Battery

Abstract

This battery comprises a first electrode, a second electrode, and a solid electrolyte layer positioned between the first electrode and the second electrode, the first electrode having a collector body and an active material layer positioned between the collector body and the solid electrolyte layer, and the active material layer including Bi as the main component of the active material.

Description

[Technical Field]

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

[0002] In recent years, research and development of lithium secondary batteries has been actively conducted. Battery characteristics such as charge / discharge voltage, charge / discharge cycle life characteristics, and storage characteristics are greatly affected by the electrodes used. For this reason, efforts are being made to improve battery characteristics by improving the electrode active material.

[0003] For example, lithium secondary batteries have long been proposed that use electrodes made of aluminum, silicon, tin, or the like that electrochemically alloy with lithium during charging. Patent Document 1 discloses a lithium secondary battery that includes a negative electrode, a positive electrode, and an electrolyte, each made of an alloy containing silicon, tin, and a transition metal. Patent Document 2 discloses a lithium secondary battery that includes a negative electrode that uses a silicon thin film provided on a current collector as an active material, a positive electrode, and an electrolyte. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4898737 [Patent Document 2] Patent No. 3733065 Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure provides a battery with good cycle characteristics. [Means for solving the problem]

[0006] The battery of the present disclosure comprises: A first electrode; A second electrode; a solid electrolyte layer located between the first electrode and the second electrode; Equipped with the first electrode has a current collector and an active material layer located between the current collector and the solid electrolyte layer, The active material layer contains Bi as a main component of the active material. [Effects of the Invention]

[0007] According to the present disclosure, a battery having good cycle characteristics can be provided. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view schematically illustrating an example of the configuration of a battery 1000 according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a graph showing the relationship between the thickness of the active material layer made of a Bi plating layer and the density of the active material. [Figure 3] FIG. 3 is a graph showing an example of the X-ray diffraction pattern of an active material layer made of a Bi plating layer formed on a copper foil and of Bi powder. [Figure 4] FIG. 4 is a graph showing the results of a charge / discharge test of the test cell according to Example 1. [Figure 5] FIG. 5 is a graph showing the results of a charge-discharge cycle test of the test cell according to Example 1. [Figure 6] FIG. 6 is a graph showing the results of a charge / discharge test of the test cell according to Example 2. [Figure 7] FIG. 7 is a graph showing the results of a charge-discharge cycle test of the test cell according to Example 2. [Figure 8] FIG. 8 is a graph showing the results of a charge / discharge test of the test cell according to Example 3. [Figure 9] FIG. 9 is a graph showing the results of a charge-discharge cycle test of the test cell according to Example 3. [Figure 10] FIG. 10 is a graph showing the results of a charge / discharge test of the test cell according to Example 4. [Figure 11] FIG. 11 is a graph showing the results of a charge-discharge cycle test of the test cell according to Example 4. [Figure 12] FIG. 12 is a graph showing the results of a charge / discharge test of the test cell according to Example 5. [Figure 13] FIG. 13 is a graph showing the results of a charge-discharge cycle test of the test cell according to Example 5. [Figure 14] FIG. 14 is a graph showing the results of a charge / discharge test of the test cell according to Example 6. [Figure 15] FIG. 15 is a graph showing the results of a charge-discharge cycle test of the test cell according to Example 6. [Figure 16] FIG. 16 is a graph showing the results of a charge / discharge test of the test cell according to Example 7. [Figure 17] FIG. 17 is a graph showing the results of a charge-discharge cycle test of the test cell according to Example 7. [Figure 18] FIG. 18 is a graph showing the results of a charge-discharge cycle test of the test cells according to Reference Examples 1 and 2. In FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] (Findings that formed the basis of this disclosure) As described in the section of the "Background Art," efforts are being made to improve the battery characteristics of lithium secondary batteries by improving the electrode active materials.

[0010] When lithium metal is used as the negative electrode active material, lithium secondary batteries with high energy density per weight and per volume can be obtained. However, in lithium secondary batteries with this configuration, lithium precipitates in a dendrite-like form during charging. Part of the precipitated lithium metal reacts with the electrolyte, resulting in low charge / discharge efficiency and poor cycle characteristics.

[0011] In response to this, carbon, particularly graphite, has been proposed as an anode. In carbon-based anodes, charging and discharging occur through the insertion and extraction of lithium into and from the carbon. In anodes with this structure, lithium metal does not precipitate in a dendritic form due to the charge-discharge mechanism. Furthermore, lithium secondary batteries employing such anodes have excellent reversibility due to the topotactic reaction, resulting in charge-discharge efficiencies approaching 100%. For these reasons, lithium secondary batteries employing anodes made of carbon, particularly graphite, have been put to practical use. However, the theoretical capacity density of graphite is 372 mAh / g, approximately one-tenth the theoretical capacity density of lithium metal (3884 mAh / g). Therefore, the active material capacity density of anodes using graphite is low. Furthermore, because the actual capacity density of graphite is nearly equal to the theoretical capacity density, the capacity of anodes using graphite is limited.

[0012] In response to these challenges, lithium secondary batteries have long been proposed that use electrodes made of aluminum, silicon, tin, or the like, which electrochemically alloy with lithium during charging. The capacity density of metals that alloy with lithium is significantly greater than that of graphite. Silicon, in particular, has a high theoretical capacity density. Therefore, electrodes made of aluminum, silicon, tin, or the like, which alloy with lithium, are promising as negative electrodes for batteries that exhibit high capacity, and various secondary batteries using such negative electrodes have been proposed (Patent Document 1).

[0013] However, negative electrodes using metals that alloy with lithium as described above expand when they absorb lithium and contract when they release lithium. Repeated expansion and contraction during charging and discharging causes the alloy, which is the electrode active material, to pulverize, deteriorating the current collection characteristics of the negative electrode, resulting in insufficient cycle performance. Several attempts have been made to address these drawbacks. For example, attempts have been made to deposit silicon on a roughened current collector by sputtering or vapor deposition, or to deposit tin by electroplating (Patent Document 2). In these attempts, the active material, i.e., the metal that alloys with lithium, forms a thin film that adheres closely to the current collector, so that current collection performance is hardly impaired even when the negative electrode repeatedly expands and contracts due to the absorption and release of lithium.

[0014] However, forming the active material by sputtering or vapor deposition as described above is not practical due to the high manufacturing costs. Forming the active material by electroplating, which has low manufacturing costs, is practical, but electroplating silicon is very difficult. Furthermore, tin, which is easy to electroplat, has the problem of poor discharge flatness, making it difficult to use as a battery electrode.

[0015] Bismuth (Bi) is also an example of a metal that alloys with lithium. Bi forms compounds with lithium (Li), called LiBi and Li3Bi. There is almost no difference between the potentials of LiBi and Li3Bi. On the other hand, tin, which has poor discharge flatness, forms several compounds with lithium, and the potentials of each compound are quite different from each other. In other words, Bi does not have the property of large potential differences between the multiple compounds formed with lithium, as tin does. For this reason, electrodes containing Bi as an active material have excellent discharge flatness because their potential is flat. Therefore, electrodes containing Bi as an active material are considered suitable as battery electrodes.

[0016] However, when batteries equipped with electrodes containing an active material layer containing Bi as the main active material component were repeatedly charged and discharged, their capacity sometimes decreased to one-third or less of the initial capacity after about 20 cycles.

[0017] As a result of further investigations, the inventors have found that when an active material layer containing Bi as a main component of the active material repeatedly expands and contracts due to repeated charge and discharge, the nonaqueous electrolyte enters cavities generated in the active material layer, thereby destroying the structure of the active material layer and reducing the electron conduction paths in the active material layer.

[0018] As a result of extensive research into overcoming the above-mentioned problems, the present inventors have completed the battery of the present disclosure described below.

[0019] (Summary of one aspect of the present disclosure) The battery according to the first aspect of the present disclosure comprises: A first electrode; A second electrode; a solid electrolyte layer located between the first electrode and the second electrode; Equipped with the first electrode has a current collector and an active material layer located between the current collector and the solid electrolyte layer, The active material layer contains Bi as a main component of the active material.

[0020] In the battery according to the first embodiment, the electrolyte layer is a solid electrolyte layer. Therefore, even if the active material layer containing Bi as the main component of the active material repeatedly expands and contracts due to charge and discharge, the electrolyte does not penetrate into the active material layer, and reduction of the electron conduction path in the active material layer can be suppressed. Therefore, the battery according to the first embodiment has good cycle characteristics.

[0021] In a second aspect of the present disclosure, for example, in the battery according to the first aspect, the solid electrolyte layer may include a halide solid electrolyte, and the halide solid electrolyte does not include sulfur.

[0022] The battery according to the second embodiment has good cycle characteristics.

[0023] In a third aspect of the present disclosure, for example, in the battery according to the second aspect, the halide solid electrolyte may be a compound consisting of Li, M1, and X1, where M1 is at least one selected from the group consisting of metal elements and metalloid elements other than Li, and X1 is at least one selected from the group consisting of F, Cl, Br, and I.

[0024] The battery according to the third embodiment has a higher capacity and good cycle characteristics.

[0025] In a fourth embodiment of the present disclosure, for example, in the battery according to the third embodiment, M1 may include Y, and X1 may include Cl and Br.

[0026] The battery according to the fourth embodiment has a higher capacity and good cycle characteristics.

[0027] In a fifth aspect of the present disclosure, for example, in the battery according to the first aspect, the solid electrolyte layer may include a sulfide solid electrolyte.

[0028] The battery according to the fifth embodiment has good cycle characteristics.

[0029] In a sixth aspect of the present disclosure, for example, in the battery according to the fifth aspect, the solid electrolyte layer may consist essentially of a sulfide solid electrolyte.

[0030] The battery according to the sixth embodiment has a higher capacity and good cycle characteristics.

[0031] In a seventh aspect of the present disclosure, for example, in the battery according to either the fifth or sixth aspect, the sulfide solid electrolyte may have an argyrodite-type crystal structure.

[0032] The battery according to the seventh embodiment has a higher capacity and good cycle characteristics.

[0033] In an eighth aspect of the present disclosure, for example, in the battery according to any one of the fifth to seventh aspects, the composition formula of the sulfide solid electrolyte is Li7-a AS 6-a X2 a Here, A is at least one selected from the group consisting of P and As, X2 is at least one selected from the group consisting of Cl, Br, and I, and a satisfies 0≦a≦1.

[0034] The battery according to the eighth embodiment has a higher capacity and good cycle characteristics.

[0035] In a ninth aspect of the present disclosure, for example, in the battery according to any one of the fifth to eighth aspects, the sulfide solid electrolyte may have a composition formula of Li6PS5Cl.

[0036] The battery according to the ninth embodiment has a higher capacity and good cycle characteristics.

[0037] In a tenth aspect of the present disclosure, for example, in the battery according to any one of the first to ninth aspects, the density of the active material is 6.0 g / cm 3 or more and 9.8g / cm 3 Here, the density of the active material refers to the density of the active material when the battery is in a fully discharged state when the first electrode is a negative electrode, and refers to the density of the active material when the battery is in a fully charged state when the first electrode is a positive electrode.

[0038] The battery according to the tenth embodiment has a high capacity and good cycle characteristics.

[0039] In an eleventh aspect of the present disclosure, for example, in the battery according to the tenth aspect, the density of the active material is 7.5 g / cm 3 or more and 9.8g / cm 3 It may be the following:

[0040] The battery according to the eleventh embodiment has a higher capacity and good cycle characteristics.

[0041] In a twelfth aspect of the present disclosure, for example, in the battery according to any one of the first to eleventh aspects, when the height intensity of the maximum peak present in a diffraction angle 2θ range of 26° or more and 28° or less in an X-ray diffraction pattern of the active material layer obtained by surface X-ray diffraction measurement using Cu-Kα radiation is defined as I(1), and the height intensity of the maximum peak present in a diffraction angle 2θ range of 37° or more and 39° or less is defined as I(2), the ratio of I(2) to I(1), I(2) / I(1), may be 0.29 or more.

[0042] The battery according to the twelfth embodiment has a higher capacity and good cycle characteristics.

[0043] In a thirteenth aspect of the present disclosure, for example, in the battery according to the twelfth aspect, the I(2) / I(1) may be 0.57 or less.

[0044] The battery according to the thirteenth embodiment has a higher capacity and good cycle characteristics.

[0045] In a fourteenth aspect of the present disclosure, for example, in the battery according to any one of the first to thirteenth aspects, the active material layer may contain simple Bi.

[0046] The battery according to the fourteenth embodiment has a higher capacity and good cycle characteristics.

[0047] In a fifteenth aspect of the present disclosure, for example, in the battery according to any one of the first to fourteenth aspects, the active material layer may contain at least one selected from the group consisting of LiBi and Li3Bi.

[0048] The battery according to the fifteenth embodiment has a higher capacity and good cycle characteristics.

[0049] In a sixteenth aspect of the present disclosure, for example, in the battery according to any one of the first to fifteenth aspects, the active material layer may contain only simple Bi as the active material.

[0050] The battery according to the 16th aspect has a higher capacity and good cycle characteristics.

[0051] In the 17th aspect of the present disclosure, for example, in the battery according to any one of the 1st to 16th aspects, the active material layer may not contain an electrolyte.

[0052] According to the 17th aspect, a battery having a higher capacity per volume and good cycle characteristics can be obtained.

[0053] In the 18th aspect of the present disclosure, for example, in the battery according to any one of the 1st to 17th aspects, the current collector may contain Cu.

[0054] The battery according to the 18th aspect has a higher capacity and good cycle characteristics.

[0055] In the 19th aspect of the present disclosure, for example, in the battery according to any one of the 1st to 18th aspects, the active material layer may be a plating layer.

[0056] According to the 19th aspect, a battery having a higher capacity per volume and good cycle characteristics can be obtained.

[0057] In the 20th aspect of the present disclosure, for example, in the battery according to any one of the 1st to 19th aspects, the first electrode may be a negative electrode and the second electrode may be a positive electrode.

[0058] The battery according to the 20th aspect has a higher capacity and good cycle characteristics.

[0059] In the 21st aspect of the present disclosure, for example, in the battery according to any one of the 1st to 20th aspects, the second electrode may contain a compound represented by the following compositional formula (1). LiNi x Me 1-x O2···(1) Here, x satisfies 0 < x ≦ 1, and Me is at least one element selected from the group consisting of Mn, Co, and Al.

[0060] The battery according to the twenty-first aspect can reduce the manufacturing cost of the second electrode, can increase the average discharge voltage, and has a higher capacity and good cycle characteristics.

[0061] In the twenty-second embodiment of the present disclosure, for example, in the battery of the twenty-first embodiment, x may satisfy 0.5≦x≦1.

[0062] The battery according to the twenty-second embodiment has a higher capacity and good cycle characteristics.

[0063] (Embodiments of the present disclosure) Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The following descriptions are all comprehensive or specific examples. The numerical values, compositions, shapes, film thicknesses, electrical characteristics, secondary battery structures, etc. shown below are merely examples and are not intended to limit the present disclosure.

[0064] FIG. 1 is a cross-sectional view schematically illustrating an example of the configuration of a battery 1000 according to an embodiment of the present disclosure.

[0065] The battery 1000 includes a first electrode 101, a second electrode 103, and a solid electrolyte layer 102 located between the first electrode 101 and the second electrode 103. The first electrode 101 includes a current collector 100 and an active material layer 104 located between the current collector 100 and the solid electrolyte layer 102. The active material layer 104 contains Bi as a main active material component.

[0066] In battery 1000, the electrolyte layer is solid electrolyte layer 102. Therefore, even if active material layer 104, which contains Bi as a main active material component, repeatedly expands and contracts due to charge and discharge, the electrolyte does not enter into active material layer 104. This prevents the reduction in the electron conduction path in active material layer 104 due to repeated charge and discharge. Therefore, battery 1000 has good cycle characteristics.

[0067] Battery 1000 is, for example, a lithium secondary battery. Hereinafter, an example will be described in which the metal ions absorbed and released in active material layer 104 of first electrode 101 and second electrode 103 during charging and discharging of battery 1000 are lithium ions.

[0068] The phrase "active material layer 104 contains Bi as the main active material component" means that "in active material layer 104, the component that is contained in the largest amount by molar ratio as the active material is Bi."

[0069] According to the above configuration, good charge-discharge cycle characteristics can be obtained.

[0070] The density of the active material contained in the active material layer 104 is 6.0 g / cm 3 or more and 9.8g / cm 3 It may be the following:

[0071] According to the above configuration, better charge / discharge cycle characteristics can be obtained.

[0072] Here, in this specification, the density of the active material contained in the active material layer 104 of the first electrode 101 refers to the density of the active material contained in the active material layer 104 when the battery 1000 is in a fully discharged state if the first electrode 101 is a negative electrode, and refers to the density of the active material contained in the active material layer 104 when the battery 1000 is in a fully charged state if the first electrode 101 is a positive electrode. In other words, the density of the active material contained in the active material layer 104 of the first electrode 101 specified in this specification refers to the density of the active material contained in the active material layer 104 when lithium ions have been released from the active material layer 104 due to full charge or full discharge. Here, the "fully charged state" of the battery disclosed herein refers to a state in which the battery has been charged at a constant current (e.g., 0.05 C relative to the theoretical capacity) to a predetermined voltage (e.g., the negative electrode potential is 0 V vs. a lithium reference electrode). Furthermore, the "fully discharged state" of the battery of the present disclosure refers to a state in which the battery is discharged at a constant current (e.g., 0.05 C relative to the theoretical capacity) to a predetermined voltage (e.g., a negative electrode potential of 2 V versus a lithium reference electrode). The density of the active material contained in the active material layer 104 can be determined, for example, by removing the active material from the active material layer 104 and calculating the density of the removed active material using, for example, the Archimedes method. As an example, when the active material layer 104 is formed of a thin film essentially consisting of an active material, the density of the active material can be obtained by removing at least a portion of the thin film as a sample and calculating the density of the sample using, for example, the Archimedes method. Here, a thin film essentially consisting of an active material means a thin film having an active material content of 90 mass % or more.

[0073] The main component of the active material is Bi, and the density of the active material is 6.0 g / cm 3 or more and 9.8g / cm 3The active material layer 104 described below may be composed of, for example, Bi formed into a thin film (hereinafter referred to as "Bi thin film"). When the active material layer 104 is composed of a high-density Bi thin film that satisfies the density range described above and is provided in contact with the current collector 100, it can have high adhesion to the current collector 100. With this configuration, the active material, i.e., Bi, a metal that alloys with lithium, is in the form of a thin film and adheres to the current collector 100, so that even if Bi repeatedly expands and contracts due to the absorption and release of lithium, the electron conduction path can be maintained. Therefore, when the density of the active material contained in the active material layer 104 of the first electrode 101 in the present disclosure is 6.0 g / cm 3 or more and 9.8g / cm 3 When the active material contained in the active material layer 104 of the first electrode 101 is 6.0 g / cm or less, the current collecting ability is unlikely to decrease even if the active material layer 104 repeatedly expands and contracts due to the absorption and release of Li. 3 or more and 9.8g / cm 3 If the following densities are satisfied, the battery 1000 can have good cycle characteristics.

[0074] Furthermore, the active material layer 104 made of a Bi thin film that satisfies the above density range is an active material layer with a high active material density, and can provide sufficient electron conduction paths. Therefore, the first electrode 101 provided with the active material layer 104 made of a Bi thin film can achieve a higher capacity than an electrode in which the active material layer is formed of Bi powder. Therefore, when the active material contained in the active material layer 104 of the first electrode 101 is 6.0 g / cm 3 or more and 9.8g / cm 3 When the following density is satisfied, the battery 1000 of the present disclosure can achieve high capacity in addition to good cycle characteristics.

[0075] The density of the active material contained in the active material layer 104 is 6.5 g / cm 3 or more and 9.8g / cm 3 It may be less than 7.0 g / cm 3 or more and 9.8g / cm 3When the first electrode 101 includes the active material layer 104 containing such a higher density active material, the battery 1000 can have better cycle characteristics and a higher capacity.

[0076] The density of the active material contained in the active material layer 104 is 7.5 g / cm 3 or more and 9.8g / cm 3 In particular, it may be 7.5 g / cm 3 First electrode 101 including active material layer 104 containing the above-described high-density active material can further improve the cycle characteristics and capacity of battery 1000.

[0077] In the X-ray diffraction pattern of the active material layer 104 obtained by surface X-ray diffraction measurement using Cu-Kα radiation, when the height intensity of the maximum peak present in the diffraction angle 2θ range of 26° or more and 28° or less is defined as I(1) and the height intensity of the maximum peak present in the diffraction angle 2θ range of 37° or more and 39° or less is defined as I(2), the ratio of I(2) to I(1), I(2) / I(1), may be 0.29 or more.

[0078] Here, the maximum peak present in the diffraction angle 2θ range of 26° to 28° in the X-ray diffraction pattern corresponds to the peak derived from the (1,0,-1,2) plane of elemental Bi. Furthermore, the maximum peak present in the diffraction angle 2θ range of 37° to 39° in the X-ray diffraction pattern corresponds to the peak derived from the (1,0,-1,4) plane of elemental Bi. A peak intensity ratio I(2) / I(1) of 0.29 or greater indicates that the ratio of the (1,0,-1,4) plane to the (1,0,-1,2) plane of elemental Bi having a trigonal crystal structure of space group R-3m is high on the surface of the active material layer 104. This indicates that the orientation of the (1,0,-1,4) plane is stronger on the surface of the active material layer 104. An active material layer 104 having such orientation in the crystal structure of elemental Bi on its surface can have high adhesion to the current collector 100. Therefore, since the active material layer 104 has such surface orientation, the current collection performance is less likely to decrease even when the active material layer 104 repeatedly expands and contracts due to charging and discharging, and the battery 1000 of the present disclosure can have better cycle characteristics and higher capacity.

[0079] The peak intensity ratio I(2) / I(1) may be 0.57 or less.

[0080] According to the above configuration, better charge / discharge cycle characteristics can be obtained.

[0081] The X-ray diffraction pattern of active material layer 104 can be obtained by X-ray diffraction measurement by the θ-2θ method using Cu-Kα radiation with wavelengths of 1.5405 Å and 1.5444 Å, that is, wavelengths of 0.15405 nm and 0.15444 nm.

[0082] The diffraction angle of a peak in an X-ray diffraction pattern is defined as the angle at which the signal-to-noise ratio (i.e., the ratio of signal S to background noise N) is 1.3 or more and the peak width at half maximum is 10° or less. The half width is the maximum intensity of the X-ray diffraction peak. MAX When the intensity is I MAXThe width is expressed as the difference between the two diffraction angles that are half the value of the square root of the diffraction angle.

[0083] Active material layer 104, which contains Bi as the main component of the active material and is made of a Bi thin film that satisfies the density and surface orientation ranges described above, can be produced by, for example, electroplating. A method for producing first electrode 101 by producing active material layer 104 by electroplating is, for example, as follows.

[0084] First, a substrate for electroplating is prepared. In the case of the first electrode 101, for example, a current collector 100 serves as the substrate. As an example, copper foil is prepared as the current collector 100. After pre-degreasing the copper foil with an organic solvent, one side is masked and the foil is immersed in an acidic solvent for degreasing, thereby activating the copper foil surface. The activated copper foil is connected to a power source so that a current can be applied. The copper foil connected to the power source is immersed in a bismuth plating bath. The bismuth plating bath may contain, for example, Bi 3+ An organic acid bath containing ions and an organic acid is used. Then, a current is applied to the copper foil while controlling the current density and application time, thereby electroplating Bi on the unmasked surface of the copper foil. After electroplating, the copper foil is removed from the plating bath, washed with pure water, and dried. These methods yield a first electrode 101 equipped with an active material layer 104 formed by electroplating Bi. The bismuth plating bath used to form the active material layer 104 is not particularly limited and can be appropriately selected from known bismuth plating baths capable of depositing a thin film of simple Bi. The organic acid bath used in the bismuth plating bath may be an organic sulfonic acid bath, a gluconic acid and ethylenediaminetetraacetic acid (EDTA) bath, or a citric acid and EDTA bath. Alternatively, a sulfuric acid bath may be used as the bismuth plating bath. An additive may also be added to the bismuth plating bath.

[0085] Here, we will examine the relationship between the thickness of the active material layer produced by electroplating Bi and the density of the active material. Hereinafter, active material layer 104 produced by electroplating Bi may be referred to as an "active material layer made of a Bi-plated layer."

[0086] FIG. 2 is a graph showing the relationship between the thickness of an active material layer formed from a Bi plating layer and the density of the active material. The density of the active material in this case can be determined by measuring the density of the active material layer formed from the Bi plating layer. Samples of the active material layer formed from a Bi plating layer were prepared in the same manner as in Example 1 described below. However, the application time of current to the copper foil serving as the plating substrate was adjusted to target plating thicknesses of 1 μm, 3 μm, 5 μm, and 10 μm, and four active material layer samples were prepared. The relationship between the thickness of the active material layer and the density of the active material was determined from the mass, area, and thickness of the active material layer. The thickness of the obtained Bi plating layer was measured using an X-ray fluorescence analyzer (SEA6000VX, manufactured by Seiko Instruments Inc.). The thicknesses of the active material layer in the four samples were 1.5 μm, 4.5 μm, 6.2 μm, and 10 μm. As shown in the graph in FIG. 2, when the active material layer was a Bi plating layer, the density of the active material was 7.5 g / cm. 3 to 9.8 g / cm 3 It can be seen that

[0087] In addition, the surface structure of the active material layer made of Bi plating layer was analyzed by surface X-ray diffraction measurement. The sample of the active material layer made of Bi plating layer used for surface X-ray diffraction measurement was prepared in the same manner as the sample used to confirm the relationship between the thickness of the active material layer and the density of the active material. For comparison, X-ray diffraction measurement was also performed on Bi powder.

[0088] 3 is a graph showing an example of the X-ray diffraction patterns of an active material layer made of a Bi plating layer formed on a copper foil and of Bi powder. The X-ray diffraction pattern was measured from the surface of the Bi plating layer, i.e., in the thickness direction of active material layer 104, using an X-ray diffractometer (MiNi Flex, manufactured by RIGAKU) by the θ-2θ method using Cu-Kα rays with wavelengths of 1.5405 Å and 1.5444 Å.

[0089] Table 1 shows the calculated intensity ratio I(2) / I(1) between the maximum peak height intensity I(1) in the diffraction angle 2θ range of 26° to 28° and the maximum peak height intensity I(2) in the diffraction angle 2θ range of 37° to 39° in the X-ray diffraction patterns of Bi plating layers and Bi powder obtained by surface X-ray diffraction measurement using Cu-Kα radiation. Table 1 shows the measurement results for Bi plating layers of various thicknesses and three measurements of Bi powder.

[0090] [Table 1]

[0091] As shown in Table 1, the ratio I(2) / I(1) of the active material layer 104 fabricated by electroplating Bi is 0.29 or greater. Therefore, the surface of the active material layer 104 fabricated by electroplating Bi exhibits a higher ratio of the (1,0,-1,4) plane to the (1,0,-1,2) plane of the Bi element, which has a trigonal crystal structure with a space group of R-3m. This indicates that the (1,0,-1,4) plane is more strongly oriented on the surface of the active material layer 104. Furthermore, comparing the X-ray diffraction patterns of the Bi plating layer and the Bi powder in the X-ray diffraction patterns shown in FIG. 3, the peak intensity I(3) at a diffraction angle 2θ of 40° is higher in the Bi plating layer with a thickness of 3 μm or greater. This indicates that the Bi plating layer is oriented such that the (2,-1,-1,0) plane of the Bi element, which has a trigonal crystal structure with a space group of R-3m, is the surface. For Bi-plated layers with a thickness of less than 3 μm, the surface roughness of the copper foil substrate may have an influence, and it is thought that differences in the X-ray diffraction pattern due to orientation with Bi powder could not be fully confirmed.

[0092] Hereinafter, each component of the battery 1000 of this embodiment will be described in more detail, taking as an example a case where the first electrode 101 is a negative electrode and the second electrode 103 is a positive electrode.

[0093] [First electrode] As described above, the first electrode 101 has the current collector 100 and the active material layer 104. The active material layer 104 has the same configuration as described above. The first electrode 101 functions as a negative electrode. Therefore, the active material layer 104 contains a negative electrode active material that has the property of absorbing and releasing lithium ions. Bi contained in the active material layer 104 functions as a negative electrode active material. The active material layer 104 contains, for example, elemental Bi.

[0094] Bi is an active material that absorbs and releases lithium ions at 0.8 V relative to lithium. Bi is a metal that alloys with lithium. During charging, Bi forms an alloy with lithium, thereby absorbing lithium. That is, a lithium-bismuth alloy is generated in the first electrode 101 during charging of the battery 1000. The lithium-bismuth alloy generated includes, for example, at least one selected from the group consisting of LiBi and Li3Bi. That is, during charging of the battery 1000, the active material layer 104 includes, for example, at least one selected from the group consisting of LiBi and Li3Bi. During discharging of the battery 1000, lithium is released from the lithium-bismuth alloy, and the lithium-bismuth alloy returns to Bi.

[0095] The active material layer 104 may contain only simple Bi as the active material.

[0096] The active material layer 104 may not contain an electrolyte. For example, the active material layer 104 may be a layer made of simple Bi and / or a lithium-bismuth alloy that is generated during charging.

[0097] The active material layer 104 may be disposed in direct contact with the surface of the current collector 100 .

[0098] The active material layer 104 may be in the form of a thin film.

[0099] The active material layer 104 may be a plated layer formed by depositing Bi by plating. The active material layer 104 may be a Bi plated layer provided in direct contact with the surface of the current collector 100.

[0100] When the active material layer 104 is a plated layer provided in direct contact with the surface of the current collector 100, the active material layer 104 adheres closely to the current collector 100. This makes it possible to suppress deterioration in the current collection characteristics of the first electrode 101, which occurs when the active material layer 104 repeatedly expands and contracts. This further improves the cycle characteristics of the battery 1000. Furthermore, when the active material layer 104 is a plated layer, the active material layer 104 contains Bi, an active material, at a high density, which allows for even higher capacity to be achieved.

[0101] The active material layer 104 may contain materials other than Bi.

[0102] The active material layer 104 may further contain a conductive material.

[0103] Conductive materials include carbon materials, metals, inorganic compounds, and conductive polymers. Carbon materials include graphite, acetylene black, carbon black, ketjen black, carbon whiskers, needle coke, and carbon fibers. Graphite includes natural graphite and artificial graphite. Natural graphite includes lump graphite and flake graphite. Metals include copper, nickel, aluminum, silver, and gold. Inorganic compounds include tungsten carbide, titanium carbide, tantalum carbide, molybdenum carbide, titanium boride, and titanium nitride. These materials may be used alone or in combination.

[0104] The active material layer 104 may further contain a binder.

[0105] Examples of binders include fluorine-containing resins, thermoplastic resins, ethylene propylene diene monomer (EPDM) rubber, sulfonated EPDM rubber, and natural butyl rubber (NBR). Examples of fluorine-containing resins include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), and fluororubber. Examples of thermoplastic resins include polypropylene and polyethylene. These materials may be used alone or in combination.

[0106] The thickness of the active material layer 104 is not particularly limited and may be, for example, 1 μm or more and 100 μm or less.

[0107] The material of the current collector 100 is, for example, a metal or an alloy. More specifically, the material may be a metal or an alloy containing at least one selected from the group consisting of copper, chromium, nickel, titanium, platinum, gold, aluminum, tungsten, iron, and molybdenum. The current collector 100 may also be stainless steel.

[0108] The current collector 100 may include copper (Cu).

[0109] The current collector 100 may be in the form of a plate or foil. From the viewpoint of easily ensuring high conductivity, the negative electrode current collector may be a metal foil or a metal foil containing copper. Examples of metal foil containing copper include copper foil and copper alloy foil. The copper content in the metal foil may be 50% by mass or more, or may be 80% by mass or more. In particular, the metal foil may be a copper foil containing substantially only copper as the metal. The thickness of the current collector 100 may be, for example, 5 μm or more and 20 μm or less.

[0110] The current collector 100 may be a laminated film.

[0111] [Solid electrolyte layer] The solid electrolyte contained in the solid electrolyte layer 102 may be a halide solid electrolyte, a sulfide solid electrolyte, an oxide solid electrolyte, a polymer solid electrolyte, or a complex hydride solid electrolyte.

[0112] The solid electrolyte layer 102 may include a halide solid electrolyte.

[0113] The halide solid electrolyte refers to a solid electrolyte containing a halogen element. The halide solid electrolyte may contain not only a halogen element but also oxygen. The halide solid electrolyte does not contain sulfur (S).

[0114] The halide solid electrolyte may be a compound consisting of Li, M1, and X1. That is, the halide solid electrolyte may be, for example, a material represented by the following composition formula (2): Li α M1 β X1 γ ...Equation (2) Here, α, β, and γ are values ​​greater than 0, M1 is at least one selected from the group consisting of metal elements and metalloid elements other than Li, and X1 is at least one selected from the group consisting of F, Cl, Br, and I.

[0115] "Semi-metallic elements" are B, Si, Ge, As, Sb, and Te.

[0116] "Metal elements" are 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. In other words, this is a group of elements that can become cations when forming inorganic compounds with halogen compounds.

[0117] In the composition formula (2), M1 may include Y, and X1 may include Cl and Br.

[0118] Examples of halide solid electrolytes that may be used include Li3(Ca,Y,Gd)X16, Li2MgX4, Li2FeX14, Li(Al,Ga,In)X14, Li3(Al,Ga,In)X16, and LiI. In these solid electrolytes, the element X1 is at least one element selected from the group consisting of F, Cl, Br, and I. In the present disclosure, when an element in a formula is represented as "(Al,Ga,In)," this notation indicates at least one element selected from the group of elements in parentheses. In other words, "(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.

[0119] Another example of a halide solid electrolyte is Li a M2 b Y c a compound represented by X16. Here, a + mb + 3c = 6 and c > 0 are satisfied. M2 is at least one selected from the group consisting of a metal element other than Li and Y and a metalloid element. m represents the valence of M2. The "metalloid element" is B, Si, Ge, As, Sb, and Te. The "metal element" is all elements contained in Groups 1 to 12 of the periodic table (excluding hydrogen), and all elements contained in Groups 13 to 16 of the periodic table (excluding B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se).

[0120] To increase the ionic conductivity of the halide solid electrolyte material, M2 may be at least one selected from the group consisting of Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta, and Nb. The halide solid electrolyte may be Li3YCl6, Li3YBr6, or Li3YBr p Cl 6-p where p satisfies 0 < p < 6.

[0121] According to the above configuration, the ionic conductivity of the solid electrolyte layer 102 can be increased. Thereby, a decrease in the energy density of the battery can be reduced.

[0122] The solid electrolyte layer 102 may consist essentially of only a halide solid electrolyte. In this specification, "consisting essentially of" means that the inclusion of impurities with a content of less than 0.1% by mass is allowed. The solid electrolyte layer 102 may consist of only a halide solid electrolyte.

[0123] The solid electrolyte layer 102 may contain a sulfide solid electrolyte.

[0124] The sulfide solid electrolyte refers to a solid electrolyte containing sulfur (S). The sulfide solid electrolyte may contain not only sulfur but also a halogen element.

[0125] Examples of sulfide solid electrolytes include Li2S-P2S5, Li2S-SiS2, Li2S-B2S3, Li2S-GeS2, and Li 3.25 Ge 0.25 P 0.75 S4, or Li 10 GeP2S 12 etc. can be used.

[0126] The sulfide solid electrolyte may have an argyrodite-type crystal structure.

[0127] The sulfide solid electrolyte is Li 7-a AS 6-a X2 a Here, A is at least one selected from the group consisting of P and As, X2 is at least one selected from the group consisting of Cl, Br, and I, and a satisfies 0≦a≦1. 7-a AS 6-a X a is a sulfide solid electrolyte having an argyrodite-type crystal structure.

[0128] The sulfide solid electrolyte may be Li3PS5Cl, which is a sulfide solid electrolyte having an argyrodite-type crystal structure.

[0129] The above configuration can increase the ionic conductivity of the solid electrolyte layer 102. This can reduce the decrease in the energy density of the battery.

[0130] The solid electrolyte layer 102 may be made substantially only of a sulfide solid electrolyte. The solid electrolyte layer 102 may be made substantially only of a sulfide solid electrolyte.

[0131] The solid electrolyte layer 102 may contain an oxide solid electrolyte. Examples of oxide solid electrolytes include NASICON-type solid electrolytes such as LiTi2(PO4)3 and its element 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 typified by elemental substitution products thereof, Li3PO4 and its N-substituted products, and glasses or glass ceramics based on Li-BO compounds such as LiBO2 and Li3BO3 and to which Li2SO4, Li2CO3, etc. are added, can be used.

[0132] The solid electrolyte layer 102 may include a polymer solid electrolyte. Examples of the polymer solid electrolyte include a compound of a polymer compound and a lithium salt. The polymer compound may have an ethylene oxide structure. A polymer compound having an ethylene oxide structure can contain a large amount of lithium salt, which can further increase ionic conductivity. Examples of the lithium salt that can be used include LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), and LiC(SO2CF3)3. A single lithium salt selected from the exemplified lithium salts may be used. Alternatively, a mixture of two or more lithium salts selected from the exemplified lithium salts may be used.

[0133] The solid electrolyte layer 102 may include a complex hydride solid electrolyte, such as LiBH4-LiI or LiBH4-P2S5.

[0134] The solid electrolyte layer 102 may further contain a binder. The same materials as those usable for the active material layer 104 may be used as the binder.

[0135] The solid electrolyte layer 102 may have a thickness of 1 μm or more and 500 μm or less. When the solid electrolyte layer 102 has a thickness of 1 μm or more, the first electrode 101 and the second electrode 103 are less likely to short-circuit. When the solid electrolyte layer 102 has a thickness of 500 μm or less, the battery can operate at high power.

[0136] The shape of the solid electrolyte is not particularly limited. When the solid electrolyte is a powder material, its shape may be, for example, needle-like, spherical, oval-spherical, etc. For example, the shape of the solid electrolyte may be particulate.

[0137] For example, when the solid electrolyte is in the form of particles (for example, spheres), the median diameter of the solid electrolyte may be 100 μm or less, or may be 10 μm or less.

[0138] In the present disclosure, 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.

[0139] The solid electrolyte contained in the solid electrolyte layer 102 can be produced by the following method.

[0140] A raw material powder is prepared to have a desired composition, such as an oxide, hydroxide, halide, or oxyhalide.

[0141] For example, when the solid electrolyte is a halide solid electrolyte and the target composition is LiYBrCl, LiBr, YCl, and YBr are mixed in a molar ratio of about 3:0.66:0.33. The raw material powders may be mixed in a pre-adjusted molar ratio to compensate for composition changes that may occur during the synthesis process.

[0142] The raw material powders are reacted with each other mechanochemically (i.e., using a mechanochemical milling method) in a mixing device such as a planetary ball mill to obtain a reactant. The reactant may be fired in a vacuum or in an inert atmosphere. Alternatively, a mixture of the raw material powders may be fired in a vacuum or in an inert atmosphere to obtain a reactant. The firing is preferably carried out, for example, at a temperature of 100°C or higher and 300°C or lower for one hour or longer. In order to suppress compositional changes during firing, the raw material powders are preferably fired in a sealed container such as a quartz tube.

[0143] By these methods, the solid electrolyte of the solid electrolyte layer 102 is obtained.

[0144] When the solid electrolyte is a sulfide solid electrolyte, the sulfide solid electrolyte can be produced by the following method.

[0145] A raw material powder is prepared to have a desired composition.

[0146] For example, if the desired composition is Li6PS5Cl, Li2S, P2S5, and LiCl are mixed in a molar ratio of about 2.5:0.5:1. The raw material powders may be mixed in a pre-adjusted molar ratio to compensate for compositional changes that may occur during the synthesis process.

[0147] The raw material powders are pulverized and mixed in a mixing device such as a planetary ball mill, bead mill, or homogenizer. After drying the mixture, it is fired at 350°C or higher and 550°C or lower in an inert atmosphere or a hydrogen sulfide gas (HS) atmosphere. Firing is preferably carried out for, for example, 8 hours or longer. To suppress compositional changes during firing, the raw material powders are preferably fired in a sealed container such as a quartz tube. The fired product is then crushed or pulverized to a predetermined particle size to obtain a sulfide solid electrolyte.

[0148] [Second electrode] The second electrode 103 functions as a positive electrode. The second electrode 103 contains a material capable of occluding and releasing metal ions such as lithium ions. The said material is, for example, a positive electrode active material.

[0149] The second electrode 103 may have a current collector 105 and an active material layer 106. The active material layer 106 contains a positive electrode active material. The active material layer 106 is, for example, disposed between the current collector 105 and the solid electrolyte layer 102.

[0150] The active material layer 106 may be disposed directly on the surface of the current collector 105 and in direct contact with the current collector 105.

[0151] As the positive electrode active material, for example, a lithium-containing transition metal oxide, a transition metal fluoride, a polyanion material, a fluorinated polyanion material, a transition metal sulfide, a transition metal oxy-sulfide, or a transition metal oxy-nitride, etc. may be used. Examples of the lithium-containing transition metal oxide include LiNi 1-x-y Co x Al y O2 ((x + y) < 1), LiNi 1-x-y Co x Mn y O2 ((x + y) < 1) or LiCoO2, etc. are mentioned. In particular, when a lithium-containing transition metal oxide is used as the positive electrode active material, the manufacturing cost of the electrode can be reduced and the average discharge voltage of the battery can be increased. For example, the positive electrode active material may contain Li(Ni,Co,Mn)O2.

[0152] The second electrode 103 may contain a compound represented by the following compositional formula (1). LiNi x Me 1-x O2 ···(1) Here, x satisfies 0 < x ≤ 1, and Me is at least one element selected from the group consisting of Mn, Co, and Al. x may satisfy 0.5 ≤ x ≤ 1.

[0153] The compound represented by the above compositional formula (1) can function, for example, as a positive electrode active material.

[0154] Examples of materials for the current collector 105 include metal materials, such as copper, stainless steel, iron, and aluminum.

[0155] The second electrode 103 may include a solid electrolyte. As the solid electrolyte, any of the solid electrolytes exemplified as materials constituting the solid electrolyte layer 102 may be used.

[0156] The positive electrode active material may have a median diameter of 0.1 μm or more and 100 μm or less. When the positive electrode active material has a median diameter of 0.1 μm or more, the positive electrode active material and the solid electrolyte can form a well-dispersed state. This improves the charge / discharge characteristics of the battery. When the positive electrode active material has a median diameter of 100 μm or less, the lithium diffusion rate improves. This allows the battery to operate at high power.

[0157] The positive electrode active material may have a larger median diameter than the solid electrolyte, which allows the positive electrode active material and the solid electrolyte to be well dispersed.

[0158] From the viewpoint of the energy density and output of the battery, the ratio of the volume of the positive electrode active material to the total volume of the positive electrode active material and the solid electrolyte in second electrode 103 may be 0.30 or more and 0.95 or less.

[0159] A coating layer may be formed on the surface of the positive electrode active material to prevent the solid electrolyte from reacting with the positive electrode active material. This can suppress an increase in the reaction overvoltage of the battery. Examples of coating materials included in the coating layer include a sulfide solid electrolyte, an oxide solid electrolyte, or a halide solid electrolyte.

[0160] The thickness of the second electrode 103 may be 10 μm or more and 500 μm or less. When the thickness of the second electrode 103 is 10 μm or more, a sufficient energy density of the battery can be ensured. When the thickness of the second electrode 103 is 500 μm or less, the battery can operate at high power.

[0161] The second electrode 103 may include a conductive material to enhance electronic conductivity.

[0162] The second electrode 103 may contain a binder.

[0163] The conductive material and binder may be the same materials that can be used for the active material layer 104 .

[0164] The second electrode 103 may contain a non-aqueous electrolyte, a gel electrolyte, or an ionic liquid for the purpose of facilitating the transfer of lithium ions and improving the output characteristics of the battery.

[0165] The nonaqueous electrolyte contains a nonaqueous solvent and a lithium salt dissolved in the nonaqueous solvent. Examples of the nonaqueous solvent include a cyclic carbonate ester solvent, a chain carbonate ester solvent, a cyclic ether solvent, a chain ether solvent, a cyclic ester solvent, a chain ester solvent, or a fluorine solvent. Examples of the cyclic carbonate ester solvent are ethylene carbonate, propylene carbonate, or butylene carbonate. Examples of the chain carbonate ester solvent are dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate. Examples of the cyclic ether solvent are tetrahydrofuran, 1,4-dioxane, or 1,3-dioxolane. Examples of the chain ether solvent are 1,2-dimethoxyethane or 1,2-diethoxyethane. An example of the cyclic ester solvent is γ-butyrolactone. An example of the chain ester solvent is methyl acetate. Examples of fluorine-containing solvents include fluoroethylene carbonate, methyl fluoropropionate, fluorobenzene, fluoroethyl methyl carbonate, and fluorodimethylene carbonate. One non-aqueous solvent selected from these may be used alone. Alternatively, a mixture of two or more non-aqueous solvents selected from these may be used.

[0166] Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), and LiC(SO2CF3)3. One lithium salt selected from these may be used alone. Alternatively, a mixture of two or more lithium salts selected from these may be used. The concentration of the lithium salt is, for example, in the range of 0.5 mol / L to 2 mol / L.

[0167] The gel electrolyte may be a polymer material impregnated with a non-aqueous electrolyte, such as polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, or a polymer having an ethylene oxide bond.

[0168] Examples of cations contained in ionic liquids are: (i) aliphatic chain quaternary salts such as tetraalkylammonium or tetraalkylphosphonium; (ii) aliphatic cyclic ammoniums such as pyrrolidiniums, morpholiniums, imidazoliniums, tetrahydropyrimidiniums, piperaziniums, or piperidiniums, or (iii) Nitrogen-containing heterocyclic aromatic cations such as pyridiniums or imidazoliums.

[0169] An example of an anion found in ionic liquids is PF6 - , BF4 - , SbF6 - , AsF6 - , SO3CF3 - , N(SO2CF3)2 - , N(SO2C2F5)2 - , N(SO2CF3)(SO2C4F9) - , or C(SO2CF3)3 - is.

[0170] The ionic liquid may contain a lithium salt.

[0171] In the above, a configuration example in which the first electrode 101 is a negative electrode and the second electrode 103 is a positive electrode has been described, but the first electrode 101 may be a positive electrode and the second electrode 103 may be a negative electrode.

[0172] When the first electrode 101 is a positive electrode and the second electrode 103 is a negative electrode, the active material layer 104 is a positive electrode active material layer. That is, Bi contained in the active material layer 104 functions as a positive electrode active material. In this case, the second electrode 103, which is a negative electrode, is made of, for example, lithium metal.

[0173] The battery 1000 is basically composed of a first electrode 101, a solid electrolyte layer 102, and a second electrode 103, and is sealed in an airtight container to prevent air and moisture from entering. The shape of the battery 1000 may be a coin type, a cylindrical type, a square type, a sheet type, a button type, a flat type, a laminated type, or the like. [Example]

[0174] Hereinafter, the present disclosure will be described in detail using examples and reference examples. The following examples are merely examples, and the present disclosure is not limited to the following examples.

[0175] Example 1 <Preparation of the first electrode> As a pretreatment, copper foil (10 cm x 10 cm, thickness: 12 μm) was pre-degreased with an organic solvent, and then one side was masked and immersed in an acidic solvent to degrease the copper foil surface. Bismuth methanesulfonate was used as a soluble bismuth salt in 1.0 mol / L methanesulfonic acid. 3+ The plating bath was prepared by adding ions to a concentration of 0.18 mol / L. The activated copper foil was connected to a power source so that a current could be applied, and then immersed in the plating bath. Then, the current density was increased to 2 A / dm 2By controlling the temperature to 100°C, Bi was electroplated onto the unmasked copper foil surface to a thickness of approximately 1 μm. After electroplating, the copper foil was recovered from the acid bath, the masking was removed, and the foil was washed with pure water, dried, and punched out into a size of 2 cm x 2 cm to obtain a first electrode. That is, the first electrode of Example 1 had a configuration in which an active material layer made of a Bi plating layer was provided on a current collector made of copper foil. In the first electrode of Example 1, the density of the active material contained in the active material layer made of a Bi plating layer could be determined from the graph of FIG. 2 and was 7.5 g / cm 3 The X-ray diffraction pattern obtained by surface X-ray diffraction measurement of the active material layer made of the Bi plating layer is shown in FIG. 3, and the peak intensity ratio I(2) / I(1) is shown in Table 1. In the active material layer of the battery according to Example 1, the peak intensity ratio I(2) / I(1) was 0.29 or more.

[0176] <Preparation of solid electrolyte> In an argon atmosphere with a dew point of -60°C or less (hereinafter referred to as a "dry argon atmosphere"), raw material powders containing LiBr, YCl3, and YBr3 were prepared in a molar ratio of LiBr:YCl3:YBr3 = 3:2 / 3:1 / 3. These raw material powders were ground and mixed in a mortar to obtain a mixed powder. The resulting raw material powder mixture was then fired in an electric furnace in a dry argon atmosphere at 500°C for 3 hours to obtain a fired product. The fired product was then ground in the mortar with a pestle. In this way, a solid electrolyte having the composition Li3YBr4Cl2 was obtained.

[0177] <Preparation of test cell> The resulting first electrode was placed in an insulating outer cylinder with an inner diameter of 9.4 mm as the working electrode. Solid electrolyte Li3YBr4Cl2 (80 mg) was then laminated on the Bi-plated surface of the working electrode. Next, an indium-lithium alloy (molar ratio In:Li = 1:1) (200 mg) was laminated as the counter electrode, resulting in a laminate. The indium-lithium alloy was produced by pressing a small piece of lithium foil onto an indium foil and diffusing lithium into the indium. A pressure of 360 MPa was applied to this laminate, forming a working electrode, a solid electrolyte layer, and a counter electrode. In the laminate, the first electrode (working electrode) was 1.5 μm thick, the solid electrolyte layer was 500 μm thick, and the counter electrode was 15 μm thick.

[0178] Next, current collectors made of stainless steel were attached to the working electrode and counter electrode, and current collecting leads were attached to the current collectors.

[0179] Finally, an insulating ferrule was used to isolate the inside of the insulating outer cylinder from the outside atmosphere, and the inside of the cylinder was sealed.

[0180] As a result, a test cell of Example 1 was obtained, in which a first electrode having an active material layer formed from a Bi plating layer was used as the working electrode and a lithium-indium alloy was used as the counter electrode. The test cell prepared here is a single-electrode test cell using a working electrode and a counter electrode, and is used to test the performance of one electrode in a secondary battery. Specifically, the electrode under test was used as the working electrode, and an appropriate active material in an amount sufficient to cover the reaction at the working electrode was used as the counter electrode. Since this test cell was used to test the performance of the first electrode as a negative electrode, a large excess of lithium-indium alloy was used as the counter electrode, as is commonly used. The negative electrode whose performance was tested using such a test cell can be used as a secondary battery, for example, by combining it with a positive electrode containing a positive electrode active material such as that described in the above embodiment, such as a Li-containing transition metal oxide.

[0181] <Charge / discharge test> The charge-discharge test of the fabricated test cell was carried out under the following conditions. The theoretical capacity of Bi was 384 mAh / g, and the charge-discharge rate was 0.5 I / T based on the electrode weight. + / Li), then charge to 1.38V (2.0V vs Li + / Li), then discharge to 0V (0.62V vs Li + The test cell was charged to a capacity of 1000 mAh / g (1 / Li). The test was performed at 25°C in a thermostatic chamber. FIG. 4 is a graph showing the results of a charge / discharge test of the test cell according to Example 1. The initial charge capacity was about 380 mAh / g. The subsequent discharge capacity and charge capacity were about 300 mAh / g.

[0182] <Charge-discharge cycle test> The test cells thus fabricated were subjected to a charge-discharge cycle test, with one cycle consisting of charge and discharge, under the same conditions as those used in the charge-discharge test, to evaluate their cycle characteristics. Figure 5 is a graph showing the results of the charge-discharge cycle test for the test cell according to Example 1. It can be seen from Figure 5 that a charge-discharge capacity of 300 mAh / g or more was maintained even after 300 cycles. This charge-discharge capacity corresponds to 78% or more of the theoretical capacity of Bi, 384 mAh / g.

[0183] Example 2 <Preparation of test cell> A test cell of Example 2 was obtained in the same manner as the test cell of Example 1.

[0184] <Charge / discharge test> The charge-discharge test of the fabricated test cell was carried out under the following conditions. The theoretical capacity of Bi was 384 mAh / g, and the charge-discharge rate was 0.037 I / T based on the electrode weight. + / Li), then charge to 1.38V (2.0V vs Li + / Li), and then discharge to 0V (0.62V vs Li +The test cell was charged to a capacity of 1000 mAh / g (1 / Li). The test was performed at 25°C in a thermostatic chamber. Figure 6 shows the results of the charge / discharge test of the test cell according to Example 2. The initial charge capacity was about 380 mAh / g. The subsequent discharge capacity and charge capacity were about 370 mAh / g.

[0185] <Charge-discharge cycle test> The test cell thus fabricated was subjected to a charge-discharge cycle test under the same conditions as those used in the charge-discharge test, with one cycle consisting of charge and discharge. Figure 7 shows the results of the charge-discharge cycle test for the test cell according to Example 2. It can be seen that even after 30 cycles, a charge-discharge capacity of 350 mAh / g or more, which is 90% or more of the theoretical capacity of Bi, 384 mAh / g, was maintained.

[0186] Example 3 <Preparation of test cell> A test cell of Example 3 was obtained in the same manner as the battery of Example 1, except that the solid electrolyte Li3YBr4Cl2 (80 mg) was replaced with a sulfide solid electrolyte Li6PS5Cl (manufactured by Ampcera, 80 mg).

[0187] <Charge / discharge test> The charge-discharge test of the fabricated test cell was carried out under the following conditions: The theoretical capacity of Bi was 384 mAh / g, and the charge-discharge rate was 0.5 I / T based on the electrode weight. + / Li), then charge to 1.38V (2.0V vs Li + / Li), then discharge to 0V (0.62V vs Li + The test cell was charged to a capacity of 1000 mAh / g (1000 mAh / Li). The test was performed at 25°C in a thermostatic chamber. Figure 8 is a graph showing the results of a charge / discharge test of the test cell according to Example 3. The initial charge capacity was about 378 mAh / g. The subsequent discharge capacity and charge capacity were about 300 mAh / g.

[0188] <Charge-discharge cycle test> The test cells thus fabricated were subjected to a charge-discharge cycle test, with one cycle consisting of charge and discharge, under the same conditions as those used in the charge-discharge test, to evaluate their cycle characteristics. Figure 9 is a graph showing the results of the charge-discharge cycle test for the test cell according to Example 3. It can be seen from Figure 9 that a charge-discharge capacity of 375 mAh / g or more was maintained even after 200 cycles. This charge-discharge capacity corresponds to 97% or more of the theoretical capacity of Bi, 384 mAh / g.

[0189] Example 4 A test cell of Example 4 was obtained in the same manner as the test cell of Example 3.

[0190] <Charge / discharge test> The charge-discharge test of the fabricated test cell was carried out under the following conditions. The theoretical capacity of Bi was 384 mAh / g, and the charge-discharge rate was 0.037 I / T based on the electrode weight. + / Li), then charge to 1.38V (2.0V vs Li + / Li), and then discharge to 0V (0.62V vs Li + The test cell was charged to a capacity of 1000 mAh / g (1 / Li). The test was performed at 25°C in a thermostatic chamber. Figure 10 shows the results of the charge / discharge test of the test cell according to Example 4. The initial charge capacity was about 384 mAh / g. The subsequent discharge capacity and charge capacity were about 370 mAh / g.

[0191] <Charge-discharge cycle test> The test cell thus fabricated was subjected to a charge-discharge cycle test under the same conditions as those in the charge-discharge test, with one cycle consisting of charge and discharge. Figure 11 shows the results of the charge-discharge cycle test for the test cell according to Example 4. It can be seen that even after 20 cycles, a charge-discharge capacity of 375 mAh / g or more, which is 97% or more of the theoretical capacity of Bi, 384 mAh / g, was maintained.

[0192] Example 5 <Preparation of the first electrode (negative electrode)> As a pretreatment, copper foil (10 cm x 10 cm, thickness: 10 μm) was pre-degreased with an organic solvent, and then one side was masked and immersed in an acidic solvent to degrease the copper foil surface. Bismuth methanesulfonate was used as a soluble bismuth salt in 1.0 mol / L methanesulfonic acid. 3+ The plating bath was prepared by adding ions to a concentration of 0.18 mol / L. The activated copper foil was connected to a power source so that a current could be applied, and then immersed in the plating bath. Then, the current density was increased to 2 A / dm 2 By controlling the temperature, Bi was electroplated to a thickness of approximately 5 μm on the unmasked copper foil surface. After electroplating, the copper foil was removed from the acid bath, the masking was removed, and the copper foil was washed with pure water and dried. The resulting copper foil and Bi-plated layer laminate was then punched out to a diameter of 0.92 cm to obtain a negative electrode as the first electrode.

[0193] <Preparation of solid electrolyte> In the same manner as in Example 1, a solid electrolyte having a composition of Li3YBr4Cl2 was prepared.

[0194] <Preparation of the second electrode (positive electrode)> A positive electrode serving as a second electrode was prepared as follows.

[0195] The positive electrode active material was prepared by coprecipitation. 0.60 Co 0.20 Mn 0.20 The hydroxide represented by the formula [(OH)2] was calcined at 500°C to obtain a nickel-cobalt-manganese composite oxide. The composite oxide obtained by the coprecipitation method and lithium hydroxide LiOH were dry mixed to a molar ratio of Li / Me of 1.1, and the mixture was heated to 1000°C in an oxygen atmosphere and calcined for 10 hours. The elemental ratio of the calcined mixture was determined using an inductively coupled plasma optical emission spectrometer CIROS120 (manufactured by SPECTRO). The calculated elemental ratio was Li:Ni:Co:Mn=1.04:0.59:0.20:0.19.

[0196] The positive electrode was fabricated by coating a slurry containing the positive electrode active material onto aluminum foil in an argon atmosphere. The positive electrode active material slurry was prepared by mixing the positive electrode active material with a solid electrolyte, a conductive additive, and a binder in an argon atmosphere and dissolving the resulting mixture in tetralin. Li3YBr4Cl2 was used as the solid electrolyte. VGCF® carbon nanofiber manufactured by Showa Denko K.K. was used as the conductive additive. Tuftec® N504 hydrogenated styrene-based thermoplastic elastomer (SEBS) manufactured by Asahi Kasei Corporation was used as the binder. The positive electrode active material, solid electrolyte, conductive additive, and binder were mixed in a mass ratio of 75.8:21.4:0.8:2.0 in the slurry.

[0197] The slurry was applied to one side of a 10 μm thick aluminum foil as a positive electrode current collector. The positive electrode sheet with the slurry applied to the positive electrode current collector was dried and pressed. The resulting positive electrode sheet was then punched out to a size of φ0.92 cm to obtain a positive electrode.

[0198] <Preparation of test cell> The resulting positive and negative electrodes, each measuring 0.92 cm in diameter, were stacked in an insulating outer cylinder having an inner diameter of 9.4 mm, with the surfaces containing the active material facing each other and with 80 mg of solid electrolyte Li3YBr4Cl2 disposed between the positive electrode active material layer and the negative electrode active material layer. A pressure of 360 MPa was applied to the resulting stack in the stacking direction to form a stack consisting of a positive electrode, a solid electrolyte layer, and a negative electrode. In this stack, the positive electrode was 22 μm thick, the solid electrolyte layer was 400 μm thick, and the negative electrode was 16.5 μm thick.

[0199] Next, current collectors made of stainless steel were attached to the positive and negative electrodes, and current collecting leads were attached to the current collectors.

[0200] Finally, an insulating ferrule was used to isolate the inside of the insulating outer cylinder from the outside atmosphere, and the inside of the cylinder was sealed.

[0201] As a result of the above, a test cell of Example 5 was obtained, in which the first electrode, which was an electrode having an active material layer made of a Bi plating layer, served as a negative electrode, and the second electrode served as a positive electrode.

[0202] <Charge / discharge test> A charge / discharge test was performed on the prepared test cell under the following conditions. In the test cell, the capacity of the positive electrode active material in the positive electrode was assumed to be 200 mAh / g, and the charge / discharge test was performed at a constant current value at which the charge / discharge rate IT = 0.01, as defined by the positive electrode active material. In the charge / discharge test, the test cell was charged to 3.9 V and then discharged to 1.5 V. This charge / discharge test was performed in a thermostatic chamber at 85°C. FIG. 12 is a graph showing the results of the charge / discharge test on the test cell according to Example 5.

[0203] <Charge-discharge cycle test> The test cells thus prepared were subjected to a charge-discharge cycle test under the same conditions as those in the charge-discharge test, with one cycle consisting of charge and discharge. Fig. 13 shows the results of the charge-discharge cycle test for the test cell according to Example 5. Fig. 13 also shows the discharge capacity retention rate up to 5 cycles relative to the initial discharge capacity in the charge-discharge cycle test. The cell of Example 5 maintained 89% or more of its initial discharge capacity even after 5 cycles.

[0204] Example 6 <Preparation of the first electrode (negative electrode)> In the same manner as in Example 5, a negative electrode was produced as a first electrode.

[0205] <Solid electrolyte> The sulfide solid electrolyte Li6PS5Cl manufactured by Ampcera was used as the solid electrolyte.

[0206] <Preparation of the second electrode (positive electrode)> In the slurry containing the positive electrode active material, the positive electrode active material, solid electrolyte, conductive additive, and binder were mixed in a mass ratio of positive electrode active material:solid electrolyte:conductive additive:binder=81.0:16.2:0.8:2.0. A positive electrode serving as a second electrode was fabricated in the same manner as in Example 5, except for this point.

[0207] <Preparation of test cell> The resulting positive and negative electrodes, each measuring 0.92 cm in diameter, were stacked in an insulating outer cylinder with an inner diameter of 9.4 mm, with the surfaces containing the active material facing each other and with 80 mg of solid electrolyte Li6PS5Cl disposed between the positive and negative active material layers. A pressure of 360 MPa was applied to the resulting stack in the stacking direction to form a stack consisting of a positive electrode, a solid electrolyte layer, and a negative electrode. In this stack, the positive electrode was 22 μm thick, the solid electrolyte layer was 400 μm thick, and the negative electrode was 16.5 μm thick.

[0208] Next, current collectors made of stainless steel were attached to the positive and negative electrodes, and current collecting leads were attached to the current collectors.

[0209] Finally, an insulating ferrule was used to isolate the inside of the insulating outer cylinder from the outside atmosphere, and the inside of the cylinder was sealed.

[0210] As a result of the above, a test cell of Example 6 was obtained, in which the first electrode, which was an electrode having an active material layer made of a Bi plating layer, served as a negative electrode, and the second electrode served as a positive electrode.

[0211] <Charge-discharge cycle test> A charge / discharge test was performed on the prepared test cell under the following conditions. In the test cell, the capacity of the positive electrode active material in the positive electrode was assumed to be 200 mAh / g, and the charge / discharge test was performed at a constant current value at which the charge / discharge rate IT = 0.01, as defined by the positive electrode active material. In the charge / discharge test, the test cell was charged to 3.9 V and then discharged to 1.5 V. This charge / discharge test was performed in a thermostatic chamber at 85°C. FIG. 14 is a graph showing the results of the charge / discharge test on the test cell according to Example 6.

[0212] <Charge-discharge cycle test> The test cells thus fabricated were subjected to a charge-discharge cycle test under the same conditions as those in the charge-discharge test, with one cycle consisting of charge and discharge. Figure 15 shows the results of the charge-discharge cycle test for the test cell according to Example 6. Figure 15 also shows the discharge capacity retention rate up to five cycles relative to the initial discharge capacity in the charge-discharge cycle test. The cell of Example 6 maintained 93% or more of its initial discharge capacity even after five cycles.

[0213] Example 7 <Preparation of the first electrode (negative electrode)> In the same manner as in Example 5, a negative electrode was produced as a first electrode.

[0214] <Preparation of solid electrolyte> In the same manner as in Example 1, a solid electrolyte having a composition of Li3YBr4Cl2 was prepared.

[0215] <Preparation of the second electrode (positive electrode)> A positive electrode serving as a second electrode was prepared as follows.

[0216] The positive electrode active material was prepared by coprecipitation. 0.80 Co 0.15 Mn 0.05 The hydroxide represented by the formula [(OH)2] was calcined at 500°C to obtain a nickel-cobalt-manganese composite oxide. The composite oxide obtained by the coprecipitation method and lithium hydroxide LiOH were dry mixed to a molar ratio of Li / Me = 1.1, and the mixture was heated to 1000°C in an oxygen atmosphere and calcined for 10 hours. The elemental ratio of the calcined mixture was determined using an inductively coupled plasma optical emission spectrometer CIROS120 (manufactured by SPECTRO). The calculated elemental ratio was Li:Ni:Co:Mn = 1.04:0.81:0.15:0.04.

[0217] In an argon glove box, the prepared lithium nickel cobalt manganese composite oxide was mixed with niobium ethoxide (Sigma-Aldrich) and lithium ethoxide (Sigma-Aldrich), and the resulting mixture was dissolved in ultra-dehydrated ethanol (Fujifilm Wako Pure Chemical Industries, Ltd.) to prepare a coating solution. The mass ratio of the lithium nickel cobalt manganese composite oxide, niobium ethoxide, and lithium ethoxide in the coating solution was lithium nickel cobalt manganese composite oxide:niobium ethoxide:lithium ethoxide = 6.1:1.

[0218] The prepared lithium nickel cobalt manganese composite oxide was placed in a mortar, the above coating solution was added thereto, and after mixing, the ethanol was evaporated to obtain a powder. The obtained powder was fired at 350°C for 3 hours to obtain a lithium nickel cobalt manganese composite oxide coated with lithium niobate. This lithium nickel cobalt manganese composite oxide coated with lithium niobate was used as the positive electrode active material.

[0219] The positive electrode was fabricated by coating a slurry containing the positive electrode active material onto aluminum foil in an argon atmosphere. The positive electrode active material slurry was prepared by mixing the positive electrode active material with a solid electrolyte, a conductive additive, and a binder in an argon atmosphere and dissolving the resulting mixture in tetralin. Li3YBr4Cl2 was used as the solid electrolyte. VGCF® carbon nanofiber manufactured by Showa Denko K.K. was used as the conductive additive. Tuftec® N504 hydrogenated styrene-based thermoplastic elastomer (SEBS) manufactured by Asahi Kasei Corporation was used as the binder. The positive electrode active material, solid electrolyte, conductive additive, and binder were mixed in a mass ratio of 80.4:16.8:0.8:2.0 (positive electrode active material:solid electrolyte:conductive additive:binder).

[0220] The slurry was applied to one side of a 10 μm thick aluminum foil as a positive electrode current collector. The positive electrode sheet with the slurry applied to the positive electrode current collector was dried and pressed. The resulting positive electrode sheet was then punched out to a size of φ0.92 cm to obtain a positive electrode.

[0221] <Preparation of test cell> The resulting positive and negative electrodes, each measuring 0.92 cm in diameter, were stacked in an insulating outer cylinder having an inner diameter of 9.4 mm, with the surfaces containing the active material facing each other and with 80 mg of solid electrolyte Li3YBr4Cl2 disposed between the positive electrode active material layer and the negative electrode active material layer. A pressure of 360 MPa was applied to the resulting stack in the stacking direction to form a stack consisting of a positive electrode, a solid electrolyte layer, and a negative electrode. In this stack, the positive electrode was 22 μm thick, the solid electrolyte layer was 400 μm thick, and the negative electrode was 16.5 μm thick.

[0222] Next, current collectors made of stainless steel were attached to the positive and negative electrodes, and current collecting leads were attached to the current collectors.

[0223] Finally, an insulating ferrule was used to isolate the inside of the insulating outer cylinder from the outside atmosphere, and the inside of the cylinder was sealed.

[0224] As a result of the above, a test cell of Example 7 was obtained, in which the first electrode, which was an electrode having an active material layer made of a Bi plating layer, served as a negative electrode, and the second electrode served as a positive electrode.

[0225] <Charge / discharge test> A charge / discharge test was performed on the prepared test cell under the following conditions. In the test cell, the capacity of the positive electrode active material in the positive electrode was assumed to be 200 mAh / g, and the charge / discharge test was performed at a constant current value at which the charge / discharge rate IT = 0.01, as defined by the positive electrode active material. In the charge / discharge test, the test cell was charged to 3.9 V and then discharged to 1.5 V. This charge / discharge test was performed in a thermostatic chamber at 85°C. FIG. 16 is a graph showing the results of the charge / discharge test on the test cell according to Example 7.

[0226] <Charge-discharge cycle test> The test cells thus fabricated were subjected to a charge-discharge cycle test under the same conditions as those in the charge-discharge test, with one cycle consisting of charge and discharge. Fig. 17 shows the results of the charge-discharge cycle test for the test cell according to Example 7. Fig. 17 also shows the discharge capacity retention rate up to 10 cycles relative to the initial discharge capacity in the charge-discharge cycle test. The cell of Example 7 maintained 80% or more of its initial discharge capacity even after 10 cycles.

[0227] (Reference example 1) <Preparation of the first electrode> In the same manner as in Example 1, a first electrode was prepared by plating one surface of a copper foil (2 cm×2 cm, thickness: 12 μm) with Bi to a thickness of 1 μm.

[0228] <Preparation of test cell> The first electrode was used as the working electrode. A 0.34 μm thick Li metal was used as the counter electrode. The Li metal was doubly coated with a microporous separator (Asahi Kasei, Celgard 3401). A solution of LiPF6 dissolved in vinylene carbonate (VC) at a concentration of 1.0 mol / L was prepared as the electrolyte. In this way, the test cell of Reference Example 1 was obtained.

[0229] <Charge-discharge cycle test> The test cell of Reference Example 1 was charged at 0 V (vs Li + / Li), then charge to 2.0V (vsLi + The battery was discharged to a current of 0.6 mA (0.15 mA / cm). This constitutes one cycle, and a charge-discharge cycle test was carried out up to 25 cycles. The battery was tested in a thermostatic chamber at 25°C. 2 ) corresponds to a constant current value of 0.5 IT.

[0230] (Reference example 2) <Preparation of test cell> A test cell of Reference Example 2 was obtained in the same manner as the test cell of Reference Example 1, except that the solvent of the electrolyte was changed to fluoroethylene carbonate (FEC).

[0231] <Charge-discharge cycle test> In the same manner as in Reference Example 1, the test cell of Reference Example 2 was subjected to a charge-discharge cycle test.

[0232] Fig. 18 shows the results of charge-discharge cycle tests on the batteries according to Reference Examples 1 and 2. As shown in Fig. 18, the capacity of the batteries according to Reference Examples 1 and 2 decreased to one-third or less of the initial capacity after about 20 cycles. This is thought to be because repeated charge-discharge cycles cause the Bi plating layer to expand and contract repeatedly, which allows the nonaqueous electrolyte to enter cavities formed in the active material layer made of the Bi plating layer, destroying the structure of the active material layer and reducing the electron conduction paths in the active material layer.

[0233] These results demonstrate that the use of a solid electrolyte in the electrolyte layer significantly improves the cycle characteristics of the battery. In this example, the halide solid electrolyte Li3YBr4Cl2 was used, but similar effects can be expected to be obtained with other common solid electrolytes. [Industrial Applicability]

[0234] The battery of the present disclosure can be used, for example, as an all-solid-state lithium secondary battery. [Explanation of symbols]

[0235] 1000 batteries 100 Current Collector 101 First electrode 102 Solid electrolyte layer 103 Second electrode 104 Active material layer 105 Current collector 106 Active material layer

Claims

1. A first electrode; A second electrode; a solid electrolyte layer located between the first electrode and the second electrode; Equipped with the first electrode has a current collector and an active material layer located between the current collector and the solid electrolyte layer, the current collector contains Cu, the active material layer contains Bi as a main component of the active material, the active material layer is a plating layer, In an X-ray diffraction pattern of the active material layer obtained by surface X-ray diffraction measurement using Cu-Kα radiation, when the height intensity of the maximum peak present in a diffraction angle 2θ range of 26° to 28° is defined as I(1) and the height intensity of the maximum peak present in a diffraction angle 2θ range of 37° to 39° is defined as I(2), the ratio of I(2) to I(1), I(2) / I(1), is 0.29 or more, the first electrode is a negative electrode, the second electrode is a positive electrode, the solid electrolyte layer includes at least one selected from the group consisting of sulfur-free halide solid electrolytes and sulfide solid electrolytes, Lithium secondary battery.

2. the halide solid electrolyte is a compound consisting of Li, M1, and X1; M1 is at least one selected from the group consisting of metal elements and metalloid elements other than Li, 2. The lithium secondary battery according to claim 1, wherein X1 is at least one selected from the group consisting of F, Cl, Br, and I.

3. M1 includes Y, X1 includes Cl and Br; The lithium secondary battery according to claim 2 .

4. The solid electrolyte layer is composed substantially of a sulfide solid electrolyte. The lithium secondary battery according to claim 1 .

5. The sulfide solid electrolyte has an argyrodite-type crystal structure. The lithium secondary battery according to claim 1 .

6. The composition formula of the sulfide solid electrolyte is Li 7-a A.S. 6-a X2 a That is, The lithium secondary battery according to claim 1 . Here, A is at least one selected from the group consisting of P and As, X2 is at least one selected from the group consisting of Cl, Br, and I, and a satisfies 0≦a≦1.

7. The composition formula of the sulfide solid electrolyte is Li 6 P.S. 5 Cl, The lithium secondary battery according to claim 1 .

8. The density of the active material is 6.0 g / cm 3 or more and 9.8 g / cm 3 Below is the The lithium secondary battery according to any one of claims 1 to 7. Here, the density of the active material is the density of the active material when the battery is in a fully discharged state.

9. The density of the active material is 7.5 g / cm 3 or more and 9.8 g / cm 3 Below is the The lithium secondary battery according to claim 8.

10. The I(2) / I(1) is 0.57 or less. The lithium secondary battery according to claim 1 .

11. The active material layer contains simple Bi. The lithium secondary battery according to any one of claims 1 to 10.

12. The active material layer is made of LiBi and Li 3 Bi, The lithium secondary battery according to any one of claims 1 to 11.

13. the active material layer contains only simple Bi as an active material; The lithium secondary battery according to any one of claims 1 to 12.

14. The active material layer does not contain an electrolyte. The lithium secondary battery according to any one of claims 1 to 13.

15. The second electrode contains a compound represented by the following composition formula (1): The lithium secondary battery according to any one of claims 1 to 14. LiNi x Me 1-x Oh 2 ・・・(1) Here, x satisfies 0<x≦1, and Me is at least one element selected from the group consisting of Mn, Co, and Al.

16. x satisfies 0.5≦x≦1; The lithium secondary battery according to claim 15.

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