JP2005285578A - Battery manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery ensuring required electrolyte amount and preventing the whole exterior can from being compressed to obtain the exterior can having excellent mechanical strength and to improve battery capacity and cycle service life. <P>SOLUTION: This battery manufacturing method comprises: an electrode group storage process for storing a group 30 of electrodes in the bottomed and cylindrical exterior can 10 having a protruding part 12 formed in such a way that a part of a side wall of a main body part 11 protrudes toward the outside from the inside; a liquid pouring process for pouring electrolyte into the bottomed and cylindrical exterior can 10 storing the group 30 of electrodes; and a pressurizing molding process for pressurizing and molding the protruding part 12 so that a part of a side wall of the bottomed and cylindrical exterior can 10 protrudes toward the outside from the inside and it becomes substantially same face as an external wall face of the side wall. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a battery manufacturing method in which an electrode group formed by interposing a separator between a positive electrode and a negative electrode is housed in a bottomed cylindrical outer can and then injected with an electrolytic solution.

  In recent years, as demand for portable electronic / communication equipment such as small video cameras, mobile phones, and notebook computers increases, lithium secondary batteries represented by lithium ion batteries, nickel-hydrogen storage batteries, nickel-cadmium, etc. are used as power sources. The demand for alkaline storage batteries such as storage batteries has increased. Since this type of battery is used in portable electronic / communication equipment, it is required to have a high capacity, and therefore it is necessary to increase the filling amount of the active material. However, when an electrode group is formed by laminating an electrode with an increased active material filling amount via a separator or winding it in a spiral shape, the thickness of the electrode increases. Thickness increases.

  Here, as the diameter and thickness of the electrode group increase, the proportion of the volume occupied by the electrode group in the outer can increases, and accordingly the volume of the space between the electrode group and the outer can (remaining space) decreases. To do. Since the filling amount of the active material will increase, the amount of electrolyte injection will also have to be increased, but due to the decrease in volume of the remaining space in the outer can, the electrolyte will not easily penetrate into the can, There was a problem that the desired amount of electrolyte was not injected. In order to solve such a problem, the diameter of the outer can can be increased. However, in portable electronic / communication equipment, since the space for housing the battery is limited, the diameter of the outer can can be reduced. There is a limit to increasing it.

For this reason, when inserting an electrode group, an outer can whose diameter is slightly larger than the diameter of the electrode group is used, and after the electrode group is inserted into the outer can, the diameter of the outer can is reduced (this is called reduced diameter). ) Method has been proposed in Patent Document 1 and the like. In the method proposed in Patent Document 1, an outer can whose outer dimension is larger than the outer dimension of a battery can (outer can) in a final battery is used, and an electrode element (electrode group) is accommodated in the outer can. . Thereafter, the outer diameter of the outer can is reduced to the outer dimension of the outer can in the final battery by a diameter reducing machine. According to this method, since an outer can having an outer dimension larger than the outer dimension of the outer can in the final battery is used, a gap between the electrode group and the outer can can be secured, and liquid injection is performed before the diameter reduction. It is possible to efficiently inject a predetermined amount of electrolyte into the outer can.
Japanese Patent Laid-Open No. 11-354084

  However, in the method proposed in Patent Document 1 described above, pressurization is performed so that the entire outer can is compressed by a diameter reducing machine. For this reason, the whole electrode group will be pressed by the inner wall of the pressurized exterior can. As a result, when an electrode plate with weak mechanical strength is used, the electrode plate cracks or the electrode plate is cut, and the electrode plate or separator is damaged, making it impossible to maintain a predetermined capacity. As a result, the cycle life is shortened and internal short circuit occurs.

  Therefore, the present invention has been made to solve the above-described problems, and a battery with improved battery capacity and cycle life can be obtained by securing the necessary amount of electrolyte and preventing the entire outer can from being compressed. An object of the present invention is to provide a battery having an outer can with excellent mechanical strength.

  The present invention is a method for producing a battery produced by injecting an electrolytic solution after accommodating an electrode group formed by interposing a separator between a positive electrode and a negative electrode in a bottomed cylindrical outer can, In order to achieve the above, an electrode group storage step for storing the electrode group in a bottomed cylindrical outer can having a protruding portion formed so that a part of the side wall protrudes outward from the inside, and the electrode group A liquid injection step of injecting an electrolyte into a bottomed cylindrical outer can in which is stored, and the outer wall surface of the protruding portion of the side wall of the bottomed cylindrical outer can is substantially flush with the outer wall surface of the side wall. And a pressure forming step of pressure forming so as to be.

  As described above, when a part of the side wall of the bottomed cylindrical outer can in which the electrode group is housed has a protrusion formed so as to protrude outward from the inside, the protrusion and the electrode group A space is formed between them. For this reason, since this space part becomes the storage space of the electrolyte solution poured at the time of liquid injection, it becomes possible to secure a sufficient amount of the electrolyte solution. Then, when the protruding portion is pressed to be substantially flush with the outer wall surface of the side wall with a sufficient amount of electrolyte, the side walls other than the protruding portion are not pressed, so the mechanical strength Even when weak electrodes are used, these electrodes are not cracked or cut.

  As a result, a predetermined capacity can be maintained, the cycle life is improved, and the problem of occurrence of an internal short circuit does not occur, and a battery with improved battery capacity and cycle life can be obtained. Further, when the protruding portion is pressurized, an outer can having excellent mechanical strength can be obtained. In this case, it is desirable that the protrusions in the cylindrical battery are arranged uniformly on the side wall of the outer can so that the liquid permeability to the electrode group is uniform. In addition, the protrusion does not necessarily have to be formed continuously from the bottom of the can to the opening, but the liquid permeability to the electrode group is more uniform if formed continuously from the bottom of the can to the opening. This is desirable. Furthermore, it is desirable to arrange such that there is a portion having no protrusion at 90 °, 180 °, and 270 ° from an arbitrary portion having a side surface that is not the protrusion. In the case of an assembled battery, if the projecting portion (same on the substantially same surface after pressure molding) is arranged in this way, the assembled battery has a predetermined size without obstructing a minute projecting portion on the substantially same surface. It is because it can form.

  Next, an embodiment of the present invention will be described below with reference to FIGS. 1 to 5, but the present invention is not limited to this embodiment at all, and can be appropriately changed without changing the object of the present invention. Can be implemented. FIG. 1 is a perspective view schematically showing a substantially cylindrical bottomed outer can having a protrusion before being pressure-molded. FIG. 2 is a cross-sectional view schematically showing a process for manufacturing a substantially cylindrical bottomed outer can having the protruding portion of FIG. FIG. 3 is a cross-sectional view schematically showing a cross section in a state where the electrode group is housed in the outer can, and FIG. 3A is a cross-sectional view showing a state in which the electrode group is housed in the outer can of FIG. FIG. 3B is a cross-sectional view showing a state in which the electrode group is housed in the cylindrical outer can.

  4 is a cross-sectional view schematically showing a state where the outer can containing the electrode group is pressure-formed, and FIG. 4A is a side view of the protrusion formed in the outer can of FIG. FIG. 4B is a cross-sectional view showing a state of being pressure-molded so as to be substantially flush with the outer wall surface of FIG. 4, and FIG. 4B is an enlarged view of the Z portion of FIG. FIG. 4 is a cross-sectional view showing a state in which the outer can of FIG. 3B is not pressed, or a state in which the side wall of the outer can of FIG. FIG. 5 is a view schematically showing a bottomed outer can having a substantially rectangular tube shape, and FIG. 5 (a) is a cross-sectional view schematically showing a state having a protruding portion before being pressure-molded. 5 (b) is a cross-sectional view schematically showing a state in which the protrusion shown in FIG. 5 (a) is pressure-molded so as to be substantially flush with the outer wall surface of the side wall. FIG. 5C is a cross-sectional view schematically showing a substantially rectangular tube-shaped bottomed outer can having no protrusions.

1. Exterior Can (1) Example As shown in FIG. 1, the exterior can 10 having the projecting portion 12 of the present example has nickel plated on a base material made of iron and has a thickness (can thickness) t of 0.25 mm. (T = 0.25 mm) of a substantially cylindrical main body 11 having a bottom, and eight protrusions 12 formed so that a part of the side wall of the main body 11 protrudes outward from the inside. It consists of. In the present embodiment, the inner diameter R of the main body 11 is 17.5 mm (R = 17.5 mm), and the protrusion has a height h of 1.7 mm (h = 1.7 mm) and a bottom length l. Is an isosceles triangle having a size of 2.7 mm (l = 2.7 mm).

  In this case, the number of the protrusions 12 formed to protrude from the main body 11 is not limited to eight as described above, but as shown in FIGS. 3 (a) and 4 (a), In the cross section perpendicular to the long axis of the outer can 10, it is desirable that the protrusions 12 do not exist at positions of 0 °, 90 °, 180 °, and 270 °, respectively. And the end part of pressurization part 12a mentioned below does not cross the perpendicular (line perpendicular to the diameter) drawn on the outer surface of main part 11, ie, between a pair of perpendiculars (for example, mutually parallel) It is desirable that the length between AA and BB in FIG. 4A is R (inner diameter of the main body) + 2t (t = 0.25 mm). Here, the length R + 2t between a pair of perpendicular lines parallel to each other means that the outer dimension (R + 2t) of a cylindrical can 20 of Comparative Example 1 described later is equal. This is because an assembled battery can be formed in a predetermined size without disturbing a slightly protruding portion of substantially the same surface.

  Next, a method for producing the outer can 10 having the above-described configuration will be described with reference to FIG. First, after rolling a substrate on which a nickel plating is applied to a base material made of iron to obtain a plate material having a thickness of 0.5 mm, the plate material is punched into a circular shape or a square shape, and the diameter becomes 50 cm, for example. Such a circular plate 10a was formed. Next, using the punch 15 having the cross-sectional shape of the outer can 10 shown in FIG. 1 and the drawing die 16 as shown in FIG. 2A, as shown in FIG. Molded. Thereafter, the front throttle cylinder 10b was held by a holding member inserted in the cylinder and a redrawing die (not shown).

  Then, the operation of relatively moving the redrawing punch and the redrawing die (not shown) provided coaxially with the holding member and the redrawing die so as to be able to enter and exit the holding member is repeatedly performed. It was. As a result, as shown in FIG. 2 (c), the deep drawing cylinder 10c was formed by deep drawing the front drawing cylinder 10b and extending the side walls. Then, by repeating such an operation, as shown in FIG. 2D, the deep-drawn cylinder 10c was further deep-drawn to form a deep-drawn cylinder 10d in which the side walls were further extended. Finally, it cut | disconnected so that the length to an opening part might become predetermined length, and formed the exterior can 10 which has the protrusion part 12 on the side wall which has a seamless side wall and a bottom wall.

(2) Comparative Example On the other hand, as shown in FIG. 3 (b), the outer can 20 of the comparative example is nickel-plated on a base material made of iron and has a thickness (can thickness) t of 0.25 mm (t = It is formed from a cylindrical body with a bottom of 0.25 mm) and a bottom. In this case, the diameter (inner diameter) R of the outer can 20 is formed to be equal to the diameter R of the main body 11 of the outer can 10 of the embodiment. In the case of producing such a cylindrical outer can 20, it may be formed in the same manner as described above using a punch 15 and a drawing die 16 having a circular cross-sectional shape as shown in FIG. . In addition, an outer can 25 having a diameter (inner diameter) of 1.06R was also produced in the same manner as described above so that the inner volume was equal to that of the outer can 10.

2. Cylindrical battery (1) Preparation of positive electrode LiCoO ₂ powder having an average particle diameter of about 5 μm as a positive electrode active material and artificial graphite powder as a conductive agent are mixed so that the mass ratio is 9: 1. An agent was prepared. The positive electrode material mixture and a binder solution obtained by dissolving 5% by mass of polyvinylidene fluoride (PVdF) in an organic solvent composed of N-methyl-2-pyrrolidone (NMP) was 95: 5 in terms of solid content mass ratio. Thus, a positive electrode slurry was prepared.

This slurry was uniformly applied to both surfaces of an aluminum foil (thickness: 15 μm) as a positive electrode current collector using a doctor blade to form a positive electrode plate coated with an active material layer. In this case, the coating mass was 500 g / m ² (250 g / m ² on one side, excluding the mass of the current collector) after drying the double-side coated part. Thereafter, after passing through a dryer and drying, the dried positive plate is rolled to a predetermined thickness by a roll press so that the active material has a packing density of 3.7 g / cm ^3. Then, it was cut into a predetermined size and vacuum dried at 150 ° C. for 2 hours to produce a strip-like positive electrode.

(2) Production of negative electrode On the other hand, flaky graphite (with a d ₀₀₂ value of 3.356%, an Lc value of 1000%, and an average particle size of 20 μm) and styrene-butadiene rubber (SBR) as a binder Dispersion (solid content 48%) was dispersed in water. Thereafter, carboxymethyl cellulose (CMC) serving as a thickener was added to prepare a negative electrode slurry. In this case, the solid content after drying was adjusted so that the graphite: SBR: CMC was 100: 3: 2.

Next, the obtained negative electrode slurry was uniformly applied on both sides of a copper foil (thickness: 10 μm) as a negative electrode current collector using a doctor blade to form a negative electrode plate coated with an active material layer. In this case, the coating mass was 200 g / m ² (100 g / m ² on one side, excluding the mass of the current collector) after drying the double-side coated part. After drying, it was rolled to a predetermined thickness so that the packing density of the active material was 1.7 g / cm ³ , then cut to a predetermined size, and vacuum dried at 110 ° C. for 2 hours to produce a strip-shaped negative electrode. .

(3) Production of Cylindrical Nonaqueous Electrolyte Battery Next, a belt-like positive electrode plate and a belt-like negative electrode plate produced as described above are prepared, and a separator made of a polypropylene microporous film is interposed between them. Thus, a spiral electrode group 30 was produced by spirally winding. In this case, the diameter of the spiral electrode group 30 is wound so as to be smaller than the inner diameter R of each outer can 10 (20, 25). This electrode group 30 was inserted from the opening of the outer can 10 (20, 25) produced as described above. In addition, one curve of the spiral of the electrode group 30 shown by FIG. 3, FIG. 4 has shown the combination of a separator, a positive electrode plate, a separator, and a negative electrode plate. Next, a negative electrode current collecting tab (not shown) extending from the negative electrode plate of the electrode group 30 was welded to the bottom of the outer can 10 (20, 25).

Subsequently, 1 mol / liter of LiPF ₆ was dissolved in a mixed solvent (EC: MEC = 30: 70: volume ratio) composed of ethylene carbonate (EC) and methyl ethyl carbonate (MEC) to prepare an electrolytic solution. This electrolyte solution was poured from the opening of the outer can 10 (20, 25) in which the electrode group 30 was housed, and was left under reduced pressure for 30 minutes to fully impregnate the electrode group 30 with the electrolyte solution. In this case, when the mass difference from before injection, that is, the injection amount (g), was determined, it was found that 6.2 g was injected into the outer can 10 and the outer can 25. . It was also found that 5.1 g was injected into the outer can 20. Here, with respect to the amount of liquid injected into the outer can 20, the amount of increase in the amount of liquid injected into the outer can 10 and the outer can 25 is equal to the increase in the internal volume due to the protrusion 12 in the outer can 10. No. 25 almost coincided with the increase in internal volume due to the increase in diameter (0.06R).

  Thereafter, with respect to the outer can 10, the protruding portion 12 formed to protrude from the main body portion 11 of the outer can 10 was pressure-molded so as to be substantially flush with the outer wall surface of the main body portion 11. Here, by passing the outer can 10 through a pressure molding machine (not shown), as shown in FIG. 4A, the protruding portion 12 is pressed to form a pressure portion 12a, and the outside of the pressure portion 12a is formed. It is pressure-molded so that the surface is substantially flush with the outer wall surface of the main body 11. FIG. 4B shows an enlarged view of the pressurizing part 12a. In this way, the protruding part 12 is folded so that a part of the projecting part 12 is folded and the folded part 14 is formed. become. For this reason, only the folding portion 14 presses the electrode group 30. In addition, the entire diameter of the side wall of the outer can 25 was reduced so as to have the inner diameter R.

  Next, although not shown, after arranging a spacer on the upper part of the electrode group 30, a positive electrode lead extending from the positive electrode plate of the electrode group 30 was welded to the inner bottom part of the positive electrode terminal provided on the sealing body. After that, the sealing body is disposed in the opening of the outer can 10 (20, 25) via an insulating gasket, and the opening of the outer can 10 (20, 25) is caulked with the sealing body to hermetically seal the inside of the battery. did. Thereby, cylindrical nonaqueous electrolyte batteries (lithium secondary batteries) A1, X1, and Y1 having a design capacity of 1800 mAh and 18650 sizes (having a bottom diameter of 18 mm and a height of 65 mm) were produced. Here, the battery using the outer can 10 was designated as battery A1, the battery using the outer can 20 was designated as battery X1, and the battery using the outer can 25 was designated as battery Y1.

3. Battery Characteristics Test (1) Charge / Discharge Cycle Test Each of these batteries A1, X1, and Y1 is charged at a constant current at a room temperature (about 25 ° C.) with a charging current of 1800 mA (1 It) until the battery voltage reaches 4.2V. Then, constant voltage charging was performed until the current value reached 10 mA at a constant voltage of 4.2 V. Thereafter, a charge / discharge cycle of discharging at a discharge current of 1800 mA (1 It) until the battery voltage reached 2.75 V was repeated 500 times. At this time, when the ratio of the discharge capacity at the 500th cycle to the discharge capacity at the first cycle was determined as the capacity retention after 500 cycles, the results shown in Table 1 below were obtained.

  As is clear from the results in Table 1 above, in the battery A1 using the outer can 10 and the battery Y1 using the outer can 25, since the amount of the electrolyte in the battery is large, the capacity retention rate after 500 cycles ( %) Is large. On the other hand, in the battery X1 using the outer can 20, since the amount of the electrolyte in the battery is small, it can be seen that the capacity retention rate (%) after 500 cycles is decreased. From these facts, when using an outer can having a sufficient gap that is retained during the injection of the electrolyte solution, such as the outer cans 10 and 25, the amount of electrolyte injected increases, and the capacity retention rate (%) It is understood that this is preferable.

(2) Internal short-circuit rate Next, after assembling the batteries A1, X1, and Y1, as described above, the number of internal short-circuits was measured and the internal short-circuit rate was obtained. The results shown in Table 2 below were obtained. was gotten.

  As is clear from the results in Table 2 above, it can be seen that the battery Y1 whose diameter is reduced on the entire side wall has an internal short-circuit rate increased 10 times as compared with the battery X1 having no diameter reduction. On the other hand, it can be seen that the battery A1 obtained by pressure-molding only a part of the outer can has an internal short circuit rate equivalent to that of the battery X1 having no diameter reduction. This means that the battery A1, which is only partially pressurized as compared to the battery Y1 having a reduced diameter on the entire side wall of the outer can, can have an internal short circuit rate equivalent to that of the conventional battery X1. At the same time, it means that the cycle characteristics can be greatly improved.

(3) Drop test First, the main body 11 is formed so that the thickness (can thickness) is 0.15 mm (t = 0.15 mm), and the exterior is provided with eight protrusions 12 as in FIG. A nonaqueous electrolyte battery was produced in the same manner as the battery A1 except that the can 10 was used, and this was designated as a battery A2. Moreover, except using the cylindrical outer can 20 provided with the main-body part 21 formed so that thickness (can thickness) may be set to 0.15 mm (t = 0.15 mm), it is the same as that of the above-mentioned battery X1. A nonaqueous electrolyte battery was produced, and this was designated as battery X2.

Subsequently, using the batteries A1, A2 and the batteries X1, X2, each of the batteries A1, A2, X1, X2 was charged at a room temperature (about 25 ° C.) with a charging current of 1800 mA (1 It), and the battery voltage was 4. The battery was charged at a constant current until it reached 2 V, and charged at a constant voltage of 4.2 V until the current value reached 10 mA to obtain a fully charged state. Thereafter, when the internal resistances of these fully charged batteries A1, A2, X1, and X2 were measured, the results shown in Table 3 below were obtained. In addition, after each of these batteries A1, A2, X1, and X2 after charging was dropped 30 times onto a concrete base from a height of 1 m, the inside of each of these batteries A1, A2, X1, and X2 When the resistance was measured, the results shown in Table 3 below were obtained.

  As is clear from the results in Table 3 above, the batteries A1 and A2 showed the same internal resistance value after the drop test as before the test, whereas the batteries X1 and X2 showed the internal resistance after the test. It can be seen that the value is greatly reduced. This is considered to be because, in the batteries X1 and X2, the outer can 20 was deformed by a drop test, a minute short circuit occurred inside the battery, and the internal resistance value was greatly reduced. In addition, the battery X1 using the outer can 20 having a can thickness of 0.25 mm (t = 0.25 mm) is different from the battery X2 using the outer can 20 having a thin can thickness of 0.15 mm (t = 0.15 mm). It can be seen that the amount of decrease in internal resistance is larger.

  On the other hand, even if the battery A1 using the outer can 10 having a can thickness of 0.25 mm or the battery A2 using the outer can 10 having a thin can thickness of 0.15 mm, the internal resistance is reduced. It can be seen that the amount has hardly changed. This is because, in the outer can 10, the protrusion 12 formed to protrude from the main body portion 11 is pressurized and applied so as to be substantially flush with the outer wall surface of the side wall of the main body portion 11 after the electrolyte solution is injected. It is considered that the pressure part 12a is formed, and the strength of the outer can 10 is improved by the pressure part 12a. As a result, even if the can thickness of the outer can 10 is reduced, the internal resistance does not decrease, that is, a minute short circuit does not occur inside the battery, and the reliability is improved in each stage.

4). Next, as shown in FIG. 5 (a), the main body portion 41 is made of aluminum and has a bottom (can thickness) of approximately 0.20 mm (t = 0.20 mm) and a bottomed main body portion 41, and the main body portion. A rectangular outer can 40 comprising four projecting portions 42 formed so that a part of the side wall 41 protrudes outward from the inside was prepared. Further, as shown in FIG. 5 (c), the bottomed main body 51 is made of aluminum and has a thickness (can thickness) of 0.20 mm (t = 0.20 mm) and is not formed with a protruding portion. The provided square outer can 50 was prepared and used as an outer can 50.

  Subsequently, the spiral electrode group 30 produced in the same manner as described above was pressed flatly so as to match the planar shape of the rectangular outer can 40 (50) to form a flat electrode group (not shown). This flat electrode group was accommodated in the aforementioned rectangular outer can 40 (50). Thereafter, an electrolyte solution similar to that described above was injected from the opening of these outer cans 40 (50), and left under reduced pressure for 30 minutes to fully impregnate the electrode group with the electrolyte solution. In this case, when the mass difference from before injection, that is, the injection amount (g), was determined after injection, 5.3 g of electrolytic solution was injected into the outer can 40. It was also found that 4.5 g of electrolyte solution was injected into the outer can 50.

  Thereafter, the outer can 40 was press-molded so that the protruding portion 42 formed to protrude from the main body 41 of the outer can 40 was substantially flush with the outer wall surface of the side wall of the main body 41. Here, by passing the outer can 40 through a pressure molding machine (not shown), as shown in FIG. 5B, the protruding portion 42 is pressed to form a pressure portion 42a, and the outside of the pressure portion 42a is formed. It is pressure-molded so that the surface is substantially flush with the outer wall surface of the main body 41.

  Next, although not shown, after arranging a spacer on the upper part of the electrode group, a negative electrode current collecting tab extending from the negative electrode plate of the electrode group is welded to the inner bottom part of the terminal plate provided in the sealing body, and the positive electrode of the electrode group The sealing body was disposed in the opening of the outer can 40 (50) so that the positive electrode lead extending from the plate was sandwiched between the outer can 40 (50) and the sealing body. Next, the inside of the battery was hermetically sealed by laser welding between the peripheral wall of the opening of the outer can 40 (50) and the sealing body. As a result, 103450 size (10 mm × 34 mm × 50 mm) square nonaqueous electrolyte batteries B1 and Z1 having a design capacity of 1700 mAh were produced. Here, the battery using the outer can 40 was designated as battery B1, and the battery using the outer can 50 was designated as battery Z1.

Each of these batteries B1 and Z1 is charged at a constant current at room temperature (about 25 ° C.) with a charging current of 1700 mA (1 It) until the battery voltage reaches 4.2V, and the current value at a constant voltage of 4.2V. The battery was charged at a constant voltage until it reached 10 mA. Thereafter, a charge / discharge cycle of discharging at a discharge current of 1700 mA (1 It) until the battery voltage reached 2.75 V was repeated 500 times. At this time, when the ratio of the discharge capacity at the 500th cycle to the discharge capacity at the first cycle was determined as the capacity retention after 500 cycles, the results shown in Table 4 below were obtained.

  As is clear from the results in Table 4 above, it can be seen that, in the battery B1, the capacity retention rate (%) after 500 cycles is large because the amount of the electrolyte in the battery is large. On the other hand, in the battery Z1, since the amount of electrolyte in the battery is small, it can be seen that the capacity retention rate (%) after 500 cycles is reduced. From these things, using the exterior can 40 which formed the protrusion part 42 which protruded and formed from the main-body part 41 like the exterior can 40, after injection | pouring of electrolyte solution, this protrusion part 42 of this main-body part 41 is used. It can be seen that it is preferable to perform pressure molding so as to be substantially flush with the outer wall surface of the side wall, because the amount of electrolyte injected is increased and the capacity retention rate (%) is improved.

Next, using the battery B1 and the battery Z1 manufactured as described above, the batteries B1 and Z1 were each charged at a room temperature (about 25 ° C.) with a charging current of 1700 mA (1 It) and a battery voltage of 4.2 V. Until the current value reaches 10 mA at a constant voltage of 4.2 V and is fully charged. The thickness T1 at the center of these fully charged batteries was measured. Then, it was left to stand in a 90 degreeC thermostat for 2 hours. Next, the battery was taken out from the thermostat and the thickness T2 at the center of the battery was measured. Next, when the thickness difference between the battery thickness T2 after storage in the thermostat and the battery thickness T1 before storage in the thermostat is obtained as the amount of swelling (δ mm), the results shown in Table 5 below are obtained. It was.

  As is apparent from the results in Table 5 above, the protrusion 42 formed by protruding from the main body 41 is pressed so that the pressurizing portion 42 a is substantially flush with the outer wall surface of the main body 41. The swelling amount (δ) of the battery B1 using the outer can 40 is as small as 0.09 mm, whereas the swelling amount (δ) of the battery Z1 using the outer can 50 in which such a pressure portion is not formed. ) Is as large as 1.36 mm. This is considered to be because the strength of the outer can 40 is increased in the outer can 40 because the pressurizing portion 42a is formed.

  As described above, in the present invention, the projecting portion 12 (42) projecting from the inside toward the outside is formed in the main body portion 11 (41) of the outer can, and the projecting portion 12 is injected after the injection of the electrolytic solution. The outer can 10 (40) is formed by pressing (42) so that the pressurizing part 12a (42a) is substantially flush with the outer wall surface of the main body part 11 (41). For this reason, at the time of injecting the electrolytic solution, the space formed by the projecting portion 12 (42) becomes a storage space for the electrolytic solution, and the required amount of the electrolytic solution can be easily secured. In addition, the pressurizing part 12a (42a) formed after the electrolyte is poured serves to reinforce the strength of the outer can 10 (40). For this reason, the outer can 10 (40) does not swell, or a short-circuit or short-circuit occurs inside the battery due to dropping or the like, so that the internal resistance is not extremely reduced. It will be obtained.

In the above-described embodiment, in order to apply the present invention to a nonaqueous electrolyte battery, lithium hexafluorophosphate (LiPF ₆ ) is added to a solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed. Although the example using the non-aqueous electrolyte solution in which the solute consisting of is dissolved has been described, various other non-aqueous electrolyte solutions can be used. For example, as the solute, in addition to LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiCF ₃ (CF ₂ ) ₃ SO _3, etc. May be used.

  As the solvent, in addition to the above-mentioned mixed solvent of EC and DEC, for example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), cyclopentanone, sulfolane, 3-methylsulfolane, 2,4-dimethoxysulfolane, 3-methyl-1,3-oxazolidine-2-one, γ-butyrolactone (GBL), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC ), Butyl methyl carbonate (BMC), ethyl propyl carbonate (EPC), butyl ethyl carbonate (BEC), dipropyl carbonate (DPC), 1,2-diethoxyethane (DEE), 1,2-dimethoxyethane (DME) , Te Rahidorofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, methyl acetate, alone such as ethyl acetate, may be used a mixed solvent of these two components or three components.

  Further, in the above-described embodiment, an example in which scaly graphite is used as the negative electrode active material has been described. However, in addition to scaly graphite, a carbon-based material that can occlude / release lithium ions, such as carbon black, coke, etc. Glassy carbon, carbon fiber, or a fired body thereof, artificial graphite, amorphous oxide, or the like may be used. Moreover, when preparing negative electrode slurry, although the example which uses SBR as a binder and CMC as a thickener was demonstrated, a binder and a thickener are not restricted to this.

  For example, ethylenically unsaturated carboxylic acid esters such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, (meth) acrylonitrile, and hydroxyethyl (meth) acrylate can be used as the binder. . Furthermore, ethylenically unsaturated carboxylic acids such as acrylic acid, itaconic acid, fumaric acid and maleic acid can be used. As the thickener, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, polyacrylic acid (salt), oxidized starch, phosphoric acid starch, casein and the like can be used.

In the above-described embodiment, the example in which lithium cobaltate is used as the positive electrode active material has been described. In addition to lithium cobaltate, lithium-containing transition metal composite oxides such as lithium nickelate and lithium manganate, or dioxide dioxide Metal oxides such as manganese (MnO ₂ ), vanadium pentoxide, niobium pentoxide, and metal chalcogenides such as titanium disulfide and molybdenum disulfide can also be used.

  Furthermore, in the above-described embodiment, an example in which the present invention is applied to a non-aqueous electrolyte battery has been described. However, the present invention is not limited to the above-described non-aqueous electrolyte battery, and an alkali such as a nickel-hydrogen storage battery or nickel-cadmium is used. It is obvious that the present invention can be applied to other batteries such as a storage battery and a solid electrolyte battery.

It is a perspective view which shows typically the substantially cylindrical bottomed exterior can which has the protrusion part before pressure-molding. It is sectional drawing which shows typically the process for manufacturing the substantially cylindrical bottomed exterior can which has the protrusion part of FIG. FIG. 3A is a cross-sectional view schematically showing a cross section of the state where the electrode group is housed in the outer can, and FIG. 3A is a cross-sectional view showing the state where the electrode group is housed in the outer can of FIG. b) is a cross-sectional view showing a state in which an electrode group is housed in a cylindrical outer can. FIG. 4A is a cross-sectional view schematically showing a state in which an outer can containing the electrode group is pressure-formed, and FIG. 4A is a schematic view of a protrusion formed on the outer can in FIG. FIG. 4B is a cross-sectional view showing a state of being pressure-molded so as to be on the same plane, FIG. 4B is an enlarged view of a Z portion in FIG. 4A, and FIG. FIG. 4 is a cross-sectional view showing a state where the outer can of b) is not pressed, or a state where the side wall of the outer can of FIG. FIG. 5A is a view schematically showing a bottomed outer can having a substantially rectangular tube shape, and FIG. 5A is a cross-sectional view schematically showing a state having a protrusion before being pressure-formed, and FIG. FIG. 5A is a cross-sectional view schematically showing a state in which the protrusion shown in FIG. 5A is press-molded so as to be substantially flush with the outer wall surface of the side wall. FIG. 5C is a cross-sectional view schematically showing a substantially rectangular tube-shaped bottomed outer can having no protrusions.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Exterior can, 10a ... Circular plate, 10b ... Front drawing cylinder, 10c ... Deep drawing cylinder, 10d ... Extended deep drawing cylinder, 11 ... Main-body part, 12 ... Projection part, 12a ... Pressurization part, 13 ... Space 14 ... Folding part, 15 ... Punch, 16 ... Dice, 20, 25 ... Cylindrical outer can, 21 ... Main body part, 30 ... Electrode group, 40 ... Rectangular outer can, 41 ... Main body part, 42 ... Protruding part, 42a ... Pressure part, 50 ... Square outer can, 51 ... Body part

Claims (4)

A battery manufacturing method in which an electrode group formed by interposing a separator between a positive electrode and a negative electrode is housed in a bottomed cylindrical outer can and then injected with an electrolytic solution,
An electrode group storage step of storing the electrode group in a bottomed cylindrical outer can having a protruding portion formed so that a part of the side wall protrudes outward from the inside;
A liquid injection step of injecting an electrolyte into the bottomed cylindrical outer can in which the electrode group is housed;
A pressure forming step of forming a pressure part by pressure forming the outer wall surface of the protruding portion of the side wall of the bottomed cylindrical outer can so as to be substantially flush with the outer wall surface of the side wall. A battery manufacturing method characterized by the above.   The battery manufacturing method according to claim 1, wherein the protruding portion is formed continuously from the bottom surface of the outer can to the opening.   The outer can is a substantially cylindrical outer can whose section other than the protrusion is circular in a cross section perpendicular to the major axis, and based on an arbitrary portion other than the protrusion of the cross section, from the reference 3. The battery according to claim 1, wherein the protrusion is arranged so that a portion where the protrusion does not exist is present at positions of 90 °, 180 °, and 270 °. Manufacturing method. The outer can is a substantially cylindrical outer can whose cross section perpendicular to the major axis is circular except for the protrusions, and the protrusions are evenly arranged on the virtual circumference of the cross section. The method for producing a battery according to any one of claims 1 to 3, wherein:

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