JP4941632B2 - Negative electrode and battery - Google Patents

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. .

The negative electrode according to the present invention includes a negative electrode current collector provided with a negative electrode active material layer containing silicon as a constituent element. The negative electrode current collector includes a periodic first concavo-convex structure and the first It has a second concave-convex structure provided on the surface of the concavo-convex structure of the period of the first relief structure, with at 10μm or 100μm or less, not more than 5 times the thickness of the negative electrode current collector, and It is at least three times the maximum roughness height of the first concavo-convex structure, and the second concavo-convex structure has a surface roughness Rz _JIS of 1.0 μm or more and 5.0 μm or less, and a contour curve element The average length RSm is smaller than the period of the first uneven structure, and the total thickness of the negative electrode current collector and the negative electrode active material layer is 16 μm or more and 100 μm or less .

The battery according to the present invention includes an electrolyte together with a positive electrode and a negative electrode. The negative electrode is provided with a negative electrode active material layer containing silicon as a constituent element on the negative electrode current collector. first and uneven structure, have a second concave-convex structure provided on a surface of the first concave-convex structure, the period of the first relief structure, with at 10μm or 100μm or less, the negative electrode current collector It is 5 times or less the thickness of the body and 3 times or more of the maximum roughness height of the first concavo-convex structure, and the second concavo-convex structure has a surface roughness Rz _JIS of 1.0 μm or more. 5.0 μm or less, the average length RSm of the contour curve element is smaller than the period of the first uneven structure, and the total thickness of the negative electrode current collector and the negative electrode active material layer is 16 μm or more and 100 μm or less It is.

According to the negative electrode of the present invention, since the negative electrode current collector is provided with the periodic first uneven structure, the stress due to the expansion and contraction of the negative electrode active material layer can be uniformly dispersed, and the first Since the second uneven structure is provided on the surface of the uneven structure, the adhesion between the negative electrode current collector and the negative electrode active material layer can be improved. Therefore, the adhesiveness between the negative electrode current collector and the negative electrode active material layer can be increased, and the current collecting property can be improved. Therefore, according to the battery of the present invention using this negative electrode, excellent cycle characteristics can be obtained. In particular, the period of the first uneven structure is 10 μm or more and 100 μm or less, and the size of the second uneven structure is in the range of 1.0 μm or more and 5.0 μm or less in the surface roughness Rz _JIS. 5 times or less the thickness of the negative electrode current collector, the period of the first concavo-convex structure is 3 times or more the maximum roughness height of the first concavo-convex structure, and the average length of the contour curve elements of the second concavo-convex structure The thickness RSm is made smaller than the period of the first concavo-convex structure, and the total thickness of the negative electrode current collector and the negative electrode active material layer is set in the range of 16 μm or more and 100 μm or less, thereby obtaining a higher effect. be able to.

Further, if the thickness of the negative electrode active material layer so as to 50μm or less, or contains oxygen as the constituent element anode active material layer, the content thereof number% 5 atomic% to 40 atomic less By doing so, a higher effect can be obtained.

  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, for example, a structure in which a negative electrode current collector 11 having a pair of opposed surfaces is provided with a negative electrode active material layer 12 containing silicon as a constituent element. Although FIG. 1 shows the case where the negative electrode active material layer 12 is provided on one surface of the negative electrode current collector 11, the negative electrode active material layer 12 may be provided on both surfaces of the negative electrode current collector 11.

  The negative electrode current collector 11 is preferably made of a metal material having high conductivity, and particularly preferably made of a copper (Cu) foil or a copper alloy foil. On the surface of the negative electrode current collector 11, at least in a region where the negative electrode active material layer 12 is provided, a first concavo-convex structure 11A and a second concavo-convex structure 11B finer than the first concavo-convex structure 11A are provided. Is formed.

The first concavo-convex structure 11 </ b> A is formed periodically, and can uniformly disperse stress due to expansion and contraction of the negative electrode active material layer 12. Relief structure, circular, polygonal, or any shape such as streamlined or lattice. In addition, when providing 11 A of 1st uneven structures on both surfaces of the negative electrode collector 11, the uneven structure of both surfaces may correspond, but it is not necessary to correspond. The period T of the first concavo-convex structure 11A is preferably in the range of 10 μm to 100 μm, for example. This is because the stress can be more uniformly dispersed within this range.

  The period T of the first concavo-convex structure 11A is preferably 5 times or less the thickness d of the negative electrode current collector 11, and more preferably 0.5 times or more. That is, the ratio T / d of the period T of the first uneven structure 11A to the thickness d of the negative electrode current collector 11 is preferably 5 or less, and more preferably 0.5 or more. Furthermore, the period T of the first concavo-convex structure 11A is preferably at least 3 times the maximum roughness height h of the first concavo-convex structure 11A, more preferably 10 times or less. That is, the ratio T / h of the period T to the maximum roughness height h of the first concavo-convex structure 11A is preferably 3 or more, and more preferably 10 or less. This is because a higher effect can be obtained within these ranges.

The second concavo-convex structure 11 </ b> B is formed on the surface of the first concavo-convex structure 11 </ b> A, and can improve the adhesion between the negative electrode current collector 11 and the negative electrode active material layer 12. The size of the second concavo-convex structure 11B is preferably in the range of 1.0 μm or more and 5.0 μm or less in the surface roughness Rz _JIS defined in JIS B0601, for example. In the second concavo-convex structure 11B, for example, the average length RSm of the contour curve elements defined in JIS B0601 is preferably smaller than the period T of the first concavo-convex structure 11A. This is because a higher effect can be obtained within such a range.

  The negative electrode active material layer 12 is preferably formed at least partly by, for example, one or more methods selected from the group consisting of a vapor phase method, a liquid phase method, a firing method, and a thermal spray method. It may be formed by combining two or more. Breakage due to expansion and contraction of the negative electrode active material layer 12 due to charge / discharge can be suppressed, and the negative electrode current collector 11 and the negative electrode active material layer 12 can be integrated, and electron conduction in the negative electrode active material layer 12 This is because the performance can be improved. Note that the “firing method” means that a layer formed by mixing a powder containing an active material and a binder is heat-treated in a non-oxidizing atmosphere or the like, so that the volume density is higher than that before the heat treatment and the denser. It means the method of forming a layer.

  The negative electrode active material layer 12 may also be formed by coating, specifically including a negative electrode active material and, if necessary, a binder such as polyvinylidene fluoride. However, as described above, it is preferable that at least a part is formed by the vapor phase method, the liquid phase method, the firing method, or the thermal spraying method.

  The negative electrode active material layer 12 is preferably alloyed with the negative electrode current collector 11 at least at a part of the interface. Specifically, the constituent elements of the negative electrode current collector 11 are diffused in the negative electrode active material layer 12, the constituent elements of the negative electrode active material layer 12 are diffused in the negative electrode current collector 11, or they are mutually diffused at the interface. preferable. This is because the adhesion can be further improved. Note that in this specification, the above-described element diffusion is also included in one form of alloying.

  The negative electrode active material layer 12 may contain silicon alone, may contain an alloy, or may contain a compound, but may have an amorphous phase containing silicon. preferable. This is because the stress due to expansion and contraction can be reduced. The negative electrode active material layer 12 preferably contains oxygen (O) as a constituent element. This is because expansion and contraction of the negative electrode active material layer 12 can be suppressed and stress can be relaxed. At least a part of oxygen contained in the negative electrode active material layer 12 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 12 does not include a film that is formed on the surface of the negative electrode active material layer 12 due to decomposition of the electrolytic solution by charge and discharge. Therefore, when the oxygen content in the negative electrode active material layer 12 is calculated, oxygen contained in this coating is not included.

  The thickness of the negative electrode active material layer 12 is preferably 50 μm or less, and the total thickness of the negative electrode current collector 11 and the negative electrode active material layer 12 is preferably 16 μm or more and 100 μm or less. This is because within this range, stress due to expansion and contraction of the negative electrode active material layer 12 can be relaxed. The thickness of the negative electrode active material layer 12 is the sum of the thickness of the negative electrode active material layer 12 provided on both surfaces when the negative electrode active material layer 12 is provided on both surfaces of the negative electrode current collector 11. is there.

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

  First, the first concavo-convex structure 11A is formed periodically on the metal foil by pressing or the like, and the second concavo-convex structure 11B is formed by etching, blasting, plating, or the like, and the negative electrode current collector 11 is manufactured. . Either the first uneven structure 11A or the second uneven structure 11B may be formed first. Next, the negative electrode active material layer 12 is formed on the negative electrode current collector 11 by a vapor phase method, a liquid phase method, a firing method, a thermal spraying method, coating, or the like. Moreover, you may form into a film combining those 2 or more methods. 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. Note that although the negative electrode active material layer 12 and the negative electrode current collector 11 may be alloyed at the same time when the negative electrode active material layer 12 is formed, the negative electrode active material layer 12 is formed in a vacuum atmosphere after forming the negative electrode active material layer 12. Alternatively, heat treatment may be performed in a non-oxidizing atmosphere to form an alloy. Thereby, the negative electrode 10 shown in FIG. 1 is obtained.

  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. In FIG. 2, the depiction of the first concavo-convex structure 11A and the second concavo-convex structure 11B in the negative electrode current collector 11 is omitted.

  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 metal such as stainless steel or aluminum (Al), for example.

  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 (Ni), 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 (Li) as a positive electrode active material, and a carbon material or the like as necessary. A conductive material and a binder such as polyvinylidene fluoride may be included. As a positive electrode material capable of inserting and extracting lithium, for example, a lithium-containing metal composite oxide represented by a 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 (Co) 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 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 12 expands and contracts greatly with this charge / discharge, the stress is uniformly dispersed by the first concavo-convex structure 11A provided on the negative electrode current collector 11, and the negative concavo-convex structure 11B provides the negative electrode. Since the adhesion between the current collector 11 and the negative electrode active material layer 12 is improved, peeling of the negative electrode active material layer 12 and the like are suppressed, and the current collection property is improved.

  When the negative electrode active material layer 12 is formed by a vapor phase method or the like, for example, as shown in FIG. 3, the negative electrode active material layer 12 has a plurality of columnar primary particles 12A grown in the thickness direction. However, due to the expansion and contraction due to charge and discharge, the primary particles 12A are divided into a plurality of aggregates to form a plurality of secondary particles 12B. In this case, in this secondary battery, the stress is uniformly dispersed by the first uneven structure 11A, and the adhesion between the negative electrode current collector 11 and the negative electrode active material layer 12 is improved by the second uneven structure 11B. Therefore, the variation in the size of the secondary particles 12A is reduced, the average size is smaller than, for example, the period T of the first uneven structure 11A, and the average length RSm of the contour curve elements of the second uneven structure 11B. Bigger than. As a result, the stress is more uniformly dispersed, and peeling of the negative electrode active material layer 12 is suppressed. The average size of the secondary particles 12A is obtained by, for example, observing the surface of the negative electrode active material layer 12 with an SEM (Scanning Electron Microscope) or the like and averaging the diameters of circumscribed circles of the respective secondary particles 12A. It is a thing.

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

  FIG. 4 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. 5 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 35 interposed therebetween, and the outermost peripheral portion is protected by a protective tape 36. In FIG. 5, the depiction of the first uneven structure 11A and the second uneven structure 11B in the negative electrode current collector 11 is omitted.

  The negative electrode 10 has a structure in which a negative electrode active material layer 12 is provided on both surfaces of a negative electrode current collector 11. 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 35 is in a so-called gel state by holding the electrolytic solution in a holding body made of a polymer compound. 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 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 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. 4 and 5 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 for example, by applying heat, the monomer is polymerized to form a polymer compound, and the gel electrolyte 35 is formed. Thereby, the secondary battery shown in FIGS. 4 and 5 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, the first concavo-convex structure 11A is provided on the negative electrode current collector 11 and the second concavo-convex structure 11B is provided on the surface thereof. Stress due to expansion and contraction of the negative electrode active material layer 12 can be uniformly dispersed by the structure 11A, and adhesion between the negative electrode current collector 11 and the negative electrode active material layer 12 can be improved by the second uneven structure 11B. it can. Therefore, the adhesiveness between the negative electrode current collector 11 and the negative electrode active material layer 12 can be increased, and the current collecting property can be improved. Therefore, excellent cycle characteristics can be obtained.

In particular, if the period T of the first concavo-convex structure 11A is 10 μm or more and 100 μm or less, and the size of the second concavo-convex structure 11B is 1.0 μm or more and 5.0 μm or less in the surface roughness Rz _JIS. Alternatively, if the period T of the first concavo-convex structure 11A is set to 5 times or less the thickness d of the negative electrode current collector 11, or the period T of the first concavo-convex structure 11A is set to the first concavo-convex structure 11A. If the maximum roughness height h is 3 times or more, or the average length RSm of the contour curve element of the second uneven structure 11B is made smaller than the period T of the first uneven structure 11A. If so, a higher effect can be obtained.

  Further, if the total thickness of the negative electrode current collector 11 and the negative electrode active material layer 12 is set in the range of 16 μm or more and 100 μm or less, or the thickness of the negative electrode active material layer 12 is set to 50 μm or less. Alternatively, if the negative electrode active material layer 12 contains oxygen as a constituent element and the content thereof is 5 atomic% to 40 atomic%, a higher effect can be obtained.

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

( Experimental Example 1-1)
The negative electrode 10 shown in FIG. 1 was produced. First, a rolled copper foil having a thickness of 20 μm was prepared, and the surface was roughened by wet etching to form the second concavo-convex structure 11B. The surface roughness Rz _JIS was measured and found to be 3.0 μm. Next, the copper foil whose surface was roughened was embossed to form a periodic first uneven structure 11A on the surface. Specifically, a concavo-convex structure was formed on the surface of the transfer roll by a laser, and the first concavo-convex structure 11A was transferred to the copper foil by pressing the copper foil using the transfer roll. The first concavo-convex structure 11A has a shape in which ring-shaped concave portions are periodically formed, and the cycle T is 50 μm. When the prepared negative electrode current collector 11 was cut out by a microtome and observed by SEM, the first uneven structure 11A was transferred to the surface of the copper foil, and the fine second uneven structure 11B was formed on the surface. It was confirmed that it was formed.

  Subsequently, on the surface of the negative electrode current collector 11 on which the first concavo-convex structure 11A and the second concavo-convex structure 11B were formed, silicon was deposited by electron beam evaporation to form a negative electrode active material layer 12 having a thickness of 6 μm. . At that time, oxygen gas was introduced into the atmosphere to adjust the oxygen content in the negative electrode active material layer 12. About the produced negative electrode 10, when the cross section was cut out with the microtome and observed with SEM, a mode that the several primary particle 12A was growing in columnar shape was observed. Moreover, 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 12 was amorphous. Furthermore, when elemental analysis was performed using EDX (energy dispersive X-ray analyzer), the oxygen content in the negative electrode active material layer 12 was 4 atomic%.

As Comparative Example 1-1 with respect to Experimental Example 1-1, a negative electrode was manufactured in the same manner as Experimental Example 1-1 except that only the first uneven structure was formed without forming the second uneven structure. did. As Comparative Example 1-2, a negative electrode was produced in the same manner as in Experimental Example 1-1 except that only the second uneven structure was formed without forming the first uneven structure. As Comparative Example 1-3, except that the first concavo-convex structure and the second concavo-convex structure were not formed, and the rolled copper foil was used as it was as the negative electrode current collector, other than that of Experimental Example 1-1 Thus, a negative electrode was produced.

Next, a coin-type test battery as shown in FIG. 2 was produced using the produced negative electrode 10 of Experimental Example 1-1 and Comparative Examples 1-1 to 1-3. The counter electrode is a lithium metal plate, a porous polypropylene film is used for the separator, and 1 mol of LiPF ₆ is mixed in a solvent in which ethylene carbonate and diethyl carbonate are mixed in a mass ratio of ethylene carbonate: diethyl carbonate = 3: 7 as the electrolyte. A solution dissolved at a concentration of / l was used.

With respect to the produced test batteries of Experimental Example 1-1 and Comparative Examples 1-1 to 1-3, 50 cycles of charge / discharge were performed at a current density of 1 mA / cm ² , and the ratio of the discharge capacity of 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. Further, the test battery of Experimental Example 1-1 was disassembled after 50 cycles of charge and discharge, and the surface state of the negative electrode 10 was observed by SEM. As a result, a plurality of primary particles 12A gathered to form a plurality of secondary particles 12B. When the average size of the secondary particles 12B was measured as described in the embodiment, it was about 30 μm.

As shown in Table 1, according to Experimental Example 1-1 in which the first concavo-convex structure 11A and the second concavo-convex structure 11B were formed on the negative electrode current collector 11, Comparative Example 1 in which only one of them was provided. As compared with Comparative Example 1-3 in which neither -1, 1-2 nor both were provided, the discharge capacity retention rate could be greatly improved. In other words, it was found that the cycle characteristics can be improved by forming the periodic first uneven structure 11A and the second uneven structure 11B on the surface of the negative electrode current collector 11.

( Experimental examples 2-1 to 2-21)
The first period T and the surface roughness Rz _JIS of the second uneven structure 11B of the concavo-convex structure 11A except that were changed as shown in Table 2, other Examples 1-1 Similarly anode 10 And a test battery was prepared. The period T of the first concavo-convex structure 11A was changed within the range of 9 μm to 101 μm, and the surface roughness Rz _JIS of the second concavo-convex structure 11B was changed within the range of 0.9 μm to 5.1 μm. Experimental Example 2-10 is the same as Experimental Example 1-1. For the manufactured test batteries of Experimental Examples 2-1 to 2-21, the discharge capacity retention rate was determined in the same manner as in Experimental Example 1-1. The obtained results are shown in Table 2 and FIG.

As shown in Table 2 and FIG. 6, the discharge capacity retention rate tends to decrease as the period T of the first concavo-convex structure 11A increases, and then decreases. As the surface roughness Rz _JIS was increased, the surface roughness was improved and then decreased. That is, the period T of the first concavo-convex structure 11A is preferably in the range of 10 μm to 100 μm, and the surface roughness Rz _JIS of the second concavo-convex structure 11B is preferably in the range of 1 μm to 5 μm. I understood that.

( Experimental examples 3-1 to 3-7)
Except that the thickness d of the negative electrode current collector 11 and the period T of the first concavo-convex structure 11A were changed as shown in Table 3, the negative electrode 10 and the test battery were the same as in Experimental Example 1-1. Produced. Incidentally, the experimental examples 3-1 to 3-4 are those the thickness d of the negative electrode current collector 11 and 20 [mu] m, and the period T of the first uneven structure 11A was varied in the range of 102μm from 30 [mu] m, Experiment In 3-5 to 3-7, the period T of the first concavo-convex structure 11A is set to 60 μm, and the thickness d of the negative electrode current collector 11 is changed within the range of 11 μm to 40 μm. For the manufactured test batteries of Experimental Examples 3-1 to 3-7, the discharge capacity retention ratio was determined in the same manner as in Experimental Example 1-1. The obtained results are shown in Table 3 and FIG. 7 together with the results of Experimental Example 1-1.

  As shown in Table 3 and FIG. 7, when the ratio T / d of the period T of the first concavo-convex structure 11A to the thickness d of the negative electrode current collector 11 exceeds 5, there is a tendency that the discharge capacity maintenance ratio decreases. It was. That is, it was found that the period T of the first concavo-convex structure 11A is preferably 5 times or less the thickness d of the negative electrode current collector 11.

( Experimental examples 4-1 to 4-10)
Except that the period T of the first concavo-convex structure 11A is 30 μm, and the maximum roughness height h and the thickness of the negative electrode active material layer 12 of the first concavo-convex structure 11A are changed as shown in Table 4. Otherwise, the negative electrode 10 and the test battery were produced in the same manner as in Experimental Example 1-1. In Experimental Examples 4-1 to 4-4, the maximum roughness height h of the first concavo-convex structure 11A is 5 μm, and the ratio T / h of the period T to the maximum roughness height h of the first concavo-convex structure 11A is set. 6 and the thickness of the negative electrode active material layer 12 was changed within a range of 6 μm to 51 μm. In Experimental Examples 4-5 to 4-7, the maximum roughness height h of the first concavo-convex structure 11A was 10 μm. , the ratio T / h of the period T to the maximum roughness height h of the first uneven structure 11A and 3, which the thickness of the anode active material layer 12 was varied in the range of 51μm from 30 [mu] m, experiment In 4-8 to 4-10, the maximum roughness height h of the first uneven structure 11A is 11 μm, and the ratio T / h of the period T to the maximum roughness height h of the first uneven structure 11A is 2.7. The thickness of the negative electrode active material layer 12 is changed within the range of 30 μm to 51 μm. For the manufactured test batteries of Experimental Examples 4-1 to 4-10, the discharge capacity retention ratio was determined in the same manner as in Experimental Example 1-1. The obtained results are shown in Table 4 and FIG.

  As shown in Table 4 and FIG. 8, when the ratio T / h of the period T to the maximum roughness height h of the first concavo-convex structure 11A is smaller than 3, the thickness of the negative electrode active material layer 12 is 50 μm. When the value exceeds 1, the discharge capacity retention rate tends to decrease. That is, the period T of the first concavo-convex structure 11A is preferably at least three times the maximum roughness height h of the first concavo-convex structure 11A, and the thickness of the negative electrode active material layer 12 is preferably 50 μm or less. It turned out to be preferable.

( Experimental examples 5-1 to 5-12)
The average length RSm of contour curve elements of the period T and the second uneven structure 11B of the first uneven structure 11A except that were changed as shown in Table 5 and the other in the same manner as in Experimental Example 1-1 Thus, a negative electrode 10 and a test battery were produced. In Experimental Examples 5-1 to 5-4, the period T of the first concavo-convex structure 11A is set to 30 μm, and the average length RSm of the contour curve element of the second concavo-convex structure 11B is changed within a range of 5 μm to 31 μm. In Experimental Examples 5-5 to 5-8, the period T of the first uneven structure 11A is 60 μm, and the average length RSm of the contour curve elements of the second uneven structure 11B is in the range of 20 to 61 μm. In Experimental Examples 5-9 to 5-12, the period T of the first uneven structure 11A is 100 μm, and the average length RSm of the contour curve element of the second uneven structure 11B is 40 m to 101 μm. It was changed within the range. For the manufactured test batteries of Experimental Examples 5-1 to 5-12, the discharge capacity retention ratio was determined in the same manner as in Experimental Example 1-1. The results obtained are shown in Table 5.

  As shown in Table 5, when the average length RSm of the contour curve element of the second concavo-convex structure 11B is larger than the period T of the first concavo-convex structure 11A, the discharge capacity retention rate tends to decrease. . That is, it was found that it is preferable to make the average length RSm of the contour curve element of the second concavo-convex structure 11B smaller than the cycle T of the first concavo-convex structure 11A.

Further, the test battery of Experimental Example 5-1 was disassembled after 50 cycles of charge and discharge, and the surface state of the negative electrode 10 was observed by SEM. As a result, a plurality of primary particles 12A gathered to form a plurality of secondary particles 12B. When the average size of the secondary particles 12B was measured as described in the embodiment, it was about 10 μm. That is, it was found that the average size of the secondary particles 12B is smaller than the period T of the first concavo-convex structure 11A and larger than the average length RSm of the contour curve elements of the second concavo-convex structure 11B. .

( Experimental examples 6-1 to 6-4)
The thickness of the thickness d and the negative electrode 10 of the anode current collector 11 except that were changed as shown in Table 6, the other is to prepare a negative electrode 10 and a test cell in the same manner as in Experimental Example 1-1. For the manufactured test batteries of Experimental Examples 6-1 to 6-4, the discharge capacity retention ratio was determined in the same manner as in Experimental Example 1-1. The results obtained are shown in Table 6.

  As shown in Table 6, as the thickness d of the negative electrode current collector 11 and the thickness of the negative electrode 10 were increased, the discharge capacity retention rate tended to decrease after being improved. In other words, it was found that the total thickness of the negative electrode current collector 11 and the negative electrode active material layer 12 was preferably 16 μm or more and 100 μm or less.

( Experimental examples 7-1 to 7-5)
Except that the first uneven structure 11A and the second uneven structure 11B were formed on both surfaces of the negative electrode current collector 11, a negative electrode 10 and a test battery were produced in the same manner as in Experimental Example 1-1. At that time, the period T of the first concavo-convex structure 11A and the surface roughness Rz _JIS of the second concavo-convex structure 11B on the surface on the side where the negative electrode active material layer 12 is formed and the opposite surface are shown in Table 7. It was changed as follows. For the produced test batteries of Experimental Examples 7-1 to 7-5, the discharge capacity retention ratio was determined in the same manner as in Experimental Example 1-1. The results obtained are shown in Table 7.

As shown in Table 7, the experimental examples 7-1 to 7-5 also, Examples 1-1 and similar good results were obtained. That is, the first concavo-convex structure 11A and the second concavo-convex structure 11B may be formed on one side or both sides of the negative electrode current collector 11, or the first concavo-convex structure 11A may coincide on both sides. It turns out that it is not necessary.

( Experimental examples 8-1 to 8-4)
The oxygen content in the anode active material layer 12 except that were changed as shown in Table 8, the other is to prepare a negative electrode 10 and the test electrode in the same manner as in Experimental Example 1-1. The oxygen content was controlled by adjusting the amount of oxygen gas introduced when the negative electrode active material layer 12 was formed, and the analysis was performed in the same manner as in Experimental Example 1-1. With respect to the produced test batteries of Experimental Examples 8-1 to 8-4, the discharge capacity retention ratio was determined in the same manner as in Experimental Example 1-1. The obtained results are shown in Table 8 together with the results of Experimental Example 1-1.

  As shown in Table 8, when the oxygen content was increased, the discharge capacity retention rate was improved, and after showing the maximum value, a tendency to decrease was observed. That is, it has been found that excellent effects can be obtained if the oxygen content in the negative electrode active material layer 12 is in the range of 5 atomic% to 40 atomic%.

( Experimental example 9-1)
A test battery was fabricated in the same manner as in Experimental Example 1-1, except that an electrolyte mixed with 4-fluoro-1,3-dioxolan-2-one was used instead of ethylene carbonate. For the manufactured test battery of Experimental Example 9-1, the discharge capacity retention rate was determined in the same manner as in Experimental Example 1-1. The obtained results are shown in Table 9 together with the results of Experimental Example 1-1.

As shown in Table 9, according to Experimental Example 9-1, the discharge capacity retention rate could be further improved as compared with Experimental Example 1-1. That is, it was found that the cycle characteristics can be further improved by using 4-fluoro-1,3-dioxolan-2-one as the electrolytic solution.

( Experimental example 10-1)
First, a rolled copper foil having a thickness of 20 μm was prepared, and the second concavo-convex structure 11B and the first concavo-convex structure 11A were formed in the same manner as in Experimental Example 1-1 to produce the negative electrode current collector 11. The surface roughness Rz _JIS of the second uneven structure 11B was 3.0 μm, and the period T of the first uneven structure 11A was 30 μm. Next, silicon particles having an average particle diameter of 1 μm are used as a negative electrode active material, 90% by mass of the silicon particles and 10% by mass of polyvinylidene fluoride as a binder are mixed using a dispersion medium, and the negative electrode current collector 11 is mixed. After applying to the surface on which the first concavo-convex structure 11A and the second concavo-convex structure 11B were formed, heat treatment was performed at 350 ° C. for 10 hours, and the negative electrode active material layer 12 was formed by pressing to produce the negative electrode 10. . The thickness of the negative electrode active material layer 12 was 6 μm. Further, when the oxygen content in the negative electrode active material layer 12 was examined in the same manner as in Experimental Example 1-1, it was 4 atomic%.

As Comparative Example 10-1 with respect to Experimental Example 10-1, a negative electrode was produced in the same manner as Experimental Example 10-1, except that only the first uneven structure was formed without forming the second uneven structure. did. As Comparative Example 10-2, a negative electrode was produced in the same manner as in Experimental Example 10-1, except that only the second uneven structure was formed without forming the first uneven structure. As Comparative Example 10-3, except that the first concavo-convex structure and the second concavo-convex structure were not formed, and the rolled copper foil was used as it was as the negative electrode current collector, the others were the same as Experimental Example 10-1. Thus, a negative electrode was produced.

Next, a test battery was produced in the same manner as in Experimental Example 1-1 using the produced negative electrode 10 of Experimental Example 10-1 and Comparative Examples 10-1 to 10-3, and the discharge capacity retention rate at the 50th cycle was determined. Asked. Table 10 shows the obtained results.

As shown in Table 10, similarly to Experimental Example 1-1, according to Experimental Example 10-1, the discharge capacity retention rate could be significantly improved as compared with Comparative Example 10-3. That is, it was found that the same result can be obtained even when the negative electrode active material layer 12 is formed by another method.

( Experimental examples 11-1 to 11-6, 12-1 to 12-9, 13-1 to 13-12)
In Experimental Examples 11-1 to 11-6, except that the thickness d of the negative electrode current collector 11 and the period T of the first concavo-convex structure 11A were changed as shown in Table 11, the other examples were the same as in Experimental Example 10- In the same manner as in Example 1, a negative electrode 10 and a test battery were produced.

In Experimental Examples 12-1 to 12-9, other than the experiment , except that the maximum roughness height h of the first uneven structure 11A and the thickness of the negative electrode active material layer 12 were changed as shown in Table 12. A negative electrode 10 and a test battery were produced in the same manner as in Example 10-1.

In Experimental Examples 13-1 to 13-12, except that the period T of the first uneven structure 11A and the average length RSm of the contour curve elements of the second uneven structure 11B were changed as shown in Table 13. Otherwise, the negative electrode 10 and the test battery were produced in the same manner as in Experimental Example 10-1.

That is, in Experimental Examples 11-1 to 11-6, 12-1 to 12-9, and 13-1 to 13-12, the negative electrode active material layer 12 was formed by a firing method, and the conditions of the negative electrode current collector 11 and the negative electrode The thickness of the active material layer 12 is changed as shown in Tables 11-13. The discharge capacity retention rate was determined for the manufactured test batteries of each experimental example in the same manner as in Experimental example 1-1. The obtained results are shown in Tables 11 to 13 together with the results of Experimental Example 10-1.

  As shown in Table 11, when the ratio T / d of the period T of the first concavo-convex structure 11A to the thickness d of the negative electrode current collector 11 exceeded 5, the discharge capacity retention rate tended to decrease. Further, as shown in Table 12, when the ratio T / h of the period T to the maximum roughness height h of the first concavo-convex structure 11A is smaller than 3, the negative electrode active material layer 12 has a thickness of 50 μm. When it exceeded, the tendency for a discharge capacity maintenance factor to fall was seen. Furthermore, as shown in Table 13, when the average length RSm of the contour curve element of the second concavo-convex structure 11B becomes larger than the period T of the first concavo-convex structure 11A, the discharge capacity retention rate tends to decrease. It was.

  That is, even when the negative electrode active material layer 12 is formed by another method, the period T of the first concavo-convex structure 11A is preferably 5 times or less the thickness d of the negative electrode current collector 11, It was found that the period T of the concavo-convex structure 11A is preferably 3 times or more the maximum roughness height h of the first concavo-convex structure 11A, and the thickness of the negative electrode active material layer 12 is preferably 50 μm or less. . Moreover, it turned out that it is more preferable to make the average length RSm of the contour curve element of the 2nd uneven structure 11B smaller than the period T of the 1st uneven structure 11A.

( Experimental examples 14-1 to 14-4)
A negative electrode 10 and a test electrode were produced in the same manner as in Experimental Example 10-1, except that the oxygen content in the negative electrode active material layer 12 was changed as shown in Table 14. The oxygen content was adjusted by changing the oxygen content in the negative electrode active material used when forming the negative electrode active material layer 12, and the analysis was performed in the same manner as in Experimental Example 1-1. With respect to the manufactured test batteries of Experimental Examples 14-1 to 14-4, the discharge capacity retention ratio was determined in the same manner as in Experimental Example 1-1. The obtained results are shown in Table 14 together with the results of Experimental Example 10-1.

  As shown in Table 14, when the oxygen content was increased, the discharge capacity retention rate was improved, and after showing the maximum value, a tendency to decrease was observed. That is, even when the negative electrode active material layer 12 is formed by other methods, excellent effects can be obtained if the oxygen content in the negative electrode active material layer 12 is in the range of 5 atomic% to 40 atomic%. It turns out that it is obtained.

  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 embodiment and examples, as shown in FIG. 1, the case where the groove-shaped concave portions are periodically provided as the first concave-convex structure 11 </ b> A has been shown. The concave portions and the convex portions may be alternately formed in a wave shape, or the concave portions and the convex portions having the same size may be alternately formed. Also good.

  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 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 schematic sectional drawing explaining the state of the negative electrode after charging / discharging. It is a disassembled perspective view showing the structure of the other secondary battery using the negative electrode shown in FIG. FIG. 5 is a cross-sectional view illustrating a structure taken along line II of the secondary battery illustrated in FIG. 4. And the period T of the first uneven structure, and the surface roughness Rz _JIS of the second relief structure is a characteristic diagram showing the relationship between the discharge capacity retention ratio. It is a characteristic view showing the relationship between the ratio T / d of the period T of the 1st uneven structure with respect to the thickness d of a negative electrode collector, and a discharge capacity maintenance factor. It is a characteristic view showing the relationship between the ratio T / h of the period T to the maximum roughness height h of the first uneven structure, the thickness of the negative electrode active material layer, and the discharge capacity retention rate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Negative electrode, 11 ... Negative electrode collector, 11A ... 1st uneven structure, 11B ... 2nd uneven structure, 12 ... Negative electrode active material layer, 12A ... Primary particle, 12B ... Secondary particle, 21 ... Exterior cup , 22 ... outer can, 23, 33 ... positive electrode, 23A, 33A ... positive electrode current collector, 23B, 33B ... positive electrode active material layer, 24, 34 ... separator, 25 ... gasket, 31, 32 ... lead, 30 ... electrode winding Rotating body 35 ... Electrolyte 36 ... Protective tape 41 ... Exterior member 42 ... Adhesion film

Claims (8)

The anode current collector, the negative electrode active material layer containing silicon (Si) is provided et al is as a constituent element,
The negative electrode current collector, possess a periodic first relief structure, and a second concave-convex structure provided on a surface of the first relief structure,
The period of the first uneven structure is not less than 10 μm and not more than 100 μm, is not more than 5 times the thickness of the negative electrode current collector, and is not less than 3 times the maximum roughness height of the first uneven structure. Yes,
The size of the second concavo-convex structure is 1.0 μm or more and 5.0 μm or less in terms of surface roughness Rz _JIS , and the average length RSm of the contour curve element is smaller than the period of the first concavo-convex structure. ,
The negative electrode wherein the total thickness of the negative electrode current collector and the negative electrode active material layer is 16 μm or more and 100 μm or less . The negative electrode according to claim 1 , wherein the negative electrode active material layer has a thickness of 50 μm or less. 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%. Bei example a cathode, an anode,
In the negative electrode, a negative electrode current collector is provided with a negative electrode active material layer containing silicon (Si) as a constituent element,
The negative electrode current collector, possess a periodic first relief structure, and a second concave-convex structure provided on a surface of the first relief structure,
The period of the first uneven structure is not less than 10 μm and not more than 100 μm, is not more than 5 times the thickness of the negative electrode current collector, and is not less than 3 times the maximum roughness height of the first uneven structure. Yes,
The size of the second concavo-convex structure is 1.0 μm or more and 5.0 μm or less in terms of surface roughness Rz _JIS , and the average length RSm of the contour curve element is smaller than the period of the first concavo-convex structure. ,
A battery in which the total thickness of the negative electrode current collector and the negative electrode active material layer is 16 μm or more and 100 μm or less . The battery according to claim 4 , wherein the negative electrode active material layer has a thickness of 50 μm or less. The negative electrode active material layer has a plurality of secondary particles formed by aggregating a plurality of primary particles,
The average size of the secondary particles is smaller than the period of the first relief structure, the greater than average length RSm of contour curve elements of the second relief structure, the battery of claim 4, wherein. The battery according to claim 4 , wherein the negative electrode active material layer contains oxygen as a constituent element, and the content thereof is 5 atomic% to 40 atomic%. The battery according to claim 4 , wherein the electrolyte includes a carbonic acid ester derivative having a halogen atom.

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