JP2008293955A - Negative electrode active material, and secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: a secondary battery having a high capacity and excellent cycle characteristics; and a negative electrode active material used for the same. <P>SOLUTION: A negative electrode 22 contains a negative electrode active material capable of reacting with lithium. The negative electrode active material contains at least tin, iron, cobalt, and carbon as constituent elements; the content of carbon is ≥11.9 mass% and ≤29.7 mass%; the rate of the total in iron and cobalt to the total of tin, iron, and cobalt is ≥26.4 mass% and ≤48.5 mass%; and the rate of cobalt to the total of iron and cobalt is ≥9.9 mass% and ≤79.5 mass%. Accordingly, cycle characteristics are improved while maintaining a high capacity. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a negative electrode active material containing tin, iron, cobalt, and carbon as constituent elements, and a secondary battery using the same.

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

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

  From such a background, a technique for achieving a high capacity with a carbon material by selecting a carbonization raw material and production conditions has been developed (see, for example, Patent Document 1). However, when such a carbon 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 secondary battery is configured becomes low. I cannot expect a big improvement in the point. 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 surpasses carbon materials, research is being conducted on alloy materials that apply the fact that a certain metal is electrochemically alloyed with lithium and that it is reversibly generated and decomposed. For example, a high-capacity negative electrode using a Li—Al alloy or a Sn alloy has been developed, and further, a high-capacity negative electrode made of a Si alloy has been developed (see, for example, Patent Document 2).

  However, the Li—Al alloy, Sn alloy, or Si alloy expands and contracts with charge and discharge, and the negative electrode is pulverized every time charge and discharge are repeated.

Therefore, as a method for improving cycle characteristics, it has been studied to suppress expansion by alloying tin and silicon. For example, it is proposed to alloy tin with a transition metal such as iron or cobalt. (For example, refer to Patent Documents 3 to 8 and Non-Patent Documents 1 to 3). Also, like Mg ₂ Si has been proposed (e.g., see Non-Patent Document 4). In addition, Sn · A · X having a Sn / (Sn + A + V) ratio of 20 atomic% to 80 atomic% (A is at least one transition metal, X is at least one selected from the group consisting of carbon, etc.) (For example, refer to Patent Document 9), a metal compound capable of being alloyed with a carbon material capable of absorbing and releasing lithium (A _1-x B _x : A is tin or silicon, B is iron or cobalt, etc.) ) Are distributed (for example, see Patent Document 10).
JP-A-8-315825 US Pat. No. 4,950,566, etc. JP 2004-022306 A JP 2004-063400 A Japanese Patent Laying-Open No. 2005-078999 JP 2006-107772 A JP 2006-128051 A JP 2006-344403 A JP 2000-311681 A JP 2004-349253 A “Journal of the Electrochemical Society”, 1999, No. 146, p405 “Journal of the Electrochemical Society”, 1999, No. 146, p414 “Journal of the Electrochemical Society”, 1999, No. 146, p423 “Journal of the Electrochemical Society”, 1999, No. 146, p4401

  However, even when the above-described method is used, the effect of improving the cycle characteristics cannot be said to be sufficient, and the fact is that the features of the high-capacity negative electrode in the alloy material are not fully utilized. For this reason, a method for further improving the cycle characteristics is being sought.

  The present invention has been made in view of such problems, and an object thereof is to provide a secondary battery having a high capacity and excellent cycle characteristics and a negative electrode active material used therefor.

  The negative electrode active material of the present invention contains at least tin, iron, cobalt, and carbon as constituent elements, the carbon content is 11.9% by mass or more and 29.7% by mass or less, and tin, iron, and cobalt are included. The ratio of the total of iron and cobalt to the total is 26.4% to 48.5% by mass, and the ratio of cobalt to the total of iron and cobalt is 9.9% to 79.5% by mass Yes, having a reaction phase capable of reacting with an electrode reactant, and a half-value width of a diffraction peak obtained by X-ray diffraction (a peak seen when the diffraction angle 2θ is between 41 ° and 45 °) is 1.0 ° That's all.

  The secondary battery of the present invention includes an electrolyte together with a positive electrode and a negative electrode, the negative electrode contains a negative electrode active material containing at least tin, iron, cobalt and carbon as constituent elements, and the carbon content in the negative electrode active material is 11. 9 mass% or more and 29.7 mass% or less, and the ratio of the total of iron and cobalt to the total of tin, iron and cobalt is 26.4 mass% or more and 48.5 mass% or less. The ratio of cobalt to the total of 9.9 mass% or more and 79.5 mass% or less, the negative electrode active material has a reaction phase capable of reacting with the electrode reactant, and is obtained by X-ray diffraction of the negative electrode active material The half-value width of a diffraction peak (a peak seen when the diffraction angle 2θ is between 41 ° and 45 °) is 1.0 ° or more.

  According to the negative electrode active material of the present invention, it has a reaction phase capable of reacting with the electrode reactant, and is a diffraction peak obtained by X-ray diffraction (a peak seen when the diffraction angle 2θ is between 41 ° and 45 °). Is at least 1.0 °. In this case, since tin is included as a constituent element, a high capacity can be obtained. Moreover, it contains iron and cobalt as constituent elements, the ratio of the total of iron and cobalt to the total of tin, iron, and cobalt is 26.4 mass% or more and 48.5 mass% or less, and the total of iron and cobalt Since the ratio of cobalt to 9.9 mass% or more and 79.5 mass% or less is set, cycle characteristics are improved while maintaining a high capacity. Furthermore, since carbon is contained as a constituent element and the carbon content is set to 11.9 mass% or more and 29.7 mass% or less, cycle characteristics are further improved. Therefore, according to the secondary battery of the present invention using this negative electrode active material, high capacity can be obtained and excellent cycle characteristics can be obtained.

  Furthermore, the negative electrode active material includes at least one member selected from the group consisting of aluminum, titanium, vanadium, chromium, niobium, and tantalum as a constituent element, or at least one selected from the group consisting of nickel, copper, zinc, gallium, and indium. By including one or both of them, the cycle characteristics can be further improved. In particular, when both are included, the former content is 0.1% by mass or more and 9.9% by mass or less, and the latter content is 0.5% by mass or more and 14.9% by mass or less. An effect can be obtained.

  Furthermore, if the negative electrode active material contains silver as a constituent element, the cycle characteristics can be further improved. In particular, when the content is 0.1% by mass or more and 9.9% by mass or less, a higher effect can be obtained.

  In addition, as a constituent element in the negative electrode active material, at least one selected from the group consisting of aluminum, titanium, vanadium, chromium, niobium and tantalum, and at least one selected from the group consisting of nickel, copper, zinc, gallium and indium If seeds and silver are included, cycle characteristics can be further improved.

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

  The negative electrode active material according to an embodiment of the present invention is capable of reacting with an electrode reactant such as lithium, and includes tin, iron, and cobalt as constituent elements (first to third constituent elements). Is included. This is because tin has a high reaction capacity because the reaction amount of lithium per unit mass is high. Moreover, it is difficult to obtain sufficient cycle characteristics with tin alone, but the cycle characteristics are improved by including iron and cobalt.

  The content of iron and cobalt is preferably in the range of 26.4% by mass or more and 48.5% by mass or less in terms of the ratio of iron and cobalt to the total of tin, iron and cobalt. It is more preferable if it is in the range of mass% or more and 48.5 mass% or less. If the ratio is low, the content of iron and cobalt will be reduced and sufficient cycle characteristics will not be obtained, and if it is high, the content of tin will be reduced and capacity exceeding conventional negative electrode materials such as carbon materials will not be obtained. is there.

  Further, the cobalt content is a ratio of cobalt to the total of iron and cobalt, and is preferably in the range of 9.9 mass% or more and 79.5 mass% or less, and 29.5 mass% or more and 79.5 mass%. It is more preferable if it is within the range of% mass or less. When the ratio is low, the cobalt content decreases and sufficient cycle characteristics cannot be obtained. When the ratio is high, the tin content decreases and a capacity exceeding the conventional negative electrode material such as a carbon material cannot be obtained.

  This negative electrode active material also contains carbon as a constituent element (fourth constituent element) in addition to tin, iron and cobalt. This is because inclusion of carbon improves the cycle characteristics.

  The carbon content is preferably in the range of 11.9 mass% to 29.7 mass%, in the range of 14.9 mass% to 29.7 mass%, and more preferably 17.8 mass% or more. It is more preferable if it is in the range of 29.7% by mass or less. This is because a high effect can be obtained within this range.

  In particular, the negative electrode active material further includes at least one member selected from the group consisting of aluminum, titanium, vanadium, chromium, niobium, and tantalum in addition to tin, iron, cobalt, and carbon as a constituent element (fifth constituent element). Preferably it contains seeds. This is because the inclusion of these improves the cycle characteristics.

  Moreover, it is preferable that the negative electrode active material further contains at least one selected from the group consisting of nickel, copper, zinc, gallium and indium as a constituent element (sixth constituent element). This is because the inclusion of these improves the cycle characteristics.

  The negative electrode active material may contain only the fifth constituent element in addition to the first to fourth constituent elements, or may contain only the sixth constituent element, or both of them. May be included. In this case, if both are included, a higher effect can be obtained. In particular, when both are included, the content of the fifth constituent element is preferably in the range of 0.1 mass% or more and 9.9 mass% or less, and the content of the sixth constituent element is 0.00. It is preferably in the range of 5% by mass or more and 14.9% by mass or less. This is because a higher effect can be obtained.

  In addition, the negative electrode active material preferably contains silver as a constituent element (seventh constituent element) in addition to tin, iron, cobalt, and carbon. This is because the cycle characteristics are further improved by containing silver.

  The silver content is preferably in the range of 0.1% by mass to 9.9% by mass, and more preferably in the range of 0.9% by mass to 9.9% by mass. This is because a higher effect can be obtained.

  This negative electrode active material may contain only the fifth and sixth constituent elements in addition to the first to fourth constituent elements, or may contain only the seventh constituent element, May be included. In this case, if all are included, a higher effect can be obtained.

  This negative electrode active material has a low crystallinity or amorphous phase. This phase is a reaction phase capable of reacting with lithium or the like, and thereby excellent cycle characteristics can be obtained. This reaction phase contains, for example, each of the above-described constituent elements, and is considered to be low-crystallized or amorphized mainly by carbon. A diffraction peak obtained by X-ray diffraction of this phase is seen when the diffraction angle 2θ is 20 ° or more and 50 ° or less when CuKα ray is used as the specific X-ray and the drawing speed is 1 ° / min. . Whether the diffraction peak obtained by X-ray diffraction corresponds to the reaction phase capable of reacting with lithium or the like is compared with the X-ray diffraction chart before and after the electrochemical reaction with lithium or the like. Can be easily determined. For example, if the position of the diffraction peak changes before and after an electrochemical reaction with lithium or the like, it corresponds to a reaction phase capable of reacting with lithium or the like.

  In particular, the half-value width of a diffraction peak obtained by X-ray diffraction of the negative electrode active material (a peak seen when the diffraction angle 2θ is between 41 ° and 45 °) is CuKα ray as the specific X-ray, and the insertion speed is When it is 1 ° / min, it is 1.0 ° or more. This is because lithium and the like can be occluded and released more smoothly, and the reactivity with the electrolyte can be further reduced.

  Here, the definition of the half width of the diffraction peak to which the above-described range (1.0 ° or more) is applied is as follows. As described above, a broad diffraction peak of the reaction phase appears between 2θ = 20 ° and 50 °, and there are two distinct peaks in the diffraction peak at around 30 ° and around 43 °. To do. At this time, the diffraction peak to which the above-described range (1.0 ° or more) is applied is a peak around 43 ° (41 ° to 45 °). In order to obtain the half width of this peak, after fitting a peak of 41 ° to 45 ° with reference to a broad peak baseline seen between 20 ° and 50 °, the peak intensity becomes half value. What is necessary is just to calculate the peak width in height. The peak at 41 ° to 45 ° does not disappear even after the electrode reaction, and the peak intensity does not change even after the electrode reaction. Therefore, the above half-value width is calculated with good reproducibility from the X-ray diffraction result. In addition, it is possible to stably check whether the half width satisfies the above-described range condition (1.0 ° or more).

  Note that the negative electrode active material may have a phase containing a simple substance or a part of each constituent element in addition to the above-described low crystallinity or amorphous phase.

  Furthermore, in the negative electrode active material, it is preferable that at least a part of carbon that is a constituent element is bonded to a metal element or a metalloid element that is another constituent element. The decrease in cycle characteristics is thought to be due to aggregation or crystallization of tin or the like, but this aggregation or crystallization is suppressed when carbon is combined with other elements.

  Examples of the measurement method for examining the bonding state of elements include X-ray photoelectron spectroscopy (XPS). In this XPS, soft X-rays (Al-Kα rays or Mg-Kα rays are used in a commercially available apparatus) are irradiated on a sample, and the kinetic energy of photoelectrons jumping out from the surface is measured. This is a method for examining the composition and bonding state of elements in the nm region.

  The binding energy of the core orbital electrons of the element changes in a first approximation in correlation with the charge density on the element. For example, when the charge density of the carbon element decreases due to an interaction with an element present in the vicinity, the outer electrons such as 2p electrons decrease, so the 1s electron of the carbon element exerts a strong binding force from the shell. Will receive. That is, the binding energy increases as the charge density of the element decreases. In XPS, when the binding energy increases, the peak shifts to a high energy region.

  In XPS, the peak of the carbon 1s orbital (C1s) appears at 284.5 eV in an energy calibrated apparatus so that the peak of the gold atom 4f orbital (Au4f) is obtained at 84.0 eV if it is graphite. . Moreover, if it is surface contamination carbon, it will appear at 284.8 eV. In contrast, when the charge density of the carbon element is high, for example, when it is bonded to an element more positive than carbon, the C1s peak appears in a region lower than 284.5 eV. That is, when at least a part of carbon contained in the negative electrode active material is bonded to another constituent element such as a metal element or a metalloid element, the peak of the synthetic wave of C1s obtained for the negative electrode active material is 284. Appears in the region lower than 5 eV.

  In the XPS measurement of the negative electrode active material, when the surface is covered with surface-contaminated carbon, it is preferable to lightly sputter the surface with an argon ion gun attached to the XPS apparatus. Moreover, when the negative electrode active material to be measured is present in the negative electrode of a secondary battery described later, the secondary battery is disassembled and the negative electrode is taken out and then washed with a volatile solvent such as dimethyl carbonate. This is for removing the low-volatile solvent and the electrolyte salt present on the surface of the negative electrode. These samplings are desirably performed under an inert atmosphere.

  In XPS measurement, for example, the C1s peak is used to correct the energy axis of the spectrum. Usually, since surface-contaminated carbon exists on the surface of the substance, the C1s peak of the surface-contaminated carbon is set to 284.8 eV, which is used as an energy standard. In XPS measurement, the waveform of the C1s peak is obtained as a form including the surface contamination carbon peak and the carbon peak in the negative electrode active material. For example, by analyzing using commercially available software, The surface contamination carbon peak and the carbon peak in the negative electrode active material are separated. In the waveform analysis, the position of the main peak existing on the lowest bound energy side is used as the energy reference (284.8 eV).

  This negative electrode active material is manufactured by, for example, mixing raw materials of each constituent element, melting them in an electric furnace, a high frequency induction furnace, an arc melting furnace, and the like, and then solidifying them. In addition, the negative electrode active material is also produced by a method utilizing mechanochemical reaction such as various atomizing methods such as gas atomizing or water atomizing, various roll methods, mechanical alloying method or mechanical milling method. Especially, it is preferable to manufacture by the method using a mechanochemical reaction. This is because the negative electrode active material has a low crystallinity or an amorphous structure. As this method, for example, a planetary ball mill device can be used.

  The raw material may be a mixture of individual constituent elements, but an alloy is preferably used for some constituent elements other than carbon. By adding carbon to such an alloy and synthesizing it by a method using the mechanical alloying method, it is possible to have a low crystallization or amorphous structure and shorten the reaction time. Because it can. The raw material may be in the form of a powder or a lump.

  Carbon used as a raw material may be any of carbon materials such as non-graphitizable carbon, graphitizable carbon, graphite, pyrolytic carbon, coke, glassy carbon, organic polymer compound fired body, activated carbon or carbon black. 1 type (s) or 2 or more types can be used. Among these, coke includes 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 configuration of the first secondary battery. The secondary battery described here is, for example, a lithium ion secondary battery in which the capacity of the negative electrode is represented by the capacity associated with insertion and extraction of lithium as an electrode reactant.

  This secondary battery has a wound electrode body 20 in which a belt-like positive electrode 21 and a belt-like negative electrode 22 are stacked via a separator 23 and wound inside a substantially hollow cylindrical battery can 11. ing. The battery structure including the battery can 11 is called a cylindrical type. The battery can 11 is made of, for example, iron plated with nickel, and one end and the other end thereof are closed and opened, respectively. A liquid electrolyte (so-called electrolytic solution) is injected into the battery can 11 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.

  The battery lid 11 is attached to the open end of the battery can 11 by caulking a gasket 17 through a gasket 17 and a safety valve mechanism 15 and a heat sensitive resistance element (Positive Temperature Coefficient; PTC element) 16 provided inside the battery lid 14. The inside of the battery can 11 is sealed. The battery lid 14 is made of the same material as the battery can 11, for example. The safety valve mechanism 15 is electrically connected to the battery lid 14 via the heat sensitive resistance element 16, and when the internal pressure of the secondary battery exceeds a certain level due to an internal short circuit or external heating, the disk plate 15A is reversed and 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 thereof.

  The wound electrode body 20 is wound around a center pin 24, for example. 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 (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 welding to the safety valve mechanism 15, and the negative electrode lead 26 is electrically connected to the battery can 11 by welding.

  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 one surface or both surfaces of a positive electrode current collector 21A having a pair of 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 includes, 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 or 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, mainly Li _x MO ₂ (wherein M represents one or more transition metals, x is different depending on the charge / discharge state of the secondary battery, and is generally 0.05 ≦ x ≦ 1.1). Examples thereof include lithium composite oxides. As the transition metal M constituting the lithium composite oxide, cobalt, nickel or manganese (Mn) is preferable. Specific examples of such a lithium composite oxide include LiCoO ₂ , LiNiO ₂ , Li _x Ni _y Co _1-y O ₂ (where x and y vary depending on the charge / discharge state of the secondary battery, and generally 0 < x <1 <y <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 one or both surfaces of a negative electrode current collector 22A having a pair of surfaces, similarly to the positive electrode 21. The negative electrode 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. Thus, by including the negative electrode active material according to the present embodiment, in this secondary battery, high capacity is obtained, and cycle characteristics and initial charge / discharge efficiency are improved. In addition to the negative electrode active material according to the present embodiment, the negative electrode active material layer 22B may also include other negative electrode active materials and 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 / discharge cycle characteristics and also functions as a conductive agent. Examples of the carbon material include those similar to those used when producing the negative electrode active material.

  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 if the amount of carbon material is small, the conductivity of the negative electrode 22 may decrease, and if it is large, the capacity may decrease.

  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 both electrodes. The separator 23 is made of, for example, a porous film made of a synthetic resin such as polytetrafluoroethylene, polypropylene, or polyethylene, or a porous film made of ceramic, and two or more kinds of these porous films are laminated. The structure may be different.

  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, since the decomposition reaction of the solvent in the negative electrode 22 is suppressed, cycle characteristics are improved. Specific examples of such carbonic acid ester derivatives include 4-fluoro-1,3-dioxolan-2-one represented by Chemical Formula 1, 4-difluoro-1,3-dioxolane represented by Chemical Formula 2 -2-one, 4,5-difluoro-1,3-dioxolan-2-one represented by Chemical formula 3, 4-difluoro-5-fluoro-1,3-dioxolan-2-one represented by Chemical formula 4 4-chloro-1,3-dioxolan-2-one represented by Chemical Formula 5, 4,5-dichloro-1,3-dioxolan-2-one represented by Chemical Formula 6 and 4 represented by Chemical Formula 7 -Bromo-1,3-dioxolan-2-one, 4-iodo-1,3-dioxolan-2-one represented by Chemical Formula 8, 4-fluoromethyl-1,3-dioxolane- represented by Chemical Formula 9 2-one or 4-trifluoro represented by the formula 10 Chill-1,3-dioxolan-2-one, and the like. Of these, 4-fluoro-1,3-dioxolan-2-one is preferable. This is because a higher effect can be obtained.

The solvent may be composed only of a carbonic acid ester derivative, but is preferably mixed 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 ionic conductivity is increased. The content of the carbonate ester derivative is preferably in the range of 0.1% by mass or more and 80% by mass or less with respect to the entire solvent. This is because if the content is small, the effect of suppressing the decomposition reaction of the solvent in the negative electrode 22 may not be sufficient, and if the content is large, the viscosity may increase and the ionic conductivity may decrease.

Examples of the electrolyte salt include lithium salts, and one kind may be used alone, or two or more kinds may be mixed and used. 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.

  This secondary battery is manufactured as follows, for example.

  First, for example, after preparing a positive electrode mixture by mixing a positive electrode active material and, if necessary, a conductive agent and a binder, the positive electrode mixture slurry is dispersed in a mixed solvent such as N-methyl-2-pyrrolidone. And Subsequently, the positive electrode mixture slurry is applied to the positive electrode current collector 21A and dried, and then compressed to form the positive electrode active material layer 21B, thereby producing the positive electrode 21. Thereafter, the positive electrode lead 25 is welded to the positive electrode 21.

  Further, 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 mixed solvent such as N-methyl-2-pyrrolidone To make a negative electrode mixture slurry. Subsequently, the negative electrode mixture slurry is applied to the negative electrode current collector 22A, dried, and then compressed to form the negative electrode active material layer 22B, whereby the negative electrode 22 is manufactured. Thereafter, the negative electrode lead 26 is welded to the negative electrode 22.

  Subsequently, the positive electrode 21 and the negative electrode 22 are wound through the separator 23, 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. 21 and the negative electrode 22 are accommodated in the battery can 11 while being sandwiched between the pair of insulating plates 12 and 13. Subsequently, after injecting the electrolyte into the battery can 11, 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 the 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 released from the positive electrode 21 and inserted in the negative electrode 22 through the electrolyte. When discharging is performed, for example, lithium ions are released from the negative electrode 22 and inserted into the positive electrode 21 through the electrolyte.

  As described above, according to the negative electrode active material according to the present embodiment, there is a reaction phase capable of reacting with the electrode reactant, and a diffraction peak (diffraction angle 2θ of 41 ° or more and 45 ° or less) obtained by X-ray diffraction. The full width at half maximum of the peak (between) is 1.0 ° or more. In this case, since tin is included as the first constituent element, a high capacity can be obtained. In addition, iron and cobalt are included as the second and third constituent elements, and the ratio of the total of iron and cobalt to the total of tin, iron, and cobalt is 26.4% by mass to 48.5% by mass, Since the ratio of cobalt to the total of cobalt and cobalt is 9.9 mass% or more and 79.5 mass% or less, cycle characteristics are improved. Furthermore, since carbon is contained as the fourth constituent element and the content thereof is set to 11.9 mass% or more and 29.7 mass% or less, cycle characteristics are further improved. Thereby, compared with the case where content of iron is less than content of cobalt, cycling characteristics improve significantly, maintaining a high capacity | capacitance. Therefore, according to the secondary battery using the negative electrode active material described above, a high capacity can be obtained and excellent cycle characteristics can be obtained.

  Furthermore, the negative electrode active material contains at least one member selected from the group consisting of aluminum, titanium, vanadium, chromium, niobium and tantalum as the fifth constituent element, or nickel, copper, zinc, gallium and the sixth constituent element By including at least one member selected from the group consisting of indium, cycle characteristics can be further improved. In this case, a higher effect can be obtained by including both constituent elements. In particular, when both constituent elements are contained, the content of the fifth constituent element is set to 0.1 mass% or more and 9.9 mass% or less, and the content of the sixth constituent element is set to 0.5 mass% or more and 14 mass% or less. If it is .9% by mass or less, a higher effect can be obtained.

  Furthermore, if the negative electrode active material contains silver as the seventh constituent element, the cycle characteristics can be further improved. In particular, when the content is 0.1% by mass or more and 9.9% by mass or less, a higher effect can be obtained.

  In addition, if the negative electrode active material contains all of the fifth to seventh constituent elements, the cycle characteristics can be further improved.

(Secondary secondary battery)
FIG. 3 illustrates an exploded perspective 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. This secondary battery is, for example, a lithium ion secondary battery, like the first secondary battery, and the battery structure including the film-shaped exterior member 40 is called a laminate film type.

  For example, the positive electrode lead 31 and the negative electrode lead 32 are each led out in the same direction from the inside of the exterior member 40 toward the outside. The positive electrode lead 31 and the negative electrode lead 32 are made of, for example, 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. The exterior member 40 is disposed, for example, 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 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.

  In addition, the exterior member 40 may be configured by 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 configuration along line IV-IV of the spirally wound electrode body 30 shown in FIG. The wound electrode body 30 is formed by winding a positive electrode 33 and a negative electrode 34 after being laminated via a separator 35 and an electrolyte layer 36, and an outermost peripheral portion thereof 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 configuration 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 is the same as that of the positive electrode current collector 21A and the positive electrode active material layer in the first secondary battery described above. This is the same as 21B, the negative electrode current collector 22A, the negative electrode active material layer 22B, and the separator 23.

  The electrolyte layer 36 includes an electrolytic solution and a polymer compound that holds the electrolytic solution, and has a so-called gel shape. The gel electrolyte is preferable because high ion conductivity is obtained and leakage of the secondary battery is prevented. The configuration of the electrolytic solution (that is, the solvent and the electrolyte salt) is the same as that of the electrolytic solution in the first secondary battery described above. Examples of the polymer compound include a fluorine-based polymer compound such as polyvinylidene fluoride or a copolymer of vinylidene fluoride and hexafluoropropylene, an ether-based polymer compound such as polyethylene oxide or a crosslinked product containing polyethylene oxide, And polyacrylonitrile. In particular, from the viewpoint of redox stability, a fluorine-based polymer compound is desirable.

  In place of the electrolyte layer 36 in which the electrolytic solution is held by the polymer compound, the electrolytic solution may be used as it is. In this case, the electrolytic solution impregnates the separator 35.

  The secondary battery including the gel electrolyte layer 36 is manufactured, for example, as follows.

  First, after preparing a precursor solution containing a solvent, an electrolyte salt, a polymer compound, and a mixed solvent, the precursor solution is applied to each of the positive electrode 33 and the negative electrode 34 to volatilize the mixed solvent, whereby the electrolyte layer 36 is formed. Subsequently, the positive electrode lead 31 is attached to the end portion of the positive electrode current collector 33A by welding, and the negative electrode lead 32 is attached to the end portion of the negative electrode current collector 34A by welding. Subsequently, 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 laminate, and the laminate is wound in the longitudinal direction, and then a protective tape 37 is attached to the outermost peripheral portion. The wound electrode body 30 is formed by bonding. Finally, for example, the wound electrode body 30 is sandwiched between the exterior members 40, and the outer edge portions of the exterior members 40 are sealed and sealed by thermal fusion or the like. At this 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.

  Note that the secondary battery including the gel electrolyte layer 36 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, respectively, the positive electrode 33 and the negative electrode 34 are stacked and wound via the separator 35, and the outermost peripheral portion thereof. By adhering the protective tape 37, a wound body that is a precursor of the wound electrode body 30 is formed. Subsequently, the wound body is sandwiched between the exterior members 40, and the outer peripheral edge portion excluding one side is heat-sealed to form a bag shape and stored in the interior of the exterior member 40. Subsequently, an electrolyte composition including a solvent, an electrolyte salt, a monomer that is a raw material of the polymer compound, a polymerization initiator, and other materials such as a polymerization inhibitor as necessary is prepared, and the exterior member Inject into 40. Finally, the opening of the exterior member 40 is heat-sealed and sealed in a vacuum atmosphere, and then heat is applied to polymerize the monomer to form a polymer compound, thereby forming the gel electrolyte layer 36. Thereby, the secondary battery shown in FIGS. 3 and 4 is completed.

  This secondary battery operates in the same manner as the first secondary battery, and can obtain the same effect.

(Third secondary battery)
FIG. 5 shows a cross-sectional configuration of the third secondary battery, and this secondary battery is, for example, a lithium ion secondary battery as in the case of the first 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 arranged so as to face each other with an electrolyte layer 55 interposed therebetween. It is housed in the member 56. The configuration of the exterior member 56 is the same as that of the exterior member 40 in the second secondary battery 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 is arranged so that the negative electrode active material layer 54B side faces the positive electrode active material layer 52B. 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 the same as the positive electrode current collector 21A, the positive electrode active material layer 21B, and the negative electrode in the first secondary battery described above. This is the same as the current collector 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, any inorganic solid electrolyte or 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. As the polymer compound of the polymer solid electrolyte, for example, an ether polymer compound such as polyethylene oxide or a crosslinked product containing polyethylene oxide, an ester polymer compound such as polymethacrylate, an acrylate polymer compound, etc. Alternatively, they can be mixed or copolymerized.

  The polymer solid electrolyte is 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 may be formed by applying heat to polymerize the monomer to obtain a polymer compound.

  The inorganic solid electrolyte may be 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 or CVD (Chemical Vapor Deposition), or a sol-gel method. Formed by phase method.

  This secondary battery operates in the same manner as the first or second secondary battery, and can obtain the same effect.

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

(Examples 1-1 to 1-7)
First, a negative electrode active material was prepared. That is, prepare tin powder, iron powder, cobalt powder and carbon powder as raw materials, alloy tin powder, iron powder and cobalt powder to make tin / iron / cobalt alloy powder, then add carbon powder to it Dry mixed. At this time, the ratio of raw materials (raw material ratio: mass%) was changed as shown in Table 1. Specifically, the ratio of the total of iron and cobalt to the total of tin, iron and cobalt (hereinafter referred to as (Fe + Co) / (Sn + Fe + Co) ratio) is 32% by mass, iron and cobalt The ratio of cobalt to the total (hereinafter referred to as Co / (Fe + Co) ratio) was fixed at 50% by mass, and the carbon raw material ratio was changed within the range of 12% by mass to 30% by mass. Subsequently, 20 g of the above mixture was set in a reaction vessel of a planetary ball mill apparatus manufactured by Ito Seisakusho together with about 400 g of steel balls having a diameter of 9 mm. Subsequently, after replacing the inside of the reaction vessel with an argon (Ar) atmosphere, the operation time of 10 minutes at a rotational speed of 250 revolutions per minute and the pause for 10 minutes are increased until the total operation time (reaction time) reaches 30 hours. Repeated. Finally, after the reaction vessel was cooled to room temperature, the synthesized negative electrode active material powder was taken out, and coarse powder was removed through a 280 mesh sieve.

  The composition of the obtained negative electrode active material was analyzed. At this time, the carbon content was measured by a carbon / sulfur analyzer, and the tin, iron and cobalt contents were measured by ICP (Inductively Coupled Plasma) emission analysis. The analysis values (% by mass) are shown in Table 1. The raw material ratios and analysis values shown in Table 1 are values obtained by rounding off the numerical values with two digits after the decimal point, and the same values are shown in the following series of examples and comparative examples.

  When the obtained negative electrode active material was subjected to X-ray diffraction, a diffraction peak was observed between 2θ = 20 ° and 50 °. Of these, the half width of the diffraction peak observed between 2θ = 41 ° and 45 ° is shown in Table 1. Furthermore, when the element bonding state in the negative electrode active material was measured by XPS, a peak P1 was obtained as shown in FIG. When this peak P1 was analyzed, a peak P2 of surface contamination carbon and a peak P3 of C1s in the negative electrode active material on the lower energy side were obtained. In any of Examples 1-1 to 1-7, the peak P3 was obtained in a region lower than 284.5 eV. That is, it was confirmed that carbon in the negative electrode active material was bonded to other elements.

Next, a coin-type secondary battery shown in FIG. 7 was produced using the above-described negative electrode active material powder. In this secondary battery, a test electrode 61 using a negative electrode active material is accommodated in a positive electrode can 62, a counter electrode 63 is attached to a negative electrode can 64, and they are stacked via a separator 65 impregnated with an electrolytic solution. It is caulked through the gasket 66. When producing the test electrode 61, the negative electrode active material powder 70 parts by mass, the conductive agent and other negative electrode active material graphite 20 parts by mass, the conductive agent acetylene black 1 part by mass, and the binder After mixing 4 parts by mass of a certain polyvinylidene fluoride and dispersing in an appropriate solvent to form a slurry, the slurry was applied to a copper foil current collector, and after drying, punched into a pellet having a diameter of 15.2 mm. As the counter electrode 63, a metal lithium plate punched to a diameter of 15.5 mm was used. As the electrolytic solution, a solution obtained by dissolving LiPF6 as an electrolyte salt in a mixed solvent in which ethylene carbonate (EC), propylene carbonate (PC), and dimethyl carbonate (DMC) were mixed was used. At this time, the composition of the mixed solvent was EC: PC: DMC = 30: 10: 60 by mass ratio, and the concentration of the electrolyte salt was 1 mol / dm ³ .

  The initial charge capacity (mAh / g) of this coin-type secondary battery was examined. The initial charge capacity is constant current charging at a constant current of 1 mA until the battery voltage reaches 0.2 mV, then constant voltage charging at a constant voltage of 0.2 mV until the current reaches 10 μA. From the above, the charge capacity per unit mass obtained by removing the mass of the copper foil current collector and the binder was determined. In addition, the charge here means a lithium insertion reaction into the negative electrode active material. The results are shown in Table 1 and FIG.

  Moreover, the cylindrical secondary battery shown in FIGS. 1 and 2 was produced using the above-described negative electrode active material powder. That is, a positive electrode active material made of nickel oxide, a ketjen black as a conductive agent, and a polyvinylidene fluoride as a binder are masses of nickel oxide: ketjen black: polyvinylidene fluoride = 94: 3: 3. The mixture was mixed at a ratio and dispersed in N-methyl-2-pyrrolidone as a mixed solvent to obtain a positive electrode mixture slurry. Subsequently, the positive electrode mixture slurry is uniformly applied to both surfaces of the positive electrode current collector 21A made of a strip-shaped aluminum foil, dried, and then compression-molded with a roll press to form the positive electrode active material layer 21B. A positive electrode 21 was produced. After that, the positive electrode lead 25 made of aluminum was attached to one end of the positive electrode current collector 21A.

  Moreover, after apply | coating and drying the negative mix slurry containing the negative electrode active material mentioned above uniformly on both surfaces of 22 A of negative electrode collectors which consist of strip | belt-shaped copper foil, the negative electrode active material layer was compression-molded with a roll press machine. The negative electrode 22 was produced by forming 22B. Thereafter, a negative electrode lead 26 made of nickel was attached to one end of the negative electrode current collector 22A.

  Subsequently, the separator 23 was prepared, and the negative electrode 22, the separator 23, the positive electrode 21, and the separator 23 were laminated in this order, and then the laminated body was wound many times in a spiral shape to produce the wound electrode body 20. . Subsequently, the wound electrode body 20 is sandwiched between the pair of insulating plates 12 and 13, the negative electrode lead 26 is welded to the battery can 11, and the positive electrode lead 25 is welded to the safety valve mechanism 15. The wound electrode body 20 was housed inside the battery can 11. Finally, the above-described electrolytic solution was injected into the battery can 11 by a decompression method, thereby completing a cylindrical secondary battery.

  The cycle characteristics of this cylindrical secondary battery were examined. In this case, first, constant current charging is performed until the battery voltage reaches 4.2 V at a constant current of 0.5 A, and then constant voltage charging is performed until the current reaches 10 mA at a constant voltage of 4.2 V. The first cycle charge / discharge was performed by discharging at a constant current of 25 A until the battery voltage reached 2.6 V. After the second cycle, constant current charging is performed until the battery voltage reaches 4.2 V at a constant current of 1.4 A, and then constant voltage charging is performed until the current reaches 10 mA at a constant voltage of 4.2 V. The battery was discharged at a constant current of 0 A until the battery voltage reached 2.6V. Thereafter, in order to examine the cycle characteristics, the ratio of the discharge capacity at the 300th cycle to the discharge capacity at the second cycle, that is, the capacity retention rate (%) = (discharge capacity at the 300th cycle / discharge capacity at the second cycle) × 100 was determined. The results are shown in Table 1 and FIG.

  As Comparative Example 1-1 with respect to Examples 1-1 to 1-7, except that carbon powder was not used as a raw material, the negative electrode active material and the other were the same as in Examples 1-1 to 1-7. A secondary battery was produced. Further, as Comparative Examples 1-2 to 1-5, except that the carbon raw material ratio was changed as shown in Table 1, other than that, the negative electrode active material was the same as in Examples 1-1 to 1-7 And the secondary battery was produced.

  For the negative electrode active materials of Comparative Examples 1-1 to 1-5, the half width of the diffraction peak observed between 2θ = 41 ° and 45 ° was measured. The results are shown in Table 1. Moreover, when the bonding state of the elements was measured by XPS, the peak P1 shown in FIG. 6 was obtained in Comparative Examples 1-2 to 1-5. When this peak P1 was analyzed, a peak P2 of surface contamination carbon and a peak P3 of C1s in the negative electrode active material were obtained in the same manner as in Examples 1-1 to 1-7. Obtained in a region lower than 0.5 eV. That is, it was confirmed that at least a part of carbon contained in the negative electrode active material was bonded to another element. On the other hand, in Comparative Example 1-1, a peak P4 was obtained as shown in FIG. When this peak P4 was analyzed, only the peak P2 of surface contamination carbon was obtained.

  Further, for the secondary batteries of Comparative Examples 1-1 to 1-5, the initial charge capacity and the cycle characteristics were examined in the same manner as in Examples 1-1 to 1-7. The results are shown in Table 1 and FIG.

  As can be seen from Table 1 and FIG. 8, in Examples 1-1 to 1-7 in which the content of carbon in the negative electrode active material is in the range of 11.9 mass% to 29.7 mass, the content is The capacity retention rate was dramatically improved as compared with Comparative Examples 1-1 to 1-5 which were out of the range, and the initial charge capacity was also improved. In this case, the capacity retention ratio and the initial charge capacity were higher when the carbon content was in the range of 14.9% by mass or more, and further 17.8% by mass or more. In particular, in Examples 1-1 to 1-7, the full width at half maximum was 1.00 ° or more.

  That is, if the carbon content is 11.9 mass% or more and 29.7 mass% or less, the capacity and cycle characteristics can be improved, and within the range of 14.9 mass% or more and 29.7 mass% or less, Furthermore, it has been found that it is more preferable if it is in the range of 17.8% by mass or more and 29.7% by mass or less.

(Examples 2-1 to 2-8)
A negative electrode active material and a secondary battery were produced in the same manner as in Examples 1-1 to 1-7, except that the raw material ratio of tin, iron, cobalt, and carbon was changed as shown in Table 2. . Specifically, the carbon raw material ratio is 18% by mass, the Co / (Fe + Co) ratio is constant at 50% by mass, and the (Fe + Co) / (Sn + Fe + Co) ratio is 26% by mass or more. It changed within the range of 48 mass% or less.

  In addition, as Comparative Examples 2-1 to 2-5 with respect to Examples 2-1 to 2-8, the (Fe + Co) / (Sn + Fe + Co) ratio was changed as shown in Table 2. Except for the above, anode active materials and secondary batteries were produced in the same manner as in Examples 2-1 to 2-8.

  For the anode active materials of Examples 2-1 to 2-8 and Comparative Examples 2-1 to 2-5, the compositions were analyzed in the same manner as in Examples 1-1 to 1-7. The results are shown in Table 2. Further, the negative electrode active material was subjected to X-ray diffraction, and the half width of a diffraction peak observed between 2θ = 41 ° and 45 ° was measured. The results are also shown in Table 2. Furthermore, when the peak obtained by measuring the negative electrode active material by XPS was analyzed, as in Examples 1-1 to 1-7, the peak P2 of surface contamination carbon and the peak P3 of C1s in the negative electrode active material The peak P3 was obtained in a region lower than 284.5 eV in all cases. That is, it was confirmed that at least a part of carbon contained in the negative electrode active material was bonded to another element. In addition, for the secondary battery, the initial charge capacity and the cycle characteristics were examined in the same manner as in Examples 1-1 to 1-7. The results are shown in Table 2 and FIG.

  As can be seen from Table 2 and FIG. 10, Examples 2-1 to 2- have a (Fe + Co) / (Sn + Fe + Co) ratio in the range of 26.4% by mass or more and 48.5% by mass or less. 8, the capacity retention rate was dramatically improved over Comparative Examples 2-1 to 2-3 in which the ratio was less than 26.4% by mass, and Comparative Examples 2-4 and 2 exceeding 48.5% by mass. The initial charge capacity was improved over -5. In this case, the capacity retention ratio was higher when the (Fe + Co) / (Sn + Fe + Co) ratio was 29.2% by mass or more. In particular, in Examples 2-1 to 2-8, the full width at half maximum was 1.00 ° or more.

  That is, when the (Fe + Co) / (Sn + Fe + Co) ratio is 26.4% by mass or more and 48.5% by mass or less, the capacity and cycle characteristics can be improved, and 29.2% by mass or more. It turned out that it is more preferable if it shall be in the range of 48.5 mass% or less.

(Examples 3-1 to 3-7)
A negative electrode active material and a secondary battery were produced in the same manner as in Examples 1-1 to 1-7, except that the raw material ratio of tin, iron, cobalt, and carbon was changed as shown in Table 3. . Specifically, the carbon material ratio is 18% by mass, the (Fe + Co) / (Sn + Fe + Co) ratio is constant at 32% by mass, and the Co / (Fe + Co) ratio is at least 10% by mass. It changed within the range of 80 mass% or less.

  In addition, as comparative examples 3-1 to 3-4 with respect to examples 3-1 to 3-7, except that the Co / (Fe + Co) ratio was changed as shown in Table 3, the other examples A negative electrode active material and a secondary battery were produced in the same manner as in 3-1 to 3-7.

  For the anode active materials of Examples 3-1 to 3-7 and Comparative Examples 3-1 to 3-4, the compositions were analyzed in the same manner as in Examples 1-1 to 1-7. The results are shown in Table 3. Further, the negative electrode active material was subjected to X-ray diffraction, and the half width of a diffraction peak observed between 2θ = 41 ° and 45 ° was measured. The results are also shown in Table 3. Furthermore, when the peak obtained by measuring the negative electrode active material by XPS was analyzed, as in Examples 1-1 to 1-7, the peak P2 of surface contamination carbon and the peak P3 of C1s in the negative electrode active material The peak P3 was obtained in a region lower than 284.5 eV in all cases. That is, it was confirmed that at least a part of carbon contained in the negative electrode active material was bonded to another element. In addition, for the secondary battery, the initial charge capacity and the cycle characteristics were examined in the same manner as in Examples 1-1 to 1-7. The results are shown in Table 3 and FIG.

  As can be seen from Table 3 and FIG. 11, in Examples 3-1 to 3-7 in which the Co / (Fe + Co) ratio is in the range of 9.9 mass% or more and 79.5 mass% or less, the ratio is The capacity retention rate is improved as compared with Comparative Examples 3-1 and 3-2 which are less than 9.9% by mass, and the initial charge capacity is improved as compared with Comparative Examples 3-3 and 3-4 which is more than 79.5% by mass. did. In this case, the capacity retention ratio was higher when the (Fe + Co) / (Sn + Fe + Co) ratio was 29.5% by mass or more. In particular, in Examples 3-1 to 3-7, the full width at half maximum was 1.00 ° or more.

  That is, if the (Fe + Co) / (Sn + Fe + Co) ratio is 9.9 mass% or more and 79.5 mass% or less, the capacity and cycle characteristics can be improved, and 29.5 mass% or more. It turned out that it is more preferable if it is in the range of 79.5% by mass or less.

(Examples 4-1 to 4-17)
As raw materials, tin powder, iron powder, cobalt powder and carbon powder, aluminum powder, titanium powder, vanadium powder, chromium powder, niobium powder and tantalum powder, nickel powder, copper powder, indium powder, zinc powder and gallium powder In the same manner as in Examples 1-1 to 1-7, except that the raw material ratio of tin, iron, cobalt, carbon, aluminum, etc. and nickel was changed as shown in Table 4, An active material and a secondary battery were produced. Specifically, the carbon raw material ratio is constant at 18% by mass, the (Fe + Co) / (Sn + Fe + Co) ratio at 32% by mass, and the Co / (Fe + Co) ratio at 50% by mass, respectively. The ratio of materials such as aluminum and nickel was appropriately changed. When producing a negative electrode active material, tin powder, iron powder and cobalt powder were alloyed to produce tin / iron / cobalt alloy powder, which was then mixed with carbon powder, aluminum powder and nickel powder. . The composition of the negative electrode active materials of Examples 4-1 to 4-17 was analyzed in the same manner as in Examples 1-1 to 1-7. At this time, the contents of aluminum and nickel and the like were measured by ICP emission analysis. The results are shown in Table 5. Further, the negative electrode active material was subjected to X-ray diffraction, and the half width of a diffraction peak observed between 2θ = 41 ° and 45 ° was measured. The results are shown in Table 6. Furthermore, when the peak obtained by measuring the negative electrode active material by XPS was analyzed, as in Examples 1-1 to 1-7, the peak P2 of surface contamination carbon and the peak P3 of C1s in the negative electrode active material The peak P3 was obtained in a region lower than 284.5 eV in all cases. That is, it was confirmed that at least a part of carbon contained in the negative electrode active material was bonded to another element. In addition, for the secondary battery, the initial charge capacity and the cycle characteristics were examined in the same manner as in Examples 1-1 to 1-7. The results are shown in Table 6, FIG. 12 and FIG.

  As can be seen from Tables 4 to 6, Examples 4-1 to 4-17 containing only aluminum or the like, or containing only nickel or the like, or both aluminum and nickel, etc. Compared to Example 1-3, the capacity retention rate was improved to the same level or higher while maintaining substantially the same initial charge capacity. In this case, as can be seen from Tables 4 to 6 and FIGS. 12 and 13, when attention is paid to the content of titanium representing aluminum and the content of copper representing nickel etc., titanium or copper The capacity retention rate was higher when both were included than when both were included. When both are included, the titanium content is in the range of 0.1% by mass to 9.9% by mass, and the copper content is in the range of 0.5% by mass to 14.9% by mass. The capacity maintenance rate became higher. In particular, in Examples 4-1 to 4-17, the full width at half maximum was 1.00 ° or more.

  That is, the negative electrode active material includes at least one member selected from the group consisting of aluminum, titanium, vanadium, chromium, niobium, and tantalum, or includes at least one member selected from the group consisting of nickel, copper, zinc, gallium, and indium. It has been found that the cycle characteristics can be further improved by including both of them. Moreover, the case where both are included is more preferable. In that case, the content of aluminum or the like is 0.1% by mass or more and 9.9% by mass or less, and the content of nickel or the like is 0.5% by mass or more and 14.9% by mass. It has been found that it is more preferable to set it to not more than%.

(Examples 5-1 to 5-9)
Except that tin powder, iron powder, cobalt powder and carbon powder, and silver powder were prepared as raw materials, and the raw material ratio was changed as shown in Table 7, the other examples were 1-1-1 A negative electrode active material and a secondary battery were produced in the same manner as in 1-7. Specifically, the carbon raw material ratio is constant at 18% by mass, the (Fe + Co) / (Sn + Fe + Co) ratio at 32% by mass, and Co / (Fe + Co) at 50% by mass, respectively. The raw material ratio was changed within the range of 0.1 mass% or more and 15 mass% or less. When producing the negative electrode active material, tin powder, iron powder and cobalt powder were alloyed to produce tin / iron / cobalt alloy powder, and then carbon powder and silver powder were mixed therewith. The composition of the negative electrode active materials of Examples 5-1 to 5-9 was analyzed in the same manner as in Examples 1-1 to 1-7. At this time, the silver content was measured by ICP emission analysis. The results are shown in Table 7. Further, the negative electrode active material was subjected to X-ray diffraction, and the half width of a diffraction peak observed between 2θ = 41 ° and 45 ° was measured. The results are also shown in Table 7. Furthermore, when the peak obtained by measuring the negative electrode active material by XPS was analyzed, as in Examples 1-1 to 1-7, the peak P2 of surface contamination carbon and the peak P3 of C1s in the negative electrode active material The peak P3 was obtained in a region lower than 284.5 eV in all cases. That is, it was confirmed that at least a part of carbon contained in the negative electrode active material was bonded to another element. In addition, for the secondary battery, the initial charge capacity and the cycle characteristics were examined in the same manner as in Examples 1-1 to 1-7. The results are shown in Table 7 and FIG.

  As can be seen from Table 7 and FIG. 14, in Examples 5-1 to 5-9 containing silver, the capacity retention rate was maintained while maintaining substantially the same initial charge capacity as compared to Example 1-3 not containing silver. Improved. In this case, when the silver content is in the range of 0.1 mass% to 9.9 mass%, and further in the range of 0.9 mass% to 9.9 mass%, the capacity retention rate is more It became high. In particular, in Examples 5-1 to 5-9, the full width at half maximum was 1.00 ° or more.

  That is, if silver is contained in the negative electrode active material, the cycle characteristics can be further improved, and the content thereof is in the range of 0.1 mass% or more and 9.9 mass% or less, and further 0.9 mass. It was found that it was more preferable if it was in the range of not less than% and not more than 9.9% by mass.

(Examples 6-1 to 6-10)
Raw materials include tin powder, iron powder, cobalt powder and carbon powder, silver powder, aluminum powder, titanium powder, vanadium powder, chromium powder, niobium powder and tantalum powder, nickel powder, copper powder, indium powder and zinc powder. Example 1-1 to 1-1 except that the raw material ratio of tin, iron, cobalt, carbon, silver, aluminum, etc. and nickel was changed as shown in Table 8 In the same manner as in Example 7, a negative electrode active material and a secondary battery were produced. Specifically, the carbon material ratio is 18% by mass, the silver material ratio is 1% by mass, the (Fe + Co) / (Sn + Fe + Co) ratio is 32% by mass, and the Co / (Fe + Co) ratio. Was made constant at 50% by mass, and the ratio of raw materials such as aluminum and nickel was appropriately changed. When producing the negative electrode active material, tin powder, iron powder and cobalt powder are alloyed to produce tin / iron / cobalt alloy powder, and then carbon powder, silver powder, aluminum powder, nickel powder, etc. Were mixed. The compositions of the negative electrode active materials of Examples 6-1 to 6-10 were analyzed in the same manner as in Examples 1-1 to 1-7. The results are shown in Table 9. Further, the negative electrode active material was subjected to X-ray diffraction, and the half width of a diffraction peak observed between 2θ = 41 ° and 45 ° was measured. The results are shown in Table 10. Furthermore, when the peak obtained by measuring the negative electrode active material by XPS was analyzed, as in Examples 1-1 to 1-7, the peak P2 of surface contamination carbon and the peak P3 of C1s in the negative electrode active material The peak P3 was obtained in a region lower than 284.5 eV in all cases. That is, it was confirmed that at least a part of carbon contained in the negative electrode active material was bonded to another element. In addition, for the secondary battery, the initial charge capacity and the cycle characteristics were examined in the same manner as in Examples 1-1 to 1-7. The results are shown in Table 10.

  As can be seen from Tables 8 to 10, in Examples 6-1 to 6-10 containing silver, aluminum, etc. and nickel, etc., Example 1-3 not containing them, or Example 5-3 containing only silver Compared to, the capacity maintenance rate improved while maintaining almost the same initial charge capacity. In particular, in Examples 6-1 to 6-10, the full width at half maximum was 1.00 ° or more.

  That is, the negative electrode active material includes at least one selected from the group consisting of silver, aluminum, titanium, vanadium, chromium, niobium, and tantalum, and at least one selected from the group consisting of nickel, copper, zinc, gallium, and indium. It was found that the cycle characteristics can be further improved by including the above.

(Examples 7-1 to 7-5)
The negative electrode active material was the same as in Example 1-3, except that the reaction time for synthesizing the negative electrode active material was changed as shown in Table 11 to change the crystallinity (half-value width). And the secondary battery was produced. Specifically, the carbon raw material ratio is constant at 18% by mass, the (Fe + Co) / (Sn + Fe + Co) ratio at 32% by mass, and the Co / (Fe + Co) ratio at 50% by mass, respectively. The half width was set to 1.00 ° or more.

  In addition, as Comparative Examples 4-1 and 4-2 with respect to Examples 7-1 to 7-5, except that the reaction time and the half-value width were changed as shown in Table 11, the others were Example 1-3. In the same manner, a negative electrode active material and a secondary battery were produced.

  For the negative electrode active materials of Examples 7-1 to 7-5 and Comparative Examples 4-1 and 4-2, X-ray diffraction was performed on the negative electrode active materials in the same manner as in Examples 1-1 to 1-7, and 2θ = The half width of the diffraction peak observed between 41 ° and 45 ° was measured. The results are shown in Table 11. Further, when the peak obtained by measuring the negative electrode active material by XPS was analyzed, as in Examples 1-1 to 1-7, the surface contamination carbon peak P2 and the C1s peak P3 in the negative electrode active material The peak P3 was obtained in a region lower than 284.5 eV in all cases. That is, it was confirmed that at least a part of carbon contained in the negative electrode active material was bonded to another element. In addition, for the secondary battery, the initial charge capacity and the cycle characteristics were examined in the same manner as in Examples 1-1 to 1-7. The results are shown in Table 11 and FIG.

  As can be seen from Table 11 and FIG. 15, in Examples 7-1 to 7-5 in which the half width is 1.00 ° or more, Comparative Examples 5-1 and 5 in which the half width is less than 1.00 °%. The capacity maintenance rate and the initial charge capacity improved dramatically compared to -2.

  That is, it was found that the capacity and cycle characteristics can be improved if the half width is 1.0 ° or more.

  From these, as is clear from the results shown in Tables 1 to 11, FIG. 8, and FIGS. 10 to 15, the negative electrode active material has a reaction phase capable of reacting with lithium and the like, and the negative electrode active material The half-value width of a diffraction peak obtained by X-ray diffraction (a peak seen when the diffraction angle 2θ is between 41 ° and 45 °) is 1.0 ° or more, and the negative electrode active material is tin and iron as constituent elements And cobalt and carbon at least, the carbon content is 11.9 mass% or more and 29.7 mass% or less, and the total ratio of iron and cobalt to the total of tin, iron and cobalt is 26.4 mass% When the ratio of cobalt to the total of iron and cobalt is 9.9 mass% or more and 79.5 mass% or less, the capacity and cycle characteristics are confirmed to be improved.

  The present invention has been described with reference to the embodiments and examples. However, the present invention is not limited to the embodiments described in the above embodiments and examples, and various modifications can be made. For example, in the above-described embodiments and examples, the lithium ion secondary battery in which the capacity of the negative electrode is represented by the capacity associated with insertion and extraction of lithium is described as the type of the secondary battery. is not. In the secondary battery of the present invention, the negative electrode material capable of occluding and releasing lithium has a smaller charge capacity than that of the positive electrode, so that the capacity of the negative electrode is less than the capacity associated with the insertion and removal of lithium. The present invention can be similarly applied to a secondary battery including a capacity accompanying precipitation and dissolution and represented by the sum of the capacities.

  Further, in the above-described embodiments and examples, a case where the battery structure is a cylindrical type, a laminate film type, a sheet type or a coin type, or a secondary battery whose element structure is a wound structure will be specifically described. However, the secondary battery of the present invention is a secondary battery having another battery structure such as a button type or a square type, or a secondary battery having another element structure such as a laminated structure in which a plurality of positive and negative electrodes are stacked. Can be applied similarly.

  In the above-described embodiments and examples, the case where lithium is used as the electrode reactant has been described. However, as long as it can react with the negative electrode active material, a long-period cycle such as sodium (Na) or potassium (K) is used. In the case of using other group 1 elements in the table, group 2 elements in the long-period periodic table such as magnesium or calcium (Ca), other light metals such as aluminum, or lithium or alloys thereof, this The invention can be applied and the same effect 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-described embodiments and examples, the carbon content in the negative electrode active material or the secondary battery of the present invention is described with respect to the appropriate range derived from the results of the examples. The possibility that the content is outside the above range is not completely denied. In other words, the appropriate range described above is a particularly preferable range for obtaining the effect of the present invention, and the content may be slightly deviated from the above range as long as the effect of the present invention is obtained. This is not limited to the above-described carbon content, but the half-value width of a diffraction peak obtained by X-ray diffraction (a peak seen when the diffraction angle 2θ is between 41 ° and 45 °), tin, iron, and cobalt. The same applies to the ratio of the total of iron and cobalt to the total of the above, the ratio of cobalt to the total of iron and cobalt, the content of aluminum, the content of nickel, the content of silver, and the like.

It is sectional drawing showing the structure of the 1st secondary battery which concerns on one embodiment of this invention. It is sectional drawing which expands and represents a part of winding electrode body shown in FIG. It is a disassembled perspective view showing the structure of the 2nd secondary battery which concerns on one embodiment of this invention. It is sectional drawing showing the structure along the IV-IV line of the wound electrode body shown in FIG. It is sectional drawing showing the structure of the 3rd secondary battery which concerns on one embodiment of this invention. It is a figure showing an example of the peak obtained by the X ray photoelectron spectroscopy about the negative electrode active material produced in the Example. It is sectional drawing which shows the structure of the coin-type secondary battery produced in the Example. It is a characteristic view showing the relationship between the carbon content in the negative electrode active material, the capacity retention rate, and the initial charge capacity. It is a figure showing an example of the peak obtained by the X ray photoelectron spectroscopy about the negative electrode active material produced by the comparative example. It is a characteristic view showing the relationship between the ratio of the sum total of iron and cobalt with respect to the sum total of tin, iron, and cobalt in a negative electrode active material, a capacity retention, and initial charge capacity. It is a characteristic view showing the relationship between the ratio of the cobalt with respect to the sum total of iron and cobalt in a negative electrode active material, a capacity | capacitance maintenance factor, and initial stage charge capacity. It is a characteristic view showing the relationship between the content of titanium in the negative electrode active material, the capacity retention rate, and the initial charge capacity. It is a characteristic view showing the relationship between the copper content in the negative electrode active material, the capacity retention rate, and the initial charge capacity. It is a characteristic view showing the relationship between the silver content in the negative electrode active material, the capacity retention rate, and the initial charge capacity. It is a characteristic view showing the relationship between the half value width of the diffraction peak obtained by X-ray diffraction, a capacity | capacitance maintenance factor, and initial charge capacity.

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, 66 ... Gasket, 20, 30 ... Winding 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 ... protection Tape, 40, 56 ... exterior member, 41 ... adhesion film, 50 ... electrode body, 61 ... test electrode, 62 ... positive electrode can, 63 ... counter electrode, 64 ... negative electrode can.

Claims (20)

As a constituent element, at least tin (Sn), iron (Fe), cobalt (Co), and carbon (C) are included,
The carbon content is 11.9 mass% or more and 29.7 mass% or less, and the ratio of the total of iron and cobalt to the total of tin, iron and cobalt is 26.4 mass% or more and 48.5 mass% or less. The ratio of cobalt to the total of iron and cobalt is 9.9 mass% or more and 79.5 mass% or less,
Having a reaction phase capable of reacting with the electrode reactant,
A negative electrode active material, wherein a half-value width of a diffraction peak obtained by X-ray diffraction (a peak observed when a diffraction angle 2θ is between 41 ° and 45 °) is 1.0 ° or more.   The negative electrode active material according to claim 1, wherein a 1s peak of carbon is obtained in a region lower than 284.5 eV by X-ray photoelectron analysis.   Furthermore, as a constituent element, at least one selected from the group consisting of aluminum (Al), titanium (Ti), vanadium (V), chromium (Cr), niobium (Nb) and tantalum (Ta) is included. The negative electrode active material according to claim 1.   The constituent element further includes at least one selected from the group consisting of nickel (Ni), copper (Cu), zinc (Zn), gallium (Ga) and indium (In). Negative electrode active material.   Furthermore, as a constituent element, at least one selected from the group consisting of aluminum, titanium, vanadium, chromium, niobium and tantalum and at least one selected from the group consisting of nickel, copper, zinc, gallium and indium are included. The negative electrode active material according to claim 1, wherein:   6. The negative electrode according to claim 5, wherein the content of at least one member selected from the group consisting of aluminum, titanium, vanadium, chromium, niobium and tantalum is 0.1% by mass or more and 9.9% by mass or less. Active material.   6. The negative electrode active material according to claim 5, wherein the content of at least one member selected from the group consisting of nickel, copper, zinc, gallium and indium is 0.5% by mass or more and 14.9% by mass or less. .   Furthermore, silver (Ag) is contained as a structural element, The negative electrode active material of Claim 1 characterized by the above-mentioned.   The negative electrode active material according to claim 8, wherein the silver content is 0.1 mass% or more and 9.9 mass% or less.   Furthermore, as a constituent element, at least one selected from the group consisting of aluminum, titanium, vanadium, chromium, niobium and tantalum, at least one selected from the group consisting of nickel, copper, zinc, gallium and indium, and silver The negative electrode active material according to claim 1, comprising: A secondary battery comprising an electrolyte together with a positive electrode and a negative electrode,
The negative electrode contains a negative electrode active material containing at least tin, iron, cobalt and carbon as constituent elements,
The carbon content in the negative electrode active material is 11.9% by mass or more and 29.7% by mass or less, and the ratio of the total of iron and cobalt to the total of tin, iron and cobalt is 26.4% by mass or more and 48%. 0.5% by mass or less, and the ratio of cobalt to the total of iron and cobalt is 9.9% by mass or more and 79.5% by mass or less.
The negative electrode active material has a reaction phase capable of reacting with an electrode reactant,
A secondary battery characterized in that a half-value width of a diffraction peak obtained by X-ray diffraction of the negative electrode active material (a peak seen when a diffraction angle 2θ is between 41 ° and 45 °) is 1.0 ° or more. .   The secondary battery according to claim 11, wherein a 1 s peak of carbon is obtained in a region lower than 284.5 eV by X-ray photoelectron analysis.   The secondary battery according to claim 11, wherein the negative electrode active material further includes at least one selected from the group consisting of aluminum, titanium, vanadium, chromium, niobium, and tantalum as a constituent element.   The secondary battery according to claim 11, wherein the negative electrode active material further includes at least one selected from the group consisting of nickel, copper, zinc, gallium, and indium as a constituent element.   The negative electrode active material further includes, as a constituent element, at least one selected from the group consisting of aluminum, titanium, vanadium, chromium, niobium, and tantalum, and at least one selected from the group consisting of nickel, copper, zinc, gallium, and indium. The secondary battery according to claim 11, comprising one type.   The content of at least one member selected from the group consisting of aluminum, titanium, vanadium, chromium, niobium, and tantalum in the negative electrode active material is 0.1% by mass or more and 9.9% by mass or less. Item 16. A secondary battery according to Item 15.   The content of at least one member selected from the group consisting of nickel, copper, zinc, gallium, and indium in the negative electrode active material is 0.5% by mass or more and 14.9% by mass or less. The secondary battery as described.   The secondary battery according to claim 11, wherein the negative electrode active material further contains silver as a constituent element.   The secondary battery according to claim 18, wherein a content of silver in the negative electrode active material is 0.1% by mass or more and 9.9% by mass or less.   The negative electrode active material further includes, as a constituent element, at least one selected from the group consisting of aluminum, titanium, vanadium, chromium, niobium, and tantalum, and at least one selected from the group consisting of nickel, copper, zinc, gallium, and indium. The secondary battery according to claim 11, comprising one type and silver.

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