Electrochemical cell
By employing a negative electrode tank structure with a double-cylinder section and a stepped section in the electrochemical unit, the durability and sealing performance of the negative electrode tank are enhanced, the problem of reduced sealing performance during reflow soldering is solved, and the capacitance and reliability are increased.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SEIKO INSTR INC
- Filing Date
- 2021-09-17
- Publication Date
- 2026-06-09
AI Technical Summary
During reflow soldering, the sealing performance of the electrochemical unit is easily affected, and as the capacitance increases, the peripheral wall of the metal can becomes larger in the height direction, resulting in a decrease in sealing performance.
The negative electrode can adopts a structure with a double-cylinder section and a stepped section. The outer cylinder is set larger in the axial direction to enhance the durability of the peripheral wall of the negative electrode can, and excellent sealing performance is achieved by strong pressure from the gasket. At the same time, deformation of the negative electrode can is avoided during riveting.
This method achieves the goal of maintaining the sealing of the electrochemical unit during reflow soldering, and avoids deformation of the negative electrode tank while increasing the capacitance, thus ensuring the capacitance and reliability of the electrochemical unit.
Smart Images
Figure CN114388946B_ABST
Abstract
Description
[0001] Citations of relevant applications
[0002] This application claims priority to Japanese Patent Application No. 2020-168691, filed on October 5, 2020, the contents of which are incorporated herein by reference. Technical Field
[0003] This invention relates to electrochemical units. Background Technology
[0004] As a container for an electrochemical unit, there is a type of container that is sealed by riveting the opening of an outer metal can while a gasket is sandwiched between the openings of a pair of metal cans. In such electrochemical units, techniques to improve sealing have been developed to enhance reliability. For example, in a coin-shaped battery disclosed in International Publication No. 2013 / 046644, the negative electrode can (sealing plate) includes: a first curved portion formed at the boundary between the top surface and the second sidewall; a second curved portion formed following the first curved portion; a third curved portion formed following the second curved portion; and a descending portion formed following the third curved portion, with the radius of curvature of the first curved portion and the radius of curvature of the second curved portion defined. Therefore, when the opening end of the positive electrode can (battery casing) is riveted, the pressure applied to the second sidewall of the negative electrode can is distributed over a wider range, thereby significantly suppressing deformation of the negative electrode can during the riveting process.
[0005] However, in recent years, small non-aqueous electrolyte secondary batteries, as a type of electrochemical unit, have required support for reflow soldering to improve soldering efficiency when mounting circuit boards. For example, in the non-aqueous electrolyte secondary battery disclosed in Japanese Patent Application Publication No. 2019-160619, the solvent has achieved heat resistance that can withstand the heating during reflow soldering by including ethylene carbonate (EC) and vinylene carbonate (VC) in a glycol dimethyl ether solvent. Summary of the Invention
[0006] However, during reflow soldering, the internal pressure of the electrochemical unit container can easily rise due to heating during installation, thus requiring further improvement in sealing.
[0007] Furthermore, electrochemical units that can be reflow soldered require increased capacitance without increasing the mounting area. Therefore, when increasing the capacitance by thickening the electrochemical unit, the peripheral walls of a pair of metal cans become larger in the height direction. Consequently, if the pressure is distributed over a wider range during the riveting process described above, the peripheral walls of the negative electrode can are pressurized over a wider range, which may cause deformation of the negative electrode can and reduce its sealing performance.
[0008] Therefore, the present invention provides an electrochemical unit with excellent sealing performance and large capacitance that can be reflow soldered.
[0009] Solution for solving the problem
[0010] The electrochemical unit according to the first aspect of the present invention comprises: a positive electrode can formed as a bottomed cylindrical shape, having a bottom and a positive electrode can peripheral wall portion extending axially in a first direction from the outer periphery of the bottom; a negative electrode can formed as a topped cylindrical shape, having a top and a negative electrode can peripheral wall portion extending axially in a second direction from the outer periphery of the top, and inserted into the inner side of the positive electrode can; and a gasket disposed between the positive electrode can peripheral wall portion and the negative electrode can peripheral wall portion, which is pressed against the outer peripheral surface of the negative electrode can by contracting the opening edge of the positive electrode can, the negative electrode can peripheral wall portion having: a double cylindrical portion extending from the opening edge of the negative electrode can toward the top in the first direction; and a stepped portion connecting the top and the double cylindrical portion, the stepped portion having: a first curved portion bending from the outer periphery of the top toward the second direction. The first bend extends radially outward from the edge of the second bend in the second direction; and the second bend extends radially outward from the outer periphery of the second bend in the second direction. The double-cylinder portion has: an inner cylinder portion extending radially outward from the edge of the third bend in the second direction; an outer cylinder portion surrounding the inner cylinder portion from the radially outward side; and a folded portion disposed at the opening edge of the negative electrode can, connecting the inner cylinder portion and the outer cylinder portion. The gasket is disposed at least along the radially outward side of the outer cylinder portion and in the first direction. The edge of the outer cylinder portion in the first direction is located in the first direction more than the center between the two ends of the negative electrode can in the axial direction, and in the second direction more than the edge of the third bend in the first direction.
[0011] According to the electrochemical unit of the first embodiment, since the outer cylinder portion can be provided in a larger axial direction, the peripheral wall of the negative electrode can be given high durability against pressure from the radially outer side. Therefore, by contracting the opening edge of the positive electrode can and forcefully pressurizing the gasket, the negative electrode can be fully secured from the first direction and the radially outer side. Correspondingly, since the outer cylinder portion does not protrude further in the first direction than the third bend, it is possible to prevent the outer cylinder portion from sinking into the gasket arranged along the first direction of the outer cylinder portion. Therefore, even with forceful pressure on the gasket, damage caused by contact between the gasket and the outer cylinder portion can be prevented. Therefore, it is possible to prevent moisture from entering the interior from the surface of the gasket through the opening of the positive electrode can, thus providing excellent sealing performance even for electrochemical units with increased thickness to increase capacitance. Therefore, a reflow-solderable electrochemical unit with excellent sealing performance and large capacitance can be provided.
[0012] In the electrochemical unit according to the second aspect of the present invention, in the electrochemical unit according to the first aspect described above, the edge of the outer cylinder portion in the first direction is located in the first direction more than the edge of the inner cylinder portion in the first direction.
[0013] According to the electrochemical unit involved in the second method, the entire inner cylinder can be surrounded by the outer cylinder. As a result, the dual-structure portion can be provided to the maximum extent in the double cylinder, thus providing high durability through the double cylinder.
[0014] The electrochemical unit according to the third aspect of the present invention, in the electrochemical unit according to the first or second aspect described above, the gasket has: an annular base disposed between the bottom of the positive electrode can and the opening edge of the negative electrode can; an outer wall portion protruding from the outer periphery of the base in the first direction and extending circumferentially throughout the entire circumference, and disposed between the peripheral wall portion of the positive electrode can and the peripheral wall portion of the negative electrode can; and an inner wall portion such that the inner side of the peripheral wall portion of the negative electrode can protrudes from the base in the first direction and extends circumferentially throughout the entire circumference, wherein the thickness of the base portion in the axial direction is greater than the maximum thickness of the outer wall portion and the inner wall portion in the radial direction.
[0015] According to the electrochemical unit involved in the third method, the wall thickness, especially in the portion near the base, can be ensured. Therefore, in an electrochemical unit where the thickness is increased to increase capacitance, the strength of the gasket can be ensured. Furthermore, since a sufficient number of gaskets are arranged between the bottom of the positive electrode can and the opening edge of the negative electrode can, the positive and negative electrode cans can be fully and tightly sealed to the gaskets during the riveting process of the positive electrode can. Thus, an electrochemical unit with excellent sealing performance can be formed. Furthermore, the axial length of the peripheral wall of the negative electrode can is reduced by increasing the axial base thickness. Therefore, the area of the peripheral wall of the negative electrode can that is pressurized by the gaskets is reduced, thereby reducing the force applied to the peripheral wall of the negative electrode can. Therefore, deformation of the negative electrode can is suppressed.
[0016] In the electrochemical unit according to the fourth aspect of the present invention, in any of the electrochemical units according to the first to third aspects described above, the end of the outer peripheral surface of the outer cylinder in the first direction is chamfered throughout the entire circumference.
[0017] According to the electrochemical unit involved in the fourth method, excessive pressure can be suppressed from being applied from the outer cylinder to the gasket disposed in the first direction of the outer cylinder. Therefore, even if the gasket is subjected to strong pressure, damage caused by contact between the gasket and the outer cylinder can be suppressed. Attached Figure Description
[0018] Figure 1 This is a cross-sectional view of the battery involved in the implementation method.
[0019] Figure 2 This is a longitudinal cross-sectional view of the battery according to the embodiment, and a view showing the state before the outer casing is sealed.
[0020] Figure 3 This is a longitudinal cross-sectional view showing the gasket of the embodiment.
[0021] Figure 4 This is a longitudinal cross-sectional view of the negative electrode tank according to an embodiment. Detailed Implementation
[0022] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Furthermore, in the following description, components having the same or similar functions will be labeled with the same reference numerals. Also, repeated descriptions of these components will sometimes be omitted. The non-aqueous electrolyte secondary battery (electrochemical unit) of the embodiments is a secondary battery formed by accommodating an active material serving as a positive or negative electrode and a separator within a container. Furthermore, in the following description, the non-aqueous electrolyte secondary battery will be referred to simply as a battery.
[0023] Figure 1 This is a cross-sectional view of the battery involved in the implementation method.
[0024] like Figure 1 As shown, the battery 1 in this embodiment is a so-called coin-shaped (button-shaped) battery. The battery 1 in this embodiment is a small coin-shaped battery with an outer diameter of approximately 5 mm and a thickness of approximately 2 mm. However, the outer diameter of the battery 1 is not limited to this. The battery 1 includes: a circular outer casing 3 as viewed from above; a positive electrode 5, a negative electrode 7, and a separator 9 disposed within the outer casing 3; and an electrolyte 11 filled within the outer casing 3. The outer casing 3 includes: a positive electrode container 20 and a negative electrode container 60 assembled to the positive electrode container 20 with an insulating gasket 30. Details regarding the outer casing 3 will be described later.
[0025] The positive electrode 5 and the negative electrode 7 are arranged opposite each other with a diaphragm 9 in between. The positive electrode 5 is electrically connected to the inner surface of the positive electrode container 20 via the positive electrode current collector 13. The negative electrode 7 is electrically connected to the inner surface of the negative electrode container 60 via the negative electrode current collector 15. Alternatively, the positive electrode 5 can be directly connected to the positive electrode container 20, thus enabling the positive electrode container 20 to function as a current collector. Similarly, the negative electrode 7 can be directly connected to the negative electrode container 60, thus enabling the negative electrode container 60 to function as a current collector. An electrolyte 11, which is filled into the outer casing 3, is impregnated on the positive electrode 5, the negative electrode 7, and the diaphragm 9.
[0026] In the positive electrode 5, the type of positive electrode active material is not particularly limited; for example, a material containing lithium manganese oxide is preferred as the positive electrode active material. The content of the positive electrode active material in the positive electrode 5 is determined by considering factors such as the required discharge capacity of the battery 1, and can be in the range of 50% to 95% by mass. If the content of the positive electrode active material is above or below the lower limit of the above preferred range, sufficient discharge capacity is easily obtained. If the content of the positive electrode active material is below or below the upper limit of the above preferred range, the positive electrode 5 is easily formed.
[0027] The positive electrode 5 may also contain conductive additives. Hereinafter, the conductive additive used in the positive electrode 5 will sometimes be referred to as a "positive electrode conductive additive." Examples of positive electrode conductive additives include carbonaceous materials such as furnace black, Ketjen black, acetylene black, and graphite. One of the above-mentioned positive electrode conductive additives may be used alone, or two or more may be used in combination.
[0028] The positive electrode 5 may also contain an adhesive. Hereinafter, the adhesive used in the positive electrode 5 will sometimes be referred to as the "positive electrode adhesive." As the positive electrode adhesive, materials such as polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), polyacrylic acid (PA), carboxymethyl cellulose (CMC), and polyvinyl alcohol (PVA) can be selected. Furthermore, the positive electrode adhesive can be used alone or in combination with two or more of the above materials. The content of the positive electrode adhesive in the positive electrode 5 can be, for example, 1 to 20% by mass. As the positive electrode current collector 13, a conductive resin adhesive using carbon as a conductive filler can be used.
[0029] In addition, in this embodiment, the positive electrode 5, as the positive electrode active material, may contain other positive electrode active materials besides the aforementioned lithium manganese oxide. For example, the positive electrode 5, as the positive electrode active material, may also contain any one or more of other oxides such as molybdenum oxide, lithium iron phosphate compound, lithium cobalt oxide, lithium nickel oxide, and vanadium oxide.
[0030] The type of negative electrode active material in negative electrode 7 is not particularly limited; for example, silicon oxide is preferred as the negative electrode active material. In addition, the negative electrode active material in negative electrode 7 is preferably composed of silicon oxide represented by SiOx (0≤x<2).
[0031] In addition to SiOx (0≤x<2) mentioned above, the negative electrode 7 may also contain other negative electrode active materials as the negative electrode active material. For example, the negative electrode 7 may also contain other negative electrode active materials such as Si or C. When particulate SiOx (0≤x<2) is used as the negative electrode active material, its particle size (D50) is not particularly limited. For example, the particle size (D50) of the negative electrode active material can be selected in the range of 0.1 to 30 μm, preferably in the range of 1 to 10 μm. If the particle size (D50) of SiOx is less than the lower limit of the above range, the reactivity may increase due to factors such as storage / use of battery 1 in harsh high temperature and high humidity environments or reflow treatment, which may damage the battery characteristics. In addition, if the particle size (D50) of SiOx exceeds the upper limit of the above range, the discharge rate may decrease.
[0032] The content of the negative electrode active material, SiOx (0 ≤ x < 2), in the negative electrode 7 is determined by considering factors such as the required discharge capacity of battery 1. The content of the negative electrode active material in the negative electrode 7 can be selected in the range of 50% by mass or more, preferably in the range of 60 to 80% by mass. If the content of the negative electrode active material composed of the above-mentioned elements in the negative electrode 7 is above the lower limit of the above range, it is easy to obtain a sufficient discharge capacity. Furthermore, if the content of the negative electrode active material composed of the above-mentioned elements is below the upper limit, it is easy to form the negative electrode 7.
[0033] The negative electrode 7 may also contain conductive additives. Hereinafter, the conductive additives used in the negative electrode 7 will sometimes be referred to as "negative electrode conductive additives." The negative electrode conductive additives are the same as the positive electrode conductive additives.
[0034] The negative electrode 7 may also contain an adhesive. Hereinafter, the adhesive used for the negative electrode 7 will sometimes be referred to as the "negative electrode adhesive". As a negative electrode adhesive, polyvinylidene fluoride (PVDF) or styrene-butadiene rubber (SBR), polyacrylic acid (PA), carboxymethyl cellulose (CMC), polyimide (PI), polyamide-imide (PAI), etc. can be selected.
[0035] Furthermore, the negative electrode binder can be one of the aforementioned materials used alone, or a combination of two or more. Additionally, when polyacrylic acid is used as the negative electrode binder, the pH of the polyacrylic acid can be pre-adjusted to 3-10. In this case, pH adjustment can be performed using alkali metal hydroxides such as lithium hydroxide or alkaline earth metal hydroxides such as magnesium hydroxide. The content of the negative electrode binder in the negative electrode 7 is, for example, in the range of 1-20% by mass.
[0036] The separator 9 is located between the positive electrode 5 and the negative electrode 7. Furthermore, in the battery 1 of this embodiment, a lithium body 17, such as a lithium foil, is disposed between the negative electrode 7 and the separator 9. The separator 9 is an insulating membrane with high ion permeability and mechanical strength. As the separator 9, it can be made of glass such as alkali glass, borosilicate glass, quartz glass, or lead glass, or nonwoven fabric made of resins such as polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polyethylene terephthalate (PET), polyamide-imide (PAI), polyamide, or polyimide (PI). Among these, glass nonwoven fabric is preferred as the separator 9, and borosilicate glass nonwoven fabric is more preferred. Glass nonwoven fabric has excellent mechanical strength and high ion permeability, thus reducing internal resistance and increasing discharge capacity. The thickness of the separator 9 can be determined by considering the size of the battery 1 or the material of the separator 9. The thickness of the separator 9 can be, for example, 5 to 300 μm.
[0037] Electrolyte 11 is typically a product in which a supporting salt is dissolved in a non-aqueous solvent. In this embodiment, the non-aqueous solvent of electrolyte 11 is tetraethylene glycol dimethyl ether (TEG) as the main solvent and diethoxyethane (DEE) as the secondary solvent, and further contains ethylene carbonate (EC) and vinylene carbonate (VC) as additives. The non-aqueous solvent is usually determined considering the required heat resistance or viscosity of electrolyte 11. In addition to tetraethylene glycol dimethyl ether, triethylene glycol dimethyl ether, pentaethylene glycol dimethyl ether, diethylene glycol dimethyl ether, etc., can also be used as the main solvent to constitute the dimethyl glycol ether solvent.
[0038] The electrolyte 11 in this embodiment uses a non-aqueous solvent containing ethylene carbonate (EC), tetraethylene glycol dimethyl ether (TEG), and diethoxyethane (DEE). With this configuration, DEE and TEG solvate with Li ions that form a supporting salt. Since the donor number (DN) of DEE is higher than that of TEG, DEE selectively solvates with Li ions. Thus, DEE and TEG solvate with Li ions that form a supporting salt, thereby protecting the Li ions. Therefore, even if moisture enters the interior of the non-aqueous electrolyte secondary battery under high temperature and humidity conditions, for example, the reaction between moisture and Li is prevented, thus suppressing the decrease in discharge capacity and improving storage characteristics.
[0039] The proportions of the aforementioned solvents to the non-aqueous solvents in electrolyte 11 are not particularly limited. For example, they can be selected within the range of TEG: 30% to 48.5% by mass; DEE: 30% to 48.5% by mass; EC: 0.5% to 10% by mass; and VC: 2% to 13% by mass (totaling 100%). If the proportions of TEG, DEE, and EC contained in the non-aqueous solvents are within the above ranges, then the solvation of Li ions by DEE as described above can achieve the effect of protecting Li ions.
[0040] Even within the aforementioned range, the VC content is preferably in the range of 2.5% by mass to 10% by mass, more preferably in the range of 5.0% by mass to 7.5% by mass. Regarding the upper limit of the TEG and DEE content, it is preferably 48.25% by mass or less, more preferably 48% by mass or less. When the VC content is in the range of 2% by mass to 13% by mass, even when subjected to heating during reflow soldering, the thickness change on the outer casing 3 composed of the positive electrode container 20 and the negative electrode container 60 is small, and the increase in internal resistance can be reduced. Furthermore, when the VC content is in the range of 2.5% by mass to 10.0% by mass, even when subjected to heating during reflow soldering, the thickness change in the containing container 2 can be further reduced, and the increase in internal resistance can be further reduced. Even within these ranges, the VC content is most preferably in the range of 5.0% by mass to 7.5% by mass.
[0041] Examples of supporting salts include organic lithium acid salts such as LiCH3SO3, LiCF3SO3, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiC(CF3SO2)3, LiN(CF3SO3)2, and LiN(FSO2)2; and lithium salts such as inorganic lithium acid salts such as LiPF6, LiBF4, LiB(C6H5)4, LiCl, and LiBr. Among these, lithium salts, compounds with lithium-ion conductivity, are preferred as supporting salts, and LiN(CF3SO2)2, LiN(FSO2)2, and LiBF4 are more preferred. In particular, from the viewpoint of heat resistance and low reactivity with moisture, and to fully exert preservation properties, LiN(CF3SO2)2 is preferred as a supporting salt. One of the above-mentioned materials can be used alone, or two or more can be used in combination as a supporting salt.
[0042] The content of the supporting salt in the electrolyte 11 can be determined by considering factors such as the type of supporting salt. For example, the content of the supporting salt in the electrolyte 11 is preferably 0.1 to 3.5 mol / L, more preferably 0.5 to 3 mol / L, and particularly preferably 1 to 2.5 mol / L. If the concentration of the supporting salt in the electrolyte 11 is too high or too low, it will cause a decrease in conductivity, which may negatively affect the battery characteristics.
[0043] The outer casing 3 is described in detail.
[0044] The outer casing 3 includes: a bottomed cylindrical positive electrode can 20; an annular gasket 30 embedded inside the positive electrode can 20; and a topped cylindrical negative electrode can 60 inserted into the opening of the positive electrode can 20 and assembled to the positive electrode can 20 via the gasket 30. The outer casing 3 forms a receiving space between the positive electrode can 20 and the negative electrode can 60 to accommodate the positive electrode 5 and the negative electrode 7. The positive electrode can 20 and the negative electrode can 60 are arranged apart from each other with the gasket 30 sandwiched between them. The opening edge 21 of the positive electrode can 20 is narrowed by riveting, and the gasket 30 is pressed against the outer peripheral surface of the negative electrode can 60, thereby sealing the outer casing 3. The positive electrode can 20, the negative electrode can 60, and the gasket 30 are arranged such that their respective central axes are located on a common axis. Hereinafter, this common axis is referred to as axis O. In addition, the direction along axis O is referred to as the axial direction, the direction orthogonal to axis O and extending radially from axis O is referred to as the radial direction, and the direction of rotation around axis O is referred to as the circumferential direction. Furthermore, the opening direction of the axial positive electrode tank 20 is defined as "upper" (first direction), and the opposite direction of "upper" is defined as "lower" (second direction). In addition, the cross section along the axis O is called the "longitudinal section".
[0045] Figure 2 This is a longitudinal cross-sectional view of the battery according to the embodiment, and a diagram showing the state before the outer casing is sealed. Furthermore, in Figure 2 The diagrams of the contents of the positive electrode 5 and the negative electrode 7 are omitted.
[0046] like Figure 2 As shown, the positive electrode can 20 is formed into a cylindrical shape with an upward opening. The positive electrode can 20 includes: a circular plate-shaped bottom 22; and a positive electrode can peripheral wall portion 24 extending upward from the outer periphery of the bottom 22 throughout the entire circumference towards the opening edge 21 of the positive electrode can 20. The positive electrode can 20 is formed by deep drawing or other processes of stainless steel sheet. Materials such as SUS316L or SUS329J4L can be used as the material for the positive electrode can 20.
[0047] Figure 3 This is a longitudinal cross-sectional view showing the gasket according to the embodiment. Furthermore, in Figure 3 The image shows the individual state of the gasket 30 before it is assembled into the positive electrode tank 20 and the negative electrode tank 60.
[0048] like Figure 3 As shown, the gasket 30 includes: a base 31 extending circumferentially throughout the entire circumference; a gate portion 36 protruding radially inward from the inner circumference of the base 31; an outer wall portion 41 extending upward from the outer circumference of the base 31 throughout the entire circumference; and an inner wall portion 51 extending upward from the inner circumference of the base 31 inside the outer wall portion 41 throughout the entire circumference.
[0049] The base 31 includes: a bottom surface 32 facing downwards; a top surface 33 facing upwards between the outer wall portion 41 and the inner wall portion 51; and an inner peripheral surface 34 extending upwards from the inner periphery of the bottom surface 32. The outer periphery of the bottom surface 32 is formed into a curved surface that protrudes downwards and radially outwards, following the inner surface shape of the boundary between the bottom 22 and the peripheral wall portion 24 of the positive electrode tank 20. The lower portion of the inner peripheral surface 34 extends upwards and radially inwards from the inner periphery of the bottom surface 32. The upper portion of the inner peripheral surface 34 extends axially upwards from the upper edge of the lower portion of the inner peripheral surface 34.
[0050] The gate portion 36 is provided throughout the entire circumference in the circumferential direction. The gate portion 36 is formed on the boundary between the upper and lower parts of the inner circumferential surface 34. However, the gate portion 36 may also be formed on one of the upper and lower parts of the inner circumferential surface 34. The outer surface of the gate portion 36 has an upper surface 37 that is inclined upward in a direction more inclined than radially. The upper surface 37 is inclined relative to radially in longitudinal section and extends upward from the radially inner side to the outer side to connect with the upper part of the inner circumferential surface 34. However, the upper surface 37 may also connect with the inner circumferential surface of the inner wall portion 51.
[0051] The outer wall portion 41 is cylindrical. The inner circumferential surface of the outer wall portion 41 includes a chamfered portion 42, a guide portion 43, a sealant retaining portion 44, and a curved portion 45. These chamfered portions 42, guide portions 43, sealant retaining portions 44, and curved portions 45 are provided throughout the entire circumference. The chamfered portion 42 is formed at the upper opening edge of the outer wall portion 41. The chamfered portion 42 faces upward and radially inward. The guide portion 43 is adjacent to the lower part of the chamfered portion 42. The guide portion 43 extends downward from the chamfered portion 42. The guide portion 43 extends axially with a constant inner diameter.
[0052] The sealant holding portion 44 is located below the guide portion 43. The sealant holding portion 44 has an uneven structure capable of retaining a fluid sealant. The sealant can be, for example, asphalt or epoxy resin, polyamide resin, butyl rubber adhesive, etc. The sealant is applied to the sealant holding portion 44 and then dried before use. The sealant holding portion 44 includes: a plurality of protrusions 46 that project radially inward and are axially arranged in the longitudinal section (five in the illustrated example); and grooves 47 formed between adjacent protrusions 46. The protrusions 46 and grooves 47 are annular and extend circumferentially throughout the entire circumference. The protrusions 46 gradually taper towards the radially inward direction. The front end of the protrusion 46 is located further radially inward than the guide portion 43. The bottom of the groove 47 is located radially at the same position as the guide portion 43.
[0053] The curved portion 45 is adjacent to the lower part of the sealant retaining portion 44. The curved portion 45 is radially outward and recessed downward. The curved portion 45 extends in an arc shape in longitudinal section. The lower end of the curved portion 45 is smoothly connected to the top surface 33 of the base 31.
[0054] The inner wall portion 51 is formed in a cylindrical shape. The upper edge 51a of the inner wall portion 51 is located lower than the height center 41C of the outer wall portion 41. The height center 41C of the outer wall portion 41 is located at the axial center of the upper edge (top surface 33) of the base 31 and the upper edge 41a of the outer wall portion 41. The upper edge 51a of the inner wall portion 51 is located axially at approximately the same position as the upper edge of the sealant holding portion 44. In the illustrated example, the upper edge 51a of the inner wall portion 51 is located slightly above the upper edge of the sealant holding portion 44. The inner peripheral surface 52 of the inner wall portion 51 extends axially with a constant inner diameter. The inner peripheral surface 52 of the inner wall portion 51 has the same inner diameter as the upper part of the inner peripheral surface 34 of the base 31 and is continuous with the inner peripheral surface 34 of the base 31. The outer peripheral surface 53 of the inner wall portion 51 extends obliquely relative to the axial direction. The outer peripheral surface 53 of the inner wall portion 51 is smoothly connected to the top surface 33 of the base portion 31. The lower end of the outer peripheral surface 53 extends in an arc shape in the longitudinal section. The lower end of the outer peripheral surface 53 is recessed with a radius of curvature smaller than that of the curved portion 45 of the inner peripheral surface of the outer wall portion 41. The outer peripheral surface 53 extends radially inward from the lower end. As a result, the inner wall portion 51 gradually thins from the lower end upward. Except for its lower end, the outer peripheral surface 53 extends in a straight line in the longitudinal section.
[0055] The outer peripheral surface of the gasket 30 extends from the base 31 to the outer wall portion 41. The outer peripheral surface of the gasket 30 includes a tapered portion 56. Viewed radially, the tapered portion 56 overlaps with the guide portion 43 and the sealant retaining portion 44. Viewed radially, the upper end portion 56u of the tapered portion 56 is positioned higher than the guide portion 43. Viewed radially, the lower end portion 56l of the tapered portion 56 is positioned lower than the sealant retaining portion 44. In this embodiment, the tapered portion 56 is formed on the entire outer peripheral surface of the gasket 30. The tapered portion 56 extends radially outward in a manner that gradually increases in diameter from downward. In other words, the tapered portion 56 extends radially outward from its lower end portion 56l upward. Thus, the tapered portion 56 is inclined downward in a direction more inclined than radially outward. The tapered portion 56 extends in a straight line in longitudinal section.
[0056] The axial thickness of the base 31 of the gasket 30 is greater than the maximum radial thickness of the outer wall portion 41 and the maximum radial thickness of the inner wall portion 51. Furthermore, the axial thickness of the base 31 of the gasket 30 is the interval between the top surface 33 and the bottom surface 32 of the base 31.
[0057] The gasket 30 is preferably formed of a resin, for example, with a heat distortion temperature of 230°C or higher. If the heat distortion temperature of the resin material used in the gasket 30 is 230°C or higher, the gasket 30 will deform significantly due to reflow soldering or heating during battery use, thus preventing leakage of the electrolyte 11. Examples of materials for the gasket 30 include, for example, polyphenylene sulfide (PPS) or polyethylene terephthalate (PET), polyamide, liquid crystal polymer (LCP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA), polyetheretherketone resin (PEEK), polyether nitrile resin (PEN), polyetherketone resin (PEK), polyacrylate resin, polybutylene terephthalate resin (PBT), polycyclohexanedimethyl terephthalate resin, polyethersulfone resin (PES), polyaminobismaleimide resin, polyetherimide resin, fluororesin, etc. Furthermore, materials in which glass fiber, mica whiskers, ceramic powder, etc., are added at an addition amount of 30% by mass or less are preferably used.
[0058] Figure 4 This is a longitudinal cross-sectional view of the negative electrode tank according to an embodiment.
[0059] like Figure 4As shown, the negative electrode can 60 is formed into a cylindrical shape with an opening facing downwards. The negative electrode can 60 has a circular plate-shaped top 62 and a negative electrode can peripheral wall portion 64 extending downwards from the outer periphery of the top 62 throughout the entire circumference toward the opening edge 61 of the negative electrode can 60. The negative electrode can 60 is formed by deep drawing or similar processes on a stainless steel sheet. Materials such as SUS316L, SUS329J4L, and SUS304 can be used as the material for the negative electrode can 60. Alternatively, a cladding material formed by pressing copper or nickel onto stainless steel can also be used as the material for the negative electrode can 60.
[0060] The outer peripheral surface of the negative electrode can peripheral wall 64 extends in such a way that its diameter increases from the outer peripheral edge of the top 62 toward the opening edge 61 of the negative electrode can 60. The negative electrode can peripheral wall 64 has a double cylindrical portion 71 extending upward from the opening edge 61 of the negative electrode can 60 toward the top 62 and a stepped portion 65 connecting the top 62 and the double cylindrical portion 71.
[0061] The stepped portion 65 extends uniformly throughout the entire circumference in the circumferential direction. The stepped portion 65 includes a first curved portion 66, a second curved portion 67, and a third curved portion 68. The first curved portion 66 is connected to the outer periphery of the top 62. The first curved portion 66 bends downward from the outer periphery of the top 62 and extends downward. The first curved portion 66 bends at 90°. The first curved portion 66 bends with a constant first radius of curvature in the longitudinal section of the outer periphery of the negative electrode tank peripheral wall portion 64. The second curved portion 67 bends radially outward from the lower edge of the first curved portion 66 and extends downward. The second curved portion 67 bends at 90°. The second curved portion 67 bends with a constant second radius of curvature in the longitudinal section of the outer periphery of the negative electrode tank peripheral wall portion 64. The second radius of curvature is smaller than the first radius of curvature. The third curved portion 68 bends downward from the outer periphery of the second curved portion 67 and extends downward. The third curved portion 68 bends at 90°. The third bend 68 bends with a constant third radius of curvature in the longitudinal section of the outer circumferential surface of the negative electrode tank peripheral wall 64. The third radius of curvature is smaller than the first radius of curvature. In the illustrated example, the third radius of curvature is equal to the second radius of curvature. Furthermore, as long as the lower end of the third bend 68 is continuous with the upper edge 72a of the inner cylinder 72 (described later), the second bend 67 and the third bend 68 can also bend at an obtuse angle of less than 90°. In addition, in the illustrated example, a portion extending axially in a straight line in the longitudinal section is provided between the first bend 66 and the second bend 67, but there is no particular limitation on whether such a straight-line extending portion exists.
[0062] The double-cylinder portion 71 has an integral structure that folds over at the opening edge 61 of the negative electrode tank 60. The double-cylinder portion 71 includes: an inner cylinder portion 72 that extends downward from the lower end edge of the stepped portion 65 throughout the entire circumference; an outer cylinder portion 73 that surrounds the inner cylinder portion 72 from the radially outer side; and a folded portion 74 that is provided at the opening edge 61 of the negative electrode tank 60 and connects the inner cylinder portion 72 and the outer cylinder portion 73.
[0063] The inner cylinder 72 is continuous with the third bend 68, extending axially with a constant inner diameter and a constant outer diameter. The upper edge 72a of the inner cylinder 72 coincides axially with the center of curvature of the third bend 68 in the longitudinal section.
[0064] The folded portion 74 connects the lower edge of the inner cylinder portion 72 to the lower edge of the outer cylinder portion 73. The folded portion 74 bends and extends radially outward at 180° from the lower edge of the inner cylinder portion 72. The lower surface of the folded portion 74 extends in a convex curved shape that protrudes downward in the longitudinal section.
[0065] The outer cylinder portion 73 extends upwards from the folded portion 74, covering the entire circumference. The outer cylinder portion 73 extends axially along the outer circumferential surface of the inner cylinder portion 72 with a constant inner diameter and a constant outer diameter. The inner circumferential surface of the outer cylinder portion 73 may either be in contact with the outer circumferential surface of the inner cylinder portion 72 or slightly spaced apart. The outer diameter of the outer cylinder portion 73 is equal to the inner diameter of the guide portion 43 of the gasket 30. The upper edge 73a of the outer cylinder portion 73 is formed as a plane orthogonal to the axial direction. The upper edge 73a of the outer cylinder portion 73 is located further (above) than the center 60C between the two ends of the negative electrode can 60 axially. The upper edge 73a of the outer cylinder portion 73 is located higher than the upper edge 72a of the inner cylinder portion 72. In other words, the outer cylinder portion 73 protrudes upwards more than the inner cylinder portion 72. The upper edge 73a of the outer cylinder portion 73 is located lower than the upper edge 68a of the third bend portion 68. Furthermore, the upper edge 68a of the third bend portion 68 coincides with the boundary of the second bend portion 67 and the third bend portion 68 in the outer peripheral surface of the negative electrode tank peripheral wall portion 64, and the angle between the tangent direction and the axial direction of the outer peripheral surface of the negative electrode tank peripheral wall portion 64 in the longitudinal section is the maximum value.
[0066] A chamfered portion 75 is formed at the upper end of the outer peripheral surface of the outer cylinder portion 73. The chamfered portion 75 is formed over the entire circumference. In the illustrated example, the chamfered portion 75 has a so-called square chamfer shape. However, the normal direction of the chamfered portion 75 is not limited to a direction inclined at 45° to the radial direction. Alternatively, the chamfered portion 75 may also have a so-called rounded chamfer shape.
[0067] like Figure 2As shown, the negative electrode can 60 is installed onto the gasket 30 with sealant (not shown) applied to the sealant holding portion 44 of the gasket 30. The double-cylinder portion 71 of the negative electrode can 60 is inserted into the annular groove between the outer wall portion 41 and the inner wall portion 51 of the gasket 30. The lower edge of the double-cylinder portion 71 (the opening edge 61 of the negative electrode can 60) abuts against the top surface 33 of the base portion 31 of the gasket 30. The outer circumference of the outer cylindrical portion 73 of the double-cylinder portion 71 is in close contact with the inner circumference of the outer wall portion 41 of the gasket 30. The outer circumference of the outer cylindrical portion 73 contacts at least the entire sealant holding portion 44 of the outer wall portion 41 of the gasket 30. In the illustrated example, the double-cylinder portion 71 compresses the protrusion 46 of the sealant holding portion 44 of the gasket 30 (see reference 46) through the outer cylindrical portion 73. Figure 3 The outer cylinder 73 is inserted into the inner side of the outer wall portion 41 in a manner that allows it to be inserted. The chamfered portion 75 and the upper edge 73a of the outer cylinder portion 73 are located higher than the sealant holding portion 44 and lower than the upper edge 41a of the outer wall portion 41. The negative electrode can 60 is inserted into the inner side of the positive electrode can 20 together with the gasket 30 in a state of being installed to the gasket 30. The negative electrode can 60 is configured such that the top 62 protrudes upward from the positive electrode can 20.
[0068] The gasket 30 is inserted into the opening of the positive electrode can 20 from above. The bottom surface 32 of the base 31 of the gasket 30 contacts the upper surface of the bottom 22 of the positive electrode can 20. The outer peripheral surface of the gasket 30 covers the entire circumference and is in close contact with the inner peripheral surface of the peripheral wall 24 of the positive electrode can. The outer peripheral surface of the gasket 30 covers the entire axial length and is in contact with the inner peripheral surface of the peripheral wall 24 of the positive electrode can. Here, the gasket 30 is formed in a single piece such that the tapered portion 56 of the outer peripheral surface faces downwards further than the radially outer side, so that by inserting it into the positive electrode can 20, it is pressed radially inwards by the peripheral wall 24 of the positive electrode can. As a result, the outer wall 41 of the gasket 30 is deformed such that the portion of the negative electrode can 60 that is radially spaced apart is displaced radially inwards. In the illustrated example, the portion of the outer wall 41 of the gasket 30 that is located above the outer cylindrical portion 73 of the negative electrode can 60 is displaced radially inwards. As a result, the upper part of the guide portion 43 on the inner circumferential surface of the outer wall portion 41 of the gasket 30 bulges radially inward above the outer cylinder portion 73 of the negative electrode tank 60.
[0069] like Figure 1As shown, the positive electrode can 20 is riveted to reduce the upper part of the peripheral wall 24 of the positive electrode can. The opening edge 21 of the positive electrode can 20 is reduced to a radially inward position relative to the upper edge 73a of the outer cylinder 73 of the negative electrode can 60. By reducing the upper part of the peripheral wall 24 of the positive electrode can, the gasket 30 is deformed to move radially inward relative to the portion of the negative electrode can 60 that is radially spaced apart. As a result, the outer wall 41 of the gasket 30 is positioned from the radially outer side of the outer cylinder 73, passing over the top of the outer cylinder 73 and extending over the third bend 68. Moreover, the outer wall 41 is in close contact from above with the chamfered portion 75 and the upper edge 73a of the outer cylinder 73 of the negative electrode can 60, as well as the third bend 68 of the stepped portion 65. In addition, the negative electrode can 60 is secured downward via the gasket 30 and the upper part of the peripheral wall 24 of the positive electrode can. Accordingly, the base 31 is pressed by the opening edge 61 of the negative electrode can 60, so that the gasket 30 deforms the outer peripheral surface 53 of the inner wall portion 51 along the inner peripheral surface of the negative electrode can peripheral wall portion 64.
[0070] As explained above, in the battery 1 of this embodiment, the upper edge 73a of the outer cylinder portion 73 of the negative electrode can 60 is located above the center 60C between the two ends of the negative electrode can 60 in the axial direction, and below the upper edge 68a of the third bend 68. With this configuration, the outer cylinder portion 73 can be made larger in the axial direction, thus providing higher durability to the peripheral wall portion 64 of the negative electrode can against pressure from the radially outer side. Therefore, the opening edge 21 of the positive electrode can 20 can be contracted to forcefully press the gasket 30, thereby fully securing the negative electrode can 60 from above and radially outward. Correspondingly, since the outer cylinder portion 73 does not protrude further upward than the third bend 68, it is possible to prevent the outer cylinder portion 73 from sinking into the gasket 30 disposed above the outer cylinder portion 73. Therefore, even with forceful pressure on the gasket 30, damage caused by contact between the gasket 30 and the outer cylinder portion 73 can be suppressed. Therefore, it is possible to prevent moisture from transferring from the opening of the positive electrode container 20 to the surface of the gasket 30 and entering the interior, thus providing excellent sealing performance even for the battery 1, which is thickened to increase capacitance. Therefore, a reflow-solderable battery 1 with excellent sealing performance and large capacity can be provided.
[0071] Furthermore, the upper edge 73a of the outer cylinder portion 73 is located higher than the upper edge 72a of the inner cylinder portion 72. With this configuration, the outer cylinder portion 73 can completely surround the inner cylinder portion 72. Therefore, the dual-structure portion in the double cylinder portion 71 can be maximized, thus providing the double cylinder portion 71 with higher durability.
[0072] In the gasket 30, the thickness of the axially oriented base 31 is greater than the maximum thickness of both the radially oriented outer wall portion 41 and inner wall portion 51. This configuration ensures the wall thickness of the outer wall portion 41, particularly the portion near the base 31. Therefore, in a battery 1 where the thickness is increased to maximize capacitance, the strength of the gasket 30 can be ensured. Furthermore, since a sufficient number of gaskets 30 are disposed between the bottom 22 of the positive electrode can 20 and the opening edge 61 of the negative electrode can 60, a tight seal between the positive electrode can 20, the negative electrode can 60, and the gaskets 30 can be achieved during the riveting process of the positive electrode can 20. Consequently, a battery 1 with excellent sealing performance can be formed.
[0073] Furthermore, the axial length of the peripheral wall portion 64 of the negative electrode can be reduced by increasing the thickness of the base portion 31 in the axial direction. Therefore, by reducing the area of the peripheral wall portion 64 of the negative electrode can that is pressurized by the gasket 30, the force applied to the peripheral wall portion 64 of the negative electrode can can be reduced. Consequently, deformation of the negative electrode can 60 can be suppressed.
[0074] A chamfered portion 75 is formed at the upper end of the outer peripheral surface of the outer cylinder portion 73. This prevents excessive pressure from the outer cylinder portion 73 from being applied to the gasket 30 positioned above the outer cylinder portion 73. Therefore, even if the gasket 30 is subjected to strong pressure, damage caused by contact between the gasket 30 and the outer cylinder portion 73 can be prevented.
[0075] Furthermore, the present invention is not limited to the embodiments described above with reference to the accompanying drawings, and various modifications within the scope of this technology are conceivable.
[0076] For example, in the above embodiment, the gasket 30 contacts the upper surface of the bottom 22 of the positive electrode can 20, but a diaphragm and a positive electrode may also be disposed between the gasket and the bottom of the positive electrode can, for example.
[0077] In addition, in the above embodiment, the first curved portion 66, the second curved portion 67 and the third curved portion 68 are curved with constant curvature, but the curvature of the first curved portion, the second curved portion and the third curved portion can also be varied.
[0078] The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments. Additions, omissions, substitutions, and other modifications can be made to the structure without departing from the spirit of the present invention. The present invention is not limited by the foregoing description, but only by the scope of the appended claims.
Claims
1. An electrochemical unit, comprising: A positive electrode can is formed into a bottomed cylindrical shape, having a bottom and a positive electrode can peripheral wall portion extending from the outer periphery of the bottom along a first axial direction; A negative electrode can is formed in the shape of a topped cylinder, having a top and a negative electrode can peripheral wall extending from the outer periphery of the top along a second direction along the axial direction, and is inserted into the inner side of the positive electrode can; and A gasket, disposed between the peripheral walls of the positive electrode can and the peripheral walls of the negative electrode can, is pressed against the outer peripheral surface of the negative electrode can by contracting the opening edge of the positive electrode can. The peripheral wall of the negative electrode tank has: The double-cylinder section extends from the opening edge of the negative electrode can toward the top along the first direction; and The stepped section connects the top and the double-cylinder section. The stepped portion has: The first curved portion bends and extends from the outer periphery of the top in the second direction; The second bend extends radially outward from the edge of the first bend in the second direction; and The third bend extends and bends from the outer periphery of the second bend in the second direction. The double-cylinder section has: The inner cylinder portion extends from the edge in the second direction of the third curved portion toward the second direction; An outer cylinder portion that surrounds the inner cylinder portion from the radially outer side; and A folding section is provided at the edge of the opening of the negative electrode tank, connecting the inner cylinder portion and the outer cylinder portion. The gasket is disposed at least along the outer side of the radial direction of the outer cylinder and in the first direction. The edge of the outer cylinder in the first direction is located further along the first direction than the center between the two ends of the negative electrode can in the axial direction, and further along the second direction than the edge of the third curved portion in the first direction. The gasket has: An annular base is disposed between the bottom of the positive electrode can and the edge of the opening of the negative electrode can; An outer wall portion, protruding from the outer periphery of the base in the first direction and extending circumferentially throughout the entire circumference, is disposed between the peripheral wall portion of the positive electrode tank and the peripheral wall portion of the negative electrode tank; and The inner wall portion protrudes from the base toward the first direction and extends along the circumference throughout the entire circumference. The axial dimension of the base is greater than the maximum dimension of both the radial dimension of the outer wall portion and the inner wall portion. The edge of the inner wall portion in the first direction is located further in the second direction than the center of the outer wall portion in the axial direction.
2. The electrochemical unit as described in claim 1, wherein, The edge of the outer cylinder in the first direction is located further in the first direction than the edge of the inner cylinder in the first direction.
3. The electrochemical unit as described in claim 1 or claim 2, wherein, The end of the outer circumference of the outer cylinder in the first direction is chamfered throughout the entire circumference.