JP2006216374A - Negative electrode material and battery using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a negative electrode material having high capacity and repeatedly usable; and to provide a battery using it. <P>SOLUTION: This negative electrode material includes a particulate outer shell part 2 having a vacancy 1 in its inside, and a nucleus part 3 present in the vacancy 1. The outer shell part 2 is formed of a porous body of silicon dioxide, and the nucleus part 3 is formed of a material containing at least one kind out of a metal element and a semimetal element capable of forming an alloy with Li, for instance, Si as a constituent element. Even if the volume of the nucleus part 3 is drastically changed by storage and release of Li, shape collapse can be suppressed by absorbing the volume change by the vacancy 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a negative electrode material containing at least one of a metal element and a metalloid element as a constituent element, and a battery using the same.

  With recent advances in electronic technology, small portable electronic devices such as camera-integrated video tape recorders, mobile phones, and laptop computers have been developed. As these portable power sources, secondary batteries that are small, lightweight, and have high energy density. Development is strongly demanded. As a secondary battery that meets such a demand, for example, there is a lithium ion secondary battery using a carbon material such as graphite for the negative electrode.

However, graphite has an upper limit in capacity as defined by the composition C ₆ Li of the first stage graphite intercalation compound, and it is difficult to further increase the capacity. Therefore, it has been studied to use silicon (Si), tin (Sn), or an alloy thereof as a negative electrode material capable of achieving higher capacity (for example, see Patent Document 1).
JP 2000-311681 A

  However, the negative electrode material using silicon or tin as described above has a large change in volume with the absorption and release of lithium, and its shape collapses. Therefore, the charge / discharge characteristics are lower than that of the carbon material, and the capacity is high. There was a problem that it was difficult to make use of the features.

  The present invention has been made in view of such problems, and an object thereof is to provide a negative electrode material having a high capacity and capable of being repeatedly used, and a battery using the same.

  The negative electrode material of the present invention has a particulate outer shell portion having pores therein, and a core portion present in the pores and containing at least one of a metal element and a metalloid element as a constituent element Is.

  The battery of the present invention is provided with an electrolyte together with a positive electrode and a negative electrode, and the negative electrode is present in a particulate outer shell having pores therein, and in the pores, and includes a metal element and a semi-element as constituent elements. A negative electrode material having a core containing at least one of metal elements is contained.

  According to the negative electrode material of the present invention, since the core is provided in the outer shell having holes, even if the volume of the core changes greatly, the change can be absorbed by the holes. , Shape collapse can be suppressed. Therefore, according to the battery of the present invention using this negative electrode material, a high capacity can be obtained and excellent charge / discharge characteristics can be obtained.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a configuration of a negative electrode material according to an embodiment of the present invention. This negative electrode material has a particulate outer shell portion 2 having pores 1 inside, and a core portion 3 that is present in the pores 1 and occludes and releases electrode reactants.

  Even if the volume of the core part 3 changes greatly as the electrode reactant is occluded and released, the outer shell part 2 absorbs the volume change by the holes 1 and suppresses the collapse of the shape. The outer shape of the outer shell 2 may be either spherical or non-spherical, and the thickness of the outer shell 2 is preferably 100 nm or more, for example. This is because the strength is required so that it does not collapse even when the volume of the core 3 changes.

  Although not shown, the outer shell 2 preferably has a communication hole that allows the air hole 1 to communicate with the outside. For example, the outer shell 2 is preferably formed of a porous body. This is because the electrode reactant is supplied to the core 3. Although the material which comprises the outer shell part 2 is not specifically limited, For example, the oxide or nitride which can occlude and discharge | release an electrode reactant is preferable. This is because the capacity can be obtained also from the outer shell portion 2, and the oxide and nitride can keep the shape because the volume change due to insertion and extraction of the electrode reactant is small.

  The core 3 may be either spherical or non-spherical, and includes at least one of a metal element and a metalloid element as a constituent element. For example, when the electrode reactant is lithium, it is made of a material containing at least one of a metal element and a metalloid element capable of forming an alloy with lithium as a constituent element. This material may be a single element or an alloy or a compound of a metal element or a metalloid element, or may have at least a part of one or more of these phases. 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.

  Examples of metal elements or metalloid elements capable of forming an alloy with lithium include magnesium (Mg), boron (B), arsenic (As), aluminum (Al), gallium (Ga), indium (In), silicon, Germanium (Ge), tin, lead (Pb), antimony (Sb), bismuth (Bi), cadmium (Cd), silver (Ag), zinc (Zn), hafnium (Hf), zirconium (Zr), yttrium (Y ), Palladium (Pd) or platinum (Pt).

  Among these, tin, lead, silicon, germanium, aluminum, or indium is preferable, and a group 14 metal element or metalloid element in the long-period periodic table is more preferable, and silicon or tin is particularly preferable. This is because a larger capacity can be obtained.

These alloys or compounds, for example, those represented by the chemical formula Ma _s Mb _t Li _u or a chemical formula Ma _p Mc _q Md _r,. In these chemical formulas, Ma represents at least one of a metal element and a metalloid element capable of forming an alloy with lithium, and Mb represents at least one of a metal element and a metalloid element other than lithium and Ma. , Mc represents at least one of non-metallic elements, and Md represents at least one of metallic elements and metalloid elements other than Ma. The values of s, t, u, p, q, and r are s> 0, t ≧ 0, u ≧ 0, p> 0, q> 0, and r ≧ 0, respectively.

Specific examples of these alloys or compounds include LiAl, AlSb, CuMgSb, SiB ₄ , SiB ₆ , Mg ₂ Si, Mg ₂ Sn, Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoSi ₂ , NiSi ₂ , _{CaSi 2, CrSi 2, Cu 5} Si, FeSi 2, MnSi 2, NbSi 2, TaSi 2, VSi 2, WSi 2, ZnSi 2, SiC, Si 3 N 4, Si 2 N 2 O, AsSn, AuSn, CaSn 3 , CeSn ₃ , CoCu ₂ Sn, Co ₂ MnSn, CoNiSn, CoSn ₂ , Co ₃ Sn ₂ , CrCu ₂ Sn, Cu ₂ FeSn, CuMgSn, Cu ₂ MnSn, Cu ₄ MnSn, Cu ₂ NiSn, CuSn, Cu ₃ Sn, _{Cu 6 Sn 5, FeSn 2,} IrSn, IrSn 2, LaSn 3, MgNi 2 Sn, Mg 2 Sn, Mn _{i 2 Sn, MnSn 2, Mn} 2 Sn, Mo 3 Sn, Nb 3 Sn, NdSn 3, NiSn, Ni 3 Sn, PdSn, Pd 3 Sn, Pd 3 Sn 2, PrSn 3, PtSn, PtSn 2, Pt 3 Sn , PuSn ₃ , RhSn, Rh ₃ Sn ₂ , RuSn ₂ , SbSn, SnTi ₂ , Sn ₃ U, SnV ₃ , SiO _v (0 <v ≦ 2), SnO _w (0 <w ≦ 2), SnSiO ₃ , LiSiO Or LiSnO.

  In the case where the outer shell 2 is made of an oxide or nitride, the metal element or metalloid element contained in the outer shell 2 and the core 3 may be the same or different.

  FIG. 2 shows a manufacturing method of the negative electrode material shown in FIG. First, as shown in FIG. 2A, for example, an intermediate layer 4 made of aluminum oxide or the like is formed on the surface of the particulate core 3 by a sol-gel method or the like. Next, as shown in FIG. 2B, for example, the outer shell portion 12 is formed on the surface of the intermediate layer 4 by a sol-gel method or plating. Subsequently, the intermediate layer 4 is removed by, for example, treatment with an acid or the like. Thereby, the negative electrode material shown in FIG. 1 is obtained.

  This negative electrode material is used for a secondary battery as follows, for example. In the secondary battery described below, the case where lithium is used as the electrode reactant will be described.

(First battery)
FIG. 3 shows a cross-sectional structure of the first secondary battery. This secondary battery is called a so-called cylindrical type, and a winding in which a strip-like positive electrode 21 and a strip-like negative electrode 22 are laminated and wound inside a substantially hollow cylindrical battery can 11 via a separator 23. An electrode body 20 is provided. The battery can 11 is made of, for example, iron plated with nickel, and has one end closed and the other end open. Inside the battery can 11, an electrolytic solution that is a liquid electrolyte is injected and impregnated in the separator 23. In addition, a pair of insulating plates 12 and 13 are arranged perpendicular to the winding peripheral surface so as to sandwich the winding electrode body 20.

  At the open end of the battery can 11, a battery lid 14, a safety valve mechanism 15 provided inside the battery lid 14 and a heat sensitive resistance element (Positive Temperature Coefficient; PTC element) 16 are interposed via a gasket 17. It is attached by caulking, 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 electrode 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.

  For example, a center pin 24 is inserted in the center of the wound electrode body 20. A positive electrode lead 25 made of aluminum or the like is connected to the positive electrode 21 of the spirally wound electrode body 20, and a negative electrode lead 26 made of nickel (Ni) or the like is connected to the negative electrode 22. The positive electrode lead 25 is electrically connected to the battery lid 14 by being welded to the safety valve mechanism 15, and the negative electrode lead 26 is welded to and electrically connected to the battery can 11.

  FIG. 4 shows an enlarged part of the spirally wound electrode body 20 shown in FIG. The positive electrode 21 has, for example, a structure in which a positive electrode active material layer 21B is provided on both surfaces of a positive electrode current collector 21A having a pair of opposed surfaces. The positive electrode current collector 21A is made of, for example, 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, one or more of positive electrode materials capable of inserting and extracting lithium as a positive electrode active material, and a conductive material such as a carbon material and polyfluoride as necessary. A binder such as vinylidene may be included. As the positive electrode material capable of inserting and extracting lithium, for example, a lithium composite oxide containing lithium and a transition metal element, or a lithium phosphate compound containing lithium and a transition metal element is preferable. This is because high voltage can be generated and capacity can be increased.

The lithium composite oxide or lithium phosphate compound preferably contains at least one member selected from the group consisting of cobalt (Co), nickel and manganese (Mn) as a transition metal element, and further contains other elements. May be. 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-j Co _j O ₂ (j <1)) or lithium manganese composite oxide (Li _x Mn ₂ O ₄ ) having a spinel structure. Examples of the lithium phosphate compound, for example, lithium-iron phosphate compound (LiFePO _4), a lithium-iron-manganese phosphate compound _{(LiFe 1-k Mn k PO} 4 (k <1)) can be mentioned.

  The negative electrode 22 has, for example, a structure in which a negative electrode active material layer 22B is provided on both surfaces of a negative electrode current collector 22A having a pair of opposed surfaces, as with the positive electrode 21. The anode current collector 22A is made of, for example, a metal foil such as a copper foil.

  The negative electrode active material layer 22B includes, for example, the negative electrode material according to the present embodiment as a negative electrode active material, and includes a conductive material and a binder as necessary. Thereby, in this secondary battery, while being able to obtain a high capacity | capacitance, the outstanding charging / discharging characteristic can be acquired now. The negative electrode material may be used alone or in combination of two or more different compositions. The negative electrode active material layer 22B may also include other negative electrode active materials in addition to the negative electrode material according to the present embodiment. Examples of the other negative electrode active material include a carbon material that can occlude and release lithium. The carbon material is preferable because it has excellent charge / discharge characteristics and also functions as a conductive material.

  The separator 23 separates the positive electrode 21 and the negative electrode 22 and allows lithium ions to pass through while preventing a short circuit of current due to contact between the two electrodes. The separator 23 is made of, for example, a porous film made of synthetic resin such as polytetrafluoroethylene, polypropylene, or polyethylene, or a porous film made of ceramic, and has a structure in which two or more kinds of porous films are laminated. It may be said.

  The electrolytic solution impregnated in the separator 23 includes a solvent and an electrolyte salt dissolved in the solvent. Examples of the solvent include propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4- Examples thereof include methyl-1,3-dioxolane, diethyl ether, sulfolane, methyl sulfolane, acetonitrile, propionitrile, anisole, acetate ester, butyrate ester, and propionate ester. Any one type of solvent may be used alone, or two or more types may be mixed and used.

  It is more preferable that the solvent contains a cyclic carbonate derivative having a halogen atom. This is because the decomposition reaction of the solvent in the negative electrode 22 can be suppressed, and the cycle characteristics can be improved. Examples of such carbonic acid ester derivatives include 4-fluoro-1,3-dioxolan-2-one, 4-difluoro-1,3-dioxolan-2-one, 4,5-difluoro-1,3-dioxolane. 2-one, 4-difluoro-5-fluoro-1,3-dioxolan-2-one, 4-chloro-1,3-dioxolan-2-one, 4,5-dichloro-1,3-dioxolane-2 -One, 4-bromo-1,3-dioxolan-2-one, 4-iodo-1,3-dioxolan-2-one, 4-fluoromethyl-1,3-dioxolan-2-one, or 4-tri There is fluoromethyl-1,3-dioxolan-2-one, among which 4-fluoro-1,3-dioxolan-2-one is preferred. This is because a higher effect can be obtained.

Examples of the electrolyte salt include lithium salts such as LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ , LiCH ₃ SO ₃ , LiCF ₃ SO ₃ , LiCl, or LiBr. Any one electrolyte salt may be used alone, or two or more electrolyte salts may be mixed and used. The electrolyte salt is preferably a lithium salt, but may not be a lithium salt. This is because it is sufficient that lithium ions contributing to charging / discharging are supplied from the positive electrode 21 or the like.

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

  First, for example, a positive electrode active material and, if necessary, a conductive material and a binder are mixed to prepare a positive electrode mixture, which is dispersed in a mixed solvent such as N-methyl-2-pyrrolidone to obtain a positive electrode mixture slurry. Make it. Next, the positive electrode mixture slurry is applied to the positive electrode current collector 21A, dried and compressed to form the positive electrode active material layer 21B, and the positive electrode 21 is manufactured. Subsequently, the positive electrode lead 25 is welded to the positive electrode 21.

  Further, for example, the negative electrode material according to the present embodiment is mixed with a conductive material and a binder as necessary to prepare a negative electrode mixture, which is dispersed in a mixed solvent such as N-methyl-2-pyrrolidone. A negative electrode mixture slurry is prepared. Next, the negative electrode mixture slurry is applied to the negative electrode current collector 22A, dried and compressed to form the negative electrode active material layer 22B, and the negative electrode 22 is manufactured. Subsequently, the negative electrode lead 26 is welded to the negative electrode 22.

  After that, the positive electrode 21 and the negative electrode 22 are wound through the separator 23, and the tip of the positive electrode lead 25 is welded to the safety valve mechanism 15, and the tip of the negative electrode lead 26 is welded to the battery can 11. The positive electrode 21 and the negative electrode 22 are sandwiched between a pair of insulating plates 12 and 13 and stored in the battery can 11. Next, the electrolytic solution is injected into the battery can 11. 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 through a gasket 17. Thereby, the secondary battery shown in FIGS. 3 and 4 is completed.

  In the secondary battery, when charged, for example, lithium ions are extracted from the positive electrode 21 and inserted in the negative electrode 22 through the electrolytic solution. When discharging is performed, for example, lithium ions are released from the negative electrode 22 and inserted in the positive electrode 21 through the electrolytic solution. At that time, in the negative electrode 22, the negative electrode material expands and contracts with insertion and extraction of lithium. However, in this embodiment, since the core portion 3 is provided in the outer shell portion 2 having the pores 1, The change in volume of the core 3 is absorbed by the holes 1, and the collapse of the shape is suppressed.

  As described above, according to the negative electrode material according to the present embodiment, since the core portion 3 is provided in the outer shell portion 2 having the pores 1, the volume of the core portion 3 greatly changes with charge / discharge. However, the shape collapse of the negative electrode material and the negative electrode active material layer 22B can be suppressed by absorbing the volume change by the holes 1. Therefore, high capacity can be obtained and excellent charge / discharge characteristics can be obtained.

(Second battery)
FIG. 5 shows the structure of the second secondary battery. In this secondary battery, a wound electrode body 30 to which a positive electrode lead 31 and a negative electrode lead 32 are attached is housed in a film-like exterior member 40, and can be reduced in size, weight, and thickness. ing.

  The positive electrode lead 31 and the negative electrode lead 32 are respectively led out from the inside of the exterior member 40 to the outside, for example, in the same direction. The positive electrode lead 31 and the negative electrode lead 32 are each made of a metal material such as aluminum, copper, nickel, or stainless steel, and each have a thin plate shape or a mesh shape.

  The exterior member 40 is made of, for example, a rectangular aluminum laminated film in which a nylon film, an aluminum foil, and a polyethylene film are bonded together in this order. For example, the exterior member 40 is disposed so that the polyethylene film side and the wound electrode body 30 face each other, and the outer edge portions are in close contact with each other by fusion bonding or an adhesive. An adhesive film 41 is inserted between the exterior member 40 and the positive electrode lead 31 and the negative electrode lead 32 to prevent intrusion of outside air. The adhesion film 41 is made of a material having adhesion to the positive electrode lead 31 and the negative electrode lead 32, for example, a polyolefin resin such as polyethylene, polypropylene, modified polyethylene, or modified polypropylene.

  The exterior member 40 may be made of a laminated film having another structure, a polymer film such as polypropylene, or a metal film instead of the above-described aluminum laminated film.

  FIG. 6 shows a cross-sectional structure taken along line II of the spirally wound electrode body 30 shown in FIG. The wound electrode body 30 is formed by stacking and winding a positive electrode 33 and a negative electrode 34 with a separator 35 and an electrolyte 36, and the outermost periphery is protected by a protective tape 37.

  The positive electrode 33 has a structure in which a positive electrode active material layer 33B is provided on both surfaces of a positive electrode current collector 33A. The negative electrode 34 has a structure in which a negative electrode active material layer 34B is provided on both surfaces of a negative electrode current collector 34A, and the negative electrode active material layer 34B and the positive electrode active material layer 33B are arranged to face each other. The configurations of the positive electrode current collector 33A, the positive electrode active material layer 33B, the negative electrode current collector 34A, the negative electrode active material layer 34B, and the separator 35 are respectively the positive electrode current collector 21A, the positive electrode active material layer 21B, and the first secondary battery. This is the same as the anode current collector 22A, the anode active material layer 22B, and the separator 23.

  The electrolyte layer 36 includes an electrolytic solution and a polymer compound serving as a holding body that holds the electrolytic solution, and has a so-called gel shape. A gel electrolyte is preferable because high ion conductivity can be obtained and battery leakage can be prevented. The configuration of the electrolytic solution is the same as that of the first secondary battery. The polymer compound is, for example, a fluorine polymer compound such as polyvinylidene fluoride or a copolymer of vinylidene fluoride and hexafluoropropylene, an ether polymer compound such as polyethylene oxide or a crosslinked product containing polyethylene oxide, or polyacrylonitrile. Etc. In particular, from the viewpoint of redox stability, a fluorine-based polymer compound is desirable.

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

  First, after preparing the positive electrode 33 and the negative electrode 34 in the same manner as in the first secondary battery, each of the positive electrode 33 and the negative electrode 34 is a precursor solution containing a solvent, an electrolyte salt, a polymer compound, and a mixed solvent. And the mixed solvent is volatilized to form the electrolyte layer 36. After that, the positive lead 31 is attached to the end of the positive current collector 33A by welding, and the negative lead 32 is attached to the end of the negative current collector 34A. Next, the positive electrode 33 and the negative electrode 34 on which the electrolyte layer 36 is formed are stacked via the separator 35, wound in the longitudinal direction, and a protective tape 37 is adhered to the outermost peripheral portion to form the wound electrode body 30. . Subsequently, for example, the wound electrode body 30 is sandwiched between the exterior members 40, and the outer edges of the exterior members 40 are sealed and sealed by thermal fusion or the like. At that time, the adhesion film 41 is inserted between the positive electrode lead 31 and the negative electrode lead 32 and the exterior member 40. Thereby, the secondary battery shown in FIGS. 5 and 6 is completed.

  Further, this secondary battery may be manufactured as follows. First, as described above, the positive electrode 33 and the negative electrode 34 are prepared, and after the positive electrode lead 31 and the negative electrode lead 32 are attached, the positive electrode 33 and the negative electrode 34 are stacked and wound via the separator 35, and are wound around the outermost periphery. The protective tape 37 is bonded to form a wound body that is a precursor of the wound electrode body 30. Next, the wound body is sandwiched between exterior members 40, and the outer peripheral edge except for one side is heat-sealed into a bag shape, a solvent, an electrolyte salt, a monomer that is a raw material for the polymer compound, a polymerization initiator, If necessary, an electrolyte composition containing another material such as a polymerization inhibitor is injected. Subsequently, after the opening of the exterior member 40 is heat-sealed and sealed, a gel-like electrolyte layer 36 is formed by applying heat to polymerize the monomer to form a polymer compound. Assemble the secondary battery shown.

  This secondary battery operates in the same manner as the first secondary battery described above, and has the same effect.

(Third battery)
FIG. 7 illustrates a cross-sectional configuration of the third secondary battery. In this secondary battery, a plate-like electrode body 50 in which a positive electrode 52 to which a positive electrode lead 51 is attached and a negative electrode 54 to which a negative electrode lead 53 is attached is disposed so as to face each other with an electrolyte layer 55 interposed therebetween. It is housed in the exterior member 56. The configuration of the exterior member 56 is the same as that of the exterior member 40 described above.

  The positive electrode 52 has a structure in which a positive electrode current collector 52A is provided with a positive electrode active material layer 52B. The negative electrode 54 has a structure in which a negative electrode active material layer 54B is provided on a negative electrode current collector 54A, and the negative electrode active material layer 54B and the positive electrode active material layer 52B are arranged to face each other. The configurations of the positive electrode current collector 52A, the positive electrode active material layer 52B, the negative electrode current collector 54A, and the negative electrode active material layer 54B are respectively the positive electrode current collector 21A, the positive electrode active material layer 21B, and the negative electrode current collector of the first secondary battery. The same as the body 22A and the negative electrode active material layer 22B.

  The electrolyte layer 55 is made of, for example, a solid electrolyte. As the solid electrolyte, for example, an inorganic solid electrolyte or a polymer solid electrolyte can be used as long as the material has lithium ion conductivity. Examples of the inorganic solid electrolyte include those containing lithium nitride or lithium iodide. The polymer solid electrolyte is mainly composed of an electrolyte salt and a polymer compound that dissolves the electrolyte salt. Examples of the polymer compound of the solid polymer electrolyte include, for example, an ether polymer compound such as polyethylene oxide or a crosslinked product containing polyethylene oxide, an ester polymer compound such as polymethacrylate, and an acrylate polymer compound. Or can be copolymerized.

  The polymer solid electrolyte can be formed, for example, by mixing a polymer compound, an electrolyte salt, and a mixed solvent, and then volatilizing the mixed solvent. Moreover, after dissolving electrolyte salt, the monomer which is a raw material of a polymer compound, a polymerization initiator, and other materials such as a polymerization inhibitor as necessary in a mixed solvent, the mixed solvent is volatilized, It can also be formed by polymerizing the monomer by applying heat to form a polymer compound.

  The inorganic solid electrolyte is formed on the surface of the positive electrode 52 or the negative electrode 54 by a gas phase method such as sputtering, vacuum deposition, laser ablation, ion plating, CVD (Chemical Vapor Deposition), or sol-gel method. It can be formed by a liquid phase method.

  This secondary battery operates in the same manner as the first secondary battery described above, and has the same effect.

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

  A negative electrode material was produced as follows. First, a silicon powder having an average particle diameter of 10 μm is prepared as a material constituting the core part 3, and the silicon powder is immersed in an ethanol solution of aluminum butoxide and then baked at 1000 ° C. in the air. An intermediate layer 4 made of aluminum oxide was formed. Next, this was impregnated with an aqueous ethanol solution of tetramethyl silicate and then fired at 1000 ° C. in the air to form the outer shell portion 2 made of a porous material on the surface of the intermediate layer 4. Subsequently, this was immersed in a 1N hydrochloric acid solution for 12 hours, washed with distilled water and dried.

  When the particles thus obtained were observed with a transmission electron microscope (TEM), the core 3 of the silicon particles was present in the hollow outer shell 2 having an outer diameter of about 15 μm. It was confirmed that Moreover, when the outer shell 2 was identified by X-ray photoelectron spectroscopy, it was found that the outer shell 2 was composed of silicon oxide.

  Next, a coin-type test battery as shown in FIG. 8 was produced using the obtained negative electrode material. In this test battery, a test electrode 61 using the negative electrode material of this example is accommodated in an exterior member 62, and a counter electrode 63 made of metallic lithium is attached to the exterior member 64, and a separator 65 impregnated with an electrolytic solution is interposed therebetween. After being laminated, they are caulked through a gasket 66.

  The test electrode 61 was formed by mixing 85 parts by mass of the obtained negative electrode material, 10 parts by mass of artificial graphite as a conductive material, and 5 parts by mass of polyvinylidene fluoride as a binder. As the electrolyte, a solution obtained by dissolving LiPF as an electrolyte salt at a concentration of 1 mol / l in a solvent in which ethylene carbonate and dimethyl carbonate were mixed in an equal volume was used, and a polypropylene porous membrane was used as the separator 65. . The size of the test battery was 20 mm in diameter and 2.5 mm in thickness.

  As a comparative example for this example, a test battery was fabricated in the same manner as in this example, except that silicon powder having an average particle size of 10 μm was used as the negative electrode material.

  A charge / discharge test was performed on the manufactured test batteries of Examples and Comparative Examples, and the initial discharge capacity and the discharge capacity retention rate were obtained. At that time, charging is performed at a constant current of 1 mA until the battery voltage reaches 0 mV, and then charging is performed at a constant voltage of 0 V until the current value is attenuated to 20 μA. Constant current discharge was performed until the battery voltage reached 1.2 V at a constant current. In this evaluation, the process in which lithium is occluded in the test electrode 61 and the voltage of the test battery decreases is called charging, and the reverse process is called discharging. The initial discharge capacity was calculated as the discharge capacity at the first cycle, and the discharge capacity maintenance ratio was calculated as a percentage of the discharge capacity at the 50th cycle with respect to the discharge capacity at the first cycle. The obtained results are shown in Table 1.

  As shown in Table 1, according to the present example, both the initial discharge capacity and the discharge capacity retention rate were higher than those of the comparative example. That is, it has been found that if the core portion 3 is provided in the outer shell portion 2 having the holes 1, the charge / discharge characteristics such as capacity and capacity retention rate can be improved.

  Although the present invention has been described with reference to the embodiments and examples, the present invention is not limited to the embodiments and examples, and various modifications can be made. For example, in the above-described embodiments and examples, a secondary battery having a coin type, a sheet type, and a winding structure has been specifically described. However, the present invention provides an exterior member such as a button type or a square type. The present invention can be similarly applied to a secondary battery having another shape used or a secondary battery having a stacked structure in which a plurality of positive and negative electrodes are stacked.

  In the embodiments and examples, the case where lithium is used as the electrode reactant has been described. However, if it is possible to react with the negative electrode material, other materials in the long-period periodic table such as sodium (Na) or potassium (K) can be used. The present invention is also applied to the case of using a Group 1 element, a Group 2 element in a long-period periodic table such as magnesium or calcium (Ca), another light metal such as aluminum, lithium, or an alloy thereof. And similar effects can be obtained. At that time, a positive electrode active material or a non-aqueous solvent that can occlude and release the electrode reactant is selected according to the electrode reactant.

It is sectional drawing showing the structure of the negative electrode material which concerns on one embodiment of this invention. It is sectional drawing showing the manufacturing process of the negative electrode material shown in FIG. It is sectional drawing showing the structure of the 1st secondary battery using the negative electrode material shown in FIG. It is sectional drawing which expands and represents a part of winding electrode body in the secondary battery shown in FIG. It is sectional drawing showing the structure of the 2nd secondary battery using the negative electrode material shown in FIG. It is sectional drawing showing the structure along the II line of the winding electrode body shown in FIG. It is sectional drawing showing the structure of the 3rd secondary battery using the negative electrode material shown in FIG. It is sectional drawing which shows the structure of the coin-type test battery produced in the Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Hole, 2 ... Outer shell part, 3 ... Core part, 4 ... Middle layer, 11 ... Battery can, 12, 13 ... Insulation board, 14 ... Battery cover, 15 ... Safety valve mechanism, 15A ... Disc board, 16 ... Heat resistance element, 17, 66 ... gasket, 20, 30 ... wound electrode body, 21, 33, 52 ... positive electrode, 21A, 33A, 52A ... positive electrode current collector, 21B, 33B, 52B ... positive electrode active material layer, 22, 34, 54 ... negative electrode, 22A, 34A, 54A ... negative electrode current collector, 22B, 34B, 54B ... negative electrode active material layer, 23, 35, 65 ... separator, 24 ... center pin, 25, 31, 51 ... positive electrode Lead, 26, 32, 53 ... negative electrode lead, 36, 55 ... electrolyte layer, 37 ... protective tape, 40, 56, 62, 64 ... exterior member, 41 ... adhesive film, 50 ... electrode body, 61 ... test electrode, 63 ... counter electrode.

Claims (6)

A particulate outer shell having pores therein;
A negative electrode material comprising: a core part present in the pores and containing at least one of a metal element and a metalloid element as a constituent element.   The negative electrode material according to claim 1, wherein the outer shell portion is made of an oxide porous body.   The negative electrode material according to claim 1, wherein the core includes at least one of silicon and tin as a constituent element. A battery comprising an electrolyte together with a positive electrode and a negative electrode,
The negative electrode has a particulate outer shell portion having pores therein, and a negative electrode material present in the pores and a core portion containing at least one of a metal element and a metalloid element as a constituent element A battery comprising:   The battery according to claim 4, wherein the outer shell portion is made of a porous body of oxide. The battery according to claim 4, wherein the core includes at least one of silicon and tin as a constituent element.

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