JP2008226812A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery where an anode active material having large expansion/contraction is used and which has a large battery capacity and is superior in reliability. <P>SOLUTION: The nonaqueous electrolyte secondary battery is provided at least with an anode 2 constituted of a cylindrical body 15, made of lamination of an n layers (n≥2) of cylindrical body portions which are formed on a convex portion 13 of a current collector with convex portions 13, and which have standing inclined directions different from each other in a longitudinal direction; a cathode 1 provided with a cathode mixture layer, containing a cathode active substance which can reversibly store and release lithium ion on both sides of a cathode current collector; and a separator 3 provided between the cathode 1 and the anode 2. The top end of the cylindrical body portion provided on the upper most layer of the cylindrical body of the anode 2 is in a stands inclined, directed toward a terminal direction of winding. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cylindrical nonaqueous electrolyte secondary battery, and specifically to the structure of the negative electrode.

  In recent years, as electronic devices become more portable and cordless, secondary batteries such as nickel metal hydride and lithium ion, which are small and light and have a high energy density, have attracted attention as power sources for driving them.

  The lithium ion secondary battery includes a positive electrode made of a lithium-containing composite oxide, a negative electrode containing 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 materials increase in volume when they occlude lithium ions. For example, when using a negative electrode comprising a negative electrode active material composed of Si, in the state in which lithium ions are maximum amount occluded, the anode active material is represented by Li _{4.4 Si,} it was changed from Si to Li _{4.4 Si} The volume increase rate at the time is 4.12 times.

  Therefore, the negative electrode active material expands and contracts due to insertion and extraction of lithium ions, and there is a possibility that peeling due to a decrease in the adhesion between the negative electrode active material and the negative electrode current collector may occur during repeated charge / discharge cycles. .

In order to solve this problem, a method is disclosed in which irregularities are provided on the surface of the current collector, and a thin-film negative electrode material is formed thereon so as to be inclined with respect to a plane perpendicular to the main surface of the negative electrode material. (For example, refer to Patent Document 1). Thereby, it is shown that the stress generated by the expansion / contraction of charge / discharge can be dispersed in a direction parallel to the main surface of the negative electrode material and a direction perpendicular thereto, thereby suppressing the occurrence of wrinkles and peeling.
JP-A-2005-196970

  According to the secondary battery of Patent Document 1, an electrode group is formed by laminating a separator and a positive electrode on a columnar negative electrode material that is inclined and formed on a convex portion of a current collector, and these are wound to form a cylindrical type. The next battery is manufactured. However, since the group diameter of the electrode group becomes large due to the expansion of the negative electrode material due to the occlusion of lithium ions, it is necessary to consider the shape change of the electrode group in advance so that the size can be accommodated in the battery case. For this reason, there is a problem that the space in the battery case cannot be used effectively and the improvement of the battery capacity is limited. In addition, since the dimensions of the secondary battery are defined by the dimensions of the battery case, a large stress is generated in the columnar negative electrode material due to the expansion of the electrode group. In addition, since the columnar negative electrode material is bonded to the current collector, particularly at the convex portion, there is a problem that stress concentrates on the bonded portion and the columnar negative electrode material peels from the current collector. Moreover, even when not peeling, wrinkles and deformation may occur in the current collector. As a result, cycle characteristics and reliability may be lowered.

  The present invention solves the above-mentioned problem, avoids expansion of the electrode group, and further disperses stress concentration at the junction of the negative electrode material, thereby increasing the battery capacity and improving reliability such as cycle characteristics and high rate characteristics. An object of the present invention is to provide a nonaqueous electrolyte secondary battery excellent in the above.

  In order to achieve the above-described object, the non-aqueous electrolyte secondary battery of the present invention has different oblique directions in the longitudinal direction of the current collector formed on the convex portion of the current collector having the convex portion. A positive electrode mixture comprising a negative electrode comprising a columnar body formed by stacking columnar body parts in n (n ≧ 2) stages, and a positive electrode active material capable of reversibly occluding and releasing lithium ions on both surfaces of the positive electrode current collector A positive electrode having a layer and a separator provided oppositely between the positive electrode and the negative electrode, and the tip of the columnar body portion provided at the uppermost stage of the columnar body of the negative electrode is in the terminal direction at the time of winding It has a configuration that is obliquely directed.

  With this configuration, it is possible to disperse and reduce the stress concentration on the joint portion with a columnar body including a plurality of columnar body portions having different oblique directions. In addition, during charging, the shape of the electrode group changes due to horizontal stress acting on the negative electrode current collector due to expansion of the columnar body, and during discharge, the electrode group simply returns to the original electrode group shape. The group can be designed with the same inner diameter as the battery case. As a result, the battery capacity can be further improved by increasing the electrode area as well as improving the battery capacity by the negative electrode active material. In addition, a highly reliable nonaqueous electrolyte secondary battery with significantly improved cycle characteristics and high rate characteristics can be realized.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to improve battery capacity, the highly reliable nonaqueous electrolyte secondary battery which improved the cycle characteristic and the high rate characteristic significantly is realizable.

  According to a first aspect of the present invention, there are n (n ≧ 2) columnar body portions having different oblique directions in the longitudinal direction of the current collector formed on the convex portion of the current collector having the convex portions. Between the positive electrode and the negative electrode, a positive electrode having a positive electrode mixture layer including a positive electrode active material capable of reversibly occluding and releasing lithium ions on both surfaces of the positive electrode current collector, At least a separator provided opposite to the columnar body, and the tip of the columnar body portion provided at the uppermost stage of the columnar body of the negative electrode has an oblique configuration toward the terminal direction during winding.

  With this configuration, it is possible to disperse and reduce the stress concentration on the joint portion with a columnar body including a plurality of columnar body portions having different oblique directions. In addition, during charging, the shape of the electrode group changes due to horizontal stress acting on the negative electrode current collector due to expansion of the columnar body, and during discharge, the electrode group simply returns to the original electrode group shape. The group can be designed with the same inner diameter as the battery case. As a result, the battery capacity can be further improved by increasing the electrode area as well as improving the battery capacity by the negative electrode active material. In addition, a highly reliable nonaqueous electrolyte secondary battery with significantly improved cycle characteristics and high rate characteristics can be realized.

  According to a second aspect of the present invention, in the first aspect, the columnar body has a configuration in which the columnar body is tilted toward the terminal direction during winding. Thereby, the exposure of the collector at the time of charge can be suppressed, and a nonaqueous electrolyte secondary battery excellent in reliability can be realized.

  According to a third aspect of the present invention, in the second aspect, the tip of the columnar body portion provided at the uppermost stage of the columnar body has a configuration in which the tip is inclined toward the start end direction during winding. Thereby, since the inclination direction of the columnar body portion at the tip is not limited, a non-aqueous electrolyte secondary battery having excellent design freedom can be realized.

  According to a fourth aspect of the present invention, in the first aspect, the content ratio of the elements constituting the columnar body portion is changed in the obliquely extending width direction of the columnar body portion. As a result, when the negative electrode active material absorbs lithium ions and expands, the oblique angle of the columnar body portion can be changed, and contact with the adjacent columnar body can be suppressed. A water electrolyte secondary battery is obtained.

  According to a fifth aspect of the present invention, in the fourth aspect, the change direction of the content ratio of the odd-numbered and even-numbered elements of the columnar body portion is different. Thereby, it can suppress that the expansion direction of the columnar body by occlusion of lithium ion deviates, and can maintain the space | gap between columnar bodies.

  According to a sixth aspect of the present invention, in the fourth or fifth aspect, at least in a charged state, an acute angle formed by the center line of the columnar body portion and the plane of the current collector is the discharge side. It has a configuration that is larger than the angle of the state. Thereby, the space | gap between columnar bodies is maintained with respect to expansion | swelling of the columnar body by occlusion of lithium ion, and a deformation | transformation of an electrode plate can be suppressed.

According to a seventh aspect of the present invention, in the first aspect, 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. Thereby, the negative electrode for nonaqueous electrolyte secondary batteries using a high capacity | capacitance active material is obtained.

  In an eighth aspect of the present invention, in the seventh aspect, a material represented by SiOx containing at least silicon is used as the active material. As a result, a nonaqueous electrolyte secondary battery with high electrode reaction efficiency, high capacity and relatively low price can be obtained.

  According to a ninth aspect of the present invention, in the eighth aspect, the x value of the silicon-containing material is set to an acute angle with respect to the angle formed by the center line of the columnar body portion and the plane of the current collector. It has the structure which increases continuously toward the side which forms an obtuse angle from the side to form.

  As a result, it is possible to reversibly change the oblique angle of the columnar body while protecting the columnar body from mechanical stress due to sudden stress fluctuations accompanying expansion during charging and discharging.

  Hereinafter, embodiments of the present invention will be described 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 1)
1 is a cross-sectional view of a nonaqueous electrolyte secondary battery according to Embodiment 1 of the present invention. FIG. 2 (a) is a plan view schematically showing a state in which the electrode group of the nonaqueous electrolyte secondary battery in Embodiment 1 of the present invention is wound, and FIG. 2 (b) is a plan view of FIG. 2 (a). It is a partial expanded sectional view explaining the structure of a negative electrode in detail.

  As shown in FIG. 1, a cylindrical nonaqueous electrolyte secondary battery (hereinafter referred to as “battery”) includes a positive electrode 1 having a positive electrode lead 8 made of, for example, aluminum, and a positive electrode 1 facing the positive electrode 1, for example, made of copper The electrode group 4 is wound as shown in FIG. 2A through the separator 3 and the negative electrode 2 having the negative electrode lead 9 at one end. Then, the insulating plates 10a and 10b are mounted on the upper and lower sides of the electrode group 4 and inserted into the battery case 5, the other end of the positive electrode lead 8 is used as the sealing plate 6, and the other end of the negative electrode lead 9 is used as the battery case 5. Weld to the bottom. Further, a non-aqueous electrolyte (not shown) that conducts lithium ions is injected into the battery case 5, and the open end of the battery case 5 is caulked to the sealing plate 6 via the gasket 7. The positive electrode 1 includes a positive electrode current collector 1a and a positive electrode mixture layer 1b containing a positive electrode active material.

  Further, as will be described in detail below, the negative electrode 2 includes, as shown in FIG. 2B, a negative electrode current collector 11 (hereinafter referred to as “current collector”) having a concave portion 12 and a convex portion 13, and at least A columnar body portion is laminated on n (n ≧ 2) stages provided in an inclined manner on the convex portion, and is composed of, for example, a zigzag-shaped columnar body 15. At this time, among the columnar body portions constituting the columnar body 15, the tip of the columnar body portion provided at the uppermost stage of the columnar body is directed toward the terminal direction (winding end direction) when winding the electrode group. A columnar body is provided so as to be inclined. In addition, the columnar body portion is formed by sequentially changing the content ratio of elements formed on the convex portion 13 of the current collector 11 in the longitudinal direction of the current collector. And the columnar body part 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.

Here, the positive electrode mixture layer 1b 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 1b 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 1a used for the positive electrode 1, 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. When using at least an electrolyte solution, a separator 3 such as a nonwoven fabric or a microporous film made of polyethylene, polypropylene, aramid resin, amideimide, polyphenylene sulfide, polyimide, etc. is used between the positive electrode 1 and the negative electrode 2, and the electrolyte solution is used for this. It is preferable to impregnate. 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 the same binder as used for the positive electrode 1 and the negative electrode 2 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 1 and the negative electrode 2 instead of the separator. Alternatively, the gel-like nonaqueous electrolyte may be disposed adjacent to the separator 3.

  The current collector 11 of the negative electrode 2 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 columnar body part constituting the columnar body 15 of the negative electrode 2 has a theoretical capacity density that reversibly occludes / releases lithium ions such as silicon (Si) and tin (Sn), and exceeds 833 mAh / cm ³ . An active material can be used. With such an active material, the effect of the present invention can be exhibited with any of a single active material, an alloy, a compound, a solid solution, and a composite active material containing a silicon-containing material and a tin-containing material. That is, as a silicon-containing material, Si, SiOx (0 <x ≦ 2.0), or any one of them, Al, In, Cd, Bi, Sb, B, Mg, Ni, Ti, Mo, Co, Ca, 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 Cr, 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 ≦ 2.0), SnO ₂ , SnSiO ₃ , LiSnO, or the like can be applied.

  These materials may constitute a negative electrode active material alone, or a plurality of types of materials may constitute a negative electrode active material. Examples of constituting the negative electrode active material by the plurality of types of 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. It is done.

  Hereinafter, with reference to FIG. 3 and FIG. 4, the operation of the secondary battery using the negative electrode (hereinafter sometimes referred to as “negative electrode”) of the nonaqueous electrolyte secondary battery and the negative electrode in Embodiment 1 of the present invention will be described. This will be described in detail. Hereinafter, a negative electrode active material (hereinafter referred to as “active material”) represented by SiOx (0 ≦ x ≦ 2.0) containing at least silicon will be described as an example.

  FIG. 3A is a partial cross-sectional schematic diagram showing the structure of the negative electrode according to Embodiment 1 of the present invention, and FIG. 3B shows the change in the value of x in the width direction of the active material of the same embodiment. It is a schematic diagram to explain. FIG. 4 (a) is a partial cross-sectional schematic view showing a state before charging of the secondary battery using the negative electrode in Embodiment 1 of the present invention, and FIG. 4 (b) shows the negative electrode in the same embodiment. It is a partial cross section schematic diagram which shows the state after charge of the used secondary battery.

  As shown in FIG. 3A, a concave portion 12 and a convex portion 13 are provided on at least the upper surface of the current collector 11 made of a conductive metal material such as copper foil. Then, an active material represented by SiOx constituting the negative electrode 2 is obliquely formed on the upper portion of the convex portion 13 by an oblique vapor deposition method using, for example, a sputtering method or a vacuum vapor deposition method. The columnar body 15 is formed in the shape of the columnar body portion 2). At this time, the columnar body 15 is formed in a zigzag shape with, for example, a plurality of columnar body portions.

  Hereinafter, the columnar body 15 formed by laminating the columnar body portions 151, 152, and 153 having n = 3 will be specifically described as an example. However, if n ≧ 2, the present invention is not limited thereto. Needless to say.

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 portion 13 of the current collector 11 and the plane (AA-AA) of the current collector 11. Are formed so as to form a crossing angle (hereinafter referred to as “an oblique angle”) θ ₁ . Then, the columnar body portion 152 of the columnar body 15 has an oblique angle θ ₂ on the columnar body portion 151 so that the center line (B) in the oblique direction and the plane (AA-AA) of the current collector 11 have an oblique angle θ ₂ . Is formed. Further, the columnar body portion 153 of the columnar body 15 has an oblique angle θ _{3 formed} on the columnar body portion 152 between the center line (C) in the oblique direction and the plane (AA-AA) of the current collector 11. Is formed. The oblique angles θ ₁ , θ ₂ , and θ ₃ may be the same angle or different angles as long as the adjacent columnar bodies 15 do not contact each other.

  Further, the columnar body parts 151, 152, 153 constituting the columnar body 15 are, for example, odd-numbered columnar body parts 151, 153 and even-numbered columnar body parts, as schematically shown in FIG. The element content ratios in the width direction of 152, for example, the direction in which the value of x changes are different. That is, the value of x is sequentially increased from the oblique angle side forming the acute angle of the columnar body portions 151, 152, and 153 toward the obtuse angle side. In addition, in FIG.3 (b), although the value of x is shown changing linearly, it is not restricted to this. Here, the width direction is, for example, the winding direction of the negative electrode 2.

Further, the columnar body 15 formed in a three-step shape in a slanted manner on the convex portion 13 of the current collector 11 has a volume due to occlusion of lithium ions during charging of the nonaqueous electrolyte secondary battery. Inflate. At this time, along with the expansion of the volume, the oblique angles θ ₁ , θ ₂ , and θ ₃ of the columnar body portions 151, 152, and 153 of the columnar body 15 are set as described in detail with reference to FIG. As a result, the columnar body 15 is deformed to rise, for example. On the contrary, as shown in FIG. 4 (a), the volume shrinks and the oblique angles θ ₁ , θ ₂ , and θ ₃ become smaller due to the release of lithium ions during discharge, and the initial zigzag folded columnar body. It will be close to 15.

  Further, as shown in FIG. 4A, in the charging start state, the columnar body 15 having the three-stage columnar body portion is inclined on the convex portion 13 of the current collector 11, so that the columnar body When the projection 15 is viewed from the positive electrode 17, the concave portion 12 of the current collector 11 is partially shielded by the columnar body 15 with respect to the positive electrode 17. Therefore, the lithium ions released from the positive electrode 17 during charging are blocked from reaching the concave portion 12 of the current collector 11 by the negative columnar body 15 and most of the lithium ions are occluded in the columnar body 15. Is suppressed. As the lithium ions are occluded, the oblique angle of the three columnar body portions increases. The columnar body may have a tilted angle of 90 ° or less and a zigzag folded shape when charging is completed, but it is preferable to design the columnar body at a tilted angle of 90 °.

  Furthermore, as shown in FIG. 4B, when discharging a fully charged battery, the columnar body 15 composed of the three-stage columnar body portion expanded by charging is in a state of rising from the current collector 11. Become. Therefore, the electrolytic solution 18 between the adjacent columnar bodies 15 can easily move between the columnar bodies 15. 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, high-rate discharge and low temperature discharge characteristics can be greatly improved.

  At this time, the fully charged columnar body 15 expands due to occlusion of lithium ions and receives stress in the electrode thickness direction. Conventionally, in the case of a one-stage oblique columnar body, the stress is concentrated as a moment on the joint between the convex portion 13 of the current collector 11 and the columnar body, and the joint is easily peeled off. In addition, the electrode group swells due to expansion, but since the diameter of the electrode group is defined by the battery case 5, there is a problem that the electrode group is deformed in order to relieve this stress.

  Therefore, the effect on the shape change of the electrode group will be described with reference to FIG. 5 by using the negative electrode in the first embodiment of the present invention.

  As shown by the arrows in FIG. 5, the expansion stress acting on the separator and the positive electrode due to the expansion of the columnar body is decomposed and applied to the columnar body by its reaction force and horizontal component force.

  That is, the negative columnar body 15 in contact with the separator 3 of the electrode group 4 applies an expansion stress to the separator 3, and the reaction force is applied to the columnar body 15 itself. However, the reaction force reduces the stress concentration at the joint due to the spring effect that relaxes at the bending point between the columnar body parts provided in a zigzag shape and the structure with a reduced moment (the length of the columnar body part is short). Reduced. As a result, it is possible to obtain a nonaqueous electrolyte secondary battery that is excellent in reliability and cycle characteristics that hardly cause peeling and deformation.

  On the other hand, the columnar body moves in the direction of the winding start end due to the horizontal component of the expansion stress. As a result, the electrode group is tightened by the expansion of the negative electrode, and the outer diameter of the electrode group is offset by the expansion and the tightening of the negative electrode and hardly changes. As a result, deformation of the electrode group can be suppressed. Furthermore, the electrode group is almost equal to the inner diameter of the battery case, and the dimensional change due to insertion / extraction of lithium ions can be reduced. Therefore, it is possible to realize a highly reliable non-aqueous electrolyte secondary battery by preventing relative movement between the battery case and the electrode group due to the drop or impact of the secondary battery.

  Hereinafter, the mechanism in which the columnar body 15 reversibly changes the oblique angle due to occlusion / release of lithium ions will be described with reference to FIG. In the present invention, the columnar body is composed of n stages, but in order to facilitate the description, a columnar body composed of one columnar body portion will be described as an example. However, it goes without saying that the n-stage configuration functions in the same mechanism.

  FIG. 6A is a partial cross-sectional schematic diagram illustrating a state before charging of the negative electrode columnar body according to the first exemplary embodiment of the present invention, and FIG. 6B is a diagram after charging of the negative electrode columnar body according to the same exemplary embodiment. It is a partial cross-section schematic diagram which shows the state.

  The columnar body 15 shown in FIG. 6 is, as shown in FIG. 3B, the lower side where the center line (AA) of the columnar body 15 and the plane (AA-AA) of the current collector 11 form an acute angle. From 15a toward the upper side 15b forming the obtuse angle of the columnar body 15, the element content ratio of the active material made of SiOx is changed so that the value of x continuously increases. In general, an active material made of SiOx has a smaller expansion amount due to occlusion of lithium ions as the value of x increases from 0 to 2.

That is, as shown in FIG. 6A, the expansion stress generated by expansion due to occlusion of lithium ions during charging is changed from the expansion stress F1 on the lower side 15a of the columnar body 15 to the expansion stress F2 on the upper side 15b. Smaller continuously. As a result, the oblique angle θ formed by the center line (AA) of the columnar body 15 and the plane (AA-AA) of the current collector ₁₁ changes from θ ₁₀ to θ ₁₁ , and FIG. The columnar body 15 rises in the direction indicated by the arrow. On the contrary, the expansion stress is reduced by contraction caused by releasing lithium ions during discharge. As a result, obliquely erected angle theta of the columnar body 15, changes to theta ₁₀ from theta _11, in the direction indicated by the arrow in FIG. 6 (b), so that the columnar body 15 is deformed.

  As described above, the tilt angle of the columnar body 15 is reversibly changed by the insertion and extraction of lithium ions.

  Hereinafter, the manufacturing method of the columnar body of the negative electrode for a nonaqueous electrolyte secondary battery according to Embodiment 1 of the present invention will be described with reference to FIGS.

  FIG. 7 is a partial schematic cross-sectional view illustrating a method for forming a columnar body composed of n = 3 columnar body portions of the negative electrode for a nonaqueous electrolyte secondary battery according to Embodiment 1 of the present invention. It is a schematic diagram explaining a manufacturing apparatus.

  Here, the manufacturing apparatus 40 for forming the columnar body shown in FIG. 8 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. In addition, although this manufacturing apparatus 40 showed an example which forms a columnar body by forming the columnar body part of n steps on one side of the current collector, the columnar body is actually formed on both sides of the current collector. An apparatus configuration for manufacturing the is generally used.

  First, as shown in FIG. 7A and FIG. 8, using a strip-shaped electrolytic copper foil having a thickness of 30 μm, the concave portion 12 and the convex portion 13 are formed on the surface by plating, and the convex portion 13 is, for example, high A current collector 11 having a thickness of 5 μm, a width of 10 μm, and an interval of 20 μm is prepared. Then, the current collector 11 is prepared between the unwinding / winding roll 41 and the winding / unwinding roll 45 shown in FIG.

Next, as shown in FIG. 7B and FIG. 8, the 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 ₁ (for example, 55 °), and a drawing is formed on the convex portion 13 of the current collector 11. Incident from the direction of the arrow inside. 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. Further, the current collector 11 fed to the film-forming roll 44a is a film formation range in the mask 42 is restricted area, the active material of SiOx obtained by binding Si and oxygen at an angle theta ₁ on the convex portion 13, The first-stage columnar body 151 is formed at a predetermined height (thickness), for example, 7 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. 7B, 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.

Next, as shown in FIG. 7C and FIG. 8, the current collector 11 in which the first columnar body portion 151 is formed on the convex portion is sequentially sent to the film forming roll 44 b. Then, an angle ω ₂ (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 44 b. For example, an active material such as Si (scrap silicon: purity 99.999%) is evaporated from a vapor deposition source 43b provided at a position of 55 °, for example, and the first columnar body portion 151 of the current collector 11 is Incident light is incident from the direction of the arrow in the drawing. 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. at an angle theta _2, a predetermined height (thickness), the second stage of columnar body portion 152 is formed, for example, 7 [mu] m. 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 in FIG. 7C, 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 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. 7D and 8, 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. 7B). (Thickness), for example, 7 μm. At this time, in the third columnar body portion 153 shown in FIG. 7D, 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 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. Thereby, the negative electrode which has the columnar body 15 which consists of a three-stage columnar body part is produced.

  In addition, although the column-shaped body which consists of a column-shaped body part of n = 3 steps was demonstrated to the example above, it is not restricted to this. For example, by repeating the steps of FIG. 7B and FIG. 7C, a columnar body composed of arbitrary n stages (n ≧ 2) of 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. 8 may be arranged in series, and an n-stage columnar body may be manufactured while moving the current collector in one direction.

  In the above description, the columnar body is formed on one side of the current collector. However, actually, the columnar body is formed on the convex portions on both sides of the current collector. In this case, by changing the configuration of the manufacturing apparatus, after forming the columnar body on one surface of the current collector, the columnar body may be formed on the other surface. Good. Thereby, a negative electrode can be produced with high productivity.

(Embodiment 2)
FIG. 9A is a partial enlarged cross-sectional view showing the structure of the negative electrode in the second embodiment of the present invention, and FIG. 9B is the width of the active material constituting each columnar body portion in the second embodiment of the present invention. It is a schematic diagram explaining the change of the value of x of a direction. Also in this embodiment, since the cylindrical battery similar to that in FIG. 1 is used, detailed description is omitted. Further, constituent materials such as the positive electrode mixture layer, the positive electrode current collector, the negative electrode current collector, and the columnar body portion are the same as those in the first embodiment, and thus detailed description thereof is omitted.

  The present embodiment is implemented in that the entire columnar body composed of n = 7 columnar body portions is formed obliquely on the convex portion of the current collector and in the terminal direction when the negative electrode is wound. This is different from the first form.

  That is, as shown in FIG. 9A, the concave portion 12 and the convex portion 13 are provided on at least the upper surface of the current collector 11 made of a conductive metal material such as copper foil. Then, an active material represented by SiOx constituting the columnar body 250 is folded on the upper portion of the convex portion 13 by, for example, an oblique vapor deposition method using a sputtering method or a vacuum vapor deposition method. It is formed in the shape of a columnar body 250 including (n ≧ 2) columnar body portions. FIG. 9A shows a state where, for example, the columnar body portion 251 to the columnar body portion 257 are folded and formed in n = 7 stages. At this time, the odd-numbered and even-numbered columnar body portions constituting the columnar body 250 are formed obliquely in different directions as indicated by the line BB in the drawing. At the same time, by changing the heights of the odd-numbered and even-numbered columnar body portions, the entire columnar body 250 is formed obliquely. For example, in FIG. 9A, the heights of the odd-numbered columnar body portions 251, 253, 255, and 257 are set to the even-numbered columnar body portions 252 in order to obliquely stand in the terminal direction during winding. Longer than 254, 256. As a result, the entire columnar body 250 and the columnar body portion 257 at the front end are formed in an inclined state in the terminal direction at the time of winding as indicated by the line BB in the drawing.

  Further, the columnar body portion 251 to the columnar body portion 257 constituting the columnar body 250 are, for example, odd-numbered columnar body portions 251, 253, 255, and 257 and even-numbered stages, as schematically shown in FIG. 9B. The columnar body portions 252, 254, and 256 are provided so that the content ratio of elements in the width direction, 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 portion 251 to the columnar body portion 257 toward the obtuse angle side. In addition, in FIG.9 (b), although the value of x is shown changing linearly, it is not restricted to this.

  An electrode group of a non-aqueous electrolyte secondary battery using the negative electrode having the above structure will be described with reference to FIG. Since it is basically the same as that of the first embodiment shown in FIG. 2, it will be briefly described.

  FIG. 10 (a) is a plan view schematically showing a winding state of the electrode group of the nonaqueous electrolyte secondary battery according to Embodiment 2 of the present invention, and FIG. 10 (b) is a plan view of FIG. 10 (a). It is a partial expanded sectional view explaining the structure of a negative electrode in detail. FIG. 11A is a partial cross-sectional schematic view showing a state before charging of the secondary battery using the negative electrode in Embodiment 2 of the present invention, and FIG. 11B shows the negative electrode in the same embodiment. It is a partial cross section schematic diagram which shows the state after charge of the used secondary battery.

  As shown in FIG. 10A, the positive electrode 1 provided with the positive electrode lead 8 and the negative electrode 2 provided with one end of the negative electrode lead 9 facing the positive electrode 1 are wound through a separator 3 to form an electrode group 4. Is configured. As shown in FIG. 10B, the negative electrode 2 has a current collector 11 having a concave portion 12 and a convex portion 13, and at least n = 7 columnar columns provided obliquely on the convex portion. It is comprised with the columnar body 250 of the shape which folded and laminated | stacked the body part. At this time, among the respective columnar body portions constituting the columnar body 250, the tip end of the columnar body portion 257 provided at the uppermost stage of the columnar body 250 is a terminal direction (winding end direction) at the time of winding to form the electrode group. A columnar body portion 257 is provided so as to be inclined toward the surface.

  And, the columnar body 250 formed on the convex portion 13 of the current collector 11 in an inclined shape with n = 7 steps is formed by occlusion of lithium ions during charging of the nonaqueous electrolyte secondary battery. , Its volume expands. At this time, with the expansion of the volume, each oblique angle of the columnar body portion 251 to the columnar body portion 257 of the columnar body 250 increases as described in detail with reference to FIG. As a result, the columnar body 250 is deformed to stand up, for example. On the other hand, as shown in FIG. 11A, due to the release of lithium ions at the time of discharge, the volume shrinks and each oblique angle becomes smaller, becoming closer to the initial folded columnar body 250. .

  In addition, as shown in FIG. 11A, in the charging start state, the columnar body 250 having n = 7 columnar body portions is inclined on the convex portion 13 of the current collector 11, When the columnar body 250 is viewed by projection from the positive electrode 17, the concave portion 12 of the current collector 11 is partially shielded by the columnar body 250 with respect to the positive electrode 17. Therefore, the lithium ions released from the positive electrode 17 during charging are blocked from reaching the recess 12 of the current collector 11 directly by the negative columnar body 250, and most of the lithium ions are occluded in the columnar body 250. Is suppressed. Then, as described with reference to FIG. 6 in the first embodiment, as the lithium ions are occluded, the oblique angles of the seven columnar body portions are increased.

  Furthermore, as shown in FIG. 11B, when discharging a fully charged battery, a columnar body 250 composed of seven-stage columnar portions expanded by charging rises in a vertical direction with respect to the current collector 11. It becomes the state. Therefore, the electrolytic solution 18 between the adjacent columnar bodies 250 can easily move between the columnar bodies 250. And since the electrolyte solution 18 between the columnar bodies 250 can be easily convected through the gaps between the columnar bodies 250, movement of lithium ions and the like are not hindered. As a result, high-rate discharge and low temperature discharge characteristics can be greatly improved.

  Further, the fully charged columnar body 250 expands due to occlusion of lithium ions and receives stress in the electrode thickness direction, as described with reference to FIG. 5 in the first embodiment. At this time, stress is applied to the columnar body 250 by being decomposed into its reaction force and horizontal component force.

  At this time, the reaction force applied to the columnar body 250 itself is relaxed between the respective columnar body portions provided in the folded shape, and the moment between the columnar bodies is reduced by reducing the height between the columnar bodies. Stress concentration on the part can be reduced. As a result, it is possible to obtain a nonaqueous electrolyte secondary battery that is excellent in reliability and cycle characteristics that hardly cause peeling and deformation.

  On the other hand, the horizontal component force applied to the columnar body 250 moves the negative electrode of the electrode group in the winding start end direction and tightens the electrode group. Thereby, the expansion | swelling of the negative electrode by occlusion of the lithium ion at the time of charge is offset, and it becomes difficult to change the outer diameter of an electrode group. As a result, deformation of the electrode group can be suppressed. In addition, since the dimensional change due to insertion and extraction of lithium ions can be reduced, the outer shape of the electrode group can be made substantially equal to the inner diameter of the battery case. Therefore, it is possible to realize a highly reliable non-aqueous electrolyte secondary battery by preventing relative movement between the battery case and the electrode group due to the drop or impact of the secondary battery.

  In addition, the manufacturing method of the columnar body 250 of the negative electrode for a nonaqueous electrolyte secondary battery in the second embodiment of the present invention is basically the same as the negative electrode of the first embodiment described with reference to FIGS. Since there is, explanation is omitted. That is, the negative electrode of the present embodiment is different from the negative electrode of the first embodiment in that the number of columnar body portions constituting the columnar body and the height of the columnar body portion in the direction in which the columnar body is tilted are It is different in that it is formed higher than the body part, and the manufacturing method is the same.

  In the above-described embodiment, the columnar body composed of n = 7 columnar body portions has been described as an example. However, the present invention is not limited to this. For example, n = 7 stages or more and n = 10 stages to n = 100 stages may be used, and can be arbitrarily designed according to required capacity, cycle characteristics, and reliability.

  Hereinafter, another example of the negative electrode according to Embodiment 2 of the present invention will be described with reference to FIG. FIG. 12 is a partially enlarged cross-sectional view showing the structure of another example of the negative electrode according to Embodiment 2 of the present invention.

  As shown in FIG. 12, the negative electrode of the present embodiment is such that the tilted direction of the uppermost columnar body portion 358 of the columnar body 350 is tilted in the starting direction when the electrode group indicated by the CC line is wound. Thus, the structure of the negative electrode is different. Note that constituent materials such as the positive electrode mixture layer, the positive electrode current collector, the negative electrode current collector, and the columnar body, the manufacturing method, and the like are the same as those in the above embodiment, and thus the description thereof is omitted.

  That is, as shown in FIG. 12, the current collector 11 is provided with a concave portion 12 and a convex portion 13, and an active material represented by SiOx is folded on the upper portion of the convex portion 13 in the state of n = It is formed in the shape of the columnar body 350 including the columnar body portions 351 to 358 of eight stages. At this time, the odd-numbered columnar body portions 351, 353, 355, and 357 constituting the columnar body 350 and the even-numbered columnar body portions 352, 354, 356, and 358 are different as shown by the CC line in the drawing. It is formed obliquely in the direction.

  Accordingly, by tilting the entire columnar body 350 in the terminal direction at the time of winding, the tilted direction of the uppermost columnar body portion 358 of the columnar body 350 is not limited and can be arbitrary. Therefore, a negative electrode with a high degree of design freedom can be realized.

  In the above embodiment, a columnar body made up of n = 8 columnar body portions has been described as an example, but the present invention is not limited to this. For example, n = 8 stages or more and n = 10 stages to n = 100 stages may be used, and can be arbitrarily designed according to required capacity, cycle characteristics, and reliability.

  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-shaped electrolytic copper foil having a thickness of 30 μm and having protrusions formed on the surface thereof at intervals of 20 μm using a plating method 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 introduced into the vacuum vessel from the oxygen introduction nozzle by using a vapor deposition unit (unitized vapor deposition source, crucible, and electron beam generator). And the value of x was changed in the width direction made of SiOx to produce a first columnar body portion. At this time, the inside of the vacuum vessel was in 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.

Further, the columnar body portion was formed at a film forming speed of about 8 nm / s by adjusting a predetermined inclination angle at which the current collector moves so that the average angle of the angles ω ₁ and ω ₂ was 60 °. . Thereby, a first-stage columnar body part (for example, a height of 7 μm) was formed. Similarly, the second and third columnar body portions (for example, 7 μm in height) were formed by the formation method described in Embodiment 1, and a three-stage columnar body was formed. Further, similarly, a columnar body was formed on the other surface of the current collector.

  When the angle of the columnar body in the negative electrode with respect to the plane of the current collector was evaluated by cross-sectional observation using a scanning electron microscope (Hitachi S-4700), the oblique angle θ of the columnar body portion of each step was about 41. °. At this time, the thickness (height) of the formed columnar body was 21 μm with respect to the normal direction.

  In addition, when the oxygen distribution was examined by measuring the line distribution in the cross-sectional direction of the columnar body portions of each step constituting the negative electrode columnar body using EPMA, the widths of the first columnar body portion and the second columnar body portion were measured. In the direction, 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 first-stage columnar body part and the second-stage columnar body part. The range of x at this time was 0.1 to 2, and the average was 0.6.

  As described above, a negative electrode provided with columnar bodies having different oxygen element content ratios at least in the width direction in which each columnar body portion is inclined is obtained.

  Thereafter, 12 μm of Li metal was deposited on the negative electrode surface by vacuum deposition. Further, an exposed portion of 30 mm was provided on a Cu foil not facing the positive electrode on the inner peripheral side of the negative electrode, and a negative electrode lead made of Ni was welded.

(2) Production of positive electrode A positive electrode having a positive electrode active material capable of occluding and releasing 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. An N-methyl-2-pyrrolidone (NMP) solution of polyvinylidene fluoride (PVDF) as a binder (product number # 1320 manufactured by Kureha Chemical Industry Co., Ltd.) was added to the obtained powder, and the weight of PVDF was 3 parts by weight. It mixed so that it might become. An appropriate amount of NMP was added to the obtained mixture to prepare a positive electrode mixture paste. The obtained paste for positive electrode mixture was applied onto a positive electrode current collector (thickness 15 μm) made of aluminum (Al) foil by using a doctor blade method, and the density of the positive electrode mixture layer was 3.5 g / cc, thickness It was rolled to 140 μm and sufficiently dried at 85 ° C. This was cut into a width of 57 mm and a length of 800 mm to obtain a positive electrode. An exposed portion of 30 mm was provided on an Al foil not facing the negative electrode on the inner peripheral side of the positive electrode, and a positive electrode lead made of Al was welded.

(3) Production of Battery The negative electrode and the positive electrode produced as described above were wound through a polypropylene separator having a thickness of 20 μm to constitute an electrode group. Then, the obtained electrode group is inserted into a cylindrical battery case (material: iron / Ni plating, diameter 18 mm, height 65 mm) opened on only one side, and an insulating plate is placed between the battery case and the electrode group. After arranging and welding the negative electrode lead and the battery case, the positive electrode lead and the sealing plate were welded to produce a battery.

  The obtained battery was dried by heating to 60 ° C. in vacuum, and then non-aqueous containing ethylene carbonate (EC): dimethyl carbonate (DMC): ethyl methyl carbonate (EMC) = 2: 3: 3 (volume ratio) A nonaqueous electrolyte secondary battery was fabricated by injecting 5.8 g of an electrolytic solution in which 1.2 mol / dm 3 of LiPF 6 was dissolved in a solvent and caulking the sealing plate with a battery case. This is sample 1.

(Example 2)
A negative electrode was produced in the same manner as in Example 1 except that the columnar body was formed with n = 5 steps and the height of each columnar body portion was about 4 μm.

  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. The range of x at this time was 0.1 to 2, and the average was 0.6.

  Sample 2 was a nonaqueous electrolyte secondary battery produced by the same method as in Example 1 except that the above negative electrode was used.

(Example 3)
A negative electrode was formed in the same manner as in Example 1 except that the columnar body was formed with n = 10 steps, the height of each columnar body portion was approximately 2 μm, and the oblique direction of the first columnar body portion was reversed. Was made.

  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. The range of x at this time was 0.1 to 2, and the average was 0.6.

  Sample 3 was a nonaqueous electrolyte secondary battery produced by the same method as in Example 1 except that the negative electrode was used.

Example 4
For the columnar body, a negative electrode was produced in the same manner as in Example 1 except that the average angle of the angles ω ₁ and ω ₂ was 50 °.

  The oblique angle of the columnar body portion of each step was about 31 °, 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 (the value of x) was opposite in the first and third columnar body parts and the second columnar body part. The range of x at this time was 0.1 to 2, and the average was 0.6.

  Sample 4 was a nonaqueous electrolyte secondary battery produced by the same method as in Example 1 except that the negative electrode was used.

(Example 5)
A negative electrode was produced in the same manner as in Example 1 except that the pressure inside the vacuum vessel was 1.7 Pa in an oxygen atmosphere, and the thickness of the columnar body portion of each step was 8 μm.

  The oblique angle of the columnar body portion of each step was about 41 °, and the thickness (height) of the formed columnar body was 24 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 (the value of x) was opposite in the first and third columnar body parts and the second columnar body part. The range of x at this time was 0.1 to 2, and the average was 0.3.

  Thereafter, 14 μm of Li metal was deposited on the negative electrode surface by vacuum deposition.

  Sample 5 was a nonaqueous electrolyte secondary battery produced by the same method as in Example 1 except that the above negative electrode was used.

(Example 6)
Example except that the columnar body is formed with n = 7 steps, the height of each odd-numbered columnar body portion is about 3.5 μm, and the height of each even-numbered columnar body portion is about 2.5 μm. In the same manner as in Example 1, a negative electrode was produced.

  In addition, the oblique angle of the columnar body part of each step was about 41 °, the oblique angle of the entire columnar body was about 41 °, and the thickness (height) of the formed columnar body was 21.5 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. The range of x at this time was 0.1 to 2, and the average was 0.6.

  Sample 6 was a non-aqueous electrolyte secondary battery produced by the same method as in Example 1 except that the above negative electrode was used.

(Example 7)
The columnar body was formed in the same manner as in Example 1 except that the height of each odd-numbered columnar body portion was about 3 μm and the height of each even-numbered columnar body portion was about 2 μm. Thus, a negative electrode was produced. Then, the uppermost columnar body portion of the columnar body was formed obliquely in the direction of the starting end during winding.

  In addition, the tilting angle of the columnar body portion of each step was about 41 °, the tilting angle of the entire columnar body 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. The range of x at this time was 0.1 to 2, and the average was 0.6.

  Sample 7 was a non-aqueous electrolyte secondary battery produced by the same method as in Example 1 except that the negative electrode was used.

(Example 8)
Except that the columnar body is formed with n = 35 steps, the height of each odd-numbered columnar body portion is about 0.7 μm, and the height of each even-numbered columnar body portion is about 0.5 μm. In the same manner as in Example 1, a negative electrode was produced.

  The oblique angle of the columnar body portion of each step was about 41 °, the oblique angle of the entire columnar body was about 41 °, and the thickness (height) of the formed columnar body was 21.1 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. The range of x at this time was 0.1 to 2, and the average was 0.6.

  Sample 8 was a nonaqueous electrolyte secondary battery produced by the same method as in Example 1 except that the above negative electrode was used.

Example 9
Example except that the columnar body is formed with n = 40 steps, the height of each odd-numbered columnar body portion is about 0.6 μm, and the height of each even-numbered columnar body portion is about 0.4 μm. In the same manner as in Example 1, a negative electrode was produced. Then, the uppermost columnar body portion of the columnar body was formed obliquely in the direction of the starting end during winding.

  In addition, the tilting angle of the columnar body portion of each step was about 41 °, the tilting angle of the entire columnar body 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. The range of x at this time was 0.1 to 2, and the average was 0.6.

  Sample 9 was a nonaqueous electrolyte secondary battery produced by the same method as in Example 1 except that the negative electrode was used.

(Comparative Example 1)
A negative electrode was produced in the same manner as in Example 1 except that a columnar body was formed with a height (thickness) of 20 μm in one step and the tip inclined obliquely in the winding end direction.

  In addition, when the angle with respect to the plane of the collector of the columnar body in a negative electrode 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.

  A nonaqueous electrolyte secondary battery produced by the same method as in Example 1 except that the above negative electrode was used is referred to as Sample C1.

(Comparative Example 2)
A negative electrode was produced in the same manner as in Example 1 except that a columnar body was formed with a height (thickness) of 20 μm in one step and the tip tilted in the winding start direction.

  In addition, when the angle with respect to the plane of the collector of the columnar body in a negative electrode 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.

  A nonaqueous electrolyte secondary battery produced by the same method as in Example 1 except that the above negative electrode was used is referred to as Sample C2.

(Comparative Example 3)
A negative electrode was produced in the same manner as in Comparative Example 2, except that the columnar body was composed of n = 3 steps and the height of each columnar body portion was about 7 μm.

  In addition, when the angle with respect to the plane of the collector of the columnar body in a negative electrode 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 21 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.

  A nonaqueous electrolyte secondary battery produced by the same method as in Example 1 except that the above negative electrode was used is referred to as Sample C3.

  The following evaluation was performed on each non-aqueous electrolyte secondary battery produced 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, the design capacity (2800 mAh) is charged until the battery voltage reaches 4.2 V at a constant current of 0.7 C / hour, and is attenuated to a current value of 0.05 C at a constant voltage of 4.2 V. Voltage charging was performed. Then, it rested for 30 minutes.

  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 time rate. The discharge capacity at this time was defined as the battery capacity.

(Capacity maintenance rate)
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 (2800 mAh), the battery voltage is charged at a constant current of 0.5 C / hour until the battery voltage reaches 4.2 V, and the charge current is changed to a current value of 0.05 C at a constant voltage of 4.2 V. The battery was charged until it dropped. 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 1.0C. And it stopped for 30 minutes after discharge.

  The charge / discharge cycle was defined as one cycle and repeated 300 times. And the value which expressed the percentage of the discharge capacity of each cycle, such as the 100th cycle, the 300th cycle, etc. with respect to the discharge capacity of the 1st cycle 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.

(Measurement of electrode group diameter)
First, the state of deformation of the electrode group was confirmed by CT (computer tomography) scanning in a fully charged state of the battery that had undergone the charge / discharge cycle.

  And the group diameter of the electrode group was measured by the process of CT scan image. At this time, a secondary battery having a group diameter of 17.50 mm as the group diameter of the electrode group was first selected and measured based on the position of the negative electrode lead, and the change in the group shape at the 300th cycle with respect to the 100th cycle was shown as a percentage. .

  The specifications and evaluation results of Sample 1 to Sample 9 and Sample C1 to Sample C3 are shown in (Table 1) and (Table 2) below.

  FIG. 13 shows the evaluation results of Sample 1 and Sample C1 as an example of charge / discharge cycle characteristics.

  As shown in (Table 1) and (Table 2) and FIG. 13, when Sample 1 and Sample C1 were compared, there was no difference in capacity retention rate at about the 100th cycle at the beginning of the cycle. However, in the 300th cycle, the sample 1 showed a capacity maintenance rate of about 81%, while the sample C1 showed a capacity maintenance rate of about 48% and the sample C2 dropped to about 40%.

  Further, no significant deformation of the electrode group was observed in the batteries other than the sample C2. However, when the battery after evaluation was disassembled and the negative electrode was observed, in the sample C1 in which the columnar body was composed of one columnar body portion, the columnar body was often peeled off. This is presumably because the expansion / contraction stress due to charging / discharging concentrated on the junction between the current collector and the columnar body. Note that, as a factor that the capacity of the sample C1 shown in FIG.

  Although not shown, in sample C2, it was not possible to reach up to 300 cycles due to deformation of the electrode group. Deformation was observed at the 100th cycle. When the battery was disassembled, many columnar bodies were peeled off.

  On the other hand, in Sample 1, peeling of the columnar body was hardly observed. This is presumably because the stress at the joint is dispersed by the bending points between the columnar body portions.

  In addition, in the sample C3 in which the columnar body is composed of the three-stage columnar body portion, although the cycle characteristics superior to the sample C2 are exhibited due to the multi-stage, the deformation of the electrode group is seen at 300 cycles, Peeling of the columnar body occurred mainly.

  Further, Sample 2, Sample 3, and Samples 6 to 9 in which the number of steps of the columnar body portion was increased showed a tendency that the cycle characteristics improved as the number of steps increased. At this time, the electrode group was not deformed and there was no significant change.

  In addition, Sample 4 in which the tilt angle of the columnar body was reduced showed excellent cycle characteristics as compared with Sample 1. This is considered that the expansion / contraction stress due to charging / discharging is more distributed to the horizontal component force, and the effect in the winding direction appears remarkably.

  Further, in Sample 5 in which the columnar body is formed by reducing the oxygen partial pressure, the value of x of the columnar body is small, that is, the column is easily expanded, so that a larger stress is generated. As a result, the cycle characteristics are slightly deteriorated as compared with Sample 1. However, by setting the winding direction of the uppermost columnar body portion as the terminal direction, it was possible to obtain cycle characteristics superior to that of the sample C3 in which the expansion and contraction of the columnar body was small.

  Samples 6 and 7 and Samples 8 and 9 in which the slanted direction of the columnar body is the winding end and only the slanting direction of the uppermost columnar body part is changed to the winding end direction and the winding start end direction. In comparison, the capacity retention rates of Sample 7 and Sample 9 were slightly smaller. This is probably because the reaction force received by the columnar body when the electrode group expands is slightly different depending on the oblique direction of the uppermost columnar body portion.

  Further, comparing sample 7 and sample 9 with sample C2 and sample C3, the capacity retention rate of sample 7 and sample 9 was large, and the rate of change in group diameter was small. This is because even if the tilted direction of the uppermost columnar body portion is the same as the winding start end direction, the tilted direction of the entire columnar body is not inclined toward the winding start end direction, so that stress is applied due to expansion / contraction of the columnar body. It is considered that the change in the group diameter has become larger because it cannot be absorbed and the tightening effect cannot be obtained.

  INDUSTRIAL APPLICABILITY The present invention is useful for realizing a non-aqueous electrolyte secondary battery with high capacity and excellent reliability, which is expected to have a great demand in the future, using an active material having large expansion / contraction.

Sectional drawing of the nonaqueous electrolyte secondary battery in Embodiment 1 of this invention (A) A plan view schematically showing a state in which the electrode group of the nonaqueous electrolyte secondary battery in Embodiment 1 of the present invention is wound (b) A part for explaining in detail the configuration of the negative electrode in FIG. 2 (a) Enlarged sectional view (A) Schematic diagram of a partial cross section showing the structure of the negative electrode in the first embodiment of the present invention (b) Schematic diagram explaining the change in the value of x in the width direction of the active material in the first embodiment of the present invention. (A) Partial cross-sectional schematic diagram showing a state before charging of the secondary battery using the negative electrode according to Embodiment 1 of the present invention (b) After charging of the secondary battery using the negative electrode according to Embodiment 1 of the present invention Partial cross-sectional schematic diagram showing the state of The figure explaining the effect with respect to the shape change of the electrode group by using the negative electrode in Embodiment 1 of this invention (A) Partial cross-sectional schematic diagram showing a state before charging of the negative electrode columnar body according to Embodiment 1 of the present invention (b) Partial cross section showing a state after charging of the negative electrode columnar body according to Embodiment 1 of the present invention. Pattern diagram Partial cross-sectional schematic diagram for explaining a method of forming a columnar body composed of n = 3 columnar body portions of the negative electrode for a nonaqueous electrolyte secondary battery according to Embodiment 1 of the present invention. The schematic diagram explaining the manufacturing apparatus of the columnar body which consists of a columnar body part of n = 3 step | paragraph of the negative electrode for nonaqueous electrolyte secondary batteries in Embodiment 1 of this invention (A) Partial enlarged sectional view showing the structure of the negative electrode in Embodiment 2 of the present invention (b) Changes in the value of x in the width direction of the active material constituting each columnar body portion in Embodiment 2 of the present invention Schematic diagram to explain (A) A plan view schematically showing a winding state of an electrode group of a nonaqueous electrolyte secondary battery in Embodiment 2 of the present invention (b) A part for explaining in detail the configuration of the negative electrode in FIG. Enlarged sectional view (A) Partial cross-sectional schematic diagram showing a state before charging of the secondary battery using the negative electrode in the second embodiment of the present invention (b) After charging of the secondary battery using the negative electrode in the second embodiment of the present invention Partial cross-sectional schematic diagram showing the state of The partial expanded sectional view which shows the structure of another example of the negative electrode in Embodiment 2 of this invention The figure which shows an example of the charging / discharging cycle characteristic in the sample of an Example and a comparative example

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,17 Positive electrode 1a Positive electrode collector 1b Positive electrode mixture layer 2 Negative electrode 3 Separator 4 Electrode group 5 Battery case 6 Sealing plate 7 Gasket 8 Positive electrode lead 9 Negative electrode lead 10a, 10b Insulating plate 11 Negative electrode collector (collector)
12 Concave part 13 Convex part 15,250,350 Columnar body 15a Lower side 15b Upper side 18 Electrolyte 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 151,152,153,251,252,253,254,255,256,257,351,352,353,354,355,356,357,358 Columnar body

Claims (9)

A columnar body formed by stacking columnar body portions having different oblique directions in the longitudinal direction of the current collector formed on the convex portion of the current collector having a convex portion in n (n ≧ 2) stages. A negative electrode composed of a body,
A positive electrode having a positive electrode mixture layer containing a positive electrode active material capable of reversibly occluding and releasing lithium ions on both sides of the positive electrode current collector;
A separator provided oppositely between the positive electrode and the negative electrode,
The non-aqueous electrolyte secondary battery, wherein a tip of the columnar body portion provided at the uppermost stage of the columnar body of the negative electrode is inclined toward a terminal direction at the time of winding. The non-aqueous electrolyte secondary battery according to claim 1, wherein the columnar body is obliquely inclined toward a terminal direction at the time of winding. 3. The nonaqueous electrolyte secondary battery according to claim 2, wherein a tip end of the columnar body portion provided at the uppermost stage of the columnar body is obliquely inclined toward a starting end direction at the time of winding. 2. The nonaqueous electrolyte secondary battery according to claim 1, wherein a content ratio of an element constituting the columnar body portion is changed in an oblique width direction of the columnar body portion. 5. The nonaqueous electrolyte secondary battery according to claim 4, wherein a change direction of the content ratio of the elements of the odd-numbered stages and the even-numbered stages of the columnar body portions is different. 6. The acute angle side angle formed by the center line in the oblique direction of the columnar body portion and the plane of the current collector at least in the charged state is larger than the angle in the discharged state. The non-aqueous electrolyte secondary battery described in 1. 2. The nonaqueous electrolyte secondary battery according to claim 1, wherein an 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. 8. The nonaqueous electrolyte secondary battery according to claim 7, wherein a material represented by SiOx containing at least silicon is used as the active material. The value of x of the material containing silicon is changed from the side forming the acute angle to the side forming the obtuse angle with respect to the intersection angle between the center line in the oblique direction of the columnar body and the plane of the current collector. The nonaqueous electrolyte secondary battery according to claim 8, wherein the nonaqueous electrolyte secondary battery is continuously increased.

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