Battery

Abstract

A battery 2000 according to the present disclosure comprises a positive electrode 201, a negative electrode 203, and an electrolyte layer 202 which is provided between the positive electrode 201 and the negative electrode 203, wherein the positive electrode 201 contains a positive electrode active material 111 and a first solid electrolyte 112, the electrolyte layer 202 contains a second solid electrolyte 113, the first solid electrolyte 112 contains lithium and two or more types of anions, the second solid electrolyte 113 contains lithium and two or more types of anions, and the molar ratio of Br to the two or more types of anions contained in the first solid electrolyte 112 is lower than the molar ratio of Br to the two or more types of anions contained in the second solid electrolyte 113.

Description

[Technical Field]

[0001] The present disclosure relates to batteries. [Background technology]

[0002] Patent Document 1 discloses a battery that uses an indium-containing halide as a solid electrolyte. Patent Document 2 discloses a deterioration in battery characteristics due to oxidative decomposition of iodine in the halide solid electrolyte. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-244734 [Patent Document 2] International Publication No. 2019 / 146236 Summary of the Invention [Problem to be solved by the invention]

[0004] In the prior art, there is a need to improve the charge and discharge efficiency of batteries. [Means for solving the problem]

[0005] In one embodiment of the present disclosure, the battery comprises: A positive electrode and a negative electrode; an electrolyte layer provided between the positive electrode and the negative electrode; Equipped with the positive electrode includes a positive electrode active material and a first solid electrolyte, the electrolyte layer includes a second solid electrolyte; the first solid electrolyte contains lithium and two or more types of anions, the second solid electrolyte contains lithium and two or more types of anions, The molar ratio of Br in the two or more types of anions contained in the first solid electrolyte is smaller than the molar ratio of Br in the two or more types of anions contained in the second solid electrolyte. [Effects of the Invention]

[0006] According to the present disclosure, the charge and discharge efficiency of a battery can be improved. [Brief explanation of the drawings]

[0007] [Figure 1A] FIG. 1A is a cross-sectional view showing a schematic configuration of a battery according to a second embodiment. [Figure 1B] FIG. 1B is a cross-sectional view showing a schematic configuration of a battery according to a modified example. [Figure 2] FIG. 2 is a graph showing the results of the LSV measurement. [Figure 3] FIG. 3 is a graph showing discharge curves at the time of initial discharge of the secondary batteries of the example and the comparative example. [Figure 4] FIG. 4 is an SEM image of a cross section of a secondary battery of an example that has been subjected to a debromination treatment. [Figure 5A] FIG. 5A is a graph showing the abundance ratio of each anion in the dashed line portion in FIG. [Figure 5B] FIG. 5B is a partially enlarged view of FIG. 5A. DETAILED DESCRIPTION OF THE INVENTION

[0008] (Embodiment 1) The battery according to the first embodiment includes a positive electrode, a negative electrode, and an electrolyte layer disposed between the positive electrode and the negative electrode. The positive electrode includes a positive electrode active material and a first solid electrolyte. The electrolyte layer includes a second solid electrolyte. The first solid electrolyte includes lithium and two or more types of anions. The second solid electrolyte includes lithium and two or more types of anions. The molar ratio of Br in the two or more types of anions contained in the first solid electrolyte is smaller than the molar ratio of Br in the two or more types of anions contained in the second solid electrolyte.

[0009] According to the above configuration, the charge / discharge efficiency of the battery can be improved.

[0010] Patent Document 1 mentions that in an all-solid-state secondary battery containing a solid electrolyte made of a compound containing indium, it is desirable that the potential of the positive electrode active material against Li is 3.9 V or less on average, and this allows a film made of decomposition products due to oxidative decomposition of the solid electrolyte to be formed well, resulting in good charge-discharge characteristics. Also, examples of positive electrode active materials with an average potential against Li of 3.9 V or less include LiCoO2, LiNi 0.8 Co 0.15 Al 0.05 Common layered transition metal oxide cathodes such as O2 are disclosed.

[0011] Patent Document 2 discloses that iodine-containing halide solid electrolytes have poor electrochemical stability and undergo continuous oxidation-reduction, resulting in oxidative decomposition even when a positive electrode with an average discharge voltage of 3.9 V or less is used relative to a Li electrode. On the other hand, it also discloses that bromine-containing halide solid electrolytes exhibit good charge-discharge characteristics even when charged at a voltage of 4.0 V or more relative to a Li electrode. Furthermore, it discloses that, in order to suppress the oxidative decomposition of iodine-containing solid electrolytes, the positive electrode active material is coated with a solid electrolyte composed of lithium, a metal or semimetal element, and chlorine or bromine.

[0012] On the other hand, the inventors have found through their investigations that even when a positive electrode contains a solid electrolyte containing bromine but not iodine, bromine oxidation occurs when the battery is charged at a potential of 3.5 V or higher relative to the Li electrode, resulting in a decrease in the charge / discharge efficiency of the battery. Here, bromine oxidation refers to the extraction of electrons from bromine in the solid electrolyte when an electronically conductive material, such as a current collector or active material, comes into contact with the bromine-containing solid electrolyte and the solid electrolyte is exposed to a potential of 3.5 V or higher relative to the Li electrode. During battery charging, electrons are extracted from the bromine in the solid electrolyte along with the extraction of electrons from the active material, resulting in an excess amount of electricity. On the other hand, during discharge, no reversible reduction reaction originating from bromine occurs, resulting in a decrease in the ratio of the amount of electricity during charging to the amount of electricity during discharge, i.e., the charge / discharge efficiency. Therefore, it is desirable for the solid electrolyte to not contain elements with low redox potentials, such as bromine and iodine.

[0013] However, since bromine and iodine have higher electronic polarizability than chlorine and fluorine, solid electrolytes containing bromine and iodine have a smaller energy barrier for lithium ion conduction and exhibit high lithium ion conductivity. Conversely, solid electrolytes containing only chlorine and / or fluorine have low ionic conductivity, resulting in large discharge polarization and reduced charge / discharge efficiency.

[0014] Furthermore, since halogens have high electronegativity and ionicity, they are not easily stabilized by other cations or anions contained in the solid electrolyte. Therefore, attention should be paid to the element that contributes to oxidation, i.e., the ratio of bromine in the anions, rather than the composition of the solid electrolyte as a whole, including the cations.

[0015] In one embodiment of the present disclosure, the positive electrode includes a positive electrode active material and a first solid electrolyte. The electrolyte layer includes a second solid electrolyte. The first solid electrolyte includes lithium and two or more anions. The second solid electrolyte includes lithium and two or more anions. The molar ratio of bromine in the two or more anions contained in the first solid electrolyte is smaller than the molar ratio of bromine in the two or more anions contained in the second solid electrolyte. This configuration reduces the probability of contact between the bromine in the first solid electrolyte and materials with electronic conductivity, such as the current collector and the positive electrode active material, in the positive electrode. This reduces oxidation of the first solid electrolyte. Furthermore, when bromine, which has high electronic polarizability, is contained, the first solid electrolyte exhibits higher ionic conductivity than a solid electrolyte that does not contain bromine. This improves the charge / discharge efficiency of the battery.

[0016] The first solid electrolyte includes, for example, a material represented by the following composition formula (1): In composition formula (1), M1 includes at least one element selected from the group consisting of metal elements and metalloid elements other than Li, and X1 is an anion other than Cl and Br. The following conditions are satisfied: a1>0, b1>0, c1≧0, d1≧0, c1+d1>0, and e1≧0.

[0017] Li a1 M1 b1 Br c1 Cl d1 X1 e1 ···(1)

[0018] The anion other than Cl and Br is not particularly limited. Examples of the anion other than Cl and Br include oxygen and iodine (I). X1 may be I.

[0019] Metalloid elements include B, Si, Ge, As, Sb, and Te. Metal elements include all elements in groups 1 to 12 of the periodic table except hydrogen, and all elements in groups 13 to 16 except B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se. Metal elements are a group of elements that can become cations when forming inorganic compounds with halogens or halogen compounds. M1 includes at least one element selected from the group consisting of these elements.

[0020] The second solid electrolyte includes, for example, a material represented by the following composition formula (2): In composition formula (2), M2 includes at least one element selected from the group consisting of metal elements and metalloid elements other than Li, and X2 is an anion other than Cl and Br. The following conditions are satisfied: a2>0, b2>0, c2≧0, d2≧0, c2+d2>0, and e2≧0.

[0021] Li a2 M2 b2 Br c2 Cl d2 X2 e2 ···(2)

[0022] The anion other than Cl and Br is not particularly limited. Examples of the anion other than Cl and Br include oxygen and iodine (I). X2 may be I.

[0023] Like M1, M2 includes at least one element selected from the group consisting of the above elements. M2 may be the same as or different from M1.

[0024] The total amount of substance of anions in the first solid electrolyte is defined as α1, and the amount of substance of bromine anions in the first solid electrolyte is defined as β1. The total amount of substance of anions in the second solid electrolyte is defined as α2, and the amount of substance of bromine anions in the second solid electrolyte is defined as β2. In this case, the relationship β1 / α1<β2 / α2 is satisfied.

[0025] According to the above configuration, ion transport through the first solid electrolyte and the second solid electrolyte can be facilitated, and the charge / discharge efficiency of the battery can be further improved.

[0026] The first solid electrolyte may contain Br as an essential element. One of the two or more anions contained in the first solid electrolyte may be Br. In this case, the first solid electrolyte exhibits high ionic conductivity. This allows for higher charge / discharge efficiency.

[0027] The second solid electrolyte may contain Br as an essential element. One of the two or more anions contained in the second solid electrolyte may be Br. In this case, the second solid electrolyte exhibits high ionic conductivity. This allows for higher charge / discharge efficiency.

[0028] The two or more anions contained in the first solid electrolyte may be the same as or different from the two or more anions contained in the second solid electrolyte. In the former case, material costs can be reduced. In the latter case, the degree of freedom in material design is increased.

[0029] The electrolyte layer may have a first electrolyte layer and a second electrolyte layer. The first electrolyte layer includes a second solid electrolyte. The second electrolyte layer is a layer located between the positive electrode and the first electrolyte layer and includes a third solid electrolyte. The third solid electrolyte may include lithium and two or more types of anions.

[0030] The third solid electrolyte may contain Br as an essential element. One of the two or more anions contained in the third solid electrolyte may be Br. In this case, the third solid electrolyte exhibits high ionic conductivity. This allows for higher charge / discharge efficiency.

[0031] The two or more anions contained in the third solid electrolyte may be the same as or different from the two or more anions contained in the first solid electrolyte. In the former case, material costs can be reduced. In the latter case, the degree of freedom in material design increases. For the same reason, the two or more anions contained in the third solid electrolyte may be the same as or different from the two or more anions contained in the second solid electrolyte.

[0032] The third solid electrolyte includes, for example, a material represented by the following composition formula (3): In composition formula (3), M3 includes at least one element selected from the group consisting of metal elements and metalloid elements other than Li, and X3 is an anion other than Cl and Br. The following conditions are satisfied: a3>0, b3>0, c3≧0, d3≧0, c3+d3>0, and e3≧0.

[0033] Li a3 M3 b3 Br c3 Cl d3 X3 e3 ···(3)

[0034] The anion other than Cl and Br is not particularly limited. Examples of the anion other than Cl and Br include oxygen and iodine (I). X3 may be I.

[0035] Like M1, M3 includes at least one element selected from the group consisting of the above-mentioned elements. M3 may be the same as or different from M1. M3 may be the same as or different from M2.

[0036] The total amount of substance of anions in the first solid electrolyte is defined as α1, and the amount of substance of bromine anions in the first solid electrolyte is defined as β1. The total amount of substance of anions in the second solid electrolyte is defined as α2, and the amount of substance of bromine anions in the second solid electrolyte is defined as β2. The total amount of substance of anions in the third solid electrolyte is defined as α3, and the amount of substance of bromine anions in the third solid electrolyte is defined as β3. In this case, the relationship β1 / α1≦β3 / α3<β2 / α2 is satisfied.

[0037] The above configuration prevents the positive electrode active material from being exposed from the positive electrode and coming into contact with the first electrolyte layer, which would otherwise cause oxidation of the solid electrolyte, and is therefore more effective in improving the charge / discharge efficiency of the battery.

[0038] In the composition formula (1), the ratio a1 / (c1+d1+e1) can be in the range of 0.3 to 0.6. When X1 is a halogen, the ratio a1 / (c1+d1+e1) represents the ratio of the amount of lithium to the total amount of halogen.

[0039] In the composition formula (2), the ratio a2 / (c2+d2+e2) can be in the range of 0.3 to 1. When X2 is a halogen, the ratio a2 / (c2+d2+e2) represents the ratio of the amount of lithium to the total amount of halogen.

[0040] According to the above configuration, the ionic conductivity of the first solid electrolyte and the second solid electrolyte can be improved, and higher charge / discharge efficiency can be achieved.

[0041] In addition to the ratio a1 / (c1+d1+e1) being in the range of 0.3 to 0.6 and the ratio a2 / (c2+d2+e2) being in the range of 0.3 to 1, in composition formula (3), the ratio a3 / (c3+d3+e3) may be in the range of 0.3 to 1. When X3 is a halogen, the ratio a3 / (c3+d3+e3) represents the ratio of the amount of substance of lithium to the total amount of substance of the halogens.

[0042] According to the above configuration, the ionic conductivity of the first solid electrolyte, the second solid electrolyte, and the third solid electrolyte can be improved, and higher charge / discharge efficiency can be achieved.

[0043] The ratio α3 / β3 may vary in the thickness direction of the second electrolyte layer, and the ratio α3 / β3 on the positive electrode side may be lower than the ratio α3 / β3 on the first electrolyte layer side.

[0044] This structure can prevent damage to the battery due to thermal shock. The continuous change in material composition in the second electrolyte layer causes the thermal expansion coefficient of the third solid electrolyte to change stepwise. This makes it less likely to break even when the temperature changes suddenly.

[0045] The positive electrode may contain an electron-conductive material, which may be a conductive additive described below.

[0046] In the above configuration, oxidation of the first solid electrolyte by the electron conductive material is suppressed, and therefore the effect is more effectively exhibited.

[0047] M1 and M2 may contain Y.

[0048] M1 and M2 may include Y and Zr.

[0049] M3 may contain Y.

[0050] According to the above configuration, the ionic conductivity of the third solid electrolyte can be improved, and higher charge / discharge efficiency can be achieved.

[0051] M3 may include Y and Zr.

[0052] According to the above configuration, the ionic conductivity of the third solid electrolyte can be improved, and higher charge / discharge efficiency can be achieved.

[0053] The positive electrode active material may contain a lithium-containing transition metal oxide. The positive electrode active material may have a layered structure.

[0054] According to the above configuration, the energy density of the battery can be improved.

[0055] The battery of the present disclosure can be manufactured by the following method. First, a laminate is prepared that includes a positive electrode, a negative electrode, and an electrolyte layer disposed between the positive electrode and the negative electrode. The positive electrode includes a positive electrode active material and a first solid electrolyte. The electrolyte layer includes a second solid electrolyte. The first solid electrolyte includes lithium and two or more types of anions. The second solid electrolyte includes lithium and two or more types of anions. The laminate is then charged at a constant voltage equal to or higher than the voltage at which the potential of the positive electrode becomes equal to the oxidation potential of bromine contained in the first solid electrolyte.

[0056] According to the above configuration, the configuration of the present disclosure can be realized more simply.

[0057] The first solid electrolyte, the second solid electrolyte, and the third solid electrolyte can be produced, for example, by the following method.

[0058] Prepare raw material powders of binary halides so that they have the desired composition ratio. For example, to produce Li3YBr3Cl3, prepare LiCl and YBr3 in a molar ratio of 3:1.

[0059] At this time, by selecting the type of raw material powder, it is possible to determine "Li", "M1", "M2", "M3", "X1", "X2", and "X3" in the above composition formula. In addition, by adjusting the raw material compounding ratio and synthesis process, it is possible to adjust the above values ​​"a1", "b1", "c1", "d1", "e1", "a2", "b2", "c2", "d2", "e2", "a3", "b3", "c3", "d3", and "e3".

[0060] After thoroughly mixing the raw material powders, the raw material powders are mixed and pulverized by mechanochemical milling, and then reacted. Alternatively, after thoroughly mixing the raw material powders, the resulting mixture may be fired in an inert atmosphere.

[0061] As a result, the above-mentioned solid electrolyte is obtained.

[0062] The constitution of the crystalline phase in the solid electrolyte (ie, the crystalline structure) can be determined by adjusting the reaction method and reaction conditions of the raw material powders.

[0063] The adjustment method of the composition parameters "a1", "b1", "c1", "d1", "e1", "a2", "b2", "c2", "d2", "e2", "a3", "b3", "c3", "d3" and "e3" is not particularly limited. For example, during the production of the solid electrolyte, the mixing ratio of the raw material powder may be adjusted so as to satisfy the relationship of c1 / (c1 + d1 + e1) ≤ c3 / (c3 + d3 + e3) < c2 / (c2 + d2 + e2), the solid electrolyte may be produced, and the battery may be produced so as to satisfy the above relationship. Alternatively, the parameters may be adjusted electrochemically, that is, by passing an electric current, during or after the production of the battery.

[0064] (Embodiment 2) FIG. 1A is a cross-sectional view showing a schematic configuration of the battery 2000 in Embodiment 2. The battery 2000 in Embodiment 2 includes a positive electrode 201, an electrolyte layer 202, and a negative electrode 203. The description of Embodiment 1 can be applied to Embodiment 2.

[0065] The positive electrode 201 includes a positive electrode active material 111 and a first solid electrolyte 112.

[0066] The electrolyte layer 202 is disposed between the positive electrode 201 and the negative electrode 203. The electrolyte layer 202 includes a second solid electrolyte 113.

[0067] Specifically, the electrolyte layer 202 has a first electrolyte layer 202a and a second electrolyte layer 202b. The first electrolyte layer 202a includes a second solid electrolyte 113. The second electrolyte layer 202b is a layer located between the positive electrode 201 and the first electrolyte layer 202a and includes a third solid electrolyte 114.

[0068] The thickness of the first electrolyte layer 202a may be 100 nm or more and 100 μm or less. When the thickness of the first electrolyte layer 202a is 100 nm or more, the short circuit between the positive electrode and the negative electrode can be more effectively suppressed. When the thickness of the first electrolyte layer 202a is 100 μm or less, the operation at high output can be realized.

[0069] The thickness of the second electrolyte layer 202b may be 1 nm or more and 100 μm or less. When the thickness of the second electrolyte layer 202b is 1 nm or more, oxidation of the first electrolyte layer 202a can be reliably suppressed. When the thickness of the second electrolyte layer 202b is 100 μm or less, high-power operation can be achieved.

[0070] Halide solid electrolytes may be used as the first solid electrolyte 112, the second solid electrolyte 113, and the third solid electrolyte 114. Examples of halide solid electrolytes that may be used include Li3YBr6, Li3YBr3Cl3, Li3YBr2Cl4, Li3YCl6, and compounds obtained by substituting some of the cations in these compounds with Zr.

[0071] The first solid electrolyte 112, the second solid electrolyte 113, and the third solid electrolyte 114 may be halide solid electrolytes having different compositions. That is, the molar ratio of bromine in the second solid electrolyte 113 may be greater than the molar ratio of bromine in the first solid electrolyte 112.

[0072] According to the above configuration, the charge / discharge characteristics of the battery 2000 can be further improved.

[0073] The first solid electrolyte 112, the second solid electrolyte 113, and the third solid electrolyte 114 may each be a mixture of solid electrolytes having different compositions, such as a mixture of Li3YBr6 and LiCl, or a mixture of Li3YCl3Br3 and Li3YCl6.

[0074] The above configuration can further improve the charge / discharge characteristics of battery 2000. Note that first solid electrolyte 112, second solid electrolyte 113, and third solid electrolyte 114 do not necessarily need to contain sulfur.

[0075] The shape of each of the first solid electrolyte 112, the second solid electrolyte 113, and the third solid electrolyte 114 is not particularly limited and may be, for example, needle-like, spherical, oval-spherical, or scale-like. For example, the shape of the first solid electrolyte 112 may be particulate. Similarly, the shape of the second solid electrolyte 113 may be particulate. The shape of the third solid electrolyte 114 may be particulate.

[0076] When the first solid electrolyte 112 is particulate (for example, spherical), the median diameter of the particles of the first solid electrolyte 112 may be 100 μm or less. When the median diameter is 100 μm or less, the positive electrode active material 111 and the first solid electrolyte 112 can be well dispersed in the positive electrode 201. This improves the charge / discharge characteristics of the battery 2000. Furthermore, the median diameter of the particles of the first solid electrolyte 112 may be 10 μm or less.

[0077] According to the above configuration, in the positive electrode 201, the positive electrode active material 111 and the first solid electrolyte 112 can be well dispersed.

[0078] As used herein, the term "median diameter" refers to the particle size when 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 measurement device or an image analysis device.

[0079] The positive electrode active material 111 includes a material that has the property of absorbing and releasing metal ions (e.g., lithium ions). For example, lithium-containing transition metal oxides, transition metal fluorides, polyanion materials, fluorinated polyanion materials, transition metal sulfides, transition metal oxysulfides, transition metal oxynitrides, etc. can be used as the positive electrode active material 111. In particular, when a lithium-containing transition metal oxide is used as the positive electrode active material 111, the manufacturing cost can be reduced and the average discharge voltage can be increased.

[0080] The positive electrode active material 111 may contain Li and at least one element selected from the group consisting of Mn, Co, Ni, and Al. Examples of such materials include Li(NiCoAl)O2, Li(NiCoMn)O2, and LiCoO2.

[0081] The positive electrode active material 111 may include a single active material, or may include a plurality of active materials having different compositions.

[0082] In this embodiment, the positive electrode active material 111 may be Li(NiCoMn)O2.

[0083] According to the above configuration, the energy density and charge / discharge efficiency of the battery 2000 can be further increased.

[0084] The positive electrode active material 111 has, for example, a particle shape. There are no particular limitations on the shape of the particles of the positive electrode active material 111. The shape of the particles of the positive electrode active material 111 can be needle-like, spherical, oval-spherical, or scale-like.

[0085] The median diameter of the particles of first solid electrolyte 112 may be smaller than the median diameter of the particles of positive electrode active material 111 .

[0086] According to the above configuration, in the positive electrode 201, the first solid electrolyte 112 and the positive electrode active material 111 can be dispersed in a better state.

[0087] The median diameter of the particles of the positive electrode active material 111 may be 0.1 μm or more and 100 μm or less.

[0088] When the median particle diameter of the positive electrode active material 111 is 0.1 μm or more, the positive electrode active material 111 and the first solid electrolyte 112 can be well dispersed in the positive electrode 201. As a result, the charge / discharge characteristics of the battery 2000 are improved.

[0089] When the median diameter of the particles of the positive electrode active material 111 is 100 μm or less, lithium diffuses quickly within the particles of the positive electrode active material 111. This allows the battery 2000 to operate at a high output.

[0090] The median diameter of the particles of the positive electrode active material 111 may be larger than the median diameter of the particles of the first solid electrolyte 112. This allows the positive electrode active material 111 and the first solid electrolyte 112 to form a well-dispersed state.

[0091] The positive electrode 201 may include a plurality of particles of the first solid electrolyte 112 and a plurality of particles of the positive electrode active material 111 .

[0092] In the positive electrode 201, the content of the first solid electrolyte 112 and the content of the positive electrode active material 111 may be the same as or different from each other.

[0093] The volume ratio "v1:100-v1" of the positive electrode active material 111 to the first solid electrolyte 112 contained in the positive electrode 201 may satisfy 30≦v1≦95. When 30≦v1 is satisfied, the energy density of the battery 2000 is sufficiently ensured. Furthermore, when v1≦95 is satisfied, high-power operation is possible.

[0094] The thickness of the positive electrode 201 may be 10 μm or more and 500 μm or less. When the thickness of the positive electrode 201 is 10 μm or more, the energy density of the battery 2000 is sufficiently ensured. When the thickness of the positive electrode 201 is 500 μm or less, high-power operation is possible.

[0095] The electrolyte layer 202 is a layer containing an electrolyte. The electrolyte is, for example, a solid electrolyte. That is, the electrolyte layer 202 may be a solid electrolyte layer.

[0096] The electrolyte layer 202 may include, as a solid electrolyte, at least one selected from the group consisting of a halide solid electrolyte, a sulfide solid electrolyte, an oxide solid electrolyte, a polymer solid electrolyte, and a complex hydride solid electrolyte.

[0097] As the halide solid electrolyte, the materials explained as specific examples of the first solid electrolyte 112, the second solid electrolyte 113, and the third solid electrolyte 114 are used.

[0098] According to the above configuration, the power density and charge / discharge characteristics of the battery 2000 can be further improved.

[0099] The electrolyte layer 202 may include a halide solid electrolyte having a composition different from that of the first solid electrolyte 112, the second solid electrolyte 113, and the third solid electrolyte 114. That is, the electrolyte layer 202 may include a halide solid electrolyte having a composition different from that of the first solid electrolyte 112.

[0100] The electrolyte layer 202 may include another electrolyte layer as a third electrolyte layer provided between the first electrolyte layer 202a and the negative electrode 203. The other electrolyte layer includes a fourth solid electrolyte. The fourth solid electrolyte may be any of the materials exemplified as materials usable for the first solid electrolyte 112, the second solid electrolyte 113, and the third solid electrolyte 114.

[0101] The solid electrolytes exemplified below can be used alone or in combination as the first solid electrolyte 112. The same applies to the second solid electrolyte 113 and the third solid electrolyte 114.

[0102] The halide solid electrolyte is represented, for example, by the following composition formula (4): In composition formula (4), α, β, and γ each independently have a value greater than 0. M includes at least one element selected from the group consisting of metal elements and metalloid elements other than Li. X includes at least one element selected from the group consisting of F, Cl, Br, and I.

[0103] Li α M β X γ ···(4)

[0104] Metalloid elements include B, Si, Ge, As, Sb, and Te. Metal elements include all elements in groups 1 to 12 of the periodic table except hydrogen, and all elements in groups 13 to 16 except B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se. Metal elements are a group of elements that can become cations when forming inorganic compounds with halogens or halogen compounds.

[0105] Examples of halide solid electrolytes that can be used include Li3YX6, Li2MgX4, Li2FeX4, Li(Al,Ga,In)X4, and Li3(Al,Ga,In)X6.

[0106] The above configuration can improve the output density of the battery 2000. In addition, the thermal stability of the battery 2000 can be improved, and the generation of harmful gases such as hydrogen sulfide can be suppressed.

[0107] In this disclosure, when an element in a formula is expressed as "(Al, Ga, In)", this notation indicates at least one element selected from the group of elements in parentheses. That is, "(Al, Ga, In)" is synonymous with "at least one element selected from the group consisting of Al, Ga, and In". The same applies to other elements. Halide solid electrolytes exhibit excellent ionic conductivity.

[0108] In the composition formula (4), M may contain Y (=yttrium).

[0109] The composition formula (4) may satisfy 2.5≦α≦3, 1≦β≦1.1, and γ=6.

[0110] In the composition formula (4), X may include at least one selected from the group consisting of Cl and Br.

[0111] According to the above configuration, the ionic conductivity of the solid electrolyte can be further improved, thereby improving the output density of the battery.

[0112] The halide solid electrolyte containing Y may be a compound represented by the following composition formula (5).

[0113] Li a M b Y c X6···(5)

[0114] Composition formula (5) satisfies a+mb+3c=6 and c>0. In composition formula (5), M includes at least one element selected from the group consisting of metal elements and metalloid elements other than Li and Y. m is the valence of M. X includes at least one element selected from the group consisting of F, Cl, Br, and I. M includes at least one element selected from the group consisting of Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta, and Nb. Specific examples of Y-containing halide solid electrolytes include Li3YF6, Li3YCl6, Li3YBr6, Li3YI6, Li3YBrCl5, Li3YBr3Cl3, Li3YBr5Cl, Li3YBr5I, Li3YBr3I3, Li3YBrI5, Li3YClI5, Li3YCl3I3, Li3YCl5I, Li3YBr2Cl2I2, Li3YBrCl4I, Li 2.7 Y 1.1 Cl6, Li 2.5 Y 0.5 Zr 0.5 Cl6, Li 2.5 Y 0.3 Zr 0.7 Cl6 and the like can be used.

[0115] According to the above configuration, the output density of the battery 2000 can be further improved.

[0116] Sulfide solid electrolytes include Li2S-P2S5, Li2S-SiS2, Li2S-B2S3, Li2S-GeS2, and Li 3.25 Ge 0.25 P 0.75 S4, Li 10 GeP2S 12 These can be used in addition to LiX, Li2O, MO q , Li p MOq The element X in "LiX" is at least one element selected from the group consisting of F, Cl, Br, and I. q " and "Li p MO q "The element M is at least one element selected from the group consisting of P, Si, Ge, B, Al, Ga, In, Fe, and Zn. q " and "Li p MO q " p and q in this expression are independent natural numbers.

[0117] According to the above configuration, since the battery contains a sulfide solid electrolyte with excellent reduction stability, a low potential negative electrode material such as graphite or metallic lithium can be used, and the energy density of the battery 2000 can be improved.

[0118] Examples of oxide solid electrolytes include NASICON-type solid electrolytes, such as LiTi2(PO4)3 and its elemental substitution products, (LaLi)TiO3-based perovskite-type solid electrolytes, and Li 14 ZnGeO 16 , Li4SiO4, LiGeO4 and their element-substituted LISICON-type solid electrolytes, Li7La3Zr2O 12 Garnet-type solid electrolytes, such as those substituted with LiN and its element, LiN and its H-substituted compounds, LiPO4 and its N-substituted compounds, and glass or glass ceramics containing a base material containing Li-BO compounds such as LiBO2 and LiBO3 to which a material such as LiSO4 or LiCO3 has been added can be used.

[0119] As the polymer solid electrolyte, for example, a compound of a polymer compound and a lithium salt can be used. The polymer compound may have an ethylene oxide structure. By having an ethylene oxide structure, the polymer compound can contain a large amount of lithium salt, thereby further increasing ionic conductivity. As the lithium salt, LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), LiC(SO2CF3)3, etc. can be used. As the lithium salt, one type of lithium salt selected from these may be used alone, or a mixture of two or more types of lithium salts selected from these may be used.

[0120] Examples of the complex hydride solid electrolyte that can be used include LiBH4-LiI and LiBH4-P2S5.

[0121] According to the above configuration, the output density of the battery 2000 can be improved.

[0122] The electrolyte layer 202 may contain a solid electrolyte as a main component, i.e., the electrolyte layer 202 may contain 50% or more of the solid electrolyte in terms of weight ratio relative to the total weight of the electrolyte layer 202 (i.e., 50% by weight or more).

[0123] According to the above configuration, the charge / discharge characteristics of the battery 2000 can be further improved.

[0124] The electrolyte layer 202 may contain a solid electrolyte in a weight ratio relative to the total weight of the electrolyte layer 202 of 70% or more (ie, 70% by weight or more).

[0125] According to the above configuration, the charge / discharge characteristics of the battery 2000 can be further improved.

[0126] The electrolyte layer 202 contains a solid electrolyte as a main component, and may further contain unavoidable impurities, or starting materials, by-products, decomposition products, etc. used in synthesizing the third solid electrolyte 114.

[0127] The electrolyte layer 202 may contain 100% solid electrolyte in terms of weight percentage relative to the total weight of the electrolyte layer 202 (ie, 100 wt %), excluding unavoidable impurities.

[0128] According to the above configuration, the charge / discharge characteristics of the battery 2000 can be further improved.

[0129] As described above, the electrolyte layer 202 may be made of only a solid electrolyte.

[0130] The electrolyte layer 202 may contain only one solid electrolyte selected from the above-mentioned group of solid electrolytes, or may contain two or more solid electrolytes selected from the above-mentioned group of solid electrolytes. The multiple solid electrolytes have different compositions. For example, the electrolyte layer 202 may contain a halide solid electrolyte and a sulfide solid electrolyte.

[0131] 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, high-power operation can be achieved.

[0132] The negative electrode 203 includes a material having the property of absorbing and releasing metal ions (for example, lithium ions). The negative electrode 203 includes, for example, a negative electrode active material.

[0133] The negative electrode active material may be a metal material, a carbon material, an oxide, a nitride, a tin compound, a silicon compound, or the like. The metal material may be a simple metal. Alternatively, the metal material may be an alloy. Examples of the metal material include lithium metal and lithium alloys. Examples of the carbon material include natural graphite, coke, partially graphitized carbon, carbon fiber, spherical carbon, artificial graphite, and amorphous carbon. From the viewpoint of capacity density, silicon (Si), tin (Sn), a silicon compound, or a tin compound may be used.

[0134] The negative electrode 203 may contain a solid electrolyte. The above-described configuration increases the lithium ion conductivity inside the negative electrode 203, enabling high-power operation. The above-described materials may be used as the solid electrolyte.

[0135] 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, the particles of the negative electrode active material and the solid electrolyte can be well dispersed in the negative electrode 203. This improves the charge / discharge characteristics of the battery 2000. Furthermore, when the median diameter of the particles of the negative electrode active material is 100 μm or less, lithium diffusion within the particles of the negative electrode active material is accelerated. This allows the battery 2000 to operate at high power.

[0136] The median diameter of the particles of the negative electrode active material may be larger than the median diameter of the particles of the solid electrolyte contained in the negative electrode 203. This allows the negative electrode active material and the solid electrolyte to be well dispersed.

[0137] When the volume ratio of the negative electrode active material to the solid electrolyte in the negative electrode 203 is expressed as "v2:100-v2", the volume ratio v2 of the negative electrode active material may satisfy 30≦v2≦95. When 30≦v2 is satisfied, the energy density of the battery 2000 is sufficiently ensured. Furthermore, when v2≦95 is satisfied, high-power operation is possible.

[0138] 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, the energy density of the battery 2000 is sufficiently ensured. When the thickness of the negative electrode 203 is 500 μm or less, high-power operation is possible.

[0139] At least one of the positive electrode 201, the electrolyte layer 202, and the negative electrode 203 may contain a binder to improve adhesion between particles. The binder is used to improve the binding properties of the materials constituting the electrodes. Examples of binders include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamideimide, polyacrylonitrile, polyacrylic acid, polymethyl acrylate, polyethyl acrylate, polyhexyl acrylate, polymethacrylic acid, polymethyl methacrylate, polyethyl methacrylate, polyhexyl methacrylate, polyvinyl acetate, polyvinylpyrrolidone, polyether, polyethersulfone, hexafluoropolypropylene, styrene-butadiene rubber, and carboxymethyl cellulose. The binder may be 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. Alternatively, a mixture of two or more materials selected from these may be used as the binder.

[0140] At least one of the positive electrode 201 and the negative electrode 203 may contain a conductive aid for the purpose of enhancing electron conductivity. Examples of the conductive aid include graphites such as natural graphite or artificial graphite, carbon blacks such as acetylene black and ketjen black, conductive fibers such as carbon fibers or metal fibers, metal powders such as carbon fluoride and aluminum, conductive whiskers such as zinc oxide or potassium titanate, conductive metal oxides such as titanium oxide, and conductive polymer compounds such as polyaniline, polypyrrole, and polythiophene. When a carbon conductive aid is used, cost reduction can be achieved.

[0141] The battery 2000 in Embodiment 2 can be configured as batteries of various shapes such as coin type, cylindrical type, square type, sheet type, button type, flat type, and laminated type.

[0142] (Modification example) FIG. 1B is a cross-sectional view showing a schematic configuration of a battery 3000 in a modification example. The battery 3000 includes a positive electrode 201, a negative electrode 203, and an electrolyte layer 202. The electrolyte layer 202 corresponds to the first electrolyte layer 202a described in Embodiment 2. That is, the configuration of the battery 3000 is the same as that of the battery 2000 except that it does not have the second electrolyte layer 202b. The description regarding the battery 2000 can be applied to the battery 3000 unless there is a technical contradiction.

Examples

[0143] Hereinafter, the details of the present disclosure will be described using examples and comparative examples.

[0144] <<Measurement of oxidation potential of Br>> (Production of evaluation battery 1) LiBr and YBr3 were prepared as raw material powders in a molar ratio of LiBr:YBr3 = 3:1 in an argon atmosphere with a dew point below -60°C. The resulting raw material powder mixture was then milled using a planetary ball mill (Fritsch, P-7 model) at a rotation speed of 600 rpm for 25 hours. This resulted in Li3YBr6 powder. Hereafter, this solid electrolyte will be referred to as "LYB."

[0145] LYB and acetylene black were prepared in a mass ratio of 93:7 in an argon atmosphere with a dew point of −60° C. or less. These were mixed in an agate mortar to produce a mixed material.

[0146] In an insulating outer cylinder, 80 mg of sulfide solid electrolyte, 20 mg of LYB, and 5 mg of the above-mentioned mixed material were stacked in this order. Li6PS5Cl powder was used as the sulfide solid electrolyte. A pressure of 720 MPa was applied to the resulting stack.

[0147] Next, an In-Li foil was laminated on the sulfide solid electrolyte layer as a negative electrode. A pressure of 80 MPa was applied to the laminate consisting of the mixed material, electrolyte layer, and negative electrode.

[0148] Next, stainless steel current collectors were placed on the top and bottom of the laminate. Current collecting leads were attached to the current collectors. Finally, the insulating outer cylinder was sealed using an insulating ferrule to isolate the inside of the insulating outer cylinder from the outside atmosphere.

[0149] In this way, an evaluation battery 1 for evaluating the oxidation potential of Br was obtained. The evaluation battery 1 had a layered structure of (LYB+acetylene black) / LYB / sulfide solid electrolyte layer / In—Li.

[0150] (Preparation of Evaluation Battery 2) In an argon atmosphere with a dew point below -60°C, raw material powders of LiCl, YCl3, and YBr3 were prepared in a molar ratio of LiCl:YCl3:YBr3 = 3.000:0.333:0.666. These were ground and mixed in a mortar. The resulting raw material powder mixture was then fired in an argon atmosphere using an electric furnace at 500°C for 3 hours. The resulting material was then ground using a pestle and mortar. This resulted in a powder of Li3YBr2Cl4. Hereinafter, this solid electrolyte will be referred to as "LYBC."

[0151] Except for using LYBC, evaluation battery 2 was fabricated in the same manner as evaluation battery 1. Evaluation battery 2 had a stacked structure of (LYBC + acetylene black) / LYBC / sulfide solid electrolyte layer / In-Li.

[0152] (Preparation of Evaluation Battery 3) In an argon atmosphere with a dew point of -60°C or less, LiCl and YCl3 were prepared as raw material powders in a molar ratio of LiCl:YCl3 = 2.7:1.1. Next, the resulting raw material powder mixture was milled using a planetary ball mill (Fritsch, P-7 model) at a rotation speed of 600 rpm for 25 hours. 2.7 Y 1.1 A powder of Cl6 was obtained. Hereinafter, this solid electrolyte will be referred to as "LYC".

[0153] (Preparation of Evaluation Battery 3) Except for using LYC, evaluation battery 3 was fabricated in the same manner as evaluation battery 1. Evaluation battery 3 had a stacked structure of (LYC + acetylene black) / LYC / sulfide solid electrolyte layer / In-Li.

[0154] (LSV measurement) Linear sweep voltammetry (LSV) measurements were performed on the evaluation battery. First, the evaluation battery was placed in a thermostatic chamber set at 25°C. The evaluation battery was connected to a potentiogalvanostat and LSV measurements were performed. In the LSV measurements, the sweep rate was set to 10 mV / s. The scan range was set from OCV (open circuit voltage) to 4.0 V vs. In-Li. In the LSV measurements, the current response when the potential was swept from OCV to 4.0 V was plotted.

[0155] Figure 2 is a graph showing the results of LSV measurements. In LSV measurements, when the sweep potential reaches a certain potential, the solid electrolyte oxidizes at that potential and current flows. As can be seen from Figure 2, LYB had an oxidation potential of 2.9 V relative to In-Li. LYBC had an oxidation potential of 3.1 V relative to In-Li. LYC had an oxidation potential of 3.5 V relative to In-Li.

[0156] When Br is contained in the solid electrolyte, such as LYB or LYBC, an oxidation current rises around 2.9 V to 3.1 V, indicating that this potential range is the oxidation potential of Br in the solid electrolyte. By adding 0.6 V, the potential of the In-Li alloy relative to Li, to the potential of LYB (2.9 V), the oxidation potential of Br in the solid electrolyte relative to Li can be calculated. That is, according to the results of evaluation battery 1 (LYB), the oxidation potential of Br in the solid electrolyte relative to the potential of Li was 3.5 V.

[0157] LYC had an oxidation potential of 3.5 V relative to In-Li. This oxidation potential of 3.5 V corresponds to 4.1 V relative to Li. In other words, if the solid electrolyte contains Cl, prolonged exposure to a potential of 4.1 V or higher is thought to oxidize the Cl in the solid electrolyte, causing the structure of the solid electrolyte to collapse.

[0158] These results indicate that the potential suitable for debromination of Br-containing solid electrolytes is in the range of more than 3.5 V and less than 4.1 V relative to Li.

[0159] In this measurement, the point at which the current value reached 0.05 mA was taken as the oxidation potential of each solid electrolyte. The rise of the oxidation current varies depending on the measurement temperature, the conditions for manufacturing the evaluation battery, etc. Therefore, the oxidation potential obtained in this measurement is thought to have an error range of about ±0.2 V.

[0160] Relative to In-Li, LYB had an oxidation potential of 2.9 V. Relative to In-Li, LYBC had an oxidation potential of 3.1 V. This indicates that even if the solid electrolyte contains Br, a difference of about 0.2 V can occur in the oxidation potential depending on the composition of the solid electrolyte.

[0161] [Secondary battery production] <<Example 1>> In an argon atmosphere with a dew point below -60°C, raw material powders of LiCl, YCl3, and YBr3 were prepared in a molar ratio of LiCl:YCl3:YBr3 = 3.000:0.333:0.666. These were ground and mixed in a mortar. The resulting raw material powder mixture was then fired in an argon atmosphere using an electric furnace at 500°C for 3 hours. The resulting material was then ground using a pestle and mortar. This yielded Li3YBr2Cl4 powder.

[0162] In an argon atmosphere with a dew point of -60°C or lower, the positive electrode active material Li(Ni,Co,Mn)O2 (hereafter referred to as NCM), the solid electrolyte LYBC, and the conductive additive vapor-grown carbon fiber (VGCF, manufactured by Showa Denko K.K.) were prepared in a mass ratio of 71:27:2. These were mixed in an agate mortar to produce a positive electrode mixture.

[0163] In an insulating outer cylinder, 80 mg of sulfide solid electrolyte, 20 mg of LYBC, and 19.5 mg of the above-mentioned positive electrode mixture were stacked in this order. Li6PS5Cl powder was used as the sulfide solid electrolyte. A pressure of 720 MPa was applied to the resulting stack to obtain a positive electrode and electrolyte layer.

[0164] Next, Li foil was laminated on the electrolyte layer on the side opposite to the side in contact with the positive electrode. A pressure of 80 MPa was applied to the positive electrode, electrolyte layer, and Li foil to produce a laminate of the positive electrode, electrolyte layer, and negative electrode.

[0165] Next, stainless steel current collectors were placed on the top and bottom of the laminate. Current collecting leads were attached to the current collectors. Finally, the insulating outer cylinder was sealed using an insulating ferrule to isolate the inside of the insulating outer cylinder from the outside atmosphere.

[0166] Next, a current of 0.140 mA was passed through the stack up to 3.65 V, and then the stack was charged at a constant voltage of 3.65 V. Charging was stopped when the current decayed to 0.028 mA. The stack was then discharged at a constant current to 2.5 V. This series of processes constitutes a debromination process. The debromination process involves charging the stack at a constant voltage equal to or higher than the voltage at which the potential of the positive electrode becomes equal to the oxidation potential of bromine contained in the solid electrolyte. Specifically, the debromination process involves charging the stack at a constant current until the potential of the positive electrode reaches a voltage equal to the oxidation potential of bromine contained in the solid electrolyte, and charging the stack at a constant voltage equal to or higher than the voltage at which the potential of the positive electrode becomes equal to the oxidation potential of bromine contained in the solid electrolyte. The voltage during constant voltage charging may be equal to or higher than the voltage at which the potential of the positive electrode becomes equal to the oxidation potential of bromine contained in the solid electrolyte and lower than the battery voltage at which the potential becomes equal to the oxidation potential of chlorine.

[0167] In this manner, the secondary battery of the example was fabricated.

[0168] <<Comparative Example 1>> A secondary battery was fabricated in the same manner as in Example, except that the debromination treatment was not carried out.

[0169] [Composition analysis] The secondary battery of the example was disassembled, and the power generating element including the positive electrode, electrolyte, and negative electrode was removed from the insulating outer cylinder. The power generating element was cut in the thickness direction and then smoothed by argon ion milling. Then, a composition analysis was performed near the interface between the positive electrode and the electrolyte layer using a field emission scanning electron microscope-energy dispersive X-ray analyzer (FE-SEM-EDX) to determine c1, c2, c3, d1, d2, d3, e1, e2, and e3 in composition formulas (1), (2), and (3).

[0170] Fig. 4 is an SEM image of a cross section of a debrominated positive electrode and electrolyte layer, and Fig. 5A is a graph showing the abundance ratio of each anion in the dashed line area in Fig. 4.

[0171] [Charge / discharge test] The secondary batteries of the example and comparative examples were placed in a thermostatic chamber at 25°C. The secondary batteries were charged at a constant current of 0.140 mA, and charging was terminated at a voltage of 4.3 V. Next, the secondary batteries were discharged at the same current of 0.140 mA, and discharging was terminated at a voltage of 2.5 V. The results are shown in Table 1 and FIG. 3.

[0172] The charge-discharge efficiencies of the secondary batteries of the Example and Comparative Examples are shown in Table 1. The charge-discharge efficiency of the secondary battery of the Comparative Example was 90%. The charge-discharge efficiency of the secondary battery of the Example was 92%. The charge-discharge efficiency was improved by performing the debromination treatment. The charge-discharge efficiency here is the value obtained by dividing the initial discharge capacity by the initial charge capacity.

[0173] [Table 1]

[0174] 3 is a graph showing the discharge curves of the secondary batteries of the Example and Comparative Example at the time of the first discharge. As shown in FIG. 3, no significant difference was observed in the discharge curves between the Example and Comparative Example. In other words, the debromination treatment did not have a significant effect on the discharge curve at the time of the first discharge.

[0175] As shown by the dashed line in Fig. 4, a composition analysis was performed by EDX on a cross section of the secondary battery of the example from the electrolyte layer to the positive electrode, and the results are shown in Fig. 5A and Fig. 5B.

[0176] Figure 5A is a graph showing the abundance ratio of each anion in the dashed line area in Figure 4 in terms of atomic ratio. Figure 5B is a partially enlarged view of Figure 5A. The anions are oxygen, bromine, and chlorine. The ratio of each anion was calculated from the composition ratio measured by EDX. The regions used for the calculation are Regions 1, 2, and 3 shown in Figures 5A and 5B. Each region had a width of 1 μm. The ratio of Br anions was calculated using the average value of data from multiple points within each region. The results are shown in Table 2. Note that in the cross-sectional SEM image, the region corresponding to Region 3 did not contain particles of the positive electrode active material, and Region 3 was sufficiently separated from the particles of the positive electrode active material. These facts support the conclusion that Region 3 is a region representative of the first solid electrolyte contained in the positive electrode.

[0177] [Table 2]

[0178] The definitions of α1, α2, α3, β1, β2, and β3 in Table 2 are as follows: The solid electrolyte contained in the positive electrode is defined as the first solid electrolyte. The solid electrolytes contained in the electrolyte layer are defined as the second solid electrolyte (negative electrode side) and the third solid electrolyte (positive electrode side). The total amount of substance of anions in the first solid electrolyte is defined as α1, and the amount of substance of bromine anions in the first solid electrolyte is defined as β1. The total amount of substance of anions in the second solid electrolyte is defined as α2, and the amount of substance of bromine anions in the second solid electrolyte is defined as β2. The total amount of substance of anions in the third solid electrolyte is defined as α3, and the amount of substance of bromine anions in the third solid electrolyte is defined as β3.

[0179] As can be seen from the β1 / α1 values ​​shown in Table 2, the molar ratio of Br among the anions contained in the solid electrolyte (first solid electrolyte) in the positive electrode was 0.19. The molar ratio of Br among the anions contained in the solid electrolyte constituting the electrolyte layer was 0.36 or 0.30. In other words, the molar ratio of Br among the anions contained in the solid electrolyte (first solid electrolyte) in the positive electrode was smaller than the molar ratio of Br among the anions contained in the solid electrolyte (second solid electrolyte) constituting the electrolyte layer. In other words, the graphs shown in Figures 5A and 5B show the relationship β1 / α1<β2 / α2.

[0180] In Figure 5B, region 1 corresponds to first electrolyte layer 202a described with reference to Figure 1A and includes a second solid electrolyte. Region 2 corresponds to second electrolyte layer 202b described with reference to Figure 1A and includes a third solid electrolyte. However, the initial compositions of the solid electrolytes used in regions 1 and 2 were the same.

[0181] As shown in Figure 5B, the composition of the electrolyte layer changed toward the interface between the electrolyte layer and the positive electrode. That is, the molar ratio of Br in the anions contained in region 2, which corresponds to the second electrolyte layer, was smaller than the molar ratio of Br in the anions contained in region 1, which corresponds to the first electrolyte layer. That is, the graphs shown in Figures 5A and 5B show the relationship β1 / α1≦β3 / α3<β2 / α2.

[0182] Furthermore, the molar ratio of Br gradually decreased in region 2 corresponding to the second electrolyte layer. That is, in region 2 corresponding to the second electrolyte layer, the ratio β3 / α3 on the positive electrode side was lower than the ratio β3 / α3 on the first electrolyte layer side.

[0183] The graphs shown in FIGS. 5A and 5B are normalized so that the total amount of anions is 1.

[0184] Oxygen is not an element contained in the raw materials used to prepare the solid electrolyte. It is believed that oxygen is an element inevitably contained in the solid electrolyte due to oxygen gas in the air, water in the air, and the positive electrode active material. The debromination treatment may have promoted the introduction of oxygen into the solid electrolyte.

[0185] Next, EDX measurement of the secondary battery of the comparative example was performed in the same manner as in the example. Then, the molar ratio of bromine to the total of bromine and chlorine was calculated for each of the electrolyte layer and the positive electrode. For the secondary battery of the example, the molar ratio of bromine to the total of bromine and chlorine was also calculated for each of the electrolyte layer and the positive electrode. Oxygen was excluded from the calculation in order to compare the example and the comparative example while eliminating the influence of oxygen derived from the positive electrode active material.

[0186] In the secondary battery of the comparative example, the atomic ratio of Br to the sum of Br and Cl in the electrolyte layer was roughly consistent with the atomic ratio of Br to the sum of Br and Cl in the positive electrode. In contrast, in the secondary battery of the example, the atomic ratio of Br to the sum of Br and Cl in the solid electrolyte contained in the positive electrode was significantly lower than the atomic ratio of Br to the sum of Br and Cl in the electrolyte layer. This is thought to be the result of a reduction in the bromine concentration in the solid electrolyte contained in the positive electrode due to the debromination treatment.

[0187] From the above results, it is believed that by making the bromine concentration in the solid electrolyte contained in the positive electrode lower than the bromine concentration in the electrolyte layer, side reactions due to oxidation can be suppressed even when the potential of the positive electrode exceeds the oxidation potential of bromine during charging, thereby improving charge-discharge efficiency. [Industrial Applicability]

[0188] The battery of the present disclosure can be used, for example, as an all-solid-state secondary battery.

Claims

1. A positive electrode and a negative electrode; an electrolyte layer provided between the positive electrode and the negative electrode; Equipped with the positive electrode includes a positive electrode active material and a first solid electrolyte, the electrolyte layer includes a second solid electrolyte; the first solid electrolyte contains lithium and two or more types of anions, the second solid electrolyte contains lithium and two or more types of anions, the first solid electrolyte and the second solid electrolyte contain Br, a molar ratio of Br in the two or more types of anions contained in the first solid electrolyte is smaller than a molar ratio of Br in the two or more types of anions contained in the second solid electrolyte; The first solid electrolyte contains a material represented by the following composition formula (1): Li a1 M1 b1 Br c1 Cl d1 X1 e1 ・・・(1) In the composition formula (1), M1 includes at least one element selected from the group consisting of metal elements and metalloid elements other than Li, and X1 is an anion other than Cl and Br, a1>0, b1>0, c1>0, d1≧0, c1+d1>0, and e1≧0 are satisfied; The second solid electrolyte contains a material represented by the following composition formula (2): Li a2 M2 b2 Br c2 Cl d2 X2 e2 ・・・(2) In the composition formula (2), M2 includes at least one element selected from the group consisting of metal elements and metalloid elements other than Li, and X2 is an anion other than Cl and Br, A battery in which a2>0, b2>0, c2>0, d2≧0, c2+d2>0, and e2≧0 are satisfied.

2. the electrolyte layer includes a first electrolyte layer and a second electrolyte layer, the first electrolyte layer includes the second solid electrolyte; the second electrolyte layer is a layer located between the positive electrode and the first electrolyte layer, and includes a third solid electrolyte; The third solid electrolyte contains a material represented by the following composition formula (3): Li a3 M3 b3 Br c3 Cl d3 X3` e3 ・・・(3) In the composition formula (3), M3 includes at least one element selected from the group consisting of metal elements and metalloid elements other than Li, and X3 is an anion other than Cl and Br, a3>0, b3>0, c3≧0, d3≧0, c3+d3>0, and e3≧0 are satisfied; 2. The battery according to claim 1, wherein a relationship of β1 / α1≦β3 / α3<β2 / α2 is satisfied, where α1 is the total amount of substance of anions in the first solid electrolyte, β1 is the amount of substance of bromine anions in the first solid electrolyte, α2 is the total amount of substance of anions in the second solid electrolyte, β2 is the amount of substance of bromine anions in the second solid electrolyte, α3 is the total amount of substance of anions in the third solid electrolyte, and β3 is the amount of substance of bromine anions in the third solid electrolyte.

3. In the composition formula (1), the ratio a1 / (c1+d1+e1) is in the range of 0.3 to 0.6, 2. The battery according to claim 1, wherein in the composition formula (2), the ratio a2 / (c2+d2+e2) is in the range of 0.3 to 1.

4. In the composition formula (1), the ratio a1 / (c1+d1+e1) is in the range of 0.3 to 0.6, In the composition formula (2), the ratio a2 / (c2+d2+e2) is in the range of 0.3 to 1, 3. The battery according to claim 2, wherein in the composition formula (3), the ratio a3 / (c3+d3+e3) is in the range of 0.3 to 1.

5. when the total amount of substance of anions in the third solid electrolyte is defined as α3 and the amount of substance of bromine anions in the third solid electrolyte is defined as β3, the ratio β3 / α3 changes in the thickness direction of the second electrolyte layer, The battery according to claim 2 or 4, wherein the ratio β3 / α3 on the positive electrode side is lower than the ratio β3 / α3 on the first electrolyte layer side.

6. 6. The battery of claim 1, wherein the positive electrode comprises an electronically conductive material.

7. The battery of claim 1 , wherein M1 and M2 comprise Y.

8. The battery of claim 1 or 7, wherein M1 and M2 comprise Y and Zr.

9. The battery of claim 2 , wherein M3 comprises Y.

10. The battery of claim 2 or 9, wherein M3 comprises Y and Zr.

11. The battery of claim 1 , wherein the positive electrode active material comprises a lithium-containing transition metal oxide.

12. A method for manufacturing a battery, comprising: The battery comprises: A positive electrode and a negative electrode; an electrolyte layer provided between the positive electrode and the negative electrode; Equipped with the positive electrode includes a positive electrode active material and a first solid electrolyte, the electrolyte layer includes a second solid electrolyte; the first solid electrolyte contains lithium and two or more types of anions, the second solid electrolyte contains lithium and two or more types of anions, the first solid electrolyte and the second solid electrolyte contain Br, a molar ratio of Br in the two or more types of anions contained in the first solid electrolyte is smaller than a molar ratio of Br in the two or more types of anions contained in the second solid electrolyte; The first solid electrolyte contains a material represented by the following composition formula (1): Li a1 M1 b1 Br c1 Cl d1 X1 e1 ・・・(1) In the composition formula (1), M1 includes at least one element selected from the group consisting of metal elements and metalloid elements other than Li, and X1 is an anion other than Cl and Br, a1>0, b1>0, c1>0, d1≧0, c1+d1>0, and e1≧0 are satisfied; The second solid electrolyte contains a material represented by the following composition formula (2): Li a2 M2 b2 Br c2 Cl d2 X2 e2 ・・・(2) In the composition formula (2), M2 includes at least one element selected from the group consisting of metal elements and metalloid elements other than Li, and X2 is an anion other than Cl and Br, a2>0, b2>0, c2>0, d2≧0, c2+d2>0, and e2≧0 are satisfied; The manufacturing method includes: preparing a laminate including the positive electrode, the electrolyte layer, and the negative electrode; Charging the stack at a constant voltage equal to or higher than a voltage at which a potential of the positive electrode becomes equal to an oxidation potential of bromine contained in the first solid electrolyte and lower than 4.1 V with respect to Li; A method for manufacturing a battery, comprising:

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