JP2013073804A - Cathode can for lithium battery, lithium battery, and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cathode can for a lithium battery, which is reduced in dimensional variation and can be manufactured at a low cost.SOLUTION: A cathode can 11 for a lithium battery is molded in a cylindrical shape comprising an opening part 16, a body part 17, and a bottom part 18 by pressing a stainless steel material. A sealing body is attached to the opening part 16 of the cathode can 11, and a cathode mixture is stored in the body part 17. In the cathode can 11, the opening part 16 is formed so that its plate thickness T1 is thinner than a plate thickness T2 of the body part 17.

Description

  The present invention relates to a positive electrode can for a lithium battery produced by pressing a stainless steel material, a lithium battery provided with the positive electrode can, and a method for producing the lithium battery.

  The bobbin-type lithium battery includes a bottomed cylindrical positive electrode can, a cylindrical positive electrode mixture disposed on the inner periphery of the positive electrode can, a bottomed cylindrical separator disposed in a hollow portion of the positive electrode mixture, And a lithium negative electrode disposed inside the separator, and a sealing body disposed so as to close the opening of the positive electrode can.

  2. Description of the Related Art Conventionally, a battery has been proposed in which a body portion of a battery can is formed thinner than the opening side to increase the battery internal volume (see, for example, Patent Document 1). In general, a positive electrode can used for a lithium battery is manufactured by pressing a stainless steel material in order to ensure corrosion resistance. Here, when the stainless steel material is pressed, work hardening occurs. Therefore, conventionally, the positive electrode can is softened by performing annealing (heat treatment) for relaxing work hardening as a subsequent process of the pressing process. As a result, even if the opening of the positive electrode can is formed thick, sealing can be performed.

JP 2002-151017 A

  However, when the heat treatment is performed after the positive electrode can is made like the conventional lithium battery, the processing cost and the equipment cost increase. Further, since the positive electrode can is softened by the heat treatment, the positive electrode can is easily deformed, the dimensional accuracy is deteriorated, and the variation in can strength is increased. Therefore, it becomes easy to cause trouble in the manufacturing process. As a result, the defect rate during production of the lithium battery increases, and the manufacturing cost of the battery increases.

  This invention is made | formed in view of said subject, The objective is to provide the positive electrode can for lithium batteries which can improve a dimensional variation and can be manufactured at low cost. Another object is to provide a lithium battery that can be manufactured at low cost using the positive electrode can for a lithium battery. Furthermore, another object is to provide a method of manufacturing a lithium battery that can suppress the manufacturing cost of the lithium battery.

  Means [1] to [5] for solving the above problems are listed below.

  [1] A positive electrode can for a lithium battery in which a stainless steel material is pressed and formed into a cylindrical shape having an opening, a body, and a bottom, and a sealing body is attached to the opening. The positive electrode can for a lithium battery, wherein a thickness of the opening is thinner than a thickness of the barrel.

  According to the invention described in Means 1, when a stainless steel material is pressed to form a cylinder, work hardening of the stainless steel material occurs. For this reason, when the plate | board thickness of an opening part is thick and the intensity | strength of an opening part becomes large, a sealing process will become difficult and the annealing (heat processing) after can-making will be needed. In the present invention, unlike the prior art, the opening is formed thinner than the body, so that the opening can have an appropriate strength without heat treatment and can be sealed. . Moreover, even if the thickness of the opening is reduced, the strength is increased by work hardening at the time of press working, so that the strength after the sealing process can be sufficiently secured. Furthermore, since there is no need to perform heat treatment as in the prior art, it is possible to reduce dimensional variation and strength variation of the positive electrode can. In addition, since the heat treatment cost and equipment cost can be reduced, the positive electrode can can be manufactured at low cost.

  [2] The lithium battery positive electrode can according to [1], wherein the thickness of the opening is not less than 0.5 times and not more than 0.8 times the thickness of the barrel.

  According to the invention described in Means 2, since the plate thickness of the opening is set in the above-mentioned preferable range, the sealing processability and the strength after the sealing process can be ensured.

  [3] A positive electrode can for a lithium battery according to means 1 or 2, wherein the can has a Vickers hardness Hv of 250 or more after canning by press working.

  According to the invention described in the means 3, since the Vickers hardness Hv after canning is 250 or more, the sealing process can be reliably performed by thinning the opening. Moreover, sufficient strength can be ensured even if the opening is thinned.

  Specifically, the plate thickness of the opening is preferably 0.12 mm or more and 0.2 mm or less, and in this case, the Vickers hardness Hv after canning is more preferably 300 to 400. If it does in this way, it will become possible to cancel the strength fall by thinning of an opening by work hardening at the time of can making.

  [4] A lithium battery comprising the positive electrode can according to any one of means 1 to 3.

  According to the invention described in the means 4, since the positive electrode can with little dimensional variation can be used, the production yield of the lithium battery is improved. As a result, the manufacturing cost of the lithium battery can be kept low.

  [5] A method for manufacturing a lithium battery as described in means 4, wherein a pressing process is performed using a stainless steel material, and the opening portion, the body portion, and the bottom portion are provided, and the opening portion has a thickness greater than the plate thickness of the body portion. A can manufacturing process for manufacturing a cylindrical positive electrode can with a thinner plate thickness, and a sealing process for placing the sealing body in the opening and sealing the opening without performing heat treatment as a subsequent process of the can manufacturing process A process for producing a lithium battery comprising the steps of:

  According to the invention described in means 5, since a stainless steel material is used, work hardening occurs after the can manufacturing process of the positive electrode can, but heat treatment is not performed by forming a thin plate thickness of the opening of the positive electrode can. The sealing step can be performed. In this case, since it is not necessary to perform heat treatment, it is possible to reduce heat treatment costs and equipment costs, and it is possible to reduce dimensional variation and strength variation of the positive electrode can. Therefore, a lithium battery can be manufactured using a positive electrode can with little dimensional variation and strength variation, and the production yield of the lithium battery is improved. As a result, the manufacturing cost of the lithium battery can be kept low.

  As described above in detail, according to the inventions described in the means 1 to 3, the dimensional variation can be improved and a positive electrode can for a lithium battery can be manufactured at a low cost. Moreover, according to the invention described in the means 4 or 5, the manufacturing cost of the lithium battery can be suppressed.

Sectional drawing which shows schematic structure of the lithium battery of one embodiment. Sectional drawing which shows the positive electrode can of a lithium battery.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing a schematic configuration of a lithium battery in the present embodiment. Moreover, FIG. 2 is sectional drawing which shows the positive electrode can used for the lithium battery.

  As shown in FIG. 1, in the lithium battery 10 of the present embodiment, a cylindrical positive electrode mixture 12 is loaded inside a positive electrode can 11, and a hollow portion of the positive electrode mixture 12 is interposed via a separator 13. A lithium negative electrode 14 is disposed. The lithium battery 10 of the present embodiment is a bobbin type primary battery having a size of 16 mm in diameter and 30 mm in height.

  Inside the positive electrode can 11, a nonaqueous electrolyte solution 15 is injected up to above the positive electrode mixture 12 and the lithium negative electrode 14. The non-aqueous electrolyte 15 is made of, for example, a solution containing lithium perchlorate as a solute and propylene carbonate (PC) and 1,2-dimethoxyethane (DME) as a solvent.

  The positive electrode mixture 12 is produced, for example, by press-molding a positive electrode mixture powder in which manganese dioxide, graphite, and a powder fluororesin as a binder are mixed into a cylindrical shape. In the present embodiment, two positive electrode mixtures 12 are stacked and loaded inside the positive electrode can 11 along the axial direction thereof. Note that the positive electrode ring 30 is disposed as a spacer immediately above the positive electrode mixture 12.

  The lithium negative electrode 14 is produced by rolling (bending) into a cylindrical shape using a metal plate of lithium metal. In addition, the separator 13 is formed by double-rolling a separator base paper made of a nonwoven fabric made of polypropylene, and then heat-bonding a part of the bottom part and the body part with one end part being the bottom part folded. It is formed in a bottomed cylindrical shape.

  The positive electrode can 11 is a pressed product manufactured by, for example, pressing a stainless steel material such as SUS304, and is formed into a bottomed cylindrical shape having an opening 16, a body portion 17, and a bottom portion 18. A positive terminal 19 projects from the center of the bottom 18 of the positive electrode can 11. The Vickers hardness Hv of the positive electrode can 11 is about 300 to 400. The opening 16 of the positive electrode can 11 is sealed by a sealing body 24 including a metal negative electrode terminal 21, a metal sealing plate 22, and a resin gasket 23.

  Specifically, a groove-shaped bead portion 26 is formed in the opening 16 of the positive electrode can 11 along the outer peripheral surface of the positive electrode can 11. Then, the ring-shaped gasket 23, the sealing plate 22, and the negative electrode terminal 21 are fitted in this order above the bead portion 26 of the positive electrode can 11. In this state, the positive electrode can 11 is hermetically sealed by caulking the opening 16 of the positive electrode can 11 inside the can. In the present embodiment, the negative electrode terminal 21 and the sealing plate 22 are formed using a stainless steel material similarly to the positive electrode can 11, and the gasket 23 is formed using polypropylene.

  A negative electrode current collector 27 is provided on the inner side surface of the lithium negative electrode 14. The lead portion 27a of the negative electrode current collector 27 protrudes from the upper end surface of the lithium negative electrode 14, passes through the central opening 23a of the gasket 23, and is connected to the lower surface of the sealing plate 22 by welding.

  In the negative electrode terminal 21, a blade protrusion 29 protruding toward the inside of the battery is provided at a substantially central portion. The blade protrusion 29 is formed by notching a part of the negative electrode terminal 21 and bending the notched part downward.

  In the lithium battery 10, when the inside of the battery becomes abnormal due to misuse or the like, gas may be generated inside the battery. In this case, when the battery internal pressure reaches a predetermined pressure, the sealing plate 22 is pushed outward by the pressure and contacts the blade protrusion 29 of the negative terminal 21. Then, a hole is formed in the contact portion of the blade projection 29 in the sealing plate 22, and the gas in the battery is released to the outside of the battery through the hole. Thus, the sealing plate 22 and the blade protrusion 29 function as a safety valve mechanism, and the rupture of the lithium battery 10 is prevented in advance.

  Next, the configuration of the positive electrode can 11 used in the lithium battery 10 of the present embodiment will be described in detail.

  As shown in FIG. 2, the positive electrode can 11 is formed such that the inner diameter D <b> 2 of the trunk portion 17 is smaller than the inner diameter D <b> 1 of the opening 16. Further, in the positive electrode can 11, the plate thickness T <b> 1 of the opening 16 is thinner than the plate thickness T <b> 2 of the trunk portion 17. Specifically, the plate thickness T1 of the opening 16 is, for example, 0.2 mm, and the plate thickness T2 of the trunk portion 17 is, for example, 0.25 mm. In the positive electrode can 11, the boundary portion between the opening 16 and the trunk portion 17 is inclined so as to decrease in diameter toward the trunk portion 17 side (lower side in FIG. 2). More specifically, inclined surfaces 28 a and 28 b are formed on the inner surface side and the outer surface side of the positive electrode can 11 at the boundary portion between the opening portion 16 and the body portion 17. The inner diameter D2 is smaller.

  In addition, in the positive electrode can 11, the inner surface of the body portion 17 in which the positive electrode mixture 12 is disposed has a surface roughness Ra larger than that of the opening 16, for example, the surface is rough so that the surface roughness Ra is 3 μm to 7 μm. It has become. By roughening the surface of the body portion 17 in this way, the contact area between the positive electrode mixture 12 and the positive electrode can 11 is increased, and the discharge performance of the lithium battery 10 is enhanced.

  Next, the manufacturing method of the lithium battery 10 in this Embodiment is demonstrated.

  First, the positive electrode mixture 12, the separator 13, the lithium negative electrode 14, the nonaqueous electrolytic solution 15, and the sealing body 24 (the negative electrode terminal 21, the sealing plate 22, and the gasket 23) are prepared and prepared in advance.

  Further, a plate-like stainless steel material is prepared, and the positive electrode can 11 is manufactured by multistage drawing processing in which deep drawing is performed in stages (can making process). In the multistage drawing process, the positive electrode can 11 is manufactured by adjusting the mold clearance so that the plate thickness T2 of the body portion 17 is smaller than the plate thickness T1 of the opening portion 16.

  Thereafter, the positive electrode mixture 12 formed into a cylindrical shape is inserted into the bottomed cylindrical positive electrode can 11, and the positive electrode ring 30 is fitted thereon. In addition, the positive electrode can 11 used here is one that has not been annealed (heat treated) as a post-process of the can manufacturing process. Further, a cylindrical lithium negative electrode 14 is inserted into the separator 13, and the integrated separator 13 and lithium negative electrode 14 are inserted and disposed in the hollow portion of the positive electrode mixture 12 of the positive electrode can 11. And in the positive electrode can 11, the bead part 26 is formed by pressing a disk-shaped roller to the side surface of the opening part 16 vicinity, and rotating a positive electrode can periphery.

  Next, the gasket 23 is placed above the bead portion 26 of the positive electrode can 11, and the sealing plate 22 is connected to the lead portion 27 a of the negative electrode current collector 27 by spot welding. Thereafter, the nonaqueous electrolytic solution 15 is injected into the positive electrode can 11 to above the positive electrode mixture 12 and the lithium negative electrode 14. Further, the sealing plate 22 and the negative electrode terminal 21 are disposed on the gasket 23 placed on the bead portion 26 of the positive electrode can 11, and the opening end portion of the positive electrode can 11 is subjected to curling and drawing processing. 11 is sealed (sealing step). Thereby, the lithium battery 10 of FIG. 1 is completed.

Examples will be described below. Here, several types of lithium batteries 10 having the above-described configuration were manufactured using positive electrode cans 11 having different specifications. Table 1 shows the specifications of the positive electrode can 11 used here (eight types of numbers 1 to 8). Note that the number 8 sample has the same specifications as the current product that is currently commercialized.

  As shown in Table 1, in each sample, the thickness of the body portion 17 (plate thickness T2) is set to 0.25 mm, and the thickness of the opening portion 16 (plate thickness T1) is set to 0.10 mm to 0.25 mm. ing. Specifically, the plate thickness T1 of the opening 16 is set to 0.1 mm for the number 1 sample, 0.12 mm for the number 2 sample, 0.15 mm for the number 3 and 4 samples, and to the number 5 and 6 samples. The thickness is 0.2 mm, which is thinner than the body portion 17. In the number 7 sample and the number 8 sample, the plate thickness T1 of the opening 16 is set to 0.25 mm, which is the same as the plate thickness T2 of the trunk portion 17.

  Furthermore, in the sample of No. 8, the positive electrode can 11 which has been subjected to the same heat treatment as the prior art (temperature range of 1010 ° C. to 1150 ° C., about 0.5 hours to 2 hours) is used. Then, the positive electrode can 11 which was not heat-processed was used. In the samples of Nos. 1 to 7, the Vickers hardness Hv of the positive electrode can 11 was about 300 to 400 by work hardening of press working. On the other hand, in the sample of No. 8, the work hardening of the positive electrode can 11 was relaxed by performing the heat treatment, and the Vickers hardness Hv was 200. This hardness is almost the same as that of the stainless steel material before press working.

Each sample was evaluated for sealing processability, high-temperature storage leakage, sealing pressure resistance, and discharge performance. The results are shown in Table 2.

  As shown in Table 2, the sample No. 1 is processed into a wave shape because the plate thickness T1 of the opening 16 is as thin as 0.1 mm. For this reason, it becomes impossible to perform sealing processing reliably. Further, in the sample of No. 7, since the hardness was large and the plate thickness T1 of the opening 16 was as thick as 0.25 mm, the sealing process could not be performed. On the other hand, the samples Nos. 2 to 6 have high hardness, but the plate thickness T1 of the opening 16 is thin, so that the strength is suitable for the sealing process, and sufficient sealing processability can be obtained. In the sample of No. 8, although the plate thickness T1 of the opening 16 was as thick as 0.25 mm, the hardness was reduced by the heat treatment, so that sufficient sealing workability was obtained.

  Regarding the high temperature storage liquid leakage, the sealing pressure resistance value, and the discharge performance, the samples of Nos. 2 to 6 and 8 that could be sealed were evaluated. Here, the high-temperature storage leakage property was confirmed by storing the lithium battery 10 (30 test samples) in a constant temperature bath at 70 ° C. for 100 days to check for leakage. In the samples Nos. 2 to 6 and 8, no leakage was confirmed in all 30 lithium batteries 10.

  Further, the sealing pressure resistance value was measured by the following method. That is, the opening 16 is sealed in a state where the battery contents (the positive electrode mixture 12, the lithium negative electrode 14, the nonaqueous electrolytic solution 15, etc.) are not accommodated in the positive electrode can 11. Then, the sealing pressure | voltage resistance value was measured by applying a pressure in the positive electrode can 11 through the test through-hole (illustration omitted) formed in the bottom part 18 grade | etc.,. The number of test samples is 10, and the sealing pressure resistance value is obtained as an average value of the 10 samples. When the sealing pressure resistance value of the number 8 sample was 100, the number 2 to 6 samples had a pressure resistance value of 95 to 97. Thus, in the samples of Nos. 2 to 6, the sealing pressure resistance value was almost the same as that of the number 8 sample (current product), and it was confirmed that the reliability of the sealing portion was sufficiently ensured. .

  In the evaluation of the discharge performance, under the test temperature of 20 ° C., a 1 KΩ resistor is connected to the lithium battery 10 of each sample and continuous discharge is performed until the battery voltage drops from the initial value of 3 V to a predetermined voltage of 2 V or less. The discharge time of was measured. Here, when the discharge time of the sample of No. 8 (current product) is 100, the samples of No. 2 to 6 have the same discharge time, and sufficient discharge performance was ensured.

  Based on the above results, it is preferable to set the plate thickness T1 of the opening 16 to 0.12 mm or more and 0.20 mm or less (0.5 to 0.8 times the plate thickness T2 of the body portion 17). I understood it.

  Therefore, according to the present embodiment, the following effects can be obtained.

  (1) In the lithium battery 10 of the present embodiment, the plate thickness T2 of the trunk portion 17 is set to 0.25 mm, and the plate thickness T1 of the opening 16 is set to 0.12 mm to 0.20 mm (plate thickness T2 of the barrel portion 17). 0.5 times or more and 0.8 times or less). Thus, if the opening part 16 is formed thinner than the trunk | drum 17 in the positive electrode can 11, since the opening part 16 becomes moderate intensity | strength without heat processing, the sealing process of the positive electrode can 11 can be performed. Moreover, even if the opening 16 is made thinner, the strength is increased by work hardening, so that the strength of the sealing portion after the sealing processing can be sufficiently ensured.

  (2) In the manufacturing method of the lithium battery 10 of the present embodiment, the heat treatment as in the prior art is not performed after the can manufacturing process of the positive electrode can 11. For this reason, the processing cost and equipment cost of heat processing can be reduced, and the positive electrode can 11 and the lithium battery 10 can be manufactured at low cost. In addition, since no heat treatment is performed, the dimensional variation and strength variation of the positive electrode can 11 can be reduced. Therefore, the production yield of the lithium battery 10 is improved by manufacturing the lithium battery 10 using the positive electrode can 11 with less dimensional variation and strength variation. As a result, the manufacturing cost of the lithium battery 10 can be kept low.

  (3) In the positive electrode can 11 of the present embodiment, since the inner diameter D1 of the opening 16 is larger than the inner diameter D2 of the body portion 17, the positive electrode mixture 12 and the sealing body 24 are inserted into the positive electrode can 11 from the opening 16 side. Etc., and the lithium battery 10 can be easily manufactured.

  In addition, you may change embodiment of this invention as follows.

  In the positive electrode can 11 of the present embodiment, inclined surfaces 28 a and 28 b are formed on the inner surface side and the outer surface side at the boundary portion between the opening portion 16 and the trunk portion 17, and the opening is larger than the plate thickness T <b> 2 of the trunk portion 17. Although the plate thickness T1 of the portion 16 has been reduced, the present invention is not limited to this. For example, at the boundary portion between the opening 16 and the body portion 17, only the inner surface side may be inclined to make the plate thickness T1 of the opening portion 16 thinner than the plate thickness T2 of the body portion 17, or only the outer surface side. The plate thickness T1 of the opening 16 may be made thinner than the plate thickness T2 of the body portion 17 by being inclined.

  In the above embodiment, the lithium battery 10 is a primary battery, but the present invention may be applied to a lithium secondary battery.

  Next, in addition to the technical ideas described in the claims, the technical ideas grasped by the embodiments described above are listed below.

  (1) The positive electrode can for a lithium battery according to any one of the means 1 to 3, wherein the Vickers hardness Hv after canning by pressing is 300 to 400.

  (2) The positive electrode can for a lithium battery according to any one of the means 1 to 3, wherein a thickness of the opening is 0.12 mm or more and 0.2 mm or less.

  (3) The positive electrode can for a lithium battery according to any one of the means 1 to 3, wherein a bead portion for mounting a sealing body for closing the opening portion is formed in the opening portion.

  (4) The positive electrode can for a lithium battery according to any one of the means 1 to 3, wherein an inner diameter of the body is smaller than an inner diameter of the opening.

  (5) The positive electrode can for a lithium battery according to any one of the means 1 to 3, which is manufactured by deep drawing.

DESCRIPTION OF SYMBOLS 10 ... Lithium battery 11 ... Positive electrode can as a positive electrode can for lithium batteries 16 ... Opening part 17 ... Trunk part 24 ... Sealing body T1 ... Thickness of opening part T2 ... Thickness of trunk | drum part

Claims (5)

A stainless steel material is press-processed and formed into a cylindrical shape having an opening, a body and a bottom, and is a positive electrode can for a lithium battery in which a sealing body is attached to the opening,
The positive electrode can for a lithium battery, wherein a thickness of the opening is thinner than a thickness of the barrel.   2. The positive electrode can for a lithium battery according to claim 1, wherein a thickness of the opening is not less than 0.5 times and not more than 0.8 times a thickness of the body portion.   The positive electrode can for a lithium battery according to claim 1 or 2, wherein the Vickers hardness Hv after making the can by press working is 250 or more.   A lithium battery comprising the positive electrode can according to any one of claims 1 to 3. It is a manufacturing method of the lithium battery according to claim 4,
A can-making process for producing a cylindrical positive electrode can which is pressed using a stainless steel material and has an opening, a body and a bottom, and the plate thickness of the opening is thinner than the plate thickness of the body. ,
A method for manufacturing a lithium battery, comprising: a sealing step in which a sealing body is disposed in the opening without sealing and the opening is sealed as a subsequent step of the can making step.

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