JP2007128767A - Active material manufacturing method and battery - Google Patents

Abstract

An active material manufacturing method capable of easily and uniformly containing Li, and a battery using the active material obtained thereby.
A negative electrode active material layer 12B is formed by melting and solidifying a raw material containing a first element capable of forming an alloy with Li, a second element capable of forming an alloy with the first element, and Li. Contains synthesized active material. The first element is preferably Si or Sn, and the second element is preferably Co, Fe, Cu or Ni. The ratio of the first element to the second element is preferably in the range of 99: 1 to 50:50 in terms of the atomic ratio of the first element: second element, and the total of the first element and second element and Li The ratio is an atomic ratio of (first element + second element): Li, and is preferably in the range of 99: 1 to 50:50.
[Selection] Figure 1

Description

  The present invention relates to a method for producing an active material capable of electrochemically inserting and extracting lithium (Li), and a battery using the active material obtained thereby.

  In recent years, as mobile devices have higher performance and more functions, there is a demand for higher capacities of secondary batteries serving as power sources thereof. Secondary batteries that meet this requirement include lithium ion secondary batteries, but those currently in practical use use graphite for the negative electrode, so the battery capacity is saturated and it is difficult to achieve significant increases in capacity. . Therefore, it has been studied to use silicon (Si), tin (Sn), or an alloy thereof as an active material capable of achieving higher capacity (for example, see Patent Document 1).

However, when silicon or tin is used as the active material, a portion of the lithium occluded during the first charge is inactivated, and lithium that does not participate in charge / discharge remains in the active material, resulting in a decrease in capacity. Or the cycle characteristics deteriorate. Therefore, it has been studied to store lithium in the active material in advance. For example, Patent Document 2 describes a method for inserting lithium by attaching lithium powder around active material particles. Patent Document 3 describes a method of occluding lithium by immersing active material particles in a solvent in which lithium is dispersed.
JP 2000-311681 A JP-A-5-234621 Japanese Patent Laid-Open No. 5-54912

  However, these methods have problems that it is difficult to uniformly store lithium in the active material, and that these steps are complicated and time-consuming.

  The present invention has been made in view of such problems, and an object thereof is to provide a method for producing an active material capable of easily and uniformly containing lithium, and a battery using the active material obtained thereby. There is.

  The method for producing an active material of the present invention is to produce an active material containing lithium, a first element capable of forming an alloy with lithium, a second element capable of forming an alloy with the first element, and lithium. The process includes melting and solidifying a raw material containing the first element, the second element, and lithium.

  The battery of the present invention includes an electrolyte together with a positive electrode and a negative electrode, and the negative electrode includes a first element capable of forming an alloy with lithium, a second element capable of forming an alloy with the first element, lithium, and the like. The active material is obtained by melting and solidifying a raw material containing the first element, the second element and lithium.

  According to the method for producing an active material of the present invention, since the raw material containing the first element, the second element, and lithium is melted and solidified, lithium can be easily contained in the active material. The uniformity of lithium in the active material can be improved. Therefore, according to the battery of the present invention, since the active material obtained thereby is used, battery characteristics such as capacity and cycle characteristics can be improved.

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

  The manufacturing method of the active material which concerns on one embodiment of this invention manufactures the active material containing the 1st element which can form an alloy with lithium, the 2nd element which can form an alloy with the 1st element, and lithium To do. First, an active material is synthesized by melting and solidifying a raw material containing a first element, a second element, and lithium.

  Examples of the first element include magnesium (Mg), boron (B), arsenic (As), aluminum (Al), gallium (Ga), indium (In), silicon, germanium (Ge), tin, and lead. (Pb), antimony (Sb), bismuth (Bi), cadmium (Cd), hafnium (Hf), yttrium (Y), palladium (Pd) or platinum (Pt), including one of them alone However, two or more kinds may be included. Among them, the first element is preferably a group 14 metal element or metalloid element in the long-period periodic table, and particularly preferably silicon or tin. This is because a larger capacity can be obtained.

  Examples of the second element include cobalt (Co), iron (Fe), copper (Cu), nickel (Ni), silver (Ag), zinc (Zn), zirconium (Zr), manganese (Mn), titanium ( Ti) or niobium (Nb) may be mentioned, and one of them may be included alone, or two or more thereof may be included.

  The ratio of the first element to the second element is preferably in the range of 99: 1 to 50:50, in the range of 99: 1 to 70:30, in terms of the atomic ratio of the first element to the second element. It is more preferable if it is inside. By adding the second element, the expansion and contraction of the active material can be reduced, and alloying may be difficult due to the difference in melting point between the first element and lithium alone, but melting becomes easy. is there. However, when the amount of the second element is increased, the volume energy density is decreased.

  The ratio of the sum of the first element and the second element to lithium is preferably in the range of 99: 1 to 50:50 in terms of the number ratio of (first element + second element): lithium. . By adding lithium, the decrease in capacity due to the inactivation of lithium can be compensated. However, when the amount of lithium increases, metallic lithium is deposited on the surface of the active material, and charge / discharge efficiency decreases. Because it ends up. The composition of the produced active material can be analyzed by an energy dispersive X-ray fluorescence spectrometer (EDX) or EPMA (Electron Probe Microanalysis).

  The raw material may be a single constituent element or an alloy. A method for melting and solidifying the raw material is not particularly limited, but it is preferable to rapidly cool and solidify. This is because quenching reduces the size of crystallites of the active material, increases anisotropy, and disperses stress due to expansion. Examples of the rapid solidification method include a roll spinning method, a melt drag method, a direct casting and rolling method, a spinning solution spinning method, a spray forming method, a splat cooling method, a melt extraction method, a rotating electrode method, a gas atomizing method, and a single roll. Method or water atomization method. Among these, since lithium reacts violently with water, a gas atomizing method or a single roll method is preferable. The average size of the crystallites is preferably 5 nm or more and 100 nm or less, and more preferably 50 nm or less.

  In addition, after synthesize | combining an active material, it is preferable to carry out the pulverization classification as needed. The average particle size of the active material is preferably 500 nm or more and 20 μm or less in terms of median diameter, more preferably 10 μm or less, and even more preferably 5 μm or less. This is because if the particle size is too small, the surface area becomes large and the reactivity becomes large, and if the particle size is too large, the volume change due to expansion and contraction becomes large and the powder is easily pulverized.

  As described above, according to the method for manufacturing an active material according to the present embodiment, since the raw material containing the first element, the second element, and lithium is melted and solidified, lithium is easily added into the active material. While being able to contain, the uniformity of lithium in an active material can be improved.

  The active material obtained by this manufacturing method is used for a secondary battery as follows, for example.

(First secondary battery)
FIG. 1 shows the configuration of the first secondary battery. This secondary battery is a so-called coin-type battery, in which a negative electrode 12 accommodated in an exterior cup 11 and a positive electrode 14 accommodated in an exterior can 13 are stacked via a separator 15. The peripheral portions of the outer cup 11 and the outer can 13 are sealed by caulking through an insulating gasket 16. The exterior cup 11 and the exterior can 13 are made of, for example, a metal such as stainless steel or aluminum.

  The negative electrode 12 includes, for example, a negative electrode current collector 12A and a negative electrode active material layer 12B provided on the negative electrode current collector 12A.

  The anode current collector 12A is preferably made of a metal material containing at least one metal element that does not form an intermetallic compound with lithium. This is because when lithium and an intermetallic compound are formed, they expand and contract with charge / discharge, structural destruction occurs, current collection performance decreases, and the ability to support the negative electrode active material layer 12B decreases. Examples of the metal material composing the anode current collector 12A include a simple substance or an alloy of copper, nickel, titanium, iron, cobalt, or chromium.

  The surface of the negative electrode current collector 12A is preferably roughened, and the surface roughness Ra is preferably 0.1 μm or more. This is because the adhesion between the negative electrode current collector 12A and the negative electrode active material layer 12B can be improved. Further, the surface roughness Ra of the negative electrode current collector 12A is preferably 3.5 μm or less. This is because if the surface roughness is too large, the negative electrode current collector 12A may be easily cracked as the negative electrode active material layer 12B expands. The surface roughness Ra is the arithmetic average roughness Ra defined in JIS B0601, and the surface roughness Ra of the negative electrode current collector 12A in which at least the negative electrode active material layer 12B is provided is It may be within the above-mentioned range.

  The negative electrode active material layer 12B contains an active material obtained by the manufacturing method according to the present embodiment, and may contain a conductive material or a binder as necessary. The active material may be used alone or in combination of two or more having different compositions. The negative electrode active material layer 12B may also contain other active materials in addition to the active material obtained by the manufacturing method according to the present embodiment.

  The positive electrode 14 includes, for example, a positive electrode current collector 14A and a positive electrode active material layer 14B provided on the positive electrode current collector 14A so that the positive electrode active material layer 14B side faces the negative electrode active material layer 12B. Is arranged. The positive electrode current collector 14A is made of, for example, aluminum, nickel, stainless steel, or the like.

The positive electrode active material layer 14B includes, for example, any one or more of positive electrode materials capable of inserting and extracting lithium as a positive electrode active material, and a conductive material such as a carbon material and the like as necessary. A binder such as polyvinylidene fluoride may be included. As the positive electrode material capable of inserting and extracting lithium, for example, a lithium-containing metal composite oxide represented by the general formula Li _x MIO ₂ is preferable. This is because the lithium-containing metal composite oxide can generate a high voltage and has a high density, so that the capacity of the secondary battery can be further increased. MI is one or more kinds of transition metals, and for example, at least one of cobalt and nickel is preferable. x varies depending on the charge / discharge state of the battery and is usually a value in the range of 0.05 ≦ x ≦ 1.10. Specific examples of such a lithium-containing metal composite oxide include LiCoO _{2 and} LiNiO ₂ .

  The separator 15 separates the negative electrode 12 and the positive electrode 14 and allows lithium ions to pass through while preventing a short circuit of current due to contact between the two electrodes. The separator 15 is made of, for example, polyethylene or polypropylene.

  The separator 15 is impregnated with an electrolytic solution that is a liquid electrolyte. This electrolytic solution contains, for example, a solvent and an electrolyte salt dissolved in this solvent, and may contain an additive as necessary. Examples of the solvent include ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 1,3-dioxol-2-one, 4-vinyl-1,3-dioxolan-2-one, or a halogen atom. Non-aqueous solvents such as carbonic acid ester derivatives are included. Any one of the solvents may be used alone, or two or more of them may be mixed and used. Among them, it is preferable to use at least one of 1,3-dioxol-2-one and 4-vinyl-1,3-dioxolan-2-one because the decomposition reaction of the electrolytic solution can be suppressed. In addition, it is preferable to use a carbonic acid ester derivative having a halogen atom because the decomposition reaction of the electrolytic solution can be suppressed.

  The carbonic acid ester derivative having a halogen atom may be either a cyclic compound or a chain compound, but the cyclic compound is preferable because a higher effect can be obtained. Such cyclic compounds include 4-fluoro-1,3-dioxolan-2-one, 4-chloro-1,3-dioxolan-2-one, 4-bromo-1,3-dioxolan-2-one Or 4,5-difluoro-1,3-dioxolan-2-one, among which 4-fluoro-1,3-dioxolan-2-one is preferred. This is because a higher effect can be obtained.

Examples of the electrolyte salt include lithium salts such as LiPF ₆ , LiCF ₃ SO _{3, and} LiClO ₄ . Any one electrolyte salt may be used alone, or two or more electrolyte salts may be mixed and used.

  This secondary battery can be manufactured, for example, as follows.

  First, for example, an active material obtained by the manufacturing method according to the present embodiment and a conductive material or a binder as necessary are prepared to prepare a negative electrode mixture, which is dispersed in a mixed solvent and mixed with the negative electrode mixture. An agent slurry is prepared. Next, this negative electrode mixture slurry is applied to the negative electrode current collector 12A, dried, and then subjected to pressure molding to form the negative electrode active material layer 12B, thereby producing the negative electrode 12.

  In addition, for example, a positive electrode active material and, if necessary, a conductive material and a binder are mixed to prepare a positive electrode mixture, which is dispersed in a mixed solvent to prepare a positive electrode mixture slurry. Next, the positive electrode mixture slurry is applied to the positive electrode current collector 14A, dried and compressed to form the positive electrode active material layer 14B, and the positive electrode 14 is manufactured. Subsequently, the negative electrode 12, the separator 15 impregnated with the electrolytic solution, and the positive electrode 14 are stacked, put into the outer cup 11 and the outer can 13, and sealed by caulking them. Thereby, the secondary battery shown in FIG. 1 is obtained.

  In the secondary battery, when charged, for example, lithium ions are released from the positive electrode 14 and inserted in the negative electrode 12 through the electrolytic solution. When the discharge is performed, for example, lithium ions are released from the negative electrode 12 and inserted in the positive electrode 14 through the electrolytic solution. At that time, even if a part of the lithium is inactivated, the negative electrode 12 is replenished with lithium contained in advance, and the capacity reduction is suppressed.

(Second battery)
FIG. 2 shows the configuration of the second secondary battery. In this secondary battery, the wound electrode body 20 to which the leads 21 and 22 are attached is housed in a film-like exterior member 30 and can be reduced in size, weight, and thickness. The leads 21 and 22 are led out from the inside of the exterior member 30 to the outside, for example, in the same direction. The leads 21 and 22 are made of a metal material such as aluminum, copper, nickel, or stainless steel, respectively, and have a thin plate shape or a mesh shape, respectively.

  The exterior member 30 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 30 is disposed, for example, so that the polyethylene film side and the electrode winding body 20 face each other, and the outer edge portions are in close contact with each other by fusion bonding or an adhesive. An adhesion film 31 for preventing the entry of outside air is inserted between the exterior member 30 and the leads 21 and 22. The adhesion film 31 is made of a material having adhesion to the leads 21 and 22, for example, a polyolefin resin such as polyethylene, polypropylene, modified polyethylene, or modified polypropylene.

  The exterior member 30 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. 3 shows a cross-sectional structure taken along line II of the electrode winding body 20 shown in FIG. The electrode winding body 20 is obtained by laminating a negative electrode 23 and a positive electrode 24 via a separator 25 and an electrolyte 26 and winding them, and the outermost periphery is protected by a protective tape 27.

  The negative electrode 23 has a structure in which a negative electrode active material layer 23B is provided on both surfaces of a negative electrode current collector 23A. The positive electrode 24 also has a structure in which the positive electrode active material layer 24B is provided on both surfaces of the positive electrode current collector 24A, and the negative electrode active material layer 23B and the positive electrode active material layer 24B are arranged to face each other. The configurations of the negative electrode current collector 23A, the negative electrode active material layer 23B, the positive electrode current collector 24A, the positive electrode active material layer 24B, and the separator 25 are respectively the negative electrode current collector 12A, the negative electrode active material layer 12B, and the first secondary battery. This is the same as the positive electrode current collector 14A, the positive electrode active material layer 14B, and the separator 15.

  The electrolyte layer 26 is constituted by a so-called gel electrolyte in which an electrolytic solution is held in a holding body made of a polymer compound. A gel electrolyte is preferable because high ion conductivity can be obtained and battery leakage can be prevented. The configuration of the electrolytic solution is the same as that of the first secondary battery. An example of the polymer material is polyvinylidene fluoride.

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

  First, after making the negative electrode 23 and the positive electrode 24 in the same manner as in the first secondary battery, an electrolyte layer 26 in which an electrolytic solution is held in a polymer compound is formed on each of the negative electrode 23 and the positive electrode 24, and the lead 21 , 22 are attached. Next, the negative electrode 23 and the positive electrode 24 on which the electrolyte layer 26 is formed are stacked via the separator 25 and wound, and the protective tape 27 is adhered to the outermost peripheral portion to form the electrode winding body 20. Subsequently, for example, the electrode winding body 20 is sandwiched between the exterior members 31, and the outer edges of the exterior members 31 are in close contact with each other by thermal fusion or the like and sealed. At that time, an adhesive film 32 is inserted between the leads 21 and 22 and the exterior member 31. Thereby, the secondary battery shown in FIGS. 2 and 3 is completed.

  Moreover, you may manufacture as follows. First, the negative electrode 23 and the positive electrode 24 are prepared, and the leads 21 and 22 are attached. Then, the negative electrode 23 and the positive electrode 24 are laminated and wound via the separator 25, and the protective tape 27 is adhered to the outermost periphery. Then, a wound body that is a precursor of the electrode wound body 20 is formed. Next, the wound body is sandwiched between the exterior members 31 and the outer peripheral edge except for one side is heat-sealed into a bag shape, and then the electrolyte, the monomer that is a raw material of the polymer compound, the polymerization initiator, An electrolyte composition containing another material such as a polymerization inhibitor is injected into the exterior member 31 as necessary. Subsequently, the opening of the exterior member 31 is heat-sealed in a vacuum atmosphere and sealed, and heat is applied to polymerize the monomer to form a polymer compound, thereby forming the gel electrolyte layer 26. Thereby, the secondary battery shown in FIGS. 2 and 3 is completed.

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

  As described above, according to the present embodiment, since the active material manufactured by the above-described manufacturing method is used, lithium can be replenished more efficiently, and battery characteristics such as capacity and cycle characteristics are improved. Can be made.

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

(Examples 1-1 and 1-2)
First, an active material having a composition ratio of 63: 7: 30 in terms of the number ratio of silicon: copper: lithium was synthesized using a silicon simple substance, a copper simple substance, and a lithium simple substance. At that time, in Example 1-1, synthesis was performed by a gas atomizing method, and in Example 1-2, synthesis was performed by a single roll method. The gas atomization method is a method in which a melt is sprayed into a gas to be cooled and solidified, and the single roll method is a method in which a melt is sprayed on a cooling roll to be cooled and solidified. Next, the synthesized active material was pulverized and classified using a zirconia ball and an agate pot, so that the average particle size was 1 μm in terms of median diameter. The average particle size was measured with a particle size distribution measuring device.

  Subsequently, a coin-type secondary battery as shown in FIG. 1 was produced using the produced active material. The negative electrode 12 is made of a roughened copper foil having a thickness of 12 μm, in which 8.5 parts by mass of the produced active material and 1.5 parts by mass of polyvinylidene fluoride as a binder are mixed using a dispersion medium. After coating and drying on the negative electrode current collector 12A, pressure forming was performed, and heat treatment was performed at 400 ° C. for 12 hours in a vacuum atmosphere to form the negative electrode active material layer 12B.

The positive electrode 14 is a positive electrode collector made of an aluminum foil by mixing lithium cobaltate (LiCoO ₂ ) powder as a positive electrode active material, carbon black as a conductive material, polyvinylidene fluoride as a binder, and a dispersion medium. After applying and drying the electric body 14A, the positive electrode active material layer 14B was formed by pressure forming. A porous film made of polypropylene is used for the separator 15, and LiPF ₆ is added at a concentration of 1 mol / liter in a solvent in which 50% by mass of 4-fluoro-1,3-dioxolan-2-one and 50% by mass of diethyl carbonate are mixed. 1 kg dissolved was used.

  Moreover, as Comparative Example 1-1 with respect to Examples 1-1 and 1-2, 8.5 parts by mass of silicon copper alloy powder having an average particle diameter of 1 μm and 1.5 parts by mass of polyvinylidene fluoride were used as a dispersion medium. After coating and drying on a negative electrode current collector made of a roughened copper foil having a thickness of 12 μm, the lithium foil having a thickness of 1 μm was placed thereon and pressure-molded, and then in a vacuum atmosphere at 400 ° C. for 12 hours. A secondary battery was fabricated in the same manner as in Examples 1-1 and 1-2, except that the negative electrode active material layer was formed by performing the heat treatment.

  As Comparative Example 1-2, 8.5 parts by mass of silicon copper alloy powder having an average particle diameter of 1 μm and 1.5 parts by mass of polyvinylidene fluoride were mixed using a dispersion medium, and roughened copper having a thickness of 12 μm. A negative electrode current collector made of foil, applied, dried, and pressure-molded is immersed in a hexane solution in which lithium powder having an average particle size of 100 μm is dispersed, dried, and then dried at 400 ° C. in a vacuum atmosphere at 400 ° C. A secondary battery was fabricated in the same manner as in Examples 1-1 and 1-2, except that the negative electrode active material layer was formed by performing heat treatment for a period of time.

  In addition, the composition of the silicon copper alloy powder used in Comparative Examples 1-1 and 1-2 was 63: 7 in terms of the atomic number ratio of silicon: copper. In Comparative Examples 1-1 and 1-2, the amount of lithium occluded in the active material was estimated from the amount of electricity produced by producing a test battery using lithium as a counter electrode. As a result, the composition of the active material was 63: 7: 30 in terms of the number ratio of silicon: copper: lithium.

A charge / discharge test was performed on the fabricated secondary batteries of Examples and Comparative Examples to determine the discharge capacity retention rate. At that time, charging is constant current and constant voltage charging under conditions of current density of 1 mA / cm ² and upper limit voltage of 4.2 V, and discharging is constant current discharging under conditions of current density of 1 mA / cm ² and final voltage of 2.5 V. Went. The discharge capacity retention rate was calculated by using the ratio of the discharge capacity at the 15th cycle to the discharge capacity at the 1st cycle as a percentage. The obtained results are shown in Table 1.

  As shown in Table 1, according to Examples 1-1 and 1-2, the discharge capacity retention ratio could be improved as compared with Comparative Examples 1-1 and 1-2. That is, it has been found that battery characteristics such as cycle characteristics can be improved by synthesizing an active material by melting and solidifying a raw material containing the first element, the second element, and lithium.

(Examples 2-1 to 2-6)
An active material and a secondary battery were produced in the same manner as in Example 1-1 except that the composition of the active material was changed as shown in Table 2. Further, as Comparative Example 2-1 with respect to Examples 2-1 to 2-6, the active material and the active material were the same as in Example 1-1 except that lithium was not added when the active material was produced. A secondary battery was produced. As Comparative Example 2-2, an active material and a secondary battery were produced in the same manner as in Example 1-1 except that copper was not added when the active material was produced. As Comparative Example 2-3, a secondary battery was fabricated in the same manner as in Example 1-1 except that silicon powder having an average particle diameter of 1 μm was used as the active material.

  For the secondary batteries of Examples 2-1 to 2-6 and Comparative Examples 2-1 to 2-3, charging and discharging were performed in the same manner as in Example 1-1, and the discharge capacity retention rate was obtained. Moreover, about the active material produced in Examples 2-1 to 2-6 and Comparative Examples 2-1 and 2-2, the X-ray-diffraction measurement was performed and the average magnitude | size of the crystallite was computed from the half value width of the crystal peak. . The results are shown in Table 2.

  As shown in Table 2, according to Examples 2-1 to 2-6, the discharge capacity retention ratio could be improved more than Comparative Examples 2-1 to 2-3. That is, it has been found preferable to use an active material containing the first element, the second element, and lithium.

(Examples 3-1 to 3-3)
An active material and a secondary battery were produced in the same manner as in Example 1-1 except that the average particle diameter of the active material was changed as shown in Table 3. For the secondary batteries of Examples 3-1 to 3-3, charging and discharging were performed in the same manner as in Example 1-1, and the discharge capacity retention ratio was obtained. Moreover, also about the active material produced in Examples 3-1 to 3-3, the average magnitude | size of the crystallite was computed from the half value width of the crystal peak obtained by X-ray diffraction. The results are shown in Table 3.

  As shown in Table 3, a high discharge capacity retention rate was obtained in all cases, but the discharge capacity retention rate tended to improve as the average particle size of the active material was reduced. That is, it has been found that it is more preferable if the average particle size of the active material is 20 μm or less, and further 10 μm or less.

(Examples 4-1 to 4-3)
An active material and a secondary battery were produced in the same manner as in Example 1-1 except that the average size of the crystallites of the active material was changed as shown in Table 4. For the active materials prepared in Examples 4-1 to 4-3, the average size of the crystallites was calculated from the half width of the crystal peak obtained by X-ray diffraction. Moreover, also about the secondary battery of Examples 4-1 to 4-3, it charged / discharged similarly to Example 1-1, and calculated | required the discharge capacity maintenance factor. The results are shown in Table 4.

  As shown in Table 4, a high discharge capacity retention ratio was obtained in all cases, but the discharge capacity retention ratio was improved by reducing the average size of the active material crystallites. That is, it has been found that it is more preferable that the average size of the crystallites of the active material is 100 nm or less, further 50 nm or less.

(Examples 5-1 and 5-2)
The active material and the secondary material were the same as in Example 1-1 or Example 1-2 except that the active material was synthesized by a gas atomizing method or a single roll method using a tin simple substance instead of the silicon simple substance. A battery was produced.

  Further, as Comparative Examples 5-1 and 5-2 with respect to Examples 5-1 and 5-2, tin copper alloy powder having an atomic ratio of tin: copper of 63: 7 was used instead of silicon copper alloy powder. Except for this, a secondary battery was fabricated in the same manner as in Comparative Examples 1-1 and 1-2. That is, in Comparative Example 5-1, lithium was occluded by attaching a lithium foil, and in Comparative Example 5-2, lithium was occluded by being immersed in a hexane solution in which lithium powder was dispersed. For Comparative Examples 5-1 and 5-2, the amount of lithium occluded was examined in the same manner as Comparative Examples 1-1 and 1-2. As a result, the composition of the active material was 63: 7: 30 in terms of the atomic ratio of tin: copper: lithium.

  For the secondary batteries of Examples 5-1 and 5-2 and Comparative Examples 5-1 and 5-2, charging and discharging were performed in the same manner as in Examples 1-1 and 1-2, and the discharge capacity retention rate was obtained. It was. The results are shown in Table 5.

  As shown in Table 5, according to Examples 5-1 and 5-2, the discharge capacity retention ratio could be improved as compared with Comparative Examples 5-1 and 5-2. That is, even when other elements are used as the first element, if the active material is synthesized by melting and solidifying the raw material containing the first element, the second element, and lithium, the cycle characteristics, etc. It was found that the battery characteristics can be improved.

(Examples 6-1 to 6-6)
An active material and a secondary battery were produced in the same manner as in Example 5-1, except that the composition of the active material was changed as shown in Table 6. Moreover, as Comparative Example 6-1 with respect to Examples 6-1 to 6-6, the active material and the active material were the same as in Example 5-1 except that lithium was not added when the active material was produced. A secondary battery was produced. As Comparative Example 6-2, an active material and a secondary battery were produced in the same manner as in Example 5-1, except that copper was not added when the active material was produced.

  For the secondary batteries of Examples 6-1 to 6-6 and Comparative Examples 6-1 and 6-2, charge and discharge were performed in the same manner as in Example 1-1, and the discharge capacity retention ratio was obtained. In addition, for the active materials prepared in Examples 6-1 to 6-6 and Comparative Examples 6-1 and 6-2, the average crystallite size was calculated from the half-value width of the crystal peak obtained by X-ray diffraction. . The results are shown in Table 6.

  As shown in Table 6, according to Examples 6-1 to 6-6, the discharge capacity retention ratio could be improved as compared with Comparative Examples 6-1 and 6-2. That is, it was found that it is preferable to use another element as the first element.

  Although the present invention has been described with reference to the embodiments and examples, the present invention is not limited to the embodiments and examples, and various modifications can be made. For example, in the above-described embodiments and examples, the case where an electrolytic solution which is a liquid electrolyte or a so-called gel electrolyte is used has been described, but another electrolyte may be used. Examples of other electrolytes include solid electrolytes having ionic conductivity, a mixture of a solid electrolyte and an electrolyte solution, and a mixture of a solid electrolyte and a gel electrolyte.

  As the solid electrolyte, for example, a polymer solid electrolyte in which an electrolyte salt is dispersed in a polymer compound having ion conductivity, or an inorganic solid electrolyte made of ion conductive glass or ionic crystals can be used. Examples of the polymer compound of the solid polymer electrolyte include, for example, an ether polymer compound such as polyethylene oxide or a crosslinked product containing polyethylene oxide, an ester polymer compound such as polymethacrylate, and an acrylate polymer compound. Or can be copolymerized. In addition, as the inorganic solid electrolyte, one containing lithium nitride or lithium phosphate can be used.

  In the above embodiments and examples, the coin type and wound laminate type secondary batteries have been described. However, the present invention is not limited to a cylindrical type, a square type, a button type, a thin type, a large size, or a laminated laminate type. The present invention can be similarly applied to a secondary battery having the shape. In addition, the present invention can be applied not only to secondary batteries but also to primary batteries.

It is sectional drawing showing the structure of the 1st secondary battery using the active material obtained by the manufacturing method of the active material which concerns on one embodiment of this invention. It is sectional drawing showing the structure of the 2nd secondary battery using the active material obtained by the manufacturing method of the active material which concerns on one embodiment of this invention. It is sectional drawing showing the structure along the II line | wire of the electrode winding body shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Exterior cup, 12, 23 ... Negative electrode, 12A, 23A ... Negative electrode current collector, 12B, 23B ... Negative electrode active material layer, 13 ... Outer can, 14, 24 ... Positive electrode, 14A, 24A ... Positive electrode current collector, 14B , 24B ... positive electrode active material layer, 15, 25 ... separator, 16 ... gasket, 20 ... electrode wound body, 21, 22 ... lead, 26 ... electrolyte layer, 27 ... protective tape, 30 ... exterior member, 31 ... adhesive film

Claims (4)

A method for producing an active material comprising a first element capable of forming an alloy with lithium (Li), a second element capable of forming an alloy with the first element, and lithium,
A method for producing an active material, comprising: a step of melting and solidifying a raw material containing the first element, the second element, and lithium. The ratio of the first element and the second element is in the range of 99: 1 to 50:50 in terms of the atomic ratio of the first element: second element,
The ratio between the total of the first element and the second element and lithium is within the range of 99: 1 to 50:50 in terms of the number ratio of (first element + second element): lithium. The method for producing an active material according to claim 1. The method for producing an active material according to claim 1, wherein an active material containing at least one of silicon (Si) and tin (Sn) is produced as the first element. A battery including an electrolyte together with a positive electrode and a negative electrode,
The negative electrode contains an active material including lithium, a first element capable of forming an alloy with lithium (Li), a second element capable of forming an alloy with the first element, and lithium.
The active material is obtained by melting and solidifying a raw material containing the first element, the second element, and lithium.

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