JP6102726B2 - Method for manufacturing positive terminal - Google Patents

Description

The present invention relates to a method for manufacturing a positive electrode terminal.

  A lithium ion secondary battery, which is a kind of power storage device, has been put into practical use in the technical field of heavy equipment such as hybrid cars, electric cars, forklifts, electronic devices, or smart grids. In a technical field that requires a high-voltage or large-capacity battery, a power storage module including a plurality of lithium ion secondary batteries electrically connected by a connecting member (bus bar) is used.

  A lithium ion secondary battery includes a positive electrode, a negative electrode, a separator sandwiched between the positive electrode and the negative electrode, a case that houses the electrode assembly, a positive electrode that is electrically connected to the positive electrode, And a negative electrode terminal that is electrically connected to the negative electrode and penetrates the lid of the case. In the power storage module, the connection member electrically connects the positive electrode terminal or the negative electrode terminal of each lithium ion secondary battery to the positive electrode terminal or the negative electrode terminal of another lithium ion secondary battery. The connection member is made of, for example, a conductive material (Cu-based material) whose main component is copper having low electrical resistance and low Joule heat.

  The positive electrode includes a metal foil and a positive electrode active material that covers the metal foil. As the metal foil for the positive electrode, aluminum that does not easily react with the positive electrode active material is suitable. On the other hand, the negative electrode includes a metal foil and a negative electrode active material covering the metal foil. As the metal foil for the negative electrode, for example, copper having a low electric resistance is used. The positive electrode terminal is made of, for example, a conductive material (Al-based material) whose main component is aluminum that is easily welded to the positive electrode metal foil. For the same reason, the negative electrode terminal is made of, for example, a Cu-based material.

  In the manufacture of the positive electrode terminal, a molded body is produced from an Al-based material by processing such as die casting, extrusion molding, cutting, or threading. Since burrs are formed on the molded body during processing, it is necessary to remove the burrs.

  Patent Document 1 below discloses a method of removing burrs from a die-cast product by shot blasting a shot material (shot material) made of stainless steel, glass, ceramics, polycarbonate, or the like onto the die-cast product.

JP 2001-105317 A

  In the manufacture of the positive electrode terminal, when the projection material is projected onto the molded body, the projection material may adhere to the molded body and remain on the surface of the completed positive electrode terminal. When the projection material is made of a metal having a higher natural potential (corrosion potential) than the Al-based material, such as stainless steel, the positive electrode terminal made of the Al-based material in the presence of water or an electrolyte solution (for example, salt water) Is more susceptible to corrosion than blasting material. The larger the natural potential difference between the Al-based material and the projection material, the easier the positive electrode terminal corrodes. When the positive electrode terminal corrodes, the electrical resistance value between the positive electrode terminal and the connection member increases. Further, the larger the natural potential difference between the positive electrode terminal and the connection member, the easier the positive electrode terminal corrodes. For example, when the connecting member is made of a Cu-based material having a high natural potential, the positive electrode terminal is easily corroded.

  When a projection material made of an insulating material such as glass, ceramics or polycarbonate is used instead of the projection material having a high natural potential, the projection material is interposed between the positive electrode terminal and the connection member, and the positive electrode terminal and the connection member The electrical resistance value during the period increases.

  When a projection material made of a hard material such as stainless steel, glass, or ceramics is used, the surface of the positive electrode terminal is deformed by the collision of the projection material, and the surface roughness of the positive electrode terminal is increased. A large number of pointed portions exist on the rough surface of the positive electrode terminal, and the positive electrode terminal is easily corroded starting from the pointed portion. Moreover, when the surface roughness of the positive electrode terminal increases, the surface area of the positive electrode terminal increases. As the surface area of the positive electrode terminal increases, the corrosion resistance of the positive electrode terminal decreases.

The present invention has been made in view of the problems of the prior art, it is possible to suppress corrosion of the positive electrode terminal, provides a process for producing a positive electrode terminal capable of removing burrs and from the positive terminal For the purpose.

  The manufacturing method of the positive electrode terminal which concerns on 1 side of this invention is a manufacturing process which produces the molded object which has a protrusion part, a projection material is projected on a molded object, and a part of projection material is made to adhere to the end surface of a protrusion part. A shot blasting step, the molded body is made of pure aluminum, and the projection material is made of zinc or a zinc alloy.

  In the shot blasting process included in the method for manufacturing a positive electrode terminal according to one aspect of the present invention, burrs can be removed from the molded body. Moreover, the protective layer which consists of zinc or a zinc alloy can be formed in at least one part of the end surface of the protrusion part of a molded object, and corrosion of a positive electrode terminal can be suppressed.

According to the present invention, it is possible to suppress corrosion of the positive electrode terminal, manufacturing method of the positive electrode terminal capable of removing burrs is provided and the positive terminal.

FIG. 1 is a schematic perspective view of a power storage module according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of a power storage device provided in the power storage module of FIG. FIG. 3 is a schematic cross-sectional view of the power storage device taken along line III-III in FIG. 2. FIG. 4 is a schematic cross-sectional view of a positive electrode terminal included in the power storage device of FIG. FIG. 5 is an enlarged view of a portion where the positive electrode terminal is located in the power storage device of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of the drawings, the same or equivalent components are denoted by the same reference numerals. The present invention is not limited to the following embodiments.

(Power storage module)
As shown in FIG. 1, the power storage module 86 includes a plurality of power storage devices 10 and a plurality of connection members 74 (bus bars). The plurality of power storage devices 10 are electrically connected by connection members 74. The connection member 74 may be plate-shaped, for example. A partition wall 88 may be provided between the power storage devices 10. The partition wall portion 88 prevents a short circuit between the power storage devices 10 and promotes heat dissipation of the power storage device 10. The plurality of power storage devices 10 may be arranged so as to overlap along the short side direction of the lid portion 18 of the case 12. In the example of the power storage module 86 shown in FIG. 1, five power storage devices 10 are connected in series.

  The number of power storage devices 10 is not limited and may be two or more. For the sake of explanation, one of the adjacent power storage devices 10 is referred to as a first power storage device 10A, and the other power storage device 10 is referred to as a second power storage device 10B.

The electrical connection form of the plurality of power storage devices 10 may be a series connection or a parallel connection. When a plurality of power storage devices 10 are connected in series, a positive terminal 22 _P of the first power storage device 10A, a negative terminal 22 _N of the second power storage device 10B is, is physically connected by a connecting member 74 Just do it. When a plurality of power storage devices 10 are connected in parallel, the positive terminal 22 _P of the first electric storage apparatus 10A, a positive terminal 22 _P of the second power storage device 10B are physically connected by a connecting member 74, the and the negative terminal 22 _N of the one power storage device 10A, a negative terminal 22 _N of the second power storage device 10B is, only to be physically connected by a connecting member 74.

Below, the case where the electrical storage apparatus 10 is a lithium ion secondary battery is demonstrated. As shown in FIGS. 2 and 3, the power storage device 10 accommodates the electrode assembly 14 having the positive electrode 32, the negative electrode 34, and the separator 36 sandwiched between the positive electrode 32 and the negative electrode 34, and the electrode assembly 14. a case 12 which is electrically connected to the positive electrode 32, a positive terminal 22 _P passing through the lid 18 of the case 12 is electrically connected to the negative electrode 34, negative electrode terminal extending through the lid 18 of the case 12 22 _N.

The positive electrode 32 includes a metal foil and a positive electrode active material layer covering the metal foil. The positive electrode active material layer covers one side or both sides of the metal foil. At one edge of the positive electrode 32 is a tab 38 made of a metal foil that is not covered with the positive electrode active material. The positive electrode 32 is connected to the conductive member 40 via the tab 38. Conductive member 40 connected to the tab 38 is connected to the positive terminal 22 _P. In other words, the positive terminal 22 _P is electrically connected to the positive electrode 32 through the tab 38 and the conductive member 40. The positive electrode active material may be, for example, a composite oxide containing lithium and a transition metal (such as an oxide containing Li, Ni, Co, and Mn). The positive electrode 32 may have a sheet shape.

The negative electrode 34 includes a metal foil and a negative electrode active material layer that covers the metal foil. The negative electrode active material layer covers one side or both sides of the metal foil. At one edge of the negative electrode 34 is a tab 44 made of a metal foil that is not covered with the negative electrode active material layer. The negative electrode 34 is connected to the conductive member 46 via the tab 44. Conductive member 46 connected to the tab 44 is connected to the negative terminal 22 _N. In other words, the negative electrode terminal 22 _N is electrically connected to the negative electrode 34 via the tab 44 and the conductive member 46. The negative electrode active material is, for example, a carbon-based material such as graphite or hard carbon, an element alloying with lithium (Sn or Si), an elemental compound having an element alloying with lithium, or a polymer material such as polyacetylene or polypyrrole. It may be. The negative electrode 34 may have a sheet shape.

  For example, the separator 36 may be a porous film made of a synthetic resin such as polytetrafluoroethylene, polypropylene, or polyethylene, or a porous film made of ceramics.

  In the electrode assembly 14, each of the positive electrode active material layer of the positive electrode 32 and the negative electrode active material layer of the negative electrode 34 faces the separator 36. In the electrode assembly 14, a plurality of positive electrodes 32 and a plurality of negative electrodes 34 may be alternately stacked via separators 36.

The case 12 includes a case main body 16 that accommodates the electrode assembly 14, and a lid portion 18 that closes one open end of the case main body 16. The lid 18 may be joined to the open end of the case body 16 by, for example, laser welding. The shape of the case 12 may be a rectangular parallelepiped, for example. The case body 16 and the lid 18 may be made of a metal such as aluminum or stainless steel, for example. The case 12 is filled with the non-aqueous electrolyte 20 together with the electrode assembly 14. The lid portion 18, a pair of positive terminal 22 _P and the negative terminal 22 _N are spaced apart from each other.

As shown in FIGS. 4 and 5, the positive electrode terminal 22 </ b> _P includes, for example, a base end portion 50, a protruding portion 52, and a protective layer 68 that covers at least a part of the end surface 58 of the protruding portion 52. The base end portion 50 is disposed inside the case 12. The protruding portion 52 protrudes from the base end portion 50 to the outside of the case 12 through the insertion hole 24 formed in the lid portion 18. The end surface 58 of the protruding portion 52 faces the connection member 74. Protective layer 68 is interposed between the connecting member 74 and the projecting portion 52 of the positive terminal 22 _P, connected by contact with the member 74, a positive terminal 22 _P are connected to connecting member 74 electrically. The protective layer 68 may cover the entire end surface 58 of the protruding portion 52. Some of the protruding portion 52 of the positive terminal 22 _P may be in direct contact with the connecting member 74. Proximal end 50 of the positive terminal 22 _P is connected to the conductive member 40. The base end part 50 may be columnar (for example, cylindrical). The diameter of the base end portion 50 is larger than the diameter of the insertion hole 24. The protrusion 52 may be columnar (for example, columnar). The protrusion 52 is smaller than the diameter of the insertion hole 24. The positive terminal 22 _P, the insertion hole 62 extending toward the base end portion 50 from the end face 58 of the projecting portion 52 is formed. The length of the insertion hole 62 (depth) may be shorter than the length of the positive terminal 22 _P.

Proximal end 50 and the projection 52 of the positive terminal 22 _P is made of pure aluminum (Al). Pure aluminum is, for example, aluminum having a purity of 99.00% by mass to 100% by mass. Pure aluminum may contain silicon (Si) or iron (Fe) as a trace amount of impurities. Pure aluminum is displayed with, for example, 1000s of symbols based on JIS (Japanese Industrial Standard, JIS H4100). The pure aluminum according to JIS H4100 may be, for example, A1085, A1080, A1070, A1050, A1050A, A1060, A1100, A1200, A1N00, or A1N30.

  The protective layer 68 is made of zinc alone (Zn) or a zinc alloy. The zinc alloy may be an alloy containing, for example, at least one metal (subcomponent) selected from the group consisting of iron, nickel, copper, aluminum, tin, and magnesium, and zinc (main component). The zinc content in the zinc alloy may be 92% by mass or more.

Portion 74b which faces the end face 58 of the projecting portion 52 of the positive terminal 22 _P in the connecting member 74 is composed of tin (Sn). That is, the portion made of tin in the connection member 74 contacts the protective layer 68 that covers the end surface 58. The connection member 74 may include a base material 74a made of a metal other than tin (for example, a Cu-based material or an Al-based material) and a tin plating layer (74b) that covers the surface of the base material. The tin plating layer may cover only the portion of the surface of the base material 74a that contacts the end surface 58. The tin plating layer may cover the entire surface of the base material 74a. The entire connecting member 74 may be made of tin.

The negative terminal 22 _N, for example, may consist Cu-based material (e.g., copper or copper alloy). If the negative terminal 22 _N being Cu based material, since the self-potential of the Cu-based material is higher than that of pure aluminum, the negative electrode terminal 22 _N is hard to corrode than the positive terminal 22 _P. Therefore, when the negative electrode terminal 22 _N being Cu based material, the negative electrode terminal 22 _N may not include the protective layer 68. Configuration and dimensions of the negative electrode terminal 22 _N, except that without the protective layer 68 may be the same as the positive terminal 22 _P. That is, the negative electrode terminal 22 </ b> _N includes the base end portion 50 and the protruding portion 52. The base end portion 50 is disposed inside the case 12. The protruding portion 52 protrudes from the base end portion 50 to the outside of the case 12 through the insertion hole 24 formed in the lid portion 18. By the end face 58 of the projecting portion 52 of the negative electrode terminal 22 _N is in contact with the connecting member 74 connects the negative terminal 22 _N is connected to member 74 electrically. Proximal end 50 of the negative electrode terminal 22 _N is connected to the conductive member 46. The base end part 50 is. It may be columnar (for example, cylindrical). The diameter of the base end portion 50 is larger than the diameter of the insertion hole 24. The protrusion 52 may be columnar (for example, columnar). The protrusion 52 is smaller than the diameter of the insertion hole 24. The negative terminal 22 _N, the insertion hole 62 extending toward the base end portion 50 from the end face 58 of the projecting portion 52 is formed. The length of the insertion hole 62 (depth) may be shorter than the length of the negative terminal 22 _N.

If the negative terminal 22 _N consists of pure aluminum, the negative electrode terminal 22 _N may comprise a protective layer 68, the shape of the negative electrode terminal 22 _N may be any identical to the positive terminal 22 _P.

As shown in FIG. 5, the bolt 76 (first fixed member) is inserted into the insertion hole 62 of the positive terminal 22 _P. The shaft of the bolt 76 is fitted into a hole 84 (or a notch) formed in the connection member 74. Connecting member 74, a head of the bolt 76, a protective layer 68 covering the end face 58 of the positive terminal 22 _P, sandwiched between. Thus, the connecting member 74 is fixed to the positive electrode terminal 22 _P by a bolt 76 (first fixing member). The insertion hole 62 is a female screw portion that is screwed with the shaft (male screw portion) of the bolt 76. That is, the insertion hole 62 is a screw hole into which a bolt is screwed.

The protruding portion 52 of the positive terminal 22 _P is fitted into the opening of the fixing nut 28 (second fixing member) through the insertion hole 24 of the lid portion 18. The lid portion 18 is sandwiched between the base end portion 50 of the positive electrode terminal 22 _P and the fixing nut 28. Thus, the positive terminal 22 _P is fixed to the lid 18 by a fixing nut 28 (second fixing member). A male screw portion (screw region 56) may be formed on the side peripheral surface (outer peripheral surface) 54 of the protruding portion 52. The screw region 56 may be provided in a region near the end surface 58 of the protruding portion 52 on the side peripheral surface 54. There may be a non-screw region where no screw groove is formed between the screw region 56 and the base end portion 50 on the side peripheral surface 54. This non-screw region may be fitted into an insertion hole 24 formed in the lid portion 18 of the case 12. A screw portion (female screw portion) may be formed on the inner surface of the opening of the fixing nut 28. The female screw portion of the fixing nut 28 threaded region 56 of the positive terminal 22 _P of the protruding portion 52 (male screw portion) may be screwed.

  The first insulating member 26 is interposed between the fixing nut 28 and the lid portion 18 and between the protruding portion 52 and the lid portion 18. The first insulating member 26 may be, for example, an annular member having insulating properties, and may be made of resin, for example. The first insulating member 26 is interposed between the fixing nut 28 and the lid portion 18 and between the protruding portion 52 and the lid portion 18.

Between the positive terminal 22 proximal end 50 of the _P and the lid portion 18, the second insulating member 30 is interposed. The second insulating member 30 may surround the base portion of the protruding portion 52. The second insulating member 30 may be a member having elasticity and insulation, for example. Second insulating member 30, by interposing between the positive terminal 22 proximal end 50 of the _P lid 18, the case 12 is sealed.

Negative terminal 22 _N and the other member (connecting member 74, a bolt 76 (first fixed member), a fixing nut 28 (second fixing member), the lid portion 18, the first insulating member 26 and the second insulating member the positional relationship between the 30) may be the same as the case of the positive terminal 22 _P.

Pure aluminum constituting the positive electrode terminal 22 _P reacts with oxygen in the atmosphere. Therefore, on the end face 58 of the positive terminal 22 _P of the protruding portion 52 is an oxide film of aluminum is formed. The oxide film, because it has a function of suppressing oxidation of pure aluminum, a positive terminal 22 _P made of pure aluminum originally excellent in corrosion resistance. However, the force due to vibration or the like, to act against the connecting member 74 in contact with the positive terminal 22 _P or positive terminals 22 _P, the oxide film in the positive terminal 22 _P surface that faces the connecting member 74 is broken, pure aluminum Is exposed. If the protective layer 68 is not provided, the pure aluminum is exposed in the presence of water or an electrolyte solution (for example, salt water) because the natural potential of pure aluminum is lower than that of a conventional connection member made of only a Cu-based material. the positive terminal 22 _P corrodes the parts as a starting point. As a result, the electric resistance value between the positive terminal 22 _P and the connecting member 74 is increased.

However, in the present embodiment, a protective layer 68 made of zinc alone or a zinc alloy having a small difference in natural potential from pure aluminum covers the end surface 58 of the protruding portion 52. A protective layer 68 is interposed between the end surface 58 of the protrusion 52 and the connection member 74. That is, the protective layer 68 is in direct contact with the connection member 74. Further, in this embodiment, the portion which contacts the connecting member 74 and the positive terminal 22 _P is made of a tin lower natural potential than Cu-based material. That is, in this embodiment, as compared with the case of using the connecting member 74 made of only Cu-based material, the difference in natural potential between the connecting member 74 and the positive terminal 22 _P is small. For example, the natural potential of copper is about 0.345V, the natural potential of tin is about -0.146V, and the natural potential of pure aluminum is about -1.337V. For these reasons, in the present embodiment, when there is no protective layer 68, or the connection member 74 as compared with a case made of only Cu-based material, inhibiting corrosion of the projecting portion 52 of the positive terminal 22 _P made of pure aluminum be able to.

(Method for manufacturing positive electrode terminal)
Method for producing a positive terminal 22 _P of the electric storage device 10 is provided is provided with a shaping step and a shot blasting process.

In the molding step, for example, a molded body including a base end portion and a protruding portion protruding from the base end portion is produced. Proximal end of the molded body corresponds to the proximal end portion 50 of the positive terminal 22 _P shown in FIGS. Protrusion of the molded body corresponds to the protruding portion 52 of the positive terminal 22 _P shown in FIGS. The molded body may be formed with an insertion hole extending from the end surface of the protruding portion toward the base end portion. Insertion hole of the molded body corresponds to the insertion hole 62 of the positive terminal 22 _P shown in FIGS.

The molded body is produced by a process such as die casting, extrusion molding, cutting or threading. During processing, burrs are formed on the molded body. The molded body is made from pure aluminum. Since the hardness of pure aluminum is relatively low among metal materials, it is easy to mold. Pure aluminum, which is a raw material of the molded body is the same as the pure aluminum constituting the positive terminal 22 _P of the.

In the shot blast process, the projection material is projected onto the molded body. Projection material burrs collide with burr of the molded body is removed, the positive terminal 22 _P can be obtained. The projection material is particles made of zinc alone or a zinc alloy. The zinc simple substance or zinc alloy constituting the projection material is the same as the zinc simple substance or zinc alloy constituting the protective layer 68 described above.

When the projecting material collides with the end face of the projecting portion of the molded body, mechanical alloying of pure aluminum constituting the molded body and a part of the projecting material occurs (mechanical alloying), and the projecting material of the projecting portion of the molded body It adheres mechanically to the end face. As a result, the protective layer 68 which is firmly adhered to the end surface 58 of the positive terminal 22 _P of the protruding portion 52 is formed. Protective layer 68 formed by the shot blast process, easily separated from the end face 58 of the positive terminal 22 _P of the protruding portion 52 is excellent in mechanical durability.

The protective layer 68 is made of zinc alone or a zinc alloy. The natural potential of zinc alone or a zinc alloy is lower than the natural potential (for example, about −0.57 V) of stainless steel constituting the conventional projection material. For example, the natural potential of zinc alone is about −0.762V. On the other hand, the natural potential of the pure aluminum constituting the projecting portion 52 of the positive terminal 22 _P is, for example, about -1.337V. Therefore, the difference in natural potential between the protective layer 68 and the protrusion 52 is smaller than the difference in natural potential between the conventional projection material made of stainless steel and the protrusion 52. Thus, in the present embodiment, by using the natural potential difference is small shot material the positive terminal 22 _P, suppressing the corrosion of the positive terminal 22 _P due to the natural potential difference between the positive terminal 22 _P and the projection member Can do.

A projection material made of zinc alone or a zinc alloy has conductivity. Therefore, in the present embodiment, it is possible to glass, as compared with the case of using a shot material made of ceramic or insulating material such as polycarbonate, to suppress a decrease in conductivity of the positive terminal 22 _P accompanying the deposition of the shot material.

The hardness of the zinc simple substance or zinc alloy constituting the projection material is lower than that of a conventional projection material such as stainless steel, glass or ceramics, and is lower than that of pure aluminum. Thus, in this embodiment, compared with the case of using the conventional shot material, deformation of the surface of the molded body due to deburring (end face of the projection) is suppressed, the increase in the surface roughness and surface area of the positive terminal 22 _P Is suppressed. By suppressing the increase in the surface roughness and surface area of the positive terminal, the corrosion resistance of the positive terminal 22 _P is improved. That is, since the projection material made of zinc alone or zinc alloy is soft and easily deformed, the protective layer 68 can be easily formed on the surface of the molded body without excessively damaging the surface of the molded body made of soft pure aluminum.

The Vickers hardness of a projection material should just be 40-50HV, for example. The Vickers hardness of the projection material may be 0.3 to 0.43 times or 0.35 to 0.38 times the Vickers hardness of pure aluminum. When using a shot material having such a Vickers hardness, easy to remove burrs, easy to suppress deformation of the surface of the molded body due to deburring the (roughening), the end surface of the projecting portion 52 of the positive terminal 22 _P 58 is easily covered with the protective layer 68. The larger the hardness of the projection material, the easier the burrs are removed, and the surface of the molded body tends to be deformed with deburring. As the hardness of the projection material is smaller, the surface of the molded body is less likely to be deformed, burrs are more difficult to remove, and the projection material tends to remain on the surface of the molded body.

The particle size of the projection material may be, for example, 150 to 750 μm. The air pressure for projecting the projection material onto the molded body may be, for example, 0.1 to 0.3 MPa. The distance between the injection port of the projection material and the molded body in the shot blasting apparatus may be, for example, 50 to 150 mm. The projection time may be, for example, 5 to 45 seconds. When carrying out shot blasting process under these conditions, it is easy to remove burrs, easy to suppress deformation of the surface of the molded body due to deburring the (roughening), the end faces of the positive terminal 22 _P of the projections 52 58 Is easily covered with the protective layer 68.

Surface roughness Ra of the end surface 58 of the projecting portion 52 of the positive terminal 22 _P obtained in the shot blasting process (the plane including the protective layer 68) may be at 1.0μm or less, even 0.7μm or less Good. As the surface roughness Ra of the end face 58 is smaller, the corrosion resistance of the end face 58 tends to be improved.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. For example, the present invention may be in the following forms.

An insertion hole 62 formed in the positive terminal 22 _P or the negative terminal 22 _N, bound form of the first fixing member is not limited to fastening by screws. For example, the first fixing member has a head portion and a shaft portion extending from the head portion, and the screw groove may not be cut in the shaft portion. That is, the surface of the shaft of the first fixing member may be smooth. A screw groove may not be formed on the inner surface of the insertion hole 62. In this case, the shaft portion of the first fixing member is press-fitted into the insertion hole 62.

The projecting portion 52 of the positive terminal 22 _P protrusions 52 or the negative terminal 22 _N, the bound form of the second fixing member is not limited to fastening by screws. For example, the thread groove may not be formed on the side peripheral surface 54 of the protrusion 52. No thread groove may be formed on the inner surface of the opening of the second fixing member. That is, the inner surface of the opening of the second fixing member may be smooth. In this case, the protrusion 52 is press-fitted into the opening of the second fixing member.

  The positive electrode terminal may not be provided with a base end portion but may be a columnar terminal including a protruding portion and a protective layer. In this case, the power storage device may include a connection plate placed on the surface of the lid portion facing the outside of the case, and a columnar connection portion that penetrates the lid portion and protrudes to the inside of the case. One end face of the positive electrode terminal (end face not covered with the protective layer) may be in contact with the surface of one end of the connection plate. That is, the positive electrode terminal may stand on the surface of one end of the connection plate. The end surface of one end of the connecting portion (the end passing through the lid) may be in contact with the back surface of the other end of the connecting plate. One end surface (the end surface not covered with the protective layer) of the positive electrode terminal may be fitted into a through hole or a notch formed in one end of the connection plate. One end of the connecting portion may be fitted into a through hole or a notch formed in the other end of the connecting plate. The positive electrode terminal may be welded to the connection plate. The connection part may be welded to the connection plate. The positive terminal may be bonded to the connection plate. The connecting portion may be bonded to the connecting plate. The positive electrode terminal may be electrically connected to the connection portion via the connection plate. The connecting portion may be electrically connected to the positive electrode in the case. A structure including such a positive electrode terminal, a connection plate, and a connection portion is called a Z terminal.

  The power storage device only needs to include a positive electrode and a negative electrode, and is not limited to a lithium ion secondary battery. For example, the power storage device may be a metal lithium secondary battery, a nickel hydride secondary battery, an electric double layer capacitor, or a lithium ion capacitor.

[Experiment 1]
A plate-like test piece made of pure aluminum (A1100 based on JIS H4100) was produced. The dimension of the test piece was 5 mm × 20 mm × 50 mm. The Vickers hardness of the test piece (pure aluminum) was 115 to 130 HV. The electrical resistivity of the test piece at 20 ° C. was 28.2 nΩ · m. A shot blasting process for projecting a projecting material made of zinc alone or a zinc alloy onto a test piece was performed. The Vickers hardness, average particle diameter, and electrical resistivity of the projection material used in Experimental Example 1 were values shown in Table 1 below. In the shot blasting process, a blasting device (centrifugal projector) manufactured by Shinto Blator was used.

  After the shot blasting process, the surface roughness Ra of the surface (projection surface) of the test piece on which the projection material was projected was measured. The surface roughness Ra was measured according to the standard of JIS B0601. Table 1 shows the surface roughness Ra of the test piece of Experimental Example 1.

A salt spray test specified in JIS Z2371 was conducted to evaluate the corrosion resistance of the test piece after the shot blasting process. In the test, the specimens were exposed to salt water for 250 hours. Based on the following formula, the corrosion weight loss ratio (unit:% by weight) of the test piece was calculated. The corrosion weight loss ratio of the test piece of Experimental Example 1 is shown in Table 1 below.
Corrosion weight loss ratio = {(W ₀ −W ₁ ) / W ₀ } × 100
In the above formula, W ₀ is the weight of the test piece after the shot blasting process and before the salt spray test. W ₁ is the weight of the test piece after the salt spray test.

[Experiment 2]
In Experimental Example 2, a projection material made of zirconium oxide (ZrO ₂ ) shown in Table 1 below was used instead of the projection material made of zinc alone or a zinc alloy. The shot blasting process of Experimental Example 2 was performed in the same manner as in Experimental Example 1 except that the projection material was different. Table 1 below shows the surface roughness Ra of the test piece of Experimental Example 2 measured by the same method as Experimental Example 1. The corrosion weight loss ratio of Experimental Example 2 measured by the same method as Experimental Example 1 is shown in Table 1 below.

[Experiment 3]
In Experimental Example 3, a projection material made of aluminum oxide (Al ₂ O ₃ ) shown in Table 1 below was used instead of the projection material made of zinc alone or a zinc alloy. The shot blasting process of Experimental Example 3 was performed in the same manner as in Experimental Example 1 except that the projection material was different. Table 1 below shows the surface roughness Ra of the test piece of Experimental Example 3 measured by the same method as Experimental Example 1. The corrosion weight loss ratio of Experimental Example 3 measured by the same method as Experimental Example 1 is shown in Table 1 below.

[Experimental Example 4]
In Experimental Example 4, a projection material made of stainless steel (SUS430) shown in Table 1 below was used instead of the projection material made of zinc alone or a zinc alloy. The shot blasting process of Experimental Example 4 was performed in the same manner as in Experimental Example 1 except that the projection material was different. Table 1 below shows the surface roughness Ra of the test piece of Experimental Example 4 measured by the same method as Experimental Example 1. The corrosion weight loss ratio of Experimental Example 4 measured by the same method as Experimental Example 1 is shown in Table 1 below.

  As shown in Table 1, it was confirmed that both the surface roughness Ra and the corrosion weight loss ratio of the test piece of Experimental Example 1 using the projection material made of zinc alone or a zinc alloy were smaller than the other test pieces. .

  By comparing the surface roughness Ra and the corrosion weight loss ratio of the test pieces of Experimental Examples 1 to 3, it was confirmed that the smaller the surface roughness Ra of the test piece, the smaller the corrosion weight loss ratio. That is, it was confirmed that the corrosion weight loss ratio of the test piece depends on the surface roughness of the test piece after the shot blasting process.

  The surface roughness of the test piece of Experimental Example 2 was the same as the surface roughness of the test piece of Experimental Example 4. However, the corrosion weight loss ratio of the test piece of Experimental Example 2 was smaller than the corrosion weight loss ratio of the test piece of Experimental Example 4. That is, the corrosion weight loss ratio of the test piece of Experimental Example 4 using the projection material made of SUS430 having a high natural potential was larger than that of the test piece of Experimental Example 2. From this, it was confirmed that the corrosion weight loss ratio of the test piece depends not only on the surface roughness of the test piece after the shot blasting process but also on the composition of the test piece (natural potential of the test piece).

10 ... electric storage unit, 12 ... case, 18 ... lid portion, 14 ... electrode assembly, ₂₂ P ... positive terminal, ₂₂ N ... negative terminal, 32 ... positive electrode, 34 ... Negative electrode, 36 ... Separator, 50 ... Base end, 52 ... Projection, 58 ... End face, 68 ... Protective layer, 74 ... Connection member (bus bar), 74b... Part of the connecting member that faces the end face of the projecting portion, 86.

Claims (1)

A molding step for producing a molded body having a protrusion, and
A shot blasting step of projecting a projection material onto the molded body and attaching a part of the projection material to an end surface of the projecting portion;
With
The molded body is made of pure aluminum,
The projection material is made of zinc or a zinc alloy.
Manufacturing method of positive electrode terminal.

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