Composition, battery, and method for manufacturing the composition

Abstract

A composition of the present disclosure includes a compound including Li and at least one selected from the group consisting of Zr, Al, and F, and a solvent. The compound is particulate and has an average particle size of less than 0.68 μm. A battery 1000 of the present disclosure includes a positive electrode 201, a negative electrode 203, and an electrolyte layer 202 provided between the positive electrode 201 and the negative electrode 203, wherein at least one selected from the group consisting of the positive electrode 201, the negative electrode 203, and the electrolyte layer 202 includes the solidified composition of the present disclosure.

Description

Technical Field

[0001] The present disclosure relates to a composition, a battery, and a method for manufacturing the composition.

Background Art

[0002] Patent Document 1 discloses an all-solid-state battery using a sulfide solid electrolyte.

[0003] Patent Document 2 discloses LiBF4 as a fluoride solid electrolyte material.

Prior Art Documents

Non-Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present disclosure is to provide a composition suitable for improving the ionic conductivity of a solid electrolyte material.

Means for Solving the Problems

[0006] The composition of the present disclosure includes a compound containing at least one selected from the group consisting of Zr, Al, and F and Li, a solvent, and the compound is in particulate form and has an average particle diameter of less than 0.68 μm.

Effects of the Invention

[0007] The present disclosure provides a composition suitable for improving the ionic conductivity of a solid electrolyte material.

Brief Description of the Drawings

[0008] [Figure 1] Figure 1 shows a cross-sectional view of the battery 1000 according to the second embodiment. [Figure 2A] Figure 2A shows a scanning electron microscope (SEM) image obtained to evaluate the particle size of the particles contained in the composition according to Example 1. [Figure 2B] Figure 2B shows an SEM image obtained to evaluate the particle size of the particles contained in the composition according to Example 2. [Figure 2C] Figure 2C shows an SEM image obtained to evaluate the particle size of the particles contained in the composition according to Example 3. [Figure 2D] Figure 2D shows an SEM image obtained to evaluate the particle size of the particles contained in the composition according to Example 4. [Figure 2E] [[ID=第十九]]Figure 2E shows an SEM image obtained to evaluate the particle size of the particles contained in the composition according to Example 5. [Figure 2F] Figure 2F shows an SEM image obtained to evaluate the particle size of the particles contained in the composition according to Example 6. [Figure 2G] Figure 2G shows an SEM image obtained to evaluate the particle size of the particles contained in the composition according to Example 7. [Figure 2H] Figure 2H shows an SEM image obtained to evaluate the particle size of the particles contained in the composition according to Example 8. <000011)]] [Figure 2I] Figure 2I shows an SEM image obtained to evaluate the particle size of the particles contained in the composition according to Example 9. [Figure 2J] Figure 2J shows an SEM image obtained to evaluate the particle size of the particles contained in the composition according to Example 10. [Figure 2K] Figure 2K shows an SEM image obtained to evaluate the particle size of the particles contained in the composition according to Example 11. [Figure 2L] )]] [Figure 2L] Figure 2L shows an SEM image obtained to evaluate the particle size of the particles contained in the composition according to Example 12. [Figure 2M]Figure 2M shows an SEM image obtained to evaluate the particle size of the particles contained in the composition according to Example 13. [Figure 2N] Figure 2N shows an SEM image obtained to evaluate the particle size of the particles contained in the composition according to Example 14. [Figure 2O] Figure 2O shows an SEM image obtained to evaluate the particle size of the particles contained in the composition according to Reference Example 1. [Figure 3] Figure 3 shows a schematic diagram of a pressure-molding die 300 used to evaluate the ionic conductivity of a solid electrolyte material. [Figure 4] Figure 4 is a graph showing the Cole-Cole plot obtained by impedance measurement of the solid electrolyte material according to Example 1. [Figure 5] Figure 5 is a graph showing the initial discharge characteristics of batteries according to Example 1 and Comparative Example 1. [Modes for carrying out the invention]

[0009] Embodiments of the present disclosure will be described below with reference to the drawings.

[0010] (First Embodiment) The composition according to the first embodiment comprises a compound containing at least one selected from the group consisting of Zr, Al, and F, and Li, and a solvent. The compound is particulate and has an average particle diameter of less than 0.68 μm. The average particle diameter of the particulate compound is determined by morphological observation using SEM images. Specifically, first the composition according to the first embodiment is dried (e.g., vacuum dried) to extract the particles of the compound, and an SEM image of the particles is obtained. Forty primary particles of the compound are randomly selected from the obtained SEM image, the directional diameter (Ferret diameter) of the selected primary particles is measured, the particle diameters of the bottom 10 of the 40 particles are discarded, and the average particle diameter is calculated by the simple average of the particle diameters of the remaining 30 particles.

[0011] The composition according to the first embodiment is suitable for improving the ionic conductivity of solid electrolyte materials.

[0012] The solidified product (i.e., solid electrolyte material) obtained by removing the solvent from the composition according to the first embodiment is a solid electrolyte material having improved lithium ion conductivity. In the solvent removal process, the solid electrolyte material is generated when heat is applied to the compounds contained in the composition according to the first embodiment. In order to efficiently advance this generation reaction, it is desirable that the particle size of the particles dispersed in the composition be small. Specifically, if the average particle size is less than 0.68 μm, the generation reaction proceeds efficiently, and a solid electrolyte material with improved ionic conductivity can be obtained. Furthermore, if the raw materials react with each other during the process of micronization or dispersion of the raw materials to form a precursor of the solid electrolyte material, it is expected that the generation reaction of the solid electrolyte material will proceed even more efficiently.

[0013] To further improve the ionic conductivity of the resulting solid electrolyte material, the average particle size of the compound contained in the composition according to the first embodiment may be 0.5 μm or less, 0.3 μm or less, or 0.2 μm or less. The lower limit of the average particle size of the compound is not particularly limited, but the average particle size may be, for example, 0.01 μm or more.

[0014] The solid electrolyte material obtained from the composition of the first embodiment (hereinafter referred to as "solid electrolyte material according to the first embodiment") can be used to obtain a battery with excellent charge-discharge characteristics. An example of such a battery is an all-solid-state battery. The all-solid-state battery may be a primary battery or a secondary battery.

[0015] The solvent included in the composition according to the first embodiment may contain a compound having at least one functional group selected from the group consisting of ester groups and hydroxyl groups. The inclusion of compounds having these functional groups as a solvent allows for efficient reduction of the particle size of dispersed particles, i.e., the above compound, in the composition according to the first embodiment.

[0016] The solvent included in the composition according to the first embodiment may include at least one selected from the group consisting of γ-butyrolactone, propylene carbonate, butyl acetate, ethanol, dimethyl sulfoxide, and tetralin.

[0017] The composition according to the first embodiment may be prepared, for example, by using a planetary ball mill to grind a compound such as LiF, ZrF4, or AlF3 in a mixed state with a solvent, thereby simultaneously micronizing and dispersing the compound. With such a method, the synthesis, micronization, and slurrying of the solid electrolyte material can be carried out simultaneously, and it is expected that the number of steps can be reduced.

[0018] As described above, the compounds included in the composition according to the first embodiment may be raw materials for solid electrolyte materials. For example, the compounds included in the composition according to the first embodiment may be raw materials for solid electrolytes containing Li, Zr, Al, and F.

[0019] The composition according to the first embodiment may contain at least one compound selected from the group consisting of LiF, Li2ZrF6, and Li3AlF6.

[0020] The solid electrolyte material according to the first embodiment is preferably sulfur-free. Sulfur-free solid electrolyte materials do not generate hydrogen sulfide when exposed to the atmosphere, thus offering superior safety. The sulfide solid electrolyte disclosed in Patent Document 1 may generate hydrogen sulfide when exposed to the atmosphere.

[0021] When the composition according to the first embodiment contains F, the solid electrolyte material according to the first embodiment may have high oxidation resistance because it contains F. This is because F has a high oxidation-reduction potential. On the other hand, because F has high electronegativity, it has a relatively strong bond with Li. As a result, the lithium ion conductivity of solid electrolyte materials containing Li and F is usually low. For example, LiBF4 disclosed in Patent Document 2 has a conductivity of 6.67 × 10⁻⁶. -9It has a low ionic conductivity of S / cm. In contrast, if the solid electrolyte material obtained from the composition of Embodiment 1 further contains Zr and Al in addition to Li and F, for example, it has an ionic conductivity of 7 × 10⁻⁶. -9 It can have a high ionic conductivity of S / cm or higher.

[0022] To enhance the ionic conductivity of the solid electrolyte material, the solid electrolyte material according to the first embodiment may contain anions other than F. Examples of such anions are Cl, Br, I, O, or Se.

[0023] To improve the oxidation resistance of the solid electrolyte material, the ratio of the amount of substance of F to the total amount of substance of the anions constituting the solid electrolyte material according to the first embodiment may be 0.50 or more and 1.0 or less.

[0024] The solid electrolyte material according to the first embodiment may consist substantially of Li, Zr, Al, and F. Here, "the solid electrolyte material according to the first embodiment consists substantially of Li, Zr, Al, and F" means that the ratio (i.e., mole fraction) of the total amount of substance of Li, Zr, Al, and F to the total amount of substance of all elements constituting the solid electrolyte material according to the first embodiment is 90% or more. For example, this ratio (i.e., mole fraction) may be 95% or more. The solid electrolyte material according to the first embodiment may consist only of Li, Zr, Al, and F.

[0025] The solid electrolyte material according to the first embodiment may contain elements that are inevitably mixed in. Examples of such elements are hydrogen, oxygen, or nitrogen. Such elements may be present in the raw material powder of the solid electrolyte material or in the atmosphere used for manufacturing or storing the solid electrolyte material.

[0026] To further enhance the ionic conductivity of the solid electrolyte material, in the solid electrolyte material according to the first embodiment, the ratio of the amount of Li to the total amount of Zr and Al may be 1.12 or more and 5.07 or less.

[0027] The solid electrolyte material according to the first embodiment may be a material represented by the following compositional formula (1).

[0028] Li 6-(4-x)b (Zr 1-x Al x ) b F6···(1) In formula (1), the mathematical formulas: 0 < x < 1, and 0 < b ≤ 1.5 are satisfied. The solid electrolyte material containing such a crystal phase has high ionic conductivity.

[0029] That is, the composition according to the first embodiment contains Li, Zr, Al, and F, and in the composition according to the first embodiment, Li, Zr, Al, and F may satisfy a molar ratio of Li:Zr:Al:F = [6 - (4 - x)b]:(1 - x)b:xb:6. In this case, x and y satisfy 0 < x < 1, and 0 < b ≤ 1.5.

[0030] In order to increase the ionic conductivity of the solid electrolyte material, in formula (1), the mathematical formula: 0.01 ≤ x ≤ 0.99 may be satisfied. Desirably, the mathematical formula: 0.2 ≤ x ≤ 0.95 may be satisfied.

[0031] The upper limit value and the lower limit value of the range of x in formula (1) may be defined by any combination selected from the numerical values of 0.01, 0.2, 0.4, 0.5, 0.5, 0.7, 0.8, 0.95, and 0.99.

[0032] In order to increase the ionic conductivity of the solid electrolyte material, in formula (1), the mathematical formula: 0.7 ≤ b ≤ 1.3 may be satisfied. Desirably, the mathematical formula:​​​​​​​The solid electrolyte material according to the first embodiment is Li 2.8 Zr 0.2 Al 0.8 It may be F6.

[0035] The solid electrolyte material according to the first embodiment may be crystalline or amorphous.

[0036] The shape of the solid electrolyte material according to the first embodiment is not limited. Examples of the shape are needle-like, spherical, or ellipsoidal. The solid electrolyte material obtained from the composition of the first embodiment may be particles. The solid electrolyte material obtained from the composition of the first embodiment may have the shape of a pellet or a plate.

[0037] <Manufacturing method of the composition> The composition according to the first embodiment is manufactured, for example, by the following method.

[0038] A raw material composition containing a compound containing at least one selected from the group consisting of Zr, Al, and F and Li, and a solvent (for example, an organic solvent) are mixed while being pulverized in a mixing device. The raw material composition may further contain, in addition to the above compound, another compound serving as a raw material for the solid electrolyte material, depending on the composition of the intended solid electrolyte material.

[0039] As an example, when the composition of the intended solid electrolyte material is Li 2.8 Zr 0.2 Al 0.8 F6, LiF, ZrF4, and AlF3 are prepared at a molar ratio of about 2.8:0.2:0.8. The raw material powder may be mixed at a pre-adjusted molar ratio so as to offset the compositional changes that may occur in the synthesis process. The raw material powder (raw material composition) and the organic solvent are put into a mixing device such as a planetary ball mill and mixed while being pulverized. That is, wet ball milling is performed. The raw material powder may be mixed before being put into the mixing device.

[0040] The composition according to the first embodiment is obtained by separating the balls after mixing. At this time, the added raw material composition is also pulverized, and it is expected that the particle size of the particles of the raw material composition dispersed in the solvent in the composition according to the first embodiment will be smaller than that of the added raw material. The particle size of the dispersed raw material composition particles can be determined, for example, by the same method as the method for determining the average particle size of the particulate compound in the composition according to the first embodiment described above.

[0041] <Method for manufacturing solid electrolyte materials> The solid electrolyte material according to the first embodiment is obtained from the composition according to the first embodiment. For example, it is manufactured by the following method.

[0042] A solid product is obtained by drying the composition according to the first embodiment at a temperature corresponding to the boiling point of the solvent used. The resulting solid is then crushed, for example, in a mortar and pestle to obtain a reaction product, i.e., the solid electrolyte material according to the first embodiment.

[0043] The resulting reaction product may be calcined in a vacuum or an inert atmosphere. Calcination is carried out, for example, at a temperature of 100°C or higher and 300°C or lower for at least one hour. To suppress compositional changes during calcination, calcination may be carried out in a sealed container such as a quartz tube.

[0044] (Second Embodiment) The second embodiment will now be described. Matters described in the first embodiment will be omitted as appropriate.

[0045] The battery according to the second embodiment comprises a positive electrode, an electrolyte layer, and a negative electrode. The electrolyte layer is located between the positive electrode and the negative electrode.

[0046] At least one selected from the group consisting of a positive electrode, an electrolyte layer, and a negative electrode contains a solidified product of the composition according to the first embodiment (i.e., a solid electrolyte material according to the first embodiment).

[0047] The battery according to the second embodiment has excellent charge and discharge characteristics because it contains the solid electrolyte material according to the first embodiment.

[0048] Figure 1 shows a cross-sectional view of the battery 1000 according to the second embodiment.

[0049] The battery 1000 according to the second embodiment comprises a positive electrode 201, an electrolyte layer 202, and a negative electrode 203. The electrolyte layer 202 is provided between the positive electrode 201 and the negative electrode 203.

[0050] The positive electrode 201 contains a positive electrode active material 204 and a solid electrolyte 100.

[0051] The electrolyte layer 202 contains an electrolyte material.

[0052] The negative electrode 203 contains a negative electrode active material 205 and a solid electrolyte 100.

[0053] The solid electrolyte 100 includes, for example, the solid electrolyte material according to the first embodiment. The solid electrolyte 100 may also be particles containing the solid electrolyte material according to the first embodiment as the main component. Particles containing the solid electrolyte material according to the first embodiment as the main component mean particles in which the most abundant component in terms of molar ratio is the solid electrolyte material according to the first embodiment. The solid electrolyte 100 may also be particles made of the solid electrolyte material according to the first embodiment.

[0054] The positive electrode 201 contains a material capable of intercalating and releasing metal ions (e.g., lithium ions). This material is, for example, the positive electrode active material 204.

[0055] Examples of positive electrode active material 204 include lithium-containing transition metal oxides, transition metal fluorides, polyanions, fluorinated polyanion materials, transition metal sulfides, transition metal oxyfluorides, transition metal oxysulfides, or transition metal oxynitrides. Examples of lithium-containing transition metal oxides include Li(Ni,Co,Mn)O2, Li(Ni,Co,Al)O2, or LiCoO2.

[0056] In this disclosure, "(A, B, C)" means "at least one selected from the group consisting of A, B, and C."

[0057] The shape of the positive electrode active material 204 is not limited to a specific shape. The positive electrode active material 204 may be particles. The positive electrode active material 204 may have a median diameter of 0.1 μm or more and 100 μm or less. When the positive electrode active material 204 has a median diameter of 0.1 μm or more, the positive electrode active material 204 and the solid electrolyte 100 can be well dispersed in the positive electrode 201. This improves the charge and discharge characteristics of the battery 1000. When the positive electrode active material 204 has a median diameter of 100 μm or less, the lithium diffusion rate within the positive electrode active material 204 is improved. This allows the battery 1000 to operate at high power.

[0058] The positive electrode active material 204 may have a median diameter larger than that of the solid electrolyte 100. This allows the positive electrode active material 204 and the solid electrolyte 100 to be well dispersed in the positive electrode 201.

[0059] In order to improve the energy density and output of the battery 1000, the ratio of the volume of the positive electrode active material 204 to the sum of the volume of the positive electrode active material 204 and the volume of the solid electrolyte 100 in the positive electrode 201 may be 0.30 or more and 0.95 or less.

[0060] A coating layer may be formed on at least a portion of the surface of the positive electrode active material 204. The coating layer can be formed on the surface of the positive electrode active material 204, for example, before mixing with a conductive additive and a binder. Examples of coating materials included in the coating layer are sulfide solid electrolytes, oxide solid electrolytes, or halide solid electrolytes. If the solid electrolyte 100 contains a sulfide solid electrolyte, the coating material may contain the solid electrolyte material according to the first embodiment in order to suppress the oxidative decomposition of the sulfide solid electrolyte. If the solid electrolyte 100 contains the solid electrolyte material according to the first embodiment, the coating material may contain an oxide solid electrolyte in order to suppress the oxidative decomposition of the solid electrolyte material. As the oxide solid electrolyte, lithium niobate, which has excellent stability at high potentials, may be used. By suppressing oxidative decomposition, the overvoltage rise of the battery 1000 can be suppressed.

[0061] To improve the energy density and output of battery 1000, the positive electrode 201 may have a thickness of 10 μm or more and 500 μm or less.

[0062] The electrolyte layer 202 contains an electrolyte material. This electrolyte material is, for example, a solid electrolyte material. This solid electrolyte material may include the solid electrolyte material according to the first embodiment. The electrolyte layer 202 may also be a solid electrolyte layer.

[0063] The electrolyte layer 202 may contain 50% by mass or more of the solid electrolyte material according to the first embodiment. The electrolyte layer 202 may contain 70% by mass or more of the solid electrolyte material according to the first embodiment. The electrolyte layer 202 may contain 90% by mass or more of the solid electrolyte material according to the first embodiment. The electrolyte layer 202 may consist only of the solid electrolyte material according to the first embodiment.

[0064] Hereinafter, the solid electrolyte material according to the first embodiment will be referred to as the first solid electrolyte material. A solid electrolyte material different from the first solid electrolyte material will be referred to as the second solid electrolyte material.

[0065] The electrolyte layer 202 may contain not only a first solid electrolyte material but also a second solid electrolyte material. In the electrolyte layer 202, the first solid electrolyte material and the second solid electrolyte material may be uniformly dispersed. The layer made of the first solid electrolyte material and the layer made of the second solid electrolyte material may be stacked along the stacking direction of the battery 1000.

[0066] The battery according to the second embodiment may comprise a positive electrode 201, a second electrolyte layer, a first electrolyte layer, and a negative electrode 203 in this order. Here, the solid electrolyte material contained in the first electrolyte layer may have a lower reduction potential than the solid electrolyte material contained in the second electrolyte layer. This allows the solid electrolyte material contained in the second electrolyte layer to be used without reduction. As a result, the charge and discharge efficiency of the battery 1000 can be improved. For example, if the second electrolyte layer contains the first solid electrolyte material, the first electrolyte layer may contain a sulfide solid electrolyte to suppress the reductive decomposition of the solid electrolyte material. This improves the charge and discharge efficiency of the battery 1000. The second electrolyte layer may also contain the first solid electrolyte material. Since the first solid electrolyte material has high oxidation resistance, a battery with excellent charge and discharge characteristics can be realized.

[0067] The electrolyte layer 202 may consist solely of the second solid electrolyte material.

[0068] The electrolyte layer 202 may have a thickness of 1 μm or more and 1000 μm or less. If the electrolyte layer 202 has a thickness of 1 μm or more, the positive electrode 201 and the negative electrode 203 are less likely to short-circuit. If the electrolyte layer 202 has a thickness of 1000 μm or less, the battery 1000 can operate at high output.

[0069] Examples of second solid electrolyte materials are Li2MgX4, Li2FeX4, Li(Al,Ga,In)X4, Li3(Al,Ga,In)X6, or LiI, where X is at least one selected from the group consisting of F, Cl, Br, and I.

[0070] To improve the energy density and output of the battery 1000, the electrolyte layer 202 may have a thickness of 1 μm or more and 1000 μm or less.

[0071] The negative electrode 203 contains a material capable of intercalating and releasing metal ions (e.g., lithium ions). This material is, for example, the negative electrode active material 205.

[0072] Examples of negative electrode active materials 205 are metallic materials, carbon materials, oxides, nitrides, tin compounds, or silicon compounds. Metallic materials may be elemental metals or alloys. Examples of metallic materials are lithium metal or lithium alloys. Examples of carbon materials are natural graphite, coke, carbon in the process of graphitization, carbon fibers, spheroidal carbon, artificial graphite, or amorphous carbon. From the viewpoint of capacity density, preferred examples of negative electrode active materials are silicon (i.e., Si), tin (i.e., Sn), silicon compounds, or tin compounds.

[0073] The negative electrode active material 205 may be selected considering the reduction resistance of the solid electrolyte material contained in the negative electrode 203. For example, if the negative electrode 203 contains a first solid electrolyte material, the negative electrode active material 205 may be a material capable of intercalating and releasing lithium ions at a voltage of 0.27 V or higher relative to lithium. Examples of such negative electrode active materials are titanium oxide, indium metal, or lithium alloy. An example of titanium oxide is Li4Ti5O 12 The negative electrode active material is either LiTi2O4 or TiO2. By using the above negative electrode active material, the reductive decomposition of the first solid electrolyte material contained in the negative electrode 203 can be suppressed. As a result, the charge and discharge efficiency of the battery 1000 can be improved.

[0074] The shape of the negative electrode active material 205 is not limited to a specific shape. The negative electrode active material 205 may be particles. The negative electrode active material 205 may have a median diameter of 0.1 μm or more and 100 μm or less. When the negative electrode active material 205 has a median diameter of 0.1 μm or more, the negative electrode active material 205 and the solid electrolyte 100 can be well dispersed in the negative electrode 203. This improves the charge and discharge characteristics of the battery 1000. When the negative electrode active material 205 has a median diameter of 100 μm or less, the lithium diffusion rate within the negative electrode active material 205 is improved. This allows the battery 1000 to operate at high power.

[0075] The negative electrode active material 205 may have a larger median diameter than the solid electrolyte 100. This allows the negative electrode active material 205 and the solid electrolyte 100 to be well dispersed in the negative electrode 203.

[0076] In order to improve the energy density and output of the battery 1000, the ratio of the volume of the negative electrode active material 205 to the sum of the volume of the negative electrode active material 205 and the volume of the solid electrolyte 100 in the negative electrode 203 may be 0.30 or more and 0.95 or less.

[0077] To improve the energy density and output of the battery 1000, the negative electrode 203 may have a thickness of 10 μm or more and 500 μm or less.

[0078] At least one selected from the group consisting of a positive electrode 201, an electrolyte layer 202, and a negative electrode 203 may contain a second solid electrolyte material for the purpose of enhancing ionic conductivity, chemical stability, and electrochemical stability.

[0079] The second solid electrolyte material may be a sulfide solid electrolyte.

[0080] Examples of sulfide solid electrolytes include Li2S-P2S5, Li2S-SiS2, Li2S-B2S3, Li2S-GeS2, and Li 3.25 Ge 0.25 P 0.75 S4, or Li 10 GeP2S12 That is the case.

[0081] If the electrolyte layer 202 contains a first solid electrolyte material, the negative electrode 203 may contain a sulfide solid electrolyte to suppress the reductive decomposition of the solid electrolyte material. By covering the negative electrode active material with an electrochemically stable sulfide solid electrolyte, contact between the first solid electrolyte material and the negative electrode active material can be suppressed. As a result, the internal resistance of the battery 1000 can be reduced.

[0082] The second solid electrolyte material may be an oxide solid electrolyte.

[0083] Examples of oxide solid electrolytes are: (i) NASICON-type solid electrolytes such as LiTi2(PO4)3 or its elemental substitutions, (ii) Perovskite-type solid electrolytes such as (LaLi)TiO3, (iii) Li 14 ZnGe4O 16 , LISICON-type solid electrolytes such as Li4SiO4, LiGeO4 or their elementally substituted counterparts, (iv)Li7La3Zr2O 12 or a garnet-type solid electrolyte such as an elemental substitution thereof, (v) Li3PO4 or its N-substituted derivatives, That is the case.

[0084] As described above, the second solid electrolyte material may be a halide solid electrolyte.

[0085] Examples of halide solid electrolytes are Li2MgX4, Li2FeX4, Li(Al,Ga,In)X4, Li3(Al,Ga,In)X6, or LiI, where X is at least one selected from the group consisting of F, Cl, Br, and I.

[0086] Other examples of halide solid electrolytes include Li a Me b Y cThis is a compound represented by Z6. Here, a+mb+3c=6 and c>0 are satisfied. Me is at least one selected from the group consisting of metallic elements other than Li and Y and metalloid elements. Z is at least one selected from the group consisting of F, Cl, Br, and I. m represents the valence of Me. "Metalloid elements" are B, Si, Ge, As, Sb, and Te. "Metallic elements" are all elements in groups 1 through 12 of the periodic table (except hydrogen), and all elements in groups 13 through 16 of the periodic table (except B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se).

[0087] To improve the ionic conductivity of the halide solid electrolyte, Me may be at least one selected from the group consisting of Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta, and Nb.

[0088] The halide solid electrolyte may be Li3YCl6 or Li3YBr6.

[0089] The second solid electrolyte material may be an organic polymer solid electrolyte.

[0090] Examples of organic polymer solid electrolytes include polymer compounds and lithium salt compounds.

[0091] Polymer compounds may have an ethylene oxide structure. Polymer compounds having an ethylene oxide structure can contain a large amount of lithium salt, and therefore their ionic conductivity can be further increased.

[0092] Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), or LiC(SO2CF3)3. One lithium salt selected from these may be used alone, or a mixture of two or more lithium salts selected from these may be used.

[0093] At least one selected from the group consisting of the positive electrode 201, the electrolyte layer 202, and the negative electrode 203 may contain a non-aqueous electrolyte, a gel electrolyte, or an ionic liquid to facilitate the transfer of lithium ions and improve the output characteristics of the battery.

[0094] The non-aqueous electrolyte contains a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent.

[0095] Examples of non-aqueous solvents include cyclic carbonate solvents, linear carbonate solvents, cyclic ether solvents, linear ether solvents, cyclic ester solvents, linear ester solvents, or fluorinated solvents. Examples of cyclic carbonate solvents are ethylene carbonate, propylene carbonate, or butylene carbonate. Examples of linear carbonate solvents are dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate. Examples of cyclic ether solvents are tetrahydrofuran, 1,4-dioxane, or 1,3-dioxolane. Linear ether solvents are 1,2-dimethoxyethane or 1,2-diethoxyethane. An example of a cyclic ester solvent is γ-butyrolactone. An example of a linear ester solvent is methyl acetate. Examples of fluorinated solvents are fluoroethylene carbonate, methyl fluoropropionate, fluorobenzene, fluoroethyl methyl carbonate, or fluorodimethylene carbonate. One non-aqueous solvent selected from these may be used alone, or a combination of two or more non-aqueous solvents selected from these may be used.

[0096] Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), or LiC(SO2CF3)3. One lithium salt selected from these may be used alone, or a mixture of two or more lithium salts selected from these may be used. The concentration of the lithium salt is, for example, in the range of 0.5 mol / L or more and 2 mol / L or less.

[0097] Polymer materials impregnated with a non-aqueous electrolyte can be used as the gel electrolyte. Examples of polymer materials include polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, or polymers having ethylene oxide bonds.

[0098] Examples of cations contained in ionic liquids are: (i) aliphatic chain quaternary salts such as tetraalkylammonium or tetraalkylphosphonium, (ii) Aliphatic cyclic ammonium compounds such as pyrrolidiniums, morpholiniums, imidazoliniums, tetrahydropyrimidiniums, piperadiniums, or piperidiniums, (iii) Nitrogen-containing heterocyclic aromatic cations such as pyridinium or imidazolium That is the case.

[0099] An example of anion contained in an ionic liquid is PF6. - BF4 - SbF6 - AsF6 - , SO3CF3 - , N(SO2CF3)2 - , N(SO2C2F5)2 - , N(SO2CF3)(SO2C4F9) - , or C(SO2CF3)3 - That is the case.

[0100] The ionic liquid may contain lithium salts.

[0101] At least one selected from the group consisting of a positive electrode 201, an electrolyte layer 202, and a negative electrode 203 may contain a binder to improve the adhesion between particles.

[0102] Examples of binders include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aramid resins, polyamides, polyimides, polyamide-imides, polyacrylonitrile, polyacrylic acid, polymethyl acrylate, polyethyl acrylate, polyhexyl acrylate, polymethacrylic acid, polymethyl methacrylate, polyethyl methacrylate, polyhexyl methacrylate, polyvinyl acetate, polyvinylpyrrolidone, polyethers, polyethersulfone, hexafluoropolypropylene, styrene-butadiene rubber, or carboxymethylcellulose. Copolymers can also be used as binders. Examples of such binders are copolymers of two or more materials selected from the group consisting of tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinylidene fluoride, chlorotrifluoroethylene, ethylene, propylene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid, and hexadiene. A mixture of two or more materials selected from these may also be used as a binder.

[0103] At least one of the positive electrode 201 and the negative electrode 203 may contain a conductive additive to improve electronic conductivity.

[0104] Examples of conductive additives are: (i) Graphites such as natural graphite or artificial graphite, (ii) Carbon blacks such as acetylene black or Ketjen black, (iii) Conductive fibers such as carbon fibers or metal fibers, (iv) Carbon fluoride, (v) Metal powders such as aluminum, (vi) Conductive whiskers such as zinc oxide or potassium titanate, (vii) Conductive metal oxides such as titanium oxide, or (viii) Conductive polymer compounds such as polyaniline, polypyrrole, or polythiophene, Therefore, to reduce costs, the conductive additives described in (i) or (ii) above may be used.

[0105] Examples of battery shapes according to the second embodiment include coin-shaped, cylindrical, prismatic, sheet-shaped, button-shaped, flat, or stacked types.

[0106] The battery according to the second embodiment may be manufactured, for example, by preparing a material for forming a positive electrode, a material for forming an electrolyte layer, and a material for forming a negative electrode, and then fabricating a laminate in which the positive electrode, electrolyte layer, and negative electrode are arranged in that order by a known method. [Examples]

[0107] The present disclosure will be described in more detail below with reference to examples and comparative examples.

[0108] <Example 1> (Creation of a portrait) In an argon atmosphere with a dew point of -60°C or lower (hereinafter referred to as a "dry argon atmosphere"), LiF, ZrF4, and AlF3 were prepared as raw material powders in a molar ratio of LiF:ZrF4:AlF3 = 2.8:0.2:0.8. These raw material powders, along with 1 mmΦ balls (25 g), were placed in a 45 cc pod for a planetary ball mill. γ-butyrolactone (GBL) was added dropwise to the pod as an organic solvent to achieve a solid content ratio of 50%. Here, the solid content ratio is calculated as {(mass of raw materials) / (mass of raw materials + mass of solvent)} × 100. Milling was performed using a planetary ball mill at 500 rpm for 12 hours. After milling, the balls were separated to obtain the composition according to Example 1.

[0109] (Evaluation of dispersed particle size) To the composition from Example 1, GBL was added to achieve a solid content ratio of 10%, and the mixture was thoroughly stirred. The dispersed particles were extracted by vacuum drying the diluted composition at 50°C. If high heat is applied when removing the solvent, the particles may fuse together upon solidification, making accurate evaluation of particle size difficult. Therefore, vacuum drying is preferable when evaluating the particle size of dispersed particles.

[0110] To make the grain boundaries of the extracted dispersed particles more visible, the particles were leveled in a mortar as needed. A scanning electron microscope (SEM, Hitachi High-Tech Innovations, Regulus8230) was used for morphological observation. In the obtained SEM images, 40 primary particles were randomly selected, and the directional diameter of the selected primary particles was measured. The diameters of the bottom 10 particles were discarded, and the average particle diameter was calculated by simply averaging the diameters of the remaining 30 particles. The observation magnification was 50,000x. Figure 2A shows an SEM image obtained to evaluate the particle size of the particles contained in the composition according to Example 1. The average particle diameter of the dispersed particles in Example 1 was 0.127 μm.

[0111] (Preparation of solid electrolyte materials) The composition according to Example 1 was dried at 200°C for 1 hour under a nitrogen flow using a mantle heater. The resulting solid was ground in a mortar to obtain the powder of the solid electrolyte material according to Example 1. The solid electrolyte material according to Example 1 is Li 2.8 Zr 0.2 Al 0.8 It had a composition represented by F6.

[0112] (Evaluation of ionic conductivity) Figure 3 shows a schematic diagram of a pressure-molding die 300 used to evaluate the ionic conductivity of a solid electrolyte material.

[0113] The pressure forming die 300 comprised a punch upper section 301, a frame 302, and a punch lower section 303. The frame 302 was formed from insulating polycarbonate. The punch upper section 301 and the punch lower section 303 were formed from electronically conductive stainless steel.

[0114] Using the pressure molding die 300 shown in Figure 3, the ionic conductivity of the solid electrolyte material according to Example 1 was evaluated by the following method.

[0115] In a dry atmosphere having a dew point of -30°C or lower, the powder of the solid electrolyte material according to Example 1 was filled into the inside of a pressure molding die 300. Inside the pressure molding die 300, a pressure of 400 MPa was applied to the solid electrolyte material according to Example 1 using the upper part of the punch 301 and the lower part of the punch 303.

[0116] With pressure still applied, the upper part 301 and lower part 303 of the punch were connected to a potentiostat (BioLogic, VSP300) equipped with a frequency response analyzer. The upper part 301 of the punch was connected to the working electrode and potential measurement terminals. The lower part 303 of the punch was connected to the counter electrode and reference electrode. The impedance of the solid electrolyte material was measured at room temperature using electrochemical impedance measurement.

[0117] Figure 4 is a graph showing the Cole-Cole plot obtained by impedance measurement of the solid electrolyte material according to Example 1.

[0118] In Figure 4, the real value of the impedance at the measurement point where the absolute value of the phase of the complex impedance is smallest was considered to be the resistance value to ion conduction of the solid electrolyte material. This real value is indicated by the arrow R in Figure 4. SE Refer to [reference]. Using the resistance value, the ionic conductivity was calculated based on the following formula (2).

[0119] σ=(R SE ×S / t) -1 ...(2) Here, σ represents the ionic conductivity. S represents the contact area between the solid electrolyte material and the upper part 301 of the punch. That is, S is equal to the cross-sectional area of ​​the hollow part of the frame 302 in Figure 3. SEt represents the resistance value of the solid electrolyte material in impedance measurement. t represents the thickness of the solid electrolyte material. That is, in Figure 3, t represents the thickness of the layer formed from the powder 101 of the solid electrolyte material.

[0120] The ionic conductivity of the solid electrolyte material obtained from the composition according to Example 1, measured at 25°C, was 4.92 × 10⁻⁶. -7 The value was S / cm.

[0121] (Battery construction) In a dry argon atmosphere, the solid electrolyte material and the active material LiCoO2 according to Example 1 were prepared in a volume ratio of 30:70. These materials were mixed in an agate mortar. In this way, a cathode mixture was obtained.

[0122] In an insulating cylinder with an inner diameter of 9.5 mm, Li3PS4 (57.41 mg), the solid electrolyte material according to Example 1 (26 mg), and the above-mentioned positive electrode mixture (9.1 mg) were layered in this order. A pressure of 300 MPa was applied to the resulting laminate to form a first electrolyte layer, a second electrolyte layer, and a positive electrode. That is, the second electrolyte layer formed from the solid electrolyte material according to Example 1 was sandwiched between the first electrolyte layer and the positive electrode. The thicknesses of the first and second electrolyte layers were 450 μm and 150 μm, respectively.

[0123] Next, metallic Li (thickness: 200 μm) was laminated onto the first electrolyte layer. A pressure of 80 MPa was applied to the resulting laminate to form a negative electrode.

[0124] Next, current collectors made of stainless steel were attached to the positive and negative electrodes, and current collector leads were attached to the current collectors.

[0125] Finally, an insulating ferrule was used to isolate the inside of the insulating cylinder from the outside atmosphere, thereby sealing the inside of the cylinder. In this way, the battery according to Example 1 was obtained.

[0126] (Charge / Discharge Test) Figure 5 is a graph showing the initial discharge characteristics of the battery according to Example 1. The initial charge-discharge characteristics were measured by the following method.

[0127] The battery according to Example 1 was placed in a constant temperature bath at 85°C.

[0128] 13.5 μA / cm 2 The battery according to Example 1 was charged to a voltage of 4.2V at a current density of 0.01C.

[0129] Next, 13.5 μA / cm 2 The battery according to Example 1 was discharged until it reached a voltage of 2.5V at the given current density.

[0130] The charge-discharge test results showed that the battery according to Example 1 had an initial discharge capacity of 943 μAh.

[0131] <Examples 2 to 14> (Preparation of compositions and solid electrolyte materials) In Examples 2 to 14, LiF, ZrF4, and AlF3 were prepared as raw material powders in a molar ratio of LiF:ZrF4:AlF3 = 2.8:0.2:0.8.

[0132] The solvent type, solid content ratio, ball diameter, ball quantity, and processing time for the milling process of the composition are shown in Table 1.

[0133] The compositions according to Examples 2 to 13 were obtained in the same manner as in Example 1, except for the conditions shown in Table 1.

[0134] In Example 14, LiF, ZrF4, and AlF3 were prepared as raw material powders in a molar ratio of LiF:ZrF4:AlF3 = 2.8:0.2:0.8. These raw material powders were milled using a planetary ball mill at 500 rpm for 12 hours with ethanol as the solvent. The resulting slurry, after separating the balls, was dried at 100°C for 1 hour. In this way, a finely powdered raw material mixture (hereinafter referred to as "fine raw material") was obtained. The fine raw material and GBL were added to a screw tube so that the solid content ratio was 30%, and the mixture was stirred using a stirrer to obtain the composition according to Example 14.

[0135] (Evaluation of dispersed particles) In the same manner as in Example 1, dispersed particles were extracted from the compositions of Examples 2 to 14 and evaluated by SEM. The particle sizes of the dispersed particles are shown in Table 1. Figures 2B to 2N show SEM images obtained to evaluate the particle sizes of the particles contained in the compositions of Examples 2 to 14, respectively.

[0136] (Preparation of solid electrolyte materials) Using the compositions from Examples 2 to 14, solid electrolyte materials according to Examples 2 to 14 were obtained in the same manner as in Example 1, except for the drying conditions shown in Table 1.

[0137] (Evaluation of ionic conductivity) The ionic conductivity of the solid electrolyte materials in Examples 2 to 14 was measured in the same manner as in Example 1. The results are shown in Table 1.

[0138] (Charge / Discharge Test) Using the solid electrolyte materials from Examples 2 to 14, batteries according to Examples 2 to 13 were obtained in the same manner as in Example 1.

[0139] A charge-discharge test was performed using the batteries from Examples 2 to 14 in the same manner as in Example 1. As a result, the batteries from Examples 2 to 14 charged and discharged well, similar to the battery from Example 1.

[0140] <Reference example 1> In a dry argon atmosphere, LiF, ZrF4, and AlF3 were prepared as raw material powders in a molar ratio of LiF:ZrF4:AlF3 = 2.8:0.2:0.8. These raw material powders were ground and mixed in a mortar. The resulting mixture and GBL were added to a screw-cap tube to a solid content ratio of 30%, and stirred using a stirring bar. In this way, the composition according to Reference Example 1 was obtained.

[0141] As described above, ball milling was not performed in Reference Example 1.

[0142] By drying the composition according to Reference Example 1 in the same manner as in Example 1, a solid electrolyte material according to Reference Example 1 was obtained.

[0143] In Reference Example 1, the ionic conductivity of the solid electrolyte material and the particle size of the dispersed particles were measured in the same manner as in Example 1. Figure 2O shows an SEM image obtained to evaluate the particle size of the particles contained in the composition according to Reference Example 1.

[0144] The ionic conductivity measured at 25°C was unmeasurable due to the high resistance value. This is thought to be because the average particle size of the compounds contained in the composition according to Reference Example 1 was large, at 0.68 μm or more, and therefore the compound with the desired composition (i.e., the solid electrolyte material) was not formed.

[0145] <Comparative Example 1> LiBF4 was used as the solid electrolyte material, and the ionic conductivity was measured in the same manner as in Example 1 above. As a result, the ionic conductivity measured at 25°C was 6.67 × 10⁻⁶. -9 The value was S / cm.

[0146] A battery according to Comparative Example 1 was obtained in the same manner as in Example 1, except that the solid electrolyte material from Comparative Example 2 was used as the solid electrolyte for the positive electrode mixture and the electrolyte layer.

[0147] A charge-discharge test was performed using the battery from Comparative Example 1 in the same manner as in Example 1. Figure 5 is a graph showing the initial discharge characteristics of the battery from Comparative Example 1. As a result, the initial discharge capacity of the battery from Comparative Example 1 was 0.01 μAh or less. In other words, the battery from Comparative Example 1 neither charged nor discharged.

[0148] [Table 1]

[0149] <Consideration> The solidified product obtained by drying the compositions from Examples 1 to 14, i.e., the solid electrolyte material from Examples 1 to 14, has a viscosity of 7 × 10 at room temperature. -9 It has ionic conductivity of S / cm or higher.

[0150] In contrast to the compositions of Examples 1 to 13, in which the raw material compositions were pulverized using a wet ball mill in GBL (Glass Ball Liquid), the composition of Example 14 was prepared by dispersing pre-finely pulverized raw material particles in GBL, the solvent constituting the composition. However, the solid electrolyte material prepared using the composition of Example 14 had an ionic conductivity comparable to that of the solid electrolyte materials prepared using the compositions of Examples 1 to 13. This confirms that pulverizing the raw material compositions in the solvent constituting the composition is not essential, and that compositions obtained by using pre-finely pulverized raw material compositions and dispersing them in a solvent are also suitable for improving the ionic conductivity of solid electrolyte materials.

[0151] On the other hand, the powder obtained by drying the composition according to Reference Example 1 was not a compound with the desired composition, as described above, and therefore its lithium ion conductivity could not be confirmed.

[0152] Therefore, it can be said that the smaller the particle size of the particles dispersed in the composition, the more efficiently solid electrolyte materials can be produced.

[0153] The solid electrolyte materials according to Examples 1 to 14 do not contain sulfur, and therefore do not generate hydrogen sulfide.

[0154] As described above, the compositions according to this disclosure can provide a solid electrolyte material having high lithium-ion conductivity and are suitable for providing a battery that can be charged and discharged well. [Industrial applicability]

[0155] The compositions of this disclosure are used, for example, in all-solid-state lithium-ion secondary batteries. [Explanation of symbols]

[0156] 100 solid electrolyte 101 Powder of solid electrolyte material 201 Positive electrode 202 Electrolyte layer 203 Negative electrode 204 Cathode active material 205 Anode active material 300 pressure molding dies 301 Punch Top 302 Frame type 303 Punch bottom 1000 batteries

Claims

1. A compound comprising at least one selected from the group consisting of Zr, Al, and F, and Li, Solvent and, A composition comprising, The compound is particulate and has an average particle diameter of less than 0.68 μm. The composition comprises Li, Zr, Al, and F. Li, Zr, Al, and F satisfy the molar ratio Li:Zr:Al:F = [6-(4-x)b]:(1-x)b:xb:

6. The conditions 0 < x < 1 and 0 < b ≤ 1.5 are satisfied. composition.

2. The above composition contains LiF, Li as the compound 2 ZrF 6 , and Li 3 AlF 6 Includes at least one selected from the group consisting of, The composition according to claim 1.

3. The solvent comprises a compound having at least one functional group selected from the group consisting of ester groups and hydroxyl groups. The composition according to claim 1.

4. The solvent comprises at least one selected from the group consisting of γ-butyrolactone, propylene carbonate, butyl acetate, ethanol, dimethyl sulfoxide, and tetralin. The composition according to claim 1.

5. The aforementioned compound is a raw material for a solid electrolyte material. The composition according to claim 1.

6. positive electrode, Negative electrode, and An electrolyte layer provided between the positive electrode and the negative electrode, Equipped with, At least one selected from the group consisting of the positive electrode, the negative electrode, and the electrolyte layer contains a solidified product of the composition described in any one of claims 1 to 5. battery.

7. A method for producing the composition according to any one of claims 1 to 5, The process includes a step of grinding the raw material composition containing the compound. A method for producing a composition.

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