JP2008305646A - Battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery capable of preventing liquid leakage when subjected to a heat cycle. <P>SOLUTION: The battery includes: a container 1; a battery cap 5 which is disposed in an opening of the container 1 and has a mounting hole 11; an insulating gasket 7 having a cylindrical portion 16 inserted into the mounting hole 11 of the battery cap 5, and a collar 15 which is formed on an end of the cylindrical portion 16 and covers the periphery of the mounting hole 11 of the battery cap 5; and a rivet 8 for an output terminal of the positive or negative electrode, provided with a shank swaged and fixed to the battery cap 5 in the state of being inserted into the cylindrical portion 16 of the insulating gasket 7 and a head 18 which is formed on an end of the shank and is disposed on the collar 15 of the insulating gasket 7, wherein a surface coming into contact with the collar 15 on the head 18 of the rivet 8 is formed with a groove 21 which has a loop shape along the border line of the outside of the surface or a loop shape to be a concentric pattern with respect to the shank. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a battery.

  In recent years, with the development of electronic devices, lithium secondary batteries have been developed as non-aqueous electrolyte secondary batteries that are small, lightweight, have high energy density, and can be repeatedly charged and discharged. Recently, it is suitable for in-vehicle secondary batteries mounted on hybrid cars and electric cars, and secondary batteries for power storage used for power leveling. Development of non-aqueous electrolyte secondary batteries is also desired. As such a secondary battery, for example, as described in Patent Document 1, lithium titanium oxide (lithium titanium composite oxide) having a small particle size (average particle size of primary particles is 1 μm or less) as a negative electrode active material. A non-aqueous electrolyte secondary battery that can be rapidly charged and discharged with high power and has excellent cycle performance has been developed.

  On the other hand, a metal can has been put into practical use as an exterior member for housing the nonaqueous electrolyte secondary battery as described above. In such a sealed battery, the opening of the battery case is sealed with a lid. An output terminal rivet is fixed to the lid through a plastic gasket so as to penetrate the lid wall inward and outward. The gasket also serves as an insulator that avoids direct contact between the rivet and the lid. In this case, the rivet has a head portion exposed on the outer surface of the gasket and a shaft portion fitted into the gasket, and is crimped to the lower end of the shaft portion so as to be integrated with the gasket and fixed to the lid.

  However, due to variations in the finished dimensions of the shaft and the shaft insertion hole, variations in the amount of deformation of the shaft during caulking, etc., the degree of close contact with the shaft insertion hole of the shaft is insufficient, resulting in a seal failure and causing liquid leakage There was a case. In particular, when a heat cycle in which a use in a low temperature environment and a use in a high temperature environment are repeated alternately in a temperature range of, for example, −30 ° C. to 80 ° C., creep occurs due to expansion and contraction of the gasket. A decrease in performance was observed.

  The sealed batteries described in Patent Documents 2 and 3 have a configuration in which electrode terminals having a polarity different from the polarity of the battery can are attached by caulking through an insulating member. In order to improve the sealing performance of this sealed battery, Patent Documents 2 and 3 use electrode terminals as described below. The electrode terminal used in Patent Document 2 is an electrode lead-out pin composed of a collar portion and a cylindrical portion coupled to the collar portion, and the cylindrical portion and the collar portion are in contact with the insulating member on the surface. It has a part whose diameter is larger than the meeting part. Since such an electrode lead-out pin requires only a small amount of deformation at the time of caulking, the amount of deformation of each member (inner insulating plate, metal plate and external insulating plate) into which the electrode is inserted becomes small. It is said that the airtightness between the members is improved. On the other hand, in Patent Document 3, the flange portion of the electrode lead-out pin is bitten into the insulating member by forming a convex portion and a concave portion having a sharp tip at the contact surface with the insulating member in the flange portion of the electrode lead-out pin, The displacement of the insulating member when the electrode lead-out pin is attached by caulking is eliminated.

However, according to the sealed battery described in Patent Document 2, in the caulking and fixing by pressing from above and below the electrode lead-out pin, the large-diameter portion does not always expand, and the variation in the sealing strength increases, resulting in a heat cycle. Insufficient liquid leakage resistance. On the other hand, in Patent Document 3, in order to cause the flange portion of the electrode lead-out pin to bite into the insulating member, the shape of the convex portion and the concave portion is an acute shape. Insufficient liquid leakage resistance.
JP-A-2005-123183 JP 2001-185100 A JP 2003-173767 A

  An object of this invention is to provide the battery which can prevent the liquid leakage at the time of performing a heat cycle.

The battery according to the present invention includes a container,
A positive electrode and a negative electrode housed in the container;
A battery lid disposed in the opening of the container and having a mounting hole;
An insulating gasket having a cylindrical portion inserted into the mounting hole of the battery lid, and a flange formed at one end of the cylindrical portion and covering a peripheral edge of the mounting hole of the battery lid;
A shaft portion that is caulked and fixed to the battery lid in a state of being inserted into the cylindrical portion of the insulating gasket; and a head portion that is formed at one end of the shaft portion and disposed on the flange portion of the insulating gasket; A battery comprising the positive electrode or the negative electrode output terminal rivet,
The surface of the rivet that is in contact with the flange portion is formed with an annular groove portion that is concentric with the shaft portion or an annular shape along a contour line outside the surface.

  ADVANTAGE OF THE INVENTION According to this invention, the battery which can prevent the liquid leakage at the time of performing a heat cycle can be provided.

A nonaqueous electrolyte battery according to an embodiment of the present invention will be described with reference to FIGS. As shown in FIG.1 and FIG.2, the electrode body 2 and electrolyte solution are accommodated in the battery case (container) 1 of the oblong box shape which the upper surface opened. The battery case 1 is formed by deep drawing an aluminum plate or an aluminum alloy plate and also serves as an output terminal on the positive electrode side. The electrode body 2 is obtained by winding a sheet-like positive electrode using a lithium-containing cobalt oxide such as LiCoO ₂ as an active material and a sheet-like negative electrode using graphite as an active material in a spiral shape with a separator interposed therebetween. The whole is formed by pressing so that the cross section thereof is the same square shape as the cross section of the battery case 1.

The active materials for the positive electrode and the negative electrode are not limited to the above types. For example, as the positive electrode active material, various oxides such as manganese dioxide, lithium manganese composite oxide (for example, LiMn ₂ O ₄ , LiMnO _2). ), Lithium-containing nickel oxide (eg, LiNiO ₂ ), lithium-containing nickel cobalt oxide (eg, LiNi _0.8 Co _0.2 O ₂ ), lithium-containing iron oxide, lithium-containing vanadium oxide, titanium disulfide, Examples include chalcogen compounds such as molybdenum disulfide. On the other hand, examples of the negative electrode active material include graphite materials or carbonaceous materials other than graphite (for example, coke, carbon fiber, spherical carbon, pyrolytic vapor phase carbonaceous material, resin fired body, etc.), chalcogen compounds (for example, two (E.g., titanium sulfide, molybdenum disulfide, niobium selenide, etc.), light metals (eg, aluminum, aluminum alloys, magnesium alloys, lithium, lithium alloys, etc.), lithium titanium oxides (eg, spinel type lithium titanate), etc. Can do. Moreover, as a separator, a microporous film | membrane, a woven fabric, a nonwoven fabric, the laminated material of the same material or different materials among these, etc. can be used. Examples of the material for forming the separator include polyethylene, polypropylene, ethylene-propylene copolymer, and ethylene-butene copolymer.

The non-aqueous electrolyte is prepared by dissolving an electrolyte (for example, a lithium salt) in a non-aqueous solvent. Examples of the non-aqueous solvent include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), γ-butyrolactone (γ -BL), sulfolane, acetonitrile, 1,2-dimethoxyethane, 1,3-dimethoxypropane, dimethyl ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran and the like. Nonaqueous solvents may be used alone or in combination of two or more. Examples of the electrolyte include lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium hexafluoroarsenide (LiAsF ₆ ), and trifluoromethanesulfone. Examples thereof include lithium salts such as lithium acid lithium (LiCF ₃ SO ₃ ). The electrolyte may be used alone or in combination of two or more. The amount of electrolyte dissolved in the non-aqueous solvent is desirably 0.2 mol / L to 3 mol / L.

  The positive electrode conductive tab 3 is electrically connected to the positive electrode of the electrode body 2, and the tip thereof is led out from the upper surface of the electrode body 2. On the other hand, the negative electrode conductive tab 4 is electrically connected to the negative electrode of the electrode body 2, and the tip thereof is led out from the same upper surface of the electrode body 2.

  The sealing member is caulked and fixed to the battery lid 5 via the insulating gasket 7, the battery lid 5 closing the upper surface opening of the battery case 1, the plastic insulating plate 6 disposed on the back surface of the battery lid 5. A negative output terminal rivet 8 and a washer 9 that is fixed simultaneously with the rivet 8 are provided.

  The battery lid 5 is disposed in the upper surface opening of the battery case 1 and is fixed to the battery case 1 by welding or the like, for example. The battery lid 5 is made of a press-molded product made of an aluminum plate material or an aluminum alloy plate material, and a rectangular recess 10 serving as a receiving seat for an insulating gasket is formed near the center of the upper surface. A mounting hole 11 is opened in a cylindrical shape in the recess 10 of the battery lid 5. A vent 12 is formed at one end of the battery lid 5 (on the right side in FIG. 2) to break and release gas when the case internal pressure exceeds a certain value. An electrolyte solution inlet 13 is opened at the other end of the battery lid 5 (left side in FIG. 2). The electrolyte solution inlet 13 is closed with a plug 14 after the electrolyte solution is injected. The plug 14 is fixed to the battery lid 5 by welding.

  The insulating plate 6 is a rectangular insulating resin plate having a circular hole 6a in which a shaft portion of a rivet is inserted near the center.

  As shown in FIGS. 2 and 3, the insulating gasket 7 includes a flange portion (a flange portion) 15 that covers the periphery of the mounting hole 11 of the battery lid 5, and a round shaft-shaped boss portion that protrudes from the lower surface of the flange portion 15. (Cylindrical part) 16 is formed of a plastic molded product integrally formed. A shaft insertion hole 17 into which the shaft portion of the rivet is fitted is provided in the center of the boss portion 16 so as to penetrate vertically. The flange portion 15 has a rectangular shape, and has an outer wall portion 15a that rises upward at an outer peripheral portion thereof.

  The negative output terminal rivet 8 includes a rectangular head portion 18, a shaft portion 19 having a smaller diameter than the head portion 18, and a shaft body having a caulking shaft portion 20 formed at the lower end of the shaft portion 19. The caulking shaft portion 20 has a hollow cylindrical shaft shape that opens downward. When performing caulking and fixing, the lower half side of the cylindrical wall of the caulking shaft portion 20 is expanded in diameter and caulked and deformed. As shown in FIGS. 3 and 4, a surface (hereinafter referred to as a seal surface) in contact with the flange portion 15 (excluding the outer wall portion 15 a) in the head portion 18 is concentric with the shaft portions 19 and 20. A plurality of annular grooves 21 (regions indicated by hatching in FIG. 4) are formed. As shown in FIG. 3, the groove 21 has a rectangular cross section obtained when the head 18 is cut in the radial direction. The rivet 8 is formed from aluminum or an aluminum alloy.

  Instead of forming the groove portion 21 concentrically with respect to the shaft portions 19 and 20, the groove portion may be formed in an annular shape along the contour line outside the seal surface. An example of this is shown in FIG. Since the upper surface of the head portion 18 of the rivet 8 has a rectangular shape as shown in FIG. 2, the shape drawn by the contour line outside the sealing surface of the head portion 18 is rectangular. A plurality of annular grooves 21 are formed along the outer contour line.

  The washer 9 has an annular shape and is made of, for example, aluminum or an aluminum alloy.

  The sealing member is assembled in the following procedure. As shown in FIG. 2, the flange portion 15 of the insulating gasket 7 is disposed in the concave portion 10 of the battery lid 5, and the boss portion 16 of the insulating gasket 7 is inserted into the mounting hole 11 of the battery lid 5 and these are fitted together. . The head portion 18 of the rivet 8 is inserted into the flange portion 15 of the insulating gasket 7, and the shaft portion 19 of the rivet 8 is further inserted into the shaft insertion hole 17 of the insulating gasket 7 and fitted. Thereafter, a perforated washer 9 is inserted through the insulating plate 6 into the shaft portion 19 penetrating downward from the battery lid 5. Next, when the head 18 of the rivet 8 is pressed downward to fix the position thereof and the lower end of the caulking shaft 20 is pressed upward, the shaft 19 and the caulking shaft 20 of the rivet 8 are slightly more than in the free state. The diameter is expanded (expanded). As a result, the shaft portion 19 of the rivet 8 comes into close contact with the shaft insertion hole 17 of the insulating gasket 7 and the gap between the mounting hole 11 of the battery lid 5 and the insulating gasket 7 is sealed. It is fixed by caulking through an insulating gasket 7.

  The conductive tab 4 on the negative electrode side is welded to the washer 9 of the assembly, and the conductive tab 3 on the positive electrode side is welded to the inner surface of the battery lid 5. Thereafter, the battery lid 5 is fitted into the opening of the battery case 1, and then the fitting surface between the battery lid 5 and the battery case 1 is welded and sealed. Finally, after injecting the electrolyte into the battery case 1 from the electrolyte inlet 13, the plug 14 is inserted into the electrolyte inlet 13 and welded, and the electrolyte inlet 13 is sealed to complete the battery. To do.

  As a result of diligent research, the present inventor has determined that the cause of leakage in the heat cycle is the following (1) and (2).

  (1) When the use in a low temperature environment and the use in a high temperature environment are performed alternately as in a heat cycle, the insulating gasket 7 alternates between an expansion reaction in a high temperature environment and a shrinkage reaction in a low temperature environment. Will be repeated. As a result, creep occurs in the insulating gasket 7.

  (2) The stress applied to the insulating gasket 7 is the largest at the boss portion 16 located between the shaft portions 19 and 20 of the rivet 8 and the mounting hole 11 of the battery lid 5. The flange portion 15 is hardly applied. Therefore, according to the conventional configuration, the stress easily escapes from the boss portion 16 to the flange portion 15, and the result appears as stress relaxation in the boss portion 16.

  When the heat cycle is repeated, as a result of the above phenomena (1) and (2), the stress applied to the boss portion 16 of the insulating gasket 7 gradually decreases. As a result, the position of the insulating gasket is likely to shift, and liquid leakage occurs from the gap formed at that time.

  In the present invention, an annular groove portion 21 is formed concentrically with the shaft portions 19 and 20 on the seal surface of the head portion 18 of the rivet 8 or is annularly formed along the contour line outside the seal surface. A plurality of are formed. In the heat cycle, although the insulating gasket 7 repeatedly expands and contracts, the resulting volume change is absorbed by the groove 21, so that there is a gap between the head 18 of the rivet 8 and the recess 10 of the battery lid 5. It becomes difficult to form.

  Further, the formation of the groove portion 21 increases the contact area between the sealing surface of the head portion 18 of the rivet 8 and the flange portion 15 of the insulating gasket 7. As a result, since the stress applied to the flange portion 15 of the insulating gasket 7 increases, the stress applied to the boss portion 16 is difficult to escape to the flange portion 15. Therefore, stress relaxation at the boss portion 16 can be suppressed.

  As a result, stress relaxation of the insulating gasket 7 in the heat cycle is suppressed, and in addition to the structure in which the gap is difficult to be formed, it is possible to avoid leakage in the heat cycle.

  Further, since the groove portion 21 has a rectangular shape in a cross section obtained when the head portion 18 of the rivet 8 is cut in the radial direction, the groove portion 21 does not have an acute angle, so that the insulating gasket 7 is damaged. Can be prevented.

  The depth D of the groove portion 21 is desirably 1/2 or more and 4/5 or less of the thickness T of the flange portion 15 (outer wall portion 15a) of the insulating gasket 7. Thereby, the effect by the groove part 21 can fully be acquired. In addition, the thickness T of the flange portion 15 means a thickness of a portion not between the sealing surface of the head portion 18 of the rivet 8 and the upper surface of the battery lid 5, that is, the thickness of the outer wall portion 15a.

  The depth D of the groove portion 21 and the thickness T of the outer wall portion 15a of the flange portion 15 are measured by the method described below.

  The rivet caulking portion of the battery lid 5 is taken out, embedded in an epoxy resin in the cross-section manufacturing operation, and cured to prepare a rivet caulking cross-section manufacturing sample. Next, the rivet portion of this sample is divided into two equal parts, and a sample (an example is shown in FIG. 3) in which a cross section including the center line of the rivet can be observed is created. The dimension of the depth D of the groove part 21 and the thickness T of the outer wall part 15a of the flange part 15 is measured by microscopic observation of the corresponding part.

  As shown in FIG. 3 described above, it is desirable to form a plurality of grooves 21, but one groove may be used. Further, the effect of suppressing stress relaxation at the boss portion 16 of the insulating gasket 7 is enhanced when the groove portion 21 is not provided at the boundary portion between the seal surface of the head portion 18 and the shaft portion 19.

  The insulating gasket 7 is made of, for example, polypropylene (PP), thermoplastic fluororesin, or the like. In particular, a thermoplastic fluororesin is desirable. The insulating gasket 7 made of thermoplastic fluororesin is hardly corroded by the electrolytic solution. In addition, since this insulating gasket 7 is excellent in heat resistance, creep phenomenon and stress relaxation hardly occur from the beginning. Therefore, when the insulating gasket 7 made of thermoplastic fluororesin is used, the insulating gasket 7 can maintain the properties as an elastic body over a wide temperature range from low temperature to high temperature (for example, in the range of −40 ° C. to 100 ° C.). The stress fluctuation accompanying the temperature change occurs almost regularly, and the stress relaxation in the heat cycle can be further suppressed. Examples of the thermoplastic fluororesin include tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA) and tetrafluoroethylene-hexafluoropropylene copolymer (FEP).

  In the above embodiment, the case where the rivet 8 is a negative terminal has been described, but it may be a positive terminal. Further, although the rivet 8 is disposed on the upper surface of the battery lid 5 via the flange portion 15 of the insulating gasket 7, it can also be disposed on the lower surface of the battery lid 5.

  Hereinafter, preferred embodiments of the present invention will be described.

Example 1
In the embodiment shown in FIGS. 1 to 4 described above, two annular groove portions 21 are formed concentrically with the shaft portions 19 and 20 on the seal surface of the head portion 18 of the rivet 8. The depth D is 2 / 3T (T is the thickness of the outer wall of the flange portion of the insulating gasket, 0.3 mm in the embodiment), the width of the groove 21 is 0.4 mm, and the sealed square lithium An ion battery was assembled.

  The insulating gasket 7 made of tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA) was used, and the material of the battery case 1, the battery lid 5, the rivet 8, and the washer 9 was aluminum.

(Example 2)
A sealed prismatic lithium ion battery having the same configuration as in Example 1 was assembled except that the depth D of the groove portion 21 was set to 1 / 2T.

(Example 3)
A sealed prismatic lithium ion battery having the same configuration as in Example 1 was assembled except that the depth D of the groove 21 was 4 / 5T.

Example 4
A sealed prismatic lithium ion battery having the same configuration as in Example 1 was assembled except that the depth D of the groove portion 21 was set to 1 / 3T.

(Comparative example)
A sealed prismatic lithium ion battery was assembled in the same manner as in Example 1 except that the groove was not provided.

  A heat cycle test was performed on the prismatic lithium ion batteries of the above-described Examples and Comparative Examples. The method is held at −30 ° C. for 2 hours and then at + 80 ° C. for 2 hours. This was regarded as one cycle, and after 100 cycles, the leakage of the electrolyte was examined. There are 100 test cells each. Table 1 shows the results.

Moreover, the storage test for 1 year was done with respect to the battery of the Example after a heat cycle test in the environment of a humidity of 93% at 60 degreeC. The capacity after the storage test when the capacity before the storage test is 100% is shown in Table 1 below.

  As is clear from Table 1, the prismatic lithium ion batteries of Examples 1 to 4 in which the groove portion was formed on the sealing surface of the rivet head had less leakage rate in the heat cycle than the comparative example, and high reliability. It turns out that it has sex. Further, by comparing Examples 1 to 4, leakage occurred in Examples 1 to 3 in which the depth D of the groove was set to 1/2 to 4/5 of the thickness T of the flange portion (outer wall portion) of the insulating gasket. It was found that there was no rate, and capacity deterioration after storage at high temperature was reduced.

  As described above in detail, according to the present invention, it is possible to provide a sealed battery having a structure in which a rivet for an output terminal is caulked and fixed to a gasket, and excellent in reliability without liquid leakage due to a heat cycle or the like. In particular, it is suitable as a vehicle-mounted secondary battery mounted on a hybrid vehicle or an electric vehicle, and a power storage secondary battery used for power leveling.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

The perspective view of the battery which concerns on embodiment of this invention. The disassembled perspective view of the battery shown in FIG. The principal part expanded sectional view of the sealing member of the battery of FIG. The top view seen from the axial side about the rivet used with the battery of FIG. The top view seen from the axial side about another rivet used with the battery of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Battery case, 2 ... Electrode body, 3 ... Positive electrode tab, 4 ... Negative electrode tab, 5 ... Battery cover, 6 ... Insulating plate, 6a ... Circular hole, 7 ... Insulating gasket, 8 ... Rivet, 9 ... Washer, 10 ... Recessed part, 11 ... Mounting hole, 12 ... Vent, 13 ... Electrolyte inlet, 14 ... Plug, 15 ... Flange part, 15a ... Outer wall part, 16 ... Boss part, 17 ... Shaft insertion hole, 18 ... Head, 19 ... Shaft part, 20 ... caulking shaft part, 21 ... groove part.

Claims (5)

A container,
A positive electrode and a negative electrode housed in the container;
A battery lid disposed in the opening of the container and having a mounting hole;
An insulating gasket having a cylindrical portion inserted into the mounting hole of the battery lid, and a flange formed at one end of the cylindrical portion and covering a peripheral edge of the mounting hole of the battery lid;
A shaft portion that is caulked and fixed to the battery lid in a state of being inserted into the cylindrical portion of the insulating gasket; and a head portion that is formed at one end of the shaft portion and disposed on the flange portion of the insulating gasket; A battery comprising the positive electrode or the negative electrode output terminal rivet,
The battery is characterized in that the surface of the rivet in contact with the flange portion is formed with an annular groove portion along the outline of the outer surface of the rivet or an annular groove portion concentric with the shaft portion. .   2. The battery according to claim 1, wherein a depth of the groove portion is ½ or more and 4/5 or less of a thickness of the flange portion of the insulating gasket.   The battery according to claim 1, wherein the insulating gasket is made of a thermoplastic fluororesin.   The battery according to any one of claims 1 to 3, wherein the flange portion of the insulating gasket covers a peripheral edge of the mounting hole on the upper surface of the battery lid.   The battery according to any one of claims 1 to 4 is a nonaqueous electrolyte battery.

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