Material for forming a negative electrode for all-solid-state lithium-ion secondary batteries, and all-solid-state lithium-ion secondary batteries

Abstract

When an all-solid-state lithium battery (LiB) using silicon as the negative electrode active material is charged and discharged, the size of the amorphous silicon blocks that spontaneously and non-uniformly form is controlled to be as uniform as possible, improving cycle characteristics and increasing current density. [Solution] A negative electrode active material layer made of a composition for forming a negative electrode of an all-solid-state lithium-ion secondary battery containing silicon crystals is formed at intervals on island-shaped protrusions, and a connecting layer made of the composition for forming a negative electrode of an all-solid-state lithium-ion secondary battery is formed on the bottom surface of the grooves of the negative electrode active material layer formed between the island-shaped protrusions, and the negative electrode active material layer formed continuously with the island-shaped protrusions is on the negative electrode current collector. Negative electrode current collector base area 1 cm 2 The surface area of ​​the negative electrode active material layer is 1.25 to 31.25 cm². 2 And, Negative electrode current collector base area 1 cm 2 The number of island-shaped protrusions per unit area is 5 × 10 4 ~5×10 7 A material for forming the negative electrode of an all-solid-state lithium-ion secondary battery.

Description

[Technical Field]

[0001] This invention relates to a material for forming a negative electrode for all-solid-state lithium-ion secondary batteries. Furthermore, this invention relates to an all-solid-state lithium-ion secondary battery using a negative electrode obtained from the said forming material. [Background technology]

[0002] Lithium-ion secondary batteries (hereinafter sometimes abbreviated as "LiB") are widely used because they have a high energy density among secondary batteries. A well-known type of lithium-ion secondary battery is a non-aqueous electrolyte LiB, which consists of a positive electrode containing an active material such as lithium cobalt oxide (LiCoO2) or lithium iron phosphate (LiFePO4), and a negative electrode containing an active material capable of intercalating and releasing lithium ions, separated by a separator, and filled with a non-aqueous electrolyte, which is an electrolyte consisting of a lithium salt such as LiBF4 dissolved in an organic solvent such as ethylene carbonate. Charging and discharging of a non-aqueous electrolyte LiB is performed by the movement of lithium ions from the secondary battery between the positive and negative electrodes via the non-aqueous electrolyte, and the insertion and removal of lithium ions from the active materials of the positive and negative electrodes.

[0003] With the expanding applications of batteries, large batteries such as automotive batteries and stationary batteries are attracting attention. Ensuring safety is even more important for large batteries than for small batteries, and all-solid-state lithium-ion secondary batteries (all-solid-state LiBs) have been proposed, which are safer and more reliable than LiBs that use liquid electrolytes, because they replace the liquid electrolyte with an inorganic solid electrolyte, making it easier to ensure safety even when scaled up.

[0004] Furthermore, carbon has conventionally been used as the negative electrode active material for LiBs. From the perspective of increasing capacity, the use of silicon as the negative electrode active material is being considered. Silicon has a theoretical capacity density of 4200 mAh / g (volume capacity density of 2370 mAh / cm³) as a negative electrode active material. 3), which has a capacity-to-weight ratio approximately 11 times higher and a capacity-to-volume ratio approximately 3 times higher than that of carbon, and is expected to dramatically increase the capacity of secondary batteries.

[0005] However, silicon undergoes a very large volume change of about 400% during charge and discharge, so degradation such as pulverization and isolation caused by the expansion and contraction of silicon occurs during repeated charge and discharge cycles. As a result, the charge-discharge efficiency and cycle life characteristics are poor, and these issues have become obstacles particularly in large-sized batteries for electrified vehicles that are premised on long-term use.

[0006] For this reason, although high capacity density is expected from lithium ion secondary batteries using silicon as a negative electrode active material, their practical application has been difficult. Various technical proposals have been made from the perspective of suppressing electrode collapse accompanying the expansion and contraction of silicon during charge and discharge. Patent Document 1 (Japanese Unexamined Patent Publication No. 2003-109590) discloses a negative electrode material in which volume change is mitigated by doping silicon with phosphorus, boron or aluminum. Patent Document 2 (Japanese Unexamined Patent Publication No. 2005-11699) proposes a battery structure that absorbs the volume change of the negative electrode and reduces the influence of the volume change by controlling the density of the negative electrode and the size of the gaps inside the battery. However, the secondary batteries described in these patent documents use non-aqueous electrolytes, which are not preferable from the viewpoint of safety as mentioned above.

[0007] In addition, Patent Document 3 (Japanese Unexamined Patent Publication No. 2021-68706) exemplifies silicon as one of the negative electrode materials for all-solid-state LiB, but there is no use example, therefore there is no description of the problems of silicon pulverization and isolation caused by repeated charge and discharge, and there is no suggestion of a solution to these problems. Further, although it is described as an all-solid-state battery, it uses an ionic liquid and is not an all-solid-state battery in the strict sense, and the risk of liquid leakage has not been eliminated.

[0008] Non-Patent Document 1 proposes an all-solid-state lithium battery using silicon crystal particles having an average particle diameter of 0.8 to 3.9 μm as a negative electrode active material. It is presumed that by using silicon crystals having a specific particle size, appropriate voids are generated in the negative electrode active material layer, and the voids alleviate stress during volume change caused by expansion and contraction of the negative electrode active material, so that micronization of the negative electrode active material does not occur and isolation thereof is also suppressed.

[0009] As described above, from the viewpoint of improving safety and capacity, although there is high demand for realizing an all-solid-state lithium battery using silicon as a negative electrode active material, conventionally proposed techniques have many technical problems as mentioned above.

[0010] In order to solve such problems, the present inventor focused on the technology described in Non-Patent Document 1, produced a lithium battery using silicon crystal particles as a negative electrode active material, and attempted to evaluate its characteristics. As a result, improvement in cycle characteristics was observed, so further studies were conducted and the structure of the negative electrode active material layer was carefully examined. It was confirmed that, when a battery having a negative electrode active material layer using silicon crystal particles of the above-mentioned specific particle size is assembled and charged / discharged, part or all of the silicon crystal particles become amorphous, and as shown in the SEM image in FIG. 5, the particles are divided into block shapes and densified in each block. The blocked negative electrode active material layer is dense and adheres closely to the negative electrode current collector, thus exhibiting excellent electronic conductivity. In addition, gaps are formed between the respective blocks, and it is considered that the gaps alleviate stress during volume change caused by expansion and contraction of each block, thereby suppressing micronization and isolation of silicon, which is the negative electrode active material.

[0011] However, the sizes of the respective blocks spontaneously generated during charge and discharge and the gaps between the respective blocks are not uniform. For this reason, there is a possibility that volume change caused by expansion and contraction of blocks having non-uniform sizes cannot be completely alleviated by gaps having non-uniform widths. That is, when large blocks are adjacent to each other with a narrow gap, the blocks may contact each other and collapse during charge and discharge, leading to micronization and isolation.

[0012] Furthermore, since many of the grooves formed between the blocks extend to the negative electrode current collector, solid electrolyte may penetrate the interface between the blocks and the negative electrode current collector, creating gaps and potentially promoting the isolation of silicon.

[0013] Thus, in this technology, there are concerns that variations in performance, such as discharge performance and durability, may occur among the resulting all-solid-state LiBs, which could pose problems in industrial implementation.

[0014] Therefore, in Patent Document 4, the present inventors have proposed pre-shaping the negative electrode active material layer, which is made of an all-solid-state lithium-ion secondary battery negative electrode formation composition containing silicon crystals, into blocks. By pre-shaping the negative electrode active material layer, the size of each block that spontaneously forms during charging and discharging, and the gaps between each block can be controlled to some extent, thereby controlling contact between blocks during charging and discharging and reducing the miniaturization and isolation of the active material.

[0015] While the above configuration improves cycle characteristics, further improvements in current density are desired for lithium-ion batteries (LiBs) using silicon as the active material. Improving current density shortens the time required for charging and discharging. [Prior art documents] [Patent Documents]

[0016] [Patent Document 1] Japanese Patent Publication No. 2003-109590 [Patent Document 2] Japanese Patent Publication No. 2005-11699 [Patent Document 3] Japanese Patent Publication No. 2021-68706 [Patent Document 4] Patent No. 7492094 [Non-patent literature]

[0017] [Non-Patent Document 1] Machida, Shinya et al. (2022) "Fabrication of coated silicon electrodes and their application to negative electrodes for all-solid-state batteries," Proceedings of the 2022 Autumn Meeting of the Japan Society of Powder and Powder Metallurgy, 2-60A [Overview of the project] [Problems that the invention aims to solve]

[0018] Therefore, the inventors conceived the present invention to solve the aforementioned problems by controlling the size of amorphous silicon blocks, which are spontaneously and non-uniformly generated when an all-solid-state LiB using silicon as the negative electrode active material is charged and discharged, to be as uniform as possible, and by making it difficult for gaps to be generated between the blocks and the negative electrode current collector in the grooves formed between the blocks, thereby improving the cycle characteristics and increasing the surface area of ​​the negative electrode active material layer, which increases the reaction field between Li ions and the active material, improving the current density. [Means for solving the problem]

[0019] To solve these problems, the present invention encompasses the following: (1) A negative electrode active material layer made of a composition for forming a negative electrode of an all-solid-state lithium-ion secondary battery containing silicon crystals is formed at intervals on the island-shaped protrusions, and a connecting layer made of the composition for forming a negative electrode of an all-solid-state lithium-ion secondary battery is formed on the bottom surface of the grooves of the negative electrode active material layer formed between the island-shaped protrusions, and the negative electrode active material layer formed continuously with the island-shaped protrusions is on the negative electrode current collector, Negative electrode current collector base area 1 cm 2 The surface area of ​​the negative electrode active material layer is 1.25 to 31.25 cm². 2 And, Negative electrode current collector base area 1 cm 2 The number of island-shaped protrusions per unit area is 5 × 10 4 ~5×10 7 A material for forming the negative electrode of an all-solid-state lithium-ion secondary battery. (2) The material for forming a negative electrode of an all-solid-state lithium-ion secondary battery according to (1), wherein the width of the island-shaped protrusions is in the range of 1 μm to 30 μm, the height is in the range of 2 μm to 25 μm, the spacing between the island-shaped protrusions is in the range of 1 μm to 20 μm, and the thickness of the connecting layer is in the range of 3 μm to 10 μm. (3) The material for forming a negative electrode of an all-solid lithium-ion secondary battery according to (1), wherein the negative electrode active material layer on the negative electrode current collector is formed in a pattern of cylindrical, elliptical prism, polygonal prism, frustoconical, elliptical frustoconical, polygonal frustoconical, conical, elliptical conical, polygonal pyramidal, linear, and lattice shapes of island-shaped protrusions. (4) An all-solid-state lithium-ion secondary battery having a positive electrode, a negative electrode, and a solid electrolyte layer, An all-solid-state lithium-ion secondary battery characterized in that the negative electrode is made of an all-solid-state lithium-ion secondary battery negative electrode forming material described in any one of (1) to (3). (5) The all-solid-state lithium-ion secondary battery according to (4), wherein the solid electrolyte layer is also present in the groove portion. [Effects of the Invention]

[0020] In the present invention, when producing an all-solid-state lithium battery, silicon crystal is used as a negative electrode active material, island-shaped protrusions made of a negative electrode-forming composition containing the negative electrode active material are formed, and on the bottom surface of the groove formed between the island-shaped protrusions, a layer formed of the composition for forming a negative electrode of an all-solid-state lithium-ion secondary battery (hereinafter referred to as a "connection layer") is continuously formed with the island-shaped protrusions, thereby forming a negative electrode active material layer on a negative electrode current collector to obtain an all-solid-state lithium battery negative electrode-forming material which is a precursor of an all-solid-state lithium battery negative electrode. When an all-solid-state lithium-ion secondary battery is assembled using this all-solid-state lithium battery negative electrode-forming material and charged / discharged, part or all of the silicon crystal particles serving as the negative electrode active material become amorphous and densified. At the same time, while substantially maintaining the shape and size of the island-shaped protrusions, the negative electrode active materials fuse to form a block-shaped mass. This block-shaped mass is less likely to collapse even due to expansion and contraction during charge and discharge of the all-solid-state lithium battery, resulting in good cycle characteristics. Furthermore, since each of the above blocks is in close contact with the negative electrode current collector and the solid electrolyte, high electron conductivity and ion conductivity can be achieved without using an electron conductivity imparting agent or an ion conductivity imparting agent, and the current density during charge and discharge can be increased. In addition, in the dense block described above, the formation of large cracks is suppressed, so the phenomenon that the solid electrolyte penetrates into the silicon block during charge and discharge is less likely to occur, and capacity reduction due to silicon micronization and isolation can be avoided. A solid electrolyte can be present in the grooves (gaps) between the blocks, which has a function of absorbing volume expansion during charge and discharge, and makes it difficult for the negative electrode to collapse due to volume change, which is a problem caused by repeated use. Furthermore, by forming a connection layer on the bottom surface of the groove formed between the island-shaped protrusions, the phenomenon that the solid electrolyte penetrates into the interface between silicon and the negative electrode current collector can be effectively prevented, and the isolation of silicon can be prevented, thereby further improving the cycle characteristics of the all-solid-state lithium battery.

[0021] Furthermore, the bottom area of the negative electrode current collector is 1 cm 2 the surface area of the negative electrode active material layer per unit is 1.25 to 31.25 cm 2 and the bottom area of the negative electrode current collector is 1 cm 2 the number of the island-shaped protrusions per unit is 5×10 4 to 5×10 7Because island-like protrusions are formed to create individual protrusions, the reaction field between Li ions and the active material increases, improving the current density.

[0022] Furthermore, in a preferred embodiment, by pre-forming the negative electrode active material layer in a pattern, the size of the amorphous silicon blocks formed after charging and discharging can be made uniform, and the spacing between each block can also be made uniform.

[0023] As a result, all-solid-state lithium-ion secondary batteries with good cycle characteristics and high current density during charging and discharging can be obtained with extremely little variation in performance between products. [Brief explanation of the drawing]

[0024] [Figure 1] This is a schematic cross-sectional view showing one embodiment of the material for forming an all-solid-state LiB anode according to the present invention. [Figure 2] This is a schematic plan view showing one embodiment of the material for forming an all-solid-state LiB anode according to the present invention. [Figure 3] This is a plan view showing another embodiment of the all-solid-state LiB anode forming material according to the present invention. [Figure 4] This is a schematic cross-sectional view showing one aspect of the state of the all-solid-state LiB according to the present invention before charging and discharging. [Figure 5] This is an SEM image showing the state in which the active material layer has become blocked after charging and discharging in an all-solid-state lithium battery (LiB) in which the all-solid-state LiB negative electrode active material layer is formed on the entire surface of the negative electrode current collector. [Modes for carrying out the invention]

[0025] Embodiments of the present invention will be described below. First, negative electrode active material particles for all-solid-state lithium-ion secondary batteries will be described, followed by a composition for forming a negative electrode for all-solid-state lithium-ion secondary batteries containing the particles, and further, an all-solid-state lithium-ion secondary battery containing a negative electrode material obtained using the same, and a negative electrode for all-solid-state lithium-ion secondary batteries.

[0026] In this specification, an all-solid-state battery refers to a battery that does not contain liquid substances such as non-aqueous electrolytes or ionic liquids as an electrolyte.

[0027] The negative electrode forming material for all-solid-state lithium-ion secondary batteries is a laminate formed immediately after coating and drying a negative electrode forming composition for all-solid-state lithium-ion secondary batteries onto a negative electrode current collector, and contains negative electrode active material before charging and discharging. During charging and discharging, the silicon crystal particles, which are the negative electrode active material, become amorphous and fuse together into block-like structures, becoming denser.

[0028] (Negative electrode active material particles for all-solid-state lithium-ion secondary batteries) The negative electrode active material particles for all-solid-state lithium batteries used in this invention consist of silicon crystals. When a battery is assembled using this negative electrode active material and charged and discharged, some or all of the silicon crystal particles become amorphous, fuse together, and densify. As a result, a negative electrode is obtained with less capacity reduction due to silicon miniaturization and isolation, and the cycle characteristics are improved.

[0029] The term "silicon crystal" refers to both polycrystalline and single-crystal silicon. Therefore, the negative electrode active material particles of the present invention may be polycrystalline silicon particles, single-crystal silicon particles, or a mixture thereof. Polycrystalline silicon particles may be obtained by crushing and classifying polycrystalline silicon rods obtained by the so-called Siemens process. Single-crystal silicon particles may be obtained by crushing and classifying single-crystal silicon obtained by the so-called Czochralski process. Alternatively, they may be obtained by crushing and classifying metallic silicon obtained by the silica reduction method. Silicon crystals exhibit clear peaks when measured by X-ray diffraction.

[0030] The average particle size of the silicon crystal particles is preferably 0.3 to 10 μm, and more preferably 0.8 to 3.0 μm, from the viewpoint of promoting block formation and densification of the negative electrode active material layer. Note that the average particle size refers to the 50% cumulative diameter (D50) as measured by the particle size distribution by laser scattering method.

[0031] Silicon crystal particles having the following characteristics are more preferable from the viewpoint of promoting block formation and densification of the negative electrode active material layer.

[0032] The particle shape will be irregular when obtained by grinding, but other shapes such as spherical can also be used without particular restrictions. To improve the adhesion between the silicon particles and the binder components described later, the silicon particles may be subjected to a surface treatment.

[0033] While the purity of the silicon crystal is not particularly limited, in this invention, the purity of the silicon crystal is preferably 90% by mass or higher. Specifically, it is preferable to use silicon with an oxygen concentration of less than 5.0% by mass, a nitrogen concentration of less than 1.0% by mass, and a halogen element concentration of less than 0.1% by mass. Since oxygen, nitrogen, and halogen elements combine with Li, they form irreversible capacities, which degrades the battery's performance, so it is preferable to control them within the above ranges.

[0034] Furthermore, doped silicon can be used in this invention because it may improve the chemical stability to sulfide-based solid electrolytes or improve the diffusibility of lithium. Preferably, elements with a single crystal atomic radius larger than that of silicon are used as doping agents. Examples of such elements include P, Ge, Sn, and Sb. When silicon is alloyed with such elements, the interatomic distances are wider than in pure silicon, and it is expected that the insertion and removal of Li will proceed more smoothly.

[0035] (Composition for forming the negative electrode of an all-solid-state lithium-ion secondary battery) The above-mentioned negative electrode active material is mixed with the components constituting the negative electrode to form a negative electrode forming composition, and a negative electrode is obtained by forming a negative electrode active material layer on a negative electrode current collector. When a battery is assembled using the above-mentioned negative electrode active material and charged and discharged, some or all of the silicon crystal particles become amorphous, fuse into blocks, and become denser in each block. The block-formed negative electrode active material layer is dense and adheres closely to the negative electrode current collector, thus exhibiting excellent electronic conductivity. For this reason, with the all-solid-state LiB of this embodiment, the amount of electronic conductivity imparting agent used can be reduced, and in some cases, it can even be omitted.

[0036] In other words, the composition for forming an all-solid-state LiB anode contains the above-mentioned anode active material particles, and preferably the content of the electron conductivity imparter is 5 parts by mass or less per 100 parts by mass of the anode active material particles. According to the present invention, since the proportion of the electron conductivity imparter is reduced, the relative amount of active material particles can be increased, which can contribute to improving capacity. The content of the electron conductivity imparter in the composition for forming an all-solid-state LiB anode is preferably 3% by mass or less, more preferably 1% by mass or less, and more preferably substantially absent.

[0037] The composition for forming an all-solid-state LiB anode may contain an ion conductivity imparting agent to improve ion conductivity. As such an ion conductivity imparting agent, a solid electrolyte described later can be used. If the amount of ion conductivity imparting agent is too high, the relative amount of active material particles decreases, and the cycle characteristics also deteriorate. Therefore, the content of the ion conductivity imparting agent in the composition for forming an all-solid-state LiB anode is preferably 30% by mass or less, more preferably 20% by mass or less, and more preferably substantially absent.

[0038] The composition for forming the all-solid-state LiB anode may contain a binder, plasticizer, etc. The total amount of these components is preferably 20 parts by mass or less, and more preferably 15 parts by mass or less, per 100 parts by mass of anode active material particles. If the amount of binder or plasticizer is too high, the amount of active material in the anode active material layer will relatively decrease, which is undesirable for increasing battery capacity.

[0039] Examples of binders include thermosetting resins such as thermosetting polyimide, phenolic resin, acrylic resin, epoxy resin, urea resin, melamine resin, unsaturated polyester resin, and polyurethane; cellulose derivatives such as carboxymethylcellulose, hydroxypropylmethylcellulose, hydroxypropylcellulose, ethylcellulose, hydroxyethylcellulose, and hydroxymethylcellulose, or water-soluble polymers such as polyvinyl alcohol; polycarbonate resins such as polypropylene carbonate; polyvinylidene fluoride, etc.; styrene-butadiene copolymer (so-called SBR rubber), styrene-propylene copolymer, and styrene-ethylene-propylene copolymer (so-called SES and SEPS).

[0040] Furthermore, the all-solid-state LiB anode forming composition may include a dispersion medium for coating when forming island-shaped protrusions made of the all-solid-state LiB anode forming composition (described later) on the anode current collector. The dispersion medium can be appropriately selected from alcohols, aldehydes, ketones, ethers, esters, amides, imides, aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, heterocyclic compounds, etc. For example, methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, pentyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol, 2-ethylhexyl alcohol, benzyl alcohol, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, ethylene glycol monoisopropyl ether, diethylene glycol monoisopropyl ether, triethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, diethylene glycol butyl ether, triethylene glycol monobutyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, ethyl acetate. n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, hexyl acetate, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether acetate, ethylene glycol monoisopropyl ether acetate, diethylene glycol monoisopropyl ether acetate, triethylene glycol monoisopropyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monobutyl ether acetate, triethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate, hexane, nonane, decane, isodecane, dodecane, isododecane, turpentine, naphthenic solvents, isoparaffinic solvents, cyclohexane, methylcyclohexane, dimethylcyclohexane, ethylcyclohexane, alkylcyclohexane, toluene,Examples of dispersion media include xylene, aromatic high-boiling point solvents, acetone, methyl ethyl ketone, methyl pentyl ketone, methyl isobutyl ketone, cyclohexanone, terpineol, dihydroterpineol, and dihydroterpineol acetate, NMP (N-methylpyrrolidone), methoxybenzene, diethyl ether, dipropyl ether, and dibutyl ether. These may be used individually or in combination. The amount of dispersion media used should be appropriately determined so that the viscosity of the paste containing the all-solid-state LiB anode forming composition is optimal for the anode active material layer formation method. Such dispersion media is removed by drying after coating the paste containing the all-solid-state LiB anode forming composition.

[0041] (Material for forming negative electrodes in all-solid-state lithium-ion secondary batteries) A material for forming an all-solid-state LiB negative electrode is obtained by forming a negative electrode active material layer made of the above-mentioned all-solid-state LiB negative electrode formation composition on a negative electrode current collector. The negative electrode formation material is one of the components that make up the battery and functions as a negative electrode itself, but when the LiB is assembled and charged and discharged, the silicon crystal becomes amorphous, so its crystal structure is different from that of the negative electrode inside the battery after charging and discharging.

[0042] The packing density of silicon, which is the active material in the negative electrode active material layer described above, is preferably in the range of 35 to 55% by volume, and more preferably in the range of 40 to 50% by volume. Because the packing density of the active material is low and voids exist in the negative electrode active material layer, lithium ions are absorbed into the silicon active material during charging and discharging, and the volume expansion during amorphous formation (lithium-silicon alloy formation) can be mitigated. The packing density of the active material described above can be adjusted by the particle size or particle size distribution of the silicon particles, the amount of binder added, etc. Note that the packing density of the active material in the negative electrode active material layer refers to the ratio of the volume of silicon to the volume of the negative electrode.

[0043] Generally, copper foil, nickel foil, or SUS foil is used as the negative electrode current collector, but other conductive metal foils may also be used. The negative electrode current collector may be electrolytic copper with a rust-preventive surface treatment. The thickness of the negative electrode current collector is not particularly limited, but from the viewpoint of miniaturization of the battery and handling, a thickness of 3 μm to 100 μm is usually used, and when using the roll-to-roll method, a thickness of 5 μm to 50 μm is preferably used. The shape of the negative electrode current collector may be a sheet without holes, or a sheet with holes such as a two-dimensional mesh, a three-dimensional net, or perforated metal. The surface of the negative electrode current collector may be subjected to known surface treatments, such as mechanical surface treatment, etching, chemical conversion treatment, anodizing, wash primer, corona discharge, and glow discharge.

[0044] In a negative electrode active material layer containing silicon crystals, during charging and discharging, the silicon crystal particles, which are the negative electrode active material, become amorphous and fuse into blocks, becoming denser. However, because the block formation of the negative electrode active material layer occurs spontaneously during charging and discharging, the size, shape, and gaps between blocks tend to be uneven. When the size, shape, and gaps between blocks are uneven, the expansion and contraction during charging and discharging can cause adjacent blocks to come into contact, generating a compressive force that can cause the blocks to crack. As a result, the negative electrode active material may become finer and isolated, leading to a decrease in capacity. In addition, many of the grooves formed between blocks reach the negative electrode current collector, and the intrusion of solid electrolyte into the interface between the blocks and the negative electrode current collector creates gaps, promoting block delamination and exacerbating silicon isolation.

[0045] The inventors diligently investigated means to control the size, shape, and spacing of spontaneously generated blocks, and conceived of forming the negative electrode active material layer of the all-solid-state LiB negative electrode material in advance with island-like protrusions and spacing them apart, and forming a connecting layer to cover the bottom of the grooves formed between these island-like protrusions.

[0046] In other words, as shown in Figure 1 (cross-sectional view) and Figure 2 (plan view), the all-solid-state LiB negative electrode forming material 10 of this embodiment has a negative electrode active material layer 2 made of the all-solid-state LiB negative electrode forming composition on a negative electrode current collector 1, the negative electrode active material layer 2 has island-shaped protrusions 11 formed at intervals, and a connecting layer 13 made of the all-solid-state lithium-ion secondary battery negative electrode forming composition is formed continuously with the island-shaped protrusions on the bottom surface of the grooves 12 formed between the island-shaped protrusions.

[0047] In the all-solid-state LiB negative electrode forming material 10 of this embodiment, the bottom area of ​​the negative electrode current collector 1 is 1 cm². 2 The surface area of ​​the negative electrode active material layer 2 is 1.25 to 31.25 cm². 2 The length is preferably 1.5 to 30 cm. 2 And more preferably 3.0 to 25 cm 2 That is the case.

[0048] The bottom area of ​​the negative electrode current collector 1 is the area of ​​the plane viewed from below in the configuration shown in Figure 1, and is equal to the area of ​​the all-solid-state LiB negative electrode forming material 10 viewed from above in this embodiment. The surface area of ​​the negative electrode active material layer 2 is the sum of the areas of the top surface, side surface, and connecting layer 13 of the island-shaped protrusions 11. Although numerous negative electrode active material particles exist within the negative electrode active material layer 2, the surface area of ​​the particles inside the negative electrode active material layer 2 is not included in the surface area of ​​the negative electrode active material layer 2. In other words, the surface area of ​​the negative electrode active material layer 2 is the apparent sum of the areas of the top surface, side surface, and connecting layer 13 of the island-shaped protrusions 11.

[0049] Furthermore, the bottom area of ​​the negative electrode current collector is 1 cm². 2 The number of island-shaped protrusions per unit area is 5 × 10 4 ~5×10 7 There are individual units, preferably 1 × 10 5 ~4×10 7 The number of units is 1.5 × 10, and more preferably 1.5 × 10 5 ~3×10 7 There are individual island-shaped protrusions. The number of island-shaped protrusions can be confirmed by observation from the upper surface of the negative electrode active material layer 2.

[0050] In the all-solid-state LiB anode forming material 10 of this embodiment, numerous fine island-like protrusions are formed as described above, which increases the reaction field between Li ions and the active material, thereby improving the current density.

[0051] The preferred dimensions of each part of the negative electrode active material layer 2 formed on the negative electrode current collector will be explained with reference to Figure 1. The width (W) of the island-shaped protrusion 11 is preferably in the range of 1 μm to 30 μm, more preferably 2 μm to 25 μm, and particularly preferably 3 μm to 20 μm. The width (W) of the island-shaped protrusion refers to the length measured from the rising part of the island-shaped protrusion. Furthermore, the above length refers to the distance between opposing sides if there are opposing sides such as in a quadrilateral, the diameter if it is a circle, and the equivalent diameter if it is a polygon with an odd number of sides.

[0052] The height (H) of the island-shaped protrusions 11 is preferably in the range of 5 μm to 25 μm, more preferably 7 μm to 22 μm, and particularly preferably 10 μm to 20 μm. The height (H) of the island-shaped protrusions 11 refers to the distance from the surface of the connecting layer 13 to the highest point of the island-shaped protrusions 11.

[0053] The spacing (P) between the island-shaped protrusions 11 is preferably in the range of 1 μm to 20 μm, more preferably 2 μm to 18 μm, and particularly preferably 5 μm to 15 μm. The spacing (P) between the island-shaped protrusions 11 refers to the distance between the rising portions of opposing island-shaped protrusions.

[0054] The thickness (t) of the connecting layer 13 is preferably in the range of 5 μm to 10 μm, more preferably 5.5 μm to 9.5 μm, and particularly preferably 6 μm to 9 μm. The thickness (t) of the connecting layer 13 refers to the average thickness of the negative electrode active material layer present between the surface of the current collector and the rising portion of the island-shaped protrusion 11.

[0055] The ratio (H / W) of the height (H) of the island-shaped protrusion 11 to the width (W) of the island-shaped protrusion 11 is preferably in the range of 1 / 15 to 25 / 1, more preferably 1 / 2 to 10 / 1, and particularly preferably 7 / 10 to 5 / 1.

[0056] Note that the width, height, spacing of each island-shaped protrusion 11 and the thickness of the connecting layer 13 do not need to be constant; it is sufficient if their average values ​​fall within the above range. Furthermore, if the width, height, spacing of each island-shaped protrusion 11 and the thickness of the connecting layer 13 differ depending on the measurement location, it is particularly preferable that each measured value falls within the above range. In a preferred embodiment, the width, height, spacing of each island-shaped protrusion 11 and the thickness of the connecting layer 13 are constant, and the island-shaped protrusions 11 are formed in a pattern.

[0057] It is preferable that the width, height, and spacing of the island-shaped protrusions 11 are within the above range, as this suppresses the effects of expansion and contraction between the island-shaped protrusions during charging and discharging after the formation of the all-solid-state LiB. In other words, even after charging and discharging after the formation of the all-solid-state LiB, the block maintains the outer shape and spacing of the island-shaped protrusions almost, resulting in stable performance. Furthermore, it is preferable that the thickness (t) of the connecting layer 13 is within the above range, as this makes it less likely for the negative electrode active material layer to become blocked at the bottom surface of the groove 12 even after charging and discharging after the formation of the all-solid-state LiB, thus reliably preventing exposure of the negative electrode current collector at the bottom surface of the groove 12.

[0058] In the all-solid-state LiB anode forming material 10 of this embodiment, numerous fine island-like protrusions are formed as described above, which increases the reaction field between Li ions and the active material, thereby improving the current density.

[0059] The shape of the island-shaped protrusion 11 is not particularly limited. Figures 1 and 2 show the case where the island-shaped protrusion 11 is a rectangular prism, but it may also be cylindrical (Figure 3), elliptical, triangular, square, pentagonal, hexagonal, or other polygonal prism shapes. It may also be a frustum of a cone, an elliptical, or a frustum of a polygon, such as a triangular, square, pentagonal, or hexagonal frustum. It may also be a cone, an elliptical cone, a polygonal pyramid, a linear or lattice shape, or a combination thereof.

[0060] The island-shaped protrusions 11 may be covered with the solid electrolyte when the entire solid LiB is formed, and the solid electrolyte may also penetrate the grooves 12.

[0061] To form a negative electrode active material layer made of an all-solid-state LiB negative electrode forming composition on a negative electrode current collector, it is recommended to make the all-solid-state LiB negative electrode forming composition into a paste with a solvent, form a pattern on the negative electrode current collector, and then dry the solvent. The coating method is not particularly limited as long as it can form the fine island-like protrusions described above. Simple methods for forming fine island-like protrusions include, for example, embossing, photolithography, thermal transfer, roll transfer, and nanoimprint. Drying should be carried out at a temperature sufficient to allow the solvent used to evaporate completely.

[0062] As described above, when a LiB is assembled using an all-solid-state LiB negative electrode forming material having island-shaped protrusions 11 formed by forming an all-solid-state LiB negative electrode forming composition in a predetermined pattern on a negative electrode current collector, and charging and discharging is performed, although complete control is difficult, the negative electrode active material layer becomes amorphous and densified while generally maintaining the shape of the island-shaped protrusions 11. As a result, the size and shape of each block originating from the island-shaped protrusions 11, as well as the grooves between each block, become uniform, and contact between adjacent blocks can be suppressed even when expansion and contraction due to charging and discharging are repeated. As a result, atomization and isolation of the negative electrode active material are less likely to occur, and a decrease in capacity can be prevented. Moreover, due to the presence of the connecting layer 13, the negative electrode current collector 1 is not exposed at the bottom of the groove 12 even after charging and discharging. When the negative electrode current collector 1 is exposed at the bottom of the groove 12, the solid electrolyte penetrates the interface between the negative electrode current collector 1 and the block through the exposed portion, creating a gap that isolates the negative electrode active material. However, in this invention, such isolation can be effectively prevented by providing the connecting portion 13.

[0063] Furthermore, in the all-solid-state LiB anode forming material 10 of this embodiment, since a large number of fine island-like protrusions are formed as described above, the reaction field between Li ions and the active material increases, and the current density is improved.

[0064] The material for forming an all-solid-state LiB negative electrode has the negative electrode active material layer 2 on the negative electrode current collector 1, but a solid electrolyte layer may also be formed on the negative electrode active material layer. The solid electrolyte is not particularly limited, but commonly used sulfide-based solid electrolytes and oxide-based solid electrolytes can be given as examples. Sulfide-based solid electrolytes are advantageous because they have high lithium ion conductivity. Oxide-based solid electrolytes are chemically relatively stable and are advantageous from the viewpoint of high voltage resistance. When an oxide-based solid electrolyte is used for the solid electrolyte layer, a general-purpose ion conductive material may be used in combination as needed to improve lithium ion conductivity.

[0065] Sulfide-based solid electrolytes contain, for example, lithium, phosphorus, and sulfur, and may also contain elements such as O, Al, B, Si, Ge, and I. Specifically, amorphous Li3PS4, amorphous 40LiI·60Li3PS4 (mol%), Li7P2S8I, β-Li3PS4, α-Li3PS4, Li7P3S 11 Crystals or similar materials are used. Argyrodite-based solid electrolytes may also be used.

[0066] Such sulfide-based solid electrolytes can be obtained by known methods. For example, lithium sulfide (Li2S) and phosphorus pentasulfide (P2S5) can be prepared as starting materials, and the Li2S and P2S5 can be mixed in a molar ratio of approximately 50:50 to 80:20, then melted and rapidly cooled. Alternatively, they can be produced by mechanical milling, or by known wet methods such as the suspension method, solution method, or sol-gel method.

[0067] The sulfide-based solid electrolyte obtained by the above method is amorphous. While it can be used in this amorphous state, it can also be heat-treated to produce a crystalline sulfide-based solid electrolyte. Crystallization is expected to improve lithium ion conductivity.

[0068] Oxide-based solid electrolytes include, for example, Li 5+X La3(Zr X ,A 2-X )O 12(In the formula, A is one or more elements selected from the group consisting of Sc, Ti, C, Y, Nb, Hf, Ta, Al, Si, Ga, Ge, Sn, and X is 1.4 ≤ X ≤ 2), Li 1+X Al X Ti 2-X (PO4)3 (X is 0 ≤ X ≤ 1), Li 3X La 2 / 3-X Examples include TiO3 (where X is 0 ≤ X ≤ 2 / 3). These materials have high ionic conductivity at room temperature and high electrochemical stability.

[0069] From the viewpoint of electrochemical stability, insulating particles such as silica (SiO2) particles, γ-alumina (Al2O3) particles, ceria (CeO2) particles, and zirconia (ZrO2) particles may be added to the oxide-based solid electrolyte. Alternatively, other known metal oxide particles may be used.

[0070] The above solid electrolyte is preferably one with a Young's modulus (25°C) of 10 to 70 GPa, more preferably 15 to 30 GPa, because when the negative electrode active material densifies into blocks, the solid electrolyte can easily fill the gaps between the blocks, thus maintaining higher ionic conductivity. Examples of solid electrolytes with a Young's modulus (25°C) of 10 to 70 GPa include amorphous Li3PS4, LiX-Li3PS4 (X=I,Br,Cl) glass, β-Li3PS4, α-Li3PS4, and Li7P3S 11 Crystal, Li 10 GeP2S 12 Examples include LGPS crystalline solid electrolytes, such as Li6PS5X (X=I,Br,Cl), and argyrodite crystals, such as Li6PS5X (X=I,Br,Cl).

[0071] The thickness of the solid electrolyte layer is preferably 500 nm to 1000 μm, and more preferably 1 μm to 500 μm. If the thickness is 500 nm or more, a solid-state battery with stable performance can be manufactured without chipping or cracking. If the thickness is 1000 μm or less, a solid-state battery with sufficiently low resistance can be manufactured.

[0072] When a battery is assembled using the above-described all-solid-state LiB anode forming material and then charged and discharged, as described above, some or all of the silicon crystal particles, which are the anode active material, become amorphous, and the island-shaped protrusions are densified into a block-like structure while maintaining almost the shape and spacing of the island-shaped protrusions, thereby exhibiting the unique effects of the present invention described above.

[0073] Generally, when silicon is used as the negative electrode active material, the theoretical maximum charge capacity of an all-solid-state lithium battery is approximately 3600 mAhg. -1 However, the practical charge / discharge usage range is approximately 1000-3000mAhg. -1 This is within the range. In other words, it is presumed that the reason why the all-solid-state LiB according to the present invention exhibits stable battery performance with good cycle characteristics over a long period of time is that the shape, size, and spacing of the blocks generated by charging and discharging are controlled by the shape, size, and spacing of the island-shaped protrusions 11, and furthermore, due to the interaction with the connecting layer 13, it is difficult for grooves reaching the negative electrode current collector 1 to be formed, and also because the volume change of the generated blocks is small. Furthermore, in the half-cell configured in the embodiment described later, the above range corresponds to a potential state of +0.02V to +1.0V relative to the counter electrode such as a metallic lithium electrode.

[0074] Furthermore, according to conventional knowledge, when silicon is used as the negative electrode active material, the charge / discharge capacity decreases as the current density increases. Therefore, in practical terms, the current density during charge / discharge of all-solid-state LiBs is 0.1~0.4 mA / cm². -2 It is used within this range. In contrast, in the present invention, the current density is 0.6 mA / cm². -2 Even when increased to the above level, it does not show a significant decrease in capacity and maintains good cycle characteristics. In other words, the fact that the all-solid-state LiB according to the present invention exhibits battery performance with good cycle characteristics stably for an extremely long period of time is thought to be partly due to the small volume change of the block based on the island-shaped protrusions during use, the stable interface with the solid electrolyte, and the fact that the connecting layer 13 remains even after charging and discharging, which prevents the solid electrolyte from entering between the negative electrode current collector 1 and the block.

[0075] Furthermore, in a preferred embodiment, since the island-shaped protrusions are formed in a patterned manner, the blocks after charging and discharging are also formed according to this pattern, which has the advantage of extremely small performance variation among all-solid-state LiB products.

[0076] (All-solid-state lithium-ion rechargeable battery) As shown in Figure 6, the all-solid-state lithium-ion secondary battery of the present invention comprises a positive electrode current collector 5, a positive electrode active material layer 4, a negative electrode active material layer 2, a negative electrode current collector 1, and a solid electrolyte layer 3, with the negative electrode being formed using an all-solid-state LiB negative electrode forming material. When a LiB is assembled using the all-solid-state LiB negative electrode forming material and charged and discharged, some or all of the silicon crystals contained in the all-solid-state LiB negative electrode forming material become amorphous. Furthermore, as a result of charging and discharging, some or all of the silicon forms an alloy with lithium. That is, after assembling and charging / discharging the LiB, the crystal structure of the negative electrode active material layer differs from the silicon crystal before assembly, and is composed of some or all amorphous silicon. In this specification, the negative electrode active material after charging and discharging may simply be described as "amorphous silicon," but this amorphous silicon may contain silicon crystals or may be alloyed with lithium.

[0077] When the battery is charged, the silicon particles in the negative electrode layer absorb lithium, causing them to expand in volume. During this process, the silicon particles fuse together and become amorphous. The tiny voids between the silicon particles are pushed out, forming dense blocks in the form of island-like protrusions isolated by grooves (depending on the size of the island-like protrusions, grooves may be created inside that do not reach the negative electrode current collector). As a result, even if the expansion rate of the silicon particles themselves due to charging is about 300%, the increase in the thickness of the negative electrode layer itself is suppressed to about 1.5 times.

[0078] During discharge, the silicon attempts to return to its original volume due to lithium release, but the solid electrolyte, which is relatively softer than the silicon block, is drawn into the voids around the block, resulting in almost no reduction in the thickness of the negative electrode layer itself.

[0079] The solid electrolyte layer 3 is made of the solid electrolyte. In the all-solid-state LiB of the present invention, the components other than the negative electrode can be the same as those of known all-solid-state LiBs and are not particularly limited. The positive electrode consists of a positive electrode active material layer 4 and a positive electrode current collector 5, and known positive electrode active material and current collector may be used. [Examples]

[0080] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0081] (Average particle size of silicon) The average particle size and standard deviation of silicon were determined from the laser diffraction / scatter light intensity using a LA-950S2 laser (manufactured by Horiba, Ltd.).

[0082] (Specific surface area of ​​silicon) The specific surface area of ​​the silicon particles was determined by gas adsorption measurement using the constant-volume method with BELSORP-miniX (manufactured by MicrotracBEL).

[0083] (Charge-discharge cycle test) The charge / discharge test was performed using a BTS-2004H (manufactured by Nagano Corporation), with a current density of 0.1 mAcm². -2 A constant current density test was conducted. The measurement temperature was 25°C, and only the initial charge amount was 3000mAhg. -1 However, the initial discharge amount is 2000mAhg -1 This was done. Also, from the second time onward, the state after the initial discharge was set to 0mAhg. -1 The amount of charge from there is 2000mAhg -1 The discharge capacity is 2000mAhg. -1 This was done by using the aforementioned 2000mAhg -1 The battery was repeatedly charged and discharged.

[0084] The evaluation results of the charge-discharge cycle test were determined in the cycle test to be the set capacity of 2000mAhg. -1 This is shown as the number of cycles achieved while maintaining a discharge capacity of 90% or more. However, the initial charge capacity is 3,000mAh -1 Those who failed to reach the target and ended the test were marked with "NG".

[0085] (Current density measurement) The charge / discharge test was performed using a BTS-2004H (manufactured by Nagano). Initial current density: 0.1 mAcm -2 A constant current density test was performed. The measurement temperature was 25°C, and only the initial charge amount was 3000mAhg. -1 However, the initial discharge amount is 2000mAhg -1 This was done. Furthermore, from the second time onward, the current density was set to 0.2 mAcm². -2 The state after the initial discharge is 0mAhg -1 The amount of charge from there is 2000mAhg -1 The discharge capacity is 2000mAhg. -1 This was done by using the aforementioned 2000mAhg -1 After every five charge-discharge cycles, the current density will be 0.4 mAcm². -2 , 0.6 mAcm -2 , 0.8 mAcm -2 , 1.0 mAcm -2 , 2.0 mAcm -2 , 5.0 mAcm -2 7.5 mAcm -2 , 10.0 mAcm -2 The evaluation was conducted after increasing the discharge amount to 2000mAhg. -1 Table 1 shows the maximum current density at the point when the condition was maintained.

[0086] (Battery materials) We assembled half-cells using the materials listed below and evaluated the structure and characteristics of the negative electrode. Opposite Lithium (Li) foil: 0.1mm film thickness (manufactured by Honjo Metal Co., Ltd.) Indium (In) foil: film thickness 0.127 mm (manufactured by Aldrich) negative electrode Negative electrode current collector: CF-T7F-35 (manufactured by Fukuda Metal Foil & Powder Industry Co., Ltd.) The negative electrode active material layer consisted of a mixture of 90 parts silicon crystal particles and 10 parts thermosetting polyimide resin. The thermosetting polyimide resin used was DreamBond (product name) manufactured by IST Corporation. Solid electrolyte: a-40LiI·60Li3PS3 (fabricated by mechanical milling) Polycrystalline silicon manufactured by Tokuyama Corporation was used as the raw material for the silicon crystal particles, which were pulverized using a planetary mill. The average particle size of the silicon crystal particles was 1.02 μm, and the specific surface area was 14.1 m². 2 It was / g.

[0087] (Manufacturing of negative electrodes) An appropriate amount of photoimprint resin was dropped onto a PET film (Toyobo Co., Ltd., Cosmoshine A4160, 188 μm thick), and the pattern surface of a Ni electroformed mold with a cylindrical hole pattern was pressed against it. UV irradiation was then performed from the PET film side to cure the resin. Subsequently, the Ni mold was peeled off to form a cylindrical pillar pattern on the surface of the PET film.

[0088] Next, the patterned surface of the PET film with the cylindrical pillar pattern was superimposed on a PP film (Santox-CP LU02, manufactured by RM Tohcello Co., Ltd., 60 μm thick), and thermal imprinting was performed under vacuum conditions of 120°C × 24 kN to form a cylindrical hole pattern on the surface of the PP film.

[0089] 360 mg of the above-mentioned polycrystalline silicon particles and a polyimide solution (24.7 wt% NMP solution) were mixed to a solid content of 40 mg, and NMP (N-methylpyrrolidone) was added to obtain a composition for forming an all-solid-state LiB anode. The composition was stirred for 2 hours (rotation 1056 rpm, revolution 1600 rpm) and degassed for 6 minutes (rotation 290 rpm, revolution 1360 rpm).

[0090] The obtained coating solution was applied flatly to the entire surface of the negative electrode current collector using a doctor blade (feed speed 1.9 mm / sec, blade gap 25 μm). After drying at room temperature for more than half a day, the active material layer was heated to 80°C, and the patterned side of the heat-imprinted PP film was pressed against it for 30 minutes. The polyimide was cured by heater heating under vacuum (250°C, 30 minutes), and then further heated under a mixed gas atmosphere of nitrogen and oxygen (350°C, 30 minutes) to obtain a negative electrode forming material having cylindrical island-like protrusions with the height, width, and spacing shown in Table 1, at the intervals shown in Table 1.

[0091] A sheet of negative electrode material was punched out to a diameter of 9 mm and placed in an insulating die. 65 mg of solid electrolyte particles were loaded onto the negative electrode sheet, and a uniaxial press was performed at a molding pressure of 560 MPa. The thickness of the solid electrolyte layer after pressing was 300-400 μm. After removing the upper punch, a counter electrode, made by stacking metal foils of In and Li punched out to a diameter of 6 mm in the order of In / Li / In, was placed on top of the solid electrolyte layer, and a uniaxial press was performed again at a pressure of approximately 50 MPa to fabricate an all-solid-state half-cell. The assembly of the above half-cells was carried out entirely in an argon atmosphere inside a glove box, with the influence of outside air blocked, to eliminate the effects of oxygen, nitrogen, moisture, etc. The above battery evaluation was performed on the obtained half-cells. The results are shown in Table 1.

[0092] [Table 1] [Explanation of Symbols]

[0093] 1...Negative electrode current collector 2...Negative electrode active material layer 3...Solid electrolyte layer 4...Cathode active material layer 5...Positive electrode current collector 10…Materials for forming negative electrodes in all-solid-state lithium-ion secondary batteries 11…Negative electrode active material layer (island-shaped protrusions) 12… Groove 13…Connection Layer 20… All-solid-state lithium-ion secondary battery

Claims

1. A negative electrode active material layer made of a composition for forming the negative electrode of an all-solid-state lithium-ion secondary battery containing silicon crystals is formed at intervals on island-shaped protrusions, and a connecting layer made of the same composition is formed on the bottom surface of the grooves of the negative electrode active material layer formed between the island-shaped protrusions, and the negative electrode active material layer formed continuously with the island-shaped protrusions is located on the negative electrode current collector. Negative electrode current collector base area 1 cm² ２ The surface area of ​​the negative electrode active material layer is 1.25 to 31.25 cm². ２ And, Negative electrode current collector base area 1 cm² ２ The number of island-shaped protrusions per unit area is 5 × 10 ４ ~5 x 10 ７ A material for forming the negative electrode of an all-solid-state lithium-ion secondary battery.

2. The material for forming a negative electrode of an all-solid-state lithium-ion secondary battery according to claim 1, wherein the width of the island-shaped protrusions is in the range of 1 μm to 30 μm, the height is in the range of 2 μm to 25 μm, the spacing between the island-shaped protrusions is in the range of 1 μm to 20 μm, and the thickness of the connecting layer is in the range of 3 μm to 10 μm.

3. The material for forming a negative electrode of an all-solid-state lithium-ion secondary battery according to claim 1, wherein the negative electrode active material layer on the negative electrode current collector is formed in a pattern of island-shaped protrusions, which are cylindrical, elliptical, polygonal prism, frustocone, elliptical frustocone, polygonal frustocone, cone, elliptical cone, polygonal pyramidal, linear, and grid shapes.

4. An all-solid-state lithium-ion secondary battery having a positive electrode, a negative electrode, and a solid electrolyte layer, An all-solid-state lithium-ion secondary battery characterized in that the negative electrode is made of the all-solid-state lithium-ion secondary battery negative electrode forming material described in any one of claims 1 to 3.

5. The all-solid-state lithium-ion secondary battery according to claim 4, wherein the solid electrolyte layer is also present in the groove portion.

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