Negative electrode for nonaqueous electrolyte secondary battery and nonaqueous electrolyte secondary battery having the same

Abstract

The present invention provides a negative electrode for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery equipped with the negative electrode. By suppressing the formation of voids within a porous metal body, this suppresses endurance degradation and structural degradation of the electrode, thereby improving energy density and cycle durability. The negative electrode for a non-aqueous electrolyte secondary battery comprises a current collector formed of a porous metal body, a negative electrode material disposed within the pores of the porous metal body, and a second negative electrode active material. The negative electrode material comprises: a first negative electrode active material disposed on the inner surfaces of the pores and composed of a silicon-based material; a framework-forming agent disposed on the first negative electrode active material and containing a silicate having siloxane bonds; and a second negative electrode active material disposed on the framework-forming agent.

Description

Technical Field

[0001] The present invention relates to a negative electrode for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery including the negative electrode. Background Art

[0002] In recent years, non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries are not only small and lightweight, but also can obtain high power, and therefore their use in automobiles and the like is increasing. The so-called non-aqueous electrolyte secondary battery is a battery system that uses an electrolyte that does not use water as the main component as the electrolyte, and is a general term for a storage device that can be charged and discharged. For example, there are known lithium ion batteries, lithium polymer batteries, all-solid-state lithium batteries, lithium-air batteries, lithium-sulfur batteries, sodium ion batteries, potassium ion batteries, multivalent ion batteries, fluoride batteries, sodium-sulfur batteries, etc. The non-aqueous electrolyte secondary battery is mainly composed of a positive electrode, a negative electrode, and an electrolyte. Moreover, when the electrolyte has fluidity, a separator is further inserted between the positive electrode and the negative electrode to form it.

[0003] For example, a technique has been disclosed in which, for the purpose of improving battery life, a skeleton-forming agent containing a silicate having siloxane bonds is present at least on the surface of the active material, and the skeleton-forming agent is allowed to penetrate from the surface into the interior (see, for example, Patent Document 1). This technique forms a strong skeleton around the active material, and is therefore believed to improve battery life. Furthermore, a technique has been disclosed in which the skeleton-forming agent is applied to a negative electrode containing a silicon (Si)-based active material (see, for example, Patent Document 2).

[0004] [Prior art literature]

[0005] [Patent Document]

[0006] Patent Document 1: Japanese Patent No. 6369818

[0007] Patent Document 2: Japanese Patent No. 6149147 Summary of the Invention

[0008] [Problems to be solved by the invention]

[0009] In addition, the non-aqueous electrolyte secondary battery is required to increase the energy density. In order to increase the energy density, it is believed that increasing the thickness of the negative electrode or making the negative electrode active material high-density is effective. However, the existing technology has a limit on the thickness of the negative electrode in the production of the negative electrode. Specifically, the practical thickness of the existing mixture layer that can be coated on the collector foil is less than 100μm. If the film thickness is greater than 100μm, problems such as uneven coating, cracking, and peeling will occur, making it difficult to produce the negative electrode with high precision.

[0010] In addition, due to the balance between the adhesive force of the binder and the expansion and contraction of the negative electrode active material, there is a limit to the amount of negative electrode active material per unit area from the perspective of durability. Specifically, the limit of the negative electrode active material capacity per unit area is 4 mAh / cm 2 (film thickness is 50μm) or so. If it is more, sufficient cycle performance cannot be maintained. On the other hand, if the active material capacity is less than 4mAh / cm 2 , then no improvement in energy density can be expected.

[0011] In order to solve the above-mentioned problem, it is considered to apply a porous metal body to the current collector of the negative electrode of a non-aqueous electrolyte secondary battery, and to fill the electrode mixture into the porous metal body. It is known that in a non-aqueous electrolyte secondary battery, when a current collector composed of a porous metal body is applied to the negative electrode, an electrode active material composed of a silicon-based material is applied to the negative electrode active material, and a skeleton forming agent covering the current collector and the electrode active material is applied, if the skeleton forming agent does not penetrate sufficiently into the interior of the negative electrode, voids will be generated inside the porous metal body. In addition, it is also known that a non-aqueous electrolyte secondary battery using such a negative electrode will undergo structural degradation inside the electrode due to repeated charge and discharge, thereby deteriorating the battery performance.

[0012] Therefore, it is desired to have a negative electrode for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery having the negative electrode, which can suppress the generation of voids inside the porous metal body to suppress durability degradation and structural degradation of the electrode and improve energy density and cycle durability.

[0013] The present invention is completed in view of the above content, and its purpose is to provide a negative electrode for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery equipped with the negative electrode, which can suppress the durability degradation and structural degradation of the electrode by suppressing the generation of voids inside the porous metal body, and improve the energy density and cycle durability.

[0014] [Methods of solving the problem]

[0015] (1) In order to achieve the above-mentioned purpose, the present invention provides a negative electrode for a non-aqueous electrolyte secondary battery, which has a current collector composed of a porous metal body and a negative electrode material arranged in the pores of the porous metal body, wherein the negative electrode material comprises: a first negative electrode active material, which is arranged on the inner surface of the pores and is composed of a silicon-based material; a skeleton forming agent, which is arranged on the first negative electrode active material and contains a silicate having a siloxane bond; and a second negative electrode active material, which is arranged on the skeleton forming agent.

[0016] (2) In the negative electrode for a non-aqueous electrolyte secondary battery according to (1), the negative electrode material may further include a conductive auxiliary agent, and the conductive auxiliary agent may be arranged between the skeleton-forming agent and the second negative electrode active material.

[0017] (3) In the negative electrode for a non-aqueous electrolyte secondary battery according to (1) or (2), the skeleton-forming agent may contain a silicate represented by the following general formula (1).

[0018] A2O·nSiO2…Formula (1)

[0019] In the general formula (1), A represents an alkali metal

[0020] (4) In the negative electrode for a nonaqueous electrolyte secondary battery according to any one of (1) to (3), the porous metal body may be a foamed metal body.

[0021] (5) The present invention also provides a non-aqueous electrolyte secondary battery comprising the negative electrode for a non-aqueous electrolyte secondary battery according to any one of (1) to (4).

[0022] [Effects of the Invention]

[0023] According to the present invention, a negative electrode for a nonaqueous electrolyte secondary battery and a nonaqueous electrolyte secondary battery including the negative electrode can be provided, which can suppress the generation of voids inside a porous metal body, thereby suppressing durability degradation and improving energy density. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a diagram schematically showing the configuration of a negative electrode for a non-aqueous electrolyte secondary battery according to the first embodiment of the present invention.

[0025] Figure 2 This is a diagram schematically showing the configuration of a negative electrode for a non-aqueous electrolyte secondary battery in the case where a conductive auxiliary agent and a binder are further included according to the first embodiment of the present invention.

[0026] Figure 3 This is a graph showing the relationship between the number of cycles and the active material capacity (mAh / g) in Examples 1 to 4 and Comparative Example 1. DETAILED DESCRIPTION

[0027] Below, with reference to the attached Figure 1 An embodiment of the present invention will be described in detail.

[0028] [negative electrode]

[0029] Figure 1This figure schematically illustrates the configuration of a negative electrode 1 for a non-aqueous electrolyte secondary battery according to this embodiment. The negative electrode 1 for a non-aqueous electrolyte secondary battery according to this embodiment comprises a current collector 11 formed of a porous metal body and a negative electrode material 12 disposed within the pores of the porous metal body. Furthermore, the negative electrode material 12 comprises: a first negative electrode active material 13 disposed on the inner surface of the pores and composed of a silicon-based material; a framework-forming agent 14 disposed on the first negative electrode active material 13 and containing a silicate having a siloxane bond; and a second negative electrode active material 17 disposed on the framework-forming agent.

[0030] For example, by applying this embodiment to a negative electrode for a lithium-ion secondary battery, a negative electrode for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery including this negative electrode can be provided. These negative electrodes can suppress the increase or decrease in voids within the porous metal body, thereby suppressing endurance degradation and structural degradation of the electrode, and can improve energy density and cycle durability. The following describes in detail an example of applying this embodiment to a negative electrode for a lithium-ion secondary battery, and various additions, modifications, or deletions may be made without departing from the scope of the present invention.

[0031] As the current collector 11, a current collector 11 composed of a porous metal body is used. Examples thereof include mesh, woven fabric, non-woven fabric, embossed body, punched body, expanded metal, and foam body, with foam body being preferred. Among them, foam body having a three-dimensional network structure with continuous pores is preferably used, and Celmet (registered trademark) (manufactured by Sumitomo Electric Industries, Ltd.) and the like can be used.

[0032] The material of the porous metal body is not particularly limited as long as it has electron conductivity and can conduct electricity with the electrode material it holds. For example, conductive metals such as Al, Al alloys, Ni, Ni-Cr alloys, Fe, Cu, Ti, Cr, Au, Mo, W, Ta, Pt, Ru, and Rh, and conductive alloys containing two or more of these conductive metals (stainless steel (SUS304, SUS316, SUS316L, YUS270, etc.)) can be used. In addition, when a material other than the above-mentioned conductive metals or conductive alloys is used, for example, a multilayer structure in which different metals such as Cu or Ni are coated on Fe can be used. Among them, Ni or a Ni alloy is preferably used because of its excellent electron conductivity and reduction resistance.

[0033] The thickness of the porous metal body is preferably 10 μm or more, more preferably 50 μm or more. The thickness of the porous metal body is preferably 1 mm or less, more preferably 800 μm or less.

[0034] The average pore diameter of the porous metal body is preferably 800 μm or less. By ensuring that the average pore diameter of the porous metal body is within this range, the distance between the first negative electrode active material 13 filled or supported within the porous metal body and the metal skeleton is stabilized, improving electron conductivity and suppressing increases in the battery's internal resistance. Furthermore, even if volume changes occur during charging and discharging, shedding of the electrode mixture can be suppressed.

[0035] The specific surface area of ​​the porous metal body is preferably 1000 to 10000 m 2 / m 3 This is 2 to 10 times the specific surface area of ​​conventional collector foils. By keeping the specific surface area of ​​the porous metal body within this range, the contact between the electrode mixture and the collector 11 is improved, thereby suppressing the increase in the internal resistance of the battery. A more preferred specific surface area is 4000 to 7000 m 2 / m 3 .

[0036] The porosity of the porous metal body is preferably 90 to 99%. By making the porosity of the porous metal body within this range, the filling amount of the electrode mixture can be increased, thereby improving the energy density of the battery. Specifically, if the porosity exceeds 99%, the mechanical strength of the porous metal body will decrease significantly, and it will be easy to be damaged by the volume change of the electrode caused by charging and discharging. On the contrary, if it is less than 90%, not only the filling amount of the electrode mixture decreases, but also the ion conductivity of the electrode decreases, making it difficult to obtain sufficient input and output characteristics. From these viewpoints, a more preferred porosity is 93 to 98%.

[0037] The electrode weight per unit area of ​​the porous metal body is preferably 1 to 100 mg / cm 2 By making the electrode weight per unit area of ​​the porous metal body within this range, the active material capacity can be fully demonstrated, and the electrode can display the capacity as designed. A more preferred electrode weight per unit area is 5 to 60 mg / cm 2 .

[0038] As the first negative electrode active material 13, a substance that can reversibly absorb and release lithium ions is used. Specifically, a negative electrode active material composed of a high-capacity silicon-based material is used. As silicon-based materials, there are silicon alone, silicon alloys, silicon oxides, silicon compounds, etc. Here, the so-called silicon alone refers to crystalline or amorphous silicon with a purity of 95% by mass or more. The so-called silicon alloy refers to a Si-M alloy containing silicon and other transition elements M. M can be, for example, Al, Mg, La, Ag, Sn, Ti, Y, Cr, Ni, Zr, V, Nb, Mo, etc. It can also be an infinite solid solution alloy, eutectic alloy, hypoeutectic alloy, hypereutectic alloy, or peritectic alloy. The so-called silicon oxide refers to silicon oxide or a complex containing silicon alone and SiO2. The element ratio of Si to O is 1 relative to Si and O is 1.7 or less. The so-called silicon compound is a substance formed by chemical bonding of silicon with two or more other elements. Among them, silicon alone is preferred in terms of being able to form a good interface layer described later. Alternatively, a material obtained by mixing or compositely combining a carbon-based material with a silicon-based material may be used.

[0039] In the present invention, the first negative electrode active material 13 is preferably disposed on the inner surfaces of the pores of the porous metal body.

[0040] The shape of the silicon-based material is not particularly limited, and may be spherical, elliptical, faceted, ribbon-shaped, fibrous, flaky, toroidal, or hollow powder. These may be single particles or granules.

[0041] The negative electrode active material 13 made of silicon-based materials has an expansion coefficient of 10% or more during charge and discharge. This means that the negative electrode active material 13 significantly expands and contracts during charge and discharge. Using the skeleton-forming agent 14 described below can suppress the durability degradation caused by this expansion and contraction.

[0042] From the viewpoint of achieving excellent cycle characteristics of the electrode and high input-output characteristics, the particle size of the silicon-based material is preferably 1.0 μm to 15 μm.

[0043] From the perspective of ensuring conductivity when the active material expands and contracts during charge and discharge, the amount (weight per unit area) of the first negative electrode active material 13 supported in the porous metal body is preferably 1.0 to 12 mg / cm 2 The more preferred loading amount (weight per unit area) of the first negative electrode active material 13 is 2.0 to 8.0 mg / cm 2 .

[0044] Furthermore, the first negative electrode active material 13 may also include a carbon-based material (graphite, hard carbon, soft carbon, etc.) and / or a conductive additive 15 in addition to the silicon-based material. When the first negative electrode active material 13 includes the carbon-based material and / or the conductive additive 15, the content of the conductive additive 15 is preferably 1 to 10% by mass, based on the total amount of the first negative electrode active material 13, the carbon-based material, and the conductive additive 15 being 100% by mass, from the perspective of improving battery output. A more preferred content of the conductive additive 15 is 2 to 7% by mass.

[0045] The skeleton forming agent 14 contains a silicate having a siloxane bond. More specifically, the skeleton forming agent 14 preferably contains a silicate represented by the following general formula (1).

[0046] A2O·nSiO2…Formula (1)

[0047] In the general formula (1), A represents an alkali metal. A is preferably at least one of lithium (Li), sodium (Na), and potassium (K). By using this alkali metal silicate having a siloxane bond as a skeleton-forming agent, a lithium-ion secondary battery having high strength, excellent heat resistance, and excellent cycle life can be obtained.

[0048] In addition, in the general formula (1), n ​​is preferably 1.6 or more and 3.9 or less. By making n within this range, when the skeleton forming agent 14 is mixed with water to form a skeleton forming agent liquid, a moderate viscosity can be obtained, and when the skeleton forming agent 14 is applied to the negative electrode containing silicon as the negative electrode active material 13 as described later, it is easy for the skeleton forming agent 14 to penetrate into the negative electrode material 12. Therefore, a lithium ion secondary battery with high strength, excellent heat resistance and excellent cycle life can be obtained more reliably. More preferably, n is 2.0 or more and 3.5 or less.

[0049] The silicate is preferably amorphous. Because amorphous silicates contain disordered molecular arrangements, they do not break in a specific direction like crystals. Therefore, by using an amorphous silicate as the framework-forming agent 14, cycle life characteristics are improved.

[0050] For example, by applying the skeleton forming agent liquid to the negative electrode containing silicon as the first negative electrode active material 13, the skeleton forming agent 14 will penetrate between the first negative electrode active material 13. Therefore, it is speculated that the silicon constituting the negative electrode active material 13 and the silicate constituting the skeleton forming agent 14 will fuse, for example, the hydrolyzed silicate undergoes a dehydration reaction (condensation reaction of the silanol group) by heating, thereby forming a siloxane bond (-Si-O-Si-). That is, in the negative electrode 1 for lithium ion secondary batteries of this embodiment, an interface layer composed of an inorganic substance is formed at the interface between the first negative electrode active material 13 and the skeleton forming agent 14, and the interface layer contains silicon derived from the siloxane bond and an alkali metal generated by the hydrolysis of the silicate, etc. Moreover, it is speculated that due to the existence of this interface layer, the first negative electrode active material 13 and the skeleton former 14 will be firmly combined, and as a result, the metal skeleton of the collector 11 composed of a porous metal body and the skeleton former 14 can be used to fix or carry the first negative electrode active material 13 inside the porous metal body, thereby obtaining excellent cycle life characteristics.

[0051] In the present invention, the skeleton forming agent 14 is preferably disposed on the first negative electrode active material 13. This is because the metal skeleton of the current collector 11 composed of a porous metal body and the skeleton forming agent 14 can fix or support the first negative electrode active material 13 inside the pores of the porous metal body.

[0052] In this embodiment, the ratio of alkali metal atoms in the interface layer relative to all constituent atoms is preferably higher than the ratio of alkali metal atoms in the skeleton-forming agent 14 relative to all constituent atoms. More specifically, the ratio of alkali metal atoms in the interface layer relative to all constituent atoms is preferably at least five times the ratio of alkali metal atoms in the skeleton-forming agent 14 relative to all constituent atoms. This strengthens the bond between the first negative electrode active material 13 and the skeleton-forming agent 14, further suppressing delamination due to expansion and contraction of the first negative electrode active material 13 during charge and discharge, or wrinkling or cracking of the current collector 11, thereby further improving cycle life.

[0053] The thickness of the interface layer is preferably 3 to 30 nm. By setting the thickness of the interface layer within this range, the bond between the first negative electrode active material 13 and the skeleton-forming agent 14 becomes stronger, further suppressing the expansion and contraction of the first negative electrode active material 13 during charge and discharge, which may cause delamination or wrinkles or cracks in the current collector 11, thereby further improving the cycle life.

[0054] The skeleton-forming agent 14 of this embodiment may also contain a surfactant. This improves the lyophilicity of the skeleton-forming agent 14 with respect to the negative electrode material 12, allowing the skeleton-forming agent 14 to uniformly penetrate the negative electrode material 12. Consequently, a uniform skeleton is formed between the first negative electrode active material 13 within the negative electrode material 12, further improving cycle life characteristics.

[0055] The content (density) of the skeleton forming agent 14 relative to the negative electrode material 12 is preferably 0.5 to 2.0 mg / cm 2 If the content of the skeleton forming agent 14 relative to the negative electrode material 12 is within this range, the effect of using the skeleton forming agent 14 can be more reliably exerted.

[0056] When the total solid content of the first negative electrode active material 13, the skeleton former 14 and the second negative electrode active material 17 is set to 100% by mass, the content of the skeleton former 14 is preferably 3.0 to 40.0% by mass. If the content of the skeleton former 14 is within this range, the effect produced by using the skeleton former 14 can be more reliably exerted. By setting the content of the skeleton former 14 in the negative electrode material 12 to 3.0% by mass or more, the function of the skeleton former 14 can be more fully obtained. In addition, by setting the content of the skeleton former 14 to 40.0% by mass or less, the energy density can be further prevented from decreasing. The more preferred content of the skeleton former 14 is 5.0 to 30.0% by mass.

[0057] Here, in the negative electrode 1 for a non-aqueous electrolyte secondary battery of this embodiment, the skeleton-forming agent 14 is disposed at least at the interface between the negative electrode material 12 and the current collector 11. More specifically, the skeleton-forming agent 14 is disposed not only at the interface between the current collector 11 and the negative electrode material 12 but also uniformly throughout the negative electrode material 12 and dispersed between the first negative electrode active materials 13. In contrast, in conventional negative electrodes for non-aqueous electrolyte secondary batteries, the skeleton-forming agent is unevenly distributed on the surface of the negative electrode material.

[0058] Furthermore, the lithium-ion secondary battery negative electrode 1 of this embodiment contains a second negative electrode active material 17. As the second negative electrode active material, one that exhibits minimal or no expansion or contraction during charge and discharge is preferably used. It is speculated that by including the second negative electrode active material 17 within the pores of the current collector 11 formed of a porous metal body, the skeleton-forming agent 14 can fill the voids created within the pores if insufficient penetration of the current collector 11 occurs, thereby suppressing the shedding of the negative electrode material 12 that occurs during expansion and contraction of the first negative electrode active material 13.

[0059] In the present invention, the second negative electrode active material is preferably disposed on the skeleton-forming agent. This is because the second negative electrode active material can be disposed within the voids created by disposing the first negative electrode active material 13 and the skeleton-forming agent 14 in the order described within the pores of the porous metal body. Furthermore, unlike the first negative electrode active material, the second negative electrode active material does not necessarily need to be bound to or fixed to the skeleton-forming agent.

[0060] Specific materials preferably used as the second negative electrode active material include silicon monoxide (SiO), silicon carbide (SiC), tin (Sn), graphite, carbon-based materials (graphite (Gr), hard carbon, soft carbon, etc.), lithium titanate (LTO), etc., and one or more of these can be used. From the perspective of improving energy density, silicon monoxide is preferred.

[0061] From the viewpoint of energy density, the weight per unit area of ​​the second negative electrode active material is preferably 1 to 40 mg / cm 2 The more preferred weight per unit area of ​​the second negative electrode active material is 5 to 15 mg / cm 2 Furthermore, from the perspective of suppressing endurance degradation and improving energy density, the total weight per unit area of ​​the first negative electrode active material and the second negative electrode active material is preferably 10 to 50 mg / cm 2 More preferably, the total weight per unit area of ​​the first negative electrode active material and the second negative electrode active material is 10 to 20 mg / cm 2 .

[0062] From the viewpoint of energy density and durability, the mixing ratio of the first negative electrode active material to the second negative electrode active material is preferably 1:2 to 1:5 by weight, and more preferably 1:2 to 1:3 by weight.

[0063] The thickness of the non-aqueous electrolyte secondary battery negative electrode 1 of this embodiment, comprising the above-described structure, is preferably 50 μm to 1000 μm. When the thickness of the non-aqueous electrolyte secondary battery negative electrode 1 is within this range, degradation over time can be suppressed and energy density can be increased compared to conventional methods. A more preferred thickness of the non-aqueous electrolyte secondary battery negative electrode 1 is 150 μm to 800 μm.

[0064] Furthermore, in the negative electrode 1 for a non-aqueous electrolyte secondary battery of this embodiment, the distance between the porous metal current collector 11 and the first negative electrode active material 13 is preferably 50 μm or less. When the distance between the porous metal current collector 11 and the first negative electrode active material 13 is 50 μm or less, endurance degradation can be suppressed. More preferably, the distance between the porous metal current collector 11 and the first negative electrode active material 13 is 30 μm or less.

[0065] In addition, the negative electrode 1 for lithium ion secondary batteries of the present embodiment may contain a conductive additive 15. As the conductive additive 15, there is no particular limitation as long as it has electron conductivity, and metals, carbon materials, conductive polymers, conductive glass, etc. can be used. Specifically, acetylene black (AB), Ketjen black (KB), furnace black (FB), thermal black, lamp black, channel black, drum black, disc black, carbon black (CB), carbon fiber (such as vapor grown carbon fiber VGCF (registered trademark)), carbon nanotubes (CNT), carbon nanohorns, graphite, graphene, glassy carbon, amorphous carbon, etc. can be mentioned, and one or more of them can be used.

[0066] In this embodiment, when a conductive additive is included, the use of a carbon black-based carbon material, a furnace-based carbon material, or a fibrous carbon material can improve the conductivity within the electrode and reduce the internal resistance. Furthermore, the use of a graphene-based carbon material as the conductive additive 15 can suppress structural degradation of the electrode caused by repeated charge and discharge, thereby improving cycle durability.

[0067] In this embodiment, when the conductive aid 15 and / or the binder 16 are included, the content of the conductive aid 15 is preferably 0 to 20.0% by mass, based on the total amount of the first negative electrode active material 13, the conductive aid 15, the binder 16, and the second negative electrode active material 17 being 100% by mass. When the content of the conductive aid 15 is within this range, the conductivity can be improved without decreasing the negative electrode capacity density, and sufficient voids can be formed within the negative electrode material 12 to accommodate the skeleton-forming agent 14. A more preferred content of the conductive aid 15 is 2 to 10% by mass.

[0068] In the present embodiment, when the conductive auxiliary agent 15 is included, the conductive auxiliary agent 15 preferably has a bulk density of 0.04 to 0.25 mg / cm 3 By setting the bulk density of the conductive aid 15 within this range, the skeleton forming agent 14 can be fully impregnated, thereby fully exerting the effect of the skeleton forming agent 14. A more preferred bulk density of the conductive aid 15 is 0.04 to 0.15 mg / cm 3 .

[0069] In the present invention, when the non-aqueous electrolyte secondary battery negative electrode 1 contains the conductive auxiliary agent 15 , it is preferably disposed between the skeleton-forming agent and the second negative electrode active material 17 .

[0070] When the non-aqueous electrolyte secondary battery negative electrode 1 of this embodiment contains a conductive additive 15, the conductive additive is also disposed at least at the interface between the current collector 11 and the negative electrode material 12, specifically, on the surfaces of the current collector 11, the first negative electrode active material 13, and the framework-forming agent 14, and in the gaps formed by their arrangement. More specifically, the conductive additive 15 is disposed not only at the interface between the current collector 11 and the negative electrode material 12, but also throughout the negative electrode material 12, and is also dispersed in the gaps formed between the first negative electrode active material 13 and between the current collector 11, the first negative electrode active material 13, and the framework-forming agent 14. In contrast, when conventional non-aqueous electrolyte secondary battery negative electrodes contain a conductive additive, the conductive additive is unevenly distributed on the surface of the negative electrode material.

[0071] In addition, the negative electrode 1 for lithium ion secondary batteries of the present embodiment may contain a binder 16. As the binder 16, for example, a single organic material may be used: polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), polyimide (PI), polyamide, polyamideimide, aromatic polyamide, polyacrylic resin, styrene-butadiene rubber (SBR), ethylene-vinyl acetate copolymer (EVA), styrene-ethylene-butylene-styrene copolymer (SEBS), carboxymethyl cellulose (CMC), xanthan gum, polyvinyl alcohol (PVA), ethylene-vinyl alcohol, polyvinyl butyral (PVB), ethylene-vinyl alcohol, polyethylene (PE), polypropylene (PP), polyacrylic acid, lithium polyacrylate, sodium polyacrylate, potassium polyacrylate, ammonium polyacrylate, polymethyl acrylate, polyethyl acrylate, polyacrylamide, polypropylene Acid esters, epoxy resins, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), nylon, vinyl chloride, silicone rubber, nitrile rubber, cyanoacrylate, urea resin, melamine resin, phenol resin, latex, polyurethane, silanized polyurethane, nitrocellulose, dextrin, polyvinyl pyrrolidone, vinyl acetate, polystyrene, allyl chloride, resorcinol resin, polyaromatic resin, modified silicone, methacrylic resin, polybutene, butyl rubber, 2-acrylic acid, cyanoacrylate, methyl methacrylate, glycidyl methacrylate, acrylic acid oligomer, 2-hydroxyethyl acrylate, alginic acid, starch, lacquer, sucrose, animal glue, casein, cellulose nanofibers, etc.; two or more thereof may be used in combination.

[0072] In addition, an adhesive obtained by mixing the various organic adhesives and inorganic adhesives can also be used. Examples of the inorganic adhesive include silicate, phosphate, sol, and cement. For example, a single inorganic material can be used: lithium silicate, sodium silicate, potassium silicate, cesium silicate, guanidine silicate, ammonium silicate, fluorosilicate, borate, lithium aluminate, sodium aluminate, potassium aluminate, aluminum silicate, lithium aluminate, sodium aluminate, potassium aluminate, polyaluminum chloride, polyaluminum sulfate, polyaluminum sulfate silicate, aluminum sulfate, aluminum nitrate, ammonium alum, lithium alum, sodium alum, potassium alum, chrome alum, iron alum, manganese alum, nickel ammonium sulfate, diatomaceous earth, polyzirconoxane, polytantaloxane, mullite, white carbon black, silica sol, colloid Silica, fumed silica, alumina sol, colloidal alumina, fumed alumina, zirconia sol, colloidal zirconia, fumed zirconia, magnesia sol, colloidal magnesia, fumed magnesia, calcium oxide sol, colloidal calcium oxide, fumed calcium oxide, titania sol, colloidal titanium dioxide, fumed titanium dioxide, zeolite, silicoaluminophosphate zeolite, sepiolite, montmorillonite, kaolin, saponite, aluminum phosphate, magnesium phosphate, calcium phosphate, iron phosphate, copper phosphate, zinc phosphate, titanium phosphate, manganese phosphate, barium phosphate, tin phosphate, low-melting glass, plaster, gypsum, magnesium cement, litharge cement, Portland cement, blast furnace cement, fly ash cement, silica cement, phosphate cement, concrete, solid electrolyte, etc.; two or more thereof may be used in combination.

[0073] In addition, when the present embodiment contains a binder 16, the first negative electrode active material 13 and the skeleton forming agent 14 are firmly bonded together by the interface layer formed by using the skeleton forming agent 14, so the entire amount of the binder 16 can be used. When the present embodiment contains a conductive auxiliary agent 15 and / or a binder 16, when the total amount of the first negative electrode active material 13, the conductive auxiliary agent 15, the binder 16, and the second negative electrode active material 17 is set to 100% by mass, the content of the binder 16 is preferably 0.1 to 60% by mass. By setting the content of the binder 16 within this range, the ion conductivity can be improved without reducing the negative electrode capacity density, and high mechanical strength can be obtained, thereby achieving more excellent cycle life characteristics. A more preferred content of the binder 16 is 0.5 to 30% by mass.

[0074] In the present invention, when the negative electrode 1 for a nonaqueous electrolyte secondary battery contains the binder 16 , the binder 16 is preferably disposed between the skeleton-forming agent 14 and the second negative electrode active material 17 and between particles of the negative electrode active material 17 .

[0075] When a conductive aid and / or binder is contained in this embodiment, the content of the skeleton former 14 needs to be calculated taking into account the solid content mass of the conductive aid and the binder. Specifically, when the total solid content of the negative electrode active material 13, the skeleton former 14, the conductive aid 15, the binder 16 and the second negative electrode active material 17 is set to 100% by mass, the content of the skeleton former 14 is preferably 3.0 to 40.0% by mass when the conductive aid and / or binder are contained. If the content of the skeleton former 14 is within this range, the effect of using the skeleton former 14 can be more effectively exerted. By setting the content of the skeleton former 14 in the negative electrode material 12 to 3.0% by mass or more, the function of the skeleton former 14 can be more fully obtained. Moreover, by setting the content of the skeleton former 14 to 40.0% by mass or less, the energy density can be further prevented from decreasing. The more preferred content of the skeleton former 14 is 5.0 to 30.0% by mass.

[0076] [positive electrode]

[0077] Next, a description will be given of a positive electrode when a lithium ion secondary battery is constructed using the negative electrode.

[0078] The positive electrode active material is not particularly limited as long as it is a positive electrode active material commonly used in lithium ion secondary batteries. For example, positive electrode active materials such as alkali metal transition metal oxides, vanadium, sulfur, solid solution systems (lithium excess systems, sodium excess systems, potassium excess systems), carbon systems, and organic systems can be used.

[0079] The positive electrode for lithium ion secondary battery of this embodiment may also contain a skeleton forming agent as in the negative electrode. As the skeleton forming agent, the same skeleton forming agent as in the negative electrode can be used, and the preferred content of the skeleton forming agent is also the same as that of the negative electrode.

[0080] The positive electrode for the lithium ion secondary battery of this embodiment may also contain a conductive additive. As the conductive additive, the various conductive additives that can be used in the negative electrode can be used. The preferred content of the conductive additive is the same as that of the negative electrode.

[0081] The positive electrode for the lithium-ion secondary battery of this embodiment may also contain a binder. As the binder, for example, a single organic material such as polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), hexafluoropropylene, tetrafluoroethylene, polyacrylic resin, alginic acid, etc. may be used; or two or more may be used in combination. In addition, a binder formed by mixing these organic binders with an inorganic binder may be used. Examples of inorganic binders include silicate-based, phosphate-based, sol-based, and cement-based binders.

[0082] As the current collector for the positive electrode, as long as it is a material with electronic conductivity and capable of being energized with the positive electrode active material maintained, there is no particular limitation. For example, conductive materials such as C, Ti, Cr, Ni, Cu, Mo, Ru, Rh, Ta, W, Os, Ir, Pt, Au, Al, and alloys containing two or more of these conductive materials (for example, stainless steel or Al-Fe alloy) can be used. When using a material other than the conductive material, for example, it can be a multilayer structure of different metals such as Al on iron or a multilayer structure of different elements such as C on Al. With respect to the viewpoint that conductivity is high and stability in the electrolyte is high, as a current collector, preferably C, Ti, Cr, Au, Al, stainless steel, etc., further with respect to the viewpoint of oxidation resistance and material cost, preferably C, Al, stainless steel, etc. More preferably, Al or Al alloy covered with carbon, stainless steel covered with carbon.

[0083] In addition, the shape of the current collector used in the positive electrode includes linear, rod-shaped, plate-shaped, foil-shaped, and porous shapes. Among them, porous shapes can be used in terms of increasing the packing density and facilitating the penetration of the skeleton-forming agent into the active material layer. Regarding porous shapes, meshes, woven fabrics, non-woven fabrics, embossed bodies, punched bodies, drawn metal meshes, or foam bodies can be mentioned. Porous metal bodies similar to those used for the negative electrode can also be used.

[0084] [Diaphragm]

[0085] In the lithium-ion secondary battery of this embodiment, a separator commonly used in lithium-ion secondary batteries can be used. For example, a polyethylene microporous membrane, a polypropylene microporous membrane, a glass nonwoven fabric, an aromatic polyamide nonwoven fabric, a polyimide microporous membrane, a polyolefin microporous membrane, or the like can be used as the separator.

[0086] [Electrolytes]

[0087] In the lithium-ion secondary battery of this embodiment, an electrolyte commonly used in lithium-ion secondary batteries can be used as the electrolyte. Examples include electrolyte solutions in which an electrolyte is dissolved in a solvent, gel electrolytes, solid electrolytes, ionic liquids, and molten salts. Here, the electrolyte solution refers to an electrolyte solution in which an electrolyte is dissolved in a solvent.

[0088] As the electrolyte of a lithium-ion secondary battery, it is necessary to contain lithium ions as the carrier responsible for conduction. Therefore, as the electrolyte salt of a lithium-ion secondary battery, as long as it is an electrolyte salt used in a lithium-ion secondary battery, there is no particular limitation, and preferably a lithium salt. As the lithium salt, at least one or more selected from the following groups can be used, or two or more can be used in combination, the group including lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium trifluoromethanesulfonate (LiCF3SO4), lithium bis(trifluoromethanesulfonyl)imide (LiN(SO2CF3)2), lithium bis(pentafluoroethanesulfonyl)imide (LiN(SO2C2F5)2), lithium bis(oxalatoborate) (LiBC4O8), etc.

[0089] The solvent for the electrolyte is not particularly limited as long as it is a solvent for the electrolyte used in lithium-ion secondary batteries. For example, at least one selected from the following group can be used, or two or more can be used in combination. The group includes propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), γ-butyrolactone (GBL), methyl-γ-butyrolactone, dimethoxymethane (DMM), dimethoxyethane (DME), vinylene carbonate (VC), vinyl ethylene carbonate (EVC), fluoroethylene carbonate (FEC), and ethylene sulfite (ES).

[0090] The concentration of the electrolyte solution (the concentration of the salt in the solvent) is not particularly limited, but is preferably 0.1 to 3.0 mol / L, and more preferably 0.8 to 2.0 mol / L.

[0091] Ionic liquids or molten salts are classified into pyridine-based, alicyclic amine-based, aliphatic amine-based, and the like according to the type of cation (positive ion). By selecting the type of anion (negative ion) to be combined with them, a variety of ionic liquids or molten salts can be synthesized. Among the cations, there are ammonium ions such as imidazolium salts and pyridinium salts, phosphonium ions, inorganic ions, and the like. Examples of anions include bromide ions, halogen-based ions such as trifluoromethanesulfonate, boron-based ions such as tetraphenylborate, and phosphorus-based ions such as hexafluorophosphate.

[0092] Ionic liquids or molten salts can be obtained by the following known synthesis methods, for example, by reacting cations such as imidazolinium with Br - 、Cl - , BF 4- PF 6- 、(CF3SO2)2N - CF3SO 3- 、FeCl 4- If it is an ionic liquid or a molten salt, it can function as an electrolyte even without adding an electrolyte.

[0093] Solid electrolytes are categorized into sulfide, oxide, hydride, and organic polymer types. Most of these solid electrolytes are amorphous or crystalline, consisting of salts and inorganic derivatives as charge carriers. Because they eliminate the need for flammable aprotic organic solvents like electrolytes, they are less likely to ignite or leak gases or liquids, making them a promising secondary battery with exceptional safety.

[0094] [Manufacturing method]

[0095] Next, a method for manufacturing the lithium ion secondary battery of this embodiment will be described.

[0096] The method for manufacturing a negative electrode for a lithium-ion secondary battery of this embodiment has a first step, which is to form a negative electrode layer precursor by applying a negative electrode material containing a first negative electrode active material to a current collector and drying it. The negative electrode layer precursor is configured with the first negative electrode active material inside the pores of a current collector composed of a porous metal body. For example, on the one hand, a nickel porous body is prepared, and the nickel porous body is obtained by manufacturing a nickel porous material with a thickness of 1000μm and pre-rolling it into a roll. On the other hand, the first negative electrode active material is mixed with N-methyl-2-pyrrolidone or water to prepare a paste slurry as the negative electrode material. Then, the slurry-like negative electrode material is filled and applied to the interior of the nickel porous body, dried, and then subjected to a voltage regulation process, thereby obtaining a negative electrode layer precursor.

[0097] In addition, the negative electrode layer precursor may also be kept in a wet state instead of being dried as described above. In addition, in addition to the slurry coating, for example, the following methods may also be mentioned: using chemical plating or sputtering, evaporation, gas deposition, immersion, intrusion, chemical vapor deposition (CVD), atomic layer deposition (ALD), etc., so that the negative electrode active material (precursor) forms a negative electrode active material layer inside the porous collector and is integrated. Among them, from the perspective of the lyophilicity of the skeleton forming agent and the cost of electrode manufacturing, the slurry filling coating method or the immersion method is preferred.

[0098] In the first step, the negative electrode material slurry may contain a carbon-based material and / or a conductive additive. In this case, for example, the first negative electrode active material, the carbon-based material, and / or the conductive additive may be mixed with N-methyl-2-pyrrolidone or water to prepare a paste slurry. The negative electrode layer precursor may be obtained by following the same procedures as in the first step.

[0099] The method for manufacturing a negative electrode for a lithium-ion secondary battery according to this embodiment includes a second step in which the negative electrode layer precursor formed in the first step is impregnated with a skeleton-forming agent and dried to harden the skeleton-forming agent, thereby forming a skeleton for the negative electrode active material layer. The skeleton-forming agent contains a silicate having a siloxane bond or a phosphate having a phosphate bond. The second step allows the skeleton-forming agent to be disposed on the first negative electrode active material.

[0100] For example, a skeleton forming agent liquid containing a skeleton forming agent can be prepared by refining a silicate having a siloxane bond or a phosphate having a phosphate bond by a dry or wet process and adjusting it with water. At this time, a surfactant can also be mixed. As a dry method, for example, SiO2 is added to water in which an alkali metal hydroxide is dissolved, and the mixture is treated in an autoclave at 150°C to 250°C to produce an alkali metal silicate. As a wet method, for example, a mixture containing an alkali metal carbonate and SiO2 can be calcined at 1000°C to 2000°C and dissolved in hot water to produce the skeleton forming agent.

[0101] Next, a skeleton forming agent liquid is applied to the surface of the negative electrode layer precursor to coat the first negative electrode active material. In addition to the method of immersing the negative electrode layer precursor in a tank storing a skeleton forming agent liquid, the skeleton forming agent can also be applied by dripping the skeleton forming agent onto the surface of the negative electrode layer precursor, spraying, screen printing, curtain coating, spin coating, gravure coating, die coating, etc. The skeleton forming agent applied to the surface of the negative electrode layer precursor will penetrate into the interior of the negative electrode and enter the gaps between the first negative electrode active material and the conductive additive. Then, the skeleton forming agent is dried by heat treatment to harden it. Thus, the skeleton forming agent forms the skeleton of the first negative electrode active material layer.

[0102] Regarding the heat treatment, if the temperature is high, the heat treatment time can be shortened and the strength of the skeleton forming agent is improved. Preferably, it is 80°C or more, more preferably 100°C or more, and ideally 110°C or more. In addition, as long as the collector does not melt, the upper limit temperature of the heat treatment is not particularly limited. For example, it can be increased to the melting point of copper, that is, about 1000°C. In the case of a conventional electrode, the upper limit temperature is estimated to be much lower than 1000°C because of the carbonization of the binder or the softening of the collector. In the present embodiment, by using a skeleton forming agent, the skeleton forming agent exhibits excellent heat resistance and is stronger than the strength of the collector. Therefore, the upper limit of the temperature is 1000°C.

[0103] The heat treatment time can be 0.5 to 100 hours. The heat treatment environment can be in the air, but it is preferably performed in a non-oxidizing environment to prevent oxidation of the current collector.

[0104] The method for manufacturing a negative electrode for a lithium-ion secondary battery of this embodiment also includes a third step of forming a negative electrode layer by applying a negative electrode material containing a second negative electrode active material to the negative electrode layer precursor formed in the second step and drying the resultant. The third step allows the second negative electrode active material to be disposed on the skeleton-forming agent.

[0105] For example, the negative electrode layer precursor can be obtained by filling and coating the prepared slurry of the negative electrode material containing the second negative electrode active material on the negative electrode layer precursor, drying it, and then performing a voltage regulation process. In the method of introducing the electrode mixture containing the second negative electrode active material, in addition to the slurry coating, the following methods can also be cited: using chemical plating, sputtering, evaporation, gas deposition, impregnation, pressing, etc. to fill the second negative electrode active material into the negative electrode layer precursor and integrate it. Among them, from the perspective of electrode manufacturing cost, the slurry filling and coating method is preferred.

[0106] Here, in the method for producing a negative electrode for a lithium ion secondary battery of this embodiment, the ratio of the density B of the negative electrode layer formed in the second step to the density A of the negative electrode layer precursor formed in the first step, that is, B / A, is 0.9.

[0107] In the method for producing a negative electrode for a lithium ion secondary battery of this embodiment, the density A of the negative electrode layer precursor formed in the first step is set to 0.5 to 2.0 g / cm 3 As a result, the ratio B / A of the density B of the negative electrode layer to the density A of the negative electrode layer precursor (i.e., the density increase ratio) can be more reliably made within the above range, thereby enhancing the effect of the skeleton forming agent. The more preferred range of the density A of the negative electrode layer precursor is 0.6 to 1.5 g / cm 3 By setting the density A of the negative electrode layer precursor to 0.6 g / cm 3 As described above, the energy density decrease caused by the decrease in electrode density can be suppressed by setting the density A of the negative electrode layer precursor to 1.5 g / cm 3 Below, the capacity reduction can be suppressed.

[0108] ​Furthermore, in the method for manufacturing a negative electrode for a lithium-ion secondary battery of this embodiment, a step may be included between the second and third steps: forming a conductive path in the negative electrode layer precursor by impregnating the negative electrode layer precursor formed in the second step with a conductive agent solution containing a conductive auxiliary agent and / or a binder and then drying the solution. This step allows the conductive auxiliary agent and / or the binder to be positioned between the skeleton-forming agent within the negative electrode layer precursor and the second negative electrode active material.

[0109] For example, a conductive agent solution is prepared by dissolving or dispersing a conductive additive and / or a binder in N-methyl-2-pyrrolidone or water, and then the conductive agent solution is applied to the surface of the negative electrode layer precursor to coat the negative electrode layer precursor with the conductive agent solution.

[0110] In addition to immersing the negative electrode layer precursor in a tank containing the conductive agent solution, the conductive agent solution containing the conductive agent solution can also be applied by dripping the skeleton-forming agent onto the surface of the negative electrode layer precursor, spraying, screen printing, curtain coating, spin coating, gravure coating, die coating, etc. In addition to disposing the conductive agent and / or binder between the skeleton-forming agent and the second negative electrode active material, the conductive agent and binder applied to the surface of the negative electrode layer precursor can also penetrate into the interior of the negative electrode layer precursor and enter the gaps between the first negative electrode active material, the skeleton-forming agent, etc.

[0111] The positive electrode for lithium-ion secondary batteries of the present invention has a process for manufacturing the positive electrode by applying a positive electrode material containing a positive electrode active material, a conductive auxiliary agent and a binder to a current collector, drying it and rolling it. For example, on the one hand, aluminum foil is prepared, which is obtained by manufacturing a rolled aluminum foil with a thickness of 10 μm and pre-rolling it into a roll. On the other hand, a paste slurry is prepared by mixing the positive electrode active material, the binder, the conductive auxiliary agent, etc. as the positive electrode material. Then, the slurry-like positive electrode material is applied to the surface of the aluminum and dried, and then subjected to a rolling process to obtain the positive electrode. In addition, a foam porous body composed of metal can also be used as the current collector. It is characterized in that the current collector is filled with an electrode mixture. The method of filling the current collector with the electrode mixture is not particularly limited. For example, the following method can be cited: by applying pressure by a press-in method, the slurry containing the electrode mixture is filled into the interior of the mesh structure of the current collector. After filling the electrode mixture, the filled current collector is dried and then pressed to increase the density of the electrode mixture, thereby adjusting the density to a desired value.

[0112] Finally, the resulting negative and positive electrodes are cut into the desired sizes, joined via a separator, and sealed while immersed in an electrolyte to produce a lithium-ion secondary battery. The structure of the lithium-ion secondary battery can be applied to existing battery forms or structures such as stacked batteries or wound batteries.

[0113] [Effect]

[0114] According to this embodiment, the following effects can be achieved.

[0115] In this embodiment, there is a collector 11 composed of a porous metal body and a negative electrode material 12 arranged in the pores of the porous metal body. The negative electrode material 12 includes a first negative electrode active material 13 arranged on the inner surface of the pore and composed of a silicon-based material, a skeleton former 14 arranged on the first negative electrode active material 13 and containing a silicate with a siloxane bond, and a second negative electrode active material 17 arranged on the skeleton former.

[0116] First, by using a porous metal body as the current collector 11, the negative electrode material 12 can be fixed in a micrometer-order region by the porous metal skeleton, thereby suppressing separation and cracking of the negative electrode.

[0117] Furthermore, by using the framework-forming agent 14 as the negative electrode material 12, the negative electrode material 12 can be fixed in the nanoscale region. More specifically, by forming a third phase composed of the framework-forming agent 14 at the interface between the current collector 11 composed of a porous metal body and the negative electrode active material 13 disposed on the inner surface of the pores of the current collector, the current collector 11 and the negative electrode active material 13 are firmly bonded within the pores of the current collector, thereby suppressing shedding during expansion and contraction, thereby suppressing durable degradation.

[0118] In addition, the second negative electrode active agent 17 is arranged in the voids of the porous metal body to which the first negative electrode active material 13 is bonded using the skeleton forming agent 14, that is, on the skeleton forming agent 14. This can help inhibit the shedding of the negative electrode material 12 caused by the expansion and contraction of the first negative electrode active material 13, thereby inhibiting the structural degradation of the electrode, and achieving an increase in energy density and an increase in cycle durability.

[0119] Therefore, by disposing the second negative electrode active agent 17 on the skeleton-forming agent 14 that binds the first negative electrode active material 13 to the pores of the current collector 11, even when the negative electrode uses a first negative electrode active material 13 composed of a silicon-based material with a high capacity and a large expansion and contraction rate, the negative electrode structure can be maintained during full charge and discharge cycles with a state of charge (SOC) of 0 to 100. Furthermore, when the negative electrode is thickened to increase capacity and weight per unit area, it is possible to suppress detachment and disconnection of the conductive path, thereby achieving high cyclability and an overwhelmingly high energy density.

[0120] In addition to the configuration of this embodiment, Figure 2When the negative electrode for a non-aqueous electrolyte secondary battery contains a conductive aid 15 and / or a binder 16 as shown, it not only helps to suppress the shedding of the negative electrode material 12 caused by expansion and contraction, but also helps to maintain the electrode structure and reduce the internal resistance. Therefore, the structural degradation of the electrode is further suppressed, and the improvement of energy density and cycle durability can be better achieved.

[0121] Therefore, by further including a conductive additive 15 and / or a binder 16 in the configuration of the first embodiment, not only can the shedding of the negative electrode material 12 during expansion and contraction be suppressed, but it can also help maintain the electrode structure and reduce internal resistance. Therefore, even when the negative electrode uses a first negative electrode active material 13 composed of a silicon-based material with a high capacity and a high expansion and contraction rate, the negative electrode structure can be more effectively maintained during full charge and discharge cycles with an SOC of 0 to 100. Furthermore, when the negative electrode is thickened, resulting in higher capacity and a higher weight per unit area, shedding and disconnection of the conductive path can be further suppressed, achieving better cyclability and achieving an even more overwhelmingly high energy density.

[0122] In addition, the present invention is not limited to the above-mentioned embodiments, and modifications and improvements within the scope of achieving the purpose of the present invention are included in the present invention. For example, a non-aqueous electrolyte secondary battery is a secondary battery (electricity storage device) that uses a non-aqueous electrolyte such as an organic solvent as an electrolyte. In addition to lithium-ion secondary batteries, it also includes sodium-ion secondary batteries, potassium-ion secondary batteries, magnesium-ion secondary batteries, calcium-ion secondary batteries, etc. In addition, a lithium-ion secondary battery refers to a secondary battery that does not use water as a main component of a non-aqueous electrolyte and is a battery that contains lithium ions as carriers responsible for conductivity. For example, there are lithium-ion secondary batteries, metal lithium batteries, lithium polymer batteries, all-solid-state lithium batteries, air lithium-ion batteries, etc. In addition, other secondary batteries are also the same. Here, a non-aqueous electrolyte that does not use water as a main component refers to an electrolyte whose main component is not water. That is, it is a well-known electrolyte used in non-aqueous electrolyte secondary batteries. Even if the electrolyte contains a small amount of water, it can function as a secondary battery, but because it will adversely affect the cycle characteristics, storage characteristics, and input-output characteristics of the secondary battery, it is ideal to use an electrolyte that does not contain water as much as possible. In reality, the water in the electrolyte is preferably less than 5000ppm.

[0123] [Example]

[0124] Next, examples of the present invention will be described, but the present invention is not limited to these examples.

[0125] <Example 1>

[0126] [Production of negative electrode]

[0127] A slurry containing silicon (particle size 1-3 μm) as the first negative electrode active material and the conductive additives shown in Table 1 was prepared. The prepared slurry was then filled into "Nickel-Celmet" (registered trademark) manufactured by Sumitomo Electric Industries, Ltd. as a current collector, dried, and then subjected to voltage regulation to obtain a negative electrode layer precursor.

[0128] Separately, a 10% by mass aqueous solution of K2O·3SiO2 was prepared as a skeleton-forming agent solution containing a skeleton-forming agent and water. The negative electrode layer precursor obtained above was immersed in the prepared skeleton-forming agent solution. After immersion, the negative electrode precursor was heated at 160°C and dried.

[0129] A conductive agent solution containing the conductive additives shown in Table 1 and polyvinylidene fluoride (PVdF) as a binder was prepared. The negative electrode layer precursor obtained above was immersed in the prepared conductive agent solution. After the immersion, the negative electrode layer precursor was dried to obtain the negative electrode layer precursor.

[0130] A slurry containing the compounds shown in Table 1 was prepared as a second negative electrode active material. The prepared slurry was then filled into the negative electrode layer precursor obtained above and dried to obtain a negative electrode having a negative electrode layer formed thereon.

[0131] [Production of positive electrode]

[0132] Prepare LiNi 0.5 Co 0.2 Mn 0.3 O2 (particle size 5-15 μm) is used as the positive electrode active material. 94% by mass of the positive electrode active material, 4% by mass of carbon black as a conductive additive, and 2% by mass of polyvinylidene fluoride (PVdF) as a binder are mixed and the obtained mixture is dispersed in an appropriate amount of N-methyl-2-pyrrolidone (NMP) to prepare a positive electrode mixture slurry. Prepare a slurry with a thickness of 1.0 mm, a porosity of 95%, a cell count of 46-50 cells / inch, a pore diameter of 0.5 mm, and a specific surface area of ​​5000 m 2 / m 3 The aluminum foam is used as the current collector. The coating amount is 90 mg / cm 2 The prepared positive electrode mixture slurry was applied to the current collector in a manner of , dried at 120° C. for 12 hours in a vacuum, and then roll-pressed at a pressure of 15 tons to prepare a positive electrode for a lithium ion secondary battery in which the pores of the foamed aluminum were filled with the electrode mixture.

[0133] [Manufacturing of lithium-ion secondary batteries]

[0134] A 25 μm-thick microporous membrane composed of a three-layer laminate of polypropylene / polyethylene / polypropylene was prepared as a separator and punched into a size of 100 mm in length by 90 mm in width. The positive electrode for a lithium-ion secondary battery and the negative electrode for a lithium-ion secondary battery obtained above were stacked in the order of positive electrode / separator / negative electrode / separator / positive electrode / negative electrode to produce an electrode stack.

[0135] The tab leads are then ultrasonically welded to the current collecting areas of each electrode. The electrode stack, with the tab leads welded to it, is inserted into a bag-shaped, heat-sealed secondary battery aluminum laminate to create a laminated battery. An electrolyte solution consisting of 1.2 mol of LiPF6 dissolved in a solvent consisting of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate in a volume ratio of 3:4:3 is prepared and injected into the laminated battery to create a lithium-ion secondary battery.

[0136] <Examples 2 to 4>

[0137] As the second negative electrode active material, a slurry containing the negative electrode active material shown in Table 1 was prepared. Then, the prepared slurry was filled into the negative electrode layer precursor and dried in the same manner as in Example 1, thereby obtaining negative electrodes of Examples 2 to 4 having negative electrode layers formed thereon.

[0138] In addition, the positive electrodes of Examples 2 to 4 had the same coating amount as in Example 1 changed to 45 mg / cm 2 The other parts were produced in the same manner as in Example 1. Furthermore, a battery was produced in the same manner as in Example 1.

[0139] Comparative Example 1

[0140] The negative electrode was prepared in the same manner as in Examples 1 to 4, except that the second negative electrode active material was not used.

[0141] In addition, the positive electrode of Comparative Example 1 was prepared by changing the coating amount of Example 1 to 45 mg / cm 2 The other parts were produced in the same manner as in Example 1. Furthermore, a battery was produced in the same manner as in Example 1.

[0142] [Aging test]

[0143] An aging test was performed on each of the Examples and Comparative Examples. The aging test was performed at a test environment temperature of 25°C.

[0144] [Durability test]

[0145] A cycle life test was conducted on each of the Examples and Comparative Examples. The cycle life test was conducted at a test environment temperature of 25° C., a current density of 0.2 C-rate, and a cutoff potential of 2.5 to 4.2 V.

[0146] [Table 1]

[0147]

[0148]

[0149] Note: Gr stands for graphite. Also, “-” indicates not used.

[0150] Figure 3 This is a graph showing the relationship between the number of cycles and the active material capacity (mAh / g) of Examples 1 to 4 and Comparative Example 1. Figure 3 It can be seen that according to this embodiment, a negative electrode for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery having the negative electrode can be obtained, in which even if the number of cycles increases, the reduction in the capacity of the active material is still small, thereby suppressing durable degradation and structural degradation of the electrode, and improving energy density and cycle durability.

[0151] Reference numerals

[0152] 1: Negative electrode for non-aqueous electrolyte secondary batteries

[0153] 11: Current collector

[0154] 12: Anode material

[0155] 13: First negative electrode active material (negative electrode active material composed of silicon-based material)

[0156] 14: Skeleton former

[0157] 15: Conductive additive

[0158] 16: Adhesive

[0159] 17: Second negative electrode active material

Claims

1. A negative electrode for a non-aqueous electrolyte secondary battery, comprising: A current collector composed of a porous metal body, and a negative electrode material disposed in the pores of the porous metal body, The negative electrode material comprises: a first negative electrode active material, which is arranged on the inner surface of the pore and is composed of silicon, silicon alloy, or a composite containing silicon and SiO2; a skeleton forming agent, disposed on the first negative electrode active material and containing an alkali metal silicate having a siloxane bond; and The second negative electrode active material is disposed on the skeleton forming agent. The skeleton forming agent is dispersed among the first negative electrode active materials. The second negative electrode active material is arranged in the gaps formed by arranging the first negative electrode active material and the skeleton-forming agent in the order described in the pores of the porous metal body. The second negative electrode active material is silicon monoxide (SiO). 2 . The negative electrode for a non-aqueous electrolyte secondary battery according to claim 1 , wherein the negative electrode material further comprises a conductive auxiliary agent, and the conductive auxiliary agent is disposed between the skeleton-forming agent and the second negative electrode active material. 3 . The negative electrode for a non-aqueous electrolyte secondary battery according to claim 1 , wherein the negative electrode material further contains a binder.

4. The negative electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein the skeleton-forming agent contains a silicate represented by the following formula (1): A2O•nSiO2 …Formula (1) In the above formula (1), A represents an alkali metal, and n represents 1.6 or more and 3.9 or less. 5 . The negative electrode for a non-aqueous electrolyte secondary battery according to claim 1 , wherein the porous metal body is a foamed metal body. 6 . A non-aqueous electrolyte secondary battery comprising the negative electrode for a non-aqueous electrolyte secondary battery according to claim 1 .

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