Cathode material and battery

Abstract

The positive electrode material (1000) of the present disclosure includes a positive electrode active material (110) and a coating layer (111). The coating layer (111) contains a first solid electrolyte and coats 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 coated active material (130). When the pore volume of the positive electrode active material (110) is represented by V α and the pore volume of the coated active material (130) is represented by V β , the specific surface area of the positive electrode active material (110) is represented by S α and the specific surface area of the coated active material (130) is represented by S β , at least one of the following is satisfied: 0.20 < V β / V α < 0.88 and 0.81 < S β / S α < 0.97.

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.

[0003] Prior Art Documents

[0004] Patent Document 1: International Publication No. 2018 / 025582

[0005] Non-Patent Document 1: Journal of Power Sources 159(2006), p193-199. Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] In the prior art, an improvement in the initial efficiency of a battery has been desired.

[0008] Means for Solving the Problems

[0009] A positive electrode material according to one aspect of the present disclosure includes a positive electrode active material and a coating layer,

[0010] The coating layer contains a first solid electrolyte and coats at least a part of the surface of the positive electrode active material,

[0011] The positive electrode active material and the coating layer constitute a coated active material,

[0012] When the pore volume of the positive electrode active material is represented by V α 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 at least one of 0.20 < V β / V α < 0.88 and 0.81 < S β / S α < 0.97 is satisfied.

[0013] Effects of the Invention

[0014] According to the present disclosure, the initial efficiency of a battery can be improved. Brief Description of the Drawings

[0015] Figure 1 It is a cross-sectional view showing a schematic structure of the positive electrode material in Embodiment 1.

[0016] Figure 2 This is a cross-sectional view showing the general structure of the battery in Embodiment 2. Detailed Embodiment

[0017] (Insight underlying the present disclosure)

[0018] Patent Document 1 discloses that all-solid-state secondary batteries containing a halide solid electrolyte exhibit good charge-discharge characteristics.

[0019] On the other hand, the present inventors conducted intensive studies and 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 speculate that the reason for the relationship between the contact state and the charge-discharge efficiency lies in the balance between the electron resistance and the interfacial resistance. Specifically, if the contact rate between the positive electrode active material and the solid electrolyte is low, the interfacial resistance increases, and if the contact rate between the positive electrode active material and the solid electrolyte is high, the electron resistance increases. To solve this problem, the key lies in achieving a contact state between the positive electrode active material and the solid electrolyte that suppresses both resistance components to a low resistance.

[0020] Non-Patent Document 1 discloses that all-solid-state secondary batteries containing a sulfide solid electrolyte exhibit good charge-discharge characteristics.

[0021] On the other hand, the present inventors conducted intensive studies and found that when the positive electrode active material comes into contact with the sulfide solid electrolyte, the sulfide solid electrolyte undergoes oxidative decomposition during the charging of the battery. To solve this problem, it is considered to coat the surface of the positive electrode active material with a solid electrolyte having oxidation stability.

[0022] Here, the present inventors believe that the contact state between the positive electrode active material and other solid electrolytes can be adjusted according to the degree of coating of the positive electrode active material by the solid electrolyte. In particular, since the halide solid electrolyte has higher oxidation stability than the sulfide solid electrolyte, the oxidative decomposition of other solid electrolytes can also be suppressed by the coating layer of the halide solid electrolyte.

[0023] (Summary of one technical solution of the present disclosure)

[0024] The positive electrode material according to the first technical solution of the present disclosure includes a positive electrode active material and a coating layer,

[0025] The coating layer contains a first solid electrolyte and coats at least a part of the surface of the positive electrode active material,

[0026] The positive electrode active material and the coating layer constitute a coated active material,

[0027] When the pore volume of the positive electrode active material is V αIt is represented that the pore volume of the coated active material is V β It is represented that the specific surface area of the positive electrode active material is S α It is represented that the specific surface area of the coated active material is S β When represented, it satisfies at least one selected from 0.20 < V β / V α < 0.88 and 0.81 < S β / S α < 0.97

[0028] According to the above technical configuration, the initial efficiency of the battery can be improved

[0029] In the second technical solution of the present disclosure, for example, on the basis of the positive electrode material involved in the first technical solution, 0.60 ≤ V β / V α ≤ 0.76 can be satisfied. According to such a technical configuration, the initial efficiency of the battery can be effectively improved

[0030] In the third technical solution of the present disclosure, for example, on the basis of the positive electrode material involved in the first or second technical solution, 0.86 ≤ S β / S α ≤ 0.89 can be satisfied. According to such a technical configuration, the initial efficiency of the battery can be effectively improved

[0031] In the fourth technical solution of the present disclosure, for example, on the basis of the positive electrode material involved in any one of the first to third technical solutions, when the weight of the positive electrode active material is represented by W α and the weight of the coated active material is represented by W β it can satisfy 0.90 < W α / W β < 0.99. According to such a technical configuration, the initial efficiency of the battery can be effectively improved

[0032] In the fifth technical solution of the present disclosure, for example, on the basis of the positive electrode material involved in the fourth technical solution, 0.95 ≤ W α / W β ≤ 0.975 can be satisfied. According to such a technical configuration, the initial efficiency of the battery can be effectively improved

[0033] In the sixth technical solution of the present disclosure, for example, on the basis of the positive electrode material involved in any one of the first to fifth technical solutions, the thickness of the coating layer can be greater than 14 nm and less than 167 nm. According to such a technical configuration, the charge and discharge efficiency of the battery can be effectively improved

[0034] In the seventh technical solution of the present disclosure, for example, on the basis of the positive electrode material involved in any one of the first to sixth technical solutions, the thickness of the coating layer can be 32 nm or more and 71 nm or less. According to such a technical configuration, the charge and discharge efficiency of the battery can be effectively improved.

[0035] In the eighth technical solution of the present disclosure, for example, on the basis of the positive electrode material involved in any one of the first to seventh technical solutions, the first solid electrolyte can be represented by the following compositional formula (1), where α1, β1, and γ1 can each independently be a value greater than 0, M1 can include at least one element selected from metal elements other than Li and metalloid elements, and X1 can include at least one selected from 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.

[0036] Li α1 M1 β1 X1 γ1 ··· Formula (1)

[0037] In the ninth technical solution of the present disclosure, for example, on the basis of the positive electrode material involved in the eighth technical solution, M1 can include yttrium. According to such a technical configuration, the charge and discharge characteristics of the battery can be further improved.

[0038] In the tenth technical solution of the present disclosure, for example, on the basis of the positive electrode material involved in the eighth or ninth technical solution, 2.5 ≤ α1 ≤ 3, 1 ≤ β1 ≤ 1.1, and γ1 = 6 can be satisfied. According to such a technical configuration, the charge and discharge characteristics of the battery can be further improved.

[0039] In the eleventh technical solution of the present disclosure, for example, on the basis of the positive electrode material involved in any one of the eighth to tenth technical solutions, X1 can include at least one selected from Cl and Br. According to such a technical configuration, the charge and discharge characteristics of the battery can be further improved.

[0040] In the twelfth technical solution of the present disclosure, for example, on the basis of the positive electrode material involved in any one of the eighth to eleventh technical solutions, the first solid electrolyte can contain Li 3 YBr 2 Cl 4 . According to such a technical configuration, the charge and discharge efficiency of the battery can be further improved.

[0041] In the thirteenth technical solution of the present disclosure, for example, on the basis of the positive electrode material involved in any one of the first to twelfth technical solutions, the positive electrode active material can include Ni, Co, and Mn. According to such a technical configuration, the energy density and charge and discharge efficiency of the battery can be further improved.

[0042] In the 14th technical solution of the present disclosure, for example, on the basis of the positive electrode material involved in any one of the 1st to 13th technical solutions, a second solid electrolyte may further be included. According to such a technical configuration, the ionic conductivity of the positive electrode material can be sufficiently ensured.

[0043] In the 15th technical solution of the present disclosure, for example, on the basis of the positive electrode material involved in the 14th technical solution, 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 it may satisfy 0.05 < V γ / V δ < 0.97. According to such a technical configuration, the energy density and charge-discharge efficiency of the battery can be further improved.

[0044] In the 16th technical solution of the present disclosure, for example, on the basis of the positive electrode material involved in the 14th or 15th technical solution, 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 include at least one element selected from metal elements and metalloid elements other than Li, and X2 may include at least one selected from 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.

[0045] Li α2 M2 β2 X2 γ2 ··· Formula (3)

[0046] In the 17th technical solution of the present disclosure, for example, on the basis of the positive electrode material involved in the 16th technical solution, M2 may include yttrium. According to such a technical configuration, the charge-discharge characteristics of the battery can be further improved.

[0047] In the 18th technical solution of the present disclosure, for example, on the basis of the positive electrode material involved in the 16th or 17th technical solution, it may satisfy 2.5 ≤ α2 ≤ 3, 1 ≤ β2 ≤ 1.1, and γ2 = 6. According to such a technical configuration, the charge-discharge characteristics of the battery can be further improved.

[0048] In the 19th technical solution of the present disclosure, for example, on the basis of the positive electrode material involved in any one of the 16th to 18th technical solutions, X2 may include at least one selected from Cl and Br. According to such a technical configuration, the charge-discharge characteristics of the battery can be further improved.

[0049] In the 20th technical solution of the present disclosure, for example, on the basis of the positive electrode material involved in any one of the 16th to 19th technical solutions, the second solid electrolyte may include Li3 YBr 2 Cl 4 According to such a technical configuration, the charge-discharge efficiency of the battery can be further improved.

[0050] In the 21st technical solution of the present disclosure, for example, on the basis of the positive electrode material involved in the 14th or 15th technical solution, the second solid electrolyte may include a sulfide solid electrolyte. According to such a technical configuration, the charge-discharge efficiency of the battery can be further improved.

[0051] The battery according to the 22nd technical solution of the present disclosure includes a positive electrode, a negative electrode, and an electrolyte layer disposed between the positive electrode and the negative electrode.

[0052] The positive electrode includes the positive electrode material involved in any one of the 14th to 21st technical solutions.

[0053] According to the above technical configuration, the initial efficiency of the battery can be improved.

[0054] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0055] (Embodiment 1)

[0056] Figure 1 It is a cross-sectional view showing a general structure of the positive electrode material 1000 in Embodiment 1.

[0057] The positive electrode material 1000 in Embodiment 1 includes a coated active material 130. The coated 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 coats at least a part of the surface of the positive electrode active material 110.

[0058] The coating layer 111 is a layer containing the 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, except for inevitable impurities, materials other than the first solid electrolyte are not 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.

[0059] The positive electrode material 1000 further includes a second solid electrolyte 100. The shape of the second solid electrolyte 100 is, for example, particulate. Through the second solid electrolyte 100, the ion conductivity of the positive electrode material 1000 can be sufficiently ensured.

[0060] 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 ion conductivity.

[0061] The coating layer 111 can uniformly coat the positive electrode active material 110. The coating layer 111 inhibits the direct contact between the positive electrode active material 110 and the second solid electrolyte 100, and inhibits side reactions of the second solid electrolyte 100. As a result, the charge-discharge characteristics of the battery are improved, and an increase in the reaction overvoltage of the battery can be inhibited.

[0062] The coating layer 111 may also coat only a part of the surface of the positive electrode active material 110. The particles of the positive electrode active material 110 are in direct contact with each other via the portion not coated by the coating layer 111, whereby the electron conductivity between the particles of the positive electrode active material 110 is improved. As a result, high-output operation of the battery can be achieved.

[0063] In the positive electrode material 1000, the pore volume of the positive electrode active material 110 is represented by V α The pore volume of the coated active material 130 is represented by V β The specific surface area of the positive electrode active material 110 is represented by S α The specific surface area of the coated active material 130 is represented by S β At this time, in the positive electrode material 1000, at least one of 0.20 < V β / V α <0.88 and 0.81 < S β / S α <0.97 is satisfied.

[0064] When the pore volume V α of the positive electrode active material 110 and the pore volume V β of the coated active material 130 satisfy the relationship of 0.20 < V β / V α <0.88, the battery using the positive electrode material 1000 shows excellent initial efficiency. The ratio V β / V α of the pore volumes represents the ratio of the change in the pore volume when the coating layer 111 is provided. The change in the pore volume reflects the coating state of the coating layer 111 on the positive electrode active material 110. As the coating of the coating layer 111 on the positive electrode active material 110 progresses, the pore volume ratio V β / V α decreases. The less the coating layer 111 coats the positive electrode active material 110, the pore volume ratio V β / V αThe higher, the better. The ideal coverage state not only helps to properly balance the electronic resistance and the interface 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 process of the battery. As a result, the initial efficiency of the battery is improved.

[0065] The "initial efficiency" refers to the ratio of the discharge capacity to the charge capacity in the first cycle after the battery is completed.

[0066] The pore volume V of the positive electrode active material 110 α refers to the pore volume V of the particles of the positive electrode active material 110 α The pore volume V of the coated active material 130 β refers to the pore volume V of the particles of the coated active material 130 β In fact, since it is difficult to measure the pore volume of a single particle, the pore volume V α can be the pore volume of a group of particles of the positive electrode active material 110. The pore volume V β can be the pore volume of a group of particles of the coated active material 130.

[0067] The ratio of the pore volumes V β / V α preferably satisfies the relationship of 0.60 ≤ V β / V α ≤ 0.76. When the ratio of the pore volumes V β / V α is within such a range, the initial efficiency of the battery can be effectively improved.

[0068] The pore volumes V α and V β refer to 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 diameter distribution is obtained from the desorption isothermal curve, and the total pore volume (unit: cm 3 / g) is calculated from the pore diameter distribution.

[0069] When the specific surface area S α of the positive electrode active material 110 and the specific surface area S β of the coated active material 130 satisfy the relationship of 0.81 < S β / S α < 0.97, the battery using the positive electrode material 1000 shows excellent initial efficiency. The ratio of the specific surface areas S β / S αIndicates the ratio of the change in specific surface area when the coating layer 111 is provided. The change in specific surface area reflects the coating state of the coating layer 111 on the positive electrode active material 110. As the coating of the coating layer 111 on the positive electrode active material 110 progresses, the specific surface area ratio S β / S α decreases. The less the coating layer 111 coats the positive electrode active material 110, the higher the specific surface area ratio S β / S α . An ideal coating state not only helps to appropriately balance the electron resistance and the interface 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 process of the battery. As a result, the initial efficiency of the battery is improved.

[0070] The specific surface area S α of the positive electrode active material 110 refers to the specific surface area S α of the particle group of the positive electrode active material 110. The specific surface area S β of the coated active material 130 refers to the specific surface area S β of the particle group of the coated active material 130.

[0071] The specific surface area ratio S β / S α preferably satisfies the relationship of 0.86 ≤ S β / S α ≤ 0.89. When the specific surface area ratio S β / S α is within such a range, the initial efficiency of the battery can be effectively improved.

[0072] 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.

[0073] As another parameter reflecting the coating state of the coating layer 111 on the positive electrode active material 110, a change in weight can be cited. 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 coated 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. When the weight ratio W α / W β is within such a range, the initial efficiency of the battery can be effectively improved.

[0074] When the weight W of the positive electrode active material 110 α and the weight W of the coated active material 130 β satisfy the relationship of 0.90 < W α / W β < 0.99, the battery using the positive electrode material 1000 shows excellent initial efficiency. The weight ratio W α / W β represents the ratio of the change in weight when the coating layer 111 is provided. The change in weight reflects the coating state of the coating layer 111 on the positive electrode active material 110. As the coating of the coating layer 111 on the positive electrode active material 110 progresses, the weight ratio W α / W β decreases. The less the coating layer 111 coats the positive electrode active material 110, the higher the weight ratio W α / W β . The ideal coating state not only helps to properly balance the electron resistance and the interface 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 process of the battery. As a result, the initial efficiency of the battery is improved.

[0075] The weight W of the positive electrode active material 110 α refers to the weight W of the particle group of the positive electrode active material 110 α . The weight W of the coated active material 130 β refers to the weight W of the particle group of the coated active material 130 β .

[0076] The weight ratio W α / W β preferably satisfies the relationship of 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 effectively improved.

[0077] The thickness of the coating layer 111 is, for example, 1 nm or more. If 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. Therefore, the charge-discharge efficiency of the battery can be improved.

[0078] The thickness of the coating layer 111 can 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 technical configuration, the charge-discharge efficiency of the battery can be effectively improved.

[0079] The thickness of the coating layer 111 can be measured by the following method. First, ion milling treatment is performed on the coated active material 130. Then, cross-sectional observation of the particles of the coated active material 130 is carried out with an electron microscope. The thickness of the coating layer 111 is measured at any plurality of points (for example, 3 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.

[0080] 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 dry it, the positive electrode active material 110 before the formation of the coating layer 111 can be obtained.

[0081] The positive electrode active material 110, the coating layer 111, and the second solid electrolyte 100 will be described in more detail.

[0082] (Coating layer 111)

[0083] As the first solid electrolyte contained in the coating layer 111, a material with low electronic conductivity and antioxidant properties can be used. For example, as the first solid electrolyte, a halide solid electrolyte or the like can be used.

[0084] 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 improved, and the rise of the reaction overvoltage of the battery can be further suppressed.

[0085] The first solid electrolyte contained in the coating layer 111 can be a halide solid electrolyte.

[0086] The halide solid electrolyte is represented, for example, by 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 metal elements other than Li and metalloid elements. X1 contains at least one selected from F, Cl, Br, and I.

[0087] Li α1 M1 β1 X1 γ1 ···Formula (1)

[0088] "Metalloid element" includes B, Si, Ge, As, Sb, and Te.

[0089] "Metal elements" include all elements contained in Groups 1 to 12 of the periodic table except hydrogen, and all elements contained in Groups 13 to 16 except B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se. That is, metal elements are a group of elements that can become cations when forming inorganic compounds with halogen compounds.

[0090] The halide solid electrolyte represented by the formula (1) has a higher ionic conductivity than halide solid electrolytes such as LiI composed of only Li and halogen elements. Therefore, when the halide solid electrolyte represented by the formula (1) is used in a battery, the output characteristics of the battery can be improved.

[0091] In the present disclosure, when an element in a formula is represented as "(Al, Ga, In)", this expression means 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 Al, Ga, and In". The same applies to other elements.

[0092] In the composition formula (1), M1 may contain Y (yttrium). That is, Y may be included as a metal element in the first solid electrolyte.

[0093] Based on the above technical configuration, the ionic conductivity of the first solid electrolyte can be further improved. As a result, the charge-discharge characteristics of the battery can be further improved.

[0094] The composition formula (1) may satisfy 2.5 ≤ α1 ≤ 3, 1 ≤ β1 ≤ 1.1, and γ1 = 6.

[0095] Based on the above technical configuration, the ionic conductivity of the first solid electrolyte can be further improved. As a result, the charge-discharge characteristics of the battery can be further improved.

[0096] X1 may contain at least one selected from Cl and Br. X1 may also contain both Cl and Br.

[0097] Based on the above technical configuration, the ionic conductivity of the first solid electrolyte can be further improved. As a result, the charge-discharge characteristics of the battery can be further improved.

[0098] The halide solid electrolyte containing Y may be a compound represented by the following composition formula (2).

[0099] Li a Me b Y c X 6 ··· Formula (2)

[0100] 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 metal elements other than Li and Y and metalloid elements. m is the valence of Me. X contains at least one selected from F, Cl, Br, and I.

[0101] Me may contain at least one selected from Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta, and Nb.

[0102] Based on the above technical configuration, the ionic conductivity of the first solid electrolyte can be further improved. Furthermore, the halide solid electrolyte may not contain sulfur.

[0103] 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 Cl and Br. In the compositional formula (A1), 0 < d < 2 is satisfied.

[0104] Li 6-3d Y d X 6 ··· formula (A1)

[0105] Based on the above technical configuration, the ionic conductivity of the first solid electrolyte can be further improved. Thus, the charge and discharge efficiency of the battery can be further improved.

[0106] 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 Cl and Br.

[0107] Li 3 YX 6 ··· formula (A2)

[0108] Based on the above technical configuration, the ionic conductivity of the first solid electrolyte can be further improved. Thus, the charge and discharge efficiency of the battery can be further improved.

[0109] 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.

[0110] Li 3-3δ Y 1+δ Cl 6 ··· formula (A3)

[0111] Based on the above technical configuration, the ionic conductivity of the first solid electrolyte can be further improved. Thus, the charge and discharge efficiency of the battery can be further improved.

[0112] 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.

[0113] Li 3-3δ Y 1+δ Br 6 ··· Formula (A4)

[0114] Based on the above technical configuration, the ionic conductivity of the first solid electrolyte can be further improved. Thus, the charge-discharge efficiency of the battery can be further improved.

[0115] 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 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.

[0116] Li 3-3δ+a Y 1+δ-a Me a Cl 6-x Br x ··· Formula (A5)

[0117] Based on the above technical configuration, the ionic conductivity of the first solid electrolyte can be further improved. Thus, the charge-discharge efficiency of the battery can be further improved.

[0118] 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 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.

[0119] Li 3-3δ Y 1+δ-a Me a Cl 6-x Br x ··· Formula (A6)

[0120] Based on the above technical configuration, the ionic conductivity of the first solid electrolyte can be further improved. Thus, the charge-discharge efficiency of the battery can be further improved.

[0121] 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 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.

[0122] Li 3-3δ-a Y 1+δ-a Me a Cl 6-x Br x ··· Formula (A7)

[0123] Based on the above technical composition, the ionic conductivity of the first solid electrolyte can be further improved. Thus, the charge-discharge efficiency of the battery can be further improved.

[0124] 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 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.

[0125] Li 3-3δ-2a Y 1+δ-a Me a Cl 6-x Br x ··· Formula (A8)

[0126] Based on the above technical composition, the ionic conductivity of the first solid electrolyte can be further improved. Thus, the charge-discharge efficiency of the battery can be further improved.

[0127] As the first solid electrolyte, for example, Li 3 YX 6 、Li 2 MgX 4 、Li 2 FeX 4 、Li(Al,Ga,In)X 4 、Li 3 (Al,Ga,In)X 6 etc. Among them, X contains at least one element selected from Cl and Br.

[0128] Li 3 YX 6 The representative composition of Li 3 YBr 2 Cl 4 . The first solid electrolyte may contain Li 3 YBr 2 Cl 4 .

[0129] The first solid electrolyte may be Li 2.7 Y 1.1 Cl 6 、Li 3 YBr6 or Li 2.5 Y 0.5 Zr 0.5 Cl 6 。

[0130] According to the above technical configuration, the charge-discharge efficiency of the battery can be further improved.

[0131] (The second solid electrolyte)

[0132] The second solid electrolyte 100 contains a material with high ionic conductivity. The second solid electrolyte may 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 metal elements and metalloid elements other than Li. X2 contains at least one selected from F, Cl, Br, and I.

[0133] Li α2 M2 β2 X2 γ2 ···Formula (3)

[0134] According to the above technical configuration, the ionic conductivity of the second solid electrolyte 100 can be further improved. Thus, the charge-discharge efficiency of the battery can be further improved.

[0135] In the compositional formula (3), M2 may contain Y. That is, Y can be contained as a metal element in the second solid electrolyte 100.

[0136] According to the above technical configuration, the ionic conductivity of the second solid electrolyte 100 can be further improved. Thus, the charge-discharge efficiency of the battery can be further improved.

[0137] The compositional formula (3) can satisfy 2.5 ≤ α2 ≤ 3, 1 ≤ β2 ≤ 1.1, and γ2 = 6.

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

[0139] In the compositional formula (3), X2 may contain at least one selected from Br (= bromine) and Cl (= chlorine).

[0140] According to the above technical configuration, the ionic conductivity of the second solid electrolyte 100 can be further improved. Thus, the charge-discharge efficiency of the battery can be further improved.

[0141] In the compositional formula (3), X2 may contain Br and Cl.

[0142] Based on the above technical composition, 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.

[0143] The second solid electrolyte 100 may be a compound represented by the following compositional formula (B1). Here, in the compositional formula (B1), X includes at least one selected from F, Cl, Br, and I. In the compositional formula (B1), 0 < d < 2 is satisfied.

[0144] Li 6-3d Y d X 6 ··· Formula (B1)

[0145] Based on the above technical composition, 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.

[0146] The second solid electrolyte 100 may be a compound represented by the following compositional formula (B2). Here, in the compositional formula (B2), X includes at least one selected from F, Cl, Br, and I.

[0147] Li 3 YX 6 ··· Formula (B2)

[0148] Based on the above technical composition, 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.

[0149] 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 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.

[0150] Li 3-3δ+a Y 1+δ-a Me a Cl 6-x-y Br x I y ··· Formula (B3)

[0151] Based on the above technical composition, 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.

[0152] 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 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.

[0153] Li 3-3δ Y 1+δ-a Me a Cl 6-x-y Br x I y ··· Formula (B4)

[0154] Based on the above technical 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.

[0155] 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 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.

[0156] Li 3-3δ-a Y 1+δ-a Me a Cl 6-x-y Br x I y ··· Formula (B5)

[0157] Based on the above technical 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.

[0158] 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 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.

[0159] Li 3-3δ-2a Y 1+δ-a Me a Cl 6-x-y Br x I y ··· Formula (B6)

[0160] Based on the above technical 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.

[0161] As the second solid electrolyte 100, for example, Li 3 YX 6 、Li 2 MgX 4 、Li 2 FeX 4 、Li(Al,Ga,In)X 4 、Li 3 (Al,Ga,In)X 6 etc. Among them, X includes at least one selected from F, Cl, Br, and I.

[0162] The representative composition of Li 3 YX 6 is, for example, Li 3 YBr 2 Cl 4 . The second solid electrolyte 100 may contain Li 3 YBr 2 Cl 4 .

[0163] Based on the above technical configuration, the charge and discharge efficiency of the battery can be further improved.

[0164] The second solid electrolyte 100 may contain a sulfide solid electrolyte. As the sulfide solid electrolyte, for example, Li 2 S-P 2 S 5 、Li 2 S-SiS 2 、Li 2 S-B 2 S 3 、Li 2 S-GeS 2 、Li 3.25 Ge 0.25 P 0.75 S 4 、Li 10 GeP 2 S 12 etc. LiX, Li 2 O, MO q 、Li p MO q etc. can be added to these. Here, the element X in "LiX" is at least one element selected from F, Cl, Br, and I. "MO q " and "Li p MO qThe element M in “” is at least one element selected from P, Si, Ge, B, Al, Ga, In, Fe, and Zn. “MO q ” and “Li p MO q ” where p and q are each independently natural numbers.

[0165] 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 Li 2 S-P 2 S 5 。

[0166] Li 2 S-P 2 S 5 has a high ionic conductivity and is stable to redox. Therefore, by using Li 2 S-P 2 S 5 , the charge-discharge efficiency of the battery can be further improved. Furthermore, 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 the halogen element.

[0167] (Positive electrode active material)

[0168] The positive electrode active material 110 includes a material having the property of occluding and releasing metal ions (such as lithium ions). As the positive electrode active material 110, for example, a lithium-containing transition metal oxide (such as Li(NiCoAl)O 2 , Li(NiCoMn)O 2 , LiCoO 2 , etc.), a transition metal fluoride, a polyanion material, a fluorinated polyanion material, a transition metal sulfide, a transition metal oxysulfide, a transition metal oxynitride, etc. In particular, when a lithium-containing transition metal oxide is used as the positive electrode active material 110, the manufacturing cost can be reduced and the average discharge voltage can be increased.

[0169] 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 manganate. For example, the positive electrode active material 110 may be Li(NiCoMn)O 2 。

[0170] According to the above technical configuration, the energy density and charge-discharge efficiency of the battery can be further improved.

[0171] The shape of the second solid electrolyte 100 in Embodiment 1 is not particularly limited and may be, for example, needle-shaped, spherical, ellipsoidal, etc. For example, the shape of the second solid electrolyte 100 may be particulate.

[0172] 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 coated 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.

[0173] According to the above technical configuration, in the positive electrode material 1000, the coated active material 130 and the second solid electrolyte 100 can form a good dispersion state.

[0174] In Embodiment 1, the median diameter of the second solid electrolyte 100 may be smaller than the median diameter of the coated active material 130.

[0175] According to the above technical configuration, in the positive electrode material 1000, the second solid electrolyte 100 and the coated active material 130 can form a better dispersion state.

[0176] The median diameter of the coated active material 130 may be 0.1 μm or more and 100 μm or less.

[0177] When the median diameter of the coated active material 130 is 0.1 μm or more, in the positive electrode material 1000, the coated 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.

[0178] When the median diameter of the coated active material 130 is 100 μm or less, the diffusion rate of lithium in the coated active material 130 can be sufficiently ensured. Therefore, the battery can operate at a high output.

[0179] The median diameter of the coated active material 130 may be larger than the median diameter of the second solid electrolyte 100. Thereby, the coated active material 130 and the second solid electrolyte 100 can form a good dispersion state.

[0180] In the positive electrode material 1000, as Figure 1 shown, the second solid electrolyte 100 and the coated active material 130 may be in contact with each other. At this time, the coating layer 111 and the positive electrode active material 110 are in contact with each other.

[0181] The positive electrode material 1000 may include a plurality of particles of the second solid electrolyte 100 and a plurality of particles coated with the active material 130.

[0182] In the positive electrode material 1000, the content of the second solid electrolyte 100 and the content of the coated active material 130 may be the same as or different from each other.

[0183] In this specification, the "median diameter" refers to the particle diameter 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 type measuring device or an image analysis device.

[0184] The first solid electrolyte and the second solid electrolyte 100 contained in the coating layer 111 can be manufactured by the following method.

[0185] Prepare a raw material powder of a binary halide having a mixing ratio that is the target composition. For example, when making Li 3 YCl 6 , prepare LiCl and YCl 3 in a molar ratio of 3:1.

[0186] At this time, by selecting the type of the raw material powder, "M", "M1", "M2", "Me", "X", "X1", and "X2" in the above composition formula can be determined. In addition, by adjusting the raw materials, the mixing ratio, and the synthesis process, the above values "α1", "β1", "γ1", "α2", "β2", "γ2", "d", "δ", "a", "x", and "y" can be adjusted.

[0187] After thoroughly mixing the raw material powders, use the method of mechanochemical grinding to mix, crush, and react the raw material powders with each other. Alternatively, after thoroughly mixing the raw material powders, sinter them in a vacuum.

[0188] Thereby, the first solid electrolyte and the second solid electrolyte containing the crystal phase as described above are obtained.

[0189] 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.

[0190] The coated active material 130 can be manufactured by the following method.

[0191] Mix the powder of the positive electrode active material 110 and the powder of the first solid electrolyte at an appropriate ratio to obtain a mixture. Perform a grinding process on the mixture to impart mechanical energy to the mixture. The grinding process can use a mixing device such as a ball mill. In order to suppress the oxidation of the material, the grinding process can be performed in a dry atmosphere and an inert atmosphere.

[0192] The coated active material 130 can be manufactured by a dry particle compounding method. The treatment using the dry particle compounding method includes imparting at least one type of mechanical energy selected from 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.

[0193] The apparatus that can be used in the manufacturing method of the coated active material 130 is not particularly limited, and it can be an apparatus capable of imparting mechanical energies such as impact, compression, and shear to the mixture of the positive electrode active material 110 and the first solid electrolyte. As the apparatus capable of imparting mechanical energy, a ball mill, "MECHANOFUSION" (manufactured by Hosokawa Micron Corporation), "NOBILTA" (manufactured by Hosokawa Micron Corporation), and other compression-shear type processing apparatuses (particle compounding apparatuses) can be cited.

[0194] "MECHANOFUSION" is a particle compounding apparatus that uses a dry mechanical compounding technique that applies strong mechanical energy to multiple different raw material particles. In MECHANOFUSION, particle compounding is caused by imparting mechanical energies such as compression, shear, and friction to the powder raw materials introduced between a rotating container and a pressing head.

[0195] "NOBILTA" is a particle compounding apparatus that uses a dry mechanical compounding technique that develops particle compounding technology for compounding using nanoparticles as raw materials. NOBILTA manufactures composite particles by imparting mechanical energies of impact, compression, and shear to multiple raw material powders.

[0196] In "NOBILTA", a rotor configured to have a predetermined gap with the inner wall of a horizontally cylindrical mixing container rotates at a high speed, and the raw material powder is repeatedly subjected to a process of being forced to pass through the gap multiple times. Thereby, forces 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 processing time, and the charging amount can be appropriately adjusted.

[0197] By mixing the coated active material 130 and the second solid electrolyte 100, the positive electrode material 1000 is obtained. 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 can be mixed using an instrument such as a mortar, or the coated active material 130 and the second solid electrolyte 100 can be mixed using a mixing apparatus such as a ball mill.

[0198] There is no particular limitation on the mixing ratio of the coated active material 130 and the second solid electrolyte 100 either. 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 , adjust the mixing ratio of the coated active material 130 and the second solid electrolyte 100 to satisfy 0.05 < V γ / V δ < 0.97. Thereby, the energy density and charge-discharge efficiency of the battery 2000 can be further improved.

[0199] 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 effectively improved.

[0200] (Embodiment 2)

[0201] Hereinafter, Embodiment 2 will be described. The description that duplicates that of the above Embodiment 1 will be appropriately omitted.

[0202] Figure 2 is a cross-sectional view showing the general structure of the battery 2000 in Embodiment 2.

[0203] The battery 2000 in Embodiment 2 includes a positive electrode 201, an electrolyte layer 202, and a negative electrode 203.

[0204] The positive electrode 201 contains the positive electrode material 1000 in Embodiment 1.

[0205] The electrolyte layer 202 is disposed between the positive electrode 201 and the negative electrode 203.

[0206] According to the above technical configuration, the initial efficiency of the battery 2000 can be improved.

[0207] 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 can be satisfied. When 30 ≤ v1 is satisfied, the energy density of the battery 2000 can be sufficiently ensured. In addition, when v1 ≤ 95 is satisfied, high-output operation can be achieved.

[0208] The thickness of the positive electrode 201 can 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 can be sufficiently ensured. When the thickness of the positive electrode 201 is 500 μm or less, high-output operation can be achieved.

[0209] The electrolyte layer 202 is a layer containing an electrolyte. This electrolyte is, for example, a solid electrolyte (i.e., the third solid electrolyte). That is, the electrolyte layer 202 can be a solid electrolyte layer.

[0210] 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 can be used.

[0211] 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 can be used. That is, the electrolyte layer 202 can contain a halide solid electrolyte having the same composition as the first solid electrolyte and / or the second solid electrolyte.

[0212] According to the above technical configuration, the output density and charge-discharge characteristics of the battery 2000 can be further improved.

[0213] In addition, the third solid electrolyte can be a halide solid electrolyte having a composition different from that of the first solid electrolyte and the second solid electrolyte. That is, the electrolyte layer 202 can contain a halide solid electrolyte having a composition different from that of the first solid electrolyte and the second solid electrolyte.

[0214] According to the above technical configuration, the charge-discharge characteristics of the battery can be further improved.

[0215] When the third solid electrolyte is a sulfide solid electrolyte, as the sulfide solid electrolyte, Li 2 S-P 2 S 5 、Li 2 S-SiS 2 、Li 2 S-B 2 S 3 、Li 2 S-GeS 2 、Li 3.25 Ge 0.25 P 0.75 S 4 、Li 10 GeP 2 S 12 etc. LiX, Li 2O, MO q , Li p MO q etc. Element X in "LiX" is at least one element selected from F, Cl, Br, and I. "MO q " and "Li p MO q " The element M in is at least one element selected from P, Si, Ge, B, Al, Ga, In, Fe, and Zn. "MO q " and "Li p MO q " The p and q in are each independently a natural number.

[0216] As the third solid electrolyte, the same sulfide solid electrolyte as the second solid electrolyte in Embodiment 1 can be used. That is, the electrolyte layer 202 can contain a sulfide solid electrolyte having the same composition as the second solid electrolyte in Embodiment 1.

[0217] According to the above technical 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 increased. In addition, according to the structure in which the electrolyte layer 202 contains the same sulfide solid electrolyte as the second solid electrolyte 100, the charge-discharge characteristics of the battery 2000 can be improved.

[0218] When the third solid electrolyte is an oxide solid electrolyte, as the oxide solid electrolyte, for example, NASICON-type solid electrolytes represented by LiTi 2 (PO 4 ) 3 and its element substitution products, perovskite-type solid electrolytes of the (LaLi)TiO 3 system, LISICON-type solid electrolytes represented by Li 14 ZnGe 4 O 16 , Li 4 SiO 4 , LiGeO 4 and its element substitution products, garnet-type solid electrolytes represented by Li 7 La 3 Zr 2 O 12 and its element substitution products, Li 3 N and its H substitution products, Li 3 PO 4 and its N substitution products, to those containing LiBO 2 , Li 3 BO 3Adding Li to the matrix materials such as Li-B-O compounds 2 SO 4 、Li 2 CO 3 and other materials to obtain glass, glass-ceramics, etc.

[0219] 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 can have an ethylene oxide structure. By having an ethylene oxide structure, the polymer compound can contain a relatively large amount of lithium salt, and thus the ionic conductivity can be further improved. As the lithium salt, LiPF 6 、LiBF 4 、LiSbF 6 、LiAsF 6 、LiSO 3 CF 3 、LiN(SO 2 CF 3 ) 2 、LiN(SO 2 C 2 F 5 ) 2 、LiN(SO 2 CF 3 )(SO 2 C 4 F 9 )、LiC(SO 2 CF 3 ) 3 and so on. As the lithium salt, one lithium salt selected from them can be used alone, or a mixture of two or more lithium salts selected from them can be used.

[0220] When the third solid electrolyte is a complex hydride solid electrolyte, as the complex hydride solid electrolyte, for example, LiBH 4 -LiI, LiBH 4 -P 2 S 5 and so on can be used.

[0221] The electrolyte layer 202 can contain the third solid electrolyte as a main component. That is, the electrolyte layer 202 can contain, for example, 50% or more of the third solid electrolyte based on the weight ratio of the whole electrolyte layer 202.

[0222] According to the above technical configuration, the charge-discharge characteristics of the battery 2000 can be further improved.

[0223] The electrolyte layer 202 can contain 70% or more of the third solid electrolyte based on the weight ratio of the whole electrolyte layer 202.

[0224] Based on the above technical configuration, the charge and discharge characteristics of the battery 2000 can be further improved.

[0225] The electrolyte layer 202 contains a third solid electrolyte as a main component, and may also contain inevitable impurities, or starting materials, by-products, and decomposition products used in synthesizing the third solid electrolyte, etc.

[0226] Except for the inevitably mixed impurities, the electrolyte layer 202 may contain 100% of the third solid electrolyte based on the weight ratio of the entire electrolyte layer 202.

[0227] Based on the above technical configuration, the charge and discharge characteristics of the battery 2000 can be further improved.

[0228] As described above, the electrolyte layer 202 may be composed only of the third solid electrolyte.

[0229] 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.

[0230] 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 achieved.

[0231] The negative electrode 203 contains a material having the property of occluding and releasing metal ions (such as lithium ions). The negative electrode 203 contains, for example, a negative electrode active material.

[0232] 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 also 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.

[0233] The negative electrode 203 may contain a solid electrolyte. As the solid electrolyte, the solid electrolytes exemplified as the materials constituting the electrolyte layer 202 can be used. According to the above structure, the lithium ion conductivity inside the negative electrode 203 can be improved, and operation at high output can be achieved.

[0234] 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-discharge characteristics of the battery 2000 are improved. In addition, when the median diameter of the negative electrode active material is 100 μm or less, the diffusion of lithium in the negative electrode active material becomes faster. Therefore, the battery 2000 can operate at a high output.

[0235] 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 of the particles of the negative electrode active material and the particles of the solid electrolyte can be formed.

[0236] Regarding the volume ratio "v2:100 - v2" of the negative electrode active material and the solid electrolyte contained in the negative electrode 203, 30 ≤ v2 ≤ 95 can be satisfied. When 30 ≤ v2, a sufficient energy density of the battery 2000 can be ensured. When v2 ≤ 95, operation at a high output can be achieved.

[0237] 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, a sufficient energy density of the battery 2000 can be ensured. In addition, when the thickness of the negative electrode 203 is 500 μm or less, operation at a high output can be achieved.

[0238] In at least one of the positive electrode 201, the electrolyte layer 202, and the negative electrode 203, a binder may be contained in order to improve the adhesion between the particles. The binder is used to improve the adhesion of the materials constituting the electrode. Examples of the binder include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aromatic polyamide resin, polyamide, polyimide, polyamideimide, polyacrylonitrile, polyacrylic acid, methyl polyacrylate, ethyl polyacrylate, hexyl polyacrylate, polymethacrylic acid, methyl polymethacrylate, ethyl polymethacrylate, hexyl polymethacrylate, polyvinyl acetate, polyvinylpyrrolidone, polyether, polyethersulfone, hexafluoropropylene, styrene-butadiene rubber, carboxymethyl cellulose, etc. In addition, as the binder, 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 can be used. In addition, two or more selected from them can also be mixed and used as the binder.

[0239] To improve the electronic conductivity, at least one of the positive electrode 201 and the negative electrode 203 may contain a conductive additive. As the conductive additive, for example, graphite-based materials such as natural graphite or artificial graphite, carbon black-based materials such as acetylene black or Ketjen black, conductive fiber-based materials such as carbon fiber or metal fiber, metal powder-based materials such as carbon fluoride or aluminum, conductive whisker-based materials such as zinc oxide or potassium titanate, conductive metal oxides such as titanium oxide, conductive polymer compounds such as polyaniline, polypyrrole, or polythiophene can be used. When using a carbon conductive additive, cost reduction can be achieved.

[0240] In addition, the battery in Embodiment 2 can be configured as a battery in various shapes such as coin type, cylindrical type, square type, thin film type, button type, flat type, or laminated type.

[0241] Examples

[0242] Hereinafter, the details of the present disclosure will be described using examples and comparative examples.

[0243] 《Example 1》

[0244] [Production of the second solid electrolyte]

[0245] In an argon glove box with a dew point of -60°C or lower, LiCl, LiBr, and YCl as raw material powders 3 were weighed in a molar ratio of LiCl:LiBr:YCl 3 = 1:2:1. The obtained mixture was ground using a planetary ball mill (manufactured by Fritsch, model P-5) under the conditions of 25 hours and 600 rpm. Thus, a powder of the second solid electrolyte represented by the composition formula Li 3 Y 1 Br 2 Cl 4 (hereinafter referred to as LYBC) was obtained.

[0246] [Production of the first solid electrolyte]

[0247] In an argon glove box with a dew point of -60°C or lower, LiCl, LiBr, and YCl as raw material powders 3 were weighed in a molar ratio of LiCl:LiBr:YCl 3 = 1:2:1. The obtained mixture was ground using a planetary ball mill (manufactured by Fritsch, model P-5) under the conditions of 25 hours and 600 rpm. Thus, a powder of the first solid electrolyte represented by the composition formula Li 3 Y 1 Br 2 Cl 4 was obtained.

[0248] [Production of the coated active material]

[0249] As the positive electrode active material, a powder of Li(NiCoMn)O 2 (hereinafter referred to as NCM) was prepared. A coating layer composed of Li 3 Y 1 Br 2 Cl 4 was formed on the NCM. The coating layer was formed by compression-shear treatment using a particle compounding device (NOB-MINI, manufactured by Hosokawa Micron Corporation). Specifically, the positive electrode active material and the first solid electrolyte were weighed at a weight ratio of 97.5:2.5, and treated under the conditions of a plate gap of 2 mm and a treatment time of 10 min, thereby obtaining the coated active material of Example 1.

[0250] [Fabrication of Positive Electrode Material]

[0251] 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 sum of the first solid electrolyte and the second solid electrolyte) became 73:27. They were mixed in an agate mortar, thereby fabricating the positive electrode material of Example 1.

[0252] [Example 2]

[0253] In the compression-shear treatment for fabricating the coated active material, the weight ratio of the positive electrode active material to the first solid electrolyte was changed to 95:5, and the positive electrode material of Example 2 was obtained in the same manner as in Example 1 except for this.

[0254] [Example 3]

[0255] [Fabrication of Sulfide Solid Electrolyte]

[0256] In an argon glove box with a dew point of -60°C or lower, Li 2 S and P 2 S 5 were weighed at a molar ratio of Li 2 S:P 2 S 5 = 75:25. They were pulverized and mixed in a mortar to obtain a mixture. Then, the mixture was ground using a planetary ball mill (manufactured by Fritsch, model P-7) under the conditions of 10 hours and 510 rpm. Thus, a glassy solid electrolyte was obtained. The glassy solid electrolyte was heat-treated in an inert atmosphere at 270°C for 2 hours. Thus, a glass-ceramic solid electrolyte Li 2 S-P 2 S5 .

[0257] [Fabrication of Cathode Material]

[0258] In an argon glove box, the coated active material of Example 1 and Li as the second solid electrolyte were weighed such that the volume ratio of NCM to the solid electrolyte (the sum of the first solid electrolyte and the second solid electrolyte) was 50:50 2 S-P 2 S 5 . They were mixed in an agate mortar, thereby fabricating the cathode material of Example 3.

[0259] <<Comparative Example 1>>

[0260] Except for using NCM without a coating layer, the cathode material of Comparative Example 1 was obtained by the same method as in Example 1.

[0261] <<Comparative Example 2>>

[0262] In the compression-shear treatment during the fabrication of the coated active material, the weight ratio of the cathode active material to the first solid electrolyte was changed to 99:1, and the cathode material of Comparative Example 2 was obtained by the same method as in Example 1 except for this.

[0263] <<Comparative Example 3>>

[0264] In the compression-shear treatment during the fabrication of the coated active material, the weight ratio of the cathode active material to the first solid electrolyte was changed to 90:10, and the cathode material of Comparative Example 3 was obtained by the same method as in Example 1 except for this.

[0265] <<Comparative Example 4>>

[0266] Except for using NCM without a coating layer, the cathode material of Comparative Example 4 was obtained by the same method as in Example 3.

[0267] [Measurement of Pore Volume]

[0268] Regarding Example 1, Example 2, Example 3, Comparative Example 2, and Comparative Example 3, the pore volume V of NCM as the cathode active material was measured using a gas adsorption measurement device (Autosorb-3 manufactured by Quantachrome Corporation) by the method described above α and the pore volume V of the coated active material β . The pore volume ratio V β / V α .

[0269] [Measurement of Specific Surface Area]

[0270] 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 Corporation), the specific surface area S of NCM as the positive electrode active material was measured by the method described above. α and the specific surface area S of the coated active material β . The ratio of the specific surface areas S β / S α was calculated from the measurement results.

[0271] [Measurement of weight]

[0272] Regarding Example 1, Example 2, Example 3, Comparative Example 2, and Comparative Example 3, based on the weight W α of NCM as the positive electrode active material and the weight W β of the coated active material, the weight ratio W α / W β was calculated.

[0273] [Volume ratio of solid electrolytes]

[0274] The volume V γ of the first solid electrolyte relative to the volume V δ of the second solid electrolyte was calculated as the ratio V γ / V δ . As the volume V γ of the first solid electrolyte and the volume V δ of the second solid electrolyte, the usage amounts of the first and second solid electrolytes when fabricating the positive electrode material were used.

[0275] [Measurement of the thickness of the coating layer]

[0276] Regarding Example 1, Example 2, Example 3, Comparative Example 2, and Comparative Example 3, the thickness d of the coating layer in the coated active material was measured by the method described above. The ion milling treatment of the coated active material was performed using a cross-section polisher (SM-09010 manufactured by JEOL Ltd.) under the conditions of an acceleration voltage of 5 kV and a processing time of 8 hours. The cross-section observation of the particles of the coated active material was performed using a scanning electron microscope (SU-70 manufactured by Hitachi High-Technologies Corporation) 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 3 points within the observation field of view.

[0277] [Fabrication of battery]

[0278] Using the positive electrode material, Li 3 Y 1 Br 2 Cl 4 and glass-ceramic Li2 S-P 2 S 5 , perform the following steps.

[0279] First, in the insulating outer cylinder, stack 60 mg of Li 2 S-P 2 S 5 , 20 mg of Li 3 Y 1 Br 2 Cl 4 , and the positive electrode material in this order. At this time, the positive electrode material is weighed so that the weight of the positive electrode active material becomes 14 mg. Press and mold the obtained laminate at a pressure of 720 MPa to obtain a positive electrode and a solid electrolyte layer.

[0280] Next, stack metallic Li (with a thickness of 200 μm) on the solid electrolyte layer on the side opposite to the side in contact with the positive electrode. Press and mold the obtained laminate at a pressure of 80 MPa to fabricate a laminate composed of a positive electrode, a solid electrolyte layer, and a negative electrode.

[0281] Then, arrange stainless steel current collectors above and below the laminate. Attach current collecting leads to each current collector.

[0282] Finally, seal the insulating outer cylinder by using an insulating hoop to isolate the inside of the outer cylinder from the external atmosphere, and fabricate a battery.

[0283] Through the above, batteries of Examples 1 to 3 and Comparative Examples 1 to 4 were fabricated respectively.

[0284] [Charge test]

[0285] Using the batteries of Examples 1 to 3 and Comparative Examples 1 to 4, a charge test was carried out under the following conditions.

[0286] Place the battery in a thermostat at 25°C.

[0287] Constant-current charge the battery with a current value of 140 μA at a rate of 0.05 C (20-hour rate) relative to the theoretical capacity of the battery until the voltage reaches 4.3 V. After a rest time of 20 minutes, constant-current discharge the battery with a current value of 140 μA at a rate of 0.05 C (20-hour rate) until the voltage reaches 2.5 V.

[0288] Calculate the ratio of the discharge capacity obtained above to the charge capacity as the initial efficiency. The results are shown in Table 1.

[0289] Table 1

[0290]

[0291] "Investigation"

[0292] From the results of Example 1, Example 2, and Comparative Examples 1 to 3, it can be confirmed that in the positive electrode material using a positive electrode active material having a coating layer containing a first solid electrolyte, the initial efficiency of the battery varies according to the state of the coating layer.

[0293] Specifically, when 0.20 < V β / V α < 0.88, an initial efficiency of 89% is achieved. It is considered that the coating layer helps to balance low electron resistance and low interfacial resistance.

[0294] In addition, when 0.81 < S β / S α < 0.97, an initial efficiency of 89% is achieved. It is considered that the coating layer helps to balance low electron resistance and low interfacial resistance.

[0295] In addition, when 0.90 < W α / W β < 0.99, an initial efficiency of 89% is achieved. It is considered that the coating layer helps to balance low electron resistance and low interfacial resistance.

[0296] When 14 nm < d < 167 nm, an initial efficiency of 89% is achieved. It is considered that the coating layer helps to balance low electron resistance and low interfacial resistance.

[0297] According to the results of Example 3 and Comparative Example 4, in the case of using a sulfide solid electrolyte as the second solid electrolyte, by using a positive electrode material in which the surface of the positive electrode active material is coated with a halide solid electrolyte, the initial efficiency of the battery is improved. It is considered that this is the result of suppressing the oxidation of the sulfide solid electrolyte.

[0298] Industrial Applicability

[0299] The battery of the present disclosure can be used, for example, as an all-solid-state lithium secondary battery or the like.

[0300] Explanation of Reference Numerals

[0301] 1000 Positive electrode material

[0302] 100 Second solid electrolyte

[0303] 110 Positive electrode active material

[0304] 111 Coating layer

[0305] 130 Coated active material

[0306] 2000 Battery

[0307] 201 Positive electrode

[0308] 202 Electrolyte layer

[0309] 203 Negative electrode

Claims

1. A positive electrode material comprising a positive electrode active material and a coating layer, wherein the coating layer contains a first solid electrolyte and coats at least a part of the surface of the positive electrode active material, the positive electrode active material and the coating layer form a coated active material, When 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 and 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 , at least one of the following is satisfied: 0.20 < V β / V α < 0.88 and 0.81 < S β / S α < 0.97 When the weight of the positive electrode active material is represented by W α and the weight of the coated active material is represented by W β it satisfies 0.90 < W α / W β < 0.99, the thickness of the coating layer is greater than 14 nm and less than 167 nm, the positive electrode material further contains a second solid electrolyte, 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 it satisfies 0.05 < V γ / V δ < 0.

97.

2. The positive electrode material according to claim 1, Satisfying 0.60 ≤ V β / V α ≤ 0.

76.

3. The positive electrode material according to claim 1 or 2, Satisfy 0.86 ≤ S β / S α ≤ 0.

89.

4. The positive electrode material according to claim 1 or 2, Satisfy 0.95 ≤ W α / W β ≤ 0.

975.

5. The positive electrode material according to claim 1 or 2, the thickness of the coating layer is 32 nm or more and 71 nm or less.

6. The positive electrode material according to claim 1 or 2, the first solid electrolyte is represented by the following compositional formula (1), Li α1 M1 β1 X1 γ1 ··· Formula (1) wherein, α1, β1 and γ1 are each independently a value greater than 0, M1 contains at least one element selected from metal elements other than Li and metalloid elements, and X1 contains at least one selected from F, Cl, Br and I.

7. The positive electrode material according to claim 6, M1 contains yttrium.

8. The positive electrode material according to claim 6, 2.5 ≤ α1 ≤ 3, 1 ≤ β1 ≤ 1.1 and γ1 = 6 are satisfied.

9. The positive electrode material according to claim 6, X1 contains at least one selected from Cl and Br.

10. The positive electrode material according to claim 6, The first solid electrolyte contains Li 3 YBr 2 Cl 4 .

11. The positive electrode material according to claim 1 or 2, the positive electrode active material contains Ni, Co and Mn.

12. The positive electrode material according to claim 1 or 2, the second solid electrolyte is represented by the following compositional formula (3), Li α2 M2 β2 X2 γ2 ··· Formula (3) wherein, α2, β2 and γ2 are each independently a value greater than 0, M2 contains at least one element selected from metal elements other than Li and metalloid elements, and X2 contains at least one selected from F, Cl, Br and I.

13. The positive electrode material according to claim 12, M2 contains yttrium.

14. The positive electrode material according to claim 12, 2.5 ≤ α2 ≤ 3, 1 ≤ β2 ≤ 1.1 and γ2 = 6 are satisfied.

15. The positive electrode material according to claim 12, X2 contains at least one selected from Cl and Br.

16. The positive electrode material according to claim 12, The second solid electrolyte contains Li 3 YBr 2 Cl 4 .

17. The positive electrode material according to claim 1 or 2, the second solid electrolyte contains a sulfide solid electrolyte.

18. A battery comprising a positive electrode, a negative electrode and an electrolyte layer disposed between the positive electrode and the negative electrode, wherein the positive electrode contains the positive electrode material according to any one of claims 1 to 17.

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