JP2008293883A - Conductive goods, anode material, their manufacturing method, plating liquid, and lithium secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide novel conductive goods, a lithium secondary battery with high capacity, a high output, and excellent in cycle characteristics, and its anode material, and further, provide plating liquid for forming the anode material. <P>SOLUTION: Conductive goods having organic polymer fiber dispersed in a metal-plated film formed on a base body, a collector, and an active material layer are provided, and in addition, the metal-plated film made as the active material layer is alloyed with lithium, an anode material structured of the organic polymer material, and plating liquid are provided. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a conductive article, a negative electrode material and a production method thereof, a plating solution, a negative electrode material for a lithium secondary battery, a plating solution for producing the material, a lithium secondary battery, and a product using the battery. .

  In recent years, with the spread of electronic devices such as notebook computers and mobile phones, and the rapid spread of hybrid vehicles against the background of global warming, secondary batteries used as power sources have become smaller and have higher energy density. It is requested. Conventionally, nickel-cadmium batteries, nickel-hydrogen batteries, and the like have been mainstream as secondary batteries, but there are great expectations for the performance improvement of lithium secondary batteries that are promising in terms of further miniaturization and higher energy density.

  When lithium metal is used as the negative electrode material, the lithium theoretical capacity is very high at 3860 mAh / g, but there is a drawback that dendrites are deposited during charging, which increases the internal resistance of the battery accompanying charging / discharging and decreases charging / discharging efficiency. . In addition, this dendrite may eventually break through the separator and reach the positive electrode side, causing an internal short circuit. For these reasons, lithium secondary batteries using lithium metal as the negative electrode material have problems in reliability and cycle life.

  Currently, carbon materials that can occlude and release lithium ions are used as a negative electrode material to replace lithium metal, and have been put into practical use. Usually, in a carbon material negative electrode, the possibility of internal short-circuiting due to lithium dendrite precipitation is low. However, the theoretical capacity of graphite, which is one of the carbon materials, is 372 mAh / g, which is as small as about one-tenth of the theoretical capacity of a single lithium metal. Further, since the manufacturing process is complicated and the yield is low, there is a disadvantage that the manufacturing cost increases.

As another negative electrode material, a metal material alloyed with lithium is known. For example, the composition formulas of the compounds containing the most lithium such as silicon (Si), tin (Sn), and zinc (Zn) are Li ₂₂ Si ₅ , Li ₂₂ Sn ₅ , and LiZn, respectively. Since it does not precipitate, there is no problem of internal short circuit due to dendrite. The respective theoretical capacities are 4199 mAh / g, 993 mAh / g, and 410 mAh / g, respectively, which are all larger than the theoretical capacity of graphite. However, in the case of Sn simple material, for example, the volume change is 3.59 times as large as lithium is inserted, so that there is a disadvantage that the cycle life is short.

  In such a background, in order to solve the above-described drawbacks, alloying of metals such as Si, Sn, Zn and metals that do not occlude lithium, thinning of the active material layer, and non-reactive substances such as organic polymers Attempts have been made to improve the composite, active material manufacturing method and current collector processing method.

  In the following Patent Documents 1 to 4, it is proposed to form a Sn or Sn alloy thin film on the current collector surface and use this as a negative electrode. For example, as the tin alloy used as the negative electrode material, one or two selected from the group consisting of an alloy of antimony, bismuth, lead, copper, zinc and the like and tin, a tin bismuth alloy film, copper, zinc, cobalt and iron Tin alloys including the above have been reported, and electroplating methods and the like have been disclosed as means for forming tin or tin alloy thin films.

  Further, in Patent Document 5 below, an intermediate between the lithium occlusion capacity of the current collector and the lithium occlusion capacity of the tin plating layer or the tin alloy plating layer is provided at the interface between the current collector and the tin plating layer or the tin alloy plating layer. An electrode for a secondary battery in which a layer having lithium storage capacity is formed has been proposed. Further, in Patent Document 6 below, from a material in which a tin or tin alloy film having a structure in which fine plating particles are substantially continuous deposited from an electroplating solution having a specific composition is formed on one side or both sides of a current collector. An electrode material for a secondary battery is proposed.

  As described above, various attempts have been made to form a tin or tin alloy thin film on the surface of the current collector by a surface treatment method such as electroplating, and use this as a negative electrode material for a lithium secondary battery.

  Patent Document 7 below discloses a negative electrode material having a base made of a sheet-like non-conductive material having a fine structure, and an active material layer made of tin or a tin alloy formed on the surface of the base and the internal surface of the fine structure. Has been proposed. Patent Document 5 discloses a non-aqueous electrolyte secondary battery, and carbon fibers, metal fibers, and the like are disclosed as a conductive agent for the negative electrode, but there is no description of using non-conductive organic polymer fibers.

  Moreover, in patent document 8, although adding carbon fiber and a metal fiber is described as a negative electrode electrically conductive material, forming a negative electrode active material by plating is not described.

Japanese Patent Laid-Open No. 11-242954 JP 2001-068094 A JP 2001-068095 A JP 2002-198091 A JP 2003-157833 A JP 2003-142088 A JP 2005-129254 A JP 2000-173593 A

  However, in spite of the various studies described above, a negative electrode material having a sufficient cycle life that can be practically used has not been obtained.

  Even when tin or a tin alloy thin film is formed on a current collector by the methods described in Patent Documents 1 to 4, tin has a large volume change in the negative electrode material due to the charge / discharge reaction, and the change is repeated. It is thought that the material cracks and the particles become finer. The refined material is considered to have a space between the particles, the electron conductivity deteriorates, and the portion that cannot participate in the electrochemical reaction increases, resulting in a decrease in charge / discharge capacity.

  On the other hand, unlike the negative electrode material composed only of the above-described metal, as described in Patent Document 7, the substrate made of a sheet-like non-conductive material having a microstructure, the surface of the substrate, and the microstructure internal surface In the case of a negative electrode material having an active material layer made of tin or tin alloy formed, the base made of a non-conductive material relaxes the volume change of the negative electrode material during charge and discharge, and the capacity retention rate at the 50th cycle of the example is Compared to the comparative example. However, since the active material metal exists only on the surface of the non-conductive material, the net amount of the active material is small, and it is difficult to significantly improve the capacity per volume. Even if the amount of the active material layer is increased, it is difficult to deposit the active material metal efficiently inside the sheet because the material supply of the plating solution from the inside of the sheet to the outside of the sheet is large. Furthermore, since it is a thin film, the resistance value to the current collector is large, which causes the internal resistance of the battery to increase.

  The present invention provides a novel conductive article that can be used for a conductive material and the like, a novel negative electrode material, and a lithium secondary battery having a high capacity and excellent charge / discharge cycle characteristics, and an electronic device and an automobile using the same. An object of the present invention is to provide a plating solution for forming a system, and further a conductive article and a negative electrode material.

  The conductive article of the present invention is a conductive article characterized in that organic polymer fibers are dispersed in a metal plating film formed on a substrate, and the negative electrode material comprises a current collector and an active material. In the negative electrode material of a lithium secondary battery comprising a material layer, it is dispersed in the plating film.

  According to the present invention, there is provided a novel conductive article that is flexible and can absorb the stress of expansion / contraction, and has a high capacity with enhanced utilization efficiency, and volume expansion / contraction and pulverization associated with charge / discharge. A negative electrode material for a lithium secondary battery and a lithium secondary battery excellent in cycle characteristics that can be suppressed can be provided.

  The lithium secondary battery of the present invention is formed by dispersing organic polymer fibers in a metal plating film for alloying a negative electrode active material for lithium secondary batteries with lithium, in particular, by incorporating microfibrils or microfibril bundles. It is possible to provide a mobile device such as a hybrid vehicle or an electric vehicle that uses a battery and is small, high energy, and highly practical.

  Furthermore, according to the present invention, it is possible to provide a system in combination with the lithium secondary battery and a generator that requires load leveling using natural energy such as wind power generation.

  Moreover, according to the present invention, a plating solution for forming the conductive article and the negative electrode material of the present invention can be provided.

  In the conductive article and the negative electrode material of the present invention, the organic polymer fiber is present in crystal particles of a metal plating film that is alloyed with lithium. In particular, in the case of a negative electrode material, the active material layer is preferably tin or a tin alloy.

  The organic polymer fiber is more preferably hydrophilic or partially water-soluble so that the fiber can be well dispersed in the plating solution. The organic polymer fiber preferably has an elastic modulus of 100 GPa or more and a strength of 2 GPa or more, and contains at least one of cellulose, aramid, nylon or derivatives thereof. Thereby, the electroconductive article and negative electrode material which are rich in a softness | flexibility and stress relaxation property are obtained.

  In addition, the negative electrode material according to the present invention may have a distribution in which the content of the organic polymer fiber contained in the active material layer differs in the film thickness direction. Further, a part of the organic polymer fiber may be exposed on the surface of the active material layer.

  Moreover, after forming the active material layer which consists of the metal alloyed with lithium and the said organic polymer fiber on a collector, it can also be set as the negative electrode material heat-processed. Thereby, a negative electrode material having stable characteristics can be obtained. The current collector may have an uneven shape on its surface. The lithium battery of this invention consists of said negative electrode material, positive electrode material, electrolyte solution, a separator, and a sealing material. The system of the present invention can be configured in combination with a transporter on which a lithium battery is mounted, at least one electronic device, and a generator.

  The electroplating solution of the present invention contains Sn salt, supporting electrolyte, organic polymer fiber and at least one additive, and the organic polymer fiber is dispersed in the solution. In particular, a plating solution in which organic polymer fibers contain microfibrils or microfibril bundles having a fiber diameter of 1 μm or less as a main component and are dispersed in the plating solution. The fiber length is preferably about 10 to 500 μm.

  Also, a first metal such as a Sn salt, a salt of a second metal alloyed with the first metal, a supporting electrolyte, an organic polymer fiber and at least one or more additives such as a reducing agent, a complexing agent, an interface A plating solution in which an activator or the like is dissolved or dispersed in a liquid. In particular, a plating solution in which the organic polymer fiber contains microfibrils or a microfibril bundle having a fiber diameter of 1 μm or less as a main component and is dispersed in the plating solution is preferable.

  Furthermore, the electroless plating solution of the present invention contains a Sn salt, a reducing agent, a complexing agent, organic polymer fibers, and at least one or more additives. In addition, a first metal, for example, an Sn salt, a salt of a second metal alloyed with the first metal, a reducing agent, a complexing agent, an organic polymer fiber, and necessary additives are dissolved or dispersed in a liquid. It is a plating solution. The organic polymer fiber is a plating solution containing a microfibril or a microfibril bundle having a fiber diameter of 1 μm or less as a main component and dispersed in the plating solution. Organic polymer fibers are unsuitable for shapes such as woven and non-woven fabrics where the fibers are constrained to each other and cannot be freely dispersed in the plating solution.

  By setting it as the negative electrode material of this invention, a high capacity density can be obtained compared with a carbon material. In addition, by including fine organic polymer fibers in the negative electrode active material layer, the elasticity of itself and the driving force that swells when absorbing the electrolyte solution change the volume of the metal accompanying the insertion and extraction of lithium. As a result, excellent cycle characteristics are exhibited. In particular, in the negative electrode material formed using the plating solution of the present invention, the active material metal is formed while taking in the fine fibers present in the plating solution, so that grain growth is suppressed and fine active material particles are obtained. .

  In the negative electrode material of the present invention, it is preferable that fine organic polymer fibers exist in the crystal grains. As a result, it is possible to remarkably suppress capacity reduction due to charge / discharge cycles accompanying cracking and pulverization of the active material layer. In addition, since the contact area between the active material metal and the organic polymer fiber is large, volume change can be efficiently reduced, and in addition, the electrolyte solution can smoothly penetrate from the electrolyte bulk to the active material surface. It is possible to improve the utilization efficiency of the active material and the output density.

  Hereinafter, embodiments of the present invention will be described in detail. The negative electrode material of the present invention is a negative electrode material capable of electrochemically and reversibly inserting and releasing lithium ions. Fig.1 (a) shows the negative electrode material which is embodiment of this invention. The negative electrode material 1 is composed of a current collector 2, an active material metal or alloy 3, and organic polymer fibers 4 mainly composed of microfibrils or microfibril bundles. Organic polymer fibers mainly composed of microfibrils or microfibril bundles are incorporated into a metal plating film that is alloyed with lithium, such as a Sn metal plating film or a Sn alloy. Excellent charge / discharge cycle characteristics due to the role of organic polymer fibers in suppressing expansion / contraction caused by charge / discharge. Since the negative electrode material of the present invention contains a metal that forms an alloy with lithium, such as Sn or Zn, as a constituent element, it can contribute to an increase in capacity of the lithium secondary battery.

  Although the film thickness of the active material layer containing an active material metal and organic polymer fiber is not specifically limited, 1 micrometer-100 micrometers are preferable. When the thickness is less than 1 μm, a sufficient charge / discharge capacity cannot be secured, and when the thickness exceeds 100 μm, the inside of the active material cannot be used efficiently and the internal resistance increases. Moreover, when winding a negative electrode material, handling becomes difficult.

  In the negative electrode material of the present invention, a form in which a part of the organic polymer fiber is exposed on the surface of the active material metal plating film is more preferable. That is, when the organic polymer fiber is exposed on the surface, the electrolyte solution can smoothly penetrate from the electrolyte solution bulk to the active material surface, and the utilization efficiency of the active material can be improved. This organic polymer fiber is particularly preferably one having lubricity.

  In another example of the negative electrode material of the present invention, as shown in FIG. 1 (b), the organic polymer fiber content contained in the active material layer has a distribution or concentration gradient that differs in the film thickness direction. It may be. That is, a structure in which the content of organic polymer fibers increases from the current collector to the active material surface direction, or a structure in which layers with a high content of organic polymer fibers and layers with a low content are alternately laminated, There is no particular limitation. By adopting the above structure, in addition to the effect of volume relaxation of the fine organic polymer fiber itself, volume relaxation in a larger region is enabled.

  In the negative electrode material used in the present invention, as an active material metal, a metal that can be alloyed with lithium or an alloy thereof, which can be plated and formed, can be used. As a specific example, Sn, Zn, or the like can be used. The alloy alloyed with lithium is selected from metals such as Sn and Zn, and elements of groups 13 to 15 of the third to sixth periods and groups 8 to 12 of the fourth to sixth periods of the periodic table. An alloy with at least one metal can be used. Specific examples include Al, Si, P, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Ag, Cd, In, Sb, Au, Hg, Tl, Pb, and Bi. . In particular, an alloy of Sn and at least one metal selected from the group consisting of zinc, copper, antimony, bismuth, cobalt, and iron is preferable.

  The Sn content in the alloy is preferably about 30% by weight or more, and more preferably about 50% by weight or more. The active material layer may be formed on one side or both sides of the current collector.

  The negative electrode material of the present invention contains organic polymer fibers in the active material layer. The organic polymer fiber shown in this specification is preferably composed mainly of a microfibril or a microfibril bundle having a fiber diameter of 1 μm or less. Specifically, 70% or more of the organic polymer fibers taken into the active material film are constituted by microfibrils or microfibril bundles having a fiber diameter of 1 μm or less.

  Further, when the value obtained by dividing the fiber length by the fiber diameter is defined as an aspect, a fiber having an aspect ratio of 1.5 or more is preferable. The fiber diameter was confirmed by a scanning electron microscope (SEM). That is, 10 points are arbitrarily observed at a magnification of 10,000 on the surface and cross section of the negative electrode material active material of the present invention, and defined as a measured value of the width of the fiber present in the SEM image. However, in the SEM image, when it can be clearly confirmed that several microfibril bundles are intertwined and have a fiber width of 1 μm or more, it is not regarded as a microfibril bundle. In addition, the component ratio of microfibrils or microfibril bundles in the fiber was determined by observing 10 points on the surface and cross section of the negative electrode active material of the present invention at a magnification of 30,000 times in the same manner as the fiber length measurement. It is defined as the proportion of fibers of 1 μm or less among the fibers present inside.

  A high-pressure homogenizer, a disc refiner, or the like is used as a method for producing microfibrils or microfibril bundles, and the high-pressure homogenizer is a particularly effective means. A known high-pressure homogenizer can be used. For example, a high-pressure pump, a valve device that discharges the liquid to be processed from the high-pressure pump at a high pressure, a valve seat device that collides with the discharged liquid, and a high-pressure pump suction side of the processing liquid. By repeatedly performing an operation of applying a strong shearing force to the fiber using a device having a circulation channel, a fiber mainly composed of a microfibril or a microfibril bundle can be obtained.

  One method for producing the active material layer used in the present invention is a plating method such as electroplating or electroless plating. When Sn is used as the active material metal, it can be formed by directly plating the current collector using a liquid containing an Sn salt, a supporting electrolyte, and an additive and further dispersed with organic polymer fibers. Further, not only the Sn salt but also a metal salt to be alloyed with Sn can be added to the plating solution and alloyed. A plating solution in which organic polymer fibers are dispersed in a known Sn plating solution or Sn alloy plating solution can also be used.

  In the case of electroplating, the content of the organic polymer fiber in the active material layer can be easily adjusted by the applied current, the stirring speed, and the like. By changing the processing conditions during plating, the active material layer can be formed by changing the content of the organic polymer fiber in the film thickness direction.

  In the present invention, since the presence of moisture is not desirable in the lithium battery, in the present invention, in order to avoid the remaining of the processing solution such as the plating solution after the formation of the active material layer, as a pretreatment of the battery assembly, the negative electrode with the electrolyte for the lithium battery Thoroughly clean and replace the material.

  By further heat-treating the obtained active material, it is possible to change the composition state to be different from the alloy composition obtained by plating and to stabilize the characteristics.

  The organic polymer fiber used in the present invention may be either natural fiber or synthetic fiber, and may be either a thermoplastic resin or a thermosetting resin. An organic polymer fiber containing a microfibril or a microfibril bundle having a fiber diameter of 1 μm or less as a main component is particularly preferable.

  Preferred organic polymer fibers in the present invention include, for example, cellulose, meta- or para-type aromatic polyamide, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene butadiene rubber, tetrafluoroethylene-hexa. Fluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride- Chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer (ETFE resin), polychlorotrifluoroethylene (PCTFE), vinylidene fluoride-pentafluoro Lopylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer (ECTFE), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether -A tetrafluoroethylene copolymer and the derivative | guide_body of the said material can be mentioned.

  These materials can be used alone or as a mixture. Among these materials, those having good dispersibility in the plating solution and having an elastic modulus of 100 GPa or more and a strength of 2 GPa or more are more preferable. Furthermore, since the organic polymer fiber is incorporated in the battery as it is as a component of the electrode, it is preferably flame retardant. The flame retardant fiber may itself be flame retardant, or may be a fiber subjected to flame retardant treatment. In order to adjust the affinity with the active material metal, a functional group having an affinity for the metal may be introduced on the surface of the organic polymer fiber.

  The weight content of the organic polymer fiber is preferably 20% to 90% of the weight of the negative electrode active material (plating, additive and organic polymer fiber). If it is less than 20%, the amount of the active material can be increased, but a sufficient amount of the electrolyte does not penetrate into the active material layer, resulting in a decrease in utilization efficiency. Moreover, there is concern that volume expansion during occlusion of lithium cannot be withstood, cracking or pulverization of the active material metal proceeds significantly, and charge / discharge cycle characteristics deteriorate. On the other hand, when the content of the organic polymer fiber exceeds 90%, the permeability of the electrolytic solution is good and the utilization efficiency of the negative electrode material is improved. It is thought that a simple battery cannot be obtained.

  The negative electrode current collector used in the present invention may be anything as long as it is an electronic conductor that does not cause a chemical change in the constructed battery. For example, in addition to stainless steel, nickel, copper, titanium, carbon, conductive resin, etc., the surface of copper or stainless steel coated with carbon, nickel, or titanium is used. In particular, copper or a copper alloy is preferable.

  As the shape, a foil, a net, a punched body, a lath body, a porous body, a foamed body, a molded body of a fiber group, and the like are used. The thickness is not particularly limited, but a thickness of 1 to 500 μm is used. Moreover, as shown in FIG.1 (c), it is desirable to attach the roughening layer 5 etc. which have an unevenness | corrugation on the surface of the electrical power collector 2. FIG. Although the electrolytic copper foil can be used as it is, a roughening method for improving the adhesion between the copper foil and the resin interface used in the printed wiring board manufacturing process can be used as a means for providing the unevenness. Specifically, electrolytic roughening plating, electrolytic etching, and further blackening treatment, that is, a method of chemically roughening by immersing in an aqueous solution mainly composed of sodium chlorite and sodium hydroxide, etc. . After the roughening treatment, for example, it is preferable to use, as a current collector, a material obtained by reducing copper oxide generated by blackening treatment to copper by immersing in an aqueous solution containing dimethylamine borane and sodium hydroxide.

Although it does not specifically limit as a positive electrode material used for this invention, A well-known lithium containing transition metal oxide can be used. For _{example, Li x CoO 2, Li x} NiO 2, Li x MnO 2, Li x (Co y Ni 1-y O 2, Li x Co y M 1-y O z, Li x Ni 1-y M y O z _{, Li x Mn 2 O 4,} Li x Mn 2-y M y O 4 (M = Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, B (Wherein x = 0 to 1.2, y = 0 to 0.9, z = 2.0 to 2.3), where the value of x is It is a value before the start of discharge, and is increased or decreased by charging / discharging.It is also possible to mix and use a plurality of different positive electrode materials.The average particle diameter of the positive electrode active material particles is not particularly limited, but is 1 to 30 μm. It is preferable that

  The positive electrode conductive agent and binder used in the present invention are not particularly limited as long as they are electron conductive materials that do not cause a chemical change in the charge / discharge potential of the positive electrode material used, and known materials can be used. .

  The positive electrode current collector used in the present invention is not particularly limited as long as it is an electron conductor that does not cause a chemical change at the charge / discharge potential of the positive electrode material used, and a known material can be used. For example, as the material, in addition to stainless steel, aluminum, titanium, carbon, conductive resin, etc., the surface of aluminum or stainless steel coated with carbon or titanium is used. In particular, aluminum or an aluminum alloy is preferable. The surface of these materials can be oxidized and used. Further, it is desirable to make the current collector surface uneven by surface treatment. As the shape, a foil, a net, a punched body, a lath body, a porous body, a foamed body, a molded body of a fiber group, and the like are used. The thickness is not particularly limited, but a thickness of 1 to 500 μm is used.

  The nonaqueous electrolyte used in the present invention is composed of a solvent and a solute lithium salt. It does not specifically limit as a non-aqueous solvent, A well-known material can be used. For example, cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), dimethyl carbonate (DMC), diethyl carbonate (DEC), Chain carbonates such as ethyl methyl carbonate (EMC) and dipropyl carbonate (DPC), aliphatic carboxylic acid esters such as methyl formate, methyl acetate, methyl propionate and ethyl propionate, and γ-lactones such as γ-butyrolactone , Chain ethers such as 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE), ethoxymethoxyethane (EME), cyclic ethers such as tetrahydrofuran and 2-methyltetrahydrofuran, dimethyl sulfoxide 1,3- Dioxolane, formamide, acetamide, dimethylformamide, dioxolane, acetonitrile, propylnitrile, nitromethane, ethyl monoglyme, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone And aprotic organic solvents such as 3-methyl-2-oxazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethyl ether, 1,3-propane sultone, anisole, dimethyl sulfoxide, N-methylpyrrolidone, etc. Can be used alone or in admixture of two or more.

Although it does not specifically limit as a lithium salt, A well-known material can be used. For example, LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAlCl ₄ , LiSbF ₆ , LiSCN, LiCl, LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , Li (CF ₃ SO ₂ ) ₂ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiB ₁₀ Cl ₁₀ , lower aliphatic lithium carboxylate, LiCl, LiBr, LiI, chloroborane lithium, lithium tetraphenylborate, imides and the like, and one or two kinds of electrolytes using these The above can be mixed and used.

  In addition to the electrolytic solution, a solid electrolyte such as a gel electrolyte can also be used. Furthermore, other compounds may be added to the electrolyte for the purpose of improving discharge and charge / discharge characteristics. For example, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, pyridine, hexaphosphoric acid triamide, nitrobenzene derivatives, crown ethers, quaternary ammonium salts, ethylene glycol dialkyl ether and the like can be mentioned.

  The separator used in the present invention is not particularly limited, but an insulating microporous thin film having a large ion permeability and a predetermined mechanical strength can be used. Sheets, nonwoven fabrics or woven fabrics made of olefinic polymers such as polypropylene and polyethylene, or glass fibers or the like are used because of their resistance to organic solvents and hydrophobicity. The pore diameter of the separator is desirably in a range in which the positive and negative electrode materials, the binder, and the conductive agent detached from the electrode sheet do not permeate, for example, 0.01 to 1 μm is desirable. The thickness of the separator is generally 10 to 300 μm. The porosity is determined according to the permeability of electrons and ions, the material, and the film thickness, but is generally preferably 30 to 80%.

  The shape of the battery can be applied to any of a coin type, a button type, a sheet type, a laminated type, a cylindrical type, a flat type, a square type, a large type used for an electric vehicle, and the like.

  Further, the nonaqueous electrolyte secondary battery of the present invention can be used for a portable information terminal, a portable electronic device, a small electric power storage device for home use, a motorcycle, an electric vehicle, a hybrid electric vehicle, etc., but is not particularly limited thereto. I don't mean.

  The example which produced the lithium secondary battery with the said material and manufacturing method is demonstrated based on an Example below. However, the present invention is not limited to these examples.

Example 1
A rolled copper foil (100 × 100 mm, film thickness 12 μm) was used as a current collector. As a pretreatment for plating, electrolytic degreasing was performed in an aqueous alkaline solution at room temperature at a current density of 1 A / dm ² for 1 minute, and then washed with water. Next, after pickling in 10% sulfuric acid aqueous solution, it was washed with water. Using the treated copper foil, Sn electroplating was performed on the surface.

Plating conditions were performed in a plating solution at 50 ° C. for 40 minutes at a current density of 5 mA / cm ² , and liquid agitation was appropriately adjusted by bubbling. The plating solution was a mixture of 0.2 M tin chloride dihydrate, 0.5 M potassium pyrophosphate, 0.075 M glycine, and 5 mL / L aqueous ammonia solution, and the concentration of cellulose treated with microfibrils as organic polymer fibers was 0. What was added so that it might become 5 wt% was used. Microfibril-treated cellulose was obtained by preparing a solution in which commercially available water-soluble cellulose was mixed with pure water so as to be 1 wt%, and repeating the micronization treatment 100 times with a high-pressure homogenizer. The plated copper foil was washed with water and dried to prepare a negative electrode material.

(Example 2)
In this example, a negative electrode was produced according to Example 1 except that the surface of the copper foil used as a current collector was roughened instead of the sulfuric acid pickling after electrolytic degreasing. In addition, the roughening process was performed in the following procedures. The electrolytically degreased and washed copper foil was immersed in a mixed solution of 15 g / L sodium hydroxide, 90 g / L sodium chlorite, and 30 g / L sodium phosphate 12 hydrate for 2 minutes at 70 ° C. and washed with water. Then, it was immersed in a mixed solution of 6 g / L dimethylamine borane and 5 g / L sodium hydroxide at 45 ° C. for 2 minutes, washed with water and dried.

(Examples 3 and 4)
In Examples 3 and 4, the negative electrodes produced in accordance with Examples 1 and 2 were Sn-plated again with an Sn plating solution containing no fiber to a thickness of 0.5 μm, and FIG. As shown in the schematic cross-sectional view of the negative electrode, a negative electrode in which the organic polymer fiber was not exposed on the plating film surface was produced.

(Examples 5 to 8)
In Examples 5 to 8, negative electrodes were prepared in accordance with Examples 1 to 4, respectively, except that the current density during plating was changed from 0.5 mA / cm ² to 10 mA / cm ² .

(Examples 9 to 16)
In Examples 9 to 16, negative electrodes were produced by performing heat treatment on the negative electrodes produced in accordance with Examples 1 to 8, respectively. The heat treatment was performed in vacuum at 250 ° C. for 3 hours.

(Examples 17 to 32)
Examples 17 to 32 are examples in which a microfibril-treated aramid fiber was used as the organic polymer fiber, and negative electrodes were produced in accordance with Examples 1 to 16, respectively.
(Comparative Example 1)
As a comparative example, Sn plating was performed in the same manner as in Example 1 using an Sn plating solution that did not contain organic polymer fibers, to produce a negative electrode.

As described above, using each of the obtained negative electrode materials, a lithium foil is used as a counter electrode, and a 1: 1 mixed solution of ethylene carbonate and dimethyl carbonate in which 1 mol / L LiPF ₆ is dissolved is used as an electrolytic solution to prepare a cell. They were evaluated for cycle characteristics in the voltage range of 0~1V at a current density of cm ^2. The evaluation results are shown in Table 1. The capacity maintenance rate at 100 cycles is shown as the ratio of the capacity at the 100th cycle to the capacity at the first cycle.

  When the negative electrodes obtained in Examples 1 to 32 were used, the capacity retention rate after 100 cycles was higher than that of Comparative Example 1, and the cycle characteristics were good. In particular, when using the negative electrodes of Examples 14 and 30 in which the current collector surface was roughened, plated while changing the current density during plating, and the surface coating was not performed with the active material metal, and the heat treatment was performed. It was found that the cycle characteristics were further improved. This is presumably because the surface of the current collector was roughened, and the Sn plating film and the copper of the current collector formed a compound layer in the heat treatment step, thereby improving the adhesion. In addition, by including fine organic polymer fibers in the negative electrode active material layer, the elastic force of the anode and the driving force that expands by absorbing the electrolyte solution change the volume of the metal accompanying the insertion and extraction of lithium. It can be suppressed, and as a result, it is considered that excellent cycle characteristics were exhibited. Furthermore, by changing the current value during plating, the content of the organic polymer fiber differs with respect to the film thickness direction of the plating film, and not only the volume relaxation in the fine area but also the volume relaxation in the larger area. It seems to be possible.

  Here, the optical microscope image of the negative electrode surface produced in Example 1, and the SEM image of a cross section are shown in FIG.2 and FIG.3. Organic polymer fibers were present on the active material metal surface. It is considered that the organic polymer fibers are exposed on the active material metal surface, so that the electrolyte solution can smoothly penetrate from the electrolyte solution bulk to the active material surface, and the utilization efficiency of the active material is improved. Further, as shown in the cross-sectional image, fibers were present not only in the crystal grain boundaries but also in the crystal grains. In the negative electrode material formed using the plating solution of the present invention, the active material metal is formed while taking in the fine fibers present in the plating solution, so that the grain growth is suppressed and fine active material particles are formed. . The presence of organic polymer fibers not only in the crystal grain boundaries but also in the crystal flow is considered to have exhibited the effect of remarkably suppressing the capacity drop due to charge / discharge cycles accompanying cracking and pulverization of the active material layer. .

(Examples 33 to 64)
Examples 33 to 64 were prepared according to Examples 1 to 32, respectively, except that Sn and Cu alloy plating solutions were used as plating solutions. The plating solution was 60 g / L tin sulfate, 60 g / L copper sulfate pentahydrate, 100 g / L sulfuric acid, 10 g / L cresolsulfonic acid, 1 g / L hydroquinone, 50 g / L ethylene glycol, 2 g / L polyoxy A solution obtained by adding cellulose or aramid treated with microfibril as an organic polymer fiber to a mixed solution of ethylene lauryl ether to a concentration of 0.5 wt% was used. The bath temperature was 25 ° C. and the current density was 5 mA / cm ² . In addition, when implementing, changing the electric current at the time of plating, it implemented, changing between 3-7 mA / cm < ² >.
(Comparative Example 2)
As Comparative Example 2, Sn copper alloy plating was performed in the same manner as in Example 33 using a SnCu alloy plating solution that does not contain organic polymer fibers, to prepare a negative electrode material.

As described above, using each of the obtained negative electrode materials, a lithium foil is used as a counter electrode, and a 1: 1 mixed solution of ethylene carbonate and dimethyl carbonate in which 1 mol / L LiPF ₆ is dissolved is used as an electrolytic solution to prepare a cell. The cycle characteristics were evaluated in a voltage range of 0-1 V with a current density of cm ² . The evaluation results are shown in Table 2.

  When the negative electrode materials obtained in Examples 33 to 64 were used, the capacity retention rate after 100 cycles was higher than that of Comparative Example 2, and the cycle characteristics were good. Furthermore, it turned out that cycling characteristics are improving more compared with Examples 1-32. In particular, the negative electrodes of Examples 46 and 62 were used in which the current collector surface was roughened, plated while changing the current density during plating, and then subjected to heat treatment without surface coating with an active material metal. In some cases, it was found that the cycle characteristics were further improved. This is considered to be because the adhesion between the Sn copper plating film and the current collector was improved in the current collector surface roughening and heat treatment steps, as in Examples 1-32. In addition, the cycle characteristics are improved as compared with the single Sn plating film only by using the alloy plating film, but by containing fine organic polymer fibers in the alloy plating film, the volume can be relaxed more effectively. It is thought that excellent cycle characteristics were developed.

  In addition to the above SnCu alloy as an active material metal constituting the negative electrode material, Sn salt and Al, Si, P, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Ag, Cd, In, Sb, A negative electrode was prepared using a plating solution in which a salt of Au, Hg, Tl, Pb, Bi and organic polymer fibers were dispersed, but, as in the case of SnCu alloy, fine organic polymer fibers were not contained in the plating film. As compared with the above, the effect of improving the cycle characteristics was recognized.

  In addition, Zn and a Zn alloy were selected as the active material metal constituting the negative electrode material, and a negative electrode was prepared using a plating solution in which organic polymer fibers were dispersed in the same manner as Sn plating, but the effect of improving cycle characteristics was also recognized. .

  The conductive article of the present invention is used as a conductive material or an electrode material for various batteries. In particular, it is useful as a negative electrode material for lithium secondary batteries.

The cross-sectional schematic diagram of the negative electrode material by the form of the Example of this invention. The microscope picture of the negative electrode material surface by embodiment of this invention. The SEM image of the negative electrode material cross section by embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Negative electrode material, 2 ... Current collector, 3 ... Active material metal, 4 ... Organic polymer fiber, 5 ... Roughening layer, 6 ... Active material metal dense layer.

Claims (31)

  A conductive article characterized in that organic polymer fibers are dispersed in a metal plating film formed on a substrate.   2. The conductive article according to claim 1, wherein the organic polymer fiber is non-uniformly dispersed in the metal plating film in a thickness direction of the metal plating film.   3. The conductive article according to claim 2, wherein the organic polymer fiber is dispersed in the metal plating film with a concentration gradient in the thickness direction of the plating film.   The conductive article according to any one of claims 1 to 3, wherein the organic polymer fiber contains a microfibril or a microfibril bundle having a fiber diameter of 1 µm or less as a main component.   The conductive article according to claim 1, wherein a part of the fiber is exposed from the plating film.   2. The conductive article according to claim 1, wherein the metal plating is formed by electroplating or electroless plating of a single metal or alloy.   The conductive article according to claim 1, wherein the organic polymer fiber is present in crystal particles of the metal plating film.   A negative electrode material for a secondary battery including a current collector and an active material layer, wherein the active material layer includes a metal or alloy plating film capable of combining with lithium ions and organic polymer fibers dispersed in the plating film. Negative electrode material.   9. The negative electrode material according to claim 8, wherein the organic polymer fiber contains microfibril or a microfibril bundle having a fiber diameter of 1 μm or less as a main component.   9. The negative electrode material according to claim 8, wherein the active material layer is a metal plating film that is alloyed with lithium, and the organic polymer fiber is present in crystal particles of the metal plating film.   11. The negative electrode material according to claim 8, wherein the content of the organic polymer fiber contained in the active material layer has a distribution different in the film thickness direction.   The negative electrode material according to claim 8, wherein a part of the organic polymer fiber is exposed on the surface of the active material layer.   The negative electrode material according to claim 8, wherein the negative electrode material is formed by heat treatment.   A negative electrode material, wherein the current collector according to claim 8 is made of a metal that does not alloy with lithium.   The negative electrode material according to claim 8, wherein the surface of the current collector has an uneven shape.   The negative electrode material according to claim 8, wherein the active material layer is Sn or an Sn-containing alloy.   The negative electrode material according to claim 8, wherein the organic polymer fiber is hydrophilic.   The negative electrode material according to any one of claims 8 to 12, wherein the organic polymer fiber has an elastic modulus of 100 GPa or more and a strength of 2 GPa or more.   16. The negative electrode material according to claim 8, wherein the organic polymer fiber contains at least one of cellulose, aramid, nylon, and derivatives thereof.   At least a part of the conductive substrate or the substrate that can be plated is immersed in a plating solution containing a metal salt and an organic polymer fiber, and the organic polymer fiber is plated while stirring the plating solution together with the organic polymer fiber. A method for producing a conductive article, wherein plating is performed so as to be taken into a film.   The method for manufacturing a conductive article according to claim 20, wherein the plating is electroplating or electroless plating.   A plating solution for producing a conductive article comprising a metal salt dissolved in a liquid constituting the plating solution and an organic polymer fiber dispersed in the liquid.   The plating solution for producing a conductive article according to claim 22, wherein the organic polymer fiber is a microfibril or a microfibril bundle having a fiber diameter of 1 µm or less.   A plating solution for producing a conductive article comprising a first metal salt, a salt of a second metal alloyed with the metal, a supporting electrolyte, and organic polymer fibers.   25. The plating solution for manufacturing a conductive article according to claim 24, wherein the first metal salt is a Sn salt, and the salt of the second metal is a metal salt alloyed with Sn.   A plating solution for producing a negative electrode material comprising an Sn salt, a metal salt alloyed with Sn, a reducing agent, a complexing agent, and organic polymer fibers.   26. The negative electrode material according to claim 25, wherein the organic polymer fiber contains a microfibril or a microfibril bundle having a fiber diameter of 1 μm or less as a main component and is dispersed in a plating solution. Plating solution.   A lithium secondary battery comprising the negative electrode material according to any one of claims 8 to 19, a positive electrode material, an electrolytic solution, a separator, and a sealing material.   A mobile body on which the lithium secondary battery according to claim 28 is mounted.   An electronic device on which the lithium secondary battery according to claim 28 is mounted.   A system comprising a combination of the lithium secondary battery according to claim 28 and a generator.

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