Solid-state battery and method for manufacturing a solid-state battery

Abstract

The present invention relates to a solid-state battery and a manufacturing method of a solid-state battery. A solid-state battery includes a negative electrode layer and a solid electrolyte layer adjacent to the negative electrode layer, the negative electrode layer containing a negative electrode active material and a solid electrolyte, the negative electrode active material containing a complex including a plurality of particles and particles not included in the complex, wherein at least a portion of the particles not included in the complex is embedded in the solid electrolyte layer.

Description

Technical Field

[0001] This disclosure relates to solid-state batteries and methods for manufacturing solid-state batteries. Background Technology

[0002] The practical application of secondary batteries using solid electrolytes (hereinafter also referred to as solid-state batteries) as rechargeable secondary batteries has been studied. There are cases where the electrodes of solid-state batteries contain both active materials and solid electrolytes to promote the movement of ions between the active material particles within the electrodes.

[0003] It is known that the volume of the negative electrode active material contained in the negative electrode of a secondary battery changes significantly during battery charging (when ions are trapped) and discharging (when ions are released). Furthermore, it has been pointed out that when the negative electrode active material repeatedly expands / contracts in volume during battery charging / discharging, the bonding state between the active material particles and the solid electrolyte within the negative electrode may change, leading to battery degradation.

[0004] It has been proposed to cover the surface of the negative electrode active material with a sulfide solid electrolyte as a countermeasure to suppress the volume change of the negative electrode active material with battery charge / discharge (for example, see Japanese Patent Application Publication No. 2021-128857). Summary of the Invention

[0005] Solid-state batteries have a layer containing a solid electrolyte disposed between the positive and negative electrodes (hereinafter also referred to as the solid electrolyte layer). The solid electrolyte layer acts as a separator separating the positive and negative electrodes and provides a path for ions to move between the positive and negative electrodes.

[0006] It has been pointed out that the change in the bonding state between the negative electrode and the solid electrolyte layer is the reason why the resistance increases with the charging / discharging of the solid-state battery.

[0007] In view of the above, this disclosure is intended to provide a solid-state battery in which the bonding state of the negative electrode and the solid electrolyte layer is maintained in an advantageous manner, and a method for manufacturing the solid-state battery.

[0008] This disclosure includes the following aspects.

[0009] <1> A solid-state battery includes a negative electrode layer and a solid electrolyte layer adjacent to the negative electrode layer.

[0010] The negative electrode layer contains a negative electrode active material and a solid electrolyte, and

[0011] The negative electrode active material contains a complex comprising multiple particles and particles not contained in the complex, wherein at least a portion of the particles not contained in the complex are embedded in the solid electrolyte layer.

[0012] <2> according to <1> The solid-state battery, wherein the negative electrode active material contains the element Si.

[0013] <3> according to <1> or <2> The solid-state battery includes a structure in which a positive electrode layer, a solid electrolyte layer, a negative electrode layer and a negative electrode current collector are sequentially disposed on both sides of the positive electrode current collector.

[0014] <4> A manufacturing basis <1> to <3> A method for a solid-state battery according to any one of the following, the method comprising forming a negative electrode layer on a solid electrolyte layer, the negative electrode layer containing a solid electrolyte and a negative electrode active material in a composite state containing a plurality of particles.

[0015] The formation of the negative electrode layer includes applying pressure to the negative electrode layer such that at least a portion of the particles contained in the composite are separated from the composite.

[0016] <5> according to <4> The method includes:

[0017] A positive electrode layer is formed on both sides of the positive current collector;

[0018] A solid electrolyte layer is formed on the positive electrode layer; and

[0019] A negative electrode layer is formed on the solid electrolyte layer.

[0020] According to this disclosure, a solid-state battery in which the bonding state of the negative electrode and the solid electrolyte layer is maintained in an advantageous manner, and a method for manufacturing the solid-state battery are provided. Attached Figure Description

[0021] Figure 1 This is a schematic cross-sectional view illustrating an example of the configuration of the negative electrode structure included in a solid-state battery; and

[0022] Figure 2 This is a schematic cross-sectional view illustrating an example of a positive electrode center-type layered structure contained in a solid-state battery. Detailed Implementation

[0023] The following describes an implementation as an example of this disclosure. The description and examples are intended to illustrate implementation methods and do not limit the scope of this disclosure.

[0024] In this disclosure, any numerical range described by the expression "from * to" means that the numerical values ​​described before and after "to" are included in the range as the minimum and maximum values, respectively.

[0025] In this disclosure, within a range of values ​​expressed in a phased manner, the maximum or minimum value listed in a given range can be replaced by the maximum or minimum value of another range of values ​​expressed in a phased manner. Furthermore, within the range of values ​​presented in this disclosure, the maximum or minimum value of a given range can be replaced by the value described in the embodiments.

[0026] In this disclosure, where multiple materials correspond to one component of a composition, unless otherwise stated, the amount of that component in the composition refers to the total amount of the multiple materials present in the composition.

[0027] In this disclosure, a combination of two or more preferred aspects is a more preferred aspect.

[0028] In this disclosure, the term "step" includes not only independent steps that can be distinguished from other steps, but also steps that cannot be clearly distinguished from other steps, as long as the purpose of the step is achieved.

[0029] In this disclosure, the term "solid-state battery" refers to a secondary battery that uses at least a solid electrolyte as the electrolyte. Therefore, the solid-state battery as described in this disclosure includes batteries referred to by different names, such as all-solid-state batteries and semi-solid-state batteries.

[0030] Solid-state batteries

[0031] One embodiment of this disclosure is a solid-state battery comprising a negative electrode layer and a solid electrolyte layer adjacent to the negative electrode layer. The negative electrode layer contains a negative electrode active material and a solid electrolyte, and the negative electrode active material contains a complex comprising a plurality of particles and particles not contained in the complex, wherein at least a portion of the particles not contained in the complex are embedded in the solid electrolyte layer.

[0032] In this disclosure, the negative electrode layer refers to a layer containing at least a negative electrode active material, and the solid electrolyte layer refers to a layer containing at least a solid electrolyte.

[0033] In the following description, the structure formed by the negative electrode layer and the solid electrolyte layer adjacent to the negative electrode layer may be referred to as the "negative electrode structure".

[0034] Figure 1 This is a cross-sectional view schematically illustrating an example of the configuration of the negative electrode structure included in the solid-state battery of this disclosure.

[0035] like Figure 1 As shown, the negative electrode structure of the solid-state battery of this disclosure includes a negative electrode layer 40 and a solid electrolyte layer 30 adjacent to the negative electrode layer 40.

[0036] The negative electrode layer 40 contains negative electrode active material particles 42 and a solid electrolyte 44. The negative electrode active material particles 42 contain a complex 42A comprising multiple particles and particles 42B not contained in the complex. At least a portion of the particles 42B not contained in the complex are embedded in the solid electrolyte layer 30.

[0037] The negative electrode layer of a solid-state battery is typically subjected to high-voltage pressing to increase the density of the negative electrode layer and the bonding strength between the negative electrode layer and its adjacent layers (i.e., the solid electrolyte layer and the negative electrode current collector).

[0038] As a result of the inventors' research, it has been found that if a negative electrode layer containing negative electrode active material particles in a complex state formed by multiple particles is subjected to a pressing treatment, the bonding strength between the negative electrode layer and the solid electrolyte layer is significantly improved compared to the case where a negative electrode layer in which the negative electrode active material particles do not form a complex is subjected to a pressing treatment.

[0039] To investigate the cause, the interface between the negative electrode layer and the solid electrolyte layer was observed after pressing the negative electrode layer in which the negative electrode active material particles were in a composite state. The results showed that some of the particles separated from the composite were embedded in the solid electrolyte layer.

[0040] On the other hand, after pressing the negative electrode layer in which the negative electrode active material particles are not in a composite state, no negative electrode active material particles embedded in the solid electrolyte layer were observed at the interface between the negative electrode layer and the solid electrolyte layer.

[0041] Based on the above, it is speculated that the improved bonding strength between the negative electrode layer and the solid electrolyte layer is due to the negative electrode active material particles embedded in the solid electrolyte layer.

[0042] The reason why particles separated from the composite material are embedded in the solid electrolyte layer when the negative electrode layer containing negative electrode active material particles in a composite state is believed to be, for example, as follows.

[0043] In the unpressed negative electrode layer, the solid electrolyte exists around the negative electrode active material particles. Therefore, when pressing is performed, the solid electrolyte surrounding the negative electrode active material particles deforms and covers the surface of the negative electrode active material particles. As a result, it is believed that the embedding of the negative electrode active material particles into the solid electrolyte layer is inhibited.

[0044] On the other hand, if the negative electrode active material contained in the unpressed negative electrode layer is in a composite state, the composite will be destroyed by the pressing process, and some particles will separate from the composite. The particles that have just separated from the composite after the pressing process are not covered by the solid electrolyte. Therefore, it is believed that particles that have separated from the composite and are located near the interface with the solid electrolyte layer may be embedded in the solid electrolyte layer.

[0045] In this disclosure, the pressing process performed on the negative electrode layer can be a process of transferring the negative electrode layer onto the solid electrolyte layer, or it can be a process performed on the negative electrode layer that has already been formed on the solid electrolyte layer.

[0046] In this disclosure, examples of composites containing multiple particles are composites containing multiple (e.g., two to ten) particles (i.e., primary particles). The composite may also contain an adhesive for bonding the primary particles.

[0047] There are no particular limitations on the method for manufacturing a negative electrode active material in a composite state, and it can be performed by known methods. For example, a negative electrode active material in a composite state can be manufactured by a method comprising the following steps: preparing a composition containing primary particles, a binder, and a solvent for forming the composite; forming droplets of the composition; and removing the solvent from the droplets.

[0048] The composite containing multiple particles has voids within it. These voids within the composite have the effect of mitigating the volume change of the negative electrode active material.

[0049] There are no particular limitations on the particle size of the composite of negative electrode active materials and the primary particles contained in the negative electrode layer. For example, the particle size of the composite can be selected from the range of 5 μm to 50 μm, and the particle size of the primary particles can be selected from the range of 0.5 μm to 5 μm.

[0050] There are no particular restrictions on the material of the negative electrode active material contained in the negative electrode layer. For example, it can be selected from the materials for negative electrode active materials described below.

[0051] From the viewpoint of forming a state in which particles not included in the composite are embedded in the solid electrolyte layer, it is preferable that the negative electrode active material is an active material containing Si.

[0052] From the viewpoint of forming a state in which particles not included in the complex are embedded in the solid electrolyte layer, it is preferable that the solid electrolyte layer contains a sulfide solid electrolyte.

[0053] The solid-state battery of this disclosure may include multiple negative electrode structures. There is no particular limitation on the number of negative electrode structures included in the solid-state battery of this disclosure, and it may be selected from, for example, a range of 2 to 100.

[0054] In the case of a solid-state battery comprising multiple negative electrode structures, all negative electrode structures may satisfy the above conditions (i.e., at least a portion of the particles not included in the composite in the negative electrode layer are embedded in the solid electrolyte layer), or only a portion of the negative electrode structures may satisfy the above conditions.

[0055] From the viewpoint of maintaining the bonding state between the negative electrode layer and the solid electrolyte layer in an advantageous manner, among all the negative electrode structures contained in the solid-state battery of this disclosure, preferably more than 50% of the negative electrode structures satisfy the above conditions, more preferably more than 70% of the negative electrode structures satisfy the above conditions, and even more preferably more than 80% of the negative electrode structures satisfy the above conditions.

[0056] (Example of solid-state battery structure)

[0057] The solid-state battery disclosed herein may include a structure in which a positive electrode layer, a solid electrolyte layer, a negative electrode layer and a negative electrode current collector are sequentially disposed on both sides of the positive electrode current collector (hereinafter also referred to as a positive electrode center-type layered structure).

[0058] Figure 2 An example of a positive electrode center-type layered structure included in the solid-state battery of this disclosure is shown.

[0059] like Figure 2 As shown, the positive electrode center-type layered structure 100 is in a state in which a first negative electrode current collector 50A, a first negative electrode layer 40A, a first solid electrolyte layer 30A, a first positive electrode layer 20A, a positive electrode current collector 10, a second positive electrode layer 20B, a second solid electrolyte layer 30B, a second negative electrode layer 40B, and a second negative electrode current collector layer 50B are sequentially arranged.

[0060] Solid-state batteries with a positive electrode center-type layered structure can be manufactured, for example, by methods including the steps described below.

[0061] In the following description, there are instances where the first negative electrode layer and the second negative electrode layer are referred to as "negative electrode layer" without distinction between them, instances where the first negative electrode current collector and the second negative electrode current collector are referred to as "negative electrode current collector" without distinction between them, instances where the first positive electrode layer and the second positive electrode layer are referred to as "positive electrode layer" without distinction between them, instances where the first positive electrode current collector and the second positive electrode current collector are referred to as "positive electrode current collector" without distinction between them, and instances where the first solid electrolyte layer and the second solid electrolyte layer are referred to as "solid electrolyte layer" without distinction between them.

[0062] (Step 1)

[0063] In step 1, a positive electrode layer is formed on both surfaces of the positive current collector, and a laminate 1 is obtained (layer structure: first positive electrode layer / positive current collector / second positive electrode layer). There are no particular limitations on the method for forming the positive electrode layer on the two surfaces of the positive current collector, and it can be selected from coating, transfer printing, etc. The laminate 1 can be subjected to pressing treatment as needed.

[0064] Depending on the requirements, end fillers can be provided at the ends of the positive electrode layers formed on both surfaces of the positive current collector. The end fillers serve multiple functions, such as adjusting the shape of the positive electrode layer ends and preventing the positive electrode layer from contacting the expanded negative electrode layer during charging. The material for the end fillers can be selected from electrically insulating materials, such as resin.

[0065] (Step 2)

[0066] In step 2, a solid electrolyte layer is formed on the positive electrode layer formed on both surfaces of the positive electrode current collector, and a laminate 2 is obtained (layer structure: first solid electrolyte layer / first positive electrode layer / positive electrode current collector / second positive electrode layer / second solid electrolyte layer). There are no particular limitations on the method for forming the solid electrolyte layer on the positive electrode layer, and it can be selected from coating, transfer printing, etc. From a processability point of view, the transfer printing method, which allows for the simultaneous formation and pressing of the solid electrolyte layer, is preferred.

[0067] (Step 3)

[0068] In step 3, a negative electrode layer is formed on the solid electrolyte layer formed on the positive electrode layer, and a laminate 3 is obtained (layer structure: first negative electrode layer / first solid electrolyte layer / first positive electrode layer / positive current collector / second positive electrode layer / second solid electrolyte layer / second negative electrode layer). There are no particular limitations on the method for forming the negative electrode layer on the solid electrolyte layer, and it can be selected from coating, transfer printing, etc. From a processability point of view, the transfer printing method, which allows for the simultaneous formation and pressing of the negative electrode layer, is preferred.

[0069] (Step 4)

[0070] In step 4, a negative electrode current collector is disposed on the negative electrode layer formed on the solid electrolyte layer, and a laminate 4 is obtained (layer structure: first negative electrode current collector / first negative electrode layer / first solid electrolyte layer / first positive electrode layer / positive electrode current collector / second positive electrode layer / second solid electrolyte layer / second negative electrode layer / second negative electrode current collector). The laminate 4 may be subjected to pressing treatment as needed.

[0071] When the negative electrode layer formed on the solid electrolyte layer in step 3 is bonded to the negative electrode current collector, step 4 can be omitted.

[0072] In solid-state batteries manufactured by methods including the steps described above, the negative electrode layer is subjected to pressure (during pressing or transfer) less often than the positive electrode layer.

[0073] Therefore, in the method including the above steps, sufficient pressure can be applied to the positive electrode layer to increase its density, while the pressure applied to the negative electrode layer can be controlled to a desired level. Thus, solid-state batteries containing a positive electrode-centered layered structure tend to exhibit a good balance of battery characteristics.

[0074] The negative electrode layer of the solid-state battery manufactured by the method including the above steps is formed on the solid electrolyte layer formed on the positive electrode layer in step 2. Therefore, the solid electrolyte layer formed thereon in step 3 is in a state in which the negative electrode active material particles in the negative electrode layer are not easily embedded due to the application of pressure.

[0075] In this regard, in the solid-state battery of this disclosure, at least a portion of the negative electrode active material particles in the negative electrode layer are embedded in the solid electrolyte layer. Therefore, even if the solid-state battery is manufactured by a method including the steps described above (i.e., even if the solid-state battery contains a positive electrode-centered layered structure), the bonding state between the negative electrode layer and the solid electrolyte layer can be maintained in an advantageous manner.

[0076] The components constituting the solid-state battery of this disclosure are described below. In the following description, there are instances where the negative electrode current collector and the positive electrode current collector are referred to as "current collectors" without distinction, where the negative electrode layer and the positive electrode layer are referred to as "electrodes" without distinction, and where the negative electrode active material and the positive electrode active material are referred to as "electrode active materials" without distinction.

[0077] (Clottery Collector)

[0078] The type of current collector included in the solid-state battery disclosed herein is not particularly limited, and the current collector may be selected from known current collectors.

[0079] Specific examples of materials for current collectors include metals selected from Ag, Cu, Au, Al, Ni, Fe, and Ti, as well as alloys containing these metals.

[0080] In one embodiment of this disclosure, the positive current collector may contain Al, and the negative current collector may contain Cu.

[0081] There are no particular restrictions on the thickness of the current collector, and the choice can be made by taking into account the type and size of the battery obtained by using the current collector.

[0082] The thickness of the current collector can be, for example, 5 μm or more, 10 μm or more, or 20 μm or more.

[0083] The thickness of the current collector can be, for example, less than 120 μm, less than 80 μm, or less than 60 μm.

[0084] (Electrode layer)

[0085] The solid-state battery disclosed herein contains an electrode layer that includes at least an electrode active material, and may also contain a binder, conductive material, solid electrolyte, etc., as needed.

[0086] Specific examples of negative electrode active materials include carbon materials, active materials containing element Si, lithium metal, lithium-containing alloys, metals or alloys that can form alloys with lithium, oxides, and transition metal nitrides.

[0087] Examples of carbon materials include graphite materials, amorphous carbon materials, carbon black, and activated carbon. Examples of graphite materials include natural graphite and synthetic graphite. Examples of amorphous carbon materials include hard carbon, soft carbon, coke, mesophase carbon microspheres (MCMB), and mesophase pitch carbon fibers (MCF). Graphite materials can be coated with metals or amorphous carbon.

[0088] Examples of active materials containing elemental Si include elemental silicon, silicon alloys (e.g., alloys of Si and one or more metals selected from the group consisting of Sn, Ti, Fe, Ni, Cu, Co and Al), porous silicon, silicon inclusion compounds, and silicon oxides.

[0089] Specific examples of positive electrode active materials include composite oxides containing lithium and transition metals (hereinafter also referred to as composite oxides).

[0090] Examples of composite oxides include composite oxides with layered crystal structures, composite oxides with spinel-type crystal structures, and composite oxides with olivine-type crystal structures.

[0091] Specific examples of composite oxides with layered crystal structures include compounds represented by LiMO2 (where M is at least one transition metal selected from the group consisting of Ni, Co, and Mn), and compounds formed by adding different elements to such compounds. Representative examples of composite oxides with layered crystal structures include LCO (lithium cobalt oxide), NCM (lithium nickel cobalt manganese oxide), and NCA (lithium nickel oxide or lithium nickel cobalt aluminum oxide).

[0092] Specific examples of composite oxides with spinel-type crystal structures include LiMn2O4.

[0093] Specific examples of composite oxides with olivine-type crystal structures include LiMPO4 (where M is Fe, Co, Ni, or Mn).

[0094] The electrode active material contained in the electrode layer can be only one type, or it can be a combination of two or more types.

[0095] The electrode active material can be in the form of, for example, fibrous, spherical, or sheet-like materials.

[0096] For example, the volume average particle size of the electrode active material can be selected from the range of 5 μm to 50 μm.

[0097] The volume-average particle size of the electrode active material is the value (D50) when 50% of the volume-based particle size distribution obtained by laser diffraction / scattering is accumulated from the small particle size side.

[0098] Specific examples of adhesives include polyvinylidene fluoride (PVdF), polyethylene, polypropylene, polyethylene terephthalate, cellulose, nitrocellulose, carboxymethyl cellulose, polyethylene oxide, polyepichlorohydrin, polyacrylonitrile, styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), polyacrylate, polymethacrylate, and polytetrafluoroethylene (PTFE).

[0099] The electrode layer may contain only one type of adhesive, or it may contain a combination of two or more adhesives.

[0100] Examples of conductive materials include carbon materials, metals, conductive oxides, and conductive nitrides.

[0101] Specific examples of carbon materials include graphite, carbon black (such as acetylene black, thermal cracking carbon black, and furnace black), carbon nanotubes (CNTs), carbon nanofibers (CNFs), and vapor-grown carbon fibers (VGCFs). TM ).

[0102] The electrode layer may contain only one type of conductive material, or it may contain a combination of two or more conductive materials.

[0103] Examples of solid electrolytes contained in the electrode layer include sulfide solid electrolytes, oxide solid electrolytes, and polymer solid electrolytes.

[0104] From the perspective of battery performance, sulfide solid electrolytes and polymer solid electrolytes are preferred as solid electrolytes, and from the perspective of thermal stability, sulfide solid electrolytes are preferred.

[0105] The solid electrolyte contained in the electrode layer can be only one type, or it can be a combination of two or more types.

[0106] Examples of sulfide solid electrolytes include compounds containing a metal element used as a conductor and sulfur (S).

[0107] Examples of metallic elements include Li, Na, K, Mg, and Ca. Among them, Li is preferred as a metallic element.

[0108] The sulfide solid electrolyte may contain Li and S, and at least one selected from the group consisting of P, Si, Ge, Al, and B. Preferably, the sulfide solid electrolyte contains Li, S, and P (hereinafter also referred to as LPS-type sulfide solid electrolyte).

[0109] From the perspective of ionic conductivity, sulfide solid electrolytes can contain halogen elements, such as Cl, Br, and I. From the perspective of chemical stability, sulfide solid electrolytes can contain oxygen (O).

[0110] Specific examples of LPS-type sulfide solid electrolytes include Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, LiBr-LiI-Li2S-P2S5, and Li2S-P2S5-Z. m S n (where m and n are positive numbers, and Z is Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, and Li2S-SiS2-Li x MO y (In the formula, x and y are positive numbers, and M is P, Si, Ge, B, Al, Ga or In).

[0111] In the above description, the symbol "Li2S-P2S5" refers to a sulfide solid electrolyte obtained by using Li2S and P2S5 as raw materials. The same applies to other symbols.

[0112] In LPS-type sulfide solid electrolytes, sulfide solid electrolytes obtained by using Li2S and P2S5 are preferred, and sulfide solid electrolytes that satisfy the following formula are even more preferred:

[0113] Li 3+x+5y P 1-y S4 (0 <x≤0.6, 0<y≤0.2)。

[0114] Examples of oxide solid electrolytes include those with NASICON (Na3Zr2PSi2O) 12 Compounds with a NASICON-type crystal structure exhibit high ionic conductivity and excellent atmospheric stability.

[0115] Examples of compounds having a NASICON-type crystal structure include lithium-containing phosphates. Examples of phosphates include Ti-containing complex lithium phosphates (e.g., Li...). 1+x Al x Ti 2-x (PO4)3), and compounds in which all or part of the Ti in the above-mentioned complex lithium phosphate salts is replaced by tetravalent transition metals such as Ge, Sn, Hf, Zr or trivalent transition metals such as Al, Ga, In, Y, La.

[0116] Specific examples of compounds with a NASICON-type crystal structure include Li-Al-Ge-PO materials (Li 1+ x Al x Ge 2-x (PO4)3), Li-Al-Zr-PO based materials (Li 1+x Al x Zr 2-x (PO4)3) and Li-Al-Ti-PO materials (Li 1+ x Al x Ti 2-x (PO4)3).

[0117] Examples of polymeric solid electrolytes include mixtures (complexes) of polymeric compounds and electrolyte salts. Specific examples of polymeric compounds include polyether-based polymeric compounds such as polyethylene oxide (PEO) and polypropylene oxide (PPO), polyamine-based polymeric compounds such as polyethyleneimine (PEI), and polysulfide-based polymeric compounds such as polysulfide (PAS). Polyether-based polymeric compounds are preferred.

[0118] (Solid electrolyte layer)

[0119] The solid electrolyte layer contained in the solid-state battery of this disclosure contains a solid electrolyte.

[0120] There are no particular restrictions on the type of solid electrolyte contained in the solid electrolyte layer, and it can be selected from the solid electrolytes that can be included in the electrode layer as described above.

[0121] When the electrode layer contains a solid electrolyte, the solid electrolyte in the electrode layer and the electrolyte in the solid electrolyte layer may be the same or different.

[0122] The solid electrolyte layer may contain only one type of solid electrolyte, or it may contain a combination of two or more types of solid electrolytes.

[0123] The solid electrolyte contained in the solid electrolyte layer can be a composite solid electrolyte that includes inorganic solid electrolytes and polymer solid electrolytes.

[0124] The solid electrolyte layer may contain a liquid electrolyte (electrolyte) in addition to a solid electrolyte. For example, the solid electrolyte layer may contain an amount of electrolyte less than 10% by mass relative to the total amount of electrolyte.

[0125] If the solid-state battery of this disclosure contains an electrolyte as the electrolyte, there are no particular restrictions on the type of electrolyte, and known electrolytes can be used.

[0126] Specific examples of electrolytes include liquids in which lithium salts such as LiPF6 or LiFSi are dissolved in organic solvents.

[0127] Specific examples of organic solvents include cyclic or chain carbonates such as ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). The solvent may be a mixture of two or more solvents and may be a mixture containing both cyclic and chain carbonates.

[0128] The solvent may contain additives such as vinylene carbonate (VC).

[0129] (Outer packaging)

[0130] The solid-state battery disclosed herein may also have an outer packaging. The outer packaging houses an electrode stack, which includes at least a current collector, an electrode layer, and a solid electrolyte layer. Examples of outer packaging include laminated outer packaging and shell-type outer packaging. The laminated outer packaging may be formed from a laminate (laminated film) having a metal layer comprising a metal such as aluminum and a heat-sealing layer comprising a resin that melts upon heating.

[0131] (Constrained Members)

[0132] The battery disclosed herein may also have a constraint member. The constraint member applies constraint pressure to the electrode stack in the thickness direction.

[0133] The constraint pressure applied in the thickness direction of the electrode stack can be, for example, 0.1 MPa or more, 1 MPa or more, or 5 MPa or more.

[0134] The constraint pressure applied in the thickness direction of the electrode stack can be, for example, less than 100 MPa, less than 50 MPa, or less than 20 MPa.

[0135] (Applications of solid-state batteries)

[0136] There are no particular limitations on the application of the solid-state batteries disclosed herein. Examples of representative applications include use as power sources for vehicles, electronic devices, or energy storage systems. Specifically, the batteries of this disclosure are preferably used as power sources for vehicles, and more preferably as drive power sources for hybrid electric vehicles, plug-in hybrid electric vehicles, or electric vehicles.

[0137] Examples of vehicles include electric four-wheeled vehicles, electric two-wheeled vehicles, gasoline-powered vehicles, and diesel-powered vehicles. Examples of electric four-wheeled vehicles include battery electric vehicles (BEVs), plug-in hybrid electric vehicles (PHEVs), and hybrid electric vehicles (HEVs). Examples of electric two-wheeled vehicles include electric motorcycles and electric-assist bicycles.

[0138] <Solid-state battery manufacturing method>

[0139] One embodiment of this disclosure is a method for manufacturing a solid-state battery, the method comprising:

[0140] A negative electrode layer is formed on a solid electrolyte layer, the negative electrode layer containing a solid electrolyte and a negative electrode active material in a complex state containing multiple particles.

[0141] The formation of the negative electrode layer includes applying pressure to the negative electrode layer such that at least a portion of the particles contained in the composite are separated from the composite.

[0142] According to the method of this disclosure, it is possible to manufacture a solid-state battery in which the bonding state of the negative electrode layer and the solid electrolyte layer is maintained in an advantageous manner.

[0143] In the method of this disclosure, the magnitude of the pressure applied to the negative electrode layer is not particularly limited, as long as it is sufficient to separate at least a portion of the particles contained in the composite from the composite. In the method of this disclosure, the particles separated from the composite due to the pressure applied to the negative electrode layer are not covered by the solid electrolyte. Therefore, according to the method of this disclosure, it is readily possible to obtain a state in which the particles separated from the composite are embedded in the solid electrolyte layer.

[0144] In the method disclosed herein, applying pressure to the negative electrode layer can be a process of transferring the negative electrode layer onto a solid electrolyte layer, or a process of treating the negative electrode layer already formed on the solid electrolyte layer.

[0145] The solid-state battery manufactured using the method of this disclosure can be a solid-state battery containing a positive electrode center-type layered structure. That is, the method of this disclosure can sequentially include:

[0146] A positive electrode layer is formed on both sides of the positive current collector.

[0147] A solid electrolyte layer is formed on the positive electrode layer, and

[0148] A negative electrode layer is formed on the solid electrolyte layer.

[0149] According to the above method, a solid-state battery containing a positive electrode center-type layered structure and capable of maintaining the bonding state of the negative electrode layer and the solid electrolyte layer in an advantageous manner can be manufactured.

[0150] In the above methods, there are no particular restrictions on the methods for forming the positive electrode layer, the solid electrolyte layer, and the negative electrode layer, and they can be selected from coating methods, transfer methods, etc.

[0151] There are no particular restrictions on the methods used to perform the above steps, and they can be selected from coating methods, transfer methods, etc.

Claims

1. A solid-state battery, comprising a negative electrode layer and a solid electrolyte layer adjacent to the negative electrode layer, The negative electrode layer contains a negative electrode active material and a solid electrolyte, and The negative electrode active material contains a complex comprising multiple particles and particles not contained in the complex, wherein at least a portion of the particles not contained in the complex are embedded in the solid electrolyte layer.

2. The solid-state battery according to claim 1, wherein the negative electrode active material contains Si element.

3. The solid-state battery according to claim 1 or claim 2, comprising a structure in which a positive electrode layer, a solid electrolyte layer, a negative electrode layer and a negative electrode current collector are respectively disposed on both sides of the positive electrode current collector.

4. A method for manufacturing a solid-state battery according to claim 1 or claim 2, the method comprising forming a negative electrode layer on a solid electrolyte layer, the negative electrode layer containing a solid electrolyte and a negative electrode active material in a composite state containing a plurality of particles. The formation of the negative electrode layer includes applying pressure to the negative electrode layer such that at least a portion of the particles contained in the composite are separated from the composite.

5. The method according to claim 4, comprising: A positive electrode layer is formed on both sides of the positive current collector; A solid electrolyte layer is formed on the positive electrode layer; as well as A negative electrode layer is formed on the solid electrolyte layer.

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