JP2007109416A - Cathode active substance, method for manufacturing the same, and battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cathode active substance with high capacity, a battery that uses it, and a method for manufacturing the cathode active substance having high capacity. <P>SOLUTION: A cathode 22 contains the cathode active substance capable of reacting with lithium. Raw materials are mixed in a helium atmosphere or in a vacuum of 133 Pa or lower by a method using a mechanochemical reaction, to be synthesized into the cathode active substance. This reduces an amount of a gas component captured by the cathode active substance, and therefore makes a true specific gravity and the capacity of the cathode active substance higher. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a negative electrode active material synthesized using a mechanochemical reaction, a battery using the same, and a method for producing a negative electrode active material using a mechanochemical reaction.

  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 these, 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 non-graphitizable carbon or a carbon material such as graphite that exhibits a relatively high capacity and can obtain good cycle characteristics is widely used. However, considering the recent demand for higher capacity, further increase in capacity of carbon materials has become an issue.

From such a background, for example, an intermetallic compound with lithium (Li) such as silicon (Si) or tin (Sn) is formed as a negative electrode active material capable of achieving both high capacity exceeding the carbon material and excellent cycle characteristics. There has been proposed a material obtained by mechanically alloying or amorphizing a material containing an element and a material containing an element that does not form an intermetallic compound with lithium (for example, see Patent Documents 1 to 3).
JP 2000-311681 A International Publication No. 04/100291 Pamphlet JP 2005-71772 A

  For such a method, for example, a method using a mechanochemical reaction such as a mechanical alloying method is used. Further, these methods are performed under an inert atmosphere such as argon gas or nitrogen gas in order to prevent oxidation of the synthesized negative electrode active material.

  However, since argon gas or nitrogen gas hinders the aggregation of pulverized powder in the production process and the subsequent alloying or amorphization, there is a problem that the production efficiency is lowered. In addition, the argon gas or nitrogen gas taken into the negative electrode active material has a problem in that the true specific gravity of the negative electrode active material is lowered and the capacity is lowered.

  The present invention has been made in view of such problems, and an object thereof is to provide a high-capacity negative electrode active material, a battery using the same, and a method for producing a high-capacity negative electrode active material.

  The first negative electrode active material of the present invention is synthesized by mixing raw materials by a method utilizing a mechanochemical reaction, and contains helium (He).

  The second negative electrode active material of the present invention is at least one member selected from the group consisting of tin and manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu) as constituent elements. And carbon (C), and helium.

  The third negative electrode active material of the present invention is synthesized by mixing raw materials in a vacuum of 133 Pa or less by a method utilizing a mechanochemical reaction.

  The manufacturing method of the 1st negative electrode active material of this invention includes the process of mixing a raw material by the method using a mechanochemical reaction in helium atmosphere.

  The manufacturing method of the 2nd negative electrode active material of this invention includes the process of mixing a raw material by the method using a mechanochemical reaction in the vacuum of 133 Pa or less.

  A first battery of the present invention includes an electrolyte together with a positive electrode and a negative electrode, and the negative electrode includes a negative electrode active material synthesized by mixing raw materials by a method using a mechanochemical reaction. The substance contains helium.

  A second battery according to the present invention includes an electrolyte together with a positive electrode and a negative electrode, and the negative electrode includes tin as a constituent element and at least one selected from the group consisting of manganese, iron, cobalt, nickel, and copper. A negative electrode active material containing carbon, and the negative electrode active material contains helium

  A third battery of the present invention is provided with an electrolyte together with a positive electrode and a negative electrode. The negative electrode is synthesized by mixing raw materials in a vacuum of 133 Pa or less by a method utilizing a mechanochemical reaction. Contains substances.

  According to the first negative electrode active material of the present invention, since the raw materials are mixed and synthesized by a method utilizing a mechanochemical reaction and further contain helium, the true specific gravity can be increased. Therefore, according to the first battery of the present invention using this negative electrode active material, a high capacity can be obtained.

  According to the second negative electrode active material of the present invention, the capacity can be increased because tin is included as a constituent element. Moreover, since at least one kind selected from the group consisting of manganese, iron, cobalt, nickel, and copper and carbon are included, cycle characteristics can be improved. Further, since helium is included, the true specific gravity can be increased and the capacity can be increased. Therefore, according to the second battery of the present invention using this negative electrode active material, a high capacity and excellent cycle characteristics can be obtained.

  According to the third negative electrode active material of the present invention, since the raw materials are mixed and synthesized in a vacuum of 133 Pa or less by a method utilizing a mechanochemical reaction, the true specific gravity can be increased. Therefore, according to the third battery of the present invention using this negative electrode active material, a high capacity can be obtained.

  According to the first negative electrode active material manufacturing method of the present invention, since the raw material is mixed in a helium atmosphere by a method using a mechanochemical reaction, the first negative electrode active material of the present invention is included. Can be manufactured efficiently.

  In particular, a material containing tin as a constituent element, a material containing at least one of the group consisting of manganese, iron, cobalt, nickel and copper as a constituent element and a material containing carbon as a constituent element are used as raw materials. Thus, the second negative electrode active material of the present invention can be easily produced.

  According to the second negative electrode active material manufacturing method of the present invention, since the raw material is mixed by a method using a mechanochemical reaction in a vacuum of 133 Pa or less, the third negative electrode of the present invention is included. An active material can be produced efficiently.

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

[First Embodiment]
The negative electrode active material according to one embodiment of the present invention can react with lithium or the like, and is synthesized by mixing raw materials by a method using a mechanochemical reaction in a helium atmosphere. As a result, the gas component taken into the negative electrode active material can be reduced and can be efficiently synthesized in a short time, and the true specific gravity of the synthesized negative electrode active material can be increased to improve the capacity. ing.

  Since this negative electrode active material is synthesized as described above, it contains helium, but its content is preferably 1.0 atomic% or less. This is because the true specific gravity can be further improved.

  The negative electrode active material preferably contains tin as a constituent element and at least one selected from the group consisting of manganese, iron, cobalt, nickel, and copper. This is because tin has a high reaction amount of lithium per unit mass or unit volume, and a high capacity can be obtained. Moreover, it is difficult to obtain sufficient cycle characteristics with tin alone, but the cycle characteristics can be improved by including manganese, iron, cobalt, nickel, or copper. In addition to these, it is preferable that carbon is included as a constituent element. This is because the cycle characteristics can be further improved by including carbon.

  Since this negative electrode active material is also synthesized by mixing by a method utilizing a mechanochemical reaction, the constituent elements of the negative electrode active material can be densely compounded, and the crystallinity is low or amorphous. It is possible to have a phase. Therefore, excellent cycle characteristics can be obtained. Examples of the method using mechanochemical reaction include a mechanical alloying method and a mechanical milling method. In this method, for example, a planetary ball mill device or a vibration mill can be used.

In addition, a method using a mechanochemical reaction is performed, for example, in a sealed container such as stainless steel. However, it is preferable that this sealed container has high airtightness to the extent that it can always block outside air. This is because if the airtightness is low and air is mixed, the pulverized powder is oxidized and the performance of the synthesized negative electrode active material is degraded. Furthermore, the helium pressure in the sealed container is preferably 1 × 10 ⁵ Pa (760 Torr) or less. This is because the gas component taken into the negative electrode active material can be further reduced.

  As a raw material, a material containing tin as a constituent element, a material containing at least one of the group consisting of manganese, iron, cobalt, nickel and copper as a constituent element, and a material containing carbon as a constituent element are used. Is preferred. Accordingly, as described above, tin can be included as a constituent element, at least one of the group consisting of manganese, iron, cobalt, nickel, and copper, and carbon, and a material including carbon. This is because a lower crystalline or amorphous phase can be formed by using. As a raw material, each constituent element may be used alone, but it is preferable to use an alloy for a part of the material other than the material containing carbon. This is because by adding a material containing carbon to such an alloy and synthesizing it by a method utilizing a mechanochemical reaction, it is possible to have a further low crystallization or amorphous phase. In addition, the form of the raw material may be in the form of a powder or a lump.

  Examples of the carbon used as a raw material include carbon materials such as non-graphitizable carbon, graphitizable carbon, graphite, pyrolytic carbons, coke, glassy carbons, organic polymer compound fired bodies, activated carbon, and carbon black. 1 type (s) or 2 or more types can be used. Among these, cokes include pitch coke, needle coke, and petroleum coke. Organic polymer compound fired bodies are carbonized by firing polymer compounds such as phenol resin and furan resin at an appropriate temperature. What you did. The shape of these carbon materials may be any of fibrous, spherical, granular or scale-like.

  This negative electrode active material is used for a secondary battery as follows, for example.

(First secondary battery)
FIG. 1 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 (Al) 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 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. 2 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 or one surface 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. The positive electrode active material layer 21B contains, for example, any one or more of positive electrode active materials capable of inserting and extracting lithium, and a conductive agent such as a carbon material and polyvinylidene fluoride as necessary. It may contain a binder.

Examples of the positive electrode active material capable of inserting and extracting lithium include titanium sulfide (TiS ₂ ), molybdenum sulfide (MoS ₂ ), niobium selenide (NbSe ₂ ), and vanadium oxide (V ₂ O ₅ ). Examples thereof include metal sulfides or metal oxides that do not contain lithium. Further, a lithium composite mainly composed of Li _x MO ₂ (wherein M represents one or more transition metals, x is different depending on the charge / discharge state of the battery, and is generally 0.05 ≦ x ≦ 1.10.) An oxide etc. are also mentioned. As the transition metal M constituting the lithium composite oxide, cobalt, nickel or manganese is preferable. Specific examples of such a lithium composite oxide include LiCoO ₂ , LiNiO ₂ , Li _y Ni _z Co _1-z O ₂ (where y and z vary depending on the charge / discharge state of the battery, and generally 0 <y < , 0 <z <1), and lithium manganese composite oxide having a spinel structure.

  The negative electrode 22 has, for example, a structure in which a negative electrode active material layer 22B is provided on both surfaces or one surface of a negative electrode current collector 22A having a pair of opposed surfaces, similarly to 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 active material according to the present embodiment, and includes a binder such as polyvinylidene fluoride as necessary. As described above, by including the negative electrode active material according to the present embodiment, the secondary battery can obtain a high capacity and improve the cycle characteristics. In addition to the negative electrode active material according to the present embodiment, the negative electrode active material layer 22B may include other negative electrode active materials or other materials such as a conductive agent. Examples of the other negative electrode active material include a carbon material that can occlude and release lithium. This carbon material is preferable because it can improve charge and discharge efficiency and also functions as a conductive agent. As a carbon material, the thing similar to what was used when manufacturing a negative electrode active material is mentioned, for example.

  The ratio of the carbon material is preferably in the range of 1% by mass to 95% by mass with respect to the negative electrode active material of the present embodiment. This is because when the carbon material is small, the conductivity of the negative electrode 22 decreases, and when the carbon material is large, the battery capacity decreases.

  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, Examples include 4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methyl sulfolane, acetonitrile, propionitrile, anisole, acetic acid ester, butyric acid ester or propionic acid 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. Specific examples of such cyclic carbonate derivatives include 4-fluoro-1,3-dioxolan-2-one represented by Chemical Formula 1 (1) and 4-difluoro represented by Chemical Formula 1 (2). -1,3-dioxolan-2-one, 4,5-difluoro-1,3-dioxolan-2-one shown in Chemical formula 1 (3), 4-difluoro-5-fluoro shown in Chemical formula 1 (4) -1,3-dioxolan-2-one, 4-chloro-1,3-dioxolan-2-one shown in Chemical formula 1 (5), 4,5-dichloro-1,3 shown in Chemical formula 1 (6) -Dioxolan-2-one, 4-bromo-1,3-dioxolan-2-one shown in Chemical formula 1 (7), 4-iodo-1,3-dioxolan-2-one shown in Chemical formula 1 (8) 4-fluoromethyl-1,3-dioxolan-2-one shown in Chemical formula 1 (9), Rui include 4-trifluoromethyl-1,3-dioxolan-2-one expressed in 1 (10) of, among others, 4-fluoro-1,3-dioxolan-2-one is desired. This is because a higher effect can be obtained.

The solvent may be composed only of this cyclic carbonate derivative, but is preferably used by mixing with a low boiling point solvent having a boiling point of 150 ° C. or lower at atmospheric pressure (1.01325 × 10 ⁵ Pa). . This is because the ion conductivity can be increased. The content of the carbonate ester derivative is preferably in the range of 0.1% by mass to 80% by mass with respect to the entire solvent. If the amount is small, the effect of suppressing the decomposition reaction of the solvent in the negative electrode 22 is not sufficient.

As electrolyte salt, lithium salt is mentioned, for example, 1 type may be used independently, and 2 or more types may be mixed and used for it. 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. 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 is mixed with a conductive agent and a binder as necessary to prepare a positive electrode mixture, and dispersed in a solvent such as N-methyl-2-pyrrolidone to produce a positive electrode mixture slurry To do. 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.

  In addition, for example, a negative electrode active material according to the present embodiment and, if necessary, another negative electrode active material and a binder are mixed to prepare a negative electrode mixture, and a solvent such as N-methyl-2-pyrrolidone is used. Disperse to prepare a negative electrode mixture slurry. 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. 1 and 2 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. Here, since the negative electrode 22 contains a negative electrode active material synthesized by mixing raw materials by a method using a mechanochemical reaction in a helium atmosphere, the capacity is improved.

(Secondary secondary battery)
FIG. 3 shows the configuration 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 accommodated 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. 4 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 obtained by stacking and winding a positive electrode 33 and a negative electrode 34 with a separator 35 and an electrolyte layer 36 interposed therebetween, and the outermost peripheral portion 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 one or 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 one surface or both surfaces of a negative electrode current collector 34A, and the negative electrode active material layer 34B side is disposed so as to face the positive electrode active material layer 33B. Yes. 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 negative electrode current collector 22A. The same as the negative electrode 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. The gel electrolyte layer 36 is preferable because high ion conductivity can be obtained and battery leakage can be prevented. The structure of the electrolytic solution (that is, the solvent and the electrolyte salt) is the same as that of the cylindrical secondary battery shown in FIG. 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, a precursor solution containing an electrolytic solution, a polymer compound, and a mixed solvent is applied to each of the positive electrode 33 and the negative electrode 34, and the mixed solvent is volatilized to form the electrolyte layer 36. After that, the positive electrode lead 31 is attached to the end of the positive electrode current collector 33A by welding, and the negative electrode lead 32 is attached to the end of the negative electrode current collector 34A by welding. Next, the positive electrode 33 and the negative electrode 34 on which the electrolyte layer 36 is formed are laminated via a separator 35 to form a laminated body, and then the laminated body is wound in the longitudinal direction, and a protective tape 37 is adhered to the outermost peripheral portion. Thus, the wound electrode body 30 is formed. Finally, 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 heat 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. 3 and 4 is completed.

  Further, this secondary battery may be manufactured as follows. First, the positive electrode 33 and the negative electrode 34 are prepared as described above, and after the positive electrode lead 31 and the negative electrode lead 32 are attached to the positive electrode 33 and the negative electrode 34, the positive electrode 33 and the negative electrode 34 are stacked via the separator 35 and wound. Rotate and adhere the protective tape 37 to the outermost periphery to form a wound body that is a precursor of the wound electrode body 30. Next, the wound body is sandwiched between the exterior members 40, and the outer peripheral edge except for one side is heat-sealed to form a bag shape, and is stored inside the exterior member 40. Subsequently, an electrolytic solution, a monomer that is a raw material of the polymer compound, and a composition for an electrolyte that includes a polymerization initiator and other materials such as a polymerization inhibitor as necessary are prepared. Inject inside.

  After injecting the electrolyte composition, the opening of the exterior member 40 is heat-sealed and sealed in a vacuum atmosphere. Next, if necessary, heat is applied to polymerize the monomer to form a polymer compound, thereby forming the gel electrolyte layer 36, and assembling the secondary battery shown in FIGS.

  The operation of this secondary battery is the same as that of the first secondary battery.

  Thus, according to the negative electrode active material according to the present embodiment, since the raw materials are mixed and synthesized by a method using a mechanochemical reaction and contain helium, the true specific gravity can be increased. Therefore, according to the 1st or 2nd secondary battery which concerns on this Embodiment using this negative electrode active material, a high capacity | capacitance can be obtained.

  Further, when the negative electrode active material contains tin as a constituent element, the capacity can be further increased. Furthermore, if at least one kind selected from the group consisting of manganese, iron, cobalt, nickel and copper and carbon are included, cycle characteristics can be improved.

  According to the method for producing a negative electrode active material according to the present embodiment, since the raw materials are mixed by a method using a mechanochemical reaction in a helium atmosphere, the negative electrode active material according to the present embodiment is efficiently mixed. Can be manufactured.

  In particular, a material containing tin as a constituent element, a material containing at least one of the group consisting of manganese, iron, cobalt, nickel and copper as a constituent element and a material containing carbon as a constituent element are used as raw materials. Thus, a negative electrode active material containing these elements as constituent elements can be easily produced.

[Second Embodiment]
The negative electrode active material according to the second embodiment of the present invention is capable of reacting with lithium or the like, and is synthesized by mixing raw materials in a vacuum by a method utilizing a mechanochemical reaction. As a result, the gas component taken into the negative electrode active material can be reduced and can be efficiently synthesized in a short time, and the true specific gravity of the synthesized negative electrode active material can be increased to improve the capacity. ing.

  This negative electrode active material preferably contains tin as a constituent element and at least one selected from the group consisting of manganese, iron, cobalt, nickel and copper. This is because tin has a high reaction amount of lithium per unit mass or unit volume, and a high capacity can be obtained. Moreover, it is difficult to obtain sufficient cycle characteristics with tin alone, but the cycle characteristics can be improved by including manganese, iron, cobalt, nickel, or copper. In addition to these, it is preferable that carbon is included as a constituent element. This is because the cycle characteristics can be further improved by including carbon.

  In addition, since this negative electrode active material is synthesized by mixing by a method using a mechanochemical reaction, the constituent elements of the negative electrode active material can be densely combined, and the crystalline property is low or amorphous. It is possible to have a phase. Therefore, excellent cycle characteristics can be obtained. Examples of the method using the mechanochemical reaction include the method described in the negative electrode active material according to the first embodiment, and the same apparatus can be used.

  Further, the inside of the sealed container at the time of synthesis is in a vacuum state of 133 Pa (1 Torr) or less. This is because the oxidation of the pulverized powder can be prevented and the performance of the synthesized negative electrode active material can be prevented from being lowered, and the gas component taken into the negative electrode active material can be reduced.

  As the raw material, the same material as described in the first embodiment can be used, and the same effect can be obtained.

  This negative electrode active material can be used, for example, in the first secondary battery or the second secondary battery described in the first embodiment, and acts in the same manner as in the first embodiment.

  According to the negative electrode active material according to the present embodiment, since the raw materials are mixed and synthesized in a vacuum of 133 Pa or less by a method using a mechanochemical reaction, the true specific gravity can be increased. Therefore, according to the 1st or 2nd secondary battery using this negative electrode active material, a high capacity | capacitance can be obtained.

  Further, when the negative electrode active material contains tin as a constituent element, the capacity can be further increased. Furthermore, if at least one kind selected from the group consisting of manganese, iron, cobalt, nickel and copper and carbon are included, cycle characteristics can be improved.

  According to the method for producing a negative electrode active material according to the present embodiment, since the raw materials are mixed by a method utilizing a mechanochemical reaction in a vacuum of 133 Pa or less, the negative electrode active material according to the present embodiment is It can be manufactured efficiently.

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

(Examples 1-1 to 1-3)
A negative electrode active material was prepared. First, tin powder, cobalt powder, and carbon powder are prepared as raw materials, and tin powder and cobalt powder are alloyed to produce tin-cobalt alloy powder. Then, carbon powder is added to the alloy powder and dry mixing is performed. did. At that time, the raw material ratio (mass ratio) was set to cobalt: tin: carbon = 28.8: 51.2: 20. Subsequently, 20 g of this mixture was set together with about 400 g of steel balls having a diameter of 9 mm in a reaction vessel of a planetary ball mill manufactured by Ito Seisakusho. Next, the atmosphere in the reaction vessel is removed using a vacuum pump, and a helium atmosphere, a vacuum state of 133 Pa, or a vacuum state of 13.3 Pa (0.1 Torr) is obtained, and the rotation speed is 250 rpm for 10 minutes. The operation and the pause for 10 minutes were repeated until a predetermined time was reached. Thereafter, the synthesized negative electrode active material powder was taken out by cooling the reaction vessel to room temperature, and coarse powder was removed through a 280 mesh sieve.

  As Comparative Examples 1-1 to 1-4 with respect to Examples 1-1 to 1-3, the atmosphere in the synthesis, that is, the atmosphere in the reaction vessel is an argon atmosphere, a nitrogen atmosphere, air, or 1333 Pa (10 Torr). A negative electrode active material was synthesized in the same manner as in Examples 1-1 to 1-3 except that the vacuum state was achieved.

  The true specific gravity of the negative electrode active materials of Examples 1-1 to 1-3 and Comparative Examples 1-1 to 1-4 was examined. The results are shown in Table 1. Note that the true specific gravity of the negative electrode active material is an evaluation index that directly reflects the amount of gas taken in. The larger the amount of gas taken in, the more voids in the negative electrode active material and the smaller the true specific gravity.

  Using the obtained negative electrode active material powder, a coin-type secondary battery as shown in FIG. 5 was produced, and the initial charge capacity was examined. In this coin-type battery, the test electrode 51 using the negative electrode active material of the present example is accommodated in the exterior member 52, and the counter electrode 53 is attached to the exterior member 54, and is laminated via the separator 55 impregnated with the electrolytic solution. After that, it is caulked through the gasket 56.

  The test electrode 51 was prepared by mixing the obtained negative electrode active material powder, the conductive agent and graphite as another negative electrode active material, acetylene black as a conductive agent, and polyvinylidene fluoride as a binder. The slurry was dispersed in a solvent to form a slurry, which was then applied onto a copper foil current collector, dried and then punched into pellets having a diameter of 15.2 mm.

As the counter electrode 53, a metal lithium plate punched to a diameter of 15.5 mm was used. As the electrolytic solution, a solution obtained by dissolving LiPF ₆ as an electrolyte salt in a mixed solvent of ethylene carbonate, propylene carbonate, and dimethyl carbonate was used.

  The initial charge capacity is constant current charging until the battery voltage reaches 0.2 mV at a constant current of 1 mA, and then constant voltage charging is performed until the current reaches 10 μA at a constant voltage of 0.2 mV. The charge capacity per unit mass obtained by subtracting the mass of the copper foil current collector and the binder from the mass was calculated and calculated by multiplying this by the true specific gravity. In addition, the charge here means a lithium insertion reaction into the negative electrode active material. The results are shown in Table 1.

  As can be seen from Table 1, according to Examples 1-1 to 1-3 in which the negative electrode active material was synthesized in a helium atmosphere or in a vacuum state of 133 Pa or less, an argon atmosphere, a nitrogen atmosphere, air, or a vacuum exceeding 133 Pa was used. The true specific gravity was higher than Comparative Examples 1-1 to 1-4 in which the negative electrode active material was synthesized in the state, and the initial charge capacity was improved.

  That is, it has been found that the capacity can be increased if the negative electrode active material is synthesized by mixing the raw materials in a helium atmosphere or in a vacuum of 133 Pa or less by a method utilizing a mechanochemical reaction.

(Examples 2-1 to 2-6)
A secondary battery was fabricated in the same manner as in Examples 1-1 to 1-3 except that the negative electrode active material was synthesized by changing the reaction time. The reaction time was 75 or 50 in the ratio when the reaction time in Examples 1-1 to 1-3 was 100.

  As Comparative Examples 2-1 to 2-8 with respect to Examples 2-1 to 2-6, except that the negative electrode active material was synthesized by changing the reaction time, the rest was the same as Comparative Examples 1-1 to 1-4. A secondary battery was manufactured. The reaction time was 75 or 50 in a ratio when the reaction time in Comparative Examples 1-1 to 1-4 (that is, the reaction time in Examples 1-1 to 1-3) was 100.

  About the obtained negative electrode active material, it carried out similarly to Examples 1-1 to 1-3, and calculated | required true specific gravity. For the secondary battery, the initial charge capacity was determined in the same manner as in Examples 1-1 to 1-3. The results are shown in Table 2.

  As can be seen from Table 2, Examples 2-1 and 2 in which the negative electrode active material was synthesized in a helium atmosphere or in a vacuum state of 133 Pa or less by changing the reaction time as in Examples 1-1 to 1-3. -3, 2-5 or Examples 2-2, 2-4, and 2-6, Comparative Example 2-1 in which the negative electrode active material was synthesized in an argon atmosphere, a nitrogen atmosphere, air, or a vacuum state exceeding 133 Pa , 2-3, 2-5, 2-7 or Comparative Examples 2-2, 2-4, 2-6, 2-8, respectively, the true specific gravity was higher and the initial charge capacity was improved.

  That is, if the negative electrode active material is synthesized by mixing the raw materials in a helium atmosphere or in a vacuum of 133 Pa or less by a method utilizing a mechanochemical reaction, the capacity is increased even if the reaction time is changed. I found out that I could do it.

(Examples 3-1, 3-2, 4-1, 4-2, 5-1, 5-2, 6-1, 6-2)
A negative electrode active material was synthesized in the same manner as in Examples 1-1 and 1-2, except that manganese powder, iron powder, nickel powder, or copper powder was used instead of cobalt powder. Was made.

  Comparative Examples 3-1, 4-1, 5-1, 6 to Examples 3-1, 3-2, 4-1, 4-2, 5-1, 5-2, 6-1, 6-2 1 except that the atmosphere in the reaction vessel was changed to an argon atmosphere, and the others were Examples 3-1, 3-2, 4-1, 4-2, 5-1, 5-2, 6-1, A negative electrode active material was produced in the same manner as in 6-2, and a secondary battery was produced.

  About the obtained negative electrode active material, it carried out similarly to Examples 1-1 to 1-3, and calculated | required true specific gravity. Moreover, about the negative electrode active material of Example 3-1, 4-1, 5-1 and 6-1, the amount of helium in a negative electrode active material was investigated by X-ray photoelectron spectroscopy (XPS). . Further, for the secondary battery, the initial charge capacity was determined in the same manner as in Examples 1-1 to 1-3. In Table 3, the numerical values described before each constituent element of the negative electrode active material represent the mixing amount of each element by mass ratio.

  As can be seen from Table 3, as in Examples 1-1 and 1-2, a negative electrode active material was synthesized in a helium atmosphere or in a vacuum state of 133 Pa or less using manganese, iron, nickel or copper instead of cobalt. According to Examples 3-1, 3-2, 4-1, 4-2, 5-1, 5-2, 6-1, 6-2, Comparative Example 3 in which the negative electrode active material was synthesized in an argon atmosphere The true specific gravity was higher than each of -1,4-1,5-1,6-1, and the initial charge capacity was improved.

  That is, even when other raw materials are used, the negative electrode active material may be synthesized by mixing the raw materials in a helium atmosphere or in a vacuum of 133 Pa or less by a method using a mechanochemical reaction. It turns out that it can be raised.

  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 embodiments and examples, the coin type and the secondary battery having a winding structure have been specifically described, but the present invention is not limited to other shapes such as a button type, a sheet type, or a square type. The present invention can be similarly applied to a secondary battery having the above-described structure or a secondary battery having another 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, other group 1 elements in a long-period periodic table such as sodium (Na) or potassium (K), or magnesium ( The present invention can also be applied to the case of using elements of Group 2 in the long-period periodic table such as Mg) or calcium (Ca), other light metals such as aluminum, lithium, or alloys thereof. The effect of 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.

  Further, in the above embodiment and examples, the case where an electrolytic solution is used as the electrolyte is described, and in the above embodiment, the case where a gel electrolyte in which the electrolytic solution is held in a polymer compound is used is also described. Other electrolytes may be used. Other electrolytes include, for example, ion conductive inorganic compounds such as ion conductive ceramics, ion conductive glass or ionic crystals, or other inorganic compounds, or a mixture of these inorganic compounds and an electrolyte or gel electrolyte. The thing which was done is mentioned.

It is sectional drawing showing the structure of the secondary battery which concerns on one embodiment of this invention. It is sectional drawing which expands and represents a part of winding electrode body in the secondary battery shown in FIG. It is a disassembled perspective view showing the structure of the other secondary battery which concerns on one embodiment of this invention. It is sectional drawing showing the structure along the II line of the winding electrode body shown in FIG. It is sectional drawing which shows the structure of the coin-type battery produced in the Example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Battery can, 12, 13 ... Insulation board, 14 ... Battery cover, 15 ... Safety valve mechanism, 15A ... Disc board, 16 ... Heat sensitive resistance element, 17, 56 ... Gasket, 20, 30 ... Winding electrode body, 21 , 33 ... positive electrode, 21A, 33A ... positive electrode current collector, 21B, 33B ... positive electrode active material layer, 22, 34 ... negative electrode, 22A, 34A ... negative electrode current collector, 22B, 34B ... negative electrode active material layer, 23, 35 , 55 ... separator, 24 ... center pin, 25, 31 ... positive electrode lead, 26, 32 ... negative electrode lead, 36 ... electrolyte layer, 37 ... protective tape, 40, 52, 54 ... exterior member, 41 ... adhesion film, 51 ... Test electrode, 53 ... counter electrode.

Claims (14)

  A negative electrode active material synthesized by mixing raw materials by a method using a mechanochemical reaction, comprising helium (He).   The negative electrode active material according to claim 1, wherein the helium content is 1.0 atomic% or less. As a constituent element, tin (Sn), at least one selected from the group consisting of manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni) and copper (Cu), and carbon (C) A negative electrode active material comprising:
A negative electrode active material comprising helium (He).   4. The negative electrode active material according to claim 3, wherein the helium content is 1.0 atomic% or less.   A negative electrode active material synthesized by mixing raw materials in a vacuum of 133 Pa or less by a method utilizing a mechanochemical reaction. A method for producing a negative electrode active material, comprising a step of mixing raw materials in a helium (He) atmosphere by a method utilizing a mechanochemical reaction.   A material containing tin (Sn) as a constituent element and at least one selected from the group consisting of manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni) and copper (Cu) as a raw material The method for producing a negative electrode active material according to claim 6, wherein a material containing an element and a material containing carbon (C) as a constituent element are used. The manufacturing method of the negative electrode active material characterized by including the process of mixing a raw material by the method using a mechanochemical reaction in the vacuum of 133 Pa or less.   A material containing tin (Sn) as a constituent element and at least one selected from the group consisting of manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni) and copper (Cu) as a raw material The method for producing a negative electrode active material according to claim 8, wherein a material containing an element and a material containing carbon (C) as a constituent element are used. A battery comprising an electrolyte together with a positive electrode and a negative electrode,
The negative electrode includes a negative electrode active material synthesized by mixing raw materials by a method using a mechanochemical reaction,
The negative electrode active material contains helium (He).   The battery according to claim 10, wherein a content of helium in the negative electrode active material is 1.0 atomic% or less. A battery comprising an electrolyte together with a positive electrode and a negative electrode,
The negative electrode includes tin (Sn) as a constituent element, at least one selected from the group consisting of manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu), and carbon ( C) and a negative electrode active material containing,
The negative electrode active material contains helium (He).   The battery according to claim 12, wherein the content of helium in the negative electrode active material is 1.0 atomic% or less. A battery comprising an electrolyte together with a positive electrode and a negative electrode,
The battery includes a negative electrode active material synthesized by mixing raw materials by a method using a mechanochemical reaction in a vacuum of 133 Pa or less.

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