Positive electrode material and battery

Abstract

A positive electrode material 1000 according to the present disclosure includes a positive electrode active material 110 and a coating layer 111 that includes a first solid electrolyte and covers at least a part of the surface of the positive electrode active material 110. The positive electrode active material 110 and the coating layer 111 constitute a coating active material 130, and where the pore volume of the positive electrode active material 110 is represented by Vα, the pore volume of the coating active material 130 is represented by Vβ, the specific surface area of the positive electrode active material 110 is represented by Sα, and the specific surface area of the coating active material 130 is represented by Sβ, at least one selected from the group consisting of 0.20 < Vβ / Vα < 0.88 and 0.81 < Sβ / Sα < 0.97 is satisfied.

Description

Technical Field

[0001] The present disclosure relates to a positive electrode material and a battery.

Background Art

[0002] Patent Document 1 discloses a battery using a halide as a solid electrolyte. Non-Patent Document 1 discloses a battery using a sulfide as a solid electrolyte.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Non-Patent Documents

[0004]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the prior art, improvement of the initial efficiency of a battery is desired.

Means for Solving the Problems

[0006] The positive electrode material in one aspect of the present disclosure is a positive electrode active material, a first solid electrolyte, and a coating layer covering at least a part of the surface of the positive electrode active material, and includes the positive electrode active material and the coating layer constitute a coating active material, the pore volume of the positive electrode active material is represented by V α and the pore volume of the coating active material is represented by V β and the specific surface area of the positive electrode active material is S αrepresented by, the specific surface area of the coating active material being S β when represented by, 0.20 < V β / V α < 0.88, and, 0.81 < S β / S α < 0.97, at least one selected from the group consisting thereof is satisfied.

Advantages of the Invention

[0007] According to the present disclosure, the initial efficiency of the battery can be improved.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0009] (Findings underlying the present disclosure) Patent Document 1 discloses that an all-solid-state secondary battery including a halide solid electrolyte exhibits good charge-discharge characteristics.

[0010] On the other hand, as a result of intensive studies, the present inventors have found that the contact state between the positive electrode active material and the halide solid electrolyte is related to the charge-discharge efficiency. The present inventors have speculated that the reason why the contact state is related to the charge-discharge efficiency lies in the balance between the electron resistance and the interfacial resistance. Specifically, when the contact rate between the positive electrode active material and the solid electrolyte is low, the interfacial resistance increases, and when the contact rate between the positive electrode active material and the solid electrolyte is high, the electron resistance increases. In order to solve this problem, it is important to realize a contact state between the positive electrode active material and the solid electrolyte that suppresses the two resistance components to a low resistance.

[0011] Non-Patent Document 1 discloses that an all-solid-state secondary battery including a sulfide solid electrolyte exhibits good charge-discharge characteristics.

[0012] On the other hand, as a result of intensive studies by the present inventors, it has been found that when a positive electrode active material is in contact with a sulfide solid electrolyte, the sulfide solid electrolyte is oxidatively decomposed during charging of the battery. In order to solve this problem, it is conceivable to coat the surface of the positive electrode active material with a solid electrolyte having oxidation stability.

[0013] Here, the present inventors considered that the contact state between the positive electrode active material and another solid electrolyte might be adjustable depending on the degree of coating of the solid electrolyte on the positive electrode active material. In particular, since the halide solid electrolyte has higher oxidation stability than the sulfide solid electrolyte, it is also possible to suppress the oxidative decomposition of other solid electrolytes by the coating layer of the halide solid electrolyte.

[0014] (Summary of one aspect according to the present disclosure) The positive electrode material according to the first aspect of the present disclosure is a positive electrode active material, a coating layer containing a first solid electrolyte and covering at least a part of the surface of the positive electrode active material, and the positive electrode active material and the coating layer constitute a coated active material, wherein the pore volume of the positive electrode active material is represented by V α and the pore volume of the coated active material is represented by V β the specific surface area of the positive electrode active material is represented by S α and the specific surface area of the coated active material is represented by S β when represented by, 0.20 < V β / V α < 0.88, and 0.81 < S β / S α < 0.97, at least one selected from the group consisting of is satisfied.

[0015] According to the above configuration, the initial efficiency of the battery can be improved.

[0016] In the second aspect of the present disclosure, for example, in the positive electrode material according to the first aspect, 0.60 ≤ V β / V α≦0.76 may be satisfied. According to such a configuration, the initial efficiency of the battery can be surely improved.

[0017] In a third aspect of the present disclosure, for example, in the positive electrode material according to the first or second aspect, 0.86 ≦ S β / S α ≦0.89 may be satisfied. According to such a configuration, the initial efficiency of the battery can be surely improved.

[0018] In a fourth aspect of the present disclosure, for example, in the positive electrode material according to any one of the first to third aspects, when the weight of the positive electrode active material is W α and the weight of the coating active material is W β 0.90 < W α / W β <0.99 may be satisfied. According to such a configuration, the initial efficiency of the battery can be surely improved.

[0019] In a fifth aspect of the present disclosure, for example, in the positive electrode material according to the fourth aspect, 0.95 ≦ W α / W β ≦0.975 may be satisfied. According to such a configuration, the initial efficiency of the battery can be surely improved.

[0020] In a sixth aspect of the present disclosure, for example, in the positive electrode material according to any one of the first to fifth aspects, the thickness of the coating layer may be greater than 14 nm and less than 167 nm. According to such a configuration, the charge-discharge efficiency of the battery can be surely improved.

[0021] In a seventh aspect of the present disclosure, for example, in the positive electrode material according to any one of the first to sixth aspects, the thickness of the coating layer may be 32 nm or more and 71 nm or less. According to such a configuration, the charge-discharge efficiency of the battery can be surely improved.

[0022] In an eighth aspect of the present disclosure, for example, in the positive electrode material according to any one of the first to seventh aspects, the first solid electrolyte may be represented by the following compositional formula (1), where α1, β1, and γ1 may each independently be a value greater than 0, M1 may contain at least one element selected from the group consisting of metal elements and metalloid elements other than Li, and X1 may contain at least one selected from the group consisting of F, Cl, Br, and I. When the halide solid electrolyte represented by formula (1) is used in a battery, the output characteristics of the battery can be improved. Li α1 M1 β1 X1 γ1 ··· Formula (1)

[0023] In a ninth aspect of the present disclosure, for example, in the positive electrode material according to the eighth aspect, the M1 may contain yttrium. According to such a configuration, the charge and discharge characteristics of the battery can be further improved.

[0024] In a tenth aspect of the present disclosure, for example, in the positive electrode material according to the eighth or ninth aspect, 2.5 ≦ α1 ≦ 3, 1 ≦ β1 ≦ 1.1, and γ1 = 6 may be satisfied. According to such a configuration, the charge and discharge characteristics of the battery can be further improved.

[0025] In an eleventh aspect of the present disclosure, for example, in the positive electrode material according to any one of the eighth to tenth aspects, the X1 may contain at least one selected from the group consisting of Cl and Br. According to such a configuration, the charge and discharge characteristics of the battery can be further improved.

[0026] In a twelfth aspect of the present disclosure, for example, in the positive electrode material according to any one of the eighth to eleventh aspects, the first solid electrolyte may contain Li3YBr2Cl4. According to such a configuration, the charge and discharge efficiency of the battery can be further increased.

[0027] In a 13th aspect of the present disclosure, for example, in the positive electrode material according to any one of the 1st to 12th aspects, the positive electrode active material may contain Ni, Co, and Mn. According to such a configuration, the energy density and charge-discharge efficiency of the battery can be further increased.

[0028] In a 14th aspect of the present disclosure, for example, the positive electrode material according to any one of the 1st to 13th aspects may further contain a second solid electrolyte. According to such a configuration, sufficient ion conductivity in the positive electrode material can be ensured.

[0029] In a 15th aspect of the present disclosure, for example, in the positive electrode material according to the 14th aspect, when the volume of the first solid electrolyte is represented by V γ and the volume of the second solid electrolyte is represented by V δ , 0.05 < V γ / V δ < 0.97 may be satisfied. According to such a configuration, the energy density and charge-discharge efficiency of the battery can be further increased.

[0030] In a 16th aspect of the present disclosure, for example, in the positive electrode material according to the 14th or 15th aspect, the second solid electrolyte may be represented by the following compositional formula (3), where α2, β2, and γ2 may each independently be a value greater than 0, M2 may contain at least one element selected from the group consisting of metal elements and metalloid elements other than Li, and X2 may contain at least one selected from the group consisting of F, Cl, Br, and I. When the halide solid electrolyte represented by formula (3) is used in the battery, the output characteristics of the battery can be improved. Li α2 M2 β2 X2 γ2 ··· Formula (3)

[0031] In a 17th aspect of the present disclosure, for example, in the positive electrode material according to the 16th aspect, the M2 may contain yttrium. According to such a configuration, the charge-discharge characteristics of the battery can be further improved.

[0032] In the 18th aspect of the present disclosure, for example, in the positive electrode material according to the 16th or 17th aspect, 2.5 ≦ α2 ≦ 3, 1 ≦ β2 ≦ 1.1, and γ2 = 6 may be satisfied. According to such a configuration, the charge-discharge characteristics of the battery can be further improved.

[0033] In the 19th aspect of the present disclosure, for example, in the positive electrode material according to any one of the 16th to 18th aspects, the X2 may include at least one selected from the group consisting of Cl and Br. According to such a configuration, the charge-discharge characteristics of the battery can be further improved.

[0034] In the 20th aspect of the present disclosure, for example, in the positive electrode material according to any one of the 16th to 19th aspects, the second solid electrolyte may include Li3YBr2Cl4. According to such a configuration, the charge-discharge efficiency of the battery can be further increased.

[0035] In the 21st aspect of the present disclosure, for example, in the positive electrode material according to the 14th or 15th aspect, the second solid electrolyte may include a sulfide solid electrolyte. According to such a configuration, the charge-discharge efficiency of the battery can be further improved.

[0036] The battery according to the 22nd aspect of the present disclosure a positive electrode including a positive electrode material according to any one of the 14th to 21st aspects, a negative electrode, an electrolyte layer provided between the positive electrode and the negative electrode, and includes.

[0037] According to the above configuration, the initial efficiency of the battery can be improved.

[0038] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0039] (Embodiment 1) FIG. 1 is a cross-sectional view showing a schematic configuration of a positive electrode material 1000 in Embodiment 1.

[0040] The positive electrode material 1000 in Embodiment 1 includes a coating active material 130. The coating active material 130 includes a positive electrode active material 110 and a coating layer 111. The shape of the positive electrode active material 110 is, for example, particulate. The coating layer 111 covers at least a part of the surface of the positive electrode active material 110.

[0041] The coating layer 111 is a layer containing a first solid electrolyte. The coating layer 111 is provided on the surface of the positive electrode active material 110. The coating layer 111 may contain only the first solid electrolyte. "Containing only the first solid electrolyte" means that, excluding inevitable impurities, no materials other than the first solid electrolyte are intentionally added. For example, raw materials of the first solid electrolyte, by-products generated when producing the first solid electrolyte, etc. are included in the inevitable impurities.

[0042] The positive electrode material 1000 further includes a second solid electrolyte 100. The shape of the second solid electrolyte 100 is, for example, particulate. According to the second solid electrolyte 100, sufficient ionic conductivity in the positive electrode material 1000 can be ensured.

[0043] The positive electrode active material 110 is separated from the second solid electrolyte 100 by the coating layer 111. The positive electrode active material 110 may not be in direct contact with the second solid electrolyte 100. This is because the coating layer 111 has ionic conductivity.

[0044] The coating layer 111 may uniformly coat the positive electrode active material 110. The coating layer 111 suppresses direct contact between the positive electrode active material 110 and the second solid electrolyte 100 and suppresses side reactions of the second solid electrolyte 100. As a result, the charge and discharge characteristics of the battery are improved, and an increase in the reaction overvoltage of the battery can be suppressed.

[0045] The coating layer 111 may cover only a part of the surface of the positive electrode active material 110. Through the portion not covered by the coating layer 111, the particles of the positive electrode active material 110 are in direct contact with each other, thereby improving the electronic conductivity between the particles of the positive electrode active material 110. As a result, the battery can operate at high output.

[0046] In the positive electrode material 1000, the pore volume of the positive electrode active material 110 is V α represented thereby, and the pore volume of the coating active material 130 is V β represented thereby, the specific surface area of the positive electrode active material 110 is S α represented thereby, and the specific surface area of the coating active material 130 is S β represented thereby. At this time, in the positive electrode material 1000, 0.20 < V β / V α < 0.88, and at least one selected from the group consisting of 0.81 < S β / S α < 0.97 is satisfied.

[0047] When the pore volume V α of the positive electrode active material 110 and the pore volume V β of the coating active material 130 satisfy the relationship of 0.20 < V β / V α < 0.88, the battery using the positive electrode material 1000 exhibits excellent initial efficiency. The ratio V β / V α of the pore volumes represents the rate of change of the pore volume when the coating layer 111 is provided. The change in the pore volume reflects the coating state of the positive electrode active material 110 by the coating layer 111. The more the coating of the positive electrode active material 110 by the coating layer 111 progresses, the lower the ratio V β / V α . The less the coating of the positive electrode active material 110 by the coating layer 111, the higher the ratio V β / V α . The ideal coating state not only contributes to appropriately balancing the electron resistance and the interfacial resistance, but also suppresses the formation of an oxide film due to the oxidative decomposition of other solid electrolytes (the second solid electrolyte 100) during the charging of the battery. As a result, the initial efficiency of the battery is improved.

[0048] "Initial efficiency" means the ratio of the discharge capacity to the charge capacity in the first cycle after the completion of the battery.

[0049] The pore volume V α of the positive electrode active material 110 is the pore volume V α of the particles of the positive electrode active material 110means the pore volume V of the coating active material 130 β is the pore volume V of the particles of the coating active material 130 β means. Actually, since it is difficult to measure the pore volume of one particle, the pore volume V α can be the pore volume of the particle group of the positive electrode active material 110. The pore volume V β can be the pore volume of the particle group of the coating active material 130.

[0050] The ratio V of the pore volume β / V α is preferably in the relationship of 0.60 ≦ V β / V α ≦ 0.76. When the ratio V of the pore volume β / V α is in such a range, the initial efficiency of the battery can be surely improved.

[0051] The pore volumes V α and V β mean the total pore volume and can be measured by the following method. First, an isothermal adsorption curve is measured using a gas adsorption amount measuring device. By the BJH method, the pore size distribution is obtained from the desorption isothermal curve, and the total pore volume (unit: cm 3 / g) is calculated from the pore size distribution.

[0052] The specific surface area S of the positive electrode active material 110 α and the specific surface area S of the coating active material 130 β When 0.81 < S β / S α < 0.97 is satisfied, the battery using the positive electrode material 1000 shows excellent initial efficiency. The ratio S of the specific surface areas β / S α represents the rate of change of the specific surface area when the coating layer 111 is provided. The change in the specific surface area reflects the coating state of the positive electrode active material 110 by the coating layer 111. The more the coating of the positive electrode active material 110 by the coating layer 111 progresses, the lower the ratio S of the specific surface areas β / S α becomes. The less the coating of the positive electrode active material 110 by the coating layer 111, the lower the ratio S of the specific surface areas β / S αrises. The ideal coating state not only contributes to appropriately balancing the electronic resistance and the interfacial resistance, but also suppresses the formation of an oxide film due to the oxidative decomposition of another solid electrolyte (second solid electrolyte 100) during charging of the battery. As a result, the initial efficiency of the battery is improved.

[0053] The specific surface area S of the positive electrode active material 110 α means the specific surface area S of the particle group of the positive electrode active material 110 α The specific surface area S of the coating active material 130 β means the specific surface area S of the particle group of the coating active material 130 β is meant.

[0054] The ratio of the specific surface areas S β / S α is desirably in the relation of 0.86 ≦ S β / S α ≦ 0.89. When the ratio of the specific surface areas S β / S α is in such a range, the initial efficiency of the battery can be reliably improved.

[0055] The specific surface areas S α and S β can be measured by the following method. First, an isothermal adsorption curve is measured using a commercially available gas adsorption amount measuring device. The specific surface area (unit: m 2 / g) is calculated from the desorption isothermal curve by the BET analysis method.

[0056] Another parameter reflecting the coating state of the positive electrode active material 110 by the coating layer 111 is a change in weight. In the positive electrode material 1000, the weight of the positive electrode active material 110 is represented by W α and the weight of the coating active material 130 is represented by W β At this time, in the positive electrode material 1000, 0.90 < W α / W β < 0.99 is satisfied. When the ratio of the weights W α / W β is in such a range, the initial efficiency of the battery can be reliably improved.

[0057] The weight W of the positive electrode active material 110 α and the weight W of the coating active material 130 β satisfy 0.90 < W α / W β < 0.99, the battery using the positive electrode material 1000 exhibits excellent initial efficiency. The weight ratio W α / W β represents the ratio of the weight change when the coating layer 111 is provided. The weight change reflects the coating state of the positive electrode active material 110 by the coating layer 111. The more the coating of the positive electrode active material 110 by the coating layer 111 progresses, the lower the weight ratio W α / W β . The less the coating of the positive electrode active material 110 by the coating layer 111, the higher the weight ratio W α / W β . The ideal coating state not only contributes to appropriately balancing the electron resistance and the interfacial resistance, but also suppresses the formation of an oxide film due to the oxidative decomposition of other solid electrolytes (the second solid electrolyte 100) during the charging of the battery. As a result, the initial efficiency of the battery is improved.

[0058] The weight W of the positive electrode active material 110 α means the weight W of the particle group of the positive electrode active material 110 α . The weight W of the coating active material 130 β means the weight W of the particle group of the coating active material 130 β .

[0059] The weight ratio W α / W β desirably satisfies the relationship 0.95 ≤ W α / W β ≤ 0.975. When the weight ratio W α / W β is within such a range, the initial efficiency of the battery can be surely improved.

[0060] The thickness of the coating layer 111 is, for example, 1 nm or more. When the thickness of the coating layer 111 is appropriately adjusted, the contact between the positive electrode active material 110 and the second solid electrolyte 100 can be suppressed, and the side reaction of the second solid electrolyte 100 can be suppressed. For this reason, the charge and discharge efficiency of the battery can be improved.

[0061] The thickness of the coating layer 111 may be greater than 14 nm and less than 167 nm. The thickness of the coating layer 111 is preferably 32 nm or more and 71 nm or less. According to such a configuration, the charge and discharge efficiency of the battery can be surely improved.

[0062] The thickness of the coating layer 111 can be measured by the following method. First, the coated active material 130 is subjected to ion milling. Then, a cross-sectional observation of the particles of the coated active material 130 is performed with an electron microscope. The thickness of the coating layer 111 is measured at any plurality of points (for example, three points) within the observation field of view. The average value of the obtained measurement values can be regarded as the thickness of the coating layer 111.

[0063] It is also possible to remove the coating layer 111 from the coated active material 130 and measure the pore volume, specific surface area, etc. of the positive electrode active material 110. For example, by using a solvent in which the coating layer 111 is soluble and the positive electrode active material 110 is insoluble to remove the coating layer 111 and drying it, the positive electrode active material 110 before forming the coating layer 111 can be obtained.

[0064] The positive electrode active material 110, the coating layer 111, and the second solid electrolyte 100 will be described in more detail.

[0065] (Coating layer 111) As the first solid electrolyte contained in the coating layer 111, a material having low electron conductivity and oxidation resistance can be used. For example, a halide solid electrolyte or the like can be used as the first solid electrolyte.

[0066] The halide solid electrolyte has high ionic conductivity and high potential stability. Therefore, by using the halide solid electrolyte, the charge and discharge efficiency of the battery can be further increased, and the increase in the reaction overvoltage of the battery can be further suppressed.

[0067] The first solid electrolyte contained in the coating layer 111 can be a halide solid electrolyte.

[0068] The halide solid electrolyte is represented by, for example, the following compositional formula (1). In compositional formula (1), α1, β1, and γ1 are each independently a value greater than 0. M1 contains at least one element selected from the group consisting of metal elements other than Li and metalloid elements. X1 contains at least one selected from the group consisting of F, Cl, Br, and I.

[0069] Li α1 M1 β1 X1 γ1 ··· Formula (1)

[0070] The "metalloid elements" include B, Si, Ge, As, Sb, and Te.

[0071] The "metal elements" include all elements contained in Groups 1 to 12 of the periodic table excluding hydrogen, and all elements contained in Groups 13 to 16 excluding B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se. That is, the metal elements are a group of elements that can become cations when forming a halide compound and an inorganic compound.

[0072] The halide solid electrolyte represented by formula (1) has a higher ionic conductivity compared to halide solid electrolytes such as LiI composed only of Li and halogen elements. Therefore, when the halide solid electrolyte represented by formula (1) is used in a battery, the output characteristics of the battery can be improved.

[0073] In the present disclosure, when an element in a formula is represented as "(Al, Ga, In)", this notation indicates at least one element selected from the group of elements within the parentheses. That is, "(Al, Ga, In)" is synonymous with "at least one selected from the group consisting of Al, Ga, and In". The same applies to other elements.

[0074] In compositional formula (1), M1 may contain Y (= yttrium). That is, the first solid electrolyte may contain Y as a metal element.

[0075] According to the above configuration, the ionic conductivity of the first solid electrolyte can be further improved. Thereby, the charge and discharge characteristics of the battery can be further improved.

[0076] The compositional formula (1) may satisfy 2.5 ≤ α1 ≤ 3, 1 ≤ β1 ≤ 1.1, and γ1 = 6.

[0077] According to the above configuration, the ionic conductivity of the first solid electrolyte can be further improved. Thereby, the charge and discharge characteristics of the battery can be further improved.

[0078] X1 may contain at least one selected from the group consisting of Cl and Br. X1 may contain Cl and Br.

[0079] According to the above configuration, the ionic conductivity of the first solid electrolyte can be further improved. Thereby, the charge and discharge characteristics of the battery can be further improved.

[0080] The halide solid electrolyte containing Y may be a compound represented by the following compositional formula (2).

[0081] Li a Me b Y c X6 ··· Formula (2)

[0082] The compositional formula (2) satisfies a + mb + 3c = 6 and c > 0. In the compositional formula (2), Me contains at least one element selected from the group consisting of metal elements and metalloid elements other than Li and Y. m is the valence of Me. X contains at least one selected from the group consisting of F, Cl, Br, and I.

[0083] Me may contain 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.

[0084] According to the above configuration, the ionic conductivity of the first solid electrolyte can be further improved. Note that the halide solid electrolyte may not contain sulfur.

[0085] The first solid electrolyte may be a compound represented by the following compositional formula (A1). Here, in the compositional formula (A1), X is at least one element selected from the group consisting of Cl and Br. In the compositional formula (A1), 0 < d < 2 is satisfied.

[0086] Li 6-3d Y d X6 ··· Formula (A1)

[0087] According to the above configuration, the ionic conductivity of the first solid electrolyte can be further improved. Thereby, the charge and discharge efficiency of the battery can be further improved.

[0088] The first solid electrolyte may be a compound represented by the following compositional formula (A2). Here, in the compositional formula (A2), X is at least one element selected from the group consisting of Cl and Br.

[0089] Li3YX6 ··· Formula (A2)

[0090] According to the above configuration, the ionic conductivity of the first solid electrolyte can be further improved. Thereby, the charge and discharge efficiency of the battery can be further improved.

[0091] The first solid electrolyte may be a compound represented by the following compositional formula (A3). Here, in the compositional formula (A3), 0 < δ ≦ 0.15 is satisfied.

[0092] Li 3-3δ Y 1+δ Cl6 ··· Formula (A3)

[0093] According to the above configuration, the ionic conductivity of the first solid electrolyte can be further improved. Thereby, the charge and discharge efficiency of the battery can be further improved.

[0094] The first solid electrolyte may be a compound represented by the following compositional formula (A4). Here, in the compositional formula (A4), 0 < δ ≦ 0.25 is satisfied.

[0095] Li 3-3δ Y 1+δ Br6 ··· Formula (A4)

[0096] According to the above configuration, the ionic conductivity of the first solid electrolyte can be further improved. Thereby, the charge and discharge efficiency of the battery can be further improved.

[0097] The first solid electrolyte may be a compound represented by the following compositional formula (A5). Here, in the compositional formula (A5), Me is at least one element selected from the group consisting of Mg, Ca, Sr, Ba, and Zn. In the compositional formula (A5), -1 < δ < 2, 0 < a < 3, 0 < (3 - 3δ + a), 0 < (1 + δ - a), and 0 ≦ x ≦ 6 are satisfied.

[0098] Li 3-3δ+a Y 1+δ-a Me a Cl 6-x Br x ··· Formula (A5)

[0099] According to the above configuration, the ionic conductivity of the first solid electrolyte can be further improved. Thereby, the charge and discharge efficiency of the battery can be further improved.

[0100] The first solid electrolyte may be a compound represented by the following compositional formula (A6). Here, in the compositional formula (A6), Me is at least one element selected from the group consisting of Al, Sc, Ga, and Bi. In the compositional formula (A6), -1 < δ < 1, 0 < a < 2, 0 < (1 + δ - a), and 0 ≦ x ≦ 6 are satisfied.

[0101] Li 3-3δ Y 1+δ-a Me a Cl 6-x Brx ···Formula (A6)

[0102] According to the above configuration, the ionic conductivity of the first solid electrolyte can be further improved. Thereby, the charge-discharge efficiency of the battery can be further improved.

[0103] The first solid electrolyte may be a compound represented by the following compositional formula (A7). Here, in the compositional formula (A7), Me is at least one element selected from the group consisting of Zr, Hf, and Ti. In the compositional formula (A7), -1 < δ < 1, 0 < a < 1.5, 0 < (3 - 3δ - a), 0 < (1 + δ - a), and 0 ≦ x ≦ 6 are satisfied.

[0104] Li 3-3δ-a Y 1+δ-a Me a Cl 6-x Br x ···Formula (A7)

[0105] According to the above configuration, the ionic conductivity of the first solid electrolyte can be further improved. Thereby, the charge-discharge efficiency of the battery can be further improved.

[0106] The first solid electrolyte may be a compound represented by the following compositional formula (A8). Here, in the compositional formula (A8), Me is at least one element selected from the group consisting of Ta and Nb. In the compositional formula (A8), -1 < δ < 1, 0 < a < 1.2, 0 < (3 - 3δ - 2a), 0 < (1 + δ - a), and 0 ≦ x ≦ 6 are satisfied.

[0107] Li 3-3δ-2a Y 1+δ-a Me a Cl 6-x Br x ···Formula (A8)

[0108] According to the above configuration, the ionic conductivity of the first solid electrolyte can be further improved. Thereby, the charge-discharge efficiency of the battery can be further improved.

[0109] As the first solid electrolyte, for example, Li3YX6, Li2MgX4, Li2FeX4, Li(Al,Ga,In)X4, Li3(Al,Ga,In)X6, etc. can be used. Here, X contains at least one element selected from the group consisting of Cl and Br.

[0110] A typical composition of Li3YX6 is, for example, Li3YBr2Cl4. The first solid electrolyte may contain Li3YBr2Cl4.

[0111] The first solid electrolyte is Li 2.7 Y 1.1 Cl6, Li3YBr6 or Li 2.5 Y 0.5 Zr 0.5 Cl6 may also be used.

[0112] According to the above configuration, the charge and discharge efficiency of the battery can be further improved.

[0113] (The second solid electrolyte) The second solid electrolyte 100 contains a material having high ionic conductivity. The second solid electrolyte can be a halide solid electrolyte. As the second solid electrolyte 100, a compound represented by the following compositional formula (3) can be used. In the compositional formula (3), α2, β2, and γ2 are each independently a value greater than 0. M2 contains at least one element selected from the group consisting of metal elements other than Li and metalloid elements. X2 contains at least one selected from the group consisting of F, Cl, Br, and I.

[0114] Li α2 M2 β2 X2 γ2 ··· Formula (3)

[0115] According to the above configuration, the ionic conductivity of the second solid electrolyte 100 can be further improved. Thereby, the charge and discharge efficiency of the battery can be further improved.

[0116] In the compositional formula (3), M2 may contain Y. That is, the second solid electrolyte 100 may contain Y as a metal element.

[0117] According to the above configuration, the ionic conductivity of the second solid electrolyte 100 can be further improved. Thereby, the charge and discharge characteristics of the battery can be further improved.

[0118] The compositional formula (3) may satisfy 2.5 ≦ α2 ≦ 3, 1 ≦ β2 ≦ 1.1, and γ2 = 6.

[0119] According to the above configuration, the ionic conductivity of the second solid electrolyte 100 can be further improved. Thereby, the charge and discharge characteristics of the battery can be further improved.

[0120] In the compositional formula (3), X2 may contain at least one selected from the group consisting of Br (= bromine) and Cl (= chlorine).

[0121] According to the above configuration, the ionic conductivity of the second solid electrolyte 100 can be further improved. Thereby, the charge and discharge characteristics of the battery can be further improved.

[0122] In the compositional formula (3), X2 may contain Br and Cl.

[0123] According to the above configuration, the ionic conductivity of the second solid electrolyte 100 can be further improved. Thereby, the charge and discharge characteristics of the battery can be further improved.

[0124] The second solid electrolyte 100 may be a compound represented by the following compositional formula (B1). Here, in the compositional formula (B1), X contains at least one selected from the group consisting of F, Cl, Br, and I. In the compositional formula (B1), 0 < d < 2 is satisfied.

[0125] Li 6-3d Y d X6 ··· Formula (B1)

[0126] According to the above configuration, the ionic conductivity of the second solid electrolyte 100 can be further improved. As a result, the charge and discharge efficiency of the battery can be further improved.

[0127] The second solid electrolyte 100 may be a compound represented by the following compositional formula (B2). Here, in the compositional formula (B2), X contains at least one selected from the group consisting of F, Cl, Br, and I.

[0128] Li3YX6 ··· Formula (B2)

[0129] According to the above configuration, the ionic conductivity of the second solid electrolyte 100 can be further improved. As a result, the charge and discharge efficiency of the battery can be further improved.

[0130] The second solid electrolyte 100 may be a compound represented by the following compositional formula (B3). Here, in the compositional formula (B3), Me is at least one element selected from the group consisting of Mg, Ca, Sr, Ba, and Zn. In the compositional formula (B3), -1 < δ < 2, 0 < a < 3, 0 < (3 - 3δ + a), 0 < (1 + δ - a), 0 ≤ x < 6, 0 < y ≤ 6, and (x + y) < 6 are satisfied.

[0131] Li 3-3δ+a Y 1+δ-a Me a Cl 6-x-y Br x I y ··· Formula (B3)

[0132] According to the above configuration, the ionic conductivity of the second solid electrolyte 100 can be further improved. As a result, the charge and discharge efficiency of the battery can be further improved.

[0133] The second solid electrolyte 100 may be a compound represented by the following compositional formula (B4). Here, in the compositional formula (B4), Me is at least one element selected from the group consisting of Al, Sc, Ga, and Bi. In the compositional formula (B4), -1 < δ < 1, 0 < a < 2, 0 < (1 + δ - a), 0 ≦ x < 6, 0 < y ≦ 6, and (x + y) < 6 are satisfied.

[0134] Li 3-3δ Y 1+δ-a Me a Cl 6-x-y Br x I y ··· Formula (B4)

[0135] According to the above configuration, the ionic conductivity of the second solid electrolyte 100 can be further improved. Thereby, the charge and discharge efficiency of the battery can be further improved.

[0136] The second solid electrolyte 100 may be a compound represented by the following compositional formula (B5). Here, in the compositional formula (B5), Me is at least one element selected from the group consisting of Zr, Hf, and Ti. In the compositional formula (B5), -1 < δ < 1, 0 < a < 1.5, 0 < (3 - 3δ - a), 0 < (1 + δ - a), 0 ≦ x < 6, 0 < y ≦ 6, and (x + y) < 6 are satisfied.

[0137] Li 3-3δ-a Y 1+δ-a Me a Cl 6-x-y Br x I y ··· Formula (B5)

[0138] According to the above configuration, the ionic conductivity of the second solid electrolyte 100 can be further improved. Thereby, the charge and discharge efficiency of the battery can be further improved.

[0139] The second solid electrolyte 100 may be a compound represented by the following compositional formula (B6). Here, in the compositional formula (B6), Me is at least one element selected from the group consisting of Ta and Nb. In the compositional formula (B6), -1 < δ < 1, 0 < a < 1.2, 0 < (3 - 3δ - 2a), 0 < (1 + δ - a), 0 ≦ x < 6, 0 < y ≦ 6, and (x + y) < 6 are satisfied.

[0140] Li 3-3δ-2a Y 1+δ-a Me a Cl 6-x-y Br x I y ··· Formula (B6)

[0141] According to the above configuration, the ionic conductivity of the second solid electrolyte 100 can be further improved. Thereby, the charge and discharge efficiency of the battery can be further improved.

[0142] As the second solid electrolyte 100, for example, Li3YX6, Li2MgX4, Li2FeX4, Li(Al, Ga, In)X4, Li3(Al, Ga, In)X6, etc. can be used. Here, X contains at least one selected from the group consisting of F, Cl, Br, and I.

[0143] A typical composition of Li3YX6 is, for example, Li3YBr2Cl4. The second solid electrolyte 100 may contain Li3YBr2Cl4.

[0144] According to the above configuration, the charge and discharge efficiency of the battery can be further increased.

[0145] The second solid electrolyte 100 may contain a sulfide solid electrolyte. As the sulfide solid electrolyte, for example, Li2S - P2S5, Li2S - SiS2, Li2S - B2S3, Li2S - GeS2, Li 3.25 Ge 0.25 P 0.75 S4, Li 10 GeP2S 12 etc. can be used. To these, LiX, Li2O, MO q 、Lip MO q etc. may be added. Here, the element X in "LiX" is at least one element selected from the group consisting of F, Cl, Br, and I. MO q ", and "Li p MO q ", the element M in "" is at least one element selected from the group consisting of P, Si, Ge, B, Al, Ga, In, Fe, and Zn. "MO q ", and "Li p MO q ", p and q in "" are each independent natural numbers.

[0146] In Embodiment 1, the second solid electrolyte 100 may be a sulfide solid electrolyte. For example, the sulfide solid electrolyte may contain lithium sulfide and phosphorus sulfide. The sulfide solid electrolyte may be Li2S-P2S5.

[0147] Li2S-P2S5 has high ionic conductivity and is stable against oxidation-reduction. Therefore, by using Li2S-P2S5, the charge-discharge efficiency of the battery can be further improved. Note that the halide solid electrolyte used as the first solid electrolyte and the second solid electrolyte may contain an oxygen atom as an anion other than a halogen element.

[0148] (Cathode active material) The cathode active material 110 includes a material having the property of occluding and releasing metal ions (e.g., lithium ions). As the cathode active material 110, for example, lithium-containing transition metal oxides (e.g., Li(NiCoAl)O2, Li(NiCoMn)O2, LiCoO2, etc.), transition metal fluorides, polyanion materials, fluorinated polyanion materials, transition metal sulfides, transition metal oxysulfides, transition metal oxynitrides, etc. can be used. In particular, when a lithium-containing transition metal oxide is used as the cathode active material 110, the manufacturing cost can be reduced and the average discharge voltage can be increased.

[0149] In Embodiment 1, the positive electrode active material 110 may contain Ni, Co, and Mn. The positive electrode active material 110 may be lithium nickel cobalt manganese oxide. For example, the positive electrode active material 110 may be Li(NiCoMn)O2.

[0150] According to the above configuration, the energy density and charge-discharge efficiency of the battery can be further increased.

[0151] The shape of the second solid electrolyte 100 in Embodiment 1 is not particularly limited, and may be, for example, needle-like, spherical, ellipsoidal, etc. For example, the shape of the second solid electrolyte 100 may be particulate.

[0152] For example, when the shape of the second solid electrolyte 100 in Embodiment 1 is particulate (e.g., spherical), the median diameter may be 100 μm or less. When the median diameter is 100 μm or less, the coating active material 130 and the second solid electrolyte 100 can form a good dispersion state in the positive electrode material 1000. Therefore, the charge-discharge characteristics of the battery are improved. In Embodiment 1, the median diameter of the second solid electrolyte 100 may be 10 μm or less.

[0153] According to the above configuration, in the positive electrode material 1000, the coating active material 130 and the second solid electrolyte 100 can form a good dispersion state.

[0154] In Embodiment 1, the median diameter of the second solid electrolyte 100 may be smaller than the median diameter of the coating active material 130.

[0155] According to the above configuration, in the positive electrode material 1000, the second solid electrolyte 100 and the coating active material 130 can form a better dispersion state.

[0156] The median diameter of the coating active material 130 may be 0.1 μm or more and 100 μm or less.

[0157] When the median diameter of the coating active material 130 is 0.1 μm or more, in the positive electrode material 1000, the coating active material 130 and the second solid electrolyte 100 can form a good dispersion state. As a result, the charge-discharge characteristics of the battery are improved.

[0158] When the median diameter of the coating active material 130 is 100 μm or less, the diffusion rate of lithium in the coating active material 130 is sufficiently ensured. Therefore, the battery can operate at high power.

[0159] The median diameter of the coating active material 130 may be larger than the median diameter of the second solid electrolyte 100. Thereby, the coating active material 130 and the second solid electrolyte 100 can form a good dispersion state.

[0160] In the positive electrode material 1000, the second solid electrolyte 100 and the coating active material 130 may be in contact with each other as shown in FIG. 1. At this time, the coating layer 111 and the positive electrode active material 110 are in contact with each other.

[0161] The positive electrode material 1000 may include a plurality of particles of the second solid electrolyte 100 and a plurality of particles of the coating active material 130.

[0162] In the positive electrode material 1000, the content of the second solid electrolyte 100 and the content of the coating active material 130 may be the same as or different from each other.

[0163] In this specification, the "median diameter" means the particle diameter when the cumulative volume in the volume-based particle size distribution is equal to 50%. The volume-based particle size distribution is measured by, for example, a laser diffraction type measuring device or an image analysis device.

[0164] The first solid electrolyte and the second solid electrolyte 100 contained in the coating layer 111 can be manufactured by the following method.

[0165] Prepare a raw material powder of a binary halide to achieve the mixing ratio of the target composition. For example, when preparing Li3YCl6, prepare LiCl and YCl3 in a molar ratio of 3:1.

[0166] At this time, by selecting the type of raw material powder, "M", "M1", "M2", "Me", "X", "X1", "X2" in the above composition formula can be determined. Also, by adjusting the raw materials, mixing ratio, and synthesis process, the above values of "α1", "β1", "γ1", "α2", "β2", "γ2", "d", "δ", "a", "x", "y" can be adjusted.

[0167] After thoroughly mixing the raw material powders, use the method of mechanochemical milling to mix, grind, and react the raw material powders with each other. Or, after thoroughly mixing the raw material powders, they may be sintered in a vacuum.

[0168] Thereby, a first solid electrolyte and a second solid electrolyte containing the crystal phase as described above are obtained.

[0169] The composition (i.e., crystal structure) of the crystal phase in the solid electrolyte can be determined by adjusting the reaction method and reaction conditions of the raw material powders with each other.

[0170] The coating active material 130 can be manufactured by the following method.

[0171] Mix the powder of the positive electrode active material 110 and the powder of the first solid electrolyte in an appropriate ratio to obtain a mixture. Perform a milling process on the mixture to impart mechanical energy to the mixture. For the milling process, a mixing device such as a ball mill can be used. In order to suppress the oxidation of the material, the milling process may be performed in a dry and inert atmosphere.

[0172] The coating active material 130 may be manufactured by a dry particle composite method. The treatment by the dry particle composite method includes applying at least one mechanical energy selected from the group consisting of impact, compression, and shear to the positive electrode active material 110 and the first solid electrolyte. The positive electrode active material 110 and the first solid electrolyte are mixed in an appropriate ratio.

[0173] The apparatus used in the manufacturing method of the coating active material 130 is not particularly limited, and may be an apparatus capable of applying mechanical energy such as impact, compression, and shear to the mixture of the positive electrode active material 110 and the first solid electrolyte. Examples of the apparatus capable of applying mechanical energy include compression shear type processing apparatuses (particle composite apparatuses) such as a ball mill, "Mechanofusion" (manufactured by Hosokawa Micron Corporation), and "Novilta" (manufactured by Hosokawa Micron Corporation).

[0174] "Mechanofusion" is a particle composite apparatus using a dry mechanical composite technology by applying strong mechanical energy to a plurality of different material particles. In Mechanofusion, mechanical energy such as compression, shear, and friction is applied to the powder raw material introduced between the rotating container and the press head, thereby causing particle composite.

[0175] "Novilta" is a particle composite apparatus using a dry mechanical composite technology developed from the particle composite technology for performing composite using nanoparticle as a raw material. Novilta manufactures composite particles by applying mechanical energy of impact, compression, and shear to a plurality of raw material powders.

[0176] In "Novilta", inside a horizontally cylindrical mixing container, a rotor arranged to have a predetermined gap with the inner wall of the mixing container rotates at high speed, and the process of forcibly passing through the gap with respect to the raw material powder is repeated a plurality of times. Thereby, a force of impact, compression, and shear can be applied to the mixture to produce composite particles of the positive electrode active material 110 and the first solid electrolyte. Conditions such as the rotation speed of the rotor, the treatment time, and the charging amount can be appropriately adjusted.

[0177] The positive electrode material 1000 is obtained by mixing the coated active material 130 and the second solid electrolyte 100. The method of mixing the coated active material 130 and the second solid electrolyte 100 is not particularly limited. For example, the coated active material 130 and the second solid electrolyte 100 may be mixed using an instrument such as a mortar, or the coated active material 130 and the second solid electrolyte 100 may be mixed using a mixing device such as a ball mill.

[0178] The mixing ratio of the coated active material 130 and the second solid electrolyte 100 is also not particularly limited. For example, when the volume of the first solid electrolyte in the coated active material 130 is represented by V γ and the volume of the second solid electrolyte 100 is represented by V δ the mixing ratio of the coated active material 130 and the second solid electrolyte 100 is adjusted so that 0.05 < V γ / V δ < 0.97 is satisfied. Thereby, the energy density and charge-discharge efficiency of the battery 2000 can be further increased.

[0179] The volume ratio V γ / V δ preferably satisfies the relationship of 0.13 ≤ V γ / V δ ≤ 0.43. When the volume ratio V γ / V δ is within such a range, the initial efficiency of the battery can be surely improved.

[0180] (Embodiment 2) Hereinafter, Embodiment 2 will be described. Descriptions overlapping with those of the above-described Embodiment 1 will be omitted as appropriate.

[0181] FIG. 2 is a cross-sectional view showing a schematic configuration of the battery 2000 in Embodiment 2.

[0182] The battery 2000 in Embodiment 2 includes a positive electrode 201, an electrolyte layer 202, and a negative electrode 203.

[0183] The positive electrode 201 includes the positive electrode material 1000 in Embodiment 1.

[0184] The electrolyte layer 202 is disposed between the positive electrode 201 and the negative electrode 203.

[0185] According to the above configuration, the initial efficiency of the battery 2000 can be improved.

[0186] Regarding the ratio “v1:100 - v1” of the volume of the positive electrode active material 110 contained in the positive electrode 201 to the total volume of the first solid electrolyte and the second solid electrolyte 100, 30 ≤ v1 ≤ 95 may be satisfied. When 30 ≤ v1 is satisfied, the energy density of the battery 2000 is sufficiently ensured. Also, when v1 ≤ 95 is satisfied, operation at high power becomes possible.

[0187] The thickness of the positive electrode 201 may be 10 μm or more and 500 μm or less. When the thickness of the positive electrode 201 is 10 μm or more, the energy density of the battery 2000 is sufficiently ensured. When the thickness of the positive electrode 201 is 500 μm or less, operation at high power becomes possible.

[0188] The electrolyte layer 202 is a layer containing an electrolyte. The electrolyte is, for example, a solid electrolyte (i.e., the third solid electrolyte). That is, the electrolyte layer 202 may be a solid electrolyte layer.

[0189] As the third solid electrolyte contained in the electrolyte layer 202, a halide solid electrolyte, a sulfide solid electrolyte, an oxide solid electrolyte, a polymer solid electrolyte, or a complex hydride solid electrolyte may be used.

[0190] When the third solid electrolyte is a halide solid electrolyte, as the halide solid electrolyte, the same halide solid electrolyte as the first solid electrolyte and / or the second solid electrolyte in Embodiment 1 may be used. That is, the electrolyte layer 202 may contain a halide solid electrolyte having the same composition as the composition of the first solid electrolyte and / or the second solid electrolyte.

[0191] According to the above configuration, the output density and charge / discharge characteristics of the battery 2000 can be further improved.

[0192] Further, the third solid electrolyte may be a halide solid electrolyte having a composition different from those of the first and second solid electrolytes. That is, the electrolyte layer 202 may contain a halide solid electrolyte having a composition different from those of the first and second solid electrolytes.

[0193] According to the above configuration, the charge-discharge characteristics of the battery can be further improved.

[0194] When the third solid electrolyte is a sulfide solid electrolyte, examples of the sulfide solid electrolyte include Li2S-P2S5, Li2S-SiS2, Li2S-B2S3, Li2S-GeS2, Li 3.25 Ge 0.25 P 0.75 S4, Li 10 GeP2S 12 and the like. LiX, Li2O, MO q , Li p MO q and the like may be added thereto. The element X in "LiX" is at least one element selected from the group consisting of F, Cl, Br, and I. The element M in "MO q " and "Li p MO q " is at least one element selected from the group consisting of P, Si, Ge, B, Al, Ga, In, Fe, and Zn. The p and q in "MO q " and "Li p MO q " are each an independent natural number.

[0195] As the third solid electrolyte, the same sulfide solid electrolyte as the second solid electrolyte in Embodiment 1 may be used. That is, the electrolyte layer 202 may contain a sulfide solid electrolyte having the same composition as that of the second solid electrolyte in Embodiment 1.

[0196] According to the above configuration, since a sulfide solid electrolyte with excellent reduction stability is included, a negative electrode material with a low potential such as graphite or metallic lithium can be used, and the energy density of the battery 2000 can be improved. Also, according to the configuration in which the electrolyte layer 202 includes the same sulfide solid electrolyte as the second solid electrolyte 100, the charge and discharge characteristics of the battery 2000 can be improved.

[0197] When the third solid electrolyte is an oxide solid electrolyte, examples of the oxide solid electrolyte include NASICON-type solid electrolytes typified by LiTi2(PO4)3 and its element-substituted compounds, perovskite-type solid electrolytes of the (LaLi)TiO3 system, Li 14 ZnGe4O 16 , LISICON-type solid electrolytes typified by Li4SiO4, LiGeO4 and their element-substituted compounds, garnet-type solid electrolytes typified by Li7La3Zr2O 12 and their element-substituted compounds, glasses or glass ceramics in which materials such as Li2SO4 and Li2CO3 are added to base materials containing Li-B-O compounds such as Li3N and its H-substituted compound, Li3PO4 and its N-substituted compound, LiBO2, and Li3BO3 may be used.

[0198] When the third solid electrolyte is a polymer solid electrolyte, as the polymer solid electrolyte, for example, a compound of a polymer compound and a lithium salt can be used. The polymer compound may have an ethylene oxide structure. By having an ethylene oxide structure, the polymer compound can contain a large amount of lithium salt, so that the ionic conductivity can be further increased. As the lithium salt, LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), LiC(SO2CF3)3, etc. can be used. As the lithium salt, 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.

[0199] When the third solid electrolyte is a complex hydride solid electrolyte, examples of the complex hydride solid electrolyte that can be used include LiBH4-LiI, LiBH4-P2S5, and the like.

[0200] The electrolyte layer 202 may contain the third solid electrolyte as a main component. That is, the electrolyte layer 202 may contain 50% or more of the third solid electrolyte, for example, by weight ratio with respect to the entire electrolyte layer 202.

[0201] According to the above configuration, the charge-discharge characteristics of the battery 2000 can be further improved.

[0202] The electrolyte layer 202 may contain 70% or more of the third solid electrolyte, by weight ratio with respect to the entire electrolyte layer 202.

[0203] According to the above configuration, the charge-discharge characteristics of the battery 2000 can be further improved.

[0204] While containing the third solid electrolyte as a main component, the electrolyte layer 202 may further contain inevitable impurities, or starting materials, by-products, and decomposition products used when synthesizing the third solid electrolyte.

[0205] Excluding inevitable impurities due to contamination, the electrolyte layer 202 may contain 100% of the third solid electrolyte, by weight ratio with respect to the entire electrolyte layer 202.

[0206] According to the above configuration, the charge-discharge characteristics of the battery 2000 can be further improved.

[0207] As described above, the electrolyte layer 202 may be composed only of the third solid electrolyte.

[0208] The electrolyte layer 202 may contain two or more of the materials listed as the third solid electrolyte. For example, the electrolyte layer 202 may contain a halide solid electrolyte and a sulfide solid electrolyte.

[0209] 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, the positive electrode 201 and the negative electrode 203 can be more reliably separated. When the thickness of the electrolyte layer 202 is 300 μm or less, operation at high output can be realized.

[0210] The negative electrode 203 contains a material having the property of occluding and releasing metal ions (for example, lithium ions). The negative electrode 203 includes, for example, a negative electrode active material.

[0211] As the negative electrode active material, a metal material, a carbon material, an oxide, a nitride, a tin compound, a silicon compound, etc. can be used. The metal material may be a single metal. Or, the metal material may be an alloy. Examples of the metal material include lithium metal, lithium alloy, etc. Examples of the carbon material include natural graphite, coke, carbon in the process of graphitization, carbon fiber, spherical carbon, artificial graphite, amorphous carbon, etc. From the viewpoint of capacity density, silicon (Si), tin (Sn), a silicon compound or a tin compound can be used.

[0212] The negative electrode 203 may contain a solid electrolyte. As the solid electrolyte, the solid electrolyte exemplified as the material constituting the electrolyte layer 202 may be used. According to the above configuration, the lithium ion conductivity inside the negative electrode 203 is increased, and operation at high output becomes possible.

[0213] The median diameter of the particles of the negative electrode active material may be 0.1 μm or more and 100 μm or less. When the median diameter of the particles of the negative electrode active material is 0.1 μm or more, in the negative electrode, the negative electrode active material and the solid electrolyte can form a good dispersion state. Thereby, the charge and discharge characteristics of the battery 2000 are improved. Also, when the median diameter of the negative electrode active material is 100 μm or less, the lithium diffusion in the negative electrode active material becomes faster. For this reason, the battery 2000 can operate at high output.

[0214] The median diameter of the particles of the negative electrode active material may be larger than the median diameter of the solid electrolyte contained in the negative electrode 203. Thereby, a good dispersion state between the particles of the negative electrode active material and the particles of the solid electrolyte can be formed.

[0215] Regarding the volume ratio "v2:100 - v2" of the negative electrode active material and the solid electrolyte included in the negative electrode 203, 30 ≤ v2 ≤ 95 may be satisfied. When 30 ≤ v2, sufficient energy density of the battery 2000 can be ensured. When v2 ≤ 95, operation at high output can be realized.

[0216] The thickness of the negative electrode 203 may be 10 μm or more and 500 μm or less. When the thickness of the negative electrode 203 is 10 μm or more, sufficient energy density of the battery 2000 can be ensured. Also, when the thickness of the negative electrode 203 is 500 μm or less, operation at high output can be realized.

[0217] At least one of the positive electrode 201, the electrolyte layer 202, and the negative electrode 203 may contain a binder for the purpose of improving the adhesion between particles. The binder is used to improve the binding property of the materials constituting the electrode. Examples of the binder include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamideimide, polyacrylonitrile, polyacrylic acid, methyl polyacrylate ester, ethyl polyacrylate ester, hexyl polyacrylate ester, polymethacrylic acid, methyl polymethacrylate ester, ethyl polymethacrylate ester, hexyl polymethacrylate ester, polyvinyl acetate, polyvinyl pyrrolidone, polyether, polyethersulfone, hexafluoropolypropylene, styrene butadiene rubber, carboxymethyl cellulose, etc. Also, as the binder, a copolymer 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 can be used. Also, two or more selected from these may be mixed and used as the binder.

[0218] At least one of the positive electrode 201 and the negative electrode 203 may contain a conductive assistant for the purpose of enhancing the electron conductivity. Examples of the conductive assistant include graphites such as natural graphite or artificial graphite, carbon blacks such as acetylene black and ketjen black, 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. When a carbon conductive assistant is used, cost reduction can be achieved.

[0219] Note that the battery in Embodiment 2 can be configured as batteries of various shapes such as coin type, cylindrical type, rectangular type, sheet type, button type, flat type, and laminated type.

Examples

[0220] Hereinafter, the details of the present disclosure will be described using examples and comparative examples.

[0221] <<Example 1>> [Production of the second solid electrolyte] In an argon glove box with a dew point of -60°C or lower, the raw material powders LiCl, LiBr, and YCl3 were weighed so that the molar ratio was LiCl:LiBr:YCl3 = 1:2:1. Using a planetary ball mill (manufactured by Fritsch, P-5 type), the mixture obtained under the conditions of 25 hours and 600 rpm was milled. As a result, a powder of the second solid electrolyte represented by the composition formula of Li3Y1Br2Cl4 (hereinafter referred to as LYBC) was obtained.

[0222] [Production of the first solid electrolyte] In an argon glove box with a dew point below -60 °C, the raw material powders LiCl, LiBr, and YCl3 were weighed so that the molar ratio was LiCl:LiBr:YCl3 = 1:2:1. Using a planetary ball mill (manufactured by Fritsch, model P-5), the mixture obtained under the conditions of 25 hours and 600 rpm was milled. As a result, a powder of the first solid electrolyte represented by the composition formula Li3Y1Br2Cl4 was obtained.

[0223] [Preparation of Coated Active Material] As the positive electrode active material, powder of Li(NiCoMn)O2 (hereinafter referred to as NCM) was prepared. A coating layer made of Li3Y1Br2Cl4 was formed on the NCM. The coating layer was formed by a compression-shear treatment using a particle composite device (NOB-MINI, manufactured by Hosokawa Micron Corporation). Specifically, the positive electrode active material and the first solid electrolyte were weighed so that the weight ratio was 97.5:2.5, and processed under the conditions of blade clearance: 2 mm and processing time: 10 min to obtain the coated active material of Example 1.

[0224] [Preparation of Positive Electrode Material] In an argon glove box, the coated active material of Example 1 and the second solid electrolyte were weighed so that the volume ratio of NCM to the solid electrolyte (the total of the first solid electrolyte and the second solid electrolyte) was 73:27. By mixing these in an agate mortar, the positive electrode material of Example 1 was prepared.

[0225] <<Example 2>> The positive electrode material of Example 2 was obtained in the same manner as in Example 1, except that in the compression-shear treatment for preparing the coated active material, the weight ratio of the positive electrode active material to the first solid electrolyte was changed to 95:5.

[0226] <<Example 3>> [Preparation of Sulfide Solid Electrolyte] In an argon glove box with a dew point of -60°C or lower, the raw material powders Li2S and P2S5 were weighed so that the molar ratio was Li2S:P2S5 = 75:25. These were pulverized and mixed in a mortar to obtain a mixture. Then, using a planetary ball mill (manufactured by Fritsch, model P-7), the mixture was milled for 10 hours under the conditions of 510 rpm. Thereby, a glassy solid electrolyte was obtained. The glassy solid electrolyte was heat-treated in an inert atmosphere at 270°C for 2 hours. Thereby, as the second solid electrolyte, Li2S-P2S5, which is a glass-ceramic solid electrolyte, was obtained.

[0227] [Fabrication of the positive electrode material] In an argon glove box, the coating active material of Example 1 and Li2S-P2S5 as the second solid electrolyte were weighed so that the volume ratio of NCM to the solid electrolyte (the total of the first solid electrolyte and the second solid electrolyte) was 50:50. By mixing these in an agate mortar, the positive electrode material of Example 3 was fabricated.

[0228] [[Comparative Example 1]] A positive electrode material of Comparative Example 1 was obtained in the same manner as in Example 1, except that NCM without a coating layer was used.

[0229] [[Comparative Example 2]] A positive electrode material of Comparative Example 2 was obtained in the same manner as in Example 1, except that in the compression-shear treatment for fabricating the coating active material, the weight ratio of the positive electrode active material to the first solid electrolyte was changed to 99:1.

[0230] [[Comparative Example 3]] A positive electrode material of Comparative Example 3 was obtained in the same manner as in Example 1, except that in the compression-shear treatment for fabricating the coating active material, the weight ratio of the positive electrode active material to the first solid electrolyte was changed to 90:10.

[0231] [[Comparative Example 4]] A positive electrode material of Comparative Example 4 was obtained in the same manner as in Example 3, except that NCM without a coating layer was used.

[0232] [Measurement of pore volume] Regarding Example 1, Example 2, Example 3, Comparative Example 2, and Comparative Example 3, using a gas adsorption measurement device (Autosorb-3 manufactured by Quantachrome), by the method described above, the pore volume V of NCM, which is the positive electrode active material α and the pore volume V of the coating active material β were measured. From the measurement results, the ratio V of the pore volumes β / V α was calculated.

[0233] [Measurement of Specific Surface Area] Regarding Example 1, Example 2, Example 3, Comparative Example 2, and Comparative Example 3, using a gas adsorption measurement device (Autosorb-3 manufactured by Quantachrome), by the method described above, the specific surface area S of NCM, which is the positive electrode active material α and the specific surface area S of the coating active material β were measured. From the measurement results, the ratio S of the specific surface areas β / S α was calculated.

[0234] [Measurement of Weight] Regarding Example 1, Example 2, Example 3, Comparative Example 2, and Comparative Example 3, from the weight W of NCM, which is the positive electrode active material α and the weight W of the coating active material β , the ratio W of the weights α / W β was calculated.

[0235] [Volume Ratio of Solid Electrolyte] The ratio V of the volume V of the first solid electrolyte to the volume V of the second solid electrolyte δ was calculated. As the volume V of the first solid electrolyte γ and the volume V of the second solid electrolyte γ / V δ , the usage amounts of the first solid electrolyte and the second solid electrolyte during the production of the positive electrode material were used. γ and the volume V of the second solid electrolyte δ Regarding the measurement of the thickness of the coating layer

[0236] [Measurement of Thickness of Coating Layer] Regarding Example 1, Example 2, Example 3, Comparative Example 2, and Comparative Example 3, the thickness d of the coating layer in the coating active material was measured by the method described above. The ion milling treatment of the coating active material was performed using a cross-section polisher (manufactured by JEOL Ltd., SM-09010) under the conditions of an acceleration voltage of 5 kV and a processing time of 8 hours. The cross-sectional observation of the particles of the coating active material was performed using a scanning electron microscope (manufactured by Hitachi High-Technologies Corporation, SU-70) under the conditions of an acceleration voltage of 2 kV and a magnification of 100 times. The thickness of the coating layer was determined from the average film thickness at three points within the observation field of view.

[0237] [Fabrication of Battery] Using a positive electrode material, Li3Y1Br2Cl4, and glass-ceramic Li2S-P2S5, the following steps were carried out.

[0238] First, in an insulating outer cylinder, 60 mg of Li2S-P2S5, 20 mg of Li3Y1Br2Cl4, and the positive electrode material were laminated in this order. At this time, the positive electrode material was weighed so that the weight of the positive electrode active material was 14 mg. The obtained laminate was pressure-molded at a pressure of 720 MPa to obtain a positive electrode and a solid electrolyte layer.

[0239] Next, on the side opposite to the side in contact with the positive electrode, metallic Li (thickness 200 μm) was laminated on the solid electrolyte layer. The obtained laminate was pressure-molded at a pressure of 80 MPa to fabricate a laminate composed of a positive electrode, a solid electrolyte layer, and a negative electrode.

[0240] Next, stainless steel current collectors were disposed above and below the laminate. Current collection leads were attached to each current collector.

[0241] Finally, the insulating outer cylinder was sealed using an insulating ferrule to block the inside of the outer cylinder from the outside air atmosphere, and a battery was fabricated.

[0242] Thus, the batteries of Example 1 to 3 and Comparative Example 1 to 4 were fabricated respectively.

[0243] [Charging Test] Using the batteries of Examples 1 to 3 and Comparative Examples 1 to 4, a charge test was carried out under the following conditions.

[0244] The battery was placed in a thermostat at 25°C.

[0245] The battery was charged at a constant current with a current value of 140 μA, which is 0.05 C rate (20-hour rate) with respect to the theoretical capacity of the battery, until the voltage reached 4.3 V. After a rest time of 20 min elapsed, the battery was discharged at a constant current with a current value of 140 μA, which is 0.05 C rate (20-hour rate), until the voltage reached 2.5 V.

[0246] The ratio of the discharge capacity to the charge capacity obtained above was calculated as the initial efficiency. The results are shown in Table 1.

[0247]

Table 1

[0248] <<Discussion>> From the results of Example 1, Example 2, and Comparative Examples 1 to 3, it was confirmed that in the positive electrode material using the positive electrode active material having the coating layer containing the first solid electrolyte, the initial efficiency of the battery varies depending on the state of the coating layer.

[0249] Specifically, when 0.20 < V β / V α < 0.88 was satisfied, an initial efficiency of 89% was achieved. It is considered that the coating layer contributed to the coexistence of low electron resistance and low interfacial resistance.

[0250] Also, when 0.81 < S β / S α < 0.97 was satisfied, an initial efficiency of 89% was achieved. It is considered that the coating layer contributed to the coexistence of low electron resistance and low interfacial resistance.

[0251] Also, when 0.90 < W α / W βWhen <0.99 was satisfied, an initial efficiency of 89% was achieved. It is considered that the coating layer contributed to the compatibility of low electron resistance and low interfacial resistance.

[0252] When 14nm < d < 167nm was satisfied, an initial efficiency of 89% was achieved. It is considered that the coating layer contributed to the compatibility of low electron resistance and low interfacial resistance.

[0253] From the results of Example 3 and Comparative Example 4, when a sulfide solid electrolyte was used as the second solid electrolyte, the initial efficiency of the battery was improved by using a positive electrode material in which the surface of the positive electrode active material was coated with a halide solid electrolyte. This is considered to be the result of suppressing the oxidation of the sulfide solid electrolyte.

Industrial Applicability

[0254] The battery of the present disclosure can be used, for example, as an all-solid-state lithium secondary battery or the like.

Explanation of Symbols

[0255] 1000 Positive electrode material 100 Second solid electrolyte 110 Positive electrode active material 111 Coating layer 130 Coating active material 2000 Battery 201 Positive electrode 202 Electrolyte layer 203 Negative electrode

Claims

1. A positive electrode active material, a first solid electrolyte, and a coating layer that contains the first solid electrolyte and covers at least a part of the surface of the positive electrode active material, a second solid electrolyte, wherein the positive electrode active material and the coating layer constitute a coated active material, The pore volume of the positive electrode active material is V α is represented by, and the pore volume of the coating active material is V β is represented by, the specific surface area of the positive electrode active material is S α is represented by, and the specific surface area of the coating active material is S β When represented by, 0.20 < V β / V α < 0.88, and, 0.81 < S β / S α < 0.97, at least one selected from the group consisting thereof is satisfied, the first solid electrolyte is represented by the following compositional formula (1): Liα1M1β1X1γ1... Formula (1) where α1, β1, and γ1 are each independently a value greater than 0, M1 contains at least one element selected from the group consisting of metal elements other than Li and metalloid elements, X1 contains at least one selected from the group consisting of F, Cl, Br, and I, the second solid electrolyte contains a sulfide solid electrolyte or is represented by the following compositional formula (3): Liα2M2β2X2γ2... Formula (3) where α2, β2, and γ2 are each independently a value greater than 0, M2 contains at least one element selected from the group consisting of metal elements other than Li and metalloid elements, X2 contains at least one selected from the group consisting of F, Cl, Br, and I, a positive electrode material.

2. 0.60 ≤ V β / V α ≤ 0.76 is satisfied The positive electrode material according to Claim 1.

3. 0.86 ≤ S β / S α ≤ 0.89 is satisfied The positive electrode material according to Claim 1 or 2.

4. The weight of the positive electrode active material is W α is represented by, and the weight of the coating active material is W β When represented by, 0.90 < W α / W β < 0.99 is satisfied, The positive electrode material according to any one of Claims 1 to 3.

5. 0.95 ≤ W α / W β ≤ 0.975 is satisfied The positive electrode material according to Claim 4.

6. The positive electrode material according to any one of Claims 1 to 5, wherein the thickness of the coating layer is greater than 14 nm and less than 167 nm. The positive electrode material according to any one of Claims 1 to 5.

7. The positive electrode material according to any one of Claims 1 to 6, wherein the thickness of the coating layer is 32 nm or more and 71 nm or less. The positive electrode material according to any one of Claims 1 to 6.

8. The positive electrode material according to any one of Claims 1 to 7, wherein M1 contains yttrium. The positive electrode material according to any one of Claims 1 to 7.

9. The positive electrode material according to any one of Claims 1 to 8, wherein 2.5 ≤ α1 ≤ 3, 1 ≤ β1 ≤ 1.1, and γ1 = 6 are satisfied. The positive electrode material according to any one of Claims 1 to 8.

10. The positive electrode material according to any one of Claims 1 to 9, wherein X1 contains at least one selected from the group consisting of Cl and Br. The positive electrode material according to any one of Claims 1 to 9.

11. The first solid electrolyte contains Li3YX6, Li2MgX4, Li2FeX4, Li(Al, Ga, In)X4, or Li3(Al, Ga, In)X6, where X contains at least one selected from the group consisting of Cl and Br, The positive electrode material according to any one of Claims 1 to 7.

12. The first solid electrolyte is Li 3 YBr 2 Cl 4 and contains The positive electrode material according to claim 11.

13. The positive electrode active material contains Ni, Co, and Mn, The positive electrode material according to any one of claims 1 to 12.

14. The volume of the first solid electrolyte is V γ is represented, and when the volume of the second solid electrolyte is V δ is represented, 0.05 < V γ / V δ < 0.97 is satisfied The positive electrode material according to any one of claims 1 to 13.

15. M2 contains yttrium, The positive electrode material according to any one of claims 1 to 14.

16. 2.5 ≤ α2 ≤ 3, 1 ≤ β2 ≤ 1.1, and γ2 = 6 are satisfied, The positive electrode material according to any one of claims 1 to 15.

17. X2 contains at least one selected from the group consisting of Cl and Br, The positive electrode material according to any one of claims 1 to 16.

18. The second solid electrolyte contains Li3YX6, Li2MgX4, Li2FeX4, Li(Al, Ga, In)X4, or Li3(Al, Ga, In)X6, X contains at least one selected from the group consisting of F, Cl, Br, and I, The positive electrode material according to any one of claims 1 to 14.

19. The second solid electrolyte is Li 3 YBr 2 Cl 4 and contains The positive electrode material according to claim 18.

20. The second solid electrolyte contains Li2S - P2S5, Li2S - SiS2, Li2S - B2S3, Li2S - GeS2, Li3.25Ge0.25P0.75S4, or Li10GeP2S12, The positive electrode material according to any one of claims 1 to 14.

21. The second solid electrolyte contains Li2S - P2S5, The positive electrode material according to claim 20.

22. A positive electrode containing the positive electrode material according to any one of claims 1 to 21, A negative electrode, An electrolyte layer provided between the positive electrode and the negative electrode, A battery comprising the above.

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