CN219553699U

CN219553699U - Secondary battery

Info

Publication number: CN219553699U
Application number: CN202090001120.2U
Authority: CN
Inventors: 哈什·D·亚加德
Original assignee: Murata Manufacturing Co Ltd
Current assignee: Murata Manufacturing Co Ltd
Priority date: 2020-03-25
Filing date: 2020-11-17
Publication date: 2023-08-18
Anticipated expiration: 2030-11-17
Also published as: JPWO2021192405A1; WO2021192405A1

Abstract

The secondary battery is provided with: a wound electrode; and a plurality of electrode terminals connected to the electrode and separated from each other. The plurality of electrode terminals each include a bent front end portion, and the plurality of front end portions are spaced apart from each other so as not to overlap with each other.

Description

Secondary battery

Technical Field

The present technology relates to a secondary battery.

Background

Since various electronic devices such as mobile phones are popular, secondary batteries have been developed as small-sized and lightweight power sources capable of obtaining high energy density. The secondary battery includes a positive electrode, a negative electrode, and an electrolyte.

Various studies have been made on the constitution of secondary batteries. Specifically, the electrode is connected to a metal frame via a collector tab (see patent document 1, for example). At the end of the current collector, a bent sheet is used to connect the electrode to a metal frame (see patent document 2, for example). A plurality of electrodes are stacked on each other (for example, see patent document 3). A plurality of tabs are stacked on each other and welded to each other (see patent document 4, for example).

Prior art literature

Patent literature

Patent document 1: U.S. Pat. No. 9564654 Specification

Patent document 2: U.S. patent application publication 2011/0091753 specification

Patent document 3: chinese patent No. 106505236 specification

Patent document 4: chinese patent No. 101714624 specification

Disclosure of Invention

Various studies have been made on the constitution of the secondary battery, but the energy density per unit volume of the secondary battery is insufficient, and thus there is room for improvement.

The present technology has been made in view of the above-described problems, and an object thereof is to provide a secondary battery capable of increasing the energy density per unit volume.

The secondary battery according to one embodiment of the present technology includes: a wound electrode; and a plurality of electrode terminals connected to the electrode and separated from each other, the plurality of electrode terminals respectively including bent front end portions, the plurality of front end portions being spaced apart from each other in a non-overlapping manner.

According to the secondary battery of one embodiment of the present technology, the electrode is wound, and a plurality of electrode terminals separated from each other are connected to the electrode, the plurality of electrode terminals respectively including bent front end portions, the plurality of front end portions being spaced apart from each other in a non-overlapping manner, so that the energy density per unit volume can be increased.

The effects of the present technology are not necessarily limited to those described herein, and may be any of a series of effects related to the present technology described later.

Drawings

Fig. 1 is a perspective view showing the structure of a secondary battery according to an embodiment of the present technology.

Fig. 2 is a sectional view showing an enlarged configuration of the secondary battery shown in fig. 1.

Fig. 3 is a perspective view showing the structure of the battery element shown in fig. 2.

Fig. 4 is a plan view showing a structure of the battery element shown in fig. 2 when viewed from the upper side.

Fig. 5 is a cross-sectional view showing the structure of the battery element shown in fig. 2 when viewed from the lower side.

Fig. 6 is a cross-sectional view showing the structure of the battery element shown in fig. 2 in an enlarged manner.

Fig. 7 is a cross-sectional view showing an enlarged configuration of the connection terminal shown in fig. 2.

Fig. 8 is a perspective view showing the structure of a battery can used in a secondary battery manufacturing process.

Fig. 9 is a plan view showing the structure of a positive electrode used in a secondary battery manufacturing process.

Fig. 10 is a plan view showing the structure of a negative electrode used in a secondary battery manufacturing process.

Fig. 11 is an enlarged cross-sectional view showing the structure of a secondary battery (battery element) of a comparative example.

Fig. 12 is a plan view showing the structure of a positive electrode used in the process of manufacturing the secondary battery according to modification 4.

Fig. 13 is a plan view showing the structure of a negative electrode used in the process of manufacturing the secondary battery according to modification 4.

Fig. 14 is a cross-sectional view showing the structure of the secondary battery according to modification 5.

Fig. 15 is a cross-sectional view showing the structure of the secondary battery according to modification 6.

Detailed Description

An embodiment of the present technology will be described in detail below with reference to the drawings. The sequence of the description is as follows.

1. Secondary battery

1-1. Formation of

1-2. Action

1-3 method of manufacture

1-4 actions and effects

2. Modification examples

3. Comparison of volumetric energy Density

< 1 Secondary Battery >)

First, a secondary battery according to an embodiment of the present technology will be described.

The secondary battery described herein is a secondary battery having a flat and columnar three-dimensional shape, and more specifically, a secondary battery having a battery structure called a so-called coin type, button type, or the like. As described later, the secondary battery has a pair of bottom portions facing each other and a side wall portion located between the pair of bottom portions, and in the secondary battery, the height is smaller than the outer diameter. The "outer diameter" refers to the diameter of each of a pair of bases, while the "height" refers to the distance from the surface of one base to the surface of the other base.

The principle of charge and discharge of the secondary battery is not particularly limited, but a secondary battery having a battery capacity obtained by intercalation and deintercalation of an electrode reactant is described herein. The secondary battery includes a positive electrode, a negative electrode, and an electrolyte, and in the secondary battery, in order to prevent an electrode reaction substance from depositing on the surface of the negative electrode during charging, 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.

The type of the electrode reaction substance is not particularly limited, and specifically, is a light metal such as an alkali metal or an alkaline earth metal. The alkali metal is lithium, sodium, potassium, etc., and the alkaline earth metal is beryllium, magnesium, calcium, etc.

Hereinafter, the case where the electrode reaction material is lithium will be exemplified. A secondary battery that utilizes intercalation and deintercalation of lithium to obtain battery capacity is a so-called lithium ion secondary battery. In this lithium ion secondary battery, lithium is intercalated and deintercalated in an ionic state.

< 1-1. Composition >

Fig. 1 shows a three-dimensional structure of a secondary battery, and fig. 2 shows an enlarged cross-sectional structure of the secondary battery shown in fig. 1. Fig. 3 shows a three-dimensional structure of the battery element 20 shown in fig. 2, corresponding to fig. 1. Fig. 4 and 5 show the planar structure of the battery element 20 shown in fig. 2, respectively. Fig. 6 shows an enlarged cross-sectional structure of the battery element 20 shown in fig. 2, and fig. 7 shows an enlarged cross-sectional structure of the connection terminal 50 shown in fig. 2.

In the following description, for convenience, the upper side in fig. 1 to 3 and 6 is referred to as the upper side of the secondary battery, and the lower side in fig. 1 to 3 and 6 is referred to as the lower side of the secondary battery.

In fig. 2, for simplicity of illustration, the positive electrode 21, the negative electrode 22, the separator 23, the positive electrode lead 31, the negative electrode lead 32, the positive electrode tab 41, and the negative electrode tab 42, which will be described later, are each shown in a linear shape.

Fig. 4 shows a state in which the battery element 20 is viewed from the upper side (the side where the positive electrode tab 41 is disposed), while fig. 5 shows a state in which the battery element 20 is viewed from the lower side (the side where the negative electrode tab 42 is disposed).

Fig. 4 to 6 show not only the battery element 20 but also the positive electrode tab 41 and the negative electrode tab 42. In this case, for simplifying the illustration, the number of the positive electrode lead 31 (the distal end portion 31B) and the negative electrode lead 32 (the distal end portion 32B) is reduced as compared with fig. 2. Specifically, in fig. 4 to 6, 10 positive electrode leads 31 are shown as a plurality of positive electrode leads 31, and 10 negative electrode leads 32 are shown as a plurality of negative electrode leads 32, respectively.

The secondary battery described here is a button-type secondary battery, and therefore, as shown in fig. 1 and 2, has a three-dimensional shape having a height H smaller than an outer diameter D, that is, a flat and columnar three-dimensional shape. Here, the solid shape of the secondary battery is flat and cylindrical (columnar).

The size of the secondary battery is not particularly limited, and for example, the outer diameter d=3 mm to 30mm and the height h=0.5 mm to 70mm. The ratio (D/H) of the outer diameter D to the height H is preferably 25 or less, while being larger than 1.

The secondary battery includes a battery element 20, a plurality of positive electrode leads 31, and a plurality of negative electrode leads 32. More specifically, the secondary battery includes the battery element 20, the plurality of positive electrode leads 31, the plurality of negative electrode leads 32, the battery can 10, the positive electrode tab 41, the negative electrode tab 42, the connection terminal 50, and the gasket 60.

[ Battery can ]

As shown in fig. 1 and 2, the battery can 10 is a hollow exterior member that accommodates the battery element 20, the plurality of positive electrode leads 31, the plurality of negative electrode leads 32, and the like.

Here, the battery can 10 has a flat and cylindrical three-dimensional shape according to the three-dimensional shape of the flat and cylindrical secondary battery. Therefore, the battery can 10 has a pair of bottom portions M1, M2 facing each other and a side wall portion M3 located between the bottom portions M1, M2. The side wall portion M3 is connected to the bottom portion M1 at an upper end portion and connected to the bottom portion M2 at a lower end portion. As described above, since the battery can 10 has a cylindrical shape, the planar shape of each of the bottom portions M1 and M2 is circular, and the surface of the side wall portion M3 is a convex curved surface.

The battery can 10 includes a container portion 11 and a lid portion 12 joined to each other, and the container portion 11 is sealed by the lid portion 12. Here, the container portion 11 and the lid portion 12 are welded to each other.

The container 11 is a member that accommodates the battery element 20 therein, and is a hollow flat and cylindrical member that is open at its upper end and closed at its lower end. The container 11 has an opening 11K (see fig. 8) for accommodating the battery element 20, as will be described later, in a state before being sealed by the lid 12.

The lid 12 is a substantially disk-shaped member for sealing the container 11, and is welded to the container 11 as described above. Thereby, the opening 11K provided in the container 11 is closed by the lid 12. The lid 12 is provided with a through hole 12K. The through hole 12K is a hole for attaching the connection terminal 50 to the cover 12, and has an inner diameter ID.

As described above, the battery can 10 is a welded can in which two members (the container portion 11 and the lid portion 12) are welded to each other. As a result, the welded battery can 10 is a single component as a whole, that is, a component which cannot be separated into two components (the container portion 11 and the lid portion 12) later.

The battery can 10, which is a welded can, has no portion that is folded over each other, and also has no portion in which two or more members overlap each other.

The "portion having no mutual folding" means: a portion of the battery can 10 is not processed to be folded with each other. In addition, "a portion where two or more members do not overlap" means: after the secondary battery is completed, since the battery can 10 is physically one component, the battery can 10 cannot be separated into two or more components after the fact. That is, the battery can 10 is not in a state in which two or more members are overlapped with each other and combined so that they can be separated into two or more members later.

In particular, the battery can 10 as a welded can is a can different from a crimp (crimp) can formed by a caulking process, and is a so-called non-crimp can. This is because the volume of the internal element space in the battery can 10 increases, and thus the energy density per unit volume of the secondary battery increases. The "element space volume" refers to: the volume (effective volume) of the internal space of the battery can 10 that can be used to house the battery element 20 that participates in the charge-discharge reaction.

Here, the battery can 10 (the container 11 and the lid 12) has conductivity. As a result, the battery can 10 is connected to the battery element 20 (the negative electrode 22) via the plurality of negative electrode leads 32 and the negative electrode tab 42, and thus functions as an external terminal of the negative electrode 22. This is because the secondary battery may not have an external terminal of the negative electrode 22 separate from the battery can 10, and thus the element space volume is not reduced by the presence of the external terminal of the negative electrode 22. Thereby, the element space volume increases, and thus the energy density per unit volume of the secondary battery increases.

Specifically, the battery can 10 (the container 11 and the lid 12) includes one or more of conductive materials such as a metal material and an alloy material. Here, the battery can 10 includes any one or two or more of iron, copper, nickel, stainless steel, an iron alloy, a copper alloy, a nickel alloy, and the like in order to function as an external terminal of the negative electrode 22. The type of stainless steel is not particularly limited, and specifically SUS304, SUS316, and the like. The type of the material forming the container 11 and the type of the material forming the lid 12 may be the same or different from each other.

As described later, the battery can 10 (the lid 12) is insulated from the connection terminal 50 functioning as the external terminal of the positive electrode 21 via the gasket 60. This is because contact (short circuit) of the battery can 10 (external terminal of the negative electrode 22) and the connection terminal 50 (external terminal of the positive electrode 21) can be prevented.

[ Battery element ]

The battery element 20 is an element (power generating element) that performs a charge-discharge reaction, and includes an electrode for charge-discharge and an electrolyte solution as a liquid electrolyte. The electrode is wound around a winding shaft as a center, and an electrolyte is impregnated into the electrode. The "winding axis" is a virtual axis that becomes the center when the electrode is wound.

Specifically, as shown in fig. 2 to 6, since the charge/discharge electrode includes the positive electrode 21 and the negative electrode 22, the battery element 20 includes the positive electrode 21, the negative electrode 22, the electrolyte, and the separator 23. Thus, the positive electrode 21 and the negative electrode 22 are wound around the winding shaft while facing each other with the separator 23 interposed therebetween. In fig. 2 to 6, illustration of the electrolytic solution is omitted.

Here, the battery element 20 has a three-dimensional shape identical to that of the battery can 10, and thus has a flat and cylindrical three-dimensional shape. This is because, when the battery element 20 is housed in the battery can 10, a so-called dead zone (a gap between the battery can 10 and the battery element 20) is less likely to occur than when the battery element 20 has a three-dimensional shape different from that of the battery can 10, and the internal space of the battery can 10 can be effectively utilized. Thereby, the element space volume increases, and thus the energy density per unit volume of the secondary battery increases.

More specifically, the positive electrode 21 and the negative electrode 22 are stacked on each other with the separator 23 interposed therebetween, and are wound in the winding direction R1 in a state where the positive electrode and the negative electrode are stacked on each other with the separator 23 interposed therebetween. That is, the battery element 20 is a so-called wound electrode body, and therefore has a winding center space 20K on the winding core. Here, since the positive electrode 21 and the negative electrode 22 are wound so that the negative electrode 22 is disposed on the outer side of the positive electrode 21, the negative electrode 22 is disposed on the outermost periphery. The number of windings of each of the positive electrode 21, the negative electrode 22, and the separator 23 is not particularly limited, and thus can be arbitrarily set.

(cathode)

The positive electrode 21 is one of a pair of electrodes for performing charge-discharge reaction, and includes a positive electrode current collector 211 and a positive electrode active material layer 212, as shown in fig. 6.

The positive electrode current collector 211 is a current collector for supporting the positive electrode 21 of the positive electrode active material layer 212, and has a pair of surfaces on which the positive electrode active material layer 212 is provided. The positive electrode current collector 211 contains the same material as the material forming the connection terminal 50. The type of the material forming the positive electrode current collector 211 and the type of the material forming the connection terminal 50 may be the same or different from each other.

The positive electrode active material layer 212 is an active material layer of the positive electrode 21 that performs a charge-discharge reaction, and is provided on both surfaces of the positive electrode current collector 211. The positive electrode active material layer 212 may be provided only on one surface of the positive electrode current collector 211. The positive electrode active material layer 212 contains any one or two or more positive electrode active materials capable of intercalating and deintercalating lithium. The positive electrode active material layer 212 may further contain a positive electrode binder, a positive electrode conductive agent, and the like.

The positive electrode active material is a lithium-containing compound such as a lithium-containing transition metal compound containing lithium and one or more transition metal elements as constituent elements. The lithium-containing transition metal compound is one or more of an oxide, a phosphoric acid compound, a silicic acid compound, a boric acid compound, and the like.

(negative electrode)

The anode 22 is the other of the pair of electrodes for performing charge-discharge reaction, and includes an anode current collector 221 and an anode active material layer 222, as shown in fig. 6.

The negative electrode current collector 221 is a current collector of the negative electrode 22 supporting the negative electrode active material layer 222, and has a pair of surfaces on which the negative electrode active material layer 222 is provided. The negative electrode current collector 221 contains the same material as the material forming the battery can 10. The type of the material forming the negative electrode current collector 221 and the type of the material forming the battery can 10 may be the same or different from each other.

The anode active material layer 222 is an active material layer of the anode 22 that performs charge-discharge reaction, and is provided on both sides of the anode current collector 221. The negative electrode active material layer 222 may be provided only on one surface of the negative electrode current collector 221. The negative electrode active material layer 222 contains any one or two or more of negative electrode active materials capable of intercalating and deintercalating lithium. The negative electrode active material layer may contain a negative electrode binder, a negative electrode conductive agent, and the like.

The negative electrode active material is a carbon material, a metal material, or the like. The carbon material is graphite or the like. The metal-based material contains one or more of a metal element and a half metal element capable of forming an alloy with lithium as constituent elements, and specifically contains silicon, tin, and the like as constituent elements. The metal-based material may be a single material, an alloy material, a compound material, a mixture of two or more of these materials, or a material containing two or more of these phases.

(diaphragm)

As shown in fig. 6, the separator 23 is an insulating porous film interposed between the positive electrode 21 and the negative electrode 22, and allows lithium ions to pass through while preventing a short circuit between the positive electrode 21 and the negative electrode 22. The separator 23 contains one or two or more kinds of polymer compounds such as polyethylene.

(electrolyte)

The electrolyte is impregnated into each of the positive electrode 21, the negative electrode 22, and the separator 23, and contains a solvent and an electrolyte salt. The solvent includes any one or two or more of a carbonate compound, a carboxylate compound, and a nonaqueous solvent (organic solvent) such as a lactone compound. The electrolyte salt contains one or more of light metal salts such as lithium salts.

[ multiple Positive electrode leads ]

The plurality of positive electrode leads 31 are a plurality of electrode terminals (a plurality of positive electrode terminals) connected to the positive electrode 21, and are separated from each other. That is, the plurality of positive electrode leads 31 are arranged in the winding direction R1 so as to be isolated from each other and not to be in contact with each other.

As shown in fig. 3 and 6, the plurality of positive electrode leads 31 extend in the extending direction R2 intersecting the winding direction R1. Here, the positive electrode lead 31 extends in one direction (upper direction R2A) of two directions (upper direction R2A and lower direction R2B) included in the extending direction R2.

The number of the positive electrode leads 31 is not particularly limited, and may be arbitrarily set as long as it is plural. In this case, the larger the number of positive electrode leads 31 is, the lower the resistance of the secondary battery is. Here, as described above, the case where the secondary battery includes 10 positive electrode leads 31 is exemplified.

The positive electrode lead 31 includes a distal end portion 31B (distal positive electrode terminal portion) bent in a bending direction R3 intersecting the extending direction R2 (upward direction R2A). More specifically, the positive electrode lead 31 includes, in order from the side near the positive electrode 21, an extension 31A extending in the extension direction R2 (upward direction R2A) and a tip 31B bent in the bending direction R3. Therefore, the secondary battery (the plurality of positive electrode leads 31) includes a plurality of front end portions 31B, and the plurality of front end portions 31B are isolated so as not to overlap each other. As shown in fig. 4, the plurality of distal ends 31B are arranged in a substantially line along the extending direction of the positive electrode tab 41.

The bending angle of the distal end portion 31B, that is, the angle defined by the extension portion 31A and the distal end portion 31B (the angle defined by the extension direction R2 and the bending direction R3) is not particularly limited, and specifically, 90 °. This is because the positive electrode tab 41 becomes easy to connect to the plurality of front end portions 31B.

The bending direction R3 in which the distal end portion 31B is bent is not particularly limited as long as it is a direction intersecting the extending direction R2 (upward direction R2A). Accordingly, the bending directions R3 in which the plurality of distal end portions 31B are respectively bent may be the same as each other or may be different from each other. Of course, only a part (two or more and less than the total number) of the plurality of distal end portions 31B may be bent in the same bending direction R3.

Here, the tip 31B is bent in either one of two directions (the in-roll direction R3A and the out-roll direction R3B) included in the bending direction R3. The "in-roll direction R3A" refers to a direction toward the inside of winding of the battery element 20 as a wound electrode body, i.e., a direction toward the winding core (winding center space 20K) of the battery element 20, and the "out-roll direction R3B" refers to a direction toward the outside of winding of the battery element 20, i.e., a direction away from the winding core (winding center space 20K). More specifically, the plurality of distal end portions 31B are respectively bent in the in-roll direction R3A.

The positive electrode lead 31 is made of the same material as the positive electrode current collector 211 described above, and is made of the same material as the connection terminal 50. The type of the material forming the positive electrode lead 31 and the type of the material forming the connection terminal 50 may be the same or different from each other.

In particular, the positive electrode lead 31 is connected to the positive electrode current collector 211 in the positive electrode 21. This is because the electrical conductivity between the positive electrode lead 31 and the positive electrode 21 can be improved. Here, the plurality of positive electrode leads 31 are integrated with the positive electrode current collector 211. That is, in the positive electrode current collector 211, at positions different from each other (positions where the plurality of positive electrode leads 31 are arranged), a part of the positive electrode current collector 211 protrudes in the extending direction R2 (upward direction R2A), and therefore the protruding part becomes the positive electrode lead 31. This is because the positive electrode lead 31 is less likely to be detached from the positive electrode 21, and the electrical conductivity between the positive electrode lead 31 and the positive electrode 21 is further improved.

[ multiple negative electrode leads ]

The plurality of negative electrode leads 32 have substantially the same configuration as the plurality of positive electrode leads 31, except that they are connected to the negative electrode 22 and have different extending directions R2.

Specifically, the plurality of negative electrode leads 32 are a plurality of electrode terminals (a plurality of negative electrode terminals) connected to the negative electrode 22, and are separated from each other. That is, the plurality of negative electrode leads 32 are arranged in the winding direction R1 so as to be isolated from each other and not to be in contact with each other.

As shown in fig. 3 and 6, the plurality of negative electrode leads 32 extend in the extending direction R2 intersecting the winding direction R1. Here, the negative electrode lead 32 extends in the other direction (lower direction R2B) of the two directions (upper direction R2A and lower direction R2B) included in the extending direction R2.

That is, the extending direction R2 of the positive electrode lead 31 and the extending direction R2 of the negative electrode lead 32 are different from each other. Therefore, the direction in which the plurality of positive electrode leads 31 are connected to the positive electrode 21 and the direction in which the plurality of negative electrode leads 32 are connected to the negative electrode 22 are different from each other. Here, since the extending direction R2 of the negative electrode lead 32 is the lower direction R2B and the extending direction R2 of the positive electrode lead 31 is the upper direction R2A with respect to the extending direction R2 of the positive electrode lead 31, the extending direction R2 of the positive electrode lead 31 and the extending direction R2 of the negative electrode lead 32 are opposite to each other. This is because there is no need to provide a gap for preventing short-circuiting between the plurality of positive electrode leads 31 and the plurality of negative electrode leads 32, and therefore the element space volume can be ensured.

The number of the negative electrode leads 32 is not particularly limited as long as it is plural, and thus can be arbitrarily set. In this case, the larger the number of negative electrode leads 32, the lower the resistance of the secondary battery. Here, as described above, the case where the secondary battery includes 10 negative electrode leads 32 is exemplified.

The negative electrode lead 32 includes a distal end portion 32B (distal negative electrode terminal portion) bent in a bending direction R3 intersecting the extending direction R2 (lower direction R2B). More specifically, the negative electrode lead 32 includes, in order from the side close to the negative electrode 22, an extension portion 32A extending in the extension direction R2 (lower direction R2B) and a tip portion 32B bent in the bending direction R3. Therefore, the secondary battery (the plurality of negative electrode leads 32) includes a plurality of front end portions 32B, and the plurality of front end portions 32B are isolated so as not to overlap each other. As shown in fig. 5, the plurality of distal ends 32B are arranged in a substantially line along the extending direction of the negative electrode tab 42.

The details regarding the bending angle of the distal end portion 32B, that is, the angle defined by the extension portion 32A and the distal end portion 32B are the same as those regarding the bending angle of the distal end portion 31B described above.

The bending direction R3 in which the distal end portion 32B is bent is not particularly limited as long as it is a direction intersecting the extending direction R2 (lower direction R2B). Accordingly, the bending directions R3 in which the plurality of distal end portions 32B are respectively bent may be the same as each other or may be different from each other. Of course, only a part (two or more and less than the total number) of the plurality of distal end portions 32B may be bent in the same bending direction R3.

Here, the tip end portion 32B is bent in either one of two directions (the in-roll direction R3A and the out-roll direction R3B) included in the bending direction R3. However, as described above, when the positive electrode 21 and the negative electrode 22 are wound so that the negative electrode 22 is disposed further to the outside than the positive electrode 21, it is preferable that the tip end portion 32B located at the outermost side of the winding among the plurality of tip end portions 32B is bent in the in-roll direction R3A rather than the out-roll direction R3B. This is because even the outer diameter of the whole of the battery element 20 including the negative electrode lead 32 does not increase due to the presence of the front end portion 32B, and therefore the element space volume can be ensured.

Referring to fig. 6, the "tip end portion 32B located at the outermost winding side of the plurality of tip end portions 32B" refers to two tip end portions 32B located at both ends of the 10 tip end portions 32B (tip end portion 32B located at the rightmost side and tip end portion 32B located at the leftmost side).

More specifically, the plurality of distal end portions 32B are respectively bent in the in-roll direction R3A. That is, not only the two distal ends 32B located at the outermost side of the winding, but also all the other distal ends 32B are bent in the in-winding direction R3A.

The negative electrode lead 32 includes the same material as the material forming the battery can 10, as in the case of the negative electrode current collector 221 described above. The type of the material forming the negative electrode lead 32 and the type of the material forming the battery can 10 may be the same or different from each other.

As described above, since the battery can 10 is connected to the battery element 20 (the negative electrode 22) via the plurality of negative electrode leads 32 and the negative electrode tab 42, it functions as an external terminal of the negative electrode 22. Thus, the plurality of negative electrode leads 32 are connected to the battery can 10 via the negative electrode tab 42, and thus are electrically connected to the battery can 10.

In particular, the anode lead 32 is connected to the anode current collector 221 in the anode 22. This is because the electrical conductivity between the anode lead 32 and the anode 22 can be improved. Here, the plurality of negative electrode leads 32 are integrated with the negative electrode current collector 221. That is, in the negative electrode current collector 221, at positions different from each other (positions where the plurality of negative electrode leads 32 are arranged), a part of the negative electrode current collector 221 protrudes in the extending direction R2 (downward direction R2B), and therefore the protruding part becomes the negative electrode lead 32. This is because the negative electrode lead 32 is less likely to be detached from the negative electrode 22, and the electrical conductivity between the negative electrode lead 32 and the negative electrode 22 is further improved.

[ Positive electrode tab ]

The positive electrode tab 41 is an electrode wiring (positive electrode wiring) of the positive electrode 21 for collecting the current from the plurality of positive electrode leads 31, and is connected to the plurality of tip portions 31B as shown in fig. 4 and 6. Here, the positive electrode tab 41 extends in one direction, more specifically, in a direction along the arrangement direction of the plurality of tip portions 31B. The positive electrode tab 41 is connected not only to the plurality of front end portions 31B but also to the connection terminal 50.

The method of connecting the plurality of distal ends 31B to the positive electrode tab 41 is not particularly limited, and among them, welding is preferable. That is, the positive electrode tab 41 is preferably welded to the plurality of distal end portions 31B. This is because the positive electrode tab 41 is easily and firmly joined to the plurality of distal end portions 31B, and thus high connection strength and excellent electrical conductivity can be obtained. The type of the welding method is not particularly limited, and specifically, any one or two or more of an ultrasonic welding method, a laser welding method, and the like are used.

The method of connecting the positive electrode tab 41 to the connection terminal 50 is not particularly limited, and specifically, the method is the same as the method of connecting the positive electrode tab 41 to the plurality of distal end portions 31B.

The positive electrode tab 41 includes the same material as the material forming the connection terminal 50, as in the positive electrode current collector 211 described above. The type of the material forming the positive electrode tab 41 and the type of the material forming the connection terminal 50 may be the same or different from each other.

[ negative electrode tab ]

The negative electrode tab 42 is an electrode wiring (negative electrode wiring) of the negative electrode 22 for collecting the current from the plurality of negative electrode leads 32, and is connected to the plurality of tip portions 32B as shown in fig. 5 and 6. Here, the negative electrode tab 42 extends in one direction, more specifically, in a direction along the arrangement direction of the plurality of tip portions 32B. The negative electrode tab 42 is connected not only to the plurality of front end portions 32B but also to the battery can 10.

The welding process may be performed from the outside toward the inside of the battery can 10 (the bottom M2 of the container portion 11), that is, the welding process may be performed on the negative electrode tab 42 through the battery can 10, whereby the battery can 10 may be welded to the negative electrode tab 42. The type of the welding method is not particularly limited, and as described above, is any one or two or more of an ultrasonic welding method, a laser welding method, and the like.

The extending direction of the negative electrode tab 42 is not particularly limited, and specifically, the extending direction is the same as the extending direction of the positive electrode tab 41. The method of connecting the negative electrode tab 42 to the plurality of distal end portions 32B is the same as the method of connecting the positive electrode tab 41 to the plurality of distal end portions 31B. The method of connecting the negative electrode tab 42 to the battery can 10 is not particularly limited, and specifically, the method of connecting the positive electrode tab 41 to the connection terminal 50 is the same.

The negative electrode tab 42 includes the same material as the material forming the battery can 10, as with the negative electrode current collector 221 described above. The type of the material forming the negative electrode tab 42 and the type of the material forming the battery can 10 may be the same or different from each other.

[ connection terminal ]

As shown in fig. 1 and 2, the connection terminal 50 is a terminal for external connection to the electronic device when the secondary battery is mounted on the electronic device, and is attached to the battery can 10 (the lid 12).

Here, as described above, the connection terminal 50 is connected to the battery element 20 (positive electrode 21) via the plurality of positive electrode leads 31 and the positive electrode tab 41, and thus functions as an external terminal for the positive electrode 21. Thus, when the secondary battery is used, the secondary battery is connected to the electronic device via the connection terminal 50 (external terminal of the positive electrode 21) and the battery can 10 (external terminal of the negative electrode 22), and therefore the electronic device can operate using the secondary battery as a power source.

The connection terminal 50 includes any one or two or more of conductive materials such as a metal material and an alloy material. Specifically, the connection terminal 50 includes any one or two or more of aluminum, aluminum alloy, stainless steel, and the like in order to function as an external terminal of the positive electrode 21.

Here, as shown in fig. 7, the connection terminal 50 includes terminal portions 50A, 50B, 50C.

The terminal portion 50A is inserted into the through hole 12K, and has a cylindrical three-dimensional shape. The terminal portion 50A has an outer diameter OD (ODA) smaller than the inner diameter ID of the through hole 12K. The terminal portion 50B is disposed outside the battery can 10 and has a cylindrical three-dimensional shape. The terminal portion 50B is connected to the upper end portion of the terminal portion 50A, and has an outer diameter OD (ODB) larger than the inner diameter ID of the through hole 12K. The terminal portion 50C is disposed inside the battery can 10 and has a cylindrical three-dimensional shape. The terminal portion 50C is connected to the lower end portion of the terminal portion 50A, and has an outer diameter OD (ODC) larger than the inner diameter ID of the through hole 12K. The outer diameters ODB and ODC may be the same or different from each other. Here, the outer diameters ODB, ODC are the same as each other.

That is, the connection terminal 50 has a substantially cylindrical three-dimensional shape in which the outer diameter OD decreases in the middle. This is because the outer diameter ODB is larger than the inner diameter ID, so that the terminal portion 50B is difficult to pass through the through hole 12K, and the outer diameter ODC is larger than the inner diameter ID, so that the terminal portion 50C is difficult to pass through the through hole 12K. This is because the connection terminal 50 is fixed to the cover 12 by the pressing force of the respective terminal portions 50B and 50C against the cover 12. Thus, the connection terminal 50 is less likely to be detached from the battery can 10.

[ gasket ]

As shown in fig. 1 and 2, the spacer 60 is an insulating member disposed between the battery can 10 (the lid 12) and the connection terminal 50, and insulates the connection terminal 50 from the battery can 10. Thereby, the connection terminal 50 is fixed to the cover 12 via the spacer 60. The spacer 60 is made of one or two or more of insulating materials such as polypropylene and polyethylene.

The installation range of the spacer 60 is not particularly limited. Here, the spacer 60 is disposed in a gap between the cover 12 and the connection terminal 50.

[ others ]

The secondary battery may further include any one or two or more of other components not shown.

Specifically, the secondary battery is provided with a safety valve mechanism. When the internal pressure of the battery can 10 becomes equal to or higher than a certain level due to internal short-circuiting, external heating, and the like, the safety valve mechanism cuts off the electrical connection between the battery can 10 and the battery element 20. The installation position of the safety valve mechanism is not particularly limited, and the safety valve mechanism is preferably installed at either one of the bottom portions M1 and M2, and is preferably installed at the bottom portion M2 where the connection terminal 50 is not installed.

The secondary battery includes an insulator between the battery can 10 and the battery element 20. The insulator includes any one or two or more of an insulating film, an insulating sheet, and the like, and is used to prevent a short circuit between the battery can 10 and the battery element 20 (positive electrode 21). The installation range of the insulator is not particularly limited, and can be arbitrarily set.

The battery can 10 is provided with a filling hole and an opening valve. The filling hole is sealed after filling the electrolyte into the battery can 10. The opening valve is ruptured when the internal pressure of the battery can 10 reaches a certain level or more due to internal short circuit, external heating, and the like, thereby releasing the internal pressure thereof. The installation position of each of the filling hole and the opening valve is not particularly limited, and is one of the bottoms M1 and M2, preferably the bottom M2 where the connection terminal 50 is not provided, similarly to the installation position of the safety valve mechanism described above.

< 1-2 action >

At the time of charging the secondary battery, in the battery element 20, lithium is deintercalated from the positive electrode 21, and the lithium is intercalated into the negative electrode 22 via the electrolyte. In addition, at the time of discharging the secondary battery, lithium is deintercalated from the negative electrode 22 in the battery element 20, and the lithium is intercalated into the positive electrode 21 via the electrolyte. During this charge and discharge, lithium is intercalated and deintercalated in an ionic state.

< 1-3. Manufacturing method >

Fig. 8 to 10 show the respective configurations of the battery can 10, the positive electrode 21, and the negative electrode 22 used in the manufacturing process of the secondary battery. Specifically, fig. 8 shows a three-dimensional structure of the battery can 10, which corresponds to fig. 1. Fig. 9 shows the planar configuration of the positive electrode 21, and fig. 10 shows the planar configuration of the negative electrode 22.

In fig. 8, the container portion 11 and the lid portion 12 are shown separated from each other because the lid portion 12 is before welding the container portion 11. Fig. 9 shows a state before the positive electrode 21 is wound, and fig. 10 shows a state before the negative electrode 22 is wound.

In the following description, reference is made to fig. 1 to 7, which have already been described, together with fig. 8 to 10.

Here, in order to assemble the battery can 10, a container portion 11 and a lid portion 12 that are separated from each other are used. The container portion 11 is a member in which the bottom portion M2 and the side wall portion M3 are integrated with each other, and has the opening 11K as described above. The connection terminal 50 is mounted in advance in the through hole 12K of the cover 12 via the spacer 60. Further, since the bottom portion M2 and the side wall portion M3 are separated from each other, the container portion 11 may be prepared by welding the side wall portion M3 to the bottom portion M2.

[ production of Positive electrode ]

After a positive electrode slurry in which a positive electrode active material or the like is dispersed or dissolved in a solvent such as an organic solvent is prepared, the positive electrode slurry is coated on both sides of the strip-shaped positive electrode current collector 211.

In this case, as shown in fig. 9, the positive electrode current collector 211 in which the plurality of positive electrode leads 31 (the extending portions 31A and the distal end portions 31B) extending in the extending direction R2 (the upward direction R2A) are integrated is used, and the positive electrode slurry is not applied to the surface of the positive electrode lead 31 but is applied only to the surface of the positive electrode current collector 211. Since the positions of the plurality of positive electrode leads 31 in the winding direction R1 are set so as to be substantially aligned in a row when the positive electrode 21 is wound in the subsequent step, the distance between the adjacent positive electrode leads 31 gradually increases from the inside of the winding toward the outside of the winding.

Thus, the positive electrode active material layer 212 is formed on both sides of the positive electrode current collector 211, and thus the positive electrode 21 including the positive electrode current collector 211 and the positive electrode active material layer 212 is manufactured. As described above, the plurality of positive electrode leads 31 have been connected (integrated) to the positive electrode 21 (positive electrode current collector 211).

[ production of negative electrode ]

The negative electrode 22 is produced by substantially the same steps as those for producing the positive electrode 21, except that a negative electrode active material or the like is used instead of the positive electrode active material or the like.

Specifically, after a negative electrode slurry in which a negative electrode active material or the like is dispersed or dissolved in a solvent such as an organic solvent is prepared, the negative electrode slurry is applied to both surfaces of the strip-shaped negative electrode current collector 221.

In this case, as shown in fig. 10, the negative electrode current collector 221 in which the plurality of negative electrode leads 32 (the extending portion 32A and the tip portion 32B) extending in the extending direction R2 (the lower direction R2B) are integrated is used, and the negative electrode paste is not applied to the surface of the negative electrode lead 32 but is applied only to the surface of the negative electrode current collector 221. Since the positions of the plurality of negative electrode leads 32 in the winding direction R1 are set so as to be substantially aligned when the negative electrode 22 is wound in the subsequent step, the distance between the negative electrode leads 32 adjacent to each other gradually increases from the inside of the winding toward the outside of the winding.

Thus, the anode active material layer 222 is formed on both sides of the anode current collector 221, and thus the anode 22 including the anode current collector 221 and the anode active material layer 222 is manufactured. As described above, the plurality of anode leads 32 have been connected (integrated) to the anode 22 (anode current collector 221).

[ production of electrolyte ]

Electrolyte salt is added to the solvent. Thus, the electrolyte salt is dispersed or dissolved in the solvent, thereby preparing the electrolyte.

[ Assembly of Secondary Battery ]

First, the positive electrode 21 to which the plurality of positive electrode leads 31 are connected and the negative electrode 22 to which the plurality of negative electrode leads 32 are connected are stacked on each other with the separator 23 interposed therebetween, and then the positive electrode 21, the negative electrode 22, and the separator 23 are wound, whereby a wound body (not shown) to which the respective positive electrode leads 31 and negative electrode leads 32 are connected is produced. The wound body has the same structure as that of the battery element 20 except that each of the positive electrode 21, the negative electrode 22, and the separator 23 is not impregnated with the electrolyte.

Next, as shown in fig. 3 to 5, the positive electrode tab 41 is connected to the plurality of positive electrode leads 31 (the plurality of distal end portions 31B) using a welding method or the like, and the negative electrode tab 42 is connected to the plurality of negative electrode leads 32 (the plurality of distal end portions 32B) using a welding method or the like. The details of the welding method are as described above, and the same applies to the following description.

Next, the wound body to which each of the plurality of positive electrode leads 31, the plurality of negative electrode leads 32, the positive electrode tab 41, and the negative electrode tab 42 is connected is housed in the container 11 from the opening 11K. In this case, the negative electrode tab 42 is connected to the container portion 11 using a welding method or the like.

Next, after the lid 12, to which the connection terminal 50 is attached via the spacer 60, is placed on the container 11 so as to cover the opening 11K, the lid 12 is bonded to the container 11 by a welding method or the like. In this case, the positive electrode tab 41 and the like are connected to the connection terminal 50 using a welding method or the like. Accordingly, the container 11 and the lid 12 are joined to each other, and therefore, the battery can 10 is assembled using the container 11 and the lid 12, and the plurality of positive electrode leads 31, the plurality of negative electrode leads 32, the positive electrode tab 41, the negative electrode tab 42, and the wound body are housed in the battery can 10.

Finally, after the electrolyte is injected into the battery can 10 from the not-shown injection hole, the injection hole is sealed. Thus, the wound body (positive electrode 21, negative electrode 22, and separator 23) is impregnated with the electrolyte, and battery element 20 as a wound electrode body is produced. Therefore, the battery element 20 is sealed inside the battery can 10, and the secondary battery is assembled.

[ stabilization of Secondary Battery ]

And charging and discharging the assembled secondary battery. The ambient temperature, the number of charge/discharge cycles (the number of cycles), and various conditions such as charge/discharge conditions can be arbitrarily set. Thus, a coating film is formed on the surface of the negative electrode 22 or the like, and the state of the secondary battery is electrochemically stabilized. Thus, the button secondary battery using the flat and cylindrical battery can 10 is completed.

< 1-4 actions and effects >

According to the secondary battery, the positive electrode 21 is wound, and a plurality of positive electrode leads 31 separated from each other are connected to the positive electrode 21, the plurality of positive electrode leads 31 each including a bent front end portion 31B. Therefore, the energy density per unit volume can be increased for the reasons described below.

Fig. 11 shows an enlarged cross-sectional structure of the secondary battery (battery element 20) of the comparative example, corresponding to fig. 6. The secondary battery of this comparative example has the same configuration as that of the secondary battery of the present embodiment shown in fig. 6, except for the following description.

Specifically, the secondary battery of the comparative example includes a plurality of positive electrode leads 31, but does not include the positive electrode tab 41. In the secondary battery of the comparative example, some of the plurality of front end portions 31B (all of the remaining front end portions 31B except the two front end portions 31B located at the innermost side of the winding) are extended in the in-winding direction R3A, and therefore the plurality of front end portions 31B overlap each other. The overlapping distal end portions 31B are joined to each other by welding.

In the secondary battery of the comparative example, as shown in fig. 11, the plurality of positive electrode leads 31 each include the tip portion 31B, and therefore, the plurality of tip portions 31B can be connected to each other by overlapping them with each other. Thus, even if a plurality of positive electrode leads 31 (a plurality of distal end portions 31B) are used, the plurality of positive electrode leads 31 can be collected.

However, since the plurality of front end portions 31B overlap each other, the occupied volume of the plurality of positive electrode leads 31 that do not participate in the charge-discharge reaction increases greatly, and therefore the height (element height HV) of the entire battery element 20 including even the plurality of positive electrode leads 31 increases greatly.

Thus, when the internal volume of the battery can 10 is fixed and the number of windings (outer diameter) of the battery element 20 is fixed, the element height HV is greatly increased by using a plurality of positive electrode leads 31, and thus the element space volume is significantly reduced. As described above, this element space volume is the volume (effective volume) of the internal space of the battery can 10 that can be used to house the battery elements 20 (the positive electrode 21 and the negative electrode 22) that participate in the charge-discharge reaction.

Therefore, in the secondary battery of the comparative example, although the plurality of positive electrode leads 31 can be collected, the element space volume is significantly reduced, and therefore it is difficult to increase the energy density per unit volume.

In contrast, in the secondary battery of the present embodiment, as shown in fig. 6, the plurality of positive electrode leads 31 (the plurality of tip portions 31B) are separated from each other, and the plurality of tip portions 31B are connected to the positive electrode tab 41. Thus, even if the plurality of positive electrode leads 31 are separated from each other, the plurality of positive electrode leads 31 can be collected by using the positive electrode tab 41.

Further, since the plurality of tip portions 31B do not overlap with each other, the occupied volume of the plurality of positive electrode leads 31 which do not participate in the charge-discharge reaction does not increase significantly, and therefore the element height HV does not increase significantly. Further, even when the positive electrode tab 41 is used together with the plurality of positive electrode leads 31, if the thickness of the positive electrode tab 41 is sufficiently small, the element height HV does not greatly increase. As is clear from a comparison between the element height HV (fig. 6) of the secondary battery of the present embodiment and the element height HV (fig. 11) of the secondary battery of the comparative example, the element height HV does not significantly increase even when the positive electrode tab 41 is used in this way.

Thus, when the internal volume of the battery can 10 is fixed and the number of windings (outer diameter) of the battery element 20 is fixed, the element height HV does not increase significantly even if a plurality of positive electrode leads 31 are used, and therefore the element space volume increases. In this case, even if the positive electrode tab 41 is used together with the plurality of positive electrode leads 31, the element height HV does not increase greatly, and therefore the element space volume also increases.

Therefore, in the secondary battery of the present embodiment, the element space volume can be increased while collecting current from the plurality of positive electrode leads 31, and therefore the energy density per unit volume can be increased.

The functions and effects of the respective configurations of the positive electrode 21 and the plurality of positive electrode leads 31 (the plurality of distal ends 31B) described herein are similarly obtained by the configurations of the negative electrode 22 and the plurality of negative electrode leads 32 (the plurality of distal ends 32B).

That is, in the secondary battery of the comparative example, since the plurality of tip portions 32B overlap each other, the occupied volume of the plurality of negative electrode leads 32 increases greatly, and therefore the element height HV increases greatly. Therefore, the element space volume is significantly reduced, and thus it is difficult to increase the energy density per unit volume.

In contrast, in the secondary battery of the present embodiment, since the plurality of distal ends 32B do not overlap each other, the occupied volume of the plurality of negative electrode leads 32 does not increase significantly, and therefore the element height HV does not increase significantly. In this case, even if the negative electrode tab 42 is used together with the plurality of negative electrode leads 32, the element height HV does not increase greatly. Therefore, the element space volume increases, and thus the energy density per unit volume can be increased.

In the secondary battery of the present embodiment, in particular, if the tip end portion 32B located on the outermost side of the winding among the plurality of tip end portions 32B is bent in the bending direction R3 (in-winding direction R3A), the energy density per unit volume can be further increased for the reasons described below.

When the positive electrode 21 and the negative electrode 22 are wound so that the negative electrode 22 is disposed on the outer side of the positive electrode 21, the negative electrode lead 32 is disposed on the outermost periphery. In this case, when the distal end portion 32B located at the outermost winding side of the plurality of distal end portions 32B is bent in the roll-out direction R3B, the distal end portion 32B may protrude outward from the battery element 20 according to the length of the distal end portion 32B (the length extending in the roll-out direction R3B).

When the front end portion 32B protrudes outward from the battery element 20, the outer diameter of the entire battery element 20 including even the plurality of negative electrode leads 32 increases due to the presence of the front end portion 32B that does not participate in the charge-discharge reaction. Therefore, the element space volume is reduced by using the plurality of negative electrode leads 32, and thus the energy density per unit volume is reduced.

In contrast, when the tip end portion 32B located at the outermost side of the winding among the plurality of tip end portions 32B is bent in the in-winding direction R3A, the tip end portion 32B does not protrude outward from the battery element 20, and therefore the outer diameter of the entire battery element 20 including even the plurality of negative electrode leads 32 does not increase. Therefore, even if a plurality of negative electrode leads 32 are used, the volume of the element space is not reduced, and thus the energy density per unit volume increases.

In addition, if the secondary battery includes the positive electrode tab 41 connected to the plurality of front end portions 31B, the plurality of positive electrode leads 31 can be collected using the positive electrode tab 41 even if the plurality of front end portions 31B are separated from each other. Further, as described above, even if the positive electrode tab 41 is used, the element height HV does not increase greatly as long as the thickness of the positive electrode tab 41 is sufficiently small. Therefore, even if the plurality of distal end portions 31B are separated from each other, the plurality of positive electrode leads 31 are collected while the energy density per unit volume is ensured by using the positive electrode tab 41, and thus a higher effect can be obtained.

In this case, if the positive electrode tab 41 is welded to the plurality of front end portions 31B, the positive electrode tab 41 is easily and firmly connected to the plurality of front end portions 31B. Therefore, by obtaining high connection strength and excellent electrical conductivity, the plurality of positive electrode leads 31 can be stably collected using the positive electrode tab 41, and a higher effect can be obtained.

The same effects and actions are obtained by the structure of the positive electrode tab 41 described herein, and by the structure of the negative electrode tab 42. That is, if the secondary battery includes the negative electrode tab 42 connected to the plurality of tip portions 32B, even if the plurality of tip portions 32B are separated from each other, the plurality of negative electrode leads 32 can be collected while the energy density per unit volume is ensured using the negative electrode tab 42, and thus a higher effect can be obtained. In addition, if the negative electrode tab 42 is welded to the plurality of tip portions 32B, the plurality of negative electrode leads 32 can be stably collected using the negative electrode tab 42, and thus a higher effect can be obtained.

In addition, if the plurality of positive electrode leads 31 include the tip portions 31B, respectively, the plurality of tip portions 31B are separated from each other, and the plurality of negative electrode leads 32 include the tip portions 32B, respectively, the plurality of tip portions 32B are separated from each other, the element height HV does not increase significantly even if each of the plurality of positive electrode leads 31 and the plurality of negative electrode leads 32 that do not participate in the charge-discharge reaction is used. Therefore, the element space volume is further increased compared to the case where only the plurality of positive electrode leads 31 (the plurality of tip portions 31B) are separated from each other or only the plurality of negative electrode leads 32 (the plurality of tip portions 32B) are separated from each other, and therefore the energy density per unit volume can be further increased.

In addition, if the directions in which the plurality of positive electrode leads 31 are connected to the positive electrode 21 and the directions in which the plurality of negative electrode leads 32 are connected to the negative electrode 22 are different from each other, that is, the extending directions R2 of the plurality of positive electrode leads 31 and the extending directions R2 of the plurality of negative electrode leads 32 are different from each other, the energy density per unit volume can be further increased for the reasons described below.

In the case where the extending directions R2 of the plurality of positive electrode leads 31 and the extending directions R2 of the plurality of negative electrode leads 32 are the same as each other, more specifically, in the case where both extending directions R2 are the upper direction R2A, if the positive electrode tab 41 to which the plurality of positive electrode leads 31 are connected and the negative electrode tab 42 to which the plurality of negative electrode leads 32 are connected are isolated from each other in the height direction (up-down direction in fig. 6), it is possible to prevent a short circuit between the positive electrode tab 41 and the negative electrode tab 42.

However, in order to isolate the positive electrode tab 41 and the negative electrode tab 42 from each other in the height direction, a gap must be provided between the positive electrode tab 41 and the negative electrode tab 42, and therefore the element height HV increases by the amount of the gap. Therefore, the element space volume is reduced due to the presence of the gap which does not participate in the charge-discharge reaction, and thus the energy density per unit volume is reduced.

However, in the case where the extending directions R2 of the plurality of positive electrode leads 31 and the extending directions R2 of the plurality of negative electrode leads 32 are different from each other, more specifically, in the case where the extending direction R2 of the former is the upper direction R2A and the extending direction R2 of the latter is the lower direction R2B, the positive electrode tab 41 and the negative electrode tab 42 are sufficiently separated from each other. Thus, the element height HV does not increase since the above-described gap for short-circuit prevention is not required. Therefore, since the element space volume is not reduced, the energy density per unit volume increases.

In addition, if the plurality of negative electrode leads 32 are electrically connected to the battery can 10, the battery can 10 functions as an external terminal of the negative electrode 22, and thus the secondary battery may not have an external terminal of the negative electrode 22 separate from the battery can 10. Accordingly, no new external terminal of the anode 22 is required, and accordingly the element space volume increases, so that the energy density per unit volume can be further increased.

In addition, if the positive electrode 21 includes the positive electrode current collector 211 and the positive electrode active material layer 212, the plurality of positive electrode leads 31 are integrated with the positive electrode current collector 211, the positive electrode leads 31 are less likely to fall off from the positive electrode 21, and since the electrical conductivity between the positive electrode leads 31 and the positive electrode 21 is improved, a higher effect can be obtained, as compared with the case where the plurality of positive electrode leads 31 are subsequently connected to the positive electrode current collector 211 due to the plurality of positive electrode leads 31 and the positive electrode current collector 211 being separated from each other.

The actions and effects of the respective configurations of the plurality of positive electrode leads 31 and the positive electrode current collector 211 described herein are similarly obtained by the respective configurations of the plurality of negative electrode leads 32 and the negative electrode current collector 221. That is, if the plurality of negative electrode leads 32 are integrated with the negative electrode current collector 221, the negative electrode leads 32 are less likely to fall off from the negative electrode 22, and the electrical conductivity between the negative electrode leads 32 and the negative electrode 22 is improved, so that a higher effect can be obtained.

In addition, if the secondary battery is flat and columnar, that is, if the secondary battery is a button-type secondary battery, the energy density per unit volume is effectively increased in a small secondary battery that is limited in size, and thus a higher effect can be obtained.

< 2. Modification >

As described below, the configuration of the secondary battery can be changed as appropriate. Any two or more of the following modified examples may be combined with each other.

Modification 1

In fig. 6, the plurality of positive electrode leads 31 (the plurality of front end portions 31B) are separated from each other, so the positive electrode tab 41 is connected to the plurality of front end portions 31B, while the plurality of negative electrode leads 32 (the plurality of front end portions 32B) are separated from each other, so the negative electrode tab 42 is connected to the plurality of front end portions 32B.

However, it is also possible that: in the plurality of positive electrode leads 31, as shown in fig. 6, the plurality of tip portions 31B separated from each other are connected to the positive electrode tab 41, while in the plurality of negative electrode leads 32, as shown in fig. 11, the plurality of tip portions 32B are overlapped with each other without using the negative electrode tab 42.

Alternatively, it may be: in the plurality of positive electrode leads 31, as shown in fig. 11, the plurality of tip portions 31B are overlapped with each other without using the positive electrode tab 41, while in the plurality of negative electrode leads 32, as shown in fig. 6, the plurality of tip portions 32B separated from each other are connected to the negative electrode tab 42.

In any case, as compared with the case shown in fig. 11, that is, the case where the plurality of front end portions 31B are overlapped with each other without using the positive electrode tab 41 in the plurality of positive electrode leads 31 and the plurality of front end portions 32B are overlapped with each other without using the negative electrode tab 42 in the plurality of negative electrode leads 32, the element space volume increases according to the decrease in the element height HV, and therefore the same effect can be obtained.

Modification 2

In fig. 6, the plurality of positive electrode leads 31 extend in the extending direction R2 (upward direction R2A), and the plurality of negative electrode leads 32 extend in the extending direction R2 (downward direction R2B). Therefore, the plurality of positive electrode leads 31 and the plurality of negative electrode leads 32 extend in mutually different directions (in this case, mutually opposite directions).

However, the plurality of positive electrode leads 31 and the plurality of negative electrode leads 32 may extend in the same direction as each other. In this case, both the plurality of positive electrode leads 31 and the plurality of negative electrode leads 32 may extend in the extending direction R2 (the upper direction R2A), or both the plurality of positive electrode leads 31 and the plurality of negative electrode leads 32 may extend in the extending direction R2 (the lower direction R2B).

Even in this case, if the gap for preventing short-circuiting is sufficiently small, the element space volume increases in correspondence with the decrease in the element height HV as compared with the secondary battery of the comparative example (fig. 11), and therefore the same effect can be obtained.

In addition, as described above, in order to avoid an increase in the element height HV due to the gap for preventing short-circuiting, as shown in fig. 6, it is preferable that the plurality of positive electrode leads 31 and the plurality of negative electrode leads 32 extend in mutually different directions.

In this case, for the sake of care, the description is not limited to the case where the plurality of positive electrode leads 31 extend in the extending direction R2 (the upper direction R2A) and the plurality of negative electrode leads 32 extend in the extending direction R2 (the lower direction R2B). That is, it may be: the plurality of positive electrode leads 31 extend in the extending direction R2 (the lower direction R2B), while the plurality of negative electrode leads 32 extend in the extending direction R2 (the upper direction R2A).

Modification 3

In fig. 2 to 6, the connection terminal 50 is connected to the battery element 20 (positive electrode 21) via a plurality of positive electrode leads 31 and positive electrode tabs 41, while the battery can 10 is connected to the battery element 20 (negative electrode 22) via a plurality of negative electrode leads 32 and negative electrode tabs 42. Therefore, the connection terminal 50 functions as an external terminal of the positive electrode 21, and the battery can 10 functions as an external terminal of the negative electrode 22.

However, it is also possible that: the connection terminal 50 is connected to the battery element 20 (negative electrode 22) via a plurality of negative electrode leads 32 and negative electrode tabs 42, while the battery can 10 is connected to the battery element 20 (positive electrode 21) via a plurality of positive electrode leads 31 and positive electrode tabs 41. Therefore, it is also possible to: the connection terminal 50 functions as an external terminal of the negative electrode 22, and the battery can 10 functions as an external terminal of the positive electrode 21.

In this case, the connection terminal 50 includes any one or two or more of iron, copper, nickel, stainless steel, an iron alloy, a copper alloy, a nickel alloy, and the like in order to function as an external terminal of the negative electrode 22. The battery can 10 includes any one or two or more of aluminum, aluminum alloy, stainless steel, and the like in order to function as an external terminal of the positive electrode 21.

Even in this case, the secondary battery can be connected to the electronic device via the connection terminal 50 (external terminal of the negative electrode 22) and the battery can 10 (external terminal of the positive electrode 21), and therefore the same effects can be obtained. In this case, the positive electrode tab 41 may be welded to the battery can 10 (the bottom M2 of the container 11) by performing a welding process on the positive electrode tab 41. Details regarding the kind of the welding method are as described above.

Modification 4

In fig. 9, a plurality of positive electrode leads 31 are integrated with a positive electrode current collector 211.

However, it is also possible that: as shown in fig. 12 corresponding to fig. 9, the plurality of positive electrode leads 31 are separated from the positive electrode current collector 211, and thus the plurality of positive electrode leads 31 are then connected to the positive electrode 21. In this case, a plurality of positive electrode leads 31 may be attached to the positive electrode active material layer 212. Alternatively, it may be: since the positive electrode current collector 211 is partially exposed by removing a part of the positive electrode active material layer 212, a plurality of positive electrode leads 31 are attached to the exposed part of the positive electrode current collector 211.

When the plurality of positive electrode leads 31 are separated from the positive electrode current collector 211, the length (the dimension in the extending direction of the extending portion 31A) of the extending portion 31A of each of the plurality of positive electrode leads 31 is not particularly limited, but is preferably as large as possible. This is because the connection area between the plurality of positive electrode leads 31 and the positive electrode 21 increases, and thus the resistance of the secondary battery decreases. Here, the extension 31A extends to the lower end of the positive electrode 21.

Even in this case, since the energy density per unit volume increases in accordance with the increase in the element space volume, the same effect can be obtained.

As shown in fig. 13 corresponding to fig. 10, modification 4 described herein with respect to each of the plurality of positive electrode leads 31 and the positive electrode current collector 211 may be applied to each of the plurality of negative electrode leads 32 and the negative electrode current collector 221.

That is, the plurality of anode leads 32 may be separated from the anode current collector 221, and thus the plurality of anode leads 32 may be subsequently connected to the anode 22 (the anode current collector 221 or the anode active material layer 222). The length of the extension 32A of each of the plurality of negative electrode leads 32 is not particularly limited, but is preferably as large as possible. Here, the extension 32A extends to the upper end of the anode 22. Even in this case, since the energy density per unit volume increases in accordance with the increase in the element space volume, the same effect can be obtained.

Of course, modification 4 described herein may be applied to both of the plurality of positive electrode leads 31 and the plurality of negative electrode leads 32, or may be applied to only one of the plurality of positive electrode leads 31 and the plurality of negative electrode leads 32.

Modification 5

In fig. 2, a connection terminal 50 having a substantially cylindrical three-dimensional shape in which the outer diameter OD varies in the middle of the connection terminal is used, and the connection terminal includes terminal portions 50A, 50B, and 50C.

However, as shown in fig. 14 corresponding to fig. 2, a disk-shaped connection terminal 70 may be used instead of the above-described substantially cylindrical connection terminal 50. In this case, the lid 12 is partially recessed because the lid 12 is folded so as to partially protrude toward the inside of the container 11. Thus, a part of the lid 12 is bent so as to form a step toward the center of the lid 12, and thus the lid 12 has a recess 12P. Inside the recess 12P, a through hole 12K is provided in the lid 12.

The disk-shaped connection terminal 70 is disposed inside the recess 12P via the spacer 80, and is connected to the positive electrode tab 41 via the connection wiring 71. Here, the outer diameter of the connection terminal 70 is smaller than the inner diameter of the recess 12P, and thus the connection terminal 70 is isolated from the cover 12 at the periphery. Thus, the pad 80 is disposed only in a part of the area between the connection terminal 70 and the cover 12, more specifically, only in the area where the connection terminal 70 and the cover 12 can contact each other if the pad 80 is not present. Details about the gasket 80 are the same as those about the gasket 60.

Here, the connection terminal 70 is formed of a clad (clad) material including an aluminum layer and a nickel layer in this order from the side near the pad 80. In the clad material, an aluminum layer and a nickel layer are roll-bonded to each other.

In this case, the secondary battery can be connected to the electronic device via the connection terminal 70 (external terminal of the positive electrode 21) and the battery can 10 (external terminal of the negative electrode 22), and therefore the same effect can be obtained.

In this case, in particular, since the connection terminal 70 is accommodated in the recess 12P, the connection terminal 70 does not protrude from the lid 12, and therefore the height H of the secondary battery is smaller than in the case where the connection terminal 50 protrudes from the lid 12 (fig. 2). Therefore, the element space volume increases, and thus the energy density per unit volume can be further increased.

Modification 6

In fig. 2, a battery can 10 is used as a welded can (no-curl can). However, as shown in fig. 15 corresponding to fig. 2, a battery can 90 as a crimp can may be used instead of the battery can 10 as a welding can described above.

The battery can 90 includes a container 91 and a lid 92 that are separated from each other, and a gasket 93 interposed between the container 91 and the lid 92. The container 91 is a container-like member having one open end, and has a bottom M4 and a side wall M5. The lid 92 is a container-like member having one end open, similar to the container 91, and has a bottom M6 and a side wall M7. The cover 92 is attached to the container 91 so that the side wall M7 overlaps the side wall M5 from the outside, and the side wall M7 is caulked to the side wall M5 via the gasket 93. Thereby, the lid 92 is fixed to the container 91 by caulking, and the battery element 20 is housed in the container 91 and the lid 92. The details about the spacer 93 are the same as those about the spacer 60.

Here, the welding process is performed from the outside toward the inside of the container portion 91 (bottom portion M4), and the welding process is performed on the positive electrode tab 41 through the container portion 91, whereby the container portion 91 is welded to the positive electrode tab 41. The welding process is performed from the outside toward the inside of the lid 92 (bottom portion M6), and the welding process is performed on the negative electrode tab 42 through the lid 92, whereby the lid 9 is welded to the negative electrode tab 42. The type of the welding method is not particularly limited, and as described above, it is any one or two or more of an ultrasonic welding method, a laser welding method, and the like.

In this case, the secondary battery can be connected to the electronic device via the container portion 91 (external terminal of the positive electrode 21) and the lid portion 92 (external terminal of the negative electrode 22), and therefore the same effect can be obtained.

Although not specifically shown here, in the case of using the battery can 90 as a crimp can, each of the positive electrode tab 41 and the negative electrode tab 42 may be omitted. Specifically, the plurality of front end portions 31B may be connected to the container portion 91 (bottom portion M4) by omitting the positive electrode tab 41, while the plurality of front end portions 32B may be connected to the lid portion 92 (bottom portion M6) by omitting the negative electrode tab 42. In this case, it is needless to say that the container portion 91 may be welded to each of the plurality of front end portions 31B by performing the welding process on the plurality of front end portions 31B via the container portion 91, and the cover portion 92 may be welded to each of the plurality of front end portions 32B by performing the welding process on the plurality of front end portions 32B via the cover portion 92.

< 3 comparison of volumetric energy Density >

Here, the energy density per unit volume of the secondary battery (fig. 6) of the present embodiment and the energy density per unit volume of the secondary battery (fig. 11) of the comparative example are logically (mathematically) compared with each other. In order to simplify the comparison of the energy density per unit volume, the element height HV influencing the energy density per unit volume is compared.

[ comparison in the case where the number of front ends was changed ]

Table 1 shows the comparison result of the element heights HV in the case where the number of the positive electrode leads 31 (the distal end portions 31B) and the number of the negative electrode leads 32 (the distal end portions 32B) were changed, respectively.

Here, as described below, for each of the secondary batteries of the present embodiment and the secondary batteries of the comparative example, the total thickness (μm) related to the element height HV was calculated, and then, based on the total thickness of both, the improvement rate (%) of the element height HV related to the secondary battery of the present embodiment was calculated. In this case, the width (dimension in the up-down direction in fig. 6 and 11) of the battery element 20 participating in the charge-discharge reaction was set to 4mm (=4000 μm).

Specifically, first, the thickness of the front end portion 31B, the thickness of the front end portion 32B, the thickness of the positive electrode tab 41, and the thickness of the negative electrode tab 42 were each fixed to 10 μm, and the number of the front end portions 31B and the number of the front end portions 32B were each varied in the range of 2 to 9.

Next, the total thickness (μm) is calculated based on the thickness of the front end portion 31B, the thickness of the front end portion 32B, the thickness of the positive electrode tab 41, and the thickness of the negative electrode tab 42. The total thickness is the sum of the thicknesses of the plurality of front end portions 31B (=the thickness×the number of front end portions 31B), the sum of the thicknesses of the plurality of front end portions 32B (=the thickness×the number of front end portions 32B), the thickness of the positive electrode tab 41, and the thickness of the negative electrode tab 42.

Specific examples of the total thickness are listed below. The total thickness of the secondary battery of the comparative example in the case where the number of front end portions 31 b=5, the thickness of front end portions 31 b=10 μm, the number of front end portions 32 b=5, and the thickness of front end portions 32 b=10 μm is: total thickness= (5×10 μm) + (5×10 μm) =100 μm. Note that, when the number of front end portions 31 b=5, the thickness of front end portions 31 b=10 μm, the thickness of positive electrode tab 41=10 μm, the number of front end portions 32 b=5, the thickness of front end portions 32 b=10 μm, and the thickness of negative electrode tab 42=10 μm, the total thickness of the secondary battery of the present embodiment is: total thickness = 10 μm +10 μm = 40 μm.

Next, the reduction amount (μm) of the element height HV of the secondary battery according to this embodiment was calculated by subtracting the total thickness calculated for the secondary battery according to this embodiment from the total thickness calculated for the secondary battery of the comparative example.

Finally, the improvement rate (%) of the element height HV of the secondary battery according to the present embodiment was calculated based on the above-described reduction amount and the width (=4000 μm) of the battery element 20. The improvement rate is calculated based on the following calculation formula: improvement rate= (reduction amount/width of battery element 20) ×100, i.e., improvement rate= (reduction amount/4000) ×100. The improvement ratio represents a ratio of improvement in the element height HV of the secondary battery of the present embodiment as compared with the element height HV of the secondary battery of the comparative example. That is, the larger the value of the improvement rate, the more the element height HV in the secondary battery of the present embodiment improves as compared to the secondary battery of the comparative example.

TABLE 1

/>

As shown in table 1, in the secondary battery of the present embodiment, when the number of front end portions 31B and the number of front end portions 32B are 3 or more, respectively, the element height HV is reduced (the reduction amount is greater than 0 μm) as compared with the secondary battery of the comparative example, and therefore the element height HV is improved (the improvement rate is greater than 0%).

Specifically, in the secondary battery of the comparative example, since the plurality of front end portions 31B overlap each other, when the number of front end portions 31B increases, the total thickness of the plurality of front end portions 31B increases, and since the plurality of front end portions 32B overlap each other, when the number of front end portions 32B increases, the total thickness of the plurality of front end portions 32B increases. Accordingly, the total thickness of the plurality of distal ends 31B and the plurality of distal ends 32B gradually increases according to the number of distal ends 31B and the number of distal ends 32B.

In contrast, in the secondary battery of the present embodiment, since the plurality of front end portions 31B do not overlap each other, even if the number of front end portions 31B increases, the total thickness of the plurality of front end portions 31B does not increase, and since the plurality of front end portions 32B do not overlap each other, even if the number of front end portions 32B increases, the total thickness of the plurality of front end portions 32B does not increase. Thus, even if the number of the front end portions 31B and the number of the front end portions 32B are increased, the total thickness of the plurality of front end portions 31B and the plurality of front end portions 32B is fixed.

Even if the positive electrode tab 41 and the negative electrode tab 42 are used, if the thicknesses of the positive electrode tab 41 and the negative electrode tab 42 are not excessively large, the total thickness of the plurality of front end portions 31B, the plurality of front end portions 32B, the positive electrode tab 41, and the negative electrode tab 42 becomes sufficiently small as compared with the secondary battery of the comparative example.

As described above, in the secondary battery of the present embodiment, when the number of front end portions 31B and the number of front end portions 32B are 3 or more, respectively, the element height HV decreases, and therefore the energy density per unit volume increases, as compared with the secondary battery of the comparative example.

In this case, in particular, the improvement rate gradually increases according to the number of the distal ends 31B and the number of the distal ends 32B, and therefore the energy density per unit volume further increases.

[ comparison of the case where the thickness of the distal end portion was changed ]

Table 2 shows the comparison result of the element heights HV in the case where the thickness of the positive electrode lead 31 (the distal end portion 31B) and the thickness of the negative electrode lead 32 (the distal end portion 32B) were changed, respectively.

Here, the total thickness, the reduction amount, and the improvement rate are calculated by the same procedure, except that the thickness of the tip portion 31B and the thickness of the tip portion 32B are changed, respectively, instead of changing the number of the tip portions 31B and the number of the tip portions 32B, respectively. In this case, the number of the distal ends 31B and the number of the distal ends 32B are fixed to 10, and the thickness of the positive electrode tab 41 and the thickness of the negative electrode tab 42 are fixed to 10 μm, respectively, while the thickness of the distal ends 31B and the thickness of the distal ends 32B are varied in the range of 6 μm to 13 μm, respectively.

TABLE 2

As shown in table 2, in the secondary battery of the present embodiment, the element height HV is reduced compared to the secondary battery of the comparative example, and therefore the element height HV is improved, independently of the thickness of the front end portion 31B and the thickness of the front end portion 32B.

Specifically, in the secondary battery of the comparative example, since the plurality of front end portions 31B overlap each other, when the thickness of the front end portion 31B increases, the total thickness of the plurality of front end portions 31B increases greatly, and the plurality of front end portions 32B overlap each other, and therefore when the thickness of the front end portion 32B increases, the total thickness of the plurality of front end portions 32B increases greatly. Thus, the total thickness of the plurality of distal ends 31B and the plurality of distal ends 32B is greatly increased, and is sharply increased in response to the increase in the thickness of the distal ends 31B and the thickness of the distal ends 32B, respectively.

In contrast, in the secondary battery of the present embodiment, since the plurality of front end portions 31B do not overlap each other, even if the thickness of front end portion 31B increases, the total thickness of the plurality of front end portions 31B does not increase substantially, and since the plurality of front end portions 32B do not overlap each other, even if the thickness of front end portion 32B increases, the total thickness of the plurality of front end portions 32B does not increase substantially. Thus, the total thickness of the plurality of distal ends 31B and the plurality of distal ends 32B does not increase significantly, but gradually increases according to the increase in the thickness of the distal ends 31B and the thickness of the distal ends 32B, respectively.

As described above, in the secondary battery of the present embodiment, unlike the secondary battery of the comparative example, even if the thickness of the front end portion 31B and the thickness of the front end portion 32B are increased, respectively, the element height HV is sufficiently reduced, and therefore the energy density per unit volume is increased.

In this case, in particular, the improvement rate gradually increases according to the increase in the thickness of the distal end portion 31B and the thickness of the distal end portion 32B, respectively, and thus the energy density per unit volume further increases.

[ comparison of the cases in which the thickness of the positive electrode tab and the thickness of the negative electrode tab were changed, respectively ]

Table 3 shows the comparison result of the element heights HV when the thicknesses of the positive electrode tab 41 and the negative electrode tab 42 were changed, respectively.

Here, the total thickness, the reduction amount, and the improvement rate are calculated by the same procedure, except that the thickness of the positive electrode tab 41 and the thickness of the negative electrode tab 42 are changed, respectively, instead of changing the number of the tip portions 31B and the number of the tip portions 32B, respectively. In this case, the number of the distal ends 31B and the number of the distal ends 32B are fixed to 10, and the thickness of the distal ends 31B and the thickness of the distal ends 32B are fixed to 10 μm, respectively, and the thickness of the positive electrode tab 41 and the thickness of the negative electrode tab 42 are varied in the range of 10 μm to 24 μm, respectively.

TABLE 3

As shown in table 3, in the secondary battery of the present embodiment, the element height HV was reduced compared to the secondary battery of the comparative example, and therefore the element height HV was improved, independently of the thickness of the positive electrode tab 41 and the thickness of the negative electrode tab 42.

Specifically, in the secondary battery of the comparative example, the positive electrode tab 41 and the negative electrode tab 42 are not used, and therefore the total thickness of the plurality of front end portions 31B and the plurality of front end portions 32B is fixed regardless of the thickness of each of the positive electrode tab 41 and the negative electrode tab 42. Since the plurality of distal ends 31B overlap each other and the plurality of distal ends 32B overlap each other, when the number of distal ends 31B is large, the total thickness of the plurality of distal ends 32B increases significantly, and when the number of distal ends 32B is large, the total thickness of the plurality of distal ends 32B increases significantly.

In contrast, in the secondary battery of the present embodiment, since the positive electrode tab 41 and the negative electrode tab 42 are used, when the thickness of the positive electrode tab 41 and the thickness of the negative electrode tab 42 are increased, the total thickness of the plurality of front end portions 31B, the plurality of front end portions 32B, the positive electrode tab 41, and the negative electrode tab 42 is increased. However, since the plurality of distal ends 31B do not overlap each other, the total thickness of the plurality of distal ends 31B does not increase even if the number of distal ends 31B increases, and since the plurality of distal ends 32B do not overlap each other, the total thickness of the plurality of distal ends 32B does not increase even if the number of distal ends 32B increases. Thus, even if the thickness of the positive electrode tab 41 and the thickness of the negative electrode tab 42 are increased, the total thickness of the plurality of front end portions 31B, the plurality of front end portions 32B, the positive electrode tab 41, and the negative electrode tab 42 is increased only by the amount by which the thickness of the positive electrode tab 41 and the thickness of the negative electrode tab 42 are increased, and thus not only is not greatly increased, but also is gradually increased in response to the increase in the thickness of the positive electrode tab 41 and the thickness of the negative electrode tab 42, respectively.

Even if the positive electrode tab 41 and the negative electrode tab 42 are used, the total thickness of the positive electrode tab 41 and the negative electrode tab 42 is sufficiently smaller than that of the secondary battery of the comparative example as long as the thicknesses thereof are not excessively large.

As described above, in the secondary battery of the present embodiment, unlike the secondary battery of the comparative example, even if the thickness of the positive electrode tab 41 and the thickness of the negative electrode tab 42 are increased, the element height HV is not greatly increased but sufficiently reduced, and therefore the energy density per unit volume is increased.

In this case, in particular, the improvement ratio gradually decreases in accordance with the increase in the thickness of the positive electrode tab 41 and the increase in the thickness of the negative electrode tab 42, respectively. Therefore, in order to ensure the energy density per unit volume, it is preferable that the thickness of the positive electrode tab 41 and the thickness of the negative electrode tab 42 are not extremely increased, respectively.

Although the present technology has been described above with reference to one embodiment and example, the configuration of the present technology is not limited to the configuration described in the one embodiment and example, and various modifications are possible.

Specifically, a case where a liquid electrolyte (electrolyte solution) is used is described, but the type of the electrolyte is not particularly limited, and thus a gel-like electrolyte (electrolyte layer) may be used, or a solid electrolyte (solid electrolyte) may be used.

Although the case where the electrode reaction material is lithium is described, the electrode reaction material is not particularly limited. Specifically, as described above, the electrode reaction material may be other alkali metals such as sodium and potassium, or alkaline earth metals such as beryllium, magnesium and calcium. The electrode reaction material may be another light metal such as aluminum.

The effects described in the present specification are merely examples, and thus the effects of the present technology are not limited to the effects described in the present specification. Therefore, other effects can be obtained by the present technology.

Claims

1. A secondary battery, characterized by comprising:

a wound electrode; and

a plurality of electrode terminals connected to the electrodes and separated from each other,

the plurality of electrode terminals respectively include bent front end portions,

a plurality of the front end portions are spaced apart in a non-overlapping manner,

the plurality of electrode terminals are arranged in a direction of winding the electrode,

the tip end portions of the plurality of tip end portions located at the outermost side of the winding are bent toward the inner side of the winding.

2. The secondary battery according to claim 1, wherein,

the secondary battery further comprises: electrode wiring connected to a plurality of the front end portions.

3. The secondary battery according to claim 2, wherein,

the electrode wiring is welded to a plurality of the front end portions.

4. The secondary battery according to any one of claim 1 to 3, wherein,

the electrode comprises a positive electrode and a negative electrode,

the positive electrode includes a plurality of positive electrode terminals as the plurality of electrode terminals connected to the positive electrode,

the plurality of positive electrode terminals respectively include a front end positive electrode terminal portion as the front end portion, the negative electrode includes a plurality of negative electrode terminals as the plurality of electrode terminals connected to the negative electrode,

the plurality of negative terminals include tip negative terminal portions as the tip portions, respectively.

5. The secondary battery according to claim 4, wherein,

the directions in which the plurality of positive electrode terminals are connected to the positive electrode and the directions in which the plurality of negative electrode terminals are connected to the negative electrode are different from each other.

6. The secondary battery according to claim 4, wherein, in turn,

the secondary battery includes an electroconductive exterior member accommodating the positive electrode, the negative electrode, the plurality of positive electrode terminals, and the plurality of negative electrode terminals,

one of the plurality of positive terminals and the plurality of negative terminals is electrically connected to the exterior member.

7. The secondary battery according to claim 5, wherein, in turn,

8. The secondary battery according to any one of claims 5 to 7, wherein,

the electrode includes a current collector and an active material layer,

the plurality of electrode terminals are integrated with the current collector.

9. The secondary battery according to any one of claims 5 to 7, wherein,

the secondary battery is a flat and columnar secondary battery.