All-solid-state battery

Abstract

The present application relates to an all-solid battery having: a positive electrode layer including a positive electrode current collector layer and a positive electrode active material layer; a negative electrode layer including a negative electrode current collector layer and a negative electrode active material layer; and a solid electrolyte layer including a solid electrolyte, a half width (G-FWHM) of a G band of a Raman spectrum of each of the positive electrode active material layer and the negative electrode active material layer is 40 (cm －1 ) or less.

Description

Technical Field

[0001] The present invention relates to an all-solid-state battery.

[0002] This application claims priority based on Japanese Patent Application No. 2020-39383, filed in Japan on March 6, 2020, the contents of which are incorporated herein by reference. Background Art

[0003] In recent years, with the development of portable devices such as personal computers and mobile phones, the demand for batteries as their power sources has greatly expanded. In batteries used for such applications, liquid electrolytes (electrolytes) such as organic solvents have been used as media for ion mobility. In batteries using such electrolytes, problems such as leakage of the electrolyte may occur.

[0004] To address these issues, the development of all-solid-state batteries is progressing. These batteries use solid electrolytes instead of liquid electrolytes, with all other components constructed from solids. Because the electrolyte in these batteries is solid, there are no concerns about leakage or drying up of the electrolyte, and they are also less susceptible to corrosion-induced degradation of battery performance. Among these, all-solid-state batteries are being actively researched in various fields as secondary batteries that can easily achieve high charge / discharge capacity and energy density.

[0005] However, compared to batteries using liquid electrolytes, all-solid-state batteries using solid electrolytes generally still suffer from the problem of lower discharge capacity. Among them, Li₃V₂(PO₄)₃ (hereinafter referred to as LVP323), a sodium superion conductor (NASICON)-type phosphate-based active material, has multiple redox potentials (3.8V, 1.8V). Using it in a symmetrically charged positive / negative electrode battery can produce a 2V-class all-solid-state battery. However, compared to using LiCoO₂ as the active material, LVP323 suffers from lower electron conductivity, resulting in higher internal resistance and lower discharge capacity. Therefore, to improve this electron conductivity, multiple conductors oriented approximately perpendicular to the stacking direction are included in the electrode layer or current collector layer, thereby increasing the in-plane electron conductivity within the electrode layer or current collector layer. In particular, there are concerns about metal oxidation in the current collector during firing, leading to the inclusion of carbon (Patent Document 1).

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Patent No. 5804208 Summary of the Invention

[0009] Technical problem to be solved by the invention

[0010] However, even the all-solid-state battery disclosed in Patent Document 1 still has room for improvement in discharge capacity, and further reduction in internal resistance of the all-solid-state battery is required.

[0011] The present invention has been developed in view of the problems of the conventional technology, and an object of the present invention is to provide an all-solid-state battery with further reduced internal resistance.

[0012] Technical solutions to technical problems

[0013] The inventors of the present invention have conducted intensive research to achieve the above-mentioned problem and found that in an all-solid-state battery having a solid electrolyte layer between a pair of electrodes, the full width at half maximum (G-FWHM) of the G band measured by Raman spectroscopy in the positive electrode active material layer and the negative electrode active material layer is 40 (cm －1 ) or less carbon particles, the internal resistance of the battery can be reduced by adding a small amount, thus completing the present invention.

[0014] That is, according to the present invention, there is provided the following all-solid-state battery.

[0015] One embodiment of the present invention relates to an all-solid-state battery, characterized in that it comprises: a positive electrode layer comprising a positive electrode current collector layer and a positive electrode active material layer; a negative electrode layer comprising a negative electrode current collector layer and a negative electrode active material layer; a solid electrolyte layer comprising a solid electrolyte, wherein the positive electrode active material layer and the negative electrode active material layer have a full width at half maximum (G-FWHM) of the G band of the Raman spectrum of 40 (cm －1 ) or less carbon particles.

[0016] According to this structure, the internal resistance of the all-solid-state battery can be reduced. －1 The full width at half maximum (G-FWHM) of the peak near the －1 ) or less carbon particles have good crystallinity as a graphite structure, small periodic disorder, and thus high thermal stability. Even in the case of a process such as sintering followed by heat treatment, they can easily remain in the electrode. Therefore, high electron conductivity can be obtained by a small amount of addition, and a high-density electrode can be achieved. Moreover, since these carbon particles have high crystallinity, the electron conductivity is high. Therefore, by mixing the carbon particles with an active material to form an electrode, the electron conductivity of the electrode can be improved by a small amount of addition, and the internal resistance of the all-solid-state battery can be reduced.

[0017] Furthermore, a small amount of voids may be formed near the carbon particles due to evaporation of carbon during heat treatment or the like.

[0018] In the all-solid-state battery of one embodiment of the present invention, regarding the carbon particles, when the long side of the carbon particles is a and the short side is b, the ratio thereof may be 1.0<a / b.

[0019] This structure, by using carbon particles with low shape anisotropy, allows them to be densely packed into the active material along with the active material particles, increasing the contact area with the active material and enabling smooth electron transfer. This improves the electron conductivity in the electrode and reduces the internal resistance of the all-solid-state battery.

[0020] In the all-solid-state battery of one embodiment of the present invention, the particle size distribution of the carbon particles may have a D10 of 0.1 μm or more and a D90 of 5.0 μm or less.

[0021] This structure allows the carbon particles to contact the active material without creating gaps between them and the active material, ensuring smooth electron exchange and reducing the internal resistance of the all-solid-state battery. However, when fine particles with a D10 of less than 0.1 μm are included, the carbon particles evaporate during heat treatment and other processes, preventing the full effect.

[0022] In the all-solid-state battery of one embodiment of the present invention, the positive electrode active material layer and the negative electrode active material layer may contain 0.5 (wt %) or more and 15.0 (wt %) or less of carbon particles, respectively.

[0023] Within the carbon particle content of this structure, the carbon particles are in sufficient contact with each other, which can improve the electronic conductivity of the electrode and suppress the substantial decrease in the amount of active material, thereby reducing the internal resistance of the all-solid-state battery while obtaining a high capacity.

[0024] Effects of the Invention

[0025] According to the present invention, an all-solid-state battery with reduced internal resistance can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a cross-sectional view of the all-solid-state battery of this embodiment. DETAILED DESCRIPTION

[0027] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, in the accompanying drawings, the same symbols are marked for the same or equivalent parts, and repeated descriptions are omitted. In addition, the dimensional ratios of the drawings are not limited to the illustrated ratios. In the drawings used in the following description, in order to facilitate understanding of the features of the present invention, the features are sometimes magnified for convenience. Therefore, the dimensional ratios of the various components recorded in the drawings are sometimes different from the actual ones. The materials, sizes, shapes, etc. illustrated in the following description are only examples, and the present invention is not limited thereto. The implementation can be appropriately changed within the scope of not changing the gist and being able to achieve the effect. For example, the configurations described in different embodiments or the configurations described in the examples can be appropriately combined for implementation. In this embodiment, one direction of the stacking direction is sometimes referred to as the upper direction and the lower direction, but the upper and lower mentioned here are not necessarily the same as the direction in which gravity is applied.

[0028] (All-solid-state battery)

[0029] Figure 1 1 is a schematic cross-sectional view showing a structure for explaining the concept of the all-solid-state battery 10 of this embodiment. Figure 1 As shown, the all-solid-state battery 10 of this embodiment includes at least one positive electrode layer 1, at least one negative electrode layer 2, and a solid electrolyte 3 at least partially sandwiched between the positive electrode layer 1 and the negative electrode layer 2. The positive electrode layer 1 and the negative electrode layer 2 are sequentially stacked via the solid electrolyte layer 3 to form a stack 4. The positive electrode layer 1 is connected to a terminal electrode 5 provided at one end, and the negative electrode layer 2 is connected to a terminal electrode 6 provided at the other end.

[0030] The positive electrode layer 1 is an example of a first electrode layer, and the negative electrode layer 2 is an example of a second electrode layer. Either the first or second electrode layer functions as a positive electrode, while the other functions as a negative electrode. The positive or negative polarity of the electrode layer changes depending on which polarity is connected to the terminal electrodes 5 and 6.

[0031] The positive electrode layer 1 includes a positive electrode collector layer 1A and a positive electrode active material layer 1B formed on one or both surfaces of the positive electrode collector layer 1A. The positive electrode active material layer 1B may not be present on the side of the positive electrode collector layer 1A that does not face the negative electrode layer 2. The negative electrode layer 2 includes a negative electrode collector layer 2A and a negative electrode active material layer 2B formed on one or both surfaces of the negative electrode collector layer 2A. The negative electrode active material layer 2B may not be present on the side of the negative electrode collector layer 2A that does not face the positive electrode layer 1. For example, the positive electrode layer 1 or the negative electrode layer 2 located at the top or bottom of the stack 4 may not have the positive electrode active material layer 1B or the negative electrode active material layer 2B on one side.

[0032] The all-solid-state battery 10 of this embodiment is an all-solid-state battery having a solid electrolyte layer 3 between a pair of electrode layers. The positive electrode active material layer 1B and the negative electrode active material layer 2B contained in the pair of electrode layers have a G band with a half width (G-FWHM) of 40 (cm －1 ) or less. More preferably, the carbon particles have a G band half width (G-FWHM) of 24 (cm －1 ) or less carbon particles.

[0033] According to this structure, the internal resistance of the all-solid-state battery 10 can be reduced. That is, the G band (1580 cm －1 The full width at half maximum (G-FWHM) of the peak near the －1 ) or less carbon particles have good crystallinity as a graphite structure and little periodic disorder, thus having high thermal stability. Even in the case of a process accompanied by heat treatment such as sintering, they can easily remain in the electrode. Therefore, high electron conductivity can be obtained by adding a small amount, and a high-density electrode can be achieved. Moreover, since these carbon particles have high crystallinity, they have high electron conductivity. Therefore, by mixing the carbon particles with an active material to form an electrode, the electron conductivity of the electrode can be increased by adding a small amount, and the internal resistance of the all-solid-state battery 10 can be reduced.

[0034] Furthermore, a small amount of voids may be formed near each carbon particle due to evaporation of carbon during heat treatment or the like.

[0035] The half width of the G band of the Raman spectrum of the carbon particles of this embodiment can be measured, for example, using a microscopic laser Raman spectrometer (device name: NRS-7100, manufactured by JASCO Corporation) at an excitation wavelength of 532 nm and 1580 cm －1 The half-width of the peaks appearing nearby is calculated.

[0036] The positive electrode active material layer 1B and the negative electrode active material layer 2B of the all-solid-state battery 10 of this embodiment further preferably contain carbon particles having a ratio of 1.0<a / b, where the long side of the particle is a and the short side is b.

[0037] According to this structure, by using carbon particles with low shape anisotropy, they can be densely packed in the active material together with the active material particles, increasing the contact area with the active material and promoting smooth electron transfer. Therefore, the electron conductivity in the electrode can be improved, and the internal resistance of the all-solid-state battery 10 can be reduced.

[0038] The positive electrode active material layer 1B and the negative electrode active material layer 2B of the all-solid-state battery 10 of this embodiment further preferably contain carbon particles having a particle size distribution with a D10 of 0.1 μm or greater and a D90 of 5.0 μm or less. D10 is the diameter of particles representing 10% by volume of the cumulative volume in a distribution curve obtained by particle size distribution measurement using the equivalent circle diameter calculated based on the area data of the carbon particles. Furthermore, D90 is the diameter of particles representing 90% by volume of the cumulative volume in a distribution curve obtained by particle size distribution measurement.

[0039] This configuration allows the carbon particles to contact the active material without creating gaps between them and the active material, thereby enabling smooth electron exchange and reducing the internal resistance of the all-solid-state battery 10. Furthermore, by excluding fine particles with a D10 of less than 0.1 μm, evaporation of the carbon particles during processes such as heat treatment can be suppressed, ensuring sufficient effects.

[0040] The positive electrode active material layer 1B and the negative electrode active material layer 2B of the all-solid-state battery 10 of the present embodiment preferably contain 0.5 (wt %) or more and 15.0 (wt %) or less of carbon particles, respectively.

[0041] According to the carbon particle content of this structure, the contact between the carbon particles becomes sufficient, which can improve the electronic conductivity as an electrode and suppress the substantial reduction in the amount of active material. Therefore, the internal resistance of the all-solid-state battery 10 can be reduced while obtaining a high capacity.

[0042] (Carbon particles)

[0043] The G band (1580 cm-1) of the Raman spectrum of the carbon particles of this embodiment －1 The full width at half maximum (G-FWHM) of the peak near the －1 ) or less, and can be either artificial synthetic or natural mineral.

[0044] (Solid Electrolyte)

[0045] At least a portion of the solid electrolyte layer 3 is sandwiched between the positive electrode layer 1 and the negative electrode layer 2. Figure 1 As shown, at least a portion of the solid electrolyte layer 3 may be located in the in-plane direction of the positive electrode layer 1 and the negative electrode layer 2 .

[0046] For the solid electrolyte in the solid electrolyte layer 3, for example, a material having ion conductivity and negligible electronic conductivity is used. Examples of solid electrolytes include lithium halides, lithium nitrides, lithium oxyacid salts, and their derivatives. In addition, Li-P-O compounds such as lithium phosphate (Li3PO4), LIPON (LiPO4) obtained by mixing nitrogen in lithium phosphate, and the like can be cited.4－x N x ), Li4SiO4 and other Li-Si-O compounds, Li-P-Si-O compounds, Li-VSi-O compounds, La with perovskite structure 0.51 Li 0.35 TiO 2.94 、La 0.55 Li 0.35 TiO3、Li 3x La 2 / 3－x Perovskite compounds such as TiO3, compounds having a garnet structure containing Li, La, and Zr, and particularly preferably compounds having a sodium superion conductor structure. The compound having a sodium superion conductor structure is composed of Li x M y (PO4)3 (x = 1 to 2, y = 1 to 2, M = at least one of Ti, Ge, Al, Ga, and Zr), wherein a portion of P may be substituted by B, Si, etc. Examples of compounds having a sodium superion conductor structure include Li 1.3 Al 0.3 Ti 1.7 (PO4)3 or Li 1.5 Al 0.5 Ge 1.5 (PO4)3.

[0047] (Negative electrode active material)

[0048] The negative electrode active material layer 2B contains a negative electrode active material. The negative electrode active material can be selected from Li4Ti5O 12 , oxides of at least one element among Ti, Nb, W, Si, Sn, Cr, Fe, Mo, phosphorus-containing compounds such as Li3V2(PO4)3, LiFePO4, etc.

[0049] (Positive electrode active material)

[0050] The positive electrode active material layer 1B contains a positive electrode active material. The positive electrode active material can be LiCoO2, LiCo 1 / 3Ni 1 / 3 Mn 1 / 3 O2 and other layered compounds, LiMn2O4, LiNi 0.5 Mn 1.5 Spinel materials such as O4, phosphorus-containing compounds such as Li3V2(PO4)3 and LiFePO4, etc. As long as at least one of the positive electrode active material and the negative electrode active material contains the carbon material of the present invention, the effects of the present invention can be achieved.

[0051] There is no clear distinction between the active materials that constitute the positive electrode active material layer 1B and the negative electrode active material layer 2B. By comparing the potentials of the compounds in the positive electrode active material layer 1B and the compounds in the negative electrode active material layer 2B, the compound showing a higher potential can be used as the positive electrode active material, and the compound showing a lower potential can be used as the negative electrode active material. In addition, if the compound has both lithium ion release and lithium ion storage functions, the active materials that constitute the positive electrode active material layer 1B and the negative electrode active material layer 2B can also be made of the same material. By making the active materials that constitute the positive electrode active material layer 1B and the negative electrode active material layer 2B the same material, a non-polar all-solid-state battery is obtained. Therefore, there is no need to specify the direction when installing on the circuit board, which can make installation easier.

[0052] (Current Collector)

[0053] The materials constituting the positive electrode current collector layer 1A and the negative electrode current collector layer 2A are preferably materials with high electrical conductivity, such as silver, palladium, gold, platinum, aluminum, copper, and nickel. Copper is particularly preferred because it does not readily react with lithium aluminum titanium phosphate and is effective in reducing the internal resistance of all-solid-state batteries. The materials constituting the current collector layers may be the same or different in the positive electrode layer 1 and the negative electrode layer 2.

[0054] Furthermore, the positive electrode current collector layer 1A and the negative electrode current collector layer 2A of the all-solid-state battery of the present embodiment preferably contain a positive electrode active material and a negative electrode active material, respectively.

[0055] The positive electrode collector layer 1A and the negative electrode collector layer 2A preferably contain the positive electrode active material 1B and the negative electrode active material 2B, respectively, because the adhesion between the positive electrode collector layer 1A and the positive electrode active material layer 1B and the adhesion between the negative electrode collector layer 2A and the negative electrode active material layer 2B are improved.

[0056] (Terminal electrode)

[0057] The terminal electrodes 5 and 6 are formed in contact with the side surfaces of the sintered body. The terminal electrodes 5 and 6 are connected to external terminals and are responsible for donating and accepting electrons to and from the sintered body.

[0058] A material with high electrical conductivity is preferably used for the terminal electrodes 5 and 6. For example, silver, gold, platinum, aluminum, copper, tin, nickel, gallium, indium, and alloys thereof can be used.

[0059] (Method for manufacturing all-solid-state batteries)

[0060] In the method for manufacturing an all-solid-state battery of this embodiment, first, the materials for the positive electrode current collector layer, positive electrode active material layer, solid electrolyte layer, negative electrode active material layer, and negative electrode current collector layer are paste-formed, applied, and dried to produce green sheets (first step). Next, these green sheets are stacked to produce a laminate (second step). The resulting laminate is then fired to complete the battery (third step).

[0061] (First process)

[0062] First, prepare a positive electrode active material, a negative electrode active material, and a carbon material. If the active material contains a compound of two or more elements, a mixed material comprising the compounds of each element can be prepared. Alternatively, if a solid electrolyte is mixed with the active material, a mixed material can also be prepared.

[0063] The method for producing the pastes for the positive electrode active material layer and the negative electrode active material layer is not particularly limited. For example, the pastes can be prepared by mixing the positive electrode active material, negative electrode active material, and carbon material in a carrier. Here, the term "carrier" refers to a general term for liquid media. The carrier contains a solvent and a binder. Using this method, a paste for the positive electrode collector layer, a paste for the positive electrode active material layer, a paste for the solid electrolyte layer, a paste for the negative electrode active material layer, and a paste for the negative electrode collector layer can be produced.

[0064] The prepared paste is applied to a substrate such as PET in the desired order, dried as needed, and then peeled off to produce a green sheet. The paste application method is not particularly limited, and known methods such as screen printing, coating, transfer, and doctor blade methods can be used.

[0065] (Second process)

[0066] The green sheets are stacked in the desired order and number of layers, and aligned and cut as needed to produce a laminate. When producing parallel or series-parallel batteries, it is preferred to align and stack them so that the end faces of the positive and negative electrodes do not align with each other.

[0067] When producing the laminate, the active material layer units described below may be prepared to produce the laminate.

[0068] In this method, first, a solid electrolyte layer paste is formed into a sheet on a PET film using a doctor blade method to obtain a solid electrolyte sheet. Then, a positive electrode active material layer paste is printed on the solid electrolyte sheet by screen printing and dried. Next, a positive electrode collector layer paste is printed on it by screen printing and dried. The positive electrode active material layer paste is further printed on it again by screen printing and dried, and then the PET film is peeled off to obtain a positive electrode active material layer unit. Thus, a positive electrode active material layer unit is obtained in which a positive electrode active material layer paste, a positive electrode collector layer paste, and a positive electrode active material layer paste are formed in sequence on the solid electrolyte layer sheet. A negative electrode active material layer unit is also produced by the same steps to obtain a negative electrode active material layer unit in which a negative electrode active material layer paste, a negative electrode collector layer paste, and a negative electrode active material layer paste are formed in sequence on the solid electrolyte sheet.

[0069] A positive electrode active material layer unit and a negative electrode active material layer unit are stacked with a solid electrolyte sheet interposed therebetween. The units are staggered so that the positive current collector paste of the first positive electrode active material layer unit only extends from one end surface, while the negative current collector paste of the second negative electrode active material layer unit only extends from the other surface. Solid electrolyte sheets of a predetermined thickness are further stacked on both sides of the stacked units to create a laminate.

[0070] The produced laminated bodies are pressure-bonded together while being heated, and the heating temperature is set to 40 to 95°C, for example.

[0071] (Third Process)

[0072] The laminated body after compression bonding is heated to 600° C. to 1100° C. in a nitrogen atmosphere and fired for a firing time of, for example, 0.1 to 3 hours. This firing completes the sintered body.

[0073] Furthermore, in order to efficiently draw current from the sintered body, a terminal electrode may be provided. The terminal electrode is connected to one end of the positive electrode layer extending from one side of the sintered body and one end of the negative electrode layer extending from one side of the sintered body, respectively. Thus, a pair of terminal electrodes are formed in a manner of clamping one side of the sintered body. As methods for forming the terminal electrodes, sputtering, screen printing, or dip coating may be cited. In the screen printing method and dip coating method, a terminal electrode paste containing metal powder, resin, and solvent is prepared and formed into a terminal electrode. Next, a baking process for removing the solvent and a protective and mounting plating process are performed on the surface of the terminal electrode. On the other hand, in the sputtering method, since a protective layer or a mounting layer can be formed on the terminal electrode, a baking process and a plating process are not required.

[0074] By going through the above-described steps, an all-solid-state battery can be manufactured.

[0075] Furthermore, the present invention is not necessarily limited to the above-described embodiments, and various modifications may be made without departing from the scope of the present invention. Specifically, the various configurations and combinations thereof in the above-described embodiments are merely examples, and additions, omissions, substitutions, and other modifications may be made without departing from the scope of the present invention.

[0076] Example

[0077] [Examples 1 to 4]

[0078] The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[0079] (Preparation of Positive Electrode Active Material)

[0080] In order to confirm the effect of this embodiment, Li3V2(PO4)3 is used as the active material. LiPO3 and V2O3 are used as the starting raw materials. After weighing the starting raw materials, they are mixed and crushed in ethanol using a ball mill (120rpm / zirconia ball) for 16 hours. After separating and drying the mixed powder of the starting raw materials from the balls and ethanol, it is pre-fired using a magnesium oxide crucible. The pre-fired is carried out at 950°C for 2 hours in a reducing atmosphere, and then in order to crush the pre-fired powder, it is treated in ethanol using a ball mill (120rpm / zirconia ball) for 16 hours. After separating and drying the crushed powder from the balls and ethanol, Li3V2(PO4)3 powder is obtained.

[0081] (Preparation of Negative Electrode Active Material)

[0082] The same powder as that of the positive electrode active material was used as the negative electrode active material.

[0083] (Preparation of Solid Electrolyte)

[0084] Use Li produced by the following method 1.3 Al 0.3 Ti 1.7 (PO4)3 is used as a solid electrolyte. Li2CO3, Al2O3, TiO2, and NH4H2PO4 are used as starting materials and wet mixed in ethanol as a solvent using a ball mill for 16 hours. The mixed powder of the starting materials is separated from the balls and ethanol and dried, and then pre-fired in an alumina crucible at 850°C in the atmosphere for 2 hours. Thereafter, in order to crush the pre-fired powder, it is treated in ethanol using a ball mill (120 rpm / zirconia ball) for 16 hours. The crushed powder is separated from the balls and ethanol and dried to obtain a powder.

[0085] (Active material mixed with carbon material)

[0086] In order to verify the effect of this embodiment, as Examples 1 to 4, the following carbon materials were used: D10 was 0.25 μm and D90 was 4.5 μm, a / b was 3, and the G band half width (G-FWHM) was 10, 18, 24, and 39 (cm －1 ). In addition, the above-mentioned Li3V2(PO4)3 is used as the active material. First, carbon materials having respective G-band half widths (G-FWHM) are weighed in amounts of 10.7, 11.3, 12.6, and 13.5 (wt%) relative to Li3V2(PO4)3, and mixed using a ball mill in an organic solvent. The powder is separated from the balls and the organic solvent and dried to obtain a mixed powder of the carbon material and Li3V2(PO4)3. The amount of carbon material added relative to Li3V2(PO4)3 is recorded in the table as the feed addition amount.

[0087] (Preparation of Pastes for Positive Electrode Active Material Layer and Negative Electrode Active Material Layer)

[0088] Regarding the paste for the positive and negative active material layers, 15 parts of ethyl cellulose as a binder and 65 parts of dihydropinene as a solvent are added to 100 parts of a mixed powder of the above-mentioned carbon material and Li3V2(PO4)3, and the mixture is mixed and dispersed using three rollers to make the paste for the positive and negative active material layers.

[0089] (Preparation of Solid Electrolyte Layer Paste)

[0090] Using the above Li 1.3 Al 0.3 Ti 1.7 (PO4)3 powder was used as the solid electrolyte. 100 parts of ethanol and 200 parts of toluene were added to 100 parts of this powder as a solvent and wet-mixed using a ball mill. Then, 16 parts of a polyvinyl butyral binder and 4.8 parts of butyl benzyl phthalate were added and mixed to prepare a solid electrolyte layer paste.

[0091] (Fabrication of Solid Electrolyte Layer Sheet)

[0092] The solid electrolyte layer paste was formed into a sheet using a PET film as a substrate by a doctor blade method to obtain a solid electrolyte layer sheet having a thickness of 15 μm.

[0093] (Preparation of Pastes for Positive and Negative Electrode Collector Layers)

[0094] After Cu powder and Li3V2(PO4)3 powder are mixed in a weight ratio of 100:9, 10 parts of ethyl cellulose as a binder and 50 parts of dihydropinene as a solvent are added, and mixed and dispersed with three rollers to prepare a paste for the positive electrode collector layer and a paste for the negative electrode collector layer.

[0095] (Preparation of terminal electrode paste)

[0096] Cu powder, glass powder, acrylic resin and terpineol are mixed and dispersed to prepare a Cu terminal electrode paste.

[0097] (Fabrication of Active Material Layer Unit)

[0098] An electrode current collector layer paste was screen-printed onto the solid electrolyte layer sheet to a thickness of 5 μm and dried at 80°C for 10 minutes. A positive electrode active material layer paste was screen-printed onto the sheet to a thickness of 5 μm and dried at 80°C for 10 minutes to form a positive electrode layer unit. Separately, a negative electrode active material layer paste was screen-printed onto the solid electrolyte layer sheet to a thickness of 5 μm and dried at 80°C for 10 minutes. Furthermore, an electrode current collector layer paste was screen-printed onto the sheet to a thickness of 5 μm and dried at 80°C for 10 minutes to form a negative electrode layer unit. The PET film was then peeled off.

[0099] (Production of Laminated Body)

[0100] A laminate is produced by stacking a positive electrode layer unit, a negative electrode layer unit, and a solid electrolyte layer sheet in the order of solid electrolyte layer, positive current collector layer, positive active material layer, solid electrolyte layer, negative active material layer, negative current collector layer, and solid electrolyte layer. The units are stacked so that the positive current collector layer of the positive electrode layer unit protrudes only from one end face, and the negative current collector layer of the negative active material layer unit protrudes only from the other end face. The laminate is then formed by thermocompression bonding and then cut to produce a laminate.

[0101] (Production of Sintered Body)

[0102] The resulting laminate was debindered and then co-fired to produce a sintered body. For debindering, the temperature was raised in nitrogen at a rate of 50°C / hour to a firing temperature of 700°C and held at this temperature for 10 hours. For co-firing, the temperature was raised in nitrogen at a rate of 200°C / hour to a firing temperature of 850°C and held at this temperature for 1 hour. After firing, the laminate was naturally cooled.

[0103] Furthermore, it was confirmed that the residual carbon content in the electrode active material layer region of the obtained sintered body was approximately 10 (wt %).

[0104] (Fabrication of terminal electrodes)

[0105] A pair of terminal electrodes was formed by applying a Cu terminal electrode paste to the end surfaces of the sintered body and heat-treating it at 600°C for 15 minutes in an N2 atmosphere. This completed the all-solid-state battery. (Evaluation of the G-band Full Width at Half Maximum (G-FWHM) of the Raman Spectrum of Carbon Particles in the Electrode Active Material Layer)

[0106] The electrode active material layer region of the obtained sintered body was exposed by grinding or the like and smoothed, and Raman spectra were measured using a microscopic laser Raman spectrometer (NRS-7100, manufactured by JASCO Corporation). －1 The half-width of the peaks appearing nearby is calculated.

[0107] (Evaluation of the Long Side a and Short Side b of Carbon Particles in Electrode Active Material)

[0108] The electrode active material layer region of the obtained sintered body is exposed and smoothed by grinding or the like. For 100 or more carbon particles in the field of view, the length of each carbon particle in the longest axis direction is defined as a, and the length of each carbon particle in the shortest axis direction is defined as b. The ratio can be calculated as a / b. Regarding the SEM magnification, an appropriate value is selected depending on the particle size of the carbon particles. The magnification is selected so that 100 or more and 300 or less particles are observed in the field of view. The a / b ratio of all carbon particles in the field of view is determined and the average is calculated.

[0109] (Evaluation of Particle Size Distribution of Carbon Particles in Electrode Active Material Layer)

[0110] The electrode active material layer region of the resulting sintered body was exposed and smoothed by grinding or other means. Scanning electron microscopy (SEM) observation was then performed, and the area of ​​each particle was measured using image processing for at least 200 particles in the field of view. The equivalent circle diameter was calculated from this area data, with the particle size at a cumulative volume of 10% by volume being designated as D10, and the particle size at a cumulative volume of 90% by volume being designated as D90.

[0111] (Evaluation of Carbon Content in Electrode Active Material Layer)

[0112] The electrode active material layer region of the obtained sintered body was separated and pulverized, and the carbon / sulfur analyzer (manufactured by LECO Japan Co., Ltd., device name: CS-844) was used as an analyzer to perform measurement by combustion-infrared absorption method in an oxygen gas flow.

[0113] (Relative density determination)

[0114] The apparent dimensions of the resulting sintered body are measured and the volume is calculated. The weight of the sintered body is then divided by the volume to obtain the density of the sintered body. Meanwhile, the theoretical density is obtained using the shape, size, and specific gravity of each component of the sintered body. Specifically, to obtain the theoretical density, the dimensions of each component of the sintered body are first calculated. Here, the components of the sintered body refer to the solid electrolyte layer, the positive electrode active material layer, the positive electrode current collector layer, the negative electrode active material layer, and the negative electrode current collector layer. Next, the volume of each component is calculated based on the shape and size of each component of the solid electrolyte layer. Next, the specific gravity of each component of the solid electrolyte layer is multiplied by the calculated volume. The specific gravity of each component is calculated using a known specific gravity. The weight of the sintered body is then calculated by adding these components. Furthermore, the calculation is performed taking into account the abundance ratio of the positive electrode active material and the negative electrode active material, which contain active material and carbon. Next, the theoretical density is obtained by dividing the calculated weight of the sintered body by the volume of the sintered body. The ratio of the obtained sintered body density to the theoretical density is then calculated as the relative density. The relative density was obtained from (sintered body density / theoretical density).

[0115] (Impedance Evaluation)

[0116] The obtained laminate was mounted on a fixture fixed with a spring-loaded pin using an impedance / gain-phase analyzer (1260A, manufactured by Solartron Analytical). The internal resistance was measured at a frequency of 0.005 Hz and an AC applied voltage of 0.05 V. The obtained internal resistance values ​​are shown in Table 1. 7 (Ω) is considered good.

[0117] (Evaluation of charge and discharge characteristics)

[0118] The resulting laminate was then mounted on a fixture secured with a spring-loaded pin using a charge-discharge tester, and the charge-discharge capacity was measured. The measurement conditions were a current of 2 μA and a voltage range of 0 V to 1.6 V during both charge and discharge. The measured discharge capacities are shown in Table 1. A discharge characteristic value greater than 1.5 μAh was considered good.

[0119] [Comparative Example 1]

[0120] In this comparative example, the following carbon material was used: D10 was 0.25 μm, D90 was 4.5 μm, a / b was 3, and G-FWHM was 43 (cm －1 ). In addition, the above-mentioned Li3V2(PO4)3 powder was used as the active material.

[0121] The carbon material was weighed to a concentration of 16.3 wt% relative to Li₃V₂(PO₄)₃ and mixed in an organic solvent using a ball mill. The powder was separated from the balls and the organic solvent and dried to obtain a mixed powder of the carbon material and Li₃V₂(PO₄)₃. Furthermore, a laminate was prepared using the same method as in Example 1, followed by debinding and sintering using the same method. The discharge characteristics of the laminate were evaluated using the same method as in Example 1. Table 1 shows the measured internal resistance values ​​and discharge capacity.

[0122] As can be seen from Table 1, by using carbon materials and active materials within the scope of the present invention in the active material layer, even if a small amount is added, an effective residual amount can be contained, thereby achieving a dense electrode site and showing significantly low internal resistance as an all-solid-state battery. It can also be seen that a high discharge capacity is achieved.

[0123] [Table 1]

[0124]

[0125] [Examples 5 to 12]

[0126] (Active material mixed with carbon material)

[0127] In order to verify the effect of this embodiment, the following carbon materials were used as Examples 5 to 12: D10 was 0.25 μm, D90 was 4.5 μm, G-FWHM was 18 (cm －1 ), and a / b were 1.0, 1.1, 1.5, 5.0, 10.0, 50.0, 100.0, and 200.0, respectively. The aforementioned Li₃V₂(PO₄)₃ powder was used as the active material. These carbon materials were weighed to a ratio of 11.3 wt% relative to the Li₃V₂(PO₄)₃ and mixed using a ball mill in an organic solvent. The powder was separated from the balls and the organic solvent and dried to obtain a mixed powder of the carbon material and Li₃V₂(PO₄)₃.

[0128] (Preparation of Pastes for Positive Electrode Active Material Layer and Negative Electrode Active Material Layer)

[0129] Regarding the paste for the positive and negative active material layers, 15 parts of ethyl cellulose as a binder and 65 parts of dihydropinene as a solvent are added to 100 parts of a mixed powder of the above-mentioned carbon material and Li3V2(PO4)3, and the mixture is mixed and dispersed using three rollers to make the paste for the positive and negative active material layers.

[0130] (Preparation of Solid Electrolyte Layer Paste)

[0131] Using the above Li 1.3 Al 0.3 Ti1.7 (PO4)3 powder was used as the solid electrolyte. 100 parts of ethanol and 200 parts of toluene were added to 100 parts of this powder as a solvent and wet-mixed using a ball mill. Then, 16 parts of a polyvinyl butyral binder and 4.8 parts of butyl benzyl phthalate were added and mixed to prepare a solid electrolyte layer paste.

[0132] (Fabrication of Solid Electrolyte Layer Sheet)

[0133] The solid electrolyte layer paste was formed into a sheet using a PET film as a substrate by a doctor blade method to obtain a solid electrolyte layer sheet having a thickness of 15 μm.

[0134] (Preparation of Pastes for Positive and Negative Electrode Collector Layers)

[0135] After mixing Cu powder and Li3V2(PO4)3 powder in a weight ratio of 100:9, 10 parts of ethyl cellulose as a binder and 50 parts of dihydropinene as a solvent were added, and the mixture was mixed and dispersed using three rollers to prepare a paste for the positive electrode collector layer and a paste for the negative electrode collector layer.

[0136] (Preparation of terminal electrode paste)

[0137] Silver powder, epoxy resin, and solvent are mixed and dispersed to create a thermosetting terminal electrode paste.

[0138] (Fabrication of Active Material Layer Unit)

[0139] A positive electrode current collector layer paste was screen-printed onto the solid electrolyte layer sheet to a thickness of 5 μm and dried at 80°C for 10 minutes. A positive electrode active material layer paste was screen-printed onto the sheet to a thickness of 5 μm and dried at 80°C for 10 minutes to form a positive electrode layer unit. Separately, a negative electrode active material layer paste was screen-printed onto the solid electrolyte layer sheet to a thickness of 5 μm and dried at 80°C for 10 minutes. Subsequently, a negative electrode current collector layer paste was screen-printed onto the sheet to a thickness of 5 μm and dried at 80°C for 10 minutes to form a negative electrode layer unit. The PET film was then peeled off.

[0140] (Production of Laminated Body)

[0141] A single-layer product is obtained by stacking a positive electrode layer unit, a negative electrode layer unit, and a solid electrolyte layer sheet in the order of solid electrolyte layer, positive current collector layer, positive active material layer, solid electrolyte layer, negative active material layer, negative current collector layer, and solid electrolyte layer. The units are stacked so that the positive current collector layer of the positive electrode unit protrudes only from one end face, and the negative current collector layer of the negative electrode unit protrudes only from the other end face. The stack is then formed by thermocompression bonding and then cut to produce a laminate.

[0142] (Production of Sintered Body)

[0143] The resulting laminate was debindered and then co-fired to obtain a sintered body. For debindering, the temperature was raised in nitrogen at a rate of 50°C / hour to a firing temperature of 700°C and held at this temperature for 10 hours. For co-firing, the temperature was raised in nitrogen at a rate of 200°C / hour to a firing temperature of 850°C and held at this temperature for 1 hour. After firing, the laminate was naturally cooled.

[0144] Furthermore, it was confirmed that the residual carbon content in the electrode active material layer region of the obtained sintered body was approximately 10 (wt %).

[0145] (Fabrication of terminal electrodes)

[0146] A terminal electrode paste was applied to the end surfaces of the sintered body and thermally cured at 150°C for 30 minutes to form a pair of terminal electrodes. This completed the all-solid-state battery.

[0147] (Evaluation of the Half Width (G-FWHM) of the Raman Spectrum G Band of Carbon Particles in the Electrode Active Material Layer)

[0148] The electrode active material layer region of the obtained sintered body was exposed by grinding or the like and smoothed, and Raman spectra were measured using a microscopic laser Raman spectrometer (NRS-7100, manufactured by JASCO Corporation). －1 The half-width of the peaks appearing nearby is calculated.

[0149] (Evaluation of the Long Side a and Short Side b of Carbon Particles in Electrode Active Material)

[0150] The electrode active material layer region of the obtained sintered body can be exposed and smoothed by grinding or the like, and observed under a scanning electron microscope (SEM), for 100 or more particles in the field of view, the length in the longest axis direction is set to a, the length in the shortest axis direction is set to b, and the ratio thereof is calculated as a / b. Regarding the magnification of the SEM, an appropriate value is selected according to the particle size of the carbon particles, and the magnification at which 100 or more and 300 or less particles are observed in the field of view is selected. In addition, the a / b of the carbon particles is calculated as the average a / b of all the carbon particles in the field of view.

[0151] (Evaluation of Particle Size Distribution of Carbon Particles in Electrode Active Material)

[0152] The electrode active material layer region of the resulting sintered body was exposed and smoothed by grinding or other means. Scanning electron microscopy (SEM) observation was then performed, and the area of ​​each particle was measured using image processing for at least 200 particles in the field of view. The equivalent circle diameter was calculated from this area data, with the particle size at a cumulative volume of 10% by volume being designated as D10, and the particle size at a cumulative volume of 90% by volume being designated as D90.

[0153] (Evaluation of Carbon Content in Electrode Active Material)

[0154] The electrode active material layer region of the obtained sintered body was separated and pulverized, and the carbon / sulfur analyzer (manufactured by LECO Japan Co., Ltd., device name: CS-844) was used as an analyzer to perform measurement by combustion-infrared absorption method in an oxygen gas flow.

[0155] (Relative density determination)

[0156] The apparent dimensions of the resulting sintered body are measured and the volume is calculated. The weight of the sintered body is divided by the volume to obtain the density of the sintered body. Separately, the theoretical density for the given dimensions is calculated and the ratio of the obtained density of the sintered body to the theoretical density is calculated to obtain the relative density.

[0157] (Impedance Evaluation)

[0158] The obtained laminate was mounted on a fixture fixed with a spring-loaded pin using an impedance / gain-phase analyzer, and the internal resistance was measured. The measurement was performed at a frequency of 0.005 Hz and an AC applied voltage of 0.05 V. The obtained internal resistance values ​​are shown in Table 2. The internal resistance value was less than 1×10 7 (Ω) is considered good.

[0159] (Evaluation of charge and discharge characteristics)

[0160] The resulting laminate was then mounted on a fixture secured with spring-loaded pins using a charge-discharge tester, and the charge-discharge capacity was measured. The measurement conditions were a current of 2 μA and a voltage range of 0 V to 1.6 V during both charge and discharge. The measured discharge capacities are shown in Table 2.

[0161] As can be seen from Table 2, all-solid-state batteries using carbon materials having an a / b ratio within the range of the present invention for both the positive and negative electrode active material layers exhibit significantly low internal resistance. Furthermore, it can be seen that when the a / b ratio is within the range of 1.1 to 100.0, even lower internal resistance is achieved, and good discharge capacity is obtained. Furthermore, when the a / b ratio is within the range of 1.5 to 5.0, even lower internal resistance is achieved, and even better discharge capacity is obtained.

[0162] [Table 2]

[0163]

[0164] [Examples 13 to 15]

[0165] (Active material mixed with carbon material)

[0166] In order to verify the effect of this embodiment, the following carbon materials were used as Examples 13 to 15: －1 ), a / b is 3, D10 is 0.1μm and D90 is 5μm (Example 13), D10 is 0.2μm and D90 is 5.5μm (Example 14), D10 is 0.08μm and D90 is 4.0μm (Example 15). In addition, the above-mentioned Li3V2(PO4)3 powder is used as the active material. These carbon materials are weighed in a manner of 11.3wt% relative to Li3V2(PO4)3 and mixed using a ball mill in an organic solvent. The powder is separated from the balls and the organic solvent and dried to obtain a mixed powder of the carbon material and Li3V2(PO4)3.

[0167] (Preparation of Pastes for Positive Electrode Active Material Layer and Negative Electrode Active Material Layer)

[0168] Regarding the paste for the positive and negative active material layers, 15 parts of ethyl cellulose as a binder and 65 parts of dihydropinene as a solvent are added to 100 parts of a mixed powder of the above-mentioned carbon material and Li3V2(PO4)3, and the mixture is mixed and dispersed using three rollers to make the paste for the positive and negative active material layers.

[0169] (Preparation of Solid Electrolyte Layer Paste)

[0170] Using the above Li 1.3 Al 0.3 Ti 1.7 (PO4)3 powder was used as the solid electrolyte. 100 parts of ethanol and 200 parts of toluene were added to 100 parts of this powder as a solvent and wet-mixed using a ball mill. Then, 16 parts of a polyvinyl butyral binder and 4.8 parts of butyl benzyl phthalate were added and mixed to prepare a solid electrolyte layer paste.

[0171] (Fabrication of Solid Electrolyte Layer Sheet)

[0172] The solid electrolyte layer paste was formed into a sheet using a PET film as a substrate by a doctor blade method to obtain a solid electrolyte layer sheet having a thickness of 15 μm.

[0173] (Preparation of Pastes for Positive and Negative Electrode Collector Layers)

[0174] After mixing Cu powder and Li3V2(PO4)3 powder in a weight ratio of 100:9, 10 parts of ethyl cellulose as a binder and 50 parts of dihydropinene as a solvent were added, and the mixture was mixed and dispersed using three rollers to prepare a paste for the positive electrode collector layer and a paste for the negative electrode collector layer.

[0175] (Preparation of terminal electrode paste)

[0176] Silver powder, epoxy resin, and solvent are mixed and dispersed to create a thermosetting terminal electrode paste.

[0177] (Fabrication of Active Material Layer Unit)

[0178] A positive electrode current collector layer paste was screen-printed onto the solid electrolyte layer sheet to a thickness of 5 μm and dried at 80°C for 10 minutes. A positive electrode active material layer paste was screen-printed onto the sheet to a thickness of 5 μm and dried at 80°C for 10 minutes to form a positive electrode layer unit. Separately, a negative electrode active material layer paste was screen-printed onto the solid electrolyte layer sheet to a thickness of 5 μm and dried at 80°C for 10 minutes. Subsequently, a negative electrode current collector layer paste was screen-printed onto the sheet to a thickness of 5 μm and dried at 80°C for 10 minutes to form a negative electrode layer unit. The PET film was then peeled off.

[0179] (Production of Laminated Body)

[0180] A single-layer product is obtained by stacking a positive electrode layer unit, a negative electrode layer unit, and a solid electrolyte layer sheet in the order of solid electrolyte layer, positive current collector layer, positive active material layer, solid electrolyte layer, negative active material layer, negative current collector layer, and solid electrolyte layer. The units are stacked so that the positive current collector layer of the positive electrode unit protrudes only from one end face, and the negative current collector layer of the negative electrode unit protrudes only from the other end face. The stack is then formed by thermocompression bonding and then cut to produce a laminate.

[0181] (Production of Sintered Body)

[0182] The resulting laminate was debindered and then co-fired to obtain a sintered body. For debindering, the temperature was raised in nitrogen at a rate of 50°C / hour to a firing temperature of 700°C and held at this temperature for 10 hours. For co-firing, the temperature was raised in nitrogen at a rate of 200°C / hour to a firing temperature of 850°C and held at this temperature for 1 hour. After firing, the laminate was naturally cooled.

[0183] Furthermore, it was confirmed that the residual carbon content in the electrode active material layer region of the obtained sintered body was approximately 10 (wt %).

[0184] (Fabrication of terminal electrodes)

[0185] A terminal electrode paste was applied to the end surfaces of the sintered body and thermally cured at 150°C for 30 minutes to form a pair of terminal electrodes. This completed the all-solid-state battery.

[0186] (Evaluation of the Half Width (G-FWHM) of the Raman Spectrum G Band of Carbon Particles in the Electrode Active Material Layer)

[0187] The electrode active material layer region of the obtained sintered body was exposed by grinding or the like and smoothed, and Raman spectra were measured using a microscopic laser Raman spectrometer (NRS-7100, manufactured by JASCO Corporation). －1 The half-width of the peaks appearing nearby is calculated.

[0188] (Evaluation of the Long Side a and Short Side b of Carbon Particles in Electrode Active Material)

[0189] The electrode active material layer region of the obtained sintered body is exposed by grinding or the like and smoothed, and according to the scanning electron microscope (SEM) observation, for 100 or more particles in the field of view, the length in the longest axis direction is set to a, and the length in the shortest axis direction is set to b, and their ratio can be calculated as a / b. Regarding the SEM magnification, an appropriate value is selected according to the particle size of the carbon particles, and the magnification at which more than 100 and less than 300 particles are observed in the field of view is selected. In addition, the a / b of the carbon particles is calculated as the average a / b of all the carbon particles in the field of view. (Evaluation of the particle size distribution of carbon particles in the electrode active material)

[0190] The electrode active material layer region of the resulting sintered body was exposed and smoothed by grinding or other means. Scanning electron microscopy (SEM) observation was then performed, and the area of ​​each particle was measured using image processing for at least 200 particles in the field of view. The equivalent circle diameter was calculated from this area data, with the particle size at a cumulative volume of 10% by volume being designated as D10, and the particle size at a cumulative volume of 90% by volume being designated as D90.

[0191] (Evaluation of Carbon Content in Electrode Active Material)

[0192] The electrode active material layer region of the obtained sintered body was separated and pulverized, and the carbon / sulfur analyzer (manufactured by LECO Japan Co., Ltd., device name: CS-844) was used as an analyzer to perform measurement by combustion-infrared absorption method in an oxygen gas flow.

[0193] (Relative density determination)

[0194] The apparent dimensions of the resulting sintered body are measured and the volume is calculated. The density of the sintered body is obtained by dividing the weight of the sintered body by the volume. Separately, the theoretical density for the given dimensions is calculated and the ratio of the obtained density to the theoretical density is calculated to obtain the relative density.

[0195] (Impedance Evaluation)

[0196] The obtained laminate was mounted on a fixture fixed with a spring-loaded pin using an impedance / gain-phase analyzer, and the internal resistance was measured. The measurement was performed at a frequency of 0.005 Hz and an AC applied voltage of 0.05 V. The obtained internal resistance values ​​are shown in Table 3. The internal resistance value was less than 1×10 7 (Ω) is considered good.

[0197] (Evaluation of charge and discharge characteristics)

[0198] The resulting laminate was then mounted on a fixture secured with a spring-loaded pin using a charge-discharge tester, and the charge-discharge capacity was measured. The measurement conditions were a current of 2 μA and a voltage range of 0 V to 1.6 V during both charge and discharge. The measured discharge capacities are shown in Table 3. A discharge characteristic value greater than 1.5 μAh was considered good.

[0199] As can be seen from Table 3, all-solid-state batteries using carbon materials having D10 and D90 within the ranges of the present invention for the positive electrode active material layer and the negative electrode active material layer, respectively, exhibit significantly low internal resistance. It is also clear that when D10 is 0.1 μm or greater and D90 is 5.0 μm or less, even lower internal resistance is exhibited, and good discharge capacity is achieved.

[0200] [Table 3]

[0201]

[0202] [Examples 16 to 21]

[0203] (Active material mixed with carbon material)

[0204] In order to verify the effect of this embodiment, the following carbon materials were used: G-FWHM of 18 (cm －1), a / b is 3, D10 is 0.25μm and D90 is 4.5μm. In addition, the above-mentioned Li3V2(PO4)3 powder was used as the active material. In Examples 16 to 21, these carbon materials were weighed in amounts of 0.49wt%, 0.58wt%, 1.13wt%, 7.12wt%, 16.95wt% and 18.08wt% relative to Li3V2(PO4)3, respectively, and mixed using a ball mill in an organic solvent. By separating the powder from the balls and the organic solvent and drying it, a mixed powder of the carbon material and Li3V2(PO4)3 was obtained.

[0205] (Preparation of Pastes for Positive Electrode Active Material Layer and Negative Electrode Active Material Layer)

[0206] Regarding the paste for the positive and negative active material layers, 15 parts of ethyl cellulose as a binder and 65 parts of dihydropinene as a solvent are added to 100 parts of a mixed powder of the above-mentioned carbon material and Li3V2(PO4)3, and the mixture is mixed and dispersed using three rollers to make the paste for the positive and negative active material layers.

[0207] (Preparation of Solid Electrolyte Layer Paste)

[0208] Using the above Li 1.3 Al 0.3 Ti 1.7 (PO4)3 powder was used as the solid electrolyte. 100 parts of ethanol and 200 parts of toluene were added to 100 parts of this powder as a solvent and wet-mixed using a ball mill. Then, 16 parts of a polyvinyl butyral binder and 4.8 parts of butyl benzyl phthalate were added and mixed to prepare a solid electrolyte layer paste.

[0209] (Fabrication of Solid Electrolyte Layer Sheet)

[0210] The solid electrolyte layer paste was formed into a sheet using a PET film as a substrate by a doctor blade method to obtain a solid electrolyte layer sheet having a thickness of 15 μm.

[0211] (Preparation of Pastes for Positive and Negative Electrode Collector Layers)

[0212] After mixing Cu powder and Li3V2(PO4)3 powder in a weight ratio of 100:9, 10 parts of ethyl cellulose as a binder and 50 parts of dihydropinene as a solvent were added, and the mixture was mixed and dispersed using three rollers to prepare a paste for the positive electrode collector layer and a paste for the negative electrode collector layer.

[0213] (Preparation of terminal electrode paste)

[0214] Silver powder, epoxy resin, and solvent are mixed and dispersed to create a thermosetting terminal electrode paste.

[0215] (Fabrication of Active Material Layer Unit)

[0216] A positive electrode current collector layer paste was screen-printed onto the solid electrolyte layer sheet to a thickness of 5 μm and dried at 80°C for 10 minutes. A positive electrode active material layer paste was screen-printed onto the sheet to a thickness of 5 μm and dried at 80°C for 10 minutes to form a positive electrode layer unit. Separately, a negative electrode active material layer paste was screen-printed onto the solid electrolyte layer sheet to a thickness of 5 μm and dried at 80°C for 10 minutes. Subsequently, a negative electrode current collector layer paste was screen-printed onto the sheet to a thickness of 5 μm and dried at 80°C for 10 minutes to form a negative electrode layer unit. The PET film was then peeled off.

[0217] (Production of Laminated Body)

[0218] A single-layer product is obtained by stacking a positive electrode layer unit, a negative electrode layer unit, and a solid electrolyte layer sheet in the order of solid electrolyte layer, positive current collector layer, positive active material layer, solid electrolyte layer, negative active material layer, negative current collector layer, and solid electrolyte layer. The units are stacked so that the positive current collector layer of the positive electrode unit protrudes only from one end face, and the negative current collector layer of the negative electrode unit protrudes only from the other end face. The stack is then formed by thermocompression bonding and then cut to produce a laminate.

[0219] (Production of Sintered Body)

[0220] The resulting laminate was debindered and then co-fired to obtain a sintered body. For debindering, the temperature was raised in nitrogen at a rate of 50°C / hour to a firing temperature of 700°C and held at this temperature for 10 hours. For co-firing, the temperature was raised in nitrogen at a rate of 200°C / hour to a firing temperature of 850°C and held at this temperature for 1 hour. After firing, the laminate was naturally cooled.

[0221] Furthermore, it was confirmed that the residual carbon contents in the electrode active material layer region of the obtained sintered bodies were 0.43, 0.51, 1.00, 6.30, 15.00, and 16.00 (wt %), respectively.

[0222] (Fabrication of terminal electrodes)

[0223] A terminal electrode paste was applied to the end surfaces of the sintered body and thermally cured at 150°C for 30 minutes to form a pair of terminal electrodes. This completed the all-solid-state battery.

[0224] (Evaluation of the Half Width (G-FWHM) of the Raman Spectrum G Band of Carbon Particles in the Electrode Active Material Layer)

[0225] The electrode active material layer region of the obtained sintered body was exposed by grinding or the like and smoothed, and Raman spectra were measured using a microscopic laser Raman spectrometer (device name: NRS-7100 (manufactured by JASCO Corporation) at an excitation wavelength of 532 nm and 1580 cm －1 The half-width of the peaks appearing nearby is calculated.

[0226] (Evaluation of the Long Side a and Short Side b of Carbon Particles in Electrode Active Material)

[0227] The electrode active material layer region of the obtained sintered body can be exposed and smoothed by grinding or the like, and observed under a scanning electron microscope (SEM), for 100 or more particles in the field of view, the length in the longest axis direction is set to a, the length in the shortest axis direction is set to b, and the ratio thereof is calculated as a / b. Regarding the magnification of the SEM, an appropriate value is selected according to the particle size of the carbon particles, and the magnification at which 100 or more and 300 or less particles are observed in the field of view is selected. In addition, the a / b of the carbon particles is calculated as the average a / b of all the carbon particles in the field of view.

[0228] (Evaluation of Particle Size Distribution of Carbon Particles in Electrode Active Material)

[0229] The electrode active material layer region of the resulting sintered body was exposed and smoothed by grinding or other means. Scanning electron microscopy (SEM) observation was then performed, and the area of ​​each particle was measured using image processing for at least 200 particles in the field of view. The equivalent circle diameter was calculated from this area data, with the particle size at a cumulative volume of 10% by volume being designated as D10, and the particle size at a cumulative volume of 90% by volume being designated as D90.

[0230] (Evaluation of Carbon Content in Electrode Active Material)

[0231] The electrode active material layer region of the obtained sintered body was separated and pulverized, and the carbon / sulfur analyzer (manufactured by LECO Japan Co., Ltd., device name: CS-844) was used as an analyzer to perform measurement by combustion-infrared absorption method in an oxygen gas flow.

[0232] (Relative density determination)

[0233] The apparent dimensions of the resulting sintered body are measured and the volume is calculated. The weight of the sintered body is divided by the volume to obtain the density of the sintered body. Separately, the theoretical density for the given dimensions is calculated and the ratio of the obtained density to the theoretical density is calculated to obtain the relative density.

[0234] (Impedance Evaluation)

[0235] The obtained laminate was mounted on a fixture fixed with a spring-loaded pin using an impedance / gain-phase analyzer, and the internal resistance was measured. The measurement was performed at a frequency of 0.005 Hz and an AC applied voltage of 0.05 V. The obtained internal resistance values ​​are shown in Table 4. The internal resistance value was less than 1×10 7 (Ω) is considered good.

[0236] (Evaluation of charge and discharge characteristics)

[0237] The resulting laminate was then mounted on a fixture secured with a spring-loaded pin using a charge-discharge tester, and the charge-discharge capacity was measured. The measurement conditions were a current of 2 μA and a voltage range of 0 V to 1.6 V during both charge and discharge. The measured discharge capacities are shown in Table 4. A discharge characteristic value greater than 1.5 μAh was considered good.

[0238] As can be seen from Table 4, all-solid-state batteries using carbon materials within the present invention's content range for both the positive and negative electrode active material layers produce significantly densified sintered bodies with low internal resistance. Furthermore, when the carbon particle content is 0.5 (wt%) or more and 15.0 (wt%) or less, even lower internal resistance is achieved, along with excellent discharge capacity. Furthermore, when the carbon particle content is 1.00 (wt%) or more and 15.0 (wt%) or less, even lower internal resistance is achieved, along with even better discharge capacity.

[0239] [Table 4]

[0240]

[0241] As described above, the all-solid-state battery of the present invention is effective in reducing internal resistance.

[0242] Explanation of symbols

[0243] 1: positive electrode layer; 2: negative electrode layer; 3: solid electrolyte layer; 4: laminate; 5, 6: terminal electrodes; 10: all-solid-state battery.

Claims

1. An all-solid-state battery, characterized in that: have: a positive electrode layer comprising a positive electrode current collector layer and a positive electrode active material layer; a negative electrode layer comprising a negative electrode current collector layer and a negative electrode active material layer; and a solid electrolyte layer comprising a solid electrolyte, The positive electrode active material layer and the negative electrode active material layer each have a G band half width (FWHM) of 40 cm in Raman spectrum. －1 The following carbon particles, The carbon particles contained in the positive electrode active material layer and the negative electrode active material layer have a particle size distribution in which D10 is 0.1 μm or more and D90 is 5.0 μm or less.

2. The all-solid-state battery according to claim 1, wherein: When the long side of the carbon particle is represented by a and the short side is represented by b, the ratio thereof is 1.0<a / b.

3. The all-solid-state battery according to claim 1, wherein: The positive electrode active material layer and the negative electrode active material layer contain 0.5 wt % or more and 15.0 wt % or less of the carbon particles, respectively.

4. The all-solid-state battery according to any one of claims 1 to 3, wherein: When the long side of the carbon particle is a and the short side is b, the ratio of the long side to the short side of the carbon particle satisfies 1.5≤a / b≤5.

0. In the particle size distribution of the carbon particles, D10 is 0.25 μm or less and D90 is 4.5 μm or more.

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