SOLID BATTERY

Abstract

It is an object of the present invention to provide a solid-state battery with a high discharge capacity in which lithium vanadium phosphate is used as the positive electrode active material layer and the negative electrode active material layer. According to the present invention, the positive electrode active material layer and the negative electrode active material layer of the solid-state battery, which has a solid electrolyte between a pair of electrodes, contain the lithium vanadium phosphate, the lithium vanadium phosphate contains a polyphosphate compound containing Li and V, and contains the lithium vanadium phosphate Li3V2(PO4)3 as the main phase as well as 1.0 wt% or more and 15.0 wt% or less Li3PO4 based on Li3V2(PO4)3, thereby providing a high discharge capacity.

Description

[0001] The present invention relates to a solid-state battery which has a high discharge capacity and high safety and can be manufactured at low cost. STATE OF THE ART

[0002] In recent years, with the development of portable devices such as personal computers, mobile phones, and the like, the demand for batteries used as their power sources has increased significantly. A battery used for such applications conventionally uses a liquid electrolyte (electrolyte solution), such as an organic solvent, as the medium for ion movement. A problem such as electrolyte leakage can occur in batteries using this type of electrolyte solution.

[0003] To overcome this problem, the development of a solid-state battery is being pursued. This battery uses a solid electrolyte instead of a liquid electrolyte, and all other components are solid. Because the electrolyte in such a solid-state battery is a solid, there is no need to worry about liquid leakage, loss of electrolyte, etc., and problems such as degradation of battery performance due to corrosion are less likely to occur. Furthermore, the solid-state battery is being actively investigated in various aspects as a secondary battery, which can easily achieve high charge and discharge capacity and energy density.

[0004] However, a solid-state battery using a solid electrolyte still suffers from the problem of having a lower discharge capacity compared to a battery using a liquid electrolyte. It is disclosed that Li3V2(PO4)3 (a polyphosphate-based electrode active material with a variety of redox potentials (3.8 V, 1.8 V)) is used for a positive and a negative electrode to produce a battery with symmetrical electrodes, thereby improving charge and discharge cycle characteristics; however, an improvement in discharge capacity is not disclosed (Patent 1). Furthermore, if Li3V2(PO4)3 of stoichiometric composition is used as the sintered body active material for either the positive or the negative electrode, the composition of the grain boundary formed during the sintering process becomes non-uniform, hindering lithium-ion conductivity.Therefore, a high discharge capacity cannot be achieved.

[0005] Therefore, there is still room for improvement in the discharge capacity of the solid-state battery disclosed in patent specification 1. patent specifications

[0006] Patent Document 1: JP2002-530835A SUMMARY

[0007] The present invention was made in view of the above-mentioned problems in the prior art and it is an object of the present invention to provide a solid-state battery with a high discharge capacity.

[0008] The inventors conducted intensive investigations to solve the problem described above. As a result, the inventors discovered that a positive electrode active material layer and a negative electrode active material layer contain lithium vanadium phosphate, and that in a polyphosphate compound containing Li and V, the amount of Li3PO4 contained in the lithium vanadium phosphate corresponds to a certain capacity, and consequently, the present invention is complete.

[0009] This means that, according to the present invention, a solid-state battery as described below is provided.

[0010] The solid-state battery of the present invention is characterized in that the solid-state battery comprises a solid electrolyte layer between a pair of electrode layers, wherein a positive electrode active material layer and a negative electrode active material layer, which form the pair of electrode layers, contain lithium vanadium phosphate, the lithium vanadium phosphate contains a polyphosphate compound containing Li and V, the lithium vanadium phosphate contains Li3V2(PO4)3 as the main phase, and the lithium vanadium phosphate contains 1.0 wt.% or more and 15.0 wt.% or less Li3PO4 based on Li3V2(PO4)3.

[0011] According to this design, the Li3PO4 present in a grain boundary section of the positive electrode active material layer or the negative electrode active material layer can reduce structural disorder caused at a grain boundary interface, thus enabling the formation of a uniform grain boundary. Consequently, a reduction in lithium ion conductivity between the crystal grains can be suppressed, high ion conductivity can be achieved, and high capacity can be obtained.

[0012] The solid-state battery of the present invention is characterized in that the solid-state electrolyte layer contains lithium-aluminum-titanium-phosphate.

[0013] If, according to this design, a lithium-aluminum-titanium-phosphate solid electrolyte is used for the solid electrolyte layer, the formation of a non-uniform grain boundary, such as one that impedes lithium ion movement, can be suppressed at these interfaces, since a grain boundary between the positive electrode active material and the solid electrolyte or a grain boundary between the negative electrode active material and the solid electrolyte is uniformly bonded using polyphosphate-based ceramics. This prevents a reduction in ionic conductivity and thus a high capacity.

[0014] The solid-state battery of the present invention is characterized in that the solid-state electrolyte material consisting of the phosphate compound Li f Al g Ti h P i O j(where f, g, h, i and j are numbers such that 0.5≤f≤3.0, 0.0 <g≤1,0, 1,0≤h≤2,0, 2,8≤i≤3,2 beziehungsweise 9,25<j≤15,0 erfüllen) ist.

[0015] Since, according to this structure, Li f Al g Ti h P i O j (where f, g, h, i and j are numbers such that 0.5≤f≤3.0, 0.0 <g≤1,0, 1,0≤h≤2,0, 2,8≤i≤3,2 beziehungsweise 9,25<j≤15,0 erfüllen) mit einer hohen Lithiumionenleitfähigkeit als das Lithium-Aluminium-Titan-Phosphat verwendet wird, kann eine höhere Kapazität erhalten werden.

[0016] The solid-state battery of the present invention is characterized in that the pair of electrode layers and the solid electrolyte layer arranged between the pair of electrode layers have a relative density of 80% or above.

[0017] According to the present invention, a solid-state battery with a high discharge capacity can be provided. List of characters Fig. Figure 1 is a diagram illustrating a solid-state battery of the present embodiment. DETAILED DESCRIPTION OF EXECUTION FORMS

[0018] Preferred embodiments of the present invention are described below with reference to the accompanying drawings. Furthermore, the same or corresponding components in the drawings are designated by the same reference numeral, and a further description is omitted. Moreover, the dimensional ratio in the drawings is not limited to the ratio shown. [Solid body battery]

[0019] Fig. Figure 1 is a diagram showing a conceptual structure of a solid-state battery. 1 illustrated by the present embodiment. As shown in Fig. The solid state battery is shown in 1. 1 in the present embodiment by layers of a positive electrode layer 2and a negative electrode layer 3 by means of a solid electrolyte layer 4 formed, whereby the positive electrode layer 2 from a packing layer 5 , a positive electrode current collector layer 6 and a positive electrode active material layer 7 consists and the negative electrode layer 3 from a negative electrode active material layer 8 , a negative electrode current collector layer 9 and a packing layer 5 consists.

[0020] The solid-state battery of the present embodiment is preferably a solid-state battery comprising a solid electrolyte layer between a pair of electrode layers, wherein the positive electrode active material layer and the negative electrode active material layer forming the pair of electrode layers contain lithium vanadium phosphate, the lithium vanadium phosphate contains a polyphosphate compound containing Li and V, the lithium vanadium phosphate contains Li3V2(PO4)3 as the main phase, and the lithium vanadium phosphate contains 1.0 wt.% or more and 15.0 wt.% or less Li3PO4 based on Li3V2(PO4)3.

[0021] By using, according to this setup, the positive electrode active material layer and the negative electrode active material layer described above, the Li3PO4 present in a grain boundary section of both active material layers can reduce structural disorder caused at a grain boundary interface, thus enabling the formation of a uniform grain boundary. Consequently, a reduction in lithium ion conductivity between the crystal grains can be suppressed, high ion conductivity can be achieved, and high capacity can be obtained.

[0022] Furthermore, the Li3V2(PO4)3, used as the lithium vanadium phosphate of the present embodiment, can be distinguished from Li3PO4 and lithium iron phosphate by performing an X-ray diffraction method on a sample. ICDD card no. 01-072-7074 is used for the lithium vanadium phosphate, ICDD card no. 01-071-5981 is used for Li3PO4, and ICDD card no. 01-070-6684 is used for the lithium iron phosphate. Additionally, a ratio of the above compounds can be calculated using the reference intensity ratio recorded in the ICDD card.

[0023] Furthermore, the solid electrolyte layer in the solid-state battery of the present embodiment preferably contains lithium aluminum titanium phosphate.

[0024] If, according to this design, a solid electrolyte containing lithium aluminum titanium phosphate is used for the solid electrolyte layer, then, due to the high ionic conductivity of the solid electrolyte, the movement of lithium ions, even between the positive and negative electrodes, is facilitated, and consequently, a higher capacity can be achieved. Furthermore, since the lithium vanadium phosphate active material and the solid electrolyte containing the lithium aluminum titanium phosphate are homogeneous polyphosphate-based ceramics in the present embodiment, it is difficult for a non-uniform grain boundary, such as one that hinders lithium ion movement, to form at an interface between them, thereby improving the charging and discharging capacity.

[0025] In the solid-state battery of the present invention, Li is preferably used f Al g Ti h P i O jwith a high lithium ion conductivity than the lithium aluminum titanium phosphate described above (where f, g, h, i and j are numbers that 0.5≤f≤3.0, 0.0 <g≤1,0, 1,0≤h≤2,0, 2,8≤i≤3,2 beziehungsweise 9,25<j≤15,0 erfüllen).

[0026] Since, according to this structure, Li f Al g Ti h P i O j (where f, g, h, i and j are numbers such that 0.5≤f≤3.0, 0.0 <g≤1,0, 1,0≤h≤2,0, 2,8≤i≤3,2 beziehungsweise 9,25<j≤15,0 erfüllen) mit einer hohen Lithiumionenleitfähigkeit als das Lithium-Aluminium-Titan-Phosphat verwendet wird, kann eine höhere Lade- und Entladekapazität erhalten werden. (Method for producing a ceramic material)

[0027] The lithium vanadium phosphate material of the present embodiment can be obtained by subjecting a mixed starting material, formed by mixing a Li compound, a V compound and a phosphate compound or a Li phosphate compound, to heat treatment. Furthermore, the lithium vanadium phosphate material can also be obtained by adding Li3PO4 to the mixed starting material after heat treatment and mixing. Additionally, the lithium aluminum titanium phosphate material can be obtained by subjecting a mixed starting material, formed by mixing a Li compound, an Al compound, a Ti compound and a phosphate compound or a Ti phosphate compound, to heat treatment.

[0028] The lithium compound described above could be, for example, LiOH or a hydrate thereof, Li₂CO₃, LiNO₃, CH₃COOLI, or the like. The volatile compound described above could be, for example, V₂O₃, V₂O₅, or the like. The phosphate compound described above could be, for example, H₃PO₄, NH₄H₂PO₄, (NH₄)₂HPO₄, or the like. Furthermore, the lithium phosphate compound described above could be, for example, LiPO₃, Li₃PO₄, Li₄P₂O₇, Li₅P₃O₄. 10 , Li6P4O 14 or something similar.

[0029] Furthermore, the Al compound described above could be, for example, Al₂O₃, Al(OH)₃, Al₂(SO₄)₃, or the like. The Ti compound described above could be, for example, TiO₂, Ti₂O₃, TiC₆. 14 , Ti(OR)4 or the like. The Ti phosphate compound described above could, for example, be TiP2O7, Ti3P4O 16 or something similar.

[0030] An example of a process for producing the lithium vanadium phosphate of the present embodiment is set out. In the process for producing the compound, (a) a process for mixing the starting material is first carried out, then (b) a heat treatment process is carried out, and finally (c) a pulverization process is carried out. These processes are described below in sequence. Process for mixing the starting material

[0031] In the process for mixing the starting material with respect to the lithium vanadium phosphate, the method can be used in which starting materials are each weighed such that the amounts of Li and P are greater than those of their stoichiometric composition, and then mixed, or the method in which Li3PO4 is added to the lithium vanadium phosphate of stoichiometric composition and then mixed. Furthermore, a carbonate, sulfate, nitrate, oxalate, chloride, hydroxide, oxide, phosphate, or the like of any element can be used as the starting material. Of these, an oxide or starting material obtained as lithium phosphate does not produce undesirable gas during heat treatment and is therefore preferable, and a carbonate that produces carbon dioxide or a hydroxide that produces water vapor after thermolysis is even more preferred.The mixing process can be carried out by dry mixing and pulverizing without a solvent, or by wet mixing and pulverizing in a solvent. However, from the standpoint of improving mixing performance, wet mixing and pulverizing in a solvent is preferable. For example, a planetary mill, attritor, ball mill, or similar device can be used in the mixing process. Regarding the solvent, one in which lithium is sparingly soluble is preferable, and an organic solvent such as ethanol is more suitable. The mixing time depends on the quantity being mixed, but it can range from, for example, 1 hour to 32 hours.Furthermore, regarding lithium aluminum titanium phosphate, the process can also be used in which starting materials are weighed in such a way as to obtain a desired composition and then mixed using any method. calcination process

[0032] In the calcination process for lithium vanadium phosphate, a mixed powder obtained during the mixing process is calcined. In this case, the calcination temperature is preferably the temperature at which a change in the state of the starting material occurs (for example, a phase transition or the like) or a higher temperature. For example, if Li₂CO₃ is used as one of the starting materials, the calcination temperature is preferably the temperature at which the carbonate decomposes to produce the desired lithium vanadium phosphate phase or a higher temperature. In particular, the calcination temperature is preferably set to 600°C to 1000°C. Furthermore, a calcination atmosphere is preferably an inert gas atmosphere or a reducing gas atmosphere. Regarding lithium aluminum titanium phosphate, a mixed powder obtained during the mixing process is also calcined.In particular, the calcination temperature is preferably set to 800°C to 1000°C. Furthermore, the calcination atmosphere is preferably one in which titanium is not reduced, and it is particularly preferably an air atmosphere. pulverization process

[0033] The pulverization process is a process for producing a powder with a suitable particle size and distribution from the material obtained after reaction and agglutination during the calcination process. Pulverization can be carried out by dry pulverization without a solvent or by wet pulverization in a solvent. For example, a planetary mill, an attritor, a ball mill, or similar equipment can be used in the pulverization process. To ensure more stable pulverization of the lithium vanadium phosphate, the solvent is preferably an organic solvent such as ethanol. While the pulverization time depends on the quantity being pulverized, it can be set, for example, from 0.5 to 32 hours.

[0034] Furthermore, pulverization can be carried out after Li3PO4 has been added to a calcined product obtained during the calcination process.

[0035] According to the manufacturing process described above, deviations in composition can be precisely suppressed because the mixed powder of the starting materials is calcined at a relatively low temperature. Furthermore, the process for producing the lithium vanadium phosphate of the present invention is not limited to this method, and other manufacturing processes can also be used.

[0036] The solid-state battery of the present embodiment is formed by layers of the positive electrode layer 2 and the negative electrode layer 3 via the solid electrolyte layer 4 formed, whereby the positive electrode layer 2 from the packing layer 5, the positive electrode current collector layer 6 and the positive electrode active material layer 7 consists and the negative electrode layer 3 from the negative electrode active material layer 8 , the negative electrode current collector layer 9 and the packing layer 5 consists of the positive electrode current collector layer. 6 and the negative electrode current collector layer 9 They can contain a conventionally known current collector used in a lithium secondary battery, and they can be manufactured using a conventional method. (Electricity collector)

[0037] The material used for the current collector layer of the solid-state battery in the present embodiment is preferably one with high electrical conductivity; for example, silver, palladium, gold, platinum, aluminum, copper, nickel, or the like are preferable. In particular, copper is less likely to react with the lithium-aluminum-titanium phosphate and is also effective in reducing the internal resistance of the solid-state battery; therefore, copper is preferable. Furthermore, the material used for the current collector layer in the positive and negative electrode layers can be the same or different.

[0038] Furthermore, the positive electrode current collector layer and the negative electrode current collector layer of the solid-state battery of the present embodiment preferably contain the positive electrode active material and the negative electrode active material, respectively.

[0039] In the situation where the positive electrode current collector layer and the negative electrode current collector layer contain the positive electrode active material and the negative electrode active material respectively, the adhesion between the positive electrode current collector layer and the positive electrode active material layer and the adhesion between the negative electrode current collector layer and the negative electrode active material layer are improved, and consequently this situation is preferable. (Method for manufacturing the solid-state battery)

[0040] The solid-state battery of the present embodiment can be produced by processing each material of the positive electrode current collector layer, the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, and the negative electrode current collector layer into a paste; layering and drying to form green films; layering the green films to produce a layered body; and then firing the resulting layered body.

[0041] The process for preparing a paste is not subject to any particular restrictions. For example, a powder of any of the aforementioned materials can be mixed with a carrier to obtain a paste. Here, "carrier" is a general term for a medium in a liquid phase. The carrier contains a solvent and a binder. A paste for the positive electrode current 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 current collector layer can be prepared using the process described above.

[0042] The produced pastes are layered onto a substrate such as PET in a predetermined sequence and dried if necessary. The substrate is then peeled off to produce a green film. The layering process is not subject to any particular restrictions, and a known method such as screen printing, coating, transfer printing, or doctor blade application can be used.

[0043] The manufactured green films are layered in a predetermined sequence and with a predetermined number of layers. Alignment, cutting, and similar processes are then carried out as needed to produce a layered block. When manufacturing a battery with parallel or series-parallel mixed circuits, it is preferable to align the layers and then layer them in such a way that the end faces of the positive electrode layer and the negative electrode layer are not aligned.

[0044] During the production of a layered block, an active material unit described below can be prepared to produce the layered block.

[0045] In the manufacturing process, the paste for the solid electrolyte is first formed into a film on a PET sheet using a doctor blade process to obtain the solid electrolyte film; then, the paste for the positive electrode active material layer is screen-printed onto the solid electrolyte film and subsequently dried. Next, the paste for the positive electrode current collector layer is screen-printed onto it and then dried. Finally, the paste for the positive electrode active material is also screen-printed onto it and dried, and then the PET film is peeled off to obtain the positive electrode layer unit.In this way, the positive electrode layer unit is obtained, in which the paste for the positive electrode active material layer, the paste for the positive electrode current collector layer, and the paste for the positive electrode active material layer are successively formed on the solid electrolyte film. The negative electrode layer unit, in which the paste for the negative electrode active material layer, the paste for the negative electrode current collector layer, and the paste for the negative electrode active material layer are successively formed on the solid electrolyte film, is obtained in the same way.

[0046] A positive electrode layer unit and a negative electrode layer unit are stacked such that the solid electrolyte film is sandwiched between them. At this stage, the units are stacked in an offset manner, with the positive electrode current collector layer of the positive electrode layer unit extending only to one end face and the negative electrode current collector layer of the negative electrode layer unit extending only to the other end face. The solid electrolyte films, which have a predetermined thickness, are then stacked on both sides of the stacked unit to create a stacked block.

[0047] The resulting layered blocks are joined together under pressure. This joining process is carried out under pressure while heating, with the heating temperature set, for example, to between 40°C and 95°C.

[0048] The bonded, layered block is heated to 500°C to 750°C in an atmosphere of, for example, nitrogen, hydrogen, and water vapor to remove the binder. The layered block is then heated to 600°C to 1100°C in a nitrogen atmosphere to initiate a firing process. The firing time is set, for example, to 0.1 to 3 hours. The layered body is completed through this firing process.

[0049] The pair of electrode layers and the solid electrolyte layer (located between the electrode layers) of the layer body, after sintering, have a relative density of 80% or higher. When the relative density is high, the diffusion path of mobile ions within the crystal is readily connected, and the ionic conductivity can be improved. EXAMPLES [Example 1]

[0050] The content of the present invention is described in detail with reference to examples and comparative examples, but the present invention is not limited to the examples below. (Production of the positive electrode active material)

[0051] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 3,10 V 2,00 (PO4) 3,03The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. First, the starting materials were weighed and mixed, then pulverized in ethanol for 16 hours using a ball mill (120 rpm / zirconium oxide ball). After separating the powder from the ball and ethanol and drying, a mixed powder of the starting materials was calcined using a magnesia crucible. Calcination was carried out in a reducing atmosphere at 850°C for 2 hours. The calcined powder was then pulverized in ethanol for 16 hours using a ball mill (120 rpm / zirconium oxide ball). The lithium vanadium phosphate powder was obtained after separating the pulverized powder from the ball and ethanol and drying.Using an X'Pert PRO MPD produced by PANalytical and the reference intensity ratio recorded in the ICDD chart, a ratio between Li3V2(PO4)3 and Li3PO4 was determined by X-ray diffraction. This confirmed that 1.0 wt% Li3PO4 was present. (Production of the negative electrode active material)

[0052] The same powder was used for the negative electrode active material as for the positive electrode active material described above. (Production of the paste for the positive electrode active material layer and the paste for the negative electrode active material layer)

[0053] The pastes for the positive electrode active material layer and the negative electrode active material layer were prepared by adding 15 parts of ethylcellulose, used as a binder, and 65 parts of dihydroterpineol, used as a solvent, to 100 parts of the lithium vanadium phosphate powder, and then kneading and dispersing the mixture using a three-roll mill. (Production of the paste for the solid electrolyte layer)

[0054] When the solid electrolyte was Li f Al g Ti h P i O j(where f=1.3, g=0.3, h=1.7, i=3.0, and j=12.0) was used, which was prepared by the following procedure. Li₂CO₃, Al₂O₃, TiO₂, and NH₄H₂PO₄ were used as starting materials, ethanol was used as the solvent, and wet mixing was carried out using a ball mill for 16 hours. After separation from the ball and ethanol and subsequent drying, the mixed powder of the starting materials was calcined in an aluminum oxide crucible in air at 850°C for 2 hours. The calcined powder was then pulverized in ethanol using a ball mill (120 rpm / zirconium oxide ball) for 16 hours. The pulverized powder was separated from the ball and ethanol and then dried to obtain a powder.

[0055] Next, 100 parts ethanol and 200 parts toluene, used as solvents, were added to 100 parts of the powder, and then wet mixing was carried out using a ball mill. Afterward, 16 parts polyvinyl butyral binder and 4.8 parts benzyl butyl phthalate were added and then mixed to produce the paste for the solid electrolyte layer. (Production of the film for the solid electrolyte layer)

[0056] A PET film was used as a substrate, and then the paste for the solid electrolyte layer was formed into a film using a doctor blade process to obtain a solid electrolyte layer film with a thickness of 15 µm. (Production of the paste for the positive electrode current collector layer and the paste for the negative electrode current collector layer)

[0057] Cu powder and lithium vanadium phosphate powder were mixed at a weight ratio of 100:9; then 10 parts of ethyl cellulose, used as a binder, and 50 parts of dihydroterpineol, used as a solvent, were added and then mixed and dispersed using a three-roll mill to produce the pastes for the current collector layer. (Production of the active material unit)

[0058] The paste for the electrode current collector layer was screen-printed to a thickness of 5 µm onto the solid electrolyte layer film described above and then dried at 80°C for 10 minutes. Next, the paste for the electrode active material layer was screen-printed to a thickness of 5 µm and then dried at 80°C for 10 minutes to form the positive electrode layer assembly. Similarly, the paste for the negative electrode active material layer was screen-printed to a thickness of 5 µm onto the solid electrolyte layer film and then dried at 80°C for 10 minutes. Next, the paste for the negative electrode current collector layer was screen-printed to a thickness of 5 µm and then dried at 80°C for 10 minutes to form the negative electrode layer assembly. Finally, the PET film was removed. (Production of the layered body)

[0059] The positive electrode layer unit, the negative electrode layer unit, and the solid electrolyte layer film were layered such that the solid electrolyte layer, the positive electrode current collector layer, the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, the negative electrode current collector layer, and the solid electrolyte layer were formed sequentially to obtain a layered product. At this stage, the units were layered in an offset manner, with the positive electrode current collector layer of the positive electrode layer unit extending only to one end face and the negative electrode current collector layer of the negative electrode layer unit extending only to the opposite end face.The layered product was then shaped using thermocompression bonding and then cut to produce the layered body. (Production of the sintered body)

[0060] The resulting layered body underwent a debinding process and was simultaneously fired to produce a sintered body. During the debinding process, the layered body was heated in nitrogen at a rate of 50°C / hour to a firing temperature of 700°C and held at this temperature for 10 hours. During the simultaneous firing process, the layered body was heated in nitrogen at a rate of 200°C / hour to a firing temperature of 850°C and then held at this temperature for 1 hour. After firing, the layered body was cooled naturally. Following the simultaneous firing, the external dimensions of the resulting battery were 3.2 mm × 2.5 mm × 0.4 mm. (Evaluation of charging and discharging performance)

[0061] A charge and discharge tester was used to measure the charge and discharge capacities. The resulting layer was mounted onto a clamping device using a clamping pin. The charging and discharging conditions were as follows: a current of 2 µA and a voltage of 0 V to 1.8 V. The measured discharge capacity is shown in Table 1. A sufficient discharge capacity threshold for practical use was 2.5 µAh. [Example 2]

[0062] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 3,20 V 2,00 (PO4) 3,07The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 2.0 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 1, and the layered product was subsequently manufactured using the same method. Debinding and sintering were then carried out using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 1. The results of the measured discharge capacity are shown in Table 1. [Example 3]

[0063] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 3,40 V 2,00 (PO4) 3,13The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 5.0 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 1, and the layered product was subsequently manufactured using the same method. Debinding and sintering were then carried out using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 1. The results of the measured discharge capacity are shown in Table 1. [Example 4]

[0064] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 3,80 V 2,00 (PO4) 3,30The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 8.0 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 1, and the layered product was subsequently manufactured using the same method. Debinding and sintering were then carried out using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 1. The results of the measured discharge capacity are shown in Table 1. [Example 5]

[0065] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 4,60 V 2,00 (PO4) 3,53The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 13.0 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 1, and the layered product was subsequently manufactured using the same method. Debinding and sintering were then carried out using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 1. The results of the measured discharge capacity are shown in Table 1. [Example 6]

[0066] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 4,90 V 2,00 (PO4) 3,63The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 15.0 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 1, and the layered product was subsequently manufactured using the same method. Debinding and sintering were then carried out using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 1. The results of the measured discharge capacity are shown in Table 1. [Comparison example 1]

[0067] In this comparative example, the starting materials were weighed in such a way that the lithium vanadium phosphate Li 2,90 V 2,00 (PO4) 2,97 The starting materials used were Li2CO3, LiPO3, V2O3 and NH4H2PO4. The lithium vanadium phosphate powder was obtained using the same method as in Example 1. Subsequently, an evaluation was performed using the same X-ray diffraction method as in Example 1. This confirmed the presence of 0.0 wt% Li3PO4. Furthermore, the lithium-aluminum-titanium-phosphate powder was obtained using the same method as in Example 1, and the layered product was then manufactured using the same method. Debinding and sintering were then carried out using the same method to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same method as in Example 1. The results of the measured discharge capacity are presented in Table 1. [Comparative example 2]

[0068] In this comparative example, the starting materials were weighed in such a way that the lithium vanadium phosphate Li 3,02 V 2,00 (PO4) 3,00The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 0.8 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 1, and the layered product was subsequently manufactured using the same method. Debinding and sintering were then carried out using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 1. The results of the measured discharge capacity are shown in Table 1. [Comparative example 3]

[0069] In this comparative example, the starting materials were weighed in such a way that the lithium vanadium phosphate Li 5,00 V 2,00 (PO4) 3,67The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 16.0 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 1, and the layered product was subsequently manufactured using the same method. Debinding and sintering were then carried out using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 1. The results of the measured discharge capacity are shown in Table 1. [Comparative example 4]

[0070] Furthermore, this comparative example showed the case where lithium iron phosphate (which was considered a polyphosphate compound) was used instead of lithium vanadium phosphate.

[0071] The starting materials were weighed in such a way that the lithium iron phosphate Li1, 04 Fe 1,00 P 1,01 O 4,05The starting materials used were Li₂CO₃, FeO, and NH₄H₂PO₄. First, the starting materials were weighed and mixed, then pulverized in ethanol for 16 hours using a ball mill (120 rpm / zirconium oxide ball). After separating the powder from the ball and ethanol and drying, a mixed powder of the starting materials was calcined using a magnesia crucible. Calcination was carried out in a reducing atmosphere at 800°C for 2 hours. The calcined powder was then pulverized in ethanol for 16 hours using a ball mill (120 rpm / zirconium oxide ball). The lithium iron phosphate powder was obtained after separating the pulverized powder from the ball and ethanol and drying.Using an X'Pert PRO MPD manufactured by PANalytical and the reference intensity ratio recorded in the ICDD chart, the ratio between LiFePO4 and Li3PO4 was determined by X-ray diffraction. This confirmed the presence of 1.0 wt% Li3PO4. The lithium-aluminum-titanium phosphate powder was then obtained using the same procedure as in Example 1, and the layered product was subsequently fabricated using the same procedure. Debinding and sintering were then performed using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 1. The results of the measured discharge capacity are shown in Table 1. [Comparative example 5]

[0072] The starting materials were weighed in such a way that the lithium iron phosphate Li 1,3 ofe 1,00 P 1,11 O 4,40The starting materials used were Li₂CO₃, FeO, and NH₄H₂PO₄. The lithium iron phosphate powder was obtained using the same procedure as in Comparative Example 4. Using an X'Pert PRO MPD prepared by PANalytical and the reference intensity ratio recorded in the ICDD chart, the ratio between LiFePO₄ and Li₃PO₄ was determined by X-ray diffraction. This confirmed the presence of 7.5 wt% Li₃PO₄. Furthermore, the lithium aluminum titanium phosphate powder was obtained using the same procedure as in Example 1, and the layered product was then fabricated using the same procedure. Debinding and sintering were also performed using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 1. The results of the measured discharge capacity are shown in Table 1. [Comparative example 6]

[0073] The starting materials were weighed in such a way that the lithium iron phosphate Li 1,65 Fe 1,00 P 1,16 O 4,90The starting materials used were Li₂CO₃, FeO, and NH₄H₂PO₄. The lithium iron phosphate powder was obtained using the same procedure as in Comparative Example 4. Using an X'Pert PRO MPD prepared by PANalytical and the reference intensity ratio recorded in the ICDD chart, the ratio between LiFePO₄ and Li₃PO₄ was determined by X-ray diffraction. This confirmed that 14.3 wt% Li₃PO₄ was present. Furthermore, the lithium aluminum titanium phosphate powder was obtained using the same procedure as in Example 1, and the layered product was then fabricated using the same procedure. Debinding and sintering were also performed using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 1. The results of the measured discharge capacity are shown in Table 1.

[0074] Table 1 shows that the solid-state battery produced by applying the lithium vanadium phosphate containing Li3PO4 in a quantity range according to the present invention to the active material layer was able to achieve a significantly higher discharge capacity. [Table 1] Main phase Li3PO4 (wt%) There f To the g You h Pious j Discharge capacity of the manufactured battery (µAh) f g h i j Example 1 Li3V2(PO4)3 1,0 1,30 0,30 1,70 3,00 12,00 3,05 Example 2 Li3V2(PO4)3 2,0 1,30 0,30 1,70 3,00 12,00 3,20 Example 3 Li3V2(PO4)3 5,0 1,30 0,30 1,70 3,00 12,00 4,25 Example 4 Li3V2(PO4)3 8,0 1,30 0,30 1,70 3,00 12,00 5,13 Example 5 Li3V2(PO4)3 13,0 1,30 0,30 1,70 3,00 12,00 4,67 Example 6 Li3V2(PO4)3 15,0 1,30 0,30 1,70 3,00 12,00 4,08 Comparative example 1 Li3V2(PO4)3 0,0 1,30 0,30 1,70 3,00 12,00 2,14 Comparative example 2 Li3V2(PO4)3 0,8 1,30 0,30 1,70 3,00 12,00 2,28 Comparative example 3 Li3V2(PO4)3 16,0 1,30 0,30 1,70 3,00 12,00 1,80 Comparative example 4 LiFePO4 1,0 1,30 0,30 1,70 3,00 12,00 1,39 Comparative example 5 LiFePO4 7,5 1,30 0,30 1,70 3,00 12,00 2,33 Comparative example 6 LiFePO4 14,5 1,30 0,30 1,70 3,00 12,00 1,85 [Example 7](Production of the positive electrode active material)

[0075] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 3,10 V 2,00 (PO4) 3,03The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same method as in Example 1. Subsequently, an evaluation was performed using the same X-ray diffraction method as in Example 1. This confirmed the presence of 1.0 wt% Li₃PO₄. (Production of the negative electrode active material)

[0076] The same powder was used for the negative electrode active material as for the positive electrode active material described above. (Production of the paste for the solid electrolyte layer)

[0077] When the solid electrolyte was Li f Al g Ti h P i O j(where f=1.02, g=0.13, h=1.91, i=3.0 and j=12.03) was used. Li2CO3, TiO2 and NH4H2PO4 were used as starting materials, and the lithium aluminum titanium phosphate powder was obtained using the same method as in Example 1.

[0078] Next, 100 parts ethanol and 200 parts toluene, used as solvents, were added to 100 parts of the powder, and then wet mixing was carried out using a ball mill. Afterward, 16 parts polyvinyl butyral binder and 4.8 parts benzyl butyl phthalate were added and then mixed to produce the paste for the solid electrolyte layer. (Production of the film for the solid electrolyte layer)

[0079] A PET film was used as a substrate, and then the paste for the solid electrolyte layer was formed into a film using a doctor blade process to obtain a solid electrolyte layer film with a thickness of 15 µm. (Production of the paste for the positive electrode current collector layer and the paste for the negative electrode current collector layer)

[0080] Cu powder and lithium vanadium phosphate powder were mixed at a weight ratio of 100:9; then 10 parts of ethyl cellulose, used as a binder, and 50 parts of dihydroterpineol, used as a solvent, were added and then mixed and dispersed using a three-roll mill to produce the pastes for the current collector layer. (Production of the active material unit)

[0081] The paste for the electrode current collector layer was screen-printed to a thickness of 5 µm onto the solid electrolyte layer film described above and then dried at 80°C for 10 minutes. Next, the paste for the electrode active material layer was screen-printed to a thickness of 5 µm and then dried at 80°C for 10 minutes to form the positive electrode layer assembly. Similarly, the paste for the negative electrode active material layer was screen-printed to a thickness of 5 µm onto the solid electrolyte layer film and then dried at 80°C for 10 minutes. Next, the paste for the negative electrode current collector layer was screen-printed to a thickness of 5 µm and then dried at 80°C for 10 minutes to form the negative electrode layer assembly. Finally, the PET film was removed. (Production of the layered body)

[0082] The positive electrode layer unit, the negative electrode layer unit, and the solid electrolyte layer film were layered such that the solid electrolyte layer, the positive electrode current collector layer, the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, the negative electrode current collector layer, and the solid electrolyte layer were formed sequentially to obtain a layered product. At this stage, the units were layered in an offset manner, with the positive electrode current collector layer of the positive electrode layer unit extending only to one end face and the negative electrode current collector layer of the negative electrode layer unit extending only to the opposite end face.The layered product was then shaped using thermocompression bonding and then cut to produce the layered body. (Production of the sintered body)

[0083] The resulting layered body underwent a debinding process and was simultaneously fired to produce a sintered body. During the debinding process, the layered body was heated in nitrogen at a rate of 50°C / hour to a firing temperature of 700°C and held at this temperature for 10 hours. During the simultaneous firing process, the layered body was heated in nitrogen at a rate of 200°C / hour to a firing temperature of 850°C and then held at this temperature for 1 hour. After firing, the layered body was cooled naturally. Following the simultaneous firing, the external dimensions of the resulting battery were 3.2 mm × 2.5 mm × 0.4 mm. (Evaluation of charging and discharging performance)

[0084] The charge and discharge tester was used to measure the charge and discharge capacities by mounting the resulting layered body onto a clamping device using a clamping pin. The measurement conditions involved charging and discharging with a current of 2 µA and a voltage ranging from 0 V to 1.8 V. The measured discharge capacity is shown in Table 2. A sufficient discharge capacity threshold for practical use was 2.5 µAh. [Example 8]

[0085] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 3,40 V 2,00 (PO4) 3,13The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 5.0 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 7, and the layered product was subsequently manufactured using the same procedure. Debinding and sintering were then carried out using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 7. The results of the measured discharge capacity are shown in Table 2. [Example 9]

[0086] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 4,90 V 2,00 (PO4) 3,63The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 15.0 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 7, and the layered product was subsequently manufactured using the same procedure. Debinding and sintering were then carried out using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 7. The results of the measured discharge capacity are shown in Table 2. [Comparative example 7]

[0087] In this comparative example, the starting materials were weighed in such a way that the lithium vanadium phosphate Li 3,02 V 2,00 (PO4) 3,00The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 0.8 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 7, and the layered product was subsequently manufactured using the same procedure. Debinding and sintering were then carried out using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 7. The results of the measured discharge capacity are shown in Table 2. [Comparative example 8]

[0088] In this comparative example, the starting materials were weighed in such a way that the lithium vanadium phosphate Li 5,00 V 2,00 (PO4) 3,67The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 16.0 wt% Li₃PO₄. Furthermore, the lithium aluminum titanium phosphate powder was obtained using the same procedure as in Example 7, and the layered product was then manufactured using the same procedure. Debinding and sintering were then carried out using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 7. The results of the measured discharge capacity are shown in Table 2. [Example 10](Production of the positive electrode active material)

[0089] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 3,10 V 2,00 (PO4) 3,03 The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same method as in Example 1. Subsequently, an evaluation was performed using the same X-ray diffraction method as in Example 1. This confirmed the presence of 1.0 wt% Li₃PO₄. (Production of the negative electrode active material)

[0090] The same powder was used for the negative electrode active material as for the positive electrode active material described above. (Production of the paste for the solid electrolyte layer)

[0091] When the solid electrolyte was Li f Al g Ti h P i O j(where f=1.5, g=0.5, h=1.5, i=3.0 and j=12.0) was used. Li2CO3, Al2O3, TiO2 and NH4H2PO4 were used as starting materials, and the lithium aluminum titanium phosphate powder was obtained using the same method as in Example 1.

[0092] Next, 100 parts ethanol and 200 parts toluene, used as solvents, were added to 100 parts of the powder, and then wet mixing was carried out using a ball mill. Afterward, 16 parts polyvinyl butyral binder and 4.8 parts benzyl butyl phthalate were added and then mixed to produce the paste for the solid electrolyte layer. (Production of the film for the solid electrolyte layer)

[0093] A PET film was used as a substrate, and then the paste for the solid electrolyte layer was formed into a film using a doctor blade process to obtain a solid electrolyte layer film with a thickness of 15 µm. (Production of the paste for the positive electrode current collector layer and the paste for the negative electrode current collector layer)

[0094] Cu powder and lithium vanadium phosphate powder were mixed at a weight ratio of 100:9; then 10 parts of ethyl cellulose, used as a binder, and 50 parts of dihydroterpineol, used as a solvent, were added and then mixed and dispersed using a three-roll mill to produce the pastes for the current collector layer. (Production of the active material unit)

[0095] The paste for the electrode current collector layer was screen-printed to a thickness of 5 µm onto the solid electrolyte layer film described above and then dried at 80°C for 10 minutes. Next, the paste for the electrode active material layer was screen-printed to a thickness of 5 µm and then dried at 80°C for 10 minutes to form the positive electrode layer assembly. Similarly, the paste for the negative electrode active material layer was screen-printed to a thickness of 5 µm onto the solid electrolyte layer film and then dried at 80°C for 10 minutes. Next, the paste for the negative electrode current collector layer was screen-printed to a thickness of 5 µm and then dried at 80°C for 10 minutes to form the negative electrode layer assembly. Finally, the PET film was removed. (Production of the layered body)

[0096] The positive electrode layer unit, the negative electrode layer unit, and the solid electrolyte layer film were layered such that the solid electrolyte layer, the positive electrode current collector layer, the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, the negative electrode current collector layer, and the solid electrolyte layer were formed sequentially to obtain a layered product. At this stage, the units were layered in an offset manner, with the positive electrode current collector layer of the positive electrode layer unit extending only to one end face and the negative electrode current collector layer of the negative electrode layer unit extending only to the opposite end face.The layered product was then shaped using thermocompression bonding and then cut to produce the layered body. (Production of the sintered body)

[0097] The resulting layered body underwent a debinding process and was simultaneously fired to produce a sintered body. During the debinding process, the layered body was heated in nitrogen at a rate of 50°C / hour to a firing temperature of 700°C and held at this temperature for 10 hours. During the simultaneous firing process, the layered body was heated in nitrogen at a rate of 200°C / hour to a firing temperature of 850°C and then held at this temperature for 1 hour. After firing, the layered body was cooled naturally. Following the simultaneous firing, the external dimensions of the resulting battery were 3.2 mm × 2.5 mm × 0.4 mm. (Evaluation of charging and discharging performance)

[0098] The charge and discharge tester was used to measure the charge and discharge capacities by mounting the resulting layered body onto a clamping device using a clamping pin. The measurement conditions involved charging and discharging with a current of 2 µA and a voltage ranging from 0 V to 1.8 V. The measured discharge capacity is shown in Table 2. A sufficient discharge capacity threshold for practical use was 2.5 µAh. [Example 11]

[0099] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 3,40 V 2,00 (PO4) 3,13The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 5.0 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 10, and the layered product was fabricated using the same method. Debinding and sintering were then performed using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 10. The results of the measured discharge capacity are shown in Table 2. [Example 12]

[0100] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 4,90 V 2,00 (PO4) 3,63The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 15.0 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 10, and the layered product was subsequently manufactured using the same method. Debinding and sintering were then performed using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 10. The results of the measured discharge capacity are shown in Table 2. [Comparative example 9]

[0101] In this comparative example, the starting materials were weighed in such a way that the lithium vanadium phosphate Li 3,02 V 2,00 (PO4) 3,00The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 0.8 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 10, and the layered product was fabricated using the same procedure. Debinding and sintering were then performed using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 10. The results of the measured discharge capacity are shown in Table 2. [Comparative example 10]

[0102] In this comparative example, the starting materials were weighed in such a way that the lithium vanadium phosphate Li 5,00 V 2,00 (PO4) 3,67The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 16.0 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 10, and the layered product was fabricated using the same method. Debinding and sintering were then performed using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 10. The results of the measured discharge capacity are shown in Table 2. [Example 13](Production of the positive electrode active material)

[0103] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 3,10 V 2,00 (PO4) 3,03 The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same method as in Example 1. Subsequently, an evaluation was performed using the same X-ray diffraction method as in Example 1. This confirmed the presence of 1.0 wt% Li₃PO₄. (Production of the negative electrode active material)

[0104] The same powder was used for the negative electrode active material as for the positive electrode active material described above. (Production of the paste for the solid electrolyte layer)

[0105] When the solid electrolyte was Li f Al g Ti h P i O j(where f=2.0, g=1.0, h=1.0, i=3.0 and j=12.0) was used. Li2CO3, Al2O3, TiO2 and NH4H2PO4 were used as starting materials, and the lithium aluminum titanium phosphate powder was obtained using the same method as in Example 1.

[0106] Next, 100 parts ethanol and 200 parts toluene, used as solvents, were added to 100 parts of the powder, and then wet mixing was carried out using a ball mill. Afterward, 16 parts polyvinyl butyral binder and 4.8 parts benzyl butyl phthalate were added and then mixed to produce the paste for the solid electrolyte layer. (Production of the film for the solid electrolyte layer)

[0107] A PET film was used as a substrate, and then the paste for the solid electrolyte layer was formed into a film using a doctor blade process to obtain a solid electrolyte layer film with a thickness of 15 µm. (Production of the paste for the positive electrode current collector layer and the paste for the negative electrode current collector layer)

[0108] Cu powder and lithium vanadium phosphate powder were mixed at a weight ratio of 100:9; then 10 parts of ethyl cellulose, used as a binder, and 50 parts of dihydroterpineol, used as a solvent, were added and then mixed and dispersed using a three-roll mill to produce the pastes for the current collector layer. (Production of the active material unit)

[0109] The paste for the electrode current collector layer was screen-printed to a thickness of 5 µm onto the solid electrolyte layer film described above and then dried at 80°C for 10 minutes. Next, the paste for the electrode active material layer was screen-printed to a thickness of 5 µm and then dried at 80°C for 10 minutes to form the positive electrode layer assembly. Similarly, the paste for the negative electrode active material layer was screen-printed to a thickness of 5 µm onto the solid electrolyte layer film and then dried at 80°C for 10 minutes. Next, the paste for the negative electrode current collector layer was screen-printed to a thickness of 5 µm and then dried at 80°C for 10 minutes to form the negative electrode layer assembly. Finally, the PET film was removed. (Production of the layered body)

[0110] The positive electrode layer unit, the negative electrode layer unit, and the solid electrolyte layer film were layered such that the solid electrolyte layer, the positive electrode current collector layer, the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, the negative electrode current collector layer, and the solid electrolyte layer were formed sequentially to obtain a layered product. At this stage, the units were layered in an offset manner, with the positive electrode current collector layer of the positive electrode layer unit extending only to one end face and the negative electrode current collector layer of the negative electrode layer unit extending only to the opposite end face.The layered product was then shaped using thermocompression bonding and then cut to produce the layered body. (Production of the sintered body)

[0111] The resulting layered body underwent a debinding process and was simultaneously fired to produce a sintered body. During the debinding process, the layered body was heated in nitrogen at a rate of 50°C / hour to a firing temperature of 700°C and held at this temperature for 10 hours. During the simultaneous firing process, the layered body was heated in nitrogen at a rate of 200°C / hour to a firing temperature of 850°C and then held at this temperature for 1 hour. After firing, the layered body was cooled naturally. Following the simultaneous firing, the external dimensions of the resulting battery were 3.2 mm × 2.5 mm × 0.4 mm. (Evaluation of charging and discharging performance)

[0112] The charge and discharge tester was used to measure the charge and discharge capacities by mounting the resulting layered body onto a clamping device using a clamping pin. The measurement conditions involved charging and discharging with a current of 2 µA and a voltage ranging from 0 V to 1.8 V. The measured discharge capacity is shown in Table 2. A sufficient discharge capacity threshold for practical use was 2.5 µAh. [Example 14]

[0113] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 3,40 V 2,00 (PO4) 3,13The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 5.0 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 13, and the layered product was fabricated using the same procedure. Debinding and sintering were then performed using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 13. The results of the measured discharge capacity are shown in Table 2. [Example 15]

[0114] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 4,90 V 2,00 (PO4) 3,63The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 15.0 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 13, and the layered product was fabricated using the same method. Debinding and sintering were then performed using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 13. The results of the measured discharge capacity are shown in Table 2. [Comparative example 11]

[0115] In this comparative example, the starting materials were weighed in such a way that the lithium vanadium phosphate Li 3,02 V 2,00 (PO4) 3,00The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 0.8 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 13, and the layered product was fabricated using the same procedure. Debinding and sintering were then performed using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 13. The results of the measured discharge capacity are shown in Table 2. [Comparative example 12]

[0116] In this comparative example, the starting materials were weighed in such a way that the lithium vanadium phosphate Li 5,00 V 2,00 (PO4) 3,67The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 16.0 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 13, and the layered product was fabricated using the same procedure. Debinding and sintering were then performed using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 13. The results of the measured discharge capacity are shown in Table 2. [Example 16](Production of the positive electrode active material)

[0117] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 3,10 V 2,00 (PO4) 3,03 The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same method as in Example 1. Subsequently, an evaluation was performed using the same X-ray diffraction method as in Example 1. This confirmed the presence of 1.0 wt% Li₃PO₄. (Production of the negative electrode active material)

[0118] The same powder was used for the negative electrode active material as for the positive electrode active material described above. (Production of the paste for the solid electrolyte layer)

[0119] When the solid electrolyte was Li f Al g Ti h P i O j(where f=2.1, g=1.1, h=0.9, i=3.0 and j=12.0) was used. Li2CO3, Al2O3, TiO2 and NH4H2PO4 were used as starting materials, and the lithium aluminum titanium phosphate powder was obtained using the same method as in Example 1.

[0120] Next, 100 parts ethanol and 200 parts toluene, used as solvents, were added to 100 parts of the powder, and then wet mixing was carried out using a ball mill. Afterward, 16 parts polyvinyl butyral binder and 4.8 parts benzyl butyl phthalate were added and then mixed to produce the paste for the solid electrolyte layer. (Production of the film for the solid electrolyte layer)

[0121] A PET film was used as a substrate, and then the paste for the solid electrolyte layer was formed into a film using a doctor blade process to obtain a solid electrolyte layer film with a thickness of 15 µm. (Production of the paste for the positive electrode current collector layer and the paste for the negative electrode current collector layer)

[0122] Cu powder and lithium vanadium phosphate powder were mixed at a weight ratio of 100:9; then 10 parts of ethyl cellulose, used as a binder, and 50 parts of dihydroterpineol, used as a solvent, were added and then mixed and dispersed using a three-roll mill to produce the pastes for the current collector layer. (Production of the active material unit)

[0123] The paste for the electrode current collector layer was screen-printed to a thickness of 5 µm onto the solid electrolyte layer film described above and then dried at 80°C for 10 minutes. Next, the paste for the electrode active material layer was screen-printed to a thickness of 5 µm and then dried at 80°C for 10 minutes to form the positive electrode layer assembly. Similarly, the paste for the negative electrode active material layer was screen-printed to a thickness of 5 µm onto the solid electrolyte layer film and then dried at 80°C for 10 minutes. Next, the paste for the negative electrode current collector layer was screen-printed to a thickness of 5 µm and then dried at 80°C for 10 minutes to form the negative electrode layer assembly. Finally, the PET film was removed. (Production of the layered body)

[0124] The positive electrode layer unit, the negative electrode layer unit, and the solid electrolyte layer film were layered such that the solid electrolyte layer, the positive electrode current collector layer, the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, the negative electrode current collector layer, and the solid electrolyte layer were formed sequentially to obtain a layered product. At this stage, the units were layered in an offset manner, with the positive electrode current collector layer of the positive electrode layer unit extending only to one end face and the negative electrode current collector layer of the negative electrode layer unit extending only to the opposite end face.The layered product was then shaped using thermocompression bonding and then cut to produce the layered body. (Production of the sintered body)

[0125] The resulting layered body underwent a debinding process and was simultaneously fired to produce a sintered body. During the debinding process, the layered body was heated in nitrogen at a rate of 50°C / hour to a firing temperature of 700°C and held at this temperature for 10 hours. During the simultaneous firing process, the layered body was heated in nitrogen at a rate of 200°C / hour to a firing temperature of 850°C and then held at this temperature for 1 hour. After firing, the layered body was cooled naturally. Following the simultaneous firing, the external dimensions of the resulting battery were 3.2 mm × 2.5 mm × 0.4 mm. (Evaluation of charging and discharging performance)

[0126] The charge and discharge tester was used to measure the charge and discharge capacities by mounting the resulting layered body onto a clamping device using a clamping pin. The measurement conditions involved charging and discharging with a current of 2 µA and a voltage ranging from 0 V to 1.8 V. The measured discharge capacity is shown in Table 2. A sufficient discharge capacity threshold for practical use was 2.5 µAh. [Example 17]

[0127] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 3,40 V 2,00 (PO4) 3,13The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 5.0 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 16, and the layered product was fabricated using the same procedure. Debinding and sintering were then performed using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 16. The results of the measured discharge capacity are shown in Table 2. [Example 18]

[0128] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 4,90 V 2,00 (PO4) 3,63The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 15.0 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 16, and the layered product was subsequently manufactured using the same procedure. Debinding and sintering were then carried out using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 16. The results of the measured discharge capacity are shown in Table 2. [Example 19](Production of the positive electrode active material)

[0129] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 3,10 V 2,00 (PO4) 3,03 The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same method as in Example 1. Subsequently, an evaluation was performed using the same X-ray diffraction method as in Example 1. This confirmed the presence of 1.0 wt% Li₃PO₄. (Production of the negative electrode active material)

[0130] The same powder was used for the negative electrode active material as for the positive electrode active material described above. (Production of the paste for the solid electrolyte layer)

[0131] When the solid electrolyte was Li f Al g Ti h P i O j(where f=0.5, g=0.02, h=1.0, i=2.8 and j=9.28) was used. Li2CO3, Al2O3, TiO2 and NH4H2PO4 were used as starting materials, and the lithium-aluminum-titanium-phosphate powder was obtained using the same method as in Example 1.

[0132] Next, 100 parts ethanol and 200 parts toluene, used as solvents, were added to 100 parts of the powder, and then wet mixing was carried out using a ball mill. Afterward, 16 parts polyvinyl butyral binder and 4.8 parts benzyl butyl phthalate were added and then mixed to produce the paste for the solid electrolyte layer. (Production of the film for the solid electrolyte layer)

[0133] A PET film was used as a substrate, and then the paste for the solid electrolyte layer was formed into a film using a doctor blade process to obtain a solid electrolyte layer film with a thickness of 15 µm. (Production of the paste for the positive electrode current collector layer and the paste for the negative electrode current collector layer)

[0134] Cu powder and lithium vanadium phosphate powder were mixed at a weight ratio of 100:9; then 10 parts of ethyl cellulose, used as a binder, and 50 parts of dihydroterpineol, used as a solvent, were added and then mixed and dispersed using a three-roll mill to produce the pastes for the current collector layer. (Production of the active material unit)

[0135] The paste for the electrode current collector layer was screen-printed to a thickness of 5 µm onto the solid electrolyte layer film described above and then dried at 80°C for 10 minutes. Next, the paste for the electrode active material layer was screen-printed to a thickness of 5 µm and then dried at 80°C for 10 minutes to form the positive electrode layer assembly. Similarly, the paste for the negative electrode active material layer was screen-printed to a thickness of 5 µm onto the solid electrolyte layer film and then dried at 80°C for 10 minutes. Next, the paste for the negative electrode current collector layer was screen-printed to a thickness of 5 µm and then dried at 80°C for 10 minutes to form the negative electrode layer assembly. Finally, the PET film was removed. (Production of the layered body)

[0136] The positive electrode layer unit, the negative electrode layer unit, and the solid electrolyte layer film were layered such that the solid electrolyte layer, the positive electrode current collector layer, the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, the negative electrode current collector layer, and the solid electrolyte layer were formed sequentially to obtain a layered product. At this stage, the units were layered in an offset manner, with the positive electrode current collector layer of the positive electrode layer unit extending only to one end face and the negative electrode current collector layer of the negative electrode layer unit extending only to the opposite end face.The layered product was then shaped using thermocompression bonding and then cut to produce the layered body. (Production of the sintered body)

[0137] The resulting layered body underwent a debinding process and was simultaneously fired to produce a sintered body. During the debinding process, the layered body was heated in nitrogen at a rate of 50°C / hour to a firing temperature of 700°C and held at this temperature for 10 hours. During the simultaneous firing process, the layered body was heated in nitrogen at a rate of 200°C / hour to a firing temperature of 850°C and then held at this temperature for 1 hour. After firing, the layered body was cooled naturally. Following the simultaneous firing, the external dimensions of the resulting battery were 3.2 mm × 2.5 mm × 0.4 mm. (Evaluation of charging and discharging performance)

[0138] The charge and discharge tester was used to measure the charge and discharge capacities by mounting the resulting layered body onto a clamping device using a clamping pin. The measurement conditions involved charging and discharging with a current of 2 µA and a voltage ranging from 0 V to 1.8 V. The measured discharge capacity is shown in Table 2. A sufficient discharge capacity threshold for practical use was 2.5 µAh. [Example 20]

[0139] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 3,40 V 2,00 (PO4) 3,13The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 5.0 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 19, and the layered product was fabricated using the same procedure. Debinding and sintering were then performed using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 19. The results of the measured discharge capacity are shown in Table 2. [Example 21]

[0140] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 4,90 V 2,00 (PO4) 3,63The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 15.0 wt% Li₃PO₄. Furthermore, the lithium aluminum titanium phosphate powder was obtained using the same procedure as in Example 19, and the layered product was then manufactured using the same procedure. Debinding and sintering were then carried out using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 19. The results of the measured discharge capacity are shown in Table 2. [Comparative example 13]

[0141] In this comparative example, the starting materials were weighed in such a way that the lithium vanadium phosphate Li 3,02 V 2,00 (PO4) 3,00The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 0.8 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 19, and the layered product was fabricated using the same procedure. Debinding and sintering were then performed using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 19. The results of the measured discharge capacity are shown in Table 2. [Comparative example 14]

[0142] In this comparative example, starting materials were weighed in such a way that the lithium vanadium phosphate Li5, 00 V2, 00 (PO4)3, 67The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 16.0 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 19, and the layered product was subsequently manufactured using the same procedure. Debinding and sintering were then carried out using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 19. The results of the measured discharge capacity are shown in Table 2. [Example 22](Production of the positive electrode active material)

[0143] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 3,10 V 2,00 (PO4) 3,03 The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same method as in Example 1. Subsequently, an evaluation was performed using the same X-ray diffraction method as in Example 1. This confirmed the presence of 1.0 wt% Li₃PO₄. (Production of the negative electrode active material)

[0144] The same powder was used for the negative electrode active material as for the positive electrode active material described above. (Production of the paste for the solid electrolyte layer)

[0145] When the solid electrolyte was Li f Al g Ti h P i O j(where f=0.5, g=0.02, h=2.0, i=3.2 and j=12.28) was used. Li2CO3, Al2O3, TiO2 and NH4H2PO4 were used as starting materials, and the lithium-aluminum-titanium-phosphate powder was obtained using the same method as in Example 1.

[0146] Next, 100 parts ethanol and 200 parts toluene, used as solvents, were added to 100 parts of the powder, and then wet mixing was carried out using a ball mill. Afterward, 16 parts polyvinyl butyral binder and 4.8 parts benzyl butyl phthalate were added and then mixed to produce the paste for the solid electrolyte layer. (Production of the film for the solid electrolyte layer)

[0147] A PET film was used as a substrate, and then the paste for the solid electrolyte layer was formed into a film using a doctor blade process to obtain a solid electrolyte layer film with a thickness of 15 µm. (Production of the paste for the positive electrode current collector layer and the paste for the negative electrode current collector layer)

[0148] Cu powder and lithium vanadium phosphate powder were mixed at a weight ratio of 100:9; then 10 parts of ethyl cellulose, used as a binder, and 50 parts of dihydroterpineol, used as a solvent, were added and then mixed and dispersed using a three-roll mill to produce the pastes for the current collector layer. (Production of the active material unit)

[0149] The paste for the electrode current collector layer was screen-printed to a thickness of 5 µm onto the solid electrolyte layer film described above and then dried at 80°C for 10 minutes. Next, the paste for the electrode active material layer was screen-printed to a thickness of 5 µm and then dried at 80°C for 10 minutes to form the positive electrode layer assembly. Similarly, the paste for the negative electrode active material layer was screen-printed to a thickness of 5 µm onto the solid electrolyte layer film and then dried at 80°C for 10 minutes. Next, the paste for the negative electrode current collector layer was screen-printed to a thickness of 5 µm and then dried at 80°C for 10 minutes to form the negative electrode layer assembly. Finally, the PET film was removed. (Production of the layered body)

[0150] The positive electrode layer unit, the negative electrode layer unit, and the solid electrolyte layer film were layered such that the solid electrolyte layer, the positive electrode current collector layer, the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, the negative electrode current collector layer, and the solid electrolyte layer were formed sequentially to obtain a layered product. At this stage, the units were layered in an offset manner, with the positive electrode current collector layer of the positive electrode layer unit extending only to one end face and the negative electrode current collector layer of the negative electrode layer unit extending only to the opposite end face.The layered product was then shaped using thermocompression bonding and then cut to produce the layered body. (Production of the sintered body)

[0151] The resulting layered body underwent a debinding process and was simultaneously fired to produce a sintered body. During the debinding process, the layered body was heated in nitrogen at a rate of 50°C / hour to a firing temperature of 700°C and held at this temperature for 10 hours. During the simultaneous firing process, the layered body was heated in nitrogen at a rate of 200°C / hour to a firing temperature of 850°C and then held at this temperature for 1 hour. After firing, the layered body was cooled naturally. Following the simultaneous firing, the external dimensions of the resulting battery were 3.2 mm × 2.5 mm × 0.4 mm. (Evaluation of charging and discharging performance)

[0152] The charge and discharge tester was used to measure the charge and discharge capacities by mounting the resulting layered body onto a clamping device using a clamping pin. The measurement conditions involved charging and discharging with a current of 2 µA and a voltage ranging from 0 V to 1.8 V. The measured discharge capacity is shown in Table 2. A sufficient discharge capacity threshold for practical use was 2.5 µAh. [Example 23]

[0153] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 3,40 V 2,00 (PO4) 3,13The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 5.0 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 22, and the layered product was fabricated using the same procedure. Debinding and sintering were then performed using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 22. The results of the measured discharge capacity are shown in Table 2. [Example 24]

[0154] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 4,90 V 2,00 (PO4) 3,63The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 15.0 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 22, and the layered product was fabricated using the same procedure. Debinding and sintering were then performed using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 22. The results of the measured discharge capacity are shown in Table 2. [Example 25](Production of the positive electrode active material)

[0155] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 3,10 V 2,00 (PO4) 3,03 The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same method as in Example 1. Subsequently, an evaluation was performed using the same X-ray diffraction method as in Example 1. This confirmed the presence of 1.0 wt% Li₃PO₄. (Production of the negative electrode active material)

[0156] The same powder was used for the negative electrode active material as for the positive electrode active material described above. (Production of the paste for the solid electrolyte layer)

[0157] When the solid electrolyte was Li f Al g Ti h P i O j(where f=0.5, g=1.0, h=1.0, i=2.8 and j=10.75) was used. Li2CO3, Al2O3, TiO2 and NH4H2PO4 were used as starting materials, and the lithium aluminum titanium phosphate powder was obtained using the same method as in Example 1.

[0158] Next, 100 parts ethanol and 200 parts toluene, used as solvents, were added to 100 parts of the powder, and then wet mixing was carried out using a ball mill. Afterward, 16 parts polyvinyl butyral binder and 4.8 parts benzyl butyl phthalate were added and then mixed to produce the paste for the solid electrolyte layer. (Production of the film for the solid electrolyte layer)

[0159] A PET film was used as a substrate, and then the paste for the solid electrolyte layer was formed into a film using a doctor blade process to obtain a solid electrolyte layer film with a thickness of 15 µm. (Production of the paste for the positive electrode current collector layer and the paste for the negative electrode current collector layer)

[0160] Cu powder and lithium vanadium phosphate powder were mixed at a weight ratio of 100:9; then 10 parts of ethyl cellulose, used as a binder, and 50 parts of dihydroterpineol, used as a solvent, were added and then mixed and dispersed using a three-roll mill to produce the pastes for the current collector layer. (Production of the active material unit)

[0161] The paste for the electrode current collector layer was screen-printed to a thickness of 5 µm onto the solid electrolyte layer film described above and then dried at 80°C for 10 minutes. Next, the paste for the electrode active material layer was screen-printed to a thickness of 5 µm and then dried at 80°C for 10 minutes to form the positive electrode layer assembly. Similarly, the paste for the negative electrode active material layer was screen-printed to a thickness of 5 µm onto the solid electrolyte layer film and then dried at 80°C for 10 minutes. Next, the paste for the negative electrode current collector layer was screen-printed to a thickness of 5 µm and then dried at 80°C for 10 minutes to form the negative electrode layer assembly. Finally, the PET film was removed. (Production of the layered body)

[0162] The positive electrode layer unit, the negative electrode layer unit, and the solid electrolyte layer film were layered such that the solid electrolyte layer, the positive electrode current collector layer, the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, the negative electrode current collector layer, and the solid electrolyte layer were formed sequentially to obtain a layered product. At this stage, the units were layered in an offset manner, with the positive electrode current collector layer of the positive electrode layer unit extending only to one end face and the negative electrode current collector layer of the negative electrode layer unit extending only to the opposite end face.The layered product was then shaped using thermocompression bonding and then cut to produce the layered body. (Production of the sintered body)

[0163] The resulting layered body underwent a debinding process and was simultaneously fired to produce a sintered body. During the debinding process, the layered body was heated in nitrogen at a rate of 50°C / hour to a firing temperature of 700°C and held at this temperature for 10 hours. During the simultaneous firing process, the layered body was heated in nitrogen at a rate of 200°C / hour to a firing temperature of 850°C and then held at this temperature for 1 hour. After firing, the layered body was cooled naturally. Following the simultaneous firing, the external dimensions of the resulting battery were 3.2 mm × 2.5 mm × 0.4 mm. (Evaluation of charging and discharging performance)

[0164] The charge and discharge tester was used to measure the charge and discharge capacities by mounting the resulting layered body onto a clamping device using a clamping pin. The measurement conditions involved charging and discharging with a current of 2 µA and a voltage ranging from 0 V to 1.8 V. The measured discharge capacity is shown in Table 2. A sufficient discharge capacity threshold for practical use was 2.5 µAh. [Example 26]

[0165] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 3,40 V 2,00 (PO4) 3,13The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 5.0 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 25, and the layered product was fabricated using the same procedure. Debinding and sintering were then performed using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 25. The results of the measured discharge capacity are shown in Table 2. [Example 27]

[0166] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 4,90 V 2,00 (PO4) 3,63The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 15.0 wt% Li₃PO₄. Furthermore, the lithium aluminum titanium phosphate powder was obtained using the same procedure as in Example 25, and the layered product was then manufactured using the same procedure. Debinding and sintering were then carried out using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 25. The results of the measured discharge capacity are shown in Table 2. [Example 28](Production of the positive electrode active material)

[0167] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 3,10 V 2,00 (PO4) 3,03 The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same method as in Example 1. Subsequently, an evaluation was performed using the same X-ray diffraction method as in Example 1. This confirmed the presence of 1.0 wt% Li₃PO₄. (Production of the negative electrode active material)

[0168] The same powder was used for the negative electrode active material as for the positive electrode active material described above. (Production of the paste for the solid electrolyte layer)

[0169] When the solid electrolyte was Li f Al g Ti h P i O j(where f=0.5, g=1.0, h=2.0, i=3.2 and j=13.75) was used. Li2CO3, Al2O3, TiO2 and NH4H2PO4 were used as starting materials, and the lithium-aluminum-titanium-phosphate powder was obtained using the same method as in Example 1.

[0170] Next, 100 parts ethanol and 200 parts toluene, used as solvents, were added to 100 parts of the powder, and then wet mixing was carried out using a ball mill. Afterward, 16 parts polyvinyl butyral binder and 4.8 parts benzyl butyl phthalate were added and then mixed to produce the paste for the solid electrolyte layer. (Production of the film for the solid electrolyte layer)

[0171] A PET film was used as a substrate, and then the paste for the solid electrolyte layer was formed into a film using a doctor blade process to obtain a solid electrolyte layer film with a thickness of 15 µm. (Production of the paste for the positive electrode current collector layer and the paste for the negative electrode current collector layer)

[0172] Cu powder and lithium vanadium phosphate powder were mixed at a weight ratio of 100:9; then 10 parts of ethyl cellulose, used as a binder, and 50 parts of dihydroterpineol, used as a solvent, were added and then mixed and dispersed using a three-roll mill to produce the pastes for the current collector layer. (Production of the active material unit)

[0173] The paste for the electrode current collector layer was screen-printed to a thickness of 5 µm onto the solid electrolyte layer film described above and then dried at 80°C for 10 minutes. Next, the paste for the electrode active material layer was screen-printed to a thickness of 5 µm and then dried at 80°C for 10 minutes to form the positive electrode layer assembly. Similarly, the paste for the negative electrode active material layer was screen-printed to a thickness of 5 µm onto the solid electrolyte layer film and then dried at 80°C for 10 minutes. Next, the paste for the negative electrode current collector layer was screen-printed to a thickness of 5 µm and then dried at 80°C for 10 minutes to form the negative electrode layer assembly. Finally, the PET film was removed. (Production of the layered body)

[0174] The positive electrode layer unit, the negative electrode layer unit, and the solid electrolyte layer film were layered such that the solid electrolyte layer, the positive electrode current collector layer, the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, the negative electrode current collector layer, and the solid electrolyte layer were formed sequentially to obtain a layered product. At this stage, the units were layered in an offset manner, with the positive electrode current collector layer of the positive electrode layer unit extending only to one end face and the negative electrode current collector layer of the negative electrode layer unit extending only to the opposite end face.The layered product was then shaped using thermocompression bonding and then cut to produce the layered body. (Production of the sintered body)

[0175] The resulting layered body underwent a debinding process and was simultaneously fired to produce a sintered body. During the debinding process, the layered body was heated in nitrogen at a rate of 50°C / hour to a firing temperature of 700°C and held at this temperature for 10 hours. During the simultaneous firing process, the layered body was heated in nitrogen at a rate of 200°C / hour to a firing temperature of 850°C and then held at this temperature for 1 hour. After firing, the layered body was cooled naturally. Following the simultaneous firing, the external dimensions of the resulting battery were 3.2 mm × 2.5 mm × 0.4 mm. (Evaluation of charging and discharging performance)

[0176] The charge and discharge tester was used to measure the charge and discharge capacities by mounting the resulting layered body onto a clamping device using a clamping pin. The measurement conditions involved charging and discharging with a current of 2 µA and a voltage ranging from 0 V to 1.8 V. The measured discharge capacity is shown in Table 2. A sufficient discharge capacity threshold for practical use was 2.5 µAh. [Example 29]

[0177] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 3,40 V 2,00 (PO4) 3,13The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 5.0 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 28, and the layered product was fabricated using the same procedure. Debinding and sintering were then performed using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 28. The results of the measured discharge capacity are shown in Table 2. [Example 30]

[0178] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 4,90 V 2,00 (PO4) 3,63The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 15.0 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 28, and the layered product was fabricated using the same procedure. Debinding and sintering were then performed using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 28. The results of the measured discharge capacity are shown in Table 2. [Comparative example 15]

[0179] In this comparative example, the starting materials were weighed in such a way that the lithium vanadium phosphate Li 3,02 V 2,00 (PO4) 3,00The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 0.8 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 28, and the layered product was fabricated using the same procedure. Debinding and sintering were then performed using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 28. The results of the measured discharge capacity are shown in Table 2. [Comparative example 16]

[0180] In this comparative example, the starting materials were weighed in such a way that the lithium vanadium phosphate Li 5,00 V 2,00 (PO4) 3,67The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 16.0 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 28, and the layered product was fabricated using the same procedure. Debinding and sintering were then performed using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 28. The results of the measured discharge capacity are shown in Table 2. [Example 31](Production of the positive electrode active material)

[0181] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 3,10 V 2,00 (PO4) 3,03 The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same method as in Example 1. Subsequently, an evaluation was performed using the same X-ray diffraction method as in Example 1. This confirmed the presence of 1.0 wt% Li₃PO₄. (Production of the negative electrode active material)

[0182] The same powder was used for the negative electrode active material as for the positive electrode active material described above. (Production of the paste for the solid electrolyte layer)

[0183] When the solid electrolyte was Li f Al g Ti h P i O j(where f=3.0, g=0.1, h=1.0, i=2.8 and j=10.65) was used. Li2CO3, Al2O3, TiO2 and NH4H2PO4 were used as starting materials, and the lithium aluminum titanium phosphate powder was obtained using the same method as in Example 1.

[0184] Next, 100 parts ethanol and 200 parts toluene, used as solvents, were added to 100 parts of the powder, and then wet mixing was carried out using a ball mill. Afterward, 16 parts polyvinyl butyral binder and 4.8 parts benzyl butyl phthalate were added and then mixed to produce the paste for the solid electrolyte layer. (Production of the film for the solid electrolyte layer)

[0185] A PET film was used as a substrate, and then the paste for the solid electrolyte layer was formed into a film using a doctor blade process to obtain a solid electrolyte layer film with a thickness of 15 µm. (Production of the paste for the positive electrode current collector layer and the paste for the negative electrode current collector layer)

[0186] Cu powder and lithium vanadium phosphate powder were mixed at a weight ratio of 100:9; then 10 parts of ethyl cellulose, used as a binder, and 50 parts of dihydroterpineol, used as a solvent, were added and then mixed and dispersed using a three-roll mill to produce the pastes for the current collector layer. (Production of the active material unit)

[0187] The paste for the electrode current collector layer was screen-printed to a thickness of 5 µm onto the solid electrolyte layer film described above and then dried at 80°C for 10 minutes. Next, the paste for the electrode active material layer was screen-printed to a thickness of 5 µm and then dried at 80°C for 10 minutes to form the positive electrode layer assembly. Similarly, the paste for the negative electrode active material layer was screen-printed to a thickness of 5 µm onto the solid electrolyte layer film and then dried at 80°C for 10 minutes. Next, the paste for the negative electrode current collector layer was screen-printed to a thickness of 5 µm and then dried at 80°C for 10 minutes to form the negative electrode layer assembly. Finally, the PET film was removed. (Production of the layered body)

[0188] The positive electrode layer unit, the negative electrode layer unit, and the solid electrolyte layer film were layered such that the solid electrolyte layer, the positive electrode current collector layer, the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, the negative electrode current collector layer, and the solid electrolyte layer were formed sequentially to obtain a layered product. At this stage, the units were layered in an offset manner, with the positive electrode current collector layer of the positive electrode layer unit extending only to one end face and the negative electrode current collector layer of the negative electrode layer unit extending only to the opposite end face.The layered product was then shaped using thermocompression bonding and then cut to produce the layered body. (Production of the sintered body)

[0189] The resulting layered body underwent a debinding process and was simultaneously fired to produce a sintered body. During the debinding process, the layered body was heated in nitrogen at a rate of 50°C / hour to a firing temperature of 700°C and held at this temperature for 10 hours. During the simultaneous firing process, the layered body was heated in nitrogen at a rate of 200°C / hour to a firing temperature of 850°C and then held at this temperature for 1 hour. After firing, the layered body was cooled naturally. Following the simultaneous firing, the external dimensions of the resulting battery were 3.2 mm × 2.5 mm × 0.4 mm. (Evaluation of charging and discharging performance)

[0190] The charge and discharge tester was used to measure the charge and discharge capacities by mounting the resulting layered body onto a clamping device using a clamping pin. The measurement conditions involved charging and discharging with a current of 2 µA and a voltage ranging from 0 V to 1.8 V. The measured discharge capacity is shown in Table 2. A sufficient discharge capacity threshold for practical use was 2.5 µAh. [Example 32]

[0191] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 3,40 V 2,00 (PO4) 3,13The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 5.0 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 31, and the layered product was fabricated using the same procedure. Debinding and sintering were then performed using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 31. The results of the measured discharge capacity are shown in Table 2. [Example 33]

[0192] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 4,90 V 2,00 (PO4) 3,63The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 15.0 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 31, and the layered product was fabricated using the same procedure. Debinding and sintering were then performed using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 31. The results of the measured discharge capacity are shown in Table 2. [Comparative example 17]

[0193] In this comparative example, the starting materials were weighed in such a way that the lithium vanadium phosphate Li 3,02 V 2,00 (PO4) 3,00The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 0.8 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 31, and the layered product was fabricated using the same procedure. Debinding and sintering were then carried out using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 31. The results of the measured discharge capacity are shown in Table 2. [Comparative example 18]

[0194] In this comparative example, the starting materials were weighed in such a way that the lithium vanadium phosphate Li 5,00 V 2,00 (PO4) 3,67The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 16.0 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 31, and the layered product was fabricated using the same procedure. Debinding and sintering were then performed using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 31. The results of the measured discharge capacity are shown in Table 2. [Example 34](Production of the positive electrode active material)

[0195] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 3,10 V 2,00 (PO4) 3,03 The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same method as in Example 1. Subsequently, an evaluation was performed using the same X-ray diffraction method as in Example 1. This confirmed the presence of 1.0 wt% Li₃PO₄. (Production of the negative electrode active material)

[0196] The same powder was used for the negative electrode active material as for the positive electrode active material described above. (Production of the paste for the solid electrolyte layer)

[0197] When the solid electrolyte was Li f Al g Ti h P i O j(where f=3.0, g=0.1, h=2.0, i=3.2 and j=13.65) was used. Li2CO3, Al2O3, TiO2 and NH4H2PO4 were used as starting materials, and the lithium-aluminum-titanium-phosphate powder was obtained using the same method as in Example 1.

[0198] Next, 100 parts ethanol and 200 parts toluene, used as solvents, were added to 100 parts of the powder, and then wet mixing was carried out using a ball mill. Afterward, 16 parts polyvinyl butyral binder and 4.8 parts benzyl butyl phthalate were added and then mixed to produce the paste for the solid electrolyte layer. (Production of the film for the solid electrolyte layer)

[0199] A PET film was used as a substrate, and then the paste for the solid electrolyte layer was formed into a film using a doctor blade process to obtain a solid electrolyte layer film with a thickness of 15 µm. (Production of the paste for the positive electrode current collector layer and the paste for the negative electrode current collector layer)

[0200] Cu powder and lithium vanadium phosphate powder were mixed at a weight ratio of 100:9; then 10 parts of ethyl cellulose, used as a binder, and 50 parts of dihydroterpineol, used as a solvent, were added and then mixed and dispersed using a three-roll mill to produce the pastes for the current collector layer. (Production of the active material unit)

[0201] The paste for the electrode current collector layer was screen-printed to a thickness of 5 µm onto the solid electrolyte layer film described above and then dried at 80°C for 10 minutes. Next, the paste for the electrode active material layer was screen-printed to a thickness of 5 µm and then dried at 80°C for 10 minutes to form the positive electrode layer assembly. Similarly, the paste for the negative electrode active material layer was screen-printed to a thickness of 5 µm onto the solid electrolyte layer film and then dried at 80°C for 10 minutes. Next, the paste for the negative electrode current collector layer was screen-printed to a thickness of 5 µm and then dried at 80°C for 10 minutes to form the negative electrode layer assembly. Finally, the PET film was removed. (Production of the layered body)

[0202] The positive electrode layer unit, the negative electrode layer unit, and the solid electrolyte layer film were layered such that the solid electrolyte layer, the positive electrode current collector layer, the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, the negative electrode current collector layer, and the solid electrolyte layer were formed sequentially to obtain a layered product. At this stage, the units were layered in an offset manner, with the positive electrode current collector layer of the positive electrode layer unit extending only to one end face and the negative electrode current collector layer of the negative electrode layer unit extending only to the opposite end face.The layered product was then shaped using thermocompression bonding and then cut to produce the layered body. (Production of the sintered body)

[0203] The resulting layered body underwent a debinding process and was simultaneously fired to produce a sintered body. During the debinding process, the layered body was heated in nitrogen at a rate of 50°C / hour to a firing temperature of 700°C and held at this temperature for 10 hours. During the simultaneous firing process, the layered body was heated in nitrogen at a rate of 200°C / hour to a firing temperature of 850°C and then held at this temperature for 1 hour. After firing, the layered body was cooled naturally. Following the simultaneous firing, the external dimensions of the resulting battery were 3.2 mm × 2.5 mm × 0.4 mm. (Evaluation of charging and discharging performance)

[0204] The charge and discharge tester was used to measure the charge and discharge capacities by mounting the resulting layered body onto a clamping device using a clamping pin. The measurement conditions involved charging and discharging with a current of 2 µA and a voltage ranging from 0 V to 1.8 V. The measured discharge capacity is shown in Table 2. A sufficient discharge capacity threshold for practical use was 2.5 µAh. [Example 35]

[0205] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 3,40 V 2,00 (PO4) 3,13The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 5.0 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 34, and the layered product was fabricated using the same procedure. Debinding and sintering were then performed using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 34. The results of the measured discharge capacity are shown in Table 2. [Example 36]

[0206] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 4,90 V 2,00 (PO4) 3,63The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 15.0 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 34, and the layered product was fabricated using the same procedure. Debinding and sintering were then carried out using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 34. The results of the measured discharge capacity are shown in Table 2. [Example 37](Production of the positive electrode active material)

[0207] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 3,10 V 2,00 (PO4) 3,03 The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same method as in Example 1. Subsequently, an evaluation was performed using the same X-ray diffraction method as in Example 1. This confirmed the presence of 1.0 wt% Li₃PO₄. (Production of the negative electrode active material)

[0208] The same powder was used for the negative electrode active material as for the positive electrode active material described above. (Production of the paste for the solid electrolyte layer)

[0209] When the solid electrolyte was Li f Al g Ti h P i O j(where f=3.0, g=1.0, h=1.0, i=2.8 and j=12.0) was used. Li2CO3, Al2O3, TiO2 and NH4H2PO4 were used as starting materials, and the lithium aluminum titanium phosphate powder was obtained using the same method as in Example 1.

[0210] Next, 100 parts ethanol and 200 parts toluene, used as solvents, were added to 100 parts of the powder, and then wet mixing was carried out using a ball mill. Afterward, 16 parts polyvinyl butyral binder and 4.8 parts benzyl butyl phthalate were added and then mixed to produce the paste for the solid electrolyte layer. (Production of the film for the solid electrolyte layer)

[0211] A PET film was used as a substrate, and then the paste for the solid electrolyte layer was formed into a film using a doctor blade process to obtain a solid electrolyte layer film with a thickness of 15 µm. (Production of the paste for the positive electrode current collector layer and the paste for the negative electrode current collector layer)

[0212] Cu powder and lithium vanadium phosphate powder were mixed at a weight ratio of 100:9; then 10 parts of ethyl cellulose, used as a binder, and 50 parts of dihydroterpineol, used as a solvent, were added and then mixed and dispersed using a three-roll mill to produce the pastes for the current collector layer. (Production of the active material unit)

[0213] The paste for the electrode current collector layer was screen-printed to a thickness of 5 µm onto the solid electrolyte layer film described above and then dried at 80°C for 10 minutes. Next, the paste for the electrode active material layer was screen-printed to a thickness of 5 µm and then dried at 80°C for 10 minutes to form the positive electrode layer assembly. Similarly, the paste for the negative electrode active material layer was screen-printed to a thickness of 5 µm onto the solid electrolyte layer film and then dried at 80°C for 10 minutes. Next, the paste for the negative electrode current collector layer was screen-printed to a thickness of 5 µm and then dried at 80°C for 10 minutes to form the negative electrode layer assembly. Finally, the PET film was removed. (Production of the layered body)

[0214] The positive electrode layer unit, the negative electrode layer unit, and the solid electrolyte layer film were layered such that the solid electrolyte layer, the positive electrode current collector layer, the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, the negative electrode current collector layer, and the solid electrolyte layer were formed sequentially to obtain a layered product. At this stage, the units were layered in an offset manner, with the positive electrode current collector layer of the positive electrode layer unit extending only to one end face and the negative electrode current collector layer of the negative electrode layer unit extending only to the opposite end face.The layered product was then shaped using thermocompression bonding and then cut to produce the layered body. (Production of the sintered body)

[0215] The resulting layered body underwent a debinding process and was simultaneously fired to produce a sintered body. During the debinding process, the layered body was heated in nitrogen at a rate of 50°C / hour to a firing temperature of 700°C and held at this temperature for 10 hours. During the simultaneous firing process, the layered body was heated in nitrogen at a rate of 200°C / hour to a firing temperature of 850°C and then held at this temperature for 1 hour. After firing, the layered body was cooled naturally. Following the simultaneous firing, the external dimensions of the resulting battery were 3.2 mm × 2.5 mm × 0.4 mm. (Evaluation of charging and discharging performance)

[0216] The charge and discharge tester was used to measure the charge and discharge capacities by mounting the resulting layered body onto a clamping device using a clamping pin. The measurement conditions involved charging and discharging with a current of 2 µA and a voltage ranging from 0 V to 1.8 V. The measured discharge capacity is shown in Table 2. A sufficient discharge capacity threshold for practical use was 2.5 µAh. [Example 38]

[0217] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 3,40 V 2,00 (PO4) 3,13The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 5.0 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 37, and the layered product was fabricated using the same procedure. Debinding and sintering were then performed using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 37. The results of the measured discharge capacity are shown in Table 2. [Example 39]

[0218] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 4,90 V 2,00 (PO4) 3,63The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 15.0 wt% Li₃PO₄. Furthermore, the lithium aluminum titanium phosphate powder was obtained using the same procedure as in Example 37, and the layered product was then manufactured using the same procedure. Debinding and sintering were then carried out using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 37. The results of the measured discharge capacity are shown in Table 2. [Example 40](Production of the positive electrode active material)

[0219] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 3,10 V 2,00 (PO4) 3,03 The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same method as in Example 1. Subsequently, an evaluation was performed using the same X-ray diffraction method as in Example 1. This confirmed the presence of 1.0 wt% Li₃PO₄. (Production of the negative electrode active material)

[0220] The same powder was used for the negative electrode active material as for the positive electrode active material described above. (Production of the paste for the solid electrolyte layer)

[0221] When the solid electrolyte was Li f Al g Ti h P i O j(where f=3.0, g=1.0, h=2.0, i=3.2 and j=15.0) was used. Li2CO3, Al2O3, TiO2 and NH4H2PO4 were used as starting materials, and the lithium-aluminum-titanium-phosphate powder was obtained using the same method as in Example 1.

[0222] Next, 100 parts ethanol and 200 parts toluene, used as solvents, were added to 100 parts of the powder, and then wet mixing was carried out using a ball mill. Afterward, 16 parts polyvinyl butyral binder and 4.8 parts benzyl butyl phthalate were added and then mixed to produce the paste for the solid electrolyte layer. (Production of the film for the solid electrolyte layer)

[0223] A PET film was used as a substrate, and then the paste for the solid electrolyte layer was formed into a film using a doctor blade process to obtain a solid electrolyte layer film with a thickness of 15 µm. (Production of the paste for the positive electrode current collector layer and the paste for the negative electrode current collector layer)

[0224] Cu powder and lithium vanadium phosphate powder were mixed at a weight ratio of 100:9; then 10 parts of ethyl cellulose, used as a binder, and 50 parts of dihydroterpineol, used as a solvent, were added and then mixed and dispersed using a three-roll mill to produce the pastes for the current collector layer. (Production of the active material unit)

[0225] The paste for the electrode current collector layer was screen-printed to a thickness of 5 µm onto the solid electrolyte layer film described above and then dried at 80°C for 10 minutes. Next, the paste for the electrode active material layer was screen-printed to a thickness of 5 µm and then dried at 80°C for 10 minutes to form the positive electrode layer assembly. Similarly, the paste for the negative electrode active material layer was screen-printed to a thickness of 5 µm onto the solid electrolyte layer film and then dried at 80°C for 10 minutes. Next, the paste for the negative electrode current collector layer was screen-printed to a thickness of 5 µm and then dried at 80°C for 10 minutes to form the negative electrode layer assembly. Finally, the PET film was removed. (Production of the layered body)

[0226] The positive electrode layer unit, the negative electrode layer unit, and the solid electrolyte layer film were layered such that the solid electrolyte layer, the positive electrode current collector layer, the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, the negative electrode current collector layer, and the solid electrolyte layer were formed sequentially to obtain a layered product. At this stage, the units were layered in an offset manner, with the positive electrode current collector layer of the positive electrode layer unit extending only to one end face and the negative electrode current collector layer of the negative electrode layer unit extending only to the opposite end face.The layered product was then shaped using thermocompression bonding and then cut to produce the layered body. (Production of the sintered body)

[0227] The resulting layered body underwent a debinding process and was simultaneously fired to produce a sintered body. During the debinding process, the layered body was heated in nitrogen at a rate of 50°C / hour to a firing temperature of 700°C and held at this temperature for 10 hours. During the simultaneous firing process, the layered body was heated in nitrogen at a rate of 200°C / hour to a firing temperature of 850°C and then held at this temperature for 1 hour. After firing, the layered body was cooled naturally. Following the simultaneous firing, the external dimensions of the resulting battery were 3.2 mm × 2.5 mm × 0.4 mm. (Evaluation of charging and discharging performance)

[0228] The charge and discharge tester was used to measure the charge and discharge capacities by mounting the resulting layered body onto a clamping device using a clamping pin. The measurement conditions involved charging and discharging with a current of 2 µA and a voltage ranging from 0 V to 1.8 V. The measured discharge capacity is shown in Table 2. A sufficient discharge capacity threshold for practical use was 2.5 µAh. [Example 41]

[0229] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 3,40 V 2,00 (PO4) 3,13The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 5.0 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 40, and the layered product was fabricated using the same procedure. Debinding and sintering were then performed using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 40. The results of the measured discharge capacity are shown in Table 2. [Example 42]

[0230] To verify the effect of the present embodiment, starting materials were weighed such that the lithium vanadium phosphate Li 4,90 V 2,00 (PO4) 3,63The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 15.0 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 40, and the layered product was fabricated using the same procedure. Debinding and sintering were then performed using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 40. The results of the measured discharge capacity are shown in Table 2. [Comparative example 19]

[0231] In this comparative example, the starting materials were weighed in such a way that the lithium vanadium phosphate Li 3,02 V 2,00 (PO4) 3,00The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 0.8 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 40, and the layered product was fabricated using the same procedure. Debinding and sintering were then carried out using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 40. The results of the measured discharge capacity are shown in Table 2. [Comparative example 20]

[0232] In this comparative example, the starting materials were weighed in such a way that the lithium vanadium phosphate Li 5,00 V 2,00 (PO4) 3,67The starting materials used were Li₂CO₃, LiPO₃, V₂O₃, and NH₄H₂PO₄. The lithium vanadium phosphate powder was obtained using the same procedure as in Example 1. It was then evaluated using the same X-ray diffraction method as in Example 1. This confirmed the presence of 16.0 wt% Li₃PO₄. The lithium aluminum titanium phosphate powder was then obtained using the same procedure as in Example 40, and the layered product was fabricated using the same procedure. Debinding and sintering were then carried out using the same procedure to obtain the solid-state battery. The discharge performance of the layered product was evaluated using the same procedure as in Example 40. The results of the measured discharge capacity are shown in Table 2.

[0233] Table 2 shows that the solid-state battery produced by applying the lithium vanadium phosphate containing Li3PO4 in a quantity range according to the present invention to the active material layer was able to achieve a significantly higher discharge capacity. [Table 2] Main phase Li3PO4 (wt%) There f To the g You h P i OR j Discharge capacity of the manufactured battery (µAh) f g h i j Example 7 Li3V2(PO4)3 1,0 1,02 0,13 1,91 3,00 12,03 3,22 Example 8 Li3V2(PO4)3 5,0 1,02 0,13 1,91 3,00 12,03 4,49 Example 9 Li3V2(PO4)3 15,0 1,02 0,13 1,91 3,00 12,03 4,32 Example 10 Li3V2(PO4)3 1,0 1,50 0,50 1,50 3,00 12,00 3,05 Example 11 Li3V2(PO4)3 5,0 1,50 0,50 1,50 3,00 12,00 4,25 Example 12 Li3V2(PO4)3 15,0 1,50 0,50 1,50 3,00 12,00 4,08 Example 13 Li3V2(PO4)3 1,0 2,00 1,00 1,00 3,00 12,00 2,51 Example 14 Li3V2(PO4)3 5,0 2,00 1,00 1,00 3,00 12,00 3,11 Example 15 Li3V2(PO4)3 15,0 2,00 1,00 1,00 3,00 12,00 3,03 Example 16 Li3V2(PO4)3 1,0 2,10 1,10 0,90 3,00 12,00 2,51 Example 17 Li3V2(PO4)3 5,0 2,10 1,10 0,90 3,00 12,00 2,91 Example 18 Li3V2(PO4)3 15,0 2,10 1,10 0,90 3,00 12,00 2,73 Example 19 Li3V2(PO4)3 1,0 0,50 0,02 1,00 2,80 9,28 2,58 Example 20 Li3V2(PO4)3 5,0 0,50 0,02 1,00 2,80 9,28 3,59 Example 21 Li3V2(PO4)3 15,0 0,50 0,02 1,00 2,80 9,28 3,45 Example 22 Li3V2(PO4)3 1,0 0,50 0,02 2,00 3,20 12,28 2,74 Example 23 Li3V2(PO4)3 5,0 0,50 0,02 2,00 3,20 12,28 3,82 Example 24 Li3V2(PO4)3 15,0 0,50 0,02 2,00 3,20 12,28 3,67 Example 25 Li3V2(PO4)3 1,0 0,50 1,00 1,00 2,80 10,75 2,64 Example 26 Li3V2(PO4)3 5,0 0,50 1,00 1,00 2,80 10,75 3,27 Example 27 Li3V2(PO4)3 15,0 0,50 1,00 1,00 2,80 10,75 3,18 Example 28 Li3V2(PO4)3 1,0 0,50 1,00 2,00 3,20 13,75 2,51 Example 29 Li3V2(PO4)3 5,0 0,50 1,00 2,00 3,20 13,75 2,96 Example 30 Li3V2(PO4)3 15,0 0,50 1,00 2,00 3,20 13,75 2,88 Example 31 Li3V2(PO4)3 1,0 3,00 0,10 1,00 2,80 10,65 2,77 Example 32 Li3V2(PO4)3 5,0 3,00 0,10 1,00 2,80 10,65 3,20 Example 33 Li3V2(PO4)3 15,0 3,00 0,10 1,00 2,80 10,65 3,00 Example 34 Li3V2(PO4)3 1,0 3,00 0,10 2,00 3,20 13,65 2,53 Example 35 Li3V2(PO4)3 5,0 3,00 0,10 2,00 3,20 13,65 2,85 Example 36 Li3V2(PO4)3 15,0 3,00 0,10 2,00 3,20 13,65 2,68 Example 37 Li3V2(PO4)3 1,0 3,00 1,00 1,00 2,80 12,00 2,64 Example 38 Li3V2(PO4)3 5,0 3,00 1,00 1,00 2,80 12,00 3,06 Example 39 Li3V2(PO4)3 15,0 3,00 1,00 1,00 2,80 12,00 2,87 Example 40 Li3V2(PO4)3 1,0 3,00 1,00 2,00 3,20 15,00 2,56 Example 41 Li3V2(PO4)3 5,0 3,00 1,00 2,00 3,20 15,00 2,88 Example 42 Li3V2(PO4)3 15,0 3,00 1,00 2,00 3,20 15,00 2,70 Comparative example 7 Li3V2(PO4)3 0,8 1,02 0,13 1,91 3,00 12,03 1,36 Comparative example 8 Li3V2(PO4)3 16,0 1,02 0,13 1,91 3,00 12,03 1,31 Comparative example 9 Li3V2(PO4)3 0,8 1,50 0,50 1,50 3,00 12,00 1,29 Comparative example 10 Li3V2(PO4)3 16,0 1,50 0,50 1,50 3,00 12,00 1,02 Comparative example 11 Li3V2(PO4)3 0,8 2,00 1,00 1,00 3,00 12,00 0,80 Comparative example 12 Li3V2(PO4)3 16,0 2,00 1,00 1,00 3,00 12,00 0,63 Comparative example 13 Li3V2(PO4)3 0,8 0,50 0,02 1,00 2,80 9,28 1,08 Comparative example 14 Li3V2(PO4)3 16,0 0,50 0,02 1,00 2,80 9,28 1,04 Comparative example 15 Li3V2(PO4)3 0,8 0,50 1,00 2,00 3,20 13,75 0,89 Comparative example 16 Li3V2(PO4)3 16,0 0,50 1,00 2,00 3,20 13,75 0,86 Comparative example 17 Li3V2(PO4)3 0,8 3,00 0,10 1,00 2,80 10,65 0,96 Comparative example 18 Li3V2(PO4)3 16,0 3,00 0,10 1,00 2,80 10,65 0,90 Comparative example 19 Li3V2(PO4)3 0,8 3,00 1,00 2,00 3,20 15,00 0,86 Comparative example 20 Li3V2(PO4)3 16,0 3,00 1,00 2,00 3,20 15,00 0,81

[0234] As described above, the solid-state battery of the present invention was effective in improving discharge capacity. By providing a solid-state battery with high capacity, it has made a significant contribution, particularly in the field of electronics. Reference symbol list 1 solid-state battery 2 Positive electrode layer 3 Negative electrode layer 4 Solid electrolyte layer 5 packing layer 6 Positive electrode current collector layer 7 Positive electrode active material layer 8 Negative electrode active material layer 9 Negative electrode current collector layer QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2002530835 A

[0006]

Claims

[1] Solid-state battery comprising a solid electrolyte layer between a pair of electrode layers, wherein a positive electrode active material layer and a negative electrode active material layer forming the pair of electrode layers contain lithium vanadium phosphate, the lithium vanadium phosphate contains a polyphosphate compound containing Li and V, the lithium vanadium phosphate contains Li3V2(PO4)3 as the main phase, and the lithium vanadium phosphate contains 1.0 wt% or more and 15.0 wt% or less Li3PO4 based on Li3V2(PO4)3. [2] Solid-state battery according to claim 1, wherein the solid electrolyte layer contains lithium aluminum titanium phosphate. [3] Solid-state battery according to claim 2, wherein the material of the solid electrolyte is Li f Al g Ti h P i O j is, where f, g, h, i and j are numbers such that 0.5≤f≤3.0, 0.0 <g≤1,0, 1,0≤h≤2,0, 2,8≤i≤3,2 beziehungsweise 9,25<j≤15,0 erfüllen.[4] Solid-state battery according to any one of claims 1 to 3, wherein the pair of electrode layers and the solid electrolyte layer arranged between the pair of electrode layers have a relative density of 80% or above.< / g≤1,0,>