CN108365170B - Negative electrode for lithium ion secondary battery and lithium ion secondary battery - Google Patents
Negative electrode for lithium ion secondary battery and lithium ion secondary battery Download PDFInfo
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- CN108365170B CN108365170B CN201810067791.8A CN201810067791A CN108365170B CN 108365170 B CN108365170 B CN 108365170B CN 201810067791 A CN201810067791 A CN 201810067791A CN 108365170 B CN108365170 B CN 108365170B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/134—Electrodes based on metals, Si or alloys
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
- H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention provides a negative electrode for a lithium ion secondary battery and a lithium ion secondary battery, which can restrain the reduction of charge-discharge cycle performance and ensure the required energy capacity. A negative electrode (1) for a lithium ion secondary battery comprises a first negative electrode member (2) and a second negative electrode member (3), wherein the first negative electrode member (2) comprises a flat plate-like current collector (21) and a first tin coating (22) covering the surface thereof and having a thickness in the range of 100 to 1200 nm; the second negative electrode member (3) is provided with a conductive mesh-shaped current collector (32), and a second tin coating (33) which covers the surface of the mesh-shaped current collector (32) and has a thickness in the range of 100 to 1200nm, and the second negative electrode member (3) has a space (34) surrounded by the second tin coating (33). At least 1 second negative electrode member (3) is laminated on the first tin coating (22).
Description
Technical Field
The present invention relates to a negative electrode for a lithium ion secondary battery and a lithium ion secondary battery.
Background
Conventionally, a lithium ion secondary battery has been known as a secondary battery used as a power source for portable electronic devices and 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, and for example, it is known to use a material obtained by forming a tin coating having a thickness of 10 to 300 μm on the surface of a current collector as the negative electrode of the lithium ion secondary battery (for example, see patent document 1).
However, the tin coating film expands greatly in volume when absorbing lithium ions, and peels off from the surface of the current collector when repeating charge and discharge reactions, thereby causing a problem that the charge and discharge cycle performance of the lithium ion secondary battery is lowered. In order to solve the above problem, a negative electrode for a lithium ion secondary battery is known, which is obtained by using a mesh network formed of fine copper wires as a current collector and plating the current collector with tin (see, for example, patent document 2).
Documents of the prior art
Patent document
Patent document 1: japanese patent laid-open publication No. 2001-68094
Patent document 2: japanese laid-open patent publication No. 2008-91035
Disclosure of Invention
Problems to be solved by the invention
However, even when a mesh network formed of fine copper wires is used as a current collector, the tin coating expands in large volume when absorbing lithium ions, and is similarly peeled from the surface of the current collector when repeating charge and discharge reactions, and thus improvement is desired.
In view of the above, an object of the present invention is to provide a negative electrode for a lithium ion secondary battery, which can ensure a desired energy capacity while suppressing a decrease in charge-discharge cycle performance without peeling off a tin coating formed on the surface of a current collector even when charge-discharge reactions are repeated.
It is another object of the present invention to provide a lithium ion secondary battery including the negative electrode for a lithium ion secondary battery.
Means for solving the problems
In order to achieve the above object, a negative electrode for a lithium ion secondary battery according to the present invention includes:
a first negative electrode member comprising a flat plate-like current collector and a first tin coating having a thickness in the range of 100 to 1200nm, the first tin coating covering the surface of the flat plate-like current collector; and
a second negative electrode member comprising: a mesh collector having conductivity, and a second tin coating film having a thickness in a range of 100 to 1200nm covering a surface of the mesh collector, the second negative electrode member having a space surrounded by the second tin coating film;
at least 1 of the second negative electrode members is laminated on the first tin coating of the first negative electrode member.
In the negative electrode for a lithium ion secondary battery of the present invention, the first negative electrode member includes a flat plate-like current collector and a first tin coating film covering a surface of the flat plate-like current collector. Here, the first tin coating has a thickness in the range of 100 to 1200nm, and therefore, when lithium ions are absorbed, volume expansion can be suppressed, and even when charging and discharging are repeated in a lithium ion battery, peeling from the current collector can be prevented, and deterioration of charge and discharge cycle performance can be suppressed.
When the thickness of the first tin coating is less than 100nm, the effect of absorbing lithium ions as a negative electrode active material becomes too small, and when the thickness of the first tin coating is more than 1200nm, volume expansion cannot be suppressed when absorbing lithium ions.
On the other hand, in the negative electrode for a lithium ion secondary battery of the present invention, it is difficult to secure a required energy capacity only by the first tin coating having a thickness in the above range. Therefore, in the negative electrode for a lithium ion secondary battery according to the present invention, at least 1 of the second negative electrode members is laminated on the first tin film of the first negative electrode member.
The second negative electrode member includes: the conductive net-shaped current collector comprises a net-shaped current collector having conductivity, and a second tin coating film having a thickness of 100 to 1200nm and covering the surface of the net-shaped current collector. The second negative electrode member has a space surrounded by the second tin coating by covering the surface of the mesh-like current collector with the second tin coating.
As a result, when the second negative electrode member is laminated on the first tin film of the first negative electrode member, the space surrounded by the second tin film is filled with the electrolyte in the lithium ion battery. Therefore, both the first tin coating and the second tin coating can be brought into good contact with lithium ions via the electrolyte solution, and a required energy capacity can be ensured.
In the negative electrode for a lithium ion secondary battery according to the present invention, at least 1 second negative electrode member may be laminated on the first negative electrode member, and the energy capacity of the negative electrode for a lithium ion secondary battery may be adjusted depending on the number of the second negative electrode members.
The reason why the thickness of the second tin coating is set to be in the range of 100 to 1200nm is the same as that of the first tin coating.
In the negative electrode for a lithium ion secondary battery of the present invention, the first tin coating film and the second tin coating film may be formed by electroless plating, but are preferably formed by electroplating. By using electroplating, the tin coating has good adhesion to the current collector, and a large-area tin coating can be easily formed at low cost.
The lithium ion secondary battery of the present invention may further include: the negative electrode for a lithium ion secondary battery, the positive electrode disposed opposite to the second negative electrode member, and the electrolyte solution.
Drawings
Fig. 1 is a schematic cross-sectional view showing one configuration example of a negative electrode for a lithium-ion secondary battery of the present invention.
Fig. 2 is a plan view of the second negative electrode member shown in fig. 1.
Fig. 3 is a schematic cross-sectional view showing one configuration example of a lithium-ion secondary battery of the present invention.
Fig. 4 is a graph showing the relationship between the thickness of the first tin coating film in the first negative electrode member and the charge-discharge cycle performance.
Fig. 5 is a plan view showing a key part structure of a metal mesh plate used in a mesh-like current collector.
Fig. 6 is an assembly diagram showing another configuration example of the lithium-ion secondary battery of the present invention.
Fig. 7 is a graph showing charge and discharge cycle performance of the lithium ion secondary battery of the present invention.
Description of the symbols
Negative electrode for 1 lithium ion secondary battery
2 first negative electrode Member
3 second negative electrode Member
4. 16 lithium ion secondary battery
21 flat plate-like current collector
22 first tin coating film
31 thin line
32. 34 mesh collector
33 second tin coating.
Detailed Description
Next, embodiments of the present invention will be described in further detail with reference to the drawings.
As shown in fig. 1, a negative electrode 1 for a lithium ion secondary battery of the present embodiment includes a first negative electrode member 2 and a second negative electrode member 3. The first negative electrode member 2 includes a flat plate-like current collector 21 and a first tin coating 22 covering at least one surface of the flat plate-like current collector 21. The second negative electrode member 3 is laminated on the first tin coating 22, and includes: a mesh-like current collector 32 formed of thin wires 31 having conductivity, and a second tin coating 33 covering the surface of the thin wires 31.
The flat plate-like current collector 21 is not particularly limited as long as it is a material having conductivity, and for example, a flat plate-like current collector made of aluminum, copper, steel, titanium, or the like can be used. Further, as the material of the flat plate-like current collector 21, tin may also be used. At this time, the flat plate-like current collector 21 also serves as the first tin coating film 22. The thickness of the flat plate-like current collector 21 is preferably thin in order to increase the energy density of the battery, but if it is too thin, handling becomes difficult and productivity decreases, and therefore, it is preferably in the range of 5 to 50 μm. In addition, the flat plate-like current collector 21 may have its surface cut or dissolved to form irregularities.
The first tin coating film 22 has a thickness in the range of 100 to 1200 nm. The first tin coating 22 can be formed by electroplating or electroless plating, and is preferably formed by electroplating because it has good adhesion to the flat plate-like current collector 21 and can easily and inexpensively form a coating having a large area.
When the first tin coating film 22 is formed by electroplating, it can be performed by: the flat plate-like current collector 21 is immersed in an acid such as nitric acid, hydrochloric acid, or sulfuric acid, or washed with water to remove dirt, oxide film, and the like on the surface, and then immersed in a plating bath in which a tin salt such as tin chloride is dissolved in an acid such as sulfuric acid, and energized at a predetermined temperature. At this time, β naphthol, gelatin, cresol sulfonic acid may be dissolved in an appropriate amount to form a more uniform first tin coating 22. 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. The thickness of the first tin coating 22 can be controlled by the energization time.
The thin wire 31 forming the mesh-like current collector 32 is not particularly limited as long as it is a material having electrical conductivity, and for example, a wire formed of aluminum, copper, steel, titanium, or the like can be used. As a material of the thin wire 31, tin may be used. At this time, the thin wire 31 also serves as the second tin coating film 33. The thin wire 31 may be made of the same material as the flat plate-like current collector 21 or may be made of a different material.
The thickness of the mesh-like current collector 32 is preferably thin in order to increase the energy density of the battery, but if it is too thin, handling becomes difficult and productivity decreases, and therefore, the thickness is preferably in the range of 3 to 500 μm.
The second tin coating 33 has a thickness in the range of 100 to 1200nm and can be formed by the same method as the first tin coating 22. At this time, as shown in fig. 2, since the second tin coating 33 is formed on the surface of the thin wire 31, the second negative electrode member 3 includes a space 34 surrounded by the second tin coating 33.
In the second negative electrode member 3, the mesh-like current collector 32 may be formed by weaving the thin wires 31 in the crosswise direction, or may be formed by uniformly forming holes such as punched metal on a foil made of a conductive material. Further, the mesh-like current collector 32 may be a metal mesh plate formed in a diamond shape or a tortoise-shell shape by introducing slits in a staggered manner and expanding on a flat plate formed of a material having conductivity, such as a metal plate. In the case of a mesh in a staggered form obtained by weaving fine wires, gaps between the fine wires are opened or closed at the time of bending or stretching, and therefore, the gap interval is not constant, and the second negative electrode member 3 is deformed even by applying a very small force at the time of manufacturing the second negative electrode member 3, and it is difficult to manufacture the second negative electrode member 3. On the other hand, compared with a mesh in a staggered form obtained by weaving fine wires, a punched metal or a metal mesh sheet has a certain degree of hardness when bent, and therefore, the shape is easily fixed, and the gap does not open or close even with a certain degree of expansion and contraction. Therefore, in a battery cell in which the second negative electrode member 3 is bent in the battery cell, such as a cylindrical battery cell or a wound battery cell, a punched metal or a metal mesh plate is more preferable than a mesh having a staggered shape obtained by weaving fine wires. In addition, the punched metal or the metal mesh plate can be bent, and thus, the punched metal or the metal mesh plate can also be applied to a battery with a flexible shape.
When the mesh-like current collector 32 is formed by weaving the thin wires 31 in a longitudinal and transverse direction, the interval (mesh opening) of the thin wires 31 is, for example, in the range of 1 to 50 μm. In addition, when the mesh-like current collector 32 is formed by a metal mesh plate, for example, the range of the line width is 0.001 to 10mm, the size of the short side of the opening is 0.01 to 10mm, and the size of the long side of the opening is 0.05 to 50mm is achieved.
The diameter of the space 34 in the second negative electrode member 3 is preferably in the range of 0.001 to 48 μm, and more preferably in the range of 1 to 40 μm when the mesh-like current collector 32 is an object in which the thin wires 31 are woven in the longitudinal and transverse directions, so that the electrolyte is easily infiltrated when the lithium-ion secondary battery 4 described later is formed, and the resistance is not increased. When the mesh-like current collector 32 is formed of a metal mesh plate, the diameter of the space 34 in the second negative electrode member 3 is preferably in the range of 0.001 to 10mm, and more preferably in the range of 1 to 500 μm. When the mesh-like current collector 32 is formed by weaving the thin wires 31 in a crisscross manner or by a metal mesh plate, the porosity of the second negative electrode member 3 is preferably 1% or more.
In the present embodiment, 1 second negative electrode member 3 is stacked on the first negative electrode member 2 as an example of the negative electrode 1 for a lithium ion secondary battery. However, the negative electrode 1 for a lithium ion secondary battery may be formed by stacking at least 1 second negative electrode member 3 on the first negative electrode member 2, and a plurality of second negative electrode members 3 may be further stacked. The number of the second negative electrode members 3 is not particularly limited, and is preferably in the range of 1 to 5 for easy production.
Further, since the first negative electrode member 2 has conductivity and also functions as a current collector, a mixture layer containing a negative electrode active material may be disposed between the first negative electrode member 2 and the second negative electrode member 3. Examples of the negative electrode active material include artificial graphite, natural graphite, hard carbon, soft carbon, silicon oxide, tin, silver, aluminum, zinc, lead, germanium, lithium, and the like, or an alloy thereof. The mixture layer containing the negative electrode active material may be formed by adding a binder, a conductive additive, or the like to the negative electrode active material to prepare a slurry and applying the slurry onto the first negative electrode member 2, or may be formed by disposing a foil made of the negative electrode active material on the first negative electrode member 2. Thereafter, the second negative electrode member 3 is disposed on the mixture layer.
The negative electrode 1 for a lithium ion secondary battery of the present embodiment can be used, for example, in the lithium ion secondary battery 4 shown in fig. 3.
The lithium ion secondary battery 4 is configured by disposing a negative electrode 1 for a lithium ion secondary battery, a separator 6 impregnated with an electrolyte solution, and a positive electrode 7 inside a battery cell 5. In the lithium ion secondary battery 4, the negative electrode 1 for a lithium ion secondary battery is disposed so that the second negative electrode member 2 faces the positive electrode 7 with the separator 6 interposed therebetween. The positive electrode 7 includes a positive electrode current collector 71 and a positive electrode mixture layer 72, and is disposed such that the positive electrode mixture layer 72 faces the separator 6. The flat plate-like current collector 21 and the mesh-like current collector 32 of the negative electrode 1 for a lithium ion secondary battery are connected to the negative electrode lead 8, and the positive electrode current collector 71 of the positive electrode 7 is connected to the positive electrode lead 9.
In the lithium-ion secondary battery 4, as the separator 6, for example, a separator made of a synthetic resin such as polyethylene can be used. As the electrolyte solution to be impregnated into the separator 6, a phosphate ester represented by the following general formula (1) may be used as a solvent, and a lithium salt may be dissolved in the solvent as a supporting salt.
In the general formula (1), R1、R2、R3The alkyl group, alkenyl group, alkynyl group, and other linear hydrocarbon groups, or groups obtained by substituting fluorine for part of hydrogen may be the same or different from each other. Further, since the viscosity becomes too high and handling becomes difficult if the number of carbon atoms of the linear hydrocarbon group is increased, the number of carbon atoms is preferably 7 or less, and more preferably 3 or less.
The phosphate ester is preferably trimethyl phosphate, triethyl phosphate, tris (trifluoroethyl) phosphate, or the like, in view of having an appropriate viscosity and high solubility in a lithium salt as a supporting salt.
The lithium salt may be LiPF6、LiAsF6、LiAlCl4、LiClO4、LiBF4、LiSbF6、Li2SO4、Li3PO4、Li2HPO4、LiH2PO4、LiCF3SO3、LiC4F9SO3LiN (FSO) containing imide anion2)2、LiN(CF3SO2)2、LiN(C2F5SO2)2、LiN(CF3SO2)(C2F5SO2)、LiN(CF3SO2)(C4F9SO2) LiN (CF) having a five-membered ring structure2SO2)2(CF2) LiN (CF) having a six-membered ring structure2SO2)2(CF2)2And the like. Further, the lithium salt may include LiPF6Wherein at least 1 fluorine atom is substituted with a fluoroalkyl group5(CF3)、LiPF5(C2F5)、LiPF5(C3F7)、LiPF4(CF3)2、LiPF4(CF3)(C2F5)、LiPF3(CF3)3And the like. In this case, the pH of the electrolyte is preferably in the range of 4 to 10.
The additive may be added in an amount of 60 vol% or less as long as the pH of the electrolyte is 4 to 10. Examples of the additive include Vinylene Carbonate (VC), Vinyl Ethylene Carbonate (VEC), Ethylene Carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), Ethyl Methyl Carbonate (EMC), Propylene Carbonate (PC), dimethoxyethane having an ether group, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, triethylene glycol dimethyl ether, succinic acid (anhydride), maleic acid (anhydride), γ -butyrolactone, γ -valerolactone, ethylene sulfide, sulfolane, an ionic liquid, a boric acid ester, acetonitrile, phosphazene, and the like, and a substance obtained by fluorinating a part of hydrogen groups in these compounds.
Further, the tin may be peeled from the current collector by repeating expansion and contraction of the tin due to repetition of charge and discharge, and may be gelled by adding a polymerization initiator or a polymer to the electrolyte solution so as not to diffuse in the liquid. As the polymerization initiator and the polymer, polyvinylidene fluoride hexafluoropropylene (PVDF-HFP), (poly) acrylonitrile, (poly) acrylic acid, polymethyl methacrylate, and the like can be used, but not limited thereto. Further, a crosslinking agent may be added to these. In order to gel the electrolyte, after the batteries are manufactured, the respective batteries may be heated to thermally polymerize the electrolyte for use, but after the first few cycles of charge and discharge, the temperature may be raised to gel the electrolyte.
Further, as a method of preventing tin fine particles from diffusing in a liquid, a solid electrolyte may also be used. As the solid electrolyte, Li can be used3PO4、Li7La3Zr2O12、La2/3-xLixTiO3、Li0.33La0.55TiO3、Li1.3Al0.7Ti1.3(PO4)3An isooxide solid electrolyte; liaGexPySz(a, x, y are arbitrary values), LiSiPSCl, LSPPS (Lil)0.35[Sn0.27Si1.08]P1.65S12(Li3.45[Sn0.09Si0.36]P0.55S4Or a sulfur-based solid electrolyte obtained by adding a halogen element thereto; polyethylene oxide (PEO), polyethylene oxide-LiTFSI, lithium phosphate oxynitride (LiPON), and the like. These materials are not volatile, and therefore, it is considered that they contribute to improvement in safety as compared with a liquid electrolyte.
The concentration of the supporting salt in the electrolyte is preferably in the range of 0.1 to 3mol/L, and more preferably in the range of 0.6 to 1.5 mol/L.
The current collector 71 in the positive electrode 7 is not particularly limited as long as it is a material having conductivity, and for example, a current collector 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 increase the energy density of the battery, but if it is too thin, handling becomes difficult and productivity decreases, and therefore, it is preferably in the range of 5 to 50 μm.
The positive electrode mixture layer 72 in the positive electrode 7 may be formed by: the positive electrode active material is mixed with an appropriate amount of a binder such as polyvinylidene fluoride (PVDF), diluted with N-methylpyrrolidone, and the slurry thus prepared is applied to the current collector 71 by a doctor blade method or the like and applied. The positive electrode mixture layer 72 preferably has a high positive electrode active material content relative to the total amount, and for example, the positive electrode active material content is preferably 85 mass% or more. In addition, the positive electrode mixture layer 72 may include a conductive auxiliary agent in addition to the positive electrode active material and the binder.
The positive electrode active material may be LiMnO2、LixMn2O4(0<x<2)、Li2MnO3、LixMn1.5Ni0.5O4(0<x<2) Lithium manganate having a layered structure or lithium manganate having a spinel structure; LiCo2O2、LiNiO2Or a compound in which a part of the transition metal is substituted with another metal; LiNi1/3Co1/3Mn1/3O2Lithium transition metal oxides having no more than half of the total of the specific transition metals; compounds that make Li in excess of the stoichiometric composition in these lithium transition metal oxides; LiFePO4And compounds having an olivine structure.
In addition, as the positive electrode active material, a material In which a part of the metal In these metal oxides is substituted with Al, Fe, P, Ti, Si, Pb, Sn, In, Bi, Ag, Ba, Ca, Hg, Pd, Pt, Te, Zn, La, or the like can be used. Particularly, preferred is LiαNiβCoγAlδO2(1. ltoreq. alpha. ltoreq.2, beta + gamma + delta. ltoreq.1, beta. ltoreq.0.7, gamma. ltoreq.0.2) or LiαNiβCoγMnδO2(1≤α≤1.2、β+γ+δ＝1、β≥0.1、γ≤0.2)。
The positive electrode active material may be used alone or in combination of 2 or more of the compounds.
In the positive electrode 7, iron sulfide, iron disulfide, sulfur, polysulfide, Li may be used instead of the positive electrode mixture layer 723VO4And the like as the positive electrode active material. Further, a radical material such as a nitroxyl compound which forms a partial structure of a nitroxyl radical can be used. In the case of these positive electrode active materials, since there is no lithium source in the battery, it is desirable to dope (dope) lithium into the negative electrode in advance by short-circuiting with a lithium source, vapor deposition, or the like.
Examples
Next, examples of the present invention and comparative examples are shown.
[ reference examples 1 to 4, comparative reference example 1 ]
In this reference example, first, a copper foil (50mm × 50mm) having a thickness of 20 μm was used as the flat plate-shaped current collector 21, the surface thereof was washed with sulfuric acid, the other surface was masked with an epoxy tape, and the other surface was immersed in an electroless plating bath heated to 50 ℃. Next, the flat plate-shaped current collector 21 on which the first tin coating film 22 was formed was cut into a size of 26mm × 44mm, thereby producing the first negative electrode member 2. At this time, 5 types of first negative electrode members 2 having the first tin coating 22 with the thicknesses of 230nm, 440nm, 770nm, 1200nm, and 2000nm were prepared by adjusting the immersion time.
Then, LiCoO as a positive electrode active material was added2A slurry was prepared by mixing a conductive auxiliary agent and polyvinylidene fluoride (PVDF) as a binder at a mass ratio of 92:4:4, and the obtained slurry was applied onto an aluminum foil (50mm × 50mm) having a thickness of 15 μm by a doctor blade method to form a positive electrode mixture layer. The aluminum foil on which the positive electrode mixture layer was formed was cut into a size of 25mm × 44mm, thereby producing a positive electrode.
Next, a polyethylene separator (30mm × 50mm) having a thickness of 25 μm was disposed between each first negative electrode member 2 and the positive electrode, and the polyethylene separator was impregnated with an electrolyte solution to obtain an object, which was vacuum-sealed to form a laminate battery cell, to prepare a laminate battery cell having the first negative electrode member 2 as a negative electrode as shown in fig. 15 kinds of lithium ion secondary battery. The electrolyte contains LiPF at a concentration of 1.0mol/L in a triethyl phosphate solvent6。
Next, the lithium ion secondary battery was charged to an upper limit potential of 4.05V at a charging current of 0.1mA in an environment of 25 ℃, was stopped for 10 minutes, and was discharged to 2.5V, and the operation was performed for 10 cycles, and the discharge capacity (mAh) after each cycle was measured to evaluate the charge-discharge cycle performance of the first negative electrode member 2.
Fig. 4 shows the results of reference example 1 in which the first tin coating 22 had a thickness of 230nm, reference example 2 in which the first tin coating had a thickness of 440nm, reference example 3 in which the first tin coating had a thickness of 770nm, reference example 4 in which the first tin coating had a thickness of 1200nm, and comparative reference example 1 in which the first tin coating had a thickness of 2000 nm.
As is clear from fig. 4, in the case of comparative reference example 1 in which the first tin coating 22 had a thickness of 2000nm, the discharge capacity decreased with repeated cycles, whereas in the case of reference examples 1 to 4 in which the first tin coating 22 had a thickness of 230 to 1200nm, the initial discharge capacity was maintained even with repeated cycles, and excellent charge and discharge cycle performance was obtained.
Accordingly, it is expected that the lithium ion secondary battery using the negative electrode 1 for a lithium ion secondary battery obtained by laminating the second negative electrode member 3 on the first negative electrode member 2 having the first tin coating 22 with a thickness of 100 to 1200nm can secure a required energy capacity while suppressing a decrease in charge-discharge cycle performance.
[ example 1 ]
In this example, first, a first tin coating 22 having a thickness of 400nm was formed on one surface thereof by electroless plating in the same manner as in reference examples 1 to 4, except that a copper foil having a thickness of 10 μm was used as the flat plate-like current collector 21. Next, the flat plate-like current collector 21 on which the first tin coating film 22 was formed was punched out into a disk shape having a diameter of 14mm, thereby producing the first negative electrode member 2.
Next, a second tin coating (not shown) having a thickness of 400nm was formed by performing electroless plating on the non-shielded portion in the same manner as the first negative electrode member 2, except that the front and back surfaces of one end portion of the copper metal mesh plate (made by COSMO co., ltd.) 34 shown in fig. 5 were covered with an epoxy tape. The expanded metal 34 had a thickness of 26 μm, and as shown in fig. 5, a mesh-like current collector having a line width W of 0.14mm, an opening short side dimension SW of 0.64mm, and an opening long side dimension LW of 1.3mm was formed.
Next, the portion where the second tin film of the expanded metal 34 was formed was punched out into a disk shape having a diameter of 14mm to prepare the second negative electrode member 3, and the portion (shielded portion) of the expanded metal 34 connected to the second negative electrode member 3 where the second tin film was not formed was punched out into a half disk shape having a diameter of 14mm to form the lead portion 35.
Next, as shown in fig. 6, a separator 12 made of stainless steel having a diameter of 15mm and a thickness of 1mm, a first negative electrode member 2, a second negative electrode member 3, a separator 13 made of polyethylene having a diameter of 19mm and a thickness of 20 μm, and a lithium foil 14 having a diameter of 16mm and a thickness of 100 μm as a counter electrode were laminated on a lower cover 11 made of stainless steel having a diameter of 20mm and a thickness of 2mm, the separator 13 was impregnated with an electrolyte solution, and the resultant was sealed with an upper cover 15 made of stainless steel having a bottomed cylindrical shape having an outer diameter of 1.8mm and an inner depth of 2mm, thereby producing a button cell (half cell) 16 as a lithium ion secondary battery. At this time, the first negative electrode member 2 is disposed so that the first tin coating 22 is on the second negative electrode member 3 side. Further, the lead member 35 is bent as indicated by a single-dot broken line in fig. 6 so as to be inserted between the lower cover 11 and the separator 12, thereby having a function of promoting current collection by the second negative electrode member 3.
The electrolyte contained LiPF at a concentration of 1.0mol/L in triethyl phosphate/dimethyl carbonate (DEC)/fluoroethylene carbonate (FEC) (8/1/1 ═ vol%) solvent6. The button cell 15 has the lower cover 11 as one electrode plate and the upper cover 14 as a counter electrode plate, and a seal (not shown) made of an insulator is disposed between the lower cover 11 and the upper cover 15. The separator 12 has a first negative electrode member 2, a second negative electrode member 3, a separator 13, and a counter electrode which are closely fitted between the first negative electrode member and the upper cover 15, and are sandwiched between the lower cover 11 and the upper cover 15The lithium foil 14 functions as the adjacent component.
Next, when the coin cell 16 obtained in the present example was charged and discharged at a voltage in the range of 0.1 to 2V for 15 cycles based on a current amount of 1C, the maintenance rate after 15 cycles was 111% with respect to the initial charge capacity of 0.4 mAh. The results are shown in FIG. 7.
In the button cell 16 obtained in the present example, it is considered that the reason why the charge capacity increases in the process of repeating the cycle is that the electrolytic solution gradually permeates into the second negative electrode member 3 from the hole portions (openings) of the metal mesh plate 34 as the mesh-like current collector, and the reaction area increases.
[ example 2 ]
In this example, a coin cell 16 as a lithium ion secondary battery was produced in exactly the same manner as in example 1, except that 2 second negative electrode members 3 were stacked on the first negative electrode member 2.
Next, when the button cell 16 obtained in the present example was charged and discharged at a voltage in the range of 0.1 to 2V for 15 cycles based on a current amount of 1C, the maintenance rate after 15 cycles was 100% with respect to the initial charge capacity of 0.63 mAh. The results are shown in FIG. 7.
[ example 3 ]
In this example, an electrolyte solution prepared by mixing 8 wt% of PVDF-HFP with triethyl phosphate/dimethyl carbonate (DMC)/FEC (80/1/1 vol%) and further dissolving LiPF at 1.0mol/L was used6A button cell 16 was produced in the same manner as in example 1 except for the electrolyte solution thus obtained.
Next, when the coin cell 16 obtained in the present example was heated at 60 ℃ for 1 hour to gel the electrolyte, and then charged and discharged at a voltage in the range of 0.1 to 2V for 15 cycles based on a current amount of 1C, the maintenance rate after 15 cycles was 99% with respect to the initial charge capacity of 0.36 mAh. The results are shown in FIG. 7.
The coin cell 16 of the present example in which the electrolyte solution was gelled showed a capacity retention rate almost the same as that of the coin cell 16 of example 1 in which the electrolyte solution was liquid, and showed a constant capacity retention rate from the initial stage, and was referred to as a cell with high reliability.
[ comparative example 1 ]
In this comparative example, a coin cell 16 as a lithium ion secondary battery was produced in exactly the same manner as in example 1, except that the second negative electrode member 3 was not laminated on the first negative electrode member 2 at all.
Next, when the coin cell 16 obtained in the present comparative example was charged and discharged at a voltage in the range of 0.1 to 2V for 15 cycles based on a current amount of 1C, the maintenance rate after 15 cycles was 91% with respect to the initial charge capacity of 0.14 mAh. The results are shown in FIG. 7.
As is clear from fig. 7, according to the lithium ion secondary batteries (button cells 16) of examples 1 and 2 including the second negative electrode member 3, it is possible to secure a required energy capacity while suppressing a decrease in charge-discharge cycle performance. Further, according to the lithium ion secondary battery of example 2, by making the number of second negative electrode members 3 larger than that of the lithium ion secondary battery of example 1, a large energy capacity can be further ensured.
On the other hand, it is understood that the lithium ion secondary battery of comparative example 1, which does not include the second negative electrode member 3 at all, is inferior to the lithium ion secondary batteries of examples 1 and 2 in terms of not only insufficient energy capacity but also deterioration of charge-discharge cycle performance, compared to the lithium ion secondary batteries of examples 1 and 2.
Claims (12)
1. A negative electrode for a lithium ion secondary battery, comprising:
a first negative electrode member having a flat plate-like current collector and a first tin coating film covering the surface of the flat plate-like current collector and having a thickness in the range of 100 to 1200 nm; and
a second negative electrode member comprising: a mesh collector having conductivity, and a second tin coating film covering the surface of the mesh collector and having a thickness in the range of 100 to 1200nm, the second negative electrode member having a space surrounded by the second tin coating film;
at least 1 of the second negative electrode members is laminated on the first tin coating of the first negative electrode member.
2. The negative electrode for a lithium-ion secondary battery according to claim 1,
the flat plate-like current collector is composed of one metal selected from the group consisting of: aluminum, copper, steel, titanium.
3. The negative electrode for a lithium-ion secondary battery according to claim 1,
the flat plate-like current collector has a thickness in the range of 5 to 50 μm.
4. The negative electrode for a lithium-ion secondary battery according to claim 1,
the mesh current collector is composed of one material selected from the group consisting of: a mesh body formed by weaving fine wires vertically and horizontally, punching metal and a metal mesh plate.
5. The negative electrode for a lithium-ion secondary battery according to claim 4,
the net body in which the filaments are woven in a crisscross manner is composed of one metal filament selected from the group consisting of: aluminum, copper, steel, titanium, tin.
6. The negative electrode for a lithium-ion secondary battery according to claim 4,
the net body formed by weaving the thin wires vertically and horizontally has a mesh opening in the range of 1-50 mu m.
7. The negative electrode for a lithium-ion secondary battery according to claim 4,
the metal mesh plate is provided with a line width within a range of 0.001-10 mm, an opening short side dimension within a range of 0.01-10 mm, and an opening long side dimension within a range of 0.05-50 mm.
8. The negative electrode for a lithium-ion secondary battery according to claim 1,
the mesh collector has a thickness in the range of 3 to 500 [ mu ] m.
9. The negative electrode for a lithium-ion secondary battery according to claim 1,
the first tin coating film or the second tin coating film is a plating film.
10. The negative electrode for a lithium-ion secondary battery according to claim 1,
the negative electrode member includes a mixture layer containing a negative electrode active material between the first negative electrode member and the second negative electrode member.
11. The negative electrode for a lithium-ion secondary battery according to claim 10,
the negative active material contained in the mixture layer is at least one material selected from the group consisting of: artificial graphite, natural graphite, hard carbon, soft carbon, silicon oxide, tin, silver, aluminum, zinc, lead, germanium, lithium, or alloys of these materials.
12. A lithium ion secondary battery is characterized by comprising:
a negative electrode, a positive electrode and an electrolyte,
the negative electrode includes: a first negative electrode member having a flat plate-like current collector and a first tin coating film covering one surface of the flat plate-like current collector and having a thickness in the range of 100 to 1200 nm; and a second negative electrode member including: a second tin coating film which covers the surface of the reticular current collector and has a thickness of 100-1200 nm; the second negative electrode member has a space surrounded by the second tin coating; the second negative electrode member is laminated on the first tin coating of the first negative electrode member;
the positive electrode and the second negative electrode member are disposed to face each other.
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
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| JP2017-012581 | 2017-01-26 | ||
| JP2017012581 | 2017-01-26 | ||
| JP2017-198321 | 2017-10-12 | ||
| JP2017198321 | 2017-10-12 | ||
| JP2017226668A JP6745782B2 (en) | 2017-01-26 | 2017-11-27 | Negative electrode for lithium-ion secondary battery and lithium-ion secondary battery |
| JP2017-226668 | 2017-11-27 |
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| CN108365170A CN108365170A (en) | 2018-08-03 |
| CN108365170B true CN108365170B (en) | 2021-03-30 |
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| JP4123507B2 (en) * | 2002-04-04 | 2008-07-23 | ソニー株式会社 | Battery and negative electrode manufacturing method |
| JP5389391B2 (en) * | 2008-07-31 | 2014-01-15 | 出光興産株式会社 | Electrode material sheet for lithium battery, solid lithium battery, and device including solid lithium battery |
| US9240585B2 (en) * | 2011-02-28 | 2016-01-19 | Applied Materials, Inc. | Manufacturing of high capacity prismatic lithium-ion alloy anodes |
| US20150017550A1 (en) * | 2012-03-22 | 2015-01-15 | Sumitomo Electric Industries, Ltd. | Metal three-dimensional network porous body for collectors, electrode, and non-aqueous electrolyte secondary battery |
| CN103794754B (en) * | 2012-11-02 | 2017-04-12 | 华为技术有限公司 | Composite negative electrode and preparation method thereof as well as electrochemical power source and application thereof |
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