solid-state batteries

Abstract

To provide a solid-state battery that suppresses the increase in internal resistance due to charging and discharging. [Solution] The solid battery comprises a first current collector, a first electrode layer, an electrolyte layer, a second electrode layer, and a second current collector in this order, the first current collector includes a resin layer in contact with the first electrode layer, the first electrode layer includes an electrode active material, and the electrode active material is a resin for the active material.

Description

[Technical Field]

[0001] This disclosure relates to solid-state batteries. [Background technology]

[0002] In recent years, the importance of rechargeable batteries has increased, and in addition to rechargeable batteries with electrolytes, the development of solid-state batteries using solid electrolytes is progressing. All-solid-state batteries, an example of solid-state batteries, are batteries that have a solid electrolyte layer instead of an electrolyte, and because they do not use flammable organic solvents, safety devices can be simplified, and they are superior in terms of manufacturing cost and productivity.

[0003] As a negative electrode layer used in all-solid-state batteries, a negative electrode layer is known in which the negative electrode active material is a composite particle having multiple particles containing Si or Sn elements and a binder, and which can suppress the deterioration of cycle characteristics due to volume changes of the negative electrode active material during charging and discharging (Patent Document 1). Furthermore, a negative electrode active material powder capable of improving battery characteristics is known, which has a fluorinated layer on the surface of secondary particles formed from single particles made of Si, Sn, etc. (Patent Document 2). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2019-121557 [Patent Document 2] Japanese Patent Publication No. 2021-057216 [Overview of the project] [Problems that the invention aims to solve]

[0005] When using materials that undergo volume changes as the negative electrode active material, it is difficult to completely suppress the volume change of these materials during charging and discharging, and in some cases, the internal resistance can increase significantly.

[0006] One embodiment of this disclosure aims to solve the problem of providing a solid-state battery that suppresses the increase in internal resistance due to charging and discharging. [Means for solving the problem]

[0007] The means for solving the problem include the following: <1> A solid-state battery comprising, in this order, a first current collector, a first electrode layer, an electrolyte layer, a second electrode layer, and a second current collector, wherein the first current collector includes a resin layer in contact with the first electrode layer, the first electrode layer includes an electrode active material, and the electrode active material has an active material resin. <2> The electrode active material contains secondary particles, and the secondary particles contain a plurality of primary particles and an active material resin. <1> Solid-state batteries as described above. <3> The resin layer includes a resin for the resin layer, and the active material resin and the resin for the resin layer share a common structure. <1> or <2> Solid-state batteries as described above. <4> The resin layer contains a resin for the resin layer, and the active material resin and the resin for the resin layer contain common functional groups. <1> ~ <3> A solid battery as described in any one of the following. <5> The resin layer contains a resin for the resin layer, and the active material resin and the resin for the resin layer contain a common resin. <1> ~ <4> A solid battery as described in any one of the following. <6> The resin layer includes a resin for the resin layer, and the active material resin and the resin for the resin layer include a structure represented by at least one of formulas (1) and (2). <1> ~ <5> A solid battery as described in any one of the following.

[0008] [ka]

[0009] [ka]

[0010] In formula (1), R represents an alkyl group, an allyl group, a hydroxyl group, a carboxyl group, a methoxy group, or an ethoxy group, and n in formulas (1) and (2) independently represents an integer of 1 or more. <7> The resin layer contains a resin for the resin layer, and the resin for the active material and the resin for the resin layer include the structure represented by formula (1) or the structure represented by formula (2). The solid battery according to any one of <1> to <5>.

[0011]

Chemical formula

[0012]

Chemical formula

[0013] In formula (1), R represents an alkyl group, an allyl group, a hydroxyl group, a carboxy group, a methoxy group, or an ethoxy group, and n in formula (1) and formula (2) each independently represents an integer of 1 or more. <8> The resin for the active material is the solid battery according to any one of <1> to <7>, which is capable of adhering to the resin layer. <9> The first current collector further has a metal layer. The solid battery according to any one of <1> to <8>. <10> The first current collector is a conductive resin current collector. The solid battery according to any one of <1> to <9>. <11> The resin layer has a region to which the electrode active material adheres. The solid battery according to any one of <1> to <10>. <12> The electrode active material contains Si element. The solid battery according to any one of <1> to <11>. <13> The metal layer is a nickel foil, and the first current collector includes the nickel foil and the resin layer in this order. The solid battery according to <9>. <14> The first electrode layer contains a binder, and the binder is at least one selected from the group consisting of styrene-butadiene rubber, polyvinylidene fluoride, and vinyl resin. The solid battery according to any one of <1> to <13>. <15> The solid battery according to any one of <1> to <14>, which is an all-solid-state battery.

Advantages of the Invention

[0014] According to one embodiment of the present disclosure, a solid-state battery is provided that suppresses the increase in internal resistance due to charging and discharging. [Brief explanation of the drawing]

[0015] [Figure 1] Figure 1 is a schematic cross-sectional view of the negative electrode of a solid-state battery in one embodiment of the present disclosure. [Figure 2] Figure 2 is a graph showing the measurement results of the normalized resistance increase rate in the examples and comparative examples. [Modes for carrying out the invention]

[0016] In this disclosure, a numerical range indicated using "~" means a range that includes the numbers written before and after "~" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. In the numerical ranges described in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the values ​​shown in the examples. In this disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In this disclosure, unless otherwise specified, the amount of each component refers to the total amount of multiple substances if there are multiple substances corresponding to each component. When embodiments are described in this disclosure with reference to the drawings, the configuration of such embodiments is not limited to the configuration shown in the drawings. Furthermore, the sizes of the components in each figure are conceptual, and the relative relationships between the sizes of the components are not limited thereto.

[0017] <Solid battery> A solid-state battery (hereinafter also referred to as a solid-state battery) according to one embodiment of the present disclosure comprises, in this order, a first current collector, a first electrode layer, an electrolyte layer, a second electrode layer, and a second current collector. The first current collector includes a resin layer in contact with the first electrode layer, and the first electrode layer includes an electrode active material. The electrode active material has an active material resin.

[0018] The first current collector and the first electrode layer, or the second current collector and the second electrode layer, each constitute an electrode of the solid-state battery. When the first current collector and the first electrode layer constitute the negative electrode, the second current collector and the second electrode layer constitute the positive electrode. Conversely, when the first current collector and the first electrode layer constitute the positive electrode, the second current collector and the second electrode layer constitute the negative electrode. Therefore, the solid-state battery comprises a negative electrode, an electrolyte layer, and a positive electrode.

[0019] The following describes an embodiment in which the first current collector and the first electrode layer constitute the negative electrode, and the second current collector and the second electrode layer constitute the positive electrode. In this embodiment, the first current collector is a negative electrode current collector, the first electrode layer is a negative electrode layer, the second current collector is a positive electrode current collector, and the second electrode layer is a positive electrode layer.

[0020] In solid-state batteries, it is known that expansion and contraction can occur in the negative electrode active material contained in the negative electrode layer during charging and discharging. This expansion and contraction of the negative electrode active material can lead to crack formation in the negative electrode layer, delamination between the negative electrode current collector and the negative electrode layer, and other issues, resulting in an increase in internal resistance. For example, Si-based active materials containing the element Si are high-capacity active materials, but they tend to expand significantly. Thus, especially when using negative electrode active materials with large expansion rates, such as Si-based active materials, it is desirable to be able to suppress the increase in internal resistance due to expansion and contraction during charging and discharging, as this can greatly contribute to improving the battery's cycle characteristics.

[0021] The inventors investigated ways to suppress the delamination between the current collector and the electrode layer in order to suppress the increase in internal resistance during charging and discharging in solid-state batteries. They found that, for example, by using a negative electrode active material containing a resin (active material resin) that is adhesive to a negative electrode current collector having a resin layer in the negative electrode layer, delamination between the negative electrode current collector and the negative electrode layer is suppressed even when the negative electrode active material expands and contracts.

[0022] Although the mechanism by which delamination between the current collector and the electrode layer is suppressed is not clear, it is presumed that the current collector has a resin layer containing resin, and the electrode layer has an active material resin containing active material resin, and that the current collector and the electrode layer are connected by resin, thereby effectively suppressing delamination between the current collector and the electrode layer by providing an anchoring effect.

[0023] (Negative electrode) A negative electrode according to one embodiment of the present disclosure includes a negative electrode current collector and a negative electrode layer. The negative electrode current collector may include a resin layer, or it may include a negative electrode substrate layer and a resin layer. By including a resin layer in the negative electrode current collector and the negative electrode layer including an electrode active material and the electrode active material having an active material resin, delamination between the negative electrode current collector and the negative electrode layer is suppressed, and the increase in internal resistance during charging and discharging is suppressed.

[0024] (Negative electrode current collector) The negative electrode current collector includes a resin layer and can be configured to include a negative electrode base layer and a resin layer. The negative electrode includes a resin layer (or a negative electrode base layer, resin layer), and a negative electrode layer in that order. As shown in Figure 1, the negative electrode 10 according to one embodiment of the present disclosure includes, in this order, a negative electrode substrate layer 11, a resin layer 12, and a negative electrode layer 13.

[0025] (Resin layer) The resin layer is in contact with the negative electrode layer on one side, and if the negative electrode current collector has a negative electrode base layer, it is in contact with the negative electrode base layer on the other side. The resin layer contains a resin for the resin layer. The resin for the resin layer is preferably one that can adhere to the active material resin of the electrode active material in the negative electrode substrate layer and the negative electrode layer. Adhesion between the resin for the resin layer and the active material resin means that the resin for the resin layer and the active material resin can be chemically or physically bonded and connected. In an all-solid-state battery, it is preferable that the resin for the resin layer and the active material resin have regions where they are chemically or physically bonded and firmly connected to each other in at least one of the following states: before charging, during charging, after charging, before use, during use, and after use.

[0026] Examples of resin layers that can be bonded to the negative electrode substrate layer and the active material resin include resins that melt or soften when heated. Examples of resins that melt or soften upon heating include polyolefins such as polyethylene and polypropylene, polyamides, polyesters such as polyethylene terephthalate, polyurethanes, thermoplastic resins such as ethylene vinyl acetate copolymer, rubber resins such as butadiene rubber (BR) and styrene-butadiene rubber (SBR), fluoride resins such as polyvinylidene fluoride (PVdF), and vinyl resins such as polyvinyl chloride, polyvinylidene chloride, vinyl acetate, polyvinyl alcohol, and styrene resin.

[0027] From the viewpoint of adhesion with the active material resin, it is preferable that the resin for the resin layer contains a structure common to that of the active material resin. The common structure will be described later in the description of the active material resin. Furthermore, from the viewpoint of adhesion with the active material resin, it is preferable that the resin for the resin layer contains functional groups common to the active material resin. The common functional groups will be described later in the description of the active material resin. Furthermore, from the viewpoint of adhesion with the active material resin, it is preferable that the resin for the resin layer contains a resin common to the active material resin. The common resin will be described later in the description of the active material resin.

[0028] The resin layer may contain a conductive material in addition to the resin for the resin layer. By including a conductive material, the resin layer can be made into a conductive resin layer. If the negative electrode current collector has a conductive resin layer, it can be made into a conductive resin current collector and does not necessarily have the negative electrode base layer described later. Examples of conductive materials include carbon materials, conductive polymers, and metal particles. The conductive material may be used alone or in combination of two or more types. Examples of carbon materials include particulate carbon materials and fibrous carbon materials. Examples of particulate carbon materials include acetylene black (AB) and Ketjenblack (KB). Examples of fibrous carbon materials include carbon nanotubes (CNT), carbon nanofibers (CNF), and vapor-grown carbon fibers (VGCF). Examples of conductive polymers include polythiophene, polyacetylene, poly(p-phenylene), and polyisothianaphthene. Examples of metal particles include nickel, copper, iron, and stainless steel. Among the above, the anchoring effect is enhanced, and the active material layer is separated from the resin current collector, improving the cycle characteristics. From the viewpoint of further suppressing the decrease, the conductive material preferably contains a carbon material, more preferably contains at least one of acetylene black (AB) and vapor-grown carbon fiber (VGCF), and even more preferably contains vapor-grown carbon fiber (VGCF).

[0029] The conductive material content is preferably 10% to 50% by mass, and more preferably 15% to 43% by mass, relative to the total solid content of the negative electrode current collector.

[0030] Even with expansion and contraction of the electrode active material, from the viewpoint of the resin layer adhering to the active material resin of the electrode active material in the negative electrode substrate layer and the negative electrode layer, the thickness of the resin layer is preferably 1 μm or more, and more preferably 3 μm or more. The thickness of the resin layer is preferably 50 μm or less, and more preferably 30 μm or less.

[0031] Preferably, the resin layer has a region to which the electrode active material of the negative electrode layer adheres. By having a region where the resin layer and the electrode active material of the negative electrode layer adhere, delamination between the negative electrode current collector and the negative electrode layer is suppressed even if the electrode active material expands and contracts during charging and discharging, thereby suppressing the increase in internal resistance due to charging and discharging in the solid-state battery.

[0032] (Negative electrode base material layer) The negative electrode substrate layer can be one of the materials known to serve as the current collector for the negative electrode. The negative electrode substrate layer may be made of metal, resin, or any other material. Aluminum foil, nickel foil, titanium foil, copper foil, etc., can be used as the metal negative electrode substrate layer. The negative electrode substrate layer made of resin can be a known resin current collector, and a conductive resin current collector, which is a composite material containing a resin such as polyethylene or phenolic resin and a conductive filler such as graphite, can be used.

[0033] The negative electrode base layer is preferably one on which a resin layer can be formed. The material of the negative electrode base layer may be selected according to the type of resin to be formed on the negative electrode base layer. The negative electrode base layer is preferably a metal foil from the viewpoint of adhesion to the resin layer and electronic conductivity. Specifically, nickel, aluminum, copper, SUS, etc. are preferred as metal foils, and it is more preferable that the nickel foil is in contact with the resin layer. The negative electrode current collector preferably contains nickel foil and a resin layer in this order. The negative electrode substrate layer may consist of two layers of different types, or it may consist of only one layer.

[0034] The negative electrode substrate layer is preferably a conductive resin current collector, from the viewpoint of adhesion to the negative electrode layer and ability to follow the expansion and contraction of the electrode active material. Known conductive resin current collectors can be used.

[0035] (Fabrication of the negative electrode current collector) The negative electrode current collector can be manufactured to include a negative electrode substrate layer and a resin layer, and can be manufactured by known manufacturing methods. For example, it can be manufactured by coating a composition containing a resin for the resin layer onto the negative electrode substrate layer.

[0036] (Negative electrode layer) The negative electrode layer contains a negative electrode composite material. The negative electrode composite material contains a negative electrode active material. The negative electrode active material may be in the form of particles. If the negative electrode active material is in the form of particles, the particles have an active material resin. It is preferable that the active material resin is adhesive to the resin layer.

[0037] (Negative electrode active material) The negative electrode active material comprises a resin layer and an active material resin. The active material resin is preferably adhesive to the resin layer. The negative electrode active material may also be in particulate form. The particulate active material may contain at least one of primary and secondary particles. The negative electrode active material or the particulate active material preferably contains silicon (Si). When the negative electrode active material includes an active material resin and particles, the gaps formed between the particles mitigate expansion and contraction, effectively suppressing separation between the current collector and the electrode layer. The distinction between primary and secondary particles in a particle-shaped active material can be made by observation using a scanning electron microscope (SEM).

[0038] (primary particle) The primary particles are preferably Si-based active materials containing Si element. Examples of Si-based active materials include elemental Si, Si alloys, Si oxides, Si carbides, and Si oxide carbides (silicon oxycarbide). Si alloys are alloys in which Si element is the main component. Examples of metals other than Si in Si alloys include at least one of W, Mo, Cr, V, Nb, Fe, Ti, Zr, Hf, and Os. An example of a Si oxide is SiO. Furthermore, the Si-based active material may have a diamond-type crystalline phase as its main phase, a clathrate type I crystalline phase as its main phase, or a clathrate type II crystalline phase as its main phase.

[0039] The primary particles may be solid particles or porous particles, but the latter is preferred. Because porous particles have voids inside, they can absorb volume changes of the porous particles, and as a result, volume changes of the negative electrode layer due to charging and discharging can be reduced.

[0040] The porosity of porous particles may be, for example, 4% or more, or 10% or more. On the other hand, the porosity of porous particles may be, for example, 40% or less, or 20% or less. The porosity can be determined by the following procedure. First, a cross-section is made from the electrode layer containing the active material by ion milling. Then, the cross-section is observed with an SEM (scanning electron microscope) to obtain a photograph showing the porous particles. From the obtained photograph, the silicon portion and the void portion are separated using image analysis software and binarized. The areas of the silicon portion and the void portion are determined, and the porosity (%) is calculated from the following formula. Porosity (%) = (Area of ​​voids) / ((Area of ​​silicon) + (Area of ​​voids)) × 100

[0041] Porous particles preferably have many minute voids with a pore diameter of 100 nm or less. Voids with a pore diameter of 100 nm or less can suppress crushing by pressing compared to voids with a pore diameter of 100 nm or more. The void volume X (cumulative void volume) of voids with a pore diameter of 100 nm or less is, for example, 0.05 ml / g or more, may be 0.10 ml / g or more, or may be 0.12 ml / g or more. On the other hand, the void volume X is, for example, 0.40 ml / g or less. The void volume in this disclosure can be determined, for example, by BET measurement.

[0042] It is preferable that porous particles have many minute voids with a pore diameter of 50 nm or less. Voids with a pore diameter of 50 nm or less can further suppress the collapse of voids by pressing compared to voids with a pore diameter greater than 50 nm and a pore diameter of 100 nm or less. The void amount Y of voids with a pore diameter of 50 nm or less is, for example, 0.05 cc / g or more, may be 0.075 ml / g or more, or may be 0.10 ml / g or more. On the other hand, the void amount Y is, for example, 0.25 ml / g or less.

[0043] The porous particles preferably have many minute voids with a pore diameter of 10 nm or less. Voids with a pore diameter of 10 nm or less can accommodate the precipitated Li with a higher packing efficiency compared to voids with a pore diameter of 10 nm or more, thus suppressing volume changes due to charging and discharging. The void volume Z of voids with a pore diameter of 10 nm or less is, for example, 0.015 ml / g or more, may be 0.02 ml / g or more, or may be 0.03 ml / g or more. On the other hand, the void volume Z is, for example, 0.09 ml / g or less.

[0044] One example of a method for forming porous particles is to produce a LiSi alloy by reacting solid primary particles (Si-based active material) with metallic Li, and then remove Li from the LiSi alloy. The LiSi alloy can be obtained, for example, by mixing primary particles (Si-based active material) and metallic Li. The molar ratio of Li to Si (Li / Si) is, for example, 1.0 or higher, may be 2.0 or higher, 3.0 or higher, or 4.0 or higher. On the other hand, Li / Si is, for example, 8.0 or lower. A method for removing Li from the LiSi alloy can be, for example, by reacting the LiSi alloy with a Li extractant. Examples of Li extractants include alcohols such as methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, and 1-hexanol; and acids such as acetic acid, formic acid, propionic acid, and oxalic acid.

[0045] Another example of a method for forming porous particles is to produce an MgSi alloy by reacting solid primary particles (Si-based active material) with metallic Mg, and then removing Mg from the MgSi alloy. The MgSi alloy can be obtained, for example, by heating a mixture of primary particles (Si-based active material) and metallic Mg. The ratio of Mg to Si (Mg / Si) is, for example, 1.0 or more, may be 1.5 or more, or 2.0 or more. On the other hand, the Mg / Si ratio is, for example, 6.0 or less. As a method for removing Mg from the MgSi alloy, for example, the MgSi alloy can be heated in an inert gas atmosphere containing oxygen to change the Mg in the Mg-Si alloy to MgO, and then the MgO can be removed with an acid solution. Examples of acid solutions include aqueous solutions containing hydrochloric acid (HCl) and hydrogen fluoride (HF).

[0046] The particle size D50 of the primary particles is not particularly limited, but may be, for example, 0.3 μm or more, or 0.5 μm or more. On the other hand, the particle size D50 of the primary particles may be, for example, 3.0 μm or less, or 2.5 μm or less. In this disclosure, the particle size D50 is the cumulative 50% particle size in the volume-based particle size distribution measured by a laser diffraction particle size distribution analyzer. Furthermore, starting from the fine particle side, the cumulative 10% particle diameter in the volume-based particle size distribution measured by a laser diffraction particle size distribution analyzer is defined as particle diameter D10, and the cumulative 90% particle diameter is defined as particle diameter D90. (D90-D10) / D50 represents the spread of the distribution, and the smaller the value of (D90-D10) / D50, the narrower the distribution. For primary particles, (D90-D10) / D50 is not particularly limited, but for example, it may be between 0.1 and 3.0, or between 0.3 and 2.0.

[0047] The BET specific surface area of ​​the primary particle is not particularly limited, but for example, 1 m 2 / g or more, 10m 2 It may be more than / g, 20m 2 It may be more than / g, 30m 2 It may be greater than or equal to / g. On the other hand, the BET specific surface area of ​​the primary particles is, for example, 200m². 2It is less than / g and 150m 2 It may be less than / g.

[0048] The primary particles have an active material resin. Preferably, the active material resin is adhesive to the resin layer. The active material resin will be described later. By having an active material resin that is adhesive to the resin layer in the primary particles, the resin layer and the active material resin adhere to each other, and even if the particles expand and contract during charging and discharging, delamination between the negative electrode current collector and the negative electrode layer is suppressed, thereby suppressing the increase in internal resistance due to charging and discharging in the solid-state battery.

[0049] The primary particles having the active material resin are not particularly limited, and may be any of the following: primary particles having the active material resin on a part of their surface, primary particles being coated with the active material resin, etc. The method for forming primary particles having an active material resin is not particularly limited, but one example is spray drying. Spray drying is a method of coating particles with resin by spraying a slurry in which particles and resin are dispersed in a solvent and drying it.

[0050] (Secondary particles) Secondary particles are particles formed by the aggregation of multiple primary particles. Secondary particles include aggregates of primary particles, granulated materials, etc. When the particles of this disclosure include secondary particles, the primary particles of the secondary particle granules are immobilized with an active material resin. The resin used for the active material will be discussed later.

[0051] The particle size D50 of the secondary particles is, for example, 2.5 μm or more and less than 20 μm. The particle size D50 of the secondary particles may be 3.0 μm or more, or 5.0 μm or more. On the other hand, the particle size D50 of the secondary particles may be 19 μm or less, 17 μm or less, or 15 μm or less. Furthermore, in the secondary particles, (D90-D10) / D50 is not particularly limited, but may be, for example, 0.1 or more and 5.0 or less, or 0.3 or more and 1.0 or less.

[0052] The ratio of the particle size D50 of primary particles to the particle size D50 of secondary particles is not particularly limited, but for example it may be 3% or more and 60% or less, 5% or more and 40% or less, or 7% or more and 25% or less.

[0053] The method for forming secondary particles is not particularly limited, but examples include granulation by spray drying (such as the spray drying method). In the spray drying method, a slurry containing multiple primary particles, an active material resin, and a dispersion medium is dried by spraying it into hot air. When forming secondary particles that include porous particles as primary particles, first, porous primary particles may be prepared, and then secondary particles may be formed using those primary particles. Alternatively, solid primary particles may be prepared, then secondary particles may be formed using those primary particles, and then the primary particles constituting the secondary particles may be made porous.

[0054] (Resin for active materials) The active material resin is preferably a resin that can adhere to the resin layer. One type of active material resin may be used, or two or more types may be used. The statement that the active material resin can adhere to the resin layer means that the active material resin can chemically or physically bond with the resin layer resin contained in the resin layer, and that the active material resin and the resin layer can be bonded together. In an all-solid-state battery, it is preferable that the active material resin and the resin layer have regions that are chemically or physically bonded to each other and firmly bonded together in at least one of the following states: before charging, during charging, after charging, before use, during use, and after use.

[0055] It is preferable that the active material resin and the resin layer resin contain a structure represented by at least one of the following formulas (1) and (2). It is preferable that the active material resin and the resin layer resin each have a structure represented by at least one of the following formulas (1) and (2) so that they adhere to each other properly. It is even more preferable that the active material resin and the resin layer resin each have a main chain containing a structure represented by at least one of the following formulas (1) and (2).

[0056] [ka]

[0057] [ka]

[0058] In formula (1), R represents an alkyl group, an allyl group, a hydroxyl group, a carboxyl group, a methoxy group, or an ethoxy group, and n in formulas (1) and (2) independently represents an integer of 1 or more. These groups may be substituted or unsubstituted. Examples of substituted or unsubstituted alkyl groups represented by R include alkyl groups having 1 to 10 carbon atoms, such as methyl, ethyl, propyl, and isopropyl groups. The alkyl group described above may be linear, branched, or have a cyclic structure. Examples of substituents include halogen atoms, alkyl groups, allyl groups, phenyl groups, alkenyl groups, alkoxy groups, ester groups, carbonyl groups, sulfonyl groups, amino groups, amide groups, and combinations thereof. The allyl, carboxyl, methoxy, or ethoxy group represented by R may be substituted or unsubstituted. Examples of substituents include halogen atoms, alkyl groups, allyl groups, phenyl groups, alkenyl groups, alkoxy groups, ester groups, carbonyl groups, sulfonyl groups, amino groups, amide groups, and combinations thereof.

[0059] The active material resin and the resin for the resin layer only need to have a structure represented by at least one of formulas (1) and (2), and the combination is not limited. For example, the active material resin may have the structure represented by formula (1) and the resin for the resin layer may have the structure represented by formula (1); the active material resin may have the structure represented by formula (1) and the resin for the resin layer may have the structure represented by formula (2); the active material resin may have the structure represented by formula (2) and the resin for the resin layer may have the structure represented by formula (1); or the active material resin may have the structure represented by formula (2) and the resin for the resin layer may have the structure represented by formula (2).

[0060] It is preferable that the active material resin and the resin for the resin layer contain a common structure. This is preferable because the active material resin and the resin for the resin layer contain a common structure, which allows them to adhere properly to each other. Common structural features include vinyl polymerization structures in which ethylenically unsaturated double bonds are polymerized.

[0061] The active material resin and the resin layer resin preferably contain the structure shown in formula (1) or the structure shown in formula (2). It is preferable that the active material resin and the resin layer resin both contain either the structure shown in formula (1) or formula (2) in common, so that they adhere properly to each other.

[0062] It is preferable that the active material resin and the resin layer resin contain common functional groups. This is preferable because the active material resin and the resin layer resin contain common functional groups, which allows them to bond properly. Common functional groups include the phenyl group, among others.

[0063] Examples of active material resins include rubber-based resins such as butadiene rubber (BR) and styrene-butadiene rubber (SBR), fluoride-based resins such as polyvinylidene fluoride (PVdF), and vinyl resins such as polyvinyl chloride, polyvinylidene chloride, vinyl acetate, polyvinyl alcohol, and styrene resin.

[0064] It is preferable that the active material resin and the resin layer resin contain a common resin. This is preferable because the active material resin and the resin layer resin contain a common resin, which allows them to bond properly. Common resins include those listed above as active material resins, specifically rubber-based resins such as butadiene rubber (BR) and styrene-butadiene rubber (SBR), fluoride-based resins such as polyvinylidene fluoride (PVdF), and vinyl resins such as polyvinyl chloride, polyvinylidene chloride, vinyl acetate, polyvinyl alcohol, and styrene resin.

[0065] In secondary particles, the ratio of the active material resin to the total of multiple primary particles and the active material resin may be, for example, 1% by mass or more and 30% by mass or less, or 5% by mass or more and 25% by mass or less. On the other hand, secondary particles may be sintered bodies formed by the aggregation of multiple primary particles that contain the active material resin.

[0066] (solid electrolyte) The negative electrode composite may contain a solid electrolyte. Examples of solid electrolytes include inorganic solid electrolytes such as sulfide solid electrolytes, oxide solid electrolytes, nitride solid electrolytes, and halide solid electrolytes.

[0067] Sulfide solid electrolytes are solid electrolytes that contain sulfur (S) as the main component of the anionic element. Examples of sulfide solid electrolytes include solid electrolytes containing Li, X (where X is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In), and S. Sulfide solid electrolytes may contain one element as X, or two or more elements. It is preferable that sulfide solid electrolytes contain P as X. Sulfide solid electrolytes may further contain at least one of O and halogen elements. Examples of halogen elements include F, Cl, Br, and I.

[0068] The sulfide solid electrolyte may be glass (amorphous), glass ceramics, or crystalline. The sulfide solid electrolyte may have a crystalline phase. Examples of the crystalline phase include, for example, Thio-LISICON type crystalline phase, argyrodite type crystalline phase, and LGPS type crystalline phase.

[0069] The composition of the sulfide solid electrolyte is not particularly limited, and examples thereof include xLi2S·(1-x)P2S5 (0.5≦x<1), yLiI·zLiBr·(100-y-z)(xLi2S·(1-x)P2S5) (0.5≦x<1, 0≦y≦30, 0≦z≦30). In these compositions, x preferably satisfies 0.7≦x≦0.8. Further, as another example of the composition of the sulfide solid electrolyte, Li 7-x PS 6-x X X is included. X is at least one of F, Cl, Br, and I, and x satisfies 0≦x≦2. Further, as another example of the composition of the sulfide solid electrolyte, Li 4-x Me 1-x P x S4 (0<x<1) is included. Me is at least one of Al, Zn, In, Ge, Si, Sn, Sb, Ga, and Bi.

[0070] The oxide solid electrolyte is a solid electrolyte containing oxygen element as the main component of the anion element, the nitride solid electrolyte is a solid electrolyte containing nitrogen element as the main component of the anion element, and the halide solid electrolyte is a solid electrolyte containing halogen element as the main component of the anion element. Any known solid electrolyte can be adopted as these solid electrolytes. The solid content ratio of the solid electrolyte in the negative electrode composite material is, for example, 10% by mass or more and 50% by mass or less, and may be 20% by mass or more and 40% by mass or less.

[0071] The particle size D50 of the solid electrolyte is not particularly limited, but for example, it is 0.05 μm or more and less than 2.0 μm. The particle size D50 of the solid electrolyte may be 0.1 μm or more, 0.2 μm or more, or 0.3 μm or more. On the other hand, the particle size D50 of the solid electrolyte may be 1.8 μm or less, 1.5 μm or less, 1.2 μm or less, or 1.0 μm or less.

[0072] Furthermore, the ratio of the particle size D50 of the solid electrolyte to the particle size D50 of the secondary particles (SE / Si2) is not particularly limited, but may be, for example, 0.5% or more, 1.0% or more, 1.2% or more, or 1.5% or more. On the other hand, the above ratio (SE / Si2) may be, for example, 15% or less, 12% or less, 10% or less, or 5% or less.

[0073] (Other materials) The negative electrode composite may further contain a conductive material. Examples of conductive materials include carbon-based conductive materials and metallic conductive materials. Examples of carbon-based conductive materials include particulate carbon-based conductive materials such as acetylene black (AB) and Ketjenblack (KB), and fibrous carbon-based conductive materials such as carbon fibers, carbon nanotubes (CNTs), and carbon nanofibers (CNF). Furthermore, the fibrous carbon-based conductive material is preferably carbon nanotubes (CNTs) such as single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). When the conductive material is particulate, the particle size D50 of the conductive material is not particularly limited, but may be, for example, 10 nm or more and 10 μm or less, 20 nm or more and 1 μm or less, or 30 nm or more and 500 nm or less. The solid content ratio of the conductive material in the negative electrode composite is, for example, 0.05% by mass or more and 3% by mass or less.

[0074] The negative electrode composite may further contain a binder that does not constitute secondary particles, in addition to the active material resin that constitutes the secondary particles described above. The types of binders are the same as those described above for active material resins. Specifically, these include rubber resins such as butadiene rubber (BR) and styrene-butadiene rubber (SBR), fluoride resins such as polyvinylidene fluoride (PVDF), and vinyl resins such as polyvinyl chloride, polyvinylidene chloride, vinyl acetate, polyvinyl alcohol, and styrene resin. In other words, the negative electrode layer contains a binder, and the binder is preferably styrene-butadiene rubber, polyvinylidene fluoride, or vinyl resin. The solid content ratio of the binder in the negative electrode composite is, for example, 0.1% by mass or more and 5% by mass or less.

[0075] The negative electrode mixture may or may not contain a dispersion medium. Examples of dispersion media include butyl acetate, butyl butyrate, mesitylene, tetralin, heptane, and N-methyl-2-pyrrolidone (NMP). When the negative electrode mixture contains a dispersion medium, the solid content ratio of the negative electrode mixture is, for example, 20% by mass or more and 80% by mass or less. Furthermore, the negative electrode mixture is usually used in batteries, and is preferably used in solid-state batteries.

[0076] The method for manufacturing the negative electrode mixture is not particularly limited. As described in "C. Method for Manufacturing the Negative Electrode Mixture" below, particles that are the negative electrode active material may be prepared and the negative electrode mixture may be obtained. The particles that constitute the negative electrode active material may include primary and secondary particles. For example, when producing secondary particles by a spray-drying method, by adjusting the production conditions (for example, by relatively reducing the amount of active material resin added), secondary particles can be formed from primary particles and active material resin, while some of the primary particles remain without being converted into secondary particles, resulting in a negative electrode active material that includes both primary and secondary particles. The primary particles that were not converted into secondary particles remain as primary particles, and as a result, a negative electrode mixture containing both primary and secondary particles is obtained.

[0077] (positive electrode) A positive electrode according to one embodiment of this disclosure includes a positive electrode current collector and a positive electrode layer. The positive electrode current collector includes a positive electrode substrate layer. The positive electrode layer typically contains a positive electrode composite material. The positive electrode composite material contains at least a positive electrode active material and may further contain at least one of a solid electrolyte, a conductive material, and a binder.

[0078] Examples of positive electrode active materials include oxide active materials. Examples of oxide active materials include LiCoO2, LiMnO2, LiNiO2, LiVO2, and LiNi 1 / 3 C 1 / 3 Mn 1 / 3 O2, LiLiLi 0.8 Co 0.15 Al 0.05 Rock salt layered active materials such as O2, LiMn2O4, Li4Ti5O 12 , Li(Ni 0.5 Mn 1.5 Examples include spinel-type active materials such as O4, and olivine-type active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4.

[0079] A coating layer containing a Li-ion conductive oxide may be formed on the surface of the oxide active material. This is because it can suppress the reaction between the oxide active material and the solid electrolyte (especially sulfide solid electrolytes). Examples of Li-ion conductive oxides include LiNbO3. The thickness of the coating layer is, for example, 1 nm to 30 nm.

[0080] The solid electrolyte, conductive material, and binder used in the positive electrode composite material are the same as those described for the negative electrode layer. The thickness of the positive electrode layer is, for example, 0.1 μm or more and 500 μm or less, and may be 0.1 μm or more and 100 μm or less, or 0.1 μm or more and 50 μm or less. As for the method of forming the positive electrode layer, for example, a method of coating a positive electrode composite material containing a dispersion medium onto a positive electrode current collector and drying it can be used.

[0081] (electrolyte layer) The electrolyte layer is formed between the positive electrode layer and the negative electrode layer and contains a solid electrolyte. The electrolyte layer may further contain a binder. The solid electrolyte and binder are the same as those described in "A. Negative Electrode Composite Material" above. The thickness of the electrolyte layer is, for example, 0.1 μm or more and 500 μm or less, and may be 0.1 μm or more and 100 μm or less, or 0.1 μm or more and 50 μm or less.

[0082] (Other configurations) In one embodiment of the present disclosure, a solid-state battery preferably has a positive electrode current collector that collects current from the positive electrode layer. Examples of materials for the positive electrode current collector include SUS, aluminum, nickel, iron, titanium, and carbon. On the other hand, examples of materials for the negative electrode current collector include SUS, copper, nickel, and carbon.

[0083] The solid-state battery in this disclosure may further include a restraining jig that applies restraining pressure to the positive electrode layer, electrolyte layer, and negative electrode layer along the thickness direction. The restraining pressure is, for example, 0.1 MPa or more, may be 1 MPa or more, or 5 MPa or more. On the other hand, the restraining pressure is, for example, 100 MPa or less, may be 50 MPa or less, or 20 MPa or less.

[0084] (solid battery) A solid-state battery comprises a negative electrode, an electrolyte layer, and a positive electrode in that order. The negative electrode has a negative electrode current collector and a negative electrode layer, and the positive electrode has a positive electrode layer and a positive electrode current collector. The type of solid-state battery is not particularly limited, but is typically a lithium-ion battery. Furthermore, the solid-state battery in this disclosure may be a primary battery or a secondary battery, but is preferably a secondary battery. This is because it can be repeatedly charged and discharged, making it useful, for example, as an in-vehicle battery. The solid-state battery may be a semi-solid-state battery or a fully solid-state battery. A fully solid-state battery is preferred.

[0085] Applications of solid-state batteries include, for example, power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), battery electric vehicles (BEVs), gasoline cars, and diesel cars. In particular, their use as power sources for hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), or battery electric vehicles (BEVs) is preferred. Solid-state batteries may also be used as power sources for other mobile devices (e.g., trains, ships, aircraft), and as power sources for electrical products such as information processing devices. Furthermore, the manufacturing method of solid-state batteries is not particularly limited, and known methods can be employed. [Examples]

[0086] The present disclosure will be described in more detail below with reference to examples. [Example 1] 1. Fabrication of the negative electrode layer (Preparation of primary particles) 0.65 g of Si particles (manufactured by Kojun Chemical) and 0.60 g of Li metal (manufactured by Honjo Metal) were mixed in an agate mortar under an Ar atmosphere to obtain a LiSi precursor. In a glass reactor under an Ar atmosphere, 1.0 g of the LiSi precursor and 125 ml of dispersion medium (1,3,5-trimethylbenzene, manufactured by Nacalai Tesque) were mixed using an ultrasonic homogenizer (UH-50, manufactured by SMT). The resulting LiSi precursor dispersion was cooled to 0°C, and 125 ml of ethanol (manufactured by Nacalai Tesque) as a Li extraction solvent was added dropwise, and the mixture was reacted for 120 minutes. After the reaction, 50 ml of acetic acid (manufactured by Nacalai Tesque) was added dropwise, and the mixture was reacted for another 60 minutes. After the reaction, the liquid and solid reactants were separated by suction filtration. The obtained solid reactants were vacuum-dried at 120°C for 2 hours to recover porous primary particles (nanoporous Si). The recovered primary particles were classified, and the particle size D50 of the primary particles was adjusted to 1.5 μm.

[0087] (Preparation of secondary particles) The obtained primary particles (nanoporous Si) and a PVDF-HFP-based binder (manufactured by Kureha Corporation) were dispersed and partially dissolved in dimethyl carbonate (manufactured by Nacalai Tesque Corporation) in a primary particle:binder ratio (mass ratio) of 100:13.3 to obtain a slurry. This slurry was sprayed into a spray dryer under a nitrogen gas atmosphere at 140°C and dried to obtain secondary particles formed by the aggregation of multiple primary particles. The obtained secondary particles were classified, and the particle size D50 of the secondary particles was adjusted to 10 μm.

[0088] (Fabrication of the negative electrode layer) A resin slurry prepared by mixing vinyl resin and carbon, which are resins for the resin layer, in an organic solvent in a mass ratio of 50:50 was coated onto a negative electrode current collector (Ni foil) using the blade method, dried on a hot plate at 80°C for 30 minutes, and then dried again at 170°C for 30 minutes to obtain a negative electrode current collector having a resin layer. The primary and secondary particles obtained above were mixed in a volume ratio of primary:secondary particles = 5:95 to obtain a negative electrode active material. 1.0 g of the obtained negative electrode active material, 0.04 g of conductive material (VGCF, manufactured by Showa Denko), 0.776 g of sulfide solid electrolyte (LiI-LiBr-Li3PS4-based sulfide solid electrolyte, D50 = 0.2 μm), 0.02 g of binder resin for the active material (PVDF, manufactured by Kureha), and 1.7 g of butyl butyrate (manufactured by Kishida Chemical) were mixed using an ultrasonic homogenizer (UH-50, manufactured by SMT) to prepare a negative electrode slurry (negative electrode composite). This negative electrode slurry was coated onto the resin layer on the negative electrode current collector obtained above using the blade method, and dried on a hot plate at 100°C for 30 minutes to obtain a negative electrode layer (thickness 30 μm). Table 1 shows the resin for the resin layer and the resin for the active material used in Example 1.

[0089] 2. Fabrication of the positive electrode layer Positive electrode active material (LiNi coated with LiNbO3) 0.8 Co 0.15 Mn 0.05A positive electrode slurry was prepared by mixing 1.5g of O2, 0.023g of conductive material (VGCF, manufactured by Showa Denko), 0.239g of sulfide solid electrolyte (LiI-LiBr-Li3PS4-based sulfide solid electrolyte, D50=0.2μm), 0.011g of binder (PVDF, manufactured by Kureha), and 0.8g of butyl butyrate (manufactured by Kishida Chemical) using an ultrasonic homogenizer (UH-50, manufactured by SMT). This positive electrode slurry was coated onto a positive electrode current collector (Al foil) using the blade method and dried on a hot plate at 100°C for 30 minutes to obtain a positive electrode layer.

[0090] 3. Preparation of the solid electrolyte layer A binder solid electrolyte was added to an organic solvent. After addition, the mixture was kneaded using an ultrasonic homogenizer to obtain a solid electrolyte slurry. The obtained solid electrolyte slurry was coated onto an aluminum foil to obtain a solid electrolyte layer.

[0091] 4. Battery construction Each electrode layer prepared in steps 1-3 above was formed into a strip. The composite surfaces of the positive electrode layer and the solid electrolyte layer were aligned and roll-pressed at 165°C and a pressure of 50kN·cm to remove the Al foil, thereby transferring the solid electrolyte layer to the positive electrode layer. Similarly, the composite surfaces of the negative electrode layer and the solid electrolyte layer were aligned and roll-pressed at 25°C and a pressure of 50kN·cm to remove the transfer foil (Al foil), thereby transferring the solid electrolyte layer to the negative electrode layer. The negative electrode with the transferred solid electrolyte layer was punched out with a diameter of 13.00 mm, and the positive electrode layer with a diameter of 11.28 mm using a punching machine. The solid electrolyte layer was then transferred to the negative electrode using a uniaxial press. The punched negative electrode and positive electrode layers were placed facing each other to form a battery. Finally, current extraction tabs were attached to the positive and negative electrodes, sealed in aluminum laminate using a vacuum laminating sealer, and restrained with a pressure of 5 MPa to fabricate the battery.

[0092] [Examples 2 to 9, and Comparative Examples 1 to 3] A battery was manufactured in the same manner as in Example 1, except that the resin for the resin layer and the resin for the active material were as shown in Table 1. In the column for the resin layer in Table 1, where it is written as "no resin layer", a negative electrode current collector without a resin for the resin layer, i.e., a negative electrode current collector made of Ni foil, was used, and the negative electrode slurry was coated onto the Ni foil. Table 1 shows the resins used for the resin layer and active material in Examples 2 to 9. Table 1 shows the active material resins used in Comparative Examples 1 to 3.

[0093] (evaluation) <Peel Strength Evaluation> In the examples and comparative examples, the negative electrode layer prepared in section 4 above was punched out to a diameter of 11.28 mm, and samples were prepared using LUMiFrac (manufactured by MS Scientific Co., Ltd.). The adhesive strength (peel strength) between the composite layer and the current collector layer was measured. Furthermore, the normalized peel strength was calculated for each, with Comparative Example 1 set to 100. The results are shown in the "Normalized Peel Strength" column of Table 1. The sample was prepared by attaching the object to be measured to the adapter, securing it with a support sheet, and then attaching a test stamp (weight). The measurement conditions involved increasing the load on the sample at 10 rpm (revolutions per minute) / second (approximately 0.2 N / second), with a measurement ambient temperature of 25°C, and a bonding area of ​​approximately 78 cm² with a diameter of 10 mm. 2 That was the case.

[0094] <Battery Resistance Evaluation> In each of the all-solid-state batteries for the example and comparative example prepared in section 4 above, the resistance was adjusted to 3.7V, and the initial resistance was calculated from the voltage drop after 5 seconds of discharge at a 5C rate. Furthermore, the resistance was measured again after 40 cycles at a 1 / 3C rate, 3.0V~4.2V, and 60℃, and the resistance after durability was calculated. The increase rate was calculated from the initial resistance value and the resistance value after durability testing, and the normalized resistance increase rate was further calculated for each, with Comparative Example 1 set to 100. The calculated results are shown in the "Normalized Resistance Increase Rate" column of Table 1, and the "Normalized Resistance Increase Rate" is also indicated in the graph shown in Figure 2.

[0095] [Table 1]

[0096] The compounds used are shown below in Table 1. PVDF: Polyvinylidene fluoride (weight-average molecular weight: 800,000) Vinyl resin: Polyacetal (weight-average molecular weight: 500,000) SBR: Styrene-butadiene rubber (weight-average molecular weight: 200,000)

[0097] As shown in Table 1 and Figure 2, it was demonstrated that a solid electrolyte using a negative electrode containing an active material resin and a resin layer resin exhibits improved peel strength, reduced resistance increase rate, and suppressed internal resistance increase due to charging and discharging. [Explanation of symbols]

[0098] 10 negative electrode 11 Negative electrode base material layer 12 resin layer 13. Negative electrode layer

Claims

1. The device comprises a first current collector, a first electrode layer, an electrolyte layer, a second electrode layer, and a second current collector, in this order. The first current collector includes a resin layer in contact with the first electrode layer. The first electrode layer comprises an electrode active material, The electrode active material is a solid battery having a resin for the active material.

2. The electrode active material includes secondary particles, The solid battery according to claim 1, wherein the secondary particles include a plurality of primary particles and the active material resin.

3. The aforementioned resin layer includes a resin for the resin layer, The solid battery according to claim 1, wherein the resin for the active material and the resin for the resin layer have a common structure.

4. The aforementioned resin layer includes a resin for the resin layer, The solid battery according to claim 1, wherein the resin for the active material and the resin for the resin layer contain a common functional group.

5. The aforementioned resin layer includes a resin for the resin layer, The solid battery according to claim 1, wherein the resin for the active material and the resin for the resin layer include a common resin.

6. The aforementioned resin layer includes a resin for the resin layer, The solid battery according to claim 1, wherein the active material resin and the resin layer resin each include a structure represented by at least one of formulas (1) and (2). 【Chemistry 1】 【Chemistry 2】 In formula (1), R represents an alkyl group, an allyl group, a hydroxyl group, a carboxyl group, a methoxy group, or an ethoxy group, and n in formulas (1) and (2) independently represents an integer of 1 or more.

7. The aforementioned resin layer includes a resin for the resin layer, The solid battery according to claim 1, wherein the active material resin and the resin layer resin include a structure represented by formula (1) or a structure represented by formula (2). 【Transformation 3】 【Chemistry 4】 In formula (1), R represents an alkyl group, an allyl group, a hydroxyl group, a carboxyl group, a methoxy group, or an ethoxy group, and n in formulas (1) and (2) independently represents an integer of 1 or more.

8. The solid battery according to claim 1, wherein the active material resin is bondable to the resin layer.

9. The solid battery according to claim 1, wherein the first current collector further comprises a metal layer.

10. The solid battery according to claim 1, wherein the first current collector is a conductive resin current collector.

11. The solid battery according to claim 1, wherein the resin layer has a region to which the electrode active material adheres.

12. The solid battery according to claim 1, wherein the electrode active material comprises the element Si.

13. The aforementioned metal layer is nickel foil, The solid battery according to claim 9, wherein the first current collector comprises nickel foil and the resin layer in that order.

14. The first electrode layer comprises a binder, The solid battery according to claim 1, wherein the binder is at least one selected from the group consisting of styrene-butadiene rubber, polyvinylidene fluoride, and vinyl resin.

15. A solid-state battery according to any one of claims 1 to 14, which is an all-solid-state battery.

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