JP2011096504A - Nonaqueous electrolyte secondary battery and manufacturing method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery superior in charge and discharge cycle characteristics wherein a winding object can be smoothly housed in an outer package. <P>SOLUTION: In the nonaqueous electrolyte secondary battery, a nonaqueous electrolyte battery contains the winding object and a nonaqueous electrolyte are enclosed in the outer package, wherein a separator is interposed between a positive electrode plate and a negative electrode plate and they are wound to provide the winding object. In the nonaqueous electrolyte battery, two or more fine porous resin layers are laminated and integrated to make the separator. The separator contacting the outer surface side of the electrode plate of the positive and negative electrode plates positioned at the outermost periphery side of the winding object faces a front peripheral part of the separator in contact with the outer surface side of the electrode plate positioned at the outermost periphery at 1/3 round or more without interposing the positive and negative electrode plates but with or without the separator in contact with the inner surface side of the electrode plate positioned at the outermost periphery. Further, the separator in contact with the outer surface side of the electrode plate positioned at the outermost periphery is not fixed to the winding object. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a non-aqueous electrolyte secondary battery and a method for manufacturing the same.

  Non-aqueous electrolyte secondary batteries typified by lithium-ion batteries are characterized by high energy density, so they can be used not only for power supplies for portable devices, but also for power tools and hybrid electric vehicles. I am doing.

  In such a non-aqueous electrolyte secondary battery, a lithium transition metal oxide such as lithium cobaltate, lithium nickelate, or lithium manganate capable of reversibly occluding and releasing lithium ions is used as a positive electrode active material. The positive electrode active material is mixed with a binder, a conductive agent, and the like, applied onto an aluminum foil, and used as a positive electrode plate.

  On the other hand, as the negative electrode active material, carbonaceous materials such as natural graphite, artificial graphite and coke are used. And a negative electrode active material is mixed with a binder etc., and it apply | coated on copper foil and is used as a negative electrode plate.

  The positive electrode plate and the negative electrode plate are processed to a predetermined size, wound up through a resin microporous separator to form a wound body, and enclosed in an exterior body together with an electrolyte.

  Usually, the outermost peripheral part of the winding body is fixed in order to facilitate the insertion into the exterior body. Examples of the fixing method of the outermost peripheral part include a method using an adhesive tape disclosed in Patent Document 1 and a method of fixing the outermost peripheral separator disclosed in Patent Document 2 by thermal welding.

  By the way, since the crystal structure of the positive electrode active material and the negative electrode active material of the nonaqueous electrolyte secondary battery expands and contracts with charge / discharge, the thickness of the positive electrode plate and the negative electrode plate coated with this change with charge / discharge. In addition, the wound body obtained by winding these also expands and contracts. However, since the outermost periphery of the winding body is fixed, the stress of expansion and contraction is accumulated inside the winding body, and the positive electrode plate and the negative electrode plate are deformed, or the electrolyte that has penetrated into the winding body is squeezed out. This causes a problem that the charge / discharge cycle is lowered.

Therefore, in Patent Document 3 and Patent Document 4, when the wound body is housed in the exterior body and the electrolytic solution is injected into the exterior body, the adhesive force of the adhesive tape that fixes the outermost peripheral portion by the electrolytic solution is reduced. It has been considered that the deterioration of the battery characteristics is suppressed by loosening the winding state of the winding body.

JP 2000-268877 A JP 2006-302800 A JP-A-11-176475 JP-A-11-176476

  However, some adhesive components of the adhesive tape may adversely affect battery performance by dissolving in the electrolyte. On the other hand, if the outermost periphery is not fixed, the outer diameter increases when the winding body is stored in the exterior body and the outermost separator or electrode plate is turned over and damaged, or the winding state is loosened. It becomes impossible to store in the exterior body.

Therefore, the present invention reduces the stress of expansion / contraction of the electrode plate that can be received by charging / discharging after the wound body is housed in the exterior body without any trouble and after being housed in the exterior body. An object of the present invention is to provide a nonaqueous electrolyte secondary battery having improved charge / discharge cycle characteristics.

  In order to solve the above-described problems, the present invention provides a separator in which two or more microporous resin layers are laminated and integrated, and of the positive electrode plate and the negative electrode plate, the electrode is located on the outermost peripheral side of the winding body. A separator in contact with the outer surface side of the plate is located on the outermost periphery without passing through the positive electrode plate and the negative electrode plate and with or without a separator in contact with the inner surface side of the electrode plate located on the outermost periphery. The separator is in contact with the outer peripheral side of the separator that is in contact with the outer surface side of the electrode plate for 1/3 or more times, and the separator that is in contact with the outer surface side of the electrode plate located on the outermost periphery is not fixed to the winding body. Features.

  A separator in which two or more microporous resin layers are laminated and integrated has an interface between the layers, but it easily accumulates charges and is easily charged with static electricity. With the above configuration, due to this static electricity, the separator further extended from the end of the outermost positive electrode plate or negative electrode plate is adsorbed to the front peripheral separator. The winding of the winding body is held by this electrostatic adsorption, and the winding body is smoothly stored in the exterior body. After being housed in the exterior body, static electricity is discharged in the process of injecting the electrolyte, and the outermost peripheral portion of the wound body is not fixed, so that the winding can be loosened. In this state, the wound body can expand and contract following the expansion and contraction of the electrode plate due to charge and discharge, and no stress is accumulated in the wound body, so a non-aqueous electrolyte secondary battery with good charge / discharge cycle characteristics Is obtained.

  In the above configuration, the separator to be extended is the separator that is in contact with the outer surface side of the electrode plate located on the outermost peripheral side of the winding body among the positive electrode plate and the negative electrode plate, without the positive electrode plate and the negative electrode plate being interposed. It is necessary to extend 1/3 or more rounds to the front peripheral part of the separator in contact with the outer surface side of the electrode plate located on the outermost periphery, without or through the separator in contact with the inner surface side of the electrode plate located on the outer periphery. is there. When the extension is less than 1/3, the winding due to static electricity is insufficient. On the other hand, since the separator does not contribute to the battery capacity, even if the separator is extended more than necessary, the proportion of the separator in the wound body increases, the energy density decreases, the diameter of the wound body increases, and the exterior May be difficult to store in the body. Therefore, it is preferable that the length of the separator to be extended is two or less.

  In the above configuration, the separator on the front peripheral portion is a separator on which the separator extension can be in direct contact without passing through the positive electrode plate and the negative electrode plate, and is on the winding start side of the winding body as viewed from the separator extension. Indicates.

  Moreover, the separator of a winding body exists in what the outer peripheral side of a separator becomes a positive electrode plate, and what has the outer peripheral side of a separator become a negative electrode plate. Those separators are continuous at the center (winding start portion) of the winding body, and are one separator before winding, and may start winding at approximately half of each separator. The winding start part may be connected with an adhesive tape or the like. Further, each separator is not connected at the center of the winding body, and is two separators before winding, and they may be wound together.

  In the above configuration, the separator in which two or more microporous resin layers are laminated and integrated may be one in which resin layers of different materials are adjacently stacked and integrated. The separator having such a configuration is preferable because different components are opposed to each other at the laminated integrated interface, so that static electricity is easily accumulated, and the separator extension portion of the winding body is strongly adsorbed to the separator on the front periphery. As such a separator, the resin layer can be a laminate of three layers in the order of polypropylene, polyethylene, and polypropylene. In addition, since it becomes difficult to manufacture a laminated separator having more than three layers, the number of laminated layers is preferably up to three.

  In the above structure, the separator may be a laminate of three layers of polyethylene, and the inorganic oxide particles may be dispersed in the surface layer. The inorganic oxide particles can be silicon oxide.

  When inorganic oxide particles such as silicon oxide are dispersed in the resin layer, the resin layer easily accumulates static electricity. Therefore, it is preferable to disperse the inorganic oxide particles in the layer on the surface side of the laminated separator, because the separator extension portion of the wound body is strongly adsorbed to the separator on the front periphery.

  In the above configuration, the exterior body can be cylindrical.

  A cylindrical wound body is produced and stored in the cylindrical outer package, but the cylindrical wound body is more easily affected by the shape than the flat wound body and is easily unwound. Therefore, the effect of the configuration of the present invention is greater in the cylindrical winding body than in the flat winding body. As the material of the exterior body, a material that can hold the wound body or the electrolyte, such as a metal such as iron or aluminum, or a laminate material in which the surface of a metal foil such as aluminum is coated with a resin layer is used.

  The present invention also provides a non-aqueous electrolyte having a winding step in which a wound body is formed by winding a positive electrode plate and a negative electrode plate through a separator in which two or more resin layers are laminated and integrated. A method for manufacturing a secondary battery, wherein the winding step includes a separator in contact with an outer surface side of an electrode plate located on an outermost peripheral side of the winding body among the positive electrode plate and the negative electrode plate. The front peripheral portion of the separator that is in contact with the outer surface side of the electrode plate located at the outermost periphery, without or through the separator that is in contact with the inner surface side of the electrode plate that is located at the outermost periphery without passing through the negative electrode plate A non-aqueous electrolyte secondary battery is manufactured by making it face 1/3 or more and adsorbing it by static electricity.

According to the above manufacturing method, the separator end of the outermost peripheral part of the wound body is not fixed with an adhesive tape or the like, and is adsorbed to the separator on the front periphery using static electricity, so that the wound body can be stored in the exterior body without unwinding. . And since a winding body does not accumulate | store the stress of expansion / contraction of an electrode plate accompanying charging / discharging, a nonaqueous electrolyte secondary battery provided with favorable charging / discharging cycle characteristics can be manufactured.

According to the present invention, it is possible to provide a nonaqueous electrolyte secondary battery in which the wound body can be easily housed in the exterior body and charge / discharge cycle characteristics are improved.

It is a perspective view which cut | disconnects and shows the nonaqueous electrolyte secondary battery manufactured by embodiment to the vertical direction. It is a principal part expanded sectional view which shows typically the state of a winding body outermost periphery part.

  A mode for carrying out the present invention will be described with reference to the drawings, taking a non-aqueous electrolyte secondary battery as an example. In addition, this invention is not limited to the following form, In the range which does not change the summary, it can change suitably and can implement.

  FIG. 1 is a perspective view showing the cylindrical nonaqueous electrolyte secondary battery manufactured in the embodiment cut in the vertical direction. FIG. 2 is a cross-sectional view of the outermost periphery of the wound body.

[Embodiment]
As shown in FIG. 1, the non-aqueous electrolyte secondary battery 10 of the example uses a winding body 14 in which a positive electrode plate 11 and a negative electrode plate 12 are wound in a spiral shape with a separator 13 interposed therebetween. The wound body 14 is provided with insulating plates 15 and 16 on the upper and lower sides, respectively, and is housed inside a cylindrical metal outer can 17 having a bottom that also serves as a negative electrode terminal. The current collecting tab 12a of the negative electrode plate 12 is welded to the inner bottom portion of the outer can 17 and the current collecting tab 11a of the positive electrode plate 11 is equipped with a safety valve 18 and is welded to the bottom of the sealing body 19 serving as a positive electrode terminal. A non-aqueous electrolyte (not shown) is injected into the outer can 17, and the opening of the outer can 17 is sealed with a sealing body 19 via a gasket 21.

  The method for producing the non-aqueous electrolyte secondary battery is as follows.

<Preparation of positive electrode plate>
94: 3: 3 (mass ratio) of a positive electrode active material in which nickel manganese lithium cobaltate and lithium cobaltate are mixed at a mass ratio of 1: 9, carbon black as a conductive agent, and polyvinylidene fluoride as a binder. And the mixture was dispersed in N-methyl-2-pyrrolidone to obtain a paste. This paste was uniformly applied to both sides of a 15 μm thick aluminum foil by a doctor blade method and dried by heating to produce a dry electrode plate having an active material layer formed on the aluminum foil. The dried electrode plate was compressed to a thickness of 0.13 mm with a roller press and cut into a predetermined size, and then a current collecting tab 11a was attached to produce a positive electrode plate 11.

<Preparation of negative electrode plate>
Graphite as a negative electrode active material, styrene butadiene rubber as a binder, and carboxymethyl cellulose as a viscosity modifier were mixed at 96: 2: 2 (mass ratio), and the mixture was dispersed in water to obtain a paste. This paste was uniformly applied to both surfaces of a 10 μm thick copper foil by a doctor blade method and dried by heating to produce a dry electrode plate having an active material layer formed on the copper foil. The dried electrode plate was compressed to a thickness of 0.12 mm with a roller press, cut into a predetermined size, and then a current collecting tab 12a was attached to prepare the negative electrode plate 12.

<Preparation of wound body>
The wound body was prepared by winding the positive electrode plate 11, the negative electrode plate 12, and the separator 13 using a winder so that the positive electrode plate 11 and the negative electrode plate 12 were insulated by the separator 13. At this time, as shown in FIG. 2, a separator 133 (hereinafter sometimes referred to as the outermost peripheral separator) in contact with the outer surface of the outermost peripheral electrode plate (the negative electrode 12 in the case of FIG. 2) is the terminal end of the negative electrode plate. A separator extension portion 134 was provided so as to be extended by 1/3 of the circumference from 121, and was adsorbed to the separator 132 on the front circumference by static electricity. The separator is a polypropylene (PP) -polyethylene (PE)-, in which both sides of a 12 μm thick polyethylene (PE) microporous layer are sandwiched and integrated by a 2 μm thick polypropylene (PP) microporous layer. A three-layer laminated separator of polypropylene (PP) was used. The separator used was prepared by coextruding three layers of molten resin. In FIG. 2, the two separators are equally extended by 1/3 of the circumference at the outermost peripheral part, but only one separator at the outermost circumference may be extended.

<Production of electrolyte>
Lithium hexafluorophosphate as an electrolyte salt was dissolved in an amount of 1.2 mol / liter in a non-aqueous solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 30:70 (25 ° C., 1 atm). An electrolyte was prepared by dissolving vinylene carbonate in an amount of 2% by mass as an additive.

<Battery assembly>
The wound body was housed in the outer can 17, the negative electrode current collector tab 12 a was welded to the inner can bottom of the outer can, and the positive electrode current collector tab 11 a was welded to the bottom of the sealing body 19. Then, a predetermined amount of the electrolyte is injected into the outer can 17, the opening of the outer can 17 is sealed with the sealing body 19 through the gasket 21, and the cylindrical non-aqueous electrolyte secondary battery (diameter 18 mm, high 65 mm, design capacity 2.7 Ah).

Example 1
The nonaqueous electrolyte secondary battery of Example 1 was produced as described above.

(Example 2)
A nonaqueous electrolyte secondary battery of Example 2 was fabricated in the same manner as in the above embodiment, except that the separator extension was set to 1/2 turn from the end of the negative electrode plate.

(Example 3)
A polyethylene-polyethylene-polyethylene polyethylene-polyethylene-polyethylene layer in which both sides of a polyethylene microporous layer having a thickness of 12 μm are sandwiched and bonded together by a polyethylene layer having a thickness of 2 μm in which silicon oxide fine particles (average particle size 0.05 μm) are dispersed. A nonaqueous electrolyte secondary battery of Example 3 was produced in the same manner as in the above embodiment except that a three-layer laminated separator was used. The silicon oxide of the polyethylene layer is a three-layer laminated separator by kneading molten polyethylene and silicon oxide at a temperature equal to or higher than the melting temperature of polyethylene and dispersing it in polyethylene, and coextruding it with molten polyethylene in which silicon oxide is not dispersed. What was used was used.

Example 4
A nonaqueous electrolyte secondary battery of Example 4 was produced in the same manner as in the above embodiment, except that the separator of Example 3 was used and the separator extension was set to 1/2 turn from the end of the negative electrode plate.

(Comparative Example 1)
The above implementation was performed except that a single-layer separator consisting only of a polyethylene layer having a thickness of 16 μm was used as the separator, and the end of the separator was fixed with an adhesive tape consisting of a 35 μm thickness obtained by applying an acrylic resin adhesive to a polyethylene substrate. A nonaqueous electrolyte secondary battery of Comparative Example 1 was produced in the same manner as the embodiment.

(Comparative Example 2)
A nonaqueous electrolyte secondary battery of Comparative Example 2 was produced in the same manner as in the above embodiment, except that the separator of Comparative Example 1 was used and the end of the separator was not fixed with an adhesive tape.

(Comparative Example 3)
A nonaqueous electrolyte secondary battery of Comparative Example 3 was produced in the same manner as in the above embodiment, except that the separator extension was made 1/4 turn from the end of the negative electrode plate.

(Comparative Example 4)
The nonaqueous electrolyte secondary battery of Comparative Example 4 is the same as the above embodiment except that the separator of Example 3 is used, and the separator extension at the outermost peripheral portion is made 1/4 turn from the end of the negative electrode plate. Was made.

(Winding body insertion test into outer can)
The wound wound body is allowed to stand for 10 minutes, and then the number (number of defects) in which the wound body cannot be inserted directly from the opening of the outer can is measured by hand, and the defect rate (number of defects / number of tests × 100). ) Was calculated. The results are shown in Table 1 below. In addition, what was not able to insert a winding body in an outer can as it was was wound up by hand, inserted in the outer can, and assembled the battery.

(Charge / discharge cycle test)
The produced non-aqueous electrolyte secondary battery was charged to 4.3 V with a constant current of 2.7 A (1 It), and after reaching 4.3 V, it was charged at a constant voltage up to 54 mA (1/50 It) at 4.3 V. It was. Next, constant current discharge was performed up to 3 V at 2.7 A (1 It), and the discharge capacity was measured. This charge and discharge was defined as one cycle and repeated 300 cycles. Table 1 below shows the results calculated as the remaining capacity ratio = (discharge capacity at the 300th cycle) / (discharge capacity at the first cycle) × 100.

Table 1 shows the condition settings and test results of the above Examples and Comparative Examples.

  From Table 1 above, the following can be seen. That is, the comparative example 1 which fixed the outermost peripheral part separator of the winding body with the adhesive tape, and Example 1 which was made to adsorb | suck to the separator of the front periphery by static electricity, without fixing the outermost peripheral part separator of a winding body with the adhesive tape. 4 and Comparative Examples 2 to 4 show that the remaining capacity ratio in the charge / discharge cycle test of Comparative Example 1 is reduced. This is because the battery of Comparative Example 1 has the outermost peripheral portion fixed with an adhesive tape, and stress due to expansion / contraction of the electrode plate due to charge / discharge accumulated, so that the electrode plate is deformed or the electrolyte is wound up. It is thought that it was squeezed out from the body and the characteristics were lowered. On the other hand, since the batteries of Examples 1 to 4 and Comparative Examples 2 to 4 do not have the outermost peripheral separator fixed, the winding body can be loosened, and stress due to expansion / contraction of the electrode plate accompanying charge / discharge Is not accumulated, and is considered to have good characteristics.

  Furthermore, compared with Example 1 and Example 3 using a three-layer laminated separator, Comparative Example 1 which is a single-layer separator has a very high insertion defect rate of the wound body into the outer can. This is considered to be because the static electricity of the single-layer separator is weak and unwinding occurs unless the outermost peripheral portion is fixed, and subsequent insertion into the outer can becomes difficult. On the other hand, the static electricity of the three-layer laminated separator is strong, and even if the outermost peripheral part is not fixed, the outermost peripheral part and the separator on the front peripheral part are strongly adsorbed and the unwinding of the winding body is less likely to occur. Conceivable.

  In Comparative Examples 3 and 4 in which the separator extension at the outermost peripheral part is shorter than those in Example 1, Example 2, Example 3 and Example 4 in which the separator extension at the outermost peripheral part is 1/3 or more, winding is High insertion failure rate of body cans. Further, in the comparison between Example 1 and Example 2 and Example 3 and Example 4 in which the length of the separator extension at the outermost peripheral part is different, Example 2 and Example 4 with the longer separator extension at the outermost peripheral part are better. The insertion failure rate is low. This is considered that the longer the separator extension at the outermost peripheral part, the larger the area that can be adsorbed by the separator on the front circumference, and it is more strongly adsorbed and becomes difficult to unwind. If the separator extension at the outermost periphery is 1/3 or more, the insertion failure rate is greatly reduced as compared with a wound body of less than 1/3. Therefore, the separator extension at the outermost periphery needs to be 1/3 or more. It is.

  In addition, the structure of the layer of the laminated separator may be a laminate of different resins as in Example 1 or Example 2, or a laminate of the same resin as in Example 3 or Example 4 of the present invention. The effect is seen.

  Moreover, even if inorganic oxide particles such as silicon oxide are dispersed in the resin layer as in Example 3 and Example 4, the effect of the present invention is observed.

(extra content)
In the above embodiment, polyethylene and polypropylene were used as the resin layer of the separator, but the separator is not limited to these. Polyimide resin, polyvinylidene fluoride, polytetrafluoroethylene, polyamide / imide resin, polyamide resin, polyacrylonitrile resin A resin capable of forming a microporous film such as polyvinyl alcohol resin can be used.

  Moreover, a well-known method can be used for the lamination | stacking integration method of a resin layer. In addition to the method of melting and coextrusing each resin layer as in the above embodiment, a method of bonding a single layer of resin using heat and pressure may be used.

  Moreover, in the said Example, although silicon oxide was used as an inorganic oxide particle, it is not limited to this, Aluminum oxide, titanium oxide, zinc oxide, lithium phosphate, etc. can be used.

  As described above, according to the present invention, the wound body can be smoothly accommodated in the exterior body, and a nonaqueous electrolyte secondary battery with improved charge / discharge characteristics can be provided. Therefore, industrial applicability is great. .

DESCRIPTION OF SYMBOLS 10 Nonaqueous electrolyte secondary battery 11 Positive electrode plate 11a Positive electrode current collection tab 111 Positive electrode termination 12 Negative electrode plate 12a Negative electrode current collection tab 121 Negative electrode termination 13 Separator 131 Separator termination 132 Front separator 133 134 Separator extension 14 Winding body 15, 16 Insulating plate 17 Exterior can 18 Safety valve 19 Sealing body 21 Gasket

Claims (7)

A winding body formed by winding these through a separator between a positive electrode plate and a negative electrode plate;
A non-aqueous electrolyte,
In a non-aqueous electrolyte battery in which is enclosed in an exterior body,
In the separator, two or more microporous resin layers are laminated and integrated,
Of the positive electrode plate and the negative electrode plate, a separator that is in contact with the outer surface side of the electrode plate located on the outermost peripheral side of the winding body is located on the outermost periphery without interposing the positive electrode plate and the negative electrode plate. With or without a separator in contact with the inner surface side of the electrode plate opposed to the front peripheral part of the separator in contact with the outer surface side of the electrode plate located on the outermost periphery, more than 1/3 of the circumference,
The separator which contacts the outer surface side of the electrode plate located at the outermost periphery is not fixed to the winding body.
2. The non-aqueous electrolyte secondary battery according to claim 1, wherein the separator in which two or more microporous resin layers are stacked and integrated has resin layers of different materials adjacent to each other and stacked and integrated.
The non-aqueous electrolyte secondary battery according to claim 1, wherein the separator has three layers laminated in the order of polypropylene, polyethylene, and polypropylene.
3. The non-aqueous electrolyte 2 according to claim 1, wherein the separator is formed by integrating three layers of polyethylene, and inorganic oxide particles are dispersed in a surface layer of the polyethylene. Next battery.
The non-aqueous electrolyte secondary battery according to claim 4, wherein the inorganic oxide is silicon oxide.
The nonaqueous electrolyte secondary battery according to claim 1, wherein the outer package has a cylindrical shape.
Manufacture of a non-aqueous electrolyte secondary battery having a winding step of winding a resin layer between a positive electrode plate and a negative electrode plate via a separator in which two or more resin layers are laminated and integrated to form a wound body A method,
In the winding step, the separator in contact with the outer surface side of the electrode plate located on the outermost peripheral side of the winding body among the positive electrode plate and the negative electrode plate does not pass through the positive electrode plate and the negative electrode plate, and With or without a separator in contact with the inner surface side of the electrode plate located on the outermost periphery, the electrostatic force is caused to face the front peripheral part of the separator in contact with the outer surface side of the electrode plate located on the outermost periphery more than 1/3 times. The manufacturing method of the nonaqueous electrolyte secondary battery characterized by making it adsorb | suck by.

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