Negative electrode and method for manufacturing negative electrode

Abstract

The main purpose of the present disclosure is to provide a negative electrode capable of satisfactorily suppressing deterioration of a negative electrode current collector. In the present disclosure, the problem is solved by a negative electrode used in a battery, the negative electrode having, in this order, a negative electrode current collector as an Al current collector, a resin formed on the surface of the Al current collector, and a negative electrode active material layer, the resin layer containing a resin and Ni particles as a conductive auxiliary agent, the negative electrode active material layer contains a negative electrode active material having a reaction potential of 0.3 V (Li + / Li) or less.

Description

Technical Field

[0001] This disclosure relates to a negative electrode and a method for manufacturing a negative electrode. Background Technology

[0002] In recent years, with the rapid popularization of electronic devices such as personal computers and mobile phones, the development of batteries used as their power source has been continuously advancing. Furthermore, in the automotive industry, the development of batteries for hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), or battery electric vehicles (BEVs) is also progressing steadily.

[0003] For example, Patent Document 1 discloses a stacked battery having a power generation element and an outer casing housing the power generation element. The power generation element is formed by stacking multiple single-cell layers in series. These multiple single-cell layers are obtained by sequentially stacking a positive current collector, a positive active material layer, an electrolyte layer, a negative active material layer, and a negative current collector. At least one of the positive and negative current collectors includes a conductive resin layer. The power generation element also has a resistance-reducing layer adjacent to the resin layer on the outer surface of the single-cell layer containing the resin layer. Furthermore, Patent Document 1 discloses that the resistance-reducing layer may also contain a metallic material.

[0004] Furthermore, Patent Document 2 discloses a method for manufacturing a current collector for a negative electrode of a lithium-ion secondary battery having a copper film. Patent Document 3 discloses a negative electrode in a secondary battery comprising: a negative electrode current collector made of Al, and a negative electrode active material layer formed on at least one surface of the negative electrode current collector, wherein a plating layer made of Ni and / or Cr is formed on the surface of the negative electrode current collector on which the negative electrode active material layer is formed. Patent Document 4 discloses a lithium-ion secondary battery having a substrate and a negative electrode layer, the substrate having a base material and a plating layer, the base material being made of an alloy with aluminum as the main component, the plating layer comprising nickel and phosphorus and being formed by plating on the surface of the base material, and the negative electrode layer comprising a negative electrode active material that forms an intermetallic compound with lithium.

[0005] Existing technical documents

[0006] Patent Document 1: International Publication No. 2016 / 031688

[0007] Patent Document 2: Japanese Patent Application Publication No. 2020-187932

[0008] Patent Document 3: Japanese Patent Application Publication No. 2020-119696

[0009] Patent Document 4: Japanese Patent Application Publication No. 2020-091997 Summary of the Invention

[0010] From the perspective of increasing energy density by making the battery lighter, and from the perspective of improving battery heat dissipation to suppress battery degradation, it is conceivable to use Al (aluminum) as the material for the negative electrode current collector. On the other hand, Al has a relatively high reaction potential. Therefore, if a material with a lower reaction potential than Al is used as the negative electrode active material, the negative electrode current collector (Al current collector) will react with the carrier ions before the negative electrode active material, which may lead to the degradation of the negative electrode current collector.

[0011] This disclosure was made in view of the above-mentioned actual situation, and its main purpose is to provide a negative electrode that can effectively suppress the degradation of the negative current collector.

[0012] [1] A negative electrode for a battery, the negative electrode comprising, in sequence: a negative electrode current collector as an Al current collector, a resin formed on the surface of the Al current collector, and a negative electrode active material layer.

[0013] The aforementioned resin layer contains resin and Ni particles as a conductive additive.

[0014] The aforementioned negative electrode active material layer contains a reaction potential of 0.3V (Li). + Negative electrode active materials below / Li). [2]

[0016] According to the negative electrode described in [1], in the above resin layer, the weight ratio of the Ni particles to the above resin is 4.3 or less. [3]

[0018] According to the negative electrode described in [1] or [2], the average particle size (D) of the above-mentioned Ni particles is 50 () is below 500nm. [4]

[0020] The negative electrode according to any one of [1] to [3] contains a Si-based active material as the above-mentioned negative electrode active material. [5]

[0022] A method for manufacturing a negative electrode, which is a method for manufacturing a negative electrode as described in any one of [1] to [4], includes a slurry preparation step, a resin layer formation step, and a negative electrode active material layer formation step.

[0023] In the above-described slurry preparation process, a resin slurry containing the above-described resin, the above-described Ni particles, and a solvent is prepared.

[0024] In the above-described resin layer formation process, the resin slurry is applied to the surface of the Al current collector and dried to form the resin layer.

[0025] In the above-mentioned negative electrode active material layer formation process, the negative electrode active material layer is formed on the surface of the above-mentioned resin layer.

[0026] In this disclosure, the effect of effectively suppressing the degradation of the negative electrode current collector is achieved. Attached Figure Description

[0027] Figure 1 This is a schematic cross-sectional view illustrating the negative electrode in this disclosure.

[0028] Figure 2 This is a schematic cross-sectional view illustrating the battery in this disclosure.

[0029] Figure 3 This is a flowchart illustrating a method for manufacturing the negative electrode in this disclosure.

[0030] Figure 4 This is a coordinate graph representing the result of evaluation 1.

[0031] Explanation of reference numerals in the attached figures

[0032] 1… Negative current collector (Al current collector)

[0033] 2…resin layer

[0034] 3…Negative electrode active material layer

[0035] 5… Positive electrode active material layer

[0036] 6…Positive current collector

[0037] CA…Positive electrode

[0038] AN… Negative electrode

[0039] EL…electrolyte layer

[0040] 10… batteries Detailed Implementation

[0041] The following is a detailed description of the negative electrode and its manufacturing method in this disclosure. The figures shown below are schematic diagrams, and the size and shape of the parts have been appropriately exaggerated for ease of understanding.

[0042] A. Negative electrode

[0043] Figure 1 This is a schematic cross-sectional view illustrating the negative electrode in this disclosure. Figure 1 The negative electrode AN shown comprises, in sequence: a negative electrode current collector 1 serving as an Al current collector, a resin layer 2 formed on the surface of the Al current collector 1, and a negative electrode active material 3. The resin layer 2 contains resin and Ni particles as a conductive additive. Furthermore, the negative electrode active material layer 3 contains a reaction potential of 0.3V (Li). + Negative electrode active materials below / Li).

[0044] According to this disclosure, a resin layer containing resin and Ni particles is disposed on the surface of the Al current collector, thereby suppressing the reaction (deterioration) of the Al current collector. For example, when using Si-based and C-based active materials, the reaction potential is low (0.3V (Li... + When materials of the following types (e.g., Al and Li) are used as the negative electrode active material, an ion conduction pathway may form between the negative electrode current collector (Al current collector) and the carrier ions (e.g., Li ions), causing the negative electrode current collector to deteriorate due to the reaction between Al and Li. In this respect, in the negative electrode of this disclosure, a resin layer is disposed between the negative electrode active material layer and the Al current collector. Therefore, the electrolyte in the negative electrode active material layer and the Al current collector do not come into contact, and no conduction pathway for carrier ions is formed, thus suppressing the reaction of the Al current collector. Furthermore, from the viewpoint of conductivity, it is generally assumed that the resin layer contains conductive additives such as acetylene black (AB). Regarding this, as mentioned above, carbon (carbon-based conductive additives) may react with Al. In contrast, in this disclosure, the resin layer contains Ni particles as a conductive additive. Ni is a material that is less likely to react with Al compared to carbon-based conductive additives, thus more effectively suppressing the deterioration of the Al current collector.

[0045] 1. Negative current collector

[0046] The negative current collector in this disclosure is an Al current collector. An Al current collector is a current collector that uses aluminum (Al) as the main raw material. The Al current collector can be elemental Al or an Al alloy. In an Al alloy, the proportion of Al element relative to all metal elements is 50 mol% or more, can be 70 mol% or more, or can be 90 mol% or more. On the other hand, in an Al alloy, the proportion of Al element relative to all metal elements is, for example, 99 mol% or less. Furthermore, the shape of the Al current collector is, for example, foil or mesh. The thickness of the Al current collector is not particularly limited, but is, for example, 1 μm or more and 50 μm or less.

[0047] 2. Resin layer

[0048] The resin layer is a layer disposed on the surface of the Al current collector. Specifically, it is a layer disposed between the Al current collector and the negative electrode active material layer in the thickness direction of the negative electrode. Furthermore, the resin layer contains resin and Ni particles as a conductive additive.

[0049] Examples of the aforementioned resins include thermoplastic resins, thermosetting resins, and conductive polymers. The resin layer preferably contains a thermoplastic resin. A thermoplastic resin is a resin that softens upon heating. The softening temperature of the thermoplastic resin is, for example, 100°C or higher and 200°C or lower. Examples of thermoplastic resins include poly(meth)acrylic acid, poly(meth)acrylate, polyethylene, polypropylene, polyethylene terephthalate, polyether nitrile, polyimide, polyamide, polytetrafluoroethylene, polyacrylonitrile, poly(meth)acrylate, polyvinyl chloride, polyvinyl acetate, polyvinyl alcohol, and halogenated vinyl resins. Furthermore, "(meth)acrylic acid" is a concept that includes both acrylic acid and methacrylic acid, and "(meth)acrylate" is a concept that includes both acrylic esters and methacrylates.

[0050] Examples of thermosetting resins include epoxy resins and vinyl ester resins. The resin layer typically contains a cured product formed by curing the thermosetting resin. Additionally, examples of conductive polymers include polyaniline and polypyrrole. Furthermore, the resin layer may contain one or more types of resin.

[0051] Ni particles function as conductive additives in the resin layer. In this disclosure, Ni particles are particles containing Ni as the main element; they can be particles of elemental Ni or particles of Ni alloys. The resin layer as a conductive additive may contain only Ni particles or may contain other materials besides Ni particles, but the former is preferred. Even in the latter case, the resin layer preferably contains Ni particles as the main conductive additive. "Containing Ni particles as the main conductive additive" means that the proportion of Ni particles in the resin layer relative to all conductive additives is 50% by weight or more. The proportion of Ni particles can be 60% by weight or more, 80% by weight or more, 90% by weight or more, or 95% by weight or more. On the other hand, the proportion of Ni particles (the proportion of Ni particles when the resin layer contains multiple conductive additives) is, for example, 99% by weight or less. Furthermore, it is preferable that the resin layer as a conductive additive does not contain carbon-based conductive additives.

[0052] The average particle size of Ni particles (D) 50 There are no specific limitations, for example, below 500nm. 50 It can be below 400nm, or it can be below 300nm. On the other hand, D 50 For example, it can be 10nm or above, 50nm or above, 100nm or above, or 200nm or above. 50 It refers to the cumulative 50% of the particle size in the volume-based particle size distribution obtained based on a laser diffraction particle size distribution device.

[0053] In the resin layer, the weight ratio of Ni particles to resin is not particularly limited; for example, it can be 4.3 or less, 4.0 or less, 3.0 or less, 2.6 or less, or 1.5 or less. On the other hand, the weight ratio of Ni particles can be 0.5 or more, 1.0 or more, 1.5 or more, or 2.0 or more.

[0054] Furthermore, the proportion (by weight) of Ni particles relative to the total amount of resin and Ni particles in the resin layer is not particularly limited; for example, it can be 30% by weight, or 40% by weight or more, or 50% by weight or more. On the other hand, the proportion of Ni particles relative to the total amount of resin and Ni particles can be, for example, 90% by weight or less, or 80% by weight or less, or 70% by weight or less, or 60% by weight or less. Additionally, the proportion of Ni particles relative to all components in the resin layer can be, for example, 25% by weight or more.

[0055] The thickness of the resin layer is not particularly limited; for example, it can be 0.5 μm or more, or 1 μm or more. On the other hand, the thickness of the resin layer can be, for example, 10 μm or less, or 5 μm or less.

[0056] 3. Negative electrode active material layer

[0057] The negative electrode active material layer contains a reaction potential of 0.3V (Li). + Negative electrode active materials below / Li).

[0058] The reaction potential of the negative electrode active material can be 0.2V (Li + / Li) below, or 0.1V (Li) + / Li) or below. On the other hand, the reaction potential of the negative electrode active material is, for example, -0.5V (Li) + The reaction potential of the negative electrode active material can be determined by cyclic voltammetry (CV).

[0059] Examples of anode active materials include Si-based, carbon-based, and Li-based active materials. Si-based active materials are those containing the element Si. Examples of Si-based active materials include elemental Si, Si alloys, and Si oxides. Si alloys preferably contain Si as a main component. The proportion of Si in the Si alloy is, for example, 50 mol% or more and 99 mol% or less.

[0060] Carbon-based active materials are inorganic active materials containing carbon (C), such as graphite, hard carbon, and soft carbon. Li-based active materials are active materials containing lithium (Li), such as elemental Li and Li alloys.

[0061] The shape of the negative electrode active material can be exemplified by, for example, particulate or layered structures. The average particle size (D) of the negative electrode active material... 50 For example, the particle size can be 10 nm or larger, or even 100 nm or larger. On the other hand, the average particle size (D) of the negative electrode active material... 50 For example, it can be 50 μm or less, or even 20 μm or less. The proportion of negative electrode active material in the negative electrode active material layer is, for example, 50% by weight or more and 80% by weight or less.

[0062] The negative electrode active material layer may also contain at least one of a conductive additive, a binder, and an electrolyte, as needed. Examples of binders include rubber-based components such as butadiene rubber (BR), acrylic butadiene rubber (ABR), and styrene butadiene rubber (SBR), as well as fluorinated binders such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE). The proportion of binder in the negative electrode active material layer is, for example, 0.01% by weight or more and 5% by weight or less.

[0063] Examples of conductive additives include carbon materials. Examples of carbon materials include particulate carbon materials such as acetylene black (AB) and Ketjen black (KB), and fibrous carbon materials such as carbon fibers, carbon nanotubes (CNTs), and carbon nanofibers (CNFs). The proportion of the conductive additive in the negative electrode active material layer is, for example, 0.01% by weight or more and 10% by weight or less.

[0064] Examples of electrolytes include solid electrolytes. Examples of solid electrolytes include inorganic solid electrolytes such as sulfide solid electrolytes, oxide solid electrolytes, and halide solid electrolytes. Sulfide solid electrolytes contain sulfur (S) as the main anionic element. Oxide solid electrolytes contain oxygen (O) as the main anionic element. Halide solid electrolytes contain halogen as the main anionic element. Among these, sulfide solid electrolytes are preferred.

[0065] Other examples of solid electrolytes include polymer electrolytes, gel electrolytes, and other organic solid electrolytes. Liquid electrolytes (electrolytes) can also be cited as examples. The proportion of electrolyte in the negative electrode active material layer is, for example, 30% by weight or more and 80% by weight or less.

[0066] There is no particular limitation on the thickness of the negative electrode active material layer, for example, it can be above 0.5 μm and below 1000 μm.

[0067] 4. Battery

[0068] The negative electrode in this disclosure is used in the battery. Figure 2 This is a schematic cross-sectional view showing an example of a battery in this disclosure. Figure 2The battery 10 shown has: a positive electrode CA having a positive active material layer 5 and a positive current collector 6; a negative electrode AN having a negative current collector 1, a resin layer 2 and a negative active material layer 3; and an electrolyte layer EL disposed between the positive electrode CA and the negative electrode AN. In particular, in the battery 10 of this disclosure, the negative electrode AN is the aforementioned negative electrode.

[0069] The positive electrode active material layer contains at least a positive electrode active material. The positive electrode active material can be a conventionally known component used in batteries. Examples of positive electrode active materials include oxide active materials. Furthermore, the positive electrode active material layer may also contain at least one of an electrolyte, a conductive material, and a binder. The electrolyte, conductive material, and binder are the same as described above, and therefore their description is omitted here.

[0070] The electrolyte layer contains at least an electrolyte. Preferably, the electrolyte layer contains the aforementioned solid electrolyte. Alternatively, the electrolyte layer may also contain a liquid electrolyte.

[0071] Batteries typically have a positive current collector and a negative current collector. The positive and negative current collectors can be made of materials that are already known.

[0072] The battery disclosed herein can be a liquid-based battery or a solid-state battery. Furthermore, the solid-state battery can be a semi-solid-state battery or a fully solid-state battery. There is no particular limitation on the type of battery; a typical example is a lithium-ion rechargeable battery. Additionally, there is no particular limitation on the application of the battery; examples include power sources for hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), battery electric vehicles (BEVs), gasoline vehicles, and diesel vehicles. It is particularly preferred for use as a power source for driving hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), or battery electric vehicles (BEVs). Furthermore, the battery disclosed herein can be used as a power source for mobile bodies other than vehicles (e.g., trains, ships, aircraft) and also as a power source for electronic products such as information processing devices.

[0073] B. Manufacturing method of the negative electrode

[0074] Figure 3 This is a flowchart illustrating a method for manufacturing the negative electrode in this disclosure. For example... Figure 3 As shown, in the method for manufacturing the negative electrode, firstly, a resin slurry containing the aforementioned resin, Ni particles, and solvent is prepared (slurry preparation step). Next, the resin slurry is coated onto the surface of the Al current collector and dried to form the aforementioned resin layer (resin layer formation step). Then, the aforementioned negative electrode active material layer is formed on the surface of the aforementioned resin layer (negative electrode active material layer formation step).

[0075] In the negative electrode manufacturing method disclosed herein, a resin slurry containing resin, Ni particles, and solvent is coated onto the surface of an Al current collector and dried to form a resin layer. In other words, the resin layer is formed by a coating method. This allows for the simple manufacture of the negative electrode. Furthermore, since a resin slurry is used, a resin layer with well-dispersed Ni particles can be formed, which further suppresses the reaction of the Al current collector.

[0076] 1. Slurry preparation process

[0077] In the slurry preparation process, a resin slurry containing resin, Ni particles, and solvent is produced. The information regarding the resin, Ni particles, and negative electrode active material is the same as described in "A. Negative Electrode".

[0078] Regarding the solvent, there are no particular limitations as long as it can disperse the above components. Furthermore, the solvent in this disclosure is not only strictly a solvent, but also includes the concept of a dispersion medium. Examples of solvents include organic solvents such as butyl butyrate, dibutyl ether, heptane, and tetrahydrofuran. The ratio of resin to Ni particles in the resin slurry is the same as described in "A. Negative Electrode".

[0079] There are no particular limitations on the preparation method of the resin slurry. For example, methods such as using an ultrasonic dispersion device to stir and mix the resin, Ni particles, and solvent can be cited. Furthermore, the stirring and mixing process can be performed only once or more. In the latter case, for example, a method can be described by pre-mixing the resin and Ni particles, and then adding the solvent for further mixing.

[0080] 2. Resin layer formation process

[0081] In the resin layer formation process, the above-mentioned resin slurry is applied to the surface of the Al current collector and dried to form the resin layer. The resin layer is the same as described in "A. Negative Electrode".

[0082] The amount of resin slurry applied should be adjusted appropriately to form the desired resin layer. Furthermore, regarding drying conditions (drying temperature and drying time), there are no particular limitations as long as the solvent in the resin slurry can be removed, and adjustments can be made as needed.

[0083] 3. Negative electrode active material layer formation process

[0084] In the negative electrode active material layer formation process, a negative electrode active material layer is formed on the surface of the resin layer (the surface opposite to the Al current collector). There are no particular limitations on the method for forming the negative electrode active material layer; for example, a coating method using a negative electrode slurry can be cited.

[0085] The negative electrode slurry contains at least a negative electrode active material and a solvent, and may also contain at least one of a conductive additive, a binder, and an electrolyte, as needed. The negative electrode active material and solvent are as described above. The solvent may be the same as or different from the solvent in the resin slurry. The proportions of the negative electrode active material, conductive additive, binder, and electrolyte in the negative electrode slurry are the same as those described in "A. Negative Electrode". Furthermore, the negative electrode slurry may also be prepared before the resin layer formation process.

[0086] The application method is the same as described above. Furthermore, the description of the negative electrode active material layer is the same as that in "A. Negative Electrode".

[0087] 4. Other processes

[0088] In the manufacture of the negative electrode, a pressing process may also be included to densify the laminate containing the Al current collector, resin layer, and negative electrode active material layer. Pressing can be done by rolling or uniaxial pressing. The pressure in the pressing process is, for example, 100 MPa or more and 800 MPa or less. The pressing process can be carried out at room temperature or under heating.

[0089] The negative electrode manufactured through the above process is the same as the one described in "A. Negative Electrode".

[0090] Furthermore, this disclosure is not limited to the embodiments described above. The embodiments described above are illustrative, and all solutions that have substantially the same technical concept and achieve the same effect as those described in the claims of this disclosure are included within the technical scope of this disclosure.

[0091] [Example]

[0092] [Example 1]

[0093] As described below, a half cell was fabricated as an evaluation battery.

[0094] Vinyl resin and Ni particles (ni elemental particles, D) 50 =300nm) were weighed and mixed at a weight ratio of 28:72. Furthermore, the weight ratio of Ni particles to ethylene-based resin was 2.6. Solvent was added to the resulting mixture, and it was repeatedly mixed six times for 30 seconds each using an ultrasonic homogenizer. This yielded a resin slurry. The resin slurry was coated onto a 15μm thick negative electrode current collector (Al foil) using a doctor blade method and dried on a heating plate at 50°C for 20 minutes. Subsequently, it was further dried on a heating plate at 150°C for 30 minutes. This yielded a negative electrode component having a negative electrode current collector and a resin layer.

[0095] 100 mg of sulfide solid electrolyte (SE: Li2S-P2S5 series sulfide solid electrolyte) was added to a 10 mm cylindrical container and pressed at 100 MPa using SUS pins. This produced a sheet of solid electrolyte. The aforementioned negative electrode component and Li foil were punched to 11.28 mm. An Al foil, resin layer, sheet (solid electrolyte layer), and Li foil were sequentially arranged in a 11.28 mm cylindrical container and clamped using SUS pins. Furthermore, a constraint fixture was used to constrain the material with a pressure of 2 MPa. This produced an evaluation battery (half-cell).

[0096] [Example 2 and Example 3]

[0097] Except for changing the proportion of Ni particles in the resin layer as shown in Table 1, an evaluation battery was manufactured in the same manner as in Example 1.

[0098] Table 1

[0099] Resin (by weight %) Ni particles (wt%) Ni particles / resin Example 1 28 72 2.6 Example 2 38 62 1.6 Example 3 19 81 4.3

[0100] [Comparative Example 1]

[0101] As the negative electrode component, an Al foil with a thickness of 15 μm (a negative electrode component without a resin layer) was used, and the evaluation battery was fabricated in the same manner as in Example 1.

[0102] [Comparative Example 2]

[0103] Ethylene resin and acetylene black were weighed and mixed at a weight ratio of 60:40. The resulting mixture was used to form a resin layer, and a negative electrode component and an evaluation battery were fabricated in the same manner as in Example 1.

[0104] [Comparative Example 3]

[0105] The ethylene-based resin and VGCF-H were weighed and mixed at a weight ratio of 60:40. The resulting mixture was used to form a resin layer, and a negative electrode component and an evaluation battery were fabricated in the same manner as in Example 1.

[0106] [Rating 1]

[0107] The flow current was measured after 100 hours using an electrochemical measuring apparatus (VMP300) with each half-cell set to a constant voltage of 0.1V. The current value of Comparative Example 2 was set to 100V for comparison. The results are shown below. Figure 4 .

[0108] like Figure 4As shown, the current value could not be measured in Examples 1 to 3, confirming that no reaction of the Al current collector occurred. On the other hand, large current values ​​were measured in Comparative Examples 1 to 3, confirming that the Al current collector had reacted (deteriorated). It is believed that although the current values ​​of Comparative Examples 2 and 3, which have a resin layer, are smaller than those of Comparative Example 1, the Al reaction itself occurred because carbon-based conductive additives were contained as conductive additives.

[0109] [Example 4]

[0110] As described below, a full-cell (all-solid-state) battery was fabricated as an evaluation battery.

[0111] (Fabrication of the positive electrode stack)

[0112] By using the positive electrode active material (NCA:LiNi) 0.8 Co 0.15 Al 0.05 The cathode slurry was prepared by stirring O2, a sulfide solid electrolyte (SE: Li2S-P2S5-based sulfide solid electrolyte), vapor-grown carbon fiber (VGCF), polyvinylidene fluoride (PVdF) binder, and butyl butyrate using an ultrasonic dispersion device. The weight ratio of NCA, SE, VGCF, and binder in the cathode slurry was 78.3:18.8:2.9:2.8. The cathode slurry was coated onto the cathode current collector (Al foil) using a doctor blade method and dried on a heating plate at 50°C for 20 minutes. Subsequently, it was further dried on a heating plate at 150°C for 30 minutes. This yielded a cathode with a cathode current collector and a cathode active material layer.

[0113] A slurry containing a sulfide solid electrolyte (SE: Li₂S-P₂S₅-based sulfide solid electrolyte), an acrylate butadiene rubber (ABR) binder, heptane, and butyl butyrate was prepared by ultrasonic dispersion. The weight ratio of SE to binder in the slurry was 99.4:0.6. The SE slurry was applied to a stainless steel (SUS) foil using a scraper method and dried on a heated plate at 50°C for 1 minute. Subsequently, it was further dried on a heated plate at 150°C for 30 minutes. This yielded a transfer component with an SE layer.

[0114] The positive electrode and transfer component are stacked with the positive active material layer and the SE layer facing each other, and pressed using a roller press at a pressure of 50 kN / cm and a temperature of 160°C. After pressing, the SUS foil of the transfer component is peeled off, and the laminate is punched into 1 cm pieces. 2 The size of the cathode stack was thus obtained.

[0115] (Fabrication of the negative electrode stack)

[0116] Vinyl resin and Ni particles (ni elemental particles, D) 50 =300nm) were weighed and mixed at a weight ratio of 28:72. Furthermore, the weight ratio of Ni particles to ethylene-based resin was 2.6. Solvent was further added to the mixture, and it was mixed using an ultrasonic homogenizer for 30 seconds × 6 times. This produced a resin slurry. The resin slurry was coated onto a 15μm thick negative electrode current collector (Al foil) using a scraper method and dried on a heating plate at 50°C for 20 minutes. Subsequently, it was further dried on a heating plate at 150°C for 30 minutes. This yielded a negative electrode current collector with a resin layer.

[0117] A negative electrode slurry was obtained by stirring the negative electrode active material (silicon), sulfide solid electrolyte (SE: Li2S-P2S5-based sulfide solid electrolyte), vapor-grown carbon fiber (VGCF), polyvinylidene fluoride (PVdF) binder, and butyl butyrate using an ultrasonic dispersion device. The weight ratio of silicon, SE, VGCF, and binder was 49:41.2:7.5:6.6. The negative electrode slurry was coated onto a resin layer using a doctor blade method and dried on a heating plate at 50°C for 20 minutes. Subsequently, it was further dried on a heating plate at 150°C for 30 minutes. This yielded a negative electrode having a negative current collector, a resin layer, and a negative electrode active material layer sequentially.

[0118] The transfer component was fabricated in the same manner as described above. The negative electrode and the transfer component were laminated with the negative electrode active material layer and the SE layer facing each other, and pressed using a roller press at a pressure of 50 kN / cm and a temperature of 160°C. After pressing, the SUS foil of the transfer component was peeled off, and the laminate was punched to a 1 cm diameter. 2 The size was determined. Transfer components were further overlapped on the pressed SE layer and pressed using a flat uniaxial press (pressing pressure 100 MPa, temperature 25°C). Subsequently, the SUS foil from which the transfer components were peeled off was punched into 1.08 cm pieces. 2 The size of the anode material was determined. Thus, a negative electrode stack with two SE layers superimposed on the negative electrode active material layer was obtained.

[0119] (The fabrication of an all-solid-state battery)

[0120] The above-described positive electrode stack and negative electrode stack were stacked with the SE layers facing each other. The stack was pressed using a planar uniaxial press at a pressing pressure of 500 MPa and a temperature of 160°C. This yielded an all-solid-state battery.

[0121] [Reference Example]

[0122] As the negative electrode current collector, a Ni foil without a resin layer was used, and the evaluation battery was fabricated in the same manner as in Example 4.

[0123] [Rating 2]

[0124] The battery was clamped between two constraint plates, and the two constraint plates were fastened with a constraint pressure of 10 MPa using a fastening part to fix the distance between the constraint plates. For the constrained battery, constant current charging was performed at a current value of 0.1C until 4.05V, followed by low-voltage charging at 4.05V until a current value of 0.01C. Subsequently, constant current discharging was performed at a current value of 0.1C until 2.5V, followed by low-voltage discharging at 2.5V until a current value of 0.01C. This charge-discharge cycle was repeated to obtain the discharge capacity of the second cycle. The discharge capacity of the reference example was used as 100 for relative evaluation. The results are shown in Table 2.

[0125] Table 2

[0126] Example 4 Reference Example Discharge capacity (relative value) 100 100

[0127] As shown in Table 2, no difference was observed in the discharge capacity of the second cycle between Example 4 and the Reference Example. This confirms that current collector degradation is a problem unique to Al current collectors.

Claims

1. A negative electrode for a battery, the negative electrode comprising, in sequence: a negative electrode current collector as an Al current collector, a resin formed on the surface of the Al current collector, and a negative electrode active material layer. The resin layer contains resin and Ni particles as a conductive additive. The negative electrode active material layer contains Li-based... + / Li is a negative electrode active material with a reaction potential below 0.3V.

2. The negative electrode according to claim 1, wherein the weight ratio of the Ni particles to the resin in the resin layer is 4.3 or less.

3. The negative electrode according to claim 1, wherein the Ni particles have a D 50 The average particle size is below 500 nm.

4. The negative electrode according to claim 1, wherein the negative electrode active material contains a Si-based active material.

5. A method for manufacturing a negative electrode, comprising a slurry preparation step, a resin layer formation step, and a negative electrode active material layer formation step, according to any one of claims 1 to 4. In the slurry preparation process, a resin slurry containing the resin, the Ni particles, and the solvent is prepared. In the resin layer formation process, the resin slurry is applied to the surface of the Al current collector and dried to form the resin layer. In the negative electrode active material layer formation process, the negative electrode active material layer is formed on the surface of the resin layer.

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