Battery

Abstract

The present invention improves charge / discharge characteristics. This battery has a positive electrode, a negative electrode, and an electrolyte layer that contains a solid electrolyte. The negative electrode comprises: a negative electrode current collector layer; a negative electrode active material layer residing on the electrolyte layer side with respect to the negative electrode current collector layer; and a negative electrode intermediate layer that is in contact with the negative electrode current collector layer and the negative electrode active material layer. The solid electrolyte contains S. The negative electrode current collector layer contains Cu. The negative electrode active material layer contains Si. The negative electrode intermediate layer contains Cu and Si. The molar ratio of Si to Cu in the negative electrode intermediate layer is 0.13-1.20.

Description

battery

[0001] The present disclosure relates to batteries.

[0002] Patent Document 1 discloses a battery having an electrolyte layer containing a solid electrolyte containing sulfur, an anode current collector layer containing copper, and an anode active material layer containing silicon.

[0003] International Publication No. 2022 / 244303

[0004] In the battery disclosed in Patent Document 1, the copper in the negative electrode current collector layer may react with sulfur in the electrolyte layer, resulting in a deterioration in charge-discharge characteristics.

[0005] The present disclosure has been made in view of the above, and aims to provide a battery with improved charge / discharge characteristics.

[0006] A battery according to one embodiment includes a positive electrode, a negative electrode, and an electrolyte layer containing a solid electrolyte. The negative electrode includes a negative electrode current collector layer, a negative electrode active material layer on the electrolyte layer side of the negative electrode current collector layer, and a negative electrode intermediate layer in contact with the negative electrode current collector layer and the negative electrode active material layer. The solid electrolyte includes S, the negative electrode current collector layer includes Cu, the negative electrode active material layer includes Si, and the negative electrode intermediate layer includes Cu and Si. The molar ratio of Si to Cu in the negative electrode intermediate layer is 0.13 or more and 1.20 or less.

[0007] According to the present invention, the charge / discharge characteristics can be improved.

[0008] Fig. 1 is a schematic cross-sectional view showing an example of a battery according to the first embodiment. Fig. 2 is a diagram showing an image observed by a scanning electron microscope (SEM) showing a cross section of a negative electrode according to the first embodiment. Fig. 3 is a diagram showing a Raman spectrum of a negative electrode active material layer of a battery according to Example 1.

[0009] Hereinafter, embodiments of the present disclosure will be described. Note that the present disclosure is not limited to these embodiments. Furthermore, in the present disclosure, numerical values ​​include ranges that are rounded off.

[0010] First Embodiment FIG. 1 is a schematic cross-sectional view showing an example of a battery according to a first embodiment. The battery 1 in the first embodiment is, for example, an all-solid-state battery in which the electrolyte is solid, and is a lithium-ion secondary battery. As shown in FIG. 1, the battery 1 includes a protective layer 10, a positive electrode 20, a negative electrode 30, and an electrolyte layer 40. In the example of FIG. 1, the battery 1 has a structure in which the sheet-like positive electrode 20, the negative electrode 30, and the electrolyte layer 40 are stacked.

[0011] In the drawings showing this embodiment, the Z direction refers to the stacking direction of the positive electrode 20, the negative electrode 30, and the electrolyte layer 40, the X direction refers to a direction perpendicular to the Z direction and parallel to the cross section of FIG. 1, and the Y direction refers to a direction perpendicular to the X direction and the Z direction. In addition, in describing this embodiment, one of the X directions may be referred to as the +X direction and the other as the −X direction. Similarly, one of the Z directions may be referred to as the +Z direction and the other as the −Z direction.

[0012] The protective layer 10 is a layer provided to physically and chemically protect the battery 1. In plan view in the Z direction, the protective layer 10 is provided so as to overlap the stack of the positive electrode 20, the negative electrode 30, and the electrolyte layer 40, and in the example of Fig. 1, the protective layer 10 is provided on both sides in the Z direction of the stack of the positive electrode 20, the negative electrode 30, and the electrolyte layer 40. The material of the protective layer 10 is not particularly limited as long as it is an insulator, and examples thereof include resin, glass, and ceramics.

[0013] The positive electrode 20 includes a positive electrode current collector layer 21 and a positive electrode active material layer 22 .

[0014] The positive electrode current collector layer 21 is a conductive layer. In the example of FIG. 1 , the end face of the positive electrode current collector layer 21 in the +X direction is exposed and can be connected to the outside. That is, the end face of the positive electrode current collector layer 21 in the +X direction serves as the positive electrode of the battery 1. The material of the positive electrode current collector layer 21 is not particularly limited as long as it is conductive, and examples thereof include metal materials such as silver, palladium, gold, platinum, aluminum, copper, and nickel, and carbon materials.

[0015] The positive electrode active material layer 22 is a layer containing a positive electrode active material. The positive electrode active material layer 22 is laminated on the positive electrode current collector layer 21. The positive electrode active material is not particularly limited, and examples thereof include at least one selected from the group consisting of a lithium-containing phosphate compound having a Nasicon structure, a lithium-containing phosphate compound having an olivine structure, a lithium-containing layered oxide, and a lithium-containing oxide having a spinel structure. An example of a lithium-containing phosphate compound having a Nasicon structure is Li ３ V ２ (P.O. ４ ) ３ Examples of lithium-containing phosphate compounds having an olivine structure include Li ３ Fe ２ (P.O. ４ ) ３ , LiMnPO ４ An example of a lithium-containing layered oxide is LiCoO ２ , LiCo １／３ Ni １／３ Mn １／３ O ２ An example of a lithium-containing oxide having a spinel structure is LiMn ２ O ４ , LiNi ０．５ Mn １．５ O ４ etc.

[0016] The material contained in the positive electrode active material layer 22 is not limited to the positive electrode active material, and may also contain a solid electrolyte or a sintering aid, which will be described later. The sintering aid is not particularly limited, and examples thereof include lithium oxide, sodium oxide, potassium oxide, boron oxide, silicon oxide, bismuth oxide, and phosphorus oxide.

[0017] Fig. 2 is a diagram showing an image observed by a scanning electron microscope (SEM) showing a cross section of the negative electrode according to the first embodiment. The negative electrode in Fig. 2 is the negative electrode of the battery according to Example 1, which will be described later. As shown in Figs. 1 and 2 , the negative electrode 30 has a negative electrode current collector layer 31, a negative electrode active material layer 32, and a negative electrode intermediate layer 33.

[0018] The negative electrode current collector layer 31 is a conductive layer that does not substantially contain silicon (Si). In the example of FIG. 1 , the negative electrode current collector layer 31 has an exposed end face in the −X direction that can be connected to the outside. That is, the end face in the −X direction of the negative electrode current collector layer 31 serves as the negative electrode of the battery 1.

[0019] The negative electrode current collector layer 31 contains copper (Cu). In the first embodiment, the negative electrode current collector layer 31 is a copper foil. The material of the negative electrode current collector layer 31 is not limited to this, and the negative electrode current collector layer 31 may further contain a metal material other than copper, such as nickel, iron, palladium, gold, platinum, or aluminum. The negative electrode current collector layer 31 is not limited to being composed of a single layer, and may include multiple layers, such as a metal layer other than copper coated with copper on the negative electrode active material layer 32 side.

[0020] The negative electrode active material layer 32 is a layer containing a negative electrode active material and is a layer that does not substantially contain copper (Cu). In the example of FIG. 1 , the negative electrode active material layer 32 is provided in the +Z direction of the negative electrode current collector layer 31.

[0021] The negative electrode active material layer 32 contains silicon (Si) as the negative electrode active material. This can improve the charge / discharge characteristics of the battery 1. The negative electrode active material layer 32 also preferably contains amorphous Si. Compared to crystalline Si, amorphous Si can suppress expansion and contraction of the negative electrode active material layer during charge / discharge, and can suppress deterioration of the capacity characteristics of the battery. Whether or not amorphous Si is contained can be measured by Raman spectroscopy. More specifically, in the Raman spectrum measured by Raman spectroscopy for the negative electrode active material layer 32, a Raman shift of 480 cm －１ If a peak is observed in the vicinity, it can be determined that the negative electrode active material layer 32 contains amorphous Si. In the first embodiment, the negative electrode active material layer 32 is made of amorphous Si.

[0022] In the first embodiment, the negative electrode active material layer 32 is a layer made of a negative electrode active material. As shown in FIG. 2 , the negative electrode active material layer 32 is a layer in which the negative electrode active material is continuous from the surface on the −Z direction side (the surface on the negative electrode current collector layer 31 side) to the surface on the +Z direction side (the surface on the electrolyte layer 40 side). In other words, the negative electrode active material layer 32 does not substantially contain components of the electrolyte layer 40 (e.g., solid electrolyte). This allows the capacity of the battery 1 to be increased. Examples of the continuous body include a pressure-molded body or sintered compact of only the negative electrode active material, and a film formed by plating, sputtering, vapor deposition, or the like, but may also be a metal foil, a wafer, or the like.

[0023] The negative electrode intermediate layer 33 is a layer containing silicon (Si) and copper (Cu). The surface of the negative electrode intermediate layer 33 on the −Z direction side is in contact with the negative electrode current collector layer 31, and the surface of the negative electrode intermediate layer 33 on the +Z direction side is in contact with the negative electrode active material layer 32. In the first embodiment, the negative electrode intermediate layer 33 is made of a Si—Cu alloy (Si ｘ Cu ｙ ). As a result, the anode intermediate layer 33 is in close contact with the anode current collector layer 31 and the anode active material layer 32, which can suppress side reactions between the anode current collector layer 31 and the electrolyte layer 40, thereby improving charge / discharge characteristics. The anode intermediate layer 33 is preferably formed continuously in the X direction between the anode current collector layer 31 and the electrolyte layer 40, but may have a partially discontinuous region. In other words, the surface of the anode current collector layer 31 facing the electrolyte layer 40 and the surface of the electrolyte layer 40 facing the anode 30 may be in partial contact with each other.

[0024] The molar ratio of Si to Cu in the negative electrode intermediate layer 33 is 0.13 or more and 1.20 or less. By setting the ratio within this range, Cu and Si can suitably form an alloy. This improves the charge / discharge characteristics of the battery. It is presumed that the charge / discharge characteristics are improved because an increase in the resistance of the negative electrode 30, more specifically, the resistance between the negative electrode active material layer 32 and the negative electrode current collector layer, can be suppressed. A molar ratio of Si to Cu in the negative electrode intermediate layer 33 of 0.25 or more and 0.61 or less is more preferable in terms of suppressing an increase in the resistance of the negative electrode 30. In the following description, it is assumed that the negative electrode intermediate layer 33 is a Si-Cu alloy (Si ｘ Cu ｙ ), the molar ratio of Si to Cu in the negative electrode intermediate layer 33 may be described as x / y.

[0025] The molar ratio of Si to Cu in the negative electrode intermediate layer 33 can be measured by the following method. First, a cross section of the battery 1 along the stacking direction is observed with a scanning electron microscope (SEM). Here, the region observed with the SEM is a rectangular region including the central portion of the negative electrode 30 and having a side length of 30 μm to 40 μm. Next, the boundary between the negative electrode intermediate layer 33 and the negative electrode current collector layer 31 and the boundary between the negative electrode intermediate layer 33 and the negative electrode active material layer 32 are identified in the region. As shown in FIG. 2 , the negative electrode current collector layer 31, the negative electrode active material layer 32, and the negative electrode intermediate layer 33 can be distinguished because they appear as regions with different shading in the SEM image. Next, quantitative analysis is performed using an energy dispersive X-ray fluorescence spectrometer (EDX) at three arbitrary points in the region between the boundary between the negative electrode intermediate layer 33 and the negative electrode current collector layer 31 and the boundary between the negative electrode intermediate layer 33 and the negative electrode active material layer 32, where the distance in the stacking direction to the boundary between the negative electrode intermediate layer 33 and the negative electrode current collector layer 31 is approximately the same as the distance in the stacking direction to the boundary between the negative electrode intermediate layer 33 and the negative electrode active material layer 32. Here, the three points are positioned at least 5 μm apart from each other in the X direction. Then, the molar ratio of Si to Cu at each of the three points is calculated based on the spectrum observed by EDX, and the arithmetic average of the calculated molar ratios at the three points can be calculated as the molar ratio of Si to Cu in the negative electrode intermediate layer 33.

[0026] The thickness of the negative electrode intermediate layer 33 is preferably greater than 0.5 μm, and more preferably 0.6 μm or greater. By setting the thickness within this range, a side reaction between the electrolyte layer 40 and the negative electrode current collector layer, which will be described later, can be sufficiently suppressed. A thickness of 0.8 μm or greater is more preferable in terms of sufficiently suppressing a reaction between S contained in the electrolyte layer 40 and Cu contained in the negative electrode current collector layer. The thickness of the negative electrode intermediate layer 33 is preferably smaller than 2.2 μm, and more preferably 2.0 μm or less. Setting the thickness within this range reduces the resistance due to the negative electrode intermediate layer 33, and improves the electrical capacity of the battery 1. A thickness of 1.7 μm or less is more preferable in terms of reducing the resistance due to the negative electrode intermediate layer 33.

[0027] The thickness of the negative electrode intermediate layer 33 can be measured by the following method. First, a cross section of the battery 1 along the stacking direction is observed with a scanning electron microscope (SEM). Here, the region observed with the SEM is a rectangular region including the central portion of the negative electrode 30 and having a side length of 30 μm to 40 μm. Next, the boundary between the negative electrode intermediate layer 33 and the negative electrode current collector layer 31 and the boundary between the negative electrode intermediate layer 33 and the negative electrode active material layer 32 are identified in the region. Next, the distance in the stacking direction from the boundary between the negative electrode intermediate layer 33 and the negative electrode current collector layer 31 to the boundary between the negative electrode intermediate layer 33 and the negative electrode active material layer 32 is measured at at least five points. Here, the five points are positioned at least 5 μm apart from each other in a direction perpendicular to the stacking direction. The thickness of the negative electrode intermediate layer 33 can then be calculated as the arithmetic average of the distances measured at the five points.

[0028] The electrolyte layer 40 is a layer that does not substantially contain a positive electrode active material or a negative electrode active material, and is a layer provided between the positive electrode 20 and the negative electrode 30. In the first embodiment, the electrolyte layer 40 includes a solid electrolyte. Here, the solid electrolyte is an ion conductor that includes sulfur (S), such as Li ６ P.S. ５ Cl, Li ３ P.S. ４ , Li ４ SnS ４ By using a solid electrolyte containing S, the formability of the electrolyte layer 40 can be improved, and a good bonding interface with the positive electrode active material layer 22 can be formed.

[0029] The side reinforcing portions 60 are provided to prevent short circuits in the battery 1. In the example of Fig. 1, the side reinforcing portions 60 are provided on the X-direction and Y-direction end surfaces of the positive electrode 20, the negative electrode 30, and the electrolyte layer 40. The material of the side reinforcing portions 60 is not particularly limited as long as it is an insulator, and examples thereof include resin, glass, and ceramics.

[0030] The negative electrode and the battery according to the first embodiment are not limited to those described above. For example, the negative electrode active material layer may contain a conductive material. In this case, the electronic conductivity of the negative electrode can be improved.

[0031] The battery according to the first embodiment may also be a battery having an exterior body (case). That is, the battery according to the first embodiment may be a battery in which a laminate including the positive electrode 20, the negative electrode 30, and the electrolyte layer 40 is housed in an exterior body made of metal, ceramics, or the like.

[0032] As described above, the battery 1 according to the first embodiment includes a positive electrode 20, a negative electrode 30, and an electrolyte layer 40 containing a solid electrolyte. The negative electrode includes a negative electrode current collector layer 31, a negative electrode active material layer 32 located on the electrolyte layer side of the negative electrode current collector layer 31, and a negative electrode intermediate layer 33 in contact with the negative electrode current collector layer 31 and the negative electrode active material layer 32. The solid electrolyte includes S (sulfur). The negative electrode current collector layer 31 includes Cu (copper). The negative electrode active material layer 32 includes Si (silicon). The negative electrode intermediate layer 33 includes Cu and Si. The molar ratio of Si to Cu in the negative electrode intermediate layer 33 is 0.13 or more and 1.20 or less. This can suppress side reactions between the electrolyte layer 40 and the negative electrode current collector layer, improving charge / discharge characteristics.

[0033] In a preferred embodiment, the molar ratio of Si to Cu in the negative electrode intermediate layer 33 is 0.25 or more and 0.61 or less, which can further suppress side reactions between the negative electrode current collector layer and the electrolyte layer, thereby further improving the charge / discharge characteristics.

[0034] In a desirable embodiment, the thickness of the negative electrode intermediate layer 33 is greater than 0.5 μm and smaller than 2.2 μm. This sufficiently suppresses side reactions between the electrolyte layer 40 and the negative electrode current collector layer, reduces the resistance due to the negative electrode intermediate layer 33, and improves the charge / discharge characteristics.

[0035] In a more desirable embodiment, the thickness of the negative electrode intermediate layer 33 is 0.8 μm or more and 1.7 μm or less. This more sufficiently suppresses side reactions between the electrolyte layer 40 and the negative electrode current collector layer, and further reduces the resistance due to the negative electrode intermediate layer 33, thereby further improving the charge / discharge characteristics.

[0036] In a preferred embodiment, the negative electrode active material layer 32 contains amorphous Si, which can suppress expansion and contraction of the negative electrode active material layer during charge and discharge, and can suppress deterioration of the capacity characteristics of the battery.

[0037] An example of a method for manufacturing the negative electrode of the battery according to the first embodiment will be described below. Note that the method for manufacturing the negative electrode of the battery according to the first embodiment is not limited to the following method.

[0038] The negative electrode of the battery according to the first embodiment can be manufactured by, for example, ion plating. The manufacturing process of the negative electrode of the battery according to the first embodiment includes the steps of preparing a negative electrode current collector layer, generating silicon vapor, ionizing a portion of the silicon vapor, and forming a Si-containing film on the negative electrode current collector layer. In this embodiment, the Si-containing film is a film containing Si, and corresponds to the negative electrode active material layer and the negative electrode intermediate layer.

[0039] In the step of preparing the negative electrode current collector layer, copper foil to become the negative electrode current collector layer is cut into a predetermined shape and set in an ion plating device.

[0040] In the process of generating silicon vapor, the inside of the ion plating device is evacuated, and then an electron beam is irradiated onto silicon scraps contained in a crucible installed inside the ion plating device to generate silicon vapor.

[0041] In the process of ionizing a portion of the silicon vapor, thermions are collided with the silicon vapor to ionize a portion of the silicon. The thermions that collide with the silicon vapor are emitted from a filament provided in the ion plating device. Here, by increasing the current (ionization current) passed through the filament, the proportion of silicon that is ionized can be increased, and therefore the molar ratio of Si to Cu in the negative electrode intermediate layer and the thickness of the negative electrode intermediate layer can be increased.

[0042] In the process of forming a Si-containing film on the negative electrode current collector layer, partially ionized silicon vapor comes into contact with the negative electrode current collector layer, forming a Si-containing layer having a thickness of 5 μm or more on the negative electrode current collector layer. At this time, a negative electrode active material layer made of amorphous Si is formed on the negative electrode current collector layer, but since the negative electrode current collector layer is heated to 300°C or higher, a negative electrode intermediate layer made of a Si-Cu alloy is formed between the negative electrode current collector layer and the negative electrode active material layer. A potential (bias) relative to a reference potential can be applied to the negative electrode current collector layer. By increasing the absolute value of the bias applied to the negative electrode current collector layer, the molar ratio of Si to Cu in the negative electrode intermediate layer can be increased. Furthermore, by extending the time for which the bias is applied to the negative electrode current collector layer, the molar ratio of Si to Cu in the negative electrode intermediate layer can be increased, thereby increasing the thickness of the negative electrode intermediate layer.

[0043] Examples of the present embodiment will be described below. Note that the present embodiment is not limited to the following examples. Table 1 shows examples of the present embodiment and comparative examples.

[0044]

[0045] Example 1 The negative electrode according to Example 1 was fabricated by the following method. After evacuating the interior of an ion plating apparatus, an electron beam was irradiated onto silicon scraps contained in a crucible installed within the ion plating apparatus to generate silicon vapor. Next, an ionization current was passed through a filament installed within the ion plating apparatus to emit thermions, which collided with the silicon vapor to ionize a portion of the silicon. Here, the acceleration voltage of thermions was 30 V, and the ionization current was 20 A. The partially ionized silicon vapor was then brought into contact with the negative electrode current collector layer, and a negative electrode intermediate layer containing Si and a negative electrode active material layer were formed over 10 minutes. Here, copper foil was used as the negative electrode current collector layer, and a bias of −400 V was applied to the negative electrode current collector layer for 10 minutes while the negative electrode intermediate layer and the negative electrode active material layer were being formed on the negative electrode current collector layer. The negative electrode according to Example 1 was fabricated through the above process.

[0046] For the negative electrode according to Example 1, the molar ratio (x / y) of Si to Cu in the negative electrode intermediate layer was measured by the following method. First, a cross section along the stacking direction of the negative electrode according to Example 1 was observed using an SEM (Hitachi High-Technologies Corporation, S-4800). Here, the region observed using the SEM was a rectangular region including the central portion of the negative electrode, with one side measuring 30 μm to 40 μm. Next, the boundary between the negative electrode intermediate layer and the negative electrode current collector layer and the boundary between the negative electrode intermediate layer and the negative electrode active material layer were identified in that region. Next, quantitative analysis was performed using EDX at three arbitrary points within the region between the boundary between the negative electrode intermediate layer and the negative electrode current collector layer and the boundary between the negative electrode intermediate layer and the negative electrode active material layer, where the distance in the stacking direction to the boundary between the negative electrode intermediate layer 33 and the negative electrode current collector layer 31 was approximately the same as the distance in the stacking direction to the boundary between the negative electrode intermediate layer 33 and the negative electrode active material layer 32. The three points were positioned at least 5 μm apart from each other. The molar ratio of Si to Cu at each of the three points was calculated based on the spectrum observed by EDX, and the arithmetic mean of the calculated molar ratios for the three points was calculated as the molar ratio of Si to Cu (x / y) in the negative electrode intermediate layer. As a result, the x / y values ​​for the negative electrode intermediate layer according to Example 1 were as shown in Table 1.

[0047] The thickness of the negative electrode intermediate layer of the negative electrode according to Example 1 was measured by the following method. First, a cross section of the negative electrode according to Example 1 along the stacking direction was observed using an SEM (Hitachi High-Technologies Corporation, S-4800). Here, the region observed using the SEM was a rectangular region including the central portion of the negative electrode, with one side measuring 30 μm to 40 μm. Next, the boundary between the negative electrode intermediate layer and the negative electrode current collector layer and the boundary between the negative electrode intermediate layer and the negative electrode active material layer were identified in this region. Next, the distance in the stacking direction from the boundary between the negative electrode intermediate layer and the negative electrode current collector layer to the boundary between the negative electrode intermediate layer and the negative electrode active material layer was measured at at least five points. Here, the five points were positioned at least 5 μm apart from each other in a direction perpendicular to the stacking direction. Then, the arithmetic mean of the distances measured at the five points was calculated as the thickness of the negative electrode intermediate layer. As a result, the thickness of the negative electrode intermediate layer according to Example 1 was the value shown in Table 1.

[0048] 3 is a diagram showing a Raman spectrum for the negative electrode active material layer of the battery according to Example 1. Raman spectroscopy was performed on the negative electrode active material layer of the negative electrode according to Example 1 using a Raman spectrometer (NRS-3000, JASCO Corporation), and the Raman spectrum shown in FIG. 3 was obtained. As shown in FIG. 3, the Raman spectrum for the negative electrode active material layer according to Example 1 shows a peak at 480 cm －１ Therefore, it is clear that the negative electrode active material layer of the negative electrode according to Example 1 contains amorphous silicon.

[0049] The electrolyte layer according to Example 1 was formed by disposing Li as a solid electrolyte in a zirconia cylinder having a diameter of 10 mm. ６ P.S. ５ 100 mg of Cl powder is 1 tf / (cm ２ The mixture was compressed at a speed of 1000 kJ / min and pelletized.

[0050] The battery according to Example 1 was fabricated by the following method. First, the negative electrode fabricated above was punched out to a diameter of 8 mm, and the negative electrode was laminated so that the surface of the negative electrode active material layer side was in contact with the electrolyte layer. ２ ·min). Then, a counter electrode made of an In—Li alloy was attached to the electrolyte layer. Then, a stainless steel foil was attached as a counter electrode current collector, and the pressure was increased to 1 tf / (cm２ The laminate was pressed in the stacking direction at a pressure of 1 / 2 sq. min. Thus, the battery according to Example 1 was fabricated.

[0051] <Charge / Discharge Test> The prepared battery was subjected to a charge / discharge test under the following conditions. The prepared battery was charged to an upper limit voltage using the following charge / discharge method and charge / discharge current, and then discharged to a lower limit voltage using the following charge / discharge method and charge / discharge current. The charge capacity, discharge capacity, and coulombic efficiency were measured. Here, the coulombic efficiency was calculated as the ratio of the discharge capacity to the charge capacity. Charging / discharging method: CC Charging / discharging current: 0.05 C Lower limit voltage: -0.57 V (0.05 V vs. Li ＋ / Li) Upper limit voltage: 0.88V (1.5V vs. Li ＋ / Li)

[0052] Example 2 In Example 2, a negative electrode was fabricated in the same manner as in Example 1, except that a bias of −400 V was applied to the negative electrode current collector layer for 1 minute, and then a bias of 200 V was applied for 9 minutes. For the fabricated negative electrode, the x / y and thickness of the negative electrode intermediate layer were measured, and the x / y and thickness of the negative electrode intermediate layer were found to have the values ​​shown in Table 1. In addition, a battery was fabricated using the fabricated negative electrode in the same manner as in Example 1, and charge / discharge measurements were performed.

[0053] In Example 3, a negative electrode was fabricated in the same manner as in Example 1, except that a bias of −200 V was applied to the negative electrode current collector layer for 10 minutes. For the fabricated negative electrode, the x / y and thickness of the negative electrode intermediate layer were measured, and the x / y and thickness of the negative electrode intermediate layer were found to be the values ​​shown in Table 1. In addition, a battery was fabricated using the fabricated negative electrode in the same manner as in Example 1, and charge / discharge measurements were performed.

[0054] Example 4 In Example 4, a negative electrode was fabricated in the same manner as in Example 1, except that a bias of −100 V was applied to the negative electrode current collector layer for 10 minutes. For the fabricated negative electrode, the x / y and thickness of the negative electrode intermediate layer were measured, and the x / y and thickness of the negative electrode intermediate layer were found to be the values ​​shown in Table 1. In addition, a battery was fabricated using the fabricated negative electrode in the same manner as in Example 1, and charge / discharge measurements were performed.

[0055] Example 5 In Example 5, a negative electrode was fabricated in the same manner as in Example 1, except that no bias was applied to the negative electrode current collector layer. For the fabricated negative electrode, the x / y and thickness of the negative electrode intermediate layer were measured, and the x / y and thickness of the negative electrode intermediate layer were found to be the values ​​shown in Table 1. In addition, a battery was fabricated using the fabricated negative electrode in the same manner as in Example 1, and charge / discharge measurements were performed.

[0056] Comparative Example 1 In Comparative Example 1, a negative electrode was fabricated in the same manner as in Example 1, except that a bias of 0 V was applied for 10 minutes to the negative electrode current collector layer for thermions emitted from the filament, and the ionization current was set to 10 A. For the fabricated negative electrode, the x / y and thickness of the negative electrode intermediate layer were measured, and the x / y and thickness of the negative electrode intermediate layer were found to have the values ​​shown in Table 1. In addition, a battery was fabricated using the fabricated negative electrode in the same manner as in Example 1, and charge / discharge measurements were performed.

[0057] Comparative Example 2 In Comparative Example 2, a negative electrode was fabricated in the same manner as in Example 1, except that the ionization current was set to 30 A. For the fabricated negative electrode, the x / y and thickness of the negative electrode intermediate layer were measured, and the x / y and thickness of the negative electrode intermediate layer were found to have the values ​​shown in Table 1. In addition, a battery was fabricated using the fabricated negative electrode in the same manner as in Example 1, and charge / discharge measurements were performed.

[0058] As shown in Table 1, Examples 1 to 5, in which the molar ratio of Si to Cu (x / y) in the negative electrode intermediate layer was 0.13 or more and 1.20 or less, had improved charge capacity, discharge capacity, and coulombic efficiency compared to Comparative Example 1, in which x / y was less than 0.13, and Comparative Example 2, in which x / y was greater than 1.20. This shows that the charge / discharge characteristics can be improved by having the molar ratio of Si to Cu (x / y) in the negative electrode intermediate layer be 0.13 or more and 1.20 or less.

[0059] As shown in Table 1, Examples 1 to 5, in which the molar ratio of Si to Cu (x / y) in the negative electrode intermediate layer was 0.25 or more and 0.61 or less, showed improved charge capacity, discharge capacity, and coulombic efficiency compared to Comparative Example 1, in which x / y was less than 0.25, and Comparative Example 2, in which x / y was greater than 0.61. This demonstrates that the charge / discharge characteristics can be improved by ensuring that the molar ratio of Si to Cu (x / y) in the negative electrode intermediate layer is 0.25 or more and 0.61 or less.

[0060] As shown in Table 1, Examples 1 to 5, in which the thickness of the negative electrode intermediate layer was greater than 0.5 μm and less than 2.2 μm, had improved charge capacity, discharge capacity, and coulombic efficiency compared to Comparative Example 1, in which the thickness of the negative electrode intermediate layer was 0.5 μm or less, and Comparative Example 2, in which the thickness of the negative electrode intermediate layer was 2.2 μm or more. This shows that the charge / discharge characteristics can be improved by making the thickness of the negative electrode intermediate layer greater than 0.5 μm and less than 2.2 μm.

[0061] As shown in Table 1, Examples 1 to 5, in which the thickness of the negative electrode intermediate layer was 0.8 μm or more and 1.7 μm or less, had improved charge capacity, discharge capacity, and coulombic efficiency compared to Comparative Example 1, in which the thickness of the negative electrode intermediate layer was less than 0.8 μm, and Comparative Example 2, in which the thickness of the negative electrode intermediate layer was more than 1.7 μm. This shows that the charge / discharge characteristics can be improved by setting the thickness of the negative electrode intermediate layer to 0.8 μm or more and 1.7 μm or less.

[0062] The above-described embodiments are intended to facilitate understanding of the present disclosure and are not intended to limit the present disclosure. The present disclosure may be modified or improved without departing from the spirit thereof, and equivalents thereof are also included in the present disclosure.

[0063] The present invention may also take the following forms: (1) A battery having a positive electrode, a negative electrode, and an electrolyte layer containing a solid electrolyte, wherein the negative electrode includes: a negative electrode current collector layer; a negative electrode active material layer on the electrolyte layer side of the negative electrode current collector layer; and a negative electrode intermediate layer in contact with the negative electrode current collector layer and the negative electrode active material layer, wherein the solid electrolyte includes S, the negative electrode current collector layer includes Cu, the negative electrode active material layer includes Si, and the negative electrode intermediate layer includes Cu and Si, and wherein the molar ratio of Si to Cu in the negative electrode intermediate layer is 0.13 to 1.20. (2) The battery according to (1), wherein the molar ratio of Si to Cu in the negative electrode intermediate layer is 0.25 to 0.61. (3) The battery according to (1) or (2), wherein the thickness of the negative electrode intermediate layer is greater than 0.5 μm and less than 2.2 μm. (4) The battery according to (3), wherein the thickness of the negative electrode intermediate layer is 0.8 μm or more and 1.7 μm or less. (5) The battery according to any one of (1) to (3), wherein the negative electrode active material layer contains amorphous Si.

[0064] REFERENCE SIGNS LIST 1 Battery 10 Protective layer 20 Positive electrode 21 Positive electrode current collector layer 22 Positive electrode active material layer 30 Negative electrode 31 Negative electrode current collector layer 32 Negative electrode active material layer 33 Negative electrode intermediate layer 40 Electrolyte layer 60 Side reinforcing portion

Claims

1. A battery having a positive electrode, a negative electrode, and an electrolyte layer containing a solid electrolyte, wherein the negative electrode comprises: a negative electrode current collector layer; a negative electrode active material layer on the electrolyte layer side of the negative electrode current collector layer; and a negative electrode intermediate layer in contact with the negative electrode current collector layer and the negative electrode active material layer, wherein the solid electrolyte comprises S, the negative electrode current collector layer comprises Cu, the negative electrode active material layer comprises Si, and the negative electrode intermediate layer comprises Cu and Si, and the molar ratio of Si to Cu in the negative electrode intermediate layer is 0.13 or more and 1.20 or less.

2. The battery according to claim 1, wherein the molar ratio of Si to Cu in the negative electrode intermediate layer is 0.25 or more and 0.61 or less.

3. The battery according to claim 1, wherein the thickness of the negative electrode intermediate layer is greater than 0.5 μm and less than 2.2 μm.

4. The battery according to claim 3, wherein the thickness of the negative electrode intermediate layer is 0.8 μm or more and 1.7 μm or less.

5. The battery according to any one of claims 1 to 4, wherein the negative electrode active material layer contains amorphous Si.

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