JP2008258139A - Negative electrode for nonaqueous electrolyte secondary battery, its manufacturing method, and nonaqueous electrolyte secondary battery using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a negative electrode for a nonaqueous electrolyte secondary battery excelling in high capacity and a charge-discharge cycle characteristic; its manufacturing method; and a nonaqueous electrolyte secondary battery using it. <P>SOLUTION: This negative electrode for a nonaqueous electrolyte secondary battery reversibly storing and releasing lithium ions includes: a collector 11 having a rough surface having a surface roughness Ra at least on one surface; and a columnar body 15 formed on the rough surface of the collector 11, having content ratios of elements sequentially-changed in the longitudinal direction of the collector 11, and composed by stacking columnar body parts 151-155 in (n) tiers (n≥2), and has a structure where the changing direction of the content ratios of elements in the odd-numbered tiers of the columnar body parts 151-155 is different from that of the content ratios of the elements in the even-numbered tiers thereof. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a non-aqueous electrolyte secondary battery having excellent charge / discharge characteristics, and more specifically, a non-aqueous electrolyte having high capacity, excellent charge / discharge cycle characteristics, and low deformation during charge / discharge suitable for a wound battery. The present invention relates to a negative electrode for an electrolyte secondary battery, a manufacturing method thereof, and a non-aqueous electrolyte secondary battery using the same.

  A lithium ion secondary battery, which represents a nonaqueous electrolyte secondary battery, is characterized by high electromotive force and high energy density while being lightweight. Therefore, the demand for lithium ion secondary batteries as driving power sources for various types of portable electronic devices such as mobile phones, digital cameras, video cameras, and notebook computers and mobile communication devices is increasing.

  The lithium ion secondary battery includes a positive electrode made of a lithium-containing composite oxide, a negative electrode including a negative electrode active material that occludes and releases lithium metal, a lithium alloy, or lithium ions, and an electrolyte.

In recent years, instead of carbon materials such as graphite that have been conventionally used as negative electrode materials, research has been reported on elements that have occlusion of lithium ions and whose theoretical capacity density exceeds 833 mAh / cm ³ . . For example, as an element of the negative electrode active material having a theoretical capacity density exceeding 833 mAh / cm ³ , there are silicon (Si), tin (Sn), germanium (Ge) alloyed with lithium, and oxides and alloys thereof. Among them, silicon-containing particles such as Si particles and silicon oxide particles are widely studied because they are inexpensive.

However, these elements increase in volume when lithium ions are occluded during charging. For example, if the negative electrode active material is Si, in a state in which lithium ions are maximum amount storage is represented by _{Li 4.4} Si, by changing from Si to _{Li 4.4} Si, the volume is 4 at the time of discharging Increased 12 times.

  Therefore, in particular, when a negative electrode active material is formed by depositing a thin film of the above elements on a current collector by CVD or sputtering, the negative electrode active material expands and contracts due to insertion and extraction of lithium ions, and a charge / discharge cycle There was a possibility that peeling due to a decrease in adhesion between the negative electrode active material and the negative electrode current collector occurred during the repetition of the above.

  In order to solve the above-described problem, a configuration in which a negative electrode active material thin film deposited on a current collector is separated into a columnar shape by a cut formed in the thickness direction (see, for example, Patent Document 1) is disclosed. . In addition, a method is disclosed in which irregularities are provided on the surface of the current collector, a negative electrode active material thin film is deposited thereon, and voids are formed in the thickness direction by etching (see, for example, Patent Document 2). Furthermore, a method has been proposed in which a mesh is disposed above the current collector, and a negative electrode active material thin film is deposited through the mesh, thereby suppressing deposition of the negative electrode active material in a region corresponding to the mesh frame (for example, And Patent Document 3).

Further, as shown in FIG. 7, the surface of the current collector 251 is provided with irregularities, and a thin-film negative electrode material is inclined (θ) with respect to the main surface (AA-AA) of the negative electrode material thereon. A forming method is disclosed (for example, see Patent Document 4). As a result, it was shown that the stress generated by the expansion and contraction of charge / discharge can be dispersed in the direction parallel to the main surface of the negative electrode material and in the direction perpendicular thereto, thereby suppressing the occurrence of wrinkles and peeling.
JP 2002-83594 A JP 2003-17040 A JP 2002-279974 A JP-A-2005-196970

  However, in the secondary battery shown in Patent Document 1, since the space between the columnar bodies is small, the expansion of the columnar bodies cannot be sufficiently absorbed in the space. Therefore, the columnar body may expand in the height direction or the current collector may extend. In the case of a wound cylindrical battery or prismatic battery formed of such a current collector, there is a problem that the electrode group is deformed by charge and discharge, resulting in a decrease in cycle characteristics.

  In addition, the negative electrode manufacturing method shown in Patent Document 2 forms columnar bodies by etching. However, in order to provide a sufficient gap in the space between the columnar bodies, there are many portions to be removed by etching (approximately 50%), and material loss is caused. There is a problem that there are many. Moreover, although material loss can be reduced by reducing the space between the columnar bodies, the space between the columnar bodies is reduced similarly to the problem of the battery of Patent Document 1, so that the expansion of the columnar bodies is sufficiently absorbed in the space. Can not do it. Therefore, it has the same problem as Patent Document 1.

  Moreover, the manufacturing method of the negative electrode shown in patent document 3 forms a columnar body by masking with a mesh. This manufacturing method has a problem that the manufacturing cost is high as compared with a method not using a mesh.

  Further, in the secondary battery shown in Patent Document 4, as shown in FIG. 7A, since the space between the columnar bodies 253 formed on the current collector 251 is small, the lithium ions are occluded. As shown in FIG. 3, the expansion of the columnar body 253 cannot be sufficiently absorbed or relaxed in the space. Therefore, it has the same problem as Patent Document 1 and Patent Document 2.

  The present invention has been made in order to solve the above-described problems. In a wound cylindrical and prismatic battery, the non-aqueous electrolyte is excellent in cycle characteristics by suppressing the deformation of the electrode group with an increase in capacity. It aims at realizing the negative electrode for secondary batteries, its manufacturing method, and a nonaqueous electrolyte secondary battery using the same.

  In order to achieve the above-described object, the present invention provides a negative electrode for a non-aqueous electrolyte secondary battery that reversibly occludes and releases lithium ions, and has a rough surface having a surface roughness Ra on at least one surface. A columnar body formed by laminating a columnar body portion in which the content ratio of elements formed on the rough surface of the current collector and the current collector sequentially changes in the longitudinal direction of the current collector in n (n ≧ 2) stages And the change direction of the content ratio of the odd-numbered and even-numbered elements of the columnar body portion is different.

  Thereby, it has a columnar body formed in a size substantially corresponding to the surface roughness Ra, and a space for absorbing the expansion of the columnar body can be maintained. As a result, a negative electrode having a current collector with high capacity and low expansion and elongation can be realized. In addition, since columnar bodies of various sizes corresponding to the surface roughness Ra are randomly formed, the columnar bodies are appropriately brought into contact with each other, improving the current collecting property, and improving the cycle characteristics. A negative electrode for a secondary battery can be realized.

  The negative electrode for a non-aqueous electrolyte secondary battery according to the present invention is a method for manufacturing a negative electrode for a non-aqueous electrolyte secondary battery that reversibly occludes and releases lithium ions, at least on one side of the current collector. A first step for forming a rough surface having a surface roughness Ra, a second step for forming the first-stage columnar body on the rough surface obliquely, and a first-stage columnar body on the columnar body part. The third step of forming a second-stage columnar body that is obliquely inclined in a direction different from the portion, and the second and third steps are repeated to change the oblique-direction of the odd-numbered and even-numbered columnar body portions. And a fourth step of forming a columnar body having n (n ≧ 2) stages.

  This makes it possible to easily produce a negative electrode for a non-aqueous electrolyte secondary battery that has excellent reliability and does not generate wrinkles in the current collector while maintaining the gaps between the columnar bodies with high material yield and low cost. Can do.

  The nonaqueous electrolyte secondary battery of the present invention includes the above-described negative electrode for a nonaqueous electrolyte secondary battery, a positive electrode capable of reversibly occluding and releasing lithium ions, and a nonaqueous electrolyte. As a result, a non-aqueous electrolyte secondary battery having high safety and excellent reliability is produced.

  According to the negative electrode for a non-aqueous electrolyte secondary battery of the present invention, a method for producing the same, and a non-aqueous electrolyte secondary battery using the same, a current collector is maintained while maintaining a high capacity using an active material having large expansion and contraction. Thus, a non-aqueous electrolyte secondary battery excellent in cycle characteristics can be realized. Furthermore, such a negative electrode can be manufactured efficiently and easily.

  A first invention of the present invention is a negative electrode for a non-aqueous electrolyte secondary battery that reversibly occludes and releases lithium ions, a current collector having a rough surface with a surface roughness Ra on at least one surface, a current collector A columnar body configured by stacking n (n ≧ 2) columnar body portions in which the content ratio of elements formed on the rough surface of the body sequentially changes in the longitudinal direction of the current collector, The change direction of the content ratio of the odd-numbered and even-numbered elements of the body part is different.

  Thereby, it has a columnar body formed in a size substantially corresponding to the surface roughness Ra, and a space for absorbing the expansion of the columnar body can be maintained. As a result, a negative electrode with high capacity and small expansion and elongation can be realized. In addition, columnar bodies of various sizes corresponding to the surface roughness Ra are randomly formed, so that the columnar bodies are in proper contact with each other to improve current collection, and an electrolyte is efficiently used between the columnar bodies. Therefore, a negative electrode for a non-aqueous electrolyte secondary battery having excellent cycle characteristics can be realized.

  According to a second aspect of the present invention, in the first aspect, the current collector has a surface roughness Ra of 0.5 μm to 8 μm.

  Thereby, a columnar body can be formed with a size in a specific range substantially corresponding to the surface roughness Ra, and stress relaxation and voids can be effectively formed.

  According to a third aspect of the present invention, in the first aspect or the second aspect, the columnar body viewed from the longitudinal direction and the upper surface of the current collector has a different shape substantially corresponding to the surface roughness Ra of the current collector. Is formed.

  Thereby, columnar bodies having a size in a specific range corresponding to the surface roughness Ra are randomly arranged, and the electron conductivity is maintained while efficiently relaxing the stress and voids during expansion and contraction of the columnar bodies. Can be improved. Further, the electrolytic solution is efficiently retained between the columnar bodies. As a result, cycle characteristics can be improved.

  According to a fourth aspect of the present invention, in the first to fourth aspects, at least in a discharge state, the n-stage columnar body portion of the columnar body is formed obliquely on the rough surface of the current collector. At the same time, the odd-numbered steps and the even-numbered steps are stacked in a folded manner in the thickness direction.

  Thereby, even if it raises the height of a columnar body, the space between columnar bodies can be ensured moderately.

  According to a fifth invention of the present invention, in the first to fourth inventions, the void ratio occupied by the space is 25% or more and 45% or less with respect to the space between the columnar bodies in the discharged state. It is what.

  Accordingly, the electron conductivity can be improved while the stress relaxation and voids during the expansion and contraction of the columnar bodies are efficiently maintained, and the electrolytic solution can be efficiently retained between the columnar bodies. As a result, cycle characteristics can be improved.

According to a sixth invention of the present invention, in the first to fifth inventions, an active material having a theoretical capacity density exceeding 833 mAh / cm ³ at least reversibly occluding and releasing lithium ions is used as the columnar body portion. It was. Thereby, the negative electrode for nonaqueous electrolyte secondary batteries using a high capacity | capacitance active material is produced.

  According to a seventh aspect of the present invention, in the sixth aspect, a material represented by SiOx containing at least silicon is used as the active material. Thereby, the negative electrode for nonaqueous electrolyte secondary batteries with high electrode reaction efficiency, high capacity | capacitance, and comparatively cheap is produced.

  According to an eighth aspect of the present invention, in the seventh aspect, the value x of the silicon-containing material is set to an intersection angle between the center line in the oblique direction of the columnar body portion and the center line in the thickness direction of the current collector. On the other hand, it is increased from the side forming the acute angle toward the side forming the obtuse angle.

  Thereby, the crack of the columnar body by the stress distortion accompanying the expansion | swelling at the time of charging / discharging can be suppressed.

  A ninth invention of the present invention is a method for producing a negative electrode for a non-aqueous electrolyte secondary battery that reversibly occludes and releases lithium ions, and has a rough surface having a surface roughness Ra on at least one surface of a current collector. A first step of forming, a second step of forming the first columnar body portion obliquely on the rough surface, and an inclination of 2 on the columnar body portion in a direction different from that of the first columnar body portion. The third step of forming the columnar body of the step, the second step, and the third step are repeated to change the oblique direction of the odd-numbered and even-numbered columnar bodies to n (n ≧ 2) steps A fourth step of forming a columnar body made of

  Thereby, it is possible to easily produce a negative electrode for a non-aqueous electrolyte secondary battery that is excellent in reliability and does not generate wrinkles in the current collector while maintaining the gaps between the columnar bodies.

  In the tenth aspect of the present invention, the columnar bodies viewed from the longitudinal direction and the upper surface of the current collector are formed in different shapes substantially corresponding to the surface roughness Ra of the current collector.

  Thereby, columnar bodies having a size in a specific range corresponding to the surface roughness Ra can be randomly arranged, and stress relaxation and voids during expansion and contraction of the columnar bodies can be efficiently maintained. Furthermore, cycle characteristics can be improved by improving the electronic conductivity and efficiently retaining the electrolyte between the columnar bodies.

  An eleventh aspect of the present invention includes the negative electrode for a nonaqueous electrolyte secondary battery according to any one of the first to eighth aspects, a positive electrode that reversibly occludes and releases lithium ions, and a nonaqueous electrolyte. It is a non-aqueous electrolyte secondary battery. Thereby, a non-aqueous electrolyte secondary battery having a high capacity and excellent cycle characteristics is produced.

  Hereinafter, embodiments of the present invention will be described with the same reference numerals given to the same portions with reference to the drawings. The present invention is not limited to the contents described below as long as it is based on the basic characteristics described in this specification.

(Embodiment)
FIG. 1 is a cross-sectional view of a nonaqueous electrolyte secondary battery in an embodiment of the present invention.

  As shown in FIG. 1, a laminated nonaqueous electrolyte secondary battery (hereinafter sometimes referred to as a “battery”) has a negative electrode 1 described in detail below and a negative electrode 1 that reduces lithium ions during discharge. The electrode group 4 is composed of a positive electrode 2 and a porous separator 3 interposed between them to prevent direct contact between the negative electrode 1 and the positive electrode 2. The electrode group 4 and an electrolyte (not shown) having lithium ion conductivity are accommodated in the exterior case 5. The separator 3 is impregnated with an electrolyte having lithium ion conductivity. Further, one end of a positive electrode lead (not shown) and a negative electrode lead (not shown) is connected to the positive electrode current collector 2 a and the negative electrode current collector 1 a, respectively, and the other end is led out of the exterior case 5. Has been. Further, the opening of the outer case 5 is sealed with a resin material. The positive electrode 2 includes a positive electrode current collector 2a and a positive electrode mixture layer 2b supported on the positive electrode current collector 2a.

  Further, as will be described in detail below, the negative electrode 1 has a current collector having a rough surface composed of a concave portion and a convex portion having a surface roughness Ra of 0.5 μm to 8 μm, and at least obliquely on the convex portion. The columnar body portions are stacked in discretely provided n (n ≧ 2) stages, and are configured with, for example, zigzag columnar bodies 1b, which are randomly arranged. The columnar body portion is formed by sequentially changing the content ratio of elements formed on the convex portion of the current collector in the longitudinal direction of the current collector. Furthermore, the columnar body portion formed by stacking in n (n ≧ 2) stages is formed so that the changing direction of the content ratio of the odd-numbered and even-numbered elements is different. In the above description, the concave portion and the convex portion are described as rough surfaces for convenience, but an arbitrary shape is meant. For example, it may be a corrugated shape having peaks and valleys, or may have a jagged shape. Moreover, the above-mentioned longitudinal direction means the oblique direction in which the columnar body part demonstrated by the following manufacturing methods is formed obliquely. In general, the winding direction of the electrode group is shown in the case of a cylindrical battery, but cannot be specified in the case of a stacked battery. Therefore, in the following description, the direction in which the columnar body portion obliquely includes the longitudinal direction is described as the width direction.

Here, the positive electrode mixture layer 2b includes LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , or a lithium-containing composite oxide such as a mixture or composite compound thereof as a positive electrode active material. In addition to the above, as the positive electrode active material, olivine type lithium phosphate represented by the general formula of LiMPO ₄ (M = V, Fe, Ni, Mn), Li ₂ MPO ₄ F (M = V, Fe, Ni, Mn) ) Lithium fluorophosphate represented by the general formula can also be used. Further, a part of these lithium-containing compounds may be substituted with a different element. Surface treatment may be performed with a metal oxide, lithium oxide, a conductive agent, or the like, or the surface may be subjected to a hydrophobic treatment.

  Positive electrode mixture layer 2b further includes a conductive agent and a binder. As the conductive agent, natural graphite and artificial graphite graphite, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black and other carbon black, conductive fibers such as carbon fiber and metal fiber, Metal powders such as carbon fluoride and aluminum, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, and organic conductive materials such as phenylene derivatives can be used.

  Examples of the binder include PVDF, polytetrafluoroethylene, polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamideimide, polyacrylonitrile, polyacrylic acid, polyacrylic acid methyl ester, polyacrylic acid ethyl ester, polyacrylic acid. Acrylic hexyl ester, polymethacrylic acid, polymethacrylic acid methyl ester, polymethacrylic acid ethyl ester, polymethacrylic acid hexyl ester, polyvinyl acetate, polyvinylpyrrolidone, polyether, polyethersulfone, hexafluoropolypropylene, styrene butadiene rubber, Carboxymethyl cellulose and the like can be used. Two types selected from tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinylidene fluoride, chlorotrifluoroethylene, ethylene, propylene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid, and hexadiene A copolymer of the above materials may be used. Two or more selected from these may be mixed and used.

  As the positive electrode current collector 2 a used for the positive electrode 2, aluminum (Al), carbon, conductive resin, or the like can be used. Further, any of these materials may be surface-treated with carbon or the like.

  As the non-aqueous electrolyte, an electrolyte solution in which a solute is dissolved in an organic solvent, or a so-called polymer electrolyte layer containing these and non-fluidized with a polymer can be applied. At least in the case of using an electrolyte solution, a separator 3 consisting of a single layer or a plurality of layers such as a nonwoven fabric or a microporous membrane made of polyethylene, polypropylene, aramid resin, amideimide, polyphenylene sulfide, polyimide, etc. between the positive electrode 2 and the negative electrode 1 It is preferable to impregnate this with an electrolyte solution. Further, the inside or the surface of the separator 3 may contain a heat-resistant filler such as alumina, magnesia, silica, and titania. Apart from the separator 3, a heat-resistant layer composed of these heat-resistant fillers and a binder similar to that used for the positive electrode 2 and the negative electrode 1 may be provided.

The nonaqueous electrolyte material is selected based on the redox potential of each active material. Solutes preferably used for non-aqueous electrolytes include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAlCl ₄ , LiSbF ₆ , LiSCN, LiCF ₃ SO ₃ , LiNCF ₃ CO ₂ , LiAsF ₆ , LiB ₁₀ Cl ₁₀ , lower aliphatic. Lithium carboxylate, LiF, LiCl, LiBr, LiI, lithium chloroborane, bis (1,2-benzenediolate (2-)-O, O ′) lithium borate, bis (2,3-naphthalenedioleate (2 -)-O, O ') lithium borate, bis (2,2'-biphenyldiolate (2-)-O, O') lithium borate, bis (5-fluoro-2-olate-1-benzenesulfone) acid -O, O ') borate salts such as lithium _{borate, (CF 3 SO 2) 2} NLi, LiN (CF 3 SO 2) (C 4 ₉ SO _2), applicable salts used in _{(C 2 F 5 SO 2)} 2 NLi, etc. tetraphenyl lithium borate, typically a lithium battery.

  Further, the organic solvent for dissolving the salt includes ethylene carbonate (EC), propylene carbonate, butylene carbonate, vinylene carbonate, dimethyl carbonate (DMC), diethyl carbonate, ethyl methyl carbonate (EMC), dipropyl carbonate, methyl formate, acetic acid. Methyl, methyl propionate, ethyl propionate, dimethoxymethane, γ-butyrolactone, γ-valerolactone, 1,2-diethoxyethane, 1,2-dimethoxyethane, ethoxymethoxyethane, trimethoxymethane, tetrahydrofuran, 2-methyl Tetrahydrofuran derivatives such as tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, dioxolane derivatives such as 4-methyl-1,3-dioxolane, formamide, aceto Toamide, dimethylformamide, acetonitrile, propylnitrile, nitromethane, ethyl monoglyme, phosphoric acid triester, acetate ester, propionate ester, sulfolane, 3-methylsulfolane, 1,3-dimethyl-2-imidazolidinone, 3-methyl 2-Oxazolidinone, propylene carbonate derivatives, ethyl ether, diethyl ether, 1,3-propane sultone, anisole, mixtures of one or more such as fluorobenzene, and the like solvents commonly used in lithium batteries Applicable.

  Furthermore, vinylene carbonate, cyclohexyl benzene, biphenyl, diphenyl ether, vinyl ethylene carbonate, divinyl ethylene carbonate, phenyl ethylene carbonate, diallyl carbonate, fluoroethylene carbonate, catechol carbonate, vinyl acetate, ethylene sulfite, propane sultone, trifluoropropylene carbonate, Additives such as dibenzofuran, 2,4-difluoroanisole, o-terphenyl, m-terphenyl and the like may be contained.

The non-aqueous electrolyte is composed of one or more kinds of polymer materials such as polyethylene oxide, polypropylene oxide, polyphosphazene, polyaziridine, polyethylene sulfide, polyvinyl alcohol, polyvinylidene fluoride, polyhexafluoropropylene, and the like. May be used as a solid electrolyte. Moreover, you may mix with the said organic solvent and use it in a gel form. Further, lithium nitride, lithium halide, lithium oxyacid _{salt, Li 4 SiO 4, Li 4} SiO 4 -LiI-LiOH, Li 3 PO 4 -Li 4 SiO 4, Li 2 SiS 3, Li 3 PO 4 -Li Inorganic materials such as ₂ S—SiS ₂ and phosphorus sulfide compounds may be used as the solid electrolyte. When a gel-like nonaqueous electrolyte is used, the gel-like nonaqueous electrolyte may be disposed between the positive electrode 2 and the negative electrode 1 instead of the separator. Alternatively, the gel-like nonaqueous electrolyte may be disposed adjacent to the separator 3.

  The current collector of the negative electrode 1 is made of a metal foil such as stainless steel, nickel, copper, or titanium, or a thin film of carbon or conductive resin. Further, surface treatment may be performed with carbon, nickel, titanium or the like. The thickness of the current collector is 5 μm to 50 μm. Preferably they are 8 micrometers or more and 40 micrometers or less, and 10 micrometers-35 micrometers are especially desirable. Further, the tensile strength of the current collector is preferably 3 N / mm or more at 1% elongation, but it is particularly desirable to use a current collector having a tensile strength of 6 N / mm or more. As a result, the occurrence of wrinkles and deformation of the current collector due to the expansion stress of the columnar body can be reduced.

The columnar body portion constituting the columnar body 1b of the negative electrode 1 has a theoretical capacity density that reversibly occludes and releases lithium ions, such as silicon (Si) and tin (Sn), exceeding 833 mAh / cm ³ . A negative electrode active material can be used. With such a negative electrode active material, the effect of the present invention can be exerted with any of a single negative electrode, an alloy, a compound, a solid solution, and a composite negative electrode active material containing a silicon-containing material or a tin-containing material. . That is, as a silicon-containing material, Si, SiOx (0 <x <2), or any one of them, Al, In, Cd, Bi, Sb, B, Mg, Ni, Ti, Mo, Co, Ca, Cr, An alloy, compound or solid solution in which a part of Si is substituted with at least one element selected from the group consisting of Cu, Fe, Mn, Nb, Ta, V, W, Zn, C, N, and Sn. Can be used. As the tin-containing material, Ni ₂ Sn ₄ , Mg ₂ Sn, SnOx (0 <x <2), SnO ₂ , SnSiO ₃ , LiSnO, or the like can be applied.

  These negative electrode active materials may be comprised independently, and may be comprised by multiple types of negative electrode active materials. Examples of the plurality of types of negative electrode active materials include a compound containing Si, oxygen, and nitrogen, and a composite of a plurality of compounds containing Si and oxygen and having different constituent ratios of Si and oxygen.

  Hereinafter, a negative electrode for a non-aqueous electrolyte secondary battery (hereinafter sometimes referred to as “negative electrode”) in an embodiment of the present invention will be described in detail with reference to FIGS. 2 to 4. Hereinafter, a negative electrode active material (hereinafter referred to as “active material”) represented by SiOx (0 <x ≦ 1.3) containing at least silicon will be described as an example.

  2A is a partial schematic cross-sectional view showing the structure of the negative electrode in the embodiment of the present invention, and FIG. 2B illustrates the change in the value of x in the width direction of the active material of the embodiment. It is a schematic diagram to do. FIG. 3A is a partial cross-sectional schematic view showing a state before charging of the secondary battery using the negative electrode in the embodiment of the present invention, and FIG. 3B is viewed from the columnar body side of FIG. It is a partial top view of a negative electrode. 4A is a partial cross-sectional schematic view showing a state after charging of the secondary battery using the negative electrode in the embodiment of the present invention, and FIG. 4B is a view from the columnar body side of FIG. It is the partial top view of the negative electrode seen. In the drawings, the positive electrode and the current collector are drawn so as to face each other directly, but this is for ease of explanation, and basically the surface of most current collectors is columnar. It is covered with the body.

  That is, as shown in FIG. 2A, the surface roughness Ra is 0.5 μm to 8 μm on at least the upper surface of the current collector 11 made of a conductive metal material such as a 30 μm thick copper (Cu) foil. The concave portions and the small convex portions 12 and the large convex portions 13 are provided at random to form a rough surface. When the surface roughness Ra is less than 0.5 μm, it is difficult to form a discrete columnar structure. Therefore, the current collector 11 is wrinkled or deformed due to expansion and contraction due to insertion and extraction of lithium ions. Absent. In addition, when the surface roughness Ra exceeds 8 μm, the surface of the current collector covered with the columnar body has a large area directly facing the positive electrode, so that lithium is liable to be precipitated, and the capacity is reduced due to lithium precipitation. It is not preferable.

  For example, on the upper portions of the large convex portion 13 having a surface roughness of 8 μm and the small convex portion 12 having a surface roughness of 1 μm, the active material represented by SiOx constituting the negative electrode 1 is, for example, a sputtering method or a vacuum deposition method. It is formed in the shape of a columnar body 15 made up of n (n ≧ 2) stages of columnar body portions that are tilted by an oblique vapor deposition method. At this time, the columnar body is composed of, for example, a plurality of columnar body portions, which are formed in a zigzag folded shape. Further, as shown in FIG. 4B, the columnar bodies 15 are formed in an arbitrary size and a random arrangement corresponding to the surface roughness Ra of the current collector 11.

  Hereinafter, the columnar body 15 formed by laminating the columnar body portions 151, 152, 153, 154, and 155 having five stages on the large convex portion 13 will be described in detail, but n ≧ If it is two steps, it is not limited to this. Although not specifically described below, the columnar body formed on the small convex portion 12 of the current collector 11 is also formed at the same time. Therefore, the small convex portion 12 and the large convex portion 13 may be simply expressed as a convex portion.

First, the columnar body portion 151 of the columnar body 15 includes at least the center line (A) in the oblique direction of the columnar body portion 151 on the convex portions 12 and 13 of the current collector 11 and the center of the current collector 11 in the thickness direction. line (AA-AA) and the intersecting angle is formed so as to form (hereinafter, may be referred to as "obliquely erected angle") theta _1. Next, the columnar body part 152 of the columnar body 15 has an oblique center line (B) and a center line (AA-AA) in the thickness direction of the current collector 11 on the columnar body part 151. The vertical angle θ ₂ is formed. Next, the columnar body portion 153 of the columnar body 15 has an oblique center line (C) and a center line (AA-AA) in the thickness direction of the current collector 11 on the columnar body portion 152. It is formed so as to form an upright angle theta _3. Next, the columnar body part 154 of the columnar body 15 has an oblique center line (D) and a center line (AA-AA) in the thickness direction of the current collector 11 on the columnar body part 153. The vertical angle θ ₄ is formed. Next, the columnar body portion 155 of the columnar body 15 has an oblique center line (E) and a center line (AA-AA) in the thickness direction of the current collector 11 on the columnar body portion 154. The vertical angle θ ₅ is formed. Note that the oblique angles θ ₁ , θ ₂ , θ ₃ , θ ₄ , and θ ₅ may be the same angle or different angles if the adjacent columnar bodies 15 do not come into contact with each other due to expansion and contraction during insertion and extraction of lithium ions. It may be.

  Further, as shown in FIG. 2B, the columnar body portions 151 to 155 constituting the columnar body 15 are, for example, odd-numbered columnar body portions 151, 153, and 155 and even-numbered columnar body portions 152 and 154. The content ratio of elements in the width direction of, for example, the direction in which the value of x changes is different. That is, the value of x is sequentially increased from the oblique angle side forming the acute angle of the columnar body parts 151 to 155 toward the obtuse angle side. In addition, in FIG.2 (b), although the value of x is shown changing linearly, it is not restricted to this.

  Furthermore, as shown in FIG. 4, when discharging a fully charged secondary battery, the columnar body 15 composed of the five-stage columnar body portions expanded by charging is in an upright state with respect to the current collector 11. . Therefore, the electrolytic solution 18 between adjacent columnar bodies 15 can easily move through the columnar bodies 15 as indicated by arrows in the drawing. And since the electrolyte solution 18 between the columnar bodies 15 can be easily convected through the gaps between the columnar bodies 15, the movement of lithium ions and the like are not hindered. As a result, the movement of the electrolytic solution can follow the expansion and contraction of the columnar body during charge and discharge, and cycle characteristics can be improved. At this time, the porosity between the columnar bodies at the time of formation is preferably 45% or more. Furthermore, the porosity of the discharge state in charge / discharge is particularly preferably 25% or more and 45% or less. Here, the porosity is the ratio of the total space between the columnar bodies formed on the current collector to the product of the area of the current collector and the height (thickness) of the columnar bodies. In addition, when the porosity at the time of discharge exceeds 45%, lithium tends to precipitate on the collector surface. Moreover, when the porosity at the time of discharge is less than 25%, the columnar body is liable to come into contact with the expansion due to occlusion of lithium ions at the time of charging, which causes the current collector to be wrinkled or deformed.

  Further, as shown in FIGS. 3B and 4B, the columnar bodies 15 are randomly arranged on the surface of the current collector 11 with different sizes and shapes. Therefore, even if a large columnar body expands due to occlusion of lithium ions, a small columnar body existing between them can be deformed, for example, to relieve stress due to contact of the large columnar body. And since a small columnar body fills the clearance gap between large columnar bodies, a large columnar body and a small columnar body contact moderately, electronic conductivity is improved, and cycling characteristics improve. Furthermore, the exposed area of the current collector facing the positive electrode 17 can be reduced. In addition, since the gap in which the electrolytic solution moves can be secured by the small columnar body, the movement of the electrolytic solution easily follows the expansion and contraction of the columnar body during charging and discharging, and the cycle characteristics are further improved.

  In the present invention, the columnar body is formed by stacking n-stage columnar body parts having different oblique directions. When the amount of active material capable of occluding and releasing lithium ions is made equal, the columnar body at each stage The height (thickness) of the part can be reduced. As a result, the amount of expansion at the tip of the columnar body portion at each stage is reduced as compared with the case where it is configured by one columnar body. That is, the gap due to the interval between adjacent columnar bodies is less likely to be narrowed due to the expansion of the columnar bodies, and therefore, pressing between the columnar bodies is less likely to occur. Therefore, since the tolerance for expansion of the columnar body can be greatly increased, more lithium ions can be occluded and the battery capacity can be improved.

  Moreover, even if the columnar body expands, the gap between the adjacent columnar bodies can be largely maintained by the columnar body including the n-stage columnar body portions. And since adjacent columnar bodies are hard to contact, generation | occurrence | production of the stress by the contact of a collector is prevented and the wrinkles and peeling by it can be prevented beforehand. On the other hand, even when the columnar bodies are in contact, the large columnar bodies and the small columnar bodies are randomly arranged, so the small columnar bodies prevent contact between the large columnar bodies and relieve the stress. can do. As a result, a nonaqueous electrolyte secondary battery excellent in charge / discharge cycle characteristics can be realized.

  According to the present embodiment, it is possible to manufacture a non-aqueous electrolyte secondary battery excellent in cycle life characteristics while suppressing deformation of electrodes such as expansion, wrinkling, and elongation while enabling high capacity.

  Hereinafter, the manufacturing method of the columnar body of the negative electrode for a nonaqueous electrolyte secondary battery in the embodiment of the present invention will be described with reference to FIGS.

  FIG. 5 is a partial cross-sectional schematic diagram for explaining a method of forming a columnar body composed of n = 5 columnar body portions of the negative electrode for a nonaqueous electrolyte secondary battery in the embodiment of the present invention. FIG. It is a schematic diagram explaining an apparatus.

  Here, the manufacturing apparatus 40 for forming the columnar body shown in FIG. 6 includes the unwinding / winding roll 41, the film forming rolls 44a and 44b, the winding / unwinding roll 45, the vapor deposition source 43a, in the vacuum vessel 46. 43 b, a mask 42 and oxygen nozzles 48 a and 48 b, and the pressure is reduced by a vacuum pump 47. The manufacturing apparatus 40 shows an example in which the columnar body is formed by forming n-stage columnar body portions on one side of the current collector, but in practice, the columnar bodies are disposed on both sides of the current collector. The device configuration to be manufactured is common.

  First, as shown in FIG. 5A and FIG. 6, a strip-shaped electrolytic copper foil having a thickness of 30 μm is used, and the surface roughness Ra is 0.5 μm to 8 μm using, for example, an etching method. A current collector 11 in which concave and convex portions are randomly formed is produced. And the collector 11 is installed between the winding / unwinding roll 41 and the winding / unwinding roll 45 shown in FIG.

Next, as shown in FIG. 5B and FIG. 6, an angle with respect to the normal direction of the current collector 11 using a vapor deposition unit (a unit obtained by vapor deposition source, crucible, and electron beam generator). An active material such as Si (scrap silicon: purity 99.999%) is evaporated from a vapor deposition source 43a provided at a position of ω (for example, 55 °), and on the convex portion of the current collector 11 in the drawing Incident from the direction of the arrow. At the same time, oxygen (O ₂ ) is supplied from the oxygen nozzle 48 a toward the current collector 11. At this time, for example, the inside of the vacuum vessel 46 was set to an oxygen atmosphere having a pressure of 3.5 Pa. And the oxygen nozzle 48a is installed in the position different from the vapor deposition source 43a, as shown in FIG. The current collector 11 sent to the film forming roll 44a is a region where the film forming range is limited by the mask 42, and an active material of SiOx in which Si and oxygen are combined is formed on the convex portions 12 and 13 at an angle θ _1. Thus, the first columnar body portion 151 is formed at a predetermined height (thickness), for example, 1 μm to 5 μm. At this time, depending on the positional relationship between the vapor deposition source 43 a and the oxygen nozzle 48 a and the convex portion of the current collector 11, the value of x of SiOx to be deposited is columnar in a state where it sequentially changes with respect to the moving direction of the current collector 11. A body 15 is formed. For example, in FIG. 5B, the value of x on the right side in the drawing is small, and the value of x on the left side in the drawing is large.

Next, as shown in FIGS. 5C and 6, the current collector 11 having the first-stage columnar body portion 151 formed on the convex portion is sequentially sent to the film forming roll 44 b. Then, an angle ω (for example, with respect to the normal direction of the current collector 11) is used by using a vapor deposition unit (a vaporization source, a crucible, and an electron beam generator unitized) provided to face the film forming roll 44b. The active material such as Si (scrap silicon: purity 99.999%) is evaporated from the vapor deposition source 43b provided at a position of 55 °), and the first columnar body portion 151 of the current collector 11 has a drawing. Incident from the direction of the arrow inside. At the same time, oxygen (O ₂ ) is supplied from the oxygen nozzle 48 b toward the first-stage columnar portion 151 of the current collector 11. At this time, the oxygen nozzle 48b is installed at a position different from the vapor deposition source 43b as shown in FIG. The current collector 11 sent to the film forming roll 44b is a region where the film forming range is limited by the mask 42, and the SiOx active material in which Si and oxygen are combined is placed on the first columnar body 151. The second-stage columnar body portion 152 is formed at a predetermined height (thickness), for example, 1 μm to 5 μm at an angle θ ₂ . At this time, similarly to the first columnar body portion 151, x of SiOx to be formed depends on the positional relationship between the vapor deposition source 43 b and the oxygen nozzle 48 b and the first columnar body portion 151 of the current collector 11. It is formed in a state where the values are sequentially changed with respect to the moving direction of the current collector 11. For example, in the second columnar body portion 152 of FIG. 5C, the value of x on the left side in the drawing is small and the value of x on the right side in the drawing is large. As a result, the first-stage columnar body portion 151 and the second-stage columnar body portion 152 are formed so that the change direction of the value of x is opposite to the moving direction of the current collector and is inclined. It is manufactured with different angles and oblique directions.

  Next, as shown in FIGS. 5D and 6, the unwinding / winding roll 41 and the winding / unwinding roll 45 are driven in reverse to form the second columnar body portion 152. The current collector 11 is returned to the film forming roll 44a, and the third-stage columnar body portion 153 is placed on the second-stage columnar body portion 152 at a predetermined height (see FIG. 5B). (Thickness), for example, 4 μm to 6 μm. At this time, in the third columnar body portion 153 shown in FIG. 5D, the value of x on the right side in the drawing is small, and the value of x on the left side in the drawing is large. As a result, the second-stage columnar body portion 152 and the third-stage columnar body portion 153 are inclined while the change direction of the value of x is opposite to the moving direction of the current collector. It is manufactured with different angles and oblique directions. In the above case, the first-stage columnar body 151 and the third-stage columnar body 153 are formed in the same direction.

  Next, as shown in FIGS. 5E and 6, the columnar body portions 154 and 155 are predetermined on the columnar body portion 153 by repeating the steps of FIGS. 5B and 5C. Are formed at a height (thickness) of 4 μm to 6 μm, for example. Thereby, the negative electrode which has the columnar body 15 which consists of a 5-stage columnar body part is produced.

  In addition, although the column-shaped body which consists of a columnar body part of n = 5 steps was demonstrated to the example above, it is not restricted to this. For example, by repeating the steps of FIG. 5B and FIG. 5C, a columnar body composed of arbitrary n (n ≧ 2) columnar body portions can be formed.

  Further, in the manufacturing apparatus 40 described above, the columnar body is produced by reversing the unwinding / winding roll 41 and the winding / unwinding roll 45, but the present invention is not limited to this, and various apparatus configurations are possible. . For example, a plurality of film forming rolls shown in FIG. 6 may be arranged in series, and an n-stage columnar body may be manufactured while moving the current collector in one direction. Furthermore, after forming a columnar body on one surface of the current collector, the current collector may be inverted to form a columnar body on the other surface of the current collector. Thereby, a negative electrode can be produced with high productivity.

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, this invention is not limited to a following example, Unless it changes the summary of this invention, it can change and use the material etc. to be used.

Example 1
(1) Production of negative electrode The columnar body of the negative electrode was produced using the production apparatus shown in FIG.

  First, as a current collector, a strip-like electrolytic copper foil having a thickness of 30 μm in which concave and convex portions having surface roughness Ra of 0.5 μm, 1 μm, 2 μm, 4 μm, 6 μm, and 8 μm were formed was used.

  Then, Si is used as an active material for the negative electrode, and an oxygen gas having a purity of 99.7% is orthogonal to the vapor deposition source by using a vapor deposition unit (a vaporization source, a crucible, and an electron beam generator unitized). A columnar body having a value of x changed in the width direction made of SiOx was produced by introducing the oxygen nozzle 48a disposed in the vicinity of the current collector into the vacuum vessel of the manufacturing apparatus. At this time, the inside of the vacuum vessel 46 was an oxygen atmosphere with a pressure of 3.5 Pa. Further, at the time of vapor deposition, the electron beam generated by the electron beam generator was deflected by the deflection yoke and irradiated to the vapor deposition source. In addition, the end material (scrap silicon: purity 99.999%) produced when forming a semiconductor wafer was used for the vapor deposition source.

The columnar body was formed at a film formation rate of about 8 nm / s by adjusting the shape of the opening of the mask 42 so that the angle ω was 55 °. As a result, a first-stage columnar body (height 4 μm) was formed. Similarly, by the formation method described in the embodiment, the second to fifth columnar body portions were formed, and a five-stage columnar body (for example, a height of 20 μm) was formed. At this time, columnar body has been formed are disposed at random by the cross-sectional area of 1μm ² ~70μm ² (area when projected from the positive electrode).

  When the angle of the columnar body in the negative electrode with respect to the center line of the current collector was evaluated by cross-sectional observation using a scanning electron microscope (S-4700 manufactured by Hitachi), the oblique angle of the columnar body portion of each step was about 41. °. At this time, the thickness (height) of the formed columnar body was 20 μm with respect to the normal direction.

  Further, when the oxygen distribution was examined by measuring the line distribution in the cross-sectional direction of each columnar body part constituting the negative columnar body using an electron beam probe microanalyzer (hereinafter referred to as “EPMA”), In the width direction of the columnar body part and the even-numbered columnar body part, the oxygen concentration (value of x) continuously increased in the (180-θ) direction from the oblique angle θ side. The increasing direction of the oxygen concentration (value of x) was opposite in the odd-numbered columnar body portions and the even-numbered columnar body portions. The range of x at this time was 0.1 to 2, and the average was 0.6.

  As described above, a negative electrode including a columnar body including five columnar body portions having different sizes on the convex portion of the current collector was produced.

  Thereafter, 15 μm of Li metal was deposited on the negative electrode surface by vacuum deposition.

  Thereafter, an exposed portion of the current collector was provided on the Cu foil not facing the positive electrode of the negative electrode, and a Cu negative electrode lead was welded.

(2) Production of positive electrode A positive electrode having a positive electrode active material capable of inserting and extracting lithium ions was produced by the following method.

First, 93 parts by weight of LiCoO ₂ powder as a positive electrode active material and 4 parts by weight of acetylene black as a conductive agent were mixed. To this powder, an N-methyl-2-pyrrolidone (NMP) solution of polyvinylidene fluoride (PVDF) as a binder (product number # 1320 manufactured by Kureha Chemical Industry Co., Ltd.) is added, and the weight of PVDF becomes 3 parts by weight. Mixed. An appropriate amount of NMP was added to this mixture to prepare a positive electrode mixture paste. This positive electrode mixture paste was applied onto both surfaces of a current collector using a doctor blade method on a positive electrode current collector (thickness 15 μm) made of aluminum (Al) foil, and the density of the positive electrode mixture layer was 3. It was rolled to 5 g / cc and a thickness of 170 μm, dried sufficiently at 85 ° C., and cut to form a positive electrode. An exposed portion was provided on an Al foil not facing the negative electrode on the inner peripheral side of the positive electrode, and an Al positive electrode lead was welded.

(3) Production of Battery The negative electrode and the positive electrode produced as described above were laminated via a separator made of porous polypropylene having a thickness of 25 μm to constitute a 40 mm × 30 mm square electrode group. Then, an electrode group is impregnated with an ethylene carbonate / diethyl carbonate mixed solution of LiPF ₆ as an electrolytic solution and accommodated in an outer case (material: aluminum), and an opening of the outer case is sealed to produce a stacked battery. did. The design capacity of the battery was 90 mAh. This is designated as Samples 1, 2, 3, 4, 5, 6.

(Example 2)
Six negative electrodes having different surface roughness Ra were produced in the same manner as in Example 1 except that the pressure inside the vacuum vessel was formed in an oxygen atmosphere of 1.7 Pa.

  The oblique angle of the columnar body portion of each step was about 41 °, and the thickness (height) of the formed columnar body was 20 μm.

  Further, from EPMA, in the width direction of each columnar body portion, the oxygen concentration (value of x) continuously increased in the (180-θ) direction from the oblique angle θ side. The increasing direction of the oxygen concentration (value of x) was in the opposite direction between the odd-numbered columnar body portions and the even-numbered columnar body portions. At this time, the range of x was 0.1 to 2, and the average was 0.3.

  Thereafter, 10 μm of Li metal was deposited on the negative electrode surface by vacuum deposition.

  Samples 7, 8, 9, 10, 11, and 12 were non-aqueous electrolyte secondary batteries produced by the same method as in Example 1 except that the negative electrode was used.

(Example 3)
The columnar body was made of a negative electrode having a different surface roughness Ra and a battery using the same by the same method as in Example 1 except that the thickness of each columnar body portion was 2 μm and n = 10 steps. This is designated as Samples 13, 14, 15, 16, 17, and 18.

Example 4
As the current collector, a strip-like electrolytic copper foil with a thickness of 30 μm having a concave portion and a convex portion with a surface roughness Ra of 2 μm is used, and the angle ω is 30 °, 40 °, 50 °, 60 °, and 70 °. A negative electrode and a battery using the negative electrode were produced in the same manner as in Example 1 except for using the negative electrode. Thereby, different negative electrodes having a porosity of 40% to 65% were produced. This is designated as Samples 19, 20, 21, 22, and 23.

(Example 5)
The columnar body was made of a negative electrode having a different surface roughness Ra and a battery using the same in the same manner as in Example 1 except that the thickness of each columnar body portion was 1 μm and n = 20 steps was formed. This is designated as Samples 24, 25, 26, 27, and 28.

(Example 6)
The columnar body was prepared in the same manner as in Example 1 except that the thickness of each columnar body portion was 0.7 μm and n = 30 steps, and a negative electrode having a different surface roughness Ra and a battery using the same were produced. . This is designated as Samples 29, 30, 31, 32, and 33.

(Example 7)
Except for the columnar body, the thickness of each columnar body part was 0.5 μm, and n = 40 steps, and a negative electrode having a different surface roughness Ra and a battery using the same were produced in the same manner as in Example 1. . This is designated as Samples 34, 35, 36, 37, and 38.

(Example 8)
Except for the columnar body having a thickness of each columnar body portion of 0.4 μm and n = 50 steps, a negative electrode having a different surface roughness Ra and a battery using the same were produced in the same manner as in Example 1. . This is designated as Samples 39, 40, 41, 42, 43.

Example 9
The columnar body was prepared with a negative electrode having a different surface roughness Ra and a battery using the same in the same manner as in Example 1 except that the thickness of each columnar body portion was 0.2 μm and n = 100 steps was formed. . This is designated as Samples 44, 45, 46, 47, and 48.

(Comparative Example 1)
Negative electrodes having different surface roughness Ra were prepared in the same manner as in Example 1 except that a columnar body was formed by tilting in one step at a height (thickness) of 20 μm.

  The angle of the columnar body in the negative electrode with respect to the center line of the current collector was evaluated by cross-sectional observation using a scanning electron microscope (Hitachi S-4700). The oblique angle of the columnar body was about 41 °. . At this time, the formed columnar body had a thickness (height) of 20 μm.

  Further, when the oxygen distribution was examined by measuring the line distribution in the cross-sectional direction forming the columnar body of the negative electrode using EPMA, the oxygen concentration (value of x) in the (180-θ) direction from the oblique angle θ side in the width direction. Increased continuously. The range of x was 0.1 to 2, and the average was 0.6.

  Samples C1, C2, C3, C4, C5, and C6 are non-aqueous electrolyte secondary batteries manufactured by the same method as in Example 1 except that the negative electrode is used.

(Comparative Example 2)
A negative electrode and a battery using the same were produced in the same manner as in Example 1 except that a rolled copper foil having a surface roughness Ra of less than 0.5 μm was used as the current collector. This is designated as Sample C7.

(Comparative Example 3)
A negative electrode and a battery using the same were produced in the same manner as in Example 1 except that a strip-like electrolytic copper foil having a surface roughness Ra of 20 μm was used as a current collector. This is designated as Sample C8.

  The following evaluation was performed on each non-aqueous electrolyte secondary battery produced as described above.

(Measurement of porosity of negative electrode)
The porosity of the negative electrode after film formation was calculated from the weight and thickness of the formed active material and the true specific gravity of the active material. 2.2 g / cc (SiOx) was used as the true specific gravity of the active material.

  The porosity of the negative electrode after charge / discharge was calculated by the same method as described above by measuring the thickness of the active material after charge / discharge. In particular, the porosity in the discharged state was calculated as described above.

(Measurement of battery capacity)
Each nonaqueous electrolyte secondary battery was charged / discharged under the following conditions at 25 ° C. environmental temperature.

  First, with respect to the design capacity (90 mAh), the battery is charged at a constant current of 1.0 C (90 mA) at a time rate of 4.2 V until the battery voltage reaches 4.2 V, and a time rate of 0.05 C (4.5 mA at a constant voltage of 4.2 V). ) Was performed at a constant voltage to attenuate the current value. Then, it rested for 30 minutes.

  Then, it discharged with the constant current until the battery voltage fell to 2.5V with the current value of the time rate 0.2C (18mA).

  And the above was made into 1 cycle and the discharge capacity of the 3rd cycle was made into the battery capacity.

(Charge / discharge cycle characteristics)
Each nonaqueous electrolyte secondary battery was repeatedly charged and discharged under the following conditions at an ambient temperature of 25 ° C.

  First, with respect to the design capacity (90 mAh), charging is performed at a constant current of 1.0 C (90 mA) until the battery voltage reaches 4.2 V, and at a constant voltage of 4.2 V, the charging current is 0.05 C (time rate). The battery was charged until the current value decreased to 4.5 mA). And it stopped for 30 minutes after charge.

  Thereafter, the battery was discharged at a constant current until the battery voltage dropped to 2.5 V at a current value of 0.2C (18 mA). And it stopped for 30 minutes after discharge.

  The charge / discharge cycle was defined as one cycle, which was repeated 500 times. And the value which expressed the ratio of the discharge capacity of the 500th cycle with respect to the discharge capacity of the 1st cycle in percentage was made into the capacity maintenance rate (%). That is, the closer the capacity retention rate is to 100, the better the charge / discharge cycle characteristics.

  Furthermore, the thickness of the electrode group at the third cycle and the thickness of the electrode group at the 500th cycle are measured by CT photographs, and the thickness obtained by subtracting the thickness of the electrode group at the third cycle from the thickness of the electrode group at the 500th cycle is cycled. It was set as the deformation amount of the electrode group by.

  The specifications and evaluation results of Sample 1 to Sample 28 are shown in (Table 1), and the specifications and evaluation results of Sample 29 to Sample 48 and Sample C1 to Sample C8 are shown in (Table 2).

  As shown in (Table 1) and (Table 2), when Sample 1 to Sample 6 and Sample C1 to Sample C6 are compared, deformation of the electrode group at the time of 500 cycles is suppressed and the capacity retention rate is improved. It is clear. This is considered to be due to the improvement in the porosity of the negative electrode and the optimal arrangement of the space for absorbing expansion between the columnar bodies. Furthermore, in Samples C1 to C6, the inclination of the columnar body changes with charge and discharge, and stress tends to concentrate on the joint interface with the convex part, whereas in Samples 1 to 6, stress is applied to each columnar body part. It was found to be dispersed. These phenomena are also thought to contribute to the improvement of cycle characteristics.

  Samples 7 to 12 with different oxygen ratios and Samples 13 to 18 and Samples 24 to 24 with the number of columnar body portions changed to 10, 20, 30, 40, 50, and 100. In 48, the same effect as Sample 1 to Sample 6 was obtained. Furthermore, with the increase in the number of steps of the columnar body portion, there was a tendency that the porosity increased slightly and the capacity maintenance rate at the 500th cycle improved. This is considered to be due to the fact that as the number of steps increases, the columnar body becomes thinner and the symmetry of the shape of the columnar body becomes higher.

  Further, when the results of Sample 19 to Sample 23 in which the porosity of the negative electrode produced by changing the angle ω from 30 ° to 70 ° was changed, the porosity of the negative electrode at the time of formation was 45% or more, and the negative electrode after discharge In the negative electrode having a porosity of 25% to 45%, the deformation of the electrode group due to the cycle and the improvement of the cycle characteristics were observed.

  Further, in the sample C7 in which the surface roughness Ra of the current collector was less than 0.5 μm and the sample C8 in which the surface roughness Ra was 20 μm, the cycle characteristics were remarkably deteriorated. The cause of this is considered to be the result that the relaxation effect between the columnar bodies due to the decrease in the adhesion between the columnar bodies and the current collector and the decrease in the porosity cannot be obtained.

  From the above results, it is possible to provide a nonaqueous electrolyte secondary battery excellent in cycle characteristics by suppressing the deformation of the electrode group accompanying the cycle by using the negative electrode produced by the production method of the present invention.

  In the above embodiment, the example using SiOx as the active material of the columnar body has been described, but it is not particularly limited as long as it is an element capable of reversibly occluding and releasing lithium ions. For example, Al, In, Zn At least one element composed of Cd, Bi, Sb, Ge, Pb and Sn is preferable. Furthermore, as the active material, materials other than the above-described elements may be included. For example, a transition metal or a 2A group element may be contained.

  In the present invention, the shape and interval of the protrusions formed on the current collector are not limited to the contents described in the above embodiments, and can form an oblique columnar body. Any shape is acceptable.

  Further, the oblique angle formed by the center line of the columnar body and the centerline of the current collector, and the shape and dimensions of the columnar body are not limited to the above-described embodiment, and the manufacturing method of the negative electrode and the non-use It is appropriately changed according to the required characteristics of the water electrolyte secondary battery.

  ADVANTAGE OF THE INVENTION According to this invention, the nonaqueous electrolyte secondary battery excellent in charging / discharging cycling characteristics can be provided, enabling high capacity | capacitance. Therefore, it is useful as a secondary battery from a portable electronic device such as a mobile phone, a notebook PC, and a PDA to which a large demand is expected in the future to a large electronic device.

Sectional drawing of the nonaqueous electrolyte secondary battery in embodiment of this invention (A) Schematic diagram of a partial cross section showing the structure of the negative electrode in the embodiment of the present invention (b) Schematic diagram explaining the change in the value of x in the width direction of the active material of the embodiment (A) Partial cross-sectional schematic diagram showing the state before charging of the secondary battery using the negative electrode in the embodiment of the present invention (b) Partial plan view of the negative electrode seen from the columnar body side of FIG. (A) Partial cross-sectional schematic diagram showing a state after charging of the secondary battery using the negative electrode in the embodiment of the present invention (b) Partial plan view of the negative electrode seen from the columnar body side of FIG. The partial cross section schematic diagram explaining the formation method of the columnar body which consists of the columnar body part of n = 5 step | paragraph of the negative electrode for nonaqueous electrolyte secondary batteries in embodiment of this invention The schematic diagram explaining the manufacturing apparatus which produces the columnar body which consists of an n-stage columnar body part of the negative electrode for nonaqueous electrolyte secondary batteries in embodiment of this invention (A) Partial cross-sectional schematic diagram showing the structure of a conventional negative electrode before charging (b) Partial cross-sectional schematic diagram showing the structure of a conventional negative electrode after charging

Explanation of symbols

1 Negative electrode 1a, 11 Current collector (Negative electrode current collector)
DESCRIPTION OF SYMBOLS 1b, 15 Columnar body 2,17 Positive electrode 2a Positive electrode collector 2b Positive electrode mixture layer 3 Separator 4 Electrode group 5 Exterior case 12 Small convex part (convex part)
13 Large convex part (convex part)
DESCRIPTION OF SYMBOLS 18 Electrolyte 40 Production apparatus 41 Unwinding / winding roll 42 Mask 43a, 43b Deposition source 44a, 44b Film forming roll 45 Winding / unwinding roll 46 Vacuum container 47 Vacuum pump 48a, 48b Oxygen nozzle 151, 152, 153 154,155 Columnar body

Claims (11)

A negative electrode for a non-aqueous electrolyte secondary battery that reversibly occludes and releases lithium ions, the current collector having a rough surface with a surface roughness Ra on at least one surface, and formed on the rough surface of the current collector A columnar body formed by stacking n (n ≧ 2) columnar body portions in which the content ratio of the generated elements sequentially changes in the longitudinal direction of the current collector, and the odd-numbered stages of the columnar body portions And a negative electrode for a non-aqueous electrolyte secondary battery, characterized in that the change direction of the content ratio of the even-numbered elements is different. 2. The negative electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein the current collector has a surface roughness Ra of 0.5 μm to 8 μm. The columnar body as viewed from the longitudinal direction and the upper surface of the current collector is formed in a different shape substantially corresponding to the surface roughness Ra of the current collector. The negative electrode for nonaqueous electrolyte secondary batteries as described. At least in the discharged state, the n-stage columnar body portion of the columnar body is formed obliquely on the rough surface of the current collector, and the odd-numbered stages and even-numbered stages are folded in the thickness direction. The negative electrode for a nonaqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the negative electrode is laminated. The void ratio occupied by the space is 25% or more and 45% or less with respect to the space occupying between the columnar body and the columnar body in a discharged state. 2. A negative electrode for a nonaqueous electrolyte secondary battery according to item 1. The active material having a theoretical capacity density of at least 833 mAh / cm ³ capable of reversibly occluding and releasing at least lithium ions is used as the columnar body portion, according to any one of claims 1 to 5. The negative electrode for nonaqueous electrolyte secondary batteries as described. The negative electrode for a nonaqueous electrolyte secondary battery according to claim 6, wherein a material represented by SiOx containing at least silicon is used as the active material. The obtuse angle is formed from the side forming the acute angle with respect to the intersection angle between the center line in the oblique direction of the columnar body portion and the center line in the thickness direction of the current collector. The negative electrode for a nonaqueous electrolyte secondary battery according to claim 7, wherein the negative electrode is increased toward the side of the nonaqueous electrolyte secondary battery. A method for producing a negative electrode for a non-aqueous electrolyte secondary battery that reversibly occludes and releases lithium ions,
A first step of forming a rough surface having a surface roughness Ra on at least one surface of the current collector;
A second step of forming the first-stage columnar body portion obliquely on the rough surface;
A third step of forming a second-stage columnar body obliquely inclined in a different direction from the first-stage columnar body part on the columnar body part;
The second step and the third step are repeated to form the columnar body having n (n ≧ 2) stages by changing the oblique direction of the odd-numbered and even-numbered columnar body portions. When,
The manufacturing method of the negative electrode for nonaqueous electrolyte secondary batteries characterized by including. The non-aqueous solution according to claim 9, wherein the columnar body viewed from the longitudinal direction and the upper surface of the current collector is formed in a different shape substantially corresponding to a surface roughness Ra of the current collector. A method for producing a negative electrode for an electrolyte secondary battery. A negative electrode for a nonaqueous electrolyte secondary battery according to any one of claims 1 to 8, a positive electrode capable of reversibly occluding and releasing lithium ions, and a nonaqueous electrolyte. Non-aqueous electrolyte secondary battery.

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