JP2007123141A - Anode and battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anode which can improve cycle characteristics and provide a battery using the same. <P>SOLUTION: On an anode collector 11 has an anode active substance layer 13 with a conductive adhesive layer 12 between. The conductive adhesive layer 12 is composed of conductive particles and a binding material. A mass ratio of the conductive particles to the binding material is preferably in a range between 70:30 and 95:5. An average particle diameter of the conductive particles is preferably in a range between 0.01 μm or more and 20 μm or less. The anode active substance layer 13 has an amorphous phase containing Si as a component element. Furthermore, the anode active substance layer 13 contains oxygen as a component element and its content is preferably in a range of 5 atom no.% or more and 40 atom no.% or less. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a negative electrode containing silicon (Si) as a constituent element and a battery using the negative electrode.

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 demand include lithium ion secondary batteries, but those currently in practical use use graphite for the negative electrode, so the battery capacity is in a saturated state, and there is a significant increase in capacity. difficult. Thus, it has been studied to increase the capacity by using silicon for the negative electrode (see, for example, Patent Document 1).
JP 2004-171876 A

  However, silicon has a large expansion / contraction due to charging / discharging. Therefore, when charging / discharging is repeated, the negative electrode active material layer is detached from the negative electrode current collector due to the stress due to expansion / contraction, resulting in a decrease in current collection and cycle characteristics. There was a problem that.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a negative electrode and a battery that can improve adhesion between the negative electrode current collector and the negative electrode active material layer and current collection. .

  In the negative electrode according to the present invention, a negative electrode active material layer is provided on a negative electrode current collector through a conductive adhesive layer having conductive particles and a binder, and the negative electrode active material layer contains silicon as a constituent element. It has an amorphous phase.

  The battery according to the present invention is provided with an electrolyte together with a positive electrode and a negative electrode, and the negative electrode has a negative electrode active material layer interposed between a negative electrode current collector and a conductive adhesive layer having conductive particles and a binder. The negative electrode active material layer provided has an amorphous phase containing silicon as a constituent element.

  According to the negative electrode of the present invention, since the negative electrode active material layer having an amorphous phase containing silicon is provided via the conductive adhesive layer, stress due to expansion and contraction of the negative electrode active material layer can be relieved. In addition, the adhesion between the negative electrode current collector and the negative electrode active material layer can be improved. In addition, current collection can be improved. Therefore, according to the battery of the present invention using this negative electrode, excellent cycle characteristics can be obtained.

  In particular, if the ratio of the conductive particles to the binder in the conductive adhesive layer is within the range of 70:30 to 95: 5 in terms of the mass ratio of the conductive particles to the binder, If the average particle size is in the range of 0.01 μm or more and 20 μm or less, a higher effect can be obtained.

  Furthermore, if the negative electrode current collector is made of a copper foil or copper alloy foil having a thickness of 50 μm or less and the ten-point average roughness Rz is 1.0 μm or more and 4.0 μm or less, the negative electrode active material A higher effect can be obtained if the layer contains oxygen as a constituent element and the content thereof is 5 atomic% to 40 atomic%.

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

  FIG. 1 illustrates a cross-sectional configuration of a negative electrode 10 according to an embodiment of the present invention. The negative electrode 10 has a structure in which, for example, a negative electrode current collector 11 is provided with a negative electrode active material layer 12 containing silicon as a constituent element via a conductive adhesive layer 13. The conductive adhesive layer 12 and the negative electrode active material layer 13 may be formed on both surfaces of the negative electrode current collector 11 or may be formed on one surface.

  The negative electrode current collector 11 is preferably made of a metal material having high conductivity, and particularly preferably made of a copper foil or the same alloy foil. The thickness of the negative electrode current collector 11 is preferably 50 μm or less, for example. This is because if the thickness is too large, stress is applied due to the expansion and contraction of the negative electrode active material layer 13, and the adhesiveness between the negative electrode current collector 11 and the negative electrode active material layer 13 decreases. Further, the thickness of the negative electrode current collector 11 is preferably 20 μm or more. This is because if the thickness is too thin, the ability to support the negative electrode active material layer 13 is reduced.

  The surface of the negative electrode current collector 11 is preferably roughened. This is because the adhesion between the negative electrode current collector 11 and the conductive adhesive layer 12 can be improved. The surface roughness of the negative electrode current collector 11 is a ten-point average roughness Rz described in JIS B0601 Appendix 1, and is preferably in the range of 1.0 μm or more and 4.0 μm or less. This is because a higher effect can be obtained. The surface roughness of the negative electrode current collector 11 may be at least within the above range in the region where the negative electrode active material layer 13 is provided via the conductive adhesive layer 12.

  The conductive adhesive layer 12 includes, for example, conductive particles and a binder, thereby relieving stress due to expansion and contraction of the negative electrode active material layer 13 while ensuring conductivity, and a negative electrode current collector. 11 and the negative electrode active material layer 13 can be improved in adhesion. The thickness of the conductive adhesive layer 12 is preferably 0.1 μm or more and 20 μm or less. This is because if the thickness is too thin, the stress relaxation effect by the conductive adhesive layer 12 cannot be obtained, and if the thickness is too thick, the conductivity decreases.

  Examples of the conductive particles include metal particles and carbon particles, and one kind thereof may be used alone, or two or more kinds may be mixed and used. Examples of the metal particles include gold (Au), silver (Ag), copper (Cu), tin (Sn), bismuth (Bi), zinc (Zn), nickel (Ni), palladium (Pd), chromium (Cr ), Indium (In), antimony (Sb), aluminum (Al), germanium (Ge), tungsten (W), molybdenum (Mo), manganese (Mn), titanium (Ti) or magnesium (Mg) The thing which consists of. Examples of the carbon particles include carbon black. The average particle diameter of the conductive particles is preferably in the range of 0.01 μm to 20 μm. If the average particle size is too small, the conductive particles aggregate, resulting in a distribution of conductivity. If the average particle size is too large, the contact between the conductive particles is reduced and the conductivity is reduced. It is.

  Examples of the binder include thermoplastic resins and thermosetting resins, and any one of them may be used alone, or two or more kinds may be mixed and used. As a thermoplastic resin, what has a hydrogen bondable functional group is preferable. This is because a higher effect can be obtained. This is considered to be because wettability is improved by hydrogen bonding with the metal. Examples of the functional group having hydrogen bonding include a hydrogen group, an amide group, a urea group, an imide group, an ester group, an ether group, a thioether group, a sulfone group, and a ketone group. Examples of the thermoplastic resin having hydrogen bonding properties include phenoxy resin, thermoplastic polyurethane, polyvinyl butyral, polyamide, thermoplastic polyimide, polyamideimide, polycarbonate, polyphenylene ether, polyvinyl ether, polysulfone, polyvinyl alcohol, polyvinyl formal, poly Examples thereof include vinyl acetate, methacrylic resin, and ionomer resin.

  Examples of the thermosetting resin include epoxy resin, phenol resin, polyimide, polyurethane, melamine resin, and urea resin. Examples of the epoxy resin include bilphenol A type epoxy resin, bisphenol F type epoxy resin, novolac type epoxy resin, halogenated bisphenol type epoxy resin, resorcin type epoxy resin, tetrahydroxyphenol ether type epoxy resin, polyalcohol polyglycol Type epoxy resin, glycerin triether type epoxy resin, polyolefin type epoxy resin, epoxidized soybean oil, cyclopentadiene dioxide, or vinylcyclohexene dioxide. Among these, bilphenol A type epoxy resin or novolak type epoxy resin is preferable.

  The ratio of the conductive particles to the binder in the conductive adhesive layer 12 is preferably in the range of 70:30 to 95: 5 in terms of the mass ratio of the conductive particles to the binder. When the proportion of the conductive particles is increased, the conductivity is improved but the adhesiveness is lowered. Conversely, when the proportion of the binder is increased, the adhesiveness is improved but the conductivity is lowered.

  The negative electrode active material layer 13 preferably has an amorphous phase containing silicon. This is because the stress due to expansion and contraction can be reduced. Moreover, it is preferable that at least a part of the negative electrode active material layer 13 is formed by a vapor phase method. When the negative electrode active material layer 13 is formed by the vapor phase method, the stress applied to the negative electrode current collector 11 due to the expansion and contraction of the negative electrode active material layer 13 is large, but the stress is relieved by the conductive adhesive layer 12 and is excellent. This is because characteristics can be obtained.

  In the negative electrode active material layer 13, silicon may be included as a simple substance, an alloy, or a compound. Examples of constituent elements other than silicon include tin, nickel, copper, iron (Fe), cobalt (Co), manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, and chromium. The negative electrode active material layer 13 preferably contains oxygen (O) as a constituent element. This is because expansion and contraction of the negative electrode active material layer 13 can be suppressed and stress can be relaxed. At least a part of oxygen contained in the negative electrode active material layer 13 is preferably bonded to silicon, and the bonding state may be silicon monoxide, silicon dioxide, or other metastable state. The oxygen content in the negative electrode active material layer 13 is preferably in the range of 5 atomic% to 40 atomic%. If it is less than this, a sufficient effect cannot be obtained, and if it is more than this, the irreversible capacity increases. Note that the negative electrode active material layer 13 does not include a coating film that is formed on the surface of the negative electrode active material layer 13 due to decomposition of the electrolyte solution by charge and discharge. Therefore, when the oxygen content in the negative electrode active material layer 13 is calculated, oxygen contained in the coating is not included.

  This negative electrode 10 can be manufactured as follows, for example.

  First, for example, conductive particles and a binder are mixed using a dispersion medium, applied to the negative electrode current collector 11, and then the dispersion medium is removed to form the conductive binder layer 12. Next, the negative electrode active material layer 13 is formed on the conductive binder layer 12 by, for example, a vapor phase method. Examples of the vapor phase method include a physical deposition method and a chemical deposition method. Specifically, a vacuum deposition method, a sputtering method, an ion plating method, a laser ablation method, a CVD (Chemical Vapor Deposition; chemical vapor deposition). ) Method. At that time, when oxygen is added to the negative electrode active material layer 13, for example, oxygen is introduced into the atmosphere. Thereby, the negative electrode 10 shown in FIG. 1 is obtained.

  The negative electrode active material layer 13 is formed by using, for example, an amorphous powder containing silicon as a constituent element, mixing with a binder as necessary, and applying the mixture onto the conductive adhesive layer 12. Alternatively, heat treatment may be performed to such an extent that it does not crystallize. Furthermore, you may make it form the negative electrode active material layer 13 combining these and a gaseous-phase method.

  This negative electrode 10 is used for the following secondary batteries, for example.

  FIG. 2 shows the configuration of the secondary battery. This secondary battery is a so-called coin-type battery, in which the negative electrode 10 accommodated in the exterior cup 21 and the positive electrode 23 accommodated in the exterior can 22 are stacked via a separator 24. is there.

  The peripheral portions of the outer cup 21 and the outer can 22 are sealed by caulking through an insulating gasket 25. The exterior cup 21 and the exterior can 22 are made of, for example, a metal such as stainless steel or aluminum.

  The positive electrode 23 includes, for example, a positive electrode current collector 23A and a positive electrode active material layer 23B provided on the positive electrode current collector 23A so that the positive electrode active material layer 23B side faces the negative electrode active material layer 12. Is arranged. The positive electrode current collector 23A is made of, for example, aluminum, nickel, stainless steel, or the like.

The positive electrode active material layer 23B 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 positive electrode 23 is prepared by mixing a positive electrode active material, a conductive material, and a binder, for example, and preparing a mixture slurry by dispersing the mixture in a dispersion medium. Is applied to a positive electrode current collector 23A made of a metal foil, dried, and then compression molded to form the positive electrode active material layer 23B.

  The separator 24 separates the negative electrode 10 and the positive electrode 23 and allows lithium ions to pass through while preventing a short circuit of current due to contact between both electrodes. The separator 24 is made of, for example, polyethylene or polypropylene.

  The separator 24 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, by laminating the negative electrode 10, the separator 24 impregnated with the electrolytic solution, and the positive electrode 23, placing them in the outer cup 21 and the outer can 22, and caulking them. it can.

  In the secondary battery, when charged, for example, lithium ions are extracted from the positive electrode 23 and inserted in the negative electrode 10 through the electrolytic solution. When discharging is performed, for example, lithium ions are released from the negative electrode 10 and inserted in the positive electrode 23 via the electrolytic solution. Although the negative electrode active material layer 13 expands and contracts with this charge and discharge, in the present embodiment, the negative electrode active material layer 13 has an amorphous phase containing silicon and is provided with the conductive binder layer 12. Therefore, the stress due to the expansion and contraction of the negative electrode active material layer 13 is relieved.

  The negative electrode 10 according to the present embodiment may be used for the following secondary battery.

  FIG. 3 shows the configuration of the secondary battery. In this secondary battery, the wound electrode body 30 to which the leads 31 and 32 are attached is housed in a film-like exterior member 41, and can be reduced in size, weight, and thickness. The leads 31 and 32 are led out from the inside of the exterior member 41 to the outside, for example, in the same direction. The leads 31 and 32 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 41 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 41 is disposed, for example, so that the polyethylene film side and the electrode winding body 30 face each other, and the outer edge portions are in close contact with each other by fusion or an adhesive. An adhesion film 42 for preventing the entry of outside air is inserted between the exterior member 41 and the leads 31 and 32. The adhesion film 42 is made of a material having adhesion to the leads 31 and 32, for example, a polyolefin resin such as polyethylene, polypropylene, modified polyethylene, or modified polypropylene.

  The exterior member 41 may be made of a laminated film having another structure, a polymer film such as polypropylene, or a metal film instead of the above-described aluminum laminated film.

  FIG. 4 shows a cross-sectional structure taken along line II of the electrode winding body 30 shown in FIG. The electrode winding body 30 is obtained by laminating and winding the negative electrode 10 and the positive electrode 33 with the separator 34 and the electrolyte layer 35 interposed therebetween, and the outermost peripheral portion is protected by a protective tape 36.

  The negative electrode 10 has a structure in which a negative electrode active material layer 13 is provided on both surfaces of a negative electrode current collector 11 via a conductive binder layer 12. The positive electrode 33 also has a structure in which the positive electrode active material layer 33B is provided on both surfaces of the positive electrode current collector 33A, and the positive electrode active material layer 33B and the negative electrode active material layer 12 are arranged to face each other. The configurations of the positive electrode current collector 33A, the positive electrode active material layer 33B, and the separator 34 are the same as those of the positive electrode current collector 23A, the positive electrode active material layer 23B, and the separator 24 described above.

  The electrolyte layer 35 is configured 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 coin-type secondary battery shown in FIG. An example of the polymer material is polyvinylidene fluoride.

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

  First, on each of the negative electrode 10 and the positive electrode 33, an electrolyte layer 35 in which an electrolytic solution is held in a holding body is formed, and leads 31 and 32 are attached. Next, the negative electrode 10 on which the electrolyte layer 35 is formed and the positive electrode 33 are laminated via the separator 34 and wound, and the protective tape 36 is adhered to the outermost peripheral portion to form the electrode winding body 30. Subsequently, for example, the electrode winding body 30 is sandwiched between the exterior members 41, and the outer edge portions of the exterior members 41 are sealed and sealed by thermal fusion or the like. At that time, the adhesion film 42 is inserted between the leads 31 and 32 and the exterior member 41. Thereby, the secondary battery shown in FIGS. 3 and 4 is completed.

  Moreover, you may manufacture as follows. First, after the leads 31 and 32 are attached to the negative electrode 10 and the positive electrode 33, the negative electrode 10 and the positive electrode 33 are laminated and wound via the separator 34, and the protective tape 36 is adhered to the outermost peripheral portion to A wound body that is a precursor of the wound body 30 is formed. Next, the wound body is sandwiched between exterior members 41, and the outer peripheral edge except for one side is heat-sealed into a bag shape, and then the electrolyte, the monomer that is the 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 41 as necessary. Subsequently, the opening of the exterior member 41 is heat-sealed and sealed in a vacuum atmosphere, and heat is applied to polymerize the monomer to form a polymer compound, thereby forming the gel electrolyte layer 35. Thereby, the secondary battery shown in FIGS. 3 and 4 is completed.

  The operation of this secondary battery is the same as that of the coin-type secondary battery shown in FIG.

  As described above, according to the present embodiment, since the negative electrode active material layer 13 having an amorphous phase containing silicon is provided via the conductive adhesive layer 12, the negative electrode active material layer 13 is expanded and contracted. The stress can be relaxed, and the adhesion between the negative electrode current collector 11 and the negative electrode active material layer 13 can be improved. In addition, current collection can be improved. Therefore, excellent cycle characteristics can be obtained.

  In particular, if the ratio of the conductive particles and the binder in the conductive adhesive layer 12 is within the range of 70:30 to 95: 5 in terms of the mass ratio of the conductive particles: binder, the conductive particles A higher effect can be obtained if the average particle diameter is within the range of 0.01 μm or more and 20 μm or less.

  Furthermore, if the thickness of the negative electrode current collector 11 is 50 μm or less and the ten-point average roughness Rz is 1.0 μm or more and 4.0 μm or less, the negative electrode active material layer 13 contains oxygen as a constituent element. And if the content shall be 5 atomic% or more and 40 atomic% or less, a higher effect can be acquired.

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

(Example 1-1)
The negative electrode 10 shown in FIG. 1 was produced. First, silver particles having an average particle diameter of 2 μm were prepared as conductive particles, and a mixture of thermoplastic polyimide and bisphenol A type epoxy resin at a mass ratio of 1: 1 was prepared as a binder. Next, 80% by mass of conductive particles and 20% by mass of a binder are mixed using isopropyl alcohol as a dispersion medium, and the negative electrode current collector 11 made of a copper foil having a surface roughness Rz of 1.0 μm and a thickness of 20 μm is formed. After coating, isopropyl alcohol was volatilized to form a conductive binder layer 12 having a thickness of 1 μm.

  Subsequently, a negative electrode active material layer 13 having a thickness of 6 μm was formed on the conductive binder layer 12 by depositing silicon by an electron beam evaporation method. At that time, oxygen gas was introduced into the atmosphere, and oxygen was added to the negative electrode active material layer 13. When the produced negative electrode 10 was subjected to X-ray diffraction measurement and Raman spectroscopic measurement, it was confirmed that the crystallinity of silicon in the negative electrode active material layer 13 was amorphous. When elemental analysis was performed using EDX (energy dispersive X-ray analyzer), the oxygen content in the negative electrode active material layer 13B was 5 atomic%. Furthermore, when the cross section of the produced negative electrode 10 was cut out with a microtome and the structure was examined using a scanning electron microscope (SEM) and EDX together, the negative electrode current collector 11 and the negative electrode active material layer 13 were In the meantime, it was confirmed that the conductive binder layer 12 was formed.

  As Comparative Example 1-1 with respect to Example 1-1, except that the conductive binder layer was not formed and the negative electrode active material layer was directly formed on the negative electrode current collector, the rest was the same as Example 1-1. A negative electrode was produced in the same manner.

  As Comparative Example 1-2, except that the negative electrode active material layer was formed on the negative electrode current collector through the conductive binder layer, and then heat treatment was performed at 800 ° C. for 10 hours, the others were Example 1. A negative electrode was produced in the same manner as in Example-1. When X-ray diffraction measurement was performed on the negative electrode of Comparative Example 1-2, a peak attributable to silicon was observed. That is, it was confirmed that the crystallinity of silicon in the negative electrode active material layer changed from amorphous to crystalline.

  As Comparative Example 1-3, a negative electrode was produced in the same manner as in Example 1-1 except that the method for forming the negative electrode active material layer was changed. The negative electrode active material layer was formed by mixing crystalline silicon particles, polyvinylidene fluoride, and a dispersion medium, applying the mixture on the conductive binder layer, volatilizing the dispersion medium, and then performing heat treatment.

  As Comparative Example 1-4, the negative electrode active material layer was formed in the same manner as in Comparative Example 1-3 without forming the conductive binder layer, and the negative electrode was the same as in Example 1-1. Was made. That is, using the same negative electrode current collector as in Example 1-1, a crystalline silicon powder was applied and heat-treated to form a negative electrode active material layer.

Next, a coin-type test battery as shown in FIG. 2 was produced using the produced negative electrode 10 of Example 1-1 and Comparative Examples 1-1 to 1-4. The counter electrode is a lithium metal plate, a porous polypropylene film is used as a separator, and 1 mol of LiPF ₆ is mixed in a solvent in which ethylene carbonate and diethyl carbonate are mixed in a volume ratio of ethylene carbonate: diethyl carbonate = 1: 2 as an electrolyte. A solution dissolved at a concentration of / l was used.

The manufactured test batteries of Example 1-1 and Comparative Examples 1-1 to 1-4 were charged and discharged at a current density of 1 mA / cm ² for 50 cycles, and the ratio of the discharge capacity at the 50th cycle to the first cycle was determined. It calculated | required as a discharge capacity maintenance factor. The results are shown in Table 1.

  As shown in Table 1, according to Example 1-1 in which the conductive adhesive layer 12 was provided and the silicon crystallinity of the negative electrode active material layer 13 was amorphous, the conductive adhesive layer was not provided. Compared to Comparative Example 1-1, the discharge capacity retention rate could be significantly improved. On the other hand, according to Comparative Example 1-2 in which the crystallinity of silicon in the negative electrode active material layer was crystalline, the discharge capacity retention rate could not be improved even when the conductive adhesive layer was provided. Moreover, also in Comparative Example 1-3 in which the negative electrode active material layer is formed by firing using crystalline silicon powder, the discharge capacity retention rate is improved as compared with Comparative Example 1-4 in which the conductive adhesive layer is not provided. I couldn't.

  That is, it was found that the cycle characteristics can be improved by providing the conductive adhesive layer 12 and making the negative electrode active material layer 13 have an amorphous phase containing silicon.

(Examples 2-1-1 to 2-6-3)
Except that the mixing ratio of the conductive particles and the binder in the conductive adhesive layer 12 and the thickness of the conductive adhesive layer 12 were changed as shown in Table 2, the others were the same as in Example 1-1. A negative electrode 10 and a test battery were produced. In addition, Example 2-3-3 is the same as Example 1-1. For the produced test batteries of Examples 2-1-1 to 2-6-3, the discharge capacity retention ratio was determined in the same manner as in Example 1-1. The obtained results are shown in Table 2.

  As shown in Table 2, the discharge capacity retention rate tends to decrease after increasing the proportion of the conductive particles in the conductive adhesive layer 12, and the thickness of the conductive adhesive layer 12 is increased. Accordingly, the discharge capacity retention rate tended to decrease after improving. That is, if the ratio of the conductive particles and the binder in the conductive adhesive layer 12 is within the range of 70:30 to 95: 5 in terms of the mass ratio of the conductive particles: binder, the conductive adhesive layer 12 It has been found that if the thickness of the layer 12 is in the range of 0.1 μm or more and 20 μm or less, an excellent effect can be obtained.

(Examples 3-1 to 3-19)
A negative electrode 10 and a test battery were produced in the same manner as in Example 1-1 except that the type of conductive particles in the conductive adhesive layer 12 was changed as shown in Table 3. For the produced test batteries of Examples 3-1 to 3-19, the discharge capacity retention ratio was determined in the same manner as in Example 1-1. The obtained results are shown in Table 3 together with the results of Example 1-1.

  As shown in Table 3, all were able to obtain a high discharge capacity retention rate as in Example 1-1. That is, it was found that an excellent effect can be obtained by using any conductive particle.

(Examples 4-1 to 4-7)
A negative electrode 10 and a test battery were produced in the same manner as in Example 1-1 except that the average particle diameter of the conductive particles in the conductive adhesive layer 12 was changed as shown in Table 4. For the produced test batteries of Examples 4-1 to 4-7, the discharge capacity retention ratio was determined in the same manner as in Example 1-1. The obtained results are shown in Table 4 together with the results of Example 1-1.

  As shown in Table 4, there was a tendency that the discharge capacity retention rate improved and then decreased as the average particle size of the conductive particles was increased. That is, it has been found that excellent effects can be obtained if the average particle diameter of the conductive particles is in the range of 0.01 μm to 20 μm.

(Examples 5-1 to 5-6)
A negative electrode 10 and a test battery were produced in the same manner as in Example 1-1 except that the type of thermosetting resin used as the binder in the conductive adhesive layer 12 was changed as shown in Table 5. . For the manufactured test batteries of Examples 5-1 to 5-6, the discharge capacity retention ratio was determined in the same manner as in Example 1-1. The obtained results are shown in Table 5 together with the results of Example 1-1.

  As shown in Table 5, all were able to obtain a high discharge capacity retention rate as in Example 1-1. That is, it was found that excellent effects could be obtained even if the type of resin was changed.

(Examples 6-1-1 to 6-2-4)
A negative electrode 10 and a test battery were produced in the same manner as in Example 1-1 except that the surface roughness Rz or thickness of the negative electrode current collector 11 was changed as shown in Table 6. In addition, Example 6-1-2 and Example 6-2-1 are the same as Example 1-1. For the manufactured test batteries of Examples 6-1 to 6-2-4, the discharge capacity retention ratio was determined in the same manner as in Example 1-1. The results obtained are shown in Table 6.

  As shown in Table 6, as the surface roughness Rz of the negative electrode current collector 11 is increased, the discharge capacity retention rate tends to decrease and then decreases. When the thickness of the negative electrode current collector 11 is increased, the discharge capacity maintenance is maintained. The rate tended to decrease. That is, if the surface roughness Rz of the negative electrode current collector 11 is in the range of 1.0 μm or more and 4.0 μm or less, and the thickness of the negative electrode current collector 11 is in the range of 20 μm or more and 50 μm or less, excellent. It was found that the effect can be obtained.

(Examples 7-1 to 7-4)
A negative electrode 10 and a test battery were produced in the same manner as in Example 1-1 except that the oxygen content in the negative electrode active material layer 13 was changed as shown in Table 7. The oxygen content was controlled by adjusting the amount of oxygen gas introduced when the negative electrode active material layer 13 was formed, and the analysis was performed in the same manner as in Example 1-1. For the produced test batteries of Examples 7-1 to 7-4, the discharge capacity retention ratio was determined in the same manner as in Example 1-1. The obtained results are shown in Table 7 together with the results of Example 1-1.

  As shown in Table 7, there was a tendency for the discharge capacity retention rate to improve and then decrease as the oxygen content was increased. That is, it was found that excellent effects can be obtained if the oxygen content in the negative electrode active material layer 13 is in the range of 5 atomic% to 40 atomic%.

  Although the present invention has been described with reference to the embodiments and examples, the present invention is not limited to the above embodiments and examples, and various modifications can be made. For example, in the above-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, a coin type or wound laminate type secondary battery has 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 negative electrode which concerns on one embodiment of this invention. It is sectional drawing showing the structure of the secondary battery using the negative electrode shown in FIG. It is a disassembled perspective view showing the structure of the other secondary battery using the negative electrode shown in FIG. It is sectional drawing showing the structure along the II line of the secondary battery shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Negative electrode, 11 ... Negative electrode collector, 12 ... Conductive binder layer, 13 ... Negative electrode active material layer, 21 ... Exterior cup, 22 ... Exterior can, 23, 33 ... Positive electrode, 23A, 33A ... Positive electrode collector , 23B, 33B ... positive electrode active material layer, 24, 34 ... separator, 25 ... gasket, 31, 32 ... lead, 30 ... electrode winding body, 35 ... electrolyte layer, 36 ... protective tape, 41 ... exterior member, 42 ... Adhesive film

Claims (18)

The negative electrode current collector is provided with a negative electrode active material layer through a conductive adhesive layer having conductive particles and a binder,
The negative electrode active material layer has an amorphous phase containing silicon as a constituent element. The ratio between the conductive particles and the binder in the conductive adhesive layer is in a range of 70:30 to 95: 5 in terms of a mass ratio of conductive particles: binder. The negative electrode described. The conductive adhesive layer includes, as the conductive particles, gold (Au), silver (Ag), copper (Cu), tin (Sn), bismuth (Bi), zinc (Zn), nickel (Ni), palladium ( Pd), chromium (Cr), indium (In), antimony (Sb), aluminum (Al), germanium (Ge), tungsten (W), molybdenum (Mo), manganese (Mn), titanium (Ti) and magnesium ( 2. The negative electrode according to claim 1, comprising at least one of metal particles including at least one of the group consisting of Mg) and carbon particles. 2. The negative electrode according to claim 1, wherein an average particle diameter of the conductive particles is in a range of 0.01 μm to 20 μm. The negative electrode according to claim 1, wherein the conductive adhesive layer includes at least one of a thermoplastic resin and a thermosetting resin as the binder. The conductive adhesive layer has at least one thermosetting member selected from the group consisting of a thermoplastic resin having hydrogen bonding properties and an epoxy resin, a phenol resin, a polyimide, a polyurethane, a melamine resin, and a urea resin as the binder. The negative electrode according to claim 5, further comprising a functional resin. 2. The negative electrode according to claim 1, wherein the negative electrode current collector is made of a copper foil or a copper alloy foil having a thickness of 50 μm or less, and a ten-point average roughness Rz is 1.0 μm or more and 4.0 μm or less. . The negative electrode according to claim 1, wherein at least a part of the negative electrode active material layer is formed by a vapor phase method. The negative electrode according to claim 1, wherein the negative electrode active material layer contains oxygen as a constituent element, and the content thereof is 5 atomic% to 40 atomic%. A battery comprising an electrolyte together with a positive electrode and a negative electrode,
The negative electrode is provided with a negative electrode active material layer on a negative electrode current collector through a conductive adhesive layer having conductive particles and a binder,
The negative electrode active material layer has an amorphous phase containing silicon as a constituent element. The ratio between the conductive particles and the binder in the conductive adhesive layer is in a range of 70:30 to 95: 5 in terms of a mass ratio of conductive particles: binder. The battery described. The conductive adhesive layer includes, as the conductive particles, gold (Au), silver (Ag), copper (Cu), tin (Sn), bismuth (Bi), zinc (Zn), nickel (Ni), palladium ( Pd), chromium (Cr), indium (In), antimony (Sb), aluminum (Al), germanium (Ge), tungsten (W), molybdenum (Mo), manganese (Mn), titanium (Ti) and magnesium ( 11. The battery according to claim 10, comprising at least one of metal particles including at least one of the group consisting of Mg) and carbon particles. The battery according to claim 10, wherein an average particle diameter of the conductive particles is in a range of 0.01 μm to 20 μm. The battery according to claim 10, wherein the conductive adhesive layer includes at least one of a thermoplastic resin and a thermosetting resin as the binder. The conductive adhesive layer has at least one thermosetting member selected from the group consisting of a thermoplastic resin having hydrogen bonding properties and an epoxy resin, a phenol resin, a polyimide, a polyurethane, a melamine resin, and a urea resin as the binder. The battery according to claim 14, comprising: a functional resin. The battery according to claim 10, wherein the negative electrode current collector is made of a copper foil or a copper alloy foil having a thickness of 50 μm or less, and a ten-point average roughness Rz is 1.0 μm or more and 4.0 μm or less. . The battery according to claim 10, wherein at least a part of the negative electrode active material layer is formed by a vapor phase method. The battery according to claim 10, wherein the negative electrode active material layer contains oxygen as a constituent element, and the content thereof is 5 atomic% to 40 atomic%.

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