41 to the electrode terminal 20 while detouring the shortest route midway between the positive electrode 41 and the electrode terminal 20.

[0090] This is because an excess portion of the positive electrode lead 50 is secured, that is, a margin is generated with respect to the length of the positive electrode lead 50. This prevents the electrode terminal 20 from being difficult to separate from the lid portion 12 due to the positive electrode lead 50 being unintentionally pulled when the internal pressure of the outer casing can 10 rises excessively, and the electrode terminal 20 is more likely to function as an opening valve. FIG. 1 shows a case in which the positive electrode lead 50 is folded back only once in the middle between the positive electrode 41 and the electrode terminal 20. Here, the positive electrode lead 50 extends to a position beyond the winding center space 40S, and then is folded back to be connected to the electrode terminal 20.

[0091] [Negative lead] 1, the negative electrode lead 60 is housed inside the outer can 10 and is a member that connects the negative electrode 42 of the battery element 40 to the outer can 10. Specifically, the negative electrode lead 60 is connected to the negative electrode current collector 42A of the negative electrode 42, and is also connected to the storage section 11 of the outer can 10.

[0092] Here, the secondary battery is provided with one negative electrode lead 60. However, the secondary battery may be provided with two or more negative electrode leads 60. As the number of negative electrode leads 60 increases, the electrical resistance of the battery element 40 decreases.

[0093] The details regarding the material of the negative electrode lead 60 are similar to the details regarding the material of the negative electrode current collector 42A. However, the materials of the negative electrode lead 60 and the negative electrode current collector 42A may be the same as or different from each other.

[0094] The connection position of the negative electrode lead 60 to the negative electrode 42 is not particularly limited and can be set arbitrarily. That is, the negative electrode lead 60 may be connected to the negative electrode 42 at the outermost circumference, may be connected to the negative electrode 42 at the innermost circumference, or may be connected to the negative electrode 42 midway through winding between the outermost circumference and the innermost circumference. FIG. 1 shows a case where the negative electrode lead 60 is connected to the negative electrode 42 at the outermost circumference.

[0095] Here, the negative electrode lead 60 is physically separated from the negative electrode current collector 42A, and is therefore separate from the negative electrode current collector 42A. As a result, the negative electrode lead 60 is connected to the negative electrode current collector 42A using a welding method or the like. However, since the negative electrode lead 60 is physically continuous with the negative electrode current collector 42A, it may be integrated with the negative electrode current collector 42A.

[0096] The way in which the negative electrode lead 60 is routed between the negative electrode 42 and the storage section 11 is not particularly limited and can be set arbitrarily.

[0097] [A pair of insulating plates] The insulating plates 71 and 72 are disposed so as to sandwich the battery element 40 in the height direction, and therefore face each other via the battery element 40. Each of the insulating plates 71 and 72 contains one or more types of insulating materials such as polyimide. The insulating plate 71 has a through hole 71K at a position overlapping a part or the whole of the winding center space 40S. FIG. 1 shows a case where the inner diameter of the through hole 71K is larger than the inner diameter of the winding center space 40S and the through hole 71K overlaps the whole of the winding center space 40S.

[0098] [Sealant] The sealant 73 is a member that protects the periphery of the positive electrode lead 50, and is a so-called protective tape. The sealant 73 has a tubular structure that covers the periphery of the positive electrode lead 50, and contains one or more of insulating polymer compounds such as polypropylene, polyethylene terephthalate, and polyimide. As a result, the positive electrode lead 50 is insulated from the exterior can 10 (lid portion 12) and the battery element 40 (negative electrode 42) via the sealant 73. The coverage of the positive electrode lead 50 with the sealant 73 is not particularly limited and can be set arbitrarily.

[0099] <1-2. Operation> In order to explain the operation of the secondary battery, Fig. 3 shows a cross-sectional configuration corresponding to Fig. 1. Below, the operation during charging and discharging will be explained first, and then the operation when an abnormality occurs will be explained.

[0100] [Charge / discharge operation] During charging, in battery element 40, lithium is released from positive electrode 41 and is absorbed in negative electrode 42 via the electrolyte. During discharging, in battery element 40, lithium is released from negative electrode 42 and is absorbed in positive electrode 41 via the electrolyte. During charging and discharging, lithium is absorbed and released in an ionic state.

[0101] [Action when an abnormality occurs] When the internal pressure of the outer can 10 rises excessively, as described above, the electrode terminal 20 is strongly pressed outward in response to the internal pressure, and the electrode terminal 20 is separated from the lid portion 12 as shown in Fig. 3. This allows the internal pressure to be released through the gap generated between the electrode terminal 20 and the lid portion 12, thereby preventing the outer can 10 from bursting. Fig. 3 shows a case in which the electrode terminal 20 is partially separated from the lid portion 12.

[0102] <1-3. Manufacturing method> Fig. 4 shows a cross-sectional configuration corresponding to Fig. 1 in order to explain the manufacturing process of the secondary battery. However, Fig. 4 shows a state in which the storage section 11 and the lid section 12 are separated from each other. In the following explanation, Fig. 1 and Fig. 2, which have already been explained, will be referred to in addition to Fig. 4 as necessary.

[0103] When manufacturing a secondary battery, positive electrode 41 and negative electrode 42 are produced and an electrolyte solution is prepared according to the procedure described below, and then the positive electrode 41, negative electrode 42, and electrolyte solution are used to assemble the secondary battery.

[0104] 4, a housing portion 11 and a lid portion 12 that are physically separated from each other are used to form an exterior can 10. As described above, this housing portion 11 has an opening portion 11K. As described above, the electrode terminal 20 is fixed in advance to the lid portion 12 having the recessed portion 12U via the gasket 30.

[0105] [Preparation of positive electrode] First, a paste-like cathode mixture slurry is prepared by putting a cathode mixture in which a cathode active material, a cathode binder, a cathode conductive agent, and the like are mixed together into a solvent. The solvent may be an aqueous solvent or an organic solvent. The details of the solvent described here are the same in the following. Next, the cathode mixture slurry is applied to both sides of the cathode current collector 41A to form a 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, and thus the cathode 41 is produced.

[0106] [Preparation of negative electrode] First, a negative electrode mixture in the form of a mixture of a negative electrode active material, a negative electrode binder, a negative electrode conductive agent, and the like is poured into a solvent to prepare a paste-like negative electrode mixture slurry. Next, the negative electrode mixture slurry is applied to both sides of the negative electrode current collector 42A to form the negative electrode active material layer 42B. Finally, the negative electrode active material layer 42B is compression molded using a roll press or the like. Details regarding the compression molding of the negative electrode active material layer 42B are the same as those regarding the compression molding of the positive electrode active material layer 41B. As a result, the negative electrode active material layer 42B is formed on both sides of the negative electrode current collector 42A, and the negative electrode 42 is produced.

[0107] [Preparation of electrolyte] An electrolyte salt is added to a solvent, whereby the electrolyte salt is dispersed or dissolved in the solvent, and an electrolyte solution is prepared.

[0108] [Secondary battery assembly] First, the positive electrode lead 50, the periphery of which is partially covered with a sealant 73, is connected to the positive electrode current collector 41A of the positive electrode 41 by using a welding method or the like. In addition, the negative electrode lead 60 is connected to the negative electrode current collector 42A of the negative electrode 42 by using a welding method or the like. The welding method is one or more of resistance welding and laser welding. The details of the welding method described here are the same hereinafter.

[0109] Next, the positive electrode 41 connected to the positive electrode lead 50 and the negative electrode 42 connected to the negative electrode lead 60 are stacked together with the separator 43 interposed therebetween. Next, the positive electrode 41, the negative electrode 42, and the separator 43 are wound to prepare a wound body (not shown) having a winding central space 40S. This wound body has a similar configuration 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.

[0110] Next, the insulating plates 71 and 72 are arranged so as to face each other via the wound body, and then the insulating plates 71 and 72 are housed together with the wound body through the opening 11K inside the storage section 11. In this case, the negative electrode lead 60 is connected to the storage section 11 by using a welding method or the like.

[0111] Next, the electrolyte is injected from the opening 11K into the storage section 11. This causes the wound body (positive electrode 41, negative electrode 42, and separator 43) to be impregnated with the electrolyte, thereby producing the battery element 40. In this case, a part of the electrolyte is supplied into the inside of the winding central space 40S, and the electrolyte is impregnated into the wound body from the inside of the winding central space 40S.

[0112] Next, the opening 11K is covered with the lid 12 to which the electrode terminal 20 is fixed via the gasket 30, and then the lid 12 is welded to the storage section 11 by a welding method. In this case, the positive electrode lead 50 is connected to the electrode terminal 20 via the through hole 12K by using a welding method or the like.

[0113] As a result, the housing portion 11 and the lid portion 12 are welded together to form the exterior can 10, and the battery element 40 and the like are housed inside the exterior can 10, thereby assembling the secondary battery.

[0114] [Stabilization of secondary batteries] The assembled secondary battery is charged and discharged. Conditions such as the environmental temperature, the number of charge / discharge cycles (number of cycles), and the charge / discharge conditions can be set arbitrarily. As a result, a coating is formed on the surface of the negative electrode 42, etc., and the state of the secondary battery is electrochemically stabilized.

[0115] Thus, the battery element 40 and other components are sealed inside the exterior can 10, completing the secondary battery.

[0116] <1-4. Actions and Effects> According to this secondary battery, a battery element 40 is housed inside an exterior can 10 having an aspect ratio (outer diameter D / height H) of 0.1 or more and less than 1, and a lid portion 12 having a through hole 12K is welded to a storage portion 11 in the exterior can 10. An electrode terminal 20 is fixed to the lid portion 12 via a gasket 30, and the fixing strength of the electrode terminal 20 to the lid portion 12 is smaller than the welding strength of the lid portion 12 to the storage portion 11. Therefore, for reasons described below, excellent battery capacity characteristics and excellent safety can be obtained.

[0117] Fig. 5 shows a cross-sectional configuration of a secondary battery of a first comparative example, and corresponds to Fig. 1. Fig. 6 shows a cross-sectional configuration of a secondary battery of a second comparative example, and corresponds to Fig. 1.

[0118] As shown in FIG. 5, the secondary battery of the first comparative example has the same configuration as the secondary battery of the present embodiment shown in FIG. 1, except for the points described below.

[0119] The secondary battery of the first comparative example is different from the secondary battery of this embodiment that has an exterior can 10 which is a welded can (crimpless can), and has an exterior can 80 which is a crimped can. The secondary battery of the first comparative example also has a battery lid 91, a safety valve mechanism 92, a thermosensitive resistor (PTC element) 93, and a gasket 94.

[0120] The outer can 80 has a three-dimensional hollow cylindrical shape with one end closed and the other end open. The material of the outer can 80 is the same as the material of the outer can 10.

[0121] A battery lid 91, a safety valve mechanism 92, and a PTC element 93 are crimped via a gasket 94 to one end (open end) of the open exterior can 80. As a result, the battery lid 91, the safety valve mechanism 92, and the PTC element 93 are each fixed to the exterior can 80, and the open end of the exterior can 80 is sealed by the battery lid 91. The material of the battery lid 91 is the same as the material of the exterior can 80. The safety valve mechanism 92 and the PTC element 93 are each provided inside the battery lid 91, and the safety valve mechanism 92 is electrically connected to the battery lid 91 via the PTC element 93. The gasket 94 contains an insulating material such as polypropylene.

[0122] In this safety valve mechanism 92, when the internal pressure of the exterior can 80 rises excessively, the disk plate 92A is inverted, thereby releasing the internal pressure and cutting off the electrical connection between the battery lid 91 and the battery element 40. To prevent abnormal heat generation due to a large current, the electrical resistance of the PTC element 93 increases with an increase in temperature.

[0123] As shown in FIG. 6, the secondary battery of the second comparative example has the same configuration as the secondary battery of the present embodiment shown in FIG. 1, except for the points described below.

[0124] The secondary battery of the second comparative example includes an exterior can 10 which is a welded can (crimpless can) like the secondary battery of this embodiment, except that no recess 12U is provided in lid portion 12. Moreover, the secondary battery of the second comparative example includes an electrode terminal 110 and a gasket 120 instead of electrode terminal 20 and gasket 30.

[0125] The electrode terminal 110 is fixed to the lid 12 via a gasket 120, and has a so-called rivet-like three-dimensional shape. Specifically, the electrode terminal 110 includes a small outer diameter portion and a pair of large outer diameter portions connected to the small outer diameter portion. The small outer diameter portion is inserted into the through hole 12K and has an outer diameter smaller than the inner diameter of the through hole 12K. One of the large outer diameter portions is disposed outside the lid 12 and has an outer diameter larger than the inner diameter of the through hole 12K. The other large outer diameter portion is disposed inside the lid 12 and has an outer diameter larger than the inner diameter of the through hole 12K. As a result, the electrode terminal 110 is fixed to the lid 12 via the gasket 120 by utilizing the pressing force of the pair of large outer diameter portions against the lid 12.

[0126] Since the gasket 120 is interposed between the lid portion 12 and the electrode terminal 110, the electrode terminal 110 is insulated from the lid portion 12 via the gasket 120. Details regarding the material of the gasket 120 are similar to the details regarding the material of the gasket 30.

[0127] The secondary battery of the first comparative example is equipped with a safety valve mechanism 92, as shown in Fig. 5. In this case, if the internal pressure of the outer can 80 rises excessively, the pressure is released by utilizing the safety valve mechanism 92, as described above. This prevents the outer can 80 from exploding, thereby providing excellent safety.

[0128] However, in the secondary battery of the first comparative example, not only the battery element 40 but also special mechanisms and elements such as a safety valve mechanism 92 and a PTC element 93 are housed inside the exterior can 80. In this case, when the height H of the secondary battery is constant, the element space volume is reduced by the amount of the special mechanisms and elements housed inside the exterior can 80, and more specifically, the element space volume is reduced because the height of the battery element 40 is reduced. This reduces the battery capacity due to a reduction in volumetric energy density, and thus the battery capacity characteristics are degraded.

[0129] For these reasons, the secondary battery of the first comparative example has excellent safety, but the battery capacity characteristics are degraded, so that the battery capacity characteristics and safety are not compatible. Therefore, it is difficult to obtain both excellent battery capacity characteristics and excellent safety.

[0130] 6, the secondary battery of the second comparative example does not include special mechanisms and elements such as a safety valve mechanism 92 and a PTC element 93, and therefore the special mechanisms and elements do not need to be housed inside the exterior can 10. In this case, when the height H of the secondary battery is constant, the element space volume increases by the amount of the special mechanisms and elements that are not housed inside the exterior can 10, and more specifically, the height of the battery element 40 increases, so that the element space volume increases. As a result, the battery capacity increases in accordance with the increase in volumetric energy density, and excellent battery capacity characteristics can be obtained.

[0131] However, in the secondary battery of the second comparative example, even if the internal pressure of the outer can 10 rises excessively, the internal pressure cannot be released, which may cause the outer can 10 to burst, thereby reducing safety.

[0132] For these reasons, the secondary battery of the second comparative example has excellent battery capacity characteristics but has a reduced safety, so that the battery capacity characteristics and safety are not compatible. Therefore, like the secondary battery of the first comparative example, it is difficult to obtain excellent battery capacity characteristics and excellent safety.

[0133] In contrast, the secondary battery of this embodiment does not include special mechanisms and elements such as the safety valve mechanism 92 and the PTC element 93 as shown in Fig. 1, and therefore the special mechanisms and elements do not need to be housed inside the exterior can 10. In this case, as described above, when the height H of the secondary battery is constant, the element space volume increases by the amount of the special mechanisms and elements that are not housed inside the exterior can 10, and therefore the element space volume increases. As a result, the battery capacity increases in accordance with the increase in volumetric energy density, and excellent battery capacity characteristics can be obtained.

[0134] Moreover, when the internal pressure of the outer can 10 rises excessively, the electrode terminal 20 functions as a safety valve as described above, and the internal pressure is released using the electrode terminal 20. In this case, the fixing strength of the electrode terminal 20 to the lid portion 12 is particularly smaller than the welding strength of the lid portion 12 to the storage portion 11, and therefore, as described above, the electrode terminal 20 is more likely to function as a relief valve before the outer can 10 bursts. Furthermore, since the aspect ratio is 0.1 or more and less than 1, as described above, the electrode terminal 20 is more likely to function stably as a relief valve while the volumetric energy density is guaranteed. This prevents the outer can 10 from bursting, and therefore excellent safety is achieved.

[0135] For these reasons, the secondary battery of the present embodiment not only has excellent battery capacity characteristics, but also has excellent safety, so that the battery capacity characteristics and safety are compatible. Therefore, it is possible to obtain excellent battery capacity characteristics and excellent safety.

[0136] In particular, in the secondary battery of this embodiment, if the aspect ratio is 0.6 or less, the volume energy density increases and accordingly the battery capacity characteristics improve, so that a greater effect can be obtained.

[0137] Furthermore, if the fixing ratio is 1.13 to 3.37, an appropriate balance is achieved between the sealing property and the openability of the outer can 10 and the electrode terminal 20. Therefore, while the fixing strength of the electrode terminal 20 to the lid portion 12 is ensured under normal circumstances, the electrode terminal 20 is more likely to function as a release valve when an abnormality occurs, thereby obtaining a greater effect.

[0138] Furthermore, if the electrode terminal 20 is disposed on the outside of the lid portion 12, the electrode terminal 20 will be more likely to separate from the lid portion 12 when the internal pressure of the outer casing can 10 increases excessively, thereby achieving a greater effect.

[0139] Furthermore, if the gasket 30 contains polypropylene (melting point: 130° C. to 250° C.), the balance between the sealing property and the openability for the outer can 10 and the electrode terminal 20 is optimized. Therefore, while the fixing strength of the electrode terminal 20 to the lid portion 12 is guaranteed under normal circumstances, the electrode terminal 20 can easily function as a release valve when an abnormality occurs, thereby obtaining a higher effect.

[0140] Furthermore, if the battery element 40 has a winding central space 40S and the through hole 12K is disposed at a position overlapping a part or the whole of the winding central space 40S, the internal pressure is easily transmitted to the electrode terminal 20. Therefore, the electrode terminal 20 can easily function as a release valve, and a higher effect can be obtained.

[0141] In this case, if the inner diameter of the through hole 12K is larger than the inner diameter of the winding central space 40S, the exposed area of ​​the electrode terminal 20 at the through hole 12K increases, so that the electrode terminal 20 can more easily function as a release valve, thereby achieving an even greater effect.

[0142] Furthermore, if the positive electrode lead 50 is folded back one or more times between the positive electrode 41 and the electrode terminal 20, a margin is generated in the length of the positive electrode lead 50. Therefore, the electrode terminal 20 can easily function as an open valve without being affected by the positive electrode lead 50, and thus a higher effect can be obtained.

[0143] Furthermore, if the cover portion 12 has a recessed portion 12U that partially protrudes toward the inside of the storage portion 11 and the electrode terminal 20 is disposed inside the recessed portion 12U, the energy density per volume increases as the height H of the secondary battery becomes smaller, thereby obtaining a greater effect.

[0144] Furthermore, as long as the positive electrode 41 is electrically connected to the electrode terminal 20 and the negative electrode 42 is electrically connected to the exterior can 10, the secondary battery does not need to have a separate external connection terminal for the positive electrode 41 and an external connection terminal for the negative electrode 42. Therefore, the volumetric energy density increases with an increase in the element space volume, and therefore a greater effect can be obtained.

[0145] Furthermore, if the secondary battery is a cylindrical secondary battery, the volumetric energy density increases sufficiently as the aspect ratio becomes sufficiently small, and therefore a greater effect can be obtained.

[0146] Furthermore, if the secondary battery is a lithium ion secondary battery, a sufficient battery capacity can be stably obtained by utilizing the absorption and release of lithium, so that a higher effect can be obtained.

[0147] <2. Modifications> The configuration of the secondary battery described above can be modified as appropriate, as described below. However, with regard to the series of modified examples described below, any two or more types may be combined with each other.

[0148] [Variation 1] In Fig. 1, the recessed portion 12U is formed by bending the cover portion 12 so as to partially protrude toward the inside (downward) of the storage portion 11. However, as shown in Fig. 7 corresponding to Fig. 1, the recessed portion 12U may be formed by bending the cover portion 12 so as to partially protrude toward the outside (upward) of the storage portion 11. In this case, as in the case shown in Fig. 1, excellent battery capacity characteristics are obtained in accordance with an increase in volumetric energy density, and excellent safety is also obtained in accordance with the electrode terminal 20 functioning as an release valve, so that similar effects can be obtained.

[0149] However, assuming that the height H of the secondary battery is constant, when the recess 12U protrudes toward the outside of the storage section 11 (FIG. 7), the volumetric energy density may decrease due to a decrease in the element space volume compared to when the recess 12U protrudes toward the inside of the storage section 11 (FIG. 1). Therefore, in order to increase the volumetric energy density in accordance with an increase in the element space volume, it is preferable that the recess 12U protrudes toward the inside of the storage section 11 rather than toward the outside of the storage section 11.

[0150] [Variation 2] In Fig. 1, a recess 12U is provided in the lid 12, and an electrode terminal 20 is disposed on the outside of the lid 12, so that the electrode terminal 20 is stored inside the recess 12U. However, as shown in Fig. 8 corresponding to Fig. 1, the lid 12 may not be provided with a recess 12U, and the electrode terminal 20 may be disposed on the outside of the lid 12. In this case, too, similar to the case shown in Fig. 1, excellent battery capacity characteristics and excellent safety can be obtained, and therefore similar effects can be obtained.

[0151] [Variation 3] 1, the positive electrode 41 is connected to the electrode terminal 20 via a positive electrode lead 50, and the negative electrode 42 is connected to the outer can 10 (storage section 11) via a negative electrode lead 60. As a result, the electrode 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.

[0152] However, although not specifically shown here, the positive electrode 41 may be connected to the exterior can 10 (storage section 11) via the positive electrode lead 50, and the negative electrode 42 may be connected to the electrode terminal 20 via the negative electrode lead 60. In this way, the electrode terminal 20 may function as an external connection terminal for the negative electrode 42, and the exterior can 10 may function as an external connection terminal for the positive electrode 41.

[0153] 1, the secondary battery does not need to have a separate external connection terminal for the positive electrode 41 and a separate external connection terminal for the negative electrode 42. Therefore, the volumetric energy density increases with an increase in the element space volume, and the same effect can be obtained.

[0154] In this case, it is particularly preferable that the negative electrode lead 60 is connected to the electrode terminal 20 via the winding central space 40S. This is because a decrease in the number of windings of the positive electrode 41 and the negative electrode 42 caused by the way the negative electrode lead 60 is routed is prevented, and the battery capacity is guaranteed. Note that, in order to guide the negative electrode lead 60 into the winding central space 40S, a through hole for passing the negative electrode lead 60 may be provided in the insulating plate 72.

[0155] [Variation 4] A porous membrane separator 43 was used. However, although not specifically shown here, a laminated separator including a polymer compound layer may also be used.

[0156] Specifically, the laminated separator includes a porous film having a pair of surfaces, and a polymer compound layer provided on one or both surfaces of the porous film. This is because the adhesiveness of the separator to each of the positive electrode 41 and the negative electrode 42 is improved, thereby suppressing misalignment (winding misalignment) of the battery element 40. This makes it difficult for the secondary battery to swell even if a decomposition reaction of the electrolyte occurs. The polymer compound layer includes a polymer compound such as polyvinylidene fluoride. This is because polyvinylidene fluoride and the like have excellent physical strength and are electrochemically stable.

[0157] Either or both of the porous film and the polymer compound layer may contain one or more of a plurality of insulating particles. This is because the insulating particles dissipate heat when the secondary battery generates heat, improving the safety (heat resistance) of the secondary battery. The insulating particles contain either or both of an inorganic material and a resin material. Specific examples of inorganic materials include aluminum oxide, aluminum nitride, boehmite, silicon oxide, titanium oxide, magnesium oxide, and zirconium oxide. Specific examples of resin materials include acrylic resin and styrene resin.

[0158] When a laminated separator is produced, 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 film. In this case, a plurality of insulating particles may be added to the precursor solution as necessary.

[0159] Even when this laminated separator is used, the same effect can be obtained because lithium ions are movable between the positive electrode 41 and the negative electrode 42. In this case, as described above, the safety of the secondary battery is particularly improved, and therefore, a greater effect can be obtained.

[0160] [Variation 5] An electrolyte solution that is a liquid electrolyte is used, but an electrolyte layer that is a gel electrolyte may also be used, although this is not specifically shown.

[0161] In a battery element 40 using an electrolyte layer, a positive electrode 41 and a negative electrode 42 are laminated 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. The electrolyte layer is interposed between the positive electrode 41 and the separator 43, and is also interposed between the negative electrode 42 and the separator 43.

[0162] 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 and the like. When forming the electrolyte layer, a precursor solution containing an electrolytic solution, a polymer compound, a solvent, and the like is prepared, and then the precursor solution is applied to one or both sides of each of the positive electrode 41 and the negative electrode 42.

[0163] 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 is particularly prevented as described above, so that a higher effect can be obtained. EXAMPLES

[0164] An embodiment of the present technology will be described.

[0165] <Experimental Examples 1 to 4 and Comparative Examples 1 to 5> As described below, after the secondary battery was fabricated, the battery characteristics of the secondary battery were evaluated.

[0166] [Preparation of secondary battery] The cylindrical lithium ion secondary battery shown in FIGS. 1 and 2 was fabricated by the following procedure.

[0167] (Preparation of positive electrode) First, the positive electrode active material (lithium-containing compound (oxide) LiNi 0.8 Co 0.15 Al 0.05A positive electrode mixture was prepared by mixing 91 parts by mass of ethylenediaminetetraacetate (O2), 3 parts by mass of a positive electrode binder (polyvinylidene fluoride), and 6 parts by mass of a positive electrode conductive agent (graphite). The positive electrode mixture was then poured into a solvent (N-methyl-2-pyrrolidone, an organic solvent), and the solvent was stirred to prepare a paste-like positive electrode mixture slurry. The positive electrode mixture slurry was then applied to both sides of a positive electrode current collector 41A (aluminum, thickness = 15 μm) using a coating device, and the positive electrode mixture slurry was then dried to form a positive electrode active material layer 41B. Finally, the positive electrode active material layer 41B was compression molded using a roll press machine. As a result, the positive electrode 41 was produced.

[0168] (Preparation of negative electrode) First, 93 parts by mass of the negative electrode active material (natural graphite, which is a carbon material, and silicon oxide (SiO), which is a metal-based material) and 7 parts by mass of the negative electrode binder (polyvinylidene fluoride) were mixed together to prepare a negative electrode mixture. In this case, the mixing ratio (weight ratio) of the negative electrode active material was natural graphite:silicon oxide=93:7. Next, the negative electrode mixture was put into a solvent (N-methyl-2-pyrrolidone, which is an organic solvent), and the solvent was stirred to prepare a paste-like negative electrode mixture slurry. Next, the negative electrode mixture slurry was applied to both sides of the negative electrode current collector 42A (copper, thickness=12 μm) using a coating device, and then the negative electrode mixture slurry was dried to form the negative electrode active material layer 42B. Finally, the negative electrode active material layer 42B was compression-molded using a roll press machine. In this way, the negative electrode 42 was produced.

[0169] (Preparation of electrolyte) After adding electrolyte salt (lithium salt LiPF6) to a solvent (carbonate ester compounds ethylene carbonate and diethyl carbonate), the solvent was stirred. In this case, the mixing ratio (weight ratio) of the solvent was ethylene carbonate:diethyl carbonate=30:70, and the content of the electrolyte salt was 1 mol / kg relative to the solvent. In this way, an electrolyte solution was prepared.

[0170] (Secondary battery assembly) First, the positive electrode lead 50, the periphery of which was partially covered with a sealant 73 (polyimide tape), was welded by resistance welding to the positive electrode current collector 41A of the positive electrode 41. In addition, the negative electrode lead 60 was welded by resistance welding to the negative electrode current collector 42A of the negative electrode 42.

[0171] Next, the positive electrode 41 and the negative electrode 42 were stacked on top of each other with a separator 43 (polyethylene, thickness = 16 μm) interposed therebetween, and then the positive electrode 41, the negative electrode 42 and the separator 43 were wound to produce a wound body having a winding central space 40S (inner diameter = 3 mm).

[0172] Next, insulating plates 71 and 72 (polyimide, thickness = 50 μm) were arranged so as to face each other through the wound body, and then the insulating plates 71 and 72 were stored together with the wound body inside the cylindrical storage section 11 (nickel-plated iron, thickness = 0.2 mm, outer diameter = 18.2 mm) from the opening 11K. In this case, the negative electrode lead 60 was welded to the storage section 11 by using a resistance welding method.

[0173] Next, the electrolyte was injected from the opening 11K into the inside of the storage section 11. As a result, the wound body was impregnated with the electrolyte, and a battery element 40 (outer diameter = 17.5 mm, height = 60 mm) having a wound central space 40S was produced.

[0174] Next, the opening 11K was shielded using a plate-shaped (approximately disk-shaped) lid 12 (SUS, thickness = 0.15 mm, inner diameter of circular recess 12U = 16.2 mm, inner diameter of through hole 12K = 13 mm) to which a plate-shaped (disk-shaped) electrode terminal 20 (aluminum, thickness = 0.3 mm, outer diameter = 15.85 mm) was fixed (thermally fused) via a gasket 30 (polypropylene, thickness = 0.07 mm), and then the lid 12 was welded to the storage section 11 using a laser welding method. In this case, the positive electrode lead 50 was welded to the electrode terminal 20 via the through hole 12K using a resistance welding method.

[0175] As a result, the housing portion 11 and the lid portion 12 were used to form the exterior can 10 (fixing ratio=1.13), and the battery element 40 and the like were housed inside the exterior can 10, thereby assembling a secondary battery.

[0176] When assembling this secondary battery, the aspect ratio was changed by changing the height H (mm) while keeping the outer diameter D (= 18.2 mm) constant. Details regarding the aspect ratio are shown in Table 1.

[0177] (Stabilization of secondary batteries) The assembled secondary battery was charged and discharged for one cycle in a room temperature environment (temperature = 23°C). During charging, the battery was charged at a constant current of 0.1C until the voltage reached 4.2V, and then charged at a constant voltage of 4.2V until the current reached 0.05C. During discharging, the battery was discharged at a constant current of 0.1C until the voltage reached 2.5V. 0.1C is the current value at which the battery capacity (theoretical capacity) is fully discharged in 10 hours, and 0.05C is the current value at which the battery capacity is fully discharged in 20 hours.

[0178] In this way, a cylindrical lithium ion secondary battery using the exterior can 10, which is a welded can, and the plate-shaped electrode terminals 20 was completed.

[0179] The fixing strength of the electrode terminal 20 to the cover portion 12 (kgf / cm 2 ) and the welding strength (kgf / cm 2 ) are as shown in Table 1.

[0180] [Production of other secondary batteries] For comparison, a cylindrical secondary battery (lithium ion secondary battery) shown in FIG. 5 was fabricated using the same procedure, except that outer can 80, which is a crimped can, was used instead of outer can 10, which is a welded can.

[0181] In this case, a battery lid 91 (nickel-plated iron, thickness = 0.3 mm), a safety valve mechanism 92, and a PTC element 93 were housed inside an exterior can 80 (nickel-plated iron, thickness = 0.2 mm) having an open end, and then the open end of the exterior can 80 was crimped via a gasket 94 (polypropylene, thickness = 0.45 mm) to fix the battery lid 91, the safety valve mechanism 92, and the PTC element 93 to the exterior can 80 (distance from the upper end of the battery lid 91 to the lower end of the safety valve mechanism 92 = 3.4 mm). In this case, the positive electrode lead 50 was welded to the safety valve mechanism 92 by using a resistance welding method.

[0182] For comparison, a cylindrical secondary battery (lithium ion secondary battery) shown in Fig. 6 was fabricated by the same procedure, except that an exterior can 10 without a recess 12U was used, and a rivet-shaped electrode terminal 110 (aluminum, outer diameter of large outer diameter part = 5 mm, outer diameter of small outer diameter part = 2 mm) and a gasket 120 (perfluoroalkoxyalkane (PFA), thickness = 0.3 mm) were used instead of the plate-shaped electrode terminal 20 and gasket 30. In this case, the positive electrode lead 50 was welded to the electrode terminal 110 by using a resistance welding method.

[0183] [Evaluation of battery characteristics] The battery characteristics (battery capacity characteristics and safety) of the secondary battery were evaluated, and the results shown in Table 1 were obtained.

[0184] (Battery capacity characteristics) The discharge capacity (battery capacity (mAh)), which is an index for evaluating the battery capacity characteristics, was measured by charging and discharging the secondary battery. The charging and discharging conditions were the same as those for stabilizing the secondary battery described above.

[0185] In this case, the volumes of the outer cans 10 and 80 (L = dm 3 ) and the capacity (mAh) of the battery element 40, the volumetric energy density (volume E density (Wh / L=Wh / dm 3 )) was also calculated.

[0186] (safety) Here, two types of tests (a heating test and a continuous discharge test) were carried out to evaluate the safety.

[0187] In the heating test, first, the secondary battery was charged in a room temperature environment. The charging conditions were the same as those for stabilizing the secondary battery described above. Then, the charged secondary battery was placed on a hot plate. In this case, the orientation of the secondary battery was adjusted so that the lower part of the secondary battery (the end of the secondary battery on the opposite side to the side where the electrode terminals 20 and the battery cover 91 are arranged) was in contact with the surface of the hot plate. Finally, the secondary battery was heated (heating temperature = 200°C) using a hot plate, and the state of the secondary battery (state after heating), which is an index for evaluating safety (heating test), was visually confirmed.

[0188] As a result, the case where the electrode terminal 20 functioned as an open valve and the outer can 10 did not burst (the lid portion 12 separated from the storage portion 11) was judged as "A." The case where the electrode terminal 20 not only functioned as an open valve but also the outer can 10 burst (however, the battery element 40 was not released from the inside of the outer can 10 to the outside) was judged as "B." The case where the electrode terminal 20 did not function as an open valve and the outer can 10 burst (in particular, the battery element 40 was released from the inside of the outer can 10 to the outside) was judged as "C."

[0189] In the continuous discharge test, the secondary battery was first charged in the same manner as in the heating test. Then, the secondary battery was continuously discharged 30 times in a room temperature environment while measuring the temperature of the secondary battery, and the state of the secondary battery (state after continuous discharge), which is an index for evaluating safety (continuous discharge test), was visually confirmed. The discharge conditions were the same as those for stabilizing the secondary battery described above, except that the current during discharge was changed to 5C. 5C is the current value at which the battery capacity is fully discharged in 0.2 hours.

[0190] As a result, when the electrode terminal 20 did not function as a release valve and the temperature of the secondary battery was 60°C or lower, it was judged as "A." When the electrode terminal 20 did not function as a release valve and the temperature of the secondary battery was 120°C or lower, it was judged as "B." When the electrode terminal 20 functioned as a release valve and the temperature of the secondary battery was 130°C or higher, it was judged as "C."

[0191] [Table 1]

[0192] [Consideration] As shown in Table 1, the battery capacity characteristics and safety each varied greatly depending on the configuration of the secondary battery.

[0193] Specifically, when the exterior can 80, which is a crimped can, was used (Comparative Example 1), both the state after heating and the state after continuous discharge were good, but the battery capacity decreased due to a decrease in the volumetric energy density.

[0194] In addition, when a welded outer can 10 was used, but a rivet-shaped electrode terminal 110 was used (Comparative Example 2), the battery capacity increased in accordance with the increase in volumetric energy density, and the condition after continuous discharge was also good, but the condition after heating deteriorated.

[0195] Furthermore, when a welded exterior can 10 and a plate-shaped electrode terminal 20 were used with an aspect ratio of 1 (Comparative Example 3), the state after heating and the state after continuous discharge were both good, but the battery capacity was significantly reduced due to a significant decrease in the volumetric energy density. This resulted in a fundamental decrease in the amount of heat generated during discharge and when an abnormality occurred.

[0196] When a welded outer can 10 and a plate-shaped electrode terminal 20 were used and the aspect ratio was less than 1 but the fixing strength was greater than the welding strength (Comparative Example 4), the battery capacity increased with an increase in volumetric energy density, and the condition after continuous discharge was good, but the condition after heating deteriorated.

[0197] In addition, when a welded outer can 10 and a plate-shaped electrode terminal 20 were used and the fixing strength was smaller than the welding strength, but the aspect ratio was less than 0.1 (Comparative Example 5), the battery capacity increased significantly in accordance with the significant increase in volumetric energy density, but the post-heating state and the post-continuous discharge state both deteriorated.

[0198] In contrast, when a welded outer can 10 and a plate-shaped electrode terminal 20 were used, the aspect ratio was 0.1 or more and less than 1, and the fixing strength was smaller than the welding strength (Examples 1 to 4), a good post-heating state and a good post-continuous discharge state were both ensured, and the battery capacity increased with an increase in volumetric energy density.

[0199] That is, when Example 2, in which the aspect ratio is constant (=0.28), is compared with Comparative Examples 1, 2, 4, and 5, when the aspect ratio is greater than or equal to 0.1 and less than 1 and the fixing strength is smaller than the welding strength using outer can 10, which is a welded can, and plate-shaped electrode terminals 20 (Example 2), not only are the post-heating state and the post-continuous discharge state good, but the battery capacity (volumetric energy density) also increases, unlike when all of these conditions are not met (Comparative Examples 1, 2, 4, and 5).

[0200] In particular, when all of the above conditions were satisfied, when the aspect ratio was 0.60 or less (Examples 1 to 4), a sufficient battery capacity (volume energy density) was obtained while a good state after heating and a good state after continuous discharge were both obtained.

[0201] <Examples 5 to 8> As shown in Table 2, secondary batteries were fabricated in the same manner except for changing the fixing ratio, and the safety of the secondary batteries was then evaluated. In this case, the fixing ratio was changed by changing the inner diameter of the through hole 12K while keeping the outer diameter (=15.85 mm) of the electrode terminal 20 constant. In addition, in order to evaluate the safety, a high-temperature storage test was performed instead of a continuous discharge test, along with a heating test.

[0202] In the high-temperature storage test, the secondary battery was charged using the same procedure as in the heating test, and then the charged secondary battery was stored inside the thermostatic chamber (storage time = 1 hour). In this case, the temperature inside the thermostatic chamber was increased while the temperature of the secondary battery was measured, and the state of the secondary battery was visually confirmed to determine the open temperature of the secondary battery, which is an index for evaluating safety (heating test), that is, the minimum temperature (°C) at which the electrode terminal 20 functioned as a release valve.

[0203] [Table 2]

[0204] As shown in Table 2, a good post-heating state was obtained even when the fixed ratio was changed. In this case, particularly when the fixed ratio was 1.13 to 3.37 (Examples 2, 6, and 7), the release temperature was within the appropriate range (=130°C to 150°C).

[0205] In detail, if the opening temperature is lower than 130° C., the electrode terminal 20 may function unintentionally as an opening valve depending on the increase in internal pressure (amount of gas generated) during discharge of the secondary battery and during storage of the secondary battery in a high-temperature environment. Also, if the opening temperature is higher than 150° C., in the event of a sudden increase in internal pressure, the outer can 10 may burst unintentionally before the electrode terminal 20 functions as an opening valve. As a result, when the opening temperature is within an appropriate range, the balance between the sealing property and the openability of the outer can 10 and the lid portion 12 is optimized.

[0206] [summary] From the results shown in Tables 1 and 2, when a battery element 40 is housed inside an exterior can 10 having an aspect ratio (outer diameter D / height H) of 0.1 or more and less than 1, a lid portion 12 having a through hole 12K is welded to a storage portion 11 in the exterior can 10, an electrode terminal 20 is fixed to the lid portion 12 via a gasket 30, and the fixing strength of the electrode terminal 20 to the lid portion 12 is smaller than the welding strength of the lid portion 12 to the storage portion 11, the battery capacity characteristics (battery capacity and volumetric energy density) are improved while safety (post-heating state and post-continuous discharge state) is ensured. Thus, excellent battery capacity characteristics and excellent safety were obtained.

[0207] Although the present technology has been described above with reference to an embodiment and examples, the configuration of the present technology is not limited to the configuration described in the embodiment and examples and can be modified in various ways.

[0208] Specifically, the electrode reactant is lithium, but the type of the electrode reactant is not particularly limited. Specifically, the electrode reactant may be other alkali metals such as sodium and potassium, as described above, or alkaline earth metals such as beryllium, magnesium, and calcium. In addition, the electrode reactant may be other light metals such as aluminum.

[0209] 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. an exterior member having an outer diameter and a height; A battery element housed inside the exterior member; An insulating sealing member; a terminal member supported by the exterior member via the sealing member; a lead member electrically connecting the terminal member and the battery element; Equipped with a ratio of the outer diameter to the height is greater than or equal to 0.1 and less than or equal to 0.6; The exterior member is a housing member having an opening and housing the battery element therein; a cover member welded to the storage member, closing the opening and having a through hole; Including, the terminal member is fixed to the cover member via the sealing member and covers the through hole, the lead member passes through the through hole and is directly connected to the terminal member; a fixing strength of the terminal member to the cover member is smaller than a welding strength of the cover member to the housing member; battery.

2. a ratio of an outer diameter of the terminal member to an inner diameter of the through hole is equal to or greater than 1.13 and equal to or less than 3.37; 10. The battery of claim 1.

3. The terminal member is disposed outside the cover member. The battery according to claim 1 or 2.

4. The sealing member includes polypropylene having a melting point of 130° C. or more and 250° C. or less. The battery according to any one of claims 1 to 3.

5. The battery element includes a positive electrode and a negative electrode that are wound while facing each other, and has a winding center space at the center where the positive electrode and the negative electrode are wound, The through hole is disposed at a position overlapping at least a portion of the winding central space. The battery according to any one of claims 1 to 4.

6. The inner diameter of the through hole is larger than the inner diameter of the winding central space.

6. The battery of claim 5.

7. The battery cell further includes a wiring member that connects the battery element and the terminal member to each other, The wiring member is folded back one or more times between the battery element and the terminal member. The battery according to any one of claims 1 to 6.

8. The cover member has a recessed portion, In the recessed portion, the cover member is bent so as to partially protrude toward the inside of the storage member, The terminal member is disposed inside the recess. The battery according to any one of claims 1 to 7.

9. The battery element includes a positive electrode and a negative electrode, one of the positive electrode and the negative electrode is electrically connected to the terminal member; The other of the positive electrode and the negative electrode is electrically connected to the exterior member. The battery according to any one of claims 1 to 8.

10. It is a cylindrical battery. The battery according to any one of claims 1 to 9.

11. It is a lithium-ion secondary battery. The battery of any one of claims 1 to 10.

Images