JP2018120849A - Negative electrode for lithium ion secondary battery, manufacturing method of the same, and lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a negative electrode for a lithium ion secondary battery capable of suppressing deterioration of charge and discharge cycle performance and securing a required energy capacity, a manufacturing method of the same, and a lithium ion secondary battery.SOLUTION: A negative electrode 1 for a lithium ion secondary battery includes at least one laminate structure composed of two current collectors 21, 22 and a negative electrode active material layer 31 sandwiched between the current collectors 21, 22.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a negative electrode for a lithium ion secondary battery, a method for producing the same, and a lithium ion secondary battery.

  Conventionally, a lithium ion secondary battery is known as a secondary battery used for a power source of a portable electronic device or the like.

  It has been studied to use tin having a theoretical capacity larger than that of a carbon material as the negative electrode active material of the lithium ion secondary battery. For example, a tin film layer having a thickness of 10 to 300 μm was formed on the surface of the current collector layer. It is known to use those for the negative electrode of the lithium ion secondary battery (for example, see Patent Document 1).

JP 2001-68094 A

  However, the tin film layer has a very large volume expansion when occluded lithium ions, and peels off from the surface of the current collector layer when repeated charge / discharge reaction, so the charge / discharge cycle performance of the lithium ion secondary battery is There is an inconvenience of lowering.

  The present invention eliminates such inconvenience, and even when the charge / discharge reaction is repeated, the tin film formed on the surface of the current collector is not peeled off, and the decrease in charge / discharge cycle performance can be suppressed. And it aims at providing the negative electrode for lithium ion secondary batteries which can ensure a required energy capacity, and its manufacturing method.

  Moreover, the objective of this invention is also providing the lithium ion secondary battery provided with the said negative electrode for lithium ion secondary batteries.

  In order to achieve such an object, the negative electrode for a lithium ion secondary battery of the present invention has at least one laminated structure composed of two current collectors and a negative electrode active material layer sandwiched between both current collectors. It is characterized by.

  The negative electrode for a lithium ion secondary battery of the present invention has a negative electrode active material layer sandwiched between two current collectors and restrained by both current collectors. In addition, it is possible to prevent the negative electrode active material layer from being peeled off from the current collector, and to suppress a decrease in charge / discharge cycle performance.

  In the negative electrode for a lithium ion secondary battery of the present invention, the negative electrode active material layer may be made of one material selected from the group consisting of a tin film, an aluminum film, and an aluminum alloy film. At this time, it is preferable that the tin film is made of a tin plating film.

  Moreover, the negative electrode for lithium ion secondary batteries of this invention WHEREIN: The said electrical power collector shall consist of metal powder or metal powder which equips the surface with a tin plating film. At this time, the metal film may be a metal foil or a metal plating film. The film may be a foil, a plate, or a state in which particles are arranged in a thin film.

  The negative electrode for a lithium ion secondary battery of the present invention includes a first step of forming a negative electrode active material layer made of a tin plating film on a current collector made of a metal film, and a negative electrode formed in the first step. A second step of forming a current collector made of a metal plating film having a thickness in the range of 1000 nm or less on the active material layer, wherein the first step and the second step are performed at least once. It can manufacture advantageously by the manufacturing method performed one by one.

  The negative electrode for a lithium ion secondary battery of the present invention is formed by the first step of forming a tin plating film on the surface of the metal powder and obtaining the metal powder having the tin plating film on the surface, and the first step. A second step of preparing a slurry containing metal powder having a tin plating film on the surface, and a third step of applying the slurry prepared in the second step onto a current collector made of a metal film Or a manufacturing method including a step of forming a current collector made of a metal plating film on both front and back surfaces of a negative electrode active material layer made of an aluminum film or an aluminum alloy film.

  Further, the lithium ion secondary battery of the present invention is disposed between the negative electrode for the lithium ion secondary battery, a positive electrode disposed facing the negative electrode active material layer of the negative electrode, and the negative electrode and the positive electrode. And an electrolyte layer that has been prepared.

The typical sectional view showing the example of 1 composition of the negative electrode for lithium ion secondary batteries of the present invention. 2A is a schematic cross-sectional view showing a first step of the method for manufacturing the negative electrode for lithium ion secondary battery shown in FIG. 1, and FIG. 2B is a second method for manufacturing the negative electrode for lithium ion secondary battery shown in FIG. 2C is a schematic cross-sectional view showing the second step of the method for manufacturing the negative electrode for the lithium ion secondary battery shown in FIG. 1, and FIG. 2D is a schematic cross-sectional view showing the lithium ion secondary shown in FIG. The typical sectional view showing the 2nd 2nd process of the manufacturing method of the negative electrode for secondary batteries. The typical sectional view showing the composition of the lithium ion secondary battery of the present invention provided with the anode for lithium ion secondary batteries shown in FIG. 4A is a schematic cross-sectional view showing another configuration example of the negative electrode for a lithium ion secondary battery of the present invention, and FIG. 4B is an enlarged view of a main part of FIG. 4A. 4A is a schematic cross-sectional view showing a configuration of a lithium ion secondary battery of the present invention including the negative electrode for a lithium ion secondary battery shown in FIG. 4A. FIG. The lithium ion secondary battery of this invention WHEREIN: The graph which shows the charging / discharging characteristic in the case of providing the negative electrode which uses a tin plating film as a negative electrode active material layer. The lithium ion secondary battery of this invention WHEREIN: The graph which shows the charging / discharging characteristic in the case of providing the negative electrode which uses an aluminum film or an aluminum alloy film as a negative electrode active material layer.

  Next, embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

  As shown in FIG. 1, the negative electrode 1 for a lithium ion secondary battery according to the first aspect of the present embodiment has three layers of current collectors 21, 22, 23 and two layers of tin films 31, 32 alternately. In addition, a negative electrode active material layer is formed by the tin films 31 and 32.

  In this case, specifically, the negative electrode 1 for a lithium ion secondary battery according to the first aspect includes a first current collector 21 made of a metal foil and a first current collector 21 formed on the first current collector 21. A tin film 31, a second current collector 22 made of a metal plating film formed on the first tin film 31, a second tin film 32 formed on the second current collector 22, And a third current collector 23 made of a metal plating film formed on the second tin film 32. Here, the first tin film 31 as the negative electrode active material layer is sandwiched between the first current collector 21 and the second current collector layer 22, and the second tin film 32 as the negative electrode active material layer. Is sandwiched between the second current collector 22 and the third current collector 23.

  The negative electrode 1 for a lithium ion secondary battery according to the first embodiment shown in FIG. 1 includes two laminated structures in which a tin film is sandwiched between two current collectors as described above. The battery negative electrode 1 may further include the multilayer structure, and may further include the multilayer structure within a range of, for example, 20 or less.

  The first current collector 21 is not particularly limited as long as it is a metal foil having electrical conductivity. For example, a foil of aluminum, copper, steel, titanium, or the like can be used. The thickness of the first current collector 21 is preferably thin in order to improve the energy density of the battery, but if it is too thin, it is difficult to handle and the productivity is lowered. Is preferred. Further, the first current collector 21 may be formed with irregularities by cutting or dissolving the surface.

  The second current collector 22 and the third current collector 23 are made of, for example, a copper plating film having a thickness in the range of 1000 nm or less. The second current collector 22 and the third current collector 23 are formed by plating on the first tin film 31 or the second tin film 32 respectively formed in the previous step in the manufacturing method described later. can do. As the plating method, an electroplating method or an electroless plating method can be used. However, since the second current collector 22 and the third current collector 23 can be made more porous, the electroless plating can be performed. It is preferable to form by a method.

  The first tin film 31 and the second tin film 32 are respectively formed on the first current collector 21 and the second current collector 22 by a plating method in the manufacturing method described later. As the plating method, an electroplating method or an electroless plating method can be used, but since the adhesion to the current collectors 21 and 22 is good, a large-area film can be easily and inexpensively formed. It is preferable to form by.

  The first tin film 31 and the second tin film 32 are preferably formed to a thickness of 100 nm to 100 μm by the plating method. If the thickness is less than 100 nm, the first tin film 31 and the second tin film 32 are preferably 100 nm or more because the action of occluding lithium ions as a negative electrode active material becomes excessive. On the other hand, if it exceeds 100 μm, it will take time for the electrolyte to soak and it will be difficult to produce, so that it is preferably 100 μm or less.

  Next, with reference to FIG. 2A-FIG. 2D, the 1st manufacturing method of the negative electrode 1 for lithium ion secondary batteries is demonstrated.

  When manufacturing the negative electrode 1 for a lithium ion secondary battery, first, as shown in FIG. 2A, on the first current collector 21 made of copper foil as a metal film having a thickness in the range of 1 to 50 μm, A first tin film 31 is formed by electroplating.

  When the first tin film 31 is formed by electroplating, the first current collector 21 is immersed in an acid such as nitric acid, hydrochloric acid or sulfuric acid, or washed with water to remove dust, oxide film, or the like on the surface. Thereafter, the entire surface of one surface and a part of the other surface are masked with an epoxy tape. Then, the first current collector 21 masked is immersed in a plating bath in which a tin salt such as tin chloride is dissolved in an acid such as sulfuric acid or methanesulfonic acid, and is energized at a predetermined temperature, whereby the first A first tin film 31 is formed on an unmasked portion of the current collector 21. The thickness of the first tin film 31 can be managed by the energization time.

  The plating bath may be one in which a tin salt such as tin chloride is dissolved in an alkaline solution such as sodium hydroxide instead of sulfuric acid.

  Next, as shown in FIG. 2B, a second current collector 22 made of a copper plating film is formed on the first tin film 31 formed in the previous step by an electroless plating method.

  In the case where the second current collector 22 is formed by an electroless plating method of copper, the first current collector 21 on which the first tin film 31 is formed is mixed with sulfuric acid and disulfide as a reducing agent. It is immersed in a plating bath in which sodium phosphite is dissolved and heated to a predetermined temperature. By doing in this way, on the 1st tin film 31, and on the 1st electrical power collector 21 which is not coat | covered with the 1st tin film 31, the 2nd collector which has the thickness of the range of 1000 nm or less The electric body 22 is formed. The thickness of the second current collector 22 can be managed by the temperature of the plating bath and the immersion time. Note that the surface of the first current collector 21 on which the first tin film 31 is formed may be washed with water or the like before the second current collector 22 is formed. The plating bath may be one in which copper cyanide is dissolved in sodium hydroxide or potassium hydroxide, and Rochelle salt or ammonia is dissolved.

  Further, a mask member (not shown) that forms a minute hole having a diameter of 1 mm or less on the first tin film 31 and the first current collector 21 not covered with the first tin film 31. ) May be disposed and processed by the electroless plating method. The mask member is removed after the second current collector 22 is formed. By doing so, lithium ions can be easily transmitted through the second current collector 22.

  Next, as shown in FIG. 2C, a second tin film 32 is formed on the second current collector 22 by electroplating. The formation of the second tin film 32 can be performed in exactly the same manner as when the first tin film 31 is formed on the first current collector 21. At this time, in addition to tin, coprecipitation plating with copper, nickel, silver or the like may be performed.

  Next, as shown in FIG. 2D, by forming the third current collector 23 on the second tin film 32 formed in the previous step, the negative electrode 1 for the lithium ion secondary battery shown in FIG. Form. The formation of the third current collector 23 can be performed in exactly the same manner as when the second current collector 22 is formed on the first tin film 31.

  Further, the negative electrode 1 for a lithium ion secondary battery formed as described above may be processed to make a hole so as to improve the permeation of the electrolytic solution.

  In the thus formed negative electrode 1 for a lithium ion secondary battery, the first current collector 21 and the second current collector 21 are formed at the end of the first current collector 21 (the right end in FIG. 2D). The electric body 22 and the third current collector 23 are connected to each other.

  2A to 2D, a tin film 31 made of a tin plating film is formed on a current collector 21 made of a metal foil, and a current collector 22 made of a metal plating film is formed on the tin film 31. Thus, a laminated structure in which the tin film 31 as the negative electrode active material layer is sandwiched between the two current collectors 21 and 22 is formed. However, instead of this, an aluminum film may be used instead of the above-mentioned tin film, or a current collector made of a metal plating film may be formed on both the front and back surfaces of the aluminum film or aluminum alloy film. It is possible to form a stacked structure in which an aluminum film or an aluminum alloy film as a negative electrode active material layer is sandwiched between two current collectors.

  Examples of the aluminum alloy film include: 2000 series containing Cu, duralumin, 3000 series containing Mn, 4000 series containing Si, 5000 series containing Mg, 6000 series containing Mg and Si, Zn and Mg In addition to the above, alloy foils containing other elements can be used. Aluminum bronze, aluminum tin alloy foil, and lithium aluminum alloy foil can also be used. Furthermore, you may use what coated the slurry which consists of binders, such as auxiliary agents, such as aluminum particle and carbon, and polyvinylidene fluoride (PVDF), and what applied the aluminum paste to the electrical power collector.

  Examples of the metal forming the metal plating film include nickel, tin, silver, gold, and copper.

  The negative electrode 1 for a lithium ion secondary battery of the first aspect of the present embodiment can be used for the lithium ion secondary battery 4 shown in FIG.

  The lithium ion secondary battery 4 is configured by disposing a negative electrode 1 for a lithium ion secondary battery, an electrolyte layer 6 made of a separator impregnated with an electrolytic solution, and a positive electrode 7 inside a cell 5. Yes. In the lithium ion secondary battery 4, the negative electrode 1 for a lithium ion secondary battery is disposed such that the third current collector 23 faces the positive electrode 7 with the electrolyte layer 6 interposed therebetween. The positive electrode 7 includes a positive electrode current collector 71 and a positive electrode mixture layer 72, and the positive electrode mixture layer 72 is disposed so as to face the electrolyte layer 6. The negative electrode lead 8 is connected to the first current collector 21 of the negative electrode 1 for the lithium ion secondary battery, and the positive electrode lead 9 is connected to the positive electrode current collector 71 of the positive electrode 7.

  In the lithium ion secondary battery 4, a separator made of a synthetic resin such as polyethylene can be used as the separator. As the electrolytic solution impregnated in the separator, a phosphate ester represented by the following general formula (1) can be used as a solvent, and a lithium salt dissolved as a supporting salt in the solvent can be used.

In the general formula (1), R ¹ , R ² , and R ³ are linear hydrocarbon groups such as alkyl groups, alkenyl groups, and alkynyl groups, or groups obtained by substituting some of the hydrogens with fluorine. They may be the same or different. Moreover, since the viscosity of the linear hydrocarbon group becomes too high when the number of carbon atoms increases and handling becomes difficult, the linear hydrocarbon group preferably has 7 or less carbon atoms, more preferably 3 or less carbon atoms.

  As the phosphoric acid ester, for example, trimethyl phosphate, triethyl phosphate, tristrifluoroethyl phosphate, and the like are preferable because they have an appropriate viscosity and high solubility in the lithium salt as the supporting salt.

Examples of the lithium salt include LiPF ₆ , LiAsF ₆ , LiAlCl ₄ , LiClO ₄ , LiBF ₄ , LiSbF ₆ , Li ₂ SO ₄ , Li ₃ PO ₄ , Li ₂ HPO ₄ , LiH ₂ PO ₄ , LiCF ₃ SO ₃ , LiC. ₄ F ₉ SO ₃ , LiN (FSO ₂ ) ₂ consisting of imide anions, LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₂ F ₅ SO _{2), LiN (CF 3 SO} 2) (C 4 F 9 SO 2), LiN containing a five-membered ring structure _{(CF 2 SO 2) 2 (} CF 2), LiN having a six-membered ring structure _(CF 2 SO ₂ ) ₂ (CF ₂ ) _{2 and the} like. Further, as the lithium salt, LiPF ₅ (CF ₃ ), LiPF ₅ (C ₂ F ₅ ), LiPF ₅ (C ₃ F ₇ ), LiPF _{4 in which} at least one fluorine atom of LiPF ₆ is substituted with a fluorinated alkyl group. (CF ₃ ) ₂ , LiPF ₄ (CF ₃ ) (C ₂ F ₅ ), LiPF ₃ (CF ₃ ) _{3 and the} like can also be mentioned. In addition, alone or in combination, a sodium salt can be used in place of the above lithium salt.

  The concentration of the supporting salt in the electrolytic solution is preferably in the range of 0.1 to 3 mol / L, and more preferably in the range of 0.6 to 1.5 mol / L. In this case, the pH of the electrolytic solution is preferably in the range of 4-10. In addition, if pH of electrolyte solution exists in the range of 4-10, you may add the additive of the quantity of 50 mass% or less with respect to electrolyte solution whole quantity. Additives include vinylene carbonate (VC), vinyl ethylene carbonate (VEC), ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), propylene carbonate (PC), ether Group-containing dimethoxyethane, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, triethylene glycol dimethyl ether, (anhydrous) succinic acid, (anhydrous) maleic acid, γ-butyrolactone, γ-valerolactone, ethylene sulfite, sulfolane, ionic liquid, boron Examples thereof include acid esters, acetonitrile, phosphazene and the like, or those obtained by fluorinating a part of hydrogen.

  Further, the electrolyte layer 6 may be gelled by impregnating a separator obtained by adding a gelling material to the electrolytic solution and heating the separator. Examples of the gelling material include polymerization initiators or polymers such as polyvinylidene fluoride / hexafluoropropylene (PVDF-HFP), (poly) acrylonitrile, (poly) acrylic acid, and polymethyl methacrylate.

A solid electrolyte can also be used as the electrolyte layer 6. Examples of the solid electrolyte include Li ₃ PO ₄ , Li ₇ La ₃ Zr ₂ O ₁₂ , La _2-3-x Li _x TiO ₃ , Li _0.33 La _0.55 TiO ₃ , and Li _1.3 Al _0.7. Oxide solid electrolyte such as Ti _1.3 (PO ₄ ) ₃ , Li _a Ge _x P _y S _z , (a, x, y are arbitrary values), LiSiPSCl, LSPPS (Lil _0.35 [Sn _0.27 Si _1.08 ] P _1.65 S ₁₂ (Li _3.45 [Sn _0.09 Si _0.36 ] P _0.55 S ₄ or the like, or a sulfur-based solid electrolyte obtained by adding a halogen element thereto, polyethylene oxide (PEO), polyethylene oxide-LiTFSI, lithium phosphate oxynitride (LiPON), etc. Since these materials do not volatilize, they can be compared with liquid electrolytes. , It is thought to contribute to the improvement of safety.

  The current collector 71 in the positive electrode 7 is not particularly limited as long as it is a material having electrical conductivity. For example, a material made of aluminum, copper, steel, titanium, or the like can be used. The thickness of the current collector 71 is preferably thin in order to improve the energy density of the battery, but if it is too thin, it is difficult to handle and the productivity is lowered. Therefore, the thickness is preferably in the range of 5 to 50 μm.

  The positive electrode mixture layer 72 in the positive electrode 7 is prepared by mixing a suitable amount of a positive electrode active material and a binder such as polyvinylidene fluoride (PVDF) and diluting with N-methylpyrrolidone, using a doctor blade or the like. It can be formed by coating and applying to the current collector 71. The positive electrode mixture layer 72 preferably has a higher content of the positive electrode active material with respect to the total amount. For example, the content is preferably 85% by mass or more. The positive electrode mixture layer 72 may contain a conductive additive in addition to the positive electrode active material and the binder.

Examples of the positive electrode active material include LiMnO ₂ , Li _x Mn ₂ O ₄ (0 <x <2), Li ₂ MnO ₃ , Li _x Mn _1.5 Ni _0.5 O ₄ (0 <x <2), and the like. Lithium manganate having a layered structure or lithium manganate having a spinel structure, LiCo ₂ O ₂ , LiNiO ₂ or a compound obtained by substituting a part of its transition metal with another metal, LiNi _1/3 Co _1/3 Mn _{1 /} Lithium transition metal oxides in which specific transition metals such as ₃ O ₂ do not exceed half of the total, compounds in which Li is excessive in excess of the stoichiometric composition in these lithium transition metal oxides, and olivine structures such as LiFePO ₄ And the like.

In addition, as the positive electrode active material, some of these metal oxide metals may be Al, Fe, P, Ti, Si, Pb, Sn, In, Bi, Ag, Ba, Ca, Hg, Pd, Pt, Te. A material substituted with Zn, La, or the like can also be used. In particular, Li _α Ni _β Co _γ Al _δ O ₂ (1 ≦ α ≦ 2, β + γ + δ = 1, β ≧ 0.4, γ ≦ 0.2) or Li _α Ni _β Co _γ Mn _δ O ₂ (1 ≦ α). ≦ 1.2, β + γ + δ = 1, β ≧ 0.4, γ ≦ 0.2).

  As the positive electrode active material, any one of the above compounds may be used alone, or two or more may be used in combination.

As the positive electrode active material, iron sulfide, iron disulfide, sulfur, copper, polysulfide, Li ₃ VO ₄ or the like can also be used. A radical material such as a nitroxyl compound having a nitroxyl radical partial structure can also be used as the positive electrode active material. In the case of these positive electrode active materials, since there is no lithium source in the battery, it is desirable that the negative electrode is doped with lithium in advance by short-circuiting with the lithium source, vapor deposition, or the like.

  According to the lithium ion secondary battery 4 using the negative electrode 1 for a lithium ion secondary battery, the tin coatings 31 and 32 are separated from the current collectors 21, 22 and 23 even when charging and discharging are repeated in the lithium ion secondary battery. It is expected that the peeling can be prevented to suppress the deterioration of the charge / discharge cycle performance, and the required energy capacity can be secured.

  Next, the negative electrode 1 for a lithium ion secondary battery according to the second aspect of the present embodiment has a metal powder 24 having a tin plating film 31 on the surface on a metal foil 21 as schematically shown in FIG. 4A. It has a containing layer.

Here, in the negative electrode 1 for a lithium ion secondary battery according to the second embodiment, the first current collector C ₁ is formed by the metal foil 21 as shown in FIG. On the other hand, the current collector C < _b > ₂ is formed by the metal powder 24 and the tin plating film 31 formed on the side surface of the metal powder 24. Further, the negative electrode active material layer A ₁ is formed by the tin plating film 31 formed below the metal powder 24, while the negative electrode active material layer A ₂ is formed by the tin plating film 31 formed above the metal powder 24. Has been.

As a result, in the negative electrode 1 for a lithium ion secondary battery according to the second aspect, a laminated structure in which the negative electrode active material layer A ₁ is sandwiched between the current collectors C ₁ and C ₂ is formed.

  As the metal foil 21 of the negative electrode 1 for a lithium ion secondary battery according to the second aspect, the same metal foil 21 as the first current collector 21 of the negative electrode 1 for a lithium ion secondary battery according to the first aspect can be used. . The metal powder 24 is not particularly limited as long as it is a metal powder having electrical conductivity. For example, powder of aluminum, copper, steel, titanium, or the like can be used. The metal powder 24 preferably has an average particle diameter in the range of 100 μm or less.

  Moreover, the tin plating film 31 on the surface of the metal powder 24 can be formed in the same manner as the tin films 31 and 32 of the negative electrode 1 for the lithium ion secondary battery of the first aspect.

  The negative electrode 1 for a lithium ion secondary battery of the second aspect shown in FIG. 4A is, for example, a metal powder 24 having a tin plating film 31 on the surface is mixed with a binder and a conductive additive to form a slurry, and the slurry is a metal It can be manufactured by coating the foil 21. Further, after the coating, a current collector film may be further formed by a plating technique.

  The negative electrode 1 for lithium ion secondary batteries according to the second aspect of the present embodiment can be used for the lithium ion secondary battery 4 shown in FIG. The lithium ion secondary battery 4 shown in FIG. 5 has the same configuration as the lithium ion secondary battery 4 shown in FIG. 3 except that the negative electrode 1 of the lithium ion secondary battery 1 of the second aspect is used as the negative electrode 1. The same parts are denoted by the same reference numerals, and detailed description thereof is omitted.

  Next, examples and comparative examples of the present invention are shown.

[Example 1]
In this example, first, a 10 μm thick copper foil was used as the first current collector 21, and a 2 μm thick tin plating film was formed on the current collector 21 by electroplating to form a tin film 31. Next, a copper plating film having a thickness of 200 nm is formed on the tin film 31 by electroplating to form the second current collector 22, and the tin film 31 forms the first current collector 21 and the second current collector 22. A laminated structure sandwiched between and was formed. Next, the laminated structure was punched into a diameter of 15 mm to produce a negative electrode 1 for a lithium ion secondary battery.

Next, LiNi _0.5 Mn _0.3 Co _0.2 O ₂ as the positive electrode active material, acetylene black as the conductive auxiliary agent, and polyvinylidene fluoride (PVDF) as the binder were 94: 3: 3. A slurry was prepared by mixing at a mass ratio of (2), and the obtained slurry was applied to an aluminum foil having a thickness of 20 μm as the positive electrode current collector 71 to form a positive electrode mixture layer 72. Next, the positive electrode current collector 71 on which the positive electrode mixture layer 72 was formed was punched out to a size of 14 mm in diameter to obtain the positive electrode 7.

Next, between the negative electrode 1 and the positive electrode 4, 20 μm-thick polyethylene (diameter 20 mm) is disposed as a separator, and the separator is impregnated with an electrolytic solution to form an electrolyte layer 6. A lithium ion secondary battery 4 was produced. The electrolytic solution was prepared by mixing triethyl phosphate (TEP) and fluorinated ethylene carbonate (FEC) at a volume ratio of 80:20 to form a mixed solvent. In the mixed solvent, LiPF ₆ was added at 1.0 mol / L. What was melt | dissolved by the density | concentration was used.

  Next, charging / discharging with respect to the lithium ion secondary battery 4 was repeated with the electric current amount of 1C with the voltage of the range of 2.5-3.85V using the lithium ion secondary battery 4 produced in the present Example. FIG. 6 shows changes in charge / discharge capacity with respect to the number of charge / discharge cycles as charge / discharge characteristics at this time.

[Example 2]
In this example, first, a tin plating film 31 having a thickness of 0.2 μm was formed by electroless plating on the surface of a copper powder 24 having a particle diameter of 15 μm, and a copper powder 24 having the tin plating film 31 on the surface was obtained. . Next, the copper powder 24 having the tin plating film 31 on the surface, acetylene black as a conductive additive, and polyvinylidene fluoride (PVDF) as a binder are mixed at a mass ratio of 90: 4: 6 to obtain a slurry. The obtained slurry was coated on a copper foil 21 having a thickness of 10 μm and dried, and then punched out to a size of 15 mm in diameter to produce a negative electrode 1 for a lithium ion secondary battery.

  Next, a lithium ion secondary battery 4 was produced in the same manner as in Example 1 except that the negative electrode 1 for lithium ion secondary batteries produced in this example was used.

  Next, charge / discharge of the lithium ion secondary battery 4 was repeated in exactly the same manner as in Example 1 except that the lithium ion secondary battery 4 produced in this example was used. FIG. 6 shows changes in charge / discharge capacity with respect to the number of charge / discharge cycles as charge / discharge characteristics at this time.

Example 3
In this example, first, triethyl phosphate (TEP), fluoroethylene carbonate (FEC), and dimethyl carbonate (DMC) were mixed at a volume ratio of 70:20:10 to obtain a mixed solvent, and the mixed solvent In addition, LiPF ₆ dissolved at a concentration of 1.2 mol / L and polyvinylidene fluoride / hexafluoropropylene (PVDF-HFP) as a gelling material are mixed at a mass ratio of 90:10 to obtain an electrolytic solution. Was prepared.

  Next, a coin cell type lithium ion secondary battery 4 was produced in exactly the same manner as in Example 2 except that the electrolyte containing the gelled material was used, and the lithium ion secondary battery 4 was brought to a temperature of 60 ° C. Holding for 1 hour, the electrolyte solution was gelled to form an electrolyte layer 6.

  Next, charge / discharge of the lithium ion secondary battery 4 was repeated in exactly the same manner as in Example 1 except that the lithium ion secondary battery 4 produced in this example was used. FIG. 6 shows changes in charge / discharge capacity with respect to the number of charge / discharge cycles as charge / discharge characteristics at this time.

[Comparative Example 1]
In this comparative example, first, a copper foil having a thickness of 10 μm was used as the current collector 21, and a tin plating film having a thickness of 2 μm was formed on the current collector 21 by electroplating to form a tin film 31. Next, a laminated structure composed of the current collector 21 and the tin film 31 was punched out to a size of 15 mm in diameter to produce a negative electrode.

  Next, a lithium ion secondary battery 4 was produced in the same manner as in Example 1 except that the negative electrode 1 produced in this comparative example was used.

  Next, charge / discharge of the lithium ion secondary battery 4 was repeated in exactly the same manner as in Example 1 except that the lithium ion secondary battery 4 produced in this comparative example was used. FIG. 6 shows changes in charge / discharge capacity with respect to the number of charge / discharge cycles as charge / discharge characteristics at this time.

Example 4
In this example, first, a nickel-plated film having a thickness of 0.3 μm is formed by electroless plating on both front and back surfaces of an aluminum foil having a thickness of 15 μm as a negative electrode active material layer, thereby forming a current collector. Was formed between the two current collectors. Next, the laminated structure was punched into a diameter of 15 mm to produce a negative electrode 1 for a lithium ion secondary battery.

  Next, a lithium ion secondary battery 4 was produced in the same manner as in Example 1 except that the negative electrode 1 for lithium ion secondary batteries produced in this example was used.

  Next, charging / discharging with respect to the lithium ion secondary battery 4 was repeated with the electric current amount of 1C with the voltage of the range of 2.5-4.15V using the lithium ion secondary battery 4 produced in the present Example. FIG. 7 shows changes in charge / discharge capacity with respect to the number of charge / discharge cycles as charge / discharge characteristics at this time.

Example 5
In this example, a lithium ion secondary battery 4 was produced in the same manner as in Example 4 except that a lithium-aluminum alloy foil was used instead of the aluminum foil.

  Next, charge / discharge of the lithium ion secondary battery 4 was repeated in exactly the same manner as in Example 4 except that the lithium ion secondary battery 4 produced in this example was used. FIG. 7 shows changes in charge / discharge capacity with respect to the number of charge / discharge cycles as charge / discharge characteristics at this time.

[Comparative Example 2]
In this comparative example, first, a negative electrode 1 was produced by punching an aluminum foil having a thickness of 15 μm into a diameter of 15 mm.

Next, triethyl phosphate (TEP) and fluoroethylene carbonate (FEC) are mixed at a volume ratio of 80:20 to form a mixed solvent, and LiPF ₆ is dissolved in the mixed solvent at a concentration of 1.2 mol / L. Thus, an electrolytic solution was prepared.

  Next, a lithium ion secondary battery 4 was produced in the same manner as in Example 4 except that the negative electrode 1 produced in this comparative example and the electrolytic solution were used.

  Next, charge / discharge of the lithium ion secondary battery 4 was repeated in exactly the same manner as in Example 4 except that the lithium ion secondary battery 4 produced in this example was used. FIG. 7 shows changes in charge / discharge capacity with respect to the number of charge / discharge cycles as charge / discharge characteristics at this time.

  From FIG. 6, according to the lithium ion secondary battery 4 of Example 1 using the negative electrode 1 for lithium ion secondary batteries in which the tin film 31 is sandwiched between two current collectors 21 and 22, the tin film 31 is collected. Since it does not peel from the electric bodies 21 and 22, it is clear that the capacity deterioration can be suppressed even when the charge / discharge cycle is repeated. On the other hand, a comparison is made using a negative electrode in which the tin film 31 is formed on the current collector 21 and the current collector 22 is not provided on the tin film 31 and the tin film 31 is not sandwiched between the current collectors 21 and 22. According to the lithium ion secondary battery 4 of Example 1, since the tin film 31 peels from the current collector 21, it is apparent that capacity deterioration cannot be suppressed when the charge / discharge cycle is repeated.

  Moreover, according to the lithium ion secondary battery 4 of Example 2 using the negative electrode 1 for lithium ion secondary batteries provided with the copper powder 24 provided with the tin plating film 31 on the surface, the capacity can be increased even when the charge / discharge cycle is repeated. It is clear that deterioration can be suppressed and the capacity is improved as compared with the lithium ion secondary battery 4 of Example 1.

  Moreover, according to the lithium ion secondary battery 4 of Example 3 provided with the electrolyte layer 6 in which the electrolytic solution containing the gelling material is gelled, the deterioration of the capacity can be suppressed even when the charge / discharge cycle is repeated. It is clear that the capacity is further improved as compared with the lithium ion secondary battery 4 of Example 2. The reason why the capacity is improved by providing the electrolyte layer 6 in which the electrolytic solution containing the gelling material is gelled is that the gelled electrolytic solution reduces the active material into fine particles and diffuses the active material into the electrolytic solution. This is thought to be due to the fact that it acts as a barrier to suppress this.

  From FIG. 7, a lithium ion secondary battery comprising a current collector made of a nickel plating film on both front and back surfaces of an aluminum foil as a negative electrode active material layer, and the negative electrode active material layer sandwiched between two current collectors According to the lithium ion secondary battery 4 of Example 4 using the negative electrode 1 for aluminum, since the aluminum foil does not peel from the current collector made of the nickel plating film, the capacity deterioration can be suppressed even when the charge / discharge cycle is repeated. Is clear. Moreover, according to the lithium ion secondary battery 4 of Example 4, since the oxide film on the surface of the aluminum foil is removed by forming the nickel plating film on both the front and back surfaces of the aluminum foil by electroless plating, the side reaction It is obvious that the capacity can be improved.

  On the other hand, according to the lithium ion secondary battery 4 of Comparative Example 2 in which the aluminum foil is the negative electrode, the oxide film on the surface of the aluminum foil is not removed and the side reaction cannot be suppressed. It is clear that the capacity is reduced compared to the secondary battery 4.

  In addition, for a lithium ion secondary battery, a current collector made of a nickel plating film is provided on both front and back surfaces of an aluminum-nickel alloy foil as a negative electrode active material layer, and the negative electrode active material layer is sandwiched between two current collectors According to the lithium ion secondary battery 4 of Example 5 using the negative electrode 1, it is possible to suppress the deterioration of the capacity even when the charge / discharge cycle is repeated, and the capacity compared to the lithium ion secondary battery 4 of Example 4 is used. Is clearly improved.

  The reason why the capacity is improved by using the aluminum-nickel alloy foil as the negative electrode active material layer is that the reaction of the following formula (2) having a smaller volume expansion occurs mainly in addition to taking out lithium in the aluminum alloy as the capacity. For this reason, it is considered that the load applied to the negative electrode 1 for a lithium ion secondary battery was reduced.

2LiAl + Li → Li ₃ Al ₂ (2)

1 ... negative electrode for a lithium ion secondary battery, 21, 22 ... collector, 24 ... metal powders, 31, 32, 33 ... tin film, 4 ... lithium ion secondary battery, _{C 1,} C 2 _... collector, A ₁ , A ₂ ... negative electrode active material layer.

Claims (9)

  A negative electrode for a lithium ion secondary battery, comprising at least one laminated structure comprising two current collectors and a negative electrode active material layer sandwiched between both current collectors.   2. The negative electrode for a lithium ion secondary battery according to claim 1, wherein the negative electrode active material layer is made of one material selected from the group consisting of a tin film, an aluminum film, and an aluminum alloy film. Negative electrode for secondary battery.   3. The negative electrode for a lithium ion secondary battery according to claim 2, wherein the tin film is a tin plating film.   The negative electrode for a lithium ion secondary battery according to any one of claims 1 to 3, wherein the current collector is made of a metal film or a metal powder having a tin plating film on a surface thereof. Negative electrode for ion secondary battery.   5. The negative electrode for a lithium ion secondary battery according to claim 4, wherein the metal film comprises a metal foil or a metal plating film. A first step of forming a negative electrode active material layer made of a tin plating film on a current collector made of a metal film;
A second step of forming a current collector made of a metal plating film having a thickness in the range of 1000 nm or less on the negative electrode active material layer formed in the first step;
The method for producing a negative electrode for a lithium ion secondary battery, wherein the first step and the second step are performed at least once. Forming a tin plating film on the surface of the metal powder, and obtaining a metal powder including the tin plating film on the surface;
A second step of preparing a slurry containing metal powder comprising a tin plating film on the surface formed in the first step;
And a third step of applying the slurry prepared in the second step onto a current collector made of a metal film, and a method for producing a negative electrode for a lithium ion secondary battery.   A method for producing a negative electrode for a lithium ion secondary battery, comprising: forming a current collector made of a metal plating film on both front and back surfaces of a negative electrode active material layer made of an aluminum film or an aluminum alloy film. A negative electrode comprising at least one laminated structure comprising two current collectors and a negative electrode active material layer sandwiched between both current collectors;
A positive electrode disposed opposite to the negative electrode active material layer of the negative electrode;
A lithium ion secondary battery comprising: an electrolyte layer disposed between the negative electrode and the positive electrode.