Lithium-ion secondary battery and method for manufacturing a lithium-ion secondary battery

Abstract

To provide a high-quality lithium-ion secondary battery, and a method for manufacturing a lithium-ion secondary battery that can produce a high-quality lithium-ion secondary battery. [Solution] The electrode body 20 of the battery 1 has a positive electrode end 21 side, which is formed by winding the non-positive electrode portion 111 of the positive electrode sheet 100, on one end side in the winding axis direction. On the other end side opposite to the one end side in the winding axis direction, the electrode body 20 has a negative electrode end 22, which is formed by winding the non-negative electrode portion 111 of the negative electrode sheet 200. Furthermore, at least at the end of the winding, the negative electrode sheet 200 is located on the outer circumference of the positive electrode sheet 100, so that the negative electrode composite layer 220 has a non-facing surface 221 that does not face the positive electrode sheet 100. The electrode body 20 has a lithium carbonate foil 50 provided on the non-facing surface 221 of the negative electrode composite layer 220.

Description

Technical Field

[0001] The disclosed technology relates to a lithium-ion secondary battery and a method for manufacturing a lithium-ion secondary battery.

Background Art

[0002] Some lithium-ion secondary batteries are configured by stacking and winding a positive electrode sheet, a negative electrode sheet, and a separator, and have a flat electrode body. For example, Patent Document 1 describes a wound electrode body having a flat shape wound such that the negative electrode sheet is located on the outer peripheral side of the positive electrode sheet.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in a lithium-ion secondary battery, when an amount of lithium ions exceeding a certain level is released from the positive electrode sheet, the potential on the positive electrode side increases. Further, when the potential on the positive electrode side increases, there is a possibility that transition metals contained in the positive electrode composite layer of the positive electrode sheet may elute. Furthermore, the transition metals eluted from the positive electrode sheet may precipitate on the surface of the negative electrode sheet. That is, when lithium ions are excessively released from the positive electrode sheet, the transition metals eluted from the positive electrode sheet precipitate on the negative electrode sheet, and the quality of the lithium-ion secondary battery may deteriorate.

[0005] The disclosed technology aims to provide a high-quality lithium-ion secondary battery and a method for manufacturing a lithium-ion secondary battery capable of manufacturing a high-quality lithium-ion secondary battery.

Means for Solving the Problems

[0006] One aspect of the disclosed technology is constructed by winding together a positive electrode sheet having a positive electrode composite layer formed on the surface of a positive electrode current collector foil, a negative electrode sheet having a negative electrode composite layer formed on the surface of a negative electrode current collector foil, and a separator insulating the positive electrode sheet and the negative electrode sheet, and comprises an electrode body having two curved portions at the top and bottom, respectively, where the outer peripheral surfaces are curved, and a flat portion located between the two curved portions, where the outer peripheral surfaces of two opposing surfaces in the thickness direction are both flat, and a battery case that houses the electrode body and electrolyte, wherein the electrode body has a positive electrode composite layer formed on the positive electrode sheet The lithium-ion secondary battery has a positive electrode end formed by winding a non-formed positive electrode portion that protrudes from the negative electrode sheet, on one end in the winding axis direction, and a negative electrode end formed by winding a non-formed negative electrode portion of the negative electrode sheet where the negative electrode composite layer is not formed, protruding from the positive electrode sheet, on the other end in the winding axis direction, and at least at the end of the winding, the negative electrode sheet is located on the outer circumference side than the positive electrode sheet, so that the negative electrode composite layer has a non-facing surface that does not face the positive electrode sheet, and lithium carbonate foil is provided on the non-facing surface of the negative electrode composite layer.

[0007] In the lithium-ion secondary battery according to the above embodiment, lithium ions may move from the negative electrode material layer on the side opposite to the non-opposing side to the negative electrode material layer on the non-opposing side at the outermost periphery of the negative electrode sheet. This movement of lithium ions is less likely to occur if there are sufficient lithium ions absorbed in the negative electrode material layer on the non-opposing side, and tends to be promoted the less lithium ions absorbed in the negative electrode material layer on the non-opposing side. In addition, lithium ions absorbed in the negative electrode material layer on the non-opposing side may be released from the negative electrode material layer by combining with oxygen present in the battery case. The more lithium ions released from the negative electrode material layer on the non-opposing side by combining with oxygen, the more likely it is that lithium ions will be released from the positive electrode sheet. In contrast, in the lithium-ion secondary battery according to the above embodiment, the lithium carbonate foil can inhibit the lithium ions in the negative electrode material layer on the non-opposing side from combining with oxygen. This makes it possible to suppress the excessive release of lithium ions from the positive electrode sheet. Therefore, the lithium-ion secondary battery according to the above embodiment is of high quality in which the deposition of transition metals leached from the positive electrode sheet onto the negative electrode sheet is suppressed.

[0008] Another aspect of the disclosed technology is a method for manufacturing a lithium-ion secondary battery comprising an electrode body formed by winding together a positive electrode sheet having a positive electrode composite layer formed on the surface of a positive electrode current collector foil, a negative electrode sheet having a negative electrode composite layer formed on the surface of a negative electrode current collector foil, and a separator insulating the positive electrode sheet and the negative electrode sheet, the electrode body having two curved portions at the top and bottom, respectively, and a flat portion located between the two curved portions, where two opposing outer surfaces in the thickness direction are both flat, and a battery case for housing the electrode body and electrolyte, wherein the positive electrode sheet, negative electrode sheet and separator are formed by winding together a positive electrode sheet having a positive electrode composite layer formed on the surface of a negative electrode sheet This is a method for manufacturing a lithium-ion secondary battery, in which an electrode body is constructed by winding the negative electrode sheet so that the negative electrode non-formed portion of the negative electrode sheet, where the negative electrode composite layer is not formed, protrudes from the positive electrode sheet to the other end in the winding axis direction, and at least at the end of the winding, the negative electrode sheet is positioned on the outer circumference of the positive electrode sheet. After housing the electrode body and electrolyte in a battery case, initial charging and aging are performed. When constructing the electrode body, lithium foil is provided on the non-facing surface of the negative electrode composite layer that does not face the positive electrode sheet, and the electrolyte is made to which an additive that generates carbon dioxide when decomposed during initial charging or aging is added. [Effects of the Invention]

[0009] According to the disclosed technology, a high-quality lithium-ion secondary battery and a method for manufacturing a lithium-ion secondary battery that can produce a high-quality lithium-ion secondary battery are provided. [Brief explanation of the drawing]

[0010] [Figure 1] This is a cross-sectional view showing the schematic configuration of a battery according to an embodiment. [Figure 2] This is a perspective view of an electrode body according to an embodiment. [Figure 3] This is a cross-sectional view of the positive electrode sheet, negative electrode sheet, and separator that constitute the electrode body according to the embodiment. [Figure 4]This is a cross-sectional view of the outer circumference of the electrode body according to the embodiment. [Figure 5] This diagram illustrates lithium ion movement using a reference electrode body different from that of the embodiment. [Figure 6] This is an enlarged cross-sectional view of the positive electrode end on the outer circumference side of the electrode body according to the embodiment. [Figure 7] This is a diagram showing a first embodiment of the electrode body according to the embodiment. [Figure 8] This figure shows a second embodiment of the electrode body according to the embodiment. [Figure 9] This figure shows a third embodiment of the electrode body according to the embodiment. [Figure 10] This diagram shows the manufacturing procedure for a battery according to an embodiment. [Figure 11] This is a cross-sectional view of the electrode body before the initial charging process. [Figure 12] This is a cross-sectional view of the electrode body when carbon dioxide is generated due to the decomposition of additives during initial charging or aging. [Figure 13] This diagram illustrates a preferred electrolyte filling process when lithium foil is not present at the bottom of the electrode body. [Modes for carrying out the invention]

[0011] The embodiments of the disclosed technology will be described in detail below with reference to the attached drawings.

[0012] Figure 1 shows a cross-section of the battery 1 according to this embodiment. Figure 1 shows the X direction extending horizontally and the Z direction extending vertically. The depth direction in Figure 1 is the Y direction. In this embodiment, the vertical direction of the battery 1 is aligned with the Z direction. That is, the top of Figure 1 is the top of the battery 1. The battery 1 is a lithium-ion secondary battery.

[0013] The battery 1 is formed by housing an electrode body 20 and an electrolytic solution 40 inside a battery case 10. The electrode body 20 is composed of a positive electrode sheet 100, a negative electrode sheet 200, a separator 30, and a lithium carbonate foil 50. The electrolytic solution 40 mainly consists of an organic solvent in which a lithium salt is dissolved.

[0014] The battery case 10 is composed of a battery case main body 11 and a lid 12. The battery 1 in this embodiment is usually used with the lid 12 positioned on the upper side. An opening for housing the electrode body 20 inside the battery case main body 11 is formed at the upper part of the battery case main body 11, and the opening is blocked by the lid 12. The battery case 10 in this embodiment has an overall flat rectangular outer shape. Near both ends in the longitudinal direction of the lid 12, a positive electrode terminal 2 and a negative electrode terminal 3 are provided respectively.

[0015] The positive electrode terminal 2 is connected to a positive electrode current collecting member 4. Also, the positive electrode current collecting member 4 is connected to the positive electrode end portion 21 of the electrode body 20 inside the battery case 10. Thereby, the positive electrode terminal 2 is connected to the electrode body 20. The negative electrode terminal 3 is connected to a negative electrode current collecting member 5. Also, the negative electrode current collecting member 5 is connected to the negative electrode end portion 22 of the electrode body 20 inside the battery case 10. Thereby, the negative electrode terminal 3 is connected to the electrode body 20. The connection between the positive electrode current collecting member 4 and the positive electrode end portion 21, and the connection between the negative electrode current collecting member 5 and the negative electrode end portion 22 can be performed by, for example, welding. And the battery 1 can be charged or discharged via the positive electrode terminal 2 and the negative electrode terminal 3.

[0016] The lid 12 is provided with an injection port 13. The injection port 13 is a hole for injecting the electrolytic solution 40 into the battery case 10. The injection port 13 is blocked by a sealing member 14. The sealing member 14 is attached after the electrolytic solution 40 is injected into the battery case 10 from the injection port 13. At least a part of the electrode body 20 is immersed in the electrolytic solution 40 injected into the battery case 10.

[0017] Figure 2 is a perspective view of the electrode body 20. The electrode body 20 is constructed by winding together and overlapping long, sheet-like positive electrode sheet 100, negative electrode sheet 200, and separator 30. The electrode body 20 has a positive electrode end 21 and a negative electrode end 22 located at both ends in the X direction, which is the width direction. The electrode body 20 also has a laminated portion 23 between the positive electrode end 21 and the negative electrode end 22. The X direction is also the winding axis direction related to the winding of the electrode body 20.

[0018] The positive electrode end 21 is a portion made up of a part of the positive electrode sheet 100. The negative electrode end 22 is a portion made up of a part of the negative electrode sheet 200. The laminated portion 23 is a portion in which parts of the positive electrode sheet 100 and the negative electrode sheet 200 are laminated together with a separator 30 sandwiched between them. Figure 2 also shows the winding end 25, which is the outer end of the winding of the electrode body 20. Hereafter, the winding end 25 shown in Figure 2 will be described as specifically referring to the negative electrode sheet 200.

[0019] The flattened, wound electrode body 20 has an upper curved surface portion 61 and a lower curved surface portion 62 at the top and bottom, respectively, in the Z direction (height direction). The upper curved surface portion 61 has a curved outer surface 67. The lower curved surface portion 62 also has a curved outer surface 68. Furthermore, the electrode body 20 has a flat surface portion 60 located between the upper curved surface portion 61 and the lower curved surface portion 62. The flat surface portion 60 has two outer surfaces 65 and 66 that are opposite each other in the Y direction (thickness direction), and both are flat. In this embodiment of the electrode body 20, the winding end 25 is located at the top of the electrode body 20. Specifically, it is located near the boundary between the flat surface portion 60 and the upper curved surface portion 61.

[0020] Furthermore, the electrode body 20 in this embodiment includes a sheet-like lithium carbonate foil 50. The location of the lithium carbonate foil 50 in the electrode body 20 will be described in detail later.

[0021] Figure 3 is a cross-sectional view in the width direction of the positive electrode sheet 100, negative electrode sheet 200, and separator 30 that constitute the electrode body 20.

[0022] The positive electrode sheet 100 comprises a positive electrode current collector foil 110 and a positive electrode composite layer 120 formed on the surface of the positive electrode current collector foil 110. The positive electrode composite layer 120 is formed on both sides of the positive electrode current collector foil 110. Aluminum foil can be used as the positive electrode current collector foil 110. The positive electrode composite layer 120 is composed of a material containing at least a positive electrode active material. The positive electrode active material is a material that contributes to charging and discharging, and in lithium-ion secondary batteries, it intercalates and releases lithium ions. The positive electrode active material contains a transition metal. In addition to the positive electrode active material, the positive electrode composite layer 120 also contains appropriate materials such as binders. The binder is a material that fixes the materials constituting the positive electrode composite layer 120 to the surface of the positive electrode current collector foil 110. The positive electrode current collector foil 110 has a positive electrode non-forming portion 111 on which the positive electrode composite material layer 120 is not formed on the surface, and a positive electrode forming portion 112 on which the positive electrode composite material layer 120 is formed on the surface.

[0023] The negative electrode sheet 200 has a negative electrode current collector foil 210 and a negative electrode composite layer 220 formed on the surface of the negative electrode current collector foil 210. The negative electrode composite layer 220 is formed on both sides of the negative electrode current collector foil 210. Copper foil can be used as the negative electrode current collector foil 210. The negative electrode composite layer 220 is composed of a material containing at least a negative electrode active material. The negative electrode active material is a material that contributes to charging and discharging, and in lithium-ion secondary batteries, it intercepts and releases lithium ions. In addition to the negative electrode active material, the negative electrode composite layer 220 appropriately contains materials such as binders. The binder is a material that fixes the materials constituting the negative electrode composite layer 220 to the surface of the negative electrode current collector foil 210. The negative electrode current collector foil 210 has a negative electrode non-forming portion 211 on which the negative electrode composite material layer 220 is not formed on the surface, and a negative electrode forming portion 212 on which the negative electrode composite material layer 220 is formed on the surface.

[0024] The separator 30 is a porous insulating resin film. The electrolyte 40 injected into the battery case 10 impregnates the porous separator 30 from the edges of the electrode body 20 in the width direction. As a result, the inside of the electrode body 20 is filled with the electrolyte 40. Any electrolyte 40 that does not fit inside the electrode body 20 accumulates outside the electrode body 20 in the battery case 10.

[0025] Figure 3 shows the superposition of the positive electrode sheet 100, negative electrode sheet 200, and separator 30 in the electrode body 20. In other words, the electrode body 20 is formed by superimposing the positive electrode sheet 100, negative electrode sheet 200, and separator 30 as shown in Figure 3, and winding them so that the negative electrode sheet 200 is located on the outside of the positive electrode sheet 100. Therefore, at the end of the winding of the electrode body 20, the negative electrode sheet 200 is located on the outer circumference than the positive electrode sheet 100.

[0026] Furthermore, in the electrode body 20, the positive electrode forming portion 112 of the positive electrode sheet 100 and the negative electrode forming portion 212 of the negative electrode sheet 200 overlap. The laminated portion 23 of the electrode body 20 is formed by winding the positive electrode forming portion 112 and the negative electrode forming portion 212 while overlapping via the separator 30. In this embodiment, the width of the negative electrode forming portion 212 is slightly wider than the width of the positive electrode forming portion 112. Therefore, in the width direction, both ends of the negative electrode forming portion 212 protrude slightly compared to the ends of the positive electrode forming portion 112.

[0027] The non-formed positive electrode portion 111 protrudes beyond the negative electrode sheet 200 at one end in the width direction. The positive electrode end portion 21 of the electrode body 20 is formed when the non-formed positive electrode portion 111 is wound up with the non-formed positive electrode portion 111 protruding beyond the negative electrode sheet 200. The non-formed negative electrode portion 211 protrudes beyond the positive electrode sheet 100 at the other end in the width direction. The negative electrode end portion 22 of the electrode body 20 is formed when the non-formed negative electrode portion 211 is wound up with the non-formed negative electrode portion 211 protruding beyond the positive electrode sheet 100.

[0028] Next, the position of the lithium carbonate foil 50 in the electrode body 20 will be described. Figure 4 shows a cross-section of the outer circumference of the electrode body 20. The upper separator 30 in Figure 4 constitutes the outermost circumference of the electrode body 20. Also, at the end 25 of the winding in the electrode body 20, the negative electrode sheet 200 is located further outward than the positive electrode sheet 100. Therefore, the negative electrode sheet 200 is located inside the separator 30, which is located at the outermost circumference. In the outermost portion of the negative electrode sheet 200, the negative electrode composite layer 220 located on the outside does not face the positive electrode sheet 100. On the other hand, in the outermost portion of the negative electrode sheet 200, the negative electrode composite layer 220 located on the inside faces the positive electrode sheet 100.

[0029] Figure 4 shows the non-opposing surface 221 of the negative electrode composite layer 220, which is located on the outside and not facing the positive electrode sheet 100. The lithium carbonate foil 50 is provided on the non-opposing surface 221. More specifically, the lithium carbonate foil 50 is sandwiched between the non-opposing surface 221 and the separator 30 located on the outermost periphery. The effect of this will be explained.

[0030] Figure 5 shows a cross-section of the outer circumference of a reference electrode 29, which differs from the electrode 20 in this embodiment in that it does not have a lithium carbonate foil 50. Note that Figure 5 shows an enlarged view of only the positive electrode end 21 side of the reference electrode 29. The movement of lithium ions in the reference electrode 29 is indicated by arrows in Figure 5.

[0031] Arrow A indicates the movement of lithium ions from the positive electrode composite layer 120 of the positive electrode sheet 100 to the negative electrode composite layer 220 on the side opposite to the non-opposing surface 221 of the negative electrode sheet 200. The movement of lithium ions indicated by arrow A is a movement from the opposing positive electrode composite layer 120 to the negative electrode composite layer 220, and is associated with the charging of battery 1. As a result of the movement of lithium ions indicated by arrow A, lithium ions are released from the positive electrode composite layer 120 of the positive electrode sheet 100.

[0032] Arrow B indicates the movement of lithium ions within the negative electrode composite layer 220. That is, lithium ions that have moved to the negative electrode composite layer 220 on the side opposite to the non-opposing surface 221 due to the movement indicated by arrow A may move towards the positive electrode end 21 side within that negative electrode composite layer 220, as indicated by arrow B. This movement of lithium ions indicated by arrow B is more likely to occur when there are fewer lithium ions absorbed in the portion of the negative electrode composite layer 220 on the positive electrode end 21 side, opposite to the non-opposing surface 221.

[0033] Arrow C indicates the movement of lithium ions from the negative electrode composite layer 220 on the side opposite to the non-opposing surface 221 of the negative electrode sheet 200 to the negative electrode composite layer 220 on the non-opposing surface 221 side. That is, lithium ions that have moved to the positive electrode end 21 side portion of the negative electrode composite layer 220 due to the movement indicated by arrow B may move to the negative electrode composite layer 220 on the non-opposing surface 221 side, as indicated by arrow C. This movement of lithium ions indicated by arrow C occurs via the electrolyte 40 present on the positive electrode end 21 side of the negative electrode sheet 200, and crosses the negative electrode current collector foil 210. The electrolyte 40 present on the positive electrode end 21 side of the negative electrode sheet 200 is, for example, contained in the separator 30 that covers that area. Furthermore, the movement of lithium ions indicated by arrow C is more likely to occur when there are fewer lithium ions absorbed in the negative electrode composite layer 220 on the non-opposing surface 221 side.

[0034] Arrow D indicates the movement of lithium ions from the negative electrode composite layer 220 on the non-opposing surface 221 to the outside. That is, lithium ions that have moved to the negative electrode composite layer 220 on the non-opposing surface 221 due to the movement indicated by arrow C may move to the outside of the negative electrode composite layer 220 on the non-opposing surface 221, as indicated by arrow D. This movement of lithium ions indicated by arrow D occurs when lithium ions absorbed in the negative electrode composite layer 220 on the non-opposing surface 221 combine with oxygen present inside the battery case 10. The inside of the battery case 10 is not completely filled with electrolyte 40, and oxygen is present inside the battery case 10, for example, because air is present.

[0035] Furthermore, lithium ions that combine with oxygen as a result of the movement indicated by arrow D will no longer be able to contribute to the charging and discharging of battery 1. In other words, if the movement of lithium ions indicated by arrows A, B, C, and D continues, the amount of lithium ions absorbed in the positive electrode composite layer 120 of the positive electrode sheet 100 will decrease. That is, if the movement of lithium ions indicated by arrows A, B, C, and D continues, lithium ions will be excessively released from the positive electrode composite layer 120 of the positive electrode sheet 100. As a result, the potential on the positive electrode side will rise, and the possibility of transition metals contained in the positive electrode composite layer 120 of the positive electrode sheet 100 dissolving will increase. Moreover, if transition metals dissolve from the positive electrode sheet 100, they may precipitate on the surface of the negative electrode sheet 200, potentially degrading the quality of battery 1. Specifically, if the transition metals precipitated on the negative electrode sheet 200 grow, they may cause a short circuit inside the electrode body 20.

[0036] Figure 6 shows a cross-section of the electrode body 20 according to this embodiment on its outer circumference. Note that Figure 6 shows an enlarged view of only the portion of the electrode body 20 on the positive electrode end 21 side. As shown in Figure 6, in this embodiment, the electrode body 20 has a lithium carbonate foil 50 provided on the negative electrode composite layer 220 on the non-opposing surface 221 side. The lithium carbonate foil 50 does not contain a gas such as air inside, for example.

[0037] In the electrode body 20 of this embodiment, the presence of lithium carbonate foil 50 suppresses the binding of lithium ions absorbed in the negative electrode composite layer 220 on the non-opposing surface 221 side with oxygen. In other words, the lithium carbonate foil 50 inhibits the movement of lithium ions indicated by arrow D, which occurs in the reference electrode body 29 where the lithium carbonate foil 50 is not provided. As a result, in the electrode body 20, the decrease in lithium ions absorbed in the negative electrode composite layer 220 on the non-opposing surface 221 side is suppressed. This makes it possible to maintain a state in which sufficient lithium ions are absorbed in the negative electrode composite layer 220 on the non-opposing surface 221 side of the electrode body 20 of this embodiment.

[0038] By maintaining a state in which sufficient lithium ions are absorbed in the negative electrode composite layer 220 on the non-opposing surface 221 side, the movement of lithium ions indicated by arrow C is suppressed. In other words, the movement of lithium ions from the negative electrode composite layer 220 on the side opposite to the non-opposing surface 221 of the negative electrode sheet 200 to the negative electrode composite layer 220 on the non-opposing surface 221 side is suppressed. Therefore, a state in which sufficient lithium ions are absorbed can be maintained at the positive electrode end 21 within the negative electrode composite layer 220 on the side opposite to the non-opposing surface 221 of the negative electrode sheet 200. That is, the movement of lithium ions indicated by arrow B is also suppressed. As a result, lithium ions that moved from the positive electrode composite layer 120 to the negative electrode composite layer 220 as shown by arrow A during charging of the battery 1 can then move from the negative electrode composite layer 220 in the opposite direction to arrow A during discharging of the battery 1 and move back to the positive electrode composite layer 120. Therefore, in the battery 1 according to this embodiment, it is possible to suppress the generation of lithium ions that, after being released from the positive electrode composite layer 120, become unable to contribute to charging and discharging. Thus, the quality of the battery 1 can be maintained at a high level.

[0039] Furthermore, even if the lithium carbonate foil 50 were to come into direct contact with both the positive electrode sheet 100 and the negative electrode sheet 200, its conductivity would not be high enough to cause a short circuit. In other words, the presence of the lithium carbonate foil 50 does not degrade the quality of the battery 1.

[0040] Next, the location where the lithium carbonate foil 50 is provided will be described. As mentioned above, the lithium carbonate foil 50 is provided on the non-facing surface 221 of the negative electrode composite layer 220 outside the portion located at the outermost periphery of the negative electrode sheet 200.

[0041] As an example, Figure 7 shows an electrode body 20A of the first embodiment. In electrode body 20A, the lithium carbonate foil 50 is provided on the positive electrode side upper curved surface region 221A, which is the region along the end on the positive electrode end 21 side of the upper curved surface portion 61 of the non-facing surface 221 of the negative electrode composite layer 220. In Figure 7, the outer edge of the positive electrode side upper curved surface region 221A is highlighted with a thick line.

[0042] In this configuration, the battery 1 is typically installed with the upper curved portion 61 of the electrode body 20 facing upwards. Furthermore, the amount of electrolyte 40 is not enough to completely fill the battery case 10. Therefore, the upper part of the electrode body 20 is less immersed in the electrolyte 40 and is more likely to be exposed above the liquid level of the electrolyte 40 in the battery case 10. In other words, in the battery 1, the portion of the negative electrode composite layer 220 on the non-opposing surface 221 side that is located on the upper curved portion 61 of the electrode body 20 tends to be more prone to bonding between lithium ions absorbed in the negative electrode composite layer 220 and oxygen.

[0043] Furthermore, in the negative electrode composite layer 220 on the non-opposing surface 221 side, lithium ions are likely to move from the negative electrode composite layer 220 on the opposite side of the non-opposing surface 221 to the negative electrode composite layer 220 on the non-opposing surface 221 side, particularly on the side of the positive electrode end 21. In other words, if the lithium ions absorbed in the negative electrode composite layer 220 located in the upper curved surface region 221A on the positive electrode side are in a state where they readily combine with oxygen, the release of lithium ions from the positive electrode composite layer 120 may become excessive.

[0044] In contrast, in electrode body 20A, the lithium carbonate foil 50 is provided on the upper curved region 221A on the positive electrode side, which suppresses the lithium ions contained in the negative electrode composite layer 220 located in the upper curved region 221A on the positive electrode side from combining with oxygen. Therefore, electrode body 20A can appropriately suppress the excessive release of lithium ions from the positive electrode composite layer 120 of the positive electrode sheet 100.

[0045] Figure 8 shows an electrode body 20B of a second embodiment, which is a different example from the first embodiment. In electrode body 20B, the lithium carbonate foil 50 is provided on the positive electrode side region 221B, which is the region along the end on the positive electrode end 21 side of the non-opposing surface 221 of the negative electrode composite layer 220. In Figure 8, the outer edge of the positive electrode side region 221B is highlighted with a thick line.

[0046] Of the negative electrode composite layer 220 on the non-opposing surface 221 side, the positive electrode end 21 side is a location where lithium ions are likely to move from the negative electrode composite layer 220 on the opposite side of the non-opposing surface 221 to the negative electrode composite layer 220 on the non-opposing surface 221 side. Furthermore, even the portion of the electrode body 20 that is normally immersed in the electrolyte 40 may be exposed above the liquid surface of the electrolyte 40 within the battery case 10 depending on the tilt of the battery case 10. In the portion of the electrode body 20 exposed from the electrolyte 40, lithium ions absorbed in the negative electrode composite layer 220 on the non-opposing surface 221 side may combine with oxygen. In other words, if the lithium ions absorbed in the negative electrode composite layer 220 located in the positive electrode region 221B are in a state where they are likely to combine with oxygen, there is a possibility that the release of lithium ions from the positive electrode composite layer 120 will be excessive.

[0047] In contrast, in the electrode body 20B, the lithium carbonate foil 50 is provided on the positive electrode side region 221B, which suppresses the bonding of lithium ions and oxygen at that location and further suppresses the excessive release of lithium ions from the positive electrode sheet 100. The positive electrode side region 221B is a region that exists around the positive electrode end 21 side of the non-opposing surface 221 of the negative electrode composite layer 220. For this reason, the positive electrode side region 221B includes the positive electrode side upper curved surface region 221A related to the electrode body 20A of the first embodiment shown in Figure 7.

[0048] Figure 9 shows an electrode body 20C of a third embodiment, which is an example different from both the first and second embodiments. In electrode body 20C, the lithium carbonate foil 50 is provided on the winding end region 221C, which is the region along the winding end 25 on the non-facing surface 221 of the negative electrode composite layer 220. In Figure 9, the outer edge of the winding end region 221C is highlighted with a thick line.

[0049] Of the negative electrode composite layer 220 on the non-opposing surface 221 side, the end of the winding 25 side is a location where lithium ions are likely to move from the negative electrode composite layer 220 on the opposite side of the non-opposing surface 221 to the negative electrode composite layer 220 on the non-opposing surface 221 side, similar to the positive electrode end 21 side. Furthermore, if the portion of the electrode body 20C on the end of the winding 25 side is exposed above the liquid surface of the electrolyte 40 inside the battery case 10, a combination of lithium ions absorbed in the negative electrode composite layer 220 on the non-opposing surface 221 side and oxygen may occur in that portion. In particular, in this embodiment, where the end of the winding 25 is located near the top of the electrode body 20C, the area near the end of the winding 25 on the electrode body 20C is likely to be exposed above the liquid surface of the electrolyte 40. In other words, if the lithium ions absorbed in the negative electrode composite layer 220 located in the winding end region 221C are in a state where they readily combine with oxygen, there is a possibility that the release of lithium ions from the positive electrode composite layer 120 will become excessive.

[0050] In contrast, in the electrode body 20C, the lithium carbonate foil 50 is provided on the winding end region 221C, which suppresses the bonding of lithium ions and oxygen at that location and further suppresses the excessive release of lithium ions from the positive electrode sheet 100. The winding end region 221C is a region that extends from the positive electrode end 21 side to the negative electrode end 22 side, and includes a part of the positive electrode side region 221B related to the electrode body 20B of the second embodiment shown in Figure 8. Furthermore, in this embodiment, where the winding end 25 is located near the boundary between the flat portion 60 and the upper curved portion 61, the winding end region 221C includes a part of the positive electrode side upper curved region 221A related to the electrode body 20A of the first embodiment shown in Figure 7.

[0051] Furthermore, the electrode body 20 can be an appropriate combination of the first, second, and third embodiments described above. Preferably, the lithium carbonate foil 50 is provided at least on the upper curved surface region 221A on the positive electrode side. This is because the effect of suppressing the bonding of lithium ions and oxygen in the upper curved surface region 221A on the positive electrode side can be reliably achieved by the lithium carbonate foil 50. Therefore, for example, the electrode body 20 can be a combination of the first and third embodiments, with the lithium carbonate foil 50 provided on the upper curved surface region 221A on the positive electrode side and on the winding end region 221C. Alternatively, for example, the electrode body 20 can be a combination of the second and third embodiments, with the lithium carbonate foil 50 provided on the positive electrode side region 221B and on the winding end region 221C. Alternatively, for example, the electrode body 20 may be a configuration in which the lithium carbonate foil 50 is provided over the entire area of ​​the non-facing surface 221. Furthermore, the smaller the area where the lithium carbonate foil 50 is provided, the lower the material costs, and the cheaper the battery 1 can be.

[0052] Next, the manufacturing method of the battery 1 will be described. In this embodiment, the manufacturing procedure of the battery 1 will be described by dividing it into five steps, as shown in Figure 10: electrode body manufacturing step S11, electrode body housing step S12, electrolyte housing step S13, initial charging step S14, and aging step S15. Each step can be carried out using, for example, different equipment. Alternatively, multiple steps can be carried out using the same equipment as appropriate. Furthermore, as long as the battery 1 is manufactured properly, the order of some steps can be changed.

[0053] In electrode manufacturing process S11, the positive electrode sheet 100, the negative electrode sheet 200, and the separator 30 are stacked and wound together. Furthermore, in this embodiment, a lithium foil, which is a sheet of lithium, is provided at a predetermined position on the non-facing surface 221 of the negative electrode composite layer 220 of the negative electrode sheet 200. The position where the lithium foil is provided is, for example, the position related to the lithium carbonate foil 50 described in Figures 7, 8, and 9 above.

[0054] The lithium foil can be fixed in a predetermined position on the negative electrode sheet 200 before winding. Alternatively, for example, the lithium foil may be wound to a certain extent, and when the outermost separator 30 is wound onto the non-facing surface 221 of the negative electrode composite layer 220, it may be sandwiched in a predetermined position on the non-facing surface 221 of the negative electrode composite layer 220. When fixing the lithium foil to the negative electrode composite layer 220, for example, adhesive tape or adhesive can be used.

[0055] Furthermore, the electrode body 20 can be made flattened by, for example, winding each material into a cylindrical shape and then pressing it in the radial direction. Alternatively, the electrode body 20 can be constructed by winding each material into a flattened shape.

[0056] The positive electrode sheet 100 can be manufactured by forming a positive electrode composite layer 120 on both sides of the positive electrode current collector foil 110, while leaving a negative electrode non-formed area 111. The negative electrode sheet 200 can be manufactured by forming a negative electrode composite layer 220 on both sides of the negative electrode current collector foil 210, while leaving a negative electrode non-formed area 211.

[0057] In electrode housing step S12, the electrode body 20 is housed inside the battery case body 11. Specifically, for example, an assembly is formed by assembling the positive electrode terminal 2, negative electrode terminal 3, positive electrode current collector 4, negative electrode current collector 5, and electrode body 20 onto the lid 12, and the electrode body 20 in this assembly is housed inside the battery case body 11. After that, the lid 12 and the battery case body 11 are fixed together by joining or other means.

[0058] In the electrolyte filling step S13, the electrolyte 40 is injected through the inlet 13 of the lid 12. Furthermore, after the electrolyte 40 is injected, the inlet 13 is sealed with a sealing member 14. In this embodiment, the electrolyte filling step S13 uses an electrolyte 40 to which an additive that generates carbon dioxide when decomposed in the initial charging step S14 or the aging step S15 is added. The additive in this electrolyte 40 will be described in detail later.

[0059] In the initial charging process S14, the initial charging is performed. Initial charging is the first charging performed on battery 1.

[0060] In the aging process S15, the battery 1 is subjected to aging after its initial charge. During aging, the battery 1 is maintained at a temperature higher than room temperature for a predetermined period of time. For example, in the aging process S15, the battery 1 is maintained at a temperature of 60°C or higher.

[0061] In this embodiment of the battery 1 manufacturing method, lithium foil is provided at a predetermined position on the non-facing surface 221 of the negative electrode composite layer 220 of the negative electrode sheet 200. Figure 11 shows a cross-section of the electrode body 20 in a state prior to the initial charging process S14. Figure 11 is a cross-sectional view of the electrode body 20 on the outer circumference side, on the positive electrode end 21 side. As shown in Figure 11, lithium foil 51 is provided on the non-facing surface 221 of the negative electrode sheet 200. In this state, lithium ions are supplied from the lithium foil 51 to the negative electrode composite layer 220 on the non-facing surface 221 side on which the lithium foil 51 is provided, as indicated by arrow E. That is, sufficient lithium ions can be absorbed into the negative electrode composite layer 220 on the non-facing surface 221 side on which the lithium foil 51 is provided.

[0062] Furthermore, in the manufacturing method of the battery 1 of this embodiment, the electrolyte 40 is made by adding an additive that generates carbon dioxide when decomposed in the initial charging step S14 or the aging step S15. As the additive that generates carbon dioxide during initial charging, it is possible to use one that generates carbon dioxide when electrolyzed during charging. Specifically, as the additive that generates carbon dioxide during initial charging, for example, vinylene carbonate, ethyl carboxylic acid esters (e.g., ethyl acetate, ethyl propionate), methyl carboxylic acid esters (e.g., methyl acetate, methyl propionate), etc. As the additive that generates carbon dioxide during aging, it is possible to use one that generates carbon dioxide when thermally decomposed under the temperature environment during aging. As the additive that generates carbon dioxide during aging, for example, sodium bicarbonate, ammonium bicarbonate, etc., can be used. When using an additive that generates carbon dioxide during aging, it is preferable that the temperature during aging be 80°C or higher from the viewpoint of promoting its thermal decomposition.

[0063] Figure 12 shows a cross-section of the electrode body 20 when carbon dioxide is generated due to the decomposition of the additive during initial charging or aging. Figure 12 is also a cross-sectional view of the electrode body 20 on the outer circumference side, near the positive electrode end 21. The carbon dioxide generated in the electrolyte 40 due to the decomposition of the additive reacts with the lithium foil 51, as indicated by arrow F. Through this reaction, the lithium foil 51 becomes lithium carbonate foil 50. In other words, in this manufacturing method, the additive contained in the electrolyte 40 is decomposed and carbon dioxide is generated by the end of aging at the latest. Then, the generated carbon dioxide reacts with the lithium foil 51 to convert the lithium foil 51 into lithium carbonate foil 50.

[0064] As a result, this manufacturing method makes it possible to produce a battery 1 in which lithium ions are sufficiently absorbed in the negative electrode composite layer 220 on the non-opposing surface 221 side. Therefore, as explained by arrow C in Figure 5, it is possible to produce a battery 1 in which the movement of lithium ions from the negative electrode composite layer 220 on the side opposite to the non-opposing surface 221 to the negative electrode composite layer 220 on the non-opposing surface 221 side is further suppressed. In other words, it is possible to produce a battery 1 in which the excessive release of lithium ions from the positive electrode composite layer 120 of the positive electrode sheet 100 is further suppressed. In addition, lithium foil 51 has higher conductivity, is unstable and highly reactive compared to lithium carbonate foil 50. In this embodiment, lithium foil 51 can be changed into lithium carbonate foil 50, which has lower conductivity and is more stable, by reacting it with carbon dioxide. As a result, it is possible to produce a battery 1 with a lower possibility of short circuits, etc.

[0065] Furthermore, some additives that can be used in the electrolyte 40 may decompose during initial charging or aging, generating metal cations. Specifically, for example, sodium bicarbonate decomposes thermally during aging, producing sodium ions. When an additive that generates metal cations is used, the generated metal cations may subsequently precipitate as metal on the negative electrode sheet 200. Also, depending on the composition of the electrolyte 40, products formed by the reaction of the generated metal cations with other components in the electrolyte 40 may precipitate on the negative electrode sheet 200. In other words, when an additive that generates metal cations is used, it is preferable to keep the area in the electrolyte 40 where metal cations are generated as small as possible.

[0066] Furthermore, for example, when manufacturing a battery 1 having an electrode body 20A, if lithium foil 51 is provided on the upper part of the electrode body 20, carbon dioxide is necessary near the upper part of the battery case 10. This is to allow the lithium foil 51 to react appropriately with carbon dioxide to form lithium carbonate foil 50. On the other hand, if lithium foil 51 is not present on the lower part of the electrode body 20, that is, if lithium foil 51 is not provided in the lower region located below the electrode body 20 on the non-facing surface 221, it is not necessarily required to generate carbon dioxide in the lower part of the battery case 10. For this reason, for an electrode body 20 that has lithium foil 51 on the upper part but not on the lower part, it is preferable that the electrolyte 40 has a higher concentration of additives that generate carbon dioxide by decomposition near the upper part of the battery case 10 compared to the lower part. An example of this is shown in Figure 13.

[0067] The battery 1 shown in Figure 13 has undergone the electrolyte filling process S13. The battery 1 in Figure 13 also has an electrode body 20A in which lithium foil 51 is provided on the upper curved surface region 221A on the positive electrode side of the non-opposing surface 221 of the negative electrode composite layer 220. In other words, the negative electrode sheet 200 of the electrode body 20A has a lower region 221D in which lithium foil 51 is not provided, which is located below the electrode body 20 on the non-opposing surface 221. The lower region 221D is a region of the non-opposing surface 221 that includes at least the area of ​​the lower curved surface portion 62 of the electrode body 20A.

[0068] In the battery 1 shown in Figure 13, during the electrolyte filling process S13, the battery case 10 contains two electrolytes 40: a first electrolyte 40A and a second electrolyte 40B. The first electrolyte 40A does not contain any additives that generate carbon dioxide when decomposed during initial charging or aging. The second electrolyte 40B contains additives that generate carbon dioxide and metal cations when decomposed during initial charging or aging. In the electrolyte filling process S13, the first electrolyte 40A is first filled into the battery case 10, and after the first electrolyte 40A is filled, the second electrolyte 40B is filled.

[0069] Therefore, as shown in Figure 13, the first electrolyte 40A is accumulated in the lower part 10A of the battery case 10, and the second electrolyte 40B is contained in the upper part 10B. As a result, the concentration of the additive that generates carbon dioxide when decomposed during initial charging or aging is higher in the electrolyte 40 in the upper part 10B of the battery case 10 compared to the lower part 10A. Then, a process (initial charging process S14 or aging process S15) is performed in which carbon dioxide is generated from the additive in the electrolyte 40. This appropriately generates carbon dioxide in the area where the lithium foil 51 is present in the battery case 10, and the lithium foil 51 can be converted into lithium carbonate foil 50. In addition, metal cations are less likely to be generated in the lower part of the battery case 10. Therefore, the formation of precipitates caused by metal cations on the negative electrode sheet 200 can also be suppressed.

[0070] As described above, the battery 1 according to the above embodiment comprises an electrode body 20 and a battery case 10 that houses the electrode body 20 and the electrolyte 40. The electrode body 20 is a flat shape formed by winding a positive electrode sheet 100, a negative electrode sheet 200, and a separator 30. The flat electrode body 20 has an upper curved portion 61 located at the top, a lower curved portion 62 located at the bottom, and a flat portion 60 located between them. The electrode body 20 also has a positive electrode end 21 side on one end in the winding axis direction, which is formed when the negative electrode non-formed portion 111 of the positive electrode sheet 100 is wound in a state where it protrudes from the negative electrode sheet 200. On the other end opposite to the one end in the winding axis direction, the electrode body 20 has a negative electrode end 22, which is formed when the negative electrode non-formed portion 211 of the negative electrode sheet 200 is wound in a state where it protrudes from the positive electrode sheet 100. Furthermore, in the electrode body 20, at least at the end of the winding, the negative electrode sheet 200 is located on the outer circumference of the positive electrode sheet 100, so that the negative electrode composite layer 220 has a non-facing surface 221 that does not face the positive electrode sheet 100. The electrode body 20 has lithium carbonate foil 50 provided on the non-facing surface 221 of the negative electrode composite layer 220. Therefore, in the battery 1, the lithium carbonate foil 50 can prevent lithium ions in the negative electrode composite layer 220 on the non-facing surface 221 side from combining with oxygen. This suppresses excessive release of lithium ions from the positive electrode sheet 100. Thus, the battery 1 is of high quality in which the deposition of transition metals eluted from the positive electrode composite layer 120 of the positive electrode sheet 100 on the negative electrode sheet 200 is suppressed.

[0071] The embodiments described above are merely illustrative and do not limit the disclosed technology in any way. Therefore, the disclosed technology can naturally be improved and modified in various ways without departing from its essence.

[0072] For example, the configuration shown in the above embodiment is merely one example. For instance, the electrode body may be configured such that, at least at the end of the winding, the negative electrode sheet is located on the outer circumference of the positive electrode sheet. Also, for example, the battery case may not have an inlet, in which case the electrolyte may be supplied into the battery case through the same opening as the electrode body. Furthermore, the amount of electrolyte supplied to the battery case can be adjusted as appropriate. Also, for example, the battery according to the embodiment can be manufactured using lithium carbonate foil instead of lithium foil.

[0073] Furthermore, the disclosed technology described above includes the following means 1 to means 10. [Means 1] The electrode body is constructed by overlapping and winding a positive electrode sheet having a positive electrode composite layer formed on the surface of a positive electrode current collector foil, a negative electrode sheet having a negative electrode composite layer formed on the surface of a negative electrode current collector foil, and a separator that insulates the positive electrode sheet and the negative electrode sheet, and has at the top and bottom, respectively, two curved portions whose outer peripheral surfaces are curved, and a flat portion located between the two curved portions, where both outer peripheral surfaces facing each other in the thickness direction are flat. The battery comprises the electrode body and a battery case that houses the electrolyte, The electrode body is The positive electrode end, formed by winding the positive electrode sheet with a portion of the positive electrode material layer not formed therein protruding from the negative electrode sheet, is located on one end in the winding axis direction, and the negative electrode end, formed by winding the negative electrode sheet with a portion of the negative electrode material layer not formed therein protruding from the positive electrode sheet, is located on the other end in the winding axis direction. At least at the end of the winding, the negative electrode sheet is located on the outer circumference side of the positive electrode sheet, so that the negative electrode composite layer has a non-facing surface that does not face the positive electrode sheet. A lithium-ion secondary battery having lithium carbonate foil provided on the non-facing surface of the negative electrode composite layer.

[0074] [Means 2] A lithium-ion secondary battery as described in method 1, The aforementioned lithium carbonate foil is A lithium-ion secondary battery comprising at least one portion of the negative electrode composite layer's non-facing surface, specifically the positive electrode side upper curved surface region, which is a region along the positive electrode end side of the curved surface portion constituting the upper part of the electrode body.

[0075] [Means 3] A lithium-ion secondary battery as described in method 2, The aforementioned lithium carbonate foil is A lithium-ion secondary battery comprising at least one positive electrode side region, which is a region along the positive electrode end side of the non-facing surface of the negative electrode composite layer.

[0076] [Means 4] A lithium-ion secondary battery according to means 2 or means 3, The aforementioned lithium carbonate foil is A lithium-ion secondary battery comprising at least one non-facing surface of the negative electrode composite layer, specifically on the winding termination region, which is a region along the end of the winding end in the winding of the electrode body.

[0077] [Means 5] The electrode body is constructed by overlapping and winding a positive electrode sheet having a positive electrode composite layer formed on the surface of a positive electrode current collector foil, a negative electrode sheet having a negative electrode composite layer formed on the surface of a negative electrode current collector foil, and a separator that insulates the positive electrode sheet and the negative electrode sheet, and has at the top and bottom, respectively, two curved portions whose outer peripheral surfaces are curved, and a flat portion located between the two curved portions, where both outer peripheral surfaces facing each other in the thickness direction are flat. A method for manufacturing a lithium-ion secondary battery comprising the electrode body and a battery case for housing the electrolyte, The electrode body is constructed by winding the positive electrode sheet, the negative electrode sheet, and the separator such that the portion of the positive electrode sheet where the positive electrode composite layer is not formed extends beyond one end of the negative electrode sheet in the winding direction, and the portion of the negative electrode sheet where the negative electrode composite layer is not formed extends beyond the positive electrode sheet in the winding direction, and at least at the end of the winding, the negative electrode sheet is positioned on the outer circumference of the positive electrode sheet. After housing the electrode body and the electrolyte in the battery case, initial charging and aging are performed. When constructing the electrode body, lithium foil is provided on the non-facing surface of the negative electrode composite layer that does not face the positive electrode sheet. A method for manufacturing a lithium-ion secondary battery, using an electrolyte to which an additive that generates carbon dioxide when decomposed during initial charging or aging is added.

[0078] [Means 6] A method for manufacturing a lithium-ion secondary battery as described in means 5, A method for manufacturing a lithium-ion secondary battery, wherein when constructing the electrode body, the lithium foil is provided at least on the positive electrode side upper curved surface region, which is a region along the positive electrode end side of the curved surface portion that constitutes the upper part of the electrode body, where the positive electrode non-formed portion is wound in such a way that it protrudes from the negative electrode sheet, among the non-facing surfaces of the negative electrode composite layer.

[0079] [Means 7] A method for manufacturing a lithium-ion secondary battery as described in means 6, A method for manufacturing a lithium-ion secondary battery, wherein when constructing the electrode body, the lithium foil is provided at least on the positive electrode side region, which is the region along the positive electrode end side of the non-facing surface of the negative electrode composite layer.

[0080] [Means 8] A method for manufacturing a lithium-ion secondary battery as described in means 6, A method for manufacturing a lithium-ion secondary battery, wherein when constructing the electrode body, the lithium foil is provided at least on the winding termination region, which is a region along the end of the winding termination side in the winding of the electrode body, among the non-facing surfaces of the negative electrode composite layer.

[0081] [Means 9] A method for manufacturing a lithium-ion secondary battery as described in means 7, A method for manufacturing a lithium-ion secondary battery, wherein when constructing the electrode body, the lithium foil is provided at least on the winding termination region, which is a region along the end of the winding termination side in the winding of the electrode body, among the non-facing surfaces of the negative electrode composite layer.

[0082] [Means 10] A method for manufacturing a lithium-ion secondary battery according to any of means 5, means 6, or means 8, When constructing the electrode body, the lithium foil is not provided in the lower region of the non-facing surface, at least in the lower part of the electrode body. As the aforementioned additive, one is used that generates metal cations when decomposed during the initial charge or aging process. The battery case contains the electrode body and the first electrolyte, which is the electrolyte without the additives. A method for manufacturing a lithium-ion secondary battery, comprising: housing the electrode body and the first electrolyte in the battery case, and then housing the second electrolyte, which is the electrolyte to which the additive has been added, in the battery case. [Explanation of symbols]

[0083] 1:Battery 10: Battery case 20 (20A, 20B, 20C): Electrode body 21:Positive end 22:Negative end 30: Separator 40: Electrolyte 50: Lithium carbonate foil 51: Lithium foil 60: Flat part 61: Upper lateral curved face 62: Lower lateral curved face 100: positive electrode 110: Positive electrode current collector foil 111: Non-forming part of the positive electrode 120: Positive electrode composite layer 200: Negative electrode 210: Negative electrode current collector foil 211: Non-forming part of negative electrode 220: Negative electrode composite layer 221:Non-direction 221A: Upper curved surface area on the positive electrode side 221B: Positive electrode side domain 221C: Rewind Terminal Area 221D: Lower Domain

Claims

1. The electrode body is constructed by winding together a positive electrode sheet having a positive electrode composite layer formed on the surface of a positive electrode current collector foil, a negative electrode sheet having a negative electrode composite layer formed on the surface of a negative electrode current collector foil, and a separator that insulates the positive electrode sheet and the negative electrode sheet, with the upper and lower parts each having two curved portions whose outer peripheral surfaces are curved, and a flat portion located between the two curved portions, where both outer peripheral surfaces facing each other in the thickness direction are flat. The battery comprises the electrode body and a battery case that houses the electrolyte, The electrode body is The positive electrode end, formed by winding the positive electrode sheet with a portion of the positive electrode material layer not formed therein protruding from the negative electrode sheet, is located on one end in the winding axis direction, and the negative electrode end, formed by winding the negative electrode sheet with a portion of the negative electrode material layer not formed therein protruding from the positive electrode sheet, is located on the other end in the winding axis direction. At least at the end of the winding, the negative electrode sheet is located on the outer circumference side of the positive electrode sheet, so that the negative electrode composite layer has a non-facing surface that does not face the positive electrode sheet. A lithium-ion secondary battery having lithium carbonate foil provided on the non-facing surface of the negative electrode composite layer.

2. A lithium-ion secondary battery according to claim 1, The aforementioned lithium carbonate foil is A lithium-ion secondary battery comprising at least one portion of the negative electrode composite layer's non-facing surface, specifically the positive electrode side upper curved surface region, which is a region along the positive electrode end side of the curved surface portion constituting the upper part of the electrode body.

3. A lithium-ion secondary battery according to claim 2, The aforementioned lithium carbonate foil is A lithium-ion secondary battery comprising at least one positive electrode side region, which is a region along the positive electrode end side of the non-facing surface of the negative electrode composite layer.

4. A lithium-ion secondary battery according to claim 2 or claim 3, The aforementioned lithium carbonate foil is A lithium-ion secondary battery comprising at least one non-facing surface of the negative electrode composite layer, specifically on the winding termination region, which is a region along the end of the winding end in the winding of the electrode body.

5. The electrode body is constructed by winding together a positive electrode sheet having a positive electrode composite layer formed on the surface of a positive electrode current collector foil, a negative electrode sheet having a negative electrode composite layer formed on the surface of a negative electrode current collector foil, and a separator that insulates the positive electrode sheet and the negative electrode sheet, with the upper and lower parts each having two curved portions whose outer peripheral surfaces are curved, and a flat portion located between the two curved portions, where both outer peripheral surfaces facing each other in the thickness direction are flat. A method for manufacturing a lithium-ion secondary battery comprising the electrode body and a battery case for housing the electrolyte, The electrode body is constructed by winding the positive electrode sheet, the negative electrode sheet, and the separator such that the portion of the positive electrode sheet where the positive electrode composite layer is not formed extends beyond one end of the negative electrode sheet in the winding direction, and the portion of the negative electrode sheet where the negative electrode composite layer is not formed extends beyond the positive electrode sheet in the winding direction, and at least at the end of the winding, the negative electrode sheet is positioned on the outer circumference of the positive electrode sheet. After housing the electrode body and the electrolyte in the battery case, initial charging and aging are performed. When constructing the electrode body, lithium foil is provided on the non-facing surface of the negative electrode composite layer that does not face the positive electrode sheet. A method for manufacturing a lithium-ion secondary battery, using an electrolyte to which an additive that generates carbon dioxide when decomposed during initial charging or aging is added.

6. A method for manufacturing a lithium-ion secondary battery according to claim 5, A method for manufacturing a lithium-ion secondary battery, wherein when constructing the electrode body, the lithium foil is provided at least on the positive electrode side upper curved surface region, which is a region along the positive electrode end side of the curved surface portion that constitutes the upper part of the electrode body, where the positive electrode non-formed portion is wound in such a way that it protrudes from the negative electrode sheet, among the non-facing surfaces of the negative electrode composite layer.

7. A method for manufacturing a lithium-ion secondary battery according to claim 6, A method for manufacturing a lithium-ion secondary battery, wherein when constructing the electrode body, the lithium foil is provided at least on the positive electrode side region, which is the region along the positive electrode end side of the non-facing surface of the negative electrode composite layer.

8. A method for manufacturing a lithium-ion secondary battery according to claim 6 or claim 7, A method for manufacturing a lithium-ion secondary battery, wherein when constructing the electrode body, the lithium foil is provided at least on the winding termination region, which is a region along the end of the winding termination side in the winding of the electrode body, among the non-facing surfaces of the negative electrode composite layer.

9. A method for manufacturing a lithium-ion secondary battery according to claim 5 or claim 6, When constructing the electrode body, the lithium foil is not provided in the lower region of the non-facing surface, at least in the lower part of the electrode body. As the aforementioned additive, one is used that generates metal cations when decomposed during the initial charge or aging process. The battery case contains the electrode body and the first electrolyte, which is the electrolyte without the additives. A method for manufacturing a lithium-ion secondary battery, comprising: housing the electrode body and the first electrolyte in the battery case, and then housing the second electrolyte, which is the electrolyte to which the additive has been added, in the battery case.

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