All-solid-state lithium batteries

Abstract

A solid-state lithium battery is provided, capable of suppressing short circuits caused by the ramping of metallic Li at the outer peripheral end face. The solid-state lithium battery comprises a negative electrode layer, a solid electrolyte layer, and a positive electrode layer stacked sequentially. At least a portion of the outer peripheral end face of the solid electrolyte layer is provided with a Li-encapsulated solid, which exhibits Li reactivity.

Description

Technical Field

[0001] This application relates to all-solid-state lithium batteries. Background Technology

[0002] Lithium-ion batteries are used in a wide range of fields due to their high voltage and high energy capacity. Liquid-based batteries have long been known as lithium-ion batteries, but in recent years, all-solid-state batteries, which have the advantage of easily simplifying safety devices compared to liquid-based batteries with electrolytes containing flammable organic solvents, have been under development.

[0003] On the other hand, due to repeated charging and discharging, lithium dendrites grow in the negative electrode binder layer of all-solid-state batteries, sometimes reaching the positive electrode active material layer and causing internal short circuits. To address this problem, Patent Document 1 discloses the following technology.

[0004] Patent Document 1 discloses a lithium secondary battery having a structure in which a positive electrode active material layer, a separator layer, and a negative electrode active material layer are stacked in sequence. The negative electrode active material layer contains metallic lithium. The separator layer has a shut-off layer and one or more solid electrolyte layers. One of the solid electrolyte layers is adjacent to the negative electrode active material layer. Furthermore, the shut-off layer contains a lithium-ion conductive liquid, which reacts with metallic lithium to form an electronic insulator. The lithium secondary battery in Patent Document 1, by setting the separator layer as a two-layer structure consisting of a solid electrolyte layer and a shut-off layer, and by providing a shut-off layer on the positive electrode active material layer side, suppresses the short circuit that would occur when metallic Li deposited from the negative electrode active material layer reaches the positive electrode active material layer.

[0005] Prior art literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2020-53172 Summary of the Invention

[0007] It is known that short circuits caused by Li climbing up from the negative electrode binder layer preferentially occur at the outer peripheral end face. Therefore, it is important to suppress short circuits caused by Li climbing up from the outer peripheral end face.

[0008] While Patent Document 1's technology is believed to suppress short circuits caused by Li metal climbing up from the outer peripheral end face, this effect is difficult to maintain in battery structures. For example, when the negative electrode active material uses Si or graphite, which have expansion and contraction properties, prolonged or rapid charge-discharge cycles cause the gap between the shut-off layer and its adjacent layers to act like a pump, allowing the lithium-ion conductive liquid held inside the shut-off layer to leak to the outside. Furthermore, it is believed that this leakage becomes even greater when the battery is constrained with high voltage to reduce resistance. Moreover, when the lithium-ion conductive liquid leaks to the outside, the short-circuit suppression effect decreases, failing to achieve the initially expected effect. Therefore, the technology in Patent Document 1 has room for improvement.

[0009] Therefore, the purpose of this application is to provide an all-solid-state lithium battery that can suppress short circuits caused by the climbing of metallic Li on the outer peripheral end face, in view of the above-mentioned actual situation.

[0010] As one of the means to solve the above-mentioned problems, this disclosure provides an all-solid-state lithium battery, which is formed by sequentially stacking a negative electrode mixture layer, a solid electrolyte layer and a positive electrode mixture layer, and at least a portion of the outer peripheral end face of the solid electrolyte layer is provided with a Li-encapsulated solid, which has Li reactivity.

[0011] In the aforementioned all-solid-state lithium battery, the outer peripheral surfaces of the negative electrode binder layer, the solid electrolyte layer, and the positive electrode binder layer can be flush with each other. Furthermore, the Li-encapsulated solid can be disposed on the outer peripheral surface of the solid electrolyte layer, near the negative electrode binder layer.

[0012] Furthermore, the aforementioned all-solid-state lithium battery can include a negative electrode current collector and a positive electrode current collector. The negative electrode current collector is disposed on the surface of the negative electrode mixture layer opposite to the solid electrolyte layer, and the positive electrode current collector is disposed on the surface of the positive electrode mixture layer opposite to the solid electrolyte layer. The negative electrode current collector has a negative electrode current collector tab, and the positive electrode current collector has a positive electrode current collector tab. The negative electrode current collector tab and the positive electrode current collector tab are disposed from the same outer peripheral end face. The Li-encapsulated solid is disposed on the outer peripheral end face of the solid electrolyte layer, on the outer peripheral end face where the negative electrode current collector tab and the positive electrode current collector tab are disposed. In addition, the Li-encapsulated solid can be disposed circumferentially throughout the outer peripheral end face of the solid electrolyte layer.

[0013] According to the all-solid-state lithium battery disclosed herein, short circuits caused by the climbing of metallic Li from the outer peripheral end face can be suppressed. Attached Figure Description

[0014] Figure 1 This diagram illustrates the short circuit caused by the metal Li climbing up from the outer peripheral end face.

[0015] Figure 2 This is a cross-sectional view of the all-solid-state lithium battery 10.

[0016] Figure 3 This is a top view of the all-solid-state lithium battery 10.

[0017] Figure 4 This is a diagram illustrating the manufacturing method of the all-solid-state lithium battery 10.

[0018] Figure 5 This is a cross-sectional view used to illustrate the arrangement of the Li metal solids in the stacking direction of the evaluation batteries of Examples 1-5 and Comparative Example 1.

[0019] Figure 6 This is a top view used to illustrate the shape of the evaluation battery used in Examples 1-5 and Comparative Example 1.

[0020] Explanation of reference numerals in the attached figures

[0021] 10, 20 All-Solid-State Lithium Batteries

[0022] 11, 21 Negative current collector

[0023] 12, 22 Negative electrode mixture layer

[0024] 13, 23 Solid electrolyte layer

[0025] 14, 24 Positive electrode mixture layer

[0026] 15, 25 Positive current collector

[0027] 16Li stored solids Detailed Implementation

[0028] One of the features of the all-solid-state lithium battery disclosed herein is that a negative electrode additive layer, a solid electrolyte layer and a positive electrode additive layer are stacked sequentially, and at least a portion of the outer peripheral end face of the solid electrolyte layer is provided with a Li-encapsulated solid, which has Li reactivity.

[0029] The all-solid-state lithium battery of this disclosure has a Li-captured solid at least a portion of the outer peripheral end face of the solid electrolyte layer. The Li-captured solid is reactive with metallic Li and reacts with metallic Li that rises from the outer peripheral end face, thereby capturing metallic Li internally. Therefore, according to the all-solid-state lithium battery of this disclosure, short circuits caused by metallic Li rising from the outer peripheral end face can be suppressed.

[0030] Furthermore, in the all-solid-state lithium battery disclosed herein, the outer peripheral end faces of the negative electrode compound layer, the solid electrolyte layer, and the positive electrode compound layer are preferably flush with each other on the same plane. The term "outer peripheral end face" refers to the side surface formed by the outer edges of the negative electrode compound layer, the solid electrolyte layer, and the positive electrode compound layer when the end faces in the stacking direction of the all-solid-state lithium battery are used as the upper and lower surfaces. The phrase "outer peripheral end faces are flush with each other on the same plane" means that there are no step differences on the outer peripheral end faces, and the outer peripheral end faces of each layer are located on the same plane. However, manufacturing errors are permissible. For example, if the step difference between the layers is within 0.5 mm, it can be said that the outer peripheral end faces are flush with each other on the same plane.

[0031] In the case of an all-solid-state lithium battery where the outer peripheral surfaces are flush with each other, short circuits caused by metallic Li rising from the outer peripheral surfaces have the highest probability of occurrence. Figure 1 This will be explained in detail.

[0032] Figure 1 This diagram illustrates a short circuit caused by metallic Li rising from the outer peripheral end face in an all-solid-state lithium battery 20 where the outer peripheral end faces are flush with the same surface. The all-solid-state lithium battery 20 is a battery formed by sequentially stacking a negative electrode current collector 21, a negative electrode flux layer 22, a solid electrolyte layer 23, a positive electrode flux layer 24, and a positive electrode current collector 25. In this all-solid-state lithium battery 20 with flush surfaces, when using a negative electrode active material with expansion and contraction properties, a gap X is generated between the negative electrode flux layer 22, which expands and contracts during charging and discharging, and the solid electrolyte layer 23, which does not expand and contract. Metallic Li deposited on the negative electrode flux layer 22 moves towards the outer peripheral end face through this gap X. The metallic Li that has moved to the outer peripheral end face extends towards the positive electrode flux layer 24. Figure 1 (The arrow indicates this). Then, metallic Li reaches the positive electrode flux layer 24, causing a short circuit. Thus, metallic Li deposited on the negative electrode flux layer 22 moves towards the outer peripheral end face through the gap X, and from there climbs towards the positive electrode flux layer 24. Therefore, the short circuit caused by metallic Li climbing from the outer peripheral end face occurs most preferentially.

[0033] In conventional all-solid-state lithium batteries, the negative electrode flux layer and solid electrolyte layer are designed to be larger than the positive electrode flux layer. This creates a step difference at the outer peripheral end face between the positive electrode flux layer and the negative electrode flux layer and solid electrolyte layer, thereby suppressing the rise of metallic Li from the outer peripheral end face. From the viewpoint of suppressing short circuits caused by Li rising, it is preferable that the dimensions of the negative electrode flux layer and solid electrolyte layer are larger than the positive electrode flux layer. However, if the dimensions of each layer are different, careful consideration must be given to the pressing method and mold shape during manufacturing. Therefore, it is desirable to form each layer with approximately the same dimensions.

[0034] However, if the dimensions of each layer are uniform and the outer peripheral end faces are flush with the same plane, such as Figure 1As shown, a problem arises where metallic Li climbs up from the outer peripheral end face, causing a short circuit. Patent Document 1's technology provides an overall shut-off function for the diaphragm layer, but the short circuit that should be prioritized for suppression is the one caused by metallic Li climbing up from the outer peripheral end face. Furthermore, as mentioned above, Patent Document 1's technology raises concerns about leakage.

[0035] On the other hand, the all-solid-state lithium battery of this disclosure has Li-encapsulated solid on the outer peripheral end face of the solid electrolyte layer, which can suppress the extension of metallic Li climbing up from the outer peripheral end face into the positive electrode binder layer. Therefore, the all-solid-state lithium battery of this disclosure can suppress short circuits caused by metallic Li climbing up from the outer peripheral end face even when the outer peripheral end faces are flush with the same plane.

[0036] Furthermore, the all-solid-state lithium battery disclosed herein performs particularly well when the outer peripheral end faces are flush with the same surface, but it is not limited to this, and can also perform well when the outer peripheral end faces have step differences.

[0037] The following description of the all-solid-state lithium battery of the present disclosure will be further illustrated with reference to the all-solid-state lithium battery 10 in which the outer peripheral end faces are flush with the same surface.

[0038] [All-solid-state lithium battery 10]

[0039] Figure 2 This is a cross-sectional view of the all-solid-state lithium battery 10. Figure 3 This is a top view of the all-solid-state lithium battery 10. (See image below.) Figure 2 , Figure 3 As shown, the all-solid-state lithium battery 10 sequentially comprises a negative electrode compound layer 12, a solid electrolyte layer 13, and a positive electrode compound layer 14. Furthermore, the all-solid-state lithium battery 10 includes a negative electrode current collector 11 and a positive electrode current collector 15. The negative electrode current collector 11 is disposed on the surface of the negative electrode compound layer 12 opposite to the solid electrolyte layer 13, and the positive electrode current collector 15 is disposed on the surface of the positive electrode compound layer 14 opposite to the solid electrolyte layer. The negative electrode current collector 11 has a negative electrode current collector tab 11a protruding from its outer peripheral end face, and the positive electrode current collector 15 has a positive electrode current collector tab 15a protruding from its outer peripheral end face. Additionally, the all-solid-state lithium battery 10 has Li-encapsulated solid 16 on the outer peripheral end face of the solid electrolyte layer 13. Moreover, in the all-solid-state lithium battery 10, the outer peripheral end faces of the negative electrode compound layer 12, the solid electrolyte layer 13, and the positive electrode compound layer 14 are flush with each other.

[0040] (Negative current collector 11, positive current collector 15)

[0041] The negative current collector 11 and the positive current collector 15 can be made of metal foil or metal mesh, etc. Examples of metals include Cu, Ni, Al, Fe, and stainless steel. The thickness of the negative current collector 11 and the positive current collector 15 can be appropriately set according to the expected battery performance. For example, it can be in the range of 0.1 μm or more and 1 mm or less.

[0042] (Negative electrode mixture layer 12)

[0043] The negative electrode active material layer 12 contains a negative electrode active material. There are no particular limitations on the negative electrode active material, as long as it is a material suitable for use in all-solid-state lithium batteries and exhibits expansion and contraction during charge and discharge. For example, it can be a Si-based active material such as Si or a carbon material such as graphite. The particle size of the negative electrode active material is not particularly limited, for example, it can be in the range of 0.1 μm to 100 μm. The content of the negative electrode active material in the negative electrode layer 12 is not particularly limited, for example, it can be in the range of 10% by weight to 99% by weight.

[0044] In this specification, "particle size" refers to the particle size (D0) that constitutes the 50% cumulative value in the volumetric particle size distribution determined by laser diffraction and scattering. 50 ).

[0045] The negative electrode layer 12 may optionally contain a solid electrolyte. There are no particular limitations on the solid electrolyte, as long as it is suitable for all-solid-state lithium batteries. For example, it can be an oxide solid electrolyte or a sulfide solid electrolyte. A sulfide solid electrolyte is preferred. Examples of oxide solid electrolytes include Li7La3Zr2O. 12 Li 7-x La3Zr 1-x Nb x O 12 Li 7-3x La3Zr2Al x O 12 Li 3x La 2 / 3-x TiO3, Li 1+x Al x Ti 2-x (PO4)3, Li 1+x Al x Ge 2-x (PO4)3, Li3PO4, Li 3+ x PO 4-x N xExamples of solid electrolytes include Li3PS4, Li2S-P2S5, Li2S-SiS2, LiI-Li2S-SiS2, LiI-Si2S-P2S5, Li2S-P2S5-LiI-LiBr, LiI-Li2S-P2S5, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, and Li2S-P2S5-GeS2. The content of the solid electrolyte in the negative electrode mixture layer 12 is not particularly limited, but may range from 1% to 50% by weight.

[0046] The negative electrode binder layer 12 may optionally contain a conductive additive. There are no particular limitations on the conductive additive, as long as it is suitable for all-solid-state lithium batteries. Examples include carbon materials such as acetylene black, Ketjen black, and fumed carbon fiber (VGCF), or metal materials such as nickel, aluminum, and stainless steel. The content of the conductive additive in the negative electrode binder layer 12 is not particularly limited, for example, it may range from 0.1% to 20% by weight.

[0047] The negative electrode binder layer 12 may optionally include an adhesive. Examples of adhesives include butadiene rubber (BR), butyl rubber (IIR), acrylate butadiene rubber (ABR), carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVdF), and polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP). The content of the adhesive in the negative electrode binder layer 12 is not particularly limited, and may range from, for example, 0.1% to 20% by weight.

[0048] The content of each component in the negative electrode mixture layer 12 can be the same as before. The shape of the negative electrode mixture layer 12 is not particularly limited, but from the viewpoint of easy stacking, a sheet shape is preferred. The thickness of the negative electrode mixture layer 12 is not particularly limited, for example, it is in the range of 0.1 μm or more and 1 mm or less.

[0049] (Solid electrolyte layer 13)

[0050] The solid electrolyte layer 13 contains a solid electrolyte. The type of solid electrolyte can be the same as that used in the negative electrode mixture layer 12. The content of the solid electrolyte in the solid electrolyte layer 13 is, for example, in the range of 50% to 99% by weight.

[0051] The solid electrolyte layer 13 may optionally include a binder. The type of binder may be the same as that used for the negative electrode binder layer 12. The content of the binder in the solid electrolyte layer 13 is not particularly limited, for example, it is in the range of 0.1% to 10% by weight.

[0052] The content of each component in the solid electrolyte layer 13 can be the same as in the conventional form. The shape of the solid electrolyte layer 13 is not particularly limited, but from the viewpoint of easy stacking, a sheet shape is preferred. The thickness of the solid electrolyte layer 13 is not particularly limited, for example, it is in the range of 0.1 μm or more and 1 mm or less.

[0053] (Positive electrode mixture layer 14)

[0054] The positive electrode layer 14 contains the positive electrode active material. There are no particular limitations on the positive electrode active material as long as it can be used in an all-solid-state lithium battery. Examples include lithium cobalt oxide, lithium nickel oxide, and LiNi oxide. 1 / 3 Co 1 / 3 Mn 1 / 3 Lithium-containing composite oxides such as O2, lithium manganese oxide, and spinel-based lithium compounds. The particle size of the positive electrode active material is not particularly limited, for example, in the range of 5 μm to 100 μm. The content of the positive electrode active material in the positive electrode additive layer 14 is, for example, in the range of 50% to 99% by weight. Furthermore, the surface of the positive electrode active material can be covered by an oxide layer such as lithium niobate, lithium titanate, or lithium phosphate.

[0055] The positive electrode mixture layer 14 may optionally contain a solid electrolyte. The type of solid electrolyte may be the same as that used in the negative electrode mixture layer 12. The content of the solid electrolyte in the positive electrode mixture layer 14 may be, for example, in the range of 1% to 50% by weight.

[0056] The positive electrode layer 14 may optionally contain a conductive additive. The type of conductive additive may be the same as that used in the negative electrode layer 12. The content of the conductive additive in the positive electrode layer 14 may be, for example, in the range of 0.1% to 10% by weight.

[0057] The positive electrode layer 14 may optionally include an adhesive. The type of adhesive may be the same as that used in the negative electrode layer 12. The content of the adhesive in the positive electrode layer 14 may be, for example, in the range of 0.1% to 10% by weight.

[0058] The content of each component in the positive electrode mixture layer 14 can be the same as before. The shape of the positive electrode mixture layer 14 is not particularly limited, but from the viewpoint of easy stacking, a sheet shape is preferred. The thickness of the positive electrode mixture layer 14 is not particularly limited, for example, it is in the range of 0.1 μm or more and 1 mm or less.

[0059] (Li-stored solid 16)

[0060] Li-encapsulated solid 16 is disposed on at least a portion of the outer peripheral end face of the solid electrolyte layer 13. By disposing such Li-encapsulated solid 16 on the outer peripheral end face of the solid electrolyte layer 13, metallic Li that rises from the negative electrode binder layer 12 to the positive electrode binder layer 14 reacts with the Li-encapsulated solid 16 in the outer peripheral end face, thereby encapsulating metallic Li within the Li-encapsulated solid 16. Therefore, the all-solid-state lithium battery 10 can suppress short circuits caused by metallic Li rising from the outer peripheral end face.

[0061] The Li-encapsulated solid 16 is not particularly limited as long as it can exist stably in the solid electrolyte layer 13 and is reactive with metallic Li. For example, it can be aluminum or indium. The thickness of the Li-encapsulated solid 16 (the length in the stacking direction of the outer peripheral end face) is not particularly limited, for example, it can be 10 μm or more and 100 μm or less.

[0062] The Li-capturing solid 16 has the above-mentioned effect if it is disposed on at least a portion of the outer peripheral end face, but it is preferred to be disposed on the portion where metallic Li is easily deposited.

[0063] Specifically, it is preferably disposed on the side of the outer peripheral end face of the solid electrolyte layer 13 near the negative electrode compound layer 12. This is because metallic Li readily precipitates on the negative electrode compound layer 12. The term "side of the negative electrode compound layer 12" refers to a range from the negative electrode compound layer 12 to less than 50% in the stacking direction of the outer peripheral end face of the solid electrolyte layer 13, assuming the length from the negative electrode compound layer 12 to the positive electrode compound layer 14 is 100%. Preferably, it is in the range of 30% or less, more preferably 20% or less, even more preferably 10% or less, and particularly preferably includes the portion between the negative electrode compound layer 12 and the solid electrolyte layer 13.

[0064] Furthermore, the Li-captured solid 16 is preferably disposed on the outer peripheral end face of any current collector tab (negative current collector tab 11a and / or positive current collector tab 15a). Because the current is concentrated around the current collector tab, metallic Li is easily deposited. More preferably, it is disposed on the outer peripheral end face of the negative current collector tab 11a.

[0065] More preferably, the negative current collector tab 11a and the positive current collector tab 15a are arranged protruding from the same outer peripheral end face, and the Li-absorbing solid 16 is disposed in the outer peripheral end face of the solid electrolyte layer 13, on the outer peripheral end face where the negative current collector tab 11a and the positive current collector tab 15a are disposed.

[0066] The term "disposed on the outer peripheral end face" means that the Li-capturing solid 16 is disposed on at least a portion of the outer peripheral end face, preferably throughout the width direction of the outer peripheral end face (the direction of the outer peripheral end face orthogonal to the stacking direction). Furthermore, when the Li-capturing solid 16 is disposed throughout the width direction of the outer peripheral end face, it may be disposed on a portion (e.g., within 50% of the length of the width direction) or entirely of the width direction of any one or both of the outer peripheral end faces adjacent to the outer peripheral end face.

[0067] More preferably, the Li-absorbed solid 16 is arranged circumferentially (over the entire circumference) on the outer peripheral end face of the solid electrolyte layer 13. Figure 3 In this preferred embodiment, the placement of the current collector tab is not particularly limited.

[0068] Furthermore, in the actual case where the Li-absorbing solid 16 is disposed in the solid electrolyte layer 13, in addition to the above-mentioned matters, it is also necessary to consider the volume expansion rate of the Li-absorbing solid 16 when absorbing Li, and determine the thickness and the placement position of the outer peripheral end face.

[0069] (Manufacturing method of all-solid-state lithium battery 10)

[0070] Next, the manufacturing method of the all-solid-state lithium battery 10 will be explained. Figure 4 A diagram illustrating the manufacturing method of the all-solid-state lithium battery 10 is shown.

[0071] First, as a preliminary step, two layered solid electrolytes 13a constituting the negative electrode mixture layer 12, the positive electrode mixture layer 14, and the solid electrolyte layer 13 are fabricated (step 1). The layered solid electrolytes 13a have the same structure as the solid electrolyte layer 13, and as described later, they can be combined to fabricate the solid electrolyte layer 13.

[0072] These layers can be fabricated using known methods. For example, in fabricating the positive electrode additive layer 14, the positive electrode additive layer 14 can be fabricated by mixing the materials constituting the positive electrode additive layer 14 and pressing them under a predetermined pressure. Alternatively, the materials constituting the positive electrode additive layer 14 can be mixed with a predetermined solvent to form a slurry, which is then coated onto a substrate or the positive electrode current collector 15 and dried to fabricate the positive electrode additive layer 14. The fabrication methods for the negative electrode additive layer 12 and the layered solid electrolyte are the same.

[0073] Next, as Figure 4As shown in (a), a solid electrolyte layer 13 with Li-encapsulated solid 16 disposed on its outer peripheral end face can be obtained (second step) by placing a linear Li-encapsulated solid 16 between the edges of two layered solid electrolytes 13a, and then pressing the Li-encapsulated solid 16 between these layered solid electrolytes 13a. The pressing conditions in the second step can be appropriately set. For example, compression at 100 kN for 3 minutes, etc.

[0074] After the second process, as Figure 4 As shown in (b), a negative electrode mixture layer 12 is disposed on one surface of the solid electrolyte layer 13, and a positive electrode mixture layer 14 is disposed on the other surface, and pressure is applied (step 3). Thus, as... Figure 4 As shown in (c), an all-solid-state lithium battery 10 can be fabricated.

[0075] Here, in the third step, during pressurization, a negative current collector 11 can be disposed on the negative electrode mixture layer 12, and a positive current collector 15 can be disposed on the positive electrode mixture layer 14. If the current collectors are not disposed, a subsequent step (fourth step) can be performed where the negative current collector 11 is disposed on the negative electrode mixture layer 12 and the positive current collector 15 is disposed on the positive electrode mixture layer 14. The pressurization conditions in the third step can be the same as before.

[0076] Alternatively, when the Li-encapsulated solid 16 is disposed in the portion between the negative electrode mixture layer 12 and the solid electrolyte layer 13, the Li-encapsulated solid 16 can be disposed between the negative electrode mixture layer 12 and the solid electrolyte layer 13, and then clamped and pressurized by these layers.

[0077] [Example]

[0078] The following examples further illustrate the all-solid-state lithium battery of this disclosure. Furthermore, matters required for implementing the technology disclosed herein, other than those specifically mentioned in this specification, can be grasped by those skilled in the art based on existing technology. This disclosure can be implemented based on the content disclosed in this specification and common technical knowledge in the art. The following embodiments are not intended to limit the technology disclosed herein. Additionally, the dimensional relationships (length, width, thickness, etc.) in the accompanying drawings do not reflect actual dimensional relationships.

[0079] [Evaluation of battery manufacturing]

[0080] As described below, evaluation batteries for Examples 1-5 and Comparative Example 1 were manufactured. Additionally, Figure 5 A cross-sectional view is shown to illustrate the configuration of the Li metal solids in the stacking direction in the evaluation battery. Figure 6 A top view is shown to illustrate the shape of the battery used for evaluation.

[0081] <Example 1>

[0082] (Preparation of the positive electrode mixture layer)

[0083] Lithium cobalt oxide (LiCoO2) as the positive electrode active material and Li2S-P2S5 as the sulfide-based solid electrolyte (mass ratio: Li2S:P2S5 = 70:30) were weighed to achieve a weight ratio of positive electrode active material: sulfide-based solid electrolyte = 75:25. Then, relative to 100 parts by weight of the positive electrode active material, 4 parts by weight of PVdF-based binder and 6 parts by weight of conductive material (acetylene black) were weighed. These were formulated into butyl butyrate to a solid content of 70% by weight and kneaded using a mixer to obtain a composition (positive electrode slurry) for forming the positive electrode additive layer. The above positive electrode slurry was coated onto one side of an Al foil (positive electrode current collector) and dried to form the positive electrode additive layer.

[0084] (Preparation of the negative electrode mixture layer)

[0085] Carbon, serving as the negative electrode active material, and Li₂S-P₂S₅, serving as the sulfide-based solid electrolyte, were weighed (mass ratio: Li₂S:P₂S₅ = 70:30) to achieve a weight ratio of positive electrode active material: sulfide-based solid electrolyte = 55:45. Then, relative to 100 parts by weight of the positive electrode active material, 6 parts by weight of PVdF-based binder and 6 parts by weight of conductive material (acetylene black) were weighed. These were formulated into butyl butyrate to a solid content of 70% by weight and kneaded using a mixer to obtain a composition (negative electrode slurry) for forming the negative electrode binder layer. The negative electrode slurry was coated onto one side of a Cu foil (negative electrode current collector) and dried to form the negative electrode binder layer.

[0086] (Preparation of layered solid electrolytes)

[0087] Weigh 98 parts by weight of the same sulfide-based solid electrolyte used in the above-mentioned positive / negative electrode slurry and 2 parts by weight of SBR (styrene-butadiene rubber) based binder. Prepare them in heptane solvent to a solid content of 70% by weight, and perform ultrasonic dispersion treatment for 2 minutes using an ultrasonic dispersion device to obtain a composition (solid electrolyte slurry) for forming a solid electrolyte layer. Coat the above solid electrolyte slurry onto one side of an Al foil and allow it to dry, thereby forming a layered solid electrolyte layer.

[0088] (Evaluation of battery manufacturing)

[0089] A solid electrolyte layer was fabricated using two layered solid electrolytes, each 50 μm thick, and a Li-encapsulated solid (Al line, 25 μm thick). Specifically, the Li-encapsulated solid was placed between the two layered solid electrolytes, arranged circumferentially across the edges of the layered solid electrolytes. The Li-encapsulated solid was then sandwiched between these layered solid electrolytes and pressurized to create a solid electrolyte layer (100 μm thick) with the Li-encapsulated solid positioned on its outer peripheral end face. The pressurization condition was compression at 100 kN for 3 minutes.

[0090] Next, a negative electrode layer with a negative current collector (Cu foil) stacked on one surface of the obtained solid electrolyte layer was disposed, and a positive electrode layer with a positive current collector (Al foil) stacked on the other surface was disposed, and then constrained. At this time, the battery was fabricated with the negative and positive current collector tabs protruding from the same outer peripheral end face. The constraint condition was 5 MPa. Thus, the evaluation battery of Example 1 was fabricated.

[0091] Here, the evaluation battery of Example 1 has Figure 5 The cross section shown in (a) has Figure 6 (1) The shape shown.

[0092] <Example 2>

[0093] The evaluation battery of Example 2 uses a 100 μm thick layered solid electrolyte as the solid electrolyte layer, and Li-encapsulated solid is placed on the outer peripheral end face of the solid electrolyte layer near the negative electrode binder layer. Otherwise, it is manufactured using the same method as the evaluation battery of Example 1. The evaluation battery of Example 2 thus manufactured has… Figure 5 (b) shows the cross-section. Furthermore, the evaluation battery of Example 2 has the same characteristics as that of Example 1. Figure 6 (1) The shape shown.

[0094] <Example 3>

[0095] The evaluation battery of Example 3 has Li-encapsulated solid disposed on the outer peripheral end faces of the negative and positive current collector tabs. Otherwise, it is manufactured using the same method as the evaluation battery of Example 1. Specifically, when manufacturing the solid electrolyte layer, the Li-encapsulated solid is disposed between two layered solid electrolytes in such a way that it covers the width direction of the outer peripheral end faces of the negative and positive current collector tabs, and also covers approximately 50% of the width direction length of the two adjacent outer peripheral end faces. The evaluation battery of Example 3 manufactured in this way has… Figure 5 The cross section shown in (a) has, Figure 6 (2) The shape shown.

[0096] <Example 4>

[0097] The evaluation battery of Example 4 has negative and positive current collector tabs protruding from their opposite outer peripheral end faces. Otherwise, it is manufactured using the same method as the evaluation battery of Example 1. The evaluation battery of Example 4 thus manufactured has… Figure 5 The cross section shown in (a) has, Figure 6 (3) The shape shown.

[0098] <Example 5>

[0099] The evaluation battery of Example 5 has negative electrode current collector tabs and positive electrode current collector tabs protruding from opposite outer peripheral end faces. Otherwise, it is manufactured using the same method as the evaluation battery of Example 3. Here, the outer peripheral end face where the Li-encapsulated solid is disposed is the outer peripheral end face where the positive electrode current collector tab protrudes. The evaluation battery of Example 5 manufactured in this way has… Figure 5 The cross section shown in (a) has, Figure 6 (4) The shape shown.

[0100] <Comparative Example 1>

[0101] The evaluation battery of Comparative Example 1 was manufactured using the same method as the evaluation battery of Example 1, except that it did not have a Li-encapsulated solid electrolyte layer. The evaluation battery of Comparative Example 1 thus manufactured has… Figure 6 The shape shown in (ref).

[0102] [evaluate]

[0103] The voltage drop after a cycle test was measured using the evaluation batteries of Examples 1-5 and Comparative Example 1. The test temperature for the cycle test was 25°C. The cycle test will be described below.

[0104] First, the evaluation battery underwent initial conditioning. During initial conditioning, the charging conditions were 4.2V-CCCV charging at a current rate of 1C with a current cutoff of 0.1C, and the discharging conditions were CC3.0V cutoff with a current rate of 1C. Next, five cycles of charge-discharge were performed between 3.0V and 4.5V at 5C. Then, the battery voltage was adjusted to 4.0V, and the voltage drop after 24 hours was measured. A voltage drop of less than 2mV was marked with "◎", a drop exceeding 2mV but less than 5mV with "○", a drop exceeding 5mV but less than 15mV with "△", and all other drops with "×". The results are shown in Table 1.

[0105] Table 1

[0106]

[0107] As shown in Table 1, Examples 1-5 exhibited smaller voltage drops compared to Comparative Example 1. Since the voltage drop indicates the degree of short circuit caused by metallic Li, it can be said that Examples 1-5 were able to suppress short circuits compared to Comparative Example 1.

[0108] Examples 1 and 2 investigated the differences in effects caused by the stacking orientation of the Li-encapsulated solid. The comparison results showed that the voltage drop in Example 2 was significantly smaller. This is attributed to the fact that, as shown in Example 2, the Li-encapsulated solid was positioned on the outer peripheral end face near the negative electrode binder layer, thereby suppressing the initial rise of metallic Li on the outer peripheral end face.

[0109] Examples 1, 3-5 investigated the different placement positions of the Li-encapsulated solid in the width direction (circumferential direction) of its outer peripheral end face and the placement positions of the current collector tabs. The comparison results show that Examples 1 and 4, where the Li-encapsulated solid is placed circumferentially throughout the outer peripheral end face of the solid electrolyte layer, exhibit very small voltage drops. Furthermore, Example 3, where the Li-encapsulated solid is placed on the outer peripheral end faces of both the negative and positive current collector tabs, shows roughly the same results as Examples 1 and 4. On the other hand, Example 5, where the negative and positive current collector tabs protrude to opposite outer peripheral end faces, and the Li-encapsulated solid is placed on the outer peripheral end face of the positive current collector tab, shows a larger voltage drop compared to Examples 1, 3, and 4. From these results, it is clear that placing the Li-encapsulated solid on the outer peripheral end face where the current collector tabs are located is preferable, as current tends to concentrate around the current collector tabs, thus promoting Li deposition. It is believed that in Example 5, no Li-capturing solid was disposed on the outer peripheral end face of the electrode tab with negative current collector, so the voltage drop was greater compared with Examples 1, 3, and 4.

[0110] This disclosure is not limited to the above-described embodiments. Appropriate modifications may be made without departing from the scope of the claims and the spirit or idea of ​​the invention as read in whole from the specification. Such all-solid-state batteries with these modifications are also included within the technical scope of this disclosure.

Claims

1. A full-solid lithium battery, which is formed by sequentially stacking a negative electrode mixture layer, a solid electrolyte layer, and a positive electrode mixture layer, wherein a Li occlusion solid is provided on at least a part of an outer peripheral end surface of the solid electrolyte layer, the Li occlusion solid has Li reactivity, an outer peripheral end surface of the negative electrode mixture layer, the solid electrolyte layer, and the positive electrode mixture layer is flush with the same surface, and the Li occlusion solid protrudes outward from the same surface, the Li occlusion solid is aluminum or indium, and the Li occlusion solid is provided only on the outer peripheral end surface of the solid electrolyte layer on the side of the negative electrode mixture layer.

2. The full-solid lithium battery according to claim 1, further comprising a negative electrode current collector provided on a surface of the negative electrode mixture layer on the opposite side of the solid electrolyte layer and a positive electrode current collector provided on a surface of the positive electrode mixture layer on the opposite side of the solid electrolyte layer, the negative electrode current collector includes a negative electrode current collector tab, the positive electrode current collector includes a positive electrode current collector tab, the negative electrode current collector tab and the positive electrode current collector tab are provided protruding from the same outer peripheral end surface, and the Li occlusion solid is provided on the outer peripheral end surface of the solid electrolyte layer on which the negative electrode current collector tab and the positive electrode current collector tab are provided.

3. The full-solid lithium battery according to claim 1 or 2, wherein the Li occlusion solid is provided on the entire outer peripheral end surface of the solid electrolyte layer in the circumferential direction. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Images