Electrode body and storage element

Abstract

An electrode body (14) comprises: an active material layer including an electrode active material and an electrolytic solution; an electrode conductor (12a) having (i) a first region (121) where the active material layer is located and (ii) a second region (122) that is a region different from the first region and that is a region to which a connection terminal can be electrically connected; and a resistive portion (123) located closer to the second region than the first region of the electrode conductor and exhibiting a higher resistance than the first region to movement of the electrolytic solution along the surface of the electrode conductor.

Description

[Technical Field]

[0001] The present disclosure relates to an electrode assembly and an energy storage device including the electrode assembly. [Background technology]

[0002] Patent Document 1 discloses an example of an electrochemical cell. The electrochemical cell includes (i) a first current collector bonded to a first portion of a pouch, and (ii) a second current collector bonded to a second portion of the pouch. A first electrode material is disposed on the first current collector. A second electrode material is disposed on the second current collector. The electrochemical cell further includes a separator disposed between the first electrode material and the second electrode material. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US2019 / 0326562 Summary of the Invention

[0004] An electrode body according to one embodiment of the present disclosure comprises an active material layer containing an electrode active material and an electrolyte solution, an electrode conductor having (i) a first region in which the active material layer is located, and (ii) a second region separate from the first region and capable of electrically connecting a connection terminal, and a resistance portion located closer to the second region than the first region of the electrode conductor and exhibiting a higher resistance than the first region to the movement of the electrolyte solution along the surface of the electrode conductor on the side where the active material layer is located. [Brief explanation of the drawings]

[0005] [Figure 1] 1 is a perspective view showing the appearance of a secondary battery according to the present disclosure. [Figure 2] FIG. 1 is a perspective view showing the appearance of a unit cell according to the present disclosure. [Figure 3]FIG. 2 is an exploded model diagram showing a cross section taken along line III-III in FIG. [Figure 4] FIG. 4 is an exploded model diagram showing a cross section taken along line IV-IV in FIG. [Figure 5] FIG. 2 is a model diagram showing a specific structure of an electrode body. [Figure 6] 1 is a plan view showing the structure of the negative electrode provided in the electrode body according to the present disclosure in the vicinity of an exposed portion. FIG. [Figure 7] FIG. 10 is a diagram showing the movement of an electrolyte in an electrode conductor of a negative electrode that does not include a resistance portion. [Figure 8] 1A and 1B are diagrams showing examples of cross sections of an electrode conductor included in a negative electrode according to the present disclosure. [Figure 9] FIG. 10 is a cross-sectional view showing an outline of a resistor portion according to a first modified example. [Figure 10] FIG. 10 is a cross-sectional view showing an outline of a resistor portion according to a second modified example. [Figure 11] FIG. 10 is a plan view showing a modified example of a unit cell including a negative electrode according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0006] [Configuration of secondary battery] FIG. 1 is a perspective view showing the appearance of a secondary battery 1. The secondary battery 1 is a battery that can be charged or discharged by being electrically connected to an external terminal. For example, at least one secondary battery 1 may be mounted in an electricity storage device for use in a home, a base station, an automobile, a robot such as a drone, or a medical device. The secondary battery 1 may include a unit cell 10 (energy storage element), connection terminals 21 and 22, and a second housing 50. The configuration of the unit cell 10 will be described later.

[0007] The second housing 50 may house the unit cells 10. The second housing 50 may be formed of, for example, an aluminum pouch film or a laminate film having a metal foil layer such as stainless steel or nickel. The aluminum pouch film may be a film on which aluminum is vapor-deposited, or a film laminated with aluminum foil. The film material may be, for example, polypropylene, polyethylene, nylon, or polyethylene terephthalate. The thickness of the second housing 50 may be 50 μm or more and 300 μm or less, for example, 200 μm.

[0008] When the second housing 50 is an aluminum pouch film, the second housing 50 may have a configuration in which two aluminum pouch films are located on both sides in the stacking direction (Z-axis direction) of the unit cell 10. Furthermore, when the second housing 50 is an aluminum pouch film, the second housing 50 may have a configuration in which one aluminum pouch film is folded in half and the unit cell 10 is located inside it.

[0009] The connection terminals 21 and 22 may be terminals that are connected to external terminals in order to extract power from or supply power to the secondary battery 1. The connection terminals 21 and 22 may protrude from the inside to the outside of the second housing 50. The connection terminals 21 and 22 may be made of, for example, copper, aluminum, or nickel. The connection terminals 21 and 22 may have a thickness of 50 μm or more and 500 μm or less, for example, 200 μm. The connection terminals 21 and 22 may also be subjected to a surface treatment to improve adhesion to an adhesive member (not shown). The adhesive member bonds the connection terminals 21 and 22 to the second housing 50 located above and below the connection terminals 21 and 22 to determine the positions of the connection terminals 21 and 22 relative to the second housing 50.

[0010] 2 is a perspective view showing the appearance of the unit cell 10. As shown in FIG. 2, the unit cell 10 may include an electrode assembly 14 and a first housing 15 (housing). The electrode assembly 14 may have a sheet-like shape. The sheet-like electrode assembly 14 may include a positive electrode 11 and a negative electrode 12.

[0011] The first housing 15 may house the electrode assembly 14. The first housing 15 may have its periphery sealed while housing the electrode assembly 14. When a plurality of first housings 15 housing the electrode assembly 14 are stacked, the plurality of first housings 15 may be adhered to each other by an adhesive layer (not shown). The material of the first housing 15 may be, for example, a film-like polyethylene terephthalate (PET) or nylon. More specifically, for example, two first housings 15 may be configured to be located on both sides in the stacking direction (Z-axis direction) of the unit cells 10. The thickness of the base material of the first housing 15 may be, for example, 10 μm or more and 40 μm or less, for example, 25 μm. The material of the adhesive layer may be, for example, polypropylene or polyethylene.

[0012] The first housing 15 may be transparent, for example. Figure 2 is a diagram showing how the electrode assembly 14 can be seen through the first housing 15 by using a transparent first housing 15 for the unit cell 10.

[0013] The first housing 15 may have a cutout 16. For example, the cutout 16 may be provided in both the first housing 15 on the positive electrode 11 side and the first housing 15 on the negative electrode 12 side. By providing the cutout 16 as an unsealed portion in a portion of the unit cell 10, gas generated by a decomposition reaction of the electrolyte or a trace amount of water inside the unit cell 10 can be released to the outside of the unit cell 10. Furthermore, by providing the cutout 16, a configuration may be adopted in which a portion on the positive electrode 11 side and a portion on the negative electrode 12 side are exposed from the first housing 15. Alternatively, a configuration may be adopted in which a portion on the positive electrode 11 side and a portion on the negative electrode 12 side are not exposed from the first housing 15. In the latter case, the internal space on the positive electrode 11 side of the unit cell 10 may be connected to the external space of the unit cell 10, and the internal space on the negative electrode 12 side of the unit cell 10 may be connected to the external space of the unit cell 10. Furthermore, the first housing 15 on the negative electrode 12 side may be exposed at the position of the cutout 16 on the positive electrode 11 side, and the first housing 15 on the positive electrode 11 side may be exposed at the position of the cutout 16 on the negative electrode 12 side.

[0014] The positive electrode 11 may have an exposed portion 11e exposed from the first housing 15. The negative electrode 12 may have an exposed portion 12e exposed from the first housing 15. Specifically, the exposed portions 11e, 12e protrude from the first housing 15. The connection terminals 21 and 22 may be electrically connected to the exposed portions 11e and 12e, respectively, by, for example, ultrasonic welding, laser welding, or resistance welding. The positive electrode 11 and the negative electrode 12 will be described in detail later.

[0015] The secondary battery 1 may have a configuration in which a unit cell 10, in which the positive electrode 11 and the negative electrode 12 are housed in a first housing 15, is further housed in a second housing 50. With this configuration, the electrode assembly 14 is housed doubly, thereby improving the safety of the secondary battery 1. The second housing 50 may also be housed in an additional housing. However, the secondary battery 1 only needs to include the positive electrode 11 and the negative electrode 12, and only needs to be housed in at least one housing.

[0016] In the first embodiment, the secondary battery 1 has a configuration in which a plurality of unit cells 10 are stacked, for example, ten layers of unit cells 10 are stacked. However, the secondary battery 1 according to the present disclosure may have a plurality of layers of unit cells 10 other than ten, or may have only one layer. When the secondary battery 1 has a plurality of layers of unit cells 10, the unit cells 10 may be stacked. When the secondary battery 1 shown in FIG. 1 is viewed from above, the portion excluding the connection terminals 21 and 22 may be substantially rectangular or may have a different shape. When the unit cell 10 shown in FIG. 2 is viewed from above, the portion excluding the exposed portions 11e and 12e may be substantially rectangular or may have a different shape.

[0017] Fig. 3 is a model diagram showing an exploded cross section taken along line III-III in Fig. 1. Fig. 4 is a model diagram showing an exploded cross section taken along line IV-IV in Fig. 1. For simplicity, the second container 50 is omitted from Figs. 3 and 4. Figs. 3 and 4 mainly show the positional relationship of each component. Therefore, the thickness relationships of each component are not necessarily as shown in Figs. 3 and 4.

[0018] As shown in FIGS. 3 and 4, the secondary battery 1 may further include a first protective member 30. The first protective member 30 may protect a first connection portion electrically connecting the exposed portions 11e exposed from the first housing 15 of each unit cell 10 to each other, and a second connection portion electrically connecting the exposed portions 12e exposed from the first housing 15 of each unit cell 10 to each other. The exposed portions 11e and the exposed portions 12e may be connected to each other by, for example, ultrasonic welding, laser welding, or resistance welding. Although the exposed portions 11e of the positive electrode 11 and the exposed portions 12e of the negative electrode 12 are not connected to each other in FIGS. 3 and 4 , they are actually connected as described above.

[0019] The material of the first protective member 30 may be, for example, a film-like polyolefin or polyimide. The first protective member 30 may be adhered to the exposed portions 11e and 12e by an adhesive layer (not shown). The material of the adhesive layer of the first protective member 30 may be any material that is not easily dissolved in the electrolytic solution (electrolyte). The material of the adhesive layer may be, for example, an acrylic adhesive.

[0020] In this embodiment, the first protective member 30 may cover the first and second connecting portions and a portion of the first housing 15. This makes it difficult for stress concentration to occur when stress occurs in the exposed portion 11e or 12e, thereby reducing the possibility of the exposed portion 11e or 12e being damaged or broken near the first and second connecting portions. However, it is sufficient for the first protective member 30 to protect at least the first and second connecting portions, and it is not necessary for the first protective member 30 to cover the first and second connecting portions and a portion of the first housing 15.

[0021] 3 and 4, the positive electrode 11 may have an electrode conductor 11a and a positive electrode active material layer 11b, and the negative electrode 12 may have an electrode conductor 12a and a negative electrode active material layer 12b.

[0022] The electrode conductor 11a may be, for example, an aluminum foil. The thickness of the electrode conductor 11a may be 5 μm or more and 25 μm or less, for example, 10 μm. The electrode conductor 12a may be, for example, a copper foil. The thickness of the electrode conductor 12a may be 5 μm or more and 25 μm or less, for example, 10 μm.

[0023] FIG. 5 is a cross-sectional view showing a specific structure of the electrode body 14. As shown in FIG. 5, the positive electrode active material layer 11b (active material layer) may be a layer of a positive electrode material that is a mixture of a positive electrode active material 11c (electrode active material) and a conductive additive 11d. The negative electrode active material layer 12b (active material layer) may be a layer of a negative electrode material that is a mixture of a negative electrode active material 12c (electrode active material) and a conductive additive 12d. The positive electrode active material 11c may be, for example, lithium cobalt oxide, lithium nickel oxide, lithium iron phosphate, or lithium manganese oxide. The negative electrode active material 12c may be, for example, graphite or lithium titanate. The conductive additives 11d and 12d may be, for example, carbon black or acetylene black. However, the positive electrode active material 11c, the negative electrode active material 12c, and the conductive additives 11d and 12d are not limited to these.

[0024] The positive electrode material may have a clay-like property, obtained by mixing an electrolyte into a mixture of a positive electrode active material 11c and a conductive additive 11d. The negative electrode material may have a clay-like property, obtained by mixing an electrolyte into a mixture of a negative electrode active material 12c and a conductive additive 12d. The positive electrode 11 may be an electrode in which the positive electrode material is coated on an electrode conductor 11a. The negative electrode 12 may be an electrode in which the negative electrode material is coated on an electrode conductor 12a.

[0025] The electrolytic solution is a solution in which a lithium salt, which is an electrolyte, is dissolved in a non-aqueous solvent. The non-aqueous solvent may be a carbonate-based solvent. The carbonate-based solvent may be γ-butyrolactone, ethylene carbonate, or both γ-butyrolactone and ethylene carbonate. Furthermore, as long as the carbonate-based solvent contains at least one of γ-butyrolactone and ethylene carbonate, it may also contain other solvents. Examples of other solvents include propylene carbonate, dimethyl carbonate, dimethoxyethane, diethyl carbonate, tetrahydrofuran, and triethylene glycol dimethyl ether. The electrolyte may be lithium hexafluorophosphate or lithium bis(fluorosulfonyl)imide (LiFSI).

[0026] The electrode assembly 14 may further include a separator 13. The positive electrode 11, the negative electrode 12, and the separator 13 may be positioned such that the positive electrode active material layer 11b and the negative electrode active material layer 12b are in contact with the separator 13. That is, the unit cell 10 may have a structure in which the positive electrode 11 and the negative electrode 12 are stacked with the separator 13 interposed therebetween. The separator 13 may function as an insulating member that insulates the positive electrode 11 and the negative electrode 12. The separator 13 may be, for example, a sheet-like nonwoven fabric or a porous material.

[0027] When a porous material is used as separator 13, specifically, a porous film made of a thermoplastic resin having a melting point of about 80° C. to 140° C. may be used. As the thermoplastic resin, for example, a polyolefin polymer such as polypropylene or polyethylene, or polyethylene terephthalate may be used.

[0028] (Structure of negative electrode 12) FIG. 6 is a plan view showing the structure of the negative electrode 12 included in the electrode body 14, in the vicinity of the exposed portion 12e. For clarity, the negative electrode active material layer 12b is omitted from FIG. 6. As shown in FIG. 6, in the negative electrode 12, the electrode conductor 12a has a first region 121 and a second region 122. The first region 121 is the region where the negative electrode active material layer 12b is located. The first region 121 may be substantially the entire surface of the electrode conductor 12a on the side where the negative electrode active material layer 12b is located, excluding the exposed portion 12e. The second region 122 is a region to which the connection terminal 22 can be electrically connected. The second region 122 is a portion of the surface on the side where the negative electrode active material layer 12b is located, above the exposed portion 12e.

[0029] In the following description, the surface of the electrode conductor 12a on which the negative electrode active material layer 12b is located will be simply referred to as the surface of the electrode conductor 12a. As shown in FIG. 6 , a resistive portion 123 is disposed between the first region 121 and the second region 122 on the surface of the electrode conductor 12a. That is, the electrode body 14 includes the resistive portion 123. The resistive portion 123 has a linear shape when the electrode conductor 12a is viewed from above. A linear shape refers to a shape having a length and width that can be substantially regarded as a line. The resistive portion 123 exhibits a higher resistance to the movement of the electrolyte contained in the negative electrode active material layer 12b along the surface of the electrode conductor 12a than the first region 121. The resistive portion 123 is located closer to the second region 122 than the first region 121 of the electrode conductor 12a. The width of the linear resistive portion 123 may be 20 μm or more, for example, 50 μm.

[0030] The resistance portion 123 may be positioned so as to be interposed on any path along which the electrolyte moves from the first region 121 to the second region 122 on the surface of the electrode conductor 12a. For example, as shown in FIG. 6 , the resistance portion 123 may be positioned on the first region 121 side of the second region 122, extending between both ends of the exposed portion 12e in the left-right direction when the direction from the first region 121 to the second region 122 is defined as the forward direction. In this case, the resistance portion 123 is positioned on the path along which the electrolyte moves from the first region 121 to the second region 122, regardless of the path along which the electrolyte moves. By positioning the resistance portion 123 in this manner, it is possible to increase the resistance to the movement of the electrolyte from the first region 121 to the second region 122, regardless of the path along which the electrolyte moves. The resistance portion 123 may be positioned 3 mm or more away from the end of the first region 121 facing the second region 122.

[0031] However, resistance portion 123 does not have to be positioned so as to be present on all paths along which the electrolyte solution can move from first region 121 to second region 122. In other words, resistance portion 123 only needs to be positioned so as to be present on at least a portion of the path along which the electrolyte solution moves from first region 121 to second region 122. By positioning resistance portion 123 in this manner, resistance to the movement of the electrolyte solution increases in the path along which resistance portion 123 is present.

[0032] Furthermore, the resistance portion 123 does not necessarily have to be a separate region from the second region 122, and may be included in the second region 122. In this case, the resistance portion 123 may exhibit a higher resistance than the second region 122 to the movement of the electrolyte solution contained in the negative electrode active material layer 12b along the surface of the electrode conductor 12a.

[0033] FIG. 7 is a diagram showing the movement of the electrolyte in the electrode conductor 12a of the negative electrode 12 not including the resistance portion 123. FIG. 7 shows the movement of the electrolyte from the first region 121 side to the second region 122 side over time for four examples of the negative electrode 12. There is no difference in the manufacturing conditions, etc., between the four examples of the negative electrode 12. Reference numeral 701 in FIG. 7 is an image showing the state immediately after the formation of the negative electrode active material layer 12b. Reference numeral 702 in FIG. 7 is an image showing the state one hour after the state shown by reference numeral 701. Reference numeral 703 in FIG. 7 is an image showing the state four hours after the state shown by reference numeral 701. Reference numeral 704 in FIG. 7 is an image showing the state 12 hours after the state shown by reference numeral 701.

[0034] In each image, the darker areas are areas where the electrolyte has migrated. As indicated by reference numeral 701 in FIG. 7, migration of the electrolyte occurs immediately after the formation of the negative electrode active material layer 12b. Thereafter, as indicated by reference numerals 702 to 704 in FIG. 7, in all examples where the negative electrode 12 does not include the resistance portion 123, migration of the electrolyte progresses over time. As indicated by reference numeral 704 in FIG. 7, in all four examples, the electrolyte has reached the second region 122. If the migration of the electrolyte causes the electrolyte to reach the second region 122 where the connection terminal 22 is welded to the electrode conductor 12a, the strength of the welding of the connection terminal 22 to the second region 122 may be reduced, potentially resulting in poor connection.

[0035] FIG. 8 is a diagram showing an example of a cross section of the electrode conductor 12a. In FIG. 8, reference numeral 801 is a photograph of a wide area of ​​the cross section of the electrode conductor 12a, including the resistor portion 123 and parts of the first region 121 and the second region 122 located on either side of the resistor portion 123. In FIG. 8, reference numeral 802 is an enlarged view of region R1 in reference numeral 801. In FIG. 8, reference numeral 803 is an enlarged view of region R2 in reference numeral 801. In FIG. 8, reference numeral 804 is an enlarged view of region R3 in reference numeral 801. Region R1 is a region of the first region 121 that is separated from the resistor portion 123. Region R2 is a region between the first region 121 and the resistor portion 123. Region R3 is a region that includes the resistor portion 123.

[0036] As indicated by reference numeral 802 in FIG. 8, the surface of the electrode conductor 12a in the first region 121 is processed (roughened) to increase the surface roughness in order to facilitate application of the negative electrode active material 12c and the like. For example, the thickness of the electrode conductor 12a may be 5 μm to 25 μm. The arithmetic mean roughness Ra of the surface of the electrode conductor 12a may be 0.15 μm to 0.6 μm. The maximum height Rz of the surface of the electrode conductor 12a may be 1.2 μm to 5 μm. As indicated by reference numeral 803 in FIG. 8, the surface of the electrode conductor 12a is also processed to increase the surface roughness in the region R2. On such a surface, the resistance to the movement of the electrolyte contained in the negative electrode active material layer 12b is reduced due to capillary action caused by the unevenness on the surface. Therefore, on such a surface, the electrolyte contained in the negative electrode active material layer 12b easily moves toward the second region 122.

[0037] As indicated by reference numeral 804 in Fig. 8, the resistance portion 123 may include a region on the surface of the electrode conductor 12a that has a smaller surface roughness than the first region 121. When the resistance portion 123 includes such a region, the resistance portion 123 is less susceptible to capillary action. Therefore, the resistance portion 123 exhibits a higher resistance to the movement of the electrolyte along the surface of the electrode conductor 12a than the first region 121. That is, in the region of the resistance portion 123 that has a smaller surface roughness than the first region 121, the electrolyte contained in the negative electrode active material layer 12b is less likely to move toward the second region 122.

[0038] In the following description, a region of the resistor portion 123 having a smaller surface roughness than the first region 121 is referred to as a reduced-roughness region. The entire resistor portion 123 may be a reduced-roughness region, or only a portion of the resistor portion 123 may be a reduced-roughness region. When only a portion of the resistor portion 123 is a reduced-roughness region, the portion of the resistor portion 123 other than the reduced-roughness region may have a different configuration so as to exhibit a higher resistance to the movement of the electrolyte than the first region 121. The portion of the resistor portion 123 other than the reduced-roughness region may have, for example, a configuration described in a modified example described below.

[0039] The arithmetic mean roughness Ra in the reduced roughness region may be, for example, 0.05 μm to 0.1 μm. The maximum height Rz in the reduced roughness region may be 0.3 μm to 1.0 μm. When the reduced roughness region has such roughness, the resistance of the resistance portion 123 to the movement of the electrolyte along the surface of the electrode conductor 12a becomes sufficiently high.

[0040] In the process of providing the reduced roughness region on the surface of the electrode conductor 12a, the thickness of the electrode conductor 12a may vary. Specifically, the thickness of the electrode conductor 12a in the reduced roughness region may become smaller. If the thickness of the electrode conductor 12a becomes smaller, the strength of the electrode conductor 12a decreases.

[0041] When the thickness of the electrode conductor 12a in the reduced roughness region fluctuates, a difference occurs between the thickness of the electrode conductor 12a in the first region 121 and the thickness of the electrode conductor 12a in the reduced roughness region. The difference between the thickness of the electrode conductor 12a in the first region 121 and the thickness of the electrode conductor 12a in the reduced roughness region may be 20% or less of the thickness of the electrode conductor 12a in the first region 121. Alternatively, the thickness of the electrode conductor 12a in the reduced roughness region may not fluctuate. In that case, the difference between the thickness of the electrode conductor 12a in the first region 121 and the thickness of the electrode conductor 12a in the reduced roughness region is 0% of the thickness of the electrode conductor 12a in the first region 121. In other words, the thickness fluctuation during the process of providing the reduced roughness region on the surface of the electrode conductor 12a may be 20% or less of the thickness of the electrode conductor 12a in the first region 121. This reduces a decrease in the strength of the electrode conductor 12a in the reduced roughness region. Such a reduced roughness region may be provided, for example, by pressing the surface of the electrode conductor 12a with a roller or the like.

[0042] 8, the electrode conductor 12a may be bent convexly at the resistor portion 123 on the side opposite to the surface of the electrode conductor 12a. When the electrode conductor 12a has such a shape, the resistor portion 123 functions as a reservoir for the electrolyte. In other words, the electrolyte is less likely to move from the resistor portion 123 to the outside. This further increases the resistance of the resistor portion 123 to the movement of the electrolyte.

[0043] As described above, in the electrode body 14, the negative electrode 12 is provided with the resistance portion 123, thereby reducing the movement of the electrolyte from the first region 121 to the second region 122 on the surface of the electrode conductor 12a. Therefore, the electrode body 14 reduces the possibility of poor connection between the connection terminal 22 welded to the second region 122 and the electrode conductor 12a due to the electrolyte adhering to the second region 122.

[0044] The above description has been given of an example in which the electrode body 14 has the resistance portion 123 on the surface of the electrode conductor 12a. However, the electrode body 14 may also have the resistance portion 123 on the surface of the electrode conductor 11a.

[0045] In particular, when the surface of the electrode conductor 11a is roughened, the effect of capillary action on the movement of the electrolyte also increases on the surface of the electrode conductor 11a. That is, the electrolyte can reach the second region 122 on the surface of the electrode conductor 11a. When the electrode body 14 has a resistance portion 123 on the surface of the electrode conductor 11a, the movement of the electrolyte can be reduced even on the electrode conductor 11a whose surface is roughened.

[0046] (Variation 1) FIG. 9 is a cross-sectional view showing an outline of a resistor 123A according to a first modification of the resistor 123. As shown in FIG. 9, the resistor 123A may be a recess in the surface of the electrode conductor 12a. The resistor 123A functions as a reservoir for the electrolyte. Therefore, such a resistor 123A also exhibits higher resistance to the movement of the electrolyte along the surface of the electrode conductor 12a than the first region 121. The resistor 123A may be formed by excavating the surface of the electrode conductor 12a with a laser, for example. The depth of the resistor 123A may be 0.5 μm or more. The difference between the thickness of the electrode conductor 12a in the first region 121 and the thickness of the electrode conductor 12a in the resistor 123A may be 20% or less of the thickness of the electrode conductor 12a in the first region 121. The vicinity of the resistor 123A may be raised higher than other regions of the electrode conductor 12a. That is, the thickness of the first region 121 and the second region 122 immediately adjacent to the resistor portion 123A may be greater than the thickness of the electrode conductor 12a in the first region 121 that is separated from the resistor portion 123A.

[0047] Furthermore, the bottom or at least one side of the resistor portion 123A may have a smaller surface roughness than the first region 121. This surface roughness of the bottom or side of the resistor portion 123A increases the resistance of the resistor portion 123A to the movement of the electrolyte along the surface of the electrode conductor 12a. This further reduces the likelihood of poor connection between the connection terminal 22 and the electrode conductor 12a. When the surface roughness of the bottom or side of the resistor portion 123A is smaller than that of the first region 121, the specific surface roughness of the bottom or side may be the same as that of the reduced-roughness region. Furthermore, the bottom or at least one side of the resistor portion 123A may include a void inside its surface. The void is formed, for example, by the absorption of air surrounding the laser-heated portion during cooling after the resistor portion 123A is formed by laser irradiation, or by deformation due to expansion and contraction of the electrode conductor 12a. Alternatively, an additional recess may be formed in the surface of the electrode conductor 12a at the bottom or at least one side of the resistor portion 123A.

[0048] (Variation 2) Fig. 10 is a cross-sectional view showing an outline of resistor portion 123B according to a second modification of resistor portion 123. As shown in Fig. 10, resistor portion 123B may be a thick member located on the surface of electrode conductor 12a, separate from electrode conductor 12a. In this case, resistor portion 123B blocks the movement of the electrolyte along the surface of electrode conductor 12a, thereby exhibiting a higher resistance to the movement than first region 121.

[0049] The material for the resistor portion 123B in this modification may be any material that can be liquid-tightly bonded to the surface of the electrode conductor 12a and that is impermeable to the electrolyte. A specific example of the material for the resistor portion 123B is styrene-butadiene rubber.

[0050] (Variation 3) 11 is a plan view showing a modified example of the unit cell 10 including the negative electrode 12. In this modified example, the resistance portion 123 includes a region having a smaller surface roughness than the first region 121 (reduced roughness region).

[0051] As described above, in the unit cell 10, the first housing 15 may house the electrode assembly 14. In this case, the exposed portion 12e of the electrode conductor 12a protrudes from the first housing 15. Furthermore, as described above, the first housing 15 may have its peripheral edge sealed while housing the electrode assembly 14. In the following description, the portion where the first housing 15 is sealed along the side of the first housing 15 from which the exposed portion 12e protrudes will be referred to as the sealed portion 151.

[0052] In the first embodiment, the position of the sealing portion 151 is not particularly limited, and may be located, for example, between the first region 121 and the resistance portion 123. On the other hand, as shown in FIG. 11 , in this modification, the sealing portion 151 may be located in the resistance portion 123. The degree of adhesion of the sealing portion 151 to the reduced-roughness region included in the resistance portion 123 is higher than the degree of adhesion of the sealing portion 151 to regions other than the reduced-roughness region. In the reduced-roughness region, the close contact of the sealing portion 151 increases the resistance to the movement of the electrolyte along the surface of the electrode conductor 12a compared to when the sealing portion 151 is not in close contact with the reduced-roughness region. Therefore, in the resistance portion 123 including the reduced-roughness region, the resistance of the resistance portion 123 to the movement of the electrolyte along the surface of the electrode conductor 12a can be made even higher than when the sealing portion 151 is not located in the resistance portion 123.

[0053] As described above, the electrode assembly 14 and unit cell 10 according to the present disclosure can reduce the possibility of poor connection between the electrode conductor 12a and the connection terminal 22 welded to the second region 122, which is caused by the electrolyte adhering to the second region 122. This reduces the possibility of producing defective secondary batteries 1. This can therefore save energy and resources consumed in manufacturing defective secondary batteries 1, thereby contributing to the achievement of the Sustainable Development Goals (SDGs).

[0054] [Additional Notes] The invention according to the present disclosure has been described above based on the drawings and examples. However, the invention according to the present disclosure is not limited to the above-described embodiments. In other words, the invention according to the present disclosure can be modified in various ways within the scope of the present disclosure, and embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the invention according to the present disclosure. In other words, it should be noted that a person skilled in the art can easily make various modifications or corrections based on the present disclosure. It should also be noted that these modifications or corrections are included in the scope of the present disclosure. [Explanation of symbols]

[0055] 10 unit cells (energy storage elements) 11a Electrode conductor 11b Positive electrode active material layer (electrode active material layer) 11c Cathode active material (electrode active material) 12a Electrode conductor 12b Negative electrode active material layer (electrode active material layer) 12c Negative electrode active material (electrode active material) 121 1st area 122 Second area 123 Resistance section 14 Electrode body 15 First Detention Facility (Detention Facility) 151 Sealing part

Claims

1. an active material layer containing an electrode active material and an electrolyte; an electrode conductor having (i) a first region in which the active material layer is located, and (ii) a second region that is separate from the first region and to which a connection terminal can be electrically connected; a resistance portion located closer to the second region than the first region of the electrode conductor, and exhibiting a higher resistance to the movement of the electrolyte solution along a surface of the electrode conductor on the side where the active material layer is located than the resistance portion of the first region, The resistance portion includes a region on the surface of the electrode conductor that has a surface roughness smaller than that of the first region.

2. 2. The electrode body according to claim 1, wherein a difference between a thickness of the electrode conductor in the first region and a thickness of the electrode conductor in a region of the resistor portion having a smaller surface roughness than the first region is 20% or less of the thickness of the electrode conductor in the first region.

3. An active material layer containing an electrode active material and an electrolyte solution; an electrode conductor having (i) a first region in which the active material layer is located, and (ii) a second region that is separate from the first region and to which a connection terminal can be electrically connected; a resistance portion located closer to the second region than the first region of the electrode conductor, and exhibiting a higher resistance to the movement of the electrolyte solution along a surface of the electrode conductor on the side where the active material layer is located than the resistance portion of the first region, the resistor portion is a part of the electrode conductor, The electrode conductor is bent convexly in the resistor portion on the opposite side to the surface.

4. An active material layer containing an electrode active material and an electrolyte solution; an electrode conductor having (i) a first region in which the active material layer is located, and (ii) a second region that is separate from the first region and to which a connection terminal can be electrically connected; a resistance portion located closer to the second region than the first region of the electrode conductor, and exhibiting a higher resistance to the movement of the electrolyte solution along a surface of the electrode conductor on the side where the active material layer is located than the resistance portion of the first region, The electrode body, wherein the resistive portion is a recess in the surface of the electrode conductor.

5. 5. The electrode body according to claim 1, wherein the resistance portion is positioned so as to be interposed on any path along which the electrolyte moves from the first region to the second region on the surface of the electrode conductor.

6. An energy storage element comprising the electrode assembly according to claim 1 .

7. An active material layer containing an electrode active material and an electrolyte solution; an electrode conductor having (i) a first region in which the active material layer is located, and (ii) a second region that is separate from the first region and to which a connection terminal can be electrically connected; a resistance portion located closer to the second region than the first region of the electrode conductor and exhibiting higher resistance to the movement of the electrolyte solution along a surface of the electrode conductor on a side where the active material layer is located than the resistance portion of the first region, the resistance portion includes a region on the surface of the electrode conductor that has a surface roughness smaller than that of the first region, the energy storage element includes a housing that houses the electrode assembly, a portion of the electrode conductor protrudes from the housing; The energy storage element, wherein a sealing portion of the housing that is sealed while housing the electrode body is located at the resistor portion.

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