JP2008166155A - String-like electrochemical device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a string-like electrochemical device superior in shape freedom degree (bending freedom degree). <P>SOLUTION: This is the string-like electrochemical device in which storage elements 1 equipped with a first electrode 10, a second electrode 20, and an electrolyte layer 30 that is arranged between the first electrode 10 and the second electrode 20 and that has ion conductivity are continued in a string shape in a plurality of numbers, and electrically connected mutually in series or in parallel. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a string electrochemical device.

  In electrochemical devices, improvement in the degree of freedom of shape has been a requirement for some time. As a fibrous battery having a high degree of freedom in shape, a coaxial string-shaped (tube-shaped) battery has been proposed (for example, see Patent Document 1). This string battery has a configuration in which a positive electrode, a separator impregnated with an electrolytic solution, and a negative electrode are provided in a coaxial cable shape.

JP-A-9-7629

  However, since the string-like battery described in Patent Document 1 has a coaxial structure, there is a problem that an electrode or a current collector is cracked at the time of bending, and the element is easily broken, and the degree of bending freedom is insufficient. there were.

  This invention is made | formed in view of the subject which the said prior art has, and aims at providing the string-shaped electrochemical device excellent in the shape freedom degree (folding freedom degree).

  In order to achieve the above object, the present invention includes a first electrode, a second electrode, and an electrolyte layer having ion conductivity disposed between the first electrode and the second electrode. Provided is a string-like electrochemical device in which a plurality of power storage elements are electrically connected in series or in parallel to each other in a string form.

  According to the string-like electrochemical device of the present invention having the above-described configuration, even if a sharp bend is applied, the stress is absorbed at the connection portion between the plurality of power storage elements, so that the power storage element portion is destroyed. Can be sufficiently suppressed, and an excellent shape freedom (bending flexibility) can be obtained.

  In the string-like electrochemical device of the present invention, either or both of the first electrode and the second electrode are substantially active material particles and electronic conductivity supported on the active material particles. It is preferable that the electrode is made of a conductive additive having By using such an electrode, it is possible to reduce a region that does not contribute to the electric capacity due to the presence of the binder and the current collector in the power storage element, and to improve the energy density with respect to the conventionally proposed string-like electrochemical device, In addition, a reduction in size and weight can be realized.

  Here, the active material particles constituting the electrode are preferably primary particles. When the active material particles are primary particles, the string-like electrochemical device can be further reduced in size and weight.

  In the present invention, “an electrode consisting essentially of an active material particle and a conductive additive having electronic conductivity supported on the active material particle” means an electrode other than the active material particle and the conductive additive. It means that a constituent material (for example, a binder or the like) is not intentionally added. That is, impurities contained in the raw material, impurities mixed when the conductive additive is carried on the active material particles, and the like may be mixed in the electrode as long as the effects of the present invention are not impaired. However, the total content of the active material particles and the conductive additive in the electrode is preferably 95% by mass or more based on the total solid content of the electrode.

  Moreover, in the string-like electrochemical device of the present invention, any one or both of the first electrode and the second electrode are active material particles, a conductive auxiliary agent having electronic conductivity, and the active material particles. It is also preferable that the electrode be composed of composite particles containing a binder capable of binding the conductive aid. By using such an electrode, it is possible to reduce a region that does not contribute to the electric capacity due to the presence of the current collector in the power storage element, and it is possible to improve the energy density and reduce the size of the conventionally proposed string-like electrochemical device. And weight reduction can be realized.

  In the string-like electrochemical device of the present invention, it is preferable that the plurality of power storage elements are accommodated in a tube-shaped case having flexibility. By accommodating the electricity storage element in the flexible tube-like case, a string-like electrochemical device in which a plurality of electricity storage elements are continuous is efficiently obtained while having a good degree of freedom in shape (flexibility). Can be configured.

  Here, the tubular case is preferably made of a resin having a flexural modulus of 200 to 2000 MPa. Thereby, the shape freedom degree (folding freedom degree) of a string-like electrochemical device can be made more favorable, and sufficient intensity | strength can be maintained simultaneously.

  Furthermore, in the string-like electrochemical device of the present invention, it is preferable that the plurality of power storage elements are electrically connected in parallel by a terminal member having linear or band-like electronic conductivity. Thereby, it is possible to efficiently configure a high-capacity string-like electrochemical device in which a plurality of power storage elements are connected in parallel while having a good degree of freedom of shape (degree of freedom of bending).

  ADVANTAGE OF THE INVENTION According to this invention, the string-shaped electrochemical device excellent in the shape freedom degree (folding freedom degree) can be provided.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios.

  Further, in this specification, the anode active material particles are referred to as “anode active material particles”, and the cathode active material particles are referred to as “cathode active material particles”. Here, the “anode” in the case of “anode active material particles” is a material based on the polarity at the time of discharging of the electricity storage element (negative electrode active material), and the “cathode” in the case of “cathode active material particles”. Is based on the polarity at the time of discharging of the electricity storage element (positive electrode active material).

  First, the electrical storage element which comprises the string-like electrochemical device of this invention is demonstrated. FIG. 1 is a schematic cross-sectional view showing a preferred embodiment of a power storage element (lithium ion secondary battery) constituting the string-like electrochemical device of the present invention. FIG. 2 is a schematic diagram illustrating an example of an electrode (cathode) that constitutes the power storage element illustrated in FIG. 1.

  As shown in FIG. 1, the power storage device 1 includes a cathode 10 (first electrode), an anode 20 (second electrode), and an electrolyte layer 30 disposed between the cathode 10 and the anode 20. It is configured.

  Here, as shown in FIG. 2, the cathode 10 is substantially composed of cathode active material particles 12 (first active material particles) and a conductive auxiliary agent having electronic conductivity carried on the cathode active material particles 12. 14 (first conductive auxiliary agent) only. Similarly to the cathode 10, the anode 20 substantially has anode active material particles 22 (second active material particles) and a conductive auxiliary agent 24 having electronic conductivity carried on the anode active material particles 22 ( (Second conductive auxiliary agent) only.

  An electrolyte layer 30 having ionic conductivity is disposed between the cathode 10 and the anode 20 to form the electricity storage device 1. The cathode 10 and the anode 20 are kept in a non-contact state due to the electrolyte layer 30 interposed therebetween.

The cathode active material particles 12 constituting the cathode 10 are not particularly limited, and a known electrode active material can be used. Examples of the cathode active material particles 12 include lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), lithium manganese spinel (LiMn ₂ O ₄ ), and a general formula: LiNi _x Mn _y Co _z O _2. Composite metal oxide represented by (x + y + z = 1), lithium vanadium compound, V ₂ O ₅ , olivine-type LiMPO ₄ (where M represents Co, Ni, Mn, Fe or a metal containing a plurality of them), etc. Metal phosphate compounds, lithium titanate (Li ₄ Ti ₅ O ₁₂ ), and the like.

  The conductive auxiliary agent 14 constituting the cathode 10 is not particularly limited, and a known conductive auxiliary agent can be used. Examples of the conductive aid 14 include carbon blacks, carbon materials such as highly crystalline artificial graphite and natural graphite, metal fine powders such as copper, nickel, stainless steel and iron, a mixture of the above carbon materials and metal fine powders, ITO And the like, and the like.

The anode active material particles 22 constituting the anode 20 are not particularly limited, and a known electrode active material can be used. Examples of the anode active material particles 22 include carbon materials such as graphite, non-graphitizable carbon, graphitizable carbon, and low-temperature calcined carbon capable of occluding and releasing (intercalating or doping / dedoping) lithium ions. Metals that can be combined with lithium such as Al, Si and Sn, amorphous compounds mainly composed of oxides such as SiO ₂ and SnO ₂ , lithium titanate (Li ₄ Ti ₅ O ₁₂ ) and the like It is done.

  As the conductive auxiliary agent 24 constituting the anode 20, the same material as the conductive auxiliary agent 14 constituting the cathode 10 can be used.

  Moreover, in the electrical storage element 1, the anode may be comprised only by the particle | grains which consist of the carbon material mentioned above. Furthermore, when the electrical storage element 1 is a metal lithium secondary battery, the anode may be comprised only by the particle | grains which consist of metal lithium or a lithium alloy. The lithium alloy is not particularly limited, and examples thereof include alloys such as Li—Al, LiSi, and LiSn (here, LiSi is also handled as an alloy). In such a case, the cathode is preferably the cathode 10 composed of the cathode active material particles 12 carrying the above-described conductive additive 14.

  Moreover, in the electrical storage element 1, from the viewpoint of obtaining a superior energy density, it is preferable that either one of the cathode active material particles 12 and the anode active material particles 22 is made of a lithium composite oxide. More preferably, the material particles 12 are made of a lithium composite oxide, and the anode active material particles 22 are made of graphite.

  Moreover, when the electrical storage element 1 is an electrochemical capacitor, as the cathode active material particles 12 and the anode active material particles 22, for example, granular or fibrous activated activated carbon or metal oxide can be used. Those having a high electric double layer capacity, such as coconut husk activated carbon, pitch-based activated carbon, and phenol resin-based activated carbon, can be preferably used.

  Here, the particle diameters of the cathode active material particles 12 and the anode active material particles 22 are preferably 0.1 to 50 μm, and more preferably 1 to 30 μm. Moreover, when the electrical storage element is an electrochemical capacitor, the particle diameters of the cathode active material particles 12 and the anode active material particles 22 are preferably 0.1 to 50 μm, and more preferably 1 to 30 μm. By making the particle diameters of the cathode active material particles 12 and the anode active material particles 22 within the above range, the power storage element 1 can be sufficiently reduced in size and weight, so that the string-like electrochemical device using the same Can be sufficiently reduced in size and weight.

  Further, one or both of the cathode active material particles 12 and the anode active material particles 22 are preferably single particles, and more preferably primary particles. When the cathode active material particles 12 and the anode active material particles 22 are composed of a plurality of particles, adhesion or electrical connection between the particles tends to be insufficient. Since the cathode active material particles 12 and the anode active material particles 22 are single particles or primary particles, the above-described problems in the case of a plurality of particles can be solved, and the electricity storage device 1 and the same are used. The string electrochemical device can be more efficiently reduced in size and weight.

  Moreover, it is preferable that the average primary particle diameter of the conductive support agents 14 and 24 is 0.01-10 micrometers, and it is more preferable that it is 0.02-3 micrometers. If the average primary particle diameter is less than 0.01 μm, the electron conduction path tends to be insufficient, and if it exceeds 10 μm, the conductive auxiliary agent is too large compared to the active material particles, so that the energy density of the storage element. There is a tendency to lower.

  Further, in the cathode 10 and the anode 20, the ratio of the particle size of the active material particles to the average primary particle size of the conductive auxiliary agent (particle size of the active material particles / average primary particle size of the conductive auxiliary agent) is 5 to 5000. It is preferable that it is 10 to 1000. If the particle size ratio exceeds 5000, the electron conduction path tends to be insufficient, and if it is less than 5, the conductive assistant is too large compared to the active material particles, thereby reducing the energy density of the electricity storage device. Tend.

  Furthermore, in the cathode 10 and the anode 20, the ratio of the content of the active material particles and the conductive additive is preferably 100: 1 to 2: 1, and 60: 1 to 5: 1 in terms of mass ratio. Is more preferable. By setting the content ratio within the above range, there is a tendency that a sufficient electron conduction path can be secured without reducing the energy density.

  Moreover, in the cathode 10 and the anode 20, the coverage of the active material particle surface with the conductive assistant is preferably 20 to 90%, more preferably 30 to 80%, and 40 to 70%. Is particularly preferred. Here, the said coverage is a ratio which a conductive support agent coat | covers an active material particle, and is specifically calculated | required with the following method. That is, an SEM (Scanning Electron Microscope) photograph of the active material particles carrying the conductive assistant is taken at a magnification of 30000 times, and in the photograph, the active material particles and the conductive material adhering thereto are observed. Of the total area of the auxiliary agent, the ratio of the area occupied by the conductive auxiliary agent is determined as the coverage. When the coverage is within the above range, when the power storage device 1 is configured, the impedance can be more sufficiently reduced and a more excellent energy density can be obtained.

The conductivity of the cathode 10 and the anode 20 is preferably 1 × 10 ⁻¹ S / m or more, more preferably 1 × 10 ^{−2 to} 6.2 × 10 ⁷ S / m, and more preferably 1 × 10 6. ^{-4 to} 6.2 × 10 ⁷ S / m is particularly preferable. If this conductivity is less than 1 × 10 ⁻¹ S / m, the internal resistance of the electricity storage element tends to increase, and the substantial input / output characteristics tend to deteriorate.

  Moreover, the shape of the cathode 10 and the anode 20 is not specifically limited, For example, a substantially spherical shape may be sufficient.

  The electrolyte layer 30 may be a layer made of an electrolytic solution, or a layer made of a solid electrolyte (ceramic solid electrolyte, solid polymer electrolyte). The separator and the electrolytic solution impregnated in the separator and / or Alternatively, it may be a layer made of a solid electrolyte.

The electrolytic solution is prepared by dissolving a lithium-containing electrolyte in a non-aqueous solvent. The lithium-containing electrolyte may be appropriately selected from, for example, LiClO ₄ , LiBF ₄ , LiPF _{6 and the} like, and Li (CF ₃ SO ₂ ) ₂ N, Li (C ₂ F ₅ SO ₂ ) ₂ N, etc. and lithium imide salt, _{LiB (C 2} O ₄₎ may be used ₂ or the like. The non-aqueous solvent can be selected from, for example, ethers, ketones, carbonates and the like, and organic solvents exemplified in JP-A No. 63-121260, but in the present invention, carbonates are particularly used. Is preferred. Among carbonates, it is particularly preferable to use a mixed solvent in which ethylene carbonate is the main component and one or more other solvents are added. Usually, the mixing ratio is preferably ethylene carbonate: other solvent = 5 to 70:95 to 30 (volume ratio). Since ethylene carbonate has a high freezing point of 36.4 ° C and is solidified at room temperature, ethylene carbonate alone cannot be used as a battery electrolyte, but it can be mixed by adding one or more other solvents having a low freezing point. The freezing point of the solvent is lowered and it can be used.

  The other solvent in this case is not particularly limited as long as it lowers the freezing point of ethylene carbonate. Examples of such other solvents include diethyl carbonate, dimethyl carbonate, propylene carbonate, 1,2-dimethoxyethane, methyl ethyl carbonate, γ-butyrolactone, γ-parerolactone, γ-octanoic lactone, 1,2-diethoxy. Ethane, 1,2-ethoxymethoxyethane, 1,2-dibutoxyethane, 1,3-dioxolanane, tetrahydrofuran, 2-methyltetrahydrofuran, 4,4-dimethyl-1,3-dioxane, butylene carbonate, methyl formate, etc. Can be mentioned. By using a carbonaceous material as the anode active material particles and using the above mixed solvent, the battery capacity is remarkably improved and the irreversible capacity ratio can be sufficiently lowered.

Examples of the solid polymer electrolyte include a conductive polymer having ionic conductivity. Such a conductive polymer is not particularly limited as long as it has lithium ion conductivity. For example, a polymer compound (polyether-based polymer compound such as polyethylene oxide or polypropylene oxide, or a crosslinked polymer compound having a high molecular weight) Molecules, polyepichlorohydrin, polyphosphazene, polysiloxane, polyvinylpyrrolidone, polyvinylidene carbonate, polyacrylonitrile, etc.) monomers, and LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAsF ₆ , LiCl, LiBr, Li (CF ₃ SO ₂ ) _{2 N, LiN (C 2 F} 5 SO 2) and alkali metal salt composed mainly of ₂ lithium salt or lithium, those were complexed and the like. Examples of the polymerization initiator used for the combination include a photopolymerization initiator or a thermal polymerization initiator that is compatible with the above-described monomer.

Furthermore, as the supporting salt constituting the polymer solid electrolyte, for example, LiClO ₄ , LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CF ₂ SO ₃ , LiC (CF ₃ SO ₂ ) ₃ , LiN A salt such as (CF ₃ SO ₂ ) ₂ , LiN (CF ₃ CF ₂ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ) and LiN (CF ₃ CF ₂ CO) ₂ , or These mixtures can be mentioned.

  In the case of using a separator for the electrolyte layer 30, as a constituent material thereof, for example, one or more of polyolefins such as polyethylene and polypropylene (in the case of two or more, there is a laminate of two or more layers). And polyesters such as polyethylene terephthalate, thermoplastic fluororesins such as ethylene-tetrafluoroethylene copolymer, and celluloses. The form of the sheet includes a microporous membrane film, a woven fabric, a non-woven fabric, etc. having an air permeability measured by the method specified in JIS-P8117 of about 5 to 2000 sec / 100 cc and a thickness of about 5 to 100 μm. A solid electrolyte monomer may be impregnated into a separator and cured to be polymerized. Moreover, you may use it, making the electrolyte solution mentioned above contain in a porous separator.

As for the magnitude | size of the electrical storage element 1, it is preferable that a volume is 2 * 10 <^-12> -2 * 10 <^-4> mm < ³ >. Making the power storage element larger than necessary will substantially reduce the ion conduction path and tend to increase the impedance.

  The power storage device 1 described above can be manufactured, for example, by the following method. First, the conductive assistant (first conductive assistant 14 or second conductive assistant 24) is supported on the active material particles (cathode active material particles 12 or anode active material particles 22), and the cathode 10 and the anode 20 are mounted. Make it.

  Here, the method for supporting the conductive additive on the active material particles is not particularly limited, and for example, the following method can be used. That is, it is possible to use a method in which the active material particles and the conductive auxiliary agent are stirred in a media mill such as a ball mill and the conductive auxiliary agent is fixed to the surface of the active material particles by a physical adsorption phenomenon at that time. Moreover, it is preferable to heat-process in an inert atmosphere, after carrying out dry processing of the active material particle and the conductive support agent with a ball mill or the like. By conducting the heat treatment, the conductive additive can be more sufficiently fixed on the surface of the active material particles.

  In addition, as another method of supporting the conductive auxiliary agent on the active material particles, for example, a method of attaching a conductive auxiliary agent (carbon or the like) to the active material particles by chemical vapor deposition using a fluidized bed reactor or the like, A method of mixing substance particles and a precursor solution of a conductive additive (carbon or the like) and then heat-treating under an inert atmosphere can be used.

  Next, the electrolyte layer 30 is formed between the cathode 10 and the anode 20. Here, when the electrolyte layer 30 is a layer using a polymer electrolyte, the storage element 1 can be formed by solidifying and connecting the cathode 10 and the anode 20 using a light or thermosetting monomer. . Further, when the electrolyte layer 30 is a layer using an electrolytic solution, the electrolytic solution is put in a container such as a glass capillary, and the cathode 10 and the anode 20 are disposed opposite to each other with the electrolytic solution sandwiched in the container. The power storage element 1 can be formed. In either case, a separator may be interposed between the cathode 10 and the anode 20.

  In the electricity storage device 1 manufactured in this way, electrical connection with the outside is performed by an exposed portion of the cathode 10 and the anode 20 on the opposite side to the electrolyte layer 30.

  As described above, for the electricity storage element constituting the string-like electrochemical device of the present invention, either one or both of the first electrode and the second electrode in the electricity storage element are substantially on the active material particles and the active material particles. Although the description has been given of the case where the electrode is composed of a supported conductive agent having electron conductivity, the power storage element used in the present invention is not limited to the above.

  That is, in the electricity storage element constituting the string-like electrochemical device of the present invention, either one or both of the first electrode and the second electrode in the electricity storage element are active material particles and a conductive assistant having electronic conductivity. It is also preferable that the electrode be composed of composite particles containing an agent and a binder capable of binding them. Moreover, the electrical storage element which comprises the string-like electrochemical device of this invention may be formed using the conventionally well-known electrode. Hereinafter, a power storage device in the case where the composite particle is used for an electrode will be described.

  FIG. 3 is a schematic cross-sectional view showing an example of the basic configuration of the composite particles used for the electrodes in the electricity storage element constituting the string-like electrochemical device of the present invention. Further, FIG. 4 is a schematic cross-sectional view schematically showing the internal structure of the electrode made of composite particles.

  As shown in FIGS. 3 and 4, the composite particle P10 is composed of particles (active material particles) P1 made of an electrode active material, particles P2 made of a conductive additive, and particles P3 made of a binder. Yes. The average particle size of the composite particles P10 is not particularly limited. The composite particle P10 has a structure in which particles P1 made of an electrode active material and particles P2 made of a conductive additive are electrically coupled without being isolated. Therefore, also in the electrode, a structure is formed in which the particles P1 made of the electrode active material and the particles P2 made of the conductive auxiliary agent are electrically isolated without being isolated. An extremely good electron conduction path (electron conduction network) is three-dimensionally constructed in an electrode using composite particles having such a structure.

  The active material particles constituting the composite particles P10 used for the cathode of the energy storage device are not particularly limited, and known electrode active materials can be used. As such active material particles, the same material as the cathode active material particles 12 constituting the cathode 10 in the power storage device 1 described above can be used.

  The conductive aid constituting the composite particle P10 used for the cathode of the electricity storage device is not particularly limited, and a known conductive aid can be used. As such a conductive additive, the same material as the conductive additive 14 constituting the cathode 10 in the power storage device 1 described above can be used.

  The binder constituting the composite particle P10 used for the cathode of the energy storage device is not particularly limited as long as it can bind the above active material particles and the conductive additive. Examples of the binder include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer ( Fluororesin such as PFA), ethylene-tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyvinyl fluoride (PVF), and the like. .

  In addition to the above, the binder may be, for example, vinylidene fluoride-hexafluoropropylene-based fluororubber (VDF-HFP-based fluororubber), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene-based fluororubber (VDF- HFP-TFE fluorine rubber), vinylidene fluoride-pentafluoropropylene fluorine rubber (VDF-PFP fluorine rubber), vinylidene fluoride-pentafluoropropylene-tetrafluoroethylene fluorine rubber (VDF-PFP-TFE fluorine rubber) ), Vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene fluorine rubber (VDF-PFMVE-TFE fluorine rubber), vinylidene fluoride-chlorotrifluoroethylene fluorine rubber It may be used vinylidene fluoride fluoroelastomer of the VDF-CTFE-based fluorine rubber) and the like.

  In addition to the above, as the binder, for example, polyethylene, polypropylene, polyethylene terephthalate, aromatic polyamide, cellulose, styrene / butadiene rubber, isoprene rubber, butadiene rubber, ethylene / propylene rubber, or the like may be used. Also, thermoplastic elastomeric polymers such as styrene / butadiene / styrene block copolymers, hydrogenated products thereof, styrene / ethylene / butadiene / styrene copolymers, styrene / isoprene / styrene block copolymers, and hydrogenated products thereof. May be used. Further, syndiotactic 1,2-polybutadiene, ethylene / vinyl acetate copolymer, propylene / α-olefin (carbon number 2 to 12) copolymer and the like may be used. Further, a conductive polymer may be used.

  Moreover, you may further add to the composite particle P10 the particle | grains which consist of an electroconductive polymer as a structural component of the said composite particle P10.

For example, the conductive polymer is not particularly limited as long as it has lithium ion conductivity. For example, polymer compounds (polyether-based polymer compounds such as polyethylene oxide and polypropylene oxide, crosslinked polymers of polyether compounds, polyepichlorohydrin, polyphosphazene, polysiloxane, polyvinylpyrrolidone, polyvinylidene carbonate, polyacrylonitrile, etc.) Monomer and LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAsF ₆ , LiCl, LiBr, Li (CF ₃ SO ₂ ) ₂ N, LiN (C ₂ F ₅ SO ₂ ) ₂ lithium salt or an alkali metal salt mainly composed of lithium And the like. Examples of the polymerization initiator used for the combination include a photopolymerization initiator or a thermal polymerization initiator that is compatible with the above-described monomer.

  The active material particles constituting the composite particles P10 used for the anode of the electricity storage device are not particularly limited, and known electrode active materials can be used. As such active material particles, the same material as the cathode active material particles 22 constituting the anode 20 in the power storage device 1 described above can be used.

  Further, each constituent element other than the active material particles constituting the composite particles P10 used for the anode of the electricity storage device can use the same materials as those constituting the composite particles P10 used for the cathode.

  Further, in the electricity storage device, the anode may be composed only of particles made of the carbon material described above. Furthermore, when the storage element is a metal lithium secondary battery, the anode may be composed only of particles made of metal lithium or a lithium alloy. The lithium alloy is not particularly limited, and examples thereof include alloys such as Li—Al, LiSi, and LiSn (here, LiSi is also handled as an alloy). In such a case, the cathode is preferably composed of the composite particles P10 described above.

  In the electric storage element, from the viewpoint of obtaining a superior energy density, it is preferable that either one of the active material particles constituting the cathode and the active material particles constituting the anode is made of a lithium composite oxide. More preferably, the active material particles constituting the cathode are made of a lithium composite oxide, and the active material particles constituting the anode are made of graphite.

  Further, when the power storage element is an electrochemical capacitor, the active material particles constituting the cathode and the active material particles constituting the anode are the same as those used when the power storage element 1 described above is an electrochemical capacitor. Substances can be used.

Here, from the viewpoint of forming a contact interface with the conductive auxiliary agent, the active material particles, and the electrolyte layer in a three-dimensional and sufficient size, the particles P1 made of the electrode active materials respectively included in the anode and the cathode. In the case of a cathode, the BET specific surface area is preferably 0.1 to 1.0 m ² / g, and more preferably 0.1 to 0.6 m ² / g. Further, when the anode is preferably from 0.1 to 10 m ² / g, more preferably 0.1 to 5 m ² / g. In the case of an electrochemical capacitor, both the cathode and the anode are preferably 500 to 3000 m ² / g.

  Further, from the same viewpoint, the average particle diameter of the particles P1 made of each electrode active material is preferably 5 to 20 μm, more preferably 5 to 15 μm in the case of the cathode. Moreover, in the case of an anode, it is preferable that it is 1-50 micrometers, and it is more preferable that it is 1-30 micrometers. Furthermore, from the same point of view, the amount of the conductive assistant and the binder adhering to the electrode active material is a value of 100 × (mass of conductive assistant + mass of binder) / (mass of electrode active material). When expressed, it is preferably 1 to 30% by mass, and more preferably 3 to 15% by mass.

  Further, in the electricity storage device using the composite particle P10, the configuration other than the electrodes can be the same as that of the electricity storage device 1 described above.

  The composite particle P10 described above can be manufactured, for example, by the following method. The composite particle P10 is a composite particle containing an electrode active material, a conductive assistant, and a binder by bringing the conductive assistant and the binder into close contact with the particle P1 made of an electrode active material. It forms through the granulation process to form. This granulation process will be described.

  The granulation process will be described more specifically with reference to FIG. FIG. 5 is an explanatory view showing an example of a granulating step when producing composite particles.

  The granulation step includes a raw material solution preparation step for preparing a raw material solution containing a binder, a conductive additive, and a solvent, an air flow is generated in the fluidized tank, and particles made of an electrode active material are introduced into the air flow. A fluidized bed forming step of fluidizing the particles made of the electrode active material, and spraying the raw material liquid into the fluidized bed containing the particles made of the electrode active material, thereby attaching the raw material liquid to the particles made of the electrode active material, A spray drying step of drying, removing the solvent from the raw material liquid adhering to the surface of the particles made of the electrode active material, and bringing the particles made of the electrode active material and the particles made of the conductive auxiliary agent into close contact with each other by a binder; Including.

  First, in the raw material liquid preparation step, a solvent capable of dissolving the binder is used, and the binder is dissolved in this solvent. Next, a conductive additive is dispersed in the obtained solution to obtain a raw material liquid. In addition, in this raw material liquid preparation process, the solvent (dispersion medium) which can disperse | distribute a binder may be sufficient.

  Next, in the fluidized bed forming step, as shown in FIG. 5, an air flow is generated in the fluidized tank 5, and the particles P <b> 1 made of the electrode active material are put into the air flow, thereby making the electrode active material. Particles are fluidized.

  Next, in the spray drying step, as shown in FIG. 5, particles made of an electrode active material in which the liquid droplets 6 of the raw material liquid are sprayed into the fluidized tank 5 by spraying the liquid droplets 6 of the raw material liquid. The solvent is removed from the liquid droplet 6 of the raw material liquid adhering to the surface of the particle P1 made of the electrode active material, and simultaneously dried in the fluidized tank 5, and the particles P1 made of the electrode active material by the binder. The particles P2 made of a conductive additive are brought into close contact with each other to obtain composite particles P10.

  More specifically, the fluid tank 5 is, for example, a container having a cylindrical shape, and warm air (or hot air) L5 is introduced into the bottom thereof from the outside, and the electrode active material is contained in the fluid tank 5. An opening 52 for convection of particles consisting of is provided. Further, an opening 54 is provided on the side surface of the fluid tank 5 for allowing the droplets 6 of the raw material liquid to be sprayed to flow into the particles P1 made of the electrode active material convected in the fluid tank 5. ing. The droplets 6 of the raw material liquid containing the binder, the conductive assistant and the solvent are sprayed on the particles P1 made of the electrode active material convected in the fluidized tank 5.

  At this time, the temperature of the atmosphere in which the particles P1 made of the electrode active material are placed can be quickly removed by adjusting the temperature of the hot air (or hot air), for example. The electrode is kept at a predetermined temperature (preferably a temperature not exceeding the melting point of the binder substantially from 50 ° C., more preferably a temperature not higher than the melting point of the binder (eg, 200 ° C.)). The liquid film of the raw material liquid formed on the surface of the particles P1 made of the active material is dried almost simultaneously with the spraying of the droplets 6 of the raw material liquid. As a result, the binder and the conductive auxiliary agent are brought into close contact with the surface of the particles made of the electrode active material, thereby obtaining composite particles P10.

  Here, the solvent capable of dissolving the binder is not particularly limited as long as the binder can be dissolved and the conductive auxiliary agent can be dispersed. For example, N-methyl-2-pyrrolidone, N , N-dimethylformamide and the like can be used.

  The anode composite particles P10 and the cathode composite particles P10 are formed by changing the kind of the particles P1 made of the electrode active material.

  In the composite particle P10 formed by the method described above, the internal structure schematically shown in FIG. 3 is formed. That is, in the composite particle P10, although the particle P3 made of the binder is used, the particle P1 made of the electrode active material and the particle P2 made of the conductive auxiliary agent are electrically coupled without being isolated. The structure is formed.

  The thus obtained composite particles P10 constitute an anode and a cathode, and an electrolyte layer can be formed between the cathode and the anode in the same manner as in the case of the electricity storage device 1 described above to obtain an electricity storage device. .

  Next, the string-like electrochemical device of the present invention using the above-described power storage element will be described. FIG. 6 is a schematic cross-sectional view showing a preferred embodiment of the string-like electrochemical device of the present invention. FIG. 7 is a schematic cross-sectional view when the string-like electrochemical device shown in FIG. 6 is cut perpendicular to the longitudinal direction.

  As shown in FIGS. 6 and 7, in the string-like electrochemical device 100, two linear cathodes are used as terminal members having electron conductivity in an insulating tubular case 40 having flexibility. The terminal 16 and the two linear anode terminals 26 are disposed along the inner wall of the tubular case 40 at a predetermined interval. In the tubular case 40, a large number of the above-described power storage elements 1, the cathode 10 of the power storage element 1 and the two cathode terminals 16 are in electrical contact, and the anode 20 and the two anodes It arrange | positions in parallel so that the terminal 26 may contact electrically. Furthermore, both ends of the tubular case 40 are sealed with an insulating sealing material 42, and the power storage device 1 is sealed inside the tubular case 40. Further, the two cathode terminals 16 and the two anode terminals 26 pass through the sealing material 42 and are taken out to the outside of the tubular case 40, and the surfaces of the terminals 16 and 26 taken out to the outside are It is covered with an insulating protective material 44.

  Here, the tubular case 40 is not particularly limited as long as it is made of an insulating material having flexibility. Examples of the material of the tubular case 40 include fluorine resins such as polytetrafluoroethylene and polyvinylidene fluoride (PVdF), polypropylene, polyethylene, vinyl chloride, silicon resin, and acrylonitrile resin.

  Moreover, it is preferable that the bending elastic modulus of the tubular case 40 is 200-2000 MPa, and it is more preferable that it is 500-1300 MPa. If the flexural modulus is less than 200 MPa, the contact between the terminal and the storage element tends to become unstable during deformation, and if it exceeds 2000 MPa, deformation becomes difficult and the degree of freedom in shape tends to decrease.

  Moreover, it is preferable that the diameter (outer diameter) of the tubular case 40 is 1-2000 micrometers, and it is more preferable that it is 30-500 micrometers. When the diameter is less than 1 μm, when the tube is lengthened, the terminal tends to be thin and the resistance tends to increase. When the diameter exceeds 2000 μm, the electrode of the internal storage element tends to be thick and the impedance tends to increase.

  Furthermore, the thickness of the tubular case 40 is preferably 1/20 to 1/4 of the diameter of the power storage element, and more preferably 1/10 to 1/5. When the thickness is less than 1/20 of the diameter of the electricity storage element, the tube tends to be damaged during deformation. When the thickness exceeds 1/4 of the direct line of the electricity storage element, the shape of the string-like electrochemical device 100 is free. Tend to decrease.

  The shape of the tubular case 40 is not particularly limited, and the cross-sectional shape cut perpendicularly to the longitudinal direction may be a substantially circular shape, an elliptical shape, a polygonal shape, etc., as shown in FIG. A substantially circular shape is preferred.

  The cathode terminal 16 and the anode terminal 26 are not particularly limited as long as they are made of a material having electronic conductivity. Examples of the material of the cathode terminal 16 and the anode terminal 26 include stainless steel, gold, silver, copper, platinum, aluminum, palladium, rhodium, iridium, osmium, carbon fiber, and carbon nanotube.

  The diameters of the cathode terminal 16 and the anode terminal 26 are preferably 1/100 to 1/1 of the diameter of the electricity storage element, and more preferably 1/50 to 1/2. When the diameter is less than 1/100 of the diameter of the storage element, the cathode terminal 16 and the anode terminal 26 tend to break when the string-like electrochemical device 100 is bent, and 1/1 of the diameter of the storage element is reduced. When it exceeds, there exists a tendency for the shape freedom degree of the string-like electrochemical device 100 to fall.

  The shapes of the cathode terminal 16 and the anode terminal 26 are not particularly limited, but are preferably linear or strip-shaped. Further, the cross-sectional shape cut perpendicularly to the longitudinal direction of the cathode terminal 16 and the anode terminal 26 may be a substantially circular shape, an elliptical shape, a polygonal shape, etc., but a substantially circular shape as shown in FIG. It is preferably oval.

  Further, the number of cathode terminals 16 and anode terminals 26 is not particularly limited as long as it is one or more. From the viewpoint of ensuring more stable electrical connection between the cathode terminal 16 and the anode terminal 26 and the electricity storage element 1 when the string-like electrochemical device 100 is bent or used for a long period of time, as shown in FIG. Each is preferably two or more. However, from the viewpoint of reducing the size and weight of the string-like electrochemical device 100, the number of cathode terminals 16 and anode terminals 26 is preferably 160 or less.

  The sealing material 42 is not particularly limited as long as it is made of an insulating material. Examples of the material of the sealing material 42 include fluorine resins such as polytetrafluoroethylene (PTFE) and PVdF, epoxy resins, polypropylene (PP), polyethylene (PE), polyvinylidene chloride (PVC), phenol resins, and urea. Examples thereof include resins, melamine resins, polyesters, acrylonitrile-butadiene-styrene copolymer synthetic resins (ABS), polyethylene terephthalate (PET), polycarbonates, and silicone resins.

  The protective material 44 is not particularly limited as long as it is made of an insulating material. Examples of the material of the protective material 44 include fluorine resin such as PTFE and PVdF, epoxy resin, PP, PE, PVC, phenol resin, urea resin, melamine resin, polyester, ABS, PET, polycarbonate, silicon resin, and the like. It is done.

In the string-like electrochemical device 100, the tube-shaped case 40, the sealing material 42, and the protective material 44 may be any material that has sufficient electrical insulation properties to constitute the electrochemical device. The specific resistance is preferably 1 × 10 ¹⁴ Ω · cm or more.

  Furthermore, in the string-like electrochemical device 100, the voids in the tubular case 40 may be filled with an insulating resin (such as a thermosetting or photocurable polymer) as necessary. Thereby, the electrical storage element 1, the cathode terminal 16, the anode terminal 26, etc. can be fixed more stably.

  According to the string-like electrochemical device 100, even when a sharp bend is applied, the stress is absorbed by a connection portion (such as a gap between the power storage elements 1) between the plurality of power storage elements 1. The destruction of the portion can be sufficiently suppressed, and an excellent shape freedom (bending flexibility) can be obtained. In addition, since the power storage device 1 is configured as described above, it is possible to reduce the size and weight, and to obtain an excellent energy density. Moreover, since the electrical storage elements 1 are connected in parallel, a high capacity can be obtained.

  FIG. 8 is a schematic cross-sectional view showing another preferred embodiment of the string-like electrochemical device of the present invention. In the string-like electrochemical device 200 shown in FIG. 8, a large number of the above-described power storage elements 1 are arranged in series in an insulating tubular case 40 having flexibility. A current collector 35 is disposed between the power storage elements 1. Further, a cathode terminal 18 and an anode terminal 28 are provided at both ends of the tubular case 40 as external output terminals.

  Here, the current collector 35 is not particularly limited as long as it is a good conductor capable of sufficiently moving charges, and a known current collector can be used. For example, the current collector 35 may be a metal foil such as copper, aluminum, and stainless steel. In the string-like electrochemical device 200, the current collector 35 may have the same diameter as the inner diameter of the tubular case 40 or may be smaller than that. In addition, the string-like electrochemical device 200 may not include the current collector 35 as long as it is possible to sufficiently prevent a short circuit between the electricity storage elements 1.

  Further, the cathode terminal 18 and the anode terminal 28 are not particularly limited as long as they are made of a material having electron conductivity. Examples of the material of the cathode terminal 16 and the anode terminal 26 include stainless steel, gold, silver, copper, platinum, aluminum, palladium, rhodium, iridium, osmium, carbon fiber, and carbon nanotube.

  Moreover, as the tubular case 40, the thing similar to the tubular case 40 in the string-like electrochemical device 100 demonstrated previously can be used.

  Furthermore, in the string-like electrochemical device 200, the gap in the tubular case 40 may be filled with an insulating resin (such as a thermosetting or photocurable polymer) as necessary. Thereby, the electrical storage element 1 and the electrical power collector 35 can be fixed more stably.

  According to the string-like electrochemical device 200, even when a sharp bend is applied, the stress is absorbed by the connection portion between the plurality of power storage elements 1 (such as gaps between the power storage elements 1). The destruction of the portion can be sufficiently suppressed, and an excellent shape freedom (bending flexibility) can be obtained. In addition, since the power storage device 1 is configured as described above, it is possible to reduce the size and weight, and to obtain an excellent energy density. Moreover, since the electrical storage element 1 is connected in parallel, a high voltage can be obtained.

  The string-like electrochemical device of the present invention is not limited to the string-like electrochemical devices 100 and 200 described above. Further, in the string-like electrochemical devices 100 and 200, the power storage element is not limited to the power storage element 1 described above, and is a power storage element using a composite particle as an electrode or a power storage element using a conventionally known electrode. Also good.

  Further, the string-like electrochemical device of the present invention is not limited to a form in which a power storage element formed in advance is enclosed in a tube-like case as in the string-like electrochemical devices 100 and 200 described above. For example, two current collectors are prepared, and either a cathode or an anode is provided on the surface of each current collector in a straight line, or both are alternately provided, and a cathode and an anode of separate current collectors are provided. However, they may be bonded so as to face each other with the electrolyte layer interposed therebetween and housed in a tubular case to form a string-like electrochemical device. The formation of the cathode and anode on the current collector may be carried by placing the cathode and anode particles directly on the current collector, or once developing the cathode and anode particles in a solvent, You may spray on a collector. At this time, the current collector may be in the form of a string or ribbon that is enclosed in a tube-shaped case, or may be cut out and used after a large-area current collector is provided with an anode and a cathode. Good. When a large-area current collector is used, the cathode and the anode may be arranged linearly or alternately on the large-area current collector, and the current collector may be cut and pasted as described above. it can. In this case, it is preferable to use a spraying method with excellent position controllability, for example, an ink jet method.

  Since the string-shaped electrochemical device of the present invention has a configuration in which a plurality of power storage elements are continuously arranged, for example, a string-shaped electrochemical device having a sufficient length is prepared in advance, and from there It is also possible to cut out and use the necessary length. At this time, when the power storage elements are connected in parallel, the capacity can be adjusted by the length to be cut out, and when the power storage elements are connected in series, the voltage can be adjusted by the length to be cut out. Can do.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

(Example 1)
A mixing ratio of LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ with an average particle diameter of 20 μm as active material particles and acetylene black with an average primary particle diameter of 80 nm as a conductive auxiliary agent at a mass ratio of 95: 5. Then, it was dry-treated with a ball mill for 1 hour, and further subjected to heat treatment at 500 ° C. for 1 hour in an Ar atmosphere to give a conductive aid on the active material particles.

Moreover, the conductive polymer which has lithium ion conductivity used as an electrolyte layer was synthesize | combined on the following conditions. That is, LiN (C ₂ F ₅ SO ₂ ) ₂ (trade name: LiBETI, manufactured by 3M) and terminal acryloyl-modified alkylene oxide macromonomer (trade name: Elexcel, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., hereinafter referred to as “macromonomer”. ) Was mixed in acetonitrile to prepare a mixed solution containing LiN (C ₂ F ₅ SO ₂ ) ₂ and the macromonomer. The mixing ratio of the _{LiN (C 2 F 5 SO 2} ) 2 and the macromonomer in this _case, the O (oxygen) atoms Li atom and macromonomer constituting a _{LiN (C 2 F 5 SO 2} ) 2 When expressed in terms of a molar ratio, it was adjusted to be 1:10. Next, a photopolymerization initiator (benzophenone-based photopolymerization initiator) was further mixed into this mixed solution. In addition, the input amount of the photopolymerization initiator in this step was adjusted so that the mass of the photopolymerization initiator: the mass of Elexel = 1: 100. Next, using an evaporator, a liquid (hereinafter referred to as “Li salt macromonomer solution”) in which the viscosity was increased by removing acetonitrile from the mixed liquid obtained after the above-described step was obtained.

  Next, one active material particle (primary particle) having a diameter of 20 μm to which the above-described conductive auxiliary agent was applied was inserted into a glass tube having an inner diameter of 20 μm, and this was used as a first electrode (cathode). The coverage of the active material particle surface with the conductive auxiliary agent was confirmed by SEM photography (magnification of 30,000 times) and found to be 45%. On the cathode, 5 pl of the above Li salt macromonomer solution was dropped to form an electrolyte precursor layer. Next, one graphite particle having a diameter of 20 μm was inserted on the electrolyte precursor layer, and this was used as a second electrode (anode). Thereafter, the Li salt macromonomer was polymerized by ultraviolet irradiation to form a polymer electrolyte layer so that the shortest distance between the anode and the cathode was 10 μm. As a result, a substantially cylindrical power storage element (diameter 20 μm, thickness 50 μm) having an anode, a cathode, and an electrolyte and having a power storage capability was obtained.

  Next, as shown in FIGS. 6 and 7, four stainless steel wires having a diameter of 10 μm are disposed along the inner wall of the PTFE tube in a PTFE (polytetrafluoroethylene) tube having an inner diameter of 100 μm, and the above-described electricity storage device. 1000 pieces were arranged in parallel so that the cathode and anode of the electricity storage element were in contact with two stainless steel wires, respectively. Next, stainless steel wires are taken out from both ends of the PTFE tube, and the two stainless steel wires in contact with the cathode of the electricity storage element are used as cathode terminals, and the two stainless steel wires in contact with the anode are used as anode terminals. In a state in which the PTFE tube was taken out, both ends of the PTFE tube were sealed with epoxy resin. As a result, a fibrous (string-like) lithium ion secondary battery having a terminal voltage of 3.7 V, a length of 3 cm, and a diameter of 100 μm was obtained.

  It was confirmed that the obtained lithium ion secondary battery did not break the electrochemical element portion even when it was bent at a steep angle (270 °), and was excellent in bending flexibility.

(Evaluation of battery characteristics)
The lithium ion secondary battery obtained in Example 1 was subjected to constant current charge / discharge measurement by a four-terminal method using an electrochemical measurement system (trade name: HZ3000) manufactured by Hokuto Denko Corporation. As a result, the capacity was 2.5 μAh. Moreover, the energy density was calculated | required from the value which remove | divided the product of the reversible capacity | capacitance of the charging / discharging measurement in 0.2C, and an average operating voltage by the battery volume. As a result, the energy density of the lithium ion secondary battery obtained in Example 1 was 1 kWh / L, and it was confirmed that the energy density was excellent.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional view showing a preferred embodiment of a storage element (lithium ion secondary battery) constituting a string-like electrochemical device of the present invention. It is a schematic diagram which shows an example of the electrode (cathode) which comprises the electrical storage element shown in FIG. It is a schematic cross section which shows an example of the basic composition of the composite particle used for the electrode in the electrical storage element which comprises the string-like electrochemical device of this invention. It is a schematic cross section which shows roughly the internal structure of the electrode which consists of composite particles. It is explanatory drawing which shows an example of the granulation process at the time of manufacturing composite particle. It is a schematic cross section which shows suitable one Embodiment of the string-like electrochemical device of this invention. It is a schematic cross section at the time of cut | disconnecting the string-like electrochemical device shown in FIG. 6 perpendicularly | vertically with respect to a longitudinal direction. It is a schematic cross section which shows other suitable one Embodiment of the string-like electrochemical device of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Power storage element, 10 ... Cathode, 12 ... Cathode active material particle, 14 ... Conductive aid, 16, 18 ... Cathode terminal, 20 ... Anode, 22 ... Anode active material particle, 24 ... Conductive aid, 26, 28 ... Anode terminal, 30 ... electrolyte layer, 35 ... current collector, 40 ... tubular case, 100, 200 ... string-like electrochemical device.

Claims (7)

  A plurality of power storage elements each including a first electrode, a second electrode, and an electrolyte layer having ion conductivity disposed between the first electrode and the second electrode are continuously formed in a string shape. A string-like electrochemical device that is electrically connected to each other in series or parallel.   Either one or both of the first electrode and the second electrode is an electrode substantially made of active material particles and a conductive additive having electron conductivity carried on the active material particles. Item 2. A string-like electrochemical device according to item 1.   The string-like electrochemical device according to claim 2, wherein the active material particles are primary particles.   Either or both of the first electrode and the second electrode may bind the active material particles, the conductive aid having electronic conductivity, and the active material particles and the conductive aid. The string-like electrochemical device according to claim 1, which is an electrode composed of composite particles containing a possible binder.   The string-like electrochemical device according to any one of claims 1 to 4, wherein the plurality of power storage elements are accommodated in a tubular case having flexibility.   The string-like electrochemical device according to claim 5, wherein the tubular case is made of a resin having a bending elastic modulus of 200 to 2000 MPa. The string-like electrochemical device according to any one of claims 1 to 6, wherein the plurality of power storage elements are electrically connected in parallel by a terminal member having linear or belt-like electronic conductivity. .

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