JP6812940B2 - Manufacturing method of active material layer for all-solid-state battery and manufacturing method of all-solid-state battery - Google Patents

Description

The present disclosure relates to a method for producing an active material layer for an all-solid-state battery and a method for producing an all-solid-state battery.

An all-solid-state battery is a battery having a solid electrolyte layer between a positive electrode active material layer and a negative electrode active material layer, and has a simpler safety device than a liquid-based battery having an electrolytic solution containing a flammable organic solvent. It has the advantage of being easy to plan. In Patent Document 1, a negative electrode body having a first solid electrolyte layer and a positive electrode body having a second solid electrolyte layer are laminated so that the first solid electrolyte layer and the second solid electrolyte layer are in contact with each other. A method for manufacturing an all-solid-state battery having a joining step of heating and pressing the laminate is disclosed.

Further, Patent Document 2 discloses that a positive electrode active material and a solid electrolyte powder are mixed to prepare pellets, and heat treatment is performed at 300 ° C. for 10 minutes. Further, Patent Document 3 describes a pellet (laminate) having a positive electrode mixture containing a positive electrode active material and sulfide glass, glass ceramics, and a negative electrode mixture containing a negative electrode active material and sulfide glass in this order. Is disclosed to be prepared and fired at a temperature equal to or higher than the glass transition temperature. Further, Patent Document 4 discloses a method for manufacturing an all-solid-state battery in which a pressing process is performed under specific conditions. Further, Patent Document 5 discloses a method for producing an electrode active material layer containing an electrode active material and a sulfide solid electrolyte material that is fused to the surface of the electrode active material and has substantially no crosslinked sulfur. Has been done.

JP 2015-008073 Patent No. 6071171 Japanese Unexamined Patent Publication No. 2010-07812 JP-A-2017-010816 Japanese Unexamined Patent Publication No. 2011-060649

In order to improve the functionality of all-solid-state batteries, it is required to improve the output characteristics of all-solid-state batteries. The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a method for producing an active material layer for an all-solid-state battery having good output characteristics.

In order to solve the above problems, in the present disclosure, a preparatory step of preparing a mixture layer containing an active material and an amorphous sulfide solid electrolyte, and the mixture layer being formed into crystals of the sulfide solid electrolyte. and a hot roll press process of roller-pressing while heating at temperature above the temperature, the sulfide solid electrolyte, Li elements contained P element and S elements, PS ₄ ^3- as principal anionic structure Production of an active material layer for an all-solid-state battery, which is a material containing an ionic conductor and LiI, and the linear pressure applied in the hot roll press step is 15 kN / cm or more and 50 kN / cm or less. Provide a method.

According to the present disclosure, an active material for an all-solid-state battery having good output characteristics can be obtained by performing a predetermined hot roll press using an amorphous sulfide solid electrolyte.

In the above disclosure, the linear pressure applied in the hot roll pressing step may be 35 kN / cm or less.

In the above disclosure, the heating temperature in the hot roll pressing step may be 195 ° C. or higher.

In the above disclosure, the heating temperature in the hot roll pressing step is 5 ° C. or more higher than the crystallization temperature of the sulfide solid electrolyte, and the linear pressure applied in the hot roll pressing step is 20 kN / cm or more and 35 kN / cm. It may be as follows.

Further, in the present disclosure, a preparatory step for preparing a mixture layer containing an active material and an amorphous sulfide solid electrolyte, and a crystallization temperature for the mixture layer above the glass transition temperature of the sulfide solid electrolyte. It includes a hot roll press step of rolling pressing while heating at a temperature lower than the above, and a post-heating step of heating the mixture layer at a temperature equal to or higher than the crystallization temperature of the sulfide solid electrolyte after the hot roll pressing step. and, the sulfide solid electrolyte contains a Li element, P element, and S elements, an ion conductor containing PS ₄ ^3- as principal anionic structure, a material containing, and LiI, the hot Provided is a method for producing an active material layer for an all-solid-state battery, wherein the linear pressure applied in the roll press step is 15 kN / cm or more and 50 kN / cm or less.

According to the present disclosure, an active material for an all-solid-state battery having good output characteristics can be obtained by performing a predetermined hot roll press and a predetermined post-heating using an amorphous sulfide solid electrolyte.

In the above disclosure, the linear pressure applied in the hot roll pressing step may be 35 kN / cm or less.

In the above disclosure, the heating temperature in the hot roll pressing step may be 165 ° C. or higher.

Further, in the present disclosure, it is a method for manufacturing an all-solid battery having a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer formed between the positive electrode active material layer and the negative electrode active material layer. The present invention provides a method for producing an all-solid battery, which comprises an active material layer forming step of forming at least one of the positive electrode active material layer and the negative electrode active material layer by the above-mentioned method for producing an active material layer for an all-solid battery. ..

According to the present disclosure, an all-solid-state battery having good output characteristics can be obtained by forming the active material layer by using the above-mentioned production method.

In the present disclosure, it is possible to obtain an active material layer for an all-solid-state battery having good output characteristics.

It is the schematic sectional drawing which shows an example of the manufacturing method of the active material layer for an all-solid-state battery of this disclosure. It is the schematic sectional drawing which illustrates the active material layer for an all-solid-state battery in this disclosure. It is the schematic sectional drawing which shows an example of the manufacturing method of the all-solid-state battery of this disclosure. It is a result of the output characteristics of the all-solid-state battery obtained in Examples 1 to 3 and Comparative Examples 1 to 3. It is a result of the output characteristics of the all-solid-state battery obtained in Examples 4 and 5 and Comparative Examples 1 and 3. It is a result of the filling rate of the positive electrode active material layer produced in Examples 1 to 3 and Comparative Examples 1 and 3.

Hereinafter, the method for producing the active material layer for an all-solid-state battery and the method for producing an all-solid-state battery of the present disclosure will be described in detail. In the present disclosure, the active material layer for an all-solid-state battery may be simply referred to as an "active material layer".

A. Method for Manufacturing Active Material Layer for All-Solid-State Battery FIG. 1 is a schematic cross-sectional view showing an example of the method for manufacturing the active material layer for all-solid-state battery of the present disclosure. In FIG. 1, first, a mixture layer 10a containing an active material 1 and an amorphous sulfide solid electrolyte 2 is prepared (FIG. 1 (a), preparation step). Sulfide solid electrolyte 2 of the amorphous contains a Li element, P element, S element, a material having an ion conductor containing PS ₄ ^3- as principal anionic structure, and LiI, the. Next, the mixture layer 10a is hot-roll pressed at a predetermined temperature and linear pressure (FIG. 1 (b), hot roll press step). During the hot roll press, the sulfide solid electrolyte 2 may be heated at a temperature equal to or higher than the crystallization temperature of the sulfide solid electrolyte 2, or may be heated at a temperature equal to or higher than the glass transition temperature of the sulfide solid electrolyte 2 and lower than the crystallization temperature. In the latter case, it is preferable to heat the mixture layer 10a at a temperature equal to or higher than the crystallization temperature of the sulfide solid electrolyte 2 after the hot roll pressing step (post-heating step). As a result, the active material layer 10 is obtained (FIG. 1 (c)).

According to the present disclosure, an all-solid state having good output characteristics is obtained by performing a predetermined hot roll press or a predetermined hot roll press and a predetermined post-heating using an amorphous sulfide solid electrolyte. An active material for a battery can be obtained. In general, roll presses have the property of being more productive than flat presses. However, when using a roll press, if the linear pressure is too high, the active material layer may crack and the output characteristics may deteriorate, and if the linear pressure is too low, the active material layer cannot be sufficiently densified. , The output characteristics may deteriorate. On the other hand, in the present disclosure, an active material for an all-solid-state battery having good output characteristics can be obtained by performing a hot roll press at a predetermined linear pressure.

Further, in the present disclosure, the Li ion conductivity of the sulfide solid electrolyte can be improved by performing heat treatment (hot roll press or post-heating) at a temperature equal to or higher than the crystallization temperature of the sulfide solid electrolyte. As a result, an active material for an all-solid-state battery having good output characteristics can be obtained. Although it is difficult to predict the effect of the linear pressure of the roll press in a high temperature state of the crystallization temperature or higher, in the present disclosure, as in the examples described later, an active material for an all-solid-state battery having good output characteristics. I was able to get. In particular, good output characteristics were obtained in a range where the linear pressure was relatively low (for example, a range of 15 kN / cm or more and 35 kN / cm or less).

Further, the roll press has a characteristic that the productivity is good but the heating time is shortened as compared with the flat press. Therefore, it is difficult to predict whether the amorphous sulfide solid electrolyte will crystallize sufficiently. However, in the present disclosure, as in the examples described later, the activity for an all-solid-state battery having good output characteristics I was able to get the substance.
Hereinafter, the active material layer for an all-solid-state battery of the present disclosure will be described in more detail.

1. 1. Preparation Step The preparation step in the present disclosure is a step of preparing a mixture layer containing an active material and an amorphous sulfide solid electrolyte. An active material layer can be obtained by heat-treating the mixture layer. The mixture layer may be produced by oneself or may be purchased from another person.

(1) Sulfide solid electrolyte The sulfide solid electrolyte in the present disclosure is amorphous. “Amorphous” refers to a state in which the crystallinity can be improved by heating, and may be completely amorphous or may have slight crystallinity. Further, "completely amorphous" means a state in which no crystal peak is observed by X-ray diffraction. For the sulfide solid electrolyte, it is preferable that a halo pattern is observed, for example, in X-ray diffraction measurement.

Sulfide solid electrolyte in the present disclosure contains a Li element, P element, and S elements, containing the ion conductor containing PS ₄ ^3- as principal anionic structure, and LiI, the. The sulfide solid electrolyte may or may not further contain LiBr. Further, it is preferable that at least a part of LiI and LiBr exists in a state of being incorporated into the structure of the ionic conductor as a LiI component and a LiBr component, respectively.

The ion conductor contains a Li element, P element, and S elements, containing _PS ^{4 3-} as principal anionic structures. PS ₄ ^3- corresponds to the anion structure of the ortho-composition. Ortho generally refers to the highest degree of hydration among oxo acids obtained by hydrating the same oxide. In the present disclosure, that ortho-composition of the crystal composition, appended most Li 2 _S in sulfides. For example, in the Li ₂ SP ₂ S ₅ system, Li ₃ PS ₄ corresponds to the ortho composition.

The "PS ₄ ^3- and mainly anionic structure", the percentage of PS ₄ ^3- is, refers to the most common among all anion structures in the ionic conductor. _PS ^{4 3-} percentage of the total anionic structures are, for example not less than 60 mol%, may be more than 70 mol%, may be more than 80 mol%, may be more than 90 mol%. PS ₄ ^3- ratio of can be determined Raman spectroscopy, NMR, by XPS or the like.

The proportion of LiI in the sulfide solid electrolyte is, for example, 1 mol% or more, and may be 10 mol% or more. On the other hand, the ratio of LiI is, for example, 30 mol% or less, and may be 25 mol% or less. The ratio of LiI is preferably smaller than the ratio of the ionic conductor. The ratio of LiBr in the sulfide solid electrolyte is, for example, 1 mol% or more, and may be 10 mol% or more. On the other hand, the ratio of LiBr is, for example, 30 mol% or less, and may be 25 mol% or less. The ratio of LiBr is preferably smaller than the ratio of the ionic conductor. Further, the total ratio of the LiBr and the LiI is preferably smaller than the ratio of the ionic conductor.

The sulfide solid electrolyte in the present disclosure is preferably a material obtained by amorphizing a raw material composition containing Li ₂ S, P ₂ S ₅ and Li I. In the raw material composition, the ratio of Li ₂ S to the total of Li ₂ S and P ₂ S ₅ is, for example, 72 mol% or more, and may be 74 mol% or more. On the other hand, the ratio of the Li ₂ S is, for example, less 78 mol%, may be not more than 76 mol%. Examples of the method for amorphizing the raw material composition include mechanical milling and melt quenching. Mechanical milling is a method of mixing raw material compositions while applying mechanical energy, and examples thereof include ball mills and vibration mills.

The crystallization temperature of the sulfide solid electrolyte is, for example, 170 ° C. or higher, 180 ° C. or higher, or 190 ° C. or higher. On the other hand, the crystallization temperature of the sulfide solid electrolyte is, for example, 230 ° C. or lower, and may be 210 ° C. or lower. Further, as the shape of the sulfide solid electrolyte, for example, a particulate form can be mentioned. The average particle size (D ₅₀ ) of the sulfide solid electrolyte is, for example, 0.1 μm or more, and may be 0.5 μm or more. On the other hand, the average particle size (D ₅₀ ) is, for example, 50 μm or less, and may be 5 μm or less. The average particle size can be calculated from, for example, measurement by a laser diffraction type particle size distribution meter or a scanning electron microscope (SEM). The proportion of the sulfide solid electrolyte in the mixture layer is, for example, 1% by volume or more, and may be 10% by volume or more. On the other hand, the proportion of the sulfide solid electrolyte is, for example, 60% by volume or less, and may be 50% by volume or less.

(2) Active Material The active material in the present disclosure preferably has heat resistance sufficient to withstand the hot roll press process described later. An example of an active material is an oxide active material. Examples of the oxide active material include rock salt layered active materials such as LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , LiVO ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiMn ₂ O ₄ , Li ( Examples thereof include spinel-type active materials such as Ni _0.5 Mn _1.5 ) O ₄ and olivine-type active materials such as LiFePO ₄ , LiMnPO ₄ , LiNiPO ₄ , and LiCuPO ₄ .

Further, the surface of the active material may be coated with a coat layer. The coat layer can suppress the reaction between the active material and the sulfide solid electrolyte. Examples of the coat layer include Li ion conductive oxides such as LiNbO ₃ , Li ₃ PO ₄ , and LiPON. The average thickness of the coat layer is, for example, 1 nm or more. On the other hand, the average thickness of the coat layer is, for example, 20 nm or less, and may be 10 nm or less.

Examples of the shape of the active material include particulate matter. The average particle size (D ₅₀ ) of the active material is, for example, 0.1 μm or more and 50 μm or less. The average particle size can be calculated from, for example, measurement by a laser diffraction type particle size distribution meter or a scanning electron microscope (SEM). Further, the ratio of the active material in the mixture layer is, for example, 40% by volume or more, and may be 50% by volume or more. On the other hand, the ratio of the active material is, for example, 99% by volume or less, and may be 80% by volume or less.

(3) Mixture layer The mixture layer contains at least an active material and an amorphous sulfide solid electrolyte. Further, the mixture layer may contain at least one of a conductive material and a binder. Examples of the conductive material include carbon materials such as acetylene black, ketjen black, and carbon fiber. Examples of the binder include a fluorine-based binder such as PVdF and PTFE, a rubber binder such as butadiene rubber, and an acrylic binder.

For example, as shown in FIG. 2A, the mixture layer 10a may have the base material 11 on one surface side. The base material is not particularly limited as long as it is a member capable of holding the mixture layer, but is preferably a current collector. This is because the manufacturing process of the all-solid-state battery can be simplified. The material of the current collector is typically metal. Examples of materials suitable for the positive electrode current collector include SUS, aluminum, nickel, iron, titanium, and carbon. On the other hand, examples of materials suitable for the negative electrode current collector include SUS, copper, nickel, and carbon.

Further, for example, as shown in FIG. 2B, the mixture layer 10a may have the solid electrolyte layer 12 on one surface side. In FIG. 2B, the base material 11, the mixture layer 10a, and the solid electrolyte layer 12 are laminated in this order. The solid electrolyte layer preferably contains a sulfide solid electrolyte. As the sulfide solid electrolyte, for example, the same material as the sulfide solid electrolyte described above can be exemplified. Further, the sulfide solid electrolyte contained in the solid electrolyte layer may be amorphous or crystalline.

Further, although not shown, the mixture layer may have a solid electrolyte layer and a counterpolar active material layer on one surface side. In this case, the power generation elements (positive electrode active material layer, solid electrolyte layer, negative electrode active material layer) of the all-solid-state battery can be efficiently obtained.

(4) Method for producing a mixture layer The method for producing a mixture layer is not particularly limited as long as it can obtain a desired mixture layer, and examples thereof include a slurry method. In the slurry method, a mixture layer is obtained by applying a slurry to a substrate and drying it.

Examples of the method for preparing the slurry include a method of kneading an active material and an amorphous sulfide solid electrolyte in a dispersion medium. The dispersion medium is preferably a material that does not react with the active material and the amorphous sulfide solid electrolyte. Examples of the kneading method include an ultrasonic homogenizer, a shaker, a thin film rotating mixer, a dissolver, a homomixer, a kneader, a roll mill, a sand mill, an attritor, a ball mill, a vibrator mill, a high-speed impeller mill and the like. Examples of the coating method include a doctor blade method, a die coating method, a gravure coating method, a spray coating method, an electrostatic coating method, a bar coating method and the like.

2. 2. Hot roll pressing step and post-heating step The hot roll pressing step in the present disclosure is a step of rolling pressing the mixture layer while heating it at a predetermined temperature. Further, the post-heating step in the present disclosure is a step of heating the mixture layer at a predetermined temperature after the hot roll pressing step.

The linear pressure applied in the hot roll press step is usually 15 kN / cm or more, and may be 20 kN / cm or more. If the linear pressure is too low, the output characteristics may not be sufficiently improved. On the other hand, the linear pressure is usually 50 kN / cm or less, may be 40 kN / cm or less, or may be 35 kN / cm or less. If the linear pressure is too high, a short circuit may easily occur.

In the present disclosure, it is preferable to heat the sulfide solid electrolyte at a temperature equal to or higher than the crystallization temperature during the hot roll press. The crystallization temperature of the sulfide solid electrolyte can be measured, for example, by thermal analysis (DTA, DSC). Let T _c be the crystallization temperature of the sulfide solid electrolyte. In the present disclosure, the hot roll press may be heated at a temperature of (T _c + 3) ° C. or higher, may be heated at a temperature of (T _c + 5) ° C. or higher, or may be heated at a temperature of (T _c + 10) ° C. or higher. It may be heated at the temperature of. On the other hand, the upper limit of the heating temperature is not particularly limited, but may be, for example, (T _c + 50) ° C. or (T _c + 30) ° C. The heating temperature in the hot roll press is, for example, 195 ° C. or higher, may be 200 ° C. or higher, may be 205 ° C. or higher, or may be 210 ° C. or higher. On the other hand, the heating temperature is, for example, 245 ° C. or lower, and may be 225 ° C. or lower.

Further, it is preferable that the heating temperature in the hot roll pressing step is 5 ° C. or more higher than T _c , and the linear pressure applied in the hot roll pressing step is 20 kN / cm or more and 35 kN / cm or less. This is because the output characteristics equivalent to those when the linear pressure is relatively high (for example, when the linear pressure is 50 kN / cm) can be obtained. Since the linear pressure is low, for example, the roll press apparatus can be miniaturized and the production efficiency can be improved. The heating temperature may be higher 10 ° C. or higher than T _c, may be higher 15 ℃ higher than T _c.

On the other hand, in the present disclosure, at the time of hot roll pressing, the sulfide solid electrolyte is heated at a temperature equal to or higher than the glass transition temperature and lower than the crystallization temperature, and then heated at a temperature equal to or higher than the crystallization temperature of the sulfide solid electrolyte. It is preferable to carry out the step. The glass transition temperature ( _TG ) of the sulfide solid electrolyte can be measured, for example, by thermal analysis (DTA, DSC). In the present disclosure, the hot roll press may be heated at a temperature of ( _TG +5) ° C. or higher, may be heated at a temperature of ( _TG +10) ° C. or higher, or may be heated at a temperature of ( _TG +15) ° C. or higher. It may be heated at the temperature of. The heating temperature in the hot roll press is, for example, 165 ° C. or higher, 170 ° C. or higher, or 175 ° C. or higher. Further, in the present disclosure, the post-heating may be performed at a temperature of (T _c + 3) ° C. or higher, or may be heated at a temperature of (T _c + 5) ° C. or higher, or (T _c + 10) ° C. It may be heated at the above temperature. On the other hand, the upper limit of the heating temperature is not particularly limited, but may be, for example, (T _c + 50) ° C. or (T _c + 30) ° C. The heating temperature in the post-heating may be, for example, 195 ° C. or higher, 200 ° C. or higher, 205 ° C. or higher, or 210 ° C. or higher. On the other hand, the heating temperature is, for example, 245 ° C. or lower, and may be 225 ° C. or lower.

The heating method in the hot roll pressing step is not particularly limited, and examples thereof include a method using a heated roll and a method using a furnace. Further, the heating method in the post-heating step is not particularly limited, and examples thereof include a method using a furnace.

In the hot roll pressing step, the feed rate of the roll is not particularly limited as long as the desired active material layer can be obtained, but may be, for example, 100 m / min or less, and may be 10 m / min or less. On the other hand, the feed rate of the roll may be, for example, 0.1 m / min or more, 0.3 m / min or more, or 0.5 m / min or more. Further, the heating time in the post-heating step is not particularly limited. Examples of the heating atmosphere include an inert gas atmosphere (for example, Ar gas atmosphere) and a reduced pressure atmosphere.

3. 3. Active material layer for all-solid-state batteries The active material layer for all-solid-state batteries obtained by the present disclosure contains an active material and a crystalline sulfide solid electrolyte.

The crystalline sulfide solid electrolyte preferably has high Li ion conductivity. Above all, the sulfide solid electrolyte preferably has peaks at 2θ = 20.2 ° ± 0.5 ° and 23.6 ° ± 0.5 ° in the X-ray diffraction measurement using CuKα ray. This peak is a peak of a crystal phase having high Li ion conductivity. In addition, this crystal phase may be referred to as a high Li ion conduction phase. In addition to 2θ = 20.2 ° and 23.6 °, the high Li ion conduction phase usually peaks at 2θ = 29.4 °, 37.8 °, 41.1 °, and 47.0 °. Have. These peak positions may also move back and forth within a range of ± 0.5 °.

The crystalline sulfide solid electrolyte preferably has no peak at 2θ = 21.0 ° ± 0.5 ° and 28.0 ° ± 0.5 ° in the X-ray diffraction measurement using CuKα ray. This peak is a peak of a crystal phase having lower Li ion conductivity than a high Li ion conductive phase. In addition, this crystal phase may be referred to as a low Li ion conduction phase. In addition to 2θ = 21.0 ° and 28.0 °, the low Li ion conduction phase is usually 2θ = 32.0 °, 33.4 °, 38.7 °, 42.8 °, 44. It has a peak at 2 °. These peak positions may also move back and forth within a range of ± 0.5 °. The value (I _21.0 / I _20.2 ) of the peak intensity (I _21.0 ) of 2θ = 21.0 ° with respect to the peak intensity (I _20.2 ) of 2θ = _20.2 ° is, for example, 0. It is 4 or less, preferably 0.2 or less, and more preferably 0.1 or less. In addition, I _21.0 / I _20.2 may be 0.

The crystalline sulfide solid electrolyte preferably has a small half-value width of the peak of 2θ = 20.2 °, which is the peak of the high Li ion conductive phase. The full width at half maximum is, for example, 0.51 ° or less, preferably 0.50 ° or less, and more preferably 0.45 ° or less. The full width at half maximum refers to the full width at half maximum (FWHM) of the peak at 2θ = 20.2 °.

The active material layer preferably has a high filling rate. This is because the output characteristics are improved. The filling rate of the active material layer is, for example, 84% or more, may be 86% or more, or may be 88% or more. On the other hand, the filling rate of the active material layer is, for example, 100% or less. The thickness of the active material layer is, for example, 0.1 μm or more and 1000 μm or less. Further, the active material layer may be used in an all-solid-state battery and may be used as a positive electrode active material layer or a negative electrode active material layer.

B. Manufacturing Method of All-Solid State Battery FIG. 3 is a schematic cross-sectional view showing an example of the manufacturing method of the all-solid-state battery of the present disclosure. Note that FIG. 3 shows a case where the method described in "A. Method for producing active material layer for all-solid-state battery" is applied when forming the positive electrode active material layer.

In FIG. 3, first, a laminate having the positive electrode current collector 24, the mixture layer 21a serving as the positive electrode active material layer, and the first solid electrolyte layer 23a in this order is prepared (FIG. 3A). Next, the above-mentioned hot roll press step is performed on this laminate to obtain a positive electrode laminate having a positive electrode current collector 24, a positive electrode active material layer 21, and a first solid electrolyte layer 23a in this order (FIG. FIG. 3 (b)). Next, a negative electrode laminate having the negative electrode current collector 25, the negative electrode active material layer 22, and the second solid electrolyte layer 23b in this order is prepared by an arbitrary method (FIG. 3 (c)). Next, the first solid electrolyte layer 23a of the positive electrode laminate is arranged on one surface side of the intermediate solid electrolyte layer 23c, and the second solid electrolyte layer 23b of the negative electrode laminate is arranged on the other surface side (FIG. 3 (d)). By pressing this laminate in the thickness direction, the positive electrode active material layer 21, the negative electrode active material layer 22, and the solid electrolyte layer 23 formed between the positive electrode active material layer 21 and the negative electrode active material layer 22 An all-solid-state battery 20 having a positive electrode current collector 24 that collects electricity from the positive electrode active material layer 21 and a negative electrode current collector 25 that collects electricity from the negative electrode active material layer 22 can be obtained (FIG. 3 (e)).

According to the present disclosure, an all-solid-state battery having good output characteristics can be obtained by forming the active material layer by using the above-mentioned production method. In the present disclosure, at least one of the positive electrode active material layer and the negative electrode active material layer is formed by the method described in "A. Method for producing active material layer for all-solid-state battery". The other steps, for example, the solid electrolyte layer forming step of forming the solid electrolyte layer are not particularly limited, and any method can be adopted.

The all-solid-state battery is usually a lithium-ion battery. The all-solid-state battery may be a primary battery or a secondary battery, but is preferably a secondary battery. This is because it can be repeatedly charged and discharged, and is useful as an in-vehicle battery, for example. Examples of the shape of the all-solid-state battery include a coin type, a laminated type, a cylindrical type, and a square type.

The present disclosure is not limited to the above embodiment. The above embodiment is an example, and any object having substantially the same structure as the technical idea described in the claims of the present disclosure and exhibiting the same effect and effect is the present invention. Included in the technical scope of the disclosure.

The present disclosure will be described in more detail.

[Manufacturing example]
As starting materials, lithium sulfide _(Li 2 S, manufactured by Nippon Chemical Industrial Co., Ltd.) was used diphosphorus pentasulfide _(P 2 _{S 5,} Aldrich) and lithium iodide (LiI, Aldrich). Next, Li ₂ S, P ₂ S ₅ and Li I were weighed to a molar ratio of 15 LiI · 85 (0.75 Li ₂ S · 0.25 P ₂ S ₅ ). The weighed starting ingredients were mixed in an agate mortar for 5 minutes, the mixture was placed in a planetary ball mill container (manufactured by ZrO ₂ ), dehydrated heptane was added, and ZrO ₂ balls were added, and the container was completely sealed. .. This container was attached to a planetary ball mill machine (P7 manufactured by Fritsch), and mechanical milling was performed at a base rotation speed of 500 rpm for 40 hours. Then, heptane was removed by drying at 100 ° C. to obtain sulfide glass (amorphous sulfide solid electrolyte A). The amorphous sulfide solid electrolyte A had a glass transition temperature of 100 ° C. to 150 ° C. and a crystallization temperature of 195 ° C.

The obtained sulfide glass was placed in a glass tube, and the glass tube was placed in a closed container made of SUS. The closed container was heat-treated at 195 ° C. for 10 hours to obtain glass ceramics (crystalline sulfide solid electrolyte B). The obtained glass ceramics peaked at 2θ = 20.2 °, 23.6 °, 29.4 °, 37.8 °, 41.1 °, and 47.0 ° in XRD measurement using CuKα ray. These peaks correspond to the peaks of the high Li ion conductive phase.

[Example 1]
(Positive electrode active material layer preparation process)
The positive electrode mixture as a raw material for the positive electrode active material layer was placed in a polypropylene (PP) container. This is stirred with an ultrasonic disperser (manufactured by SMT, model: UH-50) for a total of 150 seconds, and shaken with a shaker (manufactured by Shibata Kagaku Co., Ltd., model: TTM-1) for a total of 20 minutes. To prepare a positive electrode active material slurry.

Using an applicator, this positive electrode active material slurry was applied onto an Al foil as a positive electrode current collector by the blade method. This was dried on a hot plate at 100 ° C. for 30 minutes to form a positive electrode active material layer (mixture layer) on the positive electrode current collector.

The composition of the positive electrode mixture is as follows.
-LiNi _1/3 Co _1/3 Mn _1/3 O ₂ as positive electrode active material (average particle size 6 μm)
-Butyl butyrate as a dispersion medium-VGCF as a conductive aid
-Butyl butyrate solution of PVdF binder as a binder (5% by mass)
Amorphous sulfide solid electrolyte A as a sulfide solid electrolyte (average particle size 0.5 μm)

(Negative electrode active material layer preparation process)
The negative electrode mixture as a raw material for the negative electrode active material layer was placed in a polypropylene (PP) container. This is stirred with an ultrasonic disperser (manufactured by SMT, model: UH-50) for a total of 120 seconds, and shaken with a shaker (manufactured by Shibata Kagaku Co., Ltd., model: TTM-1) for a total of 20 minutes. To prepare a negative electrode active material slurry.

Using an applicator, this negative electrode active material slurry was applied onto Cu foil as a negative electrode current collector by the blade method. This was dried on a hot plate at 100 ° C. for 30 minutes to form a negative electrode active material layer on the negative electrode current collector.

The composition of the negative electrode mixture is as follows.
-Natural graphite-based carbon as a negative electrode active material (manufactured by Mitsubishi Chemical Corporation, average particle size 10 μm)
-Butyl butyrate as a dispersion medium-Butyl butyrate solution of PVdF-based binder as a binder (5% by mass)
-Li ₂ SP ₂ S ₅ series glass ceramics containing LiI as a sulfide solid electrolyte (average particle size 0.5 μm)

(First solid electrolyte layer preparation process)
The electrolyte mixture as a raw material for the first solid electrolyte layer was placed in a polypropylene (PP) container. This is stirred with an ultrasonic disperser (manufactured by SMT, model: UH-50) for 30 seconds, and shaken with a shaker (manufactured by Shibata Kagaku Co., Ltd., model: TTM-1) for 30 minutes. A first solid electrolyte slurry was prepared.

Using an applicator, the first solid electrolyte slurry was applied onto the Al foil as a release sheet by the blade method. This was dried on a hot plate at 100 ° C. for 30 minutes to form a first solid electrolyte layer on the release sheet.

The composition of the electrolyte mixture is as follows.
-Li ₂ SP ₂ S ₅ series glass ceramics containing LiI as a sulfide solid electrolyte (average particle size 2.0 μm)
-Heptane as a dispersion medium-Heptane solution of BR-based binder as a binder (5% by mass)

(Second solid electrolyte layer preparation process)
A second solid electrolyte layer was formed on the release sheet in the same manner as in the first solid electrolyte layer preparation step.

(Intermediate solid electrolyte layer preparation process)
The electrolyte mixture as a raw material for the intermediate solid electrolyte layer was placed in a polypropylene (PP) container. This is stirred with an ultrasonic disperser (manufactured by SMT, model: UH-50) for 30 seconds, and shaken with a shaker (manufactured by Shibata Scientific Technology, model: TTM-1) for 30 minutes. An intermediate solid electrolyte slurry was prepared.

Using an applicator, the intermediate solid electrolyte slurry was applied onto the Al foil as a release sheet by the blade method. This was dried on a hot plate at 100 ° C. for 30 minutes to obtain a release sheet and a transfer sheet having an intermediate solid electrolyte layer.

The composition of the electrolyte mixture is as follows.
-Li ₂ SP ₂ S ₅ glass containing LiI as a sulfide solid electrolyte (average particle size 1.0 μm)
-Heptane as a dispersion medium-Heptane solution of BR-based binder as a binder (5% by mass)

(Positive electrode laminate manufacturing process)
The positive electrode current collector, the positive electrode active material layer (mixture layer), and the first solid electrolyte layer were laminated in this order. This laminate was set in a roll press machine and pressed at a press pressure of 15 kN / cm and a press temperature of 195 ° C. (feed speed 0.5 m / min) as the first press step to obtain a positive electrode laminate. The feed rate of 0.5 m / min corresponds to a speed of moving about 1 cm per second, and the time during which the mixture layer is in contact with the roll (heating and pressurizing time) is extremely shorter than that of a flat press. The press temperature is the temperature of the roll surface measured by a non-contact thermometer. Further, the press pressure was changed to 25 kN / cm, 35 kN / cm, and 50 kN / cm to obtain a positive electrode laminate in the same manner.

(Negative electrode laminate manufacturing process)
The negative electrode current collector, the negative electrode active material layer, and the second solid electrolyte layer were laminated in this order. This laminate was set in a roll press machine and pressed at a press pressure of 20 kN / cm and a press temperature of 25 ° C. as a second press step to obtain a negative electrode laminate.

Next, the negative electrode laminate and the transfer sheet were laminated so that the second solid electrolyte layer of the negative electrode laminate and the intermediate solid electrolyte layer of the transfer sheet faced each other. This laminate was set in a flat uniaxial press and pressed at a press pressure of 100 MPa and a press temperature of 25 ° C. for 10 seconds. Then, the transfer sheet was peeled off to obtain a negative electrode laminate having an intermediate solid electrolyte layer.

The negative electrode laminate and the positive electrode laminate were prepared so that the area of the negative electrode laminate was larger than the area of the positive electrode laminate. The area ratio of the positive electrode laminate and the negative electrode laminate was 1.00: 1.08.

(All-solid-state battery manufacturing process)
The positive electrode laminate and the negative electrode laminate having the intermediate solid electrolyte layer were laminated so that the first solid electrolyte layer of the positive electrode laminate and the intermediate solid electrolyte layer faced each other. This laminate was set in a flat uniaxial press and pressed for 1 minute at a press pressure of 200 MPa and a press temperature of 120 ° C. as a third press step. As a result, an all-solid-state battery was obtained.

[Example 2]
An all-solid-state battery was obtained in the same manner as in Example 1 except that the press temperature in the positive electrode laminate manufacturing step was changed to 205 ° C.

[Example 3]
An all-solid-state battery was obtained in the same manner as in Example 1 except that the press temperature in the positive electrode laminate manufacturing step was changed to 215 ° C.

[Example 4]
An all-solid-state battery was obtained in the same manner as in Example 1 except that the process for producing the positive electrode laminate was changed as follows. Specifically, the positive electrode current collector, the positive electrode active material layer (mixture layer), and the first solid electrolyte layer were laminated in this order. This laminate is set in a roll press machine, and as the first pressing step, it is pressed at a pressing pressure of 15 kN / cm and a pressing temperature of 165 ° C. (feeding speed 0.5 m / min), and then 195 on a hot plate for 5 minutes. After heating at ° C., a positive electrode laminate was obtained. Further, the press pressure was changed to 25 kN / cm, 35 kN / cm, and 50 kN / cm to obtain a positive electrode laminate in the same manner.

[Example 5]
An all-solid-state battery was obtained in the same manner as in Example 1 except that the post-heating temperature was changed to 205 ° C.

[Comparative Example 1]
All of the same as in Example 1 except that the sulfide solid electrolyte used for the positive electrode active material layer was changed to the crystalline sulfide solid electrolyte B and the press temperature in the positive electrode laminate manufacturing step was changed to 165 ° C. Obtained a solid state battery.

[Comparative Example 2]
All of the same as in Example 1 except that the sulfide solid electrolyte used for the positive electrode active material layer was changed to the crystalline sulfide solid electrolyte B and the press temperature in the positive electrode laminate manufacturing step was changed to 205 ° C. Obtained a solid state battery.

[Comparative Example 3]
An all-solid-state battery was obtained in the same manner as in Example 1 except that the press temperature in the positive electrode laminate manufacturing step was changed to 165 ° C. Table 1 shows the state of the sulfide solid electrolyte, the press temperature, and the post-heating temperature in each Example and each Comparative Example.

[Evaluation]
[Output characteristic evaluation]
The output characteristics of the all-solid-state batteries obtained in Examples 1 to 5 and Comparative Examples 1 to 3 were evaluated. Specifically, after CCCV charging to 4.4 V at 0.3 mA, CCCV discharging was performed to 3.0 V at 0.3 mA. Then, the battery was charged again to 3.5 V, a constant output discharge was performed between 60 mW and 180 mW, and an output value capable of discharging to 2.5 V for 5 seconds was determined. In Comparative Example 1, the output value of the all-solid-state battery manufactured under the condition of the press pressure of 50 kN / cm was set to 100, and the output characteristics (output ratio) of each all-solid-state battery were evaluated. The results are shown in FIGS. 4 and 5.

As shown in FIG. 4, Examples 1 to 3 had better output characteristics than Comparative Examples 1 to 3. In Comparative Example 1, the output characteristic was significantly lowered as the linear pressure was lowered, but in Examples 1 to 3, the deterioration of the output characteristic was suppressed even when the linear pressure was lowered. In particular, Examples 2 and 3 in which the press temperature is 5 ° C. or higher higher than the crystallization temperature of the sulfide solid electrolyte are 50 kN / cm even in the range of linear pressure of 20 kN / cm or more and 35 kN / cm or less (range of low linear pressure). The same output characteristics as in the case of were obtained. In this way, it was suggested that raising the press temperature higher than the crystallization temperature is suitable for the characteristics of the roll press (the characteristic that the production efficiency is higher but the heating time is shorter than that of the flat press). ..

Further, in Comparative Example 2, even when a crystalline sulfide solid electrolyte was used, the output characteristics were improved as compared with Comparative Example 1 by raising the press temperature. However, also in Comparative Example 2, as in Comparative Example 1, the lower the linear pressure, the greater the deterioration of the output characteristics. Further, when comparing Example 2 and Comparative Example 2 having the same press temperature, the output characteristics of Example 2 were significantly improved as compared with Comparative Example 2. In Comparative Example 3, an amorphous sulfide solid electrolyte is used, but since it is heated at a temperature lower than the crystallization temperature, the Li ion conductivity of the sulfide solid electrolyte is not improved, which is good. No output characteristics were obtained.

Further, as shown in FIG. 5, in Examples 4 and 5 in which the post-heating was performed at a temperature equal to or higher than the crystallization temperature, the same tendency as in Examples 1 to 3 was observed, and even if the linear pressure became low, The deterioration of output characteristics was suppressed.

[Measurement of filling rate]
The filling rate of the positive electrode active material layer prepared in Examples 1 to 3 and Comparative Examples 1 and 3 was measured. First, the apparent density of the positive electrode active material layer was calculated from the area, thickness and mass of the positive electrode active material layer (apparent density of the positive electrode active material layer = mass / (thickness × area)). Next, the true density of the positive electrode active material layer was calculated from the true density and content of the constituent components of the positive electrode active material layer. (True density of positive electrode active material layer = mass / Σ (content of each component / true density of each component)). The apparent density with respect to the true density was defined as the filling factor. The result is shown in FIG.

As shown in FIG. 6, in Examples 1 to 3 and Comparative Example 3, the filling rate was higher than that in Comparative Example 1. This is because the positive electrode active material layer is densified by applying heat equal to or higher than the glass transition temperature of the sulfide solid electrolyte to the positive electrode active material layer containing the amorphous sulfide solid electrolyte during hot roll pressing. It was suggested that In particular, when the linear pressure was 20 kN / cm or more, Examples 1 to 3 had a higher filling rate than Comparative Example 3. Further, in Comparative Example 3, the positive electrode active material layer is densified, but as shown in FIG. 4 described above, Comparative Example 3 has lower output characteristics than Examples 1 to 3.

1… Active material 2… Amorphous sulfide solid electrolyte 10a… Mixed material layer 10… Active material layer 11… Base material 12… Solid electrolyte layer 20… All-solid battery 21a… Mixed material layer 21… Positive electrode active material layer 22 … Negative electrode active material layer 23… Solid electrolyte layer 24… Positive electrode current collector 25… Negative electrode current collector

Claims (8)

A preparatory step to prepare a mixture layer containing an active material and an amorphous sulfide solid electrolyte, and
It has a hot roll pressing step of rolling pressing the mixture layer while heating it at a temperature equal to or higher than the crystallization temperature of the sulfide solid electrolyte.
The sulfide solid electrolyte contains a Li element, P element, and S elements, an ion conductor containing PS ₄ ^3- as principal anionic structure, a material containing a LiI,,
A method for producing an active material layer for an all-solid-state battery, wherein the linear pressure applied in the hot roll press step is 15 kN / cm or more and 50 kN / cm or less. The method for producing an active material layer for an all-solid-state battery according to claim 1, wherein the linear pressure applied in the hot roll press step is 35 kN / cm or less. The method for producing an active material layer for an all-solid-state battery according to claim 1 or 2, wherein the heating temperature in the hot roll press step is 195 ° C. or higher. The heating temperature in the hot roll press step is 5 ° C. or higher higher than the crystallization temperature of the sulfide solid electrolyte.
The production of the active material layer for an all-solid-state battery according to any one of claims 1 to 3, wherein the linear pressure applied in the hot roll press step is 20 kN / cm or more and 35 kN / cm or less. Method. A preparatory step to prepare a mixture layer containing an active material and an amorphous sulfide solid electrolyte, and
A hot roll press step of rolling pressing the mixture layer while heating it at a temperature equal to or higher than the glass transition temperature of the sulfide solid electrolyte and lower than the crystallization temperature.
After the hot roll press step, the mixture layer has a post-heating step of heating the mixture layer at a temperature equal to or higher than the crystallization temperature of the sulfide solid electrolyte.
The sulfide solid electrolyte contains a Li element, P element, and S elements, an ion conductor containing PS ₄ ^3- as principal anionic structure, a material containing a LiI,,
A method for producing an active material layer for an all-solid-state battery, wherein the linear pressure applied in the hot roll press step is 15 kN / cm or more and 50 kN / cm or less. The method for producing an active material layer for an all-solid-state battery according to claim 5, wherein the linear pressure applied in the hot roll press step is 35 kN / cm or less. The method for producing an active material layer for an all-solid-state battery according to claim 5 or 6, wherein the heating temperature in the hot roll press step is 165 ° C. or higher. A method for manufacturing an all-solid-state battery, which comprises a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer formed between the positive electrode active material layer and the negative electrode active material layer.
Forming an active material layer in which at least one of the positive electrode active material layer and the negative electrode active material layer is formed by the method for producing an active material layer for an all-solid-state battery according to any one of claims 1 to 7. A method for manufacturing an all-solid-state battery having a step.

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