JP2007066685A - Secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a secondary battery where ruptures or the like of a negative electrode current collector can be suppressed and cycle characteristics can be improved, when a negative-electrode active material containing tin (Sn) or silicon (Si) is used. <P>SOLUTION: A positive electrode 21 and a negative electrode 22 are laminated to form a winding body 20 wound up into a spiral state. In the positive electrode 21, a positive-electrode active material layer 21B is installed on one face of the positive-electrode current collector 21A, while negative-electrode active material layers 22B that contain CoSnC-containing material, for instance are installed on both faces of the negative-electrode current collector 22A. An ion permeable insulation membrane 23 as a separator is installed between the positive-electrode active material layer 21B side of the positive electrode 21 and the negative electrode 22, while insulation is carried out between the other face of the positive electrode 21 and the negative electrode 22 by an insulation membrane 24. Charging and discharging reactions take place on a face of the negative electrode 22 facing the positive-electrode active material layer 21B, thus an expansion-shrinkage pressure per unit area with respect to the negative electrode current collector 22A is reduced. The positive electrode 21 is preferably wound up so that the positive electrode active material layer 21B side faces outside. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a secondary battery having a positive electrode and negative electrode winding structure, and more particularly to a secondary battery containing tin (Sn) or silicon (Si) as an active material on the negative electrode side.

  In recent years, many portable electronic devices such as a camera-integrated VTR (video tape recorder), a mobile phone, or a notebook personal computer have appeared, and their size and weight have been reduced. Batteries used as portable power sources for these electronic devices, particularly secondary batteries, are actively used as key devices for research and development aimed at improving energy density. Among them, non-aqueous electrolyte secondary batteries (for example, lithium ion secondary batteries) can provide a larger energy density than conventional lead batteries and nickel cadmium batteries, which are conventional aqueous electrolyte secondary batteries. Considerations are being made in various directions.

  As a negative electrode active material used for a lithium ion secondary battery, a carbon-based material such as non-graphitizable carbon or graphite having a relatively high capacity and good cycle characteristics is widely used. However, considering the recent demand for higher capacity, further increase in capacity of carbon-based materials has become an issue.

  From such a background, a technique for achieving a high capacity with a carbon-based material by selecting a carbonization raw material and production conditions has been developed (see, for example, Patent Document 1). However, when such a carbon-based material is used, the negative electrode discharge potential is 0.8 V to 1.0 V with respect to lithium, and the battery discharge voltage when the battery is configured becomes low. Then we cannot expect a big improvement. Furthermore, there is a drawback that the charge / discharge curve has a large hysteresis and the energy efficiency in each charge / discharge cycle is low.

On the other hand, as a high-capacity negative electrode that exceeds carbon-based materials, research is being conducted on an alloy material that applies that a certain type of metallic lithium is alloyed electrochemically and is reversibly generated and decomposed. For example, a high-capacity negative electrode using a Li—Al alloy has been developed, and further, a high-capacity negative electrode made of a Li—Si alloy has been developed (for example, see Patent Document 2). An intermetallic compound called Cu ₆ Sn ₅ has also been developed (see, for example, Non-Patent Document 1).
Di. D. Larcher, “Journal of The Electrochemical Society”, 2000, Vol. 5, No. 147, p. 1658-1662 JP-A-8-315825 US Pat. No. 4,950,566, etc. JP-A-6-325765 JP-A-7-230800 JP 7-288130 A Japanese Patent No. 3178586

However, Li—Al alloy, Si alloy, or Cu ₆ Sn ₅ expands and contracts with charge / discharge, and is pulverized every time charge / discharge is repeated. Therefore, there is a big problem that cycle characteristics are deteriorated.

Therefore, as a technique for improving the cycle characteristics, it has been studied to replace a part with an element that does not participate in expansion / contraction due to insertion / extraction of lithium. For example, LiSi _s O _t (0 ≦ s, 0 <t <2), Li _u Si _1-v M _v O _w (M represents a metal excluding an alkali metal or a similar metal excluding silicon, and 0 ≦ u, 0 <v <1, 0 <w <2), Or the LiAgTe type-alloy is proposed (for example, refer patent documents 3-5). However, even with these negative electrode active materials, the fact is that the charge / discharge cycle characteristics are greatly deteriorated due to expansion and contraction, and the characteristics of high capacity cannot be fully utilized.

  In particular, when a positive electrode and a negative electrode are stacked with an electrolyte in between and are wound in a spiral shape, deterioration of charge / discharge cycle characteristics appears remarkably for structural reasons. That is, in a battery having such a wound structure, when the negative electrode active material repeatedly expands and contracts due to charge and discharge, the stress, the electrode, particularly the negative electrode current collector, is easily broken, and the cycle life is shortened. It was the cause.

  Conventionally, there has been proposed a structure in which an active material layer is provided only on one side of a current collector together with a positive electrode and a negative electrode (see, for example, Patent Document 6). However, in this structure, since a large expansion / contraction stress is applied only to one side of the current collector, there is a problem that the electrode, particularly the negative electrode current collector, is easily broken.

  The present invention has been made in view of such problems, and its purpose is to suppress the breakage of the negative electrode current collector and the charge / discharge cycle when a negative electrode active material containing at least one of tin and silicon is used. An object of the present invention is to provide a secondary battery capable of improving characteristics.

  The secondary battery according to the present invention has a negative electrode active material layer on both sides of a strip-shaped negative electrode current collector, a negative electrode containing at least one of tin and silicon in the negative electrode active material layer, and a strip-shaped positive electrode current collector. A positive electrode having a positive electrode active material layer on one surface of the body and constituting a wound body together with the negative electrode; an ion-permeable insulating film provided between the positive electrode active material layer side of the positive electrode and the negative electrode; An insulating film provided between the other surface and the negative electrode is provided.

  According to the secondary battery of the present invention, the positive electrode active material layer is formed on one surface of the positive electrode current collector, and the ion permeable insulating film is provided between the positive electrode active material layer side of the positive electrode and the negative electrode. Since an insulating film is provided between the other surface and the negative electrode, the charge / discharge reaction can be caused mainly on the surface facing the positive electrode active material layer of the negative electrode. Therefore, expansion / contraction stress applied to the negative electrode current collector per unit area can be reduced, and tearing or the like can be suppressed. Further, since the negative electrode active material layer is formed on both surfaces of the negative electrode current collector, the strength of the negative electrode can be increased and the breakage of the negative electrode current collector can be suppressed. Thereby, cycle characteristics can be improved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the figure, each component schematically shows the shape, size, and arrangement relationship to the extent that the present invention can be understood, and is different from the actual size.

[First Embodiment]
FIG. 1 shows a cross-sectional structure of a secondary battery according to the first embodiment of the present invention. This secondary battery is a so-called cylindrical type, and has a wound body 20 inside a substantially hollow cylindrical battery can 11. The battery can 11 is made of, for example, iron (Fe) plated with nickel (Ni), and has one end closed and the other end open. Inside the battery can 11, a pair of insulating plates 12 and 13 are arranged perpendicular to the winding peripheral surface so as to sandwich the wound body 20.

  At the open end of the battery can 11, a battery lid 14, a safety valve mechanism 15 and a thermal resistance element (Positive Temperature Coefficient; PTC element) 16 provided inside the battery lid 14, have a gasket 17 in between. The battery can 11 is attached by being caulked, and the inside of the battery can 11 is sealed. The battery lid 14 is made of, for example, the same material as the battery can 11. The safety valve mechanism 15 is electrically connected to the battery lid 14 via the heat sensitive resistance element 16, and the disk plate 15A is reversed when the internal pressure of the battery exceeds a certain level due to an internal short circuit or external heating. Thus, the electrical connection between the battery lid 14 and the wound body 20 is cut off. When the temperature rises, the heat sensitive resistance element 16 limits the current by increasing the resistance value and prevents abnormal heat generation due to a large current. The gasket 17 is made of, for example, an insulating material, and asphalt is applied to the surface.

  The wound body 20 is formed by laminating a positive electrode 21 and a negative electrode 22 with an ion-permeable insulating film 23 and an insulating film 24, which will be described later, in between and winding them in a spiral shape, with a center pin 25 at the center. Has been inserted. A positive electrode lead 26 made of aluminum (Al) or the like is connected to the positive electrode 21 of the wound body 20, and a negative electrode lead 27 made of nickel or the like is connected to the negative electrode 22. The positive electrode lead 26 is electrically connected to the battery lid 14 by being welded to the safety valve mechanism 15, and the negative electrode lead 27 is welded and electrically connected to the battery can 11.

  FIG. 2 shows a cross-sectional configuration of the positive electrode 21 shown in FIG. 1 before winding. The positive electrode 21 is obtained, for example, by providing a positive electrode active material layer 21B on one surface of a strip-shaped positive electrode current collector 21A. The positive electrode current collector 21A has, for example, a thickness of about 5 μm to 50 μm and is made of a metal foil such as an aluminum foil, a nickel foil, or a stainless steel foil.

The positive electrode active material layer 21B includes, for example, any one or more of positive electrode materials capable of occluding and releasing lithium, which is an electrode reactant, as a positive electrode active material. A conductive material and a binder such as polyvinylidene fluoride may be included. The positive electrode material capable of inserting and extracting lithium does not contain lithium such as titanium sulfide (TiS ₂ ), molybdenum sulfide (MoS ₂ ), niobium selenide (NbSe ₂ ), or vanadium oxide (V ₂ O ₅ ). Examples thereof include a metal sulfide, a metal selenide, a metal oxide, a polymer material such as polyacetylene or polypyrrole, or a lithium-containing compound containing lithium.

Among these, lithium-containing compounds are preferable because some compounds can obtain a high voltage and a high energy density. Examples of such a lithium-containing compound include a composite oxide containing lithium and a transition metal element, or a phosphate compound containing lithium and a transition metal element. In particular, cobalt (Co), nickel and manganese (Mn Among these, those containing at least one of them are preferred. This is because a higher voltage can be obtained. The chemical formula is represented by, for example, Li _x MIO ₂ or Li _y MIIPO ₄ . In the formula, MI and MII represent one or more transition metal elements. The values of x and y vary depending on the charge / discharge state of the battery, and are generally 0.05 ≦ x ≦ 1.10 and 0.05 ≦ y ≦ 1.10.

Specific examples of the composite oxide containing lithium and a transition metal element include lithium cobalt composite oxide (Li _x CoO ₂ ), lithium nickel composite oxide (Li _x NiO ₂ ), and lithium nickel cobalt composite oxide (Li _x Ni _1-z Co _z O ₂ (z <1)) or lithium manganese composite oxide (LiMn ₂ O ₄ ) having a spinel structure. Among these, a composite oxide containing nickel is preferable. This is because a high capacity can be obtained and excellent cycle characteristics can also be obtained. Specific examples of the phosphate compound containing lithium and a transition metal element include, for example, a lithium iron phosphate compound (LiFePO ₄ ) or a lithium iron manganese phosphate compound (LiFe _1-v Mn _v PO ₄ (v <1)). Can be mentioned.

  FIG. 3 shows a cross-sectional configuration of the negative electrode 22 shown in FIG. 1 before winding. The negative electrode 22 is obtained, for example, by providing a negative electrode active material layer 22B on both surfaces of a strip-shaped negative electrode current collector 22A. Thereby, in this secondary battery, it is possible to increase the strength of the negative electrode 22 and suppress the rupture of the negative electrode current collector 22A compared to the conventional structure in which the negative electrode active material layer is provided only on one surface of the negative electrode current collector. It has become. The thickness of the negative electrode active material layer 22B on one surface of the negative electrode current collector 22A and the thickness of the negative electrode active material layer 22B on the other surface may be the same or different.

  The negative electrode current collector 22A is made of, for example, a metal foil such as a copper (Cu) foil, a nickel foil, or a stainless steel foil.

  The negative electrode active material layer 22B contains a negative electrode material containing at least one of tin and silicon as a constituent element as a negative electrode active material. This is because tin and silicon have a large ability to occlude and release lithium, which is an electrode reactant, and a high energy density can be obtained. Specifically, for example, a simple substance, an alloy, or a compound of silicon, a simple substance, an alloy, or a compound of tin, or a material having one or two or more phases thereof at least in part.

  In the present invention, alloys include those containing one or more metal elements and one or more metalloid elements in addition to those composed of two or more metal elements. Moreover, the nonmetallic element may be included. There are structures in which a solid solution, a eutectic (eutectic mixture), an intermetallic compound, or two or more of them coexist. Moreover, this negative electrode material may be used individually by 1 type, and 2 or more types may be mixed and used for it.

  Examples of tin alloys include silicon, nickel, copper, iron (Fe), cobalt (Co), manganese (Mn), zinc (Zn), indium (In), and silver as second constituent elements other than tin. (Ag), titanium (Ti), germanium (Ge), bismuth (Bi), antimony (Sb), and the thing containing at least 1 sort (s) of chromium (Cr) are mentioned. As an alloy of silicon, for example, as a second constituent element other than silicon, among the group consisting of tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony and chromium The thing containing at least 1 sort (s) of these is mentioned.

  Examples of the tin compound or silicon compound include those containing oxygen (O) or carbon (C), and may contain the second constituent element described above in addition to tin or silicon.

  Among these, as this negative electrode material, tin, cobalt, and carbon are included as constituent elements, the carbon content is 9.9 mass% or more and 29.7 mass% or less, and the total of tin and cobalt is A CoSnC-containing material having a cobalt ratio of 30% by mass to 70% by mass is preferable. This is because a high energy density can be obtained in such a composition range, and excellent cycle characteristics can be obtained.

  This CoSnC-containing material may further contain other constituent elements as necessary. Examples of other constituent elements include silicon, iron, nickel, chromium, indium, niobium (Nb), germanium, titanium, molybdenum (Mo), aluminum (Al), phosphorus (P), gallium (Ga), or bismuth. Preferably, 2 or more types may be included. This is because the capacity or cycle characteristics can be further improved.

  This CoSnC-containing material has a phase containing tin, cobalt, and carbon, and this phase preferably has a low crystallinity or an amorphous structure. In this CoSnC-containing material, it is preferable that at least a part of carbon as a constituent element is bonded to a metal element or a semimetal element as another constituent element. The decrease in cycle characteristics is thought to be due to the aggregation or crystallization of tin or the like, but this is because such aggregation or crystallization can be suppressed by combining carbon with other elements. .

  The negative electrode active material layer 22B may further include other negative electrode active materials, and may include other materials that do not contribute to charging, such as a conductive agent, a binder, or a viscosity modifier. Examples of other negative electrode active materials include carbon materials such as natural graphite, artificial graphite, non-graphitizable carbon, and graphitizable carbon. Examples of the conductive agent include graphite fiber, metal fiber, and metal powder. Examples of the binder include a fluorine-based polymer compound such as polyvinylidene fluoride, or a synthetic rubber such as styrene butadiene rubber or ethylene propylene diene rubber. Examples of the viscosity modifier include carboxymethylcellulose.

  FIG. 4 illustrates an example of a cross-sectional configuration along line IV-IV of the wound body 20 illustrated in FIG. An ion-permeable insulating film 23 as a separator is provided between the positive electrode active material layer 21 </ b> B side of the positive electrode 21 and the negative electrode 22, and an insulating film 24 is provided between the other surface of the positive electrode 21 and the negative electrode 22. ing. Thereby, in this secondary battery, the charge / discharge reaction can be caused on the surface of the negative electrode 22 facing the positive electrode active material layer 21B, and the expansion / contraction pressure applied to the negative electrode current collector 22A per unit area can be reduced. It is possible to suppress tears and the like.

  The positive electrode 21 is preferably wound with the positive electrode active material layer 21B side facing outward. Since the positive electrode active material layer 21B is formed by forming a positive electrode active material powder on the positive electrode current collector 21A using a binder together with a conductive agent and compacting it with a press, as will be described later. Compared with the body 21A, the positive electrode active material layer 21B has a larger compressive elongation amount and higher mechanical strength. Therefore, when the positive electrode active material layer 21B is provided only on one surface of the positive electrode current collector 21A, the positive electrode 21 has rounded ridges with the positive electrode current collector 21A on the inner side and the positive electrode active material layer 21B on the outer side. Since the consolidated positive electrode active material layer 21B is poor in flexibility, when the positive electrode 21 is wound with the positive electrode active material layer 21B side as an inner side, the positive electrode active material layer 21B is opposed to curled folds and is likely to be cracked, broken, or broken. Even if the rounded wrinkles were not so strong or could be corrected, when the positive electrode 21 was wound with the positive electrode active material layer 21B side inside, the positive electrode current collector 21A was subjected to tensile stress, but was sufficiently consolidated. Further compressive stress is generated in the positive electrode active material layer 21B. Therefore, the positive electrode active material layer 21B is likely to buckle, crack or drop off, and the positive electrode current collector 21A is also likely to break.

  The ion-permeable insulating film 23 is composed of, for example, a porous film made of a polyolefin-based material such as polypropylene or polyethylene, or a porous film made of an inorganic material such as a ceramic nonwoven fabric. A structure in which a material film is laminated may be used.

  The ion-permeable insulating film 23 is impregnated with an electrolytic solution that is a liquid electrolyte. For example, the electrolytic solution includes a solvent and a lithium salt that is an electrolyte salt. The solvent dissolves and dissociates the electrolyte salt. Solvents include propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, and 4-methyl. 1,3 dioxolane, diethyl ether, sulfolane, methyl sulfolane, acetonitrile, propionitrile, anisole, acetic acid ester, butyric acid ester or propionic acid ester, etc. are used, and any one of these or a mixture of two or more are used. May be.

Examples of the lithium salt include LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, LiCl, or LiBr. One kind or a mixture of two or more kinds may be used.

  The insulating film 24 is for insulating the other surface of the positive electrode 21 and the negative electrode 22. As long as the insulating film 24 can maintain the electronic insulation between the positive electrode 21 and the negative electrode 22, the shape and the constituent material are not particularly limited. For example, a polyolefin-based material such as polypropylene or polyethylene, polyvinylidene fluoride, etc. Of these, vinylidene fluoride resin, polyphenylene sulfide or polyethylene terephthalate is preferable. Moreover, these may contain a filler etc. Of these, polyolefin materials such as polypropylene and polyethylene are particularly preferable. Further, the insulating film 24 preferably has a form that is less ion permeable than a porous film such as the ion permeable insulating film 23.

  For example, the secondary battery can be manufactured as follows.

  First, for example, a positive electrode active material, a conductive agent, and a binder are mixed to prepare a positive electrode mixture, and the positive electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone to obtain a paste-like material. A positive electrode mixture slurry is obtained. Subsequently, the positive electrode mixture slurry is uniformly applied to the positive electrode current collector 21A using a doctor blade or a bar coater, and the solvent is dried. Then, the positive electrode active material layer 21B is formed by compression molding using a roll press or the like. Then, the positive electrode 21 is produced.

  Next, for example, a negative electrode active material and a binder are mixed to prepare a negative electrode mixture, and the negative electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone to obtain a paste-like negative electrode mixture slurry. And Subsequently, the negative electrode mixture slurry is uniformly applied to the negative electrode current collector 22A using a doctor blade or a bar coater, and the solvent is dried. Then, the negative electrode mixture layer 22B is formed by compression molding using a roll press. Then, the negative electrode 22 is produced. The roll press machine may be used by heating. Moreover, you may compression-mold several times until it becomes the target physical-property value. Furthermore, you may use press machines other than a roll press machine.

  After forming the negative electrode 22, the positive electrode lead 26 is attached to the positive electrode current collector 21A by welding or the like, and the negative electrode lead 27 is attached to the negative electrode current collector 22A by welding or the like. After that, the positive electrode 21 and the negative electrode 22 are laminated with the ion-permeable insulating film 23 and the insulating film 24 therebetween, and are wound many times in the winding direction shown in FIGS. 2 and 3 to produce the wound body 20. .

  After the wound body 20 is manufactured, the wound body 20 is sandwiched between the pair of insulating plates 12 and 13, the negative electrode lead 27 is welded to the battery can 11, and the positive electrode lead 26 is welded to the safety valve mechanism 15. The body 20 is accommodated in the battery can 11, the electrolyte is injected into the battery can 11, and the ion-permeable insulating film 23 is impregnated. After that, the battery lid 14, the safety valve mechanism 15, and the heat sensitive resistance element 16 are fixed to the opening end of the battery can 11 by caulking the gasket 17 therebetween. Thereby, the secondary battery shown in FIG. 1 is completed.

  In this secondary battery, when charged, lithium ions are released from the positive electrode 21 and inserted in the negative electrode 22 through the electrolytic solution impregnated in the ion-permeable insulating film 23. When discharging is performed, lithium ions are released from the negative electrode 22 and inserted into the positive electrode 21 through the electrolytic solution impregnated in the ion-permeable insulating film 23. Here, an ion-permeable insulating film 23 is provided between the positive electrode active material layer 21 </ b> B side of the positive electrode 21 and the negative electrode 22, while the other surface of the positive electrode 21 and the negative electrode 22 are insulated by the insulating film 24. Therefore, the charge / discharge reaction occurs on the surface of the negative electrode 22 facing the positive electrode active material layer 21B. Therefore, the expansion / contraction pressure applied to the negative electrode current collector 22A per unit area is reduced, and tearing and the like are suppressed. Moreover, since the negative electrode active material layer 22B is provided on both surfaces of the negative electrode current collector 22A, the strength of the negative electrode 22 is increased, and the breakage of the negative electrode current collector 22A is suppressed. This improves the cycle characteristics.

  Thus, according to the present embodiment, the ion-permeable insulating film 23 is provided between the positive electrode active material layer 21B side of the positive electrode 21 and the negative electrode 22, while the other surface of the positive electrode active material layer 21B and the negative electrode 22 are provided. Since the insulating film 24 is provided between the two, the tearing of the negative electrode 22 can be suppressed and the cycle characteristics can be improved.

  Further, since the negative electrode active material layer 22B is provided on both surfaces of the negative electrode current collector 22A, the strength of the negative electrode 22 can be increased and the breakage of the negative electrode current collector 22A can be suppressed.

  Furthermore, since the negative electrode active material of the negative electrode 22 includes a material containing at least one of silicon and tin as a constituent element, particularly the above-described CoSnC-containing material, a high capacity can be obtained.

  In addition, if the positive electrode 21 is wound with the positive electrode active material layer 21B side as the outer side, the positive electrode 21 can be wound in accordance with the natural curled surface of the positive electrode 21, and the positive electrode 21 can be prevented from being cracked, broken or broken. it can.

[Second Embodiment]
FIG. 5 shows a cross-sectional configuration before winding the negative electrode 22 of the secondary battery according to the second embodiment of the present invention. In this secondary battery, the negative electrode current collector 22 </ b> A is provided with a through-hole 22 </ b> C through which lithium ions can move, and the charge / discharge reaction occurs on both surfaces of the negative electrode 22. It has the same configuration as the secondary battery of the embodiment and can be manufactured in the same manner.

The through holes 22C have, for example, an average diameter of 0.1 mm and are provided at a density of 20 holes / cm ² .

  In the present embodiment, the negative electrode current collector 22A is provided with a through hole 22C through which lithium ions can move, so that the negative electrode 22 is prevented from being broken and the cycle characteristics are improved as in the first embodiment. Can be made.

  Further, specific embodiments of the present invention will be described in detail.

(Examples 1-3)
The secondary battery described in the first and second embodiments was produced. First, lithium carbonate (Li ₂ CO ₃ ) and cobalt carbonate (CoCO ₃ ) are mixed at a ratio of Li ₂ CO ₃ : CoCO ₃ = 0.5: 1 (molar ratio), and 5 ° C. at 900 ° C. in the air. After firing for a time, lithium-cobalt composite oxide (LiCoO ₂ ) as a positive electrode active material was obtained. Next, 94 parts by mass of this lithium-cobalt composite oxide, 2 parts by mass of graphite as a conductive agent and 1 part by mass of ketjen black, and 3 parts by mass of polyvinylidene fluoride as a binder are mixed to form a positive electrode mixture. Adjusted. Subsequently, this positive electrode mixture is dispersed in N-methyl-2-pyrrolidone as a solvent to form a positive electrode mixture slurry, which is uniformly applied to one surface of a positive electrode current collector 21A made of an aluminum foil having a thickness of 15 μm and dried. Then, the positive electrode active material layer 21B was formed by compression molding with a roll press machine, and the positive electrode 21 was produced. Subsequently, a positive electrode lead 26 made of aluminum was attached to one end of the positive electrode current collector 21A.

  In addition, a CoSnC-containing material was produced as a negative electrode active material. First, 32.0 parts by mass of cobalt powder, 59.4 parts by mass of tin powder, 3.7 parts by mass of silicon powder, 3.2 parts by mass of titanium powder, and 1.7 parts by mass of indium powder are weighed as raw materials. Then, it was put into a quartz tube and melted in a high frequency melting furnace in an argon (Ar) atmosphere. Next, this was cast on a rotating disk made of copper having a diameter of 200 mm, a width of 20 mm, and a rotational speed of 3000 rpm, and rapidly cooled to produce a ribbon-like material made of cobalt, tin, silicon, titanium and indium. Subsequently, the ribbon-like material was pulverized in an argon atmosphere using a ball mill to obtain a powder material.

  After that, 16.4 g of this powder material and 3.6 g of carbon powder were dry-mixed in an agate mortar and set in a reaction vessel of a planetary ball mill (manufactured by Ito Seisakusho) together with about 400 g of steel balls having a diameter of 9 mm. Subsequently, the inside of the reaction vessel was replaced with an argon atmosphere, and a 10-minute operation at a rotation speed of 250 revolutions per minute and a 10-minute pause were repeated until the total operation time reached 30 hours. After that, the reaction vessel was cooled to room temperature, the synthesized powder was taken out, coarse powder was removed through a 280 mesh sieve, and a CoSnC-containing material was obtained.

  When the composition of the obtained CoSnC-containing material was analyzed, the mass ratio of cobalt, tin, silicon, titanium, indium and carbon was cobalt: tin: silicon: titanium: indium: carbon = 26.2: 48.7. : 3.0: 2.6: 1.4: 18.1. The carbon content was measured by a carbon / sulfur analyzer, and the contents of cobalt, tin, silicon, titanium and indium were measured by ICP (Inductively Coupled Plasma) emission analysis. Moreover, when X-ray diffraction was performed about the obtained CoSnC containing material, the half value width of the diffraction peak of the reaction phase was 4.5 deg.

  Next, 70 parts by mass of this CoSnC-containing material, 20 parts by mass of graphite as a conductive agent and a negative electrode active material, 1 part by weight of acetylene black as a conductive agent, and 4 parts by mass of polyvinylidene fluoride as a binder are mixed. The negative electrode mixture was adjusted. Subsequently, the negative electrode mixture is dispersed in N-methyl-2-pyrrolidone as a solvent to form a negative electrode mixture slurry, which is applied to both surfaces of a negative electrode current collector 22A made of a copper foil having a thickness of 12 μm, and dried. The negative electrode active material layer 22B was formed by compression molding with a press, and the negative electrode 22 was produced. After that, a negative electrode lead 27 made of nickel was attached to one end of the negative electrode current collector 22A.

  After producing the negative electrode 22, an ion-permeable insulating film 23 made of a microporous polypropylene film having a thickness of 25 μm and an insulating film 24 were prepared. As the insulating film 24, a film made of polypropylene having a thickness of 30 μm was used in Example 1, a film made of polyethylene terephthalate having a thickness of 30 μm was used in Example 2, and a film made of polyethylene film having a thickness of 30 μm was used in Example 3.

  Subsequently, an ion-permeable insulating film 23 is provided between the positive electrode active material layer 21 </ b> B side of the positive electrode 21 and the negative electrode 22, while an insulating film 24 is provided between the other surface of the positive electrode 21 and the negative electrode 22. Then, the negative electrode 22, the ion permeable insulating film 23, the positive electrode 21 and the insulating film 24 were laminated in this order to form a laminated body, and the laminated body was then wound many times in a spiral shape to produce a wound body 20.

After the wound body 20 is manufactured, the wound body 20 is sandwiched between the pair of insulating plates 12 and 13, the negative electrode lead 27 is welded to the battery can 11, and the positive electrode lead 26 is welded to the safety valve mechanism 15. The body 20 was accommodated in a battery can 11 having an inner diameter of 17.5 mm. After that, an electrolytic solution was injected into the battery can 11. As the electrolytic solution, a solution obtained by dissolving LiPF ₆ as an electrolyte salt in a content of 1 mol / dm ³ in a solvent obtained by mixing 50% by weight of ethylene carbonate and 50% by weight of diethyl carbonate was used.

  After injecting the electrolyte into the battery can 11, the battery lid 14 was caulked to the battery can 11 with the gasket 17 in between to obtain a cylindrical secondary battery having an outer diameter of 18 mm and a height of 65 mm.

  As Comparative Example 1 with respect to Examples 1 to 3, a positive electrode provided with a positive electrode active material layer on both sides of a positive electrode current collector was formed, and a negative electrode, an ion-permeable insulating film, a positive electrode, and an ion-permeable insulating film were stacked in this order. A secondary battery was produced in the same manner as in Example 1 except that the wound body was produced by winding.

Example 4
The negative electrode current collector 22A was the same as that of Example 1, except that a 12 μm thick copper foil having through holes 22C with an average diameter of about 0.1 mm provided at a density of 20 holes / cm ² was used. A secondary battery was produced.

  As Comparative Example 2 with respect to Example 4, a positive electrode provided with a positive electrode active material layer on both sides of a positive electrode current collector was formed, and a negative electrode, an ion-permeable insulating film, a positive electrode, and an ion-permeable insulating film were sequentially laminated and wound. A secondary battery was produced in the same manner as in Example 2 except that the wound body was produced.

  Moreover, as Comparative Example 3 with respect to Examples 1 to 3, a secondary battery was fabricated in the same manner as Comparative Example 1 except that graphite was used as the negative electrode active material. At that time, 95.5 parts by mass of mesocarbon microbeads (graphitized product) having an average particle diameter of 20 μm heat-treated at 2800 ° C., 3 parts by mass of an emulsion of styrene-butadiene rubber (SBR), and sodium (Na) of carboxymethyl cellulose A negative electrode mixture slurry was obtained by dispersing and mixing 1.5 parts by mass of salt with ion-exchanged water as a dispersion medium.

  Further, as Comparative Example 4, a positive electrode provided with a positive electrode active material layer on one side of a positive electrode current collector was formed, and a negative electrode, an ion-permeable insulating film, a positive electrode, and an insulating film were laminated in that order and wound to form a wound body. A secondary battery was produced in the same manner as in Comparative Example 3 except that it was produced.

  In addition, as Comparative Example 5, a positive electrode provided with a positive electrode active material layer on one side of a positive electrode current collector and a negative electrode provided with a negative electrode active material layer on one side of a negative electrode current collector were formed. A secondary battery is formed in the same manner as in Example 3 except that a negative electrode, an ion-permeable insulating film, a positive electrode, and an insulating film are laminated in this order so as to face the negative electrode active material layer and wound to produce a wound body. Was made.

About the secondary batteries of Examples 1 to 4 and Comparative Examples 1 to 5 thus obtained, the current density with respect to the positive electrode reaction area was 1 mA / cm ² , and the constant current and constant voltage charging was performed at the upper limit voltage of 4.2 V. It was carried out until the 0.01mA / cm ^2. Subsequently, the battery was discharged at a constant current up to 2.0 V at a current density of 0.5 mA / cm ² to obtain an initial capacity. Thereafter, charging / discharging was repeated 50 times under these conditions, the 50th discharge capacity was measured, and the capacity retention ratio (discharge capacity at the 50th cycle / initial capacity) × 100 (%)) with respect to the initial capacity was calculated. The results are shown in Table 1 and FIG. In Table 1, “-” indicates that charging / discharging is not possible within 50 cycles.

  As can be seen from Table 1 and FIG. 6, in Examples 1 to 4 in which the positive electrode active material layer 21B is provided on one side of the positive electrode current collector 21A, Comparative Example 1 in which the positive electrode active material layer is provided on both sides of the positive electrode current collector. , 2 was able to obtain a higher capacity retention rate. That is, the positive electrode active material layer 21B is provided on one surface of the positive electrode current collector 21A, and the ion permeable insulating film 23 is provided between the positive electrode active material layer 21B side of the positive electrode 21 and the negative electrode 22, while the other side of the positive electrode 21 is provided. It has been found that if the insulating film 24 is provided between the surface and the negative electrode 22, the negative electrode 22 can be prevented from being broken and the cycle characteristics can be improved.

  Further, in Comparative Examples 3 and 4 using graphite as the negative electrode active material, the volume change accompanying charging / discharging is small, so that the positive electrode active material layer is provided on both surfaces of the positive electrode current collector as in Comparative Example 3, or No significant difference was observed depending on whether it was provided on one side as in FIG. In other words, when the negative electrode 22 includes a CoSnC-containing material as the negative electrode active material, it was found that the cycle characteristics can be improved by providing the positive electrode active material layer 21B on one surface of the positive electrode current collector 21A.

  Furthermore, in Comparative Example 5 in which charging / discharging was not possible within 50 cycles, the internal resistance of the battery was measured and found to be infinite. When disassembled and examined, the negative electrode current collector was in the winding direction. And torn in the vertical axis direction. That is, it was found that by providing the negative electrode active material layer 22B on both surfaces of the negative electrode current collector 22A, the strength of the negative electrode 22 can be increased and the rupture of the negative electrode current collector 22A can be suppressed.

  Although the present invention has been described with reference to the embodiments and examples, the present invention is not limited to the above embodiments and examples, and various modifications can be made. For example, in the above embodiments and examples, the case where the particulate negative electrode active material is used has been described. However, the negative electrode active material layer 22B may be formed by a vapor phase method or a liquid phase method.

  Further, for example, in the above-described embodiments and examples, the case where an electrolytic solution that is a liquid electrolyte is used as a solvent has been described, but other electrolytes may be used instead of the electrolytic solution. Other electrolytes include, for example, a gel electrolyte in which an electrolyte is held in a polymer compound, a solid electrolyte having ionic conductivity, a mixture of a solid electrolyte and an electrolyte, or a solid electrolyte and a gel electrolyte. And a mixture thereof.

  Moreover, in the said embodiment and Example, although the cylindrical secondary battery which has a winding structure was demonstrated, all can be applied if this invention is a secondary battery which has a winding structure.

  Furthermore, in the above-described embodiment and examples, the case where lithium is used as the electrode reactant has been described. However, other group 1 elements in the long-period periodic table such as sodium (Na) or potassium (K), or magnesium Alternatively, the present invention can be applied to the case where a Group 2 element in a long-period periodic table such as calcium (Ca), another light metal such as aluminum, lithium, or an alloy thereof is used, and similar effects are obtained. Can be obtained. At that time, a negative electrode active material, a positive electrode active material, a solvent, or the like that can occlude and release the electrode reactant is selected according to the electrode reactant.

It is sectional drawing showing the structure of the secondary battery which concerns on the 1st Embodiment of this invention. It is sectional drawing showing the structure before winding of the positive electrode shown in FIG. It is sectional drawing showing the structure before winding of the negative electrode shown in FIG. It is sectional drawing showing the structure along the IV-IV line of the wound body shown in FIG. It is sectional drawing showing the structure before winding of the negative electrode of the secondary battery which concerns on the 2nd Embodiment of this invention. It is a figure showing the result of the Example and comparative example of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Battery can, 12, 13 ... Insulating plate, 14 ... Battery cover, 15 ... Safety valve mechanism, 16 ... Heat sensitive resistance element, 17 ... Gasket, 20 ... Winding body, 21 ... Positive electrode, 21A ... Positive electrode collector, 21B ... Positive electrode active material layer, 22 ... Negative electrode, 22A ... Negative electrode current collector, 22B ... Negative electrode active material layer, 22C ... Through-hole, 23 ... Ion permeable insulating film, 24 ... Insulating film, 25 ... Center pin, 26 ... Positive electrode lead, 27... Negative electrode lead.

Claims (3)

A negative electrode active material layer on each side of the belt-shaped negative electrode current collector, and the negative electrode active material layer includes at least one of tin (Sn) and silicon (Si);
A positive electrode having a positive electrode active material layer on one surface of a belt-like positive electrode current collector, and constituting a wound body together with the negative electrode;
An ion-permeable insulating film provided between the positive electrode active material layer side of the positive electrode and the negative electrode;
A secondary battery comprising: an insulating film provided between the other surface of the positive electrode and the negative electrode.   The secondary battery according to claim 1, wherein the negative electrode current collector has a through hole through which ions of an electrode reactant can move. The secondary battery according to claim 1, wherein the positive electrode is wound with the positive electrode active material layer side outward.

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