JP2011154859A - Core rod, coiled type electrode group for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery, and method for manufacturing the non-aqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-aqueous electrolyte secondary battery including a coiled type electrode group into whose center a core rod is inserted, in which battery reinforcing effect of a battery by the core rod is enhanced, the deformation of the core rod itself and the occurrence of an internal short-circuit are suppressed, and liquid-filling performance of the non-aqueous electrolyte into the battery is improved. <P>SOLUTION: The core rod 1 is a hollow cylinder with a splitting slit 2 that spirally goes around from one end 4 of the core rod 1 to the other end 5 along a longitudinal direction and a hollow part 3. Use of the coiled type electrode group into whose center the core rod 1 is inserted obtains the non-aqueous electrolyte secondary battery in which energy density is high, the occurrence of the internal short-circuit is suppressed and productivity is superior. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a non-aqueous electrolyte secondary battery. More specifically, the present invention mainly relates to an improvement in a hollow core rod inserted into the center portion of a wound electrode group of a nonaqueous electrolyte secondary battery.

  Nonaqueous electrolyte secondary batteries are widely used as power sources for electronic equipment, electrical equipment, machine tools, transportation equipment, and the like because of their high capacity, energy density, and output, and because they can be easily miniaturized. A typical nonaqueous electrolyte secondary battery includes a cylindrical battery in which a wound electrode group and a nonaqueous electrolyte are accommodated in a cylindrical battery case. The wound electrode group is produced by winding a separator between a positive electrode and a negative electrode.

  By using the wound electrode group, the energy density of the battery can be increased. However, the positive electrode and the negative electrode facing or close to the center of the wound electrode group are likely to be deformed (buckled) with charge / discharge. When the positive electrode or the negative electrode is deformed, an internal short circuit may occur due to the deformed portion breaking through the separator. Further, when an external stress is applied to a small cylindrical battery, an internal short circuit may occur due to deformation of the wound electrode group together with the battery case.

  Patent Document 1 includes a wound electrode group and a hollow cylindrical metal core rod (hereinafter sometimes simply referred to as “core rod”) housed in the center of the wound electrode group. A water electrolyte secondary battery is disclosed. The core rod has a linear split slit extending from one end to the other end along the longitudinal direction. In Patent Document 1, by storing the core rod in the center of the wound electrode group, the buckling of the electrode due to charge / discharge is suppressed, and when the battery case receives external stress, And that the deformation of the wound electrode group is suppressed.

  FIG. 4 is a longitudinal sectional view showing a modification of the core rod 50 of Patent Document 1. In FIG. The core rod 50 has circumferential end faces 52a and 52b along a linear slit 51 extending in the longitudinal direction. When external stress is applied to such a core rod 50, as shown in FIG. 4, one end surface 52a is recessed toward the hollow portion 53 side of the core rod 50, so that the other end surface 52b is more than one end surface 52a. Are likely to stand up. As a result, the other standing end surface 52b may press the electrode group 54 and cause an internal short circuit.

  Patent Literature 2 discloses a core rod obtained by improving the core rod of Patent Literature 1. The core rod of Patent Document 2 has a structure in which both end surfaces in the circumferential direction of the core rod of Patent Document 1 are bent toward the inner side (hollow portion) of the core rod and brought close to each other. As a result, the rigidity of the core rod is improved, and the deformation of the core rod due to external stress and the occurrence of an internal short circuit are suppressed.

Japanese Patent Laid-Open No. 4-332481 JP 2003-92148 A

  In the core rod of Patent Document 2, portions where both end surfaces in the circumferential direction are bent are concave portions on the outer peripheral surface of the core rod. For this reason, when the core rod of Patent Document 2 is inserted into the center portion of the electrode group, a gap is formed between the bent portion and the electrode group. The positive electrode and the negative electrode facing or close to this gap are likely to buckle with charge / discharge, and an internal short circuit may occur.

  Moreover, in order to produce the core rod of patent document 2, the process of rounding a metal plate into a circle and providing a slit, and the step of bending both end surfaces in the circumferential direction along the slit toward the hollow portion of the core rod. I need it. Thereby, a manufacturing process becomes complicated and the manufacturing cost of a core bar becomes high. Furthermore, when a battery is assembled using the core rod of Patent Document 2, the liquid injection property of the nonaqueous electrolyte is lowered, so that the productivity of the battery is lowered and the manufacturing cost of the battery is increased.

  An object of the present invention is to provide a core rod that is difficult to deform even when external stress is applied, hardly buckles the electrode, is easy to manufacture, and can enhance the liquid injection property of a nonaqueous electrolyte, and further, is resistant to short circuiting. It is an object of the present invention to provide a cylindrical non-aqueous electrolyte secondary battery excellent in productivity and productivity.

  The core rod of the present invention is inserted into the central part of the wound electrode group of the cylindrical non-aqueous electrolyte secondary battery, and has a split slit that spirals around from one end to the other along the longitudinal direction. It is a hollow cylinder having.

  Further, the wound electrode group for the cylindrical nonaqueous electrolyte secondary battery of the present invention includes the above-described core rod and the periphery of the above-described core rod. And an electrode group that is wound with a separator interposed therebetween.

  The cylindrical non-aqueous electrolyte secondary battery of the present invention includes a wound electrode group for the above-described cylindrical non-aqueous electrolyte secondary battery, a non-aqueous electrolyte, a battery case that houses the electrode group and the non-aqueous electrolyte. And.

  Moreover, the manufacturing method of the cylindrical nonaqueous electrolyte secondary battery of the present invention includes a wound electrode group accommodation step, an electrolyte injection step, and an electrolyte impregnation step. In the wound electrode group accommodation step, the aforementioned wound electrode group for the cylindrical nonaqueous electrolyte secondary battery is accommodated in the battery case. In the electrolyte injection step, the inside of the battery case is depressurized, and the nonaqueous electrolyte is injected into the hollow portion of the core rod included in the electrode group described above. In the electrolyte impregnation step, the electrode case is impregnated with the nonaqueous electrolyte through the split slit of the core rod by returning the inside of the battery case to atmospheric pressure.

The core rod of the present invention has a split slit that circulates in a spiral shape, so that it is difficult to deform no matter which direction external stress is applied. As a result, the occurrence of an internal short circuit due to the deformation of the core rod is suppressed. In addition, when the core rod of the present invention is inserted into the center portion of the wound electrode group, no large gap is generated between the surface of the core rod and the electrode group, so that an internal short circuit is also suppressed in this respect.
The core rod of the present invention also functions as a reinforcing material for suppressing battery deformation.

  Furthermore, the core rod of the present invention has a split slit that circulates in a spiral shape, and thus has excellent liquid-injecting properties of the nonaqueous electrolyte. When the core rod of the present invention is inserted into the center of the wound electrode group and the nonaqueous electrolyte is injected into the hollow portion of the core rod, the nonaqueous electrolyte passes through the slit and smoothly and easily into the electrode group. Impregnate. Therefore, when a cylindrical nonaqueous electrolyte secondary battery is produced using the core rod of the present invention, the time required for the nonaqueous electrolyte injection work can be shortened and productivity can be increased.

  Furthermore, the core rod of the present invention can be easily produced by rolling a metal plate cut into a predetermined shape in a predetermined direction. Therefore, the process of bending the end face toward the inside is not required, the manufacturing process is simplified, and the manufacturing cost can be reduced.

It is a perspective view which shows typically the external appearance of the core rod which is 1st Embodiment of this invention. It is a perspective view which shows the manufacturing method of the core bar shown in FIG. It is a longitudinal cross-sectional view which shows typically the structure of the nonaqueous electrolyte secondary battery which is 3rd Embodiment of this invention. It is a longitudinal cross-sectional view which shows the modification of the core rod of a prior art.

[Core]
FIG. 1 is a perspective view schematically showing an appearance of a core rod 1 according to the first embodiment of the present invention. FIG. 2 is a perspective view showing a manufacturing method of the core rod 1 shown in FIG.

  The core rod 1 is inserted into the central part of the wound electrode group of the cylindrical nonaqueous electrolyte secondary battery. The wound electrode group of the cylindrical nonaqueous electrolyte secondary battery is an electrode group in which a belt-like positive electrode and a belt-like negative electrode are wound with a separator interposed therebetween. By inserting the core rod 1 into the center of the wound electrode group, the electrode group of the second embodiment of the present invention in which the wound electrode group is disposed around the core rod 1 is obtained.

  As shown in FIG. 1, the core rod 1 is a hollow cylinder, and has a split slit 2 and a hollow portion 3 that circulate in a spiral shape. The core rod 1 has a split slit 2. Thereby, no matter which direction external stress is applied to the core rod 1, the split slit 2 absorbs or relaxes the external stress, so that the core rod 1 is hardly deformed. As a result, deformation such that one of both end surfaces in the circumferential direction along the split slit 2 is recessed and the other is standing up hardly occurs, and the occurrence of an internal short circuit due to the deformation is suppressed.

  Further, since there are no large convex portions and concave portions on the outer peripheral surface of the core rod 1, the outer peripheral surface of the core rod 1 is almost smooth. For this reason, when the core rod 1 is inserted into the center of the wound electrode group, almost the entire outer peripheral surface of the core rod 1 is in contact with the inner peripheral surface of the electrode group. As a result, there is no large gap between the outer peripheral surface of the core rod 1 and the inner peripheral surface of the electrode group that causes the electrode to buckle. Thereby, the buckling of the electrode accompanying charge / discharge hardly occurs, and the occurrence of an internal short circuit is suppressed. In addition, the split slit 2 which exists in the outer peripheral surface of the core rod 1 does not become the space | gap which causes the buckling of an electrode by adjusting a slit width suitably.

The core rod 1 also has a function as a reinforcing material that suppresses deformation of the battery.
By using a wound electrode group in which the core rod 1 is inserted in the center, it has a high energy density, a low internal resistance, a high output, and an internal short circuit that suppresses the occurrence of an internal short circuit. A water electrolyte secondary battery can be obtained.

  The split slit 2 not only functions to absorb or relieve external stress, but also functions as a passage that connects the hollow portion 3 of the core rod 1 and the wound electrode group in which the core rod 1 is inserted into the center portion. Also have. When the nonaqueous electrolyte is injected into the hollow portion 3 of the core rod 1, the nonaqueous electrolyte impregnates the wound electrode group through the slit 2, so the impregnation rate of the nonaqueous electrolyte into the wound electrode group is increased. You can speed up.

  Further, the split slit 2 is provided on almost the entire outer peripheral surface of the core rod 1 by spiraling around the outer peripheral surface of the core rod 1. As a result, the nonaqueous electrolyte is likely to be distributed almost uniformly throughout the wound electrode group.

  That is, the split slit 2 that spirals around the outer peripheral surface of the core rod 1 has a function of improving the impregnation property of the nonaqueous electrolyte into the wound electrode group. Therefore, in the manufacturing process of the cylindrical nonaqueous electrolyte secondary battery, if the nonaqueous electrolyte is injected into the hollow portion 3 of the core rod 1, the time required for injecting the nonaqueous electrolyte and impregnating the wound electrode group Can be shortened. As a result, when a cylindrical non-aqueous electrolyte secondary battery is mass-produced, productivity can be improved, variation in the performance of the final product can be reduced, and the defective product rate can be lowered. In addition, the reliability of the final product can be increased.

The split slit 2 is provided so as to circulate spirally from one end 4 to the other end 5 of the core rod 1 along the longitudinal direction of the core rod 1.
The number of turns of the split slit 2 is not particularly limited, and is selected according to the diameter and length of the core rod 1, the slit width of the split slit 2, etc., but preferably 1 to 3 times.

  If the number of turns of the split slit 2 is too small, external stress is absorbed or relaxed, and the effect of suppressing deformation of the core rod 1 may be reduced. As a result, when an external stress is applied, the core rod 1 is deformed, and an internal short circuit may occur along with the deformation. Moreover, there exists a possibility that the injectability of a nonaqueous electrolyte may fall. On the other hand, if the number of turns of the split slit 2 is too large, the action of reducing the rigidity of the core rod 1 may be greater than the action of absorbing or relaxing external stress. As a result, when an external stress is applied, the core rod 1 may be easily deformed and an internal short circuit may occur.

  The slit width of the split slit 2 is not particularly limited, and is selected according to the diameter and length of the core rod 1, the number of rounds of the split slit 2, etc., but is preferably 0.1 mm to 2 mm, more preferably 0. .2 mm to 1.5 mm. If the slit width is too small, the effect of absorbing or mitigating external stress due to the split slit 2 is reduced, the core rod 1 is likely to be deformed, and an internal short circuit may occur. Further, the impregnation property of the nonaqueous electrolyte into the electrode group may be reduced. Moreover, there exists a possibility that the shaping | molding workability for producing the core rod 1 may fall, and manufacturing cost may rise.

  On the other hand, if the slit width is too large, there is a possibility that the action of the split slit 2 reducing the rigidity of the core rod 1 is greater than the action of absorbing or relaxing external stress by the split slit 2. As a result, there is a possibility that an internal short circuit easily occurs due to the deformation of the core rod 1. Further, the split slit 2 becomes a relatively large gap, and an internal short circuit due to the buckling of the electrode may easily occur on the surface of the electrode group along the split slit 2.

  The length of the core rod 1 is not particularly limited, and is selected according to the design of the nonaqueous electrolyte secondary battery, etc. (the length in the width direction of the wound electrode group into which the core rod 1 is inserted-3 (Mm)) to (length in the width direction of the wound electrode group into which the core rod 1 is inserted (mm)) is preferable.

For example, as shown in FIG. 2, the core rod 1 is formed by winding a rectangular (or belt-like) metal plate 6 around a cylindrical body 7 in the direction of an arrow 8 (circumferential direction of the cylindrical body 7) to form a hollow cylinder. It can be produced by cutting the both ends of the hollow cylinder obtained as necessary in a direction perpendicular to its longitudinal direction.
The material of the metal plate 6 is not particularly limited, but iron, stainless steel, and the like are preferable from the viewpoint of the rigidity of the obtained core rod 1 and the chemical stability in the battery usage environment.

The thickness of the metal plate 6 can be appropriately selected according to the material of the metal plate 6, but preferably 0.05 mm to 1 mm from the viewpoint of achieving both the moldability of the metal plate 6 and the rigidity of the obtained core rod 1. More preferably, it is 0.1 mm to 0.5 mm. If the thickness of the metal plate 6 is too small, the core rod 1 may be easily deformed even if the slit 2 is formed. If the thickness of the metal plate 6 is too large, the moldability of the metal plate 6 is lowered, and it may be difficult to form the split slit 2 having a desired number of turns and a slit width.
The cylindrical body 7 is made of, for example, metal, ceramic or the like.

  The core rod 1 can be produced by a simple method in which a metal plate 6 is punched into a predetermined shape to produce a metal plate 6 and the metal plate 6 is wound. Therefore, the core rod 1 can be mass-produced at a low cost.

[Nonaqueous electrolyte secondary battery]
FIG. 3 is a longitudinal sectional view schematically showing the configuration of the nonaqueous electrolyte secondary battery 10 according to the third embodiment of the present invention.
The nonaqueous electrolyte secondary battery 10 is formed by winding a core rod 1 and a strip-shaped positive electrode 20 and a strip-shaped negative electrode 21 with a separator 22 interposed between them. The reversible electrode group 11, the positive electrode lead 23 that conducts the strip-shaped positive electrode 20 and the sealing plate 28, the negative electrode lead 24 that conducts the strip-shaped negative electrode 21 and the battery case 27, and the longitudinal direction of the wound electrode group 11 A bottomed cylindrical battery case 27 (hereinafter simply referred to as a “battery case 27”) that accommodates an upper insulating plate 25 and a lower insulating plate 26 attached to both ends, a wound electrode group 11 and a non-aqueous electrolyte (not shown). ), A sealing plate 28 that is attached to the opening of the battery case 27 and seals the battery case 27, a gasket 29 that is interposed between the battery case 27 and the sealing plate 28, and an internal pressure operation type that is supported by the sealing plate 28. Safety valve 30 That is a cylindrical battery.

Next, each component of the nonaqueous electrolyte secondary battery 10 will be described.
The strip-shaped positive electrode 20 (hereinafter simply referred to as “positive electrode 20”) includes a positive electrode current collector and a positive electrode active material layer formed on the surface of the positive electrode current collector.

  A porous substrate and a non-porous substrate can be used for the positive electrode current collector. The porous substrate is a conductive substrate having a plurality of communication holes penetrating from one surface in the thickness direction to the other surface. The communication hole may be a single pore, or may be composed of a plurality of branched and / or connected pores. Examples of the porous substrate include a mesh body, a net body, a punching sheet, an expanded metal, a lath body, a porous body, a foam, and a nonwoven fabric. Non-porous substrates include metal foils and metal sheets. Metal materials such as stainless steel, titanium, aluminum, and aluminum alloy can be used as the material for the porous substrate and the non-porous substrate.

  The thickness of the positive electrode current collector is appropriately selected according to the shape, dimensions, discharge capacity, and the like of the nonaqueous electrolyte secondary battery 10, but is preferably 1 to 500 μm, more preferably 5 to 20 μm. By setting the thickness of the positive electrode current collector within the above range, the positive electrode 20 can be reduced in weight while maintaining the strength of the positive electrode 20.

  In this embodiment, it is preferable to use a porous substrate for the positive electrode current collector. Thereby, the impregnation property to the wound electrode group 11 of a nonaqueous electrolyte further improves. More specifically, in the electrolyte impregnation step of the method for manufacturing the nonaqueous electrolyte secondary battery 10 to be described later, the wound electrode group of the nonaqueous electrolyte injected into the hollow portion 3 of the core rod 1 through the split slit 2. 11 is further impregnated. As a result, the time required for the electrolyte impregnation step is shortened, and the productivity of the nonaqueous electrolyte secondary battery 10 is improved. Further, the non-aqueous electrolyte spreads more evenly throughout the wound electrode group 11. As a result, variations in battery performance among products to be produced are greatly reduced, and the defective product rate is reduced.

  In order to obtain the above-mentioned effects by using the porous substrate more remarkably, among the porous substrates, metal foil having a communicating hole (perforation), punching sheet, expanded metal, porous metal, and non-woven fabric on which plating is applied It is preferable to use a substrate made of or the like.

The positive electrode active material layer is formed on both surfaces in the thickness direction of the positive electrode current collector. The positive electrode active material layer contains a positive electrode active material, and may contain a conductive agent, a binder, and the like.
As the positive electrode active material, a material that can occlude and release lithium ions can be used without particular limitation, but lithium-containing composite oxides and olivine-type lithium phosphate are preferable.

  The lithium-containing composite oxide is a metal oxide containing lithium and a transition metal element or a metal oxide in which a part of the transition metal element in the metal oxide is substituted with a different element. Examples of the transition metal element include Sc, Y, Mn, Fe, Co, Ni, Cu, and Cr, and Mn, Co, Ni, and the like are preferable. Examples of different elements include Na, Mg, Zn, Al, Pb, Sb, and B, and Mg, Al, and the like are preferable. A transition metal element and a different element can be used individually by 1 type or in combination of 2 or more types, respectively.

The lithium-containing composite _{oxide, Li l CoO 2, Li l} NiO 2, Li l MnO 2, Li l Co m Ni 1-m O 2, Li l Co m A 1-m O n, Li l Ni 1- _m A _m O _n , Li _l Mn ₂ O ₄ , Li _l Mn _{2−m An} O ₄ (in the above formulas, A is Sc, Y, Mn, Fe, Co, Ni, Cu, Cr, Na, Mg And at least one element selected from the group consisting of Zn, Al, Pb, Sb and B. 0 <l ≦ 1.2, m = 0 to 0.9, and n = 2.0 to 2.3. .) Etc.

For olivine type lithium phosphate, Li _l MPO ₄ (wherein l is the same as described above, M represents at least one element selected from the group consisting of Mn, Fe, Co and Ni), Li _l M ₁ during _-a X _a PO ₄ (wherein, l and M are as .X the above Mg, Ti, Zn, Nb, Mo, .a exhibits at least one element selected from the group consisting of Ta and W = 0 to 1) and the like.

  In each of the above expressions representing the positive electrode active material, the molar ratio of lithium indicated by the symbol 1 is a value immediately after the production of the positive electrode active material, and increases or decreases due to charge / discharge. A positive electrode active material can be used individually by 1 type or in combination of 2 or more types.

  Conductive agents include graphite such as natural graphite and artificial graphite, carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black and thermal black, and conductive fibers such as carbon fiber and metal fiber. And carbon fluoride. A conductive agent can be used individually by 1 type or in combination of 2 or more types.

  A polymer material can be used for the binder. Polymer materials include polyvinylidene fluoride, polyhexafluoropropylene, copolymers of vinylidene fluoride and hexafluoropropylene, polytetrafluoroethylene, polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamideimide, polyacrylonitrile, Resin materials such as polyacrylic acid, polymethyl acrylate, polyethyl acrylate, polymethacrylic acid, polymethyl methacrylate, polyethyl methacrylate, polyvinyl acetate, polyvinyl pyrrolidone, polyether, polyethersulfone, styrene butadiene rubber And water-soluble polymer materials such as carboxymethyl cellulose. A binder can be used individually by 1 type or in combination of 2 or more types.

  The positive electrode active material layer can be formed by applying the positive electrode mixture slurry to the surface of the positive electrode current collector, and drying and rolling the resulting coating film of the positive electrode mixture slurry. The positive electrode mixture slurry can be prepared by dissolving or dispersing a positive electrode active material, a conductive agent, and a binder in an organic solvent or water. As the organic solvent, dimethylformamide, dimethylacetamide, methylformamide, N-methyl-2-pyrrolidone, dimethylamine, acetone, cyclohexanone and the like can be used.

The strip-shaped negative electrode 21 (hereinafter simply referred to as “negative electrode 21”) includes a negative electrode current collector and a negative electrode active material layer formed on the surface of the negative electrode current collector.
As the negative electrode current collector, a porous substrate and a non-porous substrate can be used. As with the positive electrode current collector, porous substrates include mesh bodies, net bodies, punching sheets, expanded metals, lath bodies, porous bodies, foams, non-woven fabrics, etc., and non-porous substrates include metal foil and metal. There are sheets. Metal materials such as stainless steel, nickel, copper, copper alloy, aluminum, and aluminum alloy can be used as the material for the porous substrate and the non-porous substrate.

  The thickness of the negative electrode current collector is appropriately selected according to the shape, size, discharge capacity, and the like of the nonaqueous electrolyte secondary battery 10, but is preferably 1 to 500 μm, more preferably 5 to 50 μm. By setting the thickness of the negative electrode current collector within the above range, the negative electrode 21 can be reduced in weight while maintaining the strength of the negative electrode 21.

  In this embodiment, it is preferable to use a porous substrate for the negative electrode current collector. As a result, in the same manner as when the porous substrate is used for the positive electrode current collector, the impregnation property of the wound electrode group 11 of the nonaqueous electrolyte in the electrolyte impregnation step of the method for manufacturing the nonaqueous electrolyte secondary battery described later is improves. As a result, the productivity of the nonaqueous electrolyte secondary battery 10, the battery performance of the final product obtained, and the like can be improved, and the production time can be shortened and the defective product rate can be reduced.

From the viewpoint of obtaining such an effect, preferred porous substrates are a metal foil having a communicating hole (perforation), a punching sheet, an expanded metal, a porous metal, a substrate made of a plated nonwoven fabric, and the like.
In the present embodiment, it is preferable to use a porous substrate for either the positive electrode current collector or the negative electrode current collector, and it is more preferable to use a porous substrate for both the positive electrode current collector and the negative electrode current collector.

The negative electrode active material layer is formed on both surfaces in the thickness direction of the negative electrode current collector. The negative electrode active material layer contains a negative electrode active material, and contains a binder, a conductive agent, a thickener and the like as necessary.
Examples of the negative electrode active material include a carbon material, an alloy-based active material, lithium, a lithium alloy, and a lithium-containing composite oxide. Examples of the carbon material include natural graphite, artificial graphite, coke, graphitized carbon, carbon fiber, spherical carbon, and amorphous carbon. Examples of the alloy-based active material include silicon, silicon oxide, tin, and tin oxide. Examples of the lithium-containing composite oxide include a lithium titanium-containing oxide and a lithium vanadium-containing oxide.

  As the conductive agent and the binder, the same materials as the conductive agent and the binder contained in the positive electrode active material layer can be used, respectively. As the thickener, those commonly used in the field of non-aqueous electrolyte secondary batteries can be used, and examples thereof include carboxymethyl cellulose.

  The negative electrode active material layer can be formed, for example, by applying a negative electrode mixture slurry to the surface of the negative electrode current collector, and drying and rolling the coating film of the obtained negative electrode mixture slurry. The negative electrode mixture slurry can be prepared by, for example, dissolving or dispersing a negative electrode active material and at least one selected from the group consisting of a conductive agent, a binder, and a thickener in an organic solvent or water. As the organic solvent, the same organic solvent used for preparing the positive electrode mixture slurry can be used.

  Further, the negative electrode active material layer includes a mixture containing a negative electrode active material and at least one selected from the group consisting of a conductive agent, a binder, an adhesive, and other additives on the surface of the negative electrode current collector, It can be formed by press-bonding to a predetermined shape by press molding or the like. When an alloy-based active material is used as the negative electrode active material, the negative electrode active material layer can be formed by a vapor phase method such as a vacuum vapor deposition method.

  The separator 22 is a lithium ion permeable insulating layer disposed so as to be interposed between the positive electrode 20 and the negative electrode 21. The separator 22 can be a porous film having pores. Examples of the porous film include a microporous film, a woven fabric, and a non-woven fabric. The microporous film is a single layer film or a multilayer film (composite film). Further, two or more layers of microporous membrane, woven fabric, nonwoven fabric, etc. may be laminated and used as the separator 22.

  Various resin materials can be used as the material of the separator 22, but polyolefins such as polyethylene and polypropylene are preferable in view of durability, shutdown function, safety of the nonaqueous electrolyte secondary battery 10, and the like. The thickness of the separator 22 is preferably 5 to 50 μm, more preferably 8 to 40 μm. The porosity of the separator 22 is preferably 30 to 70%, more preferably 35 to 60%. The porosity is a percentage of the total volume of pores present in the separator 22 with respect to the volume of the separator 22.

The nonaqueous electrolyte impregnated in the wound electrode group 11 contains a lithium salt and a nonaqueous solvent.
Lithium salts include LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAlCl ₄ , LiSbF ₆ , LiSCN, LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiB ₁₀ Cl ₁₀ , lower aliphatic lithium lithium carbonate, LiCl, LiBr , LiI, LiBCl ₄ , borates, imide salts and the like. The concentration of the lithium salt in 1 liter of the non-aqueous solvent is preferably 0.5 mol to 2 mol.

  Various aprotic organic solvents can be used as the non-aqueous solvent. Specific examples thereof include cyclic carbonates such as ethylene carbonate, propylene carbonate and butylene carbonate, chain carbonates such as dimethyl carbonate, ethyl methyl carbonate and diethyl carbonate, cyclic ethers such as tetrahydrofuran and 1,3-dioxolane, 1, Examples include chain ethers such as 2-dimethoxyethane and 1,2-diethoxyethane, cyclic carboxylic acid esters such as γ-butyrolactone and γ-valerolactone, and chain esters such as methyl acetate. A nonaqueous solvent can be used individually by 1 type or in combination of 2 or more types.

  The non-aqueous electrolyte can contain an additive in addition to the lithium salt and the non-aqueous solvent. Examples of the additive include additives that improve charge and discharge efficiency such as vinylene carbonate, vinyl ethylene carbonate, and divinyl ethylene carbonate, and additives that inactivate the battery such as cyclohexylbenzene, biphenyl, and diphenyl ether. An additive can be used individually by 1 type or in combination of 2 or more types.

  An aluminum lead or the like can be used for the positive electrode lead 23. As the negative electrode lead 24, a nickel lead, a copper lead, or the like can be used. The upper insulating plate 25, the lower insulating plate 26, and the gasket 29 are manufactured by molding a rubber material, a resin material, or the like into a predetermined shape. The battery case 27, the sealing plate 28, and the safety valve 30 are manufactured by molding a metal material such as iron or stainless steel into a predetermined shape.

[Method for producing non-aqueous electrolyte secondary battery]
Next, a method for manufacturing a nonaqueous electrolyte secondary battery according to the fourth embodiment of the present invention will be described with reference to FIGS. The manufacturing method of this embodiment includes an electrode group accommodation step, an electrolyte injection step, and an electrolyte impregnation step.

(1) Electrode Group Housing Step In the electrode group housing step, the wound electrode group 11 is housed in the battery case 27. The wound electrode group 11 is produced by winding the positive electrode 20 and the negative electrode 21 with a separator 22 interposed therebetween. The core rod 1 is inserted into the center of the wound electrode group 11. In the present embodiment, the wound electrode group 11 is accommodated in the battery case 27 with the upper insulating plate 25 and the lower insulating plate 26 attached to both ends in the longitudinal direction. In the present embodiment, the positive electrode lead 23 and the sealing plate 28 are connected and the negative electrode lead 24 and the battery case 27 are connected at the same time when the wound electrode group 11 is housed in the battery case 27. These connections are made by welding or the like.

(2) Electrolyte Injection Process In the electrolyte injection process, a nonaqueous electrolyte is injected into the hollow portion 3 of the core rod 1 while the inside of the battery case 27 in which the wound electrode group 11 is housed is decompressed. . Thus, by injecting the nonaqueous electrolyte into the hollow portion 3 of the core rod 1, the injection operation can be performed easily and reliably, and the time required for the injection operation can be shortened.

The pressure reduction conditions in the electrolyte pouring step are not particularly limited, the composition of the nonaqueous electrolyte, the composition of the positive electrode active material layer and the negative electrode active material layer, the form of the positive electrode current collector and the negative electrode current collector (non-porous or porous), etc. is appropriately selected depending on various conditions, preferably ^{150~680mmHg (199 × 10 2 Pa~907 ×} 10 2 Pa). If the depressurization condition is too small, there is a risk that deterioration of components due to evaporation of the nonaqueous electrolyte, scattering to the surroundings, and the like may occur. On the other hand, if the depressurization condition is too large, the impregnation rate and the impregnation amount of the nonaqueous electrolyte into the wound electrode group 11 may be insufficient.

(3) Electrolyte impregnation step In the electrolyte impregnation step, the pressure inside the battery case 27 in which the wound electrode group 11 is accommodated is returned to atmospheric pressure. As a result, the nonaqueous electrolyte injected into the hollow portion 3 of the core rod 1 is impregnated in the wound electrode group 11 through the split slit 2 of the core rod 1. By injecting the nonaqueous electrolyte into the hollow portion 3 of the core rod 1 having the split slits 2 that spirally circulate, the impregnation rate of the nonaqueous electrolyte into the wound electrode group 11 can be increased. Further, the nonaqueous electrolyte can be distributed almost uniformly throughout the wound electrode group 11.

Thereby, the time required for the electrolyte impregnation step can be shortened, the performance of the final product can be made uniform at a high level, and the defective product rate can be reduced. As a result, productivity when mass-producing nonaqueous electrolyte secondary batteries is significantly improved, and cost reduction and quality improvement can be realized.
Such an effect is further improved when a porous substrate is used as the current collector of the positive electrode 20 and the negative electrode 21 included in the wound electrode group 11.

  After the electrolyte impregnation step, the sealing plate 28 is attached to the opening of the battery case 27 via the gasket 29, and the opening end of the battery case 27 is caulked toward the gasket 29, whereby the nonaqueous electrolyte secondary battery 10. Is obtained.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to only these examples.
Example 1
A wound electrode group and a non-aqueous electrolyte secondary battery were manufactured using the strip-shaped positive electrode, strip-shaped negative electrode and non-aqueous electrolyte produced as follows, and the separator and core rod shown below.

(1) Production of strip-shaped positive electrode 3 kg of lithium cobaltate, 12 kg of NMP (N-methyl-2-pyrrolidone) solution of polyvinylidene fluoride (trade name: PVDF # 1320, manufactured by Kureha Corporation), 1 kg of acetylene black 90 g and an appropriate amount of NMP were stirred with a double-arm kneader to prepare a positive electrode mixture slurry. This slurry was applied to both sides of an aluminum foil (positive electrode current collector) having a thickness of 15 μm, and the obtained coating film was dried and rolled to form a positive electrode active material layer, thereby producing a positive electrode having a total thickness of 160 μm. The positive electrode was cut to obtain a strip-shaped positive electrode having a width of 56 mm.

(2) Production of strip-shaped negative electrode 3 kg of artificial graphite, 75 g of a 40% by mass aqueous dispersion of a modified styrene butadiene rubber (trade name: BM-400B, manufactured by Nippon Zeon Co., Ltd.), 30 g of carboxymethyl cellulose, and an appropriate amount of water Was stirred with a double-arm kneader to prepare a negative electrode mixture slurry. This slurry was applied to both surfaces of a 10 μm thick copper foil (negative electrode current collector), and the obtained coating film was dried and rolled to form a negative electrode active material layer, thereby preparing a negative electrode having a total thickness of 180 μm. The negative electrode was cut to obtain a strip-shaped negative electrode having a width of 57 mm.

(3) Separator As the separator, a polyethylene porous film (trade name: A089, manufactured by Celgard Co., Ltd.) having a thickness of 20 μm was used.

(4) Core rod The core rod is made of cold-rolled stainless steel (SUS304-CS) with a thickness of 0.2 mm, and has a split slit that spirals around the outer peripheral surface. The diameter is 3 mm and the length is 58 mm. A cylindrical core rod was used. The slit width of the split slit was 0.5 mm, and the number of turns was 0.5.

(5) Preparation of non-aqueous electrolyte LiPF ₆ is dissolved in a mixed solvent of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate in a volume ratio of 1: 1: 1, and vinylene carbonate is further added to prepare a non-aqueous electrolyte. did. The concentration of LiPF ₆ was 1 mol with respect to 1 liter of the mixed solvent. The amount of vinylene carbonate added was 3 parts by mass with respect to 100 parts by mass of the mixed solvent.

(6) Production of non-aqueous electrolyte secondary battery (6-1) Electrode group housing step A separator is interposed between the belt-like positive electrode and the belt-like negative electrode, and these are wound to produce a cylindrical wound electrode group. . The positive electrode current collector and the lower surface of the sealing plate having the safety valve were connected by an aluminum positive electrode lead. The negative electrode current collector was connected to the inner bottom surface of an iron-bottomed cylindrical battery case (inner diameter: 18 mm) with nickel plating on the surface by a nickel negative electrode lead. After the polypropylene insulating plates were attached to both ends in the longitudinal direction of the wound electrode group, the wound electrode group was accommodated in the battery case. A core rod was inserted into the center part of the wound electrode group (center cavity, initial diameter 4 mm).

(6-2) Electrolyte injection step and electrolyte impregnation step In the state where the inside of the battery case containing the wound electrode group is decompressed (260 mmHg≈346.6 × 10 ² Pa), A nonaqueous electrolyte (5.0 g) was injected, and the reduced pressure state was maintained for 10 seconds. Thereafter, the inside of the battery case was returned to atmospheric pressure, and the wound electrode group was impregnated with the nonaqueous electrolyte through the split slit of the core rod.

  Next, a sealing plate was disposed in the opening of the battery case via a polypropylene gasket, and the opening end of the battery case was crimped to the peripheral edge of the sealing plate. Thus, a cylindrical lithium secondary battery having an inner diameter of 18 mm, a height of 65 mm, and a design capacity of 2000 mAh was produced.

(Examples 2 to 5)
Example 1 except that the number of rounds of the split slit in the core rod is changed to 1 (Example 2), 2 (Example 3), 3 (Example 4) or 4 (Example 5). In the same manner, cylindrical lithium secondary batteries having an inner diameter of 18 mm, a height of 65 mm, and a design capacity of 2000 mAh were produced.

(Examples 6 to 10)
The number of rounds of the split slit in the core rod was changed to 2 and the slit width was 0.2 mm (Example 6), 0.8 mm (Example 7), 1.5 mm (Example 8), 2 mm (implemented) Except for changing to Example 9) or 2.5 mm (Example 10), cylindrical lithium secondary batteries having an inner diameter of 18 mm, a height of 65 mm, and a design capacity of 2000 mAh were produced in the same manner as in Example 1.

(Example 11)
The number of rounds of the split slit in the core rod was changed to 2 times, and an aluminum foil having a communication hole (perforation) (thickness 15 μm, average diameter of the perforation 0.5 mm, opening rate 40%) was used as the positive electrode current collector. The same as in Example 1 except that a copper foil (thickness 10 μm, average hole diameter 0.5 mm, hole opening ratio 40%) having communication holes (perforations) was used as the negative electrode current collector. Thus, a cylindrical lithium secondary battery having an inner diameter of 18 mm, a height of 65 mm, and a design capacity of 2000 mAh was produced. The open area ratio is a percentage of the total volume of the communication holes of the current collector with respect to the volume of the current collector.

(Comparative Example 1)
The core rod is made of cold-rolled stainless steel (SUS304-CS) having a thickness of 0.2 mm, and a linear slit (slit width 0.5 mm) extending in the longitudinal direction is formed on the outer peripheral surface. A cylindrical lithium secondary battery having an inner diameter of 18 mm, a height of 65 mm, and a design capacity of 2000 mAh was produced in the same manner as in Example 1 except that a cylindrical core rod having a length of 58 mm was used.
Table 1 summarizes the characteristics of the batteries obtained in Examples 1 to 11 and Comparative Example 1.

(Test Example 1)
In producing the batteries of Examples 1 to 11 and Comparative Example 1, the inside of the battery case was reduced in pressure (260 mmHg × 10 seconds) in the electrolyte pouring step, and a nonaqueous electrolyte was poured into the hollow portion of the core rod. Subsequently, in the electrolyte impregnation step, the pressure inside the battery case was returned to atmospheric pressure, and the wound electrode group was impregnated with the nonaqueous electrolyte. Note that immediately after the pressure inside the battery case was returned to atmospheric pressure, it was visually confirmed that the nonaqueous electrolyte remained at the end of the hollow portion of each core rod.

[Impregnation area and electrolyte remaining amount]
Immediately after returning the pressure inside the battery case to atmospheric pressure, the wound electrode group was taken out of the battery case, and the impregnation area and the electrolyte remaining amount (g) were examined. The impregnated area was determined as a ratio of the total area of the positive electrode and the negative electrode impregnated with the non-aqueous electrolyte with respect to the total of the positive electrode area and the negative electrode area after loosening the wound electrode group into a flat plate shape. . Moreover, the electrolyte remaining amount was calculated | required by measuring the liquid quantity of the nonaqueous electrolyte which remains in the edge part of the hollow part of a core rod. The results are shown in Table 2.

[Impregnation time]
In the electrolyte impregnation step, immediately after the pressure inside the battery case was returned to atmospheric pressure, the time until the nonaqueous electrolyte remaining at the end of the hollow portion of the core rod disappeared visually was determined as the impregnation time (minutes). . The results are shown in Table 2.
[Internal resistance]
The internal resistance (mΩ) of the batteries of Examples 1 to 11 and Comparative Example 1 was measured, and the results are shown in Table 2.

  From Table 2, the batteries of Examples 1 to 11 have an increased non-aqueous electrolyte impregnation area and an increased impregnation rate and improved non-aqueous electrolyte impregnation compared to the conventional battery of Comparative Example 1. It is clear.

  In the batteries of Examples 1 to 11, the split slit that circulates in a spiral shape inserts a core rod formed on almost the entire outer peripheral surface into the center of the wound electrode group. When a nonaqueous electrolyte is injected into the hollow portion of such a core rod, the nonaqueous electrolyte penetrates into the wound electrode group through the slit. Therefore, in the batteries of Examples 1 to 11, it is considered that the nonaqueous electrolyte easily spreads almost uniformly throughout the wound electrode group, and the impregnation property of the nonaqueous electrolyte was improved.

  In addition, it is apparent that the battery of Example 11 is further improved in the impregnation property of the nonaqueous electrolyte as compared with the batteries of Examples 1-10. This is presumably because, in the battery of Example 11, a metal foil having communication holes was used as the positive electrode current collector and the negative electrode current collector. That is, it is considered that the impregnation area is further increased, the impregnation speed is further increased, and the impregnation property is further improved by the synergistic action of the split slit and the communication hole of each current collector.

  Also, from Table 2, it is clear that the batteries of Examples 1 to 11 have an internal resistance value of about 1/3 or less, and can have a high output as compared with the conventional battery of Comparative Example 1.

[Safety against internal short circuit]
The batteries of Examples 1 to 11 and Comparative Example 1 were fixed with a jig. A crushing force of 13 kN was applied to each battery from above the side surface of each battery through a metal plate, and the battery voltage before and after application was measured to examine the occurrence of internal short circuit.

  The batteries of Examples 2 to 4, 6 to 9 and 11 did not cause an internal short circuit, but the batteries of Examples 1, 5 and 10 and Comparative Example 1 had an internal short circuit. When each battery after the occurrence of an internal short circuit was disassembled, one of the end faces in the circumferential direction along the split slit was standing. In particular, in the battery of Comparative Example 1, the standing end face penetrated the positive electrode and the separator and reached the negative electrode.

  In the battery of Example 1, since the number of turns of the split slit is too small, it is considered that the effect of suppressing the deformation of the core rod with respect to the external stress is reduced, leading to an internal short circuit. Moreover, in the battery of Example 5, since the number of rounds of the split slit is too large, it is considered that the rigidity of the core rod was reduced and an internal short circuit occurred. In the battery of Example 10, since the width of the split slit is too large, the effect of reducing the rigidity of the core rod is greater than the effect of absorbing or relaxing external stress, and the core rod presses the electrode group from the inside. It is thought that an internal short circuit was caused due to lack of force.

  From the above results, it was found that the split slit of the core rod has a spiral shape, so that both the impregnation property of the nonaqueous electrolyte and the effect of suppressing the occurrence of internal short circuit can be achieved.

The core rod of the present invention can be used for all non-aqueous electrolyte secondary batteries using a wound electrode group, and can be particularly suitably used for small and cylindrical non-aqueous electrolyte secondary batteries.
The non-aqueous electrolyte secondary battery of the present invention can be used for the same applications as conventional non-aqueous electrolyte secondary batteries, and is useful as a main power source or auxiliary power source for electronic devices, electrical devices, machine tools, transportation devices, etc. is there. Electronic devices include personal computers, mobile phones, mobile devices, personal digital assistants, portable game devices, video cameras, and the like. The electrical equipment includes a vacuum cleaner. Machine tools include electric tools and robots. Transportation equipment includes hybrid electric vehicles, electric vehicles, fuel cell vehicles, plug-in HEVs, and the like.

DESCRIPTION OF SYMBOLS 1 Core rod 2 Split slit 3 Hollow part 4 One end 5 Other end 6 Metal plate 7 Column body 8 Arrow 10 Nonaqueous electrolyte secondary battery 11 Winding electrode group 20 Band-shaped positive electrode 21 Band-shaped negative electrode 22 Separator 23 Positive electrode lead 24 Negative electrode lead 25 Upper insulating plate 26 Lower insulating plate 27 Battery case 28 Sealing plate 29 Gasket 30 Safety valve

Claims (8)

  A central part of a wound electrode group of a cylindrical non-aqueous electrolyte secondary battery, characterized in that it is a hollow cylinder having a split slit that spirally turns from one end to the other end along the longitudinal direction. Core rod to be inserted into.   The core rod according to claim 1, wherein the split slit has a helical turn number of 1 to 3.   The core rod according to claim 1 or 2, wherein a slit width of the split slit is 0.1 mm to 2 mm.   An electrode comprising: the core rod according to any one of claims 1 to 3; and a belt-like positive electrode and a belt-like negative electrode that are wound around the core rod with a separator interposed therebetween. A wound electrode group for a cylindrical non-aqueous electrolyte secondary battery.   The positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on both surfaces of the positive electrode current collector, and the negative electrode is formed on both surfaces of the negative electrode current collector and the negative electrode current collector. The wound type for a cylindrical nonaqueous electrolyte secondary battery according to claim 4, further comprising a negative electrode active material layer, wherein each of the positive electrode current collector and the negative electrode current collector is a porous substrate having a plurality of communication holes. Electrode group.   A cylindrical non-aqueous electrolyte comprising: a wound electrode group for the cylindrical non-aqueous electrolyte secondary battery according to claim 5; a non-aqueous electrolyte; and a battery case that houses the electrode group and the non-aqueous electrolyte. Water electrolyte secondary battery. An electrode group housing step for housing the wound electrode group for the cylindrical nonaqueous electrolyte secondary battery according to claim 4 in a battery case;
An electrolyte injection step of reducing the pressure inside the battery case and injecting a nonaqueous electrolyte into the hollow portion of the core rod included in the electrode group,
An electrolyte impregnation step for impregnating the non-aqueous electrolyte into the electrode group through a slit formed in the core rod by returning the inside of the battery case to atmospheric pressure, and a method for producing a cylindrical non-aqueous electrolyte secondary battery . An electrode group housing step of housing the wound electrode group for the cylindrical nonaqueous electrolyte secondary battery according to claim 5 in a battery case;
An electrolyte injection step of reducing the pressure inside the battery case and injecting a nonaqueous electrolyte into the hollow portion of the core rod included in the electrode group,
By returning the inside of the battery case to atmospheric pressure, the non-aqueous electrolyte is passed through the slits of the core rod and the communication holes of the positive electrode current collector and the negative electrode current collector included in the electrode group, respectively. An electrolyte impregnation step for impregnating the electrode group. A method for producing a nonaqueous electrolyte secondary battery.

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