JP2017010787A - Cylindrical battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cylindrical battery having a high capacity and excellent cycle characteristics by improving a shape of a lead connected to a pole plate of a rolled electrode body.SOLUTION: A cylindrical battery of the present invention includes: an electrode body around which a positive electrode plate to which a positive electrode lead is connected and a negative electrode plate to which a negative electrode lead is connected are wound via a separator; an electrolyte; a bottomed cylinder-like outer can; and a sealed body. At least one of the positive electrode lead and the negative electrode lead has an opening that is arranged in parallel with a winding shaft of the electrode body.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a cylindrical battery provided with a wound electrode body.

  Since non-aqueous electrolyte secondary batteries have high energy density, they are widely used as driving power sources for portable electronic devices such as smartphones, tablet computers, notebook computers, and portable music players. In recent years, the use of non-aqueous electrolyte secondary batteries has expanded to power tools, electric assist bicycles, electric vehicles, etc., and non-aqueous electrolyte secondary batteries ensure high reliability over long-term use. It is demanded.

  Nonaqueous electrolyte secondary batteries are roughly classified into cylindrical batteries, rectangular batteries, and pouch-type batteries according to the shape of the battery and the type of the outer package. For the cylindrical battery, an electrode body in which a positive electrode plate and a negative electrode plate are wound through a separator is used. Leads are connected to the positive electrode plate and the negative electrode plate, respectively, and the electrode body is electrically connected to the bottom of the sealing body and the outer can through the leads.

  However, since the lead is thicker than the metal foil used as the current collector of the electrode plate, the lead cannot follow the deformation of the electrode plate even if the electrode plate is wound during the production of the electrode body. Therefore, both ends in the width direction of the lead act so as to press the electrode body in the outer peripheral direction, and the distance between the positive electrode plate and the negative electrode plate facing each other via the separator is likely to be non-uniform compared to other regions. As a result, problems such as voltage drop after charging and deterioration of cycle characteristics due to non-uniform electrode reaction occur. In addition, since the cross-sectional shape of the electrode body is unlikely to be a perfect circle due to the lead, the outer diameter of the electrode body becomes larger than expected.

  Patent Document 1 discloses a technique for providing a groove on the surface of a lead connected to an electrode plate. According to the technique, the occurrence rate of internal short circuit due to the end portion in the width direction of the lead can be reduced.

JP 2004-146160 A

  As described in Patent Document 1, it is considered that an internal short circuit caused by the end portion of the lead is suppressed by providing the groove on the surface of the lead. However, when the groove is bent, the cross section is not easily curved, and the bent groove acts to press the electrode body in the outer peripheral direction. Therefore, it cannot be avoided that the distance between the positive electrode plate and the negative electrode plate opposed via the separator becomes non-uniform compared to other regions.

  The present invention has been made in view of the above, and by improving the shape of the lead connected to the electrode plate constituting the wound electrode body, the increase in the outer diameter of the electrode body caused by the lead and the inside of the electrode body It is an object of the present invention to provide a cylindrical battery that prevents a non-uniform electrode reaction and has a high capacity and excellent cycle characteristics.

In order to solve the above problems, a sealed battery according to one embodiment of the present invention includes a positive electrode plate to which a positive electrode lead is connected, and an electrode body in which a negative electrode plate to which a negative electrode lead is connected is wound through a separator; An electrolyte solution, a bottomed cylindrical outer can, and a sealing body, wherein at least one of the positive electrode lead and the negative electrode lead has an opening disposed in parallel with the winding axis of the electrode body It is said.

  According to one embodiment of the present invention, it is possible to suppress an increase in the outer diameter of the electrode body and a non-uniform electrode reaction inside the electrode body due to the leads connected to the electrode plate. Therefore, according to one embodiment of the present invention, a cylindrical battery having a high capacity and excellent cycle characteristics can be provided.

FIG. 1 is a cross-sectional perspective view of a cylindrical non-aqueous electrolyte secondary battery according to an embodiment of the present invention. 2A is a plan view of a positive electrode plate of a cylindrical non-aqueous electrolyte secondary battery according to an embodiment of the present invention, and FIG. 2B is a cylindrical non-aqueous electrode according to an embodiment of the present invention. It is a top view of the negative electrode plate of an electrolyte secondary battery. FIG. 3 is a perspective view of an electrode body according to an embodiment of the present invention. FIG. 4 is a plan view of a lead according to an embodiment of the present invention.

  A cylindrical battery according to an embodiment of the present invention will be described using the cylindrical nonaqueous electrolyte secondary battery 10 shown in FIG. In addition, this invention is not limited to the following embodiment, In the range which does not change the summary of this invention, it can change suitably and can implement.

  As shown in FIG. 2A, the positive electrode plate 11 has positive electrode active material layers 11a formed on both surfaces of the positive electrode current collector. A part of the positive electrode plate 11 is provided with a positive electrode current collector exposed portion 11b in which the positive electrode active material layer 11a is not formed on both surfaces of the positive electrode current collector. The positive electrode lead 21 is connected to the positive electrode current collector exposed portion 11 b in parallel with the short side direction of the positive electrode plate 11.

  As the positive electrode current collector, a metal foil that can exist stably even when exposed to the positive electrode potential in a non-aqueous electrolyte can be used. Specific examples include aluminum foil and aluminum alloy foil. As the positive electrode lead connected to the positive electrode current collector, a rectangular metal piece having a thickness larger than that of the positive electrode current collector can be used. Aluminum and an aluminum alloy can be used for the metal piece.

  The positive electrode active material layer is formed, for example, by applying a positive electrode active material slurry to the surface of the positive electrode current collector and drying it. The positive electrode active material layer is compressed to a predetermined thickness by a roller. The positive electrode mixture slurry is prepared by charging a positive electrode active material and a binder into a dispersion medium and kneading. A conductive agent can also be added to the positive electrode mixture slurry. As the dispersion medium, an organic solvent such as N-methyl-2-pyrrolidone and water can be used depending on the kind of the binder. The positive electrode mixture layer is formed on one side or both sides of the positive electrode current collector.

As the positive electrode active material, a lithium transition metal composite oxide capable of inserting and extracting lithium ions can be used. Examples of the lithium transition metal composite oxide include general formula LiMO ₂ (M is at least one of Co, Ni and Mn), LiMn ₂ O ₄ and LiFePO ₄ . These can be used singly or in combination of two or more, and at least one selected from the group consisting of Al, Ti, Mg, and Zr is added, or substituted with a transition metal element. You can also.

As shown in FIG. 2B, the negative electrode plate 12 has negative electrode active material layers 12a formed on both surfaces of a negative electrode current collector. A negative electrode current collector exposed portion 12 b in which the negative electrode active material layer 12 a is not formed on both surfaces of the negative electrode current collector is provided on a part of the negative electrode plate. A negative electrode lead 22 is connected to the negative electrode current collector exposed portion 12 b in parallel with the short side direction of the negative electrode plate 12.

  As the negative electrode current collector, a metal foil that can exist stably even when exposed to a negative electrode potential in a nonaqueous electrolytic solution can be used. Specific examples include copper foil and copper alloy foil. As the negative electrode lead connected to the negative electrode current collector, a rectangular metal piece having a thickness larger than that of the negative electrode current collector can be used. Nickel, nickel alloy, copper, and copper alloy can be used for the metal piece.

  The negative electrode active material layer is formed, for example, by applying a negative electrode active material slurry to the surface of the negative electrode current collector and drying it. The negative electrode active material layer is compressed to a predetermined thickness by a roller. The negative electrode mixture slurry is prepared by charging a negative electrode active material and a binder into a dispersion medium and kneading. As the dispersion medium, an organic solvent such as N-methyl-2-pyrrolidone and water can be used depending on the kind of the binder. The negative electrode mixture layer is formed on one side or both sides of the negative electrode current collector.

  As the negative electrode active material, a carbon material that can occlude and release lithium ions or a metal material that can be alloyed with lithium can be used. Examples of the carbon material include graphite such as natural graphite and artificial graphite. Examples of the metal material include silicon and tin, and oxides thereof. A carbon material and a metal material can be used individually by 1 type or in mixture of 2 or more types.

  The electrode body 14 as shown in FIG. 3 is obtained by winding the positive electrode plate 11 and the negative electrode plate 12 through the separator 13. Both the positive electrode lead 21 and the negative electrode lead 22 are arranged in parallel with the winding axis of the electrode body 14.

  The present invention is characterized in that at least one of the positive electrode lead 21 and the negative electrode lead 22 has an opening disposed in parallel with the winding axis of the electrode body 14. Thereby, the lead can follow the deformation of the positive electrode plate 11 and the negative electrode plate 12 when the electrode body 14 is manufactured, and the lead is easily deformed so that the cross section of the lead is curved. The opening is preferably provided in both the positive electrode lead 21 and the negative electrode lead 22, but may be formed in either the positive electrode lead 21 or the negative electrode lead 22. In the case where an opening is provided in only one of the leads, it is preferable to form the opening in a lead arranged on the inner peripheral side of the electrode body 14.

  Since there is no difference between the positive electrode lead and the negative electrode lead, the size and position of the opening will be described with reference to FIG. 4 which is a common drawing of the positive electrode lead and the negative electrode lead. The positions where the openings 21a and 22a are formed are not particularly limited, but the openings 21a and 22a are preferably formed at the center in the width direction of the leads 21 and 22 (the short side direction of the leads). On the other hand, as described below, the openings 21a and 22a are preferably formed so as to be shifted from the central portion in the length direction of the leads 21 and 22 to one end side. The lengths of the regions where the openings 21a and 22a are not formed at both ends in the length direction of the leads 21 and 22 are A and B, respectively. If the A side of the leads 21, 22 protrudes from the electrode plate and the B side of the leads 21, 22 is connected to the electrode plate, the lead 21, 22 is formed when the electrode body 14 is manufactured by setting A> B. It becomes easy to follow the deformation of the electrode plate. Furthermore, it is easy to connect the portions where the leads 21 and 22 are led out from the electrode plate to the sealing body 18 or the bottom of the outer can 19. Specifically, A and B are preferably 3% or more of the length of the leads 21 and 22, and A is more preferably 10% or more of the length of the leads 21 and 22.

  The dimensions of the openings 21a and 22a are not particularly limited, but the width of the openings 21a and 22a is preferably 3% to 30% of the width of the leads 21 and 22. The length L2 of the openings 21a and 22a is preferably 30% or more and 90% or less with respect to the length L1 of the leads 21 and 22. If the widths and lengths of the openings 21a and 22a are within the above ranges, the effects of the present invention can be effectively exerted, and the mechanical strength of the leads 21 and 22 and between the leads 21 and 22 and the electrode plate can be improved. Sufficient connection strength can be secured.

  The shapes of the openings 21a and 22a can be used without any particular limitation as long as they are formed in parallel with the winding axis of the electrode body 14. As the shape of the opening, in addition to the rectangular shape shown in FIG. 4, an oval shape in which both end portions in the length direction of the opening are semicircular may be employed. The opening is preferably formed from a single opening, but the opening can also be formed by providing a plurality of openings along the length direction of the lead. When a plurality of openings are provided, the length of the opening is represented by the sum of the lengths of the openings.

  An annealing treatment can be applied to the lead provided with the opening. Since the lead is softened by the annealing treatment, the lead is easily deformed following the deformation of the electrode plate when the electrode body is wound. The annealing process can be performed at an appropriate temperature and time depending on the metal material constituting the lead.

As the separator, a microporous film mainly composed of polyolefin such as polyethylene (PE) or polypropylene (PP) can be used. The microporous membrane can be used singly or as a laminate of two or more layers. In a laminated separator having two or more layers, it is preferable that a layer mainly composed of polyethylene (PE) having a low melting point is used as an intermediate layer and polypropylene (PP) having excellent oxidation resistance is used as a surface layer. Furthermore, inorganic particles such as aluminum oxide (Al ₂ O ₃ ), titanium oxide (TiO ₂ ), and silicon oxide (SiO ₂ ) can be added to the separator. Such inorganic particles can be carried in the separator and can be applied together with a binder on the separator surface.

  As the non-aqueous electrolyte, a solution obtained by dissolving a lithium salt as an electrolyte salt in a non-aqueous solvent can be used.

  As the non-aqueous solvent, a cyclic carbonate, a chain carbonate, a cyclic carboxylic acid ester and a chain carboxylic acid ester can be used, and it is preferable to use a mixture of two or more. Examples of the cyclic carbonate include ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC). In addition, a cyclic carbonate in which part of hydrogen is substituted with fluorine, such as fluoroethylene carbonate (FEC), can also be used. Examples of the chain carbonate include dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and methyl propyl carbonate (MPC). Examples of cyclic carboxylic acid esters include γ-butyrolactone (γ-BL) and γ-valerolactone (γ-VL). Examples of chain carboxylic acid esters include methyl pivalate, ethyl pivalate, methyl isobutyrate, and methyl Pionate is exemplified.

LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ) LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) ₃ , LiAsF ₆ , LiClO ₄ , Li ₂ B ₁₀ Cl ₁₀ and Li ₂ B ₁₂ Cl ₁₂ are exemplified. Among these, LiPF ₆ is particularly preferable, and the concentration in the nonaqueous electrolytic solution is preferably 0.5 to 2.0 mol / L. Another lithium salt such as LiBF ₄ can be mixed with LiPF ₆ .

  An embodiment of the present invention will be described in detail below using a specific example.

Example 1
(Lead production)
A rectangular aluminum piece was used for the positive electrode lead 21. In the positive electrode lead 21, a rectangular opening 21 a was formed in the center of the positive electrode lead 21 in the width direction as shown in FIG. The length L2 of the opening 21a was 85% of the length L1 of the positive electrode lead 21, and the width of the opening 21a was 15% of the width of the positive electrode lead 21. Further, A is 10% of the length L1 of the positive electrode lead 21, and B is 5% of the length L1 of the positive electrode lead 21. The negative electrode lead 22 was produced in the same manner as the positive electrode lead 21 except that a rectangular nickel piece was used.

(Preparation of positive electrode plate)
94 parts by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 3 parts by mass of acetylene black as a conductive agent, and 3 parts by mass of polyvinylidene fluoride as a binder were mixed. This mixture was put into N-methyl-2-pyrrolidone (NMP) as a dispersion medium and kneaded to prepare a positive electrode active material slurry. This positive electrode active material slurry was applied to both surfaces of an aluminum positive electrode current collector having a thickness of 15 μm and dried to form a positive electrode active material layer 11a. At this time, the positive electrode current collector exposed portion 11b in which the positive electrode active material layer 11a was not formed was provided on a part of the positive electrode plate 11. This positive electrode active material layer 11a was compressed to a predetermined thickness by a roller and cut into a predetermined size. Finally, an aluminum positive electrode lead 21 was connected to the positive electrode current collector exposed portion 11b to produce the positive electrode plate 11 shown in FIG.

(Preparation of negative electrode plate)
Natural graphite as a negative electrode active material was mixed in an amount of 98 parts by mass, styrene butadiene rubber as a binder was 1 part by mass, and carboxymethyl cellulose as a thickener was 1 part by mass. This mixture was put into water as a dispersion medium and kneaded to prepare a negative electrode active material slurry. This negative electrode active material slurry was applied to both sides of a copper negative electrode current collector having a thickness of 8 μm by a doctor blade method and dried to form a negative electrode active material layer 12a. At this time, the negative electrode current collector exposed portion 12b in which the negative electrode active material layer 12a was not formed on both surfaces was provided on a part of the negative electrode current collector. Finally, a negative electrode lead 22 made of nickel was connected to the negative electrode current collector exposed portion 12b to produce the negative electrode plate 12 shown in FIG.

(Production of electrode body)
The positive electrode plate 11 and the negative electrode plate 12 produced as described above were wound through a separator 13 made of a polyethylene microporous film to produce an electrode body 14 shown in FIG. A separator 13 was disposed on the outermost periphery of the electrode body 14, and a winding stopper tape 20 was attached to the end of the winding to fix the electrode body.

(Preparation of non-aqueous electrolyte)
Ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed at a volume ratio of 30:70 to prepare a non-aqueous solvent. Lithium hexafluorophosphate (LiPF ₆ ) as an electrolyte salt was dissolved in this non-aqueous solvent at a concentration of 1 mol / L to prepare a non-aqueous electrolyte.

(Preparation of non-aqueous electrolyte secondary battery)
After the lower insulating plate 16 was disposed below the electrode body 14 and the electrode body 14 was inserted into the outer can 19, the negative electrode lead 22 was connected to the bottom of the outer can 19. Next, the upper insulating plate 15 is inserted into the upper part of the electrode body 14, and a grooving disk rotating at a position above the upper insulating plate 15 on the side surface of the outer can 19 is pressed against the groove. Processing was performed. The insulating gasket 17 was inserted into the grooved portion, and the positive electrode lead 21 was connected to the sealing body 18. Finally, after injecting the non-aqueous electrolyte into the outer can 19, the sealing body 18 is caulked and fixed to the grooved portion of the outer can 19 via the insulating gasket 17, and the diameter 18 mm and height shown in FIG. A 65 mm cylindrical nonaqueous electrolyte secondary battery 10 was produced.

(Examples 2 to 5)
Cylindrical non-aqueous electrolyte secondary batteries according to Examples 2 to 5 were produced in the same manner as in Example 1 except that the widths of the openings of the positive electrode lead and the negative electrode lead were set to the values shown in Table 1. The width of the opening shown in Table 1 is expressed as a percentage with respect to the width of the lead.

(Comparative example)
A cylindrical non-aqueous electrolyte secondary battery according to a comparative example was produced in the same manner as in Example 1 except that no opening was formed in the positive electrode lead and the negative electrode lead.

(Measurement of outer diameter of electrode body)
The outer diameters of the electrode bodies of Examples 1 to 5 and the comparative example were measured with a constant pressure caliper. Since the outer diameter of the electrode body shows different values depending on the location to be measured, the maximum value among the values measured at the central portion in the height direction of the electrode body was recorded as the outer diameter of the electrode body. Table 1 shows the average value of the outer diameters of the 10 electrode bodies of Examples 1 to 5 and Comparative Example.

(Evaluation of cycle characteristics)
The batteries of Examples 1 to 5 and the comparative example were charged at a constant current of 1 It in a 25 ° C. environment until the battery voltage reached 4.2 V, and then the current was 0.01 It at a constant voltage of 4.2 V. Charged until After 10 minutes of rest, each battery was discharged at a constant current of 1 It until the battery voltage reached 2.75V. With this charge / discharge as one cycle, 200 charge / discharge cycles were repeated. The discharge capacity at the first cycle and the discharge capacity at the 200th cycle were measured, the capacity retention rate after 200 cycles was calculated from the following formula, and the value was evaluated as the cycle characteristics. Table 1 shows the average values of the capacity retention rates of the three batteries of each example and comparative example.
Capacity maintenance rate (%)
= (Discharge capacity at 200th cycle / Discharge capacity at 1st cycle) × 100

  The electrode plates of the same size were used for the electrode bodies of Examples 1 to 5 and the comparative example. Nevertheless, it can be seen from Table 1 that the outer diameters of the electrode bodies of Examples 1 to 5 are smaller than those of the comparative example. In the electrode body of the comparative example, the end portion of the lead is a cause of increasing the outer diameter of the electrode body. The results shown in Table 1 indicate that forming an opening in the lead is effective in suppressing increase in the outer diameter of the electrode body.

  Moreover, it turns out that Examples 1-5 are exhibiting the cycling characteristics outstanding compared with the comparative example. In the wound electrode body, the distance between the positive electrode plate and the negative electrode plate facing each other through the separator is more likely to be non-uniform in the vicinity of the lead than in other regions. However, since the electrode body is closer to a perfect circle by forming the opening in the lead, the distance between the positive electrode plate and the negative electrode plate that oppose each other through the separator becomes uniform inside the electrode body. Further, from the results shown in Table 1, it can be seen that the formation of the opening in the lead has a positive influence on not only the physical shape of the electrode body but also electrochemical characteristics such as cycle characteristics.

  From Table 1, it can be seen that the width of the opening is preferably 3% or more, more preferably 10% or more with respect to the width of the lead in order to achieve the effect of the present invention more effectively. . However, the dependency of the effect of the present invention on the width of the opening is not so large, and the width of the opening can be appropriately determined from the mechanical strength of the lead and the connection strength between the lead and the electrode plate. . From such a viewpoint, the width of the opening is preferably 30% or less of the width of the lead.

  As described above, according to the present invention, it is possible to prevent an increase in the outer diameter of the electrode body and a decrease in cycle characteristics due to the leads connected to the electrode plate. That is, since the present invention can contribute to an increase in capacity and cycle characteristics of a cylindrical battery, the industrial applicability is great.

DESCRIPTION OF SYMBOLS 10 Nonaqueous electrolyte secondary battery 11 Positive electrode plate 11a Positive electrode active material layer 11b Positive electrode collector exposed part 12 Negative electrode plate 12a Negative electrode active material layer 12b Negative electrode collector exposed part 13 Separator 14 Electrode body 15 Upper insulating plate 16 Lower insulation Plate 17 Insulating gasket 18 Sealing body 19 Exterior can 20 Winding tape 21 Positive electrode lead 21a Opening portion 22 Negative electrode lead 22a Opening portion

Claims (5)

A positive electrode plate to which a positive electrode lead is connected, and an electrode body in which a negative electrode plate to which a negative electrode lead is connected is wound through a separator;
An electrolyte,
A bottomed cylindrical outer can,
A sealing body,
A cylindrical battery comprising:
At least one of the positive electrode lead and the negative electrode lead has an opening disposed in parallel with a winding axis of the electrode body;
Cylindrical battery.   2. The cylindrical battery according to claim 1, wherein the opening is disposed within a range excluding a range from each of both ends in the length direction of the lead to a position of 3% of the length of the lead.   The cylindrical battery according to claim 1 or 2, wherein a length of the opening is 30% or more and 90% or less of a length of the lead.   The cylindrical battery according to any one of claims 1 to 3, wherein the opening is disposed at a center portion of the lead in the width direction.   5. The cylindrical battery according to claim 1, wherein a width of the opening is not less than 3% and not more than 30% of a width of the lead.

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