Positive electrode active material, coated positive electrode active material, positive electrode material, and battery

Abstract

This positive electrode active substance 110 includes a complex oxide represented by compositional formula (1): LiNixMe1−xO2. In the compositional formula, x satisfies the relationship 0.5≤x<1, and Me is at least one element selected from the group consisting of Co, Mn, Al, Mg, Ca, Sr, Ba, B, Ga, Y, Ce, Sm, Gd, Er, Ti, Zr, V, Nb, Ta, Sb, Bi, Cr, Mo, and W. In an X-ray diffraction pattern obtained through X-ray diffraction measurement of the positive electrode active substance 110 using Cu-Kα rays, the ratio of the FWHM value of the peak having the highest intensity in the diffraction angle 2θ range of 40° to 50° to the FWHM value of the peak corresponding to the (111) plane of a Si crystal powder measured under the same conditions is 2.00 or less.

Description

[Technical Field]

[0001] This disclosure relates to positive electrode active materials, coated positive electrode active materials, positive electrode materials, and batteries. [Background technology]

[0002] Patent Document 1 discloses a positive electrode comprising a positive electrode mixture containing a positive electrode active material made of a composite oxide containing lithium, nickel, cobalt, and manganese, and a solid electrolyte, and an all-solid-state battery equipped with the positive electrode. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2019-125510 [Overview of the project]

[0004] This disclosure provides a positive electrode active material that can reduce the resistance of a battery.

[0005] This disclosure is, A positive electrode active material comprising a composite oxide represented by the following compositional formula (1), LiRing x Me 1-x O2···(1) Here, x satisfies 0.5 ≤ x < 1, Me is at least one selected from the group consisting of Co, Mn, Al, Mg, Ca, Sr, Ba, B, Ga, Y, Ce, Sm, Gd, Er, Ti, Zr, V, Nb, Ta, Sb, Bi, Cr, Mo, and W. In the X-ray diffraction pattern obtained by X-ray diffraction measurement of the positive electrode active material using Cu-Kα rays, the ratio of the full width at half maximum (FMAX) of the peak with the highest intensity within the diffraction angle range 2θ of 40° or more and 50° or less to the full width at half maximum of the peak corresponding to the (111) plane of the Si crystal powder measured under the same conditions is 2.00 or less. We provide a positive electrode active material.

[0006] This disclosure provides a positive electrode active material that can reduce the resistance of a battery. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a cross-sectional view showing the schematic configuration of the positive electrode material 1000 in Embodiment 3. [Figure 2] Figure 2 is a cross-sectional view showing the schematic configuration of the battery 2000 in Embodiment 4. [Figure 3] Figure 3 is a graph showing the X-ray diffraction patterns of the positive electrode active materials for Examples 1 to 8 and Comparative Example 1. [Modes for carrying out the invention]

[0008] (Knowledge that forms the basis of this disclosure) The inventors diligently researched factors that increase the resistance of lithium-ion batteries and found that the resistance of lithium-ion batteries changes when the crystallinity of the active material changes. Based on this finding, the inventors conducted further investigations and found that the resistance of lithium-ion batteries can be reduced by increasing the crystallite size of the active material particles. In this case, the crystallite size was determined by the full width at half maximum of the peak in the diffraction pattern obtained by X-ray diffraction measurement.

[0009] Based on the above findings, the present inventors have arrived at the following positive electrode active material as a novel positive electrode active material that can reduce the resistance of a battery.

[0010] (Summary of one aspect of this disclosure) The positive electrode active material according to the first aspect of this disclosure is a positive electrode active material particle mainly comprising a composite oxide represented by the following compositional formula (1), LiRing x Me 1-x O2···(1) Here, x satisfies 0.5 ≤ x < 1, Me is at least one selected from the group consisting of Co, Mn, Al, Mg, Ca, Sr, Ba, B, Ga, Y, Ce, Sm, Gd, Er, Ti, Zr, V, Nb, Ta, Sb, Bi, Cr, Mo, and W. In the X-ray diffraction pattern obtained by X-ray diffraction measurement of the positive electrode active material using Cu-Kα rays, the ratio of the full width at half maximum (FMAX) of the peak with the highest intensity within the diffraction angle range 2θ of 40° or more and 50° or less to the full width at half maximum (FMAX) of the peak corresponding to the (111) plane of Si crystal powder measured under the same conditions is 2.00 or less.

[0011] According to the positive electrode active material of the first embodiment, the resistance of the battery can be reduced.

[0012] In a second aspect of this disclosure, for example, in the positive electrode active material according to the first aspect, the ratio of the full width at half maximum of the peak may be 1.90 or less.

[0013] According to the positive electrode active material of the second embodiment, the resistance of the battery can be further reduced.

[0014] The coated positive electrode active material according to a third aspect of this disclosure is A positive electrode active material relating to the first or second embodiment, A coating material that covers at least a portion of the surface of the positive electrode active material, Includes, The aforementioned covering material is The element lithium (Li), At least one element selected from the group consisting of oxygen (O), fluorine (F), and chlorine (Cl), Includes.

[0015] According to the coated positive electrode active material of the third embodiment, the resistance of the battery can be reduced.

[0016] The cathode material relating to the fourth aspect of this disclosure is At least one selected from the group consisting of a positive electrode active material according to the first or second embodiment and a coated positive electrode active material according to the third embodiment, Solid electrolytes, Includes.

[0017] According to the positive electrode material of the fourth embodiment, the resistance of the battery can be reduced.

[0018] In a fifth aspect of this disclosure, for example, in the cathode material according to the fourth aspect, the solid electrolyte may include at least one selected from the group consisting of sulfide solid electrolytes and halide solid electrolytes.

[0019] According to the positive electrode material of the fifth embodiment, the resistance of the battery can be further reduced.

[0020] In a sixth aspect of this disclosure, for example, in the cathode material according to the fifth aspect, the halide solid electrolyte is represented by the following compositional formula (2): Li α M β X γ ...Equation (2) Here, α, β, and γ are each independently greater than 0. The aforementioned M is at least one selected from the group consisting of metallic elements other than Li and metalloid elements. The aforementioned X may be at least one selected from the group consisting of F, Cl, Br, and I.

[0021] According to the positive electrode material of the sixth embodiment, the resistance of the battery can be further reduced.

[0022] In the seventh aspect of this disclosure, for example, in the cathode material according to the sixth aspect, M may include yttrium.

[0023] According to the positive electrode material of the seventh embodiment, the resistance of the battery can be further reduced.

[0024] In eight embodiments of this disclosure, for example, in the cathode material according to the sixth or seventh embodiment, In the above composition formula (2), 2.5 ≤ α ≤ 3, 1 ≤ β ≤ 1.1, and γ=6 The condition may be met.

[0025] According to the positive electrode material of the eighth embodiment, the resistance of the battery can be further reduced.

[0026] In a ninth aspect of this disclosure, for example, in a cathode material according to any one of the sixth to eighth aspects, X may include at least one selected from the group consisting of Cl and Br.

[0027] In the battery relating to the ten aspects of this disclosure, A positive electrode comprising a positive electrode material relating to one of the fourth to ninth embodiments, The negative electrode and, The system comprises an electrolyte layer disposed between the positive electrode and the negative electrode.

[0028] The battery according to the tenth embodiment can further reduce the battery's resistance.

[0029] In an eleventh aspect of this disclosure, for example, in a battery according to any one of the sixth to eighth aspects, the electrolyte layer may include a solid electrolyte having the same composition as the solid electrolyte contained in the positive electrode material.

[0030] The battery according to the 11th embodiment can further improve charge and discharge efficiency.

[0031] In a twelfth aspect of this disclosure, for example, in a battery according to a tenth or eleventh aspect, the electrolyte layer may include a halogen solid electrolyte having a different composition from the solid electrolyte contained in the positive electrode material.

[0032] The battery according to the 12th embodiment can further reduce the battery's resistance.

[0033] In the 13th aspect of the present disclosure, for example, in the battery according to any one of the 10th to 12th aspects, the electrolyte layer may contain a sulfide solid electrolyte.

[0034] The battery according to the 13th aspect can further reduce the resistance of the battery.

[0035] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments.

[0036] (Embodiment 1) The positive electrode active material according to Embodiment 1 includes a composite oxide represented by the following compositional formula (1). LiNi x Me 1-x O2···(1) Here, in the above compositional formula (1), x satisfies 0.5≦x<1. In addition, Me is at least one selected from the group consisting of Co, Mn, Al, Mg, Ca, Sr, Ba, B, Ga, Y, Ce, Sm, Gd, Er, Ti, Zr, V, Nb, Ta, Sb, Bi, Cr, Mo, and W.

[0037] In an X-ray diffraction pattern obtained by X-ray diffraction measurement of the positive electrode active material according to Embodiment 1 using Cu-Kα radiation, a ratio of the full width at half maximum value of a peak having the highest intensity within a diffraction angle 2θ range of 40° or more and 50° or less to the full width at half maximum value of a peak corresponding to the (111) plane of Si crystal powder measured under the same conditions is 2.00 or less. Hereinafter, the full width at half maximum value of the peak having the highest intensity within the diffraction angle 2θ range of 40° or more and 50° or less in an X-ray diffraction pattern obtained by X-ray diffraction measurement using Cu-Kα radiation is referred to as "FWHM". Furthermore, the full width at half maximum value of the peak corresponding to the (111) plane of Si crystal powder measured under the same conditions is "FWHM SiThis is called "X-ray diffraction measurement of positive electrode active material according to Embodiment 1". Here, a Si standard sample is used for the Si crystal powder measured under the same conditions as the X-ray diffraction measurement of positive electrode active material according to Embodiment 1. As the Si standard sample, the standard Si crystal powder "NIST640d" manufactured by NIST (National Institute of Standards and Technology) is used.

[0038] In the positive electrode active material of Embodiment 1, the above-mentioned "FWHM Si The condition is that the ratio of FWHM to FWHM is 2.00 or less (i.e., FWHM / FWHM Si The satisfying of (≤2.00) increases the crystallite size. As a result, the positive electrode active material according to Embodiment 1 can reduce the number of grain boundaries, thereby reducing grain boundary resistance. Therefore, the positive electrode active material in Embodiment 1 can reduce the resistance of the battery.

[0039] In lithium composite oxides with a layered rock salt structure, commonly used as positive electrode active materials, the peak with the highest intensity within the diffraction angle range of 40° to 50° originates from the (104) plane diffraction. The (104) plane is known to be a crystal plane through which Li ions are moved in and out. On the other hand, the peak with the highest intensity within the diffraction angle range of 15° to 20° originates from the (003) plane. The (003) plane is known to be a crystal plane through which Li ions are not easily moved in and out. From the standpoint of crystallite size, both peaks show similar trends, but considering the possibility of orientation, the (104) plane peak allows for a more accurate evaluation of the battery's resistance.

[0040] In the positive electrode active material according to Embodiment 1, FWHM Si The ratio of FWHM to FWHM may be 1.90 or less. This allows the positive electrode active material according to Embodiment 1 to have a larger crystallite size. Therefore, the number of grain boundaries in the positive electrode active material according to Embodiment 1 is further reduced, and as a result, the grain boundary resistance can be further reduced. Therefore, the positive electrode active material according to Embodiment 1 has an FWHM / FWHM ratio of 1.Si By satisfying the condition ≤ 1.90, the battery resistance can be further reduced.

[0041] The positive electrode active material according to Embodiment 1 is not based on the FWHM value, but rather on the FWHM Si It is identified by the ratio of FWHM to . Therefore, when identifying the active material according to Embodiment 1, it is not necessary to consider measurement errors caused by the measuring device.

[0042] The positive electrode active material according to Embodiment 1 may contain the composite oxide represented by the above compositional formula (1) as its main component. Here, "main component" refers to the component that is present in the largest amount by mass. The positive electrode active material according to Embodiment 1 may contain 75% by mass or more of the composite oxide represented by the above compositional formula (1), or 90% by mass or more. The positive electrode active material according to Embodiment 1 may consist only of the composite oxide represented by the above compositional formula (1).

[0043] Furthermore, the positive electrode active material according to Embodiment 1 may further contain, in addition to the composite oxide represented by the above composition formula (1), materials that can be used as active materials for all-solid-state lithium-ion batteries, for example.

[0044] Examples of materials that can be used as active materials for all-solid-state lithium-ion batteries include LiCoO2 and LiNi. x Co 1-x O2(0 <x<0.5)、LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiMnO2, heteroatom-substituted Li-Mn spinel (e.g., LiMn 1.5 Ni 0.5 O4, LiMn 1.5 Al 0.5 O4, LiMn 1.5 Mg 0.5 O4, LiMn 1.5 Co 0.5 O4, LiMn 1.5 Fe 0.5 O4, or LiMn 1.5 Zn 0.5 O4), lithium titanate (e.g., Li4Ti5O4)12 These include lithium metal phosphate (e.g., LiFePO4, LiMnPO4, LiCoPO4, or LiNiPO4) and transition metal oxides (e.g., V2O5, MoO3).

[0045] Among the materials mentioned above, LiCoO2, LiNi x Co 1-x O2(0 <x<0.5)、LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 The material may contain at least one lithium-containing composite oxide selected from O2, LiMnO2, heteroatom-substituted Li-Mn spinel, and metallic lithium phosphate.

[0046] The positive electrode active material according to Embodiment 1 is prepared, for example, by a coprecipitation method. In the coprecipitation method, for example, a precursor consisting of a metal oxide containing Ni and Me is prepared, and the positive electrode active material according to Embodiment 1 can be prepared by calcining the precursor together with a lithium source. Si A positive electrode active material with a small full width at half maximum that satisfies the condition that "the ratio of FWHM to is 2.00 or less" can be produced, for example, by controlling firing conditions such as firing temperature and firing time. As an example, in the production of a positive electrode active material having a composition containing Co and Mn as Me, and a positive electrode active material having a composition containing Co and Al as Me, the firing temperature may be set to, for example, 760°C or higher.

[0047] To obtain a cathode active material with a smaller full width at half maximum, the cathode active material may be annealed in an oxygen atmosphere or the like. Alternatively, during the preparation of the cathode active material, the ratio of Li raw material may be higher than the stoichiometric ratio of the active material during firing. Furthermore, annealing may be performed with added Li raw material.

[0048] (Embodiment 2) Embodiment 2 will be described below. Descriptions that overlap with Embodiment 1 described above will be omitted as appropriate.

[0049] The coated positive electrode active material according to Embodiment 2 of this disclosure includes a positive electrode active material and a coating material that covers at least a portion of the surface of the positive electrode active material. The positive electrode active material in the coating material that covers at least a portion of the surface is the positive electrode active material according to Embodiment 1 described in Embodiment 1. The coating material includes lithium (Li) and at least one selected from the group consisting of oxygen (O), fluorine (F), and chlorine (Cl).

[0050] The coated positive electrode active material according to Embodiment 2 contains the positive electrode active material according to Embodiment 1, and therefore can reduce the battery's resistance. Furthermore, in the coated positive electrode active material according to Embodiment 2, at least a portion of the surface of the positive electrode active material is coated with a coating material. Therefore, the interfacial resistance between the positive electrode active material and, for example, a solid electrolyte can be reduced, thereby further reducing the battery's resistance. In addition, by providing such a coating material on the surface, the decomposition of the solid electrolyte due to contact between the solid electrolyte and the positive electrode active material can also be suppressed.

[0051] The coating material may partially cover the surface of the positive electrode active material or cover the entire surface.

[0052] As described above, the coating material comprises Li and at least one selected from the group consisting of O, F, and Cl.

[0053] When the coating material contains Li and O, the coating material may be, for example, an oxide solid electrolyte. Examples of oxide solid electrolytes that can be used as coating materials include lithium niobate, lithium phosphate, lithium titanate, and lithium tungstate. Oxide solid electrolytes have high ionic conductivity. Oxide solid electrolytes have excellent high potential stability. Therefore, by using an oxide solid electrolyte as a coating material, the resistance of the battery can be further reduced.

[0054] If the coating material includes Li and at least one selected from the group consisting of F and Cl, the coating material may be, for example, a halogenated solid electrolyte.

[0055] If the coating material contains Li, O, and at least one selected from the group consisting of F and Cl, the coating material may be, for example, an oxyhalide solid electrolyte. The coating material may also contain Li, O, and F. In this case, the coating material may also contain at least one selected from the group consisting of lithium zirconate fluoride, lithium aluminum fluoride, lithium titanate fluoride, and lithium magnesium fluoride.

[0056] The thickness of the coating material may be 1 nm or more and 100 nm or less.

[0057] By having a coating material thickness of 1 nm or more, direct contact between the positive electrode active material and, for example, the solid electrolyte is suppressed, thereby inhibiting the reaction between the positive electrode active material and the solid electrolyte. Furthermore, by having a coating material thickness of 100 nm or less, the coating material does not become too thick. As a result, the resistance of the battery can be reduced.

[0058] The coated positive electrode active material according to Embodiment 2 can be manufactured, for example, by forming a coating material on the surface of the positive electrode active material particles. Known methods can be used to form the coating material on the surface of the positive electrode active material particles. For example, liquid-phase coating, gas-phase coating, and dry particle composite methods can be used.

[0059] (Embodiment 3) Embodiment 3 will now be described. Descriptions that overlap with Embodiments 1 and 2 described above will be omitted as appropriate.

[0060] The positive electrode material according to Embodiment 3 of this disclosure comprises at least one selected from the group consisting of a positive electrode active material and a coated positive electrode active material, and a solid electrolyte. The positive electrode active material used is the positive electrode active material described in Embodiment 1. The coated positive electrode active material used is the coated positive electrode active material described in Embodiment 2.

[0061] Figure 1 is a cross-sectional view showing the schematic configuration of the positive electrode material 1000 according to Embodiment 3. In the positive electrode material 1000 shown in Figure 1, a coated positive electrode active material is used, which includes a positive electrode active material 110 and a coating material 120. The positive electrode material 1000 includes a coated positive electrode active material, which includes a positive electrode active material 110 and a coating material 120, and a solid electrolyte 100.

[0062] The solid electrolyte 100 may contain at least one selected from the group consisting of sulfide solid electrolytes and halide solid electrolytes.

[0063] If the solid electrolyte 100 contains a halide solid electrolyte, the halide solid electrolyte may be a compound represented by the following composition formula (2). Li α M β X γ ...Equation (2) Here, α, β, and γ are values ​​greater than 0. M is at least one selected from the group consisting of metallic elements and metalloid elements other than Li. X is at least one selected from the group consisting of F, Cl, Br, and I.

[0064] Here, "metalloid elements" refer to B, Si, Ge, As, Sb, and Te. "Metallic elements" refer to all elements in groups 1 through 12 of the periodic table, excluding hydrogen, and all elements in groups 13 through 16 of the periodic table, excluding B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se. In other words, "metalloid elements" or "metallic elements" are the group of elements that can become cations when forming inorganic compounds with halogen elements.

[0065] As the solid electrolyte 100, for example, Li3YX6, Li2MgX4, Li2FeX4, Li(Al,Ga,In)X4, Li3(Al,Ga,In)X6, etc. can be used. Here, X is at least one selected from the group consisting of F, Cl, Br, and I.

[0066] In this disclosure, "(A, B, C)" means "at least one selected from the group consisting of A, B, and C."

[0067] With the above configuration, the battery's resistance can be reduced. As a result, the battery's charge and discharge characteristics are improved.

[0068] The empirical formula (2) may also satisfy 2.5 ≤ α ≤ 3, 1 ≤ β ≤ 1.1, and γ = 6.

[0069] In composition formula (2), X may include at least one selected from the group consisting of Cl and Br.

[0070] In chemical formula (2), M may include yttrium (Y).

[0071] As a solid electrolyte containing Y, for example, Li a M' b Y c The compound may be represented by the empirical formula X6, where a + mb + 3c = 6 and c > 0. M' is at least one selected from the group consisting of metallic and metalloid elements other than Li and Y. m indicates the valence of M'. X is at least one selected from the group consisting of F, Cl, Br, and I.

[0072] M' 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.

[0073] Specifically, solid electrolytes containing Y include Li3YF6, Li3YCl6, Li3YBr6, Li3YI6, Li3YBrCl5, Li3YBr3Cl3, Li3YBr5Cl, Li3YBr5I, Li3YBr3I3, Li3YBrI5, Li3YClI5, Li3YCl3I3, Li3YCl5I, Li3YBr2Cl2I2, Li3YBrCl4I, Li 2.7 Y 1.1 Cl6, Li 2.5 Y 0.5 Zr0.5 Cl6, Li 2.5 Y 0.3 Zr 0.7 Cl6, etc., can be used.

[0074] With the above configuration, the battery resistance can be further reduced.

[0075] The halide solid electrolyte does not necessarily have to contain sulfur. With the above configuration, the generation of hydrogen sulfide gas can be suppressed. Therefore, it becomes possible to realize a battery with improved safety.

[0076] Furthermore, the shapes of the solid electrolyte 100 and the positive electrode active material 110 in Embodiment 3 are not particularly limited and may be, for example, needle-shaped, spherical, ellipsoidal, etc. For example, the solid electrolyte 100 and the positive electrode active material 110 may be particulate.

[0077] For example, if the solid electrolyte 100 in Embodiment 3 is particulate (e.g., spherical), the median diameter may be 100 μm or less.

[0078] When the median diameter of the solid electrolyte 100 is 100 μm or less, the positive electrode active material 110 and the solid electrolyte 100 can form a good dispersion state in the positive electrode material 1000. This improves the charge and discharge characteristics of the battery.

[0079] Furthermore, in Embodiment 3, the median diameter of the solid electrolyte 100 may be 10 μm or less.

[0080] With the above configuration, the positive electrode active material 110 and the solid electrolyte 100 can form a good dispersion state in the positive electrode material 1000.

[0081] Furthermore, in Embodiment 3, the median diameter of the solid electrolyte 100 may be smaller than the median diameter of the positive electrode active material 110.

[0082] With the above configuration, the solid electrolyte 100 and the positive electrode active material 110 can form a better dispersion state in the positive electrode material 1000.

[0083] The median diameter of the positive electrode active material 110 may be 0.1 μm or more and 100 μm or less.

[0084] When the median diameter of the positive electrode active material 110 is 0.1 μm or larger, the positive electrode active material 110 and the solid electrolyte 100 can form a good dispersion state in the positive electrode material 1000. As a result, the charge and discharge characteristics of the battery are improved.

[0085] Furthermore, when the median diameter of the positive electrode active material 110 is 100 μm or less, a sufficient diffusion rate of lithium within the positive electrode active material 110 is ensured. This enables the battery to operate at high power.

[0086] In this disclosure, “median diameter” means the particle size at which the cumulative volume in the volume-based particle size distribution is equal to 50%. The volume-based particle size distribution is measured, for example, by a laser diffraction analyzer or an image analyzer.

[0087] In the positive electrode material 1000 of Embodiment 3, the particles of the solid electrolyte 100 and the particles of the positive electrode active material 110 may be in contact with each other, as shown in Figure 1. In this case, the coating material 120 and the positive electrode active material 110 are in contact with each other.

[0088] Furthermore, the positive electrode material 1000 in Embodiment 3 may include a plurality of solid electrolyte particles 100 and a plurality of positive electrode active material particles 110.

[0089] Furthermore, in the positive electrode material 1000 of Embodiment 3, the content of the solid electrolyte 100 and the content of the positive electrode active material 110 may be the same or different.

[0090] (Embodiment 4) Embodiment 4 will now be described. Descriptions that overlap with Embodiments 1 to 3 described above will be omitted as appropriate.

[0091] Figure 2 is a cross-sectional view showing the schematic configuration of the battery 2000 in Embodiment 4.

[0092] The battery 2000 in Embodiment 4 comprises a positive electrode 201, an electrolyte layer 202, and a negative electrode 203.

[0093] The positive electrode 201 includes a positive electrode material 1000. The positive electrode material 1000 is the positive electrode material described in Embodiment 3.

[0094] The electrolyte layer 202 is placed between the positive electrode 201 and the negative electrode 203.

[0095] With the above configuration, the battery resistance can be reduced.

[0096] The volume ratio "v1:100-v1" of the positive electrode active material 110 and the solid electrolyte 100 contained in the positive electrode 201 may satisfy the condition 30≦v1≦95. If 30≦v1 is satisfied, the energy density of the battery 2000 is sufficiently ensured. Furthermore, if v1≦95 is satisfied, high-power operation becomes possible.

[0097] The thickness of the positive electrode 201 may be 10 μm or more and 500 μm or less. If the thickness of the positive electrode 201 is 10 μm or more, the energy density of the battery 2000 is sufficiently ensured. If the thickness of the positive electrode 201 is 500 μm or less, high-power operation becomes possible.

[0098] The electrolyte layer 202 is a layer containing an electrolyte material. This electrolyte material is, for example, a solid electrolyte material. That is, the electrolyte layer 202 may be a solid electrolyte layer. As the solid electrolyte, the material exemplified as the material for the solid electrolyte 100 in Embodiment 3 may be used. In other words, the electrolyte layer 202 may contain a solid electrolyte with the same composition as the solid electrolyte 100 contained in the positive electrode material 1000.

[0099] With the above configuration, the charge and discharge efficiency of the 2000 battery can be further improved.

[0100] The electrolyte layer 202 may contain a halide solid electrolyte having a different composition from the solid electrolyte contained in the positive electrode material 1000.

[0101] The electrolyte layer 202 may contain a sulfide solid electrolyte.

[0102] The electrolyte layer 202 may contain only one solid electrolyte selected from the group of solid electrolytes described above, or it may contain two or more solid electrolytes selected from the group of solid electrolytes described above. The multiple solid electrolytes may have different compositions from each other. For example, the electrolyte layer 202 may contain a halide solid electrolyte and a sulfide solid electrolyte.

[0103] The thickness of the electrolyte layer 202 may be 1 μm or more and 300 μm or less. When the thickness of the electrolyte layer 202 is 1 μm or more, short circuits between the positive electrode 201 and the negative electrode 203 are less likely to occur. When the thickness of the electrolyte layer 202 is 300 μm or less, high-power operation becomes possible.

[0104] The negative electrode 203 includes a material having the property of intercalating and releasing metal ions (e.g., lithium ions). The negative electrode 203 includes, for example, a negative electrode active material.

[0105] The negative electrode active material can be a metallic material, a carbon material, an oxide, a nitride, a tin compound, a silicon compound, etc. The metallic material may be a pure metal, or it may be an alloy. Examples of metallic materials include lithium metal and lithium alloys. Examples of carbon materials include natural graphite, coke, carbon in the process of graphitization, carbon fibers, spheroidal carbon, artificial graphite, amorphous carbon, etc. From the viewpoint of capacity density, silicon (Si), tin (Sn), silicon compounds, or tin compounds can be suitably used.

[0106] The negative electrode 203 may contain a solid electrolyte material. With the above configuration, the lithium ion conductivity inside the negative electrode 203 is increased, enabling operation at high power. As the solid electrolyte, the material exemplified in Embodiment 3 may be used. In other words, the negative electrode 203 may contain a solid electrolyte with the same composition as the solid electrolyte contained in the positive electrode material 1000.

[0107] The median diameter of the negative electrode active material may be 0.1 μm or more and 100 μm or less.

[0108] When the median diameter of the negative electrode active material is 0.1 μm or larger, the negative electrode active material and the solid electrolyte material can form a good dispersion state. As a result, the charge and discharge characteristics of the battery are improved.

[0109] Furthermore, when the median diameter of the negative electrode active material is 100 μm or less, a sufficient diffusion rate of lithium within the negative electrode active material is ensured. This enables the battery to operate at high power.

[0110] The median diameter of the negative electrode active material may be larger than the median diameter of the solid electrolyte material. This allows for the formation of a good dispersion state between the negative electrode active material and the solid electrolyte material.

[0111] The volume ratio "v2:100-v2" of the negative electrode active material and solid electrolyte material contained in the negative electrode 203 may satisfy the condition 30≦v2≦95. If 30≦v2 is satisfied, the energy density of battery 2000 is sufficiently ensured. Furthermore, if v2≦95 is satisfied, high-power operation becomes possible.

[0112] The thickness of the negative electrode 203 may be 10 μm or more and 500 μm or less. If the thickness of the negative electrode 203 is 10 μm or more, the energy density of the battery 2000 is sufficiently ensured. If the thickness of the negative electrode 203 is 500 μm or less, high-power operation becomes possible.

[0113] 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 for the purpose of improving the adhesion between particles. The binder is used to improve the bonding properties of the materials constituting the electrode. Examples of binders include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamideimide, polyacrylonitrile, polyacrylic acid, polymethyl polyacrylate, polyethyl polyacrylate, polyhexyl polyacrylate, polymethacrylic acid, polymethyl polymethacrylate, polyethyl polymethacrylate, polyhexyl polymethacrylate, polyvinyl acetate, polyvinylpyrrolidone, polyether, polyethersulfone, hexafluoropolypropylene, styrene-butadiene rubber, carboxymethylcellulose, and the like. Furthermore, a copolymer of two or more materials selected from tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinylidene fluoride, chlorotrifluoroethylene, ethylene, propylene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid, and hexadiene may be used as a binder. Alternatively, two or more materials selected from these may be mixed and used as a binder.

[0114] At least one electrode selected from the group consisting of a positive electrode 201 and a negative electrode 203 may contain a conductive additive for the purpose of enhancing electronic conductivity. Examples of conductive additives include graphites such as natural or artificial graphite, carbon blacks such as acetylene black and Ketjenblack, conductive fibers such as carbon fibers or metal fibers, metal powders such as carbon fluoride and aluminum, conductive whiskers such as zinc oxide or potassium titanate, conductive metal oxides such as titanium oxide, and conductive polymer compounds such as polyaniline, polypyrrole, and polythiophene. Using a carbon conductive additive can reduce costs.

[0115] Furthermore, the battery in Embodiment 4 can be configured as a battery of various shapes, such as coin-type, cylindrical, prismatic, sheet-type, button-type, flat-type, or stacked-type. [Examples]

[0116] The present disclosure will be described in more detail below with reference to examples.

[0117] Example 1 [Fabrication of positive electrode active material] Nickel sulfate, cobalt sulfate, and manganese sulfate were dissolved in water, and nickel, cobalt, and manganese were coprecipitated in an alkaline aqueous solution containing sodium hydroxide to produce nickel, cobalt, and manganese hydroxides. These hydroxides were filtered, dried, and thermally decomposed to produce oxides containing nickel, cobalt, and manganese in the desired ratios. These oxides were mixed with lithium hydroxide and calcined at 850°C in an oxygen atmosphere to produce the positive electrode active material LiNi 0.8 (Co, Mn) 0.2 O2 was prepared. Below is the prepared LiNi 0.8 (Co, Mn) 0.2 O2 is denoted as NCM-1. In this way, the positive electrode active material of Example 1 was obtained.

[0118] [Measurement of full width at half maximum] Figure 3 is a graph showing the X-ray diffraction pattern of the positive electrode active material according to Example 1. In other words, Figure 3 is a graph showing the X-ray diffraction pattern of NCM-1 according to Example 1.

[0119] The X-ray diffraction pattern of the solid electrolyte material according to Example 1 was measured using an X-ray diffractometer (Rigaku, MiniFlex600) in a dry environment with a dew point of -50°C or lower. Cu-Kα rays (wavelengths 1.5405 Å and 1.5444 Å) were used as the X-ray source, and the measurement was performed using the θ-2θ method. The measurement angle interval was 0.01°. The divergence angle of the diverging slit was 0.25°. The slit width of the longitudinally limited slit was 5 mm.

[0120] The value of the diffraction angle 2θ of the peak with the highest intensity within the diffraction angle 2θ range of 40° or more and 50° or less is 2θ. top And the intensity of the peak in question is set to I top The average intensity at diffraction angles 2θ from 40° to 41° was calculated as I. bg That is, I bg This represents the baseline intensity. top Half value I htop is, [(I top -I bg ) / 2+I bg ]

[0121] 40° or more and 2θ top Within the following diffraction angle range of 2θ, I htop The diffraction angle 2θ that yields the closest intensity is 2θ L This was assumed. 2θ top Within the range of above and below 50° htop The diffraction angle 2θ that yields the closest intensity is 2θ H FWHM is 2θ H and 2θ L This is the difference. The FWHM of the positive electrode active material in Example 1 was 0.24 deg.

[0122] Next, X-ray diffraction measurements were performed on Si crystal powder under the same conditions as for the positive electrode active material in Example 1. In this case, the standard sample NIST640d was used as the Si crystal powder. The value of the diffraction angle 2θ of the peak with the highest intensity within the diffraction angle 2θ range of 28.0° to 28.6° was determined as 2θ. top And the intensity of the peak in question is set to I top The intensity at a diffraction angle of 2θ of 28.0° was defined as I bg As a result, the FWHM of Si crystal powder Si It was 0.16 degrees.

[0123] [Preparation of Halide Solid Electrolytes] In an argon glove box with a dew point of -60°C or lower, raw material powders LiCl and YCl3 were weighed in a molar ratio of LiCl:YCl3 = 3:1. These were ground and mixed in a mortar. Then, the mixture was milled using a planetary ball mill at 600 rpm for 12 hours.

[0124] Based on the above, a powder of a halide solid electrolyte represented by the compositional formula Li3YCl6 was obtained.

[0125] [Fabrication of cathode materials] In an argon glove box with a dew point of -60°C or lower, the halogen solid electrolyte Li3YCl6 and NCM-1, the positive electrode active material of Example 1, were weighed in a mass ratio of Li3YCl6:NCM-1 = 25:75. These were mixed in an agate mortar to prepare the positive electrode material of Example 1.

[0126] [Preparation of sulfide solid electrolytes] In an argon glove box with a dew point of -60°C or lower, Li2S and P2S5 were weighed in a molar ratio of Li2S:P2S5 = 75:25. These were ground and mixed in a mortar. Then, using a planetary ball mill (Fritsch, P-7 type), the mixture was milled at 510 rpm for 10 hours to obtain a glassy solid electrolyte. The glassy solid electrolyte was heat-treated in an inert atmosphere at 270°C for 2 hours. This yielded a glass-ceramic sulfide solid electrolyte.

[0127] [Manufacturing of secondary batteries] The following steps were carried out using the cathode material and sulfide solid electrolyte described in Example 1 above.

[0128] First, 120 mg of sulfide solid electrolyte and 25 mg of the positive electrode material from Example 1 were layered inside an insulating outer cylinder. This was then pressure-molded at a pressure of 700 MPa to obtain the positive electrode and solid electrolyte layers.

[0129] Next, a layer of metallic Li (200 μm thick) was laminated on the side of the solid electrolyte layer opposite to the side in contact with the positive electrode, and this was then pressurized and molded at a pressure of 80 MPa to produce a laminate consisting of a positive electrode, a solid electrolyte layer, and a negative electrode.

[0130] Next, stainless steel current collectors were placed above and below the laminate, and current collection leads were attached to the current collectors.

[0131] Finally, the battery of Example 1 was fabricated by sealing the insulating outer casing with an insulating ferrule, thereby isolating the inside of the insulating outer casing from the outside air.

[0132] [Electrochemical Test] A charge-discharge test was performed using the battery from Example 1 under the following conditions.

[0133] The battery was placed in a constant temperature bath at 25°C and connected to a charge / discharge device.

[0134] The battery was charged with a constant current of 390 μA, which corresponds to a 0.1C rate (10-hour rate) relative to its theoretical capacity, up to a voltage of 4.3V. Then, constant voltage charging was performed at 4.3V, and charging was terminated at a current of 39 μA, which corresponds to a 0.01C rate (100-hour rate). Subsequently, the battery was discharged with a constant current at a 0.1C rate down to a voltage of 2.5V, and then constant voltage discharge was performed at 2.5V down to a 0.01C rate.

[0135] Subsequently, charging was performed again under the same conditions, followed by constant current discharge at a 0.1C rate down to a voltage of 3.78V, and then constant voltage discharge at 3.78V down to a 0.01C rate. Furthermore, after a period of rest, constant current discharge was performed at 6.5mA for 5 seconds. At this time, the DC resistance of the battery obtained from equation (3) below is called DCR.

[0136] DCR = (Vo - V) × S / I ... (3)

[0137] Here, Vo is the voltage before discharge for 5 seconds, V is the voltage after discharge for 5 seconds, S is the area in contact between the positive electrode and the solid electrolyte layer, and I is 6.5 mA.

[0138] The DCR of the battery in Example 1 is 58 Ω·cm. 2 That was the case.

[0139] Examples 2 to 8 [Fabrication of positive electrode active material] A mixture of nickel, cobalt, and manganese oxides and lithium hydroxide was prepared using the same procedure as in Example 1, and then calcined at 825°C in an oxygen atmosphere to produce a positive electrode active material LiNi 0.8 (Co, Mn) 0.2 O2 was prepared. In this way, the positive electrode active material NCM-2 of Example 2 was obtained.

[0140] A mixture of nickel, cobalt, and manganese oxides and lithium hydroxide was prepared using the same procedure as in Example 1, and then calcined at 800°C in an oxygen atmosphere to produce a positive electrode active material LiNi 0.8 (Co, Mn) 0.2 O2 was prepared. In this way, the positive electrode active material NCM-3 of Example 3 was obtained.

[0141] A mixture of nickel, cobalt, and manganese oxides and lithium hydroxide was prepared using the same procedure as in Example 1, and then calcined at 775°C in an oxygen atmosphere to produce a positive electrode active material LiNi 0.8 (Co, Mn) 0.2 O2 was prepared. In this way, the positive electrode active material NCM-4 of Example 4 was obtained.

[0142] Nickel sulfate, cobalt sulfate, and sodium aluminate were dissolved in water, and nickel, cobalt, and aluminum were coprecipitated in an alkaline aqueous solution containing sodium hydroxide to produce nickel, cobalt, and aluminum hydroxides. These hydroxides were filtered, dried, and thermally decomposed to produce oxides containing nickel, cobalt, and aluminum in the desired ratios. These oxides were mixed with lithium hydroxide and calcined at 850°C in an oxygen atmosphere to produce the positive electrode active material LiNi 0.8 (Co, Al) 0.2 O2 was prepared. Below is the prepared LiNi 0.8 (Co, Al) 0.2O₂ is designated as NCA-1. Thus, the positive electrode active material of Example 5 was obtained.

[0143] By following the same procedure as in Example 5, a mixture of an oxide containing nickel, cobalt, and aluminum and lithium hydroxide was prepared, and fired at 825°C in an oxygen atmosphere to obtain the positive electrode active material LiNi 0.8 (Co, Al) 0.2 O₂ was produced. Thus, the positive electrode active material NCA-2 of Example 6 was obtained.

[0144] By following the same procedure as in Example 5, a mixture of an oxide containing nickel, cobalt, and aluminum and lithium hydroxide was prepared, and fired at 800°C in an oxygen atmosphere to obtain the positive electrode active material LiNi 0.8 (Co, Al) 0.2 O₂ was produced. Thus, the positive electrode active material NCA-3 of Example 7 was obtained.

[0145] By following the same procedure as in Example 5, a mixture of an oxide containing nickel, cobalt, and aluminum and lithium hydroxide was prepared, and fired at 775°C in an oxygen atmosphere to obtain the positive electrode active material LiNi 0.8 (Co, Al) 0.2 O₂ was produced. Thus, the positive electrode active material NCA-4 of Example 8 was obtained.

[0146] [Measurement of full width at half maximum] Figure 3 is a graph showing X-ray diffraction patterns of the positive electrode active materials according to Examples 2 to 8. The full width at half maximum of the prepared positive electrode active materials of Examples 2 to 8 was measured in the same manner as in Example 1. The full width at half maximum of the positive electrode active materials of Examples 2 to 8 is shown in Table 1 below.

[0147] [Preparation of Positive Electrode Material] Positive electrode materials of Examples 2 to 8 were produced in the same manner as in Example 1, except that the positive electrode active materials of Examples 2 to 8 were each used as the positive electrode active material.

[0148] [Preparation of Battery] Batteries of Examples 2 to 8 were produced in the same manner as in Example 1, except that the positive electrode materials of Examples 2 to 8 were each used as the positive electrode material.

[0149] [Electrochemical Test] Charge-discharge tests were performed in the same manner as in Example 1 using the batteries of Examples 2 to 8. The DCR of the batteries of Examples 2 to 8 is shown in Table 1 below.

[0150] <<Comparative Example 1>> [Preparation of Positive Electrode Active Material] A mixture of an oxide containing nickel, cobalt, and manganese and lithium hydroxide was prepared by the same procedure as in Example 1, and fired at 750°C under an oxygen atmosphere to obtain a positive electrode active material LiNi 0.8 (Co, Mn) 0.2 O₂ was prepared. Thus, the positive electrode active material NCM-Ref. of Comparative Example 1 was obtained.

[0151] [Measurement of Full Width at Half Maximum] Figure 3 is a graph showing the X-ray diffraction pattern of the positive electrode active material according to Comparative Example 1. The full width at half maximum of the prepared positive electrode active material of Comparative Example 1 was measured in the same manner as in Example 1. The full width at half maximum of the positive electrode active material of Comparative Example 1 is shown in Table 1 below.

[0152] [Preparation of Positive Electrode Material] The positive electrode material of Comparative Example 1 was produced in the same manner as in Example 1, except that the positive electrode active material of Comparative Example 1 was used as the positive electrode active material.

[0153] [Preparation of Battery] The battery of Comparative Example 1 was produced in the same manner as in Example 1, except that the positive electrode material of Comparative Example 1 was used as the positive electrode material.

[0154] [Electrochemical Test] A charge-discharge test was performed in the same manner as in Example 1 using the battery of Comparative Example 1. The DCR of the battery of the Comparative Example is shown in Table 1 below.

[0155]

Table 1

[0156] ≪Consideration≫ Based on the results shown in Table 1, comparing Examples 1 to 8 with Comparative Example 1, FWHM / FWHM Si The batteries in Examples 1 to 8 that satisfy the condition ≤2.00 are FWHM / FWHM Si It was found that the DCR could be reduced compared to the battery in Comparative Example 1, where the DCR exceeded 2.0. Furthermore, from the results shown in Table 1, FWHM / FWHM Si It was also found that the DCR was further reduced when the value was 1.90 or less. Furthermore, when comparing the batteries of Examples 1 to 4, which used the same positive electrode active material NCM, it was found that the smaller the FWHM (full width at half maximum), the greater the reduction in DCR. This was also true for the batteries of Examples 5 to 8, which used the positive electrode active material NCA. [Industrial applicability]

[0157] The positive electrode active material of this disclosure can be used, for example, as the positive electrode of a battery such as an all-solid-state battery. [Explanation of Symbols]

[0158] 1000 electrode materials 100 solid electrolyte 110 Cathode active material 120 Coating material 2000 batteries 201 Positive electrode 202 Electrolyte layer 203 Negative electrode

Claims

1. A positive electrode active material comprising a composite oxide represented by the following compositional formula (1), LiNi x Me 1-x Oh 2 ・・・(1) Here, x satisfies 0.5 ≤ x < 1, Me is at least one selected from the group consisting of Co, Mn, Al, Mg, Ca, Sr, Ba, B, Ga, Y, Ce, Sm, Gd, Er, Ti, Zr, V, Nb, Ta, Sb, Bi, Cr, Mo, and W. In the X-ray diffraction pattern obtained by X-ray diffraction measurement of the positive electrode active material using Cu-Kα rays, the ratio of the full width at half maximum (FMAX) of the peak with the highest intensity within the diffraction angle range 2θ of 40° or more and 50° or less to the full width at half maximum of the peak corresponding to the (111) plane of the Si crystal powder of a standard sample using NIST640d, measured under the same conditions, is 1.60 or more and 2.00 or less. Cathode active material.

2. The ratio of the full width at half maximum of the aforementioned peak is 1.90 or less. The positive electrode active material according to claim 1.

3. The ratio of the full width at half maximum of the aforementioned peak is 1.80 or less. The positive electrode active material according to claim 2.

4. The positive electrode active material according to claim 1, A coating material that covers at least a portion of the surface of the positive electrode active material, Includes, The aforementioned covering material is Lithium element (Li) and, At least one element selected from the group consisting of oxygen (O), fluorine (F), and chlorine (Cl), including, Coated positive electrode active material.

5. At least one selected from the group consisting of the positive electrode active material described in claim 1 and the coated positive electrode active material described in claim 4, Solid electrolytes, A positive electrode material that includes [this material].

6. The solid electrolyte includes at least one selected from the group consisting of sulfide solid electrolytes and halide solid electrolytes. The positive electrode material according to claim 5.

7. The aforementioned halogen solid electrolyte is represented by the following compositional formula (2): Li α M β X γ ... Formula (2) Here, α, β, and γ are each independently greater than 0. The aforementioned M is at least one selected from the group consisting of metallic elements other than Li and metalloid elements. The aforementioned X is at least one selected from the group consisting of F, Cl, Br, and I. The positive electrode material according to claim 6.

8. The aforementioned M includes yttrium, The positive electrode material according to claim 7.

9. In the above composition formula (2), ２．５≦α≦３、 1 ≤ β ≤ 1.1, and γ = 6, The condition is met. The positive electrode material according to claim 7.

10. The aforementioned X includes at least one selected from the group consisting of Cl and Br. The positive electrode material according to claim 7.

11. A positive electrode comprising the positive electrode material described in claim 5, The negative electrode and, The system comprises an electrolyte layer disposed between the positive electrode and the negative electrode. battery.

12. The electrolyte layer includes a solid electrolyte having the same composition as the solid electrolyte contained in the positive electrode material. The battery according to claim 11.

13. The electrolyte layer includes a halogen solid electrolyte having a different composition from the solid electrolyte contained in the positive electrode material. The battery according to claim 11.

14. The electrolyte layer contains a sulfide solid electrolyte. The battery according to claim 11.

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