JP2009266737A - Lithium ion secondary battery and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a drop in charge discharge cycle characteristics or in service life by preventing bulging of a battery or generation of deformation or breakage of a negative active material layer attendant on repeating of charge discharge cycles in high performance and high output lithium secondary battery containing an alloy type negative active material. <P>SOLUTION: In a lithium secondary battery including an electrode group 1 formed by winding like a flat plate a positive electrode 5 and a negative electrode 6 containing an alloy type negative active material through a separator, a positive electrode lead 7, and a negative electrode lead 8, the positive electrode lead 7 and the negative electrode lead 8 are connected to a positive current collector and a negative current collector so as to face the electrode group 1 at the end parts on the opposite side to the axis side end part of the electrode group 1 of the positive electrode 5 and the negative electrode 6, and thereby, projection of the positive electrode lead 7 and the negative electrode lead 8 outside more than the surfaces in the thickness direction of the wound type electrode group 1 is prevented, and in this constitution, initial charge discharge is conducted under pressure. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a lithium ion secondary battery and a method for manufacturing the same. More particularly, the present invention relates to an improvement in the internal structure of a lithium ion secondary battery including a flat wound electrode group containing an alloy-based negative electrode active material.

  Lithium ion secondary batteries have high capacity and high energy density, and are easy to reduce in size and weight. For example, mobile phones, personal digital assistants (PDAs), notebook personal computers, video cameras, and portable games It is widely used as a power source for portable small electronic devices such as electronic machines. A typical lithium ion secondary battery includes a positive electrode containing a lithium cobalt compound as a positive electrode active material, a separator that is a polyolefin porous film, and a negative electrode containing a carbon material as a negative electrode active material. Is mentioned.

As described above, the lithium ion secondary battery has a high capacity and output, and has a long life. However, as the portable small electronic device is further multifunctionalized, the power consumption of the small electronic device is increased, and the lithium ion secondary battery is increased. In addition, various performance improvements are required. One of them is further increase in capacity and output, and for this purpose, for example, development of a high-capacity negative electrode active material has been promoted.
As a high-capacity negative electrode active material, an alloy-based negative electrode active material that is alloyed with lithium, such as silicon, tin, oxides thereof, compounds containing these, and alloys, has attracted attention. Since the alloy-based negative electrode active material has a high discharge capacity, it is effective for increasing the capacity of the lithium ion secondary battery. For example, the theoretical discharge capacity of silicon is about 4199 mAh / g, which is about 11 times the theoretical discharge capacity of graphite conventionally used as a negative electrode active material.

  The alloy-based negative electrode active material has a characteristic of repeating relatively large expansion and contraction as lithium ions are stored and released. For this reason, in a lithium ion secondary battery using an alloy-based negative electrode active material, when the number of charge / discharge increases, the volume expansion of the alloy-based negative electrode active material accompanying charge / discharge increases and the thickness of the battery increases. There are issues to be solved. Further, due to the expansion of the alloy-based negative electrode active material, voids are generated inside the electrode group, the negative electrode active material layer containing the alloy-based negative electrode active material is partially peeled from the current collector, and the charge / discharge cycle characteristics of the battery are There is also a problem that the lifetime of the battery is shortened.

In order to solve such a problem, for example, in a lithium ion secondary battery including a flat wound electrode group, the first charge / discharge is performed while pressing the flat portion of the electrode group in the thickness direction of the electrode group. The technique which performs is proposed (for example, refer patent document 1). The flat wound electrode used in Patent Document 1 is prepared by winding a negative electrode containing a positive electrode and an alloy-based negative electrode active material through a separator. Further, the pressure applied to the flat surface portion of the wound electrode group is defined as 1.0 × 10 ⁴ N / cm ² or more. According to Patent Document 1, it is described that a battery is prevented from swelling due to repeated charge / discharge, and a lithium ion secondary battery having excellent charge / discharge characteristics can be obtained.

  In the lithium ion secondary battery of Patent Document 1, the swelling of the battery due to repeated charge / discharge cycles is somewhat reduced, but the effect is not sufficient. Moreover, in the lithium ion secondary battery of patent document 1, the frequency with which an internal short circuit generate | occur | produces has increased compared with normal. Furthermore, Patent Document 1 only describes that only the flat portion of the flat wound electrode group is press-pressed in the thickness direction of the electrode group, and no consideration is given to the connection position of the leads. Not.

Further, the negative electrode active material layer specifically shown in Examples in Patent Document 1 is composed of an alloy-based negative electrode active material and a binder such as thermoplastic polyimide. Although such a negative electrode active material layer contains an alloy-based negative electrode active material, it does not contribute to a sufficiently high capacity and high output as desired because it contains a binder. However, when the negative electrode active material layer is formed as a vapor-deposited film or a sputtering film of an alloy-based negative electrode active material in order to improve performance, the occurrence of battery swelling, internal short-circuiting, etc. may become more prominent.
JP 2007-258084 A

  The object of the present invention is to prevent the occurrence of battery swelling, deformation and breakage of the negative electrode active material layer with repeated charge / discharge cycles, excellent charge / discharge cycle characteristics, long service life, high capacity and high output. It is providing the lithium ion secondary battery which has this.

  The inventors of the present invention have made extensive studies to solve the above problems. In the course of the research, in Patent Document 1, the cause of the risk of the occurrence of an internal short circuit due to insufficient expansion of the battery was considered. In Patent Document 1, only the flat portion of the flat wound electrode group is pressurized in the thickness direction of the electrode group. Further, although not specifically described in Patent Document 1, the positive electrode lead and the negative electrode lead are generally connected to the current collector in the plane portion of the flat wound electrode group. . For this reason, it discovered that the deformation | transformation, peeling, etc. of an active material layer were easy to generate | occur | produce in the connection part of a lead | read | reed, and its vicinity.

  That is, when the electrode group is press-pressed in the thickness direction, more stress than necessary is applied to the connecting portion of the lead due to the presence of the lead. This stress is presumed to cause partial deformation and peeling of the active material layer. Such deformation and peeling not only deteriorate the charge / discharge cycle characteristics of the battery, but also increase the number of times of charge / discharge, which may cause the battery to swell around the lead connection portion. Furthermore, a fragment of the active material layer is generated along with the deformation and peeling, and this fragment may cause an internal short circuit.

  The present inventors have further studied based on such knowledge. As a result, in the lithium ion secondary battery including the flat wound electrode group containing the alloy-based negative electrode active material, the current is collected at a position where the lead does not protrude from the surface in the thickness direction of the wound electrode group. I came up with a configuration that connects to the body. According to this configuration, even if the wound electrode group is press-pressed during the first charge / discharge, deformation and peeling of the active material layer at the lead connection portion is prevented, and the battery swells even after repeated charge / discharge. It has been found that it is difficult to occur and the risk of occurrence of an internal short circuit does not increase. Furthermore, the present inventors, due to this configuration, even when the negative electrode active material layer is a vapor-deposited film, a sputtering film or a chemical vapor deposition film of an alloy-based negative electrode active material, the occurrence of battery swelling, internal short circuit, etc. is remarkable. As a result, the present invention has been completed.

That is, the present invention includes an electrode group, a positive electrode lead and a negative electrode lead,
The electrode group includes a positive electrode including a positive electrode active material layer containing a positive electrode active material capable of inserting and extracting lithium and a positive electrode current collector, a negative electrode active material layer containing an alloy-based negative electrode active material, and a negative electrode current collector. Is a flat wound electrode group wound in a flat plate shape through a separator,
The positive electrode lead is connected to the positive electrode current collector so as not to protrude outward from the surface of the electrode group in the thickness direction,
The negative electrode lead is related to a lithium ion secondary battery that is connected to the negative electrode current collector so as not to protrude outward from the surface of the electrode group in the thickness direction, and performs initial charge / discharge under pressure.

In a preferred embodiment of the present invention, the positive electrode lead and the negative electrode lead are respectively attached to the positive electrode current collector and the negative electrode current collector so as to face the axis of the electrode group at the end opposite to the end of the electrode group on the axis line side. It is connected.
In another preferred embodiment of the present invention, the electrode group includes a bent portion in which the positive electrode and the negative electrode are bent to the axis side at the end opposite to the axis side end portion, and is bent following the surface in the thickness direction of the electrode group. On the surface of the portion, the positive electrode lead and the negative electrode lead are connected to the positive electrode current collector and the negative electrode current collector, respectively.

In still another preferred embodiment of the present invention, the positive electrode current collector and the negative electrode current collector are a current collector body having a rectangular shape, and a current collector body at an end opposite to the axis side end of the current collector body. Lead attachment portions formed so as to extend outward from each other, wherein the positive electrode lead and the negative electrode lead are respectively connected to the positive electrode current collector and the negative electrode current collector.
At this time, it is preferable that the lead attachment portion is provided so as to protrude in a direction in which the axis of the electrode group extends from the current collector body.

In the lithium ion secondary battery of the present invention, the negative electrode active material layer is preferably formed by vapor deposition, sputtering, or chemical vapor deposition.
The alloy-based negative electrode active material is preferably an alloy-based negative electrode active material containing silicon or tin.
More preferably, the alloy-based negative electrode active material containing silicon is at least one selected from the group consisting of silicon, silicon oxide, silicon nitride, silicon-containing alloy and silicon compound.
More preferably, the alloy-based negative electrode active material containing tin is at least one selected from the group consisting of tin, tin oxide, a tin-containing alloy and a tin compound.

Further, the present invention includes an electrode group, a positive electrode lead and a negative electrode lead,
The electrode group includes a positive electrode including a positive electrode active material layer containing a positive electrode active material capable of inserting and extracting lithium and a positive electrode current collector, a negative electrode active material layer containing an alloy-based negative electrode active material, and a negative electrode current collector. Is a flat wound electrode group wound in a flat plate shape through a separator,
The positive electrode lead is connected to the positive electrode current collector so as not to protrude outward from the surface of the electrode group in the thickness direction,
The negative electrode lead performs the first charge / discharge under pressure on the lithium ion secondary battery connected to the negative electrode current collector so as not to protrude outward from the surface of the electrode group in the thickness direction. The present invention relates to a method for manufacturing a lithium ion secondary battery.

  According to the present invention, although an alloy-based negative electrode active material that repeatedly expands and contracts due to insertion and extraction of lithium ions is used, even if charging and discharging are repeated for a long time, battery swelling, internal short circuit, etc. occur. It is difficult to obtain a highly safe lithium ion secondary battery. Moreover, since the lithium ion secondary battery of the present invention uses an alloy-based negative electrode active material, it has a higher capacity and higher output and a longer service life than conventional lithium ion secondary batteries.

The lithium ion secondary battery of the present invention has the following features (1) to (3).
(1) An alloy-based negative electrode active material is used as the negative electrode active material.
(2) A flat wound electrode group (hereinafter simply referred to as “electrode group”) in which the positive electrode and the negative electrode are wound in a flat plate shape with a separator interposed therebetween is used.
(3) The positive electrode lead and the negative electrode lead are connected to the positive electrode current collector and the negative electrode current collector, respectively, at positions that do not protrude outward from the surface of the electrode group with respect to the thickness direction of the electrode group.
Irregular expansion and contraction of the alloy-based negative electrode active material is suppressed by performing the first charge / discharge with the lithium ion secondary battery of the present invention having such characteristics in the pressurized state in the thickness direction. The charge / discharge cycle characteristics of the battery are significantly improved. In addition, since battery swelling and internal short-circuiting are suppressed, the safety of the battery is improved.

  In this specification, the flat wound electrode group refers to a plate shape after winding the positive electrode and the negative electrode via a separator in addition to the electrode group obtained by winding the positive electrode and the negative electrode in a flat plate shape via a separator. The electrode group formed in the above is also included. The flat wound electrode group has an axis that is an imaginary line extending in the longitudinal direction of the electrode group at the center. The axis is also called the winding axis. The flat wound electrode group has a flat shape in which a cross section in a direction perpendicular to the axis has a longitudinal direction and a short direction. The flat wound electrode group is also referred to as a flat wound electrode group.

  In the present invention, the positive electrode lead and the negative electrode lead are connected to the current collector at the specific position described above, and the electrode group is pressurized during the first charge / discharge. Thereby, it is possible to prevent an excessive stress from being applied to the connection portion between the positive electrode lead and the negative electrode lead. As a result, the electrode group can be pressurized without partially deforming and peeling the positive and negative electrode active material layers contained in the electrode group. At this time, it is estimated that a substantially constant shape is imparted to the negative electrode active material layer. This suppresses irregular expansion and contraction of the negative electrode active material layer even when the number of times of charge / discharge increases, significantly reducing deformation and voids throughout the electrode group, and causing battery swelling. Presumed to be difficult. Moreover, since no fragments of the active material layer are generated during pressurization, it is presumed that the risk of an internal short circuit does not increase.

  FIG. 1 is a drawing schematically showing a configuration of a main part (electrode group 1) of a lithium ion secondary battery which is one embodiment of the present invention. FIG. 1A is a longitudinal sectional view of the electrode group 1. In addition, illustration of a separator is abbreviate | omitted in Fig.1 (a). The separator is interposed between the positive electrode 5 and the negative electrode 6. FIG. 1B is a top view. FIG.1 (c) is a top view which shows typically the structure of the electrode group 1a of another embodiment.

  The lithium ion secondary battery of the present invention includes, for example, an electrode group 1, a positive electrode lead 7, a negative electrode lead 8, a gasket (not shown), and an exterior case (not shown). The electrode group 1 includes a positive electrode 5, a negative electrode 6, and a separator (not shown). The electrode group 1 is a flat wound electrode group in which the positive electrode 5 and the negative electrode 6 are overlapped and wound into a flat plate shape with a separator interposed therebetween. The electrode group 1 has an axis 1z, which is an imaginary line extending in the longitudinal direction, at the center. Further, in the direction perpendicular to the thickness direction of the electrode group 1, an end 5b opposite to the axial end 5a of the positive electrode 5 and an end 6b opposite to the axial end 6a of the negative electrode 6 are provided. The positive electrode 5 and the negative electrode 6 are wound so as to be located on the opposite side.

  In this specification, the axial line side end portion 5 a of the positive electrode 5 is an end portion of the positive electrode 5 located at the center of the electrode group 1. The axial side end of the positive electrode current collector is the end of the positive electrode current collector located at the center of the electrode group 1. Similarly, the axial side end 6 a of the negative electrode 6 is also an end of the negative electrode 6 located at the center of the electrode group 1. The end on the axis side of the negative electrode current collector is also the end of the negative electrode current collector located at the center of the electrode group 1.

  The positive electrode 5 includes a positive electrode current collector and a positive electrode active material layer (not shown). As the positive electrode current collector, those commonly used in this field can be used, for example, a porous or non-porous conductive substrate made of a metal material such as stainless steel, titanium, aluminum, an aluminum alloy, or a conductive resin. It is done. Examples of the porous conductive substrate include a mesh body, a net body, a punching sheet, a lath body, a porous body, a foam, a fiber group molded body (nonwoven fabric, etc.), and the like. Examples of the non-porous conductive substrate include a foil, a sheet, and a film. The thickness of the conductive substrate is not particularly limited, but is usually 1 to 500 μm, preferably 1 to 50 μm, more preferably 10 to 40 μm, and particularly preferably 10 to 30 μm.

The positive electrode active material layer is provided on one or both surfaces in the thickness direction of the positive electrode current collector, and contains a positive electrode active material capable of inserting and extracting lithium ions. Furthermore, the positive electrode active material layer may contain a conductive agent, a binder, and the like together with the positive electrode active material.
As the positive electrode active material, those commonly used in this field can be used, and examples thereof include lithium-containing composite metal oxides, olivine-type lithium salts, chalcogen compounds, and manganese dioxide. The lithium-containing composite metal oxide is a metal oxide containing lithium and a transition metal or a metal oxide in which a part of the transition metal in the metal oxide is substituted with a different element. Here, examples of the different element include Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, and B. Mn, Al, Co, Ni, Mg and the like are preferable. One kind or two or more kinds of different elements may be used.

Among these positive electrode active materials, lithium-containing composite metal oxides can be preferably used. Specific examples of the lithium-containing composite metal oxide include, for example, Li _x CoO ₂ , Li _x NiO ₂ , Li _x MnO ₂ , Li _x Co _y Ni _1-y O ₂ , and Li _x Co _y M _1-y O _{z. , Li x Ni 1-y M} y O z, Li x Mn 2 O 4, Li x Mn 2-y M y O 4, LiMPO 4, Li 2 MPO 4 F ( in the respective formulas, M is Na, Mg, It represents at least one element selected from the group consisting of Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, V and B. x = 0 to 1.2, y = 0-0.9, z = 2.0-2.3). Here, x value which shows the molar ratio of lithium increases / decreases by charging / discharging. Examples of the olivine type lithium salt include LiFePO ₄ . Examples of the chalcogen compound include titanium disulfide and molybdenum disulfide. A positive electrode active material can be used individually by 1 type, or can use 2 or more types together.

  As the conductive agent, those commonly used in this field can be used, for example, graphites such as natural graphite and artificial graphite, carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black and thermal black. , Conductive fibers such as carbon fibers and metal fibers, metal powders such as carbon fluoride and aluminum, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, phenylene derivatives, etc. And organic conductive materials. A conductive agent can be used individually by 1 type, or can be used in combination of 2 or more type as needed.

  As the binder, those commonly used in this field can be used. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene, polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamideimide, polyacrylonitrile, poly Acrylic acid, polyacrylic acid methyl ester, polyacrylic acid ethyl ester, polyacrylic acid hexyl ester, polymethacrylic acid, polymethacrylic acid methyl ester, polymethacrylic acid ethyl ester, polymethacrylic acid hexyl ester, polyvinyl acetate, polyvinylpyrrolidone, Examples include polyether, polyether sulfone, hexafluoropolypropylene, styrene butadiene rubber, modified acrylic rubber, and carboxymethyl cellulose. Also, two or more monomer compounds selected from tetrafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinylidene fluoride, chlorotrifluoroethylene, ethylene, propylene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid, hexadiene, etc. These copolymers may also be used. A binder can be used individually by 1 type, or can be used in combination of 2 or more type as needed.

  The positive electrode active material layer can be formed, for example, by applying a positive electrode mixture slurry on the surface of the positive electrode current collector, drying, and rolling as necessary. The positive electrode mixture slurry contains a positive electrode active material, and contains a conductive agent, a binder and the like as necessary. The positive electrode mixture slurry can be prepared, for example, by dissolving or dispersing a positive electrode active material and, if necessary, a conductive agent and a binder in an organic solvent. As the organic solvent, for example, dimethylformamide, dimethylacetamide, methylformamide, N-methyl-2-pyrrolidone (NMP), dimethylamine, acetone, cyclohexanone and the like can be used.

  When the positive electrode mixture slurry contains a positive electrode active material, a conductive agent, and a binder, the usage ratio of these three components is not particularly limited, but preferably the positive electrode active material with respect to the total amount of these three components used What is necessary is just to use it so that it may select suitably from the range of 80-98 weight%, 1-10 weight% of electrically conductive agents, and 1-10 weight% of binders, and a total amount may be 100 weight%. The thickness of the positive electrode active material layer is appropriately selected according to various conditions. For example, when the positive electrode active material layer is provided on both surfaces of the positive electrode current collector, the total thickness of the positive electrode active material layer is preferably about 50 to 100 μm. .

  The negative electrode 6 includes a negative electrode current collector (not shown) and a negative electrode active material layer. As the negative electrode current collector, those commonly used in this field can be used, for example, a porous or non-porous conductive substrate made of a metal material such as stainless steel, nickel, copper, copper alloy or a conductive resin. It is done. Examples of the porous conductive substrate include a mesh body, a net body, a punching sheet, a lath body, a porous body, a foam, a fiber group molded body (nonwoven fabric, etc.), and the like. Examples of the non-porous conductive substrate include a foil, a sheet, and a film. The thickness of the porous or non-porous conductive substrate is not particularly limited, but is usually 1 to 500 μm, preferably 1 to 50 μm, more preferably 10 to 40 μm, and particularly preferably 10 to 30 μm.

  The negative electrode active material layer contains an alloy-based negative electrode active material, and may further contain a binder, a conductive agent, a thickener and the like as necessary. The alloy-based negative electrode active material is a metal that occludes and releases lithium by being alloyed with lithium or a compound containing the metal. A known material can be used as the alloy-based negative electrode active material, and examples thereof include an alloy-based negative electrode active material containing silicon, an alloy-based negative electrode active material containing tin, and an alloy-based negative electrode active material containing aluminum. Among these, an alloy-based negative electrode active material containing silicon and an alloy-based negative electrode active material containing tin are preferable.

Examples of the alloy-based negative electrode active material containing silicon include silicon, silicon oxide, silicon nitride, silicon-containing alloy, and silicon compound. Examples of the silicon oxide include silicon oxide represented by the composition formula: SiO _a (0.05 <a <1.95). Examples of the silicon nitride include silicon nitride represented by the composition formula: SiN _b (0 <b <4/3). Examples of the silicon-containing alloy include an alloy containing silicon and one or more elements selected from the group consisting of Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, In, Sn, and Ti. It is done. As the silicon compound, for example, a part of silicon contained in silicon, silicon oxide, silicon nitride or silicon-containing alloy is B, Mg, Ni, Ti, Mo, Co, Ca, Cr, Cu, Fe, Mn, Examples thereof include compounds substituted with one or more elements selected from the group consisting of Nb, Ta, V, W, Zn, C, N and Sn.

Examples of the alloy-based negative electrode active material containing tin include tin, tin oxide, a tin-containing alloy, and a tin compound. Examples of the tin oxide include SnO ₂ and silicon oxide represented by a composition formula: SnO _d (0 <d <2). Examples of the tin-containing alloy include a Ni—Sn alloy, a Mg—Sn alloy, a Fe—Sn alloy, a Cu—Sn alloy, and a Ti—Sn alloy. Examples of the tin compound include SnSiO ₃ , Ni ₂ Sn ₄ , and Mg ₂ Sn.
Examples of the alloy-based negative electrode active material containing aluminum include aluminum alloys such as an Al—Mn alloy, an Al—Mn—V alloy, and an Al—Mn—Cr alloy.
Among these, silicon, tin, silicon oxide, tin oxide and the like are preferable, and silicon, silicon oxide and the like are particularly preferable. An alloy type negative electrode active material can be used individually by 1 type, or can be used in combination of 2 or more type.

  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, drying, and rolling as necessary. The negative electrode mixture slurry can be prepared by dissolving or dispersing an alloy negative electrode active material and, if necessary, a binder, a conductive agent, and a thickener in a solvent. As the binder, the conductive agent, and the solvent, the same materials as those used for the positive electrode mixture slurry can be used. Furthermore, styrene butadiene rubber particles can be used as a binder. Examples of the thickener include carboxymethyl cellulose. Furthermore, if necessary, a general negative electrode active material such as a carbon material can be contained within a range that does not impair the preferable effect of the alloy-based negative electrode active material.

  The negative electrode active material layer can be formed on the surface of the negative electrode current collector according to a known thin film forming method such as sputtering, vapor deposition, or chemical vapor deposition (CVD). The negative electrode active material layer formed by these methods has a content of the alloy-based negative electrode active material of almost 100%, and can achieve high capacity and high output. In addition, when these methods are employed, the thickness of the negative electrode active material layer can be made thinner than before, and therefore, for example, it is easy to cope with downsizing and thinning of portable electronic devices. Therefore, in the present invention, a negative electrode active material layer formed by sputtering, vapor deposition, chemical vapor deposition (CVD), or the like is preferable.

  In the present invention, a lithium metal layer may be further formed on the surface of the negative electrode active material layer. At this time, the amount of the lithium metal may be an amount corresponding to the irreversible capacity stored in the negative electrode active material layer at the first charge / discharge. The lithium metal layer can be formed, for example, by vapor deposition.

  A separator (not shown) is provided between the positive electrode 5 and the negative electrode 6. As the separator, a sheet-like material or a film-like material having a predetermined ion permeability, mechanical strength, insulation, and the like are used. Specific examples of the separator include, for example, porous sheet-like materials or film-like materials such as microporous membranes, woven fabrics, and nonwoven fabrics. The microporous film may be either a single layer film or a multilayer film (composite film). The single layer film is made of one kind of material. The multilayer film (composite film) is a single-layer film stack made of one material or a single-layer film stack made of different materials.

  Various resin materials can be used as the separator material, but polyolefins such as polyethylene and polypropylene are preferable in view of durability, shutdown function, battery safety, and the like. The shutdown function is a function that blocks the through-hole when the battery is abnormally heated, thereby suppressing ion permeation and blocking the battery reaction. If necessary, the separator may be formed by laminating two or more layers of a microporous film, a woven fabric, a non-woven fabric, and the like. The thickness of the separator is generally 10 to 300 μm, preferably 10 to 40 μm, more preferably 10 to 30 μm, and still more preferably 10 to 25 μm. Further, the porosity of the separator is preferably 30 to 70%, more preferably 35 to 60%. Here, the porosity is the ratio of the total volume of the pores existing in the separator to the volume of the separator.

  One end of the positive electrode lead 7 is connected to the positive electrode current collector, and the other end is led out of the lithium ion secondary battery from an opening of an exterior case (not shown). The positive electrode lead 7 is connected to the positive electrode current collector at a position that does not protrude outward of the electrode group 1 from the surface 1x in the thickness direction of the electrode group 1. The connection position of the positive electrode lead 7 is a position facing the axis 1z of the electrode group 1 at the end 5b opposite to the axis 5's end 5a of the positive electrode 5. Accordingly, the positive electrode lead 7 is provided on the inner side of the surface 1x in the thickness direction of the electrode group 1 and does not protrude outward from the surface 1x. As the material of the positive electrode lead 7, those commonly used in this field can be used, and examples thereof include aluminum.

  One end of the negative electrode lead 8 is connected to the negative electrode current collector, and the other end is led out of the lithium ion secondary battery from an opening of an exterior case (not shown). The negative electrode lead 8 is connected to the negative electrode current collector at a position that does not protrude outward of the electrode group 1 from the surface 1 y in the thickness direction of the electrode group 1. The connection position of the negative electrode lead 8 is a position facing the axis 1z of the electrode group 1 at the end 6b opposite to the axis 6 of the negative electrode 6a. Thereby, the negative electrode lead 8 is provided inside the surface 1y in the thickness direction of the electrode group 1 and does not protrude outward from the surface 1y. The surface 1y is a surface facing the surface 1x. The lead-out direction of the negative electrode lead 8 to the outside is the same as the lead-out direction of the positive electrode lead 7 to the outside. As the material of the negative electrode lead 8, those commonly used in this field can be used, and examples thereof include nickel.

  With the above configuration, when the electrode group 1 is pressurized in the thickness direction, it is possible to prevent the electrode group 1 from being applied with an excessive pressure. For example, if the first charge / discharge is performed under pressure with the positive electrode lead 7 and the negative electrode lead 8 connected to the surfaces 1x and 1y in the thickness direction of the electrode group 1, the electrode group 1 is locally more than necessary. It has been found by the present inventors that pressure may be applied to cause partial deformation and peeling of the active material layer. Such deformation and peeling not only cause the battery to swell and deteriorate the charge / discharge cycle characteristics, but can also cause an internal short circuit.

  Therefore, by adopting the configuration as in the present embodiment, it is possible to obtain a lithium ion secondary battery in which the expansion of the battery, the occurrence of an internal short circuit, the deterioration of charge / discharge cycle characteristics, and the like are further suppressed. In Patent Document 1, there is no special description of the lead attachment position.

  In the present embodiment, the lead-out direction of the positive electrode lead 7 and the negative electrode lead 8 to the outside of the lithium ion secondary battery is the same, but is not limited thereto. That is, as shown in FIG. 1C, an electrode group 1a in which the lead-out direction of the positive electrode lead 7 and the negative electrode lead 8 is opposite may be configured.

The electrode group 1 is impregnated with an electrolyte having lithium ion conductivity. As the electrolyte having lithium ion conductivity, a nonaqueous electrolyte having lithium ion conductivity is preferable. Examples of the non-aqueous electrolyte include a liquid non-aqueous electrolyte, a gel-like non-aqueous electrolyte, a solid electrolyte (for example, a polymer solid electrolyte), and the like.
The liquid non-aqueous electrolyte contains a solute (supporting salt) and a non-aqueous solvent, and further contains various additives as necessary. Solutes usually dissolve in non-aqueous solvents. For example, the separator is impregnated with the liquid non-aqueous electrolyte.

As the solute, those commonly used in this field can be used. For example, 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 carboxylates, LiCl, LiBr, LiI, LiBCl ₄ , borates, imide salts and the like. Examples of borates include lithium bis (1,2-benzenediolate (2-)-O, O ') and bis (2,3-naphthalenedioleate (2-)-O, O') boric acid. Lithium, bis (2,2′-biphenyldiolate (2-)-O, O ′) lithium borate, bis (5-fluoro-2-olate-1-benzenesulfonic acid-O, O ′) lithium borate Etc. Examples of the imide salts include lithium bistrifluoromethanesulfonate imide ((CF ₃ SO ₂ ) ₂ NLi), lithium trifluoromethanesulfonate nonafluorobutanesulfonate ((CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ) NLi) ), Lithium bispentafluoroethanesulfonate imide ((C ₂ F ₅ SO ₂ ) ₂ NLi), and the like. A solute may be used individually by 1 type, or may be used in combination of 2 or more type as needed. The amount of the solute dissolved in the non-aqueous solvent is preferably in the range of 0.5 to 2 mol / L.

  As the non-aqueous solvent, those commonly used in this field can be used, and examples thereof include cyclic carbonate esters, chain carbonate esters, and cyclic carboxylic acid esters. Examples of the cyclic carbonate include propylene carbonate (PC) and ethylene carbonate (EC). Examples of the chain carbonate include diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and the like. Examples of the cyclic carboxylic acid ester include γ-butyrolactone (GBL) and γ-valerolactone (GVL). A non-aqueous solvent may be used individually by 1 type, or may be used in combination of 2 or more type as needed.

  Examples of the additive include a material that improves charge / discharge efficiency and a material that inactivates the battery. A material that improves charge / discharge efficiency, for example, decomposes on the negative electrode to form a film having high lithium ion conductivity, and improves charge / discharge efficiency. Specific examples of such materials include, for example, vinylene carbonate (VC), 4-methyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, 4-ethyl vinylene carbonate, 4,5-diethyl vinylene carbonate, 4-propyl vinylene. Examples include carbonate, 4,5-dipropyl vinylene carbonate, 4-phenyl vinylene carbonate, 4,5-diphenyl vinylene carbonate, vinyl ethylene carbonate (VEC), divinyl ethylene carbonate, and the like. These may be used alone or in combination of two or more. Among these, at least one selected from vinylene carbonate, vinyl ethylene carbonate, and divinyl ethylene carbonate is preferable. In the above compound, part of the hydrogen atoms may be substituted with fluorine atoms.

  The material that inactivates the battery inactivates the battery by, for example, decomposing when the battery is overcharged to form a film on the electrode surface. Examples of such a material include benzene derivatives. Examples of the benzene derivative include a benzene compound containing a phenyl group and a cyclic compound group adjacent to the phenyl group. As the cyclic compound group, for example, a phenyl group, a cyclic ether group, a cyclic ester group, a cycloalkyl group, a phenoxy group and the like are preferable. Specific examples of the benzene derivative include cyclohexylbenzene, biphenyl, diphenyl ether, and the like. A benzene derivative can be used individually by 1 type, or can be used in combination of 2 or more type. However, the content of the benzene derivative in the liquid nonaqueous electrolyte is preferably 10 parts by volume or less with respect to 100 parts by volume of the nonaqueous solvent.

  The gel-like non-aqueous electrolyte includes a liquid non-aqueous electrolyte and a polymer material that holds the liquid non-aqueous electrolyte. The polymer material used here is capable of gelling a liquid material. As the polymer material, those commonly used in this field can be used, and examples thereof include polyvinylidene fluoride, polyacrylonitrile, polyethylene oxide, polyvinyl chloride, and polyacrylate.

  The solid electrolyte includes, for example, a solute (supporting salt) and a polymer material. Solutes similar to those exemplified above can be used. Examples of the polymer material include polyethylene oxide (PEO), polypropylene oxide (PPO), a copolymer of ethylene oxide and propylene oxide, and the like.

  For example, a metal case or a laminated laminate film case can be used as the outer case. The outer case is formed with an opening for accommodating a wound electrode group, an electrolyte, and the like inside the outer case. The gasket is a sealing member used to seal the opening of the outer case. Another general sealing member may be used in combination with the gasket. The opening of the outer case may be sealed with a sealing member other than the gasket. Moreover, you may seal directly the opening of an exterior case by welding etc., without using a sealing member.

  A lithium ion secondary battery can be manufactured as follows, for example. First, the positive electrode 5 and the negative electrode 6 are overlapped via a separator, and this is wound into a flat plate shape to produce the electrode group 1. Next, one end of the positive electrode lead 7 is connected to a predetermined position in the positive electrode current collector of the positive electrode 5, and one end of the negative electrode lead 8 is connected to a predetermined position in the negative electrode current collector of the negative electrode 6. This is inserted into the outer case, the other ends of the positive electrode lead 7 and the negative electrode lead 8 are led out of the outer case, and a nonaqueous electrolyte is injected into the outer case. In this state, a lithium ion secondary battery is obtained by welding the opening through a gasket while vacuuming the inside of the outer case.

In the present invention, the first charge / discharge is performed under pressure on the lithium ion secondary battery obtained above. The pressurizing method is not particularly limited, and examples thereof include press pressurization and hydrostatic pressurization.
In press pressurization, pressure is mainly applied to a portion in which the electrode group 1 of the lithium ion secondary battery is accommodated, and pressure in the thickness direction is applied to the electrode group 1. In press pressing, a general press pressing machine can be used. The pressure is preferably 1.0 × 10 ^{5 to} 1.0 × 10 ⁶ N / m ² . When the pressure is less than 1.0 × 10 ⁵ N / m ² , the effect of preventing the occurrence of battery swelling due to repeated charge / discharge is insufficient, and battery swelling may easily occur. On the other hand, when the pressure exceeds 1.0 × 10 ⁶ N / m ² , no further improvement in the effect is recognized, and in some cases, the active material layer is deformed, peeled off from the current collector, etc. There is a risk of swelling and internal short circuit. The pressurization is preferably performed at a temperature of about 10 to 30 ° C. and is completed in about 5 to 15 hours.

  In the hydrostatic pressure application, a substantially uniform pressure is applied in the thickness direction to the entire lithium ion secondary battery. The hydrostatic pressurization includes CIP (Cold Isostatic press) method, HIP (Hot Isostatic press) method, hot press method and the like. In the CIP method, for example, hydrostatic pressure is applied at a temperature of about 5 to 50 ° C., preferably about 10 to 30 ° C. In the HIP method, for example, hydrostatic pressure is applied under heating at 65 ° C. or higher. Considering that the object to be pressed is a lithium ion secondary battery, it is preferable to use the CIP method among these methods. The CIP method can be performed with a simple apparatus, has an advantage that heat resistance is not required for a coating film for covering an object described later, and is excellent in practicality as a manufacturing process for industrial products.

  As a specific method of hydrostatic pressure pressurization, for example, the surface of a lithium ion secondary battery is covered with a coating film for covering an object having a liquid barrier property, and this is loaded into a hydrostatic pressure pressurizer and hydrostatic pressure pressurization is performed. The method of giving is mentioned. In the case of the CIP method, for example, a synthetic resin material such as polyvinyl chloride, polyethylene, or polypropylene, or a rubber material such as natural rubber or isoprene rubber can be used as the coating film for covering an object. The coating film for covering the object can be formed on the surface of the lithium ion secondary battery by, for example, a dipping method, a vacuum packing method, or the like.

  Also, the lithium ion secondary battery is inserted into a thin metal capsule, and the metal capsule is sealed in a vacuum and sealed by electron beam welding, and this is loaded into a hydrostatic pressure device and subjected to hydrostatic pressure. A method is mentioned. Examples of the material of the metal capsule include copper and stainless steel.

The hydrostatic pressure (pressure) is not particularly limited, but is preferably 1.0 × 10 ^{5 to} 1.0 × 10 ⁶ N / m ² . When the pressure is less than 1.0 × 10 ⁵ N / m ² , the effect of preventing the occurrence of battery swelling due to repeated charge / discharge is insufficient, and battery swelling may easily occur. On the other hand, when the pressure exceeds 1.0 × 10 ⁶ N / m ² , no further improvement in the effect is recognized, and in some cases, the active material layer is deformed, peeled off from the current collector, etc. There is a risk of swelling and internal short circuit. In addition, there is a problem that a large apparatus is required and the manufacturing cost becomes high. The hydrostatic pressure is applied, for example, at a temperature of about 5 to 50 ° C., preferably about 10 to 30 ° C. and under the pressure, and is completed in about 5 to 15 hours.

On the other hand, the conditions for the first charge / discharge range from a wide range depending on the type of active material contained in the lithium ion secondary battery and the thickness of the active material layer, the configuration other than the active material, the use of the lithium ion secondary battery, etc. Although it can be selected as appropriate, an example is shown below.
The battery is charged at a constant current of 0.2 ItA until the battery voltage reaches 4.05 V, then charged at 4.2 V until the current value reaches 0.05 ItA, and then the battery voltage is 2 V at a constant current of 0.2 ItA. The discharge cycle is performed once until the voltage decreases to the first charge / discharge.
Thus, the first charge / discharge is performed under hydrostatic pressure, and the lithium ion secondary battery of the present invention is obtained.

  FIG. 2 is a drawing schematically showing a configuration of a main part (electrode group 2) of a lithium ion secondary battery which is one embodiment of the present invention. FIG. 2A is a longitudinal sectional view. In addition, illustration of a separator is abbreviate | omitted in Fig.2 (a). The separator is interposed between the positive electrode 5 and the negative electrode 6. FIG. 2B is a top view. FIG. 2C is a top view schematically showing the configuration of the electrode group 2a of another embodiment.

  The electrode group 2 is a flat wound electrode group similar to the electrode group 1, and corresponding portions are denoted by the same reference numerals and description thereof is omitted. In the electrode group 2, an end portion 5 b opposite to the axial line side end portion 5 a of the positive electrode 5 and an end portion 6 b opposite to the axial line side end portion 6 a of the negative electrode 6 are perpendicular to the thickness direction of the electrode group 2. In such a direction, the positive electrode 5 and the negative electrode 6 are wound so as to be located on one side of the electrode group 2.

  One end of the positive electrode lead 7 is connected to the positive electrode current collector, and the other end is led out of the lithium ion secondary battery from an opening of an exterior case (not shown). The positive electrode lead 7 is connected to the positive electrode current collector at a position where the positive electrode lead 7 does not protrude outward from the surface 2x of the electrode group 2 in the thickness direction. The connection position of the positive electrode lead 7 is a position facing the axis line 2z of the electrode group 2 at the end portion 5b opposite to the axial line side end portion 5a of the positive electrode 5. Accordingly, the positive electrode lead 7 is provided on the inner side of the surface 2x in the thickness direction of the electrode group 2, and does not protrude outward from the surface 2x.

  One end of the negative electrode lead 8 is connected to the negative electrode current collector, and the other end is led out of the lithium ion secondary battery from an opening of an exterior case (not shown). The negative electrode lead 8 is connected to the negative electrode current collector at a position that does not protrude outward of the electrode group 2 from the surface 2x in the thickness direction of the electrode group 2. The connection position of the negative electrode lead 8 is a position facing the axis 2z of the electrode group 2 at the end 6b opposite to the axis 6 of the negative electrode 6. Accordingly, the negative electrode lead 8 is provided on the inner side of the surface 2x in the thickness direction of the electrode group 2 and does not protrude outward from the surface 2x.

  The positive electrode lead 7 and the negative electrode lead 8 are respectively connected to the positive electrode 5 and the negative electrode 6 at the end on the same side of the electrode group 2 in the direction perpendicular to the thickness direction of the electrode group 2. An active material layer is not formed at the connection portion. The lead-out direction of the positive electrode lead 7 and the negative electrode lead 8 to the outside is the same direction in the direction in which the axis 2z of the electrode group 2 extends. The lead-out direction is not limited thereto, and may be configured as an electrode group 2a shown in FIG. In the electrode group 2a, the positive electrode lead 7 and the negative electrode lead 8 are led out to the opposite side in the direction in which the axis of the electrode group 2a extends.

  With the above configuration, when the lithium ion secondary battery is pressurized and pressed, the electrode group 2 is not locally subjected to an excessive pressure. For this reason, there is no lithium ion secondary battery in which the active material layer is not partially deformed or peeled, the battery does not swell, the internal short circuit does not occur, and the charge / discharge cycle is practically satisfactory. can get.

  FIG. 3 is a drawing schematically showing a configuration of a main part (electrode group 3) of a lithium ion secondary battery which is one embodiment of the present invention. FIG. 3A is a longitudinal sectional view. In addition, illustration of a separator is abbreviate | omitted in Fig.3 (a). The separator is interposed between the positive electrode 5 and the negative electrode 6. FIG. 3B is a top view. FIG.3 (c) is a top view which shows typically the structure of the electrode group 3a of another embodiment.

  The electrode group 3 is a flat wound electrode group similar to the electrode group 1, and corresponding portions are denoted by the same reference numerals and description thereof is omitted. In the electrode group 3, an end portion 5 b opposite to the axial line side end portion 5 a of the positive electrode 5 and an end portion 6 b opposite to the axial line side end portion 6 a of the negative electrode 6 are perpendicular to the thickness direction of the electrode 1. In the direction, the positive electrode 5 and the negative electrode 6 are wound so as to be located on opposite sides. The difference from the electrode group 1 is that the end 5b of the positive electrode 5 opposite to the axial end 5a is bent inward from the surface 3x of the electrode group 3 in the thickness direction. Similarly, the end 6 b opposite to the axial end 6 a of the negative electrode 6 is bent inward from the surface 3 y in the thickness direction of the electrode group 3.

  One end of the positive electrode lead 7 is connected to the positive electrode current collector, and the other end is led out of the lithium ion secondary battery from an opening of an exterior case (not shown). The positive electrode lead 7 is connected to the positive electrode current collector so as not to protrude outward from the surface 3x of the electrode group 3 in the thickness direction. Specifically, the positive electrode lead 7 is connected to the positive electrode current collector exposed at the surface following the surface 3x in the end portion 5b of the positive electrode 5. However, since the end portion 5b of the positive electrode 5 is bent inward from the surface 3x as described above, the positive electrode lead 7 does not protrude outward from the surface 3x.

  On the other hand, one end of the negative electrode lead 8 is connected to the negative electrode current collector, and the other end is led out of the lithium ion secondary battery from an opening of an exterior case (not shown). The negative electrode lead 8 is connected to the negative electrode current collector so as not to protrude outward from the surface 2x of the electrode group 3 in the thickness direction. Specifically, the negative electrode lead 8 is connected to the negative electrode current collector exposed on the surface following the surface 3 y in the end 6 b of the negative electrode 6. However, since the end 6b of the negative electrode 6 is bent inward from the surface 3y as described above, the negative electrode lead 8 does not protrude outward from the surface 3y.

  The positive electrode lead 7 and the negative electrode lead 8 are respectively connected to the positive electrode current collector and the negative electrode current collector at the end opposite to the electrode group 3 in the direction perpendicular to the thickness direction of the electrode group 3. An active material layer is not formed at the connection portion. Further, the lead-out direction of the positive electrode lead 7 and the negative electrode lead 8 to the outside is the same as the direction in which the axis 3z of the electrode group 3 extends. The lead-out direction is not limited thereto, and may be configured as an electrode group 3a shown in FIG. In the electrode group 3a, the positive electrode lead 7 and the negative electrode lead 8 are led out to the opposite side in the direction in which the axis of the electrode group 3a extends.

  With the above configuration, when the wound electrode group 3 is hydrostatically pressurized, no excessive pressure is locally applied to the wound electrode group 3. For this reason, there is no lithium ion secondary battery in which the active material layer is not partially deformed or peeled, the battery does not swell, the internal short circuit does not occur, and the charge / discharge cycle is practically satisfactory. can get.

  FIG. 4 is a top view schematically showing a configuration of a main part of a lithium ion secondary battery which is one embodiment of the present invention. FIG. 4A is a top view schematically showing the configuration of the positive electrode current collector 10 (negative electrode current collector 11). FIG. 4B to FIG. 4D are top views schematically showing the configuration of the electrode groups 12, 13, and 14.

  The positive electrode current collector 10 includes a current collector body 10a and a lead mounting portion 10b. The current collector main body 10a is a rectangular metal plate-like member, and one end in the longitudinal direction thereof is an axial end 10x, and the other end is an end 10y opposite to the axial end 10x. The lead attachment portion 10b is formed at the end portion 10y of the current collector body 10a so as to continue from the current collector body 10a and protrude outward from the current collector body 10a. As shown in FIG. 4, the lead attachment portion 10 b is preferably formed so as to protrude in the short direction of the positive electrode current collector 10 (that is, the direction in which the axis extends when the positive electrode current collector 10 is wound). . A positive electrode active material layer is formed on the surface of the positive electrode current collector 10 except for the lead attachment portion 10b.

  The negative electrode current collector 11 also has the same configuration as the positive electrode current collector 10. That is, the negative electrode current collector 11 includes a current collector main body 11a and a lead attachment portion 11b. The current collector main body 11a is a rectangular metal plate-like member, and one end in the longitudinal direction thereof is an axial end 11x, and the other end is an end 11y opposite to the axial end 11x. The lead attachment portion 11b is formed at the end portion 11y of the current collector body 11a so as to continue from the current collector body 11a and protrude outward from the current collector body 11a. As shown in FIG. 4, the lead attachment portion 11b is preferably formed so as to protrude in the short direction of the negative electrode current collector 11 (that is, the direction in which the axis extends when the negative electrode current collector 11 is wound). . On the surface of the negative electrode current collector 11, a negative electrode active material layer is formed except for the lead attachment portion 11b.

  The electrode group 12 shown in FIG. 4B is a flat wound electrode group in which the positive electrode 15 and the negative electrode 16 are overlapped and wound into a flat plate shape via a separator (not shown). The positive electrode 15 is obtained by forming a positive electrode active material layer on the surface of the positive electrode current collector 10 excluding the lead attachment portion 10b. The negative electrode 16 is obtained by forming a negative electrode active material layer containing an alloy-based negative electrode active material on the surface of the negative electrode current collector 11 excluding the lead attachment portion 11b. In the electrode group 12, the positive electrode 15, the negative electrode 16, and the lead attachment part 10 b of the positive electrode current collector 10 and the lead attachment part 11 b of the negative electrode current collector 11 protrude in the same direction in the extending direction of the electrode group 12. Is wound through a separator.

  In the present embodiment, the positive electrode lead 7 and the negative electrode lead 8 are connected to the back surfaces of the lead mounting portions 10b and 11b, respectively. However, the present invention is not limited to this, and these may be connected to the surface of the lead mounting portions 10b and 11b. Good. With this configuration, it is possible to prevent an extra pressure from being locally applied to the electrode group 17 when the lithium ion secondary battery is pressurized. As a result, partial deformation and peeling of the active material layer are less likely to occur, and a lithium ion secondary battery that does not cause battery swelling or internal short circuit can be obtained.

  The electrode group 13 shown in FIG. 4C has a configuration similar to that of the electrode group 12, and corresponding portions are denoted by the same reference numerals and description thereof is omitted. In the electrode group 13, the lead mounting part 10b of the positive electrode current collector 10 and the lead mounting part 11b of the negative electrode current collector 11 protrude to the opposite side in the direction in which the axis of the electrode group 13 extends and are perpendicular to the direction in which the axis extends. It is comprised so that it may be located in the edge part on the opposite side in each direction. Even with such a configuration, the same effect as the electrode group 12 can be obtained.

  The electrode group 14 shown in FIG. 4 (d) has a configuration similar to that of the electrode group 12, and corresponding portions are denoted by the same reference numerals and description thereof is omitted. In the electrode group 14, the lead mounting portion 10b and the negative electrode current collector 10b of the positive electrode current collector 10 protrude on the opposite side in the direction in which the axis of the electrode group 14 extends, and are the same side in the direction perpendicular to the direction in which the axis extends. It is comprised so that it may be located in the edge part. Even with such a configuration, the same effect as the wound electrode 12 can be obtained.

  In the lithium ion secondary battery of the present invention, the negative electrode active material layer is preferably an aggregate of a plurality of columnar bodies. This columnar body is formed to extend outward from the surface of the negative electrode current collector, and contains an alloy-based negative electrode active material. Adjacent columnar bodies are formed to be spaced apart from each other. In the case of forming a negative electrode active material layer that is an aggregate of such columnar bodies, it is preferable to provide a plurality of convex portions on the surface of the negative electrode current collector and form the columnar bodies on the surface of the convex portions.

FIG. 5 is a longitudinal sectional view schematically showing the configuration of the negative electrode 20 used in the present invention. FIG. 6 is a perspective view schematically showing the configuration of the negative electrode current collector 21 included in the negative electrode 20 shown in FIG. FIG. 7 is a longitudinal sectional view schematically showing the configuration of the columnar body 24 included in the negative electrode active material layer 23 of the negative electrode 20 shown in FIG. FIG. 8 is a side view schematically showing the configuration of the electron beam evaporation apparatus 30 for producing the columnar body 24.
The negative electrode 20 includes a negative electrode current collector 21 and a negative electrode active material layer 23. The negative electrode 20 is provided such that the negative electrode active material layer 23 faces a positive electrode (not shown) with a separator 25 interposed therebetween.
As shown in FIG. 6, the negative electrode current collector 21 is characterized in that a plurality of convex portions 22 are provided on both or one of the surfaces in the thickness direction.

  The convex portion 22 is a protrusion provided so as to extend from the surface 21 a in the thickness direction of the negative electrode current collector 21 (hereinafter simply referred to as “surface 21 a”) toward the outside of the negative electrode current collector 21. The height of the convex portion 22 is the length from the surface 21a to the portion (the most advanced portion) farthest from the surface 21a of the convex portion 22 in the direction perpendicular to the surface 21a on which the convex portion 22 is formed. That's it. The height of the convex portion 22 is not particularly limited, but is preferably formed such that the average height is about 3 to 10 μm. Moreover, although the cross-sectional diameter in the direction parallel to the surface 21a of the convex part 22 is not specifically limited, For example, it is 1-50 micrometers.

  The average height of the protrusions 22 is obtained by, for example, observing the cross section of the current collector 1 in the thickness direction of the negative electrode current collector 21 with a scanning electron microscope (SEM). It can be determined by measuring and calculating an average value from the measured values obtained. Both the convex portion 22 and the cross-sectional diameter can be measured in the same manner as the height of the convex portion 22. Note that the plurality of convex portions 22 do not have to be formed with the same height or the same cross-sectional diameter.

  The convex portion 22 has a substantially planar top at the tip portion in the growth direction. The growth direction is a direction from the surface 21 a toward the outside of the negative electrode current collector 21. Since the convex portion 22 has a flat top at the tip portion, the bonding property between the convex portion 22 and the columnar body 24 is improved. In order to increase the bonding strength, it is more preferable that the flat surface of the tip portion is substantially parallel to the surface 21a.

  The shape of the convex part 22 is circular in this Embodiment. The shape of the convex part 22 here is the convex part as viewed from above in the vertical direction when the current collector 21 is placed so that the surface opposite to the surface 21a of the negative electrode current collector 21 coincides with the horizontal plane. 22 shape. In addition, the shape of the convex part 22 is not limited to circular, For example, a polygon, an ellipse, etc. may be sufficient. The polygon is preferably a triangle to an octagon in view of manufacturing costs and the like. Furthermore, a parallelogram, trapezoid, rhombus, etc. may be used.

The number of the protrusions 22 and the spacing between the protrusions 22 are not particularly limited, depending on the size of the protrusions 22 (height, cross-sectional diameter, etc.), the size of the columnar body 24 provided on the surface of the protrusions 22, and the like. Are appropriately selected. If an example of the number of the convex parts 22 is shown, it is about 10,000 to 10 million pieces / cm ² . Moreover, it is preferable to form the convex portions 22 so that the distance between the axes of the adjacent convex portions 22 is about 2 to 100 μm.

  A protrusion (not shown) may be formed on the surface of the convex portion 22. Thereby, for example, the bondability between the convex portion 22 and the columnar body 24 is further improved, and peeling of the columnar body 24 from the convex portion 22, peeling propagation, and the like are more reliably prevented. The protrusion is provided so as to protrude from the surface of the protrusion 22 to the outside of the protrusion 22. A plurality of protrusions having a size smaller than that of the protrusion 22 may be formed. Further, the protrusion may be formed on the side surface of the convex portion 22 so as to extend in the circumferential direction and / or the growth direction of the convex portion 22. Moreover, when the convex part 22 has the planar top part in the front-end | tip part, 1 or several protrusion smaller than the convex part 22 may be formed in a top part, and also 1 or several extended long in one direction The protrusion may be formed on the top.

  The negative electrode current collector 21 can be manufactured using a technique for forming irregularities on a metal foil, a metal sheet, or the like, for example. Specifically, for example, when the shape of the convex portion 22 is a male shape, a roll (hereinafter referred to as “convex”) in which concave portions having a female shape corresponding to the convex portion 22 are regularly arranged on the surface in the axial direction. Part forming roll ”). Convex portion 22 is formed on one surface of a plate-like material such as a foil, sheet, or film having a smooth surface (hereinafter, simply referred to as “plate material for negative electrode current collector”) made of a metal material suitable for negative electrode current collector 21. In this case, a convex forming roll and a roll having a smooth surface may be press-contacted so that the respective axes are parallel to each other, and the negative electrode current collector plate may be passed through the press-contacting portion to perform pressure molding. . In this case, at least the surface of the roll having a smooth surface is preferably formed of an elastic material.

  When the convex portions 22 are formed on both surfaces of the negative electrode current collector plate, the two convex portion forming rolls are brought into pressure contact with each other so that their respective axes are parallel to each other, and the negative electrode current collector is placed on the pressure contact portion. What is necessary is just to press-mold by making the plate-shaped material pass. Here, the pressure contact pressure of the roll is the material and thickness of the negative electrode current collector plate, the shape and dimensions of the convex portion 22, the negative electrode current collector plate after pressure molding, that is, the thickness of the negative electrode current collector 21. The value is appropriately selected according to the set value.

  The convex portion forming roll can be manufactured, for example, by forming a hole which is a concave portion having a female shape corresponding to the convex portion 22 at a predetermined position on the surface of the ceramic roll. Here, as the ceramic roll, for example, a roll including a core roll and a sprayed layer is used. For the core roll, for example, a roll made of iron, stainless steel or the like can be used. The sprayed layer is formed by uniformly spraying a ceramic material such as chromium oxide on the surface of the core roll. Holes are formed in the sprayed layer. For forming the hole, for example, a general laser used for forming a ceramic material or the like can be used.

  The convex forming roll of another form includes a core roll, a base layer, and a sprayed layer. The core roll is the same as the ceramic roll core roll. The underlayer is formed on the core roll surface. A recess having a female shape corresponding to the convex portion 22 is formed on the surface of the base layer. In order to form a recess in the base layer, for example, a resin sheet having a recess on one side is molded, and the surface of the resin sheet opposite to the surface on which the recess is formed is wound around the core roll surface. What is necessary is just to adhere. Here, as the synthetic resin, those having high mechanical strength are preferable, for example, thermosetting resins such as unsaturated polyester, thermosetting polyimide, epoxy resin and fluororesin, and thermoplastic resins such as polyamide and polyether ether ketone. Can be mentioned. The sprayed layer is formed by spraying a ceramic material such as chromium oxide along the surface irregularities of the underlayer. Accordingly, the recess formed in the underlayer is formed larger by the layer thickness of the thermal spray layer than the design dimension in consideration of the layer thickness of the thermal spray layer.

  Another embodiment of the convex forming roll includes a core roll and a cemented carbide layer. The core roll is the same as the ceramic roll core roll. The cemented carbide layer is formed on the surface of the core roll and includes a cemented carbide such as tungsten carbide. The cemented carbide layer can be formed by shrink-fitting or cold-fitting a cylindrical cemented carbide to the core roll. The shrink fitting of the cemented carbide layer is to warm and expand the cylindrical cemented carbide and fit it to the core roll. The cold fitting of the cemented carbide layer means that the core roll is cooled and contracted and inserted into a cemented carbide cylinder. On the surface of the cemented carbide layer, for example, a recess having a female shape corresponding to the convex portion 22 is formed by laser processing.

  In another form of the convex portion forming roll, a recess having a female shape corresponding to the convex portion 22 is formed on the surface of the hard iron roll by, for example, laser processing. A hard iron-type roll is used for rolling manufacture of metal foil, for example. Examples of the hard iron roll include a roll made of high-speed steel, forged steel, or the like. High-speed steel is an iron-based material that has been added with a metal such as molybdenum, tungsten, or vanadium and heat treated to increase its hardness. Forged steel is a steel ingot made by casting a steel in a mold or a steel piece produced from the steel ingot, forged with a press and hammer, or forged by rolling and forging. It is an iron-based material manufactured by heat treatment.

  Further, the one or more protrusions on the surface of the convex portion 22 can be formed, for example, by forming a resist pattern on the surface of the convex portion 22 by a photoresist method and performing metal plating according to the pattern. The protrusions can also be formed by forming the protrusions 22 with dimensions larger than the design dimensions and removing a predetermined portion of the surface of the protrusions 22 by an etching method. A method combining a photoresist method and a plating method can also be used for forming the convex portions 22 themselves.

  For example, as shown in FIG. 5, the negative electrode active material layer 23 is formed as an aggregate of a plurality of columnar bodies 24 provided so as to extend from the surface of the convex portion 22 toward the outside of the negative electrode current collector 21. The columnar body 24 is provided to extend in a direction perpendicular to the surface 21 a of the negative electrode current collector 21 or with an inclination with respect to the perpendicular direction. Further, since the plurality of columnar bodies 24 are provided so as to be separated from each other with a gap between the adjacent columnar bodies 24, stress due to expansion and contraction during charge / discharge is alleviated, and the negative electrode active The material layer 23 becomes difficult to peel off from the convex portion 22, and deformation of the negative electrode current collector 21 hardly occurs.

  As shown in FIG. 7, the columnar body 24 is more preferably formed as a columnar body formed by stacking eight columnar chunks 24a, 24b, 24c, 24d, 24e, 24f, 24g, and 24h. When forming the negative electrode active material layer 23, first, the columnar mass 24 a is formed so as to cover the top of the convex portion 22 and a part of the side surface subsequent thereto. Next, the columnar chunk 24b is formed so as to cover the remaining side surface of the convex portion 22 and a part of the top surface of the columnar chunk 24a. That is, in FIG. 7, the columnar chunk 24 a is formed at one end including the top of the convex portion 22, and the columnar chunk 24 b partially overlaps the columnar chunk 24 a, but the remaining portion is the other portion of the convex portion 22. Formed at the end. Further, the columnar chunk 24c is formed so as to cover the rest of the top surface of the columnar chunk 24a and a part of the top surface of the columnar chunk 24b. That is, the columnar chunk 24c is formed so as to mainly contact the columnar chunk 24a. Further, the columnar chunk 24d is formed mainly in contact with the columnar chunk 24b. Similarly, the columnar body 24 is formed by alternately stacking the columnar chunks 24e, 24f, 24g, and 24h.

  The negative electrode active material layer 23 can be formed by, for example, an electron beam evaporation apparatus 30 shown in FIG. In FIG. 8, each member in the vapor deposition apparatus 30 is also indicated by a solid line. The vapor deposition apparatus 30 includes a chamber 31, a first pipe 32, a fixing base 33, a nozzle 34, a target 35, an electron beam generator (not shown), a power source 36, and a second pipe (not shown). The chamber 31 is a pressure-resistant container-like member having an internal space, and the first pipe 32, the fixing base 33, the nozzle 34, and the target 35 are accommodated therein. The first pipe 32 has one end connected to the nozzle 34 and the other end extending outward from the chamber 31 and is connected to a source gas cylinder or source gas production apparatus (not shown) via a mass flow controller (not shown). Examples of the source gas include oxygen and nitrogen. The first pipe 32 supplies the raw material gas to the nozzle 34.

  The fixing base 33 is a plate-like member, is supported so as to be angularly displaced or rotatable, and is provided so that the negative electrode current collector 21 can be fixed to one surface in the thickness direction. The angular displacement (rotation) of the fixed base 33 is performed between a position indicated by a solid line and a position indicated by a dashed line in FIG. The position indicated by the solid line is that the surface of the fixed base 33 on the side where the negative electrode current collector 21 is fixed faces the nozzle 34 vertically below, and the angle formed by the fixed base 33 and the horizontal straight line is α °. It is a certain position. The position indicated by the one-dot broken line is such that the surface of the fixed base 33 on the side where the negative electrode current collector 21 is fixed faces the nozzle 34 vertically downward, and the angle formed by the fixed base 33 and the horizontal straight line is (180 It is a position that is −α) °. The angle α ° can be appropriately selected according to the dimensions of the columnar body 24 to be formed.

  The nozzle 34 is provided between the fixed base 33 and the target 35 in the vertical direction, and one end of the first pipe 32 is connected thereto. The nozzle 34 mixes the vapor of the alloy-based negative electrode active material rising upward in the vertical direction from the target 35 and the raw material gas supplied from the first pipe 32, and is fixed to the surface of the fixed base 33. It is supplied to the body 21 surface. The target 35 accommodates an alloy-based negative electrode active material or its raw material. The electron beam generator irradiates the alloy-based negative electrode active material accommodated in the target 35 or its raw material with an electron beam and heats it to generate these vapors. The power source 36 is provided outside the chamber 31 and is electrically connected to the electron beam generator, and applies a voltage for generating the electron beam to the electron beam generator. The second pipe introduces a gas that becomes the atmosphere in the chamber 31. An electron beam vapor deposition apparatus having the same configuration as the vapor deposition apparatus 30 is commercially available from ULVAC, Inc., for example.

  According to the electron beam evaporation apparatus 30, first, the negative electrode current collector 21 is fixed to the fixing base 33, and oxygen gas is introduced into the chamber 31. In this state, the target 35 is irradiated with an electron beam to heat the alloy-based negative electrode active material or its raw material to generate its vapor. In the present embodiment, silicon is used as the alloy-based negative electrode active material. The generated steam rises upward in the vertical direction, and when it passes through the nozzle 34, it is mixed with the raw material gas, and then rises and is supplied to the surface of the negative electrode current collector 21 fixed to the fixed base 33. A layer containing silicon and oxygen is formed on the surface of the protrusions 22 that are not. At this time, the columnar block 24a shown in FIG. 7 is formed on the surface of the convex portion by arranging the fixing base 33 at the position of the solid line. Next, the columnar block 24b shown in FIG. 7 is formed by angularly displacing the fixed base 33 to the position of the one-dot broken line. In this way, by alternately angularly changing the position of the fixing base 33, the negative electrode active material layer 23 which is a laminate of the eight columnar chunks 24a, 24b, 24c, 24d, 24e, 24f, 24g, 24h shown in FIG. Is formed.

When the alloy-based negative electrode active material is a silicon oxide represented by, for example, SiO _a (0.05 <a <1.95), a columnar shape is formed so that a concentration gradient of oxygen is formed in the thickness direction of the columnar body 24. The body 24 may be formed. Specifically, the oxygen content may be increased at a portion close to the current collector 21, and the oxygen content may be reduced as the distance from the current collector 21 increases. Thereby, the bondability between the convex portion 22 and the columnar body 24 can be further improved.
In the case where the source gas is not supplied from the nozzle 34, the columnar body 24 mainly composed of silicon or tin is formed.

  The lithium ion secondary battery of the present invention can be used in the same applications as conventional lithium ion secondary batteries, and in particular, portable electronic devices such as personal computers, mobile phones, mobile devices, portable information terminals, and portable game devices. It can be suitably used as a power source.

Hereinafter, the present invention will be specifically described with reference to Examples, Comparative Examples, and Test Examples.
Example 1
(1) Preparation of positive electrode active material Co and Al sulfate were added to a NiSO ₄ aqueous solution so that Ni: Co: Al = 7: 2: 1 (molar ratio) to obtain an aqueous solution having a metal ion concentration of 2 mol / L. Prepared. While stirring this aqueous solution, a 2 mol / L sodium hydroxide solution was gradually added and neutralized to neutralize a ternary precipitate having a composition represented by Ni _0.7 Co _0.2 Al _0.1 (OH) _2. It was produced by a sedimentation method. This precipitate was separated by filtration, washed with water, and dried at 80 ° C. to obtain a composite hydroxide. As a result of measuring the average particle diameter of the obtained composite hydroxide with a particle size distribution meter (trade name: MT3000, manufactured by Nikkiso Co., Ltd.), the average particle diameter was 10 μm.

This composite hydroxide was heated in the atmosphere at 900 ° C. for 10 hours for heat treatment to obtain a ternary composite oxide having a composition represented by Ni _0.7 Co _0.2 Al _0.1 O. Here, lithium hydroxide monohydrate is added so that the sum of the number of atoms of Ni, Co, and Al is equal to the number of atoms of Li, and heat treatment is performed by heating at 800 ° C. for 10 hours in the air. Thus, a lithium nickel-containing composite metal oxide having a composition represented by LiNi _0.7 Co _0.2 Al _0.1 O ₂ was obtained. As a result of analyzing this lithium-containing composite metal oxide by powder X-ray diffraction, it was confirmed that the lithium-containing composite metal oxide had a single-phase hexagonal layered structure, and that Co and Al were in solid solution. Thus, a positive electrode active material having an average secondary particle size of 10 μm and a specific surface area by the BET method of 0.45 m ² / g was obtained.

(2) Production of positive electrode 100 g of the positive electrode active material powder obtained above, 3 g of acetylene black (conductive agent), 3 g of polyvinylidene fluoride powder (binder) and 50 ml of N-methyl-2-pyrrolidone (NMP) To prepare a positive electrode mixture paste. This positive electrode mixture paste was applied to both surfaces of an aluminum foil (positive electrode current collector) having a thickness of 20 μm, dried and rolled to form a positive electrode active material layer. Thereafter, the positive electrode was cut out to a size of 30 mm × 180 mm. In the obtained positive electrode, the positive electrode active material layer carried on one side of the aluminum foil had a thickness of 60 μm and a size of 30 mm × 180 mm. A positive electrode lead was connected to the surface of the aluminum foil opposite to the surface on which the positive electrode active material layer was formed.

(3) Production of Negative Electrode FIG. 9 is a side view schematically showing the configuration of the vapor deposition apparatus 40 for forming the negative electrode active material layer. The vapor deposition apparatus 40 includes a vacuum chamber 41, a current collector transport means 42, a source gas supply means 48, a plasma generation means 49, silicon targets 50a and 50b, a shielding plate 51, and an electron beam heating means (not shown). The vacuum chamber 1 is a pressure-resistant container having an internal space that can be depressurized. In the internal space, the current collector transport means 42, the source gas supply means 48, the plasmarization means 49, the silicon targets 50a and 50b, the shielding plate 51, and Houses electron beam heating means.

  The current collector conveying means 42 includes an unwinding roller 43, a can 44, a take-up roller 45, and conveying rollers 46 and 47. The unwinding roller 43, the can 44, and the conveying rollers 46 and 47 are provided so as to be rotatable around the axis. A long negative electrode current collector 21 is wound around the unwinding roller 43. The can 44 has a larger diameter than the other rollers, and includes a cooling means (not shown) therein. When the negative electrode current collector 21 is conveyed on the surface of the can 44, the negative electrode current collector 21 is also cooled. As a result, the vapor of the alloy-based negative electrode active material is cooled and deposited, and a thin film is formed. The take-up roller 45 is provided so as to be rotatable around its axis by a driving means (not shown). One end of the negative electrode current collector 21 is fixed to the take-up roller 45, and the take-up roller 45 rotates, so that the negative electrode current collector 21 passes from the take-out roller 43 through the transport roller 46, the can 44 and the transport roller 47. Are transported. Then, the negative electrode current collector 21 having a surface on which a thin film of an alloy-based negative electrode active material is formed is wound around the winding roller 45.

  The source gas supply means 48 supplies source gases such as oxygen and nitrogen into the vacuum chamber 41 when forming a thin film mainly composed of silicon or tin oxide, nitride or the like. The plasmar 49 converts the source gas supplied by the source gas supply unit 48 into plasma. The silicon targets 50a and 50b are used when forming a thin film containing silicon. The shielding plate 51 is provided so as to be movable in the horizontal direction below the can 43 in the vertical direction and above the silicon targets 50a and 50b. The horizontal position of the shielding plate 51 is appropriately adjusted according to the thin film formation state on the surface of the negative electrode current collector 21. The electron beam heating means irradiates and heats the silicon targets 50a and 50b with an electron beam to generate silicon vapor.

Using the vapor deposition device 40, a negative electrode active material layer (here, a silicon thin film) having a thickness of 5 μm was formed on the surface of the negative electrode current collector 21 under the following conditions.
Pressure in the vacuum chamber 41: 8.0 × 10 ⁻⁵ Torr
Negative electrode current collector 21: electrolytic copper foil having a length of 50 m, a width of 10 cm, and a thickness of 35 μm (manufactured by Furukawa Circuit Foil Co., Ltd.)
Winding speed of the negative electrode current collector 21 by the winding roller 45 (conveying speed of the negative electrode current collector 21): 2 cm / min. Source gas: not supplied.
Target 50a, 50b: Silicon single crystal of purity 99.9999% (manufactured by Shin-Etsu Chemical Co., Ltd.)
Electron beam acceleration voltage: -8 kV
Electron beam emission: 300 mA

  Further, a negative electrode active material layer having a thickness of 5 μm was formed on the other surface of the negative electrode current collector 21 in the same manner as described above, to produce a negative electrode. The obtained negative electrode was cut into 35 mm × 185 mm to prepare a negative electrode plate. About this negative electrode plate, lithium metal was vapor-deposited on the surface of the negative electrode active material layer (silicon thin film). By depositing lithium metal, lithium corresponding to the irreversible capacity stored in the negative electrode active material layer at the time of the first charge / discharge was supplemented. Lithium metal was deposited using a resistance heating vapor deposition apparatus (manufactured by ULVAC, Inc.) in an argon atmosphere. Lithium metal is loaded into a tantalum boat in a resistance heating vapor deposition apparatus, the negative electrode is fixed so that the negative electrode active material layer faces the tantalum boat, and a 50 A current is passed through the tantalum boat in an argon atmosphere. Deposition was performed for 10 minutes. Thus, a negative electrode plate used in the present invention was obtained.

(4) Production of battery The positive electrode plate, so that the positive electrode active material layer and the negative electrode active material layer face each other through a polyethylene microporous membrane (separator, trade name: hypopore, thickness 20 μm, manufactured by Asahi Kasei Co., Ltd.) A polyethylene microporous membrane and a negative electrode plate were overlaid. This was wound into a flat plate shape, and an aluminum positive electrode lead and a nickel negative electrode lead were connected to produce a flat plate-shaped wound electrode group shown in FIG. This electrode group was inserted into an outer case made of an aluminum laminate sheet, and an electrolyte was injected. For the electrolyte, a nonaqueous electrolytic solution in which LiPF ₆ was dissolved at a concentration of 1.0 mol / L in a mixed solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 1: 1 was used. Using. Next, the positive electrode lead and the negative electrode lead were led out from the opening of the outer case to the outside of the outer case, and the opening of the outer case was welded while vacuuming the inside of the outer case to produce a lithium ion secondary battery.

(5) Initial charge / discharge under pressure With respect to the lithium ion secondary battery obtained above, the initial charge / discharge was performed while performing pressurization. The pressurization was performed under conditions of a temperature of 25 ° C. and a pressure of 2 × 10 ⁵ N / m ² for 10 hours. The pressurizing surface of the presser of the press machine had a larger area than the entire side surface in the thickness direction of the wound electrode group, and the entire side surface in the thickness direction was uniformly pressed. In the first charge / discharge, the battery is charged at a constant current of 0.2 ItA until the battery voltage reaches 4.05 V, then charged at 4.2 V until the current value becomes 0.05 ItA, and further a constant of 0.2 ItA. It was carried out by discharging until the battery voltage dropped to 2V with current. At this time, the positive electrode lead and the negative electrode lead led out of the battery were covered with imide tape and insulated, and the tip was connected to the charger.

(Example 2)
A lithium ion secondary battery of the present invention was produced in the same manner as in Example 1 except that the production method of the negative electrode was changed as follows.
(Preparation of negative electrode)
A ceramic layer having a thickness of 100 μm was formed by spraying chromium oxide on the surface of an iron roll having a diameter of 50 mm. On the surface of this ceramic layer, a hole which is a circular recess having a diameter of 12 μm and a depth of 8 μm was formed by laser processing, and a convex forming roll was produced. The holes were in a close-packed arrangement with an axial distance of 20 μm between adjacent holes. The bottom of the hole has a substantially flat central portion, and the portion where the bottom end and the side surface of the hole are connected has a rounded shape.

  On the other hand, an alloy copper foil (trade name: HCL-02Z, thickness 20 μm, manufactured by Hitachi Cable Ltd.) containing zirconia at a ratio of 0.03% by weight with respect to the total amount at 600 ° C. in an argon gas atmosphere. Heated for 30 minutes and annealed. The alloy copper foil is passed through a pressure-contact portion where two convex portion forming rolls are pressure-contacted at a linear pressure of 2 t / cm, both sides of the alloy copper foil are pressure-molded, and the negative electrode current collector used in the present invention Was made. When a cross section in the thickness direction of the obtained negative electrode current collector was observed with a scanning electron microscope, a convex portion was formed on the surface of the negative electrode current collector. The average height of the protrusions was about 8 μm.

  The negative electrode active material layer was formed on a convex portion formed on the surface of the negative electrode current collector using a commercially available vapor deposition apparatus (manufactured by ULVAC, Inc.) having the same structure as the electron beam vapor deposition apparatus 30 shown in FIG. . The conditions for vapor deposition are as follows. In addition, the fixed base on which the negative electrode current collector having a dimension of 35 mm × 185 mm is fixed has a position of an angle α = 60 ° with respect to a horizontal straight line (a position of a solid line shown in FIG. 6) and an angle (180−α) = 120 °. (A position indicated by a one-dot broken line shown in FIG. 6) was alternately angularly displaced. Thus, a columnar negative electrode active material layer in which eight columnar chunks as shown in FIG. 9 were laminated was formed. This negative electrode active material layer grew in the direction in which the convex portion extends from the top of the convex portion and the side surface in the vicinity of the top portion.

Negative electrode active material raw material (evaporation source): silicon, purity 99.9999%, manufactured by High Purity Chemical Laboratory Co., Ltd. Oxygen released from nozzle: purity 99.7%, manufactured by Nippon Oxygen Co., Ltd.
Oxygen release flow rate from nozzle: 80 sccm
Angle α: 60 °
Electron beam acceleration voltage: -8 kV
Emission: 500mA
Deposition time: 3 minutes

The thickness T of the formed negative electrode active material layer was 16 μm. The thickness of the negative electrode active material layer is determined by observing a cross section in the thickness direction of the negative electrode with a scanning electron microscope, and for the ten negative electrode active material layers formed on the surface of the convex portion, the length from the convex portion vertex to the negative electrode active material layer vertex. Each is obtained and obtained as an average value of the ten measured values obtained. Further, when the amount of oxygen contained in the negative electrode active material layer was quantified by a combustion method, it was found that the composition of the compound constituting the negative electrode active material layer was SiO _0.5 .

  Next, lithium metal was deposited on the surface of the negative electrode active material layer. By depositing lithium metal, lithium corresponding to the irreversible capacity stored in the negative electrode active material layer at the time of the first charge / discharge was supplemented. Lithium metal was deposited using a resistance heating vapor deposition apparatus (manufactured by ULVAC, Inc.) in an argon atmosphere. Lithium metal is loaded into a tantalum boat in a resistance heating vapor deposition apparatus, the negative electrode is fixed so that the negative electrode active material layer faces the tantalum boat, and a 50 A current is passed through the tantalum boat in an argon atmosphere. Deposition was performed for 10 minutes.

(Comparative Example 1)
A lithium ion secondary battery was fabricated in the same manner as in Example 1 except that the attachment positions of the positive electrode lead and the negative electrode lead were changed to the surfaces 1x and 1y in the thickness direction of the wound electrode group 1 shown in FIG. .

(Test Example 1)
(Battery capacity evaluation)
For the lithium ion secondary batteries of Example 1 and Comparative Example 1, the charge / discharge cycle was repeated three times under the following conditions to determine the third discharge capacity. The results are shown in Table 1.
Constant current charging: 5 mA, final voltage 4.2V.
Constant voltage charging: end current 0.25 mA, rest time 20 minutes.
Constant current discharge: Current 5 mA, end voltage 2.5 V, rest time 20 minutes.

(Charge / discharge cycle characteristics)
The lithium ion secondary batteries of Example 1 and Comparative Example 1 were charged and discharged at a constant current in a range of 4.2 V to 2.5 V at a current value of 480 mA (0.2 C) in an environment of 0 ° C., and 0.2 C The discharge capacity at discharge was investigated.
Further, the process of constant current charging to 4.2 V at 1680 mA (0.7 C) in a 20 ° C. environment was repeated, followed by constant current discharging to 2.5 V at 2400 mA (1 C). Then, after 50 cycles, constant current charge / discharge was performed at 480 mA in the range of 4.2 V to 2.5 V, and the discharge capacity at 0.2 C discharge was examined. The ratio of the 0.2C discharge capacity after 50 cycles to the initial 0.2C discharge capacity was determined as the cycle capacity retention rate (%). The results are shown in Table 1.

(Battery swelling)
For the battery after the charge / discharge cycle characteristics test, the thickness of the wound electrode group was measured to determine whether the battery was swollen. The results are shown in Table 1.

  From Table 1, by changing the lead connection position as in the configuration of the present invention, even if a wound electrode group containing an alloy-based negative electrode active material is used, the occurrence of battery swelling due to repeated charge and discharge It is clear that the deterioration of the charge / discharge cycle characteristics is remarkably prevented. On the other hand, when the lead is connected to the side surface in the thickness direction of the wound electrode group (planar portion of the wound electrode), the degree of swelling of the battery due to repeated charge / discharge is significant, and the charge / discharge cycle The characteristics were also greatly reduced. This is presumably due to the fact that a large pressure was applied to the lead connecting portion during the first charge / discharge, and the active material layer was partially deformed or peeled off.

  The lithium ion secondary battery of the present invention can be used in the same applications as conventional lithium ion secondary batteries, and in particular, personal computers, mobile phones, mobile devices, personal digital assistants (PDAs), portable game devices, and video cameras. It is useful as a power source for portable electronic devices such as In addition, it is expected to be used as a secondary battery for assisting an electric motor, a power tool, a cleaner, a power source for driving a robot, a power source for a plug-in HEV, etc. in a hybrid electric vehicle, a fuel cell vehicle and the like.

It is a longitudinal cross-sectional view which shows typically the structure of the principal part of the lithium ion secondary battery which is one of the embodiment of this invention. FIG. 1A is a longitudinal sectional view. FIG. 1B is a top view. FIG.1 (c) is a top view which shows typically the structure of the electrode group of another form. It is drawing which shows typically the structure of the principal part (electrode group) of the lithium ion secondary battery which is one of the embodiment of this invention. FIG. 2A is a longitudinal sectional view. FIG. 2B is a top view. FIG. 2C is a top view schematically showing the configuration of another type of electrode group. It is drawing which shows typically the structure of the principal part (electrode group) of the lithium ion secondary battery which is one of the embodiment of this invention. FIG. 3A is a longitudinal sectional view. FIG. 3B is a top view. FIG.3 (c) is a top view which shows typically the structure of the electrode group of another form. It is drawing which shows typically the structure of the principal part of the lithium ion secondary battery which is one of the embodiment of this invention. FIG. 4A is a top view showing the configuration of the positive electrode current collector or the negative electrode current collector. 4B to 4D are top views showing the configuration of the electrode group. It is a longitudinal cross-sectional view which shows typically the structure of the negative electrode used by this invention. It is a perspective view which shows typically the structure of the negative electrode electrical power collector contained in the negative electrode shown in FIG. It is a longitudinal cross-sectional view which shows typically the structure of the columnar body contained in the negative electrode active material layer of the negative electrode shown in FIG. It is a side view which shows typically the structure of an electron beam vapor deposition apparatus. It is a side view which shows typically the structure of the vapor deposition apparatus of another form.

Explanation of symbols

1, 2, 3 Flat wound electrode group 11 Positive electrode 12 Negative electrode 13 Positive electrode lead 14 Negative electrode lead 15 Positive electrode current collector 16 Negative electrode current collector 15a, 16a Lead mounting portion 20 Negative electrode 21 Negative electrode current collector 22 Protruding portion 23 Negative electrode Active material layer 23a Columnar body 30 Electron beam deposition apparatus 40 Deposition apparatus

Claims (10)

Including electrode group, positive electrode lead and negative electrode lead,
The electrode group includes a positive electrode including a positive electrode active material layer containing a positive electrode active material capable of inserting and extracting lithium and a positive electrode current collector, a negative electrode active material layer containing an alloy-based negative electrode active material, and a negative electrode current collector. Is a flat wound electrode group wound in a flat plate shape through a separator,
The positive electrode lead is connected to the positive electrode current collector so as not to protrude outward from the surface of the electrode group in the thickness direction,
The negative electrode lead is a lithium ion secondary battery that is connected to the negative electrode current collector so as not to protrude outward from the surface of the electrode group in the thickness direction, and performs initial charge / discharge under pressure.   The positive electrode lead and the negative electrode lead are respectively connected to the positive electrode current collector and the negative electrode current collector so as to face the axis of the electrode group at the end opposite to the end of the electrode group on the axis line side. The lithium ion secondary battery described in 1.   The electrode group includes a bent portion in which the positive electrode and the negative electrode are bent to the axial side at the end opposite to the axial end portion, and the positive electrode lead and the negative electrode on the surface of the bent portion following the surface in the thickness direction of the electrode group The lithium ion secondary battery according to claim 1, wherein the lead is connected to the positive electrode current collector and the negative electrode current collector.   The positive electrode current collector and the negative electrode current collector are formed so as to extend outward from the current collector main body at a rectangular current collector main body and an end portion on the opposite side to the axial end portion of the current collector main body. 2. The lithium ion secondary battery according to claim 1, further comprising a lead attachment portion, wherein the positive electrode lead and the negative electrode lead are respectively connected to the positive electrode current collector and the negative electrode current collector in the lead attachment portion.   The lithium ion secondary battery according to claim 4, wherein the lead attachment portion is provided so as to protrude in a direction in which an axis of the electrode group extends from the current collector body.   The lithium ion secondary battery according to any one of claims 1 to 5, wherein the negative electrode active material layer is formed by vapor deposition, sputtering, or chemical vapor deposition.   The lithium ion secondary battery according to any one of claims 1 to 6, wherein the alloy-based negative electrode active material is an alloy-based negative electrode active material containing silicon or tin.   The lithium ion secondary battery according to claim 7, wherein the alloy-based negative electrode active material containing silicon is at least one selected from the group consisting of silicon, silicon oxide, silicon nitride, silicon-containing alloy, and silicon compound.   The lithium ion secondary battery according to claim 7, wherein the alloy-based negative electrode active material containing tin is at least one selected from the group consisting of tin, tin oxide, a tin-containing alloy, and a tin compound. Including electrode group, positive electrode lead and negative electrode lead,
The electrode group includes a positive electrode including a positive electrode active material layer containing a positive electrode active material capable of inserting and extracting lithium and a positive electrode current collector, a negative electrode active material layer containing an alloy-based negative electrode active material, and a negative electrode current collector. Is a flat wound electrode group wound in a flat plate shape through a separator,
The positive electrode lead is connected to the positive electrode current collector so as not to protrude outward from the surface of the electrode group in the thickness direction,
The negative electrode lead performs the first charge / discharge under pressure on the lithium ion secondary battery connected to the negative electrode current collector so as not to protrude outward from the surface of the electrode group in the thickness direction. A method for producing a lithium ion secondary battery.

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