Battery

Abstract

This battery 1000 comprises a positive electrode 100, a negative electrode 200, and an electrolyte layer 300 provided between the positive electrode 100 and the negative electrode 200. The electrolyte layer 300 includes a first electrolyte layer 301 and a second electrolyte layer 302. The second electrolyte layer 302 is provided between the first electrolyte layer 301 and the negative electrode 200. The first electrolyte layer 301 does not contain Br. The second electrolyte layer 302 contains Br and S.

Description

battery

[0001] This disclosure relates to batteries.

[0002] Patent Document 1 discloses a battery in which the electrolyte layer comprises a first electrolyte layer and a second electrolyte layer, and the first electrolyte layer and the second electrolyte layer contain a halogen solid electrolyte.

[0003] International Publication No. 2019 / 146294

[0004] Batteries, such as those disclosed in Patent Document 1, which have multiple electrolyte layers and include a halogen solid electrolyte, have room for improvement in terms of high-temperature resistance. Therefore, this disclosure provides a battery that can improve high-temperature resistance.

[0005] The battery of this disclosure comprises a positive electrode, a negative electrode, and an electrolyte layer provided between the positive electrode and the negative electrode, wherein the electrolyte layer includes a first electrolyte layer and a second electrolyte layer, the second electrolyte layer is provided between the first electrolyte layer and the negative electrode, the first electrolyte layer does not contain Br, and the second electrolyte layer contains Br and S.

[0006] According to this disclosure, it is possible to provide a battery that can improve high-temperature resistance.

[0007] Figure 1 is a cross-sectional view showing a schematic configuration of an example of a battery according to the present disclosure. Figure 2 is a cross-sectional view showing a schematic configuration of a modified example of the battery according to the present disclosure.

[0008] The embodiments of this disclosure will be described below with reference to the drawings. This disclosure is not limited to the embodiments described below.

[0009] Figure 1 is a cross-sectional view showing a schematic configuration of an example of a battery according to the present disclosure.

[0010] The battery 1000 according to this embodiment comprises a positive electrode 100, a negative electrode 200, and an electrolyte layer 300. The electrolyte layer 300 is provided between the positive electrode 100 and the negative electrode 200. The electrolyte layer 300 includes a first electrolyte layer 301 and a second electrolyte layer 302. The second electrolyte layer 302 is provided between the first electrolyte layer 301 and the negative electrode 200. The first electrolyte layer 301 does not contain Br (bromine). The second electrolyte layer 302 contains Br (bromine) and S (sulfur).

[0011] The battery 1000 according to this embodiment includes an electrolyte layer 300 comprising a first electrolyte layer 301 and a second electrolyte layer 302. In conventional batteries, when stored at high temperatures in a charged state, performance degradation such as a significant decrease in open-circuit voltage (OCV) can occur due to a reaction between the positive electrode and the solid electrolyte contained in the electrolyte layer. In contrast, in the battery 1000 according to this embodiment, the first electrolyte layer 301, which does not contain Br, is provided on the positive electrode 100 side of the electrolyte layer 300, thereby suppressing the acceleration of the reaction between the positive electrode 100 and the electrolyte layer 300 when the battery 1000 is stored at high temperatures. As a result, the battery 1000 according to this embodiment is less prone to performance degradation when stored at high temperatures, and its high-temperature resistance can be improved. In the battery 1000 according to this embodiment, the second electrolyte layer 302, which contains Br and S, is provided on the negative electrode 200 side of the electrolyte layer 300, thereby enabling good output characteristics such as the realization of high output. Thus, the battery 1000 according to this embodiment, by comprising a first electrolyte layer 301 and a second electrolyte layer 302 having the above configuration, can have good output characteristics in addition to improved high-temperature resistance.

[0012] The fact that the electrolyte layer 300 contains a first electrolyte layer 301 that does not contain Br and a second electrolyte layer 302 that contains Br and S can be confirmed by compositional analysis of a cross-section obtained by cutting the electrolyte layer 300 in the thickness direction. Compositional analysis can be performed by elemental mapping of a cross-section obtained by cutting the electrolyte layer 300 in the thickness direction. The elemental map can be obtained by scanning transmission electron microscopy or energy-dispersive X-ray spectroscopy (STEM-EDX or SEM-EDX) in combination with scanning electron microscopy.

[0013] The first electrolyte layer 301 is preferably provided in contact with the positive electrode 100, as shown in Figure 1. With this configuration, the battery 1000 can further suppress the acceleration of the reaction between the positive electrode 100 and the electrolyte layer 300 when stored at high temperatures. Therefore, the battery 1000 can further improve its high-temperature resistance while maintaining good output characteristics.

[0014] The electrolyte layer 300, the positive electrode 100, and the negative electrode 200 will be described in more detail below.

[0015] (Electrolyte layer 300) The first electrolyte layer 301 may have a configuration that includes, for example, Li, M1, and Cl, but does not contain S. Here, M1 is at least one element selected from the group consisting of metallic elements and metalloid elements other than Li. By having the first electrolyte layer 301 with such a configuration, the reaction between the positive electrode 100 and the electrolyte layer 300 when stored at high temperatures is further suppressed. Therefore, the battery 1000 can further improve its high-temperature resistance while maintaining good output characteristics.

[0016] In this specification, “metallic elements” include B, Si, Ge, As, Sb, and Te.

[0017] In this specification, "metallic elements" include all elements in Groups 1 through 12 of the periodic table, excluding hydrogen, and all elements in Groups 13 through 16 of the periodic table, excluding B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se. In other words, metallic elements are a group of elements that can form cations when forming inorganic compounds with halogen elements.

[0018] The first electrolyte layer 301 may consist substantially of Li, M1, and Cl, or it may consist solely of Li, M1, and Cl. Here, "the first electrolyte layer 301 consists substantially of Li, M1, and Cl" means that the molar ratio of the total amount of substance of Li, M1, and Cl to the total amount of substance of all elements constituting the first electrolyte layer 301 is 90% or more. As an example, this molar ratio may be 95% or more.

[0019] The first electrolyte layer 301 may contain a first solid electrolyte that does not contain sulfur. The first solid electrolyte may contain, for example, Li, M1, and Cl.

[0020] The first solid electrolyte may be represented, for example, by the following compositional formula (1): Li α1 M1 β1 Cl γ1 ...Equation (1) Here, in empirical formula (1), α1, β1, and γ1 are each independently greater than 0.

[0021] The first electrolyte layer 301 may consist substantially of the first solid electrolyte, or it may consist solely of the first solid electrolyte. Here, "the first electrolyte layer 301 consists substantially of the first solid electrolyte" means that the content of the first solid electrolyte in the first electrolyte layer 301 is 90% by mass or more. As an example, this content may be 95% by mass or more.

[0022] M1 may include at least one selected from the group consisting of Y and Zr. By including Li, at least one selected from the group consisting of Y and Zr, and Cl in the first electrolyte layer 301, the ionic conductivity of the first electrolyte layer 301 is improved. This makes it possible to further improve the output characteristics and high-temperature resistance of the battery 1000.

[0023] In order to further improve the output characteristics and high-temperature resistance of the battery 1000, the first electrolyte layer 301 may substantially consist of Li, Y, Zr, and Cl, or may consist only of Li, Y, Zr, and Cl. Here, "the first electrolyte layer 301 substantially consists of Li, Y, Zr, and Cl" means that the molar ratio of the total amount of the substances of Li, Y, Zr, and Cl to the total amount of the substances of all the elements constituting the first electrolyte layer 301 is 90% or more. As an example, the molar ratio may be 95% or more.

[0024] As described above, the second electrolyte layer 302 contains Br and S.

[0025] The second electrolyte layer 302 may contain a second solid electrolyte containing Br and S.

[0026] For example, the second electrolyte layer 302 contains a sulfide solid electrolyte. The sulfide solid electrolyte may be a sulfide solid electrolyte containing Br. That is, the second solid electrolyte may be a sulfide solid electrolyte containing Br. With this configuration, the internal resistance of the battery 1000 can be reduced and the output can be increased, so that the output characteristics can be further improved while maintaining good high-temperature resistance of the battery 1000.

[0027] 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 , Li7PS6 (argyrodite type), those in which a part of S in the above S-containing substance is substituted with a halogen element, those in which a part of Li2S-P2S5 is substituted with SiS2, etc. can be used. To these, LiX, Li2O, MO q , Li p 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 qThe 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 In "」, p and q are each independent natural numbers.

[0028] The sulfide solid electrolyte containing Br may be, for example, a sulfide solid electrolyte to which LiBr is added as the above LiX, or a sulfide solid electrolyte in which part of S or part of a halogen element other than Br is replaced by Br among the sulfide solid electrolytes exemplified above.

[0029] The second solid electrolyte contained in the second electrolyte layer 302 may have a higher ionic conductivity than the first solid electrolyte contained in the first electrolyte layer 301. With this configuration, the internal resistance of the battery 1000 can be reduced and the output can be increased, so that the output characteristics can be further improved while maintaining good high-temperature resistance of the battery 1000.

[0030] The thickness of the second electrolyte layer 302 may be greater than the thickness of the first electrolyte layer 301. According to this configuration, the output characteristics and high-temperature resistance can be made compatible at a higher level.

[0031] In order to make the output characteristics and high-temperature resistance compatible at a higher level, the thickness of the first electrolyte layer 301 may be 0.2 or more and less than 1.0 with respect to the thickness of the second electrolyte layer 302. <00001​​​​The thickness of the second electrolyte layer 302 may be, for example, 10 μm or more and 500 μm or less, 10 μm or more and 400 μm or less, or 10 μm or more and 200 μm or less. Having such a thickness for the second electrolyte layer 302 enables high-power operation of the battery 1000 and improves its output characteristics.

[0034] The thickness of the electrolyte layer 300 may be 20 μm or more and 1000 μm or less. A thickness of 1 μm or more for the electrolyte layer 300 reduces the possibility of a short circuit between the positive electrode 100 and the negative electrode 200, thereby increasing the safety of the battery 1000. A thickness of 1000 μm or less for the electrolyte layer 300 enables high-power operation.

[0035] The thickness of the first electrolyte layer 301 can be determined by observing a cross-section of the first electrolyte layer 301 in the thickness direction using a scanning electron microscope (SEM). For example, the thickness of the first electrolyte layer 301 can be measured at any number of points (e.g., 5 points) using an SEM image of the first electrolyte layer 301, and the average value can be taken as the thickness of the first electrolyte layer 301. The thicknesses of the second electrolyte layer 302 and the electrolyte layer 300 can be determined in a similar manner.

[0036] Figure 2 is a cross-sectional view showing a schematic configuration of a modified example of the battery according to the present disclosure. The electrolyte layer 310 of the modified battery 2000 shown in Figure 2 further comprises a third electrolyte layer 303 disposed between a first electrolyte layer 301 and a second electrolyte layer 302. The third electrolyte layer 303 may contain Br. The third electrolyte layer may contain Br and halogen elements other than Br. The third electrolyte layer 303 does not contain, for example, S. The third electrolyte layer may contain, for example, Br and elements constituting the first electrolyte layer.

[0037] In the battery according to the embodiment of this disclosure, the electrolyte layer may include an electrolyte layer (fourth electrolyte layer) provided between the second electrolyte layer and the negative electrode.

[0038] (Positive electrode 100) The positive electrode 100 includes, for example, a positive electrode active material and a third solid electrolyte as a positive electrode electrolyte.

[0039] The positive electrode active material includes a material having the property of intercalating and releasing metal ions (e.g., lithium ions).

[0040] Examples of positive electrode active materials include lithium-containing transition metal oxides, lithium-containing transition metal phosphates, transition metal fluorides, polyanionic materials, fluorinated polyanionic materials, transition metal sulfides, transition metal oxysulfides, and transition metal oxynitrides. In particular, when lithium-containing transition metal oxides or lithium-containing transition metal phosphates are used as the positive electrode active material, the manufacturing cost of the battery can be reduced and the average discharge voltage can be increased. Examples of lithium-containing transition metal oxides include lithium cobalt oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese oxide, and lithium nickel manganese oxide. Examples of lithium-containing transition metal phosphates include lithium iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, and lithium nickel phosphate. At least one of these positive electrode active materials can be used. The positive electrode active material may also be lithium nickel cobalt manganese oxide (Li(NiCoMn)O2, hereinafter referred to as "NCM").

[0041] The particles of the positive electrode active material may be primary or secondary particles. For example, the particles of the positive electrode active material have an average particle size of 1 μm to 10 μm. The average particle size refers to the particle diameter (median diameter) when the cumulative volume in the volume-based particle size distribution is 50%. The volume-based particle size distribution is measured, for example, by a laser diffraction particle size analyzer.

[0042] The positive electrode active material may contain a single active material, or it may contain multiple active materials having different compositions from each other.

[0043] The third solid electrolyte may be a Br-free solid electrolyte. By not including Br in the third solid electrolyte, it is possible to suppress the acceleration of the reaction between the positive electrode active material and the third solid electrolyte in the positive electrode 100 when the battery 1000 is stored at high temperatures. As a result, the high-temperature resistance of the positive electrode 100 is improved, and the battery 1000 can further improve its high-temperature resistance while maintaining good output characteristics.

[0044] The third solid electrolyte may be a solid electrolyte containing Li, M2, and Cl, but not containing S. Here, M2 is at least one element selected from the group consisting of metallic elements and metalloid elements other than Li. By having the third solid electrolyte with such a configuration, the high-temperature resistance of the positive electrode 100 is further improved, so that the battery 1000 can further improve its high-temperature resistance while maintaining good output characteristics.

[0045] The third solid electrolyte may be represented, for example, by the following compositional formula (2): Li α2 M2 β2 Cl γ2 ...Equation (2) Here, in empirical formula (2), α2, β2, and γ2 are each independently greater than 0.

[0046] M2 may include at least one selected from the group consisting of Y and Zr. By including at least one selected from the group consisting of Y and Zr as M2 in the third solid electrolyte, the ionic conductivity of the third solid electrolyte is improved. As a result, the positive electrode 100 can have improved output characteristics in addition to improved high-temperature resistance. Therefore, the output characteristics and high-temperature resistance of the battery 1000 can be further improved.

[0047] The third solid electrolyte may have the same composition as the first solid electrolyte. That is, the solid electrolyte contained in the positive electrode 100 may have the same composition as the solid electrolyte contained in the first electrolyte layer 301. This can further improve the output characteristics and high-temperature resistance of the battery 1000.

[0048] The positive electrode active material has, for example, a particle shape. The third solid electrolyte also has, for example, a particle shape.

[0049] The positive electrode active material particles may have a median diameter of 0.1 μm or more and 100 μm or less. When the positive electrode active material particles have a median diameter of 0.1 μm or more, the dispersion state of the positive electrode active material particles and the third solid electrolyte particles in the positive electrode 100 becomes good. This improves the charge and discharge characteristics of the battery 1000. When the positive electrode active material particles have a median diameter of 100 μm or less, the lithium diffusion rate within the positive electrode active material particles improves. This allows the battery 1000 to operate at high power.

[0050] The particles of the positive electrode active material may have a larger median diameter than the particles of the third solid electrolyte. This results in a good dispersion state of the particles of the positive electrode active material and the particles of the third solid electrolyte in the positive electrode 100.

[0051] In order to increase the energy density and output of the battery 1000, the ratio of the volume of the positive electrode active material to the sum of the volume of the positive electrode active material and the volume of the third solid electrolyte in the positive electrode 100 may be 0.30 or more and 0.95 or less.

[0052] At least a portion of the surface of the positive electrode active material particles may be covered with a coating layer. The coating layer may be formed on the surface of the positive electrode active material particles, for example, before mixing the positive electrode active material with a conductive additive and a binder. Examples of coating materials included in the coating layer include sulfide solid electrolytes, oxide solid electrolytes, and halide solid electrolytes.

[0053] Examples of sulfide solid electrolytes are as described above.

[0054] Examples of oxide solid electrolytes include the following materials: (i) NASICON-type solid electrolytes such as LiTi2(PO4)3 or its elemental substitutions, (ii) perovskite-type solid electrolytes such as (LaLi)TiO3, (iii) Li 14 ZnGe4O 16 , Li4SiO4, LiGeO4, or LISICON-type solid electrolytes such as elemental substitutions thereof, (iv)Li7La3Zr2O 12 (v) Garnet-type solid electrolytes such as the element-substituted thereof, (v) Li3PO4 or its N-substituted counterpart

[0055] The halide solid electrolyte may be a material represented by the following compositional formula (3).

[0056] Li α3 M3 β3 X' γ3 ...Formula (3) In empirical formula (3), α3, β3, and γ3 are each independently greater than 0, M3 is at least one selected from the group consisting of metal elements other than Li and metalloid elements, and X' is at least one selected from the group consisting of F, Cl, Br, and I.

[0057] The halogen solid electrolyte may be one of the materials exemplified above as the first solid electrolyte and the third solid electrolyte.

[0058] To increase the energy density and output of the battery 1000, the positive electrode 100 may have a thickness of 10 μm or more and 500 μm or less.

[0059] (Negative electrode 200) The negative electrode 200 includes, for example, a negative electrode active material and a solid electrolyte.

[0060] The negative electrode active material includes a material capable of intercalating and releasing metal ions such as lithium ions. Examples of negative electrode active materials include metallic materials, carbon materials, oxides, nitrides, tin compounds, and silicon compounds. The metallic material may be a pure metal or an alloy. Examples of metallic materials include lithium metal and lithium alloys. Examples of carbon materials include natural graphite, coke, carbon in the process of graphitization, carbon fibers, spheroidal carbon, artificial graphite, and amorphous carbon.

[0061] The negative electrode active material may contain Li, Ti, and O. The negative electrode active material may, for example, be an oxide containing Li and Ti. An example of an oxide containing Li and Ti is Li4Ti5O. 12 Examples include LiTi2O4. By including such a negative electrode active material in the negative electrode 200, the charge and discharge capacity of the battery 1000 is improved.

[0062] Examples of solid electrolytes included in the negative electrode 200 include sulfide solid electrolytes, oxide solid electrolytes, and halide solid electrolytes. The negative electrode 200 may also contain a sulfide solid electrolyte.

[0063] The solid electrolyte contained in the negative electrode 200 may have the same composition as the second solid electrolyte contained in the second electrolyte layer 302. This can further improve the output characteristics and high-temperature resistance of the battery 1000.

[0064] The negative electrode active material has, for example, a particle shape. The solid electrolyte contained in the negative electrode 200 also has, for example, a particle shape.

[0065] The particles of the negative electrode active material may have a median diameter of 0.1 μm or more and 100 μm or less. When the particles of the negative electrode active material have a median diameter of 0.1 μm or more, the dispersion state of the particles of the negative electrode active material and the particles of the solid electrolyte in the negative electrode 200 becomes good. This improves the charge and discharge characteristics of the battery 1000. When the particles of the negative electrode active material have a median diameter of 100 μm or less, the lithium diffusion rate within the particles of the negative electrode active material improves. This allows the battery 1000 to operate at high power.

[0066] The particles of the negative electrode active material may have a larger median diameter than the particles of the solid electrolyte contained in the negative electrode 200. This results in a good dispersion state of the particles of the negative electrode active material and the solid electrolyte in the negative electrode 200.

[0067] In order to increase the energy density and output of the battery 1000, the ratio of the volume of the negative electrode active material to the sum of the volume of the negative electrode active material and the volume of the solid electrolyte in the negative electrode 200 may be 0.30 or more and 0.95 or less.

[0068] To increase the energy density and output of the battery 1000, the negative electrode 200 may have a thickness of 10 μm or more and 500 μm or less.

[0069] (Method for manufacturing a battery) The battery 1000 according to this embodiment may be manufactured, for example, by preparing a material for forming a positive electrode, a material for forming a first electrolyte layer, a material for forming a second electrolyte layer, and a material for forming a negative electrode, and then by a known method, by creating a laminate in which the positive electrode 100, the first electrolyte layer 301, the second electrolyte layer 302, and the negative electrode 200 are arranged in this order. When manufacturing the battery 2000, a material for forming a third electrolyte layer is further prepared, and then by a known method, a laminate in which the positive electrode 100, the first electrolyte layer 301, the third electrolyte layer 303, the second electrolyte layer 302, and the negative electrode 200 are arranged in this order.

[0070] (Other Embodiments) (Note) The above description of embodiments discloses the following technologies.

[0071] (Technical 1) A battery comprising: a positive electrode; a negative electrode; and an electrolyte layer provided between the positive electrode and the negative electrode, wherein the electrolyte layer includes a first electrolyte layer and a second electrolyte layer, the second electrolyte layer is provided between the first electrolyte layer and the negative electrode, the first electrolyte layer does not contain Br, and the second electrolyte layer contains Br and S.

[0072] The above configuration makes it possible to provide a battery with improved high-temperature resistance.

[0073] (Technology 2) The battery according to Technology 1, wherein the first electrolyte layer contains Li, M1, and Cl, but does not contain S, and M1 is at least one element selected from the group consisting of metallic elements other than Li and metalloid elements.

[0074] The above configuration allows for the provision of a battery with improved high-temperature resistance.

[0075] (Technical 3) The first electrolyte layer contains a first solid electrolyte, the first solid electrolyte is represented by the following compositional formula (1), Li α1 M1 β1 Cl γ1 ...Formula (1) In the above composition formula (1), α1, β1, and γ1 are each independently greater than 0, the battery as described in Technical 2.

[0076] The above configuration allows for the provision of a battery with improved high-temperature resistance.

[0077] (Technical 4) The battery according to Technical 2 or 3, wherein M1 includes at least one selected from the group consisting of Y and Zr.

[0078] The above configuration allows for the provision of a battery with improved high-temperature resistance.

[0079] (Technical 5) The battery according to any one of Technical 2 to 4, wherein the first electrolyte layer consists of Li, Y, Zr, and Cl.

[0080] The above configuration allows for the provision of a battery with improved high-temperature resistance.

[0081] (Technical 6) The battery according to any one of Technical 1 to 5, wherein the first electrolyte layer comprises a first solid electrolyte, the second electrolyte layer comprises a second solid electrolyte, and the second solid electrolyte has a higher ionic conductivity than the first solid electrolyte.

[0082] According to the above configuration, it is possible to provide a battery with improved output characteristics in addition to good high-temperature resistance.

[0083] (Technical 7) The battery according to any one of Technical 1 to 6, wherein the thickness of the second electrolyte layer is greater than the thickness of the first electrolyte layer.

[0084] According to the above configuration, it is possible to provide a battery with improved output characteristics in addition to good high-temperature resistance.

[0085] (Technical 8) The battery according to Technical 7, wherein the thickness of the first electrolyte layer is 0.2 or more and less than 1.0 compared to the thickness of the second electrolyte layer.

[0086] According to the above configuration, it is possible to provide a battery with improved output characteristics in addition to good high-temperature resistance.

[0087] (Technical 9) The battery according to any one of Technical 1 to 8, further comprising a third electrolyte layer disposed between the first electrolyte layer and the second electrolyte layer, wherein the third electrolyte layer contains Br.

[0088] According to the above configuration, it is possible to provide a battery with improved output characteristics in addition to good high-temperature resistance.

[0089] (Technical 10) The battery according to Technical 9, wherein the third electrolyte layer further comprises a halogen element other than Br.

[0090] According to the above configuration, it is possible to provide a battery with improved output characteristics in addition to good high-temperature resistance.

[0091] (Technical 11) The battery according to Technical 9, wherein the third electrolyte layer does not contain sulfur.

[0092] The above configuration allows for further improvement of the battery's output characteristics and high-temperature resistance.

[0093] (Technical 12) The battery according to any one of Technical 1 to 11, wherein the positive electrode comprises a positive electrode active material and a third solid electrolyte, and the third solid electrolyte does not contain Br.

[0094] The above configuration allows for the provision of a battery with improved high-temperature resistance.

[0095] (Technical 13) The battery according to Technical 12, wherein the third solid electrolyte contains Li, M2, and Cl, but does not contain S, and M2 is at least one element selected from the group consisting of metallic elements and metalloid elements other than Li.

[0096] The above configuration allows for the provision of a battery with improved high-temperature resistance.

[0097] (Technical 14) The third solid electrolyte is represented by the following compositional formula (2), Li α2 M2 β2 Cl γ2 ...Formula (2) In the above composition formula (2), α2, β2, and γ2 are each independently greater than 0, the battery as described in Technical 13.

[0098] The above configuration allows for the provision of a battery with improved high-temperature resistance.

[0099] (Technical 15) The battery according to Technical 13 or 14, wherein M2 includes at least one selected from the group consisting of Y and Zr.

[0100] According to the above configuration, it is possible to provide a battery with improved output characteristics in addition to good high-temperature resistance.

[0101] (Technical 16) The battery according to any one of Technical 12 to 15, wherein the first electrolyte layer comprises a first solid electrolyte, and the third solid electrolyte has the same composition as the first solid electrolyte.

[0102] The above configuration allows for the provision of a battery with improved high-temperature resistance.

[0103] (Technical 17) The battery according to any one of Technical 12 to 16, wherein at least a portion of the surface of the positive electrode active material is covered with a coating layer containing a halide solid electrolyte.

[0104] The above configuration allows for the provision of a battery with improved high-temperature resistance.

[0105] (Technical 18) The battery according to any one of Technical 1 to 17, wherein the first electrolyte layer is in contact with the positive electrode.

[0106] The above configuration allows for the provision of a battery with improved high-temperature resistance.

[0107] (Technical 19) The battery according to any one of Technical 1 to 18, wherein the second electrolyte layer comprises a sulfide solid electrolyte, and the sulfide solid electrolyte contains Br.

[0108] According to the above configuration, it is possible to provide a battery with improved output characteristics in addition to good high-temperature resistance.

[0109] (Technical 20) The battery according to any one of Technical 1 to 19, wherein the negative electrode comprises a negative electrode active material, and the negative electrode active material comprises Li, Ti, and O.

[0110] The above configuration makes it possible to improve the battery's charge and discharge capacity.

[0111] (Technical 21) The battery according to any one of Technical 1 to 20, wherein the negative electrode contains a sulfide solid electrolyte.

[0112] According to the above configuration, it is possible to provide a battery with improved output characteristics in addition to good high-temperature resistance.

[0113] (Technical 22) The battery according to Technical 21, wherein the sulfide solid electrolyte has the same composition as the second solid electrolyte contained in the second electrolyte layer.

[0114] The above configuration provides a battery with improved output characteristics in addition to good high-temperature resistance.

[0115] (Example 1) [First Solid Electrolyte (Solid Electrolyte Constituting the First Electrolyte Layer)] Under an argon atmosphere with a dew point of -60°C or lower, the raw material powders LiCl, ZrCl4, and YCl3 were weighed in a molar ratio of LiCl:ZrCl4:YCl3 = 2.5:0.5:0.5. These were crushed and mixed in a mortar to obtain a mixture. The mixture was then milled for 12 hours at 500 rpm using φ5 mm zirconia balls and a planetary ball mill (Fritsch, P-7 type). As a result, Li 2.5 Zr 0.5 Y 0.5 A powdered first solid electrolyte (hereinafter referred to as "LZYC") having the composition of Cl6 was obtained.

[0116] [Second Solid Electrolyte (Solid Electrolyte Constituting the Second Electrolyte Layer)] A sulfide solid electrolyte containing Br, obtained by substituting a portion of the S in a sulfide solid electrolyte represented by the compositional formula Li7PS6 with Br, was prepared as the second solid electrolyte.

[0117] [Third Solid Electrolyte (Solid Electrolyte Included in the Cathode)] LZYC, the same material used for the first solid electrolyte, was prepared as the third solid electrolyte.

[0118] [Coated positive electrode active material] Under an argon atmosphere with a dew point of -60°C or lower, the raw material powders LiF, TiF4, and AlF3 were weighed in a molar ratio of LiF:TiF4:AlF3 = 2.7:0.3:0.7. These were ground and mixed in a mortar to obtain a mixture. The mixture was then milled using φ5 mm zirconia balls and a planetary ball mill (Fritsch, P-7 type) for 12 hours at 500 rpm. As a result, Li 2.7 Ti 0.3 Al 0.7A powdered solid electrolyte having the composition of F6 (hereinafter referred to as "LTAF") was obtained.

[0119] As the positive electrode active material, NCM powder (average particle size 5 μm) was prepared. The LTAF obtained above was attached to the surface of the NCM particles to form a coating layer. The coating layer was formed by compression shearing using a particle compounding device (NOB-MINI, manufactured by Hosokawa Micron Corporation). Specifically, NCM and the coating material were mixed in a mass ratio of 100:3, and the mixture was processed under conditions of rotation speed: 6000 rpm and processing time: 50 min. This obtained the coated positive electrode active material of Example 1. The target thickness of the coating layer was 10 nm.

[0120] [Preparation of Cathode Compound] The cathode compound was prepared by mixing the coated cathode active material, third solid electrolyte, and conductive additive in an agate mortar under a dry argon atmosphere. The volume ratio of coated cathode active material to third solid electrolyte was coated cathode active material:third solid electrolyte = 35:65. Carbon nanofiber was used as the conductive additive. The ratio of the mass of the conductive additive to the total mass of coated cathode active material and third solid electrolyte was 3% by mass.

[0121] [Preparation of negative electrode composite material] Under a dry argon atmosphere, Li4Ti5O is used as the negative electrode active material. 12 A negative electrode composite was prepared by mixing a solid electrolyte and a conductive additive (average particle size 2.5 μm) in an agate mortar. A sulfide solid electrolyte prepared as the second solid electrolyte was used as the solid electrolyte of the negative electrode composite. The volume ratio of negative electrode active material to solid electrolyte was negative electrode active material:solid electrolyte = 60:40. Carbon nanofiber was used as the conductive additive. The ratio of the mass of the conductive additive to the total mass of the solid electrolyte and negative electrode active material was 1% by mass.

[0122] [Battery Fabrication] Inside an insulating outer cylinder with an inner diameter of 9.4 mm, the following materials were layered in this order, with thicknesses of 580 μm for the positive electrode composite, 100 μm for the first solid electrolyte, 100 μm for the second solid electrolyte, and 810 μm for the negative electrode composite. The positive electrode composite, first solid electrolyte, second solid electrolyte, and negative electrode composite were pressure-molded at a pressure of 720 MPa. This created a laminate having a positive electrode, a first electrolyte layer, a second electrolyte layer, and a negative electrode. Next, stainless steel current collectors were placed above and below the laminate, and current collector leads were attached to the current collectors. Finally, the insulating outer cylinder was sealed using an insulating ferrule so that the inside of the insulating outer cylinder was isolated from the outside atmosphere.

[0123] [Battery Evaluation] <High Temperature Resistance Evaluation 1> The initial charge and discharge of the battery was performed, and the initial discharge capacity was determined. Next, the charged battery was stored at 120°C for 1000 hours. After that, discharge was performed. Further charge and discharge was performed to determine the recovery discharge capacity after storage. From these results, the discharge recovery rate ((recovery discharge capacity after storage / initial discharge capacity) × 100) was calculated. Initial charge and discharge and recovery charge and discharge after storage were performed at room temperature (25°C) by constant current charging with a current of 0.05C until the voltage reached 2.75V, and then constant current discharge with a current of 0.05C until the voltage reached 0.9V. Charging before storage was performed at room temperature (25°C) by constant current charging with a current of 0.05C until the voltage reached 2.75V. Discharge after storage was performed at room temperature (25°C) by constant current discharge with a current of 0.05C until the voltage reached 0.9V. The results are shown in Table 1.

[0124] (Comparative Example 1) The solid electrolyte used for the second solid electrolyte and the negative electrode was changed from Example 1. In Comparative Example 1, Li3YBr2Cl4 (hereinafter referred to as "LYBC") was used as the solid electrolyte used for the second solid electrolyte and the negative electrode. Except for these changes, the battery of Comparative Example 1 was manufactured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0125] (Comparative Example 2) The first solid electrolyte and the third solid electrolyte used in the positive electrode were changed from those in Example 1. In Comparative Example 2, all solid electrolytes, namely the first solid electrolyte, the second solid electrolyte, the solid electrolyte used in the positive electrode (third solid electrolyte), and the solid electrolyte used in the negative electrode, were made using a Br-containing sulfide solid electrolyte that was used as the second solid electrolyte in Example 1. Except for these changes, the battery of Comparative Example 2 was manufactured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0126]

[0127] As shown in Table 1, the battery of Example 1, which comprises a first electrolyte layer that does not contain Br and a second electrolyte layer that contains Br and S, had better high-temperature resistance than the batteries of Comparative Examples 1 and 2.

[0128] (Example 2) The same positive and negative electrodes as in Example 1 were used, and only the thickness of the first and second electrolyte layers was changed. A laminate was fabricated so that the thickness of the first solid electrolyte was 200 μm and the thickness of the second solid electrolyte was 400 μm.

[0129] (Example 3) Using the same positive and negative electrodes as in Example 1, the thicknesses of the first and second electrolyte layers were changed, and a fourth electrolyte layer made of LYBC was further provided between the second electrolyte layer and the negative electrode. A laminate was fabricated such that the thickness of the first solid electrolyte was 200 μm, the thickness of the second solid electrolyte was 200 μm, and the thickness of the LYBC forming the fourth electrolyte layer was 200 μm.

[0130] (Comparative Example 3) The materials of the first electrolyte layer and the second electrolyte layer in Example 2 were swapped. That is, the first electrolyte layer was made of Br-containing sulfide SE, and the second electrolyte was made of LZYC. A laminate was fabricated such that the thickness of the first solid electrolyte was 400 μm and the thickness of the second solid electrolyte was 200 μm.

[0131] <High Temperature Resistance Evaluation 2> The high temperature resistance of Example 2, Example 3, and Comparative Example 3 was evaluated. The same method as in High Temperature Characteristics Evaluation 1 was used, with storage conditions of 120°C for 100 hours. The results are shown in Table 2.

[0132]

[0133] As shown in Table 2, the battery of Example 2, which had a first electrolyte layer that did not contain Br and a second electrolyte layer that contained Br and S, exhibited good high-temperature resistance. Furthermore, Example 3, in which a LYBC layer was placed between the second electrolyte layer and the negative electrode as a fourth electrolyte layer, also exhibited excellent high-temperature resistance. In contrast, the battery of Comparative Example 3, in which the first electrolyte layer was formed of a sulfide solid electrolyte containing Br, could not be charged or discharged after being stored at high temperatures and exhibited poor high-temperature resistance.

[0134] The technology disclosed herein is useful, for example, in lithium-ion secondary batteries.

Claims

1. A battery comprising: a positive electrode; a negative electrode; and an electrolyte layer provided between the positive electrode and the negative electrode, wherein the electrolyte layer comprises a first electrolyte layer and a second electrolyte layer, the second electrolyte layer provided between the first electrolyte layer and the negative electrode, the first electrolyte layer does not contain Br, and the second electrolyte layer contains Br and S.

2. The battery according to claim 1, wherein the first electrolyte layer contains Li, M1, and Cl, but does not contain S, and M1 is at least one element selected from the group consisting of metallic elements other than Li and metalloid elements.

3. The first electrolyte layer contains a first solid electrolyte, the first solid electrolyte is represented by the following compositional formula (1), Li α1 M1 β1 Cl γ1 ...Formula (1) In the composition formula (1), α1, β1, and γ1 are each independently greater than 0, the battery according to claim 2.

4. The battery according to claim 2, wherein M1 includes at least one selected from the group consisting of Y and Zr.

5. The battery according to claim 2, wherein the first electrolyte layer is made of Li, Y, Zr, and Cl.

6. The battery according to claim 1, wherein the first electrolyte layer comprises a first solid electrolyte, the second electrolyte layer comprises a second solid electrolyte, and the second solid electrolyte has a higher ionic conductivity than the first solid electrolyte.

7. The battery according to claim 1, wherein the thickness of the second electrolyte layer is greater than the thickness of the first electrolyte layer.

8. The battery according to claim 7, wherein the thickness of the first electrolyte layer is 0.2 or more and less than 1.0 compared to the thickness of the second electrolyte layer.

9. The battery according to claim 1, further comprising a third electrolyte layer disposed between the first electrolyte layer and the second electrolyte layer, wherein the third electrolyte layer contains Br.

10. The battery according to claim 9, wherein the third electrolyte layer further comprises a halogen element other than Br.

11. The battery according to claim 9, wherein the third electrolyte layer does not contain sulfur.

12. The battery according to claim 1, wherein the positive electrode comprises a positive electrode active material and a third solid electrolyte, and the third solid electrolyte does not contain Br.

13. The battery according to claim 12, wherein the third solid electrolyte comprises Li, M2, and Cl, and does not contain S, and M2 is at least one element selected from the group consisting of metallic elements and metalloid elements other than Li.

14. The third solid electrolyte is represented by the following compositional formula (2): Li α2 M2 β2 Cl γ2 ...Formula (2) In the composition formula (2), α2, β2, and γ2 are each independently greater than 0, the battery according to claim 13.

15. The battery according to claim 13, wherein M2 includes at least one selected from the group consisting of Y and Zr.

16. The battery according to claim 12, wherein the first electrolyte layer comprises a first solid electrolyte, and the third solid electrolyte has the same composition as the first solid electrolyte.

17. The battery according to claim 12, wherein at least a portion of the surface of the positive electrode active material is covered with a coating layer containing a halide solid electrolyte.

18. The battery according to claim 1, wherein the first electrolyte layer is in contact with the positive electrode.

19. The battery according to claim 1, wherein the second electrolyte layer contains a sulfide solid electrolyte, and the sulfide solid electrolyte contains Br.

20. The battery according to claim 1, wherein the negative electrode comprises a negative electrode active material, and the negative electrode active material comprises Li, Ti, and O.

21. The battery according to claim 1, wherein the negative electrode contains a sulfide solid electrolyte.

22. The battery according to claim 21, wherein the sulfide solid electrolyte has the same composition as the second solid electrolyte contained in the second electrolyte layer.

Images