JP2023060626A - Solid state battery and manufacturing method thereof - Google Patents

Abstract

To realize a solid state battery capable of suppressing deterioration in performance caused by a positive electrode layer.SOLUTION: A solid state battery includes a positive electrode layer, a negative electrode layer, and an electrolyte layer provided therebetween. In the solid state battery, the X-ray diffraction spectrum of the positive electrode layer measured using CuKα rays contains diffraction peaks attributed to LCPO and LAGP, and the ratio P/Q of the diffraction peak intensity P at the diffraction angle 2θ=13.0±0.2° to the diffraction peak intensity Q at the diffraction angle of 2θ=14.35±0.2° in the X-ray diffraction spectrum is in the range of 0.074<P/Q<5.744. According to the solid state battery having a positive electrode layer with a P/Q ratio within such a range, the positive electrode layer has a good crystal structure, and an increase in resistance and deterioration in charge/discharge characteristics due to the positive electrode layer can be suppressed. This results in a high performance solid state battery with a positive electrode layer with excellent properties.SELECTED DRAWING: Figure 7

Description

The present invention relates to a solid state battery and a method for manufacturing a solid state battery.

A solid state battery is known as one type of battery. For example, a solid battery in which a positive electrode layer containing a positive electrode active material and a solid electrolyte is provided on one side of an electrolyte layer using a solid electrolyte, and a negative electrode layer containing a negative electrode active material and a solid electrolyte is provided on the other side. It has been known.

Regarding solid-state batteries, for example, LiMPO ₄ (M is at least one selected from the group consisting of Mn (manganese), Fe (iron), Co (cobalt), and Ni (nickel)) is used as a positive electrode active material, As a solid electrolyte, from the general formula Li _1+z M ^III _z Ti ^IV _2-z (PO ₄ ) ₃ (M ^III is Al (aluminum), Y (yttrium), Ga (gallium), In (indium), and La (lanthanum) Techniques using at least one metal ion selected from the group consisting of 0≦z≦0.6) are known. In addition, amorphous LiFePO ₄ (lithium iron phosphate) is used as the positive electrode active material, and LiPON (lithium phosphate oxynitride) or LiAl(PO ₄ ) (P ₂ O ₇ ) (aluminum phosphate pyrophosphate) is used as the solid electrolyte. Lithium) is known.

JP-A-2007-5279 International Publication No. 2015/029103 pamphlet

In a solid-state battery, the positive electrode active material of the positive electrode layer includes, in addition to the olivine type material as described above, a pyrophosphate type material such as Li ₂ Co _1-x M _x P _2-y A _y O ₇ (M is any one of Ti (titanium), V (vanadium), Cr (chromium), Ni, and Fe; A is B (boron), C (carbon), Al, Si (silicon), Ga, LCPO-based materials such as Li ₂ CoP ₂ O ₇ (lithium cobalt pyrophosphate) represented by any one of Ge (germanium), 0≦x<1, 0≦y≦0.07) are used. may be Such LCPO-based materials are materials having relatively high average potential and capacity, and are considered effective for improving the energy density of solid-state batteries.

However, an LCPO-based material is used as a positive electrode active material, and a Na super ionic conductor (NASICON) type solid electrolyte, for example, a general formula Li _1+m Al _m Ge _2-m (PO ₄ ) ₃ (0<m<1, referred to as “LAGP”), a positive electrode layer having a good crystal structure can be obtained depending on the firing conditions in the manufacturing process of the solid-state battery. may not be available. If a positive electrode layer having a good crystal structure cannot be obtained, sufficient charge/discharge characteristics cannot be obtained, and a high-performance solid-state battery may not be obtained.

In one aspect, an object of the present invention is to realize a solid-state battery capable of suppressing deterioration in performance caused by a positive electrode layer.

In one aspect, the positive electrode layer has a positive electrode layer, a negative electrode layer, and an electrolyte layer provided between the positive electrode layer and the negative electrode layer, and the first X of the positive electrode layer measured using CuKα radiation In the line diffraction spectrum, Li ₂ Co _1-x M _x P _2-y A _y O ₇ (M is any one of Ti, V, Cr, Ni, Fe, A is B, C, Al, Si , Ga or Ge, 0≦x<1, 0≦y≦0.07) and the first Li _1+m Al _m Ge _2-m (PO ₄ ) ₃ (0<m<1 ) of the first X-ray diffraction spectrum with respect to the diffraction peak intensity Q at the diffraction angle 2θ = 14.35 ± 0.2 °, the diffraction angle 2θ = 13.0 ± 0 A solid-state battery is provided in which the ratio P/Q of the diffraction peak intensities P at .2° is in the range of 0.074<P/Q<5.744.

In one aspect, a step of forming a laminate having a positive electrode layer, a negative electrode layer, and an electrolyte layer provided between the positive electrode layer and the negative electrode layer; sintering, wherein Li ₂ Co _1-x M _x P _2-y A _y O ₇ (M is selected from Ti, V, Cr, Ni, and Fe) is added to the positive electrode layer in the laminate before sintering. any one type, A is any one type of B, C, Al, Si, Ga, and Ge, 0≦x<1, 0≦y≦0.07), and the first Li _1+m Al _m Ge _2-m (PO ₄ ) ₃ (0<m<1). Diffraction attributed to the Li ₂ Co _1-x M _x P _2-y A _y O ₇ and the first Li _1+m Al _m Ge _2-m (PO ₄ ) ₃ in the X-ray diffraction spectrum of No. 1 The diffraction peak intensity at the diffraction angle 2θ = 13.0 ± 0.2° with respect to the diffraction peak intensity Q at the diffraction angle 2θ = 14.35 ± 0.2° in the first X-ray diffraction spectrum There is provided a method for manufacturing a solid battery in which the laminate is fired under a firing temperature condition in which the P ratio P/Q is in the range of 0.074<P/Q<5.744.

In one aspect, it is possible to realize a solid battery capable of suppressing deterioration in performance caused by the positive electrode layer.

It is a figure which shows an example of the manufacturing flow of a solid-state battery. It is a figure explaining the 1st example of a laminated body formation process. It is a figure explaining the 2nd example of a laminated body formation process. It is a figure explaining an example of a degreasing and baking process. It is a figure explaining an example of a current collector formation process. It is a figure which shows the example of the XRD spectrum of a positive electrode layer. It is a figure which shows an example of the relationship between the baking temperature and the predetermined diffraction peak intensity ratio of a positive electrode layer. FIG. 4 is a diagram showing a first example of the relationship between firing temperature and discharge capacity and resistance; FIG. 5 is a diagram showing a second example of the relationship between firing temperature and discharge capacity and resistance; FIG. 1 is a diagram (part 1) showing an example of an XRD spectrum of a negative electrode layer; FIG. 2 is a diagram (part 2) showing an example of an XRD spectrum of a negative electrode layer; FIG. 4 is a diagram showing an example of the relationship between the firing temperature and the predetermined diffraction peak intensity ratio of the negative electrode layer; FIG. 5 is a diagram showing an example of the relationship between the discharge capacity and the predetermined diffraction peak intensity ratio of the negative electrode layer; FIG. 2 is a diagram (part 1) showing an example of measurement results of charge-discharge characteristics of a solid-state battery; FIG. 2 is a diagram (part 2) showing an example of measurement results of charge-discharge characteristics of a solid-state battery;

As one battery, a positive electrode layer containing a positive electrode active material, a solid electrolyte, etc., a negative electrode layer containing a negative electrode active material, a solid electrolyte, etc., and a solid electrolyte layer provided between the positive electrode layer and the negative electrode layer. Solid-state batteries comprising: Unlike lithium-ion secondary batteries, solid-state batteries do not use flammable organic electrolytes. It is easy to handle in the environment, and has advantages such as being able to maintain its performance even under low and high temperature conditions.

Positive electrode active materials for solid-state batteries include, for example, Li ₂ Co _1-x M _x P _2-y A _y O ₇ (M is any one of Ti, V, Cr, Ni and Fe; is any one of B, C, Al, Si, Ga, and Ge, and an LCPO-based material represented by 0≤x<1, 0≤y≤0.07) can be used. For example, Li ₂ CoP ₂ O ₇ , which is one of such LCPO-based materials, has an average potential (vs Li/Li ⁺ ) of about 5 V and a capacity (mass-capacity density) of about 200 mAh/g. It is considered effective in improving energy density. Further, as the solid electrolyte of the solid battery, an oxide solid electrolyte, for example, a LAGP-based material, which is one of NASICON type oxide solid electrolytes, can be used. The LAGP-based material is an oxide solid electrolyte represented by the general formula Li _1+m Al _m Ge _2-m (PO ₄ ) ₃ (0<m<1), and is also called lithium germanium phosphate substituted with aluminum. . For example, _{Li1.5Al0.5Ge1.5} ( _PO4 ) ₃ can be _used as the solid electrolyte _of the solid battery.

Here, if an LCPO-based material is used as the positive electrode active material of the positive electrode layer of the solid battery, and an LAGP-based material is used as the solid electrolyte that is included in the positive electrode layer together with the LCPO-based material, the solid battery is manufactured as described later. Depending on the firing conditions, it may not be possible to obtain a positive electrode layer having a good crystal structure. For example, a good interface is not formed between the LCPO-based material and the LAGP-based material, or the reaction between the LCPO-based material and the LAGP-based material forms another crystalline phase that acts as a resistive layer between them. There are times when you feel tired. If a positive electrode layer having a good crystal structure cannot be obtained, sufficient charge/discharge characteristics cannot be obtained, and a high-performance solid-state battery may not be obtained.

For a solid battery using an LCPO-based material for the positive electrode active material of the positive electrode layer and an LAGP-based material for the solid electrolyte, in order to achieve excellent charge-discharge characteristics and high performance, it is necessary to have a good crystal structure. It is desirable to obtain a positive electrode layer having such a positive electrode layer, and to manufacture a solid-state battery using firing conditions that allow such a positive electrode layer to be obtained. A solid battery capable of suppressing deterioration in performance due to the positive electrode layer will be described below.

In the following description, the LCPO-based material is also simply referred to as "LCPO", and the case of using Li ₂ CoP ₂ O ₇ as LCPO is taken as an example. Also, the LAGP-based material is simply referred to as "LAGP".

[Manufacturing of solid-state batteries]
First, examples of materials used to form a positive electrode layer, a negative electrode layer, and an electrolyte layer provided therebetween in a solid battery will be described.

(LCPO powder)
First, powders of Li raw material, Co raw material and P raw material are prepared in amounts based on the composition of LCPO. As the Li raw material powder, for example, Li ₂ NO ₃ (lithium nitrate) is used. For example, Co(NO ₃ ) _{2 or} Co(NO ₃ ) 2.6H ₂ O (cobalt nitrate) is used as the Co raw material powder. For example, NH ₄ H ₂ PO ₄ (ammonium dihydrogen phosphate) is used as the P raw material powder. These raw material powders are weighed and prepared so as to have a composition of LCPO obtained by firing as described later, here Li ₂ CoP ₂ O ₇ .

The prepared Li raw material, Co raw material and P raw material, and further citric acid and pure water are mixed in a container such as a beaker, and the container is heated using a hot plate or the like to evaporate water. The mixture obtained by evaporating water is pulverized using an agate mortar or the like, and the pulverized mixture is calcined at a temperature of 600° C. to 700° C. for 2 to 6 hours. The sintered body obtained by sintering is pulverized using an agate mortar or the like so as to obtain a powder having a predetermined average particle size (for example, 7 μm), and the pulverized material is further pulverized using a ball mill or the like. As a result, LCPO powder adjusted to a predetermined average particle size (for example, 1 μm) is obtained.

For example, by such a method, LCPO powder used as a positive electrode active material for a positive electrode layer of a solid battery is prepared.
Note that other Li compounds such as Li ₂ CO ₃ (lithium carbonate) may be used as the Li raw material for LCPO, and other Co compounds such as CoCO ₃ (cobalt carbonate) may be used as the Co raw material. can also In forming LCPO, in addition to the above-mentioned wet process of mixing the Li, Co and P raw materials with citric acid in a liquid, the Li raw material, the Co raw material and the P raw material are mixed without using citric acid. Other methods may be adopted, such as a wet process in which pure water is added while mixing, or a dry process in which citric acid and pure water are not used.

(LAGP powder)
LAGPs can be formed using solid-phase methods. First, powders of Li ₂ CO ₃ , Al ₂ O ₃ (aluminum oxide), GeO ₂ (germanium oxide) and NH ₄ H ₂ PO ₄ as raw materials for LAGP are weighed and prepared so as to have a predetermined composition ratio. be. These raw material powders are mixed using a magnetic mortar, ball mill, or the like, and the mixture obtained by mixing is calcined at a temperature of 300° C. to 400° C. for 3 to 5 hours. The powder obtained by calcination is melted by heat treatment at a temperature of 1200° C. to 1400° C. for 1 hour to 2 hours. The material obtained by melting is quenched and vitrified. Thereby, an amorphous LAGP powder is obtained. In addition, the amorphous LAGP powder thus obtained may be sintered at, for example, 600°C to 900°C. This gives a crystalline LAGP powder. The obtained LAGP powder is pulverized and adjusted to the target particle size (average particle size D50).

For example, such a method prepares the LAGP powder used for the electrolyte layer and the cathode and anode layers of a solid-state battery. Amorphous LAGP powder or crystalline LAGP powder may be used for the electrolyte layer, positive electrode layer, and negative electrode layer of the solid battery. Both amorphous LAGP powder and crystalline LAGP powder may be used in the electrolyte layer, positive electrode layer and negative electrode layer of the solid battery.

(Electrolyte layer material)
As an example, the LAGP powder obtained by the above method (one or both of amorphous and crystalline LAGP powder) is mixed with a binder, a solvent, etc., and polyethylene terephthalate (PET) is obtained by a doctor blade method or the like. ) is coated on a carrier such as a film to form a green sheet for the electrolyte layer.

For example, LAGP powder is used as ceramic powder, and a certain amount of binder is added to the ceramic powder, and a mixture obtained by adding a certain amount of anhydrous alcohol as a solvent is mixed with a ball mill or the like to form a paste. of the electrolyte layer material. The formed paste-like electrolyte layer material is defoamed in vacuum and then coated on a PET film by a doctor blade method to form a sheet-like electrolyte layer material corresponding to the electrolyte layer. For example, one sheet-like electrolyte layer material formed by one coating in this manner can be used as the electrolyte layer green sheet. Further, in order to adjust the desired thickness, a plurality of sheets of the sheet-like electrolyte layer material formed by one coating may be laminated and pressure-bonded to form a green sheet for the electrolyte layer. The electrolyte layer green sheet containing one or a plurality of laminated sheet-like electrolyte layer materials may be cut into a predetermined planar size. For example, the electrolyte layer green sheet thus formed is used to form the electrolyte layer of a solid battery.

(Positive electrode layer material)
As an example, the LAGP powder obtained by the above method (one or both of amorphous and crystalline LAGP powder), a conductive aid, a positive electrode active material, a binder, a solvent, a plasticizer, etc. are mixed, and a doctor blade A carrier such as a PET film is coated by a method to form a positive electrode layer green sheet. LCPO, here Li ₂ CoP ₂ O ₇ is used as the positive electrode active material. Examples of conductive aids include carbon materials such as carbon nanofibers, carbon black, graphite, graphene, and carbon nanotubes, and conductive materials such as iron silicide.

For example, the LAGP powder and the positive electrode active material are mixed at a mass ratio of 50:50 to form a ceramic powder, and a certain amount of binder is added to the ceramic powder, and anhydrous alcohol is used as a solvent A mixture obtained by adding a certain amount of is mixed with a ball mill or the like to form a paste-like positive electrode layer material. The formed paste-like positive electrode layer material is defoamed in vacuum, and then coated on a PET film by a doctor blade method to form a sheet-like positive electrode layer material corresponding to the positive electrode layer. For example, one sheet-like positive electrode layer material formed by one coating in this manner can be used as a positive electrode layer green sheet. In addition, in order to adjust the desired thickness and amount of positive electrode active material, a plurality of sheet-shaped positive electrode layer materials formed by one coating are laminated and pressure-bonded to form a positive electrode layer green sheet. You can also A positive electrode layer green sheet containing one or a plurality of laminated sheet-shaped positive electrode layer materials may be cut into a predetermined planar size. For example, the positive electrode layer green sheet thus formed is used for forming the positive electrode layer of a solid battery.

As another example, the LAGP powder obtained by the above method, a conductive aid, a positive electrode active material, a binder, a dispersant, a plasticizer, a non-aqueous solvent, etc. are mixed, and the positive electrode which is a paste positive electrode layer material A layer paste is formed. For example, the positive electrode layer paste thus formed is used for forming the positive electrode layer of a solid battery by screen printing.

(Negative electrode layer material)
As an example, the LAGP powder obtained by the above method (one or both of amorphous and crystalline LAGP powder), a conductive aid, a negative electrode active material, a binder, a solvent, a plasticizer, etc. are mixed, and a doctor blade A carrier such as a PET film is coated by a method to form a negative electrode layer green sheet. The negative electrode active material includes TiO ₂ (titanium oxide), Nb ₂ O ₅ (niobium oxide), Li ₃ V ₂ (PO ₄ ) ₃ (lithium vanadium phosphate), Li ₄ Ti ₅ O ₁₂ (lithium titanate), and the like. is used. Examples of conductive aids include carbon materials such as carbon nanofibers, carbon black, graphite, graphene, and carbon nanotubes, and conductive materials such as iron silicide.

For example, the LAGP powder and the negative electrode active material are mixed in a mass ratio of 50:50 to form a ceramic powder. A mixture obtained by adding a certain amount of is mixed with a ball mill or the like to form a paste-like negative electrode layer material. The formed paste-like negative electrode layer material is defoamed in a vacuum, and then coated on a PET film by a doctor blade method to form a sheet-like negative electrode layer material corresponding to the negative electrode layer. For example, one sheet-shaped negative electrode layer material formed by one coating in this way can be used as a negative electrode layer green sheet. In addition, in order to adjust the desired thickness and amount of the negative electrode active material, a plurality of sheet-shaped negative electrode layer materials formed by one coating are laminated and pressure-bonded to form a negative electrode layer green sheet. You can also A negative electrode layer green sheet containing one or a plurality of laminated sheet-like negative electrode layer materials may be cut into a predetermined planar size. For example, the negative electrode layer green sheet thus formed is used for forming the negative electrode layer of a solid battery.

As another example, the LAGP powder obtained by the above method, a conductive aid, a negative electrode active material, a binder, a dispersant, a plasticizer, a non-aqueous solvent, etc. are mixed, and a negative electrode that is a paste negative electrode layer material A layer paste is formed. For example, the negative electrode layer paste thus formed is used for forming the negative electrode layer of a solid battery by screen printing.

Next, an example of a method for manufacturing a solid-state battery using the above materials will be described.
FIG. 1 is a diagram showing an example of the production flow of a solid-state battery.
In manufacturing a solid-state battery, first, a laminate of materials for a positive electrode layer, an electrolyte layer, and a negative electrode layer is formed (step S1). The formed laminate is heat-treated to thermally decompose the remaining binder and the like, and is degreased (step S2). The laminate after degreasing is further fired to sinter the positive electrode layer, the electrolyte layer, and the negative electrode layer (step S3). Then, current collectors are formed using a metal or the like on the surfaces of the positive electrode layer and the negative electrode layer sandwiching the electrolyte layer in the laminated body after firing (step S4). This forms the basic structure of the solid-state battery. Each process of steps S1 to S4 shown in FIG. 1 will be described with reference to FIGS. 2 to 5. FIG.

(Laminate formation)
FIG. 2 is a diagram for explaining a first example of the laminate forming process. FIG. 2(A) schematically shows a cross-sectional view of an essential part of an example of a step of crimping the green sheets for the positive electrode layer, the electrolyte layer, and the negative electrode layer, and FIG. 2(B) shows the crimped green sheets. A cross-sectional view of a main part of an example of a group is schematically shown.

In the layered body forming step shown in step S1 of FIG. 1, for example, a method as shown in FIGS. 2A and 2B is used. That is, as shown in FIG. 2A, the positive electrode layer green sheet 11, the electrolyte layer green sheet 31, and the negative electrode layer green sheet 21 prepared by the above method are combined into the positive electrode layer green sheet 11 and the negative electrode layer green sheet. The electrolyte layer green sheet 31 is sandwiched between the electrolyte layer green sheet 21 and the layer green sheet 21 , and laminated and pressure-bonded. Thereby, the laminate 2 as shown in FIG. 2B is obtained.

Each of the positive electrode layer green sheet 11 and the negative electrode layer green sheet 21 is not limited to one green sheet, and a plurality of green sheets may be laminated in advance so as to have a predetermined thickness and amount of active material. A crimped one may also be used. The electrolyte layer green sheet 31 is not limited to one green sheet, and a plurality of green sheets may be laminated in advance to have a predetermined thickness and pressure-bonded.

FIG. 3 is a diagram for explaining a second example of the laminate forming process. FIG. 3A schematically shows a cross-sectional view of a main part of an example of the positive electrode layer paste coating process, and FIG. 3B is a main part cross-sectional view of an example of the negative electrode layer paste coating process. is schematically shown.

For example, the method shown in FIGS. 3(A) and 3(B) may be used in the formation of the laminate shown in step S1 of FIG. In this method, for example, as shown in FIG. 3A, the positive electrode layer paste 12 prepared by the above method is applied to one surface of the electrolyte layer green sheet 31 prepared by the above method. It is applied by screen printing. After coating, drying is performed to remove the solvent in the positive electrode layer paste 12 . As shown in FIG. 3B, the negative electrode layer paste 22 prepared by the method described above is applied to the other surface of the electrolyte layer green sheet 31 by screen printing. After coating, drying is performed to remove the solvent in the negative electrode layer paste 22 . Thereby, the laminate 2 as shown in FIG. 3B is obtained.

The application of the positive electrode layer paste 12 and the negative electrode layer paste 22 by screen printing may be performed multiple times so as to obtain a predetermined thickness and amount of active material. In this case, the drying for removing the solvent may be performed after each screen printing, or may be performed collectively after a plurality of screen printings. Further, the electrolyte layer green sheet 31 is not limited to one green sheet, and a plurality of green sheets may be laminated in advance so as to have a predetermined thickness and press-bonded.

(degreasing and firing)
FIG. 4 is a diagram explaining an example of the degreasing and baking process. FIG. 4A schematically shows a cross-sectional view of essential parts of an example of the degreasing process, and FIG. 4B schematically shows a cross-sectional view of essential parts of an example of the baking process.

In the degreasing step shown in step S2 of FIG. 1, for example, as shown in FIG. The binder and the like remaining in the laminate 2 are removed by thermal decomposition, that is, degreasing is performed. The temperature of the heat treatment in the degreasing step varies depending on the positive electrode layer green sheet 11 or the positive electrode layer paste 12, the electrolyte layer green sheet 31, the negative electrode layer green sheet 21 or the negative electrode layer paste 22 used to form the laminate 2. It can be set based on the thermal decomposition temperature of the binder contained.

At the time of such degreasing, the positive electrode layer green sheet 11 or the positive electrode layer paste 12, the electrolyte layer green sheet 31, the negative electrode layer green sheet 21 or the negative electrode layer paste 22 used to form the laminate 2 were removed. Some sintering, such as the LAGP contained in the may be performed. The heat treatment for degreasing may be performed using a firing furnace 100 (FIG. 4(B)) as described later.

In the firing step shown in step S3 of FIG. 1, for example, the degreased laminate 2 obtained in step S2 is carried into a firing furnace 100 as shown in FIG. 4B. Then, the loaded laminate 2 is fired in an atmosphere of an inert gas such as nitrogen, for example, at a temperature higher than that for degreasing. By such firing, LAGP and the like contained in the degreased laminate 2 are sintered.

(Current collector formation)
FIG. 5 is a diagram illustrating an example of the current collector forming process. FIG. 5A schematically shows a cross-sectional view of an example of essential parts before the step of forming a current collector. FIG. 5B schematically shows a cross-sectional view of an essential part of an example of the current collector forming step.

By the firing as described above, the solid battery body 1a having the positive electrode layer 10, the electrolyte layer 30 and the negative electrode layer 20 after firing is formed as shown in FIG. 5(A). As shown in FIG. 5B, a current collector 40 and a current collector 50 are formed on the surfaces of the positive electrode layer 10 and the negative electrode layer 20 of the solid battery body 1a, respectively. For example, as the current collector 40 and the current collector 50, thin films of a metal such as Au (gold) are formed on the surfaces of the positive electrode layer 10 and the negative electrode layer 20, respectively, by sputtering or vapor deposition. The current collector 40 and the current collector 50 are obtained by coating and firing a conductive paste containing various metal particles such as Au and Ag (silver) and conductive particles such as carbon particles. may be

Current collectors respectively connected to the positive electrode layer 10 and the negative electrode layer 20 of the solid battery main body 1a having the positive electrode layer 10 and the negative electrode layer 20 and the electrolyte layer 30 provided therebetween using the above method. A solid state battery 1 comprising 40 and a current collector 50 is obtained.

When the solid-state battery 1 is charged, lithium ions are conducted from the positive electrode layer 10 through the electrolyte layer 30 to the negative electrode layer 20 and incorporated therein. transmitted and taken in. In the solid-state battery 1, charging and discharging operations are realized by such lithium ion conduction.

Here, a current collector 40 and a current collector 50 are connected to the positive electrode layer 10 and the negative electrode layer 20 of the solid battery main body 1a having the electrolyte layer 30, the positive electrode layer 10 and the negative electrode layer 20, respectively. A solid battery 1 is taken as an example. In addition, a plurality of positive electrode layers 10 and a plurality of negative electrode layers 20 are alternately laminated with an electrolyte layer 30 interposed therebetween, degreased and fired to form a solid battery body, and a plurality of solid battery body layers are formed. A current collector connected to the positive electrode layer 10 and a current collector connected to a plurality of negative electrode layers 20 may be formed to obtain a stacked solid-state battery.

[Evaluation of Solid Battery]
Next, evaluation results of the solid-state battery 1 formed under various conditions according to the above method will be described. Here, for evaluation of the solid battery 1, the following samples of the solid battery 1 were produced.

(positive electrode layer)
LCPO, which is Li ₂ CoP ₂ O ₇ here, was used as the positive electrode active material of the positive electrode layer 10 . For the LCPO of the positive electrode layer 10, Li ₂ NO ₃ is used as the Li raw material, Co(NO ₃ ) _{2.6H 2} O as the Co raw material, and NH ₄ H ₂ PO ₄ as the P raw material. , and after evaporating the moisture, pulverized with a ball mill to an average particle size of 0.5 μm was used.

LAGP was used as the solid electrolyte of the positive electrode layer 10 . Li ₂ CO ₃ , Al ₂ O ₃ , GeO ₂ and NH ₄ H ₂ PO ₄ are used as raw materials for the LAGP of the positive electrode layer 10, these are mixed in a magnetic mortar and then in a ball mill, and the mixture is placed in an alumina crucible. Amorphous LAGP obtained by a method of calcining at 300 ° C. for 5 hours and melting and quenching by heat treatment at 1300 ° C. for 2 hours (melting quenching method) is pulverized to an average particle size of 1.0 μm with a ball mill. I used what I did. As the LAGP of the solid electrolyte of the positive electrode layer 10, two types of LAGP having different average particle diameter D50 [μm] and BET specific surface area [m ² /g] as shown in Table 1 below were used.

A carbon nanotube (CNT) was used as a conductive aid for the positive electrode layer 10 .
LCPO, LAGP and CNT are mixed at a weight ratio of LCPO:LAGP:CNT=3.88:5.82:0.3, and binder, dispersant, plasticizer and non-aqueous solvent are added at predetermined ratios. to form a positive electrode layer paste 12 used for screen printing.

(Electrolyte layer)
LAGP was used as the solid electrolyte of the electrolyte layer 30 . As the LAGP of the electrolyte layer 30, amorphous LAGP obtained by the same melt quenching method as used for the positive electrode layer 10 was pulverized to an average particle size of 1.0 μm with a ball mill. A binder, a dispersant, a plasticizer, and a non-aqueous solvent were added thereto in a predetermined ratio and kneaded, and a 200 μm-thick electrolyte layer green sheet 31 was formed by a doctor blade method.

(Negative electrode layer)
TiO ₂ with an average particle size of 1.0 μm was used as the negative electrode active material of the negative electrode layer 20 . The solid electrolyte and conductive aid for the negative electrode layer 20 were the same as those for the positive electrode layer 10 , and the negative electrode layer paste 22 used for screen printing was formed in the same manner as for the positive electrode layer 10 .

Further, as the negative electrode layer paste 22, Nb ₂ O ₅ having an average particle size of 1.0 μm was used as the negative electrode active material, and the same solid electrolyte and conductive aid as those of the positive electrode layer 10 were used.
(Lamination and degreasing and firing)
The positive electrode layer paste 12 was screen-printed on one surface of the electrolyte layer green sheet 31 , and the negative electrode layer paste 22 was screen-printed on the other surface of the electrolyte layer green sheet 31 to form the laminate 2 . .

The formed laminate 2 was degreased and fired under the following conditions.
For degreasing, the temperature was raised at a rate of 50° C./hour in an air flow atmosphere, held at 500° C. for 5 hours, and cooled by natural cooling.

For firing, the temperature is raised at a rate of temperature rise of 50°C/hour in a nitrogen flow atmosphere, and the prescribed temperature in the range of 525°C to 650°C (525°C, 537°C, 550°C, 563°C, 575°C, 587°C , 600.degree. C., 612.degree. C., 625.degree.

By such degreasing and sintering of the laminate 2, a plurality of solid battery main bodies 1a having different sintering temperatures after degreasing, that is, a plurality of solid battery bodies 1a each having an electrolyte layer 30 and a positive electrode layer 10 and a negative electrode layer 20 sandwiching the electrolyte layer 30 are formed. A solid battery main body 1a was formed.

(current collector)
Au was sputtered on the surface of the positive electrode layer 10 and the negative electrode layer 20 of each solid battery main body 1a formed by changing the baking temperature after degreasing to form the current collector 40 and the current collector 50, respectively. Thus, a solid battery 1 was formed.

A plurality of samples of the solid state battery 1 were produced as described above. Table 2 summarizes the combinations of the positive electrode active material, negative electrode active material, solid electrolyte, and firing temperature of the prepared samples.

In addition, below, sample No. 1 to 7, samples using LCPO (Li ₂ CoP ₂ O ₇ ) as the positive electrode active material, TiO ₂ as the negative electrode active material, and LAGP-1 (Table 1) as the solid electrolyte were labeled as “LCPO/TiO ₂ / Also referred to as "LAGP-1". Sample no. 8 to 14, samples using LCPO (Li ₂ CoP ₂ O ₇ ) as the positive electrode active material, TiO ₂ as the negative electrode active material, and LAGP-2 (Table 1) as the solid electrolyte were labeled as “LCPO/TiO ₂ / Also referred to as "LAGP-2". Sample no. 15 to 22, samples using LCPO (Li ₂ CoP ₂ O ₇ ) as the positive electrode active material, Nb ₂ O ₅ as the negative electrode active material, and LAGP-1 (Table 1) as the solid electrolyte are referred to as “LCPO/Nb ₂ O ₅ /LAGP-1”.

(Charging and discharging characteristics)
A plurality of samples of the solid state battery 1 manufactured as described above, that is, sample No. 1 to 22 were charged and discharged under the following conditions, and the capacity (cell capacity) and voltage (cell voltage) were measured. Here, charging was performed under the condition of constant current charging at a rate of 1/20 C until the battery voltage reached 3.6 V at room temperature. For the discharge, conditions were used in which constant current discharge was performed at a rate of 1/20 C until the battery voltage reached 0.5 V at room temperature.

(X-ray diffraction measurement)
X-Ray Diffraction (XRD) measurement of the exposed positive electrode layer 10 (thickness: 5 μm) was performed on the plurality of samples of the solid battery 1 obtained as described above. From the XRD spectrum obtained by the XRD measurement, the intensity ratio (simply referred to as "ratio") of a given diffraction peak was obtained. For XRD measurement, each sample of the solid battery 1 is installed so that the positive electrode layer 10 is the outermost surface (exposed), Cu (copper) Kα rays (CuKα rays) are used, the slit width is 5 mm, the tube voltage is 40 kV, Measurement was performed under the conditions of a tube current of 30 mA and a diffraction angle 2θ of 5° to 20° at a speed of 0.1°/min.

In addition, XRD measurement was performed on the exposed negative electrode layer 20 of a plurality of samples of the solid battery 1 obtained as described above within a predetermined range of diffraction angles 2θ.
<Relationship between positive electrode layer characteristics after firing and solid battery performance>
First, an example of the relationship between the properties of the positive electrode layer 10 after firing and the performance of the solid battery 1 will be described.

FIG. 6 is a diagram showing an example of the XRD spectrum of the positive electrode layer. FIG. 6 shows sample Nos. shown in Table 2 above. 15 to 21, that is, sample Nos. using LCPO as the positive electrode active material, Nb ₂ O ₅ as the negative electrode active material, and LAGP-1 as the solid electrolyte, and firing at a temperature of 563°C to 637°C. 15-21 (LCPO/Nb ₂ O ₅ /LAGP-1) XRD spectra of cathode layer 10 are shown.

From the XRD spectrum of the positive electrode layer 10 shown in FIG. 6, when the firing temperature is 637° C. (sample No. 21), in addition to the diffraction peaks attributed to LCPO and the diffraction peaks attributed to LAGP, Li ₉ Diffraction peaks appear that are attributed to Al ₃ (P ₂ O ₇ ) ₃ (PO ₄ ) ₂ (referred to as “LAPP”).

From the XRD spectrum of the positive electrode layer 10 shown in FIG. 6, when the firing temperature is 587° C. to 625° C. (Sample Nos. 17 to 20), a diffraction peak attributed to LCPO and a diffraction peak attributed to LAGP are observed. appear. Alternatively, when the firing temperature is 587° C. to 625° C. (Sample Nos. 17 to 20), diffraction peaks attributed to LAPP appear in addition to diffraction peaks attributed to LCPO and LAGP.

From the XRD spectrum of the positive electrode layer 10 shown in FIG. 6, when the firing temperature is 575° C. or less (Samples Nos. 15 and 16), no diffraction peak attributed to LAPP appears.
The XRD spectrum of the positive electrode layer 10 may have a diffraction peak attributed to LiAlP ₂ O ₇ (lithium aluminum pyrophosphate).

Based on the knowledge obtained from the XRD spectrum of the positive electrode layer 10 as shown in FIG. Find the intensity ratio of the diffraction peaks appearing at . That is, the ratio P/Q[-] of the diffraction peak intensity P at the diffraction angle 2θ=13.0±0.2° to the diffraction peak intensity Q at the diffraction angle 2θ=14.35±0.2° is obtained.

Here, a diffraction peak attributed to LCPO (110) appears at the diffraction angle 2θ=12.9°, and a diffraction peak attributed to LAPP (002) appears at the diffraction angle 2θ=13.1°. At the diffraction angle 2θ=13.0±0.2°, it is assumed that the diffraction peak attributed to LCPO (110) and the diffraction peak attributed to LAPP (002) overlap. be. Moreover, a diffraction peak attributed to LCPO (11-1) appears at the diffraction angle 2θ=14.35°.

For XRD spectra obtained for LCPO-only samples, the ratio P/Q is the ratio of the diffraction peak intensity of LCPO (110) to that of LCPO (11-1), ie, the theoretical intensity ratio. When the ratio P/Q of the XRD spectrum after firing of the positive electrode layer 10 containing LCPO as the positive electrode active material and LAGP as the solid electrolyte is larger than the theoretical intensity ratio, the diffraction angle 2θ=12.9. It is presumed that the diffraction peak of LAPP (002) with a diffraction angle of 2θ=13.1° is superimposed on the diffraction peak of LCPO (110) with 2θ=13.1°. It is presumed that the value of the ratio P/Q provides information on the existence of a crystal phase, which is considered to be LAPP, in the positive electrode layer 10 after firing of the solid battery 1 .

FIG. 7 is a diagram showing an example of the relationship between the firing temperature and the predetermined diffraction peak intensity ratio of the positive electrode layer. FIG. 7 shows a predetermined diffraction peak intensity ratio, that is, a diffraction peak at a diffraction angle 2θ=14.35±0.2° with respect to the firing temperature [° C.] for some of the sample groups shown in Table 2 above. The ratio P/Q[−] of the diffraction peak intensity P at the diffraction angle 2θ=13.0±0.2° to the intensity Q is plotted.

Sample No. using LCPO as the positive electrode active material, TiO ₂ as the negative electrode active material, and LAGP-1 as the solid electrolyte. In 3, 4, 5, 6, 7 (LCPO/TiO ₂ /LAGP-1), the ratio P/ A tendency for Q to increase is recognized.

Sample No. using LCPO as the positive electrode active material, TiO ₂ as the negative electrode active material, and LAGP-2 as the solid electrolyte. Similarly, in 9, 11, 12, 13, and 14 (LCPO/TiO ₂ /LAGP-2), as the firing temperature increased to 537°C, 563°C, 600°C, 637°C, and 650°C, the ratio A tendency for P/Q to increase is recognized.

Sample No. using LCPO as the positive electrode active material, Nb ₂ O ₅ as the negative electrode active material, and LAGP-1 as the solid electrolyte. 15, 16, 17, 18, 19, 20, and 21 (LCPO/Nb ₂ O ₅ /LAGP-1) also had firing temperatures of 563°C, 575°C, 587°C, 600°C, 612°C, 625°C, As the temperature rises to 637°C, the tendency of the ratio P/Q to increase is recognized.

As shown in FIG. 7, when the ratio P/Q is plotted against the firing temperature, it is observed that the ratio P/Q tends to increase as the firing temperature increases, and the ratio P/Q increases from around 600 ° C. A tendency for P/Q to increase relatively sharply is recognized.

FIG. 8 is a diagram showing a first example of the relationship between the firing temperature and the discharge capacity and resistance. FIG _. 8 shows the discharge capacity (3rd Discharge capacity (2V)) [mAh/g-LCPO] and resistance estimated from the IR drop after charging (resistance after 3rd charging) [kΩ] are plotted.

Sample No. using LCPO as the positive electrode active material, TiO ₂ as the negative electrode active material, and LAGP-1 as the solid electrolyte. In 3, 4, 5, 6, and 7 (LCPO/TiO ₂ /LAGP-1), when the firing temperature is lower than 563°C, the discharge capacity tends to decrease as the resistance increases. C., 600.degree. C., and 637.degree.

Sample No. using LCPO as the positive electrode active material, TiO ₂ as the negative electrode active material, and LAGP-2 as the solid electrolyte. 8, 9, 10, 11, 12, 13, and 14 (LCPO/TiO ₂ /LAGP-2), when the firing temperature is below 550°C and above 637°C, the discharge capacity decreases as the resistance increases. At the firing temperatures of 550° C., 563° C., 600° C. and 637° C., the resistance is relatively low and the discharge capacity is relatively high at 30 mAh/g or more.

As shown in FIG. 8, in the samples using TiO ₂ as the negative electrode active material, the resistance tended to be relatively low and the discharge capacity tended to be relatively high within a certain firing temperature range, depending on the type. be done.

FIG. 9 is a diagram showing a second example of the relationship between the firing temperature and the discharge capacity and resistance. _FIG . 9 shows the discharge capacity after ₅ charge/discharge cycles (5th discharge The capacity (2V)) [mAh/g-LCPO] and the resistance (resistance after 5th charge) [kΩ] estimated from the IR drop after charging are plotted.

Sample No. using LCPO as the positive electrode active material, Nb ₂ O ₅ as the negative electrode active material, and LAGP-1 as the solid electrolyte. 15, 16, 17, 18, 19, 20, 21, 22 (LCPO/Nb ₂ O ₅ /LAGP-1), when the firing temperature is below 587°C and above 625°C, the resistance increases with A tendency for the discharge capacity to decrease is recognized, and at the firing temperatures of 587° C., 600° C., 612° C. and 625° C., the resistance is relatively low and the discharge capacity is relatively high at 70 mAh/g or more.

As shown in FIG. 9, even in the sample using Nb ₂ O ₅ as the negative electrode active material, the resistance tends to be relatively low and the discharge capacity is relatively low within a certain firing temperature range, as in FIG. A tendency to increase is recognized.

From the results shown in FIGS. 7 to 9, sample No. 2 using TiO ₂ as the negative electrode active material was found. Among samples 1 to 7, sample No. Table 3 summarizes the ratio P/Q [−], discharge capacity [mAh/g-LCPO], and resistance [kΩ] with respect to firing temperature [° C.] obtained for 3 to 7.

Further, sample No. using TiO ₂ as the negative electrode active material. Table 4 summarizes the ratio P/Q [−], discharge capacity [mAh/g-LCPO], and resistance [kΩ] with respect to firing temperature [° C.] obtained for Nos. 8 to 14.

Also, sample No. using Nb ₂ O ₅ as the negative electrode active material. Table 5 summarizes the ratio P/Q [−], discharge capacity [mAh/g-LCPO], and resistance [kΩ] with respect to firing temperature [° C.] obtained for Nos. 15 to 22.

From Tables 3 to 5, the range of the ratio P/Q when the resistance is below a relatively low constant value and the range of the ratio P/Q when the discharge capacity is above a relatively high constant value are determined. For example, the range of the ratio P/Q when the resistance is 3.8 kΩ or less, and the range of the ratio P/Q when the discharge capacity is 30 mAh/g or more (the ratio P in the thick frame of Tables 3 to 5 /Q), 0.074<P/Q<5.744. In Table 4, the ratio P/Q at a firing temperature of 550° C. is based on the tendency shown in FIG. and the ratio P/Q=0.083 at the firing temperature of 563° C. (>0.074). In addition, in view of the knowledge obtained from the measurement results of the charge-discharge characteristics (Figs. 15 and 16 and Tables 8 and 9) described later, in setting the range of the ratio P/Q, the data of the sample with a firing temperature of 650 ° C. Excluded.

Here, from Tables 3 to 5, in the range of 0.074<P/Q<0.083, there is a possibility that low resistance and high discharge capacity cannot be stably achieved. From this, the range of 0.083<P/Q<5.744 can be obtained as the range of the ratio P/Q in which the low resistance and the high discharge capacity are obtained more stably. The ratio P/Q obtained from the XRD spectrum of the positive electrode layer 10 after firing is in the range of 0.074<P/Q<5.744 as described above, or 0.083<P/Q<5.744 as described above. 744 range, it can be said that it is possible to obtain a solid battery 1 with a relatively low resistance and a solid battery 1 with a relatively high discharge capacity.

In other words, the ratio P/Q obtained from the XRD spectrum of the positive electrode layer 10 after firing is in the range of 0.074<P/Q<5.744, or in the range of 0.083<P/Q<5.744. It can be said that the solid battery 1 with relatively low resistance and the solid battery 1 with relatively high discharge capacity can be obtained by performing the firing under the firing temperature condition. That is, when the positive electrode active material is LCPO, the negative electrode active material is TiO ₂ , and the solid electrolyte is LAGP-1 (LCPO/TiO ₂ /LAGP-1; Table 3), the firing temperature is in the range of 563°C to 637°C. , or preferably in the range of 600°C to 637°C. When the positive electrode active material is LCPO, the negative electrode active material is TiO ₂ , and the solid electrolyte is LAGP-2 (LCPO/TiO ₂ /LAGP-2; Table 4), the firing temperature is in the range of 537°C to 637°C. , or a range of 563° C. to 637° C. is preferred. When the positive electrode active material is LCPO, the negative electrode active material is Nb ₂ O ₅ , and the solid electrolyte is LAGP-1 (LCPO/Nb ₂ O ₅ /LAGP-1; Table 5), the firing temperature is 575° C. A range of 625°C, alternatively a range of 587°C to 625°C is preferred.

As described above, P is the diffraction peak intensity at the diffraction angle 2θ=13.0±0.2° in the XRD spectrum of the positive electrode layer 10 after firing, and Q is the intensity of the diffraction peak in the XRD spectrum of the positive electrode layer 10 after firing. Diffraction peak intensity at diffraction angle 2θ=14.35±0.2°. A diffraction peak attributed to LCPO (110) appears at the diffraction angle 2θ=12.9°, and a diffraction peak attributed to LAPP (002) appears at the diffraction angle 2θ=13.1°. It is presumed that diffraction peaks attributed to LCPO (110) and LAPP (002) overlap at the diffraction angle 2θ=13.0±0.2°. Also, a diffraction peak attributed to LCPO (11-1) appears at the diffraction angle 2θ=14.35°.

From FIG. 7, it can be seen that the ratio P/Q tends to increase as the firing temperature rises.

If the firing temperature exceeds a certain temperature, LAPP is excessively produced in addition to LCPO and LAGP. On the other hand, if the firing temperature is lower than a certain temperature, the ionic conductivity of LAGP cannot be enhanced, and a favorable particle interface state cannot be formed between LCPO and LAGP.

It is believed that when the firing temperature is within the appropriate range, excessive generation of LAPP can be suppressed, and a favorable particle interface state can be formed between LCPO and LAGP, resulting in sufficient discharge capacity.

For example, in the case of LCPO/Nb ₂ O ₅ /LAGP-1, when the firing temperature is 587° C. to 625° C. (Sample Nos. 17 to 20), the excessive production of LAPP is suppressed and the gap between LCPO and LAGP is reduced. Good grain interface conditions are formed. On the other hand, when the firing temperature is 575° C. or lower (Sample Nos. 15 and 16), the formation of LAPP is further suppressed compared to the case where the firing temperature is 587° C. to 625° C. (Samples No. 17 to 20). It is thought that it may be possible that it becomes difficult to form a good grain interface state between the and LAGP.

The ratio P/Q obtained from the XRD spectrum of the positive electrode layer 10 after firing is in the range of 0.074<P/Q<5.744 as described above, or in the range of 0.083<P/Q<5.744. Then, a solid battery 1 with relatively low resistance and a solid battery 1 with relatively high discharge capacity can be obtained. Depending on the material used for the positive electrode layer 10, the ratio P/Q obtained from the XRD spectrum of the positive electrode layer 10 after firing is in the range of 0.074<P/Q<5.744, or 0.083<P/Q. If the firing is performed under the firing temperature condition within the range of <5.744, the solid battery 1 with relatively low resistance and the solid battery 1 with relatively high discharge capacity can be obtained.

It is obtained in a predetermined firing temperature range set based on the material used for the positive electrode layer 10, and the ratio P/Q in the XRD spectrum of the positive electrode layer 10 is in the range of 0.074<P/Q<5.744, or According to the solid battery 1 in the range of 0.083<P/Q<5.744, the positive electrode layer 10 having a favorable crystal structure is formed, and the positive electrode layer 10 causes an increase in resistance and a decrease in charge/discharge characteristics. is suppressed. Thereby, a high-performance solid-state battery 1 having a positive electrode layer 10 with excellent characteristics is realized.

<Relationship between negative electrode layer characteristics after firing and solid battery performance>
Next, an example of the relationship between the properties of the negative electrode layer 20 after firing and the performance of the solid battery 1 will be described.
10 and 11 are diagrams showing examples of XRD spectra of the negative electrode layer. FIG. 10 shows sample Nos. shown in Table 2 above. 3 to 7 (positive electrode active material LCPO/negative electrode active material TiO ₂ /solid electrolyte LAGP-1/firing temperature 550° C. to 650° C.). FIG. 11 shows sample Nos. shown in Table 2 above. 10 to 14 (positive electrode active material LCPO/negative electrode active material TiO ₂ /solid electrolyte LAGP-2/firing temperature 550° C. to 650° C.).

From the XRD spectrum of the negative electrode layer 20 as shown in FIGS. 10 and 11, the intensity ratio of diffraction peaks appearing at a given diffraction angle 2θ is obtained as follows. That is, the ratio R/S[-] of the diffraction peak intensity R at the diffraction angle 2θ=48.0±0.2° to the diffraction peak intensity S at the diffraction angle 2θ=48.7±0.2° is obtained. Here, a diffraction peak attributed to TiO ₂ (200) appears at the diffraction angle 2θ=48.0°. A diffraction peak attributed to LAGP (128) appears at the diffraction angle 2θ=48.7°.

FIG. 12 is a diagram showing an example of the relationship between the firing temperature and the predetermined diffraction peak intensity ratio of the negative electrode layer. FIG. 12 shows a predetermined diffraction peak intensity ratio, that is, a diffraction peak at a diffraction angle 2θ = 48.7 ± 0.2° with respect to the firing temperature [°C] for some of the sample groups shown in Table 2 above. The ratio R/S[−] of the diffraction peak intensity R at the diffraction angle 2θ=48.0±0.2° to the intensity S is plotted.

Sample No. using LCPO as the positive electrode active material, TiO ₂ as the negative electrode active material, and LAGP-1 as the solid electrolyte. In 3, 4, 5, 6, 7 (LCPO/TiO ₂ /LAGP-1), the ratio R/ A tendency for S to decrease is recognized. Sample No. using LCPO as the positive electrode active material, TiO ₂ as the negative electrode active material, and LAGP-2 as the solid electrolyte. In 9, 10, 11, 12, 13, and 14 (LCPO/TiO ₂ /LAGP-2), the firing temperature increased to 537°C, 550°C, 563°C, 600°C, 637°C, and 650°C. It is observed that the ratio R/S tends to decrease as the As shown in FIG. 12, when the ratio R/S is plotted against the sintering temperature, it is observed that the ratio R/S tends to decrease as the sintering temperature increases. R/S tends to decrease relatively sharply.

From FIG. 12, in the range where the firing temperature exceeds 550° C., the diffraction peak intensity R of TiO ₂ (200) and the diffraction peak intensity S of LAGP (128) are approximately the same (the ratio R/S is approximately 1). It is believed that good grain interface conditions are formed between TiO ₂ and LAGP.

FIG. 13 is a diagram showing an example of the relationship between the discharge capacity and the predetermined diffraction peak intensity ratio of the negative electrode layer. FIG. 13 shows the discharge capacity ( _3rd discharge capacity (2V)) [mAh /g-TiO ₂ ], the ratio R/S obtained from the XRD spectrum of the negative electrode layer 20 is plotted.

From FIG. 13, when the diffraction peak intensity R of TiO ₂ (200) and the diffraction peak intensity S of LAGP (128) are approximately the same (the ratio R/S is approximately 1), the comparative A tendency to obtain a high discharge capacity is recognized.

From the results as shown in FIGS. 10 to 13, sample No. 2 using TiO ₂ as the negative electrode active material. Table 6 summarizes the ratio R/S [−], discharge capacity [mAh/g-TiO ₂ ], and resistance [kΩ] with respect to firing temperature [° C.] obtained for Nos. 3 to 7.

Further, sample No. using TiO ₂ as the negative electrode active material. Table 7 summarizes the values of the ratio R/S [−], discharge capacity [mAh/g-TiO ₂ ], and resistance [kΩ] with respect to the firing temperature [° C.] obtained for Nos. 8 to 14.

From Tables 6 and 7, the range of the ratio R/S when the resistance is below a relatively low constant value and the range of the ratio R/S when the discharge capacity is above a relatively high constant value are determined. For example, the range of the ratio R / S when the resistance is 1.7 kΩ or less, and the range of the ratio R / S when the discharge capacity is 10 mAh / g or more (Ratio R in the thick frame of Tables 6 and 7 /S range) yields 0.958<R/S<4.340. Further, for example, when the range of the ratio R/S when the resistance is 1 kΩ or less and the range of the ratio R/S when the discharge capacity is 50 mAh/g or more are obtained, 0.958<R/S<1 0.575. In addition, in view of the knowledge obtained from the measurement results of charge-discharge characteristics (Figs. 15 and 16 and Tables 8 and 9) described later, in setting the range of the ratio R / S, the data of the sample with a firing temperature of 650 ° C. Excluded. In the range of 0.958<R/S<4.340 or in the range of 0.958<R/S<1.575, the ratio R/S obtained from the XRD spectrum of the negative electrode layer 20 after firing is Then, it can be said that it is possible to obtain a solid battery 1 with relatively low resistance and a solid battery 1 with relatively high discharge capacity.

In other words, the ratio R/S obtained from the XRD spectrum of the negative electrode layer 20 after firing is in the range of 0.958<R/S<4.340 or in the range of 0.958<R/S<1.575. It can be said that the solid battery 1 with relatively low resistance and the solid battery 1 with relatively high discharge capacity can be obtained by performing the firing under the firing temperature condition. That is, when the positive electrode active material is LCPO, the negative electrode active material is TiO ₂ , and the solid electrolyte is LAGP-1 (LCPO/TiO ₂ /LAGP-1; Table 6), the firing temperature is in the range of 563°C to 637°C. is preferred. When the positive electrode active material is LCPO, the negative electrode active material is TiO ₂ , and the solid electrolyte is LAGP-2 (LCPO/TiO ₂ /LAGP-2; Table 7), the firing temperature is in the range of 537°C to 637°C. , or preferably in the range of 550°C to 637°C.

It is obtained in a predetermined firing temperature range set based on the material used for the negative electrode layer 20, and the ratio R / S in the XRD spectrum of the negative electrode layer 20 is in the range of 0.958 < R / S < 4.340, or According to the solid battery 1 in the range of 0.958<R/S<1.575, the negative electrode layer 20 having a favorable crystal structure is formed, and the negative electrode layer 20 causes an increase in resistance and a decrease in charge/discharge characteristics. is suppressed. As a result, a high-performance solid-state battery 1 having a negative electrode layer 20 with excellent characteristics is realized.

<Volume energy density of solid-state battery>
Next, the results of evaluating the volumetric energy density of the solid-state battery 1 will be described.
14 and 15 are diagrams showing examples of measurement results of charge/discharge characteristics of solid-state batteries.

FIG. 14 shows sample No. LCPO using LCPO as the positive electrode active material, TiO ₂ as the negative electrode active material, and LAGP-1 as the solid electrolyte. 3 to 7 (LCPO/TiO ₂ /LAGP-1) shows measurement results of charge-discharge characteristics. Here, FIG. 14A shows sample No. 14(B) is an example of measurement results of charge-discharge characteristics of Sample No. 3 (firing temperature: 550° C.). 4 (firing temperature: 563° C.), and FIG. 5 (firing temperature of 600° C.), and FIG. 6 (firing temperature of 637° C.), and FIG. 7 (firing temperature: 650° C.).

15 also shows sample No. 1 using LCPO as the positive electrode active material, TiO ₂ as the negative electrode active material, and LAGP-2 as the solid electrolyte. 10 to 14 (LCPO/TiO ₂ /LAGP-2) shows measurement results of charge-discharge characteristics. Here, FIG. 15A shows sample No. 10 (firing temperature: 550° C.), and FIG. 11 (firing temperature: 563° C.), and FIG. 12 (firing temperature of 600° C.), and FIG. 13 (firing temperature: 637° C.), and FIG. 14 (firing temperature: 650° C.).

Table 8 summarizes the average discharge voltage [V], discharge capacity [mAh], cell energy [mWh], and volumetric energy density [mWh/L] of the solid battery 1 obtained based on the measurement results of the charge-discharge characteristics in FIG. .

Table 9 shows the average discharge voltage [V], discharge capacity [mAh], cell energy [mWh], and volumetric energy density [mWh/L] of the solid battery 1 obtained based on the measurement results of the charge-discharge characteristics of FIG. Summarize in

14 and 15, the solid battery 1 (FIGS. 14(E) and 15(E)) with a firing temperature of 650° C. (or 650° C. or higher) has a cell capacity for increasing the voltage to 3.5 V. Therefore, it was confirmed that charging under the same conditions as in the case of other firing temperatures would result in an insufficient amount of charge and a decrease in discharge capacity. In view of such knowledge, the data of the sample with the firing temperature of 650° C. is excluded in setting the ranges of the ratio P/Q and the ratio R/S.

From Table 8, sample No. LCPO was used as the positive electrode active material, TiO ₂ was used as the negative electrode active material, and LAGP-1 was used as the solid electrolyte. With 3 to 7 (LCPO/TiO ₂ /LAGP-1), volumetric energy densities exceeding 40 mWh/L (inside the bold frame in Table 8) are obtained at firing temperatures of 563°C, 600°C and 637°C. When the firing temperature is 563° C., 600° C., and 637° C., as shown in Table 3 (within the thick frame), the solid battery 1 has a relatively low resistance and a relatively high discharge capacity. A positive electrode layer 10 that can be obtained, and as shown in Table 6 (within the thick frame), a negative electrode layer that can realize a solid battery 1 that has a relatively low resistance and a relatively high discharge capacity. 20 is obtained.

That is, in the solid battery 1 using LCPO as the positive electrode active material, TiO ₂ as the negative electrode active material, and LAGP-1 as the solid electrolyte, the ratio P/ Q is in the range of 0.074<P/Q<5.744, the ratio R/S is in the range of 0.958<R/S<4.340 for the negative electrode layer 20, and the volumetric energy is greater than 40 mWh/L density is obtained.

Therefore, when LCPO is used as the positive electrode active material, TiO ₂ is used as the negative electrode active material, and LAGP-1 is used as the solid electrolyte, low resistance and high discharge capacity can be achieved at firing temperatures of 563° C., 600° C., and 637° C. Furthermore, it can be said that a high-performance solid-state battery 1 with a high volumetric energy density is realized.

Further, from Table 9, sample No. using LCPO as the positive electrode active material, TiO ₂ as the negative electrode active material, and LAGP-2 as the solid electrolyte. In 10 to 14 (LCPO/TiO ₂ /LAGP-2), when the firing temperature is 550 ° C., 563 ° C., 600 ° C., 637 ° C., the volumetric energy density exceeds 39 mWh / L, which is generally higher than 40 mWh / L (Table 9 ) is obtained. When the firing temperature was 550° C., 563° C., 600° C., and 637° C., as shown in Table 4 (within the bold frame), solid-state battery 1 with relatively low resistance and relatively high discharge capacity was obtained. It is possible to obtain a positive electrode layer 10 that can be realized, and to realize a solid battery 1 that has a relatively low resistance and a relatively high discharge capacity, as shown in Table 7 (within the thick frame). A negative electrode layer 20 is obtained.

That is, in the solid battery 1 using LCPO as the positive electrode active material, TiO ₂ as the negative electrode active material, and LAGP-2 as the solid electrolyte, the positive electrode layer 10 was The ratio P/Q is in the range of 0.074<P/Q<5.744, the ratio R/S of the negative electrode layer 20 is in the range of 0.958<R/S<4.340, and the A volumetric energy density of . The ratio P/Q when the firing temperature is 550°C is the same as that when the firing temperature is 537°C, from the tendency shown in FIG. A value (>0.074) between the ratio P/Q=0.077 and the ratio P/Q=0.083 at a firing temperature of 563° C. is estimated.

Therefore, when LCPO is used as the positive electrode active material, TiO ₂ is used as the negative electrode active material, and LAGP-2 is used as the solid electrolyte, low resistance and high discharge are obtained when the firing temperatures are 550° C., 563° C., 600° C., and 637° C. It can be said that a high-performance solid-state battery 1 with high capacity and high volumetric energy density is realized.

In the above description, the case of using Li ₂ CoP ₂ O ₇ as LCPO was taken as an example, but Li ₂ CoP ₂ O ₇ is not limited to Li 2 CoP 2 O 7 and the general formula Li ₂ Co _1-x M _x P _2-y A _y O ₇ (M is any one of Ti, V, Cr, Ni and Fe, A is any one of B, C, Al, Si, Ga and Ge, 0 ≤ x < 1, 0 ≤ y ≤0.07), the same effect as described above can be obtained.

Reference Signs List 1 solid battery 1a solid battery body 2 laminate 10 positive electrode layer 11 green sheet for positive electrode layer 12 paste for positive electrode layer 20 negative electrode layer 21 green sheet for negative electrode layer 22 paste for negative electrode layer 30 electrolyte layer 31 green sheet for electrolyte layer 40,50 Current collector 100 Firing furnace

Claims (8)

having a positive electrode layer, a negative electrode layer, and an electrolyte layer provided between the positive electrode layer and the negative electrode layer;
In the first X-ray diffraction spectrum of the positive electrode layer measured using CuKα rays,
Li ₂ Co _1-x M _x P _2-y A _y O ₇ (M is any one of Ti, V, Cr, Ni and Fe; A is B, C, Al, Si, Ga and Ge; any one of 0 ≤ x < 1, 0 ≤ y ≤ 0.07); and
containing diffraction peaks assigned to the first Li _1+m Al _m Ge _2-m (PO ₄ ) ₃ (0<m<1) and
Ratio P/ Q is
0.074<P/Q<5.744
A solid state battery characterized by a range of The solid state battery of _claim 1, wherein _the positive electrode layer comprises _Li9Al3 ( _P2O7 ) ₃ ( _PO4 ) ₂ . In the second X-ray diffraction spectrum of the negative electrode layer measured using CuKα rays,
_TiO2 ;
a second Li _1+n Al _n Ge _2-n (PO ₄ ) ₃ (0<n<1) and a diffraction peak assigned to
Ratio of the diffraction peak intensity R at the diffraction angle 2θ = 48.0 ± 0.2° to the diffraction peak intensity S at the diffraction angle 2θ = 48.7 ± 0.2° in the second X-ray diffraction spectrum R / S is
0.958<R/S<4.340
3. The solid state battery according to claim 1 or 2, wherein the range is . 4. The solid state battery of claim 3, having a volumetric energy density greater than 39 mWh/L. forming a laminate having a positive electrode layer, a negative electrode layer, and an electrolyte layer provided between the positive electrode layer and the negative electrode layer;
and firing the laminate in an inert gas atmosphere,
In the positive electrode layer in the laminate before firing,
Li ₂ Co _1-x M _x P _2-y A _y O ₇ (M is any one of Ti, V, Cr, Ni and Fe; A is B, C, Al, Si, Ga and Ge; any one of 0 ≤ x < 1, 0 ≤ y ≤ 0.07); and
a first Li _1+m Al _m Ge _2-m (PO ₄ ) ₃ (0<m<1) and
In the step of firing the laminate,
In the first X-ray diffraction spectrum measured using CuKα rays of the positive electrode layer in the laminated body after firing,
the Li ₂ Co _1-x M _x P _2-y A _y O ₇ and
including a diffraction peak attributed to the first Li _1+m Al _m Ge _2-m (PO ₄ ) ₃ and
Ratio P/ Q is
0.074<P/Q<5.744
A method for producing a solid battery, characterized in that the laminate is fired under firing temperature conditions within the range of 6. The method of manufacturing a solid-state battery according to claim 5, wherein _the positive electrode layer in the laminated _body after firing contains _Li9Al3 ( _P2O7 ) ₃ ( _PO4 ) ₂ . In the negative electrode layer in the laminate before firing,
_TiO2 ;
a second Li _1+n Al _n Ge _2-n (PO ₄ ) ₃ (0<n<1) and
In the step of firing the laminate,
In the second X-ray diffraction spectrum of the negative electrode layer in the laminated body after firing, which is measured using CuKα rays,
the _TiO2 ;
including a diffraction peak attributed to the second Li _1+n Al _n Ge _2-n (PO ₄ ) ₃ and
Ratio of the diffraction peak intensity R at the diffraction angle 2θ = 48.0 ± 0.2° to the diffraction peak intensity S at the diffraction angle 2θ = 48.7 ± 0.2° in the second X-ray diffraction spectrum R / S is
0.958<R/S<4.340
7. The method of manufacturing a solid-state battery according to claim 5, wherein the laminate is fired under a firing temperature condition within the range of . 8. The method of manufacturing a solid-state battery according to claim 7, wherein the solid-state battery manufactured using the laminate has a volumetric energy density of more than 39 mWh/L.

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