JP2014017259A - Method of manufacturing negative electrode for nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing the negative electrode of a nonaqueous electrolyte secondary battery having improved cycle characteristics, in the negative electrode of a nonaqueous electrolyte secondary battery having a three-dimensional regular arrangement porous structure (3DOM structure).SOLUTION: On a photoresist film formed on a conductive substrate, multiple micro voids are formed independently from each other. The cavities in the photoresist film are filled with micro particles, and then plating is carried out with a metal being alloyed with lithium. Thereafter, the micro particles and the photoresist film are dissolved and removed thus forming the negative electrode for a nonaqueous electrolyte secondary battery having a micro domain structure (multiple micro island-shaped). The island-shaped electrode has a height of 10-50 μm, a size of 10-30 μm, a width between island-shaped electrodes of 1-50 μm, a porosity of 50-80%, and has a columnar shape preferably.

Description

  The present invention relates to a method for producing a negative electrode for a non-aqueous electrolyte secondary battery, and more particularly, to a negative electrode for a non-aqueous electrolyte secondary battery having an electrode having a microdomain structure (many fine island-shaped structures). It relates to a manufacturing method.

  Currently, portable electronic devices such as mobile phones, laptop computers, and camera-integrated VTRs are widely used. In recent years, these portable electronic devices have a tendency to increase power consumption due to higher performance, and further increase in capacity of lithium ion secondary batteries used as power sources thereof is expected. Various methods have been proposed to achieve higher capacities of such lithium ion secondary batteries, such as increasing the electrode surface area and increasing the electrode surface area by forming irregularities on the electrode surface. Has been.

Incidentally, graphite is currently used for a negative electrode of a lithium ion secondary battery. Graphite shows a theoretical capacity of 372 mAh / g by forming an intercalation compound LiC ₆ with lithium, but currently used lithium ion secondary batteries use about 95% of this theoretical capacity. In order to further increase the capacity of the battery, it is necessary to develop a new negative electrode material.

As a negative electrode material that replaces graphite, research using a metal material that is alloyed with lithium has been conducted intensively. To date, tin, silicon, and materials containing these have formed an alloy with lithium, and have a capacity larger than 372 mAh / g. It has been reported that it can be obtained. Among these, tin can be charged and discharged by repeating alloying / dealloying with lithium, and shows a high theoretical capacity of 993 mAh / g. Therefore, tin has recently attracted attention as a negative electrode material. However, since tin becomes Li _4.4 Sn at the time of alloying, its volume expands about 4 times. This causes a problem that tin is pulverized and the current collecting property is lowered, so that good cycle characteristics are not exhibited. Until now, it has been reported that volume expansion that occurs during charging and discharging is suppressed and cycle characteristics are improved by previously alloying a metal that does not react with lithium with tin (see Non-Patent Document 1). . For example, in a tin-nickel (Sn—Ni) alloy negative electrode, good charge / discharge capacity (600 mAh / g) and cycle characteristics (capacity maintenance ratio after 50 cycles are 70%) are confirmed in a thin film (up to 1.0 μm). Yes. However, when the amount of the active material per unit area is increased, there is a problem that capacity and cycle characteristics are deteriorated. The reason why the charge / discharge capacity decreases is considered to be that the interface between the electrolytic solution and the electrode active material is small in the plate electrode. In addition, as a factor that degrades the cycle characteristics, the film thickness increases as the amount of active material increases, and the active material greatly expands and contracts as a result of alloying / dealloying with Li ⁺ ions, resulting in internal stress. This is considered to increase. In order to solve these problems, studies have been made on electrodes such as tin and tin-nickel alloys having a three-dimensionally ordered macrostructure (hereinafter abbreviated as “3DOM structure”) (eg, a three-dimensionally ordered macrostructure). , See Patent Document 1).

  FIG. 5 shows a conceptual diagram of a tin or Sn—Ni alloy electrode having a conventionally known 3DOM structure before and during charging. In the figure, the left shows the porous electrode before charging, and the right shows the porous electrode during charging. For example, a tin or Sn—Ni alloy electrode having a 3 DOM structure has regularly arranged vacancies inside the electrode, and the electrolyte can penetrate into the electrode even when the electrode film thickness increases. Is possible. In addition, the thickest part of the active material is the thickness of the frame that forms the pores of the 3DOM structure, so the active material per unit area is increased while maintaining the maximum thickness of the active material at the same level as the thin film. It can be made. Furthermore, even if volume expansion occurs due to alloying of tin and lithium, a large number of holes in the electrode can disperse internal stress and suppress deterioration of the electrode. If the deposition expansion occurs in the hole internal direction, the apparent volume change is also suppressed.

Such a tin (Sn) or tin-nickel (Sn—Ni) alloy electrode having a 3DOM structure can be easily produced by using a colloidal crystal templating method, and a colloidal particle as a template. By selecting the size, it is possible to control the size of the holes (see Patent Document 1). A scanning electron microscope (SEM) photograph of an Sn—Ni alloy electrode having a 3DOM structure formed by a colloidal crystal template method is shown in FIG. Moreover, the charging / discharging curve of this alloy electrode is shown in FIG.6 (b). From FIG. 6 (b), about 0.5 V vs. In Li / Li ⁺ , a potential flat portion due to alloying / dealloying of Li (insertion / desorption reaction of Li) was confirmed, and the discharge capacity was about 370 mAh / g. This suggests that the Sn—Ni alloy electrode having a 3DOM structure can be used as an electrode for a lithium ion secondary battery (see Non-Patent Document 2).

JP 2006-260886 A H. Mukaibo, T .; Momma, M .; Mohamedi, T .; Osaka, Journal of the Electrochemical Society, 152 (2005) pp. A560-A565 F. Ke, L .; Huang, H .; Jiang, H .; Wei, F .; Yang, S .; Sun, Electrochemistry Communications, 9 (2007) pp. 228-232

  Thus, by controlling the structure of the metal or alloy that constitutes the negative electrode for a conventional non-aqueous electrolyte secondary battery, the shape change of the electrode accompanying the expansion / contraction of the negative electrode metal or the negative electrode alloy is minimized and high. Attempts have been made to produce electrodes having high cycle characteristics while maintaining electrode capacity, but cycle characteristics are not sufficient even when tin or Sn-Ni alloy electrodes having a 3DOM structure are used. .

  FIG. 7 shows the cycle characteristics of a Sn—Ni alloy electrode having a plate-like Sn—Ni electrode and a 3DOM structure having 1.0 μm pores. As shown in FIG. 7, in both the flat Sn—Ni electrode and the 3DOM structure Sn—Ni alloy electrode, initially, the capacity tended to increase with each cycle, In the flat electrode, the capacity decreased after 14 cycles, while in the 3DOM structure Sn—Ni alloy electrode, the capacity decreased after 35 cycles. The increase in the capacity of these electrodes is considered to be due to the fact that the interface is increased by cracking the electrodes, and an active material that has not been used before is used. In addition, the cycle characteristics of the 3DOM structure Sn—Ni alloy electrode are superior to those of the flat Sn—Ni alloy electrode. The many holes in the electrode disperse the stress due to volume expansion, and This is thought to be due to the suppression of pulverization of the substance. On the other hand, FIG. 8 shows an SEM photograph after 100 cycles of the flat Sn—Ni alloy electrode and the 3DOM structure Sn—Ni alloy electrode. The decrease in capacity of the flat plate and 3DOM structure Sn—Ni alloy electrode It is thought that both the Sn—Ni alloy electrode and the 3DOM structure Sn—Ni alloy electrode were cracked in the electrode due to the volume change that occurred during charging and discharging and were divided into blocks of about 30 μm.

  As described above, in the Sn—Ni alloy electrode having the 3DOM structure, even if volume expansion occurs due to alloying of Sn and Li, minute holes in the electrode disperse internal stress and suppress deterioration of the electrode. However, when the Li alloy / dealloying reaction is repeated more than a certain amount, the capacity cannot be prevented from decreasing.

  An object of the present invention is to provide a method for producing a negative electrode with improved cycle characteristics in a negative electrode for a nonaqueous electrolyte secondary battery.

  The inventors of the present invention have made extensive studies to solve the above-mentioned problems, and by setting a metal electrode having a 3DOM structure to an island-like structure having a fine size from the beginning, that is, a microdomain structure, the cycle characteristics can be obtained. It has been found that a negative electrode having an improved resistance can be obtained, and that a negative electrode having a microdomain structure having such a 3DOM structure can be easily manufactured by combining a photoresist substrate, a colloidal crystal template method and a plating method. The present invention is based on this.

  That is, the present invention includes (1) a step of forming a large number of independent fine voids in a photoresist film on a conductive substrate, and (2) a step of filling fine particles in the voids of the photoresist film. And (3) a step of plating the substrate filled with the fine particles with a metal alloying with lithium, and (4) a step of removing the fine particles and the photoresist film. The present invention relates to a method for producing a negative electrode for a secondary battery.

  In the method for producing a negative electrode for a non-aqueous electrolyte secondary battery according to the present invention, the fine void has a cylindrical shape having a diameter of 10 to 30 μm and a depth of 10 to 50 μm. The present invention relates to a method for producing a negative electrode for a non-aqueous electrolyte secondary battery, wherein the pitch is a regular arrangement of 1 to 50 μm.

  The present invention also provides the method for producing a negative electrode for a nonaqueous electrolyte secondary battery, wherein the fine particles are made of a polymer having a particle size of 0.1 to 5 μm, and the removal of the polymer dissolves the polymer in a solvent. The present invention relates to a method for producing a negative electrode for a non-aqueous electrolyte secondary battery.

  The present invention also provides a method for producing a negative electrode for a non-aqueous electrolyte secondary battery, wherein the filled polymer is thermally welded before the plating step. The present invention relates to a method for producing a negative electrode.

  Further, the present invention provides the above-described method for producing a negative electrode for a non-aqueous electrolyte secondary battery, wherein the plating is performed by immersing the substrate in a plating bath and plating with tin or a tin-nickel alloy. The present invention relates to a method for producing a negative electrode for an electrolyte-based secondary battery.

  The negative electrode having a large number of fine porous electrodes made of metal alloying with lithium (having a microdomain structure) manufactured by the manufacturing method of the present invention is used in a conventional lithium ion secondary battery. It is possible to provide a high-power lithium-ion secondary battery that has a theoretical charge / discharge capacity of 372 mAh / g or more of a graphite negative electrode and can be mounted on an electronic device and can be reduced in size and weight. In addition, the metal porous negative electrode that is alloyed with lithium manufactured by the manufacturing method of the present invention can prevent deterioration in characteristics due to cracking of the negative electrode porous metal when repeatedly charged and discharged. Stable operation even after repeated charge and discharge. For this reason, the lithium ion secondary battery using the negative electrode manufactured by the manufacturing method of this invention has the outstanding effect that high output can be stably implement | achieved long life.

It is a drawing substitute photograph, and is a SEM photograph of a specific example of a negative electrode for a nonaqueous electrolyte secondary battery manufactured by the manufacturing method of the present invention. (A)-(c) is the plane SEM photograph of the negative electrode image | photographed changing magnification, (d)-(f) is the SEM photograph from the diagonal direction of the negative electrode image | photographed changing magnification. It is a schematic diagram explaining the manufacturing method of the negative electrode of this invention. It is a charging / discharging curve figure for 5 cycles in the constant current density conditions (0.2 mA / cm < ² >) of the negative electrode of an Example. It is a figure which shows a capacity | capacitance change when the discharge current density in the negative electrode of an Example is changed. It is a conceptual diagram of the tin or Sn-Ni alloy electrode which has a three-dimensional regular arrangement | sequence porous structure. (A) is a drawing-substituting photograph, and is a SEM photograph of a Sn—Ni alloy electrode having a three-dimensional ordered array porous structure formed by a colloidal crystal template method, and (b) is a charge / discharge curve diagram of this electrode. . FIG. 5 is a cycle characteristic diagram of an MPC Sn—Ni alloy electrode having a microdomain structure, a Sn—Ni alloy electrode having a three-dimensional ordered array porous structure formed by a colloidal crystal template method, and a plate-like Sn—Ni electrode. It is a drawing-substitute photograph, and is a scanning electron micrograph showing cracks generated in a Sn—Ni alloy electrode having a three-dimensional ordered array porous structure and a flat Sn—Ni electrode formed by a colloidal crystal template method.

  As described above, the present invention provides a microdomain structure having a large number of fine island-like electrodes made of a porous metal body alloyed with lithium on a conductive substrate by the steps (1) to (4). The present invention relates to a method for producing a negative electrode for a non-aqueous electrolyte secondary battery.

  First, a non-aqueous electrolyte secondary battery having a microdomain structure having a large number of fine island-like electrodes made of a metal porous body alloyed with lithium on a conductive substrate manufactured by the manufacturing method of the present invention The structure and material of the negative electrode will be described with reference to FIG.

  FIG. 1 is an SEM photograph showing a specific example of a negative electrode for a non-aqueous electrolyte secondary battery manufactured by the manufacturing method of the present invention. (A) to (c) are negative electrodes taken at different magnifications. (D) to (f) are photographs taken from an oblique direction of the negative electrode taken at different magnifications. As is clear from the SEM photographs of FIGS. 1A to 1F, the negative electrode for a non-aqueous electrolyte secondary battery manufactured by the manufacturing method of the present invention has a microdomain structure on a conductive substrate. A porous island-shaped electrode made of a metal alloyed with lithium is formed. In the example of FIG. 1, the island-like electrode has a cylindrical shape with a diameter of 20 μm and a height of 30 μm, and the pitch in both the X-axis direction and the Y-axis direction is 30 μm.

  First, a conductive substrate is used as the substrate of the negative electrode for a nonaqueous electrolyte secondary battery manufactured by the manufacturing method of the present invention. In the example of FIG. 1, a copper (Cu) substrate is used. However, the conductive material constituting the conductive substrate is not limited to copper, and any known material can be used as long as it has conductivity. The material which does not form an alloy with is preferable. Examples of such a preferable material include nickel, stainless steel and the like in addition to the copper. Among these, copper is preferable from the viewpoint of handling and price. The shape of the conductive substrate is practically plate-shaped or foil-shaped. As for the conductive substrate, the whole substrate may be made of a conductive material, or a layer made of a conductive material may be formed on the surface of a non-conductive substrate.

  As the material of the island-shaped electrode, tin or an alloy containing tin is a preferable material in the present invention. However, as the metal alloyed with lithium, aluminum (Al), aluminum-silicon (Al-Si) can be used. Alloy, aluminum alloy such as aluminum-copper (Al-Cu) alloy, aluminum-silicon-copper (Al-Si-Cu) alloy, aluminum-silicon-titanium (Al-Si-Ti) alloy, magnesium (Mg), silicon (Si), zirconium (Zr), chromium (Cr), gold (Au), platinum (Pt), or the like may be used. Tin-nickel alloy is preferable as the tin alloy, but iron (Fe), copper (Cu), manganese (Mn), cobalt (Co), lead (Pb), antimony (Sb), zinc (Zn) ), Molybdenum (Mo), nickel-copper (Ni-Cu) alloy, nickel-phosphorus (Ni-P) alloy, nickel-cobalt (Ni-Co) alloy, nickel-zinc (Ni-Zn) alloy, zinc-iron (Zn-Fe) alloy, copper-lead (Cu-Pb) alloy, nickel-molybdenum (Ni-Mo) alloy, nickel-tungsten (Ni-W) alloy, nickel-cobalt (Ni-Co) alloy, nickel-cobalt -An alloy such as a phosphorus (Ni-Co-P) alloy or a nickel-palladium (Ni-Pd) alloy may be used. As content of tin in a tin alloy, the thing in the range of 5 wt%-99.995 wt% is preferable, for example. The porosity of the metal porous body alloyed with lithium may be set as desired in consideration of the mechanical strength of the electrode, for example, 50 to 80%. Further, the pores are required to communicate with each other. The size of each pore (hole) is determined in consideration of the porosity, the mechanical strength of the electrode, and the like, but is usually about 0.05 to 5 μm.

  Further, the shape, size (maximum width), and height of the island-shaped electrode are cylindrical with a diameter of 20 μm and a height of 30 μm in the electrode of FIG. The size (diameter) and the height are not limited to this, and may be any as long as the object of the present invention can be achieved. For example, in addition to the circle, the shape may be a square, triangle, pentagon or more polygon, an elongated shape, or an indefinite shape. The plane size (maximum width) of the electrode may be such that the electrode is not cracked so much when repeated charging and discharging are performed in the 3DOM structure. In order to disperse stably, it is generally desirable that the thickness be about 100 μm or less, more preferably about 50 μm or less, and still more preferably about 30 μm or less. As described above, when charging and discharging are repeatedly performed using a negative electrode having a 3 DOM structure, the negative electrode having a 3 DOM structure is divided into blocks of about 30 μm, thereby reducing the characteristics of the lithium ion secondary battery. However, when the maximum width of the electrode is about 100 μm or less, the deterioration of the characteristics does not become so great. The minimum width is generally about 5 μm or more, more preferably about 10 μm or more, from the viewpoints that the electrode needs to be a porous electrode, ease of production, adhesion to a conductive substrate, and the like. Is preferred. Further, the height (thickness) of the electrode may be arbitrary, and is usually 10 μm or more for use as a power source for a mobile phone. The size between the porous electrodes may be a size that does not have a physical adverse effect on the adjacent island-shaped electrode when the porous membrane expands during charging, and the porosity of the porous body, Although it is not particularly limited because it is affected by various factors such as the size of the pores and the size of the island electrodes, it is generally about 1 μm or more, more preferably about 5 μm or more. Furthermore, the arrangement of the island electrodes may be any arrangement, but is preferably a regular arrangement from the viewpoint of production. As the shape of the porous metal, a circular shape is preferable because stress is uniformly dispersed when the electrode expands. Further, the size is preferably about 10 to 50 μm in diameter and about 10 to 100 μm in height. The circular shape has a constant pitch in the X-axis direction and the Y-axis direction, and the width between the electrodes is about 1 μm or more. It is preferable. Moreover, the thing which has shifted | deviated by a half pitch with the line of an adjacent electrode is also mentioned as a preferable thing.

  The negative electrode manufactured by the manufacturing method of the present invention has been described above. Hereinafter, the negative electrode manufacturing method of the present invention will be described with reference to FIG. However, the method for producing a negative electrode described below is only one method for producing the negative electrode of the present invention, and the method for producing the negative electrode of the present invention is limited to the following. is not.

  FIG. 2 schematically shows a method of manufacturing the negative electrode shown in FIG. 1, and FIG. 2 (a) shows a 20 μm diameter cylinder formed on a resist film on a copper layer conductive substrate provided on silicon. It is a schematic diagram which shows the state in which the concave-shaped recessed part was formed. In FIG. 2A, the conductive substrate is made of a copper layer provided on silicon. Moreover, FIG.2 (b) is a schematic diagram explaining the method to manufacture the negative electrode of this invention using the resist film which has this cylindrical recessed part.

  First, the cylindrical recess in the resist film shown in FIG. 2A is formed as follows. That is, a photosensitive resin is applied on a plate-like or foil-like conductive substrate to form a photoresist film. As described above, the conductive substrate material may be any known material as long as it has conductivity. However, a material that does not form an alloy with lithium, such as copper, nickel, and stainless steel, is preferable.

  There are two types of photoresists: positive photoresists in which the exposed part is dissolved in the developer and patterning is performed, and negative photoresists in which the non-exposed part is dissolved in the developer and patterning is performed. In view of ease of peeling, a positive photoresist such as a photosensitive resin composition containing a novolak resin and a naphthoquinone diazide photosensitive agent is preferable. The film thickness of the photoresist film may be a thickness corresponding to the desired thickness of the island-shaped porous metal electrode. The thickness varies depending on the size of the island and is usually about 10 to 100 μm in dry film thickness, but it may be thicker or thinner than this.

  Next, the photoresist film is exposed through a document (reticle) on which a desired pattern is formed, and then developed. If the photoresist film is a positive type photoresist, the exposed resist is completely removed up to the conductive substrate, and the porous metal is removed. A resist pattern is formed in which a portion where the electrode is formed is a recess. When a positive type photoresist is used, the resist film at the place where the light is applied is removed by development. Therefore, as a document, a document in which a large number of fine island-shaped patterns become light transmitting portions (transparent) is used. Used. In the case of using a negative photoresist, a document in which the island pattern portion is a light opaque portion is used. As described above, the shape of the island may be arbitrary. However, when a cylindrical electrode as shown in FIG. 1 is formed, for example, a document having a large number of fine circular patterns is used. What is necessary is just to select the light source used for exposure according to the photosensitive area | region of the photosensitive resin to be used. Usually, sufficient resolution can be obtained by ultraviolet exposure using an ultraviolet exposure apparatus such as a high-pressure mercury lamp or a metal halide lamp, but if necessary, far ultraviolet rays such as KrF or ArF excimer laser light, X-rays, and electron beams are used. May be.

  As shown in FIG. 2C, polymer fine particles such as polystyrene and PMMA (polymethyl methacrylate) are deposited in the recesses of the resist film thus formed. The pore diameter of the obtained porous body (porous body) can be controlled by the particle diameter of the polymer fine particles. The size of the polymer particles is not particularly limited as long as the size of the island-shaped electrode is porous, and the size of each island-shaped electrode is about 5 to 100 μm. In view of this, and absorption of volume change due to alloying with lithium, relaxation ability, etc., it is preferable to use a material having a size of about 0.05 to 5 μm, but the size of the fine particles is particularly limited to the above size is not. Electrophoresis can be used as a method for depositing the polymer fine particles on the conductive substrate. Alternatively, the fine particle suspension can be deposited by drying on a conductive substrate. The amount of fine particles deposited is preferably an amount that fills at least the holes of the resist film. After the polymer particles are deposited on the conductive substrate as described above, the temperature is equal to or higher than the glass transition temperature of the used polymer material and is equal to or lower than the melting point or softening temperature, for example, 80 to 120 ° C. in the case of polystyrene. The particles of the polymer particles may be fused by performing heat treatment at a degree. By performing this heat treatment, the particles are fixed when the substrate is immersed in a plating bath during the subsequent plating treatment and during plating. Moreover, it is preferable that the particles are filled in a close-packed structure on the conductive substrate. If the particles have a regular array structure on the conductive substrate, the finally obtained porous structure also has a regular array structure.

  Thereafter, as shown in FIG. 2D, a metal alloying with lithium constituting the island-shaped electrode is deposited between the fine particles by plating or the like. Any desired metal or alloy to be alloyed with lithium may be used. For example, in the case of plating, tin or an alloy containing tin, aluminum (Al), aluminum alloy (Al-Si, Al-Cu, Al- Si-Cu, Al-Si-Ti), Mg, Si, Zr, Cr, Au, Pt, etc. are mentioned, but tin or tin alloys such as Sn-Ni are preferred. The plating bath may be a conventionally known one. For example, when plating of tin and a nickel alloy, a solution obtained by dissolving a tin salt and a nickel salt in a plating bath is used. An appropriate amount of these salts is used depending on the target alloy composition. As described above, in the case of a tin alloy, the tin content is preferably in the range of 5 wt% to 99.995 wt%, for example.

  After applying the metal alloying lithium as described above by, for example, plating, the sample particles are immersed in an organic solvent that dissolves the polymer used, such as toluene, acetone, tetrahydrofuran, etc. Dissolve and remove. In this way, a negative electrode having a porous structure and having a large number of island-shaped electrodes such as tin or a tin alloy shown in FIG. 2E can be produced. The porosity of the obtained porous island electrode is preferably set to, for example, 50 to 80% in consideration of the mechanical strength of the electrode as described above. The negative electrode thus produced is used as a negative electrode plate for a lithium ion secondary battery.

  Next, a lithium ion secondary battery in which the negative electrode manufactured by the manufacturing method of the present invention is used will be described. Lithium ion secondary batteries consist of a negative electrode plate, a non-aqueous electrolyte composed of an aprotic organic solvent and a lithium salt, and a positive electrode plate, as well as other battery components such as separators, gaskets, current collectors, sealing plates, and cells. Consists of cases and the like. In the lithium ion secondary battery, the negative electrode manufactured by the above-described manufacturing method of the present invention is used as the negative electrode plate, and any other known or well-known battery components can be used. Further, the shape of the battery may be any shape including a conventionally known shape such as a cylindrical shape, a square shape, and a coin shape, and is not particularly limited. Moreover, the negative electrode manufactured by the manufacturing method of the present invention according to the battery shape may be cut into a desired size and used as a negative electrode plate, or may be manufactured as a negative electrode plate according to the battery shape. When the lithium ion secondary battery is, for example, a coin-type battery, a negative electrode plate is placed on the cell floor plate, an electrolyte and a separator are placed thereon, and a positive electrode is placed so as to face the negative electrode, and a gasket and a sealing plate In addition, the secondary battery is caulked together, but the structure or manufacturing method of the lithium ion secondary battery in which the negative electrode manufactured by the manufacturing method of the present invention is used is not limited thereto.

  Non-aqueous solvents that can be used in the electrolyte of lithium ion secondary batteries include high dielectric constant solvents such as dimethyl sulfoxide, ethylene carbonate, γ-butyrolactone, propylene carbonate, sulfolane, γ-valerolactone, and γ-octanoic lactone. Single or two organic solvents such as 1,2-dimethoxyethane, 1,2-diethoxyethane, 2-methyltetrahydrofuran, 1,3-dioxolane, tetrahydrofuran, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate and other low viscosity solvents Mixtures of more than one type can be used.

As the lithium salt used in the electrolyte of lithium ion secondary _{batteries, LiClO 4, LiPF 6, LiBF} 4, LiAsF 6, LiCF 3 lithium salt of SO ₃ and the like, one or two of these The above is dissolved in the non-aqueous solvent at a concentration of about 0.5 to 2.0 M to obtain a non-aqueous electrolyte. In the present invention, a polymer solid electrolyte that is a conductor of an alkali metal cation such as lithium ion can also be used as the electrolyte.

The material of the positive electrode body is not particularly limited, but a metal chalcogen compound that can occlude and release lithium ions during charge and discharge is preferable. Examples of such metal chalcogen compounds include vanadium oxide, vanadium sulfide, molybdenum oxide, molybdenum sulfide, manganese oxide, chromium oxide, titanium oxide, titanium sulfide, and the like. And composite oxides and sulfides. Examples of such compounds include Cr ₃ O ₈ , V ₂ O ₅ , V ₅ O ₁₈ , VO ₂ , Cr ₂ O ₅ , MnO ₂ , TiO ₂ , MoV ₂ O ₈ , TiS ₂ V ₂ S ₅ MoS _2. MoS ₃ VS ₂ , Cr _0.25 V _0.75 S ₂ , Cr _0.5 V _0.5 S _{2 and the} like. Further, LiMY ₂ (M is a transition metal such as Co and Ni, Y is a chalcogen compound such as O and S), LiM ₂ Y ₄ (M is Mn and Y is O), an oxide such as WO ₃ , CuS, Sulfides such as Fe _0.25 V _0.75 S ₂ and Na _0.1 CrS ₂ , phosphorus such as NiPS ₈ and FePS ₈ , sulfur compounds, selenium compounds such as VSe ₂ and NbSe _{3, and the} like can also be used. Currently, lithium composite oxide LiCoO ₂ is mainly used for the positive electrode. The positive electrode material described above may be mixed with a binder and applied onto a current collector to form a positive electrode plate.

  The separator that holds the electrolytic solution may be made of a material that is generally excellent in liquid retention. For example, a polyolefin resin nonwoven fabric or a porous film is used. The non-aqueous electrolyte is used by impregnating a separator that separates a positive electrode and a negative electrode. However, a high-molecular resin is added to the electrolyte to make it highly viscous or gelled to eliminate fluidity. Sometimes used.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited at all by this.

(1) Preparation of a tin-nickel alloy-based porous negative electrode having a microdomain structure (i) Production of a colloidal crystal template on a photoresist substrate A positive photoresist was applied on a silicon substrate having a copper layer on the surface, A resist film having a dry film thickness of 30 μm was formed. By developing the substrate after exposure, a photoresist substrate having a large number of regular cylindrical holes (cylinder dots) having a diameter of 20 μm and a pitch of 30 μm was obtained in the resist film.

  Next, a mold was prepared by depositing polystyrene particles, which are monodisperse spherical particles with a direct system of 1 μm, in the cylindrical dots of the photoresist substrate. First, in order to remove the air present in the dots of the photoresist substrate, ultrapure water was injected and the pressure was reduced at about 0.6 MPa for 5 minutes using a vacuum chamber. Thereafter, 10 μL of a polystyrene suspension (manufactured by Seradyn Inc., 10 wt% solid) was injected into the dots, and polystyrene particles were deposited under reduced pressure conditions of 0.08 MPa for 24 hours. The mold made of the deposited polystyrene particles was dried at room temperature and normal pressure, and then heat-treated at 110 ° C. for 10 minutes with an air dryer to fuse and bond the polystyrene particles together.

(Ii) Electroplating of Sn—Ni alloy Sn—Ni alloy plating was performed using a plating bath with the composition shown in Table 1 using the cylindrical part with a built-in fine particle polystyrene on the photoresist substrate prepared above as a mold. The cell used for Sn—Ni alloy plating used a photoresist substrate as a working electrode and an Sn plate as a counter electrode. The distance between the electrodes was 1 cm, and the cathode current density was 1.37 mA / cm ² . The bath temperature was kept at 50 ° C. and the plating time was 43 minutes.

(Iii) Elution of polystyrene After immersing the above-mentioned sample in toluene for 1 day to elute the polystyrene particles used as a template, the photoresist was dissolved and removed using acetone and ethanol to obtain a negative electrode.

(2) Performance Evaluation of Tin-Nickel Alloy Porous Negative Electrode Having Microdomain Structure The shape and crystal structure evaluation of the tin-nickel alloy porous negative electrode having the microdomain structure produced as described above were observed by SEM and Analysis using an energy dispersive X-ray spectrometer (EDS) was performed. In addition, the electrochemical characteristics were evaluated using a constant current charge / discharge measuring device. For the constant current charge / discharge measurement, a bipolar or tripolar cell was used, a sample prepared as a working electrode, and Li metal as a reference electrode and a counter electrode. As the electrolytic solution, 1 mol / dm ³ of LiClO ₄ (EC (ethylene carbonate): DEC (diethyl carbonate) = 1: 1 vol%) was used, and the charge / discharge current density was 0.2 mA / cm ² .

  FIG. 1 shows an SEM image of a porous columnar (MPC) Sn—Ni alloy electrode from which the photoresist and polystyrene mold were removed. From the SEM image, the prepared sample had a structure in which cylinders having a diameter of 20 μm and a height of about 30 μm were regularly arranged, and a sample almost reflecting the dot shape and arrangement pattern of the used photoresist substrate was obtained. Further, it was confirmed that this cylinder had macropores having a diameter of 1.0 μm reflecting the shape of polystyrene particles used as a mold, and the macropores were connected by communication holes.

  From the mapping image obtained from the EDS analysis of the produced MPC Sn—Ni alloy electrode, uniform element distribution of Sn and Ni was confirmed in the produced MPC Sn—Ni alloy. The element content of the produced Sn-Ni electrode is determined by XRF analysis (X-ray Fluorescence Spectroscopy: X-ray fluorescence analysis), and the composition ratio of Sn and Ni is Ni: Sn = 4: 6 (atomic ratio). It was confirmed that.

FIG. 3 shows a charge / discharge curve for five cycles under a constant current density condition (0.2 mA / cm ² ) of a negative electrode having an MPC Sn—Ni alloy electrode produced in this example. In this test, it can be seen from the figure that the negative electrode produced in this example is about 0.5 V vs. Flatness due to Li alloying / dealloying (Li insertion / desorption reaction) was confirmed in Li / Li ⁺ , and this result coincided with the result of FIG. The negative electrode of the present embodiment, the discharge capacity of 0.87mAh / cm ² in the first cycle (coulomb efficiency: 72%) indicates a 0.86mAh / cm ² at 5-th cycle, the capacity reduction was hardly observed .

On the other hand, FIG. 4 shows the capacity change when the discharge current density is changed in the lithium ion secondary battery using the MPC Sn—Ni alloy electrode produced in this example. 4, a negative electrode made in this example, the discharge current density 1.0 mA / cm ^2, shows a discharge capacity of about 0.8 mA / cm ^2, and the capacitance of the discharge current density 0.2 mA / cm ² Compared to 90% or more, it has good rate and characteristics.

  FIG. 7 shows the cycle characteristics of the MPC Sn—Ni alloy electrode produced in this example during 50 cycles. The negative electrode produced in this example showed a discharge capacity of 470 mAh / g in the first cycle, and the capacity retention rate was 90% even in the 50th cycle.

  As described above in detail, the negative electrode for a non-aqueous electrolyte secondary battery having a microdomain structure made of a porous metal alloyed with lithium manufactured by the manufacturing method of the present invention has a conventional 3DOM structure. A lithium ion secondary battery having excellent cycle characteristics as compared with the negative electrode having the above can be provided.

Claims (5)

(1) a step of forming a large number of independent fine voids in a photoresist film on a conductive substrate;
(2) a step of filling fine particles in the voids of the photoresist film;
(3) a step of plating the substrate filled with the fine particles with a metal alloying with lithium, and (4) a step of removing the fine particles and the photoresist film. A method for producing a negative electrode for a secondary battery.   2. The method for producing a negative electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein the fine void has a cylindrical shape having a diameter of 10 to 30 [mu] m and a depth of 10 to 50 [mu] m. A method for producing a negative electrode for a non-aqueous electrolyte secondary battery, wherein the pitch is a regular array having a pitch of 1 to 50 μm.   3. The method for producing a negative electrode for a non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the fine particles are made of a polymer having a particle size of 0.1 to 5 [mu] m, and removal of the polymer dissolves the polymer in a solvent. The manufacturing method of the negative electrode for nonaqueous electrolyte type secondary batteries characterized by the above-mentioned.   4. The method for manufacturing a negative electrode for a non-aqueous electrolyte secondary battery according to claim 3, wherein the filled polymer is thermally welded before the plating step. Manufacturing method of negative electrode.   5. The method of manufacturing a negative electrode for a non-aqueous electrolyte secondary battery according to claim 4, wherein the plating is performed by immersing the substrate in a plating bath and plating with a tin-nickel alloy. Of manufacturing negative electrode for lithium secondary battery.