Energy storage element

Abstract

To provide an energy storage element with improved reliability. [Solution] The energy storage element comprises an electrode body 400 around which an electrode plate is wound, and a container for housing the electrode body. The electrode plate has a forming portion on which a first active material layer containing Ni oxide or a second active material layer containing Si is formed. The electrode body comprises a pair of turned portions 402 and a flat portion 403 connecting the pair of turned portions. The forming portion has a convex portion 480 that protrudes in the thickness direction of the electrode plate, and the convex portion is located at least on the turned portion.

Description

Technical Field

[0001] The present invention relates to a power storage element.

Background Art

[0002] Patent Document 1 discloses a secondary battery including a wound electrode body in which a positive electrode and a negative electrode are wound around a winding axis with a separator interposed therebetween.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Here, in an electrode body formed by winding a plate electrode provided with an active material layer containing a Ni-containing oxide or an active material layer containing Si, when charged, the plate electrode may break at the starting point of the turn portion due to stress caused by expansion. When this breakage occurs, the reliability of the power storage element is impaired.

[0005] The present invention has been made by the inventors of the present application newly paying attention to the above problems, and an object thereof is to provide a power storage element with improved reliability.

Means for Solving the Problems

[0006] A power storage element according to an aspect of the present invention includes an electrode body in which a plate electrode is wound, and a container that houses the electrode body. The plate electrode includes a formed portion in which a first active material layer containing a Ni-containing oxide or a second active material layer containing Si is formed. The electrode body includes a pair of turn portions and a flat portion connecting the pair of turn portions. The formed portion includes a convex portion protruding in the thickness direction of the plate electrode, and the convex portion is disposed at least in the turn portion.

Effects of the Invention

[0007] According to the present invention, it is possible to provide an energy storage element with improved reliability. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a perspective view showing the external appearance of an energy storage element according to an embodiment. [Figure 2] Figure 2 is a perspective view showing the components arranged inside the container of the energy storage element according to the embodiment. [Figure 3] Figure 3 is a perspective view showing an overview of the configuration of the electrode body according to the embodiment. [Figure 4] Figure 4 is a cross-sectional view showing the electrode body according to the embodiment housed in a container. [Figure 5A] Figure 5A is a cross-sectional view showing a protrusion according to the embodiment. [Figure 5B] Figure 5B is a cross-sectional view showing a modified example of the protrusion according to the embodiment. [Figure 6] Figure 6 is a partial cross-sectional view showing a portion of the electrode plate forming the vicinity of the turn portion according to the embodiment. [Figure 7] Figure 7 is a block diagram showing a manufacturing apparatus for an energy storage element according to an embodiment. [Figure 8] Figure 8 is an explanatory diagram showing the state in which the container is compressed by the compression part according to the embodiment. [Figure 9] Figure 9 is a partial cross-sectional view showing a portion of the electrode body near the turn portion according to Modified Example 1. [Figure 10] Figure 10 is a partial cross-sectional view showing a portion of the electrode body near the turn portion according to Modified Example 2. [Figure 11] Figure 11 is a partial cross-sectional view showing a portion of the electrode body near the turn portion according to Modification 3. [Modes for carrying out the invention]

[0009] (1) The energy storage element according to one aspect of the present invention includes an electrode body in which electrode plates are wound, and a container that houses the electrode body. The electrode plate includes a formed portion in which a first active material layer containing a Ni-containing oxide or a second active material layer containing Si is formed. The electrode body includes a pair of turn portions and a flat portion that connects the pair of turn portions. The formed portion includes a convex portion that protrudes in the thickness direction of the electrode plate, and the convex portion is disposed at least in the turn portion.

[0010] According to the energy storage element described in (1) above, in the formed portion of the electrode plate, a first active material layer containing a Ni-containing oxide having a relatively large expansion amount or a second active material layer containing Si is formed. Further, a convex portion is disposed in the formed portion in the turn portion of the electrode body. Due to this convex portion, a gap is provided between the electrode plates in the turn portion. When the turn portion expands, the stress is absorbed by this gap, so that the stress is less likely to concentrate at the starting point of the turn portion, and the breakage of the electrode plate can be suppressed. Therefore, an energy storage element with improved reliability can be provided.

[0011] (2) In the energy storage element described in (1) above, the occupied area per unit area of the convex portion in the turn portion may be larger than the occupied area per unit area of the convex portion in the flat portion.

[0012] According to the energy storage element described in (2) above, since the occupied area of the convex portion in the turn portion is larger than the occupied area of the convex portion in the flat portion, the gap between the electrode plates can be suppressed in the flat portion. As a result, the electrode plates can be laminated densely in the flat portion, and the capacitance can be increased.

[0013] (3) In the energy storage element described in (2) above, the occupied area of the convex portion in the flat portion may be zero.

[0014] According to the energy storage element described in (3) above, since the occupied area of the convex portion in the flat portion is zero, the gap between the electrode plates can be further suppressed in the flat portion. As a result, the electrode plates can be laminated more densely in the flat portion, and the capacitance can be further increased.

[0015] (4) In the energy storage element according to (1) above, the exclusive area per unit area of the convex portion in the turn portion and the exclusive area per unit area of the convex portion in the flat portion may be equal.

[0016] According to the energy storage element described in (4) above, since the exclusive area of the convex portion in the turn portion and the exclusive area of the convex portion in the flat portion are equal, the convex portions can be formed evenly with respect to the electrode plate. Therefore, an electrode body provided with convex portions can be easily manufactured.

[0017] (5) In the energy storage element according to any one of (1) to (4) above, the electrode plate includes a positive electrode plate and a negative electrode plate. The first active material layer is formed in the forming portion of the positive electrode plate, and the second active material layer is formed in the forming portion of the negative electrode plate. The convex portion may be formed in each of the forming portion of the positive electrode plate and the forming portion of the negative electrode plate.

[0018] According to the energy storage element described in (5) above, convex portions are formed in each of the forming portion of the positive electrode plate having the first active material layer containing Ni-containing oxide and the forming portion of the negative electrode plate having the second active material layer containing Si. Therefore, the voids formed in the turn portion can be increased. As a result, the stress during expansion of the electrode body provided with the first active material layer or the second active material layer having a relatively large expansion amount can be more surely released into the voids.

[0019] (6) In the energy storage element according to any one of (1) to (5) above, the container includes a pair of wall portions sandwiching the flat portion. The pair of wall portions compress the flat portion, and the electrode plates forming the innermost circumference of the flat portion may be arranged directly or indirectly without a gap.

[0020] In this case, if the energy storage element is charged while the electrode body is compressed by a pair of walls, the active material layer on the electrode plate may peel off from the current collector foil. According to the energy storage element described in (6) above, a protrusion is arranged on the turn portion of the electrode body, so the protrusion creates a gap between the electrode plates (between the positive electrode plate and the negative electrode plate) at the turn portion. When the turn portion expands, the stress is absorbed by this gap, so stress is less likely to concentrate at the turn portion, and the fracture of the electrode plate can be suppressed.

[0021] (Embodiment) The following description of an energy storage element according to an embodiment of the present invention will be made with reference to the drawings. Note that the embodiments described below are all general or specific examples. The numerical values, shapes, materials, components, arrangement and connection configurations of components, manufacturing processes, and manufacturing process sequences shown in the following embodiments are examples only and are not intended to limit the present invention. Furthermore, dimensions are not precisely illustrated in each figure. Additionally, the same or similar components are denoted by the same reference numerals in each figure. The drawings are schematic diagrams with appropriate emphasis, omissions, and ratio adjustments to illustrate the present invention, and may differ from the actual shapes, positional relationships, and ratios.

[0022] In the following description and drawings, the direction in which the pair of terminals are aligned, the longitudinal direction of the container, and the winding axis direction of the electrode plates are defined as the X-axis direction; the thickness direction of the container is defined as the Y-axis direction; and the direction in which the container body and lid are aligned within the container is defined as the Z-axis direction. These X-axis, Y-axis, and Z-axis directions intersect each other (orthogonal in this embodiment). Depending on the orientation of the energy storage element, the Z-axis direction may not be vertical, but for the sake of explanation, the Z-axis direction will be described as vertical.

[0023] In the following explanation, for example, the "X-axis positive direction" refers to the direction of the X-axis arrow, and the "X-axis negative direction" refers to the opposite direction. The same applies to the Y-axis and Z-axis directions. When simply referred to as "X-axis direction," it means either the bidirectional or unidirectional direction parallel to the X-axis. The same applies to the terminology related to the Y-axis and Z-axis.

[0024] Furthermore, expressions indicating relative directions or orientations, such as parallel and orthogonal, include cases where the direction or orientation is not strictly accurate. For example, two directions being orthogonal does not only mean that the two directions are perfectly orthogonal, but also that they are substantially orthogonal, i.e., include a difference of a few percent. In the following explanation, when the term "insulation" is used, it means "electrical insulation." The volume resistivity of an insulating material is 1 × 10⁻⁶ 6 Preferably, it is Ωm or higher, 1 × 10 7 Ωm or greater is more preferable, 1 × 10 10 A value of Ωm or higher is even more preferable.

[0025] [Energy storage element] A general description of the energy storage element 10 according to the embodiment will be given. Figure 1 is a perspective view showing the external appearance of the energy storage element 10 according to the embodiment. Figure 2 is a perspective view showing the components arranged inside the container 100 of the energy storage element 10 according to the embodiment.

[0026] The energy storage element 10 is a secondary battery, more specifically a non-aqueous electrolyte secondary battery such as a lithium-ion secondary battery. The energy storage element 10 is used as a battery for driving or starting the engine of mobile vehicles such as automobiles, motorcycles, watercraft, ships, snowmobiles, agricultural machinery, construction machinery, automated guided vehicles (AGVs), or railway vehicles for electric railways. Examples of automobiles include electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and fossil fuel (gasoline, diesel, liquefied natural gas, etc.) vehicles. Examples of railway vehicles for electric railways include electric trains, monorails, maglev trains, and hybrid trains equipped with both diesel engines and electric motors. The energy storage element 10 can also be used as a stationary battery for household or commercial use.

[0027] The energy storage element 10 is not limited to a non-aqueous electrolyte secondary battery, but may be a secondary battery other than a non-aqueous electrolyte secondary battery, or a capacitor. The energy storage element 10 may also be a primary battery.

[0028] As shown in Figure 1, the energy storage element 10 comprises a container 100 and a pair of terminals 200 (positive and negative). As shown in Figure 2, a pair of current collectors 300 and electrode bodies 400 (positive and negative) are housed inside the container 100.

[0029] In addition to the components described above, the energy storage element 10 may also include a spacer positioned to the side of the current collector 300, a gas release valve for releasing pressure when the pressure inside the container 100 rises, and an insulating film that encloses the electrode body 400, etc. An electrolyte (non-aqueous electrolyte) is sealed inside the container 100, but this is not shown in the illustration. There are no particular restrictions on the type of electrolyte as long as it does not impair the performance of the energy storage element 10, and various types can be selected.

[0030] The container 100 comprises a rectangular cylindrical container body 110 with a bottom, and a lid 120 that closes the opening of the container body 110. The container body 110 comprises a bottom wall 111, a pair of first wall portions 112, and a pair of second wall portions 113. The bottom wall 111 is a rectangular flat plate portion with the X-axis direction as its longitudinal direction. The pair of first wall portions 112 are rectangular flat plate portions extending in the Z-axis direction from each long side of the bottom wall 111. The pair of second wall portions 113 are rectangular flat plate portions extending in the Z-axis direction from each short side of the bottom wall 111. Each first wall portion 112 and each second wall portion 113 are integrated into a rectangular cylindrical shape. The lid 120 is a rectangular flat plate with the X-axis direction as its longitudinal direction. Although not shown in the illustration, a liquid pouring port is formed in the lid 120. The liquid injection port is a part used to inject electrolyte into the container 100 during the manufacturing of the energy storage element 10, and is closed after injection.

[0031] After the electrode body 400 and the like are placed inside the container 100, the inside of the container 100 is sealed by joining the lid 120 and the container body 110 by welding or other means. The material of the container body 110 and the lid 120 is not particularly limited, but it is preferable that they be made of a weldable metal such as stainless steel, aluminum, aluminum alloy, iron, or plated steel sheet.

[0032] Terminal 200 is an electrode terminal electrically connected to the electrode body 400 via the current collector 300. That is, the positive terminal 200 is electrically connected to the positive electrode plate of the electrode body 400 via the current collector 300, and the negative terminal 200 is electrically connected to the negative electrode plate of the electrode body 400 via the current collector 300. Terminal 200 is attached to a cover 120 positioned above the electrode body 400 via an insulating gasket (not shown).

[0033] [Electrode body] Figure 3 is a perspective view showing an overview of the configuration of the electrode body 400 according to the embodiment. In Figure 3, elements such as the laminated and wound electrode plate 401 are partially unfolded and shown. In Figure 3, only some of the multiple protrusions 480 on the electrode plate 401 are schematically represented. The winding axis W shown in Figure 3 is a hypothetical axis that serves as the central axis when winding the electrode plate 401, etc.

[0034] As shown in Figure 3, the electrode body 400 comprises two electrode plates 401 and two separators 430, and is an energy storage element (power generation element) capable of storing electricity. In this embodiment, the electrode body 400 is a wound-type electrode body formed by winding two electrode plates 401 and two separators 430 without a winding core, but it may also be a wound-type electrode body wound around a winding core. As shown in Figure 3, the electrode body 400 has a flattened shape in the direction perpendicular to the winding axis W. That is, when viewed from the direction of the winding axis W, the electrode body 400 has an overall oval shape, with the oval straight portion being flat and the oval curved portion being curved. For this reason, the electrode body 400 comprises a pair of opposing turn portions 402 (curved portions that face each other in the longitudinal direction of the oval shape, with the winding axis W in between) and a flat portion 403 which is the portion between the pair of turn portions 402. The flat section 403 is the part that connects the pair of turned sections 402.

[0035] In this embodiment, the electrode body 400 comprises two electrode plates 401, a positive electrode plate 410 which is the positive electrode plate 401, and a negative electrode plate 420 which is the negative electrode plate 401. The positive electrode plate 410 is an electrode plate in which a first active material layer 414 of the positive electrode is formed on at least one of the front and back surfaces of a long, strip-shaped metal foil current collector foil 411. The negative electrode plate 420 is an electrode plate in which a second active material layer 424 of the negative electrode is formed on at least one of the front and back surfaces of a long, strip-shaped metal foil current collector foil 421. More specifically, the positive electrode plate 410 comprises a formed portion 415 in which the first active material layer 414 is formed, and a non-formed portion 416 in which the first active material layer 414 is not formed. The non-formed portion 416 is the portion in which the positive electrode current collector foil 411 is exposed. The negative electrode plate 420 comprises a formed portion 425 on which the second active material layer 424 is formed, and a non-formed portion 426 on which the second active material layer 424 is not formed. The non-formed portion 426 is the portion where the current collector foil 421 of the negative electrode is exposed.

[0036] The positive electrode current collector foil 411 is made of aluminum or an aluminum alloy, etc. The negative electrode current collector foil 421 is made of copper or a copper alloy, etc. The first active material layer 414 includes a positive electrode active material, a binder, and a conductive material, etc. The second active material layer 424 includes a negative electrode active material, a binder, and a thickener, etc. As the positive electrode active material and the negative electrode active material, any known material can be used as long as it is a material capable of intercalating and releasing charge transport ions.

[0037] The positive electrode active material contains at least a Ni-containing oxide. The Ni-containing oxide is a compound in which the molar ratio of Ni at the transition metal sites is 25% or more. For example, it is a compound represented by the chemical formula LiNiMO2 (where M is one or more metal elements selected from Mn, Co, Al, etc.). In addition to the Ni-containing oxide, other known active materials can also be used as the positive electrode active material by mixing them so that the proportion of the Ni-containing oxide is 50% by mass or more.

[0038] The negative electrode active material contains at least Si (silicon). Examples of Si-containing active materials include Si, Si alloys, Si oxides such as SiO, SiC, and Si-carbon composites (such as porous carbon filled with Si). In addition to Si-containing active materials, known active materials other than Si-containing active materials can also be used as the negative electrode active material by mixing them so that the proportion of Si-containing active material is 5% by mass or more.

[0039] The separator 430 is a microporous sheet made of resin. Any known material can be used for the separator 430, as long as it does not impair the performance of the energy storage element 10. For example, the separator 430 can be a woven fabric, a nonwoven fabric, or a synthetic resin microporous membrane made of polyolefin resin such as polyethylene, which is insoluble in organic solvents.

[0040] In this embodiment, the electrode body 400 has a positive electrode plate 410 and a negative electrode plate 420 wound around each other via a separator 430, offset from each other in the winding axis direction. The positive electrode plate 410 and the negative electrode plate 420 have portions (unformed portions 416, 426) at their respective offset ends where the active material layer is not formed and the current collector foil is exposed. In other words, the electrode body 400 has a positive electrode connection portion 456 formed by winding and stacking the unformed portion 416 at one end in the winding axis direction. The electrode body 400 has a negative electrode connection portion 466 formed by winding and stacking the unformed portion 426 at the other end in the winding axis direction. The positive electrode connection portion 456 is joined to the positive electrode current collector 300, and the negative electrode connection portion 466 is joined to the negative electrode current collector 300 (see Figure 2). As a result, the positive terminal 200 and the positive electrode connection portion 456 of the electrode body 400 are electrically connected via the positive electrode current collector 300. The negative terminal 200 and the negative electrode connection portion 466 of the electrode body 400 are electrically connected via the negative electrode current collector 300.

[0041] Figure 4 is a cross-sectional view showing the electrode body 400 according to the embodiment housed in the container 100. As shown in Figure 4, when the electrode body 400 is housed in the container 100, the winding axis W is arranged parallel to the X-axis direction. In this state, the flat portion 403 of the electrode body 400 is sandwiched between a pair of first wall portions 112. Since there is no winding core in the central part of the electrode body 400, a linear slit 409 extending in the Z-axis direction is provided between the innermost electrode plates 401 of the electrode body 400. The slit 409 is continuous throughout the entire electrode body 400 along the winding axis direction (X-axis direction).

[0042] [Multiple protrusions on the electrode plate] In the energy storage element 10 configured as described above, the electrode plate 401 provided on the electrode body 400 is provided with a plurality of protrusions 480 that project in the thickness direction. Specifically, as shown in Figure 3, each electrode plate 401 (positive electrode plate 410 and negative electrode plate 420) has a plurality of protrusions 480 on the forming portions 415 and 425. Each protrusion 480 is a point-shaped protrusion. The plan view shape of each protrusion 480 may be circular, elliptical, oblong, or polygonal.

[0043] Figure 5A is a cross-sectional view showing a protrusion 480 according to the embodiment. Here, a positive electrode plate 410 is used as an example for the electrode plate 401, but the same applies to a negative electrode plate 420. Furthermore, although an example is given in which an active material layer 414 is formed on both the front and back surfaces of the current collector foil 411, the active material layer 414 may be formed on only one of the front or back surfaces of the current collector foil 411.

[0044] As shown in Figure 5A, the protrusions 480 are formed by embossing the electrode plate 401. Because the protrusions 480 are point-like protrusions, each protrusion 480 can be easily formed using embossing. As the protrusions 480 are formed by embossing, the protrusions 480 are formed on the surface of the electrode plate 401, and recesses 481 corresponding to the protrusions 480 are formed on the back surface of the electrode plate 401. Specifically, the recesses 481 are formed in the first active material layer 414 on the back side of the electrode plate 401, and the protrusions 480 are formed in the first active material layer 414 on the front side. The cross-sectional shape of the protrusions 480 is not limited to this.

[0045] Figure 5B is a cross-sectional view showing a modified example of the protrusion 480 according to the embodiment. In Figure 5B, the first active material layer 414 on the back side of the current collector foil 411 of the electrode plate 401 is flat, but a protrusion 480b is formed on the first active material layer 414 on the front side.

[0046] Figure 6 is a partial cross-sectional view of a portion of the electrode plate 401 that forms the vicinity of the turn portion 402 according to the embodiment. In Figure 6, each protrusion 480 is exaggerated compared to its actual size in order to make it easier to understand. As shown in Figure 6, the turn portion 402 is formed in a semicircular shape in cross-section. In the turn portion 402, a gap is formed between each electrode plate 401 and the separator 430 due to each protrusion 480 and recess 481.

[0047] As shown in Figures 3 and 6, the multiple protrusions 480 are positioned on each electrode plate 401 at locations corresponding to the turn portion 402, and not at locations corresponding to the flat portion 403. Thus, the area occupied by the protrusions 480 in the flat portion 403 is zero, and therefore, the area occupied per unit area of ​​the protrusions 480 in the turn portion 402 is larger than the area occupied per unit area of ​​the protrusions 480 in the flat portion 403. The occupied area is the area of ​​the protrusions 480 within a unit area in the turn portion 402 or the flat portion 403 (if there are multiple protrusions 480, it is the sum of the areas of each protrusion 480). Also, the unit area in the turn portion 402 and the unit area in the flat portion 403 are the same area.

[0048] In each turn section 402, the multiple protrusions 480 are arranged generally evenly along the entire winding axis direction of the forming sections 415 and 425. The layout of the multiple protrusions 480 can be anything as long as they are evenly distributed, but examples include a square grid or a triangular grid. Figure 3 shows the case where the multiple protrusions 480 are distributed in a square grid, but if the multiple protrusions 480 are distributed in a triangular grid, the protrusions 480 can be arranged more densely, which is preferable from the viewpoint of increasing the voids caused by the protrusions, as will be discussed later.

[0049] [Manufacturing method for energy storage elements] Next, a method for manufacturing an energy storage element will be described. Figure 7 is a block diagram showing an energy storage element manufacturing apparatus 500 according to an embodiment. The manufacturing apparatus 500 shown in Figure 7 is used to manufacture an energy storage element, and an energy storage element 10 is produced. As shown in Figure 7, the manufacturing apparatus 500 includes an assembly section 510, a housing section 520, a container welding section 530, a liquid injection section 540, a compression section 545, a charging section 550, and a control section 560.

[0050] The assembly unit 510 assembles the terminals 200, current collector 300, gasket, and electrode body 400 onto the cover 120 to form an assembly. The assembly unit 510 includes at least one arm device for gripping and assembling the cover 120, terminals 200, current collector 300, gasket, and electrode body 400, a welding device for welding the current collector 300 to the electrode body 400, a crimping device for crimping the terminals 200 to the current collector 300, and the like.

[0051] The housing section 520 assembles the assembly into the container body 110 so that the current collector 300 and the electrode body 400 are housed inside the container body 110. At this time, the housing section 520 houses the electrode body 400 inside the container body 110 in a position where the flat portion 403 is sandwiched between a pair of first wall portions 112 of the container body 110. The housing section 520 is equipped with a fixing portion for fixing the container body 110, an arm portion for gripping and assembling the assembly relative to the fixed container body 110, and the like.

[0052] The container welding section 530 welds the container body 110 and the lid 120 together, sealing the container 100. The container welding section 530 includes a laser welding section for welding the container body 110 and the lid 120, a movable section for moving the laser welding section along the joint surface between the container body 110 and the lid 120, and the like.

[0053] The liquid injection unit 540 pours the electrolyte into the liquid injection port of the container 100 to fill the container 100 with electrolyte, and then seals the liquid injection port of the container 100. The liquid injection unit 540 is equipped with a liquid injection nozzle for pouring the electrolyte into the liquid injection port of the container 100, a sealing unit for plugging and closing the liquid injection port of the container 100, and so on. The energy storage element 10 is then completed.

[0054] The compression part 545 compresses the pair of first wall portions 112 of the container 100 by gripping them in the opposing direction (Y-axis direction). Figure 8 is an explanatory diagram showing the state in which the container 100 is compressed by the compression part 545 according to the embodiment. As shown in Figure 8, the compression part 545 is equipped with a pair of gripping parts 546 that can be opened and closed in the Y-axis direction. The pair of gripping parts 546 compress the pair of first wall portions 112 of the container 100 by gripping them in the Y-axis direction (see arrow Yc). Due to the compression by each gripping part 546, in the flat portion, the electrode plates 401 that form the innermost circumference of the electrode body 400 are arranged directly or indirectly without any gaps. Here, if no other member (such as a separator 430) is provided between the electrode plates 401 that form the innermost circumference of the electrode body 400, the electrode plates 401 will be in close contact with each other due to the compression and there will be no gaps. This case is included in the statement "the electrode plates 401 are directly and without gaps between them."

[0055] On the other hand, when a separator 430 is provided between the innermost electrode plates 401 of the electrode body 400, the electrode plates 401 and the separator 430 are pressed together, eliminating any gaps. Furthermore, in the case of an electrode body 400 equipped with a winding core, this includes a configuration in which the electrode plates 401 and the winding core are pressed together, eliminating any gaps, and a configuration in which the electrode plates 401, the separator 430, and the winding core are pressed together, eliminating any gaps. These cases are included in "the electrode plates 401 are indirectly arranged without gaps."

[0056] The pair of gripping portions 546 are positioned opposite the flat portion 403 of the electrode body 400. Specifically, the Z-axis positive end of each gripping portion 546 is positioned further in the Z-axis positive direction than the Z-axis positive end of the flat portion 403, and the Z-axis negative end of each gripping portion 546 is positioned further in the Z-axis negative direction than the Z-axis negative end of the flat portion 403. This allows the entire area of ​​the formed portions 415 and 425 in the flat portion 403 to be compressed, and the expansion of the flat portion 403 can be more reliably suppressed by each gripping portion 546.

[0057] The pair of gripping portions 546 only need to be able to compress more than half of the area of ​​the formed portions 415 and 425 on the flat portion 403, but as described above, it is preferable that they can compress the entire area of ​​the formed portions 415 and 425 on the flat portion 403.

[0058] The charging unit 550 pre-charges the energy storage element 10 that has been compressed by the compression unit 545. Pre-charging includes not only charging once before shipment, but also charging after repeated charging and discharging. The charging unit 550 includes a power supply unit that supplies power to the energy storage element 10. When discharging is performed, the charging unit 550 includes a charge / discharge unit that charges and discharges the energy storage element 10 instead of the power supply unit.

[0059] The control unit 560 is equipped with a CPU, RAM, ROM, etc., and controls the assembly unit 510, housing unit 520, container welding unit 530, liquid injection unit 540, compression unit 545, and charging unit 550 by having the CPU load a program stored in the ROM into the RAM and execute it. The program causes each unit to execute a method for manufacturing the energy storage element.

[0060] The control unit 560 controls the assembly unit 510 to assemble the terminals 200, current collector 300, gasket, and electrode body 400 onto the cover 120, thereby forming the assembly.

[0061] Subsequently, the control unit 560 controls the housing unit 520 to assemble the assembly into the container body 110 so that the current collector 300 and electrode body 400 are housed inside the container body 110. At this time, the housing unit 520 houses the electrode body 400 inside the container body 110 in a position where the flat portion 403 is sandwiched between a pair of first wall portions 112 of the container body 110. Next, the control unit 560 controls the container welding unit 530 to weld the container body 110 and the lid 120 together, sealing the container 100. Next, the control unit 560 controls the liquid injection unit 540 to pour electrolyte into the liquid injection port of the container 100 to fill the container 100 with electrolyte, and then seals the liquid injection port of the container 100. Next, the control unit 560 controls the compression unit 545 to grip the container 100 of the energy storage element 10 with the compression unit 545 and compress it. Next, the control unit 560 controls the charging unit 550 to pre-charge the compressed energy storage element 10.

[0062] During pre-charging, the electrode body 400 expands. Assuming an electrode body 400 without a protrusion 480 on the electrode plate 401, there is no void in the turned portion 402, so there is no place for stress to escape. In addition, the flat portion 403 is compressed, so not only is the rigidity of the flat portion 403 increased, but it is also in close contact with the container 100. When stress due to expansion occurs inside the electrode body 400, the stress concentrates at the boundary (starting point of the turned portion 402) between the flat portion 403, which is in close contact with the container 100 and has high rigidity, and the turned portion 402, which has no place for stress to escape (see dashed arrow Y10 shown in Figure 8). This stress concentration at the starting point of the turned portion 402 can cause fracture in the electrode plate 401 (positive electrode plate 410 and negative electrode plate 420). In particular, the first active material layer 414 containing Ni oxide expands relatively large, and the second active material layer 424 containing Si also expands relatively large. In other words, the overall expansion of the electrode body 400 is also increased, making the electrode plate 401 more prone to fracture.

[0063] In contrast, the electrode body 400 of this embodiment is provided with multiple protrusions 480 on the turn portion 402. That is, because each protrusion 480 is present on the turn portion 402, the stress caused by the expansion of the electrode body 400 is absorbed by the deformation and reduction of each protrusion 480 on the turn portion 402, or by the reduction of the void. This suppresses the concentration of stress at the starting point of the turn portion 402.

[0064] [Effects, etc.] As described above, according to this embodiment, the forming portions 415 and 425 of the electrode plate 401 are formed with a first active material layer 414 containing a Ni-containing oxide with a relatively large expansion amount or a second active material layer 424 containing Si. Furthermore, protrusions 480 are arranged on the forming portions 415 and 425 of the turn portion 402 of the electrode body 400. These protrusions 480 create a gap between the electrode plates 401 in the turn portion 402. When the turn portion 402 expands, stress is absorbed by this gap, so stress is less likely to concentrate at the starting point of the turn portion 402, and fracture of the electrode plate 401 can be suppressed. Therefore, a reliable energy storage element 10 can be provided.

[0065] Because the area occupied by the protrusions 480 in the turned section 402 is larger than the area occupied by the protrusions 480 in the flat section 403, the gaps between the electrode plates 401 can be suppressed in the flat section 403. As a result, the electrode plates 401 can be densely stacked in the flat section 403, making it possible to increase the energy density.

[0066] In particular, since the area occupied by the protrusions 480 in the flat section 403 is zero, the gap between the electrode plates 401 can be further suppressed in the flat section 403. As a result, the electrode plates 401 can be stacked more densely in the flat section 403, making it possible to further increase the energy density.

[0067] Since a protrusion 480 is formed on both the forming portion 415 of the positive electrode plate 410, which has a first active material layer 414 containing a Ni-containing oxide, and the forming portion 425 of the negative electrode plate 420, which has a second active material layer 424 containing Si, the number of protrusions 480 and voids arranged in the turn portion 402 can be increased. As a result, the stress during expansion of the electrode body 400, which has a relatively large expansion amount for the first active material layer 414 and the second active material layer 424, can be absorbed more reliably.

[0068] (modified version) The following describes various modifications of the above embodiments. In the following description, parts identical to those in the above embodiments or other modifications may be denoted by the same reference numerals and their descriptions may be omitted.

[0069] [Example 1] In the above embodiment, an electrode body 400 was shown in which protrusions 480 are provided on both the positive electrode plate 410 and the negative electrode plate 420. In this modified example 1, an electrode body 400a in which protrusions 480 are provided only on the positive electrode plate 410 will be described. Figure 9 is a partial cross-sectional view taken from a part of the vicinity of the turn portion 402a of the electrode body 400a according to modified example 1. Figure 9 corresponds to Figure 6.

[0070] As shown in Figure 9, the positive electrode plate 410 has multiple protrusions 480 in the area corresponding to the turn portion 402a, but the negative electrode plate 420a does not have multiple protrusions 480 in the area corresponding to the turn portion 402a. In other words, the negative electrode plate 420a does not have protrusions 480 throughout its entirety. Thus, even though the negative electrode plate 420a does not have protrusions 480, the protrusions 480 of the positive electrode plate 410 allow a gap to be created between the positive electrode plate 410 and the negative electrode plate 420a in the turn portion 402a.

[0071] [Differentiation 2] In the above embodiment, an example was given in which no protrusion 480 is formed on the flat portion 403 of the electrode plate 401. In this modified example 2, an electrode body 400b in which a protrusion 480b is formed on the flat portion 403b of the electrode plate 401b will be described. Figure 10 is a partial cross-sectional view taken from a part of the vicinity of the turned portion 402b of the electrode body 400b according to the modified example 2. Figure 10 corresponds to Figure 6.

[0072] As shown in Figure 10, each electrode plate 401b (positive electrode plate 410b and negative electrode plate 420b) has multiple protrusions 480b evenly distributed throughout. Therefore, the area occupied per unit area of ​​the protrusions 480b in the turned section 402b is equal to the area occupied per unit area of ​​the protrusions 480b in the flat section 403b. In this way, since the area occupied by the protrusions 480b in the turned section 402b is equal to the area occupied by the protrusions 480b in the flat section 403b, the protrusions 480b can be formed evenly across the entire electrode plate 401b. Thus, an electrode body 400b equipped with protrusions 480b can be easily manufactured.

[0073] [Difference 3] In the above embodiment, an electrode body 400 having a semicircular turn portion 402 was illustrated. However, the shape of the turn portion 402 can be anything. This modified example 3 describes an example of another shape of the turn portion. Figure 11 is a partial cross-sectional view of a part of the electrode body 400c near the turn portion 402c according to modified example 3. Figure 11 corresponds to Figure 6. As shown in Figure 11, the turn portion 402c of the electrode body 400c has a shape that is flattened in the Z-axis direction from a semicircular shape.

[0074] (others) Although an embodiment of the present invention (including its modifications; the same applies hereinafter) of an energy storage element has been described above, the present invention is not limited to the above embodiments. The embodiments disclosed herein are illustrative in all respects, and the scope of the present invention includes all modifications in the sense and scope equivalent to the claims. Configurations constructed by arbitrarily combining the components included in the above embodiments and their modifications are also included in the scope of the present invention.

[0075] In the above embodiment, the case in which the first active material layer 414 of the positive electrode plate 410 contains a Ni-containing oxide and the second active material layer 424 of the negative electrode plate 420 contains Si was illustrated. However, the first active material layer 414 of the positive electrode plate 410 does not have to contain a Ni-containing oxide, and the second active material layer 424 of the negative electrode plate 420 does not have to contain Si. The first active material layer 414 of the positive electrode plate 410 does not have to contain a Ni-containing oxide, and the second active material layer 424 of the negative electrode plate 420 does contain Si.

[0076] In the above embodiment, the example shown is that the electrode body 400 is housed in the container 100 with the winding axis W parallel to the X-axis direction. However, the electrode body 400 may also be housed in the container 100 with the winding axis W parallel to the Z-axis direction.

[0077] In the above embodiment, an example was given in which pre-charging is performed with the container 100 of the energy storage element 10 being compressed by the compression part 545. However, if the pair of first wall portions 112 of the container 100 have sufficient rigidity to not deform even if the electrode body 400 expands, the compression by the compression part 545 can be omitted. In other words, the pair of first wall portions 112 compress the flat portion 403 of the electrode body 400. When compressed, it is sufficient that the electrode plates 401 forming the innermost circumference of the electrode body 400 are arranged directly or indirectly without any gaps. Even in this case, since the convex portion 480 is arranged on the turn portion 402 of the electrode body 400, the convex portion 480 creates a gap between the electrode plates 401 in the turn portion 402. When the turn portion 402 expands, the stress is absorbed by this gap, so stress is less likely to concentrate in the turn portion 402, and the fracture of the electrode plates 401 can be suppressed. [Industrial applicability]

[0078] This invention can be applied to energy storage elements such as lithium-ion secondary batteries. [Explanation of Symbols]

[0079] 10 Energy storage elements 100 containers 110 Container body 111 Bottom wall 112 First wall (wall) 113 Second wall 120 Lid 200 terminals 300 Current collector 400, 400a, 400b, 400c electrode bodies 401, 401b plate 402, 402a, 402b, 402c Turn section 403, 403b flat part 409 Slit 410, 410b positive electrode plate 411, 421 Current collector foil 414 First active material layer 415, 425 forming part 416, 426 Non-formed part 420, 420a, 420b negative electrode plate 424 Second active material layer 430 Separator 456 Positive electrode connection 466 Negative electrode connection 480, 480b, 480c convex part 481 recess 500 Manufacturing equipment 510 Assembly Department 520 Storage Unit 530 Container weld 540 Injection section 545 Compression area 546 Gripping part 550 Live part 560 Control Unit W winding shaft Y10 Dashed arrow

Claims

1. The system comprises an electrode body with an electrode plate wound around it, and a container for housing the electrode body. The electrode plate comprises a forming portion on which a first active material layer containing a Ni-containing oxide or a second active material layer containing Si is formed. The electrode body comprises a pair of turned portions and a flat portion connecting the pair of turned portions. The forming portion includes a protrusion that protrudes in the thickness direction of the electrode plate, The aforementioned protrusion is located at least on the turn portion. Energy storage element.

2. The area occupied per unit area of ​​the protrusion in the turn portion is larger than the area occupied per unit area of ​​the protrusion in the flat portion. The energy storage element according to claim 1.

3. The area occupied by the protrusion in the flat portion is zero. The energy storage element according to claim 2.

4. The area occupied per unit area of ​​the protrusion in the turn portion is equivalent to the area occupied per unit area of ​​the protrusion in the flat portion. The energy storage element according to claim 1.

5. The aforementioned electrode plate comprises a positive electrode plate and a negative electrode plate. The first active material layer is formed on the formed portion of the positive electrode plate. The second active material layer is formed in the formed portion of the negative electrode plate. The protrusions are formed on the formed portion of the positive electrode plate and on the formed portion of the negative electrode plate. The energy storage element according to any one of claims 1 to 4.

6. The container comprises a pair of wall portions sandwiching the flat portion, The pair of wall portions are pressing against the flat portion, The electrode plates forming the innermost circumference of the flat portion are arranged directly or indirectly without any gaps between them. The energy storage element according to any one of claims 1 to 4.

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