WO2023286579A1 - 二次電池用負極および二次電池 - Google Patents

二次電池用負極および二次電池 Download PDF

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WO2023286579A1
WO2023286579A1 PCT/JP2022/025504 JP2022025504W WO2023286579A1 WO 2023286579 A1 WO2023286579 A1 WO 2023286579A1 JP 2022025504 W JP2022025504 W JP 2022025504W WO 2023286579 A1 WO2023286579 A1 WO 2023286579A1
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negative electrode
portions
secondary battery
average fiber
fiber diameter
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French (fr)
Japanese (ja)
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陽祐 古池
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Murata Manufacturing Co Ltd
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Murata Manufacturing Co Ltd
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Priority to JP2023535212A priority Critical patent/JP7718488B2/ja
Priority to CN202280048811.1A priority patent/CN117616595A/zh
Publication of WO2023286579A1 publication Critical patent/WO2023286579A1/ja
Priority to US18/411,508 priority patent/US20240154101A1/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/44—Fibrous material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • This technology relates to negative electrodes for secondary batteries and secondary batteries.
  • the secondary battery includes a positive electrode, a negative electrode, and an electrolyte, and various studies have been made on the configuration of the secondary battery.
  • a carbonaceous porous conductive substrate, a conductive agent (such as carbon nanotubes), and an active material (such as silicon) are used as materials for forming the negative electrode of a lithium ion secondary battery.
  • the porosity (porosity) of is specified (see, for example, Patent Document 1).
  • a conductive base material such as carbon fiber coated with silicon or the like is used as a negative electrode forming material for a lithium ion secondary battery, and the content (weight ratio) of silicon in the negative electrode is specified ( For example, see Patent Document 2.).
  • Copper current collectors and porous silicon having a three-dimensional network structure coated with a conductive substance such as a carbon material are used as materials for forming negative electrodes for lithium ion secondary batteries, and the porous silicon is defined (see, for example, Patent Document 3).
  • the silicon content, the carbon material content, and the porosity each have a gradient distribution (see Patent Document 4, for example).
  • JP 2007-335283 A Japanese translation of PCT publication No. 2015-531977 JP 2012-084521 A Japanese Patent Publication No. 2013-504168
  • a negative electrode for a secondary battery includes a plurality of fiber portions and a plurality of coating portions, and has a plurality of voids.
  • the plurality of fiber portions are connected to each other to form a three-dimensional network structure having a plurality of voids, and each of the plurality of fiber portions contains carbon as a constituent element.
  • Each of the plurality of covering portions covers the surface of each of the plurality of fiber portions and contains silicon as a constituent element.
  • the average fiber diameter of the plurality of fiber portions when divided into the first portion and the second portion in the thickness direction, the plurality of covering portions with respect to the sum of the weight of the plurality of fiber portions and the weight of the plurality of covering portions and at least one of the porosity is different between the first portion and the second portion.
  • a secondary battery includes a positive electrode, a negative electrode including a plurality of fiber portions and a plurality of coating portions and having a plurality of voids, a separator disposed between the positive electrode and the negative electrode, an electrolytic and a liquid.
  • the plurality of fiber portions are connected to each other to form a three-dimensional network structure having a plurality of voids, and each of the plurality of fiber portions contains carbon as a constituent element.
  • Each of the plurality of covering portions covers the surface of each of the plurality of fiber portions and contains silicon as a constituent element.
  • a plurality of fibers are formed. At least one of the average fiber diameter of the portion, the ratio of the weight of the plurality of covering portions to the sum of the weight of the plurality of fiber portions and the weight of the plurality of covering portions, and the porosity of the first portion and the second portion and differ from each other.
  • the secondary battery negative electrode includes the plurality of fiber portions and the plurality of covering portions and has a plurality of voids. and at least one of the above-mentioned average fiber diameter, proportion and porosity is different between the first portion and the second portion, resulting in excellent initial capacity characteristics, excellent loading characteristics and excellent cycling characteristics. can be obtained.
  • FIG. 2 is a cross-sectional view showing an enlarged configuration of each of the carbon fiber portion and the coating portion shown in FIG. 1;
  • FIG. FIG. 3 is another schematic diagram showing the configuration of the negative electrode for a secondary battery. It is a perspective view showing composition of a secondary battery in one embodiment of this art.
  • 5 is an enlarged sectional view showing the configuration of the battery element shown in FIG. 4;
  • FIG. 10 is a cross-sectional view showing the configuration of a negative electrode for a secondary battery of Modification 2.
  • FIG. FIG. 10 is a schematic diagram showing the configuration of a negative electrode for a secondary battery of Modification 5;
  • FIG. 3 is a block diagram showing the configuration of an application example of a secondary battery;
  • Negative electrode for secondary battery 1-1 Configuration 1-2. Configuration conditions 1-3. Manufacturing method 1-4. Action and effect 2 . Secondary Battery 2-1. Configuration 2-2. Operation 2-3. Manufacturing method 2-4. Action and effect 3. Modification 4. Applications of secondary batteries
  • Negative Electrode for Secondary Battery First, a negative electrode for a secondary battery (hereinafter simply referred to as “negative electrode”) according to an embodiment of the present technology will be described.
  • This negative electrode is used in a secondary battery, which is an electrochemical device.
  • the negative electrode may be used in electrochemical devices other than secondary batteries.
  • the type of other electrochemical device is not particularly limited, but is specifically a capacitor or the like.
  • the negative electrode absorbs and releases an electrode reactant during an electrode reaction in an electrochemical device such as the secondary battery described above.
  • the type of electrode reactant is not particularly limited, but specifically light metals such as alkali metals and alkaline earth metals.
  • Alkali metals include lithium, sodium and potassium, and alkaline earth metals include beryllium, magnesium and calcium.
  • FIG. 1 schematically shows the configuration of a negative electrode 10, which is an example of a negative electrode.
  • FIG. 2 is an enlarged cross-sectional configuration of each of the carbon fiber portion 1 and the covering portion 2 shown in FIG.
  • FIG. 1 shows only a part of the negative electrode 10, and FIG.
  • this negative electrode 10 includes a plurality of carbon fiber portions 1 and a plurality of coating portions 2, and has a plurality of voids 10G. That is, since the negative electrode 10 does not include a current collector such as a metal foil (hereinafter referred to as a "metal current collector”), it is a so-called metal current collector-less electrode.
  • a current collector such as a metal foil (hereinafter referred to as a "metal current collector")
  • the plurality of carbon fiber portions 1 are, as shown in FIG. 1, a plurality of fiber portions having an average fiber diameter AD, and each of the plurality of carbon fiber portions 1 has a fiber diameter have D.
  • the plurality of carbon fiber portions 1 are connected to each other to form a three-dimensional mesh structure having the above-described plurality of voids 10G.
  • FIG. 1 shows a case where each of the plurality of carbon fiber portions 1 is linear in order to simplify the illustration.
  • the state (shape) of each of the plurality of carbon fiber portions 1 is not particularly limited, it is not limited to a linear shape, and may be curved, branched, or in a state in which two or more of them are mixed. good.
  • the plurality of carbon fiber portions 1 are connected to each other to form a three-dimensional network structure, and more specifically, are randomly entangled with each other.
  • the plurality of carbon fiber portions 1 may be bonded to each other via a carbide (not shown) such as a polymer compound.
  • the plurality of carbon fiber portions 1 have a plurality of connection points, and the carbon fiber portions 1 are electrically connected to each other at the connection points.
  • each of the plurality of carbon fiber portions 1 contains carbon as a constituent element, it contains a so-called carbon-containing material.
  • This carbon-containing material is a general term for materials containing carbon as a constituent element.
  • the plurality of carbon fiber portions 1 contain carbon paper. This is because the plurality of carbon fiber portions 1 are sufficiently connected to each other and the average fiber diameter AD is sufficiently large, so that a sufficient conductive network (three-dimensional network structure) is formed.
  • the plurality of carbon fiber portions 1 may be a material in which a plurality of fibrous carbon materials having the above average fiber diameter AD are processed to form a three-dimensional network structure.
  • the type of fibrous carbon material is not particularly limited, but specific examples include vapor grown carbon fiber (VGCF), carbon fiber (CF), carbon nanofiber (CNF), and the like.
  • the type of fibrous carbon material may be carbon nanotube (CNT).
  • the carbon nanotube may be a single-wall carbon nanotube (single-wall carbon nanotube (SWCNT)) or a multi-wall carbon nanotube (multi-wall carbon nanotube (MWCNT)) such as a double-wall carbon nanotube (double-wall carbon nanotube (DWCNT)). good.
  • a predetermined condition is satisfied for the average fiber diameter AD (nm) of the plurality of carbon fiber portions 1. The details of this predetermined condition will be described later.
  • Each of the plurality of covering portions 2 covers the surface of each of the plurality of carbon fiber portions 1 as shown in FIG. 1, and has a thickness T1 as shown in FIG.
  • the covering portion 2 may cover the entire surface of the carbon fiber portion 1, or may cover only a part of the surface of the carbon fiber portion 1. In the latter case, a plurality of covering portions 2 may cover the surface of the carbon fiber portion 1 at a plurality of locations separated from each other.
  • FIG. 1 shows a case in which the covering portion 2 covers the entire surface of the carbon fiber portion 1 in order to simplify the illustration.
  • each of the plurality of covering portions 2 contains silicon as a constituent element, it contains a so-called silicon-containing material. This is because silicon has an excellent ability to absorb and desorb electrode reactants, so that a high energy density can be obtained.
  • the silicon-containing material is a general term for materials containing silicon as a constituent element. Therefore, the silicon-containing material may be a simple substance of silicon, a silicon alloy, a silicon compound, a mixture of two or more of them, or a material containing one or more of these phases. It's okay. However, the simple substance of silicon may contain trace amounts of impurities. That is, the purity of simple silicon may not be 100%. These impurities include impurities that are unintentionally included in the manufacturing process of elemental silicon and oxides that are unintentionally formed due to oxygen in the atmosphere. The content of impurities in simple silicon is preferably as small as possible, more preferably 5% by weight or less.
  • the silicon alloy contains, as constituent elements other than silicon, any one of metal elements such as tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony and chromium, or Contains two or more.
  • the silicon compound contains one or more of nonmetallic elements such as carbon and oxygen as constituent elements other than silicon.
  • the silicon compound may further contain, as constituent elements other than silicon, one or more of the series of metal elements described with respect to the silicon alloy.
  • silicon alloys are Mg2Si , Ni2Si , TiSi2, MoSi2 , CoSi2, NiSi2 , CaSi2 , CrSi2 , Cu5Si , FeSi2 , MnSi2 , NbSi2 , TaSi2 , VSi 2 , WSi2 , ZnSi2 and SiC.
  • the composition of the silicon alloy (mixing ratio of silicon and metal elements) can be changed arbitrarily.
  • silicon compounds include SiB 4 , SiB 6 , Si 3 N 4 , Si 2 N 2 O, SiO v (0 ⁇ v ⁇ 2) and LiSiO.
  • the range of v may be, for example, 0.2 ⁇ v ⁇ 1.4.
  • the silicon-containing material is preferably silicon alone. This is because a higher energy density can be obtained.
  • the content of silicon in each of the plurality of coating portions 2, that is, the content (purity) of silicon in the silicon-containing material is not particularly limited, but is preferably 80% by weight or more. % to 100% by weight. This is because a significantly high energy density can be obtained.
  • the coating layer contains one or more of conductive materials such as carbon-containing materials and metal materials. This is because the conductivity of the negative electrode 10 is further improved. Details regarding the carbon-containing material are given above.
  • the type of metal material is not particularly limited.
  • a silane coupling agent When forming this coating layer, a silane coupling agent, a polymer-based material, and the like are used. This is to allow the surface of the covering portion 2 to be sufficiently covered with the covering layer. By sufficiently covering the surface of the covering portion 2 with the covering layer, the decomposition reaction of the electrolytic solution on the surface of the covering portion 2 containing the silicon-containing material is suppressed.
  • the weight ratio MA (% by weight), which is the ratio of the weight M2 of the plurality of covering portions 2 to the sum of the weight M1 of the plurality of carbon fiber portions 1 and the weight M2 of the plurality of covering portions 2
  • the negative electrode 10 has a three-dimensional network structure formed by a plurality of carbon fiber portions 1, it has a plurality of voids 10G.
  • a predetermined condition is satisfied for the porosity R (% by volume) determined based on the plurality of voids 10G. The details of this predetermined condition will be described later.
  • the negative electrode 10 may further contain one or more of other materials.
  • the type of other material is not particularly limited, but specifically, it is a binder and the like. This is because the plurality of carbon fiber portions 1 and the plurality of covering portions 2 are strongly connected to each other via the binder, so that a strong conductive network is formed.
  • This binder contains one or more of polymer compounds, specific examples of which are polyimide, polyvinylidene fluoride, polyacrylic acid, styrene-butadiene rubber, and carboxymethyl cellulose. and so on.
  • FIG. 3 schematically shows another configuration of the negative electrode 10.
  • FIG. 3 unlike FIG. 1, the entire negative electrode 10 is shown.
  • the negative electrode 10 has a substantially plate-like or sheet-like structure, and is therefore thick. This thickness is the dimension in the vertical direction (thickness direction H) in FIG.
  • the three types of physical property values satisfy predetermined conditions.
  • the negative electrode 10 is bisected in the thickness direction H into the lower portion 10X (first portion) and the upper portion 10Y (second portion)
  • One or more of the ratios R are different between the lower part 10X and the upper part 10Y.
  • a dashed line is shown at the boundary between the lower part 10X and the upper part 10Y so that the lower part 10X and the upper part 10Y can be easily distinguished from each other.
  • the average fiber diameter AD may be different between the lower portion 10X and the upper portion 10Y.
  • the weight ratio MA may be different between the lower portion 10X and the upper portion 10Y.
  • the porosity R may be different between the lower part 10X and the upper part 10Y.
  • any two or more of the average fiber diameter AD, the weight ratio MA, and the porosity R may be different from each other, or the average fiber diameter AD, the weight All of the proportion MA and porosity R may be different from each other.
  • the change tendency of the average fiber diameter AD is not particularly limited. Therefore, the average fiber diameter AD may change intermittently in the thickness direction H, or may change continuously in the thickness direction H.
  • the weight ratio MA when the weight ratio MA is different between the lower portion 10X and the upper portion 10Y, the weight ratio MA may intermittently change in the thickness direction H, or the thickness The direction H may change continuously.
  • the porosity R when the porosity R is different between the lower portion 10X and the upper portion 10Y, the porosity R may intermittently change in the thickness direction H, or the thickness The direction H may change continuously.
  • the lower part 10X and the upper part 10Y may be separated from each other, or may be integrated with each other.
  • the negative electrode 10 has a two-layer structure. (target) interface exists.
  • the negative electrode 10 has a single-layer structure. No physical interface exists.
  • Average fiber diameter AD Average fiber diameter AD
  • details regarding the average fiber diameter AD are as described below.
  • the plurality of carbon fiber portions 1 have an average fiber diameter AD as described above, and the negative electrode 10 includes a lower portion 10X and an upper portion 10Y as shown in FIG. Accordingly, the plurality of carbon fiber portions 1 in the lower portion 10X have an average fiber diameter ADX, and the plurality of carbon fiber portions 1 in the upper portion 10Y have an average fiber diameter ADY.
  • the average fiber diameters ADX and ADY are different from each other.
  • the reason why the average fiber diameters ADX and ADY are different from each other is that the electrode reactant can easily move through the plurality of gaps 10G during the electrode reaction, and the electrode reaction can proceed smoothly even if the electrode reaction is repeated. This is because it becomes easier. In this case, even if the current value during the electrode reaction increases, the electrode reactant can move smoothly.
  • the procedure for calculating the average fiber diameter ADX is as described below. First, after recovering the negative electrode 10, the negative electrode 10 is washed using a washing solvent such as dimethyl carbonate. In addition, when the secondary battery provided with the negative electrode 10 is obtained, the negative electrode 10 is recovered by disassembling the secondary battery. Subsequently, the cross section of the negative electrode 10 is exposed by cutting the negative electrode 10 using an ion milling device or the like.
  • a scanning electron microscope (SEM) or a transmission electron microscope (TEM) is used to observe the cross section of the lower part 10X to acquire the observation result (observation image) of the cross section.
  • SEM scanning electron microscope
  • TEM transmission electron microscope
  • the fiber diameter D of each of the 50 carbon fiber portions 1 is measured. Finally, by calculating the average value of the fiber diameters D of 50 pieces, the average fiber diameter ADX is obtained.
  • the procedure for calculating the average fiber diameter ADY is the same as the procedure for calculating the average fiber diameter ADX described above, except that the cross section of the upper portion 10Y is observed instead of the cross section of the lower portion 10X.
  • the average fiber diameter ADX may be larger than the average fiber diameter ADY, or may be smaller than the average fiber diameter ADY.
  • the definition when the average fiber diameter ADX is larger than the average fiber diameter ADY is as explained below.
  • That the average fiber diameter ADX is larger than the average fiber diameter ADY means that when each of the 10 average fiber diameters ADX and the 10 average fiber diameters ADY is calculated, any of the 10 average fiber diameters ADX This means that each of the ten average fiber diameters ADY is larger than the average fiber diameter ADY. As a result, the minimum value among the ten average fiber diameters ADX is larger than the maximum value among the ten average fiber diameters ADY. Conversely, when an arbitrary one average fiber diameter ADX out of ten average fiber diameters ADX is smaller than an arbitrary one average fiber diameter ADY out of ten average fiber diameters ADY Therefore, the average fiber diameter ADX is not larger than the average fiber diameter ADY.
  • the average fiber diameter ADX is larger than the average fiber diameter ADY because This is to positively eliminate a configuration in which the average fiber diameter ADX accidentally becomes larger than the average fiber diameter ADY due to manufacturing factors of the negative electrode 10 or the like.
  • the average fiber diameter ADX calculated at an arbitrary location in the lower portion 10X is larger than the average fiber diameter ADY calculated at an arbitrary location in the upper portion 10Y, the lower portion If the average fiber diameter ADX calculated at another location in the upper part 10Y is smaller than the average fiber diameter ADY calculated at another location in the upper part 10Y, the average fiber diameter ADX is the average fiber diameter It should not be larger than the diameter ADY.
  • the average fiber diameter ADX is higher than the average fiber diameter ADY calculated at any place in the upper part 10Y. If it is larger, it means that the average fiber diameter ADX is larger than the average fiber diameter ADY.
  • the definition of the case where the average fiber diameter ADX is smaller than the average fiber diameter ADY is the case where the average fiber diameter ADX is larger than the average fiber diameter ADY, except that the magnitude relationship is reversed. Same as definition.
  • the average fiber diameter ADX is smaller than the average fiber diameter ADY means that when each of the 10 average fiber diameter ADX and the 10 average fiber diameter ADY is calculated, the 10 average fiber diameter ADX is smaller than each of the 10 average fiber diameters ADY. Thereby, the maximum value among the ten average fiber diameters ADX is smaller than the minimum value among the ten average fiber diameters ADY.
  • dividing the negative electrode 10 into two equal parts in the thickness direction H into the lower part 10X and the upper part 10Y means that the negative electrode 10 is divided into two equal parts in the direction in which the positive electrode and the negative electrode 10 face each other with the separator interposed therebetween.
  • the lower portion 10X is positioned closer to the separator, and the upper portion 10Y is positioned farther from the separator.
  • the average fiber diameter AD is smaller in the lower part 10X than in the upper part 10Y, it is preferable that the average fiber diameter ADX be smaller than the average fiber diameter ADY. This is because the electrode reactant can move more easily, and the electrode reaction tends to proceed more smoothly even if the electrode reaction is repeated.
  • the ratio of the average fiber diameter ADX to the average fiber diameter ADY is not particularly limited. It is preferably 0.0003 to 0.5 times the fiber diameter ADY. This is because the difference between the average fiber diameters ADX and ADY becomes sufficiently large, so that the electrode reactant can easily move, and the electrode reaction can proceed sufficiently easily even if the electrode reaction is repeated.
  • the average fiber diameter AD of the entire negative electrode 10 is not particularly limited, it is preferably from 10 nm to 12000 nm. This is because the fiber diameter D is sufficiently large in the plurality of carbon fiber portions 1 that are the main portion of the negative electrode 10 . As a result, a sufficient conductive network (three-dimensional network structure) is formed inside the negative electrode 10, so that the conductivity of the negative electrode 10 is improved.
  • each of the average fiber diameters ADX and ADY is not particularly limited as long as the average fiber diameters ADX and ADY are different from each other.
  • the average fiber diameter ADX is preferably 5 nm to 8000 nm, and the average fiber diameter ADY is preferably 100 nm to 16000 nm. . Since the difference between the average fiber diameters ADX and ADY is sufficiently large, the electrode reactant is sufficiently easily moved, and even if the electrode reaction is repeated, the electrode reaction is sufficiently easily progressed.
  • Weight ratio MA Further, details regarding the weight ratio MA are as described below.
  • the negative electrode 10 has a weight ratio MA as described above, and has a lower portion 10X and an upper portion 10Y as shown in FIG. Accordingly, the lower portion 10X has a weight ratio MAX and the upper portion 10Y has a weight ratio MAY, so the weight ratios MAX and MAY are different from each other.
  • weight ratios MAX and MAY are different from each other is that during the electrode reaction, the expansion and contraction of the negative electrode 10 is suppressed by the carbon component (plurality of carbon fiber portions 1), while the silicon component (plurality of coating portions 2) expands the electrode. This is because the reactants are more likely to be occluded and released.
  • the procedure for calculating the weight ratio MAX is as described below. First, after recovering the negative electrode 10, the negative electrode 10 is washed using a washing solvent such as dimethyl carbonate. Subsequently, by sampling the lower part 10X from the negative electrode 10, a sample for analysis is obtained. Subsequently, the weights M1 and M2 are determined by analyzing the sample using thermogravimetric differential thermal analysis (TG-DTA). Any TG-DTA device can be used to analyze the sample.
  • TG-DTA thermogravimetric differential thermal analysis
  • the weight loss when the heating temperature is increased to about 450°C becomes the weight of the electrolyte and the binder, and the heating temperature is increased from about 450°C to about 1350°C.
  • the amount of weight reduction when the pressure is applied becomes the weight (weight M1) of the carbon component (plurality of carbon fiber portions 1).
  • the weight of the residual component becomes the weight (weight M2) of the silicon component (plurality of coating portions 2).
  • the temperature (approximately 450°C) at which the amount of weight loss caused by the electrolytic solution or the like is detected may vary depending on the type of binder. Specifically, when the binder is polyvinylidene fluoride, the vanishing temperature is approximately 460° C., assuming that the minimum value of the differential curve of DTA is the vanishing temperature.
  • the weight ratio MAX is calculated based on the above formula.
  • the procedure for calculating the weight percentage MAY is the same as the procedure for calculating the weight percentage MAX described above, except that the upper portion 10Y is analyzed instead of the lower portion 10X.
  • the weight percentage MAX may be greater than the weight percentage MAY or may be less than the weight percentage MAY.
  • the definition of the magnitude relationship between the weight ratios MAX and MAY is the same as the definition of the magnitude relationship between the average fiber diameters ADX and ADY described above.
  • any of the weight ratio MAX of 10 pieces is determined to be greater than the weight ratio MAX of 10 pieces. It means that each of the 10 weight percentages MAY is larger than the other. As a result, the minimum value among the 10 weight ratios MAX is larger than the maximum value among the 10 weight ratios MAY.
  • the definition when the weight ratio MAX is smaller than the weight ratio MAY is the same as the definition when the weight ratio MAX is larger than the weight ratio MAY, except that the magnitude relationship is reversed. be.
  • the weight ratio MAX is smaller than the weight ratio MAY means that when the weight ratio MAX of 10 pieces and the weight ratio MAY of 10 pieces are calculated, all of the weight ratio MAX of 10 pieces is 10 It means that each of the weight percentages MAY is smaller. As a result, the maximum value among the 10 weight ratios MAX is smaller than the minimum value among the 10 weight ratios MAY.
  • weight ratio MAX is greater in the lower portion 10X than in the upper portion 10Y, so the weight ratio MAX is preferably greater than the weight percentage MAY. This is because the expansion and contraction of the negative electrode 10 is more suppressed, and the electrode reactant is more easily occluded and released.
  • the weight ratio MA of the entire negative electrode 10 is not particularly limited, it is preferably 40% by weight to 80% by weight. This is because the expansion and contraction of the negative electrode 10 is sufficiently suppressed, and the electrode reactant is easily absorbed and released sufficiently.
  • the weight ratios MAX and MAY are not particularly limited.
  • the weight ratio MAX is preferably 42% to 88% by weight, and the weight ratio MAY is preferably 12% to 78% by weight.
  • the difference between the weight ratios MAX and MY is sufficiently large, so that expansion and contraction of the negative electrode 10 is sufficiently suppressed, and the electrode reactant is easily absorbed and released sufficiently.
  • the negative electrode 10 has a porosity R as described above, and has a lower portion 10X and an upper portion 10Y as shown in FIG. Accordingly, the lower portion 10X has a porosity RX and the upper portion 10Y has a porosity RY, so the porosities RX and RY are different from each other.
  • the reason why the porosities RX and RY are different from each other is that the distribution of the plurality of gaps 10G is used during the electrode reaction to facilitate movement of the electrode reactant, and the electrode reaction proceeds smoothly even if the electrode reaction is repeated. This is because it becomes easier to In this case, even if the current value during the electrode reaction increases, the electrode reactant can move smoothly.
  • the porosity RX may be larger than the porosity RY, or may be smaller than the porosity RY.
  • the definition of the magnitude relation between the porosities RX and RY is the same as the definition of the magnitude relation between the average fiber diameters ADX and ADY described above.
  • any of the 10 porosities RX is larger.
  • the minimum value among the 10 porosities RX is larger than the maximum value among the 10 porosities RY.
  • the definition when the porosity RX is smaller than the porosity RY is the same as the definition when the porosity RX is larger than the porosity RY, except that the magnitude relationship is reversed. be.
  • the porosity RX is smaller than the porosity RY means that when each of the 10 porosities RX and 10 porosities RY is calculated, all of the 10 porosities RX are 10 This means that it is smaller than each of the individual porosities RY. As a result, the maximum value among the 10 porosities RX is smaller than the minimum value among the 10 porosities RY.
  • the reason why the porosity RX is smaller than the porosity RY is the manufacturing of the negative electrode 10. This is to positively exclude a configuration in which the porosity RX is accidentally smaller than the porosity RY due to the above factors.
  • porosity RX and RY Suitable size relationship between porosities RX and RY
  • the porosity R is greater in the upper portion 10Y than in the lower portion 10X, so the porosity RY is preferably larger than the porosity RX. This is because the electrode reactant can move more easily, and the electrode reaction tends to proceed more smoothly even if the electrode reaction is repeated.
  • the ratio of the porosity RY to the porosity RX is not particularly limited. It is preferably 1 to 4.5 times. This is because the difference between the porosities RX and RY becomes sufficiently large, so that the electrode reactant can move sufficiently easily, and the electrode reaction can proceed sufficiently easily even if the electrode reaction is repeated.
  • the overall porosity R of the negative electrode 10 is not particularly limited, it is preferably 40% by volume to 70% by volume. This is because the electrode reactant can move sufficiently easily, and the electrode reaction can proceed sufficiently easily even if the electrode reaction is repeated.
  • the porosities RX and RY are not particularly limited as long as the porosities RX and RY are different from each other. Among them, when the porosity RY is higher than the porosity RX, the porosity RX is preferably 20% to 67% by volume, and the porosity RY is preferably 42% to 90% by volume. Preferably. This is because the difference between the porosities RX and RY becomes sufficiently large, so that the electrode reactant can move sufficiently easily, and the electrode reaction can proceed sufficiently easily even if the electrode reaction is repeated.
  • one or more of the average fiber diameter AD, the weight ratio MA, and the porosity R are different between the lower portion 10X and the upper portion 10Y.
  • one or both of the average fiber length and the average curvature may be different between the lower portion 10X and the upper portion 10Y.
  • the average fiber length is the average value of the fiber lengths of the plurality of carbon fiber portions 1
  • the average curvature is the average value of the curvature of the plurality of carbon fiber portions 1.
  • the average thickness AT1 of the plurality of covering portions 2 is not particularly limited, but is preferably from 1 nm to 3000 nm. This is because the coating amount of the surface of the carbon fiber portion 1 by the coating portion 2 is sufficiently large, so that the conductivity of the negative electrode 10 is ensured and a sufficient energy density can be obtained in the negative electrode 10 .
  • This negative electrode 10 is manufactured by the procedure described below.
  • a plurality of fibrous carbon materials (average fiber diameter ADX) are prepared as materials for forming the lower portion 10X. Details regarding the plurality of fibrous carbon materials are as described above.
  • a silicon-containing material is deposited on each surface of the plurality of fibrous carbon materials using a vapor phase method.
  • the type of the vapor phase method is not particularly limited, but specifically, one or more of vacuum deposition, chemical vapor deposition (CVD), sputtering, and the like.
  • the covering portion 2 is formed on the surface of each of the plurality of fibrous carbon materials, so that the surface of each of the plurality of fibrous carbon materials is covered with the covering portion 2 (weight ratio MAX).
  • the coating portion 2 is formed on the surface of each of the plurality of fibrous carbon materials (weight ratio MAY ).
  • the lower portion 10X ( A porosity RX) is formed.
  • the upper portion 10Y (porosity RY) including a plurality of carbon fiber portions 1 and a plurality of covering portions 2 is formed.
  • This negative electrode 10 is assembled.
  • This negative electrode 10 includes a lower portion 10X and an upper portion 10Y that are physically separate from each other, and thus has a two-layer structure.
  • the negative electrode 10 is pressed using a pressing machine or the like, and then the negative electrode 10 is fired.
  • the porosities RX and RY can be adjusted by changing the press pressure.
  • the firing temperature can be set arbitrarily.
  • the negative electrode 10 including a plurality of carbon fiber portions 1 and a plurality of coating portions 2 and having a plurality of voids 10G is completed.
  • the average fiber diameter AD, the weight ratio MA, and the porosity R can be adjusted according to the average fiber diameters ADX, ADY, the weight ratios MAX, MAY, and the porosity RX, RY, respectively.
  • Step of forming a plurality of covering portions Subsequently, the silicon-containing material powder is introduced into the solvent. As a result, the powder of the silicon-containing material is dispersed in the solvent to prepare a dispersion.
  • This solvent may be an aqueous solvent or a non-aqueous solvent (organic solvent).
  • a binder may be added to the solvent. Details regarding this binder are as described above.
  • the dispersion is dried.
  • the insides of the plurality of carbon fiber portions 1 are impregnated with the dispersion liquid containing the powder of the silicon-containing material, so that the powder of the silicon-containing material is fixed to the surface of each of the plurality of carbon fiber portions 1 . Therefore, since the surface of each of the plurality of carbon fiber portions 1 is coated with the silicon-containing material powder, the plurality of coated portions 2 are formed.
  • the plurality of carbon fiber portions 1 may be immersed in the dispersion.
  • the impregnated amount of the dispersion liquid decreases as the distance (depth) required for the impregnation increases.
  • the amount of powder of silicon-containing material deposited on each surface of part 1 is reduced.
  • the average fiber diameter AD, the weight ratio MA, and the porosity R continuously change in the thickness direction H, so that the negative electrode 10 including the lower portion 10X and the upper portion 10Y is assembled.
  • This negative electrode 10 has a single-layer structure because it includes a lower portion 10X and an upper portion 10Y that are physically integrated with each other.
  • the average fiber diameter ADX, the weight ratio MAX and the porosity RX are different from the average fiber diameter ADY, the weight ratio MAY and the porosity RY.
  • the weight ratios MAX and MAY can be adjusted by changing the concentration of the dispersion liquid, the impregnation rate, drying conditions, and the like.
  • the porosities RX and RY can be adjusted.
  • a suction device or the like is used to extract the dispersion liquid from the side opposite to the side where the inside of the plurality of carbon fiber portions 1 is impregnated with the dispersion liquid. may be aspirated. This facilitates the impregnation of the inside of the plurality of carbon fiber portions 1 with the dispersion liquid, thereby facilitating the formation of the plurality of covering portions 2 .
  • the weight ratios MAX and MY can be adjusted by changing the suction conditions.
  • the negative electrode 10 is pressed using a pressing machine or the like, and then the negative electrode 10 is fired.
  • the porosities RX and RY can be adjusted by changing the press pressure.
  • the firing temperature can be set arbitrarily.
  • the negative electrode 10 including a plurality of carbon fiber portions 1 and a plurality of coating portions 2 and having a plurality of voids 10G is completed.
  • the average fiber diameter AD, the weight ratio MA, and the porosity R can be adjusted according to the average fiber diameters ADX, ADY, the weight ratios MAX, MAY, and the porosity RX, RY, respectively.
  • this negative electrode 10 includes the plurality of carbon fiber portions 1 and the plurality of coating portions 2 described above, and has a plurality of voids 10G. are different between the lower part 10X and the upper part 10Y.
  • a plurality of carbon fiber portions 1 containing a conductive carbon-containing material form a conductive network (three-dimensional network structure), thereby improving conductivity.
  • each of the plurality of covering portions 2 contains a silicon-containing material that is excellent in absorbing and releasing the electrode reactant, a high energy density can be obtained.
  • the electrode reactant can easily move through the plurality of gaps 10G during the electrode reaction, and the electrode reaction can be repeated.
  • the electrode reaction tends to proceed smoothly even if the In this case, especially in the upper part 10Y located farther from the separator in the secondary battery, the movement speed of the electrode reactant tends to be rate-determining. Easier to move smoothly.
  • the electrode reactant can move more easily during the electrode reaction, and even if the electrode reaction is repeated, the electrode reaction will proceed more smoothly.
  • the electrode reactants can move significantly more easily during the electrode reaction, and the electrode reaction can proceed significantly more smoothly even if the electrode reaction is repeated. Therefore, in a secondary battery using negative electrode 10, excellent initial capacity characteristics, excellent load characteristics, and excellent cycle characteristics can be obtained.
  • the negative electrode 10 described above does not require a metal current collector, it is possible to reduce the weight and increase the weight energy density (Wh/kg) as compared with the case where the metal current collector is used. You can also let
  • the average fiber diameter ADX is smaller than the average fiber diameter ADY, the plurality of carbon fiber portions 1 having a relatively small fiber diameter AD in the lower portion 10X located on the side closer to the separator in the secondary battery. is likely to be placed in the vicinity of the covering portion 2 (silicon-containing material), which facilitates elimination of defective electronic contact inside the negative electrode 10 during electrode reaction. This makes it easier for the electrode reactant to move and facilitates the electrode reaction to proceed more smoothly even if the electrode reaction is repeated, so that a higher effect can be obtained.
  • the average fiber diameter ADY is 0.0003 to 0.5 times as large as the average fiber diameter ADX, the electrode reactant will move sufficiently easily, and the electrode reaction will not occur even if the electrode reaction is repeated. Since it progresses easily enough, even higher effects can be obtained.
  • the weight ratio MAX is larger than the weight ratio MAY, expansion and contraction of the negative electrode 10 are further suppressed, and the electrode reactant is more easily occluded and released, so that a higher effect can be obtained.
  • the weight ratio MAX is 1.04 to 4.65 times the weight ratio MAY, expansion and contraction of the negative electrode 10 are sufficiently suppressed, and the electrode reactant is easily occluded and released sufficiently. , a higher effect can be obtained.
  • the electrode reactant will move more easily, and even if the electrode reaction is repeated, the electrode reaction will proceed more smoothly, resulting in a higher effect. Obtainable.
  • the porosity RY is 1.1 to 4.5 times the porosity RX, the electrode reactant will move sufficiently easily, and the electrode reaction will be sufficient even if the electrode reaction is repeated. Because it becomes easier to progress, it is possible to obtain even higher effects.
  • the average fiber diameter AD of the entire negative electrode 10 is 10 nm to 12000 nm
  • the weight ratio MA of the entire negative electrode 10 is 40% to 80% by weight
  • the porosity R of the entire negative electrode 10 is 40% to 70% by volume.
  • each of the plurality of coating portions 2 is 80% by weight or more, a significantly high energy density can be obtained while ensuring conductivity, so that a higher effect can be obtained. can.
  • the secondary battery described here is, as described above, a secondary battery in which the battery capacity is obtained by utilizing the absorption and release of the electrode reactant. I have.
  • the type of electrode reactant is not particularly limited as described above.
  • lithium ion secondary battery A secondary battery whose battery capacity is obtained by utilizing the absorption and release of lithium is a so-called lithium ion secondary battery.
  • lithium ion secondary battery lithium is intercalated and deintercalated in an ionic state.
  • the charge capacity of the negative electrode is greater than the discharge capacity of the positive electrode. That is, the electrochemical capacity per unit area of the negative electrode is set to be larger than the electrochemical capacity per unit area of the positive electrode. This is to prevent electrode reactants from depositing on the surface of the negative electrode during charging.
  • FIG. 4 shows a perspective configuration of a secondary battery.
  • FIG. 5 is an enlarged sectional view of the battery element 30 shown in FIG. However, FIG. 4 shows a state in which the exterior film 20 and the battery element 30 are separated from each other, and FIG. 5 shows only a part of the battery element 30 . 1 to 3, which have already been described, and the constituent elements of the negative electrode 10, which have already been described.
  • This secondary battery includes an exterior film 20, a battery element 30, a positive electrode lead 41, a negative electrode lead 42, and sealing films 51 and 52, as shown in FIGS.
  • the secondary battery described here is a laminated film type secondary battery using a flexible (or flexible) exterior film 20 .
  • the exterior film 20 is a flexible exterior member that houses the battery element 30, and has a sealed bag-like structure with the battery element 30 housed inside. are doing. Therefore, the exterior film 20 accommodates the electrolytic solution together with the positive electrode 31 and the negative electrode 32, which will be described later.
  • the exterior film 20 is a single film-like member and is folded in the folding direction F.
  • the exterior film 20 is provided with a recessed portion 20U (so-called deep drawn portion) for housing the battery element 30 .
  • the exterior film 20 is a three-layer laminate film in which a fusion layer, a metal layer, and a surface protection layer are laminated in this order from the inside, and when the exterior film 20 is folded, they face each other. Outer peripheral edge portions of the fusion layer are fused together.
  • the fusible layer contains a polymer compound such as polypropylene.
  • the metal layer contains a metal material such as aluminum.
  • the surface protective layer contains a polymer compound such as nylon.
  • the configuration (number of layers) of the exterior film 20 is not particularly limited, and may be one layer, two layers, or four layers or more.
  • the battery element 30 is a power generating element including a positive electrode 31, a negative electrode 32, a separator 33 and an electrolytic solution (not shown), as shown in FIGS. there is
  • the battery element 30 is a so-called laminated electrode body
  • the positive electrode 31 and the negative electrode 32 are laminated with the separator 33 interposed therebetween.
  • the number of laminations of each of the positive electrode 31, the negative electrode 32 and the separator 33 is not particularly limited.
  • a plurality of positive electrodes 31 and a plurality of negative electrodes 32 are alternately stacked with separators 33 interposed therebetween.
  • the positive electrode 31 includes a positive electrode current collector 31A and a positive electrode active material layer 31B, as shown in FIG.
  • the positive electrode current collector 31A has a pair of surfaces on which the positive electrode active material layer 31B is provided.
  • the positive electrode current collector 31A contains a conductive material such as a metal material, and a specific example of the metal material is aluminum.
  • the positive electrode current collector 31A includes protruding portions 31AT not provided with the positive electrode active material layer 31B, and the plurality of protruding portions 31AT are formed in the shape of a single lead. are joined together.
  • the projecting portion 31AT is integrated with portions other than the projecting portion 31AT.
  • the projecting portion 31AT is separate from the portion other than the projecting portion 31AT, it may be joined to the portion other than the projecting portion 31AT.
  • the positive electrode active material layer 31B contains one or more of positive electrode active materials capable of intercalating and deintercalating lithium. However, the positive electrode active material layer 31B may further contain one or more of other materials such as a positive electrode binder and a positive electrode conductor.
  • the positive electrode active material layer 31B is provided on both sides of the positive electrode current collector 31A.
  • the positive electrode active material layer 31B may be provided only on one side of the positive electrode current collector 31A on the side where the positive electrode 31 faces the negative electrode 32 .
  • a method for forming the positive electrode active material layer 31B is not particularly limited, but specifically, one or more of coating methods and the like are used.
  • the type of positive electrode active material is not particularly limited, it is specifically a lithium-containing compound.
  • This lithium-containing compound is a compound containing lithium and one or more transition metal elements as constituent elements, and may further contain one or more other elements as constituent elements.
  • the type of the other element is not particularly limited as long as it is an element other than lithium and transition metal elements, but specifically, it is an element belonging to Groups 2 to 15 in the long period periodic table.
  • the type of lithium-containing compound is not particularly limited, but specific examples include oxides, phosphoric acid compounds, silicic acid compounds and boric acid compounds.
  • oxides include LiNiO2 , LiCoO2 , LiCo0.98Al0.01Mg0.01O2 , LiNi0.5Co0.2Mn0.3O2 , LiNi0.8Co0.15Al0.05O2 , LiNi0.33Co0.33Mn0.33Mn0.33O2 .
  • 1.2Mn0.52Co0.175Ni0.1O2 Li1.15 ( Mn0.65Ni0.22Co0.13 ) O2 and LiMn2O4 .
  • _ _ Specific examples of phosphoric acid compounds include LiFePO4 , LiMnPO4 , LiFe0.5Mn0.5PO4 and LiFe0.3Mn0.7PO4 .
  • the positive electrode binder contains one or more of synthetic rubber and polymer compounds.
  • synthetic rubbers include styrene-butadiene rubber, fluororubber, and ethylene propylene diene.
  • polymer compounds include polyvinylidene fluoride, polyimide and carboxymethylcellulose.
  • the positive electrode conductive agent contains one or more of conductive materials such as carbon materials, and specific examples of the carbon materials include graphite, carbon black, acetylene black, ketjen black, and carbon nanotubes. and so on.
  • the conductive material may be a metal material, a polymer compound, or the like.
  • the negative electrode 32 faces the positive electrode 31 with the separator 33 interposed therebetween, and is capable of intercalating and deintercalating lithium. Since this negative electrode 32 has a configuration similar to that of the negative electrode 10 (the lower part 10X and the upper part 10Y) described above, it includes a plurality of carbon fiber portions 1 and a plurality of coating portions 2 and a plurality of has a gap 10G. As described above, the lower portion 10X is positioned closer to the separator 33 than the upper portion 10Y, and the upper portion 10Y is positioned farther from the separator 33 than the lower portion 10X.
  • lithium is mainly intercalated and deintercalated in each of the plurality of covering portions 2 .
  • lithium may be intercalated and deintercalated not only in each of the plurality of covering portions 2 but also in the plurality of carbon fiber portions 1 .
  • the negative electrode 32 includes a protruding portion 31AT made of a part of the carbon fiber portion 1 that is not provided with the plurality of covering portions 2, and the plurality of protruding portions 31AT is one are joined to each other so as to form a lead shape.
  • the separator 33 is an insulating porous film interposed between the positive electrode 31 and the negative electrode 32, as shown in FIG. Allows lithium ions to pass through.
  • This separator 33 contains a polymer compound such as polyethylene.
  • the electrolyte is impregnated in each of the positive electrode 31, the negative electrode 32 and the separator 33, and contains a solvent and an electrolyte salt.
  • the solvent contains one or more of non-aqueous solvents (organic solvents) such as a carbonate-based compound, a carboxylic acid ester-based compound, and a lactone-based compound, and includes the non-aqueous solvent.
  • non-aqueous solvents organic solvents
  • the electrolytic solution is a so-called non-aqueous electrolytic solution.
  • the carbonate compounds include cyclic carbonates and chain carbonates.
  • cyclic carbonates include ethylene carbonate and propylene carbonate.
  • chain carbonates include dimethyl carbonate, diethyl carbonate and ethylmethyl carbonate.
  • the carboxylic acid ester compound is a chain carboxylic acid ester or the like.
  • chain carboxylic acid esters include methyl acetate, ethyl acetate, trimethyl methyl acetate, methyl propionate, ethyl propionate and propyl propionate.
  • Lactone-based compounds include lactones. Specific examples of lactones include ⁇ -butyrolactone and ⁇ -valerolactone.
  • the electrolyte salt contains one or more of light metal salts such as lithium salts.
  • lithium salts include lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium bis(fluorosulfonyl)imide (LiN(FSO 2 ) 2 ), bis(trifluoromethanesulfonyl ) imidelithium (LiN( CF3SO2 ) 2 ), lithium bis(oxalato)borate (LiB ( C2O4 ) 2 ), lithium difluoro ( oxalato)borate (LiB ( C2O4 )F2) , lithium monofluorophosphate (Li 2 PFO 3 ) and lithium difluorophosphate (LiPF 2 O 2 ).
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium bis(fluorosulfonyl)imide
  • LiN(CF3SO2 ) 2 bis(trifluoromethanesulfonyl ) imidelithium
  • the content of the electrolyte salt is not particularly limited, but specifically, it is 0.3 mol/kg to 3.0 mol/kg with respect to the solvent. This is because high ionic conductivity can be obtained.
  • the electrode solution may further contain one or more of additives.
  • additives are not particularly limited, but specific examples include unsaturated cyclic carbonates, halogenated carbonates, phosphoric acid esters, acid anhydrides, nitrile compounds and isocyanate compounds.
  • unsaturated cyclic carbonates include vinylene carbonate, vinylethylene carbonate and methyleneethylene carbonate.
  • halogenated carbonates include halogenated cyclic carbonates and halogenated chain carbonates.
  • halogenated cyclic carbonates include ethylene monofluorocarbonate and ethylene difluorocarbonate.
  • a specific example of the halogenated chain carbonate is fluoromethyl methyl carbonate and the like.
  • Specific examples of phosphate esters include trimethyl phosphate and triethyl phosphate.
  • the acid anhydrides include dicarboxylic anhydrides, disulfonic anhydrides and carboxylic sulfonic anhydrides.
  • dicarboxylic anhydrides include succinic anhydride.
  • disulfonic anhydrides include ethanedisulfonic anhydride.
  • carboxylic acid sulfonic anhydrides include sulfobenzoic anhydride.
  • Nitrile compounds include mononitrile compounds, dinitrile compounds and trinitrile compounds. Specific examples of mononitrile compounds include acetonitrile. Specific examples of dinitrile compounds include succinonitrile. Specific examples of trinitrile compounds include 1,2,3-propanetricarbonitrile. Specific examples of isocyanate compounds include hexamethylene diisocyanate.
  • the positive electrode lead 41 is a positive electrode terminal connected to a joined body of the plurality of projecting portions 31AT of the positive electrode 31, and is led out from the inside of the exterior film 20 to the outside.
  • the positive electrode lead 41 contains a conductive material such as a metal material, and a specific example of the metal material is aluminum.
  • the shape of the positive electrode lead 41 is not particularly limited, but specifically, it is either a thin plate shape, a mesh shape, or the like.
  • the negative electrode lead 42 is a negative electrode terminal connected to a joined body of a plurality of projecting portions 32AT of the negative electrode 32, as shown in FIG. Among them, the negative electrode lead 42 is preferably connected to the carbon fiber portion 1 of the negative electrode 32 . This is because electrical conductivity between the negative electrode 32 and the negative electrode lead 42 is improved.
  • the negative electrode lead 42 contains a conductive material such as a metal material, and a specific example of the metal material is copper.
  • the lead-out direction of the negative lead 42 is the same as the lead-out direction of the positive lead 41 .
  • the details regarding the shape of the negative electrode lead 42 are the same as the details regarding the shape of the positive electrode lead 41 .
  • sealing film 51 is inserted between the packaging film 20 and the positive electrode lead 41
  • the sealing film 52 is inserted between the packaging film 20 and the negative electrode lead 42 .
  • one or both of the sealing films 51 and 52 may be omitted.
  • the sealing film 51 is a sealing member that prevents outside air from entering the exterior film 20 . Further, the sealing film 51 contains a polymer compound such as polyolefin having adhesiveness to the positive electrode lead 41, and the polyolefin is polypropylene or the like.
  • the configuration of the sealing film 52 is the same as the configuration of the sealing film 51 except that it is a sealing member having adhesion to the negative electrode lead 42 . That is, the sealing film 52 contains a polymer compound such as polyolefin that has adhesiveness to the negative electrode lead 42 .
  • a pasty positive electrode mixture slurry is prepared by putting a mixture (positive electrode mixture) in which a positive electrode active material, a positive electrode binder, and a positive electrode conductor are mixed together into a solvent.
  • This solvent may be an aqueous solvent or an organic solvent.
  • the cathode active material layer 31B is formed by applying the cathode mixture slurry to both surfaces of the cathode current collector 31A including the projections 31AT (excluding the projections 31AT).
  • the cathode active material layer 31B is compression-molded using a roll press or the like. In this case, the positive electrode active material layer 31B may be heated, or compression molding may be repeated multiple times. As a result, the cathode active material layers 31B are formed on both surfaces of the cathode current collector 31A, so that the cathode 31 is produced.
  • the negative electrode 32 including the projecting portion 32AT is manufactured by the same procedure as the manufacturing procedure of the negative electrode 10 described above.
  • the positive electrode 31 and the negative electrode 32 are alternately laminated with the separator 33 interposed to prepare a laminate (not shown).
  • This laminate has the same structure as the battery element 30 except that the positive electrode 31, the negative electrode 32, and the separator 33 are not impregnated with the electrolytic solution.
  • the plurality of projecting portions 31AT are joined together, and the plurality of projecting portions 32AT are joined together.
  • the positive electrode lead 41 is joined to the joined body of the plurality of projecting portions 31AT, and the negative electrode lead 42 is connected to the joined body of the plurality of projecting portions 32AT.
  • the exterior films 20 (bonding layer/metal layer/surface protective layer) are folded to face each other. Subsequently, by using a heat-sealing method or the like to join the outer peripheral edges of two sides of the exterior films 20 (fusion layer) that face each other, it is laminated inside the bag-like exterior film 20. accommodate the body.
  • the sealing film 51 is inserted between the exterior film 20 and the positive electrode lead 41 and the sealing film 52 is inserted between the exterior film 20 and the negative electrode lead 42 .
  • the laminate is impregnated with the electrolytic solution, so that the battery element 30, which is a laminated electrode assembly, is produced. Accordingly, the battery element 30 is enclosed inside the bag-shaped exterior film 20, so that the secondary battery is assembled.
  • the secondary battery after assembly is charged and discharged.
  • Various conditions such as environmental temperature, number of charge/discharge times (number of cycles), and charge/discharge conditions can be arbitrarily set.
  • films are formed on the respective surfaces of the positive electrode 31 and the negative electrode 32, so that the state of the secondary battery is electrochemically stabilized.
  • a secondary battery is completed.
  • the negative electrode 32 has the same configuration as the negative electrode 10 described above. Therefore, excellent initial capacity characteristics, excellent load characteristics, and excellent cycle characteristics can be obtained for the same reasons as described for the negative electrode 10 .
  • the secondary battery is a lithium-ion secondary battery
  • a sufficient battery capacity can be stably obtained by utilizing the absorption and release of lithium, so a higher effect can be obtained.
  • the negative electrode 10 may further include multiple surface portions 3 .
  • Each of the plurality of surface portions 3 is provided on the surface of each of the plurality of covering portions 2 and has a thickness T2. Moreover, each of the plurality of surface portions 3 contains one or more of ion conductive materials. This is because the ion conductivity of the negative electrode 10 is improved. The type of this ion conductive material is not particularly limited.
  • the ionically conductive material is a solid electrolyte such as lithium phosphate nitrate and lithium phosphate (Li 3 PO 4 ).
  • Li 3 PO 4 lithium phosphate
  • the composition of this lithium phosphate oxynitride is not particularly limited, it is specifically Li 3.30 PO 3.90 N 0.17 or the like.
  • the ion conductive material is a gel electrolyte in which an electrolytic solution is held by a matrix polymer compound.
  • the composition of the electrolytic solution is as described above.
  • matrix polymer compounds include polyethylene oxide and polyvinylidene fluoride.
  • the ion-conductive material preferably contains a solid electrolyte, that is, it preferably contains one or both of lithium phosphate nitrate and lithium phosphate. This is because the ion conductivity of the negative electrode 10 is sufficiently improved.
  • the surface portion 3 may be provided on the entire surface of the covering portion 2 or may be provided on only a part of the surface of the covering portion 2 . In the latter case, a plurality of surface portions 3 separated from each other may be provided on the surface of the covering portion 2 .
  • the average thickness AT2 of the plurality of surface portions 3 is not particularly limited and can be set arbitrarily.
  • the procedure for calculating the average thickness AT2 is the same as the procedure for calculating the average thickness AT1 described above, except that the thickness T2 of the surface portion 3 is measured instead of the thickness T1 of the covering portion 2.
  • the procedure for forming the plurality of surface portions 3 is as described below.
  • a solid electrolyte is used as the ion conductive material
  • the surface portion 3 is directly formed on the surface of the covering portion 2 using a vapor phase method such as sputtering.
  • a gel electrolyte is used as the ion-conducting material
  • a solution containing a solvent for dilution as well as an electrolytic solution and a matrix polymer is applied to the surface of the covering portion 2, and then the solution is dried. Details regarding the type of solvent are given above. Note that the covering portion 2 and the like may be immersed in the solution.
  • the negative electrode 10 can be applied to an all-solid-state battery by utilizing a plurality of surface portions 3 containing an ion-conducting material. This is because the expansion and contraction of the negative electrode 10 is suppressed, thereby suppressing an increase in interfacial resistance between the negative electrode 10 and the solid electrolyte. As a result, in the all-solid-state battery, it is possible to ensure safety and improve energy density at the same time.
  • the average thickness AT2 may be the same between the lower portion 10X and the upper portion 10Y, or may be the same between the lower portion 10X and the upper portion 10Y.
  • the upper part 10Y may be different from each other.
  • the average thickness AT2 of the lower part 10X may be larger than the average thickness AT2 of the upper part 10Y.
  • the average thickness AT2 of the lower portion 10X may be smaller than the average thickness AT2 of the upper portion 10Y. This is because the ionic conductivity of lithium ions inside the negative electrode 10 is further improved.
  • the definition of the magnitude relation regarding the average thickness AT2 is the same as the definition of the magnitude relation regarding the average fiber diameter AD (ADX, ADY) described above.
  • the average thickness AT2 of the upper portion 10Y is larger than the average thickness AT2 of the lower portion 10X.
  • the movement speed of the electrode reactant tends to be rate-determining in the upper part 10Y located farther from the separator. This is because the lithium ions are likely to move smoothly even if the is increased.
  • the weight M1 of the plurality of carbon fiber portions 1, the weight M2 of the plurality of coating portions 2, and the weight M3 of the plurality of surface portions 3 are The weight ratio MB (% by weight), which is the ratio of the weight M3 of the plurality of surface portions 3 to the sum of 10Y may be different from each other.
  • the negative electrode 10 has the weight ratio MB as described above, and has the lower portion 10X and the upper portion 10Y as shown in FIG. Accordingly, the lower portion 10X has a weight ratio MBX and the upper portion 10Y has a weight ratio MBY, so that the weight ratios MBX and MBY are different from each other.
  • the electrode reactant is more easily occluded and released during the electrode reaction.
  • the weight percentage MBX may be greater than the weight percentage MBY or may be less than the weight percentage MBY.
  • the definition of the magnitude relationship between the weight percentages MBX and MBY is the same as the definition of the magnitude relationship of the weight percentages MAX and MAY described above.
  • the weight ratio MB is greater in the upper portion 10Y than in the lower portion 10X. is preferably greater than the weight fraction MBX. This is because the electrode reactant is more easily occluded and released during the electrode reaction.
  • the negative electrode 10 may further include multiple additional carbon fiber portions 4 .
  • the plurality of additional carbon fiber portions 4 are a plurality of additional fiber portions having an average fiber diameter smaller than the average fiber diameter AD of the plurality of carbon fiber portions 1, as shown in FIG.
  • each of the plurality of additional carbon fiber portions 4 is fixed to the surface of each of the plurality of covering portions 2 , each of the plurality of additional carbon fiber portions 4 is connected to the surface of each of the plurality of covering portions 2 .
  • FIG. 7 shows a case in which each of the plurality of additional carbon fiber portions 4 is straight for the sake of simplification of the illustration.
  • the state (shape) of each of the plurality of additional carbon fiber portions 4 is not particularly limited, similarly to the case described regarding the state of the plurality of carbon fiber portions 1 described above.
  • the negative electrode 10 includes a plurality of carbon fiber portions 1 and a plurality of additional carbon fiber portions 4, the plurality of carbon fiber portions 1 not only form a conductive network, but also the plurality of additional carbon fiber portions 4 Since a dense conductive network is also formed, the conductivity of the negative electrode 10 is significantly improved.
  • each of a part or all of the plurality of additional carbon fiber portions 4 (the plurality of additional carbon fiber portions 4R) is connected to each of the two or more covering portions 2. This is because two or more covering portions 2 are electrically connected to each other via one or two or more additional carbon fiber portions 4R. As a result, a denser conductive network is formed, so that the conductivity of the negative electrode 10 is further improved.
  • the average fiber diameter of the plurality of additional carbon fiber portions 4 is smaller than the average fiber diameter AD of the plurality of carbon fiber portions 1.
  • the average fiber diameter AD is 1/10000 times to 1/1/10000. 2 times, preferably 1/300 times to 1/5 times. More specifically, the average fiber diameter of the plurality of additional carbon fiber portions 4 is 1 nm to 300 nm. This is because the plurality of additional carbon fiber portions 4 are easily dispersed in the interior of the negative electrode 10, so that the plurality of additional carbon fiber portions 4 are likely to form a dense conductive network.
  • the procedure for calculating the average fiber diameter of the plurality of additional carbon fiber portions 4 is as follows: After measuring the fiber diameter of each of 20 arbitrary additional carbon fiber portions 4, the average value of the 20 fiber diameters is calculated as the average fiber diameter.
  • the procedure for calculating the average fiber diameter AD is the same as described above, except that However, when the fiber diameter is small, it is preferable to use a TEM rather than a SEM to observe the cross section of the negative electrode 10 .
  • each of the plurality of additional carbon fiber portions 4 contains carbon as a constituent element
  • each of the plurality of carbon fiber portions 1 contains a carbon-containing material. Details regarding this carbon-containing material are provided above.
  • each of the plurality of additional carbon fiber portions 4 is preferably one or more of single-walled carbon nanotubes, multi-walled carbon nanotubes, and vapor-grown carbon fibers. This is because, since the average fiber diameter is sufficiently small, the plurality of additional carbon fiber portions 4 are easily dispersed sufficiently inside the negative electrode 10, and a denser conductive network is easily formed.
  • the conductivity of the negative electrode 10 is significantly improved, so a higher effect can be obtained.
  • the average fiber diameter of the plurality of additional carbon fiber portions 4 is the same between the lower portion 10X and the upper portion 10Y.
  • the lower part 10X and the upper part 10Y may be different from each other.
  • the average fiber diameter in the lower part 10X may be larger than the average fiber diameter in the upper part 10Y.
  • the average fiber diameter in the side portion 10X may be smaller than the average fiber diameter in the upper portion 10Y. This is because a dense conductive network is easily formed inside the negative electrode 10, and the conductivity of the negative electrode 10 is further improved.
  • the definition of the magnitude relation regarding the average fiber diameter is the same as the definition of the magnitude relation regarding the average fiber diameter AD (ADX, ADY) described above.
  • the average fiber diameter in the lower portion 10X is smaller than the average fiber diameter in the upper portion 10Y. This is because a dense conductive network is easily formed in the lower portion 10X located on the side closer to the separator in the secondary battery, so that the conductivity of the negative electrode 10 is further improved.
  • a separator 33 which is a porous membrane, was used. However, although not specifically illustrated here, instead of the separator 33, a laminated separator including a polymer compound layer may be used.
  • a laminated separator includes a porous membrane having a pair of surfaces and a polymer compound layer provided on one or both sides of the porous membrane. This is because the adhesiveness of the separator to each of the positive electrode 31 and the negative electrode 32 is improved, so that the winding misalignment of the battery element 30 is suppressed. As a result, even if a decomposition reaction of the electrolytic solution occurs, the secondary battery is less likely to swell.
  • the configuration of the porous membrane is the same as the configuration of the porous membrane described for the separator 33 .
  • the polymer compound layer contains a polymer compound such as polyvinylidene fluoride. This is because polyvinylidene fluoride or the like has excellent physical strength and is electrochemically stable.
  • One or both of the porous film and the polymer compound layer may contain one or more of a plurality of insulating particles. This is because the safety (heat resistance) of the secondary battery is improved because the plurality of insulating particles promote heat dissipation when the secondary battery generates heat.
  • the insulating particles include one or both of inorganic particles and resin particles. Specific examples of inorganic particles are particles such as aluminum oxide, aluminum nitride, boehmite, silicon oxide, titanium oxide, magnesium oxide and zirconium oxide. Specific examples of resin particles are particles of acrylic resins, styrene resins, and the like.
  • the precursor solution is applied to one or both sides of the porous membrane.
  • the porous membrane may be immersed in the precursor solution.
  • a plurality of insulating particles may be contained in the precursor solution.
  • Modification 8 An electrolytic solution, which is a liquid electrolyte, was used. However, although not specifically illustrated here, an electrolyte layer that is a gel electrolyte may be used instead of the electrolyte solution.
  • the positive electrode 31 and the negative electrode 32 are alternately laminated via the separator 33 and the electrolyte layer.
  • an electrolyte layer is interposed between the positive electrode 31 and the separator 33 and an electrolyte layer is interposed between the negative electrode 32 and the separator 33 .
  • the electrolyte layer may be interposed only between the positive electrode 31 and the separator 33 , or may be interposed only between the negative electrode 32 and the separator 33 .
  • the electrolyte layer contains a polymer compound together with an electrolytic solution, and the electrolytic solution is held by the polymer compound. This is because leakage of the electrolytic solution is prevented.
  • the composition of the electrolytic solution is as described above.
  • Polymer compounds include polyvinylidene fluoride and the like.
  • a secondary battery used as a power source may be a main power source for electronic devices and electric vehicles, or may be an auxiliary power source.
  • a main power source is a power source that is preferentially used regardless of the presence or absence of other power sources.
  • An auxiliary power supply is a power supply that is used in place of the main power supply or that is switched from the main power supply.
  • Secondary battery applications are as follows. Electronic devices such as video cameras, digital still cameras, mobile phones, laptop computers, headphone stereos, portable radios and portable information terminals. Backup power and storage devices such as memory cards. Power tools such as power drills and power saws. It is a battery pack mounted on an electronic device. Medical electronic devices such as pacemakers and hearing aids. It is an electric vehicle such as an electric vehicle (including a hybrid vehicle). It is a power storage system such as a home or industrial battery system that stores power in preparation for emergencies. In these uses, one secondary battery may be used, or a plurality of secondary batteries may be used.
  • the battery pack may use a single cell or an assembled battery.
  • An electric vehicle is a vehicle that operates (runs) using a secondary battery as a drive power source, and may be a hybrid vehicle that also includes a drive source other than the secondary battery.
  • electric power stored in a secondary battery which is an electric power storage source, can be used to use electric appliances for home use.
  • FIG. 8 shows the block configuration of the battery pack.
  • the battery pack described here is a battery pack (a so-called soft pack) using one secondary battery, and is mounted in an electronic device such as a smart phone.
  • This battery pack includes a power supply 61 and a circuit board 62, as shown in FIG.
  • This circuit board 62 is connected to a power supply 61 and includes a positive terminal 63 , a negative terminal 64 and a temperature detection terminal 65 .
  • the power supply 61 includes one secondary battery.
  • the positive lead is connected to the positive terminal 63 and the negative lead is connected to the negative terminal 64 .
  • This power source 61 is connected to the outside through a positive terminal 63 and a negative terminal 64, and thus can be charged and discharged.
  • the circuit board 62 includes a control section 66 , a switch 67 , a thermal resistance (PTC) element 68 and a temperature detection section 69 .
  • the PTC element 68 may be omitted.
  • the control unit 66 includes a central processing unit (CPU), memory, etc., and controls the operation of the entire battery pack. This control unit 66 detects and controls the use state of the power source 61 as necessary.
  • CPU central processing unit
  • memory etc.
  • the overcharge detection voltage is not particularly limited, but is specifically 4.2 ⁇ 0.05V, and the overdischarge detection voltage is not particularly limited, but is specifically 2.4 ⁇ 0.1V. is.
  • the switch 67 includes a charge control switch, a discharge control switch, a charge diode, a discharge diode, and the like, and switches connection/disconnection between the power supply 61 and an external device according to instructions from the control unit 66 .
  • the switch 67 includes a field effect transistor (MOSFET) using a metal oxide semiconductor, etc., and the charge/discharge current is detected based on the ON resistance of the switch 67 .
  • MOSFET field effect transistor
  • the temperature detection unit 69 includes a temperature detection element such as a thermistor, measures the temperature of the power supply 61 using the temperature detection terminal 65 , and outputs the temperature measurement result to the control unit 66 .
  • the measurement result of the temperature measured by the temperature detection unit 69 is used when the control unit 66 performs charging/discharging control at the time of abnormal heat generation and when the control unit 66 performs correction processing when calculating the remaining capacity.
  • First secondary batteries (Examples 1 to 20 and Comparative Example 3) were produced according to the procedure described below.
  • a positive electrode active material LiNi 0.8 Co 0.15 Al 0.05 O 2
  • a positive electrode binder polyvinylidene fluoride
  • a positive electrode conductive agent Ketjenblack
  • a plurality of fibrous carbon materials were prepared to form the lower portion 10X.
  • vapor grown carbon fibers VGCF
  • carbon nanotubes CNT
  • carbon fibers CF
  • a plurality of coating portions 2 were formed by depositing a silicon-containing material (single silicon (Si)) on the surface of each of the plurality of fibrous carbon materials using a vacuum deposition method. .
  • a silicon-containing material single silicon (Si)
  • two deposition sources were arranged so as to sandwich the plurality of fibrous carbon materials.
  • a portion of the plurality of fibrous carbon materials on which the plurality of coating portions 2 are not formed serves as the projecting portion 32AT.
  • the weight ratio MAX (% by weight) is as shown in Tables 1 and 2.
  • a plurality of covering portions 2 were formed using a plurality of fibrous carbon materials (average fiber diameter ADY) by the same procedure.
  • a plurality of two types of fibrous carbon materials having a plurality of coating portions 2 formed thereon were combined to form a plurality of carbon fiber portions 1 and A lower portion 10X including a plurality of covering portions 2 and an upper portion 10Y including a plurality of carbon fiber portions 1 and a plurality of covering portions 2 are formed, and the lower portion 10X and the upper portion 10Y are laminated to each other. rice field.
  • the negative electrode 32 was assembled.
  • the negative electrode 32 having a two-layer structure including a lower portion 10X (porosity RX) and an upper portion 10Y (porosity RY) and having a plurality of gaps 10G was completed.
  • the porosity RX (% by volume) is as shown in Tables 1 and 2.
  • this negative electrode 32 When manufacturing this negative electrode 32, by adjusting the deposition amount of the silicon-containing material, the weight ratio MAX and MAY were changed, and the deposition amount of the silicon-containing material and the pressing pressure of the negative electrode 32 were each adjusted. By doing so, the porosities RX and RY were changed.
  • one or more of the three physical property values are the lower part 10X and the upper part 10Y were made different from each other.
  • the "magnification” shown in Tables 1 and 2 represents the magnification that defines the magnitude relationship of each physical property value (average fiber diameter ADX, ADY, weight ratio MAX, MAY, and porosity RX, RY).
  • magnification regarding the porosity R represents the magnification of the porosity RY to the porosity RX. Therefore, the fact that the magnification is greater than 1 means that the porosity RY is greater than the porosity RX.
  • the positive electrode lead 41 (aluminum foil) was joined to the projecting portion 31AT, and the negative electrode lead 42 (copper foil) was joined to the projecting portion 32AT.
  • the exterior film 20 (bonding layer/metal layer/surface protective layer) so as to sandwich the laminate accommodated inside the recess 20U, one of the exterior films 20 (bonding layer)
  • the laminate was housed inside the bag-shaped exterior film 20 by heat-sealing the outer peripheral edges of the two sides to each other.
  • An aluminum laminate film laminated in order was used.
  • the laminate was impregnated with the electrolytic solution, and the battery element 30 was produced.
  • the battery element 30 was sealed inside the exterior film 20, and the secondary battery was assembled.
  • the thickness of the material layer 31B was adjusted.
  • constant-current charging was performed at a current of 0.1C until the voltage reached 4.2V
  • constant-voltage charging was performed at the voltage of 4.2V until the current reached 0.025C.
  • constant current discharge was performed at a current of 0.1C until the voltage reached 2.0V.
  • 0.1C is a current value that can completely discharge the battery capacity (theoretical capacity) in 10 hours
  • 0.025C is a current value that completely discharges the battery capacity in 40 hours.
  • the first secondary battery using the positive electrode 31 as a counter electrode for the negative electrode 32 is a so-called full cell
  • the second secondary battery using a lithium metal plate as a counter electrode for the negative electrode 32 is a so-called half cell. be.
  • This carbon nanotube dispersion contains 0.8 parts by mass of carbon nanotubes and 4.2 parts by mass of a dispersion medium (polyvinylidene fluoride).
  • the negative electrode mixture was added to a solvent (N-methyl-2-pyrrolidone, which is an organic solvent), and then the organic solvent was stirred using a rotation/revolution mixer to prepare a pasty negative electrode mixture slurry.
  • the second secondary battery (half cell) was used to evaluate the initial capacity characteristics
  • the first secondary battery full cell was used to evaluate the load characteristics and cycle characteristics. evaluated.
  • the positive electrode 31 and the negative electrode 32 are brought into close contact with each other with the separator 33 interposed therebetween.
  • the secondary battery was charged and discharged while the
  • the total weight of the negative electrode 32 described above includes the weight of the metal current collector when a metal current collector is used, whereas the weight of the metal current collector is included when the metal current collector is not used. The weight of the metal current collector is not included.
  • constant-current charging was performed at a current of 0.1C until the voltage reached 0.005V, and then constant-voltage charging was performed at the voltage of 0.005V until the current reached 0.01C.
  • constant current discharge was performed at a current of 0.1C until the voltage reached 1.5V.
  • 0.01C is a current value that can discharge the battery capacity in 100 hours.
  • constant-current charging was performed at a current of 0.2C until the voltage reached 4.2V, and then constant-voltage charging was performed at the voltage of 4.2V until the current reached 0.025C.
  • constant current discharge was performed at a current of 0.2C until the voltage reached 2.5V.
  • 0.2C is a current value that can discharge the battery capacity in 5 hours.
  • the discharge capacity (second cycle discharge capacity) was measured by charging and discharging the secondary battery for one cycle in the same environment.
  • the charge/discharge conditions were the same as the charge/discharge conditions for the first cycle, except that the current during charging and the current during discharging were each changed to 5C.
  • 5C is a current value that can discharge the battery capacity in 0.2 hours.
  • load retention rate (second cycle discharge capacity/first cycle discharge capacity) x 100. .
  • capacity retention rate (%) (discharge capacity at 200th cycle/discharge capacity at 1st cycle) x 100. .
  • the initial capacity, load retention rate, and capacity retention rate each increased.
  • the weight ratio MAX was larger than the weight ratio MAY, the initial capacity, the load retention rate, and the capacity retention rate each increased.
  • the porosity RY was higher than the porosity RX, each of the initial capacity, the load retention rate, and the capacity retention rate increased.
  • the magnification for the average fiber diameter AD was 0.0003 to 0.5
  • the initial capacity, load retention rate, and capacity retention rate were each sufficiently increased.
  • the magnification for the weight ratio MA was 1.04 to 4.65
  • the initial capacity, the load retention rate, and the capacity retention rate were each sufficiently increased.
  • the magnification for the porosity R was 1.1 to 4.5, each of the initial capacity, the load retention rate and the capacity retention rate were sufficiently increased.
  • Examples 21 to 23 As shown in Table 3, a secondary battery was produced in the same manner as in Example 1, except that a plurality of surface portions 3 containing an ion-conductive material were formed in the step of producing the negative electrode 32. The characteristics of the secondary battery (initial capacity characteristics, load characteristics and cycle characteristics) were evaluated.
  • Lithium phosphate nitrate Li 3.30 PO 3.90 N 0.17
  • lithium phosphate Li 3 PO 4
  • Table 3 shows the average thickness AT2 (nm) of the plurality of surface portions 3 in the lower portion 10X.
  • an ion conductive material was deposited on each surface of the plurality of covering portions 2 using a sputtering method.
  • lithium phosphate was used as a target
  • Lithium phosphate was used as the target.
  • Example 3 when a plurality of surface portions 3 were formed (Examples 21 to 23), compared with the case where the plurality of surface portions 3 were not formed (Example 1), the initial Each of capacity, load retention rate and capacity retention rate increased more. In particular, when a plurality of surface portions 3 were formed, the initial capacity, the load retention rate, and the capacity retention rate further increased as the magnification for the average thickness AT2 increased.
  • the negative electrode 32 (negative electrode 10) includes the plurality of carbon fiber portions 1 and the plurality of coating portions 2 described above and has a plurality of voids 10G, and the average fiber diameter
  • AD weight ratio MA
  • porosity R porosity
  • the battery structure of the secondary battery is a laminated film type.
  • the battery structure of the secondary battery is not particularly limited, and other battery structures such as cylindrical, square, coin, and button types may be used.
  • the element structure of the battery element is a laminated type.
  • the element structure of the battery element is not particularly limited, other element structures such as a wound type and a 90-fold type may be used.
  • the positive electrode and the negative electrode are wound with a separator interposed therebetween, and in the 90-fold type, the positive electrode and the negative electrode are folded in a zigzag while facing each other with the separator interposed therebetween.
  • the electrode reactant is lithium has been described, but the electrode reactant is not particularly limited.
  • the electrode reactants may be other alkali metals such as sodium and potassium, or alkaline earth metals such as beryllium, magnesium and calcium, as described above.
  • the electrode reactant may be other light metals such as aluminum.

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JP2010525549A (ja) * 2007-04-23 2010-07-22 アプライド・サイエンシズ・インコーポレーテッド ケイ素を炭素材料へ蒸着しリチウムイオン電池用アノードを形成する方法
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