JP4975993B2 - Sealed secondary battery - Google Patents

Description

  The present invention relates to a sealed secondary battery, and in particular, a battery lid including a wound electrode group and a ring-shaped current collecting member whose bottom side is supported by an axis of the wound electrode group, and having a conductive diaphragm. The present invention relates to a sealed secondary battery caulked in a battery can.

  Conventionally, sealed secondary batteries have been widely used for home appliances, and recently, lithium secondary batteries are particularly used among sealed secondary batteries. Moreover, since the lithium secondary battery has a high energy density, it has been put to practical use as a large capacity battery, for example, as an in-vehicle power source for an electric vehicle (EV) or a hybrid electric vehicle (HEV). In large-capacity batteries, a ring-shaped current collecting member is generally used to suppress the internal resistance of the battery, and the lead piece led out from the wound electrode group is joined to the ring outer periphery (periphery) of the current collecting member (For example, refer to Patent Document 1).

  Further, in the above-described lithium secondary battery, when an abnormal state such as overcharge occurs, an internal short circuit occurs between the positive and negative electrodes, and gas is generated due to decomposition of the electrolyte, which may increase the internal pressure of the battery. In order to solve this problem, the present inventors have previously proposed a sealed cylindrical lithium secondary battery having an upper lid with a built-in explosion-proof device (see Patent Document 1). The structure of this battery will be briefly described.

  As shown in FIG. 4, the sealed secondary battery 50 includes a bottomed cylindrical battery can 41 and a battery lid 45 that seals the battery can 41. A wound electrode group 42 is accommodated in the battery can 41. The electrode group 42 is supported (fixed) at the bottom of the positive electrode current collecting ring 40 at the shaft core, and the plate-shaped diaphragm 2 having an inverted portion protruding toward the electrode group 42 is fixed to the battery lid 45. Yes. A connecting plate 46 having a flat portion projecting toward the diaphragm 2 at the center is electrically and mechanically joined to the center portion of the diaphragm 2. The reversing pressure of the diaphragm 2 is set by resistance welding so that it operates (the reversing part of the diaphragm 2 is reversed to the side opposite to the electrode group 42) when the battery internal pressure reaches a predetermined pressure. The connection plate 46 and the positive electrode current collector ring 40 are connected by a strip-shaped connection lead 32. As shown in FIG. 4, the connecting lead 32 is composed of two parts, lead plates 32a and 32b. Both parts are overlapped with a plurality of strip-shaped aluminum foils, and both ends are ultrasonically welded. ing. When the battery is assembled, one end of the lead plate 32a and the connection plate 46, one end of the lead plate 32b and the positive electrode current collecting ring 20 are connected in advance by ultrasonic welding, and the electrode group 42 is accommodated in the battery can 41, After the battery can 41 is stepped, the other ends of the lead plates 32a and 32b are ultrasonically welded.

JP 2004-134204 A

  However, in the sealed secondary battery, the connection plate and the connection lead are interposed between the diaphragm and the positive electrode current collection ring, and the connection lead is bent and accommodated in the battery can. The size of the battery in the longitudinal direction is increased by an amount corresponding to the thickness of the connection lead. For this reason, the battery volume is increased and the volume efficiency is lowered, and the battery weight corresponding to the increased size of the battery can and the positive electrode current collecting ring is also increased. When used for a power supply for EVs or HEVs, an increase in battery volume leads to a decrease in vehicle interior space, and an increase in battery weight leads to a decrease in fuel consumption (fuel consumption rate). In addition, several electrical welding steps are required for electrical connection between the diaphragm and the positive electrode current collector ring, resulting in high battery costs.

  An object of the present invention is to provide a sealed secondary battery capable of reducing the weight and improving the volume efficiency in view of the above case.

In order to solve the above-mentioned problems, the present invention provides a wound electrode group , a ring-shaped current collecting member supported on the bottom side by an axis of the wound electrode group, the wound electrode group, and the current collector. A battery can having a built-in member, a battery lid caulked on the battery can and having a conductive diaphragm, a flat conductive member interposed between a bottom portion of the current collecting member and an inverted portion of the conductive diaphragm, The conductive diaphragm has an inverted portion accommodated in the ring of the current collecting member, and the conductive member has one surface joined to the bottom of the current collecting member and the other surface is electrically conductive. It is a sealed secondary battery characterized by being joined to the reversal part of the conductive diaphragm .

In the present invention, the inversion part of the conductive diaphragm is accommodated in the ring of the current collecting member, and the flat conductive member interposed between the bottom part of the current collecting member and the inversion part of the conductive diaphragm is one side. Since the side is joined to the inner bottom of the ring of the current collecting member and the other side is joined to the reversing part of the conductive diaphragm, the distance between the diaphragm and the current collecting member is reduced, and the volume efficiency of the entire battery can be improved. In addition, the conventionally used connection plate and strip-shaped connection lead can be replaced with one member of a flat plate-like conductive member, and the battery can can be made smaller, so that the weight of the battery can be reduced.

In the present invention, the peripheral portion of the current collecting member may have an end surface bent to the opposite side to the wound electrode group, and the diaphragm may be positioned so that the peripheral portion of the diaphragm faces the upper portion of the end surface. At this time, a bush may be disposed on the end face of the current collecting member, and the bush may be sandwiched between the peripheral edge of the diaphragm and the peripheral edge of the current collecting member. If the inversion part of the diaphragm and the conductive member are joined by friction stir welding, a heat source other than frictional heat is unnecessary, so that the joining work can be easily performed. Also, if the reverse part of the diaphragm and the conductive member are joined through the opening of the battery lid crimped to the battery can, the external force when caulking the battery lid to the battery can is applied to the joint between the diaphragm and the conductive member. This can be avoided and the reversing pressure of the diaphragm can be kept constant, so that the reliability of the battery can be improved.

According to the present invention, the inversion portion of the conductive diaphragm is accommodated in the ring of the current collecting member, and the flat conductive member is interposed between the bottom portion of the current collecting member and the inversion portion of the conductive diaphragm. Since one side is joined to the inner bottom of the ring of the current collecting member and the other side is joined to the reversing part of the conductive diaphragm, the distance between the diaphragm and the current collecting member is reduced, improving the volume efficiency of the entire battery. In addition, since the conventionally used connection plate and strip-shaped connection lead can be replaced with one member of the flat plate-like conductive member, the effect of reducing the weight of the battery can be obtained.

  Embodiments in which the present invention is applied to a sealed cylindrical lithium ion secondary battery will be described below with reference to the drawings.

(Constitution)
As shown in FIG. 1, the sealed cylindrical lithium ion battery 30 of this embodiment includes a wound electrode group 12. The wound electrode group 12 has a bottomed cylindrical metal battery in which a positive electrode and a negative electrode are wound around a glass-filled resin shaft 13 through a polyethylene microporous thin film separator and also serve as a negative electrode external terminal. It is accommodated (built in) in the can 11.

The positive electrode constituting the wound electrode group 12 is lithium manganese composite oxide (LiMnO ₂ , LiMn ₂ O ₄ ) or lithium obtained by replacing or doping lithium sites or manganese sites of LiMnO ₂ , LiMn ₂ O ₄ with other metal elements. Manganese transition metal complex oxide powder, conductive carbon material, binder polyvinylidene fluoride (hereinafter abbreviated as PVDF) and n-methylpyrrolidone (hereinafter abbreviated as NMP) as a viscosity adjusting solvent. A positive electrode active material mixture obtained by mixing, dispersing and kneading so as to be uniform in a Cornell despa is applied almost uniformly on both sides of the aluminum foil of the positive electrode current collector, dried, pressed, and then collected It was obtained by cutting it into a strip shape, leaving a part. A plurality of positive electrode tabs are formed in a portion left for current collection. Incidentally, the lithium manganese transition metal complex oxide has the formula _{LiMn 1-x M x O 2} , LiMn 2-x M x O 4 (M is Mn, Fe, Co, 1 or more transition metals selected from Ni, etc. ).

  On the other hand, for the negative electrode, a negative electrode active material mixture obtained by mixing a carbon material such as graphite, a binder PVDF, and a viscosity adjusting solvent NMP, and dispersing and kneading it uniformly in Cornell Despa. It was obtained by applying it almost uniformly on both sides of the copper foil of the body, cutting it into a strip shape after drying and pressing, leaving a part for current collection. A plurality of negative electrode tabs are formed in a portion left for current collection.

  The positive electrode tab and the negative electrode tab are arranged so as to be located on both end surfaces on the opposite sides of the wound electrode group 12. A positive current collecting ring 20 for current collection is fixed to the upper end of the shaft core 13, and a positive electrode tab is ultrasonically welded to the peripheral edge of the positive current collecting ring 20. As shown in FIG. 2, the positive electrode current collecting ring 20 has a peripheral edge bent upward to form an opening, and a cylindrical protrusion for fixing to the shaft core 13 has a lower (bottom side) central portion. Is formed. The hollow portion of the cylindrical projection penetrates to the bottom upper surface (the surface on the upper lid 20 side) of the positive electrode current collecting ring 20, and a hollow portion coaxial with the shaft core 13 is formed. On the upper surface of the bottom of the positive electrode current collecting ring 20, a flat plate-shaped aluminum alloy conductive plate 3 that constitutes a current-carrying path on the positive electrode side is mechanically and electrically joined by friction stir welding. The upper side of the hollow portion that penetrates to the upper surface of the bottom of the positive electrode current collecting ring 20 is closed by the conductive plate 3. An annular, polypropylene resin bush 16 is disposed on the end surface of the peripheral edge bent upward of the positive electrode current collecting ring 20.

On the other hand, as shown in FIG. 1, a negative electrode current collecting ring for current collection is fixed to the lower end of the shaft core 13, and a negative electrode tab is ultrasonically welded to the peripheral portion of the negative electrode current collecting ring. A negative electrode lead plate is fixed to the negative electrode current collecting ring. The negative electrode lead plate is joined to the inner bottom surface of the battery can 11 by resistance welding by inserting an electrode rod into a coaxial hollow portion of the positive electrode current collecting ring 20 and the shaft core 13. Are electrically connected.

  The upper lid 15 has a disk-shaped upper lid cap made of iron and nickel-plated. A cylindrical protrusion protruding upward is formed at the center of the upper lid cap, and an opening 5 for discharging gas generated inside the battery is formed on the upper surface of the protrusion. The peripheral edge of the upper lid cap is caulked by the peripheral edge of the diaphragm 2. The diaphragm 2 is made of an aluminum alloy and is formed in a dish shape having an inversion portion protruding downward (on the wound electrode group 12 side). The inversion part of the diaphragm 2 is accommodated in an opening formed in the positive electrode current collector ring 20 (in the ring of the positive electrode current collector ring 20). The dish-shaped bottom is flat and forms the center of the diaphragm 2. Between the center part and the peripheral part of the diaphragm 2, a cleavage groove 8 is formed which is thinned and is cleaved when the battery internal pressure reaches a predetermined pressure.

The bottom surface of the center portion of the diaphragm 2 is joined to the upper surface of the conductive plate 3 joined to the upper surface of the bottom portion of the positive electrode current collecting ring 20 by friction stir welding. By this joining, the bush 16 disposed on the positive electrode current collecting ring 20 is sandwiched between the diaphragm 2 and the positive electrode current collecting ring 20. The bonding strength between the diaphragm 2 and the conductive plate 3 is adjusted by friction stir welding so that when the internal pressure of the lithium ion battery 30 reaches a predetermined pressure, the diaphragm 2 is activated (the reversing part is reversed to the upper lid cap side). ing.

  The peripheral edge of the upper lid 15 is caulked to the battery can 11 via the gasket 14, and the inside of the lithium ion secondary battery 30 is sealed. Further, a non-aqueous electrolyte is injected into the battery can 11. As the non-aqueous electrolyte, a solution obtained by dissolving lithium hexafluorophosphate or lithium tetrafluoroborate in an organic solvent such as ethylene carbonate or dimethyl carbonate in an amount of about 1 mol / liter is used.

  The lithium ion secondary battery 30 is assembled in the following procedure. That is, the wound electrode group 12 is prepared, and positive and negative electrode tabs are respectively connected to the positive electrode current collecting ring 20 and the negative electrode current collecting ring, and then the wound electrode group 12 is accommodated in the battery can 11. After fixing the negative electrode side to the inner bottom surface of the battery can 11, the conductive plate 3 is joined to the upper surface of the bottom of the positive electrode current collecting ring 20 by friction stir welding. A stepping process for forming a stepped portion for placing the upper lid 15 on the battery can 11 above the wound electrode group 12 is performed, and after pouring a non-aqueous electrolyte, the upper lid 15 is placed on the stepped portion, and the battery The can 11 and the upper lid 15 are caulked. Thereafter, a rotating tool (welding jig) for welding is inserted from the opening 5 formed in the upper lid cap, and the diaphragm 2 and the conductive plate 3 are rubbed by rotating while rotating the rotating tool against the upper surface of the diaphragm 2. Join by stir welding.

  Next, operations when the lithium ion secondary battery 30 of the present embodiment is used and when the battery is abnormal will be described.

  In the lithium ion secondary battery 30 of the present embodiment, when the battery is used (normal time), the potential collected from the positive electrode passes through the positive electrode current collecting ring 20, the conductive plate 3, and the diaphragm 2 in this order. Guided to the upper lid 15. At this time, the inverted portion of the diaphragm 2 is maintained in a state of protruding toward the positive electrode current collecting ring 20 side. On the other hand, the potential collected from the negative electrode is guided to the battery can 11 of the negative electrode external terminal through the negative electrode current collecting ring and the negative electrode lead plate. As a result, a normal energization path can be secured.

  In the lithium ion secondary battery 30, the reversal pressure of the diaphragm 2 and the cleavage pressure of the cleavage groove 8 are set. Usually, the reverse pressure is larger than atmospheric pressure (for example, 1.5 MPa), and the cleavage pressure is set to a value larger than the reverse pressure (for example, 2 MPa). When a battery abnormality such as overcharge, deformation due to external force, or foreign object puncture occurs, heat is generated due to a short circuit between the positive and negative electrodes. As the capacity of the lithium ion secondary battery 30 increases, the battery internal pressure rapidly increases with thermal runaway. When the internal pressure of the battery reaches the reversal pressure of the diaphragm 2, the reversing portion of the diaphragm 2 is reversed to the upper lid cap side, so that the connection between the diaphragm 2 and the conductive plate 3 is broken and the current-carrying path is cut off. Is done. When the decomposition reaction of the nonaqueous electrolyte proceeds at an accelerated rate and the internal pressure of the battery further increases, the cleavage groove 8 set to a cleavage pressure higher than the reverse pressure of the diaphragm 2 is broken. Thereby, since the gas in the battery is released to the outside of the battery through the cleavage groove 8 and the opening 5 formed in the upper lid cap, the internal pressure of the battery is reduced. Since the reversal pressure is greater than the atmospheric pressure, once the reversing portion of the diaphragm 2 is reversed, the bottom surface of the central portion of the diaphragm 2 and the top surface of the conductive plate 3 do not come into contact again. Use is prevented.

(Action etc.)
Next, the operation and the like of the lithium ion secondary battery 30 of the present embodiment will be described.

  In the conventional lithium ion secondary battery, as shown in FIG. 3, a flat portion protruding in a trapezoidal shape is joined to the upper side of the connection plate 46 on the bottom surface of the central portion of the diaphragm 2 constituting the battery lid 45. A splitter 48 is interposed between the connection plate 46 and the diaphragm 2 for separating the connection plate 46 and the diaphragm 2 when the battery internal pressure increases. A positive electrode current collecting ring 40 disposed on the upper side of the wound electrode group 42 and the connection plate 46 are connected by a strip-shaped connection lead 32. As shown in FIG. 4, the connection lead 32 has two parts (lead pieces 32a and 32b) in which, for example, six pieces of aluminum foil having a width of 6 mm, a length of 30 mm, and a thickness of 0.1 mm are superposed and ultrasonic welded at both ends. ) And is folded (folded) and accommodated in the battery can 41. In the lithium ion secondary battery 50, the connection plate 46 having a trapezoidal protrusion, the bent connection lead 32, and the splitter 48 are accommodated in the positive electrode current collection ring 40, so that the diaphragm 2 is provided with the positive electrode current collection ring 40. It is arranged on the upper side. That is, the length in the longitudinal direction of the battery is increased by the size of the protruding portion of the connection plate 46 and the thickness of the bent connection lead 32 (twice the thickness of the lead pieces 32a and 32b). There is a need. For this reason, the battery volume is increased, the volume efficiency is lowered, and the height of the peripheral edge of the positive electrode current collecting ring 40 and the battery can 41 are increased, thereby increasing the battery weight. In addition, since the positive electrode current collecting ring 40, the connection plate 46, the connection lead 32, the diaphragm 2 and the like are joined by welding at the time of manufacturing the battery, the number of welding processes increases (generally 7 times), which increases the cost. Invite. The present embodiment is a lithium ion secondary battery that can solve these problems.

  In the lithium ion secondary battery 30 of this embodiment, the inversion part of the diaphragm 2 is accommodated in the positive electrode current collection ring 20. For this reason, the distance between the inversion part of the diaphragm 2 and the bottom part of the positive electrode current collection ring 20 becomes small. Further, in the lithium ion secondary battery 30 of the present embodiment, the flat conductive plate 3 is used for the connection between the diaphragm 2 and the positive electrode current collecting ring 20. For this reason, the two members of the connection plate 46 and the connection lead 32 used conventionally can be replaced with one member. Therefore, since the distance between the upper lid 15 and the positive electrode current collecting ring 20 is reduced, the battery volume can be reduced and the volume efficiency can be improved, and the height of the peripheral edge portion of the positive current collecting ring 20 bent toward the upper lid side Since the length of the battery can 11 can be reduced, the weight of the battery can be reduced. Moreover, by substituting with one member of the conductive plate 3, the number of weldings can be reduced, and the cost can be reduced.

  In the lithium ion secondary battery 30 of the present embodiment, the positive electrode current collector ring 20 and the conductive plate 3 are joined to each other by friction stir welding between the reversing portion of the diaphragm 2 and the conductive plate 3. In friction stir welding, the welding jig is pressed against the welded part of the two members and rotated to generate frictional heat, so that the materials of the two members are softened and melted, mixed, stirred and joined. do not need. For this reason, material softening or the like does not occur in portions other than the welded portion, the welding accuracy can be increased, and the welding operation can be easily performed.

  Furthermore, in the lithium ion secondary battery 30 of the present embodiment, the battery lid 15 is caulked to the battery can 11 and the reverse portion of the diaphragm 2 and the conductive plate 3 are welded through the opening 5. If the upper lid 15 is crimped to the battery can 11 after the diaphragm 2 and the conductive plate 3 are joined, an external force may act on the upper lid 15 and the joint portion may be broken. By joining the upper lid 15 to the battery can 11 before joining between the diaphragm 2 and the conductive plate 3, breakage of the joined portion can be avoided. Therefore, since the reverse pressure of the diaphragm 2 can be maintained constant, the battery can be reliably operated when the battery is abnormal, so that the reliability of the battery can be improved.

Furthermore, in the lithium ion secondary battery 30 of the present embodiment, a bush 16 made of polypropylene resin is interposed between the diaphragm 2 and the positive electrode current collecting ring 20. For this reason, even if a large load temporarily acts on the upper lid 15 during battery assembly, the breakage of the cleavage groove 8 formed in the diaphragm 2 due to the deformation of the resin bush 16 can be prevented. For this reason, the yield of battery manufacture can be improved and the safety | security during battery assembly work can also be ensured.

  Furthermore, in the lithium ion secondary battery 30 of the present embodiment, the hollow portion penetrating to the upper surface of the bottom of the positive electrode current collecting ring 20 is closed with the conductive plate 3. For this reason, since the pressure of the gas generated at the time of battery abnormality does not act on the hollow portion of the shaft core 13 but acts on the diaphragm 2, the reversing portion can be reliably reversed by the increase of the battery internal pressure.

  In the lithium ion secondary battery 30 of the present embodiment, the example in which the reverse pressure of the diaphragm 2 is set by the welding strength between the diaphragm 2 and the conductive plate 3 is shown, but the present invention is not limited to this. For example, it may be set by changing the thickness or strength of the diaphragm 2.

  Further, in the lithium ion secondary battery 30 of the present embodiment, the flat conductive plate 3 is exemplified, but the present invention is not limited to the shape of the conductive plate 3. For example, it can be a circular shape, a square shape, or the like. Further, in the present embodiment, the conductive plate 3 and the positive electrode current collector ring 20 are described as separate members, but both may be integrally formed. If it does in this way, the number of members can be reduced and parts management can be made easy.

  Furthermore, in the lithium ion secondary battery 30 of this embodiment, the example which used the aluminum alloy for the material of the diaphragm 2 and the electrically-conductive board 3 was shown, However, This invention is not limited to this, Aluminum, nickel alloy Other conductive materials such as conductive plastics may be used.

Furthermore, in this embodiment, lithium manganese composite oxide and lithium manganese transition metal composite oxide are exemplified as the positive electrode active material, but the present invention is not limited to these. As the positive electrode active material that can be used in other embodiments, for example, lithium nickel composite oxide (LiNiO ₂ ), lithium cobalt composite oxide (LiCoO ₂ ), or the like may be used. In the present embodiment, graphite is exemplified as the negative electrode active material, but the present invention is not limited to this, and for example, a carbon material such as amorphous carbon can be used.

  Furthermore, in the lithium ion secondary battery 30 of the present embodiment, an example in which about 1 mol / liter of lithium hexafluorophosphate is dissolved in a nonaqueous electrolytic solution in a mixed solvent such as ethylene carbonate is illustrated. There is no restriction | limiting in particular in the nonaqueous electrolyte solution which can be used by invention. Any organic solvent or lithium salt may be used as long as it is usually used for lithium ion secondary batteries. For example, a solvent using a single organic solvent or a mixture of organic solvents such as carbonates, sulfolanes, ethers, and lactones. What dissolved lithium salt in it can be used. Further, the mixing ratio of the organic solvent and the content of the lithium salt are not particularly limited.

  Furthermore, in the present embodiment, the cylindrical lithium ion secondary battery 30 is exemplified, but the present invention is not limited to this. For example, it may have a rectangular shape or a polygonal shape, and can be applied to a sealed secondary battery. Also, the battery capacity, size, etc. are not particularly limited. Furthermore, in the present embodiment, an example in which the positive electrode of the wound electrode group 12 is connected to the positive electrode current collecting ring 20 and the upper lid 15 is used as the positive electrode external terminal has been described, but the negative electrode may be connected to the upper lid 15 side. .

Next, examples of the lithium ion secondary battery 30 manufactured according to the present embodiment will be described. In addition, it describes together about the lithium ion secondary battery of the comparative example produced for the comparison. In addition, the wound electrode group used what was produced with the same dimension, and all battery capacity was 6 Ah.

(Example 1) In Example 1, after the bottom part of the diaphragm 2 is accommodated in the ring of the positive electrode current collection ring 20 and the battery can 11 and the upper cover 15 are caulked, the diaphragm 2 and the positive electrode current collection ring 20 are electrically conductive. Connection was made via plate 3 (see FIG. 1).

(Comparative example 1) In the comparative example 1, the connection board 46 and the connection lead 32 were used for the connection of the diaphragm 2 and a positive electrode current collection ring (refer FIG. 4).

<Test> The battery height and volume of the batteries of Example 1 and Comparative Example 1 were measured. In addition, the number of weldings required for connecting the current collecting ring and the upper lid during battery preparation was compared. The measurement results of battery height, volume and number of weldings are shown in Table 1 below.

As shown in Table 1, in the lithium ion secondary battery of Comparative Example 1 using the connection plate and the connection lead, the battery height was 125 mm and the volume was 507853 mm ² . In contrast, the lithium ion secondary battery 30 of Example 1 in which the diaphragm 2 and the positive electrode current collector ring 20 are connected via the conductive plate 3 and the bottom of the diaphragm 2 is accommodated in the ring of the positive electrode current collector ring 20. Shows a battery height of 123.8 mm and a volume of 502978 mm ² , all of which could be reduced. Also, the number of weldings was 5 in Comparative Example 1, whereas it was 2 in Example 1. Therefore, it was clarified that the battery of Example 1 can reduce the battery volume and improve the volume efficiency as compared with the conventional battery of Comparative Example 1. In addition, the number of weldings can be reduced, and the number of battery manufacturing steps can be reduced.

  The present invention contributes to the manufacture and sale of sealed secondary batteries in order to provide a sealed secondary battery capable of reducing the weight and improving the volumetric efficiency, and thus has industrial applicability.

It is sectional drawing which shows the sealed cylindrical lithium ion secondary battery of embodiment to which this invention is applied. It is sectional drawing which shows the junction part of the positive electrode current collection ring and conductive plate of the sealed cylindrical lithium ion secondary battery of embodiment. It is sectional drawing which shows the conventional sealed cylindrical lithium ion secondary battery. It is sectional drawing which shows the connection lead used for the conventional sealed cylindrical lithium ion secondary battery.

Explanation of symbols

2 Conductive diaphragm 3 Conductive plate (conductive member)
DESCRIPTION OF SYMBOLS 11 Battery can 12 Winding electrode group 13 Shaft core 15 Battery cover 20 Positive electrode current collection ring (current collection member)
30 Sealed cylindrical lithium ion secondary battery (sealed secondary battery)

Claims (5)

A wound electrode group ;
A ring-shaped current collecting member supported on the bottom side by the axis of the wound electrode group;
A battery can containing the wound electrode group and the current collecting member;
A battery lid caulked on the battery can and having a conductive diaphragm;
A flat conductive member interposed between the bottom of the current collecting member and the inverted portion of the conductive diaphragm;
With
The conductive diaphragm has its reversal portion housed in the ring of the current collecting member, and the conductive member has one surface joined to the bottom of the current collecting member and the other surface is the reversal of the conductive diaphragm. A sealed secondary battery, wherein the sealed secondary battery is bonded to a portion . The current collecting member has an end surface whose peripheral portion is bent to the opposite side to the wound electrode group, 2. The sealed secondary battery according to claim 1, wherein an upper portion of the end surface is positioned such that a peripheral edge portion of the diaphragm is opposed to the end surface. A bush is disposed on the end face, The sealed secondary battery according to claim 2, wherein the bush is sandwiched between a peripheral portion of the diaphragm and a peripheral portion of the current collecting member. The sealed secondary battery according to claim 1, wherein the inversion portion of the diaphragm and the conductive member are joined by friction stir welding. The sealed secondary battery according to claim 4 , wherein an inversion portion of the diaphragm and the conductive member are joined through an opening of a battery lid that is caulked to the battery can.

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